led照明毕业论文中英文资料外文翻译文献

中英文资料外文翻译文献led照明毕业论文中英文资料外文翻译文献RenewableandSustainableEnergyReviewsHigh-brightnessLEDs—EnergyefficientlightingsourcesandtheirpotentialinindoorplantcultivationABSTRACTTherapiddevelopmentofoptoelectronictechnologysincemid-1980hassignificantlyenhancedthebrightnessandefficiencyoflight-emittingdiodes(LEDs).LEDshavelongbeenproposedasaprimarylightsourceforspace-basedplantresearchchamberorbioregenerativelifesupportsystems.TheraisingcostofenergyalsomakestheuseofLEDsincommercialcropcultureimminent.Withtheirenergyefficiency,LEDshaveopenednewperspectivesforoptimizingtheenergyconversionandthenutrientsupplybothonandoffEarth.ThepotentialsofLEDasaneffectivelightsourceforindooragriculturalproductionhavebeenexploredtoagreatextent.TherearemanyresearchesthatuseLEDstosupportplantgrowthincontrolledenvironmentssuchasplanttissuecultureroomandgrowthchamber.ThispaperprovidesabriefdevelopmenthistoryofLEDsandabroadbasereviewonLEDapplicationsinindoorplantcultivationsince1990.Contents1.Introduction2.LEDdevelopment.3.Colorratiosandphotosynthesis4.LEDsandindoorplantcultivation.4.1.Planttissuecultureandgrowth4.2.Spaceagriculture84.3.Algaculture4.4.Plantdiseasereduction5.Intermittentandphotoperiodlightingandenergysaving6.Conclusion1.IntroductionWithimpactsofclimatechange,issuessuchasmorefrequentandseriousdroughts,floods,andstormsaswellaspestanddiseasesarebecomingmoreseriousthreatstoagriculture.Thesethreatsalongwithshortageoffoodsupplymakepeopleturntoindoorandurbanfarming(suchasverticalfarming)forhelp.Withproperlighting,indooragricultureeliminatesweather-relatedcropfailuresduetodroughtsandfloodstoprovideyear-roundcropproduction,whichassistinsupplyingfoodincitieswithsurgingpopulationsandinareasofsevereenvironmentalconditions.Theuseoflight-emittingdiodesmarksgreatadvancementsoverexistingindooragriculturallighting.LEDsallowthecontrolofspectralcompositionandtheadjustmentoflightintensitytosimulatethechangesofsunlightintensityduringtheday.Theyhavetheabilitytoproducehighlightlevelswithlowradiantheatoutputandmaintainusefullightoutputforyears.LEDsdonotcontainelectrodesandthusdonotburnoutlikeincandescentorfluorescentbulbsthatmustbeperiodicallyreplaced.Nottomentionthatincandescentandfluorescentlampsconsumealotofelectricalpowerwhilegeneratingheat,whichmustbedispelledfromclosedenvironmentssuchasspaceshipsandspacestations.2.LEDdevelopmentLEDisauniquetypeofsemiconductordiode.Itconsistsofachipofsemiconductormaterialdopedwithimpuritiestocreateap–njunction.Currentflowseasilyfromthep-side(anode),tothen-side(cathode),butnotinthereversedirection.Electronsandholesflowintothejunctionfromelectrodeswithdifferentvoltages.Whenanelectronmeetsahole,itfallsintoalowerenergylevel,andreleasesenergyintheformofaphoton.Thecolor(wavelength)ofthelightemitteddependsonthebandgapenergyofthematerialsformingthep–njunction.ThematerialsusedforanLEDhaveadirectbandgapwithenergiescorrespondingtonear-infrared,visibleornear-ultravioletlight.ThekeystructureofanLEDconsistsofthedie(orlight-emittingsemiconductormaterial),aleadframewherethedieisplaced,andtheencapsulationwhichprotectsthedie(Fig.1).Fig.1LEDdevelopmentbeganwithinfraredandreddevicesmadewithgalliumarsenide.Advancesinmaterialssciencehavemadepossibletheproductionofdeviceswithever-shorterwavelengths,producinglightinavarietyofcolors.J.Margolinreportedthatthefirstknownlight-emittingsolidstatediodewasmadein1907byH.J.Round.NopracticaluseofRound’sdiodewasmadeforseveraldecadesuntiltheinventionofthefirstpracticalLEDbyNickHolonyak,Jrin1962.HisLEDsbecamecommerciallyavailableinlate1960s.TheseGaAsPLEDscombinethreeprimaryelements:gallium,arsenicandphosphorustoprovidea655nmredlightwithbrightnesslevelsofapproximately1–10mcdat20mA.Astheluminousintensitywaslow,theseLEDswereonlyusedinafewapplications,primarilyasindicators.FollowingGaAsP,GaP(galliumphosphide)redLEDsweredeveloped.Thesedevicesexhibitveryhighquantumefficienciesatlowcurrents.AsLEDtechnologyprogressedthroughthe1970s,additionalcolorsandwavelengthsbecameavailable.ThemostcommonmaterialswereGaPgreenandred,GaAsPorange,andhighefficiencyredandGaAsPyellow.Thetrendtowardsmorepracticalapplications(suchasincalculators,digitalwatches,andtestequipment)alsobegantodevelop.AstheLEDmaterialstechnologybecamemoreadvanced,thelightoutputwasincreased,andLEDsbecamebrightenoughtobeusedforillumination.In1980sanewmaterial,GaAlAs(galliumaluminumarsenide)wasdevelopedfollowedbyarapidgrowthintheuseofLEDs.GaAlAstechnologyprovidessuperiorperformanceoverpreviouslyavailableLEDs.Thevoltagerequirementislower,whichresultsinatotalpowersavings.LEDscouldbeeasilypulsedormultiplexedandthusaresuitableforvariablemessageandoutdoorsigns.Alongthisdevelopmentperiod,LEDswerealsodesignedintobarcodescanners,fiberopticdatatransmissionsystems,andmedicalequipment.Duringthistime,theimprovementsincrystalgrowthandopticsdesignallowyellow,greenandorangeLEDsonlyaminorimprovementinbrightnessandefficiency.Thebasicstructureofthematerialremainedrelativelyunchanged.Aslaserdiodeswithoutputinthevisiblespectrumstartedtocommercializeinlate1980s,LEDdesignersusedsimilartechniquestoproducehigh-brightnessandhighreliabilityLEDs.ThisledtothedevelopmentofInGaAlP(indiumgalliumaluminumphosphide)visiblelightLEDs.ViaadjustingtheenergybandgapInGaAlPmaterialcanhavedifferentcoloroutput.Thus,green,yellow,orangeandredLEDscouldallbeproducedusingthesamebasictechnology.Also,lightoutputdegradationofInGaAlPmaterialissignificantlyimproved.ShujiNakamuraatNichiaChemicalIndustriesofJapanintroducedblueLEDsin1993.BlueLEDshavealwaysbeendifficulttomanufacturebecauseoftheirhighphotonenergies(>2.5eV)andrelativelyloweyesensitivity.Also,thetechnologytofabricatetheseLEDsisverydifferentandlessadvancedthanstandardLEDmaterials.Butblueisoneoftheprimarycolors(theothertwobeingredandgreen).Properlycombiningthered,green,andbluelightisessentialtoproducewhiteandfull-color.Thisprocessrequiressophisticatedsoftwareandhardwaredesigntoimplement.Inaddition,thebrightnesslevelislowandtheoveralllightoutputofeachRGBdiebeinguseddegradesatadifferentrateresultinginaneventualcolorunbalance.TheblueLEDsavailabletodayconsistofGaN(galliumnitride)andSiC(siliconcarbide)construction.TheblueLEDthatbecomesavailableinproductionquantitieshasresultinanentiregenerationofnewapplicationsthatincludetelecommunicationsproducts,automotiveapplications,trafficcontroldevices,andfull-colormessageboards.EvenLEDTVscansoonbecomecommerciallyavailable.Comparetoincandescentlight’s1000-handfluorescentlight’s8000-hlifespan,LEDshaveaverysignificantlylongerlifeof100,000h.Inadditiontotheirlonglife,LEDshavemanyadvantagesoverconventionallightsource.Theseadvantagesincludesmallsize,specificwavelength,lowthermaloutput,adjustablelightintensityandquality,aswellashighphotoelectricconversionefficiency.SuchadvantagesmakeLEDsperfectforsupportingplantgrowthincontrolledenvironmentsuchasplanttissuecultureroomandgrowthchamber.Table1isalistofsomecommontypesofLEDsascompiledfrom.Table1 SomecommontypesofLEDs. Peakwavelength(nm) Color MaterialandstructureofLEDs Substrate 730 Far-red GaAs GaP 700 Red GaP:Zn-O GaP 660 Red GaAl0.35As GaAs 650 Red GaAs0.6P GaAs 630 Orange–red GaAs0.35P0.65:N GaP 610 Orange GaAs0.25P0.75:N GaP 590 Yellow GaAs0.15P0.85:N GaP 585 Yellow GaAs0.14P0.86:N GaAs 565 Green GaP:N GaP 450 Blue GaN/SiC –3.ColorratiosandphotosynthesisThechlorophyllmoleculesinplantsinitiatephotosynthesisbycapturinglightenergyandconvertingitintochemicalenergytohelptransformingwaterandcarbondioxideintotheprimarynutrientforlivingbeings.Thegeneralizedequationforthephotosyntheticprocessisgivenas:CO2+H2O—light—>（CH2O）+O2where(CH2O)isthechemicalenergybuildingblockforthesynthesisofplantcomponents.Chlorophyllmoleculesabsorbblueandredwavelengthsmostefficiently.Thegreenandyellowwavelengthsarereflectedortransmittedandthusarenotasimportantinthephotosyntheticprocess.Thatmeanslimittheamountofcolorgiventotheplantsandstillhavethemgrowaswellaswithwhitelight.So,thereisnoneedtodevoteenergytogreenlightwhenenergycostsareaconcern,whichisusuallythecaseinspacetravel.TheLEDsenableresearcherstoeliminateotherwavelengthsfoundwithinnormalwhitelight,thusreducingtheamountofenergyrequiredtopowertheplantgrowthlamps.Theplantsgrownormallyandtastethesameasthoseraisedinwhitelight.Redandbluelightbestdrivephotosyntheticmetabolism.Theselightqualitiesareparticularlyefficientinimprovingthedevelopmentalcharacteristicsassociatedwithautotrophicgrowthhabits.Nevertheless,photosyntheticallyinefficientlightqualitiesalsoconveyimportantenvironmentalinformationtoadevelopingplant.Forexample,far-redlightreversestheeffectofphytochromes,leadingtochangesingeneexpression,plantarchitecture,andreproductiveresponses.Inaddition,photoperiod(theadjustmentoflightanddarkperiods)andlightquality(theadjustmentofred,blueandfar-redlightratio)alsohavedecisiveimpactsonphotomorphogenesis.ThesuperimposedpatternofluminescencespectrumofblueLED(450–470nm)andthatofredLED(650–665nm)correspondswelltolightabsorptionspectrumofcarotenoidsandchlorophyll.VariousplantcultivationexperimentsarepossiblewhenthesetwokindsofLEDareusedwiththeadditionoffar-redradiation(730–735nm)asthelightsource.AlongthelineoftheLEDtechnologyadvancement,LEDsbecomeaprominentlightsourceforintensiveplantculturesystemsandphotobiologicalresearches.Thecultivationexperimentswhichusesuchlightsourcesarebecomingincreasinglyactive.PlantphysiologyandplantcultivationresearchesusingLEDsstartedtopeakin1990sandbecomeinevitableinthenewmillennium.ThoseresearcheshaveconfirmedthatLEDsaresuitableforcultivationofavarietyofalgae,crop,flower,fruit,andvegetable.Someofthepioneeringresearchesarereviewedinthefollowings.Bulaetal.haveshownthatgrowinglettucewithredLEDsincombinationwithbluetubularfluorescentlamp(TFL)ispossible.Hoeneckeetal.haveverifiedthenecessityofbluephotonsforlettuceseedlingsproductionbyusingredLEDswithblueTFL.AsthepriceofbothblueandredLEDshavedroppedandthebrightnessincreasedsignificantly,theresearchfindingshavebeenabletobeappliedincommercialproduction.AsreportedbyAgenceFrancePress,CosmoPlantCo.,inFukuroi,JapanhasdevelopedaredLED-basedgrowthprocessthatusesonly60%ofelectricitythanafluorescentlightingbasedone.Tennessenetal.havecomparedphotosynthesisfromleavesofkudzu(Puerarialobata)enclosedinaleafchamberilluminatedbyLEDsversusbyaxenonarclamp.TheresponsesofphotosynthesistoCO2aresimilarundertheLEDandxenonarclampsatequalphotosyntheticirradiance.ThereisnostatisticalsignificantdifferencebetweenthewhitelightandredlightmeasurementsinhighCO2.Someleavesexhibitedfeedbackinhibitionofphotosynthesiswhichisequallyevidentunderirradiationofeitherlamptype.Theresultssuggestthatphotosynthesisresearchincludingelectrontransport,carbonmetabolismandtracegasemissionstudiesshouldbenefitgreatlyfromtheincreasedreliability,repeatabilityandportabilityofaphotosynthesislampbasedonLEDs.Okamotoetal.haveinvestigatedtheeffectsofdifferentratiosofredandblue(red/blue)photosyntheticphotonfluxdensity(PPFD)levelsonthegrowthandmorphogenesisoflettuceseedlings.TheyhavefoundthatthelettucestemlengthdecreasessignificantlywithanincreaseinthebluePPFD.TheresearchhasalsoidentifiedtherespectivePPFDratiothat(1)accelerateslettuceseedlings’stemelongation,(2)maximizesthewholeplantdryweight,(3)acceleratesthegrowthofwholeplants,and(4)maximizesthedryweightsofrootsandstems.Photosynthesisdoesnotneedtotakeplaceincontinuouslight.ThesolidstatenatureallowsLEDstoproducesufficientphotonfluxesandcanbeturnedfullyonandoffrapidly(200ns),whichisnoteasilyachievablewithotherlightsources.Thisrapidon–offfeaturehasmadeLEDsanexcellentlightsourceforphotosynthesisresearchsuchaspulsedlightingforthestudyofphotosyntheticelectrontransportdetails.Theoff/darkperiodmeansadditionalenergysavingontopoftheLEDs’lowpowerconsumption.4.LEDsandindoorplantcultivation4.1.PlanttissuecultureandgrowthTissueculture(TC),usedwidelyinplantscienceandanumberofcommercialapplications,isthegrowthofplanttissuesorcellswithinacontrolledenvironment,anidealgrowthenvironmentthatisfreefromthecontaminationofmicroorganismsandothercontaminants.AcontrolledenvironmentforPTCusuallymeansfilteredair,steadytemperature,stablelightsources,andspeciallyformulatedgrowthmedia(suchasbrothoragar).Micropropagation,aformofplanttissueculture(PTC),isusedwidelyinforestryandfloriculture.Itisalsousedforconservingrareorendangeredplantspecies.OtherusesofPTCinclude:1short-termtestingofgeneticconstructionsorregenerationoftransgenicplants,2crossbreedingdistantlyrelatedspeciesandregenerationofthenovelhybrid,3screeningcellsforadvantageouscharacters(e.g.herbicideresistance/tolerance),4embryorescue(i.e.tocross-pollinatedistantlyrelatedspeciesandthentissueculturetheresultingembryowhichwouldnormallydie),5large-scalegrowthofplantcellsinliquidcultureinsidebioreactorsasasourceofsecondaryproducts(likerecombinantproteinsusedasbiopharmaceuticals).6productionofdoubledmonoploidplantsfromhaploidculturestoachievehomozygouslinesmorerapidlyinbreedingprograms(usuallybytreatmentwithcolchicinewhichcausesdoublingofthechromosomenumber).Tissuecultureandgrowthroomindustrieshavelongbeenusingartificiallightsourcesforproduction.TheselightsourcesincludeTFL,highpressuresodiumlamp(HPS),metalhalidelamp(MHL)andincandescentlamp,etc.Amongthem,TFLhasbeenthemostpopularintissuecultureandgrowthroomindustries.However,theuseofTFLconsumes65%ofthetotalelectricityinatissueculturelab.Thatisthehighestnon-laborcosts.Asaresult,theseindustriescontinuouslyseekformoreefficientlightsources.Thedevelopmentofhigh-brightnessLEDhasmadeLEDapromisinglightsourceforplantgrowthincontrolledenvironments.Nhutetal.haveculturedstrawberryplantletsunderdifferentbluetoredLEDratiosaswellasirradiationlevelsandcompareditsgrowthtothatunderplantgrowthfluorescent.TheresultssuggestthataculturesystemusingLEDisadvantageousforthemicropropagationofstrawberryplantlets.ThestudyalsodemonstratesthattheLEDlightsourceforinvitrocultureofplantletscontributestoanimprovedgrowthoftheplantsinacclimatization.Brownetal.havemeasuredthegrowthanddrymatterpartitioningof‘HungarianWax’pepper(CapsicumannuumL.)plantsgrownunderredLEDscomparedwithsimilarplantsgrownunderredLEDswithsupplementalblueorfar-redradiation.PepperbiomassreduceswhengrownunderredLEDswithoutbluewavelengthscomparedtoplantsgrownundersupplementalbluefluorescentlamps.Theadditionoffar-redradiationresultsintallerplantswithgreaterstemmassthanredLEDsalone.Fewerleavesdevelopedunderredorredplusfar-redradiationthanwithlampsproducingbluewavelengths.Theresultsoftheirresearchindicatethatwithpropercombinationofotherwavelengths,redLEDsmaybesuitableforthecultureofplantsintightlycontrolledenvironments.4.2.SpaceagricultureBecausere-supplyisnotanoption,plantsaretheonlyoptionstogenerateenoughfood,waterandoxygentohelpmakefutureexplorersself-sufficientatspacecoloniesonthemoon,Marsorbeyond.Inordertouseplants,theremustbealightsource.StandardlightsourcesthatusedinhomesandingreenhousesandingrowthchambersforcontrolledagriculturehereonEartharenotefficientenoughforspacetravel.WhileahumanexpeditionoutsideEarthorbitstillmightbeyearsaway,thespacefarmingeffortsareaimedatdevelopingpromisingartificiallightsources.LEDs,becauseoftheirsafety,smallmassandvolume,wavelengthspecificity,andlongevity,havelongbeenproposedasaprimarylightsourceforspace-baseplantresearchchamberorbioregenerativelifesupportsystems.InfraredLEDsthatareusedinremotecontrolsdeviceshaveotheruses.Johnsonetal.haveirradiatedoat(AvenasativacvSeger)seedlingswithinfrared(IR)LEDradiationpassedthroughavisible-light-blockingfilter.Theirradiatedseedlingsexhibiteddifferencesingrowthandgravitropicresponsewhencomparedtoseedlingsgrownindarknessatthesametemperature.ThissuggeststhattheoatseedlingsareabletodetectIRLEDradiation.Thesefindingsalsoexpandthedefinedrangeofwavelengthsinvolvedinradiation–gravity(light–gravity)interactionstoincludewavelengthsintheIRregionofthespectrum.Goinsetal.growwheatunderredLEDsandcomparethemtothewheatgrownunder(1)whitefluorescentlampsand(2)redLEDssupplementedwithbluelightfrombluefluorescentlamps.TheresultsshowthatwheatgrownunderredLEDsalonedisplayedfewersubtillersandalowerseedyieldcomparedtothosegrownunderwhitelight.WheatgrownunderredLEDs+10%BFlighthadcomparableshootdrymatteraccumulationandseedyieldrelativetothosegrownunderwhitelight.TheseresultsindicatethatwheatcancompleteitslifecycleunderredLEDsalone,butlargerplantsandgreateramountsofseedareproducedinthepresenceofredLEDssupplementedwithaquantityofbluelight.TheresearchofGoinsandhisteamcontinuesinplantgrowthchambersthesizeofwalk-inrefrigeratorswithblueandredLEDstogrowsaladplantssuchaslettuceandradishes.Theyhopetheplantgrowthchamberwouldenablespacestationstafftogrowandharvestsaladgreens,herbsandvegetablesduringtypicalfourmonthtoursontheoutpost.4.3.AlgacultureAlgaculture,referstothefarmingofspeciesofalgae,hasbeenagreatsourceforfeedstock,bioplastics,pharmaceuticals,algaefuel,pollutioncontrol,aswellasdyesandcolorants.Algaculturealsoprovideshopefulfuturefoodsources.Algaecanbegrowninaphotobioreactor(PBR),abioreactorwhichincorporatessometypeoflightsource.APBRisaclosedsystem,asopposedtoanopentankorpond.Allessentialnutrientsmustbeintroducedintothesystemtoallowalgaetogrowandbecultivated.APBRextendsthegrowingseasonandallowsgrowingmorespecies.Thedevicealsoallowsthechosenspeciestostaydominant.APBRcaneitherbeoperatedin‘‘batchmode’’or‘‘continuousmode’’inwhichacontinuousstreamofsterilizedwaterthatcontainsair,nutrients,andcarbondioxideisintroduced.Asthealgaegrows,excesscultureoverflowsandisharvested.Whenthealgaegrowandmultiply,theybecomesodensethattheyblocklightfromreachingdeeperintothewater.Asaresult,lightonlypenetratesthetop7–10cmofthewaterinmostalgalcultivationsystems.Algaeonlyneedabout1/10theamountofdirectsunlight.So,directsunlightisoftentoostrongforalgae.Ameansofsupplyinglighttoalgaeattherightconcentrationistoplacethelightsourceinthesystemdirectly.Matthijsetal.haveusedLEDsasthesolelightsourceincontinuouscultureofthegreenalga(Chlorellapyrenoidosa).TheresearchfoundthelightoutputoftheLEDpanelincontinuousoperationsufficienttosupportmaximalgrowth.Flashoperationat5-pspulse‘‘on’’durationbetweendarkperiodsofupto45pswouldstillsustainnearmaximumgrowth.Whilelongerdarkperiodstendtocutthegrowthrate,thelightfluxdecreaseresultingfromsuchoperationdoesnotreducethegrowthasmuchasthatofthesimilarfluxdecreaseincontinuousoperation.TheirresearchconcludesthattheuseofflashingLEDs(whichmeansintermittentlight)inindooralgalcultureyieldedamajorgaininenergyeconomycomparingtofluorescentlightsources.Anadditionaladvantageisthatheatwastelossesaremuchsmaller.ThemostinterestingdiscoveryofthisstudymaybethataddingbluelighttotheredLEDlightdidnotchangethegrowthproperties.Inordertotakeadvantageofthebiotechnologicalpotentialofalgae,LeeandPalssonhavecalculatedtheoreticalvaluesofgasmasstransferrequirementsandlightintensityrequirementstosupporthigh-densityalgalculturesforthe680nmmonochromaticredlightfromLEDasalightsource.TheyhavealsodesignedaprototypePBRbasedonthesecalculations.Usingon-lineultrafiltrationtoperiodicallyprovidefreshmedium,theseresearchershaveachievedacellconcentrationofmorethan2×109cells/ml(morethan6.6%,vol/vol),celldoublingtimesaslowas12h,andanoxygenproductionrateashighas10mmoloxygen/lculture/h.ThisresearchindicatesthatthedevelopmentofasmallLED-basedalgalphotobioreactorsiseconomicallyachievable.AnotherresearchofalgaeviaLEDsisconductedbyNedbaletal.TheirresearchisastudyoflightfluctuationeffectsonavarietyofalgaeindiluteculturesusingarraysofredLEDstoprovideintermittentandequivalentcontinuouslightinsmall-size(30ml)bioreactors.Theresultsendorsethatthealgaegrowthratesincertaincalculatedintermittentlightcanbehigherthanthegrowthrateintheequivalentcontinuouslight.YanagiandOkamotohasgrownfivespinachplantsundertheredLEDsandanotherfiveunder40Wplantgrowthfluorescentlampsatthesamelightintensityof125mmol/m2/s.ThedrymatterproductionundertheLEDsisslightlylessthanthatunderthefluorescentlamps.TheplantleafareaundertheredLEDsisalsosmallerthanthatunderthefluorescentlamps.Nevertheless,theyreachaconclusionthatLEDscanqualifyasanartificiallig