Solar power is great as long as the sun is shining. Wind's just fine until it's calm. If we're going to use renewable sources like these as the basis of our next-generation power grid, how will we handle the times when they aren't producing?
We need a way to store that energy, for a few hours to a few days, so that we can damp out the mismatched timing between generation and demand. Pumped storage is probably the best currently available technology for that.
For a more detailed background on the technology, take a look at Northland Power's report on the proposed Marmora Project, or just head over to Wikipedia's take on the subject. In short: When electricity is cheap and plentiful, you pump water up a hill into a reservoir. When power's expensive and demand is high, you let that water run downhill through turbines – just like in a regular hydroelectric plant – to generate electricity.
Pumped storage facilities involve a substantial capital investment, but they're virtually free to operate and have an operating life spanning the better part of a century. In many cases, they can be built using existing industrial wastelands, such as abandoned open-pit mines.
These facilities are a lot more useful than their nameplate specs might suggest. A 400 MW gas-fired peaking plant really only has two efficient states, on or off. That gives you a choice of 0, or 300 to 400 MW. It's of no use when demand is low and there's a surplus of generation, and it's of little value if you only need, say, 150 MW in that region.
A 400 MW pumped storage plant, though, gives the grid operators a total range of 800 MW to play with. It can absorb 0 to 400 MW of surplus generation at off-peak times, or it can feed 0 to 400 MW back into the grid when demand is high. In a 20 to 30 gigawatt grid like Ontario's, half a dozen 400 MW pumped storage plants would be enough to shave most of the peaks down to manageable levels, and take up all the surplus power that we're currently giving away at a loss on quiet, temperate nights.
Why, then, aren't we building more of these? It seems to be just a matter of policy. Investors and project developers need enough certainty in pricing, over periods of a couple of decades, to justify putting up the hundreds of millions of dollars needed to build the facilities. Right now, the Ontario Power Authority seems to have a hard time figuring out how to issue such contracts.
The sooner we fix that bureaucratic problem, the sooner we can get some pumped storage facilities built. And the sooner we get these things built, the sooner we can stop burning expensive, polluting fossil fuels to keep the power flowing at peak times.