At what point does it become simpler to do hydrogen powered flight and use renewables to break water? Hydrogen is much easier to fly a plane with than batteries from what I understand.
edit: I mean that we would split water on the ground to make hydrogen.
Synthetic liquid methane would probably be more practical because it is so much more energy dense than hydrogen. Audi already has a pilot plant that does this.
Both options are far more realistic than electric airliners, which simply aren't possible with any battery technology which will exist in the foreseeable future.
"This week's Paris Airshow saw the launch of the world's first commercial all-electric passenger aircraft - albeit in prototype form.
Israeli firm Eviation says the craft - called Alice - will carry nine passengers for up to 650 miles (1,040km) at 10,000ft (3,000m) at 276mph (440km/h). It is expected to enter service in 2022."
"Eviation has already received its first orders. US regional airline Cape Air, which operates a fleet of 90 aircraft, has agreed to buy a "double-digit" number of the aircraft."
Carrying 9 passengers 1040 km at 440 km/h is quite a lot different than carrying 180 passengers 6150 km at 840 km/h (Airbus A320). Because batteries do not get lighter as you discharge them (fuel tanks do), simply adding more batteries gets you rapidly diminishing returns. Short range electric aircraft already exist, but transcontinental flights are likely out of reach. And if you are only traveling 1040 km, wouldn't you be better off taking a train anyway?
Looks like some of these proposals in the article are for hybrid systems with electric motor assist to the turboprop/fan during takeoff and landing so that the liquid fueled jet engine can be sized for the most efficient cruise at altitude.
Has anyone got a sense of what the issues are with moving to bio fuels/ liquid methane for aircraft?
It looks as if it's going to have to be at least a medium term solution, I havent really heard much talk about them though. Is that just because they aren't sexy compared to electric planes?
„In 2013 the round-trip efficiency of power-to-gas-storage was well below 50%, with the hydrogen path being able to reach a maximum efficiency of ~ 43% and methane of ~ 39% by using combined-cycle powerplants.“
Seeing the ecological catastrophe that biofuels are, I hope they never make planes fly on that. Entire ecosystems are being burnt down to replace them with plantations :(
Just because biofuel production is not currently done responsibly doesn't mean it can never be. The same sustainable organic farming techniques that are used to grow food crops can be used to grow fuel crops, and should be. And don't forget that most biodiesel is currently made from waste products like used cooking oil.
The roundtrip energy efficiency of such a system is less than 50%, and hydrogen is a very inconvenient liquid fuel (it requires cryogenic storage, very strong pressure vessels, and it leaks away rapidly). There are likely better ways to convert energy into a tractable liquid fuel.
How much denser do batteries have to get to feasibly power a large commercial jet from SF to LA? Do they need to include two of these inverters for redundancy?
Quite long but it's the wrong question to ask. The reason that huge jets that cost in the order of hundreds of millions and burn tens of thousands of liters of fuel per flight are interesting at all is that their scale adds up to a reasonable fuel cost per passenger.
Electric flight does not have this problem and nor does it have the scale advantage. Flying smaller electrical planes is more efficient on a kwh per passenger basis. It's also easier to build them technically.
The SF to LA route is well in range for the Eviation Alice that should hit the market in the next few years. The variant they are advertising carries 9 passengers + 2 crew or 1,250kg of useful load for a bit over 1000 kilometers (including the required extra range) using 900kwh of batteries. This thing is supposedly entering certification after next year and should start hitting the market in a few years.
This is obviously not a jet but the economics of flying this thing are very different. It completely destroys the business case for that. You charge it with cheap electricity. The unit cost is in the order of 3M$, it can fly in and out of any small airport, and it makes a lot less noise. One full charge would cost about 50-100 $ depending on how cheap you can get your electricity. Probably lower than that given improvements in cost of e.g. solar.
For the price of 1 737, you could buy a few dozen of these. It can do a lot of things a big noisy jet can't do while being cheaper at it. Imagine a fleet of about 10000 of these flying back and forth all over California to any of the dozens of small airports. Deploying that amount of planes will take a few decades probably. Over that time you can expect improvements in range, battery efficiency and economies of scale. So, bigger, faster, cheaper happens as well.
I'm not sure it will ever make sense to cram hundreds of people in an electrical plane. But why would you want to when the small ones eventually drop in price to a couple of tens to hundreds of K each and fly you from A to B autonomously for the price of a cup of coffee?
Most business jets today operate without an air hostess and some of them use only 1 pilot. I think the FAA limit for that is around 9 passengers. But you are right that that kind of cost is going to be dominating the overall cost.
Love the perspective you present. It made me smile as a system of small, cheap, efficient planes would drastically change the way we think about human movement. So much potential and IMO, a pretty classical "technologist" style paradigm-shift... Creating demand for a service that didn't exist before and simultaneously solving the original problem (expensive, polluting air travel) as a byproduct.
Probably a smaller plane takes less time to taxi, take off, land, etc. Still it seems like if you increase significantly the number of flights in and out of an airport, you'll run into some serious congestion issues.
Congestion issues are easily addressed because small electrical planes don't need huge runways and produce a lot less noise. I'm not sure if the Eviation Alice is rated for grass landings but it would not surprise me that this was possible. There are close to a hundred GA airports all over California; more if you include all the grass and dirt strips.
Additionally, you could build dozens to hundreds of airstrips in and around big cities. The Eviation Alice still takes off horizontally. But there are plenty of vtol designs out there as well.
The real issue is going to be upgrading ATC to deal with thousands of vehicles flying at the same time. Current operations with it's roots in analog technology from mid last century is just not going to scale for that.
It's been a while since I tried running numbers but I think if capacity increased 2X then electric would be a strong contender for distances under 500 miles.
In order to move to your destination, after vertical take-off you would then need to fall down a bit first in order to pick up speed before transitioning to gliding (to get wind over your wings, which provides lift to turn and fly in the right direction).
You might want to ditch those empty batteries also at the right point :)
Pilots know exactly how much fuel they have. It can be measured precisely. They know how long it will last whether the airplane is hot or cold.
Batteries are managed by statistics, guesswork, thermal readings that may not be accurate, snake oil calculations, factory assembly methods applied to solids (not mixed liquids like fuel) and a measure of overzealous investor confidence.
In order to advance the future of electric flight, first we must find a pilot who does not mind running out of fuel. Such as a robot maybe. And passengers who don't care if the pilot is happy. Or just don't tell them there isn't a human pilot.
edit: I mean that we would split water on the ground to make hydrogen.