There's no question that we need to seriously consider harvesting the sun's energy in space with massive solar panels. The big question, however, is how to get all that energy back to Earth.
NASA believes they have found the answer: Power-beaming solar-power satellites. It's a plan that was developed by John Mankins, leader of the first NASA solar-power-satellite development team in the 90s.
He calls his proposed project SPS-ALPHA, which stands for Solar Power Satellite via Arbitrarily Large PHased Array. Mankins claims that it's the “first practical solar-power satellite concept” that uses a novel “biomimetic” approach.
This project would make possible the construction of huge platforms from tens of thousands of small elements that can deliver remotely and affordably tens to thousands of megawatts using wireless power transmission to markets on Earth, as well as missions in space.
It would do this by using a large array of individually controlled thin-film mirrors, outfitted on the curved surface of a satellite. These movable mirrors would intercept and redirect incoming sunlight toward photovoltaic cells affixed to the backside of the solar power satellite’s large array.
The Earth-pointing side of this large modular circular array would be tiled with a collection of microwave-power transmission panels that generate the coherent, low-intensity beam of radio frequency energy and transmits that energy to Earth.
And what's particularly cool about this concept is that it would enable the construction of a solar-power satellite that can be assembled entirely from individual system elements that weigh no more than 110 to 440 pounds (50 to 200 kilograms), allowing all pieces to be mass produced at dramatically lower cost than traditional space systems.