Electric and Hydrogen aeroplanes - feasibility and issues

Commentary on the feasibility of electric cars that is pertinent to aviation too.

You might know Rowan Atkinson as Blackadder, but he's a long time car enthusiast and as he says, 'My first university degree was in electrical and electronic engineering, with a subsequent master’s in control systems.' He rightly points out that while low engine emissions are sexy, the total lifetime emissions including battery manufacture and short product lifetime definitely aren't.


When you start to drill into the facts, electric motoring doesn’t seem to be quite the environmental panacea it is claimed to be.

The problem lies with the lithium-ion batteries fitted currently to nearly all electric vehicles: they’re absurdly heavy, many rare earth metals and huge amounts of energy are required to make them... a lot of effort is going into finding something better. New, so-called solid-state batteries are being developed that should charge more quickly and could be about a third of the weight of the current ones – but they are years away from being on sale, by which time, of course, we will have made millions of overweight electric cars with rapidly obsolescing batteries.

[A hydrogen] system weighs half of an equivalent lithium-ion battery and a car can be refuelled with hydrogen at a filling station as fast as with petrol.

It’s sobering to think that if the first owners of new cars just kept them for five years, on average, instead of the current three, then car production and the CO2 emissions associated with it, would be vastly reduced.

A sensible thing to do would be to speed up the development of synthetic fuel, which is already being used in motor racing; it’s a product based on two simple notions: one, the environmental problem with a petrol engine is the petrol, not the engine and, two, there’s nothing in a barrel of oil that can’t be replicated by other means. Formula One is going to use synthetic fuel from 2026. There are many interpretations of the idea but the German car company Porsche is developing a fuel in Chile using wind to power a process whose main ingredients are water and carbon dioxide. With more development, it should be usable in all petrol-engine cars, rendering their use virtually CO2-neutral.
 
[A hydrogen] system weighs half of an equivalent lithium-ion battery and a car can be refuelled with hydrogen at a filling station as fast as with petrol.
That hydrogen system also gives 1/3 the range of a Li-ion battery car, or put it another way, takes 3x the energy to travel the same distance.
It’s sobering to think that if the first owners of new cars just kept them for five years, on average, instead of the current three, then car production and the CO2 emissions associated with it, would be vastly reduced.
That makes no sense. Cars are not discarded after 3/5 years, they're sold on the secondhand market. The average scrapping age of cars is nearing 20 years.
 
That makes no sense. Cars are not discarded after 3/5 years, they're sold on the secondhand market. The average scrapping age of cars is nearing 20 years.
I think the idea being put forward is that if people bought cars less frequently, emissions and car production would decrease.
 
On the other hand... the production of e-fuels uses five times the energy that you get out of them currently.

Its about the same as for hydrogen. The production of hydrogen is more efficient (85% vs. 60%) but the energy demand for pressurisation/liquidification, transport and boil off losses is much higher.

With an efficient engine (syn fuels will allow a higher efficiency) about 25 % of the electic input energy will reach the wheels, same as for hydrogen.

Aramco announced, that they will be able to produce E-Fuels for 0,8 € per liter (before tax) with solar energy.
 
To present a counterargument:


EVs already cut planet-warming emissions by two-thirds on a life cycle basis relative to combustion engine cars in the UK – and the benefits are growing.... the emissions from producing batteries, while significant, are quickly outweighed by the CO2 emissions from fuelling petrol and diesel cars.

For starters, the government’s cost-benefit analysis of its policy plans for cars talks in detail about life cycle emissions. Specifically, it mentions government-commissioned research that proves EVs offer a large and growing emissions benefit on a life cycle basis.

Echoing Carbon Brief’s findings, the analysis says: “BEVs [battery electric vehicles] are expected to reduce GHG emissions by 65% compared to a petrol car today, and this rises to 76% by 2030.”

Figures from NGO Transport and Environment show EVs can be driven two to five times further on the same energy as would be needed if using hydrogen or synthetic fuels. This thermodynamic disadvantage inevitably makes these alternatives much more costly to run than EVs.

...a new EV would start benefiting the climate in less than four years, relative to an old combustion engine.

Links included in the article.

My impression is that inevitably, multiple factors are involved and a slight change in one will have a major effect on the outcome. In this case, all of the factors are changing as technology advances and consumption patterns change. An analogy might be the Drake Equation. It seems to proceed in a neatly linear way to a conclusion, but many of the factors are unknown, affecting the next, and leading to wildly varying results - from aliens are everywhere or even we don't exist. In this case, factors are known but changing and one change up or down the chain may completely change the total advantage.

Now, does anyone remember VHS versus Beta?
 
Whisper Aero has revealed their clean sheet design of electric aircraft. It is a nine passenger hybrid-electric aircraft with a MTOW of 12,500lbs, a max cruise speed of 250kts, a battery-only range of 161-193 miles and a hybrid range of 432-464 miles. By increasing the number of blades in the ducted fan and spinning them at a sufficiently high RPM, the tonal noise goes to ultrasonic frequency range, resulting noise inaudible to human and attenuates quickly in the atmosphere. The high RPM is also compatible with electric motor performance. Also, jetfoil with outboard horizontal tail to reduce drag is another feature. More details are going to be revealed in the upcoming 2023 AIAA aviation forum.

 

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I assume the motor technology is in focus for them and not the aircraft, which shows an example for an application. I wonder now how willing others are to include it into their products, since a lot of eVTOL players are in the certification right now and probably cant go back to integrate a new motor technology.
 
If "increasing the number of blades in the ducted fan and spinning them fast enough" was all it took to make aircraft quiet, engine makers would not have needed to spend tens of billions of dollars to reduce aircraft noise. I realize Whisper Aero is dealing with quite low-powered aircraft, but still. For one thing, that air flow itself makes noise
 

“Tecnam has concluded that the time for P-Volt is not yet ripe,” the company announced, “although research activities will continue to explore new emerging technologies.”

“Only a few hundred flights would drive operators to replace the entire storage unit, with a dramatic increase in direct operating costs due to the reserves for battery replacement prices,”

So they're finally admitting what many of us have long suspected, that the battery tech available now isn't good enough to make even a small 9 seat aircraft economically viable. That also means that projects like the Eviation Alice are pretty much doomed to fail. So I guess hybrid projects like the ones being done by Ampaire with their Eco Caravan are the only viable alternatives now.


This article has even more damming nuggets of information:

"Tecnam paused the development of its all-electric P-Volt over fears that battery performance would degrade so quickly that within weeks the nine-passenger aircraft would be reduced to flying routes of under 40nm"

"He says the energy density of cells and their ability to maintain their storage capacity over hundreds of cycles were the two areas of concern."

"Based on its forecasts, Tecnam estimates that with aerospace batteries likely to cost at least $1,500/kWh, an entire 215kWh battery pack suitable for the P-Volt would come in at more than $300,000"

"Tecnam estimates that 10% battery performance degradation would complicate mission planning, as range would decrease by 20% after less than 1,000 cycles – and would drive up operating costs significantly."
 

Shame. Would have liked to have seen NASA devote more time and funding to this project rather than the pipe dream of creating a successor to Concorde which would never work with the economic and environmental realities that exist today.
 

I'm pretty sure the massive amounts of drag caused by the hull and the pontoons would drain the battery pretty quickly. Should have gone with a hybrid configuration to at least give this project some chance of becoming reality.
 

I'm pretty sure the massive amounts of drag caused by the hull and the pontoons would drain the battery pretty quickly. Should have gone with a hybrid configuration to at least give this project some chance of becoming reality.
I tend to agree
 
?

I don't understand this point. With EV airplane, battery is range, not finesse...

Let's not forget that seaplane can takeoff on a similar distance at a much higher mass and land at a higher mass on Shorter distance. Hence a seaplane with battery makes more sense than a land plane.
It is also more compliant with fire safety concerns during takeoff and landings where a high percentage of incident occurs.
 

I'm pretty sure the massive amounts of drag caused by the hull and the pontoons would drain the battery pretty quickly. Should have gone with a hybrid configuration to at least give this project some chance of becoming reality.
The Catalina had a glide ratio over 20, so this shouldn't be a huge problem as long as the plane has a large wingspan and doesn't fly very fast. Don't forgett, there are landeplanes which fly around with uncoverd wheels fully exposed to the air (Tecnam Traveller), this is surly worse than the relative small pontoons.


Edit: I'm quite sure, I heard the glide number in Rex Channel, but I might be wrong or he might be wrong also. Other sources state, the L/D ratio was about 12. Anyway, a large wing span and slow speed is still a good approach for an efficient short haul sea plane.
 
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Hmm. Of all the issues I've heard discussed with non-cryo gaseous hydrogen for vehicles, tank wall diffusion has never been raised as a serious concern. Liquid cryo hydrogen (which I think is what BMW has been using) has boil-off issues, but not anything that will reach explosive concentrations.
I doubt that. Hydrogen is explosive in air anywhere from 4% to 75% hydrogen by volume. ppm? 4% is 40,000ppm
 
When you talk about "blowing up" an enclosed garage, are you talking about "inflating" or "exploding."

Most residential garages are deliberately "porous" to allow a variety of petro-chemical fumes to vent before they reach toxic levels.

OTOH One person sneaking into the garage for a quick "smoke" could ignite a hydrogen explosion.
Exploding. Hydrogen has incredibly wide explosive limits. Anywhere from 4% to 75% is an explosion risk. And because of how hydrogen rises, it can catch in places like the underside of ceiling joists and build to an explosive concentration there, before it permeates through the ceiling or roofing materials. Happened in a test stand that was being used for multifuel vehicles. Guy came in to work one day and the blast wall of the test cell was in the parking lot.
 
Yet another startup from the Netherlands that has very ambitious plans to build a small regional airliner. Range would roughly 341 miles. It will have a modular battery back that can be quickly swapped out when a newer one becomes available to make the aircraft future-proof. I wonder if the Dutch govt would financially support this project as a way of reviving their aerospace industry.


Aviation battery tech will always be 10 years behind state of the art, because it takes 10 years to certify the new battery.
 
Not sure if it qualifies as an airplane, but there is the Regent seaglider, an all electric WIG craft that was presented recently. According to the press release, they already have 334 on order.

Related to that,


2025 looks pretty optimistic, to put it mildly. Certification of an aircraft would take longer than that. However, supposedly...

Ocean Flyer had begun discussions with Maritime New Zealand which was likely to be the safety regulator for seagliders rather than the Civil Aviation Authority, he said.

Caveats: "begun discussions" doesn't mean much, the reporter has a good CV but his areas are business and technology (that is, gadgets, not aviation).

At first glance, ekranoplans would make a lot of sense in New Zealand - most of the population is in coastal cities and there's be a demand for fast, flexible, and frequent transport across the strait between the two major islands as well around the Auckland area.
The advantage is that WIGE craft that cannot fly out of ground effect are considered boats, not airplanes. No pilot's license required, much simpler certification requirements, and flat out excellent load carrying capabilities times greatly reduced thrust required once off the water.
 
What I would like to know, is, which kind of nuclear fission reactors would be the best for ammonia ? I kind of like MSR, but HTGR seems to be "hotter" to split the hydrogen out of water ?
Old school Pressurized Water Reactors making steam, steam spins turbines, turbines spin generators, generators crack water into H2 and O2.

And you don't have to use water in the steam cycle, you can use other things. Or you use a tertiary loop to take remaining heat out of the steam once the steam turbines are done with it and have it boil ammonia and run that through a separate turbine. Like how they use flue gas heat to spin a generator in cogeneration systems. Do it right and the flue gasses are at ambient temperature when you're done.
 
Furl cells and H2 is hardly a new concept!
The breaktrough technology is supposed to be the liquid H2, which gives far greater energy density and should be compact enough to be retrofitted in existing airframes. Hence their idea of converting an existing lightplane.
Liquid Hydrogen is 14 liters per kg, and requires bulky insulation on top of that.
 
Why wouldn't be possible to evacuate through the leading edge? There is a lot of door systems that open way through smaller volume. Think at sailing ship cabin entry door for example, combining a hatch with a front access.
Usually because the leading edge of a crashed plane is either on fire or buried in the ground.
 

"As battery performance continues to be a barrier, companies are realizing hybrid designs may be the only approach to electrify small aircraft in a way that will cause buyers to see reasonable value."

I agree that hybrid propulsion is the only way forward right now. Even Embraer has admitted that a fully electric 9 seat commuter plane would not be feasible until at least 2035 due to battery limitations. But even hybrid conversions have their drawbacks:

"The claimed advantage is lower fuel consumption and emissions against a tradeoff of less speed, less payload and shorter range, plus the complexity of displacing a turbine with a piston engine"
 
I'm pretty sure the massive amounts of drag caused by the hull and the pontoons would drain the battery pretty quickly. Should have gone with a hybrid configuration to at least give this project some chance of becoming reality.
Harbour Air operating in the Seattle-Vancouver BC area has apparently swapped over completely to electric aircraft, and is doing surprisingly well with it. Recharging takes about 30-45 minutes, while their turnaround time for that specific aircraft is roughly 60 minutes. Though I am pretty sure they're quick-charging to 80% of capacity in that time, not doing a full charge.
 
News from Eviation


So, we had taxiing trials, then months of nothing, a very short first flight in September, months of nothing after that, and now they are outsourcing the design of the production version (whatever that may mean). Doesn't exactly inspire confidence. That is a pity, because I quite like the airplane.
 
Not plain fishy. But it's a small company, recently funded, that might outsource abroad a lot or provide only workforce (see Capital Vs claimed employee number) and claims to have worked on 100 aircraft projects in 4 years.

Where to begin from:

 
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News from Eviation


now they are outsourcing the design of the production version (whatever that may mean).

I think that what we’ve seen flying is a fairly crude technology demonstrator, quite a long way removed from anything that would certify and be a merchandisable product. With so much money being poured into this techno sector, I suspect a government has sensed an opportunity to bankroll a design effort in the hope it will catapult them to world leaders. The fundamental lack of a viable battery technology isn’t understood or maybe irrelevant when it comes to the deals being done.
 

This article has a paywall, so I'll briefly summarize the main points:

* After just 1 test flight totaling 8 minutes, no more flight testing will be done until the definitive version appears around 2025.

*Eviation claims that one flight generated enough data that no other test flights are necessary.

* The CEO claims that while the prototype is airworthy, “we are expending resources where we need to”. That tells me that they have financial issues and cannot afford to carry out flight tests while developing the definitive production conforming version.

* "Over recent months, Eviation has been honing the aircraft configuration: analysing which parts it can take to a certification-suitable model and which need replacing or updating, for reasons of obsolescence or producibility, for example." So the definitive version will be very different that what we see today.

* "A certification-conforming aircraft will make its debut in late 2025, leading to approval and service entry around two years later." It's going to take a bit longer than just 2 years for this aircraft to get certified. The much simpler and less complex Tecnam P2012 took almost 4 years before it entered service with Cape Air. And even then the aircraft had its share of teething issues.

* "Eviation is also considering various options for Alice manufacturing, although Davis says aircraft will likely be shipped near to customers as a kit before final assembly by one of Eviation’s service partners." That's an odd approach for manufacturing a commercial aircraft. Is it possible that they are having issues raising the funds for a production facility ? But then again considering the tiny range this aircraft will have maybe it's a stroke of genius.

* "Davis insists the firm is seeing “global interest” in the aircraft; Eviation’s backlog for the Alice now tops $4 billion and includes over 500 aircraft – a figure that has grown by around 400% over the last year." Those are not firm orders, but very soft commitments. They hope to firm up those tentative commitments over the next 2 years, and hopefully get some customers to place deposits.
 

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