Municipal transit agencies have tried to reduce the carbon footprint of their bus fleets using a range of options over the years, from biofuels and hydrogen to batteries and hybrid-electric diesel. Now a Chinese company and its U.S. partner say that ultracapacitors could offer the greenest and most economical way of powering inner-city buses….

Buses in the Shanghai pilot are made by Sunwin Bus, a Chinese joint venture company with Volvo of Sweden, and uses ultracapacitors manufactured by Shanghai Aowei. Foton America Bus, based in Germantown, TN, will be manufacturing the ultracapacitor buses that will be sold in the United States. The ultracapacitors are made of activated carbon and have an energy density of six watt-hours per kilogram. (For comparison, a high-performance lithium-ion battery can achieve 200 watt-hours per kilogram.) Clifford Clare, chief executive of Foton America, says another 60 buses will be delivered early next year with ultracapacitors that supply 10 watt-hours per kilogram.

"The ones in Shanghai right now have been on the road for three years without incident, without failure whatsoever, which in the bus industry is phenomenal," says Clare, who adds that his company is in talks with New York City, Chicago, and some towns in Florida about trialing the buses. "It will end up being a third generation of the product, which will give 20 miles [of range per charge] or better."