Solar Power Satellites
Solar power satellites (SPS) have been studied by space agencies worldwide during the past four decades. The process of acquiring energy by using a space-based solar power consists basically of three parts:
1. Collecting the solar energy in the space. Most technologies of SPS focus on photovoltaic conversion, since it is more technically feasible than the dynamic solar thermal power system. Photovoltaic systems constitutes a technology that converts the sunlight directly into electricity. It uses solar cells, which are electronic devices made of semiconductor materials that are able to absorb the solar energy and produce "free" electrons.
2. Transmitting the energy to the Earth. In this kind of system, the solar-generated power is converted to microwaves and transmitted to the Earth (wireless power transmission). Peter Glaser, a technologist in Massachusetts, was the first person to spread the idea of beaming energy to Earth via satellite. The power transmitted to the Earth has to be a non-ionizing radiation in order not to cause biological and ecological harm. The microwave beams are preferred over the laser beams because of their higher transmission efficiency.
3. Receiving the energy via a rectenna. Receivers on the surface of the planet convert the microwave beam back into DC power (by rectifying antenna) for electrical grids.
The collection of a high quantity of energy by the satellite requires a huge structure, much larger than the International Space Station. The size of the satellite would be mainly determined by the size of the collector panels and by the size of the antenna that transmits the microwave.