Solar power beamed from space ‘an achievable future’ following Caltech mission

A year ago, Caltech launched their Space Solar Power Demonstrator (SSPD-1) to test three technological innovations that would be required to make space solar power a reality:

• The ability to beam power wirelessly in space
• The efficiency, durability, and function of a variety of different types of solar cells in space
• A real-world trial of the design of a lightweight deployable structure to deliver and hold the solar cells and power transmitters.

That mission is now complete and has been judged a success: ‘Solar power beamed from space at commercial rates, lighting the globe, is still a future prospect, said Caltech President Thomas F. Rosenbaum, ‘but this critical mission demonstrated that it should be an achievable future.’

In space there is an supply of uninterrupted solar energy, constantly available without being subjected to the cycles of day and night, seasons, and cloud cover, giving access to up to eight times more power than solar panels on Earth.

While checking that the equipment was fit for purpose, the most exciting part of the project was the SSPD demonstrating its ability to wirelessly transmit power in space and to beam detectable power to Earth for the first time.

The first transmitted energy was detected by a receiver on the roof of the Gordon and Betty Moore Laboratory of Engineering on Caltech’s campus in Pasadena. The received signal appeared at the expected time and frequency, and had the right frequency shift as predicted based on its travel from orbit.

The ultimate goal is to achieve a constellation of modular spacecraft that collect sunlight, transform it into electricity, then convert it to microwaves that will be transmitted wirelessly over long distances to wherever it is needed—including locations that currently have no access to reliable power.

The efficiency of three entirely new classes of ultralight research-grade solar cells was also tested. The team collected enough data to be able to observe changes in the operation of individual cells in response to space events like solar flares and geomagnetic activity. They found, for example, tremendous variability in the performance of perovskite cells, whereas  low-cost gallium arsenide cells consistently performed well overall.

Prof. Harry Atwater, one of the principal investigators of SSPP said: ‘SSPP gave us a unique opportunity to take solar cells directly from the lab at Caltech into orbit, accelerating the in-space testing that would normally have taken years to be done. This kind of approach has dramatically shortened the innovation-cycle time for space solar technology.’