2011-07-07 Source: www.economist.com
Harvesting solar power in space, for use on Earth, comes a step closer to reality
THE idea of collecting solar energy in space and beaming it to Earth has been around for at least 70 years. In “Reason”, a short story by Isaac Asimov that was published in 1941, a space station transmits energy collected from the sun to various planets using microwave beams.
The advantage of intercepting sunlight in space, instead of letting it find its own way through the atmosphere, is that so much gets absorbed by the air. By converting it to the right frequency first (one of the so-called windows in the atmosphere, in which little energy is absorbed) a space-based collector could, enthusiasts claim, yield on average five times as much power as one located on the ground.
The disadvantage is cost. Launching and maintaining suitable satellites would be ludicrously expensive. But perhaps not, if the satellites were small and the customers specialised. Military expeditions, rescuers in disaster zones, remote desalination plants and scientific-research bases might be willing to pay for such power from the sky. And a research group based at the
This summer, Stephen Sweeney and his colleagues will test a laser that would do the job which Asimov assigned to microwaves. Certainly, microwaves would work: a test carried out in 2008 transmitted useful amounts of microwave energy between two