Renewable Energy Sources

Watt Committee: report number 22

M.A. Laughton

• Publisher: CRC Press
• Year: 1990
• ISBN:
  9781135380601
• Edition: 1
• Topic: Architecture
• Subtopic: Architecture Methods & Materials

Presents and analyses the sources of renewable energy, including advantages and disadvantages, projects implemented internationally, cost and environmental implications, and the benefits of system integration.

Part 1
INTRODUCTION TO THE REPORT

Section 1
Introduction and Summary

1.1 INTRODUCTION

This report by the Watt Committee concerns the current status of the technology and opportunities for the exploitation of renewable energy sources. Both technical and economic aspects are covered, primarily in relation to the existing pattern of demand and the organisation of energy supply in the United Kingdom.

As such the Report complements other recently published reports, particularly those by the International Energy Agency (Renewable Sources of Energy, OECD, Paris, March 1987), the UK Department of Energy (Renewable Energy in the UK: The Way Forward, Energy Paper Number 55, HMSO, London, June 1988) and the House of Lords Select Committee on the European Communities (Alternative Energy Sources: Report with Evidence, HL Paper 88, HMSO, London, June 1988). Although there are inevitably areas of overlap with these publications, nevertheless this Report provides an independent and integrated set of contributions from experts which provides fresh information, opinions and comparative analysis of this complex subject. The approach adopted has been mainly one of a general engineering viewpoint, stressing technology, economics and systems integration, but including also discussions of legal and environmental issues as appropriate.

1.2 BACKGROUND

During the period of work of the Committee’s Working Group the energy supply scene saw the drifting down of oil prices on the international markets along with growing expectations that such low prices will prevail until the end of the century. It was the steep oil price rises of the 1970s coupled with the realisation of undue oil and hence OPEC supply dependence which turned attention initially towards energy efficiency and also to the development of alternative sources. Subsequently, in the aftermath of the Chernobyl nuclear accident, safety, or rather the potential consequences of power plant failure, has become a matter of public concern. More recently, environmental questions related to the transformation of energy, especially the carbon dioxide-linked ‘greenhouse effect’ and the polluting effects of acid rain, have received growing public and political attention and thus are assuming greater importance in the planning and operation of energy supply systems.

Constraints imposed by such considerations are felt nowhere more so than in electrical power systems which constitute the main potential outlet for energy derived from renewable sources. Although some renewable resources can contribute energy effectively directly in the form of heat, it is through the medium of electrical energy that most contributions can be made.

Finally in this period the test discount rate has been changed from 5% to 8% for the public sector since the completion of the bulk of the work on the Report. In addition the decision was taken to privatise the electricity supply industry. It was considered appropriate not to treat privatisation aspects in the main body of the Report because the consequences are still in the future at the time of writing. On the other hand with such a major change to the electricity supply industry forthcoming the Working Group believe that some comment, albeit speculative, is appropriate and hence include a discussion in this Introduction.

1.3 STRUCTURE OF THE REPORT

Each renewable source of energy is considered in turn in separate sections, viz. tidal, wave, wind, small-scale hydro, geothermal, OTEC, solar thermal and photovoltaics, and biofuels. Three overarching sections follow on environmental considerations, the problems of integrating intermittent resources into a public electricity system and, finally, the economics of exploitation of renewable sources of energy. These last two sections are a particular feature of the Report and cover in considerable detail the analysis of both the novel planning and operational problems caused by the addition of large-scale and distributed intermittent sources to an electricity supply system and the appropriate methodology of economic appraisal.

With the study being focused on the United Kingdom, large-scale hydro was considered to be inappropriate, even though opportunities wider than those within the UK were considered for the other renewables.

1.3.1 The status of the respective technologies

A common theme is the technical virtuosity that is necessary both in power conversion and transmission and in the necessary civil engineering works in often hostile environments. Such advanced engineering needs are far from the Third World technological image often associated with this area of energy resource exploitation.

All technologies require further research, design and testing to a greater or lesser degree, but the emphasis in need is different from one technology to another. The potential exploitation of tidal power, small-scale hydro, ocean thermal energy conversion and biofuel processes involves mostly tried and tested technologies, whatever the severity of the engineering tasks, whereas some aspects of offshore wave and solar power are still searching for the most appropriate overall system and associated component ideas. Most areas have unanswered scientific questions, particularly concerning engineering materials, which need addressing before efficient designs can be realised; rigorous field testing of the emerging technologies is still largely a subject for the future.

Naturally with new engineering advances learning occurs only from experiences which inevitably include failures. From the evidence out of California, for example, it appears that only comparatively recently have turbines for onshore wind farms been successfully designed in appropriate sizes (less than 1 MW) which withstand the rigours imposed by the operating cycle of stresses. Much further research work remains to be done on the dynamics of cyclic stall, blade profiles, composite lightweight materials for the turbine blades, and integration with individual diesel sets in small power systems; however, some wind turbine designs have now been satisfactorily proven in three or more years’ commercial operation and, even though full-life fatigue testing remains, wind energy conversion may now be considered to be a rapidly maturing technology.

The feasibility of tidal power has also benefited from the efforts of industrial engineering design teams in the preparation of proposals for the exploitation of the Severn and Mersey estuaries. Here the engineering problems are well understood with relevant experience gained by manufacturers in other types of project. No significant new technology is required for its development and so specific designs could be realised immediately should these schemes be implemented.

Small-scale hydro power in the mini- and microrange have likewise seen design developments around well-developed technology and established manufacturing facilities. The greatest steps in innovative design have taken place in the application of microelectronics for control purposes, the use of off-the-shelf components and the imaginative exploitation of modern plastics and composites. Again, in this case if institutional barriers (as described later) could be removed, there are resources which could be immediately employed in addition to those already exploited.

With wave power, on the other hand, progress is still in a comparatively early stage, much of it of an investigative kind in university laboratories. One promising technology relates to developments of shoreline wave schemes, which exploit the amplification of wave effects in natural or artificial gullies, and are now showing genuine promise for their use in remote coastal communities with smallscale isolated electricity supplies.

Meanwhile for offshore wave power there are no agreed designs. In view of the size of the resource the engineering challenge will always retain a high profile, as is evidenced by the some 300 schemes proposed. Here the problems appear to be formidable with the range of energies involved, and the scope for university research beyond the initial stages is limited. Success will only be achieved by the greater involvement of engineering companies with offshore design and construction experience in order that ideas may be taken through to the prototype demonstration stage. Such a pattern of activity has happened in the development of wind power which, as a result, now stands at the threshold of commercial success.

Geothermal energy R & D also are activities demanding high levels of financial support, although here much of the expenditure is in meeting the costs of drilling. The Hot Dry Rock technology is still under development and further knowledge needs to be gained of many aspects of hydrofracturing in deep rock structures.

Finally, for the UK, there are the technologies concerned with biomass and solar energy. Five biomass technologies involving the processing and use of dry wastes from domestic and industrial sources, straw and forestry wastes or the digestion of wet wastes and the recovery of methane in prefabricated digesters or in landfill sites, are already demonstrably successful and in commercial use. The technologies allow the use of biofuels in larger-scale electricity generating plants without difficulty should the commercial vision of their potential allow. The Working Group noted that, with regard to the development of equipment generally in this field, the record of the United Kingdom does not compare favourably with other developed countries.

Solar thermal technologies and photovoltaics have greater potential applications in large-scale electrical power generation only in regions of the world with high solar radiation levels. In most other parts increased use would be through the more widespread adoption of active systems for heat and hot water, through passive heating systems vis-à-vis buildings, to the professional low power markets of telecommunications, cathodic protection, navigation, and a range of consumer products. Normal commercial interests ensure that the required research and development processes are being undertaken with regard to photovoltaic technology and its applications, particularly in the consumer product markets. This Report draws attention, however, to the need for the wider-scale technology transfer of solar thermal technology in the case of building design and codes of construction. Again in these respects this technology for buildings is available, but apart from water heating in sunnier countries, the applications on a significant scale in northern Europe, including the United Kingdom, are as yet comparatively limited.

The section on ocean thermal energy conversion (OTEC) is included for the sake of completeness vis-à-vis worldwide technologies. At present OTEC is demonstrable only on a very small scale, but it is also centred around well-understood plant engineering so is technically achievable without great difficulty. Further investigations need to be carried out, however, on specific cold water pipe, heat exchanger, mooring and power transmission problems before realisation. Although having no relevance to the United Kingdom’s domestic energy supply needs, the technology may well make a significant contribution in other warmer, oceanic areas of the world for offshore electric power generation and manufacturing facilities.

1.3.2 Prospects for the use of renewables: extent and economics of the exploitable resources

The extent of any exploitable resource depends, of course, on the price that the consumer is willing to pay and so any discussion of the resource base cannot be divorced from assumptions concerning price levels. A characteristic of renewable sources, as of other sources of energy, is that there is a technical resource base and a smaller economic base, which increases in size towards the technical base as the price paid for energy rises. The summary here will be confined to the renewable resources available within the United Kingdom with costs quoted in 1987 terms using a 5% test discount rate unless otherwise stated. It is convenient to measure potential contributions to the energy supply mainly in terms of the UK demand for electrical power and energy, which in 1987 were 52·5 GW maximum demand and 256 TWh respectively. In addition to giving views of costs in respective sections, the Report gives a picture of electricity generation costs based on an independent survey and an analysis of the results which are given in full in Section 13.

United Kingdom tidal power is estimated to have an economic resource of about 45 TWh/year, or approximately 17% of annual demand, which could be exploited at 6 p/kWh or less (1984 prices). Of this by far the largest contribution would come from the Severn Barrage (seaward of Weston to Cardiff) which would generate an average of 17 TWh/year over a large number of years. The design life of the project would be 120 years, but with reasonable maintenance this could be considerably extended. The total installed generating capacity from the 216 bulb set turbine generators would be 8640 MW and the capital cost is estimated at £8260 m in 1988 money with an additional cost of £850 m required for grid strengthening and stability. The cost of electricity at the barrage boundary would range from 1·7 p/kWh at 2% discount rate to 7·2 p/kWh at 10% discount rate. (The above figures are taken from the 1989 report The Severn Barrage Project: General Report, Energy Paper Number 57, published by HMSO.)

Such levels of expenditure would make the project difficult to promote wholly within the private sector. It seems, therefore, that this exceptional tidal scheme has to be regarded as a public sector project, the more so because of the widespread regional development consequences.

The same can be argued with respect to the smaller Mersey Barrage scheme which would have an estimated capital cost of £500 million and an output of 1·3 TWh/year at 3·5 p/kWh. Again the regional benefits would be considerable and so to judge such projects on the same commercial terms as other small private generation schemes is not wholly satisfactory.

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Table of contents

• COVER PAGE
• TITLE PAGE
• COPYRIGHT PAGE
• FOREWORD
• PART 1: INTRODUCTION TO THE REPORT
• PART 2: TYPES OF RENEWABLE ENERGY SOURCE
• PART 3: SYSTEM CONSIDERATIONS
• THE WATT COMMITTEE ON ENERGY: OBJECTIVES, HISTORICAL BACKGROUND AND CURRENT PROGRAMME
• MEMBER INSTITUTIONS OF THE WATT COMMITTEE ON ENERGY
• WATT COMMITTEE REPORTS