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The largest electric aircraft just flew [video]
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Re: The largest electric aircraft just flew [video]
#332Is this EV or Hybrid? The founder seems to sneak in the word "hybrid", around 1m30 mark in the video below. https://youtu.be/nM86DBOqgPM?si=5unXLmPxk6M_kmuN&t=86 Note: not being negative, I just want to ensure I understand correctly since the title might imply something else. Update: confirmed, it does use aviation fuel. > "The airplane will also include a reserve-hybrid configuration, consisting of two turbo generat…
Why do the generators specifically need aviation fuel? They aren't the actual motors.
I think the video states they are actually turboprop engines
Re: The largest electric aircraft just flew [video]
#333Doing some math. Regional jets get somewhere around 45.9 seat miles per gallon (1). So 30 seats, going 125 miles would take around 80 gallons of jet fuel. This is likely low because all the jets listed are bigger and likely flying longer flights that are more efficient but just go with it. Jet fuel has a specific energy of 12 kwh/kg and a density of 6.7 lb/gal (2). So 80 gallons of jet fuel is 536 lb, or 243 kg, and…
They discuss quite a bit of this in the video. I actually thought it was a decent walk through of why they're targeting the space they're targeting, and how they're thinking about exactly these problems.
Some items to consider from the video
1. short flights spend an large amount of energy simply having the engines running during taxi to/from the runway.
2. Take-off also consumes much more fuel than cruising.
3. 1 & 2 combine to push airlines to prefer larger & larger planes making longer trips when using fuel (it's how they're managing that 45.9 seat mile number - it get much worse for shorter trips).
4. They're already pushing the 400kwh/kg range for batteries (I believe he makes an offhand comment in the video that they're using 8 packs, with roughly the capacity/weight of 4 tesla battery packs - which would put their batteries in the ~4k lb range if we estimate by teslas pack weights. They are likely pushing to go lower than that. I think it's not crazy to consider they're targeting a production weight ~50% below your guess - in the high 3000s)
5. On top of fuel savings, one of his more compelling points is that maintenance on their engines will be much, much lower. Jet engines are expensive to service, maintain, and repair (thousands of parts, complicated designs, extreme operating conditions). Their motors are basically 450kg dc motors - it's a giant drone motor mounted on an airframe.
6. they seem to have quite a bit of interest from existing airlines (ex - united) so apparently this does seem compelling to them.
7. He quotes a $5 take-off cost in electrical power. Something like an Embraer ERJ-135 uses ~20 - 30 gallons of jet fuel for the same thing (~$100). If they target a plane that's doing very frequent takeoffs/landings, operating costs could be considerably lower, not just lower.
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Personally - I don't know if they'll make it work, but it's definitely an interesting play, with more real thought put into it than most attempts I've seen.
Re: The largest electric aircraft just flew [video]
#334Doing some math. Regional jets get somewhere around 45.9 seat miles per gallon (1). So 30 seats, going 125 miles would take around 80 gallons of jet fuel. This is likely low because all the jets listed are bigger and likely flying longer flights that are more efficient but just go with it. Jet fuel has a specific energy of 12 kwh/kg and a density of 6.7 lb/gal (2). So 80 gallons of jet fuel is 536 lb, or 243 kg, and…
There's a lot more to it than that. Just going around on the taxi, Take off and landing burns a ton of fuel for these for traditional jet engines.
This plane is designed specifically to cost less to operate. I'm pretty sure they figured it out, which is why they have over 9b in order commitments.
Re: The largest electric aircraft just flew [video]
#335Doing some math. Regional jets get somewhere around 45.9 seat miles per gallon (1). So 30 seats, going 125 miles would take around 80 gallons of jet fuel. This is likely low because all the jets listed are bigger and likely flying longer flights that are more efficient but just go with it. Jet fuel has a specific energy of 12 kwh/kg and a density of 6.7 lb/gal (2). So 80 gallons of jet fuel is 536 lb, or 243 kg, and…
This graphic always reminds me why it's so hard to beat gasoline and that batteries kinda suck. https://en.wikipedia.org/wiki/Energy_density#/media/File:Ene...
I think lithium air batteries will be the real inflection point for aeronautics. Li-air has potential density 12 kWh/kg. CATL is focused on this tech. May be some years before they are able to achieve the full potential density. Still, as the other commenters said, the efficiency of electricity make make up that difference.
Re: The largest electric aircraft just flew [video]
#336Earlier quoted context omitted.
Hybrid after the first 125 miles, total range 500 miles. Their problem is diversions - an incident at the destination airport may mean an passenger aircraft may need to land at an airport which could be a couple hundred miles away. The hybrid powerplant throws the fuel efficiency numbers off so goal is not to run it unless needed, but they could not get certification without it.
I remember reading about making ground effects electric planes for this reason. You need a reserve, but if your plane could double as a boat and was flying over water, that would satisfy the requirement.
As long as water conditions allow for a safe landing. In much of the world that severely limits when you can operate due to storms or ice. In practice routine use of ground effect vehicles will be mostly limited to lakes and inland seas with fairly benign weather. Like I don't think we're going to have regular passenger service from San Francisco to Los Angeles or Detroit to Cleveland.
Re: The largest electric aircraft just flew [video]
#337Earlier quoted context omitted.
One would assume that all combustion engines used in aviation run at an optimized RPM?
At cruise, yes. However during takeoff and go around they run at higher RPM to develop more thrust. Using batteries for takeoff and only using fuel for cruise or backup power is smart.
I think it's even more than that. The hybrid engine has to run one single RPM to drive a generator, it can be vibration insulated, probably needs to be only smaller because it doesn't have to provide the high max power the conventional motors have etc.
It's why I believe hybrid cars that use a gas motor only to charge the batteries are more reliable and more efficient.
Re: The largest electric aircraft just flew [video]
#338Earlier quoted context omitted.
The 100kwh number was based on a rate of electricity that is 1/6th the average cost of electricity in the area they did the flight. Even the absolute cheapest rate in that region is 4x the price I used. The price I quoted was a little less than the cheapest published electrical rate in North America, which isn’t in the United States. So you can barely make it work if you price electricity at a rate that doesn’t exist…
Sorry, but you’re still weirdly switching from power (kilowatts) to energy (kilowatt hours). The electric plane could easily pull 1.5 megawatts for two minutes (on takeoff) and consume 50 kWh of energy, then spend the next 45 kWh cruising around and descend on the rest. (Or similar numbers, of course.)
I understand that energy and instantaneous power draw aren’t the same. I’m working with the numbers given: over a megawatt of power draw, and the price of energy in kilowatt hours. I’m not saying that they are flying on 100kw. I’m saying that using absurdly optimistic - unrealistic, really - pricing they have alln energy budget of 100kwh to use for the entire flight of 27 min. That means that average power consumption for the entire flight is just over 200kw if they are paying slightly less than the lowest power rate on the continent (which isn’t available in the country they did this test in). We both understand that energy is power * time.
100kwh was an extremely generous amount of energy to allow for $5. Actual, real world, best case scenario industrial pricing in the region they are in would give them 50kwh for $5.
Look at your numbers again with the fantasy pricing. You are saying that they took off with a normal amount of power for a plane that size, then cruised around using an amount of power (45kw) that wouldn’t keep a two person plane 1/20th the weight airborne. Now cut that budget in half.
Even the most efficient planes on earth - single person powered gliders - need about 15-25kw to maintain level flight at much lower speeds. Keep in mind that drag increases with the square of speed, and this plane is traveling significantly faster than any of the low power planes I’m citing. Citing drag from a Tesla is kind of irrelevant because the whole way an airplane works is by creating lift via drag. The Tesla has wheels to hold the weight, so incurs a much lower penalty for weight.
The reason I’m so skeptical is that I have done the engineering calculations to convert my own very small (sub 1k pound gross) plane. It would need about 30kw/h to maintain level flight with just 1 person in it.
Again, I am incredibly impressed with the engineering and what they have accomplished. I just think that one of their marketing figures was pulled out of someone’s ass.
Re: The largest electric aircraft just flew [video]
#339Earlier quoted context omitted.
I live in Czechia, in Europe, a first-world country with dense population and a very normal road network. I am now on vacation, and I’m exactly 205 km as the crow flies from where my parents live. If I wanted to drive to them right now, it would be a 309 km trip estimated to take 3.5 hours or, avoiding highways, a 252 km trip, over 4 hours. I don’t care about the rest of your post, I just want you to understand that…
> I am now on vacation That is the key here. People go all over the world for vacation. However vacations are not normal life (at least not for the vast majority of people), and can be ignored. In normal life people have a place they live, and they have people they visit. When looking for a place to live they consider the real trips they take (not cutting through corn fields), and that guides where they move to. Peop…
I have no idea what point you’re trying to make or how is my vacation “the key here”. I’m visiting a regular Czech town that just happens to be almost exactly 125 miles from another regular Czech town (the one where my parents live), and I used those two particular towns as an example of how 125 miles can be a pretty big deal in Europe (or really anywhere in the world that’s not the US).
Re: The largest electric aircraft just flew [video]
#340Doing some math. Regional jets get somewhere around 45.9 seat miles per gallon (1). So 30 seats, going 125 miles would take around 80 gallons of jet fuel. This is likely low because all the jets listed are bigger and likely flying longer flights that are more efficient but just go with it. Jet fuel has a specific energy of 12 kwh/kg and a density of 6.7 lb/gal (2). So 80 gallons of jet fuel is 536 lb, or 243 kg, and…
This graphic always reminds me why it's so hard to beat gasoline and that batteries kinda suck. https://en.wikipedia.org/wiki/Energy_density#/media/File:Ene...
Also for traditional fuel you don’t have to carry half of the fuel - oxidizer comes from air. And then when you spend fuel, you have less weight to carry (which becomes noticeable on the plane).