The panel is designed to make the most of the light in space, which does not pass through the atmosphere, and thus retains the energy of blue waves, making it more powerful than sunlight reaching Earth . Blue light diffuses as it enters the atmosphere, which is why the sky appears blue.
“We get a ton of extra sunlight in space just because of this,” said Paul Jaffe, co-developer of the project.
Latest experiments show that the 12 x 12-inch panel is capable of producing about 10 watts of power for transmission, Jaffe told CNN. That’s about enough to power a tablet.
But the project envisions a range of dozens of panels and, if scaled up, its success could revolutionize both the way energy is produced and delivered to remote corners of the globe. This could contribute to the largest grid arrays on Earth, Jaffe said.
“Some visions have a spatial solar match or overtake today’s largest power plants – several gigawatts – so enough for a city,” he said.
The unit has not yet returned energy directly to Earth, but the technology has already proven its worth. If the project transforms into gigantic space-based solar antennas several miles away, it could broadcast microwaves that would then be converted into fuel-less electricity to any part of the planet at any time.
“The unique advantage of solar satellites over any other source of energy is this global transmissibility,” Jaffe said. “You can send electricity to Chicago and a split second later, if you need it, send it to London or Brasilia instead.”
But a key factor to prove, Jaffe said, is economic viability. “Building material for space is expensive,” he says. “And those [costs] are, over the past 10 years, starting to decline. “
There are some advantages to building in space. “On Earth we have this pesky gravity, which is useful in that it holds things in place, but causes a problem when you start to build really big things because they have to support their own weight,” said Jaffe.
The project was funded and developed by the Pentagon, the Operational Energy Capability Improvement Fund (OECIF) and the US Naval Research Laboratory in Washington, DC.
A solution during natural disasters
The temperature at which PRAM operates is key. Cooler electronic components are more efficient, Jaffe said, degrading their ability to generate energy as they heat up. The X-37B’s low Earth orbit means that it spends about half of every 90 minute loop in the dark, and therefore in the cold.
Any future version of PRAM could sit in a geosynchronous orbit, meaning that a loop takes about a day, in which the device would be mostly exposed to the sun, as it travels much further from Earth.
The experiment used heaters to try to keep the PRAM at a constant hot temperature to prove its effectiveness if it was spinning 36,000 kilometers from Earth.
It worked. “The next logical step is to expand it to a larger area that collects more sunlight, which converts more to microwaves,” Jaffe said.
Beyond that, scientists will have to test the sending of energy to Earth. The panels would know precisely where to send the microwaves – and wouldn’t accidentally fire them on the wrong target – using a technique called “retro-directive beam control.” This sends a pilot signal from the destination antenna on Earth to panels in space.
The microwave beams would not be transmitted until the pilot signal was received, meaning the receiver was up below and ready. The microwaves – which would easily be turned into electricity on Earth – could be sent to any point on the planet with a receiver, Jaffe said.
He also allayed any future fears that bad actors could use the technology to create a giant space laser. The size of the antenna needed to direct the energy to create a destructive beam would be so huge that it would be noticed over the years or months it took to put it together. “It would be extremely difficult, if not impossible,” he said, to militarize solar power from space.
DePuma said the technology, if available today, would have immediate applications in natural disasters when normal infrastructure collapsed. “My family lives in Texas and they all live without power right now in the middle of a cold front because the grid is overloaded,” DePuma said.
“So if you had a system like this, you could redirect some electricity there, and my grandma would have heat in her house again.