The Development of Thermal Coefficients of Photovoltaic Devices

Abstract

Photovoltaic modules installed in the field exhibit a wide range of operating temperatures, depending on the meteorological and environmental conditions. Their temperature influences their output power and conversion efficiency. Temperature dependence is typically described as a linear function with the temperature coefficients of open-circuit voltage, shortcircuit current and maximal output power. To analyse the development of these parameters over time, the data of modules of several technologies is evaluated, monitored from five to eight years at our outdoor test site. The measurement data is cleaned of outliers and systematic measurement errors and then translated to the irradiance of 1000 W/m2 at standard test conditions. Several discrepancies compared to the datasheet values of the photovoltaic modules are found. These discrepancies are attributed to the parameters' sensitivity to other factors, mostly pronounced in the short-circuit current. One such factor is the spectrum of the incident light. The temperature coefficients are then analysed each month to evaluate their development over time. A seasonality is found, showing a higher temperature sensitivity of the short-circuit current in the winter and a correspondingly lower sensitivity of the output power at maximum power point. However, no systematical change over time due to possible influences of module degradation in the timeframe of up to eight years was observed.

Analysis of the degradation of single‐crystalline silicon modules after 21 years of operation

“…A linear regression is performed to fit the plot of each electrical parameter versus the module temperature. These obtained results about the relative temperature coefficients agree with Mitterhofer et al 54 who state that these normalized temperature coefficients only experiment a seasonal change, but they do not vary in the long term. In contrast, Berthod et al 55 find that PV module degradation could produce a decrease of the absolute values of rel , rel , and rel .…”

Energy Yield Modeling for Optimization and Analysis of Perovskite‐Silicon Tandem Solar Cells Under Realistic Outdoor Conditions

“…Therefore, in order to predict and ultimately improve the long-term EY of solar cells and PV modules, not only optical and electrical, but also accurate thermal modeling is of high importance. [33][34][35][36][37][38] An increasing number of studies [21,24,29,31,[39][40][41] investigate the EY of multijunction solar cells by considering the temperature dependence of various cell parameters, but according to our knowledge they disregard specific aspects such as forced convective heat transfer due to wind and/or, more importantly, temperature-induced bandgap shifting that may significantly affect not only electrical properties but also the spectral absorptance and quantum efficiency characteristics of the device.…”