• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.2112-2113
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• 2011

우리나라는 연평균 강수량이 1,245mm로써, 비교적 강수량이 풍부하고 전국토의 2/3가 산지로 구성되어 있어 지형적 및 수문학적으로 수력자원 부존량이 많은 편이다. 하지만 수력자원 활용을 통한 발전소 건설은 매우 미미한데 이는 수력발전소 개발지점이 제약되어 있고 개발지점의 가동율 또한 매우 낮아 경제성 확보가 어렵기 때문이다. 수력발전은 전력수요 급증 시 부하 평준화 효과와 석유 수입대체 및 환경 친화적인 에너지원이라는 장점이 있다. 따라서 국산화된 수차발전시스템의 사용으로 초기투자비를 낮추고 하천형 수력발전소 건설을 통하여 가동율을 높인다면 우리나라의 수력발전사업은 크게 활성화 될 것이다. 본 논문에서는 하천형 수력발전소 시공사례를 통하여 주요 시공사례를 소개하고, 하천공사의 특징으로 인하여 설계 및 시공 시 반영해야 할 사항에 대해 몇 가지 소개하였다. 표준화를 통하여 건설비용을 절감, 발전 단가의 기준가격 현실화를 통한 재정적인 지원 및 법규 정비를 통한 제도적인 도움 이 세가지를 해결한다면 경쟁력 있는 소수력발전소 건설이 가능 할 것이다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.515-518
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• 2006

This paper presents the friction and wear characteristics of contact type sealing unit for a water turbine of a small hydro-power generation, which Is to stop a leakage of a circulating water from a outside of an impeller to an inside of a rolling bearing. The surface wear strongly affect to the seal life of a mechanical face seal. In this study, the hardness of a stainless steel in which is a heat-treated is 892.8 in Vickers hardness and the hardness of silicone carbide of SiC is 714.1 in Vickers hardness. The surface hardness of a heat-treated stainless steel is 25% high compared with that of a ceramic material of SiC. The contact modes of rubbing surfaces aye a dry friction a water film friction and a mixed friction that is contaminated by a dust, silt and moistures, etc. These two factors of a contact rubbing modes and a material property are very important parameters on the tribological performance such as a friction and wear between a seal ring and a seal seat. The experimental result shows that the surface hardness of a seal material is very important on the friction coefficient and a wear volume. Thus, the results recommend higher hardness of a seal material, which may reduce a friction loss and increase a wear life of primary seal components

• 전기학회논문지
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• 제58권3호
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• pp.467-477
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• 2009

Renewable Portfolio Standard (RPS) is a regulatory policy that requires the generation companies to increase the proportion of renewable energy sources such as wind, solar, LFG, fuel cell, and small hydro. Recently, Korean government decided to increase the portion of renewable energy to 3% to total electricity generation by 2012 from the current level of 0.13%. To achieve this goal, an innovative plan for market competitiveness would be required in addition to the present Feed-In-Tariff (FIT). That is Korean government has taken it into consideration to introduce a Renewable Portfolio Standard (RPS) as an alternative to FIT. This paper reviews the impact of RPS on the long-term fuel mix in 2020. The studies have been carried out with the GATE-PRO (Generation And Transmission Expansion PROgram) program, a mixed-integer non-linear program developed by Hongik university and Korea Energy Economics Institute. Detailed studies on long-term fuel mix in Korea have been carried out with four RPS scenarios of 3%, 5%, 10% and 20%. The important findings and comments on the results are given to provide an insight on future regulatory policies.

• 한국연소학회지
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• 제16권1호
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• pp.8-14
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• 2011

Biomass gasification is a promising technology in terms of clean energy and flexible options for end use such as heat, steam, electricity, gaseous or liquid fuels. In a gasification process, reduction of tar is very important because it can cause any mechanical problems and small tar implies high energy efficiency. However, generation and conversion mechanisms of tar have not been fully understood due to its complex nature. In this study, characteristics of tar generated from different gasification stages were investigated. Korean pine woodchip was used as feedstock and tar was sampled in a separate way during devolatilization and char gasification stage, investigated. As a result. more various kinds of hydro carbon compounds were identified in the devolatilization stage than char gasification stage because primary tar compounds are released mostly from pyrolysis of cellulose and hemicellulose. When the reaction temperature increased up to $900^{\circ}C$, tar composition becomes simplified into about 10 aromatic compounds mostly with 1-4 rings without substitution up to phenanthrene. The sampled tar in the char gasification stage mostly contains 5-7 simple aromatic compounds.

• 신재생에너지
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• 제8권1호
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• pp.8-17
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• 2012

The Korean government pushed ahead various policies to disseminate photovoltaic (PV), wind power, small hydro, bio-fuel, etc. Renewable energy system (RES) budget of the Korean government increased from 118 billion won of 2003 to 876.6 billion won of 2010. The R&D budgetary supports for RES increased by 6.8 times in the period 2003-2010. It is necessary to confirm RES budget expenditure that renewable energy promotion policy makes good performance evaluated in quantity level. This paper made Input-Output Table 2009 contains photovoltaic power generation equipment industry as a dependent sector and analyzed induced production effect by demand of photovoltaic power generation equipment industry. From the empirical analysis result, additional demand in photovoltaic power generation equipment induced 1.932 times of induced production in Korea. Each of industry sector has positive induced production from the additional demand in photovoltaic power generation equipment. Renewable energy promotion in photovoltaic power generation is considered together with industry policy as the option to sustain economic growth.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
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• pp.273-275
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• 1999

This paper presents a dynamic equivalencing method in large electric power system for stability analysis. This method of modeling simplified equivalents for parts of the network outside the study area is to evaluate the stability of a study area modeled in detail. Generators are closely coupled in an electrical sense tend to swing together in groups during disturbances, and this behavior can be exploited to reduce the size of the power system model. The characteristics of generators swing together are referred to as coherency Coherency groups whose generators state trajectory are similar to the other generators state trajectory in the same coherency group by a certain disturbance. In this paper, procedures for forming dynamic equivalents of control devices of coherency-based generating units are proposed and the aggregation of the control devices such as excitation system and governor-turbine system is accomplished by this method. This method can deal with the aggregation of the same type of control devices and combination of hydro and steam unit or the many types of excitation systems. etc. This method is shown to be efficient in reducing the number of control device of generating units with small error in the study group by result of case study presented latter part of this paper.

• International Journal of Fluid Machinery and Systems
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• 제2권4호
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• pp.346-352
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• 2009

The objective of the present work is to improve numerical predictions of unsteady turbulent swirling flows in the draft tubes of hydraulic power plants. We present Large Eddy Simulation (LES) results on a simplified draft tube consisting of a straight conical diffuser. The basis of LES is to solve the large scales of motion, which contain most of the energy, while the small scales are modeled. LES strategy is here preferred to the average equations strategies (RANS models) because it resolves directly the most energetic part of the turbulent flow. LES is now recognized as a powerful tool to simulate real applications in several engineering fields which are more and more frequently found. However, the cost of large-eddy simulations of wall bounded flows is still expensive. Bypass methods are investigated to perform high-Reynolds-number LES at a reasonable cost. In this study, computations at a Reynolds number about 2 $10^5$ are presented. This study presents the result of a new near-wall model for turbulent boundary layer taking into account the streamwise pressure gradient (adverse or favorable). Validations are made based on simple channel flow, without any pressure gradient and on the data base ERCOFTAC. The experiments carried out by Clausen et al. [1] reproduce the essential features of the complex flow and are used to develop and test closure models for such flows.

• 한국유체기계학회 논문집
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• 제13권4호
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• pp.37-43
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• 2010

The purpose of this study is not only to investigate the effects of air layer in the turbine chamber on the performance and internal flow of the cross-flow turbine, but also to suggest a newly developed air supply method. Field test is performed in order to measure the output power of the turbine by a new air supply method. CFD analysis on the performance and internal flow of the turbine is conducted by an unsteady state calculation using a two-phase flow model in order to embody the air layer effect on the turbine performance effectively. The result shows that air layer effect on the performance of the turbine is considerable. The air layer located in the turbine runner passage plays the role of preventing a shock loss at the runner axis and suppressing a recirculation flow in the runner. The location of air suction hole on the chamber wall is very important factor for the performance improvement. Moreover, the ratio between air from suction pipe and water from turbine inlet is also significant factor of the turbine performance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.606-607
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• 2007

This paper is about optimal flywheel capacity estimation for Ullueng-do power system. The power system of Ullueng-do has some differences with other island power system in Korea. It includes wind generator, hydro-generators as well as diesel generators. There are some problems on 600kW wind generator. Because of frequent drop of wind generator, the Ulleung-do power system have been threatened on frequency. The power frequency is 60Hz, and it should be between 59.9 and 60.1Hz. However, since the electrical inertia is small and the weight of wind generation is relatively high, generator drop of wind generation might make the power frequency out of boundary. In this paper, the flywheel energy storage system is assumed to be installed on Ulleung-do power system. Then, the maximum wind generation capacity and the optimal superconducting flywheel energy storage system capacity is estimated by the transient stability simulations.

• 한국전기전자재료학회논문지
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• 제34권5호
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• pp.327-332
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• 2021

Lithium-ion batteries (LIBs) have become a main energy storage device in various applications, such as portable appliances, renewable energy facilities, and electric vehicles. However, the poor thermal stability of LIBs may cause explosion or fire. The thermal runaway is the result of a failure of the separator inside LIB. Damages like tearing, piercing, and collapsing of the separator were simulated in a mechanical, an electrical, and a thermal way, and small discharge pulses of a few mV were detected at the time of separator damages. From the experimental results, this paper provided a method that can identify the separator failure before thermal runaway in the aspect of a potential explosion and fire prevention measures.