Among my broken-record themes is that the energy-storage solution of pumped hydropower is trivial compared to the potential value of dispatchable hydropower - that is, to stop treating hydro as a baseload energy to be released on a constant basis, and instead shape your releases around solar and other variable, renewable power sources. Looks like I babbled this here at Rabett first in 2019, and complained again in 2020 about there being no 24-hour variation in hydro use. So take a look at this chart from Mark Jacobson showing typical spring power deployment for California (light blue is hydro):
I see hydro dispatchability, without anyone proclaiming that to be the policy. The delta between daytime and nighttime hydro is comparable to the highly successful and policy-driven battery storage now happening in California (the dark blue).
What I didn't anticipate in 2019 was that dispatchable hydropower would just happen, without AFAIK a big policy decision to make it happen. I'm glad though! Maybe the invisible hand does work sometimes, even in utility operations. When you have solar (or sometimes wind) out the wazoo, then why wouldn't you cut back a bit on the reservoir releases and save them for a different time of day?
This doesn't mean we should just relax and let Adam Smith handle everything though. Achieving the next realization that reservoirs could be a seasonal battery and not just a daily one might take a little more effort. Flow releases also aren't solely for power but for water delivery and environmental purposes, both of which could be addressed over time by policy. Rights to take water at certain times could be renegotiated for a different time or location to allow dispatchability. Forebays and afterbays could be constructed to smooth out releases downriver for water delivery or environmental reasons. These would have a cost, and might not be possible in many cases, but they can be quite small compared to reservoirs, they could have their own turbines also, and you might even use cheap solar or wind power to pump water back up to the main reservoir, and get your pumped hydropower storage on the cheap.
Some of the comments in 2019 suggested dispatchable hydropower was already happening elsewhere. That's great if accurate. Some also thought it was part of Mark Jacobson's 2019 wind/water/solar plan, which it wasn't AFAICT, although it might be now, at least implicitly.
Onward. And maybe we'll call it dispatchable hydropower someday.
UPDATE: Mark Jacobson is on board:
