Abstract:
The disconnection mechanism  116  is disclosed to disconnect solar cells  5, 105  from high voltage DC cables  13, 113  which may run through the interior of a building  1  and thus represent a hazard to emergency service personnel such as firemen attending a fire in daylight hours. Thus the DC output from the cells  5, 105  can be rendered safe. The mechanism is located in an elevated position adjacent the solar cells  5, 105  but is operable by an elongated actuator  19, 119  which extends to ground level. Preferably the solar cells are individually connected via corresponding cables  223  to a terminal block  118  within a fireproof housing  117  for the disconnect mechanism  116.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from Australian Patent Application Serial No. 2011 900 984 filed on Mar. 7, 2011. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to the installation of solar cells and, in particular, to the installation of solar cells in a manner which is safe in the event of a fire engulfing the structure on which solar cells are mounted. 
         [0003]    Solar cells need to be mounted so as to receive solar radiation and for this reason are often mounted on the roof of a building. Irrespective of whether the building has one or more stories, the roof is at an elevated position which is generally difficult to access. The solar cells generate a DC output and are connected by means of a DC cable to an inverter which converts the DC output (typically 400V DC and up to approximately 15 amps) into an AC output (typically 240V or 110V) which is either used within the building or is injected into an AC mains supply. The inverter and the AC switchboard, with which it is connected, are generally located at ground level at a position which is able to be accessed in a convenient manner. Depending upon the nature of the building and the installation, the DC cable often extends through the roof cavity of the building, through cavities between walls, and the like. The route of the DC cable is generally not marked and very often the cable will have been installed after the building has been constructed. 
         [0004]    In the event of a fire, the fire brigade personnel arriving at the building will disconnect the wiring of the building from the AC mains supply, if this has not already been done by an occupant of the building or some other person who has raised the fire alarm. However, during the daylight hours, the output of the solar cells will continue to be produced notwithstanding that a fire may be raging within the building. As a consequence, the fire brigade personnel attending the fire are potentially exposed to an electrical hazard in the form of the energized DC cable which will remain energized until such time the solar cells are effectively destroyed by the fire. 
         [0005]    The genesis of the present invention is a desire to reduce the exposure of firemen and such emergency personnel to DC electrical hazards caused by the presence of solar cells mounted on buildings and similar structures. 
       SUMMARY OF THE INVENTION 
       [0006]    In accordance with a first aspect of the present invention there is disclosed a solar cell installation comprising at least one solar cell mounted in an elevated position to receive solar radiation, said solar cell having a DC output connected via a DC cable to an inverter to convert said DC output into an AC output, wherein a cut-out switch is located in an elevated position adjacent said solar cell(s) and is operable to disconnect said DC output from said DC cable, and wherein said cut-out switch adjacent said elevated position is operable by an elongated actuator which extends from said cut-out switch to an un-elevated position at, or near, ground level. 
         [0007]    In accordance with a second aspect of the present invention there is disclosed a method of isolating at least one solar cell mounted in an elevated position to receive solar radiation and producing a DC output, said method comprising: interposing a cut-out switch in a DC cable interconnecting said solar cells with an inverter to produce an AC output, said cut-out switch being located in an elevated location adjacent said solar cells and being operable to disconnect said DC output from said DC cable, connecting said cut-out switch to an elongated actuator which extends from said cut-out switch to an un-elevated position at, or near, ground level, and operating said actuator to disconnect said DC cable from said solar cell. 
         [0008]    In accordance with a third aspect of the present invention there is disclosed a cut-out switch operable remotely by an elongated actuator, said switch comprising a fireproof housing, a switch located inside said housing, and an elongated actuator having two ends, one end being connected with said switch to open and close same and the other end of said actuator having an operating handle means. 
         [0009]    In accordance with a fourth aspect of the present invention there is disclosed a solar cell installation including the abovementioned cut-out switch. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention will hereinafter be described in conjunction with the appended drawing figures wherein like numerals denote like elements. 
           [0011]      FIG. 1  is a perspective view of a two story building having a roof upon which solar cells are mounted and isolated in accordance with a first embodiment; 
           [0012]      FIG. 2  is a schematic cross-sectional view showing the mounting of the solar cells of  FIG. 1  and the operation of the actuator to disconnect same; 
           [0013]      FIG. 3  is a perspective view of the open housing in which the cut-out switch of  FIGS. 1 and 2  is mounted; 
           [0014]      FIG. 4  is a perspective view of a two story building having a roof upon which solar cells are mounted and isolated in accordance with a second embodiment; 
           [0015]      FIG. 5  is a schematic perspective view of the open housing in which the cut-out switch of the second embodiment is mounted; 
           [0016]      FIG. 6  is a perspective view of the lower end of the actuator; and 
           [0017]      FIG. 7  is a view similar to  FIG. 5  but showing the cut-out switch opened. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    The ensuing detailed description provides preferred exemplary embodiments only, and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the ensuing detailed description of the preferred exemplary embodiments will provide those skilled in the art with an enabling description for implementing the preferred exemplary embodiments of the invention. It being understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the invention, as set forth in the appended claims. 
         [0019]    To aid in describing the invention, directional terms are used in the specification and claims to describe portions of the present invention (e.g., upper, lower, left, right, etc.). These directional definitions are merely intended to assist in describing and claiming the invention and are not intended to limit the invention in any way. In addition, reference numerals that are introduced in the specification in association with a drawing figure may be repeated in one or more subsequent figures without additional description in the specification in order to provide context for other features. 
         [0020]    As seen in  FIG. 1 , a building  1  has an upper story  2  and a ground floor  3 . The upper story  2  has a roof  4  upon which a number of solar cells  5  are mounted so as to receive solar radiation. 
         [0021]    Mounted at ground level is an inverter  8  which is connected to an AC mains supply  9  which takes the form of an underground cable which leads to a housing  10  which includes both the inverter  8  and an AC switchboard  11 . A DC cable  13  interconnects the inverter  8  with a junction box  14  located adjacent the solar cells  5 . In the prior art the junction box  14  and the DC cable  13  are directly connected and so the DC cable  13  is always energized for so long as solar radiation falls on the solar cells  5 . 
         [0022]    In the prior art, this has the consequence that in the event of a fire, even though the AC switchboard  11  may be disconnected from the AC mains supply  9 , the DC cable  13  which runs through the roof cavity and a wall cavity is still energized with the output of the solar cells. 
         [0023]    In order to overcome this problem in accordance with the first embodiment of the present invention, a cut-out switch  16  having a housing  17  is mounted under the eave of the roof  4 . The housing  17  is therefore in an elevated position but is provided with an elongated actuator  19  having a handle  20  which is able to be operated by a fireman  22  ( FIG. 2 ) at ground level so as to disconnect the DC cable  13  from the output of the solar cells  5 . 
         [0024]    It will be apparent from  FIG. 2  that the DC cable  13  extends through the interior of the building  1  and, if not de-energized, represents an electrical hazard to emergency personnel such as the fireman  22  called to fight a fire, for example. 
         [0025]    Turning now to  FIG. 3 , the housing  17  and cut-out switch  16  are illustrated. The housing  17  is preferably fire resistant and contains terminals to which are connected the DC cable  13  on one side, and the solar cell cable  23  on the other side. The DC cable  13  is preferably fire rated. The elongated actuator  19  comprises a Bowden cable, or similar, having an outer sleeve  25  and an inner cable  26 , the lower end of which is connected to the handle  20 . It will be apparent that pulling the handle  20  downwardly disconnects the solar cell cable  23  from the DC cable  13 . 
         [0026]    Preferably, in this embodiment, pushing the handle upwardly does not reconnect the two cables. Thus only disconnection can take place from ground level thereby rendering the interior of the building  1  undoubtedly safe once the disconnection has taken place. Furthermore, the handle  20  in the pulled down position provides a non-transient mechanical signal that the solar cells have been isolated. In addition, the mechanical actuator  19  can be relied upon to function reliably notwithstanding the heat of any fire. 
         [0027]    Turning now to  FIGS. 4-7 , in the description of the second embodiment, like components have been allocated a designation number increased by 100 relative to the description of the first embodiment in relation to  FIGS. 1-3 . 
         [0028]    As seen in  FIG. 4 , as before building  101  has an upper story  102  and a ground floor  103 . The upper story  102  has a roof  104  upon which a number of solar cells  105  are mounted so as to receive solar radiation. 
         [0029]    Mounted at ground level is an inverter  108  which is connected to an AC mains supply  109  which takes the form of an underground cable which leads to a housing  110  which includes both the inverter  108  and an AC switchboard  111 . A DC cable  113  interconnects the inverter  108  with a housing  117 . Located within the housing  117  is a cut-out switch  116 . The housing  117  is in an elevated position and is provided with an elongated actuator  119  having a handle  120  (illustrated in more detail in  FIG. 6 ) and which is able to be operated by a fireman  122  ( FIG. 4 ) at ground level so as to disconnect the DC cable  113  from the output of the solar cells  105 . 
         [0030]    Turning now to  FIG. 5 , the housing  117  and cut-out switch  116  are illustrated. The housing  117  is preferably fire resistant and contains a terminal block  118  to which are connected a DC high voltage cable  130  on one side, and the solar cell cable(s)  123  on the other side. 
         [0031]    There are two possible ways of connecting the solar cells  105 . Traditionally, such cells have been connected together in series so that the solar cell cable  123  leading into the housing  117  carries a maximum DC voltage (and hence a minimum current). Under these circumstances, the solar cell cable  123  and the DC high voltage cable  130  have the same voltage and are simply connected together at the terminal block  118 . 
         [0032]    An alternative way of connecting the solar cells  105 , which is much to be preferred, is that each cell  105  has an individual cable as illustrated in  FIG. 4  and that all the individual cables  223  are terminated at the terminal block  118 . This arrangement is indicated by broken lines in  FIG. 7 . Under these circumstances, the individual solar cell cables  223  each carry the individual cell voltage and it is only the DC high-voltage cable  130  and the DC cable  113  which are at the high DC voltage. This provides an additional safety benefit. The solar cell cable(s)  123 ,  223  and the DC cables  113  and  130  are preferably fire rated. 
         [0033]    The elongated actuator  119  comprises a Bowden cable, or similar, having an outer sleeve  125  and an inner cable  126  the lower end of which is connected to the handle  120 . The inner cable  126  is connected to the lower part of a double pole cut-out switch  116  via a plate  131 . A cam  132  is also mounted on the plate  131  so as to rotate a pivoted flag  133 . With the handle  120  of  FIG. 6  in the upward position illustrated in  FIG. 6 , the cut-out switch  116  is connected as illustrated in  FIG. 5 , and the flag  133  points vertically downwards. However, pulling the handle  120  downwardly as seen in  FIG. 6  moves the plate  131  of  FIG. 5  downwardly thereby opening the double pole cut-out switch  116  and rotating the flag  133  into a horizontal position as seen in  FIG. 7  (and in  FIG. 4 ). As a consequence, the solar cells  105  are disconnected from the DC cable  113 . Further, the flag  133  has one side painted differently from the other so as to clearly indicate the disconnection to those at ground level. 
         [0034]    It will be apparent that in this embodiment, pushing the handle  120  upwardly does reconnect the cut-out switch  116  and thus does reconnect the two cables  113  and  130 . However, the flag  133  is, under these circumstances, rotated back to the vertical position illustrated in  FIG. 5  and thus the re-connection is apparent. As seen in  FIG. 6 , the handle  120  includes holes  135  adapted to enable the handle  120  to be locked in the cable disconnected position. As before, the inner cable  126  can be relied upon to function reliably, notwithstanding the heat of any fire. 
         [0035]    As seen in  FIG. 4 , both the DC cable  113  and the solar cell cables  123  do not extend through the interior of the building  100  and thus do not constitute an electrical hazard to any emergency personnel such as the fireman  122  called to fight a fire, for example, and who enter the interior of the building. However, this desirable wiring practice will not be previously known, in general, to such emergency personnel. 
         [0036]    The foregoing describes only two embodiments of the present invention and modifications, obvious to those skilled in the fire fighting arts, can be made thereto without departing from the scope of the present invention. 
         [0037]    For example, the junction box  14  can be located between the roof  4  and the solar cells  5 , or can be located within the ceiling cavity below the roof. Similarly, the cut-out switch housing  17  can be located between the roof  4  and the solar cells  5 , or can be located in the ceiling cavity. If the housing  17  is located within the building, the actuator  19  can be located within the building also, or can extend through an eave or wall to the exterior of the building. Furthermore, the actuator  119  is preferably arranged to have its handle  120  located adjacent the inverter  108  and AC switchboard  111 , as illustrated in  FIG. 4 , so that all electrical controls are close to each other. 
         [0038]    The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “including” or “having” and not in the exclusive sense of “consisting only of”. 
         [0039]    While the principles of the invention have been described above in connection with preferred embodiments, it is to be clearly understood that this description is made only by way of example and not as a limitation of the scope of the invention.