Solar power has become a focal point of the battle to mitigate climate change. The potential of solar power is massive—Earth receives as much solar energy in an hour as all of humanity uses in a year. Even with that much energy hitting the Earth, it is only a tiny fraction of the sun’s overall output. Some of that other solar energy hits other planets, but most is just lost to the void of deep space.
There are a number of groups that are leveraging various technologies to capture some of that lost energy. One of the most common technologies being pursued is the idea of the power satellite. Recently, one of those groups at America’s Naval Research Laboratory (NRL) hit a milestone in the development of power satellite technology by launching their Photovoltaic RF Antenna Module (PRAM) test satellite.
The idea underlying power satellites is called “power beaming.” power-beaming systems use one of three frequencies of light to transmit significant amounts of power over a distance wirelessly. Last year, NRL had a successful demonstration of a land-based power-beaming system using an infrared laser.
Doing it from space presents a whole new set of challenges though, and not necessarily just technical ones. Dr. Paul Jaffe, the technical lead on the PRAM project, described the process of being selected for an orbital launch as equivalent to Shark Tank—numerous PIs pitching their ideas for a trip to orbit. After several years of trying, PRAM finally got its time to shine on an X-37B launch on May 17th.
PRAM won’t actually shine, though—it’s surface is covered in black solar panels, and its innards consist of the first hardware ever launched to orbit that converts solar energy into microwaves. The satellite itself is relatively small (30 cm on a side), and won’t actually be transmitting any power back to Earth. Instead, it will collect data that will serve as useful comparison points to an experiment using a similar system previously conducted back on Earth.
There were several metrics from the Earth-based test that the PRAM team were hoping to replicate in space. Efficiency of conversion from solar to microwave was one of the most important factors. Without high enough efficiency, future launches might be prohibitively expensive for the amount of power the system generates.
Thermal management is another extremely…
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