Science

Probably a way to make wind and solar more viable.

Regardless, the bulk of what will allow us to have a civilization powered by renewables is going to be cutting down consumption (and staggering it with a smart grid): not driving cars, arranging and insulating buildings so that they don't lose as much of their temperature differential to the outside (and also don't need cars to get around), making things that are designed to be repaired instead of replaced, using direct combustion for heat, and human-power wherever feasible.

In short, concentrating most energy consumption at point-of-use for better efficiency and less materials, and keeping the remainder direct and human-scaled.

And imho it is still going to make more sense to fill in the gaps for the base load with biomass from coppiced trees.