Free electricity that turns off half the time and run basically randomly for the other half? Without a battery it’s useless, and you have to pay for that battery. Treating the electric grid as a battery shouldn’t be free. It’s just in this case they found the cost of battery to be greater than the value of the electricity they’re creating.
This island uses water as a battery: https://www.youtube.com/watch?v=eG4Q4kXal_U , when there's a lot of wind spinning the wind turbines, they pump up water up a mountain, and when it's less windy they let the water fall through a hydroelectric plant...
I keep coming back to electrowinning iron. When I search for papers it looks like people have started working on it again in the last ten years. I think it's not particularly high tech. Intermittent tolerant and scalable.
The idea there isn't that you store power but rather that you only run the plant when power is cheap (and then keep a large enough fresh water reservoir to serve demand until the next cheap electricity arrives). Demand management rather than supply management, effectively.
