Abstract: A method for generating power from water by pressure retarded osmosis comprises the steps of: pumping sea water into a first pathway which is at least partially defined by a first face of a membrane, said membrane comprising a distinct electrically conductive porous nanotube layer; pumping fresh water into a second pathway which is at least partially defined by a second face of the membrane to generate an osmotic pressure gradient across the membrane; and harnessing the power generated from the osmotic pressure gradient.