Why does the wind cast a shadow? What does it mean for solar energy?

15.09.2025

Published in Renewable Energy, a new study by researchers from the Geographical Institute at the HUN-REN Research Centre for Astronomy and Earth Sciences and the University of Pannonia finds that Saharan dust storms – increasingly frequent and intense across Europe – significantly affect solar irradiance and, in turn, solar power generation and the wider use of solar energy.

Having previously analysed the Hungarian context, the researchers now look beyond the Carpathian Basin in their article, ‘The shadow of the wind: the impact of Saharan dust on photovoltaic power generation in the Mediterranean’. They examine the effects of Saharan dust on photovoltaic (PV) power generation across five Mediterranean countries – Portugal, Spain, France, Italy and Greece – between 2019 and 2023.

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Relationship between atmospheric dust levels and photovoltaic (PV) output.

The analyses clearly show that photovoltaic (PV) output falls by 25–40 per cent on average during dust storms, with losses exceeding 50 per cent in extreme cases.

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Number of dusty days, PV output, cirrus cloud reflectance and variation in PV output forecasts as a function of atmospheric dust load.

The drop in solar irradiance that governs photovoltaic (PV) output is driven by two main factors: (1) absorption and scattering by dust; and (2) enhanced cirrus formation, which further reduces incoming radiation. The researchers also observed that the reflectivity (albedo) of the resulting high-level clouds increased in dusty conditions, as a higher concentration of ice-nucleating dust particles produced more, smaller ice crystals, brightening the cloud deck.

An analysis of recent episodes also revealed that current forecasting models do not adequately represent aerosol–cloud interactions, leading to systematic errors in daily PV output forecasts: Portugal and Spain typically showed underestimation of around 15 per cent, whereas Italy and Greece recorded overestimation of around 10 per cent.

The study underscores the need to develop real-time dust monitoring and forecasting systems that also account for cloud processes. With climate change expected to make Saharan dust storms increasingly frequent and intense, the authors stress that managing dust-related uncertainties is crucial for reliable grid operation in southern Europe and for planning the use of solar energy.