A new start-up working out of Stanford University is developing a new cooling technology that will take advantage of the coldness of space by exploiting a natural phenomenon called radiative cooling. With air conditioning accounting for almost 15 per cent of all energy use by buildings in the United States, the new technology aims to reduce this energy consumption by sending heat to outer space.

When thermal radiation from objects is emitted towards the sky, a portion of it is absorbed and reflected by the atmosphere. Another portion, which falls within a particular frequency range, escapes into the upper atmosphere and outer space where conditions are much colder, causing the object emitting that radiation to cool to below the temperature of the surrounding air.

Radiative cooling is proven to cool buildings at night. However, it’s not as effective during the day with the sun’s radiation counteracting the cooling effect.

Working with a colleague at Stanford, the cofounder of the start-up Sky Cool Systems, Aaswath Raman determined that it should be possible to achieve radiative cooling during the day. A paper published by the group in ‘Nature’ revealed how a device designed to combine the optical properties of three different materials and arranged in a stack of multiple layers, cooled to nearly 5°C below the ambient air temperature.

Several groups have begun the study of daytime radiative cooling with three teams recently receiving funding from ARPA-E to develop technologies for thermal power plants.

Image: Sky Cool's radiative cooling prototypes