Utilization Of Geothermal Energy Research Articles

Influence of eccentricity on the thermal performance of pipe-in-pipe heat exchanger utilized for geothermal heating, an experimental study

In the past few decades, pipe-in-pipe coaxial borehole heat exchangers (BHEs) have become increasingly widespread for building heating through the usage of medium-deep geothermal energy. Enhancing the heat transfer efficiency of BHEs is crucial in order to achieve higher efficiency in utilizing geothermal energy. This study introduced a novel consideration regarding the eccentric inner pipe as a technique to enhance the thermal performance of the pipe-in-pipe BHE. The impact of eccentricity varying from 0 to 0.9 on the BHE performance was experimentally explored to establish the correlation for Nusselt number. The convective heat transfer coefficients were obtained based on 480 sets of test results conducted under varied heating powers (200 – 4500 W/m2) and flow rates (0.16 – 1.00 m3/h). The results demonstrated that in comparison to the coaxial BHE, the eccentricity leads to a considerable enhancement in the heat transfer coefficient, ranging from 20 % to 35 %. The thermal performance is higher when the eccentricity is between 0.4 and 0.6, while the pressure loss can be decreased by 33 % − 54 %. The research results are expected to provide a theoretical basis to improve the geothermal energy utilization efficiency without improving the cost of BHE systems.

Multi-objective integrated optimization of geothermal heating system with energy storage using digital twin technology

Heat energy storage technology plays a significant role in energy systems, and the various technological solutions brought about by digitalization are especially valuable in the field of energy storage. This article proposes an innovative model based on digital twin technology to solve the supply–demand mismatch problem in geothermal heating systems. This model achieves multi-objective optimization of comprehensive cost, geothermal energy utilization rate, and carbon emission by constructing a heat storage geothermal heating system. Digital twin technology integrates data and information models of public buildings and facilitates their sharing and transmission throughout the entire lifecycle of the geothermal heating system. Initially, the proposed method employs a machine learning-based approach to accurately predict heating demand. Subsequently, the operation of the heat storage water tank and heat pump units is optimized to resolve difficulties in matching energy supply and demand. Finally, the method takes full advantage of time-of-use electricity pricing policies to reduce costs. The data utilized were collected from an office building in China over a period of six months. Experimental results demonstrate that: (1) In terms of predicting heating demand, the improved neural network proposed in this study achieved a prediction accuracy of 98%, which is a 10% improvement over comparative algorithms. Additionally, the experimental comparison of four types of errors showed that the machine learning method proposed had smaller errors across the board. (2) The method realized collaborative multi-objective optimization, and in five scenarios, the comprehensive performance index increased by up to 38.03% compared to the benchmark system. This indicates that intelligent technology is an effective means of enhancing the energy sustainability of geothermal heating systems, and the use of geothermal energy as a clean energy source effectively addresses issues related to the storage, utilization, management, and energy conservation of buildings.

Groundwater Potential for the Utilisation of Shallow Geothermal Energy from a Closed Coal Mine

Groundwater Potential for the Utilisation of Shallow Geothermal Energy from a Closed Coal Mine

Comprehensive analysis and optimization for a novel combined heating and power system based on self-condensing transcritical CO2 Rankine cycle driven by geothermal energy from thermodynamic, exergoeconomic and exergoenvironmental aspects

In this paper, a novel combined heating and power (CHP) system is proposed to realize full-scale utilization of geothermal energy and efficient multi-generation, which not only performs preferable overall performance than previous homogeneous system, but also offers an effective energy cascade utilization approach for self-condensing transcritical CO2 (TCO2) Rankine cycle. Based on the established mathematical models, the performance comparison is conducted for proving the superiority of the novel CHP system. Then, an overall performance analysis is implemented to reveal the combined effects for six key parameters on system thermodynamic, exergoeconomic and exergoenvironmental performances. Furthermore, multi-objective optimization considering system overall performance is conducted. The results show that for the novel CHP system, the largest relative improvement rate of system exergy efficiency (ηexg) and declining rate of total unit product exergy cost (cP,total) versus the previous CHP system are 15.03 % and 18.89 %, respectively. The final optimization results of ηexg, cP,total and total unit product exergy environmental impact (bP,total) are determined as 51.10 %, 14.12 $/GJ and 9.00 mPts/GJ, respectively. This paper fulfills an elaborate performance analysis and optimization for the novel CHP system, which fills the research gap of efficient and promising CHP system based on self-condensing TCO2 Rankine cycle.

Effects of saturated fluids on petrophysical properties of hot dry rock at high temperatures: An experimental study

Hydraulic fracturing is a crucial technology for efficient heat extraction from hot dry rock (HDR). The fracturing process involves the injection of large volumes of cold fluids, which can significantly affect the petrophysical properties of the rock, particularly when temperature differences and fluid-rock interactions are taken into account. However, there is a lack of research on the evolution of HDR petrophysical properties under the influence of different fluids at high temperatures. In this paper, we utilized a high-temperature high-pressure tri-axial loading system, rock spontaneous imbibition instrument, porosity-permeability tester, and thermal conductivity meter, along with comprehensive analysis techniques such as ultrasonic wave velocity monitoring, CT scanning, and nuclear magnetic resonance (NMR), to systematically investigate the effects of distilled water and nano emulsion on the physical and mechanical properties of the HDR at high temperatures. Through comparison with the experimental results of dry samples, comprehensive characteristics of physical parameters for the HDR under the influence of distilled water and nano emulsion are obtained, such as spontaneous imbibition mass and permeability, thermal physical properties, and rock mechanical parameters. The experimental results show that temperature increase promotes the formation of massive thermal damage fractures in the HDR samples, and the fluid weakens the mechanical strength of the HDR. When the effects of temperature and saturated fluids are combined, the hydraulic fracture network in the HDR samples exhibits increased complexity, contrasting with the fracture patterns observed in the heat-treated dry samples. The distilled water has a more pronounced effect on weakening the mechanical strength of the samples than the nano emulsion. Moreover, the analyses of permeability, thermal conductivity, ultrasonic wave velocity, and NMR results are consistent with the results of mechanical experiments. As the temperature rises, the wave velocity of saturated distilled water samples exceeds that of both saturated nano emulsion samples and dry samples, the velocity of the saturated fluid front in the samples increases, and the range of the fluid in the pores expands. Overall, these findings provide valuable experimental evidence and theoretical guidance for better understanding the hydro-thermal-mechanical behaviors of the HDR, which are crucial for the efficient development and utilization of geothermal energy.

Comparative analysis of machine learning techniques for predicting drilling rate of penetration (ROP) in geothermal wells: A case study of FORGE site

Enhanced Geothermal Systems (EGS) present a compelling means to unlock the considerable yet largely untapped thermal energy within the earth's crust globally. The EGS drilling cost constitutes a substantial portion, up to 60 %, of the overall expenses. Consequently, streamlining and optimizing the drilling processes for these systems hold immense economic significance, with the potential to substantially lower costs, advance the utilization of geothermal energy, and contribute significantly to the reduction of carbon emissions. This research aims to enhance EGS drilling operations by seeking ways of reducing drilling cost.In this research, we harnessed the predictive power of 10 state-of-the-art machine learning (ML) algorithms to anticipate a crucial drilling parameter: ROP. Using the FORGE dataset, we developed a code tailored for the intensive preprocessing of drilling data. This code offers many options, including various noise-removing techniques and scaling approaches. However, the primary focus of our work extends to quantifying uncertainties intrinsic to the predictions of the 10 algorithms employed. To achieve this, a comprehensive approach involved subjecting each algorithm to 40 runs, utilizing the best model from the tuning process.The results show that unaddressed uncertainties may lead to unstable model behavior, where small changes in the input data or random initialization result in significant prediction variations. Thus, models that do not account for uncertainty may be overfit to the noise in the training data, leading to poor generalization to new, unseen data. Remarkably, the results highlight the superiority of the Extreme Tree, Light Gradient Boost, Random Forest, and Gradient Boosting algorithms, showcasing mean absolute error (MAE) and R2 values within the ranges of 3.5–4.5 and 0.9–0.95, respectively. Conversely, artificial neural networks and support vector machine algorithms demonstrate comparatively lower performance, with MAE ranging from 4.7 to 6.3 and R2 from 0.85 to 0.91.Although the results presented in this work are only based on the drilling parameters from one well of the FORGE site and do not include rock properties or geological parameters, however, the proposed nuanced understanding of algorithmic performance is valuable for refining predictive models in geothermal drilling applications, ensuring robustness and reliability in the face of diverse operational scenarios. Navigating a successful workflow, adeptly processing data, and meticulously quantifying uncertainties linked to each predictive algorithm emerge as formidable yet indispensable tasks. Our research not only sheds light on these complexities but also paves the way for a strategic optimization approach based on data-driven ROP models. Therefore, the potential for substantial savings in real-time drilling operations becomes apparent, unlocking a new realm of possibilities for the geothermal energy sector.

Geothermal Energy Potential Assessment and Utilization in the Absheron Oil and Gas Region

Geothermal Energy Potential Assessment and Utilization in the Absheron Oil and Gas Region

Experimental Investigation of the Effect of Fault Reactivation Induced by Water Injection

An understanding of fault reactivation induced by water injection is of great significance for geothermal energy development and utilization. We conducted a series of water injection shear tests on low-permeability granite samples that each contained a single saw-cut fault under locally undrained conditions. Slip characteristics were analyzed by varying the fluid pressurization rate, confining pressure, and stress state of the fault to understand fault reactivation. The experimental results demonstrated that at a high pressurization rate, a higher local fluid pressure was needed to reactivate the fault than had been estimated theoretically, and the required fluid pressure increased with an increase in pressurization rate. The fluid pressurization rate and confining pressure both controlled the slip mode of the fault. The slip mode changed from dynamic slip to quasi-static slip at a high pressurization rate, and the peak slip rate of dynamic slip increased with an increasing pressurization rate. The fault showed significant stick-slip characteristics under a high confining pressure, as fault locking and reactivation phenomena occurred repeatedly. Faults with different initial stress states had little influence on the slip mode after the onset of slip.

Optimization Simulation of Different Injection and Production Parameters of Enhanced Geothermal Systems

Enhanced Geothermal System (EGS), as a key technology for the extraction and utilization of geothermal energy in deep strata and high temperature rock mass, has a broad application prospect in the field of energy. In order to understand the sustainable utilization capacity of the enhanced geothermal system, explore the influence law of different factors on the heat production capacity of geothermal Wells, and design a reasonable geothermal energy development and utilization program. The influence of different injection and production parameters on thermal recovery performance was studied by numerical simulation, and the main influencing factors were analyzed by orthogonal experiment. The results show that water injection rate has the greatest effect on the injection-production parameters, followed by well spacing and water injection temperature, and fracture opening and fracture number have the least effect. The optimal parameter combination is water injection rate of 10kg/s, well spacing 500m, water injection temperature 40℃, crack opening 0.09mm and crack number 60.

"3E" Analysis and Working Fluid Selection for a Cogeneration System for Geothermal Large Temperature Difference Utilization.

Widespread utilization of geothermal energy as a clean energy source can reduce the use of fossil fuels and thereby protect the environment. Previous combined heat and power (CHP) systems using low-temperature geothermal heat as a heat source have limited utilization of geothermal heat. In this study, a cogeneration system based on organic Rankine cycle (ORC) and absorption heat exchanger (AHE) is designed. We analyzed the thermal efficiency, exergy efficiency, and economics of the proposed system utilizing 85 °C low-temperature geothermal heat, and the optimal operating fluid for this system is discussed. The results show that the optimal working fluid for the proposed system is R245fa. Using R245fa as the working fluid, the proposed system can achieve an exergy efficiency of 61.39%, when the heat source outlet temperature can be as low as 23 °C, while the proposed system can achieve the lowest LCOE of 0.082 ($/kW ·h) when using R22 as the working fluid.

An integrated system combining MDBHE (multi-casing DBHE) and heat pump achieves heating and cooling for medium-deep geothermal energy utilization

Due to its convenient application in utilizing the medium-deep geothermal energy, the deep borehole heat exchanger has received extensive attention. Here we initiated an integrated system by coupling the multi-casing deep borehole heat exchanger (MDBHE) and heat pump to realize heat extraction and heating in the whole well in winter, and heat storage and cooling in the well upper part in summer. In the MDBHE, an annular pipe was used to store heat. Through the analysis of the simulation results of the influence of several variables on the system performance, it is found that the increase of heat storage temperature, annular pipe length and formation thermal conductivity raised the heat storage rate of the system, but the geothermal gradient is opposite. Benefiting from heat storage, the heat extraction rates in winter is also improved. Meanwhile, the heat pump elevated the heating rate by 15.9% in winter, and the cooling rate of the heat pump were respectively 19.3%, 21.5% and 23.7% less than the heat storage rate of the MDBHE based on the heat storage temperature of 40, 45 and 50 °C. Therefore, the integrated system can simultaneously satisfy the requirements of summer cooling and winter heating and maintain the formation heat balance, so that the urban heat island effect is mitigated.

Thermodynamic analysis of a coupled system based on total flow cycle and partially evaporated organic Rankine cycle for hot dry rock utilization

The total flow cycle (TFC) has a great potential to improve efficiency of geothermal energy utilization. However, it can not fully utilize the heat source due to the limited expansion ratio of the two-phase expander. To solve the problem, a coupled system of TFC and partially evaporated organic Rankine cycle (TFC-PEORC) is proposed. The thermodynamic model considering the pinch point location migration is developed, and the effects of operating parameters on the temperature matching and system performance are investigated. On this basis, system optimization is carried out. At the same time, the performance of TFC-PEORC was compared with the single-stage TFC, the coupled system of TFC and organic Rankine cycle (TFC-ORC), the coupled system of trilateral cycle and organic Rankine cycle (TLC-ORC), and the coupled system of TFC and Kalina cycle (TFC-KC) under optimal operating conditions. The results show that the net output power of TFC-PEORC has a 14.26 % increase compared to TFC, and that TFC-PEORC can provide excellent the temperature matching of the high temperature (HT) stage and the low temperature (LT) stage working fluids, thus providing the maximum net output power (84.36 kW) that is up to 1.93 % higher than TFC-ORC.

Feasibility Investigation of Geothermal Energy Heating System in Mining Area: Application of Mine Cooling and Aquifer Thermal Energy Exploitation Technique

Mine heat hazards have resulted in large amounts of high-quality coal resources in deep that cannot be mined. The mining industry is paying more and more attention to the extraction and utilization of geothermal energy in mines, while at the same time reducing the underground temperature to realize co-extraction of coal and heat. In addition, coal mines tend to burn large amounts of coal to heat mine buildings and provide hot water for workers’ daily baths, creating operating costs and increasing greenhouse gas emissions. Therefore, it is of great significance to investigate the feasibility of extracting geothermal energy to provide the daily heat load for mines. Currently, there is little research on the feasibility of geothermal energy extraction and utilization in productive mines instead of abandoned mines. In this study, according to the actual situation of Xinhu mine in eastern China, a combined geothermal water system and heat-pump heating system is proposed, aiming to effectively realize mine cooling and geothermal exploitation and utilization. The geothermal storage capacity in the area is analyzed, and an economic analysis is developed. The economic analysis indicates that the main factors affecting the feasibility of the system are the number of mine users, the distance from the geothermal production well to the mine buildings, and the coal price. The research shows that the economic efficiency of the system is better when the heating scale is larger and the distance is smaller. As coal prices rise, the combined geothermal water and heat-pump heating system will be more economical than traditional coal heating. If a mine has 2000 workers, the application of this system can prevent 334.584 t of CO2 emissions per year.

Analysis of the factors influencing heat transfer and control strategy optimization for Medium-Shallow array borehole heat exchangers

Medium-shallow array borehole heat exchangers (MSABHEs) exhibit high heat transfer capacity and low initial investments. However, limited research has been conducted on utilizing medium-shallow geothermal energy utilization for heating and cooling. In this study, a heat transfer model for MSABHEs was established. Second, the suitability of the heat transfer model was validated using experimental data. Subsequently, the model was used to analyze the impacts of the borehole spacing, terrestrial heat flow, circulating fluid flow rate, and ground depth on heat transfer in MSABHEs. Finally, an optimization strategy for the circulating fluid was proposed based on dynamic building loads, and the impacts of various circulating liquid control strategies on the heat pump performance were compared. The results indicated that the heat transfer capacity of the MSABHEs increased with increasing borehole spacing. When the spacing was greater than 8 m, thermal interference between the boreholes could be ignored. Under the condition of imbalanced cooling and heating loads, the variable flow strategy could increase the heating coefficient of performance (COP) and cooling COP of the heat pump by approximately 11.12 % and 14.28 %, respectively. Through this control method, the power consumption of the water pump could be reduced from 15840 kW to 8527 kW. These findings could provide a theoretical basis and technical guidance for MSABHE applications.

Origin of high heat flow in the back-arc basins of Sumatra: An opportunity for geothermal energy development

Volcanic arcs such as the Barisan Mountains have been identified as attractive areas for the utilization of geothermal energy, as exemplified by Ulubelu in Lampung and Sarulla in North Sumatra. However, environmental factors in the Barisan Mountains remain a primary obstacle to the exploration and exploitation of geothermal energy. The back-arc basins of Sumatra exhibit the highest heat flow worldwide; however, the heat source in this area remains a controversial issue. This study aims to investigate the origin of the high heat flow in the back-arc basins of Sumatra (North, Central, and South Sumatra basins) based on geothermal data from 384 oil wells and the current literature for geological evaluation. The findings of this study indicate that the back-arc basins of Sumatra experienced severe extensional deformation during the Tertiary Period through a large pull-apart and slab rollback mechanism. This deformation resulted in the thinning of the continental crust in this region (27–32 km) and the formation of multiple normal faults. Consequently, the presence of magma resulting from mantle upwelling implies a high heat flow in the back-arc basins of Sumatra. This condition ranks the back-arc basins of Sumatra among the highest heat flow regions of the world, with heat flows >100 mW/m2. These findings indicate that the back-arc basins of Sumatra have significant opportunities to exploit their geothermal energy potential. This study provides novel insights into the potential of geothermal energy, particularly in the back-arc basins of Sumatra.

Simulation and comprehensive 4E study of a high-efficient CCHP arrangement utilizing geothermal energy and eco-friendly heat recovery

In recent years, geothermal energy has received significant attention as it provides a sustainable and renewable energy resource for various applications. The primary objective of this study is to manage the relative irreversibility and enhance productivity through efficient utilization of geothermal energy. The present paper establishes a high-efficiency and environmentally sustainable heat integration model in a novel configuration to be a geothermal energy source having the ability to produce power, heat, and cooling. The proposed framework consists of a Kalina cycle, two organic Rankine cycles, an ammonia Rankine cycle, a single-flash power unit, and a combined cooling and power unit. The simulation of the proposed system is implemented within the Aspen HYSYS software, with an examination of its feasibility across energy, exergy, economic, and environmental considerations. The research findings indicate that the system can generate 23250.8 kW of power, 582.1 kg/s of hot water, and 2.812 kg/s of chilled water. Therefore, the total exergy destruction rate is 14104 kW, with the Kalina cycle accounting for the majority share at 40.47 % Moreover, the energy and energy efficiencies of the suggested structure are 61.81 % and 72.52 %, respectively. The environmental analysis indicates that the entire process lacks carbon dioxide emissions. Furthermore, the economic analysis reveals that the total unit exergy cost and levelized cost of energy are determined to be 5.13 $/GJ and 0.511 $/kWh, respectively. Also, the proposed system exhibits a favorable net present value of approximately 32.16 M$. Hence, the project demonstrates profitability.

The Authority of the District/City Government Related to The Utilization of Geothermal Energy According to Article 156 of Law Number 11 of 2006 Concerning the Government of Aceh

Objective: This research examines the Authority of Regency /City Governments related to Geothermal Energy Utilization based on Law No. 11/2006 on the Government of Aceh. Geothermal utilization can help the government program for clean energy utilization, considering that geothermal is a form of renewable energy that produces few greenhouse gas emissions and can maintain national energy stability and security. Based on the provisions of Article 156 of Law No. 11/2006 on the Government of Aceh which regulates the management of natural resources, district/city governments have the authority to manage natural resources in Aceh both on land and at sea, including geothermal energy. However, this authority has not been exercised by the district/city in the utilization of geothermal energy in Aceh. This article aims to determine and analyze the authority of the district/city government in utilizing geothermal energy based on Article 156 of the LoGA the Government of Aceh. This article aims to discuss and analyze the authority of the Regency / City Government in the utilization of geothermal energy sources based on Article 156 of Law No. 11/2006 concerning the Government of Aceh.
 
 Methodology: This research uses a juridical sociological approach which aims to obtain field data as primary data in analyzing the law and looking more deeply at the effectiveness of law in society. This research is supported by primary data and secondary data. Primary data was obtained by conducting field research in several districts (Central Aceh District and Aceh Besar District). While secondary data is obtained by searching the literature and regulations related to the focus of the research, data collection techniques are carried out through structured interviews with the parties involved in this study.
 
 Result and Conlusion: The authority contained in Article 156 of the LoGA has not been exercised by the district/city government in utilizing geothermal energy in Aceh, this is due to regulations issued by the central government regarding the utilization of geothermal energy in the region. Thus, it is necessary to regulate in the form of Qanun Aceh and District/ City Qanun in utilizing geothermal energy in Aceh.

Transient heat transfer simulation, sensitivity analysis, and design optimization of shallow ground heat exchangers with hollow-finned structures for enhanced performance of ground-coupled heat pumps

Ground-Coupled Heat Pumps (GCHPs) are regarded as an effective technology for building energy development and residential hot water production. The essential challenges to encompass these systems in urbanized areas are the highly drilling and initial costs of GCHPs. To overcome this challenge, researchers and industries are seeking innovative solutions by focusing on optimizing the structure of ground heat exchangers (GHXs), which act as the essential component for efficient geothermal energy extraction in GCHPs. Hence, this paper introduces a comprehensive comparative numerical investigation of an innovative U-tube GHX with a hollow-finned structure for augmenting the performance of the GCHPs. This design remarkably enhances the thermal performances, reduces the thermal resistance, therefore minimizes borehole depth, reduces drilling costs, boosts GCHP's financial viability, and bolsters geothermal energy utilization. Therefore, a series of three-dimensional analyses of transient heat extraction is executed and validated using a practical field experiment performed by the authors' research group to investigate the thermal behavior of the hollow-finned U-tube GHX at different fin configurations and compare its efficacy to typical circular U-tube GHX. More so, a parametric study and sensitivity analysis are also performed to identify the influence of critical operational and design factors on the heat extraction of the proposed hollow-finned U-tube GHX compared to the typical circular GHX. The influences of groundwater flow on the transient heat extraction were also examined. Additionally, a dimensionless shape factor is introduced to assess the implications of the U-tube geometry with hollow-finned on the thermal performance of the GHXs. Furthermore, design optimization was also conducted by examining different branched-shaped hollow-fin's U-tube GHX configurations. The findings indicate that the mean heat transfer rate of hollow-finned U-tube GHX can be increased by 44.58 % compared to the conventional circular U-tube GHX. Correspondingly, the total thermal resistance of hollow-finned U-tubes GHX was reduced by 47.71 %. It also identified that the Y-shaped hollow-finned U-tube GHX was the optimal design among the investigated configurations of branched-shaped hollow-finned U-tube GHXs, demonstrating an increase of 52.64 % compared to the conventional circular U-tube GHX. Moreover, it is revealed that a lower shape factor enhances the heat transfer rate significantly. Furthermore, the optimal mass flow rate and desired number of hollow-finned were estimated as 0.80 kg/s and six fins, respectively. Conclusively, this investigation concludes that the hollow-finned U-tube GHX can greatly enhance the heat extraction rates and reduce borehole thermal resistance, which can increase the efficiency of GCHP systems.

Analytical study of integrating downhole thermoelectric power generation with a coaxial borehole heat exchanger in geothermal wells

Geothermal power generation employing Organic Rankine Cycle (ORC) technology is a widely acknowledged and conventional approach for harnessing geothermal energy. In an innovative advancement, we propose a novel design integrating downhole thermoelectric power generation with a coaxial borehole heat exchanger. This design aims to enhance the efficiency and sustainability of geothermal energy utilization. In this innovative design, the geothermal well is divided into two distinct sections: a power generation section and a heat exchanging section, achieved through the implementation of a packer positioned from the uppermost part of the targeted zone. The process involves the injection of cold fluid downhole via an insulated pipe. Subsequently, a portion of the injected fluid is directed to flow in reverse within the casing-tubing annulus above the packer, while another portion circulates into the casing-tubing annulus below the packer before ascending through the tubing. This dual flow mechanism establishes distinct cold and hot sources for the thermoelectric generator, a key feature facilitated by this innovative design. Analytical models detailing of downhole temperature distribution for thermoelectric power have been meticulously developed. A comprehensive case study, focusing on a geothermal well with 3000 m length of power generation section and 500 m heat exchanging section, has been conducted. The results indicate that a significant generating capacity could be achieved with a higher wellhead temperature, and the payback period under different carbon tax scenarios is about 6–8 year. Furthermore, the effects of injection rate, fluid diversion ratio, and casing-tubing configuration on power performance and thermal-electricity efficiency are also discussed. This method not only enables the concurrent harvesting of geothermal energy and power generation but also operates consistently throughout the year. The results thus emphasize the viability and economic feasibility of the proposed approach.

Geothermal district heating: Energy, environmental and economic analysis of a case study in northern Italy

Geothermal district heating is a technology that has been established for over 50 years and offers a number of significant advantages. It allows multiple homes to be converted to renewable energy sources simultaneously, allows a stable heat supply with long-term fixed prices, and generally presents lower risks. The utilization of geothermal energy as a heat source for the network can be considered cost-free during operation, but has a critical economic aspect related to the initial investment. Geothermal district heating networks are in fact capital-intensive systems (CapEx), requiring substantial investments for the installation of the geothermal infrastructure. However, operating costs (OpEx) are significantly lower compared to conventional systems. This study examined the implementation of a district heating network in a medium-sized city in northern Italy. An energy and environmental impact assessment was conducted to determine the optimal plant configuration that maximises the use of the geothermal resource and minimises greenhouse gas emissions. Additionally, a sensitivity analysis was carried out to assess the impact of market variables on the overall cost of implementing the district heating network. This included an evaluation of changes in investment costs in response to variations in the value of electricity taxes -oneri di sistema-, of the revenues from the sale of thermal and electrical energy, as well as of the fuel costs. This study aims to provide a complete and detailed overview of the energy, environmental and economic implications associated with the implementation of a geothermal district heating network