太阳能热水器高聚光比聚光技术储热材料和换热方式

太阳能热水器高聚光比聚光技术储热材料和换热方式

太阳能热水器高聚光比聚光技术储热材料和换热方式太阳能热水器高聚光比聚光技术储热材料和换热方式1太阳能热发电的工作原理Workingprincipleof1solarthermalpowergeneration太阳能热发电是指利用聚光器将低密度的太阳能汇聚到焦斑处，使其生成高密度的能量，然后由工作流体将其转换成热能，再利用热能发电。目前，已经达到商业化应用水平的太阳能热发电方式主要有：塔式、槽式、碟式三种方式。Solarthermalpowergenerationreferstotheuseofcondenserlowdensitysolarconvergetothefocalpoint,theformationofhighdensityofenergy,andthenbytheworkingfluidisconvertedintoheatenergy,recyclingheatenergypowergeneration.Atpresent,thesolarthermalpowergenerationhasreachedcommercialapplicationlevelare:Tower,trough,disctypeinthreeways.1.1塔式太阳能热发电系统1.1towersolarthermalpowergenerationsystem塔式太阳能热发电系统将吸热器（单侧受光或四周受光）置于接收塔的顶部，若干台定日镜根据吸热器的类型，排列在接收塔的一侧或四周。这些定日镜自动跟踪太阳，使其反射光能够精确地投射到吸热器内。吸热器将太阳光能转变成热能，并加热盘管内流动着的介质（水或其他流体）产生中高温蒸汽（温度可达5600C以上）驱动汽轮发电机组发电。目前，塔式热发电系统总效率13%左右，聚光—吸热部分效率70%左右。研究表明，塔式热发电系统具有聚光比和温度高、热传递路程短、热损耗少、系统综合效率高等特点，极适合于大规模、大容量（一般在30～400MW之间）商业化应用。但其一次性投入较大，每台定日镜都需一个单独的二维跟踪机构，装置结构和控制系统复杂，成本较高。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槽式太阳能热发电系统1.2parabolictroughsolarthermalpowergenerationsystem槽式太阳能热发电系统，采用向一个方向弯曲的抛物线形槽式反射镜面将太阳光聚焦到位于焦线的吸热管上，使管内的传热工质（油或水）加热至一定温度，然后经热交换器产生蒸汽驱动汽轮发电机组发电。聚光—吸热装置采用一维自动跟踪系统跟踪太阳的运行。槽式热发电系统结构简单、成本较低，并可将多个聚光—吸热装置经串、并联排列，构成较大容量的热发电系统。但其聚热比较小、热传递回路长，传热工质温度难以提高，系统综合效率较低。Troughsolarthermalpowergenerationsystem,usingparabolictroughreflectorcurvatureinonedirectionfocussunlighttoheatinthefocallinepipe,theheattransferfluidinsidethetube(oilorwater)isheatedtoacertaintemperature,thenthroughtheheatexchangertoproducesteamtodriveasteamturbinegeneratorset.Condenser-automatictrackingsystemtotrackthesun'sbasedonaone-dimensionalheatabsorbingdevice.Troughsolarpowersystemhastheadvantagesofsimplestructure,lowcost,andcanbeapluralityofcondensingheatabsorbingdevice,throughaseriesofparallelarrangement,consistingoflargecapacitythermalpowergenerationsystem.Buttheheatisrelativelysmall,theheattransferlooplength,heattransferfluidtemperatureisdifficulttoimprovethecomprehensiveefficiencyofthesystem,lower.1.3碟式太阳能热发电系统The1.3dishsolarthermalpowersystem碟式太阳能热发电系统，是利用旋转抛物面反射镜，将入射阳光聚集在镜面焦点处，而在该处可放置太阳能吸热器吸收太阳能并加热工质驱动汽轮发电机组发电。碟式热发电系统采用二维跟踪使得聚光镜面始终正对太阳，故其聚光效率最高。碟式热发电系统可单机标准化生产，具有使用寿命长、综合效率高、运行灵活性强等特点，可以单机使用或多台并联使用，非常适合边远山区离网分布式发电。Dishsolarthermalpowersystem,istheuseoftheparaboloidalreflector,theincidentsunlightonthemirrorfocus,wherecanbeplacedsolarabsorberabsorbssolarenergyandheatingmediumdriveturbinepowergeneration.Disktypethermalpowergenerationsystemusing2Dtrackingthecondensermirroralwaysfacingthesun,sotheconcentrationefficiencyisthehighest.Disktypethermalpowergenerationsystemcanbesinglestandardizedproduction,hastheadvantagesoflongservicelife,highcomprehensiveefficiency,operationflexibility,canusesingleormultipleparalleluse,verysuitableforremoteareasawayfromthenetworkofdistributedgeneration.2太阳能热发电需要解决的关键技术问题Thekeytechnicalproblemsneedtobesolvedinthe2solarthermalpowergeneration太阳能热发电技术由系统设计技术、光学技术、热学技术、材料技术、电气技术等组成。下面分别对各部分中的一些关键问题进行分析。Solarthermalpowergenerationtechnologybysystemdesigntechnology,opticaltechnology,thermaltechnology,materialstechnology,electricaltechnologyetc..Thefollowinganalysisisconductedonsomekeyissuesineachpartofthe.2.1系统设计技术2.1systemdesigntechnology太阳能热发电系统优化设计的基点在于建立准确的太阳能热电站的“聚光—吸热—传热—储热—发电”过程的动态热力学模型，并进行多工况的模拟分析。研究太阳能热发电“光—热—电”系统在启动、正常运行、待机、停机和事故等多种正常和非正常工况下的性能，系统内各单元的相应动作以及对发电的影响。找到某种气象条件下电价成本最优的系统组成方案。Solarthermalpowersystemoptimizationdesignbasedondynamicthermodynamicmodeltoestablishaccuratesolarthermalpowerstation"spotlight-heat-transfer-heatstorageandpower"process,simulationanalysisandmultiplecondition.Studyofsolarthermalpowergeneration"light-heat-electricity"systematthestart,normaloperation,shutdown,standbyandaccidentandsoonmanykindsofnormalandabnormalconditionperformance,thecorrespondingactionofeachunitinthesystemandtheeffectonthegenerationof.Findthesystemcostoptimalschemecomposedsomemeteorologicalconditions.2.2光学问题The2.2opticalproblems（1）高效率低成本塔式聚光场设计。(1)withhighefficiencyandlowcosttowerconcentratordesign.在大型塔式太阳能热发电系统中，聚光场的年光学效率很大程度上决定了电站的年总发电量，聚光场的成本占电站总成本的50%，因此研究设计高效率低成本定日镜场具有重要意义。对于定日镜的光学设计，需要考虑太阳光谱特性、大角度入射的像差特性及太阳发散角的影响，以及定日镜的位置、塔高、地形、吸热器的接收角等。Inthelarge-scalesolarthermalpowertowersystem,condenserfieldopticalefficiencylargelydeterminesthetotalannualoutputfromthepowerstations,concentrationfieldofthetotalcostat50%,sothedesignofhighefficiencyandlowcostoftheheliostatfieldhasimportantsignificance.Fortheopticaldesignofheliostat,itneedstoconsidertheimpactofaberrationandthesun,thesolarspectrumcharacteristicofthedivergenceoflargeangleofincidenceangle,andthepositionofaheliostat,tower,terrain,theheatreceivingangle.（2）轻型高强度槽式聚光反射面。(2)highintensitylighttroughconcentratingreflector.采用尽量轻的反射材料和支撑结构是降低槽式聚光器成本和自身能耗的重要措施。直接采用曲面玻璃镜作为反射面的槽式聚光技术是这一代技术的代表。Usedasalightreflectingmaterialandsupportingstructureisanimportantmeasuretoreducethetroughconcentratorcostanditsenergyconsumption.Directuseofcurvedglassmirrorasthereflectingsurfacetroughconcentratingtechnologyisrepresentativeofthisgenerationtechnology.（3）高聚光比聚光技术。(3)highconcentratingratiocondensingtechnology.主要包括二次反射聚光、塔顶反射聚光、轮胎面聚光和分束聚光等技术。Includingtworeflectiveconcentrator,thereflectingcondenser,condenserandthebeamspottiresurfacetechnology.（4）光学选择性涂层。(4)opticalselectivecoating.它是对太阳辐射具有光学选择性的涂层，是各种高效吸热器的基础，具有高温化学稳定性。Itistheradiationcoatingwithopticalselectivetothesun,isthebasisofallkindsofefficientheatabsorbingdevice,hashighchemicalstability.2.3热学问题2.3thermalproblems（1）吸热器低热损机理。(1)theheatabsorberheatlossmechanism.减少吸热器的反射损失、热发射损失和自然对流损失是提高吸热器效率的关键。Toreducethereflectionloss,absorberandheatemissionlossandnaturalconvectionlossisthekeytoimprovetheheatefficiency.（2）吸热器安全性及寿命。(2)theheatabsorbersafetyandlife.吸热器长期工作在高密度、变化的辐射热流条件下，工作环境非常恶劣。又由于它是太阳能热发电的核心部件之一，吸热器损坏必然造成电站停止运行，所以，吸热器的安全性非常重要。Radiationheatfluxheatabsorberworkinginhighdensity,changesovertime,theworkenvironmentisverypoor.Andbecauseitisoneofthecorecomponentsofsolarthermalpowergeneration,heatdamagewillinevitablyleadtopowerstationstostoprunning,sotheheatabsorber,safetyisveryimportant.（3）高温传热工质。(3)hightemperatureheattransferfluid.提高吸热器工质的沸点，降低其熔点是提高工质性能的一个重要目标，也是提高发电效率的重要手段。水和混合熔融盐是目前最常用的传热储热工质。Toimprovetheheatabsorberrefrigerantboilingpoint,lowerthemeltingpointisanimportanttargetforimprovingworkingperformance,andalsoanimportantmeanstoimprovetheefficiencyofpowergeneration.Waterandmixingofthemoltensaltisthemostcommonlyusedinheattransferofthermalmassstorage.（4）储热材料和换热方式。(4)theheatstoragematerialandheatexchangemode.储热工质的工作温度范围决定了太阳能热发电设备的入口参数。要解决的关键问题包括储热材料\/换热器耦合的一体化设计方法，提高储热材料的热容、工作温度和工质的化学及物理稳定性，工质容器及输运管路的防腐等。Operatingtemperaturerangestoragethermaltransferdeterminestheentranceparametersofsolarthermalpowergenerationequipment.Keyissuestobeaddressedincludeintegrateddesignmethodofthermalstoragematerials&heatexchangercoupled,improvethephysicalandchemicalstabilityofthermalstoragematerialsheatcapacity,workingtemperatureandrefrigerant,refrigerantcontainerandanticorrosiontransportpipeline.2.4材料问题2.4material太阳能热发电系统主要包括集热、传输、蓄热与热交换以及发电等四个单元。每个单元都涉及大量的材料研究开发和应用问题。材料性能的突破可能会带来太阳能热发电效率的大幅度提高或成本大幅度下降。太阳能热发电过程中需解决的材料问题主要有以下五类：Solarthermalpowergenerationsystemincludesheatcollection,transmission,storageandexchangeofheatandpowerandotherfourunits.Eachunitissuesrelatedtoresearchanddevelopmentandapplicationoflargeamountsofmaterial.Abigincreaseorcostgreatlymaterialpropertiesmaybringaboutabreakthroughinsolarthermalpowergenerationefficiency.Materialproblemsneededtobesolvedinsolarthermalpowergenerationprocessinthefollowingfivecategories:（1）太阳光反射材料。(1)thesunlightreflectionmaterial.主要是以金属、玻璃及高分子材料为基材的太阳光反射材料的高反射率、材料反射表面防护技术、表面自洁净技术、高精度曲面反射镜等。Mainlyinmetal,glassandpolymermaterialforsolarlightreflectingmaterialsofhighreflectivity,reflectivematerialsurfaceprotectiontechnology,surfaceself-cleaningtechnology,highaccuracysurfacemirroretc..（2）光热转换材料。(2)aphotothermalconversionmaterial.主要是槽式聚光器用金属（玻璃）真空管中的相关材料，以及耐高温太阳光谱选择性涂层。Mainlytroughconcentratorwithmetal(glass)relatedmaterialsinthevacuumpipe,andhigh-temperaturesolarselectiveabsorptioncoating.（3）中高温蓄热材料。(3)inhightemperatureheatstoragematerial.无机蓄热载体（如高性能水泥混凝土、耐热纤维、隔热保温材料等）；中高温相变和化学反应蓄热介质；与蓄热材料相匹配的蓄热器结构设计。Inorganicheatcarrier(suchasthehighperformancecementconcrete,heat-resistantfiberinsulationmaterials,etc.);phasechangeandchemicalreactioninhightemperatureheatstoragemedium;regeneratorstructuredesignedtomatchtheheatstoragematerial.（4）高温热量传输介质。(4)hightemperatureheattransfermedium.高温热量传输材料和介质（水、盐、空气等）；高温热量传输管道及其热防护材料。Hightemperatureheattransfermaterialandmedium(water,salt,air);hightemperatureheattransferpipeandheatprotectionmaterial.（5）热电转换材料。(5)thethermoelectricconversionmaterial.高效热电转换材料是利用温差原理直接将热能转化成电能的新能源材料。Efficientthermoelectricconversionmaterialsistheuseoftemperaturedifferenceprincipledirectlyconvertthermalenergyintoelectricalenergynewenergymaterials.3太阳能热发电技术在中国的应用前景Applicationprospectof3solarthermalpowergenerationtechnologyinChina从中国太阳能分布情况看，西部和北部沙漠地区太阳能直射资源非常丰富。从太阳能热发电的原理可以看出，其发电过程需要适量的水，发电站需建在有水源的地方。通过有关部门的考察调研，以下几个地区适合建立大规模太阳能热发电站：FromthedistributionofsolarenergyinChina,solardirectresourcesinthewesternandnortherndesertregionisveryrich.Fromtheprincipleofsolarthermalpowergenerationcanbeseen,itsgenerationprocessrequirestherightamountofwaterpowerstationtobebuilt,inthewatersourceplace.Throughtheinvestigationandstudyofrelevantdepartments,suitableforbuildinglarge-scalesolarthermalpowerstationinthefollowingareas:3.1浑善达克沙地3.1theOtindagSandyLand分布于内蒙古高原东部，包括内蒙古锡林郭勒盟的南部和赤峰的西北部，总面积为2.14万km2。该地区太阳能辐射资源较丰富，年累计辐射量为5573MJ\/m2。降水条件较好，有不少淡水湖泊分布，水资源条件良好。LocatedintheeasternInnerMongoliaplateau,includingInnerMongolia,southernXilinguoleMengandnorthwesternChifeng,atotalareaof21400km2.Solarradiationresourcesareabundantinthearea,thecumulativeamountofradiationfor5573MJ\/m2years.Precipitationconditionisgood,therearemanyfreshwaterlakewaterresourcesdistribution,goodcondition.3.2科尔沁沙地3