New Publication from the SUNLAB: Solar Energy

We are excited to share a new publication from the SUNLAB team in Solar Energy, titled “Spectral irradiance correction of photovoltaic energy yield predictions in six high-latitude locations with measured spectra”, first-authored by PhD candidate Mandy R. Lewis.

This study addresses a critical challenge in photovoltaic (PV) performance modeling: the variability of the solar spectrum in real-world conditions and its effect on PV efficiency. While most PV models assume a standard reference spectrum, actual sunlight varies significantly with location, weather, and time.

Using measured spectral data from seven North American sites (ranging from 39.7° to 69.1° N), the authors quantified how spectral mismatch affects bifacial silicon PV energy yield. They found that instantaneous spectral impacts can range from −45% to +32%, and annual energy yield can be underestimated by up to 2.7% if spectral effects are ignored.

The study highlights that diffuse and ground-reflected irradiance—which are more prominent in cloudy and snowy conditions—cause the largest spectral errors. These effects are especially relevant for bifacial systems, which can absorb scattered and ground-reflected light on the rear side. The authors recommend applying spectral correction methods in locations with high diffuse fractions (above 35%) and for bifacial systems.

Importantly, the work also shows that limited spectral measurement wavelength range (e.g., 280–1100 nm) can misrepresent spectral effects, underscoring the need for full-spectrum irradiance data in PV modeling.

Click here for the full article.

M. R. Lewis, V. Jancowski, C. E. Valdivia, and K. Hinzer, Spectral irradiance correction of photovoltaic energy yield predictions in six high-latitude locations with measured spectra, Solar Energy 300, 113816 (2025). DOI: 10.1016/j.solener.2025.113816