Flying High with batteries – EADS Innovation Works, the corporate research and technology network of EADS, is showcasing an allelectric propulsion system concept at Le Bourget. The VoltAir technology concept platform supports the vision of a zero-emission air vehicle which could become a reality 20 years from today. VoltAir is one of the projects that are grouped under the name of eCO2avia by EADS Innovation Works as part of the EADS Group’s research towards achieving the aviation industry’s climate protection goal.
The current design calls for liquid nitrogen tanks that would be used to cool a superconducting, rear-mounted engine. The plane is designed to make short trips carrying just 50 to 70 passengers.
The VoltAir’s next-generation electric energy storage system (batteries) will power highly efficient superconducting electric motors which drive counter-rotating, shrouded propellers. Combined with a radical approach to airframe design, the expected promising developments in electric propulsion technologies could pave the way towards ultra-quiet and emission-free flight.
* No carbon dioxide emission during flight
* Next-generation energy storage
* Ultra high density electric engines
* Enhanced passenger comfort
“VoltAir is an upstream research concept, not a near-term commercial approach”, said Jean Botti, Chief Technical Officer of EADS. “Our research is very forward-looking and could be beneficial in different applications. As a systems architect for aircraft, we are pushing the envelope in this research to stimulate new ideas. The objective here is to push the envelope to move towards more electric, emission free propulsion.” Boosted by the large demand for automotive applications and emerging hybrid and fully electric cars, high-density electric energy storage systems achieved impressive advances in their capabilities during the last decade. The capabilities of today’s batteries are still far away from what is theoretically possible. New materials with promising capabilities for a new generation of energy storage are currently being investigated. Some of them are based on lithium-air and lithium-sulphur combinations.
Scientists expect these batteries to exceed energy densities of 1000 Wh/kg within the next two decades, which would mean more than doubling today’s performance. The VoltAir concept is based on the assumption that the required level of energy density can be achieved within the timeframe mentioned.
The VoltAir’s batteries are integrated in replaceable, containerised units in the fuselage hold to enable an easy replacement of depleted batteries at the airport, similar to the loading and unloading of cargo or luggage containers. Keeping the recharging and maintenance process for the batteries on the ground reduces the system’s weight and complexity onboard the aircraft and allows for fairly conventional airport operations. Turnaround times are not affected since ‘repowering’ can be considered to be at least as fast as conventional refuelling.
Conventional electric engines are known to be very efficient (up to 98% propulsive efficiency) but generally do not offer the power densities (energy output per unit weight / kilowatt per kilogramme) required for large airborne missions. The discovery of High- Temperature Superconducting (HTS) materials provides the key solution for this problem. These materials are the basis for high-energy density superconducting motors that are already becoming available today and which are expected to exceed the weight efficiency of gas turbines as their development progresses. The necessary cooling of these engines to reach superconducting temperature can be realised with low-cost and environmentally friendly liquid nitrogen. In the VoltAir Technology Platform, HTS motors are expected to reach power densities of 7-8 kW/kg with almost no electrical losses.
While the motors deliver their full power to the propellers, passengers onboard the VoltAir will enjoy the extremely low noise level of the engine. In flight, this fully electric propulsion system does not emit any carbon dioxide or nitrogen oxides.
In addition to the benefits of the propulsion system, the VoltAir Technology Platform offers improvements from the passengers’ point of view. The shaping of the fuselage in terms of width/length for improved aerodynamics will also result in very low noise levels originating from the airflow along the fuselage skin. The already very quiet electric motors are located downstream at the rear of the fuselage, far away from the cabin. VoltAir’s cabin further features a wide cross section compared to its length, giving the passenger a spacious cabin feeling. In addition to enhanced comfort, this offers potential time savings in the boarding process.