Dispatchable hydropower versus pumped storage, Round 2

August 20, 2020 Off By Brian

I've been meaning to return to this concept of dispatchable hydropower and distinguishing it from pumped hydropower storage. The tweet above shows how one example of it being used in practice. We could do much more, somewhat to help in energy crises similar to what's happening now in California, and more to smooth out renewable power-based systems generally.

Sammy Roth publishes some great work about climate and energy, and recently published eight low-carbon solutions to variability in renewable power. Pumped hydro was one of them, while dispatchable hydro was not. Glen Canyon Dam suggests it should've been.

Dispatchable hydropower is (mostly) distinguishable from pumped hydro storage in that it makes use of existing dams and reservoirs, and (mostly) doesn't build new infrastructure like pumped hydro does. Its focus is a change in how hydropower is used and released from baseload power that's used constantly, first in line to satisfy demand, to dispatchable power that - subject to other constraints that require release - is conserved and then released when needed.

I previously had some documents that I'll try to dig up from my local Community Choice Energy Aggregator that showed essentially no 24-hour variation in the hydropower they received, and that's the type of baseline use that could be saved, somewhat, for the late afternoon and evening hours when demand is up and solar is down.

I also want to distinguish this from Mark Jacobson's Wind Water Solar system for replacing all fossil fuels. He's proposing something gigantic, I'm discussing something much smaller and therefore able to be implemented much sooner. In particular, what I had read a while back was that he wants to quadruple the dispatchable power from existing dams by rebuilding their outlets. I don't know how well that would work, but I do know it would require dewatering and then mostly or entirely rebuilding the dams themselves. I'm not talking about that.

These ideas do shade into each other a bit. You can't fully turn off and turn on water from dams, they have ecological and water supply reasons for running as well. Some construction might also be helpful for dispatchable hydropower, particularly an afterbay below a dam that stores a tiny percent of the total water, maybe a day's worth or more, and can modulate the downstream releases from the main dam. The expense would be small though compared to other massive projects, or you can just not do it and still use some limited flexibility in water releases to time them for dispatchability.

Using that power in this manner could help in the shortages California is facing now, and maybe elsewhere too, along with batteries and everything else we can do to reach 100% carbon free economies.

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