All planes use electricity to some extent and even depend on it for many vital navigation, avionics and mechanical functions. However, none of these things are the same as flight itself being powered purely by electricity and aerodynamics. So far, this last frontier of electric airplanes is still the realm of tiny machines such as drones, model planes and a few prototype aircraft that are small and not at all capable of replacing commercial flights.
In other words, fully electric commercial aircraft of nearly any size remain the domain of speculative development. This of course has some very practical reasons behind it. For starters, there is the energy physics involved.
The energy density problems of flight
To give you a few examples, even the best modern lithium-ion batteries such as those used in Tesla electric cars offer energy densities of between 1.1 and 1.9 megajoules per kilogram (MJ/kg). It’s a workable quantity of energy for driving along the ground under certain optimized mechanical conditions. However, for comparison, the average energy density of aviation gas sits at 44.65 MJ/kg. That of kerosene is around 43.15 MJ/kg and even materials like burning wood and ethanol (alcohol) have energy densities of between 17 and 19 MJ/kg.
Even if we talk about the most advanced prototype aluminum-air batteries, which are being implemented in experimental all-electric planes like the Eviation “Air” private jet model, energy density approaches about 7.2 megajoules/kg. This is still well below common combustion engine fuels. Even more advanced designs include the lithium-air battery, which could theoretically reach an energy density of 43.2 MJ/kg, putting it on par with aviation gas. This however hasn’t yet been done in practice.
So, yeah, as the numbers above make extremely obvious, electrical power in the form of batteries is a long, long, long ways away from coming close to the energy density of even the most basic combustion fuel sources.
Batteries nonetheless do manage to function in cars and remarkably well in the case of newer model vehicles. This is mainly because the work required is directed at wheels that push the car forward along surfaces, which make it easy for wheels to move over them. Things change drastically with airplanes though.
The hurdles of air travel
For air travel, all of the mechanics and work involved are far more severe than with ground vehicles or even boats. This is an obvious outcome when the whole of a plane’s weight not only needs to maintain forward motion against the forces of air friction; it also needs to be sustained high aloft despite the full pull of gravity dragging it down constantly.
Even for a small plane, those are considerable requirements. For aircraft the size of passenger liners or military planes, no purely electrical technology that can fit inside an airplane comes close to offering the needed power.
Electric airplanes so far
Despite all of the above difficulties with creating combustion fuel-like energy densities in electrical motor batteries, there are fully electric passenger planes being developed already. Over 215 electric airplanes are in some sort of development stage so far and many experts predict fossil fuel-free commercial passenger or cargo flights by 2030 at the latest.
Major aeronautics brands like Rolls Royce, Boeing, EasyJet and government agencies like NASA are all investing heavily in prototype electric aircraft. Rolls Royce has had notable success with its recently-tested “Spirit of Innovation” single-passenger rotor aircraft. This compact plane uses a massive 400 KW advanced battery design and recently broke an electric flight air speed record by being flown to a velocity of 387.5 mph.
EasyJet for its part is working on completing a large passenger jet with a 186-seat capacity by 2030 with the use of sophisticated new refined aluminum air or lithium air battery types. This is under development only, For now, EasyJet’s efforts have only paid off in short flights with small electric aircraft.
Peeling back the electric plane PR
Despite these corporate and government efforts above, all current fully electric planes remain small. Theoretical battery power levels that match those of petroleum fuels have not yet materialized despite a lot of hype. Current working electric commercial plane models all remain small, much slower than their fuel-powered counterparts and require enormous battery cells compared to plane weight and size for even a relatively short flight time.
This is why stripping away PR hype is crucial for knowing the realistic prospects of having large, commercial electric planes soon. The effort is worthwhile though, because advances are being made constantly, and they make even hyped up claims of electric aircraft power more plausible.
In the meantime, technologies such as hybrid fuel/battery aircraft development have the ability to provide some relief on high fuel consumption in modern aircraft.
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