WO2019086709A1

WO2019086709A1 - Secure battery housing tray

Info

Publication number: WO2019086709A1
Application number: PCT/EP2018/080337
Authority: WO
Inventors: Björn Schreiner; Andreas Vollmer; Thorsten Mueller; Lars Kauke
Original assignee: Moog Unna Gmbh
Priority date: 2017-11-06
Filing date: 2018-11-06
Publication date: 2019-05-09
Also published as: GB201718343D0; GB2568242A

Abstract

An energy storage assembly has a housing tray for holding one or more battery cells and one or more resiliently flexible straps for securing the battery cells within the housing. The resiliently flexible straps provide sufficient restraining force whilst being flexible to absorb stresses that would otherwise be transmitted to the battery cells.

Description

Secure Battery Housing Tray

Field of invention

The invention relates to improvements in low-stress attachment and securement means. Particularly, but not exclusively, it relates to the mounting of batteries in a rotating hub of a wind turbine, wherein said batteries serve as an emergency power supply for the pitch control mechanism of the turbine rotor blades.

Background to the invention

Wind turbines having rotor blades mounted on a rotor may use pivotable rotor blades for limiting the rotational speed of the turbine in order to prevent structural damage when strong winds occur, or to stop rotation completely. By angling the rotor blade into or out of the wind, the rotational torque experienced by the rotor blades is controlled, and the rotation speed and the generated power of the wind turbine can be adjusted and maintained within operational limits.

In situations where it is critical that the rotors be stopped or have their speed otherwise limited, such as when the wind turbine is approaching overload or a structural safety threshold, it is critical that the pitch control mechanisms are functional at least for a time period that is necessary to turn all rotor blades into a so-called feathering position, where the rotor blades will bring the rotor to a halt. Accordingly, it has become standard practice to provide pitch control mechanisms with emergency backup power supplies, such that the wind turbine can reduce rotor speed even in the event of a power loss or other failure.

An emergency power supply is often provided in the form of one or more energy storage devices which are installed within the rotating hub of the wind turbine, close by the pitch control motors located at the base of each rotor blade.

As a result of their location, these energy storage devices are subject to shock, vibration and gravity induced bending, and are often inherently not mechanically robust. Further, given energy storage devices are usually made up of many smaller devices in series, the failure of a single element renders the entire device useless. As the module is a key energy source in the safety system of a wind turbine, these failures have severe implications, including injury, turbine collapse to loss of life. The current approach to this problem is to rigidly affix the energy storage devices to the inside of the hub of the wind turbine using glue or constant pressure clamping means. Conventional attachment means do not fully support the energy storage devices in a low stress manner. There are stress concentrations created either by hard fixing components or by the rotation of the assembly in the hub. Shocks and vibration are directly transferred from the rotating hub to the energy storage device. Further, such means make it difficult for the energy storage device to be accessed and/or removed for when being serviced, repaired or replaced.

One potential solution is to provide complete redundancy, but this creates two other issues. The first is that the overall pitch system reliability is reduced, meaning that increased time that the turbine cannot generate power. The second is cost. Energy storage is one of the most expensive elements within a pitch system. Thus the invented solution enables cost reduction within the pitch system.

An object of the present invention is to mitigate some of the deficiencies of the prior art mentioned above.

Summary of the invention

In accordance with an aspect of the invention, there is provided an energy storage assembly comprising a housing tray and at least one energy storage device, wherein the at least one energy storage device is retained within the housing tray by one or more resiliently flexible straps.

The use of straps as opposed to a full enclosure or clamping means allows for easy installation and removal of energy storage devices, as well as enabling easy access whilst the energy storage devices remain secured. The housing tray and straps may also be re-used, having a longer lifetime than solid housings, the structural integrity of which may be compromised on opening. Furthermore, the resiliently flexible nature of the strap material secures the energy storage devices against sustained centrifugal forces whilst being flexible enough to absorb shocks and other stresses that would otherwise be transmitted to the energy storage devices.

Preferably the resiliently flexible straps are formed of silicone, foam rubber or mechanical springs. Both foam rubber and silicone are robust, thermally and electrically insulating and low cost. Springs are low cost, light weight and can be easily tuned to balance the forces experienced by the energy storage assembly.

Preferably the one or more resiliently flexible straps are secured to the housing tray by clamping means or at least one restraining bolt. Such attachment means provide a quick and simple mechanism for securely fastening the strap to the housing. Both may be used in conjunction so as to provide a more secure fastening.

Preferably the housing tray comprises guidance and retention means for holding the at least one energy storage device. This ensures the energy storage devices are properly positioned in the housing during installation, such that the strap is effective.

Preferably the at least one energy storage device is a battery or a capacitor. Alternatively, the skilled person would be aware that the energy storage device may be any other suitable form of long term energy storage.

Preferably the capacitors is a bank of capacitors. Providing further capacitors allows for an increased energy storage capability as well as component redundancy and increased utilization of space in the hub.

Preferably the housing tray is attached to the inner surface of a rotating body, and more preferably the rotating body is the hub of a wind turbine. This allows for the energy storage assembly to be attached directly to the inside of the hub superstructure. Maximising the use of space within the hub, and preventing the need for additional mounting surfaces which may otherwise add weight or complexity to the wind turbine.

Preferably the energy storage device acts as an emergency power supply for a pitch control mechanism of a wind turbine. By providing the power supply in close proximity to the rotor blade pitch motors, electrical losses associated with excess cabling are minimised. Brief description of the drawings

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

Figure 1 is top down view of an energy storage assembly in accordance with an embodiment of the invention in an intermediate state of assembly.

Figure 2 is top down view of an energy storage assembly in accordance with an embodiment of the invention in a final state of assembly.

Figure 3 is an end view looking at a side wall of an energy storage assembly in accordance with an embodiment of the invention in an intermediate state of assembly.

Figure 4 is an end view looking at a side wall of an energy storage assembly in accordance with an embodiment of the invention in an intermediate state of assembly.

Figure 5 shows a housing tray with and intermediate wall

Figure 6 shows a clamping member with an opening for accommodating an eyelet of an intermediate wall

Figure 7 is three dimensional view of an energy storage assembly in accordance with another embodiment of the invention in a final state of assembly.

Detailed description

In order to provide a secure yet low stress holding means for an energy storage device in a housing, there is provided an energy storage assembly in accordance with the present invention.

Figure 1 shows a top view of an energy storage assembly 10. The energy storage assembly 10 comprises at least a housing tray 20, an energy storage device and two resiliently flexible straps 40 in connection with a clamping member 50 (see Fig. 2) configured to secure the energy storage device in the housing tray 20.

The housing tray 20 encloses a substantial portion of the energy storage device. The housing tray 20 has a bottom 21 (see Fig. 3), a front wall 22, a back wall 23 and two side walls 24 leaving one open side via which the energy storage device is installed within the housing tray 20 and accessed. In an alternative embodiment, the housing tray 20, at least one of its walls is shallower than the energy storage device, such that a substantial portion of the energy storage device protrudes from the housing tray 20. In this embodiment the shallower wall is the front wall 22 (see Fig. 3). In an embodiment, the housing tray 20 is thermally insulated. In a further embodiment, the housing tray 20 is electrically insulated. It would be apparent to the skilled person, within the context of the invention that the housing tray 20 with its bottom 21, front wall 22, back wall 23 and side walls 24 may be referred to as an 'enclosure', 'case', 'casing' or a 'cabinet.' In an embodiment, the housing tray 10 has a cable outlet, allowing for electrical connections to be made with the energy storage assembly 10 as well as individual energy storage devices.

In an embodiment, the energy storage device is a battery comprising a plurality of battery cells 30, which are electrically connected in series and operate in a known manner. In a further embodiment, the energy storage device is a conventional capacitor, respectively a bank of capacitors. As such, the skilled person would appreciate that any other suitable energy storage device could be used. The storage devices have connecting terminals 32 to which connecting wires 33 electrically conductive may be attached. In a further embodiment, the energy storage device is part of the emergency power supply for the pitch control mechanism of one or more wind turbine rotor blades.

In the embodiment shown in Fig. 1 to 6, the energy storage assembly 10 is provided by a series of individual energy storage devices, the battery cells 30, all secured within the housing tray 20 by the resilient ly flexible straps 40. In an assembly procedure the battery cells 30 are first inserted from the open side of the housing tray 20 into the housing tray 20. Two straps 40 of the resilient material are then placed on top surfaces 31 of the battery cells 30. Top surface 31 of the battery cells 30 means in this context the surface of the battery cells 30 that coincides with the open side of the housing tray 20. In this embodiment the top surface 31 of the battery cells is also that surface side on which the terminals 32 are situated. However, the top surface 31 of the energy storage device 30 must not necessarily be the same surface side as where the terminals 32 are situated. Similarly, in the context of the following description the adverbs "upper" and "top" signify a surface that is orientated in the same direction as the opening of the housing tray 20.

The resiliently flexible straps 40 are sized to span opposite side walls 24 of the housing tray 20 such that they span the opening of the housing tray 20. In an embodiment, there is only a single resiliently flexible strap 40. In an alternative embodiment, there are multiple resiliently flexible straps crossing the opening of the housing tray 20 in both longitudinal and traverse directions.

In a next assembly step a clamping member 50 is placed on top (see Fig. 2) of the straps 40. In one embodiment brackets extend outwards of two opposite side walls 24 of the housing tray 20, creating on each of two opposite side walls 24 a support plate 25 for supporting the clamping member 50 which also extends over the side walls 24 of the housing tray 20. The support plates 25 provide first bolt holes 26 which correspond to second bolt holes 51 of the clamping member 50. In a next assembly step restraining bolts 61 are inserted into the second bolt holes 51 of the clamping member 50 and passed through the corresponding first bolt holes 26 of the support plates 25.

Figure 3 shows in an end view, looking onto the outside of one of the two sides walls 24, this state of the assembly of the energy storage assembly 10. In this end view the resilient straps 40 are partially hidden by the support plate 25 and are partially visible in this assembly step as the resilient straps are thicker than the gap that is formed between the surface 31 of the batteries and the top surface 27 of the support plates 25. The resilient straps 40 therefore are shown in their thickness H when no pressure is exercised, assuming that the weight of the clamping member 50 is negligible.

In a last assembly step the clamping member 50 is screwed firmly onto the support plates 25 by the restraining bolts 61 and corresponding nuts 62. Figure 4 shows the state of the storage assembly 10 after the nuts 62 have been screwed onto the end of the restraining bolts 61 and have been tightened thereby pulling the clamping member 60 towards the support plates 25 against the resilient force of the resilient strap 40. The restraining bolts 61 act thereby to drive the clamping member 50 down to pinch the straps 40 between the clamping member 50 and the battery top surface 31. The support plates 25 act as a stopper and limit naturally the movement of the clamping member 50. In this way the resilient straps 40 are compressed to a pre-defined height h. With a compression ratio (H-h)/H a pre-defined pressure is achieved which is exercised by the compressed resilient straps 40 on the top surface 31 of the batteries 30. The pre-defined pressure is calculated to be sufficient enough to hold the batteries 30 in place, even when the battery tray 10 is mounted in a hub of a wind turbine and is rotated during normal operation of the wind turbine. The pressure however, must not exceed the pressure at which the housing of the batteries would crack.

The person skilled in the art appreciates that the compression ratio is a function of the physical properties of the material chosen for the resilient strap 40. In one embodiment, the resilient ly compressible strap 40 is formed of foam rubber. In an alternative embodiment, the strap 40 is formed of silicone. In a further alternative embodiment, the resiliently compressible strap 40 is one or more mechanical springs. As such, any known suitable resiliently compressible material can be employed. It would be apparent to the skilled person, within the context of the invention that the term resiliently compressible relates to a deformable material that will return to its original form when any compression forces are removed.

The end views of Fig. 3 and 4 also show an end view of the clamping member 50. In this embodiment the clamping member 50 is reinforced against bending by L-shaped edges 52 at both longest sides and a V-shaped ridge 53 along the longest middle axis of the clamping member 50. With these reinforcements a homogenous pressure can be achieved over the length of the clamping member 50.

Fig. 5 shows another embodiment of the battery tray 10 according to the invention. The battery tray 10 is assembled of stamped metal sheets which form bottom 21, front wall 22, back wall 23, and side walls 24. The diverse metal sheets are soldered with each other. Bottom wall 21, front wall 22, back wall 23 and side walls 24 may have fastening holes 28 (only shown in Fig. 6), some or all of which may be formed as slotted holes 29. The fastening holes 28 and the slotted holes 29 allow to fasten the housing tray 20 to a wall of a machine, for example in a hub of a wind turbine, at different positions. Fig. 6 shows a compression member 50 used in conjunction with the housing tray 20 of Fig. 5. In this embodiment the thickness of the metal sheet used to create the compressing member 50 may be even thinner than in the first embodiment. In addition, as can be seen further from this Figure, the compression member 50 of the second embodiment only has L-shaped edges 52 but no ridge along its longitudinal axis. Although both measures save weight, the thinner metal sheet and the missing reinforcement by a middle ridge causes a bend of the compressing member 50 so that the pressure of the resilient strap 40 is no longer homogenous. In order to counter this undesired effect, at least one fixture is adapted to pull the clamping member 50 towards a wall of the housing tray 20. In the embodiments shown in Fig. 5 and 6 the wall to which the clamping member 50 is braced against is the bottom 21 of the housing tray 20.

In the embodiment shown in Fig. 5 and 6 the fixture is an intermediate wall 70 of the housing tray 20 and is orientated parallel to the side walls 24. It may have a similar form as the side walls 24 and may be also fixed to the bottom wall 21 of the housing tray 20 by soldering. In addition to side walls 24 the intermediate wall 70 has a tap 71 that extends from one of its edges. This tap 71 comprises an eyelet 72 which corresponds to a counter eyelet 54 that extends perpendicular upwards from the clamping member 50. As this counter eyelet 54 is partially stamped out of the clamping member 50 and bent upwards it creates an empty space 55 through which the tap 71 of the intermediate wall 70 can protrude. The dimensions of the counter eyelet 54 and the eyelet 71 of the intermediate wall 70 are chosen that when the corresponding eyelets 71, 54 are connected through a bolt (not shown) or another, preferably releasable connecting means, the clamping member 50 is pulled down against the resistance of the resilient strap 40 to approximately the same level as the ends of the clamping member 50 when they are in contact with the support plates 25. By this, bending of the clamping member 50 is reduced and a relatively homogenous distribution of the pressure over the length of the clamping member 50, the resilient strap 40, and the top surfaces 31 of the batteries 30 can be achieved. If necessary, more than one intermediate wall 70 may be used to intensify this effect.

In one aspect of the invention, the eyelet 72 of the intermediate wall 70 has a constriction 73 which creates a nose 74 on both sides of the eyelet. Fig. 5a is a break out of the tap 71 and shows these details in an enlarged view. Accordingly, the opening 55 of the clamping member has a narrowing 58 which is smaller than the distance from nose tip to nose tip of the tap 71, but slightly larger than the length of the constriction of the eyelet 72. Thus the eyelet 72 and the opening 55 create a snap mechanism working against the force of the resilient material. For this purpose the position of the noses 74 are chosen such that when the compression member 50 is placed on top of the resilient material the tap 71 protrudes through the larger opening 55, but due to the resilient force of the resilient material 50 the compression member 50 is above the nose tips, preventing the narrowing 58 to engage with the constriction 73. By pushing down the compression member 50 in the region of the opening 55 against the force of the resilient material 40 the level of the constriction 73can be aligned with the level of the narrowing 58 in which case the pre-tension causes the constriction of the eyelet to snap into narrowing 58. The resilient force of the resilient material 40 pushes the compression member 50 upwards, but this movement is restricted by the noses 74 which limit the upward movement of the compression member 50 in the region around the opening 55. When accordingly dimensioned, eyelet 72 and counter eyelet 54 are now aligned with each other. This allows pushing a bolt easily through both eyelets 72, 54.

In an embodiment, the housing tray 20 is itself mounted to the inner surface of a rotating body, having an axis of rotation about a radial axis. In a preferred embodiment, the housing tray is mounted to the inner surface of the hub of a wind turbine, such that the energy storage assembly 10 is perpendicular to the radial axis of the hub. The energy storage device may be used for example for a pitch drive of a wind turbine. The housing tray 20, respectively the clamping member 50 may have handle fastening holes 57 for fastening a handle 8 and/or terminal fastening holes 58 for fastening a terminal 9. The terminal 9 may be used to provide an electrical connection of the connecting wires 33 and the pitch drive of the wind turbine.

During normal operation of a wind turbine, the hub spins with the rotor blades. Accordingly, the direction in which gravity acts on the energy storage assembly 10 varies with the rotation of the hub relative to Earth. The resiliently flexible straps 40 hold the battery cells 30 in place within the housing tray 20 using compression. This compression is tuned such that the battery cells are held securely without causing damage, with the resilient flexibility of the straps 40 ensuring harmful vibrations and/or stress forces experienced by the straps 40 are not transmitted to the battery cells 30. Therefore, there is provided an energy storage assembly 10 comprising a housing tray and at least one energy storage device, wherein the at least one energy storage device is retained within the housing tray by one or more resiliently flexible straps.

List of reference signs

10 energy storage assembly

20 housing tray

21 bottom 21

22 front wall 22

23 back wall 23

24 side wall 24

25 support plate

26 first bolt holes

27 top surface of the support plates 25

28 fastening holes

29 slotted holes

30 battery cell

31 top surfaces of a battery cell 30

32 connecting terminals

33 connecting wires

40 resiliently flexible straps

50 clamping member

51 second bolt holes

52 L-shaped edges

53 V-shaped ridge

54 counter eyelet

55 opening

56 narrowing

57 handle fastening holes

58 terminal fastening holes List of reference signs (continued)

61 bolt

62 nut

70 intermediate wall

71 tap

72 eyelet

73 constriction

74 nose

8 handle

9 terminal

Claims

1. An energy storage assembly comprising a housing tray (20) and at least one energy storage device (30), wherein the at least one energy storage device (30) is retained within the housing tray (20) by one or more resiliently flexible straps (40), wherein the resiliently flexible straps (40) are secured to the housing tray (20) by clamping means (50).

2. The energy storage assembly of claim 1 wherein a fixture (60) is arranged to pull down the clamping member (50) against the restoring force of the resilient strap (40) when the resilient strap (40) is compressed by the clamping member (50).

3. The energy storage device according to claim 2 wherein the fixture (60) has an eyelet (62) which corresponds to an counterpart eyelet (54) of the clamping member (50).

4. The energy storage device according to claim 3 wherein the eyelet (62) has a nose (64) which corresponds to a narrowing (58) of the opening forming in conjunction with the resilient strap a snap-mechanism.

5. The energy storage assembly of any preceding claim wherein the resiliently flexible straps (40) are formed of silicone.

6. The energy storage assembly of any preceding claim wherein the resiliently flexible straps (40) are formed of foam rubber.

7. The energy storage assembly of one of claims 1 to 5 wherein the one or more resiliently flexible straps are provided by mechanical springs.

8. The energy storage assembly of any preceding claim wherein the clamping means (50) are secured to a bracket (25) which limits the space between the energy storage device (30) and the clamping means to a pre-determined height (h).

9. The energy storage assembly of claim 8 wherein a height (H) of the resiliently flexible strap (40) and the height (h) of the pre-determined space between the clamping means (50) and the bracket (25) are chosen such that the compressed resiliently flexible strap (40) exercises a pre-defined pressure to the at least one energy storage device (30).

10. The energy storage assembly of any of the preceding claims wherein the pressure exercised by the compressed reliantly flexible strap is chosen sufficiently high to keep the at least one energy storage device (30) in place when the energy storage assembly is accelerated and on the other hand is chosen sufficiently low to not to cause damage to at least one energy storage device (30) when it is accelerated.

11. The energy storage assembly of any preceding claim wherein the one or more clamping means (50) are secured to the housing tray (20) by at least one restraining bolt (43).

12. The energy storage assembly of any preceding claim wherein the housing tray (20) comprises guidance and retention means for holding the at least one energy storage device (30).

13. The energy storage assembly of any preceding claim wherein the at least one energy storage device (30) is a battery.

14. The energy storage assembly of any of the preceding claims wherein the at least one energy storage device (30) is a capacitor.

15. The energy storage assembly of claim 14, wherein the capacitors is a bank of capacitors.

16. The energy storage assembly of any preceding claim wherein the housing tray (20) is attached to the inner surface of a rotating body.

17. The energy storage assembly of claim 16 wherein the rotating body is the hub of a wind turbine.

18. The energy storage assembly any preceding claim herein the energy storage device (30) acts as an emergency power supply for a pitch control mechanism of a wind turbine.