New Solar Structure Cools Buildings in Sunlight: A Way to Keep Global Warming at Bay

Here's something that could help keep global warming at bay--or at least cool you off during the summer. A new type of solar structure could vastly improve daylight cooling of buildings, cars and other structures by radiating sunlight back into space.

The researchers had to overcome two major challenges when in came to designing the new device. First, the reflector had to reflect as much of the sunlight as possible. Poor reflectors absorb too much sunlight and heat up in the process; this, in turn, defeats the cooling purpose. The second is that the structure had to efficiently radiate heat back into space. Essentially, it had to emit thermal radiation very efficiently within a specific wavelength range in which the atmosphere is nearly transparent. Outside that range, the atmosphere would simply reflect the light back down and not cool the structure as efficiently.

So how did they make it? They combined a thermal emitter and solar reflector into one device. This made it both higher performance and much more robust. In particular, they used engineered nanophotonic material created from quartz and silicon carbide in order to suppress how much heat-inducing sunlight the panel absorbed while it radiated heat in the key frequency range necessary to escape Earth's atmosphere.

After testing, the researchers found that the new device is actually capable of achieving a net cooling power in excess of 100 watts per square meter. In contrast, today's standard 10-percent-efficient solar panels generate about the same amount of power. In theory, these cooling panels could be substituted on rooftops where existing solar panels feed electricity to air conditioning systems needed to cool the building. It could help reduce the amount of power needed and could have a huge impact on how buildings are constructed. In addition, it could help areas of the world where heat is a major concern--such as desert regions--and where demand for electricity remains high year-round.

"In addition to these regions, we can foresee applications for radiative cooling in off-the-grid areas of the developing world where air conditions is not even possible at this time, said Shanhui Fan, one of the researchers, in a news release. "There are large numbers of people who could benefit from such systems."

The details of this newest construction are published in the journal Nano Letters.