Energy in the Future series: What is the potential of Supercapacitors for energy storage and transfer?

Supercapacitors are energy-storing devices that use high surface area electrode materials (such as a carbon powder) and liquid electrolytes which act as dielectrics (electrical insulators). Supercapacitors can be broken down into three main categories: double-layer capacitors (store charge electrostatically), pseudocapacitors (store charge electrochemically), and hybrid capacitors, which are a combination of double-layer capacitors and pseudocapacitors. Compared to conventional capacitors, supercapacitors have a higher capacitance (electric charge-storing capability. When compared to batteries, supercapacitors have a higher power density, lower energy density and a longer cycle life.

Like the automotive industry, the rail industry can use supercapacitors onboard rolling stock for regenerative braking and start-stop systems. The supercapacitor can use surplus energy from braking to provide energy for acceleration, while a battery can provide range and recharge the supercapacitor between surges. Excess energy could be used to power train stations via reverse-supply power substations. Consequently, this could reduce operational costs, maintenance costs, energy dependence, improve voltage stability and increase energy efficiency. In addition, supercapacitors with load levelling control can be used in conjunction with fuel cells, which could result in hybrid rolling stock with a fast and dynamic response. Results from simulations carried out by the Institute of Transportation Studies have suggested that automotive vehicles could achieve greater fuel efficiency and reduce the electrical and mechanical stress on fuel cells through the use of supercapacitors.

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