• 한국신재생에너지학회:학술대회논문집
• /
• 2008.05a
• /
• pp.13-16
• /
• 2008

Solid oxide fuel cell(SOFC) is an electrochemical energy conversion system with high efficiency and low-emission of pollution. In order to reduce the operating temperature of SOFC system under $800^{\circ}C$, the thickness reduction of YSZ electrolyte to be as thin as possible, e.g., less than 10 ${\mu}m$ are considered with the microstructure control and optimum design of unit cell. Methods for reducing the thickness of YSZ electrolyte have been investigated in coin cell. Moreover, a large unit cell($8cm{\times}8cm$) for SOFC was fabricated using an anode-supported electrolyte assembly with a thinner electrolyte layer, which was prepared by a tape casting method with a co-sintering technique. we studied the design factors such as active layer, electrolyte thickness, cathode composition, etc,. by the coin type of unit cell ahead of the fabrication process of a large unit cell and also reviewed about the evaluation technique of a large size unit cell such as interconnect design, sealing materials and current collector and so forth. Electrochemical evaluations of the unit cells, including measurements such as power density and impedance, were performed and analyzed. Maximum power density and polarization impedance of coin cell were 0.34W/$cm^2$ and $0.45{\Omega}cm^2$ at $800^{\circ}C$, respectively. However, Maxium power density of a large unit cell($5cm{\times}5cm$) decreased to 0.21W/$cm^2$ at $800^{\circ}C$ due to the increase of ohmic resistance. However, It was found that the potential value of a large unit cell loaded by 0.22A/$cm^2$ showed 0.76V at 100hrs without the degradation of unit cell.

• Journal of Hydrogen and New Energy
• /
• v.27 no.1
• /
• pp.49-62
• /
• 2016

In this study, a solid oxide fuel cell (SOFC) system model including balance of plant (BOP) for building electric power generation is developed to study the effect of operating conditions on the system efficiency and power output. SOFC system modeled in this study consists of three heat-exchangers, an external reformer, burner, and two blowers. A detailed computational cell model including internal reforming reaction is developed for a planer SOFC stack which is operated at intermediate temperature (IT). The BOP models including an external reformer, heat-exchangers, a burner, blowers, pipes are developed to predict the gas temperature, pressure drops and flow rate at every component in the system. The SOFC stack model and BOP models are integrate to estimate the effect of operating parameters on the performance of the system. In this study, the design of experiment (DOE) is used to compare the effects of fuel flow rate, air flow rate, air temperature, current density, and recycle ratio of anode off gas on the system efficiency and power output.

• Journal of Hydrogen and New Energy
• /
• v.30 no.4
• /
• pp.303-311
• /
• 2019

Reversible solid oxide fuel cell (RSOFC) has become a prospective device for energy storage and hydrogen production. Many studies have been conducted around the world focusing on system efficiency improvement and realization. The system should have not only high efficiency but also a certain level of simplicity for stable operation. External waste steam utilization was proved to remarkably increase the efficiency at solid oxide electrolysis system. In this study, RSOFC system coupled with waste steam was proposed and optimized in term of simplicity and efficiency. Ejector for fuel recirculation is selected due to its simple design and high stability. Three system configurations using ejector for fuel recirculation were investigated for performance of design condition. In parametric study, the system efficiencies at different current density were analyzed. The system configurations were simulated using validated lumped model in EBSILON(R) program. The system components, balance of plants, were designed to work in both electrolysis and fuel cell modes, and their off-design characteristics were taken into account. The base case calculation shows that, the system with suction pump results in slightly lower efficiency but stack can be operated more stable with same inlet pressure of fuel and air electrode.

• Journal of Hydrogen and New Energy
• /
• v.33 no.5
• /
• pp.557-565
• /
• 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 Hydrogen and New Energy
• /
• v.16 no.1
• /
• pp.58-65
• /
• 2005

The $LaCrO_3$-dispersed Cr alloys for metallic interconnect of solid oxide fuel cell were prepared as a function of $LaCrO_3$ content in the range of 5 to 25 vol.% and were sintered at 1500$^{\circ}C$ under an Ar atmosphere with 5 vol.% $H_2$. The sintering and oxidation behaviors of these alloys were examined. The alloys indicated a good sinterability above 95% relative density at a given sintering condition, and their sintering densities is independent on $LaCrO_3$ content. The $LaCrO_3$ particles of the sintered alloys were concentrated on interfaces of Cr particles, and the size of the Cr particles increased with decreasing $LaCrO_3$ content, which is caused by inhibited grain growth of Cr particle by $LaCrO_3$ particle. The oxidation test showed all $LaCrO_3$-dispersed Cr alloys have good oxidation resistance as compared with pure Cr, which is attributed to presence of $LaCrO_3$ at the interface at which the oxidation reaction occurs rapidly. The Cr alloys with about 15 vol.% $LaCrO_3$ are very resistant to oxidation.

• Journal of Hydrogen and New Energy
• /
• v.25 no.3
• /
• pp.280-288
• /
• 2014

SDC (Samarium doped Ceria) electrolyte was developed for Intermediate temperature SOFC ($500^{\circ}C-800^{\circ}C$) which showed a good electrical conductivity. In this study, we used sintering aids to reduce the SDC sintering temperature down to $1000^{\circ}C$, especially which can help the SOFC scale-up. In order to reduce the SDC sintering temperature, $Li_2CO_3$ and $TiO_2$ were used as a sinering aids for decreasing sintering temperature. $Li_2CO_3$ and $TiO_2$ doped SDC sintered at $1000^{\circ}C$ showed 99% of the theoretical density and higher electrical conductivity than the pure SDC sintered at $1500^{\circ}C$. When measuring the OCV (Open circuit voltage) with the $Li_2CO_3$ and $TiO_2$ doped SDC electrolyte, however, the OCV values were lower than the theoretical OCV values which means that the modified SDC still had electronic conductivity.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.8
• /
• pp.677-685
• /
• 2014

A direct carbon fuel cell (DCFC) generates electricity directly by converting the chemical energy in coal. In particular, a DCFC system with a solid oxide electrolyte and molten carbonate anode media has been proposed by SRI. In this system, however, there are conflicting effects of temperature, which enhances the ion conductivity of the solid electrolyte and reactivity at the electrodes while causing a stability problem for the anode media. In this study, the effect of temperature on the stability of a carbon-carbonate mixture was investigated experimentally. TGA analysis was conducted under either nitrogen or carbon dioxide ambient for $Li_2CO_3$, $K_2CO_3$, and their mixtures with carbon black. The composition of the exit gas was also monitored during temperature elevation. A simplified reaction model was suggested by considering the decomposition of carbonates and the catalyzed Boudouard reactions. The suggested model could well explain both the measured weight loss of the mixture and the gas formation from it.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.05a
• /
• pp.331-334
• /
• 2009

An air-independent propulsion (AIP) system based on fuel cell technologies was developed for space and underwater applications in the present study. Hydrogen peroxide was selected as an oxidizer for space and underwater power applications where air independence is a must. Catalytic decomposition of hydrogen peroxide was used to generate oxygen and water. The pure oxygen was provided to a fuel cell and the water was stored separately. Sodium borohydride in the solid state was used as a hydrogen source in the present study. Pure hydrogen can be generated by a catalytic hydrolysis reaction. A fuel cell system was fabricated to validate the fuel cell based air-independent power system and was evaluated at the various conditions.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.06a
• /
• pp.161-165
• /
• 2007

Recently by the development of the electronic engineering technology various mobile devices are developed. But their operation time need to be extended although capacity of the batteries are limited. We focused our attention to the portable SOFC system. Because SOFC has the high efficiency and a lot of strongness in comparison with other kinds of fuel cells. In addition they can be built as a self/non-reformable system and single/dual chamber system. So We evaluated some types of SOFC theoretically, and compared the results from the fuel and performance efficiency point of view.

• Journal of Energy Engineering
• /
• v.25 no.4
• /
• pp.251-258
• /
• 2016

This article reports current status of micro fuel cell-combined heat and power (${\mu}FC$-CHP) systems which utilize both power and heat generated by fuel cells. There are several options for constructing CHP systems and among them, fuel cells are the most useful and their total energy efficiency combining heat and power can reach up to about 90%. Fuel cells are classified as five types based on the electrolyte, but the most suitable fuel cell types for the ${\mu}FC$-CHP system are proton exchange membrane fuel cells (PEMFCs) and solid oxide fuel cells (SOFCs). ${\mu}FC$-CHP systems have several advantages such as decrease of the transmission-distribution loss, reduced costs of electricity due to distributed power generation, and environmental-friendliness owing to zero emission. The main drawback of the ${\mu}FC$-CHP systems is the high initial investment, however, it keeps decreasing as the technology development reduces production costs. Currently, Japan is the most leading country of the ${\mu}FC$-CHP market, however, Korea tries to expand the market by planning the deployment of 1 million units of ${\mu}FC$-CHP systems and governmental subsidiary supporting of half of the install price. In this report, integration technologies for connecting FC and CHP, and technology trends of leading countries are presented as well.