Rolls-Royce Turbogenerator For Hybrid-electric Aircraft

By Spyros Georgilidakis | June 26, 2022

Rolls-Royce has announced a turbogenerator project, for hybrid-electric aircraft and eVTOLs. It will run on SAF and eventually, on hydrogen.

Rolls-Royce Turbogenerator For Hybrid-electric Aircraft
Image: Rolls-Royce

We have seen and continue to visit several initiatives around battery-electric or hybrid aviation projects. They tend to involve small aircraft with a single-digit number of seats, or eVTOLs (electric vertical take-off and landing). Some express concerns about the feasibility of these projects, in terms of their range or gross weight – or both. And some opine that initially at least, hybrid electrics may offer more options.

So this brings us to Rolls-Royce and its development of a turbogenerator for advanced air mobility applications. In simple terms, this is a device that runs off a gas turbine, to generate electricity. This type of generator is quite common for large-scale applications – such as a backup power source for city grids. Rolls-Royce and its subsidiaries have substantial experience with these enormous machines.

Rolls-Royce Turbogenerator For Hybrid-electric Aircraft
Image: Rolls-Royce

But this application will be much smaller. Rolls-Royce will design a turbogenerator family serving a power range between 500 kW and 1,200 kW. This range is necessary, to cover a variety of different Advanced Air Mobility (AAM) applications. Rolls-Royce will design the entire unit, including the jet engine, the generator and the power electronics and distribution systems.


Rolls-Royce – Making The AAM Turbogenerator

By designing the entire turbogenerator as a unit, Rolls-Royce wants to make it as lightweight as possible. And in terms of its applications, the company believes that there will be a need for such a system for multiple designs. Working as a small APU, it could provide backup power and/or extend the range of battery-electric designs. So the system will work as a serial hybrid, charging batteries. Or, it could power electric motors directly.

Vertical Aerospace VX4. Image: Vertical Aerospace

The company wants to make it capable of running on hydrogen, offering similar functionality on hydrogen-electric or hydrogen combustion aircraft. Rolls-Royce is developing this turbogenerator in Germany, Norway and Hungary. It has funding for this project from the German Ministry for Economic Affairs and Climate Action.

The program’s goal is to create a baseline system, that will be certifiable on specific eVTOL and other aircraft designs. Some of the scepticism towards AAM vehicles is that they often involve startups, with little experience in aircraft certification. In that sense, Rolls-Royce is in a better position than most.

Tecnam’s P-Volt

We have seen that the turbine manufacturer is involved directly in several battery-electric projects. So it will be interesting to see if Rolls-Royce and its partners will use a turbogenerator on designs like the P-Volt. The range will likely be an issue with early versions of such aircraft. But to use a turbogenerator as a range extender, these aircraft will need to carry fuel, too.


1 comment

  • My ignorance I’m sure but I had to ponder for a while before realising SAF stands for Sustainable Aviation Fuel.

    Interesting article. Thanks.

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