U.S. patent application number 12/986283 was filed with the patent office on 2011-05-05 for bypass diode for photovoltaic cells.
This patent application is currently assigned to SOLAR SYSTEMS PTY LTD.. Invention is credited to John Beavis Lasich.
Application Number | 20110100427 12/986283 |
Document ID | / |
Family ID | 33452436 |
Filed Date | 2011-05-05 |
United States Patent
Application |
20110100427 |
Kind Code |
A1 |
Lasich; John Beavis |
May 5, 2011 |
BYPASS DIODE FOR PHOTOVOLTAIC CELLS
Abstract
A photovoltaic power module, comprising a substrate provided
with a circuit, one or more photovoltaic cells mounted to the
substrate and electrically connected to the circuit, and one or
more bypass diodes, each corresponding to a respective one or more
of the cells, wherein each of the diodes is located between the
substrate and the cells and between conducting portions of the
circuit.
Inventors: |
Lasich; John Beavis;
(Deepdene, AU) |
Assignee: |
SOLAR SYSTEMS PTY LTD.
Lucas Heights
AU
|
Family ID: |
33452436 |
Appl. No.: |
12/986283 |
Filed: |
January 7, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10557456 |
Nov 13, 2006 |
7888592 |
|
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PCT/AU2004/000667 |
May 19, 2004 |
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12986283 |
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60471342 |
May 19, 2003 |
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Current U.S.
Class: |
136/246 ;
257/E31.111; 438/98 |
Current CPC
Class: |
Y02E 10/50 20130101;
H01L 31/044 20141201; H01L 31/042 20130101; H01L 31/0504
20130101 |
Class at
Publication: |
136/246 ; 438/98;
257/E31.111 |
International
Class: |
H01L 31/05 20060101
H01L031/05; H01L 31/18 20060101 H01L031/18 |
Claims
1. A photovoltaic power module, comprising: a substrate thermally
couplable to a heat sink; one or more photovoltaic cells mounted to
said substrate; metallised zones constituting a circuit and
provided between said substrate and said cells, said metallised
zones being electrically and thermally coupled to said cells; and
one or more bypass diodes each corresponding to a respective one or
more of said cells; wherein each of said diodes is located between
said substrate and said cells and at least in part between
conducting portions of said metallised zones to permit reduced
separation between said cells and said metallised zones and wherein
said metallised zones underlie a substantial portion of each of
said cells, to facilitate heat flow from said cells to said
substrate.
2. A photovoltaic power module as claimed in claim 1, wherein said
circuit takes the form of a printed or laminated circuit and each
of said diodes is located between neighbouring metallised zones of
said circuit.
3. A photovoltaic power module as claimed in claim 2, wherein each
of said diodes has a thickness that is substantially equal to or
less than the thickness of said metallised zones.
4. A photovoltaic power module as claimed in claim 2, wherein the
substrate includes one or more recesses for at least partially
accommodating the diodes.
5. A photovoltaic power module as claimed in claim 1, wherein the
conducting portions of the circuit are contoured to fit or
accommodate said diodes.
6. A photovoltaic power module as claimed in claim 5, wherein each
of said diodes has metallised terminals that complement the shape
of said conducting portions.
7. A photovoltaic power module as claimed in claim 1, wherein said
diodes do not protrude towards said cells beyond said metallised
zones.
8. A photovoltaic power module as claimed in claim 1, wherein each
of said diodes are thermally coupled to said metallised zones via
at least two cooling paths.
9. A solar concentrator including a photovoltaic power module as
claimed in claim 1.
10. A method of bypassing one or more photovoltaic cells in a
photovoltaic power module, comprising: locating one or more bypass
diodes, each corresponding to a respective one or more of said
cells, between said cells and the substrate of said module, and at
least in part between conducting portions of metallised zones
constituting a circuit provided on said substrate between said
substrate and said cells; electrically and thermally coupling said
metallised zones to said cells such that said metallised zones
underlie a substantial portion of each of said cells in order to
facilitate heat flow from said cells to said substrate; and
electrically coupling said bypass diodes to said metallised zones
with said bypass diodes arranged to bypass a corresponding one or
more cells if a voltage across said corresponding one or more cells
drops below a predetermined level or is reversed.
11. A method as claimed in claim 10, wherein the circuit is a
printed or laminated circuit.
12. A method as claimed in claim 10, including locating each of
said diodes between neighbouring metallised zones of said
circuit.
13. A method as claimed in claim 10, including providing each of
said diodes with a thickness that is substantially equal to or less
than the thickness of said metallised zones.
14. A method as claimed in claim 10, including providing said
substrate with one or more recesses for at least partially
accommodating said diodes.
15. A method as claimed in claim 10, including contouring portions
of the circuit to fit or accommodate said diodes.
16. A method as claimed in claim 10, wherein each of said diodes
has metallised terminals that complement the shape of said
conducting portions.
Description
RELATED APPLICATION
[0001] This application is a Continuation of U.S. Ser. No.
10/557,456, filed 13 Nov. 2006, which is a National Stage of
PCT/AU2004/000667, filed 19 May 2004 which claims benefit of U.S.
provisional application Ser. No. 60/471,342, filed 19 May 2003, and
which application(s) are incorporated herein by reference. To the
extent appropriate, a claim of priority is made to each of the
above disclosed applications.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a bypass diode for a
photovoltaic cell, of particular but by no means exclusive
application in photovoltaic cell modules for use in solar
concentrators of solar photovoltaic power systems.
[0003] Multijunction solar cells are used in solar concentrator
photovoltaic power systems for generating power owing to their high
efficiency. Although such solar cells are expensive, these
efficiencies are sufficiently high to render such arrangements
economically feasible. However, to maintain the reliability of such
arrangements in which multiple cells are arranged in series, it is
desirable to have a bypass diode for each cell in a series. The
bypass diode prevents overloading of its corresponding cell when
that cell has a reduced power output owing to poor illumination or
performance, or some other malfunction. This allows the rest of the
series of cells constituting a module to continue operating.
[0004] The number of cells in series, which determines the bus
voltage, is usually greater than a hundred, so the bypassing of a
single, failed cell will result in a power loss of 1% or less. The
bypass diodes thus allow the system to keep operating with minimal
loss of output.
[0005] One existing system is illustrated in U.S. Pat. No.
6,020,555, in which each cell is connected in parallel with its
corresponding bypass diode resulting in a series of diodes in
parallel with a series of cells.
[0006] However, in existing arrangements, where the bypass diodes
are essentially adjacent to the cells, are unsuitable for systems
with closely packed cells, such as dish concentrator or central
receiver systems.
SUMMARY OF THE INVENTION
[0007] The present invention provides in a first aspect a
photovoltaic power module, comprising a substrate thermally
couplable to a heat sink, one or more photovoltaic cells mounted to
the substrate, metallised zones constituting a circuit and provided
between the substrate and the cells, the metallised zones being
electrically and thermally coupled to the cells, and one or more
bypass diodes each corresponding to a respective one or more of the
cells. Each of the diodes is located between the substrate and the
cells and at least in part between conducting portions of the
metallised zones to permit reduced separation between the cells and
the metallised zones, and the metallised zones underlie a
substantial portion of each of the cells, to facilitate heat flow
from said cells to said substrate.
[0008] Preferably the circuit takes the form of a printed or
laminated circuit and each of the diodes is located between
neighbouring metallised zones of the circuit. Preferably each of
the diodes has a thickness that is substantially equal to or less
than the thickness of the metallised zones. Thus, because the
diodes are located (along with the circuit) between the substrate
and the cells, the diodes do not prevent the solar cells from being
packed as closely as previously.
[0009] Alternatively, however, if it is not possible to obtain or
employ diodes that are sufficiently thin to be accommodated by one
of the metallised zones (which may have a thickness of only 0.3 mm)
the substrate may include one or more recesses for at least
partially (though conceivably wholly) accommodating the diodes
(preferably one diode per recess). Thus, in this embodiment the
diodes are also between the substrate and the cells (their still
being substrate material on the side of the diodes opposite the
cells), but the diodes are also at least to some extent surrounded
by substrate material.
[0010] Preferably the conducting portions of the circuit (in one
embodiment the metallised zones) are contoured to fit or
accommodate the diodes. Preferably the terminals of each of the
diodes are metallised to complement the shape of the conducting
portions.
[0011] The present invention provides in a further aspect a method
of bypassing one or more photovoltaic cells in a photovoltaic power
module, comprising locating one or more bypass diodes, each
corresponding to a respective one or more of the cells, between the
cells and the substrate of the module, and at least in part between
conducting portions of metallised zones constituting a circuit
provided on the substrate between the substrate and the cells,
electrically and thermally coupling the metallised zones to the
cells such that the metallised zones underlie a substantial
port-ion of each of the cells in order to facilitate heat flow from
the cells to the substrate, and electrically coupling the bypass
diodes to the metallised zones with the bypass diodes arranged to
bypass a corresponding one or more cells if a voltage across the
corresponding one or more cells drops below a predetermined level
or is reversed.
[0012] Preferably the circuit is a printed or laminated circuit.
Preferably each of the diodes is located between neighbouring
metallised zones of the circuit.
[0013] Preferably the method includes contouring portions of the
circuit (in one embodiment the metallised zones) to fit the diodes.
Preferably the terminals of each of the diodes are metallised to
complement the shape of the conducting portions.
[0014] In one embodiment, the method includes providing one or more
recesses in said substrate for at least partially (and in some
cases wholly) accommodating the diodes (preferably one diode per
recess). Thus, in this embodiment the diodes are located between
the cells and the substrate (their still being substrate material
on the side of the diodes opposite the cells), but the diodes are
also at least to some extent surrounded by substrate material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In order that the present invention may be more clearly
ascertained, embodiments will now be described by way of example,
with reference to the accompanying drawing, in which:
[0016] FIG. 1 is a cross-sectional view of a portion of a
photovoltaic module according to an embodiment of the present
invention;
[0017] FIG. 2 is a schematic plan view of a bypass diode and
adjacent metallised circuit of the module of FIG. 1;
[0018] FIG. 3 is a plan view comparable to FIG. 2 but more closely
to scale of the bypass diode and adjacent metallised circuit of the
module of FIG. 1; and
[0019] FIG. 4 is a cross-sectional view of a portion of a
photovoltaic module according to another embodiment of the present
invention.
DETAILED DESCRIPTION
[0020] A representative detail of a photovoltaic module according
to an embodiment of the present invention is shown in cross-section
at 10 in FIG. 1. The module includes an insulating substrate 12
with a thickness of 0.6 mm. The substrate 12 forms part of a
printed circuit comprising the substrate 12 and metallised zones
14. The metallised zones 14 have a thickness of approximately 0.3
mm.
[0021] Each of a plurality of photovoltaic cells 16 is soldered to
the metallised zones 14 by means of solder 18 (shown hashed in the
figure). For each solar cell 16, a bypass diode 20 with terminals
22a and 22b is provided between that cell 16 and the substrate 12.
Each cell 16 is connected in parallel across its respective bypass
diode 20.
[0022] The diode 20 is electrically coupled to the appropriate
portions of the metallised zones 14 of the circuit board by solder
18, so that it is in parallel with the corresponding cell 16.
[0023] In an alternative embodiment, the photovoltaic module
includes a plurality of groups of cells. Each group of cells is
then provided with a bypass diode 20, and the group of cells is
connected in parallel with its corresponding bypass diode 20.
[0024] Each bypass diode 20 has a thickness approximately equal to
or somewhat less than that of the metallised zones 14, hence also
approximately equal to or somewhat less than 0.3 mm. The bypass
diodes 20 thus do not increase the thickness of the module 10 and,
being beneath the cells 16, do not restrict how closely the cells
16 can be packed in the module 10.
[0025] It is envisaged that, during manufacture, the diodes 20
would be positioned on the solder paste printed substrate 12, after
which the solar photovoltaic cells 16 would be placed over the
diodes 20 onto the metallised zones 14. In this manner the diode is
integrated into the closely packed module 10 without requiring
additional diode space around the photovoltaic cells 16.
[0026] FIG. 2 is a plan view of cross-section AA from FIG. 1,
through the plane of the metallised zones 14 and the diode 20, with
the alignment of solar cell 16 (or, in an alternative embodiment,
cell 16 and adjacent cells 16' and 16'') shown by means of a dotted
lines. In this (plan) view, it will be apparent how the metallised
zones 14 are shaped to accommodate the diode 20 and, in particular,
terminals 22a and 22b of diode 20. Solder 18 establishes the
necessary electrical contact between the diode 20 and the
metallised zones 14 of the circuit board.
[0027] The device is shown schematically for the sake of clarity.
In reality, the diode 20 is smaller than it appears compared with
the metallised zones 14. Thus, the gap between the metallised zones
14 would typically be about 0.7 mm, widening to about 1.5 mm to
accommodate the diode 20. Thus, the area without metal for the
cells to be soldered to is small.
[0028] The width (from left to right in this view) of the
metallised zones 14 would typically be about 15 mm, while the width
(from top to bottom in this view) of cell 16 would typically be
about 10 mm. Neighbouring solar cells (16, 16', 16'') are thus very
close.
[0029] FIG. 3 is comparable to FIG. 2, but more closely to scale so
that a better idea of the relative sizes of the diode, cells and
metallised zones can be ascertained.
[0030] FIG. 4 is a cross-sectional view (comparable to that of FIG.
1) of a representative detail 30 of a photovoltaic module according
to an alternative embodiment. In this figure, like reference
numerals have been used to identify like features when compared
with the embodiment of FIG. 1.
[0031] As in the embodiment of FIG. 1, the diode module of this
embodiment includes an insulating substrate 32 with a thickness
generally of 0.6 mm. The substrate 32 forms part of a printed
circuit comprising the substrate 32 and metallised zones 14. The
metallised zones 14 have a thickness of approximately 0.3 mm.
However, bypass diode 34 (with terminals 36a and 36b) has a
thickness greater than that of diode 20 of FIG. 1 and hence greater
than that of metallised zones 14. Thus, a shallow recess 38 is
provided in substrate 32 in order to accommodate bypass diode 34 to
a depth sufficient to ensure that bypass diode 34 does not extend
upwardly beyond the metallised zones 14. The solder 18 extends
downwardly into the recess 38 to a sufficient extent to ensure good
electrical contact is made with terminals 36a and 36b.
[0032] This embodiment allows the use of diodes with a somewhat
greater thickness than in the embodiment shown in FIG. 1, which in
some applications may be desirable or necessary owing to diode
availability or cost.
[0033] Thus, the bypass diode arrangement of this invention allows
one to minimize the impedance of thermal transfer between the cell
and the substrate. Such impedance--particularly in high intensity
or high power applications--could otherwise seriously compromise
performance or even render the device impractical.
[0034] Modifications within the scope of the invention may be
readily effected by those skilled in the art. It is to be
understood, therefore, that this invention is not limited to the
particular embodiments described by way of example here and
above.
[0035] In the claims that follow and in the preceding description
of the invention, except where the context requires otherwise owing
to express language or necessary implication, the word "comprise"
or variations such as "comprises" or "comprising" is used in an
inclusive sense, i.e. to specify the presence of the stated
features but not to preclude the presence or addition of further
features in various embodiments of the invention.
[0036] Further, any reference herein to prior art is not intended
to imply that such prior art forms or formed a part of the common
general knowledge.
* * * * *