Energy solutions are often spoken about in all or nothing terms. I like the suggestion above that different solutions may be appropriate in different places. Where you have a lot of sun, focus on solar. Where you have a lot of volcanic activity, look at geo-thermal. Where there are empty landscapes not suitable for solar, set up grids of microwave collectors to receive beamed energy from satellites. Where there is lush sub-tropical vegetation, use bio-fuel as Brazil already does. Where there is nothing else, go nuclear.
We tend to think in terms of large scale economies and worldwide mono-solutions. That seems short-sighted to me. Just because the whole world runs on fossil fuels today doesn't mean it has to look to nuclear or other one-trick ponies tomorrow. The answer will be lots of different solutions, each tweaked to local circumstances. We just have to get away from the global megaproject mindset.