Solar Panels in Polluted Delhi May Have Soaked up More Energy in Lockdown

Solar panels in the Indian city of Delhi may have captured more energy than usual after skies cleared and air pollution dropped during the COVID-19 lockdown, according to a study.
After India's government implemented lockdown measures on March 24 to prevent the spread of the coronavirus, the amount of energy reaching solar panels in one part of the city shot up by 8 percent in late March, compared with the same time in 2017 and 2019, according to the study published in the journal Joule. In April, the figure rose by 6 percent.

The team was inspired to carry out the study after seeing reports social distancing measures, which meant people traveled less, were followed by reductions in air pollution. NASA satellite data, for instance, showed aerosol levels in India have dropped dramatically since March 25, and residents of the state of Punjab said they could see parts of the Himalayas for the first time in decades.

The team had previously shown that levels of particulate matter air pollution affect the energy that reaches solar panels, and decided to investigate the impact of changes in pollution levels owing to the lockdown.

The researchers looked at data on concentrations of tiny air pollution particles, known as PM 2.5, at the U.S. embassy in Delhi (one of the world's most polluted cities), and noticed levels had halved by the end of March when compared with previous years.

The researchers also assessed levels of insolation, or the amount of light radiation received by a certain object per second, at a solar panel installation in Delhi's Paschim Vihar residential area, around 10km (6 miles) from the center of Delhi. Once again, they found what appeared to be the footprint of the lockdown in the data, as higher levels of solar energy were measured.

The team said it is plausible that drops in air pollution resulted in clearer air, which may have enabled more sunlight to pass through the atmosphere and therefore increase the yield of solar panels.

The team said they hope the panels "will continue to generate record amounts of electricity as long as air pollution levels stay low." Similar results may also emerge from other cities with usually high pollution levels which have had lockdowns due to COVID-19, such as the Indian cities of Kolkata and Mumbai, China's Wuhan, where the coronavirus emerged, Dhaka, the capital of Bangladesh, Los Angeles in the U.S., and London, U.K.