Geothermal Energy Applications Research Articles

GIS analysis for the selection of optimal sites for mine water geothermal energy application: a case study of Scotland's mining regions

Water within flooded coal mines can be abstracted via boreholes or shafts, where heat can be extracted from (or rejected to) it to satisfy surface heating (or cooling) demands. Following use, water can be reinjected to the mine workings, or discharged to a surface water receptor. Four criteria have been applied, using ArcGIS, to datasets describing mine workings and mine water below the Midland Valley of Scotland, to provide an initial screening tool for suitability for mine water geothermal energy exploitation. The criteria are: (i) presence of two or more worked coal seams below site, (ii) absence of potentially unstable shallow (<30 m) workings, (iii) depth to mine water piezometric head <60 m, (iv) depth of coal mine workings <250 m. The result is the Mine Water Geothermal Resource Atlas for Scotland (MiRAS). MiRAS suggests that a total area of 370 km 2 is “optimal” for mine water geothermal development across 19 local authority areas, with greatest coverage in North Lanarkshire. This result should not be taken to suggest that mine water geothermal potential does not exist at locations outside the identified “optimal” footprint. The MiRAS does not preclude the necessity for specialist engineering and geological input during full feasibility study. Thematic collection: This article is part of the Mine Water Energy collection available at: https://www.lyellcollection.org/topic/collections/mine-water-energy Supplementary material: https://doi.org/10.6084/m9.figshare.c.7235866

Direct/indirect optimal use of shallow geothermal energy in floor radiant cooling system coupled with air-handling system

Shallow geothermal energy is used as the cold source of floor radiant cooling systems (RFCSs). A physical simulation test bench was built to study the cooling and dehumidification characteristics of an RFCS to evaluate its feasibility. Three operation modes involving direct-supply chilled water, direct-supply chilled-water coupling air-handling system (AHS), and indirect cascade utilization were evaluated. Results showed that the room could be cooled rapidly in the direct-supply chilled-water mode. When the direct-supply chilled-water temperature was lower than 16 °C, condensation occurred on the floor surface. The AHS effectively avoided condensation, and the maximum humidity ratio difference between the air inlet and outlet was 13.61 g/kg. However, the temperature difference between the chilled water and the floor surface was reduced. Under the cascade utilization mode, the cooling efficiency of the system improved, and the indoor temperature and relative humidity were maintained at 20.6–28.1 °C and 57.0–76.1 %, respectively. This study provides valuable insights into the direct application of geothermal energy in RFCSs.

Thermal Performance of Earth Air Heat Exchanger for Geothermal Energy Application in Hot Climate using CFD Simulation

The Ground Air Heat Exchanger (GAHE) is a sustainable, environment friendly, and efficient device that can be used for both heating and cooling applications. Careful design of GAHE enables efficient exploit of the earth interior energy. The design of a GAHE relies on the constant temperature of the earth interior which allows consistent and reliable source of geothermal energy. By harnessing this renewable energy, a sustainable solution for heating and cooling needs is attained while minimizing the impact on environment. In this study, the performance of GAHE was examined using ANSYS Fluent 19 R1 and SOLID WORK 16.0 software. The efficiency and Coefficient of Performance (COP) of the ETHE have been investigated. The effect of air flow rate and operation conditions on the outlet air temperature have been studied. GAHE is made of Polyvinyl Chloride (PVC) pipe of 0.1 m diameter, 0.005 m thickness and 18 m horizontal length. Computer simulations were carried out for five different air velocities (1, 2, 3, 4, and 5 m/s) at various operation conditions. Results show that the 18 m pipe length is adequate to attain useful air outlet temperature giving COP values between 0.5 and 1.3. The length of the horizontal part of GAHE can be further increased for air velocities between 3 and 5 m/s. Comparison between the results obtained by the CFD model and experimental work demonstrated that the CFD model is capable of producing results with acceptable accuracy. This suggests that the CFD software can accurately model the performance of the GAHE under different operation conditions. Increasing the length of the horizontal part of the GAHE can improve its COP when higher air velocities are used.

Applications of Geothermal Energy for Desalination: A Review Technological Advancement and Water Security

Geothermal energy, harnessed through the Earth's thermal resources, emerges as an enduring and sustainable remedy to tackle the urgent concern of water scarcity through desalination. By harnessing the innate thermal reservoirs within the planet, geothermal energy provides a distinctive avenue for generating heat and electricity, particularly when synergistically aligned with desalination procedures. To understand the insights of the implications of geothermal energy for desalination, we conducted a comprehensive literature review analysis. Main objectives of the review are to (i.) disseminate insights into geothermal-driven desalination, (ii.) explore potentialities and obstacles of geothermal-driven desalination, and (iii.) evaluate forthcoming environmental, socio-economic predicaments associated with this approach. We selected 50 peer reviewed scholarly communications published using Google Scholar from 2000 to 2022, focusing on impactful English-language publications within esteemed scientific journals. We found multi-effect evaporation/distillation (MED); multi-stage flash distillation (MSF); thermal vapor compression (TVC) and mechanical vapor compression (MVC). Membrane processes include electrodialysis (ED), reverse osmosis (RO), and membrane desalination are the common techniques used across mainly in Australia, USA, UAE, Sub-Saharan and African nations, and Japan. The integration of innovative designs of these methods can enhance the efficacy and cost-efficiency of geothermal desalination systems. Furthermore, critical environmental, social, and economic concerns linked to geothermal-driven desalination were identified. We noted that high-capacity factor for stable heat supply, independent of seasonal changes, ideal temperatures (70-90° C) for low-temperature desalination, cost-effectiveness with simultaneous power and water production, environmentally friendly with no emissions, versatile to meet energy demand across scales are some of main advantages of selection of geothermal energy for desalination. Some studies showed that geothermal energy for desalination is practical and effective, especially in areas facing water scarcity, strengthening water security. However, challenges persist, necessitating inventive solutions encompassing the pursuit of robust materials designed for high-temperature operation and streamlining energy conversion and integration processes. Other foreseen difficulties include the potential environmental impacts on geothermal reservoirs and the necessity for careful resource management to maintain a fair socio-economic equilibrium. Thus, the future research direction should be mainly focus on harnessing geothermal heat to drive the process, significantly reducing energy consumption and mitigating carbon emissions to potentially be employed across the world.
 
 Keywords: Carbon emission mitigation, Desalination, Energy conservation, Geothermal Energy, Water security

Silurian barrier reef in Lithuania: Reservoir properties and low enthalpy geothermal heat potential

The Silurian barrier reef zone in Lithuania extends for hundreds of kilometres in the narrow zone in Middle Lithuania continuing from the Saukenai reef in the north to the Vilkupiai reef in the south. After prolific Cambrian sandstone reservoirs, they are considered a secondary oil target in Lithuania. However, drilling data showed that the detected reefogenic bodies are either “dry" or saturated with water and/or viscous oil thus practically no valuable oil supply has been obtained. This study illustrates a review of the existing geological and geophysical data, acquired during oil and gas explorations since the 1960s, specifically re-analysed for geothermal purposes.The heat production rates of well doublets within the Silurian reefs range from 0.000044 to 0.24 MWh. Within the area of the Kudirka structure, 6 well doublets could be arranged from the existing 16 exploration wells, at the average distance between the producing-injecting wells of around 700 m. Kudirka has the largest reservoir volume and hence the largest reservoir heat potential (250 GWh). At the smallest distance between the doublet wells of 486 m, the thermal breakthrough would be reached after around 30 years of production-injection. Pavasaris reef shows the best geothermal capacity of a well doublet (0.241 MWh). Reservoir properties are especially good in the partially open fracture zone interval. Pavasaris reef has got 2 wells penetrating the reef, thus one doublet could be arranged within the structure. However, the available thermal energy is limited due to hydrogeological closure and small reservoir size (11.2 × 103 MWh). Other reefs (Saukenai, Vilkupiai, North Bliudziai and a reef in the north of the Vadzgirys reef belt) are small isolated structures, thus their heat potential is low. Moreover, they show low flow rates and hence thermal energy that can be extracted at their wellheads in 30 years is well below 1 × 103 MWh. The study indicates that even though the thickness of the reefal build-ups may reach up to c.90 m, the effective thickness of the reservoirs rarely reaches 20 m. Analysis of the well logs and the core sections show a high heterogeneity of the structures, and hence low recovery factors of the doublets. The distribution of effective layers is usually associated with processes such as stylolitisation and secondary fracturing with enhanced dissolution. For measured low flow rates (<9 m3/h), reusing the existing wells shows low economic viability due to the narrow diameters of the boreholes. Therefore, Silurian reefs show low potential for the application of geothermal energy in Middle Lithuania, although small geothermal projects could be achieved in the Kudirka and Pavasaris sites.

The combined application technology of solar heat utilization and ground source heat pump

Energy issues play an increasingly important role in national security and economic development. The country has put forward the policy of building energy-saving and land-saving buildings. The application of the comprehensive utilization of renewable energy in the construction field has gradually become a need for technical progress and industry development. With the official promulgation and implementation of the Renewable Energy Law in 2006, the application of solar energy, geothermal energy, and other related renewable energy in the construction industry has attracted more and more attention. However, the scope of practical application is currently limited to solar energy alone to supply domestic hot water, power generation, or ground source heat pump system heating and cooling. The actual engineering cases of the combined operation of the two are relatively few, and the unreasonable joint operation mode leads to low system efficiency. In this paper, the combined application system of solar heat utilization and ground source heat pump is elaborated and analyzed in detail, from the technical feasibility, system efficiency, and other aspects of the analysis. It emphasizes the necessity and development prospect of the comprehensive utilization of renewable energy.

Review and prospect of geothermal energy application

Review and prospect of geothermal energy application

Overview of the Potential and Utilization of Geothermal Energy on Flores Island

Geothermal energy on Flores Island is a suitable subject for a contextual approach in physics studies. Research activities, exploration, and the practical application of geothermal energy rely on fundamental physical concepts and principles. Flores Island and the surrounding archipelago are endowed with significant geothermal potential. Consequently, this research endeavor, aimed at assessing the potential and utilization of geothermal energy on Flores Island, serves as an excellent resource for contextual physics learning, particularly in the context of Flores Island. This research uses a literature study approach by reviewing related literature to obtain information about the research object. Flores Island and its neighboring island groups host 24 volcanoes. Specifically, Flores Island boasts 20 locations with geothermal potential, with resources capable of generating up to 739.5 MWe. Notably, by 2023, three Geothermal Power Plants (PLTP) will be operational on Flores Island, including Ulumbu PLTP, Mataloko PLTP, and Sokoria PLTP. These developments have positioned Flores as the first island in Indonesia to surpass the Renewable Energy mix target of 25.38%.

Infrared spectroscopy as a tool for hydrothermal alteration mineral analysis to support geothermal reservoir characterization at The Geysers, California, USA

Infrared reflectance spectroscopy (IRS), an analytical method for characterizing geologic materials, is becoming more commonly applied to geothermal energy applications. However, few case studies are available in the literature and are restricted to relatively few volcanic/geologic environments. We present an interpretation of reservoir mineralogy using IRS on drill cuttings from an active magmatic-heat-sourced geothermal system hosted in metamorphic rocks known as “The Geysers”, located in northern California and operated by Calpine Corp. Wavelength ranges investigated include the Short Wave Infrared (SWIR; 1000–2500 nm) and the Long Wave Infrared (LWIR; 2.5–20 μm). We apply this technique to a 2848 m-deep geothermal production well in the northwest Geysers, inferred to overlie a Holocene intrusion and zone of partial melt as indicated by geophysics. We utilized this non-destructive technique to analyze every drill-cuttings sample (3000+ measurements collected at ∼3.3 m intervals). We identify a zonation in mineralogy that changes from illite + chlorite ± kaolinite ± smectite ± calcite at shallow depths (0–1000 m), to illite + chlorite ± calcite at intermediate depths (1000–2200 m), to actinolite + biotite + chlorite ± tourmaline at greatest depths (2200–2848 m). We find the change at 2200 m is proximal to the inferred transition from the “normal” temperature reservoir (∼240 °C vapor-dominated convective zone) to the high temperature reservoir (up to 400 °C, conduction-dominated). We identify a possible association between 1900 nm H2O absorptions and current steam entry locations. The results of the SWIR and LWIR analysis are consistent with some caveats with newly collected bulk rock X-Ray Diffraction (XRD) data, and support and compliment previous work at the Geysers utilizing XRD and petrographic analysis.

Resource endowments effects on thermal-economic efficiency of ORC-based hybrid solar-geothermal system

Implementing a high-efficiency hybrid energy generation system requires to comprehensively analyze the influences of multiple factors on the overall performance, including system layout, design parameters, energy resource endowments. For this purpose, this study developed a thermal-economic model for a 300 kW ORC-based hybrid solar-geothermal power generation system at four sites in China, which represents different solar and geothermal energy resources. The optimal configurations of the hybrid system have been obtained for the minimal levelized cost of energy (LCOE) under a certain annual electricity generation (E). The results show that the solar resources continue to play a dominant role in the proposed hybrid system, especially in optimizing the configuration of the system design parameters for the minimum LCOE. Comparing to the individual solar system, the hybrid power generation system significantly enhances its thermal-economic efficiency across the four selected sites, with a maximum increase of 25.34% in E and a maximum decrease of 16.28% in LCOE. Especially in regions with abundant shallow hydrothermal geothermal reservoirs but average solar resources, utilizing shallow geothermal water to preheat Organic Rankine Cycle (ORC) working fluids is a relatively simple yet efficient application of geothermal energy for power generation, worthy of further promotion and implementation.

Environmental impact and thermodynamic comparative optimization of CO2-based multi-energy systems powered with geothermal energy

The continuous increase in global population and energy demands has enhanced the use of fossil fuels. The evident climate change effect in recent years has brought about the necessity to reduce fossil fuels. Hence, there exists an aggregate problem of meeting energy demands and reducing carbon emissions. Renewable energy sources have been proffered as the probable solution; however, multi-energy systems are effective options/alternatives to solving this problem. In recent literature, geothermal energy has been proposed as a renewable energy source that can continuously meet energy demands. However, there exists a significant gap in literature about the most viable temperature range for geothermal energy applications in multi-energy systems. In this study, two innovative CO2-based systems namely, high-temperature geothermal multi-energy system (HTGMES) and low-temperature geothermal multi-energy system (LTGMES) are designed, modelled, analyzed, and compared using a thermodynamic approach. While the HTGMES is modelled to predominantly use CO2 as a working fluid, a novel modified absorption system is integrated with the LTGMES. The two systems are modelled to produce electricity, cooling/refrigeration effect, space heating, hydrogen, and hot water. The energy, exergy environmental, exergy destruction, and exergoeconomic methodology is used to evaluate the performance of the innovative GMESs. Also, multi-objective optimization of the HTGMES and the LTGMES is carried out in a bid to minimize the total product unit cost and maximize overall exergy efficiency. The environmental impact analysis of the proposed system is presented considering CO2 mitigation. The results from analyses showed that the overall energetic and exergetic efficiencies in steady state are 44. 22 % and 33.5 % for the HTGMES and 45.40% and 32.9 % for the LTGMES. The optimized LCOE, LCOC, and LCOH based on the total unit cost are 0.0573 $/kWh, 0.1833 $/kWh, and 11.59 $/kg for the HTGMES; 0.0323 $/kWh, 0.0032 $/kWh, and 11.9$/kg for the LTGMES. Furthermore, the optimized exergetic performance showed that the LTGMES can achieve as high as 64.54 % and 40.96 % energy and exergy efficiency.

Insight into the dynamics of EMHD hybrid nanofluid (ZnO/CuO-SA) flow through a pipe for geothermal energy applications

Insight into the dynamics of EMHD hybrid nanofluid (ZnO/CuO-SA) flow through a pipe for geothermal energy applications

Development of geopolymer-based composites for geothermal energy applications

This paper intends to develop geopolymer-based composites for geothermal energy applications. Both silicon carbide (SiC) sand and SiC powder were applied to optimize the thermal and mechanical behaviours of geopolymer. The flexural and compressive strength of geopolymer composites with different mix designs were investigated. A novel test set-up to record the thermal conductivity were designed, and the thermal behaviours of geopolymer composites with different mix design were tested. It was found that the proper addition of SiC powder is conducive to the compressive and flexural strength of geopolymer composites, while the influence of SiC particles is insignificant. The relationship between flexural and compressive strength of geopolymer composites was also investigated, and it was found that the Portland cement association (PCA) code reached the best fitting precision. With the addition of SiC materials, the maximum thermal conductibility of geopolymeric composite can be as high as 5.35 Wm−1K−1, which is about five times higher than conventional cementitious composite. The combined application of SiC powder and SiC particle is practical to increase the thermal conductivity of geopolymer, making it a suitable material for geothermal energy applications. Based on the numerical model, it was concluded that the addition of silicon carbide is beneficial to the heat exchange rate of the energy pile and improves the heat utilization efficiency of the energy pile.

System optimization and mode modification of the solar assisted ground source heat pump system for primary schools in northern rural areas of China

With the increasing application of geothermal and solar energy in northern regions of China, it has become one of the main clean heating technologies for rural primary schools. However, the mismatch in equipment capacity has led to poor operating effect and economic efficiency of such systems. This paper puts forward experimental and analysis on a solar assisted ground source heat pump system in a primary school in Beijing's Daxing District. And then, to address the above issues, a TRNSYS model is established and verified to optimize the system strategy and form during 15 years period. What’ more, the main factors affecting solar collector selection are screened by sensitivity analysis. And through the step-by-step regression analysis, the collector selection correction model based on the coefficient Km is obtained. The results show that the temperature difference of the optimized collector control is 10 °C/1°C, and that of the supplementary heat is 20 °C/1°C. The applicable scenarios of the two system forms are different, and the energy efficiency of the system operation is increased by 23% and 23.4% respectively. In addition, the revised model ensures the balance of soil temperature for 15 years of operation under the condition of considering multiple elements, which provides a reference for the matching and selection of equipment for the same type of project in the future.

Design optimization of medium-deep borehole heat exchanger for building heating under climate change

Geothermal thermal energy with a medium-deep borehole heat exchanger (MDBHE) is a clean solution for building heating. There lacks a proper design of the MDBHE based on long-term performance evaluation, which is essential to promoting the efficient application of geothermal thermal energy for building heating. This study proposes a design optimization of the MDBHE for building heating under climate change. First, the long-term heating energy performance of the MDBHE under climate change is evaluated. Second, the operation cost is evaluated based on the long-term heating energy performance, considering the discount rate and inflation rate. Third, an optimization algorithm is employed to determine the optimal design of the diameter ratio of the inner pipe to the outer pipe, pipe depth, and inlet velocity of the MDBHE. The optimization method minimizes the cost of initial and operational expenditure while satisfying the system safety requirement. Results show that climate change should be considered, which helps to robustly reduce energy consumption and cost by 9.3%–44.4% and 3.9%–21.8% respectively, under different design conditions compared with the typical meteorology. This study contributes to the proper design of the MDBHE as a clean building heating solution.

Design considerations for developing geothermal-assisted milk pasteurization equipment

The naturally occurring heat inside the earth is renewable and sustainable and is known as geothermal energy. It is a renewable energy source that may be used in various applications, including milk pasteurization. This research focuses on the design considerations for developing geothermal-assisted milk pasteurization equipment which is first of its kind in Gujarat, India in direct application of geothermal energy. The novelty of this device is that it utilizes geothermal water (63 °C) from a self-flowing well to pasteurise milk. The utilization of direct heat energy from geothermal resource reduces the operational cost of milk pasteurization process. It discusses the various aspects of the design process, including efficiency calculation, heat exchange principles, system components, and control strategies. The study also discusses the result of the laboratory analysis of pasteurized milk considering microbiological and chemical parameters. The unit reduces the total plate count to 28,000 cfu/ml, within the recommended range for the WHO (30,000 cfu/ml). The paper concludes by discussing societal benefits and techno economic aspect of geothermal-assisted milk pasteurization equipment.

Study on the mechanical and thermal properties of one-part geopolymer composite for high performance in energy piles

One-part geopolymer is a single-component, easy-to-use geopolymer material that offers simplified and cost-effective production processes for eco-friendly building materials. This study aimed to optimize the thermal and mechanical properties of one-part geopolymer for geothermal energy applications by incorporating both silicon carbide (SiC) sand and SiC powder. Various mix designs of one-part geopolymer composites were investigated, and their flexural and compressive strength were analysed. Thermal conductivity was measured using a novel home-made test set-up. Results showed that the compressive strength of one-part geopolymer composite can be as high as 83 MPa under ambient curing condition. The relationship between flexural and compressive strength was also studied, with the PCA code providing the best fitting precision. Furthermore, the thermal conductivity of one-part geopolymer composite was significantly increased with the combined application of SiC powder and SiC particles. These findings suggest that geopolymer composites with SiC materials are suitable for geothermal energy applications.

Current Status of Renewable Energy Development in China and its Environmental Impact

Based on the “double carbon” proposal, the application area of renewable energy is becoming more and more extensive. The development of renewable energy sources inevitably has some drawbacks and even environmental impacts. In this paper, we analyze solar, hydro, geothermal and wind energy, and further explore their applications and impacts on the environment. The current renewable energy sources include solar, wind, hydro, geothermal, hydrogen and many others. These energy sources are frequently used to generate electricity in order to reduce the pollution caused by fossil fuels. At present, solar-related industries can pollute water and soil during production. The use of water energy requires the construction of power stations or dams, causing disruptions to fish migration and damaging watershed ecosystems. Wind power generation relies mainly on wind turbines, which generate noise that affects human life and hinders the survival of birds due to their large size. The application of geothermal energy has the potential to produce thermal and air pollution, and even lead to geological disasters. There is no denying that these energies pose many problems that cannot be ignored, so this paper intends to attract more scholars to pay attention to renewable energy and its drawbacks, and to further improve the use of renewable energy and reduce its environmental impacts by exploring. During China's energy development, hydrogen energy should be given priority since it has different advantages over other renewable energy in aerospace, electricity, and new energy vehicles, etc.

An alternative pathway from hot dry rock to green hydrogen by organic Rankine cycle applications

Some researchers have been focused on electricity generation using thermal energy extraction from HDRs via Organic Rankine cycles. This new research topic creates a new pathway to reach green hydrogen for countries that have geothermal power such as Turkey. In this study, a well in the Nevşehir region that does not has the potential to be used in direct geothermal energy applications due to the absence of water was examined. By using the heat obtained from HDR by injected water, the estimated amount of electricity that can be produced with a single shaft binary organic Rankine cycle was revealed by calculating the thermal energy that can be obtained from the wells which have a surface temperature of 183 °C at 2900 m 2900 m depth. In the next step, the hydrolysis of water with electricity obtained from renewable energy and the hydrogen potential that can be produced were revealed. This hydrogen, which is estimated to be produced, can be fed directly to the natural gas lines or subjected to processes such as storage or industrial usage.

A new fractal model for quantitatively investigating the contribution of microstructural evolution to geothermal extraction

As one of the most fundamental clean energy sources, geothermal energy extraction and application has undergone extensive research and analysis. Understanding fluid seepage behavior in the pore and fracture microstructure of complex reservoir is fundamental to the extraction. In this study, we provide a novel method for measuring the interplay between pore microstructure and thermal–hydrological–mechanical coupling. The fractal geothermal model developed in this study was validated for correctness by comparison with field extraction data, published model, and analytical solution. For studying thermal conduction, seepage, and fracture-matrix interactions in geothermal reservoirs, the fractal seepage model proposed in this research is superior to the traditional cubic seepage model, according to the findings. Permeability increases by about 11.7% as fractal dimension increases by 0.4%. In addition, both the produced fluid temperature and the mean reservoir temperature are inversely proportional to the pore fractal dimension and initial porosity. We can infer that different structural parameters will have an array of effects on seepage resulting from geothermal extraction, which cannot be predicted using cubic permeability models. This provides new ideas for geothermal extraction practitioners.