Investigation into the feasibility of CHP technology at Linenhall
1. The School of Electrical Engineering Systems
Dublin Institute of Technology
In partial fulfilment of the requirements for the degree
Bachelor of Science in
Electrical Services and Energy Management
Title: Investigation into and feasibility study of the employment of CHP
technology in Linenhall, DIT
By: Kevin Roche
Date: 7th May 2013
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Declaration
I hereby certify that the material, which is submitted in this assignment/project, is
entirely my own work and has not been submitted for any academic assessment other
than as part fulfilment of the assessment procedures for the programme Bachelor of
Science (Hons) Electrical Services and Energy Management (DT 712).
Signature of student________Kevin Roche_________
Date________7th May 2013___________
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Table of Contents
Declaration..................................................................................................................... ii
Table of Figures ............................................................................................................ vi
Table Of Tables.............................................................................................................vii
1.0 Chapter one: Introduction ........................................................................................1
1.1 What is CHP?...........................................................................................................2
1.2 Improved Efficiency ............................................................................................2
1.2.1 Reduction in energy costs .............................................................................3
1.2.2 Design of CHP ..............................................................................................3
1.2.3 Size of the base load......................................................................................3
1.2.4 Currently installed equipment.......................................................................4
1.2.5 Utility company.............................................................................................4
1.3 Why Should CHP Be Installed ............................................................................5
1.3.1 Demand for heat............................................................................................5
1.3.2 Security of supply .........................................................................................5
1.3.3 Environmental benefits .................................................................................5
1.3.4 Alternative to purchasing new boilers ..........................................................6
1.4 Methodology........................................................................................................7
1.4.1 Gain greater understanding of CHP technology ...........................................7
1.4.2 Collect data for Linenhall .............................................................................7
1.4.3 Analyse the data collected.............................................................................8
1.4.4 Establish load profile ....................................................................................8
1.4.5 Analyse the load and invent scenarios to best utilise CHP ...........................8
1.4.6 Investigate the viability of CHP unit ............................................................9
1.4.7 Review financing options .............................................................................9
2.0 Chapter Two: Literature review.............................................................................10
2.1 Methodical Approach.........................................................................................10
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2.2 Theoretical Approach.........................................................................................11
2.3 Factual Approach...............................................................................................12
3.0 Chapter Three: Components of a CHP System......................................................14
3.1 Prime Mover ......................................................................................................14
3.1.1 Combustion.................................................................................................15
3.2 Fuel System........................................................................................................15
3.2.1 Gas spark ignition reciprocating engines....................................................15
3.2.2 Compression ignition..................................................................................15
3.3 Generator............................................................................................................16
3.3.1 Synchronous................................................................................................16
3.3.2 Asynchronous .............................................................................................16
4.0 Chapter four: Feasibility Study..............................................................................17
4.1 Introduction........................................................................................................17
4.2 Data Evaluation..................................................................................................17
4.3 Load Profiles and Schedules..............................................................................18
4.3.1 Electrical load .............................................................................................18
4.3.2 Gas Load .....................................................................................................20
4.3.3 Analysis.......................................................................................................22
4.2 Scenario One......................................................................................................23
4.2.1 Conclusion ..................................................................................................26
4.3 Scenario Two .....................................................................................................26
4.3.1 Conclusion ..................................................................................................29
5.0 Chapter Five: Results and Analysis .......................................................................30
5.1 Financial Comparison........................................................................................30
5.1.1 Internal rate of return ..................................................................................30
5.1.2 Financial payback .......................................................................................30
5.1.3 Benefit/cost ratio.........................................................................................31
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5.1.4 Scenario one................................................................................................31
5.1.5 Scenario two................................................................................................32
5.2 Fluctuations in Energy Prices ............................................................................32
5.2.1 1% compound increase in gas prices over ten years ...................................32
5.2.2 1% compound increase in electricity prices over ten years ........................33
5.2.3 1% compound increase in electricity and gas prices over ten years ...........34
5.2.4 Conclusion ..................................................................................................34
5.3 Environmental Impact Comparison ...................................................................35
5.3.1 Co2 emissions .............................................................................................35
5.3.2 Co2 Emission reduction Comparison .........................................................36
5.3.3 Conclusion ..................................................................................................37
6.0 Chapter Six: Recommendations.........................................................................38
6.1 Selection of Plant ...............................................................................................38
6.1.1 Specification of Plant..................................................................................38
6.2 Installation of Plant ............................................................................................39
6.2.1 Prolonged payback period...........................................................................39
6.2.2 Small annual savings...................................................................................39
6.3 Positive aspects of the project............................................................................40
6.3.1 Energy savings ............................................................................................40
6.3.2 Reduction in Co2 emissions........................................................................40
6.4 Conclusion .........................................................................................................41
References....................................................................................................................42
Appendix A: Excel Scenario one, Tables & Graphs....................................................44
Appendix B: Excel Scenario two, Tables & Graphs....................................................47
Appendix C: Excel, Scenario Two Gas Price Increase Tables & Graphs ...................50
Appendix D: Excel, Scenario Two Electricity Price Increase Tables and Graphs ......52
Appendix E: Excel, Scenario Two Energy Price Increase Tables And Graphs...........54
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Table of Figures
Figure 1: Typical fuel consumption in CHP plants [CIBSE, 2009] ..............................2
Figure 2: Sizing a base load [BRECSU, 1994]..............................................................2
Figure 3: Typical small scale CHP plant [CIBSE 1999] .............................................14
Figure 4: Electrical consumption 11th-17th April 2013 ..............................................18
Figure 5: Electricity consumption 9th-15th January 2012...........................................18
Figure 6: Total electrical consumption, Dec 2011-Dec 2012 ......................................19
Figure 7: Gas consumption, 10th-17th April 2013 ......................................................20
Figure 8: Gas consumption, 25th-31st January 2013...................................................21
Figure 9: Gas consumption, 28th Nov- 4th Dec 2012 .................................................21
Figure 10: Gas consumption, 25th Nov 2012 - 17th April 2013 .................................22
Figure 11: Scenario one, simple payback and discounted cash flow comparison .......25
Figure 12: Scenario two, internal rate of return...........................................................28
Figure 13: Scenario two, simple payback and discounted cash flow comparison.......29
Figure 14: CHP scenarios, internal rate of return comparison.....................................30
Figure 15: Discounted cash flow project comparison..................................................31
Figure 16: Payback period with 1% increase p/a in Gas prices over ten years ...........33
Figure 17: Payback period with 1% increase p/a in electricity prices over ten years..33
Figure 18: Payback period with 1% increase p/a in energy prices over ten years .......34
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Table Of Tables
Table 1: Linenhall, current energy consumption .........................................................23
Table 2: Scenario one, CHP energy consumption .......................................................24
Table 3: Scenario one, projected energy savings.........................................................24
Table 4: Scenario one, net present value......................................................................25
Table 5: Linenhall, current energy consumption .........................................................27
Table 6: Scenario two, CHP energy consumption .......................................................27
Table 7: Scenario two, projected energy savings.........................................................27
Table 8: Scenario two, net present value .....................................................................28
Table 9: Co2 emissions per Kwh of fuel [Electricityinfo.org, 2011], [SEAI, 2012] ...35
Table 10: Current emission levels, Linenhall (i) .........................................................35
Table 11: Emissions levels from proposed Ener-G 50 CHP plant...............................35
Table 12: Current emission levels, Linenhall (ii) ........................................................36
Table 13: Emissions levels from proposed Ener-G 25 CHP plant...............................36
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1.0 Chapter One: Introduction
Over the course of this document the reader will be exposed to the benefits and
incentives which combined heat and power generation has to offer. After the
advantages of a CHP plant have been outlined, a feasibility study shall be undertaken
for the prospective implementation of such a CHP plant in the Linenhall building,
DIT. In depth financial and environmental analysis will provide the basis for the
study. Once the study has been complete the less technical aspect of how green
generation or a “green image” will help the campus and not only save money but also
provide a learning opportunity for students who wish to learn more about the
technology.
The DIT energy policy also states that one of DIT’s strategies is to “Adopt innovative
methods and clean technologies, including renewable resources, to improve efficiency
in existing and proposed buildings” [DIT, N/A]. The investigation into such
technologies is therefore embraced by the college, results and conclusions help to
strengthen the overall appreciation for the energy profile of the building and how it is
used.
In 2010 there were 158 small-scale CHP installations in the Ireland, with a generating
capacity of 307MW [SEAI, 2012]. The main question which must be addressed first
is, why choose CHP as a power supply option? Linenhall is already receiving
adequate power supply from its utility company, very rarely are there problems with
quality or availability of supply. What is the need to change? There are two answers
to the question posed. CHP plants, through heat recovery and clean generation, offer
improved efficiency and by association a reduction in costs. “It is the ability to
recover this heat, yielding efficiency gains together with the differential in fuel price
between raw fuels and processed electricity, which makes CHP schemes an attractive
proposition” [CIBSE, 1999]
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Figure 1: Typical fuel consumption in CHP plants
[CIBSE, 2009]
1.1 What is CHP?
Combined heat and power is “the
generation of thermal and electrical
energy in a single process” [BRECSU,
1996]. When power is generated in
industrial power stations the heat and
emissions from the process are simply
expelled into the atmosphere. The
main difference in a combined heat
and power plant is that the CHP plant
“utilises the heat produced in
electricity generation rather than releasing it wastefully into the atmosphere” [Irish
CHP association, 2004]. Small scale CHP plants are usually powered by a gas fired
turbine, but different driver fuels and arrangements are available. The process of heat
utilisation from useful heat produced in the generation of electricity is executed by
placing a heat exchanger onto the exhaust stack of the generator, this sucks heat from
the exhaust gasses and then releases, or sometimes re-circulates, the exhaust gasses.
1.2 Improved Efficiency
Conventional generation of electricity through coal or oil etc. is widely accepted to be
approximately 30-40% efficient. This means that each year power generation plants
are burning three times as much fuel as is needed. This means that three times as
many C02 emissions are produced than are ultimately necessary. “Each kWh of
electricity supplied from the
average fossil fuel power station
results in the emission of around
half a kilogram of CO2 into the
atmosphere. Typically, gas-fired
boilers emit around one fifth of a
kilogram of CO2 per unit
of heat generated”
[CIBSE,2009]. These losses are
not only a product of the in-efficient
generation techniques or out of date generators but also in the distribution of the
Figure 2: Sizing a base load [BRECSU, 1994]
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power and transportation of electricity from the plant to the end user. On average a
CHP scheme when designed and installed right can yield an “increase of 20% / 25%
in efficiency against the separate energy system it replaces” [Irish CHP association,
2004]. This is also considering that in most cases a CHP plant will only cover a base
load. A base load is a constant requirement for heat or electricity which at all times
must be maintained as shown in Figure 2: Sizing a base load [BRECSU, 1994]. There
may be an even greater saving if the current boiler system is out of date. In the area of
power generation, when It comes to CHP, “There are few solutions that offer,
simultaneously, a cleaner lower carbon environment as well as lower costs” [Irish
CHP Association, 2004]
1.2.1 Reduction in energy costs
There are a number of factors which will account for and contribute to the magnitude
of reduction in energy costs. These factors include but are not limited to
Design of the CHP
Size of the base load
Current installed equipment
Utility company
1.2.2 Design of CHP
Obviously the design of the CHP will impact on the savings yielded form it. If the
CHP is sized correctly to the base load and appropriate technology is utilised, such as
turbine and driver fuel types etc., then this will improve the efficiency. If the CHP
cannot run all of the time then the efficiency and savings yielded from the technology
will drop.
1.2.3 Size of the base load
Savings will also vary depending on how large the base load is. This factor is what
ultimately determines the viability of a CHP plant. Obviously a larger base load will
yield larger savings. This factor is why not all applications are suitable for CHP
generation, however most “hotels, hospitals, industrial processes and commercial
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buildings, where a continuous demand for both heat and power exists” [Irish CHP
Association, 2004] will be able to facilitate such a base load.
1.2.4 Currently installed equipment
Depending on how out-dated the current boiler is in a building the savings may be
greater than normal. If there is a brand new condensing boiler for example with heat
recovery technology then the energy savings will not be as great as a boiler which has
an age of ten years or older for example. This aspect of the savings will be a direct
product of the improvement in efficiency.
1.2.5 Utility company
Often overlooked as a factor for the financial savings associated with a CHP is the
current utility company supplying power to the premises. Depending on who currently
supplies electricity to the building the tariffs and rates per unit of electricity will
differ. This differential however small will lead to a change in savings and payback
period. Installation of a CHP can also allow the premises to switch to a lower tariff.
There are fees for switching tariffs so the monthly savings must be calculated against
the initial cost to assess whether this is a viable option.
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1.3 Why Should CHP Be Installed
1.3.1 Demand for heat
As the Linenhall building is a college campus, there is a constant flow of people
coming through the building. The building houses numerous classrooms, offices and
workshops for students, staff and apprentices. All of this occupied space needs to be
heated and maintained at a comfortable temperature. Hot water must also be supplied
for the use in toilets etc. for people frequenting the building. This presents the need
for constant low grade heat to be supplied and utilised in the building. The Linenhall
building is also home to a DIT fit to go gym. The presence of a gym means that there
must be a constant supply of hot water available to the showers in the changing room
facilities. These factors make the building a very good candidate for the investigation
of whether or not a CHP retrofit would benefit the energy profile and C02 emissions
of the building.
1.3.2 Security of supply
Security of supply is a major advantage of CHP generation. During normal operation
the CHP will carry the base load, even if there are voltage problems on the grid, such
as dips, sags or blackouts, the continuity of supply from the CHP will be guaranteed.
The building is closed for approximately thirteen weeks every year, for Christmas and
summer holidays, this presents a perfect opportunity to maintain and carry out any
work on the plant that are necessary. In times when the CHP is to undergo
maintenance which must be carried out immediately, the regular supply from the
distribution system operator will still be present, guaranteeing electrical supply 100%
of the time.
1.3.3 Environmental benefits
In the current social climate global warming is a hot topic. Cutting down on C02
emissions and consumption is looked upon by businesses and colleges as an
opportunity to reduce costs and gain positive media exposure if the effort made is
large enough. “A CHP unit will release less CO2 per kilowatt of energy supplied than
the equivalent combination of power station and boiler plant” [CIBSE, 1999]. For
Linenhall, with its constant demand, this can definitely create an opportunity for
positive media exposure. The government, in the white paper 2007, recognised the
opportunity of cleaner generation from CHP, stating that “We will achieve at least
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400MW from Combined Heat and Power by 2010” [DCMNR, 2007]. Even though
the installed capacity at the end of 2010 was 307MW [SEAI, 2012] there have been
strides made towards the target due to its efficient generation technique.
1.3.4 Alternative to purchasing new boilers
“Each year 6% of boilers are replaced” [Wood. J, 2008], for the most part companies
and buildings simply replace the old boiler with a more efficient newer model.
Replacement is not the only option, CHP generation units can be an alternative to
replacing old equipment if the premises fits the required design parameters. A CHP
will incur a higher initial capital cost, however the savings yielded from the unit will
far outnumber that of a new boiler unit.
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1.4 Methodology
In order to competently undergo a study into whether or not a specific CHP system
should or shouldn’t be installed the whole area of CHP and efficient design must be
understood. The following methodology shall be undertaken to firstly grasp a greater
appreciation of the broad topic of CHP and gradually narrow the topic down to
establish whether a retrofit CHP is suitable for the Linenhall premises. The steps are
as follows:
- Gain greater understanding of CHP technology
- Collect data for Linenhall
- Analyse the data collected
- Establish a load profile
- Analyse the load and invent scenarios to best utilise a CHP
- Investigate the viability of CHP unit
- Review financing options for feasible CHP plant
1.4.1 Gain greater understanding of CHP technology
Firstly it is the aim to establish a better knowledge of combined heat and power
systems. In order to design the best system for the proposed building it is important
that an in depth knowledge of the technology is acquired. Small Scale Combined Heat
and Power Application manual AM:12 [CIBSE 1999] will provide the fundamentals
for the knowledge of the subject, this publication coupled with other guides and
literature from sources such as SEAI, the Irish CHP association and textbooks will
allow one to fully grasp the area of CHP, from its design and operation to its
application and benefits.
1.4.2 Collect data for Linenhall
Once knowledge of CHP technology is attained the focus shall shift to the application
of such knowledge and the feasibility study section of the project shall commence.
Primary data from Linenhall will be collected. The website E3.ie provides daily load
schedules and profiles for both gas and electricity for the building. This shall be the
primary basis for the collection of data. Contacts will also be made with relevant
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connections in DIT such as facilities managers, energy managers and buildings
department officials in order to attain a more comprehensive and detailed picture of
how the building consumes energy and how this energy is currently supplied.
1.4.3 Analyse the data collected
The content and quality of the data will be analysed before any further steps are taken.
With a study of this nature, an investigation into the load profiles of a building and
whether a specific technology can be utilised within this building to produce energy
and financial savings, it is essential that the integrity of the data is assessed. If there
are gaps and anomalies in the data then solutions must be presented to successfully
mediate these problems and build the most accurate and reliable data set possible
from the resources available.
1.4.4 Establish load profile
Once the data and consumption figures for the building have been attained a load
profile for the building must be established. A load profile will develop a picture of
the buildings consumption and when it is needed. The load profile shall be derived
from 24 hour data available at E3.ie, once a daily load profile is constructed the
annual consumption of the building will be analysed. The annual consumption of the
building will be analysed and graphed. This graph will help to determine whether the
daily load profile is representative of the buildings average consumption or if the
energy consumption pattern varies dramatically throughout the year. Once a load
profile has been established it will be clear what base load will need to be covered by
the CHP plant for it to be running for the maximum amount of time possible.
1.4.5 Analyse the load and invent scenarios to best utilise CHP
Often in a building there is not simply one answer to solving any problem. The load
shall be analysed and a number of CHP installations shall be researched. Microsoft
excel spread sheets shall be formulated and savings from each different unit will be
established using simple payback and internal rate of return in order to establish
which of the options will be the most feasible and deliver the greatest savings in
relation to the capital investment which comes with each proposed plant.
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1.4.6 Investigate the viability of CHP unit
Once the initial rough financial comparison is completed and the best option for the
site is established, in depth analysis shall be carried out for the unit. This analysis will
not only establish how much money will be saved from the unit but also the
environmental benefits which will be provided, mainly focused on the reduction of
C02 emissions which the plant shall bring.
1.4.7 Review financing options
Finally if the feasibility of the project represents an attractive opportunity for
investment the investment and financing options shall be reviewed for the chosen
plant. Obviously capital investment from DIT would be the ideal option as no interest
would have to be paid, however this is not the only option. Different payment plans
shall be discussed. Grants and incentives for CHP systems shall also be further
investigated.
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2.0 Chapter Two: Literature review
Whilst conducting research for the question posed in this thesis, three trends were
recurring in the literature which was read and analysed, these trends are:
- Methodical approaches
- Theoretical approaches
- Factual approaches
2.1 Methodical Approach
This trend in the literature was found in un-biased sources. In particular the “Small
scale combined heat and power applications manual” [CIBSE 1999] presented a
clearly defined scope of what was needed to develop a CHP system from the start of a
project, until the end. The guides intended readership are engineers and energy
professionals, this leads the language and context of the document to be reasonably
technical, The technical mind-set of the author allowed the document to be coherent
and follow a logical pattern of design, No additional sources or literature were cited to
support the content of the document as it is read however there are an extensive list of
references and bibliography at the end of the paper, this coupled with the expertise of
the CIBSE organisation can only lead one to believe that the document is incredibly
reliable. A major concern with this source was the date it was published, CHP has
developed over the years and the CIBSE guide may not have been up to date with the
current best practices and applications in the field. Upon the evaluation of other
sources however the validity of the ““Small scale combined heat and power
applications manual” [CIBSE 1999] was confirmed.
The research question is supported by the CIBSE guide as it is simply a methodology
and framework to design a CHP system, this framework was then adapted and
moulded to fit the project in question. The context which a CHP should be considered
are given where “energy cost savings (and) environmental performance
improvements” [CIBSE 1999] are sought, giving justification for the investigation
into CHP technology in the Linenhall building.
The source “Catalogue of CHP technologies” [U.S.EPA CHPP] strengthened the
methodology which was developed based on the CIBSE guide. Developed by the
environmental protection agency of America this literature is an unbiased source
neither looking to promote or condemn CHP technology. It is intended for a broader
readership than the CIBSE guide, the information is not as technical however it
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focuses in on equations for a CHP plant. The equations are the main contribution from
this source. Comparison of efficiencies, fuel consumption and output are covered and
explained in detail. These formulae supported the research methodology and allowed
further in depth analysis and comparison to be achieved between conventional and
CHP generation.
The development of the CHP design however was only one part of the process. In
order to justify the installation of the system a financial appraisal would have to be
undertaken. The “Small scale combined heat and power applications manual” [CIBSE
1999] gives a brief outline of the financial appraisal however “Guide to energy
management” [Capehart et al, 2008] gives in depth advice and methodology to
financially appraise a project and explains the process from the basic appraisal at the
early stages up to an in depth costing and life cycle analysis. This publication is a
textbook written by accredited authors, this ensures that the content is a reliable
source to base the financial appraisal upon. It builds on the previous methodology and
completes the feasibility study. It is an essential part of the project.
2.2 Theoretical Approach
A theoretical approach refers to the literatures tendency to evaluate and approach the
topic of CHP from a perspective that deals with the theory of the process and its
benefits. No solid design or financial evaluation of the system could be based on
sections of literature such as these, however in the early stages of the process it is
useful to grasp the conceptual idea and reasons that led to the development and
promotion of the technology.
“A guide to combined heat and power in Ireland” [Irish CHP Association, 2004] for
example approaches the topic of CHP design similarly to the “Small scale combined
heat and power applications manual” [CIBSE 1999] but in a much more generally and
less technical manor. The intended readership is the general public, or companies
which may invest in the technology, rather that engineers and energy professionals.
The fact that the Irish CHP association have published the document means that the
content is inevitably biased towards the promotion of CHP. This is after all the
association’s job. The scope of the document is not obviously clear, it seems to be
loosely based around a methodology for the design of a CHP system, including a
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financial appraisal, however the information is very general, and becomes a list of the
technologies available rather than a procedure to implement them.
Similarly in “Small scale combined heat and power for buildings” [BRECSU, 1996] a
general outline of the technology and its applications is provided. It can benefit the
research topic chosen when look at as a pretext to the CIBSE guide published in 1999.
Intended for a broad readership the sections of the document such as applicability are
from a predominantly educational perspective, alerting the readers to the technology
and where they can apply it rather than how to apply it. CIBSE in their publications
have referenced BRECSU which gives the document credibility and the information
is consistent and coherent with the other literature which has been researched.
2.3 Factual Approach
The third aspect in which the literature was presented was a fact based approach. This
approach incorporated such elements as case studies into the reasoning and support
for CHP. This aspect was a universal theme across all of the literature, with the
exception of two sources, distributed generation of heat and power (Wood. J, 2008)
and “guide to energy management” [Capehart et al, 2008],
All of the literature from sources such as SEAI and CIBSE used the case studies to
promote the installation of CHP technologies. Whilst sources such as A guide to
combined heat and power in Ireland [Irish CHP Association, 2004] and Guide 176-
Small-scale combined heat and power for buildings [BRECSU, 1996] gave figures to
support case studies, such as savings and payback period etc. they did not fully
developed their case studies. Applications Manual 12 [CIBSE, 1999] however gave
numerous case studies and savings from them but also listed problems and rational
from the case studies which explained the different elements of the projects.
This unbiased look at both positive and negative aspects of projects which must be
addressed added another layer of depth to the feasibility study. Enabling it to account
for not simply savings and payback period but also enabling the consideration for
placement issues and size of the unit to be addressed.
Another aspect of the literature which was unique to one source was the utilisation of
factual based information about the broad area of CHP, including trends in generation
figures and policy which has affected it over the years. Combined heat and power in
Ireland [SEAI, 2012] approached the topic of CHP from a completely unbiased point
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of view. The authors educational writing style served the paper to provide simply an
overview of how CHP technology has grown over the years. The breakdown of CHP
into sectors and sizes in each of these allows any reader to see where CHP is
emerging and its place in the current market. Topics that are covered such as policy
support the overall research topic, as it is clear to see where the government and EU
stand on the technology and if there is likely to be any incentives or grants re-
introduced for the development of CHP plants.
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3.0 Chapter Three: Components of a CHP System
It is crucial that before the financial appraisal or design of a CHP system is begun that
one has an understanding of the basic components of a CHP system. The job of each
component and the best method in which to complete this job is a major concern in
the design and specification of a CHP plant. Regardless of what rating, make or
efficiency a selected CHP plant is, “all CHP schemes consist of a number of core
components with variations to suit the particular application” [CIBSE, 1999]. These
core components include
A prime mover
Fuel system
Generator
Heat recovery system
Cooling system
Ventilation system
Control system
3.1 Prime Mover
The prime mover of a CHP plant is the engine which drives the electrical generator. In
order to achieve maximum efficiency in the engine combustion must be achieved. For
the scope of this study the prime mover which is widely used is a reciprocating
Figure 3: Typical small scale CHP plant [CIBSE 1999]
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engine. These engines can be either gas spark ignition or compression ignition. The
difference in ignition refers to the way in which combustion is achieved in the engine.
3.1.1 Combustion
When the fuel is fed into any combustion engine it is mixed with air to provide
oxygen for the combustion process. Complete combustion or ‘stoichiometric
combustion’ is achieved when all of the fuel is converted into carbon dioxide and
water. A correct balance of air must be achieved as too little air and the produce of
combustion will be fuel rich, producing potentially lethal amounts of carbon
monoxide. If there is too much air present however then this will lead to an excess of
heat loss from the process.
3.2 Fuel System
3.2.1 Gas spark ignition reciprocating engines
Due to the availability of supply in developed countries, gas spark ignition
reciprocating engines have become the most popular CHP generation plant installed
throughout the UK and Ireland. Oil or LPG can also be used in circumstance where
there is no supply of gas however gas is the preferred option. The heat to power ratio
for these engines will be lower than other types, ranging from 0.5:1 to 2:1 [CIBSE,
1999] however supplemental firing is available to raise this ratio.
3.2.2 Compression ignition
Compression ignition can use either diesel or heavy oil to achieve combustion in the
engine.[CIBSE, 1999] dual fuel engines are also available where both oil and gas are
used to achieve combustion. Oil is typically used as a pilot fuel to ignite the gas
supply. [CIBSE, 1999]. For both of these compression ignition engine high and low
ignition ratios are available; “high compression ratios improve engine efficiency and
emission levels. However, the combustion process is less tolerant to fuel quality
variations” [CIBSE, 1999]
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3.3 Generator
“Generators create electricity by moving an electrical conductor through a magnetic
field”[CIBSE 1999]. This component of the CHP plant is where the electrical energy
is created. There are two types of generator available for this application; these are
Synchronous
(OR)
Asynchronous
The difference between the two options is the method in which they control the
frequency of the electricity which is generated.
3.3.1 Synchronous
“Synchronous generators rotate at a governed fixed speed” [CIBSE, 1999]. This speed
is a integer multiple of the supply frequency of 50Hz, e.g. 1000 rpm, 1500rpm etc.
This generation method ensures that the CHP can operate when it is separated from
the mains supply, or in the event of loss of mains power. |This is the most popular
style of generation as “The majority of CHP schemes will use synchronous
generators” [CIBSE, 1999].
3.3.2 Asynchronous
“Asynchronous generators do not have the ability to maintain a frequency” [CIBSE,
1999]. These generators rely on the mains supply to regulate the frequency which the
electricity is generated at. This presents advantages in some forms. Advantages
include, the generator being used to start up the engine using mains supply and there
is no need for complicated synchronous equipment. [CIBSE, 1999]. The major
drawback of this method however is that the loss of mains supply renders the CHP
plant useless, this means that there is no security of supply.
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4.0 Chapter four: Feasibility Study
4.1 Introduction
To fully assess the potential for a CHP plant on a site such as Linenhall, the energy
consumption and patterns must be recorded and analysed. There are two different size
CHP units which will be proposed, one with a low output and a constant operation
and the other which will give a larger output however will not be functional for as
much of the time. In order to correctly assess which option should be installed these
two scenarios shall be thoroughly investigated.
Once the simple payback for each scenario is calculated, the internal rate of return for
each will be evaluated. This method of financial appraisal affords the opportunity to
compare projects with different capital investments and compare them in terms of
savings and what today’s money will be worth in the future.
4.2 Data Evaluation
Before the feasibility study can begin the quality and reliability of the data being used
must be evaluated. The data, available online from E3.ie, spans over approximately a
year and a half. The spread sheet version of the data is separated into two tabs: gas
consumption and electricity consumption. The data is from a data logger and is
available at fifteen minute intervals, total loads and mean loads. Although the break
down and documentation of the data is comprehensive there are some concerns in
relation to the quality of the data.
The data which tracks the usage of the electrical load in the building appears to be
highly accurate and readings are consistent throughout the year, with total loads rising
and falling where it would be expected to, few gaps are present in the data.
The data available for the Gas consumption however is not as reliable as that relating
to the electrical consumption. There appear to be major gaps in the data dating from
August 2011 to January 2012, again for week long periods in April and May and once
again from early October until late November. The quality of the data that is present is
also questionable. For fifteen minute periods in the data set the gas consumption grew
to over 40,000Kw and back down to 0Kwh, these types of anomalies in the data have
happened during the early hours of the morning when the heating system shouldn’t be
in operation. For the reasons listed above the load profiles must be evaluated and
compared, this will help to build a true picture of the buildings energy usage.
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4.3 Load Profiles and Schedules
4.3.1 Electrical load
The load profile shown below in Error! Reference source not found. is for the week
of the 11th-17th April. This weekly load profile allows the consumption of the building
to be assessed for that week; however the CHP shall be installed for the whole year.
The overall annual load pattern for the building must be assessed to ensure that the
load profile shown is a fair representative of the building and ensure that the CHP is
not oversized.
Figure 4: Electrical consumption 11th-17th April 2013
0
50
100
150
200
250
0:00
1:15
2:30
3:45
5:00
6:15
7:30
8:45
10:00
11:15
12:30
13:45
15:00
16:15
17:30
18:45
20:00
21:15
22:30
23:45
Thu
Fri
Sat
Sun
Mon
Tue
Wed
27. Kevin Roche
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Figure 6: Total electrical consumption, Dec 2011-Dec 2012
From the graphs shown in Figure 4,Figure 5 and Figure 6 it is possible to compare the
load schedule at different times of the year. The weekly load profiles shown in Figure
4 and Figure 5 are visibly similar. Both profiles start to rise at approximately 7:00 in
the morning and peak during 12:00 to 16:00 steadily dropping back off again. From
the graph in Figure 6 it is also clear to see that the consumption is a steady bell curve
throughout the year, this confirms that the consumption of the building will be similar
in Autumn as it is in Spring. Taking the template of the buildings load profile from a
spring month ensures that the load is, for all intents and purposes, a base load of the
building. This sizing of a base load from a week and month with low consumption
ensures that the CHP shall not be oversized.
0
500
1,000
1,500
2,000
2,500
3,000
3,500
1-Dec-11
1-Jan-12
1-Feb-12
1-Mar-12
1-Apr-12
1-May-12
1-Jun-12
1-Jul-12
1-Aug-12
1-Sep-12
1-Oct-12
1-Nov-12
Night Kwh
Day Kwh
Total Kwh
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4.3.2 Gas Load
The gas consumption for the building shall have to be graphed and analysed. This
graphing and analysis allows the gas consumption profile of the building to be
established. It is crucial to fully comprehend the current energy profile of a building
in order to fully utilise a CHP unit. If a CHP is sized for a load greater or smaller than
the optimum load, the savings from the projects will also not be at an optimum level
and the project will suffer as a result.
As was mentioned in chapter four section 4.2 the data for the gas consumption of the
building was missing entries that spanned over months in places. This inevitably
impacted on the accuracy of the consumption figures however reasonable asumptions
were made. The gas consumption would be profiled for three weeks at different
periods and seasons of the year, ideally these loading schedules would be similar,
similar loads throughout the year would indicate that the gas consumption of the
building was steady throughout the year. Obviously the loads would be higher in
winter however it is the shape of the consumption graphs that is important. Once the
shapes ar the same and the load is sized from the month with the lowest consumption
the continuity of output from the CHP unit can be guaranteed.
After a daily load profile of the building is constructed the overall consumption of the
building shall be analysed. The overall consumption will identify how much the
buildings gas consumption rises and falls throughout the year, a peak in winter and
slow decline leading up to the summer is what would be expected to appear.
Figure 7: Gas consumption, 10th-17th April 2013
0
500
1000
1500
2000
2500
0:15
1:45
3:15
4:45
6:15
7:45
9:15
10:45
12:15
13:45
15:15
16:45
18:15
19:45
21:15
22:45
Thu
Fri
Sat
Sun
Mon
Tue
Wed
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Figure 8: Gas consumption, 25th-31st January 2013
Figure 9: Gas consumption, 28th Nov- 4th Dec 2012
0
500
1000
1500
2000
2500
3000
0:00
1:30
3:00
4:30
6:00
7:30
9:00
10:30
12:00
13:30
15:00
16:30
18:00
19:30
21:00
22:30
0:00
Fri
Sat
Sun
Mon
Tue
Wed
Thur
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0:00
1:15
2:30
3:45
5:00
6:15
7:30
8:45
10:00
11:15
12:30
13:45
15:00
16:15
17:30
18:45
20:00
21:15
22:30
23:45 Mon
Tue
Wed
Thu
Fri
Sat
Sun
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Figure 10: Gas consumption, 25th Nov 2012 - 17th April 2013
4.3.3 Analysis
From the graphs above and particularly Figure 7, Error! Reference source not
found. and Figure 9 it can be deduced that the daily and weekly load profile is
relatively stable throughout the year. In the three weeks shown, ranging from
November and January to April, there is a peak early in the morning and a maintained
load of between 300-400kwh throughout the day. The building’s, and therefore gas
consumption’s, pattern of use never alters, the building opens at approximately 7:30
each morning and closes at 21:30 each night apart from Friday and Saturday where
the hours of operation conclude at 17:30. The building is closed on a Sunday.
Another factor which compliments the theory that the gas consumption profile is
steady annually is the graph in Figure 10, showing the overall consumption of gas
from late November until mid-April. The graph clearly shows a steady consumption
of between approximately 7,000Kwh and 10,000Kwh, from this we can deduce that
the load profile of the building cannot vary wildly from one month to the next, this
confirms the theory which was presented upon analysis of the weekly load schedules.
The anomaly in the data between early February and early March is also noteworthy.
These are the class of anomalies or gaps found in the data however it is reasonable to
assume that the consumption did not spike or decline wildly within the period and that
it stayed consistent with the previous and proceeding months.
0
2,000
4,000
6,000
8,000
10,000
12,000
Night Kwh
Day Kwh
Total Kwh
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4.2 Scenario One
An Ener-G 50, 164Kw CHP system with an electrical capacity of 50Kw and thermal
output of 79Kw, shall be investigated. This scenario and rating of CHP will allow for
the unit to be in operation for 14 hours Monday to Thursday and 10 hours on Friday
and Saturday. The logic behind operating the CHP for 14 hours Monday to Friday lies
within the current load profile. The building operates from 7:30 in the morning to
9:30 at night. From the data collected the electrical load is maintained over at least
50Kw during this time and the gas consumption for heating is well in excess of 79Kw.
This allows the CHP to be operational for 100% of the time when the building is
occupied. On a Friday and Saturday however the building is operational from 7:30 to
5:30, as is suggested by the data. This means the CHP unit will be operational for 10
hours on these two days.
Days Operational hours Total
Monday-Thursday 14 56
Friday & Saturday 10 20
Total hours per week= 76
Weeks per year= 39
Total hours per year = 2964
This makes the total operational time of the CHP just over 3952 hours, when the
summer and winter months whilst the college would be closed, which amount to
thirteen weeks, are taken from this total the CHP shall be in operation for 2964 hours
per year. It is generally not considered feasible to install a CHP when the running
hours are less than 5000hours p/a however this scenario is the best option to match the
buildings current energy profile.
Table 1: Linenhall, current energy consumption
Current Consumption (Kwh)
Electrical
Hourly Weekly Annually
50 3800 148200
Thermal
Hourly Weekly Annually
92.94118 7063.529412 275477.647
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Table 2: Scenario one, CHP energy consumption
CHP consumption (Kwh)
Electrical
Hourly Weekly Annually
50 3800 148200
Thermal
Hourly Weekly Annually
79 6004 234156
Overall
Hourly Weekly Annually
164 12464 486096
Waste energy
35
Table 3: Scenario one, projected energy savings
Savings €
Electrical
Hourly Weekly Annually
3.515 267.14 10418.46
Thermal
Hourly Weekly Annually
0.571588 43.44071 1694.188
Total= 12112.65
The annual savings from the CHP unit would be just over €12,000 per annum; this
however is in terms of the value of money today. To see how the projects savings will
vary over time one must apply discount factors and discover the net present value
(NPV) of the project. Discount factors will develop a better picture of how the savings
will amount and give a more accurate idea on how long the project shall take to break
even. “The change in worth is due to two primary factors: interest (opportunity cost)
and inflation” [Capehart, 2008]. Maintenance costs shall also be factored into the
calculation of the projects NPV.
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4.2.1 Conclusion
From the financial appraisal of the project it is clear that the project will realistically
take over 11 years to pay back. For such a large capital investment of €70,000 (price
quotation from TempTech) this length of payback period is completely uneconomic.
The project would be luck to break even within the lifespan of the project. It is clear
that the installation of this CHP unit is completely un-feasible for the building.
4.3 Scenario Two
For this scenario, the Ener-G 25 CHP plant shall be investigated. The unit is an 82Kw
CHP system with an electrical load of 25kw and a thermal capacity of 38Kw.
Currently the heating system is turned on at half 7 in the morning and for the first
hour of its operation the average output from the boiler is over 1200kw, as can be
seen in Error! Reference source not found.. It will be proposed that there is a
constant supply of heat delivered to the building, Selected rooms with exposed
concrete walls shall be heated during the night. The thermal mass of such exposed
surfaces will retain heat, this means that in the morning when the heating load is at a
maximum in the building these rooms will not need to be heated at all, and the heat
can simply be released from the thermal mass, this produces a steady and balanced
temperature profile in the rooms. The plant will cease operation at 5:30 each
Saturday, as there is no need to pre-heat the building for Sunday.
Days Operational hours Total
Monday-Friday 24 96
Saturday 17.5 17.5
Total hours per week= 113.5
Weeks per year= 39
Total hours per year = 4426.5
In this scenario the plant would be operational for 4426.5 hours of the year. There is
always a minimum of 25Kw electrical power needed in the building, as shown in
Error! Reference source not found.. This aspect of the buildings energy profile will
remain as it currently is.
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Table 5: Linenhall, current energy consumption
Current Consumption (Kwh)
Electrical
Hourly Weekly Annually
25 2837.5 110662.5
Thermal
Hourly Weekly Annually
44.70588 5074.118 197890.5882
Table 6: Scenario two, CHP energy consumption
CHP consumption (Kwh)
Electrical
Hourly Weekly Annually
25 2837.5 110662.5
Thermal
Hourly Weekly Annually
38 4313 168207
Overall
Hourly Weekly Annually
82 9307 362973
Waste energy
19
Table 7: Scenario two, projected energy savings
Savings €
Electrical
Hourly Weekly Annually
1.696 192.496 7507.344
Thermal
Hourly Weekly Annually
0.274941 31.20582 1217.027
Total 8724.371
The annual savings which will arise from the installation of the CHP unit are €8724.
TempTech, the suppliers of the CHP unit have quoted a price for installation and
36. Kevin Roche
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commissioning of €40,000. This would give the unit a simple payback period of 4
years and 7 months. Once again this payback is not real in today’s money, as the
value of money changes over time. It is for this reason that the cash flow must be
discounted, this is done by performing the net present value calculation. Maintenance
costs are also factored into the equation, as they are subtracted from the savings
Table 8: Scenario two, net present value
year
Discount factor
8%
savings NPV
Discount factor
16%
savings NPV
0 1 -40,000 -40000 1 -40,000 -40000
1 0.926 7,019.00 6499.594 0.862 7,019.00 6050.378
2 0.857 7,019.00 6015.283 0.743 7,019.00 5215.117
3 0.794 7,019.00 5573.086 0.641 7,019.00 4499.179
4 0.735 7,019.00 5158.965 0.552 7,019.00 3874.488
5 0.681 7,019.00 4779.939 0.476 7,019.00 3341.044
6 0.63 7,019.00 4421.97 0.41 7,019.00 2877.79
7 0.583 7,019.00 4092.077 0.354 7,019.00 2484.726
8 0.54 7,019.00 3790.26 0.305 7,019.00 2140.795
9 0.5 7,019.00 3509.5 0.263 7,019.00 1845.997
10 0.463 7,019.00 3249.797 0.227 7,019.00 1593.313
NPV= 7090.47 NPV= -6077.17
Figure 12: Scenario two, internal rate of return
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Figure 13: Scenario two, simple payback and discounted cash flow comparison
4.3.1 Conclusion
From the financial analysis it is evident that the project has a payback period of
approximately 8.5 years. In today’s economy a payback period of generally 2-3 years
is acceptable for businesses. This desired short payback period is due to the
uncertainty of their security within the market; this acceptable payback period
however can change depending on the nature of the building.
-50,000.00
-40,000.00
-30,000.00
-20,000.00
-10,000.00
0.00
10,000.00
20,000.00
30,000.00
40,000.00
1 2 3 4 5 6 7 8 9 10 11
NPV payback
Simple payback
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5.0 Chapter Five: Results and Analysis
5.1 Financial Comparison
5.1.1 Internal rate of return
The first tool that must be used to compare the two given scenarios supplied in
chapter 4, section 4.2 and 4.3 is an internal rate of return calculation. This calculation
allows the two scenarios to be graphed and, using the same discount factors,
compared. “Internal rate of return is defined to be that value of the interest rate or
discount rate that makes the present worth of the costs of a project equal to the present
worth of the benefits of the project” [Capehart et al, 2008]. From the graph shown in
Figure 14, it is evident that the Ener-G 25 CHP plant from scenario two has the most
attractive IRR (12%) for the project. Different organisations have different minimum
attractive rates of return (MARR) [Capehart et al, 2008], this MARR serves as a
benchmark for the minimum rate of return which a project must achieve in order to
receive funding. A companies MARR will be at least, greater than the interest
received if the investment was deposited in a bank or savings bonds.
Figure 14: CHP scenarios, internal rate of return comparison
5.1.2 Financial payback
In Figure 15 it is clear to see the two projects’ payback period and the amount of
savings which will come as a result of each. Often the project with the larger capital
investment will yield superior savings due to economies of scale etc. however it is
clear to see in the diagram below that over the life cycle of the project the Ener-G 50
39. Kevin Roche
32
CHP unit from scenario one fails to catch up with the savings made by the smaller
unit running all of the time and fails to become profitable after 10 years of operation.
Figure 15: Discounted cash flow project comparison
5.1.3 Benefit/cost ratio
A benefit to cost ratio is another tool used to compare projects. The formula
“calculates the present worth of all benefits, then calculates the present worth of all
costs, and takes the ratio of the two sums.” [Capehart et al, 2008] This formula
provides an index value of the benefits form the project in relation to its encumbered
costs. Maintenance costs must be taken into account for the two projects. Maintenance
costs are calculated as .47c/Kwh [DECCUK, 2009]
NPV of maintenance costs =
[
.47×Kwh/year
100
] ×10
(1+𝐷.𝐹)10
[Capehart et al, 2008]
5.1.4 Scenario one
Present worth of Savings = €81263
Present worth of costs = €70,000
Maintenance costs
[
.47×486,096
100
] ×10
(1+0.08)10
€10,583
Benefit/Cost ratio = 1.008
-80,000.00
-70,000.00
-60,000.00
-50,000.00
-40,000.00
-30,000.00
-20,000.00
-10,000.00
0.00
10,000.00
20,000.00
1 2 3 4 5 6 7 8 9 10 11
Scenario One NPV
Scenario two NPV
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5.1.5 Scenario two
Present worth of Savings = €58,531
Present worth of costs = €40,000
Maintenance costs
[.
47×362,973)
100
] ×10
(1+0.08)10
€7,888
Benefit/Cost ratio = 1.22
Once again the Ener-G 25 CHP plant from the second scenario presented proves to be
the better and more economically viable opportunity available to install. It is evident
that, from a financially beneficial perspective, the smaller CHP unit presented in
scenario two would be the better option for installation on the premises.
5.2 Fluctuations in Energy Prices
At this stage it is apparent that the Ener-G 25 CHP unit is the most suitable for the
proposed site. Fluctuations in energy prices shall now be investigated and how they
would impact upon the project’s viability and payback period. The investigation into
the impact of energy price fluctuations is prompted by “energy forecasts for Ireland to
2020” [SEAI, 2011] as the report indicates that energy prices will rise in the period
between now and 2020. An annual increase of 1% shall be assumed as a realistic rate
of growth in energy prices, leading to a 10.4% overall rise in energy prices over a
decade. Scenarios for a separate rise in gas and electricity shall be investigated to see
their impact on the financial well- being of the project. The significance of a
simultaneous rise in both gas and electricity prices shall then be evaluated.
5.2.1 1% compound increase in gas prices over ten years
The graph in Figure 16 shows how the payback period would be extended if there was
to be a fluctuation in the energy market prices and Gas prices were to escalate at a
compound rate of 1% each year for the next ten years. It is clear that the increase in
gas prices will have an effect on the project, extending the payback period by six
months to approximately 9 years.
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34
Figure 16: Payback period with 1% increase p/a in Gas prices over ten years
5.2.2 1% compound increase in electricity prices over ten years
The main factor which generally makes CHP plants a financially viable investment is
the difference in price between electricity and the reduction in costs which generation
with natural gas presents. Figure 17 Presents a scenario where electricity prices shall
rise at a compound rate of 1% over the next ten years. The payback period is
decreased by approximately four to five months. This change doesn’t dramatically
affect the viability of the project however it does influence it slightly.
Figure 17: Payback period with 1% increase p/a in electricity prices over ten
years
-50,000.00
-40,000.00
-30,000.00
-20,000.00
-10,000.00
0.00
10,000.00
20,000.00
30,000.00
40,000.00
0 1 2 3 4 5 6 7 8 9 10
NPV payback
Simple payback
-50,000.00
-40,000.00
-30,000.00
-20,000.00
-10,000.00
0.00
10,000.00
20,000.00
30,000.00
40,000.00
1 2 3 4 5 6 7 8 9 10 11
NPV Payback
Simple Payback
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35
5.2.3 1% compound increase in electricity and gas prices over ten years
The final scenario which will assess the viability of the CHP plant in the event of
fluctuations in the energy markets will be a 1% compound increase in energy prices
for the next decade. From the graph it is clear that the two increases seem to cancel
each other out. The payback period is slightly shortened, the increase in prices will
slightly influence the payback period but would not have great impact upon it.
Figure 18: Payback period with 1% increase p/a in energy prices over ten years
5.2.4 Conclusion
In conclusion the fluctuation in energy prices, unless dramatic and sharp will not
affect the viability of the project enormously. Even a rise in gas prices when the
electricity prices are static would not have a profound effect on the project. This can
be attributed to the low electrical load which the CHP unit is producing. If the
electrical loading and capacity of the unit was higher the fluctuations would have a
much greater effect on the economic viability of the venture.
-50,000.00
-40,000.00
-30,000.00
-20,000.00
-10,000.00
0.00
10,000.00
20,000.00
30,000.00
40,000.00
1 2 3 4 5 6 7 8 9 10 11
NPV payback
Simple payback
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5.3 Environmental Impact Comparison
5.3.1 Co2 emissions
The Financial rewards and benefits have been reviewed and presented above; the
environmental benefits shall now be investigated and compared.
Table 9: Co2 emissions per Kwh of fuel [Electricityinfo.org, 2011], [SEAI, 2012]
Fuel g/Co2/Kwh
Electricity 489
Natural Gas 400
Scenario One
Table 10: Current emission levels, Linenhall (i)
Energy Fuel
KW/hour Co2 emissions
Kg/kwh
Eff.
%
Total emissions
Electricity Electricity 50 .498 40% 62.25 Kg
Heating Gas 79 .4 90% 35.1 Kg
Total hourly Co2 emissions = 97.35 Kg
Hours per year = 2964
Total Co2 emissions per annum = 288,545 Kg
Table 11: Emissions levels from proposed Ener-G 50 CHP plant
Energy Fuel Kw/hour
Co2 emissions
Kg/Kwh
Total emissions
Heating &
electricity
Gas 164 .4 65.6
Total hourly Co2 emissions = 65.6
Hours per year = 2964
Total Co2 emissions per annum = 194,438 Kg
This plant represents a total reduction in Co2 emissions of 94,107 Kg per annum. This
calculation takes into account the poor efficiencies in the conventional generation and
distribution of electricity, the process is assumed to be 40% efficient.
44. Kevin Roche
37
Scenario two
Table 12: Current emission levels, Linenhall (ii)
Energy Fuel
KW/hour Co2 emissions
Kg/kwh
Eff.
%
Total emissions
Electricity Coal 25 .489 40% 30.56 Kg
Heating Gas 38 .4 90% 16.88 Kg
Total hourly Co2 emissions = 47.44 Kg
Hours per year = 4426
Total Co2 emissions per annum = 209,969 Kg
Table 13: Emissions levels from proposed Ener-G 25 CHP plant
Energy Fuel Kw/hour
Co2 emissions
Kg/Kwh
Total emissions
Heating &
electricity
Gas 82 .4 32.8
Total hourly Co2 emissions = 32.8
Hours per year = 4426
Total Co2 emissions per annum = 145,172 Kg
For this particular scenario the annual Co2 reduction amounts to 64,797Kg. The
conventional generation process is once again deemed to be 40% efficient.
5.3.2 Co2 Emission reduction Comparison
This area is one of the few where the first scenario has been the outright winner.
Simply because the electrical load for in scenario one is double that in the second. It
appears that the overall emissions reduction obtained from scenario one is greater than
that in scenario two, however if the two projects are compared on a scaled basis the
results vary greatly.
Once the two reduction emissions are compared to each other in respect of the size of
each unit the second scenario prevails as the better option for Co2 emissions per Kwh
of installed technology. In scenario one the reductions per Kw of technology were:
94,107
164
= 573 𝐾𝑔/𝐶𝑜2/𝐾𝑤/𝑎𝑛𝑛𝑢𝑚
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In the second scenario the Kilograms of emissions per kilowatt of
installed technology were:
64,797
82
= 790 𝐾𝑔/𝐶𝑜2/𝐾𝑤/𝑎𝑛𝑛𝑢𝑚
From these calculations it is evident that the second plant gives greater emissions
savings per Kw of plant installed. The reasons for the results above are simply
because the second scenario runs for a greater amount of hours each year than the
larger capacity model.
5.3.3 Conclusion
In conclusion the plant in scenario one technically represents more benefits to the
environment than that of the smaller plant. The sheer size and capacity of the unit
overshadows the emissions savings from the second scenario. However when
compared relative to the size of the plant the CHP in scenario two represents a larger
reduction in emissions per Kw of installed technology, due to the increased hours of
operation.
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39
6.0 Chapter Six: Recommendations
6.1 Selection of Plant
It is clear from all of the previous comparison that the smaller CHP presented in
scenario two offers the greatest benefit to the site. Its low capital costs in comparison
to the larger model give further weighting to the project. The availability to leave the
unit on all of the time means that the electrical base load of the building is being
covered by a more efficient method of generation, but also the college will be
implementing innovative methods of heat storage by using exposed concrete to
capture heat during the night and release it during the day. It is for these reasons that
the Ener-G 25 CHP plant should be the preferred installation on the premises.
6.1.1 Specification of Plant
- The proposed plant will be an Ener-G 25 CHP unit.
- TempTech are the company supplying the installation and commissioning of
the plant
- TempTech’s offices in Limerick, Ireland quoted €40,000 for installation costs.
This included checking and commissioning the unit etc.
- The Plant is rated at 75Kw
- The electrical output of the unit is 25Kw
- The thermal output of the unit is 38Kw
- The engine is manufactured by Yanmar, and uses gas spark ignition and
natural aspiration, model No.4GPF98 C-1
- The overall efficiency of the unit is 85.2%
- The generator selected is an Asynchronous generator
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6.2 Installation of Plant
Once the most suitable CHP for the site has been selected the question must be posed
as whether it is feasible to install the Ener-G 25 CHP plant on site? When considering
the results which have been derived from the study in chapters four and five there is
no evidence of a significant financial incentive to justify the installation of the
proposed Ener-G 25 CHP unit in the Linenhall building, DIT. The reasons supporting
the decision not to install the CHP unit include:
- Prolonged payback period
- Relatively small annual savings
6.2.1 Prolonged payback period
One of the most influential factors in the recommendation not to install the CHP unit
is the relatively long financial payback period. The unit would take an estimated eight
to nine years before it would reach its break-even point. The average payback period
which is generally deemed acceptable in today’s economic climate is between two
and three years, anything after this period is identified as too large a risk to gamble
upon as there is not a significant reward to incentivise it. The financial aspects and
rewards of a project are essentially the factors which govern whether a it will proceed
or not, in this event there would be enough incentive to install the CHP unit.
6.2.2 Small annual savings
Once all of the factors influencing the annually costs and savings presented by the
proposed CHP unit were factored into the equation the net annual savings, in terms of
today’s money, were only €7,019. These low annual savings were ultimately the
factor which contributed to the prolonged payback period mentioned in section 6.2.1.
For a typical year this saving amounts to less than 8% of the overall bill. Essentially
the summer months when the CHP would be out of operation and therefore producing
no savings had an enormous influence the savings made by the unit. The low
electrical output of the unit was also a factor which resulted in relatively meek savings
produced by the unit. The generation of electricity is essentially where a CHP makes
savings and improves its viability, however with an electrical load of merely 25Kw
per hour the savings failed to significantly mount up.
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6.3 Positive aspects of the project
Although the overall project was deemed unsuitable for installation there were some
aspects of it which were positive and did need to be factored into the decision of
whether or not to install the plant. The positive influences of the project were
predictable as they are what makes CHP units in general a popular choice for
installation, these factors include:
- Energy savings
- Reduction in Co2 emissions
6.3.1 Energy savings
As mentioned in section 6.2.2 the CHP unit did not produce enough of an energy
saving to justify its installation, however the savings which were produced must be
noted as they were a positive aspect of the proposed installation, regardless of their
magnitude. In accordance with DIT’s corporate goal to “Minimise energy
consumption and costs” [DIT, N/A] the proposed CHP unit would have reduced
energy costs. In terms of todays’ money the proposed CHP plant represents primary
energy savings in excess of €8,000; however once maintenance costs and discount
factors were introduced it became apparent that these savings where not large enough
to justify the capital investment required to install the CHP unit.
6.3.2 Reduction in Co2 emissions
The one truly positive factor which supported the proposed installation of the Ener-G
25 CHP plant on the Linenhall premises was the reduction in Co2 emissions. Another
corporate goal to “reduce significant environmental impacts arising from energy use”
[DIT, N/A] was addressed by this aspect of the proposed installation. This corporate
goal of DIT refers to the reduction in emissions and impact from its energy
consumption. This is effectively achieved by creating a reduction of 64,797Kg/Co2
emissions from the buildings energy consumption each year. To put this saving in
perspective it is the equivalent Co2 emitted from a London bus over the course of
approximately 50,000 kilometres. [carbonindependent.org, 2009]
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6.4 Conclusion
In conclusion from all of the evidence discovered, analysed and presented over the
course of the document the benefits of the proposed installation of the Ener-G 25 CHP
unit have been outlined and discussed. These factors however could not overshadow
and compensate for the capital investment required to install the CHP unit, this
coupled with the maintenance costs and constraints on operational hours each year led
the proposed CHP unit to be ultimately un-economical and an un-attractive
investment opportunity. The study however is not considered to be a waste of time
simply because the outcome was not that which would have been desired. The
investigation into technologies and methods to reduce energy consumption is always a
worthwhile exercise and an essential element of working not only towards DIT’s
energy goals outlined in its energy policy [DIT, N/A] but also concerning individual
contributions towards the greater goals which exist in government policy such as that
of the “Government white paper” [DCMNR, 2007]. In essence the feasibility of the
CHP was deemed to be a failure whilst the significance and validity of the
investigation was recognised.
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