A team from the University of Waterloo has created a low-cost device that can power a calculator using just discarded walnut shells and a few drops of water. Their findings appear in Energy & Environmental Materials.
The coin-sized water-induced electric generator (WEG) creates electricity as water evaporates through the shell’s intricate pore network.
“With just a single droplet and the shell’s natural structure—no crushing, soaking, or complicated processing required—it works,” explained Nazmul Hossain, a Ph.D. student in mechanical and mechatronics engineering at Waterloo. “It’s a straightforward yet powerful way of transforming waste into clean energy by harnessing nature itself.”
From Hazelnut Shells to Hydrovoltaics: Nature-Inspired Energy Harvesting
The technology relies on hydrovoltaic energy harvesting, where evaporating water moves through the nut shell’s porous structure. As it flows, the water carries charged ions that interact with the shell’s surface, creating an electrical imbalance that produces power.
Hossain’s idea emerged after eating a hazelnut and examining its shell under an electron microscope. The shell’s natural network for transporting water and nutrients struck him as ideal for energy generation.
Experiments with four different nut types revealed that walnut shells delivered the highest energy output. The researchers enhanced their performance by cleaning, treating, polishing, and shaping the shells with precision.
By linking four WEG units—each containing shells, water droplets, electrodes, wires, and a 3D-printed casing—the Waterloo team successfully produced enough electricity to run an LCD calculator.
“This technology has the potential to revolutionize how we power small electronics, particularly in remote or off-grid settings,” said Hossain. “Imagine sensors, wearables, and disaster-relief tools powered by mere droplets of water.”
The team is exploring wearable WEGs powered by sweat or rain and sensors for detecting leaks. They have also tested wood as an alternative material to nut shells.
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