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SORCERER: Clean Sky wizardry for multifunctional aircraft composites

Supercap architecture scalebars

Electrically-powered aircraft mean lower carbon emissions and cleaner air, benefiting European citizens. As aircraft become increasingly electrically powered it’s important to consider new ways to carry more electrical energy onboard. Combining this aim with the ever-present need to reduce weight on aircraft using composites is the ambition of Clean Sky’s SORCERER (Structural pOweR CompositEs foR futurE civil aiRcraft) project. SORCERER focuses on the development of unique composite materials that can additionally store and deliver electrical energy.

Illustration of a structural supercapacitor developed in SORCERER
Illustration of a structural supercapacitor developed in SORCERER

SORCERER is a fitting name for the wizardry that applies Clean Sky innovation to two of the biggest challenges in aviation’s more electrified future – energy storage and lightweighting.

The project, which started in 2017 and runs until July 2020 with a budget of €1.6 million, explores the potential for combining electrical energy storage with revolutionary lightweight aircraft composites that form elements of the aircraft structure. SORCERER contributes to Clean Sky’s Multifunctional Fuselage Demonstrator programme, which focuses around validating high potential combinations of airframe, cabin, cargo and system elements, making extensive use of composite thermoplastics, and looking at how to pre-equip, or make use of, multi-purpose systems and materials. It’s a win-win proposition, pushing the frontiers of European aviation’s lead in multifunctional materials.

’This project is also an enabler for future electrical and hybrid-electric propulsion aircraft,’ says Clean Sky 2 project officer Jimmy Tchen. ’In terms of energy storage there’s a big challenge. The traditional way to minimise Illustration of a structural supercapacitor developed in SORCERER the mass of energy storage components has been to try to increase the power density of the batteries. SORCERER’s approach is to develop multifunctional material which could combine structural and energy storage functions, providing weight and volume reductions.’

The project, which is funded in part by the EU’s prestigious Horizon 2020 programme, is undertaken by a consortium led by Imperial College London (ICL) and supported by Chalmers University of Technology in Gothenburg; the Royal Institute of Technology (KTH) in Stockholm; and IMDEA Materials Institute in Madrid. The workload is divided into three interconnected streams.

Firstly, Imperial College is exploring the critical issues associated with structural supercapacitors and their adoption into aerospace platforms. This means confronting the issues associated with improved power and energy densities, encapsulation and laminate hybridisation, and multifunctional design methodologies.

The project’s second stream focuses on technical issues associated with structural batteries, an activity led by Chalmers University. Here, the materials proposed will be evaluated with respect to their future aircraft operational conditions.

Thirdly, there is a stream of activity related to structural energy generation using ionintercalated carbon fibres, and energy harvesting solutions, led by KTH. Here the focus is on enhancing efficiency and power output, with the aim of progressing this technology towards Technology Readiness Level (TRL) 3.

Demonstrator of structural supercapacitor made by project partner IMDEA
Demonstrator of structural supercapacitor made by project partner IMDEA

According to Clean Sky’s Tchen, the current state of progress is that: ’In terms of TRL maturity the structural supercapacitor is at a more mature level than the two other technologies. At the lowest maturity, energy harvesting. This will be a lab scale demo. And for the structural batteries they’re looking at a full size demonstrator.’

For the structural supercapacitors the SORCERER team plans to manufacture an aircraft door-frame beam, a structural part with embedded structural supercapacitors. But this might prompt a question. As everyone knows, batteries on mobile phones and laptops have a limited life. They don’t hold their charge so effectively after a couple of years. If an aircraft structure is also effectively a form of battery, does that mean that the airframe will have a limited life in terms of its ability to store energy?

’Yes, that is a potential issue, as it would be with batteries,’ says Professor Emile Greenhalgh, Professor of Composite Materials and Head of the Composites Centre at Imperial College London, who leads the SORCERER project. ’But the technologies we are developing are covering a range of power sources, not just batteries. For instance, the work at ICL is focused on supercapacitors, which don’t store as much energy, but have much better longevity.’

’This is not embedding batteries, but producing a material which intrinsically can undertake dual roles. This builds on worldleading knowledge and capabilities which have been developed in the UK and Spain (structural supercapacitors) and Sweden (structural batteries) over the last decade, and on learnings from a successful forerunner of this project, STORAGE, funded by an earlier EU research funding scheme. This project enables full electrification of future air transport, which is an aspiration of organisations such as Airbus, who wish to have a fully electric 100 seat aircraft by 2050,’ says Professor Greenhalgh.

SORCERER is a very important step for European aviation towards making electric aviation a reality, but there is still a long way to go. If conventional batteries were adopted for a 100 seat aircraft, the performance of the batteries would need to exceed the current state of the art by a factor of at least 10. This would mean adoption of very exotic battery chemistries which are immature. It would also mean aircraft carrying very highly concentrated sources of energy (i.e. at energy densities akin to that of explosives) – so this approach clearly has safety issues that would require extensive research and testing.

’Our alternative approach means the concentration of energy needed would be much lower, and hence would negate the same safety issues,’ says Professor Greenhalgh. ’It would also mean an overall reduction in aircraft weight, offering savings regarding environmental impact. Europe is currently world leading in this field, although China, Korea and the US are putting a lot of resources in this area. If we keep this technology in Europe, it will mean Europe will be best placed to deliver the first fully electric passenger airliner.’