Japan is aiming to collect solar power in space and zap it down to Earth using laser beams or microwaves. The government has picked companies and researchers to turn the multi-billion pound dream of unlimited clean energy into reality by 2030.

Japan has few energy resources of its own and is heavily reliant on oil imports. The predicament has forced the country to become a leader in solar and other renewable energies. This year it set ambitious greenhouse gas reduction targets, but its boldest plan to date is the Space Solar Power System.

It involves an array of photovoltaic dishes, reaching across several square miles, that hover in geostationary orbit outside the Earth's atmosphere.

"Since solar power is a clean and inexhaustible energy source, we believe that this system will be able to help solve the problems of energy shortage and global warming," Mitsubishi Heavy Industries, one of the project participants, said. "The sun's rays abound in space."

The solar cells would capture the sun's energy, which is at least five times stronger in space than on Earth, and beam it down to the ground through clusters of lasers or microwaves. These would be collected by huge parabolic antennae, likely to be located in restricted areas at sea or on dam reservoirs, Japan Aerospace Exploration Agency (Jaxa) said.

The researchers are trying for a 1-gigawatt system, equivalent to a medium-sized atomic power plant. It would produce electricity at 8 yen (about 9 cents) per kilowatt-hour - six times cheaper than its current cost in Japan.

Jaxa said the technology would be safe but conceded it might have to dispel fears of laser beams from above roasting birds or slicing up aircraft in mid-air. The government-selected consortium, called the Institute for Unmanned Space Experiment Free Flyer, includes Mitsubishi Electric, NEC, Fujitsu and Sharp.