HK1186584B - Flexible building-integrated photovoltaic structure - Google Patents

Abstract

Improved BIPV materials configured to meet various long-term requirements including, among others, a high degree of water resistance, physical durability, electrical durability, and an ability to withstand variations in temperature and other environmental conditions. In some embodiments, the disclosed BIPV materials include modules wherein two or more layers of the module are configured to be joined together during lamination to protect edge portions of the top sheet and/or back sheet of the module, such as in the vicinity of any multi-layer vapor barrier structure(s) of the module.

Description

Flexible building integrated photovoltaic structure

Technical Field

The present invention relates to photovoltaic structures, and more particularly to a flexible building-integrated photovoltaic structure.

Background

Building Integrated Photovoltaic (BIPV) materials generally include materials that generate electricity through the use of solar cells (PVcells) and are configured to be assembled on the roof or sides of a building. Once installed, the BIPV material serves as roof or side protection and simultaneously generates electricity. Thus, it is desirable for the BIPV material to be flexible and able to maintain its protective and power generating properties for extended periods of time, such as 10 years, 20 years, or even longer.

BIPV modules generally include a multilayer top sheet positioned above the solar cells and a multilayer back sheet positioned below the solar cells. The top sheet and the back sheet are each configured to protect the solar cell from component exposure, particularly from exposure to water or moisture, and are typically bonded together by a process such as lamination. To achieve this protective function, one or both of the top sheet and the back sheet may include a vapor barrier, which itself may be part of a separate multilayer structure.

Two areas of a BIPV module that may be particularly susceptible to water ingress are in the vicinity of the edge portions of the multilayer top and back sheets, particularly the vapor barrier. If water enters these edge portions, it can penetrate between the layers of the top and/or back sheet, thus compromising the mechanical and electrical stability of these structures. Thus, a BIPV module that provides improved protection for the edge portions of the top and back sheets would provide the desired improvements in mechanical stability and module life.

Disclosure of Invention

Improved BIPV materials configured to meet a variety of long-term requirements including high water repellency, physical life, electrical life, and the ability to withstand temperature variations and environmental conditions are disclosed. In some embodiments, the disclosed BIPV materials include a plurality of modules, wherein two or more layers of the modules are configured to be bonded together during lamination to protect the top sheet and/or back sheet of the module, such as adjacent to any multi-layer vapor barrier structure of the module.

Drawings

Fig. 1 is a cross-sectional view of a photovoltaic module according to aspects of the present disclosure;

fig. 2 is a cross-sectional view of another photovoltaic module according to an aspect of the present invention;

fig. 3 is a cross-sectional view of yet another photovoltaic module according to an aspect of the present invention;

fig. 4 is another cross-sectional view of the photovoltaic module of fig. 3 including the addition of an adhesive layer disposed about the module in accordance with aspects of the present disclosure;

fig. 5 is a cross-sectional view of a separate top sheet portion of a photovoltaic module according to aspects of the present invention.

Detailed Description

The present invention discloses a method and apparatus for manufacturing, assembling and installing BIPV materials, including flexible and thin film photovoltaic materials. The disclosed BIPV materials are configured to meet a variety of long-term requirements, including high water repellency, physical lifetime, electrical lifetime, and the ability to withstand temperature variations and environmental conditions. In some embodiments, the disclosed BIPV materials include a plurality of modules, wherein two or more layers of the modules are configured to be bonded together during lamination to protect the top sheet and/or back sheet of the modules, such as in the vicinity of any multi-layer vapor barrier structure of the modules.

Fig. 1 is a cross-sectional view of a photovoltaic module, generally designated 100, according to aspects of the present invention. The module 100 includes a PV cell layer, generally indicated at 102, a top sheet, generally indicated at 104, and a bottom sheet, generally indicated at 106. The module 100 may also include a roofing layer such as a butyl adhesive layer 108. As described in detail below, each PV cell layer 102, top sheet 104, and bottom sheet 106 may itself comprise a variety of material layers suitable for various purposes.

In particular, the PV cell layer 102 may include a plurality of photovoltaic cells electrically connected to each other, each having a similar structure. For example, the cells of the PV cell layer 102 may be thin film PV cells each including a semiconductor absorber layer 110 and a substrate 112 with the semiconductor absorber layer supported on the substrate 112. The semiconductor absorber layer 100 may comprise a Copper Indium Gallium Selenide (CIGS) P-type semiconductor layer and a cadmium sulfide (CdS) n-type semiconductor layer, although many other photovoltaic absorber layers are known. A description of a CIGS/CdS type photovoltaic cell is found in U.S. patent No. 7,760,992, Wnedt et al, which is incorporated by reference for all purposes. Several batteries each having a standard cross-sectional thickness of 20-40um are electrically connected in series by a conductive tape or tab (not shown) to be combined.

Top sheet 104 may include various layers such as an upper protective layer 114, an upper encapsulant layer, a vapor barrier structure 118, and a lower encapsulant layer 120.

The upper protective layer 114 of the top sheet 104 is provided to protect the underlying layers from abrasion, puncture, and impact damage (e.g., from hail), and the like. The upper protective gap may be constructed of a material such as a substantially transparent, flexible, weatherable fluoropolymer, for example, an Ethylene Tetrafluoroethylene (ETFE) polymer, having a cross-sectional thickness of about 30-150 um.

The upper encapsulant layer 116 and the lower encapsulant layer 120 may each be substantially transparent flexible layers constructed of materials such as ethylene-vinyl acetate copolymer, each having a cross-sectional thickness of 200-500 um. Generally, the upper and lower encapsulant layers 116, 120 may both be thermoplastic layers, or alternatively, one or both of the layers 116, 120 may be thermoplastic layers. The use of a non-peroxide crosslinking agent in the thermoplastic EVA material may be particularly suitable for the lower encapsulant layer 120 because the layer 120 is in close proximity to the PV cell layer 102 and the absence of peroxide material may reduce PV material degradation of the PV cell layer. In some embodiments, a package may be a multi-layer structure including, for example, an EVA layer and a separate UV absorbing layer, and the like.

Vapor barrier structure 118 itself may be a multi-layer structure having an overall cross-sectional thickness in the range of about 50-150 um. Providing a relatively thick and/or relatively thick vapor barrier structure may help avoid wrinkling of the module, particularly near its edges. Vapor barrier structure 11 will typically comprise a plurality of layers (not shown) such as a vapor barrier layer, for example, a thin layer constructed of a metal oxide material, and one or more underlying and/or overlying layers of an insulating material such as polyethylene terephthalate (PET) and/or polyethylene 2,6 naphthalate (PEN). Because PET and PEN are susceptible to damage from Ultraviolet (UV) light, an intermediate layer of EVA or some other material containing a UV barrier may be disposed between the vapor barrier layer and the PET and/or PEN layers. For the same reason, the upper encapsulation layer 116 may include a UV blocker.

Like the top sheet 104, the bottom sheet 106 may also include multiple layers, such as a bottom encapsulant layer 122 and a multi-layer back sheet 124. Unlike the layers disposed on the PV cell layer 102, however, the bottom sheet 106 of the layers need not be transparent.

In any case, the bottom encapsulant layer 122 (which is depicted in fig. 1-4 as directly contacting the bottom surface of the PV cell layer 102) may be made of a thermoplastic material such as the material designated Z68 manufactured by dnpSolar division of DNP corporation, denmark. The use of a thermoplastic material for the bottom encapsulant layer 122 may improve adhesion (which may be, for example, coated with platinum) to the PV cell backside of the layer 102, helping to reduce delamination of the bottom encapsulant layer from the PV layer. In addition, a thermoplastic bottom encapsulant layer 122 may be flexible enough to reduce the forces on the PV layer that can cause the conductive tape attached to the PV cell to bend and allow efficient non-vacuum lamination, such as rapid pressure lamination in the presence of air, while still covering the high relief structures or components disposed below the PV layer, such as bypass diodes (not shown). Providing a bypass diode in parallel with the PV cells can help avoid power loss, hysteresis effects, and damage to the module (when a particular cell is damaged, weak, or shadowed). By providing bypass diodes in the module, shielding (shielding) of the diodes from UV radiation can be achieved without reducing the sun exposure area of the module.

The backsheet 124 may include several layers, such as a thin film metal vapor barrier layer suitable for a polymer. The backsheet 124 is generally provided to protect the bottom surface of the PV cell layer 102 from water or contaminants while providing a mechanically stable module with minimal thermo-mechanical stress. Examples of structures suitable for use in the joined backsheet material structures are described, for example, in U.S. patent application No.13/104,568, which is incorporated herein by reference in its entirety.

As shown in fig. 1, module layers such as upper protective layer 114, upper encapsulant layer 116, lower encapsulant layer 120, bottom encapsulant layer 122, multi-layer backsheet structure 124, and/or adhesive layer 108 may each extend beyond vapor barrier structure 118. Thus, some or all of these layers may be provided in combination with at least one of the other layers, for example, to cover and protect the edge portions of the vapor barrier structure during a modular lamination process.

In particular, upper protective layer 114 and/or upper encapsulant layer 116 may be disposed to bond lower encapsulant layer 120, bottom encapsulant layer 122, back sheet 124, and/or any additional encapsulant layers (not shown) disposed below vapor barrier structure to cover and protect edge portions of vapor barrier structure 118. This may inhibit or even avoid the ingress of water or moisture into the layers between the vapor barrier structures, thereby increasing the stability and lifetime of the vapor barrier structures and the module as a whole.

While the foregoing has focused on the protection of the edge portions of vapor barrier structures disposed on PV cell layers, similar methods and apparatus may be used to protect the edge portions of other PV modules, such as the edge portions of a multi-layer backing. For example, various module layers such as an upper protective layer 114, an upper encapsulant layer 116, a lower encapsulant layer 120, and/or a bottom encapsulant layer 122 may be provided in combination with the adhesive layer 108 (e.g., laminated) to cover and protect the edge portions of the multi-layer backsheet 124. This may inhibit contaminants, such as moisture, from penetrating through the layers between the backsheet 124, thereby increasing the stability and life of the backsheet and the module as a whole.

Fig. 1 depicts upper protective layer 114, upper encapsulant layer 116, lower encapsulant layer 120, bottom encapsulant layer 122, back sheet 124, and adhesive layer 108 all extending more laterally beyond the lateral edge portions of vapor barrier structure 118. Similarly, each of the layers described above may further extend longitudinally beyond the longitudinal edge portions (not shown) of vapor barrier structure 118. For example, if the module 100 is manufactured in a continuous roll-to-roll process, the vapor barrier structure is used discontinuously, leaving gaps longitudinally in the various protective and encapsulating layers as they overlap the vapor barrier structure. The web is then cut across the gaps, leaving separate modules with one or more protective layers overlying the vapor barrier structure.

It is not necessary that the protective layer of all (or any) of the modules extend beyond the edge portions of the vapor barrier structure. For example, fig. 2 is a cross-sectional view of another photovoltaic module, generally designated 100', according to an aspect of the present invention. The components of module 100 'are substantially similar to those of module 100, and reference numerals having a prime (') are used similarly in fig. 2 to refer to the non-primed counterpart of fig. 1. At module 100 ', however, which is depicted prior to the lamination process, lower encapsulant layer 120', and bottom encapsulant layer 122 'each have lateral linear dimensions that are less than corresponding linear dimensions of vapor barrier structure 118'.

In the example of fig. 2, heat and/or pressure during the lamination process may cause lower encapsulant layer 120 ' and bottom encapsulant layer 122 ' to be pressed laterally outward beyond the lateral edge portions of vapor barrier structure 118 '. The same description may apply in the longitudinal direction if lower encapsulant layer 120 'and bottom encapsulant layer 122' initially have longitudinal linear dimensions that are less than the corresponding linear dimensions of the vapor barrier structure. As such, lower encapsulant layer 120 ' and bottom encapsulant layer 122 ' will have linear dimensions greater than the corresponding linear dimensions of vapor barrier structure 118 ' after base processing, and these layers are configured to cover and protect the edge portions of the vapor barrier structure. Generally, any protective layer is configured to have a linear dimension that is less than a corresponding linear dimension of the vapor barrier structure prior to lamination processing and a linear dimension that is greater than a corresponding linear dimension of the vapor barrier structure after lamination processing.

Fig. 3 is a cross-sectional view of yet another photovoltaic module, generally designated 100 ", in accordance with an aspect of the present invention. Module 100 "is substantially similar to modules 100 and 100', and double prime numbers are used to refer to corresponding components in fig. 1 and 2 having the same non-primed and primed reference numerals. In fig. 3, however, only bottom encapsulation layer 122 ″ is provided having a linear dimension smaller than a corresponding linear dimension of the vapor barrier structure before the lamination process and having a linear dimension larger than the corresponding linear dimension of the vapor barrier structure after the lamination process.

Lamination processing the module may cause a change in the cross-sectional area of one or more protective layers, regardless of the linear dimensions of any particular protective layer. For example, thermal and/or application during build-up processing may result in non-uniform cross-sectional areas of the lower encapsulant layer 120 (and 120 ', 120 ") and/or the bottom encapsulant layer 122 (and 122', 122"). In detail, after the module lamination process, the cross-sectional area of the encapsulation layers can be substantially reduced in the module edge portion compared to the cross-sectional area of the encapsulation layers in the module inner portion. In other words, the edge sealing layer of the module may be tapered during the lamination process. This results in a smaller package thickness at the edges of the vapor barrier structure, which correspondingly reduces the chance of water penetrating the package and the layer between the vapor barrier structure.

The reduction in cross-sectional area of various protective layers at the edge portion of the module may be achieved by providing a protective layer, such as an encapsulation layer, of reduced linear dimensions, as depicted in fig. 2-3. For example, one or both of the lower encapsulant layer 120 'and the bottom encapsulant layer 122' have linear dimensions less than the corresponding linear dimensions of the vapor barrier structure and back sheet prior to the module lamination process, which enables the cross-sectional area between the vapor barrier structure and back sheet at the edge portion of the module to be reduced after the module lamination process.

Fig. 4 is another cross-sectional view of photovoltaic module 100 "of fig. 3, but the module has been slightly modified in accordance with this feature of the invention. Specifically, the module 100 "now includes an adhesive layer 119" disposed on the peripheral portion of the module. In detail, fig. 4 depicts adhesive layer 119 "disposed along an edge portion of vapor barrier structure 118". This achieves adhesion of the other protective layers to the edge portions of the vapor barrier structure during the lamination process.

More generally, an adhesive layer such as layer 119 "may be provided around any module to achieve protection of the edge portions of the module after lamination processing. The adhesive layer may be constructed of an adhesive encapsulating material similar to the encapsulating material of the other modules, or it may be provided by other suitable materials to securely bond the edge portions of the vapor barrier structure and/or other layers of the module provided to protect the edge portions of the vapor barrier structure.

In some embodiments, a top sheet including a vapor barrier may be manufactured separately from the remaining BIPV modules as a stand-alone assembly. Figure 5 is a cross-sectional view of a top sheet structure, generally designated 200, which may be suitably employed by this feature of the present invention. Top sheet structure 200 includes an upper protective layer 214, an upper encapsulant layer 216, and a vapor barrier structure 218. These elements are substantially similar to corresponding elements of module 100, and are identified with similar reference numerals. Thus, a separately fabricated top sheet structure may have a cross-sectional thickness in the range of about 280-800 um. By providing a top sheet of relatively large thickness, or otherwise desirably rigid, it may help reduce possible wrinkling of the module when the top sheet is being laminated, particularly near the edges of the module.

When a top sheet such as top sheet structure 200 is separately manufactured, it may also be separately laminated, in which case the upper protective layer 214 and/or the upper encapsulation layer 216 may surround the edge portions of the vapor barrier structure during the initial lamination process. Further, the vapor barrier structure itself may include a protective layer on an underlying layer of the vapor barrier structure and/or a protective layer on an overlying layer of the vapor barrier structure, in which case one or more of these protective layers may be configured to cover and protect edge portions of the vapor barrier structure after lamination processing. In this manner, the edge portions of the vapor barrier structure may be covered and protected even before the top sheet structure and PV cells are integrated into a module. Alternatively, or in addition, the top sheet may be provided in a module and then laminated, which may result in even better protection of the edge portions of the vapor barrier.

In general, any protective layer overlying the vapor barrier wall (such as 118, 118', 118 ", or 218) and/or any protective layer underlying the vapor barrier wall may be configured to cover and protect the edge portions of the vapor barrier wall after lamination processing, whether by being combined as described above with respect to fig. 1-4, or because a separate protective layer becomes disposed around the edge portions of the vapor barrier wall as described above with respect to fig. 5. Typically, a separate topsheet structure will be laminated twice-once during its initial manufacture and a second time during its integration into a PV module, in which case protection of the edge portion of the vapor barrier may be achieved by bonding a single material around the edge portion and bonding both materials around the edge portion. In a similar manner, a separate multilayer backsheet may be provided in some embodiments with at least some of its edges protected by an initial lamination process prior to integration of the backsheet into a PV module.

Claims (18)

1. A photovoltaic module, comprising:

a plurality of photovoltaic cells electrically connected to each other, each cell comprising a semiconductor absorber layer and a substrate on which the semiconductor absorber layer is supported;

a first packaging layer under the cells;

a protective backing sheet underlying the first encapsulation layer;

a multi-layer vapor barrier structure including a vapor barrier layer on top of the cells;

a second packaging layer arranged between the steam barrier layer and the batteries; and

a third encapsulation layer on the upper layer of the vapor barrier layer;

wherein the third encapsulation layer is configured to cover and protect edge portions of the vapor barrier structure in combination with at least one of the first encapsulation layer and the second encapsulation layer.

2. The photovoltaic module of claim 1 wherein said first encapsulant layer is a thermoplastic layer and said second encapsulant layer is a thermoset layer.

3. The photovoltaic module of claim 1 wherein said first encapsulant layer and said second encapsulant layer are each thermoplastic layers.

4. The photovoltaic module of claim 1 wherein said first encapsulant layer and said second encapsulant layer are each thermoset layers.

5. The photovoltaic module of claim 1, wherein said third encapsulant layer and at least one of said first encapsulant layer and said second encapsulant layer each extend beyond said edge portion of said multilayer vapor barrier structure and are bonded during lamination processing.

6. The photovoltaic module of claim 1, wherein said first encapsulant layer is configured to have a linear dimension that is less than a corresponding linear dimension of said vapor barrier structure prior to lamination and that is greater than a corresponding linear dimension of said vapor barrier structure after lamination.

7. The photovoltaic module of claim 1, wherein said second encapsulant layer is configured to have a linear dimension that is less than a corresponding linear dimension of said vapor barrier structure prior to lamination and that is greater than a corresponding linear dimension of said vapor barrier structure after lamination.

8. The photovoltaic module of claim 1, wherein said first encapsulant layer and said second encapsulant layer are configured to have linear dimensions that are less than corresponding linear dimensions of said vapor barrier structure prior to lamination and that are greater than corresponding linear dimensions of said vapor barrier structure after lamination.

9. The photovoltaic module of claim 1 wherein said third encapsulant layer is part of a top sheet structure of said module and wherein said third encapsulant layer is bonded to said second encapsulant layer during a lamination process.

10. A photovoltaic module, comprising:

a plurality of photovoltaic cells electrically connected to each other, each cell comprising a semiconductor absorber layer and a substrate on which the semiconductor absorber layer is supported;

a first packaging layer under the cells;

a protective backing sheet underlying the first encapsulation layer;

a multi-layer vapor barrier structure including a vapor barrier layer on top of the cells;

a second packaging layer arranged between the steam barrier layer and the batteries; and

a third encapsulation layer on the upper layer of the vapor barrier layer;

wherein the encapsulation layers are configured such that after the module is laminated, the cross-sectional areas of the first encapsulation layer and the second encapsulation layer at the edge portion of the module are substantially reduced relative to the cross-sectional areas of the first encapsulation layer and the second encapsulation layer at the inner portion of the module.

11. The photovoltaic module of claim 10, wherein at least one of said first encapsulant layer and said second encapsulant layer is configured to have a linear dimension that is less than a corresponding linear dimension of said vapor barrier structure prior to lamination of said module, and to reduce a cross-sectional area between said vapor barrier structure and said back sheet at an edge portion of said module after lamination of said module.

12. The photovoltaic module of claim 10, wherein at least one of said first encapsulant layer and said second encapsulant layer is configured to have a linear dimension that is less than a corresponding linear dimension of said back sheet prior to lamination of said module, and to reduce a cross-sectional area between said vapor barrier structure at an edge portion of said module and said back sheet after lamination of said module.

13. A photovoltaic module, comprising:

a plurality of photovoltaic cells electrically connected to each other, each cell comprising a semiconductor absorber layer and a substrate on which the semiconductor absorber layer is supported;

a first packaging layer under the cells;

a protective backing sheet underlying the first encapsulation layer;

a multi-layer vapor barrier structure including a vapor barrier layer on top of the cells;

a second packaging layer arranged between the steam barrier layer and the batteries; and

a third encapsulation layer on the upper layer of the vapor barrier layer;

wherein at least one of the first encapsulation layer, the second encapsulation layer, and the third encapsulation layer is configured to bond with a fourth layer of the module to cover and protect edge portions of at least one of the vapor barrier structure and the back sheet.

14. The photovoltaic module of claim 13 wherein the fourth layer of the module is the backsheet.

15. The photovoltaic module of claim 13 wherein the fourth layer of the module is an adhesive layer.

16. The photovoltaic module of claim 13 wherein the fourth layer of the module is a fourth encapsulant layer.

17. The photovoltaic module of claim 13 wherein at least one of said encapsulant layers extends beyond said edge portion of said vapor barrier structure and bonds to said fourth layer of said module during lamination processing.

18. The photovoltaic module of claim 13, wherein said fourth layer is an adhesive layer configured to attach to an architectural surface.