Field of the invention

The present invention relates to electrical power supplies suitable for operation of in-pit mining equipment and utilising hydrogen as an energy source.

Background

Mining equipment such as the various drills, excavators and the like that are used in mining pits are conventionally run on diesel fuel, which can be produced from various sources although most is derived from petroleum. In order to reduce the environmental impact from mining equipment use it is desirable to seek operation of mining equipment powered by renewable energy sources. One approach might be to substitute petroleum based fuel with a biomass derived diesel, although there are questions about the sustainability of alternative diesel sources and the impact on other industries such as food agriculture. Another approach might be to use existing renewable energy sources, such as solar, wind energy, green-hydrogen and the like, and employ different mining equipment able to more effectively utilise the energy available, for example electrically powered mining machines.

While electrical machines can readily utilise sustainably generated electricity, a fixed grid electrical connection supplied by a renewable source is not practicable in all applications, including in mining pits. Moreover, it is infeasible at present for heavy equipment such as mining machinery that is electrically operated to simply carry its own rechargeable battery in the fashion of an electric car, since recharging the battery will still present an issue. In ordinary use, mining equipment may be frequently moved within a mining pit, but rarely leave. Accordingly, there are difficulties associated with supplying power to electrically driven mining equipment, without resorting to a fossil fuel power plant that can be located on site.

Embodiments of the present invention aim to support the use of renewable energy for operation of mining equipment while catering to the characteristics required for use in a mining pit or like environment. Summarv of the invention

In accordance with the present invention a power supply system is provided for supplying electrical power for operation of heavy equipment such as mining machinery, the power supply system having: a hydrogen fuel cell module for generating electrical power from stored hydrogen; a power electronics circuit coupled to receive electrical power generated by the fuel cell module, and having at least one output for supplying electrical power generated by the fuel cell module to an external equipment load; a battery module coupled to the power electronics circuit to allow charging of cells in the battery module using electrical power generated by the fuel cell module, and discharging of the battery cells through the at least one power electronics circuit output on demand.

The power supply system may include a trailing cable in use electrically connecting the power electronics circuit output directly to the external equipment load.

In embodiments the HFC module, battery module and power electronics circuit are housed to be together readily transportable from one location to another according to movement of the external equipment load.

The number and/or power capacity of fuel cells in the HFC module may be selected according to characteristics of the external equipment load.

The number and/or power capacity of battery cells in the battery module may be selected according to characteristics of the external equipment load.

In accordance with the present invention there is also provided a method for operation of heavy equipment such as mining machinery by electrical power, comprising: co-locating a power supply system with the heavy equipment, the power supply system having: a hydrogen fuel cell (HFC) module for generating electrical power from stored hydrogen; a power electronics circuit coupled to receive electrical power generated by the fuel cell module, and having an output for supplying electrical power generated by the fuel cell module to an external equipment load; and a battery module coupled to the power electronics circuit to allow charging of cells in the battery module using electrical power generated by the fuel cell module, and discharging of the battery cells through the power electronics circuit output on demand; and coupling the heavy equipment to receive electrical power from the power electronics circuit output by way of a trailing cable adapted to allow movement of the heavy equipment relative to the power supply system while coupled.

Co-locating the power supply system with the heavy equipment may comprise moving the power supply system to the operating location of the heavy equipment, which may be in a mining pit, for example.

Further aspects, features and advantages of the present invention will be apparent to those of ordinary skill in the art from the accompanying description and drawings.

Brief description of the drawings

In order that the invention may be more easily understood, the following detailed description of a particular embodiment is provided, presented by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a diagrammatic illustration of an offboard power unit according to an embodiment of the invention coupled to supply electrical power to a moveable mining machine;

Figure 2 shows components of the offboard power unit of Figure 1 in isolation;

Figure 3 diagrammatically illustrates offboard power unit modules according to another embodiment of the invention;

Figure 4 is a schematic circuit diagram of an offboard power unit according to an embodiment of the invention arranged to supply an alternating current electrical output;

Figure 5 is a schematic circuit diagram of an offboard power unit according to an embodiment of the invention arranged to supply an alternating or direct current electrical output; and

Figure 6 is a diagrammatic illustration of an offboard power unit according to an embodiment of the invention coupled to supply electrical power to a moveable mining machine. Detailed description

Mining, particularly open-pit mining, uses large machines for efficiency of scale. In order to power such machines using non-polluting electricity can be challenging in view of the location, environment and mode of use of the machines. Embodiments of the present invention provide an offboard power unit (OPU) for supplying electrical power to operate heavy equipment such as a moveable mining machine. The power unit is designed to be mobile with the equipment being powered. Energy for the OPU is generated from stored hydrogen through use of hydrogen fuel cells (HFCs). By sourcing 'green' hydrogen (e.g. hydrogen generated by electrolysis of water using sustainable electricity), use of the OPU according to embodiments of the invention to power mining operations can be close to 'carbon neutral' insofar as neither the energy supplied nor its use in the mining site produces carbon pollution emissions.

Figure 1 is a diagrammatic illustration of an OPU 10 coupled to supply electrical power for operation of mobile mining equipment 100 in the form of a Down-the-Hole (DTH) Drill. The OPU 10 has a fuel cell generation module 20 that includes a plurality of hydrogen fuel cells 22 and a stock of hydrogen gas stored in a collection of pressure bottles 24. The OPU also has a battery module 40 and a power electronics module 50. In this embodiment the battery module 40 and power electronics module 50 are housed together in a 20' shipping container 60 shown in Figure 1 with panels removed for an interior view. The electrical output from the fuel cell module 20 is coupled by cable link 31 to the power electronics module 50, which is also coupled to the battery module within the housing. An electrical output from the power electronics module 50 is coupled by way of a trailing cable 35 to the mobile mining equipment 100.

The trailing cable 35 in use carries a substantial level of electrical current and/or high voltage between the OPU and the equipment 100, and should therefore be sufficiently robust and insulated as for use in a mining pit or similar. The trailing cable may have a length in the order of 300 metres, which allows the equipment a range of movement without needing to relocate the OPU. Since the equipment is typically mobile and trails the cable behind it, there is preferably some kind of strong anchoring connection between the cable end and the equipment to prevent unintended disconnection physically or electrically. One way of anchoring is to wind an end portion of the cable around a circular structure that uses friction to maintain lock. The structure is connected to the equipment, but is able to pivot to allow a greater degree of freedom for movement. In addition or alternatively a cable reel of commercial variety may be included, either at the equipment end or the OPU end, for use in managing the length of cable deployed at a given time according to position and/or movement of the vehicle relative to the OPU. In consideration of magnetic flux that may be generated by current flowing through cable wound on the reel, it may be desirable to limit how many layers of cable can be wound on the reel. This is then determined by how large the reel is to accommodate more cable before needing to layer the cable on the drum.

Figure 6 is a similar view as Figure 1 , except in this instance all three of the HFC, battery and power electronics modules 20, 40, 50 are contained within a single transportable housing 60.

Figure 2 illustrates components of the OPU 10 from Figure 1 in isolation. This shows that the fuel cell unit 20 is seated on a transportable platform with safety railings 26, The housing 60 containing the power electronics and batteries and the platform 26 supporting the fuel cell module are both transportable from one place to another, within a mining pit for example. Transportation from location to location may be accomplished using a suitable forklift vehicle or the like.

Figure 3 illustrates a slightly different physical arrangement for the OPU modules 20, 40, 50 wherein all three modules are contained in different sections 61 , 62, 63 of the same transportable housing. These sections 61 , 62, 63 all form a single unit in use.

Different forms of electrically driven mining machinery may require significantly different electrical supply characteristics. For example, in terms of power requirements, the aforementioned DTH Drill (e.g. Atlas Copco D65) may require electrical supply power in the order of 400 kW, a large platform drill rig (e.g. Epiroc PV271 Blast Hole Drill with electric motor option) may need around 700 kW supply, whereas even a small (250t) mining excavator (e.g. Liebherr R9250E with electric motor option) may require 1000kW or more in electrical supply power to operate. Moreover, some equipment needs direct current supply whilst others use alternating current. Supply voltage requirements can vary also, along with duty cycles.

The range of power requirements is addressed by embodiments of the invention by allowing each of the fuel cell, battery and electronics modules to be scalable and independently configurable in capacity. This flexibility in design of the offboard power unit provides opportunity to tailor sizing of battery and hydrogen fuel cells, in particular, to suit equipment applications. Hydrogen storage can also be tailored to suit equipment duty cycle and operational requirements.

A schematic line diagram of the circuit of an OPU 10 according to an embodiment of the invention is seen in Figure 4, coupled to supply alternating current electrical power to the equipment load 100 through trailing cable 35. The fuel cell module 20 in this instance includes three individual HFCs, each comprising a 200 kW fuel cell generating up to 600A at 350-720 VDC. The individual HFCs are connected to the power electronics module 50 in parallel, wherein each is coupled to an internal 700 VDC, 2000 Amp bus bar 52 through a respective DC/DC converter 51 . The battery module 40 comprises a plurality of strings 41 of lithium titanate (LTO) rechargeable battery cells. The battery strings 41 are connected in parallel to a battery bus bar 42, which in turn is operative connected to the main bus bar 52. A high-current DC/ AC converter circuit 53 draws electrical input from the bus bar 52, and produces a 415 VAC output. In this embodiment, a step-up transformer 54 is included to generate a 6.6 kV electrical supply suitable for the particular equipment load 100. As shown, the power electronics module in this case also produces a 24 VDC output 56, via a DC/DC converter 55, for auxiliary use.

Figure 5 is a schematic line diagram of another OPU circuit 10 according to an embodiment of the invention, in this case having a higher supply capacity being configured to supply a direct current output. The bus bars 42, 52 have a correspondingly higher operating voltage of 1000 VDC (2000A). To account for the higher internal operating voltage the strings 41 of battery cells may be longer and the DC/DC converter circuits 51 for the HFCs are configured to produce the higher voltage. In the OPU circuit of Figure 5 the trailing cable 35 couples the equipment load 100 directly to the main DC bus bar 51. Here, the electrical equipment 100 has its own DC/ AC motor module that converts the 1000 VDC supply voltage for use by a 3-phase (500 kW) motor operating at 690 VAC.

A working “concept feasibility” offboard power unit has been designed, constructed, tested and used to successfully demonstrate functionality as follows: 1 ) operation of hydrogen fuel cells to charge batteries in an offboard power unit; 2) operation of equipment (electric drill rig) powered by offboard power unit DC grid connected to batteries only (charged from fuel cells); and 3) operation of equipment (electric drill rig) powered by offboard power unit DC grid connected to batteries and operating fuel cells.

Embodiments of the invention disclosed herein provide for a combination of hydrogen fuel cells and batteries to be incorporated into a portable offboard power unit to power mobile equipment via alternating current or direct current output. The fuel cells can be integral with the offboard power unit, or separate and close couple connected. Beneficially, the CPU allows for:

Replacement of conventional fossil fuel power plants (internal engine or genset) with renewable electrical power

Portability so that the CPU can be easily moved to suit equipment location

Flexibility in power source characteristics to suit a variety of mobile or fixed plant equipment applications (e.g. drill rig, excavator, pumping station, etc.)

Scalability

Island grid refueling by hydrogen source.

The invention has been described by way of non-limiting example only and many modifications and variations may be made thereto without departing from the spirit and scope of the invention. It may also be noted that while operational and functional components of the embodiments have been described and illustrated, various fasteners that may be used to secure the components together and to the door and door frame structure have been omitted in the interest of simplicity.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.