Optical transmittance measurements on a solar collector cover of cylindrical glass tubes

The transmittance of unpolarized light through a solar collector cover made of cylindrical glass tubes in a coplanar parallel close-packed array is dependent on the orientation of the cylindrical axes of the tubes in the plane of the cover. A maximum transmittance occurs when the axes are perpendicular to the plane of the angle of incidence, and a minimum transmittance occurs when the axes are parallel to the plane.At all orientations and at all angles of incidence the tubular cover has a markedly greater transmittance than does a cover formed from two parallel sheets of window glass.