Reliability-driven design optimization of si solar module under thermal cycling

Seungil Park,Changwoon Han 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8

The lifetime of solar modules is not only a reliability measure but also an important factor in increasing the competitiveness of the modules against other power generation technologies. The advancement of module technology has enabled an increase in the power lifetime warranty of Si solar modules, which is currently 25 years and is expected to increase further. To enhance the lifetime of the Si solar module under thermal cycling, numerical analysis, optimization, and experimental validation were conducted on module design. The strain energy density on the solder layer was identified as a critical measure of the reliability in thermal cycling. The solar module was numerically modeled, including the viscosity of ethylenevinyl acetate and solder layers. A series of sensitivity studies using the model revealed that the thicknesses of Cu and Si should be reduced to enhance the lifetime under thermal cycling conditions. The lifetime of the reliability-enhanced design is expected to increase by 181 %, or in the range of 156 to 209 %, under thermal cycling environments such as daily thermal fatigue in the desert. An experimental validation confirmed the design optimization.

Citric acid stabilized iron oxide nanoparticles for battery- type supercapacitor electrode

Seungil Park,C. Justin Raj,Ramu Manikandan,Byung Chul Kim,Kook Hyun Yu 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.2

We report the synthesis of citrate stabilized iron oxide (C-Fe3O4) spherical nanoparticles for supercapacitor electrodes. Thecitrate functional group present in the surface of the Fe3O4 nanoparticles effectively controls the morphology and the surfacearea of the nanostructures. The C-Fe3O4 electrodes exhibited a battery-like energy storage properties with a maximum specificcapacity of 146 Cg−1 (242 Fg−1) which is much higher than the specific capacity of citrate free Fe3O4 electrode (62 Cg−1; 112Fg−1). Moreover, the C-Fe3O4 electrode showed better cyclic stability (75%) than the citrate free Fe3O4 electrode (~35%) after1000 charge/discharge cycles.

Semipurification of Ice-crystal Controlling Protein from the Arctic Bacterium Aquaspirillum sp. KOPRI-AB30

Seungil Park,Hak Jun Kim,Soyoung Park,Ki-Won Seo,Sung-Ho Kang 한국생물공학회 2007 한국생물공학회 학술대회 Vol.2007 No.4

FAGA: Feedback-Aided Greedy Algorithm for Periodic Messages in LTE V2V Communications

Park, Seungil,Yoon, Hoyoung,Kim, Byungjun,Choi, Sunghyun IEEE 2018 IEEE Transactions on Vehicular Technology VT Vol.67 No.11

<P>Vehicle-to-vehicle (V2V) communication based on the device-to-device (D2D) communication in long term evolution (LTE) system is emerging as a key enabler for connected vehicles today. In this paper, we consider safety-related messages periodically transmitted by vehicle to announce its current status to other neighboring vehicles. The current state-of-the-art LTE V2V communication uses greedy algorithm for the transmission of such periodic messages. Greedy algorithm is known to have decent performance, but the performance is limited due to the lack of a collision–detection mechanism. In this paper, we propose <I>feedback-aided greedy algorithm (FAGA)</I> to complement the drawback of greedy algorithm. We evaluate FAGA via realistic simulations to show that it outperforms comparison schemes in terms of overall message reception ratio (MRR). As a result, it is shown that FAGA operates well even with small amount of feedback and its performance is close to the performance of centralized scheduling method. Moreover, FAGA outperforms greedy algorithm by up to 23.7% in terms of MRR performance.</P>

RA-eV2V: relaying systems for LTE-V2V communications

Park, Seungil,Kim, Byungjun,Yoon, Hoyoung,Choi, Sunghyun Editorial Department of Journal of Communications 2018 Journal of communications and networks Vol.20 No.4

<P>Emerging Long Term Evolution-based vehicle-to-vehicle (LTE-V2V) communication will support exchange of safety-related broadcast messages among vehicles. Such messages are generated periodically to announce one's own current state to other neighboring vehicles. The message reception performance in LTE-V2V drops sharply as communication distance increases if the communication channel is in a non-line-of-sight (NLOS) situation. To alleviate the problem, we propose a relaying system, called relayassisted enhanced V2V (RA-eV2V). In RA-eV2V, Road side unit (RSU) is in charge of relaying messages, received from vehicular user equipments (V-UEs). The operation of RSU is fully independent from other entities, meaning that the deployment of RSU on the road has no constraint at all. Moreover, there is no change from the current 3GPP standard operation on V-UE side either. In our realistic simulation, RA-eV2V hugely outperforms the 3GPP baseline scheme, e.g., by up to 36.5% in terms of message reception ratio in NLOS situations. Moreover, the feasibility of RA-eV2V is proven through real-map based simulation, which realistically reflects the actual situations on the roads.</P>

Surface plasmon effect of Ag nanodots embedded in amorphous Si window layers deposited on Si solar cells.

Park, Seungil,Ji, HyungYong,Kim, Myeong Jun,Peck, Jong Hyeon,Kim, Keunjoo American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.12

<P>We investigated solar cells containing temperature-dependent Ag nanodots embedded in an amorphous Si thin film layer by using hot-wire chemical vapor deposition in order to improve the properties of crystalline Si solar cells. An Ag thin film with a thickness of 10 nm was deposited by DC sputtering followed by annealing at various temperatures ranging from 250 to 850 degrees C for 15 min under N2 gas. As increasing the annealing temperature, the Ag nanodots were enlarged and the photoreflectances of the samples with Ag nanodots were lower than the reference samples in the spectral range of 200-600 nm, demonstrating the plasmon effect of Ag nanodots. The cell properties on photoluminescence spectra, quantum efficiency, and conversion efficiency were measured with the maximum values for the sample annealed at 450 degrees C, indicating that there exists an optimal size of the Ag nanodots about 15-35 nm to be effective on the enhancement of surface plasmon effect.</P>

Evolution of the large genome in <i>Capsicum annuum</i> occurred through accumulation of single‐type long terminal repeat retrotransposons and their derivatives

Park, Minkyu,Park, Jongsun,Kim, Seungill,Kwon, Jin‐,Kyung,Park, Hye Mi,Bae, Ik Hyun,Yang, Tae‐,Jin,Lee, Yong‐,Hwan,Kang, Byoung‐,Cheorl,Choi, Doil Blackwell Publishing Ltd 2012 The Plant journal Vol.69 No.6

<P><B>Summary</B></P><P>Although plant genome sizes are extremely diverse, the mechanism underlying the expansion of huge genomes that did not experience whole‐genome duplication has not been elucidated. The pepper, <I>Capsicum annuum</I>, is an excellent model for studies of genome expansion due to its large genome size (2700 Mb) and the absence of whole genome duplication. As most of the pepper genome structure has been identified as constitutive heterochromatin, we investigated the evolution of this region in detail. Our findings show that the constitutive heterochromatin in pepper was actively expanded 20.0–7.5 million years ago through a massive accumulation of single‐type <I>Ty3/Gypsy</I>‐like elements that belong to the Del subgroup. Interestingly, derivatives of the Del elements, such as non‐autonomous long terminal repeat retrotransposons and long‐unit tandem repeats, played important roles in the expansion of constitutive heterochromatic regions. This expansion occurred not only in the existing heterochromatic regions but also into the euchromatic regions. Furthermore, our results revealed a repeat of unit length 18–24 kb. This repeat was found not only in the pepper genome but also in the other solanaceous species, such as potato and tomato. These results represent a characteristic mechanism for large genome evolution in plants.</P>

Ag Nanodots Emitters Embedded in a Nanocrystalline Thin Film Deposited on Crystalline Si Solar Cells

Park, Seungil,Ryu, Sei Gi,Ji, HyungYong,Kim, Myeong Jun,Peck, Jong Hyeon,Kim, Keunjoo American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.6

<P>We fabricated crystalline Si solar cells with the inclusion of various Ag nanodots into the additional emitters of nanocrystallite Si thin films. The fabricated process was carried out on the emitter surface of p-n junction for the textured p-type wafer. The Ag thin films were deposited on emitter surfaces and annealed at various temperatures. The amorphous Si layers were also deposited on the Ag annealed surfaces by hot-wire chemical vapor deposition and then the deposited layers were doped by the second n-type doping process to form an additional emitter. From the characterization, both the Ag nanodots and the deposited amorphous Si thin films strongly reduce photo-reflectances in a spectral region between 200-400 nm. After embedding Ag nanodots in nanocrystallite Si thin films, a conversion efficiency of the sample with added emitter was achieved to 15.1%, which is higher than the 14.1% of the reference sample and the 14.7% of the de-posited sample with a-Si: H thin film after the Ag annealing process. The additional nanocrystallite emitter on crystalline Si with Ag nanodots enhances cell properties.</P>

Analysis of EL images on Si solar module under thermal cycling

Seungil Park,Changwoon Han 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.7

Thermal cycling (TC) induces defects in solar modules. The electroluminescence technique has been used to characterize the defects of solar modules, which are represented by a rectangular dark area (RDA) on the cell. In this study, the physical meaning of the RDA phenomenon on a solar module was investigated. It is proven that the RDA indicates cracks in the solder layer of the ribbon wire rather than broken electrode fingers in the solar module. For the proof, a test of TC was conducted on Si solar modules while monitoring the RDAs by EL during TC. Next, a failure analysis was performed on the RDAs, proving that the locations of the RDA coincided with the locations of the cracks in the solder layer between the Cu layer and Si wafer. Quantitative time analysis revealed that the RDA incidence in cells increased from 0 to 18 % on average over TC 1000. In addition, the larger RDA incidence at the ends of the ribbon wires of the cell was detected and explained based on the previous study result of the high increases in shear strains of the solder layer at all ends of the ribbon wire after TC. Finally, a structural numerical simulation was performed to show a low probability of cracking at the electrode finger during TC.

전기발광방법을 이용한 실리콘 태양전지모듈의 온도사이클 환경에서 열화분석연구

박승일(SeungIl Park),이수연(Suyeon Lee),한창운(Changwoon Han) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4

본 논문에서는 핵연료집합체 내진해석에 사용되는 주요 입력변수가 핵연료집합체 내진해석 평가결과에 미치는 영향을 분석하였다. 핵연료집합체 내진평가는 지지격자에 발생하는 충격하중을 지지격자 좌굴 강도와 비교하여 평가한다. 또한, 핵연료집합체 주요 부위의 상세 응력평가를 통해 ASME Section III NB에 따른 허용기준과의 비교를 통해 평가가 이루어진다. 일반적으로 핵연료집합체 내진평가를 수행할 경우 응력평가 대비 지지격자에 발생하는 충격하중 평가 여유도가 더 작은 결과를 보이고 있으며, 본 연구에서는 주요 변수의 변화에 따른 지지격자 충격하중의 변화에 대해 분석하였다. 지지격자에 발생하는 충격하중은 수평방향 원자로내부구조물 및 노심 지진해석을 통해 결정되며, 해석 입력 값으로 사용되는 주요 물성치를 변수로 결정하여 연구를 수행하였다. 본 연구에서는 핵연료집합체 감쇠비, 집합체 기계적 강성, 지지격자 Through-Grid 강성, 연료간 간격에 따른 충격하중의 변화를 확인하였다. 그 결과, through-grid 강성의 변화가 지지격자 충격하중 증가/감소에 주요한 영향을 미치는 것으로 확인되었다. 이와 같은 결과는 설계기준초과지진 조건에서의 핵연료집합체 내진해석 방법론 개발에 활용될 수 있을 것으로 사료된다.