Yeda Research and Develpment & Co. Ltd

Israel Dostrovsky

Michael Epstein

The invention relates to a process for the production of optically selective surfaces for use in solar collectors, having a predetermined ratio of absorbance .alpha..sub.s to emmitance .epsilon. of at least 10, which comprises effecting an anodic oxidation of copper, or copper applied to any substrate metal, in an alkaline bath at an elevated temperature between 50.degree. and 85.degree. C., preferably 70.degree. to 85.degree. C., and at a current density of above 1 mA/cm.sup.2 and up to 40 mA/cm.sup.2 until an increase of resistance is experienced. Substrate metals may be copper, copper plated steel, copper plated galvanized iron, copper plated nickel, nickel plated steel to which a layer of copper is applied, and the like.

Novel process for the production of optically selective surfaces

A solar collector unit comprises a body of rigid thermally insulating material having a surface in the shape of about half a cylindrical parabola, the parabolic surface being provided with a reflective surface, a conduit being positioned with its long axis in the median plane of the parabola, said conduit serving as conduit for the heat-exchange medium, the surface of said conduit facing the parabolic surface being a selective surface, a transparent cover being provided on top of the device.

Growing community of inventors

Rehovot, Israel

Israel Dostrovsky