WO2010144637A1

WO2010144637A1 - Integrated solar photovoltaic ac module

Info

Publication number: WO2010144637A1
Application number: PCT/US2010/038057
Authority: WO
Inventors: William W. Alston; S. Elise Moss; Stephen P. Holmberg; Larry C. Holmberg
Original assignee: Solar Infra, Inc.
Priority date: 2009-06-10
Filing date: 2010-06-09
Publication date: 2010-12-16

Abstract

An integrated solar photovoltaic AC module and related methods are described in which the positional, mechanical, and thermal relationships among a micro-inverter, a solar panel body, and a mounting frame are optimized such that an advantageous combination of mechanical integrity, thermal stability, and durability is provided, while also keeping overall system costs down, keeping overall system weight low, and providing a clean visual look. In one preferred embodiment, the micro-inverter is mounted underneath the solar panel body on a plate member or flange member that extends between two or more side rails of a supporting frame of the solar panel body. An air gap is maintained between the micro-inverter and the solar panel body sufficient to inhibit thermal crosstalk therebetween. The plate or flange member is securably affixed to the two or more side rails of the frame in a manner that enhances lateral shear stability of the frame.

Description

INTEGRATED SOLAR PHOTOVOLTAIC AC MODULE

[0001] This application is being filed on 9 June 2010 as a PCT International Patent application in the name of Solar Infra, Inc., a US national corporation, applicant for the designation of all countries except the US, and William W. Alston, S. Elise Moss, Stephen P. Holmberg, and Larry C. Holmberg, all citizens of the United States, applicants for the designation of the US only.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. provisional patent application Ser. No. 61/185,994, filed 10 June 2009, entitled "Integrated Solar Photovoltaic AC Module," which is incorporated by reference herein.

FIELD

[0003] This patent specification relates to solar panel mounting systems. More particularly, this patent specification relates to methods and systems for mounting a panel-specific DC-to-AC power conversion device, such as a micro-inverter, for use in conjunction with its associated solar panel.

BACKGROUND

[0004] Solar electric power generation systems, particularly those based on photovoltaic solar panels, continue to gain popularity in efforts to shift away from supply-limited, greenhouse-gas producing fossil fuels to more environmentally friendly and sustainable forms of energy. As described in U.S. Pat. 5951785, which is incorporated by reference herein, technological advancements have been made in the area of DC to AC conversion devices, often called inverters, which electronically convert the DC power generated by the photovoltaic solar panels into usable household AC power. In particular, whereas it has been common historically to install a single, relatively bulky, higher-capacity inverter device to convert the aggregate DC power from the many solar panels of an installation into usable AC power, U.S. Pat. 5951785 discusses the physical pairing of each solar panel with its own smaller, lower-capacity, dedicated inverter device such that the need for the central, higher-capacity inverter device is avoided. Although commonly called micro-inverters, these smaller devices are often simply called "inverters" as their use becomes more widespread. [0005] The use of a plurality of micro-inverters paired with respective associated solar panels can be advantageous in several respects. By way of example, DC current losses are reduced. Additionally, system modularity and ease of electrical interconnection are enhanced. For this modularity to be especially useful it is also desirable that each solar panel and its associated inverter be constructed as a single physical unit, i.e., that each inverter be integrated with an associated solar panel to form an integrated solar AC module. Such integration of solar panel and inverter into a single integrated solar AC module is especially useful in the construction of solar arrays of arbitrary size, where additional panels may be added with ease at some time subsequent to initial construction. By way of loose analogy, assuming that the proper design accommodations have been made, the installation of an additional solar panel-inverter pair unit (integrated solar AC module) to a pre-existing solar power installation might one day be considered as easy as plugging in another USB (Universal Serial Bus) hard drive into a preexisting chain of USB peripherals in a computer system. [0006] One or more issues arises in the physical integration of micro-inverters with solar panels to form into integrated solar AC modules, one or more of which is at least partially addressed by one or more of the preferred embodiments described further hereinbelow. A first issue relates to thermal stability of the integrated solar AC module, since the DC-to-AC conversion operation of the micro- inverter inevitably produces heat that needs to be effectively dissipated. In addition to the necessary avoidance catastrophic thermal runaway scenarios, it is desirable to maintain modest operating temperatures in order to ensure long lifetimes of the electronic components. A second issue relates to mechanical stability of the integrated solar AC module. In addition to an increase in overall weight, the addition of micro-inverters to solar panels can potentially alter the natural oscillatory frequencies of the solar panels, making them potentially less stable against sustained winds and/or other mechanical disturbances. Other issues relate to the physical and commercial practicality of the integrated solar AC module. For example, since many solar photovoltaic systems are installed in publicly visible places, it is desirable to avoid a cluttered, messy, or non-uniform look (not only from the top view, but in many cases also from the bottom view) that might otherwise be caused by the use of solar panels having attached micro-inverter devices. Other issues arise as would be readily apparent to one skilled in the art in view of the present disclosure.

SUMMARY [0007] Provided according to one or more preferred embodiments is an integrated solar photovoltaic AC module and related methods in which the positional, mechanical, and thermal relationships among a micro-inverter, its associated solar panel, and the associated mounting frame are optimized such that an advantageous combination of mechanical integrity, thermal stability, and durability is provided, while at the same time keeping overall system costs down, keeping overall system weight low, providing a clean visual look, and allowing for ease of system installation and maintenance. For one preferred embodiment, an integrated photovoltaic AC (PVAC) module is provided that comprises a generally planar solar panel body having a front surface for receiving solar radiation and a back surface opposite the front surface. The PVAC module further comprises a substantially rigid frame including first and second side rails securably supporting the solar panel body along different peripheral portions thereof, and a micro- inverter device having a bottom surface and a top surface. The frame further includes a generally rigid, thermally conductive plate member extending from the first side rail to the second side rail in an orientation generally parallel to the solar panel body, the plate member having an upper surface facing the back surface of the solar panel body, the plate member being securably affixed to each of the first and second side rails in a manner that enhances lateral shear stability of the frame. The bottom surface of the micro-inverter device is securably affixed along the upper surface of the plate member such that at least a portion of the micro-inverter device is vertically supported by the plate member. The frame and micro-inverter device are configured and dimensioned such that an air gap is maintained between the upper surface of the micro-inverter device and the back surface of the panel body, the air gap being sufficient to inhibit thermal crosstalk between the micro- inverter device and the solar panel body.

[0008] According to another preferred embodiment, an apparatus is provided comprising a photovoltaic solar panel, the photovoltaic solar panel comprising a generally planar panel body having a front surface for receiving solar radiation and a back surface opposite the front surface, the panel body being secured between at least one pair of opposing frame members. The apparatus further comprises a first strut member disposed across the solar panel in separation from the back surface, the first strut member being fixably extended between the opposing frame members. The apparatus further comprises a second strut member disposed across the solar panel in separation from the back surface and from the first strut member, the second strut member being fixably extended between the opposing frame members. The apparatus further comprises a micro-inverter device fixably secured between the first and second strut members in separation from the back surface.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIGS. 1 A-1 D illustrate front, back, and cross-sectional views of a prior art photovoltaic solar panel; [0010] FIGS. 2A-2C illustrate front and side cross-sectional views of a prior art mount frame;

[0011] FIGS. 3A-3D illustrate front, back, and side cross-sectional views of the solar panel of FIGS. 1 A-1 D as mounted on the mount frame of FIGS. 2A-2C; [0012] FIGS. 4A-4B illustrate back and cross-sectional views of a micro- inverter as mounted on a solar panel according to a prior art method;

[0013] FIG. 5 illustrates a back view of a micro-inverter as mounted on a solar panel according to a preferred embodiment;

[0014] FIGS. 6A-6C illustrate a back view and cross-sectional views of a micro- inverter as mounted on a solar panel according to a preferred embodiment; [0015] FIG. 7 illustrates a perspective view of a cradle member used in the mounting arrangements of FIGS. 5-6C;

[0016] FIG. 8 illustrates a perspective view of a strap member used in the mounting arrangements of FIGS. 5-6C; [0017] FIG. 9 illustrates an enhanced micro-inverter device according to a preferred embodiment;

[0018] FIGS. 10A-10B illustrate a back view and a cross-sectional view of a combined solar panel/micro-inverter assembly according to a preferred embodiment;

[0019] FIGS. 11A-11C illustrate a back view and two cross-sectional views of an integrated photovoltaic AC (PVAC) module according to a preferred embodiment;

[0020] FIG. 12 illustrates a strut member as fixedly attached to a mount frame according to a preferred embodiment;

[0021] FIG. 13 illustrates a cross-sectional view of a side rail of the PVAC module of FIGS. 11A-11 C;

[0022] FIGS. 14A-14B illustrate a back view and a cross-sectional view of the integrated PVAC module of FIGS. 11A-11 C at a different level of detail; [0023] FIG. 15 illustrates an exploded perspective view of the integrated PVAC module of FIGS. 11A-11 C and FIGS. 14A-14B;

[0024] FIGS. 16A-16D illustrate an integrated PVAC module according to a preferred embodiment;

[0025] FIG. 17A illustrates a cross-sectional view of a micro-inverter, a support flange or plate member, a side rail, and a solar panel body of an integrated PVAC module according to a preferred embodiment; and

[0026] FIG. 17B illustrates a perspective view of the micro-inverter of FIG. 17A.

DETAILED DESCRIPTION [0027] One or more of the preferred embodiments described herein is directed to optimizing the positional, mechanical, and thermal relationships among a micro- inverter, a solar panel body, and a mounting frame such that an advantageous combination of mechanical integrity, thermal stability, and durability is provided, while at the same time keeping overall system costs down, keeping overall system weight low, and allowing for ease of system installation and maintenance. Although various details such as mounting screws, tape/adhesive layers, connecting wires, electrical wire junction boxes, and the like may be omitted for clarity of presentation herein, it is to be appreciated that a person skilled in the art would be readily able to understand the locations, dimensions, and nature of such details and to implement an overall PV installation according to the preferred embodiments in view of the present disclosure without undue experimentation. [0028] For purposes of clarity in the descriptions of the preferred embodiments herein, several prior art components and configurations are first set forth in FIGS. 1A-1 D, FIGS. 2A-2C, FIGS. 3A-3D, and FIGS. 4A-4B. FIGS. 1A-1 D illustrate front, back, and cross-sectional views of a typical solar panel 102 used in many typical commercial and residential installations. Solar panel 102 comprises a panel frame 104, usually made of aluminum, that supports a generally rigid panel body 106 around a periphery thereof. As illustrated in FIG. 1 C, housed within the panel body 106 is a population of semiconductor wafers 108 suspendably secured within an encapsulating layer 110 comprising a suitable encapsulating material such as a clear, electrically insulating crosslinked ethyl vinyl acetate matrix. A glazing layer 112 is disposed above the encapsulating layer 110 on the radiation-receiving front of the panel body 106, usually comprising a clear, strong glass designed to provide optical clarity, durability, and rigidity for the panel body 106. A backsheet layer 114 covers the encapsulating layer 110 on the non-radiation-receiving back of the panel body 106, the backsheet layer 114 typically comprising a fluoropolymer film or laminate for providing physical protection, electrical insulation, and moisture protection. It is to be appreciated that solar panel 102 represents just one example of a variety of different types of solar panels with which the preferred embodiments described further herein may be advantageously used. [0029] For many common residential and commercial installations the dimensions of solar panel 102 are typically in the range of 700-900 mm on the short side and 1200-1400 mm on the long side, although recitation of such typical ranges is not to be construed as limiting the scope of the present teachings. As illustrated in FIGS. 1 B-1 D, the panel frame 104 includes flanges 104a along the short side and flanges 104b along the long side that, upon installation, are commonly abutted against corresponding surfaces of a mount frame and affixed thereto using any of a variety of screw-based or clip-based schemes. The inward extent of the flanges 104a and 104b is typically about 40-50 mm or less. [0030] FIGS. 2A-2C illustrate a front view and side cross-sectional views of a simplified version of a typical mount frame 202 upon which the solar panel 102 may be mounted. A variety of different mechanisms (not shown) for affixing the mount frame 202 to a rooftop, canopy, stand-alone support structure, etc. can be used. The mounting frame 202 is usually made of aluminum and comprises hollow, rectangular members including short side members 206 and long side members 204, and is often integrated into an array of identical mount frames that share one or more common members.

[0031] FIGS. 3A-3D illustrate front, back, and side cross-sectional views of the solar panel 102 as mounted on the mount frame 202. The mount frame 202 is designed to support the solar panel 102 around its entire periphery. Other commonly used mount frames, such as dual-rail based structures, may use fewer members and are only designed to contact the panel frame 104 at discrete points therearound, (for example, by omitting the long side members 206 and moving the short side members 204 closer together, or by omitting the short side members 204 and moving the long side members 206 closer together). It is to be appreciated that the preferred embodiments described herein can be advantageously used in conjunction with a variety of different mount frame schemes, and therefore presentation herein in the particular context of the mount frame 202 is not to be construed as limiting the scope of the present teachings. [0032] FIGS. 4A-4B illustrate the mounting of a panel-specific micro-inverter 402 for use in conjunction with an associated solar panel 102 according to one known prior art method. In one or more existing residential and/or commercial installations having a scheme similar to that of FIGS. 4A-4B, the micro-inverter 402 is similar to the Enphase Energy Micro-Inverter M175-24-208-SO-02, and comprises cantilever arms 406 integral with the chassis thereof. The cantilever arms are affixed by bolts 408 to a strut 404 that is, in turn, mounted across the back of the solar panel 102 by fixable connection (e.g., bolts) to the long side flanges 104b of the frame 104. The strut 404 is made from aluminum and is usually similar in cross-section to long side members 204 and/or short side members 206 of the mount frame 202. [0033] Micro-inverter 402 typically comprises a chassis made of cast or bent sheet aluminum within which is disposed one or more circuit boards containing the DC-to-AC conversion electronics. All such micro-inverters generate heat as a byproduct of the DC-to-AC conversion process. Some micro-inverter packaging may therefore be constructed with external fins (not shown) for enhancing convective heat transfer for the purpose of dissipating heat that is generated by the electronics. It is recognized that having such means for dissipating heat is desirable for protecting the electronics against destructive temperature excursions, in particular in high temperature environments with high solar exposure. It is also desirable to mount the micro-inverter 402 such that excess heat from the micro- inverter does not result in thermal cross-talk, in which case excess heat may raise the temperature of the solar panel which, in turn, causes a reduction in their operating efficiency. [0034] The mounting scheme of FIGS. 4A-4B is at least partially directed to providing space around the micro-inverter 402 for free convection in order to dissipate excess heat from the electronics therein, as well as for providing some amount of separation distance between the micro-inverter 402 and the panel body 106 to avoid thermal cross-talk. Exposure of the micro-inverter 402 to direct sunlight, which would exacerbate thermal problems by heating up the unit, is also avoided by virtue of its positioning in the shadow of the panel body 106. Finally, some degree of overall compactness is provided so that the combination solar panel-micro-inverter 102/402 combination will appropriately fit into mount frame systems that may be been previously designed for panel-only installations without extensive re-engineering.

[0035] However, one or more issues is brought about by the prior art mounting scheme of FIGS. 4A-4B. First, being separated somewhat from the structural members of the panel frame 104 and mount frame 202, and being supported only along the strut 404 by the finger-like cantilever arms 408, the micro-inverter 402 can be subject to damage from human mishandling (e.g., during system installation or maintenance), animal intrusions, or other gross mechanical disturbances. Second, the cantilevered nature of the mounted micro-inverter 402 can make the mechanical neighborhood thereof subject to resonating behavior in the presence of periodic forces, such as those that can be brought about by high velocity winds. Should the imposed vibrations occur at a natural resonant frequency of the

"oscillator" formed by the combination of the strut 404 with the cantilevered micro- inverter 402 and surrounding framing, substantial stresses can occur leading to fracture and/or failure not only of the cantilever arms 408 but possibly of the strut 404 and other components. Third, the manner of heat dissipation from the micro- inverter 402 is essentially limited to the single modality of convective heat dissipation from the surface the micro-inverter 402 into the air therearound, although the presence of fins (not shown) on the surface of the micro-inverter 402 can enhance this heat dissipation somewhat. Other issues arise as would be readily apparent to one skilled in the art in view of the present disclosure. [0036] FIG. 5 illustrates the mounting of a panel-specific micro-inverter 402 for use in conjunction with an associated solar panel 102 according to a preferred embodiment. Shown in FIG. 5 is a back side view of the solar panel 102 secured to the mount frame 202, the solar panel 102 comprising the generally planar panel body 106 that is secured between opposing long side members of the panel frame 104. Upper and lower strut members 504 are disposed across the back side of the panel body 106, each strut member 504 being affixed at its opposing ends (e.g., using bolts) to the long side flanges 104b of respective opposing long side members of the panel frame 104. A rigid, thermally conducting cradle member 506 is fixably secured between the upper and lower struts 504, and the inverter device 402 is fixably secured to the cradle member 506 by means including, but not limited to, a strap member 508. [0037] Referring now to an exemplary neighborhood 599 around an end of the upper strut 504, the reader's attention is briefly directed to FIG. 12. According to an alternative embodiment that is also within the scope of the present teachings, each strut member 504 is fixedly attached {e.g., by welding, adhesives, mated slots, etc.) at each end to an opposing long side member 204 of the mount frame 202, rather than to the long side flanges 104b of the opposing long side members of the panel frame 104. In still another alternative preferred embodiment (not shown), each strut member 504 is fixedly attached at each end to both the long side members 204 and the long side flanges 104b.

[0038] FIGS. 6A-6C illustrates a close-up view and two cross-sectional views of the mounting arrangement of FIG. 5. Cradle member 506 preferably comprises a stamped or otherwise formed sheet of rigid, thermally conductive, lightweight metal, with one example being 0.125-inch thick diamond plate 3821 A aluminum 5052 with a 41 % open pattern. Strap member 508 may comprise, for example, stamped 0.0625-inch thick aluminum. Cradle member 506 comprises a center plate 506b sized according to a major surface dimension (i.e., top and bottom surfaces) of the micro-inverter device 402. Cradle member 506 further comprises first and second sheet members 506a and 506c that extend between the center plate 506b and the upper and lower strut members 504, respectively, being secured thereto using bolts 610 or any of a variety of methods (e.g., welding, adhesives, mated slots, etc.). Preferably, the sheet members 506a and 506c maintain most of their width dimension (left-to-right in FIG. 6A) as they extend from the center plate 506b to the strut members 504, such that excess heat from the micro-inverter 402 is conductively urged into the sheet members 504a/504c and therethrough into the strut members 504. This conductive modality for dissipating excess micro-inverter heat advantageously combines with convective/radiative heat transfer into the surrounding air to better facilitate thermal stability of the micro-inverter and photovoltaic solar panel assembly. [0039] As illustrated in FIG. 6B, the strut members 504 and cradle member 506 are configured and positioned such that an air gap is maintained between those elements and the backside of the panel body 106. The stamped depth of the center plate 506b relative to the sheet members 506a/506c may vary depending on the size and shape of the micro-inverter 402, but should be selected so that a minimum air gap 614 of at least about 0.25 inches is maintained between the center plate 506b and the panel body 106. The mounting arrangement of FIGS. 5- 6C has been found provide an advantageous combination of positional stability, mechanical integrity, and thermal stability, while also keeping overall system costs down, keeping overall system weight low, and allowing for ease of system installation and maintenance. [0040] FIG. 7 illustrates a perspective view of the cradle member 506. The holes of the diamond plate aluminum material help facilitate convective cooling. FIG. 8 illustrates a perspective view of the strap member 508. [0041] FIG. 9 illustrates an enhanced micro-inverter device 902 according to a preferred embodiment. The enhanced micro-inverter device 902 is similar to the micro-inverter device 402, supra, except that it comprises a chassis 906 that is designed to inherently provide the mechanical support and thermal transfer characteristics of the cradle member 506, i.e., the cradle member 506 is "built in" to the chassis 906 of the enhanced micro-inverter device 902. Mounting slots/holes 908 are provided as needed for fixably attaching the enhanced micro-inverter device 902 directly to the upper and lower struts 504, supra. [0042] FIGS. 10A-10B illustrate a backside view and a cross-sectional view, respectively, of a combined solar panel/micro-inverter assembly according to another preferred embodiment, comprising a solar panel 1002 and a micro-inverter 1052. Solar panel 1002 comprises a panel frame 1004 that secures a panel body 1006 thereacross, the panel frame including flange members 1004a, 1004b, 1004c, and 1004d. The panel frame 1004 is configured and dimensioned with at least one of the flange members 1004a-d extended inward by an amount sufficient to mechanically support the micro-inverter 1052 thereon, as shown in FIG. 10B. For the preferred embodiment of FIGS. 10A-B, there are two flanges 1004b and 1004c that extend inward such that the micro-inverter 1052 can be fixably mounted on both of them near a corner of the panel body 1006. In one preferred embodiment, the flanges 1004b-1004c extend inward by at least one-third of a corresponding linear dimension of the micro-inverter 1052. Thus, for example, where the micro-inverter 1052 is 12 inches wide (left-to-right in FIG. 10A) and 9 inches long (up-to-down in FIG. 10A), the flanges 1004b and 1004c extend inward by at least 4 inches and 3 inches, respectively. In other preferred embodiments, this percentage can differ from one-third depending on the weight and other mechanical characteristics of the micro-inverter 1052. In still other preferred embodiments, the micro-inverter 1052 is positioned more leftward in FIG. 10A toward the center of the short side flange 1004c and is supported solely by that short side flange 1004c and/or the associated short side member of the panel frame 1004. In even other preferred embodiments, the micro-inverter 1052 is positioned more upward in FIG. 10A toward the center of the long side flange

1004b and is supported solely by that long side flange 1004b and/or the associated long side member of the panel frame 1004.

[0043] According to one preferred embodiment, the combined solar panel/micro-inverter assembly of FIGS. 10A-10B is provided, installed, and maintained as a single, integrated, unitary module (termed herein an "integrated photovoltaic AC module" or "integrated PVAC module") in which the panel body, frame, and micro-inverter are, from a practical perspective, physically and functionally inseparable from each other. Once the integrated PVAC module has been fabricated, usually in a controlled factory environment, it has been found advantageous to keep the panel body, frame, and micro-inverter tied to each other in terms of transport, distribution, installation, and repair. For example, if the integrated PVAC module stops working properly, it would be removed as a single unit (including the panel body, frame, and micro-inverter) and sent back to the factory or authorized service center for repair, with no field swapping or user servicing of a non-working individual components thereof.

[0044] FIGS. 11A-11C illustrate a backside view and two cross-sectional views, respectively, of a PVAC module 1101 according to a preferred embodiment. Preferably, the PVAC module 1101 is an integrated PVAC module in which a frame 1105, a panel body 1106, and a micro-inverter 1152 thereof are provided as a single, integrated unit. Preferably, the frame 1105, panel body 1106, and micro- inverter 1152 are, from a practical perspective, physically and functionally inseparable from each other, in a manner similar to the description in the preceding paragraph for "integrated photovoltaic AC module" or "integrated PVAC module". PVAC module 1101 comprises a panel body 1106 having a front surface for receiving solar radiation (the front surface facing the +z direction in FIGS. 11 A- 11C) and a back surface opposite the front surface (the back surface facing the -z direction in FIGS. 11A-11 C). PVAC module 1101 further comprises a rigid frame 1105 securably supporting the panel body 1106 around substantially an entire periphery of its back surface. The frame 1105 includes side rails 1105c and 1105a opposing each other and side rails 1105b and 1105d opposing each other, the frame 1105 thereby forming a laterally closed shape. Each of the side rails 1105a- 1105d has a top surface that contacts the back surface of the panel body 1106 along a corresponding side of the periphery.

[0045] The frame 1105 further includes a generally flat, rigid, thermally conductive flange 1105e that is securably affixed to a bottom of the side rail 1105c and extends inwardly therefrom relative to the laterally closed shape of the frame 1105. The flange 1105e has an orientation generally parallel to the panel body 1106. A bottom surface of the micro-inverter 1152 is securably affixed to the flange 1105e, and the flange 1105e extends inwardly by an amount sufficient to fully underlie and support the micro-inverter 1152. Preferably, the flange 1105e is separated from the panel body 1106 by a distance greater than a height of the micro-inverter 1152 such that the top surface of the micro-inverter device is separated from the back surface of the panel body 1106 by an air gap "g" sufficient to inhibit thermal crosstalk between the micro-inverter device and the solar panel body. [0046] By way of example and not by way of limitation, in one preferred embodiment, for conventionally sized rooftop solar panel bodies that are roughly about 900-1100 mm x 1400-1600 mm in lateral dimension and about 0.5 cm - 1.0 cm thick, and for a conventionally sized micro-inverter that is about 120-140 mm x 190-210 mm in lateral dimension and about 20-40 mm thick, and for typical micro- inverter dissipative heat outputs in the range of 20 watts, the air gap "g" should be in the range of at least about 5 mm - 10 mm.

[0047] As illustrated in FIGS. 11A-11C, the flange 1105e preferably contains through-holes or perforations 1132 in predetermined patterns 1134 (other advantageous patterns are disclosed further herein) to facilitate convective cooling. A thermally conductive pad 1154 is also provided between the bottom surface of the micro-inverter 1152 and the upper surface of the flange 1105e to further facilitate cooling of the micro-inverter 1152 by conduction into the metal frame. Preferably, the flange 1105e is securably affixed to the side rails 1105b and 1105d as shown in FIGS. 11A-11 C, such as by using fasteners 1130 (e.g., rivets, screws, etc.) and/or welds, which has been found to impart not only structural stability of the frame 1105 by virtue of enhanced lateral shear stability, but also has been found to secure the physical integrity of the solar panel body 1106 by inhibiting the occurrence of flexure-type resonant modes (up-and-down flexing, like a drum) at frequencies that are commonly associated with rooftop winds or other structural perturbations (e.g., 0.5 Hz-6 Hz). For conventionally sized solar panel bodies such as those outlined in the previous paragraph, it has been found that such securable affixation of the flange 1105e to the side rails 1105b and 1105d for the length of the inward extend of the flange 1105e (e.g., about 160 mm) can result in safely high natural resonant frequencies (e.g., above 25Hz) such that such unsafe and/or cell- damaging resonances will not occur. Resonances associated with the weight of the micro-inverter 1152 on the flange 1105e (e.g., by flexure-type resonances of the flange) are also inhibited. [0048] It is to be appreciated that the use of the term "flange" in relation to the drawing element numbered 1105e does not limit the scope of the preferred embodiments in relation to the manner in which it is securably affixed to the side rail 1105c. Thus, in one preferred embodiment, the flange 1105e can be integrally formed as part of the side rail 1105c, such as by stamping or molding during the formation of the side rail 1105c itself. However, in other preferred embodiments, the flange 1105e can be separately fabricated as a physically distinct plate that is then fastened or welded to the side rail 1105c. The flange 1105e can therefore be alternatively referenced by the more general term plate member, such alternative reference being applicable to each of the preferred embodiments described hereinabove and hereinbelow.

[0049] Preferably, frame 1105 consists primarily of aluminum, such as 6061 -T6 aluminum. Preferably, the side rails 1105b, 1105d, and 1105a have a double- boxed cross-sectional shape (see air cavities 1136 in FIG. 11 B) to provide still further mechanical strength. Optionally, the side rail 1105c may also have a double-boxed cross-section, although in the embodiment of FIGS. 11A-C it has a single-box shape to reduce its width, so that the micro-inverter 1152 can also be laterally affixed to the side rail 1105c (e.g., by screws, bolts, etc.) to even further increase mechanical integrity. Yet another advantage of the preferred embodiment of FIGS. 11A-11 C is that the micro-inverter 1152 is safely housed within a cave-like structure formed by the flange 1105e, the side rails 1105b-1105c-1105d, and the panel body 1106, and so is relatively safe from weather elements, animal intrusions, and other physical disturbances. The preferred embodiments of FIGS. 10A-10B and FIGS. 11A-11C have been found to provide particularly advantageous combinations of mechanical integrity, thermal stability, ease of device transport, ease of installation, durability, and modest fabrication and installation costs, providing an optimal balance among often competing design goals. [0050] FIG. 13 illustrates a close-up cross-sectional view of the side rail 1105d and panel body 1106. The side rails 1105b and 1105a can be similarly constructed as side rail 1105d. The double box construction of side rail 1105d is preferably an extrusion of a thermally conductive metal having a "k" value of greater than or equal to 100 VWmK, such as 6061 -T6 aluminum. The side rail 1105d is preferably made with triple webbing 1302 to form two boxes 1304 as shown, to provide substantial stiffness and resistance to snow and wind loading while adding little in weight. Panel body 1106 (which can alternatively be termed a photovoltaic stack) is captured between boxes 1304 and a top flange 1306 with adhesive, double-backed adhesive foam tape, or other material and technique as would be known to a person skilled in the art in view of the present disclosure.

[0051] FIGS. 14A-14B illustrate a backside view and a cross-sectional view of the integrated PVAC module of FIGS. 11A-11C at a different level of detail, in which the through-holes of the flange 1105e are omitted for clarity, and further illustrating electrical connections to and from the micro-inverter 1152. A junction box 1402, which is usually integrated into the panel body 1106, provides electrical access to the DC negative and DC positive outputs of the panel body 1106. A DC connection cable 1404, carrying both positive and negative DC wires, couples the junction box 1402 to the micro-inverter 1152. The micro-inverter 1152 outputs AC power over an AC output cable 1406, which connects to the remainder of the solar installation and the load by virtue of an AC connector 1408. While the DC connection cable 1404 and AC output cable 1406 connect to opposite sides of the micro-inverter 1152 in FIGS. 14A-14B, in other preferred embodiments they can connect to the same side of the micro-inverter 1152. Also shown in FIGS. 14A-14B are screws (or other fasteners) 1410 used to fixably attach the micro-inverter 1152 to the flange 1105e.

[0052] FIG. 15 illustrates an exploded perspective view of the integrated PVAC module described above with respect to FIGS. 11A-11 C and 14A-14B. FIGS. 16A- 16D illustrate further views of the integrated PVAC module described above with respect to FIGS. 11A-11 C and 14A-14B with a view toward setting forth typical dimensions according to one preferred embodiment, which are set forth by way of example and not by way of limitation. The typical dimensions set forth herein shown would enjoy one or more of the above advantages according to the preferred embodiments when used in conjunction with a micro-inverter having a typical footprint in the range of 8-10 inches (20-25 cm) long by 5-6 inches (13-15 cm) wide, a typical height (thickness) in the range of 1 -1.5 inches (2.5-3.8 cm), and a typical weight of 4-5 pounds (1.8-2.3 kg). With reference to FIGS. 16A-16D, one set of exemplary dimensions is as follows: a = 98 cm, b = 162 cm, c = 16.6 cm, d = 4.6 cm, e = 0.7 cm, f = 1.7 cm, h = 3.4 cm, j1 = 0.8 cm, j2 = 1.4 cm, k = 1.4 cm, m = 1.2 mm, n = 0.7 cm, p = 4.7 cm, and q = 2.5 cm.

[0053] FIGS. 17A-17B illustrate further views of the integrated PVAC module described above with respect to FIGS. 11A-11 C and 14A-14B. FIG. 17A illustrates a cross-sectional view of the micro-inverter 1152, the support flange or plate member 1105e, the side rail 1105c, and the solar panel body 1106. FIG. 17B illustrates a perspective view of the micro-inverter of FIG. 17A. For one preferred embodiment, the air gap "g" between the top surface of the micro-inverter 1152 and the bottom (back) surface of the panel body 1106 is about 5.8 mm. FIGS. 17A-17B further illustrate a bracket member 1702 and bolt member 1706 for fixably securing the micro-inverter 1152 to the side rail 1105c, and bracket members 1704 for fixably securing the micro-inverter 1152 to the support flange/plate member 1105e. [0054] The above-described arrangements in which the micro-inverter 1152 is fixably mounted on the flange 1105e provides several key advantages. The double box construction and interconnection among the side rails 1105a-1105b together with flange 1105e provides a rigid base such that the natural vibration frequency of the integrated assembly is typically higher than 25 Hz (25 cycles per second), a natural frequency that is extremely advantageous considering that vibration by wind is always induced at a frequency lower than 6 Hz and except for extreme conditions typically remains below 2 Hz. Furthermore, the highly thermally conductive metal flange 1105e provides a conductive conduit to disperse heat from the micro-inverter 1152, which produces heat as a byproduct of DC to AC conversion. Thermal connection from micro-inverter 1152 to flange 1105e may be enhanced using the thermally conductive pad 1154, or alternatively by using thermal grease or similar methods. Further enhancement of thermal connection from key heat-generating components within micro-inverter 1152 to the outer surface of micro-inverter 1152 may be provided by potting compound having thermal conductivity of at least 1.0 VWmK and preferably having thermal conductivity of exceeding 1.5 VWmK, such that complete thermal connection is attained from key heat-generating components within micro-inverter 1152 to metal flange 1105e for conduction and convection heat dissipation. [0055] Advantageously, the large area of flange 1105e forms an effective fin for free and forced convective heat dissipation. Slots 1132, louvers, holes or other openings in flange 1105e allow for air passage to help avoid stagnation of heated air. Note that it is important to achieve a balance between free air passage on one hand and interruption of thermal conduction and reduced structural integrity on the other. Flange 1105e furthermore serves to protect the micro-inverter 1152, junction box 1402, and DC connection cable 1404 from damage during transport, during array assembly, and from damage from flying debris during exposure of the PVAC module to high winds. Even further, flange 1105e provides visual obscuration for all electronic components on the PVAC module, thereby presenting a clean and integrated appearance. [0056] Whereas many alterations and modifications of the present invention will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that the particular embodiments shown and described by way of illustration are in no way intended to be considered limiting. By way of example, although one or more preferred embodiments are described above in the context of a one-to-one pairing of each micro-inverter with an individual solar panel, there may alternatively be scenarios in one micro-inverter is "responsible" for two adjacent solar panels (or more), in which case only one out of the two (or more) solar panels will have an associated proximal micro-inverter, and such scenarios are not outside the scope of the present teachings. [0057] By way of further example, in other scenarios, the electrical functionality of any particular micro-inverter might be divided into two (or more) discrete physical boxes ("partial micro-inverters"), each having its own different electrical functionality, wherein at least one of the partial micro-inverters is mounted according to one or more of the preferred embodiments described supra, and such scenarios are not outside the scope of the present teachings. By way of even further example, in still other scenarios, the electrical inversion responsibility for a plurality "N" solar panels might be divided among a plurality "M" of discrete physical boxes, each having its own different electrical functionality, wherein one or more of the "M" discrete boxes is mounted near a respective one of the "N" solar panels according to one or more of the preferred embodiments described supra, and such scenarios are not outside the scope of the present teachings. In still another preferred embodiment, any leftover space in the interior compartment of the micro- inverter 402 and/or the enhanced micro-inverter 902 between the electronic components and the chassis is filled with a potting compound having a thermal conductivity of at least 1 -2 W/m-K to further increase thermal stability, which also has an added benefit of providing increased mechanical shock resistance. [0058] By way of further example, while the rigid frame 1105 of FIGS. 11A-11 C is described above as securably support the panel body 1106 around substantially the entire periphery of its back surface, it would not be outside the scope of the preferred embodiments for one or more of the side rails, such as side rail 1105a, or some portions of the various side rails, to be omitted. Although there could be some loss of rigidity by such omission, the overall effect may still be tolerable, especially since overall lateral shear stability of the frame is enhanced by virtue of the affixation of the flange 1105e to the side rails 1105b and 1105d using the fasteners 1130. Therefore, reference to the details of the preferred embodiments are not intended to limit their scope, which is limited only by the scope of the claims set forth below.

Claims

CLAIMSWhat is claimed is:

1. An integrated photovoltaic AC (PVAC) module, comprising: a generally planar solar panel body having a front surface for receiving solar radiation and a back surface opposite the front surface; a substantially rigid frame including first and second side rails securably supporting said solar panel body along different peripheral portions thereof; and a micro-inverter device having a bottom surface and a top surface; wherein said frame further includes a generally rigid, thermally conductive plate member extending from said first side rail to said second side rail in an orientation generally parallel to said solar panel body, said plate member having an upper surface facing said back surface of said solar panel body, said plate member being securably affixed to each of said first and second side rails in a manner that enhances lateral shear stability of said frame; wherein said bottom surface of said micro-inverter device is securably affixed along said upper surface of said plate member such that at least a portion of said micro-inverter device is vertically supported by said plate member; and wherein an air gap is maintained between the upper surface of the micro-inverter device and said back surface of said panel body, said air gap being sufficient to inhibit thermal crosstalk between said micro-inverter device and said solar panel body.

2. The PVAC module of claim 1 , wherein said plate member supports said micro-inverter device along the entire bottom surface thereof.

3. The PVAC module of claim 1 , wherein said air gap is at least 5 mm.

4. The PVAC module of claim 1 , wherein said plate member is perforated with a population of through-holes to facilitate convective cooling.

5. The PVAC module of claim 1 , wherein said plate member is formed separately from said first and second side rails and subsequently affixed to each of said first and second side rails using fasteners.

6. The PVAC module of claim 1 , wherein said plate member is formed integrally with said first side rail and subsequently affixed to said second side rail using fasteners.

7. The PVAC module of claim 1 , wherein said first and second side rails are adjacent to each other along said periphery of the solar panel body and intersect at a nonzero angle.

8. The PVAC module of claim 1 , wherein said first and second side rails are generally opposite each other relative to the solar panel body.

9. The PVAC module of claim 1 , wherein: said solar panel body is generally rectangular in shape with two opposing long sides and two opposing short sides; said first and second side rails are respectively disposed along said two opposing long sides of said solar panel body; said frame further includes third and fourth side rails respectively disposed along said two opposing short sides of said solar panel body; and said plate member is further securably affixed to said third side rail such that a cave-like enclosure is formed by said solar panel body, said plate member, and said first, second, and third side rails, said micro-inverter device being at least partially disposed within said cave-like enclosure.

10. The PVAC module of claim 9, wherein said plate member supports said micro-inverter device along the entire bottom surface thereof, whereby said micro- inverter device is fully contained within said cave-like enclosure.

11. The PVAC module of claim 10, wherein said plate member extends inwardly from said third side rail toward said fourth side rail by a distance that is less than ten percent of a distance between said third and fourth side rails, wherein said plate member is formed integrally with said third side rail as a flanged extension thereof, and wherein said air gap is at least 5 mm.

12. An integrated photovoltaic AC (PVAC) module, comprising: a generally planar solar panel body having a front surface for receiving solar radiation and a back surface opposite the front surface; a substantially rigid frame securably supporting the solar panel body around substantially an entire periphery of said back surface thereof, said frame including first and second side rails opposing each other and third and fourth side rails opposing each other, said frame forming a laterally closed shape, each of said side rails having a top surface that contacts said back surface of the solar panel body along a corresponding side of said periphery; and a micro-inverter device having a bottom surface and a top surface; wherein said frame further includes a generally flat, rigid, thermally conductive flange member securably affixed to a bottom of said first side rail and extending inwardly therefrom relative to said laterally closed shape of said frame, said flange member having an orientation generally parallel to said solar panel body, said flange member thereby having an upper surface opposite said back surface of the solar panel body; wherein said bottom surface of said micro-inverter device is securably affixed along said upper surface of said flange member such that at least a portion of said micro-inverter is vertically supported by said flange member; and wherein said upper surface of said flange member is separated from said back surface of said solar panel body by a distance greater than a height of said micro-inverter device such that said top surface of said micro-inverter device is separated from said back surface of said panel body by an air gap sufficient to inhibit thermal crosstalk between said micro-inverter device and said solar panel body.

13. The PVAC module of claim 12, wherein said flange extends farther inward than an inward extend of said micro-inverter device such that said micro-inverter device is supported by said flange member along its entire bottom surface.

14. The PVAC module of claim 13, wherein said air gap is at least 5 mm.

15. The PVAC module of claim 14, wherein said flange member is perforated with a population of through-holes to facilitate convective cooling.

16. The PVAC module of claim 15, said flange member having two opposing lateral edges generally transverse to said first side rail, wherein said flange member is securably affixed to said third and fourth side rails along said opposing lateral edges.

17. The PVAC module of claim 16, wherein said frame including each of said side rails and said flange member consist essentially of aluminum, and wherein said third and fourth side rails have a double-boxed cross-sectional shape.

18. An apparatus, comprising: a photovoltaic solar panel comprising a generally planar panel body having a front surface for receiving solar radiation and a back surface opposite the front surface, the panel body being secured between at least one pair of opposing frame members; a first strut member disposed across the solar panel in separation from said back surface, said first strut member being fixably extended between said opposing frame members; a second strut member disposed across the solar panel in separation from said back surface and from said first strut member, said second strut member being fixably extended between said opposing frame members; and a micro-inverter device fixably secured between said first and second strut members in separation from said back surface.

19. The apparatus of claim 18, further comprising a rigid, thermally conducting cradle member fixably secured between said first and second struts in separation from said back surface, wherein said micro-inverter device is fixably secured to said cradle member.

20. The apparatus of claim 19, wherein said cradle member comprises: a center plate sized according to a major surface dimension of the micro- inverter device and being configured to receive said micro-inverter device along said major surface; and first and second sheet members extending between said center plate and said first and second strut members, respectively, wherein said sheet members maintain most of a major linear dimension of said micro-inverter for substantially all of a distance between said center plate and said first and second strut members, respectively; whereby excess heat from said micro-inverter is conductively urged into said first and second sheet members and therethrough into said first and second strut members for facilitating thermal stability of said micro-inverter and said photovoltaic solar panel.