1 week Ago By Neha Madaan
Pune: Solar radiation in the city has been declining at a rate of 0.21% per year since 1993, a new study has found. What's worse, between 2018 and 2022, a steeper decline of 1.
21% per year was found, raising several concerns. Decreased sunlight exposure can impact Vitamin D levels in people. Earlier studies over Australia, Brazil and USA have shown that reduced sunlight can also affect crop yield and quality, besides impacting food security.
Clouds and aerosols (dust and pollutants) linked to air pollution are emerging contributors to this "solar dimming" effect. The study was conducted over three decades by researchers from Savitribai Phule Pune University (SPPU), Indian Institute of Tropical Meteorology (IITM) and Aryabhatta Research Institute of Observational Sciences (ARIES). The study revealed that clouds reduced solar radiation by about 30%, while aerosols caused a reduction of nearly 18% compared to clear-sky conditions.
While this study focussed on Pune, another study by the India Meteorological Department (IMD) in 33 cities, including New Delhi, Mumbai and Ahmedabad, earlier this year found a similar reduction in global radiation between 1985 and 2019. Global radiation refers to the total amount of solar energy received on the Earth's surface. IMD scientist Dr Sudeep Kumar told TOI, "Our study found a significant decrease in global radiation in New Delhi, Shillong, Ahmedabad, Kolkata, Nagpur, Mumbai, Pune, Visakhapatnam, Goa, Chennai and Thiruvananthapuram.
Among these stations, the maximum decrease was observed over New Delhi (0.7%) and minimum decrease over Pune (0.1%).
" Scientists said that a reduction in solar radiation could also lead to a significant drop in the efficiency of solar panels. This means existing solar installations may produce less electricity than initially projected. SPPU researcher Ashwin Jadhav, who was part of the latest study, said, "The total drop is ~1.
04 W/m2 (watts per square metre) annually, with a more pronounced decrease of ~6.01 W/m2 between 2018 and 2022." He added that the increase in total cloud cover and aerosol optical depth (AOD) over the Pune region is a major factor behind this sharp decline.
SPPU faculty Dr Rohini Bhawar said that lower aerosol concentrations allow for more direct transmission of solar radiation, while higher concentrations significantly reduce radiation levels. "Seasonal solar radiation data shows how aerosol presence affects sunlight, with radiation levels falling by up to 23.51% during 2018 to 2022 compared to clear-sky conditions.
The reduction is comparable to trends observed in other regions of India, China and the Arabian Peninsula, where solar radiation has also declined due to aerosols," she said. The study also touched upon the impact of wind speed, which can contribute to atmospheric turbulence and affect the distribution of dust and aerosols. The researchers stressed on the need for action to reduce air pollution and manage aerosols, as well as the necessity to optimise solar energy systems to adapt to declining solar resource availability.
Dr PRC Rahul from IITM Pune, professor P Pradeep Kumar from SPPU and Dr Umesh Chandra Dumka from ARIES in Nainital were also part of the study, which was recently published in international journal Energy for Sustainable Development by Elsevier..
