All systems go: Europe's aviation is “en route” towards Hybrid-Electric Propulsion

The Clean Sky 2 LPA Hybrid Electric Ground Demonstrator project lays the foundation for the Rolls-Royce / Airbus Joint E-Fan X Project
The Clean Sky 2 LPA Hybrid Electric Ground Demonstrator project lays the foundation for the Rolls-Royce / Airbus Joint E-Fan X Project

As the 2020s kick off, short-medium range regional aviation is entering a new age where fuel-efficient turbine powered aircraft could start to be complemented by the entry-into-service of small hybrid-electric powered aircraft. Hybrid-electric propulsion is a major stepping stone towards achieving the longer-term dream of fully electric, truly carbon neutral (without offsetting) emission-free aviation for all flights (short, medium and potentially long-haul too).  Aligning with Europe's Flightpath 2050 goals, Clean Sky is playing a significant role in nurturing the essential techno-bricks that are required to advance the science of hybrid-electric propulsion, keeping European aviation at the forefront. 

Aviation's centre of gravity is shifting towards electrification, and the Clean Sky ecosystem plays a fundamental role in the success of that process within Europe. One of the showcase Clean Sky funded projects that is currently underway is the ambitious hybrid-electric technological demonstrator – E-Fan X. Launched by Airbus in partnership with Rolls-Royce, the programme aims to mature technology performance, safety and reliability, thereby accelerating progress on alternative propulsion.

‘When you look at the future of aviation, it is essential that alternative sustainable solutions be integrated throughout an aircraft’s lifecycle, so that fuel-burn, and ultimately CO2 emissions, are reduced,’ says Sébastien Dubois, Clean Sky Acting Head of Unit and project officer for Large Passenger Aircraft projects. ‘Clean Sky supports the equipment design and ground test campaign of the E-Fan X project, that are enabling sound assessments to be made with regards to the key challenges that we are facing.’

Airbus and Rolls-Royce have a clear roadmap that will see overall ground integration taking place over the course of 2020, in anticipation of a flight test campaign which will begin in 2021. 

To give a sense of scale and context, a medium-range, single-aisle airliner would require approximately 20 megawatts of power to generate enough thrust, using electric fans, to replace conventional turbine engines. By comparison, the E-Fan X will test a hybrid-electric propulsion system capable of outputting 2 megawatts. Fundamental architectural elements of the E-Fan X demonstrator include a generator, a 3000v DC electrical distribution supply, energy storage in the form of a high-power battery pack, an electric motor (which replaces one of the aircraft's four conventional turbofan engines), and a data transmission system on the flight deck which provides flight test instrumentation with telemetry.

Stefan Stückl, Teamleader Simulation, E-Aircraft Systems at Airbus, says: ‘Noise, NOx and CO2 emissions reduction are a core part of the EU’s Horizon 2020 ambitions. Radical new technologies will be necessary to achieve these goals. For this, we need to continue the many research and development initiatives that are underway in order to identify the most promising.’

‘Clean Sky’s contribution to this challenge will be supporting Airbus and Rolls-Royce in the design, test and integration of the two megawatt generator, the power electronics, and the techno-bricks required to cool down the systems,’ says Dubois. 

‘There is still a long way to go in terms of the commercialisation of this type of technology,’ he continues. ‘There is no miracle solution, the journey to decarbonise the aviation industry will be a long one. We will face numerous technological challenges in terms of the amount of energy, insulation, power generation, power transmission, propulsion systems, and in terms of the management of distributed propulsion system.’ 

Stückl also accentuates the benefits of the Clean Sky framework in strengthening Europe's global position in aviation, noting that: ‘Clean Sky provides a unique European platform which facilitates collaboration across the entire aerospace community in Europe. Research and development projects can be initiated and executed in a flexible and effective manner, encouraging the formation of consortia including the main players in the industry as well as SME companies.’

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