Abstract:
Solar cell modules for converting solar energy into electrical energy, such as used in a concentrating photovoltaic system. The modules have a first ventilating opening in the module housing; and a ventilating subassembly mounted on the module housing and disposed over the ventilating opening in the module housing. The ventilating subassembly has a housing having a first chamber adjacent to and in communication with the first ventilating opening in the module housing; a second chamber adjacent to the first chamber, the second chamber having a second ventilating opening to the external environment; and a filter membrane separating the first chamber from the second chamber to allow air to flow between the first chamber and the second chamber through the filter membrane.

Description:
BACKGROUND 
     Solar array modules are constructed to house solar cell receivers that mount a solar cell that converts solar energy into electrical current. The modules include a housing, and a number of lenses mounted on the housing that direct incoming solar energy to focus on a solar cell mounted on corresponding solar cell receivers. 
     The modules are often placed outdoors in various environmental conditions that may include extreme heat, cold, humidity, rain, snow, and ice. The housing protects the solar cell receivers from such environmental conditions. A vent or opening may be formed in the housing to allow air circulation. 
     SUMMARY 
     The present application is directed to a solar cell module to convert light to electricity comprising: a first housing comprising a first side and an opposing spaced-apart second side; a plurality of lenses mounted on the first side of the housing for concentrating the incoming light; a plurality of solar cell receivers on the second side of the housing, each of the plurality of solar cell receivers disposed in an optical path of one of the plurality of lenses; a first ventilating opening in the first housing; a ventilating subassembly mounted on the first housing and disposed over the ventilating opening in the first housing, the subassembly including a housing having a first chamber adjacent to and in communication with the first ventilating opening in the first housing; a second chamber adjacent to the first chamber, the second chamber having a second ventilating opening to the external environment; and a filter membrane separating the first chamber from the second chamber to allow air to flow between the first chamber and the second chamber through the filter membrane. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a solar cell module; 
         FIG. 2  is an exploded perspective view of a portion of one side of the housing of the solar cell module of  FIG. 1  including a ventilating subassembly; 
         FIG. 3  is a perspective view of a portion of one side of the housing of the solar cell module of  FIG. 1  including a ventilating subassembly mounted on the housing of the solar cell module; 
         FIG. 4  is a perspective view of the top side of the ventilating subassembly; 
         FIG. 5  is a perspective view of the bottom side of the ventilating subassembly; 
         FIG. 6  is an exploded bottom perspective view of the ventilating subassembly showing the filter membrane; and 
         FIG. 7  is an a bottom perspective view of the ventilating subassembly showing the filter membrane positioned in the ventilating assembly. 
         FIG. 8  is a partially exploded perspective view of an embodiment of a solar cell receiver including a solar cell, a metallized ceramic substrate and a heat sink. 
         FIG. 9  is an exploded perspective view of a solar cell module. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a solar cell module  10  for converting solar energy into electrical energy. The module  10  includes a housing  11  formed from three separate members that are attached together to form an interior space. A top member  60  extends across an open side of the housing  11  and includes one or more lenses  61 . One or more solar cell receivers  70  (embodiments of solar cell receivers are disclosed in US Patent Publication No. 2011/0048535, herein incorporated by reference) are positioned within the interior space of the house and are aligned with one or more the lenses  61  to receive and convert the solar energy into electrical energy. 
     The housing  11  forms a portion of the exterior of the module  10  and provides positioning and protection to the solar cell receivers  70 . The fabrication of the housing is disclosed in U.S. patent application Ser. No. 13/156,064, filed Jun. 8, 2011, herein incorporated by reference. 
     In particular, in one embodiment, the housing  11  is formed from a sheet member  20  including opposing first and second edges and opposing third and fourth edges. A first fold  25  extends across a length of the sheet member  20  between the first and second edges and separates a bottom side from a first lateral side, and a second fold that extends across the length between the first and second edges and separates the bottom side from a second lateral side. The first and second folds are spaced apart and defining opposing edges of the bottom side and respectively positioning the first and second lateral sides transverse to the bottom side. A first end member  30  is attached to the first edge of the sheet member along the bottom side and the first and second lateral sides. A second end member  40  is attached to the second edge of the sheet member along the bottom side and the first and second lateral sides. Each of the end members  30 ,  40  have an upper edge opposite from the bottom side that align with the third and fourth edges of the sheet member and form the first side of the housing; and the second side of the housing is formed by the bottom side. A more detailed depiction of the construction may be found in U.S. patent application Ser. No. 13/156,064 noted above. 
     One or more of the side members of the housing  11  may include ribs  50  that are stamped into the sheet material to increase the strength and rigidity. The ribs  50  include an elongated shape. The ribs  50  may extend along the entire height or a portion of the height between the top side and the bottom of the module. Ribs  50  may also extend along the bottom of the module (not shown) in longitudinal and/or lateral orientations, and may extend across the entirety or portion of the bottom. The ribs  50  along the housing may have the same or different shapes and/or sizes. The ribs  50  may also include separate elements that are attached to the side members. 
     The top member  60  extends across the open side of the housing  11 . In the embodiment illustrated, the outer edges  61  of the top member  60  seat within the lip  51  formed around the upper side of the housing  11 . The top member  60  may be attached to the housing  11  by an adhesive and/or one or more mechanical fasteners such as but not limited to screws, bolts, and rivets. 
     The top member  60  includes a number of lenses  62  that focus the solar energy towards the solar cell receivers  70  within the interior space of the housing  11 . In one embodiment, each of the lenses  62  directs solar energy to a specific solar cell receiver  70  positioned below the lens. In one embodiment, the top member  60  includes a total of fifteen lenses  62  that includes three rows of five lenses  62 . 
     Each of the lenses  62  may have the same or different construction, size, or shape. One specific embodiment includes each of the lenses  62  being identical. The lenses  62  may be Fresnel lenses or may be conventional spherical lenses. An advantage of Fresnel lenses is they require less material compared to a conventional spherical lens. In one embodiment, each lens  62  has a rectangular shape. In a specific embodiment, each lens is about 9 inches by 9 inches. The lenses  62  may be constructed from different materials, including but not limited to acrylic, plastic, glass, or silicone-coated glass. Each lens  62  may further include an anti-reflective coating. The array of lenses may be formed from a single acrylic, plastic, glass, or silicone-coated glass sheet mounted on the edge  61  of the housing  11 . 
     Solar cell receivers  70  are positioned in the interior space  12  of the housing  11  and aligned with the lenses  62 . Each of the solar cell receivers  70  includes a secondary optical element, a solar cell, and a heat sink  73 . The arrangement of the solar cell receivers  70  may match that of the lenses  62 . In one embodiment, the solar cell receivers  70  are arranged in an array of three rows each with five solar cell receivers  70  that correspond to the paired arrangement of the lenses  62  in the top member  60 . 
     The solar cell receivers  70  include a III-V compound semiconductor multijunction solar cell including a first surface and a second surface; a bypass diode coupled with the solar cell; a heat sink  73  positioned below the second surface of the solar cell and thermally coupled to the solar cell; and an optical element positioned above the first surface to further concentrate and guide the light onto the solar cell so that the light reaching the surface of the solar cell may be concentrated by a factor of 1000 or more. The bottom portion of the heat sinks  73 , each heat sink including a number of radiating fins, are shown in  FIG. 1  projecting from openings in the bottom of the housing  11 . 
     The housing  11  has a height measured between the bottom side  23  and the top member  60  to provide for accurate placement of each of the solar cell receivers  70  relative to the paired lens  62 . This distance may be based on the focal length of the lens  62  with one embodiment positioning each respective solar cell receiver  70  disposed at or about the focal point away from the respective lens  62 . The focal lengths of the lenses  62  may range from between about 25.4 cm (10 inches) and 76.2 cm (30 inches), with specific embodiments including focal lengths of between about 38.1 cm (15 inches) and 50.8 cm (20 inches). One specific embodiment includes a focal length of about 40.085 cm (17.75 inches). 
     The housing  11  may also include one or more vent openings  101  to allow air to move into and out of the interior space  12 . In one embodiment, the vent openings  101  are louvered, that is, they are punched from the outside of the housing  11 , so that a small overhang originally from the planer surface of the housing now extends over the actual aperture in the interior of the housing  11 . 
     As noted in the exploded representation of  FIG. 2 , the ventilating subassembly  502  is arranged so that it extends entirely over and covers the vent openings  501  to prevent water, moisture, or other contaminants from penetrating from the external atmosphere into the interior space of the housing  11 . 
       FIG. 3  is a perspective view of a portion of one side of the housing of the solar cell module of  FIG. 1  depicting the ventilating subassembly  502  mounted on the housing of the solar cell module, covering the vent openings  501 . The ventilating subassembly  502  is mounted on the housing by an adhesive seal (not shown), although other types of attachment techniques may be used as well. 
       FIG. 4  is a perspective view of the top side of the ventilating subassembly  502 . The subassembly  502  includes vent openings  503  along each of the peripheral sides, which in the depicted example includes five vent openings  503  along each of the longer sides, and three vent openings  503  along each of the shorter sides. 
       FIG. 5  is a perspective view of the bottom side of the ventilating subassembly  502 , showing the mechanical reinforcing and supporting features. In particular, there are two longitudinal supporting ribs or ridges  504  extending the length of the longer side of the ventilating subassembly  502 , beginning and ending on the side of the housing and situated between each of the three vent openings  503  along each of the shorter sides. In the other direction, there are four transverse supporting ribs or ridges  505  beginning and ending on the side of the housing and extending the length of the shorter side of the ventilating subassembly  502 , and situated between each of the five vent openings  503  along each of the longer sides. The ribs  504  and  505  intersect at various points, and at such points rise in height to a planar, generally circular plateau  507  which will form an internal supporting surface for the filter membrane. The edge of the ventilating subassembly  102  includes a planar rim  510  extending circumferentially around the periphery of the subassembly which allows the subassembly to make a flat surface to surface contact with the planar outer face of the housing  11  of the module. Slightly below the planar rim  510  is a ledge with a planar surface that also extends circumferentially around the periphery of the subassembly which allows the filter membrane  508  to be seated inside the subassembly, having a depth appropriately chosen so that the top surface of the filter membrane  508  at or slightly below the planar surface of the rim  510 . In some embodiments, the filter membrane is preferably composed of Goretex™. 
       FIG. 6  is an exploded bottom perspective view of the ventilating subassembly  102  showing the filter membrane  508  as it is positioned above the ventilating subassembly  502  and about to be inserted into place on the ledge  509 . 
       FIG. 7  is an a bottom perspective view of the ventilating subassembly  102  showing the filter membrane  508  positioned on the ledge  509  in the ventilating assembly. 
       FIG. 8  illustrates an embodiment of a solar cell receiver  100  including a solar cell  802 . In one embodiment, the solar cell  802  is a triple-junction III-V compound semiconductor solar cell which comprises atop cell, a middle cell and a bottom cell arranged in series. In another embodiment, the solar cell  802  is a multifunction solar cell having n-on-p polarity and is composed of InGaP)/(In)GaAs III-V compounds on a Ge substrate. In each case, the solar cell  802  is positioned to receive focused solar energy from a secondary optical element  104 . 
     The secondary optical element  104  is positioned between the solar cell  802  and a primary focusing element (not shown) such as a lens. The secondary optical element  104  is generally designed to collect solar energy concentrated by the corresponding lens toward the upper surface of the solar cell  802 . The secondary optical element  104  includes an entry aperture  105  that receives light beams from the corresponding lens and an exit aperture  107  that transmits the light beams to the solar cell  802 . The secondary optical element  104  includes an intermediate region  112  between the apertures  105 ,  107 . Under ideal conditions, the lens associated with the secondary optical element  104  focuses the light directly to the solar cell  802  without the light hitting against the secondary optical element  104 . 
     In most circumstances, the lens does not focus light directly on the solar cell  802 . This may occur due to a variety of causes, including hut not limited to chromatic aberration of a refractive lens design, misalignment of the solar cell  802  relative to the lens during construction, misalignment during operation due to tracker error, structural flexing, and wind load. Thus, under most conditions, the lens focuses the light such that it reflects off the secondary optical element  104 . The difference between an ideal setup and a misaligned setup may be a minor variation in the positioning of the lens of less than 1°. 
     The secondary optical element  104  therefore acts as a light spill catcher to cause more of the light to reach the solar cell  802  in circumstances when the corresponding lens does not focus light directly on the solar cell  802 . The secondary optical element  104  can include a reflective multi-layer intermediate region. The reflective multi-layer intermediate region can be formed from different materials and have different optical characteristics so that the reflectivity of the light beams off secondary optical element  104  and transmitted to the solar cell  802  optimizes the aggregate irradiance on the surface of the solar cell  802  over the incident solar spectrum. For example, in some implementations, the inner surface of the body  112  of the secondary optical element  104  can be coated with silver or another material for high reflectivity. In some cases, the reflective coating is protected by a passivation coating such as SiO 2  to protect the secondary optical element  104  against oxidation, tarnish or corrosion. 
     The body  112  of the secondary optical element  104  has one or more mounting tabs  114  for attaching the body  112  to a bracket  116  via one or more fasteners  118 . The bracket  116  is provided for mounting the secondary optical element  104  to a heat sink  120  via one or more fasteners  122 . The bracket  116  is thermally conductive so that heat energy generated by the secondary optical element  104  during operation can be transferred to the heat sink  120  and dissipated. As shown in this implementation, the secondary optical element  104  has four reflective walls. In other implementations, different shapes (e.g., three-sided to form a triangular cross-section) may be employed. The secondary optical element  104  can be made of metal, plastic, or glass or other materials. 
     In one embodiment, a concentrator  106  is disposed between the exit aperture  107  of the secondary optical element  104  and the solar cell  802 . The concentrator  106  is preferably glass and has an optical inlet  108  and an optical outlet  110 . In one embodiment, the concentrator  106  is solid glass. The concentrator  106  amplifies the light exiting the secondary optical element  104  and directs the amplified light toward the solar cell  802 . In some implementations, the concentrator  106  has a generally square cross section that tapers from the inlet  108  to the outlet  110 . In some implementations, the optical inlet  108  of the concentrator  106  is square-shaped and is about 2 cm×2 cm and the optical outlet  110  is about 0.9 cm×0.9 cm. The dimensions of the concentrator  106  may vary with the design of the solar cell module and the receiver. For example, in some implementations the dimensions of the optical outlet  110  are approximately the same as the dimensions of the solar cell  802 . In one embodiment, the concentrator  106  is a 2× concentrator. The bottom surface of the concentrator  106  can be directly attached to the upper surface of the solar cell  802  using an adhesive such as a silicone adhesive. The solar cell  802  converts the incoming sunlight directly into electricity by the photovoltaic effect. 
     A bypass diode  124  is connected in parallel with the solar cell  802 . In some implementations, the diode  124  is a semiconductor device such as a Schottky bypass diode or an epitaxially grown p-n junction. For purposes of illustration, the bypass diode  124  is a Schottky bypass diode. External connection terminal  125  is provided for connecting the solar cell  802  and the diode  124  to other devices, e.g., adjacent solar cell receivers (not shown). 
     The functionality of the bypass diode  124  can be appreciated by considering multiple solar cells  802  connected in series. Each solar cell  802  can be envisioned as a battery, with the cathode of each of the diodes  124  being connected to the positive terminal of the associated “battery” and the anode of each of the diodes  124  being connected to the negative terminal of the associated “battery.” When one of the serially-connected solar cell receivers  100  becomes damaged or shadowed, its voltage output is reduced or eliminated (e.g., to below a threshold voltage associated with the diode  124 ). Therefore, the associated diode  124  becomes forward-biased, and a bypass current flows only through that diode  124  (and not the solar cell  802 ). In this manner, the non-damaged or non-shadowed solar cell receivers  100  continue to generate electricity from the solar energy received by those solar cells. If not for the bypass diode  124 , substantially all of the electricity produced by the other solar cell receivers would pass through the shadowed or damaged solar cell receiver, destroying it, and creating an open circuit within, e.g., the panel or array. The solar cell receiver  100  also includes a ceramic substrate  126  such as an alumina substrate for mounting of the solar cell  802  and the heat sink  120  for dissipating heat generated by the solar cell  802  during operation. 
       FIG. 9  includes an exploded view of components of the solar cell module  10 . The housing  11  forms the body that supports and positions the other elements. A support member  80  is positioned within the interior space  12  of the housing  11 . The support member  80  includes a substantially planar shape with a length and width to fit in proximity to the bottom of the housing  11 . The support member  80  may contact against or be spaced away from the bottom. The dimensions of the support member  80  may be approximately the same or may be smaller than the bottom to fit within the interior space  12 . A flange  82  may extend along one or more sides to position the support member  80  within the interior space  12 . The flange  82  may engage with features  27  of the housing  11  to position the support member  80 . The support member  80  may include one or more ribs  81  to strengthen and increase the rigidity. The support member  80  may also include one or more openings  83  that align with the openings  26  in the bottom. 
     The support member  80  may further act as a shield to prevent focused solar energy from directly impinging upon the solar cell receivers  70  at areas outside of the designed areas. 
     One or more braces  90  may extend across the interior space  12  to further support the housing  11 . The braces  90  include an elongated shape with opposing ends that fit within slots  28  in the housing  11 . As illustrated in  FIG. 9 , the braces  90  include first ends that fit within slots  28  in the first side  21  and second ends that fit within slots  28  in the second side  22 . Clips  91  may be sized to fit into the slots  28  to secure the braces  90 . 
     The braces  90  may also be positioned to contact against and support the top member  60 . One of the sides  91  of the braces  90  face upward and may contact against the inner surface of the top member  60 . The sides  91  may also include protrusions  92  to further contact against the top member  60 . 
     The top member  60  extends across the open side of the housing  11 . In the embodiment illustrated, the outer edges  61  of the top member  60  seat within the lips  51  formed around the upper side of the housing  11 . The top member  60  may be attached to the housing  11  by an adhesive and/or one or more mechanical fasteners such as but not limited to screws, bolts, and rivets. 
     The top member  60  includes a number of lenses  62  that focus the solar energy towards the solar cell receivers  70  within the interior space  12  of the housing  11 . In one embodiment, each of the lenses  62  directs solar energy to a specific solar cell receiver  70  positioned below the lens. In one embodiment, the top member  60  includes a total of fifteen lenses  62  that includes three rows of five lenses  62 . 
     Each of the lenses  62  may have the same or different construction, size, or shape. One specific embodiment includes each of the lenses  62  being identical. The lenses  62  may be Fresnel lenses or may be conventional spherical lenses. An advantage of Fresnel lenses is they require less material compared to a conventional spherical lens. In one embodiment, each lens  62  has a rectangular shape. In a specific embodiment, each lens is about 9 inches by 9 inches. The lenses  62  may be constructed from different materials, including but not limited to acrylic, plastic, and glass. Each lens  62  may further include an anti-reflective coating. 
     The top member  60  may be formed as a sheet  63  and sized to extend across the open side of the housing  11 . The sheet  63  includes a series of openings each sized to receive one of the lenses  62 . The sheet  63  may be formed from various materials, including but not limited to plastic, acrylic, and aluminum. The top member  60  also extends across the open side of the housing  11  and prevents the ingress of water, rain, or ice into the interior space  12 . 
     Solar cell receivers  70  are positioned in the interior space  12  of the housing  11  and aligned with the lenses  62 . Each of the solar cell receivers  70  includes a secondary optical element  71 , a solar cell  72 , and a heat sink  73 . The arrangement of the solar cell receivers  70  may match that of the lenses  62 . In one embodiment, the solar cell receivers  70  are arranged in an array of three rows each with five solar cell receivers  70  that correspond to the paired arrangement of the lenses  62  in the top member  60 . 
     The heat sink  73  is operatively connected to the solar cell  72 . The heat sink  73  may include abase and one or more outwardly-extending wings. 
     As illustrated in  FIG. 9 , the solar cell receivers  70  are connected in series. An end connector  75  is positioned on a side of the module  10 . 
     The housing  11  may be configured for accurate alignment of each of the solar cell receivers  70  relative to its paired lens  62 . In one embodiment, the solar cell receivers  70  are mounted through the bottom side of the housing  11  with the heat sink  73  positioned outward beyond the bottom side. The solar cell  72  and the secondary optical element  71  extend through one of the openings  26  in the bottom and one of the openings  83  in the sun shield member  80  and are positioned within the interior space  12 . The sunshield member  80  is positioned on top of the receivers  70 , with the secondary optical element  71  extending through the openings  83  therein. The size of the heat sink  73  and/or the solar cell receiver  70  extends across and plugs the openings  26  to prevent the ingress of water into the interior space  12 . The solar cell receivers  70  may be attached to the housing  11  by adhesives and/or mechanical fasteners. 
     The housing  11  has a height measured between the bottom side and the top member  60  to provide for accurate placement of each of the solar cell receivers  70  relative to the paired lens  62 . This distance may be based on the focal length of the lens  62  with one embodiment positioning each respective solar cell receiver  70  disposed at or about the focal point away from the respective lens  62 . The focal lengths of the lenses  62  may range from between about 25.4 cm (10 inches) and 76.2 cm (30 inches), with specific embodiments including focal lengths of between about 38.1 cm (15 inches) and 50.8 cm (20 inches). One specific embodiment includes a focal length of about 40.085 cm (17.75 inches). 
     While particular embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from this invention and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the scope of this invention. Furthermore, it is to be understood that the invention is solely defined by the appended claims. 
     It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations).