Existing ones, particulalry those built for multiple functions (water supply, recreation) still have some use but mostly you just want to be rolling out solar and wind until you run out of fossil fuel generation to displace. Only then do you really need to start comparing whether building storage would cost less than more renewables and interconnects and hydro is unlikely to be the lowest cost option unless you're going to build the dam anyway for other reasons.
I’d be really, really be interested in primary sources for the above claim.
See Figure 1.2 Global weighted average LCOEs from newly commissioned, utility-scale renewable power generation technologies, 2010-2021
https://irena.org/-/media/Files/IRENA/Agency/Publication/202...
Hydro costs are going up, solar and wind going down. Hydro is still less than fossil fuels, which is great, but that's not the target to beat anymore, and renewables are lower and trending even lower.
And that's before the more extreme geographical constraints for siting, with good locations already used, the project sizes and the longer lead times and investment paybacks compared with renewables.
But Hydro also has flexibility, which is really useful for balancing renewables and nuclear. It's important to switch existing Hydro into this mode to make the most of it. But again, for new build, since the raw power is more expensive than renewables, the flexibility would need to be cheaper than the equivalent flexibility provided by more renewables plus batteries to win back that lost ground. And it isn't.
Same story for pumped storage. Here's a worked example for the Snowy 2 project:
https://www.solarquotes.com.au/blog/snowy-2-vs-battery-stora...
The key thing is, energy production is cheap these days. So storing energy has to compete against just building even more production and a small amount of storage. This applies to batteries as much as it does to hydro. But batteries scale down better.
”The key thing is, energy production is cheap these days.”
This is immaterial if cheap energy is unavailable when needed. See: winter (season)
“So storing energy has to compete against just building even more production and a small amount of storage.”
This is incorrect. More production is useless if the output is zero. Zero times a large number is still zero.
Again, see: winter (season)
”This applies to batteries as much as it does to hydro. But batteries scale down better.”
The problem with batteries is that they don’t scale up.
Using EVs as batteries is neither free nor always available.
https://www.theguardian.com/sustainable-business/2016/nov/06...