Energy may be stored for use during peak demand by pumping water to a high reservoir when demand is low and then releasing it to drive turbines when needed. Suppose water is pumped to a lake 102 m above the turbines at a rate of 1.39E+5 kg/s for 11.5 hours at night. How much energy is needed to do this each night?
If all this energy is released during a 12.5 hour day, at 78.3 percent efficiency, what is the average power output?