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?