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47 results on '"Khoo, Yong Sheng"'

9. Measurement and Simulation of Moisture Ingress in PV Modules in Various Climates

Author

Mitterhofer, Stefan, Slapsak, Jan, Astigarraga, Alexander, Moser, David, Hernandez, Guillermo Oviedo, Chiantore, Paolo Vincenzo, Luo, Wei, Khoo, Yong Sheng, Rabanal-Arabach, Jorge, Fuentealba, Edward, Ferrada, Pablo, Trigo Gonzalez, Mauricio, Ascencio-Vasquez, Julian, Topic, Marko, and Jankovec, Marko

Abstract

Moisture plays a critical role in the degradation process of photovoltaic (PV) modules in field conditions. A commonly used approach is to evaluate the properties of PV materials by conducting tests in climatic chambers, and then apply the Fickian diffusion model in simulations to replicate field conditions, however, without experimental verification. This study describes an experimental setup for in situ measurement of moisture in fielded minimodules, using miniature temperature and humidity sensors encapsulated within the modules. Five identical setups are deployed in different climatic regions around the world, enabling a quantitative evaluation of moisture diffusion in the field and a comparison of different climates. The relative humidity measured beside the cell follow weekly weather trends due to breathable backsheet, whereas the sensors in front of the cell react much slower to outside changes and follow seasonal trends. We show that a single 2-D simulation, which is a standard practice in published studies, is insufficient to accurately depict moisture diffusion in front of the cell. Therefore, a two-stage 2-D simulation model, combining Fickian diffusion in vertical and horizontal cross section with carefully set boundary conditions, was introduced. A comparison with measurement results showed the simulation approach to be a good compromise between the simulation accuracy and speed. Finally, the results underscore the significance of understanding the local microclimate surrounding the modules, including the interface between air and backsheet, which is necessary for precise moisture diffusion simulations.

Published
2024
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23. Design of shading‐ and hotspot‐resistant shingled modules.

Author

Clement, Carlos Enrico, Singh, Jai Prakash, Khoo, Yong Sheng, Halm, Andreas, Tune, Daniel, and Birgersson, Erik

Subjects
STRAY currents, POWER density, HIGH temperatures
Abstract

The shingled module has become an attractive interconnection architecture for its higher packing density and superior power generation. However, with longer string lengths and smaller cell areas, these modules are particularly susceptible to developing hotspots from shading elements. In this paper, a framework for the design of hotspot‐ and shading‐resistant shingled modules is presented. An electrothermal model is developed and validated extensively through specially fabricated shingled modules that allow for string‐level measurement and analysis. To investigate the relative influence of cell electrical characteristics on power loss and hotspot temperature, we perform a stochastic Monte Carlo simulation which reveals a greater sensitivity to parameters associated with the shaded cell's leakage current. A further study on cells with illumination‐dependent Jleakage shows the detriment of this light‐induced effect where higher hotspot temperatures can develop. Module‐level parameters are also investigated where string length, number of parallel strings, and cell fraction are studied in relation to their impact on module power and hotspot response. Finally, these findings are condensed into a design matrix which defines the space in which module manufacturers may configure shingled modules such that hotspots will not exceed a set threshold temperature. [ABSTRACT FROM AUTHOR]

Published
2022
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25. Bifacial modules: design options, characterisation and reliability

Author

Andreas Schneider, Eric Gerritsen, Jai Prakash, Bas van Aken, Vahid Fakhfouri, Andreas Halm, and Khoo Yong Sheng

Subjects
Reliability (semiconductor), Performance ratio, Exploit, Computer science, Facade, Building-integrated photovoltaics, Cost of electricity by source, Roof, Technical change, Reliability engineering
Abstract

Bifacial modules can be applied for large PV plants as well as for residential (flat white roof) and more specific BIPV (facade) applications and can also open up new PV application opportunities like in sound barriers or other vertical installations (fences, balconies).For bifacial PV plants, the objective is to exploit the main bifacial benefit which is a large reduction of LCOE (due to higher energy yield) with a minimal technical change or investment.

Published
2018
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27. Analysis of Hotspots in Half Cell Modules Undetected by Current Test Standards

Author

Qian, Jiadong (Harry), Clement, Carlos Enrico, Ernst, Marco, Khoo, Yong Sheng, Thomson, Andrew, Blakers, Andrew, Qian, Jiadong (Harry), Clement, Carlos Enrico, Ernst, Marco, Khoo, Yong Sheng, Thomson, Andrew, and Blakers, Andrew

Abstract

Today, hotspots are a major source of failure for photovoltaic modules in the field. Modules based on half-cut solar cells are an attractive pathway to reduce cell-to-module losses and are projected to have a 40% market share by 2028. However, the current standard for module testing IEC 61215-2 can leave critical hotspots undetected in such a module configuration. In this paper, the hotspot effect of half-cell modules using parallel connected cell substrings is studied in comparison with conventional full-cell modules. Significant hotspots are induced in both half- and full-cell modules, when suffering current mismatch, in this case induced by partial shading. When shaded by the same area, the hotspot temperature of the cell in a half-cell module is 19 °C lower than the full-cell module in this experimental work. Critically, multiple unshaded weak cells are found to dissipate heat when the parallel-connected substring is shaded. In an experimental situation with a total shading ratio of only 4%, we measure hotspots of over 90 °C-a situation that can occur in the field due to uncontrolled plant growth and bird droppings.

Published
2019

32. Quantitative Electroluminescence Imaging Analysis for Performance Estimation of PID-Influenced PV Modules

Author

Bedrich, Karl G., primary, Luo, Wei, additional, Pravettoni, Mauro, additional, Chen, Daming, additional, Chen, Yifeng, additional, Wang, Zigang, additional, Verlinden, Pierre J., additional, Hacke, Peter, additional, Feng, Zhiqiang, additional, Chai, Jing, additional, Wang, Yan, additional, Aberle, Armin G., additional, and Khoo, Yong Sheng, additional

Published
2018
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39. Field Investigations of Potential-Induced Degradation (PID) for Crystalline Silicon PV Panels in Different Climates

Author

Chen, Yifeng, primary, Hacke, Peter, additional, Khoo, Yong Sheng, additional, VanSant, Kaitlyn, additional, Wang, Zigang, additional, Luo, Wei, additional, Chai, Jing, additional, Deline, Chris, additional, Wang, Yan, additional, Aberle, Armin G., additional, Altermatt, Pietro P., additional, Feng, Zhiqiang, additional, Kurtz, Sarah, additional, and Verlinden, Pierre J., additional

Published
2017
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