Osmosis
Osmosis is the passage of a fluid like water from an area of low solute (like salt) concentration to an area of high solute concentration through a semi-permeable membrane. A semi-permeable membrane is an organic filter which performs the separation. The process involving the use of two solutions having different concentrations, releases energy which is termed osmotic energy.
The Process
When two solutions having different salinity concentrations are separated by a semi-permeable membrane, water from the side with lower salinity concentration tends to flow to the other side to decrease the salt concentration on the other side. The difference in pressure levels on the two sides leads to the flow of water through the semi-permeable membrane from the region of low salt concentration to the region of high salt concentration. This happens in order to achieve equilibrium between the two sides thus creating a high pressure on the side that currently has a higher salt concentration. This high pressure can be utilized to generate energy using a turbine and a generator.
Osmotic Power Plant
Osmotic power plants working on the principle of osmosis are the latest type of power plants to be used for generation of electricity. Osmotic power plants can be set up in places where fresh water comes in contact with sea water like estuaries. Fresh and salt water serve as the required fuel for such a plant.
Fresh and salt water are separated by the semi-permeable membrane. Fresh water is drawn by the salt water creating a pressure on the salt water side and causing the dilution of the salt water until equilibrium is established on both sides. The osmotic pressure of the diluted salt water is passed through a turbine and a generator is used to generate electricity.
The first such plant has been recently opened in Norway after around 10 years of research. The plant is more of a prototype and is being used for testing and developing a commercial model which can then be used for generating energy on a larger scale. The plant is noise and pollutant free unlike the power plants currently being used.
Advantages of osmotic energy
- Osmotic energy is renewable since all that is required is salt water and fresh water and the semi-permeable membrane. No fuel is required and brackish water is the only by-product.
- Osmotic energy is renewable since salt contained in the brackish water which is the by-product, is not used up but is utilized to force water movement across the membrane.
- Osmotic energy has little impact on the environment.
