Geothermal Energy Extraction Research Articles

A methodology for deciding on well seal options for abandonment

The energy transition to achieve net zero anthropogenic CO 2 emissions will require permanently sealing and abandoning wells or boreholes drilled for many different purposes, including: underground CO 2 storage; hydrogen storage; geothermal energy extraction; site characterization for radioactive waste repositories; and hydrocarbon extraction. It is necessary to objectively decide what sealing materials, combination of materials and methods of emplacement are optimal for a given well sealing project, taking into account the properties of lithologies penetrated, the physical and geochemical conditions around the well, the geometry of the well, and characteristics of well engineering. A workflow that would allow for a structured approach to designing well seals during well decommissioning and a set of complementary tools that will enable an informed, structured, transparent and traceable process for designing a well decommissioning sealing solution for a particular well in a given geological environment is presented in this paper. The tools include: (1) a database of Features Events and Processes; (2) a decision tree for evaluating different well sealing options and for documenting the rationale for decisions; (3) an approach for comparing options using multiple decision trees; (4) and a suite of simplified numerical models to inform judgements.

High-pressure thermal conductivity, speed of ultrasonic measurements and derived elastic modulus of sandstones with different porosity

The effect of pressure on thermal conductivity is an important for understanding the heat transfer processes in modeling applications in geothermal reservoirs and for optimization of the technology of geothermal energy extraction processes. The primary factors affecting the economics of any geothermal energy recovery process are the amount of heat present in the geothermal reservoir and rate of heat extraction, which strongly depend on the thermal properties of the reservoir rocks, which are functions of both temperature and pressure. The present paper aims to study the variation of thermal conductivity of five sandstone samples from the Germany Geothermal Field with various total (open and close) porosities of (6.8, 13.0, 15.44, 21.3, and 21.5%) with pressure up to 203 MPa, to overcome the existing lack of thermal conductivity data for the geothermal reservoir modeling. The improved steady-state heat-flow technique (contact method) was used to precisely (with an uncertainty of 4%) measure the thermal conductivity of the sandstone samples. Unlike previous studies, in the present work the effect of the contact thermal resistance on the measured values of thermal conductivity has been taken into account using a calibration procedure to increase the accuracy and reliability of the measured data. The results show that with the increase of the pressure at a fixed temperature of 293.15 K, the thermal conductivity of sandstone is linearly increasing with pressure from 0.52 to 1.73 GPa−1 depending on sandstone structural and mineralogical composition, porosity, and other characteristics, which falls in the same range reported by other authors for rock samples from different geothermal fields. The derived values of the thermal conductivity pressure coefficient are crucial for geothermal studies in order to effectively use the geothermal resources of the region, and are useful for scientific applications such as the development and testing of the accuracy, reliability, and predictive capability of existing thermal models of geothermal reservoirs. Based on the present experimental results, statistical analysis (correlation analysis) was revealed between the measured thermal conductivity of sandstone samples and open and close porosities. The role of closed and open porosities on the pressure dependence of thermal conductivity and elastic moduli is discussed. For the first time, we experimentally observed the difference of the influence of the open and closed porosities on the thermal conductivity and elastic properties of sandstones. It was experimentally confirmed that the effect of closed porosity on the thermal conductivity of sandstones is significantly greater than that of open porosity by 15 to 20%. The obtained results show that it is of great importance to study the changes in the thermal properties of the sandstones under pressure at realistic reservoir conditions for geothermal studies.

Impact of dual-fracture location on heat extraction from Enhanced geothermal system in low-permeability reservoirs

As environmental and economic issues exacerbated by traditional fossil fuels intensify, Dry Hot Rock geothermal energy has garnered significant attention due to its immense potential. Current research predominantly focuses on the heat extraction effectiveness in complex fractures within Enhanced Geothermal Systems, with relatively less emphasis on fluid behavior between large fractures. This study employs finite element software to establish a multi-horizontal well model in a low permeability reservoir (5 × 10-17 m2), analyzing the impact of different spatial configurations of two fractures on fluid flow, heat transfer, and heat extraction efficiency. The results indicate that fractures are the primary channels for fluid flow in low permeability reservoirs. Optimal heat extraction occurs when fractures are parallel, spaced 100 m apart, and perpendicular to the horizontal well, with significant threshold effects of fracture spacing and angle on temperature distribution. The highest heat extraction is achieved at a 37° intersection angle of fractures at the production well. Over a 60-year production period, reservoir extraction degrees for parallel or intersecting fractures range from 8 % to 15 %, while that for fracture communication between injection and production well horizontal segments is only 1.91 % to 3.01 %. Under the optimal injection scenario, cumulative 60-year heat production for parallel, intersecting, and communicating fractures is 2.13 × 1018J, 2.20 × 1018J, and 2.22 × 1018J, respectively, with the best heat extraction efficiency when fractures communicate. Additionally, under constant flow rate and inlet temperature, outlet temperature and system thermal power show near-linear declines, while reservoir extraction degree rises linearly. This study provides crucial theoretical support and practical guidance for the efficient extraction of geothermal energy.

Hydrothermal evolution analysis and performance optimization in multi-well fractured reservoirs for enhanced geothermal systems

The successful development of Enhanced Geothermal Systems relies on constructing high-quality fracture networks. However, the mechanism of hydrothermal evolution in geothermal reservoirs with artificial fracture networks remains poorly understood. This study aims to elucidate the mechanism of hydrothermal evolution in fractured reservoirs to optimize geothermal energy extraction. Novel metrics, namely reservoir heating efficiency and reservoir flow efficiency, were introduced to assess performance. The study comparatively investigated six fracture structures and evaluated their impact on system production. Key findings reveal that fluid flow in multiple horizontal wells fractures reservoirs efficiently, with heat effectively extracted from the edges of the Stimulated Reservoir Volume. Enhanced reservoir heating efficiency and optimized flow efficiency were achieved due to improved heat exchange and fluid diversion. Optimal hydrothermal evolution was realized with a reservoir heating efficiency of 0.2022 and a reservoir flow efficiency of 0.2398, using a configuration of a 0° rotation angle, 30 kg/s injection mass flow, 60 °C injection temperature, 3.12 mm hydraulic fracture aperture, and 200 m production well spacing. These findings provide valuable insights into reservoir design and production strategies for Enhanced Geothermal System.

Petroleum Engineering Research Shifts Focus From Oil and Gas to New Horizons

Undergraduate education in petroleum engineering (PE) has survived the latest downturn in the industry, and enrollment has started to show an uptick in numbers. However, a different trend is evident in graduate training and academic research: the number of researchers being trained in oil and gas topics is drastically dropping. The story can be summarized in Fig. 1. Funding trends in PE departments have been shifting away from oil and gas research. These shifts require large investments in skill-building, expertise, and laboratory infrastructure, which makes it much harder to reverse the trend. Consequently, the shift may permanently alter the identity of PE departments, something that will not impact only graduate education but could alter the overall identity of these departments and the workforce they train. The data shared in Fig. 1c shows that more than 50% of the 2023 research awards, which will fund graduate students earning degrees between 2025 and 2026, are going to be invested in geothermal, carbon management, hydrogen, emissions, and other topics that do not support improving oil and gas resource extraction. While 73% of the 2023 MSc and PhD graduates still studied oil and gas topics around reservoir, production, fracturing, and drilling, as shown in Fig. 1a, this number is expected to drop to under 50% for 2026 graduates. Fig. 1b reveals the accelerated trend of this transition, where only 65% of the publications generated from these departments in 2023 covered oil and gas topics. Under 60% of the 2024 and 2025 graduates who published in 2023 are building expertise in oil and gas research and development. The team collected data to study the trends over the past 10 years. It included over $137 million in external research funding and over 1,900 thesis/dissertations, in addition to over 1,100 publications in 2023. More details about these numbers can be found in SPE 220735. The trends in graduate training and research funding over the past 10 years are shown in Fig. 2, where the axis for graduate training is shifted by 3 years to account for the lag between the date funding was received and the graduation date for the students it supported. When looking at numbers rather than percentages (Fig. 3), oil and gas research funding to four of the major PE departments in the US dropped from $30 million in 2014 to under $10 million in 2023 as shown in Fig. 3a. Funding in these departments now hovers at around $20 million, where the gap was filled by transitioning to the study of sustainable geoenergy topics relating to carbon and hydrogen storage and the extraction of geothermal energy, as shown in Fig. 3b.

Feasibility of coaxial deep borehole heat exchangers in southern California

This paper investigates the feasibility of coaxial deep borehole heat exchanger (CDBHE) applications to the University of California San Diego (UCSD) campus. By collecting different geophysical source data for various formations and well logs around the UCSD campus, a multilayered thermophysical model for the ground on the site is established. Water circulation within a closed coaxial loop system considers the geothermal energy extraction under uncertainty consideration of the unknown deeper layers heat flow gradient as coupled with the variation of pipe insulation properties, flow rates, outer pipe diameter, grout, and depths between 1 and 4 km. A finite-element framework models the Navier–Stokes fluid flow and heat transfer in the CDBHE system, validated with a field test on CDBHE from the literature. Results show that a 4-km CDBHE could produce a thermal power of 600 kW under the optimum geological conditions at the UCSD site: the water flow rate of 2.78 L/s and a ground thermal gradient of 60 ℃/km. Thermal power shares from different layers indicate that deeper formation layers contribute more to the thermal power than the shallower layers because increasing the CDBHE length from 1 to 4 km can lead to a maximum of 900% increase in thermal power and a 50% expansion in thermal plume for a CDBHE with an insulated inner pipe between the upper and lower bound heat flow bounds. An inner pipe with an insulated depth of 2 km produces only 1–6% less power than a fully insulated inner pipe for the 4-km CDBHE, and thus, a partially insulated vacuum-insulated tube (VIT)-plastic inner pipe is suggested as the best practice. Furthermore, the CDBHE thermal power increases by 5% when the grout thermal conductivity increases from 1 to 3.65 W/(K∙m), close to the formation thermal conductivity, and then maintains almost the same, and the 4-km CDBHE with flow rates of 2.78–6.94 L/s at the UCSD site can directly supply a low-temperature heating radiator system for room heating. This study suggests practical ranges for geothermal energy extraction for southern California. A CDBHE with a well-insulated inner pipe of 0.05 W/(m∙K), the thermal power of lower and upper-bound heat flow cases can vary by 60% from the mean. Finally, water as the working fluid is more efficient than CO2, doubling CDBHE's thermal power. The effects of the investigated factors provide guidelines for future geothermal resource exploitation in southern California.

Comparative analysis on the radiative time-dependent water/kerosene-based Cu nanofluid through squeezing Riga plates with heat dissipation: Spectral quasilinearization technique

The time-dependent thermal management along with convective flows are vital in various heat transfer applications in engineering systems such as in automotive cooling systems, and industrial heat exchangers. Because of enhanced thermal conductivity, nanofluids are widely considered for advanced cooling systems such as electronics, aerospace, geothermal energy extraction, etc. The current analysis presents comparative results of the radiative, time-dependent flow of water/kerosene-based Copper nanofluids between squeezing Riga plates focusing on heat dissipation. Both the plates are embedded within a porous matrix and the influence of non-uniform heat source/sink and thermal convective boundary conditions is examined. Riga plates, generally utilized for their ability to generate electromagnetic fields provide greater control over the fluid flow. The problem designed with the inclusion of aforesaid factors is transformed into a non-dimensional form for the utilization of appropriate similarity functions. Further, the impacts of several effective terms on the flow profiles are presented followed by the numerical solution of the profile obtained using the spectral quasilinearization method. Moreover, some of the outstanding findings are; an increase in the fluid velocity is marked for the separation of the plates but the rate of enhancement in the case of kerosene is more pronounced than that of water. Further, irrespective to the type of fluids, the heat transfer rate enhances for the increasing heat fluid which provides the variation of thermal radiation.

Research Progress on CO2 as Geothermal Working Fluid: A Review

With the continuous increase in global greenhouse gas emissions, the impacts of climate change are becoming increasingly severe. In this context, geothermal energy has gained significant attention due to its numerous advantages. Alongside advancements in CO2 geological sequestration technology, the use of CO2 as a working fluid in geothermal systems has emerged as a key research focus. Compared to traditional water-based working fluids, CO2 possesses lower viscosity and higher thermal expansivity, enhancing its mobility in geothermal reservoirs and enabling more efficient heat transfer. Using CO2 as a working fluid not only improves geothermal energy extraction efficiency but also facilitates the long-term sequestration of CO2 within reservoirs. This paper reviews recent research progress on the use of CO2 as a working fluid in Enhanced Geothermal Systems (EGS), with a focus on its potential advantages in improving heat exchange efficiency and power generation capacity. Additionally, the study evaluates the mineralization and sequestration effects of CO2 in reservoirs, as well as its impact on reservoir properties. Finally, the paper discusses the technological developments and economic analyses of integrating CO2 as a working fluid with other technologies. By systematically reviewing the research on CO2 in EGS, this study provides a theoretical foundation for the future development of geothermal energy using CO2 as a working fluid.

Underpinnings of reservoir and techno-economic analysis for Himalayan and Son-Narmada-Tapti geothermal sites of India

The high capital cost and risks associated with the extraction process of geothermal energy are key factors in the project economics. This paper presents a comprehensive technoeconomic study based on reservoir heat and flow simulations along with the levelized cost of energy (LCOE) for two geothermal sites (Himalayan and Son-Narmada-Tapti i.e. SONATA) in India.Dual porosity reservoir simulation models were constructed and were used to obtain the cumulative and the dynamic thermal energy potentials of these sites. The simulation studies suggest that both sites are equally potent for geothermal energy extraction. Comparatively, the proven cumulative energy potentials for the Himalayan and SONATA sites are found to be 4.92–5.10 and 3.62–3.7 TW h, respectively, for the 30 years of production at a rate of 92 kg/s. This difference can be attributed mainly to higher temperatures and deeper sites at the Himalayan Province. Sensitivity analyses were conducted to assess the impact of various parameters, including porosity, permeability, fracture spacing, and thermal conductivity. The results suggest that porosity and permeability are the key enablers of efficient energy production. The economic feasibility study suggests that the LCOE costs are high for these sites ($148/MWh for the Himalayan and $137/MWh for the SONATA). These two sites have CO2 mitigation potential in the range of 3.12 and 11.36 Megatons from a single doublet well configuration considering the CO2 emissions from conventional coal-fired thermal power plants. Overall, SONATA can be the better prospect considering the logistics and operational challenges along with reservoir heat potential.

Harnessing the heat below: Efficacy of closed-loop systems in the cooper basin, Australia

Transitioning to renewable energy is vital for combating climate change and reducing CO2 emissions. Geothermal energy, sourced from the earth's crust, presents a promising alternative. While shallow geothermal energy extraction grows steadily, tapping into deep Hot Dry Rock reservoirs poses challenges. Sustainable utilization of deep geothermal energy is crucial for large-scale electricity generation. Australia's Habanero enhanced geothermal system (EGS) projects faced obstacles due to complex fracture networks. Borehole heat exchangers (BHEs) offer a solution, circulating a working fluid without direct contact with geofluids. This study assesses coaxial BHEs' feasibility in the Habanero reservoir using a 2D axisymmetric model (2D-AM), comparing it with a simpler 1D depth-integrated model (1D-DIAM). Both models yield similar outcomes. Additionally, results indicated that the production temperature of the coaxial BHE exponentially decreased from 250 °C to 100 °C within 10 h, rendering energy recovery for electricity generation unsuitable after 10 h of operation. The study proposes an energy recovery cycle of 10 h followed by a 110-h shutdown. Injection temperatures and flow rates significantly impact production efficiency, while steel casing's thermal conductivity has minimal influence on heat exchanger performance.

Eliminating Ecological Damage in Geothermal Energy Extraction: Fulfillment of Ecological Rights by Proposing Permits Standardization

Eliminating Ecological Damage in Geothermal Energy Extraction: Fulfillment of Ecological Rights by Proposing Permits Standardization

Geothermal Energy Extraction–Induced Ground Movement Monitoring by InSAR and Its Implication for Reservoir Management

Geothermal Energy Extraction–Induced Ground Movement Monitoring by InSAR and Its Implication for Reservoir Management

Triple-diffusive instabilities in Ellis fluid-saturated porous layers: Dynamics of oscillatory convection

Triple-diffusive convection in Ellis fluid-saturated porous layers has a wide array of real-world applications, including enhanced oil recovery, optimized geothermal energy extraction, and improved food processing and drug delivery systems. It also plays a crucial role in environmental management, particularly in controlling groundwater contamination and maintaining soil health by modeling pollutant transport and nutrient dynamics. This study explores the onset of convection in an Ellis fluid-saturated porous layer, influenced by three stratifying agents with differing diffusivities. A modified Darcy porous medium, salted from below, is subjected to horizontal throughflow driven by a prescribed pressure gradient. Through normal mode analysis, a linear stability analysis is conducted, resulting in explicit threshold conditions for the onset of convection. The findings reveal that convection begins with oscillatory motion, driven by the combined effects of the pressure gradient and solute concentration gradients. Notably, the study uncovers the emergence of disconnected, closed, heart-shaped oscillatory neutral curves, indicating the presence of three critical values of the solutal Darcy-Rayleigh number required to establish linear instability criteria and novel discovery for an Ellis fluid-saturated porous medium. Moreover, the results show that increasing the solutal Darcy-Rayleigh number and the Ellis power-law index stabilizes the system, while a higher Darcy-Ellis number leads to destabilization. The results obtained in the limiting cases are found to be consistent with those reported in previous studies.

Application of space renormalisation technique for spatiotemporal analysis of effective thermal conductivity in multiphase porous materials

Effective thermal conductivity (k¯) is a critical parameter influencing heat transfer in multiphase porous materials. This study introduces a computational approach using the space renormalisation technique to derive k¯ from segmented X-ray micro-CT images of porous media. By accounting for pore-scale heterogeneity, this approach enables detailed spatiotemporal analysis of k¯ in different porous structures. The application of this technique is demonstrated through the prediction and spatiotemporal analysis of k¯ in three different porous rock samples experiencing multiphase fluid flow: (i) steady-state two-phase flow in Estaillades carbonate, (ii) sequential flooding in Bentheimer sandstone, and (iii) immiscible three-phase flow in Ketton limestone. Results show distinct directional variations in k¯ according to phase saturations and redistributions, highlighting the sensitivity of the approach to the microstructural characteristics of porous media. The space renormalisation technique efficiently predicts k¯ with significantly reduced computational costs compared to traditional finite difference methods, making it suitable for real-time applications. The findings provide deeper insights into the dynamic heat transfer mechanisms in heterogeneous porous systems, with implications for various porous media applications such as enhanced oil recovery, geothermal energy extraction, and the design of heat exchangers in engineering systems.

Composites with Synergistically Enhanced Thermodynamic and Mechanical Properties for Geothermal Heat Exchangers

Geothermal energy, derived from the radioactive decay of elements within the Earth's core, is a renewable and clean energy source. The extraction of geothermal energy primarily depends on ground heat exchangers. To address the issue of incompatibility between corrosion resistance, high thermal conductivity, and mechanical performance in current ground heat exchangers, this study develops composites (PEPOE/SCA@SiC) composed of high‐density polyethylene (HDPE) modified with toughener polyethylene‐octene copolymer elastomer (POE) and silicon carbide (SiC) crystals modified with γ‐aminopropyltriethoxysilane (SCA). HDPE offers excellent corrosion resistance, SiC crystals provide efficient phonon transport, and SCA improves the interface compatibility of the composite. The thermal conductivity of PEPOE/SCA@SiC reaches 3.83 W m−1K−1, with a maximum tensile strength of 20.3 MPa, a tensile elastic modulus of up to 498 MPa, and a maximum bending stress of 22.2 MPa with a bending elastic modulus of 561 MPa. Corrosion resistance tests indicate no signs of corrosion in PEPOE/SCA@SiC when exposed to geothermal simulation fluids at 90 °C for 30 days. This study demonstrates that PEPOE/SCA@SiC composites have substantial potential for application in ground heat exchangers, offering promising prospects for advancing sustainable use of geothermal energy and environmental protection.

Application of pressure small signals extraction and amplification technology in abandoned well pattern for geothermal energy extraction and H2 storage: Numerical modeling and economic analysis

Using abandoned reservoirs for geothermal energy development and H2 storage is economical. The impact of complex fractures from long-term oil and gas extraction on geothermal energy and H2 storage is not yet clearly understood. Here, a pressure small signals extraction and amplification (PSEA) technology is developed to improve reservoir monitoring accuracy. This technology is capable of coupling many pressure transient analysis models to invert parameters for multiple scenarios. This work establishes numerical models to simulate the effects of geothermal energy extraction and H2 storage over 5000 days. Results show that this technology improves the accuracy of inverted parameters by 4–14 times. This technology adjusts the production temperature differences in a single injection-production system from 1.4K to 6.5K and the net heat power from 0.25 MW to 1.1 MW, and it can also identify an early low-rate H2 storage phase. The Non-Sorting Genetic Algorithm II calculates that the PSEA technology brings economic benefits of $704,000 and $352,000 for geothermal energy extraction and H2 storage in a single injection-production system. In conclusion, the developed monitoring technology and models improve accuracy in assessing geothermal energy development and H2 storage, preventing failures in residential heating or H2 storage projects.

Hydrogeochemical and microbial characterization of a Middle Triassic carbonate aquifer (Muschelkalk) in Berlin and geochemical simulation of its use as a high-temperature aquifer thermal energy storage

The geological formation of the Muschelkalk is widespread in the center of the North German Basin (NGB) and is increasingly attracting interest for application of geothermal energy extraction or high-temperature aquifer thermal energy storage (HT-ATES). This study investigates the Middle Triassic “Rüdersdorfer Schaumkalk”, which was the former injection horizon of the natural gas storage facility in Berlin, Germany. For the first time, detailed chemical and microbiological analyses of formation water of this Lower Muschelkalk limestone formation were conducted and hydrogeochemically characterized. In addition, a hydrogeochemical model was developed to quantify the potential reactions during HT-ATES focusing on calcite dissolution and precipitation. The main objectives of this study are: (1) to determine the origin of the water from the three wells targeting the Muschelkalk aquifer, (2) to understand changes in hydrochemistry after system operation, and (3) to evaluate the long-term sustainability of a potential HT-ATES system with increasing temperature. The target formation is encountered by several wells at about 525 m below the surface with an average thickness of 30 m. Two hydraulic lifting tests including physical, chemical, and microbial groundwater as well as gas monitoring were carried out. In addition, several downhole samples of formation fluid were collected from the aquifer at in situ pressure and temperature conditions. Fluid analysis of the saline formation water indicate a seawater origin within the Muschelkalk with subsequent evaporation and various water–rock interactions with anhydrite/gypsum, dolomite, and calcite. With a salinity of 130 g/L, dominated by Na–Cl, a slightly acidic pH between 6 and 7, and a low gas content of 3%, the formation water fits to other saline deep formation waters of the NGB. Gas concentrations and microbial communities like sulfate-reducing bacteria and methanogenic archaea in the produced water indicate several geochemical alterations and microbial processes like corrosion and the forming of biogenic methane. Geochemical simulations of calcite equilibrium over 10 HT-ATES cycles indicated a pronounced propensity for calcite precipitation up to 31 mg/kgw, within the heat exchanger. At the same time, these models predicted a significant potential for calcite dissolution, with rates up to 21 mg/kgw, in both the cold and hot reservoirs. The results from the carbonate aquifer characterized in this study can be transferred to other sites in the NGB affected by salt tectonics and have provided information on the microbiological-chemical processes to be expected during the initial use of old wells.

Techno-economic assessment of large-scale sedimentary basin stored–CO2 geothermal power generation

One approach to reducing atmospheric carbon dioxide (CO2) emissions is to adopt carbon capture utilization and storage (CCUS) strategies. This is particularly crucial for countries to achieve their net-zero goal. In this study, we investigate the techno-economic viability of a proposed CCUS process that utilizes geologically stored CO2, associated with hydrogen (H2) production from fossil fuels, as a working fluid to extract geothermal energy from deep, large-scale, sedimentary storage formations. The process ensures permanent geological storage of all injected CO2 while generating adaptable geothermal power through supercritical CO2 turbine expansion, thus, bolstering revenue and reducing the final cost of blue hydrogen production. We simulate subsurface-wellbore fluid flow and heat transport for a representative 4-way closed anticlinal Arabian reservoir and optimize system power output, including a comprehensive and integrated economic analysis. We find that CO2 captured from an equivalent blue H2 production of ∼4.1 Mt./year can be injected at an annual rate of 0.92–1 million metric tons (Mt) per well, resulting in a cumulative sequestration of ∼1.15 gigatons (Gt) of CO2 over 11.5 years. To mitigate the risks of reaching the formation parting pressure at the crest of the anticline and ensuring sufficient CO2 saturation at the production wells, phased drilling schedules and pressure-controlled injection and production are essential. With horizontal production wells, our simulations generate an average geothermal net electricity of 164 MW. The base-case economic analysis reveals a Levelized Cost of Electricity (LCOE) of 77 $/MWh and a Net Present Value (NPV) of 480 million USD over 50 years. In contrast, vertical production wells double LCOE, and the project remains unprofitable throughout its life (negative NPV). Our economic sensitivity analysis further emphasizes how the capacity factor, electricity selling price, and drilling costs govern LCOE and NPV. On the other hand, discount rates and Opex fraction are influential yet uncertain parameters affecting the system's techno-economic outlook. Therefore, our study provides valuable insights into the benefits of geothermal energy production from over 1 Gt of stored CO2 and the associated economic landscape.

The role of pit lake thermal dynamics on the thermal performance of ground heat exchangers

The addition of ground heat exchangers (GHEs) to a pit lake’s basin has the potential for abundant, clean and renewable geothermal energy extraction using shallow geothermal systems. Basin-embedded GHEs avoid direct interaction with mine water, which has been shown to impact efficiency and longevity in mine open-loop geothermal systems negatively. The now accelerated closure of open-pit coal mines presents itself as an opportunity to use this technology. However, no guidelines currently exist for designing or operating GHEs embedded in the sediment of water bodies. Furthermore, the two-way coupling between the complex annual thermal fluid dynamics that lakes are naturally subjected to and heat fluxes on the sediments and the GHE system has not been explored. In this study, we develop and validate finite element models to assess the relevance of lake thermal stratification in the performance of a geothermal system embedded in water bodies basins, e.g., on open-pit mine closures, under temperate residential thermal loads. The results show that the pit lake’s role as a thermal sink improves significantly when the lake’s thermal dynamics are accounted for, with an increase of up to 292% in the lake’s available energy budget. A minor variation in energy budget (~8%) was found whether the lake is modelled explicitly or simplified as a transient Dirichlet temperature boundary condition. This small difference vanishes if horizontal circulation along the lake is considered, highlighting the lake’s thermal energy potential. Finally, the impact on the GHE Coefficient of Performance (COP) is evaluated, with a maximum of ~15% difference among all cases.

Regression analysis of Cattaneo–Christov heat and thermal radiation on 3D Darcy flow of Non-Newtonian fluids induced by stretchable sheet

This study explores the influence of thermal radiation and heat source on magnetized flow micropolar nanofluid through a Stretchable Sheet in the presence of mobile microbes. The presence of microorganisms adds a biological dimension to the problem, affecting fluid dynamics and heat transfer, which are central to this investigation. To motivate the problem, the flow is induced by a Darcy porous exponentially stretching sheet with generalized boundary conditions. A regression analysis is conducted to analyze the interplay of various parameters on the flow and heat transfer characteristics. Additionally, similarity transformations are implemented to transform the set of partial differential equations (PDEs) into a set of ordinary differential equations (ODEs). The resulting equations are solved numerically using the shooting approach via the bvp4c platform in Matlab. The regression model quantifies the impact of each parameter and their interactions on the flow field, temperature distribution, and Darcy effects. Furthermore, the impact of involved parameters on flow, energy, volumetric concentration, density of microbes, and micro-rotations distribution are analyzed and discussed through graphs, literature, and tables. The findings of this research are crucial for various engineering, industrial, and pharmaceutical applications, including biofilm formation, geothermal energy extraction, and wastewater treatment processes.