Remotely Measuring And Controlling Specific Parameters Of Photovoltaic Modules Via A Radio Frequency Link

Abstract

Background: The efficiency of PV modules is affected by a number of factors, including installation parameters and the module surface temperature. Installation parameters of PV modules focus primarily on the tilt and orientation angles, which have to be considered for optimum output power. Furthermore, the operating temperature of a PV module must be kept within certain limits, in order to obtain optimum electrical energy efficiency, depending on the module used. Controlling these parameters of a remote PV module can prove challenging. Purpose: The purpose of this study was to measure the instantaneous surface temperature, voltage and current of a remote PV module that can be used to control some of these parameters in order to maintain a high output power. Methodology: An energy monitoring system was developed that received measurement data and sent control signals over an RF link. The PC transceiver of the system featured a CC1101 RF transceiver connected to the PC via an Arduino UNO, using a USB cable. The PV transceiver featured an Arduino Mega 2560, connected to a CC1101 RF transceiver to make the slave transceiver board, which harboured all the sensors of the system. In addition, the graphical user interface was developed for sending and receiving measurements and control signals between the PC transceiver and the PV transceiver. Results: The PV module voltage and current data was verified using a Fluke 115 DMM. The results showed a 4.9% error percentage for voltage measurements and a 3.9% error percentage for current measurements. Furthermore, a 29-day period of data showed the surface temperature to rise significantly higher than the ambient temperature during the day, indicating that there was considerable heating of the PV Module when there was solar radiation. Whereas for low temperatures measured at night, the surface temperature and the ambient temperature were fairly similar. In addition, PV module current measurements were obtained for a sunny and cloudy day of September that showed 2.32 A and 1.98 A at 11:00 am respectively. Control signals were sent using the graphical user interface from the PC transceiver that were used to activate an actuator that can adjust the orientation angle. A single click of the “Move Left” button in the interface provided an extension of 3 cm of the actuator while a single click of the “Move Right” button resulted in the actuator being retracted by 4 cm. The difference in the displacement of the actuator for the “Move Left” and “Move Right” commands was for demonstration purposes only. Control signals from the PC transceiver to activate a water sprayer (to cool the PV module) were confirmed by switching on and off a LED at the PV module transceiver. The cooling method used is but only an example, the review and selection of a cooling method did not form part of this study. Recommendations: The work presented here could be extended by modifying the graphical user interface to form part of a smart city where the adjustment to the actuator and activation of the water sprayer could be automated. Incorporating cloud storage for monitoring of the output power and surface temperature from any location at any time could also be considered.