Monitoring and Modelling Mine Water Geothermal At The Uk Geoenergy Observatory In Glasgow, Uk.

The British Geological Survey (BGS) has constructed the UK Geoenergy Observatory in Glasgow and operates this at-scale underground science laboratory on behalf of the Natural Environment Research Council and UK Research and Innovation. As one of the two new UK Geoenergy Observatories, the Glasgow Observatory facilitates collaborative research to improve understanding of subsurface processes, environmental and induced change related to mine water energy. It provides scientific and engineering infrastructure for investigating the shallow, low-enthalpy geothermal energy and thermal storage resources available in abandoned and flooded coal mine workings. Such resources could provide low-carbon renewable heating and cooling for community-scale district heating networks and other heat demands. The Glasgow infrastructure is not connected to a heat user so it is flexible for research and development. The facility includes two abstraction and two injection mine water boreholes spaced 10-190 m apart, equipped with submersible well pumps optimised for up to 12l/sec, a heat centre with three types of heat exchanger, a 200kW output heat pump/chiller for active heating or cooling of mine water in a sealed open loop, a sensor logging system, plus 8 additional boreholes and extensive environmental monitoring equipment. Borehole monitoring capability includes hybrid fibre-optic distributed temperature sensing (DTS) cables for measuring thermal change and performing heat pulse tests, and sensors for measuring geoelectrical properties. The latter use arrays of permanently installed downhole electrodes to measure subsurface electrical resistivity within the top ~90 m, enabling both in-hole and cross-hole tomography (ERT) for tracking subsurface changes in 4D. Collecting high-quality subsurface DTS monitoring data allows detection of small changes (±0.01°C) in temperature every 0.25 m along the cable, within the mine water aquifer and rock mass as part of ongoing baseline change monitoring, as well as thermal pulses during and after heat injection and extraction experiments. Together with pressure data from downhole hydrogeological data loggers, and flow and monitoring of heat pump/chiller performance, this provides an at-scale field facility for evaluating the engineering and energy performance of the various components of mine water geothermal systems. The evidence collected at the facility will improve understanding of environmental sustainability, informing regulation, and supporting public engagement in geothermal energy. An initial hydrogeological and hydrochemical conceptual model developed using borehole, pump test and baseline monitoring data has been used to interpret results from the system commissioning phase. Integrated analysis of hydrogeological, geoelectrical, thermal and geochemical data is shown to provide a much more comprehensive understanding of geothermal processes in low temperature mine water systems. Insights gained from research undertaken during commissioning will enable visiting researchers to fine-tune their proposals for research and innovation at the Glasgow Observatory.