High on batteries: can electric aircraft take off?

Poised for takeoff? Eviation's electric plane, the Alice.

Poised for takeoff? Eviation’s electric plane, the Alice.

BY MIKE STONE:

The Japan Aerospace Exploration Agency last week unveiled plans for an electric aircraft consortium amid growing interest in aviation electrification.

The move, reported in Aviation Week, followed Norway’s state aviation company, Avinor, saying in March that the country was committing itself to electric flight.

Norway wanted to be 100% electric by 2040, at least for short-haul flights, Avinor said. Norway has already shown massive state support for earth-bound electric vehicles, leading to mass adoption in the country.

So this was positive news for electric plane fans. But the news on electric aircraft is far from uniformly positive.

At the end of May, a tragic crash which left two people dead pushed aircraft electrification to the front of the news agenda for all the wrong reasons. The accident involved a Siemens-FlyEco Magnus eFusionelectric-diesel hybrid. 

Crash investigation

As of the time of writing, all prototypes are grounded. Siemens, which is backing the project and supplies the electric motors, is helping the crash investigation team.

Siemens, in collaboration with Airbus, is also involved with a 100% electric plane called E-Fan 2.0. The current model’s predecessor, the 1.2, crossed the English Channel in 2015.

To date, functioning electric aircraft prototypes have been small one or two-seater vehicles.

Another example of the trend is NASA’s X-57 Maxwell, which hopes to take off in 2018 with the help of 14 wing-mounted props, each driven by its own electric motor. But larger craft are being considered.

In 2017, EasyJet announced it wanted to begin an all-electric service within a decade. The budget airline has got into bed with start-up Wright Electric to make its dream of a 220-passenger plane with a 335-mile range a reality. 

Transitional flying forms

Bridging the gap between today’s small prototypes and the future’s potential airliners are a clutch of intermediate projects such as the Boeing-backed Zunum hybrid-electric aircraft.

With luck, it will be able to carry 12 passengers up to 700 miles. Another hopeful is the nine-passenger Alice, a fully electric plane being developed by Israeli start up Eviation Aircraft.

But as with all contenders in the electric flight arena, its developers have a number of tough questions to answer before they even take a maiden flight.

Like earth-bound electric vehicles, the number one issue in commercialization is adequate battery storage. In the case of electric planes, unsurprisingly the weight of the battery, and not just its capacity, is a critical consideration.

As the energy density of commercially available batteries is between 40 and 60 times less than jet fuel, achieving ranges of more than a few dozen miles is going to problematic. 

The problem of storage

As a result, the immediate future of electric planes, or at least helicopters or perhaps drones, seems to be in so-called flying cars, short-hop vehicles that could provide urban taxi services.

One notable example is Airbus’ Silicon Valley subsidiary A3, which is behind Vahana, an unmanned electrical aircraft which could whisk cargo or a (wealthy) solitary passenger across a congested city.

How are developers planning to address the challenge of energy density and weight in building larger aircraft?

Eviation’s CEO and founder, Omer Bar-Yohay, said Eviation has signed a $1m battery deal with South Korea manufacturer Kokam to supply its Alice aircraft with lithium-ion batteries.

The cells have an energy density of 260 watt-hours per kilogram (Wh/kg) and a long cycle life, Bar-Yohay explained. Each 920kWh battery will cost about USD$320,000. 

“Massive savings”

However, “due to massive savings in maintenance and fuel costs, our aircraft will have a direct operating cost of $0.10 per seat per mile,” Bar-Yohay claimed.

The battery, consisting of 9,400 cells distributed throughout the aircraft, is heavy, weighing in at 3.8 tons or 60% of the plane’s maximum takeoff weight. Bar-Yohay said the aircraft’s ultralight design will compensate for this.

As for how far it could travel, the CEO told Energy Storage Report: “Our Alice aircraft will have a range and IFRreserve of 650 miles.”

Currently the airline industry burns five million barrels of oil every day, contributing roughly 2.5% to total carbon emissions.

According to some estimates that proportion could rise to 22% by 2050 as other sectors emit less and air travel continues its inexorable growth. 

New methods of fueling aircraft

If that mushrooming carbon footprint can be cut back in any way, new methods of fueling aircraft need to come online and soon.

But as Bar-Yohay noted, reducing environmental impact “depends on where energy is being sourced from at the grid level.”

His contention is that whatever the source, his aircraft simply uses less energy overall, “so there’s a significant saving, no matter what.”

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