Intelligent roof coating: can reflect heat in summer and block heat loss in winter

2024-01-25

It has been learned that engineers from the Berkeley laboratory have developed a roof coating that can keep buildings warmer or cooler according to weather conditions. When the weather is warm, the material will reflect sunlight and heat, but this radiation cooling will automatically turn off in winter, reducing the energy consumption for heating and cooling.

The working principle of a radiation cooling system is to attract thermal radiation (i.e. heat) from a building and then emit it into the sky. Because the atmosphere is transparent to these wavelengths, heat escapes directly into space. Other versions use reflective surfaces such as ultra white paint to bounce sunlight and heat away and keep the building cool.

However, although these systems may keep your house cool well in summer, they will also keep it cool in winter. Therefore, in the new study, the team developed a coating that can automatically switch to capturing heat when mercury drops. They call this material temperature adaptive radiation coating (TARC).

The key to this technology is a strange compound called vanadium dioxide (VO2). In 2017, the team discovered an unusual characteristic of VO2- when it reaches 67 ° C, the material will conduct electricity but not heat, which clearly violates known physics.

Now, the team has applied this quirk to their work. The idea is that when the weather warms up, the material will absorb and emit thermal infrared light, thus keeping it away from buildings. But when the weather is cool, this material is transparent to heat, allowing it to pass directly from the sun to the building.

The research team tested the device using a 2 square centimeter TARC film patch and compared it with samples of commercial dark and white roof materials. Wireless devices are responsible for measuring changes in direct sunlight and temperature.

Sure enough, the effect of TARC was surprisingly good. According to measurements, regardless of the weather, TARC can reflect about 75% of sunlight, and when the ambient temperature is above 30 ° C, it can dissipate up to 90% of the heat into the sky. When the weather cools below 15 ° C, TARC emits 20% of the heat back.

The research team simulated the annual work of TARC in 15 different climate zones on the US mainland using collected data and estimated that ordinary households using TARC can save up to 10% of their electricity bills.

Researchers suggest that TARC can also be used as a temperature regulating material for automobiles, electronic products, satellites, and even fabrics for tents or clothing.

Next, the team will conduct experiments using a larger TARC prototype to test its practicality as a roof coating.

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