In 2022, MIT researchers built a 4-inch, 3-layer cooler using evaporation and insulation to keep food fresh without electricity

• On a hot roof in Cambridge, Massachusetts, a small experimental device sat in the sun without a fan, compressor or electrical connection.
• Its job was simply to get colder than the air around it.
• Water moved through one part of the device, heat escaped through another, and layers of insulating material helped keep the cooling from being undone by sunlight.