More on solar power!
Solar power is currently more expensive than wind energy, but this depends on the circumstances. Take a look at this map (wikipedia):
Around the equator, solar energy is more efficient. The black dots represent the area of solar panels that is needed to provide all the worlds energy (that is, electricity+fuel+all other energy).
It also explains why warmer countries like Italy and Spain invest more money in solar energy than countries with less sunshine. Though Germany is investing billions of euros in solar panels, while their efficiency is much less than in southern countries.
Solar energy is getting cheaper and more efficient because of technological improvements. At the same time, oil is getting more and more expensive (currently around $100 per barrel and increasing). This means that solar energy is the future!