You seem to be talking about storage as a separate business. But the major market for storage will be public utilities that also own generating capacity, and se

You seem to be talking about storage as a separate business. But the major market for storage will be public utilities that also own generating capacity, and sell power principally to end users. After their storage is full, maybe they sell any extra to the grid, or use it to synthesize liquid fuel for sale. Negative prices are a very, very temporary phenomenon. Very soon, all surplus generating capacity will be absorbed producing hydrogen and ammonia for sale into an unlimited market.