WO2018136415A2

WO2018136415A2 - Low cost, high frequency thermoacoustic refrigerator and refrigeration methods

Info

Publication number: WO2018136415A2
Application number: PCT/US2018/013863
Authority: WO
Inventors: Donald Alfred JORDAN Jr.; Scott David KASEN
Original assignee: Sonotherm, Llc
Priority date: 2017-01-17
Filing date: 2018-01-16
Publication date: 2018-07-26
Also published as: WO2018136415A3

Abstract

An apparatus includes an acoustic driver (also referred to as a "speaker"), a block resonator array (also referred to as a "resonator array" or "material block"), and a heat exchange assembly. The block resonator array includes a body that defines a set of resonator chambers. Each of the resonator chambers can be (but need not be) formed from multiple resonator volume portions (e.g., a first resonator volume and a second resonator volume). One of the resonator chambers and another of the resonator chambers each share (or are formed, in part, from) a common portion of the body. The heat exchange assembly includes a stack and/or regenerator, a hot heat exchanger, and a cold heat exchanger. The heat exchange assembly is operatively coupled to at least one of the resonator chambers.

Description

LOW COST, HIGH FREQUENCY THERMOACOUSTIC REFRIGERATOR AND

REFRIGERATION METHODS

Cross-Reference to Related Applications

[1001] This application claims benefit of priority to U.S. Provisional Application Serial No. 62/447,206, entitled "Low Cost, High Frequency Thermoacoustic Refrigerator and Methods of Manufacture," filed January 17, 2017, which is incorporated herein by reference in its entirety.

Background

[1002] The embodiments described herein relate generally to the field of thermoacoustic refrigeration systems.

[1003] Many of today's common refrigeration systems use a thermodynamic process called the vapor-compression cycle in which a refrigerant undergoes a series of phase changes, compression events, and expansion events to remove heat from the space which needs to be cooled (and for rejection elsewhere). To drive this process, most known refrigeration systems use a piston-driven or rotary compressor, which expends mechanical energy to induce thermodynamic changes to a refrigerant. While these systems are often quite efficient, the collection of components needed for a compression system - pistons, valves, spindles, crankshafts, dynamic seals, refrigerant - makes such known systems large and expensive. Today's compressors also use refrigerants called hydrofluorocarbons which can have many times the heat trapping potential as carbon dioxide, contributing significantly to greenhouse gas emissions.

[1004] The innovation of thermoacoustics has been proposed as a possible replacement for mechanical compressors. Thermoacoustics uses sound waves to produce the thermodynamics needed for refrigeration. In its simplest form, a known thermoacoustic refrigeration system includes an acoustic driver (also referred to as a "speaker"), a resonator tube, heat exchangers, a stack(s) and/or regenerator(s). The acoustic driver is powered to produce a sound wave. The resonator tube contains a gaseous medium (also referred to as "working fluid"). The heat exchangers are in thermal communication with the surrounding environment or other heat exchangers external to the resonator. The stack(s) and/or regenerator(s) establish a thermal pathway for heat exchange with the gas. Depending on the design of the resonator tube, a standing or traveling acoustic wave is produced in the gas by the acoustic driver, causing localized compression and expansion of the gas. Proper design and placement of the stack(s), regenerator(s), and heat exchangers in the resonator tube can exploit this thermodynamic cycle so that thermal energy is transferred from one heat exchanger to the other.

[1005] One example of a known thermoacoustic refrigerator of the standing wave type is shown in FIG. 1. The device includes an acoustic driver (or speaker), a resonator volume, a porous medium within the resonator (the porous medium is also called a stack), and hot and cold heat exchangers on each side of the stack. The acoustic driver generates a pressure wave that travels within the resonator. The entire resonator is hermetically sealed and filled with a pressurized working gas such as helium.

[1006] FIG. 2 illustrates the thermal interaction between the stack and the working fluid of a known standing wave thermoacoustic refrigeration system. When the acoustic driver is powered at the resonant frequency by electrical means a standing pressure wave is generated causing gas molecules to oscillate back and forth along the tube axis with a displacement amplitude that depends on the frequency and drive ratio of the acoustic driver and gas properties. In synchrony with the displacement are adiabatic compressions and expansions (rarefication) that alternately heat up and cool off the gas. Over an acoustic cycle a gas "packet" experiences the physical process shown in steps 1 through 4 of FIG. 2. At the first step, the gas packet is at the leftmost point of travel and has cooled from expansion to temperature Tc. Temperature Tc is cooler than stack temperature Ti so that thermal energy in the stack transfers to the gas. In step 2, the gas packet moves to the right and is simultaneously being compressed by the acoustic wave. In step 3, the gas packet is at the rightmost point of travel and now has temperature T_H which is hotter than the stack at temperature T₂. As a result, thermal energy transfers out of the gas and to the stack. Finally, in step 4, the gas packet moves to the left and undergoes an expansion, which resets the thermodynamic cycle. All of the gas packets along the stack experience this process so that thermal energy is alternately stored in the stack by one gas packet and then released from the stack to an adjacent gas packet. Thermal energy moves up the thermal gradient in this "bucket brigade" fashion, away from the cold heat exchanger (which provides refrigeration) and towards the hot heat exchanger. [1007] The advantages of known thermoacoustic cooling devices include high reliability because there are neither dynamic seals nor pistons, use of environmentally benign gases that serve as the working fluid, and simple proportional control through regulation of the drive ratio. Despite these advantages, thermoacoustics has not been widely adopted nor commercially successful on any large scale. One reason is that refrigeration industry leaders are heavily invested in the traditional piston-driven compressor technology and therefore have not developed thermoacoustic designs for large volume, low cost production or commercial use. Rather, known thermoacoustic systems have generally been confined for laboratory use by researchers in academic or federal (nonprofit) laboratories. Further, such known thermoacoustic refrigeration systems have been designed and built for low frequencies (less than 1000 Hz). These systems include resonators that are on the order of several feet in length and many inches in diameter, and include large magnetic cone speakers used for drivers. The resonator walls of these systems are fabricated from round metallic pipes or tubes to withstand high working fluid pressures (over 20 atmospheres) which can pose the serious risk of a rapid decompression event should the wall be breached. These systems are highly engineered with large safety margins and redundant safety systems which significantly add expense. Such known, highly engineered systems operate with low efficiencies (inherent in the magnetic speakers) and low power densities (due to their large size) to provide cooling on the order of hundreds to thousands of watts. Known systems of such size are not suitable for use in the high-frequency ranges (greater than 1000 Hz).

[1008] Moreover, other known thermoacoustic systems are used in cryogenic applications, and are thus not well-suited for conventional refrigeration systems.

[1009] Therefore, conventional thermoacoustic research has focused on large thermoacoustic devices that make use of high power speaker drivers to increase the overall cooling capacity and that operate at low frequencies within high pressure resonator volumes. In turn, the high cooling power from these systems compensates for low efficiencies, which have thus far plagued known thermoacoustic refrigerators. Thermoacoustic refrigerator developments have followed the development path taken by mechanical compression systems. As such, conventional thermoacoustic systems have been designed as large, bulky centralized systems for cooling. [1010] Thus, a need exists for improved devices and methods for large volume, low cost production concepts for thermoacoustic refrigeration systems.

Summary

[1011] Devices and methods for a high-frequency thermoacoustic refrigeration system that significantly lowers the upfront cost and improves the energy efficiency of thermoacoustic refrigeration devices to make thermoacoustic refrigeration commercially competitive with mechanical compression and other known refrigeration technologies are described herein. In some embodiments, an apparatus includes a high-frequency electrostatic acoustic driver (also referred to as a "electrostatic loudspeaker" or "ESL"), a block resonator array (also referred to as a "resonator array" or "material block"), and a heat exchange assembly. The block resonator array includes a body (also referred to as a wall or web). The body defines a set of resonator chambers. Each of the resonator chambers can be (but need not be) formed from multiple resonator volume portions (e.g., a first resonator volume and a second resonator volume). One of the resonator chambers and another of the resonator chambers each share (or are formed, in part, from) a common portion of the body. The heat exchange assembly includes a stack and/or regenerator, a hot heat exchanger, and a cold heat exchanger, and is operatively coupled to at least one of the resonator chambers.

Brief Description of the Drawings [1012] FIG. 1 is a schematic illustration of a prior art thermoacoustic device.

[1013] FIG. 2 is a schematic illustration showing the operational principles of a standing wave of a prior art thermoacoustic device.

[1014] FIG. 3 is a schematic illustration showing an exploded view of a thermoacoustic refrigeration system according to an embodiment.

[1015] FIG. 4 is a schematic illustration showing a cross-section view of the thermoacoustic refrigeration system shown in FIG. 3. [1016] FIG. 5 is a schematic illustration showing a perspective view of a block resonator array of the thermoacoustic refrigeration system shown in FIG. 3.

[1017] FIG. 6 is a schematic illustration showing a front view of the block resonator array shown in FIG. 5.

[1018] FIG. 7 is a schematic illustration showing a front view of a block resonator array of a thermoacoustic refrigeration system according to an embodiment.

[1019] FIG. 8 is a schematic illustration showing a front view of a block resonator array of a thermoacoustic refrigeration system according to an embodiment.

[1020] FIG. 9 is a schematic illustration showing a perspective view of a block resonator array of a thermoacoustic refrigeration system according to an embodiment.

[1021] FIG. 10 is a schematic illustration showing a perspective view of a thermoacoustic refrigeration system according to an embodiment, the thermoacoustic refrigeration system being a traveling wave thermoacoustic device.

[1022] FIG. 11 is a schematic illustration showing a front view of a refrigeration system according to an embodiment, the refrigeration system including an ESL refrigerator.

[1023] FIG. 12 is a cross-sectional schematic view of portions of an ESL refrigerator according to an embodiment that is included in the refrigeration system shown in FIG. 11, as viewed along line X-X shown in FIG. 11.

[1024] FIG. 13A is a cross-sectional schematic view of an ESL refrigerator according to an embodiment.

[1025] FIG. 13B is a cross-sectional view of the portion of the ESL refrigerator of FIG. 13A as viewed along line Y-Y shown in FIG. 13 A.

[1026] FIG. 14A is a schematic illustration showing an expanded perspective view of a portion of an ESL refrigerator according to an embodiment having a driver assembly and a resonator block. [1027] FIG. 14B is a cross-sectional view of the driver assembly of FIG. 14A as viewed along line Z-Z shown in FIG. 14A.

[1028] FIG. 15 is a cross-sectional view of a portion of an ESL refrigerator according to an embodiment.

[1029] FIG. 16A is a cross-sectional view of a portion of an ESL refrigerator according to an embodiment.

[1030] FIG. 16B is a cross-sectional view of the driver assembly of FIG. 16A as viewed along line M-M shown in FIG. 16A.

[1031] FIG. 17A is a schematic illustration showing a control circuit and a cross-sectional view of a portion of an ESL refrigerator according to an embodiment during a full operation mode of the ESL refrigerator.

[1032] FIGS. 17B is a schematic illustration showing a control circuit and a cross-sectional view of a portion of an ESL refrigerator according to an embodiment during a partial or an inhibited operation mode of the ESL refrigerator.

[1033] FIG. 18 is a schematic illustration showing a method for controlling operation of an ESL refrigerator according to an embodiment.

[1034] FIG. 19 is a schematic illustration showing an elevation view of a vehicle including an electrostatic loudspeaker (ESL) refrigeration system according to an embodiment, the ESL refrigeration system having an ESL refrigerator.

Detailed Description

[1035] Devices and methods for a high-frequency thermoacoustic refrigeration system that significantly lowers the upfront cost of thermoacoustic refrigeration devices and has the potential to make thermoacoustic refrigeration cost-competitive with mechanical compression and other known refrigeration technologies are described herein. In some embodiments, an apparatus includes an electrostatic acoustic driver (also referred to as a "electrostatic loudspeaker" or "electrostatic acoustic energy source" or "ESL"), a block resonator array (also referred to as a "resonator array" or "material block"), and a heat exchange assembly. The block resonator array includes a body (also referred to as a wall or web of material) that defines a set of resonator chambers. Each of the resonator chambers can be (but need not be) formed from multiple resonator volume portions (e.g., a first resonator volume and a second resonator volume). One of the resonator chambers and another of the resonator chambers each share (or are formed, in part, from) a common portion of the body. The heat exchange assembly includes a stack and/or regenerator, a hot heat exchanger, and a cold heat exchanger, and is operatively coupled to at least one of the resonator chambers.

[1036] In some embodiments, a method includes molding or fabricating a block resonator array from a polymer. The block resonator array defines a plurality of resonator volumes that contain a gas. The method further includes coupling an electrostatic acoustic driver to a first end of the block resonator array. A second end of the block resonator array is coupled to a heat exchange assembly. The heat exchange assembly includes a stack and/or regenerator, a hot heat exchanger, and a cold heat exchanger.

[1037] In some embodiments, an apparatus includes a block resonator array having a first side surface, a second side surface, and a wall (or body) between the first side surface and the second side surface. The first side surface is configured to be coupled to an acoustic energy source. The second side surface is configured to be coupled to a heat exchange stack. The wall defines a set of resonator volumes, each of which can be a portion of (or combined with other resonator volumes to form) a set of resonator chambers. One of the resonator volumes from the set of resonator volumes and another of the resonator volumes from the set of resonator volumes each share a common portion of the wall.

[1038] In some embodiments, an apparatus includes a body defining a first resonator volume and a second resonator volume, an electro- static loudspeaker assembly (ESL) in communication with the first resonator volume, and a heat exchanger assembly coupled to the first resonator volume and to the second resonator volume. The heat exchanger assembly includes a stack, a hot heat exchanger and a cold heat exchanger. In some embodiments, the apparatus further includes a driver housing coupled to the body that defines a pocket containing the ESL and a pocket pathway to the first resonator volume. In some embodiments, the apparatus further includes multiple ESLs, each in communication with the first resonator volume. In such embodiments, the body defines multiple pockets and a corresponding pocket pathway for each pocket. Each pocket is configured to contain one of the ESLs and each of the pocket pathways is in communication with at least the first resonator volume. In some embodiments, the body defines a set of first resonator volumes, in which each of the set of first resonator volumes shares a common portion of the body.

[1039] In some embodiments, the apparatus includes a first ESL in communication with the first resonator volume, a second ESL in communication with the first resonator volume, and a driver circuit (e.g., a signal generator) configured to transmit a signal to drive the first ESL to produce pressure waves at a first performance and the second ESL to produce pressure waves at a second performance. In some embodiments, the first ESL and the second ESL are configured such that the second performance is within 10% of the first performance. In some embodiments, the first ESL includes a first diaphragm having a first tension, the second ESL includes a second diaphragm having a second tension, the second tension being within 10% of the first tension.

[1040] In some embodiments, the body defines a pair of first resonator volumes in communication with the same ESL. In some embodiments, the ESL includes a first side portion and an opposite second side portion, and each of the pair of first resonator volumes are in communication with a corresponding one of the first and second side portions of the ESL.

[1041] In some embodiments, an ESL refrigerator includes an ESL acoustic driver, a first resonator volume, a second resonator volume, and a heat exchange assembly coupled to the first and second resonator volumes. In some embodiments, the first resonator volume and the second resonator volume are operatively coupled to form a resonator chamber. The ESL acoustic driver includes a diaphragm flanked by spacers and stators on either side. The diaphragm is under tension and is mechanically anchored at its perimeter between the insulating spacers. In some embodiments, the ESL acoustic driver is driven by an electronic circuit that includes a high- voltage power supply and a step-up transformer. The high- voltage power supply is electrically connected to the diaphragm to apply an electrostatic charge to the diaphragm. The step-up transformer is electrically connected to each of the stators to apply an alternating, opposite charge to each of the stators to drive the acoustic driver to form pressure waves within the first resonator volume. The step-up transformer is actuated by an amplifier that receives inputs from a signal output.

[1042] In some embodiments, a method of controlling a thermoacoustic refrigeration device includes sending, from an electronic driver circuit at a first time, a driver signal to a set of acoustic drivers. Each of the acoustic drivers is in communication with a corresponding first resonator volume defined within a resonator block, and each of the acoustic drivers produces a pressure wave within the corresponding first resonator volume in response to the driver signal. In some embodiments, the acoustic drivers can be ESLs. The method further includes receiving a control signal associated with a desired output level of the thermoacoustic refrigeration device. The method further includes inhibiting, at a second time and in response to the control signal, the driver signal to at least one of the acoustic drivers. In some embodiments, the method is performed as a computer-implemented method. In some embodiments, inhibiting the driver signal includes inhibiting a selected pre-determined subset of the acoustic drivers corresponding with the desired output level, in which the selected pre-determined subset is selected from a group of predetermined subsets that each correspond to an output level.

[1043] In some embodiments, an apparatus includes a resonator block defining a set of resonator volumes, a set of acoustic drivers, each within (or communicatively coupled to) one of the volumes, and an electronic circuit system. The electronic circuit system includes a signal generator and a control module. The signal generator is configured to produce a driver signal. The control module is implemented in at least one of a memory or a processing device, and is configured to send, at a first time, the driver signal to each of the acoustic drivers to produce a pressure wave within the corresponding resonator volume in response to the driver signal. The control module is configured to receive a control signal associated with a desired output level of the apparatus. The control module is configured to inhibit, at a second time and in response to the control signal, the driver signal from at least one of the set of acoustic drivers.

[1044] In some embodiments, an electrostatic loudspeaker (ESL) refrigeration system includes an ESL refrigerator. The ESL refrigerator can include varying types of thermoacoustic devices (or units) in differing arrangements and/or combinations. The ESL refrigeration system further includes a heat exchanger loop and a fan. The heat exchanger loop is coupled with one or more heat exchanger assemblies of the ESL refrigerator and circulates a cooling fluid therein to transfer heat from an area to be cooled to the heat exchanger assemblies. The fan blows air over a portion of the heat exchanger loop and into the area to be cooled. In some embodiments, the ESL refrigeration system is located within a vehicle and is controlled by an electronic control unit of the vehicle.

[1045] The term "about" when used in connection with a referenced numeric indication means the referenced numeric indication plus or minus up to 10 percent of that referenced numeric indication. For example, "about 100" means from 90 to 110.

[1046] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, the term "a member" is intended to mean a single member or a combination of members, "a material" is intended to mean one or more materials, or a combination thereof.

[1047] As used herein, a "set" can refer to multiple features or a singular feature with multiple parts. For example, when referring to set of walls, the set of walls can be considered as one wall with distinct portions, or the set of walls can be considered as multiple walls.

[1048] The term "fluid-tight" is understood to encompass hermetic sealing (i.e., a seal that is gas-impervious) as well as a seal that is only liquid-impervious. The term "substantially" when used in connection with "fluid-tight," and/or "hermetic" is intended to convey that, while total fluid imperviousness is desirable, some minimal leakage due to manufacturing tolerances, or other practical considerations (such as, for example, the pressure applied to the seal and/or within the fluid), can occur even in a "substantially fluid- tight" seal. Thus, a "substantially fluid-tight" seal or a "substantially hermetic seal" includes a seal that prevents the passage of a fluid (including gases or liquids) therethrough when the seal (e.g., a seal enclosing a resonator volume) is maintained at (or exposed to) pressures of greater than about one atmosphere and up to about twenty atmospheres.

[1049] The term "resonator volume" is understood to mean an enclosed or partially enclosed space that forms at least a portion of resonator. The term "resonator" is understood to mean a device, structure, system, assembly or other arrangement that exhibits resonant behavior such that it oscillates at specific frequencies with greater amplitude than at other frequencies. The term "acoustic resonator" is understood to mean a resonator that exhibits resonant behavior for sound waves at specific frequencies. An acoustic resonator can include, for example, one or more resonator volumes in which air vibrations at specific frequencies are enhanced. Multiple of the one or more resonator volumes can be in acoustic communication to form a larger resonator chamber. One example of this is given by multiple resonator volumes corresponding to the multiple valve pathways that are found in brass band instruments, which are each resonator volumes, and each also form a portion of the overall resonator chamber for the instrument when connected to play a particular note. As such, a device (e.g., a thermoacoustic refrigerator) can include a "first resonator volume" and a "second resonator volume" that can be in acoustic communication with each other to form a resonator chamber. A device (e.g., a thermoacoustic refrigerator) can also include a set of resonator chambers, which can each include a first resonator volume and a second resonator volume. Thus, a device can include a set of first resonator volumes and a set of second resonator volumes.

[1050] The term "driver" or "acoustic driver" is understood to mean a mechanism, device, system or components thereof for producing or driving a pressure wave within a resonator volume. A vibrating diaphragm within a resonant volume drives pressure waves within the resonant volume and, thus, acts as a driver. An electrostatic loudspeaker (ESL) includes a diaphragm that vibrates at desired frequencies to drive pressure waves within the resonant volume. Thus, an ESL acts a driver or acoustic driver for a resonant volume. Electronic circuits for powering the ESL and providing signals for the ESL to vibrate at a frequency to drive corresponding pressure waves within the resonant volume for the ESL can be considered as part of an ESL assembly and likewise act as a driver or acoustic driver for the resonant volume. Such circuits or signal generators are referred to herein as driver circuits, signal generators, or the like.

[1051] FIGS. 3 and 4 show a thermoacoustic refrigeration system 100 according to an embodiment. The thermoacoustic refrigeration system 100 includes an acoustic driver 110, two first block resonator arrays 120, two second block resonator arrays 140, and two heat exchange assemblies 160. The acoustic driver 110 is powered to generate a pressure wave in the gas within the block resonator arrays 120, 140. The acoustic driver 110 can be any suitable low mass, thin diaphragm driver that can generate soundwaves from opposing sides (dipole sound propagation) to drive two block resonator arrays simultaneously. This has the advantage of minimizing acoustic losses from the driver. These types of acoustic drivers include, but are not limited to, drivers that operate on the piezoelectric effect or the electrostatic effect. Such piezoelectric materials include polyvinylidene fluoride (PVDF) film, as an example. Electrostatic diaphragm materials include a graphene or a polymer (such as Mylar®) film or membrane sandwiched between metallic or metallic-coated stators, as examples.

[1052] The acoustic driver 110 is coupled to two first block resonator assemblies 120. As shown in FIGS. 5 and 6, the first block resonator assembly 120 includes a first side surface 124, a second side surface 125, and a body (also referred to as a block or wall) 122 that is located between the first side surface 124 and the second side surface 125. Similarly stated, the body 122 includes (or forms) the first side surface 124 on one end and the second side surface 125 on the other, opposite end. The first side surface 124 is configured to be coupled to the acoustic driver 110. As discussed in further detail below, the second side surface 125 is configured to be coupled to a heat exchange assembly 160. The body 122 defines a series of first resonator volumes 130. Each first resonator volume 130 includes a first end 131 and a second end 132. The first resonator volumes 130 can be arranged in a multitude of configurations. Specifically, the first resonator volumes 130 are arranged such that two adjacent resonator volumes share a common portion of the body 122. Similarly stated, the block resonator assembly 120 is fabricated such that a portion of the body 122 defines both a portion of a boundary of a first one of the first resonator volumes 130 and a portion of a boundary of a second one of the first resonator volumes 130. Said another way, the common portion of the body 122 is a "web" of material disposed between the adjacent ones of the first resonator volumes 130. As shown in FIG. 6, the first resonator volumes 130 of block resonator assembly 120 are arranged in a repeating unit 123 that is shaped as a square. Other configurations of resonator volumes will be discussed in further detail below. This arrangement of the first resonator volumes contained in each block resonator array 120 creates dozens or hundreds of thermoacoustic devices (or units) within one thermoacoustic refrigeration system.

[1053] The first resonator volumes 130 contain any suitable gas, which can be, for example, a pressurized gas such as helium. However, in other embodiments, any suitable gas can be used, such as air, nitrogen, argon, xenon or a mixture of any of these gases. Moreover, the gas can be sealed within the first resonator volumes 130 at any suitable pressure. For example, in some embodiments, the gas can be hermetically sealed within the first resonator volumes 130 at a pressure of between about one atmosphere and about twenty atmospheres. In some embodiments, the gas can be hermetically sealed within the resonator volumes 130 at a pressure of between about one atmosphere and about ten atmospheres. In other embodiments, the gas can be hermetically sealed within the first resonator volumes 130 at a pressure of about one atmosphere (14.7 psia). In yet other embodiments, the gas can be hermetically sealed within the first resonator volumes 130 at a pressure of greater than one atmosphere (14.7 psia), which enables a higher power density output. In some embodiments, the overall block resonator assembly 120 can be hermetically sealed about the perimeter of the block 120 to fluidically isolate the first resonator volumes 130 from the surrounds, thereby maintaining the first resonator volumes 130 at the desired pressure. In such embodiments, each of the first resonator volumes 130 may not be hermetically sealed from each other. By allowing permeation of gas between the resonator volumes 130, the process of filling the block resonator assembly 120 with gas (and maintaining the desired gas pressure therein) can be simplified. In other embodiments, however, each of the first resonator volumes 130 can be hermetically sealed from each other. In such embodiments, each of the first resonator volumes is filled and/or pressurized individually.

[1054] Each of the first resonator volumes 130 can have any suitable size and volume. In some embodiments, the small resonator volumes have the advantage over larger systems in that the first resonator volumes 130 facilitate the use of very high working gas pressures safely, dramatically increasing the power density. The acoustic driver creates an acoustic wave in the gas, causing compression and expansion of the gas within each first resonator volume 130. Proper design and placement of the stack(s) and heat exchangers in the heat exchange assembly can exploit the thermodynamic cycle created by the gas so that thermal energy is transferred from one heat exchanger to the other, as discussed in more detail below.

[1055] The block resonator arrays can be made of a polymer, polymer composite, laminated paper product, metal, or ceramic (including glass). An impermeable coating may be applied to the boundaries defining the first resonator volumes 130 to prevent egress of the working gas and/or ingress of the ambient (surrounding) gas, to maintain a pressure differential in the case where the working gas is to be held at a higher pressure than the ambient environment, and/or to minimize or eliminate water permeation (humidity). The coating may be applied to the surface of the first resonator volumes 130, the outer surface of the block resonator array 120, or both. The coating may be a ceramic, such as glass, graphite, graphene oxide, or a metallic film, or a combination thereof to inhibit both ingress/egress of gases and water permeation, while having chemical compatibility with the material of the block resonator array.

[1056] The block resonator array can be formed from one of a number of manufacturing methods including, but not limited to, injection molding, extrusion, pultrusion, additive manufacturing, transfer molding, laminating, casting or subtractive methods, including the cutting of solid block using laser cutting, stamping, punching, water-jet cutting, or milling. The chosen manufacturing method is determined, in part, by the final resonator design, and material from which the body is being manufactured. In some embodiments, the body 122 can be monolithically constructed. In yet other embodiments, the block 122 can be constructed from multiple components that are separately formed and then later joined together.

[1057] As shown in FIG. 3, the second side surface 125 of each of the two block resonator arrays 120 is coupled to a corresponding heat exchange assembly 160. Each heat exchange assembly 160 includes a hot heat exchanger 180, a stack 161, and a cold heat exchanger 170. The hot heat exchanger 180 and cold heat exchanger 170 can be finned tubes, parallel plates, screens, or any other suitable thermally conducting heat exchanger that transfers heat from the working fluid to the exterior of the first block resonator arrays 120. When the gas parcels (also referred to as gas "packets") oscillate along the resonator axis (i.e., the longitudinal axis of each first resonator volume 130), in response to acoustic driver 110, thermal energy is transferred between the stack and the gas. The thermal energy is alternately stored in the stack by one gas parcel and then released from the stack to an adjacent gas parcel. Thermal energy is exchanged between the gas and the stack, moving the energy against the gradient in a "bucket brigade" fashion, away from the cold heat exchanger and towards the hot heat exchanger to provide refrigeration. Although the heat exchanger 180 is referred to as the hot heat exchanger and the heat exchanger 170 is referred to as the cold heat exchanger, the two heat exchangers can be interchanged depending on the location of the heat exchange assembly 160 within the system 100. [1058] The stack 161 is made of any suitable material that has a low thermal conductivity in the direction along the resonator axis, higher heat capacity than the gas that is used in the system, and permits gas flow through its bulk volume. In some embodiments, for example the stack 161 can be made of a porous material, parallel plates, a pin arrangement, or sheets of thin material rolled up into a spiral. In some embodiments, the stack 161 can be constructed from Mylar® which has a thermal conductivity of 0.16 W/m-K. Other materials including ceramic, metal fibers, reticulated carbon, natural fibers including but not limited to cotton and wool, and other polymers including but not limited to PET, Kapton, and PVC can be used for the stack material. The stack geometry may be arranged such that a single material body may be used to span the resonator array and wherein porous portions of the stack body become aligned with the resonator volumes 130 to serve the function of the stack.

[1059] The heat exchange assembly 160 is also coupled to a second block resonator array 140, which in this specific example includes a closed-end resonator array. In some embodiments, the second block resonator array 140 can include various second resonator assembly configurations that are configured for desired harmonics, resonance or other performance characteristics such as, for example, an open-ended resonator assembly. In some embodiments, the second block resonator array 140 has the same characteristics as the open-ended block resonator array 120 except that the second resonator volumes defined within the second block resonator array 140 have a second side that is closed ended. In other embodiments, however, the second block resonator array 140 has different characteristics (e.g., a different diameter than the open-ended block resonator assembly 120). As shown in FIG. 4, the heat exchange assembly 160 is between the first block resonator array 120 and the second block resonator array 140, and the first and second resonator volumes with each of the corresponding block assemblies form a resonator chamber (separated by the heat exchange assembly 160) through which the acoustic waves produced by the acoustic driver 110 can travel. Thus, the first resonator volumes 130 of the open-ended first block 120 can sometimes be referred to as a "first resonator volume" or a set of first resonator volumes, and the resonator volumes of the closed ended block 140 can sometimes be referred to as a "second resonator volume" or a set of second resonator volumes. Each first resonator volume corresponds with a second resonator volume to form a resonator chamber. [1060] The components of the thermoacoustic refrigeration assembly are coupled together using any known coupling mechanism including using an adhesive bond, chemical fusion weld, or mechanical engagement to form a bond at their interface.

[1061] As described above, the resonator volumes can have a variety of configurations within a block resonator array. The configuration of the resonator volumes can impact the power density of a block resonator array. As an example, FIG. 6 shows a block resonator array 120 having first resonator volumes 130 that are arranged in a repeating unit 123 that is shaped as a square. That is, the center points of adjacent first resonator volumes 130 define a square shape when viewed in a plane that is perpendicular to the longitudinal axis of the first resonator volumes. In other embodiments, an arrangement of the resonator volumes can define any suitable unit shape. As another example, FIG. 7 shows a block resonator array 220 having a series of first resonator volumes 230 within the wall (or body) 222 that are arranged in a repeating unit 223 that is shaped as a triangle. Block resonator array 320, shown in FIG. 8, defines a series of first resonator volumes having two different sizes - a larger first resonator volume 330 and a smaller first resonator volume 335. The repeating unit 323 shows the two first resonator volumes 330 and 335 being in a mixed configuration within the repeating unit. This arrangement allows the body 322 of the first block resonator array 320 to be packed more densely than those embodiments that employ a single sized first resonator volume. While resonator volumes are shown as having a circular cross-sectional shape, the cross-sectional shape can be any suitable shape and sizes.

[1062] The resonator volumes affect the acoustic resonance characteristics of the block resonator array. Acoustic resonance, which is required for the thermoacoustic device to operate correctly, varies depending upon the length and shape of the resonator volumes. For frequencies considered here (1kHz to 60kHz), resonator lengths on the order of centimeters and millimeters are needed for operation. Another factor affecting acoustic resonance is whether the second resonator volumes have an open or closed second end. Specifically, the first resonator volumes 130 shown in FIG. 5 each have a second end 132 that is open. Conversely, the second resonator block assembly 140 is described as having a closed second end. The closed end of the second resonator block assembly 140 (or any of the resonator blocks described herein) can have any suitable geometry that produces the desired resonant characteristics. [1063] For example, FIG. 9 shows a block resonator array 420 having resonator volumes 430 that each have a second end that is closed, and that defines an enlarged spherical shape 433. In this manner, the block resonator array 420 employs Helmholtz volumes to improve the overall performance. Specifically, the resonator volumes 430 each have a first end that is open ended and a second end that is closed by a spherical volume 433. As shown, the spherical volumes for adjacent resonator volumes 430 can be alternatively formed in opposite ends of the block (or body). Under favorable conditions, the spherical volumes 433 have the effect of simulating an open end and achieving resonance while using a resonator that is half the length of a closed end resonator operating at the same frequency. The alternating arrangements of the opposite ends permit the resonator volumes 430 to be nested within the block (or body) in a compact manner that further reduces the size of the block resonator array without loss of performance.

[1064] Thermoacoustic devices include both standing wave devices and traveling wave devices. In a standing wave thermoacoustic device, the energy conversion occurs in the stack of the heat exchange assembly. As one example, the thermoacoustic refrigeration system 100 shown in FIG. 3 is a standing wave thermoacoustic device. A traveling wave thermoacoustic device includes a loop with a compliance volume and an inertance tube to bring the gas velocity and pressure oscillations into phase at the regenerator as it occurs in a traveling acoustic wave. Thus, although the first block resonator array 120 is shown and described as being suitable for a standing wave device, in other embodiments, any of the block resonator arrays can be configured for use in a traveling wave thermoacoustic device.

[1065] For example, FIG. 10 shows a traveling wave thermoacoustic refrigeration system 500. The thermoacoustic refrigeration system 500 includes two block resonator arrays 521, four resonator volumes 526, four heat exchange assemblies 560, and two acoustic drivers 510. The block resonator arrays 521 are half shells that have been bonded together to form resonator volumes 526. The resonator volumes 526 each include a first resonator volume 530 and a second resonator volume 541. The first resonator volume 530 is open at one end and connects with the second resonator volume 541 at its opposite end. The second resonator volume connects to the first resonator volume 530 at one end and extends in a "loop" shape to connect to a heat exchanger assembly 560 at its opposite end. The heat exchange assemblies 560 include hot heat exchangers (not shown), cold heat exchangers (not shown), resonators (not shown), regenerators (not shown), and/or stacks (not shown). The acoustic drivers 510 are each disposed within a pocket 590 located between a pair of adjacent resonator volumes 526. A pocket pathway 592 extends from each pocket 590 in an opposite direction and feeds into a corresponding one of the first resonator volumes 530. Each acoustic driver 510 produces a pair of standing waves in opposite directions in each of the resonator volumes. Each standing wave undergoes pressure- velocity phase shifting in the loop-shaped second resonator volume 541 and thereby pumps heat up the thermal gradient in the regenerator. The number of traveling wave thermoacoustic devices shown here is just one embodiment and not meant to be limiting. Any number of traveling wave thermoacoustic devices can be included within the thermoacoustic refrigeration system 500.

[1066] As described above, in some embodiments, a thermoacoustic refrigeration system can include one or more acoustic drivers that operate on the electrostatic effect. As one example, a front view of an electrostatic loudspeaker (ESL) refrigeration system 600 is shown according to an embodiment in FIG. 11. The ESL refrigeration system 600 can include a traveling wave thermoacoustic device, a standing wave thermoacoustic device, and/or combinations of different types and arrangements of thermoacoustic devices of the types shown and described herein. The ESL refrigeration system 600 includes an ESL refrigerator 608 that includes one or more thermoacoustic devices (or units). As such, ESL refrigerator 608 can include array-type systems like the thermoacoustic refrigeration systems 100 and 500 described herein above, and/or the ESL refrigerators 608, 708, 808 and 908 described herein below. The ESL refrigeration system 600 also includes a heat exchanger loop 665 and a fan 667. The heat exchanger loop 665 is connected with one or more heat exchanger assemblies 660 of the ESL refrigerator 608. The heat exchanger loop 665 circulates a cooling fluid therein, over which the fan 667 blows air (identified by the arrow AIR in FIG. 11) to cool the interior of structure, a person and/or another object (not shown) to be cooled. Although shown as including a fan and a heat exchanger loop 665, in other embodiments the ESL refrigeration system 600 (or any of the systems described herein) can include any components to facilitate operation, installation, or the like.

[1067] FIG. 12 shows a cross-sectional view of the ESL refrigerator 608 of the ESL refrigeration system 600 according to an embodiment. The ESL refrigerator 608 includes an ESL acoustic driver 610, a first resonator volume 620, a second resonator volume 640, and a heat exchange assembly 660 disposed between the first and second resonator volumes. Although not shown in FIG. 12, it is understood that the first resonator volume 620, the second resonator volume 640, or both the first resonator volume 620 and the second resonator volume 640 can be defined within a common body (or block). For example, in some embodiments, the first resonator volume 620 can be defined within a first block (similar to the block 120 described above) and the second resonator volume 640 can be defined within a second, separate block (similar to the block 140 described above), and the heat exchange assembly 660 can be coupled between the two blocks. In other embodiments, the first resonator volume 620 and the second resonator volume 640 can be formed as a continuous volume defined within a single block, and the heat exchange assembly 660 can be disposed within the continuous volume to separate the volume into the first resonator volume 620 and the second resonator volume 640. Similarly stated, in some embodiments, the first resonator volume 620 and the second resonator volume 640 can be defined within a monolithic structure (e.g., a single tube) within which other components (e.g., the heat exchange assembly 660, the ESL 610, or other suitable components) are disposed.

[1068] The heat exchange assembly 660 can be any suitable heat exchange assembly of the types shown and described herein. Specifically, the heat exchange assembly can include a hot heat exchanger, a stack, and a cold heat exchanger, as described with reference to the heat exchange assembly 160 above. The hot heat exchanger and cold heat exchanger can be finned tubes, parallel plates, screens, or any other suitable thermally conducting heat exchanger that transfers heat from the stack to the exterior of the device. As described above, when the gas parcels (also referred to as gas "packets") oscillate along the resonator axis (i.e., the longitudinal axis of the first resonator volume 620), in response to the actuation of the ESL acoustic drivers 610, thermal energy is transferred between the stack and the gas. The thermal energy is alternately stored in the stack by one gas parcel and then released from the stack to an adjacent gas parcel. Thermal energy moves up a thermal gradient in a "bucket brigade" fashion, away from the cold heat exchanger and towards the hot heat exchanger which provides refrigeration.

[1069] The ESL acoustic driver 610 includes a diaphragm 611 disposed between (or flanked by) spacers 613 and 615 and stators 617 and 619 on either side. The spacers 613 and 615 are electrical insulators, and the diaphragm 611 is mechanically anchored at its perimeter between the insulating spacers 613 and 615. In this manner, the diaphragm 611 can be maintained at a desired tension (or tautness). Suitable stators 617, 619 may be made from metallic or metallic-coated materials, which enable the formation of an electric field and that also permit sound propagation. Such examples include suspended wire, screen, or perforated sheet materials.

[1070] The ESL acoustic driver 610 is driven by an electronic circuit 650. The electronic circuit 610 includes a high- voltage power supply 652, a step-up transformer 654, and an audio amplifier 656. The high- voltage power supply 652 is electrically connected to the diaphragm 611 to apply an electrostatic charge. A charge resistor 653 can be connected in-line between the diaphragm 611 and the high-voltage power supply 652. The step-up transformer 654 is electrically connected to each of the stators 617 and 619. In use, the transformer 654 applies an alternating, opposite charge to each of the stators. The step-up transformer 654 is actuated by an audio amplifier 656 that receives inputs from a signal input 658.

[1071] When an electrostatic charge is applied to diaphragm 611 from the high-voltage power supply 652, and a signal is applied to stators 617 and 619 from the step-up transformer 654, the diaphragm 611 flexes. This motion moves the surrounding gaseous medium to generate pressure waves, and therefore acoustic energy. For example, with a negative electrostatic charge applied to diaphragm 611, when a positive voltage is applied to stator 619 and an opposite negative voltage is applied to stator 617, diaphragm 611 will be pulled towards the positively-charged stator 619 and pushed away from negatively-charged stator 617. The voltages applied to the stators 617 and 619 are alternated back and forth between positive and negative, thereby causing the diaphragm to alternatively move towards and away from each of the stators 617. This, in turn, produces the pressure waves. The signal input 658 controls the frequency at which the voltage alternates, and therefore, the frequency of the pressure waves produced within the first resonator volume 620. In use, the electronic circuit 650 can drive the ESL acoustic driver 610 at any suitable frequency. The frequency can be determined based on the length of the first resonator volume 620, the distance between the ESL acoustic driver 610 and the heat exchanger assembly 660, the length of the second resonator volume 640, the length of the heat exchanger assembly 660, whether the second resonator volume 640 has an open or closed end, or any other number of factors. For example, in some embodiments, the electronic circuit 650 can drive the ESL acoustic driver 610 at a frequency of greater than about 1000 Hz. In other embodiments, the electronic circuit 650 can drive the ESL acoustic driver 610 at a frequency of about 5000 Hz or greater. [1072] The diaphragm 611 (or any of the diaphragms described herein) can be constructed from any suitable electrostatic diaphragm materials, including a thin film or membrane made from graphene or a polymer (such as Mylar®, a type of polyester). In some embodiments, the diaphragm 611 (or any of the diaphragms described herein) can be coated or include a surface treatment. Moreover, as described above, the diaphragm 611 can be flanked between the spacers 613, 615 at any suitable tension. For example, in some embodiments, the diaphragm can be flanked between the spacers 613, 615 such that the radial elongation of the diaphragm material is within a desired range (e.g., between 0.1 percent and 2 percent; between 0.5 percent and 1.5 percent; about 1 percent).

[1073] Alternatively, the electrostatic charge can be introduced to the surface of diaphragm 611 as a step during manufacture, in which case the diaphragm material would be considered an electret that bears a semi-permanent or permanent electrostatic charge. In this alternative arrangement, no charge circuitry for the diaphragm 611 would be needed. In such an embodiment, the high- voltage power supply 652 shown in FIG. 12 is omitted, and the diaphragm 611 is formed as a membrane or film that is pre-charged to have an electrostatic charge, such as a constant negative or positive charge. The pre-charged membrane can be formed, for example, by a corona method and can be made from a polymer, such as from a fluoro-polymer.

[1074] The use of a pre-charged membrane to form the diaphragm can reduce components by eliminating the need for a power supply 652 to provide an electric charge to the diaphragm. In addition, the use of pre-charged membrane can reduce costs by reducing the number of components and can potentially lower energy requirements for driving the ESL acoustic driver 610. Such alternative embodiments that make use of a pre-charged membrane to form the diaphragm can operate in a similar push-pull manner of operation as charge-driven diaphragm embodiments, in that the pre-charged membrane 611 having, for example, a negative charge is pulled toward positively-charged stator 619 and pushed away from negatively-charged stator 617 when the step-up transformer applies a positive charge to stator 619 and a negative charge to stator 617. The pre-charged membrane 611 is similarly flexed in the opposite direction via opposite push-pull actuation when the step-up transformer cycles to apply opposite charges to the stators. [1075] Although the ESL acoustic driver 610 offers many advantages over conventional magnetic coil speakers, in some instances, ESLs operate under weak electrostatic forces so that large pressure wave amplitudes requiring significant displacement of the diaphragm can be difficult to generate. Therefore, the use of multiple ESLs driving more than one resonator volume or multiple resonators wherein the speaker to resonator volume ratio is greater than 1 may be desired to produce sufficiently high sound pressure levels for the desired thermoacoustic performance. By using multiple ESL acoustic drivers per resonator volume, a thermoacoustic refrigeration system can employ the inexpensive materials and methods of manufacture, as well as the dipole sound propagation (acoustic pressure waves emanating from both speaker sides) of ESLs, while also achieving the desired sound pressure levels (SPL). For example, in some embodiments, a thermoacoustic refrigerator can operate at SPL of 130 dB or greater. In other embodiments, a thermoacoustic refrigerator can operate at SPL of 140 dB or greater.

[1076] For example, FIG. 13 A shows a cross-sectional view of a thermoacoustic refrigeration system 708 (also referred to as an ESL refrigerator 708) according to an embodiment. The ESL refrigerator 708 can be included within any suitable refrigeration system, such as the refrigeration system 600 shown and described above. The ESL refrigerator 708 generally includes the same aspects and features of ESL refrigerator 608, except as discussed herein. ESL refrigerator 708 includes multiple ESL acoustic drivers 710 that are each configured to drive a pressure wave into a common first resonator volume 720. FIG. 13B is cross- sectional view of the thermoacoustic refrigeration system 708 as viewed along line Y-Y of FIG. 13A, which shows additional views of the ESL acoustic drivers 710 and corresponding arrangements with the first resonator volume 720.

[1077] As shown in FIGS. 13 A and 13B, the ESL refrigerator 708 includes multiple ESL acoustic drivers 710, a first resonator volume 720, a second resonator volume 740, and a heat exchange assembly 760 disposed between the first resonator volume 720 and the second resonator volume 740. Although not shown in FIGS. 13 A and 13B, it is understood that the first resonator volume 720 can be defined within a common body (or block), and that the ESL acoustic drivers 710 and other components discussed herein can also be disposed in and/or defined within the common body. For example, the body (or block) can define a set of pockets 790 (also referred to as a mounting volume) within which each of the ESL acoustic drivers 710 are disposed. Each pocket 790 is in communication with a pathway 792 defined within the body, which leads to (or is in acoustic communication with) the first resonator volume 720.

[1078] The first resonator volume 720 is generally elongate with a circular cross-section, and extends in a longitudinal direction. In other embodiments, however, the first resonator volume 720 can have any suitable cross- sectional shape as described herein. Each of the pathways 792 are radially connected to the first resonator volume 720 in a hub and spoke type arrangement with the circular cross-section of the first resonator volume 720, such that each of the pathways 792 is equally spaced from an adjacent pathway 792 around the first resonator volume 720. In addition, each of the pocket pathways 792 has a pathway length, t, as it extends from one side of the acoustic driver 710 to the connection between the pathway and the first resonator volume 720. In some embodiments, the length t of each of the pocket pathways 792 are equal. In this way, the pressure waves produced by the acoustic drivers 710 constructively interfere with each other in a resonant manner within the first resonant volume 720 to generate high intensity, combined pressure waves.

[1079] Each ESL acoustic driver 710 is similar in performance and structure to the ESL acoustic driver 610 described above. Specifically, each ESL acoustic driver 710 includes a diaphragm 711 flanked by spacers 713 and 715 and stators 717 and 719 on either side. The spacers 713 and 715 are electrical insulators, and the diaphragm 711 is mechanically anchored at its perimeter between the insulating spacers 713 and 715. In this manner, the diaphragm 711 can be maintained at a desired tension (or tautness). The stators 717 and 719 are electric conductors that can enable the formation of an electric field. The acoustic drivers 710 can be driven by one or more electronic circuits (not shown) similar to the electronic circuit 650 shown in FIG. 12, which can be connected in a similar manner to the diaphragm and stators of each of the acoustic drivers 710.

[1080] Further, in some embodiments each of the acoustic drivers 710 are configured the same as each other, in that the diaphragm properties and characteristics, including diaphragm tension, are the substantially the same. Additionally, the electronic circuit can also be configured to drive the ESL acoustic drivers 710 to produce pressure waves having the same intensity and frequency. When the acoustic drivers have the same frequency and the pocket pathways 792 have the same length, t, the pressure waves constructively interfere with each other in a resonant manner within the first resonant volume 720 to generate high intensity, combined pressure waves. For example, in some embodiments, a first ESL acoustic driver 710 can be characterized by a first performance, and a second ESL acoustic driver 710 can be characterized by a second performance that is within ten percent of the first performance. Such performance can include, for example, the impedance of each ESL acoustic driver 710 as a function of frequency, the response time (or phase shift relative to the input signal), the sound pressure level output as a function of frequency, or any other suitable performance measure. Moreover, in some embodiments, the tension of the diaphragm 711 disposed between the spacers 713, 715 for a first ESL acoustic driver 710 can be within ten percent of the tension of the diaphragm of a second ESL acoustic driver 710. In this manner, multiple ESL drivers 710 can be used to cooperatively produce the desired pressure waves (frequency, SPL, and the like) within the resonator volume 720.

[1081] Although the ESL refrigerator 708 is shown as including four pockets 790 that are equally spaced (circumferentially and radially) about the first resonator volume, and within which an ESL acoustic driver 710 is contained, in other embodiments, an ESL refrigerator can include any number of pockets 790 and ESL acoustic drivers 710. For example, in some embodiments, an ESL refrigerator can include two, three, six, eight or more ESL acoustic drivers in communication with a single resonator volume. Moreover, although the ESL acoustic drivers 710 are shown as being equally spaced circumferentially about the centerline of the resonator volume 720 (i.e., the ESL acoustic drivers 710 are spaced at 90° intervals, as shown in FIG. 14), in other embodiments, the ESL acoustic drivers 710 need not be spaced at equal intervals, and can be spaced in any suitable manner about the resonator volume 720. Multiple acoustic drivers and pocket pathways can be combined to drive a common resonator volume, and multiple resonator volumes can be combined in the same resonator block to provide an increased overall output and cooling benefit. For example, FIGS. 14A and 14B show a portion of a thermoacoustic apparatus including an ESL refrigerator 808, which includes a common block 822 that defines an array of multiple first resonator volumes 820. As shown, the resonator volumes 820 are arranged such that two adjacent resonator volumes share a common portion of the block (or body) 822. Similarly stated, the block 822 is fabricated such that it defines both a portion of a boundary of adjacent first resonator volumes 820. Said another way, the common portion of the body 822 is a "web" of material disposed between the adjacent resonator volumes 820. Although shown as including three first resonator volumes 820, in other embodiments, the block 822 can include any number of resonator volumes in any suitable repeating unit, of the types shown and described herein. By including multiple resonator volumes within a single block 822, the system efficiently includes multiple thermoacoustic devices (or units) within one thermoacoustic refrigeration system.

[1082] As further shown in FIGS. 14A and 14B, the ESL refrigerator 808 includes a driver block 896 that can be coupled to one end of the block 822 of the first resonator volumes 820. FIG. 15B shows a perspective view of the rear side of the driver block 896 as viewed along line Z-Z shown in FIG. 15A. The driver block 896 defines a set of pockets 890 and pocket pathways 892 that feed into (or are in communication with) each of the first resonator volumes 820 of the resonator array block 822 on one side of the driver block, and also includes a common electronic connection 859 formed on another side of the driver block. In this manner, each of the first resonator volumes 820 is fed by multiple acoustic drivers (not shown, but which can be similar to the ESL acoustic drivers 610 and 710 shown above) that are each disposed within a pocket 890 and have a corresponding pocket pathway 892 feeding into a common one of the first resonator volumes 820. In this embodiment, each of the resonator volumes 820 is in acoustic communication with two acoustic drivers (i.e., there is a driver-to-resonator volume ratio of 2: 1). In other embodiments, the ESL refrigerator 808 can have any suitable driver-to-resonator volume ratio. The common electronic connection 859 electrically connects each of the acoustic drivers to an electronic control circuit to drive the acoustic drivers as an overall unit and/or to control individual acoustic drivers according to instructions provided by the electronic control circuit, such as electronic control circuit 650 shown in FIG. 12. In this way, the ESL refrigerator 808 can be controlled to provide desired output levels as described below in greater detail along with FIGS. 17A, 17B and 18.

[1083] By including a separately-assembled driver block 896, the ESL refrigerator 808 can take advantage of multiple benefits to provide enhanced performance for each of the first resonator volumes 820 and for the block array 822 of the resonator volumes, which increases overall performance of the ESL refrigerator 808. For example, in some embodiments, the driver block 896 can be removably coupled to the array block 822. In this manner, individual acoustic drivers can be serviced or replaced without the need to replace the entire ESL refrigerator 808. Moreover, by separately constructing the driver block 896, the performance of each acoustic driver can be tested prior to final assembly of the driver block 896 to the array block 822. [1084] Although each of the ESL acoustic drivers 710 is shown as communicating with a single first resonator volume 720, in other embodiments, an acoustic driver can communicate with or produce pressure waves during operation in pairs of resonator volumes, which further enhances the efficiency and output of the ESL refrigerator. For example, FIG. 15 shows an ESL refrigerator 908 that includes a block (not shown), three ESL acoustic drivers 910, and two heat exchanger assemblies 960. The block defines a pair of first resonator volumes 920 extending in opposite directions from each other. Each of the opposite resonator volumes 920 are connected to a corresponding heat exchanger assembly 960 and second resonator volume 940. In this way, even greater efficiency and operation of the ESL refrigerator is provided during operation by each acoustic driver 910 producing pairs of pressure waves in opposite directions. Although shown as including only one pair of opposing resonator volumes 920, in other embodiments, the block can include an array of opposing resonator volumes, similar to that shown and described above for the refrigerator system 100.

[1085] The block (or a separate driver block, not shown) defines multiple pockets 990 that each contain an acoustic driver 910 disposed therein. In addition, the block (or a separate driver block) defines a pair of pocket pathways 991, 993 extending in opposite directions from opposite sides of each of the acoustic drivers 910. The opposite pocket pathways each feed into a corresponding one of the opposite first resonator volumes 920. Thus, in use each ESL acoustic driver 910 produces pressure waves in each of the two opposing first resonator volumes 920. Similarly stated, each ESL acoustic driver 910 feeds two opposing first resonator volumes 920. Additionally, each of the first resonator volumes 920 is in communication with (or receives pressure waves) from three different ESL acoustic drivers 910. Multiple pairs of first resonator volumes 920 within an array of resonator volumes in a common resonator block combine and cooperate to operate the ESL refrigerator 908. In the specific embodiment shown in FIG. 15, ESL acoustic drivers 910 drive the pair of first resonator volumes 920 in an effective and efficient driver-to-resonator volume ratio of 3:2. In other embodiments, an ESL refrigerator can include any other driver-to-resonator volume ratios which are greater than 1.

[1086] In other embodiments, a block or body can define one or more arrays of resonator volumes that are each connected to and fed by multiple pocket pathways and pockets. Further, the pockets can be connected to pairs of pocket pathways that each lead in opposite directions and connect to different resonator volumes. As such, a corresponding acoustic driver disposed in a pocket can be connected to a pair of the pocket pathways feeding different resonator volumes and, thus, can drive pressure waves to two different resonator volumes during operation, and the resonator volumes can further be fed by multiple other acoustic drivers in a constructive, acoustic arrangement. As an example, FIGS. 16A and 16B show portions of an ESL refrigerator 1208 that includes an array of first resonator volumes 1220, which are each feed by multiple pocket pathways 1292 connected to a corresponding pocket 1290. Each of the resonator volumes 1220 are further connected to a heat exchanger assembly 1260, which is connected to a second resonator volume 1240 similar to the arrangements discussed above along with other embodiments (e.g., the refrigerators 608, 708, 908).

[1087] However, the body or block for the ESL refrigerator 1208 shown in FIGS. 16A and 16B differs from the ESL refrigerator 708 in that the ESL refrigerator 1208 defines an interconnected array of first resonator volumes 1220, pockets 1290 and pocket pathways 1292, such that each pocket is connected to a pair of pocket pathways leading in opposite directions to connect with a different first resonator volume 1220 of the array. Thus, an acoustic driver 1210 disposed in a pocket 1290 of the array of first resonator volumes 1220 of ESL refrigerator 1208 can produce pressure waves during operation for a pair of first resonator volumes 1220 in the array, and each of the first resonator volumes 1220 can be fed by multiple acoustic drivers 1210 that are connected to the first resonator volume by a corresponding pocket pathway 1292 and that are also interconnected to another one of the first resonator volume 1220.

[1088] In this way, even greater efficiency and operation of the ESL refrigerator 1208 is provided during operation by each acoustic driver 1210, which produces pairs of pressure waves in opposite directions, and is further interconnected to a pair of the first resonator volumes to feed both of the first resonator volumes during operations while the first resonator volumes are additionally being fed by multiple acoustic drivers. In other words, as shown in FIGS. 16A and 16B, beneficial features and aspects of the various embodiments described herein can be combined in a wide variety of arrangements, arrays and interconnections of resonator volumes and acoustic drivers that take advantage of the collective operations, interactions and synergistic benefits from operating multiple acoustic drivers in various acoustically constructive arrangements to drive arrays of resonator volumes. FIGS. 17A, 17B and 18 illustrate operation of an electronic controller 1050 to control operation of an ESL refrigerator 1008 in an effective manner to provide a desired level of refrigeration in a highly efficient manner. As shown in FIGS. 17 A and 17B, the electronic controller 1050 and the ESL refrigerator 1008 can be included within any suitable refrigeration system 1000 of the types shown and described herein. The ESL refrigerator 1008 can be similar to any of the ESL refrigerators shown and described herein. Specifically, the ESL refrigerator 1008 includes multiple ESL acoustic drivers 1010, each in communication with a first resonator volume 1020. The multiple first resonator volumes 1020 can be defined within any suitable block of the types shown and described herein. Each of the first resonator volumes 1020 is coupled to (or in communication with) a heat exchanger assembly 1060. The ESL acoustic drivers 1010 can be similar to any of the ESL acoustic drivers shown and described herein. The heat exchanger assemblies 1060 can be similar to any of the heat exchanger assemblies shown and described herein. Although the ESL refrigerator 1008 is shown as including a single ESL acoustic driver 1010 in communication with one of the resonator volume (i.e., a driver-to-resonator volume ratio of 1: 1), in other embodiments, the ESL refrigerator can include any number of ESL acoustic drivers in communication with any number of resonator volumes.

[1089] The electronic controller 1050 includes a memory unit 1051, a processor 1053, a signal generator 1057, and a control module 1059. The memory unit 1051 can be, for example, random access memory (RAM), memory buffers, hard drives, databases, erasable programmable read only memory (EPROMs), electrically erasable programmable read only memory (EEPROMs), read only memory (ROM), flash memory, hard disks, floppy disks, cloud storage, and/or so forth. The memory unit 1051 contains electronic instructions that can be executed by processor 1053 to provide instructions to the signal generator 1057 and control module 1059 to provide operational control signals to each of the multiple acoustic drivers 1010 disposed within an ESL refrigerator 1008, as described herein.

[1090] The processor 1053 can be any suitable processor for performing the methods described herein. In some embodiments, the processor 1053 can be configured to run and/or execute application modules, processes and/or functions associated with the ESL refrigeration system 1000. For example, the processor 1053 can be configured to run and/or execute the control module 1059 as described herein, and perform the methods associated therewith. The processor 1053 can be, for example, a Field Programmable Gate Array (FPGA), an Application Specific Integrated Circuit (ASIC), a Digital Signal Processor (DSP), and/or the like. The processor 1053 can be configured to retrieve data from and/or write data to memory, e.g., the memory unity 1051. As described herein, in some embodiments, the processor 1053 can cooperatively function with the signal generator 1057 and/or execute instructions from code to provide signals to drive the ESL acoustic drivers 1010.

[1091] The signal generator 1057 can be similar to the signal input 658 described below, and provides the signal having desired frequency to other electronic components (not shown, but which can be similar to the components of the electronic circuit 650 described herein) to cause each of the ESL acoustic drivers 1010 to perform as desired. Specifically, during operation, each of the acoustic driver 1010 are driven to produce a corresponding pressure wave within a first resonator volume 1020 to provide refrigeration via a corresponding heat exchanger assembly 1060.

[1092] The control module 1059 can be a hardware and/or software module (stored in memory unit 1051 and/or executed in the processor 1053). As described in more detail herein, the control module 1059 is configured to receive certain signals (e.g., control signals) associated with the desired output level of the ESL refrigerator 1008 and determine, based on the signal, and optimal performance for each of the ESL acoustic drivers to achieve the desired performance. For example, in some embodiments, the control signal may indicate that full cooling is required. Accordingly, the control module 1059 can send driver signals to each of the ESL acoustic drivers 1010 to produce pressure waves at a desired frequency and sound pressure wave (SPL) in each of the resonator volumes 1020 to achieve the desired refrigeration performance. In the schematic example shown in FIG. 17A, the electronic control module 1050 provides signals to operate all four acoustic drivers 1010 within resonator volumes A, B, C and D. Conversely, in other situations, the control signal may indicate that only a partial level of cooling is required. In such instances, rather than turning the entire refrigerator 1008 on or off, the control module 1059 can allow the ESL refrigerator 1008 to operate partially to achieve the desired performance. For example, the control module 1059 can inhibit certain of the ESL acoustic drivers 1010 from operating, thereby reducing the cooling output of the ESL refrigerator. In the schematic example shown in FIG. 17B, the electronic control module 1050 provides signals to operate only two acoustic drivers 1010 within resonator volumes A and B. As another example for partial cooling, the control module 1059 can reduce the SPL of the acoustic drivers 1010 from a maximum SPL by lowering the electrostatic charge on an actively charged diaphragm and/or the electric field enabled by the stators, thereby reducing the cooling output of the ESL refrigerator.

[1093] FIG. 18 shows a flow chart of a method 10 of controlling an ESL refrigerator, which is described along with FIGS. 17A and 17B. In other embodiments, the method 10 can be performed on the ESL refrigerators described herein. The electronic control module 1050, at 12, sends a driver signal at a first time to the acoustic drivers 1010 of the resonator volumes A, B, C and D causing each of the acoustic drivers 1010 to produce a pressure wave within the corresponding first resonator volume 1020. In response to the driver signals, each of the acoustic drivers 1010 continues providing repeating pressure waves. As such, the ESL refrigerator 1008 operates in a full operation mode. Thereafter, at 14, the electronic control module receives a control signal associated with a desired output level of the ESL refrigerator 1008 that is less than the output produced during the full operation mode. For example, the control signal can be transmitted by a thermostat, an automotive controller (indicating that power needs to be conserved) or the like. Based on the instructions stored in memory 1051 that can include pre-selected, subset groupings of the resonator volumes A, B, C and D and subset grouping of adjacent ones of the resonator volumes, the electronic control module 1050 determines a matching subset of the resonator volumes to operate for the desired output level.

[1094] Accordingly, at 16, the electronic control module 1050 inhibits, at a second time and in response to the control signal for the desired output level, the driver signal from at least one of the acoustic drivers 1010. In the example shown in FIG. 17B, the electronic control module has determined that operation of the subset of resonator volumes A & B best matches the desired output level. As such, the electronic control module 1050 inhibits the control signals for the resonator volumes C and D while maintaining the control signals for resonator volumes A and B. In this way, the output of the ESL refrigerator 1008 is effectively and efficiently controlled to provide the desired output level.

[1095] Alternatively, at 16, the electronic control module 1050 lowers, at a second time and in response to the control signal for the desired output level, the electrostatic charge on an actively charged diaphragm and/or the electric field enabled by the stators. Also in this way, the output of the ESL refrigerator 1008 is effectively and efficiently controlled to provide the desired output level.

[1096] It is understood that the ESL refrigeration systems and ESL refrigerators described herein can be used in many different structures, devices and arrangements to provide highly efficient cooling. For example, FIG. 19 shows an arrangement of an ESL refrigeration system 1100 disposed within a vehicle 1198, such as an electric vehicle or hybrid electric vehicle 1198. The ESL refrigeration system 1100 can provide effective cooling for the vehicle interior within minimal effect on battery life or power usage of the vehicle. The electronic control unit 1199 can provide instructions to ESL refrigerator 1108 to provide desired output cooling levels for the vehicle via a coolant loop 1165. A fan 1167 can drive air (identified as AIR) over the coolant loop to provide the desired cooling to the interior of the vehicle 1198.

[1097] While various embodiments of a thermoacoustic refrigeration system have been described above, it should be understood that they have been presented by way of example only, and not limitation. Where methods described above indicate certain events occurring in certain order, the ordering of certain events may be modified. Additionally, certain of the events may be performed concurrently in a parallel process when possible, as well as performed sequentially as described above.

[1098] Although various embodiments have been described as having particular features and/or combinations of components, other embodiments are possible having a combination of any features and/or components from any of embodiments where appropriate. For example, any of the array blocks shown and described herein can include any features of another blocks shown and described herein.

[1099] For example, although acoustic driver 110 is shown as being a device that can generate soundwaves from opposing sides to drive two block resonator arrays simultaneously, in other embodiments, an acoustic driver can produce soundwaves from a single side and can be coupled to only one block resonator array of the types shown and described herein. [1100] Although the block resonator array 420 is shown as having a spherical volume 433, in other embodiments, a closed-ended block resonator array can have any suitable shape. For example, such shapes can include an elliptical shape, a conical shape, or the like.

[1101] Although the block resonator array 100 is shown as defining a series of circular- shaped volumes 130, in other embodiments, any of the bock resonator arrays can define a series of volumes having any shape. Such shapes can include, for example, a rectangular shape, an elliptical shape, or the like.

[1102] Although the resonator volumes 133 are shown having a constant size (i.e., diameter), any of the resonator volumes can have any suitable size. For example, any sizes including tapered sizes, multiple sizes of resonator volumes (i.e., diameters) within the same block resonator array, or the like.

Claims

What is claimed:

1. An apparatus comprising:

a body defining a first resonator volume, the first resonator volume in acoustic communication with a second resonator volume;

an electro- static loudspeaker assembly (ESL) in communication with the first resonator volume; and

a heat exchanger assembly coupled to the body between the first resonator volume and the second resonator volume, the heat exchanger assembly including a stack, a hot heat exchanger and a cold heat exchanger.

2. The apparatus of claim 1, further comprising:

a driver housing, the driver housing defining a pocket containing the ESL and defining a pocket pathway to the first resonator volume, the driver housing being coupled to the body.

3. The apparatus of claim 1, further comprising:

a plurality of ESLs, the ESL being one ESL of the plurality of ESLs;

the body defining a plurality of pockets, each pocket configured to contain one of the plurality of ESLs; and

the body defining a plurality of pocket pathways, each of the plurality of pocket pathways corresponding to at least one of the plurality of pockets, each of the plurality of pocket pathways in communication with the first resonator volume.

4. The apparatus of claim 3, wherein a length of each of the plurality of pocket pathways between a pocket from the plurality of pockets and the first resonator volume is the same.

5. The apparatus of claim 3, wherein the first resonator volume has a circular cross-section, and the plurality of pocket pathways is arranged circumferentially about a center of the circular cross-section.

6. The apparatus of claim 3, wherein the first resonator volume has a larger cross-sectional area than each of the plurality of pocket pathways.

7. The apparatus of claim 1, wherein the body defines a plurality of first resonator volumes, each of the plurality of first resonator volumes sharing a common portion of the body, the apparatus further comprising:

a plurality of ESLs, the ESL being one ESL of the plurality of ESLs, each of the plurality of ESLs in communication with at least one of the plurality of the first resonator volumes.

8. The apparatus of claim 7, wherein the block is monolithically constructed.

9. The apparatus of claim 8, wherein the block is constructed from a polymer.

10. The apparatus of claim 7, wherein the plurality of first resonator volumes is arranged in a repeating unit, the repeating unit having a shape of a triangle.

11. The apparatus of claim 7, wherein the plurality of first resonator volumes each have a circular cross-sectional shape.

12. The apparatus of claim 1, wherein a diaphragm of the ESL is permanently electrostatically charged.

13. The apparatus of claim 1 , further wherein the body defines a pair of first resonator volumes, the pair of first resonator volumes including the first resonator volume, each of the pair of first resonator volumes in communication with the ESL, the body further defining a pair of second resonator volumes, the pair of second resonator volumes including the second resonator volume, the apparatus further comprising:

a pair of heat exchanger assemblies, the pair of heat exchanger assemblies including the heat exchanger assembly, each of the pair of heat exchanger assemblies in communication with a corresponding one of the first resonator volumes and a corresponding one of the second resonator volumes.

14. The apparatus of claim 13, wherein the ESL includes a first side portion and an opposite second side portion, and each of the pair of first resonator volumes are in communication with a corresponding one of the first and second side portions of the ESL.

15. The apparatus of claim 1, wherein the ESL is a first ESL, the apparatus further comprising: a second ESL in communication with the first resonator volume; and

a driver circuit configured to drive the first ESL at a first performance and the second ESL at a second performance.

16. The apparatus of claim 15, wherein first ESL and the second ESL are configured such that the second performance is within 10% of the first performance.

17. The apparatus of claim 15, wherein the first ESL includes a first diaphragm having a first tension, the second ESL includes a second diaphragm having a second tension, the second tension being within 10% of the first tension.

18. An apparatus, comprising:

an acoustic driver;

a block resonator array having a body defining a plurality of first resonator volumes, each of the first resonator volumes configured to be in acoustic communication with a corresponding second resonator volume, the acoustic driver coupled to the block resonator array and configured to produce an acoustic wave within at least one of the plurality of first resonator volumes, at least two of the plurality of first resonator volumes sharing a common portion of the body; and

a heat exchange assembly coupled to the block, the heat exchange assembly including a stack, a hot heat exchanger, and a cold heat exchanger.

19. The apparatus of claim 18, wherein:

the plurality of first resonator volumes is arranged in a repeating unit, the repeating unit having a shape of a square.

20. The apparatus of claim 18, wherein:

the plurality of first resonator volumes is arranged in a repeating unit, the repeating unit having a shape of a triangle.

21. The apparatus of claim 18, wherein one of the plurality of first resonator volumes is larger than another of the plurality of first resonator volumes.

22. The apparatus of claim 18, wherein the plurality of first resonator volumes each has a circular cross-sectional shape.

23. The apparatus of claim 18, wherein the body of the block resonator array is monolithically constructed.

24. The apparatus of claim 18, wherein the heat exchange assembly is coupled to the block resonator array such that the plurality of first resonator volumes is fluidically isolated, the at least two of the first resonator volumes containing a gas at a pressure of at least about one atmosphere.

25. The apparatus of claim 18, wherein the acoustic driver and the block resonator array are collectively configured such that the acoustic driver produces a standing wave within at least one of the plurality of first resonator volumes.

26. The apparatus of claim 18, wherein the acoustic driver and the block resonator array are collectively configured such that the acoustic driver produces a traveling wave within at least one of the plurality of first resonator volumes.

27. The apparatus of claim 18, wherein the body defines a Helmholtz volume fluidically coupled to an end portion of one of the plurality of first resonator volumes, one of the plurality of second resonator volumes including the Helmholtz volume.

28. The apparatus of claim 18, wherein the acoustic driver is a thin film driver configured to generate sound waves from opposing sides.

29. A method, comprising:

molding a block resonator array from a polymer, the block resonator array defining a plurality of resonator volumes, the resonator volumes containing a gas;

coupling an acoustic driver to a first end of the block resonator array; and

coupling a second end of the block resonator array to a heat exchange assembly, the heat exchange assembly comprising a stack, a hot heat exchanger, and a cold heat exchanger.

30. An apparatus, comprising:

a block resonator array having a wall, a first side surface, and a second side surface, the first side surface configured to be coupled to an acoustic energy source, the second side surface configured to be coupled to a heat exchanger assembly, the wall defining a plurality of resonator volumes, a first resonator volume from the plurality of resonator volumes and a second resonator volume from the plurality of resonator volumes each sharing a common portion of the wall.

31. An apparatus, comprising:

an acoustic driver; and

a block resonator array having a body defining a plurality of resonator volumes, the plurality of resonator volumes including a first resonator volume, the first resonator volume forming a loop through which an acoustic wave produced by the acoustic driver is conveyed through a compliance volume and an inertance tube.

32. The apparatus of claim 31, further including an electro-static loudspeaker assembly (ESL) including the thin film driver, the first resonator volume coupled to a first side of the ESL and the second resonator volume coupled to a second side of the ESL located opposite the first side of the ESL.

33. The apparatus of claim 32, wherein the thin film driver drives the ESL at a frequency of about 5000 Hz.

34. The apparatus of claim 32, wherein the thin film driver drives the ESL at a frequency greater 5000 Hz.

35. The apparatus of claim 32, wherein a pressure in each of the first resonator volume and the second resonator volume is about 1 atm.

36. The apparatus of claim 32, wherein a pressure in each of the first resonator volume and the second resonator volume is about 1 atm to about 20 atm.

37. The apparatus of claim 32, wherein the ESL includes a diaphragm having a tension, the diaphragm including a thin film polymer.

38. The apparatus of claim 37, wherein the thin film polymer is formed as a pre-charged membrane.

39. The apparatus of claim 37, wherein the pre-charged membrane is pre-charged by a method known as the corona method.

40. The apparatus of claim 39, wherein the pre-charged membrane is made of fluoro-polymer.

41. A computer- implemented method of controlling a thermoacoustic refrigeration device, comprising:

sending, from a driver circuit at a first time, a driver signal to a plurality of acoustic drivers, each of the acoustic drivers in communication with a corresponding resonator volume defined within a resonator block, each of the acoustic drivers producing a pressure wave within the corresponding resonator volume in response to the driver signal;

receiving a control signal associated with a desired output level of the thermoacoustic refrigeration device; and

inhibiting, at a second time and in response to the control signal, the driver signal from at least one acoustic driver from the plurality of acoustic drivers.

42. The computer- implemented method of claim 41, wherein the driver signal is produced by a control module including at least one of a transformer providing an alternating current output voltage, a frequency generator, an amplifier and a filter.

43. The computer- implemented method of claim 41, wherein inhibiting the driver signal includes inhibiting a selected pre-determined subset of the acoustic drivers corresponding with the desired output level, the selected pre-determined subset being selected from a plurality of predetermined subsets, each of the plurality of the pre-determined subsets corresponding to an output level.

44. The computer- implemented method of claim 43, wherein the selected pre-determined subset of the acoustic drivers includes a group of acoustic drivers located adjacent to each other.

45. An apparatus, comprising:

a resonator block defining a plurality of volumes;

a plurality of acoustic drivers, each within a corresponding volume; and

an electronic circuit system operatively coupled each of the plurality of acoustic drivers, the electronic circuit system including:

a signal generator configured to produce a driver signal; and

a control module implemented in at least one of a memory or a processing device, the control module configured to:

send, at a first time, a driver signal to each of the plurality of acoustic drivers to produce a pressure wave within the corresponding volume in response to the driver signal;

receive a control signal associated with a desired output level of the apparatus; and

inhibit, at a second time and in response to the control signal, the driver signal from at least one of the plurality of acoustic drivers.

46. A vehicle, comprising:

an electronic control unit (ECU); and an electrostatic speaker (ESL) refrigerator in communication with the ECU, the ESL refrigerator, including:

an acoustic driver;

a block resonator array having a body defining a plurality of resonator volumes, the plurality of resonator volumes including a first resonator volume and a second resonator volume, the first resonator volume and the second resonator volume each sharing a common portion of the body; and

a heat exchange assembly including a stack, a hot heat exchanger, and a cold heat exchanger.

47. An apparatus comprising:

a block defining a plurality of first resonator volumes;

a first electro-static loudspeaker assembly (ESL) in communication with a first one of the plurality of first resonator volumes;

a second ESL in communication with a second one of the plurality of first resonator volumes; and

48. The apparatus of claim 47, wherein first ESL and the second ESL are configured such that the second performance is within 10% of the first performance.

49. The apparatus of claim 47, wherein the first ESL includes a first diaphragm having a first tension, the second ESL includes a second diaphragm having a second tension, the first tension being within 10% of the first tension.

50. The apparatus of claim 47, wherein the block further defines:

a first pathway from the first ESL to the first one of the plurality of first resonator volumes; a second pathway from the first ESL to a third one of the plurality of first resonator volumes; a third pathway from the second ESL to the second one of the plurality of first resonator volumes; and

a fourth pathway from the second ESL to a fourth one of the plurality of first resonator volumes.

51. The apparatus of claim 50, further comprising:

a first heat exchanger assembly coupled to the first one of the plurality of first resonator volumes, the first heat exchanger assembly including a first stack, a first hot heat exchanger and a first cold heat exchanger; and

a second heat exchanger assembly coupled to the second one of the plurality of first resonator volumes, the second heat exchanger assembly including a second stack, a second hot heat exchanger and a second cold heat exchanger.

52. The apparatus of claim 47, wherein the first one of the plurality of first resonator volumes is in communication with a first side of the first ESL, the second one of the plurality of first resonator volumes is in communication with a first side of the second ESL, and the block further defines:

a third one of the plurality of first resonator volumes in communication with a second side of the first ESL, the second side of the first ESL located opposite the first side of the first ESL; and

a fourth one of the plurality of first resonator volumes in communication with a second side of the second ESL, the second side of the second ESL located opposite the first side of the first ESL.