CROSS REFERENCE TO RELATED APPLICATIONS

(00011 This application, claims the benefit of Provisional U.S. Patent Application No, 61/644,187, filed May 8, 2012, and Provisional IIS, Patent Application No. 61/764,459, filed February 13, 2013 , both of which are hereby incorporated by reference in their entirety.

BACKGROUND OF THE DISCLOSURE

1 . Field of the Disclosure

[0002] The present disclosure relates to mi apparatus and method for heat transfer using a thermoelectric device, and, in particular,, pumping heat.

2, Description of the Related Art.

[0003] Space heating and cooling is the largest energy end use in homes, and water heating is the second largest energy end use in homes. Almost every household ha at least one water heater, and about 10 percent of households replace their water heaters every year. Gas water heaters require a gas source, which is not always available. More than half of the water heaters are electrically powered. Most electric water heaters are inefficient and expensive to operate due to their resistive element heating design. An alternative to gas and electric heating and cooling, both for water and interiors is. a heat pump-based heating and/or cooli ng system.

[0004 _. 1 In the instance of a water heater, typical heat pumps use a compressor to pump heat from ambient air to the water. However, the choice of refrigerants for compressor heat pumps is limited by the refrigerants' critical temperature. High temperature refrigerants, such as R134A, may operate with a critical temperature of 100 degrees Celsius at 4 Bar, or R4I0A with a critical temperature of 70 degrees Celsius. Since the water is commonly heated to about 70 degrees Celsius, the refrigerants must, be compressed at temperatures near their critical temperatures, a process that requires more energy as the critical temperature is approached. The compressor needs to compress at a significantly higher pressure for the refrigerant to change phase and results in loss of energy efficiency. In most cases, the compressor-based heat pump water heaters are supplemented with a strip heater (resistive heater) to attain the high temperature delivery requirements of the water heater, and results in an overall decrease of system Coefficient of Performance (COP). Secondly, the variable speed compressors that can operate at these high water delivery temperatures are too expensive. The retail price of commercially-available 50 gallon water heaters is typically US$1700, compared to only US$350 for the same capacity strip heater based product. This cost difference of almost US$ 1400 implies the payback period is typically over 4 years (based on DoE's ENERGY STAR, estimated energy savings of approximately US$300 per year). As a result of this large difference between the initial price of a resistive heater based water heater and the heat pump water heater, the penetration rate of heat pump water heaters into the water heater market has been very low. What is needed is a cost effective heat pump that operates efficiently at the desired temperatures, such as for high hot water delivery temperatures.

BRIEF SUMMARY OF THE DISCLOSURE OO 51 1» aspects, the present disclosure is related to an apparatus and method for transferring heat, and, in particular, a pumping of heat using a thermoelectric generator.

j000 j One embodiment according to the present disclosure includes a thermoelectric heat pump apparatus, the apparatus comprising: a thermoelectric converter having a hot side and a cold side, the thermoelectric converter comprising: a thermoelectric stack of thermoelement layers, wherein each thermoelement layer comprises at least one thermoelement; and a first fluid loop in thermal communication with the thermoelectric stack and configured to deliver a first fluid to the thermoelectric stack in a positive temperature gradient flow direction of th thermoelectric stack. The thermoelectric stack may include one or more of: a plurality of constricted contacts layers, wherein each of the constricted contact layers comprises at least one constricted contact and wherein the constricted contact layers alternate with, thermoelement layers, and a plurality of metal sheets, wherein the metal sheets alternate with the thermoelectric layers, and wherein the metal sheets are in thermal communication with the first fluid, either directly or via heat conducting fins,

|¾O07] The thermoelements may be comprised of high power factor materials such as: i) Bio.5Sb1.5Te3, ii) ZiuSb?, hi) CeFej.sCo«.5Sb{2, iv) vii) B~ doped Si, viii) B-doped Sio,sGet , ix) Bi2T¾ S¾>.2 x) PbTe, i) AgPb^SbTeso, xii) PbTe/SrTe- Na, ΐίί) xv) Ti iSn, xvi) SrTiOs, xvii) P-doped Si, x.viii) P-doped S% _& Geo _; 2, six) xxiii) CePdn, and xxiv) YbA . In some aspects, the thermoelements may be comprised of high power factor materials with high thermal conductivity such as: i) B-doped Si, is) P-doped Si, iii) CoSb*, iv) Yb-doped CoSb.?, v) MgsSi, vi) CePd.¾, and vii) YbAl _; ¾. The thermoelements may he n-rype or p-iype and, sometimes, pairs n-type and p-type materials. The first fluid may include one or more of: i) water, ii) steam, iii) mineral oil, iv) terphenyl, and v) _. a liquid metal. In aspects where a thermoelectric stack is made of a single type of thermoelectric material, a second stack of the complementing type (p-type for n-type, and vise versa) may be used with a shared or separate fluid loop.

{OO08 The thermoelectric heat pump apparatus may include a hot side fluid loop in thermal communication with the hot side and a cold side fluid loop in thermal communication with the cold side. One or more heat exchangers may be in thermal communication, with the hot/cold side fluid loops. One of the hot/cold fluid loops may be in thermal communication with ambient while the. other is in thermal communication with a receiver of heat/cold, such as a tank or compartment.

6 09| The receiver of the heat/cold may be a fluid stored in housing and one or more eat transfer devices may be used to move heat between the fluid and the ambient air. The apparatus may include a thermal storage medium configured to be "charged" with heat/cold so that heat movement may continue when the thermoelectric converter is not operating or to suppiement operation of the thermoelectric converter. The thermal storage medium may be associated with one or more additional heat transfer devices and thermoelectric converters to move heat between the thermal storage medium and ambient. The thermal storage medium may include one or more of: i) water, ii) paraffin. Hi) a molten salt and ίν) a reversible exothermic hydration material {(KM Of in some aspects, the housing may further include a baffle disposed in the housing and configured to partially separate the third fluid .into a first portion and a second portion; a second thermoelectric converter with a second hot side and a second cold side: a third heat transfer device in thermal communication with the third fluid and in. thermal communication with one of; i) the second hot side and ii) the second cold side; and a fourth heat transfer device in thermal communication with other of; i) the second hot side and ii) the second cold side, wherein the fourth heat transfer device is in thermal communication with ambient air, and wherein the first heat transfer device and the third heat transfer device vertically separated from one another within the column.

190.11 J Another embodiment according to the present disclosure may include an apparatus for transferring heat to a first fluid, the apparatus comprising: a housing configured to store the first fluid; first heat transfer device configured to be in thermal communication with the first fluid; a first thermoelectric converter with a first hot side and a first cold side, wherein the first hot sid is in thermal communication with the first heat transfer device, and wherein the first heat transfer device is configured to transmit heat from the first hot side to the first fluid; and a second heat transfer device in thermal communication with the first cold side, and wherein the second heat transfer device is in thermal communication with ambient air and configured to transmit the cold from the first cold side to the ambient air.

[0012} Anoiher embodiment according to the present disclosure may include a thermoelectric heat pump apparatus, the apparatus comprising: a plurality of thermoelectric converters, eac having a hot side and a cold side and comprising: a stack of thermoelement layers, wherein each thermoelement layer comprises at least one thermoelement; and a first fluid loop in thermal communication with the plurality of stacks and configured to deliver a first fluid to the stacks in a positive temperature gradient flow direction. The plurality of thermoelectric converters may comprise a first thermoelectric converter and a second thermoelectric converter, and the first fluid loop is configured to recirculate a first part of the fluid from the cold side of the first thermoelectric through the first thermoelectric converter and to circulate a second part of the fluid from the cold side of the first thermoelectric to the cold side of the second thermoelectric converter. The thermoelectric heat pump apparatus may include at least one heat exchanger in thermal communi cation with the first fluid loop and a heat transfer device, and that heat transfer device may include one or more of: a second fluid loop and a thermal diode.

[0013| Anoiher embodiment according to the present disclosure includes an apparatus for moving heat relative to a first fluid, the apparatus comprising; a housing configured to store the first fluid; a first heat exchanger loop in thermal communication with the first fluid and configured to move a first heat transfer fluid; a second heat exchanger loop i thermal commo ication with ambient air and configured to move a second heat transfer fluid; and a thermoelectric converter with a hot side and 8 cold side, wherein the hot side is in thermal communication with one of the first heat exchanger loop and the second heat exchanger loop and the cold side is in thermal communication with the other of the first heat exchanger loop and the second heat exchanger loop.

(00141 Examples of the more important features of the disclosure have been summarized rather broadly in order that the detailed description thereof that follows may be better understood and in order that the contributions they represent to the art may he appreciated. There are, of course, additional features of the disclosure that will be described hereinafter and which will form the subject of the claims appended hereto,

BR IEF DESCRIPTION OF THE DRAWINGS

10015} For a detailed understanding of the present disc losure, reference should be made to the following detailed description of the embodiments, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals, wherein:

FIG. J a schematic thermoelectric fluid heater according to one embodiment of the present disclosure;

FIG. 2 is a schematic of a thermoelectric fluid heater with resistive heating element according to one embodiment of the present disclosure;

FIG. 3 is a schematic of a thermoelectric fluid heater with a thermal battery according to one embodiment of the present disclosure;

FIG. 4 is a schematic of a thermoelectric fluid heater with a thermal battery with fluid loops to transport heat according to one embodiment of the present disclosure; FIG. 5 is a schematic of a thermoelectric fluid heater with convection induced by thermoelectric converters according to one embodiment of the present disclosure;

FIG. 6 is a schema.dc of a thermoelectric converter apparatus xvith a counter-flow fluid loop adjacent to the apparatus according to one embodiment of the present disclosure;

FIG. 7 is a schematic of a thermoelectric converter apparatus with a counter-flow fluid loop flow path through the raennoelements according to one embodiment of the present disclosure;

FIG. 8 is a 3-D perspective view of a single type thermoelement stack with a counter-flow fluid through the thermoelements according to one embodiment of the present disclosure;

FIG. 9A is a schematic of an air heater using a thermoelectric converter apparatus according to one embodiment of the present disclosure;

FIG. 9 is a schematic of a water heater using a fhermoelectric converter apparatus according to one embodiment of the present disclosure; and

FIG, 10 is a schematic of a cooling system using a thermoelectric converter apparatus according to one embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

{ ^" 00.16 j Generally, the present disclosure relates to an apparatus and method for transferring heat, and, in particular, pumping heat with a theiraoelecoic converter. The present disclosure is susceptible to embodiments of different forms. They are shown in the drawings, and herein will be described hi detail, specific embodiments of the present disclosure with the understanding that the present disclosure is to be considered an exemplification of the principles of the present disclosure and is noi intended to limit the present disclosure to that iliustrated and described herein.

f 0017J The optimum COP for a thermoelectric converter for cooling operation is defined as the ratio of heat: pumped from the cold side to hot side of the cooler to the input, electrical power. The optimal COP is determined by the following relationship:

where T _c and Th are the temperatures of the cold side and hot side respectively, ZT is a dirnensionless parameter known as figure-ot-iTierit, which combines the thermoelectric properties of the material, T ^~ {T _e -f T _h )/2 and AT ^~ T _k T ₍ . .

{ ^" 00181 The heat rejected by the themjoeiecmc converter into the fluid Q _f depends on the input electrical power (Pekc) as follows:

These equations may be used to estimate the heat pump requirements for heating a fluid, such as water or air; to a target delivery temperature.

|0O19{ FIG. 1 sho ws a schematic of an apparatus 100 for heating a fluid 160 according to one embodiment of the present disclosure. The apparatus 100 may include a housing 110 designed to store the fluid 160. The fluid 160 may he a liquid or a gas. The fluid 160 may include, hut is not limited to, one or more of: water, paraffin, air, and petroleum fractions. The housing .110 may include a structural layer .116, such as stainless steel or ceramic, that will not be corroded or degraded by the fluid 1 0. The housing 1.1.0 ma include a tank or other structure that forms a compartment or chamber to hold the fluid 160. The housing 110 may also include thermal insulation 118. The housing 110 may include an inlet 114 and an outlet 112 for the fluid 160 to enter and leave the housing 110. A heat transfer device 120 may be disposed in the housing 110 such that the heat transfer device 120 is in thermal, and often physical communication with the fluid 160. Beat fins 122 may be attached to the heat transfer device 160 to increase the distribution of heat from the heat transfer device 120 into the fluid 160. The heat transfer device 120 may he any suitable device configured to transport heat energy including, but not limited to, one or more of: i) a heat pipe, ii) a thermosyphon. Hi) a thermal diode, and rv) a heat exchanger. The heat transfer device 120 may be in thermal connection with a hot side 132 of a thermoelectric converter 130. The thermoelectric converter 130 may be configured to produce a temperature differential betwee the hot side 132 and a cold side 134 in response to electrical power received from a power source 170. The thermoelectric converter 130 may he a thin-film thermoelectric device. In some embodiments, the thermoelectric converter 130 may include multiple thermoelectric devices in parallel and/or series configuration. IK. some other embodiments, the thermoelectric converter 130 may comprises of cascaded or segmented thermoelectric devices. The thermoelectric converter 130 may be disposed in the housing 1 0 such that the hot side 132 is inside the thermal insulation 118 and the cold side 134 is outside of the thermal insulation 118. A heat transfer device 140 may he disposed in thermal communication with the cold side 134 to move heat into the cold side 134 of the thermoelectric converter from the ambient The heat, transfer device 140 may include fins 142 configured to gather heat from the ambient air. In some embodiments, the ambient air may be moved through the tins 142 by a forced air supply 50, such as a fan.

|0020f As would be understood by a person of ordinary skill in the art with the benefit of the present disclosure, there may he a variety of embodiments in keeping with the design shown in FIG, 1. For example, in an aspect of air heating, the housing 1 0 ma be the walls, floor, and ceiling of a room thai hold a volume of air to be heated, In some embodiments, the housing 110 may not be enclosing, such as in the ease of a vat. In some embodiments, one or more of the heat transfer devices 120, 140 may be optional, and the fins 122, 142 may be in thermal commiinication with the hot and cold sides 132, 134, respectively. While the thermoelectric converter 130 is shown as singular and disposed at the bottom of the housing 1 0, this is exemplary and illustrative only, as there may be multiple thermoelectric converters 130 and the thermoelectric converters 130 may be disposed anywhere within the housing 110 so long as heat may be transferred between the inside and the outside of the housing 110. The thermoelectric converters 130 may be staged in series or parallel or both as desired to provide a specified heat differential or amount of heat flow between the fluid 160 and the ambient air,

(00211 FIG. 2 show ^' s a schematic of an apparatus 200 for heating a fluid 160 according to another embodiment of the present disclosure. The apparatus 200 includes the elements of apparatus 100 in FIG. 1 and, additionally, includes a resistive heating element 210. The resistive heating element 210 may receive electricity from the power source 170 {connections between the power source and the resistive heating element not shown). The resistive heating element 21.0 may be configured to supplement the heat energy being provided to the fluid .160 by the thermoelectric converter 130. The resistive heating element 2.10 is configured to provide heat to the fluid 1 0 independently or in combination with the thermoelectric converter 130. In some embodiments, the thermoelectric converter can heat and maintain the fluid 160 at a predetermined temperature and the resistive heater can be used only when a higher fluid temperature is desired.

[0022 j FIG. 3 shows a schematic of another apparatus 300 for heating the fluid 1 0 according to another embodiment, of the present disclosure. The apparatus 300 ma include elements from apparatus 100 shown in FIG. 1. The apparatus 300 may include a ihermai storage medium 310 that may be stored in a housing 320. The thermal storage medium 310 (such as a thermal battery) may include substances with high heat capacity that remain liquid in the operating temperature range of the fluid 160, including, but not limited to, one or more of: water, paraffin, and molten salts. In some embodiments, the thermal storage medium 31.0 may include substances suitable for a reversible exothermic chemical reaction. The thermal storage medium 310 may be selected based on the heating temperature range selected for the desired fluid 160. The heat transfer device .140 may he in thermal communication with the thermal storage medium 310, Heat may be supplied from the thermal storage medium 310 through die heat transfer device 140 to the cold side 134 of the thermoelectric converter 130, Another heat transfer device 330 may be disposed in ihermai communication with the thermal storage medium 310 and configured to transport heat into the thermal storage medium 310, The heat transfer device 330 may be in thermal communication with a hot side 342 of another thermoelectric converter 340. The heat transfer device 330 may include fins 332 configured to distribute heat into the thermal storage medium 31 . A. cold side 344 of the thermoelectric converter 340 may be in thermal communication with the ambient air to gather heat. Fins 350 in thermal communication with the cold side 344 may be used to increase the surface area of ambient air to increase heat gathering. In some embodiments, heat gathering may be increase using the forced air supply 150. The thermoelectric converter 340 may charge the thermal storage medium 310 while the thermoelectric converter 130 moves heat from the storage medium to the fluid 1.60. The heat transfer device 330 may be diodic in nature, which allows the heat to predominately move in one direction from the hot side 342 to the thermal storage medium 33Θ.

Π {0023) FIG. 4 shows a schematic of an apparatus 408 for heating fluid 160 according to another embodiment, of the present disclosare. A heat exchanger 410 may be disposed in thermal communication with the fluid 160 to convey heat into the fluid 160, The heat exchanger 410 may receive heat from a first pumped loop 428 containing a heat transfer fluid, such, as water or oil. The first pumped loop 428 may be in thermal communication with a hot side 432 of a thermoelectric converter 438, which is configured to supply heat to the first pumped loop 420. A cold side 434 of the thermoelectric converter 430 may be in thermal communication with a second pumped loop 440 that is configured to transport heat to the cold side 434 from an ambient air heat exchanger 458. In some embodiments, a forced air source 460 mav enhance the transfer of heat from the ambient air into the ambient air heat exchanger 450, In some embodiments, the first pumped loop 420 may circulate through thermal storage medium 310 (such as a thermal battery) via a heat exchanger loop 470. The thermal storage medium 310 may be configured to store or release heat into the first pumped loop 420 as is required to provide the desired temperature for the fluid 160. In some embodiments, the housing 328 may be at least partially enclosed b thermal insulation 488.

{0024| Some embodiments of apparatus 408 may be configured to operate in at least, three different modes. I a first mode, the thermoelectric converter 138 may move heat to the fluid 160. In a second mode, the thermoelectric converter 130 may move heat to the thermal storage medium 310. In a third mode, the thermal storage medium 318 may be used to move heat to the fluid 160. in the third mode, the thermoelectric converter 130 and the second pumped loop ma not he operating. One or more valves and/or pumps in the pumped loops 420, 448 may be configured to for performance of each of the three modes. |0025| Although the embodiments shown above depict only a single thermoelectric heat pump, hi practice the design may include multiple thermoelectric heat pumps connected thermally in parallel and electrically in. series or parallel or series/parallel configuration (depending upon the desired voltage-current characteristics). Also there are many different types of heat exchangers that can be incorporated. An exemplary heat exchanger may include a counter flow configuration of fluid flow.

[9026) FIG. 5 shows a schematic of a fluid heating apparatus 500 configured to incorporate convection induced mass flow in the fluid 160 to facilitate heat pumping according to one embodiment of the present disclosure, lire apparatus 500 may include several elements of apparatus 100 shown in FIG. Ϊ. An inlet conduit 514 may be disposed to provide the fluid 160 into the bottom of the housing 110. Since the incoming fluid through the conduit 514 is colder, this configuration supports -natural convection in the chamber. The housing 110 may be at least partially partitioned by a baffle 510 to form a col umn 520 of the fluid 160 between the baffle 510 and a wall of the bousing 110. One or more thermoelectric converters 130 may be disposed in the housing 110 and configured to pump heat into the fluid 160 through heat transfer devices 120 and fins 122. The heat transfer devices 120 and fins 122 may be disposed in the column 120. Some fluids, such as water, change density with changes in temperature. The heat added to the fluid 160 from the heat transfer devices 120 and fins 122 will cause the local temperature of the fluid 160 to increase and induce movement in the fluid 160 due to density changes. The baffle 510 may channel this induced movement into a direction along the column 520. With multiple thermoelectric converters 130 pumping heat into heat transfer devices 120 and fins 122 in thermai communication with the column 520. a flow (due to the changes in density of the fluid 160} may produce circulation throughout the fluid 160 within the housing lit). |ft027| In some embodiments, the heat transfer device 20 or the t s 122 may be optional In the inlet pipe 514 is shown delivering fluid at the bottom of the baffle 510, however, this is exemplary and illustrative only, as the inlet pipe 514 may deliver fluid anywhere in the housing 110, such as at the top of the baifle 510. As one of ordinary skill in the art would understand with the benefit of the present disclosure, apparatus 500 may be modified to transfer heat out of the fluid 160, in which case, the fluid circulation path would be reversed as the cooled fluid would sink rather than rise. In such cases, multiple thermoelectric converters may be removing heat from the fluid 160 to the ambient (instead as pumping heat into the fluid) thus causing the coldest and the densest portions of the fluid 1.60 to settle in the bottom of the apparatus .110.

[0028] A person of ordinary' ski ll in the art with the benefit of the present disclosure would understand that by reversing the heat flow of some of the elements, the direction of heat pumping may be reversed to cause a cooling of the fluid .160. In. a cooling configuration., the thermal storage medium 310 may include materials that are suitable for an appropriate temperature range for cooling the fluid 160.

[0029] In some aspects, the thermoelectric converter 130 may include its own fluid loop, herein referred to as a counter-flow fluid loop. The counter-flow fluid loop may be circulated by a mechanical or electromagnetic pump system, which may be selected based on the counter-flow fluid used in the loop. The application of the counter-flow fluid is to reduce phonon conduction in thermoelements of the thermoelectric device, wherein counter-flo refers to a flow in the direction of a positive temperature gradient. The coupled fluid flow may alter the temperature and heat flow profiles of a thermoelectric device without affecting electron transport. This alteration may increase the efficiency of the counter-flow thermoelec tric devices (FLO-TEs). |ft030| The coutiter-t ow includes a fluid ia thermal communication with the thermoelements. Suitable counter-flow fluids have good heat capacity, good, thermal conductance, and low viscosity. Exemplary and non-limiting counter-flow fluids may include water, an ethylene glycol- wafer mixture, mineral oil, terpheiryl and liquid metal. The counter-flow fluid may he selected depending on the application of the thermoelectric device and other limitations, such as operating temperature ranges.

[0031] Many thermoelectric materials are selected for their high ZT values, where

ZT ^™ - and 06' ² is referred to as the power -factor of the thermoelectric material, while

Z is the thermal conductivity of the material. Thus, in order to have a high ZT, typical thermoelectric materials must have a high enough power factor to offset the thermal conductivity component. The FLO-TE is not limited by the themioelecttic figure-of-rnerit ZT, and, thus, may attain efficiencies approaching the Garnet limit.

[00321 The performance of FLO-TE devices may be understood though the effect of several dimensionless parameters on thermoelectric device performance. The first dimensional parameter is:

β ~ vc i/λ ~ mc/k where p is density, v is velocity, e is heat -capacity of the counter-flow fluid, i is length of the TE stack, λ is thermal conductivity of the TE stack, m is the mass flow rate of the counter-flow fluid and k is the thermal conductance of a stack of TE modules. When ?> 2 _? there may be significant reduction of the phonon conduction. When /J , the coefficient of performance of the FLO-TE device is given by J! 0)

AT - σ$ where J _ijC and 3ψ are the heat flux density at the cold nd hot ends of the device, T _c is the temperature at the cold end, ΔΤ is the temperature differential across the FLO-TE, σ is the electrical conductivity of the TE material, S is the Seebeck coefficient of the thermoelectric material, R is the electrical resistaace of the stack, of TE module, and I is the current through the stack of the TE module. As would be understood by a person of ordinary skill in the art with the benefit of the present disclosure, the FLO-TE material ma include a substance that is selected on the basis of power factor and that has a high thermal conductivity, since the effects of the phonon conduction are mitigated when β > 2 . For example, ytterbium a!uminate (YbAlj has a high power factor but also a .high thermal conductivity. When β> 2 , the thermal conductivity of

Y0AI3 decreases in the FLO-TE, and, now YhAh is quite suitable for use as a thermoelectric material because of i s high ZT value when β> 2 .

Typical thin-film thermoelectric materials ma include, but are not limited to, the materials listed in Table 1. Table 1

Exemplary' FLO-TE materials may include the materials in Table 1 , and, addiiionally, the high power factor materials such as, but not limited to, the materials listed in Table 2, Table 2

[0033} For small currents (/→ 0 ), the COP ?/ H»— ~ %· the Camot COP, such thai the COP may vary as a function of curretri I . Current 1 may be expressed in terms of COP as

jfl034{ An important dimensionless paranieie Θ that defines the performance of FLO-TE heat pum is the ratio of thermoelectric ( Peltier) cooling Q _c to the heat moved by the fluid ⁽ ¾, which may be expressed as:

Q SIT

Θ■■■ ^ ■■■ ······ ... '·· ΖΓ. ; (4)

Q _f mcAT β

(00351 Θ can be modified (refined) to include the effect of imperfect coupling between the fluid and the stack of TE modules, A refined parameter β _χ can be expressed as;

where e/is the effectiveness of the heat exchange between the stack of TE modules and the fluid. &x may be of particular importance .tor refrigeration applications. An exemplary set of dimension-less parameters values for operation at 40% of Carnot COP of FLO-TE heat pump are as follows;

η ^ 0 η ₍ β - ZQ r - i.s Θ, -2,0

[0036} FIG. 6 shows a schematic of a thermoelectric apparatus 600 according to one embodiment of the present disclosure. The apparatus 600 ma include a thermoelectric stack 610 of alternating thermoelements 630 and heat conducting layers 620. in some embodiments, the heat conducting layers 620 ma be optional. Each of the thermoelements 630 has a hot side and a cold side, and the thermoelements 630 are arranged in series along the thermoelectric stack 610, such that the thermoelectric stack 61.0 is in thermal communication with a hot side thermal condutor 612 and a cold side thermal conductor 614. The hot and cold side heat conductors 612, 614, may be comprised of any suitable good thermal conductor material, such as a metal or a ceramic. The hot side heat conductor 612 and the cold side heat conductor 614 may include openings 616 and 618, respectively that are configured to receive additional fluid flow loops, including additional heat exchangers to move heat into and out of the counter- flow fluid.

[0037} Each of the thermoelements 630 is configured to generate a temperature differential in response to received electrical energy. The thermoelements 630 include n-type thermoelements 632 and a p-type thermoelements 634, which ma be paired and disposed on a metal layer 636. In some embodiments, there may be multiple pairs of thermoelements 630. In some embodiments, some of the pairs 632, 634 may be segmented, that is one pair may he composed of materials configured to operate in a first temperature range and. another pair may be composed of materials to operate at a second temperature range. For example, a segmented thermoelectric- stack may be configured to operate one series of pairs (at least one per layer) in a temperature range of 250-450 degrees Celsius and another series of pairs in a temperature range of 400-650 degrees Celsius,

{0038J The heat conducting layers 620 may be disposed between the thermoelement layers 630 and provide beat transfer between thermoelement layers 630 as well as to provide thermal coupling between the thermoelements and counter-flow fluid. The heat conducting layers 630 may be a thin metal sheet. A fluid loop 640 carrying a counter- flow fluid 650 that may flow along the thermoelectric- stack 610 and be in thermal communication with the thermoelectric stack 610. The direction of the fluid flow is along the positive temperature gradient, that is against (counter) to the direction of plionon (lattice) conduction in the thermoelectric stack, which is from the cold side 614 to the hot side 61 ., thus the fluid is referred to as (he counter- flow fluid 650.

10039! The thermal communication between the counter-flow fluid 650 and the thermoelements 630 may be enhanced by disposing optional fins 660 on the heat conducting layers 620. The fins 660 may extend into the counter-flow fluid 650. In some embodiments, the beat conducting layers 620 may extend into the counter-flow fluid 650. The counter-flow fluid 650 may be any suitable heat transfer fluid, including, but not limited to. one or more of: water, ethylene giycol-water mixtures, mineral oil, terphenyl, and a liquid metal. The counter-flow fluid 650 may absorb heat while traveling from the cold side to the hot side of the thermoelements 630. Some of the heat stored in the counter-flow fluid 630 may be transferred to the hot side of the thermoelement 630 or to the heat conducting laver 620/fin 660 associated with the thermoelement 630. {0β40| FIG. 7 shows a schematic of another FLO- ^' ΓΕ based apparatus 700 according to one embodiment of the present disclosure. The apparatos 700 has many of the same elements as apparatos 600 of FIG. 6; however, apparatus 700 includes a thermoelectric stack pair 710 that is configured so that the flow path is through the center of the ihermoelements 720 of the thermoelectric stack pair 710. The thermoelectric stack pair may include a plurality of thermoelements 720, where one side of the thermoelectric stack pair 710 is made up of n-type thermoelements 720ii and the other side of the theraioelectric stack pair 710 is made up of p~fype thermoelements 720p. The thermoelements 720 may alternate with one or more constricted contacts 730 disposed between adjacent layers of thermoelements 720. Both 720p and 720» elements are disposed on thermally conducting substrates which are stacked on one another. These substrates are in direct contact with the counter-flow fluid, which flows through the center of the thermoelectric stack, thereby achieving efficient thermal coupling between the fluid and thermoelements.

(00411 FIG. 8 shows a three-dimensional perspective of another thermoelectric stack 800 for the appar tus 700, The thermoelements 720 may be stacked with alternating constricted contacts 730 in the ihennoeieeirie stack 800. The thermoelements 720 are shown as ring-type, however, this is exemplary and illustrative, as the thermoelements 720 may have other shapes, such as cubic, rectangular solids, ovoid, etc. The thermoelements 720 may be ail n-type or all p-type. if the thermoelectric stack 800 is n-type. then a complementing p-type thermoelectric stack may be paired with the thermoelectric stack 800 to enhance performance. As shown, the cylindrical shape of thermoelectric stack 800 allows counter-flow fluid to pass through and/or around the thermoelectric stack 800. The counter-flow fluid of thermoelectric stack 800 may circulate independently from the coun ter- flow fluid of a complementing thermoelectric stack. (00421 FIG. 9A shows a schematic of an air heater 900 according to one embodiment of the present disclosure. The air heater 900 may include a heat pump 910. The heat pump 910 may include a FLO-TE apparatus 700 (or a apparatus 600) that is thermal communication with a counter-flow fluid loop 920. The cold side of the apparatus 700 may be m thermal communication with a fluid loop 930 configured to move heat from the ambient into the apparatus 700. The fluid loop 930 may b in thermal communication with ambient air and receive heat from the ambient air. The hot side of the apparatus 700 may be in thermal communication with a fluid loop 940 that is configured to transport heat from the hot side of the FLO-TE apparatus into a compartment 950 or other volume to be heated. An optional heat exchanger 960 may be configured to transfer heat between, the section of the counter-flow fluid loop 920 entering the cold side of the apparatus 700 and the fluid loop 930. Anothe optional heat exchanger 970 may be configured to transfer heat between section of the counter-flow fluid loop 920 leaving the hoi side of the apparatus 700 and the fluid loop 940.

(00431 FIG. 9B shows a schematic of a water heater 8 according to one embodiment of the present disclosure. The water heater 980 may have substantially the same elements and configuration as the air heater 900; however, the water heater 980 may include a water tank 990. The fluid loop 940 may be configured to pass through at least part of the water tank 990 in order to convey heat to the water contained therein, in one embodiment, the water tank is insulated such that leakage to ambient of the thermal energ deposited m the water is reduced.

[00441 FIG. 10 shows a schematic of a cooling system 1000 according to one embodiment of the present disclosure. As one of ordinary skill in the art would understand with the benefit of the present disclosure, cooling may be achieved by reversing the heat flow direction of a heating apparatus. The cooling system 1000 may include a. heat pump 1010. which comprises a counter- flow fluid loop 1020 and a FLO- I E apparatus 700a. The first stage FLO-TE apparatus 700a may be supplemented by additional FLO-TE apparatus 700b, 700c. The number of supplementing FLO-TE apparatuses 70 b. 700c may be selected for the hea pump 101.0 based on power and temperature requirements for the heat pump .1010 as well as the parameters β and Θ _* of the FLO-TE apparatuses 700b, 700c. The heat pump 1010 may he in thermal communication with a fluid 1050 to be cooled through a heat transfer loop 1030. The heat pump 10 0 may also be in thermal communication with ambient air temperature through another heat transfer loop 040, Heat may be pumped ^' from the hot sides of the one or more apparatuses 700 to the heat transfer 1040 configured to transport heat away from the hot sides, while heat may be pumped into the cold sides of the one or more apparatuses 700 through from the fluid loop 1030 configured to transport heat from the fluid .1050. The fluid 1050 may be identical to suitable substances for the fluid 160.

|O045| The first stage apparatus 700a may cooi tiie counter-flow fluid due to the temperature differential across the apparatus 700a, which has a hot side in thermal communication with, ambient temperature. The cooled output of cold side of the apparatus 700a may be partially recirculated through the first staae apparatus 700a from cold side to hot side and partiatlv circulated though a cold side of the supplementing apparatus 700b. The, now colder counter- flow fluid entering the cold side of the apparatus 700b may be further cooled by apparatus 700b and again partially recirculated through the apparatus 700b and partially circulated to an additional supplementing apparatus 700c. The final supplementing apparatus 700c will circulated the remaining counter-flow fluid through the final supplementing apparatus 700c from cold side to hot side. The use of two supplementing apparatuses 700b, 700c is exemplary and illustrat e only, as the loop configuration and number of supplementing apparatuses may be

J'7 modified to accommodate desired efficiency, temperature differential, heat pumping, and cost parameters. A heat exchanger 1060 may be in thermal communication with the heat transfer loop 1030 and the counter-flow fluid loop 1020 to remove heat f om the fluid 1050, Additional heat exchangers 1060a, 1060b, 1060c corresponding to recirculation Loops from apparatuses 700a, 700b ₅ 700c may be used to further extract heat from the fluid 1050. A heat exchanger 1070 ma ^¬ be used to remove heat from the counter-flow fluid loop 1020 to ambient. Additional heat exchangers (not shown) in thermal communication with the heat, transfer loop 1040 and corresponding to the apparatuses 700 may be used to increase the heat pumping to ambient. It must be noted that Θ >1.0 for the cascade cooling so that each stage has enough cooling power to provide cold fluid to the next stage and its own. flow channel. The cascade design can have single-stage if the temperature differentials are sraali or multiple stages for !arge temperature differentials.

[0046) While the disclosure has been described with reference to exemplary embodiments, it will be understood that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications will be appreciated to adapt a particular instrument, situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments failing within the scope of the appended claims.