Story: Hope Wilder

Caltech Achieves First Space-to-Earth Transmission of Space-Based Solar Power

Caltech has achieved the first-ever space-to-earth transmission of space-based solar power. Using microwaves, Caltech’s MAPLE (Microwave Array for Power-transfer Low-orbit Experiment) successfully transmitted power from space to a rooftop receiver. This groundbreaking achievement serves as a stepping stone to demonstrate the feasibility of space-based solar power in the future.

Space-based solar power (SBSP) has been under investigation since 1978. Japan, China, the US, Russia, India, and the United Kingdom are actively pursuing SBSP. Japan and China have even launched programs to pursue SBSP at scale within the next few decades. If successful, SBSP could become a powerful tool in renewable energy, helping to reduce carbon emissions. It holds the potential to provide clean power to remote areas that are currently off the grid. Unlike earth-based solar power, which is limited by land availability and the constraints of battery technology to store solar power during nights and cloudy periods, SBSP could offer a consistent and uninterrupted power supply, thanks to continuous solar exposure in space.

For SBSP to be viable, solar panels would need to be compact for transportation to space and extremely lightweight to reduce launch costs. However, there are several challenges to scaling up SBSP to be competitive, including the high costs of launches, durability issues, and the substantial size and expense of receiving stations on Earth.

The MAPLE experiment involves an array of lightweight microwave power transmitters capable of focusing and beaming energy to specific locations. If expanded, such microwave transmissions would not pose a threat to human safety. The Caltech team envisions a “constellation of sail-like solar panels” connected to these microwave transmitters in space. The space solar power units would be packed into 1 cubic meter packages and launched into space, unfolding into flat squares approximately 50 meters per side. The solar cells would face the sun, while the power transmitters would be positioned on the Earth-facing side. Caltech is currently conducting two additional experiments to test the folding mechanisms of these units and determine the best solar panels for space conditions. The results from these experiments will be announced in the coming months.

Caltech’s team prioritized lightweight technology to showcase the feasibility of future SBSP projects. “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,” said Ali Hajimiri, the project leader.

Ali Hajimiri emphasizes the potential democratization of energy access through wireless energy transfer, similar to how the internet democratized access to information. “No energy transmission infrastructure will be needed on the ground to receive this power. That means we can send energy to remote regions and areas devastated by war or natural disaster.”

Although space-based solar power still faces technical obstacles before widespread adoption, it may prove to be an effective alternative energy source in the coming decades.