Scientists have discovered a surprisingly simple way to cool buildings (and save energy at the same time)

As global warming increases, so does the need for sustainable ways to cool buildings. Now, researchers at the University of California have developed an affordable, scalable technology to cool homes and other buildings in the summer and heat them in the winter, using everyday building materials.

The study describes A new way to regulate thermal radiation. Thermal radiation is a form of electromagnetic radiation, which is emitted by a body as a result of its temperature.

Thermal radiation
Thermal radiation is just like Conduction (conduction) and convection (flow)which is the way heat escapes from a building. Heat loss due to radiation plays a major role in cavity walls and windows and in the transfer from the inner wall to the inner space. This is why special insulating layers are added to cavity walls and windows. But when it is very hot, it is not desirable for buildings to retain their heat. This problem also occurs in newly built Dutch houses, because they are well insulated.

In urban areas, where buildings are close together, it is more difficult to cool buildings than in rural areas, because urban buildings trap heat from the surrounding streets. But in the winter, these buildings lose more heat, making it harder to keep them warm.

Inspiration from the past
“When we look at historic cities like Santorini in Greece and Jodhpur in India, we see that they have been using reflective roofs and walls to keep buildings cool for centuries. Although modern technologies, such as super-white paint on roofs, have proven successful in reflecting heat, cooling walls and windows remains a complex challenge,” said lead researcher Aswath Raman of the University of California, Berkeley.

passive cooling
Now researchers have developed a passive cooling mechanism by coating walls and windows with a different material that better regulates the transfer of heat between buildings and their environment. Surprisingly, the plastic polypropylene is used for this purpose, which is processed like plastic in all sorts of household products. The inexpensive material has proven particularly effective at absorbing and radiating heat in the so-called atmospheric window, a narrow part of the infrared spectrum that allows heat to transfer between buildings and the air. “These materials may seem simple,” says Raman. “But because they are so common, they could play a major role in the thermal regulation of buildings in the near future.”

In their study, the scientists showed that these materials are able to selectively absorb thermal radiation when it is cold, and transfer heat to the environment when it is hot. In this way, the atmosphere is cooler in the summer and warmer in the winter than is possible using ordinary building materials.

Unprecedented energy savings and environmental benefits
The big advantage of this method is its completely passive nature. No active energy source is required to cool or heat buildings. This means that fewer air conditioners need to be turned on in the summer and heating systems need to operate at lower power in the winter. In addition, the new method contributes to reducing carbon dioxide emissions. “The mechanism we propose provides a sustainable way to cool and heat buildings with the seasons. We have calculated that this leads to unprecedented energy savings,” says researcher Jyotirmoy Mandal. Princeton University clearly.

vulnerable communities
According to the researchers, the new method is easy to scale up. They expect it to be particularly useful in low-income countries where there is little air conditioning and heating. These people, who are often the most affected by extreme weather conditions, could benefit greatly from propylene as a cooling or heating material.

Raman and his team are now working on plans to test the technology on a larger scale in Southern California, where it can get extremely hot in the summer. The breakthrough brings to mind a future where buildings can cool and heat themselves sustainably in one step.