Seite - 28 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 1217 Figure33.Aflywheelused in theFormulaOneracingkineticenergyrecoverysystem(KERS). Figure34. Basicflywheel components. Theflywheel is suspended in tishosingbybearings, and is connectedtoamotor-generator tostoreandsupplyenergy[61]. Table12.Characteristicsofdifferentmaterialsusedforflywheels [62]. Material Density(kg/m3) Tensile Strength(mpa) MaxEnergy Density (mj/kg) Cost (USD/kg) Monolithic material 4340steel 7700 1520 0.19 1 Composites E-glass 2000 100 0.05 11 S2-glass 1920 1470 0.76 24.6 CarbonT1000 1520 1950 1.28 101.8 CarbonAS4C 1510 1650 1.1 31.3 Currently,nosingleenergysourcecanprovidethe idealcharacteristics, i.e.,highvalueofboth powerandenergydensity. Table13showsarelativecomparisonof theenergystorages todemonstrate this fact.Hybridenergystoragescanbeusedtocounter thisproblembyemployingonesource for highenergydensityandanother forhighpowerdensity.Differentcombinationsarepossible tocreate thishybridsystem. It canbeacombinationofbatteryandultracapacitor,batteryandflywheel,or fuel cell andbattery [4]. Table14showsthestoragesystemsusedbysomecurrentvehicles. 28