Geothermal Research Articles

Determination of the Temperature Development in a Borehole Heat Exchanger Field Using Distributed Temperature Sensing

The use of geothermal borehole heat exchangers (BHEs) in combination with ground-source heat pumps represents an important part of shallow geothermal energy production, which is already used worldwide and becoming more and more important. Different measurement techniques are available to examine a BHE field while it is in operation. In this study, a field with 54 BHEs up to a depth of 120 m below ground level was analyzed using fiber optic cables. A distributed temperature sensing (DTS) concept was developed by equipping several BHEs with dual-ended hybrid cables. The individual fiber optics were collected in a distributor shaft, and multiple measurements were carried out during active and inactive operation of the field. The field trial was carried out on a converted, partly retrofitted, residential complex, “Lagarde Campus”, in Bamberg, Upper Franconia, Germany. Groundwater and lithological changes are visible in the depth-resolved temperature profiles throughout the whole BHE field.

Comparison and regional suitability evaluation of different backfill source heat pumps using TRNSYS

As global energy demand and carbon emissions continues to rise year by year, the use of renewable energy for heating becomes increasingly urgent. This study employs solar and geothermal energy to supply heat to mining facilities. Initially, three distinct heating systems for mining areas were modeled in TRNSYS: the Backfill Source Heat Pump (BSHP), the Solar Assisted Backfill Source Heat Pump (SABSHP), and the Solar Assisted Backfill Source Heat Pump with Seasonal Heat Storage (SABSHP-SHS). Following a decade of simulation, the optimal system was identified through a comparative analysis that encompassed backfill temperature equilibrium, the inlet and outlet water temperatures for buried pipes, Coefficient of Performance (COP), Partial Load Ratio (PLR), and economic factors. Over the 10-year simulation period, the COP and PLR of the SABSHP-SHS system outperformed both the BSHP and SABSHP systems, showing higher energy efficiency and better heat pump performance. To further assess the regional adaptability of the SABSHP-SHS system, simulations were conducted across four regions with diverse climatic profiles: Shijiazhuang, Yan’an, Xining, and Hegang. The analysis focused on heat collection, efficiency, backfill temperature variation, system energy consumption, and the energy efficiency ratio. The findings indicate that Hegang exhibits the highest solar heat collection efficiency at 89.9% during the non-heating season, while Xining achieves a significantly higher heat collection efficiency of 54.1% during the heating season. These results suggest that the SABSHP-SHS system is particularly effective in regions with pronounced seasonal variations, characterized by extended cold winters and brief, intense summers.

Harnessing the Power of Renewable Energy: A Study of Sustainable Sources and Technologies

This research investigates the capacity of renewable energy technologies to fulfill global energy requirements while mitigating environmental effects, concentrating on primary sources like sun, wind, hydropower, biomass, and geothermal energy. It evaluates the efficacy of various technologies for energy production, efficiency, economic viability, and reduction of carbon emissions. The findings underscore notable progress in solar and wind energy, demonstrating considerable efficiency enhancements (5% for solar PV, 10% for wind turbines) and cost reductions (67% and 64%, respectively) during the last decade. Hydropower is the most efficient energy source, converting 90% of available energy, albeit it is geographically constrained. The research highlights the environmental advantages, noting that renewable technologies substantially decrease CO₂ emissions—hydropower and wind energy prevent 250,000 and 120,000 metric tons of CO₂ annually, respectively. Nonetheless, obstacles such as the variability of solar and wind energy, elevated expenses associated with biomass and geothermal energy, and regional variations in implementation persist as substantial impediments. The research highlights the need for further developments in energy storage, grid modernization, and legislative assistance to expedite the worldwide shift towards renewable energy. This study synthesizes current statistics and trends, emphasizing the vital role of renewable energy in attaining a sustainable, low-carbon future, while also tackling ongoing economic and infrastructural problems.

Numerical investigation of heat and moisture migration in clayey and sandy soils, exploring seasonal fluctuations

Geothermal energy is widely known as a sustainable and eco-friendly energy source. For its applications, assessing the hydrothermal soil behaviour is crucial. However, the installation of ground geothermal systems at shallow depths makes them sensitive to atmospheric conditions, which affect the temperature field and the thermal balance. This paper presents the results of a numerical study investigating the hydrothermal behaviour of unsaturated soils (clay and sand), considering the meteorological variations at the ground surface. The atmospheric-soil interactions, including solar radiation, sensible heat flux, and latent heat flux, are essential for quantifying the energy balance and the hydro-thermal transfer processes taking place at the ground surface. By analysing these components, we can gain a comprehensive understanding of how energy is distributed and transferred to the soil. A numerical study was carried out using a finite element method (FEM) to assess the hydrothermal behaviour of unsaturated soils. The analysis of the obtained results from the model simulation reveals that variations in soil types have an impact on the distribution of heat and moisture migration, with both time and depth. Moreover, it appears that clayey soils show the highest efficiency in geothermal energy transfer. This research offers crucial insights into the optimization of both the design and implementation of geothermal systems.

Geophysical modeling of the middle Bogotá River Basin with support from interpretation of electrical resistivity, gravity, seismic and borehole data to evaluate potential deep aquifers

The main objective of this research was to develop a geological and geophysical modeling to infer the geometry and thickness in the sedimentary sequence of the middle basin of the Bogotá River with emphasis on the Guadalupe Group, reconstructing the stratigraphic sequence, structural setting, hydrogeological modeling, and potential geothermal uses. Various geophysical methods were applied, including vertical electrical soundings (VES), and magneto telluric soundings (MT-VES), whose results were complemented with the interpretation of seismic lines, regional and local gravity anomaly maps, and borehole data, among others, which allowed to model the subsurface from the surface to depths beyond 3000 meters, with emphasis on the interval between 500m to 1000m depth. Integrated models were developed from interpretations of electrical resistivity data, gravity and magnetic data, reflection seismic and borehole data. Based on the results, potential deep aquifers have been proposed to be confirmed by drilling. These deep aquifers can contribute to satisfy the need for water, which historically has been explored and overexploited from shallower aquifers in this sector of the basin. A recommendation was also made to consider the potential of low enthalpy thermal energy for agro-industrial purposes associated with groundwater’s temperature at the depth of this research. As a result, the modeled sedimentary sequence is characterized by a thick quaternary overburden overlying an intensively folded and faulted Neogene, Paleogene, and upper Cretaceous formations, mainly composed of siltstone, sandstones, and shale sequences of fluvial and marine environment, including facies of marine regressions and transgressions near the coastline. The penetration obtained allows establishing a high hydrogeological potential in the first 2000m depth, especially associated with the Guadalupe group, where the Labor and Tierna and Arenisca Dura formations have the highest hydrogeological potential. In addition, the preliminary estimation of thermal gradients suggest that low enthalpy geothermal energy potential is feasible to be used for the agro-industrial demand of energy of the study area.

Enhancing geothermal efficiency: Experimental evaluation of a high-temperature preformed particle gel for controlling preferential fluid flow

Enhanced Geothermal System (EGS) reservoirs represent a vital frontier in clean energy production. However, short-circulation flow within these reservoirs can significantly affect their immediate efficiency and long-term viability. Injected cold fluids moving through wide fractures or direct channels between injection and production wells reduce thermal production temperatures, disrupting energy output. Preformed Particle Gels (PPGs) have proven effective in controlling preferential fluid flow in oil and gas reservoirs, effectively regulating fluid movement. This work explores the potential of a novel High-Temperature Preformed Particle Gel (HT-PPG), designed for geothermal applications, to plug fractures in a simulated geothermal reservoir. Core flooding experiments in coated and uncoated sandstone models were conducted under varying HT-PPG sizes, swelling ratios, and fracture widths to determine gel plugging efficiency. Variations in the HT-PPG injection pressure, breakthrough pressure, and residual resistance factor (Frr) were evaluated. Water breakthrough pressures can reach 464.10 psi/ft. While the stable injection pressure of HT-PPG decreased with increasing swelling ratio and fracture width, it was higher in uncoated cores. The HT-PPG significantly sealed the fractures, drastically reducing conductivities to millidarcy levels. This work validates HT-PPG a robust solution to mitigate fluid diversion challenges in sandstone EGS reservoirs, enhancing performance and advancing sustainable geothermal energy production.

Unveiling energy transition strategy: A deep dive into China's ambitious renewable energy policy and its impact on carbon emission dynamics

Over the past 70 years, China has issued approximately 20,000 renewable energy (RE) policies. How to interpret China's ambitious RE strategy through these policy documents and assess its effectiveness has been a question of interest. Therefore, based on 15,603 Chinese RE policy documents from 1975 to 2022, this study employs text mining, Latent Dirichlet Allocation (LDA), Policy Modeling Consistency-Text Encoder (PMC-TE), and System-Generalized Method of Moments (SYS-GMM). It assesses the policy input intensity (PII) for different energy types, regions, and time periods, while also investigating the impact of PII about RE on carbon emissions. The study findings are as follows: (1)The PII is not uniform, with hydropower having the highest PII at 80,591, followed by solar (25,839) and biomass energy (18,903). The PII of wind (11,377) and geothermal energy (11,340) is similar, while hydrogen energy exhibits the weakest PII at 3488. (2)There are regional disparities in PII, with solar and wind energy being most prominent in northern regions, solar and hydropower being most significant in eastern regions, and wind and biomass energy aligning with local resources in southern regions. (3)RE policies have driven China's energy transition through four distinct phases. (4)Policy effectiveness varies, with solar, wind, and hydropower policies having the most significant impact on carbon emissions reduction, followed by biomass and geothermal energy. (5)China's government role in the RE strategy has shifted from a dominant role to a regulatory one.

Development and comprehensive analyses of a hybrid solar–geothermal driven polygeneration system: Thermodynamic, exergoeconomic, and emergoenvironmental aspects

The present research proposed an innovative polygeneration system that uses solar, geothermal, and natural gas energy to produce power, heat, steam, and freshwater. The system consists of a proton exchange membrane fuel cell, an organic Rankine cycle, and a multi-effect thermal desalination system. The study included thermodynamic, exergy, exergoeconomic, exergoenvironmental, emergy-based exergoeconomic, and emergy-based exergoenvironmental factors in its comprehensive evaluation of the system. Results underscored the financial aspect of the organic Rankine cycle and cogeneration system, incurring costs of 0.4518 $/s and 1.054 $/s respectively, while also highlighting the system's capability to produce 6 kg/s of freshwater. The environmental impact rates were quantified for the organic Rankine cycle and cogeneration system at 0.1417 and 0.4814 pts/s respectively, situating the system within its ecological context. Further, the study detailed the total efficiency and net power output of the organic Rankine cycle and cogeneration system, ranging between 32.45–33.51% and 43.25–45.83% for efficiency, and 56956–56322 kW and 50174–51898 kW for net power output r espectively, showcasing the system's operational capacity. A parametric analysis was also integral to the study, examining the impact of key parameters on the functionality of the proposed system, thereby providing a nuanced understanding of the system's performance under varying operational scenarios.

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 characterisation 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.

Effects of Different Cooling Treatments on Heated Granite: Insights from the Physical and Mechanical Characteristics.

The exploration of Hot Dry Rock (HDR) geothermal energy is essential to fulfill the energy demands of the increasing population. Investigating the physical and mechanical properties of heated rock under different cooling methods has significant implications for the exploitation of HDR. In this study, ultrasonic testing, uniaxial strength compression experiments, Brazilian splitting tests, nuclear magnetic resonance (NMR), and scanning electron microscope (SEM) were conducted on heated granite after different cooling methods, including cooling in air, cooling in water, cooling in liquid nitrogen, and cycle cooling in liquid nitrogen. The results demonstrated that the density, P-wave velocity (Vp), uniaxial compressive strength (UCS), tensile strength (σt), and elastic modulus (E) of heated granite tend to decrease as the cooling rate increases. Notably, heated granite subjected to cyclic liquid nitrogen cooling exhibits a more pronounced decline in physical and mechanical properties and a higher degree of damage. Furthermore, the cooling treatments also lead to an increase in rock pore size and porosity. At a faster cooling rate, the fracture surfaces of the granite transition from smooth to rough, suggesting enhanced fracture propagation and complexity. These findings provide critical theoretical insights into optimizing stimulation performance strategies for HDR exploitation.

Geothermal distribution and evolution of fault-controlled Linyi geothermal system: Constrained from hydrogeochemical composition and numerical simulation

This study explores the Linyi geothermal field, located in Shandong Province, China, characterized by its non-magmatic, active fault-controlled geothermal system. Utilizing a combination of geochemical analyses, temperature measurements, and numerical simulations, a detailed genetic model of the geothermal system has been developed. The analysis included extensive water geochemical and isotopic characterization to determine reservoir temperature, depth, and origin of the geothermal waters. The thermal-hydro coupling model was integrated with these data to refine the thermal distribution and assess the evolutionary dynamics of the geothermal system. Our findings indicate that the geothermal anomalies in the Linyi field are predominantly controlled by hydrothermal convection within the Ordovician and Cambrian carbonate layers, facilitated by the high permeability of the Yishu Fault. The fault acts as a crucial conduit for meteoric water recharge, which undergoes significant heating due to the geothermal gradient in deeper rock formations. Isotopic analyses of hydrogen and oxygen revealed the meteoric origin of the geothermal waters, with recharge likely originating from the nearby Yimeng Mountains. Furthermore, the study established a conceptual evolutionary model to understand the mechanisms driving the geothermal resource development in the area. It was determined that the geothermal resources are typically fault-controlled, with significant potential for further exploration due to the identified hydrothermal anomalies at the fault's footwall. The model predicts the preservation of heated meteoric water in the reservoir rock for periods ranging from 10 to 50 thousand years, providing a sustainable source of geothermal energy. This comprehensive approach not only enhances the understanding of the heat accumulation mechanism but also highlights the potential for optimizing geothermal exploration strategies within fault-controlled geothermal systems.

Two-phase closed thermosiphon with grooved the evaporator section applied for low-grade energy recovery: Thermo-hydrodynamic performance and potentials

High thermal conductivity and simple structure of two-phase closed thermosyphons (TPCTs) facilitate it extensively applied in low-grade thermal recovery, such like geothermal and solar energy exploitation. In present work, by incorporating threaded grooves into the evaporator section of the TPCTs, heat transfer performance could be significantly enhanced. Thermal transport mechanism of thermosyphons with various threaded groove structures was comprehensively investigated, and corresponding thermo-hydrodynamic performance was modelled through CFD/VOF simulations. Numerical procedures were validated well after comparison with experimental ones felled within 5.0 %. Under various heating power levels and filling ratios, heat transfer performance of thermosyphons with threaded grooves evidently surpassed that of smooth thermosyphons. Depending on delicate numerical results, critical point at 33 % filling ratio and 90 W heating power were confirmed that total thermal resistance of the grooved thermosyphon decreased almost close to 4.6 %. Furthermore, deviating from that critical point, higher heating power and lower filling ratio instead confined heat transfer performance of the threaded TPCT, which was primarily due to the rate of bubble generation and growth being significantly was slower than its detachment rate from the wall. In addition, heat and mass transfer performance of thermosyphons with threaded grooves of various pitches and apex angles were further analyzed under various conditions. Our results indicated that, when the groove apex angle turned to 90°, overall thermal transportation capability of the TPCT achieved optimal, with a decline in thermal resistance of up to 6.5 % compared to thermosyphons with smaller apex angles. Apex angle primarily affected the number of nucleation sites and the bubble detachment rate. Additionally, as the screw pitch decreased, boiling heat transfer enhancement, leading to more robust boiling heat transfer of TPCTs. Under high heating power, thermosyphons with larger screw pitch exhibited superior heat transfer performance. Overall, this innovative TPCTs with threaded grooves could be well applied in low-grade energy exploitation, particularly like as geothermal and solar energy fields.

Analysis of renewable energy resources based on frank power aggregation operators and EDAS method for circular bipolar complex fuzzy uncertainty

The model of circular bipolar complex fuzzy (Cir-BCF) sets computed based on the membership function, non-membership function, and radius among both functions for each value of the universal set. The technique of the Cir-BCF set is the modified or extended form of fuzzy sets, complex fuzzy sets, bipolar fuzzy sets, bipolar complex fuzzy sets, and simple circular bipolar fuzzy sets to cope with uncertain and vague information. In this manuscript, we describe the novel technique of frank operational laws based on Cir-BCF values for frank t-norm and frank t-conorm. Further, we simplify the model of Cir-BCF frank power averaging (Cir-BCFFPA), Cir-BCF frank power weighted averaging (Cir-BCFFPWA), Cir-BCF frank power geometric (Cir-BCFFPG), Cir-BCF frank power weighted geometric (Cir-BCFFPWG) operators, and highlighted their valuable properties, called idempotency, monotonicity, and boundedness. Moreover, analysis of renewable energy resources is very awkward and complicated, but it is natural sources of energy that are refilled constantly or relativeness quickly on a human timescale. Further, solar energy, hydroelectric energy, geothermal energy, biomass energy, and wind energy are five major sources of energy, but it is complex to find which one is the best and which one is worst. For evaluating the above problems, we construct the technique of evaluation based on the distance from the average solution (EDAS) method under the presence of the Cir-BCF numbers (Cir-BCFNs). At the end, we arrange the comparison between proposed and existing techniques based on some numerical examples to describe the validity and proficiency of the initiated information.

Design and economic analysis of an innovative multi-generation system in different Countries with diverse economic contexts

This paper presents an innovative trigeneration system designed to maximize energy utilization by simultaneously producing power, cooling, and freshwater. The system integrates multiple energy sources, including biomass, natural gas, and geothermal energy, and comprises a modified gas turbine cycle, a geothermal power plant, a triple-effect absorption refrigeration cycle, and a multi-effect desalination unit. Performance metrics are evaluated from both thermodynamic and economic perspectives across four case studies: Australia, the USA, China, and Russia. The economic feasibility analysis utilizes real-state economic data, incorporating natural gas prices, electricity prices for households, interest rates, and inflation rates specific to each country. The system achieved impressive outputs, with net power, cooling, and freshwater production rates of 6299 kW, 140.1 kW, and 13.41 kg/s, respectively. Exergy analysis revealed that the combustion chamber, heat exchanger, and multi-effect desalination units exhibit the highest irreversibility, with exergy destruction rates of 2961 kW, 1125 kW, and 995.3 kW, respectively. The fixed capital investment cost is estimated at $13.5 million, resulting in a payback period of 6.75 years and a net present value of $7.287 million. In Australia, the system demonstrated a particularly favorable economic performance, with a payback period of 3.98 years and a net present value of $36.19 million. Conversely, in China, the payback period exceeds the system's expected lifetime, highlighting the economic challenges in certain environments. These results underscore the system's potential for profitability and sustainability, particularly in regions with favorable economic conditions.

Study of the fracture propagation and the corresponding heat mining performance of multi-branch radial wells geothermal system based on the THM-D coupling model

Due to the multi-well enhanced geothermal systems can significantly improve the heat transfer efficiency and the multi-branch radial well geothermal system can reduce the well construction cost, it is necessary to investigate the fracture propagation and the heat mining performance of the multi-branch radial well geothermal system. Based on the constructed THM-D coupling model, the fracture propagation rules of multi-branch radial wells under the co-function of low-temperature induced thermal stress and radial well induced stress is explored. Then the heat mining prediction study during the heat extraction stage is conducted based on the generated fracture. Furthermore, the influence of radial well characteristic parameters on fracture propagation and the corresponding heat mining performance of multi-branch radial well geothermal system is discussed. The results show that the smaller radial well angle in multi-branch radial well system can generate a larger scope of fracture network between the included angle under the co-function of radial well induced stress and low-temperature induced thermal stress, which will correspond to a larger heat extraction scope in heat mining stage. When the radial well included angle along the direction of maximum horizontal in-situ stress is 120°, the fracture network obtained by fracturing is the most complex. Excessive branching of radial wells can lead to significant induced stress in the plane of radial wells, which will affect the propagation of the fracture network in the direction of longitudinal connection between the doublet wells, thereby affecting the corresponding heat mining performance. With the increase of radial well length, the ability to induce the formation of branching fractures raises, resulting in more complex fracture network. In the heat mining stage of 10-year development, the outlet temperature and heat mining rate respectively increased by 5.83% and 6.9% when the radial well length is 75 m compared to 50 m.

Wave energy assessment and wave converter applicability at the Pacific coast of Central America

Nowadays, numerous governments have instituted diverse regulatory frameworks aimed at fostering the assimilation of sustainable energy sources characterized by reduced environmental footprints. Solar, wind, geothermal, and ocean energies were subject to extensive scrutiny, owing to their ecological merits. However, these sources exhibit pronounced temporal fluctuations. Notably, ocean dynamics offer vast energy reservoirs, with oceanic waves containing significant amounts of energy. In the Central American Pacific context, the exploration of wave energy resources is currently underway. Accurate numerical wave models are required for applied studies such as those focused on the estimation of exploitable wave power; and even more so in Central American region of the Pacific Ocean where existing numerical models simulations have so far relied on coarse resolution and limited validation field data. This work presents a high-resolution unstructured wave hindcast over the Central American Pacific region, implemented using the third-generation spectral wave model WAVEWATCH III over the period between 1979 and 2021. The results of the significant wave height have been bias-corrected on the basis of satellite information spanning 2005 to 2015, and further validation was performed using wave buoy and acoustic Doppler current profiler (ADCP) records located in the nearshore region of the Central America Pacific coast. After correction and validation of the wave hindcast, we employed the dataset for the evaluation and assessment of wave energy and its possible exploitation using different wave energy converters (WECs). This evaluation addressed the need to diverse the energy portfolio within the exclusive economic zones of Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, Panama, Colombia, and Ecuador in a sustainable manner. Moreover, a comprehensive analysis was carried out on the advantages of harnessing wave energy, juxtaposed with the imperative of regulatory frameworks and the current dearth of economic and environmental guidelines requisite for development within the region.

Collective vision-making practice: A long-run dynamic process model for geothermal market transitioning

Michael Porter’s work on competition highlights how firms can become stagnant or ‘stuck.’ This study extends that concept to markets or fields of institutional activity, examining what occurs when an entire market becomes 'stuck.' Focusing on the geothermal energy market, the research investigates achieving long-term collective action by cultivating a shared vision and mutual understanding among stakeholders with diverse interests. The study employs a longitudinal ethnographic approach, presenting a long-run dynamic process model of collective vision-making practice. This model consists of six first-order dimensions and twelve second-order interactive behavioural practice, illustrating how stakeholders can collaboratively construct and enfold a long-term collective vision. The findings demonstrate the institutional capacity to engage stakeholders and strategically consider whole market possibilities, enabling the creation of a broadly defined collective vision. The research advances a dynamic process model that emphasises sustained institutional interactional practice. The study’s implications are to motivate thought leaders and policymakers, prompting two strategic questions: First, “How can market actors collaborate to unlock value co-creation and shape the future of a ‘stuck’ market?” This involves engaging diverse stakeholder perspectives and exploring future market-making opportunities. Second, “How can all market actors pivot in harmony with a collective vision, fostering long-term shared understandings and commitments in pursuit of market-making efforts?”, This alignment is important for progressing from research and development to the successful implementation of pilot projects and the realisation of sustainable market opportunities.

Experiences as heuristics for geothermal public perception: Testing the correlation between thermal waters recreation and geothermal energy perception

This research focuses on the question of how geothermal energy public perception is formed within a national context where news media do not pay attention to geothermal energy, and there is no active opposition to geothermal energy. The research builds on theoretical underpinnings of heuristics in energy perceptions and highlights the importance of physical experiences and associations as sources of experiential learning. Through a survey conducted among members of the general public in Slovenia, the role of thermal water recreation in shaping public perception of geothermal energy is empirically tested. The results show that, in this context, geothermal energy is highly positively assessed compared to hydro energy and nuclear energy, and that there is a correlation between frequency of thermal recreation and certain aspects of public perception of geothermal energy. The policy implications go beyond the simple recommendation of including tourism in public awareness campaigns but point to the specific vulnerability of energy acceptance in this context, where perceptions are formed based on “thinking fast”, and where the media and the public discourse on geothermal energy have not (yet) considered the potential risks and opposition to geothermal projects.

Heat transfer performance of energy pile and borehole heat exchanger: A comparative study

Geothermal structures are widely utilized to satisfy the heating and cooling demands of buildings, providing a promising alternative to the escalating scarcity of energy. As two types of geothermal heat exchangers, energy piles and borehole heat exchangers exhibit different efficiencies in extracting geothermal energy. This paper examines the thermal performance of an energy pile and a borehole heat exchanger under heating and cooling conditions through field tests, introducing the heat exchange rate per unit pipe length (q0) as a metric. Furthermore, a three-dimensional heat transfer numerical model was developed and validated. The parametric analysis was subsequently conducted to investigate the sensitivity of heat exchange efficiency to five parameters, including flow rate, inlet temperature, pipe diameter, soil thermal conductivity, and soil temperature. The results showed that the heat transfer efficiency of the borehole heat exchanger was 42.2 % and 48.7 % lower than that of the energy pile under the heating and cooling conditions, respectively. Moreover, the heat transfer efficiency of the energy pile and borehole heat exchanger is most sensitive to inlet temperature, with the latter showing greater sensitivity to pipe diameter. This study provides valuable insights into optimizing the design and operation of energy piles and borehole heat exchangers to meet the growing energy demands of buildings.

Modeling of Geothermal Energy Recovery from a Depleted Gas Reservoir: A Case Study

Modeling of Geothermal Energy Recovery from a Depleted Gas Reservoir: A Case Study