Closed circuit PRO series no 2: performance projections for PRO membranes based on actual/ideal flux ratio of forward osmosis

Pressure retarded osmosis (PRO) for hydroelectric power generation from worldwide widespread salinity gradient sources is of growing interest for large-scale clean energy generation. This approach requires membranes of specific characteristic and the evaluation of peak power density of such membranes at present time proceeds by extrapolation from theoretical curves with limited experimental data support mostly in a region far removed from the actual applied pressure of peak power generation. This study describes the use of actual/ideal flux ratio term (β) derived from PRO flux measurement at zero applied pressure (forward osmosis flux conditions) in a distinct salinity gradient for a defined membrane of known permeability coefficient (A) for the flux and power density projections of said membrane. The β-A approach for PRO flux, power density, and peak power projections is illustrated in the context of some recently reported theoretical and experimental results of several advanced Thin Film Composite-PRO membranes.