Urban heat effect tied to rooftop solar panels
Staff Reporter :
A recent study suggests that widespread use of rooftop photovoltaic solar panels (RPVSPs) in cities may increase daytime temperatures but provide cooling benefits at night.
The research, led by Dr. Ansar Khan from the University of Calcutta and Professor Mattheos Santamouris from UNSW Sydney, used mesoscale simulations to assess RPVSP impacts on urban temperatures and was published in Nature Cities.
The findings show that full rooftop solar panel coverage could elevate peak daytime temperatures by up to 1.5°C in summer, while lowering nighttime temperatures by around 0.6°C.
This warming effect is due to the panels’ high surface temperatures during the day, sometimes reaching 70°C, which adds to urban heat.
At night, however, these panels radiate stored heat, creating a cooling effect, which is increasingly important as global warming raises nighttime temperatures, explained Professor Santamouris.
The research, focusing on Kolkata, India, with additional studies
in Sydney, Austin, Athens, and Brussels, highlighted a linear relationship between temperature rise and rooftop panel coverage percentage.
The study underscores the need to balance the benefits of solar energy with urban heat management, especially in densely populated areas.
Aside from temperature effects, rooftop solar installations could also benefit urban air quality. By increasing wind speeds and dispersing pollutants, these installations may help reduce air pollution, a critical benefit for cities with high pollution levels like Kolkata.
While recognizing the daytime heat implications, the study doesn’t discourage rooftop solar. Instead, it suggests combining panels with water-based cooling solutions, which can lower panel temperatures, improve efficiency, and provide hot water.
“Cooling solar panels with water can enhance their efficiency and help manage urban heat,” added Professor Santamouris, advocating for integrated approaches to urban temperature control.
The findings have implications for Bangladesh, where the Power System Master Plan (PSMP) envisions 635MW from rooftop solar, meeting 17.3% of national electricity demand. A practical example is the rooftop solar plant at the Korean Export Processing Zone (KEPZ) in Chattogram, which started in 2021 with 16MW and plans to expand to 40MW.
The study emphasizes that while rooftop solar offers sustainable energy, using additional cooling strategies and reflective materials can optimize both energy output and urban thermal comfort, making it a balanced choice for energy and environmental management.
