PVIGR series: Experimental insights into PV rooftops and urban heat

Intro: While large-scale photovoltaic (PV) roofs are key to sustainable cities, their impacts on urban heat islands (UHI) remains debated due to a lack of experimental validation. To resolve this, our team conducted a field experiment monitoring multiple 200 m² rooftop configurations in subtropical Hong Kong—comparing bare roofs, PV roofs, and PV-integrated green roofs (PVIGRs). This study provides the first real-world evidence of their thermal trade-offs. The work has been reported in PV Magazine.

References:

[1] Chen, L., Lin, Z., Zhou, Q, Zhang, S., Li, M., Wang, Z. (2025). Impacts of photovoltaics and integrated green roofs on urban climate: Experimental insights for urban land surface modelling, Renewable and Sustainable Energy Reviews, 217 (2025) 115709. (https://doi.org/10.1016/j.rser.2025.115709)

[2] Chen, L., Zhang, S., Cheng, I., Chang, H., Chen, F., Li, M., & Wang, Z. (2025). The Resilience Paradox of Rooftop PV: Building Cooling Penalties and Heat Risks. Building and Environment, 113233. (https://doi.org/10.1016/j.buildenv.2025.113233)

Key Findings:

• PV Heat Island Effect: PV roofs elevated local air temperatures by over 4 °C on sunny days, increasing top-floor monthly cooling demand by 1.5% during heatwaves and extending “Extreme Danger” heat exposure by 29.8% during power outages.

• PVIGR Mitigation: Though PVIGRs showed no cooling above panels, they reduced PV canopy temperatures by 1.26 °C in July, lowering PV surface temp and building cooling loads.

Our works have been reported in PV Magazine and LinkedIn. These insights highlight the need for climate-adaptive PV designs to balance energy generation and urban heat resilience.