DESC:TECHNICAL FIELD
[0001] The present disclosure relates to the technical field of refrigeration systems. In particular, the present disclosure pertains to a cooler /chiller to cool fluids off-grid using solar power stored as thermal energy.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Various types of coolers are in use. They typically include a chiller that removes heat from a liquid, via a vapor-compression or absorption refrigeration cycle. The cooled liquid, which is usually water, works as a cooling media, and is used for cooling purpose. The cooled cooling media may be used in different manners depending on cooling requirement. For example, it may be circulated through a heat exchanger to cool an equipment, or another process stream, such as air or process water, or to cool and preserve perishable liquids, such as milk, juices, egg yolk etc. The cooled cooling media may also be used to cool and dehumidify air in buildings.
[0004] Conventional coolers use electrically powered refrigeration systems that work on a vapor-compression or absorption refrigeration cycle. Efforts to run such coolers using solar electric power have not been very successful. This is because of lack of availability of adequate solar power through the day and night. If batteries are used to store the power, total cost becomes high because of high power requirement to run high-capacity refrigeration unit, which proportionately increases the battery size to make it unaffordable.
[0005] In particular, when the cooler is required to preserve highly perishable product such as milk, the cooler has to cool bulk quantities, milked in mornings and evenings, below temperature of 4°C within a specified time to minimize microorganism growth. Therefore, a milk cooler requires refrigeration units with high refrigeration capacity, which is utilized at a time when solar power is not available, leading to requirement of high battery capacity, or attended expenses on account of grid power.
[0006] Because of high costs, those having cooling needs to preserve small quantities of perishable products are unable to afford their own coolers. That means they have to share a bulk cooler and have to travel, often several kilometres, to deposit their produce in the bulk cooler. Such users shall be benefited if a cost effective, small sized cooler that is not dependent on grid power could be made available to meet their requirement.
[0007] Therefore, there is a need to provide a small, modular, affordable solar driven cooling device, which can meet cooling needs of users having requirements to cool small quantities of produce.
[0008] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0009] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0010] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0011] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0012] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

OBJECTS OF THE INVENTION
[0013] A general object of the present disclosure is to provide a small, cost-effective cooler to meet requirement of individuals having requirements to cool small quantities of produce.
[0014] An object of the present disclosure is to provide a cooler that does not depend on grid power supply, and works on solar power.
[0015] An object of the present disclosure is to provide an off-grid cooler that is capable of meeting cooling needs through the day and night, i.e., including the period when solar power is not available.
[0016] Another object of the present disclosure is to provide a cooler that can rapidly chill highly perishable products to a temperature at which microorganism growth is slowed down.
[0017] Another object of the present disclosure is to provide a cooler that does not require large capacity batteries to store solar power to meet high power requirement during rapid cooling.
[0018] Another object of the present disclosure is to provide a cooling system and method that can rapidly chill highly perishable products without corresponding increase in capacity of the associated refrigeration unit.
[0019] Yet another object of the present disclosure is to provide a cooling system and method that takes care of variation in the available solar power during the course of the day.
[0020] Still another object of the present disclosure is to provide a cooling system and method that takes care of mismatch between the available solar power during the course of the day and refrigeration requirement.

SUMMARY
[0021] Aspects of the present disclosure relate to a solar driven cooler for meeting cooling needs of individuals having requirements to cool small quantities of produce. In particular, the present disclosure relates to a small, cost-effective cooler to meet requirement of individual farmers and small businesses, that makes use of all the solar radiations received during the day, and has capability to maintain cooling function through the day and night without depending on grid power. In another aspect, the proposed cooler does not need large storage batteries for storing electric power generated by solar panel during daytime for use during nights.
[0022] In an aspect, the disclosed solar-driven cooler system includes an electrical system; a refrigeration system comprising a variable frequency drive (VFD) coupled to a compressor motor; a thermal system having a liquid product storage and cooling assembly.
[0023] In an aspect, the liquid product storage and cooling assembly includes a thermal battery functioning based on a thermal storage media; and a storage tank housed within the thermal battery, to store a liquid product, the storage tank comprising walls that are thermally conductive. In an aspect, the thermal system includes one or more pumps to circulate a liquid phase of the thermal storage media such that, when required to expeditiously cool the stored liquid product, the circulated liquid thermal storage media is made to fall along an outer surface of the storage tank.
[0024] In an embodiment, the system may include a controller configured to: (i) receive, from a sensor configured to detect a temperature of a liquid product, a current temperature of the liquid product; (ii) receive, from the electrical system configured to provide an electric power to the liquid product storage and cooling assembly, a variation in a supplied electric power during a predefined period of time; and (iii) operate the liquid product storage and cooling assembly based on the variation in the supplied electric time during the predefined period of time, and the current temperature of the liquid product such that, capacity of operation of the liquid product storage and cooling assembly corresponds to the variation in the supplied electric power during the predefined period of time, and such that a temperature of the liquid product within the storage tank is within a predefined range of temperature.
[0025] In an embodiment, the electrical system includes one or more solar panels; and an inverter electrically coupled to the solar panels. The inverter may be configured to convert DC power generated by the solar panels into AC power.
[0026] In an embodiment, the compressor motor may be configured to provide cooling to the thermal storage media such that at least a portion of the thermal storage media is in a liquid phase.
[0027] In an embodiment, the compressor motor may be configured to be driven at variable speeds to deliver variable cooling based on the availability of electric power supplied via the electrical system.
[0028] In an embodiment, the system may include a battery configured to store at least a portion of supplied electric power. Further, the battery may be configured to provide the stored electric power to one or more components of the liquid product storage and cooling assembly.
[0029] An aspect of the present disclosure relates to a method for operating a solar-driven cooler system, including the steps of: (i) receiving, by a controller, from a sensor configured to detect a temperature of the liquid product, a current temperature of the liquid product; (ii) receiving, by the controller, from an electrical system configured to provide an electric power to the liquid product storage and cooling assembly, a variation in a supplied electric power during a predefined period of time; and (iii) operating, by the controller, a liquid product storage and cooling assembly based on the variation in the supplied electric time during the predefined period of time, and the current temperature of the liquid product such that, capacity of operation of the liquid product storage and cooling assembly corresponds to the variation in the supplied electric power during a predefined period of time, and such that a temperature of the liquid product within the storage tank is within a predefined range of temperature.
[0030] Yet another aspect of the present disclosure relates to a solar-driven cooler, the cooler having: a liquid product storage and cooling assembly that includes a thermal battery functioning based on a thermal storage media; and a storage tank housed within the thermal battery to store a liquid product, the storage tank comprising walls that are thermally conductive. In an aspect, the cooler includes one or more pumps to circulate a liquid phase of the thermal storage media such that, when required to expeditiously cool the stored liquid product, the circulated liquid thermal storage media is made to fall along an outer surface of the storage tank.
[0031] In an embodiment, the thermal storage media is a phase change material and the thermal battery holds thermal storage media in both the liquid phase and a solid phase of the thermal storage media.
[0032] In an embodiment, the liquid product storage and cooling assembly may include an insulated tank comprising an upper part and a lower part, wherein the lower part is configured to accommodate cooling coils.
[0033] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0034] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0035] FIG. 1 illustrates a typical graph showing variation in amount of solar radiation reaching a given area (insolation) through the day.
[0036] FIG. 2 illustrates a typical graph showing variation in insolation and it utilization during the day by a conventional solar power driven refrigeration system.
[0037] FIG. 3 illustrates an exemplary schematic representation of electrical system architecture of the proposed solar driven cooler, in accordance with embodiments of the present disclosure.
[0038] FIG. 4 illustrates an exemplary graph showing variation in insolation and it utilization during the day by the proposed solar driven cooler, in accordance with embodiments of the present disclosure.
[0039] FIG. 5 illustrates an exemplary schematic representation of thermal system architecture of the proposed solar driven cooler, in accordance with embodiments of the present disclosure.
[0040] FIG. 6 illustrates an exemplary flow diagram for the proposed method for operating a cooler, in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION
[0041] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0042] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0043] Various terms as used herein. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0044] Aspects of the present disclosure relate to a solar driven cooler for meeting cooling needs of individuals having requirements to cool small quantities of produce. In particular, the present disclosure relates to a small, cost-effective cooler to meet requirement of individual farmers and small businesses, that makes use of all the solar radiations received during the day, and has capability to maintain cooling function through the day and night without depending on grid power. In another aspect, the proposed cooler does not need large storage batteries for storing electric power generated by solar panel during daytime for use during nights. In yet another aspect, the disclosed solar driven cooler also does not require large refrigeration capacity for rapidly chilling highly perishable products, when received, within a specified time period to prevent growth of microorganisms.
[0045] In an aspect, the proposed solar driven cooler includes an improved electrical system architecture and an improved thermal system architecture that work synergistically to eliminate need to have storage batteries to store the generated electric power to meet the power requirement during periods when insolation is inadequate or not available. The synergistic working of the electrical system and the thermal system architecture also eliminates need to have a refrigeration system that matches cooling requirement to rapidly cool highly perishable products, such as milk, when received, to desired temperatures within a specified time period to avoid growth of microorganisms. The synergistic operation of the electrical system and the thermal system enables the disclosed cooler to work solely on solar power eliminating need for a backup power source, and reduces its cost to make it affordable to small farmers and businesses.
[0046] In an aspect, the electrical system of the proposed solar driven cooler includes a solar power generation system to generate electric power and a refrigeration system. The solar power generation system includes one or more photovoltaic solar panels and an inverter to convert DC power generated by the solar panels, to AC power that is suitable to run the refrigeration system. The refrigeration system includes a variable frequency drive to drive compressor of the refrigeration system at variable speeds for the refrigeration system to deliver variable cooling depending on availability of electric power from the solar power generation system. Thus, the proposed electrical system can exploit most of the insolation through the day without having to store the generated electric power in a battery bank. Specifically, the electric power generated during period when the insolation is not adequate to make the compressor run at its rated capacity, can also be used in running the refrigeration system.
[0047] In an aspect, the thermal system includes a thermal battery to store surplus cooling for use when the refrigeration system is unable to function, such as during nights when there is no insolation, or when the refrigeration system is unable to meet full cooling requirement, such as mornings and evenings when electric power generated by the solar panels is inadequate to meet power requirement of the compressor to meet full cooling requirement.
[0048] In an aspect, the thermal battery can store surplus cooling by cooling a thermal storage media. In an aspect, the thermal storage media may be a phase change material that freezes when cooled, thereby storing the cooling capacity. Thus, the thermal battery can have combination of frozen and chilled liquid thermal storage media at freezing temperature, and the chilled liquid thermal storage media can be circulated to cool a liquid product stored in a storage tank, or through a heat exchanger to cool air to cool an enclosed space. In an aspect, water may be used as the thermal storage media.
[0049] In an aspect, the storage tank can be cooled by falling film technique to cool its contents. The chilled liquid thermal storage media can be pumped and made to fall along vertical walls of the storage tank. The heated thermal storage media can return back to the liquid thermal storage media, which can remain at freezing temperature by melting of at the frozen thermal storage media.
[0050] In an aspect, cooling rate can be varied by changing the rate at which the thermal storage media is pumped. Alternatively, area of the vertical walls of the storage tank along which the chilled liquid thermal storage media is made to fall can be varied to vary the cooling rate.
[0051] In an aspect, the storage tank and the thermal battery can be integrated into a single unit comprising an insulated tank and a smaller storage tank accommodated within the insulated tank such that lower part of the insulated tank accommodates cooling coils of the refrigeration system to carry refrigerant. The thermal storage media is filled in the lower part of the insulated tank so that the cooling coils are submerged in the thermal storage media. When the refrigeration system works, the cooling of the thermal storage media by the cooling coils can result in chilling of the thermal storage media to freezing temperature, and subsequent freezing of a part of it around the cooling coils. The chilled thermal storage media in liquid form that surrounds the frozen liquid media, can be pumped for cooling the storage tank, and can fall back within the liquid thermal storage media. Thus, all the parts, i.e. the storage tank, cooling coils, pumps and the piping circulating the thermal storage media can be within the insulated tank, making it a compact integrated module.
[0052] In an aspect, the disclosed solar driven cooler can also include a battery bank to store surplus electric power, which cannot be used for running the compressor through the variable frequency drive. The stored power can be used in running accessories such as stirrers and pumps. In certain applications, the stored electric power from the battery bank can also be used to run compressor of the refrigeration system, if the situation demands, such as during cloudy conditions.
[0053] In an aspect, the cooling system may comprise a controller to control operation of the variable frequency drive so that power demand by the compressor matches the available power from the solar power generation system. The controller can also control the pumps to achieve desired cooling rates for the liquid product stored in the storage tank so that microorganism growth is minimized and the stored product retains its value.
[0054] An aspect of the present disclosure also relates to a method for operating a cooler, the method comprising the steps of: generating electric power using photovoltaic solar panels; controlling a variable frequency drive coupled to a motor of a compressor of a refrigeration system to match power demand of the compressor with the generated power; storing cooling generated by the refrigeration system in a thermal storage media; and cooling a liquid product stored in a storage tank using cooling stored in the thermal storage media. In an aspect, the step of cooling the product is done at desired rate to minimize growth of microorganism, and thereafter to maintain the product within a desired temperature range to maintain its value.
[0055] In an aspect, the method for operating the cooler may also comprise the steps of storing surplus electric power generated by the photovoltaic solar panels in a battery bank, wherein the stored electric power from the battery bank may be used to run auxiliary devices, such as, but not limited to, stirrers and pumps.
[0056] In an aspect, the method for operating the cooler may further comprise the steps of using the stored electric power from the battery bank to run the motor of the compressor to operate the refrigeration system.
[0057] An aspect of the present disclosure relates to a storage and cooling tank assembly that integrates a thermal battery and a storage tank to facilitate cooling of a stored liquid product by falling film technique. The storage and cooling tank assembly includes an insulated tank and a smaller storage tank accommodated within the insulated tank, such that lower part of the insulated tank accommodates cooling coils of a refrigeration system to carry a refrigerant. A thermal storage media is filled in the lower part of the insulated tank so that the cooling coils are submerged in the thermal storage media. When the refrigeration system works, the cooling of the thermal storage media by the cooling coils results in chilling of the thermal storage media to freezing temperature, and subsequent freezing of a part of it around the cooling coils.
[0058] The storage and cooling tank assembly further includes one or more pumps to pump the chilled thermal storage media in liquid form that surrounds the frozen liquid media. The pumped chilled liquid cooling media is made to fall along walls of the storage tank to cool the liquid product stored therein. The liquid cooling media falls back within the liquid thermal storage media for recirculation.
[0059] Embodiments explained herein relate to a solar driven cooler and method for operating a cooler that use only solar power for their power requirement. One of the challenges of using solar power to run refrigeration system of the coolers is that solar radiation varies through the day and power generated from the solar radiation does not match the power required to run the refrigeration system of the coolers. For instance, the refrigeration system of the coolers may be required to work at its peak output for rapidly cooling a product during periods when solar power is inadequate, or not available. On the other hand, at and around noon, when solar power systems provide maximum power, the refrigeration system of the coolers may be required to only maintain temperature of the already cooled product, requiring low power.
[0060] This is because solar power systems work best when the sun is shining. As the strength of sunlight varies with angle of the sun through the day and seasons, so does the strength of the sun's radiation and this affects the amount of electricity a solar power system can generate. FIG. 1 illustrates a typical graph showing variation in amount of solar radiation reaching a given area through the day, and as can be seen, insolation is highest during 11 am to 4 pm, which results in highest power generation, which directly corresponds to the insolation, during that period through the solar power systems.
[0061] FIG. 2 illustrates a typical graph showing variation in insolation and it utilization during the day by a conventional solar power driven refrigeration system. The conventional refrigeration systems incorporate compressors that have constant power demand, and therefore, they can be run using power from solar power systems only when there is adequate insolation to meet power requirement, marked as Pcomp in FIG. 2, of the compressor, such as during the period marked A in FIG. 2. During the periods of lower insolation, such as marked B in FIG. 2, electric power developed by the solar power systems is inadequate and remains unutilized by the refrigeration system. Even during the period of the refrigeration system working on solar power, the power developed may be more, as shown by region marked C in FIG. 2, than Pcomp, and shall remain unutilized.
[0062] To overcome the mismatch between the power generated by the solar power system and the power required to run the refrigeration system of the coolers, conventional solar powered coolers may include battery banks to store generated power from the solar power system that is surplus from the refrigeration system. The stored electric power from the battery bank may be used to run the refrigeration system when there is no or inadequate power from the solar power system. However, since adequate power to run the compressor is available only for a part of the day, and amount of stored power that is required to run the compressor during remaining time is large, providing batteries to store power for full dependence on the solar power becomes capital intensive and unaffordable for small farmers and businesses.
[0063] In an aspect, the cooler of the present disclosure includes an improved electrical system architecture and an improved thermal system architecture that work synergistically to eliminate need to have storage batteries to store the generated electric power to meet the power requirement of the compressor when insolation is inadequate or not available. In particular, the improved electrical system enables utilization of larger amount of insolation to run the compressor, thereby reducing the amount of electric power from the solar power system that remains unutilized by the refrigeration system. At the same time, the improved thermal system enables storage of cooling for use during periods when the refrigeration system cannot be run directly from the solar power. This eliminates demand for power from the compressor when power requirement cannot be met by the solar power system, thereby making the proposed cooler truly solar driven.
[0064] FIG. 3 illustrates an exemplary schematic representation of the electrical system 300 of the proposed solar driven cooler, which includes a solar power generation system having one or more photovoltaic solar panels 302 and an inverter 304 to convert DC power generated by the solar panels 302 to AC power. The electrical system 300 can also include a battery bank 310 to store electric power generated by the solar power system, which is surplus, not used by the refrigeration system. In an aspect, the power stored in the battery bank 310 can be used for running accessories such as stirrers and pumps (refer to FIG. 5) and other electrical accessories. In certain applications, the stored electric power from the battery bank 310 can also be used to run a compressor motor 308 if the situation demands, such as during cloudy conditions.
[0065] The electrical system also includes electrical portion of the refrigeration system having a variable frequency drive (VFD) 306 to drive a compressor motor 308 that runs a compressor of the refrigeration system to cool the thermal storage media that stores the surplus cooling. The variable frequency drive 306 enables the compressor motor 308 to run at variable speeds, such as at lower than rated speed, which reduces power consumption by the motor. Thus, the variable frequency drive 306 can be used to match power demand of the compressor motor 308 with the generated electric power, which undergoes variation due to variation in insolation during the day. Thus, the electric power generated during period when the insolation is not adequate to make the compressor run at its rated capacity, can also be used in running the refrigeration system.
[0066] FIG. 4 illustrates an exemplary graph showing variation in available power from insolation and its utilization during the day by using the variable frequency drive 306. During the period A to B, available solar power is not enough to run the compressor motor 308 even through the VFD 306. During this period, the generated electric power, shown by region marked as G, can charge battery bank 310. During the period B to C, using the VFD 306, power demand of the compressor motor 308 can be matched with the generated power to fully utilize the solar electric power for refrigeration, and there would not be any surplus power. During the period C to D, available solar power is more than the max power demand of the compressor motor 308, leaving surplus shown by region marked as H. The surplus power can be used to charge the battery bank 310.
[0067] During period D to E, and from E to F, the electrical system 300 can operate in same manner as during B to C and A to B respectively.
[0068] Thus, the proposed electrical system 300 allows for a range of electric output to run the compressor motor 308 at variable speeds with corresponding variable cooling output, combined with a smaller electric battery charging to gainfully utilize the surplus solar power.
[0069] Referring back to FIG. 3, the cooler can also include a controller 314 to control operation of the VFD 306 so that power demand by the compressor motor 308 matches the available power from the solar power system. The controller 314 can also control the pumps 508 (refer to FIG. 5) to achieve desired cooling rates for liquid stored in the storage tank so that microorganism growth is minimized and the stored product retains its value.
[0070] FIG. 5 illustrates an exemplary schematic representation of thermal system 500 of the proposed solar driven cooler, which can include a liquid product storage and cooling assembly 502 and a refrigerant circuit 550. The refrigerant circuit 550 includes a compressor 552 run by the compressor motor 308 (refer FIG. 3), a condenser 554, an expansion valve 556 and an evaporator /cooling coils 558. The cooling coils 558 can be located within the storage and cooling assembly 502.
[0071] In an aspect, the liquid product storage and cooling assembly 502 (also referred to simply as storage and cooling assembly) can serve dual purpose of firstly storing cooling generated by the refrigerant circuit 550, i.e. carry out function of thermal storage battery/thermal battery, and secondly, storing and cooling a liquid product when received therein at desired rate to minimize microorganism growth, and thereafter, maintaining its temperature within a desired range to retain value of the liquid product.
[0072] In an aspect, the function of the thermal battery is performed by an insulated tank 506 that is insulated from outside by insulation 512, and a liquid thermal storage media 514 stored therein. The cooling coil 558 of the refrigerant circuit 550 is submerged within the thermal storage media 514.
[0073] In an aspect, the thermal storage media 514 is a phase change material that freezes when cooled, thereby storing the cooling capacity. Therefore, when cool refrigerant is circulated through the cooling coil 558, the thermal storage media cools down and starts freezing, as shown by frozen thermal storage media 516 in FIG. 5, thereby storing the cooling. The thermal battery can have combination of frozen 516 and chilled liquid 514 thermal storage media at freezing temperature, and the chilled liquid thermal storage media 514 can be circulated to provide cooling. In an embodiment, water is used as the thermal storage media.
[0074] In an aspect, the storage and cooling assembly 502 also includes a storage tank 504 accommodated within the insulated tank 506 such that lower part of the insulated tank 506 is free to accommodates cooling coil 558 and the thermal storage media 514/516.
[0075] In an aspect, cooling of the liquid product stored in the storage tank 504 can be done by falling film technique using the liquid phase 514 of the thermal storage media. The chilled liquid thermal storage media 514 is pumped by pumps 508 and made to fall along vertical walls of the storage tank to form a falling film 510 along the outer surface of the storage tank 504. The heated liquid phase thermal storage media 514 returns back to bottom of the insulated tank 506. The liquid phase thermal storage media 514 can remain at freezing temperature by melting of at the frozen thermal storage media 516.
[0076] In an aspect, cooling rate can be varied by changing the rate at which the thermal storage media 514 is pumped. Alternatively, area of the vertical walls of the storage tank 504 along which the chilled liquid thermal storage media 514 is made to fall can be varied to vary the cooling rate. In an aspect, operation of one or more pumps 508 can be controlled by the controller 314 (refer to FIG. 3) based on temperature of the liquid product in the storage tank 504 as sensed by a temperature sensor. The controller 314 can be configured to operate the pumps 508 for enhanced cooling depending on difference in the sensed temperature and the desired temperature such that when liquid product is received in the storage tank 504, it is cooled to the desired temperature within a specified time period to minimize growth of microorganism. On the other hand, the controller 314 can reduce the cooling rate when the sensed temperature is found within a desired range or lower. Depending on nature of liquid product stored in the storage and cooling assembly 502, a stirrer 518 can be provided to maintain a uniform temperature through the stored product.
[0077] Thus, the the storage and cooling assembly 502 provides a compact configuration and carries out dual function of thermal storage battery/thermal battery, and storing and cooling the liquid product when received therein at desired rate to minimize microorganism growth and thereafter maintaining its temperature within a desired range to retain value of the liquid product.
[0078] It can be appreciated that ability to store cooling and use the stored cooling to meet differing cooling rate requirements, such as surge requirement to chill the freshly received liquid product within a specified time period, enables use of a refrigeration system of smaller capacity than what would have been essential to meet the surge requirement.
[0079] In an embodiment, the proposed cooler can also be used for cooling air in place of a liquid product. The storage and cooling assembly 502 can be replaced by a thermal battery, which can be based on an insulated tank to store the thermal storage media, and cooling coils of the refrigeration system to carry refrigerant. As in case of the storage and cooling assembly 502, the thermal battery can have combination of frozen and chilled liquid thermal storage media at freezing temperature, and the chilled liquid thermal storage media can be circulated through a heat exchanger to cool air.
[0080] FIG. 6 is a flow diagram for the proposed method for operating a cooler. The method includes, at step 602, generating electric power using photovoltaic solar panels, such as solar panels 302 shown in FIG. 3. At step 604 of the method, a variable frequency drive, such as VFD 306 shown in FIG. 3, coupled to a compressor motor, such as compressor motor 308 shown in FIG. 3, of a refrigeration system, is used to match power demand of the compressor motor 308 with the generated power. At step 606 of the method, the cooling generated by the refrigeration system is stored in a thermal storage media, such as thermal storage media 514/516 shown in FIG. 5; and at step 608 a liquid product stored in a storage tank, such as storage tank 504 shown in FIG. 5, is cooled using cooling stored in the thermal storage media 514/516. In an aspect, the step of cooling the liquid product is done at desired rate to minimize growth of microorganism, and thereafter to maintain the liquid product within a desired temperature range to maintain its value.
[0081] In an aspect, the method for operating the cooler may also comprise the steps of storing surplus electric power generated by the photovoltaic solar panels 302 in a battery bank, such as battery bank 310 shown in FIG. 3, wherein the stored electric power from the battery bank 310 may be used to run auxiliary devices, such as, but not limited to, stirrers, such as stirrer 518 shown in FIG. 5, and pumps, such as pumps 508 shown in FIG. 5.
[0082] In an aspect, the method for operating the cooler may further comprise the steps of using the stored electric power from the battery bank 310 to run the compressor motor 308 to operate the refrigeration system.
[0083] In an aspect, the disclosed cooler can work in different modes as summarized in the below table:

MODE COOLING REQUIRED? POWER AVAILABLE? COMPRESSOR STATUS COOLING PUMP & STIRRER STATUS
COOLING+CHARGING OF THERMAL STORAGE YES YES ON ON
COOLING ONLY (DISCHARGE OF THERMAL STORAGE) YES YES OFF ON
CHARGING OF THERMAL STORAGE NO YES ON OFF
OFF (E.G. DURING NIGHT WHEN NO SUN AND NO COOLING) NO NO NO OFF

[0084] Thus, the present disclosure provides a small, cost-effective cooler to meet requirement of small businesses that makes use of all the solar radiations received during the day, and maintains the stored liquid product at temperature within a desired temperature range without having to spend on large storage batteries for storing electric power generated by solar panel during daytime for use during nights. In another aspect, the disclosed solar driven cooler also does not require large refrigeration capacity for chilling of the received liquid product within a specified time period to avoid growth of microorganisms.
[0085] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE INVENTION
[0086] The present disclosure provides a small, cost-effective cooler to meet requirement of individuals having requirements to cool small quantities of produce.
[0087] The present disclosure provides a cooler that does not depend on grid power supply, and works on solar power.
[0088] The present disclosure provides an off-grid cooler that is capable of meeting cooling needs through the day and night, i.e., including the period when solar power is not available.
[0089] The present disclosure provides a cooler that can rapidly chill highly perishable products to a temperature at which microorganism growth is slowed down.
[0090] The present disclosure provides a cooler that does not require large capacity batteries to store solar power to meet high power requirement during rapid cooling.
[0091] The present disclosure provides a cooling system and method that can rapidly chill highly perishable products without corresponding increase in capacity of the associated refrigeration unit.
[0092] The present disclosure provides a cooling system and method that takes care of variation in the available solar power during the course of the day.
[0093] The present disclosure provides a cooling system and method that takes care of mismatch between the available solar power during the course of the day and refrigeration requirement.
,CLAIMS:1. A solar-driven cooler system, the system comprising:
an electrical system (300);
a refrigeration system comprising a variable frequency drive (VFD) (306) coupled to a compressor motor (308);
a thermal system (500) comprising:
a liquid product storage and cooling assembly (502), the assembly comprising:
a thermal battery functioning based on a thermal storage media (514, 516); and
a storage tank (504) housed within the thermal battery, to store a liquid product, the storage tank (504) comprising walls that are thermally conductive;
wherein the thermal system (500) comprises one or more pumps (508) to circulate a liquid phase of the thermal storage media (514) such that, when required to expeditiously cool the stored liquid product, the circulated liquid thermal storage media (514) is made to fall along an outer surface of the storage tank (504).

2. The system as claimed in claim 1, comprising a controller (314) configured to:
receive, from a sensor configured to detect a temperature of a liquid product, a current temperature of the liquid product;
receive, from the electrical system (300) configured to provide an electric power to the liquid product storage and cooling assembly (502), a variation in a supplied electric power during a predefined period of time; and
operate the liquid product storage and cooling assembly (502) based on the variation in the supplied electric time during the predefined period of time, and the current temperature of the liquid product such that, capacity of operation of the liquid product storage and cooling assembly (502) corresponds to the variation in the supplied electric power during the predefined period of time, and such that a temperature of the liquid product within the storage tank (504) is within a predefined range of temperature.

3. The system as claimed in claim 1, wherein the electrical system (300) comprises:
one or more solar panels (302); and
an inverter electrically coupled to the solar panels (302), wherein the inverter is configured to convert DC power generated by the solar panels (302) into AC power.

4. The solar-driven cooler system 1, wherein the compressor motor (308) is configured to provide cooling to the thermal storage media (514, 516) such that at least a portion of the thermal storage media (514) is in a liquid phase.

5. The system as claimed in claim 4, wherein the compressor motor (308) is configured to be driven at variable speeds to deliver variable cooling based on the availability of electric power supplied via the electrical system (300).

6. The system as claimed in claim 1, comprising a battery (310) configured to store at least a portion of supplied electric power and wherein the battery (310) is configured to provide the stored electric power to one or more components of the liquid product storage and cooling assembly (502).

7. A method for operating a solar-driven cooler system, the method comprising:
receiving, by a controller (314), from a sensor configured to detect a temperature of the liquid product, a current temperature of the liquid product;
receiving, by the controller (314), from an electrical system configured to provide an electric power to the liquid product storage and cooling assembly (502), a variation in a supplied electric power during a predefined period of time; and
operating, by the controller (314), a liquid product storage and cooling assembly (502) based on the variation in the supplied electric time during the predefined period of time, and the current temperature of the liquid product such that, capacity of operation of the liquid product storage and cooling assembly (502) corresponds to the variation in the supplied electric power during a predefined period of time, and such that a temperature of the liquid product within the storage tank (504) is within a predefined range of temperature.

8. A solar-driven cooler, the cooler comprising:
a liquid product storage and cooling assembly (502), the assembly comprising:
a thermal battery functioning based on a thermal storage media (514, 516); and
a storage tank (504) housed within the thermal battery, to store a liquid product, the storage tank (504) comprising walls that are thermally conductive;
wherein the cooler comprises one or more pumps (508) to circulate a liquid phase of the thermal storage media (514) such that, when required to expeditiously cool the stored liquid product, the circulated liquid thermal storage media (514) is made to fall along an outer surface of the storage tank (504).

9. The cooler as claimed in claim 8, wherein the thermal storage media (514, 516) is a phase change material and the thermal battery holds thermal storage media in both the liquid phase (514) and a solid phase (516) of the thermal storage media.

10. The cooler as claimed in claim 8, wherein the liquid product storage and cooling assembly (502) comprises an insulated tank (506) comprising an upper part and a lower part, wherein the lower part is configured to accommodate cooling coils (558).