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Last Updated: Friday, 7 December 2007, 10:34 GMT
The final frontier for solar energy
By Judith Burns
Science producer, BBC News

Artist's impression of a 'sun tower' (Image: Nasa)
A 'sun tower' is one of the concepts being considered by researchers

Scientists are assessing the possibility of embarking on a space engineering project that would eclipse the effort to construct the International Space Station.

Researchers from Europe, Japan and the US are considering the viability of building giant solar panels in a low earth orbit that would supply cheap, inexhaustible energy to industry and homes.

Building a huge array outside the Earth's atmosphere would have the advantage of having no clouds to interrupt the flow of solar energy to the arrays.

Yet the sizeable downside would be the technical challenges of construction and of getting the power down to the ground.

It's an undertaking that has been likened to the building of the Pyramids.

It would require an armada of rockets carrying tonnes of material into space on a regular basis, says Lieutenant Colonel Paul Damphousse of the Pentagon's National Security Space Office.

"That's going to require repeated sorties; not one sortie every other week or every other month," he explains.

"We're talking hundreds of sorties every week and every month."

A new dawn?

A recent study by the Pentagon concluded that a solar array in space was close to being technologically feasible, and robotics should soon make the building of large structures in space safer and quicker.

Artist's impression of a 'solardisk' (Image: Nasa)
Once we open up the medium, there's a whole new world waiting for us out there
Lt Col Paul Damphousse,
Pentagon's National Security Space Office

Nasa has already begun work on a successor to the shuttle, which should bring the costs of space transport down; currently, each launch costs nearly half a billion dollars.

Leopold Summerer of the European Space Agency believes the generation of solar power from space may be only 20 years away.

But he adds that the cost of the undertaking will mean it will have to be another international effort along the lines of the Space Station.

Robert Laine from EADS Astrium, the Anglo-French space company, says private sector involvement could help reduce costs but governments would have to take the first steps.

"Sometime in the future it will be reality," he predicts.

"It's a matter of developing the technology to make the solar panels cheaper, to send them into the sky and have the energy conversion to microwaves or optical lasers which then beam the energy down to Earth.

"All of that is demonstrated to be technically feasible. Again it's a matter of economics".

For Lt Col Damphousse, despite the technical and economic challenges, the advantages are clear.

"It opens up all the other things that we are trying to do in space; our exploration strategy, our planetary defence, commercialism in space, space tourism.

"If we're able to do this as an international effort this helps to relieve some of those pressures on resource shortages, overpopulation. This is something that's in the interest of the entire planet.

"Once we open up the medium, there's a whole new world waiting for us out there."

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