Fuel cell taxi. View of a hydrogen fuel cell in Europe's first hydrogen-powered taxi. Fuel cells convert the energy from a chemical reaction into electricity. In this case the two reagents are hydrogen and oxygen, while the waste product is water. The 5 kilowatt fuel cell charges the taxi's batteries which in turn power an electric motor. Refuelling takes around 10 minutes. Zero emission vehicles such as this are essential if urban air pollution is to be reduced. The fuel cell was developed and built by the British company ZEVCO. It was unveiled in London, England, in July 1998.