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"What if you could capture solar power in space, then send it down to Earth? What if you could launch the hundreds of modules for such a satellite, then use robots to assemble the entire array in space? You could power a military installation, a city—even on a cloudy day, even at night.
One of our key, unprecedented contributions has been testing under space-like conditions," says Dr. Paul Jaffe. He holds a module he designed for space solar power in front of the customized vacuum chamber used to test it.
(Photo: U.S. Naval Research Laboratory/Jamie Hartman)
At the U.S. Naval Research Laboratory (NRL), some of the brightest and most daring minds in satellites, space robotics, and radiofrequency are building the technologies that could lead to such an achievement.
Dr. Paul Jaffe, a spacecraft engineer at NRL, has built and tested a module to capture and transmit solar power. Even Jaffe admits the idea of an orbiting solar array that would beam energy to our planet seems kind of crazy. But, like most novel ideas, he says, "Hard to tell if it's nuts until you've actually tried."
As the Department of Defense (DoD) presses forward with energy security investments, solar power has already been proven in places like Hawaii and California. And ideally, a solar power satellite would provide power that was cost-competitive to what was locally available: about 10 cents per kilowatt hour in many places.
But the military sometimes has energy requirements in very remote areas. The U.S. Marine Corps has successfully used solar panels at Experimental Forward Operating Bases in the Middle East and for humanitarian assistance. Current practices—like running diesel generators, driving fuel over roads in hostile areas, or even dropping in fuel canisters with parachutes—make power extremely expensive and impact mission and safety.
With multiple, potentially hidden receivers, space solar power could ease logistics for DoD's deployed troops and remote bases.
The sandwich module: with a patent-pending "step" variationJaffe has built two different prototypes of a "sandwich" module. In both designs, one side receives solar energy with a photovoltaic panel, electronics in the middle convert that direct current to a radiofrequency, and the other side has an antenna to beam power away.
Jaffe sometimes gets asked about the efficiency of such a system, but the most important metric is the power cost per pound. "Launching mass into space is very expensive," says Jaffe, so finding a way to keep the components light is an essential part of his design. He can just cradle one module in his forearms.
Jaffe's research is innovative in two major ways: in design and in testing.
His sandwich module is four times more efficient than anything done previously. He also has a "novel approach to solving the thermal problem, using the 'step' module." The step module design, now in the patent process, opens up the sandwich to look more like a zig-zag. This allows heat to radiate more efficiently, so the module can receive greater concentrations of sunlight without overheating...