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At present, the circular economy is emerging as a strategy for sustainable development. What is important in promoting the circular economy is to assess its current level and take measures for assessment. This paper discusses some methodological issues in comparing and assessing the efforts for the circular economy at the international level. To this end, the authors explain the theoretical premise related to the assessment of efforts for the circular economy, establish an indicator system for assessing the efforts for the circular economy, and suggest a method for comprehensively assessing the efforts for the circular economy by country. The conclusions are that (a) the comparative evaluation of activities related to the circular economy by country requires a unified standard or category that can cover these activities, including all factors that meet sustainable development; the outcome, process, and guarantee of the circular economy, and this can be the circular economy effort and (b) the circular economy effort of a given country must synthetically be assessed by using the indicators capable of showing all aspects. These conclusions may contribute to establishing a new theoretical foundation that can include various aspects of the circular economy activities and to setting a practical and methodological foundation for evaluating each country's various activities related to the circular economy at the international level and can serve as a policy basis for identifying the weak and strong aspects of circular economy activities at the domestic or international level and establishing technological and economic measures to strengthen the weak aspects. [ABSTRACT FROM AUTHOR]

The railway power conditioner-based energy storage system (RPC-based ESS) is a promising technology to improve the regenerative braking energy (RBE) utilization and power quality of ac direct-fed (25 kV) and AT-fed (2 × 25 kV) railway power systems. However, despite its benefits from the technical perspective, economic viability must be concerned in industrial applications. The capacity is one of the critical issues affecting ESS performance in technical and economic aspects. Therefore, this paper presents a comprehensive approach to designing the capacity for the RPC-based ESS by considering multiple objectives, including the RBE utilization rate, power quality standard, and net lifetime benefit. The proposed approach develops a technical-economic model for the RPC-based ESS based on variables such as the system capacity for RBE utilization and power quality improvement, lifetime cost, and electric charge-based benefits. Moreover, the master-slave control strategy is employed to control the RPC-based ESS to implement the capacity design objectives. Finally, the correctness and effectiveness of the proposed method are validated by sufficient tests based on field load data of a Chinese traction substation. [ABSTRACT FROM AUTHOR]

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. • Exergoeconomic and exergoenvironmental assessement of copper-chlorine cycle. • Comparative evaluation of cycle operating with and without waste heat recovery. • Comparative evaluation of the modified and existing integrated cycles. • Evaluation of exergy and unit exergy cost at each state point of the cycle. [ABSTRACT FROM AUTHOR]