Pressure Retarded Osmosis: Laboratory Scale Design and Experiment

Clean forms of renewable energy with low to no environmental impact are highly desirable. Pressure Retarded Osmosis (PRO) has been a growing form of “Blue Energy” [1], a renewable energy medium involving mixing bodies of salt and fresh water. PRO systems take advantage of the pressure difference seen between freshwater and seawater by forcing fresh water across a semipermeable membrane into a body of saltwater. This transfer, through the means of forward osmosis, yields an increase in pressure on the saltwater side of the membrane. This observable increase in pressure can be used for generating electricity. A popular thought proposed has involved taking a part of this newly created pressure and diverting it back into the system with the use of a pressure exchanger. Residual pressure would then be devoted to the generation of electricity. If done correctly, a net gain can be seen between the electricity gleaned from the output of the system, and the energy consumed to run the pumps necessary for operation. The group’s aim is to design and construct a variant of the traditional PRO system for the purpose of analysis in a laboratory setting. The design proposed consists of a compact, two-membrane system that allows for the testing and analysis of forward osmosis in a closed system. While the system is not intended for actual electrical generation, it provides a medium for future experimentation.