The sun may be setting on NASA’s plans to build a space-based solar power (SBSP) satellite system to alleviate our energy needs on Earth. In January, the agency released a report that, citing launch costs specifically, concludes that generating power from orbit is simply too expensive, especially compared with solar power made right here on the planet’s surface.
That’s surprising because NASA has been interested in satellite solar power for half a century (other countries have been investing in research as well). Generating power in space for Earth-based needs, in some ways, makes sense. The sun shines continuously, 24 hours a day. There’s no air in space to attenuate sunlight, no weather to deal with, no clouds to block it. All you have to do is build a huge array of solar panels in orbit around Earth, convert the power they generate into microwaves, and then beam that to antennas on the planet’s surface, which convert it into electricity to send where it’s needed. In June, a Caltech prototype beamed power from space in this way for the very first time.
Of course, there are disadvantages. A big one is the efficiency of the microwave beam. It spreads out over distance, lowering the power received by an antenna on Earth’s surface. Also, any receiving antenna on the surface has to be huge, many square kilometers in area, which limits who can build them and where (it’s worth noting that the sci-fi trope of a dangerously powerful microwave beam causing havoc on the surface is at best an exaggeration; the beam’s energy density is far too low to have that sort of impact).
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This energy loss is exacerbated by the need to place the power satellite in geosynchronous orbit, approximately…
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