Fuel cell bus

A fuel cell bus is a bus that uses a hydrogen fuel cell as its power source for electrically driven wheels, sometimes augmented in a hybrid fashion with batteries or a supercapacitor. The only emission from the bus is water. Several cities around the world have trialled and tested fuel cell buses, with over 5,600 buses in use worldwide, the majority of which are in China. Owing to the greenhouse gas emissions and particulate pollution produced by diesel buses, transport operators have been moving towards greener and cleaner buses (such as hybrid electric buses and battery electric buses) since the early 2000s. However, battery electric buses lack range compared to diesel buses, take time to charge and have reduced energy storage in cold weather. Transport operators have therefore evaluated alternatives such as hydrogen fuel cell buses. Hydrogen fuel cells generate electricity by reacting hydrogen and oxygen in the presence of a catalyst, the by-product of which is water. This electricity is used as a power source for an electric motor, which drives the wheels of the bus. Some companies have proposed using the fuel cell as a range extender, combining it with a larger battery or a supercapacitor. Hydrogen has a higher energy density than lithium batteries, making it suitable for heavy vehicles such as buses and trucks. The provenance of hydrogen fuel varies - with green hydrogen (produced using renewable electricity) being significantly more environmentally friendly than brown hydrogen (produced by burning coal or lignite) or grey hydrogen (produced by steam heating natural gas). From the late 1980s, concern regarding diesel emissions from buses led to experimentation regarding the use of fuel cells to power vehicles. Initial proof of concept work involved demonstrating that fuel cells could be packaged into a bus, and successfully power one. Between 1994 and 1995, the Georgetown Fuel Cell Bus Program (led by Georgetown University and the United States Department of Energy) demonstrated three buses powered by a phosphoric acid fuel cell from Fuji Electric.