A Status Report on the Power Storage System of Capacitor-Electronics

Abstract

An idea of new electrical storage called ECS (Energy Capacitor System) composed from specially developed capacitors and electronic circuits, has opened up variety of applications and possibilities. A Copernican design of capacitor is provided by trading off internal resistance with energy density, and by charging serially connected capacitors from a current source to obtain better efficiency. Produced capacitors have achieved the energy density of 10 Wh/L at 2ΩF (ohms for each farad) and 16.6 Wh/L at 100ΩF, together with a record cell energy density of 27 Wh/L at 150ΩF. Problems inherent to the capacitor storage systems such as inefficient charging, imperfect utilization of stored energy, large change in terminal voltage and uneven voltage distribution to individual capacitor have been solved by combined electronic circuits. Experienced applications are ranging from solar systems to vehicles. A 15 t CNG hybrid bus powered by a 100 kW ECS has accomplished 2.36 times improvements in fuel mileage. As for power load levelers supported by Japanese national project, a 5.8 kWh system has been built and resulted 84% AC to AC, 94% DC to DC efficiency.