Patent Publication Number: US-2023148170-A1

Title: Thermal Battery And Heat Exchanger Assembly Using Phase Change Material

Description:
FIELD 
     The present disclosure relates to thermal battery and heat exchanger assembly that uses a phase change material, and to systems incorporating the thermal battery and/or heat exchanger assembly. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     A thermal storage device or battery is a device used for the purpose of storing and releasing thermal energy, which allows energy available at one time to be temporarily stored and then released at another time. Some thermal batteries also involve causing a thermal storage substance to transition thermally through a phase transition which causes even more energy to be stored and released. The thermal storage substances (phase change materials) used for thermal storage are capable of storing and releasing significant thermal capacity at the temperature that they change phase. These materials are chosen based on specific applications because there is a wide range of temperatures that may be useful in different applications and a wide range of materials that change phase at different temperatures. 
     In HVAC applications, thermal batteries enable the storing of heating or cooling energy during times of the day when electricity prices are low and/or when the HVAC system efficiency is at its peak. The stored energy may then be leveraged to perform all or a portion of heating or cooling that is required during a time of the day when electricity prices are greater and/or HVAC system efficiency is low. Thermal batteries, however, can be expensive based on the type of phase change material used, as well as the size and material required for the device holding the phase change material. 
     SUMMARY 
     This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features. 
     According to a first aspect of the present disclosure there is provided a heating and cooling (HVAC) system that includes a compressor; a first heat exchanger; a second heat exchanger; a first expansion valve positioned between the first heat exchanger and the second heat exchanger; a first reversing valve that permits the system to operate in a first mode and a second mode; and a thermal battery including a phase change material therein that is configured to selectively store and release thermal energy received from a working fluid, wherein the thermal battery includes a pair of end plates, each of the end plates including a first major surface and an opposite second major surface, the first major surfaces each including fluid inlet and a fluid outlet and the opposite second major surfaces each including a flow trough, the fluid inlet of each end plate being in communication with the flow trough formed on the opposite second major surface of the respective end plate; a plurality of flow plates sandwiched between the pair of end plates, each of the flow plates having a first side and an opposite second side, and each of the first side and the opposite second side including a flow surface, the flow surfaces of each flow plate being configured to communicate with either the flow trough of an adjacent end plate or one of the flow surfaces of an adjacent flow plate; a plurality of thermal energy transfer films that are respectively positioned between adjacent flow plates, and between each of the end plates and an immediately adjacent flow plate, such that a first flow path exists on one side of a respective thermal energy transfer film for the working fluid and a second flow path exists on an opposite side of the respective thermal energy transfer film for the phase change material; and the flow troughs and flow surfaces communicate with each other such that the working fluid that the flows through the first flow path enters the fluid inlet of one of the end plates will exit the fluid outlet of the other end plate while exchanging thermal energy with the phase change material that is provided in the second flow path that extends between the fluid inlet of the other end plate and the fluid outlet of the one end plate. 
     According to the first aspect, the compressor, the first heat exchanger, the first reversing valve, and the first expansion valve are located in a primary circuit, and the thermal battery is located in a secondary circuit that includes a third heat exchanger and a pump, wherein the second heat exchanger is shared by each of the primary circuit and the secondary circuit. 
     According to the first aspect, the working fluid is located in the secondary circuit and exchanges thermal energy with a refrigerant of the primary circuit in the second heat exchanger. 
     According to the first aspect, the secondary circuit further includes a second thermal battery, and a pair of three-way valves that are configured to either direct the working fluid to the thermal battery or the second thermal battery, or prevent the working fluid from reaching the thermal battery and the second thermal battery. 
     According to the first aspect, the HVAC system further includes a second expansion valve, wherein the thermal battery is positioned between the first and second expansion valves, and the working fluid is a refrigerant that is compressed by the compressor and that passes through each of the first heat exchanger and second heat exchanger. 
     According to the first aspect, the HVAC system further includes a second reversing valve that works in conjunction with the first reversing valve to control whether the system operates in the first mode or the second mode. 
     According to the first aspect, an orifice size of the first and second expansion valves can be modified to either expand the refrigerant or permit the refrigerant to flow therethrough without expansion. 
     According to a second aspect of the present disclosure, there is provided a heating and cooling (HVAC) system that includes a primary circuit including a refrigerant, a compressor, a first heat exchanger, a first reversing valve, a second reversing valve, an expansion valve located between the first reversing valve and the second reversing valve, and a thermal battery; and a secondary circuit including a working fluid, a pump, the thermal battery, and a second heat exchanger, wherein the compressor is configured to compress the refrigerant, the first reversing valve is configured to direct the refrigerant from the compressor to either the first heat exchanger or the thermal battery, and the second reversing valve is configured to direct the refrigerant from the thermal battery to either the expansion valve or the compressor; and the thermal battery is configured to exchange thermal energy with each of the working fluid and the refrigerant. 
     According to the second aspect, the thermal battery includes a first flow path for the working fluid and a second flow path for the refrigerant, and a plurality of phase change material storage plates that contains a phase change material for exchanging thermal energy with each of the working fluid and the refrigerant. 
     According to the second aspect, the thermal battery includes a first phase change material therein that is configured to selectively store thermal energy received from the refrigerant and release thermal energy to the refrigerant; and a second phase change material therein that is configured to selectively store thermal energy received from the working fluid and release thermal energy to the working fluid. 
     According to the second aspect, each of the phase change material storage plates include a plurality of corrugated members, the phase change material being located between each of the corrugated members. 
     According to the second aspect, each of the phase change material storage plates are sandwiched by a pair of flow plates, each of the flow plates including a plurality of dividing bars that are shaped to correspond to the corrugated members, the dividing bars of one flow plate that sandwiches the phase change material storage plate defining the first flow path for the working fluid and the dividing bars of another flow plate that sandwiches the phase change material storage plate defining the second flow path for the refrigerant. 
     According to the second aspect, each of the flow plates has a thickness less than a thickness of the phase change material storage plates. 
     According to a third aspect of the present disclosure there is provided a thermal battery including a phase change material therein that is configured to selectively store thermal energy received from a working fluid and release thermal energy to the working fluid. The thermal battery includes a pair of end plates, each of the end plates including a first major surface and an opposite second major surface, the first major surfaces each including a fluid inlet and a fluid outlet and the opposite second major surfaces each including a flow trough, the fluid inlet of each end plate being in communication with the flow trough formed on the opposite second major surface of the respective end plate; a plurality of flow plates sandwiched between the pair of end plates, each of the flow plates having a first side and an opposite second side, and each of the first side and the opposite second side including a flow surface, the flow surfaces of each flow plate being configured to communicate with either the flow trough of an adjacent end plate or one of the flow surfaces of an adjacent flow plate; a plurality of thermal energy transfer films that are respectively positioned between adjacent flow plates, and between each of the end plates and an immediately adjacent flow plate, such that a first flow path exists on one side of a respective thermal energy transfer film for the working fluid and a second flow path exists on an opposite side of the respective thermal energy transfer film for the phase change material; and the flow troughs and flow surfaces communicate with each other such that the working fluid that flows through the first flow path enters the fluid inlet of one of the end plates will exit the fluid outlet of the other end plate while exchanging thermal energy with the phase change material that is provided in the second flow path that extends between the fluid inlet of the other end plate and the fluid outlet of the one end plate. 
     According to the third aspect, the working fluid that enters the fluid inlet of the one end plate will enter the flow trough on the opposite second major surface of the one end plate and flow in a first direction before entering the flow surface of the adjacent flow plate and flowing in a second and opposite direction. 
     According to the third aspect, the pair of end plates and each of the flow plates are formed of a polymeric material that is impermeable and resistant to corrosion. 
     According to the third aspect, the thermal energy transfer films are each formed of a polymer film, and the thermal energy transfer films include one of a removable adhesive layer, an integral gasket, and a resilient sealant to sealingly engage with the end plates and the flow plates, the thermal energy transfer films are sealingly engaged with the end plates and the flow plates by being interference fit thereto, or the thermal energy transfer films are joined to the end plates and flow plates through application of heat. 
     According to the third aspect, turbulence inducing surfaces of the end plates and the flow plates each include a plurality of elongated bumps that extend across the first and second flow channels, respectively. 
     According to the third aspect, each of the flow plates includes a fluid inlet port and a fluid outlet port, wherein the fluid inlet port of a respective flow plate communicates with either the flow trough of the adjacent end plate or the fluid outlet port of the adjacent flow plate. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations and are not intended to limit the scope of the present disclosure. 
         FIG.  1    is a schematic illustration of a heating and cooling system including a thermal storage device according to a principle of the present disclosure; 
         FIG.  2    is a perspective view of a first example thermal storage device according to a principle of the present disclosure; 
         FIG.  3    is a cross-sectional view of the first example thermal storage device illustrated in  FIG.  2   ; 
         FIG.  4    is an exploded-perspective view of the first example thermal storage device illustrated in  FIG.  2   ; 
         FIG.  5    is a perspective view of a thermal energy transfer film according to a principle of the present disclosure; 
         FIG.  6    is a perspective view of a flow-surface side of an end plate used in a first example thermal storage device according to a principle of the present disclosure; 
         FIG.  7    is a perspective view of a flow plate used in the first example thermal storage device illustrated in  FIG.  2   ; 
         FIG.  8    is a perspective view of an end plate used in a second example thermal storage device according to a principle of the present disclosure; 
         FIG.  9    is a perspective view of a flow-surface side of the end plate illustrated in  FIG.  8   ; 
         FIG.  10    is a perspective view of a flow plate used in conjunction with the end plate illustrated in  FIGS.  8  and  9    to form the second example thermal storage device; 
         FIG.  11    is a perspective view of an end plate used in a third example thermal storage device according to a principle of the present disclosure; 
         FIG.  12    is a perspective view of a flow-surface side of the end plate illustrated in  FIG.  11   ; 
         FIG.  13    is a perspective view of a flow plate used in conjunction with the end plate illustrated in  FIGS.  11  and  12    to form the third example thermal storage device; 
         FIG.  14    is a perspective view of a flow plate that that may be used in a fourth example thermal storage device according to a principle of the present disclosure. 
         FIG.  15    is a schematic illustration of another heating and cooling system including a thermal storage device according to a principle of the present disclosure; 
         FIG.  16    is a schematic illustration of another heating and cooling system including a thermal storage device according to a principle of the present disclosure; 
         FIG.  17    is a perspective view of the thermal storage device used in the heating and cooling system illustrated in  FIG.  16   ; 
         FIG.  18    is a perspective view of a phase change material storage plate of the thermal storage device illustrated in  FIG.  17   ; and 
         FIG.  19    is a perspective view of a flow plate of the thermal storage device illustrated in  FIG.  17   . 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
       FIG.  1    illustrates an example HVAC system  10  that utilizes a thermal storage device or battery  12  according to a first embodiment of the present disclosure. In the illustrated embodiment, thermal battery  12  may be located within a secondary circuit or loop  14  of the HVAC system  10  that is located with an indoor structure  16 . A primary circuit or loop  18  of the HVAC system  10  may be located in a location (e.g., outdoors) that is different from the secondary loop  14 . 
     Primary loop  18  of HVAC system  10  may include a compressor  20 , a first heat exchanger  22 , a fan  23 , a second heat exchanger  24 , and a reversing valve  26  that enables primary loop  18  to operate in either a first mode (e.g., cooling) or a second mode (e.g., heating). Primary loop  18  may also include first expansion valve  28 , a first check valve  30 , a second expansion valve  32 , and a second check valve  34 . First and second check valves  30  and  34  are used so that the refrigerant can only flow through either the first expansion valve  28  or the second expansion valve  32  depending on the selected mode of operation. Electronic valves  36   a - 36   d  may be located on opposing sides of each expansion valve  28  and  32  that either permit the fluid to flow through one of the expansion valves  28  or  32  or permit the fluid to bypass one of the expansion valves  28  or  32  and flow through one of the check valves  30  or  34 . The electronic valves  36   a - d , the reversing valve  26 , and the compressor  20  may each be in communication with a controller  38  that is configured to control operation of each. 
     In the illustrated embodiment, primary loop  18  is operating in the first mode (e.g., cooling) where the reversing valve  26  enables the refrigerant compressed by the compressor  20  to travel from the compressor  20  to the first heat exchanger  22  that operates as a condenser. After the refrigerant condenses in the first heat exchanger  22 , the refrigerant travels from the first heat exchanger  22  to one of the electronic valves  36   a  located downstream therefrom where the refrigerant flow is diverted to bypass the first expansion valve  28  and pass through the first check valve  30 , through another of the electronic valves  36   b  and toward the second expansion valve  32 . Before reaching the second expansion valve  32 , the refrigerant passes through electronic valve  36   c  that permits the refrigerant to pass through to the second expansion valve  32  where the refrigerant expands (e.g., begins to evaporate). After passing through the second expansion valve  32 , the expanded refrigerant travels through electronic valve  36   d  that permits the refrigerant to flow toward second heat exchanger  24  where the refrigerant further evaporates before exiting the second heat exchanger  24 , passes through reversing valve  26  and on to compressor  20  where the cycle repeats. Although not required, an accumulator  40  may be positioned upstream of compressor  20 . 
     In the second mode (e.g., heating), the reversing valve  26  enables the refrigerant compressed by the compressor  20  to first travel from the compressor  20  to the second heat exchanger  24 , which acts as a condenser where the compressed gaseous refrigerant condenses to a liquid. After the refrigerant condenses in the second heat exchanger  24 , the refrigerant travels from the second heat exchanger  24  to one of the electronic valves  36   d  located downstream therefrom where the refrigerant flow is diverted to bypass the second expansion valve  32  and pass through the second check valve  34 , through another of the electronic valves  36   c  and toward the first expansion valve  28 . Before reaching the first expansion valve  28 , the refrigerant passes through electronic valve  36   b  that permits the refrigerant to pass through to the first expansion valve  28  where the refrigerant further expands (e.g., begins to evaporate). After passing through the first expansion valve  28 , the evaporated refrigerant travels through electronic valve  36   a  that permits the refrigerant to flow toward first heat exchanger  22  where the refrigerant further evaporates before exiting the first heat exchanger  22 , passes through reversing valve  26  and on to compressor  20  where the cycle repeats. 
     Secondary loop  14  includes thermal battery  12 , an optional second thermal battery  12 ′, a pump  42  for pumping a working fluid through secondary loop  14  that can charge and discharge thermal batteries  12  and  12 ′, a first three-way valve  44 , an optional second three-way valve  46 , the second heat exchanger  24 , a third heat exchanger  48 , and a fan  49 . An example working fluid may be water. Other working fluids known to those skilled in the art are contemplated including, for example, a glycol such as ethylene glycol or a mixture of glycols. Alternatively, a mixture of water and at least one glycol may be used. 
     The use of secondary loop  14  increases the functionality of HVAC system  10 . As noted above, primary loop  18  may operate in a first mode (e.g., cooling) and a second mode (e.g., heating). The secondary loop  14  having at least thermal battery  12  further enables HVAC system  10  to operate in a third mode where thermal battery  12  is charged, a fourth mode where thermal battery  12  may be charged or discharged while primary loop  18  functions in either the first mode or the second mode to assist with the cooling or heating provided by primary loop  18 , and in a fifth mode where the indoor structure  16  is either heated or cooled using only the secondary loop  14 . When thermal battery  12  is being “charged,” it should be understood that the thermal energy received by the phase change material therein may be such that the phase change material becomes a liquid (i.e., receives thermal energy that causes the solid phase change material to change phase to liquid), or such that the phase change material becomes a solid or semi-solid (i.e., receives thermal energy that causes the phase change material to change from liquid to a solid or semi-solid). In either case, the energy received by the phase change material can be used assist in heating and cooling of indoor structure  16 . 
     It should also be understood that the phase change material can be selected based on the desired temperature at which phase change occurs. In cooling applications, the phase change temperature should be less than or about equal to room temperature (i.e., about 70 degrees F., and ideally in the range of about 50 degrees F. to 60 degrees F.). In heating applications, the phase change temperature should be greater than room temperature (i.e., greater than 70 degrees F. up to about 100 degrees F.). In the illustrated embodiment, the thermal battery  12  can employ a single phase change material or can include multiple phase change materials. Example phase change materials include waxes and salts. 
     Charging of thermal battery  12  will now described relative to where primary loop  18  is operating in a heating mode (i.e., the second mode). During charging of thermal battery  12 , the working fluid is being pumped by pump  42  through secondary loop  14 . When the working fluid enters second heat exchanger  24 , which is operating as a condenser where the refrigerant in primary loop  18  is cooled to convert the compressed gaseous refrigerant to a liquid, the thermal energy absorbed by second heat exchanger  24  as the compressed gaseous refrigerant condenses (i.e., cools) is transferred to the working fluid. After exiting second heat exchanger  24 , the working fluid will travel to third heat exchanger  48 , which simply permits the working fluid to pass through to first three-way valve  44  that will permit the heated working fluid to pass therethrough to second three way valve  46  and then to thermal battery  12  (i.e., fan  49  is not running). As the heated working fluid passes through thermal battery  12 , the heated working fluid will exchange thermal energy with a phase-change material in the thermal battery  12 , which retains the thermal energy absorbed from the working fluid to charge the thermal battery  12  (e.g., change the phase change material in thermal battery  12  from a solid or semi-solid to a liquid). Then the cooled working fluid may exit thermal battery  12  and continue to pump  42 , where the process may be repeated. If the fan  49  is running while the heated or cooled working fluid passes through third heat exchanger  48 , the heated or cooled working fluid may be used to heat or cool indoor structure  16  (i.e., fourth or fifth mode). When thermal battery  12  is not being used, pump  42  can be turned off by a second controller  50 . 
     Alternatively, if thermal battery  12  is not being used, it should be understood that first three-way valve  44  permits thermal battery  12  to be bypassed. In this regard, three-way valve  44  may be controlled by second controller  50 , which as noted above may also be used to control pump  42 . Alternatively, three-way valve  44  and pump  42  may be controlled by controller  38 . If thermal battery  12  is being bypassed, the working fluid may continue to be circulated through secondary loop  14  by pump  42 . 
     As noted above, when thermal battery  12  is charged, thermal battery  12  may be used to assist primary loop  18  in heating or cooling indoor structure  16 . This is particularly advantageous during times of the day when electricity prices are low and/or when the HVAC system efficiency is at its peak. When thermal battery  12  is not being used or charged, thermal battery  12  may be bypassed through use of three-way valves  44  and  46 . 
     To discharge the thermal battery  12  when the phase change material therein is in a liquid phase, the working fluid may receive thermal energy (i.e., be heated) from thermal battery  12  and pumped by pump  42  towards second heat exchanger  24 , which is operating as an evaporator (i.e., primary loop  18  is operating in a cooling mode). The refrigerant in primary loop  18  can receive the thermal energy in second heat exchanger  24  from the heated working fluid received from thermal battery  12  to assist in the evaporation of the refrigerant in primary loop  18 . After exiting second heat exchanger  24 , the working fluid will travel to third heat exchanger  48 . The cooled working fluid in third heat exchanger  48  can then be used to further cool indoor structure  16 . 
     If thermal battery  12  has been charged such that the phase change material therein is in a solid or semi-solid phase, the working fluid may be cooled by thermal battery  12  and pumped by pump  42  towards second heat exchanger  24 , which may be operating as a condenser (i.e., primary loop in operating in a heating mode). The refrigerant in primary loop  18  can release thermal energy to the second heat exchanger  24  that can be received by the cooled working fluid received from thermal battery  12  to assist in the condensing of the refrigerant in the primary loop  18 . After exiting second heat exchanger  24 , the working fluid will travel to third heat exchanger  48 . The heated working fluid in third heat exchanger  48  can then be used to further heat indoor structure  16 . 
     Although not required, it should be understood that secondary loop  14  may include the above-noted second thermal battery  12 ′ in parallel with thermal battery  12 . If such a configuration is adopted, one thermal battery (e.g., battery  12 ) may be used for heating and the other thermal battery (e.g., battery  12 ′) can be used for cooling. Second three-way valve  46  permits the working fluid to flow to either the thermal battery  12  or the second thermal battery  12 ′ and may also be controlled by controller  50  or controller  38 . As noted above, the phase change material can be selected based on the desired temperature at which phase change occurs. Thus, if battery  12 ′ is being used for heating, the phase change material contained therein can be a material that changes phase at temperatures greater than room temperature (i.e., temperatures greater than 70 degrees F. and less than about 100 degrees F.). Conversely, if battery  12 ′ is being used for cooling, the phase change contained therein may change phase at temperatures less than to about equal to room temperature (i.e., at temperatures between 50 degrees F. to 70 degrees F., and ideally at temperatures between 50 degrees F. to 60 degrees F.). If primary loop  18  is being used for heating, the first three-way valve  44  may be used to bypass battery  12 ′. Conversely, if primary loop  18  is being used for cooling, the three-way valves may be used to bypass battery  12 . 
     Compressor  20  may be any type of compressor known to one skilled in the art including, for example, a capacity modulated or variable speed scroll compressor. Other types of compressors  20 , however, are contemplated including reciprocating compressors, centrifugal compressors, and the like. When compressor  20  is a capacity modulated or variable speed compressor, the compressor  20  can operate more efficiently and at a lower capacity when operated in parallel with secondary loop  14  (i.e., when used in parallel with thermal battery  12 ). The compressor  20  may operate at a higher capacity to simultaneously charge thermal battery  12  and cool/heat the indoor structure  16 . The refrigerant used by primary loop  18  may be any type of refrigerant known to one skilled in the art. 
     Now referring to  FIGS.  2  to  14   , example thermal batteries  12  according to a principle of the present disclosure are illustrated. While the below description will be relative to a thermal battery  12 , it should be understood that the below-described structures may also be used for the thermal battery  12 ′ and for the above-noted second heat exchanger  24  as described in U.S. patent application Ser. No. 17/193,293 filed Mar. 5, 2021, and assigned to Emerson Climate Technologies, Inc., which is incorporated by reference herein in its entirety. 
       FIGS.  2 - 7    illustrate a first example thermal battery  12  according to the present disclosure. Thermal battery  12  includes a pair of end plates  52   a  and  52   b , a plurality of flow plates  54  that are sandwiched by the pair of end plates  52   a  and  52   b , and a plurality of thermal energy transfer films  56 . A thermal energy transfer film  56  is located between each end plate  52   a ,  52   b  and an adjacent flow plate  54 , as well as between adjacent flow plates  54 . While five flow plates  54  are illustrated in  FIG.  4   , it should be understood that this configuration is only an example, and a greater or lesser number of flow plates  54  can be used in thermal battery  12  dependent on the application in which thermal battery  12  is to be used. 
     End plates  52   a  and  52   b  are preferably formed of a polymeric material that is impermeable and resistant to corrosion. While polymeric materials are preferable, it should be understood that end plates  52   a  and  52   b  may be formed of a metal material such as a sintered metal material, if desired. In the illustrated embodiment, end plate  52   a  includes a working fluid inlet  58   a  ( FIG.  2   ) while end plate  52   b  includes a working fluid outlet  58   b . Similarly end plate  52   b  includes a phase change material inlet  60   a  while end plate  52   a  includes a phase change material outlet  60   b . It should be understood that after thermal battery  12  has been filled with phase change material at inlet  60   a  and the phase change material begins to exit outlet  60   b , the flow of phase change material into thermal battery  12  is stopped and the inlet  60   a  and outlet  60   b  are capped (not illustrated) such that the phase change material remains stationary in the thermal battery  12  to exchange thermal energy with the working fluid that will be permitted to flow through thermal battery  12  from inlet  58   a  to outlet  58   b  when thermal battery  12  is part of the HVAC system. It should be understood, however, that the working fluid outlet  58   a  of end plate  12   b  may instead function as a working fluid inlet and working fluid inlet  58   a  may instead function as a working fluid outlet, if desired. In addition, it should be understood fluid inlets  58   a  and  60   a  and fluid outlets  58   b  and  60   b  may be unitary with end plates  52   a ,  52   b , or may be formed separately from end plates  52   a ,  52   b  and attached thereto using an adhesive (not shown), chemical bonding, welding, a threaded connection, or some other type of attachment method known to one skilled in the art. 
     In the illustrated embodiment, end plates  52   a  and  52   b  are rectangular-shaped planar members including a first major surface  62 , an opposite second major surface  64 , a first major side surface  66 , a second major side surface  68 , a third minor side surface  70 , and a fourth minor side surface  72 . First major surfaces  62  of end plates  52   a  and  52   b  define an exterior of thermal battery  12  and includes fluid inlets  58   a  and  60   a  and fluid outlets  58   b  and  60   b  extending outward therefrom at a location proximate third minor side surface  70 , while second major surface  64  of each of the end plates  52   a  and  52   b  includes a flow trough  74  similar to or the same as the flow surfaces used on flow plates  54  as shown in  FIGS.  6  and  7    and as will be described in more detail later. While fluid inlets  58   a  and  60   a  and fluid outlets  58   b  and  60   b  are illustrated as being proximate third minor side surface  70  of each of the end plates  52   a  and  52   b , it should be understood that fluid inlets  58   a  and  60   a  and fluid outlets  58   b  and  60   b  could be located elsewhere on first major surface  62  without departing from the scope of the present disclosure. 
     In addition to fluid inlets  58   a  and  60   a  and fluid outlets  58   b  and  60   b , first major surface  62  of each end plate  52   a  and  52   b  may also include a plurality of ribs  76  that increase the rigidity of end plates  52   a  and  52   b  to withstand fluid pressures and pressure fluctuations that may occur during the thermal energy exchange process. While ribs  76  are illustrated as extending diagonally from a first major side surface  66  of the end plate  52  to second major side surface  68 , it should be understood that any configuration for ribs  76  may be used so long as ribs  76  satisfactorily increase the rigidity of end plates  52   a  and  52   b  to withstand fluid pressures and pressure fluctuations that may occur during the thermal energy exchange process. 
     End plates  52   a  and  52   b  also include a plurality of apertures  78  that are each configured for receipt of a fastener (not shown) that extends through the entire width W of the thermal battery  12  (i.e., from end plate  52   a  to the opposite end plate  52   b  as best shown in  FIG.  2   ), and an outwardly extending flange  80  having through-holes  82  for rigidly attaching thermal battery  12  to a surface (not shown) that can be used to support thermal battery  12 . 
     As best shown in  FIG.  6   , second major surface  64  of end plate  52   a  defines a flow trough  74  that, in the illustrated embodiment, communicates with fluid inlet  58   a . The flow trough  34  includes a pair of flow channels  84   a  and  84   b  that are separated by a dividing wall  86 . Although only a single dividing wall  86  is illustrated, it should be understood that multiple dividing walls  86  can be used to ensure proper support of thermal energy transfer films  56 , as will be described in more detail later. As the working fluid enters from fluid inlet  58   a , the working fluid may enter either of the flow channels  84   a  and  84   b  and flow toward fourth minor side surface  72 . As the fluid flows through either of the flow channels  84   a  and  84   b , the fluid will first pass through a plurality of nubs  87  formed in each flow channel  84   a ,  84   b . Nubs  87  are designed to increase structural rigidity of end plate  52   a , as well as provide support for fluid transfer film  56 . 
     After passing through nubs  87 , the working fluid will encounter a textured or turbulence inducing surface  88  that increases the turbulence of the working fluid, which enhances thermal energy exchange of the working fluid with the thermal energy transfer film  56  positioned between the second major surface  64  of end plate  52   a  and the adjacent flow plate  54  to the phase change material on the other side of the thermal energy transfer film  56 , or vice versa. In other words, the flow of working fluid along flow channels  84   a  and  84   b  transitions from a laminar flow to a turbulent flow when the fluid encounters turbulence inducing surface  88 . 
     Turbulence inducing surface  88  includes a plurality of elongated ribs or bumps  90  that extend in a direction from first major side surface  66  toward second major side surface  68  across end plate  52   a . While bumps  90  are each illustrated as being elongated, a series of bumps  90  that appear to form a dotted line may be used instead, if desired. In addition, it should be understood that any type of dimensional feature having a variable size, shape, and quantity can be used in place of bumps  90  so long as the dimensional feature provides for a turbulent flow of the working fluid while flowing along turbulence inducing surface  88 , and assists in controlling the amount of thermal energy transfer, pressure loss of the fluid, and the effectiveness of the thermal battery  12 . 
     Dividing wall  86  includes a first section  92  located proximate fluid inlet  58   a  that transitions to second section  94  that travels along a center of end plate  52   a , which transitions to a third section  96  that is located proximate an inlet port  98   a  or  98   b  formed in the adjacent flow plate  14  ( FIG.  6   ). Third section  56  may be contoured at  100  to assist in increasing turbulence of the working fluid flow through flow trough  74 . In addition to dividing flow trough  74  into a pair of flow channels  84   a  and  84   b , dividing wall  86  also provides additional structural rigidity to end plate  52   a  to withstand fluid pressures and pressure fluctuations that may occur during the thermal energy exchange process. In addition, it should be noted that dividing wall  86  includes apertures  78  that are configured for receipt of the fasteners (not illustrated) that extend through thermal battery  12 . Thus, dividing wall  86  also provides increased structural rigidity to thermal battery  12  to withstand tightening of the fasteners (not illustrated) to an extent that thermal battery  12  will remain hermetically sealed throughout use of thermal battery  12 . 
     Thermal energy transfer films  56  ( FIGS.  4  and  5   ) are polymer films that are formed of a corrosion-resistant material such as polyether ether ketone (PEEK), polyethylene, acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), or some other type of polymer material that is corrosion-resistant and satisfactory for thermal energy exchange. Thermal energy transfer films  56  are shaped to correspond to a recess  102  formed in second major surface  64  of end plate  52   a  such that an entirety of flow trough  74  is covered by the thermal energy transfer film  56 . 
     Although not required, thermal energy transfer film  56  may include a gasket  107  integral with the thermal energy transfer film  56  and/or the thermal energy transfer film  56  may have a removable adhesive layer  109  that maintains its adhesive quality when removed from the thermal energy transfer film  56 . Alternatively, gasket  107  may be in the form of a resilient sealant that is applied to the thermal energy transfer film  56 , the thermal energy transfer film  56  may be shaped such that a perimeter of the thermal energy transfer film  56  is configured to be interference fit with an adjacent end plate  52   a ,  52   b  or flow plate  54 , or the thermal energy transfer film  56  can be joined to an end plate  52   a ,  52   b  or flow plate  54  through application of heat. 
     Thermal energy transfer film  56  includes openings  104  that permit fluid to pass from flow trough  74  to one of the inlet ports  98   a  or  98   b  of the adjacent flow plate  54 . While thermal energy transfer film  56  may also include holes  106  that correspond to apertures  78  to permit the fasteners (not shown) that bind thermal battery  12  together to pass through thermal energy transfer film  56 , it should be understood that holes  106  are optional to an extent that the fasteners (not shown) may simply pierce the polymer material of the thermal energy transfer film  56  when inserted through the thermal battery  12 . A thickness of the thermal energy transfer films  56  is variable dependent on the application in which thermal battery  12  is being used. In the illustrated embodiment, however, a thickness of the thermal energy transfer films  56  may be in the range of 0.0005 inches to 0.010 inches (0.0127 to 0.254 mm). 
     Now referring to  FIGS.  4  and  7   , the plurality of flow plates  54  will be described. Flow plates  54  may be formed of the same material as end plates  52   a  and  52   b . For example, flow plates  54  can be formed of a polymeric material or a metal material. Alternatively, flow plates  54  can be formed of a different material in comparison to end plates  52   a  and  52   b . For example, flow plates  54  can be formed of a polymeric material that is different from the polymeric material of end plates  52   a  and  52   b , or flow plates  54  can be formed of a metal material while end plates  52   a ,  52   b  are formed of a polymeric material. Regardless, the construction of each of the flow plates  54  is the same, albeit arranged alternately in opposite manners throughout the thermal battery  12 , which will be described in detail later. As best shown in  FIG.  7   , each flow plate  54  is shaped to correspond to the shape of end plate  52   a . Flow plate  54  includes a first flow surface  108  formed on a first major side  110  and a second flow surface (not shown) formed on a second major side  112  of the flow plate  54 . While the second flow surface is not illustrated in  FIG.  7   , it should be understood that the second flow surface is a mirror image of that illustrated in  FIG.  7   . 
     The flow surfaces  108  of flow plate  54  are similar to the flow troughs  74  of end plates  52   a  and  52   b . In this regard, the flow surfaces  108  include a pair of flow channels  114   a  and  114   b  that are separated by a dividing wall  116 . Although only a single dividing wall  116  is illustrated, it should be understood that multiple dividing walls  116  can be used to ensure proper support of thermal energy transfer films  56 , as will be described in more detail later. As the working fluid enters from one of the inlet ports  98   a  or  98   b , the fluid may enter either or both of the flow channels  114   a  and  114   b  and flow away from the inlet port  98   a  or  98   b . As the working fluid flows through either of the flow channels  114   a  and  114   b , the fluid will first pass through a plurality of nubs  117  formed in each flow channel  114   a ,  114   b . Nubs  117  are designed to increase structural rigidity of flow plate  54 , as well as provide support for thermal energy transfer film  56 . After passing through nubs  117 , the working fluid will encounter a textured or turbulence inducing surface  118  that increases the turbulence of the working fluid, which enhances thermal energy exchange of the working fluid with the thermal energy transfer film  56  positioned between the second major surface  64  of end plate  52   a  and the adjacent flow plate  54  to the phase change material on the other side of the thermal energy transfer film  56 , or vice versa. Turbulence inducing surface  118  includes a plurality of elongated ribs or bumps  120  that extend in a direction across flow plate  54 . While bumps  120  are each illustrated as being elongated, a series of bumps  120  that appear to form a dotted line may be used instead, if desired. 
     Dividing wall  116  includes a first section  122  located proximate inlet port  98   a  or  98   b  that transitions to second section  124  that travels along a center of flow plate  54 , which transitions to a third section  126  that is located proximate an inlet port  98   a  or  98   b  formed in the adjacent flow plate  54  ( FIG.  4   ). Third section  126  may be contoured at  130  to assist in increasing turbulence of the fluid flow through flow surface  108 . In addition to dividing flow surface  108  into a pair of flow channels  114   a  and  114   b , dividing wall  116  also provides additional structural rigidity to flow plate  54  to withstand fluid pressures and pressure fluctuations that may occur during the thermal energy exchange process. In addition, it should be noted that dividing wall  116  includes apertures  78  that are configured for receipt of the fasteners (not illustrated) that extend through thermal battery  12 . Thus, dividing wall  116  also provides increased structural rigidity to thermal battery  12  to withstand tightening of the fasteners (not illustrated) to an extent that thermal battery  12  will remain hermetically sealed throughout use of thermal battery  12 . 
     It should be understood that the shape of end plates  52   a ,  52   b  and flow plates  54  support the thermal energy transfer films  56  such that a minimum area of the thermal energy transfer film  56  is unsupported by features of the end plates  52   a ,  52   b  and flow plates  54  such as the recess  102  of the end plates  52   a ,  52   b , the dividing wall  86  and nubs  87  of the end plates  52   a ,  52   b , and the dividing wall  116  and nubs  117  of the flow plates  54 . Supporting the thermal energy transfer films  56  in this manner assists in preventing the thermal energy transfer films  56  from losing its form or leaking. Preferably, the distance of an unsupported area of the thermal energy transfer film  56  ranges between 0.25 inches to 3 inches. Thus, in larger thermal batteries  12 , it may be useful to include multiple dividing walls  86  and  116  to ensure that the distance of an unsupported area of the thermal energy transfer film  56  ranges between 0.25 inches to 3 inches. Moreover, it should be understood that end plates  52   a ,  52   b  and flow plates  54  can be formed by an injection or compression molding method, by 3D printing, or some other type of manufacturing method. Any of these methods enable end plates  52   a ,  52   b  and flow plates  54  to have each of the above-described support features in any manner or configuration desired and permits the flow troughs  74  and flow surfaces  108  to have the textured or turbulence inducing surface in any configuration desired which enables designs that can be tailored to a specific application. 
     Now flow of the working fluid through the thermal battery  12  will be described. As best shown in  FIG.  4   , the working fluid may enter thermal battery  12  through fluid inlet  58   a  of end plate  52   a  and travels through flow trough  74  toward the inlet port  98   a  of the flow plate  14   a  arranged adjacent end plate  52   a  (i.e., in a downward direction in  FIG.  4   ). While in flow trough  74  of end plate  52   a , the working fluid will exchange thermal energy with thermal energy transfer film  56  and the stationary phase change material located on the opposite side of thermal energy transfer film  56 . As the working fluid travels from flow trough  74  of end plate  52   a  toward the inlet port  98   a  of the flow plate  54   a , the working fluid will flow from flow trough  74  of end plate  62   a  through opening  104  in thermal energy transfer film  56 , and then through inlet port  98   a  of the adjacent flow plate  54   a . The working fluid will then flow in the opposite direction along flow surface  108  of the adjacent flow plate  54   a  (i.e., in an upward direction in  FIG.  4   ), which is not visible in  FIG.  4   , toward an inlet port  98   a  of an adjacent flow plate  14   b , at which time the working fluid will pass through the opening  104  in the thermal energy transfer film  56  between the flow plates  54   a  and  54   b , through the fluid inlet port  98   a  of the flow plate  54   b , and then along the flow surface  108  of the flow plate  54   b  (i.e., in a downward direction in  FIG.  4   ). During flow along flow surface  108  of flow plate  54   b  that is not visible in  FIG.  4   , the working fluid will exchange thermal energy with thermal energy transfer film  56  between flow plate  54   b  and adjacent flow plate  54   c  before entering the opening  104  in the thermal energy transfer film  56  and then through inlet port  98   a  of the flow plate  54   c . This back and forth flow through the thermal battery will continue until the working fluid exits the outlet port  58   b  of end plate  52   b.    
     Similarly, when thermal battery  12  is filled with the phase change material before capping the inlet  60   a  and outlet  60   b , the phase change material will enter the fluid inlet  60   a  of end plate  52   b  and it will travel down along flow trough  74  of end plate  52   b  toward the inlet port  98   b  of a flow plate  54   d , pass through the opening  104  in the thermal energy transfer film  56  between the end plate  52   b  and the flow plate  54   d , enter the inlet port  98   b  of the flow plate  54   d , and then travel upward along the flow surface  108  of flow plate  54   d  toward the inlet port  98   b  of the flow plate  14   e , where the process continues such that the phase change material will travel back and forth through the thermal battery  12  until the phase change material reaches the fluid outlet  60   b  of end plate  52   a  to fill the thermal battery, and at which time the fluid inlet  60   a  and fluid outlet  60   b  are capped (i.e., sealed) to maintain the phase change material in the thermal battery  12 . Then, as the working fluid flows through the thermal battery  12  as described above, thermal energy will exchange from the working fluid through the thermal energy transfer film  56  to the stationary phase change material located on the other side of the thermal energy transfer film  56 . This is possible because each side of each flow plate  54  includes a flow surface  108 . In this manner, as the working fluid travels over one side of the flow plate  54  and the phase change material is located on a side of an adjacent flow plate  54  with the thermal energy transfer film  56  located between the working fluid and the phase change material, thermal energy is exchanged between the working fluid through the thermal energy transfer film  56  to the phase change material. As noted previously, the phase change materials may be selected based on temperatures experienced in the system that incorporates the phase change material. In this regard, different phase change materials may be useful in different applications. Example phase change materials that are useful in the present disclosure include various waxes and salts. 
     In above-described embodiment, the working fluid flows through the thermal battery  12  in a counter-flow manner. The present disclosure should not be limited to such a configuration. In this regard, thermal battery  12  may be configured such that there may be a parallel-flow of the working fluid through the thermal battery  12 . In a parallel-flow thermal battery  12 , the fluid outlet  60   b  of end plate  52   a  will function as a second fluid inlet  58   a , and the fluid inlet  60   a  of end plate  52   b  will function as a second fluid outlet  52   b . In other words, if the phase change material were permitted to simultaneously freely flow through the thermal battery (note—the phase change material does not flow during use of thermal battery  12 ), the working fluid and phase change material would simultaneously enter the two fluid inlets formed on end plate  12   a  before subsequently simultaneously exiting the thermal battery  12  through the two fluid outlets formed on end plate  52   b . In such a configuration, instead of the working fluid and phase change material flowing in opposite directions while separated by the thermal energy transfer films  56  like in the counter-flow configuration, the working fluid and phase change material may each flow in the same direction while being separated by the thermal energy transfer films  56 . In either case, thermal energy is exchanged between the working fluid and the phase change material. As noted above, the phase change material only flows through the thermal battery  12  when being filled with the phase change material. Inasmuch as the inlet and outlet are capped after filling the thermal battery  12  with the phase change material, the only material that “flows” through the thermal battery during use thereof is the working fluid or refrigerant. The “parallel flow” described above is merely to distinguish the counter-flow design relative to the parallel flow design. 
     As the working fluid enters fluid inlet  58   a , the working fluid will enter the flow trough  74  of end plate  52   a  and flow towards the lower opening  104  of thermal energy transfer film  56  located between the end plate  52   a  and flow plate  54   a . The working fluid will then flow through the lower opening  104  and fluid inlet port  98   a  of flow plate  54   a  before entering the flow surface  68  of flow plate  54   a  located on the side of flow plate  14   a  that is not visible in  FIG.  4   . Then, the working fluid will flow upward along flow surface  108  of flow plate  54   a  before passing through the upper opening  104  of the thermal energy transfer film  56  located between flow plate  54   a  and  54   b , passing through fluid inlet port  98  of flow plate  54   b , and entering the flow surface  108  of flow plate  54   b  located on the side of flow plate  54   b  that is not visible in  FIG.  4   . The working fluid will continue in this fashion until exiting fluid outlet  60   b  of end plate  52   b.    
     Similarly, when filling the thermal battery  12  with the phase change material, the phase change material that enters the second fluid inlet  58   a  of end plate  52   a  will immediately pass through the upper opening  104  of thermal energy transfer film  56  between end plate  52   a  and flow plate  54   a  before entering the flow surface  108  on flow plate  54   a  that is visible in  FIG.  4   . The phase change material will flow down the visible flow surface  108  of flow plate  54   a  as the working fluid is flowing in the same direction down the flow trough  104  of end plate  52   a , while being separated by the thermal energy transfer film  56  between end plate  52   a  and flow plate  54   a . After filling, the inlet and outlets are capped. 
     Because the working fluid may be warm and the phase change material may be cool (e.g., solid or semi-solid), or vice versa, the working fluid flowing past the stationary phase change material will exchange thermal energy with each other via the thermal energy transfer film  56 . The working fluid will continue to flow back and forth in parallel relative to the stationary phase change material until the working fluid exits the thermal battery  12  through the fluid outlet formed on end plate  52   b ). 
     Now referring to  FIGS.  8 - 10   , end plates  128  and flow plates  130  that may be used in a second example thermal battery will be described. While only a single end plate  128  is illustrated in  FIGS.  8  and  9   , and only a single flow plate  130  is illustrated in  FIG.  10   , it should be understood that a thermal battery (not illustrated) including these components will include a pair of end plates  128  that sandwich a plurality of the flow plates  130 . In addition, similar to thermal battery  12 , it should be understood that thermal energy transfer films  56  will be located between the end plates  128  and an adjacent flow plate  130 , and between adjacent flow plates  130 . 
     The primary difference between a thermal battery including end plates  128  and flow plates  130  is that the dimensions of a thermal battery including these components will be less than the dimensions of the thermal battery  12  illustrated in  FIGS.  2 - 7   , which enables use in a system that uses less fluid volume in comparison to a larger fluid volume system. Thus, features that are common to end plates  128  and end plates  52   a  and  52   b , and features that are common to flow plates  130  and flow plates  14 , use the same reference numbers and description thereof will be omitted. Regardless, it should be understood that a thermal battery that uses end plates  128  and flow plates  130  functions in the same manner as the thermal battery described above. 
     Now referring to  FIGS.  11 - 13   , end plates  132  and flow plates  134  that may be used in a third example thermal battery will be described. While only a single end plate  132  is illustrated in  FIGS.  11  and  12   , and only a single flow plate  134  is illustrated in  FIG.  13   , it should be understood that a thermal battery (not illustrated) including these components will include a pair of end plates  132  and that sandwich a plurality of the flow plates  134 . In addition, similar to thermal battery  12 , it should be understood that thermal energy transfer films  56  will be located between the end plates  132  and an adjacent flow plate  134 , and between adjacent flow plates  134 . 
     The primary difference between a thermal battery including end plates  132  and flow plates  134  is that a shape of a thermal battery including these components is different from the shape of the components used in the thermal battery  12  and the thermal battery (not illustrated) that uses end plates  132  and flow plates  134 . In this regard, the shape of end plates  132  and flow plates  134  is hexagonal rather than rectangular, which enables use in a system that has different packaging requirements. While the shape of a thermal battery using end plates  132  and flow plates  134  may be different to account for packaging restraints, it should be understood that an overall size of such a thermal battery may have a greater or lesser fluid volume in comparison to the previously described thermal batteries. Thus, features that are common to end plates  132  and end plates  52   a  and  52   b , and features that are common to flow plates  134  and flow plates  44 , use the same reference numbers and description thereof will be omitted. Regardless, it should be understood that a thermal battery that uses end plates  132  and flow plates  134  functions in the same manner as the thermal battery  12  described above. 
     Now referring to  FIG.  14   , another flow plate  136  for use in a fourth example thermal battery (not illustrated) will be described. While only a single flow plate  136  is illustrated in  FIG.  14   , it should be understood that a thermal battery (not illustrated) including this component will include a pair of end plates (not shown) that sandwich a plurality of the flow plates  136 . In addition, similar to thermal battery  12 , it should be understood that thermal energy transfer films  56  will be located between adjacent flow plates  136 , and between an end plate (not illustrated) and an adjacent flow plate  136 . 
     The primary difference between a thermal battery including flow plates  136  is that a flow channel  138  that is formed on each opposing major surface  140   a  and  140   b  of the flow plate  136  are scroll-shaped, which enables the flow channel  138  to have a sufficient length to enable thermal energy exchange from the fluid flowing through the flow channel  138  while minimizing the overall size of a thermal battery (not illustrated) that includes the flow plate  136 . Flow plate  136  includes a first inlet port  142   a  that may communicate with a fluid inlet (not shown) of an end plate (not shown). The scroll-shaped flow channel  138  travels from inlet port  142   a  to an outlet port  144   a . Flow plate  136  also includes a second inlet port  142   b  that receives fluid from the outlet port  144   a  of an adjacent flow plate  136 , which then travels through the flow channel  128  to a second outlet port  144   b  that communicates with either a fluid outlet of an adjacent end plate (not shown) or with a fluid inlet  142   a  of an oppositely adjacent flow plate  136 . Thus, working fluid may flow in one direction on one side  140   a  of the plate (e.g., from inlet port  142   a  to outlet port  144   a ), while the stationary phase change material may be located in the flow channel  138  that extends in the opposite direction (e.g., from inlet port  142   b  to outlet port  144   b ) on the other side  140   b  of the flow plate  136 . 
     It should be understood that the end plates (e.g.,  52   a ,  52   b ) and flow plates (e.g.,  54 ) of each of the above-described example embodiments may have any three-dimensional shape so long as the end plates and flow plates can support a thermal energy transfer film  56  between two or more flow paths. In this regard, while thermal batteries are illustrated having rectangular plates (e.g.,  FIGS.  1 - 10   ), hexagonal (e.g.,  FIGS.  11 - 13   ), or round (e.g.,  FIG.  14   ), other three-dimensional plates are contemplated (e.g., oval, square, triangular, and other). In this regard, because the end plates and flow plates may be formed using various processes including injection or compression molding and 3D printing, the shapes, sizes, and features of the end plates and flow plates can be tailored to the specific application in which the thermal battery  12  is to be used. 
     Now referring to  FIG.  15   , another HVAC system  200  is illustrated that utilizes a thermal battery  12  that may be any thermal battery that is illustrated in  FIGS.  2 - 14   . HVAC system  200  is similar to HVAC system  10  illustrated in  FIG.  1    in that HVAC system  200  includes a compressor  20 , a first heat exchanger  22 , a second heat exchanger  24 , a first expansion valve  28 , a second expansion valve  32 , and an optional accumulator  40 . System  200  differs from system  10  in that system  200  does not include a secondary loop  14 , system  200  includes a second reversing valve  202  in addition to reversing valve  26 , and thermal battery  12  is located exterior to indoor structure  16  such that the “working fluid” in the illustrated embodiment is the refrigerant of the HVAC system  200 . It should be understood that the material that forms thermal battery  12  (i.e., the end plates and flow plates) in the illustrated embodiment is preferably formed of a metal material such as a sintered metal material to enhance thermal energy transfer between the phase change material and the refrigerant through thermal energy transfer films  56 . Thermal battery  12 , however, can also be formed of polymeric materials, if desired. 
     Similar to system  10 , HVAC system  200  may operate in a first mode (e.g., cooling) and a second mode (e.g., heating). In either mode, the flow of refrigerant is always in the same direction. For example, in the illustrated second mode, the refrigerant compressed by compressor  20  will first travel through reversing valve  26 , which directs the refrigerant toward second heat exchanger  24 , which operates as a condenser. After exiting second heat exchanger  24 , the refrigerant will pass through second reversing valve  202 , which directs the refrigerant toward second expansion valve  32 . Depending on whether thermal battery  12  is being charged or discharged, second expansion valve  32  may be used to expand the refrigerant, or an orifice size of second expansion valve  32  may be enlarged to permit second expansion valve  32  to operate as a flow-through valve. If thermal battery  12  is being charged, second expansion valve  32  may permit further expansion of the refrigerant before entering thermal battery  12 . If thermal battery  12  is being discharged, second expansion valve  32  may operate as a flow-through valve and first expansion valve  28  may permit the refrigerant to expand. If thermal battery  12  is neither being charged nor discharged and system  200  is in either the first mode or the second mode, the second expansion valve  32  will act as a flow-through valve and the first expansion valve  28  will control expansion of the refrigerant. 
     Assuming thermal battery  12  is being charged, second expansion valve  32  permits the refrigerant to expand before entering thermal battery  12 . After conducting thermal energy exchange with the phase change material of thermal battery  12 , the refrigerant exits thermal battery  12 , and passes through first expansion valve  28  that permits the refrigerant to flow through without further expansion before passing through reversing valve  26  and into first heat exchanger  22 , which acts as an evaporator. After exiting first heat exchanger  22 , the refrigerant will travel to second reversing valve  202  that permits the refrigerant to travel to accumulator  40  and subsequently the compressor  20 , where the process may then repeat. 
     In the second mode, each of the reversing valves  26  and  202  are reversed such that the refrigerant compressed by compressor  20  will first travel to first heat exchanger  22 , which acts as a condenser. After exiting the first heat exchanger  22 , the refrigerant will be directed by the second reversing valve  202  to second expansion valve  32  where, if battery  12  is being charged, the refrigerant will be permitted to pass through first expansion valve  28  without expansion, exchange thermal energy with phase change material located in battery  12 , and then flow through first expansion valve  28  where the refrigerant will expand and flow toward reversing valve  26 , which directs the refrigerant to second heat exchanger  24 , accumulator  40 , and compressor  20  where the process will repeat. 
     Now referring to  FIG.  16   , another HVAC system  300  including a thermal battery  400  is illustrated. System  300  includes a primary loop  18  and a secondary loop  14 , with thermal battery  400  being in fluid communication with the refrigerant of the primary loop  18  and the working fluid of the secondary loop  14 . The thermal battery  400  is illustrated in more detail in  FIGS.  17 - 19   . 
     The primary loop  18  of system  300  includes a compressor  20 , a heat exchanger  22 , a reversing valve  26 , an expansion valve  28 , a second reversing valve  302 , the thermal battery  400  that acts as a second heat exchanger, and an optional accumulator  40 . In the illustrated embodiment, in a first mode, the refrigerant compressed by compressor  20  first passes through reversing valve  26 , which directs the refrigerant to thermal battery  400  to charge the thermal battery  400 . After exiting thermal battery  400 , the refrigerant travels through second reversing valve  302 , which directs the refrigerant to expansion valve  28  that permits the refrigerant to expand before again passing through reversing valve  26  that directs the expanded refrigerant to heat exchanger  22 . After exiting heat exchanger  22 , the refrigerant again passes through second reversing valve  302 , which directs the refrigerant to accumulator  40  and then compressor  20  where the process may repeat. 
     In a second mode, the refrigerant compressed by compressor  20  first reaches reversing valve  26 , which directs the refrigerant to heat exchanger  22 . After exiting heat exchanger  22 , the refrigerant will travel to second reversing valve  302 , which will direct the refrigerant to expansion valve  28 , which will permit the refrigerant to expand. After expansion, the refrigerant will again pass through reversing valve  26 , which will direct the refrigerant to thermal battery  400 . After thermal energy exchange with thermal battery  400 , the refrigerant will again travel through second reversing valve  302 , which will direct the refrigerant to accumulator  40  and compressor  20 , where the process may repeat. 
     Secondary loop  14  includes thermal battery  400 , a heat exchanger  48 , and a pump  42 . The working fluid in the illustrated embodiment may be water, glycol, or a mixture thereof. As the working fluid passes through thermal battery  400 , the thermal energy stored in thermal battery  400  may be discharged for use in cooling or heating indoor structure  16  by operating fan  49 . If each of the primary loop  18  and secondary loop  14  are operating simultaneously, thermal battery  400  may be simultaneously charged and discharged. 
     Thermal battery  400  is illustrated in  FIGS.  17 - 19   . As noted above, thermal battery  400  is configured to allow the refrigerant of primary loop  18  to pass therethrough, and also configured to allow the working fluid of secondary loop  14  to pass therethrough. Thermal battery  400  includes a first end plate  402   a  and a second end plate  402   b  that sandwich a plurality of phase change material storage plates  404 . A flow plate  406  is positioned between adjacent storage plates  404 , and also positioned between a respective end plate  402   a ,  402   b  and an adjacent storage plate  404 . Although not visible in  FIG.  17   , it should also be understood that thermal energy transfer films  56  are positioned on opposing sides of each of the flow plates  406  to prevent intermixing of the refrigerant and working fluid with the phase change material(s) stored in storage plates  404 , and to enable thermal energy transfer between the refrigerant and working fluid with the phase change material(s) stored by storage plates  404 . The end plates  402   a ,  402   b , the storage plates  404 , and the flow plates  406  may each be formed of a polymeric material that is impermeable and resistant to corrosion. 
     End plate  402   a  includes a refrigerant inlet  408   a  and a working fluid outlet  410   b . End plate  402   b  includes a refrigerant outlet  408   b  and a working fluid inlet  410   a . Inasmuch as end plates  402   a  and  402   b  are substantially similar to end plates  52   a  and  52   b , further description thereof will be omitted. 
     Turning to  FIG.  18   , each storage plate  404  is a planar member having a perimeter  412  that defines a central aperture  414 . Perimeter  412  also defines a plurality of flow openings  416  that permit the refrigerant and working fluid to flow therethrough before traveling between the thermal energy transfer film  56  and flow plate  406 , as will be described in more detail later. Perimeter  412  includes a first pair of opposing elongated edges  418  that extend in parallel and a second pair of opposing elongated edges  420  that extend in parallel and connect the opposing elongated edges  418 . Angled members  422  also extend between a respective first elongated edge  418  and a respective second elongated edge  420  to form flow openings  416 . 
     In addition, a plurality of elongated dividing members  424  are arranged in central aperture  414 . In the illustrated embodiment, dividing members  422  extend in a direction from one of the second elongated edges  420  toward the other second elongated edge  420 . More specifically, the dividing members  424  extend in a direction from one of the second elongated edges  420  toward the other second elongated edge  420  between a pair of the angled members  422  that form flow openings  416 . Each dividing member  424  is a corrugated member having a plurality of first corrugations  426 . An inner profile  428  of first elongated edges  418  may also include second corrugations  430  that correspond to first corrugations  426 . Each storage plate  404  includes a phase change material located in central aperture  414 . Alternatively, one storage plate  406  can storage one phase change material and an adjacent plate can store a second and different phase change material such that the different phase change materials alternate throughout thermal battery  400 . 
     Now turning to  FIG.  19   , flow plates  406  will be described. Flow plates  406  are shaped to correspond to storage plates  404 . In this regard, flow plates  406  are planar member having a periphery  430  that defines a central opening  432 . Periphery  430  also defines a plurality of flow apertures  434  that permit the refrigerant and working fluid to flow therethrough before traveling between the thermal energy transfer film  56  and flow plate  406 . In addition, flow plates  406  each include a plurality of elongated dividing bars  434  are arranged in central opening  432  that are shaped like and correspond to dividing members  424  of storage plate  404 . Dividing bars  434  each have a thickness in a direction from a first major surface  436  to a second major surface  438  of flow plate  406  that is less than a thickness of periphery  430 . Because dividing bars  434  have a thickness that is less than that of periphery  430 , the refrigerant and working fluid are permitted to flow between dividing bars  434 , and between the thermal energy transfer films  56  located on opposing sides of flow plate  406 . 
     Now flow of the refrigerant and working fluid through the thermal battery  400  will be described. As best shown in  FIG.  17   , the refrigerant may enter thermal battery  400  through fluid inlet  408   a  of end plate  402   a . The refrigerant passes through flow opening  434  of flow plate  406   a  and enters the flow paths between dividing bars  434  and travels through the flow paths between the dividing bars  434  toward the flow opening  434  located at the bottom of the flow plate  406   a . While in the flow paths between the dividing bars  434 , the refrigerant will exchange thermal energy with thermal energy transfer film  56  and the phase change material located on the opposite side of thermal energy transfer film  56  located in storage plate  404 . 
     Similarly, the working fluid will enter thermal battery  400  through fluid inlet  410   a  on end plate  402   b . The working fluid passes through flow opening  434  of flow plate  406   c  and enters the flow paths between dividing bars  434  and travels through the flow paths between the dividing bars  434  toward the flow opening  434  located at the bottom of the flow plate  406   c . While in the flow paths between the dividing bars  434 , the working will exchange thermal energy with thermal energy transfer film  56  and the phase change material located on the opposite side of thermal energy transfer film  56  located in storage plate  404 . 
     Because two fluids are passing through thermal battery  400  simultaneously, the fluids will skip intervening flow plates  406  so as not mix with each other. For example, the refrigerant that passes through flow plate  406   a  will not flow through the flow paths of the next plate  406 , but will instead pass through an opening  104  of the thermal energy transfer film  56  and on to the next flow plate  406   b . This will continue until the refrigerant exits thermal battery  400  through outlet  408   b.    
     Similarly, the working fluid that enters thermal battery  400  through fluid inlet  410   a  on end plate  402   b  will skip the next flow plate  406 . That is, the working fluid that passes through flow plate  406   c  will not flow through the flow paths of the next plate  406 , but will instead pass through an opening  104  of the thermal energy transfer film  56  and on to the next flow plate  406   d . This will continue until the working fluid exits thermal battery  400  through outlet  410   b.    
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.