We should be using hydrogen which is produced by electrolysis of water. The hydrogen is easily stored by being absorbed into finely divided precious metals such as palladium. When the hydrogen is combined with oxygen in a fuel cell it generates energy and gives back water.
I think solar power will supply a big portion of the world’s energy in the future – it’s getting cheaper and cheaper all the time.. but I’m not convinced that it can supply everything because you need to cover too much land. We also need what’s called ‘baseload’ energy that can supply a constant output. For that we will probably need nuclear fission, or fossil fuels with carbon capture and storage … or in the future nuclear fusion. We need to use a mix of energy sources, we can’t just rely on one 🙂
We need diversity (variety) so when the sun does not shine (like in Scotland most of the time) we can rely on the wind or the waves, or when the wind does not blow we can rely on the hydro. We need a mix of reliable energy sources, and some sources you can deploy quickly for high demand times (like when everone boils the kettle during the adverts of the X-Factor final)