Solar production rose amid pandemic shutdowns

Stay-at-home orders designed to slow the spread of COVID-19 have led to improved air quality and lower greenhouse gas emissions in many places around the world. Research now shows another unintended result: lower levels of haze-causing pollution boosted solar energy production (Joule 2020, DOI: 10.1016/j.joule.2020.06.009). Delhi typically has some of the poorest air quality of any city in the world. When the city went under lockdown orders on March 20 and traffic decreased dramatically, levels of fine particulate matter—which is produced by incomplete combustion, particularly by motor vehicles—dropped to about 50% of average, says Ian Marius Peters, a photovoltaic researcher at Forschungszentrum Jülich in Germany. Peters’s group had previously shown that this type of pollution, which can make skies hazy, decreases solar energy production. They wanted to know if the opposite was also true, and performed statistical analysis of data from sunlight sensors they had installed in Delhi before the pandemic. Insolation—illumination from the sun—was up by 8% in late March and 6% in April, which should translate to the same percentage increase in solar cells’ energy output. The effect has likely been particularly pronounced in Delhi, Peters says, because pollution levels in the city are usually quite high. However, he says he’s “absolutely certain it has happened everywhere where air pollution went down.”