If alien technological civilizations exist, they almost certainly use solar energy. Along with wind, it's the cleanest, most accessible form of energy, at least here on Earth. Driven by technological advances and mass production, solar energy on Earth is expanding rapidly.
It seems likely that ETIs (Extraterrestrial Intelligence) using widespread solar energy on their planet could make their presence known to us.
If other ETIs exist, they could easily be ahead of us technologically. Silicon solar panels could be widely used on their planetary surfaces. Could their mass implementation constitute a detectable technosignature?
The authors of a new paper posted to the arXiv preprint server examine that question. The article is titled "Detectability of Solar Panels as a Technosignature," and it is scheduled for publication in The Astrophysical Journal. The lead author is Ravi Kopparapu from NASA's Goddard Space Flight Center.
In their paper, the authors assess the detectability of silicon-based solar panels on an Earth-like habitable zone planet. "Silicon-based photovoltaic cells have high reflectance in the UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept like the Habitable Worlds Observatory (HWO)," the authors write.
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