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Improving the accuracy of temperature coefficient measurement of a PV module by accounting for the transient temperature difference between cell and backsheet
Journal
Solar Energy
ISSN
0038092X
Date Issued
2022-05-01
Author(s)
Rao Golive, Yogeswara
Kottantharayil, Anil
Shiradkar, Narendra
Abstract
Accurate measurement of cell temperature inside a PV module is critical for the accurate measurement of Temperature Coefficients (TC) and Current-Voltage (I-V) characteristics corrected to Standard Test Conditions (STC). Estimating the cell temperature from the backsheet temperature while the module is heating or cooling is non-trivial because of the time-varying temperature difference between the cell and the backsheet. In this study, transient temperatures (for cell, EVA, front glass and backsheet) during heating and cooling are experimentally recorded for an inhouse laminated 4 cell multi c-Si PV coupon by inserting thermocouples during lamination. A One-Dimensional (1-D) transient simulation model using Finite Difference (FD) method is developed to observe the temperature profile along the thickness of the PV coupon. It is also used to obtain the temperature profiles for various layers for a full size 72-cell PV module as well as a glass-glass module with otherwise similar Bills of Materials. The maximum temperature difference observed between cell and backsheet was ∼ 2.35 ℃ for a glass-backsheet module and ∼ 5.3 ℃ for a glass-glass module which are heated to 75 ℃. Also, the transient temperature difference (TTD) showed an exponential decay profile after reaching the peak. The observed transient temperature difference led to ∼+7% error in the measurement of all the temperature coefficients of PV coupon or module if the backsheet temperature is used as a proxy for module / cell temperature. Accounting for this observed transient temperature difference between cell to backsheet leads to an improved accuracy of temperature coefficient measurements.
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