Controllable energy recovery for a smart PVRO desalination system

Photovoltaic reverse osmosis (PVRO) systems are a viable clean water source for many underserved communities. PVRO systems often use batteries and fixed recovery ratio energy recovery devices to operate at a constant (non-optimal) pressure. An alternate approach that eliminates expensive batteries and greatly increases water production is to optimally control the operation of the system in real-time to respond to variations in solar radiation and water conditions. This paper presents the development of a computer-controlled energy recovery device (ERD) for PVRO systems. It allows for optimal control of both the RO operating pressure and recovery ratio using an integrated computer-controlled variable nozzle/Pelton generator system. Analytical models are developed for the variable nozzle, Pelton bucket and Pelton turbine. These models are validated using a custom designed experimental system. The efficiency of the components is evaluated to demonstrate the capability of this key device for smart PVRO systems.