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Re:Airbus pioneers a superconducting powertrain cooled by li... by intrepidhero on Wednesday April 21, 2021 @09:23AM (#26889328)
This makes no sense to me. Don't you also need cryogenic systems to keep the H2 cold? Wouldn't those use waaaaay more energy than what you save with superconducting motors? Maybe they are talking about short haul flights where the H2 is ground cooled and then used as a cold sink but then in order to keep your electronics cold you're carrying lots more fuel than you need. TFA was too thin to pass the sniff test.
Re:Airbus pioneers a superconducting powertrain cooled by li... by petertodd on Wednesday April 21, 2021 @10:13AM (#26889950)
> Don't you also need cryogenic systems to keep the H2 cold? Wouldn't those use waaaaay more energy than what you save with superconducting motors?

Probably not. Cryogenic liquids like liquid H2 are typically stored in dewers, which use a vacuum as the primary insulation, along with silvered surfaces and layers of mylar film to reduce radiation losses. We've been able to make dewers with boil off rates of 1% per day or better for decades. That's more than low enough that you don't need any refrigeration at all for an aircraft application where the flight just lasts a few hours anyway.

Most likely they'll actually use less effective insulation to save weight. Fortunately for them, cryogenic liquids are commonly used in rockets, so there's already lots of know-how and technology out there for making lightweight cryogenic insulation.

Re:Airbus pioneers a superconducting powertrain cooled by li... by XorNot on Wednesday April 21, 2021 @09:31AM (#26889426)
Motors are solid 3D structures. The more power you put in not superconducting, the more heat you have to extract. Superconductors mean you only need to keep your refrigerant cool, and that's a product of insulation effectiveness, not power output.
Re:Airbus pioneers a superconducting powertrain cooled by li... by ethbr0 on Wednesday April 21, 2021 @09:51AM (#26889666)
This is the difference between electric and combustion powertrains, no?

In electric, heat is the enemy and inefficient.

In combustion, heat is a key component of the thermodynamic efficiency, unavoidable, and effectively only limited by material tolerances.

(I didn't major in physics, so someone keep me honest on the ceiling / floor efficiency equations for combustion engines?)

Re:Airbus pioneers a superconducting powertrain cooled by li... by XorNot on Wednesday April 21, 2021 @10:22AM (#26890059)
You still have to cool a combustion engine - hence why car's have radiators.

Combustion engine's are also limited by Carnot cycle engine efficiency - about 64% theoretically, no more then 50% in the real world. So you're still going to wind up having to dump progressively more heat from a fixed surface area.

Re:Airbus pioneers a superconducting powertrain cooled by li... by ethbr0 on Wednesday April 21, 2021 @10:55AM (#26890470)
(Post coffee) Cars have radiators to cool the operating structure (e.g. engine block), but that cooling's ancillary to power produced, no?

Carnot cycle was what I was grasping for.

Original point being that in a thermal engine, increasing your temperature gradient by increasing your high-temperature side (while holding exhaust constant) leads to more potential power.

Or IOW, a thermal engine that doesn't burn hot somewhere isn't going to produce much power.

(Electric being a completely different ball of wax)

Re:Airbus pioneers a superconducting powertrain cooled by li... by Tuna-Fish on Wednesday April 21, 2021 @09:49AM (#26889652)
This is effectively regenerative cooling, like what rockets are commonly using. There are no cryogenic systems onboard, but all the fuel is loaded as very cold, and you can use the fuel as a coolant just before you burn it.
Re:Airbus pioneers a superconducting powertrain cooled by li... by candiodari on Wednesday April 21, 2021 @12:16PM (#26891617)
They will, however, be using kerosene, not liquid Hydrogen. It cannot provide cryogenic temperatures.
Re:Airbus pioneers a superconducting powertrain cooled by li... by Tuna-Fish on Wednesday April 21, 2021 @01:06PM (#26892374)
Did you read the article? It was specifically about future liquid hydrogen-powered aircraft.
Re:Airbus pioneers a superconducting powertrain cooled by li... by upofadown on Wednesday April 21, 2021 @09:55AM (#26889733)
The H2 keeps itself cold by boiling away. You just need some insulation to slow down the rate to something manageable. Insulation normally uses a gas such as air to block the heat flow and as a result tends to be very light.
Re:Airbus pioneers a superconducting powertrain cooled by li... by ncmncm on Wednesday April 21, 2021 @09:43AM (#26889572)
The idea is that a large-scale LH2 flow into the system is being consumed, and perforce heated, and may be used as refrigerant on the way there. It makes perfect sense.

Rockets do this today, as indeed they have done from the earliest days, sending liquified gases through channels in the engine bell and combustion chamber before burning, keeping them both from vaporizing.

Here, the very high efficiency of electric-driven turbines is offset by the lower efficiency of fuel-cell generation, for what is expected to be a substantial net gain over burning H2 in internal combustion turbines.

The latter are the obvious first stage of deployment, taking advantage of LH2's extreme energy-to-weight ratio for reducing the takeoff fuel load by as much as 5:1. This form will probably be fielded in existing airframes, displacing some cargo space with in-hull LH2 tanks.

Re:Airbus pioneers a superconducting powertrain cooled by li... by ethbr0 on Wednesday April 21, 2021 @09:47AM (#26889613)
Re:Airbus pioneers a superconducting powertrain cooled by li... by Gravityloss on Thursday April 22, 2021 @11:13AM (#26903651)
You use the boiloff hydrogen in the power source, I assume a fuel cell in this case.

This is regularly done by LNG tanker ships. Evaporating LNG is simply routed to the engines.

Re:Airbus pioneers a superconducting powertrain cooled by li... by ginko on Wednesday April 21, 2021 @09:32AM (#26889444)
I think the idea is to use the H2 both as fuel and refrigerant.
Re:Airbus pioneers a superconducting powertrain cooled by li... by Valgrim on Wednesday April 21, 2021 @02:42PM (#26893786)
So you recover the boiloff and use it to power a generator which powers a drivetrain cooled by the liquid hydrogen. This seems like a good idea.