Electric-power generation in the UK

Applied Enerey 39 (1991) 1 19

Electric-Power Generation in the UK S. G. Reeve, R. F. Babus'Haq & S. D. P r o b e r t Department of Applied Energy, School of Mechanical Engineering, Cranfield Institute of Technology, Bedford MK43 0AL, UK

ABSTRACT An overview o]'the electric-power generation and supply industry and its new structure in the UK. as a result of the 1989 Electricity Act, is presented. The environmental issues that have arisen in connection with this industo, are summarised. The options.for UK power generation in the 21st centuo' are discussed.

NOTATION G M P T

Giga = 109 Mega = 106 Peta = l0 ~5 Tera = 1012 ABBREVIATIONS

AGR AIEP CEGB CHP DGES ESI ETSU LFG NGC OFFER PWR TDR

Advanced Gas-cooled Reactor Association of Independent Electricity Producers Central Electricity Generating Board Combined Heat and Power Director General of Electricity Supplies Electricity-Supply Industry Energy Technology Support Unit Land-Fill Gas National Grid Company Office of Electricity Regulation Pressurised-Water Reactor Test Discount Rate 1

Applied Energy 0306-2619/91/$03.50 (" 1991 Elsevier Science Publishers Ltd, England. Printed in Great Britain

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S.G. Reeve, R. F. Babus'Haq, S. D. Probert

T E C H N I C A L STRENGTHS, WEAKNESSES A N D OPPORTUNITIES Electricity is the most convenient, combustible form of energy. It can readily be converted into heat or mechanical energy and is easy to transmit to wherever required. Unfortunately, the production of electricity from the combustion of fuels is a highly inefficient process. In practice, due to irreversibilities in the various processes, the cycle efficiency is very much lower than the Carnot efficiency. The approximate figures for the UK Central Electricity Generating Board's maximum efficiencies are 23 %, 38 % or 41% for power plants equipped with either gas turbines, steam turbines (using coal or nuclear fuels), or diesel engines respectively. 1 The average efficiency for the CEGB power stations is 28%, i.e. 72% of the potential energy of the fuel used in generating the electric power is dissipated wastefully as heat via cooling towers, rivers and/or the sea. This 'wild heat'-Britain's largest untapped energy source--is equivalent to far more than twice the amount of the electricity now generated. 2 However, the problem arises because of the quality of this rejected heat. The temperatures at which this waste-heat is emitted are low ( --~20°C) and because power stations, since the industry was nationalised in the late 1940s, have usually been built in places remote from areas of high demand, the transmission of this low-grade energy to potential recipients has proved to be uneconomic. Nevertheless, a few applications, such as greenhouse heating for horticulture, have been found and exploited, but the vast majority of this waste-heat is rejected to the ambient environment. Combined Heat and Power (CHP) or cogeneration is simply a technology that seeks to rectify this wasteful situation by making a more efficient use of the heat produced, as well as the electricity generated, by a single plant. The maximum theoretically-attainable cycle-efficiency then improves (to 80-90%). CHP has been used in industry, namely at the Singer factory on Clydebank, since 1898. One of the earliest CHP schemes involving district heating in the UK was installed in 1911, in Bloom Street, Manchester to supply steam to neighbouring shops, offices and factories. 3 However, smallscale or packaged CHP is a more recent innovation: its development and implementation have become increasingly popular during the last 10 years.

THE E L E C T R I C I T Y ACT (1989) Prior to the implementation of this Act, power generation in England and Wales was controlled by the state-owned Central Electricity Generating Board (CEGB). This monopoly owned all the power stations supplying

Electric-power generation in the UK

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purchased electricity and hence controlled the unit prices at which electricity was sold (via the Area Boards) to industry, commerce and domestic consumers. One of the main purposes of the Act is to introduce competition into the industry whereby electricity can be traded in the same way as the other energy supplies, namely coal, oil and gas. The political intention is that this will lead to the industry becoming more effective so that benefits will accrue to the individual consumer in the form of lower unit prices. However, the actual outcome is still dependent on political and financial details yet to be settled. One preliminary study 4 has concluded that there will be real unit price rises, with an average increase of 9'5% per year. Similar restructuring is taking place in Scotland, with the privatisation of the North of Scotland Hydro-electric Board and the South of Scotland Electricity Board. Northern Ireland and the Republic of Ireland will not be affected directly.

The new companies The CEGB has been split. Two privately-owned generating companies, National Power and PowerGen, control all fossil-fuel and some hydroelectric power stations. The transmission role is that of the new National Grid Company. Nuclear power (because of its lack of popularity in the financial market) remains under state control via a new company called Nuclear Electric. The Area Electricity Boards, presently called Public Electricity-Supply Companies, will also be privatised. Not only will the lowvoltage power distribution function be assigned to these 12 distribution companies, they will also have the right to generate, if they so wish, up to 15% of the power that they distribute. 5 The National Grid Company (NGC) now, has two major roles. The first is its traditional one of maintaining and operating the national transmission network. This includes the links with Scotland and France, and the control of the pumped-storage hydro-electric stations at Dinorwig and Ffestiniog in Wales, for peak-load lopping at times of maximum demand. The second is its new role of controlling the wholesale market for electricity supplies. This operates on a 24-h basis. Generating companies submit bids for the quantity and unit financial charge for the electricity they intend to produce the following day. Having received all the bids, the NGC informs each generator of what will be expected of them. In this way the highest-price producer will be forced to reduce his unit costs in order to stay competitive.

Regulations Several key regulations are being applied to the industry in order to (i) foster competition between the many new companies entering the market; and (ii)

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S.G. Reeve, R. F. Babus'Haq, S. D. Probert

ensure the maintenance of a wide base of fuel resources so that any future restriction (for example, as a result of political disruption in the Middle-East region) imposed on one fuel will not disrupt the whole industry. The main regulations are: • The twelve public-supply companies are at present limited to generating only 15% of the power that they will sell. • National Power and Powergen are not allowed to hold a combined market share of more than 15% of the requirements of each public supply company until 1994. The quota will then be raised to 25% until 1998, after which all market restrictions are to be phased out. • There will be a 4-year limitation on the issue of second-tier licences concerning supplies to specific, named industrial and commercial premises taking 1 MW or less, followed by a further 4-year limitation for premises taking up to 0"1 MW. • A non-fossil-fuel obligation must be upheld by each public-supply company, whereby at least 15% of their electricity sales must come from renewable or nuclear sources. A further tranche for renewable energies intends to increase their proportion of the obligation in a series of stages, up to a total capacity of 600 MW by the year AD 2000. • A fossil-fuel levy will be introduced to help the public-supply companies meet the non-fossil-fuel obligation as well as to subsidise and distribute evenly the costs of the nuclear-power industry. The body responsible for the overall monitoring and regulation of the industry is the Office of Electricity Regulation (OFFER), under the control of the Director General of Electricity Supplies (DGES). It aims at ensuring that the consumer, whether from a major industry or a domestic user, gets a just deal.

Concerns of the independent generators One suspects that many of the rules and regulations of the Electricity Act appear to have been drawn up specifically to foster the larger generating companies while restricting the smaller independent ones, who already suffer the disadvantage of having less financial and managerial resources at their disposal. The restriction on the issuing of second-tier supply licences is the most direct inhibition to the independent generators. According to the Association of Independent Electricity Producers (AIEP), this means a potential loss of 70% of the industrial and commercial market. 6 It represents a significant interference with free choice in a market in which all competing parties are supposed to be on an equal footing. Now many independent suppliers will in practice be constrained to selling their electricity to the local distribution company.

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Up until privatisation (i.e. February 1991), there was direct conflict for the Government between trying to create fair competition, whilst simultaneously making PowerGen and National Power highly attractive to prospective financial investors. Inevitably, the two big companies possess enormous advantages, which could be further enhanced by collusion between themselves. They have already managed to raise the 15 % combined market-share permitted (as outlined above) to 25% in four regions. There is a growing concern that the DGES and O F F E R possess insufficient legislative muscle to fulfil their role fairly and unequivocally. Concerns of energy conservationists A strong argument against the privatisation of the electricity (or any other energy) supply industry comes from those who fear that the competitive drive to sell more of their form of energy or power by more companies will tend to override any desire for energy thrift (amongst their salesmen) and therefore give rise to an increasing national rate of energy demand. Privatisation usually involves considerable sales promotion of the product, as was the case with British Gas and British Steel. Media advertising is therefore likely to promote the use of a greater number of electricityintensive appliances (even though individually it is hoped that they will each be more energy-efficient) rather than making recommendations to reduce domestic consumption. Implications for CHP Unfortunately, the privatisation programme, as such, contains no direct support for, or concessions to encourage, the introduction of CHP systems. To many, this is seen as a mistake on the part of the Government. The Electricity Act has however, led to renewed discussion and fresh thinking in industrial, commercial and public sectors on all aspects of power generation and energy efficiency. Thus, CHP systems are actively being reconsidered and re-evaluated in order to determine what part they can play in the drive for cheaper energy and the implementation of more environmentally-friendly technologies. The economic viability, especially for small-scale systems, to export any excess electricity produced is still often borderline. Yet, this radically affects their overall viability, and whether or not they will be adopted. Whether any fresh arrangements will arise as a result of the sale of the Public Electricity Supply Companies (in February 1991) remains to be seen. For the present, the financially-wisest strategy is usually to design the C H P system so that all the electricity generated can be used in-house.

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S.G. Reeve, R. F. Babus'Haq, S. D. Probert

E N V I R O N M E N T A L ISSUES The electricity-supply industry (ESI) is Britain's largest single air polluter. It is responsible for producing approximately one quarter of all Britain's globalwarming pollutants and almost two-thirds of the gases causing acid rain. 7 A long-term consequence is a potentially intolerable modification to the climate via the enhanced greenhouse effect that results. The total weight of each of the major gaseous emissions resulting from the supply of electricity in the UK can be calculated from a knowledge of the weight-emissions factors, the total amount of electricity supplied and the generation-fuel mix. 8 The total electricity sales in 1987 amounted to 250 TWh, which is equivalent to 900 PJ. Coal is still the main fuel used for UK electric-power generation (see Table 1). It is relatively cheap to mine in parts of the world (e.g. Australia) and readily available in the UK. Nuclear power has been developed gradually over the past 35 years. There are currently 36 civil reactors in operation at 20 sites. These are mainly of Magnox and Advanced Gas-cooled Reactor (AGR) designs. However, the true financial viabilities of these installations are obscured because for instance of the appropriate allocations of research and decommissioning costs. The employment of oil is much less common for electrical-power generation on a large scale, though it is still used significantly for independent generation in industry and in remote locations well separated from the national grid. The only renewable-energy resource exploited on a large scale is hydro-power. The bulk of the capacity for this is located in Wales and Scotland, and, because of its fast-response time, is used mainly for demand peak-lopping. As a result of the Electricity Act and growing environmental concerns, the current (i.e. 1990) trend is towards the use of natural gas for electric-power generation in gas-turbine and combined-cycle plants. Fossil fuel SO x and NOx emissions

The combustion of fossil fuels produces pollution, which, if not controlled carefully at source, has for many years been recognised as harmful to the environment, both in the immediate locality and further afield. The emissions SO2, SO3, NO and N O 2 a r e of particular concern. Coal mined in the UK has a relatively high sulphur content. This results in high SO2 and, to a lesser extent, SO3 concentrations in the waste-gas emissions from coal-fired power stations. To combat this, flue-gas desulphurisation plants are currently being fitted to large coal-fired power stations and options to import low-sulphur coal are under consideration for other plants. Nitric oxide accounts for some 90% of the oxides of nitrogen

Electric-power generation in the UK

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TABLE 1 Sources of UK-Generated Electricity in 19898

Fuel or source o f input-energy used

% ~/ total electricity produced

Coal or coke Nuclear disintegration Oil Renewable sources

71 21 7 1

emitted as a result of fossil-fuel combustion and together with the sulphur oxides, through oxidation and dissociation of the gases already in the atmosphere, leads to an acidification of the environment and precipitation occurring in the form of so-called 'acid rain'. Oil-fired power stations also produce SOx and NOx emissions, although, as there are now few such stations in the UK, their overall contribution is relatively small. C O 2 emissions

These are a major pollutant from UK power stations: CO 2 accounts for -~ 50% of the so-called 'greenhouse gases' (see Fig. 1) currently blamed for contributing towards global warming. 9 Also CO 2 cannot be removed so easily by filtering or chemical processing as can other gases (such as SO2). The level of CO 2 emissions can be reduced primarily by cutting fossil-fuel combustion through increased energy-efficiency measures. Globally, 80% of CO 2 emissions come from the burning of fossil fuels, much of this in powergeneration plant. Throughout the UK, electricity generation is responsible 50% COz

18"/C , H~

~

6%NzO 12% 03

1/,% CFEs Fig. 1.

The percentages of the greenhouse gases existing in the atmosphere at present (Oct. 1990).

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S.G. Reeve, R. F. Babus'Haq, S. D. Probert 38% ELECTRICITY GENERATION

22% TRANSPORT 6% COMMERCE

7% DOMESTIC 17°/o INDUSTRY

Fig. 2.

Sources of C O 2 emissions in the UK by sector (a total of 542 million tonnes per annum).

for 38% of CO 2 emissions (see Fig. 2) and 90% of this comes from coal-fired stations. 9 For generating the same amount of electricity, the combustion of the necessary amounts of either oil or coal results in the emission of far more CO2 than occurs when burning natural gas, i.e. by 38-43% and 72-95% respectively (see Fig. 3). This makes gas-fired power stations appear environmentally relatively attractive. 9 Moreover, natural gas is an easier fuel to handle and transport, and the environmental pollution as a result of its combustion is also reduced significantly. However, there is still some concern expressed amongst energy conservationists regarding this practice.

/ / / / / / / / / / / /

8

/

/

/

/

/

/

/

/

////

/ / / / / / / / //// COAL

OIL

FIAS

ENERGY OUTPUT EQUIVALENTTO I THERM

Fig. 3.

The rate of C O 2 production from fossil-fuel combustion.

Electric-power generation in the UK

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It is thought to be extremely wasteful to use such a high-quality fuel to generate electricity, even at the higher efficiencies achieved by combinedcycle or combined heat and power plants, and then to use this electricity for domestic or industrial heating with a further conversion loss. For heating applications, it is far more efficient to use natural gas burnt directly at its point of end use. The debate as to the exact adverse consequences of trying to reduce CO2 emissions will continue, and so it is difficult to obtain international agreement as to which remedial actions to implement. The "Toronto Protocol' of June 1988 called for a reduction of CO2 emissions to 20% of 1988 levels by AD 2005. It is estimated that the rate of global emissions would have to be cut by 50% in order to stabilise atmospheric CO2 levels. So far the U K Government has committed itself only to stabilising U K CO 2 emissions by the year AD 2005. Some studies show that these emissions have been gradually falling over the past 20 years as a result of the decline in manufacturing industry. Nevertheless, with the projected increase of the rate of fuel use in the U K (as indicated by Energy Paper No. 58), it is difficult to see how Government expectations will be achieved. Predictions 9 for the next 15 years of the CO 2 levels resulting from U K electric-power generation according to three quite different scenarios are shown in Fig. 4. If a business-as-usual approach is followed along with the 300

[] BUSINESS AS USUAL A

WITH IMPROVEMENTS (SEE TEXT) IN ENERGY EFFICIENCY

o

WITH 7000 M W COMBINED-CYCLE GAS-FIRED CAPAZ[TY

250 I I

I

t

I I I

200

Z

150

1988

I

1990

i

1992

i

19%

i

1996

I

1998

2000

i

2002

200/,

2006

2008

YEAR

Fig. 4.

15-year predictions of the CO 2 levels under three different scenarios.

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S. G. Reeve, R. F. Babus'Haq, S. D. Probert

electricity industry's suggested demand projections, the UK emissions are likely to be 241 million tonnes per annum by the year AD2005. The Association for the Conservation of Energy, using the same predicted demand figures showed that reductions of up to 15% are possible through energy-thrift measures in the domestic (e.g. lighting), commercial (e.g. electrical appliances), and industrial (e.g. electric motors) sectors, as well as the introduction of cogeneration. If a different supply-mix is assumed, with 7000MW of combined-cycle gas-fired capacity and slightly lower than forecasted supply demands, then the prospective savings increase to over 20%, i.e. a reduction of over 40 million tonnes of CO2. Nuclear-generated electricity is often alleged to be CO 2 free. Indeed the latest working group of the United Nations Inter-Governmental Panel on Climate Change strongly advocate the use of nuclear power to curb the rate of CO 2 emissions. 1° However many of the processes essential to nuclear generation such as uranium mining, residual disposal as well as the contruction and maintenance of stations require large amounts of energy which, in thefirst instance, have to be provided via means involving fossilfuel combustion. Although current emission levels of CO 2 are low compared with those from coal-fired stations, these are likely to rise with the depletion of high-quality uranium-ore reserves. The contrary argument is that once the first station is built, future building and mining activities increasingly will use nuclear-generated electricity and so lead to further reductions of CO2 emissions. The cornerstones of any debate are the relative total costs of the rival options. In evidence submitted to the Hinckley Point Inquiry, on behalf of the Friends of the Earth by Timothy Jackson of the Stockholm Environment Institute in London, nuclear power came 15th in order of merit, with an expenditure of over £20/tonne of CO 2 saved. 11 By contrast, other measures actually reduced running costs as well as carbon-dioxide emissions, viz. improved lighting efficiency saved --~£12/tonne CO2; industrial gas-fired CHP saved ~ £13/tonne CO2; improved heating efficiency in commercial and public-sector buildings saved ~£8/tonne CO2. The premise that any action towards reducing the rate of fossil-fuel based carbon emissions will be extremely expensive for governments, is further disputed in a detailed study by the USA Government's Environmental Protection Agency. ~2 Its initial findings, for eight industrialised nations, demonstrate that it is not only possible to act without incurring enormous expenditures, but in many cases the country's economy would be strengthened rather than weakened by the suggested measures. In the case of the UK, stabilisation could be achieved at no cost to the economy. Going beyond this would cost an average of about £40 per tonne of carbon emissions reduction to bring it down to its target by the year AD 2005.

Electric-power generation & the UK

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CHP or cogeneration

By eliminating the need to burn the fuel in separate boilers, the increased fuel utilisation and the overall efficiency of CHP units means that less fuel is needed for a given energy output. This leads to an immediate reduction in the rate of waste-gas emissions and a lower rate of fuel-reserve depletion. Natural gas is much cleaner when burning than coal or oil combustion, thereby further reducing CO2 emission levels, and so helping to reduce the recent increase in the greenhouse effect. In November 1989, the British Government published its evidence to the Inter-Governmental Panel on Climate Change. It concluded that, against a background of high electricity growth, by the year AD 2020, CHP could: (i) achieve an installed UK capacity of 30 GW e across the urban CHP (15 GWe) industrial (10 GWo) and building (5 GW~) sectors; and (ii) cut the UK rate of greenhouse-gas emission by 15%. 13

F U T U R E OPTIONS The UK has been fortunate in that it has a wide diversity of energy resources from which it can meet its needs. The options for the development of these in the near future will now be assessed. Coal

The UK coal reserves are estimated to be well in excess of 200 years at present extraction rates. However, concerns over environmental pollution and the cost of its prevention have increasingly led to natural-gas-fired plants being chosen for new power stations in preference to coal-fired plant. One alternative would be to import large quantities of low-sulphur coal, which would significantly reduce the SO x emissions and reduce the need for expensive flue-gas desulphurisation plants. However, the Government is inhibited by its intention to privatise British Coal, in that it does not want (i) to permit a rapid increase of low-sulphur coal imports, and (ii) a major reduction in the tonnage of U K coal burned in UK power stations. Trade union resistance towards such proposals could also be damaging and costly. On the positive side, research into circulating and pressurised fluidisedbeds, and coal gasification combined-cycle plants is continuing: the latter two are currently at the plant demonstration stage. In addition, UK industry has remained a major purchaser of coal for power generation. Industrial coalfired C H P plants produce some 700 MW at nearly 50 sites. Also British coal has the advantage in that it is unique amongst UK fuel suppliers in not only

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S. G. Reeve, R. F. Babus'Haq, S. D. Probert

offering long-term supply agreements of up to 10 years, but also price predictability with yearly increases of no more than the annual rate of inflation for the duration of such contracts. This stability in a volatile fuel market, along with the other aforementioned factors, ensure that coal will remain a significant contributor to the electricity-generation industry in the UK for at least the next 50 years. 14 Natural gas

The use of natural-gas-fired plant for large-scale power generation is a recent practice in the UK. It has stemmed from the combination of environmental concerns associated with burning coal and technical advances in the field of combined-cycle plants, which have greatly increased system efficiencies. Schemes currently being planned and installed in the UK exceed 10 GW in capacity, i.e. the equivalent approximately of one-third of the current capacity of the coal-fired power stations. A major issue confronting gas-fired power stations is that of long-term access to gas supplies. North-Sea reserves are estimated to last about 50 years at the current rate of withdrawal, but a substantial increase in gas-fired plants would clearly reduce this period. Now, the consumers want long-term supply contracts for gas, putting the onus on the off-shore operator to match the supply to the needs of the power company. However, there are still uncertainties. If British Gas plc and the generators get into serious competition for reserves, the unit price of gas will rise. This makes an investment in gas more risky and signing up available reserves difficult, especially for the smaller independent generators. Nuclear power

This industry in the UK has frequently been beset with problems, mainly due to a combination of a wish for secrecy, technological delays and disappointments, management difficulties and public pressure groups, leading to political indecisions. The past year has seen the withdrawal of nuclear power from the privatisation programme following the admission of the true total life-cycle costs of construction, radioactive waste disposal and decommissioning. This has contributed to the cancellation of plans for the building programme of 15 new reactors in the UK. Only one pressurised-water reactor (PWR) station is currently under construction. This, the Sizewell B station, although expected to be completed on time for commissioning in AD 1994, has already incurred a substantial construction cost inflation. Some contend that the design is inherently uneconomic and a new design should have been sought before construction

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began. Many researchers believe it would still be cheaper to halt construction now and direct the then available resources towards improving energy efficiency nationwide, because this would in perpetuity save more power each year than Sizewell B is expected to generate annually. The Government has stated that capital approval for stations after Sizewell B will not be considered until a review of the prospects for nuclear power has been completed in AD 1994. In the meantime, it is seeking to extend the life of the Magnox power stations, many of which are now scheduled for decommissioning, whilst maintaining the advanced gascooled reactors (AGRs) in spite of the poor financial performances of at least three of them. This option is clearly the cheapest and most prudent for a Government which cannot be confident that it will still be in office at the end of the period it takes to build a nuclear power station and hence obtain some return on its investment. The dilemma highlights the severe political constraints suffered by such an industry under state control. Renewables

Whilst large-scale hydro-electric power has been exploited successfully in the UK, the major potentials of the other renewable technologies are as yet only realised marginally. During the last 70 years, there have been several surveys and estimates of the potential for hydro-electric developments in the UK. The Proceedings of the World Energy Conference 'World Energy Resources', published in 1986, gives a gross exploitable hydro-electric power capability for Great Britain of 5600GWh/year, whilst in May 1985 ETSU predicted that the technically exploitable potential for small-scale developments equals 1800 GWh/year, and estimated that up to 90% of these could be economically viable at a 5% TDR. 5 Since then, little has happened which materially affects this prediction. Off-shore wave p o w e r has recently received a fresh boost after revelations of incorrect costing methods used in the early 1980s by the Department of Energy when trying to assess the resource potential of wave power. For the UK, it should be capable of yielding 6 GW mean annual power. The scope for the economic use of coastline wave devices by local communities in the UK may be fairly limited, perhaps 50 units each of 200 kW, or 10 MW total. Queen's University considers this economic resource to be much greater, i.e. approximately 200-300 MW, with possible sites on nearly all the Scot's islands and the coasts of Devon and Cornwall. 5 Tidal p o w e r is still under consideration, with feasibility studies having been carried out at several prospective sites. The Severn and Mersey schemes are the most advanced of these; between them, they could supply about 7% of the UK's electricity demand. The total resource that could be exploited, at

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S. G. Reeve, R. F. Babus'Haq, S. D. Probert

a unit cost of electricity of 6pence/kWh or less, is about 45 TWh/year. However, due to the massive scale of the projects and the long-term investments required, finding financial support is the major limiting factor. With existing technology, active solar power is not at this time financially feasible for large-scale power generation in the UK. Several adverse factors (e.g. climate) have combined to inhibit the development of a satisfactory market. For instance, while the technical potential was as much as 45 million tonnes of coal equivalent annually, the high cost of the installation could reduce this to as little as 1 million tonnes per annum, s However, passive-solar design of buildings (for example, using greater ratios of south-to-north facing windows as well as including atria and conservatories in buildings) does make a significant contribution in reducing the energy costs and the demand for burning conventional fuels by as much as 40% for those buildings. On establishing the worth of the resource, it appears, in energy terms, that a contribution of up to 14 million tonnes of coal equivalent annually could be expected by implementing passive-solar design retrospectively and for new buildings. 5 Photovoltaic applications in the UK will become attractive financially only when crystalline-silicone modules cost below --~£1/W, and probably then when used in hybrid systems with wind or micro-hydro systems for relatively low ( < 100 kW) power outputs. 5 The most promising renewable option at present is wind power. Its implementation in the UK has been slow despite Britain's geographic location as one of the best for wind-energy harnessing. The gross resource on land has been estimated to be 1760TWh. ~5 The results of initial pilot schemes have been favourable. A limiting factor here, on a relatively small island such as Britain, is the considerable amount of land area required by each wind farm if it is to produce a worthwhile amount of energy. To overcome this, it has been suggested that the wind turbines should be mounted on off-shore platforms, though as yet the additional cost cannot be justified.

Municipal refuse and biomass Refuse-fired power-generation plants are another option for future development. There are currently less than 10 energy-recovery refuse-disposal plants operating in the UK. The capability is probably for well over 100 such plants. Less than 5% of household refuse in the UK is used for energy recovery. 16 Nevertheless, the resource has the potential to make a significant contribution ( ~ 14 million tonnes of coal equivalent a year) to UK energy supplies. A detailed study 17 of the likely potential for refuse-derived fuel

Electric-power generation in the UK

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indicates that it could satisfy up to 13 % of all current heat demands by UK industry. Ash-disposal and pollution-control costs are a significant proportion of the total operating costs. Two European Community directives were adopted in 1989 to limit the air pollution from new and existing plants by applying a c o m m o n set of emission limits and operating conditions for ali member states. Pollution-control equipment and the need for constant refuse loads of similar consistency and calorific value, have so far made the technology uneconomic for small-scale plants. As the rates of return sought by venture capitalists are typically in the range 20-25%, preliminary cost data suggest that the smallest economic, general refuse-burning plant producing saleable heat and electric power, would be a CHP plant fed at the rate of the least 1 tonne/h. Electric power generation alone is only likely to be economic when fed with suitable refuse at rate exceeding 3tonnes/h ( ~ 1"8 MWe). 18 Approximately 20 million tonnes of domestic refuse are produced annually in the UK, an estimated 90% of which is land-filled and, therefore, potentially available for producing methane gas. To date, it has usually been cheaper to bury refuse in land-fill sites (at --~£5/tonne) than to incinerate it (at ~£15 20/tonne). However, as the availability of suitable land-fill sites declines, so refuse-disposal costs by this method will increase. This is particularly so for specialist wastes such as non-infectious hospital refuse, disposal of which can currently cost up to £200/tonne. Scrap tyres are another waste problem currently costing £30/tonne for collection and disposal. 18 The Non Fossil-Fuel Obligation part of the 1989 Electricity Act has led several groups to investigate the prospects for specialist refuse-fired plants. The advantage of such plants is that the calorific value of the waste is much more constant than that for domestic refuse and hence greater combustion efficiencies can be achieved. By collecting the land-fill gas (LFG) emitted from the decaying refuse, and burning it, power generation can ensue. So far, there are 13 operating projects in the UK with an installed capacity of some 16 MW. Another four systems will be constructed within the next year and a further 12 are at the planning stage. If all these go ahead, the UK's total capacity will be some 55 MW by the end of 1992. Current projections estimate that a potential 200 MW of such power could be exploited by the year AD 2000.19 Shanks and McEwan plc have been using natural gas from their Stewartby refuse-disposal site in Bedfordshire since 1987, both to fire a kiln at the nearby London Brick Company and to generate electricity at a 1 MW plant utilising four spark-ignition gas engines (each rated at 275 kW output).19 A 15 MW plant is now scheduled to be built at their Brogborough site. The only types of fuel crops likely to be purposefully grown in the UK (at

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S. G. Reeve, R. F. Babus'Haq, S. D. Probert

least in the foreseable future) for their energy content will be in the form of woody biomass which can then be combusted. At present, the fuelwood market in the UK is estimated to be 250 000 tonnes/year, though residues from existing forests, at 1'5 millions tonnes/year, could easily meet the demand. 2° Other lower calorific-value biomass resources include cereal straw, natural vegetation and horticultural residues. Combined heat and power or cogeneration The installed capacity of industrial CHP in the UK declinedby 50% between 1955 and 1983, i.e. during the period when the overall industrial capacity more than doubled. Barriers to the adoption of C H P have been unfamiliarity, uncertainties about performance, apparent skilled manpower requirements, project costs and uncertainties about the future unit fuel and electricity price relationships. 21 However, greater interest has been stimulated since the Energy Act of 1983 which allowed the generation of electricity by bodies other than the Electricity Boards, so requiring the Boards to adopt more positive attitudes to the implementation of the CHP concept. A study by the Department of Energy has revealed that only about 3% of the total electricity demand in Great Britain is presently supplied by CHP plants. 22 Combined systems can be put together for large ( ~ MW) or small ( ~ kW) power requirements, and can be chosen to run on any fuel source. The Enron Corporation has successfully completed its feasibility study for the construction of a 1725 MW gas-fired independent CHP station at ICI's Wilton Works, on Teesside. The station's generating capacity is the equivalent of 3% of the current UK total electricity supply, and its proposed natural-gas consumption would represent over 6% of the total gas market. This will be the largest independent power plant to be built in the UK and the largest CHP power station in the world. It is regarded as the most advanced of the major electricity-generating projects announced since the British Government's decision to privatise the electricity-supply industry. The start-up date for this station will be early in 1993. 23 In addition, the Corporation of London has given its approval for Citygen (a joint venture between British Gas plc and Utilicom) to proceed with plans for a CHP scheme to serve the City of London. The plant is expected to be completed in three phases: the first with a base-load of 20-30 MW in time for the 1991 winter heating season, with subsequent phases to bring the capacity up to some 90 MW, within approximately 3 years. Costs are expected to be around £20 million per phase, z4 Small-scale packaged CHP units having an electrical output of 20 kW to 1 MW have been available in the UK for several years. They now represent a

Electric-power generation in the UK

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tried and tested technology in many applications, with over 500 units already installed. Most of these packages are based on spark-ignition gas engines. However, due to the recent popularity of small and medium-sized gas turbines for a wide variety of applications, compact turbines below 73 kW e output have been employed as prime movers. 25 Moreover, Sterling engines, which would be approximately the same size as a domestic gas boiler or could be scaled up to 10-12 kW e for commercial applications, have also been used. 26 The Crowtree Leisure Centre in Sunderland has to save £20 000 per year on its energy bills and also reduce the rate of emission of polluting greenhouse gases. The unique system for achieving this uses two CHP units, producing in total 280kW e output. Each unit has its own on-board computer, which is linked by a standard British Telecom line to a central computer armed with an expert system to enable it to forecast its own maintenance n e e d s . 27 CONCLUSIONS

The immediate future At present (Sept., 1990), the issues of privatisation and environmental pollution are in a state of continuous change. The privatisation programme and electricity-supply regulations are being up-dated to accommodate the consequences of many political and financial complexities. Similarly, agreements on what needs to be done concerning environmental issues, particularly global warming, are still far from being reached. After privatisation, there will be a new generation of conventional gasfired combined-cycle plants, and combined heat and power (CHP) or cogeneration stations based on a variety of fuels, including refuse. These will gradually replace the oil and a large proportion of pulverised-fuel coal-fired stations; with the nuclear and renewable component increasing only slowly. There is the strong likelihood that in 8-10 years time, coal gasification/pressurised fluidised-bed combustion/combined cycle hybrids will also be replacing conventional pulverised-fuel stations. 28 Small-scale CHP units could soon be mass produced for the domestic and commercial (e.g. hotel) markets if capita] is found to manufacture newlydeveloped energy-generation systems with high efficiency, extremely clean exhaust fumes, low noise levels and minimal maintenance costs. These should, during the next decade, cut into the traditional markets of the Electricity Boards.

Long-term future The break-up of the country into regional suppliers of electricity is likely in

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s. G. Reeve, R. F. Babus'Haq, S. D. Probert

the long term ( < 30 years) to have two major effects: (i) local Energy Boards will be established and they will generate more and more of the electric power for their local consumers, and (ii) when opportunities present, these Boards will try to become suppliers of all forms of energy, e.g. of heat (via C H P systems), and even of water.

REFERENCES 1, Anon., Statistical Yearbook 1987/1988, Central Electricity Generating Board, Department of Information and Public Affairs, London, 1988. 2. Anon., Britain's Untapped Heat Source: a Missed Opportunity? Combined Heatand-Power Association, London, 1985. 3. Babus'Haq, R. F., Probert, S. D. & Shilston, M. J., The total energy approach: evolution of combined heat and power for district heating and/or cooling. Applied Energy, 25(2) (1986) 97-163. 4. Guild, A., Price increases signal the shape of things to come for less well off. The Guardian (27 March, 1990) 12. 5. Laughton, M. A., Renewable energy sources. The Watt Committee of Energy, Report No. 22, Elsevier Science Publishers Ltd, Barking, 1990. 6. Porter, D., Commentary from the Editor's office. Independent Power News, 11, (Sept. 1989) 3. 7. Taki, Y., Babus'Haq, R. F. & Probert, S. D., Combined heat and power as a contributory means of maintaining a green environment. Applied Energy (in press). 8. Eyre, N. J., Gaseous emissions due to electricity fuel cycles in the UK. Energy and Environment Paper No. 1, Energy Technology Support Unit, Oxon, 1990. 9. Boyle, S., Taylor, L. & Brown, I., Solving the Greenhouse Dilemma: A Strategy for the UK. Association for the Conservation of Energy, London, 1989. 10. Brown, P., UN group presses for nuclear power. The Guardian (2 July, 1990) 1. 11. Jackson, T., Clean machine with a dirty bottom. The Guardian (6 July, 1990) 27. 12. Warren, A., Something for nothing. The Guardian (6 July, 1990) 27. 13. Anon., CHPA Annual Review 1989 1990. Combined Heat and Power Association, London, 1990. 14. Rooney, P., Coal fired CHP schemes. Energy Management (Feb. 22, 1990) 26-7. 15. Seizer, H., Potential of Wind Energy in the European Community: an Assessment Stu@. D. Reidel Publishing Co., New York, for the CEC, 1986. 16. Anon., The case for more investment in plants for treatment and energy recovery from refuse. Energy World, 114 (1984) 5-6. 17. Abert, J. G., Municipal waste processing in Europe: a status report on selected materials and energy recovery projects. The World Bank, Washington DC, 1985. 18. Dagnall, S., Wastes can produce power. Energy Management (Feb. 22, 1990) 31 2. 19. Richards, K., Power generation from land-fill gas. Energy Management (Feb. 22, 1990) 25. 20. Mitchell, C. P., The potential of forest biomass as a source of energy in Britain and Europe. Int. J. Biometeorol., 27(3) (1983) 209-16.

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21. Anon., Industrial CHP in the UK seen reversing downward trend of the past 28 years. Cogeneration, 6(3) (1989) 13. 22. Brown, S., A winning combination for the new power generation, Process Engineering (Aug., 1990) 4(~1. 23. Anon., 1725 MW CHP scheme. Independent Power News, 13 (April, 1990) 9. 24. Anon., City-wide CHP scheme planned. Building Services, 12(9) (1990) 5. 25. Taki, Y., Babus'Haq, R. F., Elder, R. L. & Probert, S. D., Design and analysis of a compact gas turbine for a CHP system. Heat Recoveo' Systems & CHP, 11(2/3) (1991) 149-60. 26. Anon., Cheap mini power station production plans. Heating and Air Conditioning, 60(698) (1990) 6. 27. Anon., High-tech CHP saves even more. Energy Today, 13(7) (1990) 9. 28. Sanford, L., Future generations. Professional Engineering, 2(6) (1989) 30 2.