Forty Kilojoule Carbon Double Layer
presented at the International Seminar on Double Layer Capacitors and
Similar Energy Storage Devices, December 6, 1993
David A. Evans
A high performance carbon double-layer
capacitor (DLC) was constructed using a five element equivalent circuit
model. It was designed for 15, 30, 60, or 120 V operation, depending on
buss connections. Activated carbon with sulfuric acid was used to forrn
its electrodes. The prototype had a mass of 27.5 kg and a volume of 17
liters. It stored more that 40 kJ of energy.
Power performance was measured using
resistance, constant-current, and constant-power loads. Currents as
high as 400 A and power levels up to 23 kW were used. The capacitor
would reproducibly deliver 5 kW for 4 s, 10 kW for 1.1 s, 15 kW for 0.5
s, or 20 kW for 0.1 s. Voltage imbalance problems were not encountered.
Capacitor self-discharge power was below 1 W. The feasibility of this
approach was clearly demonstrated. Design and construction details are
reported. Methods to further reduce the size and weight of large double
layer capacitor power units are described.