Then it has to work a lot differently than what you describe because that system would lose energy, not create it. Einstein has to be turning over in his grave hearing about this.
There must be a huge step in this process that you left out, otherwise there's no way it could produce power.
How in the world could you think that the water running downhill would generate more energy than it takes to pump it back to the top?
If that worked, a person could set up a hill, pump water, run a generator and get energy for free. There's no free lunch in science.
No, really, it works. ;^)
I apply the same principle when I bench press. As I lower the bar I store that energy in my muscles and I then I use part of that energy to raise the bar again. By the time I'm done lifting I'm so refreshed and full of energy I usually run a marathon.
Don't worry, you'll never explain the fundamental limits of physics to someone who knows better. :)
You're right...they're missing a step. Roughly, the plant generates power during peak (read: expensive) periods and pumps the water back during off-peak (read: cheap) periods. Energy is *not* conserved, just money. :-)
Hydro plants do this all the time - generate during the day and pump at night.
July 20, 2006: World Jump Day
Join us in the attempt to drive planet earth into a new orbit!
Scientific research has proven that this change of planetary positioning would very likely stop global warming, extend daytime hours and create a more homogenous climate.