The next solar farms might be located in space, instead of on Earth. A prototype satellite by Caltech launched in January seems to be up and running, showing its capability to wirelessly transmit power in space while sending detectable solar power back to Earth for the very first time. 

Caltech's first ultralight integrated prototype. Photo credit: Caltech

How does it work? Caltech’s satellite is equipped with a microwave transmitter. Picture a microwave transmitter as a clever device that uses microwave radiation, a specific form of energy that is able to send signals or power wirelessly. Caltech’s antenna used a transmitter with 32 flat antennas, arranged on a surface slightly larger than a dinner plate, to control the beam's direction by adjusting the timing of signals. They directed the beam towards nearby receivers, lighting up LEDs on each, and then steered it towards Earth to reach another receiver at Caltech. Although the transmitted power was only 200 milliwatts, which is less than the light from a cellphone camera, this achievement serves as a proof of concept, showcasing the potential of this new technology.

Harnessing solar power in space is not a new concept. The mid-to-late 1970’s was a fertile landscape for alternative energy research, mainly due to energy shortages and the Three-Mile Island nuclear accident of 28 March 1979. NASA’s Satellite Power System (SPS) for example, was one of the many ambitions to experiment with space-based solar power, but the expenses involved were too high at that time. Luckily, space technology has changed a lot since then: solar cells and microwave beams have become more affordable and efficient and companies such as SpaceX have been reducing the cost of space launches. 

But why should we generate solar power in space? Harvesting solar energy beyond Earth's atmosphere could mean that energy availability does not rely on weather conditions, day and night cycles, or even cloud cover. Thanks to space solar power, regions on Earth currently lacking reliable electricity could now have access to year-round power, promising a brighter future for everyone.

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