A pumped-storage plant uses an electric motor of output 100MW to raise water for 5h. The pumping (motor–pump) stage is 80% efficient, and the turbine–generator stage that later converts the stored energy back to electricity is 85% efficient.
(i) Calculate the gravitational potential energy stored in the water after the 5 h pumping period.
(ii) Determine the electrical energy that can be generated when the water is released through the turbine.
a. (i) Gravitational potential energy stored
b. (ii) Electrical energy obtainable