A light-weight photovoltaic system includes a substructure and a plurality of substantially rectangular photovoltaic modules arranged in a mutually abutting relationship in rows and columns. Each photovoltaic module includes a photovoltaic panel disposed with a predetermined spacing on a self-supporting lightweight board disposed on the substructure. The lightweight board is water pervious and formed from a substantially water repellant material. A frame member is disposed on opposite sides of each photovoltaic panel and includes a recess. A clamping system including a clamping block with an extension at opposite surfaces thereof is provided for insertion into the recesses of the frame members of abutting photovoltaic panels. A tension cable system including a tension cable extends along at least one of the rows and columns. The clamping system and the tension cable system secure an intersection between the rows and columns of the abutting photovoltaic modules.