This application claims priority from Australian Patent Application Serial No. 2011 900 984 filed on Mar. 7, 2011.
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.
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.
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.
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.
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.
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.
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.
In accordance with a fourth aspect of the present invention there is disclosed a solar cell installation including the abovementioned cut-out switch.
The present invention will hereinafter be described in conjunction with the appended drawing figures wherein like numerals denote like elements.
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.
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.
As seen in
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.
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.
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 (
It will be apparent from
Turning now to
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.
Turning now to
As seen in
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
Turning now to
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.
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
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
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
As seen in
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.
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
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”.
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.
Number | Date | Country | Kind |
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2011 900 984 | Mar 2011 | AU | national |