University at Buffalo engineers have developed a new non-electric system to cool buildings situated in crowded metropolitan areas.
The system is composed of an inexpensive polymer/aluminum film installed inside a box at the bottom of a specially designed solar shelter.
According to the engineers, the film helps keep its surroundings cool by absorbing heat from the air inside the box and transmitting that energy through the Earth’s atmosphere into outer space.
The shelter likewise serves a dual purpose: First, it helps to sponge up sunlight. Second, the shape of the walls and cone direct heat emitted by the film toward the sky.
The polymer remains cool as it dissipates heat through thermal radiation, helping cool down the environment in turn too.
“This is called radiative or passive cooling,” explains co-first author and PhD scholar Lyu Zhou, “And it’s very interesting because it does not consume electricity – it won’t need a battery or other electricity source to realize cooling.”
“One of the innovations of our system is the ability to purposefully direct thermal emissions toward the sky,” says lead researcher and associate professor Qiaoqiang Gan.
“Normally, thermal emissions travel in all directions. We have found a way to beam the emissions in a narrow direction.”
“This enables the system to be more effective in urban environments, where there are tall buildings on all sides. We use low-cost, commercially available materials, and find that they perform very well.”
The university’s shelter-and-box system measures about 18 inches tall (45.72 centimeters), 10 inches wide and 10 inches long (25.4 centimeters).
According to the engineers, the new passive cooling system could be a game changer as it helps address an important problem in the field: How radiative cooling can work during the day and in crowded urban areas.
“During the night, radiative cooling is easy because we don’t have solar input, so thermal emissions just go out and we realize radiative cooling easily,” explains co-first author and KAUST assistant professor Haomin Song. “But daytime cooling is a challenge because the sun is shining.”
“In this situation, you need to find strategies to prevent rooftops from heating up. You also need to find emissive materials that don’t absorb solar energy. Our system address these challenges.”
Image and content: University at Buffalo