This natural source of energy supplies hot water from the deeper mine passages and cool groundwater from the passages closer to the surface. As a result of natural geothermal heating, this groundwater maintains a constant temperature.
In 2005 five wells (sources) were drilled down to the underground rock gallery. Two warm wells in the northern part of Heerlen (to a depth of 700 metres below ground level) for the extraction of warm water with a temperature of about 28 °C and two cold wells in the southern part of Heerlen (to a depth of 250 metres) for the extraction of cold mine water with a temperature of about 16 °C. A fifth well, located between them, (drilled to a depth of 350 metres) serves as a discharge well for return of the cooled warm water and heated cold water.
Eight kilometres of piping
Until 2012, heating and cooling water was supplied to two end users via an eight kilometre long three-pipe mine water distribution network, called the ‘backbone’ or ‘main’. These first users were the Heerlerheide Centre (HHC) Gen Coel complex with 30,000 m² of homes, supermarket, offices, community facilities, and the office of Statistics Netherlands (CBS) with 22,000 m² of office space. In 2008 Mijnwater B.V. had the first mine water geothermal plant (Gen Coel) in the world.
This means that Minewater 1.0 customers were connected to the mine water network individually. An energy installation with heat pumps was used in each building to deliver the desired heating and cooling, depending on the weather. The warm water, which has a lower temperature than what we think of as ‘hot’ water, is not suitable for consumption or industrial use. It provides relatively low temperature warm water for heating and relatively high temperature cool water for cooling buildings and homes.