Which would be better for a 747, Batteries or Liquid Hydrogen?

Question

Batteries would be effective, but weight outlaws the idea, at least until technology has developed this concept of lowering mass..

But what about Liquid Hydrogen. Fuel is already a liquid, just like Liquid Hydrogen.. So, is it possible, as good as batteries, maybe even better? And would this be wasting Water, or would the ejected fumes be steam?

Thank you

Answer 1

Forget batteries - you couldn't carry enough to taxi out to the runway.

Liquid hydrogen is a cryogenic liquid that must be kept about 400 degrees F below zero. The tank would take the entire upper deck of 747 and I would doubt you would get the same range as Jet A.

Answer 2

If you had an unlimited source of free energy on the ground, then liquid hydrogen would be practical. It would take a lot of effort to develop safe ways to store it and transfer it, but it would be worth it.

However, right now, the cost of hydrogen is so high that there's no point in spending the billions of dollars it would take to develop the technology and build the systems needed to produce, store, and use the hydrogen.

This still may happen over the next hundred years or so, but right now the sticking point is simply that there's no cheap source of hydrogen. If you had a situation where a quantity of hydrogen and a quantity of gasoline or aviation fuel with the same amount of energy were comparable in cost, then you might see this start to happen.

Safety is the biggest issue.

Answer 3

Jet fuel is a flammable liquid at room temperature, and can be stored in a container of any shape.  Liquid Hydrogen is a flammable compressed gas, and must be stored in insulated pressure containers, like the big barrel tank that goes with the Space Shuttle.

It would not be possible to store liquid hydrogen in practical quantities in the airframe of a Boeing 747 or any equivalent airplane.

Also, the cost of producing liquid hydrogen far exceeds the cost of jet fuel, even at today's prices.  That could change if the demand for it made large scale commercial production feasible, but that is not happening now.

The US Department of Energy has studied these options in very great depth, and has not yet found a workable alternative to the refining of fossil fuels.

We appreciate your enthusiasm for these possibilities, and we hope you will go on to engineering school and develop your talents.  Maybe you will be the one who makes the breakthrough.  But it isn't happening now.

Good luck.

Answer 4

In order to use hydrogen as a fuel, it needs to be stored in high strength, pressurized containers. Up to this point, the additional weight needed for storage has been to large to overcome the weight benefit of using hydrogen. It is possible that higher strength materials would make the weight trade for hydrogen beneficial.

Even if the weight trade is favorable, a hydrogen powered aircraft would have excess drag to deal with. With kerosene, the most of the fuel is held in places that would otherwise be dead space, and entirely within the volume of the plane if there were no fuel tanks. With hydrogen, you would no longer be able to use the wings as fuel tanks (unless taking an even larger weight penalty for using non-circular cross section pressurized vessels,) where the primary fuel stores are held today. Furthermore, even in liquid form, an equivalent energy in hydrogen form is 3x the volume of Jet A, which would cause the already displaced fuel tanks to balloon.

Still more practical than batteries, though, just not as good as Jet A.

Answer 5

Impossibly cost prohibitive.

Answer 6

remember Challenger?  Hydrogen is explosive in any concentration with oxygen.  you can't store it on a plane, and it shouldn't be used in cars.

Answer 7

Liquid hydrogen wont work not because its expensive, or because its dangerous, because it is neither, it will not work because the technology does not exist to contain it in concentrations that could be used in a aircraft.

Modern electrolysis equipment is efficient enough that they have efficiency up to 85%, but there is simply no way to store it correctly.

As of the moment, the only technology that could possibly even be considered as an alternative power source for aircraft is hydrogen peroxide, either used in combination with fructose, or used in a fuel cell. The fuel cells produce at least 6 times the power of a battery of the same weight, and can be even more efficient.

The university of Purdue is working on a hydrogen peroxide fuel cell and has overcome many major problems. By using a different aluminum alloy for the reaction the Purdue machine did not produce a sludge that the Navy fuel cell had been plagued by.

Hydrogen peroxide is also available in huge amounts, over a billion pounds of it being produced in the US each year.

Answer 8

Liquid hydrogen can be very unstable, especially if the proper temperature is not maintained.  The weight of the equipment to do that would be enormous, even for a 747. The batteries, by comparison, weigh a lot less, and in this case, more efficient.