A researcher and professor of materials science and engineering at Drexel University in Philadelphia has suggested that supercapacitors could be a green energy source when used to power buses.

In an article written by Philip Ball for the Energy Quarterly feature of MRS Bulletin, Yury Gogotsi explains supercapacitors as power-storage devices that can supply onboard electrical power in hybrid vehicles. While batteries store energy in chemical form in substances that can react to release electrical energy, capacitors store it by piling up electrical charge on two electrodes. The larger the electrodes and the closer they are, the more energy can be stored.  

Supercapacitor technology is deployed on trams in Germany, as well as on Spanish and French trains, hybrid buses around the world and on garbage-collection trucks in the U.S. On buses, it can reduce carbon dioxide emissions by around 30%, officials said. The Munich, Germany-based heavy-vehicle manufacturer MAN estimates that its supercapacitor-fitted coaches each save around $4,500 a year on fuel costs.

A copy of Ball’s article can be found here.