Effect of wind on temperature patterns, electrical characteristics, and performance of building-integrated and building-applied inclined photovoltaic modules

The influence of mounting setup on the wind flow field, temperature pattern, and electrical performance of building-integrated (BIPV) and building-applied (BAPV) photovoltaic modules was investigated using wind tunnel experiments. Tests were done with an inclined 3 x 2 module for four air gap thicknesses varying from 0 cm (BIPV) to 5.5 cm (BAPV) and five freestream approaching wind speeds from 1 to 5 m s(-1). Wind speed and temperature were measured along the central line of the module, on the top (illuminated) as well as on the back (shaded) side. Short-circuit current and open-circuit voltage were determined from I-V measurements, and the maximum power was calculated. The wind and temperature patterns and the electrical performance were considerably affected by the mounting setup. The BAPV configurations were always better cooled by the wind than the BIPV setup because of the additional cooling in the air gap. Although a better cooling does not automatically guarantee a higher electrical performance, the BAPV configurations showed the highest performances in the test. In addition, the development of a boundary layer above and (in the case of BAPV) below the module and the trapping of heat into it, created a surface temperature gradient that significantly affected the electrical performance of the individual solar cells in the module. This is important because in most PV modules, solar cells are connected in series. Since the operational temperature influences mainly the open-circuit voltage, the open-circuit voltage of the whole module, and hereby the power output, will be determined by the behavior of each individual solar cell. In the tests reported here, the BAPV module with the thickest air gap (5.5 cm in this study) was the best performing configuration.