Boyle G. (Ed.) Renewable Electricity and the Grid: The Challenge Of Variability

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Renewable Electricity and the Grid

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Renewable Electricity and the Grid

The Challenge of Variability

Edited by Godfrey Boyle

London • Sterling, VA

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First published by Earthscan in the UK and USA in 2007

ISBN-13: 978-1-84407-418-1

Typeset by FiSH Books, Enfield, Middx.

Printed and bound in the UK by Cromwell Press, Trowbridge

Cover design by Nick Shah

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A catalogue record for this book is available from the British Library

Library of Congress Cataloging-in-Publication Data

Renewable electricity and the grid: the challenge of variability/Edited by

Godfrey Boyle.

p. cm.

Includes index.

ISBN-13: 978-1-84407-418-1 (hardback)

ISBN-10: 84407-418-8 (hardback)

1. Renewable energy sources. 2. Electric power production. I. Boyle,

Godfrey.

TJ808R417 2007

333. 793’2–dc22 2007016031

This publication is printed on FSC-certified and

totally chlorine-free paper. FSC (the Forest Steward-

ship Council) is an international network to promote

responsible management of the world’s forests.

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Contents

List of Figures and Tables ix

List of Contributors xiv

Preface xix

Acknowledgements xxi

List of Acronyms and Abbreviations xxii

1 Variable Renewables and the Grid: An Overview 1

Michael Laughton

Introduction 1

Renewable energy source variability 2

Grid operational requirements 11

Base-load capacity displacement with increasing wind

penetration 14

Conclusions 27

2 Wind Power on the Grid 31

David Milborrow

Introduction 31

Electricity system operation 31

Wind characteristics 36

Managing a network with wind 38

Capacity credits 41

Total extra costs of wind energy 45

Wind energy penetration levels above 20 per cent 47

The influence of national and regional differences 49

Conclusions 51

3 Renewable Resource Characteristics and Network Integration 55

Graham Sinden

Introduction 55

Renewable electricity generation in the UK 55

Characteristics 58

Renewable electricity supply and demand patterns 63

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The role of wind power in providing capacity on

electricity networks 67

Conclusions 71

4 The UK Energy Research Centre Review of the Costs

and Impacts of Intermittency 73

Robert Gross, Philip Heptonstall, Matthew Leach, Jim Skea,

Dennis Anderson and Tim Green

Introduction 73

Power system reliability and operation 74

Misconceptions and sources of controversy 77

Quantitative findings on impacts and costs 79

Summary of findings and conclusions 86

5 Wind Power Forecasting 95

Bernhard Lange, Kurt Rohrig, Florian Schlögl, Ümit Cali

and Rene Jursa

Introduction 95

Applications of wind power forecasting 97

Steps in a forecasting system 97

Numerical weather prediction 98

Different approaches to the power output forecast 99

Forecast horizon 101

Regional upscaling 103

Smoothing effect 105

Forecast accuracy 107

Example: The Wind Power Management System (WPMS) 110

‘Learning curve’ of forecasting accuracy 112

Examples of current research 113

Future challenges 117

6 Flexibility of Fossil Fuel Plant in a Renewable Energy Scenario:

Possible Implications for the UK 121

Fred Starr

Introduction 121

The UK power plant system of today 123

Advanced generating plants, energy savings and the issue

of climate change 124

Design and operation of coal- and natural gas-powered

steam plants 125

Pseudo-intermittency with today’s plants 130

vi Renewable Electricity and the Grid

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Effects on plant components and reliability 132

Intermittency and power plants of the future 136

Conclusions 140

7 The Potential Contribution of Emergency Diesel Standby

Generators in Dealing with the Variability of Renewable

Energy Sources 143

David Andrews

Introduction: Wessex Water 143

The National Grid Transco Frequency Service 143

The National Grid Transco Reserve Service 144

Reserve and standby generating capacity on the UK National Grid 144

‘Triads’: A revenue-earning opportunity 146

Other benefits: Testing diesels off load 147

8 Demand Flexibility, Micro-Combined Heat and Power and the

‘Informated’ Grid 151

Bob Everett

Introduction 151

What is needed 152

What is on offer 153

Metering and the future 155

9 A Renewable Electricity System for the UK 157

Mark Barrett

Introduction 157

Scenario context 159

A sustainable electricity system 162

System integration and optimization 167

Conclusions 178

10 Reliable Power, Wind Variability and Offshore Grids in Europe 181

Brian Hurley, Paul Hughes and Gregor Giebel

Where are the wind resources? 181

What happens when the wind does not blow? 183

The reliability of dispersed offshore wind power 187

Effect of wind farm power output forecasting 190

Delivered cost estimates for new grid and wind farms 190

Results for Europe 193

A Project for Europe: European-wide Supergrid 194

Conclusions 198

Renewable Electricity and the Grid vii

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11 Planning for Variability in the Longer Term:

The Challenge of a Truly Sustainable Energy System 201

David Infield and Simon Watson

Introduction 201

Renewable source-dominated energy supply systems 202

Energy storage and demand-side management 204

Conclusions and further research 209

Index 211

viii Renewable Electricity and the Grid

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List of Figures and Tables

IGURES

1.1 Tidal cycle and electricity generation periods for a barrage with

additional pumping at high tide 3

1.2 Typical annual variation in wave power levels 4

1.3 Wind turbine output characteristics 5

1.4 Influence of storm conditions on spot electricity prices in

Danish kroners per megawatt hour in West Denmark during

the first week of January 2005 6

1.5 Large fluctuations in wind output in the E.ON Netz network in

Germany 7

1.6 Example of longer-term changes in average annual wind speeds 8

1.7 Wind data for mainland Britain on Wednesday, 28 December 2005,

at 18:00 GMT: Light winds with cold anticyclone weather 10

1.8 Daily load variation on the UK National Grid system showing

maximum and minimum demand days from 1 July 2005 to

30 June 2006 12

1.9 National Grid demand and generation capacity available for the

12 months from 1 July 2005, with reference to the weekly system

peak load demands (SPLDs) 15

1.10 Percentage generation availability margin relative to demand

from 1 July 2005 15

1.11 Relationship between percentage of Great Britain peak demand

and overall percentage hourly wind plant load factor 16

1.12 Probability distribution of total Great Britain wind power

generation from 7600MW of dispersed wind turbines 17

1.13 Probability distributions of total generation capacity for

secure supply 19

1.14 Wind capacity credit in Great Britain relative to the National

Grid security of supply standards 21

1.15 Graphs of zero backup capacity separating the regions where

extra backup capacity is not required (left) and backup capacity

is required (right)25

1.16 Wind generation (TWh) and corresponding wind capacity for

different load factors 25

1.17 Relationship between backup capacity and installed wind

capacity for different ratios of wind load factor to thermal

plant load factor 26

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