säteilyjäähdytystä

Säteilyjäähdytystä is a Finnish term referring to radiative cooling. It is a process where an object or surface loses heat to its surroundings by emitting thermal radiation. This is a natural phenomenon that occurs for all objects with a temperature above absolute zero. The rate of radiative cooling depends on the object's emissivity, its surface area, and the temperature difference between the object and its surroundings. Objects with high emissivity, meaning they are good emitters of thermal radiation, will cool down faster.

In many applications, radiative cooling is a passive method of heat removal. For example, on a clear night, objects on Earth radiate heat into the cold expanse of outer space, leading to a drop in their temperature. This can be observed in dew formation, where surfaces cool below the ambient air temperature. Engineered surfaces can be designed to enhance radiative cooling. These surfaces often have specialized coatings that are highly emissive in specific parts of the infrared spectrum, allowing them to efficiently radiate heat away even during the daytime.

Radiative cooling has a wide range of potential applications. It can be used for passive cooling of buildings, reducing the need for air conditioning and thus saving energy. It can also be employed in electronics cooling, medical devices, and even in space applications where active cooling systems can be complex and energy-intensive. The effectiveness of radiative cooling is maximized when the surrounding environment has a lower effective temperature, such as a clear sky at night, or when specialized materials are used to direct radiation towards the cold sink of space.