Off-grid power supply system

Abstract

An electrical system for connecting a source of renewable energy to one or more appliances is described. The electrical system comprises an input port, one or more output ports, a battery, an inverter, a charge controller, a resistor network, a residual current device (RCD), and a casing that encloses the battery, inverter, charge controller, resistor network and RCD. The charge controller is configured to provide electricity generated by a renewable energy source to the battery, the inverter and / or the output ports. The resistor network is connected between the battery and a ground terminal for filtering the AC voltages produced by the inverter. The RCD is connected between the inverter and the one or more output ports and is configured to disconnect the one or more output ports from the inverter.

Description

[0001] OFF-GRID POWER SUPPLY SYSTEM

[0002] FIELD OF THE INVENTION

[0003] This invention relates to an off-grid power storage and supply unit. More particularly, this invention relates to an all-in-one electrical system for providing a safe supply of electricity from a source of renewable energy, such as a photovoltaic (PV) solar array.

[0004] BACKGROUND OF THE INVENTION

[0005] Solar power is a well-established means of providing off-grid electricity. In particular, the use of solar power has been widely adopted in rural areas as a means of elevating standards of living for those living off-grid, and for providing back-up power for those living on-grid in the event of a mains electricity black-out.

[0006] It is estimated that in 2024 there are around 746 million people living without electrical power. However, there are significant barriers to enabling these consumers - particularly in rural areas - accessing electricity via solar power in a safe and reliable way. This is because to instal a solar panel, a consumer would need to source the correct electrical equipment to ensure the safe delivery of electricity. For example, the consumer would need to source electrical components such as inverters, cabling, batteries, charge controllers that all meet the correct power and safety specifications, and connect these components correctly so that solar energy is converted into electricity efficiently and safely. It can be difficult, and expensive, to obtain the correct components - particularly in rural areas - and failing to correctly install the solar panel can lead to potential harm such as electrical shocks and burns.

[0007] The process of installing a solar panel to provide a safe and reliable source of renewable electricity is therefore complicated, expensive and potentially dangerous. It is therefore desirable to overcome or ameliorate these problems and limitations of existing systems and processes.

[0008] SUMMARY OF THE INVENTION The invention is defined by the independent claims, to which reference should now be made. Preferred features are laid out in the dependent claims.

[0009] In a first aspect of the invention, there is provided an electrical system for connecting a source of renewable energy to one or more appliances, the electrical system comprising an input port for receiving electricity generated by the renewable energy source, a battery, an inverter for converting DC voltage generated by the renewable energy source into AC voltage, one or more output ports for providing electricity from the electrical system to one or more appliances, a charge controller connected to the input port, the battery, the inverter and the one or more output ports, the charge controller for providing the electricity generated by the renewable energy source to one or more of the battery, the inverter and the one or more output ports, a resistor network connected between the battery and a ground terminal for filtering the AC voltages produced by the inverter, and a residual current device (RCD) connected between the inverter and the one or more output ports for disconnecting the one or more output ports from the inverter, and a casing that encloses the battery, inverter, charge controller, resistor network and RCD.

[0010] The first aspect of the invention advantageously enables a source of renewable electricity to be safely connected to one or more appliances and / or devices without the need of any specialist knowledge in order to provide power to those appliances and / or devices.

[0011] In an embodiment of the invention the resistor network comprises a plurality of resistors connected in parallel. This advantageously reduces the back-flow of alternating current in the electrical system, and thus mitigates AC voltages leaking to DC components.

[0012] In another embodiment the resistor network comprises a plurality of resistors connected in parallel and in series with one or more further resistors. This advantageously provides a further reduction of the back-flow of alternating current in the electrical system, and thus reduces AC voltages leaking to DC components.

[0013] In another embodiment the resistor network provides a resistance of between 800 Ohms to 8,000 Ohms. This advantageously reduces the back-flow of alternating current in the electrical system. In another embodiment the resistor network provides a resistance of between 3,000 Ohms to 8,000 Ohms. This advantageously provides a further reduction of the back-flow of alternating current in the electrical system.

[0014] In another embodiment a neutral terminal of the inverter is connected to an earth rod to create a neutral-earth bond. This advantageously improves the safety of the electrical system by ensuring the ROD disconnects the output ports in the event of current leakage.

[0015] In another embodiment a live terminal of the inverter is connected to the RCD. This advantageously improves the safety of the electrical system by ensuring the RCD disconnects the output ports in the event of current leakage.

[0016] An embodiment of the invention further comprises a DC fuse connected between the battery and the inverter, and / or connected between two terminals of the battery. This advantageously improves the safety of the electrical system by enabling the termination of current flow between the battery and the inverter and / or between battery terminals.

[0017] An embodiment of the invention further comprises a wireless communication module enclosed within the casing. This advantageously enables the electrical system to provide a user with internet connectivity.

[0018] In another embodiment the casing comprises a carrier handle. This advantageously enables the electrical system to be portable.

[0019] In another embodiment the casing is formed of non-conductive materials. This advantageously improves the safety of the electrical system by reducing the risk of electrical shocks.

[0020] An embodiment of the invention further comprises one or more battery expansion ports for connecting the system to one or more batteries external to the casing. This advantageously allows the energy storage capacity of the electrical system to be expanded with one or more external batteries.

[0021] An embodiment of the invention further comprises one or more separating sheets that segment the interior of the casing into separate compartments. This advantageously improves the safety of the electrical system by providing electrical isolation between AC and DC circuit components.

[0022] An embodiment of the invention further comprises a cooling fan disposed within the casing. This advantageously improves the performance of the electrical system by ensuring that components contained within the casing do not overheat.

[0023] In another embodiment the renewable energy source is a photovoltaic solar panel. This advantageously enables users to safely generate electricity from a readily available renewable energy source in a convenient manner.

[0024] In another embodiment the wireless communication module is configured to receive a WiFi dongle and / or a SIM card for a mobile network. This advantageously enables the electrical system to provide a user with internet connectivity via a mobile internet network and / or via a WiFi network.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0027] Figure 1 is a schematic diagram showing a schematic diagram of an electrical system in accordance with embodiments of the invention; and

[0028] Figure 2 is a schematic diagram showing an example residual current device circuit in accordance with embodiments of the invention.

[0029] DETAILED DESCRIPTION

[0030] System Overview

[0031] Figure 1 is a schematic diagram of an all-in-one electrical system 100 for safely enabling electricity generated by one or more renewable energy sources, such as a solar panel, to provide power to one or more domestic appliances or devices.

[0032] The example electrical system 100 shown in Figure 1 comprises an outer casing 101 , a first dividing sheet 102 and a second dividing sheet 103, the first and second dividing sheets providing a first compartment 110, a second compartment 120 and a third compartment 130 that are enclosed by the outer casing 101. In preferred embodiments, the first and second dividing sheets separate DC circuit components from AC circuit components and provide electrical shielding between the AC and DC circuits.

[0033] The outer casing 101 protects the electrical components contained within and, in some embodiments, includes a carry handle to enable the electrical system 100 to be easily transported. In preferred embodiments, the materials used for outer casing 101 are non- conductive. Accordingly, in case of internal electrical leakage the user is protected from electrical shocks.

[0034] In preferred embodiments, the first compartment 110 houses a battery 111. In preferred embodiments, the battery 111 is rechargeable and may store charge generated by one or more sources of renewable energy for later use by one or more domestic appliances and devices. In some embodiments, the battery 111 is an absorbent glass mat (AGM) lead-acid battery, but it will be appreciated that any battery may be used that is suitable for storing charge to be supplied to domestic appliances and devices.

[0035] In some embodiments, the electrical system 100 comprises a DC fuse (not shown) to provide over-current or short-current protection between the battery and other electrical components in the electrical system 100. In preferred embodiments, the DC fuse is connected between battery 111 and inverter 122.

[0036] The first compartment 110 may further comprise one or more battery expansion terminals 112 for connecting one or more further batteries to the electrical system 100 to increase the charge storage capacity.

[0037] In preferred embodiments, the second compartment 120 houses a fan 121 , an inverter 122, an inverter display screen 123, a charge controller 124, a charge controller display screen 125, and one or more multi-contact connector input ports 126. In some embodiments, the inverter display screen 123 and the charge controller display screen 125 may be implemented as a single display screen.

[0038] In preferred embodiments, the casing 101 includes an opening for the fan 121 . This enables fan 121 to transfer heat energy from the interior of the casing 101 generated by the inverter 122 and the charge controller 124, to the local environment surrounding the casing 101.

[0039] In preferred embodiments, inverter 122 converts DC voltages received from a source of renewable energy, and / or voltage stored by battery 111 , into AC voltages suitable for powering one or more domestic appliances or devices.

[0040] The charge controller 124 provides an interface between the renewable energy source, such as a photovoltaic (PV) solar panel array, and other electrical components in the electrical system 100.

[0041] In preferred embodiments, the casing 101 may include a further opening for the charge controller display screen 125. This enables a user to view the performance of the electrical system 100, for example the battery voltage and charge level for battery 111 , via the display screen 125. In some embodiments, the controller display screen 125 may display a a Graphical User Interface. Computer readable program instructions for implementing the graphical user interface may be stored in a computer readable storage medium within the electrical system 100, or downloaded to a computer readable storage medium via a network, for example, the Internet, a local area network (LAN), a wide area network (WAN) and / or a wireless network.

[0042] In preferred embodiments, the charge controller 124 includes a maximum power point tracking (MPPT) circuit and / or a pulse width modulation (PMW) circuit.

[0043] A renewable energy source, such as a PV array, is connected to the electrical system 100 via the multi-contact connector ports 126.

[0044] In preferred embodiments, the inverter display screen 123 enables a user to monitor the performance of the inverter, such as the energy consumption and efficiency. The inverter display screen 123 may also show the performance of other electrical components inside electrical system 100. The inverter display screen 123 may also provide a user interface to enable a user to connect the electrical system 100 to the internet and to control the operation of the electrical system 100. In some embodiments, the electrical system 100 maybe controlled by a mobile application via the user interface. As indicated above, in some embodiments the electrical system 100 comprises a single display screen embodying the functionality of both the inverter display 123 and the charge controller display 125. In preferred embodiments, the third compartment 130 houses a resistor network 131 , AC load connector(s) 132, a residual current device (RCD) 133, a wireless communication module 134, an antenna 135, one or more grounding terminals 136, one or more AC load connector terminals 137, one or more inverter switch terminals 138, and one or more DC load terminals 139.

[0045] The resistor network 131 advantageously reduces sparking and filters the AC voltage produced by the inverter such that there is substantially no AC back-flow to DC circuit components. In some embodiments, the resistor network 131 comprises one or more resistors having a resistance of between 800 Ohms to 8,000 Ohms. In preferred embodiments, the one or more resistors have a resistance of between 3,000 to 8,000 Ohms.

[0046] In some embodiments, the one or more resistors comprise a plurality of resistors connected in a parallel arrangement. In preferred embodiments, the one or more resistors comprise a plurality of resistors connected in a parallel arrangement and in series with one or more resistors.

[0047] In preferred embodiments, the resistor network 131 is connected between earth and one or more DC circuit components. For example, in the example shown in Figure 1 , the resistor network 131 is connected between earth and a negative terminal of battery 111. In some embodiments, the resistor network 131 forms part of the charge controller circuitry 124.

[0048] The RCD 133 automatically disconnects the output ports such that no electricity is delivered by the electrical system. The RCD 133 comprises a custom-developed circuit, shown in Figure 2, to enable the electrical system to operate at normal working standards, thereby providing users and devices with safety protection against earth leakage. Embodiments may also prevent short circuits and circuit overload.

[0049] In known systems, an inverter typically provides alternating current to a consumer unit. The consumer unit typically includes an established ground connection or ground rod. However, introducing an RCD into this system leads to problems because the inverter may cause electrical shocks to users without the RCD measuring any current loss. This is because the consumer unit already has an established ground connection and any electrical leakage from either the live or neutral wires will form a complete circuit with the consumer unit. The RCD will thus not detect any current loss and so would not prevent electrical shocks.

[0050] It has been appreciated that RCD circuit 200 shown in Figure 2 is able to mitigate these problems.

[0051] Figure 2 is a schematic diagram showing an RCD circuit 200 that comprises a Battery 210, an Inverter 220, a Charge Controller 230, an RCD 240, an AC load connector 250, an earth connection 260, such as an earthing rod, connected to Ground 270, a Resistor network 280, and electrical lines 290. Electrical lines 290 provide a battery positive wire 291 , a battery negative wire 292, live wires 293-294, neutral wires 295-296, and earthed wires 297-299.

[0052] As shown in the example of Figure 2, the positive and negative terminals of battery 210 are each connected to the inverter 220 and charge controller 230 via electrical lines 291 and 292 respectively. Live wire 293 is provided to AC load connector 250 via the RCD 240 and live wire 294. Neutral wire 295 is provided to AC load connector 250 via the earth connection 260, RCD 240 and neutral wire 296. A ground wire 297 is provided to the AC load connector 250 via the earth connection 260, which is connected to ground 270 via ground wire 298. Ground wire 299 is connected between ground 270 and the negative terminal of battery 210, with the resistor network 280 located on ground wire 299.

[0053] The example RCD circuit 200 provides a neutral-ground bond by connecting the neutral terminal of inverter 220, via neutral line 295, to an earth connection 260. In some embodiments, as shown in Figure 2, the neutral terminal of the RCD 240 is also connected to the earth connection 260. The neutral-ground bond effectively forces the neutral pathway 295,296 to be 0 V AC, with the live pathway 293,294 carrying the full potential difference of 240 V AC. The electrical potential energy generated by the 240V AC potential difference between the neutral and live lines is dissipated in the resistor network 280 without causing short circuiting.

[0054] In normal operation, current flows through the RCD 240 passing between inverter 220 and a consumer unit connected to the AC load connector 250 via a first electrical path 293,294,296,295 that passes through the RCD 240. The RCD 240 measures the current flow into and out of the RCD 240, and registers a fault if there is a current imbalance. In other words, if the RCD 240 determines that current is being lost somewhere along the first electrical path then it disconnects itself from the RCD circuit 200 such that no electrical current is provided to AC load connector 250.

[0055] RCD circuit 200 mitigates the problem of undetected lost current by ensuring that in the event that a person touches an electrical wire in the connected device or the AC load connector 250, then current will flow from AC load connector 250 directly to ground (via the person) via a second electrical path 293,294,270. However, because neutral line 296 is held at 0V (rather than -120V), the current flow will not return from ground 270 through the RCD 240 via neutral line 296 because there is no potential difference, and so bypasses the RCD 240. The RCD 240 will therefore detect current leakage and disconnect the AC load connector 250, limiting or preventing the person receiving an electrical shock.

[0056] Returning to Figure 1 , the AC load connectors 132 and DC load terminals 139 enable appliances and devices to receive AC or DC voltage safely from a renewable energy source via the electrical system 100.

[0057] Grounding terminal 136 provides a ground connection for the inverter 122, resistor network 131 , the AC load connectors 132, and the RCD 133.

[0058] Wireless communication module 134 and antenna 135 enable the electrical system 100 to transmit and receive wireless communication signals via a wireless communication network, such as WiFi, 3G, 4G and 5G signals. In some embodiments, the wireless communication module 134 is configured to interface with a WiFi dongle and / or mobile network SIM card. Accordingly, the electrical system 100 is able to connect to a WiFi or mobile network thereby allowing a user to access the internet without having any cabling. The wireless communication network may be a public or private network and may include one or more of a local area network (LAN), a wide area network (WAN), the Internet, a mobile telephony communication system, or a satellite communication system.

[0059] In preferred embodiments, the inverter switch terminal(s) 138 enable a user to disconnect power to the inverter 122.

[0060] Electrical system 100 receives direct current generated via the output of a renewable source, such as a photovoltaic solar panel, at one or more input connector ports 126, where it is directed to charge controller 124. The charge controller 124 may distribute the DC voltage from the PV array to the battery 111 to be stored for later consumption and to enable power regulation from the PV array. Alternatively, or additionally, the charge controller 124 may distribute DC voltage to the inverter 122. The inverter 122 changes a direct current supplied by a renewable energy source, such as a solar panel, to an alternating current for powering appliances or devices connected to the AC output ports of the electrical system. The charge controller 124 also advantageously protects the battery from reverse polarity incidents and short circuit incidents.

[0061] In preferred embodiments, an output of the inverter 122 is connected via RCD 133 to a grounding terminal 136 and to an AC load connector 132. This provides two different current paths for the AC voltage, and enables the RCD to calculate any missing current, which may be indicative of current leaking or escaping out of the electrical system in an unsafe manner.

[0062] However, the use of an RCD provides a potential electrical pathway for the AC voltage to flow to DC circuit components, potentially causing a risk of electrical shock by the DC load appliances via the DC load connectors. Accordingly, embodiments of the invention include resistor network 131 that grounds the negative terminal of battery 111. The use of the resistor network prevents current flow returning to the battery, and also prevents electrical sparking and static noise returning to the inverter 122.

[0063] When electricity is not supplied by the renewable energy source, for example at night time or during low sunlight exposure to the photovoltaic array, the inverter 122 can receive a DC voltage from the battery 111 , which is then processed in the manner described above.

[0064] Alternatively, or additionally, the charge controller 124 may distribute DC voltage from the PV array directly to one or more 12V DC terminals to provide a circuit-protected 12 V DC supply. Additionally, or alternatively, the charge controller 124 distributes DC voltage to power one or more modules within the electrical system, such as the wireless communication module 134. In preferred embodiments, the wireless communication module includes a WiFi and / or mobile internet transceiver that cooperates with antenna 135 to enable the electrical system to provide a user with internet access via a WiFi or mobile internet network. In preferred embodiments, some or all of the electrical components within electrical system 100 are connected via wiring having a predetermined gauge that is selected to ensure that there is sufficient resistance to ensure safe current levels and prevent overheating.

[0065] The features described above allow for an all-in-one system that combines battery storage, solar charge control, DC to AC conversion, a cooling fan system, a renewable energy source interface, electrical charge storage expansion via battery expansion terminals, an RCD unit, inverter isolation, a resistor network, and AC and DC load connectors.

[0066] The described electrical system accounts for all electrical equipment interactions to ensure all the parts used in the unit are within the set manufacturing specification and provide a user with an all-in-one system, rather than the user needing to themselves identify, research and ensure the correct operation of the separate electrical components forming the system. It also ensures all wiring in the electrical system meets the required safety standards for all electrical components within the system for safe and convenient user operation.

[0067] The above detailed description of embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed. For example, while processes or blocks are presented in a given order, alternative embodiments may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and / or modified. Each of these processes or blocks may be implemented in a variety of different ways. Also, while processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed in parallel or may be performed at different times.

[0068] The teachings of the invention provided herein can be applied to other systems, not necessarily the system described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments.

[0069] While some embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the disclosure.

Claims

CLAIMS1 . An electrical system for connecting a source of renewable energy to one or more appliances, the electrical system comprising: an input port for receiving electricity generated by the renewable energy source; a battery; an inverter for converting DC voltage generated by the renewable energy source into AC voltage; one or more output ports for providing electricity from the electrical system to one or more appliances; a charge controller connected to the input port, the battery, the inverter and the one or more output ports, the charge controller for providing the electricity generated by the renewable energy source to one or more of the battery, the inverter and the one or more output ports; a resistor network connected between the battery and a ground terminal for filtering the AC voltages produced by the inverter; and a residual current device (RCD) connected between the inverter and the one or more output ports for disconnecting the one or more output ports from the inverter; and a casing that encloses the battery, inverter, charge controller, resistor network and RCD.

2. The electrical system of claim 1 , wherein the resistor network comprises a plurality of resistors connected in parallel.

3. The electrical system of claim 1 , wherein the resistor network comprises a plurality of resistors connected in parallel and in series with one or more further resistors.

4. The electrical system of claim 1 , wherein the resistor network provides a resistance of between 800 Ohms to 8,000 Ohms.

5. The electrical system of claim 1 , wherein the resistor network provides a resistance of between 3,000 Ohms to 8,000 Ohms.

6. The electrical system of claim 1 , wherein a neutral terminal of the inverter is connected to an earth rod to create a neutral-earth bond.

7. The electrical system of claim 1 , wherein a live terminal of the inverter is connected to the RCD.

8. The electrical system of claim 1 , further comprising a DC fuse connected between the battery and the inverter, and / or connected between two terminals of the battery.

9. The electrical system of claim 1 , further comprising a wireless communication module enclosed within the casing.

10. The electrical system of claim 1 , wherein the casing comprises a carrier handle.11 . The electrical system of claim 1 , wherein the casing is formed of non-conductive materials.

12. The electrical system of claim 1 , further comprising one or more battery expansion ports for connecting the system to one or more batteries external to the casing.

13. The electrical system of claim 1 , further comprising one or more separating sheets that segment the interior of the casing into separate compartments.

14. The electrical system of claim 1 , further comprising a cooling fan disposed within the casing.

15. The electrical system of claim 1 , wherein the renewable energy source is a photovoltaic solar panel.

16. The electrical system of claim 1 , wherein the wireless communication module is configured to receive a WiFi dongle and / or a SIM card for a mobile network.

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