Investigation of the improvement of energy generation by pressure retarded osmosis

Abstract

Knowing the overall solute flux and the partial fluxes expressed by every single transport layer, the membrane internal interface concentrations can separately be expressed. Both the overall transport coefcient and the driving force strongly depend, among others, on the value of the structural parameter and the water permeability. Study of the interface concentrations as a function of the membrane characteristic properties and the operation conditions shows clearly the different, individual effects of the Cm, Cs interface membrane concentrations (and Csp) on the concentration difference across the membrane active layer and thus on the process efciency. The change of the value of Cs is much more sensitive on the membrane transport properties than that of the value of Cm. The high value of the structural parameter essentially destroys the membrane performance accordingly efforts of the manufacturers must be focused on lowering of its value for increase of the water permeability. The membrane performance can also be improved not only by its characteristic properties, but by the operating conditions as well, e.g. by applying different solute concentrations instead of seawater-river water pair. The higher draw solute or lower feed concentrations can serve then much higher power density. The knowledge of the individual interface concentration of every single transport layer enables the user to do more deep, more precise study of the mass transfer process during pressure retarded osmosis. Finally, it is shown reasonable agreement between the measured and predicted data.