• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권10호
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• pp.4680-4697
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• 2017

In future, since the user experience plays a more and more important role in the development of today's communication systems, quality of experience (QoE) becomes a widely used metric, which reflects the subjective experience of end users for wireless service. In addition, the energy efficiency is an increasingly important problem with the explosive growth in the amount of wireless terminals and nodes. Hence, a QoE-aware energy efficiency maximization based joint user access selection and power allocation approach is proposed to solve the problem. We transform the joint allocation process to an optimization of energy efficiency by establishing an energy efficiency model, and then the optimization problem is solved by chaotic clone immune algorithm (CCIA). Numerical simulation results indicate that the proposed algorithm can efficiently and reliably improve the QoE and ensure high energy efficiency of networks.

• 조명전기설비학회논문지
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• 제26권8호
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• pp.18-26
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• 2012

Recently, there have been suggestions that power factor should be considered to increase the efficiency of electric power supply when evaluating the performance of the electric appliances in standby mode and the related studies have been conducted to improve the efficiency standard of standby power. But, they lack the analysis of the standby power characteristics with the changes of power factor. This study is conducted to analyze the standby power characteristics of TV which is a typical home appliance and reaches a conclusion that the apparent power can be a more reasonable index which reflects the efficiency of electric power supply. It is also found that LED TVs show the best performance in standby mode. Moreover, an example to set standby power standards on TVs to be applied in the future is suggested, considering the energy efficiency policies for appliances.

• 한국화재조사학회논문지
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• 제11권1호
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• pp.66-73
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• 2008

본 연구에서는 한국전기안전공사 서울지역본부 내 전기 전자 제품을 선정하여 각 기기의 전력사용량을 측정하고, 각 기기에 대해 대기전력 차단장치인 세이버 설치 전 후의 대기전력을 측정함으로서 평상시와 전원의 "OFF"시 대기전력을 비교함으로서 절전효과를 조사하였다. 연구결과 대기전력 차단장치인 세이버를 설치하였을 경우 전기 에너지 낭비요인을 원천적으로 제거함으로서 약 18%의 절전효과가 있었으며, 대기전력을 차단함으로서 전기화재를 근원적으로 예방하고 서지 등 이상전압에 의한 충격을 방지함으로서 전기 전자제품의 수명을 연장할 수 있었다.

• International Journal of Automotive Technology
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• 제8권3호
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• pp.361-373
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• 2007

In previous work, an approach based on maximizing the efficiency of an internal combustion engine while ignoring the power conversion efficiency of other powertrain components, such as the electric motor and power battery or ultracapacitor, was implemented in the steady-state optimization of an internal combustion engine for hybrid electric vehicles. In this paper, a novel control algorithm was developed and successfully justified as the basis for maximal power conversion efficiency of overall powertrain components. Results indicated that fuel economy improvement by 3.9% compared with the conventional control algorithm under China urban transient-state driving-cycle conditions. In addition, using the view of the novel control algorithm, maximal power generation of the electric motor can be chosen.

• 전기학회논문지
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• 제62권3호
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• pp.342-348
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• 2013

It proposes an efficient control algorithm to increase electric power transmission efficiency between photovoltaic power generating system and the grid. The main controller finds a maximum efficiency condition by considering the quantity of power generated from PV arrays, the number of inverters, and efficiency of PV inverter. According to the condition, a relay board arranges a point of contract of PV arrays. By the disposition of PV arrays, it assigns the optimized power on each PV inverter. Operational principle of the proposed maximum efficiency point tracking algorithm is given in detail. To verify the validity of the proposed approach, computer-aided simulation and experiment carried out.

• KEPCO Journal on Electric Power and Energy
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• 제2권3호
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• pp.403-407
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• 2016

In general, drum-type boilers are designed for base load duty and applied under constant pressure operation mode. Recently, however conditions often occur that even drum-type boilers have to operate at partial load conditions. A feasibility study on adopting the sliding pressure operation for drum-type boiler was conducted, and corresponding performance changes and effects on the equipment were analyzed by utilizing a process simulation model. As a result, the conclusion was reached that drum type boilers are able to adopt the sliding pressure operation and can improve of net efficiency at part load operation in spite of the Rankine cycle efficiency reduction due to the decreases in main steam pressure. Because of thank to improvement of high pressure turbine stage-1 internal efficiency and power savings of boiler feed water pump. The sliding pressure operation is advantageous in terms of stress level relief for boiler tube as well as maintaining the rating steam temperature at part load condition. However, cautions are required because the drum boilers have poor dynamic response characteristics which may get worse during the sliding pressure operation.

• Journal of Electrochemical Science and Technology
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• 제12권3호
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• pp.302-307
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• 2021

Polymer electrolyte membrane (PEM) electrolyzer or alkaline electrolyzer is required to produce green hydrogen using renewable energy such as wind and/or solar power. PEM and alkaline electrolyzer differ in many ways, instantly basic materials, system configuration, and operation characteristics are different. Building an optimal water hydrolysis system by closely grasping the characteristics of each type of electrolyzer is of great help in building a safe hydrogen ecosystem as well as the efficiency of green hydrogen production. In this study, the basic operation characteristics of a kW class alkaline water electrolyzer we developed, and water electrolysis efficiency are described. Finally, a brief overview of the characteristics of PEM and alkaline electrolyzer for large-capacity green hydrogen production system will be outlined.

• Korean Chemical Engineering Research
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• 제44권5호
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• pp.489-497
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• 2006

국내 무연탄을 사용하는 미분탄 화력보일러(영동화력 2호기)를 대상으로 비교적 고효율, 저비용으로 전기를 생산하는 청정보일러인 순환유동층 보일러로의 전환 시 경제성 평가 및 민감도 분석을 수행하였다. 경제성 평가는 크게 순환 유동층 보일러로의 전환 시와 기존의 미분탄 보일러를 유지 시에 각각의 투자금액에 대한 경제성 평가와 이의 비교를수행하였으며, 더불어 전력시장의 상황 변화에 따른 경제성 민감도 분석을 수행하였다. 경제성 평가 결과, 현 상태에서는 전력산업기반기금이 지원을 받고 있는 무연탄 발전사업의 특성상 기존 보일러를 유지하는 것이 경제성 지표가 더 좋은 것으로 평가되었으나, 전력산업기반기금의 지원 형태 및 그 규모에 따라 순환유동층으로의 전환이 장기적 발전사업 및 기반기금의 효율적 집행 그리고 국가 에너지 이용률에 있어 더 좋은 경제 지표를 나타내는 것으로 평가되었다

• Current Optics and Photonics
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• 제2권2호
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• pp.179-184
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• 2018

Terahertz (THz) wave generation by periodically poled $BaTiO_3$ (PPBT) with a quasi-phase-matching (QPM) scheme based on cascaded difference-frequency generation (DFG) is theoretically analyzed. The cascaded DFG processes comprise cascaded Stokes and anti-Stokes processes. The calculated results indicate that the cascaded Stokes processes are stronger than the cascaded anti-Stokes processes. Compared to a noncascaded Stokes process, THz intensities from $20^{th}$-order cascaded Stokes processes increase by a factor of 30. THz waves with a maximum intensity of $0.37MW/mm^2$ can be generated by $20^{th}$-order cascaded DFG processes when the optical intensity is $10MW/mm^2$, corresponding to a quantum conversion efficiency of 1033%. The high quantum conversion efficiency of 1033% exceeds the Manley-Rowe limit, which indicates that PPBT is an excellent crystal for THz wave generation via cascaded DFG.

• KEPCO Journal on Electric Power and Energy
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• 제6권2호
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• pp.157-161
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• 2020

온실 가스 감축과 관련하여 BIPV (Building Integrated Photovoltaics)는 청정 에너지 자원을 바탕으로 도심의 빌딩에서 자체적으로 전력을 생산할 수 있는 중요한 기술이다. 특히, 페로브스카이트 물질은 투명성을 지니고 있으며, 다양한 색상 구현이 가능하여 BIPV용 태양전지로 주목받고 있다. 그러나 태양전지의 투과도와 효율은 서로 반비례 관계에 있어 두 인자를 모두 높이는 것은 쉽지 않은 과제이다. 따라서 본 논문에서는 투과도와 효율을 모두 높일 수 있는 반투명 페로브스카이트 태양전지 구조를 제안하고, 이를 평가하였으며, 안정성 평가를 위해 국제표준에 따른 내구성 평가를 수행하였다.