The "Key"


Many of you are maybe wondering how it is possible that we can radiate that much that an object will be that cold.


It works that way because there is a balance between the radiation in and out of any surface.

The power you can radiate is very simple:

There is a constant (Stefan Boltzman  5,67E-8) multiplied by the emissivity (almost 1) and multiplied by the absolute temperature to the power of 4 !!

It means that at 16 deg C the radiation is 400W/m2


The important key is the radiation into the surface. This radiation has to be as low as possible.

The radiation into your surface is dependent on the radiator above you, the air and the clouds.

Said easy: It is dependent on the thickness of the layer above you and the surface of the object you are looking.

Above you, there are water particles in the clouds and other gasses (greenhouse gasses). At a clear sky, it is not too much.

At a clear sky there is a certain transparency. In that part you are looking to a temperature of a few Kelvin.

You can also reduce the part of the sky where you are looking to, e.g, by parabolea. It reduces the received thermal energy.

So, the best way is to make the radiator as big as possible while reducing the view factor.

Solutions are investigated by students.