HEAT NETWORKS | MINEWATER integrating available data with knowledge of mining techniques, these values have been incorporated into a comprehensive 3D model. The estimated volume of the mined area in the Winter seam, which serves as the cold source, is approximately 13.1 million.m3, whereas the Barnsley seam has a significantly larger volume of 92.5 million.m3. In heat recovery mode, to achieve the extraction of 5oC of heat during circulation, it is necessary to store around 3.87M.m3 of water in abandoned mines. So, the minimum void volume required to support a 7MW storage system is 3.87 million. Estimating the exact void volume in Barnsleys abandoned mines is challenging. Mines worked after 1949 are anticipated to be collapsed because of high-rate excavation using the longwall Figure 2: Example of borehole data recorded from 1896 technique (where a long wall of coal is extracted in a single continuous operation), while older mines are only partially collapsed. Additionally, roadways and connections may be blocked at certain points. Figure 4 provides an estimate of the required mine volume for a range of likely parameters. It compares the Winter and Barnsley volumes with the required mine volume, ranging from the worst-case scenario to the most probable situation. The Barnsley seam appears sufficiently large, with workings likely to be connected, and is a strong candidate for providing a warm water source and possible storage. The Winter seam, for balancing the scheme, requires additional volume, which may be met locally by the Beamshaw seam, which is hydraulically connected to the Winter seam, and so doubles the capacity. A well into the deeper Beamshaw seam offers the advantage that gravity would help draw the water from the Winter to the Beamshaw seam while pumping. The overall system efficiency may drop because of higher pumping costs in deeper seams, but such a scheme could potentially heat 1,800 buildings. The results obtained will undergo further analysis to quantify the uncertainty ranges associated with this project, significantly reducing the risk of costly test boreholes. Correlating the model results with temperature measurements and flow tests should allow the assessment of the commercial viability of this project and for similar endeavours in Barnsley and beyond. This effort is important as it assists local authorities in accurately gauging uncertainties around future geothermal energy systems using minewater, a key resource that should be efficiently exploited as the UK transitions to a net zero economy. CJ ESHAGH GOUDARZI is a PhD researcher at London South Bank University Figure 3: Digitised boreholes. Nature of strata vs depth vs transmissivity Winter seam mined volume Barnsley main seam mined volume Required mine volume with 10% void space Required mine volume with 15% void space Required mine volume with 20% void space m3 Figure 4: Modelling mine volume for =5OC 36 November 2023 www.cibsejournal.com Abandoned mines can be found below 25% of the UKs buildings