COLD STORAGE DEVICE

Description

[0001] This invention relates to a cold storage device, particularly an ice-lined refrigerator and more particularly a solar powered ice-lined refrigerator, notably for vaccines and / or medical products.

[0002] To ensure their quality, longevity and effectiveness, vaccines must be stored and transported at an optimum storage temperature, generally ≥+2°C and ≤ +8°C. Exposure to higher or lower temperatures causes deterioration of the vaccines. Specialised vaccine storage refrigerators address these and other practical requirement, for example the avoidance of any significant temperature variation between different positions within a vaccine storage chamber. An example of a specialised ice-lined vaccine refrigerator is disclosed in WO 2015 / 120911. US 2004 / 0226309A1 discloses a temperature controlled pallet-sized shipping container; EP1421323 discloses a thermal barrier enclosure system; US 2018 / 023876 discloses a cooling device which is a further example of a specialised ice-lined vaccine refrigerator; US 2006 / 0107680 discloses an electrically heated jacket for refrigerant containers for charging air conditioners, freezers and heat pumps; WO 2017 / 090019 discloses devices, systems and methods for controlling environmental conditions of substances; and US6,222,160B1 discloses a food transport container with integral heater.

[0003] One aim of the present invention is to provide an improved ice-lined vaccine refrigerator.

[0004] In accordance with one of its aspects, the present invention provides a cold storage device in accordance with claim 1. Other aspects are defined in other independent claims. The dependent claims define preferred or alternative features.

[0005] In one of its aspects, the present invention is based on the realisation that a significant improvement in ice-lined cold storage devices can be made by focussing on an improved arrangement for ensuring that the temperature in the cold storage chamber does not fall below a desired minimum temperature. In the case of a vaccine refrigerator the desired minimum temperature is generally 2°C. In particular, this aspect is based upon ensuring that the temperature in the cold storage chamber does not fall below its desired minimum temperature by providing an improved arrangement for a heater within the cold storage device. The ice-lining of the storage device when in use will generally be at a temperature which is ≤ 0°C; indeed it can be advantageous for the ice-lining to be chilled to a temperature which is below its freezing temperature so as to increase the hold-over time of the cold storage device i.e. the duration for which the cold storage compartment may be maintained below its maximum permissible temperature without the supply of energy to provide active cooling. One challenge of ice-lined cold storage devices is thus how to reconcile a temperature of an ice-lining which is ≤ 0°C with a requirement for ensuring that the temperature of the cold storage compartment does not fall below, for example 2°C.

[0006] An arrangement in which: an inner liner is interposed between the cold storage compartment and the ice-lining, the inner liner comprising a sheet material having a major surface which faces towards the cold storage compartment and a major surface which faces towards the ice-lining; and an electrical heating element is arranged at one of the said major surfaces of the inner liner to provide heat to the cold storage compartment; allows for a number of synergistic advantages. These include: the ability to provide a heat source at the inner liner and thus form a heated separation between the cold storage compartment and the ice-lining; the ability in some cases to use heat conduction through the inner liner to facilitate the provision of heat around the entire cold storage compartment; the ability to use simple, compact and readily available components, for example an electrical heating element, notably an electrical heating wire; and the ability to reduce the volume of the heating arrangement, particularly to avoid the need for a heating arrangement at a base of the cold storage compartment, and thus to increase the volume of the cold storage compartment which is available for storing vaccines or other goods.

[0007] These advantages can be seen, for example, with respect to the heating arrangement disclosed in WO 2015 / 120911.

[0008] As used herein, the term "ice-lined cold storage device" means a device configured to maintain its cold storage compartment within a controlled temperature range which is below the temperature of its surroundings and to generate an ice lining which acts as a thermal capacitor; in the event of a power interruption the pre-formed ice lining absorbs heat from its surroundings and contributes to maintaining the cold storage compartment within its desired temperature range. For example, where the cold storage device is solar powered, power interruptions will occur when insufficient solar power is available to provide cooling, for example if the solar panels are shaded by clouds or at night.

[0009] The ice-lining is preferably water or a water-based ice-lining, for example water comprising one or more additive; the use of water or a water-based ice-lining, notably comprising at least 70 wt%, at least 80 wt% or at least 90 wt% water, allows the use of readily available materials, facilitates maintenance and replacement and allows the ice-lining to be provided by containers which can be filled locally rather than being transported ready-filled. Alternatively, the ice-lining may be a paraffin, a wax, and oil, a fattty acid; or a polyglycol. Preferably, the ice-lining comprises removeable icepacks; this facilitates construction, transport and maintenance.

[0010] The volume of the cold storage compartment may be ≥ 15L and / or ≤ 260L; this provides for storage or a suitable quantity of vaccines. It may be ≥ 40L, ≥ 50L or ≥ 55L and / or ≤ 1500, L ≤ 100L, ≤ 90L or ≤ 85L.

[0011] The hold over time of the cold storage device may be ≥ 10 hours, ≥ 12 hours, or ≥ 14 hours when tested with a surrounding temperature of 32°C; it may be ≥ 4 hours, ≥ 6 hours, or ≥ 8 hours when tested with a surrounding temperature of 43°C. Particularly for mains powered cold storage devices, the hold over time is preferably ≥ 20 hours with a surrounding temperature of 27°C and / or 32°C and / or 43 °C; particularly for solar powered cold storage devices, the hold over time is preferably ≥ 72 hours with a surrounding temperature of 27°C and / or 32°C and / or 43 °C.

[0012] The cold storage compartment is preferably entirely filled with air; it may be provided with a means for evacuating any condensation that forms from cooling of the air, for example a drain or water outlet.

[0013] The cooling circuit is configured, when in operation, to remove heat from the ice-lining. Preferably, the chilling of the ice-lining serves to simultaneously provide for chilling of the cold storage compartment; this simplifies construction by avoiding the need for a separate chilling arrangement for the cold storage compartment. The cooling circuit is preferably powered by a renewable energy source, more preferably by one of more solar panels. The solar panels or other power source may provide a DC voltage, notably a voltage of 12V ±2V or 24V ±2V and a power which is selected from i) a power which is ≥ 300 W, or ≥ 350 W and / or ≤ 500 W or ≤ 450W and ii) a power which is ≥ 700 W, or ≥ 750 W and / or ≤ 900 W or ≤ 850 W. The cooling circuit may be powered by a wind turbine. Alternatively, the cooling circuit may be mains powered, for example from an AC power grid. The cooling circuit may be an AC operated cooling circuit; it may be a DC operated cooling circuit, for example powered from a mains supply by an AC-DC power converter. The electrical heater is preferably powered by the same power source as the cooling circuit. The electrical heater is preferably configured to operate with a power consumption which is ≥ 5 W or ≥ 8 W and / or ≤ 50 W, ≤ 30 W or ≤ 15 W. The ability to provide an effective temperature safeguard with such low levels of power consumption of the electrical heater enables the heater to function even when a small amount of power is available which would not be sufficient to operate the cooling circuit. Thus, for example, when the ice-lined cold storage device is powered by solar panels, as dusk approaches the available solar power will fall to a level insufficient to power the cooling circuit and the ambient temperature will likewise fall. The fall in ambient temperature provides a risk of the temperature of the cold storage compartment falling below its desired minimum temperature but the lower power requirement of the electrical heater can be supplied from the lower level of power still available from the solar panels.

[0014] The ice-lining preferably extends around at least 50%, at least 60%, at least 70% or at least 80% of periphery of the cold storage compartment; this helps to ensure consistency of the temperature within the cold storage compartment. The inner lining preferably circumscribes the cold storage compartment and defines a substantially continuous perimeter of the cold storage compartment; this provides an effective separation between the cold storage compartment and the ice-lining.

[0015] The electrical heating element may comprise one of more substantially flat heating elements and / or one of more electrical heating wires; the compactness of such heating elements minimises the space that they take up. In a particularly preferred arrangement, the heating element comprises a single electrical heating wire; this may easily be arranged at one of the major surfaces of the inner liner, for example by being adhered to the major surface. Where one or more heating wire are used, the heating wire may be arranged with a sleeve, for example an electrically insulating sleeve. The electrical heating wire may be rectilinear; this simplifies its construction. Alternatively, the electrical heating wire may have an undulating or wave-like form; this may be used to increase its contact length with the inner liner and thus facilitate heat distribution. The electrical heating element is preferably attached to and / or supported by the inner liner; it may be secured to the inner liner by an adhesive, for example by an adhesive tape or a double-sided adhesive tape which holds the electrical heating element against the inner liner.

[0016] The inner liner comprises a heat conducting sheet, notably a metal sheet, having a major surface which faces towards the cold storage compartment and a major surface which faces towards the ice-lining. Particularly in this case, the electrical heating element may be arranged at, and preferably contacts, the major surface of the heat conducting sheet which faces the ice-lining. This arrangement allows good heat distribution through the metal sheet whilst using the inner liner to shield the electrical heating element from direct contact or potential damage from the cold storage compartment. The heat conducting sheet may have a thermal conductivity measured at 0°C which is ≥ 10 W.m -1< .K -1< or ≥ 20 W.m -1< .K -1< and preferably which is ≥ 50 W.m -1< .K -1< or ≥ 100 W.m -1< .K -1< . An aluminium or aluminium alloy metal sheet for the inner liner provides a useful combination of thermal conduction, physical separation and low weight. The heat conducting or metal sheet may have a thickness which is ≥ 1 mm or ≥ 2mm and / or ≤ 5mm or ≤ 4mm.

[0017] The inner liner comprises: a heat conducting sheet, notably a metal sheet, having a major surface which faces towards the cold storage compartment and a major surface which faces towards the ice-lining; and a thermally insulating material, notably a sheet of insulating foam for example expanded polypropylene or expanded polystyrene, which separates the cold storage compartment from the ice-lining and which is arranged between the heat conducting sheet and the ice-lining. The thermally insulating material may have a thermal conductivity measured at 0°C which is ≤ 100 mW.m-1.K-1 or ≤ 80 mW.m-1.K-1 and preferably which is ≤ 50 mW.m-1.K-1 or ≤ 40 mW.m-1.K-1. The inner liner preferably forms a continuous barrier between the cold storage compartment and the ice-lining having a continuous metal sheet facing the cold storage compartment and a continuous thermal insulating layer facing the ice lining. The combined effect of the insulating layer and the metal sheet of the inner liner provides an advantageous combination of thermal conduction adjacent to the cold storage compartment to mitigate temperature differences within the cold storage compartment, control of heat flow from the cold storage compartment to the ice-lining to avoid over-chilling the cold storage compartment, physical separation and low weight. Arranging the electrical heating element between the heat conducting sheet of the inner liner and the thermal insulating material of the inner liner further enhances these effects.

[0018] Arranging for the heating element to extend around at least 70%, at least 80% or at least 90% of the perimeter of the inner liner and / or the perimeter of the cold storage compartment facilitates heat distribution for the entire cold storage compartment. Arranging the electrical heating element at or near a central plane of the height of the cold storage compartment may be used to simplify the arrangement whilst ensuring that the effect of the electrical heating element extends to the entire cold storage compartment and / or entire inner liner. For example, the electrical heating element may be arranged at a position within the cold storage device which is between i) a horizontal plane which intersects a height corresponding to 25% of the height of the cold storage compartment and / or the inner liner from its base and ii) a horizontal plane which intersect a height corresponding to 75%, 65%, 60% or preferably 55% of the height of the cold storage compartment and or the inner liner from its base.

[0019] Operation of the electrical heating element may be controlled on the basis of a temperature sensor arranged within the cold storage compartment. For example, the electrical heating element may be turned on when the measured temperature approaches but has not yet reached the defined minimum temperature and turned off once a sufficient safety margin temperature has been detected. Arranging the temperature sensor to contact the inner liner, particularly an inner surface of the inner liner provides a convenient configuration. Preferably, the same temperature sensor is used to control operation of the electrical heating element and operation of the cooling circuit; this simplifies the configuration.

[0020] In accordance with a further aspect, the present invention provides a method of maintaining vaccines within a pre-defined temperature range in a cold storage device, the method comprising a) providing an ice-lined cold storage device in accordance with claim 1 comprising: a cold storage compartment arranged at an interior of the ice-lined cold storage device; an ice-lining configured to absorb heat from the interior of the cold-storage device; a cooling circuit configured, when in operation, to remove heat from the ice-lining; an inner liner arranged between the cold storage compartment and the ice-lining, the inner liner comprising a sheet material having a major surface which faces towards the cold storage compartment and a major surface which faces towards the ice-lining; and an electrical heating element arranged at one of the said major surfaces of the inner liner; and b) periodically operating the cooling circuit to remove heat from the ice-lining; and c) periodically operating the electrical heating element to provide heat to the interior of the cold storage device. The operation of the electrical heating element may be carried out subsequently to the operation of the cooling circuit. The cooling circuit and the electrical heating element may be operated simultaneously; each may be operated at a time when the other is not being operated.

[0021] One advantageous operating mode of a cold storage device, notably a cold storage device described herein, comprises a minimum temperature maintenance procedure. In this procedure, in order to avoid a risk of the temperature of the cold storage compartment falling below its minimum desired temperature, upon detection of the temperature of the cold storage compartment approaching its desired minimum temperature, a control system i) ensures that the cooling circuit is not operated to avoid removing further heat and ii) operates the electrical element to provide heat to the interior of the cold storage device.

[0022] Another advantageous operating mode of a cold storage device, notably a cold storage device described herein, comprises an enhanced ice-liner chilling procedure. In this procedure, which may be used for example upon initial start-up of the cold storage device, the electrical element is operated to provide heat during operation of the cooling circuit. This allows a greater amount of heat to be removed from the ice-lining whilst preventing the temperature of the cold storage compartment from reaching a pre-defined minimum temperature. By removing additional heat from the ice-lining in this way the hold-over time of the cold storage device can be increased.

[0023] An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, of which: Fig 1 is a schematic perspective view of an ice-lined cold storage device; Fig 2 is a schematic top view (without the lid) of the ice-lined cold storage device; Fig 3 is a schematic view showing an electrically powered cooling circuit of the ice-lined cold storage device; and Fig 4 is a schematic exploded perspective view of an inner liner and electrical heater.

[0024] The ice-lined vaccine refrigerator 10 comprises an insulated, moulded body 11 having an insulated pivoted lid 12. A cooling space 13 within the body 11 is accessible when the lid 12 is open and sealable by closing of the lid 12. Electrical components and control circuitry of the refrigerator 10 are arranged within a component housing 14 which is incorporated into the mounded body 11.

[0025] In particular, the ice-lined vaccine refrigerator 10 comprises: a vaccine storage compartment 15 within the cooling space 13; an electrically powered cooling circuit 16, a power inlet 17 adapted for connection to an external supply of DC power provided from solar panels or from an AC-DC power converter; and a compressor 18 forming part of the electrically powered cooling circuit 16 of the vaccine refrigerator 10.

[0026] The electrically powered cooling circuit 16 comprises: four flat plate evaporators 19a, 19b, 19c, 19d, each arranged at a peripheral side wall of the cooling space 13, the evaporators being fed with refrigerant which is circulated by the compressor 18 through a condenser 20, subsequently through a capillary tube or expansion valve 21 and subsequently through the evaporators before returning to the compressor 18.

[0027] An inner liner 22 is arranged within the cooling space 13, the internal periphery of the inner liner 22 defining the peripheral side walls of cold storage compartment 15. The inner liner 22 comprises a substantially continuous metal sheet 23, notably an aluminium sheet, having a thickness of 1-2mm, and a substantially continuous layer of insulation 24, notably sheets of expanded polypropylene or expanded polystyrene having a thickness of about 8mm which are adhered to and cover each major surface of the metal sheet which faces an evaporator plate 19a, 19b, 19c, 19d. This is an example of a preferred configuration in which the inner liner provides a substantially continuous sleeve or barrier which separates the cold storage compartment 15 from the ice lining.

[0028] A removeable ice pack 25a, 25b, 25c, 25d is arranged in each of the spaces between the evaporator plates 19a, 19b, 19c, 19d and the inner liner 22. The ice packs 25a, 25b, 25c, 25d thus form an ice lining which in this case provides an ice lining at each of four sides of a substantially rectangular vaccine storage compartment 15. In operation, the electrically powered cooling circuit 16 freezes the icepacks 25a, 25b, 25c, 25d which generates an ice lining and cools the vaccine storage compartment 15. As illustrated in Fig 2, the ice lining does not extent around corner sections of the cold storage compartment 15 but nevertheless extends around the majority and in the illustrated case at least 80% of the periphery of the cold storage compartment 15. Arrangement of the thermally insulated inner liner 22 between the ice packs 25a, 25b, 25c, 25d and the vaccine storage compartment 15 reduces the risk of undesirably cooling the vaccine storage compartment 15 to a temperature of below +2°C.

[0029] Fig 4 illustrates an electrical heating element in the form of a single electrical heating wire 26 which is adhered to a major surface of the inner liner 22, in this case the major surface 27 of the metal sheet 23 which faces the ice lining 25a, 25b, 25c, 25d. The electrical heating wire 26 is thus positioned between the metal sheet 23 and the insulating sheet 24 of the inner liner 22 and passes around the entire periphery of the inner liner 22 and of the cold storage compartment at a height 28 which corresponds to a horizontal plane which intersects a height corresponding to 50% of the height of the inner liner 22 from its base and which also corresponds in the illustrated example to 50% of the height of the cold storage compartment 15 from its base . The electrical wire heating element 26 comprises a wire loop within an electrically insulated sleeve with each of the two ends of the loop arranged at an electrical heating wire connector 29. A temperature sensor 30 contacts a major surface of metal sheet 23 of the inner liner 22, in the illustrated case the major surface of the inner liner 22 which is in direct contact with the air in the cold storage compartment 15, to provide an indication of the temperature of the cold storage compartment 15. The height position of the temperature sensor is preferably offset from the height position of the electrical heating wire to mitigate against direct heat transfer creating an erroneous temperature reading.List of reference numbers:

[0030] 10ice-lined vaccine refrigerator 11moulded body 12lid 13cooling space 14component housing 15vaccine storage compartment 16electrically powered cooling circuit 17power inlet 18compressor 19aevaporator 19bevaporator 19cevaporator 19devaporator 20condenser 21expansion valve 22inner liner 23metal sheet of inner liner 24insulation sheet of inner liner 25aice pack 25bice pack 25cice pack 25dice pack 26electrical heating wire 27major surface of metal sheet of inner liner 28height of electrical heating wire 29electrical heating wire connector 30temperature sensor

Claims

1. An ice-lined cold storage device (10) comprising: - a cold storage compartment (15) arranged at an interior of the ice-lined cold storage device; - an ice-lining (25a, 25b, 25c, 25d) configured to absorb heat from the interior of the cold-storage device; - a cooling circuit (16) configured, when in operation, to remove heat from the ice-lining (25a, 25b, 25c, 25d); - an inner liner (22) arranged between the cold storage compartment (15) and the ice-lining (25a, 25b, 25c, 25d), the inner liner (22) comprising a sheet material (23) having a major surface which faces towards the cold storage compartment and a major surface which faces towards the ice-lining; and - an electrical heater (26) configured to provide heat to the interior of the cold storage device; wherein - the inner liner (22) comprises i) a heat conducting sheet (23), notably a metal sheet, having a major surface which faces towards the cold storage compartment (15) and a major surface which faces towards the ice-lining (25a, 25b, 25c, 25d) and characterized in that the inner liner (22) further comprises: ii) a thermally insulating material, notably a sheet of insulating foam, which separates the cold storage compartment (15) from the ice-lining (25a, 25b, 25c, 25d) and which is arranged between the heat conducting sheet (23) and the ice-lining (25a, 25b, 25c, 25d), and in that the electrical heater (26) comprises an electrical heating element (26) arranged at one of the said major surfaces (27) of the inner liner.

2. An ice-lined cold storage device (10) in accordance with claim 1, in which the inner lining (25a, 25b, 25c, 25d) circumscribes the cold storage compartment (15) and defines a substantially continuous perimeter of the cold storage compartment.

3. An ice-lined cold storage device (10) in accordance with any preceding claim, in which the electrical heating element (26) contacts the major surface (27) of the heat conducting sheet (23) which faces towards the ice-lining.

4. An ice-lined cold storage device (10) in accordance with any preceding claim, in which the electrical heating element comprises one or more electrical heating wires.

5. An ice-lined cold storage device (10) in accordance with any preceding claim, in which the electrical heating element (26) is arranged between the heat conducting sheet (23) of the inner liner and the thermal insulating material (24) of the inner liner.

6. An ice-lined cold storage device (10) in accordance with any preceding claim, in which the electrical heating element (26) extends around at least 70% of a perimeter of the inner liner.

7. An ice-lined cold storage device (10) in accordance with any preceding claim, in which the electrical heating element (26) is arranged at a position within the cold storage device which is between i) a horizontal plane which intersects a height corresponding to 25% of the height of the cold storage compartment (15) from its base and ii) a horizontal plane which intersects a height corresponding to 75% of the height of the cold storage compartment from its base.

8. An ice-lined cold storage device (10) in accordance with any preceding claim, in which operation of the electrical heating element (26) is controlled on the basis of a temperature sensor (30) which provides an indication of a temperature of the cold storage compartment (15).

9. An ice-lined cold storage device (10) in accordance with any preceding claim, in which operation of the electrical heating element (26) is controlled on the basis of a temperature sensor (30) arranged in contact with a major surface of the inner liner (22), notably a major surface which is in direct contact with the cold storage compartment (15).

10. An ice-lined cold storage device (10) in accordance with any preceding claim, in which the ice-lined storage device is configured to operate with its cold storage compartment (15) having a temperature which is maintained between +1 °C and +9 °C, preferably having a temperature which is maintained between +2 °C and +8 °C.

11. An ice-lined cold storage device (10) in accordance with any preceding claim, in which the ice lining (25a, 25b, 25c, 25d) extends around at least 50% of the periphery of the cold storage compartment (15).

12. An ice-lined cold storage device (10) in accordance with any preceding claim, in which the ice-lined cold storage device is solar powered.

13. A method of operating an ice-lined cold storage device (10) in accordance with any of claims 1 to 12, wherein the method comprises a minimum temperature maintenance procedure in which the electrical heating element (26) is operated to provide heat in the absence of operation of the cooling circuit (16).

14. A method of operating an ice-lined cold storage device (10) in accordance with any of claims 1 to 12, wherein the method comprises an enhanced ice-liner chilling procedure in which the electrical heating element (26) is operated to provide heat during operation of the cooling circuit (16).

15. A method of maintaining vaccines within a pre-defined temperature range in a cold storage device (10) in accordance with any of claims 1 to 12, the method comprising: - periodically operating the cooling circuit to remove heat from the ice-lining; and - periodically operating the electrical heating element to provide heat to the interior of the cold storage device.