A pumped-storage hydroelectric power station is used to store energy. During periods of low electricity demand, excess energy from the grid is used to pump water from a lower reservoir to an upper reservoir, which is situated at a vertical height of 160 m above the lower reservoir, as shown in the diagram.
The electrical power input to the pump system is 6.0 MW6.0\text{ MW}6.0 MW and the overall efficiency of the pumping system is 75%.
What is the volume of water pumped into the upper reservoir when the system operates at this power for 45 minutes45\text{ minutes}45 minutes?
Density of water = 1000 kg m-3
7.7×103 m37.7 \times 10^3\text{ m}^37.7×103 m3
1.0×104 m31.0 \times 10^4\text{ m}^31.0×104 m3
1.4×104 m31.4 \times 10^4\text{ m}^31.4×104 m3
7.6×104 m37.6 \times 10^4\text{ m}^37.6×104 m3