Ultracapacitors for use in power quality and distributed resource applications

Double-layer electrochemical capacitors (EC), also known as ultra-capacitors or super-capacitors, are an emerging storage technology already being used for applications such as DC motor drives, UPS systems, and electric vehicles. The latest EC store enough energy to rival a lead-acid battery and can outperform batteries in several key performance parameters such as power density, cycle life and temperature sensitivity. Many EC designs are also more efficient and can be manufactured with metals such as nickel and carbon that are environmentally benign relative to the metals in lead-acid or nickel-cadmium batteries. As the EC technology improves further, an impressive world of applications should emerge. These applications include intermittent renewable energy storage, bulk power system peak shaving, load leveling, and various other distributed resource possibilities. This paper reviews the fundamentals of EC, their status, and expectations for future deployment.