[HN Gopher] Skeptical about electric-powered planes
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Skeptical about electric-powered planes
Author : prostoalex
Score : 65 points
Date : 2021-11-11 16:41 UTC (1 days ago)
(HTM) web link (www.planeandpilotmag.com)
(TXT) w3m dump (www.planeandpilotmag.com)
| mmmBacon wrote:
| I love this comment because it's true of a lot of hardware
| startups I've seen lately.
|
| _While they may not be very good at building airplanes, they are
| absolute savants at issuing press releases_
| evancoop wrote:
| The contrarian in this case would be making Elizabeth Holmes'
| argument "first they say you're crazy...the you change the
| world." Of course, the folks delivering such an argument are
| either peddling vaporware or actually on a path to changing the
| world. Sometimes, perhaps even the speaker does not know the side
| of the divide on which they fall?
| bklyn11201 wrote:
| For anyone else like me wondering why hydrogen is difficult for
| airplanes (not mentioned in the OP article):
|
| from https://www.bbc.com/future/article/20210401-the-worlds-
| first... --------------
|
| Hydrogen has higher energy by mass than jet fuel, but it has
| lower energy by volume. This lower energy density is because it
| is a gas at typical atmospheric pressure and temperature. The gas
| needs to be compressed or turned into a liquid by cooling it to
| extremely low temperatures (-253C) if it is to be stored in
| sufficient quantities. "Storage tanks for the compressed gas or
| liquid are complex and heavy," says Finlay Asher, a former
| aircraft engine designer at Rolls-Royce and founder of Green Sky
| Thinking, a platform exploring sustainable aviation.
|
| And there are other challenges. The energy density of liquid
| hydrogen is only about a quarter of that of jet fuel.
| ncmncm wrote:
| Probably you will want liquified H2. So, we need volume
| manufacturing of aerogel, for the tanks. If we don't go to
| wholly new airframes, we will need to sling the LH2 tanks in
| nacelles under the wings, like the engines, because the needed
| tankage volume won't fit inside normal wings. (With a new
| airframe with more internal space, the tanks could be inboard,
| but maybe you don't really want big tanks of LH2 inboard.)
|
| The LH2 would be electrolyzed on demand at the airport, using
| power delivered by transmission lines from all over, banking
| LH2 when the sun is out or the wind is blowing, when it is
| cheapest.
|
| Once these planes start flying, it will become impossible to
| compete with them, because the smaller mass of fuel needed
| translates to substantially more freight, both total capacity
| per flight, and per unit-cost of fuel. But there are still
| things to work out, so there will be an interim need to
| synthesize jet fuel from atmospheric CO2 and H2, which should
| soon get cheaper than extraction.
|
| It would be helpful if somebody were to come up with a good use
| for all the waste oxygen everyone is going to be producing.
| tuatoru wrote:
| > Probably you will want liquified H2.
|
| More likely to use solid adsorbed hydrogen. Room temperature,
| room pressure, less mass in the tanks.
|
| Adsorption has been experimented with for several decades at
| least. But modern computer power and modern processes for
| controlling material surface properties make it more likely
| than ever before.
|
| https://en.wikipedia.org/wiki/Adsorption - not specific to
| hydrogen
|
| Random PDF of study:
| https://www.cambridge.org/core/services/aop-cambridge-
| core/c...
|
| https://www.youtube.com/watch?v=U7CCq4oBgw4&t=464s - latest
| "breakthrough". One day, one of these will be real.
| ddek wrote:
| As you say, we've been working on solid adsorption for a
| long time now. Nothing has left the lab. The video presents
| an optimistic future, but we don't even have the basics
| yet.
|
| Firstly, there is a fundamental issue - H2 doesn't really
| give you anything to work with. The vast majority of
| compounds have two protons, two neutrons (rare isotopes
| have more protons). [They're distributed in the most boring
| orbitals, just spheres with no real edge to gain leverage.]
| (https://winter.group.shef.ac.uk/orbitron/atomic_orbitals/1
| s/...)
|
| This lack of leverage makes surface adsorption tricky. The
| molecule gives us nothing to grab. You won't carefully
| craft a surface that can hold H2.
|
| I think right now there's a focus on activated carbon.
| That's become a bit of a synonym for 'graphene', with it's
| well known limitations.
|
| When I studied the subject, metal-organic complexes were
| the focus. These would be extremely customisable, but if
| they worked we'd probably have seen by now. They tended to
| use heavy metals. I wasn't optimistic at the time, I
| thought anything using materials past the 4th row of the
| periodic table was unrealistic. As the metals get heavier
| they get expensive and sometimes rare. If we want to solve
| a common problem, we need common components. If your
| solution has lanthanoid, it won't scale.
|
| I was right btw. The research group closed when funding was
| reallocated. Each experiment ran the research budget of
| another group. MoC's don't really get much love any more.
|
| Anyway, we should probably think about what makes a good
| hydrogen adsorption material. I think it's pretty simple,
| you want a material that: stores a high density of
| hydrogen, is reusable, quickly picks up hydrogen, and
| quickly releases hydrogen.
|
| The latter 2 categories is the 'kinetics'. Of the materials
| we know, all (literally all) that have 'good' kinetics are
| either single use or low density. Conversely, all that are
| both multi use and relatively high density have poor
| kinetics. Additionally, most of those with good kinetics
| have unrealistic conditions, like requiring 400@C
| temperature to release the hydrogen.
| drran wrote:
| LENR scientists are using palladium and nickel to
| compress hydrogen up to 100k atmospheres (90 hydrogen
| atoms per 1 atom of palladium) at room temperature and
| pressure.
| ddek wrote:
| No?
|
| LENR is not a particularly active field of research. The
| most recent noteworthy paper is a well funded, failed,
| replication. It is a pipedream. There are almost no LENR
| scientists.
|
| I can't see any noteworthy papers for PdNi as a hydrogen
| storage mechanism. It's capability to _absorb_ (hold
| within its structure; not _adsorb_ , to hold on surface)
| hydrogen has been known for a century, if it had utility
| we would know by now.
| zoomablemind wrote:
| From a realm of sustainability, it'd be cool to dream up
| a way for having bioships [1], so that the energy would
| be accumulated in the structure while still on the
| ground, then metabolised while in-flight.
|
| Well, SkyMoos [2] would also be nice to have around.
|
| [1]:https://en.m.wikipedia.org/wiki/Bioship
|
| [2]:https://aliens.fandom.com/wiki/Skymoo
| tuatoru wrote:
| I'm glad I prompted an expert to comment! Thanks.
| ncmncm wrote:
| Less mass than what? I promise you, adsorbed hydrogen along
| with whatever it is adsorbed onto will _not_ weigh less
| than the same hydrogen, liquified. LH2 at atmospheric
| pressure does not need a heavy tank. If they can get it to
| adsorb to an aerogel, they might have something, but you
| still have to get the H2 back out.
| ddek wrote:
| The best solid adsorbed hydrogen is currently running
| about 5% the density of liquid hydrogen. Most solutions
| use either graphene or heavy metals too rare to meet mass
| demand. It's not a promising technology.
| lowbloodsugar wrote:
| For those who, like me, got confused: Hydrogen requires more
| volume for the same energy as jet fuel, but even with that
| larger volume, it is lighter than the smaller volume of jet
| fuel.
| PostThisTooFast wrote:
| Not to mention that compressing or liquifying gas takes a
| shitload of energy to begin with.
| aplummer wrote:
| This is an industry we will be trying to improve for several
| hundred years from now at least. Very good chance electric
| airplanes are not feasible today, or tomorrow, but this is a long
| game. Maybe it won't be typical batteries, and very likely not
| lithium ion batteries.
| PostThisTooFast wrote:
| I think it'll age pretty well. I want electric airplanes to be
| viable, but come on.
| jbuhbjlnjbn wrote:
| Did you know "avgas", short for "aviation gasoline", in its most
| common use, is still using lead as a countermeasure to engine
| knocking? It means, the aviation industry continues to poison the
| world by spraying lead in the form of exhaust gases everywhere.
|
| The sooner this is stopped, the better.
| upofadown wrote:
| The article mentions this indirectly, but the leaded gas issue
| is actually orthogonal to the question of the practicality of
| battery powered aircraft. Aircraft can and do work without
| leaded gasoline. The unleaded aviation gas issue has already
| been discussed to death here. It gets brought up every time
| there is any reference to anything to do with any aircraft that
| runs off gasoline.
| jeffreyrogers wrote:
| Jet aircraft use jet fuel, not avgas. Avgas is really only used
| by small GA aircraft and the FAA recently approved many of them
| to use unleaded avgas.
| JasonFruit wrote:
| The FAA in the US just approved a list of about 600 aviation
| engines to use unleaded, so that welcome change is progressing.
| occz wrote:
| Good. With that out of the way, time to build some trains.
| foobarian wrote:
| And tracks too, don't forget the tracks! :-)
| golemiprague wrote:
| The question is, can trains work on batteries or hydrogen or do
| we need the electric infrastructure, all those cables above it.
| Also, do we really need tracks? Can't we just make a dedicated
| road with self driving cars or buses, which is possible on a
| dedicated road even today?
| leoc wrote:
| Here's a half-baked idea. The big problem with many next-
| generation electric cells like lithium-airs is that they have a
| short lifespan, right? But aircraft, unlike domestic cars,
| already have a fairly intensive maintenance schedule. Might it be
| feasible to just completely replace the batteries a few times
| every year? Obviously the manufacturing cost of the batteries,
| net of whatever you recover from recycling them, would have to be
| not too crushing.
| alfor wrote:
| Not true at all:
|
| - no loss of power with insulated batteries
|
| - heat generated in battery pack and motor can heat the cabin
| with a heat pump
|
| - energy density in batteries is steadily increasing
|
| - price of batteries steadily decrease
|
| All of this would work with the tech from a current Tesla, but
| flight time will get acceptable in a few years.
|
| Car and truck are going to be 90% electric in a few years
|
| Planes are going to follow after, but not before.
| tylermauthe wrote:
| The arguments presented here are logically sound and I agree that
| we won't be replacing a Boeing 747 with electrical. I also agree
| there are a lot of companies (not just electric planes) fleecing
| investors for money for products they have no idea whether or not
| they can build but claiming they absolutely can; but taking risk
| is baked into the idea of investing and is why profit is
| justifiable for investors so I think this is a moot point.
|
| That being said, I absolutely think we will see EV planes in
| short haul -- and short haul flights are a HUGE source of
| emissions. This is good.
|
| Here's a link -- local seaplane company is moving it's fleet to
| EV planes and has been flying test flights for almost a year:
| https://www.harbourair.com/harbour-air-magnix-and-h55-partne...
| arbuge wrote:
| Electric on short haul flights really doesn't make sense to me
| either in most real-world scenarios given the energy densities
| possible from current batteries. Although you may be able to
| pull off the flights themselves without any issues, you will be
| unable to use the plane continuously because of the time you
| will need between flights to recharge. Of course, in scenarios
| where the plane is in use for only a small fraction of the
| time, this isn't a problem, but that does not apply to most
| commercial situations
|
| The most realistic way to attain "green" flights seems to me to
| be some variant of a high energy density fuel such as hydogen
| produced from green electricity... so-called "green hydrogen".
| This also solves the range limitations of batteries, besides
| charging time. There are however significant problems with
| using hydrogen too, as other comments in this thread point out.
| tylermauthe wrote:
| well... when they start doing all their flights on electric
| engines in 2022 I guess we'll see if it makes sense... did
| you read my link?
| adgjlsfhk1 wrote:
| Airplane engines are really expensive. If the electric plane
| is significantly cheaper, it could be beneficial to eat the
| lower utilization. Also bigger batteries don't necessarily
| charge slower. If you have more cells, you can force more
| power into the batteries. The charging cable will be massive,
| but that might be acceptable.
| rvense wrote:
| A number of years ago I read, I believe on this very site,
| that, in general, the main product of many of today's tech
| startups is no longer the product itself, but the idea of that
| product, and their customers are not the people who buy the
| actual product, but investors. And I think it's fair to say
| that investors are often easily affected by hype.
|
| It's probably a bit dismissive of the passion of many
| founders[0], but I have found it a useful perspective in many
| cases.
|
| [0] Honourable mention goes to the CEO of the ten-person
| company I work for. He really does believe in this ish.
| thehappypm wrote:
| I don't really buy the main counter arguments here.
|
| First, the current tech as stated in the article is short
| flights, like an hour. That's actually a niche that's already
| marketed--luxury flights to Martha's Vineyard, Tahoe, Bar Harbor.
| People are already paying for these flights today.
|
| Second, the heat issue. Batteries do suffer from cold weather but
| if it's an hour flight, with the batteries dumping their full
| charge, between thermal heating and simply insulating your
| battery it can stay warm.
| jeffreyrogers wrote:
| There's not really a viable path from those short flights to
| longer ones though and the hype of the industry is driven in
| part around electrifying airliners.
|
| And those short flights are a small fraction of airline
| emissions. I haven't run the numbers, but I don't think it can
| be more than a few percent. If a company or airline actually
| cared about reducing emissions from aviation they would look at
| using hydrogen like the Soviet Union did (I'm not talking about
| fuel cells, the jet engines used hydrogen as fuel).
| thehappypm wrote:
| The path to bigger airlines depends heavily on battery
| advances, but it doesn't mean it's impossible, either. It
| just means the second market will be Philly to New York. Then
| New York to Boston. Maybe never across an ocean.
| aaron695 wrote:
| > That's actually a niche that's already marketed
|
| So just for the rich, in luxury jets? I'm not sure you'd want
| such an expensive aircraft that can only do one hour, 20 mins.
| It's a crippled asset with a large cost.
|
| You need to chose, a plane for the people like a Cessna 172 or
| luxury jet style.
|
| Cessna 172 has the down time problem. 50 mins in the air. Hour
| to charge? (The article says 2 hours) These operations are
| pushing people through. You'd need two or three times as many
| planes.
|
| Luxury jet that's in part opulence, not sure who cares about
| making them electric.
|
| Going in the middle of these two is just a trick to make the
| situation hazy.
|
| But I also didn't get the heat issue or radio transmissions? Or
| why they couldn't Google a rubber band's specific energy.
|
| I do want a business model spec'd out. People say "flight
| schools", which is a bit like the disaster relief or for the
| military scam. Asset costs and labour and storage and down
| times to real life situations.
| HuShifang wrote:
| I think this is the key here: conceptually, there may be some
| cognitive shear around the word "plane." In the near-term VTOLs
| aren't going to be airliners or, for that matter, flying cars.
| Cessnas and helicopters, though...
| leoedin wrote:
| It's not difficult to imagine electric training aircraft. In
| fact, they already exist - Pipistrel have delivered 111 of them
| (https://www.aopa.org/news-and-media/all-
| news/2021/january/27...). They have swappable batteries and can
| fly for about an hour.
|
| The total cost of ownership must be super low compared to
| gasoline engines - there's almost no moving parts, which means no
| costly engine rebuilds.
|
| I'm very, very sceptical of electric passenger aircraft, but I
| think it's almost inevitable that electric aircraft will start to
| dominate at the training and low cost end of the market.
| Animats wrote:
| Training makes sense. As usual, range is the big issue.
|
| There was a steam powered aircraft, once, in 1938.[1][2] Looks
| like it got into the air, went around the pattern once or
| twice, and landed safely. Unclear what happened after that. The
| Smithsonian has a copy of the engine.
|
| [1] https://www.youtube.com/watch?v=J1tyRX3bXhg
|
| [2] http://rexresearch.com/besler/beslerst.htm
| lowbloodsugar wrote:
| "When a distinguished but elderly scientist states that something
| is possible, he is almost certainly right. When he states that
| something is impossible, he is very probably wrong." - Clarke,
| A.C.
|
| This guy isn't even a distinguished scientist. He's a just a
| bitter investor that lost money to a snake-oil start-up, and has
| a penchant for logical fallacies.
| sokoloff wrote:
| I likewise don't get the breathless exuberance over the prospect
| of electric airplanes. Weight matters a little bit in cars.
| Weight matters one hell of a lot in light airplanes.
| kloch wrote:
| This limitation will help motivate advances in battery tech.
| SuoDuanDao wrote:
| I gather enough people would like to commute to climate-change
| symposiums via private jet without having their lifestyle
| choices made mockery of that they'd accept an electric airplane
| with all its drawbacks.
| kurthr wrote:
| Fuel and Maintenance costs, they're about 10-20% and 30% of
| total costs (flight/ground crew, landing/taxes, and
| amortization make up much of the rest) respectively. Combined
| they are a huge portion of potential cost reduction.
| jeffreyrogers wrote:
| If it's too heavy to fly the cost reductions don't matter.
| There are no proposed designs that use batteries that can
| carry anywhere near the weight of the current generation of
| airliners.
| kurthr wrote:
| I don't think that long range jumbo jets are the target
| here. I'm also doubtful that batteries will be the dominant
| power source. I think it's speculative, but there are
| certainly DARPA funds/projects available, and they (and
| FAA) actually do care whether these can fly.
| cromulent wrote:
| Because of this, there are a number of companies working on
| synthetic aviation fuel generated by renewables.
| LittlePeter wrote:
| I have mostly questions...
|
| Are we at the theoretical limit of energy density in current
| batteries? How much more progress can we make, in theory? Could
| it be that in 20 years we find drastically better materials for
| batteries? Materials which would make electrical flight feasible.
|
| Assuming high energy-density batteries are coming, shouldn't you
| start now with developing electrical airplanes to be one step
| ahead of competition?
| evandijk70 wrote:
| Assuming that higher energy-density batteries are possible is
| an extremely big ask. Yet somehow, plane companies are valued
| as if there is a commercial business case. I think long-range
| (over 2000 km), big airplanes are as far away as fusion power
| plants. Maybe even further, as fusion does not require any
| theoretical breakthroughs. You don't see big valuations for
| companies purporting fusion power generators, but for some
| reason, you do for electric planes..
| kwhitefoot wrote:
| > plane companies are valued as if there is a commercial
| business case. I
|
| Perhaps that is because there is a large number of passengers
| who wish to fly shorter distances than 2000 km. In most
| countries all internal flights are considerably shorter than
| that.
| tuatoru wrote:
| > Are we at the theoretical limit of energy density in current
| batteries?
|
| Yes and no.
|
| Using air for the "ox" part of the redox reaction makes it
| possible to dramatically increase energy density (gravimetric
| and volumetric both).
|
| The tricky part of that is making the battery rechargeable.
| Lots of research attention is focused on it.
|
| If you want your battery totally enclosed (e.g. for use in
| vacuum or corrosive environments), than we are closer to the
| limits. Probably within a factor of 5, maybe within a factor of
| 2.
|
| > Could it be that in 20 years we find drastically better
| materials for batteries?
|
| No, the periodic table is fixed.[1] Maybe, if you are prepared
| to consider using nuclear "batteries".
|
| 1. https://en.wikipedia.org/wiki/Reduction_potential
| jareklupinski wrote:
| jumping on with one more question: would there be an advantage
| to lining the wings/flat surfaces with solar cells and patching
| them into the powertrain, helping drive even higher efficiency
| gains during optimal weather?
| davedx wrote:
| I spreadsheeted this out a few months back for a plane. It is
| absolutely not worth it.
| dsign wrote:
| I did the math for that one, though not exactly for an
| airplane, but for a boring land vehicle (think Ford Traffic).
| I assumed futuristic photovoltaics with 40% efficiency, a
| factor of 0.7 to account for angle-of-incidence
| inefficiencies, pretty much all of of the van covered in
| panels, for an area of about 16 square meters, similar to the
| wing area of a glider Schleicher ASW 22 (I couldn't find the
| wing area of a Cessna 172).
|
| The result I get is somewhere from 3 to 8 kilowatts. A quick
| search in the Internet shows that a typical car has engine
| power starting at 130 horsepowers, which is 95 kilowatts. A
| van the size of a Ford traffic probably uses twice as much,
| and the Cessna uses 132 kilowatts.
|
| So, no, I don't think we are getting aviation as it exists
| today with solar panels and batteries, but one hour twenty
| minutes in good weather will be enough for some recreational
| pursuits.
|
| I also did the math for sailplanes with solar panels. That
| looks better, if all you are looking for is activating the
| propeller for a small fraction of the total flight time, or
| having an aircraft that can go very slow (that, in fact, has
| been done). I'm just an amateur, but my opinion is that,
| without solving the energy density issue, about 98% of the
| aviation we enjoy today will be gone.
| Gibbon1 wrote:
| I think a lithium ion battery is only about 6-7% lithium by
| weight. So primary physics isn't blocking. If you could double
| that you'd be able to increase flight time from current roughly
| 90 minutes to 3 hours.
| davedx wrote:
| No we're not. The next step forwards in energy density for
| Lithium Ion batteries is likely to be 100% silicon anode Li-
| Ion. This is a very difficult manufacturing/engineering
| challenge but significant progress has been made (look up e.g.
| Sila Nano and Enovix). These give us a significant step forward
| in energy density.
|
| Then there are solid state batteries. These are more difficult.
| But again multiple companies with lots of funding are attacking
| this from all sorts of angles.
|
| The OP making this claim as if it's a law of physics is simply
| wrong.
| barbazoo wrote:
| I'm skeptical about 2.62 MB pages with dozens of ad/tracking
| dependencies for a 1700 word article.
| slownews45 wrote:
| Pax airlines over oceans etc using batteries is a bad joke. It's
| pure garbage hype.
|
| Some fantastic value around reliability and maintenance (two huge
| issues in GA market) with electric.
|
| If EPA bans leaded fuels (which they should immediately) there
| may be additional demand here.
|
| But it's going to have to be SHORT flights - think 30 - 45
| minutes. Even then the payload (useful) is going to be pretty
| poor I'd imagine.
| JasonFruit wrote:
| There's an area of aviation where a lot of innovation could
| occur, and people are excited to do it -- but the FAA is in the
| way. Ultralight aircraft, under FAR Part 103, are allowed to
| weigh up to 254 pounds dry, without fuel. Electric ultralights
| must weigh up to 254 pounds _with batteries_ , which is
| practically impossible to achieve, so ultralight pilots who would
| love to be flying clean electric aircraft are using unreliable
| two-stroke engines that spew incomplete combustion products like
| there's no tomorrow. If the FAA would revise the regulations to
| exclude the weight of batteries, like it excludes the weight of
| ballistic recovery systems or floats, it would open up a field
| for innovation and might reinvigorate ultralight aviation, but
| the FAA doesn't want to even _think_ about ultralights, and
| ultralight enthusiasts are worried that if they push matters the
| FAA will shut it down like they did ultralight instruction twenty
| years ago.
| orangepanda wrote:
| Isnt it because fuel can be dumped in an emergency, if needed?
| Cant say the same about batteries.
| jmnicolas wrote:
| But what happens "magically" at 255 pounds of weight that it
| falls in another category?
| jacobmarble wrote:
| Ultralight airplanes, and any general aviation plane I know
| of, do not have fuel dump systems. In cases where a plane is
| too heavy to land, it will often circle for a few minutes to
| burn off excess.
| JasonFruit wrote:
| Not really an option for ultralights or most private
| aircraft.
| nsxwolf wrote:
| Better than an ultralight: N540EV, a motor glider kit plane
| using the engine from an electric motorcycle. Over 700 pounds
| and it can fly anywhere under day VFR rules.
|
| https://www.youtube.com/watch?v=0jEZrBjHnQg
| Enginerrrd wrote:
| >so ultralight pilots who would love to be flying clean
| electric aircraft are using unreliable two-stroke engines that
| spew incomplete combustion products like there's no tomorrow.
|
| This is such a total non-issue, any effort at all spent on this
| would be better spent on almost any other target from a climate
| standpoint.
| JasonFruit wrote:
| I'm saying these pilots _want_ to do this innovation, not
| that ultralights are a large proportion of the problem, or
| even that GA as a whole is a significant contributor to
| pollution. But the reliability issue _is_ significant: two-
| stroke engine failure is a frequent cause of ultralight
| accidents. They require careful maintenance and in-flight
| handling to be reliable.
| slownews45 wrote:
| I think you have to count batteries. That said at least in EU I
| think there is already a big electric assist / launch sailplane
| market - is this not permitted in the US?
|
| That said, some of the electric sailplanes are in the 800lbs
| range - so that is a LOT more.
| JasonFruit wrote:
| Why not at least deduct from the batteries' weight the
| 30-pound weight of the maximum 5 gallons of gasoline? An
| ultralight has to carry that extra thirty pounds on takeoff,
| which is probably the point where the higher stall speed
| matters the most for safety; it seems reasonable to allow at
| least that much deduction for batteries. Even that would be
| an encouragement.
| slownews45 wrote:
| Not disagreeing. In my view the reliability / noise (ground
| issue) / pollution etc make an electric sustainer
| absolutely fantastic. Sailplanes can slow way down as well,
| so yes, if they crash its a problem, but these are not
| GENERALLY stall/spin into ground at high speed. Stall
| speeds can be down in 40kt range or lower.
|
| I don't follow this area closely though so have NO IDEA of
| US regulatory rules here. But the electric use cases in
| this general category seem somewhat clear?
| jacobmarble wrote:
| Maybe not possible with ultralight aircraft (those limits are
| tight!) but certainly possible with the experimental category.
| 0des wrote:
| There is the "ElectroLight" which is 103-approved, allegedly.
| https://www.aviationpros.com/aircraft/press-release/21088890...
| PowerfulWizard wrote:
| I'm optimistic about electrical. Here is a high level analysis of
| power and energy density required for some electric vertical
| takeoff aircraft, compared to some existing batteries:
| https://www.pnas.org/content/118/45/e2111164118 (h.t.
| kittyhawkcorp twitter). The necessary power density is achieved,
| the energy density needs to improve by about 2x for these
| vehicles to attain their intended range.
|
| The article also compares the range and energy efficiency to
| electric and ICE vehicles, accounting for the distance reduction
| by flying in a straight line versus driving on the road. If I
| recall it doesn't apply any extra value for time savings. The
| overall energy used in flying could be as little as 2-3x the
| energy used driving a terrestrial electric vehicle. Combine that
| with vertical takeoff and no traffic and we're looking at
| something pretty compelling.
|
| And how much does it really need to cost compared for example to
| a Tesla? The weight will be more optimized and the safety
| regulations I assume are much sterner. The technical complexity
| seems similar but the volume will be much lower. I don't think it
| really works if you need a pilot's license so full autonomy is
| probably also a prerequisite for an everyday application.
|
| I think EVTOL will still be embryonic in 2 years, but impressive
| in 5 years.
| tsimionescu wrote:
| Autonomous vehicles can't drive in a tunnel yet, and you're
| imagining flying autonomous cars in 5 years?
|
| Flying cars already exist, they're called helicopters, and they
| are not a promising consumer technology, and never will be.
| Flying heavy materials (such as human flesh and bone) is far
| too energy intensive and inevitably produces too much noise. It
| is also far too dangerous to become a consumer technology.
| deepnotderp wrote:
| 1. Autonomy in the air is far easier than on the roads
|
| 2. Helicopters have a much lower L/D ratio in forward flight
| than the tiltrotors being proposed for eVTOLs.
| tsimionescu wrote:
| 1. Yes, but autonomy in a fixed tunnel would be easier
| still, and yet the Vegas Loop is using human drivers.
|
| 2. Helicopters have the advantage of actually existing in
| many varied form factors and designs, in common civil use,
| unlike tiltrotors.
| PowerfulWizard wrote:
| Yes, in the air I'm expecting a very different scenario than
| on land. No pedestrians just an element of collision
| avoidance for birds, all vehicles legally required to be
| broadcasting their position to an automated air traffic
| control, probably maintaining 100 meters between vehicles
| versus road traffic being 1 meter from oncoming. In the air
| it would be almost a pre-planned route with a 50 meter
| collision avoidance corridor. Plus an emergency landing site
| selection process, potentially the ability to land on water
| or an emergency parachute.
|
| Part of the reason I found the paper I linked to be
| persuasive is that they predict the EVTOL aircraft only
| needing 2-3x the total energy of an EV. The energy cost in
| dollars could be less than gas for an ICE vehicle making the
| same trip. There are very light aircraft with 100HP engines,
| I'm picturing something light and birdlike.
| jeffrallen wrote:
| > In contrast, the internal combustion engine on a 172 makes
| enough heat to keep the cabin warm whenever needed
|
| Right, and it's always making that heat whether you need it or
| not. So it's a good thing your avgas has a shit-tonne more energy
| density than my batteries because you're going to need it to
| waste all that heat.
|
| Look, physics is physics, you can't cheat it. Which means pure
| electric is only good for short air trips (energy density), but
| there's plenty of room to make airplanes more efficient (internal
| combustion = waste machines).
|
| So those who are busy saying it's impossible should get out of
| the way of those who are doing it.
| ampdepolymerase wrote:
| If you want to take a plane without constant heating, be my
| guest.
| jeffrallen wrote:
| My Zoe keeps my toes warm all winter long, and it does it 30
| seconds after I turn it on in -20 c weather. My diesel needs
| 10 minutes to warm up the cabin.
|
| Heat pumps rock. Internal combustion engines suck. Fight me.
| vondur wrote:
| Heat Pumps work best above 40F (4C), and after that they
| are not very efficient. I don't believe that would be a
| good fit for an energy starved system such as an electric
| plane.
| jeffrallen wrote:
| > Heat Pumps work best above 40F
|
| [citation needed]
| whiteboardr wrote:
| "Ultralight" and "electric" don't go well together - and it will
| stay this way.
| zackbloom wrote:
| I'm much more excited about manufacturing gasoline using
| renewable energy and captured carbon. That would provide the
| energy density planes need while being legitimately carbon
| neutral.
| davedx wrote:
| The author makes quite some big claims without any evidence,
| including that "Energy density in these batteries is quickly
| reaching its theoretical limit". This is misleading bordering on
| false. Companies like Enovix [1] and Sila Nano have
| commercialized pure silicon anode batteries for small devices
| with energy densities greater than the current generation of Li-
| Ion with graphite/silicon anodes. A whole host of companies are
| attacking the "battery energy density" problem from all sorts of
| angles (including Tesla - no mention of 4680 cells in the
| article, because that would undermine its premise). There is no
| law of physics saying "350 Wh/kg is the absolute upper limit".
|
| [1] https://assets.website-
| files.com/6023ee57b22bf2f0c312206d/61...
| jeffreyrogers wrote:
| The author of this piece[0] has a fairly strong background in
| starting and running companies, so his opinion is worth more than
| the average commenter's.
|
| [0]: https://commons.erau.edu/ntas-bios/27/
| nqzero wrote:
| he writes: "watt/hours", so ymmv ...
| a-nikolaev wrote:
| Here's a video that's making a basically the same argument
| (although with a more sarcastic tone) that electric batteries
| don't have a sufficiently high energy density to power an
| economically competitive plane
| https://www.youtube.com/watch?v=dMmaG_3NnGs
| jillesvangurp wrote:
| Most electrical planes flying today will have around 160-200
| wh/kg of battery. That's not a lot but somebody is buying them
| nonetheless. The reason for that relatively modest energy density
| is that anything flying and certified now would have entered the
| certification process many years ago. The question is not if
| those batteries can be improved but by how much.
|
| Tesla already has cars on the road with batteries doing better
| than that. Their upcoming 4680 battery cells will be around 380
| wh/kg, apparently. Then there are several companies working on
| solid state batteries promising closer to 500-600 wh/kg. Sounds
| good? That's 2-3 x the range of electrical planes on the market
| now or very soon. There's nothing to be skeptical about here.
| Pretty much a done deal. With that type of battery, we'll be
| seeing planes do 400-800miles; possibly a bit more. If you think
| that's ludicrous, the Eviation Alice is currently pre-selling a
| plane that will do 440 miles. Apparently, they use 260 Wh/kg
| batteries currently. Upgrading to something with 500 wh/kg would
| pretty much get them close to a 1000 mile range.
|
| I consider 2x to be the minimum of what we can expect this
| decade. That's just a matter of updating these planes with
| batteries that are either already being produced or will be very
| soon. More a matter of when than if, really. These are first
| generation planes too. It's not a question of if they will
| improve but how quickly and by how much. Designs, engines,
| wiring, materials, etc. There still is a lot of room for
| improvements.
|
| Longer term, I'd say 4-6x current ranges should almost certainly
| be doable based on just battery improvements. My view: 4x would
| be disappointing. 6x is a good number to shoot for longer term
| and we can actually hope for more. Like 8-10x. But actually 3x
| current ranges would already be a game changer. We'll see.
| mike_d wrote:
| The Air Force has proven a system that uses renewable energy to
| power a system that combines water and carbon dioxide extracted
| from the air to produce E-Jet synthetic fuel. Currently a
| chemically similar but less environmentally sound synthetic
| fuel is approved to be mixed 50/50 with regular JP8 in military
| aircraft and they are doing acceptance testing for full
| synthetic.
|
| This effectively takes every high efficiency jet engine and
| makes it carbon neutral, with the added benefit that you don't
| need to ship the fuel anymore. At that point electric planes
| are dead.
|
| https://www.afmc.af.mil/News/Article-Display/Article/2820003...
| bernulli wrote:
| Range is one thing - what is the passenger capacity of these
| planes?
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