A Spanish-Chilean research team has found that microbial biofilms in the Atacama Desert can significantly contribute to the soiling of photovoltaic modules, reducing short-circuit current by up to around 30% under accelerated laboratory conditions. The study highlights microorganisms as active agents in PV soiling and suggests they may influence optical losses, cleaning efficiency, and future mitigation strategies in arid, high-irradiance solar regions.
FE-SEM images of biofilm-forming microbiota on PV glass surfaces from soiling samples
Image: University of Granada, Advanced Sustainable Systems, CC BY 4.0
A Spanish-Chilean research team has examined the role of microorganisms in the soiling of photovoltaic surfaces in the Atacama Desert and has found that microbial biofilms can significantly impact the performance of solar modules.
“Our work shows that microbial communities isolated from photovoltaic modules in the Atacama Desert exhibit a high tolerance to desiccation and extreme irradiance,” the research’s corresponding author, Aitor Marzo, told pv magazine. “Furthermore, they form biofilms and produce extracellular polymeric substances (EPS), a matrix composed of polysaccharides, proteins, nucleic acids, and lipids that promotes cell adhesion, the retention of mineral particles, and crust formation on the surface. FE-SEM microscopy images confirmed the presence of dense, three-dimensional matrices that encapsulate cells and mineral particles.
The researchers also detected carotenoids in strains of a genus known as Dietzia, with spectral characteristics consistent with lutein-like compounds or related xanthophylls. According to the authors, these pigments may contribute to microbial photoprotection against extreme ultraviolet (UV) radiation and partially overlap with the spectral conversion range of monocrystalline silicon PV modules, suggesting a potential additional mechanism of optical interference.
To assess the electrical impact, the researchers conducted accelerated biofilm formation tests on PV glass under controlled laboratory conditions. In these experiments, seven days of colonization were associated with short-circuit current losses ranging from 15.20% to 30.66% in samples from the University of Antofagasta, and from 11.01% to 20.12% in samples from the Atacama Desert Solar Platform, alongside an increase in surface biomass. Increased EPS deposition was found to enhance cohesion within the biofilm and reduce the effectiveness of conventional cleaning methods, such as dry brushing and rinsing, which may be partially ineffective against the protective matrix.
The authors emphasized, however, that these tests were designed as accelerated experiments to reproduce the initial stages of biofilm adhesion and consolidation within a limited laboratory timeframe. As such, the maximum losses observed represent an upper bound of biological impact and should not be directly interpreted as typical field values, where colonization occurs more gradually and is influenced by environmental factors such as irradiance, humidity, dust deposition, and nutrient availability. Nevertheless, the data confirm that high irradiance selects for resistant taxa capable of forming persistent layers.
Overall, the study concluded that microorganisms are not a passive component of soiling, but active agents that contribute to deposit consolidation, reduce optical transmittance, and decrease the effectiveness of conventional cleaning methods.
The authors added that the results highlight the need to incorporate the biological dimension into soiling predictive models and PV system mitigation strategies in arid regions. At the same time, pigmented Dietzia strains present potential biotechnological applications in coatings and self-cleaning technologies, opening new avenues for future research.
Their findings can be found in the paper “Microbial Contribution to Soiling and Its Impact on Photovoltaic Module Soiling in Arid Zones of the Atacama Desert,” published in Advanced Sustainable Systems. The research team comprised academics from the University of Granada in Spain and the University of Atacama in Chile.
Atacama has become Chile’s and Latin America’s largest solar energy hub, with dozens of large-scale utility solar plants having come online there during the past decade. It has exceptional conditions for producing solar power, and effectively, the solar power installed capacity in this region represents more than 90% of the total installed capacity in Chile.
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