Recently, roof-top photovoltaics and building integrated photovoltaic installations for residential and commercial installations have grown in volume and projections for continued growth in the United States have been high. Glass-to-glass laminated CdTe PV modules has been established as the most competitive technology among thin film photovoltaics due to high performance, lowest cost and high reliability; unfortunately overall weight of the glass-to-glass modules is governed by the thickness of the two glass sheets used for module fabrication. Reducing the weight of the photovoltaic module by replacing the back glass with enameled thin steel will reduce the module weight to improve the installation process by reducing roof loading, reducing building integrated photovoltaic mounting restrictions, and reducing the photovoltaic module installation labor. Toledo Solar, Inc. will demonstrate the use of enameled thin steel as the back encapsulation for glass CdTe PV modules. The substitution of formed enameled thin steel for glass sheets reduces the module weight and provides integral module mounting features. Phase I will test small laminated enameled thin steel/interlayer/PV glass structures to identify materials systems for enameled thin steel that can be adapted to full size photovoltaic module fabrication. Select the steel thickness based upon the mechanical needs for 0.6 meter x 1.2 meter [0.72 square meters] CdTe PV modules and mechanical pre-forming of the steel; additionally select the thickness of enamel based upon the dielectric strength required for the PV module. Fabricate a series of 0.3 m x 0.3 m [0.09 square meters] coupon size enameled steel coupons laminated to glass coupons with a polymeric interlayer. Complete mechanical strength test sequence of laminated composites
mechanical pull testing, ball drop impact testing, hail impact testing, 85°C/85% RH Thermal test and 85°C/85% RH / -40°C Freeze Cycle testing of laminated composites. Based upon the best results of the Phase I investigations, recommend an enameled thin steel material for Phase II assembly and testing of full size CdTe PV modules. Carrying the Project into a Phase II continuation will allow expansion of the CdTe PV module market acceptance in roof top and building integrated photovoltaic installations through the integration of PV module mounting structures into the laminated back surface of each module. Mechanical mounting features can be included in the thin steel prior to the enamel processing step such that additional separate module mounting clips are no longer needed for the installation of the PV module on racking structures. The steel enameling industry can incorporate all the mechanical mounting features in the steel prior to the enameling process steps analogous to current production products for the industry.The Phase II continuation will demonstrate a blending of two successful US industries; thin film CdTe photovoltaic technology and glass enameled steel technology, to open new opportunities for both industries.
