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Multi-criteria optimization of a novel process combined with a two-stage geothermal flash cycle using water electrolysis and modified bi-evaporator refrigeration units
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Flash-based geothermal cycles correspond to environmentally friendly and cost-effective processes in a renewable framework and provide an opportunity for combined cycles. However, these cycles are characterized by significant energy losses and their waste stream’s low/medium operational temperature is the principal defect for managing multiple generation arrangements without assisting other energy resources. Hence, the main aim of this study is to propose a novel polygeneration scheme, integrated with a dual-flash geothermal cycle equipped with self-superheaters, able to mitigate the discussed defect. A new coupled series and parallel design of energy recovery is established, allowing to increase the compatibility of combined cycles and enable a larger production. This design encompasses a single-effect refrigeration cycle, a modified transcritical CO2 cycle, a polymer electrolyte membrane electrolyzer, and a thermal desalination cycle. The proposed process is examined from thermodynamic, sustainability, and economic (exergoeconomic and net present value analyses) points of view. Besides, a detailed sensitivity study is conducted by which the trend of performance variables in response to the increasing five main decision parameters is viewed. Afterward, an intelligent approach relying on an artificial neural network is built to learn and validate the behavior of defined objective functions (exergetic efficiency and products’ levelized cost). Moreover, a multi-objective grey wolf optimization (MOGWO) procedure endeavors to optimize the operation of the system. According to the results of this study, flash tank 2’s inlet pressure is the effective parameter, and its mean sensitivity index equals 0.289. Besides, the aforementioned objectives are gauged at 37.45% and 0.0625 $/kWh, respectively.
The main focus of this paper is to present thermodynamic and economic analyses and multi-objective optimization of a novel geothermal-solar multigeneration system. The system aims to produce hydrogen, freshwater, electricity, cooling load, and hot water and designed based on geothermal and solar energy. After modeling and thermodynamic and economic analysis, exergy destruction rate, exergy efficiency and, cost rate were calculated for each component of the system. The results showed that the highest amount of exergy destruction was related to parabolic trough collectors (PTCs) and absorption chillers. To select the geothermal fluid of the organic Rankine cycle (ORC), several different fluids were investigated, among which isobutene was selected. By using the Group method of data handling (GMDH) neural network, a mathematical relationship was obtained between the inputs and outputs of the problem and were given as inputs to the non-dominated sorting genetic algorithm II (NSGAII)alg. The final optimal point was obtained applying the technique for order of preference by similarity to ideal solution (TOPSIS) decision criterion at which the exergy efficiency and cost rate were calculated to be 21.63% and 63.89 $/h, respectively. The meteorological data of the Zanjan, Isfahan, and Bandar Abbas cities were used to calculate the performance accurately at the TOPSIS selection point. To provide a comparison between different cities, the performance of the system was evaluated on September 17 as a sample day. On this day, the proposed system produces 26.38 kg of hydrogen and 373.8 m³ of freshwater in Isfahan.
This paper presents an overview on NSGA-II optimization techniques of machining process parameters. There are many multi objective optimization (MoGA) techniques involved in machining process parameters optimization including multi-objective genetic algorithm (MOGA), strength Pareto evolutionary algorithm (SPEA), micro genetic algorithm (Micro-GA), Pareto-archived evolution strategy (PAES), etc. This paper reviews the application of non dominated sorting genetic algorithm II (NSGA-II), classified as one of MoGA techniques, for optimizing process parameters in various machining operations. NSGA-II is a well known, fast sorting and elite multi objective genetic algorithm. Process parameters such as cutting speed, feed rate, rotational speed etc. are the considerable conditions in order to optimize the machining operations in minimizing or maximizing the machining performances. Unlike the single objective optimization technique, NSGA-II simultaneously optimizes each objective without being dominated by any other solution. peer-review under responsibility of [name organizer]
This paper intends to develop geopolymer-based composites for geothermal energy applications. Both silicon carbide (SiC) sand and SiC powder were applied to optimize the thermal and mechanical behaviours of geopolymer. The flexural and compressive strength of geopolymer composites with different mix designs were investigated. A novel test set-up to record the thermal conductivity were designed, and the thermal behaviours of geopolymer composites with different mix design were tested. It was found that the proper addition of SiC powder is conducive to the compressive and flexural strength of geopolymer composites, while the influence of SiC particles is insignificant. The relationship between flexural and compressive strength of geopolymer composites was also investigated, and it was found that the Portland cement association (PCA) code reached the best fitting precision. With the addition of SiC materials, the maximum thermal conductibility of geopolymeric composite can be as high as 5.35 Wm−1K−1, which is about five times higher than conventional cementitious composite. The combined application of SiC powder and SiC particle is practical to increase the thermal conductivity of geopolymer, making it a suitable material for geothermal energy applications. Based on the numerical model, it was concluded that the addition of silicon carbide is beneficial to the heat exchange rate of the energy pile and improves the heat utilization efficiency of the energy pile.
The present paper dealt with the performance analyses and improvement probabilities detection for the present geothermal power plant. In addition, the present study aimed to present an analysis methodology for manufacturers and users to detect deficiencies, inadequacies and probable improvements for a present system. In this study, a geothermal power plant was used as a sample system for the analyses. Analyses were applied to the plant regarding energy, exergy, economic and environmental aspects. After comprehensive analyses, it was observed that the power consumption of the fans shows dramatic change depending on the seasons. For this reason, if the location and site conditions of the facility are suitable, performing the cooling processes with water-cooled condensers instead of air-cooled condensers was suggested. Moreover, by keeping the acceptance of saturated steam inlet at the turbine, it is thought that an increase in system performance will be achieved by designing a pump system that can increase organic fluid pressures up to partially higher pressures. In addition to all these, it was recommended to analyse the effect of integrating a superheater to bring the organic fluid to the superheated vapour phase at the turbine inlet.
Gasification is one of the most promising approaches to accomplishing efficient utilization of biomass, nevertheless, it shows severe problems of low efficiency and syngas quality, which deserves further improvements. In this regard, deoxygenation-sorption-enhanced biomass gasification is proposed and experimentally explored using deoxidizer-decarbonizer materials (xCaO-Fe) for intensified hydrogen production. The materials follow the deoxygenated looping of Fe0-3e-↔Fe3+ as an electron donor and the decarbonized looping of CaO + CO2 ↔ CaCO3 as a CO2 sorbent. Specifically, the H2 yield and CO2 concentration reach 7.9 mmol·g-1 biomass and 10.5 vol%, which increases by 311% and decreases by 75%, respectively, compared with conventional gasification, confirming the promotion effect of deoxygenation-sorption enhancement. Fe embedded within the CaO phase is successfully constructed with the formation of functionalized interface structure, affirming the strong interaction between CaO and Fe. This study brings in a new concept for biomass utilization via synergistic deoxygenation and decarbonization, which will substantially boost high-quality renewable hydrogen production.
In order to increase the energy density and generate more products in a sustainable framework, the current study proposes a geothermal-driven power plant combined with an electrolyzer, boosted by an oxyfuel combustion power plant for a novel multigeneration task. The system produces power, heating, methanol, and carbon dioxide (CO2) in a coherent manner, benefiting from low-emission framework and high thermodynamic performance. This system has not been evaluated before. The proposed system consists of a combined flash and binary geothermal plant, a hydrogen production unit, an oxyfuel power unit, a heat and power generation unit, a transcritical CO2 Brayton cycle, a steam Rankine cycle, and a methanol generation unit. Hence, the proposed system is analyzed from the energy, exergy, environmental, and economic points of view. In addition, a parametric analysis is performed to assess the effects of some basic thermodynamic parameters on the cycle performance. The parametric study reveals that the increase in the working fluid temperature leads to an increase in the net power and energy and exergy efficiencies, and low pressure of the gas turbine is an important factor for enhancing the total thermodynamic efficiency of the system. Also, the system's energy and exergy efficiencies together with the total unit cost of products are found to be 47.2%, 40.34%, and 5.53 [Formula presented], respectively. Moreover, the CO2 footprint corresponding to the electricity and methanol outputs are obtained at 0.0023 [Formula presented] and 0.056 [Formula presented], respectively.
Due to the operational conditions of flash-binary geothermal cycles, it is difficult to design a multiple heat recovery technique for its waste heat. To address this deficiency and reuse its waste heat in different stages, this study proposes a novel poly-generation model considering parallel and series waste heat recovery. The prime target is to maintain the temperature and enthalpy level of the waste heat from each stage to another and provide a unified framework, leading to producing the main required products. The model comprises a transcritical carbon dioxide Rankine cycle, a desalination subsystem, a single-effect absorption refrigerator, and a low-temperature electrolyzer. To this end, a multi-aspect feasibility study is conducted from energy, exergy, and economic viewpoints, and a multi-criteria optimization is applied in four different scenarios using an artificial neural network in tandem with a multi-objective grey wolf optimization. The most suitable state of operation of each optimized scenario and the efficient scenario is defined through the TOPSIS approach. It was found that the most influential parameter affecting the performance metric was the geothermal water inlet temperature. Besides, the second scenario, i.e., exergy efficiency/total investment cost rate, resulted in the best state of operation. Finally, the optimum objective functions were gauged at 29.59% and 72.72 $/h, respectively. In this situation, the optimum net output power, cooling load, freshwater production rate, and hydrogen production rate were equal to 1666.0 kW, 1029.0 kW, 146.4 m3/day, and 1967.0 m3/day, respectively. Besides, the sustainability index and levelized cost of products were obtained to be 2.11 and 0.0602 $/kWh.
The current paper deals with the development and analysis of an innovative multigeneration plant, which is powered by geothermal energy, and integrated with the transcritical Rankine cycle (tCO2−RC), proton exchange membrane (PEM) electrolyzer, multi-effect desalination unit (MED), and ejector cooling system (ECS). The main objective of this research paper is to produce power, hydrogen, freshwater, and cooling in an environmentally benign way, by integrating the different subsystems. A comprehensive parametric analysis that is thermodynamic and economic and exergo-environmental impact assessment are addressed. For these parametric analyses, the variation of some important parameters that affect the system performance is examined and illustrated. According to the modeling findings, the net power and hydrogen production capacity of the modeled combined power plant is 982.4 kW and 0.0024 kgs⁻¹, respectively. The cycle's overall energy efficiency is computed to be 40.04%, although its exergetic efficiency is 36.31%. When the irreversibility among the plant components is compared, the highest irreversibility occurred in the PEM water heater with 1508 kW, followed by heat exchangers 1 and 2. Given the economic results, the modeled plant's cost rate is calculated to be 200.2 $/hr. In the end, it can be recommended that this modeled plant is suitable that is from the point of perspective of the performance, economy, and exergo-environmental relations.
To meet demands in agricultural sectors, the way of waste-to-useful products is an alternative to conventional processes capable of generating on-site products. This is an innovative method leading to designing a novel combined system in the current work. By means of a precise chemical and electrochemical simulation, the rice husk (an agricultural biomass fuel) is processed through a gasifier with a steam agent and is utilized in a molten carbonate fuel cell. The fuel cell's waste heat is delivered to thermal-based desalination utilizing humification and dehumidification processes. In addition, a solid oxide electrolyzer cell creates hydrogen by consuming power supplied by the fuel cell. Consequently, the system is able to meet some demands like electricity, irrigation, and chemical fertilizers. Accordingly, the system's applicability is measured by comprehensive electrochemical, technical, and environmental sensitivity analyses along with an advanced triple-objective optimization using the method of artificial neural network (ANN) + multi-objective grey wolf optimization. Regarding the objective functions, i.e., exergetic efficiency (ExEtot), exergoenvironmental impact index (EIItot), and carbon dioxide emission (CDEtot), the optimum state brings ExEtot=29.98%, EIItot=2.28, and CDEtot=391.1kg/MWh. Also, the variability of studied variables is further affected by the fuel cell's current density; its mean sensitivity index equals 0.48.
Wind turbines (WT) are prone to transient instability during weak grid faults, which is caused by their complex interactions. However, it is a challenge to analyze the transient stability, due to high-order and strong nonlinearity. Moreover, the existing works mainly focus on a phase-locked loop (PLL) system while ignoring current control, which cannot fully reflect the transient in stability mechanism. To fill this gap, this paper studies the transient stability of type-3 WT considering both PLL and current control. Firstly, to simplify the full model of type-3 WT, a slow-fast subsystem is established using the singular perturbation. Then, the sixth-order full model is simplified as a second-order slow subsystem and its small disturbance (i.e., fast subsystem). Based on it, the Lyapunov’s direct and indirect methods are adopted to analyze the stability of slow and fast subsystems, respectively. Meanwhile, the influence of various factors (e.g., the fault degree, grid inductance, current references, current controller and PLL controller) on transient stability of type-3 WT are revealed. In addition, the proposed analytical method combining singular perturbation and Lyapunov methods is a new approach to study transient stability, which can also be applied to other renewable energy resources. Finally, the analysis is validated by experiments.
Under the severe accident of the nuclear reactor, the strong coupling phenomenon exists between the transport and condensation of the steam-air-hydrogen multi-component gas in the containment atmosphere. Under this coupling effect, the flow patterns of mixture gas induced by condensation are critical to hydrogen accumulation risk assessment. The general flow characteristics of typical flow patterns were qualitatively predicted and confirmed in our previous work. However, the transient mass transfer process of multicomponent gases is complex, and flow pattern transitions are difficult to be captured. To further clarify these contents, experiments and corresponding numerical simulations are combined in the present work. The formation mechanism of the typical flow patterns is further revealed. The flow pattern transition boundaries of the mixture are quantified based on more data in confirmatory experiments. Experiments are performed under wider wall sub-cooling (ΔT = 60–110 °C) and wider range of steam concentration (Xsteam) from 16% to 90%, the volume concentration of helium in non-condensable gases (XHe/XNon) ranges from 10% to 70%. Results show that the homogeneous downward flow is generally formed when XHe/XNon < 40%. Under medium helium concentration (XHe/XNon: 42%–55%), when Xsteam > 30%, the flow pattern of the mixture gas is the separation flow. Under high helium concentration (XHe/XNon > 55%), the flow pattern of the mixture gas is the homogeneous upward flow when Xsteam > 20%. Furthermore, the empirical component correlations to classify the three flow patterns are proposed for the first time. Correlations and numerical simulation have good consistency in the prediction of flow patterns under most component conditions.
In the coming years, green energy generation and effective use of the energy source methods that are renewable energy-based multigeneration systems are becoming more significant because of environmental concerns. This study proposes a new flash-binary geothermal power plant that is united with a steam cycle, a Rankine cycle (RC) with carbon dioxide (CO2), a desalination unit, and a Proton Exchange Membrane (PEM) electrolyzer, to generate beneficial outputs, which are power, hydrogen, hot and clean water. To examine and investigate the energy efficiency, exergy efficiency, cost ratio, and emission rate of the whole plant and subsystems, thermodynamic, economic, and environmental impact analyzes are applied comprehensively. With this line perspective, the exergy destruction rate of the modeled system's parts is determined. In addition, CO2 emission rates are investigated for diverse energy generation scenarios. Next, parametric research is executed to research the impacts of changes in some important factors on plant efficiency and cost. The findings of the analysis demonstrate that the amount of the total power rate of the combined plant is found to be 1639 kW, while the hydrogen generation rate is computed as 0.002081 kgs⁻¹. As well, the energetic and exergetic efficiency of the whole plant is figured as 52.01% and 29.45%, respectively. The total cost of the entire plant is found to be 139.6 $/h. In conclusion, the energetic performance of the multigeneration plant is found to be significantly greater than that of the single-generation plant.
Renewable energy sources have great importance to deal with environmental detriments. To clean and sustainable future, various design renewable energy-assisted plants are of great importance. The current study examines the design and investigation of a double-flash binary geothermal energy-powered integrated system for useful products. For the purpose of producing hydrogen, power, heating, and drying, the proposed work basically consists of two steam turbines, a transcritical carbon dioxide Rankine cycle (tCO2-RC), a PEM electrolyzer, a domestic water heater (DHW), and a dryer. The chief target of this research study is to develop a more efficient plant as well as multigeneration productions. Additionally, detailed parametric modeling is carried out using energetically and exergetically approaches to examine this designed plant in the context of thermodynamic analysis. The variation of some parameters that influence the plant's performance, such as geothermal water temperature, flash pressure, and ambient temperature, are parametrically investigated. Subsequently, the thermodynamic simulation results show that the advised integrated plant produces 4431 kW electrical power. Also, the amount of the hydrogen generation capacity is 0.006809 kgs⁻¹. The tCO2-RC sub-plant's energetic and exergetic performance is determined as 6.18% and 27.14%, respectively. Furthermore, the suggested integrated plant's energetic and exergetic performances are 26.20% and 37.49%. From the results, it can be finalized that the integration of various systems with the geothermal power plant is successfully possible and, in this way, there will be an increase in system performances.
Initiating cost-effective and technological frameworks to exploit geothermal energy is a fundamental incentive for scientists and engineers; in this regard, flash-binary geothermal power plants are plausible for high-temperature geothermal resources. Stemming from an in-depth literature review, it is conspicuous that the thermal and exergy losses of the expansion process are significant. To shed light on this matter, an ejector-expander is integrated into the conventional expansion valve of a double-flash binary geothermal power plant to enhance the plant performance. The feasibility of the contrived notion is scrutinized from energy, exergy, thermal, and cost balance standpoints and results converged in the increase in turbine output power, energy efficiency, and exergy efficiency of approximately 7.66%, 7.64%, and 7.69%, respectively. Among all components, the condenser constituted a 45.06% share of the overall exergy destruction, whilst the turbine had an exergy destruction ratio of 22.07%. An intensive parametric study is implemented that outlined that the turbine output power, energy efficiency, and exergy efficiency of the ejector-expander power system have a maximum in a specified pressure value of the first and second separator. Another merit was a marked decrease in the unit cost of power when ejector-expander is exploited.
In this article, a new geothermal powered multigeneration system is proposed and analyzed via energy, ex-ergy, economic, and exergoenvironmental points of view as well as parametric study to see the effects of main parameter variations. This multigeneration system includes a new configuration of the organic Rankine cycle with two evaporators and expanders, heater, NaClO system, and reverse osmosis. The products of this proposed system are electricity, hydrogen, heating, potable water, and salt. Due to theoretical analysis, this system produces 1.264 GWh of electrical energy, 15.93 GWh heating, 1919 Ton salt, 86400 m 3 of potable water, and 4.397 × 10 7 m 3 of hydrogen, annually with 60% and 21% of the system energy and exergy efficiencies. The organic Rankine cycle and reverse osmosis systems have the highest and lowest percentage of exergy destruction rates. The economic analysis reveals that the system payback period is 5.3 years. The system's net present value is 668.2 million US$. The exergoenvironmental analysis shows that the exergoenvironmental, environmental damage effectiveness, and the exergy stability factors for the proposed system are 0.86, 4.414, and 0.8, respectively. The parametric study shows that increasing the geo-fluid mass flow rate, increases the system's electrical power production and exergy efficiency while decreases the system exergy efficiency.
The simultaneous production of electricity (semi-finished product), freshwater, and hydrogen uprooted from seawater has been proposed in this study through a brainchild setup based on solar energy and scrutinized from exergy and exergoeconomic perspectives. The solar subsystem consists of parabolic trough solar collectors in arrangement with thermal storage tanks capable of driving other subsystems in three different solar radiation modes (low, high, and no radiation) in the course of a day. An organic Rankine cycle is utilized to generate electricity which is consumed in a low-temperature electrolyzer to produce hydrogen. Furthermore, the cycle’s heat loss is employed to produce freshwater via a desalination unit, part of which is used as the electrolyzer feed and the rest for other purposes. The parametric study and multi-criteria optimization are conducted. It is concluded that the system’s cost per unit exergy increases by increasing current density and reduces by decreasing electrolyzer temperature and desalination top temperature. In the multi-criteria optimization case, the exergy efficiency of the system is acquired for the above-mentioned modes as 5.39%, 2.52%, and 3.61%, respectively. Moreover, the cost per unit exergy of these modes is found to be 80 $/GJ, 60.3 $/GJ, and 81.4 $/GJ, individually.
An innovative Bi-Evaporator Ejector Refrigeration Cycle (BE-ERC) working with different zeotropic mixtures is devised in this study. Next, the proposed BE-ERC system is used as binary cycle of a modified Double-Flash Geothermal Power Plant (DF-GPP) to simultaneously produce cooling and power from the same geothermal well. A comprehensive modeling of the proposed integrated system is carried out from thermodynamics laws viewpoints and the results are elaborated in detail. Based upon the results, the use of R142b/Pentane (0.6/0.4) is highly commendable due to achieving the maximum refrigeration load, Coefficient of Performance (COP), and total energy efficiency of 137.83 kW, 0.329, and 20.37%, respectively. Although net electricity and exergy efficiency were not maximum at this condition, their value was competitive. Accordingly, with the use of R142b/Pentane (0.6/0.4), the net electricity, exergy efficiency of the BE-ERC, and total exergy efficiency were calculated 18.61 kW, 2.16%, and 20.95%, respectively. Among all elements of the integral set-up, the first ejector (the main ejector in the BE-ERC) had the highest exergy destruction of 26.09 kW out of overall fuel exergy of 190.7 kW (13.68%), followed by the vapor generator with exergy destruction of 24.4 kW.
This study investigates the thermodynamic and economic aspects of a multigeneration plant for inherent production of freshwater, power, cooling and heating by utilizing geothermal energy. The developed plant utilizes geothermal energy at a target temperature of 200 °C through a single flash-binary power plant with reinjection. The results of the thermodynamic analysis show that the overall plant energy and exergy efficiency of the plant can be as high as 61 % and 37.8 %, respectively, while the plant cost varies between 160–330 $/h. Optimization results show that an optimal exergy efficiency of 58 % is achievable when the plant cost rate is 242 $/h. The results indicate that geothermal driven freshwater production is one of the most economically feasible renewable driven clean production options, while a flash/binary power plant results in higher efficiency and lower electricity costs.
Sabalan geothermal field is one of the most important geothermal fields in Iran. In this study, four novel configurations namely Single Flash-ORC (SF-ORC), Double Flash 1-ORC (DF1-ORC), Double Flash 2-ORC (DF2-ORC) and Triple Flash-ORC (TF-ORC) are proposed to produce power from two wells of the field. The configurations are assessed by thermodynamic and exergoeconomic viewpoints. The exergy and SPECO based exergoeconomic equations are developed for the components of the proposed cycles and thermodynamic as well as exergoeconomic performance parameters are calculated for the components and the cycles. A comprehensive parametric study is also carried out for the proposed configurations considering various working fluids in the ORCs. Moreover, an optimization is performed to maximize the produced power from the wells. The results depicted that the DF1-ORC produces 4.03%, 1.32% and 1.2% more power than the SF-ORC, DF2-ORC and TF-ORC, respectively, in the optimum condition. It can be concluded from the exergoeconomic analysis that the SF-ORC with R123 working fluid has the best exergoeconomic performance with the power specific cost of 3.62 $/GJ. The thermodynamic and exergoeconomic performance of the DF1-ORC is compared with previous similar studies which shows the superiority of the proposed cycle.
Hydrogen can be used for various applications in ships, but two distinctive places are the combustion processes of the marine diesel engine (MDE) or aircrafts fuelled by aircraft carriers (especially, for long-range transportations applications). For this aim, an integrated trigeneration system working with waste heat of the MDE for mainly hydrogen extraction is proposed here. In addition to hydrogen, the devised trigeneration system can produce surplus electricity and cooling at two different temperature levels. Different zeotropic mixtures are used as working fluid and their performance metrics were compared with each other. It is worthy to say that the simulated basic cooling/electricity system is new and is accounted for as another novelty of the present work. A comprehensive modeling of the proposed trigeneration system is achieved from thermodynamics laws viewpoint and results are elaborated in detail. Based upon the results, the maximum refrigeration load and trigeneration energy efficiency are calculated 166.36 kW and 42.46%, respectively, when R142b/Pentane (0.51/0.49) was used. However, to achieve lower overall exergy destruction, Butene/Isopentane (0.35/0.65) was recommended. Also, the highest trigeneration exergy efficiency is associated with Butene/Isopentane (0.35/0.65) by 18.71%, followed by Isobutene/Isopentane (0.34/0.66) by 18.53%. It is found that the auxiliary vapor generator has the highest exergy destruction by 61.5 kW, followed by ejector by 19.5 kW. At last, an intensive parametric study is also presented to propose some solution for performance enhancement of the system based on the thermodynamics parameters.
Regarding the important role of combined cooling and power (CCP) systems in improving the efficiency of power plants, and also the ability of ORC and ERC systems in the exploitation of low-to medium-grade energy sources, a novel CCP system is presented which is based on geothermal flash cycle as topping cycle, organic Rankine cycle, and ejector refrigeration as the bottoming cycle for power and cooling generation aims. This work proposes a thermodynamic and parametric analysis of the proposed system where the ORC and ERC cycles employ different mixtures of zeotropic fluids as the working fluid. The integration of ORC and ERC systems with zeotropic mixtures presents the considerable capability to combine their superiority and further enhance the system performance considerably. The superiority of the proposed system, which combines the advantages of zeotropic mixtures with ORC and ERC positive aspects, is revealed through the energy and exergy analysis. The results revealed some precious facts; for instance, the total thermal and exergetic efficiencies are calculated by 18.16% and 59.16%, correspondingly. Also, the COP and the cooling capacity of the ERC unit is obtained 0.1224 and 93.73kW, respectively. Besides, the best exergy efficiency and the lowest exergy destruction is evaluated for the system with Isopentane (0.3)/R142b (0.7) as the working fluid. Also, from the parametric study, it can be inferred that decreasing the separator pressure and increasing the heat exchanger inlet temperature leads to higher energy and exergy efficiency.
In this study, geothermal energy is considered as a renewable energy source to finally provide various useful commodities, such as electricity, hydrogen, fresh and hot water, drying, heating, and cooling. In this regard, a new geothermal power based multigenerational system is proposed to meet these demands in an environmentally-benign manner and studied thermodynamically by considering energy and exergy approaches and investigating parametrically. A combination of geothermal energy is used to achieve the most promising hydrogen generation rates and high plant performances. The results of this study indicate that the energy and exergy efficiency values of the entire plant for the selected operating conditions become 38.41% and 42.57%. In addition to thermodynamic analysis performed, parametric studies are performed to reveal how operating conditions and state parameters affect the overall system performance. According to the parametric analyses results, for given ranges an increase in ambient temperature, separator working temperature, geothermal fluid temperature and geothermal fluid mass flow rate have a positive impact on both energy and exergy efficiency of the integrated system and useful products generation rate as well.
Organic Rankine cycle (ORC) power generation system is an attractive unit applied widely to exploit low-to medium-grade energy sources. This work proposes a thermodynamic analysis and optimization of a flash-binary geothermal cycle for power generation and hydrogen production aims where the binary cycle used is an organic Rankine cycle in which different mixtures of zeotropic fluids are used as the working fluid. The integration of ORC and zeotropic mixtures presents the considerable capability to combine their superiority and further enhance the system performance considerably. The superiority of the proposed system which combines the advantages of zeotropic mixtures with ORC positive aspects, is revealed through the energy and exergy analysis. Also, the particle swarm optimizer is employed to optimize the net output power as the objective function. The results reveal some precious facts; for instance, the overall thermal and exergy efficiencies are obtained 18.9% and 57.39%, respectively for the base case. However, the optimized results demonstrate that the Pentane (0.31)/Butene (0.69) and Pentane (0.41)/Butane (0.59) combinations hold the maximum energetic efficiency of 18.96% and 18.91%, respectively. The net output powers for these combinations are 125.712kW and 124.923kW, respectively. Besides, The highest exergy efficiency belongs to Pentane (0.31)/Butene (0.69) and Pentane (0.41)/Butane (0.59) combination whose values are 57.24% and 57.10%, respectively. Also, from the parametric study, it can be inferred that increasing the generator's pinch point temperature results in a lower power generation rate of the ORC and total system.
Utilizing high-efficient systems for cooling and electricity generation from green energy resources is an efficient method of sustainable development. For this aim, an innovative hybrid cycle for simultaneous power and cooling generation is recommended. The presented system is an internal integration of double-flash ejector refrigeration and power systems. First-law and second-law analysis are employed to investigate the feasibility of the system. Besides, a single-objective optimization performed by the implementation of the GA technique. The optimal energy and exergy efficacies are achieved by 72.57% and 27.69%, respectively.
Furthermore, a thorough parametric analysis indicated that the energy and exergy efficacies could be optimized according to turbine pressure and ejector pressure. Moreover, it is showed that a higher energy efficacy and cooling capacity is obtainable by augmenting the ejector pressure, evaporator temperature, and compressor pressure ratio. Whereas, the exergy efficacy can be enhanced by increasing condenser #2 pressure. Besides, based on the exergy efficacy of each constituent of the system, the flashing chamber 1 shows the most excellent exergy efficacy among all the constitutes while the highest value of exergy is destroyed within the condenser 1.
The current study focuses on the comparative analyses of multigeneration systems integrated with an electrolyzer for the production of hydrogen, for work rate a regenerative Rankine Cycle and finally for the cooling effect vapor absorption cycle was used. The power produced by both proposed systems was observed to yield some difference based on their positioning in the system and similarly, the rate of hydrogen production from the electrolyzer was also observed. Energetic and exergetic analyses of both the systems are done including all the concerned components. Certain parameters are varied to observe the overall changes in the system along with their effect on the overall efficiencies. A comparative analysis between the two proposed systems was carried out in the present study and eventually providing an efficient system, adding up to the novelty of this publication. At the similar ambient working conditions one of the systems was observed to yield an approximately 0.45% power efficiency difference but when the working parameters were varied, the difference was observed to be abrupt. The electrolyzer has a generation rate of 0.296 g/s and 0.2648 g/s respectively for both systems at base working conditions. At 800 W/m² of solar irradiance, the Rankine-Trough-Vapour (RTV) cycle produced 11.77% more net power as compared with Vapour-Trough-Rankine (VTR) cycle. Hydrogen production is considered to be one of the most valuable asset of this analysis because of its immense use in multiple processes. Furthermore, this study suggests the most efficient system for different atmospheric conditions.
Fuel cells offer one of the most eco-friendly and efficient ways of energy production. In this study a thermo-dynamic and exergoeconomic assessment of a proton exchange membrane fuel cell (PEMFC) system at steady-state operation condition are carried out. Thereafter, the feasibility of integrating a proton exchange membrane Electrolyzer (PEME) to supply required fuel for a PEMFC, operating in the same outlet power range is investigated. The results demonstrate that increasing the current density rises the following parameters in the system: the power and power density rates of the PEMFC and PEME, the exergy destruction rate of each component , the hydrogen production and consumption rates in the cycles, the PEME output voltage, cost rate of power generation and the power cost of the PEMFC. By increasing the PEMFC output voltage, the energy and exergy efficiencies reduce. Moreover, rising the outlet temperature of the PEMFC increases the power and power density rates of the PEMFC and also the energy and exergy efficiencies of the system. While increasing the outlet and operating temperature of the PEME increases the power consumption rate and reduces the energy and exergy efficiencies. The highest energy efficiency of the PEMFC is 36.7% and corresponding maximum exergy efficiency is found 54%, while the lowest values are found 31% and 45.3%, respectively. The cost rate of the power generation by PEMFC is varied between 7.96 × 10 −4 and 1.33 × 10 −3 $/s and the corresponding rate of the exergy unit cost range is 115.6-132.2 $/GJ.
This paper investigates a combined cooling and power system driven by geothermal energy for ice-making and hydrogen production. The proposed system combines geothermal flash cycle, Kalina cycle, ammonia-water absorption refrigeration cycle and electrolyser. The geothermal energy can be efficiently converted to storable hydrogen and ice. Based on mathematical model, some key parameters are analyzed to figure out their effect on the exergetic performance. An exergy destruction analysis for all components has been performed to find out the distribution of exergy inefficiency. The system exergetic efficiency is optimized by Jaya algorithm and Genetic algorithm and the optimization results are compared. According to the parametric analysis, the exergy efficiency decreases as the back pressure of steam turbine and the back pressure of ammonia-water turbine increase. The exergy efficiency could increase first and then decline, as flash pressure, ammonia-water turbine inlet pressure and ammonia mass fraction of basic solution increase. The optimization results show that the exergy efficiency reaches 23.59%, 25.06% and 26.25% when the geothermal water temperature is 150 °C, 160 °C and 170 °C. Jaya algorithm has highly precise optimization results.
Multigeneration systems driven by renewable sources are proved as cutting-edge technologies for multiple productions purposes to curb greenhouse gas emissions. With this regard, a novel geothermal-based multigeneration system is proposed to produce multiple commodities of cooling, heating, power, and hydrogen, simultaneously, using liquefied natural gas as cold energy recovery. To demonstrate the feasibility of the proposed multigeneration system, energy, exergy, and exergoeconomic analysis are employed as the most effective tools for performance assessment of the proposed system. Also, to enhance the performance of the system, single- and multi-objective optimizations are carried out, using genetic algorithm. It is found that the proposed multigeneration system can be run with the optimum basic ammonia concentration of 0.42, geothermal inlet temperature of 160.5°C, evaporator temperature of 7.76°C, vapor generator pressure of 33 bar, mass extraction ratio of 0.2, condenser temperature of 29.01°C, separator 2 pressure of 4.99 bar, vapor generator terminal temperature difference of 7°C, and turbine 2 inlet pressure of 22.11 bar. In this case, the optimum thermal efficiency, exergy efficiency, and total SUCP (sum unit cost of the product) of the system are calculated 62.74%, 33.82%, and 125.4 $/GJ, respectively. Moreover, a comprehensive parametric study is carried out and it is shown that a higher thermal efficiency can be obtained by increasing the vapor generator pressure and evaporator temperature, or decreasing the mass extraction ratio, separator 2 pressure, turbine 2 inlet pressure, geothermal inlet temperature, vapor generator terminal temperature difference, and basic ammonia concentration.
This work is an attempt to propose and analyze a geothermal based multi-generation system. The proposed cogeneration system consists of different sections, namely: organic Rankine cycle, geothermal wells, absorption heat transformer, domestic water heater and proton exchange membrane electrolyzer. To assess the cycle’s performance, thermodynamic models were developed and a parametric study was carried out. For this purpose, energetic analysis are undertaken upon proposed system. Also, the effects of some important variables such geothermal water temperature, turbine inlet temperature and pressure on the several parameters such as energy efficiencies of the proposed system, water production, net electrical output power, hydrogen production, are investigated. It is shown that, by boosting geothermal water temperate, COP of the AHT increases and flow ratio decreases. Additionally, increasing absorber temperature leads to the reduction of energy utilization factor.
Performance of a small-scale trigeneration system driven by low-temperature geothermal sources for producing fresh water, heating (hot water) and electricity is investigated from thermodynamic and economic standpoints. This system, utilizing a single stage absorption heat transformer leads to an increase in heat source temperature to be used in single stage evaporation desalination process and also providing water heating. Furthermore, an organic Rankine cycle is used for electric power generation. The developed model is validated with available data and effects of decision variables namely geothermal source, absorber and condenser temperatures on energy and exergy efficiencies of the overall system, power to water ratio and levelized cost of energy (LCOE) are investigated. The findings show that the increase in absorber and condenser temperatures leads to lower energy and exergy efficiencies, and higher LCOE and these effects are more significant at lower geothermal temperatures. Moreover, it is estimated that LCOE of proposed system is by far lower than that of a sole ORC powered with low geothermal water sources, whereas levelized cost of water (LCOW) is just comparable with small-scale membrane desalination processes. Utilizing a 100 °C geothermal water, the proposed system has a production capacity of 0.662 kg/s fresh water, 161.5 kW power, and 246 kW heat load.
The selection of the working fluid for Organic Rankine Cycles has traditionally been addressed from systematic heuristic methods, which perform a characterization and prior selection considering mainly one objective, thus avoiding a selection considering simultaneously the objectives related to sustainability and safety. The objective of this work is to propose a methodology for the optimal selection of the working fluid for Organic Rankine Cycles. The model is presented as a multi-objective approach, which simultaneously considers the economic, environmental and safety aspects. The economic objective function considers the profit obtained by selling the energy produced. Safety was evaluated in terms of individual risk for each of the components of the Organic Rankine Cycles and it was formulated as a function of the operating conditions and hazardous properties of each working fluid. The environmental function is based on carbon dioxide emissions, considering carbon dioxide mitigation, emission due to the use of cooling water as well emissions due material release. The methodology was applied to the case of geothermal facilities to select the optimal working fluid although it can be extended to waste heat recovery. The results show that the hydrocarbons represent better solutions, thus among a list of 24 working fluids, toluene is selected as the best fluid.
In this paper, a geothermal based multi-generation energy system, including organic Rankine cycle, domestic water heater, absorption refrigeration cycle and proton exchange membrane electrolyzer, is developed to generate electricity, heating, cooling and hydrogen. For this purpose, energetic, exergetic and exergoeconomic analysis are undertaken upon proposed system. Also, the effects of some important variables, i.e. geothermal water temperature, turbine inlet temperature and pressure, generator temperature, geothermal water mass flow rate and electrolyzer current density on the several parameters such as energy and exergy efficiencies of the proposed system, heating and cooling load, net electrical output power, hydrogen production, unit cost of each system products and total unit cost of the products are investigated. For specified conditions, the results show that energy and exergy efficiencies of the proposed multi-generation system are calculated about 34.98% and 49.17%, respectively. The highest and lowest total unit cost of the products estimated approximately 23.18 and 22.73 $/GJ, respectively, by considering that geothermal water temperature increases from 185 ˚C to 215 ˚C.
The current study presents a new designed quadruple energy production system integrated with geothermal energy involving a cascade organic Rankine cycle, liquefied natural gas vaporization process, proton exchange membrane electrolyzer to produce four types of energies, namely electricity power, heating load for vaporizing liquefied natural gas, cooling effect and hydrogen. Besides conventional analyses, advanced thermodynamic and thermoeconomic analyses are conducted to determine the irreversibilities and related cost rates within the components of the desired system to find the amount of total avoidable exergy destruction rate, and total avoidable cost rates. Moreover, the effect of substantial design parameters namely, upper cycle mass flow rate, liquefied natural gas mass flow rate, geothermal mass flow rate, turbine 1 inlet pressure, liquefied natural gas pressure, geothermal pressure and condenser 1 outlet temperature are evaluated on the total avoidable exergy destruction, total avoidable exergy destruction cost and investment cost rates as well as their subdivisions. Sensitivity studies indicate that geothermal mass flow rate has a drastic positive effect on the total avoidable exergy destruction rate and total exergy destruction cost rate within 137.2% and 119.5%, respectively while condenser 1 outlet temperature improves total avoidable investment cost rate by about 0.05 $/h, as compared with other parameters. Finally, Non-dominated Sort Genetic Algorithm-II is applied to achieve the maximum improvement potential for desired system. Optimization results show that total avoidable exergy destruction rate and total avoidable exergy destruction cost rate get 3.27 and 4.9 times, respectively and total avoidable investment cost rate is improved within 17.4% relative to the base point.
Saudi Arabia is enriched by many geothermal resources located mainly at the western and southwestern parts. These resources are related to the general tectonic activity of the Red Sea and associated with a series of volcanic rocks and ridges. The Jizan area is considered as a promising geothermal system that includes a number of structural-related hot springs with surface temperature from 46 °C to 78 °C. The present work aims mainly to explore and locate the potentiality of these resources through analyzing the available satellite images, applying a number of geo-indicators and performing a 2D electric geophysical survey, as well as estimating the geothermal reserve potential for possible energy production.
The present study develops a new integrated geothermal based system, comprising of quadruple flash power plant (QFPP), quadruple effect absorption cooling system (QEACS), electrolyzer and air-conditioning process (cooling with dehumidification) for building applications. The system is designed to generate six outputs namely, power, hot water, heating, cooling, hydrogen and dry air to meet the building needs. The system analysis is carried out through energy and exergy, and parametric studies are carried out to see the effect of variation in geothermal pressure at state f2, geothermal liquid temperature, relative humidity and evaporator load on performance of the integrated system. Illustrations are also provided to display the effect of variation in geothermal liquid pressure at state f2 and geothermal liquid temperature on the exergy efficiencies as the number of output increases. The results show that the exergy efficiency increases from 0.20 to 0.28 with increase in geothermal liquid temperature from 450 K to 500 K and number of generations from single to hextuple generation. An optimization study is also carried out to find the highest possible exergy efficiency and the lowest possible exergy destruction of the hextuple generation system.
a b s t r a c t In this paper we analyze the main available data related to the geothermal system of Ischia Island, starting from the first geothermal exploration in 1939. Our aim is to define a conceptual model of the geothermal reservoir, according to geological, geochemical, geophysical and stratigraphic data. In recent times, the interest on geothermal exploitation for electricity generation in Italy is rapidly increasing and the Ischia Island is one of the main targets for future geothermal exploitation. Nowadays, one of the main economic resources of the island is the tourism, mainly driven by the famous thermal springs; so, it is crucial to study the possible interaction between geothermal exploitation and thermal spring activities. To this aim, we also analyze the possible disturbance on temperature and pressure in the shallow geothermal reservoir, due to the heat withdrawal for electric production related to small power plant size (1e5 MWe). Such analysis has been performed by using numerical simulations based on a well known thermofluid-dynamical code (TOUGH2 Ò). Obtained results show that such geothermal exploitation generates a perturbation of temperature and pressure field which, however, is confined in a small vol-ume around the well. At shallow level (0e100 m) the exploitation does not produce any appreciable disturbance, and can be made compatible with thermal spring exploitation. Moreover, such results are crucial both for the evaluation of volcanological processes in the island and for the general assessment of geothermal resource sustainability.
This paper describes the use of a low enthalpy geothermal source in Northern Greece to heat a greenhouse where flowers could be grown, especially roses. The different parts of the developed greenhouse, the heat loss calculation and the heating system are described. An analysis is given of different greenhouse heating approaches, and a description of the selection procedure, following low-cost and high-efficiency criteria. An analysis is also made of an extended heating system, which uses low temperature water or direct geothermal fluid to heat a second greenhouse similar to the first. The second greenhouse could be used for strawberry cultivation, where an inside temperature of 15°C is required.The existing greenhouse, described in this paper, proved to be very important and beneficial for this area of Northern Greece, with its numerous low enthalpy geothermal sources.
In this study the option of combined heat and power generation was considered for geothermal resources at a temperature level below 450 K. Series and parallel circuits of an Organic Rankine Cycle (ORC) and an additional heat generation were compared by second law analysis. Depending on operating parameters criteria for the choice of the working fluid were identified. The results show that due to a combined heat and power generation, the second law efficiency of a geothermal power plant can be significantly increased in comparison to a power generation. The most efficient concept is a series circuit with an organic working fluid that shows high critical temperatures like isopentane. For parallel circuits and for power generation, fluids like R227ea with low critical temperatures are to be preferred.
Thin film electrocatalyst layers with various PTFE and Nafion contents for unitized regenerative polymer electrolyte fuel cells (URFCs) were prepared by the paste method and the performance as URFC electrodes was examined. Comparing the terminal voltage versus current density curves of the URFC, it was found that the PTFE content in the electrocatalyst layer affected only the fuel cell performance; the electrode containing 5–7wt.% PTFE was appropriate for the URFC. The Nafion content in the electrode affected both the fuel cell and water electrolysis performance; the electrode containing 7–9wt.% Nafion showed good performance. The addition of a small amount of iridium catalyst (about 10at.%) to the oxygen electrode layer significantly improved the URFC performance. Catalyst loadings can be reduced to
A 1-D analysis for the prediction of ejector performance at critical-mode operation is carried out in the present study. Constant-pressure mixing is assumed to occur inside the constant-area section of the ejector and the entrained flow at choking condition is analyzed. We also carried out an experiment using 11 ejectors and R141b as the working fluid to verify the analytical results. The test results are used to determine the coefficients, ηp, ηs, φp and φm defined in the 1-D model by matching the test data with the analytical results. It is shown that the1-D analysis using the empirical coefficients can accurately predict the performance of the ejectors.RésuméDans cette étude, on a effectué une analyse unidimensionnelle pour prédire la performance d'un éjecteur fonctionnant en mode critique. Les auteurs sont partis du principe que le mélange s'effectue à pression constante dans la partie de l'éjecteur dont la section est constante et ont analysé le flux entraı̂né au niveau de l'onde de choc. Onze éjecteurs utilisant le R141b comme fluide actif ont été utilisés par les auteurs afin de vérifier les résultats analytiques. Les résultats expérimentaux sont utilisés pour déterminer les coefficients ηp, ηs, φp et φm définis dans le modèle unidimensionnel. L'étude a montré que l'analyse unidimensionnelle utilisant les coefficients empiriques peut prédire la performance des éjecteurs de façon précise.