Could tiny water droplets lower your electric bill? (+video)
Researchers report that a water droplet acquires a charge when it 'jumps' from a water-repellant surface, a find that could make power plants more efficient.
The activities of bantam water droplets in just one region of a power plant could make a significant difference in the output of power plants, scientists say.Skip to next paragraph
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A team of MIT researchers report this week that water droplets that “jump” from a water-repelling surface acquire a charge that prevents them from returning to that surface. The find makes an important leap in a burgeoning effort to harness “jumping” water droplets in making power plants more efficient.
“There has generally been a lot of buzz in this area of research,” says Nenad Miljkovic, a postdoctoral associate at MIT and a co-author on the paper, published in Nature Communications.
“The concept of jumping droplets is not new, and we have been working on it and publishing papers for a while now,” he said, referring to an earlier paper from his team, published this winter in Nano Letters. “However, none of the previous studies (including ours) had any idea that the droplets were charged.”
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A superhydrophobe is a kind of hydrophobe, a molecule with water-repellant properties. Hydrophobic molecules include fats and oils — hence the adage, “oil and water don’t mix” and the apparent fruitlessness of trying to get a homogenous salad dressing out of oil and vinegar. But a superhydrophobe is "super" because, unlike just a hydrophobe, it has a rough either micro or nanoscale structure.
When a water droplet forms on a sheet of metal coated with a superhydrophobe, the droplet can camp there only so long as it does not merge with another droplet. As soon as it weds with another droplet, the energy produced is so great that the two will “jump” away from that surface, as if in urgent deference to the surface’s severe water phobia.
Scientists have proposed that this “jumping” could be incorporated into power plant design. In power plants, steam is produced in a boiler and is then turned into mechanical energy in a turbine. Excess steam from the turbine is next converted into water in a condenser and sent back to the boiler for reuse. Right now, in current condenser designs, water congeals in a thin film on the condenser’s surface. Before new water droplets can form there, this water must fall away from the surface and be conveyed back over the boiler. This can take time.
So, if the new water droplets could be quickly removed from the condenser’s surface, making room for new droplets, the condensation process would be much more efficient, scientists say. To do so, condensers could be fitted with superhydrophobic surfaces that encourage water forming there to make an urgent departure, they say.