• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.6
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• pp.568-576
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• 2004

This paper presents a new anti-islanding method for distributed power generation system (DPGS) using renewable energy. Based on the concept of real and reactive power mismatch, three different islanding conditions are analyzed. It is shown via analysis that islanding voltage is a function of real power alone, where as its frequency is a function of both real and reactive power. Using this analysis, a new anti-islanding method is developed. The proposed protection algorithm continuously perturbs ($\pm$5%) the reactive power supplied by DPGS while simultaneously monitoring the utility voltage and frequency. If a measurable frequency deviation took place by islanding, the real power of DPGS is further reduced to 80%. This detection method is shown to be fast acting under resonant loads. Possible islanding conditions are simulated and verified with analysis. Experimental results on a 0.5kW utility-interactive fuel cell system are suggested.

• Journal of Ocean Engineering and Technology
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• v.32 no.4
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• pp.279-286
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• 2018

The use of eco-friendly energy in the offshore plant system is expanding because conventional generators are operated by fossil fuel or natural gas. Eco-friendly energy, which replaces existing power generation methods, should be capable of generating the power for lighting protection equipment, airborne fault indication, parameter measurement, and others. Most of the eco-friendly energy used in offshore plant facilities is solar and wind power. In the case of using photovoltaic power, because the structure must be constructed based as flat solar panels, it can be damaged easily by the wind. Therefore, there is a need for a new generation system composed of a spherical structure that does not require a separate structure and is less influenced by the wind. Considering these characteristics, in this study we designed, fabricated, and tested a unit that could provide the most efficient spherical photovoltaic power generation considering wind direction and wind pressure. Our test results indicated that the proposed system reduced costs because it did not require any separate structure, used eco-friendly energy, reduced carbon dioxide emissions, and expanded the proportion of eco-friendly energy use by offshore plant facilities.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.1
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• pp.118-127
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• 2011

An IGCC was evaluated as one of the next generation technologies that would be able to substitute for coal-fired power plants. According to "The 4th Basic Plan of Long-term Electricity Supply & Demand" which is developed by the Electricity Business Acts, the first IGCC will be operated at 2015. Like other new and renewable energy such as solar PV, Fuel cell, The IGCC is considered as non-competitive generation technology because it is not maturity technology. Before the commercial operation of an IGCC in our electricity market, its economic feasibility under the Korean electricity market, which is cost-based trading system, is studied to find out institutional support system. The results of feasibility summarized that under the current electricity trading system, if the IGCC is considered like a conventional plant such as nuclear or coal-fired power plants, it will not be expected that its investment will be recouped within life-time. The reason is that the availability of an IGCC will plummet since 2016 when several nuclear and coal-fired power plants will be constructed additionally. To ensure the reasonable return on investment (NPV>0 IRR>Discount rate), the availability of IGCC should be higher than 77%. To do so, the current electricity trading system is amended that the IGCC generator must be considered as renewable generators to set up Price Setting Schedule and it should be considered as pick load generators, not Genco's coal fired-generators, in the Settlement Payment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1599-1606
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• 2008

Recently, new dispersed generation systems such as photovoltaic, wind power, fuel cell etc. are energetically interconnected and operated in the distribution systems, as one of the national projects for alternative energy with the provision against oil crisis. The technical guidelines on the interconnection of dispersed generation systems have been established and conducted positively. However, protection devices (Re-closer) in primary feeder of distribution system interconnected with photovoltaic generation may cause problems with mis-operation, and then many customers could have problems like an interruption. So, this paper presents the optimal method to minimize the impact of interruption, using both the symmetric method and MATLAB/SIMULINK. And, also this paper shows the effectiveness of proposed method by simulating at the real distribution systems.

• Journal of Microbiology and Biotechnology
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• v.26 no.12
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• pp.2171-2178
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• 2016

Polyester cloth (PC) was selected as a prospective inexpensive substitute separator material for microbial fuel cells (MFCs). PC was compared with a traditional Nafion proton exchange membrane (PEM) as an MFC separator by analyzing its physical and electrochemical properties. A single layer of PC showed higher mass transfer (e.g., for $O_2/H^+/ions$) than the Nafion PEM; in the case of oxygen mass transfer coefficient ($k_o$), a rate of $50.0{\times}10^{-5} cm{\cdot}s^{-1}$ was observed compared with a rate of $20.8{\times}10^{-5}cm/s$ in the Nafion PEM. Increased numbers of PC layers were found to reduce the oxygen mass transfer coefficient. In addition, the diffusion coefficient of oxygen ($D_O$) for PC ($2.0-3.3{\times}10^{-6}cm^2/s$) was lower than that of the Nafion PEM ($3.8{\times}10^{-6}cm^2/s$). The PC was found to have a low ohmic resistance ($0.29-0.38{\Omega}$) in the MFC, which was similar to that of Nafion PEM ($0.31{\Omega}$); this resulted in comparable maximum power density and maximum current density in MFCs with PC and those with Nafion PEMs. Moreover, a higher average current generation was observed in MFCs with PC ($104.3{\pm}15.3A/m^3$) compared with MFCs with Nafion PEM ($100.4{\pm}17.7A/m^3$), as well as showing insignificant degradation of the PC surface, during 177 days of use in swine wastewater. These results suggest that PC separators could serve as a low-cost alternative to Nafion PEMs for construction of cost-effective MFCs.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.503-507
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• 2021

Sodium borohydride, NaBH₄, has many advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFC). When PEMFC is used outdoors as a transport type, it is economical to hydrolyze NaBH₄ using fresh water instead of distilled water. Therefore, in this study, hydrogen was generated using fresh water instead of distilled water during the NaBH₄ hydrolysis process. The properties of NaBH₄ hydrolysis were studied using an activated carbon-supported Co-P-B/C catalyst. Fresh water did not generate tetrahydrate during the NaBH₄ hydrolysis process, and distilled water produced tetrahydrate by-products, which consumed a lot of water during the hydrolysis process, indicating that at the end of the reaction at a high concentration of 25% or more of NaBH₄, dry by-products and unreacted NaBH₄ remained. As a result, when fresh water was used, the hydrogen yield and hydrogen generation rate were higher than that of distilled water at a high concentration of 25% or more of NaBH₄, indicating that it is suitable for use in transport-type fuel cells such as unmanned aerial vehicles.

• Journal of Energy Engineering
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• v.15 no.2 s.46
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• pp.83-95
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• 2006

This study is to establish a national vision of the hydrogen economy and design a roadmap to materialize it. A goal is set to supply 15% of final energy consumption with hydrogen energy in Korea by 2040. Selecting the transportation sorter as the main target, more than 50% of vehicles on the road will be replaced with fuel cell vehicles (FCVs) while $20{\sim}30%$ of electricity demand in the residential and commercial sectors might be replaced with power generation by fuel cells. If this goals were attained as planned, primary energy demand would be reduced by 9%, resulting in improved energy mix in which fossil fuel consumption is greatly reduced whereas renewable energy increases by 47%. Furthermore, GHG emissions will be reduced by 20% and self-sufficiency in energy is enhanced up to 23%. If the hydrogen economy is to materialize, the government needs to implement institutional arrangements such as new legislations, organizations, and fiscal measures to facilitate the process. In addition, the private sector's participation is highly recommended to mobilize fund needed for the huge investment to build an infrastructure in preparation for the hydrogen economy. Arrangements for codes and standards are also required to promote industrialization of fuel cells and hydrogen production and consumption.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.17-18
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• 2007

Solid oxide fuel cells are clean, pollution-free technology for the electrochemical generation of electricity at high efficiency. Specially, the polarization resistance between electrolyte and electrode of SOFC unit cell is of importance, because it is desirable to develop SOFC operating at intermediate temperature below $800^{\circ}C$. The LSCF cathode prepared using modified oxalate method was investigated with different electrolyte. A precursor was prepared with oxalic acid, ethanol and $NH_4OH$ solution. The LSCF precursor was prepared at $80^{\circ}C$, and pH control was 2, 6, 8, 9 and 10. The precursor powder was calcined at $800^{\circ}C$, $1000^{\circ}C$ and $1200^{\circ}C$ for 4hrs. The crystal of LSCF powders show single phase at pH 2, 6, 8 and 9, and the average particle size was about $3{\mu}m$. The LSCF cathode with heat treatment at $1200^{\circ}C$ showed a plot of electric conductivity versus temperature. Unit cell prepared from the LSCF cathode, buffer layer between cathode and electrolyte and the LSGM, YSZ, ScSZ and CeSZ electrolyte. Also interface reaction between LSCF, buffer layer and electrolyte were measured by EPMA and the polarization resistance for unit cell with cycle measure using a Solatron 1260 analyzer.

• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.587-592
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• 2016

Sodium borohydride, $NaBH_4$, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFCs). Properties of $NaBH_4$ hydrolysis reaction using unsupported Co-P-B Co-B, catalyst at high concentration $NaBH_4$ solution were studied. In order to enhance the hydrogen generation yield at high concentration of $NaBH_4$, the effect of catalyst type, $NaBH_4$ concentration and recovery of condensing water on the hydrogen yield were measured. The yield of hydrogen evolution increased as the boron ratio increased in preparation process of Co-P-B catalyst. The hydrogen yield decreased as the concentration increased from 20 wt% to 25 wt% in $NaBH_4$ solution during hydrolysis reaction using 1:5 Co-P-B catalyst. Maximum hydrogen yield of 96.4% obtained by recovery of condensing water and thinning of catalyst pack thickness in reactor using Co-P-B with Co-B catalyst and 25 wt% $NaBH_4$ solution.

• Journal of the Korean Vacuum Society
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• v.18 no.3
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• pp.164-175
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• 2009

CFD is used to analyze gas flow characteristics, power absorption, electron temperature, electron density and chemical species profile of an internal antenna type inductively coupled plasma system. An optimized grid generation technology is used for a complex real-scale models for industry. A bare metal antenna shows concentrated power absorption around rf a feeding line. Skin depth of power absorption for a system is modeled to 50 mm, which is reported 53 mm by experiments. For an application of bipolar plates for hydrogen fuel cells, multi-sheet loading ICP nitriding system is proposed using an internal ICP antenna. It shows higher atomic nitrogen density than reported simple pulsed dc nitriding systems. Minimum gap between sheets for uniform nitriding is modeled to be 39 mm.