More and more electricity is being generated from intermittent sources of power, such as solar and wind energy. Powerful electric energy storage devices are necessary to level out corresponding irregularities in the power supply. Fraunhofer scientists have recently made an important breakthrough with their development of a redox flow battery that reaches stack power up to 25 kW, with a cell size of 0.5 square meters. This is eight times larger than the previous A4-sized systems. They will be presenting the new battery for the first time at the Hannover Messe trade show (from April 8–12).