Solar Panels in Space: Is It Possible?

By putting solar panels in space, the sun will always shine anywhere on Earth. California Institute of Technology (Caltech) has obtained a significant investment to support a sci-fi-like project. 

Caltech’s Harry Atwater told Ars Technica over Zoom that this is a more advanced idea, even the space program itself. Quoting Asimov and Clarke, Atwater created an image of glossy solar panels floating in space on a large metal truss. These solar panels are all connected to hardware that converts the electricity to a form suitable to shine back down to Earth. 

Long Gestation Period

In August, Caltech declared that one of its Board of Trustees had given over $100 million to promote the advancement of space-based power. The timing is somewhat peculiar because the donor, Donald Bren, started the process over a decade ago. At that time, Bren had presented his idea to the university administration and began choosing faculty members to participate in the project. 

“At first, I was in doubt because this is an idea that’s been studied several times,” Atwater said. 

Atwater thought innovative approaches to putting solar panels in space could become a reality. He even formed a spin-off company responsible for ultralight photovoltaic hardware. Later on, Caltech researchers with relevant expertise joined him. Ali Hajimiri has done research on power conversion hardware, while Sergio Pelligrino led the development of lightweight deployable space structures. 

The collaborative expertise has been essential in developing a design that represents a significant change in ideas. According to Atwater, the critical parameter in space is not efficiency but specific power, the power per unit mass. Specifically, Atwater and his team were more concerned about watts per kilogram. 

Beaming Light

Now, how do the solar panels in space work? Most photovoltaic systems in outer space use highly efficient cells containing three light-harvesting layers. Each layer has different wavelengths of light. However, the existing design of the solar panels uses a single layer of photovoltaic material, which allows a more significant efficiency per unit of mass.

Then, the absence of efficiency per unit area is offset by spreading the photovoltaics to a large extent. Atwater described this as “thinner than the thinnest plastic bag ever”. The flexible membrane is fixed using a tensegrity structure. This relatively tiny rigid structure is secured in a proper configuration by tension. 

The space-based solar project focuses on building small, self-contained units called tiles. The individual tiles will be made into a larger tensegrity structure, with a current target of about 60 meters square. 

“Plants” Floating In Space

Atwater said that an individual structure would not provide much power so that a subsequent power plant will require several forms flying in formation. The entire system is meant to be situated in geostationary orbit so that it can remain above a single receiving station while still providing 24/7 sunlight. 

Atwater also told Ars that the proposal would make the ground receiving station almost similar to a large utility-scale solar farm. It will comprise an extensive array of rectennas to convert the microwaves sent down from space into usable power.

Way Forward

Twelve years ago, a group of people established a company with an approach to space-based power identical to the one Atwater said would not work. So, the challenging project of Caltech may perform an important function.

However, Atwater said the project aims to produce the foundational technology for a cost-effective and scalable space solar power. The target made the project successful, generating a lot of intellectual property and space-based testing from  2022 to 2023. Atwater and his team aim to find more commercial partners for the actual deployment of solar panels in space.