Batteries: thermoelectric and photoelectric – Photoelectric – Panel or array
Reexamination Certificate
2002-10-15
2004-11-23
Diamond, Alan (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Panel or array
C136S256000, C136S246000, C136S259000, C136S258000, C136S261000, C257S053000, C257S433000, C257S434000, C257S436000, C257S437000
Reexamination Certificate
active
06822157
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin film solar battery module, particularly to improvement in strength and appearance of the module.
2. Description of the Background Art
Thin film solar batteries have the advantage of needing less amount of semiconductor material as compared with solar batteries using crystal wafers. It is also appreciated that a thin film solar battery can be formed at a relatively low temperature on an inexpensive substrate such as of glass or metal. Thus, saving in terms of costs is expected with the thin film solar batteries.
Among thin film solar batteries, non-monocrystal silicon type thin film solar batteries that use amorphous silicon, thin film polycrystalline silicon or the like are preferable in view of the abundant existence of silicon material and in view that the silicon material is harmless and has no adverse effect on the environment as compared to a compound type solar battery containing Cd, Se or the like. It is thus expected that non-monocrystal silicon type thin film solar batteries will generally be used.
An amorphous silicon solar battery has a transparent electrode layer such as of SnO
2
or ZnO, a p-i-n amorphous silicon type semiconductor layer, and a metal back electrode layer sequentially stacked on a transparent substrate such as of glass. In the layering processes, each layer is divided into a plurality of elongated rectangular cell regions through scribing using a laser beam or the like. An integrated structure is thus formed wherein the divided cell regions are electrically connected in series in the direction of narrow width of the cells.
The back surface side of the thin film solar battery is sealed with a filler such as ethylene vinyl acetate (EVA) or polyvinyl butyral, and/or a multilayered sheet of polyethylene terephthalate (PET)/aluminum/PET or a back sheet such as Tedler (trademark) to form a super straight type solar battery panel (hereinafter also termed “module”). Such a thin film solar battery module is mounted to a support member such as an aluminum frame, and then generally used outdoors.
Costs of a thin film solar battery module are expected to be reduced from a viewpoint of thinness of the semiconductor layer needed for power generation, the requirement of only one mechanical structure material, simple wiring, and the like.
In a thin film solar battery module that uses a glass substrate, the flat glass substrate on which the thin film semiconductor material is to be deposited forms the front surface of the module. In the case where such a solar battery module is installed on the roof of a house or on the top or wall of a building or architecture, the front surface of the module will act as a mirror. The glare of the sun light reflected by the module will bother the eyes of the people in the neighborhood. Furthermore, the scene in the neighborhood or the clouds in the sky will be mirrored on the front surface of the solar battery module to degrade the appearance of the house or architecture to which the module is installed.
To cope with the problem of surface reflection on a solar battery module employing a flat glass substrate, conventional approaches set forth below are known.
For example, in a crystal type solar battery module, a figured glass (having a fine uneven surface) is generally employed as a cover glass protecting silicon wafers, so that the figured cover glass can also serves as an anti-glare measures for diffusing light.
With regards to a thin film solar battery module, it is disclosed in Japanese Patent Laying-Open No. 11-74552 to use a figured glass as a substrate of the module having fine unevenness on its outer surface. Japanese Patent Laying-Open No. 2001-53315 discloses that a resin containing mixed beads for diffusing light is applied on a flat surface of a glass substrate.
In a thin film solar battery module that employs a glass substrate, the glass substrate constituting the outermost surface of the module must be strong enough to withstand wind pressure, hailstorms and the like so that the thin film solar battery module having a relatively large area to obtain sufficient generated electrical power can be used outdoors.
By using a chilled glass for the glass substrate, the strength of the glass substrate will be increased, and thickness thereof can be controlled. However, it is difficult to use a chilled glass effectively for the glass substrate in a thin film solar battery. Specifically, a thin film solar battery has a transparent electrode layer such as of SnO
2
formed on the glass substrate. In order to economically form a transparent electrode layer on a glass substrate of a large area, thermal CVD (chemical vapor deposition) of a high temperature process is generally employed. This means that even if a flat glass chilled by a heat treatment is employed for the substrate, the chilled glass substrate will be annealed during the high temperature process of forming the transparent electrode layer, whereby the strengthening effect due to the chilling will be lost.
The glass substrate of a thin film solar battery module for relatively large power must be at least 3 mm in thickness to ensure its strength. However, a thicker glass substrate will increase light absorption caused by the glass to induce a problem that the power generation efficiency is degraded. Particularly in the case where the economical flat soda lime glass is employed as the material of the glass substrate, light absorption caused by the glass is so much that the power generation efficiency is significantly degraded.
In the above-described measures to use a figured glass having a fine uneven surface as the substrate (Japanese Patent Laying-Open No. 11-74552) in relation to the problem of reflection on the glass substrate surface in a thin film solar battery module, there is a problem that patterning is difficult in the laser patterning step carried out for fabrication of the thin film solar battery module, because the laser beam is scattered at the uneven surface of the glass substrate.
Also, in the measures wherein a resin containing mixed beads for scattering light is applied on the surface of a flat glass substrate (Japanese Patent Laying-Open No.2001-53315), there is a problem as to weather resistance of the resin. There is also a problem that it is difficult to form homogeneous unevenness on the surface of the glass substrate of a large area and then the appearance of the module is degraded.
In order to solve the problem of reduction in the power generation efficiency caused by light absorption in the glass substrate, a low iron glass plate of high transmittance whose usage is particularly limited to certain applications such as the glass for showrooms in museums and the like can be employed instead of the economical flat soda lime glass that is typically used in the module. However, the low iron glass plate is so expensive as to restrict cost reduction that is one advantage of the thin film solar battery.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of the present invention is to provide an economical thin film solar battery module that can reduce the undesirable effects caused by light reflected from the glass surface of the module and that can have sufficient strength without reduction in power generation efficiency.
In a thin film solar battery module of the present invention, a flat glass substrate with non-monocrystal silicon type thin film solar cells formed thereon, a space layer, and a chilled figured glass are stacked in this order. At least the light incident side of the chilled figured glass has a fine surface unevenness to cause an anti-glare effect.
The arithmetic mean surface roughness Ra of the fine unevenness on the surface of the chilled figured glass is preferably in the range of 0.001 mm-0.3 mm. Also preferably, the chilled figured glass has an average thickness more than 3 mm and is formed of low iron glass.
The flat glass substrate is preferably a flat soda lime glass having a thickness of less than 3 mm. The flat glass subst
Diamond Alan
Sharp Kabushiki Kaisha
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