Researchers have made progress towards harvesting solar energy in space and transmitting it to Earth. A satellite launched in January successfully beamed power in a microwave to targets in space and even sent some power to a detector on Earth. The California Institute of Technology (Caltech), the experiment’s builder, announced this achievement on 1 June. Sanjay Vijendran from the European Space Agency (ESA) said, “No one has done this before. They’re demonstrating this capability and bringing credibility to the topic.”
Space-based solar power has faced the challenge of credibility. To match the power output of a coal or nuclear power station, a satellite would need a vast collection area spanning kilometers, requiring numerous launches and assembly in orbit. NASA attempted a demonstration mission in the 1970s, but it would have cost $1 trillion at that time. However, advancements have been made. Solar cells and microwave beams are now cheaper and more efficient. Robots capable of assembling structures will soon be in orbit, and launch costs have been reduced. Studies commissioned by ESA and the U.K. government suggest that orbiting generators will soon generate electricity at costs comparable to nuclear plants.
Solar Energy Research
Research programs have contributed to progress. In the 1980s, Kyoto University demonstrated power beaming over short distances using suborbital rockets. In 2020, the U.S. Naval Research Laboratory launched a small panel into orbit with solar cells and microwave transmitters. The Caltech mission, funded by the Donald Bren Foundation and Northrop Grumman Corporation, aimed to take it further with lightweight, inexpensive, and flexible components. Their microwave transmitter, slightly larger than a dinner plate, consisted of 32 flat antennas that could steer the beam. They successfully directed it to microwave receivers, lighting up LEDs.
The transmitted solar energy was small, only 200 milliwatts, but it served as a proof of concept. The Caltech spacecraft has two more planned experiments: testing different solar cells for durability in space and deploying a sail-like structure to assess feasibility. Interest in space-based solar power is growing, with ESA commissioning studies on potential power station architectures. Energy supply companies are also involved, and the Kyoto team is collaborating with JAXA for orbit testing. Additionally, Virtus Solis Technologies plans to launch a solar energy pilot plant by 2026, aiming to offer commercial power before the decade ends.
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