Less efficient solar panels could increase day temperature: Study
A new study found that a complete coverage in a city with rooftop photovoltaic solar panels could increase in the day up to 1.5°C during peak summer periods and decrease at nighttime up to 0.6°C
As several central and state government schemes such as Pradhanmantri Suryodaya Yojana pushes rooftop solar adoption, a new study published by a group of scientists in India and abroad have highlighted the need for slight modifications to reduce the inadvertent heating up of already hot urban areas during summer due to rooftop photovoltaic (PV) cells.
The research published in journal Nature Cities on October 7 by researchers from IIT Kharagpur, Massachusetts Institute of Technology and University of New South Wales among others found that complete coverage in a city with rooftop photovoltaic solar panels could increase in the day up to 1.5°C during peak summer periods and decrease at nighttime up to 0.6°C.
To arrive at this data point, the researchers relied on data from five cities– Kolkata, Sydney, Austin, Athens, and Brussels. An additional review of 30 case studies from building-level to city-scale installations around the world confirmed these insights, the researchers added.
Speaking with HT, Ansar Khan, professor at the University of Calcutta and the corresponding author of the research, said while solar PVs are a vital green energy source, currently most commercial solar panels have an efficiency of 20% which means the remaining heat is spread across the environment. He said installing photovoltaic thermal (PVT) systems, in place of conventional solar panels can counter the ill-effects by reducing the release of excess heat into the environment while improving energy efficiency. “The research findings are not against PVs but suggests the need for further efficiency.”
“The thermal exchanger at the back of the hybrid PVT panels can extract heat from both the panels and the outside air, preventing PV overheating and maintaining optimal electricity generation. By reducing panel temperatures and capturing excess heat, this integrated system not only enhances PV performance but also helps mitigate the urban heat island effect, contributing to energy savings and more sustainable energy solutions,” he said. Other modifications, he suggested could be installing PVs on green roofs or roofs with reflective material or paint, he said.
Other findings of this research included that solar panel installations can increase the amount of heat released into the atmosphere, impacting local wind patterns and even delaying the onset of sea breezes. The researchers also found that additional heat also helps mix the air at lower levels, raising the height of the planetary boundary layer by over 600 metres, which could improve air quality by reducing pollution near the ground.
Commenting on the research findings, Gopala Krishnan, senior analyst, energy and power sector at Bengaluru-based think tank Center for Study of Science, Technology and Policy (CSTEP) said as the efficiency of solar-PV modules increases, the size of RPVSPs will decrease, bringing down the rate of heat transfer from the panels to the surroundings.
He added, “The scenarios assumed in the research consider 25%, 50%, and 100% coverage of rooftop area by photovoltaic solar panels (RPVSPs), which is quite ambitious given that rooftop solar is yet to be installed on 5% of the available rooftop space in India.” Instead, he said similar analyses could be conducted for lower coverage levels, such as 3%, 5%, and 10% of rooftop area. He further added future studies can incorporate computational fluid dynamics (CFD) simulations and digital surface models (DSM) of urban areas, for higher accuracy.