• Transactions of the Korean hydrogen and new energy society
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• v.33 no.5
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• pp.557-565
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• 2022

The effect of flow configuration in ammonia-fed solid oxide fuel cell are investigated by using a three-dimensional numerical model. Typical flow configurations including co-flow and counter-flow are considered. The ammonia is directly fed into the stack without any external reforming process, resulting in an internal decomposition of NH3 in the anode electrode of the stack. The result showed that temperature profile in the case of counter-flow is more uniform than the co-flow configuration. The counter-flow cell, the temperature is highest at the middle of the channel while in the case of co-flow, the temperature is continuously increased and reached maximum value at the outlet area. This leads to a higher averaged current density in counter-flow compared to that of co-flow, about 5%.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.18 no.4
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• pp.1-11
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• 2022

In this study, the thermal runaway of NCM and LFP batteries were compared and analyzed through numerical analysis under various conditions. Comparing the thermal runaway of the NCM622 (18650) battery cell and the LFP (18650) battery cell through oven test simulation, the LFP battery did not show thermal runaway, whereas the NCM622 battery temperature increased to 710℃ in 12 minutes. To observe the thermal runaway and propagation of the prismatic LFP battery cell, the internal temperature was set at 200℃ and the oven test simulation was conducted. It was found that thermal runaway occurred at 391℃ after 47 minutes. As a result of observing thermal runaway propagation by placing five NCM622 and LFP battery cells, the thermal runaway propagation was clearly observed in the case of the NCM622 battery, but in the case of the LFP battery, thermal runaway was not observed after the first cell. From the third battery cell, it was confirmed that the temperature change was very insignificant, and through this, it is considered that the LFP battery is relatively safe compared to the NCM battery in terms of the thermal runaway propagation of the battery.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.749-758
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• 2011

The present work explores the performance and operation limit of electrodialysis cell for HI concentration in sulfur iodine thermochemical hydrogen production process, For this purpose, the electrodialysis cell was assembled with Nafion 117 as a PEM membrane and two activated carbon papers as the electrodes. HIx solution was prepared with composition of HI: $I_2$: $H_2O$ = 1: 0.5~2.5: 5.2 in molar ratio. The cell and its peripheral apparatus were placed in the specially designed convective oven in order to uniformly maintain the operation temperature. As operation temperature increased, the amount of water transport from anode to cathode increased, thus reducing HI molarity in catholyte. Meanwhile, the current efficiency was constant as about 90 %, irrespective of temperature change. The cell voltage increased with initial $I_2$ mole ratio as well as anolyte to catholyte mole ratio. Moreover the cell voltage overshot took place within 10 h cell operation, which is due to the $I_2$ precipitation inside the cell. From the analysis of $I_2$ mole ratio in the anolyte, it is noted that operation limit (in $I_2$ mole ratio) of the electrodialysis cell, arising from was measured to be 3.2, which is much lower than bulk solubility limit of 4.7.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.82.2-82.2
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• 2010

The development of bipolar plate having high efficiency and chemical properties has a major impact on fuel cell applications commercialization. Even though graphite bipolar plate has high electric conductivity and chemical resistance, it has demerits about mass production and brittle property for commercialization. Hence, metallic bipolar plate can be substitute for fuel cell bipolar plate. Although its inadequate corrosion behavior under PEMFC environment lead to a deterioration of membrane by dissolved metal ions, metallic bipolar plate for PEMFC is more suitable for automotive and residential power generation system because of its high mechanical strength, low gas permeability and applicability to mass production. Therefore, several types of coating has been applied to prevent corrosion and oxide film growth and to achieve more high durability. This work presents durability of coated metal bipolar plate for low temperature PEMFC which made for fuel cell vehicle. This results showed surface treatment increase long-term durability, even electric conductivity and corrosion resistance.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.1
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• pp.24-30
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• 2003

The preparation of $PbTiO_3$ powder was carried out using the oxide starting material by hydrothermal method. The powder of a crystalline phase with perovskite structure was synthesized. The optimum conditions for the preparation of powder were as follows; hydrothermal solvent; 8M-KOH or 8M-NaOH, reaction temperature; 250~$270^{\circ}C$, run time; 10 h. The ,shape of synthesized powders were well developed crystalline faces with specific surface area of about 2.3 $\textrm m^2$/g in KOH solution and about 5.0 $\textrm m^2$/g in NaOH solution. The cell parameters of powder were a = 3.90$\AA$, c = 4.14 $\AA$ and cell volume was 57.30 $\AA^3$. The cell ratio (c/a) of powder was the same as the theoretical ratio with c/a = 1.06 and the phase transition temperature(Tc) of the powders was about $470^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.249.1-249.1
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• 2015

Quantum dots (QDs) are attracting growing attention for photovoltaic device applications because of their unique electronic, optical and physical properties. Lead sulfide (PbS) QDs are one of the most widely studied materials for the devices and known to have size-tunable properties. In this context, we investigated the relationship between the size of PbS QDs and two synthesizing conditions, a concentration of ligand, oleic acid in this work, and injection temperature. The inverted colloidal quantum dot solar cells based on the heterojunction of n-type zinc oxide layer and p-type PbS QDs were also fabricated. The size of the QDs and cell properties were observed to depend on both the QD synthesizing conditions, and hence the overall efficiency of the cell could vary even though the size of QDs used was same. The QD synthesizing conditions were finally optimized for the maximum cell efficiency.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.289-292
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• 2001

Aluminium foams, having a closed cell structure, fabricated by applying the powder compact method and an induction heating were studied. The powdered A6061 mixed with the powdered titanium hydride as a foaming agent was hot pressed into a foamable precursor. The resulting precursor was foamed by induction heating up to desired temperature. The effects of the titanium hydride content ($0.3{\~}1.5 wt.\%$), pressing pressure of the foamable precursor material (50-150kN), the forming temperature ($610{\~}690^{\circ}C$) and heating rate during foaming on the expansion behavior of the foam were investigated.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.146-151
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• 2001

Several design parameters for a 100 kW molten carbonate fuel cell stack was described. Approximately 170 cells are required to generate 100 kW at a current density of $125\;mA/cm^{2}$ with $6000\;cm^{2}$ cells. An overall heat balance was calculated to predict exit temperature. In order to limit the stack temperature in the range of $600-700^{\circ}C$, current load cannot exceed $75\;mA/cm^{2}$ at atmospheric operation. The 100 kW power is expected only under pressurization. Recycle of cathode gas by more than 50% is recommended to run the stack at $125\;mA/cm^{2}$ and 3 atm. Manifolds should be designed based on gas flow rates for the suggested operating condition.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.29-32
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• 2008

Testing was conducted to determine the performance of a residential fuel cell system when subjected to DSS and WSS operation, especially for start-up and shut-down characteristics. In terms of start-up time, it took about 70min to start output power generation and stably to reach 1kW at cold start. Measurement of the characteristics of heat and power generation were carried out at start-up and shut-down time. Fuel gas is used for heating both reformer and stack from start-up to the beginning of power generation. In terms of start-up and shut-down characteristics, it was important to control the reformer temperature precisely. The average output water temperature during the rated output operation(960W) was $63.2^{\circ}C$ constantly. The results of the investigation are being used to develop a new test protocols for residential fuel cell system.

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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• pp.568-571
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• 2005

Highly transparent ZnO films with low resistivity for thin film solar cell applications were fabricated at low temperature by rf magnetron sputtering. Al-doped ZnO films were deposited on glass substrates at a substrate temperature of $200^{\circ}C$. electrical and optical properties of the ZnO:Al films were investigated in terms of the reparation conditions. The transmittance of the ZnO:Al films in the visible range is 90 %. The lowest resistivity of the ZnO:Al films is about $5.7\times10^{-4}$ $\Omega$ cm at the Al content of 2.5 wt% with the film thickness of 500 nm. After deposition, the smooth surface of ZnO:Al films were etched in diluted HCl (0.5%) to investigate the variation of electrical and surface morphology properties due to an textured surface.