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Innovations in Aviation – electric propulsion

25th Feb 2021

The Paris Agreement on climate change entered into force in November 2016, with a goal of limiting global warming to below 2, preferably to 1.5 degrees Celsius – compared to pre-industrial levels.  According to the International Energy Agency (IEA), CO2 emissions from aviation in 2019 equated to around 2.8% of global CO2 emissions from fossil fuel combustion.  So, it’s probably no great surprise that there has been much research in recent years on ways to reduce the carbon footprint of the aviation sector.

Clearly, there was a significant reduction in aviation-related emissions in 2020 due to the travel restrictions resulting from COVID-19.  However, as the world slowly returns to a version of normality, airline travel and related emissions will increase.  So, the need and desire for innovations to help reduce aviation’s carbon footprint will remain.

Alternative fuels

Jet engines for civil aircraft have undergone improvements in efficiency over the years, but are largely still reliant on the use of kerosene as fuel.  Work has been done on so-called “drop-in” fuels, being alternative fuels which can be used in place of kerosene without requiring extensive redesign of existing engines, and related aircraft systems.

Innovations in electric propulsion

However, another area that has seen innovation in recent years is that of electric propulsion systems for aircraft.

One example is E-Fan X, which was active between 2017 to April 2020.  E-Fan X was a hybrid electric aircraft technology demonstrator programme.  The programme used a BAe 146 aircraft as a platform, and replaced the core of one of the aircraft’s four turbofan engines with a 2MW electric motor.  Power for the electric motor was provided by a turboshaft engine and generator located in the rear of the aircraft fuselage, with an air intake provided in the fuselage to feed the turboshaft engine.  Additionally, a 2MW battery was also provided in the fuselage to provide energy storage.

However, aircraft have also been developed solely employing electric power, without the need for conventionally powered engines to provide propulsion or to serve as means for generating electric power.  Much of the progress to date has been in the light aircraft sector.  Aircraft are being developed which use a large number of electrically-powered engines arranged on the aircraft – known as distributed electric propulsion.  One such example is the Lilium jet, which is intended to transport 4 passengers and a pilot over a short range, and have a 60 minute flying time.  The aircraft employs a configuration of 36 electrically-powered ducted fans arranged in different groups to provide propulsion, and able to tilt to provide vertical take-off and landing (VTOL) capability.  The integration of the fans into the structure of the wings means that the housings/nacelles for the fans can also contribute to the generation of lift.

The International Civil Aviation Organisation (ICAO) provides a non-extensive list of various projects relating to the development of aircraft employing electric propulsion systems.

As you might imagine, research and development in electric propulsion has been accompanied by an increase in patent filings in this sector.

One example of such a filing is shown here, relating to a hybrid gas-electric propulsion system for an aircraft.  For this hybrid system, power generated by two conventional jet engines is used to drive an electric motor provided in a boundary layer ingestion fan provided at the rear of the aircraft’s fuselage.  In-flight, the fan will ingest a boundary layer of air flowing over the fuselage of the aircraft, thereby reducing aircraft drag and enabling an increase in propulsive efficiency.

Another example relates to an aircraft having a propulsion system in which electrically powered ducted fans are integrated into the wings of the aircraft.  This again is a hybrid design, employing a turboshaft engine for driving a generator, with the generator providing AC power to the ducted fans.

The upscaling of electric propulsion to larger civil aircraft with longer range will present significant challenges for the future, but will also provide opportunities for innovation and the development of valuable new intellectual property.

This article is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.

Andy Williams
Senior Associate
About the author

Would you like to know more? You can talk to Andy Williams who will be able to help. Call +44 (0)1223 360 350


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