German aerospace researchers say an all-electric, zero-emissions commercial airliner feasible by 2035
Cut-out of the Bauhaus Ce-Liner concept aircraft
Thu 20 Sept 2012 – Perceived industry wisdom holds that commercial aircraft will be powered by liquid fuels for the foreseeable future, at least until the middle of century. However, respected Munich-based aviation research think tank Bauhaus Luftfahrt believes advances in battery technology could make an all-electric, emissions-free 190-seat passenger airliner feasible by 2035. Dubbed the Ce-Liner, the aircraft’s electric motive power system would come from 16 conventional LD3-size containers containing the necessary battery power to supply two rear-mounted electric motors. Also crucial to the airliner design are aerodynamically-efficient, inboard-facing C-wings that offer enhanced performance while keeping within the wingspan constraints imposed by airport gates. Bauhaus claims the range of the aircraft will reach 900 nautical miles, which it says would cover 79 per cent of all predicted flights operated by aircraft in this size category in 2035. Airbus too has looked into the future and unveiled a vision of what ‘smarter skies’ technology could be in place by 2050 to meet environmental targets.
According to Bauhaus, the most advanced lithium-ion batteries available today can provide an energy density of 300W/hour per kg but it believes that if progress of this technology is extrapolated, this could well be increased six-fold by 2035 to 2kW/hour per kg. Charging these batteries would still take around two hours, which would not be practical for a low-cost, fast turnaround airline. So Bauhaus has designed the battery packs to fit into conventional cargo containers that sit beneath the passenger floor and can be replaced while on the ramp using standard cargo loading equipment.
A downside to this is the considerable weight of the batteries and other power system requirements added to the aircraft – making it up to 50% heavier than a conventional aircraft today. This would lead to higher airport and navigation charges but this would be offset, says Bauhaus, by avoiding carbon emission taxes.
Bauhaus has yet to conduct noise footprint research on its Ce-Liner but Dr Arne Seitz of Bauhaus’ Visionary Aircraft Concepts group told GreenAir at last week’s ILA Air Show in Berlin the reduction in noise from the 30,000lb thrust motors would be considerable compared to conventional turbofan engines. Reverse thrust will be achieved by reversing the motors and the aircraft will be able to push back from the gate on its own power.
Funded and supported by the Bavarian state government and four major aerospace companies – EADS, Liebherr, IABG and MTU Aero Engines – Bauhaus says its research is driven by the EU’s ‘Flightpath 2050’ goals unveiled last year of a 75% reduction in CO2 emissions per passenger kilometre, a reduction of 90% in NOx emissions and a perceived aircraft noise reduction of 65% by 2050 compared to new aircraft in 2000.
“Our partners are product orientated and do research for themselves,” explained Seitz. “We, however, can look further into the future and have the freedom to break some taboos, and provide ideas for our partners and the academic community.
“This particular research is for one particular aircraft market segment and the search for solutions for other segments remains ongoing and the Flightpath 2050 goals, of course, cover them all.”
Finding solutions was a theme of a presentation by Airbus in London recently to the UK aviation industry and journalists in which aircraft manufacturer Airbus unveiled its own 2050 ‘Smarter Skies’ vision for sustainable aviation.
Air traffic had doubled over the past 20 years and was forecast to double again within the next 15 to 20 years, requiring 28,000 new aircraft, said Charles Champion, Executive Vice President Engineering at Airbus.
A comprehensive survey carried out by Airbus, reported Champion, showed 96% of respondents wanted air travel to be more environmentally sustainable. “It’s a number one priority,” he said.
With the EU’s ambitious Flightpath 2050 targets and the industry’s own carbon emissions goals to make the sector sustainable, the challenge was to go beyond the 70% reduction in aviation emissions achieved over the past 40 years, he said. “It’s a huge challenge. We will have to find new solutions.”
He added: “Our engineers are continuously encouraged to think widely and come up with ‘disruptive’ ideas which will assist our industry in meeting the 2050 targets we have signed up to. These and the other tough environmental targets will only be met by a combination of investment in smarter aircraft design and optimising the environment in which aircraft operates.”
The focus of the presentation was not on what the aircraft of the future might look like but rather on how aircraft might fly in 2050 and beyond, and Champion outlined five possible concepts that could play a part in dealing with more flights, fewer emissions and shorter flight times.
Reducing noise is also an Airbus consideration and it foresees aircraft taking off in a continuous ‘eco-climb’ in which the aircraft is launched through assisted take-offs using renewably powered, propelled acceleration. The steeper climb would reduce noise around airports and enable the aircraft to reach efficient cruise altitudes more quickly, as well as utilise shorter runways.
In the air, intelligent aircraft would be able to organise themselves to fly together along environmentally-efficient ‘express skyways’ to benefit from optimum conditions, and high frequency routes could be used by aircraft to fly in formations like birds and benefit from reduced drag and lower energy use.
As they reach their destination, aircraft would take low-noise and emissions-reducing free-glide steeper approaches into airports, obviating the need for engine thrust or air breaking. These approaches would also reduce the landing speed earlier and make shorter landing distances achievable, with less runway needed.
On landing, aircraft engines could be switched off sooner and runways cleared faster with autonomous, renewably-powered robot taxiing carriages transporting aircraft to their gates.
The use of renewable sources of power and sustainable biofuels will secure energy supplies and further reduce aviation’s environmental footprint in the long term, predicts Airbus. This will allow the extensive introduction of regionally sourced renewable energy close to airports, feeding both aircraft and infrastructure requirements sustainably, it says.
“For some of these concepts, a lot of work needs to be done but on others, like approaches, we are working strongly on them already,” said Champion.
“We know people want to fly more in the future and our forecasts support this. We also know that they don’t want to fly at any cost. Our focus at Airbus is on meeting this continuous growth in demand, keeping the passenger, our customers and the environment at the centre of our thinking. The future of sustainable aviation is the sum of many parts and success will require collaboration amongst all the parties who are passionate about ensuring a successful prospect for aviation.”