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附录1SolarTrackerTheSolarTrackerteamwasformedinthefallof2005fromfivestudentsinanMEdesignteam,andaSmartHouseliaison.Wecontinuedtheworkofaprevioussolartrackergroup.Thetaskwastodesignaprototypetrackingdevicetoalignsolarpanelsoptimallytothesunasitmovesoverthecourseoftheday.TheimplementationofsuchasystemdramaticallyincreasestheefficiencyofsolarpanelsusedtopowertheSmartHouse.Thisreportexaminestheprocessofdesigningandconstructingtheprototype,theexperiencesandproblemsencountered,andsuggestionsforcontinuingtheproject.1.IntroductionSolartrackingistheprocessofvaryingtheangleofsolarpanelsandcollectorstotakeadvantageofthefullamountofthesun’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.Itiseasytointerchangemotorsasneededforfurthertestingandalsoallowsforoptimizationofthefinalgearratioforresponseofthetracker.Aswithanydesignprocesstherewereseveralsetbackstoourprogress.Thefirstandforemostwasinclementweatherwhichdeniedusofvaluabletestingtime.Despitethesetbacks,webelievethisdesignandprototypetobeaveryvaluableproof-of-principle.Duringourtestingwehaveeliminatedmanyoftherepetitiveproblemswiththemotorandwiringsothatfutureworkontheprojectwillgomoresmoothly.Wealsohaveachievedourgoaloftrackingthesunina‘hands-off’demo.Wewereabletohavethetrackerrotateunderitsownpowertotheangleofthesunandstopwithoutanyassistance.ThiswasthemaingoalsetforthtousbytheSmartHousesowebelieveoursensedmotionprototypeforsolartrackingwillbethefoundationastheymoveforwardinthefuturedevelopmentandimplementationofthistechnologytothehouse.2.DefiningtheProblemTheprojectwastocompletethe“REV2”designphaseofthesolartrackertobeusedontheSmartHouse.WhiletheteamwascomprisedofmembersfromtheME160seniordesigncourse,thecustomerforthisprojectwastobetheSmartHouseorganization.JeffSchwane,arepresentativefromtheSmartHouse,wasourliaisonandcommunicatedtoourgroupthedirectionSmartHouseleadershipwishedustoproceed.AtourfirstmeetingwithJeffandTomRose,thefollowingneedswereidentified:1.Trackthesunduringtheday2.Usenoexternalpowersource3.Weatherproof4.Costeffectivepowergain5.Mustlookgood6.Solarpanelversatilei.e.canfitdifferenttypesofpanelsWiththeseneedsinhand,weconstructedaQualityFunctionDeploymentchart.ThischartcanbefoundinAppendixA.TheQFDshowedthemajorareasofconcernmighthavebeen:numberofpanels/sizeofpanels,internalpowerrequirements,motortorquerequired.Atourfirstmeetingwewerealsoabletosetupourgoalsforthesemester.Havingaworkingprototypecapableoftrackingthesunwastobethemaingoalfortheendofthesemester,butwesoonfoundthatinordertoaccomplishthis,wewouldbeforcedtoomitportionsofthedesigncriteriainhopestheywouldbeworkedoutlater.Thiswouldresultintheoptimizationofplatformspaceontherooftobeirrelevant,withourgoalbeingtohaveoneplatformtrack.Italsoledtotheassumptionthatourbasewouldnotneedtobetestedforstabilityorrequiredtobefastenedtotheroof.Withanideaofwhereweweretobegin,fromscratchwiththepossibilityofusingtheframefromthe“REV1”design,andanideaofwhereweweretofinish,withamovingprototype,weconstructedtheGanttchartthatcanbefoundinAppendixB.