How to Make Electricity in a Disused Coal Mine

A coal-mine that powered German industry for almost half a century will get a new lease on life when it’s turned into a giant battery that stores excess solar and wind energy.  The town of Bottrop, where people worked the 600 meter (1,969 foot) deep mine since 1974, will keep playing a role in providing uninterrupted power for the country, she said.

https://www.bloomberg.com/news/articles/2017-03-17/german-coal-mine-to-be-reborn-as-giant-pumped-hydropower-battery

Source: University of Duisburg-Essen