PV-powered membrane system control for continuous autonomous water solution in remote areas

A thesis submitted in partial fulfillment of the requirements for the Degree of Master of Science in Renewable Energy

This research addressed the challenge of Solar Irradiance (SI) fluctuations, which adversely affect the performance of photovoltaic-membrane (PV-membrane) systems used for water purification. These fluctuations lead to reduced permeate volume and quality, as well as increased specific energy consumption. The primary aim of this research is to incorporate mechanical energy storage and develop a hydraulic buffering control method to enhance system performance under varying SI conditions. To achieve this, a hydraulic energy storage system utilizing a bladder tank was implemented, designed to buffer periods of SI fluctuations. A control algorithm was developed that allows the hydraulic bladder accumulator to discharge during low solar irradiance periods for buffering and charge during high solar irradiance periods by monitoring power ramp down rates. Results indicate that, in the worst-case scenario of a very cloudy day, the system produced an additional 98.5 L of permeate while maintaining permeate quality within the WHO palatable limit of 1.13 mS/cm. Furthermore, the average specific energy consumption was reduced by 38%. The algorithm effectively prevented system pressure from dropping to zero, thereby maintaining system stability despite fluctuations caused by SI changes. Future investigations should focus on minimizing pump shutdowns during hydraulic buffering due to increased pressure resistance. This research contributes to sustainable water solutions in remote areas, offering a promising approach to enhance the reliability and efficiency of PV-powered membrane systems