Study on Super-capacitor Energy Storage Technology

StudyonSuperStudyonSuper--capacitorEnergycapacitorEnergyStorageTechnologyanditsStorageTechnologyanditsApplicationinPowerSystemApplicationinPowerSystemQiQi,,ZhipingZhipingTheInstituteofElectricalEngineering,CASTheInstituteofElectricalEngineering,CASOct.2006Oct.2006AutherAutherzName:QiZhiping;zEducation:graduatedfromtheInstituteofElectricalEngineering,CASandgotMasterDegreein1988.zWorkunit:TheInstituteofElectricalEngineering,CAS;zTitle:Professor;zResearchinterest:Electricalenergystorageanditsapplicationinpowerqualitycontrolandelectricalenergysaving;TheroleofenergystorageinTheroleofenergystorageinpowersystempowersystemzEnergymanagement,requiringtoprovideminutestohourspowersupply;zBridgingpower,requiringtoprovideminutespowersupply;zPowerquality,requiringtoprovidesecondstominutespower;PossibleenergystoragePossibleenergystoragetechnologyforpowerqualitytechnologyforpowerqualityzSMES:highvoltage,longlife,suitedforseveralsecondsdischarge,butstationary,expensiveforconstructingandoperating;zBattery:lowcost,butshortcyclelife,needmaintenanceandreplacement;zFlywheel:durable,butstationary;zsuper-capacitor:performancebetweenbatteryandtraditionalcapacitor,seemstobepromisingtechnologyforenergystorage.ThePrincipleofSuper-capacitorzTheelectrode:Verylargesurface,light，3000m2/g;zThedistancebetweenelectrodes:10-9m;zOperatingvoltage：organicelectrolyte(2.5-3V),aqueouselectrolyte(0.7-1V);SuperSuper--capacitortechnologycapacitortechnologyzAqueoussymmetrictechnology¾Inexpensive,lowenergydensity,lowoperatingvoltage,difficulttodesignbalancecircuit;¾Companies:ELIT,ECOND,Shuang-Deng,etc;zAqueousasymmetrictechnology¾Highenergydensity,higheroperatingvoltageandmoreexpensivethanaqueoussymmetric;¾Companies:ESMA,Shuang-Deng,AO-WEI;¾Organicsymmetrictechnology¾Wideoperatingtemperature,highenergydensity,highlysensitivetoovervoltage,expensivethanaqueous;¾Companies:Maxwell,NESSCapacitor,Panasonic,Ji-Xing,etc;FeatureoftheSuperFeatureoftheSuper--capacitorcapacitorAdvantagesAdvantageszLowimpedancecomparewithbatteryzQuicklycharge/discharge(upto1000A)zHighlifecycle(upto500000cycledtimes)zOperatingtemperaturerange(-30℃-70℃)zEnvironmentfriendlyFeatureoftheSuperFeatureoftheSuper--capacitorcapacitorLimitationsLimitationszLineardischargevoltagepreventsuseofthefullenergyspectrum;zLowenergydensityzCellshavelowvoltages:1V-3Vforalltechnology;zHighselfdischargeCurrentremarkableimprovementCurrentremarkableimprovementofsuperofsuper--capacitorperformancecapacitorperformancezNanogatecapacitorbyOkamuraLab.andJEOLLtd.zEnergydensity:50-70Wh/kgzCharging/discharginginextremelyshorttimezVerylongcyclelifeSuperSuper--capacitorenergystoragecapacitorenergystoragetechnicalproblemstechnicalproblemszEnergystoragestack¾lowcellvoltageandlowcellenergy,cellstackingisrequiredtoobtainnecessaryvoltage,powerandduration,balancecircuitbetweencellsisneeded;zEnergystoragesystem¾Cellvoltageislinearanddropsevenlyfromfullvoltagetozerovolt,DC/DCconverterisneededtoattainconstantvoltageandpowerduringdischargingEnergystoragestackdesignEnergystoragestackdesignzStackdesignrule:tosatisfythedesiredvoltage,powerandduration;¾inordertoobtainnecessaryvoltage,cellsmustbeconnectedinseriesintostring,voltagebalancecircuitofeachcellisrequired;¾inordertoobtainnecessarypowerandduration,super-capacitorstringsmustbeconnectedinparallel;EnergystoragestackdesignEnergystoragestackdesignzForcertainrequiredenergy,thestackcanbedesignedintodifferentvoltageandcharging/dischargingcurrent;zMorecellsconnectinseriesintoonestringresultinhighervoltageandlowercharging/dischargingcurrent;zLesscellsconnectinseriesintostrings,thenstringsconnectinparallelintostackresultinlowervoltageandhighercharging/dischargingcurrent;EnergystoragestackdesignEnergystoragestackdesignzTheadvantage/disadvantageforhighervoltageandlowercharging/dischargingcurrent:¾higherstackequivalentseriesresistance;¾lowervoltagebalancingefficiency;¾easytodischargemoreenergy;zTheadvantage/disadvantageforlowervoltageandhighercharging/dischargingcurrent:¾lowerstackequivalentseriesresistance;¾highervoltagebalancingefficiency;¾difficultytodelivermoreenergy;VoltagebalancetechnologyVoltagebalancetechnologyzPrinciple¾Thecapacitance,efficiencyandleakagecurrentofeachcellaredifferent;¾Ascellsarecycled,thevoltageofeachcellisdifferent;VariousvoltagebalancetechnologyVariousvoltagebalancetechnologyzEnergytransfertype¾higherefficiency;¾fastervoltagebalancespeed;¾dynamicvoltagebalance;¾circuitiscomplex;zEnergyconsumetype¾lowerefficiency;¾slowervoltagebalancespeed¾circuitissimple;EnergystoragesystemdesignEnergystoragesystemdesignBuck/BoostDC/DCConverterSuper-capacitorBankEnergyManagementAndControlDCPowerBUSDataBusEnergystoragesystemdesignEnergystoragesystemdesignzSuper-capacitorbankdesignandbi-directorDC/DCconverterdesignmustcooperatewitheachother;zUsuallytheoperatingvoltageofSuper-capacitorbankislowerthanthatofDCpowerbus;zTheESRofSuper-capacitorbankmayaffectsystemcontrolstability;SuperSuper--capacitorWorkatIEE,CAScapacitorWorkatIEE,CASEnergytransfertypeDynamicvoltagebalancecircuitSuperSu