Rolls-Royce develops hybrid aircraft engine to reduce CO2 emissions

Rolls-Royce, together with the Norwegian research organization SINTEF, is developing a hybrid aircraft engine that combines an electric motor with a combustion-based drive. This is intended to reduce an aircraft's CO₂ emissions by up to 30 percent, SINTEF announced on Monday. The technology could initially be used in aircraft for regional flights.

The electrification of air traffic beyond sport aviation is not so simple, as a lot of power is needed in flight. Battery-electric aircraft would be too heavy due to this power requirement because of the batteries needed. Fuel, on the other hand, is lighter.

Rolls-Royce and SINTEF therefore consider a hybrid drive solution – similar to hybrid vehicles – to be the best option for short-haul flights. The use on short-haul flights results from the limitations of electromobility on long-haul routes. The drive combines a combustion engine with an electric motor. The hybrid system is then intended to drive the engine blades.

However, the challenge is not solely in the development of the hybrid drive, but a gearbox also needs to be developed through which both motors can jointly deliver their power to the optimized engine blades. In addition, there is the electric drivetrain and the correct energy management for an energy-saving power supply.

Further Development Path

Initially, however, Rolls-Royce and SINTEF are working together on the electrical insulation of the stator of the hybrid drive. In an electric motor, the stator is the stationary element in which the rotor rotates.

"The stator converts the current flowing through the coils into an alternating magnetic field that drives the rotor," explained Astrid Røkke, development engineer at Rolls-Royce Electrical Norway. "The coils require insulation to prevent short circuits. This must be as thin as possible without affecting the lifespan of the insulation."

The insulation must withstand high voltages and frequencies up to 50 kHz. The problem: So far, there are only values for how much insulating materials can withstand up to a frequency of one kilohertz. For higher frequencies, this still needs to be researched to then find suitable material that can also meet the requirements for lifespan.

The path to a functional hybrid engine for regional aviation still seems long. The goal of the effort is a reduction in CO₂ emissions. Aviation accounts for about 4 percent of the total CO2 emissions of the European Union. One percent of total emissions could be saved by using hybrid engines, SINTEF explains.

(olb)