Opportunities for Osmotic Power

With the exception of the energy and resources required to fabricate and maintain a plant, osmotic power produced with seawater and fresh water is a carbon-free, renewable, clean energy source. Unlike many other forms of renewable energy such as wind and solar, osmotic power could be produced continuously and used as a base load supply.

A company taking a leading roll in the development of osmotic power is the Norwegian utility Statkraft. They have constructed a pilot process using ERI’s PX devices that is scheduled to start up in November 2009. Statkraft estimates that the global potential for the production of osmotic power from fresh water flowing into the sea is an enormous 2.6 terrawatts.

Although this discussion has focused on the use of seawater as the driving fluid for the osmotic power process, any salt water or solution with a high osmotic potential can theoretically be used in the process described above. For example, salty concentrate from a desalination process could be combined with salt-free water such as effluent from a wastewater treatment plant. Desalination concentrate has almost twice the salt content of seawater and could therefore nearly double the power produced by the same size process running on seawater. Similarly, concentrated salt water from natural or constructed evaporation ponds could be used to harness the power of the sun to drive an osmotic power process.

Other approaches that use synthesized solutions to draw water or another solvent across a semi-permeable membrane have been proposed. After being released through a turbine, these solutions are regenerated with thermal or membrane separation techniques. Some proposed methods have the potential to create osmotic pressures that are an order of magnitude higher than a seawater-based system. In all osmotic power processes, PX energy recovery devices are an essential component, maintaining high osmotic pressure in a closed loop by replacing dilute solution with concentrated solution with high efficiency.

Copyright 2009 Osmotic Power Inc.