Electric Planes Could Take to the Skies, but It’s Not as Good as It Sounds.

With a global climate disaster on the horizon, we need to reduce carbon emissions everywhere; in every industry, in every sector. Could electric planes help us?

One of those sectors is aviation, a huge contributor to global emissions. Of course, air pollution is the most commonly considered form of pollution, but there are other forms associated with planes.

Let’s explore the feasibility of electric planes? Could the future of aviation be solar?

The History of Aviation

There are two types of aircraft; lighter than air and heavier than air. As you can probably guess, if an aircraft is lighter than air, it weighs less than the weight of air which it would displace. Basically, it’s less dense than air.

Previously, the lighter than air model was widely used as we didn’t yet have the technology to create heavier than air aircraft. The period when lighter than air aircraft was widely used began with the first untethered human lighter-than-air flight on November 21, 1783, of a hot air balloon designed by the Montgolfier Brothers.

Early Light Aircraft
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Hot air balloons, the first light aircraft.

Eventually, the lighter than air period of aviation came to a sudden standstill after the Hindenburg disaster, which killed 36 people.

Why did lighter than air aircraft fail?

Although zeppelins and airships floating across the sky sound like a good (and environmentally efficient) idea, they’re not.

Unfortunately, in order to make airships lighter than air, they must be filled with a gas which is, you guessed it, lighter than air. Since there aren’t many gases which fit such criteria, engineers didn’t have much selection.

Consequently, they used hydrogen. Yes, it’s lighter than air, but it’s also highly explosive. Inevitably, this was going to lead to an accident, which was the Hindenburg disaster.

The Hindenburg disaster
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The Hindenburg Airship Catching Fire

Why not Helium?

Within Germany, hydrogen supply was strong, but the helium supply was weak. It’s a slightly heavier gas than hydrogen but isn’t explosive. The Nazis originally planned to fill the ship with helium as the track record for hydrogen airships catching fire wasn’t particularly great.

However, they ran into a problem, the US was the leading supplier of helium and wasn’t willing to sell it to other countries. This left the Germans with no choice but to use helium for the Hindenburg.

Despite the fact that hydrogen had a bad track record, the Germans were a large manufacturer or airships (zeppelins) and had seen no prior evidence from their own ships that hydrogen was dangerous.

Heavier than air – a new era of aviation?

In 1799, Sir George Cayley visualised the concept for a modern aeroplane as a fixed-wing machine which contained separate control mechanisms for lift, propulsion, and control.

As you’re probably aware, the Wright brothers made the first controlled, powered, sustained flight in 1903. This was made possible due to the introduction of a three-axis control system.

The Wright Brothers
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The Wright Brothers

After that, progress in the aviation sector progressed rapidly, seeing the first transatlantic flight in 1919 before a major development of commercial aviation after World War 2.

In the United States, commercial aircraft could get paying customers from the west coast to the east coast in a matter of a few hours.

How do electric planes work?

As I stated earlier, there are three main components which allow fixed-wing aircraft to fly. These are control, propulsion and lift. Each one of these has to be integrated with electricity and its generation. Here’s how:

Lift

Aeroplane wing shape
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Commonly, people believe that a wing is shaped so that the wing is longer on the top. This creates lift because the air moving along the bottom of the wing is lower pressure because it moves slower.

Although the wing is shaped like that, the speed of the air doesn’t directly affect lift. In fact, the air over the top of the wing is more rarified (spread out).

Fewer air particles create lower pressure, creating a suction which lifts the aircraft up. Consequently, aircraft are able to fly in high altitude because the difference in pressure matters more than the actual pressure. Despite that, aircraft do reach a limit in which the air pressure is not high enough for them to fly.

As you can probably tell, the lift of the aircraft is based on the shape of the wing and fluid mechanics, not electricity. So, where do electric planes come into this?

Usually, the kerosene, which is used as a fuel for the aircraft, is stored in the wing to maximise cabin or cargo space. Instead of fuel, electric planes would need batteries. Most likely, the batteries would be stored in the wing.

Due to the shape of the wing, it might be difficult to pack them full with batteries, causing a potential change in the wings shape.

Furthermore, if the plane is solar-powered, it would require solar panels to be placed on the wings. This would increase the weight of them, causing engineers to reconsider the material science of a traditional wing to avoid it bending and potentially snapping.

Control

Control systems in aircraft are usually either mechanical, hydro-mechanical (hydraulic), or electronic.

Firstly, the aircraft would be different to fly by the pilot due to differences in weight placement as well as the shape of the wings. This could mean that pilots require extra training.

Secondly, more control systems could be transitioned to electronic. Although this would make things easier for the pilot, it would also increase the rate of failure for the aircraft. If the electronic system fails, a redundant system would be needed to continue the operation of the plane.

On the whole, the control of the aircraft wouldn’t vary a vast amount. The basic mechanics of the aircraft would remain the same, just that there’s a big electric motor and batteries rather than fuel with an engine.

Propulsion

Depending on the plane, it is likely to use one of two main propulsion methods; jet engines and turbo-fan engines.

Most commercial passenger aircraft rely on the turbo-fan engine due to its extra efficiency over the jet counterpart. Here’s a diagram:

Aeroplane engine
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As air comes into the engine, it’s accelerated by a fan. Next, it goes into a chamber of airfoil shaped spinning blades which further compress and accelerate the air before it enters the narrowest part of the engine.

Once there, it’s mixed with fuel, hence the name ‘combustion chamber’. In order for combustion to take place, the two components needed are oxygen and fuel. However, just mixing these two components together has no effect, they must be ignited.

Similarly to lighting a barbecue, a spark is made within the chamber and the fuel is ignited, combusting with the oxygen. After that, all that’s left is the turbines before the air is thrust out the back.

Once the air reaches the nozzle, it is exhaust out of the back at a very high velocity. According to Newton’s third law, every action has an equal and opposite reaction.

Consequently, if air is thrust out the back at high speed, the aircraft will be thrust forward with the same force as the air going out the back.

Where does electricity fit in?

Aside from the potential of an electric igniter for the engine, that engine uses fuel, not electricity. So, how would an electric plane deal with propulsion?

Currently, the latest electric plane developments seem to be propellor based. Since a propellor is driven by a motor, this is easy to create. Simply attaching an electric motor and fitting the planes with batteries (like an electric car), should allow the plane to fly with correct proportions.

Easy Jet electric plane
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Easy Jet electric plane.

Unfortunately, propellor planes are more unable to fly at such high altitudes as jet engine planes. Furthermore, they can’t fly as fast. That being said, they’d be perfect for short-haul and domestic flights.

For example, a flight from London Heathrow to Edinburgh. Alternatively, a route from London to Paris or Amsterdam would be feasible. In fact, Easyjet signed a contract with an American electric aviation company to create electric planes capable of flying routes like these.

Until propulsion systems which are capable of flying fast and at high altitudes are available, electric planes are likely to be locked into short-haul flights.

In addition to the propellor limitations, a battery powerful enough to drive a turbine for an extended period of time would be very heavy and take up lots of space. Energy density must increase, perhaps with the development of solid-state battery technology.

Another method of reducing the size of the battery pack would be to add solar panels to the wings and part of the body. This would recharge the battery during flight, allowing the plane to go further on a smaller battery.

Are electric planes a good idea?

So, you’ve seen how electric planes would work, but are they actually a good idea? Here are some benefits and drawbacks of electric planes, starting with benefits:

Running Cost

Obviously, research, development and construction costs for electric planes would be expensive. However, once they’re built, airlines would save money on fuel. Electricity is considerably cheaper than kerosene in many countries.

Moreover, with solar panels, the airline could receive almost free energy, especially in areas which are particularly sunny like Nevada. Similarly to electric trucks, I think the cost of the aircraft would be offset significantly (if not fully) by the reduced cost of fuel.

Solar powered electric plane
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NASA Helios Project – Solar Powered

Other airline costs would likely stay much the same; airport fees, insurance and staff alike. The cost of a consumer ticket to fly somewhere may increase slightly in the short term due to the high initial upfront costs of the plane. Despite that, these costs would likely decrease once electric planes are fully implemented and established.

Environmental

The aviation industry seems to have taken a more environmentally sustainable approach to transport than the shipping industry. Although they both emit similar levels of CO2, the airline industry has taken steps to eliminate sut particles and cut down on other harmful greenhouse gases.

To be specific, the aviation industry generates about 900 million tonnes of CO2 each year. Electric planes could cut that number significantly.

Since the net CO2 emissions in flight would be zero, the only source of emissions can be charging and the making of the solar panels. Let’s presume that all the electricity used to charge the planes comes from renewable resources like solar and wind.

Mining to get materials for batteries of electric planes
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Although the CO2 emitted during manufacturing can be reduced, it can’t be completely eliminated. Resources like lithium still require extraction from the ground in order to make solar panels and batteries. Drilling into the ground can release gases like methane and sometimes carbon dioxide.

In addition, batteries use prescious elements which we have a limited supply of. I wrote an article on Tesla’s giant batteries, including the problems with using lithium ion batteries here.

So, the aviation industry is already relatively clean compared to other methods of transportation, but it could get better. Once vehicles become electric, the emissions created by planes will look larger. In order to reach carbon neutrality, we need to make planes electric or run on fuel-cells.

Noise and Vibration

Due to the lack of an engine, the only sounds are the motor and the propellor slicing through the air. Consequently, comfort is increased for passengers and crew on board.

Predictably, a piston engine spinning around within an aircraft body is going to create some vibration (like a washing machine). This is annoying for passengers as I’m sure you’ve realised when you’re seat vibrates slightly as you’re trying to sleep.

Energy Density

Energy density is one of the largest problems that electric aircraft are likely to face. Currently, batteries only have about 1/80th of the energy density of aircraft fuel (kerosene). This means that the planes can’t fly nearly as far as standard kerosene planes.

In order to tackle this issue, batteries would have to get far more dense, past solid state technology as we know it. So dense that we it’s difficult to conceive the technology which would be needed for such a battery.

Furthermore, the cost of research and development for such a battery would be through the roof, reducing the likelihood that anyone would be incentivised enough to develop a plane capable of flying long distances.

Initial Cost

Due to the lack of development of electric planes, as well as the engineering complexity which will be faced when developing them, electric planes will be expensive.

In addition, as global lithium deposits decrease in size, the price of lithium is likely to go up. Subsequently, the planes would become even more expensive. As I said before, the initial cost is likely to decrease with further development.

Charging

Due to the colossal amount of energy the batteries, they’d need a lot of charging. Since we don’t know the size of battery which would necessarily be required for an electric plane, it’s hard to predict the charging time.

Wind turbines which could power electric planes
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Renewables will be required to charge electric planes.

The charging speed would have to be very high, potentially over 500 kW. This would require a very high-speed charging system, and would still likely take more than 30 minutes to charge.

Safety

In the case of electric planes, safety seems nor an advantage or a disadvantage. For instance, the removal of the engine makes the plane safer due a lack of combustion.

However, the problem is that the engine is replaced with lithium-ion batteries. As you’ve probably heard, these can explode, usually under a large impact. If a lithium-ion battery is damaged, it could cause the plane to catch fire.

What about Elon Musk’s electric plane?

Elon Musk has been frequently teasing his idea for an electric jet. It’s a VTOL (vertical take off and landing) design, requiring much less runway space.

In addition, Musk wants his plane to be supersonic (faster than the speed of sound), a feat which hasn’t been seen on a consumer jet since the concord. If Tesla makes one of these, it could change the tone of consumer flight.

Conclusion – Should we be excited about electric planes?

On paper, electric planes look like a promising concept, but would they actually work? Unfortunately, an 80x energy density increase alongside developing an engine which can run off electricity seems as though it would be an enormous challenge, requiring huge amounts of funding.

Primarily, that’s the reason that I don’t think electric planes are going to be taking off anytime soon. They’re incredibly hard to develop and offer limited advantages over the already efficient kerosene powered planes.

Perhaps short-haul flights will be first to utilise electric planes, but I can’t see a flight from London to Singapore on an electric plane happening anytime within the next few decades.

Do you think electric planes will take off sometime in the near future?

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