Pressure retarded osmosis (PRO) could be a viable source of renewable energy [1, 2]. In a PRO system water from a low salinity feed solution (e.g., fresh water) permeates through a membrane into a pressurized, high salinity brine/draw solution (e.g., seawater); power is obtained by depressurizing a portion of the diluted seawater through a hydroturbine [3]. The concept of harvesting the energy generated during mixing of fresh and salt water was developed in the mid 1950s [4]. Loeb and coworkers began publishing results from PRO experiments in 1976 [5]. Further investigations of Loeb and Mehta [6], Mehta and Loeb [7, 8], and Jellinek and Masuda [9] revealed power outputs far below the expected outputs; likely due to the use of RO membranes and membrane modules that were designed for seawater desalination. Thus, the lack of suitable membranes and modules hindered the efforts to establish this technology [10]. Also, during this time, a few models were proposed to predict flux and pressure behavior in PRO [6, 8,11]; however, it was difficult to validate these models because of the lack of suitable membranes and membrane modules.
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