Systemic design and energy management of a standalone battery-less PV/Wind driven brackish water reverse osmosis desalination system

This work investigates a small-scale reverse osmosis desalination system dedicated for off-grid communities lacking freshwater. This system, constituted of motor-pumps, desalination process and hydraulic network (pipes and valves), is powered by hybrid photovoltaic-wind turbine source. It exploits hydraulic storage in water tanks filled when renewable energy is available instead of electrochemical storage. Such specificity makes the power/freshwater supply a challenging issue for these communities. To maximize freshwater production of this autonomous system, a "systemic design approach" integrating couplings between architecture, sizing, and energy management is proposed. According to the specific system architecture and its component sizing, a specific quasistatic model-based energy management strategy (EMS) is developed. In this regard, the influence of the main component sizing on the system energy efficiency and the EMS performance is analyzed. This study proved the strongly coupling between power/water management and pump sizing. According to the iterative process of the systemic design approach, simulation results showed that the EMS objective is reached by increasing the brackish water storage tank capacity and improving the system energy efficiency. The latter is achieved by choosing the pumps-combination composed of three pumps having the lowest rated powers (0.37 kW/0.37 kW/1.5 kW), but offering higher energy efficiency over other analyzed pumps-combinations.