Design Criteria and Optimization

Performance analysis of a PRO system can be carried out by solving the salt and water mass balance and the energy balance for every component included in the plant. A detailed characterization of the membrane module is crucial for an accurate prediction of the plant performance. An adequate discretization is therefore required [6-10] since local flux is substantially affected by local conditions and local polarization phenomena. 

A correct performance prediction of a PRO plant requires several assumptions regarding membrane permeability and pressure drop of the stream along the modules, efficiencies of the turbine, the pumps and the energy recovery device, length and geometry of the ducts and pressure drops introduced by the filtration system. Ambient conditions and salinity concentration for both freshwater and seawater have to be known as well. 

Increasing the hydraulic pressure reduces the flow crossing the membrane for assigned boundary conditions (membrane area, freshwater and seawater flow rate). On the other hand, since is the pressure at turbine inlet, as its value increases, more work per permeated mass unit can be produced by the turbine. The optimal p yj value is a trade-off 

In summary, a careful evaluation of the opposite effects of these three parameters should be performed in the design of a PRO plant with the ultimate aim to minimize the resulting cost of electricity and guarantee efficient operations both at the nominal point and even in 

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