Humidity-Powered Batteries? Water Vapor May Serve As Renewable Energy Source In Future

TEL AVIV, Israel — To help reduce humanity’s impact on the environment, energy scientists seek out renewable energy sources in hopes of figuring out how to harness their energy. Of course, modern technology already allows us to take advantage of wind, solar, hydroelectric, geothermal and biomass power. Now, a team from Tel Aviv University says that moisture in the air might be able to serve as yet another innovative source of renewable energy in the future.

The researchers used a famous physics property discovered by the English physicist Michael Faraday to use the humidity in the air to charge a battery.

“Water is a very special molecule. During molecular collisions, it can transfer an electrical charge from one molecule to the other. Through friction, it can build up a kind of static electricity,” explains senior author Colin Price, a professor in the Porter School of the Environment and Earth Sciences at Tel Aviv University, in a university release.

Not only can water molecules transfer electric charge to other water molecules, they can also electrify metal surfaces through friction, as Faraday discovered in the 1800s. Researchers tested such surfaces under different environmental conditions to see which humidity level contains enough water vapor to produce this effect. They constructed a miniature battery with two metal plates and tried to charge it by raising the amount of water vapor in the air.


“We found that there was no voltage between them (two metal plates) when the air was dry,” says Price. “But once the relative humidity rose above 60%, a voltage began to develop between the two isolated metal surfaces. When we lowered the humidity level to below 60%, the voltage disappeared. When we carried out the experiment outside in natural conditions, we saw the same results.”

The authors were able to charge their battery to about 1 volt. Standard AA batteries contain 1.5 volts, so the authors think their discovery is appropriate for the production of rechargeable batteries. These batteries would be great for any geographical area that gets humid for a significant part of the year.

“The results may be particularly important as a renewable source of energy in developing countries, where many communities still do not have access to electricity, but the humidity is constantly about 60%,” Price concludes.

The study is published in Nature Scientific Reports.

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