As temperatures in India break records, ancient terracotta air coolers are helping fight extreme heat

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The thought of the matka crossed Siripurapu's mind. "The water in the mud pot is naturally cool because when it evaporates, it sucks the heat from the pot. But what if I reversed that process? It struck me that we could cool the air around the terracotta in the same way," he says. In Siripurapu's design, recycled water is pumped over the terracotta. As the water evaporates from inside the terracotta's pores, it cools the air around it.

Called the Beehive, around 800-900 terracotta cones were handcrafted and arranged by CoolAnt in a honeycomb design fitted around a stainless steel framework.  "Stacking the cones like a beehive improves the surface area needed for effective cooling," says Siripurapu.

Since their first beehive installation, the company has created 35 such cooling towers in schools, public spaces, airports and commercial buildings across the country, from Pune to Jaipur. In addition to the beehive design, they’ve also experimented with designs that stack the terracotta in different shapes, and even with one that uses no water at all.

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Through videos sent by clients and site visits, CoolAnt says it has recorded a drop of up to 15C (27F), using designs like their Beehive. "It did much better than we anticipated," Siripurapu says. However, that drop in temperature depends on an area's wet bulb temperatures (a measure of both heat and humidity in the atmosphere). If it's already very humid, then there can't be such a steep drop, because the potential for evaporation is less, he notes. (Think of the sky over a city like a wet sponge – if there's already too much water, it can't absorb more.) And yet even a few degrees drop in temperature can make a crucial difference.

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