• Journal of Advanced Marine Engineering and Technology
• /
• 제39권8호
• /
• pp.856-862
• /
• 2015

Tidal current energy is an important alternative energy resource among the various ocean energy resources available. The tidal currents in the South-Western sea of Korea can be utilized for the development of tidal current power generation. Tidal power generation can be beneficial for many fishing nurseries and nearby islands in the southwest region of Korea. Moreover, tidal power generation is necessary for promoting energy self-sufficient islands. As tidal currents are always available, power generation is predictable; thus, tidal power is a reliable renewable energy resource. The selection of an appropriate hydrofoil is important for designing a tidal current turbine. This study concentrates on the selection and numerical analysis of four different hydrofoils (MNU26, NACA63421, DU91_W2_250, and DU93_W_210LM). Blade element momentum theory is used for configuring the design of a 50 W class turbine rotor blade. The optimized blade geometry is used for computational fluid dynamics (CFD) analysis with hexahedral numerical grids. Among the four blades, NACA63421 blade showed the maximum power coefficient of 0.45 at a tip speed ratio of 6. CFD analysis is used to investigate the power coefficient, pressure coefficient, and streamline distribution of a 50 W class horizontal axis tidal current turbine for different hydrofoils.

• 한국태양에너지학회 논문집
• /
• 제40권4호
• /
• pp.35-44
• /
• 2020

Currently, various policies regarding ecofriendly vehicles are being proposed to reduce carbon emissions. In this study, the required areas for charging electric vehicle (EV) batteries using electricity produced by photovoltaic (PV) power plants were estimated. First, approximately 2.4 million battery EVs, which represented 10% of the total number of vehicles, consume approximately 404 GWh. Second, the power required for charging batteries is approximately 0.3 GW, and the site area of the PV power plant is 4.62 ㎢, which accounts for 0.005% of the national territory. Third, from the available sites of buildings based on the region, Jeju alone consumes approximately 0.2%, while the rest of the region requires approximately 0.1%. Fourth, Seoul, which has the smallest available area of mountains and farmlands, utilizes 0.34% of the site for PV power plants, while the other parts of the region use less than 0.1%. The results of this study confirmed that the area of the PV power plant site for producing battery-charging power generated through the supply of EVs is very small. Therefore, it is desirable to analyze and implement more specific plans, such as efficient land use, forest damage minimization, and safe maintenance, to expand renewable energy, including PV power.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
• /
• pp.381-386
• /
• 2001

This paper reports on the development of micro power system under way at Seoul National University. The interdisciplinary tin consists of members with various backgrounds of mechanics and materials. The need for micro power systems is explained, and a turbine under development is described. Design, and fabrication are introduced, and technical challenges in each phase are described. Furthermore, the interaction between the available fabrication methods and design is explained. Design involves use of commercially available codes to analyze flow fields, and fabrication takes advantage of the silicon wafer etching processes used to manufacture semiconductor devices.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1999년도 추계종합학술대회 논문집
• /
• pp.372-375
• /
• 1999

This paper proposes a bit allocation algorithm using adaptive bandwidth for ADSL that uses the DMT technology. In certain cases for high attenuation loops the conventional algorithms are unable to assign data bits to the higher frequency tones, due to the power spectrum mask limitation recommended by ANSI Standard, even if the total power budget is not expended. In the proposed bit allocation algorithm, adjacent empty tones that would not be used merge into single tone, then additional bits is assigned to the merged empty tones. Because additional bits is allocated, most of the available power is used. The proposed algorithm show that total bit increase in about 2~9% bits more than about conventional "water-filling" and "bit removal" algorithms and that is able to use about 93% of the available budget Power

• KIEE International Transactions on Power Engineering
• /
• 제5A권4호
• /
• pp.385-389
• /
• 2005

Power transformers would appear to be simple. However, due to their nonlinear and frequency-dependent behaviors, they can be one of the most complex system components to model. It is imperative that the applied models be appropriate for the range of frequencies and excitation levels that the system experiences. Transformer modeling is not a mature field and newer improved models must be made available in ATP packages. Further, there is a lack of published guidance on recommended modeling approaches. And there is typically not enough detailed design or test information available to determine the parameters for a given model. The purpose of this paper is to develop improved transformer core models for ATP and parameter estimation methods that can efficiently utilize the limited available information such as factory test reports.

• 항공우주기술
• /
• 제3권2호
• /
• pp.50-55
• /
• 2004

이륙중량 900㎏의 CRW 비행체에 맞게 설계한 추진시스템에 대해서 회전익모드 및 천이모드에서의 성능해석을 수행하였다. 추진시스템은 터보제트엔진, 덕트류 및 노즐로 구성된다. 엔진 터빈출구부터 노즐까지의 덕트 내부유동을 1차원 유동으로 가정하여 압축성, 점성유동해석을 하였다. 특히 로터 블레이드내의 유동은 점성효과와 함께 원심력의 효과도 고려하였다. 계산결과로 회전익모드에서 요구동력을 만족시키기 위한 엔진 Throttle 범위와, 천이모드에서 요구동력 및 요구출력을 만족시키기 위한 엔진 Throttle, 유량배분, 로터회전속도, 순항 노즐면적 등을 제시하였다.

• Journal of Electrical Engineering and Technology
• /
• 제6권1호
• /
• pp.14-24
• /
• 2011

In order to facilitate the electricity market operation and trade in the restructured environment, ample transmission capability should be provided to satisfy the demand of increasing power transactions. The conflict of this requirement and the restrictions on the transmission expansion in the restructured electricity market has motivated the development of methodologies to enhance the available transfer capability (ATC) of existing transmission grids. The insertion of flexible AC transmission System (FACTS) devices in electrical systems seems to be a promising strategy to enhance single area ATC and multi-area ATC. In this paper, the viability and technical merits of boosting single area ATC and multi-area ATC using Thyristor controlled series compensator (TCSC), static VAR compensator (SVC) and unified power flow controller (UPFC) in single device and multi-type three similar and different device combinations are analyzed. Particle swarm optimization (PSO) algorithm is employed to obtain the optimal settings of FACTS devices. The installation cost is also calculated. The study has been carried out on IEEE 30 bus and IEEE 118 bus systems for the selected bilateral, multilateral and area wise transactions.

• 전기학회논문지
• /
• 제59권6호
• /
• pp.1017-1024
• /
• 2010

Under the Kyoto Protocol many countries have been requested to participate in emissions trading with the assigned $CO_2$ emissions. In this environment, it is inevitable to change the system and market operation in deregulated power systems, and then ensuring safety margin is becoming more important for balancing system security, economy and $CO_2$ emissions. Nowadays, available transfer capability (ATC) is a key index of the remaining capability of a transmission system for future transactions. This paper presents a novel approach to the ATC evaluation with $CO_2$ emissions using multi-objective particle swarm optimization (MOPSO) technique. This technique evolves a multi-objective version of PSO by proposing redefinition of global best and local best individuals in multi-objective optimization domain. The optimal power flow (OPF) method using MOPSO is suggested to solve multi-objective functions including fuel cost and $CO_2$ emissions simultaneously. To show its efficiency and effectiveness, the results of the proposed method is comprehensively realized by a comparison with the ATC which is not including $CO_2$ emissions for the IEEE 30-bus system, and is found to be quite promising.

• 전기학회논문지
• /
• 제58권3호
• /
• pp.437-443
• /
• 2009

In recent years, electric power systems have been experiencing a rapid change due to the increasing electricity market. For the effective use of power system under the deregulated environment, it is important to make a fast and accurate calculation of the maximum available transfer capability (ATC) from a supply point to a demand point. In this paper, the purpose of this research is to calculate ATC fast and accurately for securing the stability of system and raising the efficiency as a result of anticipating transmission congestion according to transmission open access progressed in the future under the regulated environment of electricity market. In this paper, a study utilized a relation of the potential energy and energy function by which calculated CCT and then utilized a relation of PEBS for transient stability ATC calculation. In this paper, ATC was calculated as RPF and Energy Function method and calculation results of each method was compared. Contingence ranking method decided the weak bus by the Eigenvalues of Jacobian matrix and overloading branches by PI-index. As a result, a study proved the fast and accurate ATC calculation method considering transient stability suggested in this paper. Through the case study using New England 39 bus system, it is confirmed that the proposed method can be used for real time operation and the planning of electric market.

• 조명전기설비학회논문지
• /
• 제22권2호
• /
• pp.94-100
• /
• 2008

가용송전용량(ATC)은 계통내의 한 지역에서 다른 지역까지 실제 전력을 증가시키는 것이다. 지금까지 ATC 계산은 대부분 정상상태에서 실행가능성을 주로 고려하여 계산되어 왔다. 하지만 ATC 평가시 과도안정도로 제약된 ATC 계산은 매우 중요한 부분이다. ATC 평가시에는 제약조건으로 열적용량, 전압 및 과도안정도로 제약된 상정사고(n-1)시 안전도 평가가 요구된다. 본 논문은 자코비안 행렬의 고유치를 이용하여 상정사고 우선순위를 선정하였고, 에너지 함수법을 이용하여 선로의 열적용량, 전압안정도 및 과도안정도를 고려한 ATC를 계산하였다.