Airbus demonstrator E-fan x receives an electric motor

Why hybrid electric planes could be the way for an economic and ecologic air transportation

Whenever it comes to discussing electric airplanes, we often hear the explanation that a battery delivers only 1MJ/kg versus 43 MJ per kilogram for kerosene, therefore it is too heavy for an airplane. But this  explanation is flawed, because it doesn’t take into account the fact that a thermic engine transforms into movement only 20% of the energy, whereas an electric engine transforms 85% of the energy into movement. That’s why an electric car with a 500 kg battery (for example a TM3) gets a range of about 530 km, about 7 times less per Kilogram than with 40 Kilograms of fuel. If we take into account only the fact that a battery delivers only 1MJ/kg versus 43 MJ per kilogram for kerosene, an electric car should have a battery that is 43 times heavier than a full fuel tank to get the same range of the latter. That’s why labelling batteries as enourmously overweight to power a plane is unfair.

Nevertheless batteries weight is still an hindrance for the efficiency of electric planes, especially when it comes to range. That’s why hybrid electric planes, carrying a small battery charged by a gas turbine generator, seem to be a viable solution, as long as batteries don’t become more performant and light. It looks like Airbus is betting on this technology.

Avro RJ100 arrives for the conversion in Toulouse

In Oktober 2019 a used RJ100 regional jet landed at Airbus in Toulouse for the conversion into hybrid electric aircraft. The aircraft manufacturer, together with Rolls Royce, wants to retrofit the jets aircraft and replace one of the engines with an electric motor.

The future test aircraft “E-Fan X” serves as a demonstrator for new hybrid technologies in aircraft construction. The “crude plane” intended for conversion, G-WEFX, arrived on Wednesday afternoon from Cranfield in England as flight “AIB01 FX” in Toulouse. In addition, the airplane already carries parts of the E-Fan X paint finish.

Now begins an extensive renovation that uses the entire cabin. So powerful batteries are installed on board, a powerful generator behind the wing in the fuselage, a 3000 volt DC system and extensive test equipment. Finally, one of the jet engines, namely the inner right engine “number 3”, is replaced by an electric motor.

If the separation of power generation and electric motor is proven, you could install the aircraft engines in other places on board in the future, such as in the fuselage, and freely install only small electric propellers or blowers at the desired location. In addition to system tests and the serial maturity of the new technology, the aircraft should also pave the way for certification.

In the long term, the aviation industry hopes to reduce CO2 emissions by 75 percent by 2050 with the new technology.