A FEASIBILITY STUDY OF USING WOOD AS AN ENERGY SOURCE FOR SMALL

COMMUNITIES IN TROPICAL COUNTRIES

Daniel Koop B. Sc. (Mech. Eng.) Thesis

2005

i

Title Page

A FEASIBILITY STUDY OF USING WOOD AS

AN ENERGY SOURCE FOR SMALL

COMMUNITIES IN TROPICAL COUNTRIES

Daniel Koop

A thesis submitted in conformity with

the requirements for a degree of

BACHELOR OF SCIENCE (MECH. ENG.)

at the University of Manitoba

Supervisor: Dr. E. Bibeau

Department of Mechanical and Manufacturing Engineering

University of Manitoba

2005

ii

Abstract

This Project is a case study concerned with exploring the feasibility of using bio-energy, specifically

wood energy, for electrical power generation, heating processes and refrigeration. Data from four

companies in Belize, Central America form the basis of this study. The four companies are located in

Spanish Lookout, in the home town of the author, and are involved with electricity generation, lumber

production, grain drying and poultry processing. Presently, the lumber mill is discarding a potential fuel in

the form of sawdust and woodchips while the electricity company is importing expensive fossil fuels. The

electricity generating company is discarding all the waste heat while additional fossil fuels are being used

for heating processes in the poultry plant and in the grain drying operations. Furthermore, refrigeration

cycles are presently powered with high grade electrical energy which could possibly be accomplished with

low grade heat energy instead. The goal of this project is to study replacing the present fossil fuel system

with a biomass system and inherent in the new system is the combination of various processes in order for

one company to use what the other company considers as waste. Improved overall efficiency and a locally

based fuel economy are sought.

The project primarily considers the analysis of a biomass combustion chamber, a steam turbine power

cycle, heat recovery systems and absorption refrigeration. The results prove that the companies would have

to haul in about three 30-ton loads of wood per work day, which is seven times the amount that the lumber

mill is presently producing as waste. There is a good possibility the additional 86 % of required biomass

could be obtained from other mills and areas of waste. Using a 10-year study period a preliminary

economic evaluation of the capital, fuel and labor cost reveals that the companies would indeed have an

equivalent annual operating cost (cost of capital = 12%) of $1,150,000 CDN with the biomass system as

opposed to $1,500,000 CDN with the present fossil fuel system. The operating cost to produce all the

energy requirements would therefore be 23 % lower with the biomass system. This benefit, however, is

offset by the fact that the biomass system has a very huge initial capital cost.

It is recommended that the companies conduct a further study that employs more detailed operational

data and incorporates forecast of demand into it. A formal proposal should be given after the more detailed

study is completed. What will be said here is that the implementation of a system could perhaps be done

gradually in some order of the following steps.

1. Recover the waste heat from the diesel generator to service part of the heating/refrigeration demand

2. Install absorption chiller units so that waste heat can power refrigeration

3. Install a relatively small biomass boiler that utilizes the waste from the lumber mill so that all the

heating, grain drying and refrigeration can be powered by low cost heat energy

4. Finally, install a large combustor-boiler and steam turbine-generator set

A biomass system has definite potential for the specific case studied and a detailed study should be

conducted to verify just exactly how good a solution it is to the energy requirements of this small town.

iii

Acknowledgements

The author would like to offer his appreciation to those who contributed to the work involved in this

thesis project. Special thanks go out to the following:

- Dr. Eric Bibeau for supervising the entire project and more specifically for all the advice he gave,

for help in formulating calculations and for sharing some of his practical knowledge on biomass

systems.

- Dr. Daniel Fraser for his indirect contributions through his Energy Conservation and Utilization

course. This course offered insight and solution techniques to the specific problem at hand.

- Mr. Wyatt for his course in economics.

- David Koop for gathering much of the required data from the companies in Spanish Lookout.

- Henry Koop for offering graphics in the form of pictures from his personal albums.

iv

Table of Contents

Title Page .................................................................................................................................................. i

Abstract....................................................................................................................................................ii

Acknowledgements..................................................................................................................................iii

Table of Contents..................................................................................................................................... iv

List of Tables............................................................................................................................................ v

List of Figures ......................................................................................................................................... vi

Nomenclature .........................................................................................................................................vii

I. Introduction ................................................................................................................................ 1

A. Problem ............................................................................................................................. 3

B. Purpose.............................................................................................................................. 4

C. Scope................................................................................................................................. 5

II. Criteria ....................................................................................................................................... 6

III. Summary of Operational Data ..................................................................................................... 6

IV. Methodology............................................................................................................................... 8

V. Calculations................................................................................................................................ 9

VI. Results...................................................................................................................................... 10

A. System Performance ........................................................................................................ 10

B. Cost Analysis................................................................................................................... 12

VII. Evaluation................................................................................................................................. 13

VIII. Recommendations..................................................................................................................... 15

IX. Conclusion................................................................................................................................ 17

X. References ................................................................................................................................ 17

Appendix A (Combustor Calculations).................................................................................................... 18

Appendix B (Power Cycle Calculations................................................................................................... 24

Appendix C (Cost analysis Calculations)................................................................................................. 29

1. Present Fossil Fuel based System ..................................................................................... 29

2. Bio-mass System.............................................................................................................. 30

v

List of Tables

Table 1 - Generating Plant ........................................................................................................................ 6

Table 2 - Poultry Plant .............................................................................................................................. 7

Table 3 - Lumber Mill............................................................................................................................... 7

Table 4 - Grain Dryers .............................................................................................................................. 7

Table 5 - Required Outputs ..................................................................................................................... 10

Table 6 - Comparative Economic Results ................................................................................................ 12

vi

List of Figures

Figure 1 - Map of North America.............................................................................................................. 1

Figure 2 - Arial Picture of Spanish Lookout .............................................................................................. 2

Figure 3 - Relative Location...................................................................................................................... 3

Figure 4 - Sawdust and Wood Chippings................................................................................................... 2

Figure 5 - Bulldozing down the Forests ..................................................................................................... 3

Figure 6 - Burning Fields .......................................................................................................................... 3

Figure 7 - Pushing Remains into Windrows............................................................................................... 4

Figure 8 - Model of Combustor and Steam Power Cycle............................................................................ 9

Figure 9 - Combustor Spread Sheet ......................................................................................................... 19

Figure 10 - Power Cycle Spread Sheet..................................................................................................... 25

Figure 11 - Cash Flow Diagram for Present System................................................................................. 30

Figure 12 - Cash Flow Diagram of the Biomass System........................................................................... 31

vii

Nomenclature a Air AR As Received AU As Used BD Bone Dry C Specific Heat C Carbon CO2 Carbon Dioxide E Energy h Specific Enthalpy H Hydrogen HHV Higher Heating Value H2O Water L Energy Loss LHV Lower Heating Value m Mass mc Moisture content mf Mass fraction M Molar Mass N Nitrogen N Number of moles N2 Dinitrogen O2 Dioxygen O Oxygen P Pressure T Temperature v Specific volume w Specific humidity y Mole fraction η Efficiency φ Relative humidity Subscripts a Air atm Atmospheric A After AR As received Comb Combustor C Carbon C Condenser CO2 Carbon Dioxide dry Dry Day Per Day e Exit eq Equipment exh Exhaust f Fuel f Saturated liquid fg Difference in property between saturated liquid and saturated vapor FG Flue gas g Saturated Vapor

viii

Gen Generator H Hydrogen H Heat Exchanger H2 Dihydrogen HW Hog Water HHV Higher Heating Value i Inlet i Ideal LHV Lower Heating Value max Maximum n/s Amount needed divided by present supply N2 Dinitrogen oa Over all O Oxygen O2 Dioxygen p Constant Pressure Par Parasitic rec Recovered R Refrigerator Rank Rankine Cycle s Stoichiometric t Total v Vapor w Wood wet Moisture in medium Year Per Year

Superscripts

. (over dot) Quantity per unit time

1

I. Introduction

This Project is a case study concerned with exploring the feasibility of using bio-energy, specifically

wood energy, for electrical power generation, heating processes and refrigeration. Data from four

companies in Belize, Central America form the basis of this study. The four companies are located in

Spanish Lookout, in the home town of the author, and are involved with electricity generation, lumber

production, grain drying and poultry processing. The companies are, Farmers Light Plant (FLP), Midwest

Lumber Mill (MLM), Central Grain Dryers (CGD) and Quality Poultry Products (QPP). Presently, the

lumber mill is discarding a potential fuel in the form of sawdust and woodchips while the electricity

company is importing expensive fossil fuels. The electricity generating company is discarding all the waste

heat while additional fossil fuels are being used for heating processes in the poultry plant and in the grain

drying operations. Furthermore, refrigeration cycles are presently powered with high grade electrical

energy which could possibly be accomplished with low grade heat energy. The goal of this project is to

study replacing the present fossil fuel system with a biomass system and inherent in the new system is the

combination of various processes in order for one company to use what the other company considers as

waste. Improved

overall efficiency and a

locally based fuel

economy are sought.

The small town is

located in the heart of

the Caribbean country

of Belize. To the right

is a map [1] of North

America that shows the

geographical location

of this country.

Figure 1 - Map of North America

2

Zooming in on the map above by a large factor an aerial picture is shown below of the little town of

Spanish Lookout [2]. The town has a population of 1500 and is basically composed of numerous small

family farms. It was first settled in 1958 by a number of immigrants originally coming from Manitoba,

Canada. When Spanish Lookout was founded it was a very lean farming town chopped out of the original

tropical jungle by a combination of the old fashion ax and the new technology of the times, the ever

powerful bulldozer. This has transformed the awesome forests into beautiful farmland.

Figure 2 - Arial Picture of Spanish Lookout

As these folks were starting to make a living out of the forest, lumber mills sprang up. In order to

produce farmlands they chopped and bulldozed down the forest and burned them. On their farmlands they

started raising corn which was used for raising poultry. Up sprang a poultry processing plant as well as an

electricity generating plant. Grain was dried by varies individual farmers for the longest time. Presently, the

biggest lumber mill is “Midwest Lumber Mill (MLM)” and the poultry processing plant is the same as ever

and is “Quality Poultry Products (OPP)”. The Electricity Generating plant is called “Farmers Light Plant

(FLP)”. The largest grain drying operation is “Central Grain Dryers (CGD)”.

3

The sketch to the side illustrates the relative locations of the four

companies and gives the approximate separating distances.

A. PROBLEM

The problem as it pertains to this project will be outline by considering

the operation of each of the four companies. The generating station is

considered first and then the poultry processing plant, the lumber mill and

the grain drying facility. A specific look is taken at the practices of these

companies keeping an energy conservation and utilization perspective in

mind.

Electricity Generation

Presently, electricity is generated by a diesel generator set. The main

set that is used has a 3000 HP engine in it. The fuel is diesel which is

imported from out of country. It is an expensive fuel to start with and it has Figure 3 - Relative Location

been experiencing significant rising in cost over the past years. Furthermore,

it is subject to heavy taxation. The retail cost of electricity is presently 40¢ CDN per kwh which is

reflective of the high cost of diesel.

Another thing noted about the generating station is that all the heat that is inherently produced in the

heat-power cycle is being dumped. This amounts to a waste of approximately 70 % of the original energy

content of the diesel. The heat energy could be employed for both heating and refrigeration purposes.

Poultry Processing Plant

The poultry processing plant has a huge demand for refrigeration as well as some demand for heating.

It is noted that space heating is not required for any of the companies since atmospheric temperatures rarely

drop to 10 ºC during any time of year. Two things are noted about the poultry processing plant which is that

they are using fossil fuels for heating purposes and more importantly, it is observed that they are using

electrical energy to power their refrigeration cycles. Their electrically driven refrigeration units are a lot

more efficient than absorption refrigeration units are, however, if heat energy is available for a much lower

price absorption refrigeration may very well compete effectively with the electrical units.

Ro

ad

QPP

MLM

CGD

FLP

1 km

15 km

0.6 km

2

Lumber Mill

Probably the biggest part of the problem with respect to the project is associated with the biomass

waste. Half of its gross biomass harvested is disposed of as waste in the form of saw dust and chippings

during the lumber cutting and shaping processes. Some of the saw dust is used for varies small applications

but the majority of it has no application and is therefore considered to have no value. It is generally left in

piles at various sites to decay via the slow and natural process or at other times it is set on fire in order to

get rid of the piles. The picture below shows one pile in the foreground as well as one at a distance [2].

Figure 4 - Sawdust and Wood Chippings

The second part of the waste biomass problem is not associated with the lumber mill but rather with

the production of farmland. In order to produce farmland a lot of the tropical forest are being cleared

annually and the next couple of pictures illustrate the general procedure through which this is done. The

first step to preparing the land for farming is to log out all the trees that are considered to be useful for

lumber production. However, due to the wide and diverse variety of trees in the typical tropical jungle,

approximately 95% of the forest is useless for lumber. These trees are simply bulldozed down as seen in the

picture below. This leaves a layer of broken up tree trunks and branches on the ground [2].

3

Figure 5 - Bulldozing down the Forests

The trees are then left to dry for about three weeks and are then set on fire. The entire field becomes

one huge ranging fire. The picture below illustrates the result [2].

Figure 6 - Burning Fields

4

The fire will calm down by the end of the first day but will usually keep burning for days or even

weeks. Even so there always remains a significant amount of unburned trunks and branches which are then

bulldozed into windrows which are eventually eliminated by further burnings over the next couple of years.

Figure 7 - Pushing Remains into Windrows

It is not known how many tons of biomass is destroyed in the vicinity of Spanish Lookout per year via

this method and it is beyond the scope of this project to determine it. It is believed though that this process

wastes many multiples of biomass of what the lumber mill wastes.

Grain Dryers

The final company considered is the grain draying operation. The only thing noted about this company

with respect to this project is that they are presently using fossil fuels to heat their grains. If a biomass

system could produce the required heat than these fossil fuels could also be replaced as well.

B. PURPOSE

The purpose of this project is very straight forward. It is to determine if it is feasible and economical to

replace the present fossil fuel system with an integrated biomass system. To do this a combustor, steam

power cycle, heat recovery system and refrigeration system will be analyzed and considered. Analyzing

5

the performance of the system is key and fundamental to the project however the economics will really

determine whether this is the beginning or end of a biomass system for this little town of Spanish Lookout.

C. SCOPE

The heat engines considered in this study is limited to one only which is the steam turbine. There are

other engines that can be used in biomass applications. Two examples would be a piston steam engine or a

gas turbine. The steam turbines are still the most popular choice and since the scope of this project will

have to be limited to one engine, the steam turbine is the only one considered. Even to do a thorough

analysis on the steam turbine would require a lot more time than what can presently be spend on this

project and therefore simplifications are made and are outlined below:

• Average properties for tropical woods are used

• Energy calculations are performed on average requirements with limited attention given to peak

and minimum values

• The analysis is based on present demand and requirements and makes no attempt to incorporate

forecasted values

• Humidity of air as well as air and wood temperatures are average yearly values

• Heat, parasitic and generator losses are assumed values

• General values for steam turbines and absorption chillers are used (note: if these items were to be

purchased the vender could probably supply this information which could then be incorporated

back into the calculations)

• Maximum and minimum temperature and pressure values for the combustor and steam cycle

equipment are used based on typical values

• The moisture content of the wood at the time of combustion is approximated based on two things:

an average from a number of tropical trees and from the approximated weight reduction values

given by the lumber mill.

As seen from the above points this analysis has many limitations of which the key ones are that

forecast of demand is not considered and that the economics are very preliminary. The study has value as a

preliminary investigation and is valuable in three ways. Firstly, determines if a further and more detailed

6

study should be conducted. Secondly, it gives the performance characteristics and a sense of operational

requirements of a biomass system. Thirdly, it gives a preliminary economic evaluation.

II. Criteria

The criteria with which the biomass system will be evaluated with are outline in this section. Four

criterions will be employed and they are as follows.

1. The most important criterion is the overall long term cost or savings that the alternative considered

could bring to the involved companies

2. Ease of operation and maintenance

3. Safety issues related to the implementation and operation of proposed technology

4. Environmental effects

The evaluation section will refer to these four things in order to determine if it is feasible and justifiable to

implement a biomass system or if the present system should be continued.

III. Summary of Operational Data

The relevant data obtained from the four companies is summarized in the Tables below. The majority

of the values are averaged. All energy figures are based on yearly records and are given in units of average

Kilo Watts.

Farmer’s Light Plant

The average power output is 700 kW, however, they have peak values as high as 1500 kW. In order to

accommodate the peaks they have a 2000 kW generator. They also have several smaller generators that are

used during low demand periods.

Table 1 - Generating Plant

Item Amount Notes

Diesel per year 1,705,300 liters $1,279,000 CDN

General use electricity 550 kW -

Refrigeration use electricity 100 kW -

Peak shaving electricity ( over 1 MW) 50 kW -

7

Quality Poultry Products

This poultry plant uses about 30 % of the electricity generated by the generator plant half of which is

used for refrigeration. They also have some heating requirements.

Table 2 - Poultry Plant

Item Amount Notes

Heating Processes 275 kW 160 ºC and 620 kPa

Heat removed by Refrigeration 400 kW To temperatures as low as 15 ºC

Midwest Lumber Mill

The waste wood products have an approximate moisture content of 30 %, however when the logs are

initially harvested they have a 50 % moisture content which translates the 2100 tons per year into 3000

harvesting tons. The majority of the logs are hauled in from within a 16 km radius around the mill for

which the hauling cost is $5.00 CDN per ton.

Table 3 - Lumber Mill

Item Amount Notes

Waste Wood Products 2100 ton/year @ 30%

moisture -

Central Grain Dryers

Specific mention is made here regarding peak requirements. The majority of the grains are dried during

a two month period of the year which obviously causes a peak in demand and furthermore the two month

period itself has its own peak. Only average figures were obtained initially and it has become beyond the

scope of this project to inquire about the exact distribution of demand.

Table 4 - Grain Dryers

Item Amount Notes

Heating requirements 225 kW Based on yearly average

All the preceding values are based on figures that were obtained from the involved companies at the

start of the project.

8

IV. Methodology

The way this project is conducted is presented in the following steps in the order they are conducted:

1. Finding the properties of the concerned biomass and in particular its chemical composition,

moisture content and its Higher Heating Value.

2. Finding the average year round atmospheric humidity and temperatures of Spanish Lookout

3. The combustor analysis

a. Calculating the latent heat losses due to the hydrogen content of the wood in order to find the

lower heating value

b. Calculate the latent heat losses associated with the moisture content of the wood

c. Find an approximate value for the general heat losses for the entire system

d. Find the maximum temperature that the flue gases can be subjected to as well as the minimum

temperature that the heat recovery system of the combustor can lower the flue gas to.

Furthermore calculate the heat capacity values of the flue gases and then calculate the losses

associated with the hot flue gases leaving the combustor.

e. Calculate the amount of heat recoverable based on the original Higher Heating Value of the

wood and the hydrogen latent heat losses, fuel moisture latent heat losses, equipment heat

losses and exiting flue gas losses.

4. Next the steam-turbine power cycle is analyzed. A simple cycle with the basic components

consisting of a heat source, steam turbine, condenser and pressurizing pumps is used. Inserted into

this model is also the absorption chiller and heat recovery system. Both the heat recovery system

and the absorption chiller replace the function of the condenser but unlike the condenser they

utilize the waste heat instead of dumping it. They are extracting heat from the turbine at a higher

temperature and pressure than the condenser. Parasitic losses are estimated and the efficiency of

the turbine is based on general values. Once all the states have been determined the energy

recovery of the turbine, heat exchanger and absorption chiller are calculated from the specific

states.

9

After both the combustor and steam turbine are analyzed all the losses of the system are

known and it is possible to predict how much wood is needed for producing the desired amount of

electricity, heating and refrigeration.

5. Finally, an economic study is conducted. The capital cost, fuel cost and operator labor cost of the

present and alternative system are considered.

V. Calculations

The majority of the calculation in this project were formulated and calculated in an excel spreadsheet.

A paper copy of these sheets is included in Appendices A & B. Appendixes A, B and C give the equations

employed in the spreadsheet using the nomenclature given at the beginning of the report. The Appendices

also describe the logic behind the calculation and proceed through them in the order of approach. Appendix

A shows the combustor calculations, appendix B the steam turbine and C shows the economic calculations.

A graphical representation of the model used is given below. Part of the model was obtained from reference

[3].

Figure 8 - Model of Combustor and Steam Power Cycle

Superheater

Economizer

Boiler

Feed Pump 1

Condenser

Turbine

20

mC mT

mR mH

Heat Exchanger

Absorption Chiller

Feed Pump 2

11

10 9

2

3

5

7

1

6 8 4

21

10

VI. Results

The following table gives the required outputs of the incorporated biomass system. This system

consists of a combustor-boiler unit, a steam turbine, a condenser, a heat recovery system and an absorption

chiller. Since the refrigeration processes are accomplished with the absorption chiller the electrical demand

is reduced by 100 kW with respect to the old system.

Table 5 - Required Outputs

Required Outputs per Year General use Electricity 600 KWe

Heat at 160 ºC & 620 kPa 500 KWth

Heat moved from -15 ºC to 25 ºC 400 KWth

The results are presented in the following two sections. The first section presents the performance of

the biomass system. The analysis started with the HHV of the biomass and explores where the energy goes.

Therefore, what is presented here is simply a percentile list of all the losses and recovery percentages of

each unit in the system. From this analysis and from the output requirements above it was then possible to

determine the size of the required system as well as the required amount of biomass needed to satisfy all the

energy requirements. Hence the second part of the results is presented showing the economic evaluation.

A. SYSTEM PERFORMANCE

The HHV of the biomass [4] is 18,678 kJ/kg. All the following percentages are with respect to the

original HHV of the wood. To clarify what is meant by that the generator losses are taken for and example.

The generator losses were estimated to be 5 % of the shaft input power produced by the turbine. In order to

project this 5 % back unto the HHV of the wood it is noted that only 8 % of the HHV is converted into

shaft power and therefore the 5 % generator loss is only 0.4 % with respect to the HHV of the biomass.

Similarly, all the other values have been projected unto the HHV in order to give a clear picture of just

exactly where the energy goes that the biomass produces.

11

Original Energy Content 0 % - 18,678 kJ/kg

Latent heat Losses due to H in Fuel 6.3 %

Latent heat Losses due to Hog Water 5.2 %

General Equipment Heat Losses 17.7 %

Flue Gas Exhaust Losses 20.7 %

Parasitic Losses 0.2 %

Condenser Losses 24.0 %

Generator Losses 0.4 %

Power Recovery 7.6 %

Heating Recovery 6.9 %

Heat Recovery for Chiller 11.0 %

Process Losses Component

Superheater

Economizer

Boiler

Condenser

Turbine

Heat Exchanger

Absorption Chiller

12

Theoretically the condenser would not need to be employed if there was enough demand for heat. The

fact that it is employed here indicates that both the absorption chiller and the heat exchanger could use

more heat without increasing the fuel input. The electrical output therefore dictates the amount of biomass

required given the present energy demands. Since 7.6 % of the higher heating value of the biomass is

converted into electrical energy the amount of electricity produced from each kilogram of BD biomass is:

kg

kJ

kg

kJEelectrical 5.1419678,18%6.7 =

=

In order to produce electricity at a rate of 700 kW the combustor would have to consume biomass at a rate:

day

kg

moistureday

kg

s

kg

kgkJ

skJ

m ARBDBDBiomass 85211

%50

432004260649.0

5.1419

700=

====&

This amount is carried over into the cost analysis section.

B. COST ANALYSIS

The cost considered here are only the capital cost, fuel cost and operator labor cost. Further

considerations are beyond the scope of this project. The table below summarizes the cost of both the

present system and of the biomass system. The study period is over a ten year period.

Table 6 - Comparative Economic Results

Item Amount (CDN) Service Life

Diesel Generator Set 170,000 5 years

Boilers, Burners & Refrigerators 80,000 5 years

Operator Labor 12,480 Annually

Natural Gas 198,740 Annually

Diesel 1,280,200 Annually Pre

sent

Sys

tem

Equivalent Annual Cost = $ 1,500,000 CDN - - -

Entire Biomass System 3,750,000 10 years

Fuel 117000 Annually

Back up 114,000 Annually

Peak Shavings 180,000 Annually

Operator Labor 70,000 Annually

Bio

ma

ss S

yste

m

Equivalent Annual Cost = $ 1,15000 CDN

13

Appendix C gives the calculations performed for the values in the table above an in particular the

calculations for the equivalent annual cost (EAC). It is note here though that a 12 % interest rate is used for

the cost of capital which is representative of what these companies pay for capital.

VII. Evaluation

Here the criteria that were given towards the beginning of the report are used to evaluate the biomass

system with. The evaluation follows the items given in the table above.

1. Economics

The first criterion was the overall long term cost or savings that the alternative considered could bring

to the involved companies. Based on the ten year period the equivalent annual cost for the biomass system

is 23 % less then for the present fossil fuel system. The staggering initial cost for the biomass system sort of

offset the benefits realized and they are a huge draw back in considering the risks involved with venturing

into using a system that is completely new and unfamiliar to the companies.

The initial capital cost is the biggest contributor to the EAC and if this value could somehow be

reduced the biomass system would become much more appealing. Used systems are available, however,

moving and installation cost are often fairly high for used systems resulting in the fact that they are not that

much cheaper than new systems. The system considered here is a 1 MW system and it is pointed out here

that the relative capital cost decreases rapidly with increasing size. Considering the capital cost and the

increasing demand for power it might be better to wait until a several MW system is required.

Labor costs are not very high in Central America and even the values here are conservative in that they

are higher than actual values. The labor cost could be reduced by further automation of the biomass system

but capital cost would increase as a result. A trade off exists between capital cost and labor cost and the

optimal situation needs to be found.

The back up costs are based on using the diesel generators and on a down time of 7 %. All systems

require maintenance and allowance for down time so if the biomass system is backed by diesel generators

the backup cost will remain. The peak shavings are also based on using the diesel generators for shaving

loads greater than 1 MW. The exact load distribution data was not obtained so a very rough estimate is

14

made. Actual data from the generating station could easily determine the exact amount required for peak

shavings which could very well be less than what is estimated. Again there exist a trade off between capital

costs and peak shavings costs and therefore an optimal plant size still needs to be determined. Also,

biomass systems do not lend themselves to fluctuation loads as well as diesel systems which makes it

necessary to have a generator for peak shavings.

The fuel cost for both systems is likely to rise over the next years. The biomass cost would rise due to

increasing labor cost and trucker’s diesel cost both of which have a relatively small impact on the annual

cost of the biomass system. Diesel costs have been on the rise over the last years and are likely to rise more

in the coming years which increases the annual costs for the present system almost directly. Again, several

years down the road the biomass system could become even more attractive.

2. Ease of operation and maintenance

The second criterion is ease of operation and maintenance. With respect to this the present system

gains favor in both respects. The biomass system requires more operators including somebody on the site

24 hours per day seven days a week. Presently, no company in Spanish Lookout has employees during the

night or even through the weekend and there would definitely be some reluctance for locals to start doing

this. Also, both operator and maintenance personnel would have to get specialized training for the biomass

system where as the present requires no specialization. Therefore operational and maintenance

considerations are in favor of continuing the present system.

3. Safety

Safety, as in the majority of engineering projects, is an important criterion in this project. The steam

system has highly pressurized equipment and because of it governments have safety regulations on the

operation of the steam equipment. However, the research done in this project does not suggest that either

one of the systems is less safe then the others and therefore not much can be said about it here.

4. Environment

Several considerations with respect to environmental issues should be made. First of all it is noted that

deforestation, especially tropical deforestation, is a big global concern [5]. The biomass system involves

harvesting logs from areas that are being clear cut and as such plays a supporting role in the cutting down

of forest. On the other hand, however, dependency on fossil fuels is also a big global concern. Biomass,

15

unlike fossil fuels, is a renewable energy source and if harvested on a sustainable basis it does not produce

any net CO2 emissions. Considering both issues it is recommendable to utilize waste biomass. At the same

time effort should be made to employ sustainable harvesting methods. The second issue is related to

emissions from the combustor. Of particular concern is the regulation of what is fed into the combustor.

Biomass combustors that perform well with respect to emissions, when raw and clean biomass is fed into

them, can become horrible polluters when things like tires and wood products with all sorts of glues and

paints on them are fed into the combustor. Spanish Lookout is still a sort of backward town with a general

sarcastic view over pollution concerns and might very well dump every thing that burns into the combustor

unless it is strictly regulated.

VIII. Recommendations

The primary recommendation is that the companies conduct a further study that employs more detailed

operational data and incorporates forecast of demand into it. This is recommended since the present and

preliminary economic study, that is based on constant diesel cost and constant power demand, already

shows a reduced equivalent annual cost. Furthermore, diesel prices are expected to go up and power

demand is also increasing both of which make the biomass system even more attractive. A formal proposal

should be given after the more detailed study is completed. What will be said here is that the

implementation of a system could perhaps be done gradually in some order of the following steps.

1. The waste heat from the diesel generator set could be recovered by using appropriate heat

exchangers. The diesel engine converts approximately 30 % of the fuel energy into electrical

energy, rejects 30 % into the jacket coolant, 30 % goes out of the exhaust and the reaming 10 % is

rejected in the form of various heat losses. The present requirements dictate the heat be in the form

of steam at 160 ºC. Since the jacket coolant of the engine is below 100 ºC this 30 % can probably

not be recovered. The generator produces an average of 700 kW of electrical energy so there is

approximately 700 kW going into the exhaust a large part of which is recoverable for the required

160 ºC steam. With this in mind it is recommended that the exact heating temperature

requirements be reviewed to see if there might be lower temperature heating requirements so the

16

jacket coolant heat can also be utilized. A thorough study including an economic analysis should

be conducted to see if the waste heat from the generator set can be utilized for heating and

refrigeration purposes.

2. Since biomass is readily available from the lumber mill and from other places a relatively small

and low pressure combustor could be installed. The combustor could be used to compliment the

heat recovered from the diesel engine. Careful consideration should be given as whether or not it

makes sense to install both the diesel engine heat recovery system and a biomass boiler. If the

diesel engine can not produce enough heat it might be more economical to install only a biomass

combustor instead of installing both. Since over $500,000 CDN is spent in heating fuel and

refrigeration electricity each year and since biomass is readily available there is a very good

chance that a great improvement can be made even without installing the entire biomass system.

3. A complete biomass system that services all heating, refrigeration and electrical power

requirements should be considered as a long term solution. The complete system may already be

profitable and furthermore it appears as if it will look even more attractive several years down the

road. Even if it is decided not to go ahead with the system yet, it is important to start considering it

so that equipment replacements in the next couple of years can be made with this in mind. For

example, the refrigeration system may need to be modified significantly in order for absorption

chillers to be incorporated into the system so replacement decisions with respect to the

refrigeration system may well be affected by plans to setup a biomass system within several years.

4. Finally, there are other possible power solutions that need to be considered before a new system is

installed. An assessment of resources such as hydro, wind, solar, tidal and other biomasses than

wood needs to be made.

Clearly, from the preceding recommendations, this project should be extended into a whole new and

detailed project. The present results will be presented to the companies and possibly the study will be

continued.

17

IX. Conclusion

In conclusion, this project is probably the beginning of a long term solution to the electrical power,

heating and refrigeration requirements of the small town of Spanish Lookout. Biomass posses to be a local

and low cost energy source for this particular small community located in the heart of the tropical country

of Belize. Further studies need to be conducted in order for formal recommendations to be made but with

the rising cost of diesel and the increasing demand for electrical power, heating and refrigeration it

certainly appears to worth exploring.

X. References [1] “Maps of World” Internet: http://www.mapsofworld.com Date accessed: April 4, 2005 [2] Henry Koop. “Photo Albums” [3] M. Tampier, D. Smith, E. Bibeau and P. Beauchemin. “Identifying Environmentally preferable uses for Biomass Resources” Internet: http://www.umanitoba.ca/engineering/mech_and_ind/prof/bibeau/research/papers/2004_ Tampier_bio mass2.pdf Date accessed: April 4, 2005 [4] “Phyllis, database for biomass and waste - Energy research Centre of the Netherlands”. Internet: http://www.ecn.nl/phyllis Date accessed [Nov. 5, 2004] [5] John H. Bodley. Anthropology and Contemporary Human Problems. Page 6 Mountain View, CA: Mayfield Publishing Company, 2001 [6] Y. A. Cengel, M. A. Boles. “Thermodynamics: An Engineering Approach”. Fourth Edition New York, NY: Mcgraw Hill, 2002 [7] Weather Base. Internet: http://www.weatherbase.com/weather/weatherall.php3?s=158587&units=us Date accessed [Nov. 5, 2004] [8] J. L. Riggs, D. D. Bedworth, S. U. Randhawa & A. M. Khan. “Engineering Economics”. Second Edition. McGraw-Hill Ryerson Limited, 1997

18

Appendix A (Combustor Calculations)

This appendix describes the calculation process for the combustor analysis in a step by step process

and presents the equations employed in the analysis. All the calculation were formulated and performed in

an excel spread sheet. A copy of the spreadsheet is on the next page. The equation numbers refer to the

particular cells in the spreadsheet.

1. The first step is to find the HHV, moisture content and composition of the considered biomass. Values

for the specific biomass were not found so average values from a number of tropical hardwoods are used.

drykg

kJHHV 18678=

The moisture content and composition are given in the spreadsheet above.

2. In order for the logs to dry they are usually harvested a year before they are processed. They have an

initial moisture content of 50 % which reduces to 30 % within the year. The waste biomass is combusted at

30 % and this is referred to the as used (AU) biomass. The biomass with no moisture in it is referred to as

bone dry (BD). The following two equations give the BD and AU masses with respect to the as received

(AR) mass:

( )ARfARfBDf mm ,,, 1 ω−= &&

( )AUf

BDfAUf

mm

,

,, 1 ω−

=&

&

3. The HHV rate in terms of kW:

BDfBDHHV mHHVE ,⋅=&

19

Figure 9 - Combustor Spread Sheet

20

4. The LHV is based on the HHV and on the amount of hydrogen in the biomass. The latent heat losses

due to the hydrogen in the biomass are calculated based on the difference between the HHV and the LHV.

It is noted that if the heat recovery system could bring the flue gas temperatures below dew point

condensation would start to occur. Latent energy could be extracted out of the flue gases in proportion to

how far the temperatures drop below the dew point. Due to two problems this project does not attempt

lowering the flue gases to condensation which are that the heat exchangers have to be bigger in order to

lower flue gas temperatures and condensation introduces corrosion problems both of which increase

expense.

( ) fgHHBDBD hmfMHHVLHV ⋅⋅−=

BDfBDLHV mLHVE ,&& =

LHVHHVLHV EEL &&& −=

5. Hog water (moisture in biomass) also produces latent heat losses.

( ) fgAUfLHVHWA hmmcEE ,, &&& −=

HWALHVHW EEL ,&&& −=

6. The next losses considered are the general equipment heat losses. These losses have not been

calculated but have been assumed to be 20 % of the sensible heat. Heat losses occur throughout the system

and are directly related to the temperature difference between the equipment and the surroundings. Since

the latent heat invested into vaporizing the moisture in the flue gases does not produce a temperature rise it

is more appropriate to calculate equipment heat losses after the latent heat has been subtracted from the

HHV.

( )eqHWAeqA LEE %1,, −= &&

( )eqHWAeq LEL %,&& =

21

In order to determine the losses associated with the heat that is carried out with the hot flue gases

exiting the combustion chamber the whole combustion processes needs to analyzed. Another reason for

analyzing the combustion process is to determine and control the maximum temperature that the flue gases

are subjected to. The higher the maximum temperature of the flue gases the higher the efficiency of the

combustor, however, it is desired to deep the gases at or below 1000 ºC in order to avoid dealing with NOx

emissions. Excess air is supplied in order to accomplish this. The following calculations illustrate the

analysis.

7. The mass fraction of the BD fuel is given in the spreadsheet above as obtained from source [4]. The

ash component is not given by the source but rather is calculated as the difference between a 100% and the

addition of all the other components. The given fractions are the BD fractions and are converted to the AU

fraction in the following manner:

( ) ( ) ( )mcmfmf BDCAUC −= 1,,

8. The stoichiometric dry air to fuel ratio and the mass flow rate of the stoichiometric dry air are as

follows:

( ) ( ) ( )

232.02

2

,,

,

OH

OH

C

OC

sdryBDf

drya

mfM

Mmf

M

Mmf

m

m−

+

=

&

&

sdrydryf

dryadryfsdrya m

mmm

,,

,,,,

⋅=

&

&&&

9. The total mass flow rate of the air including its moisture and the excess air supplied is given below.

The excess air is adjusted and supplied in order to keep the maximum flue gas temperature at a desired

value.

( )( )aexcessdryata amm ω++= 11,,&&

22

10. It is assumed that all the carbon and hydrogen is combusted completely to form carbon-dioxide and

water. The mass flow rate of CO2, O2, N2, H2O and total rate are calculated respectively.

( )

⋅=

C

COCBDfCO M

Mmfmm 2

2 ,&&

( )232.0,,

,,2

⋅⋅

⋅= excess

sdryBDf

dryaBDfO a

m

mmm

&

&&&

( ) ( ) ( )

+⋅+

= Nexcess

sdryBDf

dryaBDfN mfa

m

mmm 768.01

,,

,,2

&

&&&

( ) ( )

−++⋅

+

=

mc

mcaw

m

m

M

Mmfmm excessa

sdryBDf

drya

H

OH

HBDfOH 11

,,

,,

2

2

2&

&&&

OHNOCOFG mmmmm2222

&&&&& +++=

11. The latent heat is obtained from reference [6] at atmospheric pressure.

12. The operational availability is assumed to be 93 % which translates into 48 weeks per year.

13. The average atmospheric air temperature [7] of 25 ºC and the average relative humidity of 82 % of the

concerned geographical area are employed.

14. The saturated pressure is obtained based on the average temperature. The vapor pressure and specific

humidity are calculated using the following equations.

iTatsatg PP =

agv PP φ⋅=

vatm

va PP

Pw

−=

622.0

15. The mass fractions, number of moles, mole fractions and partial pressures of each component of the

flue gas are calculated.

( )FGt

CO

CO m

mmf

,

2

2 &

&

=

2

2

2

CO

CO

CO M

mN

&

=

23

FGt

CO

CO N

Ny

,

2

2=

atmCOCO PyP ⋅=22

16. The ideal gas specific heats of each component of the flue gases are calculated using the [6] following

equations. Two different mean temperatures are used, one for the heat addition calculation and the other for

the heat recovery calculation. The specific heat for the water will not be very accurate at low temperatures

where its behavior is not similar to an ideal gas. It is also noted that the specific heat is dependent on the

mean temperature which in turn is dependent on the maximum temperature which is dependent on the

specific heat creating a set of equations that has to be solved simultaneously.

⋅×+×−×+

=−−−

Kkg

KJ

M

TTTc

CO

FGmFGmFGmCOp

2

2

3,

92,

5,

2

,

10469.710501.310981.526.22

⋅×+×−×+

=−−−

Kkg

KJ

M

TTTc

O

FGmFGmFGmOp

2

2

3,

92,

5,

2

,

10312.1107155.010520.148.25

⋅×−×+×−

=−−−

Kkg

KJ

M

TTTc

N

FGmFGmFGmNp

2

2

3,

92,

5,

2

,

10873.2108081.0101571.090.28

⋅×−×+×+

=−−−

Kkg

KJ

M

TTTc

OH

FGmFGmFGmOHp

2

2

3,

92,

5,

2

,

10595.310055.1101923.024.32

17. The flue gas mean temperature and the heat recovery mean temperature are calculated.

2,

ieFGm

TTT

+=

2

max,

erecm

TTT

+=

18. The maximum temperature is:

iOHpNpOpCOp

eqA Tmcmcmcmc

ET

OHNOCO

++++

=22222222

,,,,

,max

&&&&

&

19. The heat recovered into the steam cycle is now calculated by:

( )( )eOHpNpOpCOpComb TTmcmcmcmcEOHNOCO

−+++= max,,,, 22222222&&&&&

CombeqAexh EEL &&& −= ,

24

Appendix B (Power Cycle Calculations)

This appendix describes the calculation process for the Rankine cycle analysis. All the calculation

were formulated and performed in an excel spread sheet which is shown pictorially on the next page. The

spread sheet also shows calculations related to configurations of the system in which heat is not being

recovered, however, this report does not compare these configurations to each other. The results of concern

are the ones that utilize heat recovery. The method of approach is to determine all the states of the working

fluid and determine the required mass flow rates. Once that is defined all the energy calculations can be

performed.

1. At the top of the spreadsheet the required outputs are given. The amount of biomass that is analyzed in

the combustion chamber is not enough to supply the demand. To carry out the calculations in this section

the combustor output is multiplied by a ratio, rn/s which is set to meet the demand.

requiredmatchesoutputelectricaluntiliteratedisr sn /

2. State 1 of the working fluid is based on the minimum pressure that the condenser is subjected to.

11 Patfhh =

3. The maximum pressure the system is subjected to is assumed 4500 kPa. State two reflects the work

done by Pump 1.

( ) 101022 hvPPh +−=

4. The maximum temperature the working fluid is subjected to is assumed to be 400 ºC.

333 PandTathh =

25

Figure 10 - Power Cycle Spread Sheet

26

5. The ideal state 4 has the same entropy as does state 3 and knowing the low pressure value that Pump 2

is producing the enthalpy of the ideal state is:

44

4

434 TatfTatfg

Tatfg

Tatfi hh

s

ssh +

−=

6. The turbine is assumed to be 51 % efficient based on which the actual state 4 is determined. The

temperature of state for can be determined based on the known pressure and enthalpy at state 4.

( )iturbine hhhh 4334 −−= η

7. The ideal and actual states 5 and 7 are determined in the same way as the ones of state 4. A certain

temperature is desired for these states so the withdrawal point on the turbine is adjusted accordingly.

ii

i

i

TatfTatfgTatfg

Tatfi hh

s

ssh

55

5

535 +

−=

( )iturbine hhhh 5335 −−= η

ii

i

i

TatfTatfgTatfg

Tatfi hh

s

ssh

77

7

737 +

−=

( )iturbine hhhh 7337 −−= η

8. States 6 and 8 depend on how much energy the heat exchanger and the absorption chiller extract from

the working fluid. In this case they are saturated liquids and 75 kPa.

66 Patfhh =

88 Patfhh =

9. State 9 is a combination of states 6 and 8.

689 hmm

mh

mm

mh

HR

H

HR

R

++

+=

27

10. State 10 is a combination of states 9 and 11.

91110 hmmm

mmh

mmm

mh

HRC

HR

HRC

C

+++

+++

=

11. State 11 accounts for the work input of Pump 2.

( ) 111111 hvPPh +−=

12. The mass flow rates are determined as follows. It is noted that the chiller efficiency is assumed to be

COP = 0.5 which is a rough value of what these chillers normally are.

23

/

hh

Erm Combsn

T −⋅

=&

&

HRTC mmmm &&&& −−=

( ) ( )87 hhCOP

Em

Chiller

ionrefrigeratbyremovedHeatR −

=&

&

( )65 hh

Em tsrequiremenHeat

H −=

&

&

13. The turbine power output is:

( ) ( ) ( )537343 hhmhhmhhmE HRCRank −+−+−=&

14. Subtracting the assumed 3 % parasitic losses:

( )parRankparA LEE %1, −= &&

15. Further subtracting the assumed 5 % generator losses produces the final electrical output of the entire

system.

( )genparAoutputelectrical LEE %1, −= &&

28

16. The heat recovered for the heating processes and the absorption refrigeration is calculated.

( )65 hhmE HprocessesHeat −= &&

( )87 hhmE Rionrefrigerat −= &&

All the performance characteristics are known from the preceding calculations. Combined with the

combustor analysis the original HHV can now be broken into all the losses and recovery components

considered throughout the biomass system. The results are presented in the Results Section of the report.

29

Appendix C (Cost analysis Calculations)

In this appendix the calculations related to the economics of the present fossil fuel system and the bio-

mass system are performed. The capital, fuel and labor cost are considered. The time value of money is

taken into account and the interest rate for the cost of capital is assumed to be 12 % throughout. This 12 %

is reflective of typical rates in the town of Spanish Lookout.

1. PRESENT FOSSIL FUEL BASED SYSTEM

The assets involved in the present system consist of the diesel generator sets, boilers for the production

of steam, electrically powered refrigeration units and the burners for the grain drying system. The fuel costs

are the diesel for the generator, natural gas for the boilers and the grain dryer burners. The operator labor

cost for all these processes is not clearly defined and for the sake of this project only the labor that is

strictly associated with power, heat and refrigeration are considered.

The generator set has a cost of $170,000 CDN and a 50,000hr (5 years) service life. The cost for the

other assets are estimated to be $80 000 CDN having the same 5 year service life. This adds up to a capital

cost of $250,000 CDN at the beginning of the 10 year study period and an equivalent amount at the end of

the year five. Diesel costs for the generator are based on data obtained from the generating facility. The

yearly amount is 1,705,300 liters of diesel at a cost of 75.07 cents per liter which adds up to $1,280,200

CDN. The amount of natural gas is 400,680 liters at 49.60 cents adding up to $198,740 CDN. The amount

of labor is estimated to be equivalent to one person working full time at 5 days a week and 8 hrs per day at

a cost of $6.00 CDN an hour. This totals to be $12,480 CDN a year. All this information is summarized on

the cash flow diagram below. It is assumed that the fuel and labor cost can be considered to occur at the

end of each year. Projecting the initial capital cost of $250,000 unto the first five years and the second

$250,000 unto the final five years the Equivalent Annual Cost (EAC1) can be calculated by the equation

below where (A/P, i , N ) is the factor for projecting a present cost to an annuity over a certain period of

time and at a certain interest rate. From Riggs [8] the factor (A/P, 12 , 5 ) = 0.27741.

30

( )( )

000,500,1

700,560,1

27741.0000,250740,198200,280,1400,12

5,12,000,250740,198200,280,1400,121

≈=

+++=+++= PAEAC

Figure 11 - Cash Flow Diagram for Present System

2. BIO-MASS SYSTEM

The assets involved in the considered biomass system are a centralized system whose main

components are a combustor, steam turbine, condenser, heat exchangers and absorption chillers. Fuel cost

consists entirely of trucking waste lumber mill products and additional biomass form fields being cleared.

The lumber mill estimated the cost for hauling in logs to be $5.00 CDN per ton. Trucking the lumber mill

waste from the mill to the power station is probably going to cost almost as much as hauling it in originally.

Therefore an even $5.00 per ton is used in calculating the fuel costs. The operation will approximately

require two laborers during the day shift and one during the evening and morning shifts totaling an

equivalent of 32 hours 365 days a year.

It was quite difficult to find what the actual cost would be for the biomass system. Different estimates

were found varying from $2,000,000 CDN to over $4,000,000 for a 1 MW system. Companies that were

contacted could not really give a quote unless a much more thorough study was done involving extensive

10 x 12,400

250,000

5

time [years]

10

250,000

10 x 1,280,200

10 x 198,740

31

data collection from the particular case. Rough estimates were obtained through conversations and

$3,750,000 CDN seemed to be an acceptable value. This value will be used in this report but it is noted that

this is a preliminary and rough estimate. The service life of it is longer than for a diesel generator and

should be at least ten years. The total amount of wood required is 23,400 ton/year. At $5.00 CDN a ton this

amounts to $117,000 CDN per year. The labor cost at $6.00 CDN an hour are $70,080 CDN. The backup

cost are $114,000 CDN and the peak shavings $180,000. All this information is summarized on the cash

flow diagram below.

It is assumed that annual costs occur at the end of each year. Projecting the initial capital cost of

$3,750,000 over the ten years the Equivalent Annual Cost (EAC1) is as before from Riggs [8] the factor

(A/P, 12 , 10 ) = 0.17698.

( )( )

000,150,1

675,144,1

000,70000,180000,114000,11717698.0000,750,3

000,70000,180000,114000,11710,12,000,750,3

≈=

++++=++++= PAEACB

Figure 12 - Cash Flow Diagram of the Biomass System

Based on this evaluation the operating cost could be reduced by 1,500,000 – 1,150,000 = $350,000 per

year.

10 x 70,000

3,750,000

5

time [years]

10

10 x 117,000

10 x 114,000