Monday, March 17, 2014

[defensesystems] NRL wants to beam solar power from satellite arrays

Military units have been exploring alternative energy sources for years in an effort to reduce the Defense Department’s considerable dependence of fossil fuels.

Marines have used solar power in Afghanistan. The Air Force uses wind turbines for power on Cape Cod. And the Army has several solar power systems, the largest at White Sands Missile Range, N.M., just to name a few examples.
The Naval Research Laboratory wants to get a little closer to the source on solar power, developing modules that could collect solar power while aboard an orbiting satellite and transmit that power to a receiver on Earth. The idea is that an array of hundreds of the modules could beam power to forces in remote areas, where current methods of fuel supply — using diesel generators, driving or airlifting fuel — are expensive and sometimes dangerous.
NRL spacecraft engineer Dr. Paul Jaffe has built two prototype modules in what he calls a “sandwich” design,according to NRL. Each has a photovoltaic panel on one side to collect energy, an antenna on the other side to beam power, and electronics in the middle to convert the current to a radio frequency, NRL said. The modules have even been tested in space-like conditions, using a homemade vacuum chamber to simulate extreme cold and powerful xenon lamps to replicate the intensity of solar concentrations.
The tests have led to modifications and improvements. "The capability we've built up with the testing and vacuum under sun concentration is something that's pretty unusual,” Jaffe said. “And we've actually gotten a couple inquiries from people who may want to use this."
The idea of using satellite systems to collected solar power for use on Earth has been around since the 1970s (and plenty of satellites use solar panels for their own power), but the expense has usually gotten in the way, not least because of the cost of launching large, heavy solar panels into space. Jaffe has focused on making his modules as light as possible, and said the design of his modules are more than four times more efficient than previous modules.
And for anyone concerned about beams of energy being blasted down from space, Jaffe said beams would only be sent to a specific, requesting receiver, and that using microwaves or lower radio frequencies that defuse the concentration of power could lesson those concerns. They wouldn’t be laser beams. In fact, lower frequencies also have the benefit of being able to transmit through bad weather. "At 2.45 gigahertz, you'll get power in a monsoon," he said.
The project still has significant hurdles to clear, including the sheer size of the planned array, which would be about a kilometer across — or nine times the size of the International Space Station. Modules would have to be launched separately and put together by robots in space, something NRL's Space Robotics Group is already researching.
Solar power from satellites may still be far off — and for some, Jaffe admits, far out — but Jaffe said it’s an option worth researching.
"Hard to tell if it's nuts until you've actually tried," he said.

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