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 peel off silicone film is removed. EXCEL SOLAR is designed for multi or single layer applications. *CIGS=Copper Indium Gallium Selenide.