Geothermal Heat Research Articles

Dated radar-stratigraphy between Dome A and South Pole, East Antarctica: old ice potential and ice sheet history

Abstract An array of information about the Antarctic ice sheet can be extracted from ice-sheet internal architecture imaged by airborne ice-penetrating radar surveys. We identify, trace and date three key internal reflection horizons (IRHs) across multiple radar surveys from South Pole to Dome A, East Antarctica. Ages of ~38 ± 2.2, ~90 ± 3.6 and ~162 ± 6.7 ka are assigned to the three IRHs, with verification of the upper IRH age from the South Pole ice core. The resultant englacial stratigraphy is used to identify the locations of the oldest ice, specifically in the upper Byrd Glacier catchment and the Gamburtsev Subglacial Mountains. The distinct glaciological conditions of the Gamburtsev Mountains, including slower ice flow, low geothermal heat flux and frozen base, make it the more likely to host the oldest ice. We also observe a distinct drawdown of IRH geometry around South Pole, indicative of melting from enhanced geothermal heat flux or the removal of deeper, older ice under a previous faster ice flow regime. Our traced IRHs underpin the wider objective to develop a continental-scale database of IRHs which will constrain and validate future ice-sheet modelling and the history of the Antarctic ice sheet.

The comparative role of physical system processes in Hudson Strait ice stream cycling: a comprehensive model-based test of Heinrich event hypotheses

Abstract. Despite their recognized significance on global climate and extensive research efforts, the mechanism(s) driving Heinrich events remain(s) a subject of debate. Here, we use the 3D thermomechanically coupled glacial systems model (GSM) to examine the Hudson Strait ice stream surge cycling and the role of three factors previously hypothesized to play a critical role in Heinrich events: ice shelves, glacial isostatic adjustment, and sub-surface ocean temperature forcings. In contrast to all previous modeling studies examining HEs, the GSM uses a transient last glacial cycle climate forcing, global viscoelastic glacial isostatic adjustment model, and sub-glacial hydrology model. The results presented here are based on a high-variance sub-ensemble retrieved from North American history matching for the last glacial cycle. Over our comparatively wide sampling of the potential parameter space (52 ensemble parameters for climate forcing and process uncertainties), we find two modes of Hudson Strait ice streaming: classic binge–purge versus near-continuous ice streaming with occasional shutdowns and subsequent surge onset overshoot. Our model results indicate that large ice shelves covering the Labrador Sea during the last glacial cycle only occur when extreme calving restrictions are applied. The otherwise minor ice shelves provide insignificant buttressing for the Hudson Strait ice stream. While sub-surface ocean temperature forcing leads to minor differences regarding surge characteristics, glacial isostatic adjustment does have a significant impact. Given input uncertainties, the strongest controls on ice stream surge cycling are the poorly constrained deep geothermal heat flux under Hudson Bay and Hudson Strait and the basal drag law. Decreasing the geothermal heat flux within available constraints and/or using a Coulomb sliding law instead of a Weertman-type power law leads to a shift from the near-continuous streaming mode to the binge–purge mode.

Hematite U-Pb dating of Snowball Earth meltwater events

The Snowball Earth hypothesis predicts global ice cover; however, previous descriptions of Cryogenian (720-635 Ma) glacial deposits are limited to continental margins and shallow marine basins. The Tavakaiv (Tava) sandstone injectites and ridges in Colorado, USA, preserve a rare terrestrial record of Cryogenian low-latitude glaciation. Injectites, ridges, and chemically weathered crystalline rock display features characteristic of fluidization and pervasive deformation in a subglacial environment due to glacial loading, fluid overpressure, and repeated sand injection during meltwater events. In situ hematite U-Pb geochronology on hematite-quartz veins, which crosscut and are cut by Tava dikes, constrain sand injection at ~690-660 Ma. We attribute early Tava sand injection episodes to basal melting associated with rifting and geothermal heating, and later injections to meltwater generation during ~661 Ma Sturtian deglaciation. A modern analog is provided by the Ross Embayment of Antarctica, where rift-related faults border sediment-filled basins, overpressurized fluids circulate in confined aquifers below ice, and extensive preglacial topography is preserved. Field evidence and geochronology in Colorado further highlight that deep chemical weathering of Proterozoic bedrock and denudation associated with the Great Unconformity predate Cryogenian injection of fluidized sand, consistent with limited glacial erosion.

Geothermo-mechanical energy conversion using shape memory alloy heat engine

AbstractThe shift towards renewable energy sources like geothermal energy has become desirable due to the recurrent energy crisis and global warming challenges influenced by fossil fuels. Geothermo-mechanical energy conversion using shape memory alloy (SMA) heat engines presents a novel and sustainable approach for harnessing geothermal energy. Shape memory alloys, known for their ability to undergo reversible phase transformations driven by temperature changes, are ideal for thermal-to-mechanical energy conversion. This paper explores the design and performance of an SMA heat engine that utilizes geothermal heat sources to drive mechanical work. The engine operates by cycling between the high-temperature geothermal environment and a cooler sink, exploiting the shape memory effect to generate mechanical motion. By integrating geothermal energy and SMA technology, this system offers a potential solution for renewable energy generation, with applications in remote or off-grid locations. The paper also investigates output power and the thermodynamic efficiency. A model is formulated and the engine behavior is simulated. A series of experiments are conducted for engine output power and efficiency. The model is compared to the experimental data for validation. The engine developed a maximum power of 3.5, 8.5, and 11.5 watts at 60, 80, and 90 °C respectively. The proposed SMA-based geothermo-mechanical energy conversion system offers a promising solution for efficient, reliable, and scalable geothermal energy harvesting. This research contributes to the development of innovative, efficient geothermal energy conversion technologies, supporting global renewable energy goals and reducing greenhouse gas emissions. This innovative energy conversion mechanism could play a key role in the future of sustainable power generation.

Ice drilling on Princess Elizabeth Land (East Antarctica) aimed to study bedrock and Late Quaternary paleoclimate

Targeted bedrock sampling was carried out on Princess Elizabeth Land (30 km south of the coast, at 69.585591° S; 76.385165° E) by drilling through 545 m thick ice. The borehole was drilled using a new, modified version of the cable-suspended Ice and Bedrock Electromechanical Drill (IBED) designed by the Jilin University (China) and under a joint scientific project between VNIIOkeangeologia, Jilin University and China University of Geosciences (Beijing). The drill site is located on the axis of a high-amplitude linear magnetic anomaly that runs parallel to the coast for more than 500 km from Princess Elizabeth Land to Mac. Robertson Land. In the next Antarctic season, borehole geophysical logging will be conducted including temperature measurements for geothermal heat flux calculations.

Resource Efficiency and the Role of Renewable Energy in Miskolc: The City’s Journey Towards Becoming a Smart City

Miskolc, which is the focus of our investigation, is the fourth most populous city in Hungary and the center of one of the most underdeveloped NUTS2 (basic territorial category for the regional policy of the European Union) regions in the European Union. The socialist heavy industry played a decisive role in the development of the city, the decline of which also left deep traces in the city. In its current position, the city tries to manage its available resources as efficiently as possible, and the city management is open to the use of modern urban development tools. This is supported by the fact that Miskolc was the first Hungarian city to join the Green Cities for Sustainable Europe movement in 2011, and then in 2015, it joined the Triangulum project of the EU Smart Cities and Communities program as a follower city. In the process of becoming a smart city, the dimensions of environmental sustainability and energy efficiency were given a prominent role, which should not be surprising considering the traditions of the city. Within this, we must first mention the construction of the geothermal central heating system, with which the city really took significant steps in this field. The main goal of the study is to develop a new smart local concept closely linked to regional development and the key energy sector, through which the local adaptation of the defining elements of the internationally defined smart city in several forms for the city of Miskolc will be presented. In our study, we review how the results achieved by Miskolc so far and the development plans for the future fit in with the smart energy developments of smart cities. Before exploring the processes in Miskolc, we will deal in more detail with the possibilities inherent in district heating and geothermal energy utilization and Hungary’s capabilities.

Analyzing the effectiveness of heat transfer in a horizontal geothermal heat exchanger using numerical methods

Analyzing the effectiveness of heat transfer in a horizontal geothermal heat exchanger using numerical methods

A Comparative Study on the Performance of Ice-Source Heat Pumps Versus Other Heat Source Heat Pumps: A Case Study in the UK

Eliminating natural gas as a fuel for heating residential and industrial units is crucial for reducing environmental pollutants. The challenge lies in finding alternative heating systems and repurposing existing infrastructures, like gas pipes. This article presents a new approach to supplying energy to heat pumps in a post-natural gas era using repurposed gas pipes to transport water for ice-source heat pumps. It highlights the advantages of ice-source heat pumps and compares their thermal performance with other types. The proposed system integrates ice-source and geothermal heat pumps, offering space efficiency, compact design, cost-effective centralization, optimized subsidies, seasonal cooling, weather resilience, and eliminates the need for new piping.This study evaluates heat pump efficiency using various low-grade heat sources: ambient air, ground, domestic wastewater, river and lake water, piped water, and latent heat. It focuses on optimizing heat pump performance under the UK's climatic conditions, addressing efficiency challenges during peak cold periods. The research demonstrates the system's robust performance in cold, densely populated areas, potentially reducing water mass for energy supply by up to 95% with a 70% ice slurry concentration. Additionally, the ice-source heat pump requires about 36.7 times less water volume than traditional systems for residential heating.

Analysis of the Heat Transfer Performance of a Buried Pipe in the Heating Season Based on Field Testing

Ground source heat pump (GSHP) systems have been widely used in the field of shallow geothermal heating and cooling because of their high thermal efficiency and environmental friendliness. A borehole heat exchanger (BHE) is the key part of a ground source heat pump system, and its performance and investment cost have a direct and significant impact on the performance and cost of the whole system. The ground temperature gradient, air temperature, seepage flow rate, and injection flow rate affect the heat exchange performance of BHEs, but most of the research on BHEs lacks field test verification. Therefore, this study relied on the results of a field thermal response test (TRT) based on a distributed optical fiber temperature sensor (DOFTS) and site hydrological, geological, and geothermal data to establish a corrected numerical model of buried pipe heat transfer and carry out the heat transfer performance analysis of a buried pipe in the heating season. The results showed that the ground temperature gradient of the test site was about 3.0 °C/100 m, and the temperature of the constant-temperature layer was about 9.17 °C. Increasing the air temperature could improve the heat transfer performance. The temperature of the surrounding rock and soil mass of the single pipe spread uniformly, and the closer it was to the buried pipe, the lower the temperature. When there is groundwater seepage, the seepage carries the cold energy generated by a buried pipe’s heat transfer through heat convection to form a plume zone, which can effectively alleviate the phenomenon of cold accumulation. With an increase in seepage velocity, the heat transfer of the buried pipe increases nonlinearly. The heat transfer performance can be improved by appropriately reducing the temperature and velocity of the injected fluid. Selecting a backfill material with higher thermal conductivity than the ground body can improve the heat transfer performance. These research results can provide support for the optimization of the heat transfer performance of a buried tube heat exchanger.

The Evolution of Powell Basin (Antarctica)

Powell Basin is an ocean basin formed as a result of the Scotia Sea evolution. The existing tectonic models propose a variety of starting and ending ages for the spreading of the basin based on seafloor magnetic anomalies. Here, we use recent magnetic field data obtained from eight magnetic profiles in Powell Basin to provide insights into the oceanic spreading evolution. The differences found between the number of anomalies on both sides of the axis and the asymmetry in the spreading rates suggest different opening models for different parts of the basin. We propose a spreading model starting in the late Eocene (38.08 Ma) and ending in the early Miocene (21.8 Ma) for the northern part of Powell Basin. For the southern part, the opening started in the late Eocene (38.08 Ma) and ended in the middle Paleogene (25.2 Ma). The magnetic data have been combined with gravity and sediment thickness data to better constrain the age models. The gravity and sediment thickness information allow us to more accurately locate the position of the extinct spreading axis. Geothermal heat flow measurements are used to understand the relationship between the low amplitudes of the magnetic anomalies and the heat beneath them. Our proposed oceanic spreading models suggest that the initial incursions of the Pacific mantle outflow into the Powell Basin occurred in the Oligocene, and the initial incursions of oceanic currents from the Weddell Sea occurred in the Eocene.

Geothermal heat flux of Ridge B region in Antarctica inferred from basal dry-wet distribution

Geothermal heat flux of Ridge B region in Antarctica inferred from basal dry-wet distribution

Divergent chimney and sloping collector design for ground heat source integrated solar chimney power plants

Divergent chimney and sloping collector design for ground heat source integrated solar chimney power plants

Numerical modelling of CO2-in-water emulsion injection into a water-saturated core

Depressurization method shows promise for methane hydrate (MH) reservoir production, but the reformation of hydrates due to a lack of geothermal heat presents a significant challenge for commercial production. This study proposes a novel approach for MH gas recovery by injecting a CO2-in-water (C/W) emulsion into an MH reservoir aquifer. The exothermic nature of CO2 hydrate formation and liquid CO2 dissolution in water in this method provides heat to the MH layer, effectively preventing hydrate reformation. Subsequently, 1-D numerical models were developed and implemented using the MATLAB Reservoir Simulation Toolbox (MRST). These models were rigorously validated against experimental data under homogeneous conditions and varying injection schemes. The investigation indicated that the average volume fraction of CO2 hydrate within the hydrate particles was found to be 55% of the volume of liquid CO2 droplets. The alternating C/W emulsion injection increased the driving force for CO2 dissolution in water, thereby promoting subsequent hydrate particle decomposition and CO2 hydrate dissolution in water, which effectively mitigated blockage within the porous medium. In conclusion, water alternating C/W emulsion injection, along with the continuous injection of a low volume fraction of liquid CO2 within the C/W emulsion, exhibits promising potential for sustained injection and provides adequate heat to the MH layer, preventing hydrate reformation. Furthermore, the developed numerical model reasonably predicts the behavior of various injection schemes. This developed model can be used for devising long term sub-seabed carbon capture and storage development plan.

Artificial intelligence application for assessment/optimization of a cost-efficient energy system: Double-flash geothermal scheme tailored combined heat/power plant

Utilizing the capabilities of artificial intelligence can lead to the development of energy systems and power supply chain that are more efficient, sustainable, and resilient. The integration of machine learning techniques within these systems provides substantial benefits and is essential for enhancing overall performance. As the global community confronts challenges like climate change and rising energy demands, machine learning will play an increasingly vital role in defining the future of energy systems. This research examines how effective regression-based machine learning techniques are for analyzing and optimizing the performance of a geothermal combined heat and power system. It focuses on creating both linear and quadratic models to assess electricity generation, heat production, and the efficiency of the entire system. The evaluation of these models is performed through residual analysis and R-squared statistics. Results indicate that quadratic models surpass linear ones, with linear model achieving an R-squared value of 88.56 % for power generation, while the quadratic model reaches an impressive R-squared level of 99.88 %. Furthermore, the study demonstrates that quadratic machine learning models hold significant promise for optimizing system performance, shown by desirability metrics exceeding 0.99. This research highlights the importance of regression-based machine learning methods in analyzing and improving geothermal combined heat and power systems.

Heat energy utilization of a double-flash geothermal source efficiently for heating/electricity supply through particle swarm optimization method

The principal aim of this article is to optimize the thermal and electrical efficiency of a geothermal combined heat and power system through metaheuristic particle swarm optimization (PSO) method. The objective of this research is to conduct a thorough analysis of the incorporation of metaheuristic PSO technique, with a specific emphasis on the potential advantages and obstacles associated with the utilization of metaheuristic approaches in improving the effectiveness of geothermal energy systems. The utilization of a double-flash geothermal system in conjunction with a transcritical carbon dioxide Rankine cycle is utilized for the co-generation of electricity and thermal energy. The research utilized a PSO method to enhance power generation, heating capacity, and overall system efficiency. The PSO algorithm was employed to determine the optimum operational parameters for a pressure level of 820 kPa and a pressure ratio of 1.59, leading to the maximization of power output to 2591.4 kW The PSO algorithm effectively identified the optimal operational parameters as a pressure of 820 kPa and a pressure ratio of 1.59, resulting in the achievement of a peak power output of 2591.4 kW. The methodology has determined that a pressure of 916.4 kPa and a pressure ratio of 1.5 represent the optimal parameters for achieving a maximum heating capacity of 12329.1 kW.

On the factors and the degree of their effect on subglacial melt and changes in the state of Antarctic subglacial lakes

ABSTRACT This study presents the results of mathematical modeling of the degree of effects of various characteristics on basal conditions in Antarctica. The model is based on the numerical solution of the one-dimensional Stefan problem. Five factors determining the nature of subglacial processes have been studied: ice thickness, snow-firn thickness, surface mass balance, air temperature, and geothermal heat flux. It was found that on the Antarctic plateau, slope, and coast, the geothermal heat flux has the greatest influence on the basal conditions. It is the heat flux that is responsible for the transition of most Antarctic lakes from a stable state to an active one (except for the ice stream regions). In areas where the ice sheet is thinner than 1,500 m, air temperature is the second most important factor affecting subglacial conditions. In areas where the glacier is thicker, the ice thickness begins to have a greater effect. The snow-firn thickness and snow accumulation have little effect on subglacial melt in most parts of Antarctica. Calculations over a 100-year period show that if meltwater accumulates on the bedrock rather than being completely channeled, it leads to a decrease in the average rate of subglacial melting by approximately 10 times.

Investigation of geochemically induced permeability alteration in geothermal reservoirs and its implications for sustainable geothermal energy production

Geothermal resources constitute a significant portion of the world's low-carbon, renewable energy potential, with about 75% classified as low-temperature. One such potential resource exists in Precambrian basement rocks underlying the Williston Basin in southern Saskatchewan, Canada, with a reservoir temperature of 120 °C. However, geochemically induced permeability alteration in these highly reactive low-temperature granitoid resources poses a significant risk to long-term heat production. To assess and potentially mitigate this risk, we conducted a geochemical and mineralogical study of both altered and unaltered samples. Our findings facilitated the parameterization of geochemical simulations of water-rock interactions to predict mineral volume changes and, by extension, draw inferences on porosity and permeability changes resulting from these interactions. The simulations indicate an increased mineral volume in both samples, yet geothermal alteration of the unaltered, and thus more reactive, rocks induced relative mineral volume changes about 30% greater than those in the altered rocks. The resulting absolute change in porosity is 0.5 vol% for the unaltered rocks and 0.35 vol% for the altered rocks. Utilizing an empirical porosity-permeability relationship, the computed change in permeability indicates that the unaltered basement rock experienced a greater change in total permeability than the altered basement rocks. Additional calculations demonstrate the sensitivity of the porosity-permeability equation to critical porosity and power exponent, forecasting various scenarios with permeability changes ranging from 1.0 × 10−13 to 1 × 10−20 m2. Consequently, we infer that altered, permeable zones of the examined Precambrian basement rocks are likely to offer favourable conditions for sustained, multi-decade heat production, and thus should be targeted over less altered zones to justify initial capital expenditures. Globally, geothermal heat extraction from these rocks remains an underexplored yet promising resource for generating reliable, low-carbon renewable energy, crucial in our efforts to decarbonize the global economy.

A numerical study on the sustainability and efficiency of deep coaxial borehole heat exchanger systems in the cold region of northeast China

Numerical simulations utilizing OpenGeoSys have been conducted on a deep coaxial borehole heat exchanger situated in the Songliao Basin. The findings reveal that the outlet temperature exhibits a downward trend as circulation flow increases, while it rises with an increase in inlet temperature. Additionally, the heat transfer power escalates with higher flow rates but diminishes as inlet temperature rises. Notably, the long-term operation results in a reduction of outlet temperature and heat transfer power. After 30 years, the decline of them is approximately 0.3 °C and 8 kW under current situation. Furthermore, long-term operation induces a decrease in formation temperature, predominantly around the vicinity of well, where the maximum temperature decline is nearly 30 °C. The reduction in formation temperature is directly proportional to the increase in flow rate and inversely proportional to inlet temperature. Within the depth range of well, the maximum influence radius expands in correlation with both the depth and duration of mining, while remaining relatively stable with variations in flow rate and inlet temperature. Following three decades of extraction, the influence radius is approximately 95m. The results provide vital scientific insights for the retrofitting of abandoned wells in Northeast China into geothermal heat exchange wells for building heating purposes.

Heat Transfer Performance Factors in a Vertical Ground Heat Exchanger for a Geothermal Heat Pump System

Ground heat pump systems (GHPSs) are esteemed for their high efficiency within renewable energy technologies, providing effective solutions for heating and cooling requirements. These GHPSs operate by utilizing the relatively constant temperature of the Earth’s subsurface as a thermal source or sink. This feature allows them to perform greater energy transfer than traditional heating and cooling systems (i.e., heating, ventilation, and air conditioning (HVAC)). The GHPSs represent a sustainable and cost-effective temperature-regulating solution in diverse applications. The ground heat exchanger (GHE) technology is well known, with extensive research and development conducted in recent decades significantly advancing its applications. Improving GHE performance factors is vital for enhancing heat transfer efficiency and overall GHPS performance. Therefore, this paper provides a comprehensive review of research on various factors affecting GHE performance, such as soil thermal properties, backfill material properties, borehole depth, spacing, U-tube pipe properties, and heat carrier fluid type and velocity. It also discusses their impact on heat transfer efficiency and proposes optimal solutions for improving GHE performance.

Decarbonising primary industries with geothermal heat – a pathway to greater direct use

ABSTRACT This paper discusses the opportunities and policy levers to increase the use of low-temperature geothermal resources in New Zealand for decarbonising primary industries, in particular, covered crops. Geothermal heat (geoheat) is a local, reliable, resilient and sustainable energy source. Low-temperature geothermal energy (220°C) is available in the Taupō Volcanic Zone with low awareness of the nationwide availability of lower temperature resources. Covered crop growers in New Zealand, needing to decarbonise their operations, are investigating the potential of utilising geoheat, following the example of the Netherlands. The Netherlands has strategically invested in low-temperature geothermal energy, utilising 80 °C water resources, from ∼ 2 to 3 km below the surface to heat greenhouses. Internationally, risk mitigation schemes and insurance programmes have proven pivotal policy instruments for fostering geothermal adoption. This paper discusses the opportunities that the adoption of using low-temperature geothermal provides to New Zealand drawing upon successful models from other countries.