Many of the B787’s systems have switched to using electric power so some people have referred to it as an “electric aircraft.”
First of all, the electricity which powers the B787 is provided by its engines.
Next are the aircraft systems. Conventional aircraft usually use a combination of electricity, hydraulics, and compressed air (high-temperature compressed air from engines) to power onboard systems. On the B787, systems which were previously powered by compressed air (cabin climate control, anti-icing systems, etc.) were switched to electric power in order to enhance energy efficiency. However, the B787 still uses hydraulics to operate the flight control surfaces, etc.
|In other words, while the percentage of systems powered by electricity has increased, the B787 has not switched to electric power completely. It is more accurate to think of the situation as replacing a natural gas kitchen range with an induction heating stovetop. It is therefore different than electric vehicles that are powered solely by batteries and electric motors.|
As previously noted, the electric generators in the B787’s engines are the main source of electric power.
The B787 is also equipped with an RAT* which can generate electricity for vital systems via wind power in the event that the six electric generators in the engines and APU become unavailable.
The Main Battery provides electricity during the brief period of time that is required for the RAT to deploy. There is also the APU Battery, but this is used for starting the APU. Neither of these batteries are used during normal flight.
*RAT = Ram Air Turbine
This system features a wind turbine connected to an electric generator and a hydraulic pump to provide power to vital aircraft systems.