Research

17 pages, 7050 KiB

Open AccessArticle

Assessment of Geothermal Resources in the North Jiangsu Basin, East China, Using Monte Carlo Simulation

by Yibo Wang, Lijuan Wang, Yang Bai, Zhuting Wang, Jie Hu, Di Hu, Yaqi Wang and Shengbiao Hu

Energies 2021, 14(2), 259; https://doi.org/10.3390/en14020259 - 06 Jan 2021

Cited by 9 | Viewed by 2079

Abstract

Geothermal energy has been recognized as an important clean renewable energy. Accurate assessment of geothermal resources is an essential foundation for their development and utilization. The North Jiangsu Basin (NJB), located in the Lower Yangtze Craton, is shaped like a wedge block of [...] Read more.

Geothermal energy has been recognized as an important clean renewable energy. Accurate assessment of geothermal resources is an essential foundation for their development and utilization. The North Jiangsu Basin (NJB), located in the Lower Yangtze Craton, is shaped like a wedge block of an ancient plate boundary and large-scale carbonate thermal reservoirs are developed in the deep NJB. Moreover, the NJB exhibits a high heat flow background because of its extensive extension since the Late Mesozoic. In this study, we used the Monte Carlo method to evaluate the geothermal resources of the main reservoir shallower than 10 km in the NJB. Compared with the volumetric method, the Monte Carlo method takes into account the variation mode and uncertainties of the input parameters. The simulation results show that the geothermal resources of the sandstone thermal reservoir in the shallow NJB are very rich, with capacities of (6.6–12) × 10²⁰ J (mean 8.6 × 10²⁰ J), (5.1–16) × 10²⁰ J (mean 9.1 × 10²⁰ J), and (3.2–11) × 10²⁰ J (mean 6.6 × 10²⁰ J) for the Yancheng, Sanduo and Dai’nan sandstone reservoir, respectively. In addition, the capacity of the geothermal resource of the carbonate thermal reservoir in the deep NJB is far greater than the former, reaching (9.9–15) × 10²¹ J (mean 12 × 10²¹ J). The results indicate capacities of a range value of (1.2–1.7) × 10²¹ J (mean 1.4 × 10²² J) for the whole NJB (<10 km). Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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25 pages, 5339 KiB

Open AccessArticle

The Optimization of the Thermal Performances of an Earth to Air Heat Exchanger for an Air Conditioning System: A Numerical Study

by Adriana Greco and Claudia Masselli

Energies 2020, 13(23), 6414; https://doi.org/10.3390/en13236414 - 04 Dec 2020

Cited by 16 | Viewed by 1863

Abstract

The aim of this paper is to research the parameters that optimize the thermal performances of a horizontal single-duct Earth to Air Heat eXchanger (EAHX). In this analysis, the EAHX is intended to be installed in the city of Naples (Italy). The study [...] Read more.

The aim of this paper is to research the parameters that optimize the thermal performances of a horizontal single-duct Earth to Air Heat eXchanger (EAHX). In this analysis, the EAHX is intended to be installed in the city of Naples (Italy). The study is conducted by varying the most crucial parameters influencing the heat exchange between the air flowing in the duct and the ground. The effect of the geometrical characteristics of the duct (pipe length, diameter, burial depth), and the thermal and flow parameter of humid air (inlet temperature and velocity) has been studied in order to optimize the operation of this geothermal system. The results reveal that the thermal performance increases with length until the saturation distance is reached. Moreover, if the pipe is designed with smaller diameters and slower air flows, if other conditions remain equal, the outlet temperatures come closer to the ground temperature. The combination that optimizes the performance of the system, carried out by forcing the EAHX with the design conditions for cooling and heating, is: D = 0.1 m s⁻¹; v = 1.5 m s⁻¹; L = 50 m. This solution could also be extended to horizontal multi-tube EAHX systems. Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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18 pages, 10392 KiB

Open AccessArticle

A Novel Ground-Source Heat Pump with R744 and R1234ze as Refrigerants

by Giuseppe Emmi, Sara Bordignon, Laura Carnieletto, Michele De Carli, Fabio Poletto, Andrea Tarabotti, Davide Poletto, Antonio Galgaro, Giulia Mezzasalma and Adriana Bernardi

Energies 2020, 13(21), 5654; https://doi.org/10.3390/en13215654 - 29 Oct 2020

Cited by 6 | Viewed by 2526

Abstract

The energy-saving potential of heat pump technology is widely recognized in the building sector. In retrofit applications, especially in old and historic buildings, it may be difficult to replace the existing distribution and high-temperature emission systems. Often, historical buildings, especially the listed ones, [...] Read more.

The energy-saving potential of heat pump technology is widely recognized in the building sector. In retrofit applications, especially in old and historic buildings, it may be difficult to replace the existing distribution and high-temperature emission systems. Often, historical buildings, especially the listed ones, cannot be thermally insulated; this leads to high temperatures of the heat carrier fluid for heating. In these cases, the main limits are related, on the one hand, to the reaching of the required temperatures, and on the other hand, to the obtaining of good performance even at high temperatures. To address these problems, a suitable solution can be a two-stage heat pump. In this work, a novel concept of a two-stage heat pump is proposed, based on a transcritical cycle that uses the natural fluid R744 (carbon dioxide) with an ejector system. The second refrigerant present in the heat pump and used for the high-temperature stage is the R1234ze, which is an HFO (hydrofluoro-olefin) fluid. This work aims to present the effective energy performance based on real data obtained in operating conditions in a monitoring campaign. The heat pump prototype used in this application is part of the H2020 Cheap-GSHP project, which was concluded in 2019. Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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34 pages, 6812 KiB

Open AccessArticle

Energy, Environmental, and Economic Analyses of Geothermal Polygeneration System Using Dynamic Simulations

by Francesca Ceglia, Adriano Macaluso, Elisa Marrasso, Carlo Roselli and Laura Vanoli

Energies 2020, 13(18), 4603; https://doi.org/10.3390/en13184603 - 04 Sep 2020

Cited by 20 | Viewed by 2525

Abstract

This paper presents a thermodynamic, economic, and environmental analysis of a renewable polygeneration system connected to a district heating and cooling network. The system, fed by geothermal energy, provides thermal energy for heating and cooling, and domestic hot water for a residential district [...] Read more.

This paper presents a thermodynamic, economic, and environmental analysis of a renewable polygeneration system connected to a district heating and cooling network. The system, fed by geothermal energy, provides thermal energy for heating and cooling, and domestic hot water for a residential district located in the metropolitan city of Naples (South of Italy). The produced electricity is partly used for auxiliaries of the thermal district and partly sold to the power grid. A calibration control strategy was implemented by considering manufacturer data matching the appropriate operating temperature levels in each component. The cooling and thermal demands of the connected users were calculated using suitable building dynamic simulation models. An energy network dedicated to heating and cooling loads was designed and simulated by considering the variable ground temperature throughout the year, as well as the accurate heat transfer coefficients and pressure losses of the network pipes. The results were based on a 1-year dynamic simulation and were analyzed on a daily, monthly, and yearly basis. The performance was evaluated by means of the main economic and environmental aspects. Two parametric analyses were performed by varying geothermal well depth, to consider the uncertainty in the geofluid temperature as a function of the depth, and by varying the time of operation of the district heating and cooling network. Additionally, the economic analysis was performed by considering two different scenarios with and without feed-in tariffs. Based on the assumptions made, the system is economically feasible only if feed-in tariffs are considered: the minimum Simple Pay Back period is 7.00 years, corresponding to a Discounted Pay Back period of 8.84 years, and the maximum Net Present Value is 6.11 M€, corresponding to a Profit Index of 77.9% and a maximum Internal Rate of Return of 13.0%. The system allows avoiding exploitation of 27.2 GWh of primary energy yearly, corresponding to 5.49∙10³ tons of CO₂ avoided emissions. The increase of the time of the operation increases the economic profitability. Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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27 pages, 4244 KiB

Open AccessArticle

Dynamic Simulation and Energy Economic Analysis of a Household Hybrid Ground-Solar-Wind System Using TRNSYS Software

by Rafał Figaj, Maciej Żołądek and Wojciech Goryl

Energies 2020, 13(14), 3523; https://doi.org/10.3390/en13143523 - 08 Jul 2020

Cited by 19 | Viewed by 3468

Abstract

The adoption of micro-scale renewable energy systems in the residential sector has started to be increasingly diffused in recent years. Among the possible systems, ground heat exchangers coupled with reversible heat pumps are an interesting solution for providing space heating and cooling to [...] Read more.

The adoption of micro-scale renewable energy systems in the residential sector has started to be increasingly diffused in recent years. Among the possible systems, ground heat exchangers coupled with reversible heat pumps are an interesting solution for providing space heating and cooling to households. In this context, a possible hybridization of this technology with other renewable sources may lead to significant benefits in terms of energy performance and reduction of the dependency on conventional energy sources. However, the investigation of hybrid systems is not frequently addressed in the literature. The present paper presents a technical, energy, and economic analysis of a hybrid ground-solar-wind system, proving space heating/cooling, domestic hot water, and electrical energy for a household. The system includes vertical ground heat exchangers, a water–water reversible heat pump, photovoltaic/thermal collectors, and a wind turbine. The system with the building is modeled and dynamically simulated in the Transient System Simulation (TRNSYS) software. Daily dynamic operation of the system and the monthly and yearly results are analyzed. In addition, a parametric analysis is performed varying the solar field area and wind turbine power. The yearly results point out that the hybrid system, compared to a conventional system with natural gas boiler and electrical chiller, allows one to reduce the consumption of primary energy of 66.6%, and the production of electrical energy matches 68.6% of the user demand on a yearly basis. On the other hand, the economic results show that that system is not competitive with the conventional solution, because the simple pay back period is 21.6 years, due to the cost of the system components. Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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24 pages, 12832 KiB

Open AccessArticle

Techno-Economic Assessment of Mobilized Thermal Energy Storage System Using Geothermal Source in Polish Conditions

by Dominika Matuszewska, Marta Kuta and Piotr Olczak

Energies 2020, 13(13), 3404; https://doi.org/10.3390/en13133404 - 02 Jul 2020

Cited by 22 | Viewed by 2866

Abstract

The paper considers technical and economic possibilities to provide geothermal heat to individual recipients using a mobile thermal storage system (M-TES) in Polish conditions. The heat availability, temperature and heat cost influence the choice of location—Bańska Niżna, near Zakopane in the southern part [...] Read more.

The paper considers technical and economic possibilities to provide geothermal heat to individual recipients using a mobile thermal storage system (M-TES) in Polish conditions. The heat availability, temperature and heat cost influence the choice of location—Bańska Niżna, near Zakopane in the southern part of the Poland. The indirect contact energy storage container was selected with phase change material characterized by a melting temperature of 70 °C and a heat storage capacity of 250 kJ/kg, in the amount of 800 kg. The economic profitability of the M-TES system (with a price per warehouse of 6000 EUR, i.e., a total of 12,000 EUR—two containers are needed) can be achieved for a heat demand of 5000 kWh/year with the price of a replaced heat source at the level of 0.21 EUR/kWh and a distance between the charging station and building (heat recipient) of 0.5 km. For the heat demand of 15,000 kWh/year, the price for the replaced heat reached EUR 0.11/kWh, and the same distance. In turn, for a demand of 25,000 kWh/year, the price of the replaced heat source reached 0.085 EUR/kWh. The distance significantly affected the economic profitability of the M-TES system—for the analyzed case, a distance around 3–4 km from the heat source should be considered. Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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26 pages, 3367 KiB

Open AccessArticle

Modelling of Polymeric Shell and Tube Heat Exchangers for Low-Medium Temperature Geothermal Applications

by Francesca Ceglia, Adriano Macaluso, Elisa Marrasso, Maurizio Sasso and Laura Vanoli

Energies 2020, 13(11), 2737; https://doi.org/10.3390/en13112737 - 29 May 2020

Cited by 11 | Viewed by 3129

Abstract

Improvements in using geothermal sources can be attained through the installation of power plants taking advantage of low and medium enthalpy available in poorly exploited geothermal sites. Geothermal fluids at medium and low temperature could be considered to feed binary cycle power plants [...] Read more.

Improvements in using geothermal sources can be attained through the installation of power plants taking advantage of low and medium enthalpy available in poorly exploited geothermal sites. Geothermal fluids at medium and low temperature could be considered to feed binary cycle power plants using organic fluids for electricity “production” or in cogeneration configuration. The improvement in the use of geothermal aquifers at low-medium enthalpy in small deep sites favours the reduction of drilling well costs, and in addition, it allows the exploitation of local resources in the energy districts. The heat exchanger evaporator enables the thermal heat exchange between the working fluid (which is commonly an organic fluid for an Organic Rankine Cycle) and the geothermal fluid (supplied by the aquifer). Thus, it has to be realised taking into account the thermodynamic proprieties and chemical composition of the geothermal field. The geothermal fluid is typically very aggressive, and it leads to the corrosion of steel traditionally used in the heat exchangers. This paper analyses the possibility of using plastic material in the constructions of the evaporator installed in an Organic Rankine Cycle plant in order to overcome the problems of corrosion and the increase of heat exchanger thermal resistance due to the fouling effect. A comparison among heat exchangers made of commonly used materials, such as carbon, steel, and titanium, with alternative polymeric materials has been carried out. This analysis has been built in a mathematical approach using the correlation referred to in the literature about heat transfer in single-phase and two-phase fluids in a tube and/or in the shell side. The outcomes provide the heat transfer area for the shell and tube heat exchanger with a fixed thermal power size. The results have demonstrated that the plastic evaporator shows an increase of 47.0% of the heat transfer area but an economic installation cost saving of 48.0% over the titanium evaporator. Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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29 pages, 6264 KiB

Open AccessFeature PaperArticle

Thermo-Economic Analysis of Hybrid Solar-Geothermal Polygeneration Plants in Different Configurations

by Francesco Calise, Francesco Liberato Cappiello, Massimo Dentice d’Accadia and Maria Vicidomini

Energies 2020, 13(9), 2391; https://doi.org/10.3390/en13092391 - 11 May 2020

Cited by 22 | Viewed by 3026

Abstract

This work presents a thermoeconomic comparison between two different solar energy technologies, namely the evacuated flat-plate solar collectors and the photovoltaic panels, integrated as auxiliary systems into two renewable polygeneration plants. Both plants produce electricity, heat and cool, and are based on a [...] Read more.

This work presents a thermoeconomic comparison between two different solar energy technologies, namely the evacuated flat-plate solar collectors and the photovoltaic panels, integrated as auxiliary systems into two renewable polygeneration plants. Both plants produce electricity, heat and cool, and are based on a 6 kWe organic Rankine cycle (ORC), a 17-kW single-stage H2O/LiBr absorption chiller, a geothermal well at 96 °C, a 200 kWt biomass auxiliary heater, a 45.55 kWh lithium-ion battery and a 25 m² solar field. In both configurations, electric and thermal storage systems are included to mitigate the fluctuations due to the variability of solar radiation. ORC is mainly supplied by the thermal energy produced by the geothermal well. Additional heat is also provided by solar thermal collectors and by a biomass boiler. In an alternative layout, solar thermal collectors are replaced by photovoltaic panels, producing additional electricity with respect to the one produced by the ORC. To reduce ORC condensation temperature and increase the electric efficiency, a ground-cooled condenser is also adopted. All the components included in both plants were accurately simulated in a TRNSYS environment using dynamic models validated versus literature and experimental data. The ORC is modeled by zero-dimensional energy and mass balances written in Engineering Equation Solver and implemented in TRNSYS. The models of both renewable polygeneration plants are applied to a suitable case study, a commercial area near Campi Flegrei (Naples, South Italy), a location well-known for its geothermal sources and good solar availability. The economic results suggest that for this kind of plant, photovoltaic panels show lower pay back periods than evacuated flat-plate solar collectors, 13 years vs 15 years. The adoption of the electric energy storage system leads to an increase of energy-self-sufficiency equal to 42% and 47% for evacuated flat-plate solar collectors and the photovoltaic panels, respectively. Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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18 pages, 9908 KiB

Open AccessArticle

Effects of Cyclic Heating and Water Cooling on the Physical Characteristics of Granite

by Xiangchao Shi, Leiyu Gao, Jie Wu, Cheng Zhu, Shuai Chen and Xiao Zhuo

Energies 2020, 13(9), 2136; https://doi.org/10.3390/en13092136 - 29 Apr 2020

Cited by 15 | Viewed by 2481

Abstract

This paper aims to study the effect of cyclic heating and flowing-water cooling conditions on the physical properties of granite. Ultrasonic tests, gas measured porosity, permeability, and microscope observations were conducted on granite after thermal treatment. The results showed that the velocity of [...] Read more.

This paper aims to study the effect of cyclic heating and flowing-water cooling conditions on the physical properties of granite. Ultrasonic tests, gas measured porosity, permeability, and microscope observations were conducted on granite after thermal treatment. The results showed that the velocity of P- and S-waves decreased as the number of thermal cycles increased. The porosity increased with the number of the thermal cycles attained at 600 °C, while no apparent changes were observed at 200 and 400 °C. The permeability increased with the increasing number of thermal cycles. Furthermore, microscope observations showed that degradation of the granite after thermal treatment was attributed to a large network of microcracks induced by thermal stress. As the number of thermal cycles increased, the number of transgranular microcracks gradually increased, as well as their length and width. The quantification of microcracks from cast thin section (CTS) images supported the visual observation. Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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26 pages, 13164 KiB

Open AccessArticle

The Effect of Groundwater Flow on the Thermal Performance of a Novel Borehole Heat Exchanger for Ground Source Heat Pump Systems: Small Scale Experiments and Numerical Simulation

by Ahmed A. Serageldin, Ali Radwan, Yoshitaka Sakata, Takao Katsura and Katsunori Nagano

Energies 2020, 13(6), 1418; https://doi.org/10.3390/en13061418 - 18 Mar 2020

Cited by 19 | Viewed by 3197

Abstract

New small-scale experiments are carried out to study the effect of groundwater flow on the thermal performance of water ground heat exchangers for ground source heat pump systems. Four heat exchanger configurations are investigated; single U-tube with circular cross-section (SUC), single U-tube with [...] Read more.

New small-scale experiments are carried out to study the effect of groundwater flow on the thermal performance of water ground heat exchangers for ground source heat pump systems. Four heat exchanger configurations are investigated; single U-tube with circular cross-section (SUC), single U-tube with an oval cross-section (SUO), single U-tube with circular cross-section and single spacer with circular cross-section (SUC + SSC) and single U-tube with an oval cross-section and single spacer with circular cross-section (SUO + SSC). The soil temperature distributions along the horizontal and vertical axis are measured and recorded simultaneously with measuring the electrical energy injected into the fluid, and the borehole wall temperature is measured as well; consequently, the borehole thermal resistance (R_b) is calculated. Moreover, two dimensional and steady-state CFD simulations are validated against the experimental measurements at the groundwater velocity of 1000 m/year with an average error of 3%. Under saturated conditions without groundwater flow effect; using a spacer with SUC decreases the R_b by 13% from 0.15 m·K/W to 0.13 m·K/W, also using a spacer with the SUO decreases the R_b by 9% from 0.11 m·K/W to 0.1 m·K/W. In addition, the oval cross-section with spacer SUO + SSC decreases the R_b by 33% compared with SUC. Under the effect of groundwater flow of 1000 m/year; R_b of the SUC, SUO, SUC + SSC and SUO + SSC cases decrease by 15.5%, 12.3%, 6.1% and 4%, respectively, compared with the saturated condition. Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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25 pages, 4493 KiB

Open AccessArticle

Entropy, Entransy and Exergy Analysis of a Dual-Loop Organic Rankine Cycle (DORC) Using Mixture Working Fluids for Engine Waste Heat Recovery

by Shuang Wang, Wei Zhang, Yong-Qiang Feng, Xin Wang, Qian Wang, Yu-Zhuang Liu, Yu Wang and Lin Yao

Energies 2020, 13(6), 1301; https://doi.org/10.3390/en13061301 - 11 Mar 2020

Cited by 16 | Viewed by 2492

Abstract

The exergy, entropy, and entransy analysis for a dual-loop organic Rankine cycle (DORC) using a mixture of working fluids have been investigated in this study. A high-temperature (HT) loop was used to recover waste heat from internal combustion engine in 350 °C, and [...] Read more.

The exergy, entropy, and entransy analysis for a dual-loop organic Rankine cycle (DORC) using a mixture of working fluids have been investigated in this study. A high-temperature (HT) loop was used to recover waste heat from internal combustion engine in 350 °C, and a low-temperature loop (LT) was used to absorb residual heat of engine exhaust gas and HT loop working fluids. Hexane/toluene, cyclopentane/toluene, and R123/toluene were selected as working fluid mixtures for HT loop, while R245fa/pentane was chosen for LT loop. Results indicated that the variation of entropy generation rate, entransy loss, entransy efficiency, and exergy loss are insensitive to the working fluids. The entransy loss rate and system net power output present the same variation trends, whereas a reverse trend for entropy generation rate and entransy efficiency, while the exergy analysis proved to be only utilized under fixed stream conditions. The results also showed that hexane/toluene is the preferred mixture fluid for DORC. Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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26 pages, 10513 KiB

Open AccessEditor’s ChoiceArticle

Low Enthalpy Geothermal Systems in Structural Controlled Areas: A Sustainability Analysis of Geothermal Resource for Heating Plant (The Mondragone Case in Southern Appennines, Italy)

by Marina Iorio, Alberto Carotenuto, Alfonso Corniello, Simona Di Fraia, Nicola Massarotti, Alessandro Mauro, Renato Somma and Laura Vanoli

Energies 2020, 13(5), 1237; https://doi.org/10.3390/en13051237 - 06 Mar 2020

Cited by 18 | Viewed by 4165

Abstract

In this study, the sustainability of low-temperature geothermal field exploitation in a carbonate reservoir near Mondragone (CE), Southern Italy, is analyzed. The Mondragone geothermal field has been extensively studied through the research project VIGOR (Valutazione del potenzIale Geotermico delle RegiOni della convergenza). From [...] Read more.

In this study, the sustainability of low-temperature geothermal field exploitation in a carbonate reservoir near Mondragone (CE), Southern Italy, is analyzed. The Mondragone geothermal field has been extensively studied through the research project VIGOR (Valutazione del potenzIale Geotermico delle RegiOni della convergenza). From seismic, geo-electric, hydro-chemical and groundwater data, obtained through the experimental campaigns carried out, physiochemical features of the aquifers and characteristics of the reservoir have been determined. Within this project, a well-doublet open-loop district heating plant has been designed to feed two public schools in Mondragone town. The sustainability of this geothermal application is analyzed in this study. A new exploration well (about 300 m deep) is considered to obtain further stratigraphic and structural information about the reservoir. Using the derived hydrogeological model of the area, a numerical analysis of geothermal exploitation was carried out to assess the thermal perturbation of the reservoir and the sustainability of its exploitation. The effect of extraction and reinjection of fluids on the reservoir was evaluated for 60 years of the plant activity. The results are fundamental to develop a sustainable geothermal heat plant and represent a real case study for the exploitation of similar carbonate reservoir geothermal resources. Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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18 pages, 6318 KiB

Open AccessArticle

Investigating the System Behaviors of a 10 kW Organic Rankine Cycle (ORC) Prototype Using Plunger Pump and Centrifugal Pump

by Xin Wang, Yong-qiang Feng, Tzu-Chen Hung, Zhi-xia He, Chih-Hung Lin and Muhammad Sultan

Energies 2020, 13(5), 1141; https://doi.org/10.3390/en13051141 - 03 Mar 2020

Cited by 7 | Viewed by 4006

Abstract

Based on a 10-kW organic Rankine cycle (ORC) experimental prototype, the system behaviors using a plunger pump and centrifugal pump have been investigated. The heat input is in the range of 45 kW to 82 kW. The temperature utilization rate is defined to [...] Read more.

Based on a 10-kW organic Rankine cycle (ORC) experimental prototype, the system behaviors using a plunger pump and centrifugal pump have been investigated. The heat input is in the range of 45 kW to 82 kW. The temperature utilization rate is defined to appraise heat source utilization. The detailed components’ behaviors with the varying heat input are discussed, while the system generating efficiency is examined. The exergy destruction for the four components is addressed finally. Results indicated that the centrifugal pump owns a relatively higher mass flow rate and pump isentropic efficiency, but more power consumption than the plunger pump. The evaporator pressure drops are in the range of 0.45–0.65 bar, demonstrating that the pressure drop should be considered for the ORC simulation. The electrical power has a small difference using a plunger pump and a centrifugal pump, indicating that the electric power is insensitive on the pump types. The system generating efficiency for the plunger pump is approximately 3.63%, which is 12.51% higher than that of the centrifugal pump. The exergy destruction for the evaporator, expander, and condenser is almost 30%, indicating that enhancing the temperature matching between the system and the heat (cold) source is a way to improve the system performance. Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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21 pages, 6923 KiB

Open AccessArticle

Geothermal Power Production from Abandoned Oil Reservoirs Using In Situ Combustion Technology

by Yuhao Zhu, Kewen Li, Changwei Liu and Mahlalela Bhekumuzi Mgijimi

Energies 2019, 12(23), 4476; https://doi.org/10.3390/en12234476 - 24 Nov 2019

Cited by 16 | Viewed by 4303

Abstract

Development of geothermal resources on abandoned oil reservoirs is considered environmentally friendly. This method could reduce the rate of energy consumption from oil fields. In this study, the feasibility of geothermal energy recovery based on a deep borehole heat exchanger modified from abandoned [...] Read more.

Development of geothermal resources on abandoned oil reservoirs is considered environmentally friendly. This method could reduce the rate of energy consumption from oil fields. In this study, the feasibility of geothermal energy recovery based on a deep borehole heat exchanger modified from abandoned oil reservoirs using in situ combustion technology is investigated. This system could produce a large amount of heat compensated by in situ combustion in oil reservoir without directly contacting the formation fluid and affecting the oil production. A coupling strategy between the heat exchange system and the oil reservoir was developed to help avoid the high computational cost while ensuring computational accuracy. Several computational scenarios were performed, and results were obtained and analyzed. The computational results showed that an optimal water injection velocity of 0.06 m/s provides a highest outlet temperature of (165.8 °C) and the greatest power output of (164.6 kW) for a single well in all the performed scenarios. Based on the findings of this study, a geothermal energy production system associated with in situ combustion is proposed, specifically for economic reasons, because it can rapidly shorten the payback period of the upfront costs. Modeling was also performed, and based on the modeling data, the proposed technology has a very short payback period of about 4.5 years and a final cumulative net cash flow of about $4.94 million. In conclusion, the present study demonstrates that utilizing geothermal resources or thermal energy in oilfields by adopting in situ combustion technology for enhanced oil recovery is of great significance and has great economic benefits. Full article

(This article belongs to the Special Issue Geothermal Energy Utilization and Technologies 2020)

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