Contoured insulation window for evacuated solar collector

An evacuated flat plate solar collector comprising, means forming a housing including a pair of opposed glass windows each having a longitudinal and lateral expanse bounded by a peripheral margin and fused together thereabout defining a partially evacuated chamber therebetween, a solar energy absorber segmented into a selected number of plates, said absorber being positioned within said chamber between said windows, fluid channel means joined to said absorber for removing heat therefrom, said fluid channel means passing into and out of said housing, said glass windows each having portions smoothly contoured to provide sufficient strength to withstand the force of atmospheric pressure exerted on one side thereof, the sealed together peripheral margins of the windows forming a peripheral support for the housing and lying within a plane, the contoured portions of each window being formed into a plurality of arcuate domes corresponding in number to the number of plates and being spaced across said window, one plate each being located within a dome, said domes projecting arcuately outwardly from said plane and being joined along adjacent portions thereof to form a plurality of intermediate supports extending across said window longitudinally and laterally of the domes and the plates, junctures of adjacent ones of said domes in one of the windows lying in the plane and freely resting against corresponding portions of the other window thereby providing intermediate mutual support for each window, and said plurality of domes being spaced apart from and out of contact with said plates so as to inhibit conductive heat losses from the solar collector.