New technology engineered at MIT bypasses the power grid to deliver passive cooling for space conditioning, food preservation and other applications. The system combines radiative cooling, evaporative cooling and thermal insulation in a compact architecture that can provide up to about 19° F (9.3° C) of cooling from the ambient temperature.

The system consists of three layers of material, which together provide cooling as water and heat pass through the device. An insulating layer of aerogel covers the top of the unit, allowing for the transmission of water vapor and infrared radiation. A hydrogel material is placed beneath to provide the water source for evaporative cooling, as water vapor forms at its surface and the vapor passes up right through the aerogel layer and out to the environment. A mirror-like layer at the bottom reflects incoming sunlight back up through the device rather than letting it heat up the materials and thus reducing their thermal load.

A small prototype, measuring just 4 inches across, was tested on a rooftop at MIT during summer conditions in Cambridge, Massachusetts. The combination of radiative and evaporative cooling proved effective, achieving 18.7° F (9.3° C) of cooling.

With additional research to reduce production costs for the aerogel, the system described in Cell Reports Physical Science could contribute to meeting the cooling needs in regions where a lack of electricity or water limits the use of conventional cooling systems.