Page - 354 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2016,9, 240 ȱ Figure10.Schematicofgas-mixingheatpumpsystemfor fullyEVs[74]. The improvementofdefrostingmethodinadditiontousingthe two-stagecycle technologyto increase theheatingperformance,wasanotherresearchhotspot.Asdescribedin[76,77],defrosting theheatsupplyandenergyconsumptionadversely impactedtheheatingperformance. Todecrease this influence,Qu et al. [78] reportedtwocontrol strategies for theelectronicexpansionvalve. They investigatedthe twocontrol strategieseffectsonreverse-cycledefrostingperformanceofanair source heatpump.Zhang et al. [79]comparedthe threedefrostingmethods, i.e., reversecycledefrosting,hot gasbypassdefrostingandphasechangethermalenergystoragedefrosting. Theexperimental results indicated that thedefrostingmethod,whichusedphasechange thermalenergystorage, couldshorten defrostingtimeandreduceenergyconsumption[80]. 3.MultipleSourceHeatPumpACSystems ThesinglesourceheatpumpACsystemcanbequalifiedtoheatandcool forEVsinmostweather conditionsbytheabovementionedmethods.However theheatingcapacityandheatingCOPdrop sharplywithdecreasingoutdoor temperature. Theheatingcapacity is insufficient inextremelycold weather. Tosolve theseproblems,manyauthorshaveproposedmultiplesourceheatpumpsystems. 3.1.AdditionalWasteHeatSource Wasteheatdischargedfromelectricdevices, suchasmotors,batteriesandinvertersof fullyEVs, is available. However, it is greatly insufficient forheating the cabindirectly. Tomaximize theuse of thewasteheat,an integratedclimatecontrol systemwasdevelopedbyGroupeEnerstat Inc. [81]. The test results showedthat theuseofadualsourceheatpump,whichusesbothairandwasteheat, wasoneof thebestmethodsforEVs. Promme[82]proposedareversibleheatpumpsystemwithan additionalheat sourcewhich couldutilize thewasteheat of thebattery, drivenelectricmotor and electroniccontrolunit.AhnandWoo[83,84] investigatedadual sourceheatpump(usingbothairand wasteheat) inEVs,which isshowninFigure11. 354