1,721,136 research outputs found
Implementation of liquid organic hydrogen carrier in H2 society: Comprehensive feasibility study on H2 supply chain
No full textSchool of Energy and Chemical Engineering (Chemical Engineering)The environmental issues derived from the usage of fossil fuels as the primary energy source have led to numerous academic, industrial, and political efforts to develop a new energy paradigm. Owing to the significant benefits of H2 from an environmental point of view, various types of efforts to develop the related crucial infrastructure to adopt H2 as the next alternative energy carrier or as the fuel by direct usage have been actively introduced. Meanwhile, regarding one of the important challenges, storage and transportation of H2, in the accomplishment of the new energy paradigm based on H2, conventional methods via compression, liquefaction, and the metal hydride require additional energy to maintain the state or show very low storage density due to the intrinsic weight of the medium. To overcome obstacles of conventional methods to store and transport the hydrogen, the concept of liquid organic hydrogen carrier was introduced as it can store produced H2 in relatively high-pressure conditions ??? hydrogenation ???, exist as the liquid state even at the standard state,
release the stored H2 again by heat supply ??? dehydrogenation ??? and the liquid organic molecules used as the H2 carrier can be recycled in the H2 supply chain.
As the detailed and preliminary feasibility study should be preceded to realize the commercialization of the newly proposed technology, the feasibility analysis model for various H2 supply chains regarding both economic and environmental perspectives is developed here to quantitatively evaluate each investigated scenario. In addition, quantified economic and environmental feasibility of the hydrogenation and dehydrogenation using several liquid organic hydrogen carriers and ammonia is evaluated and used in the developed model to reflect much detailed impact of the concept of liquid organic hydrogen carrier on the H2 supply chain.
In this study, detailed process simulation of both hydrogenation and dehydrogenation processes for eight types of liquid organic hydrogen carrier candidates ??? N-ethylcarbazole, dibenzyltoluene, formic acid, methanol, naphthalene, methylcyclohexane, benzyltoluene, and benzene ??? and ammonia is conducted with the adoption of experimental reaction kinetics. The techno-economic analysis based on the quantified results for the performance of each investigated process obtained from the developed process simulation models is also performed to evaluate unit H2 supply cost for hydrogenation and dehydrogenation processes.
In addition, the environmental assessment in terms of carbon footprint analysis quantifies the CO2 emissions, which were both directly emitted from the reaction and converted by a certain CO2 emission factor.
For the H2 supply chain to H2 fueling stations in South Korea in this study, three types of H2 production methods of steam methane reforming, coal gasification, and water electrolysis are considered and 19 countries of Qatar, Australia, USA, Oman, Malaysia, Indonesia, and Russia as the main liquefied natural gas-abundant exporter, Australia, Russia, Indonesia, Canada, USA, South Africa, Columbia, and Republic of Mozambique as the main coal exporters, and China, USA, Germany, and Italy as main renewable energy exporters are assumed.
Each investigated H2 supply chain, after the production of H2 in each exporting country, consists of procedures of H2 conditioning via compressed H2, liquefied H2, liquid organic hydrogen carriers, or ammonia, short-term storage via cavern, high-pressure tank, cryogenic tank, or oil tank, inland transportation via pipeline or truck, pre-processing to liquefied H2, liquid organic hydrogen carriers, or ammonia, and post-processing to compressed H2, liquefied H2, liquid organic hydrogen carriers, or ammonia with quantified unit H2 supply cost and unit CO2 emissions in the H2 supply chain are quantified.
Based on the developed 520 H2 supply chains and feasibility study models, the effects of the H2 demand, CO2 capture rate, recycle ratio of liquid organic hydrogen carrier, and types of energy sources are investigated in economic, environmental, and comprehensive perspectives by adopting the technique for order of preference by similarity to ideal solution. For the effect of H2 demand, ammonia and methylcyclohexane, methanol and benzene, and ammonia are revealed as promising liquid organic hydrogen carrier candidates from economic,
environmental, and comprehensive points of view. Regarding the effect of the CO2 capture rate, the methanol-based H2 supply chain is suggested as the most environmentally feasible under all CO2 capture rates investigated and the novelty of full adoption of ammonia in the H2 supply chain is shown again in the comprehensive point of view. The analysis of the effect of recycle ratio of liquid organic hydrogen carrier also reveals the novelty of full utilization of ammonia and selective adoption of methylcyclohexane in the H2 supply chain from both economic and environmental points of view. Similar to the effect of recycle ratio of liquid organic hydrogen carrier, full utilization of ammonia and selective adoption of methylcyclohexane show its significant novelty regardless of types of energy sources.
From this dissertation, the feasibility study on the liquid organic hydrogen carrier -implemented H2 supply chain model is developed and economic and environmental promises of the concept of liquid organic hydrogen carrier are suggested.clos
Highly efficient H2 production process by simultaneous H2 production and CO2 capture: Process simulation and techno-economic analysis
No full textSchool of Energy and Chemical Engineering (Chemical Engineering)Since the Industrial Revolution, ongoing CO2 emissions have caused an environmental issue, global warming. The environment of Earth has been influenced by the climate crisis, which has resulted in a rise in sea levels and frequent natural catastrophes, such as floods and drought. Worldwide nations agreed to address the climate crisis represented by ???Paris Agreement???, aiming to restrict the global average temperature rise below 2 ???, preferably 1.5 ???. In this situation, the renewable energy generated by natural resources such as solar, wind, and so on, is used to replace the carbon-based energy paradigm and achieve the Net Zero. Hence, the renewable energy capacity has grown rapidly as time passed. To store renewable energy, H2 is one of the attractive options in terms of clean production and combustion, durability, and utilization. In addition, H2 is a major component in the refining industry and NH3 production, resulting in a rise in demand for H2. However, most of the H2 is produced using a steam methane reforming process, which emits CO2 due to its low production cost. The H2 should be produced by water electrolysis using renewable energy to achieve carbon neutrality and for a sustainable energy society in the future. Here, a highly efficient H2 production system was proposed as a bridge between current steam methane reforming and the upcoming water electrolysis technology to produce H2. The H2 selective membrane and CO2 adsorbent are used in the proposed method by removing the product (i.e. H2 and CO2) from the reaction site and resulting in a positive equilibrium shift according to Le Chatelier???s Principle. Therefore, process simulation and techno-economic analysis were carried out to evaluate the proposed approach and provide technical and economic insights. For the process simulation, the reactor scale, lab scale, and industrial scale of H2 production were addressed, and a techno-economic analysis included itemized cost estimation, sensitivity analysis, feasibility analysis, and uncertainty analysis.
Based on the reactor scale process design, the effect of sweep gas direction was investigated by a 1D numerical analysis model. And it was revealed that counter-current flow could enhance the H2 permeation amount compared to the co-current flow based on the partial pressure difference. The impact of the employment of an H2 selective membrane and CO2 adsorbent was verified by showing the highest H2 production rate and the lowest CO2 emissions from the sorption-enhanced membrane reactor, which uses the membrane and adsorbent together.
Based on the lab-scale process design, the thermodynamic performance of the conventional reactor, membrane reactor, and sorption-enhanced membrane reactor, was compared in terms of H2 production, CO2 emission, and CH4 conversion. The sorption-enhanced membrane reactor presented the best performance among the three reactorshowever, the lowest levelized cost of H2 was observed for the membrane reactor due to low equipment cost. It was revealed that the levelized cost of H2 of three reactors was still challenging to reach to the one from the current method even though variation of natural gas price and CO2 tax credit was considered.
Based on the industrial scale process design, the process performance and economic feasibility were investigated depending on operating temperature. The amount of H2 production increased and levelized cost of H2 decreased according to the increase in the operating temperature. The levelized cost of H2 of $ 2.27 kgH2-1 was obtained at 700 ??? and the natural gas price was figured out as the critical factor to the levelized cost of H2. In addition, it was unveiled that the positive net present value was observed when the operating temperature was above 600 ??? and the net present value was greatly affected by H2 selling price, which was directly related to the profit.clos
Techno-economic and environmental assessment of PEM water electrolysis for green H2 production
Full text linkSchool of Energy and Chemical Engineering (Chemical Engineering)With the increased interest in environmental issues, green H2 production technology, which split H2O into H2 and O2, using electricity generated from renewable energy sources, has received much attention to de-carbonize the energy production and to achieve carbon neutrality by 2050. Green H2 is a carbon-free energy carrier, but higher unit H2 production cost from green H2 production owing to the high water electrolysis system price as well as the levelized cost of electricity generated from renewable energy sources than one from grey H2 production (i.e., methane steam reforming without carbon capture and storage), is to be solved for the realization of green H2 society. Therefore, a techno-economic assessment was conducted for green H2 production by polymer electrolyte membrane water electrolysis using electricity generated from solar photovoltaic, onshore wind, and hydropower, to identify the effect of electrochemical parameters on H2 yield, to assess the economic feasibility for current and future level based on process simulation results, and to identify how to make this technology cost-competitive by considering scale-up, technology development of polymer electrolyte membrane water electrolysis system, manufacturing cost reduction by learning-by-doing effect, and the decrease in levelized cost of electricity, increasing in the installed renewable energy capacity, in terms of capital and operating cost reduction in this work.
Based on techno-economic analysis results, economic parity analysis on green H2, which is a switching point to be equal or less than unit H2 production cost from green H2 production compared to one from grey H2 production, was performed to investigate when H2 parity can occur and then it can be clearly shown that only green H2 production using solar photovoltaic-based electricity happens to H2 parity in approximately 2040 and 2025, in current and future level, respectively.
In addition, life cycle assessment was carried out to identify the environmental impacts such as CO2 emission for global warming, ozone depletion, and fine particular matter formation, for overall green H2 production through SimaPro and find out hot-spot to account for the large portion of total environmental impacts for the entire process.
From life cycle assessment results, green H2 production using hydropower-based electricity is higher CO2 emissions than other renewable energy sources (solar photovoltaic and onshore wind) as well as even grey H2 production. Onshore wind is the best candidate as a renewable energy source for electricity generation, in terms of environmental impact.
Taken together, the analytic hierarchy process, which is one of the multi-criteria decision analyses, was conducted to determine the appropriate renewable energy source for green H2 production by polymer electrolyte membrane water electrolysis based on different weighted values of techno-economic and environmental results, under determination and uncertainty.
From analytic hierarchy process results, it can be shown that onshore wind is the attractive renewable energy source for green H2 production, when considering techno-economic and environmental aspects, simultaneously, although the best alternative should be changed according to the weighted value of criterion. Furthermore, hydropower is the most suitable renewable energy source for green H2 production at the current level, when economic feasibility is the important factor, because the levelized cost of electricity from hydropower is cheaper than others at the current level, resulting in the lower unit H2 production cost. However, the higher levelized cost of electricity due to the lower installed hydropower capacity as well as environmental issues can lead to the worst alternative to the renewable energy source for green H2 production at the future level. In the same way, relatively higher CO2 emission can result in the second alternative for solar photovoltaic, when considering high weighted values of environmental criterion, although green H2 production using solar photovoltaic-based electricity has the lowest unit H2 production cost in the future.
Therefore, techno-economic analysis, as well as environmental impact assessment results, should be taken into account, simultaneously, to determine the most appropriate renewable energy source for green H2 production by polymer electrolyte membrane water electrolysis.ope
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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