太阳能跟踪器外文翻译.docx
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太阳能跟踪器外文翻译
SolarTracker
DavidCrowe,JeffMcCormick,JoelMitchell,
ThomasStratton,JeffSchwane
December15,2005
DukeUniversitySmartHousePrattSchoolofEngineering
Abstract
TheSolarTrackerteamwasformedinthefallof2005fromfivestudentsinanMEdesignteam,andaSmartHouseliaison.Wecontinuedtheworkofaprevioussolartrackergroup.Thetaskwastodesignaprototypetrackingdevicetoalignsolarpanelsoptimallytothesunasitmovesoverthecourseoftheday.TheimplementationofsuchasystemdramaticallyincreasestheefficiencyofsolarpanelsusedtopowertheSmartHouse.Thisreportexaminestheprocessofdesigningandconstructingtheprototype,theexperiencesandproblemsencountered,andsuggestionsforcontinuingtheproject.
1.Introduction
Solartrackingistheprocessofvaryingtheangleofsolarpanelsandcollectorstotakeadvantageofthefullamountofthesun’senergy.Thisisdonebyrotatingpanelstobeperpendiculartothesun’sangleofincidence.Initialtestsinindustrysuggestthatthisprocesscanincreasetheefficiencyofasolarpowersystembyupto50%.Giventhosegains,itisanattractivewaytoenhanceanexistingsolarpowersystem.Thegoalistobuildarigthatwillaccomplishthesolartrackingandrealizethemaximumincreaseinefficiency.Theultimategoalisthattheprojectwillbecosteffective–thatis,thegainsreceivedbyincreasedefficiencywillmorethanoffsettheonetimecostofdevelopingtherigovertime.Inadditiontothefunctionalgoals,theSmartHousesetforththeotherfollowinggoalsforourproject:
itmustnotdrawexternalpower(self-sustaining),itmustbeaestheticallypleasing,anditmustbeweatherproof.
Thedesignofoursolartrackerconsistsofthreecomponents:
theframe,thesensor,andthedrivesystem.Eachwascarefullyreviewedandtested,institutingchangesandimprovementsalongthedesignprocess.Theframeforthetrackerisanaluminumprismaticframesuppliedbytheprevioussolartrackinggroup.Itutilizesan‘A-frame’designwiththerotatingaxleinthemiddle.Attachedtothebottomofthissquarechannelaxleistheplatformwhichwillhousethemainsolarcollectingpanels.Theframeitselfisatanangletodirectthepanelstowardthesun(alongwiththeinclinationoftheroof).Itsrotationtracksthesunfromeasttowestduringtheday.
Thesensordesignforthesystemusestwosmallsolarpanelsthatlieonthesameplaneasthecollectingpanels.Thesesensorpanelshavemirrorsverticallyattachedbetweenthemsothat,unlessthemirrorfacesdonotreceiveanysun,theyareshadingoneofthepanels,whiletheotherisreceivingfullsunlight.Oursensorreliesonthisdifferenceinlight,whichresultsinalargeimpedancedifferenceacrossthepanels,todrivethemotorintheproperdirectionuntilagain,themirrorsarenotseeinganysunlight,atwhichpointbothsolarpanelsonthesensorreceiveequalsunlightandnopowerdifferenceisseen.
Afterevaluationofthepreviousdirectdrivesystemforthetracker,wedesignedabeltsystemthatwouldbeeasiertomaintaininthecaseofafailure.Ononeendoftheframeisamotorthathasthedrivepulleyattachedtoitsoutputshaft.Themotorrotatesthedrivebeltwhichthenrotatesthepulleyontheaxle.Thissystemissimpleandeasilydisassembled.Itiseasyto
interchangemotorsasneededforfurthertestingandalsoallowsforoptimizationofthefinalgearratioforresponseofthetracker.
Aswithanydesignprocesstherewereseveralsetbackstoourprogress.Thefirstandforemostwasinclementweatherwhichdeniedusofvaluabletestingtime.Despitethesetbacks,webelievethisdesignandprototypetobeaveryvaluableproof-of-principle.Duringourtestingwehaveeliminatedmanyoftherepetitiveproblemswiththemotorandwiringsothatfutureworkontheprojectwillgomoresmoothly.Wealsohaveachievedourgoaloftrackingthesunina‘hands-off’demo.Wewereabletohavethetrackerrotateunderitsownpowertotheangleofthesunandstopwithoutanyassistance.ThiswasthemaingoalsetforthtousbytheSmartHousesowebelieveoursensedmotionprototypeforsolartrackingwillbethefoundationastheymoveforwardinthefuturedevelopmentandimplementationofthistechnologytothehouse.
2.DefiningtheProblem
Theprojectwastocompletethe“REV2”designphaseofthesolartrackertobeusedontheSmartHouse.WhiletheteamwascomprisedofmembersfromtheME160seniordesigncourse,thecustomerforthisprojectwastobetheSmartHouseorganization.JeffSchwane,arepresentativefromtheSmartHouse,wasourliaisonandcommunicatedtoourgroupthedirectionSmartHouseleadershipwishedustoproceed.
AtourfirstmeetingwithJeffandTomRose,thefollowingneedswereidentified:
1.Trackthesunduringtheday
2.Usenoexternalpowersource
3.Weatherproof
4.Costeffectivepowergain
5.Mustlookgood
6.Solarpanelversatilei.e.canfitdifferenttypesofpanels
Withtheseneedsinhand,weconstructedaQualityFunctionDeploymentchart.ThischartcanbefoundinAppendixA.TheQFDshowedthemajorareasofconcernmighthavebeen:
numberofpanels/sizeofpanels,internalpowerrequirements,motortorquerequired.
Atourfirstmeetingwewerealsoabletosetupourgoalsforthesemester.Havingaworkingprototypecapableoftrackingthesunwastobethemaingoalfortheendofthesemester,butwesoonfoundthatinordertoaccomplishthis,wewouldbeforcedtoomitportionsofthedesigncriteriainhopestheywouldbeworkedoutlater.Thiswouldresultintheoptimizationofplatformspaceontherooftobeirrelevant,withourgoalbeingtohaveoneplatformtrack.Italsoledtotheassumptionthatourbasewouldnotneedtobetestedforstabilityorrequiredtobefastenedtotheroof.Withanideaofwhereweweretobegin,fromscratchwiththepossibilityofusingtheframefromthe“REV1”design,andanideaofwhereweweretofinish,withamovingprototype,weconstructedtheGanttchartthatcanbefoundinAppendixB.OurgroupplannedtomeetwithJeffonceaweektomakesurewewereontrackwiththeneedsoftheSmartHouse.JeffwouldalsomeetwithTomRose,thedirectorofSmartHouse,atleastonceaweekinordertokeepeveryoneonthesamepage.Withourgoalsinmindweembarkedontheprocessofideageneration.
3.ConceptsandResearch
3.1TrackingType
Ourgroupusedabrainstormingapproachtoconceptgeneration.Wethoughtofideasfordifferentsolartrackingdevices,whichproveddifficultattimesduetotheexistingframeandconceptpresentedtousbySmartHouse.Otherconceptsweregeneratedthroughresearchofpre-existingsolartrackingdevices.OriginallyourconceptgenerationwasgearedtowardscreatingacompletelynewsolartrackeroutsideoftheconstraintsofthepreviousstructuregiventousbySmartHouse.Thisinitialbrainstorminggeneratedmanyconcepts.Thefirstonewasauni-axialtrackingsystemthatwouldtrackthesuneasttowestacrosstheskyduringthecourseofadayandreturnattheendoftheday.Thisconceptpresentedtheadvantageofsimplicityandpresenteduswiththeoptiontousematerialsfromthepreviousstructure(whichwasalsointendedtobeauni-axialtracker)inconstruction.Anothermorecomplexconceptwastotrackthesunbi-axiallywhichwouldinvolvetrackingthesunbotheasttowestandthroughouttheseasons.Theadvantageofthisconceptwasamoreefficientharvestingofsolarenergy.Thethirdconceptwastoonlytrackthroughouttheseasons.Thiswouldprovidesmallefficiencygainsbutnowherenearthegainprovidedbytrackingeasttowest.
Thedifferentstructureswecameupwithtoaccomplishtrackingmotionincludedarotatingcenteraxlewithattachedpanels,hydraulicormotorizedliftswhichwouldmovethemainpanelinthedirectionofthesun,andaroboticarmwhichwouldturntofacethesun.Theclearefficiencygainscoupledwiththesimplicityofdesignoftheuni-axialtrackingsystemandtheexistenceofusableparts(i.e.motorandaxle)fortherotatingcenteraxlestructure,ledustothechoiceoftheEasttoWesttracking,rotatingcenteraxleconcept.
3.2Structure
Oncethemethodofmotionwaschosen,itwasnecessarytogenerateconceptsforthestructuralsupportoftheaxle.SupportcouldbeprovidedbythetriangularprismaticstructurewhichwasattemptedbythepreviousSmartHousesolartrackergrouporthroughtheuseofcolumnswhichwouldsupporttheaxisoneitherside.Whiletheprismaticstructurepresentedtheadvantageofmobilityandanexistingframe,thecolumnswouldhaveprovideduswitheaseofconstruction,simplegeometricconsiderations,andeaseofprospectivemountingontheroof.Duetotheheightenedintensityoftimeconsiderations,thepreviousfinancialcommitmenttotheprismaticstructurebySmartHouse,andourlimitedbudget,thepresenceofthepre-existingframeprovedtobethemostimportantfactorindecidingonastructure.DuetothesefactorswedecidedtoworkwithintheframewhichwasprovidedtousfromthepreviousSolarTrackergroup.
3.2TrackingMotion
Oncethestructuralsupportwasfinalizedweneededtodecideonameanstoactualizethismotion.Wedecidedbetweensensedmotion,whichwouldsensethesun’spositionandmovetofollowit,andcontinuousclocktypemotion,whichwouldtrackthesunbasedonitspre-determinedpositioninthesky.Wechosetheconceptofcontinuousmotionbasedonitsperceivedaccuracyandtheexistenceofknowntimingtechnology.Duringtheevaluationstage,however,werealizedthatcontinuousmotionwouldprovedifficult.Onereasonwastheinabilitytodrawconstantvoltageandcur