ALBA: Harvesting Solar Energy

During the mission, the ALBA team, led by Atwater, measured the photovoltaic performance of three entirely new types of ultralight, research-grade solar cells that had never been tested in space before. Over the course of more than 240 days, the team evaluated these cells, some of which were custom-made in the SSPP labs and the Kavli Nanoscience Institute (KNI) at Caltech. These facilities enabled the team to quickly fabricate small, cutting-edge devices ready for flight. Looking ahead, the team plans to test larger solar cells produced using scalable, cost-effective manufacturing methods that could significantly reduce both the mass and cost of space-based solar cells.

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Currently, commercially available space solar cells are about 100 times more expensive than the solar cells used on Earth due to the expensive epitaxial growth process, where crystalline films are grown in a precise orientation on a substrate. In contrast, the SSPP solar cell team developed low-cost, nonepitaxial space cells using inexpensive production methods similar to those used for making silicon solar cells. These methods employ high-performance materials like gallium arsenide, which is commonly used in current high-efficiency space solar cells.

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The team also tested perovskite cells, which have gained attention in the solar industry for their low cost and flexibility, as well as luminescent solar concentrators that could potentially be deployed in large, flexible polymer sheets.

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Throughout ALBA’s mission, the team gathered enough data to observe how individual cells responded to space weather events such as solar flares and geomagnetic activity. For example, they found significant performance variability in the perovskite cells, while the low-cost gallium arsenide cells maintained steady performance overall.

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"SSPP provided us with a rare opportunity to take solar cells from Caltech's labs directly into space, speeding up the in-orbit testing process that would normally take years. This approach has significantly shortened the innovation cycle for space solar technology," says Atwater.