Ultracapacitors Store Energy in a Hybrid Electric Vehicle

A government/ industry/ academic cooperative has developed a hybrid electric transit bus (HETB). The goals of the development program, which continues, include doubling the fuel economy of city transit buses currently in service, and reducing emissions to one-tenth of the levels allowed by Environmental Protection Agency (EPA) standards. A unique aspect of the power system of the HETB is the use of capacitors in its the energy-storage subsystem. At a gross weight of more than 17,000 kg, this is the largest known vehicle to use capacitors to store energy.