Solar engineering of thermal processes

928 Pages·2013·6.096 MB·English

by  Duffie, John A;Beckman, William A

Solar Engineering
of Thermal Processes
Solar Engineering
of Thermal Processes
Fourth Edition
John A. Duffie (Deceased)
EmeritusProfessorofChemicalEngineering
William A. Beckman
EmeritusProfessorofMechanicalEngineering
SolarEnergyLaboratory
UniversityofWisconsin-Madison
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10 9 8 7 6 5 4 3 2 1
Contents
Preface xi 2.12 BeamandDiffuseComponentsofMonthly
PrefacetotheThirdEdition xiii Radiation 79
PrefacetotheSecondEdition xv 2.13 EstimationofHourlyRadiationfromDaily
PrefacetotheFirstEdition xvii Data 81
Introduction xxi 2.14 RadiationonSlopedSurfaces 84
2.15 RadiationonSlopedSurfaces:Isotropic
Sky 89
PARTI FUNDAMENTALS 1 2.16 RadiationonSlopedSurfaces:Anisotropic
Sky 91
2.17 RadiationAugmentation 97
1 SolarRadiation 3
2.18 BeamRadiationonMovingSurfaces 101
1.1 TheSun 3 2.19 AverageRadiationonSlopedSurfaces:Isotropic
1.2 TheSolarConstant 5 Sky 103
1.3 SpectralDistributionofExtraterrestrial 2.20 AverageRadiationonSlopedSurfaces:
Radiation 6 KTMethod 107
1.4 VariationofExtraterrestrialRadiation 8 2.21 EffectsofReceivingSurfaceOrientation
1.5 Definitions 9 onHT 112
1.6 DirectionofBeamRadiation 12 2.22 Utilizability 115
1.7 AnglesforTrackingSurfaces 20 2.23 GeneralizedUtilizability 118
1.8 RatioofBeamRadiationonTiltedSurface 2.24 DailyUtilizability 126
toThatonHorizontalSurface 23 2.25 Summary 132
1.9 Shading 29 References 133
1.10 ExtraterrestrialRadiationonaHorizontal
Surface 37
1.11 Summary 41 3 SelectedHeatTransferTopics 138
References 41
3.1 TheElectromagneticSpectrum 138
3.2 PhotonRadiation 139
2 AvailableSolarRadiation 43 3.3 TheBlackbody:PerfectAbsorberand
Emitter 139
2.1 Definitions 43 3.4 Planck’sLawandWien’sDisplacement
2.2 PyrheliometersandPyrheliometricScales 44 Law 140
2.3 Pyranometers 48 3.5 Stefan-BoltzmannEquation 141
2.4 MeasurementofDurationofSunshine 53 3.6 RadiationTables 142
2.5 SolarRadiationData 54 3.7 RadiationIntensityandFlux 144
2.6 AtmosphericAttenuationofSolar 3.8 InfraredRadiationExchangebetweenGray
Radiation 59 Surfaces 146
2.7 EstimationofAverageSolarRadiation 64 3.9 SkyRadiation 147
2.8 EstimationofClear-SkyRadiation 68 3.10 RadiationHeatTransferCoefficient 148
2.9 DistributionofClearandCloudyDays 3.11 NaturalConvectionbetweenFlatParallelPlates
andHours 71 andbetweenConcentricCylinders 149
2.10 BeamandDiffuseComponentsofHourly 3.12 ConvectionSuppression 154
Radiation 74 3.13 Vee-CorrugatedEnclosures 158
2.11 BeamandDiffuseComponentsofDaily 3.14 HeatTransferRelationsforInternal
Radiation 77 Flow 159
v
vi Contents
3.15 WindConvectionCoefficients 163 6 Flat-PlateCollectors 236
3.16 HeatTransferandPressureDropinPacked
6.1 DescriptionofFlat-PlateCollectors 236
BedsandPerforatedPlates 165
6.2 BasicFlat-PlateEnergyBalance
3.17 Effectiveness-NTUCalculationsforHeat
Equation 237
Exchangers 168
6.3 TemperatureDistributionsinFlat-Plate
References 170
Collectors 238
6.4 CollectorOverallHeatLossCoefficient 240
4 RadiationCharacteristicsofOpaque 6.5 TemperatureDistributionbetweenTubesandthe
Materials 173 CollectorEfficiencyFactor 254
6.6 TemperatureDistributioninFlow
4.1 AbsorptanceandEmittance 174 Direction 261
4.2 Kirchhoff’sLaw 176 6.7 CollectorHeatRemovalFactorandFlow
4.3 ReflectanceofSurfaces 177 Factor 262
4.4 RelationshipsamongAbsorptance,Emittance, 6.8 CriticalRadiationLevel 266
andReflectance 181 6.9 MeanFluidandPlateTemperatures 267
4.5 BroadbandEmittanceandAbsorptance 182 6.10 EffectiveTransmittance-Absorptance
4.6 CalculationofEmittanceand Product 268
Absorptance 183 6.11 EffectsofDustandShading 271
4.7 MeasurementofSurfaceRadiation 6.12 HeatCapacityEffectsinFlat-Plate
Properties 186 Collectors 272
4.8 SelectiveSurfaces 188 6.13 LiquidHeaterPlateGeometries 275
4.9 MechanismsofSelectivity 192 6.14 AirHeaters 280
4.10 OptimumProperties 195 6.15 MeasurementsofCollectorPerformance 287
4.11 AngularDependenceofSolar 6.16 CollectorCharacterizations 288
Absorptance 196 6.17 CollectorTests:Efficiency,IncidenceAngle
4.12 AbsorptanceofCavityReceivers 197 Modifier,andTimeConstant 289
4.13 SpecularlyReflectingSurfaces 198 6.18 TestData 299
References 199 6.19 ThermalTestDataConversion 302
6.20 FlowRateCorrectionstoFR(τα)n
andFR UL 305
5 RadiationTransmissionthroughGlazing:
6.21 FlowDistributioninCollectors 308
AbsorbedRadiation 202
6.22 InSituCollectorPerformance 309
6.23 PracticalConsiderationsforFlat-Plate
5.1 ReflectionofRadiation 202
Collectors 310
5.2 AbsorptionbyGlazing 206
6.24 PuttingitallTogether 313
5.3 OpticalPropertiesofCover
6.25 Summary 318
Systems 206
References 319
5.4 TransmittanceforDiffuse
Radiation 211
5.5 Transmittance-AbsorptanceProduct 213
7 ConcentratingCollectors 322
5.6 AngularDependenceof(τα) 214
5.7 SpectralDependenceofTransmittance 215 7.1 CollectorConfigurations 323
5.8 EffectsofSurfaceLayerson 7.2 ConcentrationRatio 325
Transmittance 218 7.3 ThermalPerformanceofConcentrating
5.9 AbsorbedSolarRadiation 219 Collectors 327
5.10 MonthlyAverageAbsorbedRadiation 223 7.4 OpticalPerformanceofConcentrating
5.11 AbsorptanceofRooms 229 Collectors 334
5.12 AbsorptanceofPhotovoltaicCells 231 7.5 CylindricalAbsorberArrays 335
5.13 Summary 234 7.6 OpticalCharacteristicsofNonimaging
References 234 Concentrators 337
Contents vii
7.7 OrientationandAbsorbedEnergyforCPC 10.4 Controls 429
Collectors 345 10.5 CollectorArrays:SeriesConnections 431
7.8 PerformanceofCPCCollectors 349 10.6 PerformanceofPartiallyShaded
7.9 LinearImagingConcentrators:Geometry 351 Collectors 433
7.10 ImagesFormedbyPerfectLinear 10.7 SeriesArrayswithSectionsHavingDifferent
Concentrators 354 Orientations 435
7.11 ImagesfromImperfectLinear 10.8 UseofModifiedCollectorEquations 438
Concentrators 359 10.9 SystemModels 441
7.12 Ray-TraceMethodsforEvaluating 10.10 SolarFractionandSolarSavings
Concentrators 361 Fraction 444
7.13 IncidenceAngleModifiersandEnergy 10.11 Summary 445
Balances 361 References 446
7.14 ParaboloidalConcentrators 367
7.15 Central-ReceiverCollectors 368
7.16 PracticalConsiderations 369 11 SolarProcessEconomics 447
References 370
11.1 CostsofSolarProcessSystems 447
11.2 DesignVariables 450
8 EnergyStorage 373 11.3 EconomicFiguresofMerit 452
11.4 DiscountingandInflation 454
8.1 ProcessLoadsandSolarCollector 11.5 Present-WorthFactor 456
Outputs 373 11.6 Life-CycleSavingsMethod 459
8.2 EnergyStorageinSolarProcessSystems 375 11.7 EvaluationofOtherEconomic
8.3 WaterStorage 376 Indicators 464
8.4 StratificationinStorageTanks 379 11.8 TheP ,P Method 467
1 2
8.5 Packed-BedStorage 384 11.9 UncertaintiesinEconomicAnalyses 472
8.6 StorageWalls 392 11.10 EconomicAnalysisUsingSolarSavings
8.7 SeasonalStorage 394 Fraction 475
8.8 PhaseChangeEnergyStorage 396 11.11 Summary 476
8.9 ChemicalEnergyStorage 400 References 476
8.10 BatteryStorage 402
References 406
PARTII APPLICATIONS 477
9 SolarProcessLoads 409
12 SolarWaterHeating:Activeand
9.1 ExamplesofTime-DependentLoads 410
Passive 479
9.2 Hot-WaterLoads 411
9.3 SpaceHeatingLoads,Degree-Days,
12.1 WaterHeatingSystems 479
andBalanceTemperature 412
12.2 Freezing,Boiling,andScaling 483
9.4 BuildingLossCoefficients 415
12.3 AuxiliaryEnergy 486
9.5 BuildingEnergyStorageCapacity 417
12.4 Forced-CirculationSystems 488
9.6 CoolingLoads 417
12.5 Low-FlowPumpedSystems 490
9.7 SwimmingPoolHeatingLoads 418
12.6 Natural-CirculationSystems 491
References 420
12.7 IntegralCollectorStorageSystems 494
12.8 RetrofitWaterHeaters 496
12.9 WaterHeatinginSpaceHeatingandCooling
10 SystemThermalCalculations 422
Systems 497
10.1 ComponentModels 422 12.10 TestingandRatingofSolarWater
10.2 CollectorHeatExchangerFactor 424 Heaters 497
10.3 DuctandPipeLossFactors 426 12.11 EconomicsofSolarWaterHeating 499
viii Contents
12.12 SwimmingPoolHeating 502 15.7 SolarDesiccantCooling 592
12.13 Summary 503 15.8 VentilationandRecirculationDesiccant
References 503 Cycles 594
15.9 Solar-MechanicalCooling 596
15.10 Solar-RelatedAirConditioning 599
13 BuildingHeating:Active 505
15.11 PassiveCooling 601
References 601
13.1 HistoricalNotes 506
13.2 SolarHeatingSystems 507
13.3 CSUHouseIIIFlat-PlateLiquidSystem 511 16 SolarIndustrialProcessHeat 604
13.4 CSUHouseIIAirSystem 513
13.5 HeatingSystemParametricStudy 517 16.1 IntegrationwithIndustrialProcesses 604
13.6 SolarEnergy–HeatPumpSystems 521 16.2 MechanicalDesignConsiderations 605
13.7 PhaseChangeStorageSystems 527 16.3 EconomicsofIndustrialProcessHeat 606
13.8 SeasonalEnergyStorageSystems 530 16.4 Open-CircuitAirHeatingApplications 607
13.9 SolarandOff-PeakElectricSystems 533 16.5 RecirculatingAirSystemApplications 611
13.10 SolarSystemOverheating 535 16.6 Once-ThroughIndustrialWaterHeating 613
13.11 SolarHeatingEconomics 536 16.7 RecirculatingIndustrialWaterHeating 615
13.12 ArchitecturalConsiderations 539 16.8 Shallow-PondWaterHeaters 617
References 541 16.9 Summary 619
References 619
14 BuildingHeating:PassiveandHybrid
Methods 544 17 SolarThermalPowerSystems 621
14.1 ConceptsofPassiveHeating 545 17.1 ThermalConversionSystems 621
17.2 GilaBendPumpingSystem 622
14.2 ComfortCriteriaandHeatingLoads 546
14.3 MovableInsulationandControls 546 17.3 LuzSystems 624
14.4 Shading:OverhangsandWingwalls 547 17.4 Central-ReceiverSystems 628
17.5 SolarOneandSolarTwoPowerPlants 630
14.5 Direct-GainSystems 552
14.6 Collector-StorageWallsandRoofs 557 References 633
14.7 Sunspaces 561
14.8 ActiveCollection–PassiveStorageHybrid 18 SolarPonds:EvaporativeProcesses 635
Systems 563
14.9 OtherHybridSystems 565 18.1 Salt-GradientSolarPonds 635
14.10 PassiveApplications 565 18.2 PondTheory 637
14.11 HeatDistributioninPassiveBuildings 571 18.3 ApplicationsofPonds 639
14.12 CostsandEconomicsofPassive 18.4 SolarDistillation 640
Heating 571 18.5 Evaporation 646
References 573 18.6 DirectSolarDrying 647
18.7 Summary 647
References 648
15 SolarCooling 575
15.1 SolarAbsorptionCooling 576
PARTIII DESIGN
15.2 TheoryofAbsorptionCooling 578
15.3 CombinedSolarHeatingandCooling 584 METHODS 651
15.4 SimulationStudyofSolarAir
Conditioning 585 19 SimulationsinSolarProcessDesign 653
15.5 OperatingExperiencewithSolarCooling 589
15.6 ApplicationsofSolarAbsorptionAir 19.1 SimulationPrograms 653
Conditioning 591 19.2 UtilityofSimulations 654
Contents ix
19.3 InformationfromSimulations 655 23 DesignofPhotovoltaicSystems 745
19.4 TRNSYS:ThermalProcessSimulation
23.1 PhotovoltaicConverters 746
Program 656
23.2 PVGeneratorCharacteristics
19.5 SimulationsandExperiments 663
andModels 747
19.6 MeteorologicalData 663
23.3 CellTemperature 757
19.7 LimitationsofSimulations 666
23.4 LoadCharacteristicsandDirect-Coupled
References 667
Systems 759
23.5 ControlsandMaximumPowerPoint
20 DesignofActiveSystems:f-Chart 668 Trackers 763
23.6 Applications 764
20.1 ReviewofDesignMethods 668
23.7 DesignProcedures 765
20.2 Thef-ChartMethod 669
23.8 High-FluxPVGenerators 770
20.3 Thef-ChartforLiquidSystems 673
23.9 Summary 771
20.4 Thef-ChartforAirSystems 679
References 771
20.5 ServiceWaterHeatingSystems 683
20.6 Thef-ChartResults 685
20.7 ParallelSolarEnergy-HeatPump 24 WindEnergy 774
Systems 686
20.8 Summary 690 24.1 Introduction 774
References 690 24.2 WindResource 778
24.3 One-DimensionalWindTurbineModel 786
24.4 EstimatingWindTurbineAveragePowerand
21 DesignofActiveSystemsbyUtilizability
EnergyProduction 791
Methods 692
24.5 Summary 796
References 796
21.1 HourlyUtilizability 693
21.2 DailyUtilizability 696
21.3 Theφ,f-ChartMethod 699
APPENDIXES 797
21.4 Summary 709
References 710
A Problems 797
22 DesignofPassiveandHybridHeating
Systems 711 B Nomenclature 856
22.1 ApproachestoPassiveDesign 711
22.2 Solar-LoadRatioMethod 712 C InternationalSystemofUnits 861
22.3 UnutilizabilityDesignMethod:Direct
Gain 721
D MeteorologicalData 863
22.4 UnutilizabilityDesignMethod:Collector-Storage
Walls 727
22.5 HybridSystems:ActiveCollectionwithPassive E AverageShadingFactorsfor
Storage 736
Overhangs 870
22.6 OtherHybridSystems 742
References 743 Index 887
Preface
This fourth edition emphasizes solar system design and analysis using simulations. The
designofmanysystemsthatuseconventionalenergysources(e.g.,oil,gas,andelectricity)
use a worst-case environmental condition—think of a building heating system. If the
systemcanmaintainthebuildingtemperatureduringthecoldestperiod,itwillbeableto
handlealllesssevereconditions.Tobesure,evenbuildingheatingsystemsarenowusing
simulationsduringthedesignphase.Inadditiontokeepingthebuildingcomfortableduring
theworstconditions,variousdesignchoicescanbemadetoreduceannualenergyuse.
This and earlier editions of this book describe TRNSYS (pronounced Tran-sis), a
generalsystemsimulationprogram(seeChapter19).Likeallheatingandairconditioning
systems, a solar system can be thought of as a collection of components. TRNSYS
has hundreds of component models, and the TRNSYS language is used to connect the
components together to form a system. Following the Preface to the First Edition is
the Introduction where a ready-made TRNSYS program (called CombiSys) is described
that simulates a solar-heated house with solar-heated domestic hot water. TRANSED, a
front-end program for TRNSYS is used so it is not necessary to learn how to develop
TRNSYS models to run CombiSys. CombiSys can be freely downloaded from the John
Wileywebsite(http://www.wiley.com/go/solarengineering4e).
CombiSys provides an input window where various design options can be selected
(e.g.,thecollectortypeanddesign,storagetanksize,collectororientation,andavarietyof
otherchoices).Aseriesofsimulationproblems(identifiedwithaprefix‘‘S’’followedbya
chapternumberandthenaproblemnumber)havebeenaddedtothestandardproblemsof
manychapters.The‘‘S0’’problems(thatis,Chapter0,theIntroduction)requirerunning
CombiSysandansweringgeneralquestionsthatmayrequireperformingenergybalances
anddoingsimpleeconomiccalculations.Asnewtopicsarediscussedinthistextnew‘‘S’’
problemsareintroduced,oftenwiththeobjectivetoduplicatesomeaspectofCombiSys.
With this approach it is hoped that the student will understand the inner workings of a
simulationprogramandbemadeawareofwhycertaintopicsareintroducedanddiscussed
inthetext.
The purpose of studying and understanding any topic in engineering is to make the
nextsystembetterthanthelast.PartIinthisstudyofsolarsystemscontains11chapters
devoted to understanding the operation of components (e.g., the sun, collectors, storage
systems,loads,etc.).Theresultsoftheseearlychaptersaremathematicalmodelsthatallow
thedesignertoestimatecomponentperformance(intheTRNSYSlanguage,theoutputs)
for a given set of component conditions (i.e., TRNSYS inputs). It is easy to think of
collectors,storagetanks,photovoltaicarrays,andbatteriesascomponents, buthereeven
the sun and economics are treated as components. The sun component manipulates the
available(generallymeasuredbutsometimesestimated)solarradiationdatatoobtainthe
neededsolarradiationdataonanarbitrarilyorientedsurfaceandinadesiredtimeinterval.
Thetimescaleofreportedsolardatarangesfromafewsecondstoyearly.Sometimeswe
even need to estimate the solar energy in a wavelength interval. The available measured
solar radiation data is typically energy rates (i.e., power) from a specified and easily
xi
xii Preface
calculated direction such as the ‘‘beam’’ radiation that comes directly from the sun and
the ‘‘diffuse’’ radiation that has been scattered in some generally unknown manner over
all parts of the sky. The mathematical model of the sun component must accommodate
thesevariousinputandoutputrequirements.ThefinalchapterinPartIcoverseconomics.
Generallytheobjectiveofasolarsystemistoproduceenvironmentallyfriendlypowerat
an acceptable cost. The familiar calculations of levelized cost per unit of energy and/or
life-cycle savings (versus some energy alternative) are not trivial since the time horizon
ofasolarsystemcanbemultipledecades,requiringtheestimatesoffar-futureeconomic
conditions.Theeconomicimpactofexternalitiessuchasreducedpollutantsisdifficultto
evaluatesincethesecostsarenoteasilymonetized.
PartII,chapters12through18,discussesvariousthermalsystemsthathavebeenbuilt,
theperformancemeasuredandtheresultspublished.Theyaredescriptivechapterswiththe
intentofprovidingthereaderwithafeelingofwhatcanbeaccomplished.Manyofthese
systemswerebuiltandtestedduringatimewhengovernmentswerefundinguniversities
andlaboratorieswherearequirementwastomaketheresultspublic.Mostsolarsystems
todayareprivatelyfundedandperformancedataisoftendifficultorimpossibletoobtain.
Chapters 19 through 22 of Part III are devoted to system design (sometimes called
systemsizing).Beforethelate1970spersonalcomputerswerenotavailablesosimulations
were done either by hand or on large main-frame computers and were very expensive.
Researchinto‘‘designmethods’’focusedonthedevelopmentofshort-cutdesignassistance
toreplaceexpensivesimulations.Theearliestexampleisfromtheearly1950s,whichused
a radiation statistic called ‘‘utilizability’’ to assist in solar sizing (see Section 2.22 and
Chapter21).Thenextstep,thef-chartmethod(seeChapter21)isfromthemid-1970sand
usednumericalexperimentstodevelopcorrelationsofthevariousnondimensionalgroups.
Thisprocessisnotunlikelaboratoryexperimentsthatareusedtocorrelatedimensionless
heat transfer results (the Nusselt number) to dimensionless fluid parameters (Reynolds,
Prandtl,andGrashofnumbers).Thesignificantdifferenceisthattheexperimentalresults
in the f-chart development were hundreds of detailed main-frame computer simulations
and were validated with a few year-long experiments. These design methods still have
a place in today’s engineering practice. They are extremely fast and thus provide an
inexpensive alternative to annual simulations, especially for small systems. Large (and
thereforeexpensive)systemscanaffordtobelookedatusingdetailedsimulations.Some
of the problems in these chapters compare the detailed simulations using TRNSYS with
thevariousdesignmethods.
Chapters 23 and 24 of Part III cover sizing of photovoltaic (PV) and wind energy
systems. It is obvious that the solar radiation processing developed in Chapter 2 is very
important in the design and analysis of PV systems. The detailed physics of a solar cell
iscomplex,butitisnotnecessarytounderstandthesedetailstodesignaPVsystem.The
current-voltage (I-V) characteristics of cells are discussed in detail and a mathematical
I-V modelispresentedthatisusefulindesign.Windenergysystemsareintroducedwitha
simpleanalysisthatleadstounderstandingofmanufacturerswindturbinecharacteristics.
Theperformanceofanisolatedturbineisdiscussed,butinterferenceofthewindpatterns
withclose-packedmultipleturbinesisnotdiscussed.
WILLIAMA.BECKMAN
Madison,Wisconsin