A recent study shows that the massive installation of solar panels on buildings can lead to significant temperature fluctuations, both during the day and at night.
Solar panels influence the temperature, both day and night. Photo: Shutterstock.
According to Tech Xplore , a team of scientists including Dr. Ansar Khan and Prof. Mattheos Santamouris concluded that solar panels significantly influence the local temperature.
The study indicates that widespread use of solar panels can lead to significant temperature fluctuations.
The researchers found that in an extreme scenario where all the buildings in a city were covered with solar panels, the urban temperature could rise significantly during the day, by up to 1.5°C in the hottest months, and it could drop slightly at night, by about 0.6°C.
The study published in Nature Cities does not question the crucial role of solar panels in the energy transition, but highlights the need for more complex approaches to manage their impact on the urban environment.
Professor Santamouris, the Anita Lawrence Chair in High Performance Architecture at UNSW Arts, Design & Architecture, says:Photovoltaic solar panels are a significant renewable energy technology, but they can change the local conditions of cities when they are installed on large-scale rooftops.”
He also added: “Understanding these changes is critical for policymakers considering the citywide use of RPVSPs and the strategies needed to implement them effectively.”
The study looked at the effect of solar panels in different cities including Kolkata, Sydney, Austin, Athens and Brussels. “We found that there is a linear association between the increase in temperature and the percentage of roofs covered with photovoltaic systems. In the maximum scenario of 100% coverage during peak summer, our data show that RPVSP lead to a significant increase in daytime temperature.”, says Professor Santamouris.
Professor Santamouris points out an important, often overlooked aspect of the widespread deployment of solar panels: the thermal impact. In essence, he warns that a massive coverage of solar panels could lead to a significant increase in temperature in urban areas, thereby canceling out some of the benefits achieved by reducing greenhouse gas emissions.
The fact that almost 40% of the energy produced by solar panels is redirected to cooling indicates a low efficiency of the energy system. Rather than being a net source of clean energy, the solar panels in this scenario partially contribute to the increase in total energy consumption.
“When RPVSPs are installed on roofs, they absorb a significant amount of solar energy, converting some of it into electricity and generating heat in the process. This is primarily due to the lower albedo (reflectance) of the panels, but and airflow over the top and bottom of the PVs, which amplifies the heating effect.” confesses Professor Santamouris.
During the summer, the surface of the photovoltaic panels can reach temperatures of up to 70°C, negating any cooling effect on the urban environment. However, at night, the panels radiate heat, helping to lower the air temperature. This effect is all the more important as nights get warmer due to climate change.
By influencing atmospheric dynamics, photovoltaic panels can reduce the concentration of pollutants in the air. The mechanism consists in increasing the thickness of the planetary boundary layer, which favors better ventilation and dilution of harmful substances.
Professor Santamouris also says “RPVSPs also increase the penetration of coastal sea breezes into coastal cities, while reducing the concentration of ground-level pollutants. This somewhat offsets the effect of daytime temperature rise and is important for cities like Kolkata, where the problem of pollutants is very pressing.”
