WO2017117132A1

WO2017117132A1 - Systems and methods for reducing inactive space in photovoltaic modules

Info

Publication number: WO2017117132A1
Application number: PCT/US2016/068716
Authority: WO
Inventors: Bhavananda Reddy NADIMPALLY; Jeanette Lee BEARDEN; Gang Shi; Aditya Janardan DESHPANDE; Sandeep Rammohan KOPPIKAR
Original assignee: Sunedison, Inc.
Priority date: 2015-12-31
Filing date: 2016-12-27
Publication date: 2017-07-06

Abstract

A method for producing a photovoltaic (PV) laminate is provided. The method includes positioning a first PV cell string on a first side encapsulant layer, disposing a first segment of a second side encapsulant layer on the first PV cell string, and positioning a second PV cell string adjacent to the first PV cell string. The first segment has a width greater than the first PV cell string and an overhang portion of the first segment extends beyond an edge of the first PV cell string. The overhang portion of the first segment is disposed between the first PV cell string and the second PV cell string.

Description

SYSTEMS AND METHODS FOR REDUCING INACTIVE SPACE IN PHOTOVOLTAIC MODULES

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Indian provisional patent application no. 4354/DEL/2015 , filed 31 December 2015, which is hereby incorporated by reference in its entirety.

FIELD

[0002] This disclosure relates generally to photovoltaic (PV) modules and, more specifically, reducing inactive space between strings of PV cells in photovoltaic modules .

BACKGROUND

[0003] Photovoltaic (PV) modules are typically formed as a laminate of several layers including strings of series -connected PV cells disposed in an encapsulant. To assemble the laminate, at least some known systems position several strings of PV cells on top of a sheet of

encapsulant on top of a front glass layer. A second sheet of encapsulant is placed on top of the strings of PV cells. A rear glass layer (or back sheet) is positioned on top of the second sheet of encapsulant. Heat and pressure are applied to the PV modules to melt the encapsulant layers and seal the PV cells between the encapsulant layers in the laminate .

[0004] Typical lay-up methods (i.e., the positioning or stacking of layers during lamination) for crystalline silicon PV modules may involve considerable tolerances for spacing of the strings of PV cells to prevent failure due to electrical shorting of PV cells inside the PV modules post - lamination . Such electrical shorting may be due to the PV cell strings shifting within the PV module when the encapsulant flows during the lamination process. The shifting of PV cells, along with other factors, account for losses commonly referred to as Cell To Module (CTM) losses. To reduce production failures due to CTM losses, some lay-up methods and systems add space between each string of PV cells to prevent the PV cells from shorting. However, the space between adjacent strings generally does not produce electrical energy and is referred to as "inactive space" . Some known PV modules may include 3.0 mm or more of inactive space between PV cell strings. Some PV modules include a white backsheet to reflect light from within the inactive space to the PV cells. Adding inactive space may increase the overall size of the PV module, reduce the number of PV cells included in the PV module, and/or reduce the efficiency of the PV module .

[0005] In addition, the inactive space between strings produces a visual separation between the strings of PV cells. Visually homogenous PV modules may be preferred for residential applications. In some systems, homogenous PV modules are achieved with a penalty to the CTM losses and module efficiency by using a black backsheet (or a backsheet with a color similar to the PV cells) .

[0006] This Background section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate better understanding of the various aspects of the present disclosure.

Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art .

BRIEF DESCRIPTION

[0007] In one aspect, a method for producing a photovoltaic (PV) laminate includes positioning a first PV cell string on a first side encapsulant layer, disposing a first segment of a second side encapsulant layer on the first PV cell string, and positioning a second PV cell string adjacent to the first PV cell string. The first segment has a width greater than the first PV cell string and an overhang portion of the first segment extends beyond an edge of the first PV cell string. The overhang portion of the first segment is disposed between the first PV cell string and the second PV cell string.

[0008] In another aspect, lay-up for a PV laminate includes a first side encapsulant layer, a plurality of PV cell strings disposed on the first side encapsulant layer, and a second side encapsulant layer including a plurality of segments. The first side

encapsulant layer has a width greater than a combined width of the plurality of PV cell strings. Each segment is disposed on one PV cell string and has an overhang portion extending beyond an edge of the PV cell string. The overhang portion of the segment is disposed between the PV cell string and an adjacent PV cell string.

[0009] In yet another aspect, a PV module includes a laminate and a frame circumscribing the laminate. The laminate includes a first side encapsulant layer, a second side encapsulant layer, and a plurality of PV cell strings disposed between the first side encapsulant layer and the second side encapsulant layer. Each PV cell string is separated from an adjacent PV cell string by less than one millimeter.

[0010] Various refinements exist of the features noted in relation to the above-mentioned aspects. Further features may also be incorporated in the above- mentioned aspects as well. These refinements and

additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments may be incorporated into any of the above -described aspects, alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Fig. 1 is a perspective view of an example photovoltaic (PV) module.

[0012] Fig. 2 is a cross -sectional view of the PV module shown in Fig. 1.

[0013] Fig. 3 is a perspective view of a stage of a lay-up of a PV module using an example layup method.

[0014] Fig. 4 is a perspective view of another stage of the lay-up of the PV module shown in Fig. 3.

[0015] Fig. 5 is a perspective view of another stage of the lay-up of the PV module shown in Fig. 3.

[0016] Fig. 6 is a side view of a lay-up of a PV module using another layup method. [0017] Fig. 7 is an IV graph of a PV module produces using the lay-up shown in Fig. 3 and a PV module produced using the lay-up shown in Fig. 6.

[0018] Corresponding reference characters indicate corresponding parts throughout the several views of the drawings .

DETAILED DESCRIPTION

[0019] Referring initially to Figs. 1 and 2, an example embodiment of a PV module is indicated generally at 100. A perspective view of the PV module 100 is shown in Fig. 1. Fig. 2 is a cross-sectional view of the PV module 100 taken at line A-A as shown in Fig. 1. PV module 100 includes a laminate 102 and a frame 104 circumscribing the laminate 102.

[0020] The laminate 102 includes a top surface 106 (also referred to as a sun receiving side) and a bottom surface 108 (shown in Fig. 2) . Edges 110 extend between the top surface 106 and the bottom surface 108. In this embodiment, the laminate 102 is rectangular shaped. In other embodiments, the laminate 102 may have any suitable shape. The laminate 102 has a width Vl_± and a length Li .

[0021] As shown in Fig. 2, the laminate 102 has a laminate structure that includes several layers 118. The layers 118 may include, for example, glass layers, encapsulant, non-reflective layers, electrical connection layers, n-type silicon layers, p-type silicon layers, and/or backing layers. One or more of the layers 118 may also include strings of PV cells (not shown in Figs. 1 and 2) . In the example embodiment, the laminate 102 includes (from top surface 106 to bottom surface 108) a glass layer, a front side encapsulant layer, a layer of PV cell strings (which also includes encapsulant) , a back side encapsulant layer, and a backsheet or glass layer. In other

embodiments, the laminate 102 may have more or fewer, including one, layers 118, may have different layers 118, and/or may have different types of layers 118.

[0022] Each string of PV cells within laminate 102 includes multiple PV cells connected in series. The strings of PV cells within laminate 102 are electrically connected to each other in series, parallel, or a

combination of series and parallel connections to produce a desired output voltage and current. In embodiments with multiple PV cell strings, the PV cell strings are typically coupled to each other within a junction box.

Alternatively, the PV cell strings may be coupled together within the laminate 102.

[0023] As shown in Fig. 2, the frame 104 circumscribes laminate 102. The frame 104 is coupled to the laminate 102, as best shown in Fig. 1. The frame 104 assists in protecting the edges 110 of the laminate 102 and provides additional rigidity to the PV module 100. In this embodiment, the frame 104 is constructed of four frame members 120. In other embodiments the frame 104 may include more or fewer frame members 120. The example frame 104 includes an outer surface 130 spaced apart from the laminate 102 and an inner surface 132 adjacent the laminate 102. The outer surface 130 is spaced apart from and substantially parallel to the inner surface 132. In the example embodiment, the frame 104 is made of aluminum.

More particularly, in some embodiments the frame 104 is made of 6000 series anodized aluminum. In other embodiments, the frame 104 may be made of any other suitable material providing sufficient rigidity including, for example, rolled or stamped stainless steel, plastic, or carbon fiber.

[0024] Figs. 3-5 illustrate a lay-up method of producing a PV module, such as the PV module 100 shown in Fig. 1. A first encapsulant is disposed on a protective layer. PV cell strings and strips of another encapsulant layer are positioned on the first encapsulant layer and a second protective layer is placed on the PV cell strings and the second encapsulant layer to form a lay-up for the PV module .

[0025] Fig. 3 is a perspective view of a first stage of the lay-up method for producing a lay-up 300 of a crystalline silicon (c-SI) PV module. Lay-up 300 is used to produce a laminate similar to the laminate 102 used in the PV module 100, shown in Fig. 1. In some embodiments, lay-up 300 may be used in different types of PV modules, such as non-silicon PV modules. Lay-up 300 includes a front side glass layer 310 and a front side encapsulant layer 320 positioned on the glass layer 310. Lay-up 300 may include additional, fewer, or alternative components, including those described elsewhere herein. Although the method is described herein as proceeding from a front side to a rear side, the method may also be applied to produce a layup from a rear side to a front side. Other embodiments include any other type of PV module.

[0026] Glass layer 310 is configured to permit light to pass through while preventing contaminants (e.g., dust, dirt, water) from affecting PV cells within the PV module. Glass layer 310 may be formed from a different protective material other than glass to provide similar functions, such as a plastic material.

[0027] The front side encapsulant layer 320 is configured substantially to seal and protect PV cells within the PV module. The front side encapsulant layer 320 has a relatively high light transmission to enable light to pass through to the PV cell stings (not shown in Fig. 3) . For example, the front side encapsulant layer 320 may include, but is not limited to, ethyl vinyl acetate (EVA), ionomer-based encapsulants , silicones, polyolefins, polyvinyl butyral (PVB) , thermoplastic polyurethane (TPU) , and ethylene propylene diene monomer (EPDM) .

[0028] The glass layer 310 and the front side encapsulant layer 320 have substantially similar widths W₂ and lengths L₂. The widths W_lf W₂ and lengths L_lf L₂ of the laminate 102 (shown in Fig. 1) and the glass layer 310 may be substantially similar. In other embodiments, the glass layer 310 and the front side encapsulant layer 320 may have different widths and/or lengths. For example, the front side encapsulant layer 320 may have a smaller width and/or length than the glass layer 310 to enable the encapsulant to flow outwards to the perimeter of the glass layer 310 when heated. In some embodiments, the width W of the laminate 102 (shown in Fig. 1) is approximately the same as L₂ of the glass layer 310, and the length of L₂ of the laminate 102 is approximately the same as the width W₂ of the glass layer 310.

[0029] Strings of PV cells 410 are positioned on the front side encapsulant layer 320 as shown in Fig. 4. The PV cell strings 410 are positioned one at a time. The PV cell strings 410 have a length substantially similar to the length L₂ of the glass layer 310 and the front side encapsulant layer 320. Alternatively, the PV cells strings 410 may have a length substantially similar to the width W₂ of the glass layer 310 and the front side encapsulant layer 320. In such an embodiment, the PV cell strings 410 may be positioned in a different orientation with respect to the orientation shown in Fig. 4 (e.g., rotated ninety degrees) . The PV cell strings 410 are series connected PV cells (not individually shown) that produce electrical energy from light (e.g., solar) energy. Alternatively, the PV cell strings 410 may include PV cells connected in a different configuration, such as in parallel.

[0030] PV cell strings 410 are oriented such that a light-collecting surface (not shown) faces the glass layer 310 to collect solar energy. Although not shown, the PV cell strings 410 may include electrodes, busbars, electrical connectors, reflective material, and other components to facilitate collecting solar energy and producing electrical energy. In the example embodiment, the PV cell strings 410 are electrically coupled to each other .

[0031] Segments 420 of rear side encapsulant are positioned on PV cell strings 410 to seal and protect the PV cells strings 410 and to separate each PV cell string 410 from an adjacent PV cell string 410. The segments 420 may be cut or separated from a sheet or layer similar to the front side encapsulant layer 320.

Alternatively, the segments 420 may be formed separately or in a different configuration. The segments 420 are made from the same material as the front side encapsulant layer 320. In other embodiments, the segments 420 are made from a different material. For example, the segments 420 may be reflective to reflect light to PV cell strings 410.

[0032] To form lay-up 300, a first PV cell string 412 is positioned on the front side encapsulant layer 320. A first segment or strip 422 of the rear side encapsulant is disposed on top of the first PV cell string 412. The first segment 422 of the rear side encapsulant has a width of greater than a width of the first PV cell string 412 but less than the width of two PV cell strings 410 combined. A portion 424 (also referred to as an

"overhang portion") of the first segment 422 overhangs or extends beyond one or more edges of the first PV cell string 412. In other embodiments, the segments 420 may have a width greater than a plurality of the PV cell strings 410 such that each segment 420 covers multiple PV cell strings 410. In some embodiments, the segments 420 may have a width less than the width of a PV cell string 410, but positioned to overhang an edge of the PV cell string 410 similar to as described below. Subsequent PV cell strings 410 are installed in a similar manner with one segment 420 disposed on each PV cell string 410. Each PV cell string 410 is installed substantially adjacent to a previously installed PV cell string 410.

[0033] Each overhanging portion 424 includes a gap segment 426 and an overlap segment 428. Alternatively, the overhanging portions 424 may not include the overlap segment 428. The gap segment 426 is positioned between two adjacent PV cell strings 410 and extends substantially to the front side encapsulant layer 320. The PV cells strings 410 are positioned approximate to each other such that the gap segment 426 generally fills and defines a gap 430 of inactive space between the PV cell strings 410. The width of the gap 430 may be further determined by several factors including, but not limited to, the thickness of the encapsulant, material, and lamination parameters. In the example embodiment, the gap 430 is approximately 0.5 mm wide. In other embodiments, the gap 430 may have a different width, such as 1.0 mm. The overlap segment 428 partially overlaps an adjacent PV cell string 410 to isolate the PV cell strings 410 from each other across the gap 430. The overlap segment 428 is coupled between an adjacent PV cell string 410 and the front side encapsulant layer. The installation process is repeated until each PV cell string 410 is installed. In some embodiment, the segments 420 are sized to include a rear overhanging portion (not shown in Fig. 4) opposite the overhanging portion 424. While the overhanging portion 424 is

positioned between or between and under a front surface of a PV cell string adjacent to the PV cell string 410 on which the segment is disposed, the rear overhanging portion overhangs the rear side of the other PV cell string 410 adjacent to the PV cell string 410 on which the segment is disposed .

[0034] Fig. 5 is a perspective view the lay-up 300 shown in Figs. 3 and 4 at a later stage of the method. The PV cell strings 410 are electrically coupled in a desired configuration followed by the placement of a protective material 510, such as a backsheet or glass on the PV cell strings 410 and the segments 420 of the rear side encapsulant. [0035] The protective material 510 is

configured to protect the encapsulant and the PV cell strings 410 from contaminants such as water. In the example embodiment, the protective material 510 is

configured to permit heat to pass through from the PV cell strings 410 to the outside of the PV module. The protective material 510 may include, for example, glass or a polymer sheet .

[0036] In the example embodiment, the lay-up 300 is subjected to heat and pressure to cause the

encapsulant to melt and flow to fill gaps and for a laminate. Disposing the overhanging portions 424 within the gaps 430 facilitates reduced space between adjacent PV cell strings 410 while maintaining electrical isolation across the gaps 430. Once the encapsulant solidifies, the resulting laminate is used to form into a PV module (e.g., the PV module 100, shown in Fig. 1) .

[0037] In some embodiments, rather than reducing the gap 430 between the PV cell strings, the segments 420 of the rear side encapsulant may be used in overlapping or "shingled" PV cell strings to eliminate the gap 430 completely. Fig. 6 is a side view of a portion of another lay-up 600 with shingled PV cell strings 610. The lay-up 600 is produced by the same method as lay-up 300, but the PV cell strings 610 are deliberately overlapped. In the example embodiment, PV cell strings 610 are

overlapped by approximately 4.0 mm. In other embodiments, PV cell strings 610 are overlapped by a different amount, such as 1.0 mm. The lay-up 600 further includes a glass layer 620, a front side encapsulant layer 630, and a plurality of rear side encapsulant segments 640. Each segment 640 is disposed on one of the PV cell strings 610 and includes an overhanging portion 642 that extends between the PV cell string 610 and an adjacent PV cell string 610. The overhanging portion 642 enables the PV cell strings 610 to be overlapped while maintaining electrical isolation between adjacent PV cell strings 610.

[0038] Fig. 7 is an IV graph 700 of an example experiment that was conducted to compare PV modules made using the lay-up 300 (shown in Figs. 3-5) and the lay-up 600 (shown in Fig. 6) . In the example embodiment, Module A was constructed with the lay-up 300 and Module B was constructed with the lay-up 600. Short circuit current, open circuit voltage, fill factor, and maximum power output measurements from the experiment are shown in Table 1 below. As seen in Fig. 7 and Table 1, shading caused by the overlapping PV cell strings 610 reduced the efficiency of Module B. However, overlapping the PV cell strings in Module B with the lay-up 600 may facilitate a reduced footprint of the PV cell strings and/or reduced costs to build Module B.

Table 1

[0039] Example embodiments disclosed herein include disposing a strip or segment of encapsulant on each string of PV cells of a PV module during lay-up. Each segment of encapsulant has a width greater than the PV cell string such that the segment of encapsulant extends over an edge of the PV cell string. The PV cell strings are positioned substantially adjacent to each other such that the segments of encapsulant substantially fill a gap between adjacent PV cell strings. The segments of

encapsulant act as a dielectric to prevent the adjacent PV cell strings from electrically shorting while reducing inactive space between adjacent PV cell strings.

[0040] A PV module with this lay-up method may offer the following advantages: (i) depending on module size, usage and thereby the weight of the PV module, amount of materials used in a PV module (e.g., glass, encapsulant, backsheet, etc.) may be reduced by more than 1%; (ii) depending on unit cost of materials, cost of the Bill Of Materials (BOM) may be reduced by about 1%; (iii) by using similar cells, module efficiency may be improved by more than 1%; and (iv) visually appealing surfaces with reduced space between PV cell strings. In addition, the described lay-up method may reduce the dependency on backsheets to limit losses associated with gaps between PV cell strings.

[0041] The described systems and methods facilitate reducing inactive space of PV modules while preventing PV cell strings from shorting. Reducing inactive space enables the PV modules to be designed using a reduce amount of material (i.e., increasing the cost savings of each PV module) . External connections using junction boxes and framing of the module are not affected by this method of lay-up. Other variations of this lay-up procedure include interleaving front and rear encapsulant layers and weaving a continuous encapsulant between strings to derive similar benefits.

[0042] In such embodiments, an encapsulant layer is interwoven between the PV cell strings such that the encapsulant layer alternates between coupling to the front side and rear side of the adjacent PV cell strings. The encapsulant layer substantially fills the gaps (e.g., gap 430, shown in Fig. 4) between the PV cell strings.

Sheets, segments, or strips of encapsulant are disposed on the PV cell strings to cover at least portions of the PV cell strings that are not covered by the interwoven encapsulant layer.

[0043] When introducing elements of the present invention or the embodiment (s ) thereof, the articles "a", "an", "the" and "said" are intended to mean that there are one or more of the elements. The terms "comprising", "including" and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0044] Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could

permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as "about,"

"approximately," and "substantially," is not to be limited to the precise value specified. In at least some

instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range

limitations may be combined and/or interchanged; such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise . [0045] As various changes could be made in the above without departing from the scope of the invention, it is intended that all matter contained in the above

description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

WHAT IS CLAIMED IS:

1. A method for producing a photovoltaic (PV) laminate, the method comprising:

positioning a first PV cell string on a first side encapsulant layer;

disposing a first segment of a second side encapsulant layer on the first PV cell string, the first segment having a width greater than the first PV cell string, wherein an overhang portion of the first segment extends beyond an edge of the first PV cell string; and positioning a second PV cell string adjacent to the first PV cell string, wherein the overhang portion of the first segment is disposed between the first PV cell string and the second PV cell string.

2. The method of claim 1, wherein the width of the first segment of the second side encapsulant layer is less than a width of the first and second PV cell string combined .

3. The method of claim 1, further comprising positioning the first side encapsulant layer on a

protective layer.

4. The method of claim 3, wherein the first side encapsulant layer is a front side encapsulant layer and the protective layer is a glass layer.

5. The method of claim 3, wherein the first side encapsulant layer is a rear side encapsulant layer and the protective layer is a backsheet .

6. The method of claim 1, further comprising sequentially positioning a plurality of additional PV cell strings and at least one additional segments of the second side encapsulant layer along the front encapsulant layer, wherein each additional segment of the second side

encapsulant layer is disposed on one additional PV cell string and between a pair of adjacent additional PV cell strings .

7. The method of claim 6 further comprising: electrically coupling the PV cell strings together; and

applying heat and pressure to form the first side encapsulant layer, the PV cell strings, and the segments of the second side encapsulant layer into a laminate.

8. The method of claim 1, wherein positioning a second PV cell string adjacent to the first PV cell string further comprises overlapping a portion of the first PV cell with the second PV cell.

9. The method of claim 1, wherein the first segment of the second side encapsulant layer has a

dielectric strength sufficient to prevent electrical shorting between the first PV cell string and the second PV cell string.

10. The method of claim 1, wherein positioning the second PV cell string further comprises positioning a portion of the overhang portion of the first segment of the second side encapsulant layer between the second PV cell string and the first side encapsulant layer.

11. A lay-up for a photovoltaic (PV) laminate comprising :

a first side encapsulant layer;

a plurality of PV cell strings disposed on the first side encapsulant layer, the first side encapsulant layer having a width greater than a combined width of the plurality of PV cell strings; and

a second side encapsulant layer including a plurality of segments, each segment of the plurality of segments disposed on one PV cell string of the plurality of PV cell strings and having an overhang portion extending beyond an edge of the PV cell string, wherein the overhang portion of the segment is disposed between the PV cell string and an adjacent PV cell string.

12. The lay-up of claim 10, wherein each segment of the plurality of segments has a width greater than a width of the PV cell string on which it is disposed.

13. The lay-up of Claim 11 further comprising a first protective layer and a second protective layer, wherein the first side encapsulant layer is positioned on the first protective layer and the second protective layer is positioned on the plurality of segments of the second side encapsulant layer.

14. The lay-up of Claim 13, wherein the first protective layer is a glass layer.

15. The lay-up of Claim 13, wherein the second protective layer is a backsheet .

16. The lay-up of Claim 11, wherein the second side encapsulant layer has a dielectric strength sufficient to prevent electrical shorting between adjacent PV cell strings of the plurality of PV cell strings.

17. The lay-up of Claim 11, wherein the first side encapsulant layer is a rear side encapsulant layer and the second side encapsulant layer is a front side

encapsulant layer.

18. The lay-up of Claim 11, wherein the overhang portion of each of the plurality of segments includes an overlap segment positioned between the first side

encapsulant layer and the adjacent PV cell string.

19. A photovoltaic (PV) module, the PV module comprising :

a laminate comprising:

a first side encapsulant layer;

a second side encapsulant layer;

a plurality of PV cell strings disposed between the first side encapsulant layer and the second side encapsulant layer, wherein each PV cell string is separated from an adjacent PV cell string by less than one millimeter; and

a frame circumscribing the laminate.

20. The PV module of claim 19, wherein each PV cell string is separated from an adjacent PV cell string by about one half of one millimeter.