Hydrogen in the air: electric aircraft

Aerospace companies are investigating several options for reducing the dependency of aircraft on fossil fuels, one of which is the use of hydrogen to power on-board fuel cells. These would generate electricity that could be used for a variety of purposes, from powering the aircraft itself to powering the electrical systems on board a larger airliner.

There are several electrical systems that are powered by electricity generated by the aircraft’s engines. These include the hydraulic and pneumatic systems that control the aircraft; the air-conditioning systems, lighting and heating; the anti-icing systems for wings and control surfaces; and the on-board avionics and electronic systems such as in-flight entertainment.

Another important use for electricity on a large aircraft is to start the engines, with a system known as the auxiliary power unit (APU) running motors that turn the engine rotors until they are running fast enough to compress air into the engine and start burning fuel. The APU is started up from batteries or a ground-based power unit.