Planning and Installing Solar Thermal Systems A guide for installers, architects and engineers First published by James & James (Science Publishers) Ltd in the UK and USA in 2005 Reprinted 2006,2007 0T he German Solar Energy Society (DGS LV Berlin BRB), Ecofys 2005 All rights reserved. No part of this book may be reproduced in any form or by any means electronic or mechanical, including photocopying, recording or by any information storage and retrieval system without permission in writing from the copyright holders and the publisher. ISBN-13: 978-1-84407-125-8 Typeset by Saxon Graphics Ltd, Derby Printed and bound in Croatia by Zrinski Cover design by Paul Cooper Design For a full list of publications please contact James & James / Earthscan 8-12 Camden High Street London, NW1 OJH, UK Tel: +44 (0)20 7387 8558 Fax: +44 (0)20 7387 8998 Email: [email protected] Web: www.earthscan.co.uk A catalogue record for this book is available from the British Library. Library of Congress Cataloging-in-Publication Data Planning and installing solar thermal systems : a guide for installers, architects, and engineers /the German Solar Energy Society (DGS). p. cm. Includes bibliographical references and index. ISBN 1-84407-125-1 (pbk.) 1. Solar heating--Installation. 2. Solar water heaters--Installation.3 . Solar thermal energy. I. Deutsche Gesellschaft fur Sonnenenergie. TH7413.P534 2005 697' .78--dc22 2004006812 Printed on elemental chlorine free paper This guide has been prepared as part of the GREENPro project co-funded by the European Commission. Also available in the series: Planning and Installing Bioenergy Systems: A Guide for Installers, Architects and Engineers 978-1-84407-132-6 Planning and Installing Photovoltaic Systems: A Guide for Installers, Architects and Engineers 978-1-84407-131-9 Neither the authors nor the publisher make any warranty or representation, expressed or implied, with respect to the information contained in this publication, or assume any liability with respect to the use of, or damages resulting from, this information. Cont ents Foreword xi CHAPTER 1 :S olar radiation and arguments for its use 1 1.1 Solar radiation 1 1.1.1 Solar energy 1 1.1.2 Astronomical and meteorological bases 1 1.1.3 Influence of orientation and tilt angle 8 1.1.4 Collection of dust and need for cleaning 10 1.2 The finiteness of energy resources 11 1.3 Climate change and its consequences 13 1.4 Good arguments for solar systems 14 CHAPTER 2: Components of solar thermal systems 15 2.1 How does a solar thermal system work? 15 2.2 Collectors 16 2.2.1 Unglazed collectors 19 2.2.2 Glazed flat-plate collectors 19 2.2.3 Vacuum collectors 25 2.2.4 Collector accessories 29 2.2.5 Collector characteristic curves and applications 29 2.2.6 Stagnation temperature 30 2.3 Heat stores 30 2.3.1 Storage materials 30 2.3.2 Domestic hot water stores 31 2.3.3 Buffer store 34 2.3.4 Combination stores and innovative store designs 34 2.3.5 The thermostatic mixing valve 34 2.3.6 Connection of washing machines and dishwashers 35 2.3.7 Legionella contamination 35 2.4 Solar circuit 36 2.4.1 Pipelines 36 2.4.2 Solar liquid 37 2.4.3 Solar pumps 39 2.4.4 Solar heat exchanger (heat transfer unit) 39 2.4.5 Return-flow prevention 41 2.4.6 Rapid air bleeders 41 2.4.7 Flowmeters 42 2.4.8 Safety devices in the solar circuit 43 2.4.9 Solar station 44 2.5 Controller 44 2.5.1 Control principles for temperature difference control 44 2.5.2 Digital controller with special functions 45 2.5.3 Temperature sensors 46 2.5.4 Overheating protection 48 CHAPTER 3: Systems for single-family houses 49 3.1 Introduction 49 3.2 Systems for chargingldischarging the store 50 3.2.1 Charging by means of solar energy 50 vi PLANNING AND INSTAUlNG SOLAR THERMAL WSTEMS A guide for installers, architects and engineers 3.2.2 Charging by means of auxiliary heating 51 3.2.3 Store discharge 52 3.3 Systems for heating domestic water 52 3.4 Systems for heating domestic water and space heating 54 3.4.1 Combined store system (store-in-store system) 54 3.4.2 System with buffer store, internal heat exchanger for heat removal and downpipe 54 3.4.3 Stratified store with hot water heating in once-through flow and heating support 55 3.4.4 Twin store system 55 3.5 Planning and dimensioning 55 3.5.1 Important features for preparing the quotation 55 3.5.2 The dimensioning of systems for domestic water heating 58 3.5.3 Dimensioning of systems for heating domestic water and heating support (central European conditions) 70 3.6 Costs and yields 72 3.6.1 Prices and performance 72 3.6.2 Normalised solar heat costs 75 CHAPTER 4: Installation, commissioning, maintenance and servicing 77 4.1 A brief study of roofing and materials 77 4.1.1 The purpose of the roof 77 4.1.2 Types of roof 77 4.1.3 The components of the roof 78 4.1.4 Pitched roofs 83 4.1.5 Roof installations and mountings 83 4.1.6 Flat roofs 83 4.1.7 Materials 83 4.2 Installation methods and safety 87 4.2.1 UK safety regulations 87 4.2.2 UK personal access and working at heights 87 4.2.3 Working equipment 88 4.2.4 Transport techniques 89 4.2.5 Installation techniques 90 4.3 Installation 91 4.3.1 Delivery of material 91 4.3.2 Setting up the site, preparatory work 91 4.3.3 Collector installation 91 4.3.4 Installation of the solar circuit 101 4.3.5 Store installation 104 4.3.6 Installation of fittings 107 4.3.7 Installation of sensors and controllers 109 4.4 Starting up, maintenance and servicing 110 4.4.1 Flushing out the solar circuit 110 4.4.2 Leak testing 110 4.4.3 Filling with solar liquid 111 4.4.4 Setting the pump and controller 111 4.4.5 Maintenance 111 4.4.6 Detecting and rectifying faults 112 4.5 Information sources for specific countries 116 4.5.1 USA 116 4.5.2 Australia 116 4.5.3 Canada 117 CONTENTS VII CHAPTER 5: large-scale systems 119 5.1 The fundamentals of designing the system size 119 5.1.1 Possible application areas 119 5.1.2 Initial data required for planning the solar system 119 5.1.3 System planning and design 120 5.2 Systems 123 5.2.1 Systems with domestic water store(s) 123 5.2.2 Systems with thermal buffer stores 124 5.2.3 Integration of circulation systems 126 5.3 Control of the systems 126 5.3.1 Collector circuitistorage charging circuit 127 5.3.2 Buffer tank circuit discharging 131 5.4 Heat exchangers 132 5.4.1 Design types 132 5.4.2 Collector circuit heat exchangers 134 5.4.3 Buffer tank discharge circuit heat exchangers 135 5.5 Safety technology 138 5.5.1 Collector field 138 5.5.2 Collector circuit 139 5.5.3 Buffer store circuit 140 5.5.4 Expansion vessels 141 5.5.5 Fittings on the domestic water line 141 5.6 Economic considerations 142 5.6.1 Annuity method 142 5.6.2 Types of costs for solar energy systems 143 5.7 Solar contracting 144 5.8 Solar district heating 147 5.8.1 Solar energy systems with short-term heat storage 148 5.8.2 Solar systems with long-term heat storage 148 5.8.3 Guide values for the design of solar district heating systems 149 5.8.4 Components of solar district heating systems 149 5.8.5 Practical experience 151 CHAPTER 6: Solar concentrating systems 153 6.1 Concentration of solar radiation 153 6.2 Concentrating systems providing process heat 154 6.3 Concentrating solar thermal systems for electricity generation 159 6.3.1 Parabolic trough plants 159 6.3.2 Solar tower plants 162 6.3.3 DishiStirling systems 164 6.3.4 Economics and outlook 165 CHAPTER 7: Solar heating of open-air swimming pools 167 7.1 Introduction 167 7.2 Components 167 7.2.1 Absorbers 167 7.2.2 Piping and header pipes 171 7.2.3 Materials 172 7.2.4 Pumps, heat exchangers and other components 172 7.2.5 Controllers 174 7.2.6 Covering of the swimming pool 175 7.3 Systems 176 7.3.1 Solar private open-air pool heating 176 viii PLANNING AND INSTALLING SOUR THERMAL SYmMS A guide for installers, archltects and engineers 7.3.2 Solar heating of public open-air swimming pools 177 7.3.3 Combined solar domestic water heating, open-air pool heating and room heating support 180 7.4 Planning and dimensioning 180 7.4.1 Fundamental considerations 180 7.4.2 Approximation formulae for establishing absorber surface area, volumetric flow and pressure loss 181 7.4.3 Computer-aided system dimensioning 183 7.5 Installation 184 7.5.1 Absorbers 184 7.5.2 Pipeline installation 187 7.6 Operation and maintenance 188 7.7 Costs and yields 189 7.8 Examples 189 7.8.1 Solar heating of a private swimming pool 189 7.8.2 Solar heating of a municipal open-air pool complex 190 CHAPTER 8: Solar air systems 193 8.1 Introduction 193 8.2 Components 194 8.2.1 Collector types 194 8.2.2 Fans, blowers 197 8.2.3 Piping 198 8.2.4 Heat exchangers, heat recovery units 198 8.2.5 Control 199 8.3 Systems 199 8.3.1 Air collector systems in housing construction 199 8.3.2 Factories, halls and office buildings 204 8.4 Planning and dimensioning 205 8.4.1 Fundamental considerations 205 8.4.2 Calculation of required flow rate, required collector surface area and connections of collectors 205 8.4.3 Calculation of fan power 206 8.5 Installation 206 8.5.1 Collector installation 206 8.5.2 Installation of pipelines 209 8.5.3 Positioning of the fan 209 8.6 Costs and yields 209 8.7 Examples 209 8.7.1 Domestic building, Potsdam, Germany 209 8.7.2 Solarwall on General Motors building in Ontario 211 CHAPTER 9: Solar cooling 213 9.1 Introduction 213 9.2 Theoretical bases 215 9.2.1 Overview of thermally driven cooling processes 215 9.2.2 Absorption cooling 215 9.2.3 Adsorption cooling 216 9.2.4 Desiccant cooling system 217 9.3 Integrated planning of solar coolinglair-conditionings ystems 219 9.4 System technology 222 9.4.1 Autonomous solar-powered systems versus solar-assisted systems 222 9.4.2 Which collector technology for which cooling technology? 223 9.4.3 Circuit variants 224 CONTENTS ix 9.5 System design 228 9.5.1 General procedure when designing systems 229 9.5.2 System design using empirical values 230 9.5.3 System design according to the peak load 230 9.5.4 Design of autonomous solar-powered systems 23 1 9.5.5 System design according to primary energy saving 23 1 9.6 More information 233 CHAPTER 10: Simulation programs for solar thermal systems 235 10.1 Introduction 235 10.2 Evaluation of simulation results 235 10.3 Simulation with shading 236 10.4 Market survey, classification and selection of simulation programs 236 10.5 Brief description of simulation programs 237 10.5.1 Calculation programs 237 10.5.2 Time step analysis programs 237 10.5.3 Simulation systems 241 10.5.4 Tools and help programs 243 CHAPTER 11 :M arketing and promotion 245 11.1 The fundamentals of solar marketing 245 11.1.1 Customer orientation: the central theme 245 11.1.2 The iceberg principle 245 11.1.3 The ‘pull’ concept 246 11.2 More success through systematic marketing 246 11.2.1 In the beginning is the benefit 246 11.2.2 The four pillars of the marketing concept 247 11.2.3 The range of marketing options 251 11.2.4 To the goal in six steps 261 11.3 The Soltherm Europe Initiative: European network of solar thermal marketing campaigns 265 11.3.1 Publications 265 11.3.2 Partnership 266 11.3.3 Campaigns and market activities 266 11.3.4 Co-operation 267 11.4 A good sales discussion can be enjoyable 267 11.4.1 What does ‘successful selling’ mean? 267 11.4.2 Build a bridge 268 11.4.3 Establish need 269 11.4.4 Offer a solution 271 11.4.5 Achieve a result 271 11.5 Subsidies 274 11.5.1 General information on financial support 274 11.5.2 Sources of information in the UK 274 11.5.3 Sources of information in the USA 276 11.5.4 Sources of information in Canada 277 11.5.5 EU sources 277 APPENDIX A: Glossary 279 APPENDIX B: Relevant UK solar regulations and technical standards 285 B.l General construction regulations 285 B.2 General construction standards 285 x PLANNING AND INSTALLING SOLAR THERMAL SYSTEMS A guide for installers, architects and engineers B.3 Solar standards 285 B.4 Roof standards 285 B.4.1 Acronyms for roof standards 286 B.5 Working on site, height and lifting regulations 286 APPENDIX C: Nomenclature 287 c.1 Radiation 287 c.2 Heat 287 c.3 Thermal losses 287 c.4 Temperature 287 c.5 Efficiency 287 C.6 Pressure 288 c.7 Material-specific variables 288 C.8 Volume, volumetric flow rate and flow speed 288 c.9 Angles 288 c.10 Surfaces and lengths 288 c.11 System variables 289 c.12 Financing 289 C.13 Constants 289 References and further information 291 Index 293 1 1 Solar radiation and arguments - for its use 1.1 Solar radiation 1.1.1 Solar energy The most important supplier of energy for the earth is the sun. The whole of life depends on the sun’s energy. It is the starting point for the chemical and biological processes on our planet. At the same time it is the most environmentally friendly form of all energies, it can be used in many ways, and it is suitable for all social systems. In the core of the sun a fusion process takes place in which pairs of hydrogen nuclei are fused into helium nuclei. The energy thus released is radiated into space in the form of electromagnetic radiation. As the sun is 143 million km from the earth, it radiates only a tiny fraction of its energy to the earth. In spite of this, the sun offers more energy in a quarter of an hour than the human race uses in a whole year. The age of the sun is estimated by astrophysicists to be about 5 billion years. With a total life expectation of 10 billion years the sun will be available as an energy source for another 5 billion years. Hence from our human perspective the sun offers an unlimited life. Figure 1.1. The sun: basis of all life on earth 1.1.2 Astronomical and meteorological bases On the outer edge of the earth’s atmosphere the irradiated power of the sun is virtually constant. This irradiated power or radiation intensity falling on an area of one square metre is described as the solar constant. This constant is subject to small variations influenced both by changes in the sun’s activity (sunspots) and by differences in the distance between the earth and the sun. These irregularities are mostly found in the ultraviolet range: rhey are less than 5%, and hence not significant in application of the solar constant for solar technology. The average value of the solar constant is given as I,, = 1.367 W/m2 (watts per square metre). Even based on the astronomical facts alone, the amount of solar energy available on the earth is very variable. It depends not only on the geographical latitude, but also on the time of day and year at a given location. Because of the inclination of the 2 PLANNING AND INSTALLING SOLAR THERMAL SYSTEMS A guide for installers, architects and engineers IRRADIATED POWER, IRRADIANCE, HEAT QUANTITY When we say that the sun has an irradiance, G, of for example 1000 W/m2, what is meant here is the capability of radiating a given irradiated power, @ (1000 W), onto a receiving surface of 1 m2. The watt is the unit in which power can be measured. If this power is referred, as in this case, to a unit area, then it is called the irradiance. 1 kW (kilowatt) = 103 W (1000 watts) 1 MW (megawatt) loe W (1 million watts) lo3 kW I 1 GW (gigawatt) lo9W (1t housand million watts) loe kW I 1 TW (terawatt) loi2 W (1 million million watts) = loQk W When the sun shines with this power of 1000 W for 1 hour it has performed 1 kilowatt-hour of work (1 kWh) (Work = Power x Time). If this energy were converted completely into heat, a heat quantity of 1 kWh would be produced. Irradiated power, -$ (W) Irradiance, G (W/mz) Heat quantity, O(Wh, kWh) Figure 1.2. The sun’s path at different times of the year at central European latitude (London, Berlin) earth’s axis, the days in summer are longer than those in winter, and the sun reaches higher solar altitudes in the summer than in the winter period (Figure 1.2). Figure 1.3 shows the sequence over a day of the irradiation in London on a horizontal receiving surface of 1 m2 for four selected cloudless days over the year. It is clear from the graph that the supply of solar radiation, even without the influence of the weather or clouds, varies by a factor of about 10 between summer and winter in London. At lower latitudes this effect decreases in strength, but at higher latitudes it can be even more pronounced. In the southern hemisphere the winter has the highest irradiations, as shown in Figure 1.4, which shows the sequence over a day of the irradiation in Sydney on a horizontal receiving surface of 1 m2 on three average days over the year. Even when the sky is clear and cloudless part of the sun’s radiation comes from other directions and not just directly from the sun. This proportion of the radiation, which reaches the eye of the observer through the scattering of air molecules and dust particles, is known as diffuse radiation, GdifP. art of this is also due to radiation reflected at the earth’s surface. The radiation from the sun that meets the earth without any change in direction is called direct radiation, GdirT. he sum of direct and diffuse radiation is known as global solar irradiance, GG (Figure 1.5). GG= Gdir + Gdif Unless nothing else is given, this always refers to the irradiation onto a horizontal receiving surface.’