To achieve this goal, a panel has to reflect (rather than absorb) as much sunlight as possible, as well as radiate heat back into the building. Stanford’s invention does both:
It is an effective broadband mirror for solar light — it reflects most of the sunlight. It also emits thermal radiation very efficiently within the crucial wavelength range needed to escape Earth’s atmosphere.
The panels are a combination of both a thermal emitter and a solar reflector. And the team of researchers is the first to achieve this type of sustainable cooling during daytime hours by engineering nanostructured photonic materials — forms of light radiation — to either enhance or suppress light at different wavelengths. The result? A device that can cool 100 watts per square metre. In practical terms, that means you could have 10 per cent of your roof covered with solar panels, but they would offset about 35 per cent of the AC you’d need during the most sweltering days of summer. That sounds sounds pretty cool to us. [Stanford News]