Geothermal Technology Research Articles

Dynamic correlations and volatility spillovers between subsectoral clean‐energy stocks and commodity futures markets: A hedging perspective

AbstractThis study investigates the time‐varying connectedness between subsectoral clean‐energy stocks and fossil fuel energy commodities (crude oil, natural gas, and coal) over the period of December 2013–January 2023 employing the Diebold and Yilmaz approach and the dynamic conditional correlation generalized autoregressive conditional heteroscedasticity model. According to the findings, oil transmits the highest volatility spillover shocks to biofuels, and the least to the fuel cell industry. Both natural gas and coal transmit the highest volatility spillover shocks to energy storage, and the least to geothermal and green information technology, respectively. The study also finds strong and time‐varying volatility connectedness among clean‐energy assets and fossil fuels, significantly affected by global extreme events, such as the COVID‐19 pandemic and the Russia–Ukraine conflict. Additionally, the study provides time‐varying and mean optimal hedge ratios with optimal portfolio weights for investors. The empirical results are robust, and important portfolio and policy implications based on empirical findings are provided.

Temperature effect on the stability of 3D reinforced slopes under unsaturated flow conditions

Slopes are increasingly exposed to elevated temperatures owing to extreme climates or human activities, such as droughts, heat waves, and shallow geothermal technologies. This phenomenon has worsened with global warming. However, the influence of temperature changes on slope stability has not been fully investigated from the perspective of safety. This study introduces an analytical framework for calculating the safety of three-dimensional reinforced slopes which considers the effects of temperature changes and different unsaturated flow conditions. With temperatures ranging from 10 °C to 40 °C, the matric suction of unsaturated soil is thermally sensitive, which causes change in the shear strength of unsaturated soil. To incorporate the temperature effect into the reinforced slope stability assessment, the temperature dependence of the apparent cohesion of unsaturated soil was quantified using a temperature-related effective stress model and soil–water characteristic curves. Thus, the safety factors and reinforcement strength of the slopes were deduced based on the upper-bound theorem of limit analysis. For validation, the proposed method was compared to two previously reported analytical methods, and its effectiveness was further verified through numerical simulations. Finally, the temperature effect was fully investigated and discussed by performing a series of parametric analyses, and suggestions were provided for practical engineering reference.

New multi-energy sources coupling a low-temperature sustainable central heating system with a multifunctional relay energy station

Due to short cost-effective heat transportation distance, the existing geothermal heating technologies cannot be used to develop the deep hydrothermal type geothermal fields situated far away from urban area. To solve the problem, a new multi-energy source coupling a low-temperature sustainable central heating system with a multifunctional relay energy station is put forward. As for the proposed central heating system, a compression heat pump integrated with a heat exchanger in the heating substation and a gas-fired water/lithium bromide single-effect absorption heat pump in the multifunctional relay energy station are used to lower return temperature of the primary network step by step. The proposed central heating system is analyzed by using thermodynamics and economics, and matching relationships between design temperature of return water and main line length of the primary network are discussed. The studied results indicate that, as for the proposed central heating system, the cost-effective main line length of the primary network can approach 33.8 km, and the optimal design return temperature of the primary network is 23 ℃. Besides, annual coefficient of performance and annual exergy efficiency of the proposed central heating system are about 3.01 and 42.7%, respectively.

Economic feasibility of achieving net-zero emission building (NZEB) by applying solar and geothermal energy sources to heat pump systems: A case in the United States residential sector

Buildings are one of the major sectors responsible for high energy demand and GHG emissions worldwide, which is driving expectations for implementing net-zero emission buildings (NZEBs) in many countries. Specifically, most developed countries have a carbon-neutral target set up for 2050, mandating all new buildings from then to be constructed as net-zero emission. Therefore, this paper investigated the economic feasibility of implementing NZEBs in the United States residential sector by combining a heat pump system with two renewable energy sources that are heavily supported by the federal government: solar and geothermal technologies. First, this study clearly demonstrates that “net-zero emission” is the most challenging task among neutralizing the energetic, economic, and environmental by-products from building operations. Moreover, this study analyzed the payback periods of multiple NZEB scenarios by considering the potential future changes in technology and policy necessarily required to meet the net-zero emission target by 2050. For reference, the technological and institutional factors were represented by “PV energy conversion rate” and “CO2 equivalent price of emission trading scheme (ETS)”, respectively. The results show that improving the PV energy conversion rate is much more effective in reducing the payback period of NZEBs compared to raising the CO2 equivalent price of ETS. However, the growing public awareness for this CO2 regulation policy will soon bring synergistic effect with the advancement of PV technology. In conclusion, this research framework clarifies the rather vague technological and institutional challenges that should be addressed to allow NZEBs to become economically feasible in the United States residential sector. Therefore, many building engineers, PV technicians, and policymakers should actively contribute to improving the techno-economic drivers for implementing NZEBs by 2050.

An innovative application of 5GDHC: A techno-economic assessment of shallow geothermal systems potential in different European climates

Energy consumption for thermal purposes represents the most impacting energy issue in the European building sector. In addition to space heating, space cooling is constantly growing, due also to climate change, which provokes extreme hot events in summer even in moderate climates. To approach this challenge, it is essential to invest in lowering the overall energy demand, to increase the energy conversion efficiencies and to replace fossil fuels with renewable energy sources.The research here presented deals with the European decarbonization goals and focuses on shallow geothermal technology in district thermal systems (DTS), i.e. Geo-5GDHC.The research investigates whether Geo-5GDHC can be cost-effective in different scenarios based on climatic contexts, insulation levels and the possible integration of photovoltaic and thermal technology (PVT).Through the elaboration of proper KPIs and the implementation and use of a tool specifically developed to couple a Geo-5GDHC energy assessment model with an economic analysis (PILEDHC), the research highlights results and guidelines for providing solutions for new and innovative DTS, considering both energy and economic aspects in different contexts.

Optimum operation of an ejector-assisted combined flash-binary geothermal cycle using R245fa-isopentane mixture-based secondary working fluids

Combined flash binary geothermal cycle (CFBGC) is a traditional geothermal energy conversion technology. However, in a CFBGC, substantial exergy destruction occurs during the steam flashing. To address this issue, in the present study, the steam flashing device of the conventional CFBGC is replaced by an ejector. The ejector enhances steam cycle power output by ensuring a higher steam flow rate through the high-pressure steam turbine stage. The modified cycle is designated as the ejector assisted combined flash binary geothermal cycle (EACFBGC). To take advantage of temperature glide, various compositions of R245fa-isopentane mixture are considered as secondary working fluid. Optimum operating parameters corresponding to the maximum second law efficiencies of the proposed and conventional cycles are explored by applying an iterative method. Both considered cycles yield the highest second law efficiencies with the 0.7 mol fraction of isopentane in the working fluid mixture. For geo-fluid available at 170 °C, the second law efficiency of the optimized EACFBGC is about 8.08% higher than that of the optimized conventional CFBGC. The corresponding levelized cost of electricity (LCOE) is also 5.7% lower. In a word, the proposed EACFBGC can be considered as the upgraded CFBGC with higher energy conversion efficiency and a lower LCOE.

Discussion on the Application of Geothermal Recovery Technology in Municipal Road Construction

Discussion on the Application of Geothermal Recovery Technology in Municipal Road Construction

A novel application of the geothermal asphalt pavement: A feasible E-fuel source

In this study, a novel application of geothermal technology was proposed and evaluated as a potential sustainable clean energy source. The proposed system incorporates thermoelectric generators (TEG) to transform the extracted heat from the pavement into electricity and enclose an enhanced geothermal system into the asphalt structure, intending to cool the pavement surface and provide the thermal gradient required for energy harvesting simultaneously. The study hypothesized the amplification of the thermal gradient through geothermal pipes embedded in the asphalt layer, a phase change material container in the subgrade, and an external cooling system in direct contact with the TEGs. A comprehensive experimental study was conducted to evaluate the thermal, electrical, and structural performance of the proposed geothermo-electrical asphalt pavement system. Also, a large-scale experimental physical model was established to simulate and assess the system's performance under real-life conditions. By monitoring the system's performance over six consecutive days, the results showed that the enhanced geothermal system efficiently reduced the surface temperature of the asphalt pavement by 40% and sustained a thermal gradient of around 40 °C, which was sufficient to sustainably harvest energy through using the TEGs. The harvested energy was then successfully used to charge an attached battery. The results of this study demonstrate the feasibility and potential of using geothermal technology in asphalt pavements as a sustainable energy source. Furthermore, the proposed system not only improves the performance of the pavements in terms of structural behavior but also introduces a new way of energy harvesting, opening the door for new possibilities in the renewable energy field.

Gyrotatic microorganisms analysis for radiative 3D Carreau nanofluid flow configured by activation energy and viscous dissipation

Nanoparticles and Bioconvection with microorganisms have inclusive and widespread of applications in the specialty of engineering, bioinformatics, biotechnology, mechanical energy and biosensors. Likewise, widespread utilization in diverse industries for-instance, geothermal technology, bio-medical, microelectronics, mechanical-chemistry, solar cells, chlorofluorocarbons toward nuclear reactors and exploitation, together along product degeneration, nuclear reactor chilling, oil emulsification and the thrust in the thermal conductivity accomplishment of the fluid, nuclear plant cooling has flourish an contemporary area for scientists and research scalars. The foremost manifesto of the existing investigation is to provide mathematical modeling and numerical simulation of the three-dimensional steady Bioconvection flow of Carreau nanofluids under the impact of nonlinear radiation and gyrotactic microorganisms. Furthermore, magnetohydrodynamic, activation energy and mixed convection inspirations are also measured. We constrained boundary layer theory to advance the basic PDEs for microorganism field, nanoparticle concentration, energy, momentum and mass, and thus condensed to extremely nonlinear ODEs by using the variable transformations. To scrutinize the problem, we acquired the numerical solution for present study with the help of bvp4c, a MATLAB practice. Graphical along with numerical consequences for the Sherwood number, density number of microorganism and wall heat transfer are as well accompanied. It is fascinating to note that microorganism field has been expanded due to having higher estimates of the bioconvection Peclet number and bioconvection Rayleigh number. It is also illustrated that higher values of heat generation/absorption parameter deteriorate the fluid temperature.

Numerical simulation on Geothermal extraction by radial well assisted hydraulic fracturing

The mid-deep geothermal energy is extracted from the fracture network created by hydraulic fracturing. Generally, the hydraulic fracture created in the deep thermal reservoir shows the planar shape but not the network shape, and this significantly impacts the geothermal extraction efficiency. In this study, a geothermal extraction technology by radial well assisted hydraulic fracturing, which connects hydraulic fractures to each other, was proposed. An operation technique of radial well-assisted hydraulic fracturing in geothermal reservoirs without well-developed NFs was established. The model considering evolution of fracture permeability was resolved by thermo-hydromechanical (THM) coupling numerical simulation. The results show that the radial wells should be placed vertically within a large range. The thermal production increases by 20%, about 0.25 MW as the radial well length increases from 50 m to 200 m. As many fractures as possible are needed in thermal exploitation, and the fracture number should be at least 7. The simulation demonstrates that the radial well-assisted hydraulic fracturing heat recovery method is feasible in simulation. In this thesis, a more accurate numerical simulation method of geothermal production capacity is proposed, which has engineering guiding significance for the actual development and prediction of geothermal energy.

Comprehensive performance evaluation of water and power production technologies using water-exergy nexus analysis

Insight into less-known aspects of sustainable development has been deepened through the development of the nexus between water and energy in the last decades. However, the complex sustainability problem cannot be fully investigated owing to the intrinsic shortcomings of the physical concept of energy. This study considered the exergy concept as a substitute for energy to develop water-exergy nexus analysis (WExNa) as an efficient analytical framework. Accordingly, four evaluation criteria were proposed as quantitative tools of WExNa. Consequently, seven power and seven water production technologies were analyzed considering the model uncertainties in their life cycle. A big data bank, comprising 803 water and 812 power production plants, was labeled to facilitate consideration of the spatial, temporal, and environmental variety of technologies in a stochastic data-driven program. The results showed that wind, solar, and concentrating solar power plants used the least amount of water for exergy production during the entire life cycle, whereas only geothermal power technology could compete with non-renewable power in the operating stage by an exergy dissipation for product exergy index in the range of 0.2 – 3. Despite the significance of chemicals in water production, chemical exergy dissipation was negligible compared with electrical and thermal exergies. Water treatment facilities were generally superior to desalination technologies, considering all types of exergy for water. Although multi-stage flash and electrodialysis exhibited the best and worst operation metrics among the water technologies, they dissipated the most and least exergies for water production, respectively, with an acceptable confidence considering the entire life cycle. Moreover, the contrast between conventional operation indexes and the new WExNa variables entails potentially new horizons through the sustainable evaluation of engineering systems using the proposed analysis.

Machine Learning for Geothermal Resource Exploration in the Tularosa Basin, New Mexico

Geothermal energy is considered an essential renewable resource to generate flexible electricity. Geothermal resource assessments conducted by the U.S. Geological Survey showed that the southwestern basins in the U.S. have a significant geothermal potential for meeting domestic electricity demand. Within these southwestern basins, play fairway analysis (PFA), funded by the U.S. Department of Energy’s (DOE) Geothermal Technologies Office, identified that the Tularosa Basin in New Mexico has significant geothermal potential. This short communication paper presents a machine learning (ML) methodology for curating and analyzing the PFA data from the DOE’s geothermal data repository. The proposed approach to identify potential geothermal sites in the Tularosa Basin is based on an unsupervised ML method called non-negative matrix factorization with custom k-means clustering. This methodology is available in our open-source ML framework, GeoThermalCloud (GTC). Using this GTC framework, we discover prospective geothermal locations and find key parameters defining these prospects. Our ML analysis found that these prospects are consistent with the existing Tularosa Basin’s PFA studies. This instills confidence in our GTC framework to accelerate geothermal exploration and resource development, which is generally time-consuming.

Operation Optimization of Medium-Depth Ground Source Heat Pump (MD-GSHP) Systems Based on the Improved Particle Swarm Algorithm

In recent years, the medium-depth ground source heat pump (MD-GSHP) has become a promising and potential geothermal energy heating technology. This is due to the superior characteristics of buried pipes with a small diameter, the high energy efficiency of the heat pump, the insensitivity to the ground climate, and other conditions. Among currently available studies, both the variable operating conditions and the addition of thermal storage devices have rarely been considered. Despite this, the optimization methods applied to the medium-depth GSHP system are relatively simple. In this paper, an MD-GSHP system, including the thermal storage device with variable operating conditions, was fabricated. The operation strategies of the system were optimized by employing the improved particle swarm algorithm after applying the operating costs, the coefficient of performance of the system (COP) and the geothermal energy utilization coefficient to the objective functions, and the optimization results were compared and analyzed. The results show that the predictions of the optimized operating costs, the COP of the system, and the geothermal energy utilization coefficient were found to be CNY 279.27, 6.4420, and 0.8527, respectively. The effect of the COP on the optimization effect was opposite to that of operating costs, but analogous to that of the geothermal energy utilization coefficient.

Opportunities and challenges for geological work in China in the new era

<strong>Editor’s Note:</strong> In celebration of the Geological Society of China’s centennial anniversary, a seminar titled “Groundwater and Healthy &amp; Green Development” was held on November 24‒25, 2022. It was hosted by the Geological Society of China and organised by its committees on Hydrogeology, Geothermy, Medical Geology, and Mine Water Prevention and Utilization. The seminar aimed to adapt to the new requirements of geological work in the new era and fully leverage the basic, leading, and binding roles of water resources. It sought to promote the conservation of water resources, the protection and ecological restoration of water environments, and the conversion of the cutting edge theoretical research in geothermal technology into achievements; and the advancement of interdisciplinary development of hydrogeology, geothermal geology, and medical geology. The seminar featured an important speech by Wang Min, Vice Minister of the former Ministry of Land and Resources of the PRC, which is included below.

A critical review on the effective utilization of geothermal energy

Rapid growth in the global population and associated elevated reliance on modern technology has resulted in increased demand for energy consumption. This has resulted in an increased focus on the development and generation of advanced sustainable energy systems. The swift implementation of sustainable renewable energy resource utilization and improvement in their efficiency by the modification of current technologies are the possible solutions that gave rise to the emergence of geothermal technology as a potential alternative. Geothermal technology is a non-carbon renewable energy resource that could be utilized efficiently to fulfil the energy demands while mitigating the climate change threat. According to the surveyed literature, the global geothermal energy power plant installation capacity has reached 14.3 GWe to successfully implement this sustainable alternative. In order to have a successful and uninterrupted way forward, it is essential to evaluate the constraints both in terms of technicality and economic feasibility to establish an approved framework. Moreover, the governance and monitoring regarding the social and environmental impact alongside the legal challenges should also be addressed. The significant barriers include increased capital cost, site selection, superiority of resources at diverse levels of rock bottoms, and obstruction from nearby residents that need to be addressed appropriately. As a result, policymakers will continue to seek measure that have least negative impact on environment.

An innovative compressed air energy storage (CAES) using hydrogen energy integrated with geothermal and solar energy technologies: A comprehensive techno-economic analysis - different climate areas- using artificial intelligent (AI)

The present study evaluates the optimal design of a renewable system based on solar and geothermal energy for power generation and cooling based on a solar cycle with thermal energy storage and an electrolyzer to produce hydrogen fuel for the combustion chamber. The subsystems include solar collectors, gas turbines, an electrolyzer, an absorption chiller, and compressed air energy storage. The solar collector surface area, geothermal source temperature, steam turbine input pressure, and evaporator input temperature were found to be major determinants. The economic analysis of the system showed that the solar subsystem, steam Rankine cycle, and compressed air energy storage accounted for the largest portions of the cost rate. The exergy analysis of the system demonstrated that the solar subsystem and SRC had the highest contributions to total exergy destruction. A comparative case study was conducted on Isfahan, Bandar Abbas, Mashhad, Semnan, and Zanjan in Iran to evaluate the performance of the proposed system at different ambient temperatures and irradiance levels during the year. To optimize the system and find the optimal objective functions, the NSGA-II algorithm was employed. The contradictory objective functions of the system included exergy efficiency maximization and cost rate minimization. The optimal Exergy round trip efficiency and cost rate were found to be 29.25% and 714.25 ($/h), respectively.

Thermal environment improvement of underground mine tunneling face using enhanced geothermal system technology

To solve the problem of high temperature thermal damages to the mine underground driving working face of a dry-hot-rock-enriched area, an active cooling method for fracturing water injection of the surrounding rock of the deep mine is proposed based on analysis of the heat dissipation mechanism of the surrounding rock. An artificial thermal reservoir is formed in the high temperature rock mass around the tunneling roadway by stimulation, such as a high pressure crack, and the heat energy of the surrounding rock is extracted by heat exchange of the heat-carrying fluid and the high temperature rocks mass to reduce the ambient temperature of the roadway. The design of a downhole water injection cooling system based on enhanced geothermal system technology is presented and a simplified enhanced geothermal system heats collection model is used for fluid-enclosure. Numerical simulation of the temperature field of the rock coupling shows that the temperature of the surrounding rock can be effectively reduced by increasing the water injection speed and fracture porosity, and improvement of the underground thermal environment can improve the working efficiency. For a water injection rate of 14 m/s and porosity of 0.18, the average cross-section temperature was 41.95?, which is nearly 5? lower than the original rock temperature of 46.85?.

Technical Assessment of Frozen Soil on Geothermal Heat Pump Technology in Western Canada

This study examines the thermal performance of a two-dimensional borehole system, featuring a U-shaped pipe embedded in porous soil, through the application of computational fluid dynamics. The investigation encompasses 24 cases, assessing the impact of various factors such as soil thermal conductivity (k = 1.5, 1.84, 2 W/mK), average soil temperature (T = 280-285 K), and soil moisture content (10%-55%) on ice formation and heat transfer enhancement. The k-ε turbulence model and Darcy-Forchheimer model are employed for the pipe and porous medium, respectively. Furthermore, a solidification model is utilized to monitor potential ice formation within the system. The findings reveal that an increase in soil thermal conductivity enhances heat transfer between the soil and pipe while simultaneously reducing ice formation. Additionally, higher soil moisture levels lead to an elevated outlet temperature for the pipe and decreased ice formation in the soil. Lastly, it is observed that ice formation becomes negligible when the temperature reaches 285 K.

Technological Advancements and Challenges of Geothermal Energy Systems: A Comprehensive Review

Geothermal is a renewable energy source, but this is not as often seen as other renewable energy sources, such as solar, wind, hydro, etc. Several applications could be implemented through geothermal energy, and heating &amp; cooling systems are one of them. Because of the limits of technology, it is hard to improve cooling systems as an application. To address long-term sustainable space heating and cooling, it is imperative to develop geothermal technology. It is known as the oldest, most flexible, most adaptable, and most prevalent approach toward using renewable energy. Therefore, this review has reviewed the global development and challenges of geothermal energy for cooling systems. There are large reserves of geothermal energy available around the world, and numerous scholars have emphasized its importance, but due to a lack of knowledge, no operational work has been done in using these systems for cooling up to this point. This review paper examines globally available geothermal energy sources and technologies for environmentally friendly and sustainable cooling supplies. Finally, the benefits and challenges of geothermal systems for cooling are outlined to promote local, regional, and global investment in utilizing these resources for cooling.

Thermodynamic Modeling of the Advanced Geothermal System Using Inclined Well Applications

The advanced geothermal system (AGS), also called the closed-loop geothermal technology, requires extremely long horizontal wellbore completion to compensate the deficiency for conductive heat exchange in deep reservoirs, which is technically challenge. The AGS using inclined well configuration has been proposed to improve its efficiency, but it lacks a comprehensive and quantitative evaluation in public domain. In this study, analytical models based on Duhamel’s convolution and natural coupling methods are developed to evaluate the performance of the inclined configuration. The results suggest that the inclined wellbore system can improve the outlet temperature performance of a typical horizontal configuration by 16 %. The inclined system also shows a constant temperature gain (9 °C/km in this case study) for unit increment in lateral length. In multilateral applications of the inclined well system, our sensitivity tests indicate that wellbore spacing can have significant impact on the heat energy production performance due to wellbore interferences if the distance between wells is small in 3D space. At least a 50 m distance between any two wellbores is recommended for the multi-lateral wellbore system in the well pad design. In general, 20 % (3 MWth) more heat energy can be generated and almost 1000 GWhth more heat energy could be produced at the end of 30 years by using a standard 10-laterals inclined well system in our case study.