An idea over 4,000 years old may hold the key to the future of refrigeration without electricity.
A startup called Evaptainers, based in Somerville, Massachusetts, is designing food-storage containers that cool food using evaporative cooling—the same process that keeps us cool when we sweat.
There is a huge unmet need for refrigeration in areas of the world where electricity is scarce. In part because of this, some $310 billion worth of food spoils in developing countries every year, according to the United Nations’ Food and Agriculture Organization.
Enter evaporative cooling, the process by which water removes heat as it evaporates from a surface. People have used evaporative cooling for food preservation for millennia: it’s as simple as nesting two terra-cotta pots, filling the space in between with sand, and adding water.
As the water evaporates from the sand, it takes heat with it, keeping the inner pot up to 35 °F cooler than the ambient air—no electricity required.
Researchers at Evaptainers redesigned this technology with modern materials while at MIT. In their latest prototype, the inner food-storage chamber is a soft, rubberized tub that keeps out water, and the outer layer is made of a wicking, semi-permeable fabric. Water poured into the half-inch space between the inner and outer layers evaporates through the fabric, cooling the inner tub. The container, which will hold around 60 liters, is designed to be rugged and lightweight, and packs flat.
Spencer Taylor, the company’s CEO, says feedback was positive on the 25 units of early prototypes that were recently field-tested in Morocco. He plans to test 300 to 500 units of its latest prototype later this year, distributing half and selling the rest for $25 each.
Taylor also thinks outdoorsy types in the U.S. might like the product. He hopes to have Evaptainers in stores sometime next year.
There are challenges to widespread adoption of Evaptainers, however. The devices can only reach their full cooling potential in dry climates, and, according to Taylor, their efficiency “really goes through the floor” when the humidity climbs above 40 percent.
Bishop Sanyal, a professor of urban development and planning at MIT who is not affiliated with the company, thinks Evaptainers could have a big impact on food security. One potential obstacle, though, is the price. Most Moroccan families, for example, earn between $60 and $100 per month, which means $25 is a huge financial commitment.
“We just forget that these are very poor people, and every cent matters to them,” Sanyal says.
Taylor says that if a family can invest, it will save money on food in the long run.
"That's the dream,” says Taylor. “That every house that doesn't have electricity has an Evaptainer, and it gives them more time to work, helps rural nutrition, helps food security, and ultimately reduces spoilage on a society-wide scale."