Caltech team achieves wireless energy transfer in space for first time

12th September 2023
Kristian McCann

A team of researchers at the California Institute of Technology (Caltech) university have successfully demonstrated wireless power transmission in space and the beaming of detectable energy back to Earth. This precedent was achieved through an innovative method known as Microwave Array for Power-transfer Low-orbit Experiment (MAPLE).

The successful wireless transmission of energy in space could prove a pivotal step toward harnessing the space-based solar power, offering hope for further sustainable energy sources.

MAPLE was designed by Caltech as part of its Space Solar Power Project (SSPP) and works through a network of flexible and lightweight microwave power transmitters. The method employs constructive and destructive interference between individual transmitters to direct the energy it beams without relying on any moving parts. This technology is enabled by precise timing control elements, ensuring the majority of the energy reaches its intended destination.

"Through the experiments we have run so far, we received confirmation that MAPLE can transmit power successfully to receivers in space," Bren Professor of Electrical Engineering and co-director of SSPP Ali Hajimiri said of the experiment. "We have also been able to program the array to direct its energy toward Earth, which we detected here at Caltech. We had, of course, tested it on Earth, but now we know that it can survive the trip to space and operate there."

The experiment saw two separate receiver arrays located 30 centimetres away from the transmitter which convert the received energy into DC electricity. This is then utilised to light a pair of LEDs, demonstrating the full sequence of wireless energy transmission in space. Researchers conducted these tests in space, individually lighting up each LED and shifting between them, to verify the tech's efficacy. The transmitted energy from MAPLE was detected by a receiver situated on the roof of the Gordon and Betty Moore Laboratory of Engineering on Caltech's campus in Pasadena, demonstrating the expected time, frequency, and frequency shift based on its journey from orbit.

Hajimiri emphasised the significance of this achievement, stating, "To the best of our knowledge, no one has ever demonstrated wireless energy transfer in space even with expensive rigid structures. We are doing it with flexible lightweight structures and with our own integrated circuits. This is a first."

The SSSP is a research initiative focused on the development and exploration of space-based solar power as a potential solution to address the growing global energy demand. Solar panels on satellites are currently in use, as those in geosynchronous orbit receive sunlight for over 99% of the time. Yet this energy harvested is largely used to power the satellite or its various functions. Therefore, finding a way to transmit this energy via microwaves from the vessels could prove much more efficient that terrestrial solar panels, and accelerate sustainable energy through a virtually unlimited source. It could also provide locations currently lacking reliable power infrastructure with energy, as no energy transmission infrastructure will be needed on the ground to receive this power.

"In the same way that the Internet democratised access to information, we hope that wireless energy transfer democratises access to energy," said Hajimiri.

SSPP began in 2011 when philanthropist Donald collaboration with Caltech led to the establishment of a space-based solar power research project. The prototype of space solar power, Space Solar Power Demonstrator (SSPD), was launched into orbit as part of the Transporter-6 mission on January of this year. Alongside MAPLE, SSPD includes two other experiments, Deployable on-Orbit ultraLight Composite Experiment (DOLCE) and ALBA. DOLCE showcases the architecture, packaging, and deployment mechanisms of modular space solar panels, while ALBA tests 32 different types of photovoltaic cells in the demanding space environment

China will in 2028 launch a trial satellite to test the technology for transmitting energy from a space-based power plant to Earth.

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