Photovoltaic cells in combination with single ply roofing membranes

Claim 1

A prefabricated multi-functional roofing system formed in elongated flexible sections of substantially uniform thickness constructed for being rolled up in lengths suitable for being transported to a building site for unrolling and for being affixed to a roof structure, comprising: means forming an elongate section of flat, flexible single-ply roofing membrane adapted to extend over a said roof structure; said roofing membrane having a top side for exposure to the elements and being heat reflective and a bottom side for being placed on a roof substrate of said roof structure to form a roof thereon, said membrane having a predetermined softening temperature, and further including a fibrous material for reinforcing said membrane over a wide range of temperatures; means forming a plurality of photovoltaic cells distributed in a two dimensional flat array of rows and columns arranged continuously over said membrane; electrical circuiting means for interconnecting said photovoltaic cells and for extracting electrical power therefrom, said circuiting means comprising a plurality of bus bars; means forming a flat flexible thermoplastic pottant layer extending above and below said cells and over the area of said membrane to thereby mount, cover, and adhere said cells and circuiting means over the top side of the membrane in a predetermined pattern and to encapsulate the cells in a structure sufficiently flexible to be rolled up, said pottant layer having a second predetermined softening temperature and having a thermal coefficient of expansion compatible with said roofing system; a flexible cover layer adhered on top of said roofing membrane, pottant layer, and photovoltaic cells, said cover layer being transparent, tough and weatherproof, and having a softening temperature higher than said pottant layer; said membrane and said cover layer having predetermined first and second softening temperatures and said pottant layer havaing a third softening temperature lower than said first and second softening temperatures; said membrane, pottant layer, and cover layer being assembled and joined into a composite structure by heating above the softening temperature of said pottant layer but below the softening temperature of said membrane and said cover layer to thereby fuse and adhere the layers together for forming said roofing system adapted to conform to said roof structure of any shape; and means for flexing associated with each of said layers for keeping said composite flexible enough to roll up, said flexing means including transversely extending space channels formed between adjacent columns of said array of photovoltaic cells and depression grooves formed within each of said space channels.