U.S. patent application number 13/909268 was filed with the patent office on 2014-02-06 for photovoltaic module and laminate.
The applicant listed for this patent is SunPower Corporation. Invention is credited to Gabriela E. BUNEA, David F. J. KAVULAK, Sung Dug KIM.
Application Number | 20140034111 13/909268 |
Document ID | / |
Family ID | 47389340 |
Filed Date | 2014-02-06 |
United States Patent
Application |
20140034111 |
Kind Code |
A1 |
BUNEA; Gabriela E. ; et
al. |
February 6, 2014 |
PHOTOVOLTAIC MODULE AND LAMINATE
Abstract
A photovoltaic module has a first side directed toward the sun
during normal operation and a second, lower side. The photovoltaic
module comprises a perimeter frame and a photovoltaic laminate at
least partially enclosed by and supported by the perimeter frame.
The photovoltaic laminate comprises a transparent cover layer
positioned toward the first side of the photovoltaic module, an
upper encapsulant layer beneath and adhering to the cover layer, a
plurality of photovoltaic solar cells beneath the upper encapsulant
layer, the photovoltaic solar cells electrically interconnected, a
lower encapsulant layer beneath the plurality of photovoltaic solar
cells, the upper and lower encapsulant layers enclosing the
plurality of photovoltaic solar cells, and a homogenous rear
environmental protection layer, the rear environmental protection
layer adhering to the lower encapsulant layer, the rear
environmental protection layer exposed to the ambient environment
on the second side of the photovoltaic module.
Inventors: |
BUNEA; Gabriela E.; (Santa
Clara, CA) ; KIM; Sung Dug; (Pleasanton, CA) ;
KAVULAK; David F. J.; (Fremont, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SunPower Corporation |
San Jose |
CA |
US |
|
|
Family ID: |
47389340 |
Appl. No.: |
13/909268 |
Filed: |
June 4, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13175578 |
Jul 1, 2011 |
|
|
|
13909268 |
|
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Current U.S.
Class: |
136/246 ;
136/251 |
Current CPC
Class: |
B32B 2307/402 20130101;
B32B 2307/414 20130101; Y10T 428/2495 20150115; B32B 2457/12
20130101; B32B 27/32 20130101; B32B 27/08 20130101; H01L 31/049
20141201; B32B 2262/101 20130101; B32B 27/12 20130101; Y02E 10/50
20130101; B32B 7/12 20130101; B32B 2307/31 20130101 |
Class at
Publication: |
136/246 ;
136/251 |
International
Class: |
H01L 31/048 20060101
H01L031/048; H01L 31/052 20060101 H01L031/052 |
Claims
1. A photovoltaic laminate comprising: a transparent cover layer
positioned toward a front side of a photovoltaic module, the front
side being directed towards the sun during normal operation; an
upper encapsulant layer under the transparent cover layer; a
plurality of photovoltaic solar cells under the upper encapsulant
layer; a lower encapsulant layer under the plurality of
photovoltaic solar cells, the upper and lower encapsulant layers
enclosing the plurality of photovoltaic solar cells; and a back
layer under the lower encapsulant layer, the back layer comprising
glass.
2. The photovoltaic laminate of claim 1, wherein the glass has a
white color.
3. The photovoltaic laminate of claim 2, wherein the glass also has
at least one other color.
4. The photovoltaic module of claim 1, wherein the lower
encapsulant layer has a volume resistivity of at least
5.times.10.sup.13 ohm-cm at 50 degrees Celsius.
5. The photovoltaic module of claim 1, wherein the lower
encapsulant layer has a white color.
6. The photovoltaic module of claim 1, wherein the lower
encapsulant layer is at least partially composed of a
polyethylene.
7. The photovoltaic module of claim 1, wherein the lower
encapsulant layer is at least partially composed of polyolefin.
8. The photovoltaic module of claim 1, wherein the plurality of
photovoltaic solar cells comprise back contact solar cells.
9. The photovoltaic module of claim 1, wherein the lower
encapsulant layer has a thickness of less than 650 micrometers.
10. The photovoltaic module of claim 1, wherein the cover layer
comprises an anti-reflective coating.
11. A photovoltaic laminate comprising: a plurality of photovoltaic
solar cells, each of the plurality of photovoltaic solar cells
having an upper side facing the sun during normal operation and a
lower side facing away from the sun; an encapsulant layer
surrounding and enclosing the plurality of photovoltaic solar
cells, the encapsulant layer extending between gaps in the
plurality of photovoltaic solar cells; a transparent cover layer
disposed above the upper side of the plurality of photovoltaic
solar cells and atop the encapsulant layer, the encapsulant layer
adhering to the cover layer; and a mono-stratum sealing layer below
the lower side of the plurality of photovoltaic solar cells and
beneath the encapsulant layer, the encapsulant layer adhering to
the mono-stratum sealing layer along an inner surface and having an
outer surface exposed to the ambient environment, the mono-stratum
sealing layer comprising glass.
12. The photovoltaic laminate of claim 11, wherein the glass has a
white color.
13. The photovoltaic laminate of claim 12, wherein the glass also
has a black color.
14. The photovoltaic laminate of claim 11, wherein the encapsulant
layer has a volume resistivity greater than 5.times.10.sup.13 at
50.degree. Celsius.
15. The photovoltaic laminate of claim 11, wherein the encapsulant
layer and sealing layer combine to permit less than 10
micro-amperes of electrical current to flow between the lower side
of the plurality of solar cells and the outer surface when the
electrical potential difference between the lower side of the
plurality of solar cells and the outer surface is at least 1,000
volts.
16. The photovoltaic laminate of claim 11, further comprising a
bonding layer between the sealing layer and the encapsulant
layer.
17. The photovoltaic laminate of claim 11, wherein the plurality of
photovoltaic solar cells comprises back contact solar cells.
18. A photovoltaic laminate comprising comprising: a transparent
top cover; a plurality of photovoltaic solar cells under the
transparent top cover; an encapsulant surrounding and encapsulating
the plurality of photovoltaic solar cells; and a sealing layer
under the encapsulant, the sealing layer comprising glass.
19. The photovoltaic laminate of claim 18, wherein the glass has a
white color.
20. The photovoltaic laminate of claim 19, wherein the glass also
has another color.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/175,578, filed on Jul. 1, 2011, which is
incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] Embodiments of the subject matter described herein relate
generally to photovoltaic modules and laminates. More particularly,
embodiments of the subject matter relate to construction of
laminates with high resistivity encapsulants.
BACKGROUND
[0003] Photovoltaic solar systems benefit from increased electrical
and conversion efficiency and reduced cost. Both effects
advantageously reduce the overall cost of energy produced by the
solar system. One way to reduce cost is to reduce the complexity of
the system. Another is to reduce the weight of the system.
[0004] Photovoltaic solar systems can be composed of a number of
individually-constructed photovoltaic modules. Each module can
contain and support a photovoltaic laminate. Reducing the weight or
complexity of either can improve the system. Photovoltaic modules
can be inspected to meet performance, reliability, safety, and
manufacturing specifications. Advantageously, the innovations which
improve the system cost or efficiency can permit the photovoltaic
module to continue to meet specifications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] A more complete understanding of the subject matter may be
derived by referring to the detailed description and claims when
considered in conjunction with the following figures, wherein like
reference numbers refer to similar elements throughout the
figures.
[0006] FIG. 1 is a perspective view of a photovoltaic module;
[0007] FIG. 2 is a cross-sectional view of the photovoltaic module
of FIG. 1;
[0008] FIG. 3 is a detailed view of the photovoltaic module of FIG.
2, illustrating a cross-section of an embodiment of a photovoltaic
laminate;
[0009] FIG. 4 is a detailed view of a cross-section of another
embodiment of a photovoltaic laminate; and
[0010] FIG. 5 is a detailed view of a cross-section of yet another
embodiment of a photovoltaic laminate.
DETAILED DESCRIPTION
[0011] The following detailed description is merely illustrative in
nature and is not intended to limit the embodiments of the subject
matter or the application and uses of such embodiments. As used
herein, the word "exemplary" means "serving as an example,
instance, or illustration." Any implementation described herein as
exemplary is not necessarily to be construed as preferred or
advantageous over other implementations. Furthermore, there is no
intention to be bound by any expressed or implied theory presented
in the preceding technical field, background, brief summary or the
following detailed description.
[0012] "Inhibit"--As used herein, inhibit is used to describe a
reducing or minimizing effect. When a component or feature is
described as inhibiting an action, motion, or condition it may
completely prevent the result or outcome or future state
completely. Additionally, "inhibit" can also refer to a reduction
or lessening of the outcome, performance, and/or effect which might
otherwise occur. Accordingly, when a component, element, or feature
is referred to as inhibiting a result or state, it need not
completely prevent or eliminate the result or state.
[0013] In addition, certain terminology may also be used in the
following description for the purpose of reference only, and thus
are not intended to be limiting. For example, terms such as
"upper", "lower", "above", and "below" refer to directions in the
drawings to which reference is made. Terms such as "front", "back",
"rear", "side", "outboard", and "inboard" describe the orientation
and/or location of portions of the component within a consistent
but arbitrary frame of reference which is made clear by reference
to the text and the associated drawings describing the component
under discussion. Such terminology may include the words
specifically mentioned above, derivatives thereof, and words of
similar import. Similarly, the terms "first", "second", and other
such numerical terms referring to structures do not imply a
sequence or order unless clearly indicated by the context.
[0014] Some ways to improve the cost of energy provided by a
photovoltaic solar system are to reduce the complexity of its
components, thereby reducing the cost of materials and
construction, to increase the performance of the system, thereby
increasing the power obtained for the same cost as the unimproved
system, and, to reduce the weight of the system, thereby reducing
its shipping cost. When possible, it is desirable to simultaneously
affect several of these factors.
[0015] A photovoltaic module is disclosed. The photovoltaic module
has a first side directed toward the sun during normal operation
and a second, lower side. The photovoltaic module comprises a
perimeter frame and a photovoltaic laminate at least partially
enclosed by and supported by the perimeter frame. The photovoltaic
laminate comprises a transparent cover layer positioned toward the
first side of the photovoltaic module, an upper encapsulant layer
beneath and adhering to the cover layer, a plurality of
photovoltaic solar cells beneath the upper encapsulant layer, the
photovoltaic solar cells electrically interconnected, a lower
encapsulant layer beneath the plurality of photovoltaic solar
cells, the upper and lower encapsulant layers enclosing the
plurality of photovoltaic solar cells, and a homogenous rear
environmental protection layer, the rear environmental protection
layer adhering to the lower encapsulant layer, the rear
environmental protection layer exposed to the ambient environment
on the second side of the photovoltaic module.
[0016] A photovoltaic laminate is also disclosed. The photovoltaic
laminate comprises a plurality of photovoltaic solar cells, each of
the solar cells having a upper side facing the sun during normal
operation and a lower side facing away from the sun, an encapsulant
layer surrounding and enclosing the solar cells, the encapsulant
layer extending between gaps in the solar cells, a transparent
cover layer disposed above the upper side of the plurality of solar
cells and atop the encapsulant layer, the encapsulant layer
adhering to the cover layer, and a mono-stratum sealing layer below
the lower side of the plurality of solar cells and beneath the
encapsulant layer, the encapsulant layer adhering to the sealing
layer along an inner surface and having an outer surface exposed to
the ambient environment.
[0017] A backsheet for a photovoltaic laminate is also disclosed.
The backsheet comprises a homogenous encapsulant layer and a
homogenous outer layer, wherein the encapsulant layer and outer
layer are jointly formed by co-extrusion, the encapsulant layer
adhering to the outer layer, the encapsulant layer has a volume
resistivity of at least 5.times.10.sup.13 ohm-cm, the outer layer
is resistive to fluids, the encapsulant layer has a thickness of at
least 400 micrometers, and the backsheet has an overall thickness
of less than 400 micrometers.
[0018] A photovoltaic laminate can be constructed using a very high
volume resistivity encapsulant surrounding the solar cells within
the laminate. Previously, such encapsulants encountered
difficulties with certain aspects of their composition, such as
undesirable yellowing or wearing during solar irradiation, lack of
or excessive stiffness, inability to be cheaply produced or
processed. Accordingly, encapsulants in use have been deployed in
combination with a thick backsheet behind the solar cells and
encapsulant. The backsheet exhibited certain qualities desirable
for the photovoltaic solar module, such as environmental
protection, mechanical stiffness, electrical insulation, and so on,
which were deficient in the encapsulant.
[0019] The inventors have discovered that a certain class of
materials used as encapsulants advantageously satisfy many of the
requirements of a photovoltaic solar module. A polyolefin, such as
polyethylene or polypropylene, can be used as an encapsulant for
solar cells. The volume resistivity of certain polyethylenes,
including a value above 5.times.10.sup.13 ohm-cm over a temperature
range of -40 to 90 C, has beneficial effects on both the front
surface of the solar cells, where polarization is inhibited, as
well as electrical insulating properties on the rear surface. The
associated increase in efficiency while still meeting performance
specifications enables a further improvement.
[0020] The inventors have further developed a photovoltaic module
and laminate construction which reduces material complexity and
manufacturing steps to reduce cost of construction. Instead of a
multi-layer backsheet bonded to the encapsulant, wherein the
backsheet includes an electrical insulator, multiple bonding
layers, an environmental layer, and, in some backsheets, a hybrid
encapsulant-adhesive layer, a photovoltaic module can be
constructed with a laminate containing a particular encapsulant and
mono-layer film on the underside of the laminate. Such an advanced
laminate can be constructed from an encapsulant-protective layer
co-extrusion, eliminating the need to bond the encapsulant to a
backsheet. The simplified protective layer, coupled with the easier
construction can greatly reduce manufacturing costs. The
compatibility of encapsulant and the mono-layer films can be also
improved by surface treatment techniques, including corona
treatment and plasma treatment.
[0021] FIG. 1 illustrates a photovoltaic module 100. The
photovoltaic module 100 can be constructed by surrounding a
photovoltaic laminate 110 by a frame 120 extending around the
perimeter 112 of the laminate 110. The laminate 110 can contain a
number of photovoltaic solar cells 116, which can be interconnected
together. Several photovoltaic modules 100 can be combined to
create a solar array or solar system for use in converting sunlight
to electrical energy.
[0022] The frame 120 can surround the laminate 110 on all sides, or
on several. The frame 120 can extend entirely along the edges of
the laminate 110 or only partially, such as with voids or notches,
if desired. The frame 120 can be constructed of a metal, such as
aluminum or stainless steel, a plastic, or any other selected
material. With reference to FIG. 2, where a cross-section of the
photovoltaic module 100 is shown, the frame 120 can include a notch
122 to receive and support the laminate 110.
[0023] The laminate 110 is a term for the component which includes
the photovoltaic solar cells 116 and the several layers of
enclosing and supporting materials. FIG. 3 illustrates a detailed
view of the embodiment of the laminate 110 shown in FIGS. 1 and 2.
As can be seen, the laminate 110 can be composed of several
materials. The illustrated embodiments are for descriptive purposes
only and are not to scale. The laminate 110 illustrated has a top
surface 130 which is disposed to face the sun during normal
operation. Similarly, the solar cells 116 within the laminate 110
can have upper and lower faces, wherein the upper face 117 is
directed toward the sun during normal operation and the lower face
118 is directed away.
[0024] The laminate 110 can have a transparent cover layer 136. The
cover layer 136 can be constructed of a clear, or translucent,
material, such as glass or a plastic. The cover layer 136 can be
treated with, formulated with, or have applied atop it an
anti-reflective material or coating to inhibit loss of photons at
the surface of, or through, the cover layer 136.
[0025] Beneath the cover layer 136 can be a front, top, or upper
encapsulant layer 140. In certain embodiments, a bonding or
adhesive layer 142 can be disposed between the cover layer 136 and
upper encapsulant layer 140. The adhesive layer 142 can be
uniformly distributed, or selectively deposited between the cover
and upper encapsulant layers 136, 140. The adhesive layer can be
any bonding, glue, affixation, or adhesion material.
[0026] The upper encapsulant layer 140 is so called because it is
positioned above the upper side 117 of the solar cell(s) 116. The
upper encapsulant layer 140 can, however, extend between gaps in
the solar cells 116 to contact and, in some constructions and
embodiments, merge with the lower encapsulant layer 150, which
extends beneath the solar cells 116. The upper and lower
encapsulant layers 140, 150 can entirely surround and contain the
solar cells 116, electrically insulating them from the cover layer
136 and the sealing layer 160. In some embodiments, a lower
adhesive layer 158, having characteristics similar to those
described with respect to the adhesive layer 142 can be present
between the lower encapsulant layer 150 and sealing layer 160. As
shown in the embodiment illustrated in FIG. 4, the adhesive layers
142, 158 can be omitted. In such embodiments, the encapsulant
layers 240, 250 can include any properties necessary to bond with
the surrounding components. Unless otherwise specified, numerical
indicators in FIG. 4 designate components similar to those of FIGS.
1-3, except that the number has been incremented by 100.
[0027] The encapsulant layers 140, 150 can be composed of identical
materials, allowing for a uniform enclosure of the solar cells 116.
In some embodiments, heating the encapsulant layers 140, 150 when
in physical proximity can cause melding or fusing to form a single
layer extending around and between the solar cells 116. In other
forms the encapsulant layers 140 and 150 may be composed of
dissimilar materials, and still completely enclosing the solar
cells 116.
[0028] The encapsulant layers 140, 150 can be formed of a
polyolefin material, such as polyethylene, or polypropylene.
Whether polyethylene, or propylene, or any other polyolefin, the
encapsulant used can have a Young's modulus less than 10 MPa at
room temperature or higher temperatures. In certain embodiments,
the encapsulant layers 140, 150 can have a volume resistivity of at
least 5.times.10.sup.13 ohm-cm at normal operating temperature.
Such a normal operating temperature can be between -40.degree. and
90.degree. C. Thus, the encapsulant material can have a volume
resistivity of at least 5.times.10.sup.13 ohm-cm at 60.degree., or
at 90.degree., or any other temperature value desired. The upper
encapsulant layer 140 can have a transparency sufficient to permit
passage of at least 60 percent of entering photons at each
wavelength of light between 300 to 1200 nm. The lower encapsulant
layer 150 can be transparent, colored, highly reflective, or can
have other optical or reflective properties as desired for the
embodiment. Certain embodiments can have a combination of colored
and highly reflective properties. In certain embodiments, the
encapsulant layers 140, 150 can have a mechanical stiffness
characterized by a Young's modulus of less than 10 MPa at room
temperature and higher temperatures. In some embodiments, the
encapsulant layers 140, 150 can have a thermal conductivity of at
least 0.2 W/(m-K). Thus, while polyethylene is described as an
exemplary material, any polyolefin or other material which has
these or similar properties can also serve as an encapsulant
material. One collection of materials which can be used as upper or
lower encapsulant layers is described in U.S. patent application
Ser. No. 12/818,959, filed on Jun. 18, 2010, the entirety of which
is expressly incorporated herein by reference.
[0029] The sealing layer 160 can be any single-layer, homogenous
film sufficient to provide environmental protection to the other
layers of the laminate 110. The sealing layer 160 can have a
moisture vapor transmission rate less than 40 g/m.sup.2 per 24
hours, a rate which is described herein as being resistive to
fluid, and can be constructed of any appropriate material. For
example, a flouropolymer, a polyvinylidene fluoride, a
polytetrafluoroethylene, polypropylene, polyphenylene sulfide,
polyester, polycarbonate, polyacrylate, polyamide, or polyphenylene
oxide can all be used in certain embodiments, including commercial
forms of the materials, such as TEFLON.TM. or TEDLAR.TM.. Any other
appropriate material for use as a single-stratum layer can also be
used. The sealing layer 160 can therefore serve as an environmental
protection layer. The homogenous, mono-stratum sealing layer 160
can be a film or single layer, as opposed to the multi-layered
backsheets of other photovoltaic modules. Therefore, the sealing
layer 160 can, in some embodiments, be the sole stratum between the
lower encapsulant layer 150 and the ambient environment beneath the
laminate 110. In some embodiments, the sealing layer 160 can be a
fiberglass layer or a thermally-conductive layer, such as a metal
layer or a polymer containing conductive fillers.
[0030] In certain embodiments, the sealing layer 160 can be
co-extruded with the lower encapsulant layer 150 for simplicity of
manufacture. Either the lower encapsulant layer 150 or the sealing
layer 160 can have a white or black color as desired for the
embodiment. Other colors can be chosen as desired for the
embodiment, including any color in the spectrum. The lower
encapsulant layer 150 can have a thickness of between 100 and 800
micrometers, as desired for the embodiment. Additionally, the
sealing layer 160 can have a thickness between 100 and 800
micrometers. Any combination can be used to form the overall
thickness of the pair as desired by the embodiment.
[0031] With reference again to FIGS. 1-3, the combination of lower
encapsulant layer 150 and sealing layer 160 can be used to prove
electrical insulation between the lower surface 118 of the solar
cells 116 and contact with a person touching the underside of the
sealing layer 160. Because certain embodiments of the photovoltaic
modules 100 comply with specifications requiring safe physical
contact with the underside of the module while the solar cells 116
are operating at an electrical potential of as much as 1,000 volts,
the encapsulant/sealing layer combination can insulate sufficiently
to permit less than 10 micro-amperes of current flowing under such
conditions. Alternatively, when the solar cells 116 are operating
at 1,500V the combination can electrically insulate sufficiently to
permit less than 25 micro-amperes of current. Similarly, the
combined structure of the lower encapsulant layer 150 and sealing
layer 160 can inhibit more than 50 micro-amperes of leakage current
from passing when a continuous voltage of 3000 volts is present in
lower surface 118 of the solar cells 116 for at least 1 minute.
[0032] In certain embodiments, the solar cells 116 can be back
contact and/or back-junction photovoltaic solar cells. FIG. 5
illustrates a detailed view of an alternative embodiment of a
photovoltaic laminate 310. Unless otherwise specified, numerical
indicators in FIG. 5 designate components similar to those of FIGS.
1-3, except that the number has been incremented by 200. FIG. 5
illustrates an exaggerated view of the lower surface 318 of the
solar cells 316 to emphasize the surface features 319 of a back
contact solar cell. As can be seen, the lower encapsulant layer 350
can be sufficiently thick to extend into any features of the solar
cell 316 to inhibit contact between the surface features 319 of the
solar cell 316 and the sealing layer 360. In those embodiments
wherein electrical current between the surface of the sealing layer
360 and the lower surface 318 of the solar cell 316 at a particular
operating electrical potential, such as 1,000 volts, is a desired
feature or requirement for the photovoltaic module, the lower
encapsulant layer 350 can be sufficiently thick to provide the
desired electrical insulation.
[0033] While at least one exemplary embodiment has been presented
in the foregoing detailed description, it should be appreciated
that a vast number of variations exist. It should also be
appreciated that the exemplary embodiment or embodiments described
herein are not intended to limit the scope, applicability, or
configuration of the claimed subject matter in any way. Rather, the
foregoing detailed description will provide those skilled in the
art with a convenient road map for implementing the described
embodiment or embodiments. It should be understood that various
changes can be made in the function and arrangement of elements
without departing from the scope defined by the claims, which
includes known equivalents and foreseeable equivalents at the time
of filing this patent application.
* * * * *