• Nuclear Engineering and Technology
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• v.39 no.1
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• pp.1-8
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• 2007

Hydrogen and electricity are expected to dominate the world energy system in the long term. The world currently consumes about 50 million metric tons of hydrogen per year, with the bulk of it being consumed by the chemical and refining industries. The demand for hydrogen is expected to increase, especially if the U.S. and other countries shift their energy usage towards a hydrogen economy, with hydrogen consumed as an energy commodity by the transportation, residential and commercial sectors. However, there is strong motivation to not use fossil fuels in the future as a feedstock for hydrogen production, because the greenhouse gas carbon dioxide is a byproduct and fossil fuel prices are expected to increase significantly. An advanced reactor technology receiving considerable international interest for both electricity and hydrogen production, is the modular helium reactor (MHR), which is a passively safe concept that has evolved from earlier high-temperature gas-cooled reactor (HTGR) designs. For hydrogen production, this concept is referred to as the H2-MHR. Two different hydrogen production technologies are being investigated for the H2-MHR; an advanced sulfur-iodine (SI) thermochemical water splitting process and high-temperature electrolysis (HTE). This paper describes pre-conceptual design descriptions and economic evaluations of full-scale, nth-of-a-kind SI-Based and HTE-Based H2-MHR plants. Hydrogen production costs for both types of plants are estimated to be approximately $2 per kilogram.

• Asian-Australasian Journal of Animal Sciences
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• v.24 no.4
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• pp.540-572
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• 2011

The present review focuses on the effects of energy intake on performance, changes in body tissue during lactation, and metabolic parameters in dairy cows. Especially, pre-partum nutrition and its influence on lactation are emphasized. In recent decades the increase in genetic potential of dairy cows has increased milk yield. This fact sharpens the problem of a negative energy balance in early lactation because the amount of energy required for maintenance and milk production exceeds the amount of energy cows can consume. Around parturition, reduced feed intake reinforces the situation. Continuing negative energy balance causes decreasing milk yield, fertility problems, and incidence of metabolic diseases. Hence, the cow has to rely on body reserves that were stored in late lactation and the dry period. It is evident that the nutritional status pre-partum acts as the key factor for milk yield and fertility parameters in the following lactation. Cows overfed during the foregoing gestation and which have gained large quantities of body fat have lower dry matter intake along with the need to mobilize larger quantities of body reserves in lactation. The milk yield in the following lactation is lower than in cows fed according to their requirements. Cows restrictively fed in late gestation have a higher feed intake in lactation and a lower mobilization of body reserves. The effect of energy intake post-partum plays only a minor role for performance parameters in lactation. Lipid mobilized from body reserves makes a substantial contribution to the energetic cost of milk production in early lactation and adipose tissue undergoes specific metabolic alterations. Adipose tissue is degraded to free fatty acids, which are used in liver for energy purposes. High lipid mobilisation promotes the development of a fatty liver and therefore a reduced gluconeogenesis.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.1
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• pp.39-44
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• 2023

Renewable energy such as solar and wind power is a resource that is sensitive to weather conditions and environmental changes. Since the amount of power generated by a facility can vary depending on the installation location and structure, it is important to accurately predict the amount of power generation. Using meteorological data, a data preprocessing process based on principal component analysis was conducted to monitor the relationship between features that affect energy production prediction. In addition, in this study, the prediction was tested by reconstructing the dataset according to the sensitivity and applying it to the machine learning model. Using the proposed model, the performance of energy production prediction using random forest regression was confirmed by predicting energy production according to the meteorological environment for new and renewable energy, and comparing it with the actual production value at that time.

• Journal of the Korean Institute of Gas
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• v.28 no.1
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• pp.44-52
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• 2024

This study presents a novel approach to hydrogen production by biogas from organic waste without CO₂ removal. A process model was developed to reduce the costs associated with biogas pretreatment and purification processes. Through optimization of heat exchange networks, the simulation aimed to minimize process costs, maximizing hydrogen production and flue gas temperature. The results reveal that the most efficient process model maximizes the flue gas temperature while following the constraint of the number of heat exchangers. These findings hold promise for contributing to the expansion of "Biogas-to-clean hydrogen" energy conversion technology.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.180.2-180.2
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• 2010

The purpose of this research is to analyze the sensitivity of WindSIM in complex terrain. As the flat areas for wind turbine installation become scarce globally, it becomes inevitable to install wind turbines in complex terrain. In order to predict annual energy production (AEP) in a more precise manner in complex terrain, it is of great importance to conduct such research. Three parameters: reference velocity, roughness and resolution have been chosen to see to which parameter WindSIM was the most sensitive in terms of annual energy production in complex terrain. By fixing two parameters and setting one parameter as a variable, it could be easily found that how annual energy production was effected by the change in each parameter.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.223-226
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• 2005

For $CO_2-free$ hydrogen production and better utilization of the produced carbon, catalytic decomposition of methane over rubber-grade carbon blacks manufactured from coal tar was carried out. The catalytic activities of several domestic carbon blacks were compared. A pelletized carbon black exhibited considerably lower activity and activation energy than the fluffy( loose) carbon black of the same grade. This difference is considered due to the binder that was added during pelletization. For pelletized carbon blacks, a tendency was observed that the activity per unit mass of catalyst increased with the specific surface area of the carbon black. Another tendency was also observed that the activation energy increased with the primary particle size or decrease of the specific surface area.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.312-314
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• 2008

This paper develops an algorithm for probabilistic production cost credit evaluation of wind turbine generators (WTG) with multi-state. Renewable energy resources such as wind, wave, solar, micro hydro, tidal and biomass etc. are becoming importance stage by stage because of considering effect of the environment. Wind energy is one of the most successful sources of renewable energy for the production of electrical energy. Case study demonstrates that the wind speed credit in view point of economics can be assessed by using the proposed methodology.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.5
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• pp.417-429
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• 2021

Due to fossil fuel depletion and environmental pollution, H2 production from organic waste has received an increased attention. In this study, we present an integrated process for the H2 production from biogas and evaluate the economic feasibility and sustainability via rigorous techno-economic analysis (TEA) and life-cycle assessment (LCA). Through the TEA, we determine the minimum H2 selling price using discounted cash flow analysis and investigate the main cost drivers. The environmental impact of the proposed process is quantified via LCA.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.2_1
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• pp.277-285
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• 2024

Hydrogen is considered a key energy source to achieve carbon neutrality through the global goal of 'net zero'. Due to limitations in producing green hydrogen domestically, Korean companies are interested in importing green hydrogen produced overseas. The Middle East has high-quality solar energy resources and is attracting attention as a region producing green hydrogen using renewable energy. To build a green ammonia plant, optimization of the production facility configuration and economic feasibility analysis are required. It is expected that it will contribute to reviewing the economic feasibility of constructing overseas hydrogen production plants through preliminary economic feasibility analysis.

• Korean Journal of Agricultural Science
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• v.50 no.3
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• pp.395-406
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• 2023

The large amount of energy required for successful crop production is the main challenge in greenhouse cropping systems. As a response to this challenge a comprehensive evaluation of greenhouse energy consumption was carried out in two structurally similar single-span greenhouses with different thermal curtain positions, with particular attention to energy productivity, specific energy, net energy, and energy ratio. The greenhouses are used for strawberry production. In the R-greenhouse (RGH), the thermal curtain hanged directly at the roof ridge, whereas in the Q-greenhouse (QGH), the thermal curtain was placed 5° from an imaginary vertical axis, from the middle of the roof ridge downwards to the north side of the greenhouse roof. The relevant data were recorded using standard methods. The results indicated that the energy expended in the RGH and QGH systems was 2,186.48 and 2,189.26 MJ/m², respectively. Electricity and nitrogen fertilizer contributed the highest energy input in both greenhouses and in all seasons. The output energy was 3.12 and 3.82 MJ/m², respectively, in RGH and QGH in season I and 4.40 and 4.87 MJ/m² in season II. In terms of energy expended, there was no significant difference between the two greenhouses, nor between the two seasons. These results indicate that greenhouses of the size used in this investigation are not viable in terms of energy productivity, energy-use efficiency, and subsequent economic performance. However, further studies should be conducted to scale-up the information obtained from this investigation.