Exergoeconomic analysis of a new integrated copper-chlorine cycle for hydrogen production

In this study, an exergoeconomic analysis is performed on an integrated four-step thermochemical copper-chlorine cycle developed at the Ontario Tech. University through exergy, cost, energy, and mass (EXCEM) method. A thermodynamic model is first constructed in Aspen-plus (a process simulation software) to simulate and investigate the integrated cycle through exergy and energy analyses. The capital costs, thermodynamic loss rates, and the ratio of the thermodynamic loss rate to the capital cost of various system's components are also determined. Moreover, the average unit cost of hydrogen is evaluated and the influence of several system's parameters on the unit cost of hydrogen is analyzed. The results show that the cost of hydrogen is strongly dependent on the production capacity of the plant. Based on the analysis, our system generates hydrogen at an average unit cost of 5.54 $/kg with a plant capacity of 1619.3 kg/h considering both internal (operating and maintenance costs, etc.) and external (costs of various inputs, etc.) parameters.     

Exergetic and thermoeconomic analyses of diesel engine powered cogeneration: Part 2 – Application

This paper is Part 2 of the study on the exergetic and thermoeconomic analysis of diesel engine powered cogeneration (DEPC) systems. In Part 1, formulations and procedure for such a comprehensive analysis are provided while this paper provides an application of the developed formulation that considers an actual DEPC plant installed in Gaziantep, Turkey. The plant has a total installed electricity and steam generation capacities of 25.3 MW and 8.1 tons/h at 170 °C, respectively. Exergy destructions, exergy efficiencies, exergetic cost allocations, and various exergoeconomic performance parameters are determined for the entire plant and its components. The exergy efficiency of the plant is determined to be 40.6%. The exergoeconomic analysis is based on specific cost method (SPECO) and it is determined that the specific unit exergetic cost of the power produced by the plant is 10.3 $/GJ.     

Exergoeconomic machine-learning method of integrating a thermochemical Cu–Cl cycle in a multigeneration combined cycle gas turbine for hydrogen production

Integrating new technologies into existing thermal energy systems enables multigenerational production of energy sources with high efficiency. The advantages of multigenerational energy production are reflected in the rapid responsiveness of the adaptation of energy source production to current market conditions. To further increase the useful efficiency of multigeneration energy sources production, we developed an exergoeconomic machine-learning model of the integration of the hydrogen thermochemical Cu–Cl cycle into an existing gas-steam power plant. The hydrogen produced will be stored in tanks and consumed when the market price is favourable. The results of the exergoeconomic machine-learning model show that the production and use of hydrogen, in combination with fuel cells, are expedient for the provision of tertiary services in the electricity system. In the event of a breakdown of the electricity system, hydrogen and fuel cells could be used to produce electricity for use by the thermal power plant. The advantages of own or independent production of electricity are primarily reflected in the start-up of a gas-steam power plant, as it is not possible to start a gas turbine without external electricity. The exergy analysis is also in favour of this, as the integration of the hydrogen thermochemical Cu–Cl cycle into the existing gas-steam power plant increases the exergy efficiency of the process.     

Assessment study of a four-step copper-chlorine cycle modified with flash vaporization process for hydrogen production

This paper develops a four-step copper-chlorine cycle for hydrogen production with conceptual modification through flash vaporization and evaluates its economic and environmental performances through exergy approach. The flash vaporization method is employed as a new approach for realizing the anolyte separation under vacuum conditions for reducing the thermal requirement of the anolyte separation step and consequently of the overall cycle. A flash vaporization is usually employed commercially for seawater desalination purposes. However, its utilization in a thermochemical hydrogen production process has not been considered previously which is really one of primary novelties of this investigation. The obtained results for the exergoeconomic and exergoenvironmental analyses of the conceptually modified cycle are also compared with those of the existing integrated cycle at the Ontario Tech University. The exergoeconomic analysis of the cycle has also been carried out for the cycle operating with and without waste heat recovery. In this regard, waste heat recovery from a steel furnace has been considered for supplying the required thermal energy for the hydrolysis step. The cost assessment of the cycle is carried out in the Aspen-plus. Compared with the existing cycle, the cycle with the proposed modification results in a lower unit cost of hydrogen. Moreover, a significant reduction in the unit cost of hydrogen is observed when waste heat recovery is considered for the modified cycle. The average unit hydrogen cost for the modified version of the cycle is evaluated to be 4.7 $/kg which reduces to 2 $/kg with incorporation of waste heat recovery. Furthermore, the overall environmental impact of the existing cycle can be potentially minimized by considering the proposed modification through flash vaporization.     

Modified exergoeconomic modeling of geothermal power plants

In this study, a modified exergoeconomic model is proposed for geothermal power plants using exergy and cost accounting analyses, and a case study is in this regard presented for the Tuzla geothermal power plant system (Tuzla GPPS) in Turkey to illustrate an application of the currently modified exergoeconomic model. Tuzla GPPS has a total installed capacity of 7.5 MW and was recently put into operation. Electricity is generated using a binary cycle. In the analysis, the actual system data are used to assess the power plant system performance through both energy and exergy efficiencies, exergy losses and loss cost rates. Exergy efficiency values vary between 35% and 49% with an average exergy efficiency of 45.2%. The relations between the capital costs and the exergetic loss/destruction for the system components are studied. Six new exergetic cost parameters, e.g., the component annualized cost rate, exergy balance cost, overall unavoidable system exergy destruction/loss cost rate, overall unavoidable system exergy destruction/loss cost rate, overall unavoidable system exergy production cost rate and the overall unavoidable system exergy production cost rate are studied to provide a more comprehensive evaluation of the system.     

Exergoeconomic analysis and optimization of basic,dual-pressure and dual-fluid ORCs and Kalina geothermal power plants: A comparative study

In present work, the basic, dual-pressure and dual-fluid ORCs and Kalina cycle for power generation from the geothermal fluid reservoir are compared from energy, exergy and exergoeconomic viewpoints. To do so, first thermodynamic models are applied to the considered cycles; then by developing cost flow rate balance and auxiliary equations using SPECO method for all components, the cost flow rate and unit cost of exergy for each stream are calculated. The results show that the turbine in basic and Kalina cycles and low pressure turbine in dual-pressure and dual-fluid ORCs have the maximum value of sum of total cost rate associated with exergy destruction and total capital investment cost rate. Thus, more attention should be paid for these components from the exergoeconomic viewpoint. The cycles are optimized to obtain maximum produced electrical power in the cycles as well as minimum unit cost of produced power. The optimization results show that among the considered cycles, dual-pressure ORC has the maximum value of produced electrical power. This is 15.22%, 35.09% and 43.48% more than the corresponding values for the basic ORC, dual-fluid ORC and Kalina cycle, respectively in optimal condition. Also Kalina cycle has the minimum value of unit cost of power produced and its value in optimum state is 26.23%%, 52.09% and 66.74% less than the corresponding values for the basic ORC, dual-pressure ORC and dual-fluid ORC, respectively in optimal condition. Finally a parametric study is carried out to assess the effects on thermodynamic and exergoeconomic parameters of the considered cycles of operating pressures and ammonia mass concentration.     

Exergoeconomic assessment of a geothermal assisted high temperature steam electrolysis system

Exergoeconomic formulations and procedure including exergy flows and cost formation and allocation within a high temperature steam electrolysis (HTSE) system are developed, and applied at three environmental temperatures. The cost accounting procedure is based on the specific exergy costing (SPECO) methodology. Exergy based cost-balance equations are obtained by fuel and product approach. Cost allocations in the system are obtained and effect of the second-law efficiency on exergetic cost parameters is investigated. The capital investment cost, the operating and maintenance costs and the total cost of the system are determined to be 422.2, 2.04, and 424.3 €/kWh, respectively. The specific unit exergetic costs of the power input to the system are 0.0895, 0.0702, and 0.0645 €/kWh at the environmental temperatures of 25 °C, 11 °C, and −1 °C, respectively. The exergetic costs of steam are 0.000509, 0.000544, and 0.000574 €/kWh at the same environmental temperatures, respectively. The amount of energy consumption for the production of one kg hydrogen is obtained as 133 kWh (112.5 kWh power + 20.5 kWh steam), and this corresponds to a hydrogen cost of 1.6 €/kg H₂.     

Energy and exergy analyses of a new four-step copper–chlorine cycle for geothermal-based hydrogen production

In this paper, energy and exergy analyses of the geothermal-based hydrogen production via thermochemical water decomposition using a new, four-step copper–chlorine (Cu–Cl) cycle are conducted, and the respective cycle energy and exergy efficiencies are examined. Also, a parametric study is performed to investigate how each step of the cycle and its overall cycle performance are affected by reference environment temperatures, reaction temperatures, as well as energy efficiency of the geothermal power plant itself. As a result, overall energy and exergy efficiencies of the cycle are found to be 21.67% and 19.35%, respectively, for a reference case.     

Exergoeconomic analysis of hydrogen production from biomass gasification

In this study, we investigate biomass-based hydrogen production through exergy and exergoeconomic analyses and evaluate all components and associated streams using an exergy, cost, energy and mass (EXCEM) method. Then, we define the hydrogen unit cost and examine how key system parameters affect the unit hydrogen cost. Also, we present a case study of the gasification process with a circulating fluidized bed gasifier (CFBG) for hydrogen production using the actual data taken from the literature. We first calculate energy and exergy values of all streams associated with the system, exergy efficiencies of all equipment, and determine the costs of equipment along with their thermodynamic loss rates and ratio of thermodynamic loss rate to capital cost. Furthermore, we evaluate the main system components, consisting of gasifier and PSA, from the exergoeconomic point of view. Moreover, we investigate the effects of various parameters on unit hydrogen cost, such as unit biomass and unit power costs and hydrogen content of the syngas before PSA equipment and PSA hydrogen recovery. The results show that the CFBG system, which has energy and exergy efficiencies of 55.11% and 35.74%, respectively, generates unit hydrogen costs between 5.37 $/kg and 1.59 $/kg, according to the internal and external parameters considered.     

An exergy–cost–energy–mass analysis of a hybrid copper–chlorine thermochemical cycle for hydrogen production

An exergoeconomic assessment using exergy–cost–energy–mass (EXCEM) analysis is reported of a copper–chlorine (Cu–Cl) thermochemical water splitting cycle for hydrogen production. The quantitative relation is identified between capital costs and thermodynamic losses for devices in the cycle. A correlation detected in previous assessments, suggesting that devices in energy systems are configured so as to achieve an overall optimal design by appropriately balancing thermodynamic (exergy-based) and economic characteristics of the overall system and its components, is observed to apply for the Cu–Cl cycle. Exergetic cost allocations and various exergoeconomic performance parameters are determined for the overall cycle and its components. The results are expected to assist ongoing efforts to increase the economic viability and to reduce product costs of potential commercial versions of this process. The impacts of these results are anticipated to be significant since thermochemical water splitting with a copper–chlorine cycle is a promising process that could be linked with nuclear reactors to produce hydrogen with no greenhouse gases emissions, and thereby help mitigate numerous energy and environment concerns.     

Thermo-economic analysis and optimization of the very high temperature gas-cooled reactor-based nuclear hydrogen production system using copper-chlorine cycle

An improved very high temperature gas-cooled reactor (VHTR) and copper-chlorine (Cu–Cl) cycle-based nuclear hydrogen production system is proposed and investigated in this paper, in order to reveal the unknown thermo-economic characteristics of the system under variable operating conditions. Energy, exergy and economic analysis method and particle swarm optimization algorithm are used to model and optimize the system, respectively. Parametric analysis of the effects of several key operating parameters on the system performance is conducted, and energy loss, exergy loss, and investment cost distributions of the system are discussed under three typical production modes. Results show that increasing the reactor subsystem pressure ratio can enhance the system's thermo-economic performance, and the total efficiencies and cost of producing compressed hydrogen from nuclear energy are respectively lower and higher than that of generating electricity. When the system operates at the maximum hydrogen production rate of 403.1 mol/s, the system's net electrical power output, thermal efficiency, exergy efficiency, and specific energy cost are found to be 38.77 MW, 39.3%, 41.26%, and 0.0731 $/kW·h, respectively. And when the system's hydrogen production load equals to 0, these values are respectively calculated to be 177.25 MW, 50.64%, 53.29%, and 0.0268 $/kW·h. In addition, more than 90% of the system's total energy losses are caused by condenser and Cu–Cl cycle, and about 50–60% of the system's total exergy destructions occur in VHTR. About 60% and 30% of the system's specific energy cost are respectively caused by the equipment investment and the system operation & maintenance, and the investment costs of VHTR and Cu–Cl plant are the system's main capital investment sources.     

Exergoeconomic analysis of a combined heat and power (CHP) system

This study deals with exergoeconomic analysis of a combined heat and power (CHP) system along its main components installed in Eskisehir City of Turkey. Quantitative exergy cost balance for each component and the whole CHP system is considered, while exergy cost generation within the system is determined. The exergetic efficiency of the CHP system is obtained to be 38.33% with 51 475.90 kW electrical power and the maximum exergy consumption between the components of the CHP system is found to be 51 878.82 kW in the combustion chamber. On the other hand, the exergoeconomic analysis results indicate that the unit exergy cost of electrical power produced by the CHP system accounts for 18.51 US$ GW^?1. This study demonstrates that exergoeconomic analysis can provide extra information than exergy analysis, and the results from exergoeconomic analysis provide cost‐based information, suggesting potential locations for the CHP system improvement. Copyright © 2007 John Wiley & Sons, Ltd.     

Multigeneration system exergy analysis and thermal management of an industrial glassmaking process linked with a Cu–Cl cycle for hydrogen production

A multigeneration system for hydrogen production linked with a glassmaking process via thermal management is examined in this study. The exhaust gas is interconnected with a Rankine cycle and the copper-chlorine (Cu–Cl) cycle for hydrogen production. The present system consists of a steam Rankine cycle, Cu–Cl cycle with multistage compression, double-stage organic Rankine cycle, and multi-effect desalination system. A Cu–Cl cycle based on the four-step model is employed with the proposed system. The useful system outputs are electricity, hydrogen, and fresh water. The simulation software packages utilized in the analysis and modeling are Engineering Equation Solver and Aspen Plus. The energy efficiency of the overall system is 36.5% while 38.1% is the exergy efficiency. The parametric studies are conducted to investigate the system performance. In addition, the effects of exhaust gas variables, such as flow rate, temperature, and pressure are examined to investigate the system performance.     

Thermodynamic performance assessment of boron based thermochemical water splitting cycle for renewable hydrogen production

The present study is related with the thermodynamic performance assessment of renewable hydrogen production through Boron thermochemical water splitting cycle. Therefore, all step efficiencies and overall cycle efficiency are calculated based on complete reaction. Additionally, a parametric study is conducted to determine the effect of the reference environment temperature on the overall cycle efficiency. In this regard, exergy efficiencies, exergy destruction rates and also inlet and outlet exergy rates of the cycle are calculated and presented for various reference temperatures. The exergy efficiency of the cycle is calculated as 0.4393 based on complete reaction and occurs at 298 K. This study has shown that Boron thermochemical water splitting cycle has a great potential due to cycle performance. As a result, Boron based thermochemical water splitting cycle can help achieve better environment and sustainability due to high exergetic efficiency. By the way, economic and technical issues of the storage and transportation of the hydrogen can find a proper solution if the hydrogen production reaction of the Boron thermochemical water splitting cycle takes place on-board of a vehicle.     

Energy and exergy analyses of hybrid photocatalytic hydrogen production reactor for CuCl cycle

The present paper concerns electrochemical, energy, exergy and exergoeconomic analyses of a hybrid photocatalytic-based hydrogen production reactor which is capable of replacing the electrolysis sub-system of the CuCl thermochemical cycle. Several operating parameters, such as current density, reactor temperature, ambient temperature and electrode distance, are varied to study their effects on the hydrogen production rate, the cost of hydrogen production and energy and exergy efficiencies. The present results show that the voltage drops across the anolyte solution (sol 1), catholyte solution (sol 2), an anode, cathode, and cation exchange membrane vary from 0.005 to 0.016 V, 0.004–0.013 V, 1.67–2.168 V, 0.18–0.22 V and 0.06–0.19 V, respectively with an increase in current density from 0.5 to 1.5 A/cm². The energy and exergy efficiencies of the hybrid photocatalytic hydrogen production reactor decrease from 5.74 to 4.54% and 5.11 to 4.04%, respectively with an increase in current density.     

Performance assessment of a direct steam solar power plant with hydrogen energy storage: An exergoeconomic study

Power generation and its storage using solar energy and hydrogen energy systems is a promising approach to overcome serious challenges associated with fossil fuel-based power plants. In this study, an exergoeconomic model is developed to analyze a direct steam solar tower-hydrogen gas turbine power plant under different operating conditions. An on-grid solar power plant integrated with a hydrogen storage system composed of an electrolyser, hydrogen gas turbine and fuel cell is considered. When solar energy is not available, electrical power is generated by the gas turbine and the fuel cell utilizing the hydrogen produced by the electrolyser. The effects of different working parameters on the cycle performance during charging and discharging processes are investigated using thermodynamic analysis. The results indicate that increasing the solar irradiation by 36%, leads to 13% increase in the exergy efficiency of the cycle. Moreover, the mass flow rate of the heat transfer fluid in solar system has a considerable effect on the exergy cost of output power. Solar tower has the highest exergy destruction and capital investment cost. The highest exergoeconomic factor for the integrated cycle is 60.94%. The steam turbine and PEM electrolyser have the highest share of exergoeconomic factor i.e., 80.4% and 50%, respectively.     

Thermodynamic analysis and optimization of an integrated solar thermochemical hydrogen production system

In this study, thermodynamic analysis of solar-based hydrogen production via copper-chlorine (Cu–Cl) thermochemical water splitting cycle is presented. The integrated system utilizes air as the heat transfer fluid of a cavity-pressurized solar power tower to supply heat to the Cu–Cl cycle reactors and heat exchangers. To achieve continuous operation of the system, phase change material based on eutectic fluoride salt is used as the thermal energy storage medium. A heat recovery system is also proposed to use the potential waste heat of the Cu–Cl cycle to produce electricity and steam. The system components are investigated thoroughly and system hotspots, exergy destructions and overall system performance are evaluated. The effects of varying major input parameters on the overall system performance are also investigated. For the baseline, the integrated system produces 343.01 kg/h of hydrogen, 41.68 MW of electricity and 11.39 kg/s of steam. Overall system energy and exergy efficiencies are 45.07% and 49.04%, respectively. Using Genetic Algorithm (GA), an optimization is performed to evaluate the maximum amount of produced hydrogen. The optimization results show that by selecting appropriate input parameters, hydrogen production rate of 491.26 kg/h is achieved.     

A critical review on integrated system design of solar thermochemical water-splitting cycle for hydrogen production

The development of clean hydrogen production methods is important for large-scale hydrogen production applications. The solar thermochemical water-splitting cycle is a promising method that uses the heat provided by solar collectors for clean, efficient, and large-scale hydrogen production. This review summarizes state-of-the-art concentrated solar thermal, thermal storage, and thermochemical water-splitting cycle technologies that can be used for system integration from the perspective of integrated design. Possible schemes for combining these three technologies are also presented. The key issues of the solar copper-chlorine (Cu–Cl) and sulfur-iodine (S–I) cycles, which are the most-studied cycles, have been summarized from system composition, operation strategy, thermal and economic performance, and multi-scenario applications. Moreover, existing design ideas, schemes, and performances of solar thermochemical water-splitting cycles are summarized. The energy efficiency of the solar thermochemical water-splitting cycle is 15–30%. The costs of the solar Cu–Cl and S–I hydrogen production systems are 1.63–9.47 $/kg H₂ and 5.41–10.40 $/kg H₂, respectively. This work also discusses the future challenges for system integration and offers an essential reference and guidance for building a clean, efficient, and large-scale hydrogen production system.     

Exergy and exergoeconomic assessment of hydrogen and cooling production from concentrated PVT equipped with PEM electrolyzer and LiBr-H2O absorption chiller

A novel solar based combined system is proposed to produce hydrogen and cooling. The presented cogeneration system is analyzed in detail from the viewpoints of exergy and exergoeconomic (exergy based economic analysis). The proposed system includes a concentrated PVT (CPVT), a single effect LiBr-H₂O absorption chiller and proton exchange membrane electrolyzer (PEM). Produced electrical power is consumed in the PEM electrolyzer to split water into oxygen and pure hydrogen while heat removal from the CPVT is done by the absorption chiller to guarantee its better performance. Second law analysis showed that, among the three different parts of the system, the most part of exergy destruction refers to the CPVT followed by absorption chiller unit and PEM electrolyzer. Also, it is observed that, among the absorption units' components, the highest percent of exergy destruction belongs to the generator which absorbs the heat from the CPVT. Moreover, exergoeconomic analysis revealed that the most important unit from the viewpoint of economic is the CPVT with the capital investment cost of 0.08946 $/h and an exergoeconomic factor of 28.82%.     

The evaluation of hydrogen production via a geothermal-based multigeneration system with 3E analysis and multi-objective optimization

In this study, a novel geothermal-based multigeneration system is designed and evaluated in energy, exergy and economic (3E) analyses. Besides 3E analyses, multi-objective optimization has been assessed to reach the highest exergetic effectiveness and the lowest total cost rate. To evaluate the designed plant, thermodynamic balance equations are assigned to all sub-systems found in the design. These equations are solved by using Engineering Equation Solver (EES) software. According to the analyses' results, with base parameters, total power production is 1951 kW, the hydrogen generation rate is 0.0015 kg/s, and the whole energy and exergy efficiencies are 59.53% and 53.17%. The economic analysis performed for the multigeneration system indicates that the total cost rate is 186 $/h, and the levelized energy cost is 0.102 $/kWh. These results indicate that the designed geothermal-based multigeneration system performs better than a single-generation plant in terms of efficiency and cost.