So close yet so far seems to embody the concept of commercial electric planes. Aircraft are meant to fly, but will some be able to fly silently while reducing its carbon footprint? It seems that a part of Greta Thunberg's dream is far from being realised...

The problem with electric aircraft

The main problem with electric concepts seems to be that the current batteries available are too heavy, yet cannot provide enough power, and are unable to store enough energy. Additionally, increasing the number of cells used in the battery is unfeasible, as this increases the weight and therefore the stalling speed of the aircraft:

“So if you want to add more power to a plane, you need to get a bigger battery, and to get that plane airborne despite the weight, you'll need even bigger battery that's more powerful, but that means more weight. And then you'll need an even bigger battery to offset that weight…”[Electric planes are the future of aviation, but they haven't taken off (businessinsider.com)]

The vicious cycle will continue unless batteries are more efficient, allowing them to store more energy for the same mass.

“Right now, even the best batteries have a specific energy of only 250 watt-hours per kilogram, but we have to get closer to 800 to really start flying, and that is still nothing compared to jet fuel's specific energy, which is nearly 12,000 watt-hours per kilogram.” [Electric planes are the future of aviation, but they haven't taken off (businessinsider.com)]

Also, as discussed by [Electric planes are the future of aviation, but they haven't taken off (businessinsider.com)], certification will also take time, as this new technology, despite being here from the “1970s”, or from the 1880s if you count several airship experiments from the likes of Tissander Brothers or 2 French military officers, it is only recently being thought of for commercialization. This put added scrutiny on the airworthiness of a type of aircraft which cannot usually sustain flights longer than an hour. This may even stifle creativity and stop the problem from being solved in the first place:

“A new technology known as lithium-air batteries can theoretically reach the same energy density as jet fuel. However, they are still at the laboratory stage. Given the extremely safety conscious nature of the aviation industry, it is unlikely to plan future aircraft on unproven technology.” [Electric planes are here – but they won't solve flying's CO₂ problem (theconversation.com)]

A false hope?

Not only is electric propulsion falling to be established but it is also chasing an adaptive competitor- internal combustion engines are also evolving into more fuel efficient and less polluting variants.

“The International Air Transport Association estimates that each new generation of aircraft is on average 20% more fuel-efficient than the model it replaces, and that airlines will invest US$1.3 trillion in new planes over the next decade.”[ Electric planes are here – but they won't solve flying's CO₂ problem (theconversation.com)]

In fact, why would airlines, most in the private sector and having the aim of making a profit, invest in a new, mostly untested, technology where they might encounter a bottomless money pit, when they can rapidly decrease costs, right now, by investing in new engine models, such as the Rolls Royce TrentXWB, which Airbus boasts will “25% lower operating costs, fuel burn and CO₂ emissions when compared with previous-generation aircraft”. This will not only help them save face in marketing campaigns where they can show how much they are doing for the environment, but may secure them government grants for doing it. How can new technologies save the planet if no one is going to use them?

It is not that I blame them however. A long-haul flight is impossible on a electric plane, and if the battery runs out over an ocean- there is no where for the users of the plane to go.

Solutions

A new player of the field has arrived recently on the playing field that puts forward an attempt to solve the battery crisis- Seaweed! An experiment conducted in Berkley, USA, in 2017 showed that seaweed would be able to bind the active ingredients in Lithium-sulphur batteries and react with the sulphur to keep it from dissolving, which is said to be the main problem of lithium-sulphur batteries, which are significantly cheaper and more efficient than lithium ion batteries with the ability to hold 5 times as much energy ['World’s most efficient battery' can power a smartphone for five days | The Independent | The Independent], ,and the reason they were not considered before now- the collection of lithium sulphide and lithium polysulfide that degraded the battery. This result has a coined name, Polysulphide shuttle, and is caused by the internal electrolysis in the battery- electrolytes move from one end to the charged end that they are attracted to. As lithium is a metal, it forms cations and are attracted to the cathode, or negative end of the battery, while sulphur, a nonmetal which forms anions, is attracted to the anode, or positive end, of the battery.

“The biggest challenge until now with lithium-sulphur batteries has been the instability of the cathode, which undergoes a 78 per cent change in size each time it goes through a charge cycle.”[ 'World’s most efficient battery' can power a smartphone for five days | The Independent | The Independent]

This has allowed for The Monash university, in Australia, to power an electric vehicle for more than 1000miles before needing to recharge.

 

A method of circumnavigating the certification problem is refitting existing aircraft with means of electric propulsion. This has proved to be successful, and safer, in sailplanes and motor-gliders which are designed for sustained flight even without an engine and have large gliding ratios (horizontal distance travelled: 1 meter vertically lost).

 Gliders are safe to fly by definition, even without a functioning engine, so we were able to experiment without putting anybody at risk or do harm to anyone.”[ Tine Tomažič, from the Slovenian company Pipistrel]

The first such example of this is the Alpha electro airplane by Pipistrel, which is the first all-electric 2-seater airplane. It is now used for pilot training.

The staple attribute of gliders, their long wings, are also being incorporated into other electric concepts for the future. The Boeing Sugar Volt has long, slender wings to maximise surface area. This increases the surface upon which air pushes up against, reducing the stall speed of the aircraft, increasing range. However, as longer wings means that the moments acting on the wings is larger, with the joining point to the fuselage as a pivot. This resulted in the decision to add struts to strengthen the joint, reducing the likelihood of a wing snap.

Another concept is a “blended wing” design, which increases aerodynamics by reducing drag, and reducing the energy need of the aircraft by around 20% [Electric planes are here – but they won't solve flying's CO₂ problem (theconversation.com)] However, this seems to pose new challenges:

“neither of the world’s two main aircraft manufactures, Boeing and Airbus, are actively pursuing blended wing technology. Such a major design shift has too many technical challenges to make it commercially viable right now. For example, most airports wouldn’t be able to accommodate a blended-wing aircraft.” [Electric planes are here – but they won't solve flying's CO₂ problem (theconversation.com)]

A more intermediate technology seems to be a hybrid aircraft, combining high power with low emissions. Such a project is the brainchild of Airbus, Siemens, and Rolls Royce- the EfanX, a partially retrofitted BAE 146 with an electric 2-megawatt electrical engine, out of 4 total- the remaining 3 Honeywell engines will continue running on conventional fuel.

Others, such as the Israeli firm Eviation, are designing and building their aircraft, a 9 seater named Alice, from scratch around the battery. However, this is resulting in a lengthy 2-year certification period.

In conclusion

Electric aircraft will allow us to live with “$25 tickets, quieter airports, or even shorter runways,” all working towards a “cleaner future,” [Electric planes are the future of aviation, but they haven't taken off (businessinsider.com)] but all good things take time, and we shall have to wait for electric technology to become established, and the FAA to become more accepting and less skeptical of it.

Sources:

Electric planes are the future of aviation, but they haven't taken off (businessinsider.com)

'World’s most efficient battery' can power a smartphone for five days | The Independent | The Independent

Electric planes are here – but they won't solve flying's CO₂ problem (theconversation.com)

Sulfur battery breakthrough could be the future of electric planes, trains, and automobiles, scientists say (msn.com)