We could use the clean power generation (wind, solar, etc.) to generate Hydrogen until a far more efficient method can be found. All the renewable energy sector’s downtime could be devoted to generating Hydrogen instead of paying it to shut down, like we do today in times of oversupply.
(I know I keep banging on about Hydrogen but there isn’t a more suitable fuel source to my knowledge. A small disclaimer if you will, in case there is something amazing round the proverbial corner of which I am unaware.)