UGSE1_Generation System Fundamentals Course Notes_Final 2010

COLLABORATIVE POWER ENGINEERING CENTRES OF EXCELLENCE

GENERATION SYSTEM

FUNDAMENTALS

PROF. AKHTAR KALAM

School of Engineering and Science

Victoria University

Melbourne, Victoria

Course Notes

COURSE NOTES: GENERATION SYSTEM FUNDAMENTALS Kalam, A.

2010 UGSE1_Generation System Fundamentals Course Notes_Final 2010 i

© Victoria University, 2010

No part of this material may be reproduced without permission. For enquiries and requests to access

resources, contact the API University Representative on the Australian Power Institute website:

www.api.edu.au - Collaborative Power Engineering Centres of Excellence.

http://www.api.edu.au/


2010 UGSE1_Generation System Fundamentals Course Notes_Final 2010 ii

Table of Contents

Introduction: Setting the Scene 1

Assumed Knowledge 1

Objectives 1

Teaching and Learning Approaches 1

Module Resources 2

Course Notes 2

Presentation Packs 2

Activities 2

Acknowledgment 2

Author/s and Contact Details 3

1. Conventional Generation 5

1.1 Growth of Power Systems in Australia 7

1.2 Conventional Sources of Electrical Energy – Worldwide [1-4] 8

1.2.1 Fossil Fuel 11

1.2.2 NucLear Fuel 13

1.3 Power Plants 14

1.3.1 Fossil Fuel Power Plants 16

1.3.2 Cogeneration 18

1.3.3 Gas Turbines 19

1.3.4 Hydrolectric Power Generation 20

1.3.5 Nuclear Power Stations 21

1.3.6 Magnetohydrodynamic (Mhd) Generation 23

1.3.7 Geothermal Power Plants 24

2. Non-Conventional Source 27

2.1 Renewable and Non-Conventional Energy Sources [1] 27

2.1.1 Wind Power 28


2010 UGSE1_Generation System Fundamentals Course Notes_Final 2010 iii

2.1.2 Solar Energy 29

2.1.3 Wave Energy 47

2.1.4 Biofuels 49

2.2 Energy Storage 52

2.2.1 Secondary Batteries 52

2.2.2 Fuel Cells 52

2.2.3 Hydrogen Energy Systems 68

2.3 Cogeneration and Distributed Resources 68

2.3.1 The Technology 69

2.3.2 Electrical and Mechanical Measurements 73

2.3.3 Thermal Energy 74

2.3.4 Heat and Power Production - A Brief History 78

2.3.5 Why Cogeneration Now? 79

2.3.6 Cogeneration in Australia 80

2.3.7 Cogeneration Commercial Viability 87

2.3.8 Cogeneration - The Competition 88

2.3.9 Cogeneration - The Barriers 89

2.3.10 Conclusion 89

Future 90

References 90

INTRODUCTION AND OVERVIEW

2010 UGSE1_Generation System Fundamentals Course Notes_Final 2010 1

INTRODUCTION: SETTING THE SCENE

Unlike traditional textbooks which are full of formulae and theories, this course on Generation System Fundamentals explains in simple language how power is generated, with special emphasis on Alternative Renewable Energy Generation and analysis have been minimised with everyday examples and easy-to-understand illustrations.

It opens with an explanation of an overview of generation system, later on followed with details on Alternative Energy Systems which introduce students to unconventional energy sources such as solar, wind, biomass and fuel cells; problem facing the Electricity Supply Industries in Australia and its choices. The course focuses on: Overview of major alternative sources and their energy content; environmental and economic advantages of using alternative energy generation technologies along with the concept of sustainability in order to provide the basis for the consideration of alternative energy systems The course also covers: Conventional energy systems and green house effect; evaluation and feasibility studies of solar energy, wind energy, fuel cells, hydrogen generation, bio-fuel, tidal and geothermal systems; nuclear energy; analysis and modelling of above systems; economic analysis of above systems; design of hybrid systems and integration.

In addition, the author covers specific features and fuel-types in nontechnical terms. Industry and first time exposure to undergraduate Power study will appreciate this clear explanation of how power is created.

ASSUMED KNOWLEDGE

It is assumed that you will have a basic knowledge of:

Basic Circuit theory and Electricity Supply Structure.

Fundamental knowledge or first two year engineering in traditional Electrical & electronic Engineering program.

OBJECTIVES

On completion of this module you should be able to:

1. Describe the physical aspects of generation systems.

2. Explain the various options used to generate electricity including advantages and disadvantages

3. Explain the generation system fundamentals

TEACHING AND LEARNING APPROACHES

This module is best taught through a combination of:



Group lectures presented by the instructor using the PowerPoint Slides which are part of the module material,

Group lecture discussions coordinated by the instructor,

Individual study of the notes provided to review lectures and learn details required to perform activities,

Individual efficiency reporting and renewable energy implementation assignments using industry templates, and

Power plant visit (or viewing video of the field visit).

A set of presentation packs and activities are available in addition to the course notes as a suite of

resources for this module. These are listed below and can be downloaded by visiting www.api.edu.au

– Collaborative Power Engineering Centres of Excellence.

MODULE RESOURCES

COURSE NOTES

Generation System Fundamentals

PRESENTATION PACKS

Overview and Introduction (2 hrs)

Renewable Technologies - Solar (2 hrs)

Wind energy (2 hrs)

Energy Storage – Fuel Cells (2 hrs)

Cogeneration and Distributed Resources (2 hrs)

Nuclear Energy (2 hrs)

ACTIVITIES

Tutorial 1: Distribution Performance Analysis (1.5 hrs)

Tutorial 2: Implementation of PV Renewable Energy for a Green Building Site (1.5 hrs)

ACKNOWLEDGMENT

The author wishes to thank Mr Chris Bailey from Delta Electricity. Also, this material has been

developed with the support of API.

http://www.api.edu.au/



AUTHOR/S AND CONTACT DETAILS

Prof. Akhtar Kalam

Professor

School of Engineering and Science

Victoria University

Melbourne, Victoria

Email: [email protected]

mailto:[email protected]

COURSE NOTES


1. CONVENTIONAL GENERATION

The power engineers have made maximum use of innovations (starting from a humble beginning, as

shown in Figure 1.1) to deliver electricity safely, reliably and at a minimum cost to residential homes,

commercial buildings and factories. The main components of an electric power system are the

generating stations, transmission lines and the distribution systems.

TAKE SOME TIME TO REVIEW…

Before you read on, think of the electricity generation and provision cycle in

Australia today. List as many Australian electricity companies as you can against

each of the supply phases below:

Phases List Australian companies below…

Generations

Transmission

Distribution

Retail

Figure 1.2 shows a sketch of a typical power system. With the increase in demand for electricity more

larger and economical generating units are being built with further transmission of large chunk of

power from the generating plants to major load centres.



Figure 1.1: How electricity started with humble beginning.

The generation system includes the main parts of the power plants such as turbines and generators.

The energy resources used to generate electricity in most power plants are combustible, nuclear, or

hydropower. The burning of fossil fuels or a nuclear reaction generates heat that is converted into

mechanical motion by the thermal turbines. In hydroelectric systems, the flow of water through the

turbine converts the kinetic energy of the water into rotating mechanical energy. These turbines

rotate the electromechanical generators that convert the mechanical energy into electric energy.

Figure 1.2: Main components of power systems.



The power system is extensively monitored and controlled. It has several levels of protections to

minimize the effect of any damaged component on the system ability to provide safe and reliable

electricity to all customers.

1.1 GROWTH OF POWER SYSTEMS IN AUSTRALIA

With the tremendous growth in the Australian power system industry, there has been a substantial

employer demand for people with education and training in power systems and renewable energy

integration. Manufacturing industries, mining sectors and power generation, transmission and

distribution companies are among the employers continually seeking skilful power system engineers.

Electricity Gas Australia (EGA) 2009 reports comprehensive capacity and performance data for the

electricity and gas industries in 2007-08. EGA 2009 data shows that over 1,900 MW of electricity

generation capacity has been commissioned in the period since June 2008, including the 640 MW

Uranquinty and 435 MW Tallawarra gas-fired power stations in NSW and the 320 MW Kwinana power

station in WA. A further 5,100 MW of capacity is under construction, mostly comprising gas-fired

peaking plant and wind capacity, and another 2,000 MW of capacity is also under advanced planning

to meet growing demand over the next five years.

In terms of gas supply, in 2007-08 there was approximately 110,000 kilometres of gas transmission

and distribution pipelines in Australia, with a further 467 kilometres of pipeline commissioned since

June 2008. An additional 1,900 kilometres of new pipeline infrastructure was also under

development.

Other highlights from Electricity Gas Australia 2009 include:

in 2007-08, the electricity supply industry contributed $13.8 billion to Australia’s GDP of $1,037 billion, a 2.7% increase in the gross value added by the industry on 2006-07;

in 2007-08, the downstream gas industry contributed $1.6 billion to GDP, an increase of 3.1% in the gross value added compared to 2006-07;

an 18% reduction in the system average minutes without supply (SAIDI) to 231 minutes across Australia and a decrease in the number of interruptions per customer (SAIFI) from 2.28 in 2006-07 to 2.04 in 2007-08; and

an improvement in the safety performance of the electricity generation sector.

Australia is heavily dependent on coal for electricity, more so than any other developed country

except Denmark and Greece. About 80% is derived from coal. Australia's electricity is low-cost by

world standards. Natural gas is increasingly used for electricity, especially in South Australia (SA) and

Western Australia (WA).



Electricity consumption in Australia has been growing at nearly double the rate of energy use overall.

Electricity generation takes 44% of Australia's primary energy, and in terms of final energy

consumption, electricity provides 24% of the total.

1.2 CONVENTIONAL SOURCES OF ELECTRICAL ENERGY – WORLDWIDE [1-4]

WHICH DO YOU THINK TOPS THE LIST?

Try and have a go at ranking each energy source from highest usage (1) to lowest

usage (11) at today’s rates.

Wind Solar heat

Solar photovoltaic Hydrogen

Oil Coal

Hydropower Biomass

Tidal Geothermal

Natural gas

As shown in Figure 1.3, worldwide conventional energy resources are often divided into three loosely

defined categories:

1. Fossil fuel

2. Nuclear fuel

3. Renewable resources

Fossil fuels include oil, coal, and natural gas. Renewable energy resources include hydropower, wind,

solar, hydrogen, biomass, tidal, and geothermal. All these resources can also be classified as primary

and secondary resources. The primary resources are:

1. Fossil fuel

2. Nuclear fuel

3. Hydropower

The secondary resources include all renewable energy minus hydro power. Over 99% of all electric

energy worldwide is generated from primary resources. The secondary resources, although increasing

rapidly, have not yet achieved a level comparable to the primary resources.



Figure 1.3: World energy usage.

The worldwide generation capacity from 2005-2030 is shown in Figure 1.4. As can be seen from

Figure 1.5, most electrical energy is generated by oil, coal, and natural gas. Hydroelectric energy is

limited to about 6% of the world's electrical energy because of the limited water resources suitable

for generating electricity. Nuclear energy is only 6% of the total electrical energy because of the

public resistance to building new nuclear facilities in the past 20 years.

http://upload.wikimedia.org/wikipedia/commons/8/8a/World_energy_usage_width_chart.svg



Figure 1.4: World Electricity Generation by fuel, 2005-2030.

(Source: Energy Information Administration (EIA), International Energy Annual 2005; http://www.eia.doe.gov/iea)

Figure 1.5: Worldwide energy sources.

http://upload.wikimedia.org/wikipedia/commons/c/c6/2004_Worldwide_Energy_Sources_graph.png



As can be seen from Figure 1.6, there is a tremendous increase in the Asian capacity is due to the

accelerated installation of power plants to support the societal needs and the rapid industrial

developments in the region, particularly in China and India. This tremendous increase in energy

consumption in China and India is due to its recent industrial developments and the enhancement in

its standard of living.

Figure 1.6: Worldwide energy intensity.

1.2.1 FOSSIL FUEL

Fossil fuels are formed from fossils (dead plants and animals) buried in the earth's crust for millions of

years under pressure and heat. They are composed of high carbon and hydrogen elements such as oil,

natural gas, and coal. Further, because the formation of fossil fuels takes millions of years, they are

considered non-renewable.

Since the start of the Industrial Revolution in the nineteenth century, the world is dependent on fossil

fuels for its energy needs. The bulk of fossil fuels are used in transportation, industrial processes,

generating electricity as well as residential and commercial heating. The use of fossil fuel to generate

electricity is always a subject of hot debate. Burning fossil fuels causes a wide range of pollution that

includes the release of carbon dioxide, sulphur oxides, and the formation of nitrogen oxides. These

are harmful gases that cause some health and environmental problems. Also, the availability and

prices of fossil fuels are vulnerable to world politics. Oil production and distribution are often

interrupted during wartimes and due to political tensions between nations.

Natural Gas

According to Oil and Gas Journal, Australia had 30 trillion cubic feet (Tcf) of proven natural gas

reserves as of January 2009. Around 69% of those natural gas reserves are located off the western

coast in the Carnarvon Basin. Other important fields are the Cooper/Eromanga Basin (8%) in central

http://upload.wikimedia.org/wikipedia/commons/9/95/Energy_Intensity.png



Australia and the Bass/Gippsland Basin (20%) offshore southern Australia. The remainder comes from

scattered small fields off the southern coast and in the central regions.

Oil

Oil (also referred to as petroleum) is the most widely used fossil fuel worldwide. Petroleum is

extracted from fields with layers of porous rocks filled with oil.

According to Oil and Gas Journal (OGJ), Australia had 1.5 billion barrels of proven oil reserves as of

January 1, 2009. The majority of these reserves are located off the coasts of Western Australia, the

Northern Territory, and Victoria. The Carnarvon Basin accounts for 62% of Australia's production of

crude oil, condensate and liquefied petroleum gas (LPG).

Coal

Coal is a combustible rock of organic origin composed mainly of carbon (50-98%), hydrogen (3-13%)

and oxygen with lesser amounts of nitrogen, sulphur and other elements. Some water is always

present, as are grains of inorganic matter that form an incombustible residue known as ash.

Black coal is so called because of its black colour. It varies from having a bright, shiny lustre to being

very dull and from being relatively hard to soft. It has higher energy and lower moisture content than

brown coal. Most are of Permian age (about 250 million years old), but lower-rank, younger deposits

of Triassic, Jurassic and Cretaceous ages also are important. Permian black coal from New South

Wales and Queensland is exported in large quantities to Japan, Europe, South-East Asia, and the

Americas.

The major use of black coal is for generating electricity in power stations where it is pulverised and

burnt to heat steam-generating boilers. Coal used for this process is called steaming coal. In 2006,

77% of the electricity generated in Australia was produced by coal fired power stations (includes

black and brown coals).

Brown coal, sometimes called lignite, is a relatively soft material which has a heating value only about

one-quarter of that for black coal. It has much lower carbon content than black coal and higher

moisture content. When found near the surface in thick seams, it can be mined economically on a

large scale by open-cut methods.

In Victoria, almost all of the brown coal extracted is burnt to heat steam-generating boilers in

electrical power stations located near the coal mines. It is also made into briquettes, which are used

for industrial and domestic heating in Australia and are exported. Brown coal can be used also to

produce water gas, which is used in the production of ammonia, solvents and liquid fuels. Water gas

also can be a source of industrial carbon which is used to decolourise and purify solutions and (as

char) in iron, glass, and cement manufacture.

As of 2008, Australia contained 84 billion short tons (Bst) of recoverable coal reserves. Australia is the

world's fourth largest coal producer, after China, the United States, and India, but it is the largest net

exporter.



1.2.2 NUCLEAR FUEL

Nuclear fuel is heavy nuclear material that releases energy when its atoms are forced to split and in

the process, some of its mass is lost. The nuclear fuel used to generate electricity is mostly uranium

(U), but plutonium (Pu) is also used. Uranium is found in nature and contains several isotopes. Natural

uranium is almost entirely a mixture of three isotopes: 234U, 235U, and 238U, where the left

superscripts indicate the atomic mass of the isotopes. The concentration of these isotopes in natural

uranium is 99.2% for 238U and 0.7% for 235U. However, only 235U can fission in nuclear reactors.

Since the concentration of 235U in uranium ores is very low (0.7%), an enrichment process is used to

increase its concentration in nuclear fuel. For nuclear power plants, 235U concentration is about 3¬-

5%, and for nuclear weapons, it is over 90%.

The world consumption of nuclear fuel in 2006 is shown in Figure 7. Europe and the United States led

the world in the amount of nuclear fuel used to generate electricity. The United States alone

consumed about one-third of nuclear fuel in 2006.

Figure 1.7: Worldwide consumption of nuclear fuel.



WHICH ONE REALLY TIPS THE SCALE?

Australia is a large scale economy which relies heavily on its natural coal resource

in terms of its GDP. Despite this, which fuel source discussed above would be

ideal in light of the economic, environmental and social benefits that its usage may

bring? Think of the justifications for your choice.

Note down your answer here…

1.3 POWER PLANTS

At the power plant, energy resources such as coal, oil, gas, hydropower, or nuclear power are

converted into electricity. The main parts of the power plant are the burner (in fossil plants), the

reactor (in nuclear power plants), the dam (in a hydroelectric plant), the turbine, and the generator.

Power plants can be huge in size and capacity.

Although power plants are enormous in mass, they are delicately controlled. A slight imbalance

between the input power of the turbine and the output electric power of the generator may cause a

blackout unless rapidly corrected. To avoid blackouts, the massive amount of water or steam inside

the plant must be tightly controlled at all times, which is an enormous challenge to mechanical and

structural engineers.

The largest single-block power station in Australia is a 750MW supercritical-steam coal-fired power

station at Kogan Creek, near Chinchilla in Queensland (Figure 1.8). The A$1.1bn project started up in

2007. The plant was built by an international consortium that included Babcock-Hitachi and was led

by Siemens Power Generation (PG). Kogan Creek delivers its electricity to the National Grid by joining

into the Queensland to New South Wales Interconnector at Braemar Creek substation. The plant

operates as a base load station, generating electricity continuously.



Figure 1.8: Kogan Creek Power Plant in Queensland [5].

Turbines

The function of the turbine is to rotate the electrical generator by converting the thermal energy of

the steam or the kinetic energy of the water into rotating mechanical energy. There are two types of

turbines: thermal and hydroelectric. Figure 1.9 shows a model of a hydroelectric turbine

commissioned at Wellington Dam near Collie. It consists of blades mounted on a rotating shaft and

curved to capture the maximum kinetic energy from the water. The angle of the blade can be

adjusted in some types of turbines for better control on its output mechanical power.

Figure 1.9: Wellington Dam hydro-electric turbine [6].

In thermal power plants, fossil fuels or nuclear reactions are used to produce steam at high

temperatures and pressures. The steam is passed through the blades of the thermal turbine, and

causes the turbine to rotate. The steam flow is controlled by several valves at critical locations to

ensure that the turbine is rotating at precise speed.



Generators

There are two distinct types of construction of power station synchronous generators: salient pole

rotor and cylindrical rotor machines. Hydro-generators usually have salient pole rotors with vertical

shafts and rotate slower than the other generators. The thermal generators typically have cylindrical

rotors supported horizontally. The prime mover of a hydro-generator is a water turbine. The turbo-

generators in most of the large thermal power stations supplying the base load for the power grid are

driven by steam turbines. Other generators may be driven by gas turbines, diesel motors or other

turbines/motors.

Conventional Sources of Electric Energy - Australia

Thermal (coal, oil, nuclear) and hydro generations are the main conventional sources of electric

energy. The necessity to conserve fossil fuels has forced scientists and technologists across the world

to search for unconventional sources of electric energy. Some of the sources being explored are solar,

wind and tidal sources. The conventional and some of the unconventional sources and techniques of

energy generation are briefly surveyed here with a stress on future trends, particularly with reference

to the Australian electric energy scenario.

A table of various power plants according to the type (i.e. fossil fuel, nuclear, gas turbines, etc. is

shown in Table 1.

Table 1: Examples of Power Plants According to Type

Generation Type Generator Company

Fossil fuel power plants Tarong Power Corporation, Queensland, Australia

Stanwell Corporation, Queensland, Australia

CS Energy, Queensland, Australia

Cogeneration Indian Petrochemicals, Gandhar, India

Gas turbines Tallawarra power station, NSW Australia

Hydorelectric power generation

Barron Gorge - Stanwell Corporation, Queensland, Australia

Gordon River - Hydro Tasmania, Australia

Nuclear Tricastin Nuclear Power Plant, France

Magnetohydrodynamic (MHD) generation

U-25 MHD Power Plant, Moscow Institute of High Temperature, Russia

Geothermal power plants Birsdville Cycle Plant, Queensland, Australia

Mammoth Pacific binary geothermal power plants at the Casa Diablo geothermal field, USA

CalEnergy Navy I flash geothermal power plant at the Coso geothermal field, USA

Coopers Basin - is a sedimentary geological basin located mainly in the north-east part of South Australia and extends into south-west Queensland.

1.3.1 FOSSIL FUEL POWER PLANTS

Fossil power plants (coal, oil, or natural gas) utilize the thermal cycle described by the laws of

thermodynamics to convert heat energy into mechanical energy. This conversion, however, is highly

http://en.wikipedia.org/wiki/Sedimentary

http://en.wikipedia.org/wiki/South_Australia

http://en.wikipedia.org/wiki/Queensland



inefficient as described by the second law of thermodynamics where a large amount of the heat

energy must be wasted to convert the rest into mechanical energy. The heat released during the

combustion of coal, oil or gas is used in a boiler to raise steam. In Australia, heat generation is mostly

coal (black or brown) based. Hence, discussion is confined to coal-fired boilers for raising steam to be

used in a turbine for electric generation.

The chemical energy stored in coal is transformed into electric energy in thermal power plants. The

heat released by the combustion of coal produces steam in a boiler at high pressure and

temperature, which when passed through a steam turbine, gives off some of its internal energy as

mechanical energy. The axial-flow type of turbine is normally used with several cylinders on the same

shaft. The steam turbine acts as a prime mover and drives the electric generator (alternator). A

detailed diagram of a coal fired thermal plant is shown in Figure 1.10.

The efficiency of the overall conversion process is poor and its maximum value is about 40% because

of high heat losses in the combustion gases and the large quantity of heat rejected to the condenser

which has to be given off in cooling towers or into a stream/lake in the case of direct condenser

cooling. The steam power station operates on the Rankine cycle, modified to include superheating,

feed-water heating, and steam reheating. The thermal efficiency (conversion of heat to mechanical

energy) can be increased by using steam at the highest possible pressure and temperature. With

steam turbines of this size, additional increase in efficiency is obtained by reheating the steam after it

has been partially expanded by an external heater. The reheated steam is then returned to the

turbine where it is expanded through the final states of bleeding.

Figure 1.10: Coal fired plant schematic diagram [7].

To take advantage of the principle of economy of scale (which applies to units of all sizes), the trend

has always been to go for larger sizes of units. Larger units can be installed at much lower cost per



kilowatt. They are also cheaper to operate because of higher efficiency. They require lower labour

and maintenance expenditure. There may be a saving of as high as 15% in capital cost per kilowatt by

going up from a 100 to 250 MW unit size and an additional saving in fuel cost of about 8% per kWh.

Since larger units consume less fuel per kWh, they produce less air, thermal and waste pollution, and

this is a significant advantage in our concern for environment. The only trouble in the case of a large

unit is the tremendous shock to the system when outage of such a large capacity unit occurs. This

shock can be tolerated so long as this unit size does not exceed 10% of the online capacity of a large

grid.

Although coal-fired power plants are simple in design and easy to maintain, they are major producers

of pollution. Carbon dioxide (CO2), carbon monoxide (CO), sulphur dioxide (SO2), nitrous oxides (NOx),

soot, and ashes are some of the by-products of coal combustion. In fact, coal burning by power plants

and industries is responsible for 30%-40% of the total C02 in the air. In older and unregulated plants,

most of these pollutants are vented through the stack. However, with newer technologies, large

amounts of the pollutants are trapped by filters or removed from the coal before it is burned.

Examples of the pollution reduction measures that are taken in most coal-fired plants include the

following (see http://www.acarp.com.au/abstracts.aspx?repId=C19007):

Coal is chemically treated to remove most of its sulphur before it is burned.

Filters are used to remove the particulate (primarily fly ash) and some of the exhaust gases from the boilers. There are various types of filters; among them are the wet scrubber system and the fabric filter system (example: http://www.tri-mer.com/fabric-filters.html). With the wet scrubber, the exhaust gas passes through liquid, which traps flying particulate and SO2 before the gas is vented through the stacks. The fabric filter system works like a vacuum cleaner where the particulates are trapped in bags. Collected fly ash can be processed into other industrial products: http://www.youtube.com/watch?v=cxXx3fkE5h4&feature=related.

SO2 is removed by its own scrubber system.

NOx are reduced by upgrading the boilers to low NOx burners.

CO2 removal is too expensive to implement and not all power plants use a CO2 scrubber system.

Air and thermal pollution is always present in a coal fired steam plant. The air polluting agents

(consisting of particulates and gases such as NOx, CO, CO2, SO2, etc.) are emitted via the exhaust

gases and thermal pollution is due to the rejected heat transferred from the condenser to cooling

water. Cooling towers are used in situations where the stream/lake cannot withstand the thermal

burden without excessive temperature rise. The problem of air pollution can be minimized through

scrubbers and electro-static precipitators and by resorting to minimum emission dispatch.

1.3.2 COGENERATION

Considering the tremendous amount of waste heat generated in thermal power generation, it is

advisable to save fuel by the simultaneous generation of electricity and steam (or hot water) for

industrial use or space heating. Now called trigeneration/ecogeneration, such systems have long

been common. Currently, there is renewed interest in these because of the overall increase in energy

efficiencies which are claimed to be as high as 70%.



Cogeneration of steam and power is highly energy efficient and is particularly suitable for chemicals,

paper, textiles, food, fertilizer and petroleum refining industries. Thus these industries can solve

energy shortage problem in a big way. Further, they will not have to depend on the grid power. One

advantage with the restructure of the electricity supply industry is that extra power can be sold.

There are two possible ways of cogeneration of heat and electricity: (i) Topping cycle, (ii) Bottoming

cycle. In the topping cycle, fuel is burnt to produce electrical or mechanical power and the waste heat

from the power generation provides the process heat. In the bottoming cycle, fuel first produces

process heat and the waste heat from the processes is then used to produce power.

Coal-fired plants share environmental problems with some other types of fossil-fuel plants; these

include "acid rain" and the "greenhouse" effect. Figure 1.11 illustrates an example of a cogeneration

plant producing electricity and heat.

Figure 1.11: Example of a KMW Energy cogeneration plant for the production of electricity and district heating, with

corresponding environmental systems (Source: http://www.kmwenergi.se/english/page.asp?PageId=156).

1.3.3 GAS TURBINES

With increasing availability of natural gas (methane) prime-movers based on gas turbines have been

developed on the lines similar to those used in aircraft. Gas combustion generates high temperatures

and pressures, so that the efficiency of the gas turbine is comparable to that of steam turbine.

Additional advantage is that exhaust gas from the turbine still has sufficient heat content, which is

used to raise steam to run a conventional steam turbine coupled to a generator. This is called

http://www.kmwenergi.se/english/page.asp?PageId=156



combined-cycle gas-turbine (CCGT) plant. The schematic diagram of such a plant is drawn in Figure

1.12.

Figure 1.12: Schematic of a combined-cycle gas turbine power station [8].

The $A350 million Tallawarra power station, located near Wollongong, uses the combined cycle

principle. This station is built on a 16 hectare parcel of land that was previously the site of a 320 MW

coal plant. This is one of Australia’s most environmentally efficient fossil fuel-fired power stations,

producing 70% less carbon dioxide emissions than some coal-fired power stations.

1.3.4 HYDROLECTRIC POWER GENERATION

The oldest and cheapest method of power generation is that of utilizing the potential energy of

water. The energy is obtained almost free of running cost and is completely pollution free. Of course,

it involves high capital cost because of the heavy civil engineering construction works involved. Also it

requires a long gestation period of about 5-8 years as compared to 4-6 years for steam plants.

Hydroelectric stations are designed, mostly, as multipurpose projects such as river flood control,

storage of irrigation and drinking water, and navigation. A simple schematic diagram of a hydro plant

is shown in Figure 1.13. The vertical difference between the upper reservoir and tail race is called the

head.



Figure 1.13: Schematic for a storage type hydro plant (Source: Tennessee Valley Authority).

Hydro plants are of different types such as run-of-river (use of water as it comes), pondage (medium

head) type, and reservoir (high head) type. The reservoir type plants are the ones which are

employed for bulk power generation. Often, cascaded plants are also constructed, i.e., on the same

water stream where the discharge of one plant becomes the inflow of a downstream plant.

1.3.5 NUCLEAR POWER STATIONS

From the availability point of view, nuclear fuel is the most abundant source of energy. The common

fuel for nuclear power plants is uranium; an atom of uranium produces about 107 times the energy

produced by an atom of coal. In the United States, there are over hundreds of commercial nuclear

power plants in operation generating about 20% of the total electric energy. Worldwide, there are

about 400 power plants generating as much as 70% of the energy demand in nations such as France.

However, because of public concern, few new nuclear power plants have been constructed in the

United States, and several are expected to be retired in the near future. However, with the demand

of electricity, public support for nuclear power is growing and the new trend may be to have more

nuclear fired power stations.

Just as many conventional thermal power stations generate electricity by harnessing the thermal

energy released from burning fossil fuels, nuclear power plants convert the thermal energy released

from nuclear fission. The reactor is used to convert nuclear (also known as 'atomic') energy into heat.

A reactor could also be one in which heat is produced by fusion or radioactive decay.

Nuclear power plants can generate electricity by one of two methods:

"Fission" is the splitting of heavy nuclei element such as uranium, plutonium, or thorium into many lighter elements. By this process, mass is converted into energy. Fission power plants have two main designs: boiling water reactor (BWR) and pressurized water reactor (PWR). About two



third of the nuclear reactors are pressurized water reactors (Figure 1.14), and almost all of the commercial nuclear power plants worldwide are fission reactors.

"Fusion" is a process by which two lighter elements are combined into a heavier element. The fusion technique is in the research stages and not yet fully developed for commercial power plants.

Figure 1.14: Nuclear power plant-pressurized water reactor (Source: Steffen Kuntoff -

http://en.wikiversity.org/wiki/File:Nuclear_power_plant-pressurized_water_reactor-PWR.png).

The associated merits and problems of nuclear power plants as compared to conventional thermal

plants are mentioned below:

Merits

1. A nuclear power plant is totally free of air pollution.

2. It requires little fuel in terms of volume and weight, and therefore poses no transportation

problems and may be sited, independently of nuclear fuel supplies, close to load centres.

However, safety considerations require that they be normally located away from populated

areas.

Demerits

1. Nuclear reactors produce radioactive fuel waste, the disposal of which poses serious

environmental hazards.



2. The rate of nuclear reaction can be lowered only by a small margin, so that the load on a nuclear

power plant can only be permitted to be marginally reduced below its full load value. Nuclear

power stations must, therefore, be reliably connected to a power network, as tripping of the lines

connecting the station can be quite serious and may required shutting down of the reactor with

all its consequences.

3. Because of relatively high capital cost as against running cost, the nuclear plant should operate

continuously as the base load station. Wherever possible, it is preferable to support such a

station with a pumped storage scheme.

4. The greatest danger in a fission reactor is in the case of loss of coolant in an accident. Even with

the control rods fully lowered quickly called ‘scram operation’, the fission does continue and its

after-heat may cause vaporizing and dispersal of radioactive material.

1.3.6 MAGNETOHYDRODYNAMIC (MHD) GENERATION

In thermal generation of electric energy, the heat released by the fuel is converted to rotational

mechanical energy by means of a thermocycle. The mechanical energy is then used to rotate the

electric generator. Thus two stages of energy conversion are involved in which the heat to mechanical

energy conversion has inherently low efficiency. Also, the rotating machine has its associated losses

and maintenance problems. In MHD technology, electric energy is directly generated by the hot gases

produced by the combustion of fuel without the need for mechanical moving parts.

In a MHD generator, electrically conducting gas at a very high temperature is passed in a strong

magnetic field, thereby generating electricity. High temperature is needed to ionize the gas, so that it

has good electrical conductivity. The conducting gas is obtained by burning a fuel and injecting

seeding materials such as potassium carbonate in the products of combustion. The principle of MHD

power generation is illustrated in Figure 1.15. About 50% efficiency can be achieved if the MHD

generator is operated in tandem with a conventional steam plant.

Figure 1.15: MHD Power Generator (Source: Encyclopaedia Britannica, 1999).



Though the technological feasibility of MHD generation has been established, its economic feasibility

is yet to be demonstrated. In 1986, Professor Messerle at The University of Sydney researched coal-

fueled MHD. This resulted in a 28 MWe topping facility that was operated outside Sydney. Although

many countries like US, Italy, Japan and China have researched on MHD power generators, but only

India and Russia have kept up their interest on MHD development.

1.3.7 GEOTHERMAL POWER PLANTS

(Source: http://www.ga.gov.au/image_cache/GA10663.pdf)

Geothermal energy is the heat contained within the Earth and it can be used to generate electricity

by utilising two main types of geothermal resources (Figure 1.16). Hydrothermal resources use

naturally-occurring hot water or steam circulating through permeable rock, and Hot Rock resources

produce super-heated water or steam by artificially circulating fluid through the rock. Electricity

generation from geothermal energy in Australia is currently limited to an 80kW net power plant at

Birdsville in south west Queensland. However, this is likely to change in the future as Hot Rock power

plants become increasingly commercially viable.

Worldwide there has been some use of geothermal energy in the form of steam coming from

underground in the USA, Italy, New Zealand, Mexico, Japan, Philippines and some other countries.

The present installed geothermal plant capacity in the world is about 500 MW and the total

estimated capacity is immense provided heat generated in the volcanic regions can be utilized. Since

the pressure and temperatures are low, the efficiency is even less than the conventional fossil fuelled

plants, but the capital costs are less and the fuel is available free of cost.

Potential Advantages of Geothermal Power Generation in Australia

Baseload and peaking capability: Geothermal power-plants can operate 24 hours a day, 365 days a year and are unaffected by climatic factors.

Low CO2 emissions: Binary geothermal power plants could be zero-emission (no CO2 or oxides of nitrogen and sulphur).

High availability factors: Binary power plants can usually produce electricity for 95% of the time.

Low environmental impacts: No acid rain, mine spoils, open pits, oil spills, radioactive wastes, or damming of rivers. Binary power plants occupy small land areas.

Increased energy security: Geothermal is an indigenous supply of energy, providing energy supply and pricing security.

Existing Geothermal Power in Australia

The only existing geothermal power generation in Australia is a small, 80kW net binary-cycle plant at

Birdsville in south west Queensland. This power plant utilises a low-temperature hydrothermal-type

geothermal resource, accessing 98°C groundwater from a 1,230 metre deep artesian bore that taps a

confined aquifer in the underlying Great Artesian Basin. The Great Artesian Basin spans 22% of the

Australian continent and has groundwater temperatures ranging from 30°C to 100°C at well heads.

http://www.ga.gov.au/image_cache/GA10663.pdf



Figure 1.16: Geological settings of hydrothermal and Hot Rock geothermal systems in Australia.

Future Electricity Generation in Australia using Geothermal Energy

Australia has an abundance of high-heat producing basement rocks buried under sediments. In 2007,

29 companies had applied for geothermal exploration licenses in Australia, and five companies had

begun drilling potential sites in South Australia. These are:

Geodynamics Limited (Habanero project near Innamincka);

Petratherm (Paralana and Callabonna projects);

Green Rock Energy Limited (Blanche project);

Geothermal Resources (Lake Frome project); and

Scopenergy Limited (project near Millicent and Beachport).



Geodynamics Limited is aiming to have a 40MW commercial-scale demonstration plant providing

electricity to the National Electricity Grid by the end of 2010.



2. NON-CONVENTIONAL SOURCE

With rising concerns regarding global warming and the associated impacts upon climate changes and

sea levels, the increasingly rapid depletion of fossil fuel resources and the desire to maximize security

of fossil supply, the clean, non-polluting and sustainable nature of renewable energy is assuming

increasing importance.

Governments, utilities, financial institutions and industry are taking a growing interest in promoting

the integration of renewable energy (like solar, wind etc.) into their generating systems and

investment portfolio.

Throughout Australia, government policies are in place requiring to minimise energy consumption by

15% and purchase 5% of their total consumption from Green Power supplies. In order to assess the

range of renewable energy options that can be integrated in any potential site the following actions

are required:

Identify and propose potential energy systems that can be integrated.

Provide sufficient detail that the project may proceed with detailed design of proposed system.

Ensure the final proposal is visible, innovative and promotes the project credentials.

The key project parameters for any sustainable energy proposal are:

The renewable energy system should be designed to generate electricity.

A total budget for entire project (investigation, detailed design, construction and commissioning) should be specified.

The system should comprise of proven technology.

The system should be visible and marketable.

Potential to be used as a demonstrative project and educational tool for the public.

2.1 RENEWABLE AND NON-CONVENTIONAL ENERGY SOURCES [1]

To protect environment and for sustainable development, the importance of renewable energy

sources cannot be overemphasized. It is an established and accepted fact that renewable and non-

conventional forms of energy will play an increasingly important role in the future as they are cleaner

and easier to use and environmentally benign and are bound to become economically more viable

with increased use.

Because of the limited availability of coal, there is considerable international effort into the

development of alternative/new/non-conventional/renewable/clean sources of energy. Most of the

new sources (some of them in fact have been known and used for centuries now!) are nothing but

the manifestation of solar energy, e.g., wind, sea waves, ocean thermal energy conversion (OTEC) etc.



In this section, we shall discuss the possibilities and potentialities of various methods of using solar

energy.

THINK BEFORE YOU READ

How familiar are you with the various types of non-conventional or emerging

sources of energy? Which ones do you think have the most promise in Australia?

Why?

Write down your answer here…

2.1.1 WIND POWER

Winds are essentially created by the solar heating of the atmosphere. Several attempts have been

made since 1940 to use wind to generate electric energy and development is still going on. However,

techno-economic feasibility has yet to be satisfactorily established.

Wind as a power source is attractive because it is plentiful, inexhaustible and non-polluting. Further,

it does not impose extra heat burden on the environment. Unfortunately, it is non-steady and

undependable. Control equipment has been devised to start the wind power plant whenever the

wind speed reaches 30 km/h. Methods have also been found to generate constant frequency power

with varying wind speeds and consequently varying speeds of wind mill propellers. Wind power may

prove practical for small power needs in isolated sites. But for maximum flexibility, it should be used

in conjunction with other methods of power generation to ensure continuity.

For wind power generation, there are three types of operations:

1. Small, 0.5-10 kW for isolated single premises

2. Medium, 10-100 kW for communities

3. Large, 1.5 MW for connection to the grid (Figure 2.1).



Figure 2.1: Wind energy (Source: http://rsindiagroups.com/wind_energy.html).

Wind power in Australia is a proven and reliable technology that can be and is readily deployed. At

the close of 2008, there were 50 wind farms in Australia, with a total of 756 operating wind turbines.

The total operating wind generating capacity at the end of 2008 was 1,300 MW providing 1.3% of

Australia's national electricity demand. South Australia has more than half of the nation's wind power

capacity, whilst Victoria also has a sizeable system, with large proposals for expansion.

Australia's total wind generation capacity in 2009 is 1.494 GW. By comparison Germany has 22 GW,

US 16 GW, Spain 15 GW, India 8 GW and China 6 GW. While Australia produces about 1.3% of its

electricity from wind power, it accounts for approximately 19% of electricity production in Denmark,

9% in Spain and Portugal, and 6% in Germany and the Republic of Ireland.

2.1.2 SOLAR ENERGY

The average incident solar energy received on earth's surface is about 600 W/m2 but the actual value

varies considerably. It has the advantage of being free of cost, non-exhaustible and completely

pollution-free. On the other hand, it has several drawbacks-energy density per unit area is very low, it

is available for only a part of the day, and cloudy and hazy atmospheric conditions greatly reduce the

energy received. Therefore, harnessing solar energy (Figures 2.2 and 2.3) for electricity generation,

challenging technological problems exist, the most important being that of the collection and



concentration of solar energy and its conversion to the electrical form through efficient and

comparatively economical means.

Figure 2.2: Solar photovoltaic (Source: Goswami - http://rsindiagroups.com/solar_energy.html).

Figure 2.3: Solar photovoltaic (Source: http://rsindiagroups.com/solar_energy.html).

Australia has an estimated 115 MW of installed PV power (July 2009), contributing an estimated 0.1

to 0.2% of total electricity production despite the hot, dry, and sunny climate that would make it ideal

for utilisation. This unreached grid parity is mainly due to the higher cost per kW than other power

sources because of the cost of solar panels. Feed-in tariffs and mandatory renewable energy targets

are designed to assist renewable energy commercialisation in Australia.

Solar power potential is unlimited; a 154 MW photovoltaic (PV) solar power station in Victoria is

planned and is expected to cost $420 million. It is expected to be the biggest and most efficient solar

photovoltaic power station in the world. The power station is expected to concentrate the sun by 500



times onto the solar cells for ultra high power output. The Victorian power station will generate

electricity directly from the sun to meet the annual needs of over 45,000 homes with on-going zero

greenhouse gas emissions.

2.1.2.1 HISTORY OF SOLAR PHOTOVOLTAIC ENERGY

Photovoltaic (PV) cells directly convert solar energy into electricity and were initially developed in the

1950s for use on satellites and the space program. PV cells have been the exclusive power source for

satellites orbiting the earth since the 1960s [1-3]. PV systems have been used for remote stand-alone

systems throughout the world since the 1970s. In the 1980s, commercial and consumer product

manufacturers began incorporating PV into every commercial product. In the 1990s, many utilities

are finding PV to be the best choice for thousands of small power needs.

Silicon is the main semiconductor used in commercial cells. Panels marketed are mostly made from

mono-crystalline, poly-crystalline or amorphous silicon cells. Many other materials are being

developed but have not yet achieved the production level of silicon cells.

A series of cells is inter-connected on a panel, with electrical output ranging from 10 to 100 Wp

typically. The junction of the panel or module allows building integration and to protect the cells from

the weather. Multiple panels may then be interconnected to form a string, and several strings may be

used in parallel to form an array.

Contrary to popular belief, instead of Europe, China has made aggressive and well-timed moves in the

solar race. In only five years, it has gone from being a negligible player to the world's top producer of

solar PV cells, according to a new report from the European Commission Joint Research Centre

Institute for Energy (Figure 2.4). Worldwide solar module production increased by 80% in 2008 alone,

with Asia and Europe taking the largest share while the U.S. share barely budged.

Figure 2.4: The big players in the world of PV production.

(Source: JRC PV Status Report 2009. "In 2008, China became the global leading producer of solar cells with an annual

production of about 2.4 GW, followed by Europe with 1.9 GW, Japan with 1.2 GW and Taiwan with 0.8 GW. If this trend

continues, China might have about 32% of the world-wide production capacity by 2012.")

http://ec.europa.eu/dgs/jrc/index.cfm?id=1410&obj_id=8690&dt_code=NWS&lang=en



Two major types of PV systems available in the marketplace today are flat plate and concentrators.

As the most prevalent type of PV systems, flat plate systems build the PV modules on a rigid and flat

surface to capture sunlight. This section provides a detailed explanation on different flat plate PV

technologies that can be considered and proposed for a typical BIPV (Building Integrated PV) project.

Concentrator systems use lenses to concentrate sunlight on the PV cells and increase the cell power

output as described in the next section. Comparing the two systems, flat plate systems are typically

less complicated but employ a larger number of cells while the concentrator systems use smaller

areas of cells but require more sophisticated and expensive tracking systems. Unable to focus diffuse

sunlight, concentrator systems do not work under cloudy conditions. The value of solar cell flat plate

technology and their efficiency in the generation of electricity can vary widely between the different

technologies and material. For the purpose of any BIPV project the following types of materials and

installation arrangement can be proposed.

BIPV cells are solar cells integrated into the

building whereby displacing conventional

building materials as the BIPV cells can be

applied as window glazing. BIPV systems

generally have the cells fixed between two

layers of glass (Figure 2.5). Although no light

can be transmitted through the actual PV cell,

the coordination and the spacing between the

cells can be adjusted to control the amount of

ambient light penetrating through the system,

allowing the architect to balance the

daylight/shading required.

Figure 2.5: BIPV solar cells.

(Source: http://bdslate.en.made-in-china.com)

BP Solar have a range of commercial grade

BIPV cells that are currently available on the

market (Figure 2.6). They currently offer two

types; Saturn Technology – 2.5Wp per cell and

SiN Polycrystalline – 2.2Wp per cell. Both types

are 125mm x 125mm in size and can be

supplied in any size glass up to 3.3m x 2.2m. Figure 2.6: Two types of BP Solar BIPV cells.

2.1.2.2 TYPES OF PV MODULE MATERIALS

CRYSTALLINE MATERIALS

SINGLE-CRYSTAL SILICON

A single-crystal silicon has a uniform molecular

structure (Figure 2.7). Compared to non-

crystalline materials, its high uniformity results

in higher energy conversion efficiency - the

ratio of electric power produced by the cell to

the amount of available sunlight power, i.e.

power-out divided by power-in. The

conversion efficiency for single-silicon

commercial modules ranges between 15-20%.

Not only are they energy efficient, single-



Figure 2.8: Polycrystalline

silicon.

silicon modules are

highly reliable for

outdoor power

applications. Single

crystal wafers are sliced

(approx. 1/3 to 1/2 of a

millimetre thick), from a

large single crystal ingot,

grown at around 1400°C.

The silicon must be of a

very high purity and

have a near perfect

crystal structure.

POLYCRYSTALLINE SILICON

Consisting of small grains of single-crystal

silicon, polycrystalline PV cells are less energy

efficient than single-crystalline silicon PV cells

(Figure 2.8). The grain boundaries in

polycrystalline silicon hinder the flow of

electrons and reduce the power output of the

cell. The energy conversion efficiency for a

commercial module made of polycrystalline

silicon ranges between 10 -15%. Since no

sawing is needed, the manufacturing cost is

lower. Compared to single-crystalline silicon,

polycrystalline silicon material is stronger and

the average price for a polycrystalline module

made from cast and ribbon is slightly lower

than that of a single-crystal module.

GALLIUM ARSENIDE (GaAS)

A compound semiconductor made of two

elements: gallium (Ga) and arsenic (As), GaAs

has a crystal structure similar to that of silicon

(Figure 2.9). An advantage of GaAs is that it

has a high level of light absorptivity. GaAs has

much higher energy conversion efficiency than

crystal silicon, reaching about 25 - 30%. GaAs

is popular in space applications where strong

resistance radiation damage and high cell

efficiency are required. The biggest drawback

of GaAs PV cells is the high cost of the single-

crystal substrate that GaAs is grown on.

Therefore, this PV cell has only been

considered for use in concentrator systems

where only a small area of GaAs cells is

needed.

THIN FILM MATERIALS

In a thin-film PV cell (Figure 2.10), a thin

semiconductor layer of PV materials is

deposited on supporting low-cost layer such as

glass, metal or plastic foil. Since thin-film

materials have higher light absorptivity than

crystalline materials, the deposited layer of PV

materials is extremely thin. Thinner layers of

Figure 2.7: Single-crystal

silicon.

Figure 2.9 Gallium

Arsenide PV.

Figure 2.10: Thin-film PV cell.



material yield significant cost saving. However,

thin film PV cells suffer from poor cell

conversion efficiency due to non-single crystal

structure; average thin film cell solar module

has an efficiency between 6% - 10%, requiring

larger array areas and increasing area-related

costs such as mountings. Materials used for

thin film PV modules are Amorphous Silicon

(a-Si), a non-crystalline form of silicon. The

silicon is called “amorphous” because it has a

non-crystalline structure. Amorphous silicon

can absorb 90% of the usable light energy

shining on it. Other advantages are that it can

be produced at lower temperatures and can

be deposited on low-cost substrates such as

plastic, glass, and metal. This makes

amorphous silicon ideal for BIPV products, and

the leading thin-film PV material. The electrical

output of amorphous silicon cells decreases up

to 20% over a period of time when first

exposed to sunlight, before the material

stabilises.

HYBRID

These panels utilize a combination of mono-

crystalline PV cells, surrounded by amorphous

silicon PV cells. These have excellent sensitivity

to lower light levels and indirect light. These

panels have the world's highest power

generation per installation area, for their

conversion efficiency for sunlight to electricity.

It can be as high as to 22%. These Hybrid

Sanyo panel (Figure 2.11) also have a low-

temperature manufacturing process which

means fewer materials are used, which

minimises the panel's impact on the

environment.

TEST YOUR KNOWLEDGE

Use the diagram below to fill in the details of each branch of the map

according to: 1) material composition, 2) advantages, and 3) disadvantages.

Then check your answers against the detailed descriptions above or use it to

query your lecturer in class. Print more pages if you require more space.

PV Module Materials

Sin

gle

crys

tal

silic

on

Po

lycr

ysta

llin

e

Silic

on

Th

in F

ilm M

ater

ials

GaA

S

1

2

3

1

2

3

1

2

3

1

2

3

Figure 2.11: Sanyo Hybrid Solar PV.



2.1.2.3 TYPES OF STRUCTURE FOR THE INSTALLATION

Solar panels can be mounted on top of an existing roof system in a wide variety of situations such as:

Installed in a static position facing North with a minimum tilt of 15º from horizontal (important to allow rain to wash dust from the array) any tilt between vertical and 15º could be used, but the optimal angle is latitude minus 10º (Figure 2.12). The tilt should be somewhat lower to maximise performance in summer and higher to maximise performance in winter. In most BIP projects, the PV systems can be designed to achieve the maximum power output in summer. The optimum tilt angle (β) for the modules for these applications is to be:

βopt = φ - 10° (where φ is the latitude which is 37° in Melbourne)

Figure 2.12: Roof mounted PV

Installed in trackers, which are used to keep PV panels directly facing the sun, thereby increasing the output from the panels. Trackers can nearly double the output of an array (Figure 2.13) but also increase cost and mechanical complexity.

Figure 2.13: Solar tracking system (Source: http://images.google.com.au/).

http://images.google.com.au/)



Combined with the roof material into a single

integrated solar roofing product consisting of

thin film amorphous PV cells laminated onto

roofing panels to make a single structure

(Figure 2.14).

Figure 2.14: Thin film solar panel (Source:

http://go635254.s3.amazonaws.com/cleantechnica).

2.1.2.4 CONCENTRATING SOLAR COLLECTORS TO PRODUCE ELECTRICITY [4]

By using reflectors to concentrate sunlight on the absorber of a solar collector, the size of the

absorber can be dramatically reduced, which reduces heat losses and increases efficiency at high

temperatures. Another advantage is that reflectors can cost substantially less per unit area than

collectors. This class of collector is used for high-temperature applications such as steam production

for the generation of electricity and thermal detoxification. The 3 basic types of concentrating

collectors are Parabolic dish, Parabolic trough and Power tower.

At this stage only Parabolic dish have normally been considered as an option for the BIPV project as it

is the only “proven” technology in Australia which could be offered for “small” sizes (even at times

they can be beyond the project budget) due to the “modularity” advantage, as dishes generate

electricity independently.

Minimum commercially available size for each technology are estimated to be as follows:

Parabolic dish: modular systems have been realised with total capacities up to 5 MWe. The modules have maximum sizes of 50 kWe (minimum dish size commercially available in Australia is 35 kW) (Figure 2.15).

Figure 2.15: Parabolic solar PV.

http://go635254.s3.amazonaws.com/cleantechnica



Individual Power tower: commercial plants could be sized to produce anywhere from 50 to 200 MW of electricity (Figure 2.16).

Figure 2.16: Power tower.

Individual Parabolic trough systems (Figure 2.17): currently can generate from 10 to 400 MWe. (Parabolic though first project in Australia “John Marcheff Solar project: 36 MW Concentrating Line Focus Receiver (CLFR)” was offered by the New South Wales State Government loan funding in December 2002 for first-stage testing of a commercial 20,000 m² compact linear fresnel reflector array which can supply thermal energy at 285°C/70 bar to a conventional coal-fired steam-turbine cycle preheater).

Figure 2.17: Concentrating Line Focus Receiver.

PARABOLIC DISH SYSTEMS

A parabolic dish collector is similar in appearance to a large satellite dish, but has mirror-like

reflectors and an absorber at the focal point. It uses a dual axis sun tracker.

A parabolic dish system (Figure 2.18) uses a computer to track the sun and concentrate the sun's rays

onto a receiver located at the focal point in front of the dish. Different technologies exist: the receiver

could be a thermal receiver which absorbs the concentrated beam of solar energy, converts it to heat,

and transfers the heat to the engine/generator to generate electricity or the proposed technology in

this project comprises in the heart of the system of an array of close-packed PV cells that are located



in the solar receiver, suspended above the focus of the mirrors. The cells are mounted in a way that

allows efficient dissipation of thermal energy as well as extraction of electricity. The sunlight is

concentrated 500x, and effective cooling is critical to achieve efficient performance.

Figure 2.18: Parabolic dish collector.

COMPONENTS IN A PV POWER SYSTEM [5]

In addition to PV cells, most systems require additional components, which are generally produced by

specialist commercial suppliers. These include:

inverters;

batteries;

tracking systems;

arrays to carry modules;

regulators, controllers and other electronic components.

SYSTEM CONTROL

All stand-alone PV systems normally require some form of control or power conditioning. The

complexity of the control function depends on system user requirements, the type of system and the

number of power sources included. In simple systems, battery-charge controllers interface between

the PV array and the battery while the inverter interfaces between the battery and the AC load.

THE BATTERY

For the applications requiring energy at night or during periods of low sunlight, a storage medium

must be used to ensure the autonomy of the system. Most stand-alone systems require storage. The

usual storage equipment used with stand-alone PV systems is rechargeable batteries.

The most important feature of a battery's operation is “cycling”. During the daily cycle, the battery is

charged during the day and discharged by the night-time load. Superimposed onto the daily cycle is



the seasonal cycle, which is associated with periods of reduced radiation availability. This, together

with other operating parameters (such as ambient temperature, current, voltages) affects the battery

life and maintenance requirements.

THE POWER-CONDITIONING EQUIPMENT

The electrical output of an array is usually modified or regulated in some way to ensure that it meets

the requirements of the other components. There are three main power-conditioning devices that

are commonly found in stand-alone PV systems: the charge regulator, the power point conditioner

and the inverter.

The charge regulator is the most common type of power-conditioning device. It is normally found in

all systems using rechargeable batteries. Its primary function is to manage the use of the batter by

cutting back current from the PV array when the battery is sufficiently charged. A maximum power

point tracker (MPPT) is a device that operates the PV array at the voltage that provides the maximum

power and then converts this to the output voltage required by the battery or the load. The device

allows use of a greater fraction of the energy available from the PV array and map be integrated as a

function in the charge controller. An inverter is required in systems that must supply power to the

loads. This equipment converts DC output from the battery or the array to standard AC power similar

to that supplied by the utilities. Sophisticated inverters often integrate control functions, and bi-

directional units are available. The latter can also rectify AC input to produce DC, enabling batteries to

he charged from fossil-fuel generators.

ENERGY AND POWER REQUIREMENT ASSESSMENT

An important step in the design of a stand-alone PV system is the load assessment. This step is too

often not carried out carefully enough, leading to a poor operation of the PV system. Overestimating

the load will ensure a reliable supply of electricity, but the cost of the system will be unnecessarily

high. On the other hand, underestimating the load can lead to an unreliable power supply, increased

aging of the batteries and unexpected use of a back-up diesel generator. In some cases, the system

may fail to supply a critical load. Consequently, all loads must be properly evaluated, both in terms of

power and duty cycle. This indicates the daily energy need.

The maximum-demand assessment is also important, as the system must be sized to have the

capacity to power the load. This requires an evaluation of the maximum power that might be

required at any time. Since high values will result in a more expensive system (more storage and

possibly a larger inverter would be required), it is wise to consider.

In order to choose an optimum size of the components such as storage units, inverters and so on for

optimum performance and minimum costs we have to manage the loads

either by reducing the demand peaks

or by matching demand peaks to renewable energy input peak.

If power demand curves match well with the availability of solar irradiation, the system can be

considerably smaller (and cheaper) than if this is not the case.



The daily average energy production of a PV panel (or array) can easily be evaluated by multiplying its

rated output by the average number of peak sun hour. PSH is an equivalent measure of one hour of

sunlight with at 1000 W/m2 rate of energy absorption by the earth. The number of peak sun hours

can usually be obtained from national radiation data books or can be read on solar radiation maps.

2.1.2.5 FACTORS AFFECTING PERFORMANCE

When designing a system, one must account for a number of factors that may reduce this

performance. Correction for not operating the PV panel at its maximum power point (panels are

rated at this point) if a maximum power point tracker is not used (typically up to 10%); battery

efficiency, losses of the power-conditioning system for an AC supply (inverter), from 10 to 20% losses;

the array tilt and position; this is more important for tropical circumstances than temperate areas;

temperature effects, shading, even partial, which greatly affects the performance of a panel; dust,

snow or ice accumulation, which is strongly dependent on the climatic conditions.

When sizing the system, one should take into account the seasonal variations both in demand for and

in availability of energy. On the other hand, the solar energy also varies with the seasons.

The size of the battery in a stand-alone system more dependent on the autonomy desired. This is the

number of days the battery could provide the loads without ally input from the PV array. This factor is

directly dependent on storage capacity required. This is usually a function of climate and user

requirements.

DEPTH OF DISCHARGE (DOD)

DOD indicates how much of the total capacity of the battery is used. Too deep cycling of limited

batteries reduces their life expectancy. The DOD strongly depends on the application, and can vary

from a few percent to as much as 70% the operational temperature of battery. Low temperatures

reduce the storage capacity of batteries. High temperatures are detrimental to battery longevity. The

ideal operational temperature is in the 20 to 25°C range.

The battery capacity decreases with increasing discharge current. Thus, applications requiring high

powers will need larger battery capacity than low power applications, even if the total energy

consumption is the same.

SIZE OF INVERTER

In selecting the inverter, two ratings are of particular importance: the rating in the continuous mode

and the rating in the surge mode. The inverter must be able to meet the maximum power demand

including the surge produced by loads such as motors. The inverter is inefficient when the load is

typically less than 10% of its nominal power rating.

BALANCING COST AND PERFORMANCE

The cost of PV electricity depends on

the purchase price of the array plus balance of system costs;

the type of technology;

the panel efficiency available insolation levels;



the climatic conditions (including, temperature) mounting and integration costs the cost of maintenance.

An indicator for selecting a power system is the life-cycle cost. A PV/diesel hybrid system could use

more PV and less diesel fuel or less PV (less PV means saving capital costs and more diesel means

higher maintenance costs) against more diesel and higher maintenance. The life-cycle cost can be

evaluated for different options and the choice can then be made. A PV-battery system can have more

batteries and less PV, or more PV and fewer batteries, and still meet the same requirements. In any

case there is always a trade-off between the cost and the performance of a system.

2.1.2.6 ENERGY MANAGEMENT

The storage of energy in a battery results in some loss of energy. That is, for every unit of energy

taken from a battery, more than one unit will have to be supplied to the battery. It follows that losses

can be reduced by limiting the need to draw energy from the battery. This is achieved by matching

demand and supply peaks, that is, planning high-energy-use tasks for times when renewable energy

production is high, thereby minimizing the need for storage capacity. In the case of a community

(mini-grid) system, cheaper daytime rates may he charged in order to stimulate daytime consumption

of large loads.

SYSTEM MAINTENANCE

Stand-alone PV systems are almost by definition located in remote areas and thus maintenance

requirements must be minimal and predictable, For unattended systems, such as telecommunication

repeaters, a maintenance schedule of not more than one visit a year is feasible and should be

pursued. For attended systems, such as those in remote buildings, a maintenance schedule with

weekly, monthly and semi-annual maintenance procedures is reasonable. In all cases, proper planning

is required.

MAINTENANCE OF THE ARRAY

Maintenance needs of the array vary according to the climate. In most temperate climates, these

needs are zero, but in dusty or snow conditions, regular cleaning can become crucial for proper

junctions.

MAINTENANCE OF THE BATTERIES

Batteries are the components that require most maintenance. For open lead-acid batteries, some

means of keeping sufficient electrolyte in the cell is necessary for their optimal operation.

2.1.2.7 PEAK SUN HOUR

The number of Peak Sun Hours for the day is defined as the number of hours for which energy at the

rate of 1000 W/m2 would give an amount of energy equivalent to the total energy for that day. If the

solar radiation (Figure 2.19) on a horizontal surface for the whole day is 25 MJ/m2, then we must

work out the number of hours for which radiation at the rate of 1000 W/m2 would result in the same

overall energy gained for that day. (1 kWh = 3.6 MJ). Then 25 MJ/m2 would be 6.94 kWh (25 MJ/m2



divided by conversion factor 3.6). In one hour radiation at 1000 W/m2 delivers 1 kWh of energy per

m2. Therefore to produce 6.94 kWh of energy per one square meter the radiation would have to

continue at the rate of 1000 W/m2 for 6.94 hours. Then the number of Peak Sun Hours is 6.94.

Figure 2.19 (a) : Solar radiation. Figure 2.19 (b): Solar radiation.

Figure 2.19 ( c): Mean daily sunshine.

2.1.2.8 NUMBER OF COMPONENTS

The number of PV-modules, size of batteries is shown in Table 2. In our calculations we have used the

average electricity consumption of a four family house which is 18 kWh per day. According to World

Bank a four family house consumes 2952 kWh per year. A daily average of this figure is around 8 kWh

per day which is 45% of the house we have under investigation.

There are two sets of diodes used in the interconnection of the modules. One set has the task to

block the current flowing back from battery to PV panel (blocking diode), the other set is for

bypassing the PV cell.



TABLE 2: Energy Budget Chart

Items Rated Power No. of hours per day

Weekly Energy

(Whrs)

1 Vaccine refrigerator 50 24h 1200

2 Blood banking refrigerator 50 24h 1200

3 Operating theatre light 2x250=500 2h 1000

4 Medical centrifuge 100 2h 200

5 Desk fan 115 4h 460

6 Ceiling fan 100 4h 400

7 Room light 2x50=100 4h 400

8 Radio 5 13h 65

9 TV 55 13h 715

10 Microwave 700 1/2h 350

11 Washing Machine 600 1/3h 200

12 Drier 600 1/3h 200

13 Electric Pump 750 4h 3000

14 Boiler 700 1/2h 350

15 PC and Printer 115 1h 115

Total daily Energy (Whrs) 9855

ECONOMIC ANALYSIS

A cost calculation for the PV/wind hybrid system consists of first determining capital cost for the

hybrid system and conventional alternative and the calculation of the payback period. The capital

cost of a hybrid consists of subsystem costs such as costs of photovoltaic panels, panel structure,

wind generator, batteries, inverter, power conditioning unit, system controller and miscellaneous

items such as wiring, site preparation, etc. Determination of the optimum number of PV modules,

wind generators, diesel generators and batteries in our study was not based on the economic

approach but on the quality of supply. The cost function of the system can be defined as:

oBattPV CNKNKC 21

Where:

C is the total capital cost of the grid-connected system

1K is cost of a PV module

2K is cost of a battery

PVN is number of PV modules

BattN is number of batteries



oC is the total constant costs including the cost of design, and installation. The number of batteries is

a non-linear function of PV modules.

Formula used for calculations are given in Figure 2.20.

Figure 2.20: Formula for calculations.

This equation has been written based on energy balance where the radiation incident on the panel in

peak sun hour (PSH), equal to the number of hours of the standard irradiance (1kWh/m2) which

would produce the same irradiation. PSH is numerically equal to the irradiance in 1kWh/m2 day.

BEFORE YOU READ ON…

By now, you can probably confidently list the benefits of solar energy - just Google

“benefits of solar energy” and see if you can list as many as others. With so many

benefits, why is the utility and infrastructure development of solar energy

generation limited? Who are the most that can benefit from this?

Write your response here…



FACTORS FAVOURING PHOTOVOLTAIC TECHNOLOGIES

The main factors favouring photovoltaic technologies in remote areas result from:

the high costs of conventional power sources, which are strongly affected by remote locations;

the loss of the scale-economy effect;

the relatively high price of fuel transportation and of the supply of spare parts.

BARRIERS HINDERING THE MARKET DEVELOPMENT OF PV TECHNOLOGY

The barriers to market development of PV technology are:

technological barriers;

economic barriers;

financial barriers;

social barriers;

cultural barriers;

institutional and regulatory barriers;

and the most important barrier: lack of public awareness and information about potential and specific advantages of PV technology.

TECHNICAL LESSONS LEARNED

Some technological lessons learned from past experience are:

PV modules have reached a considerable reliability and higher lifetime expectations (currently they exceed 25 years and more). Some PV experts believe that research is not so much required to further improve quality and reliability, but to reduce cost and to improve efficiencies;

In stand-alone systems, the battery is known to be the weakest link in the chain. Today batteries in PV installations present a typical lifetime between 2 to 5 years;

Electronic devices such as inverters, and charge regulators have, during the first years of use, revealed many problems, frequently less than adequate designs and low reliability, but today performances are rapidly improving;

System design is in many cases also a reason for poor performance. This is because of lack of appropriate quality and reference standards;

Standardization is an extremely important issue for market penetration of PV technology products;

User friendliness is an important issue. Appropriate designs must be orientated not so much towards technical issues, but to match social, cultural, administrative and organisational needs of users.

CURRENT MARKETS

Overall, the 42% increase between 1996 and 1997 was split equally between:



Off-grid PV markets such as:

– telecommunications and signals;

– consumer systems for homes;

– farms;

– boats;

– campers;

– commercial applications; and

the on-grid PV market such as subsidized Building Integrated PV (BIPV) market including Japanese shipments, and adding those of Germany, Switzerland, Norway and the US.

Building Integrated PV (BIPV) Architects around the world are beginning to integrate a whole host of

BIPV products into their designs, such as BIPV modules integral roof modules roofing tiles modules for

vertical curtain wall facades sloped glazing systems and skylights.

International Trends

The primary reason for phenomenal PV growth in 1997 was increased Japanese demand for PV, as

result of government programs to promote solar homes through tax incentives and subsidies. In

1997, 9,400 PV systems were installed on Japanese homes. As a result of this strong national PV

demand, Japanese shipments increased 65% to 35 MW during 1997. More than 70,000 PV-powered

homes were already available by the year 2000.

The key to the success of PV with the Japanese has been strong national government support,

including generous subsidies and forward-looking energy policies.

Europe

The European PV industry increased its production by 5% from 18.8 to 30.4 MW during 1997.

United States

As a result of increased world demand for PV, especially from Japan, US companies also increased

their shipments by 36% from 38.9 MW to 51 MW. Currently, US PV shipments account for 41.8% of

total world production.

Million Solar Roofs is an initiative to install solar energy systems on one million U.S. buildings by 2010.

This was announced by the United States president on June 26, 1997, before the United Nations

Session on Environment and Development. The initiative includes two types of solar technology,

namely photovoltaics that produce electricity from sunlight and solar thermal panels that produce

heat for domestic hot water, space heating, or heating swimming pools.

The Developing World

Outside the USA, Europe and OECD countries there are some regions that have a proven PV market or

have had very high growth in using PV systems. These regions are:



India

Indonesia

China

The Philippines

Central Asia

South Africa

The developing world, for example, is perhaps the largest potential market for PV in the near term.

The success of renewable energy projects in these nations is highly dependent on the development of

micro-lending practices and financing initiatives by foreign investors and bilateral development

agencies. The path that electricity sector reform takes in these nations is also important.

2.1.3 WAVE ENERGY

The energy content of sea waves is very high. In Australia, with several thousands of kilometers of

coast line, a vast source of energy is available. The power in the wave is proportional to the square of

the amplitude and to the period of the motion. Therefore, the long period (~10s), large amplitude

(~2m) waves are of considerable interest for power generation, with energy fluxes commonly

averaging between 50 and 70 kW/m width of oncoming wave. Though the engineering problems

associated with wave-power are formidable, the amount of energy that can be harnessed is large and

development work is in progress. Australia’s estimated near-shore wave energy resources (171,000

MW) can provide approximately four times the current national power needs. By using just 10% of

this resource (the amount of power which conservative estimates indicate can be practicably

extracted), around 35% of Australia’s current power demand could be produced.

Wave energy is an ideal source of base-load power – it is highly predictable and reliable, particularly

along the southern coastline of Australia where regular storms in the Southern Ocean deliver

constant swells to the shoreline. Analysis indicates that waves from which electricity can be

generated exist over 97.5% of the time, making it a base-load resource (Figure 2.21).

Carnegie anticipates installing 1,500 MW of CETO wave energy capacity by 2020 with projected

expansion to be 12,000MW by 2050 (Figure 2.22).



Figure 2.21: CETO Technology Power and Water Schematic. Source: Carnegie Corporation Ltd.

Figure 2.22: CETO Forecast Installed Capacity Source: Carnegie Corporation Ltd.

Ocean Thermal Energy Conversion (OTEC)

The ocean is the world's largest solar collector. Temperature difference of 20°C between warm, solar

absorbing surface water and cooler 'bottom' water can occur. This can provide a continually

replenished store of thermal energy which is in principle available for conversion to other energy

forms. OTEC refers to the conversion of some of this thermal energy into work and thence into



electricity. A proposed plant using sea temperature difference would be situated 25 km east of Miami

(USA), where the temperature difference is 17.5°C (Figure 2.23).

Figure 2.23: Closed Cycle OTEC (Image adapted from National Energy Laboratory of Hawaii Authority (NEHLA)).

Australia and its territories do not have significant 'reserves' of OTEC, although the ocean

temperature difference in the tropical regions of Australia is between 20 and 22°C. The high solar

insolation of these regions and the profile of energy users (mainly inland, isolated communities and

users) mean that OTEC is unlikely to be used in Australia in the near future. However, it has potential

applications for Australia's neighbours in the Western Pacific region.

Although there were proposals to consider Townsville to become an international centre for the

development of OTEC technology, however the significant capital and running costs of current OTEC

technologies combined with the technological immaturity of the industry make this technology

uncompetitive with conventional sources and the many other renewable energy sources at the

present time.

2.1.4 BIOFUELS

The material of plants and animals is called biomass, which may be transformed by chemical and

biological processes (Figure 2.24) to produce intermediate biofuels such as methane gas, ethanol



liquid or charcoal solid. Biomass is burnt to provide heat for cooking, comfort heat (space heat), crop

drying, factory processes and raising steam for electricity production and transport.

Renewable energy programmes are specially designed to meet the growing energy needs in the rural

areas for promoting decentralized and hybrid development so as to stem growing migration of rural

population to urban areas in search of better living conditions. It would be through this integration of

energy conservation efforts with renewable energy programmes that Australia would be able to

achieve a smooth transition from fossil fuel economy to sustainable renewable energy based

economy and bring "Energy for all" for equitable and environmental friendly sustainable

development.

Biofuels have been promoted internationally as a major response to offer the potential for improved

fuel security, lower greenhouse gas emissions, and health benefits in cities. There are also potential

benefits to rural communities in Australia (Figure 2.25). The benefits are, however, very sensitive to

the particular production system, and are not universal.

The biofuels industry is in its infancy in Australia. Future development of this industry is subject to

some critical uncertainties — most importantly, energy prices, consumer preference, Australian and

international government policy, and technology shifts.

If domestically produced biofuels were to move beyond being relevant at the margins (2–5% of

transport fuel requirements) to become part of the main game (10–20% of transport fuel

requirements), there could be some major shifts in the agricultural and forestry value chains through

to vehicle manufacture, fuel distribution and retail and the consumer.

Figure 2.24: Biomass/biofuel cycle (Source: http://rsindiagroups.com/biomass.htm).

http://rsindiagroups.com/biomass.html



Figure 2.25: New South Wales Sugar Milling Co-operative Limited, Australia (Source: Godat - Sugar Research Institute, QUT).

TEST YOUR KNOWLEDGE… AGAIN

You know the drill… Use the diagram below to fill in the details of each

branch of the map according to: 1) how energy is created, 2) advantages, and

3) disadvantages. Then check your answers against the detailed descriptions

above or use it to query your lecturer in class. Print more pages if you

require more space.

PV Module Materials

Sola

r en

ergy

Win

d p

ow

er

Bio

fue

ls

Wav

e en

ergy

1

2

3

1

2

3

1

2

3

1

2

3



2.2 ENERGY STORAGE

There are problems in storing electricity in large quantities. Energy which can be converted into

electricity can be stored in a number of ways. Storage of any nature is however very costly and its

economics must be worked out properly. Various options available are: pumped storage, compressed

air, heat, hydrogen gas, secondary batteries, flywheels and super conducting coils.

Gas turbines are normally used for meeting peak loads but are very expensive. A significant amount

of storage capable of instantaneous use would be better way of meeting such peak loads, and so far

the most important way is to have a pumped storage plant. Other methods are discussed below

briefly.

2.2.1 SECONDARY BATTERIES

Large scale battery use is almost ruled out and they will be used for battery powered vehicles and

local fluctuating energy sources such as wind mills or solar. The most widely used storage battery is

the lead acid battery, invented by Plante in 1860. Sodium-sulphur battery (200 Wh/kg) and other

combinations of materials are also being developed to get more output and storage per unit weight.

2.2.2 FUEL CELLS

Fuel Cells are not energy sources but energy conversion devices. Fuel cells have demonstrated high

efficiencies of energy conversion, low pollution emissions, reliable and quiet operation. Fuel cells

offer immense potential opportunities in the stationary power generator market (from residential

systems to MW size) and in the transport sector (engines and auxiliary power for cars, busses, trucks,

locomotives, ships). Their principle was discovered over 150 years ago and they have been used in

space and military applications for the past 40 years. However, fuel cell development for civil

applications – stationary and mobile - has accelerated in particular during the past 10 years, and

economically competitive products are expected to enter the market from 2002 onwards. This

chapter mainly covers the stationary power applications, but references to transport applications is

made as the may provide solutions to cost-effective dispersed power generators.

Fuel cell was first demonstrated by William Grove (barrister-cum-inventor) in 1839. However, the

application of fuel cells was accelerated by its utilisation in the US space programme to produce

useful power, in 1960s. Currently most other application of fuel cell is in the research stage, but with

recent debates on environmental concerns, pollution and energy conservation, future of fuel cells is

very promising.

Electricity from fuel cell is produced without rotating machines, and at efficiencies considerably

higher than those obtained from conventional fuel-burning engines and power stations. Fuel cells

have the added benefit that it has silent operation.

One area where fuel cells are set to make a big impact is in the area of cogeneration. In the past

energy was cheap, systems utilising technologies like cogeneration could not compete directly with

traditional form of electricity generation, on economic grounds. However, with restructuring in the

electricity supply industries in many of the industrialised countries and constrained put on them

through international agencies to reduce consumption of fossil fuels and CO2 production,

technologies like cogeneration will be used more widely acceptable.



Fuel cells, with their high efficiencies (even at low powers), silent operation, simplicity, reliability,

produces low concentrations of NOx, and utilise gas feedstocks (viz. natural gas, CH4, CO and H2) can

be the best type of energy converter, provided the cost could be reduced. Fuel cells boost has been

given recently with the Californian law of ‘zero emission’ on their new cars. It states 2% of the new

car sales will be required to have ‘zero emission’ by 1998 rising to 5% in 2000. Other North American

states have similar directives. Fuel cells will be preferred to storage batteries as the latter requires

difficult charging regimes and low power densities. The dc output from fuel cells can be converted to

ac via power conditioning systems known as invertors, which means they can supply electrical power

comparable to that from the electricity grid.

Hence the main likely users of fuel cells will therefore be electric vehicles and cogeneration. Other

broad potential application ranges from small remote area power systems and telecommunication

installations through to commercial buildings and ultimately to multi-megawatt power stations.

In general fuel cells convert hydrogen-containing fuels directly via an electrochemical process into

electricity and thermal energy. The electrochemical fuel conversion potentially leads to a highly

efficient and low polluting process for conversion of fuel energy to electric energy. Fuel cells can also

be viewed as complementary to renewable energy technologies, and have the potential to play a

critical role in the transition from a fossil fuel dominated world as well as in a future renewable

energy scene.

This section discusses the fuel cell energy conversion process, different types of fuel cells and their

characteristics, status of development of different fuel cells and projected market entry products. In

Australia, Ceramic Fuel Cells Ltd has been developing solid oxide fuel cell technology primarily for the

stationary power market. The company located in Melbourne’s suburb of Noble Park anticipates has

launched its first product for the small commercial sector in 2003. A fuel cell converts chemical

energy of a fuel into electricity directly, with no intermediate combustion cycle. In the fuel cell,

hydrogen is supplied to the negative electrode and oxygen (or air) to the positive. Hydrogen and

oxygen are combined to give water and electricity. The porous electrodes allow hydrogen ions to

pass. The main reason why fuel cells are not in wide use is their cost (> $ 2000/kW). Global electricity

generating capacity from full cells will grow from just 75 MW in 2001 to 15000 MW by 2010. US,

Germany and Japan may take lead for this.

Australia's first operational fuel cell was installed at the Australian Technology Park, Sydney in 1998

Figure 2.26). A phosphoric acid fuel cell, it uses natural gas which is passed through a steam reformer

to produce hydrogen produces up to 200 kW of electricity and hot water (see Figure 18).



Figure 2.26 Australia’s first fuel cell (courtesy of Cheresources).

2.2.2.1 ENERGY CONVERSION PROCESS IN FUEL CELLS

ELECTROCHEMICAL CELL PROCESSES

As electrochemical devices, fuel cells are not controlled by the Carnot cycle principles of heat engines.

The open circuit voltage or ideal voltage (Er) of a fuel cell is given by the free energy of the fuel

conversion reaction, and is typically between 1 to 1.2 V for a single cell.

Er =G/nF)

where, F is the Faraday constant and n is the number of electrons transferred.

Hydrogen is the most common fuel but in some fuel cell types conversion of CO and CH4 is also

possible:

H2 + ½ O2 H2O n=2

E = Eo + (RT/2F)ln(PH2/PH2O) + (RT/2F)ln(PO21/2)

CO + ½ O2 CO2

E = Eo + (RT/2F)ln(PCO/PCO2) + (RT/2F)ln(PO21/2)

CH4 + 2O2 CO2 + 2H2O



E = Eo + (RT/2F)ln(PCH4/P2H2OPCO2) + (RT/2F)ln(PO22)

The efficiency of the fuel cell is the product of the fuel efficiency and the electric efficiency.

φ (FC) = φ(f) + φ (e)

The fuel efficiency ϕf) is defined as:

(ϕf) = (G/H)100 = [1-(TS/H)100

Fuel efficiencies thus increase or decrease with temperature (Figure 2.27) depending whether

entropies of the fuel conversion reactions are positive or negative. For example, (ϕf) for hydrogen

decreases from 0.94 at ambient temperature to 0.71 at 1000oC, for CO from 0.91 to 0.69 and for

methane remains 1.00, and for methanol increase from 1.02 to 1.10. Practical fuel utilisations are

restricted to 80-85%.

Figure 2.27: Fuel efficiencies for H2, CO, CH4 and CH3OH.

The electri ) losses:

(ϕe) = Er – IR -

Ohmic losses are varying directly with current density. Overpotential losses can be split into activation

polarisation (act), and concentration polarisation losses (conc). A low current densities activation

polarisation losses dominate and at high current densities concentration polarisation losses (diffusion

limitations) – refer to Figure 2.28.

50

75

100

125

0 250 500 750 1000

Fuel E

ffic

iency /

%

Temperature /C

CH4 H2 CO CH3OH



Figure 2.28 V-I characteristic of Fuel Cell.

If electric losses are minimised, fuel cells have the potential for very high conversion efficiencies.

Fuel cells do not involve thermal combustion processes, the fuel conversion is an electrochemical

oxidation. In addition, the electrolyte membrane separates the oxidant (air) and the fuel. This ensures

very low NOx emissions. As fuel cells are sensitive to sulfur, compounds containing sulfur need to be

removed from the fuel before entering the fuel cell. Thus, sulfur emissions are also very low.

Calculation of fuel and oxidant required in a fuel cell:

Example: 100 kW fuel cell operated on hydrogen (H2 2H+ + 2e) at 0.7V and 80% fuel

utilisation and 50% oxygen utilisation.

(i) Fuel flow:

Current (I) = Power/voltage = 1.43x105 A

mH2 = (1.43x105)(3600/96487x2) = (1.43x105)(0.018655) [g-mol H2/h] = 5.34 kg H2/h

Uf = 80%

5.34/0.8 = 6.675 kg H2/h (75m3) fuel flow is required.

(ii) Oxidant flow: ½ of fuel flow:

1.335x103 g-mol x 5 (air) = 6.675x103 g-mol air = 192 kg air/hr

UOx = 50%



192/0.5 = 384 kg of air (about 300m3) air flow is required

SUPPORT SYSTEMS

A single cell delivers about 0.5 to 0.7V under load. To achieve useful devices cells need to be stacked

in series and parallel to a fuel cell stack. A number of these stacks will form the fuel cell module. This

module needs a life-support system and an output control. On the input side the fuel cell requires the

fuel supply system and the air supply system. The fuel supply consists of the fuel flow control, fuel

cleaning (e.g. desulfurising), fuel processing (reformer) and if required fuel inlet heat exchangers. The

air supply system consists of a filter a blower or compressor and an air inlet heat exchanger. On the

output side the fuel cell requires a power conditioning system (fast load response unit, inverter,

control system) and a heat management system to recover heat for internal (parasitic) use and for

export.

BASIC FUEL CELL SYSTEM

Figure 2.29, shows the principle of fuel-cell operation. A fuel (nearly always H2) reacts with water and

the overall reaction is:

2H2 + O2 = 2H2O

Figure 2.29 Basic Fuel Cell.

However, this reaction does not readily take place, and unless special materials are used for the

electrodes and the electrolyte, the current produced per square centimetre is extremely small and

the ohmic losses in the electrolyte very large. To overcome these problems, various types of fuel cell

have been developed, and the most successful and promising types are shown in Table 3. The

different varieties are distinguished by the electrolyte used, also the construction of the electrodes in

each case is different. However, in all types there are separate reactions at the anode and cathode,

and charged ions move through the electrolyte while electrons move round an external circuit.

Another common feature is that the electrodes must be porous, because the gases must be in contact

with the electrode and the electrolyte at the same time.

H2

air or O2

a

n

o

d

e

e

l

e

c

t

r

o

l

y

t

e

c

a

t

h

o

d

e

LOAD

- - +



In order to see the movements of ions and electrons, let us consider the actions of simple fuel cells:

The reaction in the alkali fuel cell shows that OH- ions move through the electrolyte, and water forms

at the anode. Cathode (where the cations are formed) is electrically positive terminal (EE engineers

find this phenomenon very surprising!).

Anode 2H2 + 4OH- = 4H2O + 4e-

Alkali electrolyte through electrolyte

Cathode O2 + 4e- + 2H2O = 4OH-

Water forms at the anode through external circuit.

In case of solid polymer and phosphoric-acid fuel cells, H+ ions are free to move, and water forms at

the cathode.

Anode 2H2 = 4H+ + 4e-

Acid electrolyte through electrolyte

Cathode O2 + 4e- + 4H+ = 2H2O

Water forms at the cathode through external circuit.

The operating voltage of each working cell is about 0.7V, so in order to get useful power one has to

have stack of cells. The cathode of one of the cell is joined to the anode of the other and so on, with

lowest possible resistance. It is not sufficient to join the electrodes at the edges; instead a conductive

plate is put between each cell, which should have the best possible electrical contact with the faces of

the electrodes. The plate in the same instant has to separate the air fed over the cathode and the H2

fed over the anode. Design of such bipolar separators is difficult.

A major problem with fuel cell application is that H2 fuel is not readily available, so that more

accessible fuels such as natural gas has to be converted into H2 and CO2. This adds to the size and cost

of the unit.

Table 3: Data for various fuel cell types

Type Operating temperature

Power density Approximate cost Applications

Alkali 50-100oC 80kW/m3 100W/kg Very high Space vehicles, e.g. Gemini,

Apollo, Shuttle; > 70%

Solid polymer 50-100oC 190kW/m3 100W/kg

$500/kW (1998) Buses and cars

Phosphoric acid ~200oC 4kW/m3 10W/kg $3,000/kW $1500/kW (1998)

Medium scale cogeneration systems

Molten carbonate ~600oC 35kW/m3 70W/kg N/A Medium to large scaled cogeneration systems; coal gasification plants

Solid oxide 500-1000oC >100kW/m3 N/A All cogeneration systems (2kW to multi MW) early



Type Operating temperature

Power density Approximate cost Applications

stages of development

Diesel generator 15-45kW/m3 25-100W/kg

$150-250/kW 20-750kW (Diesel storage tanks not included in cost)

Petrol engine (standard cars)

~300kW/m3 ~500W/kg

$40-100/kW Peak power from engine only (no electricity generated)

In the case of solid oxide fuel cell (SOFC), methane can be converted internally, without a separate

unit. The materials consist of zirconia-based electrolyte covered on each side with specialised

electrode materials. At around 1000oC zirconia is an excellent O2 ion conductor, hence when a fuel

gas like H2 is passed over one surface and an oxidant (usually air) is passed over the electrode, a

potential difference is created and a flow of negatively charged O2 moves across the electrolyte to

oxidise the fuel. Electrons generated at the fuel electrode then migrate through any external load to

complete the circuit. Electrical power is available as long as fuel and air flows are maintained to the

cell. Because of its efficiency and waste heat quality Westinghouse (USA) has produced 25kW units

and Sulzer (Germany) has developed 2 kW units.

Molten carbonate fuel cell (MCFC) operates at 650oC and use gases like natural gas and coal gas. At

the cathode O2 and CO2 react to form carbonate ions, which pass through the molten carbonate

electrolyte. These react with H2 or CO at the anode to produce H2O and CO2 and release two

electrons. Main problem of MCFC is the design of the electrodes (uses Ni catalyst). They have to work

longer in the electrolytes (mixture of Li and K2CO3), which is hot and corrosive. A plant in Santa Clara,

USA of 2MW capacity is being built.

Phosphoric acid fuel cell runs at 200oC. A 200kW unit runs on natural gas and is commercially

produced in USA. Cost of about $3,000/kW is not competitive, but due to government environmental

package incentives the cost is about $2,000/kW. They have good track record, as it has now been

running for about a year, has no maintenance requirements. Their disadvantage being the

temperature is not high enough to internally convert methane, as such it requires an extra unit

adding to the cost and size.

Amongst the low temperature cells alkali cell has gained commercial success. It is used to supply

power in space vehicles. It is superior to other power sources, as it has high power density and

produces water as a byproduct. The problems with this are that very high Pt loadings on the

electrodes is required to get the high power (high cost) and KOH reacts with CO2 to form K2CO3,

which degrades the electrolytes and clogs up the pores of the electrodes.

The solid polymer fuel cell (SPFC) are being used in vehicles. Research in UK has produced high

performance electrodes using very low Pt loadings. Costs are involved in the electrolytes utilising

‘proton exchange membrane (PEM)’ and bipolar plates. In Vancouver fuel cell powered buses are

being used. This has ‘zero exhaust emissions’ and many transit authorities are showing interest in

this type of vehicles. SPFC is very competitive with petrol engine in terms of power density, and if

mass produced costs can become competitive. A problem with these vehicles is that cells have to be



fuelled with H2 from cylinders. However, small, safe and efficient converter for converting liquid fuel

to H2 is going well.

2.2.2.2 TYPES OF FUEL CELLS

A number of fuel cells have been developed. Table 4 lists the most common types and Table 5

describes the electrochemical reactions.

Table 4: Most common types of fuel cells

Fuel Cell Fuel T(op) OC

Efficiency% Electrolyte

Alkaline Fuel Cell (AFC)

Proton exchange membrane FC (PEMFC)

Direct Methanol FC (DMFC)

Phosphoric acid FC (PAFC)

Molten carbonate FC (MCFC)

Solid Oxide FC (SOFC)

Pure H2

Pure H2

Methanol

H2

H2, CO, NG,HCs, alc.

as MCFC

70-200

60-90

70-100

(>100)

190-220

650

750-1000

30-451

301

40

50+

35-401

50+

(65)2

50-60

(70)2

KOH/matrix

Sulfon-F-polymer

Sulfon-F-polymer

(Novel polymer)

H3PO4/SiN matrix

Li-K-carbonate/ LiALO4 matrix

Yttria-zirconia

1 related to natural gas 2 combined cycle system

Table 5: Electrochemical reactions in various types of fuel cells:

Fuel Cell Anode Reaction Cathode Reaction

PEM and PAFC H2 2H+ + 2e ½ O2 + 2H

+ + 2e H2O

AFC H2 + 2OH- 2H2O + 2e ½ O2 + H2O + 2e 2OH

-

DMFC CH3OH + H2O CO2 + 6H+ + + 6e 3/2 O2 + 6H

+ + 6e 3 H2O

MCFC H2 + CO32-

H2O + 2e + CO2

CO + CO32-

2CO2 + 2e

½ O2 + CO2 + 2e CO32-

SOFC H2 + O2-

H2O + 2e

CO + O2-

CO2 + 2e

CH4 + 4O2-

CO2 + H2O + 8e

½ O2 + 2e O2-



Alkaline Fuel Cells have primarily been used by NASA on space missions, but recently have attracted

renewed interest for mobile applications, as potentially they can achieve higher electric efficiencies

than other low temperature fuel cells and don’t use noble metal catalysts, but are poisoned readily by

CO2.

Proton Exchange Membrane Fuel Cells operate at temperatures below 90oC. They exhibit high power

density, fast start-up and fast load response. They require pure hydrogen as fuel. Carbon monoxide is

a strong poison for PEM and therefore extensive gas cleaning for hydrogen produced from

hydrocarbon reforming is necessary. They are primarily considered mobile applications, but micro-

CHP (<10kW) for domestic applications and CHP systems (up to 300 kW) are under development. Due

to the high manufacturing volumes required for mobile applications, low capital costs are expected,

but, if the fuel hydrogen is produced from hydrocarbon fuels such as natural gas, the efficiency of

PEMFCs is only about 35%.

Direct Methanol Fuel Cells use a polymer membrane as the electrolyte similar to PEMFC, but the

anode in DMFC converts the methanol fuel directly, and thus eliminates the need for a fuel reformer.

Efficiencies of about 40% are expected for the low temperature version, and efficiencies of about 50%

for operating temperatures above 100oC. They are in an early stage of development and are

predominantly considered for mobile applications.

Phosphoric Acid Fuel Cells are the most commercially developed type of fuel cell. Several hundred co-

generation systems (50-200kW) have been tested, some up to 40000 hours. With an operating

temperature of 200oC, the fuel cell still operates only with clean hydrogen as fuel, but is more carbon

monoxide tolerant than PEMFC. Their efficiency related to Natural Gas as fuel is 40%. IFC has been

marketing 200kW systems (PC25), but appears to be slowly withdrawing from the business and is

concentrating their effort on PEM systems.

The high temperature fuel cells Molten Carbonate Fuel Cells (MCFC) and Solid Oxide Fuel Cells (SOFC)

promise the highest fuel-to-electricity efficiencies in particular for carbon based fuels. The operating

temperatures for MCFC and SOFC are 650oC and >750oC respectively. This allows a better integration

of fuel processors and fuel cell. Efficiencies on carbon based fuels are predicted to be around 50-60%

for a single cycle and above 65% for a combined cycle (Fuel Cell + gas turbine, steam turbine or

Stirling engine).

2.2.2.3 FUEL PROCESSING

The preferred fuel for fuel cells is hydrogen. Currently, the most common route for hydrogen

production is by reforming of carbon based fuels (natural gas, higher hydrocarbons and alcohols) in a

steam reforming or partial oxidation process. Natural gas is considered the fuel of choice for

stationary applications and hydrogen and methanol for mobile applications.

Steam reforming of natural gas is performed at 700-900oC and is therefore easier to couple with the

high temperature fuel cells MCFC and SOFC. In the longer term, hydrogen production may be possible

by renewable means, e.g. solar energy.

CH4 + H2O CO + 3H2

CO + H2O CO2 + H2 (watergas shift)

CH4 + 2H2O CO2 + 4H2



Three approaches are possible for reforming of hydrocarbon fuels, external reforming (the only

option for low and intermediate temperature fuel cells), integrated reforming (close thermal

integration of reformer and fuel cell stack) and internal reforming inside the fuel cell stack.

Efficiencies and operational flexibilities increase as fuel reforming is closely thermally integrated with

the fuel cell stack, but integrated and internal reforming options are only possible with high the

temperature fuel cells MCFC and SOFC. Partial oxidation allows faster start-up but in general leads to

a fuel with lower heating value, and in particular if air is used as oxidant, substantial fuel stream

dilution by nitrogen occurs.

CH4 + ½ O2 (air) CO + 2H2 + (N2)

CO + H2O CO2 + H2 .

CH4 + ½ O2 (air) + H2O CO2 + 3H2 + (N2)

The tight volume and weight limitations in the automotive applications have forced innovations

related to compact fuel processor technologies. Technologies such as microchannel reactors which

enable very high heat exchange and high reaction rates, are also applicable to stationary systems.

Gas cleaning is an integrated part of fuel processing, and the degree needed is strongly dependent on

the type of fuel cell:

i) sulfur removal from fuel source (NG, LPG, Diesel, biofuels) is essential for all fuel cells, but

some fuel cells tolerate somewhat higher levels;

ii) removal of particulates and other poisons from some bio-fuels is necessary for all fuel cells;

iii) CO removal is essential for PEMFC and PAFC;

iv) CO2 cleaning from air and fuel side is necessary for AFC.

2.2.2.4 STATUS OF DEVELOPMENT – STATIONARY AND TRANSPORT

Substantial investments in fuel cell R&D and a significant number of technology demonstration

projects during the past 10 years have sparked significant advances in fuel cell technology. First

commercial products are expected in the stationary energy market from 2002/2003 onwards and in

mobile applications from 2004.

STATIONARY APPLICATIONS

The future trend in stationary power generation appears to focus on advanced distributed energy

products, and a number of distributed generation (DG) products have entered the market or are close

to market introduction. For example, residential and commercial buildings are responsible for 32% of

natural gas on-site consumption in the USA (space and water heating). The building sector consumes

about two-thirds of all electricity generated. Highly efficient on-site co-generation systems using fuel

cells are expected to become products for improving building energy efficiency.

Distributed Generation is driven by:

Market pull: deregulation, environmental concerns, electricity price volatility; differentiation.

Technology push: emergence of new small generating technologies, advances in power electronics, smart metering;



Commercial and regulatory facilitation: DG interconnection standards, lowering of transaction costs, utilities growth strategies and market protection.

PAFCs are the only fuel cells available on a

semi-commercial scale. IFC/ONSI

Corporation is selling its P25C co-gen unit

(total systems efficiency over 80%; 35 - 40%

electric efficiency) with an output of 200kW

of electric energy. After a number of years

attempting to reduce the capital costs, IFC is

abandoning PAFC and has recently

increased its price to over US$ 5000/kW.

Figure 30 shows the P25C PAFC system

(Courtesy IFC/ONSI Corp). Over 200 of such

systems have been installed for diverse

applications such as hospitals, hotels, office

buildings, schools, utility power plants,

airports, computer centres. Combined, the units have clocked up operating times of close to 3 million

hours and the best systems showed availabilities of >90%, but on average availabilities were around

80%. A P25C unit also is operating at the Sydney Technology Park. PAFCs have been scaled into the

MW range – 1MW plants have been operated in US, Europe and Japan, and 5 and 11 MW plants in

Japan during the past 10 years. Most systems operate on Natural Gas as fuel but fuel processors have

been developed for Diesel fuel and biogas (anaerobic digester gas). Considering these are only

demonstration systems, the units proved reliable and successfully demonstrated the potential of fuel

cells. However the high installed costs make the PAFCs uneconomical, and interest in this technology

is declining rapidly.

PEMFCs (Figure 31) of varying designs have been developed by Ballard Power Systems, International

Fuel Cells, Plug Power, Siemens, H-Power, Analytical Power, Honeywell, Toyota, Fuji, Mitsubishi

Electric and a host of smaller players. Their efficiencies related to carbon fuels (natural gas) of 35%

makes them less attractive for stationary applications in particular in a scenario of rising fuel prices,

where efficiency becomes a dominant driver. However, the developers of PEMFCs hope that their fast

start-up and the anticipated low price due to large manufacturing volumes associated from their use

in mobile applications, may counteract the efficiency penalty. In addition, the fast start-up makes

PEMFCs ideal peaker and stand-by systems. Ballard/Alstom is currently operating three 250kW

systems in Europe, and a similar number has been installed in the US – very limited information on

the performance of the systems is available. Over the past 2 years micro co-gen systems (for domestic

applications) have attracted significant attention. For example, Plug Power and its partners GE-

Microgen and Vaillant are developing and demonstrating 5-7kW units for domestic applications

(Figure 5). Market entry for late 2002 has been predicted and Vaillant estimates annual European

installations of 250000 units by 2010. The drivers for such an application are somewhat uncertain,

considering the large load variations in a household and the high gas prices paid by the domestic

consumer.

Figure 30

Figure 30. P25C PAFC system (Courtesy IFC/ONSI Corp).

Figure 31. PEMFCs.



MCFCs: A number of demonstration system failures in sizes up to 2 MW, seriously damaged the

reputation of this technology, leading to the demise of a number of the development programs (ECN

in the Netherlands and MC-Power in the US). However, Fuel Cell Energy (US) in conjunction with its

German partner MTU found solutions to a number of the problems surrounding the technology

(corrosion, electrolyte seepage, CO2 recycle), and have now successfully demonstrated a 250kW unit

for over 1 year. The unit takes up a footprint of 20m2, weighs 15 tons and delivered an electric

efficiency of 52%. Fuel Cell Energy is now designing and constructing a 1.5 and 3MW unit, including

constructing a combined cycle system consisting of a MCFC and a gas turbine which is anticipated to

reach electric efficiencies of 65-70%. Fuel Cell Energy has planned a number of additional demo

systems in 2001, and has established a 6500m2 pre-production facility with a capacity of 50 MW per

year in 2001 and planned expansions to 400MW per year in 2004. Other MCFC developers include

Ansaldo in Italy and IHI and Hitachi in Japan. IHI and Hitachi are currently operating a 1 MW MCFC

plant at the Kawagoe thermal power station in Japan. The support systems (BoP) are still very bulky,

and require substantial “miniaturisation” to achieve a viable DG technology. Otherwise the

technology will be confined to multi MW sizes.

SOFCs promise to become the most efficient and

most flexible stationary power units. A number of

design configurations are being developed. The

most extensively tested configuration is the tubular

technology developed by Siemens-Westinghouse (S-

W). Westinghouse has continuously worked on this

design since its conception in the 1960s and has

scaled up the technology to 200kW. Figure 32 shows

a cell tube bundle (Courtesy S-W). Cells are 22mm in

diameter and have an active length of 1500mm with

an output of about 300W. The operating

temperature is above 1000oC. S-W started system demonstrations in 1986 with a 0.4kW system.

Table 6 summarises the field test units carried out by S-W:

Table 6: Field test units carried out by S-W

Year Size

kW

Fuel Cell type Cell length Cell number

Oper. hours

1986 0.4 H2 + CO PST 30 (cm) 24 1760

1987 3 H2 + CO PST 36 144 3012

1987 3 H2 + CO PST 36 144 3683

1987 3 H2 + CO PST 36 144 4882

1992 20 PNG PST 50 576 817

1992 20 PNG PST 50 576 2601

1992 20 PNG PST 50 576 1575

1993 20 PNG PST 50 576 7000

1994 20 PNG PST 50 576 6000

1995 27 PNG AES 50 576 5600

1995 25 PNG AES 50 576 13000

Figure 32. Cell tube bundle (Courtesy S-W).



Year Size

kW

Fuel Cell type Cell length Cell number

Oper. hours

1998 27 PNG AES 50 576 >4000

1997 100 PNG AES 150 1152 4035

1999 100 PNG AES 150 1152 >14000

2000 200 PNG AES 150 1152 254

PST...Porous support tube

AES...Air electrode support

PNG...Pipeline Natural Gas

Siemens-Westinghouse recently installed a 200kW pressurised hybrid (SOFC + MTG) in California.

These hybrids are projected to become the most efficient electric generators. S/W aims to deliver

products (300kW to MWs) into the market place in 2004. Similar to MCFCs, the S-W technology needs

to “shrink” substantially for a viable DG product. Other developers of tubular SOFC systems include

Mitsubishi HI and TOTO Corporation in Japan.

A number of developers are pursuing planar type stack designs, a geometry similar to other types of

fuel cells. These configurations are predicted to achieve lower costs and higher volume power

densities. Effort is also under way to reduce the operating temperatures to 700- 800oC. Stationary

power products under development by various developers span the capacity range 1-5kW (domestic)

to several hundred kW (commercial), open cycle as well as hybrid systems. The main developers

include: Ceramic Fuel Cells Ltd. (Australia), Sulzer Hexis (Switzerland), Global Thermoelectrics

(Canada), McDermott (US), Honeywell (US) and a number of research institutes. Sulzer Hexis and

Global Thermoelectrics are developing domestic size systems – Sulzer operates currently 8 field test

systems in Europe and Japan, and plans to enter the market with a micro co-generation unit in

2002/3. Ceramic Fuel Cells Ltd. (CFCL) is developing a 40 kW co-gen system operated on natural gas

or LPG for small commercial applications as market entry product for 2003. CFCL’s system approach is

to tightly integrate BoP (balance of plant) and stack and minimise fuel processing. The company has

been successful in developing internal reforming cells, and has also developed a fuel processor for

LPG. CFCL has constructed and tested stacks and systems up to 25 kW.

TRANSPORT APPLICATIONS

PEMFCs have attracted most interest for transport applications with the leaders being XCELLSIS (joint

venture between Ballard Power Systems, Daimler Chrysler and Ford), but most car manufacturers are

involved in fuel cell developments. Initially, due to their size, fuel cells were fitted to buses, and a

number operated in Vancouver, Chicago, California and Germany during the past 5 years. As fuel cells

became more compact - the newest stack technology from Ballard features a stack power density of

1.3kW/l - fuel cell engines for passenger cars were demonstrated. The requirements for transport

applications constitute tough goals to meet: 5000 hours of operation, over 10000 thermal cycles and

fast start-up and cool-down. Fuel processing is another formidable challenge - hydrogen storage is

difficult and costly, on board reforming of liquid fuels (methanol, petrol) requires complete removal

of CO to ppm levels.



An interesting application - a fuel cell auxiliary power unit (APU) delivering 3-5kW of electric power to

replace the alternator - was suggested by BMW 2 years ago, and a number of developers are now

considering to develop a product for this application. For gasoline and Diesel powered cars, trucks

and buses, an SOFC APU would be the ideal solution. BMW has contracted Delphi Automotive to

develop this product. The market potential of such a product for long haul transport (buses, trucks),

for military applications as well as cars is substantial, and the US Department of Energy recently

launched the SECA program – a 350 million US$ initiative (over 10 years) to develop this product.

However, substantial technical challenges (10000 thermal cycles, mechanical vibration resistance, fast

start-up and cool-down) need to be solved.

FUEL CELLS IN A RENEWABLE WORLD

Fuel cells have the potential to become an integral part of a future sustainable energy chain. To date,

fuel cells have been trialed in a number of hybrid configurations involving renewable fuels.

Demonstration examples include:

A solar hydrogen project - hydrogen produced by water hydrolysis using PV electricity (360 kW) -

involving fuel cells operated in Bavaria (Bayernwerk, BMW, Linde and Siemens) for 13 years.

CSIRO is working on a solar thermal sustainable energy project.

In high temperature fuel cells, the separation of spent air and fuel streams makes CO2 sequestration

feasible (Shell/Siemens-Westinghouse).

A number of demonstration projects in USA and Europe demonstrated the operation of fuel cells

(ONSI/IFC P25C 200 kWe PAFC) on biogas, for example anaerobic digester gas. Gas cleaning (sulfur

compounds, halogens, unsaturated hydrocarbons and solid matter) proved the major technical

challenge.

2.2.2.5 FUEL CELL PROJECTS IN AUSTRALIA

Ceramic Fuel Cells Ltd (CFCL) was established in 1992 with the objective to develop and

commercialise products based on SOFC technology.

The technology base originated in CSIRO (Figure 2.33). The company is a leading developer in planar

SOFC technology, and has development facilities (about 5000m2) in the Melbourne suburb of Noble

Park. CFCL employs over 100 staff, primarily engineers and scientists. CFCL has demonstrated SOFC

stacks and systems to 25kW in size, and is currently working on its first commercial product, which it

plans to launch in 2003.



Figure 2.33: CSIRO and implementation of its ommercial fuel cell.

An ONSI P25C 200kWe PAFC CHP system has been operating in the Australian Technology Park since

early 1999. The objective of the project is to gain experience with fuel cell co-generation systems.

Over the past 10 years fuel cells have made immense progress, and their market entry appears

imminent (2002 onwards). Invented in the 1830s and considered for the past 50 years as the new

electricity generation technology, products are expected to appear during the next 2-3 years. A

number of the technical capabilities of fuel cells such as high efficiency, low pollution, low noise and

flexible operation have been successfully demonstrated. Hurdles for commercialisation include:

development of cost effective products from the various fuel cell technologies, and

regulatory issues related DG technologies in general:

safe plant operation (gas equipment standards)

grid interconnection standards (import/export, power quality);

grid control: difficulties envisaged with current hierarchical grid (“smart” grid required); new grid control technology (hardware and software); net metering technology.

Major developments in fuel cells are in:

(1) Japan - demonstration fuel cell units have been developed,

(2) USA, UK and Canada - pioneers in this area.

Other small demonstration units are now available, e.g. a small methanol fuel cell producing enough

power to drive small motors and it costs around $30. This is an alkali fuel cell, but instead of H2 it uses

alcohol as the fuel. Fuel cells are now proving to be an emerging energy option and very soon will be

used in cogeneration systems and in ‘zero emission’ vehicles.



2.2.2.6 REFERENCES

The following websites contain extensive information on fuel cells. In addition, most developers listed

in the paper operate web sites:

World Fuel Cell Council: www.fuelcellworld.org/

Fuel Cells 2000: www.fuelcells.org/

US Fuel Cell Council: www.usfcc.com/

NETL – Fuel Cells: www.fetc.doe.gov/products/power/

American H2 Assoc.: www.clean-air.org

Energy Web Directory: www.energy.ca.gov/links/hydrogen.htm

Ceramic Fuel Cells Ltd: www.cfcl.com.au

2.2.3 HYDROGEN ENERGY SYSTEMS

Hydrogen can be used as a medium for energy transmission and storage. Electrolysis is a well-

established commercial process yielding pure hydrogen. H2 can be converted very efficiently back to

electricity by means of fuel cells. Also the use of hydrogen as fuel for aircraft and automobiles could

encourage its large scale production, storage and distribution.

2.3 COGENERATION AND DISTRIBUTED RESOURCES

Distributed Generation (DG) entails using many small generators of 2-50 MW output, installed at

various strategic points throughout the area, so that each provides power to a small number of

consumers nearby. These may be solar, mini/micro hydel or wind turbine units, highly efficient gas

turbines, small combined cycle plants, since these are the most economical choices.

Dispersed generation refers to use of still smaller generating units, of less than 500 kW output and

often sized to serve individual homes or businesses. Micro gas turbines, fuel cells, diesel, and small

wind and solar PV generators make up this category.

Dispersed generation has been used for decades as an emergency backup power source. Most of

these units are used only for reliability reinforcement. Now-a-days inverters are being increasingly

used in domestic sector as an emergency supply during black outs.

The distributed/ dispersed generators can be stand alone/autonomous or grid connected depending

upon the requirement.

In many businesses, the purchase of electricity and fuel for use of boiler plant is often regarded as a

fairly unglamorous subject. The boiler house, transformers and switchgear are seen as a necessary

evil, which merely detracts from an organisation mainstream activity; whether that be brewing beer,

making cars, paper or chemicals. Heat and power are the life-blood of any industry; essential for the

operation of everything from the lowly light bulb and radiator to the most complex process

technology. A secure supply of power and heat is therefore of paramount importance, and it must be

provided at the lowest possible cost.

http://www.fuelcellworld.org/

http://www.fuelcells.org/

http://www.usfcc.com/

http://www.fetc.doe.gov/products/power/

http://www.clean-air.org/

http://www.energy.ca.gov/links/hydrogen.htm

http://www.cfcl.com.au/



Obtaining these vital commodities at the lowest cost is traditionally the duty of the management. The

privatisation of the electricity supply industry has brought competition in to the market place for

electricity supply and buyers (Figure 2.34).

Figure 2.34 Electricity Supply Industry.

As well as the institutional changes in the electricity supply industry, there is also now an opportunity

of reducing overall costs of energy supply by using cogeneration technology.

2.3.1 THE TECHNOLOGY

Cogeneration - is essentially a philosophy. It describes the use of technology that combines the

generation of heat and electricity in a single unit in a way that is more efficient than producing heat

and electricity separately in boiler plant and at the power station. In other words, cogeneration is the

energy process whereby waste heat, produced during the generation of electricity, is utilised for

steam raising or heating.

Cogeneration plants produce both electrical or mechanical energy and thermal energy from the same

fuel source. The mechanical energy can be used for any mechanical application such as driving

motors, compressors, extruders, etc. The electrical energy can be used to meet in-house demand and

any surplus sold back to the electricity grid. The thermal energy can be converted to steam or hot

water for process application, or for drying purposes.

The engineering principles behind integrating electricity and heat supply have long been understood,

and the technology has been refined and developed over the years, so that now, modern

cogeneration systems can achieve very high fuel utilisation efficiencies. When fuel is burned in a



conventional power station, much of the energy in the fuel is converted to heat, only a fraction of

which is converted to electricity. In brown coal and gas-fired power stations, 28% to 35% of the

energy in the fuel is converted to electricity; the other 65% to 72% becomes heat that must be

disposed of (Figure 2.35).

Figure 2.35 Conventional Power Station's Utilisation.

In cogeneration, both the recovered heat and the electricity or mechanical energy are used, so

efficiency increases to 70% to 82% depending on the prime mover used. This utilisation is well over

twice that of a large conventional power station (Figure 2.36).

Figure 2.36 Cogeneration's utilisation

The economics of cogeneration schemes are most compelling for organisations with a high heat

requirement. Units range from as little as 20 kW to hundreds of MW and can be linked to public and

commercial buildings, industrial sites and community heating schemes.

Cogeneration has a very wide application in the industrial and commercial sectors, and also in public

institutions. In the industrial sector potential exist in manufacturing (petroleum, chemical, food and

beverage, textiles, paper, iron and steel, motor vehicles, glass and clay), mining and forestry. In the

commercial sector potential exist in office buildings, supermarkets, hotels, restaurants, health clubs,

computer centres and laundries. In public institutions, cogeneration is suitable for hospitals, nursing

homes, schools, libraries and prisons.



There are two obvious times to consider investing in cogeneration: first, when existing boiler capacity

needs to be replaced and second, when new buildings are being planned. Hospitals, for example are

already being designed to include a cogeneration system from inception.

Once the economics have been worked out and the investment has been made, financial savings

quickly offset the initial additional costs incurred, giving a payback in as little as two or three years.

The life of a cogeneration system can exceed fifteen years, so the savings accrue long after the initial

capital costs have been recouped.

2.3.1.1 FUELS

Cogeneration can run on virtually any fuel: solid, liquid, or gaseous. It also uses a wide variety of

generating plant types. The other fuels include - wood/wood waste, landfill gas, municipal solid

waste, industrial waste and agricultural waste. This offers terrific flexibility when choosing the

scheme that best suits an organisation's individual circumstances. The fact that so many

combinations of fuel and plant type can be employed means that there can be a scheme to match

most installations.

The fuels which one would normally associate with on-site generation schemes are oil, briquettes,

LPG and natural gas. It must be remembered, however, that the price, availability and suitability of

the fuel will govern its choice in any on-site generation scheme.

Therefore if the site is known where the plant will be installed and it has been decided whether

turbines or engines will be used, the gas supply authority may be approached for costs of making gas

available.

The gas supply authority is responsible for works required up to and including the meter/regulator

assembly. There may be costs associated with this work. The consumer is responsible for the concrete

base and chainwire mesh enclosure for the meter/regulator assembly and all works from the meter

outlet to the appliance/s. Also any water-cooling facility for the interstage gas compression to provide

the gas at the desired firing pressure should be considered.

The metering pressures available to consumers are dependent upon the pressure in the supply main

and the minimum pressure that the appliance will operate. Pressures above the standard pressures

are by special arrangement.

Just about all engines and turbines require pressures above standard.

e.g. Gas Engines = 40-400 kilopascals

Gas Turbines = 1750 kilopascals

It is most likely that the large engines and all turbines will require the supply gas pressure available at

the meter to be boosted to that specified by the equipment supplier. All costs associated with

boosting equipment are the customer's responsibility and supply/installation should be arranged with

the equipment suppliers.

2.3.1.2 COGENERATION CYCLES

A cogeneration plant basically comprises of a prime mover (gas or steam turbine or internal

combustion engine) and a waste heat recovery boiler or steam generator. Electricity (or mechanical

power) and thermal energy can be achieved through cogeneration by either a topping or a



bottoming-cycle system (Figures 2.37 and 2.38). In a topping-cycle system, fuel is burned to generate

electricity; the thermal energy exhausted from this process is then used either in an industrial

application or for space heating. In a bottoming-cycle system, the waste heat is recovered from an

industrial process application and used to generate electricity.

Combined-cycle systems generally use a topping-cycle gas turbine; the exhaust gases are then used in

a bottoming-cycle steam turbine to generate more electricity and process thermal energy. Heat

pumps may also be used with a cogeneration system to upgrade low-temperature heat for process

use.

In a topping-cycle system, fuel is burned to generate electricity and the thermal energy exhausted is

used in a process application. This is the most common form of cogeneration. This process is

applicable to any operation that uses boilers to produce steam or heat.

Topping cycle cogeneration involves converting the boiler to produce steam of higher pressure and

temperature. This steam is then piped to a turbine that runs a generator to produce electricity. The

heat is then used in the manufacturing process, or for heating or cooling.

Bottoming cycle cogeneration is generally used where an industry process produces waste heat at

high temperatures (above 300°C). In the bottoming cycle, (shown in Figure 5), waste heat from a

manufacturing process, generally with the addition of more fuel, is fed into a boiler to make steam.

The steam is then sent to a turbine, which operates a generator to produce electricity.

Alternatively, other industrial plants or large institutions may operate a gas turbine to drive a

generator for the production of electricity. Under ordinary operation, waste heat from the gas

turbine is simply discharged. With cogeneration, the heat discharged from the turbine goes into a

waste heat exchanger, which would be used to produce the heat or steam needed in the factory or

institution.

In bottoming-cycle system waste heat is recovered from a process application and used to generate

electricity. Prime movers can also be combined to produce compound, or "combined cycle"

cogeneration.

Bottoming cycle cogeneration is likely to be used in the metals, glass refractory and cement industries

but are generally less wide-spread than topping cycle systems.

The turbines used in cogeneration process can also be linked to equipment to provide mechanical

power instead of to a generator to provide electricity.

Topping cycle cogeneration has wide application in the food, pulp and paper, and chemical industries,

and in hospitals and other large institutions.

Cogeneration plants vary widely in size and packaged micro-cogen units in the size range 20 kW to 60

kW are commercially available for suitable office buildings, restaurants, hotels, etc. For units below

800 kW, diesel and gas engines is the most common type of prime motor. From approximately 800

kW to 10 MW, gas turbines or large reciprocating engines can be used. Steam cycles (steam turbines)

can also be used especially in coal, waste gas or biomass fired cogeneration systems. For applications

above 10 MW, gas and steam turbines are generally used.



Figure 2.37 Cogeneration Topping Cycle.

Figure 2.38 Cogeneration Bottoming Cycle

2.3.2 ELECTRICAL AND MECHANICAL MEASUREMENTS

Work done or energy possessed in an electrical circuit, mechanical or thermal system is measured in

the same units viz. JOULES. This is expected because mechanical, electrical and thermal energies are

interchangeable. E.g. When mechanical work is converted to heat or heat to work, the quantity of

work in Joules is equal to the quantity of heat in Joules (in the past the unit of heat energy was

‘calorie’, however 1 Calorie = 4.186 Joules. Hence thermal unit Calorie is obsolete and it is common to

express heat as Joules).

2.3.2.1 ELECTRICAL ENERGY

One joule of energy is expended electrically when one Coulomb is moved through a potential

difference of 1 Volt.

Suppose a charge of Q Coulomb moves through a potential difference of V Volts Then electrical

energy expended is = VQ.



As Q = It; V= IR; I = V/R, therefore

Electrical energy = VQ = VIt = I²t = V²t/R.

Joule is also known as Watt-second i.e. 1 Joule = 1 Watt-second. Hen we are dealing with large

amount of electrical energy, it is often convenient to express it in kilowatt hours (kWh).

1 kWh = 1000 Watt-hours = 1000 x 3600 Watt-second or Joules

1 kWh = 3600 x 10³ Joules or Watt-second.

Although this practical unit of electrical energy is kWh, from the above relationship it is easy to

convert this to Joules.

KWh is the commercial unit of electrical energy because electricity supply industries charge

consumers for the kilo watt hours of energy consumed.

2.3.3 THERMAL ENERGY

The thermal energy was originally ‘Calorie’. One Calorie is the amount of heat required to raise the

temperature of 1 gram of water through 1ºC. If S is the specific heat of a body, then amount of heat

required to raise the temperature of m gram of body through θ ºC is given by:

Heat gained = mS θ Calories

Experimentally it has been found that 1 Calorie = 4.186 Joules, so that heat in Calories can be

expressed in Joules.

Heat gained = (mS θ) x 4.186 Joules.

2.3.3.1 TARIFFS

The rate at which energy is supplied to a consumer is known as tariff.

Tariff normally includes the total cost of producing and supplying energy plus profit. The cost of

producing energy depends on the magnitude of energy consumed by the user and the load condition.

Therefore consideration has to be given to the different types of consumers (e.g. industrial, domestic

and commercial) while fixing the tariff. This makes the problem of suitable rate making highly

complicated.

Tariffs may be divided into the following groups:

(a) Domestic premises

(b) Off-peak

(c) Combined premises

(d) Commercial

(e) Agricultural

(f) Industrial



Other tariffs may be imposed due to special circumstances.

(a) applies to electrical energy used for domestic purposes in a private residence. The tariff

usually consists of a kWh charge plus a fixed quarterly charged based on the number of

rooms, floor areas, number of outlets etc.

(b) applies to electrical energy supplied to any premises usually between 10 p.m. and 7 a.m.. This

tariff consists of a kWh charge lower than that of (a) plus a fixed quarterly charge.

(c) Applies to electrical energy used for trade, business, or professional purposes as well as for

domestic purposes. For example, a shop with house or flat combined or a doctor’s surgery.

This tariff does not apply to premises in which items are manufactured or grown for sale. This

tariff is similar to (a) but the fixed quarterly charge is higher.

(d) Applies to electrical energy supplied to premises used solely for commercial purposes, but

not to premises in which items are manufactured or grown for sale. The tariff is similar to (a)

except that there is an additional fixed quarterly charge based on the maximum kVA

required.

(e) Applies to electrical energy supplied o a farm, market garden or agricultural holding. This

tariff is similar to (d).

(f) Applies to electrical energy supplied to industrial premises. This tariff is a monthly maximum

demand tariff.

Maximum demand is defined as twice the number of kVAh supplied during any thirty consecutive

minutes during the account month. This maximum demand is divided into blocks of units and a

decreasing scale of charges is applied to successive blocks.

In addition a kWh charge is made. The energy supplied during the account month is divided into

blocks of kWh and a decreasing scale of charges is applied to successive blocks. These blocks are

linked to the kVA of maximum demand. The overall effect of his tariff is that the lower the power

factor, the greater the average cost to the consumer of each kWh. For loads exceeding 100kVA,

consumers are encouraged to take their supply at 11kV or above. The substation is then the property

and responsibility of the consumers, the supply being metered on the HV side. Otherwise an

additional charge per kWh is made to cover the interest and depreciation charges on the initial cost of

the substation and the cost of transformer losses.

2.3.3.2 OTHER DEFINITIONS

(i) Demand – load requirement averaged over a suitable and specified interval of time of short

definition. Load is averaged over an interval of time, there is no such thing as instantaneous

demand.

(ii) Average Demand – average power requirement during some specified period of time of

considerable duration such as day, month or year giving daily, monthly or yearly average

demand.

kWh consume in the period

Average power = -----------------------------------

Hours in the period



(iii) Maximum Demand – greatest of all demands, which have occurred during a given period. This

interval is during a certain period such as day, month or year. This is not instantaneous

demand but the greatest average power demand occurring during any of the relatively short

intervals (usually 1 minute, 15 minute or 30 minute duration) within the period.

(iv) Demand Factor – ratio of the actual maximum demand made by the load to the rating of the

connected load.

Maximum demand

Demand Factor = -----------------------

Connected load

(v) Diversity Factor – ratio of the sum of the individual demands of different elements of a load

during a specified period to the simultaneous (or coincident) maximum demands of all these

elements of load during the same period. The value of the demand factor is always greater

than 1.

Sum of individual maximum demands

Diversity Factor = --------------------------------------------------

Maximum demand of the whole year

(vi) Load Factor – can be either operating load factor or connected load factor.

Average power

Operating load factor = -----------------------

Maximum demand

Each time interval over which the maximum demand is based and the period over which the power is

averaged must be definitely specified.

For example, the maximum demand is based on a 30-minute interval and he power is averaged over a

month, then it is known as half hour monthly load factor.

Average power input

Connected load factor = --------------------------

Connected load

Average power maximum demand

= ----------------------- x ----------------------

maximum demand connected load

(vii) Plant Factor – applied to generating plant only. Ratio of actual energy produced to the

maximum possible energy that the plant could produce during the same period.

Average demand on the plant

Plant factor = ----------------------------------

Rated capacity of the plant



Average demand maximum demand

= ---------------------- x ----------------------

maximum demand rated capacity

= load factor x utilisation factor

2.3.3.3 HEATING VALUES

It is customary to quote efficiencies for power plants on a higher heating value (HHV) basis than a

lower heating value (LHV) basis. These values differ by the way in which energy measurements are

conducted. The HHV takes into account the latent heat of condensation of water vapour in the

combustion exhaust gases, while the LHV excludes this energy. Normally boiler efficiencies are also

quoted on an HHV basis. In Australia it is conventional to use the HHV for fuels and for calculating

efficiencies. In Europe the convention is to use the LHV. Gas turbine performance is also usually

quoted on the LHV basis overseas. Heating values at constant pressure or constant volume are also

slightly different. It is normal to assume constant pressure heating values, unless extremely rigorous

analysis is being conducted.

Thermal efficiencies of electricity generation plants calculated on the basis of the fuel LHV result in

numerical values approximately 10% higher than when calculated on the basis of the HHV.

Fuel is commonly sold on an HHV basis

Gas turbines in particular, and usually reciprocating engines as well, are frequently quoted on an LHV

basis.

The difference between the two bases is significant. The HHV (also referred to as the higher calorific

value (HCV) or gross calorific value (GCF)) of a fuel is the amount of heat released if a fuel is

combusted at nominally standard atmospheric conditions and the products of combustion are

returned to this temperature and pressure, assuming the water content of the exhaust constituents is

in liquid form.

The HV calculates the heat release assuming the exhaust water content is in vapour form.

For natural gas, the difference between the two is that HHV = LHV + 11%. This difference flows

through to efficiency calculations and the calculation of fuel costs. Foe oil, coal, etc. he difference,

although less, is still significant.

2.3.3.5 COGENERATION EFFICIENCY

There is no universal standard for quoting the efficiencies. When comparing the efficiencies of

cogeneration plants with the case with “no cogeneration”, remember that the “no cogeneration”

comprises the efficiencies and losses of both a site based thermal heat raising facility (steam or hot

water) and imported electricity (which might be generated with coal, for example, then transported

to the site via a transmission system).



In calculating annual average efficiencies, the averages include the times during the year when N-1

units are operating, and allow for imported electricity (and the emissions created from the

production of this electricity) in the calculations.

The following measures are applied:

[Cogen gross elec O/P] + [imported elec] – [parasitic elec]

Net electricity η = --------------------------------------------------------------------------

[Fuel to cogen unit] + [fuel used for imported electricity]


Electrical η = -----------------------------------------------------------------------------------

[Fuel to cogen unit] + [fuel used for imported elec] [fuel for steam]

where [fuel for steam] is the fuel, which would have been used to raise the site steam (or hot water)

at the auxiliary boiler efficiency.


Overall thermal η = ---------------------------------------------------------------------------------------

[Fuel to cogen unit] + [fuel used for imported elec] + [fuel to aux boiler]

where [site steam] includes hot water as applicable.

2.3.4 HEAT AND POWER PRODUCTION - A BRIEF HISTORY

Before considering the potential for heat and power, it is useful to reflect briefly on the history of

heat and power supply and why cogeneration is so little used today.

2.3.4.1 60 YEARS AGO

Before the development of the Australian's electricity grid system, power stations were sited close to

centres of demand. This provided the opportunity, where appropriate, to utilise the waste heat from

the power station.

2.3.4.2 GROWING ELECTRICITY DEMAND

As the demand for electricity grew, the high cost of moving coal, the dominant fuel for generation,

made it economically attractive to build large power stations on, or close to, coal fields. In response,

the Grid grew to allow bulk transfers of electricity from the power stations to the demand centres -

often referred to as coal by wire.



2.3.4.3 THE SITUATION TODAY

The generating companies inherited an asset base predominantly centres upon coal-fired power

stations remote from demand centres and unable to use about two thirds of their heat input. Gas is

becoming established as a fuel for power generation and the traditional reservations about using it in

this role are defeated by the efficiencies achieved with cogeneration.

2.3.4.4 THE FUTURE

In total contrast to coal, gas can be moved relatively easily and without impacting on the

environment. Therefore, the engineering case for gas-fired cogeneration meeting local heat and

power needs is very strong. There might well be seen a reversal of the trends of the last 60 years,

with the use of the Grid declining and heat and power production being combined close to the point

of need.

2.3.5 WHY COGENERATION NOW?

Regardless of the engineering case for cogeneration, it will not "take off" unless it is economically

attractive. The two fundamental parameters that dominate commercial viability are:-

(a) primary fuel costs;

(b) the capital costs of cogeneration schemes.

2.3.5.1 FUEL PRICES

Most cogeneration schemes currently being developed are fuelled by gas. Until comparatively

recently the pricing policy, did not encourage the development of gas-fired electricity generation. It

was argued that gas was a premium fuel, too valuable for this application. This view has now

changed. Gas and Fuel Corporation (GFC) and other independent gas suppliers saw the opportunity to

expand the gas market by fuelling electricity generation. The development of combined cycle plant,

achieving efficiencies of around 50% and, of course, cogeneration schemes achieving up to 90% plus,

weakened the arguments against using gas for power generation.

Such has been the success of gas entering this market that Gas and Fuel Corporation have started

reviewing the prices for large long term contracts. Small to medium sized cogeneration schemes are

usually supplied under medium term (up to ten years) gas contracts. The economics of such schemes

are sensitive to the future gas price.

2.3.5.2 CAPITAL COST

Industrial cogeneration schemes in general utilise either reciprocating engines or, more commonly

now for larger installations, gas turbines. Concentration here is on gas turbines because they are

generally preferred for schemes of several megawatts. Gas turbine technology has been improving

rapidly in recent years producing more efficient machines. The market is developing with more

players offering a greater range of machines. Most importantly, the specific capital cost of

manufacture of gas turbine plant (in terms of $ per kW) has been falling in real terms and could

continue to do so. However, the recent weakness of the dollar could have a serious effect on the

price of equipment manufactured overseas.



There have, therefore, been developments favourable to cogeneration in the two key areas

determining commercial viability. However, other factors are also seen to encourage the

development of cogeneration in the 1990's, and beyond.

2.3.5.3 ESI PRIVATISATLON

There is little argument that when the ESI was in the public sector it was dominated by the actions of

large utilities and municipal electricity authorities. The utilities designed and built one of the best

integrated electricity supply systems in the world. However, its preference for large power stations

and its control over electricity prices worked against small scale generation. Further, the surplus

capacity within the utilities, experienced through the 1980's, meant that new plant had little capacity

value and this was reflected in the prices offered for privately generated electricity. One immediate

effect of the privatisation of the ESI is anticipated to be the fall in prices to many larger customers - a

force acting against cogeneration. However, a more enduring effect is that a true competitive market

for electricity will be established, encouraging new players to enter and more innovative approaches

being applied. It is inevitable that supply and demand will come closer into balance and in the

medium term this should produce a more favourable commercial environment for the development

of cogeneration.

2.3.5.4 THE "GREEN" TICKET

Cogeneration can genuinely be labelled a "Green" technology. The overall thermodynamic efficiency

of cogeneration is very high. Further, when gas fired, no sulphur dioxide is produced and NOx can be

effectively controlled either by steam injection or dry NOx control through the design of burners.

Finally, the application of cogeneration reduces the production of CO2 compared with the grid/boiler

approach. Although it is difficult to put a value on "green" benefits in money terms, it can do no

company any harm to be associated with environmentally friendly technology.

2.3.5.5 AGEING BOILER PLANT

In the fifties and sixties falling electricity prices, in real terms, encouraged industry to import

electricity and produce steam and hot water in conventional boiler plant. Significant amounts of low

cost, efficient package boilers were installed in the 1960's. Much of this plant is now reaching the end

of its useful life.

2.3.5.6 SECURITY OF SUPPLY

Security of supply can be of paramount importance in industrial environments. An on-site

cogeneration scheme can enhance the security of both heat and electricity supplies. In particular, it is

possible to design the electrical connections to ensure continuity of supply for the complete failure of

the Grid. Such arrangements can prove most beneficial from both commercial and, in certain

situations, safety viewpoints.

2.3.6 COGENERATION IN AUSTRALIA

Cogeneration has existed in Australia since the introduction of electricity. In the early days of

electricity, industry often provided its own power (cogeneration where the balance of heat and



power was right) and the public system provided domestic and public power. As public utility power

became more available and reliable generation on-site reduced.

The 1980's saw an upturn in cogeneration for environmental and economic reasons particularly in

Victoria and South Australia. In 1987 the Victorian State Government and State Electricity

Commission (SEC) of Victoria introduced a Cogeneration Incentives Package and about the same time

in South Australia SAGASCO established a cogeneration division.

The 1990's presents an era of great opportunities and challenges for the cogeneration industry as the

energy supply industry is transformed by the break-up of vertically integrated utilities (in Victoria) and

the introduction of competition between energy supplier and the Grid. At the end of 1999,

cogeneration and distributed generation represented 8.3% of installed generation capacity in

Australia. In the 12 months leading up to 31 December 1999, nine cogeneration projects (86.3 MW

capacity) and four non-cogeneration, distributed generation projects (205 MW capacity) were

commissioned. In addition, seven cogeneration projects (234 MW capacity) and 10 non-cogeneration

projects (294.9 MW capacity) were committed and were under construction.

Cogeneration is not just a smart technical solution to provide heat and power to industry and

commerce in a cost effective and environmentally sound manner. Cogeneration exists in a complex

competitive and regulatory environment that has capacity to prevent the full development of its

contribution to the economy and environment.

2.3.6.1 COGENERATION DATA

No authoritative information is available on the extent of non-utility cogeneration and power

production.

The best available estimate puts cogeneration capacity in Australia at about 2,200 MW, made up as

follows by industry:

Industry Capacity (MW) No. of projects

Alumina 498.5 6

Sugar 332.1 30

Paper 271 9

Nickel 261 6

Chemical 215.7 6

Misc Manufact 189.7 4

Oil Refining 183 4

Steel 73.8 3

Mineral Process 66.9 3

Health 60 25

Water 20 6

Food 13.2 10

Building 7.8 7

Education 7.6 3

Recreation 2.9 11



Industry Capacity (MW) No. of projects

TOTAL 2203.2 133

The alumina industry is the most significant industry sector, accounting for 23% of operational

capacity, 38% of electricity generation and 36% of thermal production.

Western Australia is the greatest user of cogeneration by State/Territory accounting for 35% of

operational capacity, 39% of electricity generation capacity and 32% of thermal production.

State Capacity (MW) No. of projects

ACT 0.1 1

NSW 281.9 18

NT 105 1

QLD 413.5 35

SA 215 25

TAS 15.5 2

VIC 409.7 34

WA 762.5 17

TOTAL 2203.2 133

Steam turbine projects accounted for 58% of operational capacity by prime mover technology, 57% of

electricity generation and 95% of thermal production.

Type Capacity (MW) No. of projects

CCGT 538 4

GT 285.9 19

RCP 77 53

FCELL 0.2 1

ST 1302 56

TOTAL 2203.2 133

Natural gas projects accounted for 56% of operational capacity by primary fuel, 66% of electricity

generation and 38% of thermal production. Renewable generation capacity accounted for 360.3 MW

of capacity, representing 16.4% of total generation capacity.

Fuel Type Capacity (MW) No. of projects

Natural Gas 1224.5 71

Bagasse 332.1 30

Coal 363.5 8

Waste Gas 144.3 6

Oil 109 2




Digester Gas 19.1 6

Landfill Gas 7.1 2

Waste Biomass 2 1

LPG 1.6 7

TOTAL 2203.2 133

Renewable 360.3 40

Fossil Fuel 1842.9 93

TOTAL 2203.2 133

2.3.6.2 NON-COGENERATION PROJECTS

The following charts by State/Territorty, Prime Mover Technology and Primary Fuel demonstrate key

aspects of the non-cogeneration, grid connecteds, distributed generation industry in Australia at 31

December 1999 and are based on informal survey.

State Capacity (MW) No. of projects

ACT 2 2

NSW 162.1 8

NT 65.4 3

QLD 501.5 5

SA 74.5 6

TAS 10 1

VIC 75.2 13

WA 569.3 9

TOTAL 1460 47

Type Capacity (MW) No. of projects

CCGT 415.9 4

GT 553.5 19

RCP 191.2 53

HT 75 1

ST 224.5 3

TOTAL 1460.1 47


Natural Gas 1123.9 12

Landfill Gas 94.4 21




Water Hydro 75 10

Coal Steam Meth 96.8 2

Waste Gas 60 1

Oil 10 1

TOTAL 1460.1 47

Renewable 169.4 31

Fossil Fuel 1290.7 16

TOTAL 1460.1 47

2.3.6.3 PROJECTS UNDER CONSTRUCTION

At 31 December 1999, seven cogeneration projects totalling 234 MW and ten non-cogeneration, grid

connected, distributed generation projects totalling 295 MW were committed and were under

construction. Renewable projects amounted to 13% of the overall total.

Plant Location Type/Fuel MW Capacity

COGENERATON

FOSSIL FUEL

Worsley Alumina Worsley, WA GT/natural gas 120

Worsley Alumina Worsley, WA ST/natural gas 34

Bulwer Island Bulwer Is., QLD CCGT/natural gas 37

QLD Phophate Mount Isa, QLD ST/natural gas 20

Macquarie Uni Nth Ryde, NSW RCP/natural gas 1

212

RENEWABLE

Visy Paper Tumut, NSW ST/woodwaste 17

Energy Developments Wollongong, NSW RCP/munic.waste 5

22

TOTAL COGEN 1460.1 47 234

NON-COGENERATON GRID CONNECTED DISTRIBUTED GENERATION

FOSSIL FUEL

Redbank Power Plant Redbank, NSW ST/coal tailings 120

Ladbroke Grove Power Plant

Ladbroke Grove, SA ST/natural gas 84

East Coast Power Plant Bairnsdale, VIC GT/natural gas 42

246



RENEWABLE

Pacific Power Burrinjuck, NSW HT/water 15

Stanwell Corporation Ravenhoe, QLD WT/wind 12

Pacific Power Blayney, NSW WT/wind 10

Stanwell Corporation Koomboloomba, QLD HT/water 7

Melbourne Water Werribee, VIC RCP/digester gas 2.4

Water Corporation Subiaco, WA RCP/effluent sludge 1.5

Energy Developments Jacks Gully, NSW RCP/landfill gas 1

48.9

TOTAL COGEN 294.9

Technology Types

CCGT: Combined cycle gas turbine

GT: Gas turbine

RCP: Reciprocating gas engine

ST: Steam turbine

HT: Hydro turbine

WT: Wind turbine

2.3.6.4 SEC SUPPORT FOR COGENERATION

BACKGROUND

Victoria has traditionally relied on its plentiful brown coal resources as a source of base load

electricity and on natural gas and hydro for its peak load. It is clear, however, that great potential

exists for industry and commerce to contribute economically to electricity production through

cogeneration.

The Victorian Government has given cogeneration a high profile and its support for the development

of the technology was outlined in the Government Economic Strategy Paper - "Victoria The Next

Decade" released in 1984. This was followed by the Government's paper in June 1989 on the

Greenhouse Challenge outlined Cogeneration as one of the vehicles to minimise atmospheric

emissions of greenhouse gases.

The SEC has adopted the Government's policies in its Cogeneration and Renewable Energy Strategy.

This strategy includes:-

encouraging the efficient use of fuel and helping its customers gain the benefits of energy efficiency from cogeneration and renewable energy projects;

promoting ways of reducing levels of CO2 emission into the atmosphere by encouraging technology such as cogeneration;



considering opportunities for joint ventures in potential cogeneration and renewable energy schemes;

encouraging and promoting commercially viable projects by introducing incentives to stimulate interest in cogeneration and renewable energy projects;

encouraging the development of a professional and effective cogeneration and renewable energy industry.

To further the commitment in promoting cogeneration in Victoria the following measures are taken:

Providing a market for cogenerated power by enacting a statutory commitment to purchase the power.

Providing reasonable buyback rates for cogenerated power that reward cogenerators but are not subsidised by other customers. This can be done by buying excess power at the SEC's avoided cost, that is, the amount the SEC saves by not generating the power itself.

Making payments to cogenerators who guarantee the availability of future capacity. These payments reflect the amount the SEC saves by the deferral or elimination of the need for some future power stations.

Adopting a new approach to standby supplies to remove current discrimination against cogenerators.

Examination of wheeling policies to encourage worthwhile cogeneration projects to proceed.

EXAMINING FUEL POLICIES AND PRICES

In recognition that a high proportion of potential cogenerators are now burning natural gas to produce process heat or steam, users should be encouraged to convert to cogeneration as a small addition amount of gas burned can yield an overall energy saving.

Encourage the use of coal in cogeneration systems.

Examining the pricing structure of natural gas for cogeneration. Evaluation of the merits of a separate cogeneration gas tariff and its effect on the existing Government gas pricing policy.

Encourage the use of renewable fuels and residues through provision of Government financial incentives.

Provide financial assistance for feasibility studies for projects that on initial assessment look technically feasible and economically viable.

Encourage projects to serve as local models and using early studies to evaluate effectiveness of efforts to promote cogeneration.

The key elements of the SEC incentives package for projects smaller than 10 megawatts are:

for sites which take SEC power in addition to cogeneration, the standby demand charge is waived for three years,

SEC interconnection costs are repayable over the contract period,

SEC buyback rates up to 10 MW are tied to the SEC's tariff rate and are linked to CPI increases,



financial assistance is available for feasibility studies for special projects,

a 10 year contract period that allows for escalation in buyback rates.

In 1987, the SEC in conjunction with the Victorian Government took the initiative by launching the

"Cogeneration & Renewable Energy Incentive Package" to further encourage the smaller potential

cogenerators.

ENCOURAGING COGENERATION IN THE PRIVATE AND PUBLIC SECTORS

Carrying out a detailed examination of cogeneration potential into public facilities e.g. hospitals, universities, libraries, nursing homes etc.

Installing and promoting the installation of cogeneration plants instead of constructing additional new central power stations.

Encouraging financing of Private and Public sector projects by outside investors.

UNDERTAKING AN INFORMATION AND TECHNICAL ASSISTANCE PROGRAM

Developing a marketing plan to promote the development and wider use of cogeneration.

Developing publications to promote the awareness of the opportunities arising from cogeneration in the community, particularly the industrial and commercial sectors.

Establishing a Cogeneration Advisory Group to help potential congenerators and provide a consultative service.

Some people are still surprised that the SEC synonymous with what they believe is a power

monopoly, should be promoting alternative production. The reasons are not only economically and

environmentally sound, but also ensure efficient utilisation of the State's resources. It costs the

Commission about $1.3 million to produce one megawatt of power. Therefore 500 MW of

cogeneration power will save it $650 million in capital expenditure. The SEC benefits directly by

avoiding capital borrowings, particularly for the construction of new power stations.

Cogeneration also creates new electricity supplies much faster than the Commission could plan and

build new power stations, which take many years from inception to production. Small generation

plants whether cogeneration or renewable also meet environmental licensing requirements more

easily than a new central power station. They can also introduce power into the system near to the

point of use and reduce system losses.

2.3.7 COGENERATION COMMERCIAL VIABILITY

It would be irresponsible to give the impression that cogeneration offers a panacea to all energy

problems. Commercially viable opportunities are still small in number. The main factors influencing

commercial viability are dependant on site's heat to power ratio and equipment utilisation.

2.3.7.1 HEAT/POWER RATIO

The balance of heat and power should be compatible with the cogeneration plant - of the order of 3:1

for a gas turbine based scheme. This ratio should ideally be constant, not changing drastically either



seasonally or daily. Schemes with a heat to power ratio greater or less than 3:1 would need to

consider carefully the commercial implications of exporting or importing electricity.

2.3.7.2 UTILISATION

Although the cost of cogeneration is falling in real terms, it is still relatively expensive compared with

large generating plant and shell boilers. It is, therefore, important that the plant is fully utilised. The

most viable schemes are, therefore, those that run continuously for 8000 hours/year or more.

2.3.7.3 AVOIDABLE COSTS

Where capital expenditure is required to:-

(a) replace existing boiler plant;

(b) provide extra boiler plant;

(c) increase electricity supply capacity.

The expenditure saved by employing a cogeneration scheme can be set against its capital cost. Any

savings in maintenance, manpower or even plant outage times can also be credited to the scheme.

2.3.7.4 FUEL SUPPLY/ELECTRICAL CONNECTIONS

It is helpful if a gas supply is available at the site with sufficient capacity to connect the gas turbine

without reinforcement. If the delivery gas pressure is such that gas compression is not required,

further capital and running costs are saved. At the electrical end of the cogeneration plant, it is

almost inevitable that the scheme will be run in parallel with Grid system. Ideally, connection should

be achieved without the need to reinforce the local distribution system, and without the need of

expensive modifications to the site electrical system.

2.3.7.5 SCHEME VIABILITY

Although it is dangerous to generalise about the type of schemes that are viable, however the

authors are confident that schemes of around 5 MW and upwards, can be shown to be commercially

viable. In contrast, small schemes of up to 1 MW based on reciprocating engines and connected at

low voltage, can also be shown to be attractive as electricity prices in the franchise market can still be

relatively high. Between these two limits commercial viability can still be achieved, but certainly

cannot be taken for granted.

2.3.8 COGENERATION - THE COMPETITION

The most valuable product of a cogeneration scheme is the electricity it produces. The real

competition for cogeneration is, therefore, going to be Pool delivered electricity. The establishment

of a competitive market for electricity in the "above 1 MW" sector will have reduced prices to these

customers.

There is a continuous debate about what will happen to electricity prices in the next few years. The

market is currently over-supplied. As supply and demand come more into balance, it is possible that

prices will rise, enhancing the economic attractions of an investment in cogeneration.



2.3.9 COGENERATION - THE BARRIERS

Barriers to the development of cogeneration still remain. A number of them are:

2.3.9.1 INSTITUTIONAL ARRANGEMENTS

It could be argued that one downside to the ESI privatisation is the institutional complexity of the

restructured industry:

(a) the licences;

(b) Pool membership and rules;

(c) Council connection agreements and power plant operating agreements;

(d) Use of System agreements;

(e) the Grid and Distribution codes.

2.3.9.2 MARKET POSITION

The behaviour and attitude of the municipal Council's are a key factor. Some of them may see

cogeneration, developed by other parties, as a threat to their business whilst other actively

encourage its use. It is, therefore, somewhat perverse that they maintain a position where they have

a direct input to the viability of a scheme by means of charging connection costs where they consider

reinforcement work to be necessary on their distribution system. Although it is accepted that costs

may be required to reinforce the network it is often difficult for the lay-person to establish whether

such costs are fair and reasonable.

2.3.9.3 POOLING AND SETTLEMENT

Selling excess of electricity is not just a matter of choosing a buyer. An owner of plant wishing to

export power into the distribution or transmission system generally has to follow established

guidelines.

2.3.10 CONCLUSION

Cogeneration has been demonstrated worldwide as a cost effective means of meeting industrial heat

and power demands. It also can reduce external costs of power generation activities. Cogeneration is

recognised as one of the measures which governments should be promoting and supporting in order

to improve efficiency and reduce CO2 emissions. The trend in Australia until now has been heavily

biased towards large scale thermal generation. The future of small scale generation is very much

dependant on the policies of the government. If cogeneration prices are lower than the conventional

mode prices, then the future is bright. However at present, indications are that this is not the case.

Investigations have revealed that the potential for cogeneration in Australia is very sensitive to:

(i) electricity prices, and

(ii) types of contract that may be written by cogenerators for sale of surplus power.

The future of cogeneration very much depends on the incentives that local utilities can provide.

Buybacks and levy of some sort may be more attractive to the cogenerators if they are to survive.



FUTURE

In the future, civilization will be forced to research and develop alternative energy sources. Our

current rate of fossil fuel usage will lead to an energy crisis this century. In order to survive the energy

crisis many companies in the energy industry are inventing new ways to extract energy from

renewable sources. While the rate of development is slow, mainstream awareness and government

pressures are growing.

While renewable energy is generally more expensive than conventionally produced supplies,

alternative power helps to reduce pollution and to conserve fossil fuels. Green is the rage these days,

but as the market gets flooded with everything from hybrid cars to reusable shopping bags, the ability

to do something truly innovative will be paramount.

REFERENCES

[1] Kothari, D.P. and Nagrath I.J, 2008, “Power System Engineering”, 2nd edition, Tata McGraw Hill.

[2] El-Sharkawi, M., 2009, “Electric Energy – An introduction”, 2nd edition, CRC Press.

[3] Glover, J.D. Sarma, M.S. and Overbye T.J., 2010, “Power System Analysis and Design”, 4th

edition, Cengage Learning.

[4] http://en.wikipedia.org/wiki/World_energy_resources_and_consumption.

[5] http://www.power-technology.com/projects/kogan/.

[6] http://www.worldofenergy.com.au/factsheet_water/07_fact_water_hydro_wa.html.

[7] http://www.papundits.files.wordpress.com.

[8]

http://www.edison.it/edison/export/sites/default/en/activities/energy/combined/centrale_EN

G.gif.

[9] Kothari, D.P. and Nagrath I.J, 2008, “Power System Engineering”, 2nd edition, Tata McGraw

Hill.

[10] El-Sharkawi, M., 2009, “Electric Energy – An introduction”, 2nd edition, CRC Press.

[11] Glover, J.D. Sarma, M.S. and Overbye T.J., 2010, “Power System Analysis and Design”, 4th

edition, Cengage Learning.

[12] RISE Information Portal - Information regarding renewable energy resources, technologies,

applications, systems designs and case studies.

[13] Zahedi, A., 2001, “Photovoltaic Hybrid Power System”, ESAA REidential School in Power

Engineering, Monash University.

[14] CHP & Combined Cycle Modern Power Systems, IBC Technical Services, Manchester, UK, 1992.

[15] Cogeneration and Independent Power Production; IBC Conferences, Sydney, 1994.

[16] Guide to Cogeneration in Victoria; SECV Report.

[17] Cogeneration: Helping the Customer, The State and the Environment; J. Ball; SECV Report.

[18] Cogeneration Handbook; California Energy Commission; California.



[19] Guide to Natural Gas Cogeneration; N. E. Hay; American Gas Association.

[20] Planning Cogeneration Systems; D. R. Limaye; The Fairmont Press; Atlanta, USA.

[21] Cogeneration in Victoria; Greene, D, SECV Report, 1984.

[22] Environment Protection Authority; State Environment Protection Policy, Ministry for Planning

& Environment, Victoria.

[23] Special Report on Independent Power; Power, 1994.

[24] Power System Analysis; Grainger, J J and Stevenson, W W, McGraw-Hill, 1994.

[25] Cogeneration and Gas Turbine Operation; Kalam, A, Bennett, B, Broadbent, D, Clark, G, Coulter,

R, Klebanowski, A, Smith, R and Skidmore, K, ESAA and VU, 2000.

[26] Cogeneration Ready Reckoner; Australian Cogeneration Association, 1997.

[27] Who’s Who in Australian Cogeneration 2000; Australian Cogeneration Association, 2000.

[28] Gas for Electricity Generation, ESAA.

UGSE1_Generation System Fundamentals Course Notes_Final 2010

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