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Space Power Relay

Clark Lindsey has some space-related thoughts in response to T. Boone Pickens' solar energy proposal: major hurdle, among several, with the plan would be the need to build more long distance electric power transmission lines to reach the more populated and more industrialized areas. This will be difficult since people all along the routes will fight having the lines and towers in their backyards.

Occasionally in discussions of Space Based Solar Power, the topic of microwave relay satellites comes up as a way to move power around. For example, in this paper, Reinventing the Solar Power Satellite (2004) Geoffrey Landis talks about using relay sats for distributing power to different parts of the globe from a single Solarsat. So it should be similarly possible for relay satellites to move power from the Midwest to where it's needed.

Yes, this is one of the "tiers" that Peter Glaser proposed in the development of powersats when he first came up with the idea forty (geez, has it really been that long?) years ago. He envisioned that before energy was produced in space, it might be relayed from energy-rich areas that didn't have local demand (such as a large dam in Venezuela or Brazil). He envisioned such relays as passive microwave reflectors, which are currently a major structural challenge in terms of keeping the surface the right shape within a fraction of a wavelength. But at least at GEO, they wouldn't have to move much.

Rather than giant relay sats in GEO, it might be preferable to place a constellation of relatively small ones in LEO since this would allow the beams to be much more narrow. Perhaps the switching techniques developed for Iridium/Globalstar could be built upon. Smaller beams might also lessen NIMBY resistance to transmitter/receiving sites.

Perhaps, but now you have high slew rates on the reflectors, which makes for even more of a challenge. An active phased array system can be steered electronically as it switches from rectenna to rectenna as it orbits. A reflector has to rapidly move the entire structure while maintaining its shape. The higher the orbit the better in this regard, because it won't have to slew as fast. Also, it would make LEO pretty crowded. A medium orbit (a couple kilocklicks) would probably be better, both because it would require slower motion, and would allow more ground rectennas to be seen at a time, while not cluttering up LEO. The slewing problem could be ameliorated by going to an active system, but that means that the satellite must now not only receive and convert the power, but reconvert and rebeam it to the ground, with all the attendant efficiency issues.

Anyway, I suspect that, regardless of size, NIMBY resistance to rectennas will dwarf that of resistance to transmission lines and towers, given that it's a devil they don't know.


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Brock wrote:

On the other hand, to put up a transmission line you need to ram through every NIMBY bulwark between points A and B. A rectenna builder just needs to find one jurisdiction with enough land that's willing to have one installed. Usually the incentives of jobs and/or taxes can scare up one or two such generous souls.

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This page contains a single entry by Rand Simberg published on July 9, 2008 8:07 AM.

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