Early photovoltaic systems were very inefficient, but that has improved to the point that state-of-the-art systems can now convert the sun's energy into electricity at a rate of 42 to 56 percent, according to Neville Marzwell, a NASA scientist at the Jet Propulsion Laboratory in California.
"We have made tremendous progress," he says.
And there doesn't seem to be any doubt now that wireless power transmission is practical, at least on a limited scale. A few years ago Japan flew a small airplane powered by microwaves beamed up from the ground.
Japan, incidentally, is a major player in this arena, since it has no oil or other energy resources of its own. In fact, Japanese officials have announced plans to have their first solar power satellite in operation by the year 2040, beaming energy back from space to that island nation.
That's a really ambitious goal, considering Japan's rather disappointing performance in space exploration, but Japan has everything to gain and nothing to lose.
Mars, a Bigger Priority
In this country, the idea is kicked around seriously by a growing number of scientists, but it's not exactly a tidal wave. Many say it's just too expensive to complete with other energy sources. Even NASA, which budgets about $22 million a year for the program, has not given it a high priority.
Gregg E. Maryniak, then president of the SunSat Energy Council, told the House committee hearing last year that the reason is obvious. NASA "seems fixed on the old and outmoded goal of humans to Mars" instead of concentrating on developing space-based energy sources that could benefit the entire human species.
That makes more sense, Maryniak testified, than "making a dash to Mars, planting a flag there, and then checking off that box, saying 'been there — done that.'"
But nothing is likely to come of any of this unless ways can be found to ship things into space at a fraction of the current cost. The high cost of getting there is one reason the U.S. Department of Energy, with the assistance of NASA, determined in 1979 that a large scale space power system would cost at least $275 billion in current dollars.
Supporters quickly point out that much has changed since 1979, both in technology and need. This may not be the answer, but clearly the Earth's current predicament calls for drastic, and innovative, approaches to producing sustainable, less harmful energy.
Mankins told the House subcommittee that it would take several decades to get a space-based power system operational. Maybe it's time to get cracking.
Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.