Researchers and developers around the world are trialling unconventional energy storage technologies as alternatives to lithium-ion batteries, which rely on scarce and environmentally sensitive minerals such as lithium and cobalt. In Nevada, the Crescent Dunes solar project has spent a decade heating potassium and sodium nitrate salts to 560°C to store thermal energy that can generate electricity for up to 10 hours after sunset, while Denmark has unveiled a 1GWh molten salt system capable of storing clean power for up to two weeks for use in industrial processes. Meanwhile, researchers at Tokyo University of Science have developed a wearable skin patch that converts lactate in human sweat into electricity via an enzymatic reaction, potentially eliminating the need for small disposable batteries in wearable health sensors.