Radiationskühlung

Radiationskühlung, also known as radiative cooling, is a passive cooling process that involves the emission of thermal radiation from an object to a colder environment, typically outer space. This phenomenon occurs when an object's surface temperature is higher than the temperature of its surroundings and it radiates energy in the form of infrared photons. The rate of cooling is dependent on several factors, including the emissivity of the radiating surface, its temperature, and the atmospheric conditions.

Objects on Earth naturally radiate heat into the atmosphere and space. In clear, dry conditions, especially at night, surfaces can cool significantly below ambient air temperature through this process. This is because the atmosphere is largely transparent to certain infrared wavelengths, allowing heat to escape directly into space. Clouds, on the other hand, act as a blanket, absorbing and re-emitting infrared radiation, thus reducing the effectiveness of radiative cooling.

The principle of radiative cooling has been utilized for centuries in various applications. Traditional methods include using porous ceramic vessels where water evaporates from the surface, taking heat with it, a process enhanced by radiation. More recently, advanced materials and technologies are being developed to optimize radiative cooling for applications such as reducing building temperatures without electricity, cooling electronic devices, and even for personal cooling garments. This technology offers a sustainable and energy-efficient way to combat rising temperatures.