Junction Box-Integrated Irradiance Estimator for Photovoltaic Modules Based on IoT Technology

Solar irradiance is one of the key factors that affect the efficiency of photovoltaic (PV) systems. Moreover, based on the properties of the PV module and the current irradiance value, it is possible to estimate the maximum power point of the PV array and assess possible failures, partial shadings, soiling, and degradation modes. However, the use of conventional pyranometers presents high costs and limited spot measurements. The reference solar cell addresses the issues of time constant and solar spectrum absorption, but its cost is higher than that of the pyranometer. This article proposes an irradiance estimator based on current, voltage, and temperature measurements of the PV module. The proposed method is implemented in an ESP8266 microcontroller, allowing for estimation of solar irradiance at an affordable cost. This microcontroller is equipped with a Wi-Fi module, enabling the transmission of estimation results without communication cables. This approach also allows for monitoring each PV module through the Internet, within the context of the IoT. Experimental results demonstrate an average error of 3.5% when compared with a PVA-1000S, which is used as a benchmark. This makes it a valuable tool not only for estimating irradiances but also for various applications, such as identifying faulty modules in PV strings.