(video: a supercapacitor bus recharges in Shanghai)
As gas prices are getting higher and higher, the need to find other alternatives to gas-powered buses becomes more and more urgent. High frequency bus lines have no problem in this conversion, as they can be turned into trolleybus lines without excessive cost, but this reconversion can be problematic for low frequency lines.
For this kind of lines, a solution may be the use of frequently,fast-recharging electric buses. Instead of kilometers of bus overhead wire, this kind of buses will require a network of recharging stations, each one being a short section of trolleybus overhead wire.
Two variants of this system exist, and differ mainly for the electricity storage system.
The most ancient one was the Gyrobus, experimented in the 50s in the cities of Yverdon, Gent and Kinshasa. In this variant, electricity is stored in a flywheel turning at 2000-3000 rpm. As the bus plugs into the grid, the wheel is put in motion by an electric engine. When the bus unplugs, the engine turns into a dynamo that takes back the energy stored in the flywheel and sends it to the engine. A gyrobus needed to recharge every 5-6 km, and a recharge could take from 30 seconds to 3 minutes. The high mass and spin of the flywheel of the gyrobus affected significally its behaviour on street, making Gyrobus rides smoother than average bus rides.
A new version involves the use of supercapacitors, batteries that could be recharged in a very short time. Its performance are similar to the gyrobus’s ones, the main difference being the absence of the flywheel and its consequences on buses’s beahviour. This version is currently operating in Shanghai.