The solar panel could beam energy down to remote locations. (Image Credit: U.S. Naval Research Laboratory)


Pentagon scientists have successfully tested a 12-inch solar panel in space. The prototype is designed for future systems capable of harvesting solar energy, converting it into electricity, and beaming it to any location on Earth.  The panel, called Photovoltaic Radio-frequency Antenna Module (PRAM), was launched on May 17th, 2020, aboard an Air Force X-37B Orbital Test Vehicle to collect solar energy and convert it to electricity. It currently orbits the Earth every 90 minutes.


PRAM makes the best use of sunlight that doesn’t pass through the atmosphere. This allows it to absorb the energy of blue waves, which are more powerful than the sunlight on Earth. Recent experiments demonstrate that the solar panel produces 10 watts of energy for transmission. That amount is sufficient enough to power a tablet.


The project has a bigger picture in mind: utilizing dozens of panels. If these solar panels are scaled-up, they could change how electricity is generated and delivered to other parts of the world. They could also contribute to the world’s largest grid networks.


PRAM, a 12-inch solar panel, is designed to harvest sunlight, convert it to electricity, and beam it down to Earth. (Image Credit: U.S. Navy photo by Jonathan Steffen)


However, PRAM hasn’t transmitted power to Earth yet, but the technology works. If it’s developed into massive kilometer-wide antennas, it could transmit microwaves, which would be transformed into clean energy, to any location on Earth. This technology needs to be economically feasible.


The U.S.’ X-37B space plane’s mission is secretive, with only the PRAM experiment being known for its purpose. The first results of the experiment were released in January, which shows that it’s working as expected.


PRAM operates much more efficiently in cold temperatures since the electronics degrade in their ability to generate power once they’re heated. The X-37B stays in low-earth orbit, which means that PRAM is in the dark during each 90-minute orbit around the Earth. Future versions of the solar panel might be kept in a geosynchronous orbit, where it would take a day to loop the Earth. In this circumstance, the solar panel would stay in the sunlight because it’s traveling further away.


Heaters were used on the PRAM to keep it at a consistently warm temperature. This proved that it could operate efficiently at 36,000km from Earth.  Scientists must perform more tests to ensure the energy can be transmitted. The panels would know where the microwaves are to be sent. It uses a technique called “retro-directive beam control,” which involves sending a signal from the destination antenna to the panels.


Microwave beams are sent as soon as the panels receive the signal, meaning the receiver was already in place. The microwaves could then be transmitted to any point on the Earth with a receiver. If this technology were readily available, it would be used in natural disasters when infrastructures collapse.


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