Solar Thermal Conversion. Active Solar Systems

545 Pages·2011·72.789 MB·English

by  Petros J. Axaopoulos (ed.)

EURONETRES
European Network on Education and Training
in Renewable Energy Sources
United Nations ·
Educational, Scientific and ·
SIMMETRIA PUBLICATIONS Cultural Organization .
EURONETRES
European Network on Education and Training
in Renewable Energy Sources
SOLAR THERMAL
CONVERSION
Active solar systems
Editor
Petros J. Axaopoulos
Wi th the support of
Venice Office
United Nations .
SIMMETRIA PUBLICATIONS Educational, Scientific and *
Cultural Organization ♦
ATHENS 2011
Central disposal
SIMMETRIA PUBLICATIONS
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e-mail: [email protected]
All Rights Reserved
Copyright: © 2011, Petros J. Axaopoulos
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reproduced or utilized in any form or by any means, electronic or
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storage and retrieval system, without written permission from the copyright
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The authors are responsible for the choice and the presentation of the facts
contained in this publication and for the opinions expressed therein, which
are not necessarily those of UNESCO and do not commit the Organization.
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List of contributors
Prof. Petros J. Axaopoulos
Energy Technology Department
Technological Educational Institute of Athens
Athens - Greece
Email: [email protected]
Prof. Viorel Badescu
Candida Oancea Institute
Polytechnic University of Bucharest
Spl. Independentei 313,
Bucharest 060042, Romania
Email: [email protected]
Prof. Milorad Bojlg
Faculty of Mechanical Engineering at Kragujevac
University of Kragu)evac
Sestre Janjic 6
34000 Kragujevac, Serbia
Email: [email protected]
Asst. Prof. Yannis G. Caourls
Dept, of Mechanical Engineering & Aeronautics
University of Patras
26500 (Rio) Patras, Greece
Email: [email protected]
Assoc. Prof. John Gelegenis
Energy Technology Department
Technological Educational Institute of Athens
Athens - Greece
Email: [email protected]
Dr. Myrsinl Giannouli
Senior Researcher
Solar Energy Laboratory
Physics Department, University of Patras
GR-26500 Patras, Greece
Email: [email protected]
4 SOLAR THERMAL CONVERSION - ACTIVE SOLAR SYSTEMS
Dr. Paul Gravila
West University of Timisoara
Department of Physics
Timisoara - Romania
Email: [email protected]
Dr. Soteris Kalogirou
Cyprus University of Technology
Department of Mechanical Engineering and Materials Sciences and Engineering
P.O. Box 50329
3603 Limassol - Cyprus
Email: [email protected]
Dr. Marius Paulescu
West University of Timisoara
Department of Physics
Timisoara - Romania
Email: [email protected]
Prof. Panayotis T. Tsilingiris
Energy Technology Department
Technological Educational Institute of Athens
Athens - Greece
Email: [email protected]
Prof. Panayiotis Yianoulis
Director of the Solar Energy Laboratory
Physics Department
University of Patras, GR-26500 Patras, Greece
Email: [email protected]
CONTENTS
Preface ................................................................................................................
1. Introduction
Petros l Axaopoulos
Bibliography ............................................................................................ · 18
2. The sun and its radiation
Petros l Axaopoulos
2.1 The sun ............................................................................................ 1*>
2.2 Extraterrestrial solar radiation and atmospheric effects ............. 23
2.3 Components of solar radiation ........................................................ 26
2.4 European distribution of solar irradiation ................................... 31
2.5 The measurement of solar radiation ............................................ 33
2.5.1 Pyranometer ....................................................................... 33
2.5.2 Pyrheliometer .................................................................... 36
2.5.3 Sunshine recorder ........................................... 37
References ............................................................................................... 38
Additional reading .......................................................................... 40
3. Basic principles of solar geometry
Petros J, Axaopoulos
3.1 The earth’s rotation ....................................................................... 43
3.2 Longitude and latitude ................................................................... 46
3.3 Basic solar geometry angles ......................................................... 47
3.3.1 Determination of solar angles ............................................. 51
3.4 Solar incidence angle ..................................................................... 56
3.5 Solar time ..................................................................................... 61
References ................................................................................................. 63
Additional reading .................................................................... 64
6 SOLAR THERMAL CONVERSION - ACTIVE SOLAR SYSTEMS
4. Heat transfer topics
Milorad Bojic
4.1 Conduction .......................................................................................... 65
4.2 Convection .......................................................................................... 66
4.3 Radiation ............................................................................................ 66
4.4 Combined heat-transfer .................................................................... 68
4.5 Heat exchangers ................................................................................ 73
4.6 Conclusion .......................................................................................... 79
References .................................................................................................... 79
5. Solar radiation incident on horizontal and tilted surfaces
at ground level
Viorel Badescu
5.1 Model accuracy ................................................................................ 82
5.2 Solar radiation on horizontal surfaces at ground level .............. 83
5.2.1 Models to evaluate solar irradiance values on clear sky days 85
5.2.1.1 Very simple clear sky solar irradiance models 85
5.2.1.2 Simple clear sky solar irradiance models ......... 87
5.2.2 Computation of hourly average solar irradiance ............ 92
5.2.2.1 Very simple cloudy sky models to compute hourly
average solar irradiance ...................................... 92
5.2.2.2 Simple cloudy sky models to compute hourly ave­
rage solar irradiance ....................... 93
5.2.3 Computation of daily average solar irradiation .............. 97
5.2.3.1 Computation by integration from solar irradiance
data ........................................................................ 97
5.2.3.2 Relationships to evaluate daily diffuse and beam
irradiation .............................................................. 99
5.2.4 Models to evaluate monthly averaged irradiation values 101
5.2.4.1 Relationships for global irradiation based on sun­
shine data .............................................................. 101
5.2.4.2 Relationships for global irradiation based on point
cloudiness data .................................................... 103
5.2.4.3 Relationships for diffuse and beam irradiation 104
5.3 Solar radiation on arbitrary tilted and oriented surfaces ............ 105
5.3.1 Solar irradiances on tilted surfaces .................................... 105
Contents 7
5.3.2 Daily solar irradiation on tilted surfaces .................. 109
5.3.2.1 Daily optimum tilt and orientation angles ___ 112
5.3.3 Monthly averages of daily solar irradiation on tilted surfaces 113
5.3.3.1 Monthly and seasonal optimum tilt and orientain
angles ................................................................. 116
5.4 Recommendations about computing solar radiation on horizontal
and tilted surfaces ........................................................................ 118
References .............................................................................................. 119
Glossary .................................................................................................. 121
6. Optical characteristics of materials
Marius Pauiescu and Paul Gravila
Introduction .................................................... 123
6.1 Optics summary ............................................................................ 124
6.1.1 Reflectance - transmittance - absorptance ..................... 124
6.1.2 Transmittance - absorptance product ............................. 138
6.1.3 Total emitance, absorptance and transmittance .............. 141
6.2 Transparent cover platem aterials ................................................. 144
6.3 Opaque collector plate surfaces ................................................ 146
Summary ............................................................... 149
References ..................................................................... 149
7. Solar collectors
Soteris A. Kaloglrou
7.1 Flat plate collectors (FPC) ............................................................ 152
7.1.1 Flat - plate collector components ................................... 154
7.1.1.1 Cover plate ....................................................... 154
7.1.1.2 Collector absorbing plates ................................... 155
7.1.2 Liquid heating flat-plate collectors ................................ 158
7.1.3 Air heating flat-plate collectors — ............................. 160
7.1.4 Thermal analysis for a Hat-plate collector ............... |61
7.1.4.1 Collector efficiency factor .................................. 164
7.1.5 Collector efficiency ........................................................... 168
7.1.5.1 Collector incidence angle modifier ................... 170
7.1.5.2 Collector time constant ............ 171
8 SOLAR THERMAL CONVERSION - ACTIVE SOLAR SYSTEMS
7.1.6 Collector performance and quality testing ...................... 172
7.1.7 Factors affecting the solar collector efficiency .............. 174
7.2 Evacuated tube collectors (ETC) .................................................... 181
7.3 Concentrating collectors ................................................................. 184
7.3.1 Compound parabolic collectors (CPC) ........................... 186
7.3.2 High concentration collectors ............................................ 190
7.3.2.1 Parabolic trough collectors ................................ 190
7.3.2.2 Linear fresnel reflector (LFR) .......................... 192
7.3.2.3 Parabolic dish reflector (PDR) .......................... 193
7.3.2.4 Heliostat field collector (HFC) .......................... 194
References ................................................................................................... 196
Further reading ........................................................................................... 197
Glossary ...................................................................................................... 197
8. Thermal energy storage
Panayotis T. Tsilingiris
8.1 Introduction ....................................................................................... 203
8.2 The specific heat capacity of substances ........................................ 206
8.3 The technology of sensible heat storage ........................................ 209
8.4 The analysis of the water heat storage .......................................... 211
8.4.1 The well mixed storage ..................................................... 213
8.4.2 The influence of thermal stratification ........................... 216
8.5 The analysis of heat storage in packed bed solid materials — 220
8.6 The heat storage in building elements and structures .................. 224
8.6.1 Human comfort and thermal storage ................................ 224
8.6.2 Heat storage in passive building design ........................... 225
8.6.3 The heat strorage in structural elements and the building
envelope ............................................................................... 228
8.6.4 The combined influence of thermal resistance and heat ca­
pacity in building elements ................................................ 233
8.7 Long term seasonal storage ........................................................... 238
8.7.1 Limiting dimensions of seasonal heat storage systems and
examples ............................................................................... 240
8.8 Solar ponds ...................................................................................... 249
8.8.1 The fundamental system description and operation ____ 250
8.8.2 Modeling of the physical processes ....................................‘252
8.8.3 Stability and zone boundary migration considerations .. 257
8.8.4 The potential of solar ponds as large low-grade heat sto­
rage systems ......................................................................... 259
9
Contents
8.9 Latent heat storage ....................... 261
8.9.1 The characteristics of candidate phase-change materials 261
References ............................................................................................... 269
9. Solar thermal systems
Soteris A. Kalogirou
9.1 Domestic hot water ....................................................................... 274
9.1.1 Thermosiphon systems ...................................................... 274
9.1.2 Direct circulation systems (active) .................................. 277
9.1.3 Indirect water heating systems (active) ......................... 279
9.1.4 Air systems for hot water production (active) ................. 280
9.2 Solar space heating and cooling .................................................... 281
9.2.1 Air systems ......................................................................... 283
9.2.2 Water systems ................................................................... 284
9.2.3 Heat pump systems ............................................................ 285
9.2.4 Energy saving and environmental considerations .......... 286
9.2.4.1 Application ........................................................ 289
9.3 Guaranteed solar results ............................................................... 290
9.3.1 The framework of guarantee ............................................ 293
References ................................................................................................ 294
Further reading ........................................................................................ 294
Glossary ................................................................................................... 295
Abbreviations ............................................................................................ 296
10. Active solar heating systems design
Yannis G. Caouris
Introduction .............................................................................................. 297
10.1 Preliminary analysis ...................................................................... 298
10.2 Feasibility study ....................................................... 307
10.3 Detailed design ............................................................................. 308
10.3.1 System schematic ....... 309
10.3.2 Collector subsystem .......................................................... 311
10.3.2.1 Array design ...................................................... 311
10.3.2.2 Piping design ...................................................... 317
10.3.2.3 Component requirements ................................. 319
10.3.3 Storage subsystem ............................................................. 324
10.3.4 Control subsystem ..................................................... 329
References ................................................................................................ 332