The reverse osmosis desalination system driven by the marine current turbine under dynamic conditions

Freshwater scarcity is a critical challenge in remote coastal and island regions, where access to traditional freshwater resources is limited. Reverse osmosis (RO) desalination has proven to be an effective solution; however, its high energy consumption and reliance on fossil fuels necessitate sustainable alternatives. This study develops a marine current turbine-driven desalination system designed to address the dynamic conditions of marine currents and enhance system efficiency. The proposed system adopts a direct-drive mechanism to minimize energy losses and features the design of a Clark pump, addressing the key issue of improving energy efficiency in desalination systems under fluctuating power input conditions. Additionally, a soft start process for the RO membranes has been developed, ensuring the long-term stable operation of the membranes and resolving the reliability issues of RO membranes under fluctuating power inputs. Based on operational parameters and water quality requirements, a safe operating window has been established, and a constant recovery rate and low specific energy consumption operation strategy have been developed to ensure the stable operation of the system under varying marine current velocities. Trial testing demonstrated that the system's specific energy consumption is 3.61 kWh/m³, with an energy recovery efficiency of 83.7 % for the energy recovery device. Furthermore, during the soft-start process of the RO membranes, both the feed flowrate and pressure stabilization time exceed 30 s, effectively reducing the risk of potential damage caused by hydraulic shock.