Power from Outer Space

__"Beam It Down" by Martin I. Hoffert and Seth D. Potter, in Technology Review (Oct. 1997), Massachusetts Institute of Technology, Bldg. W59, Cambridge, Mass. 02139.__

In the 1970s, Czech-American engineer Peter Glaser proposed a novel solution to the oil crises: "geosynchronous" satellites (rotating with the Earth, some 22,000 miles above the equator) could use photovoltaic cells to convert sunlight into electrical current, then transmit it via a microwave beam down to Earth. Glaser’s proposal was imaginative, but it had a few problems, not least that, with the satellites at that altitude, the receiving antennas on the ground would have to be about six miles in diameter. Not surprisingly, the National Aeronautics and Space Administration and the Department of Energy soon lost interest.

Today’s revolution in telecommunications, write Hoffert and Potter, physicists at New York University, could give Glaser’s idea an unexpected lift. By early in the next century, swarms of low-altitude communications satellites will be orbiting the globe. Teledesic Corporation, a joint venture of Microsoft chairman Bill Gates and cell phone tycoon Craig McCaw, alone plans to spend $9 billion to launch 288 communications satellites. They will use microwave beams to relay voices, video images, and data to locations around the world.

Why not equip the satellites with solar collectors and use the same microwave beams to carry electrical power? say the authors. "By piggybacking onto these fleets of communications satellites—and taking advantage of their microwave transmitters and receivers, ground stations, and control systems—solar power technology can become economically viable." The new satellites have other advantages. They will orbit only a few hundred miles above the Earth’s surface, so the receiving antennas can be much smaller (and less expensive) than in Glaser’s scheme. The solar collectors also can be much smaller—only a few hundred meters across instead of more than six miles.

A network of solar power satellites, the authors contend, could supply enough electrical power "to satisfy the needs of the human race through the next century." They admit, however, that they have a lot of convincing to do in the United States. Although Japan’s Ministry of Technology and Industry has already sponsored the design of a prototype orbiter, solar power satellites were not even mentioned in a recent U.S. National Academy of Sciences study of energy alternatives.