Self-cleaning of Si photovoltaic modules by a nanostructured TiO2spray-coating

Solar radiation represents one of the most accessible within renewable energy sources. The rapid scaling-up in the number of installed photovoltaic (PV) systems is accompanied by an increase not only in the size of the associated investments and opportunities but also of the related risks. In this context, the study of the environmental effects which may bring to a decrease in their performance during operation is attracting an ever increasing attention. One of the most critical issues is associated to on-site dirtening of PV module surfaces due to pollution, dust particles and salt crystals deposition. Such phenomena can lead to a decrease of the transmittance of solar cell glazing, causing a significant degradation of the energy conversion efficiency of PV modules. This paper deals with the characterization of polycrystalline Si modules after controlled dirtening processes made under certified laboratory protocols. PV modules coated with a proprietary self-cleaning protective film based on nanostructured TiO2 have been exposed to dust deposition and salt mist. The experimental study showed that salt mist exposition did not bring to detrimental effects both in coated and un-coated PV modules used as references. Conversely, the self-cleaning properties of n-TiO2 coated modules proved to be effective after the dust deposition process. In fact, after dust deposition, the n-TiO2 coated PV module did not show significant changes in the I-V characteristics, while the reference module showed a reduction in efficiency of about 13.5%.