On a recent weekday, Vamsi Komarala guides me up to the rooftop of the prestigious Indian Institute of Technology in New Delhi, where he teaches physics. Fields of solar panels adorn the buildings.
I swipe an index finger across one of the panels to see if weeks of monsoon rains have washed it clean. My finger comes back filthy with grit.
Vamsi tells me the panels are washed twice a week, then explains the grime: "That is because in New Delhi, we have a lot of dust."
Dust is just one factor. The capital city and much of northern India are routinely shrouded in man-made pollutants. In fact, Delhi vies with Beijing for the dirtiest air in the world.
Air pollution is the leading risk factor for most deaths and disabilities in India, a country that's home to 13 of 20 of the world's most polluted cities.
The country's dilemma is stark: To lift millions from poverty, it will require ever more energy. But most of India's electricity is generated by coal-burning power plants. Millions of new cars choke the roads each year. Add to the mix the burning of garbage and crops, and it's a toxic cocktail that makes India the third-largest contributor of greenhouse gas emissions in the world, after China and the United States.
Under pressure to cut these emissions — which contribute to global warming and climate change — India is turning to its greatest source of clean, renewable energy: sunshine.
It's drenched in it 300 days of every year. Already, solar energy is changing the landscape across New Delhi, and the deserts of Rajasthan. But pollution is diminishing its power.
Better air quality, better solar power production
A new study has found that air pollution cuts the capacity of solar panels to generate power — and the smaller the particle, the more effective it is at blocking out the sun. Some of these very particles are dirtying the solar panels on the Indian Institute of Technology rooftop.
When solar panels are clean — like the ones on the rooftop of Delhi's Habitat Center, a conference and office complex in the central part of the city — solar energy production typically doubles, according to a new study led by Duke University researchers. Julie McCarthy/NPR
Michael Bergin of Duke University's civil and environmental engineering department, the study's lead author, says tiny particulate pollution can either absorb the sun's radiation or scatter the sunlight, diffusing the light that hits solar panels. He's created a model to measure that loss — which is substantial.
"We came up with between 17 percent to 25 percent reductions in solar energy production in India and China," he says, "and we believe that the effects might be a little higher since the model we use tends to under-predict the effects."
Unaccounted for are the effects of things like burning trash, a widespread practice in India. As for deposits on solar panels, Bergin and his Indian team monitored accumulations at the Indian Institute of Technology in Gandhinagar, in the state of Gujarat — and arrived at eye-popping results.
"After we scraped the particles off, we would watch the solar energy production typically double," he says. "So in three to four weeks in northern India, often the solar energy production — if you weren't to clean these panels — decreases by a factor of two. So that's really huge."
Improving air quality would vastly improve the production of solar energy. It would, says Bergin, "have huge health benefits. So I think this is just another reason to try to clean the air."
In the face of skepticism, the government has pledged to achieve 100 gigawatts of solar capacity by 2022, five times its previous target and a goal considered extremely ambitious. (In 2014, the entire world had 181 gigawatts of solar capacity.)
Hundreds of miles north of Delhi, in the state of Uttarakhand, the air is clean. And here, changing climate conditions can seem more like an opportunity to exploit than a looming threat to fear.
Along the hairpin turns of the Himalayas, brightly colored houses appear as though they're painted on the sheer cliffs, and join the steppes as they slip into the Ganges. Roaring rivers are swollen by the summer monsoons.