Open-loop ground source heat pumps and groundwater systems : a literature review of current applications, regulations and problems

This report presents a literature study that was carried out to collect data and information required for developing a strategy to assess the suitability and sustainability of UK aquifers for (open-loop) GSHP installations. Developing such a strategy requires a good hydrogeological understanding but also a good knowledge of what GSHP systems are currently in use, how they are used, what problems are associated with their use and how they are regulated. Once this is understood, a methodology can be devised that assesses the suitability of an aquifer/location for GSHP installations and considers its sustainable use. Considering the complexity of influencing factors and processes, this is likely to include the use of numerical models and/or data management tools, such as GIS. This report collects and summarizes the information available in the contemporary literature on open-loop ground source heat pump (GSHP) applications. Chapter 1 provides a brief introduction and background information on the subject. In Chapter 2, information on the general use of open-loop GSHP technology within the UK are gathered together with statistics on the number of installations and capacities. Chapter 3 gives specific examples of schemes that are currently in operation in the UK and worldwide. Where available, this includes system-specific data such as abstraction rates, thermal capacities and information on the system’s design. Chapter 4 summarizes available information and data on the costeffectiveness of GSHP installations while Chapter 5 discusses potential problems associated with the running of such schemes. Chapter 6 is concerned with the regulation of GSHP systems. It gives a brief outline of existing regulatory approaches as currently employed within different European countries as well as the US. Finally Chapter 7 examines existing modelling approaches that have been used to investigate how GSHP schemes impact on the source aquifer. The chapter also reviews GIS-based tools that evaluate the suitability and sustainability of an aquifer for GSHP installations

Combined impacts of future land-use and climate stressors on water resources and quality in groundwater and surface waterbodies of the upper Thames river basin, UK

It is widely acknowledged that waterbodies are becoming increasingly affected by a wide range of drivers of change arising from human activity. To illustrate how this can be quantified a linked modelling approach was applied in the Thames river basin in southern UK. Changes to river flows, water temperature, river and reservoir quality were predicted under three contrasting future “storylines”; one an extension of present day rates of economic development, the others representing more extreme and less sustainable visions. Modelling revealed that lower baseflow conditions will arise under all storylines. For the less extreme storyline river water quality is likely to deteriorate but reservoir quality will improve slightly. The two more extreme futures could not be supported by current management strategies to meet water demand. To satisfy these scenarios, transfer of river water from outside the Thames river basin would be necessary. Consequently, some improvement over present day water quality in the river may be seen, and for most indicators conditions would be better than in the less extreme storyline. However, because phosphorus concentrations will rise, the invoked changes in water demand management would not be of a form suitable to prevent a marked deterioration in reservoir water quality

Geothermal Technologies : analysis of written evidence from the Environmental Audit Committee inquiry

In July 2022, The UK Parliament’s Environmental Audit Commission (EAC) launched an inquiry on geothermal technologies as part of their Technological Innovations and Climate Change inquiry (https://committees.parliament.uk/work/6777/technological-innovations-and-climatechange- geothermal-technologies/publications/). The inquiry focussed on Enhanced Geothermal Systems and Mine Water Energy Systems. It investigated the potential scale of their deployment in the UK to provide heat and power; the role geothermal technologies could have in the UK’s Energy Strategy and what barriers there are to the deployment, economic impact, and environmental impact of these technologies. As part of the inquiry, the EAC issued a call for the submission of written evidence to provide answers to one or more of the following questions: 1. What role can geothermal technologies take in the transition to net zero in the UK? 2. What barriers (technological, regulatory, or otherwise) are there to deploying operational geothermal technologies in the UK? 3. What is the scale of the potential market for geothermal energy sources and which geographic or other geological types are most suitable for exploitation of this natural resource? 4. Are current government support schemes sufficient to grow geothermal energy deployment in the UK? 5. What environmental concerns are associated with geothermal technologies, and are they appropriately accounted for in regulations? 6. What risks are there to investors, operators, and consumers of geothermal energy? How can these be mitigated? 7. How does the density of mine water systems affect their efficiency? Could widespread uptake of geothermal systems in dense population centres lead to a reduction in their ability to provide heat? 8. What economic impact could the deployment of mine water geothermal systems have on the areas in which they are deployed? The written evidence received by the EAC for this inquiry is published on the UK Parliament website at https://committees.parliament.uk/work/6777/technological-innovations-and-climatechange- geothermal-technologies/publications/written-evidence/. This report captures a qualitative analysis of this evidence. It specifically investigates what opportunities, challenges and barriers are identified by the submissions as well as the support measures that are suggested for developing a geothermal industry in the UK

Unlocking the potential of geothermal energy in the UK

This report is intended to provide technical information that complement the BGS Science Briefing Note: Deep impact: Unlocking the potential of geothermal energy for affordable low-carbon heating in the UK [1]. It gives a general overview of the deep geothermal opportunities that exist in the UK (although regional geothermal potential is not discussed here) as well as of financial, policy and regulatory actions that are needed to support the effective development and exploitation of deep geothermal resources in the UK. The recommendations are applicable to the UK government and its departments as well as to devolved administrations in Scotland, Northern Ireland and Wales, and devolved policy areas, such as heat policy and planning, in the respective nations. Following the introduction, the report is organised in three sections. In Section 1, details are given of the UK’s deep geothermal resources and how and where they could be utilised. Section 2 focuses on the experiences of continental Europe and the policies that have enabled the growth of a geothermal industry. Section 3 considers key policies and regulatory actions identified as necessary to drive the development of the UK geothermal sector from its current status of infancy to a mature technology that is universally recognised and utilised by a wide range of stakeholders, end-users and supported by investors

Nested shallow geothermal systems

The long-term sustainability of shallow geothermal systems in dense urbanized areas can be potentially compromised by the existence of thermal interfaces. Thermal interferences between systems have to be avoided to prevent the loss of system performance. Nevertheless, in this work we provide evidence of a positive feedback from thermal interferences in certain controlled situations. Two real groundwater heat pump systems were investigated using real exploitation data sets to estimate the thermal energy demand bias and, by extrapolation, to assess the nature of thermal interferences between the systems. To do that, thermal interferences were modelled by means of a calibrated and validated 3D city-scale numerical model reproducing groundwater flow and heat transport. Results obtained showed a 39% (522 MWh·yr-1) energy imbalance towards cooling for one of the systems, which generated a hot thermal plume towards the downgradient and second system investigated. The nested system in the hot thermal plume only used groundwater for heating, thus establishing a positive symbiotic relationship between them. Considering the energy balance of both systems together, a reduced 9% imbalance was found, hence ensuring the long-term sustainability and renewability of the shallow geothermal resource exploited. The nested geothermal systems described illustrate the possibilities of a new management strategy in shallow geothermal energy governance

Global groundwater modeling and monitoring: opportunities and challenges

Groundwater is by far the largest unfrozen freshwater resource on the planet. It plays a critical role as the bottom of the hydrologic cycle, redistributing water in the subsurface and supporting plants and surface water bodies. However, groundwater has historically been excluded or greatly simplified in global models. In recent years, there has been an international push to develop global scale groundwater modeling and analysis. This progress has provided some critical first steps. Still, much additional work will be needed to achieve a consistent global groundwater framework that interacts seamlessly with observational datasets and other earth system and global circulation models. Here we outline a vision for a global groundwater platform for groundwater monitoring and prediction and identify the key technological and data challenges that are currently limiting progress. Any global platform of this type must be interdisciplinary and cannot be achieved by the groundwater modeling community in isolation. Therefore, we also provide a high-level overview of the groundwater system, approaches to groundwater modeling and the current state of global groundwater representations, such that readers of all backgrounds can engage in this challenge

Characterization of a fluvial aquifer at a range of depths and scales: the Triassic St Bees Sandstone Formation, Cumbria, UK

Fluvial sedimentary successions represent porous media that host groundwater and geothermal resources. Additionally, they overlie crystalline rocks hosting nuclear waste repositories in rift settings. The permeability characteristics of an arenaceous fluvial succession, the Triassic St Bees Sandstone Formation in England (UK), are described, from core-plug to well-test scale up to ~1 km depth. Within such lithified successions, dissolution associated with the circulation of meteoric water results in increased permeability (K~10−1–100 m/day) to depths of at least 150 m below ground level (BGL) in aquifer systems that are subject to rapid groundwater circulation. Thus, contaminant transport is likely to occur at relatively high rates. In a deeper investigation (> 150 m depth), where the aquifer has not been subjected to rapid groundwater circulation, well-test-scale hydraulic conductivity is lower, decreasing from K~10−2 m/day at 150–400 m BGL to 10−3 m/day down-dip at ~1 km BGL, where the pore fluid is hypersaline. Here, pore-scale permeability becomes progressively dominant with increasing lithostatic load. Notably, this work investigates a sandstone aquifer of fluvial origin at investigation depths consistent with highly enthalpy geothermal reservoirs (~0.7–1.1 km). At such depths, intergranular flow dominates in unfaulted areas with only minor contribution by bedding plane fractures. However, extensional faults represent preferential flow pathways, due to presence of high connective open fractures. Therefore, such faults may (1) drive nuclear waste contaminants towards the highly permeable shallow (< 150 m BGL) zone of the aquifer, and (2) influence fluid recovery in geothermal fields

User guide : web tool for the initial assessment of subsurface conditions for open-loop ground source heat pump installations (West Midlands)

This report describes the use of the open-loop ground source heat pump web tool for the West Midlands and provides some technical information on the tool development and underlying data sets. Part 1 provides the background information to this study and outlines the purpose of this tool and the anticipated user groups. Part 2 explains how to use the tool. It provides detailed explanations of the different layers and their meaning within the context of GSHPs. It also explains how to use the results table and the visual summary of the results (Chernoff faces). Furthermore, this section outlines the limitations of the tool and lists the different aspects that are not considered by the tool. Where possible, it provides references and links to additional data sources that address the particular aspects which are not included in the tool. Part 3 provides more detailed information on how the individual data layers were derived. This information is not necessary to use the tool, but is included here for the interested few and for reference. In Part 4, links to data sets and additional resources are given that can help with a more detailed assessment of suitability and the planning of open-loop GSHP schemes. Please note that this tool provides only an initial assessment about whether an area may be suitable for an open-loop GSHP. You will need to undertake a detailed hydrogeological and environmental assessment of your location if you wish to install an open-loop GSHP

Nitrate concentrations in Nithsdale groundwater, 2004

This report describes the results of a survey of groundwater nitrate concentrations in the Lower Nithsdale nitrate vulnerable zone (NVZ), southwest Scotland. The survey was carried out during September 2004. Rigorous field sampling techniques were used, and the samples analysed in the BGS laboratories at Wallingford. Shallow groundwater was targeted, where the effects of recent land use (within the past 10 years) would be reflected in the samples. Twenty-one sites were sampled comprising 5 springs and 16 boreholes; all the sites were rural – thirteen were located on dairy farms. None of the boreholes showed any signs of contamination from surface water. Most were located in huts with concrete plinths, others were under manhole covers in fenced areas. The springs were more vulnerable to surface water contamination. The median concentration of nitrate from the 21 samples was 33 mg NO3 L-1. Six samples had concentrations greater than 50 mg NO3 L-1, a further 3 sites had concentrations between 40 and 50 mg NO3 L-1. All sites with concentrations greater than 40 mg NO3 L-1 are located on dairy farms. There is broad agreement between nitrate concentrations measured in this survey and a previous survey in August 2002. This current survey indicates much higher nitrate concentrations than monitored by SEPA from their 12 monitoring sites in Nithsdale. This is due to the nature of the sampled sources. The SEPA monitoring network in the area comprises deep boreholes in the Permian bedrock; age dating has shown that much of the water sampled is pre-1950s. In contrast, much of the groundwater sampled during the current survey is young – recharged within the past decade. By making corrections for the dilution factor from the older water at the SEPA sites, it is possible to estimate nitrate concentrations in the recently recharged groundwater. These corrected concentrations are considerably higher, and consistent with those measured from the shallow groundwater sources in this current survey. In the light of this present survey, it is recommended that SEPA review the monitoring network in the Lower Nithsdale. Several shallow sources, which contain a high proportion of modern water, and are regularly pumped, should be adopted, and data from the existing deep sources should be interpreted in the context of the age of the groundwater sampled