• Journal of the Korean Ceramic Society
• /
• v.56 no.2
• /
• pp.130-145
• /
• 2019

Widespread commercialization of solid oxide fuel cells (SOFCs) is expected to be realized in various application fields with the advent of cost-effective fabrication of cells and stacks in high volumes. Cost-reduction efforts have focused on production yield, power density, operation temperature, and continuous manufacturing. In this article, we examine several issues associated with processing for SOFCs from the standpoint of the bimodal packing model, considering the external constraints imposed by rigid substrates. Optimum compositions of composite cathode materials with high volume fractions of the second phase (particles dispersed in matrix) have been analyzed using the bimodal packing model. Constrained sintering of thin electrolyte layers is also discussed in terms of bimodal packing, with emphasis on the clustering of dispersed particles during anisotropic shrinkage. Finally, the structural transition of dispersed particle clusters during constrained sintering has been correlated with the structural stability of thin-film electrolyte layers deposited on porous solid substrates.

• Journal of Biosystems Engineering
• /
• v.37 no.6
• /
• pp.429-433
• /
• 2012

Purpose: While rapeseed oil, soy bean oil, palm oil and waste cooking oil are being used for biodiesel, the viscosity of them should be lowered for fuel. The most widely used method of decreasing the viscosity of vegetable oil is to convert the vegetable oil into fatty acid methyl ester but is too expensive. This experiment uses ultrasonic energy, instead of converting the vegetable oil into fatty acid methyl ester, to lower the viscosity of the waste cooking oil. Methods: For irradiation treatment, the sample in a beaker was irradiated with ultrasonic energy and the viscosity and temperature were measured with a viscometer. For heating treatment, the sample in a beaker was heated and the viscosity and temperature were measured with a viscometer. Kinematic viscosity was calculated by dividing absolute viscosity with density. Results: The kinematic viscosity of waste cooking oil and cooking oil are up to ten times as high as that of light oil at room temperature. However, the difference of two types of oil decreased by four times as the temperature increased over $83^{\circ}C$. When the viscosity by the treatment of ultrasonic energy irradiation was compared to one by the heating treatment to the waste cooking oil, the viscosity by the treatment of ultrasonic energy irradiation was lower by maximum of 22% and minimum of 12%, than one by the heating treatment. Conclusions: Ultrasonic energy irradiation lowered the viscosity more than the heating treatment did, and ultrasonic energy irradiation has an enormous effect on fuel reforming.

• Transactions of the Korean hydrogen and new energy society
• /
• v.18 no.4
• /
• pp.422-431
• /
• 2007

Polymer electrolyte membrane fuel cell(PEMFC) is very interesting power source due to high power density, simple construction and operation at low temperature. But it has problems such as high cost, improvement of performance and effect of temperature. These problems can be approached to be solved by using mathematical models which are useful tools for analysis and optimization of fuel cell performance and for heat and water management. In this paper, the present work is to develop an electrochemical model to examine the electrochemical process inside PEM fuel cell. A complete set of considerations of mass, momentum, species and charge is developed and solved numerically with proper account of electrochemical kinetics. When depth of gas channel becomes thinner, diffusion of reactant makes well into gas diffusion layer(GDL) and the performance increases. Although at low current region there is little voltage difference between experimental data of PEM fuel cell and numerical data. When the porosity size of gas diffusion layer for PEM fuel cell is bigger, oxygen diffusion occurs well and oxygen mass fraction appears high in catalyst layer.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.20 no.4
• /
• pp.491-496
• /
• 2017

The hydrogen($H_2$) is promising energy carrier of renewable energy in the microgrid system such as small village and military base due to its high energy density, pure emission and convenient transportation. $H_2$ can be generated by photocatalytic water splitting, gasification of biomass and water electrolysis driven by solar cell or wind turbine. Solid oxide electrolysis cells(SOECs) are the most efficient way to mass production due to high operating temperature improving the electrode kinetics and reducing the electrolyte resistance. The SOECs are consist of nickel-yttria stabilized zirconia(NiO-YSZ) fuel electrode / YSZ electrolyte / lanthanum strontium manganite-YSZ(LSM-YSZ) air electrode due to similarity to Solid Oxide Fuel Cells(SOFCs). The Ni-YSZ most widely used fuel electrode shows several problems at SOEC mode such as degradation of the fuel electrode because of Ni particle's redox reaction and agglomeration. Therefore Ni-YSZ need to be replaced to an alternative fuel electrode material. In this study, We studied on the Double perovskite $PrBrMnO_{5+{\delta}}$(PBMO) due to its high electric conductivity, catalytic activity and electrochemical stability. PBMO was impregnated into the scaffold electrolyte $La_{0.8}Sr_{0.2}Ga_{0.85}Mg_{0.15}O_{3-{\delta}}$(LSGM) to be synthesized at low temperature for avoiding secondary phase generated when it exposed to high temperature. The Half cell test was conducted at SOECs and SOFCs modes.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
• /
• 2004.11a
• /
• pp.133-138
• /
• 2004

Proton exchange membrane fuel cell (PEMFC) is considered as a clean and efficient energy conversion det ice for mobile and stationary applications. Anions all the components of the PEMFC, the interface between the electrolyte ,and electrode catalyst plays an important role in determining tile cell performance since the electrochemical reactions take place at the interface in contact with tile reactant gases. Therefore, to increase the interface area and obtain a high-performance PEMFC, surface of the electrolyte membrane was roughened by Ar$^{+}$ beam bombardment. The results imply that by modifying surface of the electrolyte membrane, platinum loading can be reduced significantly without performance loss. To optimize the surface treatment condition, effects of ion dose density on characteristics of the membrane/electrode interface were examined by measuring the cell performance, impedance spectroscopy, and cyclic voltammograms. Surface of the modified membranes were characterized using scanning electron microscopy and FT-IR.R.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1997.05b
• /
• pp.171-176
• /
• 1997

UO$_2$-Gd$_2$O$_3$fuel has been sintered to study the effect of powder property and sintering atmospheres on densification and microstructure. Three types of powders have been used; AUC-UO$_2$ powder and ADU-UO$_2$ powder were mixed with Gd$_2$O$_3$ Powder, and co-milled AUC-UO$_2$ and Gd$_2$O$_3$ powder. UO$_2$-(2, 5, 10)wt% Gd$_2$O$_3$pellets have been sintered at 168$0^{\circ}C$ for 4 hours in the mixture of H$_2$ and $CO_2$ gases, of which oxygen potential has been controlled by the ratio of $CO_2$ to H$_2$ gas. Densities of UO$_2$-Gd$_2$O$_3$ fuel pellets are quite dependent on powder types, and UO$_2$-Gd$_2$O$_3$ fuel using co-milled UO$_2$ powder yields the highest density. A long range homogeneity of Gd is determined by powder mixing. As the oxygen potential of sintered atmosphere increases, the sintered densities of UO$_2$-Gd$_2$O$_3$ pellets decrease but grain size increases. In addition, (U, Gd)O$_2$ solid solution becomes more homogeneous. The UO$_2$-Gd$_2$O$_3$fuel having adequate density and homogeneous microstructure can be fabricated by co-milling powder and by high oxygen potential.

• Journal of ILASS-Korea
• /
• v.28 no.3
• /
• pp.143-149
• /
• 2023

Amidst the drive towards carbon neutrality, interest in renewable synthetic e-fuels is rising rapidly. These fuels, generated through the synthesis of atmospheric carbon and green hydrogen, offer a sustainable solution, showing advantages like high energy density and compatibility with existing infrastructure. The physical properties of e-fuels can be different from those of conventional gasoline based on manufacturing methods, which requires investigations into how the physical properties of e-fuels affect the fuel injection characteristics. This study performs a comparative analysis between conventional and Fischer-Tropsch (F-T) synthetic gasoline (e-gasoline) across various fuel temperatures, including the cold start condition. The fuel properties of F-T synthetic and conventional gasoline are analyzed using a gas chromatography-mass spectrometry technique and the injection rates are measured using a Bosch-tube injection rate meter. The F-T synthetic gasoline exhibited higher density and kinematic viscosity, but lower vapor pressure compared to the conventional gasoline. Both fuels showed an increase in injection rate as the fuel temperature decreased. The F-T synthetic gasoline showed higher injection rates compared to conventional gasoline regardless of the fuel temperature.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2007.11a
• /
• pp.190-193
• /
• 2007

Present study examines the experimental results of polycyclic hydrocarbons compound prepared by norbornadiene dimerization reaction. Pentacyclic exo-t-exo, hexacyclic exo-endo, hexacyclic endo-endo isomers of NBD dimer were synthesized by selective dimerization of NBD monomer. Dimerization catalysts, reaction procedure and product analysis method were developed respectively. Through this experiment, mild reaction conditions, relatively high NBD dimer yields were obtained and this reaction technologies will be usefully applied to high energy density liquid fuel development.

• International Journal of Computer Science & Network Security
• /
• v.22 no.3
• /
• pp.37-44
• /
• 2022

Plug-in Hybrid electric vehicles (PHEV) show great potential to reduce gas emission, improve fuel efficiency and offer more driving range flexibility. Moreover, PHEV help to preserve the eco-system, climate changes and reduce the high demand for fossil fuels. To address this; some basic components and energy resources have been used, such as batteries and proton exchange membrane (PEM) fuel cells (FCs). However, the FC remains unsatisfactory in terms of power density and response. In light of the above, an electric storage system (ESS) seems to be a promising solution to resolve this issue, especially when it comes to the transient phase. In addition to the FC, a storage system made-up of an ultra-battery UB is proposed within this paper. The association of the FC and the UB lead to the so-called Fuel Cell Battery Electric Vehicle (FCBEV). The energy consumption model of a FCBEV has been built considering the power losses of the fuel cell, electric motor, the state of charge (SOC) of the battery, and brakes. To do so, the implementing a reinforcement-learning energy management strategy (EMS) has been carried out and the fuel cell efficiency has been optimized while minimizing the hydrogen fuel consummation per 100km. Within this paper the adopted approach over numerous driving cycles of the FCBEV has shown promising results.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.05a
• /
• pp.21-24
• /
• 2008

Proton Exchange Membrane Fuel Cell (PEMFC) is an attractive candidate for residential power generator due to fast start-up and stop, high efficiency, low emission, and high power density. In this study, we employ short module stack to understand the performance of the unit cell of the stack in terms of operating temperatures. To simulate the practical fuel cell stack of residential power generator, the structure and active area of the short module stack is kept the same as that of the practical fuel cell. The results shows that the electric potential of short module stack is different from the number of cells times the potential of unit cell because of cell-to-cell variation.