The invention is related generally to photovoltaic modules, and more specifically to sealing systems for improving the area utilization of light-facing surfaces of photovoltaic modules.
Photovoltaic cells are widely used for generation of electricity, where multiple photovoltaic cells are interconnected in module assemblies. Such modules may in turn be arranged in arrays, integrated into building structures or otherwise assembled to convert solar energy into electricity by the photovoltaic effect. Individual modules are encapsulated to protect the module components and photovoltaic cells from the environment. Current encapsulation techniques involve sealing photovoltaic cells between glass or polymer sheets to prevent moisture from contacting the photovoltaic cells. These sheets are generally sealed at their peripheral edges using opaque sealants that prevent light from reaching any photovoltaic cells in those areas, thereby reducing the total module area available for generating electricity. The area available for generating electricity is known as the “active area”.
There exists a need in the art to seal photovoltaic cells in a moisture resistant module without sacrificing any active area to the sealing region in order to maximize the electrical output and usable area.
In one embodiment, a photovoltaic module housing interconnected photovoltaic cells is encapsulated with a flexible front sheet comprising a moisture resistant film or a moisture resistant multi-layer film, and comprises wrapping the light-facing flexible front sheet around the non-light-facing backsheet and forming a moisture resistant seal between the front sheet and back sheet in a region behind the photovoltaic cells.
In another embodiment, a photovoltaic module housing individual photovoltaic cells is encapsulated with a flexible front sheet comprising a moisture resistant film or a moisture resistant multi-layer film, and comprises wrapping the light-facing flexible front sheet around the photovoltaic cells and forming a moisture resistant seal between the front sheet and back sheet in a region behind the photovoltaic cells.
Reference will now be made in detail to specific embodiments of the invention. Examples of the specific embodiments are illustrated in the accompanying drawings. While the invention will be described in conjunction with these specific embodiments, it will be understood that it is not intended to limit the invention to such specific embodiments. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be practiced without some or all of these specific details. In other instances, well known mechanical apparatuses and process operations have not been described in detail in order not to unnecessarily obscure the present invention.
Provided herein is a flexible, transparent encapsulating sheet incorporated into photovoltaic module configurations along with a sealing compound, wherein the sealing compound is opaque to light transmission, and the sealing region is arranged to substantially avoid blocking the light-facing or “active area” of a photovoltaic module. By placing the seal away from the active area of the photovoltaic cells, a moisture barrier can be created that can meet the minimum width requirement of the Underwriters Laboratories (UL) specification 1703 which calls for a minimum distance along any surface to the electrically active photovoltaic cells to be at least 1.3 cm. This specification, UL 1703, edition 3, as revised April 2008, is incorporated by reference herein in its entirety. By placing the moisture barrier behind the photovoltaic module, this requirement can be met while substantially avoiding blocking the light facing active area of the module. This in turn increases electrical output.
Embodiments of the present invention relate to encapsulating solar modules for environmental protection and mechanical support in order to maximize the light facing “active area.”
The structure in
The sealing material may be comprised of a material with a low WVTR. In some embodiments the WVTR may be less than 10−2 g/m2/day when measured at 38° C. and 100% relative humidity. In other embodiments the WVTR may be less than 10−3 g/m2/day when measured at 38° C. and 100% relative humidity. In still further embodiments the WVTR may be less than 10−4 g/m2/day when measured at 38° C. and 100% relative humidity. The sealing material may be comprised of various butyl rubber compounds containing, for example, a titanium zeolite desiccant to delay the onset of WVTR into the module.
In some embodiments, an anti-reflection coating is applied to the outer surface of the flexible transparent front layer. For example, a two-layer structure having a high refractive index layer with a thickness of 1 μm or less that is in contact with the flexible and transparent barrier layer, and a low refractive index layer deposited on the high refractive index layer may be used to reduce light reflection from the surface of the flexible layer, thereby increasing light transmission to the photovoltaic cells within a module. Alternatively, other anti-reflection coatings commonly known in the art may be applied, and in some embodiments may be used in combination with adhesion layers, anti-smudge layers, hard coating layers, or primer layers. In some embodiments, an anti-soiling layer, such the SOLARC™ coating manufactured by Honeywell, Inc., may be used in combination with an anti-reflection layer. In other embodiments, a hard coating layer is used without an anti-reflection layer. In other embodiments, a combination of hard coating and anti-soiling layers is used to improve the durability and ease of cleaning the photovoltaic module.
In another embodiment, the front layer is flexible and transparent and the back layer is also flexible, but not necessarily transparent, as shown in
It is to be understood that the present invention is not limited to the embodiment(s) and the example(s) described above and illustrated herein, but encompasses any and all variations falling within the scope of the appended claims. For example, as is apparent from the claims and specification, not all method steps need be performed in the exact order illustrated or claimed, but rather in any order that allows the proper formation of the solar cells of the present invention.