AU2013200939A1 - Safety Improvements for Solar Panels - Google Patents

Abstract

Abstract A solar panel is provided that has load terminals for connection to other solar panels to thereby form an array of solar panels. The solar panel includes a remotely controllable isolator assembly for disconnecting one or more of the load terminals from photovoltaic cells of the panel in order to prevent safety personnel such as firefighters being exposed to potentially lethal voltages in an emergency situation. SOLAR PANEL TERMINATION BOX 16 Load Plug 16VDI Load Socket Control Plug Control Socket 25 OM SWITCH - 23 RELAY 4 2 L _ ___1 SOLAR PANEL TERMINAfTON & EMERGENCY ISOLATOR BOX Figure 4

Description

AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION SAFETY IMPROVEMENTS FOR SOLAR PANEL ARRAYS The following statement is a description of the invention: 1 SAFETY IMPROVEMENTS FOR SOLAR PANEL ARRAYS TECHNICAL FIELD [001] The present invention is directed to a safety improvement for solar panel arrays. An aspect of the present invention is directed to a solar panel having an improved safety feature. BACKGROUND ART [002] Any references to methods, apparatus or documents of the prior art are not to be taken as constituting any evidence or admission that they formed, or form part of the common general knowledge. [003] The use of panels of solar photovoltaic cells to generate electricity in suburban situations has become relatively widespread over the last decade. In response to awareness of climate change there has been a desire to move away from reliance on coal and other carbon emitting methods of power generation. As a result there have been government grants and other initiatives to encourage city dwellers to install solar panels. [004] Solar panels comprise arrays of solar cells, or as they are also called "P.V. cells" that are typically installed on house roofs. Figure 1 for example shows a typical suburban installation comprising eight solar panels 2a to 2h. [005] Nowadays many solar panel installations are so called grid feeding systems in that they are arranged to feed into an inverter, which in turn feeds power back through a meter into the local electricity grid.

2 [006] Since the local electricity grid maintains a potential of 220 to 270 volts AC, inverters typically require that the array of solar panels provides an output of at least 250V DC, and preferably approximately 360VDC in order for the inverter to operate correctly. In order to provide such a large voltage across the array it is necessary for a number of the panels, which typically develop 24 to 36V each, to be connected in series. [007] Figure 2 depicts a typical wiring circuit for connecting an array of solar panels 2a,..,2n to an inverter 8. The solar panels have been connected in series, as indicated by series connections 4a and 4b, and in parallel as indicated by parallel connections 6a and 6b. The solar panels are typically connected to the inverter 8 via an overvoltage isolator 10 which acts to electrically isolate the solar panels from the inverter 8 in the event of the voltage "V" across the solar panels exceeding a safe level for the inverter 8. The output side of the inverter 8 typically supplies electricity to an electricity metering and distribution box for redistribution back into the local electricity grid. [008] A problem that is associated with an installation such as that discussed with reference to Figures 1 and 2 is that in the event of an emergency, such as a fire, a large DC potential V will be present across the solar panel array even if the overvoltage protection 10 is tripped. Smaller voltages will also be present across two or more of the panels that remain in series connection. These smaller voltages may also be sufficient to cause injury. [009] Usually in the event of a fire where no solar array is installed, firemen and women need only disconnect the overhead fuse at the power pole or the main switch at the property's meter box in order to disconnect power from the burning residence. However, where it is still daylight and a solar panel array is present, a high potential voltage, and 3 so a possibility of electrocution remains on the premises even after the overhead fuse and/or the main switch have been disconnected. [0010] It will be realized that there is a need for a solution that addresses the above described problem or which is at least a useful alternative to those approaches to overcoming the problem that have been employed in the past. SUMMARY OF THE INVENTION [0011] According to a first aspect of the present invention there is provided a solar panel having load terminals for connection to other solar panels to thereby form an array of solar panels, said solar panel including a remotely controllable isolator assembly for disconnecting one or more of the load terminals from photovoltaic cells of the panel. [0012] In a first embodiment of the invention the remotely controllable isolator assembly includes a current controlled relay arranged to operate a switch for open circuiting at least one of the load terminals. [0013] Preferably said relay is a normally open relay and is arranged, in response to a control current therethrough, to maintain the switch in a closed circuit position whereby said load terminals are placed in-circuit with the photovoltaic cells. [0014] Alternatively, the remotely controllable isolator assembly may comprise a voltage controlled solid state isolating device. [0015] In a preferred embodiment of the invention the remotely controllable isolator assembly includes a sensor switch that is arranged to change state from open circuit to closed circuit, or vice versa, in response to sensing a parameter associated with destructive fires, for example temperature of smoke, wherein the isolator is responsive to the sensor switch.

4 [0016] According to a further aspect of the present invention there is provided an array of solar panels including: a. an electrical isolator associated with each of said panels and arranged to selectively decouple at least one load terminal of its associated panel; b. a control module remote from the array arranged to transmit a signal for said electrical isolator to selectively decouple said load terminal ; c. at least one control link arranged to communicate a control signal from the control module to said electrical isolator of each of said panels; d. whereby upon operating the control module each of the at least one load terminals is selectively decoupled from photovoltaic cells of its panel. [0017] The at least one control link may comprise a conductor for electrical current that interconnects the electrical isolators in series. [0018] Alternatively, the at least one control link may comprise a plurality of conductors that connect corresponding ones of the electrical isolators to the control module in parallel. BRIEF DESCRIPTION OF THE DRAWING [0019] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows: 5 [0020] Figure 1. is a view of a house fitted with an array of solar panels as is known in the prior art. [0021] Figure 2 is a schematic diagram of an array of solar panels wired to a DC to AC inverter as is known in the prior art. [0022] Figure 3 is a schematic diagram of an array of solar panels incorporating a safety system according to a preferred embodiment of the invention. [0023] Figure 4 is a diagram depicting a solar panel according to a preferred embodiment of the present invention. [0024] Figure 5 is a diagram depicting a solar panel according to a variation of the preferred embodiment of the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0025] Referring now to Figure 3, in accordance with a preferred embodiment of the present invention, each of the solar panels 2a,..,2n is fitted with a corresponding isolator 12a,..,12n. In a first embodiment, as shown in figure 4 a frame 13 of the solar panel 2 supports a plurality of PV cells 15 as are known in the prior art. The PV cells are connected to terminals 17 and 19 of an isolation module 12 according to a preferred embodiment of the invention. The isolation module 12 is also housed within frame 13 of solar panel 2. [0026] Supply electrical terminals 18 (Socket Load) and 20 (Plug Load) are provided for transferring electrical power from the solar panel. These terminals 18 and 20 are used to connect the solar panel 2 in series or parallel with other panels to form the array of panels shown in Figure 3. In addition to the supply electrical terminals 18 and 20, control plug 25 and control socket 23 are also provided. The control plug 25 and control socket 23 are arranged to convey a control current Relay through relay 14. The relay 14 in turn operates isolating switch 16 in order to isolate the supply socket 18 from the PV cells 15 if required.

6 [0027] The isolator 12 comprises a box that houses the normally open relay 14, which during standard use of the panel is energised by a current Irelay so that switch 16 is closed. The current Irelay is generated by a control module 22 shown in Figure 3. Closing switch 16 places the socket load terminal 18 in circuit with the photovoltaic cells 15 of the panel 2 so that the potential difference generated by the photovoltaic cells is placed across load socket 18 and load plug 20. In the absence of energisation current Irelay the relay 14 assumes its normally open configuration and so switch 16 becomes open circuit. Consequently the potential difference 15 due to the PV cells is no longer present across socket load terminal 18 and plug load terminal 20. [0028] The current Irelay may be turned off, in order to de-energize relay 14 and thus open switch 16, either by means of control box 22 or by virtue of a sensor switch such as thermo switch 24. Alternatively, other types of sensor switches, such as a smoke sensor switch, might alternatively be used. The thermo switch 24 is in series between relay 14 and control plug 25 and is configured to become open circuit in response to a high temperature, for example due to a house fire. Upon the thermo switch 24 becoming open circuit the current Irelay ceases to flow so that relay 14 assumes its normally open state and opens switch 16. It will be realized that switch 16 will typically be integrated into the relay 14. [0029] It will therefore be understood that, in use, upon a fire breaking out in a house that has an array of solar panels installed with the isolator units 12 controlled by control module 22 that firefighters can, by means of control module 22, isolate all of the solar panels 2 and thereby deactivate the potential difference V across the solar array. Furthermore, in the event of the fire becoming entrenched the thermo switches 24 in each isolator unit 12 will independently and automatically cause the isolation to occur without the control module having to be manually operated.

7 [0030] Referring now to Figure 5, there is depicted a further embodiment of the invention in which a voltage controlled, solid state relay is employed in place of the electro-mechanical relay of Figure 4. Consequently the thermo switch 24 has been placed in a parallel configuration for voltage difference triggering of the solid state relay. [0031] In the embodiment shown in Figure 3 a single control loop 31 is used to supply a control current to all of the isolator modules 12a,..,12n, which are connected in series. It will be realized that in other embodiments of the invention the isolator units might be controlled via separate control lines or even by one or more wireless links. [0032] Any embodiment of the invention is meant to be illustrative only and is not meant to be limiting to the invention. Therefore, it should be appreciated that various other changes and modifications can be made to any embodiment described without departing from the spirit and scope of the invention.

Claims (10)

1. A solar panel having load terminals for connection to other solar panels to thereby form an array of solar panels, said solar panel including a remotely controllable isolator assembly for disconnecting one or more of the load terminals from photovoltaic cells of the panel.

2. A panel according to claim 1, wherein the remotely controllable isolator assembly includes a current controlled relay arranged to operate a switch for open circuiting at least one of the load terminals.

3. A panel according to claim 2, wherein said relay is a normally open relay and is arranged in response to a control current therethrough, to maintain the switch in a closed circuit position whereby said load terminals are placed in-circuit with the photovoltaic cells.

4. A panel according to claim 1, wherein the remotely controllable isolator assembly comprises a voltage controlled solid state isolating device.

5. A panel according to any one of the preceding claims, wherein the remotely controllable isolator assembly includes a sensor switch that is arranged to change state from open circuit to closed circuit, or vice versa, in response to a parameter associated with destructive fires, such as smoke or temperature, wherein the isolator is responsive to the sensor switch.

6. An array of solar panels including: an electrical isolator associated with each of said panels and arranged to selectively decouple at least one load terminal of its associated panel; a control module remote from the array arranged to transmit a signal for said electrical isolator to selectively decouple said load terminal ; and at least one control link arranged to communicate a control signal from the control module to said electrical isolator of each of said panels; whereby upon operating the control module each of the at least one load terminals is selectively decoupled from photovoltaic cells of its panel. 9

7. An array of solar panels according to claim 6, wherein the at least one control link comprises a conductor for electrical current that interconnects the electrical isolators in series.

8. An array of solar panels according to claim 6, wherein the at least one control link comprises a plurality of conductors that connect corresponding ones of the electrical isolators to the control module in parallel.

9. A solar panel substantially as described herein with reference to Figure 4 or Figure 5.

10. An array of solar panels in combination with a control module substantially as described herein with reference to Figure 3.