"
Sorry. I couldn't help myself. I had a solar power system customer ask me today if she could use some solar panels and batteries to pump water from her bottom dam to her top dam a kilometre away and then run it back again through a turbine to generate electricity. It was hard to keep a straight face while calmly trying to explain.
I do get where your cumming from and while a basic understanding of physics and the various laws and numbers involved can make a lot of peoples ideas look real silly.
This one springs to mind
and
Though the customers idea of the pumped hydro isn't a physics fantasy it's actually quite common and can be useful.
http://en.wikipedia.org/wiki/Pumped-sto ... lectricity
Even on a small scale. Pumped hydro can be usefull living offgrid when you have full battery's on float and excess PV energy going to wast. If you have the land and elevation head to build a pumped hydro then having your charge controller trigger a pump when your on float and pumping water up hill during the day using otherwise wasted energy (PV would just be idle if not) Pumping to a large holding tank then letting it run back through a turbine to a lower holding tank overnight is a way to get a few kwh back into your battery and lower your DOD overnight. Sure its not efficient but if the PV was just going to sit idle anyhow.
More handy for the good old days of lead acid and all the obsessing over low DOD and cycle life. But the concept is still viable.
The 1000m distance in the two dam example would make it cost prohibitive though. Personally I have a 80m head just 10m from my house and good mono pump that I already own so I was considering pumped hydro at one stage before the EV solved the excess pv output issue. Well that and getting the 25,000lt tank to the bottom of the leach infested hill without using a chinook helicopter.
Sure there are other things you could do with the excess pv output like heat water or better still what I do (charge my EV

)
Kurt