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Temperature coefficient of power (Pmax) of field aged PV modules: impact on performance ratio and degradation rate determinations
Author(s): Farrukh Mahmood; Hatif Majeed; Haider Agha; Saddam Ali; Sai Tatapudi; Telia Curtis; GovindaSamy TamizhMani
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Paper Abstract

The determinations of performance ratio (per IEC 61724 standard) and degradation rate (using slope of performance ratio over time) of photovoltaic (PV) modules in a power plant are computed based on the power (Pmax) temperature coefficient (TC) data of the unexposed modules or the exposed modules during the commissioning time of the plant. The temperature coefficient of Pmax is typically assumed to not change over the lifetime of the module in the field. Therefore, this study was carried out in an attempt to investigate the validity of this assumption and current practice. Several 18-19 years old field aged modules from four different manufacturers were tested for the baseline light I-V measurements and dark I-V measurements to determine the power temperature coefficient and series resistance for each module. Using the dark I-V and light I-V data, the series resistances (Rs) and shunt resistances (Rsh) were calculated in order to determine their impact on fill factor (FF) and hence on Pmax. The result of this work indicates a measurable drop in fill factor (FF) as the series resistance (Rs) increased which in turn increases the temperature coefficient of Pmax. This determination goes against the typical assumption that the temperature coefficient of (Pmax) for aged modules does not change over time. The outcome of this work has a significant implication on the performance ratio and degradation rate determinations based on the temperature coefficient of Pmax of new modules which is not an accurate practice for analyzing field aged modules.

Paper Details

Date Published: 23 August 2017
PDF: 7 pages
Proc. SPIE 10370, Reliability of Photovoltaic Cells, Modules, Components, and Systems X, 1037008 (23 August 2017); doi: 10.1117/12.2281840
Show Author Affiliations
Farrukh Mahmood, National Univ. of Sciences and Technology (Pakistan)
Univ. of Engineering and Technology (Pakistan)
Hatif Majeed, National Univ. of Sciences and Technology (Pakistan)
Univ. of Engineering and Technology (Pakistan)
Haider Agha, National Univ. of Sciences and Technology (Pakistan)
Univ. of Engineering and Technology (Pakistan)
Saddam Ali, National Univ. of Sciences and Technology (Pakistan)
Univ. of Engineering and Technology (Pakistan)
Sai Tatapudi, Arizona State Univ. (United States)
Telia Curtis, Arizona State Univ. (United States)
GovindaSamy TamizhMani, Arizona State Univ. (United States)


Published in SPIE Proceedings Vol. 10370:
Reliability of Photovoltaic Cells, Modules, Components, and Systems X
Neelkanth G. Dhere; Keiichiro Sakurai; Michael D. Kempe, Editor(s)

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