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Going Solar

IN ORBIT An illustration shows the spacecraft that Caltech scientists used to test their solar power technology in May. COURTESY CALTECH

One night in May, a group of people gathered around a computer monitor on a rooftop. They were scientists from the California Institute of Technology (Caltech). The monitor was linked to equipment that could receive transmissions transmission a message sent through space (noun) Our radio was receiving transmissions from a ship 10 miles off the coast. from a satellite. The satellite was 300 miles out in space.

CLOSER LOOK This photo shows the inside of MAPLE, the device that directs energy from the spacecraft to Earth.


Around 10 p.m., they got a signal. The satellite was collecting sunlight. On their monitor, the scientists watched as their equipment turned that solar energy into electrical power. “It took it a few moments to sink in,” Ali Hajimiri says. He’s one of the scientists leading the project. “Then everyone got really excited.”

TEAMWORK From left: Sergio Pellegrino, Harry Atwater, and Ali Hajimiri are the scientists leading Caltech’s experiments.


The experiment was a success. But it’s just a first step. Eventually, the scientists hope to gather the sun’s energy in giant satellites orbiting Earth and beam it down to the power grid.

Solar panels in space would produce a constant stream of power. And they would work even when it was cloudy on Earth. “In space, it’s always noon on a sunny day,” Hajimiri says.

A Lighter Satellite

The idea of solar space stations isn’t new. Science fiction writers thought of it years ago.

The problem is getting these power stations into space. The glass solar panels would have to be huge. That would make them heavy. The cost of launching the parts into orbit would be tremendous. (See “Rising Possibility.”)

So the Caltech scientists are creating a new kind of solar panel. This one is made out of lightweight materials. And they’re replacing bulky antennas with tiny ones. These fit onto ultrathin sheets (see photo). They release energy and can beam it to any spot on Earth. “You’ve gone from a giant elephant to an army of ants of these individual transmitters,” Hajimiri says.

TINY MESSENGERS Each orange square on this ultrathin tile is an antenna that emits energy that is sent to Earth.


The scientists hope to build a system that can produce enough solar power to charge a laptop from space. That work could take five years. From there, they will scale up to a full-fledged full-fledged total; complete (adjective) As she gained more clients, Myra turned dog-walking into a full-fledged business. power station.

Research Continues

Caltech is not the only organization that’s interested in solar power stations. China is planning a mission in 2028 to test its technology. And the European Space Agency is looking to build gigantic solar space stations.

For now, the Caltech scientists will continue with their experiments. Their satellite managed to send some energy to Earth. But other parts didn’t work. These include the frame for the solar panels. It failed to unfold.

PIECE BY PIECE Caltech scientists assemble the spacecraft before sending it into space.


But the recent experiment proved that the technology works in space. With more research, it could reach commercial use in the coming decades.

“While there are still hurdles to overcome for large-scale wireless energy transfer of space solar,” Hajimiri says, “this gets us closer.”

Rising Possibility


The biggest obstacle to building solar power stations in space is not the technology. It’s the cost. Launching the materials is too expensive.

That’s changing. The aerospace company SpaceX has been testing reusable rockets (above). Reusing rockets will bring down the cost of a launch. The end cost of gathering solar energy and sending it to Earth will be less. And that will make it more practical. —By Brian S. McGrath