Energy storage for a few hours is easier than fission. Seasonal energy storage, on the other hand, is much more difficult.

This is why I think a mix of clean power sources (including some nuclear) is going to be optimal.

I am of the firm belief that there are MULTIPLE feasible ways to solve the clean energy problem that we, as a society, could probably do if we put as much effort into it as we did a world war. Examples:

<>nuclear France (ultimately using breeders of uranium or thorium)

<>hydro/geothermal Iceland

<>over-built intermittent renewables buffered with grid storage and perhaps either a little hydrogen seasonal storage or a mega-grid connecting north to south

even exotic solutions like

<>inertial or magnetic confinement fusion

<>space-based solar power (which is easier than fusion)

But the optimal (both in time and money) solution is to use a mix of clean energy sources (solar, wind, hydro, geothermal, nuclear) and some storage and some demand-response (smart meters are a pretty obvious solution, here) and some increased geographical grid interconnection (UHVDC power lines).