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Could satellites plug into energy from the ground?

Lasers sited in cloud-free areas might one day power orbiting satellites, if researchers in California have their way. They predict a time when energy suppliers will set up such lasers to feed energy to power-hungry communications satellites.

Most satellites get their power from solar panels, which means the amount of energy they receive - and the power of the signals they can send - is limited by the size of the panels and the amount of sunlight they receive. So Alexander Zholents, a physicist at Lawrence Berkeley National Laboratory, is designing a laser whose powerful beam could be converted into electricity by the existing solar panels on satellites, increasing the energy they receive so they can run additional services like extra communications or TV channels that the craft would not normally have the power to operate.

"The Sun is an excellent source of power," says Zholents. "To compete with the Sun, you have to get hundreds of kilowatts." To achieve this, Zholents is designing a massive free-electron laser. Such devices rely on a soup of free-floating electrons - instead of the electrons in a substance such as a crystal - to generate the laser beam.

"There's no medium," he says. "The medium sets the limits; if you have too much energy, the crystal burns out. In free space, there's no danger of that." But Zholents estimates that building such a machine might cost about $150 million.

The most powerful free-electron laser in the world is at the Thomas Jefferson National Accelerator Facility in Virginia. It produces only 710 watts and will probably only ever reach a power level of 1 kilowatt. According to Courtland Bohn, deputy project director at the facility, Zholents' idea is technically feasible, but would take a lot of time and money to implement.

That will make it difficult to find firms interested in investing in the technology. Zholents admits that getting the idea off the ground depends on commercial support. "But I don't know whether we'll have success finding investors."