An ambitious plan to build a 600 MW pumped hydro facility in California has gotten past a thicket of interconnect issues. If built, a hydroelectric facility will create energy and pump water uphill during off-peak hours from Lake Elsinoreto to a 100 acre reservoir created in an existing canyon. When additional power is needed during peak water, water is released, powering turbines, creating electricity almost instantly. Pumped hydro is one of the oldest methods of stored power.
You will of course note that a reservoir must be built in an existing canyon. NIMBYs will not like this. The project has already taken years. Now it will do three years of feasibility studies then perhaps get the final permit. Building new energy generation facilities in California whether renewable or otherwise, takes years, sometimes decades.