Harnessing the energy in air humidity

The Lappeenranta University of Technology (LUT) is currently conducting a study with the aim of discovering methods for harnessing the energy in humidity. The aim is to develop a concept of renewable energy similar to solar panels but allowing the production of energy based on air humidity.

Relative humidity is normally at least 25 per cent. When the water particles in the air move, an electric charge builds up on their surface. As a phenomenon, the build-up and discharge of electricity on the droplets in the atmosphere has been known for a long time. The phenomenon is very complex and has thus been difficult to study. Recently researchers have developed a material that can store electrical energy created by humidity and thus allows it to be studied.

The material is a nanocomposite based on zirconium dioxide. Zirconium dioxide has high ionic conductivity: its electrical conductivity is based on the movement of oxygen ions. As droplets move on the surface of the material, the generated electricity is stored in the nanoparticles of the zirconium dioxide.

For the study, zirconium dioxide-based nanocomposites were used to create thin films that were then placed on glass surfaces containing aluminium electrodes. The nanocomposite was sprayed on the glass surface with the aid of an aerosol. Humid air was transferred to the surface of the test piece, after which an atomic-force microscope and a surface potential microscope were used to study the properties of the sample.

The microscopes were used to measure the surface contour of the sample, as well as its electric properties with different concentrations of humidity.

"We are studying the energy built up on the surface of the material, or microamperes. The measurements have reached a voltage as high as one volt. The current has amounted to some microamperes per one square centimetre," explains professor Erkki Lähderanta.

The studies indicate that a higher concentration of humidity creates a stronger electric field in the sample. This means that it is possible to use humidity to create small amounts of electricity which, in sufficiently large amounts, could be used for powering electric devices as well as other purposes. To create the perfect combination, it is necessary to find the ideal technical quantities, such as the thickness of the nanocomposite films, the number of nanoparticles in the composites, and the geometrical magnitudes of the aluminium electrodes.

The researchers estimate that in the future, devices such as mobile phones and other portable smart devices could charge themselves by utilising the humidity in the air.

"This idea could lead to large-scale innovations. In 10 to 20 years, this technology may have developed sufficiently to introduce the first prototypes to the market. The material we are researching may not be the final material, but it has plenty of potential," Lähderanta states.

The research project includes partners from Europe and the United States. The project was launched in early 2016 and will continue until September 2019.

More information:

Professor Erkki Lähderanta, tel. +358 40 554 5227, erkki.lahderanta@lut.fi