Large buildings consume a lot of energy and consequently emit a lot of heat. Keeping these buildings cool isn’t easy. In the United States, air conditioning systems account for as much as 15 percent of energy used.
Researchers at Stanford University have developed a new, ultrathin, multilayered, nanophotonic material that can help cool buildings, even on sunny days, by radiating heat away from buildings.
The team, lead by electrical engineering Professor Shanhui Fan and research associate Aaswath Raman, reported this energy-saving breakthrough in the journal Nature.
The material works in two ways. It both reflects incoming sunlight that would otherwise heat the panel, and it sends out heat from inside the building directly into space as infrared radiation.
The multilayered material measures a mere 1.8 microns thick, thinner than the thinnest sheet of aluminum foil.
Made up of of seven layers of silicon dioxide and hafnium oxide on top of a base thin layer of silver, the layers are not a uniform thickness, but are instead engineered to create a new material. Its internal structure is constructed to radiate infrared rays at a frequency that lets them pass into space without warming the air near the building.
“The result is photonic radiative cooling—a one-two punch that off-loads infrared heat from within a building, while also reflecting infrared heat from within a building , while also reflecting the sunlight that would otherwise warm it up. The result is cooler buildings that require less air conditioning,” explained electrical engineering professor Shanhui Fan. “Think about it like having a window into space.”
“Across the developing world, photonic radiative cooling makes off-grid cooling a possibility in rural regions, in addition to meeting sky-rocketing demand for air conditioning in urban areas,” Raman says.
Obviously, there is still much they can learn from this, as Raman concludes, “Though still a young technology, it could one day significantly reduce demand for electricity.”