Implementation of a supervisory control and data acquisition for a biaxial photovoltaic tracker by means of a low cost PLC Zelio

The paper project proposes the use of the PLC Zelio for the Supervisory Control And Data Acquisition (SCADA) of a biaxial photovoltaic tracker; it is therefore proposed the design of the control algorithm for automatic tracking through Zelio Soft 5.4.0, and the corresponding supervision algorithm through the SCADA software both on the Vijeo Citect platform and on the Android platform with Tesla SCADA 2. For this purpose, the Zelio SR3B261BD-24V DC with 10 digital input (24V DC) and 10 digital output (relay contacts) was used, with related additional modules. The proposed application is based on the tracking of the solar disk by using photo-resistances. Basically, the movement of the panel in the North-South direction, as well as in the East-West direction, is controlled by 12 V stepper motors. Photoresistors vary their values depending on the amount of light that hits them; hence, the differences between the values of two photoresistors will guide the movement of the actuators to maximize the incidence angle of the sun's rays on the surface of the panel.