Abstract: An evacuated solar collector receives impinging solar radiation of varying intensity and converts the same into useful thermal energy in a selected working range of the ambience. The collector has absorber and window surfaces selectively coated for rendering the conversion of solar radiation to useful thermal energy more efficient by increasing absorption, reducing reradiation, and in certain cases may include at least one electrically conductive coating on the solar window which is capable of carrying an electric current, for suppressing snow accumulation thereon.

Abstract: A conventional flat plate solar heat collector is provided with a contoured vacuum insulation window supported solely about its peripheral edge portions. The window is a composite formed from a pair of minimum thickness complementarily contoured glass sheets, which with the exception of their peripheral portions which are sealed together, are spaced apart from one another so as to provide an evacuated chamber therebetween and thus insulate one sheet from the other. The window formed by the nested or complementary contoured glass sheets is contoured in both its longitudinal and lateral directions, such that in its longitudinal direction the window is composed of a plurality of sinusoidal corrugations whereas in its lateral direction the peaks of such corrugations are contoured in the form of paraboloids so as to provide maximum uniform tensile strength to the window such that it may withstand the forces generated thereon by the atmosphere.