A German engineering professor hopes to transform a coal mine into a giant hydraulic battery in order to facilitate the usage of renewable energy.

Andre Niemann, professor of hydraulic engineering at the University of Duisburg-Essen, believes abandoned mines could be the solution to one of the chief impediments to weather-based forms of renewable energy – how to conveniently store the surplus electricity they generate to counteract the problem of intermittent supply. Professor Andre Niemann Niemann’s proposal entails…