Batteries: thermoelectric and photoelectric – Photoelectric – Panel or array
Reexamination Certificate
2000-03-14
2001-04-24
Diamond, Alan (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Panel or array
C136S244000, C136S256000, C136S258000, C257S433000, C257S434000
Reexamination Certificate
active
06222115
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-330139, filed Nov. 19, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a photovoltaic module, particularly, to a photovoltaic module comprising an improved back cover film so as to improve the environmental resistance.
A photovoltaic module, which is arranged on, for example, a roof, is subjected to a severe outdoor environment and, thus, it is strongly required to improve the environmental resistance of solar cells. Various materials of constituting members of the photovoltaic module have been studied in order to improve the environmental resistance of the solar cells.
The construction of, for example, a thin film photovoltaic module will now be described briefly. Specifically, a thin film photovoltaic module comprises a plurality of solar cells each comprising a transparent electrode layer, a photovoltaic semiconductor layer and a back electrode layer, which are stacked one upon the other on the back surface of a front cover glass. The stacked structure formed on the front cover glass is divided into a plurality of strings to form a plurality of solar cells. Also, these solar cells are connected to each other in series so as to form an integrated photovoltaic module. The back surface of the integrated photovoltaic module is sealed with an encapsulant resin such as an ethylene-vinyl acetate copolymer (EVA). Further, the encapsulant resin are protected by a weather-resistant back cover film laminated thereon.
On the other hand, a crystalline photovoltaic module comprises 20 to 30 solar cells formed by using a single crystalline semiconductor wafer having a small area and arranged on a front cover glass. These solar cells are connected to each other by wires so as to form the crystalline photovoltaic module. The back surface of the crystalline photovoltaic module is sealed with an encapsulant resin such as EVA and is further protected by a back cover film, too.
Conventionally, as a material for forming the back cover film, a fluorocarbon resin film (for example, Tedler manufactured by Du Pont), a laminate of fluorocarbon resin/aluminum (Al)/fluorocarbon resin or a laminate of fluorocarbon resin/polyethylene terephthalate (PET)/fluorocarbon resin has been used.
However, the back cover film consisting of a fluorocarbon resin film alone fails to exhibit a sufficiently high humidity resistance, with the result that the metal members sealed with the encapsulant resin such as an output take-out wire and a back electrode tend to be corroded. On the other hand, the presence of the intermediate Al layer or PET layer enables the laminate of fluorocarbon resin/Al/fluorocarbon resin or the laminate of fluorocarbon resin/PET/fluorocarbon resin to be superior to the film consisting of a fluorocarbon resin alone in the humidity resistance. However, the adhesive strength between the fluorocarbon resin film and the encapsulant resin of EVA is not sufficiently high, with the result that the resin film and the EVA tend to peel from each other over a long period of time. Consequently, the metal members inside the photovoltaic module tend to be corroded because of the moisture intrusion through the peeled portion.
As described above, the conventional photovoltaic module is not satisfactory in the adhesive strength between the encapsulant resin and the back cover film, leaving much room for further improvement of the photovoltaic module in respect of the environmental resistance.
It should also be noted that, if the intermediate Al layer is exposed to the outside in the case of using a laminate of fluorocarbon resin/Al/fluorocarbon resin, the Al layer could be brought into contact with the output take-out wire, with the result that the insulation fails to be maintained.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a photovoltaic module excellent in environmental resistance by using a back cover film having a high adhesive strength with an encapsulant resin.
According to the present invention, there is provided a photovoltaic module, comprising a transparent substrate, solar cells formed on the back surface of the transparent substrate, an encapsulant resin for sealing the solar cells, and a back cover film formed on the back surface of the encapsulant resin, wherein the back cover film comprises at least a multi-layered film of a polyethylene terephthalate-based supporting film and an amorphous polyester-based heat seal layer formed on the surface of the supporting film which is positioned on the side of the encapsulant resin.
In the present invention, the back cover film may consist of a laminate including a multi-layered film of a polyethylene terephthalate-based supporting film and an amorphous polyester-based heat seal layer, and a fluorocarbon resin film bonded to the back surface of the supporting film constituting the multi-layered film.
In the present invention, it is desirable for the multi-layered film to have a thickness of 30 to 100 &mgr;m.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
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patent: 5728230 (1998-03-01), Komori et al.
patent: 58-17685 (1983-02-01), None
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patent: WO 95/06561 (1995-03-01), None
Diamond Alan
Hogan & Hartson LLP
Kaneka Corporation
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