BACKGROUND OF THE INVENTION

1. Technical Field:

[0001] The present invention relates in general to refrigeration systems, which can used, for example, for the cold storage of perishables.

2. Description of the Related Art:

[0002] The storage and transportation of food perishables is a necessity in this age of mass commerce. Many goods and foodstuffs require refrigeration systems to prevent spoilage or degradation. If such foodstuffs are not properly maintained at their appropriate temperature range, the spoilage or degradation of foodstuffs leads to a reduction in profits, or worse, the spread of food borne illnesses. According to a food waste study published in 1997 and conducted by the USDA's Economic Research Service (ERS), it was estimated that in 1995 alone, 96 billion pounds of food were lost by retailers, foodservice, and consumers. Moreover, dairy products and fresh fruits and vegetables accounted for half of all retail losses. In the case of retailers and foodservice outlets, current economies of scale necessitate the use of large temperature-controlled storage facilities to preserve the freshness of a large volume of perishable goods, usually at a considerably high energy consumption cost. For this reason, taking measures to improve the energy efficiency and quality of existing and future refrigeration systems is critical.

SUMMARY OF THE INVENTION

[0003] In one or more embodiments, a cold storage system includes an enclosed structure having an opening sealed by a door. A mechanical refrigeration unit maintains an interior of the enclosed structure within a selected temperature range. The cold storage system may further include within the enclosed structure a rack system having one or more shelves for supporting refrigerated goods. The rack system additionally support endothermic phase change material (PCM) providing a capacitive cooling effect within the enclosed structure. In at least some embodiments, the PCM is contained in a plurality of overhead PCM containers supported by one or more support members of the rack system.

[0004] According to one aspect of the above embodiment(s), the plurality of overhead PCM containers includes endothermic PCM tubes that are disposed on one or more horizontal support members that securely attach to a plurality of vertical supports. The vertical supports may be reinforced by a horizontal cross beam bracket. According to another aspect of the above embodiment(s), the plurality of adjustable height vertical supports adjusts a height placement of the plurality of overhead PCM containers. According to another aspect of the above embodiment, additional PCM containers may be supported by the one or more shelves. For example, these additional PCM containers can be modularly reconfigurable to accommodate various storage shelf configurations. Further, the additional PCM container may be disposed in a plurality of under-shelf support brackets attached to the undersides of adjustable storage shelves of the cold storage rack. According to another aspect of the above embodiment(s), the cold storage system may includes a temperature monitor for controlling the mechanical refrigeration unit to maintain ambient temperature in the enclosed structure based upon at least a temperature of the endothermic PCM and an ambient temperature. In at least some implementations, the temperature monitor includes an outer temperature sensor for measuring a temperature of endothermic PCM adjacent to an inner surface of the PCM container, and an inner temperature sensor for measuring a temperature of endothermic PCM located at a farthest distance away from the inner surface of the PCM container.

[0005] According to one or more other embodiments, a cold storage rack includes one or more shelves for supporting refrigerated goods. The cold storage rack includes one or more support members supporting a plurality of overhead PCM containers containing endothermic PCM that provides a capacitive cooling effect with a mechanical refrigeration unit within a cold storage structure. The rack system may also include additional PCM containers supported by the one or more shelves. For example, these additional PCM containers can be disposed in a plurality of under-shelf support brackets attached to the undersides of adjustable storage shelves of the cold storage rack and may be modularly reconfigurable to accommodate various storage shelf configurations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a perspective view of an exemplary cold storage system in accordance with one embodiment;

[0007] Figure 2A is a partial perspective view of an exemplary cold storage rack in accordance with one embodiment;

[0008] Figures 2B-2C depict multiple configurations of PCM containers in accordance with one embodiment;

[0009] Figure 3 is a top plan view of several cold storage racks in a modular configuration;

[0010] Figure 4 is a side elevation view of an exemplary cold storage rack in accordance with one embodiment;

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENT

[0011] In one or more embodiments, a cold storage system employs endothermic phase change material (PCM) within an enclosed, refrigerated chamber in a manner that leverages the features of conventional mechanical refrigeration units employing forced-air chilling. In conjunction with the "active" heat exchange mode provided by the forced-air mechanical refrigeration unit, a bimodal cold storage system as disclosed herein advantageously employs a "passive" heat exchange mode in the form of an endothermic PCM container compatibly deployed within a refrigerated structure. As utilized herein, a "bimodal" cold storage system refers to a heat extraction/absorption system employing passive heat exchange mechanism in the form of an endothermic PCM in conjunction with an active heat exchange mechanism in the form of a forced-air mechanical refrigeration unit. The bimodal cold storage system efficiently addresses problems and costs associated with conventional refrigerated cold storage structures, including uneven cooling of temperature sensitive goods and ice buildup resulting from excessive condensation within the cold storage structure. Furthermore, the bimodal cold storage system's cooling mechanism reduces the required active operating time and excessive cycling of the mechanical refrigeration unit. Such reduction of active operating time and cycling of the mechanical refrigeration unit consequently reduces the overall power (kW) and energy (kWh) demands of the cold storage system, reduces repair and maintenance costs of the mechanical refrigeration unit, and extends the life the mechanical refrigeration unit.

[0012] As explained in further detail with reference to the figures, the cold storage system can be implemented within a refrigerated fixed structure (e.g., a cold storage cooler, cold storage freezer, cold storage room or cold storage warehouse) or portable cargo container or trailer having a conventional forced-air mechanical refrigeration unit that produces and directs chilled air into the interior of the refrigerated structure as required to lower and then maintain the temperature within the refrigerated structure at or below a predetermined temperature. To leverage the "active" heat exchange mode provided by the forced-air mechanical refrigeration unit, the cold storage system advantageously employs a "passive" heat exchange mode enabled by a rack system. The rack system is installed and compatibly deployed inside the cold storage structure to support endothermic PCM in various installation configurations. [0013] When in active mode, the chilled airflow from the mechanical refrigeration unit is used to bring the endothermic PCM to the required phase change or stasis temperature. In passive mode, enabled when the endothermic storage material has reached its stasis temperature, the mechanical refrigeration unit deactivates, and the activated (i.e., capacitively charged) endothermic PCM serves as a suspended, non-mechanically driven heat sink for a passive thermal convection mechanism wherein a passive convective air current resulting from natural thermal circulation is circulated throughout the interior of the refrigerated structure. The presence of this passive, endothermic PCM and natural convective air flow maintains the reduced internal temperature of the refrigerated structure for an extended period of time. The predictability of the passive mode periods enables thermal recharge cycling of the mechanical refrigeration unit to be synchronized with "off-peak" hours when the cost of electricity is lower than during peak demand hours.

[0014] The system as described is also useful in reducing or precluding excessive moisture within the refrigerated structure, which can be a significant problem. In systems relying solely on mechanical refrigeration units, excess moisture results in the buildup of ice on the cooling coils, requiring the unit to be reversed in a defrost cycle wherein the coils are defrosted. In many conventional installations, defrosting may be required several times per day and may in aggregate take multiple hours per day, resulting in a thermally inefficient and energy inefficient process.

[0015] In a preferred embodiment, the refrigerated structure is provided with additional insulating elements to reduce outside heat infiltration into the interior of the cold storage room/container from UV and radiant heat and convection. In addition, an exterior of the structure can be coated with a thermal reflective coating to reduce heat absorption from UV radiation. Moreover, panels with high insulation values can be disposed within or on the walls, ceiling or floor of the cold storage structure to achieve optimum thermal storage efficiency.

[0016] With reference now to the figures, wherein like reference numerals refer to like and corresponding parts throughout, and in particular with reference to FIG. 1, there is depicted a perspective view showing a bimodal cold storage system 100 in accordance with a preferred embodiment. Specifically, FIG. 1 illustrates that bimodal cold storage system 100 includes an enclosed refrigerated structure 101, which is a generally rectangular structure having an opening sealed by a door 102, and a mechanical refrigeration unit 103 mounted to refrigerated structure 101. To minimize thermal ingress from warmer outside temperatures, refrigerated structure 101 preferably includes insulated walls and ceilings, and optionally, an insulated floor. In various implementations, refrigerated structure 100 can be, for example, a restaurant walk-in cooler or freezer, a cold storage warehouse, a cold storage shipping container, a refrigerated trailer (reefer), etc.

[0017] The bimodal cold storage system 100 illustrated in FIG. 1 includes, as one of its thermal control modalities, a thermostatically controlled mechanical refrigeration unit 103 that monitors and regulates the temperature within an interior 104 of refrigerated structure 101 and the refrigerated contents and endothermic PCM disposed therein. To this end, mechanical refrigeration unit 103 employs a conventional evaporator/condenser system that produces chilled air and furthermore includes blowers or fans to forcefully discharge chilled, forced-air current(s) 112 into interior 104 to achieve rapid temperature control or recovery. Such mechanical refrigeration systems are well known and widely utilized to store and maintain goods within refrigerated structure 101 at reduced temperatures.

The other thermal control modality employed by refrigerated structure 101 is achieved by compatibly deploying an endothermic PCM, such as an endothermic phase change material, in conjunction with the cycling, forced-air heat extraction mechanism to achieve substantially increased thermal extraction and absorption capacity, a more even thermal gradient distribution, and a reduced cycling of mechanical refrigeration unit 103. The endothermic PCM can be advantageously deployed within various PCM containers (e.g., overhead PCM tubes 105 and under-shelf PCM containers 106) supported by a rack system 110 within refrigerated structure 101. The particular endothermic PCM chosen is dependent on the desired temperature to be maintained within refrigerated structure 101. For example, an endothermic PCM that reaches stasis at approximately -10° F (-23° C) is suitable for use in circumstances where the goods are to be maintained at or below freezing (i.e., 32° F or 0° C). For goods that must be chilled but not frozen, endothermic PCMs having a higher stasis temperature can be utilized. Temperature ranges employed for common perishable goods include, for example, a temperature range between 32° F to 55° F (0° C to 13° C) for fruit, vegetables, beer, dairy products, pharmaceuticals, and the like, or between -32° F and -20° F (-36° C to -29° C) for frozen meat, ice cream, and the like. For food storage applications, the endothermic PCM is preferably implemented utilizing a material, such as a water-based or organic-based PCM, that is non- hazardous and environmentally friendly.

[0018] Still referring to FIG. 1 and with additional reference to FIG. 2A, rack system llO.shown in a partial perspective view in FIG. 2A, will now be described. Rack system 110, which may be retrofitted within an existing refrigerated structure 101 without modification of the existing structure or originally installed in a new refrigerated structure 101, includes at least one (and possibly multiple) storage shelves 201 for supporting refrigerated goods. Storage shelf 201 is supported by adjustable height vertical supports 202, which may use, for example, perforated nested angled corner vertical supports secured by fasteners (e.g., nuts and bolts) to permit configuration (or reconfiguration) to a desired overall rack height. Overhead endothermic PCM tubes 105 are disposed on one or more horizontal support members 203, which are attached securely to height-adjustable vertical supports 202, for example, by welding, fasteners, etc. Vertical supports 202, and thus horizontal support members 203 and PCM tubes 105, are advantageously height-adjustable to allow optimal height placement of overhead endothermic PCM tubes 105. Optimal height placement of overhead endothermic PCM tubes 105 can depend on a number of factors, such as the maximum height clearance of the interior volume of refrigerated structure 101 (FIG. 1), the location of the forced-air flow ingress of mechanical refrigeration unit 103 (FIG. 1), the modular arrangement of rack system 110 (FIG. 1), the loading configuration of the cold storage goods, etc. In addition, it should be appreciated that PCM tubes 105 can be arranged with their long axes parallel to, orthogonal to, or in some other desired orientation to the forced-air flow path generated by mechanical refrigeration unit 103. Achieving the desired orientation of PCM tubes 105 to the forced-air flow path may also entail installation of PCM tubes 105 orthogonal to the long axis of rack systems 110 and bridging multiple rack systems 110. [0019] It should be noted that storage shelf 201 and horizontal support member 203 are depicted as being constructed using heavy duty wire mesh material. However, it should be appreciated that the selected material can vary between implementations. For example, solid surface and/or perforated surface may alternatively or additionally be employed. Moreover, other types of height-adjustable vertical shelf support systems such as telescopic vertical members or additional vertical support members can be employed without l niting the spirit and scope of the invention.

[0020] In addition to supporting perishable goods, storage shelf 201 is configured to support under-shelf PCM containers 106 by attachment (e.g., during initial construction or by retrofitting) of one or more under-shelf support brackets 205 to an underside of adjustable, storage shelf 201. With under-shelf support brackets 205 attached, additional under-shelf PCM containers 106 can be slidably installed under storage shelf 201. Although embodiments having various materials and dimensions are contemplated, in one example PCM containers 106 are formed of high-density polyethylene (HDPE) and have dimensions of 500 mm ^χ 250 mm ^χ 45 mm. PCM containers 106 are preferably sized to be mod xlarly reconfigurable to accommodate various storage shelf configurations. For example, FIGs. 2B-2C illustrate that PCM containers 106 can be arranged in a first orientation as shown in FIG. 2B to fit a narrow storage shelf 201 (e.g., 18" x 48") or alternatively arranged in a second orientation as shown in FIG. 2C to fit a deeper storage shelf 201 (e.g., 24" 48").

[0021] With reference now to FIG. 3, there is illustrated a top plan view of an exemplary embodiment of a cold storage rack arrangement including four cold storage racks 110 in a 2^2 split configuration. The depicted arrangement may be suitable, for example, for a restaurant's walk-in cooler or freezer. In the depicted embodiment, overhead PCM tubes 105 are longitudinally disposed in alignment with the long axis of each cold storage rack 110 upon horizontal support members 203 (e.g., wire mesh) attached to adjustable height vertical supports 202. The quantity and arrangement of PCM tubes 105 disposed on horizontal support members 203 may vary depending upon the optimal volume and/or velocity of air flow passing between PCM tubes 105. [0022] In the embodiment of FIG. 3, the stability and rigidity of cold storage racks 110 is enhanced by one or more horizontal cross beams 204 coupled between cold storage racks 110. Horizontal cross beam(s) 204 preferably link cold storage racks 110 at their tops in order to preserve adequate headroom in a walk space 301 between cold storage racks 110. The width of walk space 301, which is defined by the length of horizontal cross beam(s) 204, is preferably of sufficient width to permit convenient access to goods stored on the various storage shelves 201 on either side of walk space 301. It should be appreciated that a variety of cold storage rack arrangements and horizontal cross beam lengths fall within the spirit and scope of the invention.

[0023] Cold storage racks 110 enable the enclosing refrigerated structure in which they are disposed to benefit from the passive cooling provided by PCM tubes 105 (and optionally under- shelf PCM containers 106) without requiring any modification of the refrigerated structure or penetration of, or attachment to any of its interior surfaces. In some embodiments, the passive cooling capacity of the refrigerated structure may optionally be further augmented by the attachment of additional PCM containers to one or more of the interior surfaces of the refrigerated structure.

[0024] FIG.4 is a side elevation view of exemplary embodiment of a cold storage rack 110. In particular, FIG. 4 shows, via a cutaway view, overhead PCM tubes 105 disposed on horizontal support member 203, which is in turn attached securely to adjustable height vertical supports 202 for optimal height placement of overhead PCM tubes 105. Moreover, ends of horizontal cross beam bracket 204 attach to adjustable height vertical supports 202, providing additional structural support.

[0025] Structural members of cold storage racks 110, including vertical supports 202, shelf supports 400 and lateral braces 402, and may be implemented with bar, angle, channel, beam, square tube, round tube, etc. Although other materials may be employed, steel is presently preferred for the structural members of cold storage racks 110 due to steel's relatively low cost and high strength-to-weight ratio. In at least some embodiments, cold storage rack 110 may optionally further incorporate PCM containers (e.g., PCM tubes 404) along or within one or more of its structural members to provide additional capacitive cooling capacity. For structural members that do not have a substantially enclosed configuration, PCM containers may be secured to the structural members by ties, clamps, brackets or the like. For structural members such as tubes and channel having substantially enclosed configurations, additional attachment of the PCM containers to the structural members can be omitted.

[0026] With reference now to FIGs.5A-5B, there is illustrated an exemplary management and control system for cold storage system 100 in accordance with one embodiment. As shown in FIG. 5A, the exemplary management and control system preferably includes an electronic controller 520 communicatively coupled to multiple sensors within refrigerated structure 101. These sensors preferably include one or more PCM temperature sensors 502 that sense a PCM temperature in one or more PCM containers (e.g., overhead PCM tubes 105 or under-shelf PCM containers 106). In one embodiment shown in FIG. 5B, PCM temperature sensors 502 have a first probe 504 at or near a core region of a PCM tube 105 (or PCM container 106), and a second probe 506 at or near an outer region of a (possibly different) PCM tube 105 (or PCM container 106). Typically, the PCM temperature detected by probe 504 at the innermost point of overhead PCM tube 105 (or PCM container 106) lags behind the PCM temperature sensed by probe 506 near the inner surface of overhead PCM tube 105 (or PCM container 106) as the PCM changes phase from latent heat mode to sensible heat mode. Sensing temperature at multiple locations within the PCM can thus provide controller 520 a more accurate indication of the state of the PCM along its latent-to-sensible phase change curve (and sensible-to-latent phase change curve), where the goal of the controller 520 is to prevent complete conversion of the PCM from its latent heat mode to its sensible heat mode.

[0027] The exemplary management and control system for cold storage system 100 preferably additionally includes one or more ambient condition sensors 510 within or associated with refrigerated structure 101. For example, ambient condition sensors 510 may include an ambient temperature sensor providing temperature data indicative of the temperature of a representative location within the interior volume of refrigerated structure 101, as well as relative humidity and dew point sensors. In addition, ambient condition sensors may include a door sensor to sense the openings and closings of door 102. The ambient temperature will typically vary dynamically according to the heat transfer to and from the environment by numerous factors, the primary ones being operation of mechanical refrigeration unit 103, external ambient temperatures, and the number and duration of intrusions into refrigerated structure 101 by people and/or goods via door 102.

[0028] The management and control system preferably further includes one or more goods sensors 512 that sense the temperature and/or other parameter of the goods within refrigerated structure 101. As will be appreciated, depending upon the type of goods in question and the parameter to be sensed, goods sensor(s) 512 may be placed on an exterior of one of the goods in refrigerated structure 101 or embedded within the goods.

[0029] Controller 520 processes the sensor data received from sensors 502, 510 and 512 and, responsive thereto, controls mechanical refrigeration unit 103 in accordance with one or more control methodologies implemented alternatively or in combination. For example, the control methodologies implemented by controller 520 can be configured to maintain the interior volume of refrigerated structure 101 within a desired temperature range while:

• maintaining the PCM within desired region(s) of its phase change curves as determined from the ambient, goods, and PCM temperatures,

• minimizing or reducing power and/or energy consumption,

• minimizing or reducing utility costs,

• reducing cost of operation of mechanical refrigeration unit 103;

• increase the useful life of mechanical refrigeration unit 103;

© minimizing or reducing the cycling and/or duration of operation of mechanical refrigeration unit 103,

• preferentially operating mechanical refrigeration unit 103 during desired time periods (e.g., during off-peak hours),

• maximizing or increasing utility rebates or incentives to the utility customer,

• reducing the peak or average load of a utility system, and/or

• controlling based upon one or more additional factors.

[0030] As indicated, controller 520 may optionally be further communicatively coupled to a communication interface 522, which communicates status information and/or alarms regarding cold storage system 100 to one or more remote locations via one or more wired or wireless packet switched or circuit switched communication networks. The status information and/or alarms can be communicated, for example, to a remote server computer, mobile phone, or pager of an operator of cold storage system 100, a service provider or service technician of the operator, or an electrical utility provider. The status information and/or alarms can be communicated, for example, in a textual message, numeric message and/or a data message, communicated, for example, in an email, short message service (SMS) message, phone call, page, HTTP message, or the like.

[0031] Referring back to FIGs. 1-5B, in operation controller 520 preferably initially activates mechanical refrigeration system 103 to produce chilled, forced-air current 112, which charges the endothermic PCM contained in overhead PCM tubes 105 and under-shelf PCM containers 106 and cools interior 104 of refrigerated structure 101. Controller 520 preferably operates mechanical refrigeration unit 103 in its active chill mode until the ambient temperature of interior 104 sensed by ambient temperature sensor 506 achieves at least a first threshold temperature, the endothermic PCM achieves stasis, as indicated by temperature sensor(s) 502. and the temperature of the goods indicated by goods sensor(s) 512 reaches a second threshold temperature. In response, controller 520 suspends or substantially reduces the operation of mechanical refrigeration unit 103.

[0032] Once the PCM in overhead endothermic PCM tubes 105 and under-shelf PCM containers 106 has been thermally charged to stasis, the endothermic (i.e., heat absorbing) characteristics of the PCM significantly extends the period of time over which the internal temperature of refrigerated structure 101 and the goods disposed therein will remain at or below the predetermined maximum temperature without having to operate mechanical refrigeration unit 103. Eventually, the PCM begins to transition from the latent heat mode to the sensible heat mode and the capacitive cooling effect of the PCM wanes. Controller 520 senses this condition and operates mechanical refrigeration unit 103 in its active chill mode to recharge the PCM to its latent heat mode and maintain the goods temperature and ambient temperature of refrigerated structure 101 within desired temperature ranges.

[0033] All of the apparatus and methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While various embodiments have been described, it will be appreciated by those skilled in the art that variations may be applied to the described embodiments without departing from the concept, spirit and scope of the invention. More specifically, it will be apparent that certain components may be added to, combined with, or substituted for the components described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.