SETI & Technosignatures

Detectability of Solar Panels as a Technosignature

By Keith Cowing
Status Report
May 9, 2024
Filed under , , , , , , , , , , , , ,
Detectability of Solar Panels as a Technosignature
Reflectance of different surface components on a planet as a function of wavelength. The reflectance of silicon-based photovoltaics is shown as dashed curve. The ground model is based on the data from MODIS dataset The solar cell reflectivity data is from RELAB (Reflectance Experiments Laboratory (Pieters & Hiroi 2004) — astro-ph.IM

In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like exoplanet as a potential technosignature. 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).

Assuming that only solar energy is used to provide the 2022 human energy needs with a land cover of ~2.4%, and projecting the future energy demand assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.

Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the ultraviolet-to-visible (0.34 – 0.52 um), we find that several 100s of hours of observation time is needed to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel coverage of ~23% land coverage of a future Earth.

We discuss the necessity of concepts like Kardeshev Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even with much larger populations than today, the total energy use of human civilization would be orders of magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev Type I civilization.

Any extraterrrestrial civilization that likewise achieves sustainable population levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization as imagined in the Fermi paradox may not exist.

Ravi Kopparapu, Vincent Kofman, Jacob Haqq-Misra, Vivaswan Kopparapu, Manasvi Lingam

Comments: Accepted to The Astrophysical Journal
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Popular Physics (physics.pop-ph)
Cite as: arXiv:2405.04560 [astro-ph.IM] (or arXiv:2405.04560v1 [astro-ph.IM] for this version)
Submission history
From: Ravi Kumar Kopparapu
[v1] Tue, 7 May 2024 14:51:25 UTC (538 KB)
Astrobiology, SETI,

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻