Simulation tool for full-scale PRO systems using SWMMs

Pressure retarded osmosis (PRO) is a process that is able to convert a salinity gradient into electrical energy through a turbine. This process has gained attention as a possible renewable energy technology for integration into desalination plants to improve their energy efficiency. Despite recent efforts, PRO is not yet commercially available due to drawbacks related to, among others, PRO membrane and module development. The aim of this study is to provide a simulation tool for full-scale PRO systems that allows accurate estimates of PRO-related energy generation to be made. The proposed tool enables analysis of single-stage systems with PRO modules in series and the setting of boundary conditions per module in terms of maximum flux recovery, and maximum and minimum feed/draw flow. The HTI OsMem™ 2521 spiral wound membrane module (SWMM) was evaluated considering an 8 in. diameter (high active area). Increasing the number of SWMMs in series was found to increase permeate flow and the energy that can be generated, even when considering the pressure drop on both draw and feed side and the effect of the dilution and concentration of the draw and feed solutions. The proposed tool allows to determine the safe operating windows and operating points for maximization of energy generation for fixed and variable operating conditions.