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MENG 547 Energy Management & Utilization Chapter 5 Energy Management in Buildings Prof. Dr. Ugur Atikol, cea Director of EMU Energy Research Centre
Transcript of Energy Management & Utilization - staff.emu.edu.tr
MENG 547 Energy Management & Utilization
Chapter 5
Energy Management in Buildings
Prof. Dr. Ugur Atikol, cea Director of EMU Energy Research Centre
Presenter
Presentation Notes
Energy Auditing A process to Take inventory of components that affect building energy use. Collect information about the operational characteristics of the facility. Collect utility data. Analyze collected data. Recommend opportunities to reduce consumption. Energy and cost savings. For example: The more you know about the occupancy schedules of a building, the easier it becomes to identify set backs. Can be manual or by automated controls. Energy audits Mean different things to different individuals. Should be defined prior to beginning audit activities. This section will Review various approaches. Outline a standard approach.
Energy Utilization in Buildings
Electric energy or work
Thermal energy (using fuels such as LPG, natural gas, diesel oil etc)
Thermal energy losses or gains from the envelope
Energy Efficiency in Buildings Making more use of the available energy or doing the
same amount of work with less energy Example: Washing the same laundry with less electricity in
a washing machine
Energy conversion
device
Energy Input
Useful Energy Output or Work Done
Lost or Wasted Energy
𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬 =𝑼𝑼𝑬𝑬𝑼𝑼 𝑬𝑬𝑬𝑬𝑬𝑬 𝑶𝑼𝑶𝑶𝑼𝑶
𝑬𝑬𝑬𝑬𝑬𝑬 𝑰𝑬𝑶𝑼𝑶
Why buildings are important? Buildings consume large amounts of eneregy everywhere
in the world. Buildings account for roughly 40% of all U.S. energy use
Source: http://howcanihelpsandiego.com/lighter-side-of-green/
Energy Use in Buildings Residences: Depending on seasons heaters, air conditioners, lighting, washing
machines, television sets etc are used
Figures show the end-uses of residences in 1996 for N. Cyprus (Source: Atikol et al., 1999)
Energy Use in Buildings Hotels: Depending on seasons heaters, air conditioners, lighting,
refrigeration, television sets etc are used
Figures show the end-uses of hotels in 1997 for N. Cyprus (Source: Atikol, 2004)
Space Heating
Cold Room
Refrigeration
Lighting
Water Heating
0
2
4
6
8
10
12
14
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Hours
Dem
and,
MW
Water HeatingLightingRefrigerationCold RoomSpace Heating
Air Conditioning
Lighting
Water Heating
0
5
10
15
20
25
30
35
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Hours
Dem
and,
MW
Water HeatingLightingRefrigeratorsCold RoomsAir Conditioning
Energy Efficiency Opportunities in Buildings
Building Operation Building Envelope HVAC Systems HVAC Distribution Systems Water Heating Systems Lighting Systems Power Systems Energy Management Control Systems Heat Recovery Systems
Renewable Energy and Energy Efficiency
Source: http://lunar.thegamez.net/greentechnology/energy-efficient-house-plans/specialise-in-and-only-allow-house-designs-that-are-energy-efficient-1263x1040.jpg
Building Opperation
When the building is not occupied, the building systems should be turned off or their operation reduced to a
minimum.
Building Envelope Energy is saved when the heat exchange between the
building and the outside environment is reduced and/or solar and internal heat gains are controlled.
Winter heat losses Summer heat gains
Building Envelope Energy is saved when the heat exchange between the
building and the outside environment is reduced and/or solar and internal heat gains are controlled.
•Thermal insulation •Infiltration control •Roof color •Solar gains •Window shading •Landscaping •Window quality •Heat bridge
F - 12
Building Envelope
Thermal Insulation
1) Cushion, 2) Beam rafter, 3) Roofmate* PS thermal resistance board 4) Water proofing membrane 5) Tilling battens 6) Counter battens 7) Face wood 8) Roof cover (roof tiles, schingle)
Source:http://www.bulak.net/dow_roofmate_ps_Eng.asp
Building Envelope Insulation: Multilayer Plane Walls
totalRTT
Q 2,1, ∞∞ −=
AhAkL
AkL
Ah
RRRRR convwallwallconvtotal
22
2
1
1
1
2,2,1,1,
11 +++=
+++=
U-value = 1/Rtotal Such that:
)( 2,1, ∞∞ −××= TTAUQ
Building Envelope
Windows: Multi-glazing Windows
)( 2,1, ∞∞ −××= TTAUQ
( )4 4rad s surrQ A T Tεσ= −
Radiation heat transfer:
Heat losses through windows:
Heat loss through a single pane window Glass area: A = 0.8m × 1.5m = 1.2 m2
k = 0.78 W/m-oC. o
,1 2 o 21
1 1 0.08333 C/W(10W/m . C)(1.2m )i convR R
h A= = = =
oo 2
0.008m 0.00855 C/W(0.78W/m. C)(1.2m )glass
LRk
= = =
o,2 2 o 2
2
1 1 0.02083 C/W(40W/m . C)(1.2m )o convR R
h A= = = =
,1 ,2o
0.08333 0.00855 0.02083 0.1127 C/W
total conv glass convR R R R= + + = + +=
o,1 ,2
o[20 ( 10)] C 266W0.1127 C/Wtotal
T TQ
R∞ ∞− − −
= = =
,1 1 o1 1 ,1
,1
2.2 Cconvconv
T TQ T T QR
R∞
∞
−= → = − = − Formation of fog or frost on the
surface
Building Envelope: Example
Heat loss through a double pane window o
,11
1 0.08333 C/Wi convR Rh A
= = =
o11 3
1
0.00427 C/WglassLR R R
k A= = = =
o22
2
0.3205 C/WairLR R
k A= = =
o,2
2
1 0.02083 C/Wo convR Rh A
= = =o
,1 ,1 ,2 ,2 0.4332 C/Wtotal conv glass air glass convR R R R R R= + + + + =o
,1 ,2o
[20 ( 10)] C 69.2W0.4332 C/Wtotal
T TQ
R∞ ∞− − −
= = =
which is 1/4th of the previous result. Inner surface temperature of the window:
o1 1 ,1 14.2 CconvT T QR∞= − = no fogging
Building Envelope: Example
HVAC Systems Use efficient equipment
Ventilation requirements must be correctly determined
Efficiently designed distribution system
Controls for efficiency
Pay attention to hours of operation
Building envelope
Fuel Flow pipe
Return pipe
To radiotors, fan convectors or floor heating
Central heating Boiler
Central Heating with Boilers
Pump
η = 0.83 – 0.95
Burner
Central Heating with Boilers
HVAC Systems
Pump
AHU
FCU-1 FCU-2 FCU-3
Duct
Cool Air
Flow
Return
Flow water ~ 7 deg C Return water ~ 13 deg C
Central Cooling with Chillers
COP = 2.5 – 3.5
HVAC Systems
Room Thermostat
3-way valve
Flow
Ret
urn
Fan Condensate tray
3-way valve
Fan-coil connection
HVAC Systems
Eva
pora
tor
Con
dens
er
Compressor
Expansion valve
120 kPa -20oC
800 kPa 60oC
800 kPa 30oC
120 kPa -25oC
Heat absorbed by evaporator
Heat rejected by condenser
Gas line
Liquid line
Gas line
Liquid line
Refrigeration Cycle
Variable Speed Drives (VSDs) for Energy Efficiency in HVAC Systems Large savings can be achieved by using variable
speed drives for fans, compressors and pumps. The cube law says:
Example: If fan speed is reduced by a half, the power consumed is reduced by 1
8.
[ ][ ]3
3
old
new
old
new
RPMRPM
kWkW
=
HVAC Systems
HVAC Systems
Con
dens
er
Compressor (Variable speed drive)
Expansion valves
Atmosphere
Eva
pora
tor
Eva
pora
tor
Eva
pora
tor
Variable Refrigerant Volume (VRV) System
HVAC Systems
Outdoor unit comprise of • condenser (evaporator) • compressor • Fans
Warm Air Flow
Cool Air Flow
Indoor units comprise of: • expansion valve • evaporator (condenser) • fan
Fans
VRV System in summer mode
Atmosphere
HVAC Systems
Eva
pora
tor
Con
dens
er
Compressor
Expansion valve
Ground or Water
reservoir Heat Heat
Energy storage: Water tank
Flow
to fa
n-co
ils
Ret
urn
from
fan-
coils
Water cooling/heating with chillers orheat pump systems
HVAC Systems
Room Thermostat
3-way valve
Flow
Ret
urn
Fan Condensate tray
3-way valve
Fan-coil connection
HVAC Systems
Eva
pora
tor
Compressor (Variable speed drive)
Expansion valve E
vapo
rato
r
Eva
pora
tor
Con
dens
er
Heat
Energy sink: Water reservoir
Ground or Water Source VRV System
Heating and Cooling Degree Days
Used to evaluate effects of weather Heating and cooling degree days (HDD, CDD) Balance point temperature, Tbal is defined as that value of
the outdoor temperature, where (for a specified value of indoor temperature, Ti) the total heat loss is equal to the free heat gain (from the sun, occupants etc.)
The standard value of the balance point temperature is 18,3 °C
If Ktot is the total heat loss of the building:
gainbalitot QTTK =− )(
Heating and Cooling Degree Days To = Average daily temperature HDD = balance point temp – average daily temperature
Daily high temperature: 6,7 °C Daily low temperature: -2,2 °C Daily average temperature = (6,7 – 2,2) / 2 = 2,2 HDD = 18.3 – 2,2 = 16,1 HDD for the day
For 365 days:
Heating is only needed when To drops below Tbal
∑=
−=365
1, )(
jjobal TTHDD
Heating and Cooling Degree Days For estimating annual heating that uses a heating system with
efficiency η :
Degree-days for a balance temperature of 18oC in Europe or 65oF (18.3oC) in the United States have been widely tabulated.
HDDKQ totyrh ×=
η,
Water heating energy is conserved by reducing load requirements, reducing distribution losses, and improving the efficiency of the
water heating systems.
•Flow Restrictors •Tank and Pipe Insulation •Supply Temperatures
•Leaks and Drips •Seasonal Operation •Equipment Efficiency
Water Heating Systems
Presenter
Presentation Notes
Water Heating Systems In most facilities, heating and distribution of hot water consumes less energy than space conditioning and lighting. In certain other facilities water heating takes a much larger share of energy consumption. These are - hospitals - restaurants - kitchens - laundries Water heating energy is conserved by - reducing load requirements - reducing distribution losses - improving the efficiency of water heaters
Hot water generation with central boiler
Fuel
Hot Water Cylinder
Flow
Return
Indirect heating
To radiotors, fan convectors or floor heating
Central heating Boiler
Water Heating Systems
Pump
Photovoltaic panels
Solar Collectors
η = 0.83 – 0.95
η = 0.80 – 0.85
η = 0.15 – 0.20 Burner
Warm air
Cool air
Water Heating Systems Hot water generation with heat pump (COP = 3.0 – 5.0)
Water Heating Systems
Eva
pora
tor
Con
dens
er
Compressor
Expansion valve
Heat Heat
Energy source: Water reservoir or Lake or sea
Energy storage: Water tank
Hot
wat
er o
utle
t
Col
d w
ater
inle
t Water source heat pump system (COP = 4.0 – 7.0)
Solar electricity
Proper lighting levels Higher lamp efficiency Reduced operating hours Daylighting Lighting maintenance
Lighting Systems
Presenter
Presentation Notes
Lighting Systems Lighting accounts for a significant portion of electrical energy consumed in a building. Energy is saved and electric demand is reduced by - reducing illumination levels - improving lighting system efficiency - curtailing operating hours - using daylighting Lighting measures reduce internal heat gains. Therefore, lighting measures increase heating requirements and decrease cooling requirements. However, this heat-of-light is often a relatively expensive method of heating a building. If the building cooling plant is to be replaced, lighting ECMs can reduce the required plant size.
Power Factor Correction (High efficiency motors, ballasts, correction devices)
Improving Efficiency (Transformers, motor sizing, efficiency, and VSD)
Demand Control Cogeneration
Power Systems
100 MWh Fuel
Cogeneration 35 % Electrical efficiency 50 % Thermal efficiency
35 MWh
Power
50 MWh Heat
15 MWh Losses
Presenter
Presentation Notes
Power Systems The main reason for inefficient operation of power systems is low power factor. Power factor correction is cost-effective when utility penalties are imposed. Low power factors can be improved with - capacitors - high-efficiency motors. Additional energy can be saved with - energy efficient transformers - smaller or higher efficiency motors - variable-speed motor drives Peak power demand can be reduced by - load-shedding - cogeneration - cool storage systems that produce cold water or ice during off-peak hours Load-shedding may also reduce the total power consumption, as well as the demand. Cogeneration systems will increase the use of onsite energy, but can also replace electricity consumption with less expensive fossil energy. Also, the waste heat from the cogeneration equipment can meet thermal loads. Cool storage systems shift the chiller demand to off-peak periods, reducing on-peak demand. Evaluation of these ECMs requires a determination of the building demand profile. Several weeks of data in 15-minute intervals should be taken with a recording meter. The measurements may have to be taken both in the cooling and heating season. Many electric utilities have energy interval data available or will provide this service at a nominal charge.
Efficiency with Cogeneration
Source: http://www.nscusa.com/chp/pmicogeneration.aspx
Recuperator: A recuperator is a special purpose counter-flow heat exchanger used to recover waste heat from exhaust gases. In many types of processes, combustion is used to generate heat, and the recuperator
serves to recuperate, or reclaim this heat, in order to reuse or recycle it.
Flue type recuperator Radiation type recuperator
(Source: www.koreathermal.co.kr)
Heat Recovery Systems
Heat recovery opportunities exist where there is a need to reject heat from a constant supply of high energy fluid such
as air, water, or refrigerant.
•Boiler Stack & Blowdown •Exhaust Air •Laundry Air & Water •Refrigeration & Process Loads
Heat Recovery Systems
Presenter
Presentation Notes
Heat Recovery Systems Heat recovery is the reclamation and use of energy that is otherwise rejected from the building. Heat recovery opportunities exist where there is a need to reject heat from a constant supply of high energy fluid such as - air - stack gases - water - refrigerant - blowdown - other waste streams When applied properly, heat reclaim systems may be used to reduce both - energy consumption - peak power demand The effectiveness of a heat reclaim system for energy conservation depends on - the quantity of heat available for recovery - the temperature of heat available for recovery - the application of the reclaimed heat Include the additional maintenance of heat recovery systems in the savings analysis.
Heat Recovery Systems
Exhaust air heat recovery systems
Energy Management Control Systems
Minimize occupant control. Operate equipment only when needed. Eliminate or minimize simultaneous heating and cooling. Supply heating and cooling according to needs. Supply heating and cooling from most efficient source.
Communication Automation
Presenter
Presentation Notes
Energy Management Control Systems Rising energy costs and decreasing prices for computers and microprocessors have encouraged the use of energy management control systems (EMCS). An EMCS can efficiently control - heating - ventilation - air-conditioning - lighting - other energy-consuming equipment An EMCS selects optimum equipment operating times and setpoints as a function of - electrical demand - time - weather conditions - occupancy - heating and cooling requirements The basic control principles for building energy conservation are - Operate equipment only when needed. - Eliminate or minimize simultaneous heating and cooling. - Supply heating and cooling according to actual needs. - Supply heating and cooling from the most efficient source. Energy can be saved by automating the control of energy systems. About 100 companies manufacture EMCSs, and new technology is continually being developed. Potential users should familiarize themselves with the capabilities of energy management control systems.
