Title of Invention: Construction machinery using fuel cells

Technical Field

[0001] The following invention relates to a system for providing power to construction machines such as excavators.

Background Art

[0002] At present, construction machinery is mainly powered by internal combustion engines, usually diesel engines. These provide power for all the functions of the machines. However, diesel engines emit troublesome gases, especially C02 and there is a growing awareness of the need to reduce C02 emissions to combat climate change. To solve these problems, vehicles such as cars and buses powered by electricity is becoming more common.

[0003] The main power source for electric cars is batteries. However, these are not well suited for powering heavy construction machinery as this need significantly more power than normal cars. This translates into larger and heavier batteries which in turn might impede functionality and still not have sufficient capacity to power the unit during normal working shifts. Such machinery is also often working in areas without access to charging. Therefore, heavy construction machinery such as heavy excavators powered by batteries is not efficient. At off-the-grid locations, which is often the case at large construction sites, such equipment is not usable.

[0004] Hydrogen has the potential to provide enough energy to power such machinery if the infrastructure problem can be solved. One solution for reducing C02 emissions is therefore electric power generated by fuel cells powered by hydrogen. At present such power is used on cars in certain regions but they have not found widespread use globally. Heavier fuel cell systems are being suggested for use in trucks and other heavy equipment, but utilization is not yet wide spread. [0005] One problem with hydrogen is refilling. Due to the Joule-Thompson effect, hydrogen will heat up during filling an empty bottle at temperatures above approximately -68° C (inversion temperature for hydrogen). It will therefore require cooling. To fill a bottle to a required pressure will also require a compressor. Both these needs require an electric power source.

[0006] In KR 101179617 there is described a fuel cell excavator in which a fuel cell is used as a main power source. The excavator according to the invention includes a hydrogen storage alloy vessel for storing a hydrogen fuel in a solid state and supplying the hydrogen fuel to a fuel cell, and a supercapacitor is provided instead of a storage battery. The fuel cell excavator has two or more hydrogen storage alloy vessels and can use sequentially filled hydrogen. After use, the empty hydrogen storage alloy vessel can be replaced with a filled hydrogen storage alloy vessel, and an extra hydrogen storage alloy vessel. In addition, since the recovered empty hydrogen storage alloy container can be recharged at the charging station and supplied through the existing distribution network, it is possible to construct a new infrastructure for the supply of hydrogen fuel.

[0007] One problem with this type of arrangement is that the hydrogen alloy vessels are housed inside the excavator and therefore with difficult access for replacement. Frequent replacement for re-charging will require access to lifting equipment and be a manpower intensive and dangerous operation. Another disadvantage is the limited capacity of the hydrogen alloy vessels since there is a trade-off between weight, size and capacity when sizes have to be manageable during replacement for re-charging. An excavator needs a lot of power and this may result in frequent exchanges of the hydrogen alloy vessels. This may be difficult with sites located far from infrastructure, i.e., roads.

[0008] In CN 209873925 there is described a fuel cell powered excavator with the power source i.e., the fuel cell is arranged in a nearby power supply vehicle and connected to the excavator via a slip ring.

[0009] This arrangement has obvious shortcomings, not least in that the excavator will have only a limited manoeuvring capability.

[0010] In US 6755225 there is described a mobile hydrogen refuelling system. The station can provide pressurized hydrogen gas to external hydrogen storage vessels. Those vessels may be part of a hydrogen powered vehicle. The station can consist of a hydrogen producing subsystem to refill the tanks within the refuelling station’s hydrogen storage subsystem. The self-refilling function may be provided by a hydrogen generating device.

[0011] A large problem with this invention is the need for electricity to power the station. In a normal environment this is not difficult but it becomes a challenge in remote location where an electricity supply is not available at the site. It is not only that electricity may not be available at the site, but also that the functions (cooling and compression) require a large amount of electricity. This solution is therefore obviously not suited for use in heavy excavating or construction machinery.

Summary of Invention

[0012] The main aim of the present invention is to solve the logistics problem associated with recharging construction equipment at any location and make fuel cells a viable alternative to diesel engines.

[0013] The applicant has realized that an electricity supply is readily available at the site by utilizing the excavator’s fuel cell to provide the necessary electrical power to the resupply station This solution eliminates the need for an external electric power source. The fuel cell in the excavator, being large enough to run the excavator, will therefore also have the capacity to provide power to the resupply station. This operation may be run during breaks or during the night.

[0014] This is achieved by providing a hydrogen resupply unit close to the excavator and powering the resupply unit from the excavator by providing an electric cable between the excavator and the resupply unit.

[0015] The resupply unit includes hydrogen bottles and at least one compressor and cooler

[0016] Preferably the resupply unit is transportable to be easily transported to a location where it can be refilled from a road vehicle.

[0017] The invention also comprises a method for controlling the system where the parts are interconnected and connected to a control station. Brief Description of Drawings

[0018] [Fig.1 ] The invention shall now be described in more detail with reference to the accompanied drawings where

[0019] Fig. 1 is a diagram of the system according to the invention

[0020] Fig. 2 is a detail of the energy part of Fig. 1

[0021] Fig. 3 is a diagram of the resupply units power system, and

[0022] Fig. 4 is a diagram representing the interconnection between the units.

Description of Embodiments

[0023] In the following the invention will be described using an excavator as an example. An excavator is seen as a good but challenging candidate for conversion to fuel cells. It is often stationary or only moving short distances during work. Such machines must therefore be re-charged on the working site. Flowever, it should be understood that there may be other types of equipment that can make use of the invention, for example crushers, cranes, bulldozers, drilling machines etc.

[0024] In Fig. 1 there is shown a diagram representing an excavator 1 . This excavator is of a common type and as such is equipped with a propulsion unit, a digger and turning mechanism. Other functions may also be included, such as a cabin. These are normal parts of an excavator and are as such well known to someone skilled in the art and therefore not described in more detail.

[0025] The excavator has a main housing 11 containing one or more fuel cells 12 that provides an output of electrical energy to a motor 13. The motor is in its turn coupled to a hydraulic pump 14 that supplies pressurized hydraulic fluid via line 16 to the working parts of the excavator. Bottles 15 containing hydrogen under pressure is likewise located in the excavator. Note that there could be one or more bottles or that hydrogen alternatively may be contained in a solid-state device. [0026] The excavator has a connector 17 for a cable 24. Preferably the connector is a fast-recharging connector of a type that is standard for the recharging of electric vehicles. In this way, other equipment, such as cars, can also be recharged from the excavator electricity supply.

[0027] One typical Example to illustrate order of magnitude of key parameters for a heavy excavator:

- Engine shaft power: 180 kW

- Electric Output: 300 V DC

- Bottle Capacity H2: 40 kg at 350 or 700 bar

[0028] A movable hydrogen resupply unit 2 is located near the excavator at the construction site. The resupply unit is preferable in the form of a transportable container. In the container is arranged a number of bottles or bottles 21 of hydrogen. The resupply unit is also provided with means 22 for enabling hydrogen to be transferred from the resupply unit to the excavator. This includes compressor and cooling systems needed for H2 filling as will be described later.

A pipe 23 for hydrogen and an electric cable 24 can be connected between the excavator and the resupply unit.

[0029] The resupply unit is preferably designed as a standardized unit. It is intended to be easily transportable so that it can be moved (as indicated with the numeral 30) from the construction site to a rigging site that normally is close to roads and be refilled from, for example, a haulage vehicle 35 with a tank. The unit may have its own propulsion system but it is preferable that it is of a size that can be carried by, for example, a wheel loader. Since the excavator often is located at remote places where the access roads are poor it is important that the unit is of a size that is easily transportable.

[0030] In Fig. 2 there is shown a diagram of the power parts in the excavator. As shown, Hydrogen is stored in bottles or bottles 15. In the figure there are shown a unit with 4 bottles. This is intended as an example only as there can be as many bottles as necessary to meet the consumption needs of the excavator for a working shift. A pipe 18 connects the bottle(s) to one or more fuel cells 12. The electrical output from the fuel cell is in turn transferred via cable 19 to the electric motor 13 that in its turn powers the hydraulic pumps 14 of the excavator.

[0031] Preferably a high-capacity battery 5, or capacitor is also housed in the excavator. This may be used for powering auxiliary functions or for balancing power at fast changing loads and also act as a power source when the Fuel Cell system is not turned on. The recharge connector 17 is also shown.

[0032] In Fig. 3 is shown a diagram of the means 22 for transferring hydrogen from the resupply container to the excavator. For simplicity the diagram only shows one bottle. Preferably the container houses several bottles or flasks containing hydrogen, as shown in Fig. 2. Since the resupply unit is transportable there must be a trade-off between weight and capacity but it is envisaged that there should be enough hydrogen in the container to last for several days. The bottle(s) are connected to a compressor 25 with pipes 26. The compressor is driven by an electric motor (not shown). As stated in the preamble, it is necessary to cool the hydrogen during filling to the tank 15 in the excavator. To this end a cooler 28 is arranged in the output pipe 27. Various sensors are located in the pipes for monitoring pressure, temperature and flow (illustration only). A connector 29, preferably of the quick connector type is arranged so that the pipe 23 can be connected to the resupply unit.

[0033] In an alternative, a storage unit can be located between the compressor and the cooler. This acts as an auxiliary cooler to cool the hydrogen gas using natural convection.

[0034] In another alternative the compression is performed in several steps, having two or more compressors with coolers in between.

[0035] In the invention the electric power for powering the compressor and cooling system required for filling the excavator tanks is supplied by the fuel cells mounted in the excavator. The electric power required for this operation is significant and this unique feature is enabling the filling operation to take place anywhere without access to grid power or other local power sources. For monitoring there is a communication link between a control system with sensors in the excavator and the control system and sensors on the resupply unit. The control of the filling operation can be either by the electronics in the excavator or by electronics in the filling unit. The link can be either wireless or via a cabled connection between the excavator and the filling unit.

[0036] When envisioning the excavator being used on a construction site as for building a highway the distance between the excavator working location and the rigg site may be several kilometres. In the preferred embodiment the unit is standardized and can be loaded onto the truck or trailer pulled by a tractor for transport to a refilling station to refill the (now empty) hydrogen bottles. Alternatively, the truck may have a tank and the hydrogen can be pumped over from the tank to the bottles. Since that requires electricity, this can only be feasible if there are electric power available at the transfer site which typically would be at a rigging or workshop site.

[0037] In another alternative the resupply unit may be self-powered and able to move between the site and a rig location.

[0038] When necessary, the excavator will move the short distance from the working location and park adjacent the container. The pipe 23 and electric cable 24 is connected between the container and the excavator. The fuel cells are then operated to provide electricity through the cable 24 to the container to run the motor for the compressor 25 and the cooler 28. One concern is of course that there must be enough hydrogen available in the excavator for the needed electricity. To solve this, a continuous monitoring of system status on all units and H2 remaining capacities can be provided by a central control station such that recharging can be planned correctly.

[0039] The control system for monitoring all aspects of the running of the system is illustrated in Fig. 4. where there is shown a central control station. This may be located in the site headquarter but may normally be located remotely with communication via wireless communication channels such as over 4G or 5G networks. As illustrated, the excavator has a number of sensors to monitor state and operation of the equipment, The sensor may include pressure sensor for the hydrogen bottles, temperature sensors, sensors for electricity consumption and so on (Fig. 3). The main control station will include a computer that can calculate power consumption and warn when replenishment of hydrogen becomes necessary as well as general condition monitoring of the whole system for safety and for predictable operation.

[0040] The construction machine is such that the excavator can be a key unit for Mixed Energy Management allowing efficient selection of the right machines for different tasks, locations and machine availability. This will enable minimized C02 emissions and high overall efficiency because hydrogen fuel cell powered machines, electric machines charged from excavator fuel cell and diesel-powered machines can be utilized where they best fit. Actual C02 emissions can be monitored by the overall system and it’s built in Mixed Energy Management system will provide guide for optimizing the mix of systems.

[0041] The electrical interface for powering the resupply unit can as an alternative be connection directly to the grid power such as typically 400VAC often available at rigging site. Alternatively, it can receive electric power from another electric power source when charging itself from the bottle container j