All we need to produce electricity is heat. Heat can be used to produce steam which can power a generator. The thing is that the center of the earth is very, very hot. In fact, it's like a miniature version of the sun. All we have to do to tap in to this energy source is to drill a hole deep enough. That was always the biggest problem, but trough the experience we gathered over the years in drilling for oil it has become technically possible. If large oil companies start drilling for heat instead of for oil, that could change the way we produce electricity.