GB2292830A - Thermoelectric power generation - Google Patents

Abstract

An apparatus for generating electricity comprises a laminated stack of ferromagnetic metal 11. The stack is part of a transformer core and an a.c. circulating current is set up in the stack by eddy current induction. A heat gradient is established in the stack by means of heat sinks 14, 15. The Nernst effect converts the heat input to an output EMF which is delivered through a secondary winding. <IMAGE>

Description

THERMOELECTRIC HEAT TRANSFER APPARATUS FIELD OF INVENTION This invention relates to solid-state thermoelectric energy conversion by which electricity is generated from heat input. Specifically it concerns a development arising from research on the laminar metal stack devices, the subject of Patent No. 2,227,881 and copending patent application No. 2,267,995.

BACKGROUND OF INVENTION The background of the invention is essentially a theme arising from an experimental discovery by which a temperature gradient set up in the plane of a bimetallic lamination subjected to lateral through-flow of an electric current could deflect the heat-driven current to generate EMFs in the direction of the lateral flow. As a result it was found that the heat otherwise conducted through the metal laminations could be converted into useful electrical output, resulting in cooling.

Certain anomalous effects have been exhibited in researching this subject. In particular, using metals nickel and aluminium in combination, the efficiency of conversion of heat into electricity is much higher than would normally be expected from a thermocouple using such base metals.

In this respect, however, the research literature indicates that there is good reason from experiment for believing that the free electrons in a host metal lattice are not in thermal equilibrium with the lattice but have a very much hotter temperature. See Physics World, pp. 23-24 (August 1994) where author Stuart Brorson describes this as a 'two-temperature system'. Thus it becomes feasible to expect inflow of heat at temperature T' into a metal which adopts this as its lattice temperature on the input side and the conduction of much of that heat by electrons at a much higher temperature. By deflecting these electrons in passage so that they drive a forward EMF in the transverse direction, that EMF will be commensurate with the electron energy absorbed and so characterized by a source at a temperature much higher than T'.

It may then be expected that the temperature T of the metal lattice on the heat output side, which is normally taken as the base temperature for a Carnot efficiency factor of (T'-T)/T, would be an underestimate of the true limit on energy conversion efficiency which can be achieved with a special technique for tapping the energy of those electrons in midpassage between heat sinks at temperatures T' and T.

The deflection of the electrons is possible by the provision of a magnetic field in a direction orthogonal with respect to the heat flow direction and the output EMF direction, as is known from the Nernst Effect in thermoelectrity. This is analogous with the well known magnetohydrodynamic principle of electric power generation from heat where a magnetic field deflects a flow of ions laterally to separate the positive and negative ions into opposed lateral motion and so set up a lateral EMF from which electrical power is generated.

The research leading to this invention has focused attention on the intrinsic state of magnetism constituted by the magnetic domains in thin ferromagnetic laminations, as in nickel film, whereby no special magnetic polarization means is needed to provide the deflecting field. Indeed, as the conduction electron travels to convey heat through the lamination, so as it enters a succession of magnetic domains having alternately opposite polarization in the plane of the lamination, so the lateral EMF is directed first one way through the thickness of the lamination and then the other way.

The physical principle used by the invention, including that of the above-referenced patent, no doubt depends in some measure upon this phenomenon, because by encouraging a transverse flow of current supperimposed on the parasitic current circulations which this heat flow situation creates, so that current will at all times take the path of least resistance, meaning the path with the EMF in the direction aiding flow.

This implies cooling which feeds the balance of energy into an electrical output circuit supplied by that current.

This action augments the effect of any Peltier EMF in a bimetallic lamination, which promotes a current circulation having a similar general effect but one that is necessarily limited by Carnot efficiency criteria.

The reason is that the n and p charge carriers are created by charge separation at a temperature zero Kelvin and so in their initial thermalization at the Peltier-cooled junction they cool in measure related to the local lattice temperature T'. Their role in heat conduction brings into play the sequence of electron-phonon interactions which can upset the thermal equilibrium and energy to the electron motion making it seem as if the electrons in onward passage through the metal acquire that extra temperature already mentioned. In a sense, this non-equilibrium temperature state is no doubt a process involved in superconductivity inasmuch as that could well be a state where the normal joule heating associated with resistance is complemented by a steady transfer of heat energy from the lattice phonons to the electrons in a way which gives them a forward drive EMF.

This background summary serves therefore as background for presenting the new development which is the subject of this invention, bearing in mind that the most relevant prior art is the subject of the above-referenced patent.

BRIEF STATEMENT OF INVENTION The object of this invention is to provide a specific structural design of apparatus suitable for main power generation as based on a novel and meritorious utilization of the background principles described above.

According to one aspect of the invention, thermoelectric heat transfer apparatus comprises a first heat sink, a second heat sink, a first electrical transformer means, a second electrical transformer means and a laminated assembly of ferromagnetic elements arranged with their main surfaces in interfacing electrically conducting contact, these laminar elements being also arranged between the heat sinks with their opposite edge surfaces in electrically-insulated thermal contact with the surfaces of the first and second heat sinks, thereby to form two non-interfacing edge surfaces of metallic laminar elements across which heat may be transferred in a direction transverse to the flow direction of an electric current path through the assembly, there being externally powered circuit control means for supplying alternating current to the primary winding of the first transformer which incorporates said laminated assembly as part of its core structure, thereby to induce secondary current flow directed along the said electrical current path, and there being electrical power output circuit means comprising the second transformer which has a primary winding connected in circuit with the secondary current flow path through the thermally-activated laminated assembly of the first transformer to absorb the power thereby supplied and deliver output through a secondary winding when a temperature differential exists between the two heat sinks.

According to another aspect of the invention, thermoelectric heat transfer apparatus comprises (a) a first heat sink, (b) a second heat sink, (c) a first electrical transformer means, (d) a second electrical transformer means comprising a plurality of toroidally wound transformers and (e) a corresponding plurality of laminated assemblies of ferromagnetic elements arranged with their main surfaces in interfacing electrically conducting contact, these laminar elements being also arranged between the heat sinks with their opposite edge surfaces in electrically-insulated thermal contact with the surfaces of the first and second heat sinks, thereby to form two non-interfacing edge surfaces of metallic laminar elements across which heat may be transferred in a direction transverse to the flow direction of an electric current path through the assembly, the first transformer having a multi-sectioned primary winding, each section of which embraces a section of transformer core arranged between two adjacent laminated assemblies which also form part of the tansformer core and being externally powered circuit control means for supplying alternating current to the primary winding, thereby to induce secondary current flow directed along the said electrical current path, and there being electrical power output circuit means comprising the toroidally-wound transformers of the second transformer means each of which has a primary winding connected in circuit with the secondary current flow path through an associated thermally-activated laminated assembly of the first transformer to absorb the power thereby supplied and deliver output through a secondary winding when a temperature differential exists between the two heat sinks.

Features of the invention will be evident from the claims and the following description with reference to the accompanying drawings, but it is noted specifically that it is within the ambit of this invention for the metal laminations to be a single ferromagnetic material, such as a thin nickel sheet substance or one of steel, the limiting thickness being determined by the dimensions of the microscopic magnetic domains in the metal. A 200 micron thickness would be optimum in this regard.

This contrasts with the proposal in the earlier referenced patent specifying bimetallic laminations, but the point to note here is that there are distinct advantages in the use of the bimetallic form (a) in that the second metal can assist in a thermoelectric action which enhances the operation and (b) because the second metal can act as a conductive flow route allowing the transverse current to weave through the domain system with minimal confontation with thermally induced back EMFs.

Also to be noted is the development that distinguishes this invention from the disclosure in the early-referenced patent in respect of the polymer coupling between laminations. In the prior art proposal the polymer PVDF was used to enhance capacitance property, transverse current flow being that of a capacitor system. In this invention, there is the proposal to use a conductive polymer not as a capacitor dielectric but as a true electrical conductor which permits transverse current flow, whether d.c. or a.c. and obstructs the passage of heat in the planar direction.

Some of the features of the invention to be described concern the avoidance of inductance problems which limit transverse current flow through ferromagnetic laminations. Indeed, this aspect of the invention, which concerns how the transverse current flow is established, is probably the one having the most practical importance.

BRIEF DESCRIPTION OF DRAWINGS Fig. 1 shows a laminated metal stack positioned between two heat sinks.

Fig. 2 illustrates the principle of the Nernst Effect.

Fig. 3 shows a laminar element sub-assembly.

Fig. 4 shows a section of a laminated stack incorporating heat insulating spacer sections.

Fig. 5 shows a simple magnetic domain pattern in a ferromagnetic lamination.

Fig. 6 depicts a tranverse current flow weaving through a laminated stack comprising ferromagnetic laminations.

Fig. 7 shows a cross section of a laminated stack with provision of thermal input and electrical power output.

Fig. 8 shows the effective circuital current actions in the structure of Fig. 7.

Fig. 9 shows a plan view of a transformer core system incorporating the stack of Fig. 7 as an intermediary core member and as used for test purposes.

Fig. 10 shows a plan view of an enlarged transformer core system as can be used in an industrial version of the invention.

Fig. 11 shows a sectional front view of the apparatus shown in Fig.

10.

Fig. 12 shows a sectional end view of the apparatus shown in Fig.

10, now including the heat conduits which provide channels for the thermal input and output.

DETAILED DESCRIPTION OF INVENTION Referring to Fig. 1, a laminar stack 1, such as will be described, is sanwiched between two side heat sinks 2, 3, shown respectively as being at temperatures T' and T. When a temperature differential exists across the stack, a flow of current transversely directed with respect to the heat flow, whether a.c. or d. c. in the direction of the arrows, will derive power from the heat input source feeding the heat sink 2 at the higher temperature.

Referring to Fig. 2, the Nernst Effect provides that, if a magnetic field B exists in the direction indicated in the metal element shown and a temperature gradient exists in the laminar plane at right angles to that magnetic field, so there will be a Nernst EMF E induced in a mutually orthogonal direction.

To deploy electrical energy from that EMF powered by drawing on the heat one needs to cause electric current to flow through the thickness of the element without affected the directional sense of heat flow.

Assuming assembly of a multiplicity of such elements in a stack such as 1 in Fig. 1, that current can be arranged to flow if there is a conductive connection or interface contact between adjacent elements or if there is a thin dielectric coupling and the current throughput is that of a parallel plate capacitator.

With appropriate design the heat input can sustain an oscillatory current in such a capacitative device and that allows electrical power to be bled off as useful output, resulting in overall heat to electricity conversion.

From a practical viewpoint the design considerations involve matching the heat flow through the metal conductor to the capacity of the heat sinks. The capacitative version provides indirectly what can be relatively thick dielectric layers separating thin film metal coatings on a polymer dielectric, typically a metallized PVDF sheet, and this provides adequate restriction of heat flow confining it to the thin pathways through the metal. This allows the temperature gradient to be quite high in the metal film, typically 50 C/cm in one prototype test device, but such implementations involve very delicate assembly of the stack and require the setting up of high Q-factor resonant current oscillations at audio or higher frequencies which subject the dielectric to high voltage gradients.

This makes it desirable to seek other ways of ensuring the necessary levels of current flow transversely through the laminated assembly.

One alternative is to make use of a conductive polymer material such as polypropylene oxide, some forms of which exhibit high conductivity in thin filamentary sections across their sheet thickness whilst having high thermal resistivity parallel to their plane. The commercial availability of such materials with optimum properties suitable for application in this invention will make this mode of implementation one that that may be preferred, particularly for operation at low and ambient temperatures.

However, though that option is deemed within the scope of this invention, the major portion of this disclosure concerns the higher powered electrical engineering embodiments of the invention and these form the subject of much of the remaining description.

These involve the magnetic induction of the transverse electric current flow by building the laminated stack assembly into the core structure of a power transformer system.

Before describing this, some further detail concerning the nature of the laminar composition is now provided. To benefit from use of the Nernst Effect without providing a strong external magnetic field the laminated assembly must comprise ferromagnetic elements.

Thus, in Fig. 3, metal X and metal Y may comprise, respectively, iron and nickel, or simply steel sheet in different material forms. They require, in a non-capacitatively coupled application, an interfacing electrically conductive contact, preferably through an intervening conductive film Z. The latter may be an electrically conductive polymer or a metal film. In the latter case, to keep heat conduction loss low whilst allowing scope for some longitudinal current flow, the metal film should have a thickness no greater than one tenth that of the ferromagnetic laminar elements. For example, the laminated stack could comprise 200 micron tin steel plate with an electrolytic or sputtered tin coating of a few microns in thickness interleaved in an assembled stack with layers of 50 or 100 micron thick shim steel.The use of nickel has advantages thermoelectrically in promoting current circulation and developing a uniform temperature gradient owing to its Peltier action relative to steel, but the Nernst Effect is a sufficient thermoelectric factor in the eddycurrent situation to be described below.

It will be understood that by using alternate layers of one ferromagnetic material coated both sides with a conductor such as tin and a simple ferromagnetic sheet metal material uncoated by conductor, the latter being the thinner material, so it is easier to comply with the magnetic domain size requirement. Also, where steel is used in combination with nickel, the former is easier to plate with the other metal, if the process is electrolytic.

In Fig. 4, the stack comprises layers 4 of steel as used in tinplate, layers 5 of tin, being a plating on the layers 4, and interleaved shim steel layers 6. To control the thermal conductivity and allow sufficient temperature gradients to be set up in the stack, spacer sections 7 are included which comprise a heat insulating material. Then to allow the through conduction of electricity a connecting metal link 8, positioned on what would be a contour of constant temperature, is included in the spacer portion of the stack with a surface duly coated by a film 9 of the metal conductor should that not be a tin plated element.

The magnetic domains shown in Fig. 5 are merely diagrammatic illustration of the fact that magnetic domains in thin laminations of iron or nickel exist side by side with their magnetization polarized in opposite directions. This is particularly the case where the substance is grain orientated by cold rolling techniques such as apply to electrical sheet steels as used in transformer assembly and, though tinned steel plate and shim steel are mentioned above owing to their use in test devices, one could use electrical sheet steel of 200 micron thickness or less, provided the surface is not treated to provide electrical insulation. The good intersurface electrical contact between elements in the stack is essential and the use of commercially available tinned plate has proved to be ideal and convenient in the research leading to this invention.

By comparing Figs. 2 and 5 and noting that the arrows and arrow point or arrow head symbols in Fig. 5 indicate polarization direction, it can be seen that a given temperature gradient will set up forward EMFs E through domains of one polarization direction and opposing EMFs in the oppositely polarized domains. A current I flowing transversely through the element will seek out a route through the domains having a forward EMF. Thus, in Fig. 6, where several elements are shown in a stack, the current I is depicted as weaving through the domains having the (+) symbol. The current tracks through the intervening conductive layers 5. It is shown at one side of the stack for reasons to be explained below.

In order to promote current flow through the laminated stack it is not sufficient to apply a temperature differential and then connect an output circuit adapted to exploit oscillations in the circuit of the transverse path through the stack. Nor, for a stack having a main bulk dominated by ferromagnetic laminations, can one force an alternating current through the stack with the object of pumping heat between its side faces.

This is because the laminations present a very high inductance which resists the current flow. The inductance does, however, give the stack a characteristic resonant frequency, which is between 15 and 20 kHz in the devices tested by the Applicant and that implies some inherent capacitance effect attributable to the laminar structure even though no dielectric is used.

Accordingly, for optimum results, one needs in this latter case to promote a circulation of eddy-currents by a magnetic induction coupling and then superimpose the applied through current on that circulation so that (a) the current flow through the stack is one way at any instant and so that (b) that one way current thereby is driven out from the stack by the Nernst EMF set up by the temperature differential.

Fig. 7 shows a section through apparatus used in tests as an induction technique for generating both the eddy-current and the superimposed current component. Fig. 8 shows the equivalent electrical circuit. Note that the core section denoted 10 is included in the core system of a transformer, as shown in Fig. 9, and it comprises three subsections. The two outer sub-sections 11 are the laminated stacks and the intermediate core sub-section 12 comprises normal transformer laminations insulated from each other.

When an alternating magnetic flux is passed through the three-part core section it induces closed loop eddy-currents confined to 11 and a circuital current passing through the two stacks and the primary winding of an output transformer 13. Subject to some phase drift in the eddycurrent circuits, these all have the same clockwise or anticlockwise direction, reversing together as the a. c. flux oscillates.

Without the core sub-section 12 functioning to provide the superimposed current, the eddy-currents in 11 will harness the Nernst EMFs to enhance those currents in their confined flow inside the laminated stacks. This will replicate the pure loss situation observed with eddycurrents in power transformers and electrical machines and, owing to the thermal temperature gradients, these losses will be substantially enhanced by the Nernst action effectively reducing the circuit resistance. The latter is what accounts for the little-known, but wellresearched, 'eddy-current anomaly', which can enhance the theoretical eddy-current loss by a factor as high as 10 for cross-grain magnetization in thin cold-rolled steels.Indeed, it is knowledge concerning this anomaly and its positive indication of a definitive Nernst action that has caused the Applicant to persist in the research leading to the magnetic inductive implementations provided by this invention.

It is essential, therefore, that the current flow in the stack structures of core sub-sections 11 should be brought into the series loop through transformer 13. One can see, therefore, from Fig. 8 that if the currents in each of the three flows shown are all equal in strength, as can be assured by appropriate design matching of the flux in passage through the separate core sub-sections, then the net current in each stack will become a one way flow during one a. c. half cycle and a reverse flow in the next half cycle. However, this result is achieved by a process which ensures that the magnetic polarization is dominated by the action of the transformer powering the magnetic flux through the stacks and this precludes the current component driven through the core from setting up a circular in-plane flux around the currents.The latter would develop a high self-inductance owing to the high permeability of the ferromagnetic material. Where the latter action could arise in the apparatus of Figs. 7 and 8 in the compensated opposed-current innermost portions of the stacks this is not disadvantageous because the main current flow is through the heat gradient adjacent the input heat sides of the stack and that is the primary seat of the energy conversion process being exploited. Note that, as a function of current flow, the heat gradient will adjust by cooling to match the Nernst EMF along the stack, but the key requirement concerns the avoidance of reverse current flow in the same stack and that is a design adjustment. If the central core sub-section 12 is too large the primary of the input transformer will be delivering too much power to the secondary of the output transformer 13.If it is too small then the heat input will be generating parasitic current flow in the stacks which will merely waste heat input by feeding it through to the output coolant. The correct adjustment of this design feature concerning the core sections 10 has to involve empirical tests on a test rig such as that shown in Fig. 9 before the findings are extended to a large scale apparatus incorporating many core sections 10.

Fig. 7 shows how heat is fed into and removed from the apparatus.

A heat sink base 14 has channels through which a flow of hot gas or other heat form can be supplied. It has metal side pieces forming side heat sinks 2 which carry the heat to the outer sides of the two stacks constituting the core sub-sections 11. A suitable thermal conduction paste is used to assure thermal contact with the edges of the laminations in the stacks, whilst assuring electrical isolation.

To assure that a temperature gradient is sustained in the stacks heat has to be extracted from the inner edges of the stacks, which are similarly in thermal contact with a metal structure forming the cooler heat sinks 3 and housing the pipework 15 of a channel for the flow of coolant fluid, whether gas or liquid circulating around an external cooling system.

Centrally positioned within this heat sink structure is a stack of insulated transformer laminations which form the core sub-section 12 and generate the main circuital current component.

The action already described then relies on there being a circuit around which the stack current can flow. Thus the two stacks 11 share several laminations in their lower section to provide a linking path on the underside of the apparatus and the upper connection is made as a singleturn connecting-conductor 16 which passes through the central aperture of a toroidal transformer 17, the secondary winding of which delivers the electrical power generated from the heat input.

Referring to Fig. 9 two E-I transformer core systems are used to fabricate the basic apparatus. The E sections form the main core members 18 and the I sections are shortened to form the linking side core sections 19. There are two primary windings 20 connected to augment one another in circulating magnetic flux around the core system so as to link through the three-part core section 10. Thermal insulation 21 accounts for a small air gap between the stacks of core section 10 and the main cores members but the intermediate middle core sub-section has a close magnetic coupling, inasmuch as its cooler temperature is that of the main core and if the main core becomes hotter so it will be cooled accordingly.

In an industrial-sized embodiment of the invention the basic structure of the Fig. 9 apparatus can be adapted to assure essentially that the core is almost wholly used to support a primary winding or is used as the operative sections converting heat into electrical output.

The apparatus shown in Fig. 10 incorporates several core sections 10 and main core sections 22, with bridging core pieces 23 at each end to assure circuital flux flow. The toroidal output transformers 17 (not shown in Fig. 10) are mounted, each on a separate core section 10.

The heating and cooling arrangement (not shown in Figs. 10 or 11) is depicted in Fig. 12 and is much as described with reference to Fig. 7 except that the heating and cooling channels comprise pipework located below the main core of the apparatus. These channels are suitably heat insulated as depicted by bulk insulation 24, but the design can be seen to be adapted to simplicity of construction in that it comprises an elongated system that can be extended in units according to the power rating of the installation.

It is relevant to note that in the research leading to this invention a device such as that shown in Fig. 9, with only one of the main primary windings on power, and no central core sub-section in the test portion 10, developed such an enormous eddy-current response that at standard main power supply frequency only one tenth of the flux linking the input primary winding penetrated through to the second primary winding with the latter on no-load. This indicated that a very substantial current was circulating as that in stacks 11 in Fig. 8, sufficient in that particular test to drive almost all the flux back around the side limbs of the core as leakage flux bridging the intervening space and not linking through both end sections of the core.

With this in mind, in designing apparatus along the lines shown in Figs. 10 to 12, it is important that the spacing between the two main cores forming.the elongated structure should be sufficiently large to reduce such flux leakage and conserve the input power needed to prime the heat to electricity conversion role of the operative core sections 10.

The leakage phenomenon described occurred with a core having no insulating spacer sections such as 7 in Fig. 4 and so posing a worst case reaction but evenso, as was the purpose of the tests, the high eddycurrents in that core did not develop excessive loss owing to very substantial skin effects which confined that current to near-to-surface regions. The application of heat requires that spacer provision for optimum design use of core material.

This specification describes a modified version of the earlier invention, the subject of the above-reference patent, and develops the emphasis on the combination of the eddy-current flow induced in a laminated metallic stack, which need not be comprise bimetallic laminations, with the through-flow of a. c. current phased so as to overcome self-inductance effects and wastage of heat input by parasitic current circulation.

The claims which follow are restricted to a specific apparatus feature by which this action is incorporated in a simple but novel magnetic cored structure which combines the action of two transformer systems linked by the thermally activated current flow. The invention overcomes a problem posed by the coupling of two such transformers incorporating a laminated metal stack conductor in the linking portion of a circuit of a winding common to both transformers. It is essential to this invention that that stack is actually part of the first transformer core. It is preferably then connected in series in a loop circuit supplying the input winding of a second transformer in order that the output power can be delivered at a useful level of voltage.

Claims (9)

1 Thermoelectric heat transfer apparatus comprising a first heat sink, a second heat sink, a first electrical transformer means, a second electrical transformer means and a laminated assembly of ferromagnetic elements arranged with their main surfaces in interfacing electrically conducting contact, these laminar elements being also arranged between the heat sinks with their opposite edge surfaces in electrically-insulated thermal contact with the surfaces of the first and second heat sinks, thereby to form two non-interfacing edge surfaces of laminar elements across which heat may be transferred in a direction transverse to the flow direction of an electric current path through the assembly, there being externally powered circuit control means for supplying alternating current to the primary winding of the first transformer which incorporates said laminated assembly as part of its core structure, thereby to induce secondary current flow directed along the said electrical current path, and there being electrical power output circuit means comprising the second transformer which has a primary winding connected in circuit with the secondary current flow path through the thermally-activated laminated assembly of the first transformer to absorb the power thereby supplied and deliver output through a secondary winding when a temperature differential exists between the two heat sinks.

2. Thermoelectric heat transfer apparatus according to claim 1, wherein the laminated assembly comprises ferromagnetic elements having interfacing electrically conductive contact through an intervening conductive film.

3. Thermoelectric heat transfer apparatus according to claim 2, wherein the material forming the intervening conductive film is an electrically conductive polymer.

4. Thermoelectric heat transfer apparatus according to claim 2, wherein the material forming the intervening conductive film is a metal having a conductivity no less than that of tin and the thickness of this film is no greater than one tenth that of the ferromagnetic laminar elements.

5. Thermoelectric heat transfer apparatus according to claim 3, wherein the laminated assembly comprises two different forms of ferromagnetic lamination assembled in an alternating sequence with the intervening conductive films separating the different lamination forms.

6. Thermoelectric heat transfer apparatus according to claim 1, wherein the laminated assembly comprises a core unit which forms part of the main magnetic circuit path of the first transformer core, thereby, apart from leakage flux, linking inductively with the main magnetic flux through the primary winding of that transformer, and this unit is formed in three sections, two side sections each positioned between and in thermal contact with heat sink surfaces and an intermediate core section comprising ferromagnetic laminations electrically insulated from one another to minimize eddy-current effects in that core section, this core section providing a magnet flux linkage through a current loop circuit path formed by two side sections of the core unit and their connection in the primary circuit of the second transformer.

7. Thermoelectric heat transfer apparatus according to claim 1, wherein the laminated assembly comprises a core unit which forms part of the main magnetic circuit path of the first transformer core, thereby, apart from leakage flux, linking inductively with the main magnetic flux through the primary winding of that transformer, and this unit is formed in three sections, two side sections each positioned between and in thermal contact with heat sink surfaces and an intermediate core section comprising a ferrite core and providing a magnetic flux linkage through a current loop circuit path formed by two side sections of the core unit and their connection in the primary circuit of the second transformer.

8. Thermoelectric heat transfer apparatus comprising (a) a first heat sink, (b) a second heat sink, (c) a first electrical transformer means, (d) a second electrical transformer means comprising a plurality of toroidally wound transformers and (e) a corresponding plurality of laminated assemblies of ferromagnetic elements arranged with their main surfaces in interfacing electrically conducting contact, these laminar elements being also arranged between the heat sinks with their opposite edge surfaces in electrically-insulated thermal contact with the surfaces of the first and second heat sinks, thereby to form two non-interfacing edge surfaces of laminar elements across which heat may be transferred in a direction transverse to the flow direction of an electric current path through the assembly, the first transformer having a multi sectioned primary winding, each section of which embraces a section of transformer core arranged between two adjacent laminated assemblies which also form part of the tansformer core and being externally powered circuit control means for supplying alternating current to the primary winding, thereby to induce secondary current flow directed along the said electrical current path, and there being electrical power output circuit means comprising the toroidally-wound transformers of the second transformer means each of which has a primary winding connected in circuit with the secondary current flow path through an associated thermally-activated laminated assembly of the first transformer to absorb the power thereby supplied and deliver output through a secondary winding when a temperature differential exists between the two heat sinks.

9. Thermoelectric heat transfer apparatus according to claim 8, wherein the primary transformer has an elongated core structure with end closure pieces, and the length of the structure being detemined by the number of separate core sections and intermediate laminated assemblies, with the heat sinks having also an elongated form and comprising longitudinal channels for the flow of heating and cooling fluids.