Scientists have beamed solar power back from space, using technology placed in high orbit that allows it to collect the Sun's energy and transmit it to Earth.
The Space Solar Power Demonstrator, a prototype launched into orbit in January, last month beamed detectable power to Earth.
The demonstration by the California Institute of Technology (Caltech) uses hardware similar to solar panels and marks significant progress in global efforts to boost energy supply.
Ali Hajimiri, professor of electrical engineering and medical engineering at Caltech, said the experiment was part of the university's Space Solar Power Project.
“Through the experiments we have run so far, we received confirmation that Maple [technology being tested by the demonstrator] can transmit power successfully to receivers in space,” Mr Hajimiri said.
“We have also been able to programme the array to direct its energy towards Earth, which we detected here at Caltech.
“We had, of course, tested it on Earth but now we know that it can survive the trip to space and operate there.”
How it works
Beaming solar power from space means countries could significantly boost energy supply in an economical way.
Sunlight is about 10 times more intense at the top of Earth's atmosphere than at the surface, the European Space Agency has said.
If transmitters are placed in a high enough orbit, they could absorb sunlight on a continuous basis.
The transmitters would then be able to transfer energy to stations across the planet whenever needed.
Maple has an array of flexible lightweight microwave power transmitters that can deliver energy.
“In the same way that the internet democratised access to information, we hope that wireless energy transfer democratises access to energy,” Mr Hajimiri said.
“No energy transmission infrastructure will be needed on the ground to receive this power. That means we can send energy to remote regions and areas devastated by war or natural disaster.”
But for the plan to work, transmitters would need to be weigh less than they do now to reduce the amount of fuel needed to launch them to space.
They also need to be flexible so they can fold up inside a rocket.
The European Space Agency said some challenges still need to be addressed before space-based solar energy projects can create economically viable levels of energy.
“The biggest challenge is that the required structures need to be very large, both on Earth and in space,” the agency said on its website.
“A single solar power satellite at geostationary orbit might extend more than a kilometre across, with the receiver station on the ground needing a footprint more than 10 times larger.”
Other countries have also been working towards creating space-based solar energy.
China has plans to develop a solar power plant in space by 2028.
British firm Space Solar also has plans to create a solar energy station in space, with financial support from Saudi Arabia.
Within six years, Space Solar aims to have a trial project providing six megawatts of power from low Earth orbit, eventually leading to a two-gigawatt power station in high orbit by 2035.
