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The hydrogen liquefaction process is highly energy-intensive owing to its cryogenic characteristics, and a large proportion of the total energy is consumed in the subcooling cycle. This study aimed to develop an efficient configuration for the subcooling cycle in the hydrogen liquefaction process. The He-Ne Brayton cycle is one of the most energy-efficient cycles of the various proposed hydrogen liquefaction processes, and it was selected as the base case configuration. To improve its efficiency and economic potential, two different process configurations were proposed: (configuration 1) a dual-pressure cycle that simplified the process configuration, and (configuration 2) a split triple-pressure cycle that decreased the flow rate of the medium- and high-pressure compressors. The ortho–para conversion heat of hydrogen is considered by using heat capacity data of equilibrium hydrogen. Genetic algorithm-based optimization was also conducted to minimize the energy consumption of each configuration, and the optimization results showed that the performance of configuration 1 was worse than that of the base case configuration. In this respect, although less equipment was used, the compression load on each compressor was very intensive, which increased the energy requirements and costs. Configuration 2 provided the best results with a specific energy consumption of 5.69 kWh/kg (3.2% lower than the base case configuration). The total expense of configuration 2 shows the lowest value which is USD 720 million. The process performance improvements were analyzed based on the association between the refrigerant composition and the heat exchange efficiency. The analysis demonstrated that energy efficiency and costs were both improved by dividing the pressure levels and splitting the refrigerant flow rate in configuration 2. [ABSTRACT FROM AUTHOR]

Summary: This study mainly focuses on determining the optimal configuration that efficiently utilizes liquefied natural gas (LNG) cold energy in hydrogen precooling for liquid hydrogen production. To achieve this goal, two different configurations are designed: (a) adding LNG cold energy to the existing hydrogen precooling cycle and (b) replacing the existing hydrogen precooling cycle with LNG cold energy. An equilibrium hydrogen model is developed to reflect the thermodynamic property of ortho‐para conversion of hydrogen. Bayesian optimization is performed to determine the optimal operating conditions which minimize the specific energy consumption for all configurations. The specific energy consumption of the configuration involving hydrogen precooling with only LNG is 5.613 kWh/kg‐LH2, and it is reduced by 8.13% and 3.19% from the base case design and the configuration involving hydrogen precooling with both LNG and a mixed refrigerant cycle, respectively. In addition, a techno‐economic analysis is conducted. Compare to the base case design, the capital cost and operating cost of the design replacing hydrogen precooling with LNG are reduced by 31.76% and 11.55%, respectively. This study shows that the proposed design of replacing the hydrogen precooling cycle with an LNG stream can save energy consumption, moreover, it is highly effective for capital investment saving due to its simple configuration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon dioxide electrolysis was utilized to enhance hydrogen production performance. • A techno-economic analysis was conducted and compared with the conventional process. • Energy efficiency, economic viability, and environmental impact were all improved. • Flexibility of production is enhanced to adapt to fluctuating market conditions. • Methane leakage and carbon tax have relatively minor impact on proposed process. Conventional blue hydrogen production still leads to direct carbon emissions, as well as significant energy consumption and costs for carbon dioxide (CO 2) capture. CO 2 electrolysis, which is one of the promising carbon utilization technologies, faces challenges beyond cell performance, including downstream separation. To address these issues, this study proposes a novel hydrogen production process integrated with CO 2 electrolysis. Four integrated processes were developed based on two types of CO 2 electrolysis in which cathode separation was either included or excluded. These integrated processes eliminate atmospheric carbon emissions from fossil-fuel-based hydrogen production without requiring a carbon capture unit; furthermore, the hydrogen yield increases. These processes were evaluated in terms of energy efficiency (EE), levelized cost of hydrogen (LCOH), and process carbon emission (PCE). Among the developed processes, the high temperature CO 2 electrolysis without cathode separation (HT-CO 2 EL(w/oSep)) process exhibited the lowest LCOH and PCE. These findings demonstrate that proposed process effectively addresses the challenges associated with downstream separation and upstream heating inherent in standalone CO 2 electrolysis systems. Compared with conventional blue hydrogen production, the HT-CO 2 EL(w/oSep) process achieved 22.2% improvement in EE, 12.0% reduction in LCOH, and 82.0% decrease in PCE. Sensitivity analysis shows that the proposed process remains economically viable compared to conventional blue and green hydrogen and is more adaptable to market fluctuations. The improvement in cell performance is expected to contribute to cost savings. Even accounting for methane leakage and carbon taxes, the process shows only a modest increase in total carbon emissions and LCOH. [ABSTRACT FROM AUTHOR]

In the transition of the global energy paradigm toward decarbonization, hydrogen is expected to play a crucial role as an energy vector. To enhance the sustainability of hydrogen as an energy source, it is important to reduce costs and carbon emissions in the hydrogen production. Among various hydrogen production technologies, the autothermal reforming (ATR)-based blue hydrogen production method can stand out as a promising option in terms of both economic and environmental considerations. However, there are several bottlenecks: (i) ATR requires an air separation unit that increases the cost burden, and (ii) conventional amine-based carbon capture method consumes a significant amount of energy. To address these bottlenecks, this study proposes a novel cryogenic carbon capture process for ATR-based blue hydrogen production. In the proposed process, air separation unit are utilized not only for oxygen production but also for carbon capture. The compressed air from the air separation unit provides cooling energy to the mixture gas, leading to solidification and separation of carbon dioxide. Despite imposing an additional burden on the air separation unit, it significantly reduces the energy and cost associated with carbon capture. Consequently, there exists a trade-off relationship between the increased load on the air separation unit and the decreased load in carbon capture. This trade-off was evaluated by comparing it with the conventional absorption-based carbon capture process in terms of energy and economic aspects. The proposed process exhibits a 36.4% reduction in total energy consumption, with a particularly approximately 49.5% decrease in the energy consumed for carbon capture (0.278 kW h/kg-CO 2). The economic performance indicates an 11% decrease in the levelized cost of hydrogen (1.62$/kg-H 2), and a 45.3% decrease in CO 2 avoidance cost (40.1$/kg-CO 2). The captured solid CO 2 can offer advantages during storage and transportation. Furthermore, the potential utilization of cooling energy of solid CO 2 from an end-user perspective is expected to contribute to the establishment of a new industrial value chain. [Display omitted] • A novel cryogenic CO 2 capture process is proposed for ATR hydrogen production. • The proposed process imposes a slight burden on the ASU but simplifies CO 2 capture. • In terms of overall H 2 production, an energy saving of 36.4% was achieved. • LCOH and CO 2 avoidance cost are 1.62$/kg-H 2 and 40$/kg-CO 2 , respectively. • The economic viability variations across diverse carbon scenarios were evaluated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hybrid blue and green H 2 co-production system is developed. • Proposed system addresses each bottleneck in ATR and SOEC-based H 2 production. • The hybrid ATR–SOEC system can reduce energy consumption by up to 28.6%. • The levelized cost of hydrogen for this system is as low as $5.28/kg. Hydrogen is a clean and sustainable energy alternative to fossil fuels. Current hydrogen production methods are carbon intensive; hence, developing low-carbon hydrogen production methods is important. Among various production technologies, autothermal reforming (ATR) and solid oxide electrolysis (SOEC) are considered promising in terms of energy efficiency. However, there are several limitations: (i) ATR requires an air separation unit that consumes a large amount of energy, and (ii) SOEC, high-temperature steam electrolysis requires an electric resistance heater. To address these limitations, this study proposes a hybrid system of ATR integrated with SOEC. In the hybrid system, waste steam and heat in the ATR process are provided for the SOEC process, whereas the oxygen by-product in the SOEC process is supplied to the ATR process. In particular, the hybrid system where SOEC-generated oxygen completely satisfies the ATR reaction's oxygen demand exhibits the best thermodynamic and economic performance. This system represents a 28.6% reduction in power consumption compared to a stand-alone system that independently produces blue and green hydrogen. In addition, it exhibits enhanced economic performance with a levelized cost of hydrogen of 5.28 $/kg, which is 1.22 $/kg lower than that of the stand-alone system. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel process-level carbon contribution analysis (PCCA) method was proposed. • PCCA framework overcomes the limitations of LCA for process CO 2 evaluation. • The developed framework was applied to the naphtha cracking center. • A detailed and quantitative analysis was conducted on the CO 2 emissions. • The amount of CO 2 emissions was reduced by 8.68% compared with the base case. A well-known method for the environmental impact analysis of the chemical processes, life cycle assessment (LCA) has several limitations to apply to the process design and optimization stages. To overcome these limitations, this study proposed a novel carbon analysis and reduction method at the process level. The proposed LCA-free framework consists of four steps: process simulation, thermodynamic analysis, process-level carbon contribution analysis (PCCA), and carbon optimization. PCCA allows a detailed analysis of the CO 2 contribution of each component by mapping exergy information to the CO 2 emission. By applying the proposed method to the naphtha cracking center to minimize CO 2 emissions, CO 2 from utilities can be reduced by 8.72%. Compare to energy optimization, carbon optimization under the PCCA framework shows there is an optimal operating condition that emits less CO 2 even though requires more utility duty. The proposed framework has four clear advantages: (i) it can estimate tailored emission factors for target processes at the process level, instead of relying on average values in conventional inventory, (ii) optimize the usage of utilities by type at the process design stage from a carbon perspective, (iii) provide a direction for economic optimization by giving information on the relationship between carbon emissions and energy consumption, and (iv) quantify the reduction in carbon emissions compared to existing processes when designing newly designed carbon reduction processes. Consequently, this study establishes a powerful methodology for the rigorous carbon emission analysis for chemical processes and offers guidelines for carbon reduction at the process level. [ABSTRACT FROM AUTHOR]

Artificial intelligence has recently seen tremendous growth, and been applied to several fields, including the second-language domain. In this article, we share an innovative practice based on one of potential artificial intelligence technologies for second-language teaching and learning – artificial intelligence-based content generator, which generates texts based on user's keywords. In total, 121 young English-as-a-foreign-language learners participated in the study, with half of them having engaged in the artificial intelligence-based content generator-based activity, and the other half having received traditional English-as-a-foreign-language reading instruction. We examined the extent to which the artificial intelligence-based content generator-based activity could influence the participants' foreign language enjoyment and interests in reading English books, and the participants were given the survey addressing these variables, prior to and after the innovative practice. It was found that the condition based on the artificial intelligence-based content generator-based activity was more effective in terms of enhancing the target variables, and that the group which engaged in the artificial intelligence-based content generator-based activity was largely in favor of artificial intelligence-based content generator technology. Pedagogical implications for employing this technology in second-language contexts are provided. [ABSTRACT FROM AUTHOR]

Summary: This study focuses primarily on improving large‐scale hydrogen liquefaction process by integrating liquefied natural gas (LNG) stream to utilize LNG cold energy. For the hydrogen liquefaction process, a large amount of energy is required for the compression and the cryogenic refrigeration system. LNG is one of the main sources for producing hydrogen, and it can be an opportunity to save energy because LNG cold energy is normally discarded into seawater during regasification. The objective of this study is to reduce the specific energy consumption and specific liquefaction cost. The proposed design which produces 300 ton/day of liquid hydrogen is compared with a base case design comprising two‐stage mixed refrigerant refrigeration cycles. To minimize the specific energy consumption, multiparameter optimization is conducted by connecting simulation results to a genetic algorithm. Through the optimization, the flow rates of LNG and MR in the precooling cycle decrease by 1.08 and 21.00 kg/s, respectively. The specific energy consumption is reduced from 4.36 to 4.07 kWh/kg‐LH2. Particularly, in the precooling cycle where the LNG stream is integrated, it decreases by more than 26.40%. Regarding the specific liquefaction cost of hydrogen liquefaction, the capital expenses are reduced by 15.16%, and annual operating expenses are diminished by 9.05%. Therefore, the total specific cost liquefaction shows a reduction of approximately 7.7%. Overall, an efficient hydrogen liquefaction process will provide a guideline for LNG‐dependent countries by reducing the specific energy consumption and the specific liquefaction cost by recovering the waste cold energy. [ABSTRACT FROM AUTHOR]

Building on the work of customized chatbots for language teaching and learning and the second-language acquisition literature on corrective feedback (CF), this article showcases an innovative practice for building a tailored and task-based chatbot to provide CF. Given that extant chatbots are generally not sensitive to learners’ grammatical errors, we illustrate a way to install a CF function by using ‘action and parameters’ and ‘define prompts’ options in the chatbot-building platform known as Google DialogflowTM. Our study, which included upper-grade English-as-a-foreign language learners in South Korea, demonstrated that customized chatbots could offer CF when students made non-target utterances and elicit learner uptake successfully. Based on our innovation, we then provide directions for pedagogy on chatbot-based language learning. [ABSTRACT FROM AUTHOR]

A novel power-management-system design coupling liquid air energy storage (LAES) with liquefied natural gas (LNG) regasification is proposed that combines flexibility in responding to power demand, presented high energy efficiency and capacity. The proposed liquefied natural gas-thermal energy storage-liquid air energy storage (LNG-TES-LAES) process uses LNG cold energy via two different mechanisms. During on-peak times, when the proposed process requires no power consumption to meet the relatively higher electricity demand, LNG cold energy is recovered and stored via liquid propane. During off-peak times, the proposed process uses both cold energy from LNG and liquid propane, effectively doubling the cold energy available and enhancing the process flexibility. The liquid propane cold energy is used for air compression to reduce the power input requirement, while LNG cold energy is used mainly to liquefy air. These unique features afforded an electrical round-trip efficiency of 187.4% and an exergy efficiency of 75.1%, which are the highest among recently reported values. The energy capacity for the regasification of 1 MTPA LNG was 12.14 MW, which is adequate for bulk power management systems. By adopting flexibility, LNG cold energy has been distributed efficiently, and where LNG could be continuously regasified in the energy storage/release processes. • The proposed energy storage mechanism operates via multiple time-based modes. • LNG cold energy was effectively used for air liquefaction and air compression. • Electrical round-trip efficiency reached 187.4%, which is the highest recent value. • Exergy efficiency reached 75.1%, and the process is economically feasible. • The proposed process enabled flexible operations depending on energy demand. [ABSTRACT FROM AUTHOR]

Exergoeconomic optimization of the production of liquid air by utilizing the cold energy of liquefied natural gas (LNG) was undertaken for the first time. LNG cold energy, which is generally wasted in commercial regasification, can potentially be harnessed to produce liquid air. By using an exergoeconomic approach, the optimal design for reducing the specific energy consumption in the production of liquid air was determined, affording a 7.45% reduction in the specific energy consumption. Thermodynamic analysis revealed that the specific energy consumption could be minimized by using the optimized portion of LNG cold energy. Economic study indicated that the optimized system also afforded a 4.61% reduction in the total cost. Beyond this, the effects of both increasing and decreasing the energy recovery operations were investigated, from which the most cost effective process flow was determined. In conclusion, the most cost effective strategy for reducing the specific energy consumption for liquid air production does not necessarily require using the largest proportion of LNG cold energy. This is because although adding equipment reduces the energy consumption, it also increases the total costs beyond an optimal point. These are important findings for advancing the effort to efficiently utilize LNG cold energy. • Exergoeconomic aspects were revealed for liquid air production via LNG cold energy. • The use of LNG cold energy was optimized for more efficient liquid air production. • Cost based optimum was found as function of the number of energy recovery stages. • Optimization gave reductions of 7.45% in the energy required and 4.61% total cost. [ABSTRACT FROM AUTHOR]