Passive evaporative cooling for building-integrated photovoltaics in improving building energy efficiency

Building-Integrated Photovoltaics (BIPV) offer a sustainable solution for urban energy integration. However, excessive heat accumulation reduces PV efficiency and increases building energy consumption. Passive evaporative cooling shows promising potential as an effective strategy, attributed to its superior thermal regulation capacity and minimal energy consumption. Nevertheless, the applicability of passive evaporative cooling strategy in major BIPV systems and their performance across different building envelopes remain underexplored. This study presents a passive evaporative cooling strategy for three key types of BIPV systems namely rooftop PVs, facade PVs, CdTe PVs, and assesses its impact on building energy consumption. Results demonstrate that the strategy provides significant energy-saving benefits, especially at higher PV installation ratios and with building envelopes of greater solar absorptance. In Hong Kong, energy savings reached 16 % at a 25 % rooftop PV installation ratio, 29.4 % at 50 %, and 39.8 % at 75 %. Concrete roofs with a solar absorptance of 74 % achieved savings of 50.6 %. Furthermore, climate-zone analysis revealed that passive evaporative cooling is particularly effective in regions with high temperatures and intense solar radiation. In Guangdong, for instance, energy savings increased from 47.9 % to 50.4 % with cooling strategy integration. Overall, this work provides a strong foundation for the efficient deployment of BIPV systems and the enhancement of building energy performance.