Our utility here, Georgia Power, has numerous hydro dams across the state.
Lake Oconee was built basically as a storage battery.
Water flows through turbines from Lake Oconee into Lake Sinclair during the day to help supply the base load demand.
At night, when excess power is available, water is pumped upstream from Lake Sinclair back into Lake Oconee, and that water power is used again the next day.
I guess that fits your “time shift” statement.
They were doing pump back in Oklahoma 40 years ago, made for great fishing when they finally let us in.