Engineers from Brigham Young University (BYU) are developing extremely waterproof surfaces that they believe could dramatically improve the efficiency of both power plants and solar energy systems. These surfaces, called superhydrophobic surfaces, are extremely difficult to wet since they cause water to aggregate and form beads that sit on the surface.
If you turn to nature you can see numerous examples of naturally occurring superhydrophobic surfaces such as duck feathers, butterfly wings and lotus leaves. These surfaces efficiently repel water, causing it to clump together and form little beads because it is more attracted to itself than the surface. These surfaces have inspired many engineers in the field of biomimetics, where scientists attempt to imitate elements of nature to solve problems.
In this present study, which has been published in Physics of Fluids, engineers from BYU produced superhydrophobic surfaces by combining hydrophobic coatings with surfaces covered in either tiny posts or microscopic ridges a tenth of the size of human hair. They then tested them by examining the way that water interacts with the surface when either dropped, jetted or boiled onto them.
Image credit: BYU. Microscopic posts used to create the superhydrophobic surfaces.
Superhydrophobic coatings such as these have numerous diverse applications in industry. They can be sprayed onto clothing such as boots and jackets to make them waterproof, or circuits and grids to keep them clean. They can also be applied to the hulls of ships to prevent the growth of organisms and reduce corrosion. But lead researchers of this study, Julie Crockett and Dan Maynes, see their research being applied to increase the efficiency of energy production systems.
The majority of power plants generate energy by burning either coal or gas to produce steam that rotates a turbine. The world’s largest solar farm that opened this year in the Mojave Desert, California, produces electricity in a similar manner by using giant mirrors to direct sunlight onto boilers which also creates high-temperature steam that drives generator turbines.
Once the turbines are going, the steam produced needs to be fed back into the system to be re-used which is achieved by condensing it back into a liquid. If the condensers were manufactured with super-hydrophobic surfaces this process could be a lot more efficient. “If you have these surfaces, the fluid isn’t attracted to the condenser wall, and as soon as the steam starts condensing to a liquid, it just rolls right off,” said Crockett in a news-release. “And so you can very, very quickly and efficiently condense a lot of gas.”
According to Maynes, if these surfaces were applied to photovoltaic cells the conversion of solar energy to electricity could also be improved because it would mean that the material is kept clean.
In order to produce their superhydrophobic surfaces, the researchers etched the micro posts or ridges onto materials that were then coated with a thin layer of a hydrophobic material such as Teflon. They then used high-speed cameras to record how water interacts with the surface. They’re currently tweaking the surfaces to gain a clearer understanding of why they are so hydrophobic, for example by changing the width and angles of the ribs.
“People know about these surfaces, but why they cause droplets or jets to behave the way they do is not particularly well know,” said Crockett. “If you don’t know why the phenomena are occurring, it may or may not actually be beneficial to you.”
If you'd like to find out more, check out this YouTube video from BYU: