Backside ventilation is one of the most common passive cooling methods of PV modules in the built environment, but might be under constraint when integrating PV in the building envelope. To investigate the short and long term effect of backside ventilation on Building Integrated PV (BIPV) performance and lifespan, a comparative BIPV field test is conducted in a real life lab located in the Netherlands. The field test includes 24 modules in 4 segments with different levels of backside ventilation. PV energy output, module backside temperature, relative humidity in the air gap, and air velocity in the air gap have been monitored for three years in the period January 2013–December 2015. At the end of the monitoring period Electric Luminescence (EL) images were made and Standard Testing Condition (STC) power was determined. The ventilated segments show a similar behaviour (6% difference) in PV energy output, but the non-ventilated segment shows a strong decrease of 86% in output after three years. A maximum temperature of 72 C is reached in the ventilated segments and a maximum temperature of 83 C in the non-ventilated segment. Relative humidity (RH) levels reach a maximum of 100% in all segments. Air velocity in the non-ventilated segment is 13–39% of the air velocity in the ventilated segments. STC power determination and EL imaging show lower peak power and more defects in the non-ventilated modules, and modules placed at vertical higher positions in the non-ventilated segment have a lower power output of 50–60%. The results indicate that, considering the first generation Metal Wrap Through (MWT) modules investigated, the non-ventilated BIPV modules exposed to the highest temperatures show the lowest power output, lowest STC power and show the most damaged cells in the EL imaging. Even though PV module manufacturing shows continuous technological advances, the methodology and results of this work has added value for the prediction of BIPV operating aspects and lifespan when designing and realizing a BIPV installation. Moreover, the BIPV field test presented in this study has been a very illustrative
BIPV demonstration project for manufacturers, installers and designers
