Page - 25 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 1217 The internal resistance is lowtoo,making ithighlyefficient,but italsocauseshighoutputcurrent if chargedatastateofextremely lowSOC[56,57].AUC’s terminalvoltage isdirectlyproportional to its SOC;so it canalsooperateall throughitsvoltagerange [35]. BasicconstructionofanUCcell is shown inFigure29. EVsgothroughstart/stopconditionsquitea lot, especially inurbandrivingsituations. Thismakes thebatterydischargeratehighlychangeable. Theaveragepowerrequiredfrombatteries is low,butduringaccelerationorconditions likehill-climbahighpowerisrequiredinashortdurationof time[4,35]. Thepeakpowerrequired inahigh-performanceelectricvehiclecanbeuptosixteentimes theaveragepower[4].UCsfit inperfectly insuchascenarioas it canprovidehighpowerforshort durations. It isalso fast incapturingtheenergygeneratedbyregenerativebraking[2,35].Acombined battery-UCsystem(asshowninFigure30)negateseachother’sshortcomingsandprovidesanefficient andreliableenergysystem.The lowcost, loadlevelingcapability, temperatureadaptabilityandlong service lifeofUCsmakethemalikableoptionaswell [4,30]. Figure29.AnUCcell; a separatorkeeps the twoelectrodesapart [58]. Figure30.CombinationofbatteryandUCtocomplementeach-other’s shortcomings [59]. 4.3. FuelCell (FC) Fuelcellsgenerateelectricitybyelectrochemical reaction.AnFChasananode(A),acathode(C) andanelectrolyte (E)between them. Fuel is introduced to theanode,getsoxidized there, the ions createdtravel throughtheelectrolyte to thecathodeandcombinewith theotherreactant introduced 25