Imagine cooling homes and buildings without the need for air conditioners or electricity. A Stanford University research team believes it to be possible with the invention of a new cooling panel that can reflect sunlight, and emit heat back into outer space. Electrical engineering professor, Shanhui Fan (center), and graduate students, Aaswath Raman (left) and Eden Rephaeli (right), recently published their findings, and hope to manufacture an experimental prototype in a few months.

This new cooling panel emits thermal radiation within a specific wavelength range that will pass through the atmosphere. Any thermal radiation outside of this wavelength range “bounces off” the atmosphere, causing what we know as the greenhouse effect. Researchers had previously explored radiative cooling as a strategy against climate change, but no one was able to figure out how to use this technique during the day. The Stanford team overcame this hurdle by creating a thermal emitter that was also an extremely effective broadband mirror for solar light. Inefficient reflectors can absorb too much heat, so the panel effectively reflecting the majority of sunlight is a must. This became possible through engineering a new nanophotonic material made of quartz and silicon carbide; both are poor absorbers of sunlight.

The theoretical net cooling power of this new panel is over 100 watts per square meter. Today’s standard solar panel generates about the same amount of power. The team estimates that a typical one-story home with 10% of its roof covered in cooling panels could offset 35% of its air conditioning needs during the hottest hours of the summer. Perhaps the most exciting aspect about this new concept; it’s a passive technology. It requires absolutely no energy; it has no moving parts, and needs minimal maintenance. Once these panels are installed on the roof and sides of a structure they instantly start working. This has Professor Fan and his colleagues thinking beyond the commercial implications, and hopeful about the broader social impact. These panels could bring much needed relief to a huge percentage of the human population living near the equator. The growing need for electricity to cool these often underdeveloped areas present demanding challenges for their economies and environments. Usually this leads to a push for the development of more fossil-fuel burning power plants, which are timely, expensive, and not a realistic long-term solution. Also, many people in developing countries living completely off the grid could now have the benefits of climate control without the expensive infrastructure of power lines. Let’s not forget that these panels are not only cooling buildings, but are actually releasing heat back into outer space. If this were to become the world-wide standard for cooling buildings and homes, it could greatly offset the effects of climate change.