[ox_cable]

Pardon my ignorance, but wouldn't one way to solve the "store electricity for later" problem we have with renewable energy be to use the unused power generated at peak times to produce a stable, long term material that can be used to generate energy on demand? Example: using excess energy collected at peak times to convert large amounts of water into oxygen and hydrogen by way of electrolysis, store the hydrogen for later, and then depend on hydrogen fuel cells during periods of little to no energy collection?

[strommen]

The reason why stuff like this (electrolysis, desalination, etc.) is not widely done is that the capital cost of the facilities is too high. If you spend a bunch of money on an electrolysis plant and only run it 10% of the time, you'll never make your money back, even if your electricity is free.

[NeedMoreTea]

That is exactly how Orkney plans to enable the next ferries to be hydrogen powered, for the huge energy density compared to batteries. They already generate more from renewables than they can use for electric, heat and vehicles. Surplus is already splitting water. More here: http://www.surfnturf.org.uk/page/transport

Germany is trialling it for energy storage, has a number of trial sites running I believe, and already have some hydrogen powered trains.

Unless you need the energy density of hydrogen the simpler solutions are probably better.

[edoo]

Electrolysis to hydrogen and back to electricity is notoriously inefficient. It makes a great place to dump extra energy that MUST be burned off, but it would be more efficient to just not have that much energy that needs to be burned off. It can make sense with solar and hydro but imagine what that means with dirty energy.

[pofilat]

You are describing charging a battery: https://www.tesla.com/powerwall

Also, see Gravity battery: https://news.ycombinator.com/item?id=17789456

[throwawaycanada]

That is too inefficient and the problem of hydrogen embrittlement has not been solved.