ARTICLE | doi:10.20944/preprints202203.0173.v1
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: heat conduction; thermal properties; geothermal heat pump; damping depth
Online: 14 March 2022 (03:34:10 CET)
Undisturbed ground temperature (UGT), thermal conductivity (TC) and heat capacity (HC) are essential parameters for the design of borehole heat exchanger (BHE) and borehole thermal energy storage systems. However, field methods to assess the thermal state and properties of the sub-surface are costly and time consuming. Moreover, HC is often not evaluated but arbitrarily selected from literature considering the geological materials intercepted by boreholes. Therefore, this work aims at proposing a field heat tracing method to infer the thermal diffusivity (TD) and HC with assumption of natural transient heat conduction in the subsurface. Empirical equations were developed to reproduce a UGT profile measured along a BHE. Experimental coefficients are found with a non-linear least square solver optimization and used to calculate the damping depth and TD. Subsequently, the TD is used to evaluate HC considering TC obtained from a thermal response test (TRT). Results from this proposed heat tracing method were verified and validated against a set of TRT results and oscillatory TRT analysis using a field dual probe concept to infer HC. The example here described highlights the advantages and novelty of this fast and simple field method relying only on a single UGT profile measured before a TRT.
ARTICLE | doi:10.20944/preprints202309.1788.v1
Subject: Environmental And Earth Sciences, Water Science And Technology Keywords: geothermal fluids; micro-nanoparticles; TEM; NTA; deep hidden geothermal resources; central area of Shandong Province
Online: 27 September 2023 (05:44:12 CEST)
Micro-nanoparticles' characteristics in geothermal fluids can be applied to detect of deep hidden geothermal resources. Observations using a nanoparticle tracking analyzer (NTA) indicated that the karst geothermal water collected in the central area of Shandong Province (Jinan and Zibo) contains many natural micro-nanoparticles with sizes primarily ranging between 100 nm and 5 μm. The micro-nanoparticles’ type, shape, crystal form, and chemical composition in the samples were analyzed using transmission electron microscopy (TEM). TEM images and energy dispersive spectroscopy showed that the micro-nanoparticles in geothermal water samples were mostly amorphous, irregular, or nearly spherical, with rough edges. The micro-nanoparticles were mainly carbonates, sulfates, and chlorine-containing Fe, Ca, Na, and Mg. The characteristics of the particles can reveal the properties of the deep, hot reservoirs and aquifers from where they originate. Therefore, we believe that natural micro-nanoparticles can be essential to detecting and studying deep, hidden geothermal resources, which is a novel approach to exploring deep, hidden geothermal resources.
REVIEW | doi:10.20944/preprints202310.1728.v1
Subject: Chemistry And Materials Science, Surfaces, Coatings And Films Keywords: Geothermal power; coatings; heat exchangers; corrosion, fouling
Online: 27 October 2023 (02:37:35 CEST)
Geothermal energy is likely to be a significant contributor in achieving sustainable energy goals and net-zero emissions targets. Within geothermal power plants, heat exchangers play a critical role in harnessing this renewable energy source. However, these heat exchangers encounter significant challenges when exposed to geothermal fluids, including erosion, corrosion, and scaling, which adversely affects their performance and longevity. The current review focuses on surface engineering techniques, particularly coatings, as a highly effective and economically viable solution to address these challenges in geothermal heat exchangers. The review begins by providing an overview of geothermal energy, its significance in the context of sustainability and the important role played by heat exchangers in geothermal power generation, followed by the challenges and their impact on heat exchangers. The subsequent section focuses on surface engineering by coatings and its types employed to enhance the performance of heat exchangers. In the final part, the reader is presented with an overview of the challenges associated with the application of coatings in geothermal heat exchangers and potential future directions in this field. This review offers a detailed understanding of the critical role coatings play in improving the efficiency and service life of heat exchangers in geothermal power plants.
REVIEW | doi:10.20944/preprints202308.1267.v1
Subject: Environmental And Earth Sciences, Geophysics And Geology Keywords: geothermal energy utilization; critical raw materials (CRM); Combined Heat Power and Metal Extraction (CHPM); Petrothermal Enhanced Geothermal System (PEGS)
Online: 17 August 2023 (07:28:03 CEST)
Geothermal energy is a weather-independent, permanently available renewable energy source. In addition to producing heat and electricity, geothermal energy can be used to extract critical raw materials dissolved in the heat-carrying fluid. Researchers working on the frontiers of geothermal energy utilisation may be able to transform ultra-deep metallic mineral formations into “orebody-Enhanced Geothermal Systems”. In the planned technology, the metal-containing geological formation would be manipulated in such a way that cogeneration of energy and metals is possible and can be optimised in the future according to market needs. The potential of geothermal energy for sustainable mineral extraction and energy production aligns with Sustainable Development Goal (SDG) 7, which aims to ensure access to affordable, reliable, sustainable, and modern energy for all. This new technology could substantially decrease Europe’s dependency on importing critical metallic minerals (such as lithium and tungsten) and energy; over and above, it has a small environmental footprint, including very low carbon emissions
ARTICLE | doi:10.20944/preprints202010.0164.v1
Subject: Chemistry And Materials Science, Surfaces, Coatings And Films Keywords: Polycarbonate; plastic; greenhouse; heating requirement; geothermal energy; Turkey
Online: 8 October 2020 (09:05:06 CEST)
Greenhouse have to provide optimal climate conditions for healthy plant growth and high production. Heating of greenhouses is required for an efficient and reliable production specially during winter time in Turkey. However, even in the temperate zones, heating costs has a great portion in the total production costs. Coal is preferred as a fuel in the greenhouse heating in provinces of Turkey where there is no geothermal energy. In this study, the heating requirements and fuel cost (fossil and geothermal energy) for Antalya, Afyon, Kütahya, Denizli, and Aydın provinces in the Aegean and Mediterranean region have been identified based on long term meteorological data. The calculations were made for two model greenhouses located in an area with 1 ha representing modern greenhouses of the regions. The first is a gothic roofed plastic model greenhouse and the second is a gable roofed polycarbonate model greenhouse. According to the results of calculations, total annual heatingrequirement values ranged from 6,096,283 (for Antalya) to 20,359,946 MJ/ha (for Afyon) for the plastic greenhouse wheras these values ranged from 3,187,074 (for Antalya) to 10,643,972 MJ/ha (for Afyon) for the polycarbonate greenhouse.
ARTICLE | doi:10.20944/preprints202109.0203.v1
Subject: Engineering, Other Keywords: CO2-plume geothermal (CPG); Enhanced gas recovery (EGR); Combined CO2-EGR–CPG system; Sensitivity analysis; Reservoir simulation; Geothermal power generation
Online: 13 September 2021 (11:14:51 CEST)
There is a potential for synergy effects in utilizing CO2 for both enhanced gas recovery (EGR) and geothermal energy extraction (CO2-plume geothermal, CPG) from natural gas reservoirs. This “combined CO2-EGR–CPG system” has been introduced as a feasible approach that constitutes a CO2 Capture double-Utilization and Storage (CCUUS) system. In this study, we carry out reservoir simulations, using TOUGH2, to evaluate the sensitivity of the natural gas recovery, pressure buildup, and geothermal power generation performance of the combined system to various key reservoir and operational parameters. The reservoir parameters include horizontal permeability, permeability anisotropy, reservoir temperature, and pore-size-distribution index; while the operational parameters include wellbore diameter and ambient surface temperature. Using an example of a natural gas reservoir model, we also investigate the effects of different strategies of transitioning from the CO2-EGR stage to the CPG stage on the energy-recovery performance metrics and on the two-phase fluid-flow regime in the production well. The simulation results show that overlapping the CO2-EGR and CPG stages and having a relatively brief period of CO2 injection but no production (which we call the CO2-plume establishment stage) achieves the best overall energy (natural gas and geothermal) recovery performance. Permeability anisotropy and reservoir temperature are the parameters the natural gas recovery performance of the combined system is most sensitive to. The geothermal power generation performance is most sensitive to the reservoir temperature and the production wellbore diameter. The results of this study pave the way for future CPG-based geothermal power-generation optimization studies. For a CO2-EGR–CPG project, the results can be a guide regarding the required accuracy of the reservoir parameters during exploration and data acquisition.
ARTICLE | doi:10.20944/preprints202309.1319.v1
Subject: Engineering, Electrical And Electronic Engineering Keywords: oil reservoir; thermal profile; geothermal profile; flow rate injection
Online: 20 September 2023 (05:01:48 CEST)
Every simplification has the potential to add a systematic error to the measured value. Sometimes, the addition does not render the measurement useless. In the case of oil well flow measurements based on the thermal properties of the fluid in the well, the addition of a systematic error of up to 20% can occur if the variation in the internal energy of the fluid and, most importantly, the transient nature of heat transfer in the completion are not taken into account. This error is a mathematical consequence of the simplifications chosen. To work within the first hours of good operation, given the need for immediate application in a prototype water injection well developed and installed at the UFRN, this article presents an analytical solution for calculating the flow rate by solving the differential equations obtained by applying the principles of mass and heat transfer. As a result, at the cost of greater complexity, the systematic error drops to values of less than 1% in the first two hours of operation of the well, as seen throughout this document.
ARTICLE | doi:10.20944/preprints202303.0511.v1
Subject: Physical Sciences, Fluids And Plasmas Physics Keywords: Oil reservoir; Thermal Profile; Geothermal Profile; Flow Rate Injection
Online: 29 March 2023 (14:12:50 CEST)
This article provides insight into flow measurement techniques in water injection wells in oil production fields, with a particular focus on the initial phases of operation. Consequently, the method created by Ramey in 1962, originally intended for estimating the temperature of the injection fluid, has been adapted to calculate the flow rate. In this technique, the calculation This procedure is based on the correlation between the thermal flux formed in the well. The discrepancy between the temperatures of the injected liquid and the geothermal temperature of the reservoir is the main source of the systematic errors in Ramey’s technique. To a lesser extent, but still significant, failure to observe the injection time in a fluid variation also results in an error problem that needs the failure to adhere to the scheduled injection time for a fluid alteration also yields a notable error dilemma that needs to be fixed. The reduction of listed systematic errors is the product of the main part of this article.
ARTICLE | doi:10.20944/preprints202201.0282.v1
Subject: Business, Economics And Management, Business And Management Keywords: Project management; geothermal; co-benefits; sustainable development; innovation, operationalization
Online: 19 January 2022 (16:08:41 CET)
Despite knowledge concerning stakeholders and the economic advantages of consultation, collaboration and innovation, analysis of the sustainability implications of the geothermal industry has tended to take a high-level or systemic overview of national performance. This study seeks to begin to fill this gap in the academic and grey literature, investigating the following research question: how do projects in the Icelandic geothermal energy sector create co-benefits with stakeholders and reflect the integration of sustainable energy development (SED)? The focus of its analysis is on identifying who are the stakeholders, what are the sustainability benefits co-created with stakeholders, and when in the project lifecycle do these occur. Based on eleven semi-structured interviews with project managers in Iceland’s geothermal industry, the study identifies a broad array of stakeholders in the sector, including national and municipal governments and public sector institutions, businesses, the public, employees and landowners. The sustainability co-benefits of Iceland’s geothermal power projects are broad and cut cross all six themes of SED and multiple phases of the project lifecycle. Although the sustainability benefits are very apparent, trade-offs are reported between the pursuit of an economically efficient energy system and nature conservation. This relates to unsustainable utilization of the resources and the environmental externalities of power production and consumption. Efforts to mitigate these effects are ongoing and the further pursuit of SED is likely in Iceland given its recognition within the nation’s new energy policy and to meet ambitious greenhouse gas emissions reduction targets in the government’s climate action plan. These are issues that are prominent in other nations seeking to decarbonize energy systems through increased utilization of geothermal resources.
ARTICLE | doi:10.20944/preprints202102.0532.v1
Subject: Business, Economics And Management, Accounting And Taxation Keywords: geothermal power plant; environment issues; rural Tompaso; competitive intelligence
Online: 23 February 2021 (19:01:29 CET)
The vision of the community around Geothermal Power Plant (GPP) is the development of GPP should be based on sustainable development principles, without jeopardizing the quality of life and justice for communities surrounding the power plant. This research aims to: (i) identifying issues that arise as an impact of the development of GPP in the rural Tompaso, and (ii) finding solutions to the issues to minimize the conflict that arises from further GPP development in rural Tompaso and its surroundings. This study is based on the competitive intelligence (CI) research method. The results show that the development of GPP in Tompaso has a negative impact on the natural environment and social environment. The technical solutions offered include: (i) bioremediation by cultivating plants that absorb arsenic; (ii) biosulfurization and desulfurization for reducing air pollution, especially sulfur; (iii ) floods and extreme drought are managed by improving infrastructure and reforestation; (iv) social conflicts (land acquisition, working days, labor recruitment and settlement security) are solved by intensifying program dissemination to the community and involving local communities in decision making. The recommended policy is providing incentives to the local community through strategic programs for the development of human and natural resources.
ARTICLE | doi:10.20944/preprints202010.0083.v1
Subject: Engineering, Energy And Fuel Technology Keywords: Focus group discussion; sustainability; renewable energy development; Indonesia; geothermal
Online: 5 October 2020 (12:17:09 CEST)
The study describes in this paper uses direct evidence from processes applied for the developing economy of Indonesia, as it defines the trajectory for its future energy policy and energy research agenda. The paper makes explicit the process undertaken by key stakeholders in assessing and determining the suitability, feasibility and dynamics of the renewable energy sector. Barriers and enablers that key in selecting the most suitable renewable energy sources for developing economies for the renewable energy development have been identified from extensive analyses of research documents alongside qualitative data from the focus group discussions (FGD). The selected FGD participants encompass the collective views that cut across the political, economic, social, technological, legal and environmental aspects of renewable energy development in Indonesia. The information gained from the FGD gives insights to the outlook and challenges that are central to energy transition within the country, alongside the perceptions of renewable energy development from the influential stakeholders contributing to the process. It is notable that the biggest barriers to transition are centred on planning and implementation aspects, as it is also evident that many in the community do not adhere to the same vision.
ARTICLE | doi:10.20944/preprints202308.2183.v1
Subject: Engineering, Energy And Fuel Technology Keywords: Medium-deep; Heat transfer; Geothermal heating; Thermal interference; Life cycle
Online: 31 August 2023 (14:55:43 CEST)
Medium-deep Borehole Heat exchanger (MBHE) has been widely paid attention for building heating. In order to avoid the thermal interference of adjacent MBHEs, temperature distribution characteristics of medium-deep rock-soil was investigated in this work. The evolution on maximum rock-soil thermal affected radius (MTAR) in full life cycle was further analyzed. The results showed that the rock-soil thermal affected area (RTAA) continuously expands in both radial and vertical directions during a heating season. Several factors of thermal extraction load, fluid velocity, geothermal gradient and pipe length have main impacts on the RTAA in vertical direction. Rock-soil thermal conductivity affects the RTAA in both radial and vertical directions. In non-heating season, temperature difference of rock-soil in radial direction dominates the temperature recovery in the first year while geothermal flow nearly dominates temperature recovery after 20 years. The thermal affected radius (TAR) in the 30 th year could be determined as an effective MTAR in full life cycle. In order to decrease installed distance of adjacent MBHEs, a new well layout form by deflecting borehole was proposed. The recommended deflection angle is equal to or larger than 4 times TAR angle. This work provides scientific reference for promoting application of multiple MBHE arrays.
ARTICLE | doi:10.20944/preprints202304.0702.v1
Subject: Engineering, Civil Engineering Keywords: Geothermal Energy, Ground Temperature, Correlation Chart, Soil Types, Temperature Equation
Online: 21 April 2023 (09:27:30 CEST)
Pakistan relies mostly on fossil fuel for fulfilling its energy demand which is expensive as 11 well as not friendly for the environment. The need of the hour is to shift from fossil fuels to renew-12 able energy resources like geothermal, wind, solar etc. to cater for global warming issues. Pakistan 13 has a lot of potential geothermal sites because of several fault lines and hot springs. A sound 14 knowledge of ground temperature is essential to use geothermal energy, which is obtained by drill-15 ing boreholes and putting sensors making it an expensive procedure. Thus, to avoid huge cost for 16 drilling bore holes, particularly for ground temperature analysis, a numerical approach has been 17 considered for determining ground temperature. Furthermore, correlation charts between air and 18 ground temperatures have been developed as there were no proper studies on the ground temper-19 ature of Pakistan. Then, with the help of a boreholes drilled in National University of Sciences and 20 Technology Islamabad Pakistan, the actual ground and numerically calculated temperatures have 21 been compared which shows an error margin in the range between 0.27% for higher depths to 7.3% 22 near surface. Thus, it is shown that the proposed method is easy to implement and better than large 23 scale testing methods for the depths at which geothermal energy is extracted.
ARTICLE | doi:10.20944/preprints202105.0542.v1
Subject: Engineering, Automotive Engineering Keywords: hybridization; single-flash; geothermal; biomass; sCO2 cycle; olive residue; flexibility
Online: 24 May 2021 (08:48:56 CEST)
This study investigates the hybridization scenario of a single flash geothermal power plant with a biomass driven sCO2-steam Rankine combined cycle where a solid local biomass source, olive residue, is used as a fuel. The hybrid power plant is modeled using the simulation software EB-SILON®Professional. A topping sCO2 cycle is specifically chosen for its potential for flexible elec-tricity generation. A synergy between the topping sCO2 and bottoming steam Rankine cycles is achieved by a good temperature match between the coupling heat exchanger where the waste heat from the topping cycle is utilized in the bottoming cycle. The high temperature heat addition problem common sCO2 cycles is also eliminated by utilizing the heat in the flue gas in the bottoming cycle. Combined cycle thermal efficiency and biomass to electricity conversion efficiency of 24.9% and 22.4% are achieved, respectively. The corresponding fuel consumption of the hybridized plant is found as 2.2 kg/s.
ARTICLE | doi:10.20944/preprints202002.0413.v1
Subject: Engineering, Energy And Fuel Technology Keywords: geothermal energy; life cycle analysis; solar photovoltaic energy; wind energy
Online: 28 February 2020 (01:34:44 CET)
A Life Cycle Analysis was performed considering three existing power plants of comparable size operating with different sources of renewable energy: geothermal, solar and wind. Primary data were used for building the life cycle inventories. The geothermal power plant includes emissions treatment for removal of hydrogen sulfide and mercury. The scenario about the substitution of natural emissions from geothermal energy, with specific reference to the greenhouse effect, is also investigated performing a sensitivity analysis. The results are characterized employing a wide portfolio of environmental indicators employing the Recipe 2016 and the ILCD 2011 Midpoint+ methods; normalization and weighting are also applied using the Recipe 2016 method at endpoint level. The results demonstrate a good eco-profile of geothermal power plant with respect to other renewable energy systems and allow for a critical analysis to support potential improvements of the environmental performances.
ARTICLE | doi:10.20944/preprints201712.0006.v1
Subject: Engineering, Energy And Fuel Technology Keywords: shallow geothermal resource; borehole heat exchanger; thermal response test; TRT
Online: 1 December 2017 (11:18:32 CET)
Theory of the Thermal Response Testing (TRT) is a well-known part of sizing process of the geothermal exchange system. Multiple parameters influence accuracy of effective ground thermal conductivity measurement; like testing time, variable power, climate interferences, groundwater effect etc. To improve accuracy of the TRT we introduced procedure to additionally analyze falloff temperature decline after power test. Method is based on a premise of analogy between TRT and petroleum well testing, since origin of both procedures lies in diffusivity equation with solutions for heat conduction or pressure analysis during radial flow. Applying pressure build-up test interpretation technique to the borehole heat exchanger testing, greater accuracy could be achieved since ground conductivity could be obtained from this period. Analysis was conducted on coaxial exchanger with five different power steps, and with both direct and reverse flow regime. Each test was set with 96hr of a classical TRT, followed by 96hr of temperature decline, making it almost 2000 hours of cumulative borehole testing. Results showed that ground conductivity value could vary as much as 25% depending on test time, seasonal period and power fluctuations while thermal conductivity obtained from a falloff period gives more stable values with only 10% value variation.
ARTICLE | doi:10.20944/preprints201902.0254.v1
Subject: Engineering, Energy And Fuel Technology Keywords: Shallow geothermal, Borehole heat exchanger, Heat pump, Renewable energy, Applied thermogeology
Online: 27 February 2019 (11:58:26 CET)
When considering implementation of shallow geothermal energy as a renewable source for heating and cooling of the building, special care should be taken in hydraulic design of borehole heat exchanger system. Laminar flow can occur in pipes due to usage of glycol mixture at low temperature or inadequate flow rate. This can lead to lower heat extraction and rejection rates of the exchanger because of higher thermal resistances. Furthermore, by increasing flow rate to achieve turbulent flow and satisfactory heat transfer rate can lead to increase the pressure drop of the system and oversizing of circulation pump which leads to impairment of seasonal coefficient of performance at the heat pump. Most frequently used borehole heat exchanger system in Europe is double-loop pipe system with smooth inner wall. Lately, development is focused on implementation of different configuration as well as with ribbed inner wall which ensures turbulent flow in the system, even at lower flow rates. At a location in Zagreb, classical and extended thermal response test was conducted on three different heat exchanger configurations in the same geological environment. With classic TRT test, thermogeological properties of the ground and thermal resistance of the borehole were determined for each smooth or turbulator pipe configuration. Extended Steady-State Thermal Response Step Test (TRST) was implemented, which incorporate series of power steps to determine borehole extraction rate at the define steady-state heat transfer conditions of 0/-3°C. Results show that heat exchangers with ribbed inner pipe wall have advantages over classic double-loop smooth pipe design, in terms of greater steady state heat extraction rate and more favorable hydraulic conditions.
ARTICLE | doi:10.20944/preprints202310.1548.v1
Subject: Chemistry And Materials Science, Materials Science And Technology Keywords: Cement; Geothermal; Drying shrinkage; Fibers; Rubber; Additives; Temperature cycles; Radial cracks; Leakage; Microannulus
Online: 25 October 2023 (03:11:20 CEST)
Keywords: keyword 1; keyword 2; keyword 3 (List three to ten pertinent keywords specific to the article yet reasonably common within the subject discipline.)
ARTICLE | doi:10.20944/preprints202308.1584.v1
Subject: Engineering, Civil Engineering Keywords: Ground temperature distribution; Geothermal energy; Renewable sources; In-depth temperature acquisition; Mediterranean climate
Online: 23 August 2023 (07:49:20 CEST)
Shallow Geothermal Energy (SGE) exchanges heat with the ground. In continuous long-term operation, the initial temperature field can be disturbed, and subsurface thermal plumes can be developed. In this paper, the thermal impact of a SGE system under Mediterranean climate is handled. Temperature recordings from 104 thermal probes placed in depth along 15 monitoring boreholes are analysed. Those boreholes were drilled 1-2m from thermos-active boreholes of the case study system installed in a university building. The analysis handles one year of SGE system operation. Temperature depth profiles, reaching up to 140 m depth, were registered with a 10-minute time-step resulting in a large amount of data. Ground thermal conductivity was estimated experimentally and semi-empirically allowing to compute the initial undisturbed ground temperature profiles and compare it with the monitored values. Climate data was recorded by the university meteorological station. Globally, the measured and computed data were coherent and a non-negligible impact of the SGE system operation in the first year was observed. The building orientation as well as the nearby departments had significant impacts on shallow ground temperature. Maximum ground temperature changes, ranging from 2 to 3º C as observed in different boreholes indicating that the system is operating efficiently.
ARTICLE | doi:10.20944/preprints202305.0681.v1
Subject: Environmental And Earth Sciences, Other Keywords: alunogen; sulfate; geothermal field; Kamchatka; hydrated; crystal structure; hydrogen bonding; structure complexity; volcano
Online: 10 May 2023 (04:08:11 CEST)
Alunogen, Al2(SO4)3·17H2O, occurs as an efflorescent in acid mine drainage, low-temperature fumarolic or pseudofumarolic (at coal fires) terrestrial environments. It is considered as one of the main Al-sulfates of Martian soils demanding comprehensive crystal chemical data of natural terrestrial samples. However, structural studies of natural alunogen were carried out in 1970s without localization of H atoms and have not previously been performed for samples from geothermal fields, despite the fact that these environments are considered as proxies of the Martian conditions. The studied alunogen sample comes from Verkhne-Koshelevsky geothermal field (Koshelev volcano, Kamchatka, Russia). Its chemical formula is somewhat dehydrated, Al2(SO4)3×15.8 H2O. The crystal structure was solved and refined to R1 = 0.068 based on 5112 unique observed reflections with I > 2σ(I). Alunogen crystalizes in P-1 space group, a = 7.4194(3), b = 26.9763(9), c = 6.0549(2) Å, α = 90.043(3), β = 97.703(3), γ = 91.673(3) °, V = 1200.41(7) Å3, Z = 2. The crystal structure consists of isolated SO4 tetrahedra, Al(H2O)6 octahedra and H2O molecules connected by hydrogen bonds. The structure refinement includes Al, S and O positions that are similar to previous structure determinations and thirty-four H positions localized for the natural sample first. The study also shows the absence of isomorphic substitutions in the composition of alunogen despite the iron-enriched environment of mineral crystallization. The variability of the alunogen crystal structure is reflected in the number of “zeolite” H2O molecules and their splitting. The structure complexity of alunogen and its modifications ranges from 333-346 bits/cell for models with non-localized H atoms to 783-828 bits/cell for models with localized H atoms. The higher values correspond to higher hydration state of alunogen.
ARTICLE | doi:10.20944/preprints201701.0125.v1
Subject: Engineering, Energy And Fuel Technology Keywords: wellbore pressure analysis; equivalent circulating density; geothermal well; wellbore temperature distribution; mathematical modeling
Online: 27 January 2017 (03:10:16 CET)
The accurate wellbore pressure control not only prevents from lost circulation/blowout and fracturing formation by managing density of drilling fluid, but also improves productivity by mitigating reservoir damage. The geothermal pressure calculated by constant parameters for geothermal well would bring big error easily, as the changes of physical, rheological and thermal properties of drilling fluids with temperature were neglected. This paper researches the wellbore pressure coupling by calculating the temperature distribution with existed model, fitting the rule of density of drilling fluid with temperature and establishing mathematical models to stimulate the wellbore pressures, which is expressed as the variation of Equivalent Circulating Density (ECD) under different conditions. With this method, temperature and ECDs in the wellbore of the first medium-deep geothermal well ZK212 Yangyi Geothermal Field in Tibet were determined, and the sensitivity analysis was simulated by assumed parameters, i.e. circulating time, flow rate, geothermal gradient, diameters of wellbore, rheological models and regimes, the results indicated the geothermal gradient and flow rate were the most influence parameters on the temperature and ECD distribution, and additives added in drilling fluid should be careful which would change the properties of drilling fluid and induce the temperature redistribution. To make sure the safe drilling, velocity of pipes tripping into the hole, depth and diameter of wellbore are considered to control the surge pressure.
REVIEW | doi:10.20944/preprints202308.2185.v1
Subject: Environmental And Earth Sciences, Geochemistry And Petrology Keywords: geothermal reservoirs; cap-rocks; exploration; clay minerals; quartz; carbonates; fluid inclusions; chlorite geothermometers; flow pathways
Online: 31 August 2023 (15:03:50 CEST)
Geothermal energy aims at harnessing the heat of the Earth to produce energy, from the near-surface to great depths. Emphasis is put on geothermal reservoirs in crystalline rocks, hence vol-canic islands and crystalline basements of sedimentary basins based on three examples world-wide. Hot brines circulate in those rocks and are responsible for their hydrothermal alteration because of fluid-rock interactions. This includes dissolution of preexisting minerals and crystal-lization of newly formed ones which provide many information of crucial importance for a better exploration of those reservoirs. For example, the crystallization of clay minerals results from the dissolution of preexisting minerals (feldspar and ferro-magnesian minerals in plutonic, volcanic or metamorphic rocks) or from the direct precipitation from geothermal brines, in specific condi-tions. Clay minerals are found in both the geothermal reservoirs and in the clay-cap found above them. Other newly formed minerals such as quartz, carbonates or sulfates have also recorded the conditions of temperature and salinity encountered by fossil reservoirs which can be evaluated thanks to the study of fluid inclusions trapped during their crystallization. This paper presents results from several geothermal deep sites and surface analogues to pinpoint the role played by newly-formed minerals in the characterization of geothermal reservoirs and their cap-rock.
ARTICLE | doi:10.20944/preprints202112.0288.v1
Subject: Engineering, Civil Engineering Keywords: solar energy; geothermal energy; seasonally thawed layer; thermosyphon; heat flux; performance indicator; near-surface layer; heat shielding
Online: 17 December 2021 (12:37:39 CET)
We have suggested earlier a new sustainable method for permafrost thermal stabilization that combines passive screening of solar radiation and precipitation with active solar-powered cooling of the near-surface soil layer thus preventing heat penetration in depth. Feasibility of this method has been shown by calculations, but needed experimental proof. In this article, we are presenting the results of soil temperature measurements obtained at the experimental implementation of this method outside of the permafrost area which actually meant higher thermal loads than in Polar Regions. We have shown that near-surface soil layer is kept frozen during the whole summer, even at air temperatures exceeding +30°C. Therefore, the method has been experimentally proven to be capable of sustaining soil frozen even in more extreme conditions than expected in permafrost areas. In addition to usual building and structure thermal stabilization, the method could be used to prevent the development of thermokarst, gas emission craters, and landslides; greenhouse gases, chemical, and biological pollution from the upper thawing layers at least in the area of human activities; protection against coastal erosion; and permafrost restoration after wildfires. Using commercially widely available components, the technology can be scaled up for virtually any size objects.
ARTICLE | doi:10.20944/preprints202210.0090.v1
Subject: Environmental And Earth Sciences, Geochemistry And Petrology Keywords: Environmental isotope analyses; Strontium isotopes; Boron isotopes; Upper Jurassic carbonate aquifer; South German Molasse Basin; Tansformational Fluid Flow; Geothermal
Online: 8 October 2022 (03:17:44 CEST)
The hydrochemical composition of the Upper Jurassic groundwaters in the South German Mo-lasse Basin (SGMB) indicates a heterogeneous and varying hydrogeochemical evolution, which contradicts previous flow model concepts. For this study, the data of 88 Tertiary, Cretaceous and Upper Jurassic groundwater samples were investigated for hydrochemical elements, 2H/18O-H2O isotopes, 87Sr/86Sr ratios as well as δ11B values. In addition, the geochemical composition, 87Sr/86Sr and δ11B values were analysed from depth-oriented Upper Jurassic rock samples to delineate water-rock interactions in the aquifer systems. Slightly elevated 87Sr/86Sr ratios of the carbonates compared to the typical signatures of marine Upper Jurassic carbonates indicate a synsedimentary radiogenic influence due to the erosion of the adjacent Bohemian Massif. However, these values cannot explain the significant higher Sr-isotope fingerprint of the groundwaters in the central SGMB. Different water types occur in the Upper Jurassic aquifer, primarily distinguished by the dominant cations, calcium or sodium with subclasses of the major anions. The calcium-dominated groundwaters occur mainly at the western and northern margins of the SGMB. The sodi-um-dominated ion exchange groundwaters instead dominate in the central and eastern SGMB. With increasing strontium content, the 87Sr/86Sr ratios of the Upper Jurassic groundwater samples either indicate a strontium uptake by carbonate of the host rocks, or a prevailing radiogenic sig-nature. This implies a basic interaction with terrestrial or marine Tertiary sediments. The results illustrate a downward transformational fluid flow systematic via the thick Tertiary sediment cover into the Upper Jurassic carbonate formation in the SGMB, highlighting a new understanding on the evolution of the Upper Jurassic groundwaters and a basin-wide recharge mechanism.
REVIEW | doi:10.20944/preprints202202.0361.v1
Subject: Engineering, Energy And Fuel Technology Keywords: Hydropower; Wind, Solar; Geothermal; Firewood; Nuclear; Petroleum; Peat; Non-solid biomass; Solid biomass; Energy systems; Human energy; Animal energy
Online: 28 February 2022 (12:25:14 CET)
We live in the world that is completely entangled on energy and thus, Humankind can no longer do without it, power. With electricity being the main form of energy today, this has increased the complexity of our life today. In Uganda, electricity generation is mainly through hydropower which put the country in the bottleneck of over dependence on one source of energy. Yet, there are many energy systems out there that country can diversify its electricity generation. Therefore, the need to understand, the level of development and utilization of various energy systems has been the underlying question for this present study. Comprehensive literature survey was conducted from the electronic databases including ScienceDirect, Wiley, Sage, Scopus, Taylor & Francis, and Google Scholar. The publications in form of reports, conference papers, working papers, discussion papers, journal articles, book sections and textbooks were considered in this study. In total, 11 energy systems including human and animal energy, solid biomass (firewood), hydropower, wind, geothermal, solar, nuclear, peat, coal, petroleum, and non-solid biomass (methanol, hydrogen, ethanol, biodiesel, and biogas) are described. The current and the future development and utilization of these energy systems has been described. The challenges with their development and utilization were elaborated and the solution the challenges were presented. The hydropower with River Nile being the main river for large hydropower plant construction is the dominance energy system in Uganda. Nuclear energy will be the salvation for the country’s electric energy supply in the near future. Therefore, Uganda needs to bet big on nuclear energy.
ARTICLE | doi:10.20944/preprints202304.0221.v1
Subject: Biology And Life Sciences, Life Sciences Keywords: shallow-water vent; Tyrrhenian Sea; Tor Caldara; chemolithotroph; Alphaproteobacteria; Thalasso-spiraceae; genome; geothermal; sulfur oxidation; DNA uptake; nitrogen fixation; carbon fixation
Online: 11 April 2023 (10:31:58 CEST)
Varunaivibrio sulfuroxidans type strain TC8T is a mesophilic, facultatively anaerobic, facultatively chemolithoautotrophic alphaproteobacterium, isolated from a sulfidic shallow-water marine gas vent located at Tor Caldara, Tyrrhenian Sea, Italy. V. sulfuroxidans belongs to the family Thalassospiraceae within the Alphaproteobacteria, with Magnetovibrio blakemorei as its closest relative. The genome of V. sulfuroxidans encodes the genes involved in sulfur, thiosulfate and sulfide oxidation, as well as nitrate and oxygen respiration. The genome encodes the genes involved in carbon fixation via Calvin-Benson-Bassham cycle, in addition to genes involved in glycolysis and TCA cycle, indicating a mixotrophic lifestyle. Genes involved in the detoxification of mercury and arsenate are also present. The genome also encodes a complete flagellar complex, one intact prophage and one CRISPR, as well as a putative DNA uptake mechanism mediated by the type IVc (aka Tad pilus) secretion system. Overall, the genome of Varunaivibrio sulfuroxidans indicates that the bacterium is metabolically versatile and well-adapted to the dynamic environmental conditions of sulfidic gas vents.