An old coal mine will store surplus power from renewable energy.
Germany is undertaking a project which will convert a source for old fossil fuels into storage for renewable, clean energy. The project involves converting an old coal mine into an energy storage facility that will hold onto excess solar and wind power energy when the demands are low, only to deliver that power back into the grid when demand is high.
The Prosper-Haniel coal mine in the German state of North-Rhine Westphalia will be converted into a 200 MW pumped-storage hydroelectric reservoir. The system will be able to power 400,000 homes and acts like a giant battery. The mine, which was founded in 1863, is one of a small number of active coal mines in Germany, and produces around three million tonnes of coal per year. A lack of federal subsidies meant that the mine was slated for closure in 2018. Instead, the mine workers will remain at the site as it is converted to its new function.
A pumped storage hydroelectric facility like the one being built into the mine, involves the use of two water reservoirs. One of the reservoirs is stored at a higher altitude, and as water drains into the lower reservoir, it drives a turbine which produces electricity. Whereas a traditional hydroelectric plant would drain any water passing the turbine, this facility will instead store it, and when demand for electricity is low, it can be pumped back up to the top reservoir so it can be used again at a later time. Specific to this facility, the lower reservoir is deep down in the mine, some 1,200 meters below ground level, at the end of 25 kilometers of pipes.
The project is part of an ongoing effort in Germany known as Energiwende, or “Energy Transition”. The German government is hoping to convert some 80% of their energy to renewable sources by 2050, and with intermediate targets of 35 to 40 percent share by 2025 and 55 to 60 percent by 2035. They are already well on their way, with a third of their power coming from renewable sources in 2015.