Why is alternative energy most commonly stored in relatively expensive metal acid batteries, which have a short life, rather than hydrogen gas accumulated through electrolysis?

Hydrogen is a versatile energy source itself and with low cost technology is a cheap, clean and reliable fuel.


closed as off-topic by John Rennie, tfb, user36790, Rory Alsop, Wolpertinger Dec 22 '16 at 17:14

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question appears to be about engineering, which is the application of scientific knowledge to construct a solution to solve a specific problem. As such, it is off topic for this site, which deals with the science, whether theoretical or experimental, of how the natural world works. For more information, see this meta post." – John Rennie, tfb, Community, Rory Alsop, Wolpertinger
If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ If it was reliable, in terms of we can reply on it not to ignite, that would be great, it would be in every car in a few years, but we can't. That's one reason. $\endgroup$ – user139561 Dec 22 '16 at 12:32

Assuming you are generating electricity (say from wind or PV) and you want electricity, then there are two obvious cycles:

  • for lead-acid you charge and discharge the battery;
  • for hydrogen you crack water, store the hydrogen, and then run a fuel cell.

Lead-acid batteries can have charge-cycle efficiencies of around 80%, perhaps more. (Lithium-ion I think is even better.)

Electrolysis has an efficiency in the range of 50-70%, and fuel cells are in the range 40-60%. So the overall efficiency of the cycle is in the range 20-40%. This is not even slightly competitive.

On a large scale you can perhaps either burn the hydrogen to make steam for a steam turbine generator, or may be run a gas turbine directly. These systems have efficiencies that might touch 50%: this page and its links says that natural gas power generation can be about 43% efficient, in 2015. This is no better than fuel cells, but the plant might be cheaper.

You can also run an internal combustion engine with hydrogen: that's not a good way of generating electricity, but it might be reasonable if you want to run a car. I haven't looked up figures but I suspect that hydrogen to fuel cell to electric drive is better.

I have not touched on the energy density question: to get anything competitive you need to compress the hydrogen which requires yet more energy, some of which you may hope to recover. Even then I am not sure how competitive it is.

This is why lead-acid batteries are used.


Not the answer you're looking for? Browse other questions tagged or ask your own question.