System-Level Analysis and Optimization of Pressure Retarded Osmosis for Power Generation

This presentation focuses on system-level analysis and optimization of pressure retarded osmosis (PRO) for power generation. 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 ϒ=AL_pπ₀/Q₀, 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 DP shifts away from Dπ₀/2. 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.

Reference:

[1] Li, M. Analysis and Optimization of Pressure Retarded Osmosis for Power Generation, AIChE Journal, 61, 1233-1241, 2015.