太陽能熱水器高聚光比聚光技術儲熱材料和換熱方式

太陽能熱水器高聚光比聚光技術儲熱材料和換熱方式

太陽能熱水器高聚光比聚光技術儲熱材料和換熱方式太陽能熱水器高聚光比聚光技術儲熱材料和換熱方式1太陽能熱發(fā)電的工作原理Workingprincipleof1solarthermalpowergeneration太陽能熱發(fā)電是指利用聚光器將低密度的太陽能匯聚到焦斑處，使其生成高密度的能量，然后由工作流體將其轉換成熱能，再利用熱能發(fā)電。目前，已經(jīng)達到商業(yè)化應用水平的太陽能熱發(fā)電方式主要有：塔式、槽式、碟式三種方式。Solarthermalpowergenerationreferstotheuseofcondenserlowdensitysolarconvergetothefocalpoint,theformationofhighdensityofenergy,andthenbytheworkingfluidisconvertedintoheatenergy,recyclingheatenergypowergeneration.Atpresent,thesolarthermalpowergenerationhasreachedcommercialapplicationlevelare:Tower,trough,disctypeinthreeways.1.1塔式太陽能熱發(fā)電系統(tǒng)1.1towersolarthermalpowergenerationsystem塔式太陽能熱發(fā)電系統(tǒng)將吸熱器（單側受光或四周受光）置于接收塔的頂部，若干臺定日鏡根據(jù)吸熱器的類型，排列在接收塔的一側或四周。這些定日鏡自動跟蹤太陽，使其反射光能夠精確地投射到吸熱器內。吸熱器將太陽光能轉變成熱能，并加熱盤管內流動著的介質（水或其他流體）產(chǎn)生中高溫蒸汽（溫度可達5600C以上）驅動汽輪發(fā)電機組發(fā)電。目前，塔式熱發(fā)電系統(tǒng)總效率13%左右，聚光—吸熱部分效率70%左右。研究表明，塔式熱發(fā)電系統(tǒng)具有聚光比和溫度高、熱傳遞路程短、熱損耗少、系統(tǒng)綜合效率高等特點，極適合于大規(guī)模、大容量（一般在30～400MW之間）商業(yè)化應用。但其一次性投入較大，每臺定日鏡都需一個單獨的二維跟蹤機構，裝置結構和控制系統(tǒng)復雜，成本較高。Solarthermalpowertowersystemreceiver(unilaterallightorbyreceivinglight)onthetopofthetower,apluralityofheliostatbasedonthetypeofabsorber,arrangedinthereceivingside,oraroundthetower.Theheliostattoautomaticallytrackingthesun,sothatthereflectedlightcanbeaccuratelyprojectedtotheheatabsorberin.Heatconvertssolarenergyintoheatenergy,andtheheatingcoilinsidetheflowingmedium(waterorotherfluids)producedinhightemperaturesteam(abovethetemperatureupto5600C)drivethesteamturbinegenerator.Atpresent,thetowerthermalpowersystemtotalefficiencyofabout13%,about70%light-absorbingefficiency.Researchshowsthat,thetowerthermalpowergeneratingsystemwithconcentrationratioandhightemperature,heattransferinshortdistance,lowheatloss,comprehensivesystemefficiencyhighercharacteristic,verysuitableforlarge-scale,largecapacity(30～400MWingeneral)commercialapplication.Buttheone-timeinvestmentislarger,eachheliostatrequiresasingletwo-dimensionaltrackingmechanism,devicestructureandcontrolsystemofcomplex,highcost.1.2槽式太陽能熱發(fā)電系統(tǒng)1.2parabolictroughsolarthermalpowergenerationsystem槽式太陽能熱發(fā)電系統(tǒng)，采用向一個方向彎曲的拋物線形槽式反射鏡面將太陽光聚焦到位于焦線的吸熱管上，使管內的傳熱工質（油或水）加熱至一定溫度，然后經(jīng)熱交換器產(chǎn)生蒸汽驅動汽輪發(fā)電機組發(fā)電。聚光—吸熱裝置采用一維自動跟蹤系統(tǒng)跟蹤太陽的運行。槽式熱發(fā)電系統(tǒng)結構簡單、成本較低，并可將多個聚光—吸熱裝置經(jīng)串、并聯(lián)排列，構成較大容量的熱發(fā)電系統(tǒng)。但其聚熱比較小、熱傳遞回路長，傳熱工質溫度難以提高，系統(tǒng)綜合效率較低。Troughsolarthermalpowergenerationsystem,usingparabolictroughreflectorcurvatureinonedirectionfocussunlighttoheatinthefocallinepipe,theheattransferfluidinsidethetube(oilorwater)isheatedtoacertaintemperature,thenthroughtheheatexchangertoproducesteamtodriveasteamturbinegeneratorset.Condenser-automatictrackingsystemtotrackthesun'sbasedonaone-dimensionalheatabsorbingdevice.Troughsolarpowersystemhastheadvantagesofsimplestructure,lowcost,andcanbeapluralityofcondensingheatabsorbingdevice,throughaseriesofparallelarrangement,consistingoflargecapacitythermalpowergenerationsystem.Buttheheatisrelativelysmall,theheattransferlooplength,heattransferfluidtemperatureisdifficulttoimprovethecomprehensiveefficiencyofthesystem,lower.1.3碟式太陽能熱發(fā)電系統(tǒng)The1.3dishsolarthermalpowersystem碟式太陽能熱發(fā)電系統(tǒng)，是利用旋轉拋物面反射鏡，將入射陽光聚集在鏡面焦點處，而在該處可放置太陽能吸熱器吸收太陽能并加熱工質驅動汽輪發(fā)電機組發(fā)電。碟式熱發(fā)電系統(tǒng)采用二維跟蹤使得聚光鏡面始終正對太陽，故其聚光效率最高。碟式熱發(fā)電系統(tǒng)可單機標準化生產(chǎn)，具有使用壽命長、綜合效率高、運行靈活性強等特點，可以單機使用或多臺并聯(lián)使用，非常適合邊遠山區(qū)離網(wǎng)分布式發(fā)電。Dishsolarthermalpowersystem,istheuseoftheparaboloidalreflector,theincidentsunlightonthemirrorfocus,wherecanbeplacedsolarabsorberabsorbssolarenergyandheatingmediumdriveturbinepowergeneration.Disktypethermalpowergenerationsystemusing2Dtrackingthecondensermirroralwaysfacingthesun,sotheconcentrationefficiencyisthehighest.Disktypethermalpowergenerationsystemcanbesinglestandardizedproduction,hastheadvantagesoflongservicelife,highcomprehensiveefficiency,operationflexibility,canusesingleormultipleparalleluse,verysuitableforremoteareasawayfromthenetworkofdistributedgeneration.2太陽能熱發(fā)電需要解決的關鍵技術問題Thekeytechnicalproblemsneedtobesolvedinthe2solarthermalpowergeneration太陽能熱發(fā)電技術由系統(tǒng)設計技術、光學技術、熱學技術、材料技術、電氣技術等組成。下面分別對各部分中的一些關鍵問題進行分析。Solarthermalpowergenerationtechnologybysystemdesigntechnology,opticaltechnology,thermaltechnology,materialstechnology,electricaltechnologyetc..Thefollowinganalysisisconductedonsomekeyissuesineachpartofthe.2.1系統(tǒng)設計技術2.1systemdesigntechnology太陽能熱發(fā)電系統(tǒng)優(yōu)化設計的基點在于建立準確的太陽能熱電站的“聚光—吸熱—傳熱—儲熱—發(fā)電”過程的動態(tài)熱力學模型，并進行多工況的模擬分析。研究太陽能熱發(fā)電“光—熱—電”系統(tǒng)在啟動、正常運行、待機、停機和事故等多種正常和非正常工況下的性能，系統(tǒng)內各單元的相應動作以及對發(fā)電的影響。找到某種氣象條件下電價成本最優(yōu)的系統(tǒng)組成方案。Solarthermalpowersystemoptimizationdesignbasedondynamicthermodynamicmodeltoestablishaccuratesolarthermalpowerstation"spotlight-heat-transfer-heatstorageandpower"process,simulationanalysisandmultiplecondition.Studyofsolarthermalpowergeneration"light-heat-electricity"systematthestart,normaloperation,shutdown,standbyandaccidentandsoonmanykindsofnormalandabnormalconditionperformance,thecorrespondingactionofeachunitinthesystemandtheeffectonthegenerationof.Findthesystemcostoptimalschemecomposedsomemeteorologicalconditions.2.2光學問題The2.2opticalproblems（1）高效率低成本塔式聚光場設計。(1)withhighefficiencyandlowcosttowerconcentratordesign.在大型塔式太陽能熱發(fā)電系統(tǒng)中，聚光場的年光學效率很大程度上決定了電站的年總發(fā)電量，聚光場的成本占電站總成本的50%，因此研究設計高效率低成本定日鏡場具有重要意義。對于定日鏡的光學設計，需要考慮太陽光譜特性、大角度入射的像差特性及太陽發(fā)散角的影響，以及定日鏡的位置、塔高、地形、吸熱器的接收角等。Inthelarge-scalesolarthermalpowertowersystem,condenserfieldopticalefficiencylargelydeterminesthetotalannualoutputfromthepowerstations,concentrationfieldofthetotalcostat50%,sothedesignofhighefficiencyandlowcostoftheheliostatfieldhasimportantsignificance.Fortheopticaldesignofheliostat,itneedstoconsidertheimpactofaberrationandthesun,thesolarspectrumcharacteristicofthedivergenceoflargeangleofincidenceangle,andthepositionofaheliostat,tower,terrain,theheatreceivingangle.（2）輕型高強度槽式聚光反射面。(2)highintensitylighttroughconcentratingreflector.采用盡量輕的反射材料和支撐結構是降低槽式聚光器成本和自身能耗的重要措施。直接采用曲面玻璃鏡作為反射面的槽式聚光技術是這一代技術的代表。Usedasalightreflectingmaterialandsupportingstructureisanimportantmeasuretoreducethetroughconcentratorcostanditsenergyconsumption.Directuseofcurvedglassmirrorasthereflectingsurfacetroughconcentratingtechnologyisrepresentativeofthisgenerationtechnology.（3）高聚光比聚光技術。(3)highconcentratingratiocondensingtechnology.主要包括二次反射聚光、塔頂反射聚光、輪胎面聚光和分束聚光等技術。Includingtworeflectiveconcentrator,thereflectingcondenser,condenserandthebeamspottiresurfacetechnology.（4）光學選擇性涂層。(4)opticalselectivecoating.它是對太陽輻射具有光學選擇性的涂層，是各種高效吸熱器的基礎，具有高溫化學穩(wěn)定性。Itistheradiationcoatingwithopticalselectivetothesun,isthebasisofallkindsofefficientheatabsorbingdevice,hashighchemicalstability.2.3熱學問題2.3thermalproblems（1）吸熱器低熱損機理。(1)theheatabsorberheatlossmechanism.減少吸熱器的反射損失、熱發(fā)射損失和自然對流損失是提高吸熱器效率的關鍵。Toreducethereflectionloss,absorberandheatemissionlossandnaturalconvectionlossisthekeytoimprovetheheatefficiency.（2）吸熱器安全性及壽命。(2)theheatabsorbersafetyandlife.吸熱器長期工作在高密度、變化的輻射熱流條件下，工作環(huán)境非常惡劣。又由于它是太陽能熱發(fā)電的核心部件之一，吸熱器損壞必然造成電站停止運行，所以，吸熱器的安全性非常重要。Radiationheatfluxheatabsorberworkinginhighdensity,changesovertime,theworkenvironmentisverypoor.Andbecauseitisoneofthecorecomponentsofsolarthermalpowergeneration,heatdamagewillinevitablyleadtopowerstationstostoprunning,sotheheatabsorber,safetyisveryimportant.（3）高溫傳熱工質。(3)hightemperatureheattransferfluid.提高吸熱器工質的沸點，降低其熔點是提高工質性能的一個重要目標，也是提高發(fā)電效率的重要手段。水和混合熔融鹽是目前最常用的傳熱儲熱工質。Toimprovetheheatabsorberrefrigerantboilingpoint,lowerthemeltingpointisanimportanttargetforimprovingworkingperformance,andalsoanimportantmeanstoimprovetheefficiencyofpowergeneration.Waterandmixingofthemoltensaltisthemostcommonlyusedinheattransferofthermalmassstorage.（4）儲熱材料和換熱方式。(4)theheatstoragematerialandheatexchangemode.儲熱工質的工作溫度范圍決定了太陽能熱發(fā)電設備的入口參數(shù)。要解決的關鍵問題包括儲熱材料\/換熱器耦合的一體化設計方法，提高儲熱材料的熱容、工作溫度和工質的化學及物理穩(wěn)定性，工質容器及輸運管路的防腐等。Operatingtemperaturerangestoragethermaltransferdeterminestheentranceparametersofsolarthermalpowergenerationequipment.Keyissuestobeaddressedincludeintegrateddesignmethodofthermalstoragematerials&heatexchangercoupled,improvethephysicalandchemicalstabilityofthermalstoragematerialsheatcapacity,workingtemperatureandrefrigerant,refrigerantcontainerandanticorrosiontransportpipeline.2.4材料問題2.4material太陽能熱發(fā)電系統(tǒng)主要包括集熱、傳輸、蓄熱與熱交換以及發(fā)電等四個單元。每個單元都涉及大量的材料研究開發(fā)和應用問題。材料性能的突破可能會帶來太陽能熱發(fā)電效率的大幅度提高或成本大幅度下降。太陽能熱發(fā)電過程中需解決的材料問題主要有以下五類：Solarthermalpowergenerationsystemincludesheatcollection,transmission,storageandexchangeofheatandpowerandotherfourunits.Eachunitissuesrelatedtoresearchanddevelopmentandapplicationoflargeamountsofmaterial.Abigincreaseorcostgreatlymaterialpropertiesmaybringaboutabreakthroughinsolarthermalpowergenerationefficiency.Materialproblemsneededtobesolvedinsolarthermalpowergenerationprocessinthefollowingfivecategories:（1）太陽光反射材料。(1)thesunlightreflectionmaterial.主要是以金屬、玻璃及高分子材料為基材的太陽光反射材料的高反射率、材料反射表面防護技術、表面自潔凈技術、高精度曲面反射鏡等。Mainlyinmetal,glassandpolymermaterialforsolarlightreflectingmaterialsofhighreflectivity,reflectivematerialsurfaceprotectiontechnology,surfaceself-cleaningtechnology,highaccuracysurfacemirroretc..（2）光熱轉換材料。(2)aphotothermalconversionmaterial.主要是槽式聚光器用金屬（玻璃）真空管中的相關材料，以及耐高溫太陽光譜選擇性涂層。Mainlytroughconcentratorwithmetal(glass)relatedmaterialsinthevacuumpipe,andhigh-temperaturesolarselectiveabsorptioncoating.（3）中高溫蓄熱材料。(3)inhightemperatureheatstoragematerial.無機蓄熱載體（如高性能水泥混凝土、耐熱纖維、隔熱保溫材料等）；中高溫相變和化學反應蓄熱介質；與蓄熱材料相匹配的蓄熱器結構設計。Inorganicheatcarrier(suchasthehighperformancecementconcrete,heat-resistantfiberinsulationmaterials,etc.);phasechangeandchemicalreactioninhightemperatureheatstoragemedium;regeneratorstructuredesignedtomatchtheheatstoragematerial.（4）高溫熱量傳輸介質。(4)hightemperatureheattransfermedium.高溫熱量傳輸材料和介質（水、鹽、空氣等）；高溫熱量傳輸管道及其熱防護材料。Hightemperatureheattransfermaterialandmedium(water,salt,air);hightemperatureheattransferpipeandheatprotectionmaterial.（5）熱電轉換材料。(5)thethermoelectricconversionmaterial.高效熱電轉換材料是利用溫差原理直接將熱能轉化成電能的新能源材料。Efficientthermoelectricconversionmaterialsistheuseoftemperaturedifferenceprincipledirectlyconvertthermalenergyintoelectricalenergynewenergymaterials.3太陽能熱發(fā)電技術在中國的應用前景Applicationprospectof3solarthermalpowergenerationtechnologyinChina從中國太陽能分布情況看，西部和北部沙漠地區(qū)太陽能直射資源非常豐富。從太陽能熱發(fā)電的原理可以看出，其發(fā)電過程需要適量的水，發(fā)電站需建在有水源的地方。通過有關部門的考察調研，以下幾個地區(qū)適合建立大規(guī)模太陽能熱發(fā)電站：FromthedistributionofsolarenergyinChina,solardirectresourcesinthewesternandnortherndesertregionisveryrich.Fromtheprincipleofsolarthermalpowergenerationcanbeseen,itsgenerationprocessrequirestherightamountofwaterpowerstationtobebuilt,inthewatersourceplace.Throughtheinvestigationandstudyofrelevantdepartments,suitableforbuildinglarge-scalesolarthermalpowerstationinthefollowingareas:3.1渾善達克沙地3.1theOtindagSandyLand分布于內蒙古高原東部，包括內蒙古錫林郭勒盟的南部和赤峰的西北部，總面積為2.14萬km2。該地區(qū)太陽能輻射資源較豐富，年累計輻射量為5573MJ\/m2。降水條件較好，有不少淡水湖泊分布，水資源條件良好。LocatedintheeasternInnerMongoliaplateau,includingInnerMongolia,southernXilinguoleMengandnorthwesternChifeng,atotalareaof21400km2.Solarradiationresourcesareabundantinthearea,thecumulativeamountofradiationfor5573MJ\/m2years.Precipitationconditionisgood,therearemanyfreshwaterlakewaterresourcesdistribution,goodcondition.3.2科爾沁沙地3