We're talking about Ontario. I live in Ontario. The sky is overcast 8 months of the year. We're not building enough storage to charge for 4 months and drain for 8.
Adding pumps isn’t the same as adding battery storage. More batteries means more peak power. Peak power for hydro is limited by the peak power output of the turbines, not the dam capacity.
Overcast winter days tend to be very calm as well. These are periods of minimal solar+wind generation and maximal heating demand.
Having a grid with no baseload generation and only storage is going to spell disaster during extended cold+calm periods. Rolling blackouts when it’s -30C outside…
