Analysis and optimization of pressure retarded osmosis for power generation

Model‐based analysis and optimization of pressure retarded osmosis (PRO) for power generation is focused. The effects of membrane properties (hydraulic permeability and mass‐transfer characteristics), design conditions (inlet osmotic pressures, inlet flows, and membrane area) and operating condition (applied pressure) on power density and efficiency are systematically investigated. A dimensionless design parameter , originally developed in analysis and optimization of reverse osmosis, is used to quantify the effect of dilution in draw solution (DS) as water permeates through membrane. An optimization method is developed to maximize PRO performance. It is shown that dilution and concentration polarization significantly reduce the maximum power density, and the optimal shifts away from . Moreover, power density and efficiency follow opposite trends when varying process conditions including DS flow rate and membrane area. Enhancing membrane properties is crucial to improve the economic feasibility of PRO. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1233–1241, 2015