The largest electric plane ever

The eCaravan could be adapted to seat a grand total of nine passengers, but on its test flight it had just one seat for the pilot

 From the BBC

At a large airfield surrounded by farmland in central Washington State, an electric aeroplane recently made history. It is the biggest commercial plane ever to take off and fly powered by electricity alone. For 30 minutes on 28 May, it soared above Grant County International Airport as crowds of onlookers clapped and cheered.

The biggest electric plane ever, huh? Well, it was a modified Cessna Caravan 208B – which can take a maximum of nine passengers. And the test aircraft only had a seat installed for the pilot.

It’s a far cry from the 200-300-seater jet that takes you on weekend city breaks or work trips, never mind the huge double-decker planes that cross continents. But the “eCaravan” test flight was a success. The two companies behind it, AeroTEC and magniX, which supplied the electric motor, are chuffed with the results. Roei Ganzarski, chief executive of magniX, pointed out in a statement that the price of flying the Cessna clocked in at a mere $6 (£4.80). Had they used conventional engine fuel, the 30-minute flight would have cost $300-400 (£240-320).

It builds on previous experiments with smaller aircraft also fitted with an electric motor built by magniX. And is raises the question: when will you and I be able to fly on a larger passenger plane powered by electricity rather than fossil fuels?

The first thing to note is that long-haul flights by large aircraft are not going to become fully electric any time soon. Certainly not within the next 50 years – and the jury’s out as to whether that will even happen this century. The reason is energy density.

Energy density is usually defined in terms the number of watt-hours (Wh) you get per kilogram (kg). A current lithium-ion battery’s energy density might reach 250 Wh per kg, while the energy density of jet fuel, or kerosene, is roughly 12,000 Wh per kg.

Put like that, it might seem like electric planes stand little hope of catching up. However, the difference isn’t quite as stark as it seems because electrical propulsion systems can be designed to be more efficient, meaning that they can cover more miles on less energy. But, at present, this still leaves fossil fuel systems about 14 times more energy-rich than battery-powered alternatives. Batteries, not being fluids that merrily slosh around, are also awkward in terms of their shape and bulk. “Right now the fuel nicely fits into the wing,” says Susan Liscouët-Hanke, an aerospace engineer at Concordia University in Montreal.

Plus, a further hitch is that the weight of a battery stays the same even when it’s dead. As a traditional aircraft flies, kerosene gets used up, making the aircraft lighter. That in turn reduces the amount of fuel it needs to stay in the air.

Engineers are currently trying to build a 180-seat fully electric jet that can fly for around 500km. The budget airline EasyJet has partnered with the aviation start-up Wright Electric to design and develop such a prototype plane that, if successful, could enter commercial service as early as 2030. Its travel routes would be limited – Paris to London for instance, not much further – but narrow-body aircraft that fly short-haul routes of 1,500km or less make up around a third of aviation emissions, according to management consultants Roland Berger. By gradually introducing electric planes that could replace conventional aircraft on these short-hop trips, the environmental impact of flying could be significantly improved.

It couldn’t come too soon because, as Roland Berger also notes, aviation is the only major industry in the EU in which CO2 emissions are increasing significantly. While the industry accounts for just 3% of global CO2 emissions today, by 2050 commercial aircraft could be churning out up to 24% of worldwide emissions due to predicted growth in the sector.

Flying fully electric 180-seater aircraft commercially by 2030 is “very ambitious”, says Robert Thomson, a partner at Roland Berger. The more sober view is that by 2030 we will more likely see hybrid electric aircraft being rolled out. In these planes, propulsion is provided by batteries and electric motors alongside traditional combustion systems. “A 50-seater aircraft would become viable as a hybrid, maybe 2030, late 2020s – I think that’s the sort of timescale which is plausible,” says Thomson.

He adds that his firm has counted more than 200 electrically powered aircraft in development and the number of these projects increased by 30% between 2018 and 2019. Many of these aircraft are hybrid models. They come in all sorts of “flavours”, says Thomson, wherein electricity might provide as little as 10-20% of the plane’s propulsion. Still, in principle, these designs might be easier to develop using existing aircraft bodies.

[Read more here--the BBC's piece is a lot longer than the excerpt above]

The most likely route to long-distance zero-carbon air traffic for the next few decades will be green jetfuel.  (See previous articles about this, here, here, here, and here)  But electric planes are much cheaper to run, as the article points out.  So there will be an incentive to switch where it's feasible.