Power from Space

Futurists have envisioned satellites orbiting our planet that might collect energy from the sun — and beam it to Earth in the form of low-power microwaves.

Now scientists are seriously studying this technology. Jay Skiles is a researcher at Ames Research Center in Mountain View, California. He’s now looking at the response of alfalfa plants to long-term exposure from microwaves.

Jay Skiles: Our question is, can life survive in these very weak microwave fields?

In the atmosphere, the microwave beam would be weaker than a cell phone signal. But by the time it reached the ground, it would be broad. A typical receiving antenna might cover 100 square kilometers — about 40 square miles.

Jay Skiles: The microwave field will be on 24 hours a day, rain or shine . . .

And of course that’s every day, 365 days a year. In his initial study, Dr. Skiles didn’t find any effect on alfalfa from microwaves at specific frequencies. He’s now looking at other microwave frequencies. He says it would take about 60 satellites to meet energy needs in the U.S. alone.

Skiles says the main task now, for proponents of space-based power stations, is to convince people that this technology is safe.

In a 1968 issue of the journal Science, space-technology visionary Peter Glaser introduced the concept of building space-based power stations. Enormous arrays of solar panels in geosynchronous orbit would collect energy 24-hours a day and beam it to Earth via microwave. On the ground, the microwave beams would be collected by gigantic antennae, converted into electricity and fed into local power grids. An orbiting power-generating station might have 50 square miles of solar panels and produce the same amount of energy as a typical nuclear power plant — about one gigawatt of electricity.

Advances in technology during the past three decades have put the concept within reach, and many experts believe it is time to begin sincere research and development of orbiting power-generating stations. In 2001 the National Research Council — a division of the National Academy of Sciences — advised NASA and the Department of Energy to look into the future of such power sources.

The first concern is one of health and safety, said NASA researcher Jay Skiles. He is experimenting with alfalfa to see if low-power microwave illumination has any harmful affects on the plants. A typical collection antenna might be several miles across, and would be receiving low-power microwaves over its entire area all the time.

“You want to make it benign so humans can go in there and do repairs, or migratory waterfowl and jet airliners can fly over the receiving antennas without adverse affects,” Skiles said.

The most-promising idea for beaming power would use a 2.4 gigaherz microwave signal, according to Skiles. It would have about the same power per square centimeter as the average signal from a cellular telephone — nearly a million times less energy than a typical microwave oven uses. That power spread over the area of the collection station, however, would be a tremendous amount of energy to be converted into electricity, he said.

Less than 60 satellites could fill all of the United States? energy needs, Skiles said. The only holdups are national resolve, and the technology to undertake massive space-based construction projects. This last issue will still require significant advances in robotic technologies, according to Skiles.

FURTHER READING:

“Solar Power Satellites : The Emerging Energy Option,” Editors: Peter E. Glaser, Frank P. Davidson, Katlinka I. Csigi. New York : E. Horwood, 1993.

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