Low-temperature Geothermal Sources Research Articles

Study Outlines Challenges of Repurposing Oil and Gas Wells for Geothermal Applications

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 215751, “Challenges for Repurposing Oil and Gas Wells for Geothermal Applications,” by Livio Santos, SPE, and Arash Dahi Taleghani, SPE, The Pennsylvania State University. The paper has not been peer reviewed. _ This work provides insights into the technical and economic viability of repurposing oil and gas wells for geothermal energy production for direct heating. The potential benefits—especially for areas that are highly dependent on fossil fuels for heating—and challenges of this approach are assessed, while technical, market, and policy barriers for future development are identified. Repurposing oil and gas wells for geothermal energy requires a multidisciplinary approach that involves expertise in geology, engineering, and regulatory affairs. Introduction Repurposing abandoned wells for power generation in geothermal energy projects can present challenges because of the low temperatures associated with these wells. The low temperature gradients and thermal energy available in such wells have been found to limit overall power-generation potential. The same low-temperature geothermal resources can still be used effectively, however, for community heating applications. Community heating systems have lower temperature requirements compared with those necessary for power generation and are compatible with available heat from low-temperature geothermal sources. In particular, closed-loop geothermal systems, specifically designed for community heating, offer several advantageous features. The closed-loop design ensures that the fluid remains contained within the system. These systems are environmentally compatible because they do not extract or discharge water from natural sources. Additionally, with better control over the working fluid and heat-exchange process, closed-loop systems deliver optimized system performance, energy efficiency, and cost savings. They also require less maintenance and feature lower operational risks because of the closed circuit. Closed-loop systems offer fluid-selection flexibility and streamlined regulatory compliance. Not all abandoned wells are suitable for repurposing, however. Thorough feasibility assessments and well-integrity evaluations are necessary to ensure that the abandoned well is structurally sound, has the appropriate depth and geological characteristics, and can extract geothermal heat effectively. The condition of the well casing, cementing, and any potential wellbore damage also must be evaluated. An economic analysis is performed to assess the financial viability and cost-effectiveness of the geothermal community heating system. Finally, an environmental impact assessment evaluates the environmental consequences of the geothermal community heating system.

Proposal a new hybrid system comprising of LNG regasification and geothermal sources: Exergy, exergo-economic, and optimization

In the current research, a novel hybrid cascade power generation system including an organic Rankine cycle (ORC), Kalina cycle (KC), and LNG regasification system assisted by geothermal energy is proposed and investigated. Geothermal fluid energy is used to drive the ORC and KC; at the same time, the waste heat of ORC and KC is utilized to power the LNG cycle. The main new aspect of the current work is the integration of cold energy of re-gasification with low-temperature geothermal source combined with a thermoelectric generator. The introduced system is investigated from the thermodynamic and exergo-economic points of view by considering net power generation, energy efficiency, exergy efficiency, and sustainability index as performance indicators. The study results show that energy and exergy efficiencies of the suggested system are approximately 24.33% and 51.6%, respectively, while sustainability index and total cost rate are 2.066, and 12.68 $/h, accordingly. In addition, different operating parameters (valve 2 outlet pressure, valve 2 inlet temperature and turbines inlet and outlet pressures) are varied to assess the system’s performance comprehensively. The results of multi-criteria optimization for the suggested system represent that the output power can reach 32183.44 kW and SI = 2.062 with the total cost rate of 12.69 $/h.

Case study: Repowering of ORC system by means of experimental test bench with supercritical carbon dioxide, proposal, and field experience improvements

Although organic Rankine cycles (ORCs) have cornered the small-scale energy harvesting market, the generation capacities produced by sCO2 cycles far exceed those of ORCs, reaching higher powers and efficiencies. This paper analyzes the results of the field tests performed in 2022 at the Grupo Dragón, Nayarit, Mexico, facilities, in which the objective was to validate the operation of the ORC IDEA-10 system with a capacity of up to 10 kWe. The thermodynamic states reached during the test time lapses in which there was full operational stability and with direct loads are analyzed. The results obtained together with proposals for improvement led to compare the performance of ORCs with sCO2 systems for low temperature geothermal sources. The efficiencies of simple sCO2 cycles (5.32%) turned out to be lower than that of ORC at the same temperatures (9.7%), however, the efficiency of the sCO2 cycle improved notably in a regenerative configuration, given the properties of CO2 near its critical point, reaching efficiencies above 25% even at low temperatures compared to conventional ORCs with efficiencies below 10%. Finally, the basis for the implementation of sCO2 in low enthalpy geothermal applications was established, designing an experimental circuit with results obtained in the literature.

Geothermal energy integrated multi-effect evaporator (MEE) and multi-effect distillation (MED)-based desalination systems: an ecofriendly and sustainable solutions.

Desalination is a tried-and-true method for obtaining clean water from the ocean's brackish waters and recycling and reusing water. It requires a fair amount of energy, so it is necessary to create sustainable energy systems to lessen energy use and environmental impact. For thermal desalination procedures, thermal sources can be great heat sources. This paper's research focuses on thermoeconomically optimized multi-effect distillation and geothermal desalination systems. Collecting hot water from subsurface reservoirs is a well-established method of generating electricity through geothermal sources. Low-temperature geothermal sources, which have a temperature of less than 130°C, can be utilized for thermal desalination systems, for example, multi-effect distillation (MED). Geothermal desalination is affordable, and it is possible to produce power simultaneously. Because it only uses clean, renewable energy and produces no greenhouse gasses or other pollutants, it is also safe for the environment. The viability of any geothermal desalination plant will be influenced by the location of the geothermal resource, feed water supply, cooling water source, water market, and concentrate disposal site. Geothermal energy can directly supply heat for a thermal desalination system or indirectly give electrical power to reverse the osmosis (RO) membrane-based desalination plant.

ОПЫТ ИСПОЛЬЗОВАНИЯ ГЕОТЕРМАЛЬНОЙ ЭНЕРГИИ ПРИПОВЕРХНОСТНОГО МАССИВА ДРЕВНИХ ГРАНИТОИДОВ ДЛЯ ЦЕЛЕЙ ТЕПЛОСНАБЖЕНИЯ (ЮГ ЗАПАДНОЙ СИБИРИ)

An example of transition of the heating- and hot-water supply system to a low-temperature geothermal energy source from the Paleozoic granitoid massif is given for a secondary school building in Novosibirsk. The necessity for change the source of heat supply arose in 2018 due to wear and tear of the coal boiler house old equipment, which has provided the school with heat since it was built in 1964. At the time of the geothermal project implementation, there were already several cases of successful use of underground heat-producing probes arranged in specially drilled geothermal wells for heating public facilities in neighboring Siberian cities (Tomsk, Barnaul). However, loose sedimentary rocks there served for the source of heat energy, that greatly simplified and accelerated the tasks implementation. The described experience of heating – and hot-water supply of building due to the low energy from a shallow lying massif of ancient rocky grounds with intrusive genesis is unique for Russia and can serve as a platform for the implementation of geothermal projects in regions with complicated ground conditions and moderately cold climate.

A Comparative Study of Cooling Sources in Organic Rankine Cycle for Low-Temperature Geothermal Heat Sources

Geothermal energy refers to ground heat sources exploited for many purposes (for example, generating electricity). A steam power plant, that uses water as a medium and operating on the Rankine cycle, is a prospective technology that can be used to generate electricity utilizing geothermal heat. However, due to the thermal properties of the applied working fluid, the steam power plant has the limitation that may not utilize cold source like liquefied dimethyl ether (DME) at the temperature of around -25 °C or the extreme one, like liquefied natural gas (LNG) at the temperature of around -160 °C. For this reason, it seems that RC using an organic working fluid (so-called ORC) is an appropriate technology to utilize heat sources of extremely low temperatures. Selected ORC working fluids are considered suitable to absorb the cold source. This paper reported the thermodynamic modelling analysis and a comparison of geothermal power systems exploiting air, water, LNG, and DME as the cooling medium of the ORC. The simple scheme of ORC is used for modelling, furthermore, the Trilateral Flash Cycle (TFC) is described as a comparative study. Thanks to the LNG technology, it is already mature enough, and the method of altering the phase into liquefied form is likely to store the energy (i.e., the power to liquid). In the liquefied form, natural gas can be easily distributed and transported at a certain distance. In this model system, the result shows that LNG and DME appear to be excellent options for increasing the operating range of ORC. The modelling result shows that combining propane (a working fluid inside the cycle) and LNG (a cooling source) has a wider operating range and is a good option to exploit low-temperature geothermal heat as a power generation system. Also, using DME for both cooling sources and the working fluid inside the geothermal power system employing ORC outperforms other ones. Taking advantage of using them as a cooling source is significantly boosting the potential deriving from low-temperature geothermal energy (i.e., below 90 °C) as promising sources in the future.

Thermoeconomic analysis and multi-objective optimization of a novel trigeneration system consisting of kalina and humidification- dehumidification desalination cycles

Low-temperature geothermal heat sources have the highest share of geothermal energy in the world. Utilization of these heat sources for energy and freshwater generation can play an important role in meeting energy and freshwater demands. To do so, this study aims to propose a novel trigeneration cycle powered by low-temperature geothermal sources. The proposed system, which is an integration of Kalina and humidification-dehumidification (HDH) cycles, is used for the generation of electricity, heating, and freshwater. For the Kalina cycle, an evaporative condenser is used. It also acts as a humidifier and heater of the humidification-dehumidification desalination cycle, resulting in a reduction in the complexity of the trigeneration system. A comprehensive thermoeconomic analysis and multi-objective optimization of the new trigeneration system are performed. First, a detailed parametric study is carried out to investigate the effects of key design parameters, including turbine inlet pressure, condenser temperature, basic solution ammonia concentration, air mass flow rate and heat source temperature, on the thermoeconomic criteria. Then, a multi-objective optimization is conducted to determine the best design parameters, considering exergy and total cost rate as the objective functions. The optimal solution Pareto frontier indicates that the exergy efficiency and total cost rate vary in the range of 14.9–41.6% and 1.13–2.19 $/h, respectively. Analyses of the scattered distributions of design parameters reveal that lower heat source temperatures tend to optimize the objective functions. However, altering other design parameters has a significant effect on the trade-off between exergy efficiency and total cost rate.

Techno‐economic analysis of a hybrid solar‐geothermal power plant integrated with a desalination system

This paper proposes the use of a hybrid 5 MW power generation system combining concentrated solar thermal and solar photovoltaic technology where the efficiency of the power block is increased by taking advantage of hot water from a low-temperature geothermal source. Aiming at a case study for Winton in Queensland the pertinent meteorological data are used for our simulations. In addition, the paper analyzes the feasibility of including a thermal desalination technology that uses the waste heat from the power block for producing clean water from wastewater. Our design replaces the traditional dry cooling system with a water-cooled heat exchanger to remove the waste heat from the power block. Finally, this work explores the ratio of concentrated solar thermal and photovoltaic electricity production that optimizes the levelized cost of electricity and water production. the results indicate that the incorporation of the desalination system does not produce a significant increase in this value, and the optimal ratio of electricity production is obtained when the photovoltaic system contributes to 27.5% of the total electricity generation. Our water production cost can be as low as 40 ₵/m3 while for the combined system our minimum levelized cost of electricity figures out at 12.4 ₵/kWh to generate the base load with thermal storage.

Geothermal Energy Use in Western Siberia and Prospects for Its Innovative Application in Construction

The article gives an overview of the use of low-temperature geothermal energy sources for heat and cold supply of buildings in areas of Western Siberia. The experience of using geothermal heat pumps shows their economic efficiency and environmental friendliness. An innovative application of the low-temperature energy of the shallow subsurface soil layers is the double use of the underground foundation of a building or another structure as energy active elements of the heat-pumping system. The paper analyzes the problems why green technologies are not developing as dynamically as indicated in the Energy Program of Russia and barriers that prevent the wider use of heat pumps and systems in the heat and cold supply of buildings in the Siberian region. These include considerable regulatory and investment barriers, as well as lack of awareness about renewable energy and energy efficiency. Further, market entry remains challenging in Russia that has not fully liberalised its energy market. Furthermore, entrenched interests in conventional energy resources represent a significant barrier to effective legislation and policy implementation. Thus, huge conventional resources of oil, gas and coal in Siberia region, neighboring to Novosibirsk, Omsk and Altay districts are other obstacles to the introduction of renewable green technologies. Some examples on the limitation of barriers to geothermal heat pumps systems application in building construction are given.

Off-design performance comparison of single-stage axial turbines using CO2 and zeotropic mixture for low-temperature heat source

Organic Rankine cycle (ORC) and transcritical CO2 power cycle are two effective methods for low-grade energy utilization. Turbo-expanders of these power cycles need to maintain a high efficiency under both design and off-design conditions. In this study, the performances of two single-stage axial turbines are compared using a zeotropic mixture and CO2 as working fluids for a low-temperature geothermal source. First, a preliminary design model is established based on the mean line method. Subsequently, the input conditions for each turbine are determined and the performances of the two turbines are analyzed under the design condition. Then, the operation characteristics of the two turbines are investigated under various off-design conditions and the extent of the turbine efficiency reduction is evaluated. In addition, the effects of composition variation for the ORC turbine and the inlet temperature of the CO2 turbine are estimated respectively. The results indicate that the efficiency of the CO2 turbine is 0.875 at the design point, which is slightly higher than that of the ORC turbine as 0.864. The geometric size of the CO2 turbine is smaller than the ORC turbine apparently. The CO2 turbine has a higher efficiency over the entire operation range compared with the ORC turbine. Under the off-design conditions, the variation magnitude of the efficiency for the CO2 turbine is apparently less than that of the ORC turbine due to a lower pressure ratio and a larger flow rate.

3-E analysis and optimization of an organic rankine flash cycle integrated with a PEM fuel cell and geothermal energy

The current research deals with thermodynamic and economic analyses and optimization of a geothermal system integrated with organic Rankine flash cycle (ORFC) and a polymer electrolyte membrane fuel cell (PEM-FC). A thermodynamic model for ORFC and PEM-FC is developed to investigate employing the PEM-FC in a combined geothermal ORFC. A comparative study is carried out to determine the effect of applying PEM-FC in a geothermal based ORFC. The validation of PEM-FC simulation with experimental data from the literature shows a good agreement. The results of numerical modeling indicate that using the rejected heat in the PEM-FC instead of the low-temperature geothermal source can increase the net output power from 254.9 kW to 1628.9 kW and the exergy efficiency from 23.77% to 36.19%, in the case of R123 as working fluid for the ORC system. Furthermore, using the PEM-FC imposes 9.07 US$/h cost rate to the system. Additionally the parametric study shows that the net output power and the total cost rate of the system are two major objective functions for the optimization. Thus, a multi-objective genetic algorithm is applied to determine the optimal values of design parameters with respect to some practical constraints. The results of the multi-criteria optimization represent that the optimum value of decision variables with considered objective functions are T1=116°C , rflash=0.55 , PFC=230kPa , and P4=1208.4kPa.

Exergoeconomic comparison and optimization of organic Rankine cycle, trilateral Rankine cycle and transcritical carbon dioxide cycle for heat recovery of low-temperature geothermal water

Depleting fossil fuel resources and the horrible environmental impacts due to burning fossil fuels emphasize the importance of using renewable energy resources such as geothermal and solar energies. This paper compares performance of CO2 transcritical cycle, organic Rankine cycle, and trilateral Rankine cycle using a low-temperature geothermal heat source. Thermodynamic analysis, exergetic analysis, economic analysis, and exergoeconomic analysis are applied for each of the aforementioned cycles. In addition, a sensitivity analysis is performed on the system, and the effects of geothermal heat source temperature, evaporator pinch point temperature, and turbine inlet pressure on the cycle's performance are evaluated. Finally, the systems are optimized in order to minimize product cost ratio and maximize exergetic efficiency by using the genetic algorithm. Results indicate that the maximum thermal efficiency is approximately 13.03% which belongs to organic Rankine cycle with R123 as working fluid. CO2 cycle has the maximum exergetic efficiency, equals to 46.13%. The minimum product cost ratio refers to the organic Rankine cycle with R245fa as working fluid. Moreover, sensitivity analysis shows that increasing geothermal heat source temperature results in higher output power, product cost ratio, and exergy destruction ratio in all cycles.

Thermodynamic analysis of a combined cycle for cold storage and power generation using geothermal heat source

In the present study, an ammonia-water based combined refrigeration/power cycle, proposed previously, is assessed for the utilization of geothermal potential for variable refrigeration and power load. The work mainly focuses on the thermodynamic feasibility of usage of geothermal source for apple storage and power output at Manikaran, a small town in the Indian state of Himachal Pradesh in Himalayan region. Optimization of second law efficiency was done using a combined genetic and gradient based algorithm, for varying ambient conditions and refrigeration load requirements, considering the potential of geothermal heat source available in the area. The system demonstrates the advantage of variable refrigeration and power output ratio that makes the full utilization of a low temperature geothermal heat source all through the year.

A novel multigeneration system driven by a hybrid biogas-geothermal heat source, Part II: Multi-criteria optimization

Hybridization of biogas and geothermal energies for power plants can present a promising way to resolve drawbacks of each individual heat source from economic viewpoint, especially when low-temperature geothermal heat source is posited. Concerning this aspect of hybrid renewable heat sources, a novel hybrid biogas-geothermal multigeneration system was proposed in the first part of our study, which was modeled under privilege of thermodynamic laws. In continuation of our previous study, the current study is performed to investigate economic, environmental, and enviroeconomical aspects of the introduced system. Furthermore, single and multi-criteria optimizations of this integrated system are carried out from 4E (energy, exergy, exergoeconomic, and environmental) analysis standpoints. After the optimization, the thermal and exergy efficiencies are raised by 12.07% and 5.16%, respectively, while the overall cost of the product is decreased by 3.7%. Also, the emission rate of the suggested multigeneration system is decreased from 0.1913 kg/kJ to 0.1828 kg/kJ, showing 4.44% reduction in the greenhouse gas emission in comparison with the base mode. From enviroeconomic viewpoint, the environment penalty cost rate is reduced from 147.4 $/h to 144.4 $/h after the optimization. Finally, a comprehensive sensitivity study based on the key economic parameters is performed and results are discussed.

Thermal Comparison of an Organic Rankine Cycle Activated by a Low-Temperature Geothermal Heat Source

Thermal Comparison of an Organic Rankine Cycle Activated by a Low-Temperature Geothermal Heat Source

Parametric study on the effects of a recuperator on the design and off-design performances for a CO2 transcritical power cycle for low temperature geothermal plants

A CO2 transcritical power cycle (CDTPC) is a promising power system to utilize low temperature geothermal heat source. Many researchers mainly focus on the thermodynamic and thermo-economic performance analysis or optimization for a CDTPC, or compare the design performance of a CDTPC with that of organic Rankine cycle. The objective of this paper is to study the effects of a recuperator on the design and off-design performances of a CDTPC for low temperature geothermal plants. Detailed off-design mathematical models of the basic and regenerative CDTPCs are built to complete this study under the variable mass flow rates and temperatures of the geothermal water and the cooling water temperatures conditions by a sliding pressure operation control strategy. The results reveal that no matter how the geothermal water mass flow rate and temperature or the cooling water temperature vary, both the overall net power and overall thermal efficiency of the regenerative CDTPC system are higher than those of the basic CDTPC system. Meanwhile, a recuperator can improve the overall system performance of a CDTPC system under the both design and off-design conditions, although the recuperator might weaken the off-design behavior of some key components. In addition, a recuperator can improve off-design behaviors of the CO2 pump performance under the off-design conditions. The guidelines for the rotational speed listed in the tables for CO2 pumps might provide some reference for practical operation.

Optimal combined heat-and-power plant for a low-temperature geothermal source

This work compares the performance of four combined heat-and-power (CHP) configurations for application in a binary geothermal plant connected to a low-temperature 65/40 and a high-temperature 90/60 district heating system. The investigated configurations are the series, the parallel, the preheat-parallel and the HB4 configurations. The geothermal source conditions have been defined based on existing geothermal plants in the northwest of Europe. Production temperatures in the range of 110–150 °C and mass flow rates in the range of 100–200 kg/s are considered. The goal is to identify the best-performing CHP configuration for every set of geothermal source conditions (temperature and flow rate) and for multiple values of the heat demand. The electrical power output is used as the optimization objective and the different CHP plants are compared based on the exergetic plant efficiency. The optimal CHP plant has always a higher exergetic plant efficiency than the pure electrical power plant; up to 22.8%-pts higher for the connection to a 65/40 DH system and up to 20.9%-pts higher for the connection to a 90/60 DH system. The highest increase of the exergetic plant efficiency over the pure electrical power plant is obtained for low values of the geothermal source temperature and flow rate.

Performance optimization of low-temperature geothermal organic Rankine cycles using axial turbine isentropic efficiency correlation

Present study deals with parametric optimization and performance evaluation of an air-cooled organic Rankine system for the low-temperature geothermal source, especially considering the effects of turbine isentropic efficiency. Turbine isentropic efficiency is predicted with turbine size parameter and volume ratio, using the well-known correlation for single-stage axial turbine. Optimal performances with the objective of maximizing system exergy efficiency are compared with the common used working fluid R245fa and two environmental friendly working fluids R1234ze(E) and R1234ze(Z). Highest turbine isentropic efficiency is achieved for working fluid R1234ze(Z). The optimal turbine inlet vapor is overheating for Working fluid R1234ze(E) with the limitation of allowable minimum geothermal brine reinjection temperature. Due to the influence of turbine isentropic efficiency, optimal system exergy efficiency for working fluid R1234ze(E) is 0.4576 for the 100 kg/s geothermal source, which is slightly higher than the value of 0.4487 for the 10 kg/s geothermal source.

Thermodynamic analysis of Kalina cycle configurations for utilisation of geothermal energy

Numerical study of Kalina cycle based power generating systems has been presented to utilise low temperature geothermal heat source. Computer codes have been developed in MATLAB to evaluate the thermal properties of working fluid. The performance of systems has been analysed considering the operating parameters that suit Indian climatic conditions. Parametric analyses of the Kalina cycle configurations have been presented showing the effect of key parameters on system performance. The efficiency of low temperature Kalina cycle system is noted to be 12.95% operating at 145oC. The cycle efficiency has improved by 2% with the incorporation of an auxiliary superheater in the system. The incorporation of an auxiliary separator increases NH3 concentration in the vapour mixture and enables operation of the system at reduced pressure. Further, a combined system has been designed that produces electricity and cooling effect simultaneously. The combined cycle shows gain in thermal efficiency by 6%.

A supercritical power cycle using carbon dioxide for low temperature geothermal sources

A supercritical power cycle using carbon dioxide for low temperature geothermal sources