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Investigation of EVA Accelerated Degradation Test for Silicon Photovoltaic Modules
Jaeun Kim,Matheus Rabelo,Markus Holz,Eun-Chel Cho,Junsin Yi 한국신재생에너지학회 2021 신재생에너지 Vol.17 No.2
Renewable energy has become more popular with the increase in the use of solar power. Consequently, the disposal of defective and old solar panels is gradually increasing giving rise to a new problem. Furthermore, the efficiency and power output decreases with aging. Researchers worldwide are engaged in solving this problem by developing eco-module technologies that restore and reuse the solar panels according to the defect types rather than simple disposal. The eco-module technology not only solves the environmental problem, but also has economic advantages, such as extending the module life. Replacement of encapsulants contributes to a major portion of the module maintenance plan, as the degradation of encapsulants accounts for 60% of the problems found in modules over the past years. However, the current International Electrotechnical Commission (IEC) standard testing was designed for the commercialization of solar modules. As the problem caused by long-term use is not considered, this method is not suitable for the quality assurance evaluation of the eco-module. Therefore, to design a new accelerated test, this paper provides an overview of EVA degradation and comparison with the IEC and accelerated tests.
Optimization of ALD-HfOx Passivation Layer for PERC Solar Cells
Jaeun Kim(김자은),Junsin Yi(이준신) 한국신재생에너지학회 2021 한국신재생에너지학회 학술대회논문집 Vol.2021 No.7
Passivated emitter and rear contact (PERC) solar cell is the most dominant technology in the global solar cell market. In order to improve the efficiency of PERC solar cells, research on a passivation layer that increases the lifetime and the open circuit voltage (VOC) by inhibiting surface recombination is being actively conducted. Aluminum oxide (Al<sub>2</sub>O<sub>3</sub>) is mainly used material as a passivation layer in mass-produced solar cells. However, A is not suitable for n-type because it has a negative fixed charge. Hafnium oxide (HfOx) is one of the attractive candidates for passivation layer because it can have both of negative and positive fixed charge by controlling the deposition conditions or annealing conditions. In this study, the effects of deposition conditions and post-annealing conditions are investigated by analysis of electrical properties. Deposition rate is calculated by measuring the thickness according to the process cycle of atomic layer deposition (ALD) with controlling the pulse time of hafnium. Electrical property according to pulse time and annealing conditions is analyzed with interface trap density (Dit) and fixed charge (Qf) by C-V measurement and lifetime of carriers. Finally, the pulse time and the annealing condition are optimized with low Dit, 1.1E+12cm<sup>-2</sup> and high Qf, 6.5E+12cm<sup>-2</sup>.
Development and Test of a Cooling System for a 154 kV Superconducting Fault Current Limiter
Kim, Heesun,Han, Young Hee,Yang, Seong-Eun,Yu, Seung-Duck,Park, Byung Jun,Park, Kijun,Yoo, Jaeun,Kim, Hye-Rim,In, Sehwan,Hong, Yong Joo,Yeom, Hankil Korea Electric Power Corporation 2015 KEPCO Journal on electric power and energy Vol.1 No.1
The superconducting fault current limiter (SFCL) is an electric power device that limits the fault current immediately in a power grid. Korea Electric Power Corporation (KEPCO) has been developing a 154 kV, 2 kA SFCL since 2011 to protect power grids from increasing fault current and improve the stability and quality of electric power. This SFCL adopts 2G YBCO wires and operates at 71 K and 5 bars. In this paper, a cooling system for the 154 kV SFCL and its cooling test results are reported. This cooling system uses a Stirling-type cooler to make sub-cooled liquid nitrogen ($LN_2$), which cools the superconductor modules of the SFCL. The $LN_2$ is circulated between the cooler and the cryostat that contains superconductor modules. The $LN_2$ also plays the role of a high voltage insulator between the modules and the cryostat, so the pressure was maintained at 5 bars for high insulation performance. After installation in a test site, the cooling characteristics of the system were tested. In this operation test, some important data were measured such as temperature distribution in $LN_2$, pressure change, performance of the heat exchanger, and cooling capacity of the total system. Consequently, the results indicate that the cooling system operates well as designed.
박재언(Jaeun Park),황민철(Mincheol Whang),김종화(Jonghwa Kim),김지혜(Jihye Kim),안상민(Sangmin Ahn),이정년(Jungnyun Lee),박상인(Sangin Park),문성철(Sungchul Mun),조봉화(Bonghwa Jo) 한국HCI학회 2011 한국HCI학회 학술대회 Vol.2011 No.1
본 논문은 얼굴 표정을 인식하여 각성도를 측정하고 측정된 각성도의 정확성을 뇌파를 통해 검증함으로써 얼굴 인식에 의한 각성도 평가의 가능성을 확인하는 것이 목적이다. Web 카메라를 통해 획득한 얼굴 표정에서 눈, 눈썹, 그리고 입의 특징점 좌표를 추출하였다. 그리고 좌표간의 관계를 분석함으로써 얼굴의 각성도를 평가하였다. 얼굴의 각성도는 Ekman의 FACS(Facial Action Coding System)기법을 사용하여 각성도에 영향을 주는 5가지 AU(Action Unit) Factor를 통해 평가하였다. 동시에 얼굴 표정 인식을 통한 각성도 측정의 가능성을 확인하기 위하여 뇌파의 α파와 β파를 측정하여 객관적인 지표로서 피실험자의 각성도를 측정하였다. 자극은 각성도에 영향을 줄 수 있는 영상 자극을 사전실험을 거쳐 4가지 자극이 선택되었으며 각 자극 제시 후 주관 설문을 실시하였다. Ekman의 6가지 표정에 의한 감성 인식의 경우 모든 감성을 표현할 수 없다는 단점이 있기 때문에 Russell의 감성 2차원 모델을 사용하여 각성도를 표현하였다. 본 연구를 통해 얼굴 표정에 의한 각성도 측정을 통해 감성 모델링이 가능할 것으로 보이며 얼굴 표정에 의한 쾌감도 측정 시스템을 개발하면 완벽한 감성 모델링이 가능할 것으로 사료된다.
Design of Post Metal Shields Through Electric Field Distribution Analysis for a 154-kV SFCL
Yoo, Jaeun,Shin, Woo-Ju,Han, Young-Hee,Lee, BangWook,Kim, Hey-Rim,Yang, Seong Eun,Kim, Heesun,Yu, Seung-Duck,Park, Kijun Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3
<P>Korea Electric Power Corporation has developed a 154-kV superconducting fault current limiter (SFCL). This report is a part of the design process of the SFCL, particularly for fixation of posts supporting the superconducting element on the cryostat wall side. For supporting the superconducting element, the use of a post insulator is inevitable; however, the post insulator and cryostat with liquid nitrogen <inline-formula> <TEX-math notation='LaTeX'><TEX>$(\mbox{L}\mbox{-}\mbox{N}_{2} ) $</TEX></tex-math></inline-formula> during operation of the SFCL form three junction points where electric field is intensified. In this study, we aim to design the metal shield in order to relax the electric field intensity at triple points (TPs through numerical analysis of electric field distribution. For the electric field distribution analysis, a commercial software based on the finite-element method was employed. Each design for the metal shield was checked whether it makes the electric field intensity at the TP sufficiently lower than dielectric strength in <inline-formula> <TEX-math notation='LaTeX'><TEX>$\mbox{L}\mbox{-}\mbox{N}_{2} $</TEX></tex-math></inline-formula> for 750-kV input and whether there is any electrically weak point on the metal. The designs of the metal shields were improved through four critical steps where thermal contraction, manufacture tolerance, and insulation distance in <inline-formula> <TEX-math notation='LaTeX'><TEX>$\mbox{L}\mbox{-}\mbox{N}_{2} $</TEX></tex-math></inline-formula> were considered. It was experimentally verified that there was no electric breakdown in <inline-formula> <TEX-math notation='LaTeX'><TEX>$\mbox{L}\mbox{-}\mbox{N}_{2} $</TEX></tex-math></inline-formula> between the metal shield and the fiber-reinforced plastic post insulator for the lightning impulse test and the ac breakdown voltage test according to the IEC 60137 standard.</P>