Why and how we are going to be flying electric

June 29, 2021 2:46 AM

Cheddar explains why he believes Electric Planes are Inevitably Coming - with particular reference to the economics of short distance, commercial flights. Electric Future announces"Electric Planes have arrived" - a review of current and models and those in the immediate pipeline. Real Engineering summarises the the technical challenges and limits.

Elsewhere: The brothers Tissandier flew the first electric flight 20 years before the Wright brothers. First powered flight in 1973 on the Militky MB-E1 (no sound). Solar Impulse 2 completes a global circumnavigation in 2015. Norway plans for all short haul flights to to be electric by 2040.

Previously: Inside the airline industry's meltdown.

posted by rongorongo (31 comments total)

Another reason to put off investing in high-speed rail: it'll all be an obsolete white elephant when Elon Musk car hole electric airliners arrive.
posted by acb at 4:00 AM on June 29, 2021 [6 favorites]

The current planes will last for decades, and the best way to stop them flying is to give their customers a low cost, low carbon alternative. Very happy to see that new overnight routes are opening up across Europe. New routes from Paris to 12 cities. Scandinavia to Berlin.
posted by biffa at 4:18 AM on June 29, 2021 [9 favorites]

High speed rail is faster than an airline for anything less than 4 hours. The amount of time getting to airports, getting through security, boarding, baggage, getting to and from a remote area where the airport is all costs time that won't be improved by an electric airliner, no matter how much these people want to make fetch happen.

France is actually making the move to ban short haul flights. Which makes total sense because Paris to Lyon drops you between two city centers in two hours via train and going via plane means going out to the airport, flying, and coming back in. There are still flights but the people taking them need to connect on to further destinations.

Electric aircraft? Make jet fuel from corn using renewable energy. Totally renewable, carbon neutral. Better than trying this folly of electric aircraft. Batteries are heavy af by orders of magnitude compared to hydrocarbons. It's an equation that's never going to go the way electric aircraft proponents want it to.
posted by Your Childhood Pet Rock at 4:55 AM on June 29, 2021 [18 favorites]

Let's be clear: electric airplanes are here. Electric airliners are not, and will not be for quite some time. You will not be replacing high speed rail with zero-emission air travel any time in the near future.

Electric aircraft on the market (or nearing market) today can seat two people and stay in the air for around an hour. These are trainers. The most ambitious plan for electric aircraft that I'm aware of right now is Cape Air replacing some of their aging twin Cessnas to fly their short-haul routes like Martha's Vineyard to Logan.

I do believe there's a market for electric aircraft, but Boston to New York is not going to see them.
posted by backseatpilot at 5:11 AM on June 29, 2021 [7 favorites]

Battery electric planes have some very serious limitations based in simple physics and are not foreseen to be suitable for long haul or heavy lift flights with current or next generation batteries.

There are so many ways it doesn't scale up from the demonstration vehicles that I won't even start listing them as I'm about to go to work.

The basis for my opinion - several years industrial research work for a next-generation rechargeable battery technology company.

On preview: what backseatpilot said
posted by Glomar response at 5:15 AM on June 29, 2021 [5 favorites]

I agree, we're looking at a whole new generation of "renewable" fuels made from plant sources mostly, although there are some seriously cool developing technologies for making longer chain hydrocarbons from CO2 directly, using only electricity as an input. These RD (renewable diesels) as they are now called are chemically identical to the fuels they replace (or close, they're entirely long-chain alkanes, fully hydrogenated from the plant source triglycerides) . These have no conversion issues for diesel or kerosene burners---it's like a very high quality petrofuel. It's a much better alternative than the biodiesels of a decade ago that contained ethyl esters.

From a carbon dioxide view, they can easily be made carbon neutral. From a spills point of view, they're fairly low impact. The main issue is physical fouling on birds, but they have essentially no toxicity and would degrade in the natural world pretty quickly.

The main limitation right now is that RDs are really expensive compared to petrofuels. The fully synthetic ones are 10x more expensive at pilot scale.
posted by bonehead at 5:22 AM on June 29, 2021 [4 favorites]

Let's be clear: electric airplanes are here. Electric airliners are not, and will not be for quite some time.

I think that is the point that the Cheddar video was trying to make. A battery powered airliner is not going to be viable in the short or medium term because of some fundamental issues with battery energy density. However the equations are much more favourable for Cessna sized aircraft. Here the profit margin per passenger is miniscule with current planes (because of the costs of the fuel and the maintenance). He goes through the example of Cape Air to show how the adoption of the electric aircraft (they have ordered) on their routes, could make them the most profitable airline on earth per passenger mile.

Cessna aircraft and trains may compete on some routes: and trains will probably be a better option in those cases. But for journeys where no train is available - electric aviation looks like an appealing alternative.
posted by rongorongo at 5:27 AM on June 29, 2021 [2 favorites]

If we do build out space elevators, we can install launching stations for unpowered long-distance gliders along them.
posted by acb at 5:58 AM on June 29, 2021 [5 favorites]

A more skeptical take from AVweb. One interesting point they bring up is that the buildout of electrical infrastructure to airports for charging is going to be as big of a challenge/as much of a sticking point as the obvious challenge of battery density. They cover many of the other practical pros and cons of electric aircraft, and try to get a realistic idea of where specific companies in the industry are at.
posted by clawsoon at 6:01 AM on June 29, 2021

Is there a link to where I can buy a ticket?

Guy down the street is involved with a stealth startup making an electric plane/car/shuttle/bigassdrone, and all they need is a little seed money, just a few 10s of millions. Peanuts in that industry. But they have powerpoints!

I've seen youtube videos and it will certainly happen at some point if only at airshows. One issues is the FAA takes years to certify an upgrade to even a single instrument, once electric planes certifiably work can a new plane company survive the many years of certs before they can book the first commercial passenger? Autonomously without a pilot?
posted by sammyo at 6:14 AM on June 29, 2021

One interesting point they bring up is that the buildout of electrical infrastructure to airports for charging is going to be as big of a challenge/as much of a sticking point as the obvious challenge of battery density.

We know how to move electricity; charging infrastructure is a pure money problem. 99% of airports could have charging infrastructure in place in a couple years if there was demand.
posted by Mitheral at 7:28 AM on June 29, 2021 [3 favorites]

Is there a link where I can buy a ticket?
HarbourAir in Vancouver, have at least flown some trial commercial flights on an “E-Beaver”. Suspect they will get there first.
posted by rongorongo at 7:41 AM on June 29, 2021

charging infrastructure is a pure money problem.

That's not entirely true, and it's been one of the major roadblocks to electric rollout. To keep aircraft (especially airliner sized) economically viable, they have to be flying and not sitting around waiting for batteries to charge.

A quick back-of-the-envelope calculation: The 737-800 uses around 850 gallons per hour of jet fuel in flight. That's roughly 110,000 Megajoules per hour of energy. Even for a reasonably modest flight (2-3 hours for a plane that size), with reserves you're looking at needing pump almost half a Gigajoule of energy into some sort of storage system on the plane in a reasonable (say 20 minutes) amount of time. That's around half a megawatt of power.

With that amount of power, you're looking at trade offs between increasing component and wire sizes, onboard system weights, and added insulation needs. Plus we have the current issues of existing rechargeables having a tendency to catch fire and explode if you pump too much power into them too quickly...
posted by backseatpilot at 8:02 AM on June 29, 2021 [1 favorite]

Cheddar, the corgi on Brooklyn 99?
posted by Going To Maine at 8:04 AM on June 29, 2021 [2 favorites]

Can't they just use swappable batteries?
posted by onya at 8:15 AM on June 29, 2021

But getting a few GW to an airport? That's an awful lot cheaper than the pipelines that many of them already have supplying them with aviation fuel.
posted by ambrosen at 8:30 AM on June 29, 2021 [2 favorites]

With physics stacked against them, I'm amazed they're commercially viable anywhere. I'm glad they can take those weird government subsidized routes to small regional airports because those are useful infrastructure in case of emergency.

But this won't even replace an interstate bus, and I'm not convinced they'd even be better than an ancient packed diesel bus unless said bus' engine has a busted catalytic converter.
posted by ikea_femme at 8:42 AM on June 29, 2021

Can't they just use swappable batteries?

Well, using the 110,000 MEGAjoules per hour estimate, and a battery storage density estimate of 460 KILOjoules per kilogram of lithium ion batteries, sure. It would be a mere 240 metric tons of batteries per hour of flight that you would have to swap. This will be a bit tricky because the cargo capacity of a 737-800 is only about 19 metric tons.
posted by notoriety public at 8:50 AM on June 29, 2021 [3 favorites]

Locally, I'm excited to see the continued growth of Beta. They have identified time sensitive cargo transport as their first market - and this approach makes sense. Minimize weight of the human load, transport high value time sensitive products, make use of airport infrastructure without the TSA related delays on general public customers. My understanding is that they are beginning to get orders for the cargo version of their airplane.
posted by meinvt at 8:59 AM on June 29, 2021

My understanding is that they are beginning to get orders for the cargo version of their airplane.

How many are from drug cartels?
posted by notoriety public at 9:15 AM on June 29, 2021 [1 favorite]

110,000 MegaJoules is only (google tells me) 31,000 KWhs To use an example I know: The Cat 7495 electric rope shovel uses, depending on kit out, 1.3 MegaWatts of power on average and peaks at 3.7MW. Scale it by 10/20/30 (even just by running a few cables in parallel and the plane is charged in an hour. There are machines out there with even larger requirements. We can deliver the power to the plane no problem.

Current battery tech may not be able to accept that charge in a reasonable time (and is plane turn around really 20 minutes? Seems short.) but getting it to the plane is a solved engineering problem.

But this jumping right to a massive plane like the 737-800 is all tilting at windmills the same way electric car skeptics say electric cars will never catch on because they can't drive Seattle to LA in 18 hours. The super common (here anyways) short haul DASH-8 apparently uses 600 litres per hour. Many flights (like Kamloops-Vancouver) are only 20 minutes. It takes them way longer than 20 minutes to turn that plan around (I know because I've waited to board a late plane that I can see through the window on many occasions). That is the kind of thing that will be a stretch goal for commercial electric passenger aviation; not a 737.

I'm not convinced they'd even be better than an ancient packed diesel bus

Harbour Air's advantage is they can cross a significant water channel in just a fraction of an hour; something that the diesel bus will take at least 1.75 hours to do just for the ferry time for the Vancouver-Victoria hop and half a day Victoria-Seattle.

I don't know what the ultimate battery tech in 50 years is going to be capable of but it sure looks like we are there or nearly there for short hop small commercial service (say flights less than 1/2 hour for less than 10 people). And not in a Fusion in 10 years sort of way. There is lots of that sort of traffic in BC.
posted by Mitheral at 9:17 AM on June 29, 2021 [5 favorites]

Well, fair enough. But the big, big issue is that battery storage density is one percent of fuel storage density. How many of those short hops are viable if the fuel suddenly weighed 100 times as much? Every other logistical problem fades compared to the energy density problem.

As far as I can see, the way that problem gets solved is via carbon neutral fuel synthesis. Who is hellaciously energy intensive but at least it doesn’t rely on hand waving magical hypothetical improvements in battery density that we don’t even have a plausible physics basis for. The challenges are “merely” that it’s vastly more expensive than just pumping oil out of the ground.
posted by notoriety public at 9:29 AM on June 29, 2021 [1 favorite]

Refillable fuel cell tech isn't dead yet either, and of course the other dark horse is LH2. There are a bunch of options between petrofueled jets and electric prop-planes that I'm sure we haven't even thought of yet. It does seem clear to me however, that current batteries aren't going to be more than a niche answer to this problem.

I do think there are a few options to carbon neutral/renewable power storage out there, the question is which one is going to turn out to be practical. It could still be a banana-peel-powered Mr. Fusion.
posted by bonehead at 11:12 AM on June 29, 2021

Air travel and private automobiles are artifacts of the fossil hydrocarbon age, they'll be nowhere to be seen* in 300 years.

And that of course means we'll waste effort and countless resources on technological dead-ends instead of channeling them to things that might have a chance of being sustainable in the medium term.

* Owning a private car, or flying more than a couple times in one's lifetime (if at all), will be the equivalent of owning a helicopter in the present. That's the optimistic view, where both of these things even exist at all in future civilisation.
posted by Bangaioh at 12:35 PM on June 29, 2021 [1 favorite]

Large aircraft are already more efficient than people realize.
In Europe in 2017, the average airline fuel consumption per passenger was 3.4 L/100 km (69 mpg‑US).

That's more efficient than the most efficient gasoline car (with just a driver, no passengers). It is actually even more efficient because it goes straight 'as the crow flies' instead of meandering around roads.

There are ways to make large planes partially electric. Much of the power of a plane is needed in take-off. Airbus was building the E-Fan X hybrid plane where only one of four engines was electric. It could take off using fuel, then cruise using the the electric engine. Unfortunately, airlines were severely hit by the Covid pandemic, and the project was cancelled before its first flight.
posted by eye of newt at 12:48 PM on June 29, 2021 [2 favorites]

Huh, so if a Boeing 767-- so ~350 seats and 90 SUV's (each sitting 4 people) crossed the USA coast to coast. The plane would burn more gas then the cavalcade of SUV's? That's blown my mind-- somehow I mistakenly thought planes were better on those terms.
posted by Static Vagabond at 2:04 PM on June 29, 2021

Refillable fuel cell tech isn't dead yet either, and of course the other dark horse is LH2. There are a bunch of options between petrofueled jets and electric prop-planes that I'm sure we haven't even thought of yet.

Except airplanes use thrust not torque. It's not like a car where you get better thermodynamic efficiency from a fuel cell stack. The heat that would normally be wasted in a car engine goes to both powering the compressor for the intake stage and providing thrust on the output. You can just burn LH2 in a turbine if push comes to shove and get better thermodynamic efficiency.
posted by Your Childhood Pet Rock at 2:05 PM on June 29, 2021

High speed rail is faster than an airline for anything less than 4 hours.

Six or seven years ago I was working in Boston and wanted to visit friends on the Jersey Shore for a long weekend, so I compared flying, driving and taking the train. I looked at time, cost and hassle, and train came out in front. All three were almost the same on cost and time.

Plane was quickest to cover the distance from Logan to Newark, but once you'd figured in getting to the airport and all the checking in and getting out at the other end, it added up.

If I drove I'd have to hire a car, then there was the gas, the hassle of driving, and the fact I'd arrive tired at both ends.

Train was about the same cost, I sat on Amtrak reading and looking out of the window, and only had to remember to get off at Penn Station and change to NJ Transit. It was a surprisingly pleasant experience.
posted by 43rdAnd9th at 2:05 PM on June 29, 2021 [4 favorites]

Much of the power of a plane is needed in take-off. Airbus was building the E-Fan X hybrid plane where only one of four engines was electric. It could take off using fuel, then cruise using the the electric engine.

They have catapults on aircraft carriers specifically for the purpose of helping fighter aircraft into the air; perhaps a variant of this technology could be used in civil aviation?
posted by acb at 2:55 PM on June 29, 2021

But the big, big issue is that battery storage density is one percent of fuel storage density. How many of those short hops are viable if the fuel suddenly weighed 100 times as much?

According to RealEngineering's calculations above, lithium ion batteries are about 40 times heavier than jet fuel in terms of Mj/Kg. In an electric car, the mass of the battery doesn't matter very much in practical terms - but on planes it does because shifting that extra mass needs a lot more power: double the plane's mass and you need about 8 times more power just to take off and fly. Then you need more power still as the plane's range and cargo capacity goes up. For an aircraft of the size and range of a Cessna we would need to carry about 500Kg of batteries to cover a typical range. For a Boing 737 the weight required would be about 260 tons - about 4 times the empty plane's weight. If we reduce take those weights and reduce the range to the point where the weight of the batteries would match the usual fuel ratio of each aircraft - the Cessna would have a range of 4 hours reduced to a - still workable - 2. The 737 would drop its range from 7 hours down to a useless 20 minutes. This is why small battery powered electric aircraft with lower speeds and capacities are eminently possible to build - and why battery powered airliners are absolutely not.

The commercial addendum is that that just as a battery airliner would make no sense at all - a battery powered Cessna would make overwhelming sense.
posted by rongorongo at 10:48 PM on June 29, 2021

Huh, so if a Boeing 767-- so ~350 seats and 90 SUV's (each sitting 4 people) crossed the USA coast to coast. The plane would burn more gas then the cavalcade of SUV's?--Static Vagabond

Actually a full Boeing 767 is more efficient than the average for all European flights and gets the equivalent of 97mpg per person. A flight from LA to NY goes about 2470 miles. Driving from LA to NY requires about 2800 miles of driving.

So let's say these SUVs get about 25mpg (some do better, quite a lot do worse). That's 100mpg per person if they all have 4 people. 2800/100 = 28 gallons per person
The plane uses 2470/97 = 25 gallons per person, so the plane would burn less gasoline than 90 SUVs.
posted by eye of newt at 12:20 AM on June 30, 2021 [1 favorite]