Using electrical storms as a jumping off point, scientists at Israel’s Tel Aviv University believe they may have uncovered a new source of renewable energy. In laboratory experiments, the team was able to generate a voltage using only water and metal, which raises the prospect of batteries that can be charged with nothing but the humidity in the air.
"We sought to capitalize on a naturally occurring phenomenon: electricity from water," explains Professor Colin Price, who led the research. "Electricity in thunderstorms is generated only by water in its different phases — water vapor, water droplets, and ice. Twenty minutes of cloud development is how we get from water droplets to huge electric discharges — lightning — some half a mile in length."
Price and his team sought to tap into the potential of water droplets, which previous research has shown to be capable of charging metal surfaces through the forces of friction. In a similar vein, other studies have shown that some types of metal will generate an electrical charge in response to humidity in the air.
The team’s experiments were designed to uncover how a voltage might be generated between two metals, with one grounded, when they were subjected to high levels of humidity. When the air was dry, no voltage was produced. But once the humidity levels soared above 60 percent, a voltage began to develop, before disappearing again once the humidity started to drop. These results were reproduced in experiments conducted outside in natural conditions.
“We tried to reproduce electricity in the lab and found that different isolated metal surfaces will build up different amounts of charge from water vapor in the atmosphere, but only if the air relative humidity is above 60 percent,” says Price. “This occurs nearly every day in the summer in Israel and every day in most tropical countries."
According to the researchers, the experiments showed that humid air could be leveraged to charge surfaces to around one volt, which they say isn’t all that far away from practical use.
"If a AA battery is 1.5V, there may be a practical application in the future: to develop batteries that can be charged from water vapor in the air,"Price says. "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 percent.”
The research was published in the journal Scientific Reports.
Source: Tel Aviv University
