The global contribution of wind energy to power supplies has expanded rapidly, marked by a capacity increase from 24 GW in 2001 to 840 GW in 2021, The technology has focused on harnessing high-speed winds of 0.5 m/sec or more, limiting geographical opportunities for more widespread wind turbine installation. This constraint may be blown away with a novel system capable of translating low-grade wind into electricity even when the wind speed drops as low as 0.2 m/sec.

The approach is based on previous studies showing that energy can be harvested from the movement of raindrops on a surface by redistributing charge around the interface between droplet and surface. Droplets of an ionic liquid — 3-methyl-1-octylimidazolium chloride — are partially fixed in place by a special substrate sporting an array of nanowires made from a silicone-based polymer, polydimethylsiloxane.

The interaction of low-speed wind with the anchored droplets causes a circulating flow within that redistributes the surface charge across the liquid. This surface charge can then be tapped with a pair of electrodes placed under the center and edge of each droplet. When the wind blows in different directions, different patterns of flow circulation arise within the ionic liquid droplets.

Research published in the Proceedings of the National Academy of Sciences reports that such stratified circulating flow within a single drop can generate a voltage output of up to 0.84 V. Output was experimentally scaled up to about 60 V in a design containing many drops. Low-grade winds could potentially be exploited by this small-scale droplet-based wind farm to power LCD screens and other electronics at sites not typically deemed optimal for wind turbine siting.

Researchers from the University of Chicago, University of Birmingham (U.K.) and China’s Hebei University, South China University of Technology, Chinese Academy of Sciences, City University of Hong Kong, Zhengzhou University and Yellow River Conservancy Technical Institute contributed to this development.