Wind and solar farms have limitations that don't get widely discussed as much as they possibly should, especially since they are in vogue. (As well they should be - cleaner methods of power generations are in order and it's high time that the technology be developed.) The hitch in wind and solar is that for one, they require a certain range of conditions in order to function. Wind turbines require a wind speed between a few mph and 20 mph, so they won't be working overtime during a windstorm, and solar...speaks for itself. For two, in order for wind or solar to be able to meet raw demand, wind and solar farms require enormous expanses of land in order for construction. For instance, one American wind turbine farm in Florida required over 40,000 acres - whereas a nuclear plant capable of the same amount of electricity could be situated comfortably on between 1 to 10% of that space, in fact 4,000 acres could comfortably house 2 to 3 nuclear plants fairly easily.
The other renewable sources are hydroelectric and geothermal. Geothermal is likely the superior option, as it doesn't impact environments and aquatic ecosystems nearly to the degree that a dam does, and tidal hydroelectric generators will wreak havoc with coastlines - essentially, if there was a worldwide boom in tidal stations you could effectively kiss coral reefs and everything that goes with them goodbye, and they are in enough trouble as it is. Unfortunately, geothermal power stations aren't being actively pursued nearly to the degree that wind and solar power are.
Clearly, the most viable option of power generation is nuclear, far and away. Despite the issues presented with waste disposal and the prohibitive start up costs, nuclear reactors have a habit of paying for themselves, and since Gen 3 plus reactors have begun operation already, with Gen 4 set to debut soon, another Chernobyl isn't likely to happen again, provided reactors and sites are ran the way that they need to be in order to preserve safety. Interestingly enough, a nuclear plant in Arizona was rigged to use treated sewage water, in lieu of funneling river water to the site. (Palo Verde.)
Some sort of hybrid system should be put in place. Having all energy, even a majority for that matter, from renewable sources isn't going to be a likelihood, given the sheer demand for power, but some sort of parity around 25% renewable/75% non-renewable might be achievable. That said, the most clean energy of non-renewable energy plants is nuclear, as much as it doesn't sit well with a lot of people, it's the truth.