• Tribology and Lubricants
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• v.40 no.3
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• pp.71-77
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• 2024

Hydrogen has emerged as an eco-friendly and sustainable alternative to fossil fuels. However, the utilization of hydrogen requires high-pressure compression, storage, and transportation, which poses challenges to the durability of compressor components, particularly the diaphragm. This study aims to improve the durability of 304 stainless steel diaphragms in hydrogen compressors by optimizing their surface roughness and corrosion resistance through wet etching. The specimens were prepared by immersing 304 stainless steel in a mixture of sulfuric acid and hydrogen peroxide, followed by etching in hydrochloric acid for various durations. The surface morphology, roughness, and wettability of the etched specimens were characterized using optical microscopy, surface profilometry, and water contact angle measurements. The friction and wear characteristics were evaluated using reciprocating sliding tests. The results showed that increasing the etching time led to the development of micro/nanostructures on the surface, thereby increasing surface roughness and hydrophilicity. The friction coefficient initially decreased with increasing surface roughness owing to the reduced contact area but increased during long-term wear owing to the destruction and delamination of surface protrusions. HCl-30M exhibited the lowest average friction coefficient and a balance between the surface roughness and oxide film formation, resulting in improved wear resistance. These findings highlight the importance of controlling the surface roughness and oxide film formation through etching optimization to obtain a uniform and wear-resistant surface for the enhanced durability of 304 stainless steel diaphragms in hydrogen compressors.

• Tribology and Lubricants
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• v.40 no.3
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• pp.78-83
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• 2024

The development of eco-friendly alternative energy sources has become a global priority owing to the depletion of fossil fuels and an increase in environmental concerns. Hydrogen energy has emerged as a promising clean energy source, and hydrogen compressors play a crucial role in the storage and distribution of compressed hydrogen. However, harsh operating conditions lead to the rapid deterioration of conventional lubricants in hydrogen compressors, thereby necessitating the development of advanced lubrication technologies. This study introduces micrometer-sized silicone rubber powders as lubricant additives to enhance the lubrication performance of hydraulic oils in hydrogen compressors. We prepare silicone rubber powders by varying the ratio of the silicone rubber base to the curing agent and investigate their effects on interfacial properties, friction behavior, and wear characteristics. The findings reveal that the incorporation of silicone rubber powders positively influences the surface affinity, wettability, friction reduction, and wear resistance of the lubricants on the 304SS substrate. Moreover, we identify the optimal lubricant formulations, with a 15:1 ratio demonstrating the most effective friction reduction and a 5:1 ratio exhibiting the highest wear resistance. The controlled surface modification by the silicone rubber powder and the enhanced interfacial characteristics of the powder-containing lubricants synergistically contribute to the improved lubrication performance. These results indicate the potential of silicone rubber powder additives for the development of long-life lubrication solutions for hydrogen compressors and related applications, ultimately contributing to the advancement of sustainable energy technologies.

• Journal of Hydrogen and New Energy
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• v.35 no.4
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• pp.401-409
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• 2024

The maritime industry, responsible for 80% of global freight transport, heavily pollutes the environment through traditional fossil fuels. The International Maritime Organization aims to reduce sulfur and greenhouse gas emissions, but faces technical and financial challenges. Hydrogen fuel cells present a promising alternative with high efficiency and low emissions. This study examines the legal and regulatory frameworks needed for hydrogen bunkering across land, port, and sea. Key legislation includes the High-pressure Gas Safety Control Act, Hydrogen Economy Promotion and Hydrogen Safety Management Act, Harbor Act, Harbor Authority Act, Marine Transportation Act, and Harbor Transport Business Act. The study identifies overlapping regulations and proposes integrated solutions. The findings underscore the necessity of strict safety standards and legislative amendments to recognize hydrogen as a ship fuel. Establishing a comprehensive legal framework is essential for safe and efficient hydrogen bunkering. Continuous updates through international cooperation and standardized regulations are crucial for adopting hydrogen fuel cells, ensuring a sustainable and environmentally friendly maritime industry.

• Ocean Systems Engineering
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• v.14 no.3
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• pp.211-235
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• 2024

Th COP28 has emphasized the governments to speed up the transition away from fossil fuels to renewables such as wind and solar power in their next round of climate commitments. The steady and less turbulent wind over the ocean draws increased attention of governments, industries and researchers on exploring advanced technologies to extract energy from offshore wind. The present study numerically investigates the hydrodynamic behavior of a SPAR-type Floating Offshore Wind Turbine (FOWT) under various wave conditions and mooring line configurations. One of the major focuses of this study is investigating a freak wave's impact on a FOWT and determining its extreme responses. The study investigates the structural response under various wave impact for different configurations of mooring lines. The present study examines the wave-structure interaction under regular and freak wave conditions using numerical modelling approach. During the study, it is ensured that the natural frequency and wave induced motions of SPAR are inline with the experimental studies; thereby increasing the confidence in using the numerical model and domain for this investigation. The study considers the behaviour of slack and taut mooring arrangements under these wave conditions. The study observed that a taut mooring configuration can be efficient in restraining the FOWT motions, especially under a freak wave scenario. The Froude-Krylov force shows a non-linearity due to the non-uniform profile of the platform under all wave conditions. Overall, the study contributes to determining the performance of the mooring configurations under different wave conditions.

• Composites Research
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• v.37 no.4
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• pp.286-290
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• 2024

The rapid increase in the demand for energy has put huge pressure on fossil fuels. The continuous overutilization of these existing non-renewable energy sources has been causing severe environmental concerns. In these regards, electrochemical water splitting has gained huge attention for producing green hydrogen, a superior energy source with high gravimetric energy density (120 MJ/kg), as compared with conventional options. Electrochemical water splitting is a viable option for generating green hydrogen. However, the various limitations of state-of the art Pt/C and RuO₂- based electrocatalysts has motivated the scientific community to develop novel cathode (hydrogen evolution reaction (HER)) and anode (oxygen evolution reaction (OER)) electrocatalysts. In our present study, we have achieved a new milestone by fabricating the NiMo-based transition metal LDHs coupled V₂C MXene support based heterocatalyst. The synergistic impact of NiMo LDHs (corrosion resistance, favorable intrinsic catalytic properties, etc.) and V₂C (high electrical conductivity, pseudocapacitive behavior, etc.) has resulted in the HER and OER at smaller overpotential of 135 and 370 mV at the current density of 10 and 30 mA cm-2 in an alkaline (1.0 M KOH) environment.

• Journal of Ceramic Processing Research
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• v.21 no.2
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• pp.148-156
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• 2020

We investigated NiFe2O4/Ce0.9Gd0.1O1.95 (GDC) composites as oxygen carrier materials for chemical looping hydrogen production (CLHP). CLHP is a promising technology to simultaneously capture carbon dioxide and produce hydrogen from fossil fuels. We found that increasing GDC content increased the amount of the hydrogen production of NiFe2O4/GDC composites. Moreover, the oxygen transfer rate for the re-dox reaction increased significantly with increasing GDC content. GDC may affect the reaction kinetics of NiFe2O4/GDC composites. The finely dispersed GDC particles on the surface of NiFe2O4 can increase the surface adsorption of reaction gases due to the oxygen vacancies on the surface of GDC, and enlarge the active sites by suppressing the grain growth of NiFe2O4. The NiFe2O4/15wt% GDC composite showed no significant degradation in the oxygen transfer capacity and reaction rate during several re-dox cycles. The calculated amount of hydrogen production for the NiFe2O4/15wt% GDC composite would be 2,702 L/day per unit mass (kg).

• Journal of the Korean Association of Geographic Information Studies
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• v.17 no.1
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• pp.159-172
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• 2014

As greenhouse gas emissions have been increasing in the world, global warming is being recognized as a cause of the global problems like climate change. This is closely associated the fossil fuels. Thus renewable energy has been brought to the attention of many people as the upcoming alternative energy source to cope with the fossil drain and increased environmental regulations. Especially, the solar energy among renewable energy has drastically increased. In this study, we calculate on daylight ratio about the solar energy for buildings based on digital surface model. The digital surface model was made using the spatial information data. And it was simulated the shadow analysis using SAS. Therefore, it was suitable places to utilize the solar energy in the Gyeongsan city. Consequently, the daylight ratio was considered important factor to select region of the industry of the solar light power generation.

• Journal of Energy Engineering
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• v.24 no.3
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• pp.150-163
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• 2015

Gasification technology is one of the representative next-generation fossil fuel utilization technologies, converting low grade fossil fuels such as coal, heavy residue oil, pet-coke into highly clean and efficient energy sources. Accordingly, related market demand for gasification technology is ever increasing steadily and rapidly. A few years ago, conventional pulverized coal utilization technology had an edge over the gasification technology but the most significant technical barrier of limited capacity and availability has been largely overcome nowadays. Futhermore, it will be more competitive in the future with the advancement of related technologies such as gas turbine, ion transfer membrane and so on. China has recently completed a commercialization-capable large-scale coal gasification technology for its domestic market expansion and foreign export, rapidly becoming a newcomer in the field and competing with existing US and EU technical leadership at comparable terms. Techno-economic aspect deserves intensive attention and steady R&D efforts need to continue in organized, considering that gasification technology is quite attractive combined with $CO_2$ capture process and coal to SNG plant is economically viable in Korea where natural gas is very expensive. In the present paper, recent technology development and commercialization trend of many leading companies with coal gasification expertise have been reviewed with significant portion of literature cited from the recently held '2014 Gasification Technology Conference'.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.285-290
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• 2013

As well as the advanced development of modern society, and the environmental problems caused by the use of fossil fuels is emerging. So do not reap the performance level of the car to be able to replace existing fossil fuel and low-emission energy and technology development are continually strives. Therefore, this study aims to present the direction of the new interface 21st century Mobile Auto Electric Segway technology in the field of security and disadvantages based. The Segway is a problem because the control itself skewed by certain slope where the slope in the wrong adjustment tipping. In this study, the year saw the introduction of two pressure sensors(Load cell) used to solve these drawbacks, according to the ratio of the weight control methods. In addition, the ramps operate in a straightforward, using an acceleration sensor and a gyro sensor in order to compensate for the slope value in free control method to study looked. Measured by calculating the value of the occupant's weight and according to the inclination of the pressure sensor pressure sensing experiment results this year, we can see that the control variable for the change in body weight is greater than the inclination. Segway is also easy to control, and the stability of the ramps, etc. As a result, created using a pressure sensor.

• Journal of Plant Biotechnology
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• v.34 no.2
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• pp.111-118
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• 2007

Global warming crisis due primarily to continued green house gas emission requires impending change to renewable alternative energy than continuously depending on exhausting fossil fuels. Bioenergy including biodiesel and bioethanol are considered good alternatives because of their renewable and sustainable nature. Bioethanol is currently being produced by using sucrose from sugar beet, grain starches or lignocellulosic biomass as sources of ethanol fermentation. However, grain production requires significant amount of fossil fuel inputs during agricultural practices, which means less competitive in reducing the level of green house gas emission. By contrast, cellulosic bioethanol can use naturally-growing, not-for-food biomass as a source of ethanol fermentation. In this respect, cellulosic ethanol than grain starch ethanol is considered a more appropriate as a alternative renewable energy. However, commercialization of cellulosic ethanol depends heavily on technology development. Processes such as securing enough biomass optimized for economic processing, pretreatment technology for better access of polymer-hydrolyzing enzymes, saccharification of recalcitrant lignocellulosic materials, and simultaneous fermentation of different sugars including 6-carbon glucose as well as 5-carbon xylose or arabinose waits for greater improvement in technologies. Although it seems to be a long way to go until commercialization, it should broadly benefit farmers with novel source of income, environment with greener and reduced level of global warming, and national economy with increased energy security. Mission-oriented strategies for cellulosic ethanol development participated by government funding agency and different disciplines of sciences and technologies should certainly open up a new era of renewable energy.