MIT researchers developed a device capable of cooling to a temperature significantly lower than the ambient temperature even on a hot sunny day without power supply

by Bikram Bhatia

In the refrigerator, there is " non-electrified refrigerator " which can cool the inside without using electric power by using radiation cooling . MIT's "non-electrified refrigerator" seems to be able to "refrigerate" theoretically in a state lower than the ambient temperature by 20 degrees.

Passive directional sub-ambient daytime radiative cooling | Nature Communications
https://www.nature.com/articles/s41467-018-07293-9

A new way to provide cooling without power | MIT News
http://news.mit.edu/2018/device-provides-cooling-without-power-1128

The idea of ​​cooling things by radiative cooling is not new at all and it has been frequently used for nighttime cooling, but since the heating effect by sunlight is more than 10 times the cooling effect by radiative cooling, it is strong in the daytime There was a difficulty in using it for cooling.

Therefore, a mechanism to utilize radiative cooling well in the daytime has been considered, but in many cases, it is designed to radiate heat as mid-infrared after reflecting almost all wavelengths of sunlight As a result, multilayer materials that require several nanometers of precision for layer thickness are required due to selective reflection and radiation, which has the disadvantage of high manufacturing costs.

This time, the research team of MIT cleared the problem in an analog way that the infrared ray travels linearly and it is easy to prevent, so that the periphery of the device is covered with a thermal insulator like a parasol. Thanks to this, the material of the equipment was made with plastic film, polished aluminum, white paint, insulation, etc., and it was able to make it considerably cheaply.

by Vincent Branciforti

According to the research team, the theoretical cooling performance is "ambient temperature minus 20 degrees", and the concept model achieves "ambient temperature minus six degrees". It is thought that it is possible to reduce the load by combining it with other systems even if this system alone can not sufficiently cool it.

The team seems to find an infrared transparent insulating material to further improve the heat insulation of the equipment and not to lower the heat dissipation ability.