Sistema remoto de medição de irradiância solar para obtenção do desempenho global de sistemas fotovoltaicos

Abstract

The projects for the production of electric energy by photovoltaic (PV) systems grow year after year in Brazil. In small and medium size projects the energy production is estimated using simulation software. However, it is essential to assess the performance ratio of these systems against the calculated production, implying the measurement of solar irradiance. The challenge is to develop a low-cost device to be used in small and medium size PV systems. The electric current produced by a solar cell is directly proportional(linear) to the solar irradiance, and by coupling a resistor, a voltage value proportional to the irradiance can be obtained. A device was developed and characterized to obtain solar irradiance and transmit the data to a cloud platform. The silicon solar cell used in the device was calibrated and the solar irradiance values were compared with those obtained by a thermal pyranometer, showing a root mean square error of the order of 9.7 W/m2 in the 21 days of readings from 6 am to 6 pm. The device was installed in a photovoltaic system in Viamão - RS. During 47 days from November/2022 to January/2023, the solar irradiance data as well as the electricity production data from the photovoltaic system were sent to the cloud. The irradiance measurement allowed the identification of shading problems in the PV arrangement. The average overall performance ratio in the period was 91 %, being in line with what is expected for well-designed installed systems