Their point is interesting. If you already have hydro and add solar or wind, can you pump back into the lakes during periods of excess, and use the hydro at night?
Yeah this is a thing. If you have enough hydro you can just turn it off entirely when the renewables are going and have a 50/50 mix.
If not, it's called pumped hydro storage (or most precisely it's blie field on river pumped hydro if it's already dammed and on a river). You need to trap the water somewhere so you don't have to pump it too far. This involves building a lower reservoir and adding pumps or modifying the turbines to be two way.
If not, it's called pumped hydro storage (or most precisely it's blie field on river pumped hydro if it's already dammed and on a river). You need to trap the water somewhere so you don't have to pump it too far. This involves building a lower reservoir and adding pumps or modifying the turbines to be two way.