Medium Temperature Geothermal Resources Research Articles

A compact production plant model for green hydrogen production from medium temperature geothermal resources: A case study of the Van Lake-Zilan location

Considering the abundance of renewable energy potential in Turkey, green hydrogen derived from renewable sources holds great promise as a fuel. This paper presents a model for obtaining green hydrogen from medium-temperature geothermal sources. In this model, the Zilan location in the Van province of Turkey was identified as a suitable site for electricity and hydrogen production from low or medium-temperature geothermal sources due to its significant geothermal and water resource potential. In this regard, the installed capacity of the Organic Rankine Cycle (ORC) geothermal power plant is determined by using Monte Carlo Simulation based on the characteristics of the geothermal well at this location, and subsequently, the hydrogen production performance has been evaluated by analyzing the water of Lake Van. According to the analysis results, Lake Van was found to be efficient for hydrogen production. Hydrogen production from Lake Van water was subsequently simulated using the electrolysis method with this ORC geothermal power plant. According to the findings of this model, the hourly hydrogen production potential at this location using a 1.4 MW ORC plant, based on 2022 data, was estimated to be 18.6 kg, which is projected to increase to 28 kg based on 2050 estimated data. In addition, the techno-economic analysis of this compact green hydrogen production process was conducted in the study. The production cost of 1 kg of hydrogen was calculated to be €4.91 in 2022, while it is expected to be €1.21 in 2050. These results indicate that ORC technology will become competitive in hydrogen production in the upcoming years.

Advanced monitoring of geothermal Organic Rankine Cycles

Geothermal Organic Rankine Cycle (ORC) power plants have tremendous worldwide potential for the utilization of low- and medium-temperature geothermal resources. However, monitoring of such a system is associated with special challenges for plant operators since the generated electrical power fluctuates strongly, which is caused by mainly two reasons: Firstly, due to the changing condensation conditions caused by air-cooled condensers, and secondly, due to the formation of scaling and fouling. Therefore, the process parameters of a geothermal ORC plant are highly variable, both in terms of diurnal and seasonal fluctuations. Considering the currently applied control software in commercial ORC plants, these fluctuations result in challenges regarding a reliable identification of potential degradation processes within the ORC process.This paper presents a novel analytical and data-based methodology for advanced monitoring of the main components of a two-staged subcritical geothermal ORC system in Southern Germany. These components are the heat exchanger, turbine and air-cooled condenser. For this purpose, operational data from more than three years were preprocessed and evaluated.For the shell-and-tube evaporator, this work applies an equation-based simulation model for the calculation of the thermal resistance due to scaling and fouling. For the turbine and condenser, polynomial functions of various degrees and different objective functions for the numerical computation of regression coefficients are examined. Regression models for three years of operation of the investigated geothermal plant were computed and compared with each other.The results indicate that there are no significant negative changes in the operational performance of most ORC main components during the investigated time period. However, negative operational changes are detected over a three-year period for one turbine of the ORC system. The detailed evaluation of the turbine data reveal a decrease of the normalized isentropic efficiency by 10%, which is significantly higher than the calculated RMSE of the developed correlations, thus indicating a clear performance reduction of the turbine. The developed advanced monitoring methodology allows the operator detailed and accurate assessment of the ORC components conditions, which can not be provided by the software solutions of the commercial ORC manufacturer. Furthermore, the presented methodology can also be applied to other thermal cycle systems with similar components, such as the Kalina Cycle.Finally, a user-friendly software application, developed with the MATLAB® App Designer, is presented. The developed software tool facilitates operators to easily and precisely monitor the operation of the main components of a geothermal ORC plant.

Strata temperatures and geothermal resource evaluation in the Dongpu Depression, Bohai Bay Basin, North China

The development of geothermal resources in the Dongpu Depression can improve not only the economic benefits of the oilfield but also the ecological environment. Therefore, it is necessary to evaluate the geothermal resources in the region. Based on the heat flow, geothermal gradient and thermal properties, the temperatures and their distribution in different strata are calculated using geothermal methods, and the geothermal resource types of the Dongpu Depression are identified. The results show that the geothermal resources include low-temperature, medium-temperature and high-temperature geothermal resources in the Dongpu Depression. The Minghuazhen and Guantao Formations mainly include low-temperature and medium-temperature geothermal resources; the Dongying and Shahejie Formations include low-temperature, medium-temperature and high-temperature geothermal resources; the Ordovician rocks mainly include medium-temperature and high-temperature geothermal resources. The Minghuazhen, Guantao and Dongying Formations can form good geothermal reservoirs and are favorable layers for exploring low-temperature and medium-temperature geothermal resources. The geothermal reservoir of the Shahejie Formation is relatively poor, and the thermal reservoirs may be developed in the western slope zone and the central uplift. The Ordovician carbonate strata can provide thermal reservoirs for geothermal resources, and the Cenozoic bottom temperature is more than 150 °C except for most of the western gentle slope zone. In addition, for the same stratum, the geothermal temperatures in the southern Dongpu Depression are higher than those in the northern depression.

Experimental study on medium and low temperature geothermal ammonia power generation system based on vertical tube falling film

China’s geothermal energy resources are mainly low and medium temperature, the process of ammonia solution generation and absorption is introduced to simplify the condensation heat transfer of Karina cycle, and the vertical tube falling film structure is adopted for the generator and absorber in the system, which makes the system more suitable for medium and low temperature geothermal resources. A 5 kW ammonia water power cycle power generation experimental platform based on vertical tube falling film was built. The experimental results show that under typical working conditions, the maximum heat transfer coefficient of generator and absorber can reach 1034 w/(m2 K) and 563 w/(m2 K), respectively, and the maximum output power of the system is 3 kW.

Geothermal regime and implications for basin resource exploration in the Qaidam Basin, northern Tibetan Plateau

• Geothermal field characteristics of the Qaidam Basin, northeastern Tibetan Plateau, were analysed. • The crustal contribution to the surface heat flow was approximately 55%. • The existence of abnormally high-temperature zones significantly dominated the hydrocarbon distribution. • The Qaidam Basin is favourable for low- and medium-temperature geothermal resources development. • Certain deep high-temperature geothermal resource is prospective if using abandoned oil wells. The Qaidam Basin was formed under the background of the continuous uplift of the Tibetan Plateau, and its tectonic location imparts unique geothermal regime. The geothermal regime of the Qaidam Basin was studied based on oil-test static temperatures from 60 wells, 195 thermal conductivities measured by the optical scanning method, and 142 radiogenic heat production values. The geothermal gradient in the Qaidam Basin is 17.1–47.6 °C/km, with an average of 31.3 °C/km, and the thermal conductivity is 0.523–4.379 W/m‧K. The heat flow is 28.3–83.1 mW/m 2 , with an average of 59.6 mW/m 2 , and it is “high in the west and low in the east.” The heat flow can exceed 70 mW/m 2 in the northern marginal fold-and-thrust belt of western Kunlun and Nanyishan and generally exceeds 65 mW/m 2 in the Mangya Depression. The average radiogenic heat production rate (HPR) is 2.53 μW/m 3 , which is close to the HPR of granite in northern Tibetan Plateau. The crustal and mantle heat flows in the Qaidam Basin are 32.9 mW/m 2 and 26.7 mW/m 2 , respectively. The crustal contribution to the surface heat flow was approximately 55 %. The geothermal regime may be dominated by lithospheric thickness, HPR of sedimentary cover, and extra heat production related to late Cenozoic tectonic movement. The proven hydrocarbon reserves are primarily distributed around hydrocarbon-generating kitchens, and the existence of abnormally high-temperature zones significantly influences hydrocarbon distribution. The Qaidam Basin satisfies the fundamental temperature conditions for the development of low- and medium-temperature geothermal resources using abandoned oil and gas drilling wells.

Research on medium–low temperature geothermal power generation system

In order to make full use of the medium and low temperature geothermal resources and industrial waste heat resources, a power cycle system using ammonia–water mixed solution as the working fluid is proposed. The system can use medium and low temperature geothermal resources with a temperature of 350–450 K, and the basic circulating working fluid is ammonia aqueous solutions. Simulation calculations show that the Carnot cycle efficiency of the circulation system is 14.01%, and the theoretical cycle thermal efficiency of the circulation system is 10.28%. The article further analyzes the influence of steam turbine outlet pressure and heat source temperature on the thermal efficiency of the circulation system. This research provides a reference for the effective utilization of medium and low temperature waste heat resources.

Distributive Characteristics of Hot Dry Rocks in Sedimentary Basins of China: A Study Based on Vitrinite Reflectance of Hydrocarbon Source Rocks

Abstract Geothermal resources as a type of renewable clean energy are highly contributive to sustainable development. In this study, the geothermal resources in some sedimentary basins of China were characterized, and sedimentary basins from different eras and of different types were discussed. On this basis, the major influence factors on the geothermal resources of different regions were elaborated. The geothermal resource potentials in major sedimentary basins of China were evaluated. The geothermal resources in the sedimentary basins of China are extensively distributed and diverse, which are geologically different from East to West China. The target strata of faulted basins in East China, superimposed basins in Central China, and cratonic basins in West China are mainly Cenozoic strata, Mesozoic strata, and Paleozoic strata, respectively. These target strata experienced different types of thermal events in geological historical periods. The Cenozoic faulted basins in East China are mostly heat basins. The Cenozoic sediments are superthick and largely differ in thickness among regions. The effects of Cenozoic geothermal events and the major controlling factors both differed among regions, and the causes of differences included thermal subsidence activities and magmatic activities. These basins are major potential zones for exploitation of hot dry rocks in China. The Mesozoic superimposed basins in Central China are mostly temperate basins, and the ground temperatures nowadays are mainly controlled by thermal subsidence. The potential target zones of hot dry rocks in these basins are the Paleozoic strata in the southwest of basins, which can develop into medium-temperature geothermal resources. In the Paleozoic cratonic basins in West China, the Paleozoic marine sedimentary strata are the major target strata of hot dry rocks. The Paleozoic volcanic events little affected the formation of hot dry rocks, and the formation of major hot dry rocks relied on superthick sedimentary strata, where middle- to low-temperature geothermal resources developed.

A comprehensive data and information on low to medium temperature geothermal resources in Indonesia: a review

A comprehensive data and information on low to medium temperature geothermal resources in Indonesia: a review

Reuse of Decommissioned Hydrocarbon Wells in Italian Oilfields by Means of a Closed-Loop Geothermal System

Geological and geophysical exploration campaigns have ascertained the coexistence of low to medium-temperature geothermal energy resources in the deepest regions of Italian sedimentary basins. As such, energy production based on the exploitation of available geothermal resources associated with disused deep oil and gas wells in Italian oilfields could represent a considerable source of renewable energy. This study used information available on Italian hydrocarbon wells and on-field temperatures to apply a simplified closed-loop coaxial Wellbore Heat Exchanger (WBHE) model to three different hydrocarbon wells located in different Italian oilfields (Villafortuna-Trecate, Val d’Agri field, Gela fields). From this study, the authors have highlighted the differences in the quantity of potentially extracted thermal energy from different analysed wells. Considering the maximum extracted working fluid temperature of 100 °C and imagining a cascading exploitation mode of the heat accumulated, for Villafortuna 1 WBHE was it possible to hypothesise a multi-variant and comprehensive use of the resource. This could be done using existing infrastructure, available technologies, and current knowledge.

Developing low temperature Geothermal projects in Indonesia using pumped well technology

Indonesia’s installed electrical-grade geothermal capacity is currently limited to developments at high temperature geothermal areas; however, survey data from Badan Geologi (Geological Agency of Indonesia) suggests that a large reserve of medium and low temperature geothermal resources also exists in the country. Using electric line shaft or submersible pumps, low to medium temperature geothermal fluids can be pumped from relatively shallow depths and electricity can be generated using binary power plant technology. This has been proven to be a commercially viable development approach for geothermal systems hosted in a range of geologic settings (e.g., structural/sedimentary basins, volcanic flanks, and metamorphic terranes), and are usually situated in regions of geologic structural complexity. The heat sources for these systems can be the conductive/advective heat transfer from a magmatic body or simply related to deep circulation of fluids in a non-magmatic setting. Lateral outflows of higher temperature geothermal systems are another category of low and medium temperature geothermal resources that may be attractive development targets, potentially allowing for the expansion of presently developed systems. This paper considers the utilization of pumped wells to exploit low and medium temperature resources considering recent trends internationally and with specific regard for the Indonesian context of this technology. As discussed herein, the commercial viability of pumped wells depends on the resource characteristics (namely temperature, depth, well productivity, and gas content) as well as a number of economic and development factors. We present results of modelling the potential productivity in terms of MW/well (net) for pumped wells over a range of permeability and temperature conditions and compare the results with typical high temperature self-flow wells.

Economic appraisal and scoping of geothermal energy extraction projects using depleted hydrocarbon wells

This study offers a first step in examining a potential solution for what to do with the ever-increasing number of horizontal shale wells in the United States (and lately, Argentina and China), as they come to the end of their economic life. A comprehensive decision-making tool was developed for scoping assessments based on the technical and economic appraisal of abandoned hydrocarbon wells repurposed into enhanced geothermal systems. We specifically target near end-of-life oil and gas wells, re-commissioned to extract geothermal energy as opposed to hydrocarbons, because these potential geothermal resources are prevalent near a handful of major US population and energy demand centers, including Pittsburgh, Houston, Denver, Dallas, Oklahoma City and San Antonio. This study addresses some of the technical challenges associated with such projects. However, the main focus is on (1) the probabilistic evaluation of the economic net present value, and (2) specific solutions for possible commercial deal structures required for negotiation and project implementation. The backdrop for the test case in this study is the new Texas A&M RELLIS Campus being constructed in College Station, Texas. A successful commercial model for the use of abandoned oil and gas wells to extract low and medium temperature geothermal resources could spur further development and a pilot study is proposed for this green source of energy. Our estimations suggest a net present value of $1.2 billion could be unlocked in the US alone, through the repurposing of wells, previously used for hydrocarbon extraction only.

Deep-seated Geothermal Resources of the Parana Basin

Updated data sets on terrestrial heat flow and thermal springs have been employed in outlining the nature of deep-seated geothermal resources of the Parana basin. A 1o x1o grid system was adopted for data processing and in determinations of vertical distributions of excess temperatures. The results obtained have led to an improved understanding of the occurrence of high temperature geothermal resources and allowed estimates of associated resource base. It has been possible to identify more than 20 crustal blocks where the resource base per unit area, referred to the accessible depth limit of 6 km, are in the range of 2x1011 to 9x1011 Joules. There are indications pointing to occurrence of medium temperature geothermal resources at depths of 4 to 6 km in several sectors of the central and western parts of the basin. The area extent of such blocks has dimensions of several tens of kilometers. Most high temperature resources occur within the well-known sectors of fault-controlled magmatic activity associated with the eruption of Serra Geral flood basalts. In addition, isolated pockets of high enthalpy geothermal resources are found to be present along the northwestern border. The results have also allowed better assessments of low temperature resources of the Guarani aquifer system, which span over large areas of southern Brazil, western Uruguay and northern Argentina.

Exergoeconomic analysis and comparison between ORC and Kalina cycles to exploit low and medium-high temperature heat from two different geothermal sites

The Organic Rankine (ORC) and Kalina (KC) Cycles represent two different technologies suitable to exploit low and medium temperature geothermal heat resources. In this work, the performances of KC, CO2 and ORC cycles, the latter using different working fluids, for power generation from two geothermal fluid reservoirs are compared from an energy and exergoeconomic perspective.Two different case studies are discussed: the first one referred to a medium-temperature heat source of 212 °C (Mt. Amiata, Italy), the second one to a low-temperature heat source of 120 °C (Pomarance geothermal basin, Italy).For each case study, cost rate balances and auxiliary equations for all components were evaluated, as well as the flow rate and unit exergy cost for each stream.The results for the medium temperature case study showed that, among the considered cycles, an ORC with R1233zd(E) achieves the best exergoeconomic performance. The cost of the produced electricity was found to be 8.85 c€/kW h, which is 3% lower than that of the KC. On the other hand, for the low temperature case study, the KC shows the best performance, being able to produce 22–42% more net power than the ORC; in this case, the cost of electricity produced by the KC was found at 12.5 c€/kW h, which is 24–34% lower than the typical value for an ORC with different working fluids.

Research status of geothermal resources in China

As the representative of the new green energy, geothermal resources are characterized by large reserve, wide distribution, cleanness and environmental protection, good stability, high utilization factor and other advantages. According to the characteristics of exploitation and utilization, they can be divided into high-temperature, medium-temperature and low-temperature geothermal resources. The abundant and widely distributed geothermal resources in China have a broad prospect for development. The medium and low temperature geothermal resources are broadly distributed in the continental crustal uplift and subsidence areas inside the plate, represented by the geothermal belt on the southeast coast, while the high temperature geothermal resources concentrate on Southern Tibet-Western Sichuan-Western Yunnan Geothermal Belt and Taiwan Geothermal Belt. Currently, the geothermal resources in China are mainly used for bathing, recuperation, heating and power generation. It is a country that directly makes maximum use of geothermal energy in the world. However, China’s geothermal power generation, including installed generating capacity and power generation capacity, are far behind those of Western European countries and the USA. Studies on exploitation and development of geothermal resources are still weak.

Study of Lithium Bromide-Water Binary Solution in the Application of Hot Springs Geothermal Energy

The main geothermal resources in China are low or medium-temperature geothermal resources, these are more than 3000 hot springs, which of above 60 °C account for 24 percent of total, those are more than 720. In these hot springs bases for tourism and leisure and spa medical, the demand of electricity and air-conditioning is relatively large, so these is a very important practical significance to develop low or medium-temperature geothermal resources technology. If hot springs geothermal system uses lithium bromide-water azeotropic binary mixtures as working fluid, which not only reduces the heat loss of temperature difference, but also plays the advantages in thermodynamics and environmental aspects. Three systems of this article described all use water vapor as the working fluid, their characteristics are analyzed and compared, respectively. By analysis found that: when the demand is only for power generation and non-condensable gas content in hot springs geothermal water is not too high, the single-stage flash evaporation electrical system is more favorable; because of hot springs primarily for leisure travel and medical care function, and the demand for air conditioning and refrigeration is also large, so the combined system is more favorable.

Advances in Assessment of Geothermal Resources of South America

Updated data for 1417 localities have been assembled for purposes of assessments of geothermal resources in South America. Analyses of these data sets have allowed improved estimates of geothermal resource base and recoverable resources for thirteen countries in the continent. The results obtained have also allowed identification of more than 20 crustal blocks where the resource base per unit area (referred to the accessible depth limit of 3 km) is in the range of 100 to 1000 Giga Joules, while the recoverable resources per unit area are in the range of 1 to 100 Giga Joules. Most of the high temperature resources occur within regions of recent tectonic activities in southern and central Chile, highlands regions in Bolivia, and several localities along the magmatic arc covering western Ecuador, central volcanic belt of Colombia and northern Venezuela. In addition, isolated pockets of geothermal resources have been identified along the eastern Andean belt of Peru. There are indications of occurrence of medium and low temperature geothermal resources at depths of 1 to 3 km in several regions in the eastern sectors of the continent, mainly in the northeastern and central parts of Brazil. In addition, considerable progress has been made in assessments of low temperature resources associated with deep fracture systems in Precambrian terrains. Progress has also been achieved in assessment of low temperature resources in deep aquifers of Paleozoic sedimentary basins. The results of such estimates are currently being considered for planning large-scale exploitation of the Guarani aquifer system, which spans over large areas of western Uruguay, northern Argentina and southern Brazil.

Performance analysis of electricity generation by the medium temperature geothermal resources: Velika Ciglena case study

During the last decade, a design of an energy efficient and cost effective geothermal plant represents a significant and on-going technical challenge in all the Western Balkan countries. In the Republic of Croatia, the geothermal field Velika Ciglena is identified as one of the most valuable geothermal heat sources and probably the location where the first geothermal plant in the Western Balkan area will be built. The purpose of this work is the conceptual design and performance analysis of the binary plants–the one which operates under the Organic Rankine Cycle (ORC) and the other under Kalina (KLN) cycle–which can be used for geothermal energy utilization in Velika Ciglena. A conceptual plant design is performed by the equation-oriented modelling approach and supported by the two steady-state spreadsheet simulators. The performance analysis of all design solutions is conducted through energy and exergy analysis, and by the estimated total cost of operating units in the plant. The results of the analysis indicate that the plant design based on the ORC cycle has a higher thermodynamic efficiency and lower cost of equipment, and consequently, it is more suitable for the future geothermal plant in Velika Ciglena.

Power generation from medium temperature geothermal resources: ANN-based optimization of Kalina cycle system-34

Recent technical developments have made it possible to generate electricity from geothermal resources of low and medium enthalpy. One of these technologies is the Kalina Cycle System. In this study, electricity generation from Simav geothermal field was investigated using the Kalina cycle system-34 (KCS-34). However, the design of these technologies requires more proficiency and longer times within complex calculations. An artificial neural network (ANN) is a new tool used to make a decision for the optimum working conditions of the processes within the expertise. In this study, the back-propagation learning algorithm with three different variants, namely Levenberg–Marguardt (LM), Pola–Ribiere Conjugate Gradient (CGP), and Scaled Conjugate Gradient (SCG), were used in the network so that the best approach could be found. The most suitable algorithm found was LM with 7 neurons in a single hidden layer. The obtained weights were used in optimization process by coupling the life-cycle-cost concepts.

Exergoeconomic evaluation of electricity generation by the medium temperature geothermal resources, using a Kalina cycle: Simav case study

Recent technical developments have made it possible to generate electricity from geothermal resources with low and medium enthalpy. One of these technologies is the Kalina Cycle System (KCS-34). In this study, electricity generation from Simav geothermal field is investigated. The optimum operating conditions for the KCS-34 plant design are determined on the basis of the exergetic and life-cycle-cost concepts. With the best design, power generation of 41.2 MW and electricity production of 346.1 GWh/a can be obtained with an energetic efficiency of 14.9% and exergetic efficiency of 36.2%. It is shown that, with the currently prevailing interest and inflation rates, the plant designs considered are economically feasible for values of the present worth factor ( PWF) higher than 6.

04/01395 Multiple integrated applications for low-to medium-temperature geothermal resources in Iceland: Elíasson, E. T. and Björnsson, O. B. Geothermics, 2003, 32, (4–6), 439–450

04/01395 Multiple integrated applications for low-to medium-temperature geothermal resources in Iceland: Elíasson, E. T. and Björnsson, O. B. Geothermics, 2003, 32, (4–6), 439–450