Here’s kind of a far out idea that was in the last part of the CBC documentary Fly Me to the Moon.
David R. Criswell (Director of the Institute for Space Systems Operations at the University of Houston), proposes the construction of large-scale solar collectors on the moon’s surface, using local lunar materials. The solar energy would then be converted to microwave energy and transmitted to Earth. Criswell estimates that the entire lunar-solar power generation system could be built over a 10-year period for approximately $50 billion. Imagine that!