WO2024224232A1

WO2024224232A1 - Cooling of a battery pack of an electrically powered mobile compressor

Info

Publication number: WO2024224232A1
Application number: PCT/IB2024/053590
Authority: WO
Inventors: Quinten VAN DEN BOSSCHE
Original assignee: Atlas Copco Airpower NV
Current assignee: Atlas Copco Airpower NV
Priority date: 2023-04-28
Filing date: 2024-04-12
Publication date: 2024-10-31
Anticipated expiration: 2025-10-28
Also published as: CN222530521U; BE1031580A1; CN118867469A; BE1031580B1

Abstract

According to an embodiment, there is disclosed a mobile compressor (100) for providing a compressed gas by drawing-in ambient air, comprising a battery pack (201), configured to provide electrical power for an electric motor, and a cooling system (203), configured to cool the battery pack (201), comprising a set of conduits (204), comprising a coolant for absorbing heat from the battery pack (201), a pump for circulating the coolant through the conduits (204), a heat exchanger (112, 202) for releasing the absorbed heat to the environment, wherein the heat exchanger (112, 202) is arranged such that, when drawn-in, the ambient air flows past the heat exchanger (112, 202).

Description

COOLING OF A BATTERY PACK OF AN ELECTRICALLY POWERED MOBILE COMPRESSOR

Technical Field

[01] The present invention relates to an electrically mobile compressor powered by a battery pack, and more specifically to a cooling system for cooling the battery pack.

State of the art

[02] A compressor is a machine, designed to produce compressed gases, such as compressed air. The compressed gas at a certain working pressure is then used in a range of applications, such as, for example driving other machines such as pneumatic jackhammers and drills.

[03] Such jackhammers and drills are usually used in locations where no permanent compressed air network is present, such as a construction site. Typically, a mobile compressor is used at these locations. The term "mobile" is therefore understood to mean that such a compressor can be moved, with or without the aid of transport means and/or lifting means. In other words, a mobile compressor is a compressor that is not designed to be used stationary in a fixed location.

[04] Mobile compressors can be powered by a diesel engine such that they can operate independently. However, as they emit combustion gases and are noisy, a tendency exists to replace these diesel engines with an electric motor. A mobile compressor can then, for example, be powered by a battery pack integrated therein. In other words, the electrical power to power the compressor is provided by the battery pack.

[05] To charge the batteries of the battery pack, use can be made of an electricity grid, if available, and/or charge the batteries at a location other than the one where the mobile compressor is used. [06] Such an electrically powered mobile compressor is disclosed in BE1024040A1. The energy supply from the electricity grid can be supplemented with a battery pack, as already mentioned. When the mobile compressor is not active but connected to the electricity grid, the batteries of the battery pack can then be charged. In the absence of an electricity grid, the mobile compressor can then be powered by power, drawn from the charged batteries.

[07] However, when electrical power is drawn from the batteries, they will heat up due to internal losses. This generated heat must be efficiently and safely discharged to the environment to guarantee the proper functioning of the mobile compressor.

[08] A first difficulty is that space is limited to provide a cooling system. A reason for this is that people like to keep a mobile compressor as compact as possible. A second difficulty is that the cooling system itself must be supplied with electrical power, which reduces the autonomy of the compressor itself when it is operational and only uses the batteries.

[09] It is therefore an objective of the present invention to provide a cooling system for an electrically powered mobile compressor that overcomes one or more described disadvantages and difficulties of state of the art solutions. More specifically, it is an objective of the present invention to provide a cooling system that leads to greater autonomy of an electrically powered mobile compressor.

Summary of the Invention

[10] According to the present invention, the above-identified objective is achieved by providing an electrically powered mobile compressor according to the first claim, the compressor comprising an electric motor for driving a compressor element for supplying a compressed gas at a predefined pressure and/ or flow rate by drawing in ambient air, the compressor further comprising a battery pack, configured to provide electrical power to the electric motor, and a cooling system, configured to cool the battery pack, comprising a set of conduits, comprising a coolant, configured to absorb heat from of the battery pack, a pump, configured to circulate the coolant through the conduits, a heat exchanger, configured to release the heat, absorbed by the coolant, to the environment, characterized in that the heat exchanger is arranged such that, when drawn-in, the ambient air flows past the heat exchanger.

[11] The electrically powered mobile compressor is configured to provide compressed air at a location where generally no compressed air network is present, for example, on a construction site. On the other hand, there may be an electricity grid available to power the compressor. This potentially present electricity grid is, for example, a low-voltage grid at a certain voltage, such as 400V which is common in Europe, or 480V which is common in the United States of America. It should therefore be understood that the value of the voltage to which the mobile compressor can be connected is not limiting, but can be adapted to the region where the compressor will be used.

[12] The compressor is equipped with an electric motor to drive a compressor element. For example, the compressor element is a screw when the compressor is of the screw compressor type. Here too, it is further understood that the type of compressor element is not limiting and that other compressor elements can be used to supply the compressed gas at a predefined pressure. The value of this pressure further depends on the intended applications, and can also be adjustable.

[13] Furthermore, a mechanical coupling between the electric motor and the driven compressor element, such as a gearbox, may be present. In other words, the drive of the compressor element does not have to be a direct drive by the electric motor, but a mechanical coupling between them may also be provided. This will convert the rotary speed of the electric motor into a rotary speed, suitable for the compressor element.

[14] Moreover, the type of electric motor is also not limiting to the disclosed invention. This can be a three-phase asynchronous electric motor, as well as a three- phase permanent magnet synchronous motor. In these cases, a frequency converter will be present between an electrical distribution device and the motor. This frequency converter, also called a frequency controller, inverter, or variable speed drive, VSD, will then convert a direct voltage from the electrical distribution device to an alternating voltage with a certain frequency, suitable for the three-phase electric motor. Furthermore, both the frequency and the alternating voltage can change in order to provide a certain torque to the compressor element, depending on the required pressure of the compressed gas.

[15] Alternatively, the electric motor can be of the direct current motor type. In this case, the direct current motor can be directly connected to the electrical distribution device, but generally, a DC/DC converter will be present between the electrical distribution device and the direct current motor to be able to apply a terminal voltage suitable therefor.

[16] In addition, several electric motors may also be present, each of which individually drives a compressor element. In this case, a frequency controller can be provided for each electric motor. Another possible configuration is that a single electric motor drives two or more compressor elements. When reference is made to a current for the electric motor, this also refers to the total electric current, required to drive the one or more motors.

[17] Providing a compressed gas is further accomplished by drawing in ambient air. The term ambient air should therefore be understood to mean the air that is around and in the vicinity and therefore in the environment of the compressor. This ambient air, or air for short, is drawn-in by the compressor to compress it, where it will generally first be filtered to, among other things, avoid damage to the compressor element and to ensure the quality of the compressed gas that is supplied.

[18] The mobile compressor further comprises a battery pack, configured to provide an electrical power to the electric motor. This battery pack then comprises one or more batteries. According to a preferred embodiment, the batteries are rechargeable batteries, and the compressor further comprises an electrical connection for an electricity grid. The compressor then further comprises an electrical distribution device to which the electric motor is connected. The electrical distribution device then further comprises an on-board charger, configured to provide electrical power to this distribution device from the electricity grid, a battery management system between the distribution device and the battery pack, and a controller, configured to coordinate a power exchange between the electricity grid, the battery pack, and the electric motor. [19] This electrical distribution device is a voltage rail, also called a busbar, to distribute electricity between the various connected apparatuses. A first apparatus is the electric motor as discussed above. A consumer current then flows from the electrical distribution device to the electric motor. A second apparatus, connected to this electrical distribution device, is the on-board charger as mentioned above. The on-board charger is configured to convert electrical power from the electricity grid to a suitable value and make it available to the electrical distribution device. Usually, an alternating current from the electricity grid will be converted into a direct current. Here, an electric current will flow from the electricity grid through the on-board charger to the electrical distribution device to provide this electrical power to the various electrical consumers connected to it. Another apparatus, connected to the electrical distribution system, is the battery management system. The battery management system is configured to support power exchange between the distribution device and an assembly of one or more rechargeable batteries by monitoring the state of charge of the battery pack. To support this, a.o. the current, voltage and temperature of one or more batteries are measured and data is exchanged with a controller, based thereon. The controller then calculates a set point for the on-board charger and sends the result to the on-board charger. This allows the power exchange to take place in an optimal manner. The battery management system will also comprise a safety function to protect the batteries by not discharging them too deeply. Discharging takes place, for example, when another electrical consumer, such as the electric motor to drive the compressor element, connected to the electrical distribution device, consumes electrical power when no electricity grid is available, i.e. when the compressor works autonomously. In other words, the battery management system is a system as known in the state of the art. It will therefore ensure that the batteries of the battery pack are kept in a safe and reliable condition. This is done, among other things, by monitoring the state of charge and ensuring that the batteries are not discharged too deeply.

[20] Furthermore, the compressor comprises a cooling system to cool the battery pack. This cooling system consists of a set of conduits, configured to absorb heat originating from the battery pack. The conduits are therefore positioned such that heat, generated by the batteries, can be efficiently and safely absorbed by a coolant present in these conduits. It should further be understood that the set of conduits may comprise one single conduit that is wound between and over the batteries. Alternatively, the set of conduits can consist of several conduit, laid out in parallel. Later in the text, the term 'set of conduits' is understood to mean a single conduit, or conduits that are laid out in parallel and connected to each other to allow a coolant to flow through. The coolant is preferably a liquid, but can also be gaseous, and is therefore a cooling medium as known in the state of the art.

[21] The cooling system further comprises a pump for circulating the coolant through the set of conduits, and a heat exchanger, configured for releasing the absorbed heat from the battery pack to the environment in which the compressor is arranged. The heat exchanger then has the coolant as the first medium, which comprises the heat from the battery pack. The second medium of the heat exchanger is then the ambient air, as will be explained further. In other words, the heat from the battery pack is released to the environment using the ambient air.

[22] To make this happen efficiently, the heat exchanger is positioned in the compressor section of the battery-driven mobile compressor such that ambient air can flow past and/or through the heat exchanger. This can be done naturally or forced by means of a fan, as will be explained further. It is the ambient air that is drawn-in to cool the oil, coolant and compressed air of the mobile compressor.

[23] An advantage is that no facilities need to be provided in the battery pack, also called a compartment, to allow air flows to flow through it to cool the battery pack. This allows the battery pack to be constructed more compactly because the set of conduits can be integrated into the battery pack. In addition, the heat dissipation can also be done more efficiently because there is more control over the heat dissipation when using the set of conduits compared to an air flow. For example, during an air flow, unwanted turbulence can arise, as a result of which the heat dissipation of the battery pack on the air flow is not optimal. Moreover, no additional fan must be provided to create this forced air flow, which in turn must be provided with the necessary electrical power. By using the air flow to draw-in in the ambient air, both space and electrical power is saved. In other words, no additional airflow and fan are required to cool the battery pack. [24] Furthermore, a pump will circulate the coolant through the set of conduits and the heat exchanger, whereby, according to this embodiment, the battery pack can then be cooled to the ambient temperature according to a limit value. In a practical implementation, this will be slightly above the ambient temperature because there are inevitably losses. In this case, the coolant is a passive coolant.

[25] The coolant can also change phase when heat is absorbed. According to a preferred embodiment, the cooling system also comprises a chiller, wherein the heat exchanger of the cooling system then corresponds to the condenser of the chiller. The advantage of a chiller is that it can be cooled below ambient temperature. The chiller then comprises a pump or compressor, a condenser, an expansion component, an evaporator, and a coolant. In this case, the coolant is an active coolant.

[26] According to an embodiment, the mobile compressor further comprises a beamshaped container, arranged at the bottom side thereof and configured to house the battery pack and the cooling system, the heat exchanger then being arranged outside this beam-shaped container.

[27] The holder serves to protect the battery pack. Furthermore, the cooling system is also housed here, wherein the heat exchanger is located outside the beam-shaped container. Preferably, the heat exchanger comprises a rectangular cooling body that is positioned perpendicular to the beam-shaped holder at the top side thereof.

[28] The term top side should be understood to mean the top side when the compressor is normally placed on a surface for it to operate. The term bottom side therefore means the side facing and/or closest to this surface. Note that the compressor may further comprise a set of wheels to make it mobile, which implies that the holder should not be placed on the surface. With the help of these wheels, the compressor is towed by a vehicle. Furthermore, the longitudinal direction of the beamshaped holder will then correspond to a normal direction of travel when the compressor is towed by a vehicle.

[29] By positioning the cooling body outside this holder, and preferably at the top side thereof, the heat generated can be dissipated in an even more efficient manner. Because the specific mass of the coolant decreases with increasing temperature, this coolant will move to the heat exchanger in a partially natural manner. As a result, less power must be provided and used to control the pump in order to circulate the coolant. Moreover, the ambient air can then be allowed to flow past the heat exchanger, as will be explained further.

[30] The compressor may further comprise a housing that is arranged on the beamshaped holder as discussed above, at the top side thereof. The housing serves to shelter and protect the compressor element. It should further be understood that this shelter and protection also serves for the peripheral equipment to support the operation of the compressor, the electric motor, a buffer tank, if present, and/or other equipment, if present. The holder fits securely and snugly to the holder.

[31] The housing further comprises recesses on respective opposite sides thereof. The opposite sides are, for example and preferably, the sides seen along the longitudinal direction of the beam-shaped holder as already discussed above. Alternatively, the recesses can also be located on respective opposite sides according to the transverse direction of the beam-shaped holder. These recesses are configured such that there are one or more flow paths between them. The term flow path should be understood as a path or trajectory that an air flow can follow between and within the housing. This trajectory may be a straight line, but will generally follow a curved and winding trajectory. Moreover, the path that an air flow will follow cannot be defined a priori, but depends on various factors, such as the flow rate, the temperature, the humidity, and/or the air speed.

[32] In this case, the heat exchanger is arranged such that it intersects with this one or more flow paths. This will then cause the drawn-in air to flow through the heat exchanger to cool it. When the heat exchanger comprises a rectangular cooling body, it is preferably arranged transversely to the direction of the flow paths such that the cooling surface intersects maximally with the flow paths for efficient cooling.

[33] According to an embodiment, the compressor further comprises a fan, configured to force ambient air to flow along the flow paths. This can be done by suction and/or by letting the fan blow in the direction of the flow paths. This fan is then located above the battery pack and is also sheltered by the holder.

Brief description of the drawings

The invention will be further illustrated with reference to the figures, wherein

[34] Fig. 1A illustrates an electrically powered mobile compressor according to an embodiment of the invention; and

[35] Fig. 1 B illustrates the electrically powered mobile compressor according to Fig. 1A without housing or shelter; and

[36] Fig. 2A illustrates a first view of a beam-shaped container for housing a battery pack according to an embodiment of the invention; and

[37] Fig. 2B illustrates a second view of the beam-shaped container according to Fig. 2A.

Detailed description of the embodiments

[38] The present invention will be described with respect to certain embodiments and with reference to certain drawings, but the invention is not limited thereto and is defined only by the claims. The drawings described are only schematic and nonlimiting. In the drawings, the size of certain elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and relative dimensions do not necessarily correspond to actual practical embodiments of the invention.

[39] Furthermore, the terms first, second, third and the like are used in the description and in the claims to distinguish between similar elements and not necessarily to describe a sequential or chronological order. The terms are interchangeable under appropriate circumstances and the embodiments of the invention may be practiced in sequences other than those described or illustrated herein. [40] In addition, the terms above, below, over, below and the like in the description and claims are used for illustrative purposes and not necessarily to describe relative positions. The terms so used are interchangeable under appropriate circumstances and the embodiments of the invention described herein may be employed in orientations other than those described or illustrated herein.

[41] Furthermore, the various embodiments, although referred to as "preferred embodiments", are to be construed as exemplary means of carrying out the invention rather than as a limitation on the scope of the invention.

[42] The term “comprising” used in the claims should not be construed as being limited to the means or steps set forth below; the term does not exclude other elements or steps. The term should be interpreted as specifying the presence of the mentioned features, elements, steps or components referred to, but does not exclude the presence or addition of one or more other features, elements, steps or components, or groups thereof. The scope of the expression “a device comprising means A and B” should therefore not be limited to devices consisting only of components A and B. The meaning is that with respect to the present invention, only components A and B of the device are listed, and the claim is further construed to also include equivalents of these components.

[43] Fig. 1A illustrates an electrically powered mobile compressor 100. The mobile compressor 100 comprises a set of wheels 105 and a drawbar 106 for moving the compressor 100 using a suitable vehicle. The compressor 100 further comprises a beam-shaped holder, also referred to as container 101 , on the bottom side of the compressor 100, a frame 102, and a housing 103. It should further be noted that the wheels 105 and the drawbar 106 are connected to the container 101.

[44] The beam-shaped container 101 is configured to house a battery pack as further illustrated in Figures 2A and 2B.

[45] The frame 102 is configured to permanently support components of the compressor 100. With reference to Fig. 1 B, which illustrates the same compressor 100 as in Fig. 1A, where the housing 103 has been removed 111 , these components are visible.

[46] A first component is the compressor element in combination with the electric motor 114. The electric motor is configured to drive the compressor element to provide a compressed gas. Ambient air is used for this, and the compressed gas is supplied at a predefined pressure and/or flow rate. The electric motor is, for example, a three- phase asynchronous motor, but can also be of another type, such as a direct current motor, as already explained above.

[47] Although not illustrated, there may also be a mechanical coupling between the electric motor and the compressor element 114. This coupling is, for example, a gearbox and then ensures that the speed of the electric motor is converted into a speed, suitable for driving the compressor element 114.

[48] Furthermore, the compressor 100 is provided with a fan 116, which is located next to a heat exchanger 113 of an oil cooler for cooling the compressor element 114. Furthermore, a reservoir or buffer tank 118 is present as a buffer for storing compressed gas.

[49] It should further be understood that there are other components and apparatuses to support the proper functioning of the compressor 100, which are known to those skilled in the art.

[50] A lifting arm 117 is also connected to the frame 102, which can lift the frame 102 together with the components and other components as discussed above. The frame 102 with these components can be disconnected from the beam-shaped container 101.

[51] With reference again to Fig. 1A, as already mentioned, the housing 103 serves to protect the components of the compressor 100. This housing 103 can be connected to the frame 102 by means of clamps, such as clamp 110, whereby the housing 103 can then be removed by releasing the clamps 110, for example, for maintenance. [52] The housing 103 has further recesses 104, 107 on opposite sides thereof. Ambient air can then flow through the housing 103 and therefore over the components via these recesses 104, 107. The flow of ambient air can be further forced by the fan 116 by drawing-in or blowing air.

[53] In Fig. 2A the beam-shaped container 101 , 200, located on the bottom side of the mobile compressor 100 is further illustrated. This illustration 200 corresponds to the situation where the frame 102 with the associated devices permanently attached thereto and the housing 103 are disconnected from the container 101 , 200.

[54] The beam-shaped container 101 , 200 comprises a battery pack comprising a set of rechargeable batteries 201 which are suitable for providing electrical power for the electric motor for driving a compressor element 116. Although not illustrated, an electrical distribution device is provided for this purpose to connect the various apparatuses together such that electrical power can be exchanged.

[55] Furthermore, the container 101 , 200 comprises a battery management system 205, and a controller. This controller is configured to communicate with an on-board charger and can further communicate with an inverter, and the battery management system 205. If no inverter is present, hence when the electric motor 114 is of the direct current motor type, it is connected directly to the electrical distribution device. The controller may also be located in the container 101 , 200.

[56] Using the battery management system 205, the controller will also be able to determine what a maximum charging current is to charge the composition of the batteries 201. The battery management system 205 monitors the charging status of the batteries 201 and communicates to the controller what the maximum charging current is. Subsequently, the controller will control the on-board charger, based thereon, such that current can be drawn from an electricity grid for charging.

[57] Furthermore, the battery pack comprises a cooling system 203 for cooling the set of rechargeable batteries 201 . This cooling system 203 comprises a set of conduits 204 in which a coolant is contained and is circulated by means of a pump. Furthermore, a heat exchanger 202 is located outside the container 101 and perpendicular to it. With reference again to Fig. 1A and 1 B, this heat exchanger 202 corresponds to reference numeral 112, and is therefore not part of the components permanently connected to the frame 102, but is part of the cooling system of the battery pack, housed in the container 101 , 200.

[58] The heat exchanger 202 is then located in the air flow that can flow between the recesses 104 and 107, whether or not forced by the fan 116. As a result, the drawnin air will then flow through the heat exchanger 112, 202 to cool it. The heat exchanger 112, 202 further comprises a rectangular cooling body and is arranged transversely to the direction of these flow paths such that the cooling surface intersects maximally with the flow paths for an efficient cooling.

[59] Furthermore, the beam-shaped container 101 can be completely disconnected from the frame 102. This means that the battery pack and associated appliances can be completely disconnected from the other components of the compressor that are carried by the frame 102. However, in order to connect the frame 102 to the container 101 , holders are provided at the top side of the container 101.

[60] Such a holder is, for example, a curved edge at the top side as illustrated by reference numerals 210 and 211. Furthermore, drill holes are provided for the insertion of a bolt. The frame 102 then also has holes provided at corresponding locations, with which the frame 102 can be connected to the container 101 with the bolt through such a bore in combination with a nut. The holders with holes are then distributed over the outer edge of the container 101 at the top side thereof. The forces originating from the frame 102 are then distributed over the edge and the holders of the container 101. Furthermore, through the bolt-nut connection, both 101 and 102 are then permanently but reversibly connected to each other.

Claims

1 An electrically powered mobile compressor (100), comprising an electric motor for driving a compressor element (116) for supplying a compressed gas at a predefined pressure and/or flow rate by drawing in ambient air, the compressor (100) further comprising a battery pack (201), configured to provide electrical power to the electric motor, and a cooling system (203), configured to cool the battery pack (201) comprising:

- a set of conduits (204), comprising a coolant, configured to absorb heat from the battery pack (201);

- a pump, configured to circulate the coolant through the set of conduits (204);

- a heat exchanger (112, 202), configured to release the heat, absorbed by the coolant, to the environment;

CHARACTERIZED IN THAT the heat exchanger (112, 202) is arranged such that, when drawn-in, the ambient air flows past the heat exchanger (112, 202).

2.- The electrically powered mobile compressor (100) according to claim 1 , further comprising a beam-shaped container (101), arranged at the bottom side and configured to house the battery pack (201) and the cooling system (203), and wherein the heat exchanger (112, 202) is further arranged outside the holder (101).

3.- The electrically powered mobile compressor (100) according to claim 2, wherein the heat exchanger (112, 202) further comprises a rectangular heat sink, arranged perpendicular to the holder (101) at the top side thereof.

4.- The electrically powered mobile compressor (100) according to any one of claims 2 to 3, further comprising a housing (103) arranged on the holder (101 , 102) for sheltering the compressor element (116), the housing (101 , 102) comprising recesses (104, 107) on respective opposite sides thereof, configured to provide one or more flow paths therebetween for allowing ambient air to flow there along, and wherein the heat exchanger (112, 202) is further arranged intersectingly with one or more flow paths of the one or more flow paths.

5.- The electrically powered mobile compressor (100) according to claim 4, further comprising a fan (116) configured to force ambient air to flow along the flow paths.

6.- The electrically powered mobile compressor (100) according to any one of the preceding claims, wherein the cooling system (203) further comprises a chiller, and wherein the heat exchanger (112, 202) corresponds to a condenser of the chiller.

7.- The electrically powered mobile compressor (100) according to any one of the preceding claims, wherein the coolant comprises a cooling liquid.

8.- The electrically powered mobile compressor (100) according to any one of the preceding claims, wherein the battery pack (201) comprises one or more rechargeable batteries, the compressor (100) further comprising an electrical connection for an electricity grid, and wherein the electric motor (114) is connected to an electrical distribution device, comprising:

- an on-board charger, configured to provide electrical power to the electrical distribution device from the electricity grid; and

- a battery management system (205), configured to support a power exchange between the distribution device and the battery pack (201); and

- a controller, configured to coordinate a power exchange between the electricity grid, the battery pack (201), and the electric motor (114).