TECH

Electric Planes: How Commercial Air Travel Will Soon Be Green

This is what needs to happen for large e-planes to take off.

10/10/2017 09:09 BST

As electric cars go mainstream, it’s only natural that thoughts turn to the possibilities of an electric plane. In March this year, EasyJet teamed up with an American start-up called Wright Electric, the aim being to explore ways in which the electric plane might become commercially viable, particularly for short-haul flights of 300 miles or less.

Should the commercial e-plane become a reality, it would have huge benefits for the environment. Airplanes release something in the region of 500 million tons of carbon dioxide into the atmosphere each year, commercial aviation amounting to 2% of all manmade emissions – a figure that could rise to 22% by 2050 based on present estimates. Looked at another way, take a round-trip from London to New York and your carbon footprint is the same as heating your home for a year.

Swiss Solar Impulse 2, Getty Images

A (very) brief history of electric planes

Like the electric car, the electric plane is not a new concept. In the 1970s and 80s aviators were already experimenting with the use of electric power in gliders.

Much of this was focused on converting solar power via panels on the wings, culminating when, in 2016, the Swiss Solar Impulse 2 became the first fixed-wing aircraft to circumnavigate the globe entirely on solar energy. Remarkable feat though this was, it wasn’t exactly practical. With a maximum speed of 87 mph, not to mention damage to its batteries en route that led to substantial delays, it eventually completed the journey in 16 months.

Airbus E-Fan, Getty Images

At last, flying cars!

When it comes to using rechargeable stored energy from batteries (the same principle as used in the electric car), the story is rather different. Presently there are many kinds of e-planes out there capable of flying 2-6 people over relatively short distances. The e-Genius for example, developed by the University of Stuttgart, is a two-seater aircraft that can climb to 20,000ft, reach speeds of 142mph and distances of 300 miles, in the process burning no fuel and emitting zero emissions.

The e-Genius already has substantial competition, whether it’s from the Taurus G4, made by Slovenian manufacturer Pipistrel, the Airbus E-Fan, which crossed the English Channel in 2015, or Munich-based Lilium, to name but three. The Lilium is in fact closer to resembling the fabled flying car scientists have been promising us for decades. Pitched as a five-seater ‘flying taxi’, a two-seat prototype has already mastered a combination of vertical take-off and landing (VTOL) and wing-borne flight.

As you might expect, the e-plane has piqued the interest of NASA, and last year it launched a series of research projects aimed at finding ways to make such travel a viable commercial possibility. To this end, it’s been working on a concept called the X-57 Maxwell that uses electric motors to drive fourteen propellers on a four-seater aircraft, flying up to 175mph and using a fifth of the energy of a normal private plane.

Go big or go home

NASA has bigger ambitions, though, namely breaking into the same market that has prompted the EasyJet-Wright Electric collaboration. If an e-Plane is capable of usurping today’s commercial jet planes, the rewards will be enormous. The market is expected to exceed $22billion in the next fifteen years, and this is while commercial e-planes remain in a developmental phase. Should it become a reality, the savings on fuel costs for airlines are incalculable, never mind the environmental benefits.

But it’s precisely as the concept of the e-plane is scaled up to the size of normal passenger aircraft –planes that carry at least 150 people – that the problems begin to arise. Chief amongst these is battery technology. Even the best batteries fall a long way short of the equivalent volume of jet fuel in terms of power. The jet fuel capacity of a Boeing 787 Dreamliner is about 223,000 pounds meaning the estimated weight of a battery pack with equivalent energy would be over 4 million pounds, a figure that is presently unfeasible.

Battery technology is advancing all the time, with scientists looking beyond the lithium-ion batteries that power electric cars to things like Lithium-air batteries that utilise oxygen as an active electron carrier. One thing is certain; with the emphasis on weight reduction and aerodynamics, e-planes will look substantially different from the planes that fly today, perhaps ditching the tail-fin altogether (which increases drag) and introducing retractable propellers and winglets, allowing them to fly without using so much energy.

Getty

Hybrid planes

What we are most likely to see next mirrors the same progression we saw with cars, namely a switch to hybrids. US aviation start-up Zunum is developing a plane that combines electric and fuel power. As the battery runs low, a jet-fuel burning turbine fires up to keep it airborne. This could cut airline fuel costs by anything from 40-80% and reduce engine noise by as much as 75%.

The Boeing SUGAR Volt aims to do the same. Essentially, the fuel would be used for the periods when the plane needs the most power, namely at take-off, but once at altitude, it would switch to electric power. The engineers involved in the project suggest that it could become a commercial reality between 2030-50.

This projection is inevitably vague because no one can say for sure how the technology will develop. If there is a huge breakthrough in batteries, that timeline will radically decrease.

And when the technologies involved in electric cars, autonomous vehicles, drones and even space tourism begin to converge, the greater pool of knowledge will have an exponential impact on aviation. So who knows, within a generation the e-plane may be winging us quietly into the clouds.