Reposted from Arctic Sea Ice Forum (with minor edits):
At this point in time, pump-up hydro is our cheapest way to store electricity. Pump water up with spare electricity, let it flow back through turbines when we need electricity.
We’ve got over 20 GW of pump-up hydro in the US that we installed back when we were building nuclear reactors. There’s no way to turn them off when we don’t need the power, so we built pump-up to carry late-night surplus power to daytime peak hours.
It’s not uncommon for people to claim that there are no more places to build pump-up hydro. They usually claim the tree huggers wouldn’t allow it. (And, lots of us would object to damming any more streams.)
But how about converting some existing dams to pump-up. Might there be a couple we could use?
There’s a 1997 study of existing dams on federal land [PDF]. The researchers were interested in seeing if any were potential power producers. They looked at 871 existing dams and screened them for adequate hydraulic head (enough pressure to run a turbine), stream inflow, reasonable distance from transmission lines, outside of protected areas, etc. They found that 6 had hydro generation potential, that together they could produce 1,230 MW — enough power for 957,000 residences.
Luckily they posted a list of all 871 dams in the appendix, along with dam height/head.
I worked my way through the first 212. Out of that 212 sample, 29% (61) had at least 50′ of head, 9% (19) had at least 100′ of head, and 4% (eight) had at least 190′ of head.
In the US, we’ve got around 80,000 existing dams. We use about 2,500 currently to produce electricity. That leaves us with approximately 77,500 candidate existing dams.
Using the federal dam percentages, we might expect 22,475 with greater than 50′ of head, 6,975 with greater than 100′ of head, and 3,100 with greater than 190′ of head.
Potentially thousands of existing dams usable for pump-up storage.
Almost all dams (every dam I’ve ever visited) has a set-aside safety zone below it.
- Go a short distance from the dam and excavate a “2 to 5 day hole,” a large enough basin to hold the water that would be used for generation over the longest period in which the wind and sun let us down.
- Install a pump/turbine combo between the two reservoirs.
- Run wire.