IAP-25-124

MINELOOP: Investigating MINEwater systems using closed-LOOP geothermal technologies

Geothermal energy supports net zero targets and energy security by providing a reliable, low-carbon, local energy source. Minewater geothermal systems represent a largely untapped resource that often coincides with major population centres across the UK, but their use has been limited by technical uncertainties in open-loop systems. This PhD project will investigate the interactions between borehole heat exchangers (BHEs)/closed-loop technology and flooded minewater systems, with the aim of developing low-risk, high-performance geothermal energy solutions. The PhD will examine high-density polyethylene U-tube systems suspended in minewater voids, focussing on: i) their comparative performance to grouted BHEs, ii) the influence of minewater circulation on thermal efficiency and heat plume evolution; iii) predicting flow pathways in a real-world case study emulating a system with high throughflow rates and their implications for system performance; and iv) the potential of thermal energy storage to enhance overall efficiency.

In Year 1, coupled numerical models using state-of-the-art tools such as FEFLOW and COMSOL will be developed to simulate thermal and hydraulic behaviour under both suspended U-tubes in minewater and conventional grouted BHE configurations. In Year 2, controlled experiments will be undertaken at the Glasgow Geoenergy Observatory to observe hydraulic and thermal responses and flow pathways, generating high-quality data for model calibration. This will emulate a system with high throughflow rates and the data will be used for site characterisation and geological assessment for hypothetical development using closed-loop technology. Year 3 will integrate experimental and numerical approaches to produce robust predictive models of thermal and hydraulic processes in the subsurface. This will also include the incorporation of thermal energy storage into the system.

There will be a strong focus on investigating how different geological and hydrogeological regimes impact geothermal performance for both conventional extraction and thermal energy storage. By demonstrating how closed-loop systems—without hydraulic exchange with subsurface fluids—can be easily installed in mine workings while benefitting from natural minewater circulation, the project will provide critical insights for environmental regulators, policymakers, industry stakeholders, and the academic community.

The project will apply a mixed-methods approach combining numerical modelling, field experimentation, and hydrogeological analysis. Numerical simulations will be carried out using FEFLOW (or COMSOL/alternative) to represent coupled heat, flow, and transport processes in minewater systems, with additional model development and customisation undertaken in MATLAB or Python to extend capabilities and explore sensitivity analyses. Experimental data from controlled experiments at the Glasgow Geoenergy Observatory will provide direct evidence of hydro-thermal responses and geological characterisation, which will help to determine sustainable resource use when coupled to a suspended U-tube system. All datasets will be integrated into a comprehensive data analysis workflow, using statistical and forward modelling methods to calibrate and validate numerical models. This combined approach ensures robust understanding of U-tube–minewater interactions and supports the development of predictive tools and operational guidelines for effective deployment.

Year 1

In Year 1, the project will focus on establishing the foundations for modelling and experimental work. Key activities will include a comprehensive literature review of minewater-based geothermal systems and closed-loop borehole heat exchanger designs, providing the conceptual basis for subsequent research. Training in numerical modelling will be undertaken, with model development carried out in FEFLOW (or alternative) and complemented by custom scripts in MATLAB or Python to represent different closed-loop configurations (i.e., suspended v grouted). Alongside modelling, the experimental programme will be planned and finalised in preparation for fieldwork at the UK Geoenergy Observatory in Glasgow, including the design of transient tests, monitoring strategies, and risk assessments. The main deliverables for this phase will be operational numerical models of closed-loop performance in minewater systems, a finalised experimental design for Year 2 deployment, and the preparation and submission of a conference abstract to disseminate initial findings and establish early academic impact.

Year 2

Year 2 will focus on experimental implementation and data acquisition, combined with site-specific modelling. A subsurface experiment will be conducted at the UK Geoenergy Observatory in Glasgow, with monitoring of hydro-thermal responses across the minewater system, exploiting distributed temperature sensing and hydraulic data loggers at Glasgow. It is envisioned there will be up to 10 days of hydraulic testing designed to emulate a minewater system with high rates of throughflow. Experimental design and deployment will be closely linked to numerical model development, with site-adapted simulations created to represent groundwater flow pathways and thermal transport within the mineworkings. Collected data will be processed and analysed to characterise geological conditions, system behaviour and support model calibration. Key deliverables for this phase will include a developed minewater model for the Glasgow site, raw and processed datasets from the field experiments, and validated site-specific numerical models capturing minewater dynamics. By the end of this stage, the student will be expected to prepare and begin drafting a journal article based on the analysis of experimental results.

Year 3

Year 3 will emphasise advanced model integration and scenario analysis. Building on the validated Glasgow models, the focus will be on simulating the inclusion of suspended u-tubes within minewater systems. Parametric analyses will be performed to evaluate the influence of placement, design, and operating conditions on performance and risk, with outcomes informing practical design and operation guidance. This will also involve the incorporation of underground thermal energy storage to the system to evaluate the potential for seasonal heat storage. Deliverables will include the submission of at least one peer-reviewed journal paper, with a second manuscript in preparation focusing on combined modelling of U-tubes and mineworkings. The student will also present findings at an international conference, ensuring international academic visibility and knowledge exchange.

Year 3.5

The final 6 months will be dedicated to consolidation, synthesis, and dissemination. The primary focus will be the writing and submission of the PhD thesis, incorporating results from numerical modelling, experimental analysis, and scenario-based evaluations. Alongside thesis preparation, dissemination will include presentation at a major conference, submission of further journal manuscripts, and the publication of curated experimental datasets and models for community use. This phase will ensure the project delivers lasting academic, industrial, and policy impact through both scientific outputs and open-access resources.

The student will receive a comprehensive programme of training to support both technical and professional development. Core technical training will include in-house numerical modelling sessions, supplemented by access to specialised FEFLOW online courses to build expertise in coupled heat and flow simulations. Hands-on training will also be provided in the design, operation, and data analysis of geothermal experiments at the UK Geoenergy Observatory in Glasgow, ensuring practical skills in fieldwork and data processing. In addition, the student will have the opportunity to participate in British Geological Survey internal training workshops, which cover a range of transferable skills such as academic writing, effective presentation, and communication for different audiences.
By the end of the project, the student will have developed advanced technical skills in numerical model development, coding (MATLAB/Python) and hydrothermal data analysis, and the integration of experimental and modelling approaches. Alongside these, the student will acquire key transferable skills in presenting research, writing for academic and non-academic audiences, and engaging with stakeholders, providing a strong foundation for future academic or industry careers.