Featured Research

from universities, journals, and other organizations

Discovery of charged droplets could lead to more efficient power plants

Date:
October 2, 2013
Source:
Massachusetts Institute of Technology
Summary:
In a completely unexpected finding, researchers have discovered that tiny water droplets that form on a superhydrophobic surface, and then "jump" away from that surface, carry an electric charge. The finding could lead to more efficient power plants and a new way of drawing power from the atmosphere, they say.

Images such as this, showing droplets being shed from a superhydrophobic surface (light band at center), revealed the charging of the droplets.
Credit: Nenad Miljkovic and Daniel Preston

In a completely unexpected finding, MIT researchers have discovered that tiny water droplets that form on a superhydrophobic surface, and then "jump" away from that surface, carry an electric charge. The finding could lead to more efficient power plants and a new way of drawing power from the atmosphere, they say.

Related Articles


The finding is reported in a paper in the journal Nature Communications written by MIT postdoc Nenad Miljkovic, mechanical engineering professor Evelyn Wang, and two others.

Miljkovic says this was an extension of previous work by the MIT team. That work showed that under certain conditions, rather than simply sliding down and separating from a surface due to gravity, droplets can actually leap away from it. This occurs when droplets of water condense onto a metal surface with a specific kind of superhydrophobic coating and at least two of the droplets coalesce: They can then spontaneously jump from the surface, as a result of a release of excess surface energy.

In the new work, "We found that when these droplets jump, through analysis of high-speed video, we saw that they repel one another midflight," Miljkovic says. "Previous studies have shown no such effect. When we first saw that, we were intrigued."

In order to understand the reason for the repulsion between jumping droplets after they leave the surface, the researchers performed a series of experiments using a charged electrode. Sure enough, when the electrode had a positive charge, droplets were repelled by it as well as by each other; when it had a negative charge, the droplets were drawn toward it. This established that the effect was caused by a net positive electrical charge forming on the droplets as they jumped away from the surface.

The charging process takes place because as droplets form on a surface, Miljkovic says, they naturally form an electric double layer -- a layer of paired positive and negative charges -- on their surfaces. When neighboring drops coalesce, which leads to their jumping from the surface, that process happens "so fast that the charge separates," he says. "It leaves a bit of charge on the droplet, and the rest on the surface."

The initial finding that droplets could jump from a condenser surface -- a component at the heart of most of the world's electricity-generating power plants -- provided a mechanism for enhancing the efficiency of heat transfer on those condensers, and thus improving power plants' overall efficiency. The new finding now provides a way of enhancing that efficiency even more: By applying the appropriate charge to a nearby metal plate, jumping droplets can be pulled away from the surface, reducing the likelihood of their being pushed back onto the condenser either by gravity or by the drag created by the flow of the surrounding vapor toward the surface, Miljkovic says.

"Now we can use an external electric field to mitigate" any tendency of the droplets to return to the condenser, "and enhance the heat transfer," he says.

But the finding also suggests another possible new application, Miljkovic says: By placing two parallel metal plates out in the open, with "one surface that has droplets jumping, and another that collects them … you could generate some power" just from condensation from the ambient air. All that would be needed is a way of keeping the condenser surface cool, such as water from a nearby lake or river. "You just need a cold surface in a moist environment," he says. "We're working on demonstrating this concept."

The research team also included graduate student Daniel Preston and Ryan Enright, who was a postdoc at MIT and the University of Limerick and is now at Bell Labs Ireland, part of Alcatel-Lucent. The work received funding from the U.S. Department of Energy through the MIT Solid-State Solar-Thermal Energy Conversion Center, the Office of Naval Research and the National Science Foundation.


Story Source:

The above story is based on materials provided by Massachusetts Institute of Technology. The original article was written by David L. Chandler. Note: Materials may be edited for content and length.


Journal Reference:

  1. Nenad Miljkovic, Daniel J. Preston, Ryan Enright, Evelyn N. Wang. Electrostatic charging of jumping droplets. Nature Communications, 2013; 4 DOI: 10.1038/ncomms3517

Cite This Page:

Massachusetts Institute of Technology. "Discovery of charged droplets could lead to more efficient power plants." ScienceDaily. ScienceDaily, 2 October 2013. <www.sciencedaily.com/releases/2013/10/131002103310.htm>.
Massachusetts Institute of Technology. (2013, October 2). Discovery of charged droplets could lead to more efficient power plants. ScienceDaily. Retrieved October 31, 2014 from www.sciencedaily.com/releases/2013/10/131002103310.htm
Massachusetts Institute of Technology. "Discovery of charged droplets could lead to more efficient power plants." ScienceDaily. www.sciencedaily.com/releases/2013/10/131002103310.htm (accessed October 31, 2014).

Share This



More Matter & Energy News

Friday, October 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Jaguar Land Rover Opens $800 Million Factory in Britain

Jaguar Land Rover Opens $800 Million Factory in Britain

AFP (Oct. 30, 2014) British luxury car manufacturer Jaguar Land Rover opened a $800 million engine manufacturing centre in western England, creating 1,400 jobs. Duration: 00:45 Video provided by AFP
Powered by NewsLook.com
SkyCruiser Concept Claims to Solve Problem With Flying Cars

SkyCruiser Concept Claims to Solve Problem With Flying Cars

Buzz60 (Oct. 30, 2014) A start-up company called Krossblade says its SkyCruiser concept flying car solves the problem with most flying car concepts. Mara Montalbano (@maramontalbano) explains. Video provided by Buzz60
Powered by NewsLook.com
Mind-Controlled Prosthetic Arm Restores Amputee Dexterity

Mind-Controlled Prosthetic Arm Restores Amputee Dexterity

Reuters - Innovations Video Online (Oct. 29, 2014) A Swedish amputee who became the first person to ever receive a brain controlled prosthetic arm is able to manipulate and handle delicate objects with an unprecedented level of dexterity. The device is connected directly to his bone, nerves and muscles, giving him the ability to control it with his thoughts. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Robots Get Funky on the Dance Floor

Robots Get Funky on the Dance Floor

AP (Oct. 29, 2014) Dancing, spinning and fighting robots are showing off their agility at "Robocomp" in Krakow. (Oct. 29) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins