D2 Grids

Grid-connected low-temperature heating and cooling solutions based on mine heaters enable a sustainable contribution to the heat transition. The "D2Grids" project starts here and applies this concept through the development of the former Dannenbaum coal mine on Mark 51°7 in Bochum.



The aim of the d2grids project is to build a 5th generation heating and cooling network on Mark 51°7, the former Opel site in Bochum. Based on mine water from the former Dannenbaum colliery, the approximately 70-hectare site will be sustainably supplied with geothermal energy.

As part of D2Grids, the underground development of the Mark 51°7 site is being implemented. The mine was hydraulically developed via two directional boreholes. While the first borehole was drilled in the 8th level at about 820 m below ground (temperatures of approx. 35°C), the second borehole taps the 4th level at a depth of approx. 330 m below ground ~ 19°C) Besides the realisation of the two boreholes, the grid connection to a first pilot customer and the corresponding heat pump are also part of the project.

The operators and owners of the network are Stadtwerke Bochum and its district heating subsidiary, FUW GmbH; Fraunhofer IEG was responsible for the hydrogeological simulation of the old colliery, the mining law approval planning, the design of the boreholes and the borepaths, as well as the support and monitoring of the drilling operations. In 2022, the thermal and hydraulic productivity will be scientifically validated.

The downstream heating and cooling network is a 5th generation network. Demand-driven, bidirectional and at a low temperature level, network losses are minimised and the possibility is created to close energy loops between the connected customers.

In the Ruhr region in particular, abandoned coal mines at a number of other locations offer a large reservoir of warm mine water. D2grids on Mark51°7 provides the blueprint to be able to further realise grid-connected low-temperature heating and cooling solutions based on mine water in the short and medium term.