Comment by bluGill

> How many battery cells does it take to keep a steel mill running through the night, and how will that impact power prices for large customers?

Steel mills run when power is cheap. They historically have run at night (and only minimum power during the day) because cheap power is available at night. Of course there are lots of different steel mills, older ones can't shut down - but modern ones don't run 24x7, they run when power is cheap. Even the old 24x7 ones did their yearly maintenance in December - when power demand is highest (Christmas lights).

Wind and solar are easially predicted a few days in advance with high accuracy, and thus the mills change their shifts/output to follow the cheap power. If it is cloudy/no wind they will send their employees home (with pay) or do maintenance for that week while waiting on more cheaper energy. It takes a tremendous amount of energy to melt iron and so they manage this carefully because it makes them money. They can't deal with months of no production, but they can manage a week here and there.