Load handling device

Abstract

A load handling device (31, Fig 3) used in a frozen temperature environment such as a grided and tracked storage and retrieval system (1) comprises a driving mechanism operatively arranged to move the

Description

Technical Field The present disclosure relates to a load handling device for use in a frozen temperature environment, an enclosure for a rechargeable power source, and a storage and retrieval system comprising a grid framework structure and a load handing device. The grid framework structure comprises a supporting framework structure upon which is mounted a track system that supports remotely operated load handling devices for handling storage containers stacked in the grid framework structure. Background WO2015 / 185628A2 describes a storage and retrieval system in which stacks of storage containers are arranged within a grid framework structure. The grid framework structure comprises a supporting framework structure upon which is mounted a track system that supports remotely operated load handling devices for handling storage containers stacked in the grid framework structure. Load handling devices are typically powered by rechargeable power sources, for example rechargeable batteries. The rechargeable power sources, once depleted, either need to be recharged or replaced in order to permit the load handling device to continue operating. Charging can take a significant amount of time, and reduce the useful operational time of the load handling devices. Charging can be wired or wireless. Load handling devices can travel to charge stations located on or adjacent to the track system. Alternatively, power sources in the load handling device can be exchangeable, so that a depleted power source can be exchanged for a fully charged power source at an exchange station. This has the advantage of reducing downtime. In some applications there is a requirement for goods to be stored within a given temperature range. For example, in grocery applications, frozen goods need to be stored at a frozen temperature. This presents a challenge for automated storage and retrieval systems in that all of the components need to be able to operate at low temperatures. In particular, in order to operate load handling devices at a low temperature, the power source must be maintained within its operating temperature range. This can pose a problem for batteries in particular, which are generally not rated to operate at frozen temperatures. Battery chemistry does not perform well in cold temperatures, with reduced capacity, reduced charging rates, and accelerated aging. It is therefore advantageous to maintain the battery at a warmer temperature. Battery cells will generate heat when charged and discharged, which can be used to maintain the local temperature of the battery environment if heat transfer rate is managed. However, when the battery is not actively charging or discharging, the battery can cool down quickly. WO2021148609A1 discloses a load handling device comprising a thermal management system comprising a temperature sensor and at least one temperature regulating device configured to maintain the temperature of the rechargeable power source within a predetermined temperature range in response to a signal from the temperature sensor. WO2021148609A1 describes the problem that during charging or discharging of a battery, the thermal energy generated must be dissipated outside of the battery or the heat will build up, raising the temperature of the battery. There is a risk that the temperature of the battery will exceed a normal temperature range, resulting in poor performance and shorter life, and even thermal runaway and risk of fire. A solution is therefore needed that enables load handling devices to operate for long periods at frozen temperatures by maintaining the power source within its working temperature range. Summary This disclosure describes a load handling device for use in a frozen temperature environment, an insulating enclosure for a rechargeable power source, and a storage and retrieval system. A load handling device is provided for use in a frozen temperature environment, the load handling device comprising: i) a driving mechanism operatively arranged to move the load handling device; and ii) an enclosure to house a rechargeable power source to power the driving mechanism, the enclosure comprising a structure arranged to substantially fully enclose the power source; wherein the structure comprises aerogel insulation. Advantageously, the enclosure insulates the battery from the surrounding environment, thus enabling the rechargeable power source to be maintained within its working temperature range rather than losing too much heat to the environment. Aerogel insulation has the advantage of low thermal conductivity within a small space. An existing design of load handling device can therefore be more easily modified to be suitable for use in frozen temperature environments, since the required space envelope for the insulated enclosure is not much larger than for a non-insulated enclosure. If other insulation materials were used that have a larger space requirement, either a smaller rechargeable power source would be needed, or a more significant redesign of the load handling device would be required including moving or redesigning other components in order to accommodate a larger insulated enclosure. Furthermore, storage systems may have zones at different temperatures, for example a frozen temperature zone, a chilled temperature zone, and / or an ambient temperature zone. In such a system it is an advantage for the load handling devices used in the frozen temperature environment to be similar in design to those used elsewhere in the system, and to use the same rechargeable power source. Similar designs of load handling device will be easier to manufacture and assemble, with more parts in common and more similar assembly processes. In use, similar designs of load handling devices will be easier to maintain, require less training for maintenance staff, and have more spare parts in common. Using the same rechargeable power source for all of the load handling devices in a storage system is particularly advantageous in reducing design, manufacture, maintenance, and operational costs. The load handling device may operate in a cubic storage and retrieval system of the type described above in WO2015 / 185628A2. Alternatively, the load handling device may be any other kind of device capable of handling loads, for example a forklift truck or autonomous mobile robot (AMR) or autonomous guided vehicle (AGV). The enclosure may further comprise a heater. The heater enables the temperature within the enclosure to be maintained even when the rechargeable power source is idle. When the rechargeable power source is charging or discharging, heat is generated. However, when the rechargeable power source is not charging or discharging (for example, when the load handling device is idle), no heat is generated, so there is a riskthat the temperature inside the enclosure will drop to below the operating range of the rechargeable power source. This could result in the load handling device being stranded if the power source is unable to provide power to the driving mechanism. A heater may be located at the base of the enclosure, at the side of the enclosure, or at the top of the enclosure. The heater may be located inside the structure, so that the aerogel insulation retains heat generated by the heater. The heater may be a separate removable device. The heater may be located in a pocket of the enclosure. The heater may be built into the structure of the enclosure. In some examples, more than one heater may be provided. The enclosure may comprises skids at the base of the enclosure configured to support the rechargeable power source when received inside the enclosure. The skids support the weight of the rechargeable power source, with the advantage that other parts of the enclosure do not need to be load bearing. The skids may be a pair of skids, running in parallel along the base of the enclosure and supporting opposing sides of the rechargeable power source. The heater may be located at the base of the enclosure between the skids. This arrangement is particularly beneficial in cases where a heater is located at the base of the enclosure, because the heater can fit into the space between the skids. The heater is therefore located and retained by the skids, and the weight of the rechargeable power source rests on the skids and not on the heater. Alternatively, the rechargeable power source inside the enclosure may be supported by a frame. The frame may comprise a recess to receive the heater. This arrangement has a similar advantage to the skids, in that the weight of the rechargeable power source rests on the frame and not on the heater. The aerogel insulation may be silica aerogel insulation. The aerogel insulation may be fibre-reinforced. Aerogel as an insulation material is fragile and not easily handled. Fibre-reinforced aerogel is a material that has the advantage of better mechanical properties and greater structural integrity, while maintaining the insulation properties of aerogel. Composite materials comprising aerogel with glass wool or other fibres have good insulation properties and are also less brittle, more flexible, less liable to break, and generally easier to handle. One example is a fibre-reinforced aerogel blanket. Hydrophobic silica aerogel has the advantage of repelling water, as well as having low density and low thermal conductivity. This is particularly relevant for this application, since moisture from the surrounding air will have a tendency to condense on the outside of the enclosure. Good waterproof performance of the insulation material, as well as the structure itself, helps to ensure that moisture does not penetrate inside the enclosure and reach the rechargeable power source. The rechargeable power source may be exchangeable. When a rechargeable power source in a load handling device is depleted, the depleted rechargeable power source may be exchanged for a fully charged rechargeable power source at an exchange station. This has the advantage that the load handling device can then continue operating, without the need to wait at a charge station while the rechargeable power source is charged. The structure of the enclosure may comprise a rigid outer shell. Advantageously, the rigid outer shell means that the enclosure maintains its shape within the load handling device so that the enclosure remains within its allocated space envelope and does not interfere with other components. The structure of the enclosure may be shaped to conform to the shape of the rechargeable power source. The structure of the enclosure may be substantially cuboid in shape. The structure may be manufactured by vacuum forming. Vacuum forming is a process by which thermoplastic material is heated, stretched onto a single-surface mould, and forced against the mould by a vacuum. Vacuum forming has the advantages that it is a cheap, efficient, fast, and repeatable manufacturing method, with low tooling costs. Other manufacturing methods can be used, for example injection moulding, 3D printing, pressure forming, CNC machining. The outer shell may comprise two or more parts. The outer shell may comprise more than two parts. For example, the outer shell may comprise a base, a lid, and two or more side parts. The two or more parts of the outer shell may be held together with retaining belts. Alternatively, the two or more parts of the outer shell may be attached by any suitable attachment means, for example by snap fitting, by screws, by bolts, or by adhesive. The structure of the enclosure may comprises a flexible membrane. Advantageously, the flexible membrane is lightweight, while still being able to retain the aerogel insulation. The flexible membrane may be in the shape of a net which can be folded to form a three dimensional shape. For example, the flexible membrane may be in the shape of a net of a cuboid, which can be folded up to form a cuboid shape to enclose the rechargeable power source. Advantageously, this means that the flexible membrane can easily be unfolded back into a net shape, so can more easily be repaired or replaced. The net may be provided with attachment means along one or more edges to attach the edges together when the net is folded into a three dimensional shape. The attachment means may be releasable attachment means (for example, Velcro®). Alternatively or additionally, retaining belts can be used. In other examples, rather than a single-piece net the flexible membrane may comprise several pieces that can be attached together to form the structure of the enclosure. The flexible membrane may comprise one or more pockets for holding the aerogel insulation. The pockets in the flexible membrane can be used to enclose and retain the aerogel insulation. This is particularly advantageous when the insulation is fragile or brittle. The pockets may be reinforced for structural strength. In examples where the enclosure comprises a heater, the heater may be located in a pocket of the flexible membrane. This may be a separate pocket from the pockets holding the aerogel insulation. An enclosure is provided for a load handling device as described herein. A storage and retrieval system is provided, comprising: a) a grid framework structure comprising: i) a track system comprising a plurality of tracks arranged in a grid pattern; ii) a supporting framework structure supporting the track system; and iii) a plurality of stacks of storage containers arranged in a plurality of storage columns located below the track system; b) at least one load handling device as defined herein. Brief Description of Figures Further features and aspects of the present disclosure will be apparent from the following detailed description of illustrative embodiments made with reference to the drawings. Figure 1 schematically illustrates a grid framework structure and storage containers. Figure 2 schematically illustrates track on top of the grid framework structure illustrated in Figure 1. Figure 3 schematically illustrates load handling devices on top of the grid framework structure illustrated in Figure 1. Figure 4 schematically illustrates a single load handling device with lifting device in a lowered configuration. Figure 5 schematically illustrates cutaway views of a single load handling device with lifting device in a raised and a lowered configuration. Figure 6 (a) and (b) schematically illustrates two different perspective views of an enclosure. Figure 7 is an exploded view of the enclosure showing the parts of the outer shell. Figure 8(a) illustrates the enclosure with the outer shell removed for ease of visualisation, and Figure 8(b) is an exploded view of the insulation panels. Figure 9 is an exploded view of the lower part of the enclosure. Figure 10 illustrates the enclosure showing a rechargeable power source located inside the enclosure. Figure 11 illustrates an enclosure formed from a flexible membrane shaped like a net of a cuboid in (a) folded and (b) unfolded configurations. Figure 12 illustrates an enclosure formed from a flexible membrane where each of the faces of the net comprises a pocket, in (a) folded and (b) unfolded configurations. Detailed Description The following embodiments represent the applicant's preferred examples of how to implement the disclosure, but they are not necessarily the only examples of how that could be achieved. Grid framework structure Figure 1 illustrates a grid framework structure 1 comprising a supporting framework structure 2 supporting a track structure 13. The supporting framework structure 2 can take any suitable form. In the specific example illustrated in Figure 1, the supporting framework structure 2 comprises a plurality of upright members 3 and horizontal members 5, 7 which are supported by the upright members 3. Upright members 3 may also be referred to as upright columns 3. The horizontal members 5 extend parallel to one another and the illustrated x-axis. The horizontal members 7 extend parallel to one another and the illustrated y-axis, and transversely to the horizontal members 5. The upright members 3 extend parallel to one another and the illustrated z-axis, and transversely to the horizontal members 5, 7. The horizontal members 5, 7 form a grid pattern defining a plurality of grid cells. In the illustrated example, storage containers 9 are arranged in stacks 11 beneath the grid cells defined by the grid pattern, one stack 11 of storage containers 9 per grid cell. Figure 2 shows a large-scale plan view of a section of track structure 13 forming part of the grid framework structure 1 illustrated in Figure 1 and located on top of the horizontal members 5, 7 of the grid framework structure 1 illustrated in Figure 1. The track structure 13 may be provided by the horizontal members 5, 7 themselves (e.g. formed in or on the surfaces of the horizontal members 5, 7) or by one or more additional components mounted on top of the horizontal members 5, 7. The illustrated track structure 13 comprises x-direction tracks 17 and y-direction tracks 19, i.e. a first set of tracks 17 which extend in the x-direction and a second set of tracks 19 which extend in the y-direction, transverse to the tracks 17 in the first set of tracks 17. The tracks 17,19 define apertures 15 at the centres of the grid cells. The apertures 15 are sized to allow storage containers 9 located beneath the grid cells to be lifted and lowered through the apertures 15. The x-direction tracks 17 are provided in pairs separated by channels 21, and the y-direction tracks 19 are provided in pairs separated by channels 23. Other arrangements of track structure may also be possible. As an alternative to the supporting framework structure 2 as described with reference to Figure 1, in other examples the support framework structure comprises a plurality of prefabricated modular panels arranged in a grid pattern, the detail of which is described in WO2022034195A1, incorporated herein by reference. Any appropriate supporting framework structure 2 can be used. Load handling device Figure 3 shows a plurality of load handling devices 31 moving on top of the grid framework structure 1 illustrated in Figure 1. The load handling devices 31, which may also be referred to as robots 31 or bots 31, are provided with sets of wheels to engage with corresponding x- or y-direction tracks 17,19 to enable the load handling devices 31 to travel across the track structure 13 and reach specific grid cells. The illustrated pairs of tracks 17,19 separated by channels 21, 23 allow load handling devices 31 to occupy (or pass one another on) neighbouring grid cells without colliding with one another. As illustrated in detail in Figure 4, a load handling device 31 comprises a body 33 in or on which are mounted one or more components which enable the load handling device 31 to perform its intended functions. These functions may include moving across the grid framework structure 1 on the track structure 13 and raising or lowering containers 9 (e.g. from or to stacks 11) so that the load handling device 31 can retrieve or deposit containers 9 in specific locations defined by the grid pattern. The load handling device 31 comprises a wheel assembly 34. The embodiment of the load handling device 31 illustrated in Figure 4 comprises first and second sets of wheels 35, 37 which are mounted on the body 33 of the load handling device 31 and enable the load handling device 31 to move in the x- and / -directions along the tracks 17 and 19, respectively. In particular, two wheels 35 are provided on the shorter side of the load handling device 31 visible in Figure 4, and a further two wheels 35 are provided on the opposite shorter side of the load handling device 31 (side and further two wheels 35 not visible in Figure 4). The wheels 35 engage with tracks 17 and are rotatably mounted on the body 33 of the load handling device 31 to allow the load handling device 31 to move along the tracks 17. Analogously, two wheels 37 are provided on the longer side of the bot 31 visible in Figure 4, and a further two wheels 37 are provided on the opposite longer side of the load handling device 31 (side and further two wheels 37 not visible in Figure 4). The wheels 37 engage with tracks 19 and are rotatably mounted on the body 33 of the load handling device 31 to allow the load handling device 31 to move along the tracks 19. The wheel assembly 34 of the load handing device 31 may be driven by a driving mechanism 38. The driving mechanism 38 may comprise one or more motors. The load handling device 31 also comprises lifting device 39 configured to raise and lower storage containers 9. The illustrated lifting device 39 comprises four tapes or reels 41 which are connected at their lower ends to a container-engaging assembly 43. The container-engaging assembly 43 comprises an engaging mechanism 42 (which may, for example, be provided at the corners of the assembly 43, in the vicinity of the tapes 41) configured to engage with features of the storage containers 9. The tapes 41 may be wound up or down to raise or lower the container-engaging assembly, as required. The lifting device 39 may be driven by a driving mechanism 38. The winding up or down of the tapes 41 of the lifting device 39 may be effected or controlled by the driving mechanism 38, which may comprise one or more motors or other means. As can be seen in Figure 5, the body 33 of the illustrated load handling device 31 has an upper portion 45 and a lower portion 47. The upper portion 45 is configured to house one or more operation components (not shown). The lower portion 47 is arranged beneath the upper portion 45. The lower portion 47 comprises a container-receiving space 49 or cavity for accommodating at least part of a storage container 9 that has been raised by the lifting device 39. The container-receiving space 49 is sized such that enough of a storage container 9 can fit inside the cavity to enable the load handling device 31 to move across the track structure 13 on top of grid framework structure 1 without the underside of the storage container 9 catching on the track structure 13 or another part of the grid framework structure 1. When the load handling device 31 has reached its intended destination, the lifting device 39 controls the tapes 41 to lower the container-engaging assembly 43 and the corresponding storage container 9 out of the container-receiving space 49 in the lower portion 47 and into the intended position. The intended position may be a stack 11 of storage containers 9 or an egress point of the grid framework structure 1 (or an ingress point of the grid framework structure 1 if the load handling device 31 has moved to collect a container 9 for grid framework in the grid framework structure 1). Although in the illustrated example the upper and lower portions 45, 47 are separated by a physical divider, in other embodiments, the upper and lower portions 45, 47 may not be physically divided by a specific component or part of the body 33 of the load handling device 31. In some embodiments, the container-receiving space 49 of the load handling device 31 may not be within the body 33 of the bot 31. For example, in some embodiments, the container-receiving space 49 may be adjacent to the body 33 of the load handling device 31, e.g. in a cantilever arrangement with the weight of the body 33 of the load handling device 31 counterbalancing the weight of the container to be lifted. The specific example of a load handling device illustrated in Figures 4 and 5 shows the load handling device 31 with a body 33 that is substantially box-shaped with four sidewalls and a top wall, with the components of the load handling device 31 housed within the body 33. In other examples the body 33 may comprise an open frame or skeleton structure, within or upon which components of the load handling device 31 are supported. To enable the load handling device 31 to move on the different wheels 35, 37 in the first and second directions, the load handling device 31 includes a wheel-positioning mechanism for selectively engaging either the first set of wheels 35 with the first set of tracks 17 or the second set of wheels 37 with the second set of tracks 19. The wheel-positioning mechanism is configured to raise and lower the first set of wheels 35 and / or the second set of wheels 37 relative to the body 33, thereby enabling the load-handling device 31 to selectively move in either the first direction or the second direction across the tracks 17,19 of the grid framework structure 1. The driving mechanism(s) 38 used to drive the wheel assembly 34 and the lifting device 39 can be powered by a rechargeable power source 53. Enclosure - rigid outer shell Figure 6 illustrates an example of an enclosure 51 for a rechargeable power source. The enclosure comprises an outer shell 53, which is substantially cuboid in shape. In the illustrated example, the outer shell 53 is divided into four parts: a base 59, two side parts 57, and a lid 55. In other examples, the outer shell 51 can be a single part, or a different number of parts. The parts of the outer shell 51 in the illustrated example are held together with retaining belts 61. An electrical connection 65 is provided for electrically coupling the enclosure 51 to a load handling device when the enclosure is installed in a load handling device. Figure 7 is an exploded view showing the parts of the outer shell 53. The base 59 is substantially tray shaped, with an upturned rim around the edges. Bolt holes 63 are provided spaced at regular intervals around the rim. The two side parts 57 together form the four side walls of the outer shell 53. The outer shell is cuboid in shape so has an opposing pair of long side walls and an opposing pair of short side walls. Each of the two side parts 57 comprises a long side wall and half of each of the pair of short side walls. The side parts 57 are provided with bolt holes 63 at the top and at the bottom. When the outer shell 53 is assembled, the bolt holes 63 at the bottom of the side parts are aligned with the corresponding bolt holes 63 on the rim of the base 59, to enable the side parts 57 and the base 59 to be bolted together. The lid 55 sits on top of the two side parts 57 when assembled. The lid 55 has a downwardly extending rim around the edge, which is provided with bolt holes 63. When assembled, the bolt holes 63 on the rim of the lid 55 align with the corresponding bolt holes 63 at the top of the side parts 57, to enable the lid 55 and the side parts 57 to be bolted together. Alternatively or additionally, other means of attaching the parts of the outer shell 53 together can be used, for example snap fit, clips, or screws. Figure 8(a) illustrates the enclosure 51 with the outer shell 53 removed for ease of visualisation. Each side of the enclosure 51 is provided with an insulation panel 67. The insulation panels 67 are substantially flat plates, except for the one of the short side walls, where the insulation panel is shaped to accommodate the shape of a rechargeable power source within the enclosure 51. Reinforcing members 69 are provided on the short side walls to improve structural rigidity. Figure 8(b) is an exploded view of the insulation panels 67. Figure 9 is an exploded view of the lower part of the enclosure 51. At the bottom is the base 59 of the outer shell 53. A pair of skids 71 is provided for supporting the weight of a rechargeable power source in the enclosure 51. The skids 71 are elongated members that are positioned on top of the base 59, along the long sides of the enclosure. The insulation panel 67 is positioned between the skids 71 and on top of the base 59. The positioning of the insulation panel 67 between the skids means that the weight of the rechargeable power source is borne by the skids 71 rather than applying load to the insulation panel 67. A frame 73 rests on top of the skids 71 and overlies the insulation panel 67. The frame 73 is provided with bolt holes that align with corresponding bolt holes on the skids 71 when assembled in order to attach the frame 73 to the skids 71. The frame 73 is located and restrained by the rim of the base 59, so the skids are retained in position via their connection to the frame 73. The frame 73 is provided with a recess 75. A heater 77 fits within the recess 75 of the frame 73. The position of the heater 77 within the recess ensures that the weight of the rechargeable power source is not applied to the heater 77. Instead the rechargeable power source rests on the edges of the frame 73, which in turn are supported by the skids 71. The heater 77 in the illustrated example is in the form of a rectangular plate. A plate shaped heater provides good heat distribution, and enables heat to circulate by convection within the enclosure. In other examples, other forms of heater can be used. In some examples, more than one heater can be used. During operation, the insulation material will be sufficient to keep the temperature of the rechargeable power source within its normal operating range (for example, above 0°C). Additional heating may be required, however, in the event that the rechargeable power source does not generate any heat over a long period of time, for example if the load handling device is idle with no charging or discharging. In this situation, without additional heating the rechargeable power source will eventually reach equilibrium with the temperature of the environment. In a frozen temperature environment, in cases where the rechargeable power source is a battery, the battery management system could turn off and the load handling device could lose communication with the battery without warning. Therefore while the load handling device is idle the rechargeable power source may need additional heating to enable the load handling device to operate after a long period of idling. The heater 77 fulfils this function. Figure 10 illustrates the enclosure 51. The lid 55, one side part 57 of the outer shell, the retaining belts 61, and two insulation panels 67 have been removed from the figure for ease of visualisation. A rechargeable power source 81 is located inside the enclosure 51. Cables 79 electrically couple the rechargeable power source 81 to the electrical connection 65 of the enclosure 51, and therefore enable the rechargeable power source 81 to electrically couple to a load handling device when installed. In this example the rechargeable power source 81 is a rechargeable battery, but in other examples different power sources can be used, for example capacitors. The outer shell 53 can be manufactured using any appropriate method. For example, the outer shell can be manufactured by vacuum forming. The outer shell will be rigid so remain within its allocated space envelope inside the load handling device. Vacuum forming is a cheap, efficient, fast, repeatable manufacturing process with a low tooling cost. Other manufacturing methods can be used, for example injection moulding, 3D printing, pressure forming, CNC machining. The outer shell can be formed with ribs on the outside to add structural rigidity to the enclosure. Enclosure - flexible membrane Figure 11 illustrates another option for the enclosure. In the illustrated example the enclosure is formed from a flexible membrane shaped like a net of a cuboid. The net as shown in Figure 11(b) can be folded up to form a three dimensional cuboid shape as shown in Figure 11(a). The net comprises six faces: a base 89, a lid 87, two long side walls 83, and two short side walls 85. The base 89 adjoins the two long side walls 83 and the two short side walls 85, and the lid 87 adjoins one of the long side walls 83. One or more edges of the faces are provided with means for attaching the faces together when the net is folded up. In the illustrated example, the two short side walls 85 are each provided with two tabs 91 for attaching to the long side walls 83. The lid 87 is provided with three tabs 91, two for attaching to the short side walls 85 and one for attaching to the opposite long side wall 83. The tabs can be provided with any suitable fastening means, e.g. Velcro® or a similar hook-and-look fastening, or a press stud or button or clasp or clip or magnet. Figure 12 illustrates an enclosure formed from a flexible membrane, similar to that illustrated in Figure 11. The net as shown in Figure 12(b) can be folded up to form a three dimensional cuboid shape as shown in Figure 12(a). Each of the faces of the net comprises a pocket 93. The purpose of the pockets is to enclose and retain insulation material. For example, insulation panels such as those described above and illustrated in Figures 8 to 10 could be used. Alternatively, insulation blankets could be used. Insulation material can be inserted into each of the pockets so that each of the six faces of the enclosure (base, lid, and four side walls) is insulated, and a rechargeable power source inside the enclosure is substantially fully enclosed by the insulation material. Any suitable means can be used for holding the faces of the net together, for example tabs as illustrated in Figure 11, retaining belts, straps, or adhesive. In other examples the flexible membrane can be provided as multiple separate pieces rather than as a single piece as described above. Again, the separate pieces of flexible membrane can be attached together using any suitable means. Insulation material Aerogels are cellular solids in the form of a coherent open network of loosely packed bonded particles, with voids filled with gas. They are synthetic materials derived from a gels, in which the liquid component of the gel has been replaced with a gas. The result is a solid material with low density, high porosity, high surface area, and extremely low thermal conductivity. The low thermal conductivity of aerogels is due to their high porosity and high surface area. Aerogels are excellent thermal insulators, inhibiting heat transfer by conduction since they are mostly composed of gas, and inhibiting convection because the structure of the solid prevents the gas from circulating through. The aerogel insulation can be reinforced by fibres. The reinforcement by fibres produces a material with better mechanical properties and greater structural integrity, while the aerogel provides the insulation properties. The composite aerogel-fibre material has the positive qualities of both aerogel (low density, high porosity so highly insulating) and the fibres (stronger and less liable to break, and generally easier to handle). One example is a fibre-reinforced aerogel blanket. Aerogels have a tendency to absorb moisture, due to their large internal surface area. Aerogels can be chemically treated to make them hydrophobic and thus less likely to degrade due to structural changes caused by absorbed water. Hydrophobic silica aerogel can be used as the insulating material. As well as having low density and low thermal conductivity, the hydrophobic nature of the aerogel is particularly useful for this application, since moisture from the surrounding air will have a tendency to condense on the outside of the enclosure. Good waterproof performance of the insulation material, as well as the structure of the enclosure itself, helps to ensure that moisture does not penetrate inside the enclosure and reach the rechargeable power source. Aerogel insulation may be supplied as panels with the insulating material sandwiched between outer layers to provide rigidity and protect the aerogel, for example sheets of aluminium, or cardboard, or plasterboard. An example of a suitable aerogel insulation material is SpaceTherm®. SpaceTherm® is a commercially 5 available fibre-reinforced silica aerogel, supplied as a blanket or panel and used for insulating buildings (for example, internal wall insulation). SpaceTherm® is thinner than other materials with the same thermal performance - for example a 10mm thickness of SpaceTherm® can provide the same insulation as 50mm of polystyrene, with a thermal conductivity of 0.015 W / mK.

Claims

1. A load handling device for use in a frozen temperature environment, the load handling device comprising:i) a driving mechanism operatively arranged to move the load handling device; andii) an enclosure to house a rechargeable power source to power the driving mechanism, the enclosure comprising a structure arranged to substantially fully enclose the power source;wherein the structure comprises aerogel insulation.

2. The load handling device of claim 1, wherein the enclosure further comprises a heater.

3. The load handling device of any one of the preceding claims, wherein a heater is located at the base of the enclosure.

4. The load handling device of any one of the preceding claims, wherein the enclosure comprises skids at the base of the enclosure configured to support the rechargeable power source when received inside the enclosure.

5. The load handling device of claim 4, wherein a heater is located at the base of the enclosure between the skids.

6. The load handling device of any one of the preceding claims, wherein the aerogel insulation is silica aerogel insulation.

7. The load handling device of any one of the preceding claims, wherein the aerogel insulation is fibre-reinforced.

8. The load handling device of any one of the preceding claims, wherein the structure of the enclosure comprises a rigid outer shell.

9. The load handling device of claim 8, wherein the outer shell comprises two or more parts10. The load handling device of claim 8 or claim 9, wherein the two or more parts of the outer shell are held together with retaining belts.

11. The load handling device of any one of claims 1 to 7, wherein the structure of the enclosure comprises a flexible membrane.

12. The load handling device of claim 11, wherein the flexible membrane comprises one or more pockets for holding the aerogel insulation.

13. An enclosure for a load handling device according to any one of the preceding claims.

14. A storage and retrieval system comprising:a) a grid framework structure comprising:i) a track system comprising a plurality of tracks arranged in a grid pattern;ii) a supporting framework structure supporting the track system; andiii) a plurality of stacks of storage containers arranged in a plurality of storage columns located below the track system;b) at least one load handling device as defined in any one of claims 1 to 12.s

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