Let's take an absurd extreme case to illustrate - if you had a battery that could store 1GWh but could only discharge up to 1mW in an hour, how would you power an aluminum furnace with this battery?
Assuming you are using batteries for continuous solar power, you basically need the batteries to be able to store enough power to last through the night, and to be able to match the solar power plant's peak power - otherwise, the grid can't power the same things during the night that it can during the day, which was the whole reason we wanted the batteries in the first place.
Assuming you are using batteries for continuous solar power, you basically need the batteries to be able to store enough power to last through the night, and to be able to match the solar power plant's peak power - otherwise, the grid can't power the same things during the night that it can during the day, which was the whole reason we wanted the batteries in the first place.