Temperature coefficients of degraded crystalline silicon photovoltaic modules at outdoor conditions

The temperature effect on photovoltaic modules is usually quantified by means of some coefficients relating the variations of the open-circuit voltage, of the short-circuit current, and of the maximum power to temperature changes. In this paper, comprehensive experimental guidelines to estimate the temperature coefficients when measurements are performed outdoors are given. In addition, a correction procedure is applied to the short-circuit current to cancel out the influence of the fluctuations in the irradiance level. The experimental results shown in this paper refer to several single-crystalline silicon modules that have been operating for 21 years. Consequently, the estimated values of the temperature coefficients also account for module ageing processes. The coefficients of determination achieved in the case of the temperature coefficients of the open-circuit voltage and the maximum power are very close to one. Results concerning the temperature coefficients of the short-circuit current are also suitable if they are previously corrected.