Heat cooling currently works by taking the heat in one area, and moving it to another area where it doesn't bother us as much.
That might work simply for a computer sending the heat into your room, or by sending the hot air from your house outside of your house.
But what if you could channel heat from your house like a heatsink, and send it somewhere else away from your local neighborhood?
Can we transfer that heat somewhere else further away so that it doesn't stick around and bother us at all?
Here comes radiative cooling to the rescue! Heat can be beamed from earth into outer space.
Cool Technology
A team at Standford University had their paper published on December 13th, in which they lowered the temperature of a thermal emitter to 42 degrees Celsius below that out of the surrounding air.
A thermal emitter, like it's name suggests, emits heat, but more heat is emitted than it takes in. High performance cooling is achieved by decoupling the thermal emitter from it's local ambient environment, and recoupling it with the cold regions closer outer space.
To do this, Zhen Chen and his colleagues placed the emitter in a vacuum chamber to isolate it from the atmosphere, thereby isolating the emitter from convection or conduction heat transfer. Now that the thermal emitter could not transfer its heat to the surrounding environment for it to drop in temperature, a special window was designed on top of the vacuum chamber directed at the sky.
After 30 minutes of pumping the air out the temperature dropped by 40°C. The lowest reduction during a 24h period, was at 37°C, while the highest production was at 42.2°C at the peak of the suns exposure.
Atmospheric Bypass
Most heat but tries to escape Earth's atmosphere does not make it because they operate at wavelengths that don't pass through the atmosphere. Thermal radiation with wavelengths between 8 and 13 micrometers do pass into outer space. The matter designed by Stanford was specially designed within that range allowing it to pass directly into outer space on a clear day.
Future Tech
These are only preliminary experiments, requiring large setups, but there is promise for future technology incorporated into the convenience of our everyday lives. Ideas are from refrigerating food and medicine in areas where the ambient temperature is always hot, as the units can be built in an outside location attached to a building. Or better yet, in more developed areas it can be placed on rooftops as an air-conditioning unit and cool the whole building.
Challenges
The most challenging factor to scale in this technology for a wide range consumer application, is to find a much more cost-effective alternative to the zinc selenide vacuum chamber window that allows radiation of certain wavelengths the pass-through, like heat. But this is if you want to achieve those dramatic extreme optimal levels of cooling. You can substitute less effective materials such as silicon or aluminum for real applications, because you don't need such transparent material as zinc selenide.
And as for the future of air-conditioning, this technology won't be able to replace air conditioning everywhere because many regions are affected by overcast skies which eliminates the effectiveness of radiative cooling.
References:
- Radiative cooling to deep sub-freezing temperatures through a 24-h day–night cycle
- Future air conditioning could work by beaming heat into space
