Description:FIELD
[0001] This application and the subject matter disclosed herein (collectively referred to as the “disclosure”), generally concern thermal energy storage, and related systems and methods. More particularly, but not exclusively, this disclosure pertains to systems, methods, and components to time-shift cooling of one or more chambers or other regions of a cooling system to times when energy, e.g., low-cost energy, is available. As but one illustrative example, a cooling system can charge a thermal energy storage when energy is available and discharge the thermal energy storage during times when energy is unavailable or costly.

BACKGROUND INFORMATION
[0002] In areas where grid energy is unavailable, unreliable, or costly, cooling systems like milk coolers, cold storage, or air conditioning with a Thermal Energy Storage (TES) unit, offer optimal solutions to decrease reliance on unconventional or costly energy sources such as, for example, diesel generators. The escalating demand for cooling systems is contributing to a surge in energy consumption. Solar energy, being readily accessible, synergizes effectively with off-grid cooling systems. However, solar energy is available only during daylight hours. A TES unit can also be tailored to meet diverse requirements, such as reducing the compressor duty cycle in a vapour compression cycle to enhance reliability and leverage stored energy during times when solar energy is unavailable, e.g., during times of cloud cover or at night.
[0003] Conventionally, a TES unit is integrated into a refrigeration system to provide thermal backup. The refrigeration system may employ a vapour compression cycle, a vapour absorption cycle, or a thermoelectric cooling system. The TES unit charges when solar energy is available, storing energy in a Phase Change Material (PCM) by converting it from liquid to solid phase. When cooling is required, the stored PCM melts, providing cooling to a space to be cooled. In addition to these advantages, the TES unit can be rapidly discharged to meet substantial cooling demands, thereby reducing the necessity for a higher capacity refrigeration system.
SUMMARY
[0004] Aspects of the present disclosure pertain to cooling systems configured to shift periods of active cooling (e.g., refrigeration) to when low-cost or reliable energy is available. Other aspects pertain to methods for shifting periods of active cooling to when low-cost or reliable energy is available. The cooling system may switch over to high-cost energy when low-cost or reliable energy is not available, and Thermal Energy Storage (TES) unit is partially or completely discharged. In some aspects, the present disclosure relates to systems and methods for selectively charging and discharging the TES unit.
[0005] According to a first aspect, a cooling system has a closed-loop for circulating a coolant there through. The cooling system includes a first heat exchanger configured to cool the coolant by facilitating a transfer of heat from the coolant to a heat-transfer medium when a temperature difference between the coolant and the heat-transfer medium exceeds a threshold temperature difference. The cooling system also includes a rechargeable TES unit configured to receive the coolant from the first heat exchanger and to facilitate heat transfer between a phase-change material and the coolant. The phase-change material rejects heat to the coolant when the temperature of the phase-change material is greater than the temperature of the coolant. The phase-change material absorbs heat from the coolant when the temperature of the coolant exceeds the temperature of the phase-change material.
[0006] The cooling system also includes a first branch of the closed loop. The first branch has a second heat exchanger configured to cool a specified region (e.g., region-to-be-cooled) by facilitating a transfer of heat from the specified region to a first flow of the coolant.
[0007] The cooling system also includes a second branch of the closed loop. The second branch is fluidically coupled with the first branch in parallel and configured to facilitate a bypass flow of the coolant to bypass the first branch of the closed loop. The cooling system is configured to selectively provide a flowrate of the first flow of the coolant corresponding in part to a desired rate of cooling of the specified region.
[0008] The cooling system can be configured to selectively provide a flowrate of the bypass flow corresponding in part to a desired rate of heat transfer between the phase-change material and the coolant.
[0009] The first branch of the cooling loop can include a second pump and a second check valve. The second check valve permits fluid flow only in one direction and operates passively. The second pump and the second check valve can be together configured to provide the flowrate of the first flow of the coolant through the first branch. In such embodiments, the second branch of the cooling loop includes a first pump and a first check valve. The first pump, the second pump, the first check valve, and the second check valve can be configured to facilitate control of the flowrate of the coolant through the first branch relative to a flowrate of the coolant through the second branch.
[0010] In some embodiments, the cooling system also includes a refrigeration cooling loop configured to cool the heat-transfer medium. The refrigeration cooling loop can be powered by an intermittently available power source having an availability duty cycle. A heat capacity of the TES unit can correspond to the availability duty cycle of the intermittently available power source. In some embodiments, the cooling system is configured to selectively provide a flowrate of the bypass flow corresponding in part to whether the intermittently available power source is available to power the refrigeration cooling loop. For example, the cooling system can be configured to selectively provide the flowrate of the bypass flow in further correspondence to a desired rate of heat transfer between the phase-change material and the coolant.
[0011] In some embodiments, the cooling system is configured to selectively provide the flowrate of the bypass flow in further correspondence to whether the intermittently available power source is available to power the refrigeration cooling loop. In some such embodiments, the cooling system is configured to selectively provide the flowrate of the bypass flow in further correspondence to a desired rate of heat transfer between the phase-change material and the coolant. One example of intermittently available power source is electricity produced by solar photovoltaic panels as that is not available 24 hours a day. Another example of intermittently available power is the electricity provided by weak grid where there may be occasions when there are power outages and no electric power is available.
[0012] Cooling systems according to the first aspect can also include a refrigeration loop configured to absorb energy in the form of heat from the heat-transfer medium, as well as a controller configured to selectively operate the cooling system in a selected mode. For example, such a selected mode can include a second mode, whereby the refrigeration loop cools the heat-transfer medium sufficiently that the coolant rejects heat absorbed from the TES unit to the heat-transfer medium. Second mode can occur when the current time is in the low-cost energy time period, TES unit is not completely charged and cooled space does not have cooling requirement. Alternatively, such a selected mode can include a third mode, whereby the coolant heats the TES unit with heat absorbed from the specified region to be cooled and the coolant rejects substantially no heat to the heat-transfer medium in the refrigeration loop. Third mode can occur when the current time is not in the low-cost energy time period, refrigeration loop is not operational, TES unit is partially or completely charged and cooled space has cooling requirement. As yet another alternative, such a selected mode can include a first mode, whereby the refrigeration loop cools the heat-transfer medium sufficiently to provide a temperature difference between the coolant and the heat-transfer medium that the coolant can reject heat absorbed by the coolant from the TES and from the specified region to be cooled. First mode can occur when the current time is in the low-cost energy time period and cooled space has cooling requirement. In the first mode, TES acts as a buffer to the cooling requirements of the cooled space. If the instantaneous cooling requirement of the cooled space is higher than the instantaneous cooling output of the refrigeration unit, the deficit cooling is provided by the TES through discharging of the phase change material. In an alternate scenario, when the instantaneous cooling requirement of the cooled space is lower than the instantaneous cooling output of the refrigeration unit, the excess cooling is provided to the TES through charging of the phase change material.
[0013] In an embodiment, the TES unit may include an insulated tank to accommodate the PCM in a stack configuration.
[0014] In an embodiment, the insulated tank may include a first path and a second path, where the first path may be associated with the inlet of the coolant to the TES unit and the second path may be associated with the outlet of the coolant from the TES unit.
[0015] According to another aspect, methods for time-shifting cooling provided to a specified region are disclosed. For example, cooling can be shifted to a time when low-cost energy is available. During selected times (e.g., when low-cost or reliable energy is available), a refrigeration unit (e.g., powered by the low-cost or reliable energy) is operated to remove heat from a coolant loop. The coolant loop is configured to cool the specified region and includes a TES unit and a coolant. The TES unit is selectively charged during the selected times by conveying, with the coolant, energy in the form of heat stored by the TES unit to the refrigeration unit. During the selected times, energy in the form of heat is conveyed by the coolant from the specified region to the refrigeration unit. During times other than the selected times, the TES unit is selectively discharged to cool the specified region while refrigeration unit is not operational.
[0016] In some embodiments, the coolant loop includes a by-pass branch configured to direct a substantial portion of the coolant to by-pass the coolant from the specified region. The TES unit can be selectively charged, in part, by directing the substantial portion of the coolant through the by-pass branch. In an embodiment, the coolant loop include a flow-control device configured to direct the portion of the coolant through the by-pass branch. In an embodiment, the flow-control device can be activated with a controller responsive to an output from one or more sensors to direct the portion of the coolant through the by-pass branch.
[0017] In some embodiments, the refrigeration unit and the coolant loop are thermally coupled with each other by heat-exchangers configured to facilitate heat transfer from the coolant to the refrigeration unit. With such an embodiment, energy in the form of heat can be conveyed with the coolant from the specified region to the refrigeration unit. For example, heat can be transferred from the specified region to the coolant. The heated coolant can be conveyed from the specified region to the heat exchanger, and heat from the heated coolant can be rejected to the refrigeration unit.
[0018] In some embodiments, the TES unit includes phase-change material and the TES unit can be selectively discharged to cool the specified region. For example, heat from the specified region can be transferred to the coolant, cooling the specified region. The heated coolant can be conveyed from the specified region to the TES unit, carrying the transferred heat from the specified region to the TES unit. The heat can be rejected from the heated coolant to the phase-change material.
[0019] In some embodiments, the act of selectively charging the TES unit during the selected times occurs contemporaneously with the act of conveying energy in the form of heat with the coolant from the specified region to the refrigeration unit.
[0020] In some embodiments, the act of conveying energy in the form of heat with the coolant from the specified region to the refrigeration unit occurs at a time other than when the act of selectively charging the TES unit occurs. The selected times can be determined or chosen to coincide with (or to overlap with) times when low-cost or reliable energy is available.
[0021] In some embodiments, a heat capacity of the TES unit corresponds to an expected amount of heat to be removed from the specified region between times during which the refrigeration unit is operated to remove heat from the coolant loop.
[0022] The foregoing and other features and advantages will become more apparent from the following detailed description, which proceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Referring to the drawings, wherein like numerals refer to like parts throughout the several views and this specification, aspects of presently disclosed principles are illustrated by way of example, and not by way of limitation.
[0024] FIG. 1 illustrates a schematic representation of a conventional Thermal Energy Storage (TES) unit in a cooling system.
[0025] FIG. 2A illustrates a schematic representation of a disclosed cooling system combining a coolant loop with a refrigeration cooling system.
[0026] FIG. 2B illustrates a schematic representation of operating the cooling system shown in FIG. 2A in a first mode.
[0027] FIG. 2C illustrates a schematic representation of operating the cooling system shown in FIG. 2A in a second mode.
[0028] FIG. 2D illustrates a schematic representation of operating the cooling system shown in FIG. 2A in a third mode.
[0029] FIG. 2E illustrates a schematic representation of an electronic control architecture suitable for controlling a cooling system as in FIG. 2A.
[0030] FIG. 3 illustrates a schematic representation of disclosed flow distributions of Heat Transfer Fluid (HTF) and placement of Phase Change Material (PCM) packs in embodiments of a TES unit.
[0031] FIG. 4 illustrates a flow chart showing a disclosed method of operating a disclosed cooling system.
[0032] FIG. 5 illustrates a flow chart of a method for time-shifting cooling provided to a specified region to times when low-cost energy is available.

DETAILED DESCRIPTION
[0033] The following describes various principles related to cooling systems and more particularly, to cooling systems that incorporate a Thermal Energy Storage (TES) unit. For example, certain aspects of disclosed principles pertain to a rechargeable TES unit that can be recharged when external power is available and can be discharged when external power is unavailable. That said, descriptions herein of specific apparatus configurations and combinations of method acts are but particular examples of contemplated systems chosen as being convenient illustrative examples of disclosed principles. One or more of the disclosed principles can be incorporated in various other systems to achieve any of a variety of corresponding system characteristics.
[0034] Thus, systems having attributes that are different from those specific examples discussed herein can embody one or more presently disclosed principles, and can be used in applications not described herein in detail. Accordingly, such alternative embodiments also fall within the scope of this disclosure.
[0035] FIG. 1 illustrates a schematic representation of a conventional TES unit 102 in a cooling system 100.
[0036] Referring to FIG. 1, the cooling system 100 includes the TES unit 102, a refrigeration unit 104 connected to a first heat exchanger 108A, a cooled space 106 including a second heat exchanger 108B, and a pump 110 connected between the TES unit 102 and the cooled space 106. The refrigeration unit 104, which can include one or more of a vapour compression, absorption refrigeration, and thermoelectric cooling, is employed for cooling purposes.
[0037] The refrigeration unit 104 extracts heat from the cooling loop using one or more vapour compression, absorption refrigeration, and thermoelectric cooling methods. The first heat exchanger 108A facilitates a transfer of heat between the cooling loop and the refrigeration unit 104 and the TES unit 102. Vapour compression system is the preferred refrigeration system and that comprises of a loop with a compressor followed by a condenser, expansion valve/capillary tube, and an evaporator. Evaporator is where the actual cooling happens and the evaporator of the refrigeration system is located in the first heat exchanger 108A.
[0038] A phase-change material (PCM) can be packed inside pouches or containers called ice packs, and the PCM can be stored in a well-insulated tank, depending on storage size. This tank filled with ice packs can be referred to as a thermal battery, or “TES unit 102.” A coolant can circulate throughout the coolant loop to charge the thermal battery by removing latent heat from the PCM, which in the case of water freezes into ice, or to discharge the thermal battery by adding latent heat to the PCM, which in the case of ice melts into water. Concurrently therewith, the coolant (sometimes also referred to in the art as a “Heat Transfer Fluid” or “HTF”) can flow through a heat exchanger of the refrigeration system and a heat exchanger of a cooling application (e.g., within a space to be cooled). A control system can maintain a charge level of the thermal battery, ensuring that the thermal battery can be selectively discharged, and selectively charged. Cooling or freezing the PCM is referred to herein as “charging,” whereas warming or melting the thermal battery, thereby cooling the coolant, is referred to herein as “discharging.”
[0039] The TES unit 102, absorbs heat from the coolant, or discharges, as the coolant passes through the TES unit 102. The coolant absorbs the heat as the coolant passes through the second heat exchanger 108B in cooled space 106. The pump 110 circulates the coolant through the coolant loop when cooling is required. The second heat exchanger 108B in the cooled space 106 facilitates the transfer of heat to achieve the desired cooling effect. With a system as in FIG. 1, the coolant either does not flow at all or it flows through both the second heat exchanger 108B (and thus the cooled space 106) and the TES unit 102. Thus, cooling of the cooled space 106 cannot be decoupled from charging or discharging the TES unit 102. Nevertheless, depending on heat loads (e.g., ambient temperatures, rates of heating of the space to be cooled 106, etc.), the TES unit 102 may not be fully charged when cooling of the space to be cooled 106 is no longer required. In such a circumstance, to avoid overcooling the space to be cooled 106, the pump 110 can be shut down, which prevents charging of the TES unit 102.
[0040] Disclosed cooling systems are flexible and easy to construct, while providing the ability to charge and discharge the TES unit, whether independently or contemporaneously with removing heat from the space to be cooled. Aspects of disclosed systems and related methods are described by way of further reference to FIGs. 2A to 5.
[0041] Referring to FIG. 2A, the cooling system 200 having a closed-loop for circulating a coolant, where the cooling system 200 may include a TES unit 202, a refrigeration unit (or refrigeration unit) 204, a first heat exchanger 208A, a cooled space 206, a second heat exchanger 208B, a first pump 210A, a first check valve 212A, a second pump 210B, and a second check valve 212B. The refrigeration unit 204 may be connected to the first heat exchanger 208A. The cooled space 206 may include the second heat exchanger 208B. The first pump 210A may be connected to a first check valve 212A and the second pump 210B may be connected to the second check valve 212B through the second heat exchanger 208B. The first pump 210A and the second pump 210B may be used for circulating Heat Transfer Fluid (HTF) within the cooling system 200. The first check valve 212A and the second check valve 212B may be used to control the direction of the HTF flow. The refrigeration unit 204 may charge a thermal battery integrated within the TES unit 202, where the TES unit 202 may be connected to the first heat exchanger 208A. The position of the first heat exchanger 208A may be placed between the thermal battery and the cooling application, e.g., the cooled space 206. Therefore, a working temperature of the refrigeration system evaporator is higher, aiding in increase of coefficient of performance, compared to a working temperature in an embodiment whether the evaporator is placed elsewhere throughout the coolant loop.
[0042] In an embodiment, the first heat exchanger 208A may be configured to cool the HTF (e.g., coolant) by facilitating a transfer of heat from the coolant to a heat-transfer medium when a temperature difference between the coolant and the heat-transfer medium exceeds a threshold temperature difference. In some embodiments, the TES unit 202 may be a rechargeable TES unit 202 that may be configured to receive the coolant from the first heat exchanger and to facilitate heat transfer between a Phase-Change Material (PCM) 306 and the coolant. In some exemplary embodiments, the PCM 306 may reject heat to the coolant when a temperature of the PCM 306 is greater than a temperature of the coolant. In an embodiment, the PCM 306 may absorbs heat from the coolant when the temperature of the coolant exceeds the temperature of the heat-transfer medium.
[0043] In some embodiments, a first branch 218B of the closed loop may include the second pump 210B, the second check valve 212B, and the second heat exchanger 208B, where the second heat exchanger 208B may be configured to cool a specified region (e.g., 206) by facilitating a transfer of heat from the specified region 206 to a first flow of the coolant. In an embodiment, a second branch 218A of the closed loop may be fluidically coupled with first branch 218B in parallel. Further, in some embodiments, the first branch 218B of the closed loop may include the second pump 210B and the second check valve 212B. Further, the second branch 218A may be configured to facilitate a bypass-flow of the coolant to bypass the first branch 218B of the closed loop. In some exemplary embodiments, the refrigeration cooling loop may be powered by an intermittently available power source having an availability duty cycle. A heat capacity of the TES unit 202 may correspond to the availability duty cycle of the intermittently available power source. In an exemplary embodiment, the cooling system 200 may be configured to selectively provide a flowrate of the first flow of the coolant corresponding in part to a desired rate of cooling of the specified region 206. In some embodiment, the second pump 210B, the second check valve 212B are together configured to provide the flowrate of the first flow of the coolant substantially through the first branch 218B. In an embodiment, the first check valve 212A may permit fluid flow only in one direction and operates passively. Further, the cooling system 200 may be configured to selectively provide a substantial flowrate of the bypass flow corresponding in part to a desired rate of heat transfer between the PCM and the coolant.
[0044] In an embodiment, the first pump 210A, the second pump 210B, the first check valve 212A, and the second check valve 212B may be configured to facilitate control of the flowrate of the coolant substantially through the second branch 218A relative to a flowrate of the coolant through the first branch 218B. In some embodiments, the cooling system 200 may include a refrigeration cooling loop that may be configured to cool the heat-transfer medium. In exemplary embodiments, the refrigeration cooling loop may be powered by an intermittently available power source having an availability duty cycle, where a heat capacity of the TES unit 202 corresponds to the availability duty cycle of the intermittently available power source. In an embodiment, the cooling system 200 may be configured to selectively provide a flowrate of the bypass flow corresponding in part to whether the intermittently available power source is available to power the refrigeration cooling loop. Further, the cooling system 200 may be configured to selectively provide the flowrate of the bypass flow further corresponding in part to a desired rate of heat transfer between the phase-change material and the coolant. For example, intermittently available power source is electricity that is produced by solar photovoltaic panels as that is not available 24 hours a day. Another example of intermittently available power is the electricity provided by weak grid where there may be occasions when there are power outages and no electric power is available. Similarly, in an embodiment, the cooling system 200 may be configured to selectively provide the flowrate of the bypass flow further corresponding in part to whether the intermittently available power source is available to power the refrigeration cooling loop and there is no requirement of cooling in cooled space 206. Further, the cooling system 200 may be configured to selectively provide the flowrate of the bypass flow further corresponding in part to a desired rate of heat transfer between the PCM and the coolant. In an embodiment, the cooling system 200 may include a refrigeration loop that may be configured to absorb energy in the form of heat from the heat-transfer medium.
[0045] In an embodiment, the HTF passing through the coolant loop may absorb the heat from the desired application, e.g., the cooled space 206, and the refrigeration system 204 may extract the heat from the HTF to dissipate in the surroundings. The HTF may flow through the TES unit 202, e.g., over or among a plurality of PCM packs (e.g., 306) of the thermal battery to charge the thermal battery. For example, once the HTF is cooled and pumped into the cooled space 206 for heat exchange, the HTF may efficiently return to the TES unit 202. The cooling system 200 may extract heat from the cooled space 206, and notably, the freezing temperature point of HTF is lower than that of the PCM 306, ensuring effective and controlled thermal energy storage. In some embodiments, a HTF circuit may be used to partially or completely facilitate the cooling requirement of the cooled space 206 with the available cooling capacity of the refrigeration unit 204 by either charging or discharging of the thermal battery containing PCM packs 306.
[0046] In exemplary embodiments, the cooling system 200 may operate in various modes such as a first mode, a second mode, and a third mode. The first mode may involve either charging or discharging of the thermal battery. The second mode may involve charging the thermal battery. The third mode may involve discharging the thermal battery. It may be appreciated that the terms “first,” “second,” and “third” are used for exemplary purposes.
[0047] In an embodiment, when the current time is the low-cost energy time period, the TES unit 202 is fully charged and cooling of the cooled space 206 is required, the cooling system 200 may operate in the first mode. Similarly, in an embodiment, when the current time is the low-cost energy time period, the TES unit 202 is not fully charged and cooling is required, the cooling system 200 may operate in the first mode. In some embodiments, when the TES unit 202 is not fully charged, the current time is the low-cost energy time period, and cooling is not required in the cooled space 206, the cooling system 200 may operate in the second mode. In exemplary embodiments, when the TES unit 202 is not fully discharged, current time is not the low-cost energy time period, and cooling is required in the cooled space 206, the cooling system 200 may operate in the third mode. In some embodiments, when the TES unit 202 is discharged to a threshold and the current time is not a low-cost energy time period, the system may switch over to high-cost energy.
[0048] In exemplary embodiments, when the cooling system 200 is operating in the first mode, if the instantaneous cooling requirement of the cooled space 206 is higher than the instantaneous cooling output of the refrigeration unit 204, the deficit cooling is provided by the TES unit 202 through discharging of the PCM. In an alternate scenario, when the instantaneous cooling requirement of the cooled space 206 is lower than the instantaneous cooling output of the refrigeration unit 204, the excess cooling is provided to the TES unit 202 through charging of the PCM 306.
[0049] FIG. 2B illustrates an example schematic representation 200B of either charging or discharging of a TES unit 202 when the current time is the low-cost energy time period and cooling is needed in cooled space 206, i.e. the cooling system 200 is operating in the first mode, in accordance with embodiments of the present disclosure.
[0050] In the cooling system 200, the HTF is directed through a distinct path, serving the purpose of meeting the cooling need of the cooled space 206. The coolant downstream to the second heat exchanger 208B may be cooled by the refrigeration unit 204 while passing through the first heat exchanger 208A. The coolant may either charge or discharge the TES unit 202 while meeting the cooling need of the cooled space 206.
[0051] Referring to FIG. 2B, the activation of a second pump 210B may ensure opening of the second check valve 212B and closing of the first check valve 212A. This process allows the HTF flow path through the second heat exchanger 208B, the first heat exchanger 208A, and TES unit 202.
[0052] To enable this transition, the deactivation of the HTF flow path may be facilitated by disabling a first pump 210A. This deactivation redirects the HTF flow, optimizing the cooling system 200 for either discharging or charging of the thermal battery, and allowing the thermal battery to efficiently cater to the cooling demands.
[0053] For example, when the TES unit 202 is fully charged and cooling is required in the cooled space 206, the cooling system 200 may operate in the first mode that involves either charging or discharging of the thermal battery. This capability enables the storage of excess energy during periods of low cooling demand and the release of energy during high cooling demand periods, improving overall energy efficiency. In exemplary embodiments, when the TES unit 202 is not fully charged and cooling is required in the cooled space 206, the cooling system 200 may operate in the same mode that involves either charging or discharging of the thermal battery.
[0054] In some embodiments, during the first mode, the refrigeration loop may cool the heat-transfer medium sufficiently to provide a temperature difference between the coolant and the heat-transfer medium that the coolant may pass through the TES unit 202 and reject heat absorbed by the coolant from a specified region 206 to be cooled.
[0055] FIG. 2C illustrates an example schematic representation 200C of charging of a TES unit 202 when the current time is the low-cost energy time period and cooling is not needed in cooled space 206, i.e. the cooling system 200 is operating in the second mode, in accordance with embodiments of the present disclosure.
[0056] Referring to FIG. 2C, a cooling system configuration allows HTF flow in a distinct path. A second pump 210B may be deliberately disabled in this scenario, preventing the HTF from circulating through those channels due to the presence of second check valve 212B. Instead of enabling the second pump 210B, a first pump 210A may be enabled to direct the HTF towards a thermal battery. This activation of the first pump 210A opens the first check valve 212A and closes the second check valve 212B, which ensures that the HTF flows exclusively along the designated path leading to the thermal battery, facilitating the charging process. This feature is particularly advantageous during periods when cooling is not required in cooled space 206, allowing the cooling system 200 to efficiently charge the thermal battery without simultaneously engaging in cooling activities. For example, when the TES unit 202 is not fully charged, the current time is the low-cost energy time period, and cooling is not required in cooled space 206, the cooling system 200 may operate in the second mode that involves charging the thermal battery. In an embodiment, during the second mode a refrigeration loop may cool a heat-transfer medium sufficiently that a coolant rejects heat absorbed from the TES unit 202 to the heat-transfer medium.
[0057] FIG. 2D illustrates an example schematic representation 200D of discharging of a TES unit 202 when the current time is not the low-cost energy time period and cooling is needed in cooled space 206, i.e. the cooling system 200 is operating in the third mode, in accordance with embodiments of the present disclosure.
[0058] Referring to FIG. 2D, activation of a second pump 210B may open the second check valve 212B and close the first check valve 212A, which may initiate a directed flow of HTF towards a thermal battery, specifically to facilitate the discharging process within the TES unit 202. In an embodiment, during the third mode, a refrigeration loop may not function, the coolant may heat the TES unit 202 with heat absorbed from a specified region (e.g., 206) to be cooled and the coolant rejects substantially no heat to the heat-transfer medium in the refrigeration loop.
[0059] In an embodiment, a first pump 210A may be disabled. This deactivation ensures that the HTF does not follow through second branch 218A, effectively shutting down the flow toward the second branch 218A. In particular, consequently, by disabling the first pump 210A, the HTF is diverted away from the second the branch 218A. The pumps and check valves create a clear distinction in the HTF flow patterns. For example, when the TES unit 202 is not fully discharged, the current time is not the low-cost energy time period, and cooling is required in the cooled space 206, the cooling system 200 may operate in the third mode that involves discharging the thermal battery. In some embodiments, when cooling is not required in the cooled space 206 and the current time is the low-cost energy time period, the cooling system 200 may operate in the second mode and relies on the first pump 210A for charging the thermal battery. In some other embodiments, when cooling demand arises in the cooled space 206 and the current time is the low-cost energy time period, the cooling system 200 may operate in the first mode and the second pump 210B may enable the HTF to either charge or discharge the TES unit 202 while meeting the cooling need of the cooled space 206. This dual-purpose operation ensures the system’s adaptability and responsiveness to varying cooling requirements of the cooled space 206.
[0060] FIG. 2E illustrates an example schematic representation 200E of an electronic control architecture, in accordance with embodiments of the present disclosure.
[0061] Referring to FIG. 2E, a TES unit 202 may include sensors 216A and 216B, and a cooled space 206 may include a sensor 216C. The sensors (216A, 216B, 216C) may include, but not be limited to, temperature sensors, thermal sensors, heat sensors, thermometers, and the like. Further, the TES unit 202 may include a controller 214 for controlling charging and discharging of the thermal energy stored in the TES unit 202. Further, the controller 214 may be configured to selectively operate the cooling system in a selected mode from the group of modes such as the first, second and third modes.
[0062] FIG. 3 illustrates an example schematic representation 300 of flow distribution of HTF and placement of PCM packs (e.g., 306) in a TES unit 202, in accordance with embodiments of the present disclosure.
[0063] Referring to FIG. 3, the TES unit 202, the distribution of the HTF, and the placement of the PCM packs 306 are certain factors in optimizing the system’s efficiency and performance. For example, the PCM packs 306 may be arranged in a stack configuration, submerged within the HTF in an insulated tank 302. The HTF is a carrier of the thermal energy, which enter TES unit 300 from inlet distributor 304A and exit TES unit 300 from outlet distributor 304B. The distributors 304A and 304B assist in passing HTF through most of the PCM packs 306.
[0064] In an embodiment, when a cooling demand arises in the cooled space 206 and the current time is the low-cost energy time period, the cooling system 200 seamlessly transitions into the first mode. This process involves activating both refrigeration unit 204 and TES unit 202, allowing the thermal battery to either discharge or charge stored energy for cooling purposes. This dual functionality ensures a continuous and a balanced operation of the cooled space 206, adapting dynamically to the cooling requirements of the space it serves. Furthermore, the placement of PCM 306 within the TES unit 202 is critical for effective heat absorption and release. The PCM 306, capable of transitioning between solid and liquid states, acts as a thermal reservoir. During the charging of the TES unit 202, the PCM 306 rejects heat to the circulating HTF, undergoing a phase change and efficiently storing the thermal energy. During the discharging of the TES unit 202, the PCM 306 undergoes a reverse phase change, releasing the stored energy to provide a consistent and controlled cooling effect.
[0065] FIG. 4 illustrates a flow chart of an example method 400 for the first, second and third modes, in accordance with embodiments of the present disclosure.
[0066] Referring to FIG. 4, at block 402, the method 400 may include determining whether current time is a low-cost energy time period or not. One example of low cost energy periods include energy provided by solar photovoltaic panels installed to power the compressor. Another example may include time of use electric rate structure where electricity prices at certain hours during a day are lower compared to other hours.
[0067] At block 404, the method 400 may include determining whether a TES unit (e.g., 202) is fully charged or not, when the current time is in the low-cost energy time period. At block 406, the method 400 may include determining whether a cooling is needed or not when the TES unit 202 is fully charged.
[0068] At block 408, the current time is the low-cost energy time period and the method 400 may include either charging or discharging thermal energy when the cooling is needed in the cooled space 206. At block 410, the current time is the low-cost energy time period and the method 400 may include determining whether the cooling is needed in the cooled space 206 or not when the TES unit 202 is not fully charged.
[0069] At block 412, the current time is the low-cost energy time period and the method 400 may include charging the thermal energy when the cooling is not needed in the cooled space 206. At block 414, the current time is the low-cost energy time period and the method 400 may include either charging or discharging the thermal energy storage when the cooling is needed in the cooled space 206.
[0070] At block 416, the method 400 may include determining whether the TES unit 202 is fully discharged or not when the current time is not within the low-cost energy time period.
[0071] At block 418, the method 400 may include switching the current time to high-cost energy time period (e.g., not the low-cost energy time period) when the TES unit 202 is fully discharged to threshold and the method 400 may include to wait for the availability of the low-cost energy time period as the TES unit 202 is fully discharged. At block 420, the method 400 may include determining whether the cooling is needed or not when the TES unit 202 is not fully charged. At block 422, the current time is not the low-cost energy time period and the method 400 may include discharging the thermal energy, when the cooling is needed in the cooled space 206.
[0072] At block 424, the method 400 may include determining whether the cooling is needed or not when the current time period is high-cost energy time period. At block 426, the method 400 may include charging the thermal energy when the cooling is not needed in the cooled space 206. At block 428, the method 400 may include either charging or discharging thermal energy when the cooling is needed in the cooled space 206.
[0073] It will be appreciated that the steps shown in FIG. 4 are merely illustrative. Other suitable steps may be used, if desired. Moreover, the operations of the method 400 may be performed in any order and may include additional operations.
[0074] FIG. 5 illustrates a flow chart of a method 500 for time-shifting cooling provided to a specified region to times when low-cost energy is available, accordance with embodiments of the present disclosure.
[0075] Referring to FIG. 5, at block 502, the method 500 may include during selected times, operating a refrigeration unit (e.g., 204) to remove heat from a coolant loop configured to cool a specified region e.g., 206 the coolant loop including a TES unit (e.g., 202) and a coolant. At block 504, the method 500 may include selectively charging the TES unit 202 during the selected times by conveying, with the coolant, energy in the form of heat stored by the TES unit 202 to the refrigeration unit 204. At block 506, the method 500 may include during the selected times, conveying energy in the form of heat with the coolant from the specified region to the refrigeration unit 204. For example, heat may be transferred from the specified region 206 to the coolant. The heated coolant may be conveyed from the specified region 206 to the heat exchangers (e.g., 208A, 208B), and heat from the heated coolant may be rejected to the refrigeration unit 204. Further, the method 500 may include transferring heat from the specified region 206 to the coolant and conveying the heated coolant from the specified region 206 to heat exchangers (e.g., 208A, 208B) for rejecting heat from the heated coolant to the refrigeration unit 204. In an embodiment, the refrigeration unit 204 and the coolant loop are thermally coupled with each other by the heat exchangers configured to facilitate heat transfer from the coolant to the refrigeration unit 204.
[0076] At block 508, the method 500 may include during times other than the selected times, selectively discharging the TES unit 202 to cool the specified region 206. Further, the method 500 may include transferring heat from the specified region 206 to the coolant and conveying the heated coolant from the specified region to the TES unit 202 for rejecting heat from the heated coolant to the phase-change material 306. In some embodiments, the selected times to coincide with when low-cost energy is available. In an embodiment, the coolant loop may include a first branch 218B configured to direct a substantial portion of the coolant to the specified region 206, where the coolant loop may include a bypass branch 218A configured to direct a substantial portion of the coolant to the act of selectively charging the TES unit 202. Further, in some embodiment, the coolant loop may activate the second pump (e.g., 210B) with a controller (e.g., 214) configured to direct the substantial portion of the coolant through the first branch 218B, with the controller 214 responsive to an output from one or more sensors (e.g., 216A, 216B, and 216C). In some embodiment, the coolant loop may activate the first pump 210A with the controller 214 that may be configured to direct the substantial portion of the coolant through the bypass branch 218A with the controller 214 responsive to an output from one or more sensors. In an embodiment, a heat capacity of the TES unit 202 may correspond to an expected amount of heat to be removed from the specified region 206 between the selected times during which the act of operating the refrigeration unit 204 to remove heat from the coolant loop occurs.
[0077] The previous description is provided to enable a person skilled in the art to make or use the disclosed principles. Embodiments other than those described above in detail are contemplated based on the principles disclosed herein, together with any attendant changes in configurations of the respective apparatus or changes in order of method acts described herein, without departing from the spirit or scope of this disclosure. Various modifications to the examples described herein will be readily apparent to those skilled in the art.
[0078] Directions and other relative references (e.g., up, down, top, bottom, left, right, rearward, forward, etc.) may be used to facilitate discussion of the drawings and principles herein, but are not intended to be limiting. For example, certain terms may be used such as “up,” “down,” “upper,” “lower,” “horizontal,” “vertical,” “left,” “right,” and the like. Such terms are used, where applicable, to provide some clarity of description when dealing with relative relationships, particularly with respect to the illustrated embodiments. Such terms are not, however, intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an “upper” surface can become a “lower” surface simply by turning the object over. Nevertheless, it is still the same surface and the object remains the same. As used herein, “and/or” means “and” or “or”, as well as “and” and “or.” Moreover, all patent and non-patent literature cited herein is hereby incorporated by reference in its entirety for all purposes.
[0079] And, those of ordinary skill in the art will appreciate that the exemplary embodiments disclosed herein can be adapted to various configurations and/or uses without departing from the disclosed principles. It will be understood by one of ordinary skill in the art that the embodiments may be practiced with or without specific details described herein. For example, circuits, systems, networks, processes, and other components may be shown as components in block diagram form in order not to obscure the embodiments in unnecessary detail. In other instances, well-known circuits, processes, algorithms, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments.
[0080] Also, it is noted that individual embodiments may be described as a process which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed but could have additional steps not included in a figure. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination can correspond to a return of the function to the calling function or the main function.
[0081] Applying the principles disclosed herein, it is possible to provide a wide variety of cooling systems and related methods to shift the time of active cooling applied to a space to be cooled to times when reliable and/or low-cost energy is available. For example, the principles described above in connection with any particular example can be combined with the principles described in connection with another example described herein. Thus, all structural and functional equivalents to the features and method acts of the various embodiments described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the principles described and the features and acts claimed herein. Accordingly, neither the claims nor this detailed description shall be construed in a limiting sense, and following a review of this disclosure, those of ordinary skill in the art will appreciate the wide variety of cooling system and time-shifting techniques that can be devised using the various concepts described herein.
[0082] The appended claims are not intended to be limited to the embodiments shown herein, but are to be accorded the full scope consistent with the language of the claims, wherein reference to a feature in the singular, such as by use of the article “a” or “an” is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Further, in view of the many possible embodiments to which the disclosed principles can be applied, we reserve the right to claim any and all combinations of features and technologies described herein as understood by a person of ordinary skill in the art, including the right to claim, for example, all that comes within the scope and spirit of the foregoing description, as well as the combinations recited, literally and equivalently, in any claims presented anytime throughout prosecution of this application or any application claiming benefit of or priority from this application, and more particularly but not exclusively in the claims appended hereto.
, Claims:1. A cooling system (200) having a closed loop for circulating a coolant there through, the cooling system (200) comprising:
a first heat exchanger (208A) configured to cool the coolant by facilitating a transfer of heat from the coolant to a heat-transfer medium when a temperature difference between the coolant and the heat-transfer medium exceeds a threshold temperature difference;
a rechargeable Thermal Energy Storage (TES) unit (202) configured to receive the coolant from the first heat exchanger (208A) and to facilitate heat transfer between a phase-change material (306) and the coolant, wherein the phase-change material (306) rejects heat to the coolant when a temperature of the phase-change material (306) is greater than a temperature of the coolant, and wherein the phase-change material (306) absorbs heat from the coolant when the temperature of the coolant exceeds the temperature of the heat-transfer medium;
a first branch (218B) of the closed loop, the first branch (218B) having a second heat exchanger (208B) configured to cool a specified region (206) by facilitating a transfer of heat from the specified region (206) to a first flow of the coolant; and
a second branch (218A) of the closed loop, the second branch (218A) being fluidically coupled with the first branch (218B) in parallel and configured to facilitate a bypass flow of the coolant to bypass the first branch (218B) of the closed loop, wherein the cooling system (200) is configured to selectively provide a flowrate of the first flow of the coolant corresponding in part to a desired rate of cooling of the specified region (206).
2. The cooling system (200) of claim 1, wherein the cooling system (200) is configured to selectively provide a flowrate of the bypass flow corresponding in part to a desired rate of heat transfer between the phase-change material (306) and the coolant.
3. The cooling system (200) of claim 1, wherein the first branch (218B) of the closed loop comprises a second pump (210B) and a second check valve (212B), wherein the second pump (210B) and the second check valve (212B) are together configured to provide the flowrate of the first flow of the coolant substantially through the first branch (218B).
4. The cooling system (200) of claim 3, wherein the second branch (218A) of the closed loop comprises a first pump (210A) and a first check valve (212A), wherein the first pump (210A), the second pump (210B), the first check valve (212A), and the second check valve (212B) are configured to facilitate control of the flowrate of the coolant substantially through the second branch (218A) relative to a flowrate of the coolant through the first branch (218B).
5. The cooling system (200) of claim 1, further comprising a refrigeration cooling loop configured to cool the heat-transfer medium.
6. The cooling system (200) of claim 5, wherein the refrigeration cooling loop is powered by an intermittently available power source having an availability duty cycle, wherein a heat capacity of the TES unit (202) corresponds to the availability duty cycle of the intermittently available power source.
7. The cooling system (200) of claim 6, wherein the cooling system (200) is configured to selectively provide a flowrate of the bypass flow corresponding in part to whether the intermittently available power source is available to power the refrigeration cooling loop.
8. The cooling system (200) of claim 7, wherein the cooling system (200) is configured to selectively provide the flowrate of the bypass flow further corresponding in part to a desired rate of heat transfer between the phase-change material (306) and the coolant.
9. The cooling system (200) of claim 6, wherein the cooling system (200) is configured to selectively provide the flowrate of the first flow further corresponding in part to whether the intermittently available power source is available to power the refrigeration cooling loop.
10. The cooling system (200) of claim 9, wherein the cooling system (200) is configured to selectively provide the flowrate of the first flow further corresponding in part to a desired rate of heat transfer between the phase-change material (306) and the coolant.
11. The cooling system (200) of claim 1, further comprising:
a refrigeration loop configured to absorb energy in the form of heat from the heat-transfer medium;
a controller (214) configured to selectively operate the cooling system (200) in a selected mode from a group of modes consisting of the following:
a first mode, whereby the refrigeration loop cools the heat-transfer medium sufficiently to provide the temperature difference between the coolant and the heat-transfer medium such that the coolant passes through the TES unit (202) and rejects heat absorbed by the coolant from the specified region (206) to be cooled;
a second mode, whereby the refrigeration loop cools the heat-transfer medium sufficiently that the coolant rejects heat absorbed from the TES unit (202) to the heat-transfer medium; and
12. a third mode, whereby the refrigeration loop is not functioning, the coolant heats the TES unit (202) with heat absorbed from the specified region (206) to be cooled, and the coolant rejects substantially no heat to the heat-transfer medium in the refrigeration loop.
13. A method for time-shifting cooling provided to a specified region (206) to times when low-cost energy is available, the method comprising:
during selected times, operating a refrigeration unit (204) to remove heat from a coolant loop configured to cool the specified region (206), the coolant loop including a Thermal Energy Storage (TES) unit (202) and a coolant;
selectively charging the TES unit (202) during the selected times by conveying, with the coolant, energy in the form of heat stored by the TES unit (202) to the refrigeration unit (204);
during the selected times, conveying energy in the form of heat with the coolant from the specified region (206) to the refrigeration unit (204); and
during times other than the selected times, selectively discharging the TES unit (202) to cool the specified region (206).
14. The method of claim 12, wherein the coolant loop comprises a first branch (218B) configured to direct a substantial portion of the coolant to the specified region (206).
15. The method of claim 13, wherein the coolant loop comprises a bypass branch (218A) configured to direct a substantial portion of the coolant to the act of selectively charging the TES unit (202).
16. The method of claim 14, wherein the coolant loop activates a second pump (210B) with a controller (214) configured to direct the substantial portion of the coolant through the first branch (218B), with the controller (214) responsive to an output from one or more sensors.
17. The method of claim 14, wherein the coolant loop activates a first pump (210A) with a controller (214) configured to direct the substantial portion of the coolant through the bypass branch (218A) with the controller (214) responsive to an output from one or more sensors.
18. The method of claim 12, wherein the refrigeration unit (204) and the coolant loop are thermally coupled with each other by heat exchangers configured to facilitate heat transfer from the coolant to the refrigeration unit (204), wherein conveying energy in the form of heat with the coolant from the specified region (206) to the refrigeration unit (204) comprises:
transferring heat from the specified region (206) to the coolant;
conveying the heated coolant from the specified region (206) to the heat exchangers; and
rejecting heat from the heated coolant to the refrigeration unit (204).
19. The method of claim 12, wherein the TES unit (202) comprises a phase-change material (306) and selectively discharging the TES unit (202) to cool the specified region (206) comprises:
transferring heat from the specified region (206) to the coolant;
conveying the heated coolant from the specified region (206) to the TES unit (202); and
rejecting heat from the heated coolant to the phase-change material (306).
20. The method of claim 12, further comprising determining the selected times to coincide with when low-cost energy is available.
21. The method of claim 19, wherein a source of the low-cost energy is electric power produced by solar photovoltaic panels.
22. The method of claim 12, wherein a heat capacity of the TES unit (202) corresponds to an expected amount of heat to be removed from the specified region (206) between the selected times during which operating the refrigeration unit (204) to remove heat from the coolant loop occurs.