Water and energy go hand in hand. We use tons of water in the process of producing energy, and we often expend lots of energy in the process of cleaning our water and making it drinkable. So when weâ€™re talking about developments in desalination and water purification technologies, the key is not just finding ways to better purify water, but to do it with a low cost of energy.
A group of researchers from Yale have developed a system that utilizes a technology they call forward osmosis, not to be confused with its counterpart, reverse osmosis. We all learned at some point in our educational careers that dilute water will flow into solutions that are more concentrated with salt (or, technically, any other solute). However, it is possible to reverse that process by pushing the water really hard against a membrane that will only let water molecules through. That is reverse osmosis â€“ it gets the job done, but you need to push really hard (energy) and the flow rate is so slow that you get barely a trickle.
In forward osmosis, the salty water is once again placed in front of a membrane that is only permeable to water molecules. This time, though, an even more concentrated solution is placed on the other side of the membrane. This secondary â€œdrawâ€ solution - a proprietary mix of ammonia and carbon dioxide â€“ draws the water molecules from the salty water through the membrane.
The draw solution is designed in such a way that it can be easily removed from the water, thus leaving clean water behind as the finished product. The key, though, is that by tapping the natural osmotic forces between the salty water and the draw solution, the purification system as a whole uses only about a tenth of the energy of a comparable reverse osmosis system.
The downside is that, although the system is elegant and efficient, it might not be feasible to scale it up as large as commercial desalination plants. But we will keep our eye on Oasys, the startup which has been spawned in the course of developing this technology.
written by Actu-film.com, February 03, 2009
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