“SuperCap“ Double-Layer Capacitors

Innovative Alternative to Energy Storage Using Batteries

The issue for manufacturers of electronic components is not whether, but rather how quickly and to what extent they can contribute to environment-friendly products with innovative solutions. Using double-layer capacitors from WIMA, efficient energy storage with long service life can be realized today for wind turbines, photovoltaic applications and new drive technologies.

SuperCap C (cylindrical) and SuperCap R (rectangular) double-layer capacitors developed by WIMA are storage capacitors with very high capacitances in the farad range. SuperCaps can be cascaded in modules to meet the operation voltage of the respective application. In contrast to energy storage using batteries, the current charge state is available at any time from a SuperCap module without having to anticipate a sudden voltage collapse. Other benefits over conventional battery and rechargeable battery solutions include maintenance-free operation and a comparatively low weight.

SuperCaps as Energy Storage

SuperCap modules are suited perfectly for energy storage, where high power must be supplied/absorbed within a short period of time. This is only conditionally possible with other capacitor types and batteries.
Slip controllers are used in large-scale wind turbine systems to control the rotation speed by altering the angle of the rotor blades. The drives are mains-independent and use the electrical energy stored in batteries or double-layer capacitors. Due to the wide fluctuations in temperature in the wind tower top housing, these storage devices have to meet stringent requirements.
Generally a few 100kJs of electrical energy are required for a system start time of approx. 10 to 20 seconds when starting a micro-turbine or a fuel cell. Because of their significant maintenance, service life and weight benefits, double-layer capacitors are more frequently replacing customary starter batteries.

SuperCap modules can also be used for energy storage in photovoltaic systems, hence serving as long-term "power units". Here the capacitors can supply periodic power with higher levels of current than supplied by the photocells. The energy drawn is then recharged within a specific time using solar irradiation.

The recuperation of braking energy, such as in the automotive sector, is a real challenge in times of increasingly scarcer resources. A vast amount of kinetic energy is generally released when braking. The very high currents are generated momentarily and can be stored using SuperCap modules and be made available again when required.

The technical structure of a double-layer capacitor can be understood simply as a plate capacitor in which activated carbon is used as the electrode material. This significantly increases the surface of the electrode. To visualize this, the internal surface of the double-layer capacitor can cover a football pitch.
Solute conducting salt in the diluted or organic solvent is used as the electrolyte between the electrodes as the conductive liquid. Applying a voltage causes disassociated electrolyte molecules to accumulate as cations/anions on the carbon-coated electrode surfaces, generating the so-called double-layer.
SuperCaps can handle very high currents by virtue of their low ESR (mΩ range). They have a service life in excess of 10 years and can easily sustain more than 500,000 charge/discharge cycles. The efficiency is far higher than 90%. In contrast to other storage media, totally discharging the SuperCap does not present a risk of damage.

For further information please contact your local SPOERLE Branch Office or visit www.wima.de

© SPOERLE 2008