The sun and solar energy from space
Our sun is the largest known energy source in the universe. In the vicinity around the earth, each m2 receives 1.4KW of solar radiation, however as this solar radiation travels through the atmosphere and hits the ground, due to day-night cycles, summer-winter cycles and weather, each m2 receives just 250W.
If we were able to harness a single KM wide band around the earth in geosynchronous earth orbit (the height at which a satellite would sit), it would receive approximately the same solar energy in one year as the total amount of energy contained in the combined recoverable oil reserves on earth today (~211 Terawatt years compared to ~250 Terawatt years).
How does space-based solar power work?
Space-based solar power captures sunlight in orbit where it is constant and stronger than on earth. This then gets converted to coherent radiation and beamed down to a receiver on earth. The typical design for this would be a satellite sitting in geostationary orbit with kilometres2 of photovoltaic arrays situated either side capturing the sunlight producing the electricity. This would then be converted to radio frequencies that are best suited to atmospheric transmission and beamed down to a reference signal on earth, where the beam would picked up by a rectifying antenna and converted into electricity for the grid, delivering approx 5-10GW of electrical power to the grid.
Space-based solar power does not require any scientific breakthroughs or new physics to become reality. Since the idea was first put forward in 1968 by the Nasa engineer Peter Glaser, these breakthroughs have taken place, and all of the technologies involved have come on leaps and bounds. The international space station currently has solar panels the size of football pitches powering it, as do most satellites currently orbiting above the earth.
Space-based solar power is currently being held back as a viable energy solution by the high cost to orbit. It could not be achieved without safe, frequent (daily or weekly), cheap and reliable access to space, and the current lack of this makes it prohibitively expensive.