Outdoor Direct STC Performance Measurement of PV Modules Based on a Sun-Shading Technique

A sunshading technique to control the temperature of photovoltaic (PV) modules at 25 °C was experimentally demonstrated in order to perform the outdoor measurement of the electric output performance of PV modules under standard test conditions (STC). By intermittently shading the PV module using a sunshade, the STCs were directly obtained, and the current-voltage (I-V) curves of the PV module were obtained under sunny and partly sunny conditions. The outdoor I-V curves precisely agreed with the indoor I-V curve measured by a solar simulator. The deviation range between the outdoor I-V curves and the indoor I-V curve was less than ±2%. Furthermore, the effects of wind speed and ambient air temperature on the outdoor STC frequency were quantitatively clarified by heat transfer simulations. For example, for a wind speed of 5 m/s and an ambient temperature of 17 °C, the STC frequency reached 5 points per 10 min. The presented results suggest that the outdoor direct STC performance measurement using the proposed sun-shading technology is a feasible alternative approach to indoor I-V curve measurement.