Some scientists look down the road and see an Earth with no energy shortages, no pollution caused by fossil fuels, no rolling blackouts, no dependence on nuclear power or foreign oil, no limits on the amount of energy we can have.
Instead, they see giant solar collectors orbiting the planet, or on the surface of the moon, collecting energy from the sun and beaming it back to the Earth.
It may sound like science fiction, but it isn't.
The idea of building space-based power plants has been around for decades, but it came close to being trash-canned in the early 1970s when the National Aeronautics and Space Administration determined that it would be too costly and too technologically difficult to be practical.
The idea, first broached in 1968 by Peter Glaser, then a NASA scientist, resurfaced again during the energy crisis of the late '70s, but died back when the oil began to flow again from the Middle East.
Old Idea, New Interest
There it might have remained had it not been for a little thing called global warming. The concern over greenhouse gasses forced NASA and other organizations to take another look. It turns out that some of the showstoppers of a few years ago have been resolved.
That has led to a bit of a groundswell of support for the concept, but it's far from a done deal. Here's the way John C. Mankins, manager of advanced concepts studies for NASA, put it last year in a hearing before the U.S. House subcommittee on space and aeronautics:
"Ongoing and recent technology advances have narrowed many of the technology gaps, but major technical, regulatory and conceptual hurdles continue to exist."
In simple English, that means we're getting closer, but we've still got a long ways to go. The principal hurdle at this point appears to be cost, especially the pricy fee for putting tons of stuff in orbit. That comes at a time when many of the key components needed to cash in on the sun's energy are already available.
In it's simplest incarnation, here's how it would work.
Beaming Energy to Earth
Giant sheets of photovoltaic cells, which convert solar energy to electric current, would be unfolded in low Earth orbit by astronauts or robots, and then pushed up to about 22,300 miles above the equator where they would remain in the same spot over the Earth.
We're talking big here. The solar arrays would blanket several square miles, and to serve the growing needs of a booming population on Earth, there would have to be many of them.
Free of atmosphere or dust or clouds, the arrays would collect at least eight times more solar energy than they could if they were on the ground, according to the Electric Power Research Institute. The arrays would function for 24 hours a day, nearly every day of the year.
The electric energy collected by the arrays would be converted to microwaves and beamed back to the Earth through a process called "wireless power transmission."
That sounds a bit scary, but according to the SunSat Energy Council, a non profit organization affiliated with the United Nations, the beam would be so low in density that it wouldn't even feel warm if you happened to walk through it. As a weapon, the council says, it would be less effective than a squirt gun.
On the ground, huge collectors in remote locations would capture the microwave radiation, convert it back into an electric current, and feed it into the power grid.
Some major problems have been solved in recent years.
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.