Abstract:In the first section of the chapter, the energy storage characteristics of lithium batteries and supercapacitors are presented and compared. Of particular interest is the comparative power capability of lithium batteries and carbon/carbon supercapacitors for charge/discharge conditions to be encountered in hybrid-electric vehicles. In the next section, system considerations and advantages of combining supercapacitors and batteries for energy storage are discussed. Next laboratory and field experiences with supercapacitors in hybrid-electric vehicles are reviewed for transit bus, light-duty, and fuel cell applications. The final sections of the chapter discuss in detail simulations of vehicles on various driving cycles using supercapacitors alone and in combination with advanced batteries. The vehicle simulations treat charge sustaining micro- and mild-hybrid designs, plug-in hybrids, and fuel cell-powered vehicles. The charge-sustaining hybrid vehicles using supercapacitors alone in place of batteries are discussed in terms of the sizing of the supercapacitor unit and control strategies that optimize the fuel economy improvements achievable. For the plug-in hybrids, the emphasis is on the use of supercapacitors with advanced batteries having energy densities greater than 300 Wh/kg. It is likely that these batteries will not have proportionally higher-power density and will require the assist of supercapacitors to achieve all-electric operation even on the FUDS driving cycle. The next section of the chapter deals with fuel cell-powered vehicles and considers the use of supercapacitors to load level the fuel cell to increase system efficiency and thus reduce hydrogen consumption. In the final section of the chapter, the costs of batteries and supercapacitors are compared for charge-sustaining hybrid applications.