given range across a thin collector face in conjunction with a low height laminar interior flow having a predetermined proportionality to the bypass flow a short flow path length along the collector together with the bypass flow relationship and other parameters permit high temperature differentials to be attained accompanied by high efficiency further the mass flow through the collector may be varied within a substantial range in response to changing insolation conditions while maintaining the bypass flow in an acceptable range by incorporation of a pressure drop having mass flow dependent characteristics in the principal flow path application_number US 85625577 A description a collector panel system in accordance with the invention is depicted in generalized form in fig1 as to which it must be recognized that the drawing is not to scale inasmuch as many dimensions are extremely small relative to the total collector size in fig1 the collector panel 10 is a thin aluminum sheet here approximately 0 15 mm in thickness and having a selective low infrared emissivity coating the panel 10 contains an array of bypass flow apertures 12 having a density in the range of 2000 3000 apertures per meter 2 and aperture sizes in the range of 0 2 to 0 7 mm in this example the hole 12 diameters are 0 5 mm and the holes are.