Solar Thermal Conversion. Active Solar Systems

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
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 average 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 sunshine 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
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 plate materials ................................................. 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
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 capacity 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 storage systems ......................................................................... 259
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
11. Industrial production of flat plate liquid solar collectors
Yannis G. Caouris
11.1 The solar absorber ......................................................................... 333
11.1.1 Stamped absorbers ............................................................. 334
11.1.2 Tube absorber ................................................................... 336
11.1.3 Roll bond absorbers ......................................................... 339
11.1.4 Organic absorbers ............................................................. 339
11.2 Check for leakages and cleaning of metal absorbers ................. 340
11.3 Painting ........................................................................................... 341
11.4 Enclosure insulation and glazing .................................................. 343
References ............................................................................................... 346
12. Solar energy economics
John J. Gelegenis
Introduction ............................................................................................. 347
12.1 Economic analysis ........................................................................ 348
12.1.1 General ............................................................................ 348
12.1.2 Simplified economic indicators ........................................ 352
12.1.3 Discounted cash flows ....................................................... 356
12.2 Life cycle analysis .......................................................................... 360
12.2.1 Net present value of the investment - Life cycle solar
savings ................................................................................ 361
12.2.2 Discounted payback time .................................................. 363
12.2.3 Internal rate of return ..................................................... 364
12.2.4 Other economic indexes ................................................... 367
12.2.5 Factors affecting solar system appraisal ........................... 368
12.2.5.1 Loans ................................................................. 368
12.2.5.2 Taxation ............................................................. 370
12.2.5.3 Grants ................................................................. 371
12.2.5.4 Variation of energy prices .............................. 371
12.2.5.5 Inflation ............................................................. 371
12.3 Economic optimization ................................................................. 377
12.3.1 Maximization of life cycle savings .................................. 377
12.3.2 Consideration of uncertainties ........................................ 379
Summary .................................................................................................. 381
Nomenclature ........................................................................................... 381
Indexes ................ 382
Unsolved problems ................................................................................. 382
References ............................................................................................... 383
13. Software for active solar heating
Panayiotis Ylanoulis and Myrsini Giannouli
13.1 General considerations ................................................................... 385
13.2 Design of active solar systems .................................................... 386
13.3 Solar radiation data ....................................................................... 387
13.4 Comments on insolation data and models .................................. 389
13.5 Simulation of an active solar system —................................... 390
13.6 The TRNSYS (TRaNsient SYstems Simulation program) ........... 392
13.6.1 General ............................................................................ 392
13.6.2 Standard components in TRNSYS .................................. 393
13.6.3 Updates and new features for TRNSYS 16 ..................... 3%
13.6.4 Components (fos Sale and Free Downloadable) .............. 397
13.7 f-chart computer program ........................................................... 399
13.7.1 Program overview ...................... 399
13.7.2 Dimensionless variables (X, Y} ...................................... 400
13.7.3 Applications in various configurations ........................... 402
13.7.4 Other considerations ......................................................... 404
13.8 Programs for the design of active systems by utilizability ......... 405
References ............................................................................................... 407
14. Solar thermal applications
Panayotis T. Tsilingirls
14.1 Swimming pool heating ................................................................. 411
14.1.1 Heat balance and heat losses ............................................ 412
14.1.2 Heat loss control and solar collectors ............................ 416
14.2 Agricultural drying ................................................................ 419
14.2.1 Crop drying and solar energy .......................................... 420
14.2.2 The physical processes in drying ..................................... 421
14.2.3 The design of solar driers ........... 422
14.2.4 The use of desiccants in solar drying ............................... 426
14.3 Solar cooking ............................................................................ 430
14.4 Solar desalination ..........................................................................433
14.4.1 Fundamental physical processes and taxonomy .............. 436
14.4.2 The direct solar distillation systems ................................. 438
14.4.2.1 The heat balance in solar stills ......................... 440
14.4.2.2 The combined heat and mass transfer processes
in solar distillation systems ............................ 443
14.4.2.3 Solar still design improvements ....................... 445
14.4.3 Indirect solar distillation systems .................................... 453
14.5 Solar powered heat engines ........................................................... 457
14.5.1 Fundamental principles and thermodynamic limitations . 459
14.5.2 The solar to mechanical energy conversion ................... 463
14.5.3 The thermodynamic cycles ................................................ 464
14.5.4 The Stirling engines ........................................................... 468
14.5.5 Rankine power cycles ....................................................... 477
14.6 Solar thermal electric power systems .......................................... 483
14.6.1 Parabolic trough solar collector field technology .......... 484
14.6.2 Combined cycle systems .................................................... 495
14.6.3 Central tower systems ..................................................... 498
14.6.4 Parabolic dish systems ..................................................... 504
14.6.5 Solar pond power plants .................................................. 507
14.6.6 Comparative unit energy cost estimates ......................... 510
14.7 Solar assisted heat pump system .................................................. 511
14.8 Solar absorption and adsorption systems .................................... 522
14.8.1 Absorption solar cooling systems .................................... 523
14.8.2 Solar dessicant cooling systems ...................................... 535
References ............................................................................................................ 539