Scientists had the idea that they could generate electricity by running saltwater across an electrically charged surface. But they are not able to get a process to make enough energy to be useful. But now engineers have figured out the way to do that. Their trick was to make the water flow much more quickly, they achieved this by making the surface super water repellent.


Prab Bandaru is a mechanical Engineer and material scientist at the University of California San Diego. His team`s innovation grew out of frustration. They tried so many things but didn’t work. But there was One spur of the moment thing just happened to work. As per him, it was hardly planned. Scientists describe a surface that repels water as hydrophobic. These are the terms that come from the Greek words for water(hydro) and hating (phobic). As per UCSD team describes the material it uses as super-hydrophobic.

About the energy system

Their new energy starts with table salt or sodium chloride. This salt is made up of bonded atoms of sodium and chlorine, as its name suggests. When the atoms react to make salt, an electron from a sodium atom breaks off and attaches to a chlorine atom. This turns each neutral atom into a type of charged atom called an ion. The sodium atom has now a positive electrical charge. Opposite charges attract. So that sodium ion is now strongly attracted to the chlorine atom, which now has a negative charge.

When the salt is dissolved in water, the water molecules cause the association between the sodium and chlorine ions to loosen. As this salt water flows over a surface with a negative charge, its positively charged sodium ions will be attracted to it and slow down. Meanwhile, its negatively charged chlorine ions will keep flowing. This breaks the bond between the two atoms. And that releases the energy that had been stored within it.

The challenge

The challenge for them was to get the water to move quickly enough. As per Bandaru explained, “When the chlorine flows away fast, then the relative velocity between the slow sodium and the fast chlorine is enhanced”. So that will increase the electric power it generates. So the team described its innovation on October 3 in Nature Communication.

Daniel Tartakovsky said that This use of a super-water-repellent surface to generate energy is really, really exciting. He is an engineer at Stanford University who was not involved in the research.

Other innovations about this

Other researchers have tried to use water repellency to boost the energy production of a salt-water-electric generator. They did this by adding tiny to the surface. When the flowed over the grooves, it encountered less friction as it traveled over the air. Yet even though water flowed faster. Energy production didn’t increase very much. That is happening because the air also cut the water exposure to the negatively charged surface. His team had different plans to get around this problem. Then they tried making the surface more porous. Their idea was to speed the water`s flow by providing even more air at the surface. Afterward, they just tried replacing the air in the grooves of the surface with oil, and it worked!