Part 2 of 3 Parts (Please read Part 1 first)
Atwater, Hajimiri, and Pelligrino discussed their project as it nears a significant milestone. A test launch of prototypes into Earth orbit is expected in December of 2022.
Sergio Pellegrino said, “It was more than 10 years ago, in 2011, that conversations began with Donald Bren asking whether Caltech had any ideas when it came to research in the field of sustainable energy and space. We started discussing, in a group of faculty members, ways of building on our interests and what was happening in each of our areas that might lead to a very impactful research initiative. Over a period of a few months, we came up with a vision—I called it a dream—of three or four technology breakthroughs that, in combination, would transform the way space solar power had been previously approached.”
Ali Hajimiri added, “This concept was, in the past, truly science fiction. What made it possible for us to consider taking it from the realm of science fiction to the realm of reality was the combination of developments happening in photovoltaics in Harry’s lab, in structures in Sergio’s lab, and in wireless power transfer, which is happening in my lab. We realized that we can now pursue space solar power in a way that is becoming both practical and economical. One of the first questions that anyone asks is, “Why do you want to put photovoltaics in space?” Well, in space, where you don’t have day and night and clouds and things of that sort, you get about eight times more energy. The vision of this program is to be able to provide as much power as you need, where you need it, and when you need it.”
On the question of actual concrete progress to realize their vision, Pellgrino said, “Over a period of two years, we built and demonstrated a prototype tile. This is the key modular element that captures the sunlight and transmits the power. Through that process, we learned many things about how to design highly integrated and ultralight systems of this sort. We then developed a second prototype, 33 percent lighter than the first.”
Hahimiri added that, “This tile is the building block, as Sergio mentioned, of the larger system. It has to be fully functional, compatible, and scalable. Although it may sound simple, it’s actually quite sophisticated. These tiles are mounted on a very flexible structure that can be folded to fit in a launch vehicle. Once deployed, the structure expands, and the tiles work in concert and in synchronization to generate energy, convert it, and transfer it exactly where you need it and nowhere else.”
When asked about the next phase of the project, Atwater said that “It doesn’t get real until you actually go to space. As Sergio and Ali described, we demonstrated this key unit element called a tile in our labs. One of the lessons from that series of demonstrations was that the pathway we needed to follow for photovoltaics fundamentally had to change. We were working with what I’ll call conventional photovoltaic materials, which had to be designed in a form that was going to make it difficult to reach the mass-per-unit area and specific power goals, so we had to basically rethink the photovoltaic strategy completely. As a result, the classes of photovoltaic devices that we are testing in space have actually never flown in space before.”
Please read Part 3 next