GB2580032A

GB2580032A - Device and method for converting thermal energy into mechanical movement

Info

Publication number: GB2580032A
Application number: GB1820693.8A
Authority: GB
Inventors: Hewat Darragh
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-12-19
Filing date: 2018-12-19
Publication date: 2020-07-15
Also published as: GB201820693D0

Abstract

A device and method for converting thermal energy into mechanical movement, comprising a magnetic field source and a magnetic material having a Curie point, the magnetic material intersecting the magnetic field of the magnetic field source. A heat source 29, such as a candle or flame, heats a first portion of the magnetic material above its Curie point, in preference to a second portion of the magnetic material. The magnetic material and magnetic field source are movable relative to each other. These types of device are sometimes known as a thermo-electric motors, Curie wheels, Curie motors or pyromagnetic motors. Additional heat sources and magnetic field sources may be used. The device may comprise an annular rotor 25 and stator. The device may comprise a flame height adjustment mechanism.

Description

DEVICE AND METHOD FOR CONVERTING TT TF.RMAT, ENERGY INTO MEET TANTC AT, MOVEMENT The present invention relates generally to a device for converting thermal energy into mechanical movement and a method of converting thermal energy into mechanical movement.

It has long been established that extracting energy from thermal sources in order to perform mechanical work is desirable. Accordingly, there are many different kinds of system to suit different thermal sources and applications, for example steam turbines and Stirling engines.

According to a first aspect of the present invention, there is provided a device for converting thermal energy into mechanical movement, the device comprising: a first part comprising a magnetic field source with an associated magnetic field orientated along a first axis; and a second part comprising a magnetic material having a Curie point, the magnetic material arranged such that a first portion of the magnetic material and a second portion of the magnetic material, adjacent to the first portion of the magnetic material, intersect the magnetic field of the magnetic field source on opposing sides of the first axis; wherein the first part further comprises a heat source arranged to heat the first portion of the magnetic material above its Curie point, in preference to the second portion of the magnetic material; and wherein the second part is movable relative to the first part.

In this way, magnetic field source will magnetically attract the second (unheated) portion of the magnetic material more than the first (heated) portion of the magnetic material, thereby moving the second part such that the second portion moves toward the first axis.

The device may comprise a heat engine, in particular a thermo-magnetic motor and/or pyro-magnetic generator.

The first part may comprise a stator or a rotor. Accordingly, the second part may comprise a rotor or a stator, respectively.

The first part may further comprise: a further magnetic field source with an associated further magnetic field orientated along a further first axis; and a further heat source arranged to heat a further first portion of the magnetic material above its Curie point, in preference to a further second portion of the magnetic material adjacent to the further first portion of the magnetic material, wherein the further first and further second portions intersect the further magnetic field of the further magnetic field source on opposing sides of the further first axis.

The further first axis may be substantially parallel to, anti-parallel, perpendicular to, obliquely orientated to and/or coplanar with the first axis.

The first part may comprise still further magnetic field source and heat source pairs configured substantially as above. For example, the first part may comprise only one, at least one, more than one, two, three, four, five, six, seven, eight or more magnetic field source and heat source pairs.

In particular, each magnetic field source and heat source pair may be arranged to move the second parr in the same direction (e.g. linear and/or rotational direction).

Alternatively, the plurality of magnetic field source and heat source pairs may themselves be configured such that a first subset of said plurality of magnetic field source and hear source pairs are arranged to move the second part in a first direction and a second subset of said plurality of magnetic field source and heat source pairs are arranged to move the second part in a second direction, for example opposite the first direction.

The plurality of magnetic field source and heat source pairs may be equally spaced from one another. in particular the plurality of magnetic field source and heat source pairs may be equally spaced around the second part, e.g. spaced apart by 180 degrees, 120 degrees, 90 degrees, 72 degrees, 60 degrees, etc. Using a plurality of magnetic field source and heat source pairs improves the consistency of rotation, as imperfections in the materials and/or hot/cold spots become less obvious during rotation, particularly during start-up.

The first part may comprise a stator. In this way, relatively heavy permanent magnets need not be moved and/or, where a flame is used as the heat source, movement of the flame will not disrupt the flame due to relative movement of air relative thereto.

Movement of the second part relative to the first part may be equivalent to movement of the first part relative to the second part. Movement of the second part relative the first part may be linear and/or rotational movement.

The rotor may be configured to rotate about a rotor axis relative to the stator.

The rotor axis may be orientated substantially parallel to the first ma's. 'The rotor axis may be spaced from the first axis.

The rotor axis may be substantially vertical. In this way, construction of a rotating axle may be simplified and/or, where more than one magnetic field source and heat source pairs are employed, the effect of gravity and/or convection can be neglected. Alternatively, the rotor axis may be substantially horizontal.

The rotor may be constrained to be movable relative to the stator with only one degree of freedom, for instance rotation about a rotation axis, or translation along a translation axis. The rotor may be constrained to be movable relative to the stnor with more than one degree of freedom, for example two degrees of freedom. Alternatively, movement of the rotor relative to the stator may be unconstrained.

The magnetic field source may comprise a permanent magnet (e.g. a bar magnet) and/or electromagnet (e.g. solenoid). The associated magnetic field may substantially correspond to a dipole field having rotational symmetry about the first axis.

The magnetic field source may comprise a SinCo magnet. The magnetic field source may comprise a cylindrical magnet, which may be sized between timin and 20mm, in particular between 5mm and 15mm, more particularly between 6mrn and lOmm. The magnetic field source may have a strength of between 0.1Tesla and 1 Tcsla, in particular between 0.2Tesla and °Mesh, more particularly approximately 0.35Tesla. The magnetic The magnetic field source may be suspended from an arm bemeen 0.2mm and lOmm from the second part, in particular between 0.5mm and 5mm, more particularly approximately 1mm.

The Curie point of a magnetic material may be the temperature above which the magnetic material undergoes a sharp change in its magnetic properties, in particular above which it loses its permanent magnetic properties, above which it loses its ability to be magnetized, above which a magnetic material that otherwise exhibits permanent magnetic properties exhibits induced magnetic properties, and/or above which an otherwise ferromagnetic material becomes paramagnetic.

The magnetic material may be arranged to extend in a first direction substantially at right angles to the first axis. The first direction may be substantially tangential to the arrangement of the magnetic material in the region of the first axis.

The first portion of the magnetic material and the second portion of the magnetic material may be located substantially equidistant from the first axis. The first portion of the magnetic material and the second portion of the magnetic material may be located within the magnetic field such that they are subjected to substantially equal intensities of magnetic field strength.

The heat source being arranged to heat the first portion of the magnetic material in preference to the second portion of the magnetic material may mean that the heat source is arranged to heat the first portion of the magnetic material more than the second portion of the magnetic material.

The heat source may comprise a flame. The flame may be produced by a candle, for example comprising a wick impregnated with wax, oil, fat or other suitable flammable substance. The candle may be a tea light. The candle may be lit.

The heat source, flame and/or wick may be arranged substantially away from the first axis. The heat flame and/or wick may be arranged along a second axis, substantially parallel to and/or spaced from the first axis. The second axis may be spaced from the first axis by up to 20mm, in particular up to 15rnm, more particular up to 10mm, for example approximately 10mm, 8mm or 5rnm. The second axis may be substantially vertical.

The device may further comprise a flame height adjustment mechanism. In th way, the flame may be raised or lowered to accommodate different sizes of flame. For example, there are relatively large performance differences between c2uadles including tealights (even of the same type and batch). The user can maintain the ideal flame-torotor distance across a wide range of tealight performances (5W -45W thermal output variation is common during the burn-cycle of a tealight).

The flame height adjustment mechanism may permit raising or lowering of the flame height (e.g. by raising or lowering a candle) by at least 5mm, in particular at least lOmm, more particularly at least 20mm, for example 30mm. Ideally, a user would adjust the flame height such that the flame's tip is spaced from the second part by between lrntn and 30mm, in particular between 2mm and 20mm.

The flame height adjustment mechanism may comprise a post, upon which a platform may be disposed, and/or a platform upon which a candle may be placed.

The platform may comprise a flat disc, which may be formed of aluminium, any other metal, ceramic or any other material. The disc may be between lmm and 3mm thick, in particular approximately 2mm thick. The disc may have a knurled outer edge.

The disc may comprise an approximately 8mna diameter hole at its centre; the hole is occupied by an 8mm diameter by 2mm thick SmCo magnet. However, other thicknesses of disc (and magnet) and diameters of hole (and magnet) are also contemplated. The magnet may be used for holding a wick anchor (metal) in place on top of the platform. This locates the wick in the correct position even if the wick is not located centrally within the candle itself. The attraction between the post's magnet and the wick-anchor prevents the candle from becoming accidentally dislodged during operation. Alternative forms of holding a candle in place are also envisaged, such as a skewer, socket and/or adhesive.

The platform may be bonded to the post. the post may comprise a metal bar, and may be threaded along at least a portion of its length. The post may be between lOmm and 50mm long, in particular between 20mm and 35mm long, more particularly approximately 25mm long. 'the post may have a diameter of between 4mm and 20mm, in particular between 8mm and 18mm, more particularly approximately 16rnm diameter.

The thread may have a relatively coarse pitch; that is, at least 1.25mm, in particular at least 1.5mm, more particularly at least 1.75mm. The post may be received in a socket having a co-operating thread such that the platform may be raised or lowered by a user manipulating the knurled edge of the platform to rotate the platform, and therefore the post within the socket.

The socket may be formed by lubricating and/or greasing the thread, setting the post into a tube into which resin is poured. When the resin has set the tealight post can be unscrewed and de-greased. The tube may be brass, or some other suitable material and/or metal, and the tube may be approximately 15mm long and/or have an internal diameter of approximately 18mm; however, various other sizes may be used.

The spacing of the magnetic field source from the second part may be adjustable, for example in a similar manner as described above for the heat source.

The second part may be circular. In particular, the second part may comprise a ring, annulus, annular portion, disc and/or cylindrical surface.

The second part may have a diameter of between 5cm and 50cm, in particular between 8cm and 30cm, more particularly 1 Octn and 20cm.

The ring, annulus and/or annular portion may have a radial width of between icm and 4cm, in particular approximately 2cm.

The ring, annulus and/or annular portion may be connected to a rotation axle by at least one (or a plurality of) arms.

The second part may have a thickness of between 1mm and 3mm, in particular approximately 2nim.

The cylindrical surface may have a circumference of between 20cm and 60cm, for example approximately 24cm or 48cm. The cylindrical surface may have an axial length of between lcm and 5cm, for example approximately 2cm.

For example, when a cylindrical surface is used, the rotation axis may be approximately horizontal, and the heat source may be applied directly under the lowest portion of the cylindrical surface.

The second part may comprise a substrate to which the magnetic material is attached.

The substrate may comprise aluminium. In this way, the substrate provides relatively low magnetic interaction, relatively good thermal conduction and dissipation (i.e. it heats up and cools down quickly). Other suitable materials for the substrate are also envisaged, including brass or copper (but result in higher magnetic braking than Aluminium in accordance with Len's law), or stainless steel grade 316 (but doesn't heat up quickly and can overheat in time).

the second part may On a surface of the substrate to which heat is applied, the substrate may be roughened to improve adhesion of the magnetic material thereto.

The magnetic material may comprise 1\InZn, and in particular may comprise CF197 (produced by Cosmo herrites), and may have an Initial Permeability (at 25 degrees centigrade) of approximately 7000, a flux density (at 25 degrees centigrade) of approximately 400mT and (at 100 degrees centigrade) of approximately 260mT, a residual flux density (at 25 degrees centigrade) of approximately 150mT, and/or a Curie temperature of between 100 degrees centigrade and 150 degrees centigrade, for example approximately 120 degrees centigrade.

The magnetic material may be powdered and mixed in a 50:50 ratio (by weight) with bonding agent, e.g. Fortafix Flueseal (produced by Minkon). The resultant mixture may be applied evenly on a surface of the substrate to a depth of between 0.5mm and 2mm, in particular approximately lnam. The mixture may then be allowed to dry.

The magnetic material may be prepared by grinding to approximately 400 microns and mixed in a 60:40 ration (by weight) with bonding agent. In this way, the larger particle size requires less bonding agent, and may allow greater heat dissipation and absorption.

Ferromagnetic materials such as steel, nickel, cobalt etc. may be unsuitable because they exhibit such strong ferromagnetism that the energy required in reconfiguring their magnetic domains during rotation would be too great to allow for efficient rotation.

The substrate may comprise a matrix of a composite material, for example with the magnetic material forming an aggregate of the composite material.

The second part may be substantially homogenous; that is, the second part may comprise magnetic material in the absence of a substrate. in this way, the second part may be longer lasting and/or more robust.

The magnetic material may comprise a NiFe alloy that exhibits a Curie temperature of between 100 degrees centigrade and 150 degrees centigrade, for example approximately 120 degrees centigrade. The NiFe alloy may have a Nickel content between 29% and 36%, and may exhibit a Curie temperatures between 45 degrees centigrade and 230 degrees centigrade, respectively. The NiFe alloy may comprise approximately 32% Ni and 68% Fe, giving a Cure temperature of approximately 120 degrees centigrade.

Although the NiFe alloy has poorer thermal conductivity properties than aluminium (a typical substrate), it's thermal conductivity is far superior to that of the bonding agent and/or the mixture of magnetic material and bonding agent discussed above. Using a homogenous NiFe alloy therefore gives a faster start-up time and rotation speed.

A further advantage of using a homogenous magnetic material as the second part is that the magnetic field produced by the magnetic field source does not need to extend through a substrate (or heat need not penetrate the substrate). This increased proximity has the effect of concentrating the stator's magnetic field and lessening unwanted effects from stray field lines. This means that it is possible to employ smaller magnets and a thinner mass of magnetic material to achieve a given rotational speed.

Trnpurities and methods of working/forming the alloy for the rotor can change the ultimate Curie temperature, and these must be taken into account during manufacture.

The second part may comprise more than one type of magnetic material, to offer a range of Curie temperatures The second part (and/or the substrate) can be cast, cut from sheet material or electroformed.

The surface of the second part may be textured (e.g. by working) and/or painted (e.g. matt black) to enhance thermal absorption and dissipation processes.

The heat source and/or magnet field source may be arranged to apply a maximum heat and/or magnetic flux, respectively, to a maximal portion of the second part, for instance by centering the respective source on a middle of the annulus or ring.

The second part may be connected to the first part by a hub, for instance to allow rotation of the second part relative to the first part. The hub may comprise a thermal insulator and/or be non-magnetic. The hub may comprise arms for coupling the second part (e.g. substrate and/or homogenous magnetic material) to the first part.

The hub may comprise a spindle (e.g. polished steel, or other suitable material), which may be between imm and Ttruia diameter, in particular between 3mna and 6mna, 10 more particularly approximately 5mm diameter, and may have a length of between 20mm and 150mm, in particular between 40mm and 100trim, for example 60mm.

The spindle may be located within a sleeve (e.g. brass, or other suitable material) of internal diameter larger than the spindle (e.g. 0.5mm, 1tritn or 2mtn larger) and of length less than the spindle (e.g. up to 20mm shorter, in particular up to 10mm shorter, more particularly up to 5mm shorter). A ball bearing (e.g. of diameter similar to the diameter of the spindle, for example within 10%, 5% or 2% of the diameter) is located at the lower end of the sleeve, so that the tip of the rotor spindle rests on the ball bearing. Only one of the spindle and sleeve may be connected to the second part, in particular by the arms; the other of the spindle and sleeve being spaced from the second part and/or arms. The spindle-sleeve arrangement may be located vertically and mounted on a base.

In this way, the rotor may rotate freely without observable deviation in either plane. In an alternative arrangement, instead of a ball bearing, the hub may comprise a first permanent magnet (e.g. a ring magnet having an internal diameter of between 4rnm and 10mm, for example 6mm, which may be Neodymiun or SmCo) coupled to the spindle, with a first pole facing upwards. A similar (or identical) second magnet may be coupled to the sleeve (e.g. around one end of the sleeve) with a corresponding pole to the first pole facing downwards. In this way, repelling poles of the two magnets cause the spindle-sleeve arrangement to levitate.

In a further alternative arrangement, the ball bearing may comprise a spherical magnet. In this way, the spindle can be prevented from falling/creeping out of the sleeve when the hub is arranged substantially horizontally.

According to a second aspect of the present invention, there is provided a method of converting thermal energy into mechanical movement, the method comprising the steps of: providing the device according to any preceding claim; heating the First portion of the magnetic material above its Curie point, in preference to the second portion of the magnetic material; and allowing the magnetic field source to magnetically attract the second portion of the magnetic material more than the first portion of the magnetic material, thereby moving the second part such that the second portion moves toward the first axis.

The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by NAT21), of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.

Figure 1 is a schematic representation of a device for converting thermal energy into mechanical movement.

Figure 2 is a schematic representation of the device of figure 1, at a later point.

Figure 3 is perspective view of a device for converting thermal energy into mechanical movement.

The present invention will be described with respect to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. Each drawing may not include all of the features of the invention and therefore should not necessarily be considered to be an embodiment of the invention. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking (Jr in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that operation is capable in other sequences than described or illustrated herein. Likewise, method steps described or claimed in a particular sequence may be understood to operate in a different sequence.

Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. it is to he understood that the terms so used are interchangeable under appropriate circumstances and that operation is capable in other orientations than described or illustrated herein.

It is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are "and 13. Similarly, it is to be noticed that the term "connected", used in the description, should not be interpreted as being restricted to direct connections only. "Connected" may mean that two or more elements are either in direct physical or magnetic contact, or that two or more elements are not in direct contact with each other but yet still co-operate or interact with each other.

Reference throughout this specification to "an embodiment" or "an aspect" means that a particular feature, structure or characteristic described in connection with the embodiment or aspect is included in at least one embodiment or aspect of the present invention. Thus, appearances of the phrases "in one embodiment", "in an embodiment", or "in an aspect" in various places throughout this specification are not necessarily all referring to the same embodiment or aspect, but may refer to different embodiments or aspects. Furthermore, the particular features, structures or characteristics of any one embodiment or aspect of the invention may be combined in any suitable manner with any other particular feature, structure or characteristic of another embodiment or aspect of the invention, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments or aspects.

Similarly, it should be appreciated that in the description various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Moreover, the description of any individual drawing or aspect should not necessarily be considered to be an embodiment of the invention. Rather, as the following claims reflect, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form yet further embodiments, as will be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practised without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this

description.

In the discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is ielf preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value.

The use of the term "at least one" may mean only one in certain circumstances.

The use of the term "any" may mean "all" and/or "each" in certain circumstances.

The principles of the invention will now be described by a detailed description of at least one drawing relating to exemplary features. It is clear that other arrangements can be configured according to the knowledge of persons skilled in the art without departing from the underlying concept or technical teaching, the invention being limited only by the terms of the appended claims.

Figure 1 is a schematic representation of a device for converting thermal energy into mechanical movement, comprising a magnetic field source (permanent magnet or solenoid) 1 with an associated magnetic field 3 orientated along an axis 5, magnetic material 7 having a Curie point, the magnetic material 7 arranged such that a first portion 9 of the magnetic material 7 and a second portion 11 of the magnetic material 7, adjacent to the first portion 9 of the magnetic material 7, intersect the magnetic field 3 of the magnetic field source 1 on opposing sides of the axis 5, and a candle 13 arranged to one side of the axis 5 to heat the first portion 9 of the magnetic material 7 above its Curie point with the flame 15, in preference to the second portion of the magnetic material.

Due to magnetic material 7 in the first portion 9 being above its Curie point (and the magnetic material 7 in the second portion 11 being below its Curie point), the magnetic field source 1 magnetically attracts the second portion 11 of the magnetic material 7 more than the first portion 9 of the magnetic material 7. With the magnetic material 7 being movable relative to the magnetic field source 1, the second portion 11 of the magnetic material 7 moves toward the axis 5.

Figure 2 is a schematic representation of the device of figure 1, at a later point in which the first portion 9 of the magnetic material 7 has moved to the right and is no longer being heater by the candle 13 flame 15. The first portion 9 of the magnetic material can therefore cool down.

The second portion 11 of the magnetic material 7 has moved across the axis 5 and is now been heated by the candle 13 flame 15. A third portion 17 of the magnetic material 7 now replaced second portion 11 of the magnetic material 7 in its location to the left of the axis 5 in a similar manner to that described in figure 1, the third portion 17 of the magnetic material 7 moves toward the axis 5.

Figure 3 is perspective view of a device for converting thermal energy into mechanical movement, and in particular shows a desktop ornament for rotating a globe 19. The ornament comprises a base 21 upon which is mounted a hub 23 about which an annular rotor 25, coupled to the hub 23 via three arms 27, is free to rotate. The annular rotor comprises magnetic material as hcreinbefore described.

A candle is located immediately below a first portion of the annular rotor 25, to heat said first portion to above the Curie point of the magnetic material, with a flame 29. A curved arm 31 is fixed to the base 21 and holds a permanent magnet (not visible) beneath a cowl 33, suspended immediately over a second portion of the annular rotor 25.

The candle is located in a candle holder 35 that is configured to be movable vertically, such that the spacing of the flame from the annular rotor can be adjusted. 't he candle holder 35 comprises a sheath around the candle to reduce the effects of draughts and/or air disturbances on flame 29.

Claims

CLAIMS1. A device for converting thermal energy into mechanical movement, the device comprising: a first part comprising a magnetic field source with an associated magnetic field orientated along a first axis: and a second part comprising a magnetic material having a Curie point, the magnetic material arranged such that a first portion of the magnetic material and a second portion of the magnetic material, adjacent to the first portion of the magnetic material, intersect the magnetic field of the magnetic field source on opposing sides of the first axis; wherein the first part further comprises a heat source arranged to heat the first portion of the magnetic material above its Curie point, in preference to the second portion of the magnetic material; and wherein the second part is movable relative to the first part.
2. The device of claim 1, wherein the first part further comprises: a further magnetic field source with an associated further magnetic field orientated along a further first axis: and a further heat source arranged to heat a further first portion of the magnetic material above its Cune point, in preference to a further second portion of the magnetic material adjacent to the farther first portion of the magnetic material, wherein the further first and further second portions intersect the further magnetic field of the further magnetic field source on opposing sides of the farther first axis.
3. The device of claim 1 or claim 2, wherein the first part comprises a stator.
4. The device of any preceding claim, wherein the second part comprises a rotor configured to rotate about a rotor axis relative to the stator, the rotor axis being substantially vertical.
The device of any preceding claim, wherein the heat source comprises a flame.
6. The device of claim 5, further comprising a flame height adjustment mechanism.
7. The device of any preceding claim, wherein the second part comprises an annular portion. 5
8. A method of converting thermal energy into mechanical movement, the method comprising the steps of: providing the device according to any preceding claim; heating the first portion of the magnetic material above its Curie point, in preference to the second portion of the magnetic material; and allowing the magnetic field source to magnetically attract the second portion of the magnetic material more than the first portion of the magnetic material, thereby moving the second part such that the second portion moves toward the first axis.