A Swiss firm is building a gigantic redox‑flow battery in Laufenburg, canton Aargau. Designed to store vast amounts of renewable energy, it aims to help stabilise both the Swiss and European power grids. Unlike lithium‑ion batteries, which store energy in solid electrodes, redox‑flow batteries use liquid electrolytes. Giant tanks hold these liquids, while stacks of cells above them convert the stored chemical energy into electricity. The system is recharged using surplus renewable power – mainly solar and wind – and feeds energy back into the grid during periods of peak demand. Our short video above shows how it works.