Embossed sheet glass lens arrays for hybrid PV modules

In hybrid PV-CPV modules the glass entrance window of a silicon module is replaced by an array of lenses that concentrate direct sunlight onto very small but twice-as-efficient multijunction PV cells while transmitting indirect daylight to the silicon. Hybrid modules have the potential for conversion efficiciency nearly double that of conventional silicon PV modules, and could become a major source of utility scale solar electricity generation. But for commercial success the added costs of the lens array, small CPV cells and dual rather than single axis tracking must be kept low. Here we describe a method for forming large lens arrays directly from glass as part of large-scale float glass manufacturing. A wide, continuous sheet of newly formed and still soft glass is embossed like shower glass, by passage between two rollers. These imprint cylindrical lenses on the upper and lower surfaces, arrayed at right angles to each other. The lenses act together to form point foci, where the multijunction cells are located on the silicon cells. The cost of lens arrays mass-produced in this way should be little more than that of the flat glass sheets of conventional modules, which in many cases are already roll-formed with textured surfaces to reduce reflection. We describe experiments made with commercially available embossed glass and cylindrical lenses.