In principle, a solar panel has a metal cabinet of rectangular form in which it is mounted. Through a glass window, sunlight falls on a surface which absorbs nearly the entire field of spectral them.
In the vacuum panels, it is almost entirely removed. Heat radiation, due to its temperature, is also hindered by a glass window that is opaque to wavelength higher. This heat is retained within the panel, the balance of heat leading to a temperature higher than without the glass. This effect is known as the greenhouse effect. In modern solar panels used special glass with a little content as possible and iron with an increased resistance to hail and snow load.

• Flat solar panels

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