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[NEW DELHI] India’s nationwide lockdown from 24 March to 17 May to contain the spread of COVID-19 has had unexpected spin-offs — it reduced smog over the national capital of New Delhi by 50 per cent and helped increase generation of solar power, says a new study.

Ian Marius Peters, research scientist at the Helmholtz Institute Erlangen-Nürnberg for Renewable Energy*, US, and lead author of the study published 19 June in Joule,  says: “If you improve the air quality you actually make the renewable energy sources, especially solar, work better. So, there's a positive feedback loop there.”

“If you improve the air quality you actually make the renewable energy sources, especially solar, work better”

Ian Marius Peters, Helmholtz Institute Erlangen-Nürnberg for Renewable Energy

The researchers had previously studied how haze and air pollution alter insolation, or the amount of sunlight reaching the ground and impacting solar panels. But Peters tells SciDev.Net, India’s strict lockdown, enacted without warning on 24 March, made it much easier to quantify insolation.
 
In 2019, New Delhi was rated the world's most polluted capital city for the second straight year by IQ AirVisual, the Swiss-based group that gathers air quality data globally.

A major component of air pollution is fine atmospheric particulate matter measuring less than 2.5 microns (PM2.5) that tends to hang in the air longer than heavier particles. PM2.5 is essentially soot created by the inefficient burning of fuel by vehicles, factories and household heating and the particles can absorb or scatter light before it reaches the ground.
 
The researchers found that in late March, levels of PM2.5 over New Delhi dropped to nearly 50 per cent of that recorded at the same time the previous year, with low levels maintained throughout most of April. This corresponded with an 8.3 per cent increase in insolation after 20 March at a solar installation in central Delhi when compared to readings from 2017 — 2019. April saw an average increase in insolation of 5.9 per cent.
 
The bonus was an improvement in air quality over New Delhi, says Peters. “If you were to replace many of the prime sources of air pollution with electrified sources, it should result in an improvement in the air quality.”
 
While the researchers did not collect data for power generation, Peters says it broadly follows insolation levels.  Because of the low profit margins on solar installations, he says this kind of increase could make a significant difference to the economics of solar investments.
 
“If you change the output by absolute two per cent, that may be the entire margin that you have,” he says. “So, it can really be decisive for how much money you're actually making from the project.”

Duke University engineer Michael Bergin, who has also investigated the impact of air pollution on solar panels, says the impact could be even bigger because reduced air pollution also means less dirt settling on solar panels, which further blocks sunlight.

“Our recent study found that the influence of particulate matter soiling is roughly the same as that from the influence of ambient particulate matter,” Bergin says. “So, it is possible that the real influence of particulate matter is double the eight per cent.”
 
Because many solar installations are not based in urban areas where pollution is worst, Peters admits that it’s not clear how big an effect this phenomenon could have on India’s wider solar industry.

But Martin Wild, a climatologist at ETH Zürich in Switzerland who studies the impact of air pollution on solar radiation, says that the evidence suggests that the impacts are not restricted to the areas where air pollution is produced. “We’ve come to the conclusion that it's really a large-scale effect, not just an urban effect,” he says. 
 
This piece was produced by SciDev.Net’s Asia & Pacific desk.

*This article was edited on 2 July 2020 to correct Ian Marcus Peters' organisation affiliation.