Comparison of soiling measurement sensors for solar energy technologies

Soiling is one of the phenomena that most significantly affects the performance of concentrating solar thermal and photovoltaic systems. For its monitoring, sensors have become an important solution as accurate measurements enable the implementation of optimal cleaning strategies and help reduce the operation and maintenance costs of these systems. This study presents a comparison of four soiling monitoring devices, two of which are currently under development. The devices were evaluated during a dry summer period at the Plataforma Solar de Almería (Almería, Spain). Firstly, their ability to estimate soiling losses in photovoltaic systems was assessed. The four devices accurately tracked the reference measurements, however, a calibration was required. The discrepancies found can be attributed to the different measurement principles of each device. In addition, a comparison has been done between the influence of soiling on photovoltaic and concentrating solar systems. To this end, soiling rates were determined from hemispherical transmittance and specular reflectance measurements of samples exposed under the same conditions as the sensors. Finally, correlations were found between the optical measurements of hemispherical transmittance and specular transmittance and the sensor signals, highlighting the potential for implementing devices capable of monitoring soiling in systems that combine both solar technologies. This approach could be particularly valuable for hybrid plants, which may play a key role in global decarbonization strategies.