15 Jan 2009 05:01:10
Osmosis purifies water, generates electricity
The natural process of diffusion is harnessed in designs for systems that purify water and generate electricity using low-level heat.
Osmosis has been harnessed to develop a closed loop system for generating electricity and desalinating water at a tenth of the cost.
Yale scientists have harnessed "forward osmosis" to create a water purification system that uses one tenth of the energy as existing methods.
Doctoral student Robert McGinnis and Menachem Elimelech, chair of chemical and environmental engineering, developed the system now being commercialised by newly established company Oasys.
To purify water, it is drawn through a semi-permeable membrane from its contaminants to a solution of concentrated salts.
The salts can then be easily separated using low-level heat, such as waste heat from conventional power plants.
Using the same principle, the team has also designed a device to generate electricity.
In their osmotic heat engine, the solution of salts is kept under high pressure and as water is drawn through, the added pressure is released through a turbine.
Waste heat can then be used to separate the salts and water, which can be used again in the closed loop system.
Water management issues have been highlighted by the European Environment Agency as one of the areas that will dominate policy discussions in the coming year.http://opa.yale.edu/news/article.aspx?id=6309&s=t