On the timescale of 27 years, grid-scale storage is going to be a complete non-issue. There's already a decent amount of work being done at that level right now and battery tech has been improving at a consistent pace. Renewables can work quite well as-is with a good mix of location and source. Offshore wind is more consistent wind speeds, solar locations can mitigate light cloud coverage, solar output peaks during the times of greatest human use, and land based wind is typically dispersed over large areas.

I'm a huge proponent of nuclear power, but as things stand it isn't going to be necessary on these time tables. The value in nuclear is that it's another thing we can build now without needing to wait ten years for battery prices to continue to decline or for manufacturing capabilities to ramp up. Building 10 GW of nameplate capacity wind+solar is great. Building 10 GW of nameplate wind+solar and 5 GW of nameplate nuclear is better! That's the advantage of nuclear today, and we should fucking make use of it. That doesn't make it mandatory in the long-term.