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LiBAT develops lightweight battery powerful enough to sustain flight

22 March 2021

Using electricity from renewable energy sources to power airplanes could cut overall greenhouse gas emissions drastically. However, batteries for the electrification of aircraft propulsion systems have to be light-weight, while maintaining high energy storage and power capabilities. 

State-of-the-art battery systems are still much heavier than conventional fuel sources though, posing a serious obstacle for electrically propelled aviation. In addition to weight, safety aspects need to be thoroughly addressed. 

The LiBAT project has made a breakthrough in this field, having successfully tested a new highly innovative AC battery system, which is powerful enough to maintain level flight for a manned glider. The lightweight, compact, and highly-integrated battery rotated an electric motor with a propeller attached in a lab setting. The advanced LiBAT technology can be applied to a broad range of applications in the transport sectors, taking us one step closer to a more sustainable future.  

LiBAT combated the challenging weight targets by implementing an extraordinary level of integration and combination of advanced technologies. By integrating multi-level-inverter (MLI) technology into the battery, the LiBAT team created a unique, tuneable AC battery system that eliminates the need for additional charging or motoring power electronics and thus saves extra weight. 

Combined with powerful immersive thermal management of both cells and MLIs based on the high-tech liquid NovecTM and a suitable cell choice, both excellent energy density and power performance are realised relative to the low weight and volume of the pack. Both technologies further contribute to superior safety features. Finally, the modular design guarantees a scalable system and promotes integration into a variety of applications and architectures. 

The LiBAT design cuts the weight of the battery pack by one-third compared to conventional battery solutions, while staying compliant with key aerospace requirements, having even more impact as battery cell technology advances and higher energy densities are achieved. The weight advantages are demonstrated for state-of-the-art Lithium Ion round cells, pushing battery pack energy density to around 200 Wh/kg, compared to appr. 130 Wh/kg for conventional solutions. 

Short-range applications

This is a crucial step for low-emissions flight, targeting all the new short-range to regional range electric aircraft in development. 

Short range flight is a new development in aviation, and LiBAT allows many large scale urban air mobility, urban air cargo and regional air travel projects to move closer to entry into service. Because these new applications will offer an alternative with unmatched flexibility and speed to car and train trips, it is very important to ensure that such flights do not emit CO2. Because short-range commute flights will group passengers and will rely on a much more sophisticated traffic regulation system than is enjoyed by car traffic, suburban flying may also end up using less energy overall than suburban driving, even when the cars are electric. 

As the flight range of regional electric aircrafts grows with advancing battery technologies, they may even start to replace some of the conventional short range business flights, with a considerable potential to cut greenhouse gas emissions during operation.

LiBAT can help eliminate the need for fossil-fuel-powered tow planes that generally pull today’s leisure gliders. In general, today’s gliders have no propulsion, hence a tow plane is needed to pull the glider with a rope up to the desired altitude. 

Some examples of what the LiBat solution could be used for include electric air taxis, hybrid propulsion systems, flexible frequency auxiliary networks, electric and hybrid cars, power tools as well as large installations, e.g. marine, rail and grid storages where high voltages and very high energy and power levels are required. 

There are many roads open to LiBAT going forwards. The battery could be developed to higher TRL levels and improved upon. So far, LiBAT has only been ground tested, and seeing the battery power an actual glider prototype during take-off as well as level flight would be a reasonable next objective. On the other hand, the design could be advanced to a new level by utilising the weight saving potential of structural battery integration into aircraft architectures. Furthermore, new battery cell technologies could be considered. 

The research was conducted by the German companies TWT GmbH and LION Smart GmbH within the Clean Sky 2 programme, funded by the European Union through the Horizon 2020 initiative.

LiBAT develops lightweight battery powerful enough to sustain flight
Left: Geometrical design of one LiBAT battery string in explosion view including cells, cell holders, connectors, casing, thermal management connections, as well as Battery management and MLI boards. - Right: LiBAT demonstrator with three battery strings in a row, supplying the three phases of a motor.