COMPARISON OF INDOOR AND OUTDOOR MEASURED THERMAL COEFFICIENTS OF PHOTOVOLTAIC MODULES
DOI:
https://doi.org/10.59627/cbens.2014.2054Keywords:
Photovoltaic solar energy, Thermal coefficientsAbstract
The effect of temperature on photovoltaic modules is a crucial factor in the performance analysis of photovoltaic systems. The thermal coefficients describe the effect of temperature on the photovoltaic parameters. In order to correct the I-V curves to different conditions of temperature it is necessary to determine the change of the short circuit current with temperature (α) and the change of the open circuit voltage respect to temperature ( β). The change of maximum power respect to temperature ( γ) is also important, since it qualifies directly the efficiency loss due to temperature. The measurement of thermal coefficients of photovoltaic modules can be realized outdoor, with natural sunlight causing the heating of the module while several I-V curves are taken at different temperatures. The other way is the indoor measurement in a solar simulator. The module is placed in a thermostatic chamber to reach several temperatures and the I-V curves are measured using the flash of the solar simulators. From the I-V curves the parameters are extracted and the thermal coefficients are determined. In this work a set of thermal coefficients were previously determined indoors for several photovoltaic modules and then they were determined outdoors and the results are compared. The main objective was the comparison of the results in order to validate the outdoor procedure for measurements of thermal coefficients at ESTI (European Solar Test Installation) Ispra, Italy. The combined uncertainty of the outdoor measurement of β and γ are three times greater than the uncertainty indoor, mainly due to the temperature uncertainty outdoors. The parameter α has almost the same uncertainty in both cases. The results are completely equivalent in both cases, having intersection of the uncertainty range between the indoor and outdoor measurement.
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