In 1960, the famed theoretical physicist Freeman Dyson proposed the ultimate renewable energy technology.  Since referred to as the “Dyson Sphere,” the proposal described a group (his word: swarm) of objects orbiting around a planet’s native star in order to capture as much energy as possible.  Most likely, these objects would be solar power satellites that would then send the energy they collected back to the home planet.  Of course, this technology does not exist, and is not likely to exist for some time.