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Hydrogen is one of the highly promising clean solutions to address the concerns of energy security in the future given the rapid rate of depletion of naturally occurring hydrocarbon sources. However, it is of immense importance that hydrogen is obtained through sources that ensure sustainability. Thermochemical water-splitting processes are among such routes of hydrogen production that are both sustainable and environmentally benign. Thus, this study focuses on assessing the copper-chlorine thermochemical cycles that are among the more promising cycles of the chlorine family in terms of efficiency and cost-effectiveness. Moreover, this study considers a comparative exergoenvironmental evaluation of the four variants of the copper-chlorine cycle that vary in the number and the nature of steps. A comparison in this regard is carried out between the various steps of each cycle in terms of the component-associated environmental impact rates and environmental impact rates of energy transfer as well as the overall environmental impacts of all cycles. In addition, a comparison of the global warming potential of hydrogen synthesized through utilizing various electricity sources is also performed. Based on our evaluations, hydrolysis and electrolysis are the common steps in the five-step cycle, the four-step cycle, and the three-step cycle configuration 1 yielding the highest component-associated environmental impact rates and environmental impact rates of energy transfer, respectively. Conversely, in the three-step cycle configuration 2, the electrolysis and thermal decomposition steps yield the highest corresponding values, respectively. In addition, the three-step cycle configuration 2 (4,869 mPts/h) and the five-step cycle (3,194 mPts/h) have the highest and the lowest component-associated environmental impact rates, respectively while the five-step (530,694 mPts/h) and the four-step (248,050 mPts/h) cycles result in the highest and the lowest environmental impact rates of energy transfer, respectively. • Exergoenvironmental analyses of three variants of Cu–Cl thermochemical cycle. • Comparison of environmental impact rate of energy transfer. • Comparison of component-associated environmental impact rate. • Comparison of global warming potential for various electricity sources. [ABSTRACT FROM AUTHOR]

Thermochemical water-splitting cycles have the potential of producing large-scale and cost-effective sustainable hydrogen in an environmentally benign manner. Limited exergoenvironmental assessments have been reported in the literature which generally considers thermochemical hydrogen production and specifically the copper-chlorine (Cu–Cl) cycle in thid regard. Thus, the present investigation aims at assessing the four-step integrated Cu–Cl thermochemical cycle set-up located at the Ontario Tech University thereby contributing to the environmental impact assessment of thermochemical hydrogen production. In this study, the exergy analysis of the cycle is first performed by thermodynamically modeling and simulating the cycle in Aspen-plus. The fundamental principles of the exergoenvironmental analysis, analogous to the specific exergy costing (SPECO) methodology of the exergoeconomic evaluation, are applied to the cycle and the balanced environmental impact equations for all cycle components are developed. Based on the balanced environmental impact equations, the environmental impact rate, and the specific environmental impact at each state point is evaluated. The environmental impact levels for all the major cycle components are also obtained. The exergoenvironmental factor, the relative difference of the specific environmental impacts, and the environmental impact rate of exergy destruction for various cycle components are in this regard evaluated. Furthermore, the influence of various parameters on the cumulative and component-related rate of environmental impact as well as the exergoenvironmental factor is analyzed by conducting a detailed sensitivity analysis. According to the obtained results, the rate of environmental impact corresponding to exergy destruction dominates the component-related rate of environmental impact and thus the potential reduction in the cumulative environmental impact for various components could be achieved by improving their exergy efficiencies. The hydrolysis step accounts for 60% of the component-related environmental impact while the thermolysis step accounts for the highest environmental impact of exergy destruction ranging between 41 and 42%. The percentage difference between fossil fuel-based and renewable electricity in terms of the global warming potential ranges between 80% and 98% with the highest difference for wind and nuclear-based electricity. • Exergoenvironmental analysis of an integrated copper-chlorine thermochemical cycle. • Hydrolysis step has the highest component-related environmental impact. • Thermolysis step has the highest environmental impact of exergy destruction. • Hydrogen production capacity of 1296 kg/h. [ABSTRACT FROM AUTHOR]

This paper presents a thermodynamic study on a newly built lab-scale thermochemical copper-chlorine (Cu-Cl) cycle installed at the Clean Energy Research Laboratory (CERL) at the Ontario Tech University. This study analyzes every component of the system through energy and exergy analysis by considering the heat inputs, outputs and exergy destruction within the various units of the Cu–Cl cycle. The system is modeled and simulated using the Aspen-plus software. The mass, energy and exergy balance equations for each system component are written for analysis and assessment purposes. Based on the analysis, the maximum heat input is required for the hydrolysis reactor while the HCl-condenser-1 is found to reject the maximum heat. The results suggest that the thermolysis reactor experienced the highest exergy destruction. The effect of the flow rates of certain species within the cycle on the performance of various system units, such as heat transfer rates and production flow rates are also investigated. The overall energy and exergy efficiencies of the system are evaluated to be 6.8% and 10.4%, respectively. • Thermodynamic analysis of a new copper-chlorine thermochemical cycle. • Mass, energy, entropy and exergy balance-based investigation. • Overall system energy and exergy efficiencies of 20.9% and 31.46% respectively. • Hydrogen production rate of 1.62 kg/h. [ABSTRACT FROM AUTHOR]