太阳能热利用与技术考试题型

Assignmentforsolarthermalconversion(No.1)Thisprobleminvolvescalculationsonfoursurface:(1)verticalwest-facing;(2)verticalnorth-facing;(3)verticalsouth–facing;and(4)horizontal.Theresultsyouwillgeneratearecommonintermediatecalculationsinenergy-consciousbuildingdesign.(Averticaleast-facingsurfaceisomittedduetosymmetrywiththecorrespondingwest-facingwall.)Allcalculationsaretobeperformedfortwodates:(1)21December;(2)21June;andfortwotimesofday:(a)10:00;and(b)13:00localclocktime(notsolartimeandyouneedtoconvertfromlocalclocktimetosolartime).ThelocationisKunmingofChina,latitude=25.01oN,longitude=102.7oE(A)Calculatethecosineoftheincidenceangleforeachofthefoursurfaces,attwodifferenttimesofday,foreachofthetwodates(altogether16calculations)(B)Calculatethesunrise/sunsethour(insolartime)oneachofthefoursurfacesforeachofthetwodates.(C)Calculatethedailytotalextraterrestrialradiation(inMJ/m2)foreachofthefoursurfaces,foreachoftwodates.(Becareful,inyourcalculations,tousethesunrise/sunsethouronthesurfacesthemselves,andbecarefultousethecorrectunitoftimeandhourangle).AssignmentforSolarThermalConversion(No.2)1.Theknowledgeofthetiltandazimuthforatrackingsolarcollectorisoftenessentialinsystemdesign.Forexample,programmingthemicroprocessorthatcontrolsthetrackingrequiresanalgorithmfortherateatwhichthecollectormustmoveforeachminuteofthedayandeachdayoftheyear.Anotherexampleistrackingflat-platephotovoltaicsystems.Thecollectortiltangledependsontimeofdayanddayofyear.Thisisimportantinthecalculationofcollectibleenergysincethecollectiblediffuseandground-reflectedradiationbothdependoncollectortiltangle.Forthefollowingtrackingmodes,deriveexpressionsforboththecollectortiltandthecollectorazimuthasfunctionof:hourangle,solardeclinationangle,andlatitude.(a)horizontaleast-westaxistracking;(b)horizontalnorth-southaxistracking;(c)polaraxistracking;and(d)two-axistracking.[Hint:Insomeinstances,alittlebitofthinkingaboutthephysicalpicturecansavehoursofmessyalgebra]2.Buildingsarenotalwaysorientedtowardsduesouthornorth,andinsuchcase,itisnecessarytodoexchangeofcoordinatesystemsfordesigningtheoverhangofasouth-facingwindow.Hereisapracticaldesign:abuildingislocatedinKunmingwiththesouthwallorientedtowards30westfromsouth.Please(a)derivetheexpressionofprojectedangleofsolarraysontheplaneperpendiculartohorizontalandthesouthwallasafunctionofhourangle,solardeclinationangle,latitudeandazimuthangleofthesouthwallthroughcoordinatesexchange.(b)Supposingtheheightofthewindowish,howtodesigntheoverhangthatmakesthewindowcompletelyshadedat13:30PM(solartime)from21Mayto21Julyoftheyear,andmakesthewindowcompletelyexposedtothesunfrom21Oct.to21Feb.AssignmentforSolarEnergyThermalConversion(No.:3)Solargainthroughwindowsisessentialtopredictthermalperformanceofabuilding,andthisexerciseisconcernedwiththecalculationofsolarheatgainthroughasingleordoubleglazedwindow.Assumingthewindowglassis3mminthicknessanditsextinctioncoefficientk=40m-1,refractiveindexn=1.5.(1)Deriveexpressionsofsolartransmittancethroughasingle-glassandadouble-glasseswindow;Plotcurvesofsolartransmittancethroughbothsingle-glassanddouble-glasseswindowsvs.theincidenceangle.(2)Calculatetheequivalenttransmittancefordiffuseradiationthroughbothwindows.(3)IfthewindowsareinstalledatsouthwallofabuildinglocatedatKunming(01.25).ThemonthlyhemisphericradiationonJanuaryinKunmingisHh=396MJ/m2.Pleaseplot(a):solarradiationfallingonwindowsvs.timeoftheday(representativeday);(b):solarradiationthroughasingle-glasswindow;(c)solarradiationthroughadouble-glasseswindow.(4)Calculatethedailycollectiblesolarradiationonwindowsandthedailysolarheatgainofthebuildingswithasingle-glassandadouble-glasseswindowAssignmentforSolarThermalConversion(No:4)DesignanidealCPC(2D)withahalfacceptanceangleaandatwo-sidedverticalflatplateabsorber(assumingtheheightoftheabsorberisa)1:pleaseplotthefullCPCbytheuseofstringmethodanddescribetheprocedureofdrawingsuchaCPC.2:presenttheequationsofreflectors3:iftheCPCistruncatedwithextremeacceptedanglet,derivetheexpressionsofCt,HtandacceptedenergyfractionofincidentenergyF().AssignmentofSolarthermalconversion(No.5)1.Designanidealtwo-dimensionCPC.Theconcentratoriswest-eastalignedwiththetiltangleoftheaperturebeingsitelatitude.Forsuchdevice,theprojectionangleofsunlightontheplaneperpendiculartotheconcentratoraxisisacrucialparameterdeterminingwhetherthedirectsunlightisaccepted.(a)derivethemathematicalexpressoftheprojectionangleofsunlightontheplaneperpendiculartotheconcentratoraxis.(b)iftheCPCisrequiredtocollectdirectsunlightforatleast6h/dayinalldaysofayear,howmuchtheacceptancehalf-angleoftheconcentratorshouldbeset?Designanidealwest-eastalignedCPC(2D)withahorizontalflatone-sidedabsorberandtwoasymmetricreflectors.ThisconcentratorisdesignedtooperateinKunmingandrequiredtocollectdirectsunlightforatleast6h/dayinalldaysofayear.Designingconcentratorswithgaps:HomeworkofSolarthermalConversionNo.:7Designa2D(trough)edge-rayconcentratorforatubularabsorbertheradiusofwhichis35mm.Theacceptancehalf-angleaistobe35o.Thedesignmustincorporateagapof15mmbetweenthecylindricalabsorberandtheclosestpointofapproachofyourreflector.(a):Designacollectorformaximumconcentration,thatis,withthevirtual(“Ice-cream-cone-shape)absorberapproachdevelopedbyWinstonanddiscussedinthelecture.Explicitlywritedownallreflectorequationsyouemployandhowyouarrivedatthem.Presentacompletedrawingofyourcollector,atanyscaleyoufindconvenient(butwith1:1aspectratioofthexandyaxes).Whatisthegeometricconcentrationratio?Whatarethegaplosses(averagedovertheacceptanceangle)?Usingradiativeexchangefactorsoranymethodyoufindconvenient,showho