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Hybrid Storage

Ultracapacitors and batteries work together to solve power quality problems.

Fortnightly Magazine - June 2010

that’s handled by a primary energy source, and at times, there are peak power demands that require additional capacity. Engineers either cansize the batteries to handle peak demands, or use ultracapacitors to bridge the demand, which has the added benefit of being able to size the primary energy source.

Combinations of ultracapacitors and batteries in energy storage systems can reduce the size, weight and the number of batteries in a system. Such hybridized systems are more efficient and use fewer expensive materials. They also can extend the cycle life of the battery component, which makes the whole system greener.

Hybrid power sources consisting of batteries and ultracapacitors are being used in low- and intermediate-voltage applications. Because these systems are scalable, they have potential for use at high-voltage levels when augmented with the appropriate power electronic circuitry. In order for there to be a burgeoning of the ultracapacitor market, manufacturers will have to increase energy density further, which will make the devices more attractive from both a cost and size point of view. A number of companies are working on this problem, and preliminary research suggests energy densities of ultracapacitors have the potential to exceed the energy densities of many battery types. Some estimates suggest energy densities could be increased by as much as a factor of 100, which would allow for the wholesale replacement of batteries in many applications. Even a modest increase in energy density has the potential for replacing lead-acid storage batteries with ultracapacitors.

The future for ultracapacitors looks bright. If the energy densities and voltage level issues can be overcome at an economical price point, their usefulness in ensuring power quality will increase by orders of magnitude.