NOVELTY - The method involves pumping sea water (3) into a pathway, which is partially defined by a face of a pressure retarded osmosis membrane (2) e.g. carbon nanotube (CNT) membrane, that comprises a distinct electrically conductive porous nanotube layer with porosity between 10 to 20 percent and having CNTs. Fresh water is pumped into another pathway, which is partially defined by another face of the membrane to generate an osmotic pressure gradient across the membrane. The power generated from the osmotic pressure gradient is harnessed.    USE - Method for generating power from water by pressure retarded osmosis.    ADVANTAGE - The method enables generation of energy with very little impact on environment and renewable by the osmosis without consuming carbonic oxide, emission or toxic effluents and salts while reducing fuel costs. The method allows salinity power plants to be flexibly built with good supply of fresh water and sea water and to be adapted to local building environment or combined with existing power stations, so as to save operating cost. The membrane comprises a buckypaper as a conducting layer to allow an electric field to be applied across the membrane during osmosis to diffuse charged particles from membrane surface by thimming sedimentation layer near membrane surface, thus maintaining constant membrane throughput power generation.    DETAILED DESCRIPTION - The nanotubes are selected from a group consisting of single walled nanotubes, double walled nanotubes and multi-walled nanotubes. The nanotubes are functionalized with carboxylic acid and/or silver. The membrane comprises a support layer formed of cellulose acetate or nylon. An INDEPENDENT CLAIM is also included for an apparatus for generating power from water by pressure retarded osmosis, comprising a membrane with a distinct electrically conductive porous nanotube layer.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a set up in which osmosis is used to generate energy.    Pressure retarded osmosis membrane (2)    Sea water (3)    Turbine (4)