Although it was swept aside at the Paris Air Show last week by the torrent of orders for the Airbus A320NEO, the manufacturer’s owner EADS’ proposal for an all-electric airliner may be what replaces them in the 2030s.
This is the first plan for a completely electric large airliner. It is powered by what EADS regards as achievable electric battery technology by the time the latest airliners in service today have run out of relevance in a world where zero fossil carbon emissions will be essential for all forms of mass transport.
In the basic plan below, liquid nitrogen is used to cool superconducting electric motors driving contra-rotating shrouded propellers at the end of an easy-load wide body cabin.
While no range or payload claims were made by EADS, sources said the concept was seen as plausible replacement for the single aisle designs currently used for short to medium haul high frequency inter-city routes, meaning 737s and A320s.
Jean Botti, Chief Technical Officer for EADS, said the capabilities of today’s batteries and electric motors are far short of what is theoretically possible, and realistically deliverable within 20 years.
Botti said high temperature superconducting materials were the key to overcoming the limitations of conventional electric motors, and had the potential to exceed the weight efficiency of gas turbine engines. He said these HST electric motors were expected to reach power levels of 7-8 kW/kg and with almost no electrical losses by the 2030s.
The design envisages a completely removable battery bank, thus taking from the fuselage and wing design all of the complexity of liquid fuel tanks and distribution systems. The concept envisages that with all of the battery maintenance and recharging conducted on the ground, the replacement of the battery containers between flights would be achieved in no more than the time conventional refuelling currently takes.
The broad ovaloid shape of the fuselage also houses all of the undercarriage, allowing for a clean wing uncluttered by engine mountings or wheel housings.
Just over a year ago Boeing, under contract to NASA, revealed its hybrid electric SUGAR Volt design for a high wing 150 seat design. SUGAR stands for subsonic ultra-green aircraft research, and some of the proprietary information and supporting graphics were published by Plane Talking and Aviation Week after they were inadvertently placed in the public domain.
The Boeing proposal is better explained in that article than the EADS proposal, and like a hybrid automobile today, seeks to convert kinetic energy into battery recharging, hopefully with more efficiency than such cars today.
However the major difference between the Boeing and EADS proposals is that the latter isn’t offering a hybrid propulsion system but one that is entirely electric.
Each company’s ‘green’ credentials in these projects also depend on the source of the electricity that charges the battery packs coming from renewable sources or uranium, as the object of the power technology chain is to avoid liberating fossil sourced carbon into the atmosphere. In the case of the Boeing project this also requires the liquid fuel to come from biological or algal alternatives to kerosene refined from oil, but Boeing, like Airbus, is a major mover of such fuel research, and the progress made to date has exceeded expectations.