Table Of ContentSolar Technologies for Buildings
Ursula Eicker
University of Applied Sciences, Stuttgart, Germany
Solar Technologies for Buildings
Solar Technologies for Buildings
Ursula Eicker
University of Applied Sciences, Stuttgart, Germany
Originally published in the German language by B.G. Teubner GmbH as “Ursula Eicker: Solare
Technologien für Gebäude. 1. Auflage (1st edition)”.
Copyright © B.G. Teubner, Stuttgart/Leipzig/Wiesbaden, 2001.
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Contents
Preface ix
Abbreviations in the text xi
1 Solar energy use in buildings........................................................................................1
1.1 Energy consumption of buildings................................................................................1
1.1.1 Residential buildings............................................................................................2
1.1.2 Office and administrative buildings....................................................................4
1.1.3 Air conditioning...................................................................................................6
1.2 Meeting requirements by active and passive solar energy use...................................9
1.2.1 Active solar energy use for electricity, heating and cooling..............................9
1.2.2 Meeting heating energy requirements by passive solar energy use.................12
2 Solar irradiance............................................................................................................13
2.1 Extraterrestrial solar irradiance..................................................................................13
2.1.1 Power and spectral distribution of solar irradiance.......................................13
2.1.2 Sun–Earth geometry...........................................................................................16
2.1.2.1 Equator coordinates......................................................................................................17
2.1.2.2 Horizon coordinates.....................................................................................................20
2.1.2.3 Sun-position diagrams..................................................................................................22
2.2 The passage of rays through the atmosphere.............................................................24
2.3 Statistical production of hourly irradiance data records............................................26
2.3.1 Daily average values from monthly average values.........................................27
2.3.2 Hourly average values from daily average values............................................31
2.4 Global irradiance and irradiance on inclined surfaces..............................................34
2.4.1 Direct and diffuse irradi ance.............................................................................34
2.4.2 Conversion of global irradiance to inclined surfaces.......................................35
2.4.2.1 An isotropic diffuse irradiance model..........................................................................35
2.4.2.2 Diffuse irradiance model based on Perez.....................................................................36
2.4.3 Measurement techniques for solar irradiance..................................................39
2.5 Shading.......................................................................................................................39
3 Solar thermal energy...................................................................................................45
3.1 Solar-thermal water collectors...................................................................................45
3.1.1 Innovations.........................................................................................................45
3.1.2 System overview.................................................................................................46
3.1.3 Thermal collector types.....................................................................................47
3.1.3.1 Swimming pool absorbers............................................................................................47
3.1.3.2 Flat plate collectors......................................................................................................47
3.1.3.3 Vacuum tube collectors................................................................................................48
3.1.3.4 Parabolic concentrating collectors...............................................................................48
3.1.4 System engineering for heating drinking-water................................................49
3.1.4.1 The solar circuit and hydraulics...................................................................................49
3.1.4.2 Heat storage..................................................................................................................55
3.1.4.3 Piping and circulation losses........................................................................................60
3.1.5 System technology for heating support..............................................................61
3.1.6 Large solar plants for heating drinking water with short-term stores.............63
vi Contents
3.1.6.1 Design of large solar plants..........................................................................................66
3.1.7 Solar district heating..........................................................................................68
3.1.8 Costs and economy............................................................................................71
3.1.9 Operational experiences and relevant standards..............................................73
3.1.10 Efficiency calculation of thermal collectors......................................................74
3.1.10.1 Temperature distribution of the absorber................................................................75
3.1.10.2 Collector efficiency factor F'...................................................................................79
3.1.10.3 Heat dissipation factor F ........................................................................................79
R
3.1.10.4 Heat losses of thermal collectors.............................................................................83
3.1.10.5 Optical characteristics of transparent covers and absorber materials.....................92
3.1.11 Storage modelling..............................................................................................97
3.2 Solar air collectors....................................................................................................103
3.2.1 System engineering..........................................................................................105
3.2.2 Calculation of the available thermal power of solar air collectors...............107
3.2.2.1 Temperature-dependent material properties of air....................................................107
3.2.2.2 Energy balance and collector efficiency factor..........................................................108
3.2.2.3 Convective heat transfer in air collectors...................................................................109
3.2.2.4 Thermal efficiency of air collectors...........................................................................117
3.2.3 Design of the air circuit...................................................................................120
3.2.3.1 Collector pressure losses............................................................................................120
3.2.3.2 Air duct systems.........................................................................................................121
4 Solar cooling .......................................................................................................123
4.1 Open cycle desiccant cooling..................................................................................125
4.1.1 Introduction to the technology.........................................................................125
4.1.2 Coupling with solar thermal collectors...........................................................128
4.1.3 Costs.............................. ...................................................................................128
4.1.4 Physical and technological bases of sorption-supported air-conditioning....129
4.1.4.1 Technology of sorption wheels..................................................................................129
4.1.4.2 Air-status calculations................................................................................................130
4.1.4.3 Dehumidifying potential of sorption materials..........................................................132
4.1.4.4 Calculation of the sorption isotherms and isosteres of silica gel..............................135
4.1.4.5 Calculation of the dehumidifying performance of a sorption rotor...........................140
4.1.5 The technology of heat recovery......................................................................143
4.1.5.1 Recuperators...............................................................................................................143
4.1.5.2 Regenerative heat exchangers....................................................................................148
4.1.6 Humidifier technology.....................................................................................152
4.1.7 Design limits and climatic boundary conditions.............................................153
4.1.7.1 Demands on room temperatures and humidities........................................................153
4.1.7.2 Regeneration temperature and humidity....................................................................153
4.1.7.3 Calculation of supply air status with different climatic boundary conditions..........154
4.1.7.4 Limits and application possibilities of open sorption................................................155
4.1.8 Energy balance of sorption-supported air-conditioning................................156
4.1.8.1 Usable cooling power of open sorption.....................................................................156
4.1.8.2 Coefficients of performance and primary energy consumption................................158
4.2 Closed cycle adsorption cooling..............................................................................162
Contents vii
4.2.1 Technology and areas of application..............................................................162
4.2.2 Costs.................................................................................................................163
4.2.3 Operational principle.......................................................................................163
4.2.4 Energy balances and pressure conditions.......................................................165
4.2.4.1 Evaporator..................................................................................................................166
4.2.4.2 Condenser...................................................................................................................168
4.2.4.3 The adsorption process...............................................................................................169
4.2.4.4 Heating phase.............................................................................................................172
4.2.4.5 The desorption process...............................................................................................172
4.2.4.6 Cooling phase.............................................................................................................174
4.2.5 Coefficients of performance.............................................................................175
4.3 Absorption cooling technology................................................................................177
4.3.1 The absorption cooling process and its components......................................178
4.3.1.1 Double-lift absorption cooling process......................................................................181
4.3.1.2 Evaporator and condenser..........................................................................................182
4.3.1.3 Absorber.....................................................................................................................183
4.3.1.4 Generator....................................................................................................................185
4.3.2 Physical principles of the absorption process.................................................185
4.3.2.1 Vapour pressure curves of material pairs...................................................................185
4.3.3 Refrigerant vapour concentration...................................................................189
4.3.4 Energy balances and performance figures of an absorption cooler..............190
4.3.4.1 Ideal performance figures...........................................................................................190
4.3.4.2 Real performance figures and enthalpy balances......................................................191
4.3.5 Absorption technology and solar plants..........................................................200
5 Grid-connected photovoltaic systems..........................................................................201
5.1 Structure of grid-connected s ystems........................................................................201
5.2 Solar cell technologies.............................................................................................203
5.3 Module technology...................................................................................................203
5.4 Building integration and costs.................................................................................204
5.5 Energy production and the performance ratio of PV systems................................205
5.5.1 Energy amortisation times...............................................................................206
5.6 Physical fundamentals of solar electricity production............................................207
5.7 Current-voltage characteristics................................................................................209
5.7.1 Characteristic values and efficiency...............................................................209
5.7.2 Curve fittings to the current-voltage characteristic........................................210
5.7.2.1 Parameter adjustment from module data sheets........................................................216
5.7.2.2 Full parameter set calculation....................................................................................220
5.7.2.3 Simple explicit model for system design...................................................................221
5.7.3 I-V characteristic addition and generator interconnecting............................223
5.8 PV performance with shading..................................................................................225
5.8.1 Bypass diodes and backwards characteristics of solar cells..........................225
5.9 Simple temperature model for PV modules............................................................228
5.10 System engineering..................................................................................................231
5.10.1 DC connecting..................................................................................................231
5.10.1.1 Cable sizing............................................................................................................231
viii Contents
5.10.1.2 System voltage and electrical safety.....................................................................232
5.10.1.3 String diodes and short-circuit protection.............................................................232
5.10.2 Inverters...........................................................................................................234
5.10.2.1 Operational principle.............................................................................................234
5.10.2.2 Electrical safety and mains monitoring.................................................................235
5.10.2.3 Inverter efficiencies...............................................................................................235
5.10.2.4 Power sizing of inverters.......................................................................................238
6 Thermal analysis of building-integrated solar components......................................243
6.1 Empirical thermal model of building-integrated photovoltaics..............................244
6.2 Energy balance and stationary thermal model of ventilated double facades..........246
6.2.1 Heat transfer coefficients for the interior and facade air gap........................250
6.3 Building-integrated solar components (U- and g-values).......................................254
6.4 Warm-air generation by photovoltaic facades.........................................................257
7 Passive solar energy ......................................................................................................260
7.1 Passive solar use by glazings...................................................................................260
7.1.1 Total energy transmittance of glazings...........................................................261
7.1.2 Heat transfer coefficients of windows.............................................................263
7.1.3 New glazing systems........................................................................................265
7.2 Transparent thermal insulation................................................................................265
7.2.1 Operational Principle......................................................................................266
7.2.2 Materials used and construction.....................................................................270
7.2.2.1 Construction principles of TWD systems..................................................................270
7.3 Heat storage by interior building elements..............................................................271
7.3.1 Component temperatures for sudden temperature increases.........................274
7.3.2 Periodically variable temperatures.................................................................281
7.3.3 Influence of solar irradiance...........................................................................286
8 Lighting technology and daylight use..........................................................................288
8.1 Introduction to lighting and daylighting technology...............................................288
8.1.1 Daylighting of interior spaces.........................................................................289
8.1.2 Luminance contrast and glare.........................................................................291
8.2 Solar irradiance and light flux.................................................................................291
8.2.1 Physiological–optical basics...........................................................................292
8.2.2 Photometric radiation equivalent....................................................................292
8.2.3 Artificial light sources......................................................................................294
8.3 Luminance and illuminance.....................................................................................295
8.3.1 Luminance and adaptation of the eye..............................................................299
8.3.2 Distribution of the luminous intensity of artificial light sources....................300
8.3.3 Units and definitions........................................................................................303
8.4 Sky luminous intensity models................................................................................304
8.5 Light measurements.................................................................................................307
8.6 Daylight distribution in interior spaces...................................................................308
8.6.1 Calculation of daylight coefficients.................................................................311
References 316
Index 320
