23-11-2012, 02:10 PM
Super Capacitor
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A supercapacitor or ultracapacitor is an electrochemical capacitor that has an
unusually high energy density when compared to common capacitors.
They are of particular interest in automotive applications for hybrid vehicles and as supplementary storage for battery electric vehicles.
A typical D-cell-sized conventional electrolytic capacitor may have
capacitance of up to tens of millifarads. The same size EDLC might
reach severalfarads
As of 2011 EDLCs had a maximum working voltage of a few volts and
capacities of upto 5 kF
History:
The first supercapacitor based on a double layer mechanism was developed in
1957 by General Electric using a porous carbon electrode [Becker, H.I., “Low
voltage electrolytic capacitor”, U.S. Patent 2800616, 23 July 1957]. It was believed
that the energy was stored in the carbon pores and it exhibited "exceptionally
high capacitance",although the mechanism was unknown at that time. It was
the Standard Oil Company, Cleveland (SOHIO) in 1966 that patented a device
that stored energy in the double layer interface [Rightmire, R.A., “Electrical
energy storage apparatus”, U.S. Patent 3288641, 29 Nov 1966.].
The amount of energy stored per unit of mass is called specific energy,
which is often measured inwatt-hours per kilogram (W⋅h/kg) or megajoules per
kilogram (MJ/kg). In 2010 the highest available EDLC specific energy was 30 W⋅h/kg
(0.1 MJ/kg).Up to 85 W⋅h/kg has been achieved at room temperature in the lab.