Residential solar power generation system

Abstract

The invention relates to a system for supplying solar power to a load 306 in a residential building. The system consisting of a solar panel (PV) arrangement 202 connected in series with a DC isolator

Description

This invention relates to a renewable solar power generation system and in particular, but not limited to, a renewable solar power generation system for implementation in residential buildings having multiple solar generation sub-systems combined together to provide a whole-residence power generation system. BACKGROUND Use of fossil fuels is widely known to negatively contribute to climate change. In response, there have been increasing developments in the field of renewable or “green” power generation, which aim to lessen the climate crisis. A popular method of renewable power generation is solar power, by which electrical power is generated using solar panels. Current residential solar power systems include solar panels mounted to a residential roof and a battery, such as a Lithium battery, for example, to store generated power. The battery may then supply power to the residence in periods of low sunlight or overnight. However, these batteries are often large and bulky, presenting a problem for homeowners in terms of storage. Further, the manufacture of such batteries requires sourcing of elements, such as Lithium, which must typically be sourced from abroad. Moreover, the cost of the battery, in addition to the installation of the solar panels themselves, can be prohibitively expensive for homeowners looking to make their residence more environmentally friendly. Accordingly, there is a need for a residential solar power generation system which is able to operate without a battery. SUMMARY This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. In a first aspect, embodiments relate to a system for controlling a supply of solar power to a load. The system may comprise a solar panel arrangement operatively connected in series to a direct current isolator; and an arc fault detection device, a thyristor and the load connected in series with the direct current isolator, wherein the thyristor is configured to conduct electrical current from the solar panel arrangement to the load when a load current of the solar panel arrangement is greater than a latching current of the thyristor. This system may allow for independent powering of residential heating devices, including storage heaters, immersion heaters, ovens, pizza ovens, etc. Use of a direct current isolator allows for safe disconnection of the solar array during maintenance operations. Use of the AFDD allows for protection from arc faults. When the load current of the solar panel arrangement is greater than the latching current of the thyristor, the thyristor may be switched ‘on’, allowing for powering of the load using power generated by the solar panel arrangement. Preferably, the thyristor is configured to electrically disconnect the solar panel arrangement from the load when the load current of the solar panel arrangement is less than a holding current of the thyristor. Optionally, the load is a single cycle immersion heater. Preferably, the load is a storage heater comprising a heating element. Optionally, the load comprises at least two heating elements arranged in parallel. Optionally, each of the at least two heating elements has a power of 750W. Optionally, the storage heater comprises a thermal cutout bridge and a bi-metal thermostatic switch. The combination of the thermal cutout bridge and the bi-metal thermostatic switch may allow for bridging of components to prevent switching to open circuit and preventing a remaining arc across the contacts. Preferably, the solar panel arrangement comprises at least two photovoltaic cells arranged in a series array. Optionally, the solar panel arrangement comprises five photovoltaic cells arranged in a series array, wherein each of the five photovoltaic cells generates 5kW of power. Preferably, the system further comprises a thyristor control circuit configured to control conduction of electrical current through the thyristor. Optionally, the thyristor control circuit comprises a contactor and a snubber circuit, which are configured to actuate switching on and off of the thyristor. Preferably, the thyristor control circuit comprises a class D forced commutation circuit, which is configured to actuate switching on and off of the thyristor. Optionally, the class D forced commutation circuit comprises a primary thyristor and an auxiliary thyristor arranged in parallel. Preferably, the auxiliary thyristor is configured to switch the primary thyristor between an ‘on’ and ‘off’ state. Optionally, the system further comprises a storage battery. This may allow for storage of electricity for night-time and low sunlight hours. Preferably, the system further comprises a plurality of cables used to connect the various components of the system. Optionally, the plurality of cables are fire-resistant cables. Optionally, the plurality of cables comprise a mineral insulated copper sheath cable or a thermosetting steel wire armour (SWA). Preferably, the system further comprises a solid state DC relay. Optionally, the system further comprises an auxiliary contact and a thermostat control switch. Preferably, the system further comprises an AC transfer system, wherein the auxiliary contact and the thermostat control switch are configured to facilitate connection of the AC transfer system into the system. Optionally, the auxiliary contact and the thermostat control switch are configured to disable the thyristor connected in series with the load and the direct current isolator. Preferably, the solar panel arrangement is mounted to a residential roof. BRIEF DESCRIPTION OF THE DRAWINGS Specific embodiments of the disclosed technology will now be described in detail with reference to the accompanying figures. Like elements in the various figures are denoted by like reference numerals for consistency. Figure 1 shows a solar power generation system installed on a residential building in accordance with one or more embodiments. Figure 2 shows a circuit diagram of a residential solar power generation sub-system in accordance with one or more embodiments. Figure 3 shows a circuit diagram of a residential solar power generation sub-system in accordance with one or more embodiments. Figure 4 shows a circuit diagram of a thyristor control circuit in accordance with one or more embodiments. Figure 5 shows a circuit diagram of a thyristor control circuit in accordance with one or more embodiments. Figure 6 shows a circuit diagram of a class D forced commutation circuit in accordance with one or more embodiments. DETAILED DESCRIPTION In the following detailed description of embodiments of the disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the disclosure. However, it will be apparent to one of ordinary skill in the art that the disclosure may be practiced without these specific details. I n other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description. Throughout the application, ordinal numbers (e.g., first, second, third, etc.) may be used as an adjective for an element (i.e., any noun in the application). The use of ordinal numbers is not to imply or create any particular ordering of the elements nor to limit any element to being only a single element unless expressly disclosed, such as using the terms “before,” “after,” “single,” and other such terminology. Rather, the use of ordinal numbers is to distinguish between the elements. By way of an example, a first element is distinct from a second element, and the first element may encompass more than one element and succeed (or precede) the second element in an ordering of elements. In the following description of Figures 1-7, any component described regarding a figure, in various embodiments disclosed herein, may be equivalent to one or more like-named components described with regard to any other figure. For brevity, descriptions of these components will not be repeated regarding each figure. Thus, each and every embodiment of the components of each figure is incorporated by reference and assumed to be optionally present within every other figure having one or more like-named components. Additionally, in accordance with various embodiments disclosed herein, any description of the components of a figure is to be interpreted as an optional embodiment which may be implemented in addition to, in conjunction with, or in place of the embodiments described with regard to a corresponding like-named component in any other figure. It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Terms such as “approximately,” “substantially,” etc., mean that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide. Turning to Figure 1, there is shown a solar power generation system installed on a residential building 100. The solar power generation system includes photovoltaic cells 102, commonly referred to as solar panels, installed on the roof of the residential building 100. In one or more embodiments, the photovoltaic cells 102 may be arranged from multiple solar panels, to form a series array. The photovoltaic cells 102, for example, may have a solar output of 460 Watts and a voltage output of 50 Volts. The skilled person will be aware, however, that many different types of solar panels exist and that any photovoltaic cell may be used without departing from the scope of this disclosure. Turning now to Figure 2, there is a circuit diagram of a residential solar power generation sub-system 200 in accordance with one or more embodiments. In particular, sub-system 200 may be used to power a storage heater 212. One or more photovoltaic cells 202 may be arranged in series. For example, in one or more embodiments, five photovoltaic cells may be arranged to form a series array. In some embodiments, all photovoltaic cells 202 in the series array may be identical in terms of solar output. For example, when five photovoltaic cells are arranged in series, each photovoltaic cell may generate 5kW of power. However, the skilled person will be aware that many different combinations of types of photovoltaic cells may be used depending on the power needs of the residential building. The series array of photovoltaic cells 202 may produce direct current (DC) electricity, which may have a voltage 204 of 230 Volts. The DC electricity may then pass through a PV Array DC Isolator 206. The skilled person will be aware that a DC Isolator 206 may be installed to allow for safe disconnection of a solar array during maintenance operations. The electricity may then pass through an Arc Fault Detection Device (AFDD) 208, which may refer to a protective device installed to provide protection from arc faults. The electricity may then flow to a storage heater 212. In one or more embodiments, the storage heater 212 may include one or more elements 214 arranged in parallel. For example, in some embodiments, there may be two or three elements 214 arranged in parallel. The elements 214, for example, may have a power of 750 Watts. However, the skilled person will understand that many different types of element may be used to suit the demands of the residential building, and that any combination of elements may be used without departing from the scope of this disclosure. The storage heater 212 may also include a thermal cutout bridge 216 and a bi-metal thermostatic switch, which may be bridged to prevent switching to open circuit. Without such bridging, for example, an arc may remain across the contacts. A plurality of cables 210 may be used to connect the various electrical components within the circuit. In one or more embodiments, a fire-resistant cable, also referred to as a firetuff cable, may be used. However, there may also be embodiments in which a mineral insulated copper sheath cable or a thermosetting steel wire armour (SWA) may be used. Further, electrical apparatus enclosures may be composed of metal and electrical connections may be terminated in porcelain terminals. Turning now to Figure 3, there is shown a circuit diagram of a residential solar power generation subsystem 300 in accordance with one or more embodiments. In particular, sub-system 300 may be used to power load element 306. Similarly to sub-system 200, one or more photovoltaic cells 202 may be arranged in series. For example, in one or more embodiments, five photovoltaic cells may be arranged to form a series array. The series array of photovoltaic cells 202 may produce direct current (DC) electricity, which may have a voltage 204 of 230 Volts. The DC electricity may then pass through a PV Array DC Isolator 206. The skilled person will be aware that a DC Isolator 206 may be installed to allow for safe disconnection of a solar array during maintenance operations. The electricity may then pass through an Arc Fault Detection Device (AFDD) 208, which may refer to a protective device installed to provide protection from arc faults. A SCR thyristor 302 and corresponding thyristor control circuit 304 may be connected to the AFDD 208. The skilled person will be aware that a SCR thyristor 302 may act as a switching device, allowing for connection and disconnection of load element 306 according to demand. The load element 306 may be a household appliance comprising a heating element. For example, the load element 306 may be a kettle, a stove, an immersion heater, or a storage heater. Further, in one or more embodiments where the load element 306 is a storage heater, the storage heater may be rotated onto its back, or may have a middle brick which may be accessed via a cover, such that the storage heater may be used as an oven, such as a pizza oven or a kindling oven. In one or more embodiments, more than one load element 306 may be connected, each load element 306 being connected in parallel. In these embodiments, each load element 306 may have a corresponding SCR thyristor 302 and thyristor control circuit 304. Figure 4 shows a circuit diagram of a thyristor control circuit 400 in accordance with one or more embodiments. In one or more embodiments, the thyristor control circuit 304 shown in Figure 3 may be thyristor control circuit 400. The SCR thyristor 302 may connect to the thyristor control circuit 400 via a push button 403 between the gate 402 and the cathode 404. A first timer block 406 may be connected to the gate 402 and the cathode 404. In one or more embodiments, isolation of the load element 306 may be interlocked with triggering of the gate 402, where the trigger is the operation of push button 403, during disabling of the system. Such an arrangement may be considered an automatic safety arrangement and may be accomplished by disconnecting a power source, such as power source 405, which may be a 3 Volt battery, for example. Disconnection of power source 405 may be accomplished by switch 407, for example. Disabling of the system may also be used in situations where an AC transfer system is incorporated, which would require the SCR thyristor 302 to remain in an “off’ state. In one or more embodiments, the time delay of timer block 406 may be 0.2 seconds. However, the skilled person will understand that many different time delays may be used, and this example is not intended to be limiting in any way. Timer block 406 may include three output ports: a positive output 408, a negative output 410, and an X1 output 412. The X1 output 412 may be connected to a switch 414, which may toggle between an “on” position 414a and an “off’ position 414b. For example, in Figure 4, the switch 414 is in the off position 414b. When in the off position 414b, the switch 414 allows for connection ofthe first timer block 406 to a second timer block 416 at the X1 output 418. The second timer block 416 may have a time delay of, for example, 1 second. The second timer block 416 may also include a push button 419, which provides a connection to a power supply 420. In one or more embodiments, the power supply 420 may provide a voltage of 12 Volts, for example. The negative terminal of power supply 420 may connect to a relay coil 422, which provides a connection to a first contactor 424. The skilled person will be aware that a contactor, such as first contactor 424, is a switching device designed to repeatedly open and close a circuit. The first contactor 424 may connect to a snubber circuit 426. A snubber circuit 426, as the skilled person will be aware, is used to discharge an arc developed across the anode 428 and cathode 430 for continued operation of the SCR thyristor 302. The snubber circuit 426 may include a diode and a resistor. However, other combinations of electrical components may also be used without departing from the scope of this disclosure. For example, a diode and a capacitor may be used in place of the diode and the resistor. A second contactor 432 may be connected between the cathode 430 and the first contactor 424. In one or more embodiments, second contactor 432 may allow for connection of a transfer system, which also connects to the AC mains. However, such a connection is optional and based on customer demand / desire. In one or more embodiments, the first contactor 424 and the snubber circuit 426 may be replaced with a class D forced commutation circuit 600, an example of which is shown in Figure 6. As one skilled in the art will be aware, class D forced commutation, also referred to as auxiliary commutation, introduces two thyristors, Ti 602 and Tx 604 arranged in parallel, where the auxiliary thyristor Tx 604 may serve to switch off the primary thyristor Ti 602. A capacitor 606 may be positioned in series between Tx and a power supply 608. A diode 610 may be positioned in a reverse biased conducting orientation, such that no flow of current can take place through the circuit when the thyristors 602, 604 are in an off state. An inductor 612 may be arranged in series with the diode 610. The circuit may be completed via connection of a load 614. When a gate triggering pulse is provided to Tx 604, the thyristor is switched to an ‘on’ state, allowing for flow of current through the circuit. This flow of current charges the capacitor 606 with a similar polarity to that of the power supply 608, such that the capacitor is charged to a peak supply voltage. During this period of charging of the capacitor 606, current may pass through the load 614. Once the capacitor 606 is fully charged, the polarity across the capacitor reverse biases Tx 604, leading to it switch ‘off’. The capacitor 606 may then store the charge. Once Tx 604 is switched off, a gate triggering pulse is applied to Ti 602, switching it to an ‘on’ state. Once Ti 602 is in a conducting state, two loop currents may flow through the circuit. The first loop 616 may flow from the power supply 608, through Ti 602 and the load 614. The second loop 618 may flow from the power supply 608 through Ti 602, inductor 612, diode 610, and capacitor 606. The current through the second loop may discharge the capacitor 606, where this current may be oscillating. The negative portion of the signal may reverse bias the diode 610, such that that the second loop 618 of the circuit may be in the conducting state only during the positive portion of the signal. In this case, the inductor 612 may store energy. As the skilled person will be aware, inductors oppose changes in the current which pass through it. Accordingly, the inductor 612 may begin to release the stored energy. Due to this release of energy, the capacitor 606 may charge again, this time with an opposite polarity to that of its initial charging state. In order to commutate, or switch off, Ti 602, Tx 604 must be triggered. Once both thyristors 602, 604 are conducting at the same time, the polarity across the capacitor 606 may bring Ti 602 to a reverse biased state, switching off the primary thyristor 602. Accordingly, the auxiliary thyristor Tx 604 may be considered to be a switching device for the primary thyristor Ti 602. Referring back to Figure 4, and specifically to switch 414, when the switch 414 is in the off position 414a, the X1 output 412 may be connected to power supply 434 via switch 436. In one or more embodiments, power supply 434 may provide a 12 Volt direct current. The switch 414 may be toggled between the on position 414a and the off position 414b via relay coil 438. Auxiliary contact 440 and thermostat control switch 442 may also be included to allow for use of a transfer system connected back the AC mains. In such a situation, auxiliary contact 440 and thermostat control switch 442 ensure that the SCR thyristor 302 is turned off or otherwise disabled. Figure 5 shows a circuit diagram of a thyristor control circuit 500 in accordance with one or more embodiments. In one or more embodiments, the thyristor control circuit 304 shown in FIG. 3 may be thyristor control circuit 500. Thyristor control circuit 500 may be implemented when load 306 is a single cycle immersion heater. The SCR thyristor 302 may connect to the thyristor control circuit 400 via the gate 402 and the cathode 404. Gate 402 may be connected with a push button 506, a power supply 508 and a fuse 510, where the push button 506, the power supply 508, and the fuse 510 are all arranged in series. The fuse 510 may also be connected to a contactor 512, which may facilitate toggling of switches 514, 516. For example, toggling of switch 514 allows for connection and disconnection between gate 402 and cathode 404. Further, toggling of switch 516 allows for connection and disconnection of power supply 518 to the X1 output of a timer block 520. In one or more embodiments, power supply 518 may supply 12 Volts. Contactor 512 may be actuated via relay coil 522. A thermostat control switch 524 and a switch 526 may be connected in series with relay coil 522. In one or more embodiments, a stand alone solid state DC relay may be incorporated into a residential solar power generation sub-system as a secondary voltage source for thyristor control circuits, such as thyristor control circuits 400, 500. A stand alone solid state DC relay, as one skilled in the art will be aware, is an insulated gate bipolar transistor method of switching direct current to an electrical element, such as a transistor. The solid state DC relay may have a thermostat control switch connected in series with an input via a separate voltage source. The output of the solid state DC relay may be connected like a common household light switch, such that the series array of photovoltaic cells 202 may form a circuit with the load element 306. As in residential solar power generation sub-system 200, a subsystem comprising a solid state DC relay also includes a PV Array DC Isolator 206 and an AFDD 208. In one or more embodiments, the residential solar power generation systems described herein may also include a storage battery configured to store generated energy for use during night-time and periods of low sunlight. Embodiments of the present disclosure may provide at least one of the following advantages. Use of the systems as described herein allow for homeowners to power their homes independently of the national power grid. This allows for powering of remote residences, for example. Additionally, use of systems described herein allow for reduction or elimination of burning fossil fuels for energy generation. Moreover, systems described herein operate directly from the direct current power generated by the one or more photovoltaic cells. Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claims

1. A system for controlling a supply of solar power to a load, the system comprising:a solar panel arrangement operatively connected in series to a direct current isolator;an arc fault detection device, a thyristor and the load connected in series with the direct current isolator, wherein the thyristor is configured to conduct electrical current from the solar panel arrangement to the load when a load current of the solar panel arrangement is greater than a latching current of the thyristor; anda solid state DC relay.

2. The system of claim 1, wherein the thyristor is configured to electrically disconnect the solar panel arrangement from the load when the load current of the solar panel arrangement is less than a holding current of the thyristor.

3. The system of claim 1, wherein the load is a single cycle immersion heater.

4. The system of claim 1, wherein the load is a storage heater comprising a heating element.

5. The system of claim 4, wherein the load comprises at least two heating elements arranged inparallel.

6. The system of claim 4, wherein each of the at least two heating elements has a power of 750W.

7. The system of claim 4, wherein the storage heater comprises a thermal cutout bridge and a bi-metal thermostatic switch.

8. The system of claim 1, wherein the solar panel arrangement comprises at least two photovoltaic cells arranged in a series array.

9. The system of claim 1, further comprising a thyristor control circuit configured to control conduction of electrical current through the thyristor.

10. The system of claim 1, wherein the thyristor control circuit comprises a contactor and a snubber circuit, which are configured to actuate switching on and off of the thyristor.

11. The system of claim 1, wherein the thyristor control circuit comprises a class D forced commutation circuit, which is configured to actuate switching on and off of the thyristor.

12. The system of claim 11, wherein the class D forced commutation circuit comprises a primary thyristor and an auxiliary thyristor arranged in parallel.

13. The system of claim 12, wherein the auxiliary thyristor is configured to switch the primary thyristor between an ‘on’ and ‘off state.

14. The system of claim 1, further comprising a storage battery.

15. The system of claim 1, further comprising a plurality of cables used to connect the various components of the system.

16. The system of claim 15, wherein the plurality of cables are fire-resistant cables.

17. The system of claim 15, wherein the plurality of cables comprise a mineral insulated copper sheath cable or a thermosetting steel wire armour (SWA).

18. The system of claim 1, further comprising an auxiliary contact and a thermostat control switch.

19. The system of claim 1, further comprising an AC transfer system, wherein the auxiliary contact and the thermostat control switch are configured to facilitate connection of the AC transfer system into the system of claim 17.

20. The system of claim 1, wherein the auxiliary contact and the thermostat control switch are configured to disable the thyristor connected in series with the load and the direct current isolator.

21. The system of claim 1, wherein the solar panel arrangement is mounted to a residential roof.

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