Electric buses

An electric bus is a bus that is powered by electricity.

Electric buses can store the electricity on board, or can be fed continuously from an external source. Buses storing electricity are majorly battery electric buses, in which the electric motor obtains energy from an on-board battery, although examples of other storage modes do exist, such as the gyrobus which uses flywheel energy storage. In the second case, electricity is supplied by contact with outside power sources. For example, overhead wires, as in the trolleybus, or with non-contact conductors on the ground, as seen in the Online Electric Vehicle. This article mostly deals with buses storing the electricity on board.

As of 2017, 99% of electric buses have been deployed in China, with more than 385,000 buses on the road, which is 17% of China’s total bus fleet.^[

Buses can use capacitors instead of batteries to store their energy. Ultracapacitors can only store about 5 percent of the energy that lithium-ion batteries hold for the same weight, limiting them to a couple of miles per charge. However ultracapacitors can charge and discharge much more rapidly than conventional batteries. In vehicles that have to stop frequently and predictably as part of normal operation, energy storage based exclusively on ultracapacitors can be a solution.^[

China is experimenting with a new form of electric bus, known as Capabus, which runs without continuous overhead lines by using power stored in large on-board electric double-layer capacitors, which are quickly recharged whenever the vehicle stops at any bus stop (under so-called electric umbrellas), and fully charged in the terminus.

A few prototypes were being tested in Shanghai in early 2005. In 2006, two commercial bus routes began to use electric double-layer capacitor buses; one of them is route 11 in Shanghai. In 2009, Sinautec Automobile Technologies,^[ based in Arlington, VA, and its Chinese partner, Shanghai Aowei Technology Development Company are testing with 17 forty-one seat Ultracap Buses serving the Greater Shanghai area since 2006 without any major technical problems. Another 60 buses will be delivered early next year with ultracapacitors that supply 10 watt-hours per kilogram.

The buses have very predictable routes and need to stop regularly, every 3 miles (4.8 km), allowing opportunities for quick recharging. The trick is to turn some bus stops along the route into charging stations. At these stations, a collector on the top of the bus rises a few feet and touches an overhead charging line. Within a couple of minutes, the ultracapacitor banks stored under the bus seats are fully charged. The buses can also capture energy from braking, and the company says that recharging stations can be equipped with solar panels. A third generation of the product, will give 20 miles (32 km) of range per charge or better. Such a bus was delivered in Sofia, Bulgaria in May 2014 for 9 months’ test. It covers 23 km in 2 charges.^[