GB2621263A - Improvements relating to thermoelectric coolers, thermoelectric generators & thermoelectric assemblies - Google Patents

Abstract

A device having a first side and a second side, and comprising a first circuit and a second circuit, the first circuit comprising a first thermoelectric semiconductor, disposed so as to transfer heat when powered between the first side and the second side, and a first connection to a source of electrical power, and the second circuit comprising a second thermoelectric semiconductor, disposed so as to transfer heat when powered between the first side and the second side, and a second connection to a source of electrical power, wherein the first and second connections to a source of electrical power are controlled independently of one another.

Description

Improvements Relating to Thermoelectr° ,00iers, Thermoelectric Generators & Thermoelectric Assemblies Fielki of the Invention [1] 1h wention relates to the design, manufticiure usage, perforiiiatce and applications of thermoelectric coolers (lfills), thermoelectric generators 11111C n thermoelectric modules, and thermoelectric: assemblies.

Background of the invention

[2] The use of thermoelectric modules and assemblies to transfer heat by the Peltier method and generate power by the Seebeck method is well known for many-applications. Thermoelectric. modules and assemblies are incorporated into systems to transfer heat and/or to generate or reclaim electrical energy.

[3] Throughout the specification, the rohowing terms should be understood as defined here: a. therrnoelectrc semiconductors, or set aductors, are individi.iai chits, stacks or pieces of thermoelectric semiconductor material, such as may be incorporated into a module as defined below; b. thermoelectric modules (rEMs) are. electronic circuit ponents comprising one or more thermoelectric semiconductors, typically in a casing with electrical contact points or terminals, usually for use either in heat pumping or powergeneration; c. thermoelectric assemblies (TEAs) are devices or constructions winch incorporate one not:el:111\4s and other components to achieve a purpose, such as heat pumping or electricity generation; d. thermoelectric coolers TEMs or TEAs articularly 2.

configured,through the selection 5, COirpgnen on, for efficient use as heat pumps; c. thermoelectric generators (TEG-s) are ILEMs or -f A s particularly configured, through the selection of materials, components and so on, for efficient use in electrica power generation [4] it will be appreciated that TILCs and TECis are essentially interchangeable since any thennoelectric module. will demonstrate the 1)eltier effect when a current is applied across it, and the Seebeck effect when a temperature difference is applied across it. Nevertheless mmon for TEGs and TECs to be formed differently, for example being optimizecl for operation m different environments or for different efficiency priorities.

[5] Applying a current through a thermoelectric semiconductor create.s a flux,drawing heat from one side and radiating heat on the other. Electrical energy is converted into heat energy with tile semiconductors acting as resisters, 'Ibis is known as the Peltier effect.

[6] A temperature differential existing across a thermoelectric semi-( causes electrical eneigy to be generated in it. The greater the temperature difference between the hot and cold sides, the greater the electrical energy generation This is called the Seebeck effect, [7] Thermoefec..tric assemblies ofi.en comprise thermoelectric semiconductors or modules, thermally conducting plates, rind opuionally heat sinks at fans. A typical thermoelectric assembly arrangement consists of semiconductors placed between thermally conductive plates with the heat sinks mounted onto the plates, optionally with fans to increase the movement of the surrounding fluid such as air) across or within the heat sinks.

[8] Thermoelectric semiconductors or modules can operate tndnidually, can be grouped together in stacks, or can form part of a system. The number of semiconductors or modules in a system, the application and variation of electrical current (both in terms of magnitude and direction), and the temperature differential across modules can be controlled to provide flexible operation.

[9] Typically, a controllable power source connected to the terminals of a thermoelectric module will pass an electrical current through the semiconductors therein, which are arranged electrically in series, to transfer heat across the. thermoelectric module, resulting in a hot side and a cold side. Reversing the polarity of the electric current changes the direction of the heat transfer and reverses the hot side and the cold side.

[10] TECs are solid state he-at pumps having thermally conductive plates or heat sinks exposed to the hot and cold sides. Electrical energy is applied, to transfer heat from the cold side to the hot side. When the applied current is switched off, the heat will return from the hot side to the cold side by thermal conduction within the module or assembly:, until thermal equilibrium is achiev-ed across the device, [11] Furthermore, as the temperature difference increases across a A, it becomes less efficient as a heat pump and the heat transfer stows until the device, itself heats up and transfers heat back to the cold side.

[12] Because the. hot and cold sides are close together, and thermally coupled, it is difficult to thermally insulate them in order to stop or reduce the reverse. heat transfer. A solution is needed to overcome these disadvantages of the prior art.

sum man, of the Invention [13] The invention provides for a multi-circuit............... or a lEA nth a plurality of individually controlled and powered semiconductors or TELMs.

[14] In a first aspect, the invention relates to a TRRE comprising at least two circuits, each circuit including at least one semiconductor. Hach circuit is ctintrolled independently of the other. 'the circuits can be controlled independently to apply a current across their respective semiconductors in either direction, or not to apply a current. The provision of at least two individually controlled circuits of semiconductors in the same module not only allows heat transfer in either direction with the individual circuits acting in concert (when all circuits are controlled to annly a current of the. same polarity across their respective semiconductors), but also allows for the individual circuits to act independently against each other, in order to reduce the unwanted return of heat across the Thli'A due to the laws of thermodynamics, as will be explained in 'more detail below.

[15] For example, applying a current of the same polarity to both circuits of a two-circuit TF.NT accordiiw to the first aspect of the invention, creates a hot side and a cold side of the TEM, with heat being transferred from the cold side to the hot side by the semiconductors of both circuits, working in conceit. If, when a condition is reached at which the current to the Trim would typically be stopped or reduced, for exam.ple when a desired heat difference has been achieved, or a limit to efficiency has been reached, the supply of current to the semiconductors of only one of the circuits is stopped or reduced, the semiconductors of the other circuit (Which are still powered, perhaps at a reduced power level) will counteract the natural heat transfer from the hot side to cold, preventing an unwanted return to thermal equilibrium without necessarily continuing to increase the temperature difference between the hot and cold sides. It \\Till be clear that this increases the flexibility of control over prior art TEIVISs.

10161 Within the TENT of this example, a state is reached in which the Process of reverse heat transfer (hot to cold) and powered heat transfer coat: to Ii ot) cancel one another OIn, so there t change to the temperature difference across the device.

10171 When die desired temperature difference is achieved across theft:ENT, the current is withdrawn or reduced across the. semiconductors of one circuit, but h orcer to avotd heat return tng across di a TEM and lost the. desired temperature. ciiffdrencc the. current is maintained. (perhaps at a reduced i level) to the other ciicult" creating thermal balance across the device resisting any net heat transfer from one side to the other.

[018] The natural heat transkr counteracted by the still-active circuit will generate a current in the now inactive circuit. This can be stored in an energy storage system such as a battery or a supercapacitor. Alternatively" a suitable, switchable electrical connection between the circuits can be pnivickd such that the energy generated in. the inactive circuit contributes to the continued nowe u of the active circuit.

[019] Within a semiconductors same rnaten lvi of this first aspect invention, t he the separate circuits can be n. de of substantially the circuits can have 11c talts and design. Alternatively, different circuits of the device can be made of different materials, components and designs in order to achieve a wider variety of performances characteristics. For example, a 'TEM could incorporate at least one circuit of emiconducto for more efficient use in TIlfs and at least one circuit ot stmic.onc!uctors selected. for more efficient use in TEGs, wherein the TEC semiconductors have higher internal resistances for greater heat transfer, while the TEC semiconductors have lower resistances for greater current generation. Such a TEM would x.

enable individual circuits to work together or independently, to maximize the efficiency of heat transfer, power generation, and/or the maintenance of desired temperature differences. Other devices according to this first aspect of the invention could comprise circuits whic a each comprise a niixture of TLC semiconductors and TEG semiconductors.

[20] Incorporating separate circuits of TEC semiconducu)rs and TEx.; semiconductors within the same TEM also allows for efficient electricity generation in the circuit when a current is applied only to the Tfl(l. circuit.

It -will be understood that power can be generated in the presence of a heat difference across die module when neither circuit is powered.

[21] The particular characteristics of a TEM according to this aspect: of the invention will be selected according to the intended function. Control systems for particular TEMs will be configured to achieve multiple performance targets, with circuits acting together or in opposition, to transfer heat, to counter any unwanted transfer of heat, and in generate power.

[22] -In a second aspect of the invention, a TEA comprises two or more individually controlled 't liNfs, operable either in concert to transfer heat M desired direction, or in opposition to limit unwanted movement of heat and/or generate electrical energy.

[23] For example, in s first mode, both TENts act to transfer heat from a cold side to a hot side of the TEA. Once a particular temperature gradient exists across the TEA and it is desirable to slow or stop further heat transfer and limit any reverse heat movement, in a stoond imxie one cat" the Ti Ms is switched off (or its power is reduced) while the other TEM continues to be powered to the degree necessary to match the natural reverse heat across the TEA, creating a thermal 'balance' across the assembly, preventing the net movement of heat through the TEA and maintaining the temperature difference between the hot and cold sides of the device with finer control.

[24] Individually control mg and powering multiple TENts \vithin the assembly allows for a greater range of operations and increased flexibility. Another example mode of op:it:art:in is both modules being switched off in the 1)1CLSCnce of a heat differCIICC: :ICCOSS the assembly, in iiyhtch rase both modules WE ll venerate nower.

[25] incorporating separate modules within the. same assembly also allows for efficient electricity generation in one module when a current is applied only to the other. It win be understood that power can be. generated in the presence of a heat difference across the module when neither circuit is powered.

[26] In a further embodiiinent of the second aspect, a ILL module is positioned on the cold side of the TEA and a TEC,: module is positioned on the hot side, with both modules controlled separately and powered from either a single common power source or from separate respective power sources An electric current applied to either or both modules will absorb heat on the cold side and transfer heat towards the hot side, When, for example, a performance target is achieved and the current is stopped. to the TEG module, any reverse heat transfer through said TEG module will generate an electrical current. This current can be used to contribute to the powering of the TEL device; which continues to be powered so as to reduce the net reverse heat transfer across the assembly, A suitable, switchable electrical connection between the modules can be provided to facilitate this. The electricity generated in the TEL module could alternatively be stored in a power storage device such as a battery or super capacitor for later use. it will be clear that it could equally be put to any other conventional use. The modules in the TEA could., alternatively, be identical, or a combination of other different configurations.

[27] The greater the temperature gradient across the TEA, tie greater the thermal conduction rate and current generation in the 'LEG module.

[28] In summary, having multiple circuits of semiconductors within thermoelectric modules, or individually controlled thermoelectric modules within a thermoelectric assembly, allows for more flexible operation, finer control and less c.-nergy wastage. This may 'include a staged reduction of Powered heat pumping, and a smoother transi6ort to a holding position to maintain hot and cold side. temperatures, and simultaneous power :tenet-au [29] hor exiiinple, in conventional may be reached during a heat pumping operation when the VA approaches its performance li]mits5 wherein the temperature difference across the assembly is so great that ft tither heat pumping is difficult, in such a siination, the 'lltt,ts within ihe assembly heat at due to ternai resistance, and start counterpia:ta;CtiVek Ii0C":-.1,1t; the cold side he prior art response is to simply switch off the TEA, but this allows heat to transi.er naturally from the not side to the cold sujic., wasting the energy used to VUllip ff) the I, CS phiCC r le Vefliiili allows lot a stepping down of the power supplied to etiear. punw as the teniperatuire difference across Me assembh uacia.ases, while preventing the net reverse transfer of hea ata OS?, the assembly with the reduced power supply to one circuit or module, at the same Little. as ICC] Some of energy spent lac( the unpowertai module or circuit

Statement of invention

10301 A first facet of the invention provides a device having a first side and a second side, and comprising a first circuit and a second circuit, the first circuit comprising a first thermoelectric semiconductor, disposed so as to transfer heat when powered between the first side and the second side, and a first controllable connection to a source of electrical power, and the second circuit comprising a second thermoelectric semiconductor, disposed so as to transfer heat when powered between the first side and the second side, and a second controllable connection to a source of electrical power, wherein the first and second connections to a source of electrical power are controlled independently of one another. A switchable electrical connection is provided between the first circuit and the second circuit, such that electrical energy generated by the thermoelectric semiconductor of one circuit can be switchably supplied to the other circuit.

[031] The device may be a thennoelectric module. Alternatively, the device may be a thermoelectric assembly, wherein the first circuit is contained within a first thermoelectric module, and the second circuit is contained within a second thermoelectric module.

[032] The first thermoelectric semiconductor may be configured as a thermoelectric cooler. The second thermoelectric semiconductor may be configured as a thermoelectric generator.

[033] A second facet of the invention provides a method of controlling a device according to the first facet of the invention, comprising the steps of: a. Controlling the first and second connections to a supply of electrical power to supply electrical power of a first polarity respectively to the first and second circuits, such that the first and second thermoelectric semiconductors pump heat from the first side to the second side; b. When a predetermined thermal or efficiency condition is reached, stopping the electrical power to the first circuit.

[034] The method may comprise the further step of: c. When the predetermined thermal or efficiency condition is reached, reducing the supply of power to the second circuit.

[35] The method may also comprise the further step of: d. Connecting the second circuit to the first circuit so as to supply power generated in the first circuit to the second circuit.

[36] The predetermined thermal or efficiency condition may one of: a predetermined temperature difference between the first side and the second side; an absolute temperature target on at least one side.

Brief Description of the Drawings

[37] The ivention will be descnbecl, by way of example only. with reference to particular cmjDodtmcn ts depicted or represen.te.d in the following drawings: [38] Figure I depicts an example of mcircuit thermoelectric moduje.

[39] Fgire 2 depicts a duai.--circuit thermoelectric module.

[40] Figure 3 depicts a thermoelectric assembly incorporating two thermoelecttic modules, heat sinks and fans.

Detailed Description

[41] ligures 1 and 2 depict a dual circuit example of the lrst aspect of the InventIon, M which thermoelectric module 10 incorporates a plurality ot semiconductors 12 connected in two series circuits A, B, wherein adjacent semiconductors 12 are connected by connecting plates 16, and each circuit A, B is connected to a source of electrical power by means of contacts or terminals 18. The semiconductors can be configured for optimal Performance as either TECds or a mixture of the two. The semiconductors 12 are sandwiched between thermally conductive ceramic plates 14. The. two circuits A, B are controlled and powered independently.

They may ii iergy st'jrae systerris such as battei Cony@ s pri circuitry will also be provided, but this will not be described since it will be clear to the skilled person that it is incjdental to the ation.

[42] fiigur.icts an t tnbocli1neiit of the second aspect o ill Veit 17i DTI. A thermoelectric 1-110 1 1 incorporates TEMs 26, 28, each comprising se.niiconductor devices 12, ceramic plates 14, interconnects 16 and electric circuit connections 18. the first module 26 is proximate \vita will be a cold side in use and the second module 28 is proximate what will be the hot side in use. The modules are sandwiched between heat sinks 20 and fans 22. Other conventional heat transfer improving means will be apparent to the skilled person, and can be used with the invention instead of or as well as heat sinks 20 and fans 22.

[43] A spacer inot shown) may optionally be situated between the 'BEMs 26" 28" rnade of sonle suitable thei:tnially conductive material_ [44] Optionally, the first ThM 26 can be a module second rEm 28 can be a TEC; module. This is p advantageous when the one direction, as has device only ordinarily be used to pump i been explained above. Other configurations of semiconductors 12 and modules 26, 28 are also contemplated, depending on the intended function.

[45] In the Figures, thermodynamic modules and assemblies 10, 11 are depicted individually. When purring the invention into practice, both modules and assemblies might be used individually or in groups, or different types might be used in cooperation.

[46] As descnied above, the dual circuit thermoelectric module two individually controlled circuits A. B. where each c separate res iectiv( ctors 12 linked by ntercorinects 16 and electrical circuit connections 18. The dual circuits can be controlled and were(' * Indivi ally t-t riove h one or other dire * logetlier in concert Hasler:- -at in one or other direction; * With only one circuit powered at a time; * Au different respective power levels; * With neither it powered (in order to generate power iti both circuits due to the temperature difference across the module).

[47] It will be appreciated that the same principles can be extended to embodiments with more than two circuits.

[48] As described above, therrnoeiectnc assemblies ii. can comprise multiple thermoelectric modules, controllable individually. The modules can be controlled and powered: * individually to move heat in one or other direction; * her incect EratiSfern inc or other direction; * 's}Vith only one module powered at ti * At different respectlevels; * With neither module powered to generate a both due to the tel -e -e across the assembly) [049] embodiment of the first aspect-hasbeen described with twe circuits. The pnncipl es of the mvntion are euaTly applicable to m with more than two circuits, wnerein each of the circuits is controlled and powered individirally. For example, three circuits may be provided,or four circuits. there is no upper limit to the number of circuits in the first aspect of the invention, [50] The individual powering and controlling of the circuits in the fir

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aspect of t ie nvention may be perfomaed hya single control system and/or Dower te connected to each circuit. Alternatively, each circuit may aave an i cliviclual control system and/or power source. In modules with more than two circuits, some circuits may he controlled together in groups, for example independently or operating counter to other groups of circuits, [51] The circuits depicted in Figure 2 are disposed on a substrate interieaved spiral configuration. This may have advantages in terms of the even spread of semiconductors from each c icut, but it is not the only suitable confituration. The circuits may be arranged m any suitable configuration with respect to the. module and each other, depending on the. intended purpose.

[52] The embodiment of the second aspect has been described with two modules. The principles of the invention are equally a-pplicable to assemblies with more than two modules, wherein each of the modules is controlled and powered individualiy. For example. three modules may be otovidect, or four module 1-no upper limit te the numbe.r modules in the second aspect of the invention.

[53] The individual powering and controlling nodules in the second aspect of ihe invention may be performed by a smgle cuntrel system and/or power Source connected to each module_ At each module may have an individual control system and/or power source. In assemblie rta note chari two 7modules may.e controlled together tai groups; for example independently or operating counter to ocher groups of modules.

[54] The modules depicted in Figure 3 are disposed in a layered sand ntigurabon.may have advantages a term conduction of heat through the assembly, one module at a time, but the only suitable configuration. The modules may be arranged any suitable configuration with respect to die assembly and each other, depending on the intended purpose.

[55] The invention has been described with reference to a number of preferred embodiments. The embodiments enable the skilled reader to make the invention, but do not limit the scope of the invention. The scope of the invention is defined by the claims.

Claims (9)

1. Claims 1. A device having a first side and a second side, and comprising a first circuit and a second circuit, the first circuit comprising a first thermoelectric semiconductor, disposed so as to transfer heat when powered between the first side and the second side, and a first controllable connection to a source of electrical power, and the second circuit comprising a second thermoelectric semiconductor, disposed so as to transfer heat when powered between the first side and the second side, and a second controllable connection to a source of electrical power, wherein the first and second connections to a source of electrical power are controlled independently of one another, and a switchable electrical connection is provided between the first circuit and the second circuit, such that electrical energy generated by the thermoelectric semiconductor of one circuit can be switchably supplied to the other circuit.
2. 2. A device according to claim 1 wherein the device is a thermoelectric module.
3. 3. A device according to claim 1 wherein the device is a thermoelectric assembly and the first circuit is contained within a first thermoelectric module, and the second circuit is contained within a second thermoelectric module.
4. 4. A device according to any preceding claim, wherein the first thermoelectric semiconductor is configured as a thermoelectric cooler.
5. 5. A device according to any preceding claim, wherein the second thermoelectric semiconductor is configured as a thermoelectric generator.
6. 6. A method of controlling a device according to any one of claims 1 to 6, comprising the steps of: a. Controlling the first and second connections to a supply of electrical power to supply electrical power of a first polarity respectively to the first and second circuits, such that the first and second then loelectric semiconductors pump heat from the first side to the second side; b. When a predetermined thermal or efficiency condition is reached, stopping the electrical power to the first circuit.
7. 7. A method of controlling a device according to claim 7 comprising the further step of: c. When the predetermined thermal or efficiency condition is reached, reducing the supply of power to the second circuit.
8. 8. A method of controlling a device according to claim 8 comprising the further step of: d. Connecting the second circuit to the first circuit so as to supply power generated in the first circuit to the second circuit.
9. 9. A method of controlling a device according to any one of claims 7 to 9, wherein the predetermined thermal or efficiency condition is one of: a predetermined temperature difference between the first side and the second side; an absolute temperature target on at least one side.