Old Coal Mines Adapted to Create Geothermal Energy
Recently the town of Heerlen in the Netherlands repurposed an old abandoned coal mine into a brilliant source of geothermal energy. The project takes advantage of flooded underground mine shafts, using their thermal energy to power a large-scale district heating system. Dubbed the Minewater Project, the new system recently went online and provides 350 homes and businesses in the town with hot water and heating in the winter and cool water in the summer.
In the Netherlands, coal was one of the main sources of energy from the turn of the century up until around 1959, when large amounts of cheap natural gas were discovered in the north. The coal industry lost market share and mine after mine was closed down – in the city of Heerlen, for instance, the coal mine was closed and the shafts were flooded with water and have been unused for the last 30 years.
District heating and cooling involves providing hot or cold water to a number of businesses or homes in an area in order to heat or cool the building. Sometimes the hot or cold water is used for an industrial process, but mostly the water flows through pipes to individual buildings and into radiators designed to transfer heat into a room. This is achieved through economies of scale by producing large amounts of water for individuals and operating much like an electric grid. The system now in place in The Netherlands in Heerlen makes use of an abandoned site, essentially a brownfield, and uses the naturally occurring geothermal heat to warm the water that has flooded the underground mines.
Five new wells were drilled in various locations around town to access the underground mine shafts. Each well is 700 meters (2,300 ft) deep and can pump out nearly 80 cubic meters (2,800 cubic feet) of water per hour. The water temperature at the bottom of the well is 32 C (89 F) and gradually cools to 28 C at the surface. Warm water from the mine is brought to the surface where a heat pump extracts the heat in order to supply hot water to households in the area. Meanwhile the Minewater is pumped back down 450 meters to be reheated. In the summer, to provide cooling, water will be pumped from a much shallower depth of 250 meters, where it is not so warm.
The area supplied by the Minewater is a relatively new development and includes a supermarket and a brand new cultural center and library as well as many homes and businesses. While the cost of the heating and cooling is not much different than before, customers can be assured of stable prices in the future compared to the cost they could incur by using fossil fuels.
The Netherlands, which is also experimenting with energy generation from chicken manure, is just one of the test sites for this new technology. Other test sites for the Minewater Project include Aachen, Germany and Lorraine, France. Much of the technology for this project is being developed as needed, since there is no precedent for this type of geothermal energy project. At the beginning of October the Minewater Conference was held in Heerlen to discuss the technology and hold workshops and meetings to improve the project. The attendees produced a very interesting video on their work and progress.
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