Post on 03-Feb-2022
TECHNOLOGICAL AND ECONOMIC
EVALUATION OF DISTRICT COOLING
WITH ABSORPTION COOLING SYSTEMS
IN GÄVLE (SWEDEN)
Elixabet Sarasketa Zabala
June 2009
Master’s Thesis in Energy Systems
uuir
DEPARTMENT OF TECHNOLOGY AND BUILT ENVIRONMENT
Master Programme in Energy Systems
Examiner: Ulf Larsson
Supervisor: Åke Björnwall
Preface
This investigation, as final Thesis Project of Master in Energy Systems
(University of Gävle), was started to carry out in February, in collaboration with
the company Gävle Energi AB. Many people have been involved answering my
questions, providing me with information and so forth; some of those are
mentioned below.
First of all, I would like to thank Åke Björnwall, my supervisor at Gävle
Energi AB, very much for his attention, help and support. His knowledge,
comments, guidance and advices have been essential for the development of my
work. Needless to say that I have learnt a lot from him.
Secondly, I would like to thank the rest of workers at Gävle Energi AB,
who have done everything they can to help me, in addition to make pleasant my
stay in the company.
I would also like to thank Ulf Larsson at the University of Gävle for his
help. Furthermore, I am very grateful for all information I have received from
other companies.
Finally, I do not forget the invaluable support of my mother, Rosa, during
all my studies.
No one mentioned, no one forgotten.
Gävle, June 2009
Elixabet Sarasketa Zabala
Abstract
Gävle Energi AB is a company which produces electricity as well as heat
that is delivered through a district heating network in the municipality of Gävle.
Apart from that, as cooling demand is large when seen from a global perspective,
at present it is building a district cooling network based on refrigerant compressor
technology with the idea of replacing less efficient individual HVAC systems in
the city center.
High electricity prices lead to reduce its use as far as possible, so it is also
needed to consider absorption systems as cooling technology. This way, the main
aim of this thesis is to analyze possible benefits with the use of heat driven
absorption chillers compared with conventional vapour compressor chillers.
For carrying out this investigation, first of all background and literature
study have been essential. As a result, information about cooling technologies,
district energy and cogeneration plants is gathered in this work.
The research is focused on three areas of the victinity of Gävle: city center,
Kungsbäck and Johannesbergsvägen.
In the first area, Gävle Energi AB might take the opportunity of using a
new ORC plant in biomass based cogeneration system that Bionär is planning to
build at LEAF, turning it into a trigeneration plant. So how bigger the installation
should be (according to the expected cooling demand that has been calculated in
the earliest steps) and the profits related to extra electricity production are
estimated in this study, in addition to examine the absorption chillers to be
introduced and their operational conditions.
On the other hand, Mackmyra whisky factory, which is in Valbo
nowadays, is going to build a new plant in Kungsbäck. Likewise, it is considering
that extra steam might be produced to fire absorption chillers and fulfil the
cooling demand of the hospital (Gävle Sjukhus), technological park
(Teknikparken) and university (Högskolan i Gävle), which are located in this area.
Like this, the same methodology as for LEAF has been followed for making
decisions.
Finally, there is Johannesbergsvägen area, where Johannes CHP plant is (a
description of the plant is included in the Appendix) and which is runned by
Gävle Energi AB. This plant is shut down in summer, as the demand for district
heating is low, and hence, electricity production, from which the company makes
a profit, is cut and restricted. A good solution to increase electricity output in
warm periods is to introduce absorption cooling technology, as it is run on steam
or hot water. Thus, Johannes could be the third trigeneration plant in Gävle that
would supply Hemlingby shopping centers (which are located less than two
kilometers far away from the production site) with cooling. Thus, the task has
been also to decide on installations and gauge the profits.
Next Table 0. gathers together costs, amount of heat that would be
demanded to produce and accordingly generated electricity in each of the three
production sites. It has been decided that double-effect chillers sets in the first two
cases and single-effect hot-water fired absorption cooling machines in the last one
might be introduced.
Table 0. Costs of absorption cooling installations, extra heat to be produced for the
absorption chillers and extra electricity output in the three studied sites
PRODUCTION
SITE &TOTAL
COOLING
LOAD
INVESTMENT
COST [SEK]
OPERATIONAL
COSTS
[SEK/year]
HEATING
DEMAND
[MWh/year]
ELECTRICITY
PRODUCTION
[MWh/year]
LEAF
21 385 MWh/year 22 627 000 4 753 485 17 977 4 135
MACKMYRA
9 298 MWh/year 17 700 000 2 504 835 7 819 1 173
JOHANNES
8 496 MWh/year 8 800 000 3 561 396 10 460 3 033
Furthermore, explanations and calculations regarding distribution systems
are presented, as these are also a component of district cooling systems.
Nevertheless, they are not taken into consideration for final decisions, since
necessary pumps and piping system would be the same in case of using vapour
compressor chillers for cooling production.
Lastly, it has been come to the conclusion that a sustainable energy system
for Gävle for fulfilling the cooling demand can be the erection of district cooling
networks with trigeneration plants by producing cooling in heat driven absorption
cooling machines. Despite larger investment cost of absorption systems compared
to compression ones, total costs after roughly five years are lower. Moreover,
electric coefficient of performance is about 23% higher for the absorption cooling
technology and there is a great electricity output too, which makes possible to
reduce electrical loads, to use the biofuel in an effective way and, last but not
least, to decrease global carbon dioxide emissions.
I
TABLE OF CONTENTS
CHAPTER 1. INTRODUCTION ..................................................................... 1
1.1. BACKGROUND ....................................................................................... 2
1.1.1. COOLING AND ITS PRODUCTION .................................................................... 2
1.1.2. GÄVLE ENERGI AB AND ITS PLANS FOR THE FUTURE................................ 3
1.2. PURPOSE .................................................................................................. 4
1.3. SCOPE....................................................................................................... 4
1.4. LIMITATIONS .......................................................................................... 5
1.5. METHOD .................................................................................................. 5
1.6. OUTLINE OF THE THESIS...................................................................... 6
CHAPTER 2. COOLING SYSTEM TECHNOLOGIES ................................ 8
2.1. REFRIGERANT COMPRESSOR INSTALLATIONS ................................ 10
2.1.1. COMPRESSOR AND SYSTEM EFFICIENCY ..................................................... 12
2.2. ABSORPTION COOLING INSTALLATIONS .......................................... 13
2.2.1. CONSIDERATIONS FOR DIMENSIONING ABSORPTION CIRCUITS............. 17
2.2.2. WORKING FLUID ............................................................................................... 18
2.2.2.1. WATER/ LITHIUM BROMIDE (H2O/ LiBr) .......................................... 19
2.2.2.2. AMMONIA/WATER (NH3/ H2O) ........................................................... 20
2.2.2.3. COMPARISON BETWEEN WATER/ LITHIUM BROMIDE AND
AMMONIA/WATER SOLUTIONS.......................................................... 21
2.2.3. PRIMARY ENERGY ............................................................................................ 25
2.2.4. TYPES OF ABSORPTION CHILLERS ................................................................ 26
2.2.4.1. SINGLE-EFFECT ABSORPTION CHILLERS ....................................... 27
2.2.4.2. DOUBLE-EFFECT ABSORPTION CHILLERS ..................................... 28
2.3. REFRIGERANT COMPRESSOR TECHNOLOGY VERSUS
ABSORPTION COOLING TECHNOLOGY ............................................ 30
CHAPTER 3. DISTRICT COOLING SYSTEM ............................................ 35
3.1. PRODUCTION ........................................................................................... 37
3.1.1. COGENERATION. BENEFITS WITH ABSORPTION COOLING ...................... 37
TABLE OF CONTENTS
II
3.2. COOLING DISTRIBUTION SYSTEM....................................................... 39
3.2.1. PIPING NETWORK ............................................................................................. 39
3.2.2. MATERIALS FOR THE PIPES ............................................................................ 40
CHAPTER 4. PROCESS ................................................................................. 41
4.1. GATHERING OF INFORMATION ABOUT EXISTING
INSTALLATIONS AND PRESENT SITUATION ..................................... 42
4.1.1. STEAM BOILERS AT LEAF AND KAPPA ........................................................ 42
4.1.2. BIOFUELED JOHANNES CHP PLANT .............................................................. 44
4.1.3. MACKMYRA ...................................................................................................... 46
4.1.4. REFRIGERATION COMPRESSOR COOLING PROJECT .................................. 47
4.2. GATHERING OF DATA: CUSTOMERS. LOAD REQUIRED AND
DISTANCES ............................................................................................... 48
4.3. ANALYSIS OF ABSORPTION COOLING PLANTS ................................ 51
4.3.1. ABSORPTION CHILLERS .................................................................................. 51
4.3.3.1. STUDY OF THE OPERATIONAL CONDITIONS ................................. 52
4.3.2. REST OF THE EQUIPMENTS ............................................................................ 52
CHAPTER 5. RESULTS ................................................................................. 56
5.1. PRODUCTION PLANTS ............................................................................ 57
5.1.1. LEAF .................................................................................................................... 57
5.1.1.1. OPERATIONAL CONDITIONS ............................................................. 57
5.1.1.2. COSTS .................................................................................................... 58
5.1.1.2.1. INVESTMENT COSTS .......................................................... 58
5.1.1.2.2. OPERATIONAL COSTS ........................................................ 59
5.1.1.2.3. TOTAL COSTS ...................................................................... 59
5.1.2. MACKMYRA ....................................................................................................... 61
5.1.2.1. OPERATIONAL CONDITIONS ............................................................. 61
5.1.2.2. COSTS .................................................................................................... 62
5.1.2.2.1. INVESTMENT COSTS .......................................................... 62
5.1.2.2.2. OPERATIONAL COSTS ........................................................ 62
5.1.2.2.3. TOTAL COSTS ...................................................................... 63
5.1.3. JOHANNES .......................................................................................................... 64
5.1.3.1. OPERATIONAL CONDITIONS ............................................................. 64
5.1.3.2. COSTS .................................................................................................... 64
5.1.3.2.1. INVESTMENT COSTS .......................................................... 65
5.1.3.2.2. OPERATIONAL COSTS ........................................................ 65
5.1.3.2.3. TOTAL COSTS ...................................................................... 65
5.1.4. SENSITIVITY ANALYSIS ................................................................................... 67
5.1.4.1. LEAF ...................................................................................................... 67
5.1.3.2. MACKMYRA ......................................................................................... 69
TABLE OF CONTENTS
III
5.1.3.2. JOHANNES ............................................................................................ 71
5.2. COMPRESSION TECHNOLOGY VERSUS ABSORPTION
TECHNOLOGY. COMPARISON FOR LEAF PRODUCTION SITE......... 72
5.3. DISTRIBUTION SYSTEM ......................................................................... 75
5.3.1. INSTALLATION .................................................................................................. 75
5.3.3. COST OF THE MAIN PIPING NETWORKS ....................................................... 75
CHAPTER 6. DISCUSSIONS ......................................................................... 76
6.1. PRODUCTION PLANTS ............................................................................ 77
6.2. MOST PROFITABLE TECHNIQUE FROM ECONOMIC POINT OF
VIEW. SUSTAINABILITY ........................................................................ 80
6.3. COOLING DEMAND VERSUS COSTS AND BENEFITS OF
ABSORPTION COOLING TECHNOLOGY .............................................. 83
6.3.1. ELECTRICITY PRODUCTION AND CONSUMPTION ...................................... 83
6.3.2. COSTS AND PROFITS. THE BEST OPTIONS .................................................... 84
CHAPTER 7. CONCLUSIONS ....................................................................... 86
REFERENCES ................................................................................................. 88
APPENDICES .................................................................................................. 92
Appendix 1. PLANNED REFRIGERANT COMPRESSION
INSTALLATION ................................................................ 93
A1.1. INSTALLATION ................................................... 93
A1.2. COOLING LOAD ................................................. 99
A1.3. INPUT LOAD AND COSTS ................................ 100
A1.4. TOTAL COSTS ................................................... 102
A1.5. PAY-BACK TIME FOR THE INVESTMENTS... 103
Appendix 2. EXPECTED COOLING DEMAND ................................ 104
TABLE OF CONTENTS
IV
Appendix 3. SPECIFICATIONS AND CALCULATIONS
REGARDING ABSORPTION COOLING
INSTALLATIONS ........................................................... 108
A3.1. ABSORPTION CHILLERS.................................. 108
A3.1.1. MODELS AND THEIR CHARACTERISTICS ........ 108
A3.1.2. INVESTMENT COSTS ........................................... 118
A3.1.3. OPERATIONAL CONDITIONS ............................. 119
A3.2. THE REST OF EQUIPMENTS ............................ 131
Appendix 4. MAPS OF CUSTOMERS AND DISTANCES FROM
THE PRODUCTION SITES ............................................ 133
Appendix 5. CALCULATIONS ABOUT DIMENSIONS OF PIPES,
DISTRIBUTION PUMPS AND THEIR COSTS ............ 140
A5.1. DIMENSIONING ................................................. 140
A5.2. COSTS ................................................................. 146
Appendix 6. FALUN COOLING PROJECT: A REFERENCE ......... 150
A6.1. INSTALLATION ................................................. 150
A6.2. TOTAL COSTS.................................................... 152
Appendix 7. EXTRA INFORMATION ABOUT JOHANNES
POWER PLANT............................................................... 153
V
LIST OF FIGURES
Figure 1. Refrigerant compression cycle ........................................................... 10
Figure 2. Temperature-Entropy (T-s) diagram for a Vapour-Compression
Refrigeration Cycle ........................................................................... 11
Figure 3. Scheme of basic absorption cycle ....................................................... 14
Figure 4. Schematic of the fundamental absorption refrigeration system ........... 17
Figure 5. Ammonia/Water absorption cycle ...................................................... 20
Figure 6. Crystallization temperatures of water/lithium bromide solution
against the mass concentration of lithium bromide ............................. 21
Figure 7. Maximum system pressures against the condenser temperature .......... 22
Figure 8. Minimum system pressures against the evaporator temperature ......... 23
Figure 9. COP of the absorption systems against the condenser temperature
(heat exchanger efficiency 0,6) .......................................................... 24
Figure 10. COP of the absorption systems against the generator temperature
(heat exchanger efficiency 0,6) ........................................................ 24
Figure 11. COP of the absorption systems against the evaporator temperature
(heat exchanger efficiency 0,6) ........................................................ 25
Figure 12. Cooling cycle schematic .................................................................. 27
Figure 13. Double-Effect Water/Lithium Bromide Absorption Chiller
Schematic ....................................................................................... 28
Figure 14. Sketch for a double effect absorption heat pump in a log pressure-
temperature diagram ........................................................................ 29
Figure 15. Comparison between compression and absorption technologies
using ammonia as refrigerant and cooling water with a temperature
of 25 ºC ........................................................................................... 31
Figure 16. Components of district cooling systems ........................................... 36
Figure 17. District cooling system (or district heating system) .......................... 36
Figure 18. An schematic of cogeneration process that shows the consumed
and produced power in the whole system ........................................ 37
Figure 19. Illustration of a CHP plant connected to a district heating network ... 38
Figure 20. Energy efficiency of ORC units in cogeneration applications ............ 43
Figure 21. ORC plant in biomass based cogeneration system ............................. 43
Figure 22. Johannes CHP plant before 2003 ...................................................... 44
Figure 23. Production of heat (for District Heating) and electricity at
Johannes .......................................................................................... 45
Figure 24. Existing electric boiler in Mackmyra ................................................ 46
Figure 25. Existing and planned boilers at Mackmyra ........................................ 47
Figure 26. Three cooling production and customer sites and main pipes ............ 49
Figure 27. Cooling power to be produced in different sites during the year ........ 53
Figure 28. Typical piping diagram of an absorption system ............................... 56
Figure 29. Graph that shows the breakdown of total costs for 10 years at
LEAF ............................................................................................... 60
LIST OF FIGURES
VI
Figure 30. Graph that shows the breakdown of total costs for 10 years in
Mackmyra production site ................................................................ 63
Figure 31. Graph that shows the breakdown of total costs for 10 years in
Johannes production site .................................................................. 66
Figure 32. Comparison of cooling installations with absorption and
compression machines at LEAF ....................................................... 74
Figure 33. Increased heat load for the three absorption plants and the possible
extra electricity that would be produced ........................................... 79
Figure 34. Increased heat and electricity load in the probable Johannes
trigeneration plant ............................................................................ 79
Figure 35. Required operational conditions of the boiler for the cooling plant at
Johannes .......................................................................................... 80
Figure 36. Comparison of total costs for ten years for the different cooling
production technologies at LEAF ..................................................... 81
Figure 37. Electricity production and consumption according to the cooling
demand in three different scenarios .................................................. 84
Figure 38. Costs and profits (due to electricity production) according to the
cooling demand in three different scenarios ...................................... 84
Figure A1. 1. Draft of the whole compression installation.................................. 90
Figure A1. 2. Draft of the devices of the compression installation...................... 90
Figure A1. 3. Maintenance costs in the course of time ....................................... 99
Figure A3. 1. Water streams (steam and DH) at Johannes CHP plant ............... 111
Figure A3. 2. Cooling demand load curve (2008) divided in periods
according to the power needed to be produced ........................... 116
Figure A4. 1. Map of the city center with the main pipe that leaves LEAF
production site and its length ..................................................... 130
Figure A4. 2. Map with the customers, pipes and distances for Mackmyra
production site ........................................................................... 132
Figure A4. 3. Map with the customers for Johannes production site, pipe and
its length .................................................................................... 134
Figure A4. 4. Map of the shopping centers under construction in Hemlingby ... 135
Figure A4. 5. Map of the future residential area close to Johannes plant .......... 136
Figure A5. 1. SBI monogram showing the parameters of the different pipes .... 140
Figure A5. 2. Differential pressures in a direct return distribution system with
one terminal unit ........................................................................ 141
Figure A5. 3. Piping excavation section ........................................................... 143
Figure A5. 4. Distribution system cost split up in its components and their
contribution to the total cost....................................................... 145
Figure A6. 1. Draft of the whole cooling installation in Falun .......................... 147
Figure A7. 1. Scheme of Johannes CHP plant .................................................. 150
Figure A7. 2. Fuel storage and conveyor belt carrying biofuel to the boiler at
Johannes .................................................................................... 151
Figure A7. 3. Bubble Fluidized Bed (BFB) boiler of Johannes CHP plant ....... 152
LIST OF FIGURES
VII
Figure A7. 4. Illustrative drawing of Olga turbine and components .................. 153
Figure A7. 5. Olga turbine on the left side and heat exchangers on the right
Side. Johannes CHP plant .......................................................... 153
Figure A7. 6. Schematic of the FGC at Johannes ............................................. 154
Figure A7. 7. Detailed scheme of the condensate treatment plant at Johannes .. 154
VIII
LIST OF TABLES
Table 1. Production sites and customers ............................................................ 4
Table 2. Absorption working fluids´ properties ................................................ 23
Table 3. Comparison of parallel and series flow for double-effect water/lithium
bromide cycles .................................................................................... 29
Table 4. Energy saving with cogeneration for α = 0,54 ..................................... 33
Table 5. Summary of characteristics for cooling options .................................. 34
Table 6. Comparison between two 1000kW chillers ......................................... 34
Table 7. Different types of plants using a steam boiler and their
characteristics ..................................................................................... 38
Table 8. Cooling load demand at each site ....................................................... 50
Table 9. Possibilities to fulfill the cooling demand in the city center by using
steam-fired absorption chillers ............................................................ 51
Table 10. Possibilities to fulfill the cooling demand in Kungsbäck by using
steam-fired absorption chillers ........................................................... 52
Table 11. Possibilities to fulfill the cooling demand corresponding to Johannes
plant ................................................................................................. 54
Table 12. Cooling that should be produced for different sites during the year .... 55
Table 13. Power and steam demand of different chillers sets for the required
cooling load at LEAF during the year ................................................ 57
Table 14. Biofuel (for producing steam), electricity and water consumption.
LEAF ................................................................................................ 58
Table 15. Investment costs [SEK] for LEAF ..................................................... 58
Table 16. Operational costs at LEAF ................................................................ 59
Table 17. Total costs of LEAF absorption cooling plants for 10 years ............... 59
Table 18. Power and steam demand of different chillers sets for the required
cooling load in Mackmyra production during the year ....................... 61
Table 19. Biofuel (for producing steam), electricity and water consumption.
Mackmyra ......................................................................................... 61
Table 20. Investment costs [SEK] for Mackmyra .............................................. 62
Table 21. Operational costs in Mackmyra production site ................................. 62
Table 22. Total costs of Mackmyra absorption cooling plants for 10 years ........ 63
Table 23. Power and hot water demand of chillers set for the required cooling
load at Johannes during the year ........................................................ 64
Table 24. Biofuel (for producing steam), electricity and water consumption.
Johannes ............................................................................................ 64
Table 25. Investment costs [SEK] for Johannes................................................. 65
Table 26. Operational costs in Johannes production site .................................... 65
Table 27. Total costs of Johannes absorption cooling plant for 10 years ............ 65
Table 28. Operational conditions of different chillers sets at LEAF during
the year when the cooling demand is 10% higher than the estimated
one .................................................................................................... 67
LIST OF TABLES
IX
Table 29. Total costs of LEAF absorption cooling plants for 10 years when the
cooling demand is 10% higher than the estimated one ....................... 67
Table 30. Operational conditions of different chillers sets at LEAF during the
year when the cooling demand is 10% lower than the estimated one .. 68
Table 31. Total costs of LEAF absorption cooling plants for 10 years when the
cooling demand is 10% lower than the estimated one ........................ 68
Table 32. Operational conditions of different chillers sets in Mackmyra
production site during the year when the cooling demand is 10%
higher than the estimated one ............................................................ 69
Table 33. Total costs of Mackmyra absorption cooling plants for 10 years
when the cooling demand is 10% higher than the estimated one ........ 69
Table 34. Operational conditions of different chillers sets in Mackmyra
production site during the year when the cooling demand is 10%
lower than the estimated one.............................................................. 70
Table 35. Total costs of Mackmyra absorption cooling plants for 10 years
when the cooling demand is 10% lower than the estimated one ......... 70
Table 36. Operational conditions of different chillers sets in Johannes
production site during the year when the cooling demand is 10%
higher than the estimated one ............................................................ 71
Table 37. Total costs of Johannes absorption cooling plants for 10 years when
the cooling demand is 10% higher than the estimated one .................. 71
Table 38. Operational conditions of different chillers sets in Johannes
production site during the year when the cooling demand is 10%
lower than the estimated one.............................................................. 71
Table 39. Total costs of Johannes absorption cooling plants for 10 years when
the cooling demand is 10% lower than the estimated one ................... 71
Table 40. Operational conditions of the existing cooling project but with
absorption machines .......................................................................... 73
Table 41. Power and steam demand of chillers set for the required cooling load
in the existing cooling project but with absorption machines ............. 73
Table 42. Operational costs in the existing cooling project but with absorption
machines ........................................................................................... 73
Table 43. Total costs of the existing cooling project but with absorption
machines for 10 years ........................................................................ 73
Table 44. Data about the distribution systems ................................................... 75
Table 45. Cost of the distribution systems ......................................................... 75
Table 46. Operational conditions and costs of distribution pumps ..................... 75
Table 47. Most adequate chillers and costs & profits for the three production
sites ..................................................................................................... 78
Table 48. Annual benefits of absorption cooling technology at LEAF after 10
years .................................................................................................... 81
LIST OF TABLES
X
Table R. 1. Information about personal contacts ............................................... 88
Table A1. 1. Pump specifications of compression cooling installation I ............ 92
Table A1. 2. Pump specifications of compression cooling installation II ........... 93
Table A1. 3. Pump specifications of compression cooling installation III .......... 93
Table A1. 4. Pump specifications of compression cooling installation IV .......... 93
Table A1. 5. Pump specifications of compression cooling installation V ........... 93
Table A1. 6. Pump specifications of compression cooling installation VI .......... 94
Table A1. 7. Pump specifications of compression cooling installation VII ........ 94
Table A1. 8. Pump specifications of compression cooling installation VIII ....... 94
Table A1. 9. Vapour Compressor chillers specifications I ................................. 94
Table A1. 10. Vapour Compressor chillers specifications II .............................. 95
Table A1. 11. Vapour Compressor chillers specifications III ............................. 95
Table A1. 12. Heat exchanger specifications of compression cooling
installation .................................................................................. 95
Table A1. 13. Operational conditions of VKA1 and VKA2 compressors
(YRWCWCT3550C) in time steps .............................................. 96
Table A1. 14. Operational conditions of VKA4 and VKA5 compressors
(YKKKKLH95CQF) in time steps .............................................. 96
Table A1. 15. Operating time for cooling delivering during the year ................. 96
Table A1. 16. Power needed in the compression cooling installation during the
year ............................................................................................ 97
Table A1. 17. Input load VKA1 and VKA2 compressors (YRWCWCT3550C)
in time steps................................................................................ 98
Table A1. 18. Input load VKA4 and VKA5 compressors (YKKKKLH95CQF)
in time steps................................................................................ 98
Table A1. 19. Total input load and operating costs in the compression cooling
installation .................................................................................. 99
Table A1. 20. Costs of the compressor refrigerant system ................................. 99
Table A1. 21. Pay-back times for the compression installation ......................... 100
Table A1. 22. Total costs for the refrigeration compression system for the first
10 years ..................................................................................... 100
Table A2. 1. Cooling demand of possible future customers in the city center
and additional data ....................................................................... 101
Table A2. 2. Customers and their cooling demand in Kungsbäck ..................... 103
Table A2. 3. Cooling demand for Johannes production site .............................. 104
Table A3. 1. Production data and pressure of the first steam stream extracted
from the turbine ........................................................................... 112
Table A3. 2. Price comparison of single- and double-effect units ..................... 115
Table A3. 3. Investment costs for different absorption chiller units .................. 116
Table A3. 4. Average city center´s cooling demand in time steps for 2008 ....... 117
Table A3. 5. Cooling load to be produced and working power of different
chillers (double- and single- effect) at LEAF during the year ....... 118
Table A3. 6. Cooling power to be supplied to the chillers at LEAF during the
year .............................................................................................. 118
LIST OF TABLES
XI
Table A3. 7. Cooling load to be produced and working power of different
chillers (double- and single- effect) at LEAF during the year when
the cooling demand is 10% higher than the estimated one ............ 119
Table A3. 8. Cooling power to be supplied to the chillers at LEAF during the
year when the cooling demand is 10% higher than the estimated
one ............................................................................................... 119
Table A3. 9. Cooling load to be produced and working power of different
chillers (double- and single- effect) at LEAF during the year when
the cooling demand is 10% lower than the estimated one ............. 120
Table A3. 10. Cooling power to be supplied to the chillers at LEAF during the
year when the cooling demand is 10% lower than the estimated
one ............................................................................................ 120
Table A3. 11. Cooling load to be produced and working power of different
chillers (double- and single- effect) in Mackmyra production
site during the year .................................................................... 121
Table A3. 12. Cooling power to be supplied to the chillers during the year and
necessary cooling towers in Mackmyra production site .............. 121
Table A3. 13. Cooling load to be produced and working power of different
chillers (double- and single- effect) in Mackmyra production site
during the year when the cooling demand is 10% higher than the
estimated one ............................................................................. 122
Table A3. 14. Cooling power to be supplied to the chillers during the year and
necessary cooling towers in Mackmyra production site when the
cooling demand is 10% higher than the estimated one................ 122
Table A3. 15. Cooling load to be produced and working power of different
chillers (double- and single- effect) in Mackmyra production site
during the year when the cooling demand is 10% lower than the
estimated one ............................................................................. 123
Table A3. 16. Cooling power to be supplied to the chillers during the year and
necessary cooling towers in Mackmyra production site when the
cooling demand is 10% lower than the estimated one ................. 123
Table A3. 17. Cooling load to be produced and working power of different
chillers in Johannes production site during the year.................... 124
Table A3. 18. Cooling power to be supplied to the chillers during the year and
necessary cooling towers in Johannes production site ................ 125
Table A3. 19. Cooling load to be produced and working power of different
chillers in Johannes production site when the cooling demand is
10% higher than the estimated one ............................................. 125
Table A3. 20. Cooling power to be supplied to the chillers in Johannes
production site during the year when the cooling demand is 10%
higher than the estimated one ..................................................... 126
Table A3. 21. Cooling load to be produced and working power of different
chillers in Johannes production site when the cooling demand is
10% lower than the estimated one .............................................. 126
LIST OF TABLES
XII
Table A3. 22. Cooling power to be supplied to the chillers in Johannes
production site during the year when the cooling demand is 10%
lower than the estimated one ...................................................... 127
Table A3. 23. Required cooling towers and heat exchangers´ technical data..... 128
Table A5. 1. Dimensioning of pipes and pressure drop (part I) ......................... 137
Table A5. 2. Dimensioning of pipes and pressure drop (part II) ....................... 138
Table A5. 3. PE Pressure Pipes for water supply: EN 12201, ISO 4427 ........... 142
Table A5. 4. Data of the pipes needed .............................................................. 143
Table A5. 5. Values of parameters C and B for the required dn ....................... 144
Table A5. 6. Total cost of the pipes .................................................................. 144
Table A5. 7. Calculation of the pipes´ costs ..................................................... 145
Table A5. 8. Needed distribution pumps and their cost .................................... 146
Table A6. 1. Reference specifications about absorption chiller in Falun .......... 148
Table A6. 2. Investment costs for different installations in Falun ..................... 149
Table A6. 3. Input electric power in Falun installations .................................... 149
Table A7. 1. Characteristics of the obtained outputs at Johannes ...................... 153
CHAPTER 1
2
Introduction
This chapter is a definition of the thesis, which describes the issues to be
studied and the reasons for their investigation, as well as the main purpose, scope,
limitations and so forth.
In general terms, the task can be summed up as the evaluation of
technological and economic possibilities regarding district cooling with
absorption cooling technology at three specific sites in the victinity of Gävle.
1.1. BACKGROUND
1.1.1. COOLING AND ITS PRODUCTION
It is a fact that cooling demand is as high as or even higher than heating
demand, since it is needed for both thermal comfort and many industrial processes
and, in addition, it is required more energy for producing cooling than heating.
Hence, production of cold could be very profitable for energy companies when it
is a part of the existing energy system.
District cooling system (DCS) offers massive and collective cooling
energy production, which is higher in efficiency than the conventional plants at
individual premises, and allows users to utilise building space more effectively
[1]. Generally, the chilled water for pipeline distribution is produced by
refrigerant compressor technique; nonetheless, it is needed to face up to a large
electricity consumption, which involves a large expense due to the deregulation of
the european electricity market.
In 2004 Sweden became part of a common european electricity market and
swedish plant will therefore meet higher european prices, which will lead to a
Chapter 1. INTRODUCTION
3
precarious scenario because of its intensive utilization of electricity [2].
Consequently, the use of electricity has to be decreased, for instance by changing
energy carrier when it is used for non-electricity specific purposes. To reach this
target, the choice of absorption facilities as cooling technology is clear.
Absorption cooling sytem uses heat as fuel, which make it possible to
combine with cogeneration plants and make the most of surplus heat. Moreover, it
is especially benefitial in summer periods when there is a large amount of waste
heat and electricity generation needs to be therefore reduced or stopped.
1.1.2. GÄVLE ENERGI AB AND ITS PLANS FOR THE
FUTURE
Gävle Energi AB is an energy company that belongs to Gävle community
and it develops, produces and sells products and services in energy and
communication with great view of the environment and nature. The company
owns and runs most of the electricity as well as district heating network in the
municipality of Gävle.
Gävle Energi AB not only ensures short-term goals but it has always long-
term objectives to contribute actively to the Gävle region's development. Thus, as
cooling demand is large when seen from a global perspective, it is building a
district cooling network which will be finished in a near future. In a first step, the
planned production of cold is based on refrigerant compressor technology and at
present, it is thinking of future possibilities of using absorption cooling systems
because of its low operational costs.
This way, the company wants to study the construction of district cooling
systems by absorption cooling facilities for three small islands as large customers:
city center, Hemlingby shopping centers and, finally, Kungsbäck area (university,
hospital and technological park as a whole). Power for producing cold for these
Chapter 1. INTRODUCTION
4
sites could be supplied by steams boilers at LEAF, Johannes and future
Mackmyra whisky factory respectively.
Table 1. Production sites and customers
SITE NEARBY LARGE
CUSTOMER
1) Planned biofueled ORC plant at LEAF
production site in Gävle Planned network in the central
of Gävle.
2) Planned production site of Mackmyra
whiskys in Kungsbäck HiG, Gävle general hospital and
technological park
3) Biofueled steam boiler at Johannes CHP
plant Hemlingby shopping centers
It needs to be underlined that customers and areas have been chosen
according to the possible disposal production sites. If other adequate steam boilers
were, perhaps Gävle Energi AB might think about other customer islands in the
victinity of Gävle.
1.2. PURPOSE
The aim of this thesis is to study economic and technological aspects of
absorption cooling in the three cases already presented (see Table 1.). Therefore,
it is required to decide needed size of installations in order to analyze costs and
profits.
1.3. SCOPE
A district cooling system consists of three primary components: central
plant (production), distribution system and customer system (market). The first
two will be studied, starting from technological aspects and going through
economic ones after.
Chapter 1. INTRODUCTION
5
It should be investigated the following with regards to each of the three
sites in Gävle:
- Operational conditions (maximum/minimum power, hours of operation per
year and so forth).
- Operational and investment cost of absorption system installations.
- Cost of distribution systems by only concentrating on costs of main pipes
(from production plant to customer substations).
- Most economical size of installations.
1.4. LIMITATIONS
Even though more aspects ought to be taken into account, the matters
mentioned in the scope are at focus and neither investment costs of steam boilers
nor costs regarding customer substations should be considered. On the one hand,
boilers either already exist or will be built anyway (this way, operational costs of
producing steam for absorption chillers are also not pondered because boilers are
working anyway and extra costs are negligible). On the other hand, it is very
difficult to estimate the cost of customer facilities and furthermore, they will be
the same whichever way the cold is produced (the main aim is to compare cooling
production systems).
Moreover, it has to be underlined that the research is only centred on those
three areas of the municipality.
1.5. METHOD
First of all, the issues of the thesis and reasons why they are interesting to
investigate have been analyzed. In this way, the project has been specified and
tasks for carrying it out have been defined in depth. Afterwards, a literature study
Chapter 1. INTRODUCTION
6
has been done to get enough knowledge about subjects: cooling technologies,
district cooling systems and CHP plants using biofueled steam boilers.
Secondly, in the project´s early stages, it has been got in touch with
consultants of Gävle Energi AB and experts at absorption cooling (Ramboll) and
refrigerant compressor (SWECO) technologies for gathering together information
about real installations and equipments in the market, as well as for examining
them from different points of view.
Once different parts have been understood, it has been gone ahead with the
thesis by concentrating on the real cases the investigation had to be focused on.
Like this, it has been asked for data about customers´ cooling demand (load
required), distribution distances and so on to make a first estimation of needed
size of the installations and thus, the operational conditions.
The next step has been to decide on production plant size, for later weigh
costs up. This has let profits of the new technology be known as regards extra
electricity production and use of steam for cooling production. And, to finish with
the production part, the compression installation has been compared with
absorption one and, in addition, a sensitivity analysis, which ranges over size of
equipments, costs and profits, has been done.
Last but not least, decisions regarding distribution systems have been
made and costs has been also assessed.
1.6. OUTLINE OF THE THESIS
Chapter 2 explains the existing two main cooling production systems,
refrigerant compressor and absorption technologies, but it is mainly concentrated
on absorption installations. Then, it is finished with a comparison between them
and advantages as well as disadvantages are discussed.
Chapter 1. INTRODUCTION
7
In Chapter 3 district cooling systems are presented. Section 3.1. describes
production plants shortly, that is, what cogeneration or a CHP plant is and profits
of working with them. Section 3.2. is about cooling distribution systems, which
covers both characteristics of the piping networks (Section 3.2.1.) and type of
pipes which are going to be used (Section 3.2.2.).
Chapter 4 studies thoroughly the real cases. This way, firstly it is presented
the current situation and future plans (Section 4.1.). Thereafter, it is explained
how decisions about production sites and customer areas have been made, in
addition to sum up collected data about cooling demands and estimations about
distances (Section 4.2.). Finally, data researchs and analysis regarding absorption
cooling plants are included (Section 4.3.).
In Chapter 5 the obtained results are shown. Firstly, operational conditions
and total costs of all production sites are gathered together (Section 5.1.).
Moreover, Section 5.2. presents compression and absorption cooling systems´
comparison based on the existing project at LEAF. Lastly, Section 5.3. decribes
the distribution systems and the costs they involve.
To finalize, there is the most important part: discussions and conclusions
(Chapter 6), where types of absorption chillers to be used are decided, economical
and technological aspects of the two cooling production technologies are
compared and it is reasoned out which the best solution is.
CHAPTER 2
9
Cooling system technologies
Production of cold is like considering extraction of heat. There are several
procedures that allow it, which are based on the fact that the heat can be
transferred from one to another body with a difference in temperature by
conduction and radiation. In this way, there are several procedures: chemicals,
physicals and systems that are based on phase transformation of substances.
Likewise, refrigerating machines can be classified into: adsorption, absorption,
compression and ejector machines. [3]
In industry, refrigerant compressor and absorption cooling systems are
mostly used. Refrigerant cycles for vapour compression and absorption are similar
in that both evaporate and condensate a refrigerant at different pressures to
produce chilled water. Nevertheless, a vapour compressor chiller uses a
mechanical means to compress and carry refrigerant vapour to condenser, whereas
absorption chiller establishes differential pressure depending on a thermodynamic
process that involves refrigerant and water. In addition, the energy source is
electricity for compression chillers, while it is heat for absorption ones. It bears
mentioning that there are also other heat-driven cooling alternatives, which are
ejector, desiccant and hybrid heat-driven cooling technologies.
Next stage is to study both technologies.
Chapter 2. COOLING SYSTEM TECHNOLOGIES
10
2.1. REFRIGERANT COMPRESSOR INSTALLATION
The most common cooling system used is refrigerant compressor
technology, vapour compression heat pump to be precise. It is widely used for
residential and commercial cooling, food refrigeration and automobile air
conditioning. [4]
Vapour-compression system is a work-driven cycle that is illustrated in
Figure 1. Main parts of the system are: condenser, evaporator, compressor and
expansion valve. Depending on the system, it is possible to find more accessories,
such as units to purge and valves for controlling the flow of refrigerant.
Figure 1. Refrigerant compression cycle [5]
The evaporator is a heat exchanger where refrigerant is evaporated at the
expense of cooling space. It can be either an air coil, if air is directly cooled, or a
chiller (shell heat exchanger) if it cools a liquid.
The compressor increases the pressure of refrigerant vapour, which is
coming from the evaporator, in order to rise its temperature. The cooling capacity
is regulated by varying the output of the compressor in most of the systems.
Chapter 2. COOLING SYSTEM TECHNOLOGIES
11
The condenser is a heat exchanger where high-pressure refrigerant vapour,
which is coming from the compressor, is cooled down until it is transformed into
liquid. The cooling media can be air or water; larger systems use water since it
allows reducing the condensing temperature, whereas small systems and those
with limitation of water release directly heat to the air.
Some systems can have an accumulator, which depends on evaporator and
condenser sizes and capacities, and pipes. It is actually a storage tank for liquid
refrigerant.
In this way, how a vapour-compression cycle operates can be summed up
(Figure 2.). First, input work in the compressor rises the pressure and temperature
of the refrigerant (State 2). Then, refrigerant vapour with high pressure and
temperature passes through the condenser, where it is converted into liquid by
rejecting heat to ambient air (State 3). After that, refrigerant passes through an
expansion valve where its temperature and pressure is reduced (State 4). Finally,
low-pressure liquid refrigerant is transformed into low pressure vapour in the
evaporator by absorbing heat from ambient environment (State 1). The cycle is
completed when low pressure refrigerant enters the compressor. [5]
Figure 2. Temperature-Entropy (T-s) diagram for a Vapour-Compression Refrigeration
Cycle (Source: http://www.qrg.northwestern.edu/thermo/design-library/refrig/refrig.html)
Chapter 2. COOLING SYSTEM TECHNOLOGIES
12
It is common a temperature lift of up to 50°C between evaporator and
condenser and if water cooled chillers are used, a coefficient of performance
(COP)1 of 4,5 can be reached.
Nowadays, the most usual refrigerants are ammonia (NH3) and R134A
(CHF2CHF2).
2.1.1. COMPRESSOR AND SYSTEM EFFICIENCY
The system efficiency analysis requires compressor design and
compression process characteristics study [4]:
a. Selection of refrigerant
The potential system efficiency depends on refrigerant used.
Regarding compressors, centrifuging compressors work well at low
pressures and high specific volumes whereas alternative compressors work better
at high pressures and small specific volumes.
Likewise, refrigerant’s temperature in the condenser and evaporator
depends on cold and warm areas, which also define pressure regions. According
to the previous description, high pressure is needed in the evaporator and low in
the condenser.
1 The coefficient of performance for compression refrigerant systems is:
COPcooling = ∆Qcold /∆W
where ∆Qcold is the heat moved from the cold reservoir (to the hot reservoir) and ∆W is the work
consumed by the system.
Chapter 2. COOLING SYSTEM TECHNOLOGIES
13
Thus, refrigerant has to be selected taking into account required saturation
pressure and temperature for each particular application. Moreover, it is necessary
to consider chemical stability, toxicity, how corrosive it is and cost.
b. Flow in the compressor
The kinetic energy of the flow is influenced by its turbulence, which
entails its conversion in waste heat energy. But leakages are the main problem of
the compressor.
c. Primary energy: compressor driver
All energy input in a compression system goes into the compressor driver,
which can be an electric motor (mostly), a reciprocating engine, a gas turbine or
another machine.
2.2. ABSORPTION COOLING INSTALLATIONS
Absorption cooling cycle is similar to compression cycle, which uses a
volatile refrigerant. Refrigerant vaporizes alternately under low pressure in the
evaporator, by absorbing cooling latent heat from materia to be cooled, and
condenses at high pressure, delivering latent heat into condensing means.
The main difference between absorption and compression cycles is, as
shortly mentioned before, the motivating force that makes refrigerant to flow
through the system and provides the differential pressure required between
evaporating and condensing processes. In the absorption cycles, the compressor is
replaced by an absorber and a generator (as it is shown schematically in Figure 3.,
components to the left of the dashed Z-Z line are the same as the ones used in
compression cycles). Moreover, while energy required in compression cycles is
Chapter 2. COOLING SYSTEM TECHNOLOGIES
14
provided by compressor’s mechanical work, energy input in absorption cycles is
in the form of heat supplied directly to the generator, which is typically steam or
hot water.
Figure 3. Scheme of basic absorption cycle [5]
The system consists of four basic components: evaporator and absorber,
which are located on the low pressure side of the system, and generator and
condenser, which are located on the high pressure side. Two fluids are used,
refrigerant and absorbent. The flow of refrigerant follows the cycle condenser-
evaporator-absorber-generator-condenser, while absorbent goes from the absorber
to the generator and returns to the absorber.
The sequence of operation is as follows: high pressure liquid refrigerant
leaving the condenser passes through an expansion or restrictor device which
reduces the pressure of refrigerant before it goes into the low pressure evaporator.
Refrigerant vaporizes in the evaporator by means of absorbing latent heat of the
material being cooled and low pressure refrigerant vapour is absorbed through a
not restricted conduit to the absorber, where it is mixed in a solution together with
the absorbernt.
Refrigerant flows from the evaporator to the absorber because vapour
pressure of solution absorbent-refrigerant is lower in the absorber than vapour
Chapter 2. COOLING SYSTEM TECHNOLOGIES
15
pressure of refrigerant in the evaporator. Vapour pressure of solution absorbent-
refrigerant in the absorber determines the pressure in low-pressure side of the
system and accordingly, refrigerant´s evaporating temperature. In turn, vapour
pressure of solution absorbent-refrigerant depends on absorber’s nature,
temperature and concentration. The lower the temperature of absorbent is and, in
addition, the higher its concentration is, the pressure in the solution will be lower.
As refrigerant vapour from the evaporator is dissolved in absorbing
solution, volume of refrigerant decreases (compression) and heat is released. To
keep the temperature and vapour pressure at the required level in absorbent
solution, heat released in the absorber (which sums up latent heat of condensation
of refrigerant vapour and heat from the absorption) should be given off to
surroundings. Since the efficiency of absorber increases as the temperature of
absorbent solution decreases, it is clear that the efficiency of the absorber depends
on the temperature of refrigerant available.
When refrigerant vapour is dissolving in absorbing solution, resistance
(percentage of refrigeration) and vapour pressure of the solution is increasing.
Therefore, it is necessary to make continuously more concentrate the solution in
order to keep the vapour pressure of it low enough, just as it is required in the
evaporator. This is got by eliminating constantly the ―strong‖ absorbing solution
from the absorber and flowing again through the generator, where it is evaporated
by means of a heat source. In this way, the ―weak‖ absorbing solution is returned
to the absorber, where it absorbs more refrigerant vapour from the evaporator.
According to all this, since the absorber is in the low pressure side of the
system and the generator in the high pressure one, the ―strong‖ solution must be
pumped from the absorber to the generator and the ―weak‖ solution must be
returned through a pressure reducing valve or restrictor to the absorber.
Refrigerant is not compressed in the process of increasing its pressure, since it has
to take place in the absorber. Consequently, power required by the pump is
relatively small.
Chapter 2. COOLING SYSTEM TECHNOLOGIES
16
In the generator, solution is heated up and refrigerant is evaporated; like
that, it is separated from absorbent. Afterward, obtained high pressure refrigerant
vapour passes to the condenser, where its latent heat goes outside and it is
condensed. Finally, it is ready for starting again the cycle.
With regard to the ―weak‖ solution that remains in the generator, as before
described, it is returned to the absorber through the return pipe. Relative resistance
on the ―weak‖ solution is controlled by the amount of heat supplied to generator.
[4], [6], [7]
Once how the system works is known, it has to be underlined that
maximum efficiency in the system is attained when pressure difference between
low and high pressure sides in the system is as small as possible (by maintaining
pressure in its low side as high as possible and as low as possible in the high
pressure side). It should be remembered that the pressure in the low pressure side
is mainly determined by absorbing solution’s vapour pressure, which in turn
depends on the temperature and concentration of the solution. Since control of
temperature in the solution is limited by available temperature of refrigerant,
control in the low pressure side (evaporator) is usually obtained by means of
varying concentration of absorbing solution.
The next stage is to study whether efficiency can be improved even more.
This can be achieved by introducing a heat exchanger between the ―strong‖
solution that goes to the generator and the ―weak‖ solution (with high
temperature) that returns from the generator to the absorber. As temperature of the
solution that goes to the generator is increased, whereas it is decreased in that
which goes to the absorber, it is needed to supply the generator with less heat as
well as to cool down less in the absorber. [7]
From Figure 4. in the next page it can be seen an illustration of the
described absorption system, where streams 11-12 represent heat source (steam or
hot water), streams 15-16 cooling water, streams 17-18 district cooling water,
streams 13-14 cooling water and so forth.
Chapter 2. COOLING SYSTEM TECHNOLOGIES
17
Figure 4. Schematic of the fundamental absorption refrigeration system [8]
Furthermore, as well as in compression cycles, some gas is created in
liquid refrigerant when it goes from the condenser to the evaporator, as a result of
a pressure drop while it is passing through an expansion devise (valve).
Consequently, effect of the refrigerant is reduced. Therefore, cooling effect and
efficiency of the system would be improved if refrigerant that goes from the
condenser to the evaporator was subcooled by means of introducing a heat
exchanger between the evaporator and absorber.
2.2.1. CONSIDERATIONS FOR DIMENSIONING
ABSORPTION CIRCUITS
It is more difficult to dimension absorption systems than compression
ones. That is due to the fact that they work according to the thermodynamic
balance, which changes depending on environmental conditions. For this reason,
to determine whether instantaneous performance of certain equipments is correct,
Chapter 2. COOLING SYSTEM TECHNOLOGIES
18
it is necessary to measure periodically purity of water and saline solutions. With
this purpose, there are used instruments, such as decanting pumps, and chemical
additives are added.
Moreover, the efficiency depends on the quantity and quality of energy
consumed in the generator. Hence, for those reasons, it is very important to obtain
thermodynamic equilibrium (Qin = Qout → QE + QG = QC + QA).
2.2.2. WORKING FLUID
All absorption chillers just work as the presented basic cycle (Figure 3.),
but their design and performance are based on the used working fluids (refrigerant
and absorber). Likewise, their efficiency depends widely on (in addition to what
has been explained before) properties of the working fluid.
Desirable properties are [9]:
Large affinity between absorbent and refrigerant.
Low heat of mixing.
An absorbent with very low volatility (refrigerant vapour that goes to the
generator should contain few or nothing of absorbent).
Low pressures, close to the atmospheric pressure, to minimize leakages.
High latent heat of refrigerant, for minimizing flow rate.
The most conventional medias (refrigerant/absorbent) are water/lithium
bromide and ammonia/water. Absorption chillers working with the first ones use
water as refrigerant and lithium bromide as absorbent, whereas ammonia is the
refrigerant and water the absorbent in the second combination.
Chapter 2. COOLING SYSTEM TECHNOLOGIES
19
2.2.2.1. WATER/ LITHIUM BROMIDE (H2O/LiBr)
Lithium bromide as absorbent has the advantage of not being volatile (it is
an hygroscopic salt), so it is not needed to purify desorbed water vapour.
Nevertheless, it can crystallize easily.
The use of water as refrigerant is restricted by its freezing point. Hence, it
must be used above 0 ºC but it may be achieved up to 5ºC.
Water/lithium bromide systems are typically used for production of chilled
water for air conditioning systems in large buildings. Available sizes of these
machines range from 10 to 1500 tons and their COP2 is between 0,7 and 1,2 [5].
2.2.2.2. AMMONIA/WATER (NH3/H2O)
High volatility of water makes to be necessary the introduction of a
rectifier (reflux condenser) after the generator so that water steam that refrigerant
contains is eliminated before it goes into the condenser. Otherwise, temperature in
the evaporator is increased and consequently, cooling capacity decreases.
Moreover, it may form ice in the evaporator and expansion device.
2 The coefficient of performance for absorption cooling systems is defined as:
COPcooling = ∆Qcold /Qh where ∆Qcold is the heat moved from the cold reservoir (to the hot
reservoir), that is, the refrigeration capacity, and Qh the heating energy.
Chapter 2. COOLING SYSTEM TECHNOLOGIES
20
Figure 5. Ammonia/Water absorption cycle [5]
The mixture ammonia/water requires higher pressure and larger
temperature differences: the driving temperature is usually 140 ºC.
With regards to the temperature of refrigerant, it is allowed to use much
lower temperatures, around -60 ºC (the freezing temperature of ammonia is
-77,7 ºC).
Concentration of ammonia has to be controlled as the mixture could
become explosive if there is 15,5-27% of ammonia by volume (although
ammonia/air mixtures are barely inflammable). [10]
Ammonia/water systems are more common for small tonnages, from 3 to
25 tons, and have generally COPs of around 0,5. This way, they are usually used
in air conditioning systems. [5]
The use of ammonia as refrigerant has a large disadvantage. Toxicity of
ammonia3 makes its use not possible in no well-ventilated areas. There might not
3 Ammnois is caustic, has a pungent smell and is toxic.
Chapter 2. COOLING SYSTEM TECHNOLOGIES
21
be problems in an industry (since emissions from ammonia/water chillers could be
solved in water and, as a result, a caustic solution would be formed), but they can
be harmful to occupants in commercial and residential buildings. [11]
2.2.2.3. COMPARISON BETWEEN WATER/LITHIUM BROMIDE AND
AMMONIA/WATER SOLUTIONS
Water/lithium bromide solution has two problems mainly: it exists the
possibility of solid formation and the absorbent (LiBr) crystallizes at moderate
concentrations. Then, this mixture can be normally used only when the absorber is
water cooled, which temperature is kept by means of reconcentrating and
controlling the absorbent solution. [12]
Figure 6. Crystallization temperatures of water/lithium bromide solution against the mass
concentration of lithium bromide [12]
Thereby, temperature difference between evaporator and absorber cannot
be higher than 40°C in order to avoid risk for crystallization. If higher temperature
lifts are required, it is needed either to change chiller configuration or to use
another working pair with higher hygroscopic temperature lift. [13]
Other disadvantages regarding water/lithium bromide pair are the low
pressure (see Figure 7. and Figure 8.) that is required (improperly operated or
Chapter 2. COOLING SYSTEM TECHNOLOGIES
22
maintained units can lead to leak of atmospheric air into them) and the high
viscosity of the solution. On the contrary, it is very safe and has high volatility
ratio, affinity and stability, in addition to high latent heat. [12]
Figure 7. Maximum system pressures against the condenser temperature [12]
Figure 8. Minimum system pressures against the evaporator temperature [12]
As it can be observed from previous Figure 7. and Figure 8., operation
pressures of the ammonia/water system are higher than water/lithium bromide
ones.
Chapter 2. COOLING SYSTEM TECHNOLOGIES
23
An evaporator temperature of around 3-4°C is normal for water/lithium
bromide systems if the lowest temperature in the cooling net is 6°C [13]. A
temperature of 30°C in the absorber and condenser would be reasonable for
applications with low temperature cooling water (temperature in the condenser
will set pressure in the generator) [13].
Ammonia/water systems are more complex than the water/lithium bromide
ones (rectifier and so) and their performance depend on design parameters (it is
required higher pressure and larger temperature differences). For this reason,
construction of plants using ammonia is more expensive. Moreover, better heat
recovery means is required [12].
Next Table 2. sums up properties of both solutions.
Table 2. Absorption working fluids´ properties [14]
PROPERTY AMMONIA/WATER WATER/LITHIUM
BROMIDE
RE
FR
IGE
RA
NT
High latent
heat Good Excellent
Modearate
vapor pressure Too high Too low
Low freezing
temperature Excellent Limited application
Low viscosity Good Good
AB
SO
RB
EN
T Low
vapour
pressure
Poor Excellent
Low
viscosity Good Good
MIX
TU
RE
No solid fase Excellent Limited application
Low toxicity Poor Good
High affinity
between
refrigerant and
absorbent
Good Good
Chapter 2. COOLING SYSTEM TECHNOLOGIES
24
In this way, let´s say that water/lithium bromide systems have much less
problems and are simple to operate, although concentration of the mixture has to
be controlled to prevent crystallization. Likewise, its COP (also limited by
crystalization) is higher.
Figure 9. COP of the absorption systems against the condenser temperature (heat exchanger
efficiency 0,6) [12]
Figure 10. COP of the absorption systems against the generator temperature (heat
exchanger efficiency 0,6) [12]
Chapter 2. COOLING SYSTEM TECHNOLOGIES
25
Figure 11. COP of the absorption systems against the evaporator temperature (heat
exchanger efficiency 0,6) [12]
Even though absorption cycles are mostly based on water/lithium bromide
solutions (ammonia/water systems are unusual in the market), there are a lot of
applications where ammonia/water can be used and especially where lower
temperatures are needed. Main industrial applications for refrigeration are in the
temperature range below 0ºC, which is the field for the binary system
ammonia/water [11]. Hence, absorption systems using water as refrigerant are
commonly used for air conditioning, whereas ammonia is used in large-tonnage
industrial applications (such as food industry and slaughter houses) [12].
Consecuently, calculations of this thesis are based on water/lithium bromide
systems.
2.2.3. PRIMARY ENERGY
There are two parts that need energy supply in absorption cycles: the
generator and pump, which need heat and electricity respectively.
The required electricity represents 1-2% of the total cooling effect. With
regards to the heat, depending on how absorption chillers are fired, the system can
be:
Chapter 2. COOLING SYSTEM TECHNOLOGIES
26
Direct-fired system. Gas or another type of fuel is burned in the system.
This system is used in residential applications to produce chilled water
at 6ºC. In addition, it can supply hot water if an auxiliary heat exchanger is
introduced.
Indirect-fired system. Fuel is steam or high temperature water that comes from
a separate source such as CHP plants, geothermal, solar or waste heat. This
thesis studies these ones.
Finally, it cannot be left behind that the absorber as well as condenser are
cooled down by a refrigeration tower, which energy consumption has to be
considered. Natural water, such as water from the river, can be used instead of
cooling towers for optimizing overall efficiency of the system.
2.2.4. TYPES OF ABSORPTION CHILLERS
Although simple or single-effect absorption cycles (see Figure 5.) have
just been studied, there are more types of absorption equipments in the market.
The most common are single-effect (water/lithium bromide or ammonia/water)
and double-effect (water/lithium bromide) chillers. Nevertheless, there are
advanced H2O/LiBr cycles, such as low-temperature or half-effect chillers and
triple-effect absorption chillers (the latest ones are in development), as well as two
stage ammonia/water systems. Moreover, energy storage is possible in
water/lithium bromide systems in the form of chemical potential difference [14].
The main difference between single- and double-effect absorption chillers
is that the last ones uses two stages of lithium bromide solution reconcentration,
which increases efficiency and reduces therefore energy consumption.
Chapter 2. COOLING SYSTEM TECHNOLOGIES
27
2.2.4.1. SINGLE-EFFECT ABSORPTION CHILLERS
Single-effect absorption chillers use low-presure steam or hot water as
energy source. The typical temperature range is from 93 to 132 °C. [5]
The COP for these chillers is, depending on the model, around 0,7 [13]
(for instance, Carrier 16TJ-41 and 16TJ-42 have a COP of 0,73 and 0,72
respectively).
Figure 12. Cooling cycle schematic
(Source: Carrier-Sanyo)
Chapter 2. COOLING SYSTEM TECHNOLOGIES
28
2.2.4.2. DOUBLE-EFFECT ABSORPTION CHILLERS
Because of the relative low COP associated with single-effect machines, it
is difficult for them to compete economically with conventional vapour
compression systems except for low waste heat applications where the input
energy is free [14]. Double-effect technology, which purpose is to increase COP
of the cycle, is much more competitive.
Double-effect absorption chillers, which are also known as super
absorbers, use a second generator, condenser and heat exchanger that operate at
higher temperature. Likewise, they require higher driving heat temperature and
use steam.
Figure 13. Double-Effect Water/Lithium Bromide Absorption Chiller Schematic [5]
Schematic of double-effect machine provided as Figure 13. shows that the
cycle includes two solution heat exchangers, which represents that internal heat
exchange is achieved in practice by means of incorporating these two components
into a single transfer device [14]. Low pressure condenser and generator operate
Chapter 2. COOLING SYSTEM TECHNOLOGIES
29
at approximately the same conditions as the ones of a single-effect mahine [14].
Operating temperature and pressure of high pressure devices can be inferred from
Figure 14., which represents pressure-temperature chart schematic of double-
effect water/lithium bromide chiller.
Figure 14. Sketch for a double effect absorption heat pump in a log pressure-temperature
diagram [13]
The COP of two stages cycles is in the range of 1,0 to 1,2 [14] (for
instance, Carrier 16NK-53 has a COP of 1,42).
Design for a double-effect absorption chiller is more complex compared to
a single-effect chiller. How to connect solution circuits is one of the major design
choices: parallel or series flow are the basic options [14]. A summary of
performance of different types of double-effect technology configurations is
presented in Table 3. (results are based on the same heat exchanger sizes and
external fluid loop conditions).
Table 3. Comparison of parallel and series flow for double-effect water/lithium bromide
cycles [14]
CONFIGURATION COP CAPACITY [KW]
Parallel 1,325 354,4
Serie, high-pressure generator first 1,244 371,1
Serie, low-pressure generator first 1,238 370,2
Chapter 2. COOLING SYSTEM TECHNOLOGIES
30
As it can be seen from Table 3. in the previous page, parallel flow
configuration is the best option according to the COP. Nevertheless, capacity
favors series flow configurations.
Even though a double-effect system needs more devices than a single-
effect one, if a cooling tower is needed as a heat sink, less cooling tower capacity
is needed per unit cooling effect due to the higher COP in a double-effect chiller
[13]. Taking this into account, total system cost may be comparable to a single-
effect chiller [13].
2.3. REFRIGERANT COMPRESSOR TECHNOLOGY
VERSUS ABSORPTION COOLING
TECHNOLOGY
As it has already been said, absorption cycles have some common
characteristics with vapour compression cycles, but they differ in two important
aspects:
1. Constitution of the compression process. In absorption cooling system
vapour is not compressed between the evaporator and condenser, but
refrigerant is absorbed by a secondary substance (absorbent) in order to
form a liquid solution that is compressed to high pressure.
As the average specific volume of liquid solution is much lower
than the average specific volume of refrigerant vapour, less work is
needed. So absorption cooling systems have the advantage of, compared to
vapour compression systems, requiring less power for compression.
2. In absorption systems a means should be introduced to recover the coolant
steam from liquid solution before refrigerant enters the condenser, where it
Chapter 2. COOLING SYSTEM TECHNOLOGIES
31
is transferred heat from a source at a relatively high temperature. This
makes economic residual heat and steam that otherwise would be thrown
away untapped in environment.
Therefore, application of absorption equipments is a really interesting
alternative for decreasing electricity consumption. Furthermore, companies which
use steam in their processes have an additional advantage, since they would be
using waste or residual steam.
Heat demand in absorption systems is higher than in compression ones.
Actually, it can be, depending on evaporation temperature, more than three times
higher; nevertheless, it has to bear in mind that waste heat is often used as driving
heat. With regards to energy demand, following diagrams (Figure 15.), which
show ratios between driving energy and produced refrigeration capacity, can be
studied for making a comparison.
Figure 15. Comparison between compression and absorption technologies using ammonia as
refrigerant and cooling water with a temperature of 25 ºC [10]
Chapter 2. COOLING SYSTEM TECHNOLOGIES
32
As it can be observed from the diagrams (Figure 15.), COP for absorption
technology is much less affected by a drop in evaporating temperature. This is a
significant advantage in overall economy. [11]
Initial costs for an absorption system are higher than for a compressor one
of the same cooling capacity as:
Absorption system needs more metallic materials in heat exchangers.
Lower pressures are requiered in absorption technologies, which implies
higher diameter of tubes in order to reduce pressure losses.
Size of condenser water pump is generally a function of flow rate per unit
cooling capacity. Cooling technologies with lower COP typically require a
significantly higher condenser water flow rate and, consequently, a larger
pump too, than those technologies with higher COP. Similarly, absorption
chillers require larger cooling tower capacity than electric chillers because of
larger volume of water.
It is needed more space for absorption systems since the equipments are
bigger.
In addition, cost and volume of absorption machines increase when temperature of
the generator is low.
A compression cooling machine needs roughly 0,5 kWh of electricity for
providing 1 kWh cooling, whereas in an absorption process 1-1,2 kWh of heat is
needed for that [15]. Regarding energy costs, it works out cheaper and more
efficient to supply energy directly in form of heat than when it must go through
several stages of transformation. Undoubtedly, economical advantages of
absorption systems depend on how the driving heat is produced: it is generally not
economic when a boiler has to be installed to generate cooling, but it is an
interesting technology when waste heat or renewable energies with low price are
used, as well as when capacity of the boiler is available all the time.
If investment and running costs are taken into consideration, absorption
systems can compete against compression systems when the price of electricity is
Chapter 2. COOLING SYSTEM TECHNOLOGIES
33
from 8 to 9 times higher than the cost of heat. In CHP plants, high investment cost
of absorption machines are thwart by the more efficient use of fuel (see Table 4.).
Table 4. Energy saving with cogeneration for α 4 = 0,54
CHP
SEPARATE
ELECTRICITY
production
(condensing plants)
SEPARATE
HEAT
production
(steam boiler)
TOTAL FUEL
CONSUMPTION
FUEL
CONSUMPTION 100 73,3 63,6 136,9
EFFICIENCY 0,88 0,42 0,9
ELECTRICITY
PRODUCTIOIN 30,8 30,8 ―
HEAT
PRODUCTION 57,2 ― 57,2
During warm periods, heat in excess in CHP plants decreases electricity
production, since those plants are dimensioned for the heating demand in winter
and hot water is only needed in summer. On the contrary, cooling demand
increases in summer, so it takes the advantage of using the excess of heat for
cooling systems.
Finally, operation and maintenance can be mentioned. The most important
part in compression systems is compressor´s work, whereas it is the equilibrium
obtained by thermodynamic effects in absorption systems. For this reason,
operating with absorption technologies is more complicated (see Section 2.2.1.).
In this way, to sum up, absorption refrigeration systems´ operating
characteristics can be listed [10]:
- It is driven by ―economic‖ heat (waste or ―free‖ heat) and it has low
consumption of electricity.
- Simple design and maintenance (no moving machinery).
- Long service life.
- It is reliabiled, then it is more available.
- Environmentaly ―friendly‖ working media (in addition, it is easy to
clean effluent gases) and oil-free refrigerant. It is very clean and heat
4 Electric-thermal ratio: α = Wel/Qheat = ηel/ηt where Wel is the electrical power output, Qheat is the
useful thermal power output, ηel is the electrical efficiency and ηt is the thermal efficiency.
Chapter 2. COOLING SYSTEM TECHNOLOGIES
34
transfer resistances due to contamination are not produced. In addition,
carbon dioxide emissions are reduced at the same time.
- Low noise level and there is no vibrations.
The earliest three characteristics are the most important criteria when comparing
absorption systems with vapour compression systems.
To finish with cooling technologies, Table 5. summarizes their
characteristics and Table 6. makes a short comparison between them.
Table 5. Summary of characteristics for cooling options [13]
TECHNOLOGY COP
(cooling) COPel
5
DRIVING HEAT
TEMPERATURE
[°C]
SCALE
[kWcooling]
Conventional (Single-effect)
H2O/LiBr absorption chiller 0,7 20-50 120 >250
Double-effect
H2O/LiBr absorption chiller 1,2 15-40 150-170 >350
NH3/H2O absorption chiller 0,5 10-25 >100 ―
Vapour compression chiller ― 1-5 ― ―
Table 6. Comparison between two 1000kW chillers [10]
5 It only includes the chiller electricity consumption for absorption systems
CHAPTER 3
36
District Cooling System
Distrist cooling system or technology delivers coolant, commonly chilled
water, from a central refrigeration plant to multiple buildings through a
distribution network. At each connection point of the distribution mains, energy is
delivered to the terminal devices at the user premises to meet their space/process
cooling requirements [1].
District cooling system is mainly made up of three components: cooling
production plant, distribution network and building substations.
Figure 16. Components of district cooling systems
Figure 17. District cooling system (or district heating system
6) [15]
6 The same concept applies when it comes to district heating systems.
Chapter 3. DISTRICT COOLING SYSTEM
37
District energy systems enable to use energy in a more efficient way and
reduce greenhouse gas emissions because, on the one hand, it is used a central
refrigeration plant instead of many small machines which are less efficient and, on
the other hand, it is produced electricity for the central grid that can replace other
electricity sources such as coal-fired plants.
3.1. PRODUCTION
3.1.1. COGENERATION. BENEFITS WITH INTEGRATION
OF COOLING TECHNOLOGY
Cogeneration (combined heat and power, CHP) is the use of a power
station for simultaneous generation of both electricity and useful heat
(conventional power plants produce but not use a large amount of heat). That is, it
is an energy conversion technology where two separate systems are integrated
together by a cascade of thermal energy [14]. Thus, it can be led to increase the
system performance7 by designing systems that can use the heat: the efficiency of
energy production can be increased from current levels that range from 35% to
55%, to over 80% [16]. In addition, some of the obligatory heat rejection is at a
high enough temperature to supply energy for comfort heating and cooling.
Figure 18. An schematic of cogeneration process that shows the consumed and produced
power in the whole system [15]
7 Overall efficiency: ηtot = ηel + ηt = We/Qfuel + Qheat /Qfuel = (Wel + Qheat)/Qfuel
It is also called energy utilization factor, EUF.
Chapter 3. DISTRICT COOLING SYSTEM
38
Figure 19. Illustration of a CHP plant connected to a district heating network
(Source: Gävle Energi AB)
This way, shopping malls and blocks of business, university and collages,
hospitals, industries and so forth take the advantage of the economic benefits
provided by a central plant, through the use of boilers that produce hot water or
steam for heating and vapour compression or steam-driven absorption
refrigeration machines that produce chilled water for cooling.
Table 7. Different types of plants using a steam boiler and their characteristics
HEATING CONDENSING
BOILER
Flexible, low operating and investment costs
No full use of all heat in the fuel
CHP plant
(BIOFUELED STEAM BOILER)
Heat and electricity production
Full use of heat in the fuel
TRIGENERATION plant
(BIOFUELED STEAM BOILER)
Heat, electricity and cooling production
Energy Export → CO2-negative
"Free" energy
There is only one requirement for the integration of two technologies:
temperature of available heat from one system must be adequate to fulfil
requirements of the mating system. The source of energy for district energy
systems is usually a steam boiler, which is fired, in the cases to be considering in
this thesis, by biofuel.
Chapter 3. DISTRICT COOLING SYSTEM
39
3.2. COOLING DISTRIBUTION SYSTEM
3.2.1. PIPING NETWORK
Flow in cooling (as well as in heating) distribution systems varies with the
load, so the flow through each substation is regulated by two-way control valves.
The reasons for this are mainly to lower pumping costs and to increase the
difference between supply and return temperatures, which affects the efficiency of
the whole system [15]: a higher supply and return temperature differential is able
to lower the distribution pump power consumption, but will increase the heat loss
at pipe surfaces [17]. Consequently, a high return temperature is preferable in
district cooling system. This way, forward temperature is roughly 6 °C and return
temperature is alternatively between 12 and 16 °C.
Anyway, distribution losses can be almost always neglected in district
cooling systems since temperature difference between outdoor and forward water
is very low and the resistances are therefore despised. For this reason, there is not
needed, unlike in district heating, to insulate the pipes. This makes cooling
distribution systems cheaper than heating ones.
Control valves must regulate the flow, but the pressure too. The available
differential pressure becomes lower at substations which are furthest away in the
system (because of greater pressure drops caused by the increased flow in the
distribution system) and it might not be enough for the required flow. Hence,
either another pump has to be used or the speed of the existing one has to be
increased to maintain the differential pressure. [15]
Chapter 3. DISTRICT COOLING SYSTEM
40
3.2.2. MATERIALS FOR THE PIPES
There are different types of pipes depending on the application (pressure,
gravity, drainage and so on). In this case, pressure pipe systems are studied.
There are polyethylene (PE), polypropylene (PP), PVC and PEX pipes, in
addition to steel and cooper ones. For water applications, PE pipes are widely
used because their quality is high and they are economic at the same time. This
way, polyethylene pressure pipes offer the following benefits:
- Cost saving with faster installation
- Long life time and maintenance free
- Suitability for renovation
- Corrosion resistance
- Flexibility (it allows ground movement)
- Joint thightness
Plastic pipes are much cheaper than, for instance, steel ones. As the last
ones are widely used in district heating systems, let´s say that the material for
cooling pipes is less costly. Likewise, construction of networks works out cheaper
than as appropiate for district heating pipes.
CHAPTER 4
42
Process
4.1. GATHERING OF INFORMATION ABOUT
EXISTING INSTALLATIONS AND PRESENT
SITUATION
4.1.1. STEAM BOILERS AT LEAF AND KAPPA
There is an oil steam boiler at LEAF
8 nowadays, which has a maximum
capacity of 5 MW and produces satured vapour at 8 bar. The average power it
operates is 2 MW all over the year except for 48 h at Easter.
In addition, there is Kappa paper mill close to that boiler, which has
another oil boiler of 2 MW and produces steam at 12 bar for 80 hours per week9.
In this way, Bionär10
is thinking about building a new biofueled steam
boiler which would replace those two11
. It is wanted to make the most of that and
it is therefore planning to produce electricity too. Ramboll consultancy has
considered building a biomass fired CHP plant based on Organic Rankine Cycle
(ORC), as a low capacity boiler to produce needed steam at roughly 70 bar (which
requires a sophisticate water purification system) and a turbine are much more
expensive.
8 It is a factory which is located in Gävle and produces confectionery, candy and pastilles. 9 It is working 5 days/week, not at weekends, and 16h/day, not during night. 10 It is a subsidiary of Gävle Energy AB, which owns the 45%. One of the customers of Bionär is
LEAF. 11 Although the operating times of the boilers are different, the new boiler can work at 2 MW
during the day and increase its capacity during the night, when it can be produced the steam
which is needed in the paper mill during the day (storage in accumulator vessels).
4. PROCESS
43
Figure 20. ORC plant in biomass based cogeneration system
(Source: http://www.turboden.it/en/products.asp)
ORC units have high overall energy efficiency: 20% of the thermal power
is transformed into electric power, while 78% remains as steam. Nowadays, it is
planning to build a TURBODEN 14 CHP plant that costs 5 300 000 SEK and
which performance is 1,26 MW of net active electric power and 5,35 MW of
steam (α = 0,23), with a biomass consumption of 7,63 MW.
.
Figure 21. Energy efficiency of ORC units in cogeneration applications
(Source: http://www.turboden.it/en/products.asp)
Gävle Energi AB, as knows of this project, might take the opportunity to
use this installation turning it into a trigeneration plant by means of introducing an
absorption cooling system that would use the steam produced in it. Hence, it is
needed an even bigger ORC unit and to make a decision about it is one of the
tasks of this project.
4. PROCESS
44
4.1.2. BIOFUELED JOHANNES CHP PLANT
Johannes CHP plant (Figure 22.), which is owned by Gävle
Kraftvärme AB12
, is located in the south of Gävle, exactly in Johannesbergsvägen.
Figure 22. Johannes CHP plant before 2003 (Source: Gävle Energi AB)13
The steam boiler was built in 1999, which aim is to produce heat to deliver
in the district heating network of the municipality. It is a Bubble Fluidized Bed
(BFB) boiler and has a maximum capacity of 77 MW, whereas the minimum
power output is 20 MW.
Johannes is not able to fulfil the heating demand of Gävle in winter, so
waste heat is bought from Korsnäs pulp and paper mill in Gävle for distributing it
in the system. In summer time, when the demand decreases noticeably (as it is
only needed for hot water), the steam coming from Korsnäs is enough to meet
customer requirements and therefore, the boiler at Johannes is shut down (in other
periods, its power output is reduced). Last year (2008) the plant was operating
6500 hours continiously (24 h/day), which means that it was stopped roughly
95 days during summer.
In 2003 a backpressure turbine of 22 MW was introduced, turning this way
the installation into a cogeneration plant. This enables to increase profits to great
extends; actually, the company makes money from electricity, although its
12 It owns all production facilities in Gävle Energi AB but it is owned 100% by Gävle Energi AB. 13 The turbine is missing since it was introduced in 2003.
4. PROCESS
45
production has to be managed according to the heating demand of the
municipality.
Taking into consideration average values, 320 GWh of steam are
produced, which entails 406,4 GWh of biofuel consumption. With regards to
electricity, the production is around 97 GWh (as α value is 0,29), which means a
large profit.
Figure 23. Production of heat (for District Heating) and electricity at Johannes
The next challenge could be to introduce an absorption cooling plant and
Johannes would have to do with a trigeneration, which would be able to fulfil the
cooling demand in the shopping centers (Hemlingby) close to that by means of a
distribution system. Furthermore, electrically driven refrigeration devices that are
mainly used for the turbine could be replaced. And last but not least, the boiler
could be kept running almost the whole year with a large income because of the
electricity produced (there are possibilities to increase electricity output by
increased heat load from heat-driven chillers, especially in June-August. See
Figure 23.)
For more information about Johannes CHP plant, see Appendix 7.
4. PROCESS
46
4.1.3. MACKMYRA
Nowadays, Mackmyra Svensk Whisky is located in Valbo, at the outskirts
of Gävle. There is an electric boiler with a capacity of 850 kW that operates
continuously all over the year14
, which is owned by Bionär.
Figure 24. Existing electric boiler in Mackmyra (Source: Gävle Energi AB)
According to an already approved project, a new plant, Mackmyra
Whiskyby, will be probably built with a bigger production capacity. It is planned
to be in Western Kungsbäck, just at the west of the central Gävle and few
kilometers from the existing distillery, and it will be built in several stages,
starting in the second half of this year (2009).
A bigger distillery entails, among other things, the necessity of a bigger
boiler. Thus, it has been proposed to replace the electric boiler by a biofueled
boiler with capacity doubled so that it could be turned into a cogeneration plant by
introducing a turbine. This means that, in addition to produce steam needed in the
factory, profits would be increased because of electricity output.
It could be even thought about a bigger boiler and a third step could take
place. As well as for LEAF, Gävle Energi AB might turn it into a trigeneration
plant where cold would be produced by firing absorption cooling machines with
steam. It is estimated that it would be needed a ten times bigger boiler;
14 ≈ 8760 h/year. It is only switched off because of breakdowns and maintenance.
4. PROCESS
47
nonetheless, it will be calculated according to the cooling demand in that site of
the victinity.
Figure 25. Existing and planned boilers at Mackmyra (different stages)
4.1.4. REFRIGERATION COMPRESSOR COOLING
PROJECT
The refrigerant compressor cooling project, which plans to fulfil the
cooling demand in the city center by producing chilled water at LEAF and
delivering it by district system, is being built now and it is thought the first stage
will be finished for next summer (2009). Nowadays, there is only one customer,
which has a cooling demand of roughly 250 kW.
The drafts of installations and equipments needed are in Appendix 1.
According to the calculations, that can be also seen in Appendix 1., the investment
cost for the installation is 22 629 000 SEK, which has a pay-back time of
approximately 10 years. There are needed roughly 4 240 675 kWh of electricity
per year for running the whole installation, which means 4 240 675 SEK per year,
and there are produced 7 142 836 kWh of cooling per year by means of
compression technology. With regards to the maintenance costs, those are time
dependant and 170 000 SEK for the first year (see Section A1.4. in Appendix 1.).
This way, the total cost of the system for ten years is 66 204 500 SEK.
4. PROCESS
48
4.2. GATHERING OF DATA: CUSTOMERS. LOAD
REQUIRED AND DISTANCES
Once different existing possibilities of building absorption cooling systems
have been studied, two small islands with future large district cooling customers
have been defined: Hemlingby shopping centers in Johannesbergsvägen and
Kungsbäck area, which would comprise the university (Högskolan i Gävle),
hospital (Gävle Sjukhus) and technological park (Teknikparken). This way, the
production sites would be Johannes and planned new Mackmyra whisky factory.
Moreover, the city center is also subject of investigation, so that it is the
third island, which cooling demand could be supplied by introducing absorption
chillers at LEAF. Then, it will have to be studied if it is economic to replace the
compression refrigeration plant.
4. PROCESS
49
Figure 26. Three cooling production and customer sites and main pipes
4. PROCESS
50
Next Table 8. shows different cooling demands for the planned three
production sites (see Appendix 2.).
Table 8. Cooling load demand at each site
PRODUCTION
SITE/AREA
CUSTOMER
COOLING
DEMAND
[MW]
LEAF/CITY CENTER
LEAF 2,5
CITY CENTER 9,0
11,5 TOTAL
MACKMYRA/
KUNGSBÄCK
MACKMYRA ± 0
HOSPITAL 1,7
UNIVERSITY 1,8
TECHNOLOGIC PARK 1,0
5,0 TOTAL
JOHANNES/
JOHANNESBERGSVÄGEN
JOHANNES 1,4
HEMLINGBY SHOPPING
CENTERS 2,0
3,4 TOTAL
Regarding distribution systems, as it can be seen in Appendix 4., the main
pipe in the city center is 1370 meters long. Far away from the city center,
Johannesbergsvägen area is and, according to the estimations (see Appendix 4.),
there are 1775 m between the plant and the buildings that need cooling. The third
and last area is Kungsbäck, where it would be needed a pipe from Mackmyra to
the hospital, 2390 m, and to the university too, 810 m; nonetheless, it could be
used the same pipe for both of them in the first 500 meters (see Appendix 4.).
4. PROCESS
51
4.3. ANALYSIS OF ABSORPTION COOLING PLANTS
4.3.1. ABSORPTION CHILLERS
Next task is to study the absorption cooling machines to be used. There are
mainly two options, starting with a premise that they have to be steam-fired:
single- and double-effect steam-fired absorption chillers. The difference between
them is that the double-effect has two generators, thus a better COP and higher
cost, roughly from 2 to 2,5 times the price of the single-effect.
Single-effect absorption chillers are designed for using available low
sature pressure waste steam (100-150 kPa), so they are a recovery solution. With
regards to double-effect chillers, they use satured steam at around 500-800 kPa. In
this context, as mentioned before (Section 2.2.2.3.), water/lithium bromide units
are only considered
Following Table 9. and Table 10. gather information about different
possible installations (calculations and specifications are in Appendix 3.). Even
though chillers with highest cooling capacity have been considered, they cannot
cover the cooling demand and therefore, it is necessary to add several units in
parallel.
Table 9. Possibilities to fulfill the cooling demand in the city center by using steam-fired
absorption chillers
PRODUCTION
SITE
DOUBLE-EFFECT STEAM-
FIRED ABSORPTION
CHILLER: TSA-16NK- 81
SINGLE-EFFECT STEAM-
FIRED ABSORPTION
CHILLER: TSA-16TJ- 53
NUMBER OF CHILLERS NUMBER OF CHILLERS
LEAF 3 5
4. PROCESS
52
Table 10. Possibilities to fulfill the cooling demand in Kungsbäck by using steam-fired
absorption chillers
PRODUCTION
SITE
DOUBLE-EFFECT STEAM-
FIRED ABSORPTION
CHILLER: TSA-16NK- 81
SINGLE-EFFECT STEAM-
FIRED ABSORPTION
CHILLER: TSA-16TJ-53
NUMBER OF CHILLERS NUMBER OF CHILLERS
MACKMYRA 2 2
At first, it was focused on steam-fired machines for being more efficient.
Nonetheless, it has been deduced it is not possible their use at Johannes plant from
the analysis of steam streams. During summer, when the boiler is at its minimum
capacity nowadays, the pressure of the steam leaving the turbine is lower than
1 bar (see Table A3. 1.), which is the minimum pressure required for satured
steam needed in single-effect steam-fired absorption chillers. It would be possible
to use high-pressure super-heated steam that enters the turbine (see Figure A3. 1.);
however, it is not an interesting alternative as electricity production would be
therefore reduced (it would mean going down in profits). As a result,
water/lithium bromide single-effect hot water-fired absorption chillers have been
studied (Table 11.).
Table 11. Possibilities to fulfill the cooling demand corresponding to Johannes plant
PRODUCTION
SITE
SINGLE-EFFECT HOT WATER-FIRED
ABSORPTION CHILLER: TSA-16LJ- 53
NUMBER OF CHILLERS
JOHANNES
2
4.3.1.1. STUDY OF OPERATIONAL CONDITIONS
Cooling demand changes during the year mainly because of climatic
conditions (time period). Despite total or maximum cooling demand is only
known, an estimation can be made for the whole year (see Section A3.3.,
Appendix 3.):
4. PROCESS
53
Table 12. Cooling that should be produced for different sites during the year
TIME PERIOD
COOLING
POWER PRODUCTION [kW]
LEAF MACKMYRA JOHANNES
Winter time: 15 November-15 March 895 389 1556
15 March-1 April & 1-15 November 3512 1527 2011
April & 15 October-1 November 4683 2036 2214
1-15 May & 15 September-15 October 6749 2934 2574
15 May-15 June & 15 August-15 September 9779 4252 3101
Summer time: 15 June-15 August 11500 5000 3400
Figure 27. Cooling power to be produced in different sites during the year
In winter the cooling demand is very low. Hence, there is no need for
producing cooling at LEAF (899 kW) and Mackmyra (389 kW) due to the fact
that free cooling is allowed in this time of the year15
. With regards to Johannes
(1556 kW), there is no river around the plant, so it is necessary to fulfil the
demand in another way. As heat demand is the highest in winter, produced hot
water cannot be used for firing absorption chillers (all heat ought to be delivered
in the district heating network) and consequently, the best solution would be to
use the already existing cooling and HVAC systems in Hemlingby and Johannes
during winter.
15 The river is far away from Mackmyra production site but the customers (university and
hospital) are quite close to it. Therefore, it is possible to introduce heat exchangers there for
free cooling in this area.
4. PROCESS
54
4.3.2. THE REST OF EQUIPMENTS
Figure 28. Typical piping diagram of an absorption system (Source: Carrier-Sanyo)
The operation of chillers needs additional devices and equipments:
- Cooling towers.
- Chilled water pumps and cooling water pumps for each chiller.
- Strainier, pressure gauge and drain trap, which should be near the steam inlet,
for each chiller.
- Air vent valve in each of the chilled and cooling water lines.
- Shut-off valve to prevent the steam flow into the chiller during shut-down.
- Etc.
Necessary pumps, valves, pipes, etc. inside production installations cannot
have been calculated because of limited provided information. Thus, same
investment and operational costs (power input) as for absorption cooling project
which has just been built in Falun (see Appendix 6.) have been considered.
Regarding cooling towers, they produce cold water for cooling down
absorbers and condensers inside the chillers and their size is decided according to
the required cooling power. This equipment can be replaced by a heat exchanger
at LEAF, as water from the river is cold enough.
4. PROCESS
55
Lastly, there are two more heat exchangers which are planning to be used
for free cooling at LEAF and Mackmyra in winter time.
Specifications about cooling equipments (cooling towers and heat
exchangers) are gathered together in Table A3. 8. (Appendix 3.).
CHAPTER 5
57
_ Results
5.1. PRODUCTION PLANTS
5.1.1. LEAF
5.1.1.1. OPERATIONAL CONDITIONS
Table 13. Power and steam demand of different chillers sets for the required cooling load at LEAF during the year
16 Operation hours data are taken from Anders Kedbrant estimations, Table A1. 15. (Appendix 1.), for all calculations because of lack of information.
TIME PERIOD
NUMBER OF
CHILLERS
WORKING
COOLING LOAD16
[MWh]
POWER SUPPLY
TO CHILLERS
[MWh]
STEAM SUPPLY
TO CHILLERS
[MWh]
16NK-81 16TJ-53 FREE
COOLING
ABSORPTION
COOLING 16NK-81 16TJ-53 16NK-81 16TJ-53
15 November-15 March — — 862,78 — — — — —
15 March-1 April & 1-15 November 1 2 — 856,93 2,62 1,72 750,96 1412,95
April & 15 October-1 November 1 2 — 1704,61 3,90 2,56 1483,92 2811,27
1-15 May & 15 September-15 October 2 3 — 2902,07 9,22 4,54 2543,56 4785,81
15 May-15 June & 15 August-15 September 3 4 — 6571,49 21,61 9,46 5759,41 10836,57
15 June-15 August 3 5 — 8487 23,73 12,99 7438,75 13993,87
TOTAL [MWh/year] 862,78 20 522,10 61,08 31,27 17 976,60 33 840,46
5. RESULTS
58
Table 14. Biofuel (for producing steam), electricity and water consumption. LEAF
16NK-81 16TJ-53 TOTAL BIOFUEL CONSUMPTION
17 [GWh/year] 25,71 48,39
ELECTRIC POWER
SUPPLY [MWh/year]
CHILLERS 61,08 31,27
REST OF THE PLANT18
450,82 TOTAL 511,91 482,10
5.1.1.2. COSTS
5.1.1.2.1. INVESTMENT COSTS Table 15. Investment costs [SEK] for LEAF
3 ABSORPTION CHILLERS
TSA-16NK- 81 (CARRIER-SANYO) 3 * 6 200 000
5 ABSORPTION CHILLERS TSA-16TJ- 53
(CARRIER-SANYO) 5 * 2 700 000
BACK-UP COMPRESSOR CHILLER 19
YRTBTBT0550C (YORK) 600 000
BACK-UP COMPRESSOR CHILLER
YRTBTBT0550C (YORK) 600 000
3 HEAT EXCHANGERS
S121-IS10-502-TMTL47-LIQUIDE (Sondex)
+
FILTERS BSG350/1,0P (Bernoulli)
3 * 619 000 5 HEAT EXCHANGERS (+ FILTER)
MX25-MFMS (Alfa Laval) 5 * 550 000
HEAT EXCHANGER (+FILTER)
TL10-BFG 120 000
HEAT EXCHANGER (+FILTER)
TL10-BFG 120 000
REST OF THE INSTALLATION20 1 450 000 REST OF THE INSTALLATION 1 450 000
TOTAL [SEK] 22 627 000 TOTAL [SEK] 18 420 000
NOTE: all specifications are in Appendix 3.
17 Biofuel consumption in the ORC CHP plant (TURBODEN 14) = 1,43 MW biofuel/MW steam 18 Reference: Falun Cooling Project (see Appendix 6.).
Considered operation hours = chiller´s operation hours. It is known that submersible pumps for the whole installation are working the whole year
but data about them is missing.
It has been assumed the same for both Mackmyra and Johannes production plants. 19 The considered back-up chiller is the one planned for compression refrigeration project (VKA3). It is only considered its investment cost as it is not
usually running (it is just started up because of breakdowns and when the cooling demand is higher than the expected one). Calculations for
Mackmyra and Johannes production sites are also based on the same compressor. 20 Reference: Falun Cooling Project (see Appendix 6.).
It has been assumed the same for both Mackmyra and Johannes production plants.
5. RESULTS
59
5.1.1.2.2. OPERATIONAL COSTS
Table 16. Operational costs at LEAF
21
16NK-81 16TJ-53 BIOFUEL [SEK/year]
-165 SEK/MWh-22 4 241 579,13 7 984 657,3
ELECTRICITY [SEK/year] - 1 SEK/kWh-
511 906,24 482 095,36
TOTAL [SEK/year] 4 753 485,4 8 466 752,7
5.1.1.2.3. TOTAL COSTS
PAY-BACK time of the equipments (chillers, pumps, etc.) is roughly 10
years (the investment is recovered approximately after ten years). Thus, costs are
calculated for this period of time:
Table 17. Total costs of LEAF absorption cooling plants for 10 years
16NK-81 16TJ-53
TOTAL
COSTS [SEK]
INVESTMENT 22 627 000 70 164 854
18 420 000 103 087 527
OPERATING 47 534 854 84 667 527
PROFITS: ELECTRICITY
PRODUCTION [SEK]
- 770 SEK/MWh-23
- 31 836 561 - 59 931 460
TOTAL [SEK] 38 328 293 43 156 067
Maintenance costs are very low because there are few components that
demand maintenace and there is just cleaning work mainly. As a result, these
costs can be neglected.
21 Operational costs of producing steam are not considered as explained in Chapter 1
(Limitations). 22 Biofuel price was 150 SEK/MWh in 2008. As it is rising all the time, it has been considered
10% more expensive for the future. 23 Electricity selling price to the grid was 700 SEK/MWh in 2008. As it is rising all the time, it has
been estimated that profits are 10% larger in the future.
Electricity selling price is made up of two major parts: actual electricity (MWh) delivered
into the electrical grid (400 SEK/MWh) + green certificates, GCs (1 MWh = 1 certificate;
300 SEK/MWh).
5. RESULTS
60
Next graph, Figure 29., compares all costs for different chillers sets at
LEAF.
Figure 29. Graph that shows the breakdown of total costs for 10 years at LEAF
After ten years, there are only operational costs, which are lower for
16NK-81 chillers set. If profits due to electricity production are taken into
account, costs for fulfilling customer’s demand in the city center will be
1 569 829 SEK/year and 2 473 607 SEK/year for 16NK-81 and 16TJ-53 chillers
set installations respectively.
5. RESULTS
61
5.1.2. MACKMYRA
5.1.2.1. OPERATIONAL CONDITIONS
Table 18. Power and steam demand of different chillers sets for the required cooling load in Mackmyra production during the year
Table 19. Biofuel (for producing steam), electricity and water consumption. Mackmyra
16NK-81 16TJ-53 TOTAL BIOFUEL CONSUMPTION
24 [GWh/year] 11,18 20,90
ELECTRIC POWER
SUPPLY [MWh/year]
CHILLERS 34,15 15,09
COOLING TOWERS (fans) 26,32 43,49
REST OF THE PLANT 450,82 TOTAL 511,30 509,40
TOTAL WATER FOR COOLING TOWERS [m3/year] 37 147,6 34 148,2
24 It has been assumed that the biofuel consumption in the future boiler at Mackmyra is the same as in the one at LEAF, as the boiler might be small
and its efficiency is not therefore very high.
TIME PERIOD
NUMBER OF
CHILLERS
WORKING
COOLING LOAD [MWh]
POWER SUPPLY
TO CHILLERS
[MWh]
STEAM SUPPLY
TO CHILLERS
[MWh]
16NK-81 16TJ-53 FREE
COOLING
ABSORPTION
COOLING 16NK-81 16TJ-53 16NK-81 16TJ-53
15 November-15 March — — 375 — — — — —
15 March-1 April & 1-15 November 1 1 — 372,59 2,62 0,86 326,51 614,35
April & 15 October-1 November 1 1 — 741,10 3,90 1,28 649,46 1221,98
1-15 May & 15 September-15 October 1 2 — 1261,62 4,61 3,03 1105,60 2080,23
15 May-15 June & 15 August-15 September 1 2 — 2857,34 7,20 4,73 2503,99 4711,36
15 June-15 August 2 2 — 3690 15,82 5,20 3233,68 5989,37
TOTAL [MWh/year] 375 8922,66 34,15 15,09 7819,23 14 617,29
5. RESULTS
62
5.1.2.2. COSTS
5.1.2.2.1. INVESTMENT COSTS
Table 20. Investment costs [SEK] for Mackmyra
2 ABSORPTION CHILLERS
TSA-16NK- 81 (CARRIER-SANYO) 2 * 6 200 000
2 ABSORPTION CHILLERS TSA-16TJ- 53
(CARRIER-SANYO) 2 * 2 700 000
BACK-UP COMPRESSOR CHILLER
YRTBTBT0550C (YORK) 600 000
BACK-UP COMPRESSOR CHILLER
YRTBTBT0550C (YORK) 600 000
2 COOLING TOWERS
OCT09HB05-5-90 (Vestas Aircoil) 2 * 1 595 000
2 COOLING TOWERS
OCT09HB03-3-120 (Vestas Aircoil) 2 * 998 000
HEAT EXCHANGER (+ FILTER)
TL6-BFG 60 000
HEAT EXCHANGER (+ FILTER)
TL6-BFG 60 000
REST OF THE INSTALLATION 1 450 000 REST OF THE INSTALLATION 1 450 000
TOTAL [SEK] 17 700 000 TOTAL [SEK] 9 506 000
5.1.2.2.2. OPERATIONAL COSTS
Table 21. Operational costs in Mackmyra production site
16NK-81 16TJ-53 BIOFUEL [SEK/year]
-165 SEK/MWh- 1 844 948,48 3 448 948,8
ELECTRICITY [SEK/year]
- 1 SEK/kWh- 511 296,31 509 404,38
WATER [SEK/year]
- 4 SEK/m3- 148 590,4 136 592,8
TOTAL [SEK/year] 2 504 835,19 4 094 945,98
5. RESULTS
63
5.1.2.2.3. TOTAL COSTS
Table 22. Total costs of Mackmyra absorption cooling plants for 10 years
16NK-81 16TJ-53
TOTAL
COSTS [SEK]
INVESTMENT 17 700 000 42 748 352
9 506 000 50 455 460
OPERATING 25 048 352 40 949 460
PROFITS: ELECTRICITY
PRODUCTION [SEK]
- 770 SEK/MWh-25
- 9 031 216 - 16 882 966
TOTAL [SEK] 33 717 136 33 572 494
Next graph, Figure 30., compares all costs for different chillers sets in
Mackmyra production site.
Figure 30. Graph that shows the breakdown of total costs for 10 years
in Mackmyra production site
After ten years, if profits due to electricity production are taken into
account, costs for fulfilling customer’s demand in Kungsbäck area will be
25 Assumption: α = 0,15. It has to be quite smaller than for Johannes (α = 0,29) since the boiler is
smaller and works at lower pressure. The smaller the boiler is, the lower the efficiency is.
Moreover, the lower pressure in the boiler is, the lower electricity production is (α value
depends mainly on the pressure of the boiler).
5. RESULTS
64
1 601 714 SEK/year and 2 406 649 SEK/year for 16NK-81 and 16TJ-53 chillers
set installations respectively.
5.1.3. JOHANNES
5.1.3.1. OPERATIONAL CONDITIONS
Table 23. Power and hot water demand of chillers set for the required cooling load at
Johannes during the year
5.1.3.2. COSTS
Table 24. Biofuel (for producing steam), electricity and water consumption. Johannes
26 Biofuel consumption in Johannes = 1,27 GWh biofuel/GWh steam 27 HVAC systems´cooling factor: COP =cooling/(electricity to compressor) = 2-3. As the systems
are not new and operational conditions are unknown, COP = 2 has been considered.
TIME PERIOD
NUMBER OF
16LJ-53
CHILLERS
WORKING
ABSORPTION
COOLING
LOAD [MWh]
POWER
SUPPLY TO
CHILLERS
[MWh]
HOT
WATER
SUPPLY TO
CHILLERS
[MWh]
15 November-15 March — — — —
15 March-1 April
1-15 November 2 490,68 1,72 733,84
April
15 October-1 November 2 805,90 2,56 1204,65
1-15 May
15 September-15 October 2 1106,82 3,03 1654,47
15 May-15 June
15 August-15 September 2 2083,87 4,73 3115,98
15 June-15 August 2 2509,2 5,20 3750,75
TOTAL [MWh/year] 6996,47 17,23 10459,69
16LJ-53 TOTAL BIOFUEL CONSUMPTION
26 [GWh/year] 13,28
ELECTRIC POWER
SUPPLY [MWh/year]
CHILLERS 17,23
HVAC systems (winter time)27
749,99
COOLING TOWERS (fans) 36,50
REST OF THE PLANT 450,82 TOTAL 1254,55
TOTAL WATER FOR COOLING TOWERS [m3/year] 28 753,8
5. RESULTS
65
5.1.3.2.1. INVESTMENT COSTS
Table 25. Investment costs [SEK] for Johannes
2 ABSORPTION CHILLERS
TSA-16LJ- 53 (CARRIER-SANYO) 2 * 2 700 000
BACK-UP COMPRESSOR CHILLER
YRTBTBT0550C (YORK) 600 000
2 COOLING TOWERS OCT09HB02-2-120 (Vestas Aircoil)
2 * 675 000
REST OF THE INSTALLATION 1 450 000
TOTAL [SEK] 8 800 000
5.1.3.2.2. OPERATIONAL COSTS
Table 26. Operational costs in Johannes production site
16LJ-53 BIOFUEL [SEK/year]
-165 SEK/MWh- 2 191 828,57
ELECTRICITY [SEK/year] - 1 SEK/kWh-
1 254 551,77
WATER [SEK/year]
- 4 SEK/m3- 115 015,2
TOTAL [SEK/year] 3 561 395,54
5.1.3.2.3. TOTAL COSTS
Table 27. Total costs of Johannes absorption cooling plant for 10 years
16NK-81
TOTAL
COSTS [SEK]
INVESTMENT 8 800 000 44 413 955
OPERATING 35 613 955
PROFITS: ELECTRICITY
PRODUCTION [SEK]
- 770 SEK/MWh-
- 23 356 493
TOTAL [SEK] 21 057 462
Next graph, Figure 31., shows all costs for 10 years in Johannes
production site.
5. RESULTS
66
Figure 31. Graph that shows the breakdown of total costs for 10 years
in Johannes production site
After ten years, if profits due to electricity production are taken into
account, costs for fulfilling customer’s demand in Johannesbergsvägen area will
be 1 225 746 SEK/year.
5. RESULTS
67
5.1.4. SENSITIVITY ANALYSIS
Apart from studying different production sites according to possible
customers´ demand, a sensitivity analysis28
, which ranges over size of absorption
units and other equipments, costs and profits, has been carried out for when the
cooling demand is both ten percent higher and lower than the estimated one.
5.1.4.1. LEAF
When cooling demand is 10% higher, one more 16 TJ-53 single-effect
absorption chiller is needed at LEAF. Hence, one more MX25-MFMS (Alfa Laval)
heat exchanger for cooling down single-effect chillers set (with six chillers in
parallel) has to be introduced too. Furthermore, it cannot be left behind that
cooling load is also higher in winter time (1012,7 kW).
Next Table 28. and Table 29. gather together new operational conditions
and total costs respectively.
Table 28. Operational conditions of different chillers sets at LEAF during the year when the
cooling demand is 10% higher than the estimated one
Table 29. Total costs of LEAF absorption cooling plants for 10 years when the cooling
demand is 10% higher than the estimated one
16NK-81 16TJ-53
TOTAL
COSTS [SEK]
INVESTMENT 22 627 000 75 758 141
21 670 000 124 300 077
OPERATING 53 131 141 102 630 077
PROFITS: ELECTRICITY
PRODUCTION [SEK] - 36 007 749 - 73 355 610
TOTAL [SEK] 39 750 391 50 944 467
28 Calculations in this Section 5.1.4. are based on the same assumptions and estimations as for the
three cases studied before.
TOTAL
COOLING LOAD
[MWh/year]
TOTAL STEAM
SUPPLY
[MWh/year]
TOTAL
ELECTRICITY
SUPPLY
[MWh/year]
TOTAL BIOFUEL
CONSUMPTION
[MWh/year]
FREE
COOL.
ABSORP.
COOL. 16NK-81 16TJ-53 16NK-81 16TJ-53 16NK-81 16TJ-53
976,24 23 198,59 20 331,87 41 420,45 515,81 489,85 29 074,58 59 231,24
5. RESULTS
68
When cooling demand is 10% lower, chiller configurations do not change;
either three 16NK-81 units or five 16TJ-53 units in parallel are still needed. In this
case, 779 kW of free cooling are necessary.
Following Table 30. and Table 31. show, on the one hand, new total
cooling load and operational conditions; on the other hand, the total costs (take
note that investment costs are the same).
Table 30. Operational conditions of different chillers sets at LEAF during the year when the
cooling demand is 10% lower than the estimated one
Table 31. Total costs of LEAF absorption cooling plants for 10 years when the cooling
demand is 10% lower than the estimated one
16NK-81 16TJ-53
TOTAL
COSTS [SEK]
INVESTMENT 22 627 000 64 577 824
18 420 000 92 672 852
OPERATING 41 950 824 74 252 852
PROFITS: ELECTRICITY
PRODUCTION [SEK] - 27 699 356 - 52 114 385
TOTAL [SEK] 36 878 468 40 558 467
TOTAL
COOLING LOAD
[MWh/year]
TOTAL STEAM
SUPPLY
[MWh/year]
TOTAL
ELECTRICITY
SUPPLY
[MWh/year]
TOTAL BIOFUEL
CONSUMPTION
[MWh/year]
FREE
COOL.
ABSORP.
COOL. 16NK-81 16TJ-53 16NK-81 16TJ-53 16NK-81 16TJ-53
750,96 17 845,07 15 640,52 29 426,53 504,70 482,10 22 365,94 42 079,94
5. RESULTS
69
5.1.4.2. MACKMYRA
When cooling demand is 10% higher, one more 16 TJ-53 single-effect absorption chiller is also required in Mackmyra production
site. This way, one more OCT09HB03-3-120 (Vestas Aircoil) cooling tower is needed too. Likewise, roughly 39 kW cooling/year more
ought to be produced by means of free cooling in winter.
New total cooling load and operational conditions as well as total costs are shown in Table 32. and Table 33.
Table 32. Operational conditions of different chillers sets in Mackmyra production site during the year
when the cooling demand is 10% higher than the estimated one
Table 33. Total costs of Mackmyra absorption cooling plants for 10 years
when the cooling demand is 10% higher than the estimated one
16NK-81 16TJ-53
TOTAL
COSTS [SEK]
INVESTMENT 17 700 000 44 893 151
13 204 000 58 100 671
OPERATING 27 193 151 44 896 671
PROFITS: ELECTRICITY
PRODUCTION [SEK] - 9 934 004 - 18 689 819
TOTAL [SEK] 34 959 146 39 410 852
TOTAL COOLING
LOAD [MWh/year]
TOTAL STEAM
SUPPLY
[MWh/year]
TOTAL
ELECTRICITY
SUPPLY
[MWh/year]
TOTAL BIOFUEL
CONSUMPTION
[MWh/year]
TOTAL WATER
CONSUMPTION
[m3/year]
FREE
COOL.
ABSORP.
COOL. 16NK-81 16TJ-53 16NK-81 16TJ-53 16NK-81 16TJ-53 16NK-81 16TJ-53
413,03 9 814,79 8 600,87 16 181,66 512,05 510,02 12 299,24 23 139,78 44 472,4 40 396,1
5. RESULTS
70
When cooling demand is 10% lower, it is only necessary one 16NK-81 double-effect absorption chiller (one less) and, therefore,
only one OCT09HB05-5-90 (Vestas Aircoil) cooling tower too. Regarding demanded cooling in winter, 351 kW are just required.
Following Table 34. and Table 35. gather together new total cooling load as well as operational conditions and total costs,
respectively.
Table 34. Operational conditions of different chillers sets in Mackmyra production site during the year
when the cooling demand is 10% lower than the estimated one
Table 35. Total costs of Mackmyra absorption cooling plants for 10 years
when the cooling demand is 10% lower than the estimated one
16NK-81 16TJ-53
TOTAL
COSTS [SEK]
INVESTMENT 9 905 000 32 734 801
9 506 000 47 097 672
OPERATING 22 829 801 37 591 672
PROFITS: ELECTRICITY
PRODUCTION [SEK] - 8 127 503 - 15 293 040
TOTAL [SEK] 24 607 298 31 804 632
TOTAL COOLING
LOAD [MWh/year]
TOTAL STEAM
SUPPLY
[MWh/year]
TOTAL
ELECTRICITY
SUPPLY
[MWh/year]
TOTAL BIOFUEL
CONSUMPTION
[MWh/year]
TOTAL WATER
CONSUMPTION
[m3/year]
FREE
COOL.
ABSORP.
COOL. 16NK-81 16TJ-53 16NK-81 16TJ-53 16NK-81 16TJ-53 16NK-81 16TJ-53
337,93 8 030,28 7 036,80 13 240,73 511,07 498,42 10 062,62 18 934,24 27 893,3 34 148,2
5. RESULTS
71
5.1.4.3. JOHANNES
The installations remain the same in Johannes production site when
cooling demand is 10 % higher or lower. Cooling load and hence, operational
conditions are only changed.
Next Table 36. and Table 38. show the new operational conditions and
Table 37. and Table 39. the consistent new total costs.
Table 36. Operational conditions of different chillers sets in Johannes production site during
the year when the cooling demand is 10% higher than the estimated one
Table 37. Total costs of Johannes absorption cooling plants for 10 years
when the cooling demand is 10% higher than the estimated one
16LJ-53
TOTAL
COSTS [SEK]
INVESTMENT 8 800 000 45 664 168
OPERATING 36 864 168
PROFITS: ELECTRICITY
PRODUCTION [SEK] - 24 543 860
TOTAL [SEK] 21 120 308
Table 38. Operational conditions of different chillers sets in Johannes production site during
the year when the cooling demand is 10% lower than the estimated one
Table 39. Total costs of Johannes absorption cooling plants for 10 years
when the cooling demand is 10% lower than the estimated one
16LJ-53
TOTAL
COSTS [SEK]
INVESTMENT 8 800 000 43 140 656
OPERATING 34 340 656
PROFITS: ELECTRICITY
PRODUCTION [SEK] - 22 158 526
TOTAL [SEK] 20 982 130
TOTAL
ABSORPTION
COOLING
LOAD
[MWh/year]
TOTAL HOT
WATER
SUPPLY
[MWh/year]
TOTAL
ELECTRICITY
SUPPLY
[MWh/year]
TOTAL BIOFUEL
CONSUMPTION
[MWh/year]
TOTAL WATER
CONSUMPTION
[m3/year]
7 353,12 10 991,43 1 268,15 13 959,11 28 753,8
TOTAL
ABSORPTION
COOLING
LOAD
[MWh/year]
TOTAL HOT
WATER
SUPPLY
[MWh/year]
TOTAL
ELECTRICITY
SUPPLY
[MWh/year]
TOTAL BIOFUEL
CONSUMPTION
[MWh/year]
TOTAL WATER
CONSUMPTION
[m3/year]
6 639,31 9 923,21 1 241,36 2 079 408,443 28 324,8
5. RESULTS
72
5.2. COMPRESSION TECHNOLOGY VERSUS
ABSORPTION TECHNOLOGY. COMPARISON
FOR LEAF PRODUCTION SITE
Technological possibilities and aspects of absorption cooling systems at
three specific sites in the victinity of Gävle, as well as the costs and profits
(economic aspects), have been evaluated. Nevertheless, the main aim of this thesis
is to analyze possible benefits with the use of heat driven absorption chillers
instead of conventional vapour compressor chillers. Thus, compression cooling
machines at LEAF have been replaced by equivalent absorption ones in order to
make a comparison.
Compression cooling installation (see Appendix 1.) will be made up of
five chillers: VKA1 (1254 kW), VKA2 (1254 kW), VKA3 (717 kW), VKA4
(3226 kW) and VKA5 (3226 kW), which are going to be replaced except for
VKA3, as it is a back-up chiller that would be also used in the absorption cooling
plant. The rest of the installation (building, pumps and so on)29
as well as
operational conditions30
remain the same.
This way, four double-effect steam fired absorption chillers are going to be
introduced: two 16NK-41 (1371 kW) and other two 16NK-71 (3446 kW), which
has been choosen taking into account different sizes and models of chillers that
exist in the market. Both VKA1 and VKA2 could be replaced with just a single
bigger absorption machine (16NK-62); nevertheless, five machines ought to be in
total so that absorption cooling installation would have been also built in two
stages31
. Likewise, an installation with single-effect absorption chillers is not
29 KM1 pumps are not taken into consideration as electricity consumption of absorption chillers,
which belongs with pumps, is calculated. Regarding distribution pumps, those are taken into
account in this case as they are also included in the costs of the refrigeration compression
installation. 30 Compression cooling plant is using free cooling not only in winter but all around the year
except for May-August (altogether 1936 h/year). Even though it is not right (it should be used only in winter time: ≈ 15 November-15 March), the same operational conditions have been
considered so that new calculations are comparable with the existing compression project. 31 There are only VKA1 and VKA2 cooling machines in the first stage of the compressor
refrigerant cooling project and one of them is a back-up chiller. For that reason, there are two
small compressor chillers when the installation is totally built (in addition to VKA4 and
VKA5) instead of a bigger one.
5. RESULTS
73
studied since more than four absorption chillers would be needed (their maximum
capacity is 2461 kW).
Next, all calculations are shown.
Table 40. Operational conditions of the existing cooling
project but with absorption machines
OPERATING TIME
[h/year]
CAPACITY [kW]
VKA1 →16NK-41,1
VKA2 →16NK-41,2
VKA4 →16NK-71,1
VKA5 →16NK-71,2
44,28 1254 3226
487,08 940,5 2419,5
605,16 627 1613
339,48 315,5 806,5
Table 41. Power and steam demand of chillers set for the required cooling load in the
existing cooling project but with absorption machines
VKA1 →16NK-41,1
VKA2 →16NK-41,2
VKA4 →16NK-71,1
VKA5 →16NK-71,2
TOTAL
[MWh/year]
STEAM SUPPLY
TO THE CHILLERS
[MWh/year]
2 * 876,51 2 * 2249,84 6252,67
TOTAL POWER SUPPLY
TO THE CHILLERS
[MWh/year]
2 * 9,78 2 * 15,99 51,53
TOTAL BIOFUEL
CONSUMPTION
[MWh/year]
2 * 1253,42 2 * 3217,30 8941,37
Table 42. Operational costs in the existing cooling project but with absorption machines
ELECTRICITY [SEK/year]
- 1 SEK/kWh-
CHILLERS 51 530,11
REST OF THE EQUIPMENTS 3 192 656
BIOFUEL [SEK/year] - 165 SEK/MWh- 1 475 326,19
TOTAL [SEK/year] 4 719 512,30
Table 43. Total costs of the existing cooling project but with
absorption machines for 10 years
INVESTMENT COSTS
[SEK]
COOLING
EQUIPMENTS
VK3 600 000
16NK-41 2 * 3 000 000
16NK-71 2 * 5 300 000
BUILDING 4 000 000
PIPES INSIDE THE BUILDING 4 500 000
PUMPS AND FILTERS INSIDE THE BUILDING
3 000 000
TOTAL 28 700 000
COSTS OF OPERATION [SEK] 47 195 123
PROFITS: ELECTRICITY
PRODUCTION [SEK]
- 770 SEK/MWh-
- 11 073 544
TOTAL [SEK] 64 821 579
5. RESULTS
74
Next Figure 32. gathers together all information about both cooling installations at LEAF.
Figure 32. Comparison of cooling installations with absorption and compression machines at LEAF
ORC
α = 0,23
ABSORPTION COOLING INSTALLATION COMPRESSION COOLING INSTALLATION
28 700 000 SEK 22 629 000 SEK
6253 MWh
steam
3245 MWh
electricity
0,001 SEK/MWh
8941 MWh
biofuel
165 SEK/MWh
4241 MWh
electricity
0,001 SEK/MWh 7143 MWh 7143 MWh
COOLING COOLING
1438 MWh electricity
to the grid
770 SEK/MWh
MAINTENANCE
COSTS
[SEK]
= 170 000 x when x = 1 x: years
= 340 000 – 10 200 x when 1 < x ≤ 5
= 289 000 + 89 250 (x – 5) when x ≥ 6
TOTAL COSTS FOR 10 YEARS:
64 821 579 SEK
(profits due to electricity production are
taken into account)
TOTAL COSTS FOR 10 YEARS:
66 204 500 SEK
5. RESULTS
75
5.3. DISTRIBUTION SYSTEM
5.3.1. INSTALLATION
The most important information about the main networks is gathered in the
following Table 44. Calculations and estimations, as well as all explanations, are
presented in Appendix 5.
Table 44. Data about the distribution systems
PRODUCTION
SITE
PIPE
KWH PE
(PN10)
DISTANCE
[m]
INTERNAL
DIAMETER
OF THE
PIPE
[mm]
EXTERNAL
DIAMETER
OF THE
PIPE,
dn [mm]
CHILLED
WATER
FLOW
[m3/h]
ΔP
[kPa]
(in the
distribution
system)
LEAF LEAF 1370 175 200 771 328
MACKMYRA
Mackmyra I 500 262 315
317 250
Mackmyra II 310 166 200
Mackmyra III 1890 203 250
JOHANNES Johannes 1775 370 450 171 718
5.3.3. COST OF THE MAIN PIPING NETWORKS
Total costs of the distribution systems for each of the three studied sites
can be seen in the next Table 45. They are made up of cost for distribution pumps
and pipes; the later one includes, apart from the material (pipe itself), digging,
construction and calculation plus quality control costs. Moreover, Table 46.
gathers together power consumption of the distribution pumps as well as
operational costs. For further information, see Section A5.2. in Appendix 5.
Table 45. Cost of the distribution systems
PRODUCTION
SITE
PUMP COST
[SEK]
PIPES COST
[SEK]
TOTAL COSTS
[SEK]
LEAF 110 000 6 850 000 6 960 000
MACKMYRA 62 000 16 621 100 16 683 100
JOHANNES 69 000 9 577 900 9 646 900
Table 46. Operational conditions and costs of distribution pumps
PRODUCTION SITE
ELECTRIC POWER SUPPLY
TO DISTRIBUTION PUMPS
[MWh/year]
OPERATIONAL
COSTS [SEK/year]
- 1 SEK/kWh-
LEAF 336,04 336 040
MACKMYRA 119,39 119 390
JOHANNES 193,20 193 200
CHAPTER 6
77
Discussions
Amount of provided information was limited and to collect accurate
information was difficult. Therefore, results are only approximations, as they are
based on quiet a lot assumptions. As a result, definitive conclusions cannot be
come up with.
6.1. PRODUCTION PLANTS
To finish with this research, one of the tasks is to make a decision about
more adequate types of absorption chillers to be used. In the case of Johannes
cooling production plant, hot-water absorption cooling machines ought to be
introduced as there are no more options from the technical point of view.
Regarding the other two sites, investment costs are higher for double-effect steam
fired chillers than for single-effect ones, whereas operational costs are much
more, about 50%, lower. Both scenarios, LEAF and Mackmyra, can be examined
in depth.
On the one hand, investment costs for double-effect installation are
4 207 000 SEK higher at LEAF. Nevertheless, operational costs are
3 713 268 SEK lower per year, which means that the initial extra costs would be
paid back in less than 2 years. If profits due to electricity output are taken into
consideration, the difference in annual costs would not be so large, but still
903 778 SEK/year (in this case, higher investment costs would be paid back in
5 years).
On the other hand, despite double-effect facilities cost 8 194 000 SEK
more than single-effect ones at Mackmyra, operational costs are
6. DISCUSSIONS
78
1 590 110 SEK lower per year. As a result, the extra investment costs are paid
back in 5 years. This time rises up to 10 years if produced electricity is taken into
account.
Therefore, needless to say that it is more profitable to introduce double-
effect chillers in both sites, since the pay-back times for extra investments are
short and the earnings would be considerable. This way, costs and profits for the
possible future three absorption cooling plants in Gävle would be those that are
gathered together in the following Table 47.
Table 47. Most adequate chillers and costs & profits for the three production sites
PRODUCTION
SITE
ABSORPTION
CHILLERS SETS
INVESTMENT
COST [SEK]
OPERATIONAL
COSTS
[SEK/year]
PROFITS
FROM
ELECTRICITY
PRODUCTION
[SEK/year]
LEAF
3 double-effect
chillers (4652 kW)
in parallel
22 627 000 4 753 785 3 183 656
MACKMYRA
2 double-effect
chillers (4652 kW)
in parallel
17 700 000 2 504 835 903 122
JOHANNES
2 single-effect hot
water chillers
(1846 kW) in
parallel
8 800 000 3 561 396 2 335 649
Next graph in Figure 33. shows total heat that might be produced in
different biofuel boilers for the three absorption plants and accordingly obtained
extra electricity output.
6. DISCUSSIONS
79
Figure 33. Increased heat load for the three absorption plants and the possible extra
electricity that would be produced
In Figure 23. was shown that when the load in the district heating network
is low there is almost none electricity production in Johannes CHP plant. In
addition, it is shut down during summer, June-August. If heat driven absorption
chillers were introduced, heat load and therefore, electricity output, would be
increased as it is shown in the next graph in Figure 34.
Figure 34. Increased heat and electricity load in the probable Johannes trigeneration plant
6. DISCUSSIONS
80
Nevertheless, this heat load would not be even enough to keep the boiler
running during summer because of efficiency problems, that is, the minimum
working capacity. The graph in Figure 35. shows that the boiler would have to
work at around 5 MW, whereas it is shut down when the loading is lower than
25% of its maximum capacity (20 MW).
Figure 35. Required operational conditions of the boiler for the cooling plant at Johannes
Consequently, cooling production at Johannes is a contribution but at
present it is not possible to keep the plant running during summer because of the
minimum load problem. It might be feasible if either heat or cooling market grew
in the future.
6.2. MOST PROFITABLE TECHNIQUE FROM
ECONOMIC POINT OF VIEW. SUSTAINABILITY
Next graph in Figure 36. depicts all costs for the two different cooling
systems with absorption and vapour compressor technologies at LEAF. It has to
be underlined that the comparison is limited since water from the river is used for
cooling down the chillers and one of the main differences between these machines
is the required size of cooling towers.
6. DISCUSSIONS
81
Figure 36. Comparison of total costs for ten years for the different cooling production
technologies at LEAF
The larger investment costs of the absorption cooling compared to
compression cooling, 6 071 000 SEK, are paid back after five years (4,39 years)
because of lower electricity consumption and larger fuel utilization32
, in addition
to increased electricity production.
Next Table 48. gathers together annual benefits after the first 10 years
when using absorption chillers instead of compression cooling machines:
Table 48. Annual benefits of absorption cooling technology at LEAF after 10 years
CASE
ELECTRICITY
CONSUMPTION
[MWh/year]
ELECTRICITY
PRODUCTION
[MWh/year]
PROFITS
FROM
ELECTRICITY
[SEK/year]
LEAF 8905 kW - 996 1438 1 107 354
32 It bears reminding from Section 2.3. that absorption systems can compete against compression
ones when price of electricity is around 8 times higher than cost of heat.
6. DISCUSSIONS
82
An efficiency comparison between system including absorption or vapour
compressor chillers can be made too. If overall system is taken into account, total
efficiency for compressor cooling system is 58% higher33
. Nevertheless, if
internal electricity consumption is analyzed, the coefficient of performance
(COPel) is 23% greater for the absorption machines’ installation34
, as absorption
chillers only use electricity for pumping the absorbent solution whereas
compression ones are driven by electric power.
Deregulation and real-time pricing for electricity give an incentive to
manage electrical loads. A compression chiller is a very big target when looking
for ways to reduce electrical loading and to control costs. Thus, absorption units
allow it without sacrificing either performance or reliability.
Moreover, as mentioned before, an absorption cooling system contributes
to an increased electricity production. Hence, it gives good opportunities of
utilizig the biofuel in an effective way.
This way, it is come to the conclusion that a sustainable energy system for
Gävle for meeting the cooling demand can be the erection of district cooling
networks with trigeneration plants by producing cooling in heat driven absorption
cooling machines. Increasing of the energy system with a third output (cooling)
would optimize the system even more. Furthermore, it is also very good from
environmental point of view, since extra electricity produced could be sold as
green in the Swedish market and it could replace, this way, margin produced
electricity.
It bears mentioning that the system border of electricity production and
consumption has to be taken into consideration when studying environmental
aspects and, like this, carbon dioxide emissions. From global point of view,
electricity production in Gävle would affect European energy system and total
33 ηTOT, compression system = Wcooling/Welectricity = 1,684
ηTOT, absorption system = (Wcooling + Welectricity)/(Qfuel + Welectricity) = 0,705
34 COPel, compression chillers set = Wcooling/Welectricity = 1,684
COPel, absorption chillers set = Wcooling/Welectricity = 2,201
6. DISCUSSIONS
83
CO2 emissions would be therefore negative. However, the local emissions would
be negatively affected because of increased use of fuel; anyway, biofuel, that is,
clean fuel, would be used.
6.3. COOLING DEMAND VERSUS COSTS AND
BENEFITS OF ABSORPTION COOLING
TECHNOLOGY
There are three scenarios that it does not even compare at all to each other
as the installations are quiet different. Even though double-effect steam fired
chillers might be at both LEAF and Mackmyra production sites, water from the
river could be used for cooling down the chillers at LEAF whereas cooling towers
are required at Mackmyra, which entails electricity consumption and higher
investment costs for the latest case. Regarding Johannes production site, although
it also needs cooling towers, steam is not used, but hot water.
As a result, each case is going to be studied separately.
6.3.1. ELECTRICITY PRODUCTION AND CONSUMPTION
The environmental and economical effects with absorption systems
compared with vapour compression ones are consistently positive and become
more and more evident with higher cooling demands and higher electricity prices
(note Figure 37. in the next page).
6. DISCUSSIONS
84
Figure 37. Electricity production and consumption according to the
cooling demand in three different scenarios
6.3.2. COSTS AND PROFITS. THE BEST OPTIONS
Figure 38. Costs and profits (due to electricity production) according
to the cooling demand in three different scenarios
Johannes absorption cooling plant with hot-water chillers is the smallest
one. The previous graph in Figure 38. shows how investment costs are kept
JOHANNES
6. DISCUSSIONS
85
constant with variations of ±10% in cooling demand. This means the same
machines can be used to produce up to 10% more than required cooling nowadays
with higher profits, as electricity output together with income from customers
increase while variation in costs of operation is little.
On the other hand, steam-fired chillers are under study. The trend at LEAF
is the same as at Johannes. However, there is a big difference at Mackmyra when
demand decreases by 10%: investment costs are 44% lower. Therefore, the best
option would be to build smaller installations and meet the cooling demand in
Kungsbäck area by other means. This could be accomplished in two different
ways: by storing energy or by making the network smaller and using another.
The university, which cooling demand is 1,8 MW, could be connected to
the network in the city center, as it is not far away from Konserthuset (where the
main pipe might reach). In addition, as mentioned earlier, there would be no
problem to produce required extra cooling with the same facility at LEAF.
Research on advantages and disadvantages of this option could make possible the
execution of a new thesis project.
Regarding energy storage, accumulator tanks for chilled water should be
considered for many reasons: problems to fulfil the cooling demand, dynamic
demand during the year, security in the system and so forth. Consecuently, further
research into those systems could be done.
CHAPTER 7
87
Conclusions
This research seeks to compare compression and absorption cooling
technologies and to make a decision about which one is the best solution, in
addition to deal with the analysis of three trigeneration plants with absorption
cooling systems in Gävle. In connection with this, next all interesting made
conclusions are summed up and gathered together.
- Development of district cooling systems with trigeneration plants that
produce chilled water in absorption machines is the best solution to
meet the cooling demands.
Benefits with absorption systems compared with vapour
compression ones become more and more evident with higher cooling
demands and higher electricity prices.
- It is more profitable to introduce double-effect steam-fired absorption
chillers than single-effect ones.
- Even though steam-fired chillers are more efficient, single-effect hot
water chillers might be introduced at Johannes, as the pressure of the
steam leaving the turbine is lower than the required one for steam fired
cooling machines.
- The cooling plant at Johannes might be a contribution, but at present
it is not feasible because of boiler´s minimum load problem.
- It would be more profitable to increase the production of cooling in
10% over the demand at LEAF and Johannes. Nevertheless, regarding
Mackmyra production site, the best option would be to build smaller
installations and meet the demand by other means.
REFERENCES
REFERENCES
89
[1] T.T. Chow, K.F. Fong, A.L.S. Chan, R.Yau, W.H. Au, V. Cheng, Energy
modelling of district cooling system for new urban development, Energy and
Building 36 (2004) 1153-1162.
[2] L. Trygg, B. G. Karlsson, Industrial DSM in a deregulated European
electricity market-a case study of 11 plants in Sweden, Department of
Mechanical Engineering, Division of Energy Systems, Linköping Institude of
Technology, Linköping S-581 83, Sweden.
[3] A. Rojey, Cold producing process, 4,037,426 United States Patent.
[4] M. J. Moran, H. N. Shapiro, ―Fundamentos de termodinámica técnica”
(Fundamentals of Engineering Thermodynamics), Reverté (2004). ISBN 84-
291-4313-0.
[5] United States Departament of Energy (DOE), Mississippi Cooling, Heating,
and Power (micro-CHP) and Bio-fuel Center, micro- Cooling, Heating, and
Power (m-CHP) Instructional Module, Mississippi State, MS 39762
(December 2005 First Printing).
[6] R. Gianfrancesco, Method and apparatus for the absorption-cooling of a fluid,
5,177,979 United States Patent.
[7] R. Darío Ochoa V., ‖Absorción como una alternativa de ahorro de energía”
(Absorption as alternative for saving energy), Tecnología Empresarial S.A.
(2003). [8] A. Şencan, K. A. Yakut, S. A. Kalogirou, Exergy analysis of lithium
bromide/water absorption systems, Renewable Energy 30 (2005) 645-657.
[9] G. Cohen, A. Rojey, Absorbers used in absorption heat pumps and
refrigerators, 4,299,093 United States Patent.
[10] Y. Hassan, Cold from Waste Energy. The Absorrption System, Mechanical
Department, Sudan University.
[11] D W Hudson, Gordon Brothers Industries Pty Ltd, Ammonia absoption
refrigeration plant, The official journal of AIRAH (August 2002).
[12] I. Horuz, A comparison between ammonia-water and water-lithium bromide
solutions in vapor absorption refrigeration systems, PII S0735-
1933(98)00058-X.
[13]M. Rydstrand, Heat driven cooling in district energy systems, KTH Chemical
Engineering and Technology, Stockholm (2004). ISBN 91-7283-794-2.
[14] K.E. Herold, R.Radermacher, S. A. Klein, Absorptioni Chillers and Heat
Pumps, CRC Press (1996). ISBN 0-8493-9429-9.
REFERENCES
90
[15] P. E. Nilsson, Achieving the Desired Indoor Climate. Elergy Efficiency
Aspects od Systen Design, Studentlitteratur, Lund (2003). ISBN 91-44-03235-
8.
[16] M.A. Rosen, M. N. Le, I. Dincer, Efficiency analysis of a cogeneration and
district energy system, Applied Thermal Engineering 25 (2005) 147-159.
[17] F. Lin, J. Yi, Y. Weixing, Q. Xuzhong, Influence of supply and return water
temperatures on the energy consumption of a district cooling system, Applied
Thermal Engineering 21 (2001) 511-521.
INTERNET SOURCES:
1. http://www.air-conditioning-and-refrigeration-guide.com/refrigeration-
cycle.html
2. http://www.qrg.northwestern.edu/thermo/design-library/refrig/refrig.html,
Design of Vapour-Compression Refrigeration Cycles
3. http://www.commercial.carrier.com, Absorption Chillers
4. http://www.nationmaster.com/encyclopedia/Gas-absorption-refrigerator
5. http://www.grappa.co.yu/b/index.php?page=shop.getfile&file_id=36&product_
id=48&option=com_virtuemart&Itemid=30, Carrier-Sanyo Super Absorption
16LJ 11-53
6. http://www.kwhpipe.com
7. http://www.carrier.com
8. http://www.turboden.it/en/products.asp
BROCHURES:
1. 16TJ Single-Effect Steam-fired chillers (Carrier-Sanyo).
2. 16NK Double-Effect Steam-Fired Absorption Chillers (Carrier-Sanyo).
3. 16LJ Single-Effect Hot water-fired chillers (Carrier-Sanyo).
4. The Complete Pipework Solution (KWH Pipe).
5. PE Pressure Pipe Systems (KWH Pipe).
6. OCR technology, biomass application (TURBODEN).
REFERENCES
91
PERSONAL CONTACTS:
Table R. 1. Information about personal contacts
NAME COMPANY/ CAPACITY INFORMATION AREA OF EXPERTISE
Åke Björnwall Gävle Energi AB: Project & Development
Supervisor
Tel direct 026 – 17 86 15
ake.bjornwall@gavle.se
- General
- Gävle Energi
Håkan Rannestig Gävle Energi AB: Manager P&U 026-17 26 60
Cooling project
Ulf Hedman Ramböll Sverige AB (www.ramboll.se)
Consultant
Tel direct 026-149507
ulf.hedman@ramboll.se
- Boiler-projects
- Absorption cooling
Anders Kedbrant SWECO Systems AB (www.sweco.se)
Consultant
Tel direct 026-66 20 02
Mobil 0706-623262
anders.kedbrant@sweco.se
- Existing project
- Compression
Refrigeration
Per-Arne Vahlund Gävle Energi AB: Marketing 026-17 86 80 Customer data
Inger Wiklund Gävle Energi AB: Documentation 026-17 86 59 GIS
Greger Berglund Gävle Energi AB: Project Manager 026-17 85 25
Distribution system
Lucas Enström Gävle Energi AB: Operation Manager 026-17 26 65
lucas.enstrom@gavle.se
Johannes CHP plant
Daniel Widman Falu Energi & Vatten AB : Project Manager
Tel direct 023-77049052
daniel.widman@fev.se
District Cooling project in
Falun
- Sale assistants: Tomas Lundgren and Tyko Sandell from Carrier, Thomas Nyström from Z&I Pumps, Anna Schlegel
from Grudfos, Robert Lindberg from Baltimore Air Coil (BAC), etc.
APPENDICES
93
Appendix 1. PLANNED REFRIGERANT COMPRESSION INSTALLATION
A1.1. INSTALLATION
Figure A1. 1. Draft of the whole compression installation (Source: Anders Kedbrant, SWECO)
Appendix 1. Planned refrigeration compression installation
94
Figure A1. 2. Draft of the devices of the compression installation (Source: Anders Kedbrant, SWECO)
1st
stage
1st
stage
2nd
stage
2nd
stage
Appendix 1. Planned refrigeration compression installation
95
INSTALLATION ON ITS FIRST STAGE
- Submersible pumps for the whole installation: KM1-P6A and KM1-P6B
- Main pumps for the distribution pipes: KB1-P6A and KB1-P6B
► Cooling water in the distribution system:
FORWARD PIPE: 5,5 °C
RETURN PIPE: 13,2 °C
- 2 cooling machines (compressor, evaporator, condenser): VKA1 and
VKA2
o 2 dry single pumps: KB1-P1 and KB1-P2
o 2 dry single pumps: KM1-P1 and KM1-P2 (they keep set flow in the
condenser).
- Heat exchanger unit: KB1-VVX1
MACHINES AND DEVICES TO BE INTRODUCED IN THE
SECOND STAGE
- 3 cooling machines (compressor, evaporator, condenser): VKA3, VKA4
and VKA5
o 3 dry single pumps: KB1-P3, KB1-P4 and KB1-P5
o 3 dry single pumps: KM1-P3, KM1-P4 and KM1-P5
PUMPS:
Table A1. 1. Pump specifications of compression cooling installation I
TYPE KM1-P6A / P6B
(SUBMERSIBLE, BRUNN1, BRUNN2)
PROCEDURE
DRY SINGLE PUMP
Wilo / FA 25.93D WITH ENGINE FK34.1-
6/50
MEDIA WATER 20°C
FLOW 265 l/s
MAXIMUM PRESSURE 150 kPa
POWER 75 kW
RATED CURRENT 151 A
MINIMUM EFFICIENCY 88 %
Appendix 1. Planned refrigeration compression installation
96
Table A1. 2. Pump specifications of compression cooling installation II
TYPE KB1-P6A / P6B
PROCEDURE Grundfos / : TP300/590/4 A-F-A DBUE or
equivalent
MEDIA WATER 5,5°C
FLOW 320 l/s
MAXIMUM PRESSURE 400 kPa
POWER 200 kW
RATED CURRENT 340/196 A
MINIMUM EFFICIENCY ---
Table A1. 3. Pump specifications of compression cooling installation III
TYPE KB1-P1, KB1-P2
PROCEDURE DRY SINGLE PUMP
Wilo / : IL 150/190-5,5/4 or equivalent
MEDIA WATER 5,5°C
FLOW 45 l/s
MAXIMUM PRESSURE 50 kPa
POWER 5,5 kW
RATED CURRENT 11,4 A
MINIMUM EFFICIENCY 71 %
Table A1. 4. Pump specifications of compression cooling installation IV
TYPE KB1-P3
PROCEDURE DRY SINGLE PUMP
Wilo / IL 80/170-2,2/4
MEDIA WATER 5°C
FLOW 25 l/s
MAXIMUM PRESSURE 50 kPa
POWER 2,2 kW
RATED CURRENT 4,7 A
MINIMUM EFFICIENCY 67 %
Table A1. 5. Pump specifications of compression cooling installation V
TYPE KB1-P4, KB1-P5
PROCEDURE DRY SINGLE PUMP
Wilo / IL 200/240-15/4
MEDIA WATER 5°C
FLOW 110 l/s
MAXIMUM PRESSURE 70 kPa
POWER 15 kW
RATED CURRENT 28,5 A
MINIMUM EFFICIENCY 76 %
Appendix 1. Planned refrigeration compression installation
97
Table A1. 6. Pump specifications of compression cooling installation VI
TYPE KM1-P1, KM1-P2
PROCEDURE DRY SINGLE PUMP
Wilo / IL 100/170-3/4
MEDIA WATER 20°C
FLOW 40 l/s
MAXIMUM PRESSURE 45 kPa
POWER 3 kW
RATED CURRENT 6,4 A
MINIMUM EFFICIENCY 73 %
Table A1. 7. Pump specifications of compression cooling installation VII
TYPE KM1-P3
PROCEDURE DRY SINGLE PUMP
Wilo / IL 100/160-2,2/4
MEDIA WATER 5°C
FLOW 30 l/s
MAXIMUM PRESSURE 45 kPa
POWER 2,2 kW
RATED CURRENT 4,7 A
MINIMUM EFFICIENCY 77 %
Table A1. 8. Pump specifications of compression cooling installation VIII
TYPE KM1-P4, KM1-P5
PROCEDURE DRY SINGLE PUMP
Wilo / IL 200/240-7,5/6
MEDIA WATER 5°C
FLOW 80 l/s
MAXIMUM PRESSURE 50 kPa
POWER 7,5 kW
RATED CURRENT 16 A
MINIMUM EFFICIENCY 74 %
CHILLERS:
Table A1. 9. Vapour Compressor chillers specifications I
TYPE VKA1, VKA2
MODEL: YRWCWCT3550C
REFRIGERANT R134 A
MAXIMUM CAPACITY 1254 kW
INPUT POWER 187 kW
VOLTAGE 400/ 50 Hz
Appendix 1. Planned refrigeration compression installation
98
Table A1. 10. Vapour Compressor chillers specifications II
TYPE VKA3
MODEL: YRTBTBT0550C
REFRIGERANT R134 A
MAXIMUM CAPACITY 717 kW
INPUT POWER 110 kW
VOLTAGE 400/ 50 Hz
Table A1. 11. Vapour Compressor chillers specifications III
TYPE VKA4, VKA5
MODEL: YKKKKLH95CQF
REFRIGERANT R134 A
MAXIMUM CAPACITY 3226 kW
INPUT POWER 451 kW
VOLTAGE 400/ 50 Hz
FREE COOLING HEAT EXCHANGER UNIT:
Table A1. 12. Heat exchanger specifications of compression cooling installation
TYPE/MANUFACTURER KB1-VVX1 AlfaLaval
CAPACITY 500 kW
STREAMS TEMPERATURE 4,5/15 ºC (primary)
5,5/165 ºC (secondary)
FLOW 11,3 l/s (primary & secondary)
PRESSURE DROP 96,9 kPa (primary)
98,8 kPa (secondary)
VKA2 is a back-up chiller in the first stage. When the second stage is
built, both VKA1 and VKA2 will be working together with VKA4 and VKA5 and
VKA3 will be the back-up chiller (it is not considered for calculations).
All calculations, which are shown next, are for the whole installation.
Appendix 1. Planned refrigeration compression installation
99
A1.2. COOLING LOAD
Table A1. 13. Operational conditions of VKA1 and VKA2 compressors
(YRWCWCT3550C) in time steps
% LOAD
CAPACITY
[kW] COP
% OPERATING
(during year)
OPERATING
TIME
[h/year]
COOLING
LOAD
[kWh/year]
100 1254 6,712 3 44,28 55 527,12
75 940,5 7,524 33 487,08 458 098,74
50 627,0 7,377 41 605,16 379 435,32
25 315,5 4,679 23 339,48 107 105,94
TOTAL
1476
(see Table A1. 15.) 1 000 167,12
Table A1. 14. Operational conditions of VKA4 and VKA5 compressors
(YKKKKLH95CQF) in time steps
% LOAD
CAPACITY
[kW]
COP
% OPERATING
(during year)
OPERATING
TIME
[h/year]
COOLING
LOAD
[kWh/year]
100 3226,0 7,148 3 44,28 142 847,28
75 2419,5 7,830 33 487,08 1 178 490,06
50 1613,0 7,868 41 605,16 976 123,08
25 806,5 6,350 23 339,48 273 790,62
TOTAL 1476 2 571 251,04
NOTE: the following Table A1. 15. shows the operation hours.
Table A1. 15. Operating time for cooling delivering during the year
Month Days hours/day hours/month
January 31 8 248
February 28 8 224
March 31 8 248
April 30 8 240
May 31 12 372
June 30 12 360
July 31 12 372
August 31 12 372
September 30 8 240
October 31 8 248
November 30 8 240
December 31 8 248
Free cooling (1936 h/year)
Compression refrigeration (1476 h/year)
Appendix 1. Planned refrigeration compression installation
100
Thus, as there are two YRWCWCT3550C compressors and other two
YKKKKLH95CQF,
TOTAL COOLING LOAD PRODUCED BY COMPRESSION
REFRIGERATION TECHNOLOGY: 7 142 836,32 kWh/year
A1.3. INPUT LOAD AND COSTS
Table A1. 16. Power needed in the compression cooling installation during the year
INPUT POWER
[kW]
OPERATING TIME
[h/year] INPUT
LOAD
[kWh/year]
Winter
time
Winter
time
Shut down
compressors
FIR
ST
ST
AG
E
KM1-P6A 75 22,5 1476 1936 6260 295 110
KM1-P6B 75 22,5 1476 1936 6260 295 110
KB1-P6A 200 60 1476 1936 6260 786 960
KB1-P6B 200 60 1476 1936 6260 786 960
VKA1/VKA2
see
Table
A1. 17. ― 1476 ― ― 149 046,48
KB1-P1 5,5 ― 1476 ― ― 8118
KB1-P2 5,5 ― 1476 ― ― 8118
KM1-P1 3 ― 1476 ― ― 4428
KM1-P2 3 ― 1476 ― ― 4428
KB1-VVX1 ― 500 ― 1936 968 000
SE
CO
ND
ST
AG
E
VKA2 see
Table
A1. 17. ― 1476 ― ― 149 046,48
VKA3 110 ― ― ― ― ―
VKA4
see
Table
A1. 18. ― 1476 ― ― 359 465,04
VKA5
see
Table
A1. 18. ― 1476 ― ― 359 465,04
KB1-P3 2,2 ― ― ― ― ―
KB1-P4 15 ― 1476 ― ― 22 140
KB1-P5 15 ― 1476 ― ― 22 140
KM1-P3 2,2 ― ― ― ― ―
KM1-P4 7,5 ― 1476 ― ― 11 070
KM1-P5 7,5 ― 1476 ― ― 11 070
TOTAL 4 240 675,04
Appendix 1. Planned refrigeration compression installation
101
Working the whole year (when the compressors are shut down too)
30% of the total power is just used in winter time and when
the compressors are not working
It is ony used in winter time, when free cooling is allowed
NOTES:
- Following Table A1. 17. and Table A1. 18. show input load for different
compressors in time steps.
Table A1. 17. Input load VKA1 and VKA2 compressors
(YRWCWCT3550C) in time steps
%
LOAD
INPUT
POWER
[kW]
OPERATING
TIME
[h/year]
INPUT
LOAD
[kWh/year]
100 187 44,28 8 280,36
75 140,25 487,08 68 312,97
50 93,5 605,16 56 582,46
25 46,75 339,48 15 870,69
TOTAL 1476 149 046,48
Table A1. 18. Input load VKA4 and VKA5 compressors
(YKKKKLH95CQF) in time steps
%
LOAD
INPUT
POWER
[kW]
OPERATING
TIME
[h/year]
INPUT
LOAD
[kWh/year]
100 451 44,28 19 970,28
75 338,25 487,08 164 754,81
50 225,5 605,16 136 463,58
25 112,75 339,48 38 276,37
TOTAL 1476 359 465,04
- Input loads for pumps should be calculated in the same way, as they
depend on the cooling load (system curve). Nevertheless, their design
curves are unkown and therefore, it has been considered they are working
at their maximum capacity except for winter time (and when compressors
are shut down too), when they work at 30% of the maximum capacity
(minimum capacity).
Appendix 1. Planned refrigeration compression installation
102
Finally, Table A1. 19. gathers together total needed load in the system and
operational costs.
Table A1. 19. Total input load and operating costs in the compression cooling installation
TOTAL INPUT LOAD [kWh/year] 4 240 675
OPERATING COSTS [SEK/year] -1SEK/kWh- 4 240 675
A1.4. TOTAL COSTS
Table A1. 20. Costs of the compressor refrigerant system
Evolution of maintenance costs (it includes parts and working time,
412 h/year, of 2 people) is shown in Figure A1. 3. below:
Figure A1. 3. Maintenance costs in the course of time
INVESTMENT
COSTS
[SEK]
COOLING EQUIPMENTS 11 129 000
BUILDING 4 000 000
PIPES INSIDE THE BUILDING 4 500 000
PUMPS AND FILTERS
INSIDE THE BUILDING 3 000 000
TOTAL: 22 629 000
COSTS OF
OPERATION
[SEK/year]
4 240 675
MAINTENANCE
COSTS
[SEK]
1st year
2nd
year
3th
year …
5th
year
6th
year …
10th
year
159 800 149 600 139 400 … 119 000 89 250 89 250 89 250
Appendix 1. Planned refrigeration compression installation
103
A1.5. PAY-BACK TIME FOR THE INVESTMENTS
Table A1. 21. Pay-back times for the compression installation
INVESTMENTS PAY-BACK TIME [years]
COOLING EQUIPMENT (compression machine) 10
PIPES 20-30
PUMPS AND FILTERS 10
As the depreciation of equipments is in roughly 10 years (the investment is
recovered), costs can be calculated for this period of time:
Table A1. 22. Total costs for the refrigeration compression
system for the first 10 years
INVESTMENT COSTS [SEK] 22 629 000
COSTS OF OPERATION [SEK] 42 406 750
MAINTENANCE COSTS 35
[SEK] 1 168 750
TOTAL [SEK] 66 204 500
Thus, TOTAL COSTS FOR 10 YEARS are: 66 204 500 SEK
6 620 450 (SEK/year)
Later on, after the first 10 years, there will be only operational and
maintenance costs.
35 Total maintenance costs are equal to the area under the curve in Figure A1. 3. This way, they
will be: (51000*5/2) + (119000-89250)*5 + (89250*10) = 1168750 SEK for ten years.
104
Appendix 2. EXPECTED COOLING DEMAND
A. CITY CENTER (LEAF)
Table A2. 1. Cooling demand of possible future customers in the city center and additional data
OWNER
NAME
OF
ESTATE
ADDRESS
N°
COOLING
INSTALLED
COOLING
DEMAND
[KW]
NOTES
Yes No
Norrporten
Kv Hövdingen, N skepparg 2 1 X 150
Kv Notanus, N Strandgatan 1 2 X 70
Kv Syndicus Kyrkogatan 4 3 X 200
Länsstyrelsen, Borgmästarplan 2 4 X Not interested
Polishuset S Centralg 1-3 5 X 350 New cooling system installed 2007
Kv Vulkanus S Sjötullsgatan 6 X 100 ‖Byggforskningen‖
Kv Vasen Lantmäterigatan 7 X 700
Kv Kapellbacken Skomakargatan 1 8 X 400 ‖Skattehuset‖
Kv. Klockstapeln Vågskrivargatan 5 9 X 200
Kv Gevalia Nygatan 25-27 10 X 250 Cooling machine installed 2004
Norrvidden Kv Skampålen 11 X 400 Present cooling system contain R22.
Kv Lektorn 12 X 200 Cooling machine installed 1998
Diös Fastigheter
Norr 23:5
(‖Skandihuset‖)
13 X 200 Old cooling machine which
need to be replaced
Postterminalen 14 X 100
Kv Nattväktaren 15 X 700 Cooling machine installed 2000
Sankt George:1 16 X 40
Kv Hoppet 17 X 40
Kv Pechlin ―Folksamhuset‖ 18 X 100 New cooling machine installed 2005
Appendix 2. Expected cooling demand
105
Table A2.1 (continuation). Cooling demand of possible future customers in the city center and additional data
OWNER
NAME
OF
ESTATE
ADDRESS
N°
COOLING
INSTALLED
COOLING
DEMAND
[KW]
NOTES
Yes No
Gavlegårdarna Alderholmen
servicehus
19 X 30
Building not erected yet.
Gavlefastigheter Kv Trähästen Förvaltningshuset 20 X 400 ―Sure‖ customer
Biblioteket ―The library‖ 21 X 700
Kv Tomväkaren
―Kommunhuset‖ 22 X 300
Teatern ―The theatre‖ 24 X 300 Need cooling solution
Konserthuset 25 350 Problem with present solution
Boultbee 26 Have two machines built 2004
Kv Kärrlandet ―Nian‖ 27 X 700 Cooling machines installed 2004.
Boetten Gamla domstolarna 28 X 45 Existing customer
Drottningatan 48 29 X 20
Kraft Foods Kv Alderholmen 30 X 500 100 kW sure, 400 kW potential
Handelsbanken Kv Skolstuvan 31 X 200
Länsmuséet Kv Plantagen ―The museum‖ 32 X 250
Jernhusen station AB Centralstationen ―Railway station‖ 33 X 60 New cooling machines installed 2005.
Banverket Kv Storön 34 X 100 Need to expand present capacity
Allokton Kv Gesällen 35 X 350
F2 Hyresbostäder Kv Borgen 36 X 40
Folkets Hus 37 X 120 Not interested at present
Kv islandsskolan 38 X 40
Norr 23:3 39 X 100 Contact by SWECO
Appendix 2. Expected cooling demand
106
Total cooling demand in the city center is 8905 kW (data for
Konserthuset was missing but it has been considered slightly bigger than for the
theatre because it is quite bigger building but activities going on there are similar).
Nevertheless, taking into account that it is unkown cooling demand of some
places (such as nº 26) and there could be more customers in the future, it is
considered a cooling demand of 9000 kW. In addition, LEAF itself needs
2500 kW of cooling. Like this,
TOTAL COOLING DEMAND FOR LEAF PRODUCTION SITE:
11 500 kW
B. KUNGSBÄCK AREA (MACKMYRA)
Table A2. 2. Customers and their cooling demand in Kungsbäck
CUSTOMER COOLING DEMAND [kW]
HOSPITAL 1700
UNIVERSITY 1800
TECHNOLOGIC PARK 1000
4500 kW has to be delivered through the main pipe of district cooling
distribution system that leaves the cooling production plant. However, it is needed
to increase production output power since the whisky factory might use cold as
well. Anyway, this cooling demand would not be much, as there is not any
cooling system in the current factory and storage rooms that are planning to build
would be underground, where temperature would be adequate (under 17 ºC). This
way,
TOTAL COOLING DEMAND FOR MACKMYRA PRODUCTION SITE:
≈ 5000 kW
Appendix 2. Expected cooling demand
107
C. JOHANNESBERGSVÄGEN AREA (JOHANNES)
Table A2. 3. Cooling demand for Johannes production site
CUSTOMER COOLING DEMAND [kW]
HEMLINGBY SHOPPING CENTERS 2000
Cooling demand of possible customers in Johannesbergsvägen area is
2000 kW. Moreover, cooling is also used at Johannes CHP plant, mainly for
the refrigeration of the turbine, which is produced by electrically driven
devices. Thus, this cooling system could be also replaced and it is like this
planning to produce the cooling needed too, which is roughly 1,3-1,4 MW, in
the absorption plant. So,
TOTAL COOLING DEMAND FOR JOHANNES PRODUCTION SITE:
3400 kW
108
Appendix 3. SPECIFICATIONS AND CALCULATIONS
REGARDING ABSORPTION COOLING
INSTALLATIONS
A3.1. ABSORPTION CHILLERS
A.3.1.1. MODELS AND THEIR CHARACTERISTICS
A. LEAF AND MACKMYRA
- SINGLE-EFFECT STEAM-FIRED ABSORPTION CHILLERS:
Carrier-Sanyo 16TJ
Appendix 3. Specifications and calculations regarding absorption cooling installations
109
(Source: Carrier-Sanyo)
Appendix 3. Specifications and calculations regarding absorption cooling installations
110
According to the brochure, 16TJ-53 absorption chiller consumes 5460 kg/h
satured steam at 100 kPa. It is known that the enthalpy of satured vapour at 1 bar
is 2675,5 kJ/kg [4] (Pressure Table of Properties of Satured Water), so:
Thus,
4,1 MW satured steam
at 1 bar 2,5 MW cooling
On the other hand, electric and cooling power to be supplied are:
P = 400V * 11,0 A * 0,8 (power factor that most generators use) = 3520 W
Pelectricity supply = 3,52 kW
P = 159 kg/s * 4,2 kJ/(kg.K) * (38,4 – 29,4) K= 6010,2 kW
Pcooling supply = 6,01 MW
Take note that the relation between capacity of the chiller used and cooling
water power as well as steam needed can be considered linear (part-load curve is
almost linear). However, the cooling water flow is usually constant. That is, i.e. an
16TJ-53 absorption chiller working at 50% of its maximum capacity (1230,5 kW)
needs 2028,92 kW of satured steam and 3005,1 kW of cooling (the water flow is
159 l/s). With regards to the electric power supply (for pumps), it is constant.
5460 kg
* 1 h
* 2675,5 kJ
= 4057,84 kW satured steam h 3600 s kg
16TJ-53
ABSORPTION
CHILLER
Appendix 3. Specifications and calculations regarding absorption cooling installations
111
- DOUBLE-EFFECT STEAM-FIRED ABSORPTION CHILLERS:
Carrier-Sanyo 16NK
Appendix 3. Specifications and calculations regarding absorption cooling installations
112
(Source: Carrier-Sanyo)
Appendix 3. Specifications and calculations regarding absorption cooling installations
113
According to the brochure, 16NK-81 absorption chiller consumes
5300 kg/h satured steam at 784 kPa. It is known that the enthalpy of satured
vapour at 8 bar is 2769,1 kJ/kg [4] (Pressure Table of Properties of Satured
Water), so:
Thus,
4,1 MW satured steam
at 8 bar 4,7 MW cooling
On the other hand, electric and cooling power to be supplied are:
P = 400V * 33,5 A * 0,8 = 10 720 W
Pelectricity supply = 10,72 kW
P = 333,9 kg/s * 4,2 kJ/(kg.K) * (35,4 – 29,4) K= 8414,28 kW
Pcooling supply = 8,41 MW
5300 kg
* 1 h
* 2769,1 kJ
= 4076,71 kW satured steam h 3600 s kg
16NK-81
ABSORPTION
CHILLER
Appendix 3. Specifications and calculations regarding absorption cooling installations
114
B. JOHANNES
Figure A3. 1. Water streams (steam and DH) at Johannes CHP plant (Source: Gävle Energi AB)
Appendix 3. Specifications and calculations regarding absorption cooling installations
115
Next Table A3. 1. shows pressures of the first steam stream extracted from
the turbine related to electricity and district heating production capacities during
the year. The values in blue point out the steam cannot be used in absorption
chillers. The last four values belong to summer period, when the boiler is running
at its minimum capacity (20 MW).
Table A3. 1. Production data and pressure of the first steam stream extracted from the
turbine (Source: Gävle Energi AB)
ELECTRICITY
[MW]
DISTRICT HEATING
[MW]
P
[kPa]
23,704 56,168 1
24,367 59,375 1,044
20,531 55,589 2,25
19,848 52,422 2,23
21,738 50,532 0,8835
11,137 34,355 2,13
10,679 32,022 2,12
12,687 30,004 0,5511
3,602 18,624 2,05
3,683 18,555 2,05
4,244 15,991 0,7415
4,449 15,723 0,7409
4,677 15,558 0,4139
4,877 15,28 0,4136
As the pressure of steam is not suitable during peak periods of cooling
demand (summer)36
, a steam-fired absorption machine cannot be introduced.
36 It is not considered the last steam stream leaving the turbine since its pressure is even lower.
Appendix 3. Specifications and calculations regarding absorption cooling installations
116
- SINGLE-EFFECT HOT WATER-FIRED ABSORPTION
CHILLERS: Carrier-Sanyo 16LJ
Appendix 3. Specifications and calculations regarding absorption cooling installations
117
(Source: Carrier-Sanyo)
Appendix 3. Specifications and calculations regarding absorption cooling installations
118
According to the brochure, 16LJ-53 absorption chiller consumes 73 l/s hot
water (95,0 °C → 86,0 °C) at its maximum cooling capacity. This is a heat supply
of:
P = m * Cp * ∆T
P [kW] = 73 [kg/s] * 4,2 [kJ/kg K] * 9 [K] = 2759,4 kW
Pheat supply = 2759 kW
On the other hand, electric and cooling power to be supplied are:
P = 400V * 11,0 A * 0,8 = 3520 W
Pelectricity supply = 3,52 kW
P = 119,2 kg/s * 4,2 kJ/(kg.K) * (38,4 – 29,4) K= 4505,76 kW
Pcooling supply = 4,51 MW
A3.1.2. INVESTMENT COSTS
Next Table A3. 2. shows price and capacity comparison of different
chillers (LJ and TJ units compared to NK units).
Table A3. 2. Price comparison of single- and double-effect units
(Source: Carrier-Sanyo)
Appendix 3. Specifications and calculations regarding absorption cooling installations
119
Investment costs for different needed models are the followings
(Table A3. 3.):
Table A3. 3. Investment costs for different absorption chiller units
(Source: Ulf Hedman, Ramboll)
ABSORPTION CHILLER PRICE [SEK]
16TJ-53 2 700 000
16LJ-53 2 700 000
16NK-81 6 200 000
16NK-71 5 300 000
16NK-41 3 000 000
A3.1.3. OPERATIONAL CONDITIONS
According to the estimations Anders Kedbrant did for refrigerant
compression cooling project, the cooling demand load curve in the city center for
2008 is as shown in Figure A3. 2., which has been divided in different cooling
power production periods.
Figure A3. 2. Cooling demand load curve (2008) divided in periods according to
the power needed to be produced
8900
7568
5223
3624
2718
693
Appendix 3. Specifications and calculations regarding absorption cooling installations
120
Information from the previous graph (Figure A3. 2.) is gathered in
Table A3. 4.
Table A3. 4. Average city center´s cooling demand in time steps for 2008
TIME PERIOD
COOLING
DEMAND
[kW]
% of max.
power 37
PRODUCTION
HOURS
(reference:
compression
refrigeration project)
Winter time:
15 November-15 March 693 7,79 964
15 March-1 April
1-15 November 2718 30,54 244
April
15 October-1 November 3624 40,72 364
1-15 May
15 September-15 October 5223 58,69 430
15 May-15 June
15 August-15 September 7568 85,03 672
Summer time:
10 June-15 August 8900 100 738
NOTE: There is no production of cooling in winter time, since free
cooling is allowed (it is needed to introduce a heat
exchanger).
Taking into account calculated percentages, cooling load during the year can
be estimated for the three production sites that are subject of studying:
37 Information from first column can be translated into percentages taking the maximum power as
reference.
Appendix 3. Specifications and calculations regarding absorption cooling installations
121
A. LEAF
Table A3. 5. Cooling load to be produced and working power of different chillers (double- and single- effect) at LEAF during the year
TIME PERIOD
% of
max.
power
COOLING
POWER
PRODUCTION
[kW]
NUMBER OF CHILLERS WORKING
& CAPACITY [kW]
TSA-16NK-81 TSA-16TJ-53
15 November-15 March 7,79 895,45 — —
15 March-1 April & 1-15 November 30,54 3512,02 3512 1756 1756
April & 15 October-1 November 40,72 4682,70 4652 (max.) 2342 2342
1-15 May & 15 September-15 October 58,69 6748,82 3375 3375 2250 2250 2250
15 May-15 June & 15 August-15 September 85,03 9778,88 3260 3260 3260 2445 2445 2445 2445
15 June-15 August 100 11500 3834 3834 3834 2300 2300 2300 2300 2300
NOTE: minimum working power of absorption chillers is 20% of their maximum capacity
Table A3. 6. Cooling power to be supplied to the chillers at LEAF during the year
TIME PERIOD COOLING OF CHILLERS –free cooling- [kW]
TSA-16NK-81 TSA-16TJ-53
15 November-15 March — —
15 March-1 April & 1-15 November 6352,31 4288,46 4288,46
April & 15 October-1 November 8414,28 5719,58 5719,58
1-15 May & 15 September-15 October 6104,51 6104,51 5494,9 5494,9 5494,9
15 May-15 June & 15 August-15 September 5896,51 5896,51 5896,51 5482,69 5482,69 5482,69 5482,69
15 June-15 August 6934,73 6934,73 6934,73 5617,01 5617,01 5617,01 5617,01 5617,01
NOTE: Heat exchangers are going to be calculated for cooling down the chillers when they are working at their maximum capacity
(security margin, just in case). Although cooling water flow is better to be constant, in this case it needs to be changed as
conditions of free cooling (temperature of water from the river), that is, the cooling power, cannot be controlled. Therefore,
necessary water flow can be set by a valve just before it goes into the chillers.
Appendix 3. Specifications and calculations regarding absorption cooling installations
122
Table A3. 7. Cooling load to be produced and working power of different chillers (double- and single- effect) at LEAF during the year
when the cooling demand is 10% higher than the estimated one
TIME PERIOD
% of
max.
power
COOLING
POWER
PRODUCTION
[kW]
NUMBER OF CHILLERS WORKING
& CAPACITY [kW]
TSA-16NK-81 TSA-16TJ-53
15 November-15 March 7,79 1012,7 — —
15 March-1 April & 1-15 November 30,54 3970,2 3970 1985 1985
April & 15 October-1 November 40,72 5293,6 2647 2647 1766 1766 1766
1-15 May & 15 September-15 October 58,69 7529,7 3815 3815 1908 1908 1908 1908
15 May-15 June & 15 August-15 September 85,03 11053,9 3685 3685 3685 2211 2211 2211 2211 2211
15 June-15 August 100 13000 4334 4334 4334 2600 2600 2600 2600 2600 2600
Table A3. 8. Cooling power to be supplied to the chillers at LEAF during the year
when the cooling demand is 10% higher than the estimated one
TIME PERIOD COOLING OF CHILLERS –free cooling- [kW]
TSA-16NK-81 TSA-16TJ-53
15 November-15 March — —
15 March-1 April & 1-15 November 7180,72 4847,72 4847,72
April & 15 October-1 November 4787,75 4787,75 4312,89 4312,89 4312,89
1-15 May & 15 September-15 October 6900,36 6900,36 4659,68 4659,68 4659,68 4659,68
15 May-15 June & 15 August-15 September 6665,22 6665,22 6665,22 5399,66 5399,66 5399,66 5399,66 5399,66
15 June-15 August 7839,10 7839,10 7839,10 6349,66 6349,66 6349,66 6349,66 6349,66 6349,66
Appendix 3. Specifications and calculations regarding absorption cooling installations
123
Table A3. 9. Cooling load to be produced and working power of different chillers (double- and single- effect) at LEAF
during the year when the cooling demand is 10% lower than the estimated one
TIME PERIOD
% of
max.
power
COOLING
POWER
PRODUCTION
[kW]
NUMBER OF CHILLERS WORKING
& CAPACITY [kW]
TSA-16NK-81 TSA-16TJ-53
15 November-15 March 7,79 779 — —
15 March-1 April & 1-15 November 30,54 3054 3054 1527 1527
April & 15 October-1 November 40,72 4072 4072 2036 2036
1-15 May & 15 September-15 October 58,69 5869 2935 2935 1957 1957 1957
15 May-15 June & 15 August-15 September 85,03 8503 4252 4252 2126 2126 2126 2126
15 June-15 August 100 10000 3334 3334 3334 2000 2000 2000 2000 2000
Table A3. 10. Cooling power to be supplied to the chillers at LEAF during the year
when the cooling demand is 10% lower than the estimated one
TIME PERIOD COOLING OF CHILLERS –free cooling- [kW]
TSA-16NK-81 TSA-16TJ-53
15 November-15 March — —
15 March-1 April & 1-15 November 5523,91 3729,21 3729,21
April & 15 October-1 November 7365,21 4972,27 4972,27
1-15 May & 15 September-15 October 5308,57 5308,57 4779,34 4779,34 4779,34
15 May-15 June & 15 August-15 September 7690,78 7690,78 5192,07 5192,07 5192,07 5192,07
15 June-15 August 6030,35 6030,35 6030,35 4884,36 4884,36 4884,36 4884,36 4884,36
Appendix 3. Specifications and calculations regarding absorption cooling installations
124
B. MACKMYRA
Table A3. 11. Cooling load to be produced and working power of different chillers
(double- and single- effect) in Mackmyra production site during the year
TIME PERIOD
% of
max.
power
COOLING
POWER
PRODUCTION
[kW]
NUMBER OF CHILLERS WORKING
& CAPACITY [kW]
TSA-16NK-81 TSA-16TJ-53
15 November-15 March 7,79 389,33 — —
15 March-1 April & 1-15 November 30,54 1526,97 1527 1527
April & 15 October-1 November 40,72 2035,96 2036 2036
1-15 May & 15 September-15 October 58,69 2934,27 2934 1467 1467
15 May-15 June & 15 August-15 September 85,03 4251,69 4252 2126 2126
15 June-15 August * 100 5000 2500 2500 2461 (max.) 2461
* TSA-16TJ- 53. Back-up chiller can be used to produce extra cooling (78 kW) which is needed
Table A3. 12. Cooling power to be supplied to the chillers during the year and necessary cooling towers in Mackmyra production site
TIME PERIOD
COOLING OF CHILLERS [kW] COOLING TOWERS NEEDED
TSA-16NK-81 TSA-16TJ-53 TSA-16NK-81 TSA-16TJ-53
15 November-15 March — — Capacity: 7691 kW
Flow: 1202,04 m3/h
ΔTmax. = 5,76 K
Capacity: 6010 kW
Flow: 572,4 m3/h
ΔTmax. = 9 K
15 March-1 April & 1-15 November 2762,12 3729,21
April & 15 October-1 November 3682,60 4972,27
1-15 May & 15 September-15 October 5306,86 3582,68 3582,68 Capacity: 4523 kW
Flow: 1202,04 m3/h
ΔTmax. = 3,39 K
Capacity: 6010 kW
Flow: 572,4 m3/h
ΔTmax. = 9 K
15 May-15 June & 15 August-15 September 7690,78 5192,07 5192,07
15 June-15 August 4522,14 4522,14 6010,2 6010,2
Appendix 3. Specifications and calculations regarding absorption cooling installations
125
Table A3. 13. Cooling load to be produced and working power of different chillers (double- and single- effect) in Mackmyra
production site during the year when the cooling demand is 10% higher than the estimated one
TIME PERIOD
% of
max.
power
COOLING
POWER
PRODUCTION
[kW]
NUMBER OF CHILLERS WORKING
& CAPACITY [kW]
TSA-16NK-81 TSA-16TJ-53
15 November-15 March 7,79 428,45 — —
15 March-1 April & 1-15 November 30,54 1679,7 1680 1680
April & 15 October-1 November 40,72 2239,6 2240 2240
1-15 May & 15 September-15 October 58,69 3227,95 3228 1614 1614
15 May-15 June & 15 August-15 September 85,03 4676,65 2338 2338 2338 2338
15 June-15 August 100 5500 2750 2750 1833 1833 1833
Table A3. 14. Cooling power to be supplied to the chillers during the year and necessary cooling towers in Mackmyra
production site when the cooling demand is 10% higher than the estimated one
TIME PERIOD
COOLING OF CHILLERS [kW] COOLING TOWERS NEEDED
TSA-16NK-81 TSA-16TJ-53 TSA-16NK-81 TSA-16TJ-53
15 November-15 March — —
Capacity: 5839 kW
Flow: 1202,04 m3/h
ΔTmax. = 4,37 K
Capacity: 5710 kW
Flow: 572,4 m3/h
ΔTmax. = 8,98 K 15 March-1 April & 1-15 November 3038,69 4102,86
April & 15 October-1 November 4051,59 5470,48 Capacity: 5710 kW
Flow: 572,4 m3/h
ΔTmax. = 8,98 K 1-15 May & 15 September-15 October 5838,63 3941,68 3941,68
Capacity: 4975 kW
Flow: 1202,04 m3/h
ΔTmax. = 3,72 K 15 May-15 June & 15 August-15 September 4228,84 4228,84 5709,81 5709,81 Capacity: 4477 kW
Flow: 572,4 m3/h
ΔTmax. = 7,04 K 15 June-15 August 4974,05 4974,05 4476,51 4476,51 4476,51
Appendix 3. Specifications and calculations regarding absorption cooling installations
126
Table A3. 15. Cooling load to be produced and working power of different chillers (double- and single- effect)
in Mackmyra production site during the year when the cooling demand is 10% lower than the estimated one
TIME PERIOD
% of
max.
power
COOLING
POWER
PRODUCTION
[kW]
NUMBER OF CHILLERS WORKING
& CAPACITY [kW]
TSA-16NK-81 TSA-16TJ-53
15 November-15 March 7,79 350,55 — —
15 March-1 April & 1-15 November 30,54 1374,3 1374 1374
April & 15 October-1 November 40,72 1832,4 1832 1832
1-15 May & 15 September-15 October 58,69 2641,05 2641 1321 1321
15 May-15 June & 15 August-15 September 85,03 2826,35 3826 1913 1913
15 June-15 August 100 4500 4500 2250 2250
Table A3. 16. Cooling power to be supplied to the chillers during the year and necessary cooling towers in Mackmyra
production site when the cooling demand is 10% lower than the estimated one
TIME PERIOD
COOLING OF CHILLERS [kW] COOLING TOWERS NEEDED
TSA-16NK-81 TSA-16TJ-53 TSA-16NK-81 TSA-16TJ-53
15 November-15 March — —
Capacity: 8140 kW
Flow: 1202,04 m3/h
ΔTmax. = 6,09 K
Capacity: 5495 kW Flow: 572,4 m3/h
ΔTmax. = 8,64 K
15 March-1 April & 1-15 November 2485,22 3355,55
April & 15 October-1 November 3313,62 4474,07
1-15 May & 15 September-15 October 4776,89 3226,12 3226,12 Capacity: 5495 kW
Flow: 572,4 m3/h
ΔTmax. = 8,64 K
15 May-15 June & 15 August-15 September 6920,26 4671,87 4671,87
15 June-15 August 8139,35 5494,90 5494,90
Appendix 3. Specifications and calculations regarding absorption cooling installations
127
C. JOHANNES
Table A3. 17. Cooling load to be produced and working power of different chillers in Johannes production site during the year
TIME PERIOD
% of max.
power for
Hemlingby
COOLING
POWER
PRODUCTION
FOR
HEMLINGBY
[kW]
TOTAL
COOLING
POWER
PRODUCTION
[kW]
NUMBER OF TSA-16LJ-53
CHILLERS WORKING
& CAPACITY [kW]
15 November-15 March 7,79 155,8 1555,8 —
15 March-1 April & 1-15 November 30,54 610,8 2010,8 1006 1006
April & 15 October-1 November 40,72 814,4 2214,4 1107 1107
1-15 May & 15 September-15 October 58,69 1173,8 2573,8 1287 1287
15 May-15 June & 15 August-15 September 85,03 1700,6 3100,6 1551 1551
15 June-15 August 100 2000 3400 1700 1700
NOTE: Cooling demand in Johannes represents the cooling needed for the turbine itself (to cool it
down because of friction energy generated by turbine´s axis and generator). Therefore, it is the
same all over the year, that is, it does not depend on the time period (outdoor temperature). This
way, cooling demand during the year has been estimated for Hemlingby shopping centers and
then, 1,4 MW for Johannes have been added up to each of them.
Appendix 3. Specifications and calculations regarding absorption cooling installations
128
Table A3. 18. Cooling power to be supplied to the chillers during the year
and necessary cooling towers in Johannes production site
TIME PERIOD COOLING OF
CHILLERS [kW]
COOLING TOWERS
NEEDED
15 November-15 March — Capacity: 4150 kW
Flow: 858,24 m3/h
ΔTmax. = 8,70 K
15 March-1 April & 1-15 November 2455,47 2455,47
April & 15 October-1 November 2701,99 2701,99
1-15 May & 15 September-15 October 3141,34 3141,34 Capacity: 4150 kW
Flow: 858,24 m3/h ΔTmax. = 8,70 K
15 May-15 June & 15 August-15 September 3785,72 3785,72
15 June-15 August 4149,40 4149,40
Table A3. 19. Cooling load to be produced and working power of different chillers in Johannes production site
when the cooling demand is 10% higher than the estimated one
TIME PERIOD
% of max.
power for
Hemlingby
COOLING
POWER
PRODUCTION
FOR
HEMLINGBY
[kW]
TOTAL
COOLING
POWER
PRODUCTION
[kW]
NUMBER OF TSA-16LJ-53
CHILLERS WORKING
& CAPACITY [kW]
15 November-15 March 7,79 171,38 1571,38 —
15 March-1 April & 1-15 November 30,54 671,88 2071,88 1036 1036
April & 15 October-1 November 40,72 895,84 2295,84 1148 1148
1-15 May & 15 September-15 October 58,69 1291,18 2691,18 1346 1346
15 May-15 June & 15 August-15 September 85,03 1870,66 3270,66 1635 1635
15 June-15 August 100 2200 3600 1800 1800
Appendix 3. Specifications and calculations regarding absorption cooling installations
129
Table A3. 20. Cooling power to be supplied to the chillers in Johannes production site during the year
when the cooling demand is 10% higher than the estimated one
TIME PERIOD COOLING OF
CHILLERS [kW]
COOLING TOWERS
NEEDED
15 November-15 March — Capacity: 4394 kW
Flow: 858,24 m3/h
ΔTmax. = 9,22 K
15 March-1 April & 1-15 November 2528,69 2528,69
April & 15 October-1 November 2802,07 2802,07
1-15 May & 15 September-15 October 3285,35 3285,35 Capacity: 4394 kW
Flow: 858,24 m3/h ΔTmax. = 9,22 K
15 May-15 June & 15 August-15 September 3990,75 3990,75
15 June-15 August 4393,48 4393,48
Table A3. 21. Cooling load to be produced and working power of different chillers in Johannes production site
when the cooling demand is 10% lower than the estimated one
TIME PERIOD
% of max.
power for
Hemlingby
COOLING
POWER
PRODUCTION
FOR
HEMLINGBY
[kW]
TOTAL
COOLING
POWER
PRODUCTION
[kW]
NUMBER OF TSA-16LJ-53
CHILLERS WORKING
& CAPACITY [kW]
15 November-15 March 7,79 140,22 1540,22 —
15 March-1 April & 1-15 November 30,54 549,72 1949,72 975 975
April & 15 October-1 November 40,72 732,96 2132,96 1066 1066
1-15 May & 15 September-15 October 58,69 1056,42 2456,42 1228 1228
15 May-15 June & 15 August-15 September 85,03 1530,54 2930,57 1465 1465
15 June-15 August 100 1800 3200 1600 1600
Appendix 3. Specifications and calculations regarding absorption cooling installations
130
Table A3. 22. Cooling power to be supplied to the chillers in Johannes production site during
the year when the cooling demand is 10% lower than the estimated one
TIME PERIOD COOLING OF
CHILLERS [kW]
COOLING TOWERS
NEEDED
15 November-15 March — Capacity: 3906 kW Flow: 858,24 m3/h
ΔTmax. = 8,19 K
15 March-1 April & 1-15 November 2379,80 2379,80
April & 15 October-1 November 2601,92 2601,92
1-15 May & 15 September-15 October 2997,33 2997,33 Capacity: 3906 kW
Flow: 858,24 m3/h
ΔTmax. = 8,19 K
15 May-15 June & 15 August-15
September 3575,81 3575,81
15 June-15 August 3905,32 3905,32
Appendix 3. Specifications and calculations regarding absorption cooling installations
131
A3.2. THE REST OF EQUIPMENTS
Table A3. 23. Required cooling towers and heat exchangers´ technical data
PRODUCTION SITE COOLING TOWERS HEAT EXCHANGERS (+FILTER)
-chillers´cooling down-
HEAT EXCHANGERS
(+FILTER)
-free cooling-
LEAF
16NK-81
chillers —
S121-IS10-502-TMTL47-LIQUIDE (Sondex)
Flow: 339 kg/s
Capacity: 8505 kW
FILTER: BSG350/1,0P (Bernoulli)
TL10-BFG (Alfa Laval)
Flow: 38,7 l/s
Capacity: 895,0 kW 16TJ-53
chillers —
MX25-MFMS (Alfa Laval)
Flow: 241,4 l/s
Capacity: 6010 kW
MACKMYRA
16NK-81
chillers
OCT09HB05-5-90 (Vestas Aircoil)
Flow: 1221 m3/h. Evaporation: 10,9 m3/h
Capacity: 5988 kW
Number of fans: 5
Air flow/fan: 30,41 m3/s. Rotation speed: 439 rpm
Electric power supply/fan: 6,1 kW
—
TL10-BFG (Alfa Laval)
Flow: 16,8 l/s
Tin = 12,2ºC. Tout = 6,7 ºC
16TJ-53
chillers
OCT09HB03-3-120 (Vestas Aircoil)
Flow: 573 m3/h. Evaporation: 7,7 m3/h
Capacity: 8499 kW
Number of fans: 3
Air flow/fan: 21,29 m3/s. Rotation speed: 340 rpm
Electric power supply/fan: 5,14 kW
—
JOHANNES 16LJ-53
chillers
OCT09HB02-2-120 (Vestas Aircoil)
Flow: 429 m3/h. Evaporation: 5,7 m3/h
Capacity: 4483 kW
Number of fans: 2
Air flow/fan: 23,91 m3/s. Rotation speed: 531 rpm
Electric power supply/fan: 7,3 kW
— —
Appendix 3. Specifications and calculations regarding absorption cooling installations
132
NOTE 1: Power of cooling towers is determined by fan´s air flow (cooling
water flow is constant), of which relation can be considered to be
linear. For calculating power of fans (electricity supply), following
equations are used:
q1/q2 =n1/n2
P1/P2 = (n1/n2)3
where:
- q: fan´s air flow
- n: fan´s rotation speed (rpm)
- P: power
NOTE 2: Size of equipments
- LEAF. Same heat exchangers have been considered for the three cases
since differences between the needed capacities are not so large and, in
addition, those equipments can work at 10% higher capacity than the
specified one.
- MACKMYRA. The highest capacity between required cooling
equipments have been approximately taking into consideration to make
the decision about the cooling towers to be introduced. They are valid for
all cases as the flow is constant, so they will work according to the needed
cooling capacity (they are too big in some cases but data about more
adequate towers could not be obtained).
- JOHANNES. Cooling tower has been choosen so that it can cover the
cooling demand in the three cases, as the differences are not so large.
133
Appendix 4. MAPS OF CUSTOMERS AND DISTANCES FROM THE PRODUCTION SITES
A. CITY CENTER (LEAF)
Figure A4. 1. Map of the city center with the main pipe that leaves LEAF production site and its length
Appendix 4. Plans of customers and distances from the production sites
134
It has been followed the same way for the main pipe as in the refrigerant
compression cooling project, since the production site and customers are the same
and, in addition, as necessary remarks for this decision have been already taken
into account.
Appendix 4. Plans of customers and distances from the production sites
135
B. KUNGSBÄCK AREA (MACKMYRA)
Figure A4. 2. Map with the customers, pipes and distances for Mackmyra production site
Appendix 4. Plans of customers and distances from the production sites
136
The pipe which arrives at hospital from Mackmyra would need to go
through the technologic park, since it is also a customer. This way, it has been
decided to follow the direction of roads and the existing district heating
installation.
Appendix 4. Plans of customers and distances from the production sites
137
C. JOHANNESBERGSVÄGEN AREA (JOHANNES)
Figure A4. 3. Map with the customers for Johannes production site, pipe and its length
HEMLINGBY SHOPPING CENTERS
Johannes
Appendix 4. Plans of customers and distances from the production sites
138
The absorption plant at Johannes would be used to fulfil the cooling
demand of the existing Hemlingby shopping center and buildings which are under
construction now, with a total cooling floor area of 35 000 m2
(see Figure A4. 4.).
The extension is expected to be finished by this summer (2009).
Figure A4. 4. Map of the shopping centers under construction in Hemlingby
For this reason, the main distribution pipe is planning to be between all
these buildings. Once the pipe would leave the constructed area, it would go
through the forest, since its digging is cheaper than road´s, and cross E4 highway
taking the advantage that it already exists a tunnel there. Thereafter, it would
reach the production plant as drawn because of the possibility of future customers
over there. Next Figure A4. 5. shows the future plan of the municipality of
building a new area close to Johannes CHP plant.
Appendix 4. Plans of customers and distances from the production sites
139
Figure A4. 5. Map of the future residential area close to Johannes plant
140
Appendix 5. CALCULATIONS ABOUT DIMENSIONS OF PIPES, DISTRIBUTION PUMPS
AND THEIR COSTS
A5.1. DIMENSIONING
Table A5. 1. Dimensioning of pipes and pressure drop (part I)
PRODUCTION
SITE PIPES CUSTOMER
COOLING
DEMAND
[kW]
DISTANCE
[m]
MASS FLOW
[kg/s]
VOLUMETRIC
FLOW
[m3/h]
LEAF LEAF CITY CENTER 9000 1370 214,29 771,43
MACKMYRA
Mackmyra I
HOSPITAL 1700
UNIVERSITY 1800
TECHNOLOGIC
PARK 1000
TOTAL 4500 500 107,14 385,71
Mackmyra II UNIVERSITY 1800 310 42,86 154,29
Mackmyra III
HOSPITAL 1700
TECHNOLOGIC
PARK 1000
TOTAL 2700 1890 64,29 231,43
JOHANNES Johannes
HEMLINGBY
SHOPPING
CENTERS 2000 1775 47,62 171,43
NOTE: Mass flow: P [kW] = m [kg/s] * Cp [kJ/kg K] * ∆T [K] → m = P/Cp/∆T
Appendix 5. Calculations about dimensions of pipes, distribution pumps and their costs
141
Table A5. 2. Dimensioning of pipes and pressure drop (part II)
PRODUCTION
SITE PIPES CUSTOMER
CROSS
SECTION OF
THE PIPE [m2]
INTERNAL
DIAMETER
OF THE PIPE
[mm]
RESISTANCE
[Pa/m]
PRESSURE
LOSS for
each pipe [Pa]
PRESSURE FOR
DISTRIBUTION
PUMP [Pa] 38
LEAF LEAF CITY CENTER 0,11 369,44 65 89050 328100
MACKMYRA
Mackmyra I
HOSPITAL
UNIVERSITY
TECHNOLOGIC
PARK
TOTAL 0,05 261,24 100 50000 25000
Mackmyra II UNIVERSITY 0,02 165,22 175 54250 258500
Mackmyra III
HOSPITAL
TECHNOLOGIC
PARK
TOTAL 0,032 202,35 130 245700 641400
JOHANNES Johannes
HEMLINGBY
SHOPPING
CENTERS
0,02 174,16 160 284000 718000
NOTES (in the next page):
38 As the flow passes through pipes and other components in the system, the pressure decreases. Thus, it is needed a pressure difference in the system which is
generated in the pump and which is progressively dissipated by pressure losses in the distribution system with increasing distance from the pump. This is
shown in schematic Figure A5. 2.
Appendix 5. Calculations about dimensions of pipes, distribution pumps and their costs
142
NOTES:
- Diameter of pipes: ø = 2 √(A/π)
- The cross section of pipes has been calculated for a velocity of water flow of 2 m/s
(it is usually between 1 and 3 m/s for large pipes), for considering it the most
suitable (Greger Berglund).
- The resistances have been calculated by using a SBI nomogram that can be seen in
the following page (Figure A5. 1.).
- Pressure increase that is needed (distribution pump) has been calculated considering
that there is a pressure drop of 150 kPa in the customer site (Greger Berglund),
although it is usually enough with 30-50 kPa –safety margin-.
Appendix 5. Calculations about dimensions of pipes, distribution pumps and their costs
143
Figure A5. 1. SBI monogram showing the parameters of the different pipes
Appendix 5. Calculations about dimensions of pipes, distribution pumps and their costs
144
Figure A5. 2. Differential pressures in a direct return distribution
system with one terminal unit
Distribution losses could be calculated as following:
(Source: lecture of Energy Systems, HIG, by Heimo Zeinko)
Nevertheless, they are not taken into consideration because of being very small.
There is only a temperature difference of 4ºC between the water that goes through
pipes and outside, so the resistances are therefore almost zero.
Appendix 5. Calculations about dimensions of pipes, distribution pumps and their costs
145
Going back to the diameter of pipes, outer diameters have been obtained
by using the following Table A5. 3. once internal diameters (see Table A5. 2.)
have been calculated.
Table A5. 3. PE Pressure Pipes for water supply: EN 12201, ISO 4427
(Source: PE Pressure Pipe Systems brochure)
Appendix 5. Calculations about dimensions of pipes, distribution pumps and their costs
146
Finally, Table A5. 4. shows the dimension of pipes needed.
Table A5. 4. Data of the pipes needed
PIPES MATERIAL dn 39
[mm]
LEAF KWH PE, PN10 40 450
Mackmyra I KWH PE, PN10 315
Mackmyra II KWH PE, PN10 200
Mackmyra III KWH PE, PN10 250
Johannes KWH PE, PN10 200
A5.2. COSTS
A. DIGGING FOR PIPES AND TOTAL COSTS
The distribution system in ground looks like it is shown in Figure A5. 3..
Ground is dug and two pipes, forward and return ones, are introduced keeping the
distances (Greger Berglund) that can be observed in the figure. The hole is filled
with sand.
Figure A5. 3. Piping excavation section
39 dn: nominal outer diameter 40 PN: nominal pressure. Maximum pressure for plastic pipes is 10 bar (PN10).
Appendix 5. Calculations about dimensions of pipes, distribution pumps and their costs
147
The values of parameters B and C from Figure A5. 3. depend on the outer
diameter, dn. Those are gathered in Table A5. 5.
Table A5. 5. Values of parameters C and B for the required dn
(Source: Greger Berglund, Gävle Energi AB)
dn [mm] C [mm] B [mm]
200 400 1000
250 450 1100
315 525 1250
NOTE: data for dn = 315 mm was missing, so the values have been interpolated
from the values of the original data and rounded off.
When pipes are going through water (as appropiate for LEAF), the
installation is totally different. Pipes are placed in the bottom of the river (or sea,
in other cases), keeping a distance of described C value between them. It would be
750 mm for LEAF pipes (dn = 450).
Next, costs of the main distribution system are shown, Table A5. 6.,
without taking into account the pumps.
Table A5. 6. Total cost of the pipes
(Source: Greger Berglund, Gävle Energi AB, and Anders Kedbrant, SWECO)
PIPE COST SINGLE
PIPE [SEK/m]
COUNTRY SIDE
MACKMYRA I 3408
MACKMYRA II 2698
MACKMYRA III 3053
JOHANNES 2698
WATER –river- LEAF 2500
Cost for pipes in countryside can be splitted up in its different
components. This way, the following graph in Figure A5. 4. shows it in
percentages.
Appendix 5. Calculations about dimensions of pipes, distribution pumps and their costs
148
Figure A5. 4. Distribution system cost split up in its components and their contribution to
the total cost
Finally, total costs of the distribution system except for the pumps can be
calculated:
Table A5. 7. Calculation of the pipes´ costs
PRODUCTION
SITE PIPE
DISTANCE
[m]
COST
[SEK/m]
COST
PER PIPE
[SEK]
TOTAL
COST
[SEK]
LEAF LEAF 1 370 2500 3 425 000 6 850 000
MACKMYRA
Mackmyra I 500 3 408 1 704 000 3 408 000
Mackmyra II 310 2 698 836 380 1 672 760
Mackmyra III 1 890 3 053 5 770 170 11 540 340
TOTAL 16 621 100
JOHANNES Johannes 1 775 2 698 4 788 950 9 577 900
Appendix 5. Calculations about dimensions of pipes, distribution pumps and their costs
149
B. PUMPS
Table A5. 8. Needed distribution pumps and their cost (Source: Zander & Ingeström AB)
PRODUCTION
SITE
Q 41
[m3/h]
P
[kPa] PUMP TYPE
MAX.
POWER
CONS.
[kW]
PRICE
[SEK]
LEAF 771,43 328,1 KENFLO centrifugal
pump, KPS 30-250 77,4 110 000
MACKMYRA 317,14 250 KENFLO centrifugal
pump, ISO 200x150-315 27,5 62 000
JOHANNES 171,43 718 KENFLO centrifugal
pump, ISO 100x65-250 44,5 69 000
NOTE: Electric power consumption cannot be calculated in accordance
with pumps´ working power during the year as their design curves
are unkown. Thus, it has been assumed that they work the same
way as pumps from compression refrigerant cooling project and
therefore considered that they are working at their maximum
capacity all over the year except for winter time and for when
chillers are shut down, when they work at 30% of the maximum
capacity.
41 Q: volumetric flow
150
Appendix 6. FALUN COOLING PROJECT: A REFERENCE
A6.1. INSTALLATION
Figure A6. 1. Draft of the whole cooling installation in Falun (Source: Daniel Widman, Falu Energi & Vatten AB)
Appendix 6. Falun cooling project: a reference
151
Table A6. 1. Reference specifications about absorption chiller in Falun
(Source: Carrier-Sanyo)
There are additional remarkable devices in the installation, such as:
- A compression chiller of 1290 kW. It has two functions: to keep cooling in
reserve and to fulfil the demand in periods of higher loads.
- Two BAC (Baltimore Air Coil) VXT 470 cooling towers.
- Grundfos pumps. Distribution pumps: FK-P01 (50 kW).
Appendix 6. Falun cooling project: a reference
152
A6.2. TOTAL COSTS
Table A6. 2. Investment costs for different installations in Falun
COST OF THE WHOLE INSTALLATION [SEK] 10 000 000
COST OF THE COMPRESSION COOLING MACHINE [SEK] 1 500 000
COST OF THE ABSORPTION CHILLER [SEK] 2 700 000
COST OF THE COOLING TOWERS [SEK] 2 * 675 000
COST OF THE DISTRIBUTION PUMPS [SEK] 100 000
Like this, the COST of the INSTALLATION without distribution pumps,
chillers and cooling towers is 1 450 000 SEK.
Maintenance costs are very low, so they are therefore not taken into
account. With regards to operational costs, they are calculated as sum of electric
power needed and water for cooling towers (it is assumed that steam is free). This
way, it is needed to assess costs for 250 kW plus 50 kW per each distribution
pump of electricity (≈1 SEK/kWh) and 10 m3/h of water (≈4 SEK/ m
3).
Total electric consumption of the whole installation is made up of:
Table A6. 3. Input electric power in Falun installations
TOTAL 250 kW
POWER SUPPLY TO THE ABSORPTION CHILLER 5,84 kW 42
POWER SUPPLY TO THE COOLING TOWERS
(there are 2 fans in each cooling tower) 2 * 30,0 kW
POWER NEEDED IN THE REST OF THE INSTALLATION 184,16 kW
NOTE: Compressor chiller´s input power at its maximum capacity is
300 kW. Nevertheless, it is not included as it is seldom
working.
42 P = 7,3 kVA * 0,8 (power factor that most generators use) = 5,84 kW
153
Johannes plant has a biofueled steam boiler, where there are mainly burnt
bark, forest residues and waste wood43
. Nonetheless, it is needed oil to start up the
plant (which takes between 12 and 18 hours) and unfortunately, this fuel has to be
also sometimes used because of technical problems.
Next, basic scheme of the plant is shown in Figure A7. 1. for explaining
how it operates thereafter.
Figure A7. 1. Scheme of Johannes CHP plant (Source: Gävle Energi AB)
The different types of biofuel, which are stored according to their
composition in different piles outside (see Figure A7. 2.), are mixed and carried
43 The blending changes frecuently, which depends on the availability of different fuels, costs and
so forth.
Appendix 7. EXTRA INFORMATION ABOUT
JOHANNES POWER PLANT
1
4
5
7
8
9
10
1. FUEL INTAKE
2. SIEVING (fuel mixer)
3. FUEL STORAGE
4. CONVEYOR BELT FOR BIOFUEL UP TO THE BOILER
5. STEAM BOILER
6. DIRECT CONDENSER
7. TURBINE
8. VESSEL ACCUMULATORS
9. ELECTROSTATIC PRECIPITATOR
10. FLUE GAS CONDENSER (FGC)
11. CHIMNEY STACK
12. CONTROL ROOM
13. OIL TANK
14. AMMONIA TANK
11
2
3
6
12
13 14
Appendix 7. Extra information about Johannes power plant
154
into a silo (sieving). Afterwards, the fuel mixture is put on a fuel storage building.
This place has a fuel capacity of a weekend production, since there is nobody
working on fulfilling it during this period.
Figure A7. 2. Fuel storage
44 and conveyor belt carrying biofuel to the boiler at Johannes
The biofuel mixture is transported to the boiler using a conveyor belt
(which gets in a fuel container) as means of transport (see Figure A7. 2.), where it
is then burned. The steam boiler, which scheme is shown in Figure A7. 3., is a
Bubble Fluidized Bed (BFB) with a maximum capacity of 77 MW.
Biofuel enters the boiler through two intakes together with some air (it is
injected in order to avoid flames go into fuel silo). Primary air goes in the bottom,
where a sand bed is. There, solid fuel is suspended on upward-blowing jets of air
and a turbulent mixing is achieved. As a result, more effective combustion and
heat transfer take place.
The combustion heats water, which is coverted into superheated steam at
high and constant pressure. The steam leaving the boiler goes thereafter to the
turbine.
44 This picture was taken the 24th of March of 2009, when it was still winter. Despite the snow
and cold weather, biofuel keeps well since it is warm inside due to reactions (aerobic
decomposition of organic matter) that take place in there.
Appendix 7. Extra information about Johannes power plant
155
Figure A7. 3. Bubble Fluidized Bed (BFB) boiler of Johannes CHP plant
(Source: Gävle Energi AB)
The turbine called Olga was installed in 2005, which means that there
was previously a direct condenser instead that was used to cool down the steam by
means of district heating return water (it is still in there in case of a breakdown or
higher heating demands). It is a backpressure turbine, model Siemens SST-600,
which works in two steps and has a power output capacity of 22 MW (see
Figure A7. 4. and left side of Figure A7. 5.), where electricity is produced by
expanding and cooling the steam.
The exhaust steam leaving the turbine is then condensed in two heat
exchangers (see right side of Figure A7. 5.) and the water that extracts heat from
the steam goes to the supply pipe of the district heating network. When heat
supply is higher than the demand, hot water is stored, what there are two heat
accumulators for, and this way, it is delivered when the demand is higher
(compensation of load variations).
Characteristics of obtained electricity and water for district heating are
gathered in Table A7. 1.
29 kg/s
94 bar
Appendix 7. Extra information about Johannes power plant
156
Figure A7. 4. Illustrative drawing of Olga turbine and components
(Source: Gävle Energi AB)
Figure A7. 5. Olga turbine on the left side and heat exchangers on the right side. Johannes
CHP plant
Table A7. 1. Characteristics of the obtained outputs at Johannes
ELECTRICITY
Power 23MW
Generator voltage 11 kV
DISTRICT HEATING
Power 50 MW
Forward temperature 96 ºC
Return temperature 67 ºC
Exhaust gases leaving the boiler go through an electrostatic precipitator in
order to eliminate particulate matter and after that heat is extracted in a flue-gas
Turbine
Generator
Heat exchangers
Appendix 7. Extra information about Johannes power plant
157
condensation system (see Figure A7. 6. and for more specified information,
Figure A7. 7.). This waste heat is also used in the district heating network and
sand-ashes, together with the sand extracted from the bottom of the boiler and
cleaned in a rotational sieve, are recycled for reutilizing them in the boiler.
Figure A7. 6. Schematic of the FGC at Johannes (Source: Gävle Energi AB)
Figure A7. 7. Detailed scheme of the condensate treatment plant at Johannes
(Source: Gävle Energi AB)
Moreover, there is a water purification system where ultrapure water
(conductivity < 20 μS/m) is obtained as it is required for the boiler. The
technology is called EDI (electrodeionisation), which combines ion exchange and
membrane filtering.