Selective radiative cooling with MgO and/or LiF layers

A selective radiative cooling material consisting of:

• an infrared-reflective substrate, and
• layers of material consisting of a layer of magnesium oxide in a ceramic form and a layer of lithium fluoride in a polycrystalline form.

In a thermally selective radiative cooling system, the improvement comprising a selective radiative cooling material, said material consisting of:

• an infrared-reflective substrate which inhibits absorption at wavelengths shorter than about 8 microns, said substrate consisting of a metallic layer selected from the group consisting of aluminum, copper and zinc, and
• at least one layer of material which is at least non-absorptive, if not transparent, at wavelengths shorter than about 8 microns, absorptive at wavelengths from about 8-13 microns, and reflective at wavelengths longer than about 13 microns, said at least one layer of material being selected from the group consisting of ceramic magnesium oxide, polycrystalline lithium fluoride, and mixtures thereof.

A thermally selective radiative cooling system comprising:

• a device to be cooled,
• a selective radiative cooling means mounted on said device to be cooled, said means being constructed of material which inhibits absorption at wavelengths shorter than about 8 microns, is absorptive at wavelengths from about 8 to 13 microns, and reflects radiation at wavelengths longer than about 13 microns, said material consisting of a layer of infrared-reflective material, and at least one layer of material selected from the group consisting of magnesium oxide in a ceramic form, lithium fluoride in a polycrystalline form, and mixtures thereof, and
• a convection barrier positioned in spaced relation to said selective radiative cooling means.