Wave powered reverse osmosis (WPRO) is an emerging field of study, bridging the fields of renewable energy and reverse osmosis (RO). WPRO utilizes the energy in the ocean waves to generate the required pressure for RO. As such the RO pressure is continually varying with time, thus requiring a transient model to simulate its effect. This work presents a transient one-dimensional model applicable for WPRO, based on finite volume discretization with explicit time steps to solve for the concentration variation in the polarization layer, assuming lumped parameters parallel to the membrane. The model accounts for the time variation of concentration polarization and the associated fluctuations in permeate flux and concentration. Results indicate that concentration polarization is lower for a sinusoidal RO pressure than for a constant RO pressure because it allows the wall concentration to discharge during the periods when RO is not taking place. WPRO produces less than one-third the rate of permeate compared to a corresponding constant pressure RO system, however the power requirements are approximately one-tenth, in addition to the fact that WPRO is powered by a renewable source. So WPRO is predicted to deliver a greater quantity of permeate per unit energy supplied than conventional RO. (C) 2010 Elsevier B.V. All rights reserved.