The demise of coal mines as countries turn to renewable energy leaves behind employment losses in the surrounding communities and large tracts of unusable land.
Germany may have found a solution to the problem. It is turning one of its old coal mines into a giant 'battery station' that will be a pumped storage plant that will provide hydroelectric power and provide energy to around 400,000 homes.
After half a century of service, the Prosper-Haniel hard coal mine in the northwest of the country is due to be shut down in 2018, when it will be converted into pumped storage plant.
Researchers from several German universities are working with private engineering firms and the government on the project, and have been running feasibility studies on the site since 2012 in anticipation of the 2018 conversion.
The almost 2,000 foot mine provides something the surrounding area doesn't have naturally – elevation. That's crucial for a pumped storage plan. Usually, a reservoir is on high ground and it feeds the water in the valley below.
With the coal mine, water power turbines will generate electricity from the falling water, which is then pumped back up again during periods of low demand.
As for the battery part of the equation, water will be pumped out of the mine during a particularly sunny or windy day, effectively storing the energy as a volume of water in the top reservoir until it was needed.
There are approximately 16 miles of shafts in the complex, with the potential to have 35 million cubic feet of water flowing through them, helped by gravity.
While pumped hydroelectric storage facilities like this typically use up more energy than they generate, they are important in balancing electricity loads during peak times, when other renewable energy sources – like sunshine and wind – might not be available.
The transformed 200 megawatt plant would also utilize energy from wind turbines, solar panels, and biomass sources installed on the surface above the mine.
A positive byproduct of the project will be employment. This is particularly important for areas that have traditionally relied on fossil fuel production for their livelihood.
If the Prosper-Haniel plant comes online in 2018 as planned, it will help the surrounding North-Rhine Westphalia region meet its target of having 30 percent of its energy coming from renewable sources by 2025.
Other mine conversions are currently being proposed in the United States. Work is also underway in an abandoned gold mine in Australia.