GB2612642A - Heat engine and method of manufacture - Google Patents

Abstract

A heat engine comprises a housing 2, a first liquid 3 and a second liquid 4 located within the housing. The first liquid has a higher density and lower boiling point than the second liquid. The heat engine further comprises a heat exchanger 6, 22 which transfers heat to the first liquid to evaporate the first liquid to form a first liquid vapour. The heat engine also comprises at least one fluid flow member 10, 27 which to moves in response to a fluid flow created by the interaction of the first liquid vapour and the second liquid. The heat exchanger is adapted to receive heat from thermal radiation and or one or more geothermal heat sources. The liquid-gas phase change of the first fluid provides an alternative mechanism for converting heat into work with numerous advantages. The heat engine has minimal moving parts, a relatively long lifetime, does not require a specific fuel, does not directly release toxic or un-environmentally friendly gases, and can be adapted to a specific source of waste heat.

Description

1 Heat Enoine and Method of Manufacture 3 The present invention relates to a heat engine and method of manufacture. In particular, 4 the described heat engine utilises a phase change of a fluid to convert thermal energy to mechanical energy.

7................ the Invention 9 A heat engine is a cyclic device which converts heat into work, or in other words, thermal energy into mechanical energy. In general, a heat engine contains a workino substance, 11 such as a gas or fluid, that absorbs heat from a high temperature reservoir, does work on 12 its surrounding and releases heat as it returns to its initial state. There exist numerous 13 different types of heat engines known in the art which operate on this basic principle, such 14 as an internal combustion engine.

16 The working substance of a heat engine cyclically undergoes changes in pressure, 17 temperature, and volume as well as the addition and removal of heat. For example, within 18 an internal combustion engine, a gas comprising a fuel-air mixture is compressed and then 19 ignited causing the gas to subsequently expand and drive a piston. The motion of the 1 piston if configured to expel the ignited gas and draw in unignifed gas for the cycle to continue.

4 Despite their ubiquitous use, there are numerous disadvantages to an internal combustion engine. An internal combustion engine requires a fuel to operate and cannot operate on 6 waste heat from an external high temperature (TH) source, It is necessary to ignite the fuel 7 to drive a piston which creates noise and requires numerous moving components, 1 hese 8 components can degrade and fail with use over time, requiring regular maintenance and 9 ultimately limiting the lifetime of the engine. Furthermore, a suitable fuel for an internal combustion engine is typically limited to expensive, refined gaseous or liquid hydrocarbon 11 compounds. In addition, the combustion of the fuel results in undesirable toxic and 12 environmentally unfriendly gases. internal combustion engines are also not scalable and 13 so are not suitable for large scale power generation.

An external combustion engine operates by an external high temperature (TH) source 16 heating a working fluid through a heat exchanger or engine wall. The heat causes the 17 working fluid to expand driving a piston. External combustion engines, such as steam 18 engines, can exploit numerous types of heat sources and such engines are widely used.

19 Nevertheless, these engines are typically suited to large scale power production so are large, heavy, expensive devices, which can be unsafe and relatively inefficient. An 21 external combustion engine also comprises moving components which creates noise and 22 requires maintenance.

1 Summary of the nvention

3 It is an object of an aspect of the present invention to provide a heat engine that obviates 4 or at least mitigates one or more of the aforesaid disadvantages of the heat engines known in the art.

7 According to a first aspect or the present invention there is provided a heatengine 8 comprising: 9 a housing; a first liquid and a second liquid located within the housing, the first liquid having a 11 higher density and lower boiling point than the second liquid; 12 a heat exchanger to transfer heat to the first liquid to evaporate the first liquid to form 13 a first liquid vapour; and 14 at least one fluid flow member to move in response to a fluid flow created by the interaction of the first liquid vapour and the second liquid.

17 fvtost preferably, the noosing is sealable. The heat engine is a closed heat engine. In this 18 arrangement the first and or second liquids are not added and or removed during 19 operation.

21 Preferably, the first and second liquids occupy an interior volume ot the housing. 'The first 22 and second liquids may mix within the interior volume of the housing.

24 Preferably, the first liquid is located within a first portion of the housing. The second liquid is located within a second portion of the housing.

27 Most preferably, the first liquid is de-mineralised water and the second liquid is Xylene.

28 Alternatively, the first liquid is de-mineralised water and the second liquid is kerosene, 29 Alternatively, the first liquid is decafluoropentane and the second liquid is de-mineralised water. Alternatively, the first liquid is chloroform and the second liquid is de-mineralised 31 water.

33 Preferably, an operating temperate range of the heat engine is between 110 to 150 t, 34 Alternatively, the operating temperature range of the heat engine is between 70 to 90 °C.

1 Preferably, the heat exchanger transfers heat tram an external high temperature heat source to the first liquid.

4 Preferably; the heat exchanger is the first portion of the housing. Alternatively; the heat exchanger is a pipe. The pipe may pass through the first portion of the housing.

7 Optionally, the heat engine may further comprise one or more pellets. The one or more 8 pellets are located within the interior volume of the heat engine. The one or more pellets 9 are suspended within the hrst liquid and or second liquid. The density of the one or more pellets is between the density of the first liquid and second liquid. The pellets are 11 chemically unreacfive with the first liquid, second liquid, and or first liquid vapour.

12 Preferably; the pellets are magnetically neutral. Alternatively, the pellets are magnetic.

14 Most preferably, the at least one fluid flow member may take the form of one or more rods.

The one or more rods may comprise a first end and a second end. The first ends of the 16 one or more rods are preferably mounted to an interior surface of the housing. The one or 17 more rods may extend into the interior volume of the housing. The second ends of the one 18 or more rods are preferably free to move. The second ends of the one or more rods are 19 preferably located towards a central axis or the housing.

21 Preferably; the one or more rods are uniformly distributed about the inlerior surface.

22 Alternatively, the one or more rods are non-uniformly distributed about the interior surface.

24 Preferably, the one or more rods are orientated perpendicular to the interior surface.

Alternatively, the one or more rods are orientated non-perpendicular to the interior surface.

27 Preferably, the one or more rods are uniformly dimensioned. Alternatively, the one or 28 more rods are non-uniformly dimensioned.

Preferably, the one or more rods comprise the same material composition. The one or 31 more rods may comprise brass. Alternatively, the one or more rods comprise different 32 material compositions.

34 Optionally, the at least one fluid flow member may take the form of one or more plates.

The one or more plates preferably comprise one or more perforations. The one or more 1 plates are preferably dimensioned in the form of a circular cross-section of the housing.

The one or more plates may be mounted to the interior surface of the housing. The one or 3 more plates may intersect the central axis of the housing.

Optionally, the at least one fluid flow member may take the form of one or more 6 diaphragms. The one or more diaphragms may comprise one or more perforations.

8 Optionally, the at least one fluid flow member may take the form of one or more pellets.

9 The one or more pellets are magnetic.

11 Preferably, the using comprises an inlet port and an outlet port. The inlet and outlet 12 ports are preferably sealable.

14 Optionally, the heat engine further comprises a condensing loop. The condensing loop transfers heat to an external low temperature heat sink from the first liquid vapour. The 16 condensing loop preferably condenses the first liquid vapour and returns the first liquid to 17 the first portion of the housing.

19 Optionally, the heat engine further comprises a sink. The sink may comprise the first liquid. The sink is preferably connected to the housing. The sink maintains the level of the 21 first liquid within the first portion ol the housing.

23 According to a second aspect of the present invention there is provided an energy 24 harvesting system comprising a heat engine in accordance with the first aspect of the present invention, an energy conversion means and an external high temperature heat 26 source.

28 Optionally, the energy harvesting system may further comprise an external low 29 temperature heat sink.

31 Most preferably, the energy harvesting system may further comprise a vibrational lens.

33 Preferably, the vibrational lens comprises at least two focusing members, each of the at 34 least two focusing members having a first end for attachment to a source of vibration and a second end, wherein the at least two focusing members are arranged such that the 1 separation between the focusing members decreases from the first ends towards the second ends.

4 Most preferably, the at least two focusing members each comprise a first portion located between the first end and second end. The first portions of the at least two focusing 6 members are angled relative to each other such that the at least two focusing members 7 converge at the second ends.

9 Preferably, the at least two focusing members each comprise a second portion located at the first end. Preferably, the second portions of the at least two focusing members are 11 substantially parallel.

13 Most preferably, the vibrational lens further comprises a bookplate. The first ends of the at 14 least two focusing members may be fixed to the bookplate. The second portions of the at least two focusing members may be fixed to the bookplate.

17 Preferably, the at least two focusing members each comprise a third portion located at the 18 second end. The third portions of the at least two focusing members are substantially 19 parallel, The third portions of the at least two focusing members define a focal point of the vibrational lens.

22 Preferably, the at least two focusing members comprise brass.

24 Optionally, the at least two focusing members comprise two or more layers and or coatings. The two or more layers and or coatings may exhibit different vibrational and or 26 thermal characteristics. The at least two layers and or coatings may comprise different 27 dimensions, materials, densities and or grain structures.

29 Optionally, the at least two focusing members comprise a first layer and a second layer.

The first layer is fixed to the second layer. The first layer may comprise brass. The 31 second layer may comprise steel.

33 Optionally, the vibrational lens further comprises one or more springs, The one or more 34 springs connect the at least two focusing members.

1 Optionally, the vibrauonal lens further comprises one or more weights attached to one or more of the at least two locusing members.

4 Optionally, the vibrational u her comprises a dynamic control system. The dynamic control system changes the vibrational characteristics of the vibrational lens during 6 operation, The dynamic control system may adjust the stiffness of the spring. The 7 dynamic control system may adjust the location and or magnitude of the weights.

9 Optionally,the vibrational lens may comprise three focusing members.

11 Most preferably, the focusing members are focusing plates.

13 Alternatively, the focusing members are focusing rods.

Most preferably, the first end of the vibrati 4kti lens is fixed to the heat engine.

17 Most preferably, he energy conversion means is located at the second end of the 18 vibrational lens. Preferably, the energy conversion means is located between the third 19 portions of the at least two focusing members.

21 Optionally, the housing of the heat engine further comprises sealable openings. The rods 22 of the heat engine are directly connected to the focusing members of the vibrational lens.

23 The rods pass through the sealable openings.

Preferably, the energy conversion means is one or more piezoelectric crystals, 26 Alternatively, the energy conversion means is one or more coils.

28 Alternatively, the energy conversion means is a coil. The coil may be wound around the 29 housing of the heat engine.

31 Embodiments of the second aspect of the invention may comprise leatures to implement 32 the preferred or optional features of the first aspect of the invention or vice versa.

34 According to a third aspect of the present invention there is provided a method of manufacturing a heat engine comprising, 1 providing a housing, providing a first liquid and a second liquid located within the housing, the first liquid 3 having a higher density and lower boiling point than the second liquid; 4 providing a neat exchanger to evaporate the first liquid to form a first liquid vapour; and 6 providing at least one fluid flow member that moves in response to a fluid flow 7 created by the interaction of the first liquid vapour and he second liquid, 9 Preferably, he method of manufacturing a heal engine may further comprise determining the characteristics of an external high temperature heat source.

12 Preferably; determining the characteristics of the external high temperature heat source 13 may include determining the temperature, energy, power, variability and or duration of the 14 external high temperature heat source.

16 Preferably, the method of manufacturing a heal engine may further comprises determining 17 optimum parameters of a heat engine for use with the external high temperature heat 18 source.

Preferably; determining the optimum parameters of a heat engine for use with the external 21 high temperature heat source may further comprise utilising the characteristics of the 22 external high temperature heat source.

24 Preferably, determining the optimum parameters of a heat engine may comprise determining: the dimensions of the heat engine; the volume, relative ratio and chemical 26 composition of the first and second liquids; the distribution, orientation, dimensions and or 27 material composition of the at least one fluid flow member; the operational proximity of the 28 heat engine to the high temperature (TH.) heat source; if a condensing loop is required; and 29 if a sink is required.

31 Embodiments of the third aspect of the invention may comprise features to implement the 32 preferred or optional features of the first and or second aspect of the invention or vice 33 versa.

1 According to a fourth aspect of the present invention there is provided a method of manufacturing an energy harvesting system comprising, 3 providing a heat engine in accordance with third aspect of the present invention; 4 providing an external high temperature heat source; and providing an energy conversion means.

7 Preferably, the method of manufacturing an energy harvesting system comprises providing 8 an external low temperature heat sink.

Preferably, the method of manufacturing an energy haR'estin.g system may comprise 11 providing a vibrational lens.

13 Preferably, providing a vibrational lens comprises, 14 providing at least two focusing members, each having a first end and a second end; and 16 arranging the at least two focusing members such that the separation between the 17 at least two focusing members decreases from the first ends towards the second 18 ends.

Preferably; providing a vibrational lens further comprises determining the characteristics of 21 the heat engine.

23 Preferably, determining the characteristics of the heat engine comprises quantifying any 24 one of the following parameters: the dimensions of the heat engine, the dimensions of at least one fluid flow member and the frequency characteristics of any mechanical 26 vibrations.

28 Preferably, providing a vibrational lens may further comprise determining the optimum 29 parameters of the vibrational lens for use with the heat engine.

31 Preferably, determining the optimum parameters oi a vibrational lens comprises 32 determining an optimum length, width and or depth of the at least two focusing members; 33 and or the optimum separation of the first ends of the at least two focusing members; and 34 or the optimum separation of the second ends of the at ieast two focusing members; and or the optimum distance for the at least two Focusing members to converge; and or the 1 optimum material or materials for the at least two focusing members; and or the optimum coefficient of thermal expansion of the material or materials of the at least two focusing 3 members.

Optionally, determining the optimum parameters may alsoinclude: determining the depth 6 of a first layer and a second layer of the at least two focusing plates; the material of the 7 first layer; and the material of the second layer. The first layer may comprise brass, the 8 second layer may comprise steel.

Preferably, providing the heat engine is performed before providing vibraflon lens.

12 Optionally, the method of manufacturing a vibrational energy harvesting system may be 13 iterative. The heat engine may be optimised following providing the vibrational lens.

Embodiments of the fourth aspect of the invention may comprise features to implement the 16 preferred or optional features of the first, second and or third aspects of the invention or 17 vice versa.

19 According to a Iifth aspect of the present invention there is provided a heat engine comprising: 21 a housing; 22 a first liquid and a second liquid located within the housing, the first liquid having a 23 higher density and lower boiling point than the second liquid; 24 a heat exchanger to transfer heat to the first liquid to evaporate the first liquid to form a first liquid vapour; and 26 at least one fluid flow member to move in response to a fluid flow created by the 27 interaction of the first liquid vapour and the second liquid, 28 wherein the heat exchanger is adapted to receive heat from thermal radiation and or 29 one or more geothermal heat sources.

31 Most preferably, the heat exchanger is adapted to receive heat from thermal radiation 32 wherein the thermal radiation comprises solar radiation.

34 Most preferably, the first and second liquids occupy an interior volume of the housing.

1 Preferably, the first liquid is located within a first portion of,e hoLising and the second liquid is located within a second portion of the housing.

4 Optionally, the heat engine further comprises one or more filament portions. The one or more filament portions are an extension of the first portion of the housing. The first liquid 6 is located within both the first portion of the housing and the one or more filament portions.

8 Preferably, the heat exchanger comprises the first portion of the housing. Additionally, or 9 alternatively; the heat exchanger comprises the one or more filament portions.

Additionally, or alternatively, the heat exchanger comprises a pipe and or a portion of a 11 pipe. Additionally, or alternatively, the heat exchanger comprises a conductive plate 12 thermally connected to a conductive coil, wherein the conductive plate is located on the 13 exterior of the housing and the conductive coil extends into the interior volume of the 14 housing.

16 Embodiments of the fifth aspect of the invention may comprise features to implement the 17 preferred or optional features of the first, second third and or fourth aspects of the 18 invention or vice versa.

According to a sixth aspect of the present invention there is provided an energy harvesting 21 system comprising a heat engine in accordance with fifth aspect of the present invention, 22 an energy conversion means and an external high temperature heat source.

24 Optionally; the energy harvesting system further comprises a fluid circulation system configured to transfer heat.

27 Preferably, the external high temperature heat source comprises thermal radiation. Most 28 preferably, the external high temperature heat source comprises solar radiation, Preferably, the energy harvesting system further comprises one or more optical lenses and 31 or one or more mirrors suitable for focusing thermal radiation. The one or more optical 32 lenses and or one or more mirrors are mounted on one or more stands. The one or more 33 stands each comprise a pivot arrangement suitable for adjusting and or optimising the 34 angle and or orientation of the one or more optical lenses and or one or more mirrors.

1 Optionally, the one or more optical lenses and or one or more mirrors are configured to focus thermal radiation towards the heat exchanger of the heat engine.

4 Optionally, the fluid circulation system comprises a solar fluid circulation system with a fluid within a vessel, pipes connecting the vessel to the housing of the heat engine and a 6 pump the circulate the fluid along the pipe between the vessel and the heat engine.

8 Optionally, the one or more optical lenses and or one or more mirrors are configured to 9 focus thermal radiation towards the fluid and or vessel or the solar fluid circulation system.

11 Most preferably, the external high temperature heat source comprises one or more 12 geothermal heat sources.

14 Optionally, the one or more filament portions of the heat engine are located and or orientated to extend towards the one or more geothermal heat sources.

17 Optionally, the fluid circulation system comprises a geothermal fluid circulation system with 18 a fluid contained within pipes and a pump to circulate the fluid around the pipes, wherein 19 the pipes extend between the geothermal heat source and the heat engine.

21 Preferably, the energy harvesting system Fur her comprises one or more vibrational lenses.

23 Embodiments of the sixth aspect of the invention may comprise features to implement the 24 preferred or optional features of the first, second third, fourth and or fifth aspects of the invention or vice versa.

27 According to a seventh aspect of the present invention there is provided a method Of 28 manufacturing a heat engine comprising, 29 providing a housing, - providing a first liquid and a second liquid located within the housing, the first liquid 31 having a higher density and lower boiling point than the second liquid; 32 -providing a heat exchanger to evaporate the first liquid to form a first liquid vapour; 33 and 34 -providing at least one fluid flow member that moves in response to a fluid flow created by the interaction of the first liquid vapour and the second liquid, wherein the heat exchanger is adapted to receive heat from thermal radiation and or one or more geothermal heat sources.

4 Embodiments of the seventh aspect of the invention may comprise features to implement the preferred or optional features of the first, second third, fourth, lit h and or sixth aspects 6 of the invention or vice versa.

8 According to an eighth aspect of the present invention there is provided a method of 9 manufacturing an energy harvesting system comprising, providing a heat engine in accordance with seventh aspect of the present 11 in 12 providing an external high temperature heat source; and 13 providing an energy conversion means.

Embodiments of the eighth aspect of the invention may comprise features to implement 16 the preferred or optional features of the first, second third, fourth, fifth, sixth and or seventh 17 aspects of the invention or vice versa.

19 BhelDescrlpUonofDrawings C. 21 There will now be described, by way of example only, various embodiments of the 22 invention with reference to the drawings, of which: 24 Figure 1 presents a schematic cross-sectional view of a heat engine in accordance with an embodiment of the present invention; 27 Figure 2 presents a cutaway perspective view of the heat engine of Figure 1; 29 Figure 3 presents a schematic cross-sectional view of the heat engine of Figure 1 in operation; 32 Figure 4 presents a schematic cross-sectional view of an alternative embodiment of the 33 heat engine of Figure 1 in operation; 1 Figure 5 presents a cutaway perspective view of an alternative embodiment of the heat engine of Figure 1; 4 Figure 6 presents a schematic cross-sectional view of an energy harvesting system comprising the heat engine of Figure 1; 7 Figure 7 presents a perspecfive view of a vibrational ens employed w;thin the vibrational 8 energy harvesting system of Figure 6; Figure 8 presents a schematic cross-sectional view of the vibrational lens of Figure 7; 12 Figure 9 presents a plot of (a) a voltage generated by a piezoelectric crystal located at a 13 second end of the vibrational lens of Figure 7, when the vibrational lens is attached to an 14 internal combustion engine and (b) a voltage generated by a reference piezoelectric crystal; 17 Figure 10 presents a schematic cross-sectional view of an alternative embodiment of the 18 vibrational lens at Figure 7; Figure 11 presents a schematic cross-sectional view of a further alternative embodiment of 21 the vibrational lens of Figure 7; 23 Figure 12 presents a schematic cross-sectional view of yet another alternative 24 embodiment of the vibrational lens of Figure 7; 26 Figure 13 presents a schematic cross-sectional view an alternative embodiment of the 27 energy harvesting system of Figure 6; 29 Figure 14 presents a flow chart of the method of manufacturing the heat engine of Figure 1; 32 Figure 15 presents a schematic cross-sectional view of an alternative energy harvesting 33 system of Figure 6; 1 Figure 16 presents a schematic cross-sectional view of a further alternative energy harvesting system of Figure 6; 4 Figure 17 presents a schematic cross-secUonal view of another alternative energy harvesting system of Figure 6; 7 Figure 18 presents a schematic cross-s -ma; view of an alternative energy harves!9 8 system of Figure 6; and Figure 19 presents a schematic cross-sectional view of a further alternative energy 11 harvesting system of Figure 6.

13 In the description which follows, like parts are marked throughout the specification and 14 drawings with the same reference numerals. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and 16 features of embodiments of the invention.

18 Detailed Desc tion of he Preferred Embodiments An explanation of the present invention wifl now be described with reference to Figures 1 21 to 19.

23 frteat.c:n_gjpe Figure 1 depicts a heat engine 1 a comprising a substantially cylindrical, sealable housing 26 2. The housing 2 comprises stainless steel, specifically, SA5,16 GR.65. For ease of 27 understanding, Figures 1 also depicts a cylindrical coordinate system with r, 6, and z axes.

29 The heat engine is can be seen to comprise a first liquid 3 and a second liquid 4 both of which are located within the housing 2. The first and second liquids 3, 4 occupy an interior 31 volume 5 of the housing 2. The First liquid 3 has a higher density but lower boiling point in 32 comparison to the second liquid 4. As such, whilst the first and second liquids 3, 4 are free 33 to mix within the housing 2, the first liquid 3 locates within a first portion 6 of the housing 2, 34 at the base of the housing 2, and the second liquid 4 locates within a second portion 7 of the housing 2, above the first liquid a By way of example, the first liquid 3 may be de-mineralised water and the second liquid 4 3 may be Xylene. The density of de-mineralised water is approximately 12 times that of 4 Xylene and clemineralised water has a boiling point of 100 °C which is lower than the boiling point of Xylene, 138.5 °C. De-mineralised water and Xylene are both in a liquid 6 stale at room temperature (20 "C) and pressure. A heat engine la comprising de- 7 mineralised water and Xylene as the first and second liquids 3, 4 is suitable for operation 8 at a temperature between 110 °C and 150 'C.

Further examples of the first and second liquids 3, 4 are provided in Table I along with an 11 operating temperature range of a heat engine la comprising the first and second liquids 3, 12 4. All of the first and second liquids 3, 4 in Table I are in a liquid state at room temperature 13 (20 °C) and pressure. Furthermore, it will be appreciated that different operating 14 temperature ranges to those detailed in Table I, such as an operating temperature range lower than 70 -90 DC, could be achieved by using different first and second liquids 3, 4 16 and different combinations of the first and second liquids 3,4 beyond the disclosed liquids 17 and combinations in Table I. 19 Table Examples of the first, second liquid and an operating temperature range of a heat engine comprising the first and second liquids First Liquid Second Liquid Operating Temperature i Range (°C) De-mineralised water Xylene 110-150 De-mineralised water Kerosene 110-150 Decafluoropentane De-mineralised water 70 --90 Chloroform De-mineralised water 70 -90 22 The heat engine la also comprises a heat exchanger which transfers heat from an 23 external high temperature (TH) heat source 8 to the first liquid 3 in order to evaporate a 24 quantity of the first liquid 3. The first liquid 3 is not directly exposed to the external high temperature (TH) heat source or any external fluid carrying heat from the external high 26 temperature (TH) heat source 8. In the embodiment of Figure 1 the heat exchanger takes 27 the form of the first portion 6 of the housing 2.

1 The heat engine la further comprises at least one fluid flow member 9. As can be clearly seen in Figure 2, the at least one fluid flow member takes the form of rods 10. Each rod 3 10 has a first end 11 and a second end 12. The first ends 11 of the rods 10 are mounted 4 to an interior surface 13 of the housing 2. The rods 10 extend into the interior volume 5 of the housing 2. The second ends 12 of the rods 10 are free to move and are located 6 towards a central axis 14 of the housing 2. The rods 10 are distributed across the interior 7 surface 13 of the housing 2 in both Band z. directions. The rods 10 are located in the 8 second portion 7 of the housing 2. Figures 1 to 3 depict the rods 10 as being uniformly 9 distributed about the interior surface 13, orientated perpendicular to the interior surface 13 and all of uniform dimensions such as length. The rods 10 may be made from bronze and 11 or brass as the relatively high density effectively transmits any movement or mechanical 12 vibrations.

14 The housing 2 comprises a sealable inlet port 15 and a sealable outlet port 16. The sealable inlet port 15 is located at a top end 17 of the housing 2, through the second 16 portion 7 of the housing 2 and provides a means for adding the first and second liquids 3, 17 4 into the housing 2. Similarly, the sealable outlet port 16 is located, at a base end 18 of 18 the housing 2, through the first portion 6 of the housing 2 and provides a means for 19 draining the first and second liquids 3, 4 from the housing 2. In order to fill and maintain the housing 2 at a positive pressure, the first and second liquids 3, 4 may be pumped to 21 arid from the housing 2 by a pumping system 19.

23 Figure 3 shows the heat engine la of Figure 1 in operation, in other words converting 24 thermal energy into mechanical energy. The heat engine la is a closed engine such that first and second liquids 3, 4 are not added or removed during operation. The first portion 6 26 of the housing 2 is exposed to the external high temperature (TH) heat source 8 resulting in 27 thermal energy being transferred through the housing 2, to the first liquid 3. As such, a 28 portion of the first liquid 3 evaporates to form a first liquid vapour. The first liquid vapour 29 takes the form of gaseous bubbles 20. The gaseous bubbles 20 have a lower density than both the first liquid 3 and the second liquid 4. As such, the gaseous bubbles 20 move in 31 the positive z-direction, into the second portion 7 ol the housing 2 and through the second 32 liquid 4. The thermal enemy from the external high temperature (TH) heat source 8 is 33 converted into kinetic energy in the form of the motion of the gaseous bubbles 20.

1 The interaction, in the form of relative motion and or thermal gradients, of the gaseous bubbles 20 and the second liquid 4 creates a fluid flow. More specifically, the fluid flow 3 includes the flow of the first liquid 3, second liquid 4 and gaseous bubbles 20. For 4 example, the fluid flow is depicted by the arrows in Figure 3. This fluid flow may be Laminar and or turbulent. The fluid flow induces movement in the rods 10, or more 6 specifically, the fluid flow induces mechanical vibrations within the rods 10. As such, the 7 kinetic energy of the gaseous bubbles 20 is converted into mechanicai vibrational energy.

8 For example, the Laminar fluid flow of the gaseous bubbles 20 may result in the gaseous 9 bubbles 20 directly colliding with the rods 10, deflecting the rods 10. Furthermore, the turbulent fluid flow of the gaseous bubbles 20 and second liquid 4 may induce movement II and or mechanical vibrations within the rods 10.

13 Each gaseous bubble 20 dissipates kinetic and thermal energy. As a result, each gaseous 14 bubble 20 will eventually condense to form a liquid bubble 21 of the first liquid 3. The liquid bubbles 21 sink back towards the base end 18, into the first portion 6 of the housing 16 2 as the density of the liquid bubbles 21 is greater than the density of the second liquid 4.

17 An advantage of the liquid bubbles 21 sinking back through the second portion 7 of the 18 housing 2, is the liquid bubbles 21 may further create fluid flows and induce movement 19 and or mechanical vibrations within the rods 10.

21 As an alternative embodiment, instead of being cylindrical, it will be appreciated fit 22 housing 2 could take any regular or non-regular three-dimensional shape.

24 As an additional or alternative embodiment, the heat exchanger may take the form of a pipe 22 which passes through the first portion 6 of the housing 2, see the heat engine lb 26 of Figure 4. An external fluid carrying the heat from the external high temperature (TH) 27 heat source 8 passes through the pipe indirectly transferring the heat to the first liquid 3.

28 The pipe 22 is more efficient at transferring heat to the first liquid 3 than through the first 29 portion 6 of the housing 2, as the pipe 22 has greater thermal contact with the first liquid 3.

31 As an additional or alternative embodiment, the distribution of the rods 10 may be non- 32 uniform. As another additional or alternative embodiment, the rods 10 may be orientated 33 non-perpendicular to the interior surface 13. As a further additional or alternative 34 embodiment, the dimensions of the rods 10, such as the rods length, may vary. As yet another further additional or alternative embodiment, the material composition of the rods 1 10 may vary. Furthermore, the distribution, orientation, dimensions and material composition of the rods 10 may be computationally optimised.

4 As an additional or alternative embodiment, the heat engine lb of Figure 4, further comprises pellets 23a. The pellets 23a are located within the interior volume 5 of the heat 6 engine lb, suspended within the first and second liquids 3, 4. The pellets 23a move about 7 the interior volume 5 of the housing 2 in response to the fluid flow created by the 8 interaction of the gaseous bubbles 20 and the second liquid 4. The pellets 23a collide with 9 the rods 10 inducing further movement, or more specifically, mechanical vibrations within the rods 10, in addition to the movement induced directly by the flub flow. The density of I the pellets 23a is between the density of the first and second liquids 3, 4 such that the 12 pellets 23a are not too heavy or buoyant when suspended within the first and second 13 liquids 3, 4. Furthermore, the pellets 23a are chemically unreactive with the first liquid 3, 14 second liquid 4 and gaseous bubbles 20. The pellets 23a are also magnetically neutral.

The dimensions and material composition of the pellets 23a may be optimised to achieve 16 the desired interaction with the fluid flow. As a further additional or alternative 17 embodiment, the pellets 23b may be magnetic, as discussed further below in the context 18 of Figure 15.

As an additional or alternative embodiment, the heat engine lb of Figure 4, further 21 comprises a condensing loop 24. Instead of the gaseous bubbles 20 passively 22 condensing once they have lost sufficient energy within the housing 2, the condensing 23 loop 24 actively condenses the gaseous bubbles 20. More specifically, once the gaseous 24 bubbles 20 have traversed through the second portion 7 of the housing 2, the gaseous bubbles 16 pass through the condensing loop 24 where an external low temperature (TL) 26 heat sink 25 actively cools the gaseous bubbles 20 such that they condense to liquid 27 bubbles 21. The liquid bubbles 21 are returned to the first portion 6 of the housing 2. A 28 condensing loop 24 may be advantageous if, for example, the gaseous bubbles 20 29 accumulate at the fop end 17 of the housing 2, 31 As another additional or alternative feature, the heat engine lb of Figure 4, further 32 comprises a sink 26 of the first liquid 3. The sink 26 is connected to the housing 2 and 33 maintains the level of the first liquid 3 within the first portion 6 of the housing 2. As the first 34 liquid 3 evaporates within the heat engine 1 b, this may induce non negligible changes in 1 pressure and or volume within the heat engine lb. The sink 26 minimises any changes in pressure and or volume.

4 As an additional or alternative embodiment, instead of the rods 10, the at least one fluid flow member may take the form of a plate 27 comprising perforations 28, as depicted by 6 the heat engine lc of Figure 5. The plate 27 is dimensioned in the form of a circular cross- 7 section of the housing 25 mounted to the interior surface 13 of the housing 2 and orientated 8 to intersect the central axis 14. The fluid flow induces movement and or mechanical 9 vibrations within the plate 27. For example, the fluid flow of the gaseous and liquid bubbles 20, 21 are blocked by the plate 27 and redirected through the perforations 28 11 inducing movement and or mechanical vibrations in the plate 27. The size, distribution 12 and relative location of the perforations 28 can be optimised to enhance the turbulent fluid 13 flows within the heat °mine lc. As a further additional or alternative feature, the plate 27 14 may be flexible, in other words, the fluid flow member takes the form of a diaphragm with perforations.

17 The process of heat transfer to the first liquid 3, evaporation of the first liquid 3 to form 18 gaseous bubbles 20, energy transfer from the gaseous bubbles 20 to the fluid flow 19 member (in other words the rods 10, plate 27 and or diaphragm) and condensation of the gaseous bubbles 20 to form liquid bubbles 21 is repeated forming a cycle. The 21 mechanical energy (in other words the movement arid or vibrations) can be further 22 converted into electrical energy.

24 Energy Harvesthig System 26 Figure 6 depicts the heat engine 1 and the external high temperature (Tti) heat source 8 as 27 part of an energy harvesting system 29a, more specifically, a vibrational energy harvesting 28 system, The vibrational energy harvesting system 29a further comprises an energy 29 conversion means 30. The energy harvesting system may optionally comprise the external low temperature (IL) heat sink 25 if required to condense the gaseous bubbles 31 20. Furthermore, the vibrational energy harvesting system 29a may optionally comprise a 32 vibrational lens 31.

34 Figures 7 and 8 depict a suitable vibrational lens 31a for use in the energy harvesting system 29a. The vibrational lens 31a may be of a type as described in the applicants co- 1 pending LIK patent application number GB1911017.0. As such, the vibrational lens 31a comprises a backplate 32 and two focusing members. The focusing members take the 3 form of a first focusing plate 33 and a second focusing plate 34. The first and second 4 focusing plates 33, 34 each have a first end 35 and a second end 36. The first and second focusing plates 33, 34 each comprise a first portion 37, having a length y, located 6 between a second portion 38, at the first end 35, and a third portion 39, at the second end 7 36.

9 The second portion 38 of the first and second focusing plates 33, 34 is fixed to the backplate 32. As shown in Figure 7, the second portion 38 is angled to be substantially 11 parallel and in contact with the backplate 32 such that the second portion 38 is fixed to the 12 backplate 32 by welding. In addition to or as an alternative to welding, the fixture means 13 may take the form of an adhesive, a nut and a bolt, rivets, a combination thereof or any 14 other suitable alternative.

16 The second portions 38 of the first and second focusing plates 33, 34 are fixed to the 17 backpiate 32 at substantially the same orientation and separated by distance a, as can be 18 seen in Figure 8.

As can also be seen in Figure 8, the first portions 37 of the first and second focusing plates 21 33, 34, are angled relative to the backplate 32 such that they converge towards each 22 other. In the presently described embodiment, the first portions 37 of the first and second 23 focusing plates 33, 34, are angled relative to the backplate 32 such that they converge 24 towards a point at a distance p along a normal to the backplate 32 located midway (a12) between the second portions 38 of the first and second focusing plates 33, 34.

27 The third portions 39 at the second end 36 of the first and second focusing plates 33, 34 28 are angled to be substantially parallel, and preferably perpendicular to the backplate 32, 29 and act as the focal point of the vibrational lens 31a.

31 As depicted in Figures 6, the vibrational lens 31a is attached to the heat engine 1. The 32 backplate 32 of the vibrational lens 31a is fixed to the heat engine 1, by for example nuts 33 and bolts, welding and or any other appropriate, equivalent means or combination thereof.

34 Mechanical vibrations induced in the rods 10 of the heat engine 1 are transmitted through the housing 2 01 the heat engine 1 to the vibrational lens 31a.

As can clearly be seen in Figure 6, located between the third portions 39 oi the first and 3 second focusing plates 33, 34 is the energy conversion means 30 which takes the form of 4 one or more piezoelectric crystals 40. The piezoelectric crystals 40 are connected to electrical components 41 and directed to, for example, an appropriate electrical load (not 6 shown) by cables 42. The one or more piezoelectric crystals 40 convert vibrational 7 mechanical energy originating from the heat engine 1 into useful electrical energy. An 8 alternative energy conversion means could take the form of nano-coils and magnets.

It will be appreciated that in an additional or alternative embodiment of the energy 11 harvesting system 29a, the piezoelectric crystals 40 may be attached directly to the heat 12 engine 1. However, in the embodiment as depicted by Figure 6, the piezoelectric crystals 13 40 are attached to the vibrational lens 31 as more electrical energy can be generated, as 14 generically demonstrated by Figure 9.

16 Figure 9a shows the voltage as a function of time, generated by a piezoelectric crystal 40 17 located between the third portions 39 of the first and second focusing plates 33, 34 of the 18 vibrational lens 31a when the vibrational lens 31a is attached to an internal combustion 19 engine which acts as a vibrational source, taking the place of the heat engine 1. Figure 9a depicts a root mean-square voltage of 0.743 V. Figure 9b shows the voltage as a function 21 of time, generated by a reference piezoelectric crystal (not shown in the Figures) directly 22 attached the internal combustion engine. Figure 9b depicts a root mean-square voltage 23 0.003 V. The piezoelectric crystal 40 between the third portions 39 generates a voltage 24 approximately 248 times greater than the voltage of the reference piezoelectric crystal.

26 The reason for this is that vibrational lens 31a transmits, converges and or focuses 27 vibrations from the first end 35 to the second end 36 of the focusing plates 33, 34. As 28 such, the focusing plates 33, 34 could be considered equivalent to a cantilever as the first 29 end 35 of each focusing plate 33, 34 is fixed to the backplate 32, and the second end 36 is free to move, actuating the piezoelectric crystals 40.

32 The focusing plates 33, 34 are substantially triangular, as can clearly be seen in Figure 7.

33 The first end 35 of the focusing plates 33, 34 are equivalent to the base of a triangle and 34 the second end 36 equivalent to the (truncated) tip of a triangle. The triangular shape of 1 the focusing plates 33, 34 minimises the space required to house the vibrational lens 31a at the perpendicular distance p from backplate 32 whilst maintaining functionality.

4 The vibration lens 31a as depicted in Figures 6 to 8 is made from brass due to the relatively high density of brass which facilitates efficient transmission of vibrational 6 mechanical energy through the vibrational lens 31a. The vibrational lens 31a may 7 alternatively be made from other metals, alloys or even non-metallic materials, such as 8 ceramics, suitable for transmitting vibrational energy.

As an additional or alternative feature, the vibrational lens Sib of Figure 10, further I comprises a spring 43 between the first and second focusing plates 33, 34. it will be 12 appreciated that the vibrational lens 31b could comprise multiple springs 43. Similarly, as 13 a further additional or alternative feature the vibrational lens 31c of Figure 11, further 14 comprises a weight 44 attached to the first focusing plates 33. Again, it will be appreciated that the vibrational lens 31c may comprise multiple weights 44 of equal or non-equal 16 weight located on both or just one of the first and second focusing plates 33, 34. As a 17 further alternative the vibrational lens 31 may comprise both a spring 43 and a weight 44.

18 Both the spring 43 and the weight 44 modify the vibrational characteristics of the 19 vibrational lens 31b, 31c by damping and or changing the resonant frequency of the vibrational lens 31b, 31c, which provides a mechanism to optimise the characteristics of 21 the vibrational lens 31b, 31c. Figures 10 and 11 show the vibrational lens 31b, 31c may 22 additionahy comprise a dynamic control system 45 to dynamically adjust the stiffness of 23 the spring 43 and or location of the weight 44 on the first and or second focusing plates 33, 24 34 and or the magnitude of the weight 44 on the first and or second focusing plates 33, 34.

For example, the weight 44 may take the form of a container into which water may be 26 pumped in and or out of by means of the dynamic control system 45. The dynamic control 27 system 45 facilitates modifying the vibrational characteristics of the vibrational lens 31b, 28 31c during operation.

As another additional or alternative feature, the focusing members may comprise multiple 31 layers and or coatings. The dilferent layers and or coatings may exhibit different 32 vibrational and or thermal characteristics due to comprising, for example, different 33 dimensions, materials, densities and or grain structures.

1 For example, Figure 12 depicts focusing plates 33, 34 comprising a first, outer layer 46 and a second, inner 47 layer. The second, inner layer 47 may be less dense than the 3 outer layer 46. It is found this arrangement improves the transmission of vibrations 4 through the vibrational lens 31d. As another example, the grain structure of the first, outer layer 46 may be more aligned in comparison to the grain structure of the second, inner 6 layer 47. Again, this arrangement improves the transmission of vibrations through the 7 vibrational lens 31d. As another example, the first layer 46 may be made from brass and 8 the second layer 47 may be made from steel.

In addition, it is further noted the relative physical properties of the first, outer layer 46 and 11 the second, inner layer 47 may be reversed such that for example, the second, inner layer !, 47 may be more dense than the first, outer layer 46. As a further alternative, the grain 13 structure of the first, outer layer 46 may be less aligned in comparison to the grain 14 structure of the second, inner layer 47. The physical properties of the different layers such as the dimensions, materials, densities and or grain structures are optimised according to 16 the desired vibrational and or thermal characteristics which ultimately depends on 17 frequency characteristics of the vibrational source, in other words, the heat engine 1.

19 As a further alternative, the vibrational lens 31a, 31b, 31c, 31d may comprise more or less than two focusing plates 33, 34. For example, a vibration lens 31a, 31b, 31c, 31d with just 21 a first focusing plate 33 could actuate piezoelectric crystals 40 located at the second end 22 36 of the first focusing plate 33 against the heat engine 1, more specifically, a protruding 23 portion of the housing 2. Conversely, a vibrational lens, 31a, 31b, 31c, 31d with three 24 focusing plates 33, 34 may comprise two sets of piezoelectric crystals 40, one set of piezoelectric crystals 40 between the second end 36 of a first and a second focusing 26 plates, and the other set of piezoelectric crystals between the second 34 and third 48 27 focusing plates, as shown in Figure 13.

29 As yet another alternative, instead of the vibrational lens 31a, 3lh, 31c, 31d comprising a backplate 32, the focusing plates 33, 34 may be fixed directly to the heat engine 1.

32 Figure 13 shows another additional or alternative embodiment of an energy harvesting 33 system 29b, where the housing 2 of the heat engine 1 may comprises sealable openings 34 49 such that the rods 10 pass through the housing 2 and directly connect to the focusing plates 33, 34 of the vibrational lens 31a, 31b, 31c, 31d. As such, the mechanical 1 vibrations induced in the rods 10 can propagate along the rods 10 and directly along the focusing plates 33,34 of the vibrational lens 31a, 31b, 31c, 31d. In this embodiment, as 3 the rods 10 connect directly to the focusing plates 33, 34, a bookplate 32 is not required.

4 The openings 49 are sealable, with or without the rods 10 passing through the openings 49, to ensure the housing 2 does not leak.

7 As a further alternative, instead of the vibrational lens 31a, 31b, 31c, 31d comprising 8 focusing plates 33, 34, the focusing members could take the form of focusing rods. The 9 focusing rods may just be an extension of the rods 10 of the heat engine 1. Furthermore, the planar layers 46,47 of the focusing plates 33, 34 as depicted in Figure 12 are 11 equivalent to concentric layers and or coatings of a focusing rod. Advantageously, 12 focusing rods take up less space than the focusing plates 33, 34.

14 Method of Manufacturing a Heat Engine 16 Figure 14 shows a flow chart for a method of manufacturing the heat engine 1. The 17 method comprises: providing a housing (S1001); providing a first and second liquid located 18 within the housing, the first liquid having a higher density and lower boiling point than the 19 second liquid (51002); providing a heat exchanger to transfer heat to the first liquid to evaporate the first liquid to form a first liquid vapour (S1003); and providing at least one 21 fluid flow member to move in response to a fluid flow created by the interaction ol the first 22 liquid vapour and second liquid (S1004).

24 In addition, the method of manufacturing the heat engine 1 may optionally comprise characterising the external high temperature (TO heat source 8. For example, this may 26 include characterising the temperature, energy, power, variability and or duration of the 27 external high temperature (TH) heat source 8. In the context of the present invention, the 28 term high temperature (TO broadly refers to any temperature above ambient temperature.

As a further addition, the method of manufacturing the heat engine 1 may optionally 31 comprise utilising the characteristics of the high temperature (Li) heat source 8 to 32 determine the optimum parameters of a heat engine 1. For example, this optimisation 33 process may include determining: the dimensions of the heat engine 1; the volume, 34 relative ratio and chemical composition of the first and second liquids 3, 4; the distribution, orientation, dimensions and material composition of the rods 10; the operational proximity 1 of the heat engine 1 to the high temperature (TO heat source 8; if a condensing loop 24 is required; and if a sink 26 is required. As an example of the parameter dependency, the 3 higher the temperature and power of the external high temperature (TH) heat source 3, the 4 greater the maximum viable size (i.e. dimensions, volume) of the heat engine 1. When choosing the first and second liquids 3, 4 factors such as the heat capacity, relative density 6 and relative boiling points are key considerations. It is advantageous to optimise the heat 7 engine 1 as this ensures the heat engine 1 can operate, for example, the externai high 8 temperature (TH) heat source 8 will provide enough heat to evaporate any quantity of the 9 first liquid 3. Furthermore, the optimisation ensures the heat engine 1 can operate efficiently.

I

12 Method of Manufacturing a Vibrational Energy Flarvestino System 14 A method of manufacturing an energy harvesting system 29 comprises providing a heat engine 1 in accordance with the flow chart depicted in Figure 14 and as described above, 16 providing an external high temperature OA heat source Sand providing an energy 17 conversion means 30.

19 As an additional or alternative feature, the method of manufacturing an energy harvesting system 29 may optionally comprise providing an external low temperature (TL) heat sink 21 25.

23 As a further additional or alternative feature, the method of manufacturing an energy 24 harvesting system 29 may optionally comprise providing a vibrational lens 31a, 31b, 31c 31d. The vibrational lens 31a, 31b, 31c 31d is manufactured such that it is optimised for a 26 specific heat engine 1. Providing a vibration lens 31a, 31b, 31c 31d may comprise, 27 determining the characteristics of the heat engine 1 such as the dimensions of the heat 28 engine 1, the dimensions of the fluid flow member (i.e. rods 10) and most significantly the 29 frequency characteristics of the mechanical vibrations induced within the rods 10.

31 In addition, providing a vibrational lens 31a, 31b, 31c 31d may optionally comprise 32 determining the optimum parameters for a vibrational lens 31a, 31b, 31c 31d for 33 harvesting the mechanical vibrational energy from the heat engine 1. This includes 34 determining the shape and dimensions of the vibrational lens 31a, 31b, 31c 31d such as, distances a, and y. More specifically, the optimisation may include dimensioning the 1 length y of the focusing plates 33, 34, to match an average resonant frequency across the operational range of the heat engine I. 4 Furthermore, providing a vibrational lens may optionally comprise providing a vibrational lens 31a, 31b, 31c 31d according to the optimum parameters. More specifically, the 6 focusing plates 33.34 of the vibrational lens 31a, 31b, 31c 31d are provided by water jet 7 cutting brass plates to the required dimensions and introducing appropriate bends in 8 focusing plates 33, 34. The focusing plates 33, 34 are welded to the backplate 32.

Providing a vibrational lens may optionally comprise further optimising the parameters of 11 the vibrational lens 31a, 31b, 31c 31d according to factors such as: the type of energy 12 conversion means located at the second end 36 of the focusing plates 33, 34; the number 13 of focusing plates 33, 34 the vibrational lens 31a, 31b, 31c 31d comprises; the space 14 available to house the vibrational lens 31a, 311o, 31c 31d; and more generally the operational constraints and desired performance characteristics. For example, the first 16 portions 37 of the first and second focusing plates 33, 34 are not limited to converging midway between the second portions 38 of the first and second focusing plates 33, 34. In 18 other words, the first portions 37 of the focusing plates 33, 34 may be asymmetrically 19 angled relative to the backplate 32 to fit within the available space and or for a desired performance of the vibrational lens 31a, 31b, 31c 31d.

22 As describe above, the heat engine 1 is optimised for a specific external high temperature 23 (TO heat source 8. Therefore, when manufacturing an energy harvesting system 29 it 24 may be suboptimal to provide the vibrational lens 31a, 31b, 31c 31d without first manufacturing and characterising the heat engine 1. However, it is noted that this method 26 may be iterative. For example, parameters of the heat engine 1 may be altered to 27 optimise the vibrational lens 31a, 31b, 31c 31d and energy harvesting system 29.

29 Alternative Heat Enoine and Energy Harvesting System 31 Figure 15 depicts an alternative heat engine 1 as part of an alternative energy harvesting 32 system 29c. The heat engine 1 and energy harvesting system 29c depicted in Figure 15 33 may comprise the same preferable and optional features as the heat engines 1 and energy 34 harvesting systems 29 depicted in any of Figures 1 to 14.

1 Instead of the at least one fluid flow member 9 taking the form of rods 10, a plate 27 and or a diaphragm, the at least one fluid flow member 9 of the heat engine 1 of Figure 15 takes 3 the form of at least one magnetic pellet 23h located within the interior volume 5 of the heat 4 engine 1 and suspended within the first and or second liquids 3, 4. The magnetic pellets 23b move about the interior volume 5 of the housing 2 in response to the fluid flow created 6 by the interaction of the gaseous bubbles 20 and the second liquid 4. The thermal energy 7 of the external high temperature (1 H) heat source 8 is converted into mechanical energy in 8 the form of motion of the magnetic pellets 23b. In this embodiment it may be preferably for 9 the housing 2 to comprise a non-magnetic material such as Aluminium.

11 As well as the heat engine 1, the alternative energy harvesting system 29 comprises an 12 external high temperature (TH) heat source 8 and an energy conversion means 30.

13 Instead of piezoelectric crystals 40, the energy conversion means 30 takes the form of a 14 coil 50, wound around the housing 2 of the heat engine 1. The coil 50 may comprise copper although other alternative magnetically inductive materials may be employed. It 16 will also be appreciated by the skilled reader that the location the coil 50 may vary from 17 that shown in Figure 15. For example the coil 50, or at least a portion of the coil 50, may 18 be located within the housing 2.

The motion of the magnetic pellets 23b within the heat engine 1 induces useful electrical 21 energy within the coil 50. This energy harvesting system 29 relies on magnetic induction 22 instead of mechanical vibrations to harvest the thermal energy originating from the 23 external high temperature (TH) heat source 8.

As an additional or alternative embodiment, the at least one fluid flow member 9 of a heat 26 engine 1 may take the form of both rods 10 and magnetic pellets 23b. The fluid flow 27 created by the interaction of the gaseous bubbles 20 and the second liquid 4, induces both 28 mechanical vibrations within the rods 10 and the motion of the magnetic pellets 23b.

29 Correspondingly, the energy conversion means 30 of an energy harvesting system 29 may be both piezoelectric crystals 40 and a coil 50. The piezoelectric crystals 40 convert the 31 mechanical vibrational energy into useful electrical energy and the motion of the magnetic 32 pellets 23b induces useful electrical energy within the coil 50. As well as inducing 33 electrical energy, the motion of the magnetic pellets 23b may advantageously also collide 34 with the rods 10 inducing further mechanical vibrations.

1 Figure 16 depicts an alternative energy haivesting system 29d comprising a heat engine 1 which may comprise the same preferable and optional features as the heat engines 1 and 3 energy harvesting devices 29a, 29b, 29c of Figures 1 to 15.

As can be seen in Figure 16, the energy harvesting system 29d further comprises optical 6 lenses 51. In operation, the optical lenses 51 focus thermal radiation in the form of solar 7 radiation 52 towards the heat engine 1. In particular, the optical lenses 51 focus the solar 8 radiation 52 towards the heat exchanger of the heat engine 1. The heat exchanger 9 transfers heat from the solar radiation 52 to the first liquid 3. As such, the solar radiation 52 acts as the external high temperature (TH) heat source 8.

I

12 As with previous embodiments, the heat exchanger can take the form of the first portion 6 13 of the housing 2. As an additional or alternative feature, the heat exchange can take the 14 form of a conductive plate 53 thermally connected to a conductive coil 54. The conductive plate 53 is located on the exterior of the housing 2 and the conductive coil 54 extends into 16 the housing 2. The solar radiation 52 is focused on the conductive plate 53, heat is 17 transmitted along the conductive coil 54 and then the heat is transferred to first liquid 3.

18 Advantageously, in comparison to the heat exchanger taking the form of the first portion 6 19 of the housing 2, the conductive plate 53 and conductive coil 54 arrangement can more efficiently and evenly transfer heat from the solar radiation 52 to the first liquid 3.

22 The optical lenses 51 are mounted in position by a stand 55. The stand 55 comprises a 23 pivot arrangement 56 which facilitates adjusting and or optimising the angle and or 24 orientation of the optical lenses 51 relative to the heat engine 1.

26 It will be appreciated that as an additional or alternative feature the optical lenses could 27 take the form of a mirror, more specifically, a parabolic mirror array.

29 Figure 17 depicts an alternative energy harvesting system 29e comprising a heat engine 1 which may comprise the same preferable and optional features as the heat engines I and 31 energy harvesting devices 29a" 29b, 29c, 29d of Figures Ito 16, 33 Similar to the embodiment of Figure 16, the energy harvesting system 29e of Figure 17 34 comprises optical lenses 51 suitable for focusing solar radiation 52. However, in contrast to the embodiment of Figure 16, the energy harvesting system 29e of Figure 17 comprises 1 a fluid circulation system 57e. The fluid circulation system 57e comprises a fluid 58 within a vessel 59, pipes 60 connecting the vessel 59 to the housing 2 of the heat engine 1 and a 3 pump 61 to circulate the fluid 58 along the pipes 60 between the vessel 59 and the heat 4 engine 1. Similar to the embodiment of Figure 4, the heat exchanger of the heat engine 1 of Figure 17 takes the form of the portion of the pipe 60 which passes through the first 6 portion 6 of the housing 2.

8 In operation, optical lenses 51 focus solar radiation 52 upon the fluid 58 and or the vessel 9 59 ol the fluid circulation system 57e. The fluid 58 directly and or indirectly, through the vessel 59, absorbs heat from the solar radiation 52. The heated fluid 58 is then circulated 11 about the pipes 60 by the pump 6110 transfer the heat to the first liquid 3 within the heat 12 engine 1. The fluid 58 does not mix with the first liquid 3.

14 As an example, the fluid 58 of the fluid circulation system 57e may take the form of liquid sodium which can hold heat for a relatively long time as has a relatively high specific heat 16 capacity. In this embodiment, the liquid sodium can be considered a thermal battery as 17 can retain heat from the solar radiation 52, and continue to transfer heat to the first liquid 3 18 within the heat engine -I, even when the solar radiation 52 is no longer focused upon the 19 fluid 58 and or the vessel 59.

21 To surnrnarise, the energy harvesting systems 29d, 29e of Figures 16 and 17 are 22 configured to generate electricity by harnessing heat from thermal radiation, for example, 23 solar radiation. In other words, the external high temperature (TO heat source which 24 drives the heat engines 1 depicted in Figures 16 and 17 is solar radiation.

26 Figures 18 depicts an alternative enemy harvesting system 29f comprising a heat engine 1 27 which may comprise the same preferable and optional features as the heat engines 1 and 28 energy harvesting devices 29a, 29b, 29c, 29d, 29e of Figures 1 to 17.

As can be seen from Figure 18, the energy harvesting system 29f comprises a fluid 31 circulation system 571 configured to transfer heat from a subterranean hotspot 62 to the 32 first liquid 3 within the heat engine 1. In this embodiment, the fluid circulation system 57f 33 comprises fluid 58 contained within pipes 60 and a pump 61 to circulate the fluid 58 34 around the pipes 60. Similar to the embodiment of Figures 4 and 17, the heat exchanger 1 of the heat engine 1 of Figure 18 takes the form of the portion of the pipe 60 which passes through the first portion 6 of the housing 2.

4 In operation, fluid 58 in close proximity to the subterranean hotspot 62 absorbs heat. The heated fluid 58 is then circulated by the pump 61 to the heat engine 1. The heat is 6 transferred from the fluid 58 to the first liquid 3 within!he heat engine 1.

8 Figures 19 depicts an alternative energy harvesting system 29g comprising a heat engine 9 1 which may comprise the same preferable and optional features as the heat engines 1 and energy harvesting devices 29a, 29b, 29c, 29d, 29e, 29e of Figures Ito 18.

12 Similar to the embodiment of Figure 18, the energy harvesting system 29g of Figure 19 13 transfers heat from a subterranean hotspot 62 to the heal engine 1. However, instead of 14 employing a fluid 58 to carry heat between the subterranean hotspot 62 and the heat engine 1, the housing 2 of the heat engine 1 comprises a filament portion 63 originating 16 from the base end 18 of the housing 2. The filament portion 63 is located and orientated 17 to extend towards the subterranean hotspot 62. The filament portion 63 could be 18 considered an extension of the first portion 6 of the housing 2. The first liquid 3 locates 19 within both the first portion 6 and filament portion 63 of the housing 2. The heat exchanger of the heat engine 1 of Figure 19 takes the form of the filament portion 63 of the housing 2, 21 and specifically, the region of the filament portion 63 closest to the subterranean hotspot 22 62.

24 In operation, heat is transferred from the subterranean hotspot 62, through the filament portion 63 of the housing 2, to the first liquid 3 within the filament portion 63. it will be 26 appreciated that the heat engine -I may comprise two or more filament portions 63 each 27 extending towards one or more subterranean hotspots 62.

29 The energy harvesting systems 29f, 29g of Figures 18 and 19 are configured to generate electricity by harnessing heat from a subterranean hotspot. In other words, the external 31 high temperature (O heat source which drives the heat engine 1 is the subterranean 32 hotspot, also termed a geothermal heat source. It will be appreciated that the terms 33 subterranean hotspot and geothermal heat source may comprise a radioactive decay heat 34 source.

1 It will be appreciated that the external high temperature (ft) heat source Which drives a heat engine 1 may be a combination of heat sources. For example, the external high 3 temperature (TH) heat source may comprise, solar radiation 52, one or more subterranean 4 hotspots 62 and any other alternative or additional source of heat, such as waste heat from a data centre, or combination thereof. As such, the corresponding energy harvesting 6 system 29 may comprise a combination of features from Figures 1610 19, such as, optical 7 lenses 51 in combination with a filament portion 63, as well as the Features from Figures 1 8 to 15.

The heat engine 1 has numerous advantages. The heat engine 1 does not rely on 11 conventional thermodynamic cycles, but instead provides an alternative mechanism of 12 converting heat into work by utilising a phase change of the first liquid 3 to create fluid 13 flows and the subsequent interaction with the rods 10.

The heat engine 1 operates primarily on changes in temperature as well as the addition 16 and removal of heat. Changes in pressure and volume, whilst might be present due to the 17 intrinsic relationship to temperature, are not fundamental to the operation of the heat 18 engine 1. In other words, the heat engine 1 does not reply on the expansion of a gas to 19 perform work. As such, the heat engine 1 has minimal moving components, reducing the amount of maintenance that may be required and maximising the lifetime of the device.

21 Also, as there are minimal moving components, the heat engine 1 is relatively quiet.

23 The heat engine 1 is not limited to a specific type of fuel so can utilise a variety of external 24 high temperature (Th) heat sources 8 ranging in temperature and power. Depending on the origin of the external high temperature (TH) heat source 8, the heat engine 1 does not 26 result in the release of toxic and un-environmentally friendly gases.

28 Furthermore, the heat engine 1 is scalable as can be adapted for different external high 29 temperature (TH) heat sources B ranging in temperature and power. As such, the dimensions of the heat engine 1 can be adapted to the desired size and resulting expense.

31 The heat engine 1 is a sealed device with minimal moving components so is relatively 32 safe.

34 The heat engine 1 is customisable as the rods 10 can be optimised for a specific external high temperature (TH) heat source 8.

A heat engine is disclosed. The heat engine comprises a housing, a first liquid and a 3 second liquid located within the housing. The first liquid has a higher density and lower 4 boiling point than the second liquid. The heat engine further comprises a heat exchanger which transfers heat to the first liquid to evaporate the first liquid to form a first liquid 6 vapour. The heat engine also comprises at least one fluid flow member which to moves in 7 response to a fluid flow created by the interaction of the first liquid vapour and the second 8 liquid. The heat exchanger is adapted to receive heat from thermal radiation and or one or 9 more geothermal heat sources. The liquid-gas phase change of the first fluid provides an alternative mechanism for converting heat into work with numerous advantages. The heat 11 engine has minimal moving parts, a relatively long lifetime, does not require a specific fuel, 12 does not directly release toxic or un-environmentally friendly gases, and can be adapted to 13 a specific source of waste heat.

Throughout the specification, unless the context demands otherwise, the terms "comprise" 16 or "include", or variations such as "comprises" or "comprising", 'includes" or "including' will 17 be understood to imply the inclusion of a stated integer or group of integers, but not the 18 exclusion of any other integer or group of integers. Furthermore, unless the context clearly 19 demands otherwise, the term "or" will be interpreted as being inclusive not exclusive.

21 The foregoing description of the invention has been presented for purposes of illustration 22 and description and is not intended to be exhaustive or to limit the invention to the precise 23 form disclosed. The described embodiments were chosen and described in order to best 24 explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and with various 26 modifications as are suited to the particular use contemplated. Therefore, further 27 modifications or improvements may be incorporated without departing from the scope of 28 the invention as defined by the appended claims.

Claims (25)

1 Claims 3 1. A heat engine comprising; 4 a housing; a first liquid and a second liquid located within the housing, the first liquid having a 6 higher density and lower boiling point than the second liquid; 7 a heat exchanger to transfer heat to the first liquid to evaporate the first liquid to form a 8 first liquid vapour; and 9 at least one fluid flow member to move in response to a fluid flow created by the interaction of the first liquid vapour and the second liquid, 11 wherein the heat exchanger is adapted to receive heat from thermal radiation and or 12 one or more geothermal heat sources.14

2. A heat engine as claimed in claim 1 wherein the first and second liquids occupy an interior volume of the housing.17

3. A heat engine as claimed in either of claims 1 or 2 wherein, the first liquid is located 18 within a first portion of the housing and the second liquid is located within a second 19 portion of the housing.21

4. A heat engine as claimed in any of the preceding claims wherein, he heat engine 22 further comprises one or more filament portions.24

5. A heat engine as claimed in claim 5 wherein, the one or more filament portions are an extension of the first portion of the housing.27

6. A heat engine as claimed in either of claims 5 or 6 wherein, the first liquid is located 28 within both the first portion of the housing and the one or more filament portions.

7. A heat engine as claimed in ally of claims 3 to 6 wherein, the heat exchanger 31 comprises the first portion of the housing.33

8. A heat engine as claimed in any of claims 4 to 7 wherein, the heat exchanger 34 comprises the one or more filament portions.1

9. A heat engine as claimed in any of the preceding claims wherein, the heat exchanger comprises a pipe and or a portion of a pipe.4

10. A heat engine as claimed in any of the preceding claims wherein, the heat exchanger comprises a conductive plate thermally connected to a conductive coil, wherein the 6 conductive plate is located on the exterior of the housing and the conductive coil 7 extends into the interior volume of the housing.9

11. An energy harvesting system comprising a hear engine as claimed in any of claims 1 to 10, an energy conversion means and an external high temperature heat source.12

12. An energy harvesting system as claimed in claim 11 wherein, the energy harvesting 13 system further comprises a fluid circulation system configured to transfer heat.

13. An energy harvesting system as claimed in either of claims 11 or 12 wherein the 16 external high temperature heat source comprises thermal radiation.18

14. An energy harvesting system as claimed in claim 13 wherein, the energy harvesting 19 system further comprises one or more optical lenses and or one or more mirrors suitable for focusing thermal radiation.22

15. An energy harvesting system as claimed in claim 14 wherein, the one or more optical 23 lenses and or one or more mirrors are mounted on one or more stands.

16. An energy harvesting system as claimed in claim 15 wherein, the one or more stands 26 each comprise a pivot arrangement suitable for adjusting and or optimising the angle 27 and or orientation of the one or more optical lenses and or one or more mirrors.29

17, An energy harvesting system as claimed in any of claims 14 to 16 wherein, the one or more optical lenses and or one or more mirrors are configured to focus thermal 31 radiation towards the heal exchanger of the heal engine.33

18. An energy harvesting system as claimed in any of claims 13 to 17 wherein, the fluid 34 circulation system comprises a solar fluid circulation system with a fluid within a vessel, 1 pipes connecting the vessel to the housing of the heat engine and a pump the circulate the fluid along the pipe between the vessel and the heat engine.4

19. An energy harvesting system as claimed in claim 18 wherein, the one or more optical lenses and or one or more mirrors are configured to focus thermal radiation towards 6 the fluid and or vessel or the solar fluid circulation system.8

20. An energy harvesting system as claimed in any of claims 11 to 19 wherein, the 9 external high temperature heat source comprises one or more geothermal heat sources.12

21. An energy harvesting system as claimed in claim 20 wherein, the one or more filament 13 portions of the heat engine are located and or orientated to extend towards the one or 14 more geothermal heat sources.16

22. An energy harvesting system as claimed in either of claims 20 or 21 wherein, the fluid 17 circulation system comprises a geothermal fluid circulation system with a fluid 18 contained within pipes and a pump to circulate the fluid around the pipes, wherein the 19 pipes extend between the geothermal heat source and the heat engine.21

23. An energy harvesting system as claimed in any o claims 11 to 22 wherein, he energy 22 harvesting system further comprises one or more vibrational lenses.24

24. A method of manufacturing a heat engine comprising, providing a housing, 26 - providing a first liquid and a second liquid located within the housing, the first 27 liquid having a higher density and lower boiling point than the second liquid; 28 -providing a heat exchanger to transfer heat to the first liquid to evaporate the 29 first liquid to form a first liquid vapour; and -providing at least one fluid flow member that moves in response to a fluid flow 31 created by the interaction of the first liquid vapour arid the second liquid, 32 wherein the heat exchanger is adapted to receive heat from thermal radiation 33 and or one or more geothermal heat sources.

25. A method of manufacturing an energy harvesting system comprising, 1 providing a heat engine according to the method of claim 24; - providing an external high temperature heat source; and 3 -providing an energy conversion means.