EXCEL SOLAR is a polyester reinforced ALPA® polymer modified bitumen waterproofing membrane. The finish on the surface is a peel-off silicone film and undersurface is a thermofusible film. Top layer in Excel Solar PV Flex waterproofing system. Axter SOLAR PVFLEX CIGS* flexible photovoltaic modules are adhered in situ to the membrane surface, into the ALPA binder, when the film is heated. EXCEL SOLAR is designed for multi or single layer applications. *CIGS=Copper Indium Gallium Selenide.