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The field of thermoelectric energy harvesting has gained significant attention as a sustainable method to convert waste heat into useable electricity. This assessment focuses on the recent advancements in thermoelectric materials and their application in harvesting energy from geothermal micro-seepage a relatively untapped but promising source of renewable energy. We systematically analyze recent studies to assess the performance of various thermoelectric materials under geothermal conditions, evaluate the integration of thermoelectric systems with geothermal sources, and identify the key challenges and research gaps that persist in this domain. The paper aims to provide a roadmap for future research, highlighting the potential of thermoelectric technology to contribute to sustainable energy solutions while addressing the limitations that must be overcome for large-scale deployment. • Thermoelectric materials convert geothermal microseepage heat. • Innovative advancements in thermoelectric technology. • System integration with geothermal sources evaluated. • Key challenges and research gaps identified. • Roadmap proposed for future research directions. [ABSTRACT FROM AUTHOR]

This study aims to provide a comprehensive review of the potential of geothermal energy for producing hydrogen, with a focus on the Australian context where low-temperature geothermal reservoirs, particularly hot sedimentary aquifers (HSAs), are prevalent. The work includes an overview of various geothermal technologies and hydrogen production routes, and evaluates potential alternatives for hydrogen production in terms of energy and exergy efficiency, economic performance, and hydrogen production rate. Values for energy efficiency are reported in the literature to range from 3.51 to 47.04%, 7.4–67.5% for exergy efficiency, a cost ranging from 0.59 to 5.97 USD/kg of hydrogen produced, and a hydrogen production rate ranging from 0.11 to 5857 kg/h. In addition, the article suggests and evaluates multiple metrics to appraise the feasibility of HSAs geothermal reservoirs, with results tailored to Australia but that can be extended to jurisdictions with similar conditions worldwide. Furthermore, the performance of various hydrogen production systems is investigated by considering important operating conditions. Lastly, the key factors and possible solutions associated with the hydro-geological and financial conditions that must be considered in developing hydrogen production using low-temperature geothermal energy are summarised. This study shows that low-temperature HSAs (∼100 °C) can still be used for hydrogen generation via supplying power to conventional electrolysis processes by implementing several improvements in heat source temperature and energy conversion efficiency of Organic Rankine Cycle (ORC) power plants. Geothermal production from depleted or even active oilfields can reduce the capital cost of a hydrogen production system by up to 50% due to the use of pre-existing wellbores, under the right operating conditions. Thus, the results of this study bring novel insights in terms of both the opportunities and the challenges in producing clean hydrogen from geothermal energy, applicable not only to the hydro-geological and socio-economic conditions in Australia but also worldwide, exploring the applicability of geothermal energy for clean hydrogen production with similar geothermal potential. [Display omitted] • The review discusses solutions for clean hydrogen from low-temperature geothermal energy. • Energy and exergy efficiencies range from 3.51 to 47.04% and 7.4–67.5%, respectively. • Hydrogen rates and costs are 0.11–5857 kg/h and 0.59–5.97 USD/kg, respectively. • Low-temperature aquifers (∼100 °C) can be used for hydrogen generation via electrolysis. • New insights in opportunities and challenges for producing hydrogen are identified. [ABSTRACT FROM AUTHOR]

The current study examines a novel multigeneration plant that uses geothermal energy to produce clean and sustainable products. The process includes a re-compression supercritical Brayton power plant (re-sBC), an ejector cooling unit (EJCS), a humidifier dehumidifier desalination (HDH) unit, a Proton-Exchange Membrane (PEM) process, and a hot water preparation unit. The designed plant is able to generate hot water, cooling, power, hydrogen, and freshwater using the geothermal source. In the current paper, the thermodynamic analysis, CO 2 emission assessment, and exergoenvironmental index evaluation are executed to determine the system efficiency and the association between the system and the environment. A thorough parametric examination is fulfilled, to show how the system indicators impact efficiency and generated products. According to analysis data, the proposed multigeneration plant is able to generate 1278 kW of heating load, 229.6 kW of refrigeration capacity, and 109.5 kW of net power rate. Additionally, the capacity of the freshwater is 0.1188 kgs − 1 and the hydrogen is 0.001317 kgs − 1 . This developed system emits a total of 117 tonnes of CO 2 emissions per year for these useful outputs. In conclusion, the energetic and exergetic performance of the suggested MG plant are 14.09 % and 23.35 %, respectively. • A sustainable geothermal energy-based MG is proposed. • The thermodynamic, emission, and environmental analysis is conducted. • Design and evaluation of the Green hydrogen production and storage. • Re-compressed sBC integrated into geothermal driven MG plant. • Total energy and exergy efficiency is computed as 14.09 % and 23.35 %, respectively. [ABSTRACT FROM AUTHOR]

Pyrite is a ubiquitous sulfide mineral found in diverse geological settings and holds great significance in the formation of Au deposits as well as the safe utilization of groundwater due to its remarkable ability to incorporate substantial amounts of As. However, despite its importance, there remains a dearth of fundamental data on the partitioning of As between pyrite and fluid, which is key for accurately modeling the As distribution in these environments. Here, we present new insights into the partitioning behavior of As between pyrite and fluid at conditions that mimic natural fluid systems. Pyrite was synthesized by replacement of natural siderite in hydrothermal experiments at 200 °C and pH 5 applying a wide range of fluid As concentrations, spanning from 0.001 to 100 µg/g. The As distribution and concentration in synthetic pyrite was analyzed by quantitative LA-ICP-MS mapping providing a high spatial resolution and sensitivity at 2–3 µm image pixel size at a detection limit of ∼1 µg/g at the single pixel scale. Pyrite-fluid partitioning coefficients (D As (py/fluid)) between synthetic pyrite and experimental fluid agree with previously published data for high fluid As concentrations of 1 µg/g to 100 µg/g (D As < 2000). However, at low As concentrations in the experimental fluid (<1 µg/g), a steep increase in the D As (py/fluid) values of up to ∼30,000 was detected, demonstrating even stronger As partitioning into pyrite. This is confirmed by the analyses of natural pyrite that precipitated from As-poor fluids (0.3–0.4 ng/g) within a deep anoxic aquifer in SE Sweden. The discovery holds significant implications for the mobility and scavenging of As, which in turn is important for understanding the formation and fingerprinting of mineral deposits as well as for the secure utilization of groundwater resources. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive Life Cycle Cost Assessment (LCCA) of geothermal-assisted hydrogen liquefaction, explicitly focusing on the Afyon Geothermal Power Plant (AGPP) as a case study. The study evaluates the economic viability and sustainability of integrating geothermal energy into hydrogen liquefaction. The results of the LCCA contribute to the ongoing discourse on sustainable energy solutions, offering a nuanced understanding of the economic considerations associated with geothermal-assisted hydrogen liquefaction. The study serves as a model for assessing the economic feasibility of similar systems, fostering informed decision-making in the pursuit of cleaner and more economically sustainable energy pathways. This study has conducted a technical and economic investigation of liquid hydrogen production using geothermal heat and electricity effects. Geothermal water pre-cools the hydrogen by providing heat to the absorption system. Then, the electricity generated in the geothermal plant is used to work in the liquefaction cycle. The generated electricity is used to liquefy hydrogen in the liquefaction cycle. The capacity of the electricity generated from the AGPP produced here is 2621 kW. The proposed system can be achieved by pre-cooling unit H 2 up to −30 °C at 120 °C and 150 kg/s geothermal source. In the liquefaction cycle, 0.84 kg/s H 2 can be liquefied. As a result, the total energy efficiency of the proposed system can be calculated as 32.4% and exergy efficiency as 15.4%. The system's net present value (NPV) was calculated as 65,320,000 $. When life cycle cost analysis was performed using the levelized annual cost (LAC) method, the project's levelized cost was calculated as 7,673,000 $/yr. The unit cost of the liquid hydrogen produced is 1.252 $/kg. This system's discounted payback period (N dpp) is calculated as 3.48. Configuration of geothermal assisted hydrogen generation system. [Display omitted] • A techno-economic evaluation of a hydrogen liquefaction system is introduced. • The Life Cycle Cost Assessment of liquefied hydrogen is conducted. • Using geothermal water in an absorption system, H 2 gas can be pre-cooled to −30 °C. • In the liquefaction cycle, using geothermal energy, 0.84 kg/h H 2 can be liquefied. • Liquefied hydrogen market cost and system payback period are calculated as 1.252 $/kg and 3.48 years, respectively. [ABSTRACT FROM AUTHOR]

This study pioneers a transformative approach to sustainable energy recovery, repurposing abandoned petroleum wells in the Nigerian Chad Basin as a triplet-deep closed-loop heat exchanger. We employed a computational numerical approach to designed two deep closed loop systems, which share a common production well, and to evaluate the thermal performance as well as its sustainability over a period of 25 years. The geometrical configuration consists of two injection wells, which converge to the common production one doubling the flow rate at surface and minimising the heat loss during the ascent of the fluid. The availability of detailed abandoned well specifications enabled us to constrain three-dimensional geological and thermal models of the undisturbed underground and, subsequently, to simulate numerically the production temperature and the thermal disturbance in the surrounding rocks. A comprehensive sensitivity analysis optimized the best operational design for total recovered thermal energy and uninterrupted heat recovery. When the deep close loop heat system operates with a fluid circulation rate of 0.03 m³s⁻1 and an injection temperature of 20 °C, it sustains a production temperature of over 100 °C, which generates total recovered thermal energy of 9730 TW th and 817 TW e over 25 years (9000 days). The average annual thermal and electricity productions of 389 TW th and 33 TW e , respectively, are more than the demand of the entire population of Magumeri district. The study's findings offer practical implications for policymakers, industry stakeholders, and local communities, emphasising the potential for socio-economic development while fostering environmental stewardship in the Nigerian Chad Basin. • Novel approach to developed three abandoned wells into deep borehole heat exchanger. • A comprehensive sensitivity analysis optimized the best operational design. • Periodic interchangeable operation between loop one and loop two is adopted. • Total recovered thermal energy of 9730 TWth was recovered • 817 TWe of electricity using geothermal binary plant was generated. [ABSTRACT FROM AUTHOR]

The extensive use of coal and oil for heating, electricity generation and cooling of buildings contributes to various environmental problems, both locally and globally. One of the feasible solutions to the climatic issues currently in this region is using sustainable energy sources. Hydrogen is an alternative option to fossil resources generated from sustainable energy sources. It is a form of energy that is both ecologically safe and sustainable. Hydrogen may now be produced in several different ways, including by reforming hydrocarbons, the Electrolysis of water, and Steam reforming of fossil fuels. However, because there is a finite supply of fossil fuels and a change in climate conditions due to the emission of CO 2 & other contaminants, there has been a focus on producing hydrogen using renewable resources. This study reviews an H 2 production system that combines geothermal & solar energy, the two primary renewable energy sources and a hybrid solar-geothermal system. This study looked into different aspects, like the working fluid for water electrolysis, the geothermal fluid temperature, and the type of power cycle. Comparative analysis was also performed on numerous GPPs, including flash, ORC cycles, binary, flash-binary, and solar collectors; this covers investigations on the rates and costs of producing hydrogen. • This paper looks at three different approaches of producing hydrogen using renewable energy sources. • An innovative renewable energy system that depends on solar and geothermal power. • An integrated system consists of geothermal and solar energy, an electrolyzer, and a fuel cell unit. • Hydrogen production as a function of design factors including working fluid, electrolysis temperature, and cycle type. • Producing hydrogen from geothermal and solar energy is a cost-effective and potentially profitable solution. [ABSTRACT FROM AUTHOR]

The present research aims at development and design of a new high-efficiency power/hydrogen co-production framework running by biomass/geothermal renewable resources. In this regard, to attain global energy transition goals based on green hydrogen utilization of renewable resources instead of conventional fossil fuel-based routes for hydrogen production is followed. The proposed system structure consists mainly of a gas turbine coupled to a geothermal assisted Rankine unit which extracts the gas turbine wasted heat to run a water electrlyzer for H 2 production. To illustrate a comprehensive performance evaluation, technical (thermodynamic), environmental and economic aspects are considered and assessed. Eight performance indices are evaluated including: power and hydrogen productions, thermal and exergetic efficiencies, environmental damage and emission index, L C O P and overall system cost. In addition, a bi-objective optimization is implemented with respect to efficiency and product cost. Results show that, the cogeneration framework under optimum condition, operates with exergetic efficiency of 42.37 % and l e v e l i z e d p r o d u c t c o s t o f 68.52 $ / M W h , whose emitted CO 2 is 0.7443 k g / k W h. Also, compared to basic design point conditions, it is found out that optimization leads to performance enhancements by 7.5%, 9.0% and 7.7% for the three mentioned indicators, respectively. • Proposal of power/hydrogen cogeneration structure driven by biomass-geothermal energies. • Thermodynamic, environmental and economic evaluations for proposed hybrid structure. • Determination of optimum operation via two-objective optimization. • AcHieving 9.0% reduction in levelized product cost by optimization. [ABSTRACT FROM AUTHOR]

In this study, an integrated energy system is deployed to generate electricity, heating, cooling, and domestic hot water for a community considering three fully renewable energy source scenarios: biofuel (Case I), solar-biofuel (Case II), and geothermal energy (Case III). The proposed systems are modeled, assessed, optimized, and compared thermodynamically, economically, and environmentally; in addition, a proton exchange membrane electrolyzer (PEME) is utilized to convert the surplus electricity to stored hydrogen to raise the exergy efficiency and package value-added. Mathematical models are fully developed from thermodynamic and economic perspectives, taking a cumulative inflation rate into account via the Consumer Price Index (CPI). The novelty of the study is to focus on the comparison of the proposed renewable resources as energy inputs for the same condition (community loads), as there is a gap in this regard in the literature. Presented systems are optimized using Non-dominated Sorting Genetic Algorithm-II (NSGA-II) for minimum net costs as well as maximum exergy efficiency to reach the optimum operating conditions for each case during the peak cooling and heating loads. Moreover, for a more precise comparison of the proposed cases from an exergetic, economic, and environmental point of view, dynamic (hourly) behaviors of systems are analyzed over a year. A comprehensive parametric study is carried out to reckon the influence of borehole drilling depth, geofluid mass flow rate, and soil temperature gradient on case III to appraise its competitiveness in different locations, as well as the effects of the number of collectors on total cost rate and exergy efficiency for case II. Results indicate the annual net costs of $107.1k, $99.5k, and -$505.1k (where the negative sign stands for "income" instead of "cost") and average exergy efficiencies of 19.1 %, 26.3 %, and 41.3 % for cases I, II and III respectively. [ABSTRACT FROM AUTHOR]

Designing a ploy-generation system to produce various products is an effective method to improve the common power plant's performance. Hence, the current investigation proposes a green poly-generation system driven by geothermal and flue gas. The proposed scheme consists of an organic Rankine cycle, proton exchange membrane electrolyzer, saline water desalination unit, and Allam cycle to produce power, hydrogen, and freshwater. The produced oxygen in the electrolyzer feeds the Allam cycle to perform an oxyfuel process to achieve zero CO 2 emission. Per the 4E analysis, the system produces 27,720 kW net power, 931 kmol/h hydrogen, and 616.7 kmol/h freshwater. In this way, the energy and exergy efficiencies are obtained at about 16.87% and 51.65%. The total exergy destruction rate is estimated at about 78,926 kW, in which the organic Rankine cycle and its vapor generator have the highest portions among the different parts and equipment by about 69% and 18.87%. The sensitivity analysis indicates that by the CO 2 recycle ratio of 60%, the highest energy and exergy efficiencies reach 19.3% and 54.33%. Furthermore, the unit cost of hydrogen and electricity productions are 0.07$/kWh and 7.24 $/GJ, which is a considerable reduction compared to similar methods. [ABSTRACT FROM AUTHOR]

[Display omitted] • The environmental effects of nuclear and geothermal energy are explored. • The Novel Quantile ARDL method is employed for the period 1990Q1-2019Q4. • Nuclear and geothermal energy raises the environmental footprint at the majority quantiles. • Urbanization contributes to a sustainable environment only with low environmental degradation. • Agricultural-based activities reduce the environmental footprint in the long run. The global issue of atmospheric variations and global warming caused by diverse anthropogenic behaviors is a global concern. There is apprehension about preserving an uncontaminated atmosphere and attaining optimal nuclear and geothermal energy utilization with agriculture sector development. In this regard, this paper investigates the influence of nuclear energy, geothermal energy, agriculture development, and urbanization on carbon emissions and ecological footprint from 1990Q1 to 2019Q4 in the case of China. The findings of unit root tests reveal that all variables are stationary at first integration order, and cointegration test findings confirm the presence of long-run relationships among series. The quantile autoregressive distributive lag (QARDL) method findings demonstrate that nuclear energy, geothermal energy, and urbanization statistically correlate with CO2 emissions and ecological footprint across all quantiles, indicating that these determinants have contributed to environmental degradation. Whereas agricultural development has a statistically significant and negative influence on the environment, implying that agriculture has a pollution-mitigation impact. Based on these empirical findings, several policy implications are presented to preserve environmental quality to achieve the 2030 Sustainable Development Goals (SDGs) target. [ABSTRACT FROM AUTHOR]

Geothermal energy is a promising solution to provide multiple outputs at different temperatures and under different conditions. In this current work, a geothermally powered multigeneration cycle is planned, suggested and studied including a Kalina cycle, an organic Rankine cycle, a thermoelectric generators, a double effect absorption refrigeration system, a dryer, a domestic water heater, a multi-effect desalination processes, a greenhouse, and hydrogen production and storage units. The main objective of this study is to generate power, cooling, heating, hot water, drying, greenhouse heating, hydrogen, oxygen, and freshwater in an environmentally harmless approach. An elaborated thermodynamic analysis of the developed research is calculated by energy and exergy efficiency methods. Furthermore, the parametric modeling is employed to calculate the effect of significant variables on the examined study and subsystems' efficiency. Looking the analysis's findings reveal that the evaluated model's net power generation rate is approximately 298 k W. Additionally, the cooling and heating rates of this integrated combined plant are 1169 k W and 1783 k W , respectively. Moreover, the examined plant produces 0.000392 k g / s of hydrogen and 2.77 k g / s of freshwater. Finally, the examined cycle energy and exergy performance is computed as 0.4248 and 0.3826, respectively. • A new design geothermal energy based combined plant is proposed. • Investigating the integration of the different subsystems. • To examine the fresh water and green hydrogen generation with geothermal energy. • To conduct comprehensive thermodynamic performance analysis. • The overall energy and exergy efficiencies are 0.4248 and 0.3826, respectively. [ABSTRACT FROM AUTHOR]

In this study, energy, exergy and exergy-economic analyses of a novel system that simultaneously generates cooling effect, heat, electricity, hot water and desalinated water for a zero-energy building are presented. It is aimed to evaluate the feasibility of using a solar-geothermal system to meet the energy and water demands of a residential building using exergy-economic indexes. The multi-generation system operates based on solar and geothermal energies, and it consists of proton exchange membrane (PEM) electrolyser, PEM fuel cell, photovoltaic system, and a desalination system with a pressure exchanger. Results indicate that energy and exergy efficiencies in cooling mode are 13.27% and 32.44%, respectively, and in heating mode are 17.25% and 42.4%, respectively. The largest exergy destruction occurs in the photovoltaics and organic Rankine cycle. It is observed that the turbine and boiler have the highest portion in the exergy destruction of the organic Rankine cycle. The capital investment and operating and maintenance cost rate, and the cost of produced distilled water are 4.288 ($/h), 67.63 (c$/m3), respectively. Moreover, the unit exergy costs of power, heating and cooling effect are investigated. The exergy-economic factor and the cost of exergy destruction for the entire system are 57.38% and 4.288 ($ h) , respectively. • A novel multigeneration system for zero-energy building is proposed. • The exergy unit cost of generated power, heating and cooling are calculated. • The energy and exergy efficiencies of the system is higher in heating mode. • The exergetic performance of the system deteriorates at higher solar irradiation. [ABSTRACT FROM AUTHOR]

This paper introduces and evaluates a novel multi-generation structure that employs geothermal energy and utilizes waste heat from flue gas. This innovative structure includes a combined flash and binary geothermal system, a multi-effect desalination subsystem, a proton electrolyte membrane electrolyzer, a steam Rankine cycle, and a dual-pressure organic Rankine cycle. The proposed plant is evaluated from energy, exergy, economic, and environmental viewpoints. Moreover, a detailed parametric analysis is performed to study the effect of different parameters on the system performance. Results obtained demonstrate that this proposed process can generate 21.93 kg/s of fresh water, 346.1 kg/h of green hydrogen, 2739 kg/h of green oxygen, and 19,090 kW of power. Furthermore, the overall energy, exergy, electrical efficiencies, and total unit cost of the product for this new process are determined to be 16.44%, 53%, 8.7%, and 4.56 $/GJ, respectively. Additionally, through exergy analysis, it is established that the Proton Electrolyte Membrane Electrolyzer boasts the highest efficiency within the proposed process, with an exergy efficiency of 88.84%. Its contribution to the total irreversibility of the system is calculated at 1%. Moreover, the analysis reveals that the combined flash and binary geothermal system is the most significant contributor to irreversibility, accounting for 58% of the total, while turbine 2 represents 35.53% of the system's overall irreversibility. From an environmental perspective, employing this proposed process for power generation leads to an annual saving of 44,482,754 liters of petroleum. From an economic standpoint, the total investment cost of the proposed process amounts to $20,743,728. Among the subsystems, the combined flash-binary geothermal system incurs the highest investment cost, representing 41% of the total, while the proton electrolyte membrane electrolyzer has the lowest cost share at 6%. [Display omitted] [ABSTRACT FROM AUTHOR]

The integration of renewable energy sources, such as solar, biomass, and geothermal, with other technologies and energy production cycles holds the potential to significantly enhance power generation processes' efficiency. A novel trigeneration structure is introduced that harnesses geothermal energy and waste energy from flue gases. The proposed system comprises several key components, like combined flash and binary geothermal system, a water desalination unit, a Kalina power and cooling cycle, and organic Rankine cycles. The system is analyzed from various perspectives, encompassing energy, exergy, economic, and environmental viewpoints. This assessment allows for a holistic understanding of the trigeneration structure's performance, considering its energy efficiency, exergetic effectiveness, economic viability, and environmental impact. By combining elements, the trigeneration system aims to optimize the utilization of geothermal energy while efficiently converting waste energy from flue gases into useful power. The implementation and evaluation of this trigeneration structure offer promising prospects for sustainable and more effective power generation, promoting the integration of renewable resources with existing energy production technologies. The potential benefits of this approach could lead to a more environmentally friendly and economically viable solution for meeting our energy demands. [ABSTRACT FROM AUTHOR]

[Display omitted] • Special difficulties of geothermal drilling, completion and fracturing are reviewed. • Commonly used geothermal drilling and completion technologies are investigated. • State-of-the-art geothermal fracturing methods are reviewed and compared. • Novel heat extraction methods & their applicable reservoir conditions are concluded. Global warming induced by excessive carbon dioxide emission generated from fossil fuels consumption is becoming increasingly severe. Development and utilization of clean and renewable energy is a significant measure to contribute for the carbon neutrality. Geothermal resource is an important clean and renewable energy, because of its advantages of abundant reserves, exploitation without restrictions from the climate and season. Extracting heat from the high temperature geothermal reservoir requires well drilling, completion and fracturing. However, due to some particular conditions in geothermal development, such as high temperature, erosion, leakage, and hard rocks, traditional petroleum well drilling and completion technologies are not well applicable in the geothermal industry. In this paper, the state-of-the-art geothermal drilling, and completion technologies as well as several fracturing methods, such as foam drilling, air hammer drilling, hydrothermal jet drilling, expansion casing technology, high temperature resistant drilling fluid and cement, chemical stimulation and thermal stimulation are comprehensively reviewed. Besides, heat extraction performances of water and CO 2 as working fluids in the geothermal system are discussed. A few novel heat extraction methods including closed loop, open loop, enhanced geothermal systems are compared and analyzed. This review is expected to provide suggestions for research fields worthy of study for geothermal drilling and exploitation. [ABSTRACT FROM AUTHOR]

This study presents a new geothermal-based system for power generation and liquid hydrogen production. Depending on the network requirements, part of the generated power is supplied to the network and the remaining part enters the PEM electrolyzer to produce hydrogen. The produced hydrogen is then pre-cooled by the ejector cooling cycle before entering the liquefaction cycle. The ejector refrigeration cycle not only uses geothermal waste heat but also facilitates the liquefaction process through precooling hydrogen; therefore, it significantly improves the overall performance of the integrated system. In addition, the modified liquefaction cycle is suggested, which is superior to common ones. After simulating, some key parameters are identified and a comprehensive parametric research is carried out to investigate the thermodynamic, economic and environmental performance in different conditions. The optimization procedure is implemented through a genetic algorithm approach and the objective functions are defined. The results reveal that the double flash power cycle has the greatest effect on exergy destruction rate and total cost rate. In the optimal case, the total cost rate, the liquefied hydrogen rate, the total exergy efficiency, net power generation, and C O 2 reduction rate are determined as 181.71 $/h, 59.92 kg/h, 25.27%, 4.03 MW, and 1421.2 kg/h, respectively. Also, coupling an artificial neural network with genetic algorithm significantly lessens optimization time. [Display omitted] • A novel geothermal-based system for hydrogen liquefaction is proposed. • A comprehensive energy, exergy, economic and environmental (4E) analysis is applied. • Performing a machine learning optimization method to reduce the calculation time. • The double flash cycle has the highest exergy destruction rate among the subsystems. [ABSTRACT FROM AUTHOR]

Energy tunnel has attracted increasing interest in preventing tunnel frost damage and providing energy for space conditioning through utilizing geothermal energy from ground source heat pump (GSHP) system. The energy lining system, composed of heat pump units, lining buried with geothermal heat exchangers (GHEs), and supply pipes, is one of the most popular energy tunnel systems. Despite their good potential for geothermal energy exploitation, studies on their design approach are still insufficient, particularly for cold region energy tunnels. In this work, we propose an innovative design framework for optimization of the heat extraction section in the energy tunnel by combing numerical simulation and Simulated Annealing (SA). The numerical model reproduces a horseshoe-shaped tunnel segment equipped with an energy lining system, generating heat power activated by circulating heat carrier fluid. And the simulation provides key input parameters, involving heat extraction power, the ground temperature field, and heating demand, for the algorithm, hence the heat extraction section range is optimized using SA. Influences of four design parameters (i.e. , ground temperature, inlet fluid temperature, circulating fluid flowrate, and pipe spacing) and three axial temperature distribution characteristics (i.e. , overall temperature along the tunnel axis, airflow characteristics, and temperature difference between the tunnel entrance and exit) dominating temperature profiles along the tunnel axis on the optimal range design are investigated. Major findings include: (1) the optimal range is sensitive to the temperature field along the tunnel axis, and the normalized optimal length decreases by 91.3% with the normalized feasible range increases 1099.6% as the average temperature inside the tunnel rises from −2.5 °C to 5 °C; (2) increasing flowrate and lowering the temperature of the inlet fluid can yield a reduction in the optimal length of up to 29.2% and 64.3% separately; (3) a relatively sparse pipe arrangement can save cost without comprising the optimal length. This study presents a smart and efficient approach for designing the heat extraction section of the energy tunnel, which is promising in more complex conditions and capable of guiding practical applications. [ABSTRACT FROM AUTHOR]

To date, the tunnel lining GHEs have encountered issues with the relatively low heat exchange rate and the rapid decline of heat exchange rate with time. This is because the huge heat accumulation around the tunnel lining GHEs obstructs the heat transfer between the absorber pipe and the surrounding rock during the GHEs operation. Hence, to improve the heat accumulation and enhance heat exchange rate, the two-phase closed thermosyphon (TPCT), an efficient device for long-distance heat transfer, was employed in the tunnel lining GHEs to build a thermally induced channel between absorber pipes and the surrounding rock, accelerating heat transfer between the absorber pipe and surrounding rock. The heat transfer model of the tunnel lining GHEs using TPCTs was built to analyze the thermal performance enhancement mechanism of tunnel lining GHEs using TPCTs for building cooling with different thermal conductivities of primary lining concrete and surrounding rock, and convective heat transfer coefficients (CHTCs) on tunnel internal walls. The results showed that throughout a 90-day operation, TPCTs dramatically boosted the heat injection rate of tunnel lining GHEs from 16.5 to 27.0 W/m2 with an increase of 63.6%. Thermal conductivities of the primary tunnel lining concrete have significant effects on the heat injection rates of the GHEs with TPCTs. The heat injection rates increased from 27.0 to 36.4 W/m2 as thermal conductivities of the concrete increased from 1.85 to 10.7 W/m K, and the enhancement rate ranged from 63.6% to 94.7% when compared to tunnel lining GHEs without TPCTs. The enhancement rate of tunnel lining GHEs with TPCTs decreased with increasing thermal conductivity of surrounding rock and CHTC, reaching up to 122.1% under the thermal conductivity of 1.4 W/m K and CHTC of 0 W/m2 K. Overall, TPCT greatly enhances the heat injection rate of tunnel lining GHEs, implying that it is a promising technology. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel hybrid system using geothermal energy and fuel gas in a co-feed structure is proposed. The main objectives include improving the sustainability of a gas turbine cycle associated with a geothermal power plant and reducing carbon emissions. To this end, a novel multi-waste heat recovery process was developed in which the heated airflow in the gas turbine cycle was directed to the geothermal flash cycle to increase the viability of the flash process in this unit. A parallel heat recovery structure then used part of the waste heat from the gas turbine cycle to start a supercritical carbon dioxide cycle and also improve the performance of the geothermal flash cycle. Hence, two organic Rankine cycles were used in the geothermal flash cycle. The other part of the waste heat from the gas turbine cycle was consumed in a cascade framework in a steam Rankine cycle and a desalination plant in combination with a domestic water heater. The defined structure was simulated and a comprehensive study was done from the viewpoints of energy, exergy, environment, and thermoeconomics. This structure reduced the total irreversibility as well as the carbon dioxide emissions compared to the existing literature data. • Proposal of an innovative process based on gas turbine cycle and geothermal energy. • Application of Aspen HYSYS simulation, 4E analysis, and parametric study. • This system produces 121200 kW of power, 30.03 kg s of fresh water, and 205.16 kg s of heat. • Energy and exergy efficiencies and products' unit cost of are 49%, 36%, and 12.79 $ GJ. • CO2 footprints related to the power and all the products are 0.55 and 0.387 kg CO 2 kWh. [ABSTRACT FROM AUTHOR]

The hybrid renewable energy-based power generation systems offer a reliable solution to mitigate the drawbacks of individual energy source. In this respect the biomass and geothermal energies have some well-known advantages (such as continuous provision) over the solar and wind energies. In the present paper, two integration modes are proposed for hybridization of geothermal heat with a biomass-driven gas turbine based combined power cycle. The Mode 1 configuration employs geothermal heat to increase the temperature of feedwater before the deaerator, whereas the Mode 2 structure applies the geothermal energy to generate more steam for the low pressure steam turbine. Detailed exergetic, environmental and economic appraisals are carried out to examine the hybrid systems performances. In order to represent an accurate comparison of the suggested hybridization modes, the systems are optimized to achieve minimum levelized electricity cost. The results have indicated better performance for Mode 2 hybridization scenario over the Mode 1. The former system yields 10.0% greater exergy efficiency with 20.1% less electricity cost compared to Mode 1, while it can generate 22.5% more electricity. Also, it brings about 22.5% lower CO 2 emission. However, the Mode 2 configuration possess one drawback compared to Mode 1, which is its higher overall system cost rate by 17.9%. The results show that, the higher cost rate of Mode 2 configuration is mainly due to larger pressure ratio of the air compressor which causes more costs for the compressor and gas turbine components. • Geothermal energy is hybridized with biomass energy to enhance the power generation. • Different hybridization modes are offered and optimized. • Exergetic, economic and environmental remediation investigations are conducted. • Levelized cost of electricity is estimated for each hybrid modes. [ABSTRACT FROM AUTHOR]

It is universally acknowledged that climate change brings widespread attention to solar greenhouse plant carbon sequestration. Suitable technologies in solar greenhouses were, are, and will be play a leading role in this vital transition. The primary aim of this research is to examine the energy efficiency and carbon sequestration potential of a solar-assisted ground-source heat pump (SAGSHP) heating system. This hybrid system, which integrates a horizontal ground-source heat pump (GSHP) system with PVT and heat storage, can efficiently fulfill the heating demands of a greenhouse and function as a positive energy building. Four plants include cucumber, tomato, cowpea, and lettuce were selected to compare the carbon absorption effects. Results show that the hybrid system outperforms conventional systems, with a coefficient of performance (COP) of 6.71 during peak hours and PVT efficiency over 57.88%, which effectively meet the heat load of the greenhouse and keep the indoor heat comfortable. In addition, for the carbon sequestration potential of four plants, tomato exhibited the highest photosynthetic carbon sequestration of 3522 kgCO 2 ·m−2. Cowpea showed the strongest daily carbon sequestration capacity at 26.86 gCO 2 m−2d−1 and better economic income. Through the application of this enhanced solar greenhouse, people can enhance the utilization of solar energy, establish flexible interaction between energy and information flow, and make a promising option for sustainable building design. [ABSTRACT FROM AUTHOR]

To maximize the economic benefits of geothermal energy production, it is essential to optimize geothermal reservoir management strategies, in which geologic uncertainty should be considered. In this work, we propose a closed-loop optimization framework, based on deep learning surrogates, for the well control optimization of geothermal reservoirs. In this framework, we construct a hybrid convolution–recurrent neural network surrogate, which combines the convolution neural network (CNN) and long short-term memory (LSTM) recurrent network. The convolution structure can extract spatial information of reservoir property fields and the recurrent structure can approximate sequence-to-sequence mapping. The trained model can predict time-varying production responses (rate, temperature, etc.) for cases with different permeability fields and well control sequences. In this closed-loop optimization framework, production optimization, based on the differential evolution (DE) algorithm, and data assimilation, based on the iterative ensemble smoother (IES), are performed alternately to achieve a real-time well control optimization and to estimate reservoir properties (e.g. permeability) as the production proceeds. In addition, the averaged objective function over the ensemble of geologic parameter estimates is adopted to consider geologic uncertainty in the optimization process. Geothermal reservoir production cases are examined to evaluate the performance of the proposed closed-loop optimization framework. Our results show that the proposed framework can achieve efficient and effective real-time optimization and data assimilation in the geothermal reservoir production process. • A hybrid convolution–recurrent neural network is constructed as a surrogate for geothermal production problems. • A closed-loop optimization framework is proposed for geothermal energy production. • Data assimilation and well control optimization can be achieved simultaneously for the geothermal reservoir. • The deep learning surrogate can speed up the optimization and data assimilation processes. [ABSTRACT FROM AUTHOR]

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. • ORC applied on HDR to obtain green hydrogen to enrich NG grid up to 42% (by volume). • A single shaft dual pressure binary ORC is employed to produce electricity from HDR. • Optimum electrolyser is determined up to ORC, HDR results and EPDK reports. • 183 °C HDR surface temperature is enough to produce 34 M Nm3/year green hydrogen. [ABSTRACT FROM AUTHOR]

The current paper deals with the development and analysis of an innovative multigeneration plant, which is powered by geothermal energy, and integrated with the transcritical Rankine cycle ( t C O 2 − R C), proton exchange membrane (PEM) electrolyzer, multi-effect desalination unit (MED), and ejector cooling system (ECS). The main objective of this research paper is to produce power, hydrogen, freshwater, and cooling in an environmentally benign way, by integrating the different subsystems. A comprehensive parametric analysis that is thermodynamic and economic and exergo-environmental impact assessment are addressed. For these parametric analyses, the variation of some important parameters that affect the system performance is examined and illustrated. According to the modeling findings, the net power and hydrogen production capacity of the modeled combined power plant is 982.4 kW and 0.0024 kgs−1, respectively. The cycle's overall energy efficiency is computed to be 40.04%, although its exergetic efficiency is 36.31%. When the irreversibility among the plant components is compared, the highest irreversibility occurred in the PEM water heater with 1508 kW, followed by heat exchangers 1 and 2. Given the economic results, the modeled plant's cost rate is calculated to be 200.2 $/hr. In the end, it can be recommended that this modeled plant is suitable that is from the point of perspective of the performance, economy, and exergo-environmental relations. • A novel multigeneration plant motivated by geothermal energy is proposed. • Modeling and analysis of a multigeneration plant for power, hydrogen, cooling, and freshwater production. • Energy, exergy, economic, and exergo-environmental index analyses are conducted. • Investigating the green and sustainable hydrogen generation method with PEM electrolyzer. • The overall energy and exergy efficiencies are 40.04% and 36.31%, respectively. [ABSTRACT FROM AUTHOR]

One of the biggest challenges in developing renewable energy, such as geothermal energy, is understanding how to be accepted by the community impacted by the development. However, very few studies attempted to numerically express the time-dependent process of social acceptance in renewable energy projects. We quantify how social acceptance for a geothermal energy project is acquired from the involved communities. First, we present a compartment model for simulating how the numbers of supporters and opponents of developing geothermal energy change over several decades. We then introduce a time-varying index, an effective susceptibility number (R e), similar to the effective reproduction number used in modeling epidemiologic phenomena. Second, we share our findings about the history of the number of supporters and opponents of the geothermal power plant construction project in Japan based on the articles published in local and national newspapers between 1970 and 2020. Our simulation results show that the proposed compartment model could predict documented changes in the numbers of supporters and opponents. Also, the effective susceptibility number (R e) could represent the frequency of interactions among the community members. We suggest that an effort should be made to avoid having R e < 1 in the community, to maintain a steady increase in the number of supporters to eventually acquire the social acceptance of a geothermal energy project. Our simple but novel approach using the compartment model will help better understand the dynamics and predict the community acceptance process in geothermal and other renewable energy projects. [ABSTRACT FROM AUTHOR]

[Display omitted] • Availability of RES in the MENA region was summarized. • Suitable renewable energy storage systems in MENA was introduced. • Desalination plants powered by RES in MENA were investigated. • Al-khafji solar seawater RO plant in KSA was discussed. The Middle East and North Africa (MENA) countries are rapidly growing in population with very limited access to freshwater resources. To overcome this challenge, seawater desalination is proposed as an effective solution, as most MENA countries have easy access to saline water. However, desalination processes have massive demand for energy, which is mostly met by fossil fuel-driven power plants. The rapid technological advancements in renewable energy technologies, along with their gradually decreasing cost place renewable energy-driven power plants and processes as a promising alternative to conventional fuel-powered plants. In the current work, renewable energy-powered desalination in the MENA region is investigated. Various desalination technologies and renewable energy resources, particularly those available in MENA are discussed. A detailed discussion of suitable energy storage technologies for incorporation into renewable energy desalination systems is also included. The progress made in implementing renewable energy into power desalination plants in MENA countries is summarized and analyzed by describing the overall trend and giving recommendations for the potential amalgamation of available renewable energies (REs) and available desalination technologies. Finally, a case study in the MENA region, the Al Khafji solar seawater reverse osmosis (SWRO) desalination plant in the Kingdom of Saudi Arabia KSA, is used to demonstrate the implementation of REs to drive desalination processes. [ABSTRACT FROM AUTHOR]

The aquifer thermal energy storage (ATES) system is an efficient method to overcome the gap between energy supply and demand over time and space. Heat storage and preservation abilities are key issues of a successful ATES project. However, most of previous studies only focus on heat storage and recovery abilities of the ATES, while the heat preservation ability of aquitards is neglected. Besides, effects of key factors on heat losses into aquitards still remain unclear, which makes appropriately selecting reservoirs for the heat storage challenging. Thus, the heat loss efficiency is defined to represent the heat preservation ability of aquitards, through which ATES thermal performances are comprehensively evaluated. Effects of key factors on thermal performances are analyzed and optimal reservoirs for the heat storage are recommended. Results indicated that key factors had different impacts on heat losses and thermal recovery. The conduction was the major loss mode and was sensitively affected by aquitard parameters. An aquifer with a lower thermal conductivity, a higher porosity and a superior heat capacity was more suitable for the heat storage. The aquitard with lower porosity, thermal conductivity and heat capacity was better. On the premise of sealing, increasing the aquitard permeability was conducive. [ABSTRACT FROM AUTHOR]

Due to the increasing importance of cooling applications, geothermal trigeneration systems might be of high interest in the future. This work aims at evaluating different plant layouts against the background of more advanced plant configurations and part load behaviour. Five different plant configurations are analysed for geothermal heat source temperatures between 110 and 150 °C. The highest net power output is achieved by an advanced serial-parallel configuration (ASPC), but in case of high heating and cooling demand, a standard serial-parallel configuration is more favourable. For the considered base demand scenario of 130 °C, the ASPC results in an annual net power generation of 20.94 GWh, which is 6.9% higher than the second favourable configuration. The application of a recuperator within the ORC system has a significant impact on the serial concepts, but only marginally increases the power output of the parallel layouts. Comparing two exergetic efficiencies highlights that the assumed definition can result in a different ranking of the plant layouts. Considering the exergy that is transferred from the brine to the trigeneration system reveals the highest exergetic efficiency for a serial configuration, while the focus on the available exergy flow reveals the highest efficiency for the ASPC layout. Considering a brine temperature of 130 °C results in a maximal achievable second law efficiency of 34.1% if evaluating the available exergy flow. The evaluation of the pay-back period reveals that the ASPC results in the shortest pay-back period of 13.8 years. • Investigation of several plant configurations considering part-load operation. • Highest net power output is achieved by an advanced serial-parallel configuration. • For each plant configuration, there is an optimal desorber temperature of the AC. • A pay-back period of 14 years can be achieved. [ABSTRACT FROM AUTHOR]

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 ($/h), respectively. • Optimal design of a renewable system based on solar and geothermal energy for power generation and cooling. • The system was thermodynamically modeled in EES. • To optimize the system and find the optimal objective functions, the NSGA-II algorithm was employed. • The optimal Exergy round trip efficiency and cost rate were found to be 29.25% and 714.25 ($/h). [ABSTRACT FROM AUTHOR]

An innovative multi-generation energy system is proposed to generate simultaneous power, drinking water, cooling, heating, and H 2. The aimed plant comprised of an absorption chiller, a heat pump unit, a reverse osmoses unit, a double flash cycle, and a proton exchange membrane. The devised system is surveyed comprehensively based on the thermodynamic, thermo-economic, and exergoenvironmental indicators for offering an in-depth assessment of the plant. Besides, multi-objective optimization has been employed in the proposed system. The net proportions of output work, unit cost, thermal and exergetic efficiencies, and H 2 , and purified water production of the system are 99.25 kW, 124 $/GJ, 24.4%, 32.1%, 1.218 kg/h, and 0.9662 kg/s, separately. The outcomes related to thermodynamic and thermo-economic evaluations demonstrate that the greatest amount of total cost rate occurred in the first employed turbine. Owing to the findings of the parametric study, by increasing geothermal temperature, exergoenvironmental parameters are reduced, and with increasing the pressure of FT1, cooling load and energetic efficiency increase while SUCP, net output work, and exergetic efficiency decrease dramatically. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, a novel geothermal-based multigeneration system is designed and evaluated in energy, exergy and economic (3E) analyses. Besides 3E analyses, multi-objective optimization has been assessed to reach the highest exergetic effectiveness and the lowest total cost rate. To evaluate the designed plant, thermodynamic balance equations are assigned to all sub-systems found in the design. These equations are solved by using Engineering Equation Solver (EES) software. According to the analyses' results, with base parameters, total power production is 1951 kW, the hydrogen generation rate is 0.0015 kg/s, and the whole energy and exergy efficiencies are 59.53% and 53.17%. The economic analysis performed for the multigeneration system indicates that the total cost rate is 186 $/h, and the levelized energy cost is 0.102 $/kWh. These results indicate that the designed geothermal-based multigeneration system performs better than a single-generation plant in terms of efficiency and cost. [Display omitted] • A new geothermal energy-based multinational plant is presented. • A detailed thermodynamically assessment for more effective design is performed. • Energy and exergy efficiencies for the present combined plant are evaluated. • Exergoeconomic assessment and optimization of this plant are conducted. [ABSTRACT FROM AUTHOR]

The use of geothermal energy from tunnels offers an environmentally friendly option for heating and cooling of buildings in the vicinity of the tunnel structure. In the research project "Thermocluster", the geothermal potential of the Brenner Base Tunnel (BBT) was analysed and the utilization of the low-temperature heat to the city of Innsbruck was evaluated. A possible optimization on the geothermal performance was explored by separating colder sectional discharges from the total tunnel water drainage system. Further, the use of decentralized and centralized heat pumps, as well as heat distribution with different district heating networks (local low temperature heating and cooling networks, low-temperature network, classic district heating network), was investigated using process simulation. The results indicate that an optimization of the temperature of a subset of the total tunnel water discharge is possible. Furthermore, it could be shown that wide fluctuations in the efficiency of the heat pump can be expected. In addition, a rough cost estimation regarding the installation and distribution costs of the tunnel heat with different heat network variants is provided. This shows that the variant using decentralized heat pumps in the buildings and distribution via an anergy network is the most favourable in terms of installation. • Geothermal usage of tunnel heat in Austria. • Analysis of the geothermal potential and optimization. • Simply measures to increase the geothermal potential. • Performance estimation of heat pumps using tunnel heat. [ABSTRACT FROM AUTHOR]

Renewable energy- based multigeneration systems have been proposed as a viable means of achieving a net-zero future as these systems can decarbonize the power and energy sector simultaneously. Although there has been significant development in this research field, the large sizes of the existing systems in literature are a major setback in the adoption/implementation of these systems. Furthermore, the unavailability of solar and wind energy during some hours daily makes solar or wind energy-based multigeneration systems undesirable in many applications. Considering the urgency/importance of attaining a net-zero emission future, this study presents a novel multi-energy system that can bridge the existing gaps in literature. Therefore, the thermodynamics, economic, and environmental analysis novel CO2-based geothermal micro-multi-energy system that is hybridized with a concentrated solar photovoltaic/thermal system and wind turbine is presented in this paper. The proposed energy system presents an innovative method that can be effectively used to decarbonize future energy production. The multi-energy system is modeled to produce electricity, refrigeration effect, space heating, hydrogen, and hot water. The economic study in this paper also analyzed the Levelized cost of electricity (LCOE), Levelized cost of cooling (LCOC), and Levelized cost of hydrogen (LCOH). A multi-objective optimization operation is also carried out on the modeled system in order to determine the optimal exergy efficiency and total product unit cost. The steady-state performance analyses showed that the overall energetic and exergetic efficiencies of the system are 48,61% and 88.31% and these efficiencies can be as high as 51.76% and 95.08% respectively when the system is optimized with reference to exergy efficiency. The LCOE, LCOC, and LCOH at the optimal total product unit cost are 0.04529 $/kWh, 0.004564 $/kWh, and 28.86 $/kg. [ABSTRACT FROM AUTHOR]

This study investigates a subcritical Organic Rankine Cycle (ORC) power plant using a Tesla turbine with R236ea as the working fluid, driven by geothermal hot water at 120 °C and a flow rate of 1 kg/s. The research examines the impact of varying turbine inlet steam qualities, from 0 (saturated liquid) to 1 (saturated vapor), on power output and isentropic efficiency. A homogeneous two-phase flow model was developed and validated against experimental and numerical results, showing good agreement with differences of approximately 10 %. The findings reveal that the highest power output of 12.91 kW is achieved with saturated liquid at the turbine inlet, while the isentropic efficiency remains stable between 70.1 % and 74.8 %, peaking at saturated vapor conditions. Economic analysis using metrics such as Levelized Cost of Electricity (LCOE), Net Present Value (NPV), Payback Period (PbP), and Internal Rate of Return (IRR) shows that the saturated liquid configuration is most viable, with an LCOE of 64 €/MWh, NPV of 61 k€, PbP of 8.29 years, and IRR of 13.9 % at 5 % discount rate and 114 €/MWh electricity price, outperforming conventional systems. • Comprehensive analysis of Tesla turbine performance with varying inlet steam qualities. • Novel homogeneous two-phase flow model validated against experimental and CFD data. • Maximum power output (12.91 kW) achieved with saturated liquid at turbine inlet. • Stable turbine efficiency (70–74 %) across all steam qualities, peaking at vapor phase. • Most economical configuration at x3 = 0, with LCOE of 64 €/MWh at 5 % discount rate. [ABSTRACT FROM AUTHOR]

[Display omitted] • The developed models monitor fracture evolution behavior. • The developed model assesses the impact of rock damage on heat extraction. • Thermal stress, shock, and pressure drive rock damage and fracture evolution. • Developed models confirm geothermal development feasibility in Babbage Oilfield. Geothermal energy, a clean and renewable source, has garnered significant attention. The excellent physical properties of supercritical carbon dioxide make it an ideal fluid for geothermal development. Fractures act as channels for the efficient seepage and heat transfer of supercritical carbon dioxide. Consequently, the macroscopic fracture damage and evolution induced by the flow of supercritical carbon dioxide impact heat extraction efficiency. Here, pseudo-pressure (multi-stage induced fracture and non-Darcy multi-stage fractured) and temperature well-testing (multi-stage induced fracture thermal and non-Darcy multi-stage fractured temperature) models are developed to monitor the fractures evolution during heat transfer. The finite element method, superposition principle, and Duhamel principle are utilized to establish the proposed models. Numerical models that either consider or disregard rock damage and fracture evolution are developed to simulate and compare the efficiency of heat extraction. The COMSOL Multiphysics 6.1 software is used to solve a heat extraction transient evaluation model. A workflow for utilizing the developed models is proposed, followed by an economic sensitivity analysis. Finally, the models are applied to field cases in the Babbage Oilfield to guide the extraction of geothermal energy. Core displacement experiments are conducted to validate its accuracy, and a differential economic analysis method demonstrates its economic benefits. Results show that the well-testing models invert parameters related to reservoir and fracture evolution. Rock damage and fracture evolution during a heat extraction process are primarily influenced by thermal stress, thermal shock, and pressure-driven effects. As production progresses, fracture permeability and porosity increase, rock elastic modulus decreases, and production temperature drops. Comparing the results with versus without considering rock damage and fracture evolution reveals that their maximum pressure difference is 14% and their maximum temperature difference is 5%. The production pseudo-pressure has the greatest impact on fracture evolution. The injection temperature has the most significant effect on heat extraction efficiency, followed by injection pressure, fracture permeability, and a mass flow rate, with elastic modulus having the least impact. The maximum differential economic benefit for a single horizontal well injection-production system reaches $293,000. Field case studies from the Babbage Oilfield demonstrate the practicality of the developed models and workflow. In summary, the models, workflow, and economic analysis methods proposed in this work provide guidance for engineers in formulating more optimized heat extraction schemes. [ABSTRACT FROM AUTHOR]

The subway source heat pump system (SSHPS) incorporating a tunnel lining capillary heat exchanger (CHE) is an efficient technology for mitigating thermal degradation in subway tunnels while fully harnessing geothermal energy for heating and cooling purposes. Although extensive research has been conducted on the performance of tunnel lining heat exchangers, a practical engineering design method is still lacking. The objective of this study is to analyze the heat transfer characteristics of tunnel lining CHEs under typical design conditions and subsequently determine the optimal design conditions based on the analysis results. A numerical model of tunnel lining CHEs was developed using ANSYS, based on a demonstration project of SSHPS in Qingdao. Subsequently, the heat transfer performance of CHEs under various design parameters was simulated and analyzed. Finally, a statistical analysis was conducted to examine the impact of different factors on the heat transfer performance of CHEs. The analysis results indicate that the tunnel air temperature has the most significant influence, followed by the CHE inlet temperature parameter and the length of CHE laying pipe. The impact of the CHE inlet flow velocity is minimal. It is recommended that, during the design stage of a CHE heat exchanger, priority should be given to controlling the tunnel air temperature, optimizing the CHE inlet temperature and pipe length, and setting a minimum possible CHE inlet flow velocity. The optimal combination of design parameters for the tunnel lining CHEs were determined as follows: under the cooling mode, a tunnel air temperature of 23 °C, a CHE design inlet temperature of 39 °C, a laying pipe length of 6 m, and an inlet flow velocity of 0.08 m/s; under the heating mode, a tunnel air temperature of 20 °C, a design inlet temperature of 4 °C, a laying pipe length of 6 m, and an identical flow velocity of 0.08 m/s. This study can serve as a valuable reference for tunnel lining CHE design in practical engineering. [ABSTRACT FROM AUTHOR]

The utilization of ground-embedded structures for harnessing geothermal energy in space heating and cooling has gained significant attention over the past two decades. In this context, this paper reviews the use of tunnels, commonly known as energy tunnels, for exploiting shallow geothermal energy, providing an overview of the current status and future prospects. The different tunnel construction methods and their respective thermal activation processes are described. The factors influencing thermal performance and mechanical responses are analysed, alongside the economic and environmental benefits. This review confirms the viability of energy tunnels as a sustainable and renewable solution, as several studies have demonstrated their potential in providing a substantial amount of thermal energy and reducing natural gas consumption and significantly cutting CO 2 emissions. Energy tunnels can also potentially provide a reliable solution for road de-icing or enable efficient thermal energy storage when groundwater flow is negligible. Finally, current, and future innovations aimed at maximizing shallow geothermal exploitation are discussed, with a call for further research to explore additional thermal retrofitting techniques for the existing tunnels, innovative additions for lining concrete, fluid and pipe materials and integrating energy tunnels with other renewable energy sources in district heating networks. [ABSTRACT FROM AUTHOR]

• Numerical simulation for the action range of carbon dioxide blasting-induced cracking of HDR was conducted, in which the cooling effect of drilling fluid on the HDR reservoir close to the wellbore is taken into consideration. • The reservoir's material properties in the damaged section were established using fitting functions with temperature difference. Additionally, the temperature field of the reservoir in the affected region was established using temperature distribution functions. • The process of carbon dioxide blasting to stimulate HDR reservoir is modelled. The findings demonstrate that multiple stress concentrations occur during the carbon dioxide blasting process that causes HDR to crack. • The blasting crushing zone's scope is greatly influenced by the beginning temperature, but the fracture zone's scope is mostly unaffected. The extent of the crushing zone, which primarily determines the distribution of the blasting fracture zone, is not significantly impacted by the pressure plate's thickness. A cutting-edge technique for igniting hot dry rock (HDR) reservoirs is carbon dioxide blasting. The cooling effect of the drilling fluid was taken into consideration during a numerical simulation of the action range of carbon dioxide blasting-induced cracking. A temperature difference was used to determine the reservoir's material properties. Additionally, temperature distribution functions were used to create the temperature field in the reservoir. The blasting load is calculated using the pertinent theories and formulas of explosive blasting, and the process of blasting carbon dioxide to excite the HDR reservoir is modeled using COMSOL. The findings show that several stress concentrations take place during the blasting process. The fracture zone is created by the tensile stress concentration outside of the crushing zone, whereas the compressive stress concentration close to the blast hole creates the crushing zone. Furthermore, the effectiveness of carbon dioxide blasting fracturing would be affected by the beginning temperature and pressure plate thickness. Although the scope of the fracture zone is mostly unchanged, the initial temperature has a significant impact on the blasting crushing zone. The size of the crushing zone, which determines how the blasting fracture zone is distributed, is unaffected by the pressure plate's thickness. [ABSTRACT FROM AUTHOR]

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

The techno-economic evaluation of geothermal resources requires knowledge of the geofluid's thermophysical properties. While the properties of pure water and some specific brines have been studied extensively, no universally applicable model currently exists. This can result in a considerable degree of uncertainty as to how different geothermal resources will perform in practice. Geofluid modelling has historically been focused on two research fields: 1) partitioning the geofluid into separate phases, and 2) the estimation of the phases' thermophysical properties. Models for the two fields have commonly been developed separately. Recognising their potential synergy, we introduce GeoProp , a novel geofluid modelling framework, which addresses this application gap by coupling existing state-of-the-art fluid partitioning simulators, such as Reaktoro , with high-accuracy thermophysical fluid property computation engines, like CoolProp and ThermoFun. GeoProp has been validated against field experimental data as well as existing models for some incompressible binary fluids. We corroborate GeoProp's efficacy at modelling the thermophysical properties of geothermal geofluids via a case study on the heat content of different geofluids. Our results highlight the importance of accurately characterising the thermophysical properties of geofluids in order to quantify the resource potential and optimise the design of geothermal power plants. [ABSTRACT FROM AUTHOR]

Integrated assessment model (IAM) scenarios examining pathways to achieve the goals of the Paris Agreement stress the necessity of deploying carbon dioxide removal (CDR) methods, of which direct air capture (DAC) is viewed as one of the most promising. This study undertakes both a geospatial analysis and techno-economic assessment of potential heat sources for DAC to examine the economic impact of different renewable heat source systems on the capture costs of large-scale LT-DAC plants. It does this by determining the location of these plants through the paradigm of identifying the ideal geographic and economic environment for the selected heat sources. Thus, the research aims to answer the following research questions: What heat sources are optimally suited for low-temperature (LT) DAC and what conditions are feasible for setup? Which geographic locations represent the ideal environment within Europe for each heat source? How do the selected heat sources and geographic locations impact the economic viability of LT-DAC? Drawing on Climeworks' LT-DAC approach as a focal case, the heat sources of geothermal energy, parabolic trough collector (PTC), industrial waste heat (IWH), and high-temperature heat pump (HTHP) were chosen, to be separately deployed in Iceland, Spain, Germany, and Norway, respectively. Spain emerged as a highly promising location for the PTC, IWH, and HTHP systems while Iceland is most suitable for the geothermal, IWH, and HTHP systems. Norway is a promising country mostly for deploying a HTHP system, whereas Germany faces primarily environmental and legal barriers. The techno-economic assessment identified great variation in the LCOD costs for the different heat source systems, with the geothermal energy system exhibiting the lowest costs at 175.63 €/tCO 2 followed by the IWH, PTC, and HTHP systems. Future LCOD costs could potentially see a significant reduction of up to 66 % depending on the heat source system based on projected decreases in DAC CAPEX costs. A cost comparison revealed that current carbon price levels within the European Emission trading scheme are not expected to be sufficiently high enough to drive large investments in the development and scaling of LT-DAC. Cost levels of CCS technologies and LT-DAC could however be comparable, in particular for the geothermal energy system. [ABSTRACT FROM AUTHOR]

The study of heat transfer in coal and rock masses is crucial for thermal storage engineering and geothermal utilization in abandoned mines. Nevertheless, previous research on heat transfer in this field has frequently neglected the interconnection between the flow and heat transfer of heat-working substances (HWS) within three-dimensional microcracks. To reveal the above mechanism, first, the multi-factor influence mechanism of coal and rock heat conduction was analyzed based on the gray system theory. Subsequently, meshes of the matrix and fractures were reconstructed using the digital core simulation technology based on scanning electron microscopy and computed tomography. Finally, a multi-dimensional and multi-scale coal conjugate heat transfer model was built. The results indicate that the heat flux of heat transfer in coal and rock in the heat inflow direction is 3.03–6.44 times as high as that in the direction perpendicular to the heat inflow direction. As the heat transfer of HWS continues, the influence of coal and rock composition diminishes, and the development degree of fractures becomes the major factor affecting heat transfer. Furthermore, alterations in phase state will result in modifications to the conjugated heat transfer mechanism. This study can provide guidance for HWS selection in abandoned mines. [ABSTRACT FROM AUTHOR]

Renewable energy sources, such as solar, wind, water and geothermal are abundant and replenished by nature, making them crucial for both present and future sustainable energy needs while significantly reducing greenhouse gas emissions, environmental pollution and can mitigate adverse climate change. This review work focusses on the recent applications of nanotechnology in energy production from renewable and sustainable energy sources. The recent advances in the application of nanoparticles and their nanofluids in solar panels, waste heat recovery, fuel cells, wind and hydropower turbines, and geothermal energy are discussed in detail. Moreover, this review highlights the role of nanotechnology in the conversion of biomass to bioenergy and biogas upgrading techniques. In addition, contribution of nanotechnology in carbon dioxide capture via various methods have also been discussed, which is closely associated with renewable energy production. This research reviewed various nanofluids for heat transfer across different equipment used in renewable energy production, comparing their performance to aid in nanoparticle selection for specific tasks. The review article explicitly addresses challenges in applying nanofluids for renewable energy, bridging the gap between nanotechnology and renewable energy generation. While nanoparticle applications hold promise for industries, challenges must be addressed for their full integration into industrial processes. Currently, nanofluid use in wind and hydropower energy is limited, but research potential exists for lubricating agent applications and energy recovery. • Review on the application of nanotechnology in renewable energy. • Role of nanoparticles in energy production from biomass to bioenergy. • Contribution of nanotechnology in carbon capture. • Challenges in applications of nanofluids in renewable energy. [ABSTRACT FROM AUTHOR]

This study aims to calculate and analyze the energy requirement and improve the efficiency and sustainability of greenhouse (GH) agriculture by integrating renewable energy sources (RES) and advanced control systems into a hybrid solar-GH heating and cooling solution. The proposed system incorporates both geothermal and photovoltaic (PV) energy to optimize performance, particularly during the colder seasons. The analysis focuses on three widely used double-layer polyethylene materials in Canadian GHs, Thermax, SolaWrap, and SunSaver, evaluating their thermal insulation and light management properties. For a practical test, a typical 1000 m 2 GH is designed to calculate the energy requirements for heating and cooling, specifically tailored to the climatic conditions of Regina, using the three types of polyethylene. An energy and cost analysis is performed considering various energy sources to meet these demands. The research calculates and compares the power generation from building-integrated photovoltaics (BIPV) with traditional maximum power point tracking (MPPT) PV systems and integrates a 5-stage controller with HVAC damper control to further optimize energy consumption under different scenarios. The simulations performed using TRNSYS and SketchUp provide detailed monthly energy consumption and cost breakdowns for each polyethylene type. Additional insights include monthly power generation from both PV and BIPV systems, as well as contributions from geothermal energy. The findings present a comprehensive energy analysis, highlight potential cost savings and system efficiencies, and offer valuable information to advance sustainable GH agriculture in cold climates. • Integration of BIPV, ground heat exchanger, and heat pump in a greenhouse HVAC system. • Comparative analysis of power between BIPV and MPPT PV systems of the same size. • Control system optimizes HVAC damper performance using ambient and greenhouse temperatures. • Results show data on temperature dynamics, energy consumption, and system performance. [ABSTRACT FROM AUTHOR]

Alternative powerplant layouts to commonly applied flash technology is investigated for the water dominant geothermal location of Amiata Mountain, Italy. The proposed solution avoids flashing the brine stream by a borehole pump capable of maintaining pressurized conditions, thus reducing the amount of non-condensable gases released when reaching the ground level. Therefore, the need of a gas treatment section is completely avoided. The heat recovered from the hot brine at ground level is transferred to different supercritical CO 2 cycle configurations, equipped with high efficiency Printed Circuit Heat Exchangers (PCHE). The optimal 45.5 % calculated exergy efficiency was achieved for the recuperative cycle with intercooling and reheat, which however didn't show the optimal electricity costs (8.092 c€/kWh) because of the more complex heat exchangers network. The lowest cost of electricity (7.4 c€/kWh) was found for the recuperative cycle configuration. These costs are in line with the current levels of geothermal binary cycles, but almost doubled compared to the current single flash + ORC solution, due to a 40–50 % reduction of power output with sCO 2 cycles. On the other hand, sCO 2 binary cycles could guarantee an almost zero environmental impact, which is the main reason for social concerns related to the current flash powerplants. • Non conventional CO2 binary cycles to exploit geothermal resources are investigated. • The solutions allow zero emissions due to the full reinjection of geothermal brine. • The power cycles are compared with exergy and exergoeconomic methodologies. • The recuperative IC/RH cycle has the best performance and electricity cost. • The HX pressure losses significantly influence performance and energy costs. [ABSTRACT FROM AUTHOR]