Photovoltaic Performance Characterization Based on Solar Spectrum Variations

The electrical output of photovoltaic (PV) systems depends not only on total irradiance and temperature but also on the detailed distribution of photon energies in the incident solar spectrum. Standard test conditions employ the AM1.5G spectrum, yet field‐deployed modules routinely experience solar spectral shapes that differ markedly with latitude, season, atmospheric aerosol loading and installation geometry. These variations can induce systematic gains or losses in energy yield of several per cent even for established silicon technologies, and of up to double‐digit percentages for multi‐junction or emerging thin‐film cells. Characterization approaches fall into two broad classes: proxy‐based methods that use readily measured atmospheric and irradiance parameters (air mass, clearness index, precipitable water) to infer spectral influence, and direct spectral correction functions (SCFs) that exploit spectroradiometric data or scalar indices derived from the spectrum itself. Scalar indices include the average photon energy (APE), depth of key absorption bands (notably water vapour), the spectral mismatch factor (MMF) and the useful fraction of the spectrum. Recent work has demonstrated that SCFs built on spectral indices can substantially outperform proxy‐based corrections, enabling more accurate site- and technology-specific yield forecasts. Practical applications range from refined power-plant performance modelling and financial risk assessment to real-time fault detection and optimum tilt-and-azimuth design under variable sky conditions.

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Photovoltaic Performance Characterization Based on Solar Spectrum Variations publication trend

The graph below shows the total number of articles in photovoltaic performance characterization based on solar spectrum variations across all publications each year (not limited to Nature Index journals).

Technical terms

Spectral Correction Function (SCF): A mathematical model that adjusts a PV module’s reference performance to account for deviations in the incident solar spectrum from the standard test spectrum.

Average Photon Energy (APE): The irradiance-weighted mean energy of photons in a measured solar spectrum, used as a scalar index of spectral shape.

Spectral Mismatch Factor (MMF): The ratio of the module’s short-circuit current under the actual spectrum to that under the reference spectrum, quantifying sensitivity to spectral shifts.

Water Absorption Band Depth: A measure of the relative attenuation at specific wavelengths (typically around 650–670 nm) due to atmospheric water vapour, employed to distinguish spectra with similar APE but differing shape.

References

1. Review of methods to account for the solar spectral influence on photovoltaic device performance. Energy (2024).
2. Predictability and interrelations of spectral indicators for PV performance in multiple latitudes and climates. Solar Energy (2023).
3. Modelling the spectral influence on photovoltaic device performance using the average photon energy and the depth of a water absorption band for improved forecasting. Energy (2023).