We already do electricity -> hydrogen generation, the hydrogen is then stored in underground pumped storage (empty gas wells), and can be used in place of natural gas.
Although presumably if you set up one of these facilities you need it running 24/7 to be profitable not just when there is a lull in demand elsewhere.
If you find a cheap solution to power storage, you can make a lot of money. This is the key enabler for a 100% renewable grid.