Photovoltaic Power Load-Matching Challenge in a Reverse Osmosis Water Desalination System

In a directly-coupled photovoltaic (PV) powered membrane (PV-membrane) system, there are two key challenges. Firstly, variations in system performance occur due to fluctuations in solar power supply, caused by changes in solar irradiance (SI). Secondly, suboptimal load-matching often leads to the underutilization of daily PV energy. The latter occurs when the primary electrical load in the system, the pump, reaches its maximum demand (pump head). This results in excess PV energy being underutilised, particularly during peak sunlight hours, thereby reducing load-matching efficiency. In this study, this challenge is investigated on a PV-membrane system operating on different solar days: “sunny” and “partly cloudy”. The results indicate a lower load-matching of about 95% on a sunny day, compared to about 99% on a partly cloudy day, indicating that more PV energy is underutilised on a sunny day. Moreover, charging of battery during the period of excess PV supply did not remarkably enhance the load-matching, as charge controller reduces PV power during battery charging stages. This work serves as an investigation to highlight the impact of suboptimal load-matching on PV-membrane systems and to indicate the need for controlled optimization methods to improve system performance during daily operations.