We live on a finite planet, resources are limited, most stuff is running out etc. The good news is that there are resources that rely on the sun in one way or another, that are getting constantly renewed, i.e. renewables. These are solar, wind, hydro and biomass (or woodfuel). But biomass is not quite a 'renewable' as we've assumed even without the issue of using arable land to feed power stations instead of people.