Power Generation With Pressure Retarded Osmosis

Energy can be generated from two streams of different salt concentration using the osmotic pressure difference. Different methods have been proposed to harvest this energy. Pressure retarded osmosis (PRO) is investigated as a viable method and most promising technology. In PRO process, pure water permeates through a semi permeable membrane from the low hydrostatic pressure stream (feed solution) to the higher hydrostatic pressure stream (draw solution) due to the osmotic pressure difference. This increases the volume flow rate of the pressurized draw stream and energy is obtained by depressurizing the draw stream through a hydro turbine. In this study a one-dimensional computational model is developed to precisely estimate the power production under different operating conditions. Different feed and draw solution concentrations are used to estimate the power production from PRO. The maximum power density (power per unit membrane area), using available membrane characteristics, obtained from seawater–freshwater streams is 2.6 W/m² and for the disposed brine–seawater streams is 9.1 W/m². The performance of PRO process is very sensitive to the membrane characteristics in particular to the water permeability and PRO module configuration.