外文翻譯-溫差發(fā)電技術(shù)的研究進(jìn)展及現(xiàn)狀

Thermoelectricpowergeneration,alsocalledthermoelectricpowergeneration,isakindofgreenenvironmentalprotection.Thethermoelectricpowergenerationtechnologyhastheadvantagesofsimplestructure,stronganddurable,nomovingparts,nonoise,longservicelife,etc..Canmakereasonableuseofsolarenergy,geothermalenergy,industrialwasteheatandlowgradeenergyintoelectricity.Theresearchofthermoelectricpowergenerationtechnologybeganin1940s.Becauseofitssignificantadvantages,thermoelectricpowergenerationinaviation,militaryandotherfieldshasbeenwidelyused,theUnitedStates,formerSovietUnionhasdevelopedathousandsofradioisotopeornuclearreactortemperaturedifferencegeneratorusedasemptyasked,marineequipmentofpowersupply.Withtheincreasingdepletionoffossilenergy,theUnitedStates,Japan,theEuropeanUnionandotherdevelopedcountriespaymoreattentiontotheresearchofthermoelectricpowergenerationtechnologyinthecivilfield,andhasmadeconsiderableprogress.Researchindomesticthermalpowergeneration,mainlyinelectricaltheoryandthermoelectricmaterialsbyresearch,aimedattemperaturehairappliancesoptimizationandprovidetheoreticalguidanceforthepreparationofthermoelectricmaterialswithexcellentproperties,althoughChinaistheworldlargestsemiconductorthermoelectricdeviceoutputcountry,butinthetemperaturedifferencehairappliancesintegrateddesignandapplicationresearchisstillverylack.Therefore,thestudyofthermoelectricpowergenerationhasaveryrealisticsignificance.Isintroducedinthispaperprincipleofthermoelectrictechnology,reviewstheresearchprogressandstatusquoofdomesticandforeign,tocommoncommercialthermoelectricmoduleasanexample,thepowergenerationefficiencyofthermoelectricpowergenerationinthepresenceoflow,thermoelectricitycomponentandshortservicelife,reliabilityareanalyzed,andcountermeasuresareputforward.Withtheimprovementoftheperformanceofthermoelectricmaterialsandtheincreaseofthereliabilityofthermoelectriccomponents,theapplicationofthermoelectricpowergenerationhasabroadprospect.1workingprincipleCompletethetemperaturedifference,sothathightemperaturethermoelectricpowerisbasedonthermoelectricmaterialSeebeckeffectdevelopedapowergenerationtechnology,thePtypeandNtypetwokindofdifferenttypesofthermoelectricmaterials(Ptypeholerichmaterials,Ntypeiselectronrichmaterial)isconnectedtotheformationofaPNjunction,isplacedinahightemperaturestate,andtheotherendisformedatlowtemperature,duetothethermalexcitation,pifthereexistsalocallyconnected)typematerialendhole(electron)concentrationishigherthanthatofthelowtemperatureend,sointhisconcentrationgradientdrivenBu,holesandelectronstothelowtemperaturesidediffusion,resultingintheformationofelectricpotentialthermoelectricmaterialsthroughthelowtemperatureendofthehightemperatureendoftheinputofheatenergydirectlyintoelectricalenergy.APNjunctionalone,electromotiveforcecanbeformedisverysmall,andifsomanyseriesofPNjunctionCome,cangetenoughhighvoltage,becomeathermoelectricpowerplant2domesticandinternationalthermoelectricpowergenerationtechnologyresearchprogress2.1researchprogressinforeigncountriesSincethediscoveryoftheSeebeckeffectsince1821Seebeck,foreignthethermoelectricgenerationofalargenumberofstudies,in1947,firstthethermoelectricgeneratoravailable,efficiencyisonly1.5%.In1953,Loffeacademicianresearchteamsuccessfullydevelopedtheuseofcoaloillamps,tractorheatasaheatsourceofthermoelectricpowerplant,intheuseofelectricitydifficultareasforsmallpowersupply.Inthesixtiesofthe20thcentury,somematerialswithgoodthermoelectricproperties,theresearchupsurgeofthermoelectricpowergenerationreachedapeak,especiallytheformerSovietUnionandtheUnitedStates,duetothepromotionofnationaldefense,militaryandotherspecialindustry,applicationanddevelopmentofthermoelectricgenerationtechnologyrapidly.Bytheendof1960s,theformerSovietUnionhasmademorethan1000radioactiveisotopethermoelectricgenerator(RTG),whichiswidelyusedinsatellitepowersupply,beaconandnavigationmark,anditsaverageservicelifeismorethan10years.TheUnitedStatesisalsounwillingtolagbehind,anditsdevelopmentofthelongestRTGworkQuestionhasbeenover30years.June1961U.S.SNAP-3Aenergysystemsputintouse,theoutputpowerof2.7W,powergenerationefficiencyof5.1%.TheRTG}outputpower,whichwasusedonthelaunchofJupiterandSaturnin1977,hasreached155W.Inearly1980s,theUnitedStatescompletedthedevelopmentofthe500-1000Wmilitarythermoelectricgenerator,andinthelate80'stoenterthearmyequipment.Withtheenergycrisisandenvironmentalpollution,peoplebegantopayattentiontothevalueofthermoelectricpowergenerationinwasteheatutilization,manycountrieshavedevelopedthermoelectrictechnologyasamediumandlong-termenergydevelopmentplan.Japanlaunchedaseriesofto"solidwastecombustionenergyrecoveryresearchprogram"inthetitleofthegovernmentplanisstudiedforthesolidwasteincinerationfurnacewasteheatpowergenerationtechnology,combiningtheturbinesandthermoelectricgenerator,toachievemaximumutilizationoftheheatofthedifferentscalegarbageincineration.2003NovemberU.S.DepartmentofEnergyannouncedfundedPacificNorthwestNationalLaboratory,MichiganTechnologyUniversityandotherunits,focusingontheirresearchinhighperformancethermoelectricmaterialsandapplicationtechnology,especiallytheuseofindustrialwasteheat.Inrecentyears,theutilizationofthelowgradeheatsourcehasbecomethemaindirectionoftheresearchonthetechnologyofthermalpowergeneration.Maneewan,suchastheuseofsteelplateplacedontheroofofthesolarcollectortoabsorbtheheatandtheenvironmentofthetemperaturedifferencebetweenpowergeneration,todrivetheaxialflowwind})Ltoguidethenaturalconvectionoftheroofair,soastocooltheroof.Ridaandsoon,thethermalsideofthethermoelectricgeneratorisconnectedwiththeouterwallofthecookingstoveinthecountry,andthecoldendisarrangedintheair,andthetemperatureofthefurnacewallandtheenvironmentareusedtogenerateelectricity,andtheoutputpoweris4.2W.HASEBEetal.Thesummerhightemperaturesurfaceastheheatsource,heatexchangetubeforthecollector.By19groupsofthermoelectriccomponents.Intheheatpipeliquidflowrateis0.7L/min,outputpowerof3.6wthacher,fundedbytheU.S.DepartmentofenergyandNewYorkStateEnergyResearchanddevelopmentauthorityinthedevelopmentofvehicleexhaustwasteheatpowergenerationsystem,theuseofthegroupof20hz-20thermoelectricmodule,thermoelectricmaterialsforBitebasedmaterials,vehiclespeedof112km/h,maximumtemperaturedifference174DEGC,maximumoutputpowerof255W,2006,bsstscientistsandBMWjointlyannounced,commercialvehicletemperaturedifferencegeneratorwillbeputintooperationin2013.Douglasandsoonthedynamicchangeoftheheatsource,thedesignofmultimoduleInteractionLoopthermoelectricgenerator,underthesameheatsource,themaximumoutputpowerincreasedby25%.2.2domesticresearchprogressDomesticresearchonthermoelectricpowergenerationisrelativelylate,anditismainlyfocusedontheresearchofthetheoryandthepreparationofthermoelectricmaterials.ChenJincanresearchgroupfrom1980sbegantostudythebasictheoryofthermoelectricgenerator,thethermoelectricpropertiesoftheoptimizationandanalysis,getalotofmeaningfulresults[no.QuJianetal.LiYudongetal.Analysisoftheperformanceofthelowtemperaturedifferencegeneratorfromthepointofviewofexergy.JiaLeietal.TheinfluenceofThompsonGeontheoutputpowerofthelowtemperatureandlargetemperaturedifferenceconditionscannotbeignored.JiaYangEtc.atemperaturethermoelectriccouplinganalysismodel,tothenumericalcalculationmethodanalysisthethermoelectricmaterialparametersandtheirvariationonelectricalcharacteristicsof,drawtheconclusion,materialthermalconductivity,electricalresistivityandSeebeckcoefficientonthegeneratorefficiencyofconversionarenonlinear,whichinfluencecoefficientofthermalconductivityofthemostobvious.DePeng,andanalysisthethermoelectricthermalenvironment,looploadresistanceparametersandthermoelectricmonomersofconnectionwaysofoperatingperformanceoftheelectricappliance,itisconcludedthattoimprovethermoelectricgeneratoratthehotendheatfluxorincreasedcoldendoftheheattransfercoefficientcanincreasetheelectricaloutputpowerandtheefficiencyofthermoelectricconversionofconclusion.SuJingfangstudiedthesystem.Andtheenvironment,systemandsystemoffluxrelation,propertiesofthesystemtomakeoptimizationbasedthermoelectricgeneratoroptimizationdesignmodel,andusingVB6.0(MicrosoftVisualBasic6.0)languageasadevelopmenttool,ActiveXDataObjectAccessdatabase,thepreparationofthethermoelectricgeneratordesignsoftware.QianWeiqiangthroughstudyontheelectricalpropertiesoflowgradeheatsourceofsmallsemiconductortemperaturedifference,summarizestheelectromotiveforceandinternalresistanceandtransmissionpowerparameterchangeswiththeexternalcircuit,temperature,generatingmodulegeometryfactors.Wealsostudytheseriesandparallelconnectionthermoelectricmoduleperformance.Fromthepointofviewofnon-equilibriumthermodynamics,themodelofthelowtemperaturedifferenceofthesinglelayerandmultipleelectricappliancesinthelowtemperatureandlowtemperaturestabilitywasestablished.StudyonthermoelectricgeneratorintheinternalstructureandexternalforthemovementofthethermalconditionsBu,combinedwithexperiment,itisconcludedthatthebestmatchingcoefficients,poweroutputandefficiencyarewiththemaximumtemperaturedifferenceapproximatelinearly,andpointsoutthepowergenerationefficiencyislowintheroottherelyontheimprovementofthematerialproperties.Justeastoftheoreticalanalysisandexperimentalstudycombinedbysimulatingthetankventtubeneartheareaofrefrigeratingcondition,bycoolingconditionevaluationofinfraredstealtheffect,itisconcludedthattotankexhaustwasteheatastheheatsourcewillbetheapplicationofthermoelectrictechnologytothetanks,infraredstealthfeasibleconclusion.3.1generationefficiencyAtpresent,theefficiencyofthermoelectricpowergenerationisgenerally5%-7%,farlessthan40%ofthermalpowergeneration.Themainreasonisthattheperformanceofthermoelectricmaterialsisnotgood,ontheotherhandisthematchingofelectricalappliancesfactory.3.1.1thermoelectricmaterialsThermoelectricmaterials,asthecorepartofthermoelectricdevices,directlydeterminetheperformanceofthedevice.TheoptimalvalueofZTisthemostimportantparametertomeasuretheperformanceofthermoelectricmaterials.ThehighertheZTvalue,thebetterthethermoelectricpropertiesofthematerials,thehighertheenergyconversionefficiency.Bi2T3;roomtemperatureZTvalueofabout1,isthemostwidelyusedthermoelectricmaterials.ButthethermoelectricpowergenerationefficiencyofBi2T3materialsisstilllessthan10%.IftheZTvalueofthematerialcanbeincreasedtoabout3,thedifferenceintemperaturewillbecomparabletothatoftheconventionalpowergeneration.Therefore,peopleareactivelylookingforanddevelopmentofhighmeritofnewthermoelectricmaterials,thepresentresearchhotspots:cobaltbasedoxidethermoelectricmaterials,quasicrystalmaterials,superlatticethermoelectricmaterials,nanothermoelectricmaterials.TerasakidiscoveredforthefirsttimeNaCo2O4singlecrystalatroomtemperatureBuhasahigherSeebeckcoefficient,lowresistivityandlowthermalconductivity,thiscausedpeople'sattention,butNaCo2O4inairdeliquescentandmorethan1073Kvolatile,sopeoplelooktoanotherdrillbasedoxidesofCa-Co-Osystem.TheFunahashistudypredicts:Ca2Co2O5inT=873K,ZT=1.22.7.Quasicrystallinethermoelectricmaterialsin1984byShechtmanandotherfirstfoundthatinrecentyearscausedconcern.Thiskindofmaterialhasgoodthermodynamicstability,highresistivity,andhasanegativecoefficientofthermalconductivity,sotheconductiveperformanceisgood,andthethermalconductivityislow.AquasicrystallinethermoelectricmaterialwithZT=1.6atroomtemperaturewaspredicted.Thesuperlatticeisamultilayerheterogeneousstructureformedbytheperiodicalternatinggrowthoftwokindsofsemiconductorsinglecrystalfilms,andeachlayercontainsseveralorevenseverallayers.Duetothespecialstructureandsemiconductorsuperlatticeelectrons(orholes)energywillappearnewquantization,resultingintheincreaseofthedensityofStatesandthereforesuperlatticematerialwithmanynewfeatures.VenkatasubramanianandothermetalorganiccompoundsGasphasedeposition(MOCVE)methodtoprepareBi-Tebasedalloyfilm,ZTvaluereached2.4300K.DresselhausofBinanowiresandquantumwellsystemafteralargenumberofstudiespredictedthatthequantumconfinementeffectcanbeobtainedbysuperlatticeZTvalueofmorethan3ofthematerial.Nanothermoelectricmaterialsisanotherhotresearchtopicinthefieldofthermoelectricmaterials,andtheachievementsareoutstandinginthefieldofZhejiangUniversity.ZhaoXinbingandotherresearchfoundthatthetraditionalBi-Tebasedthermoelectricmaterialstoadd15%containingBi2T3;nanotubepowder,canmakethethermoelectricpropertiesofmaterialsincreasedbyabout20%.Cao,ZT=1.28(Bi,Sb)2Te3wereobtainedbyhydrothermalsynthesis.ZHAOandsoonthroughthenanometerpowderdoping,theZTvalueispreparedtoexceed1.5oftheBi2Te3-Sb2Te3andGeTe-AgSbTe2nanostructurematerials.3.1.2matchingproblemOutputpowerandpowergenerationefficiencyofthermoelectricgeneratorandhightemperatureendtemperature(Th).Lowtemperature(Tc),thermoelectricpowergenerationcircuitcurrent(I),loadresistance(R),electricalresistance(R)andotherfactorsarecloselyrelated.Underdifferentconditions,thedifferenceoftheperformanceofthethermoelectricgeneratorisgreat.QuJianandotherapplicationsoffinitetimethermodynamictheorytoanalyzetheworkingperformanceofthermoelectricgenerator,andgettheconclusionthatthereisthebestparameterworkingarea.PanYuZhuo,suchastheuseofnonequilibriumthermodynamicsoptimizationcontroltheoryanalysisofthermoelectricmodel,numericalsimulationresultsshowthatthematchingundertheconditionoftheworkingparametersofoutputpowerandgeneratingefficiencycanbewereincreasedby39%and20%electricalthermaldesignisalsoaffectingpowergenerationefficiencyareimportantfactors.Inordertomaintainahightemperature,oftenincreasetheheatdissipationdevicegeneratorinlowtemperatureside,sothattheheatdissipationinatimelymanner.Cheinstudynotedthatwhenthedevicethermalresistanceisgreaterthanthemaximumresistanceoftheradiator,theradiatorwillsmallcandispersewalkingdevicegeneratesheat,andthereforethermoelectricgeneratormatchingthecoldendheatdissipationwayalsoaffecttheelectricalperformanceoftheimportantfactors.Atpresentthemainheatdissipationmethod:airandliquidcoolingandheattransformation.Aircoolingisdividedintonaturalandforcedaircooling.Naturalair-cooledheatexchangerisacertainshapeoffinradiator.Theheatresistanceisdirectlyrelatedtothefindensityandtheareaoftheradiator.Thethermoelectricarewidelyappliedintheelectricapplianceisforcedaircooling,radiator(heatsink)combinedwiththefan,coldendheatconductiontothelargerareaoffinwithforcedcoolingheatdissipationintotheair.Thethermalresistancedependsonthewindspeed,thegreaterthewindspeed,thesmallerthethermalresistance.Forcedaircoolingcaneffectivelyimprovetheheattransfercoefficientoftheheatsink,reducetheheatdissipationarea,andthestructureissimple,easytoimplement,soitiswidelyused.Duetoaunitofliquidheatcapacitywassignificantlylargerthanthatofthegas,andliquidcoolingthanair-cooledhasbettercoolingeffect.Studieshaveshownthatliquidcoolingforheattransfercoefficientthanthenaturalaircoolingof100to1000times,sizeonthermalresistancemainlyandliquidflowvelocity,flowislarge,thermalresistanceislow.Atpresent,theliquidcoolingmethodsmainlyincludeliquidjetcooling,microchannelliquidcoolingandmacrowatercooling.Phasechangeheatdissipationistousephasechangematerialphasechangetoabsorbheattoheat.Theheatdissipationmethodissuitablefortheapplicationoftheintermittentworkingsituation,andthemostresearchistheheatdissipationwithphasechangeheatsiphontube.TheresultsofEsartetshowthatthephasetransitionheatsiphoncanobviouslyimprovetheuniformityofheatfluxontheheattransfersurface,reducethethermalresistanceandheatdissipation.3.2reliabilityissuesTheexistenceof3.2.1andmechanicalstressTocommonsandwichtypethermoelectricmodule,forexample,toachievehighpowergenerationefficiency,usuallyrequirepowercomponentsinhotandcoldendformingalargertemperaturedifference,whichwillcausecoldendisconnectedattheendoftheshrinkageorthermalconnectingsheetexpansion,resultinginmechanicalstress.MechanicalstressontheexistenceoftherigidjointsorP,narmiseasytofracturemayeventuallyleadtothedamageofthethermocouple,soastoshortentheservicelifeofthethermoelectricmodule.Inordertoincreasetheresistance,thethicknessofthetransitionlayerissmallerthan0.3mm;(3)thematrixmaterialischanged.Duetoitshighstrength,goodthermalconductivityandlowprice,ithasbecomeoneofthemostwidelyusedmatrixmaterials.Butthehardnessoftheceramicpieceislarge,itiseasytocauseP,Npowerarmbroken.Iftherearesomeflexibleandcansupporttheroleofnewmaterialstoreplacetheceramicpieces,throughtheflexibilityofthematrixtoalleviatethemechanicalstress,willbeabletoeffectivelysolvetheproblemofelectricalarmfracture.3.2.2environmentalfactors(1)moisture.Thereareatleastthreekindsofmaterials,thermoelectricmaterials,solderandconnectingsheetmaterials.Theingressofmoisture,inthecoldjunctionnearthecondensation,formingprimarybatteries,thusproducedtheeffectofelectrolyticcorrosionatthejoint,leadsolderresistanceincreases,finalweldingheadwascompletelydamaged.Itisbettertomakethethermoelectriccomponentsworkinvacuumortoprotecttheinsulationmaterial;(2)hightemperature.Hightemperaturecandamagetheaccelerator.Thereasonistheoxidationandsublimationofthesolder,whichacceleratesthediffusionofcopperandotherimpuritiesintothethermoelectricmaterials.Therearereportsof300K,thediffusionrateofimpuritiesis10-6cm/simpuritydiffusioncausedbymaterialSeebeckcoefficientandtheelectricalconductivitydecreasesrapidly.Atpresent,thecommonlyusedsolutionisinthecopperconnectionpieceandtheelementendsurfacenickelplating,butthenickelplatingprocessisnotideal.4conclusionsDuetoitsuniqueadvantages,thethermoelectricpowergenerationtechnologyhasshownagoodapplicationprospectinaerospaceandmilitaryfields.Atthesametime,asakindofgreenenvironmentalprotection,theapplicationofthecivilfieldinrecentyearshasdevelopedrapidly.Althoughtheefficiencyofthermoelectricpowergenerationisgenerallylowerthan10%,butwiththeelectricalresearchanddevelopmentofnewhighperformancethermoelectricmaterialsandreliableperformanceofthetemperaturedifference,temperaturedifferencepowergenerationtechnologywillbemoregreatlyplaytheadvantageoftheuseoflowgradeenergy.Accordingtotheresearchprogressofthermalpowergenerationtechnologyathomeandabroad,theresearchprogresscanbecarriedoutfromthefollowingthreeaspects:(1)theproblemoflowthermoelectricpowerefficiencyisthefirstonetobreakthroughtheimprovementoftheperformanceofthermoelectricmaterials.Doping,crystalstructure,lowdimensional,superlatticestructureandnanotechnologycanefficientlyimprovethethermoelectricfigureofmerit,andthusbecomethedevelopmentdirectionofthermoelectricmaterials;(2)byANSYSnumericalsimulationandexperimentalstudyoncombinedapproach,ofthethermoelectricelectricalparametersoptimization.Atthesametimeonthelowtemperaturesideimplementationreasonablethermalmanagement,makethetemperaturedifferencegeneratorinthematchingconditions,isalsoanimportantwaytoimprovetheefficiencyofpowergeneration;(3)temperaturedifferencepowergenerationapplicationsincreasinglywidespread,asapartofthesystem,thermoelectricitycomponentreliabilityproblemscannotbeignored.Structuralimprovementcaneffectivelyreducethemechanicalstress,someoftheauxiliarymeasurescanreducetheimpactofenvironmentalfactors,buttherearestillmanyneedstoimprovethework.溫差發(fā)電技術(shù)的研究進(jìn)展及現(xiàn)狀溫差發(fā)電又叫熱電發(fā)電，是一種綠色環(huán)保的發(fā)電方式。溫差發(fā)電技術(shù)具有結(jié)構(gòu)簡(jiǎn)單，堅(jiān)固耐用，無(wú)運(yùn)動(dòng)部件，無(wú)噪聲，使用壽命長(zhǎng)等優(yōu)點(diǎn)?？梢院侠砝锰?yáng)能、地?zé)崮堋⒐I(yè)余熱廢熱等低品位能源轉(zhuǎn)化成電能。溫差發(fā)電技術(shù)的研究最早開始于20世紀(jì)40年代。由于其顯著的優(yōu)點(diǎn)，溫差發(fā)電在航空、軍事等領(lǐng)域得到了廣泛的應(yīng)用，美國(guó)，前蘇聯(lián)先后研發(fā)了數(shù)千個(gè)放射性同位素或核反應(yīng)堆溫差發(fā)電器用作空問(wèn)、海洋裝置的電源。隨著化石能源的日趨枯竭，美國(guó)、日本、歐盟等發(fā)達(dá)國(guó)家更加重視溫差發(fā)電技術(shù)在民用領(lǐng)域的研究，并取得了長(zhǎng)足的進(jìn)展。國(guó)內(nèi)溫差發(fā)電方面的研究，主要集中在發(fā)電器理論和熱電材料制備方面的研究，旨在為溫差發(fā)電器的優(yōu)化提供理論指導(dǎo)和制備性能優(yōu)良的熱電材料，雖然我國(guó)是世界上最大的半導(dǎo)體熱電器件輸出國(guó)，但是在溫差發(fā)電器綜合設(shè)計(jì)和應(yīng)用方面的研究還很欠缺，因此研究溫差發(fā)電有著非?，F(xiàn)實(shí)的意義。本文介紹了溫差發(fā)電技術(shù)的原理，回顧了國(guó)內(nèi)外的研究進(jìn)展及現(xiàn)狀，以常見的商用溫差電組件為例，對(duì)溫差發(fā)電中存在的發(fā)電效率低，溫差電組件使用壽命短，可靠性不高等問(wèn)題進(jìn)行了分析，并提出了應(yīng)對(duì)策略。隨著熱電材料性能的提高和溫差電組件可靠性的增加，溫差發(fā)電應(yīng)用前景廣闊。1工作原理溫差發(fā)電是基于熱電材料的塞貝克效應(yīng)發(fā)展起來(lái)的一種發(fā)電技術(shù)，將P型和N型兩種不同類型的熱電材料(P型是富空穴材料，N型是富電子材料)一端相連形成一個(gè)PN結(jié)，置于高溫狀態(tài)，另一端形成低溫，則由于熱激發(fā)作用，P<N)型材料高溫端空穴(電子)濃度高于低溫端，因此在這種濃度梯度的驅(qū)動(dòng)卜，空穴和電子就開始向低溫端擴(kuò)散，從而形成電動(dòng)勢(shì)，這樣熱電材料就通過(guò)高低溫端問(wèn)的溫差完成了將高溫端輸入的熱能直接轉(zhuǎn)化成電能的過(guò)程。單獨(dú)的一個(gè)PN結(jié)，可形成的電動(dòng)勢(shì)很小，而如果將很多這樣的PN結(jié)串聯(lián)起來(lái)，就可以得到足夠高的電壓，成為一個(gè)溫差發(fā)電器廠2國(guó)內(nèi)外溫差發(fā)電技術(shù)的研究進(jìn)展2.1國(guó)外研究進(jìn)展自1821年Seebeck發(fā)現(xiàn)塞貝克效應(yīng)以來(lái)，國(guó)外對(duì)溫差發(fā)電進(jìn)行了大量的研究，1947年，第一臺(tái)溫差發(fā)電器問(wèn)世，效率僅為1.5%。1953年，Loffe院士研究小組成功研制出利用煤油燈、拖拉機(jī)熱量作熱源的溫差發(fā)電裝置，在用電困難地區(qū)作小功率電源之用。20世紀(jì)60年代，一些具有較好熱電性能的材料，溫差發(fā)電的研究熱潮達(dá)到高峰，特別是前蘇聯(lián)和美國(guó)，由于國(guó)防、軍事等特殊行業(yè)的推動(dòng)，溫差發(fā)電技術(shù)的應(yīng)用發(fā)展迅速。到20世紀(jì)60年代末，前蘇聯(lián)先后制造了1000多個(gè)放射性同位素溫差發(fā)電器（RTG)，廣泛用于衛(wèi)星電源、燈塔和導(dǎo)航標(biāo)識(shí)，其平均使用壽命超過(guò)10年。美國(guó)也不甘落后，其開發(fā)的RTG最長(zhǎng)工作時(shí)問(wèn)已超30年。1961年6月美國(guó)SNAP-3A能源系統(tǒng)投入使用，輸出功率為2.7W，發(fā)電效率5.1%。1977年發(fā)射的木星、土星探測(cè)器上使用的RTG}輸出功率已達(dá)到155W。20世紀(jì)80年代初，美國(guó)又完成500-1000W軍用溫差發(fā)電機(jī)的研制，并于80年代末正式進(jìn)入部隊(duì)裝備。隨著能源危機(jī)和環(huán)境污染的加劇，人們開始關(guān)注溫差發(fā)電在廢余熱利用中的價(jià)值，很多國(guó)家已將發(fā)展溫差電技術(shù)列為中長(zhǎng)期能源開發(fā)計(jì)劃。日本開展了一系列以“固體廢物燃燒能源回收研究計(jì)劃”為題的政府計(jì)劃，研究用于固體廢物焚燒爐的廢熱發(fā)電技術(shù)，將透平機(jī)和溫差發(fā)電機(jī)結(jié)合，實(shí)現(xiàn)不同規(guī)模垃圾焚燒熱的最大利用。2003年11月美國(guó)能源部宣布資助太平洋西北國(guó)家實(shí)驗(yàn)室、密西根技術(shù)大學(xué)等單位，重點(diǎn)支持他們?cè)诟咝阅軣犭姴牧虾蛻?yīng)用技術(shù)方面的研究，特別是工業(yè)余熱廢熱的利用。近年來(lái)，對(duì)低品位熱源的利用成為溫差發(fā)電技術(shù)研究的大方向。Maneewan等利用置于屋頂?shù)匿摪逦仗?yáng)能集熱升溫與環(huán)境之問(wèn)的溫差發(fā)電，帶動(dòng)軸流風(fēng)})L引導(dǎo)屋頂空氣自然對(duì)流，從而給屋頂降溫。Rida等將溫差發(fā)電器熱端與該國(guó)一種做飯的火爐外壁連接，冷端置于空氣中，利用爐壁高溫與環(huán)境的溫差來(lái)發(fā)電，輸出功率達(dá)4.2W。Hasebe等利用夏日路面高溫做熱源，熱交換管為集熱器，采用19組溫差電組件，在熱管管內(nèi)液體流速為0.7L/min時(shí)，輸出功率3.6WThacher等在美國(guó)能源部和紐約州能源研究開發(fā)權(quán)利機(jī)構(gòu)資助下開發(fā)的汽車尾氣余熱發(fā)電系統(tǒng)，使用20組HZ-20溫差電組件，熱電材料為Bi-Te基材料，汽車時(shí)速112km/h時(shí)，最大溫差174℃，最大輸出功率255W，2006年，BSST的科學(xué)家和BMW聯(lián)合宣布，商用的汽車溫差發(fā)電器將于2013年投入使用。Douglas等針對(duì)熱源動(dòng)態(tài)變化情況，設(shè)計(jì)出多模塊交互回路溫差發(fā)電器，在相同熱源下，輸出功率最大提高25%。2.2國(guó)內(nèi)研究進(jìn)展國(guó)內(nèi)在溫差發(fā)電方面的研究起步相對(duì)較晚，主要集中在理論和熱電材料的制備等方面的研究。陳金燦課題組從20世紀(jì)80年代開始對(duì)溫差發(fā)電器的基礎(chǔ)理論進(jìn)行研究，對(duì)溫差發(fā)電器的性能進(jìn)行優(yōu)化分析，得到很多有意義的成果[no。屈健等李玉東等提出從火用的角度對(duì)低溫差下發(fā)電器的工作性能進(jìn)行分析。賈磊等提出低溫及大溫差工況下湯姆遜熱對(duì)輸出功率的影響不可忽略的觀點(diǎn)。賈陽(yáng)等建立溫差發(fā)電器熱電禍合分析模型，以數(shù)值計(jì)算的方法分析了熱電材料物性參數(shù)及其變化對(duì)發(fā)電器工作特性的影響，得出結(jié)論，材料的導(dǎo)熱系數(shù)、電阻率及塞貝克系數(shù)對(duì)發(fā)電器轉(zhuǎn)換效率的影響均為非線性，其中導(dǎo)熱系數(shù)的影響最明顯。德鵬等分析了溫差發(fā)電器的熱環(huán)境、回路中負(fù)載電阻等參數(shù)及溫差電單體對(duì)的連接方式對(duì)發(fā)電器工作性能的影響，得出提高溫差發(fā)電器熱端加熱熱流或增加冷端的換熱系數(shù)均能提高發(fā)電器的輸出功率及熱電轉(zhuǎn)換效率的結(jié)論。蘇景芳研究了系統(tǒng)與環(huán)境，系統(tǒng)與系統(tǒng)之問(wèn)的熱流關(guān)系，對(duì)系統(tǒng)的性能特性作出優(yōu)化，建立溫差發(fā)電器優(yōu)化設(shè)計(jì)模型，同時(shí)以VB6.0(Mi-crosoftVisualBasic6.0)語(yǔ)言作為開發(fā)工具，ActiveX數(shù)據(jù)對(duì)象訪問(wèn)數(shù)據(jù)庫(kù)，編寫了溫差發(fā)電器設(shè)計(jì)軟件。錢衛(wèi)強(qiáng)通過(guò)對(duì)低品位熱源半導(dǎo)體小溫差發(fā)電器性能的研究，總結(jié)了電動(dòng)勢(shì)、內(nèi)阻及輸功率等參數(shù)隨外電路、溫度、發(fā)電組件幾何尺寸等因素的變化規(guī)律，另外研究了串、并聯(lián)情況下溫差電組件的性能。李偉江從非平衡熱力學(xué)角度出發(fā)，建立單層多電偶發(fā)電器在低溫差下穩(wěn)定工作的模型。研究溫差發(fā)電器在內(nèi)部結(jié)構(gòu)和外部換熱條件變化情況下的運(yùn)行規(guī)律，與實(shí)驗(yàn)相結(jié)合，得出最佳匹配系數(shù)下，輸出功率和發(fā)電效率均隨最大溫差近似呈線性變化，同時(shí)指出解決發(fā)電效率低的問(wèn)題根本上依靠的是材料性能的改善。剛現(xiàn)東理論分析和實(shí)驗(yàn)研究相結(jié)合，通過(guò)模擬坦克排氣筒附近區(qū)域制冷狀況，由降溫情況評(píng)估紅外隱身效果，得出以坦克尾氣余熱為熱源將溫差電技術(shù)應(yīng)用于坦克紅外隱身完全可行的結(jié)論。3.1發(fā)電效率目前，溫差發(fā)電的效率一般為5%-7%，遠(yuǎn)低于火力發(fā)電的40%。最主要的原因是熱電材料性能不理想，另一方面是發(fā)電器的匹配問(wèn)題廠。3.1.1熱電材料的限制熱電材料作為熱電器件的核心部分，性能的好壞直接決定器件效能的優(yōu)劣。優(yōu)值ZT是衡量熱電材料性能最重要的參數(shù)。ZT值越高，材料的熱電性能越好，能量轉(zhuǎn)換效率越高。Bi2T3;室溫下ZT值1左右，是使用最廣泛的熱電材料。但是以;Bi2T3材料制作的溫差發(fā)電器發(fā)電效率依然低于10％。如果能把材料的ZT值提高到3左右，溫差發(fā)電將可以與傳統(tǒng)的發(fā)電方式相媲美。為此，人們積極尋找和開發(fā)具有較高優(yōu)值的新型熱電材料，目前的研究熱點(diǎn)有:鉆基氧化物熱電材料、準(zhǔn)晶體材料、超晶格薄膜熱電材料、納米熱電材料等。Terasaki等首次發(fā)現(xiàn)NaCo2O4單晶在室溫卜具有較高的Seebeck系數(shù)，較低的電阻率和較低的熱導(dǎo)率，為此引起人們的關(guān)注，但是NaCo2O4在空氣中易潮解且超過(guò)1073K時(shí)易揮發(fā)，所以人們把目光轉(zhuǎn)向另一種鉆基氧化物Ca-Co-O系。Funahashi的研究預(yù)測(cè):Ca2Co2O5在T≥873K時(shí)，ZT=1.2一2.7。準(zhǔn)晶體熱電材料1984年由Shechtman等首次發(fā)現(xiàn)，近年來(lái)引起關(guān)注。這種材料熱力學(xué)穩(wěn)定性好，電阻率高，具有負(fù)的導(dǎo)熱系數(shù)，故導(dǎo)電性能好，導(dǎo)熱性能低。有研究預(yù)言室溫下可得到ZT=1.6的準(zhǔn)晶體熱電材料。超晶格是由兩種材料的半導(dǎo)體單晶薄膜周期性交替生長(zhǎng)形成的多層異質(zhì)結(jié)構(gòu)，每層薄膜含幾個(gè)以至幾}一個(gè)原子層。由于這種特殊結(jié)構(gòu)，半導(dǎo)體超晶格中的電子(或空穴)能量將出現(xiàn)新的量子化，進(jìn)而引起態(tài)密度的提高，因此超晶格材料具有許多新的特性。Venkatasubramanian等采用金屬有機(jī)化合物氣相沉積(MOCVE)法將Bi-Te基合金制備成超晶格薄膜,300K時(shí)ZT值達(dá)到2.4。Dresselhaus對(duì)Bi納米線及量子阱系統(tǒng)的大量研究后預(yù)言，通過(guò)超晶格量子限制效應(yīng)可以得到ZT值大于3的材料。納米熱電材料是熱電材料的另一研究熱點(diǎn)，浙江大學(xué)在此領(lǐng)域成果卓著。趙新兵等研究發(fā)現(xiàn)傳統(tǒng)Bi-Te基熱電材料中添加15%的含有Bi2T3;納米管粉末，可以使材料的熱電性能提高20%左右。Cao等采用水熱合成法熱壓后得到ZT=1.28的(Bi,Sb)2Te3;納米熱電材料。ZHAO等通過(guò)納米粉末摻雜，制得ZT值均超過(guò)1.5的Bi2Te3-Sb2Te3和GeTe-AgSbTe2納米結(jié)構(gòu)材料。3.1.2匹配問(wèn)題溫差發(fā)電器的輸出功率和發(fā)電效率與高溫端溫度(Th）。低溫端溫度(Tc)，溫差發(fā)電回路電流(I)，負(fù)載電阻(R)，發(fā)電器內(nèi)阻(r)等因素密切相關(guān)。在不同條件下，溫差發(fā)電器的性能差別較大。屈健等應(yīng)用有限時(shí)問(wèn)熱力學(xué)理論對(duì)半導(dǎo)體溫差發(fā)電器的工作性能進(jìn)行了分析，得到溫差發(fā)電存在最佳參數(shù)工作區(qū)的結(jié)論。潘玉灼等采用非平衡態(tài)熱力學(xué)優(yōu)化控制理論分析溫差電模型，數(shù)值模擬結(jié)果表明:最匹配參數(shù)工作條件下輸出功率和發(fā)電效率可分別提高39%和20%發(fā)電器熱設(shè)計(jì)也是影響發(fā)電效率的重要因素。為了保持較高的溫差，往往在發(fā)電器低溫端增加散熱裝置，以使熱量及時(shí)散失。Chein研究指出當(dāng)器件熱阻大于散熱器最大熱阻時(shí)，散熱器將小能夠散走器件產(chǎn)生的熱量，因此與溫差發(fā)電器匹配的冷端散熱方式也是影響發(fā)電器性能的重要因素。目前主要的散熱方式有:風(fēng)冷、液冷和相變散熱。風(fēng)冷又分為自然風(fēng)冷和強(qiáng)制風(fēng)冷。自然風(fēng)冷換熱器是一定形狀的翅片散熱器。熱阻大小與翅片密度、散熱器面積直接相關(guān)。目前溫差發(fā)電器中應(yīng)用較多的是強(qiáng)制風(fēng)冷，散熱器(如熱沉)與風(fēng)扇結(jié)合，低溫端熱量傳導(dǎo)到更大面積的翅片上，借助強(qiáng)制散熱將熱量散失到空氣中。熱阻取決于風(fēng)速，風(fēng)速越大，熱阻越小。強(qiáng)制風(fēng)冷可有效地提高散熱器的對(duì)流換熱系數(shù)，減小散熱面積，而且結(jié)構(gòu)簡(jiǎn)單，易于實(shí)現(xiàn)，因而應(yīng)用廣泛。因液體的單位熱容較氣體大，因而液冷比風(fēng)冷有更好的冷卻效果，研究表明液冷換熱系數(shù)比自然風(fēng)冷散熱大100-1000倍，熱阻大小主要與液體的流速有關(guān)，流速越大，熱阻越低。目前應(yīng)用的液體散熱方式主要有液體噴射冷卻、微通道液體冷卻和宏觀水冷管路冷卻。相變散熱是利用相變材料相態(tài)變化時(shí)吸收熱量來(lái)散熱。這種散熱方式適用于問(wèn)歇式工作場(chǎng)合，目前研究最多的是帶相變熱虹吸管散熱。Esartet的研究結(jié)果表明帶相變熱虹吸管可明顯提高熱流在傳熱面的均勻性，減小熱阻，散熱較好。3.2可靠性問(wèn)題3.2.1和機(jī)械應(yīng)力的存在以常見的三明治式溫差電組件為例，要達(dá)到較高的發(fā)電效率，通常要求發(fā)電組件冷熱端之問(wèn)形成較大溫差，這將造成冷端連接片收縮或熱端連接片膨脹，從而產(chǎn)生機(jī)械應(yīng)力。機(jī)械應(yīng)力的存在使得剛性的接頭或P,N電臂很容易斷裂，最終可能導(dǎo)致溫差電偶的損壞，從而縮短了溫差電組件的使用壽命。為了小增加電阻，要求過(guò)渡層厚度小超過(guò)0.3mm;(3)改變基體材料。金屬化陶瓷片由于強(qiáng)度高、導(dǎo)熱性好、價(jià)格低廉，因而成為目前使用最廣泛的基體材料。但是陶瓷片硬度大，極易造成P,N電臂折斷。如果采用有一定柔性而又能起支撐作用的新材料來(lái)代替陶瓷片，通過(guò)基體的柔性來(lái)緩解機(jī)械應(yīng)力，將能有效地解決電臂斷裂的問(wèn)題。3.2.2環(huán)境因索濕氣。焊接處至少存在熱電材料、焊料和連接片材料三種物質(zhì)。濕氣進(jìn)入，在冷接頭附近結(jié)露，