Improvements concerning contact bridges of thermoelectric components, use of a thermoelectric component, system for hot water preparation and thermocouple

Abstract

Thermoelectric component with an electrically and thermally insulating substrate (1) arranged between a hot side and a cold side, extending in a substrate plane, with at least two thermolegs (4n, 4p) made of thermoelectrically active material, which extend through the substrate from the hot side to the cold side, and which are electrically contacted with one another on one of the two sides by means of a contact bridge (5) and thus form a thermocouple, characterized by that the contact bridge has a surface on its side facing the hot side and / or the cold side, the area of which is larger than the area of a comparison surface lying in the substrate plane, which is formed by an imaginary projection of the contact bridge onto the substrate plane and, that the contact bridge between the two thermocouple legs extends along a path (W) which is longer than the distance between the two thermocouple legs measured in the substrate plane, wherein the contact bridge forms a loop, bump or dent (8) which is facing the substrate or facing away from the substrate and is connected on the inside with is provided with hollow grooves (10).

Description

[0001] The invention relates to a thermoelectric component according to claim 1, as well as to its use according to claim 10, in particular in a system for preparing hot water according to claim 12. Furthermore, the invention relates to a thermocouple according to claim 13.

[0002] A thermoelectric component is an energy converter that converts thermal energy into electrical energy using the thermoelectric effect described by Peltier and Seebeck. Since the thermoelectric effect is reversible, any thermoelectric component can also be used to convert electrical energy into thermal energy: so-called Peltier elements serve to cool or heat objects by consuming electrical power. Peltier elements are therefore also considered thermoelectric components within the meaning of the invention. Thermoelectric components that convert thermal energy into electrical energy are often referred to as thermoelectric generators (TEGs).

[0003] Examples and introductions to thermoelectric components can be found at: • Thermoelectrics Handbook, DM Rowe (ed.), Taylor&Francis, 2006, ISBN 978-0-8493-2264-8 • Thermoelectrics Goes Automotive, D. Jänsch (ed.), expert verlag GmbH, 2011, ISBN 978-3-8169-3064-8; • JP 2006 - 032 850 A; • EP 0 773 592 A2; • US 6 872 879 B1; • US 2005 / 0 112 872 A1; • DE 102009025032A1; • US 2003 / 0 102 554 A1; • EP 0 117 743 A2; • WO 2011 / 009 935 A1; • JP 2004 - 265 988 A

[0004] A simple and economically advantageous process for the production of thermoelectric components is described in WO 2013 / 144 106 A2.

[0005] A variety of thermoelectrically active materials have been described in the prior art. For example, alloys from the class of semiconducting bismuth tellurides (particularly with additional amounts of selenium and / or antimony) are suitable for commercial use. These alloys can be used to construct a thermocouple, doped with p-type and n-type conductivity.

[0006] Other thermoelectrically active material classes include: semi-Heusler materials, various silicides (especially magnesium and iron), various tellurides (lead, tin, lanthanum, antimony, and silver), various antimonides (zinc, cerium, iron, ytterbium, manganese, cobalt, and bismuth; sometimes also referred to as Zintl phases), TAGS, silicon germanides, and clathrates (especially those based on germanium). In addition to these semiconductor materials, thermoelectric components can also be manufactured from combinations of most common metals, as is the case with commercially available thermocouples for temperature measurement, such as Ni-CrNi. However, the achievable figures of merit (thermoelectric "efficiencies") are significantly lower than those of the aforementioned semiconductor materials.

[0007] Technically implemented thermoelectric components typically have a multitude of closely spaced thermocouple legs, consisting of alternating n- and p-doped semiconductor material. To form active thermocouples, these legs must be electrically connected to each other, typically resulting in a series circuit of alternating n- and p-doped semiconductor legs. The electrical connection between any two semiconductor legs to form a thermocouple is called a contact bridge.

[0008] High electrical and thermal conductivity in contact bridges is generally ensured primarily by the choice of materials, so copper, silver, and aluminum, or special alloys, are preferred. Most current TE components use semiconductors that are only suitable for temperatures up to approximately 250 °C, so common tin- or silver-based solders are usually used for the electrical and mechanical connection of the TE legs and contact bridge. The outer coating of the TE component is usually formed by a coating layer made of electrically insulating ceramic materials or polymers.

[0009] A conventional TE component consists of various layers of mechanically bonded materials, which often have very different thermal expansion coefficients. In addition, a high temperature gradient exists perpendicular to this layer structure during operation. All of this leads to high thermomechanical stresses in and at the joints between the individual materials. To counteract mechanical damage, including cracking, delamination, and / or deformation, either sufficiently elastic intermediate layers must be provided or the components must be dimensioned sufficiently solid to withstand this.In some cases, the outermost layers on both sides of a TE component, which are intended to ensure external electrical insulation and protect the internal current-carrying components from the effects of substances, are not firmly connected to the underlying contact bridges, but are simply placed on top of them or connected to them via elastic adhesive layers or thermal pastes. This prevents thermomechanical shear stresses from being transferred between these insulation layers (usually made of ceramic materials with low thermal expansion coefficients) and the underlying contact bridges (made of highly electrically conductive metals, usually with very high thermal expansion coefficients), thus preventing harmful mechanical effects. However, this purely physical, adhesive, or paste contact significantly impairs heat transfer between the exterior of the TE component and its internal semiconductor structures.Thus, when the TE component is used as a thermoelectric generator, part of the externally available temperature gradient is lost for conversion in the thermoelectrically active inner part, thus reducing efficiency and the achievable electrical output. When used as a Peltier element, the performance index decreases analogously, resulting in a lower heat flow from the cold to the hot side for the same electrical output.

[0010] A special design of thermoelectric components of the aforementioned type is known from WO 2008 / 061823 A2. A special feature of these components is that their thermocouple legs extend through a so-called substrate, which thus separates the hot side from the cold side. This allows for particularly cost-effective production. If the substrate also has good thermal insulation, such a thermoelectric component can also exhibit improved electrical efficiency under the same hot and cold side conditions compared to conventional thermoelectric components. However, this thermoelectric component also has the disadvantages described above.

[0011] In light of this prior art, the object of the invention is to provide a thermoelectric component that avoids such disadvantages. In particular, problems with thermomechanical stresses between the different materials are to be solved and the heat transfer between the TE component and the heat transfer media is to be improved.

[0012] To solve this problem, the contact bridge in the component according to the invention is designed as follows: Instead of a flat and thus as short as possible connection between the contact points of two adjacent TE legs, the contact bridge is preferably designed to be cranked, ie it preferably has at least one fold or curvature, so that the contact bridge not only extends planar orthogonally to the macroscopic heat flow direction through the TE component, but also has a preferably variable extension in the direction of the heat flow.

[0013] The contact bridge has a surface on its side facing the hot side and / or the cold side whose surface area is larger than the surface area of a comparison surface lying in the substrate plane, which is formed by an imaginary (perpendicular) projection of the contact bridge onto the substrate plane. According to the invention, the contact bridge is designed such that it extends between the contact surfaces of both associated thermocouple legs along a path that is longer than the shortest possible path between these two contact surfaces. The contact bridge forms a loop, bump, or indentation that faces the substrate or faces away from it. The contact bridge is provided with concave grooves on the inside of the bend.

[0014] In connection with thermomechanical stresses, this has a similar effect to the compensating bends commonly used in pipeline construction and thus reduces shear stresses in particular in the joints between contact bridges and thermolegs.

[0015] Due to the folding / bending / bulging, the contact bridges no longer necessarily form a flat surface orthogonal to the direction of the heat flow through the thermoelectric component. Depending on the embodiment, the regions of the contact bridges according to the invention that are located between the connection zones to the TE legs can protrude out of or into this imaginary plane (see figures). The former is of course hardly compatible with the structure of a conventional TE component, in which electrically insulating plates / layers rest on the contact bridges and form the outer shell of the components. Second, in an otherwise conventional design, the contact bridges must have sufficient free space to expand "inwards", i.e. between the TE legs. In a TE component without a substrate fixing the TE legs, this is usually intrinsic.In a TE component with a substrate that secures the TE legs, there should be a sufficiently large free space between the outer surface of the substrate and the contact bridge. This is most easily achieved by having the TE legs, including the frontal diffusion barrier layer and electrical connection layer (e.g., solder), protrude from the substrate plane. Alternatively, the contact bridge itself should be designed, for example, in an M-shape in side section, with legs parallel to the heat flow direction, which establish contact with the TE legs.

[0016] If the fold / bend / bulge of the contact bridges protrudes from the TE legs, these contact bridges have an enlarged contact area for heat transfer compared to simple conventional planar contact bridges. This creates a structured outer surface on the outside of the TE component instead of a smooth one, similar to finned heat exchanger structures. When a heat transfer medium (fluid) flows over it, this can also potentially create turbulence zones. Increased contact area and the generation of turbulence significantly increase the heat transfer coefficient between the heat transfer medium and the contact bridges. This reduces the thermal resistance of the system consisting of heat transfer media and TE component, and the electrical efficiency of the TE component can increase. However, it is then important that, if necessary,Chemical or physical attacks and / or undesirable effects on the components of the TE component must be avoided by external protective coatings and / or seals. The electrical resistances in the contact bridges designed according to the invention must also be kept low. This may require compensating for a longer current flow path by using larger material cross-sections or selecting materials with even lower specific electrical resistances.

[0017] The design described here achieves the following advantages: a) Lower thermal resistance of the TE component between the hot and cold sides, thus achieving optimal electrical efficiency and maximum electrical power. b) Better heat transfer between heat transfer media and TE component in case the contact bridges are designed as fins. c) Avoiding damage to the TE component due to thermomechanical stresses.

[0018] The general inventive idea and accordingly the subject matter of the invention is a thermoelectric component with an electrically and thermally insulating substrate arranged between a hot side and a cold side, with at least two thermocouple legs made of thermoelectrically active material, which extend through the substrate from the hot side to the cold side, and which are electrically contacted with one another on one of the two sides by means of a contact bridge and thus form a thermocouple, which is characterized in that the contact bridge has, on its side facing the hot side and / or the cold side, an (enlarged) surface, the area of which is larger than the area of a comparison surface lying in the substrate plane, which is formed by an imaginary (vertical) projection of the contact bridge onto the substrate plane (or in other words: the area of the surface,The area formed by an imaginary outline of the contact bridge on the substrate plane must be smaller than the area formed by the side of the contact bridge surface facing the hot side and / or the cold side, assuming that this surface lies in a plane. The contact bridge extends between the two thermocouple legs along a path that is longer than the distance between the two thermocouple legs measured along the substrate. The contact bridge forms a loop, bump, or dent that faces the substrate or faces away from it. The contact bridge is provided with concave grooves on the inside of the bend.

[0019] Another important basic idea of the invention is to provide the contact bridge with a triple function: the electrical contacting of the thermocouple legs to form the thermocouple, the compensation of thermomechanical stresses, and the thermal coupling of fluid heat transfer media and thermocouple legs. The thermoelectric component according to the invention can therefore also be considered a thermoelectrically active heat exchanger, which, in contrast to systems with conventional thermoelectric components, already has intrinsic heat exchanger structures, whereas in conventional systems these are usually contained in adjacent, separate components that still need to be effectively thermally connected.

[0020] Conversely, the thermoelectric component can be used as a heat pump without moving parts, which transfers heat energy from the cold side to the hot side while absorbing electrical power. In this way, the cold side can be cooled or the hot side heated.

[0021] The thermoelectric component has a contact bridge that is not flat and has a raised portion that protrudes from the plane, which can face toward or away from the substrate. Components according to the invention have a contact bridge that forms a loop, dent, or bulge, which can face toward or away from the substrate. Such a contact bridge can be produced particularly easily using forming technology. The loop can also be formed parallel to the substrate plane. The contact bridge is preferably designed to be offset or curved.

[0022] To increase its flexibility, the contact bridge is provided with concave grooves on the inside of the bend. Additional concave grooves on the inside of the bends can facilitate the manufacturing (bending / folding) of the contact bridges and further improve the bendability / elasticity of the component when installed. Concave grooves in this configuration are easy to manufacture. However, they increase the susceptibility to corrosion and complicate the application of a continuous protective coating.

[0023] The thermoelectric component according to the invention can have a contact bridge in which the surface of the contact bridge has at least partially a structured, preferably three-dimensionally structured surface, wherein the structuring is preferably formed from elevations and / or depressions. If the contact bridge is designed as a rib, it preferably has an at least partially, preferably three-dimensionally structured surface to further improve heat transfer between the heat transfer fluid and the contact bridge. A three-dimensionally structured surface can be achieved most simply by roughening.

[0024] Thermoelectric components according to the invention have a contact bridge that extends between the two thermocouple legs along a path that corresponds to or is longer than the distance between the two thermocouple legs measured in the substrate plane, and preferably has at least one comb, preferably at least one comb pointing away from the substrate plane. The contact bridge preferably has at least one comb extending along the path and pointing away from the substrate plane. Thermoelectric components according to the invention preferably have a contact bridge that advantageously has a U-, M-, I-, T-, or double-T-shaped cross-section, preferably a U-shaped cross-section, wherein preferably at least one of the legs pointing away from the substrate plane forms a comb.In the case of a U-shaped cross-section, one or both, preferably both, of the legs of the U, which preferably point away from the substrate plane, can (each) form a comb.

[0025] It can be advantageous if the contact bridge partially decouples the functions of "electrical conduction" and "thermal conduction" / "heat coupling" through spot or line welding (or other material connection). This allows for a shorter path for the current.

[0026] In the thermoelectric component according to the invention, the substrate material can be selected from a wide variety of suitable materials. Preferred materials are described, for example, in WO 2013 / 144 106 A2. The substrate can be planar or flat, kinked, curved, or bent. The substrate can be inflexible or flexible or bendable. If the substrate is flexible or bendable, the thermoelectric component according to the invention can be easily adapted to the structural conditions. Preferred thermoelectric components according to the invention are those in which the substrate is symmetrical with respect to the substrate plane and is preferably planar or flat, kinked, curved, or bent.

[0027] It may be advantageous if the thermoelectric component according to the invention has a cladding layer that is preferably arranged substantially parallel to the substrate and preferably touches the contact bridges at least at certain points. The cladding layer is particularly preferably designed to define a space extending between the cladding layer and the substrate, through which the contact bridge runs. It may be advantageous if this space is filled with a stationary or flowing heat transfer fluid.

[0028] In addition to or instead of the cladding layer, the thermoelectric component according to the invention can be provided with a coating that electrically insulates the contact bridges and / or the substrate, preferably the contact bridge and the substrate, particularly preferably the entire component (with the exception of the electrical supply and discharge lines), and is preferably resistant to the media present.

[0029] The enveloping layer and / or the coating can, for example, contain or consist of a thermoplastic polymer, such as polyethylene, polypropylene, polyamide, or aluminum nitride, or be based on an alkoxysilane-containing composition, such as tetraethoxysilane-containing compositions. The enveloping layer is preferably formed by a component made of a plastic. The coating can be formed, for example, by a lacquer, a potting compound, a film, or a deposit.

[0030] The thermoelectric components according to the invention can be provided with the encapsulation layer and / or a coating using known technical methods. The encapsulation layer can be applied, in particular, by techniques such as pressing, gluing, or foil deep-drawing. The coating can be applied, for example, by spraying, dipping, or deposition.

[0031] A particular embodiment of the invention provides a covering layer arranged substantially parallel to the substrate, which contacts the contact bridge at its bridgeheads, such that a space extending between the covering layer and the substrate is defined, through which the contact bridge extends and which can be filled with a heat transfer fluid that is stationary or flows through an external drive (e.g., a pump). In such a configuration, the heat transfer fluid is surrounded or flowed around the contact bridge, so that the heat exchange between the fluid and the thermocouple leg is particularly effective.

[0032] The thermoelectric components according to the invention can be manufactured as described in the prior art. The thermoelectric components according to the invention are preferably manufactured as described in WO 2013 / 144 106 A2, to which reference is made in particular with regard to the materials used and the manufacturing processes for the individual components, as well as the assembly to form the thermoelectric component.

[0033] The heat transfer fluid is particularly stationary when heat from outside the cladding layer needs to be coupled into the contact bridge. The heat transfer fluid's sole task here is to achieve a lower thermal resistance in the free space between the substrate, cladding layer, and contact bridges than that which would result if the free space were filled only with gas (e.g., air). This reduces the thermal resistance of the entire component between the hot and cold sides, which can increase electrical efficiency. This stationary fluid can therefore also be a curing or hardened polymer or a potting compound, which merely requires a certain viscosity or flowability for introduction into the previously free space.

[0034] However, heat can also be actively transported to the contact bridges via the heat transfer fluid. In this case, a flowing heat transfer fluid is selected, driven by an external drive (e.g., a pump).

[0035] The preferred heat transfer fluids are liquid or gaseous media with a high specific heat capacity, such as water, alcohol, hydrocarbon-based oils, or silicone. Air can also be used as a heat transfer fluid. While air does not have a high heat capacity, it is often readily available, inexpensive, and clean, so the disadvantage of its low heat capacity can be offset.

[0036] The thermoelectric component can be used as a thermoelectric generator, i.e., to convert heat flow from the hot side to the cold side into electrical power. The voltage is tapped at the legs. In this way, thermal energy can be converted into electrical energy.

[0037] In particular, the TEG according to the invention can be used to exploit low-calorific heat sources such as groundwater, soil heat, exhaust air, exhaust gases, wastewater, or warm cooling water. Such heat flows are common in nature and in technology and, due to their low temperature level, have so far been difficult to exploit economically. Thermoelectric utilization is possible with the present invention.

[0038] Conversely, the thermoelectric component can be used to convert electrical power into a heat flow from the cold side to the hot side, i.e. as a heat pump.

[0039] The heat pump is particularly suitable for domestic hot water preparation. Accordingly, the water to be heated is arranged on the hot side and ambient air on the cold side. The water can then be heated electrically in an energy-efficient manner. The invention therefore also relates to a system for hot water preparation that includes a thermoelectric component according to the invention. Conversely, a thermoelectric component according to the invention used in a system for hot water preparation is also the subject of the invention.

[0040] If available, the low-calorie heat sources mentioned above can also be used to heat water instead of ambient air.

[0041] Since the special design of the contact bridge is essential to the invention, a thermocouple formed from two thermocouple legs made of thermoelectrically active material that are electrically contacted with one another by means of a contact bridge and extend at a distance from one another is also the subject of the invention, provided that the contact bridge is designed according to the invention.

[0042] The invention will now be explained in more detail using exemplary embodiments. These are shown in the following: Fig. 1: first embodiment not according to the invention with slightly cranked contact bridge; Fig. 2: second embodiment not according to the invention with strongly cranked contact bridge; Fig. 3: embodiment according to the invention, as Fig. 2, but with coves; Fig. 4: fourth embodiment not according to the invention with inwardly looped contact bridge, additionally with outer enveloping layer; Fig. 5: non-inventive embodiment, as Fig. 4, but with reinforced bridgehead; Fig. 6: non-inventive embodiment, as Fig. 5, but with contact bridge looped outwards; Fig. 7: Single thermocouple with cranked contact bridge not according to the invention.

[0043] The first embodiment of a thermoelectric component according to the invention is shown in Fig. 1. It comprises a substrate 1 made of an electrically and thermally insulating material, such as a ceramic, a polymer, or a composite material. The substrate 1 is a substantially flat structure, in the simplest case a flat plate. The substrate 1 separates a hot side 2 from a cold side 3 of the thermoelectric component.

[0044] The substrate can also be curved. The flat section of the substrate shown in the figures can then be considered an infinitesimal part of a curved substrate, so that the geometric considerations described here can also be applied to curved substrates.

[0045] Two thermocouple legs 4n, 4p are embedded in the substrate 1. The first, 4n, consists of an n-doped thermoelectrically active semiconductor material such as bismuth telluride. The second, 4p, consists of the corresponding p-doped semiconductor material. Both thermocouple legs 4n, 4p extend perpendicular to the plane of the substrate 1, from the hot side 2 to the cold side 3.

[0046] On the hot side 2, the two thermocouple legs 4n, 4p are electrically connected to form a thermocouple. This is achieved via a contact bridge 5 made of an electrically and thermally conductive material such as silver, copper, or aluminum. The contact bridge 5 is soldered to the thermocouple legs 4n, 4p (but could also be attached in another way). Between the solder 6 and the thermocouple legs 4n, 4p there is a barrier layer 7, which can be made of nickel, for example, and prevents the solder 6 from diffusing into the semiconductor material.

[0047] The contact bridge 5 extends between the two thermocouple legs 4n, 4p along a path W that is longer than the distance d between the two thermocouple legs 4n, 4p measured along the substrate 1. This is due to a loop 8 of the contact bridge 5, with which the contact bridge 5 points away from the substrate 1. The extension of the contact bridge 5 by its loop 8 results in a larger surface area of the contact bridge 5, thus improving the heat flow across the contact bridge. The heat flows across the contact bridge 5 and through the legs 4n, 4p toward the cold side 3. Due to the thermoelectric activity of the semiconductor materials, an electrical voltage can then be tapped at the thermocouple legs 4n, 4p.

[0048] Conversely, by applying an electrical voltage to the thermocouple legs, a heat flow can be induced from the cold side to the hot side. The thermoelectric element then functions as a heat pump, i.e., as a cooling element for the cold side and as a heating element for the hot side.

[0049] The substrate is made of a thermally insulating material. This means that the thermal conductivity of the substrate material is lower than that of the thermoelectric active material. This means that hardly any heat exchange takes place between the hot and cold sides via the substrate itself, but primarily, preferably exclusively, via the thermocouple legs. The thermoelectric component is therefore significantly more efficient because almost the entire heat flow between the hot and cold sides is utilized thermoelectrically. The substrate material must prevent thermal short circuits between the hot and cold sides.

[0050] Advantageously, a plurality of such thermocouples are provided within the substrate 1. These are typically connected in series using associated contact bridges to achieve a higher electrical voltage. Thus, in such a component with more than two thermocouple legs 4n, 4p, contact bridges 5 are located on both the hot and cold sides. However, to simplify the illustration of the invention, only one thermocouple with one contact bridge 5 on the hot side has been shown.

[0051] Fig. 2 shows a second embodiment, not according to the invention, in which the contact bridge 5 is more strongly cranked than in Fig. 1, which results in a further significant extension of the path W along which the contact bridge 5 extends, compared to the distance d between the thermocouple legs 4n, 4p. The contact bridge 5 thus has a large surface in contact with a heat transfer fluid 9. The surface of the contact bridge 5 can be roughened or otherwise three-dimensionally structured to further enlarge the surface and thus further improve the heat exchange between the heat transfer fluid 9 and the contact bridge 5.

[0052] In Fig. 3, this embodiment has been further developed according to the invention in that the contact bridge 5 has been provided with concave grooves 10 on the inside of the bending area to further improve the bendability of the contact bridge 5. In this way, the contact bridge 5 can respond better to thermal stresses caused by different expansion coefficients of the materials in contact with one another: substrate 1, thermoelectric active material 4n, 4p, nickel barrier 7, solder 6, and contact bridge 5. The outwardly bent contact bridge 5 acts like an expansion bend of a pipeline.

[0053] In Fig. 4 shows a further embodiment not according to the invention, which is characterized by an outer cladding layer 11. The cladding layer 11 serves to electrically insulate and encapsulate the thermoelectric component. It can be made, in particular, of plastic, ceramic, such as aluminum nitride, composite materials of both of the aforementioned classes, or metal with an electrically insulating coating. The cladding layer 11 extends essentially parallel to the substrate 1 and rests on the bridgeheads 12 of the contact bridge 5. In this way, a cavity 13 is formed between the cladding layer 11 and the substrate 1, through which the loop 8 of the contact bridge 5, which here faces inwards, extends. The cavity 13 can be flooded with a stationary or flowing heat transfer fluid. However, the flow can also occur from the outside.

[0054] To enlarge the cavity 13, the Fig. 5, the contact bridge is provided with a base 14 in the area of its bridge heads 12. This allows an extension of the loop and thus the path length of the contact bridge and additionally an enlargement of the contact surface in the area of the base 14. Fig. 5, the cavity 13 is filled with a heat transfer fluid 9.

[0055] As in Fig. As shown in Figure 6, the loop 8 can also be bent outward so that it points away from the substrate 1. The sockets 14 are accordingly arranged between the bridgehead 12 and the cladding layer 11.

[0056] A preferred embodiment of the invention provides for the use of the thermoelectric component as a heat pump in a system for hot water preparation. For this purpose, water to be heated is provided as heat transfer fluid 9 on the hot side 2, on either side of any cladding layer. Ambient air or another available low-calorific heat source is located on the cold side 3. By applying a voltage to the thermocouple legs 4n, 4p, the heat from the colder environment on the cold side 3 is transferred via the thermocouple legs 4n, 4p and the contact bridge 5 to the water to be heated, thereby heating the water. The thermoelectric component then operates like a heat pump, but does not require any moving parts, in particular a compressor, or (climate-damaging) refrigerant.Of course, the system can also be equipped with an additional, alternative heating source for the water to be heated, such as an electric resistance heater or a gas or oil burner. The thermoelectric component then serves to provide additional, energy-efficient heating of the boiler water by utilizing the heat available in the ambient air.

[0057] Fig. 7 shows that the advantageously designed contact bridges can also be used without a substrate in a thermocouple formed from two thermocouple legs 4n, 4p made of thermoelectrically active material, which are electrically contacted by means of a contact bridge 5 and extend at a distance from one another, in which the contact bridge 5 extends between the two thermocouple legs 4n, 4p along a path W which is longer than the shortest distance d measured between the thermocouple legs. The thermocouple legs do not have to run parallel. List of reference symbols 1 substrate 2 Hot side 3 Cold side 4n first thermocouple leg (n-conducting) 4p second thermocouple leg (p-conducting) 5 Contact bridge 6 Lot 7 Barrier layer W Path of the contact bridge between the centers of the thermocouple legs d shortest center-to-center distance of the thermocouple legs 8 loop 9 Heat transfer fluid 10 cove 11 Shell layer 12 Bridgehead 13 Cavity 14 bases

Claims

[1] Thermoelectric component with an electrically and thermally insulating substrate (1) arranged between a hot side and a cold side, extending in a substrate plane, with at least two thermolegs (4n, 4p) made of thermoelectrically active material, which extend through the substrate from the hot side to the cold side, and which are electrically contacted with one another on one of the two sides by means of a contact bridge (5) and thus form a thermocouple, characterized by , that the contact bridge has a surface on its side facing the hot side and / or the cold side, the area of which is larger than the area of a comparison surface lying in the substrate plane, which is formed by an imaginary projection of the contact bridge onto the substrate plane and, that the contact bridge between the two thermocouple legs extends along a path (W) which is longer than the distance between the two thermocouple legs measured in the substrate plane, wherein the contact bridge forms a loop, bump or dent (8) which is facing the substrate or facing away from the substrate and is connected on the inside with is provided with hollow grooves (10). [2] Thermoelectric component according to claim 1, wherein the contact bridge is cranked or bent. [3] Thermoelectric component according to one of claims 1 to 2, characterized by that the contact bridge has a comb. [4] Thermoelectric component according to one of claims 1 to 3, characterized by that the contact bridge has a U-, M-, I-, T- or double-T-shaped cross-section, wherein preferably at least one of the legs pointing away from the substrate plane forms a comb. [5] Thermoelectric component according to one of claims 1 to 4, characterized by that the surface of the contact bridge has at least partially a structured surface, preferably consisting of elevations and / or depressions. [6] Thermoelectric component according to one of claims 1 to 5, characterized by that the substrate is flat or curved. [7] Thermoelectric component according to one of claims 1 to 6, characterized by a covering layer arranged substantially parallel to the substrate and touching the contact bridges at least at certain points, such that a space extending between the covering layer and the substrate is defined, through which space the contact bridge runs. [8] Thermoelectric component according to claim 7, characterized by that the space is filled with a stationary or flowing heat transfer fluid. [9] Thermoelectric component according to one of claims 1 to 8, characterized bythat the contact bridges and / or the substrate is / are provided with an electrically insulating coating which is resistant to the media present, wherein the coating in particular contains or consists of a thermoplastic polymer, such as polyethylene, polypropylene, polyamide, or aluminum nitride, or is based on an alkoxysilane-containing composition, such as tetraethoxysilane. [10] Use of a thermoelectric component according to one of claims 1 to 9 for converting electrical power into a heat flow from the cold side to the hot side or for converting a heat flow from the hot side to the cold side into electrical power. [11] Use according to claim 10 for heating water by absorbing electrical power, wherein the water to be heated is arranged on the hot side and a low-calorific water, in particular exhaust gas, exhaust air, ambient air, ground heat, groundwater, waste water, process water, return cooling water or other lukewarm water, is arranged on the cold side. [12] System for hot water preparation, characterized by a thermoelectric component according to one of claims 1 to 9. [13] Thermocouple formed from two thermocouple legs made of thermoelectrically active material, which are electrically contacted with one another by means of a contact bridge according to claim 1 and are spaced apart from one another.

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