Electrical engineers at Stanford University published an article describing their cooling invention in last month’s NanoLetters. What they discovered is a metal-dielectric photonic structure that radiates sunlight keeping what’s inside cool. What are the implications of their invention? Buildings and homes that can be kept cool without air conditioning. Automobiles that no longer turn into ovens in the heat of a summer day.
So what is a metal-dielectric photonic structure? It is material that does two things:
- acts like a mirror to solar light reflecting the Sun’s energy,
- emits what it reflects within a specific range of wavelength to not contribute to the greenhouse effect.
How can it do this, that is, reflect the heat of the Sun away from a building without heating the atmosphere around the building? The scientists created a thermal emitter and solar reflector in one using nanophotonic materials. The material both suppresses the heat from sunlight but also radiates it efficiently so that it doesn’t hang round but escapes right out of the Earth’s atmosphere.
The net cooling exceeds 100 watts per square meter, about the same amount of power as current solar panels generate at 10% efficiency. A single-family home clad in this new material could easily reduce its air conditioning needs by 35% or more even on the hottest summer days, and do this without drawing on any power source.
Such a passive cooling technology would serve well in much of the Developing World where power infrastructure to drive air conditioning is non-existent or heavily reliant on the burning of fossil fuels. And for areas off the grid, a technology like this presents an ideal solution for keeping buildings and homes cool during hot summers.