# Homework Help: Electric ower Problem

1. Nov 1, 2006

### bosox3790

Some electric-power companies use water to store energy. Water is pumped by reversible turbine pumps from a low to a high reservoir. To store the energy produced in 1.0 hour by a 115 MW (115 106 W) electric-power plant, how many cubic meters of water will have to be pumped from the lower to the upper reservoir? Assume the upper reservoir is 600 m above the lower and we can neglect the small change in depths within each. Water has a mass of 1000 kg for every 1.0 m3.

This problem has completely confused me. How do I do this?

2. Nov 1, 2006

### Office_Shredder

Staff Emeritus
How much energy is produced in one hour by a 115 MW electric power plant?

Then, consider the energy is being stored as potential gravitational energy. So what is the potential energy of the water? From here, you should be able to solve for the mass of the water

3. Nov 1, 2006

### nlg

We know the potential energy and calculate the mass of the water that has to be transported.

"1.0 hour by a 115 MW (115 106 W) "

E=115106 W
H=600m
m=?

E=m*g*h <=> m=E/g*h

115106/9.82*600*1000 ~ 7032953/1000 ~7000 m³

4. Nov 1, 2006

### bosox3790

I tried that and it doesnt work.