These reflect nearly all the sunlight energy and cool their surroundings night and day by controlled black body emmisive radiation. (interestingly, for cooling applications, per unit area they are more power efficient than solar panels + AC, because solar only is working during the day, whereas passive cooling films also work at night)
https://en.m.wikipedia.org/wiki/Wet-bulb_temperature
If I were in a position of decision making in India, I would invest in large deployments of passive radiative cooling films: https://www.3m.com/3M/en_US/energy-conservation-us/applicati...
These reflect nearly all the sunlight energy and cool their surroundings night and day by controlled black body emmisive radiation. (interestingly, for cooling applications, per unit area they are more power efficient than solar panels + AC, because solar only is working during the day, whereas passive cooling films also work at night)