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."