Perspective on ultracapacitors for electric vehicles

Recent advances in the performance of chemical double layer capacitors (DLC) with aqueous and nonaqueous electrolytes have made it possible to seriously consider them for commercialization. Nonaqueous (organic) carbon based laboratory monopolar devices have recently met key US Department of Energy (DOE) mid-term specifications (>5 W h/kg, >500 W/kg and >100000 life cycles) for load-leveling electric vehicles batteries. All DLC technologies currently under development by DOE are discussed. Each technology has distinct advantages and none are clear winners at this time. A study has been completed by the General Electric Company on the interface electronics needed to best utilize the energy of capacitors while load-leveling batteries. System costs are presented based on this study, several battery technologies, and capacitor projections