Abstract:
A unitized photovoltaic assembly is disclosed. A unitized photovoltaic assembly consists of a unitary frame designed to retain a plurality of photovoltaic modules. The unitary frame is formed by orienting a plurality of rails in the lateral direction above and mounted to a plurality of struts oriented in the vertical direction. Once the unitary framed is formed, photovoltaic modules slide into slots running the length of the rails and are thus retained in the unitary frame. Also added to the unitary frame are a series of power conversion elements, retaining brackets, mounting brackets, and cleaning elements. The completed unitized photovoltaic assembly can be fabricated off-site, transported as a single unit and installed to a roof or other surface with the use of a specialized lifting frame, also disclosed. Additional unitized photovoltaic assemblies can be mechanically and electrically interconnected to form a complete photovoltaic system.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is a continuation of U.S. patent application Ser. No. 13/065,104, filed Mar. 15, 2011, the entirety of which is incorporated by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
       [0003]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The present invention is in the field of photovoltaic panels. More particularly, the present invention is in the technical field of photovoltaic panel mounting systems. 
         [0006]    2. Description of the Related Art 
         [0007]    Photovoltaic, or solar, systems have emerged as a popular source of alternative energy. However, numerous deficiencies exist in current mounting devices and methods of installation. Striking a balance between customizability and efficiency of installation is paramount to the design and implementation of a successful photo voltaic system. 
         [0008]    While many available photovoltaic systems are highly customizable, they lack in efficiency. Current installation methods, commonly referred to as build-on-site, require multiple steps taking place over several days of construction. First, workers must attach mounting devices to the surface or underlying substructure. Each additional mounting device requires penetration of the roof surface with a lag bolt, which compromises the roof&#39;s weather resistant barrier. Measurements are then taken and framing members are cut to length and mounted. Next, workers must measure, cut and install large amounts of wiring and component connections. Finally, photovoltaic modules are added individually until a completed photovoltaic array is formed. Each photovoltaic module must also be secured to the framework by additional mounting hardware. In many methods, this requires the added steps of inserting, positioning and tightening several nuts, bolts and washers per panel. Furthermore, addition of an aftermarket panel cleaning system results in added labor costs and risks possible damage to the installed photovoltaic panels. 
         [0009]    In addition, the on-site installation of electrical wiring and power conversion elements creates unsafe working conditions for installers. When conventional string inverters are used as part of the system, the photovoltaic panels must be electrically connected in series as they are installed resulting in live, high-voltage, DC current on the roof The use of string inverters also requires that extreme measures be taken to insure that all elements of the framing system are securely grounded. The installers must work around this live power to install additional strings of panels and their associated components. The large array of tools and components that must be loaded onto the sloped roof surface and controlled during installation makes build-on-site construction a complex and hazardous process. 
         [0010]    Once installed, photovoltaic arrays are subjected to varying climates and must be able to withstand high winds and snow accumulation. Current systems, such as the one described above, are entirely dependent on the underlying roof surface to maintain their form. Additional mounting points can marginally increase the stability and load capacity of these build-on-site systems, but require additional penetrations to the roof surface. One of the major disadvantages to build on-site construction is that framing members exist as independent components rather than as an integrated framework. During installation the framing members are secured directly to the mounting devices without the added benefit of stabilizing cross members. Each row of photovoltaic panels is therefore mechanically independent from the adjacent rows. Because of this, many roof surface mounting points are required and there is no system wide load sharing. The inability to create an integrated framework makes build-on-site systems inefficient for carrying high wind and snow loads. 
         [0011]    The increased demand for solar systems brings with it a need for a safer and more efficient means of producing and deploying them. Therefore, a need exists in the industry for a new and useful integrated, multi-module, photovoltaic mounting system capable of off-site prefabrication, transportation and installation as a unitized assembly. 
       BRIEF SUMMARY OF THE INVENTION 
       [0012]    The present disclosure is directed to an apparatus and method for fixing photovoltaic modules within a unitized photovoltaic assembly and installing on a roof or other surface. Central to the unitized photovoltaic assembly is a unitary frame support structure. The unitary frame is formed from horizontal rails and vertical struts positioned in uniform rows and columns respectively. The unitary frame is discussed herein in the context of being installed on a sloping residential roof In this context, the term “horizontal” used in connection with the rails means that each rail extends laterally along the sloping roof without a substantial change in inclination along its length, and the term “vertical” used in connection with the struts means that each strut is inclined along its length so that one end of the strut is vertically higher than the other end. The rails are solidly affixed to the struts by welding or other means. Each rail is a uniform structure having a double “I” cross-section and receiving slots. Opposing edges of the photovoltaic panels are retained within these receiving slots. Retaining brackets and spacer clips are provided for maintaining the photovoltaic panels within the receiving slots. Unlike existing systems, the unitized photovoltaic assembly is not solely dependent on the support of the underlying surface to maintain its form. As a result, less mounting hardware is required to obtain a rigid structure, which reduces the number of roof surface penetrations and installation time. This has the added benefit of reducing damage to the roof surface caused by workers walking on it. 
         [0013]    Installation is further streamlined with the inclusion of additional elements during the off-site fabrication process. Power conversion elements are affixed to the unitary frame and pre-wired to the photovoltaic panels. The wiring includes polarized connector elements at the terminal ends allowing adjacent unitized photovoltaic assemblies to be easily connected to one another. Also, a spray head is installed for cleaning the photovoltaic panels and tubing is connected for carrying cleaning fluids. By pre-assembling these systems, workers will no longer be subjected to hazardous conditions while maneuvering tools, materials and themselves around live wires on a sloped roof surface. 
         [0014]    The unitized photovoltaic assembly is designed to integrate with adjacent assemblies to form a completed array. Various assembly configurations are possible including, but not limited to, IX2, IX3, 2X2 and 2X3 depending on the size and shape of the installation surface. Adjacent assemblies are structurally joined with mounting interlocks adding to the rigidity and load carrying capacity of the completed system. Mounting interlocks are attached to the end of a strut or rail and engage with corresponding mounting interlocks on adjacent assemblies. Electrical wiring and tubing are also connected between adjacent assemblies to complete the system. 
         [0015]    In order to form a completed system, each unitized photo voltaic assembly is installed from above with the use of a specialized lifting frame. Since larger unitized photo voltaic assemblies are not sufficiently rigid to stand alone, the lifting frame provides additional support to prevent the assembly from flexing and causing damage to the photo voltaic panels. Use of the specialized lifting frame in conjunction with a crane alleviates the need for photovoltaic panels to be individually carried up a ladder to the roof surface. The lifting frame includes a plurality of tabs and in some instances a “U” channel, which engage and stabilize the horizontal rails of the unitary frame. Cables attached to the lifting frame are adjustable to match the slope of the roof surface. Once positioned, the unitized photovoltaic assembly is lowered onto the roof surface and secured to conventional mounting devices that have been pre-installed on the roof or other surface. The type of mounting devices will vary depending on the installation surface. 
         [0016]    The foregoing is intended to provide a broad description of the present invention in order to demonstrate its contributions to the art and better understand the descriptions to follow. These and other features of the present invention will be readily apparent to persons of ordinary skill in the art upon reading the entirety of this disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0017]      FIG. 1  is a perspective view of a unitized photovoltaic assembly  100  according to the present invention. 
           [0018]      FIG. 2  is a perspective view of unitary frame  110  according to the present invention. 
           [0019]      FIG. 3  is a perspective view of horizontal rails  104  according to the present invention. 
           [0020]      FIG. 4A  is an exploded view of retaining bracket  140   a  according to the present invention. 
           [0021]      FIG. 4B  is a perspective view of retaining brackets  140   a, b  according to the present invention. 
           [0022]      FIG. 5A  is an isolated view of spacer  160  according to the present invention. 
           [0023]      FIG. 5B  is a cross-sectional view of spacer  160  according to the present invention. 
           [0024]      FIG. 6  is a perspective view of struts  106  according to the present invention. 
           [0025]      FIG. 7A  is an isolated view of mounting interlock  170   a  according to the present invention. 
           [0026]      FIG. 7B  is a perspective view of mounting interlocks  170   a,b  according to the present invention. 
           [0027]      FIG. 8  is a perspective view of lifting frame  190  according to the present disclosure. 
           [0028]      FIG. 9  is a perspective view of lifting frame  190  engaged with a unitized photovoltaic array  100  according to the present invention. 
           [0029]      FIG. 10  is a cross-sectional view of lifting frame  190  engaged with a unitized photovoltaic array  100  according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    The present disclosure describes an apparatus for mounting photovoltaic modules, herein referred to as a unitized photovoltaic assembly  100 . The preferred embodiment as shown in  FIGS. 1 through 11 , comprises a unitary frame  110  constructed to retain multiple photovoltaic modules  102  and various other elements. The unitized photovoltaic assembly  100  is designed for off-site fabrication, and can be transported and installed as a single unit, thereby reducing the time and resources required for build on-site construction. 
         [0031]    In the preferred embodiment of unitized photo voltaic assembly  100 , shown in  FIG. 1 , a unitary frame  110  provides the structural framework for the mounting of various elements. As shown, nine photovoltaic modules  102  are arranged into three rows defined by unitary frame  110 . Alternatively, unitary frame  110  can be adjusted to accommodate more or less photovoltaic modules  102 , depending on the application requirements. The Photovoltaic modules  102  are maintained within unitary frame  110  by a plurality of retaining brackets  140   a, b  at the ends of each row in addition to spacers  160  between adjacent photovoltaic modules  102 . 
         [0032]    The unitized photovoltaic assembly  100  is secured to a surface  150  with repositionable mounting brackets  152 . More specifically, mounting brackets  152  are attached to the unitary frame  110  and bolted to mounting devices  156 . The mounting devices  156  are preinstalled to the surface  150  in accordance with local building codes. In the present embodiment, mounting devices  156  are bolted to rafters  154 . Various types of mounting devices  156 , common within the industry, may be utilized. In some instances, mounting devices  156  may not be necessary, in which case mounting brackets  152  can be secured directly to the surface  150 . 
         [0033]    Also shown in  FIG. 1 , are mounting interlocks  170   a, b.  Mounting interlocks  170   a, b  are secured to the unitary frame  110  and are used to mechanically interconnect adjacent unitized photovoltaic assemblies  100  to form a complete system. Because of mounting interlocks  170   a, b,  various arrangements of unitized photovoltaic assemblies  100  can be created, which have the added benefit of increased load sharing across the completed system. 
         [0034]      FIG. 2  shows unitary frame  110  in further detail, without photovoltaic modules  102 . The unitary frame  110  is comprised of a plurality of rails  104  mounted above and welded to a plurality of struts  106  at cross points  108 . Brackets or fasteners could also be used in place of welding to mount rails  104  to struts  106 . Fabrication in this manner creates a unified framework central to the formation of the unitized photo voltaic assembly  100 . In the preferred embodiment, additional elements are attached to unitary frame  110  prior to installation. Additional elements may include, but are not limited to, power conversion elements  112 , spray head  118 , wiring  114 , tubing  120 , retaining brackets  140   a, b,  mounting interlocks  170   a, b  and mounting brackets  152 . 
         [0035]    In the preferred embodiment, power conversion elements  112  are micro-inverters, which are attached to unitary frame  110  beneath photovoltaic modules  102 . The micro-inverters convert power from unregulated direct current (DC) to alternating current (AC) or to regulated DC depending on the installation requirements. Each power conversion element  112  is electrically connected to a corresponding photovoltaic module  102 . Individual power conversion elements  112  are also connected to one another by wiring  114 . Wiring  114  is generally attached to unitary frame  110  and terminates at the perimeter of unitized photovoltaic assembly  100  with polarized power connectors  116   a, b.  Polarized power connector  116   a  can be connected to  116   b  of an adjacent unitized photovoltaic assembly  100  permitting a plurality of unitized photovoltaic assemblies  100  to aggregate their power by providing feed in and feed out paths for electrical power and control signals. The polarized power connectors  116   a, b  can also be connected to a power collection unit when unitized photovoltaic assembly  100  is an original or terminal assembly. In this manner, minimal effort is required to wire the completed system. 
         [0036]    The preferred embodiment also includes at least one assembly spray head  118  attached to unitary frame  110 . Spray head  118  directs cleaning fluids into a spray pattern covering photovoltaic modules  102 . Spray head  118  is connected to tubing  120  by a “T” spray connector  122 . In an alternate embodiment, when spray head  118  is the final sprayer, spray connector  122  is an elbow instead of a “T”. Tubing  120  supplies alternately, clear and soapy water from a pressure source (not shown). Tubing  120  is also generally attached to the unitary frame  110  and terminates at the perimeter of unitized photovoltaic assembly  100  with fluid connectors  124   a, b.  Fluid connectors  124   a, b  allow cleaning fluid to flow to and from adjacent unitized photovoltaic assemblies  100 . 
         [0037]    The addition of elements to the unitary frame  110  in this manner provides for a plug-and-play unitized photovoltaic assembly  100 . This system allows for additional unitized photovoltaic assemblies  100  to be added with minimal connections and little or no additional wiring or tubing. Also, pre-wiring and the use of low-voltage power conversion elements  112  eliminates hazardous live wiring on the roof surface  150  creating a safer working environment. 
         [0038]    As referred to above, the main structural components of unitary frame  110  are rails  104  and struts  106 .  FIG. 3  illustrates the uniform structural cross-section of rails  104 . An extrusion process forms rails  104  with a uniform double “I” cross section designed to resist flexure. In the preferred embodiment, rails  104  are made from aluminum alloy, but other material having similar strength to weight properties could also be used. The structure of rails  104  provides U-shaped receiving slots  130  for retaining photovoltaic modules  102 . In the preferred embodiment, rails  104  are oriented laterally and substantially parallel to one another. When arranged in this manner, photovoltaic modules  102  can be slideably retained by their opposing edges within slots  130 . In the illustrated embodiment the slots  130  present smooth support surfaces upon which photovoltaic module edges can slide. The retained opposing edges of photovoltaic modules  102  can be either the long or short edges. Accordingly, the length and arrangement of rails  104  are determined by the dimensions, orientation and number of photovoltaic modules  102  to be retained. Additionally, rails  104  provide U-shaped receiving slots  132  for accepting mounting interlocks  170   a,b  and retaining brackets  140   a, b.  Rails  104  also include holes  136  for the securing of mounting interlocks  170   a, b  and retaining brackets  140   a, b.    
         [0039]      FIGS. 4A and 4B  more closely illustrate retaining brackets  140   a, b,  shown generally in  FIG. 1 . Retaining brackets  140   a,b,  laterally retain photovoltaic modules  102  within slots  130 . In the present embodiment, individual retaining bracket assemblies  140   a,b  comprise a retaining element  142  that engages the outer edge of the end most photovoltaic modules  102  in each row so as to block the photovoltaic modules from sliding out of the unitary frame  110 . Retaining element  144  is attached to an L bracket  144  by fastener  146 . L bracket  144  includes a threaded hole  148  for receiving fastener  146 . Removal of fastener  146  allows retaining element  142  to be disengaged from photovoltaic module  102 . This will allow partial or complete removal of photovoltaic modules  102  from unitary frame  110 . Furthermore, L bracket  144  is affixed to the ends of rails  104  within receiving slots  132 . Specifically, L bracket  144  includes holes  158 , which align with holes  136  on rails  104 . A bolt or other fastener engages holes  158  and holes  136  to secure L bracket  144  to rails  104 . The main deference between retaining brackets  140   a  and  140   b  is the orientation of L bracket  144 , depending on which side of rail  104  it is positioned. 
         [0040]    Additionally, during installation of unitized photovoltaic assembly  100  it may be helpful to disengage the retaining element  142  and slide photovoltaic modules  102  partially out of the unitary frame  110  in order to gain access to mounting brackets  152  or to additional elements of the system described above. As shown in  FIGS. 3 and 5B , the surfaces of the U-shaped receiving slot  130  in each rail  104  are flat and smooth, as are surfaces of the edges of the photovoltaic module  102 , thus enabling the photovoltaic modules  102  to slide relative to the unitary frame  110 . 
         [0041]      FIGS. 5A and 5B  show spacer  160 . Spacer  160  comprises a clip  162 , which attaches to photovoltaic modules  102 . Spacer  160  includes fins  164 . Fins  164  contact the edges of adjacent photovoltaic modules  102  thereby maintaining a gap  180 . Gap  180  is useful for allowing the expansion and contraction of photovoltaic modules  102  during temperature changes. Spacer  160  is sufficiently resilient to allow such expansion and contraction of the photovoltaic modules  102 . Additionally, gap  180  provides a space for lifting frame  190  to engage unitary frame  110 , discussed below. 
         [0042]      FIG. 6  shows the uniform structural cross-section of struts  106 , shown generally in  FIG. 2 . An extrusion process forms struts  106  with an “I” cross-section designed to resist flexure. Struts  106  are preferably made from aluminum alloy, but other material having similar strength to weight properties could also be used. The design of struts  106  provides U-shaped receiving slots  134  for accepting interlock elements  170 . Struts  106  also provide mounting surfaces for additional elements attached to unitary frame  110 , discussed above. In the present embodiment, struts  106  are oriented generally in the vertical direction to align with the roofs underlying rafters  154 . It is important to note that struts  106  must not be aligned with gaps  180  as this will prevent lifting frame  190  from engaging with unitary frame  110 . 
         [0043]    The preferred embodiment includes interlocks  170   a, b,  shown in  FIGS. 7A and 7B , in order to maintain a mechanical relationship between adjacent unitized photovoltaic assemblies  100 , thereby contributing to the structural integrity and load sharing capacity of the completed system. Interlocks  170   a, b  are attached to the ends of rails  104  and struts  106  within receiving slots  132  and  134 , respectively. Mounting interlocks  170   a,b  include holes  178 , which align with holes  136  or  138  depending on whether they are mounted to rails  104  or struts  106 . As shown in  FIG. 7A , interlocks  170  also provide a ledge  174 . Ledge  174  is positioned face up or face down in order to engage a corresponding adjacent ledge  174 . The interaction between adjacent interlocks  170   a,b  is more clearly demonstrated in  FIG. 7B . Interlocks  170   a, b  also include a locking hole  176  to accept a fastener  202 , thereby mechanically joining adjacent unitized photovoltaic assemblies  100 . Mounting interlocks  170   a  and  170   b  are mirrored so that corresponding locking holes  176  will align during the joining of unitized photovoltaic assemblies  100 . 
         [0044]    Also shown in  FIG. 7B , are mounting brackets  152  for securing unitized photovoltaic assembly  100  to a surface. Mounting brackets  152  are attached to rails  104  or struts  106  of the unitary frame  110 . During installation, mounting brackets  152  are secured to standard mounting devices  156  using bolts  208 . Prior to installation of the unitized photovoltaic assembly  100 , mounting devices  156 , are installed to the surface  150  and secured with lag bolts  206  to underlying rafters  154 .  FIG. 1  more broadly illustrates the use of mounting brackets  152  for securing unitary frame  110  to a surface  150 . In some instances, mounting devices  156  may not be required, in which case mounting brackets  152  can be directly attached to surface  150  or underlying rafters  154 , depending on the local building code. 
         [0045]      FIGS. 8 ,  9  and  10  relate to the structure and use of lifting frame  190 . Unitary frame  110  is designed to maintain the general structure of unitized photovoltaic assembly  100 , but it is not significantly rigid to support photovoltaic modules  102  independently. Merging lifting frame  190  with unitized photovoltaic assembly  100  provides the necessary rigidity to inhibit bending of unitary frame  100  and thereby prevents damage to photovoltaic modules  102  during installation. 
         [0046]    Lifting frame  190  comprises a framework having a plurality of tabs  192  and rail supports  194   a, b  for engaging unitary frame  110 . More specifically, tabs  192  pass through gaps  180  to engage corresponding horizontal rails  104 . Vertical rail supports  194   a  are comprised of two “C” channels oriented back to back with tabs  192  positioned between them. Tabs  192  are secured to rail supports  194   a  with bolts  212 , as shown in  FIG. 10 . Horizontal cross rail supports  194   b,  also “C” channels, are attached to the horizontal rail supports  194   a  with bolts  210 . Bolts  210  and  212  are used to allow for lifting frame  190  to be adjusted for unitized photovoltaic assemblies  100  of varying sizes. For large assemblies  100  additional rail supports  194   a  can be added including additional tabs  192 . 
         [0047]    In the preferred embodiment, lifting frame  190  is connected to a crane hook  200  by cables  198  attached to holes  196 , as shown in  FIG. 9 . The cables  198  can be attached to different holes  196  and repositioned in relation to the crane hook  200  to achieve varying angles in order to match the slope of the installation surface  150 . After unitized photovoltaic assembly  100  is installed on the roof or other surface  150 , lifting frame  190  is disengaged from unitized photovoltaic assembly  100  and re-used. 
         [0048]    Although the present invention has been described in accordance with the embodiments shown and contains many specifics, these descriptions should not be construed as limiting the spirit of the invention or scope of the appended claims.