Many of them were built to make nuclear plants more efficient.. nuclear plants turbines are most efficient at full power.. so they would store the water during the night (when demand is low) and then use it the next day to handle peak demand.
So they were also made to start generating electricity quickly.. the one above takes 5-10minutes.. but there are others that respond within a minute. Much faster than starting a oil-fired generator.
These account for the vast majority (90%+) of stored capacity worldwide.
There's no reason they couldn't be used to store solar/wind energy.
There's a couple in Scotland, where I grew up. My school did a tour once. (The tour was uninspired and rather dull. The nuclear reactor tour was way more interesting.)
They're strictly limited as to how much they can store. Ben Cruachan (the one I visited) can generate 440MW for up to 22 hours before the reservoir empties. It's used for emergencies and buffer usage spikes; Ben Cruachan can spin up in two minutes from standby, or thirty seconds if they have some warning, and is used to provide power while the much slower reacting gas or coal plants rev up. I don't know how quickly it can pump water uphill, but it's probably a lot slower than it consumes it. Round-trip efficiency looks to be ~70%.
According to Wikipedia the UK uses about 40GW of electricity at peak, so you'd need a hundred Ben Cruachans to store enough to run the country for under a day.
See the grey border around the water? Hydro power reservoirs are ecologically pretty bad --- freshwater life isn't equipped to deal with what are basically irregular tides, and so the shorelines are always completely barren.
Here's one (built in 1977.. uses power from the grid), and can produce 3000MW (stores 24000MWH): http://thinkprogress.org/climate/2013/08/27/2524501/hydro-pu...
Many of them were built to make nuclear plants more efficient.. nuclear plants turbines are most efficient at full power.. so they would store the water during the night (when demand is low) and then use it the next day to handle peak demand.
So they were also made to start generating electricity quickly.. the one above takes 5-10minutes.. but there are others that respond within a minute. Much faster than starting a oil-fired generator.
These account for the vast majority (90%+) of stored capacity worldwide.
There's no reason they couldn't be used to store solar/wind energy.