Coin-sized generator harvests energy from waste walnut shells

Researchers at the University of Waterloo have developed a coin-sized water-induced electric generator (WEG) that produces electricity by harnessing the evaporation of water from walnut shells, an abundant agricultural waste. This device leverages hydrovoltaic energy harvesting, where evaporating water moves charged ions through the porous walnut shell structure, creating an electrical current without complex processing. The WEG can generate enough power to operate small electronics like calculators, demonstrating a simple, low-cost, and sustainable approach to energy generation from natural waste materials. Among various nut shells tested, walnut shells showed the highest efficiency, especially after cleaning, polishing, and precise shaping. The WEG units consist of treated walnut shells combined with electrodes, wires, and a 3D-printed casing. By connecting multiple units, the researchers successfully powered an LCD calculator, highlighting potential applications in remote or off-grid settings. Future research aims to develop wearable versions that harvest energy from sweat or raindrops and explore practical uses such as water-leak sensors.