WO2007129006A2

WO2007129006A2 - Improved newcomen type steam engine with controlled condensation of vapour

Info

Publication number: WO2007129006A2
Application number: PCT/GB2007/001380
Authority: WO
Inventors: William Alexander Courtney
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-04-26
Filing date: 2007-04-16
Publication date: 2007-11-15
Anticipated expiration: 2008-10-26
Also published as: WO2007129006A3

Abstract

This invention converts low-grade thermal energy into mechanical energy. Potable water is produced as a by-product. Figure 1 depicts a solar powered version. A glazed evaporation chamber encloses a saline water trough (2). The trough and evaporation chamber have a warm end (3) and a cool end (4). The evaporation chamber is heated directly by solar energy (5), and also, at the warm end, by solar energy reflected from a sun tracking mirror (6). After passing through the second turbo-generator (9), the vapour becomes super-cooled. The super-cooled vapour is seeded, allowing a small fraction of the vapour to condense out as potable water. The condensation process liberates latent heat, lifting the temperature of the residual vapour plus air mixture, to a higher temperature, at which the vapour is just saturated.

Description

Improved Newcoroen type steam engine

Technical Field

This invention relates to improvements in engines used to convert low-grade thermal energy or heat, into mechanical energy, electricity or other forms of energy. Examples of low grade heat include waste heat currently dumped into the environment by fossil fuel and nuclear power stations, waste heat generated by manufacturing processes including the compression of gases and the manufacturing of cement Natural sources of low grade heat include geothermal, solar energy and solar energy collected indirectly from sea water.

When the engine is run using sea or brackish water as a thermal energy capture or transfer medium, potable water is produced as a by-product, when a fraction of the undrinkable water evaporates. If a mixture of two liquids, having different boi I in,g points at normal atmospheric pressure is used as a medium, the engine may also be used to separate the two liquids by fractional distillation. According to the present invention, there is provided, a device for converting thermal energy into mechanical energy, comprising a chain of serially linked engines powered by kinetic energy extracted from moving vapour, with warm vapour being fed into the first engine and then successively through all the engines, with the vapour doing external work to produce mechanical energy inside each engine, with a consequence that the vapour cools and becomes super-saturated on exiting from at least some of the engines, characterised by the super-saturated vapour then partially condensing, releasing sufficient latent heat to warm the residual vapour so it becomes saturated again, before entering the next engine in the chain.

Brief description of the drawings

Figure 1 is a schematic diagram depicting the principle components of a solar powered version of the invention.

Figures 2a, 2b, 2c and 2d provide further clarification of the vapour seeding process by illustrating the differences in behaviour when a gas and a seeded saturated vapour pass through a constriction.

Figure 3 is a schematic diagram illustrating some super-saturated vapour seeding mechanisms.

Figure 4 depicts an alternative arrangement that offers funnelling of the vapour, prior to it passing through the turbine.

Figure 5 depicts a kinetic energy rejuvenation chamber used to boost the kinetic energy of the saturated water vapour or vapour plus air mixture.

Figure 6 depicts an illustrative example of an East to West section through a trough that has additional features, to encourage liquid convection current flows. Figure 7 depicts a view of a vertical facet of a spiral version of the invention.

Figure 8 depicts a plan view of the kinetic energy rejuvenation chambers of another version of the invention.

Figure 9 depicts a plan view of the kinetic energy regeneration and condensation chambers, for a version of the invention fed by the injection of hot water vapour.

Figure 10 depicts a compression pump; suitable for compressing large volumes of low density gas plus vapour mixtures back up to atmospheric pressure.

Figure 11 depicts part of the of the freeze desalination version of the invention.

Figure 12 depicts part of a freeze desalination version of the invention used to re-warm the working gas back to about ambient temperature.

Figure 13 depicts an innovative turbine design that may be used as part of the invention. Figure 14 is a schematic diagram depicting a West to- East vertical cross section of a solar powered version of the invention, at right angles to the cross- section depicted in Figure I .

Figure 15 illustrates how parallel solar powered deyices may be grouped under a common Fresnel lens canopy.

Figure 16 illustrates how, especially at the cool end of solar powered versions of the invention, additional shading can be added, to ensure that the condensing vapour always has access to cooler water above it. Figure 17 depicts a variation on the design shown m Figure 16.

The prior art

When Thomas Newcomen invented his atmospheric steam engine round about 1712, he helped to launch the industrial revolution.

The temperature of the boiler water was raised to just above 100⁰C, allowing the steam generated to exert a pressure slightly in excess of one atmosphere. This steam pushed a piston up a cylinder bore, open to the atmosphere at the far end. A jet of cold water was then injected into the steam, causing it to condense. As a consequence, the atmospheric pressure was no longer counter-balanced, so the excess pressure pushed the piston down its cylinder. By Finking the piston to a water pump, the Newcomen engine could be used to pump water out of deep mines.

The engineer James Watt was one of the first people to grasp the concept of latent heat. He realised that the Newcomen engine was restricted to an efficiency of less than 10%, mainly because a large fraction of the thermal energy used to raise a head of stea"ra was used unproductively bringing about a phase change, converting water into to steam. This phase change energy, which became known as latent heat was recovered when the steam condensed back into water at the end of the steam cycle. However, the condensation occurred at a lower temperature than .the original evaporation, so the latent heat liberated could not be re-cycled.

Watt and his successors have reduced the latent heat problem by designing steam engines that employ steam starting at higher temperatures and pressures, compared with Newcomen's design, while still keeping the temperature at which the steam condensed out as low as possible. In a modern coal fired power station. For example, which operates on a'Rankin thermodynamic cycle, the steam is heated to about 600°C. It then condenses out at a temperature of 30 to 35 ^UC and a pressure of about 6% of atmospheric pressure. Unfortunately, although^' Watt's approach reduces the latent heat problem by reducing the fraction of the total thermal energy in the steam trapped as latent heat it does not resolve it. Consequently, modern coal fired power stations a limited to an efficiency of about 40%. with the bulk of the residual 60% of the energy having to be disposed of as low grade heat.

Improvements to Newcomen type steam engines have" previously been revealed by the present inventor in patent application GB 051 1946.6 (Courtney). The earlier Courtney invention included two separate vapour flows. The first or primary vapour increased' .in vapour density as it passed from the cool to the warm end of a long primary evaporation chamber, then decreased in density, as it passed through a series of condensation chambers, in alternating series with turbines. The condensing first vapour evaporated a second liquid, to form a second or secondary vapour, which condensed out, as it passed through a single condensation chamber, underneath and in thermal contact, with the primary evaporation chamber. In order to gain kinetic energy, to motivate the turbines, the first vapour was required to pass through a large number of parallel sided tubes, comparable in total surface area, to the total area of the thermally conducting interface between the primary evaporation chamber and the underlying condensation chambers.

The present invention improves on Courtney's prior, art by dispensing with the need for primary and secondary vapours, replacing them with a single vapour flow. It also includes a number of other improvements, which are revealed below.

Disclosure of the invention

The new device is similar to the original Newcomen engine, in that (i) it can operate effectively with an upper working temperature of about 100⁰C; (ii) it exploits the properties of saturated water or other saturated vapours, as in Newcomen's engine, rather than unsaturated, super-heated vapours, as in Watt's engine, (iii) the pressure drops required to motivate bulk movement of the working elastic fluid (gas/vapour) are .produced by density reduction due to condensation, rather than due to expansion of the working fluid. In acknowiedgement of its historical legacy, the invention is referrer to as an "Improved Newcomen type Engine." But it should be understood hat the scope of the invention is not limited to an upper temperature of 100°C, nor is it limited to water as the liquid source for saturated vapours. The present invention offers several improvements on the original Newcomen design. These are:

1 . The incorporation of a chain of turbines, successively operating at lower temperatures.

2. Thermal rejuvenation at intervals along th'e chain, allowing the chain of steam turbines to operate at high levels of thermal efficiency,, without violating the Carnot thermodynamic efficiency equation.

3. Positive thermal feedback loops to reduce low grade heat losses.

4. For small versions of the invention, where drag forces are significant, partial condensation of saturated vapour, to rejuvenate the kinetic energy- of the residual vapour, prior to entering each successive engine or turbine along the chain.

5. Some versions include modified displacement pumps, to compress large volumes of low pressure air/vapour back to atmospheric pressure.

It should be noted that for the Improved Newcomen Engine to have a reasonably compact size, the initial steam temperature needs to be at least 100⁰C. So, for example, if the engine is linked to the cool end a conventional coal fired power generator system, the Rankin cycle needs to be closed down at a temperature in excess of 100^uC.

The manner in which these improvements work together will be illustrated by examining a solar powered version of the device, when used to generate electricity and drinking (potable) water.

Figure 1 is a schematic diagram depicting the principle components of a solar powered version of the invention. Item 1 is a glazed evaporation chamber enclosing a saline water filled trough 2. The rough and evaporation chamber have a warm end 3 and a cool end 4 at about ambient temperature. The evaporation chamber and its contents are heated directly by solar energy 5, and also, at the warm end, by solar energy reflected from a sun tracking mirror 6. The space ,above the water trough is filled with a mixture of air and water vapour. In order to simplify the design and minimise construction costs, this version of the invention preferably, but not essentially, operates with vapour plus air pressure close to atmospheric pressure, with a gentle drop in pressure towards the warm end. At the cool end of the trough, air dominates the mixture. At the warm end, where the water temperature may be 100¹¹C, water vapour dominates the mixture. If the pressure at the warm end of the evaporation chamber is one atmosphere, the temperature of the water vapour may exceed.1OO^UC. provided that the vapour is not saturated. A notional coupling pipe 7 (which in reality may be. small gaps in the glazing) minimises pressure differences between the mean pressure in the interior of the evaporation chamber and the external atmosphere.

The following explanation assumes that the temperature of the water vapour exceeds 100⁰C and that the vapour is unsaturated at its highest temperature. A small pressure difference draws the air plus water vapour mix. through the first turbo-generator 8, with the mixture cooling, so that the exiting water vapour is close to saturation, because external work has been done in generating electricity. A suitable first turbo-generator will be revealed below with reference to Figure 13. After passing through the second turbo-generator 9, the vapour becomes super-cooled. The super-cooled (super-saturated) vapour exists in a state of unstable equilibrium. In the first thermal regenerator 10, the vapour is seeded, allowing a small fraction of the vapour to condense out as potable water. The condensation process liberates latent heat, lifting the temperature of the residual vapour plus air mixture, to a higher temperature, at which the vapour is just saturated. Consequently, the mixture exits the first thermal energy rejuvenator at a temperature which is only slightly lower than the temperature at which it entered the preceding turbo-generator. Further details of the thermal rejuvenation process will be revealed below with reference to Figures 2a, 2b, 2c and 2d. The thermal rejuvenator region is housed inside a thermally insulated diverging port, which leads on to (an optional) kinetic energy rejuvenation chamber 11. Also optionally, depending on the specific version of the current invention, this chamber is in good direct or indirect thermal contact with the overlying brine trough. A small fraction of the vapour condenses as it traverses the length of the optional kinetic energy rejuvenation chamber. The pressure drop accelerates the air plus vapour mixture, which is further accelerated as it exits the chamber via a converging-exit port. This convergence is achieved in part, by the increasing diameter of a cowling over the generator mounted on the rotational axis of the turbogenerator unit 12.

In some versions of the invention revealed below, the ducting between engines has a uniform cross sectional area. That is, the diverging and converging ports are dispensed with.

The sequence consisting of a turbo-generator, thermal rejuvenator and kinetic energy rejuvenator can be repeated many times until most of the latent heat in the water vapour has been unlocked and the residual mixture has cooled to ambient temperature. However, for the solar powered version of the invention, there are advantages in closing down the sequence with a final turbo-generator 13 at a fairly high temperature of say about 7O⁰C. At this temperature, the saturated vapour pressure of water is 30% of normal atmospheric pressure. The bulk of the remaining water vapour is then allowed to condense out in a long condensation chamber 14, in good thermal contact with the overlying brine trough. The advantages of closing down the chain at a fajrly high temperature are: (i) the number of turbines in the chain is reduced; (ϋ) the ratio of potable watέr tø power output is increased. Air has to be introduced into the evaporation chamber, to maintain equilibrium with the external atmosphere, but the air fraction in circulation round' the device is non productive. This is because the electricity produced when the air is cooled and its partial pressure drops on passing through the gciiLTatorb Ii, offset by the work done in compressing the air back to atmospheric pressure, at the end of the chain Some mechanical and thermal energy losses are unavoidable, so the presence of the air fraction inevitably leads to slight drop in overall efficiency. Compression is achieved using a compression pump 15.

The ratio of potable water to power output for the solar powered version of the invention is flexible. If the primary need is production of potable water, the- turbo-generator chain can be closed down at a higher temperature than 70 ⁰C, with a larger fraction of the latent heat being fed back into the saline water in the evaporation chamber

The thermal regeneration and vapour seeding mechanisms will now be explained in further detail. The explanation will refer to water, but it is also valid for other liquids.

If an insulated closed container encloses a mixture of water and water vapour, a state of dynamic equilibrium will rapidly be achieved between the vapour and the liquid states, with the rate at which molecules move out of the liquid surface into the vapour being equal to the rate at which molecules having the same mean kinetic energy leave the vapour for the liquid. In this dynamic equilibrium state, the vapour is said to be saturated with the pressure it exerts being the saturated vapour pressure for that temperature.

If thermal energy is added to the container, it will -heat up. In moving to this higher temperature, there will be a temporary imbalance with more molecules leaving the liquid than entering it. A new, higher saturated vapour pressure will rapidly be established.

If some water vapour is now transferred to a second thermally insulated container at the same temperature, the saturated vapour pressure can be maintained if sufficient heat is added to the water in the first container to produce the additional vapour required. But if thermal energy is extracted from the vapour en-route to the second container, by making the vapour do external work for example, by drawing it through a turbo-generator, the vapour has to cool for the total energy of the system to be conserved.

If the container is clean, dry and has smooth walls, the cooled vapour could theoretically remain in its "super-cooled" vapour state without condensing" out. In reality, this does not happen if the vapour is super-cooled by more than about 0.2 - 0.3 K.

This is because small foreign or electrically charged/polarised particles present in the vapour will seed condensation, causing the formation of small liquid-droplets. Further condensation can then take place at the surface of the droplets. Condensation releases latent heat, warming up the residual vapour. At a microscopic level, the apparent transfer of heat from liquid to residual vapour can be seen as a culling process, with the slowest moving vapour molecules having the highest probability of condensing out. A new equilibrium temperature is then reached, which-is slightly lower than the original saturated vapour temperature, prior to the external work being done. ^■ At the end of this regenerative process the vapour has .returned to saturation conditions and been partially re-heated, but at the cost of a slight loss in vapour density and pressure. The vapour cannot make a full return to its original temperature, unless^' work is done on it, or the vapour is placed in thermal contact with a warmer body.

Figures 2a, 2b and 2c provide further clarification o.f his regeneration process by illustrating the differences in behaviour when a gas and -a seeded saturated vapour pass through a constriction. In order to clarify the explanation for skilled engineers, these three explanatory diagrams have an intentional resemblance to Venturi tubes.

Figure 2a will be used to explain the potential and kinetic energy changes when a gas flows through a constriction in a wide tube. The tube is assumed to be well lagged, so that there are no heat or any other energy exchanges with the external environment. Before reaching the funnel 1, the tube has a wide diameter and the gas has a low velocity.

On passing through the constriction 2, the gas is forced to accelerate, increasing its bulk kinetic energy. This is offset by a reduction in potential energy, manifested as a drop in measured static gas pressure. These energy changes can be explained by considering the gas at a molecular level: In the wide diameter section of the tube, the velocity vector for all molecules includes a component equal to that at which the gas as a bulk is moving forward. Inside the constriction, the forward velocity of ail the molecules increases. But the sum of all the velocity vectors of the molecules currently inside the constriction must be identical to the sum of their velocities before they entered the constriction, because no energy passes through the walls of the tube. Seen from the moving frame of reference of any molecule inside the constriction, the relative velocities of its neighbours appear to decrease. In accordance with the well established kinetic theory of gases, this is manifested at a macroscopic level as a drop in static pressure. The gas returns to its original low velocity after emerging from the diverging section 3, assuming drag forces are negligible and the initial and final sections of the tube have the same cross sectional areas. The temperature of the gas drops with static pressύre.as the constriction is entered, and then increases with static pressure on reaching the diverging port.

Figure 2b depicts a similar constricted tube to that depicted in Figure 2a but with a notional turbo generator, 1 introduced, to generate electricity. In order for total energy to be conserved the gas leaving the tube must be cooler than the gas entering the tube, assuming steady state flow. Two cooling mechanisms are in operation: "

(i) Cooling of the gas as it enters the constriction and its static pressure drops.

(ii) Cooling of the gas as it does external work driving the turbo-generator.

Figure 2c highlights important differences, if the gas is replaced by an unsaturated vapour or a gas plus unsaturated vapour mixture. The unsaturated vapour, suffers the same two cooling mechanisms, as for a gas, before reaching the diverging port. If the first cooling mechanism drives the vapour into a super- saturated state, then some condensation will occur. This causes a drop in vapour density. Latent heat will also be liberated. At a molecular level, this means'that lower velocity molecules have been culled to form water droplets, increasing the root mean square velocity of the molecules that remain in the vapour state.

If saturated vapour or vapour that is close to saturation impacts on the turbine blades, then the vapour will become super-cooled or super-saturated on impact, providing a second opportunity for a drop in static pressure and the release of latent heat inside the constricted region.

On emerging from the exit port, the temperature of the vapour will rise, but it will exist at a lower pressure than before entering the constriction, due to the condensation. Optional micro-roughened seeding surfaces such as 1 and 2 along the streamlines assist in^'the process of condensation. Figure 2d depicts a similar system to that discussed with reference to Figure 2c but with a chain of sets of turbine blades 1 -5 all mounted on the same shaft. Five sets are depicted for illustrative purposes, but this is in no way intended to limit the number of sets .in the turbine chain. For the purposes of mathematic modelling of this invention, each set of turbine blades can be considered as a separate engine, because it experiences different vapour velpcity impact conditions. If the chain includes sufficient sets of turbine blades, the vapour will at some stage become super-saturated as it gives up bulk kinetic energy to the engine it is currently interacting with. The practical implication is this; if the chain of sets of turbine blades is sufficiently numerous, some thermal rejuvenation will eventually take place.

Figure 3 is a schematic diagram illustrating some super-saturated vapour seeding mechanisms. Item 1 depicts negative ions discharged from an array of high voltage point electrodes, 2 is a complimentary spiked, grounded metal surface which possesses an induced positive charge, because of its proximity to the negatively charged electrodes. Item 3 is a weak/ alpha particle source, 4 is particle rich flue gas drawn from a coal fired boiler furnace and injected into the thermal rejuvenation chamber by means of a jet pump. Item 5 represents salt particles naturally present in the vapour, if it originates from a brine filled trough. Item 6 is a thin film of condensate water,-flat on a microscopic scale. These examples are not intended to limit in any way the types of super-saturated vapour seeding mechanisms covered by the invention. It is only necessary for some seeding mechanist to be present, for the thermal rejuvenation process to occur.

The use of miniaturised turbo-generators, as depicted in Figure 2c is probably not a practical proposition. Figure 4 depicts an alternative arrangement that provides a fluid accelerating entrance port. This port may include nozzles which deflect the vapour impacting on to the turbine blades in order to maximise the conversion of linear kinetic energy stored in the moving vapour to rotational kinetic energy in the rotating blades. In this illustrative example, item 1 is an electricity generator, having its rotor coupled to a circular array of turbine blades such -as' 2. A cowling 3 faces up-wind and in collaboration with the side walls 4, funnels the vapour. A second cowling 5 faces down-wind. In collaboration with the side walls this acts as a diverging exit port. In this illustrative example, the side walls are shown as being parallel, but this is not intended to be a restriction on the design. The external walls may vary in cross sectional circumference at different points along their length to tailor the flow of the vapour. Seeding can take place at any surface shape that helps to reduce the free surface energy of a condensing vapour droplet. The potential surfaces include flaws and other miniscule protrusions in the surfaces of the rotating turbine blades.

Any liquid condensing on the turbine blades will migrate at speed to the tips of the blades. A small gap may be left between the blade tips and the radially adjacent housing, to allow the liquid to run down the housing walls and be drained off. In order to discourage vapour from the preceding nozzles taking the path of least resistance and passing through the blade tip-housing gap, the radial dimension of the blades may exceed the extreme distance between the nozzles directing the vapour onto the blades, with the diameter of the housing being reduced at the location of the nozzles. That is, the tips of the blades fit into a recess in the housing, as seen from inside the housing.

Condensate water droplets from the thermal and kinetic energy regenerators will be carried towards the next turbine in the chain by the moving vapour and air mixture. A number of techniques can be used to capture the droplets. These include mesh filters, electrostatic precipitation, gravity and inertial mass separation. The first three techniques preferably take place near the entry ports for the kinetic energy generators, the fourth technique as close as possible to the following turbine blades, where the suspended droplet velocity is highest. Gravitational and inertial mass separation techniques work best if the moving fluids are forced to make sharp turns by including a plurality of U bends in the enclosing ducting and adding a plurality of internal partitions along the flow lines for the moving vapour. For gravitational separation, the U bends need to be vertical and are preferably assisted by electrostatic precipitation. Electrostatic precipitation also acts as a seeding mechanism.

For small versions of the invention, where viscous drag forces are significant, some form of kinetic energy rejuvenation may be necessary, to maintain vapour flows.

Figure 5 depicts a kinetic energy rejuvenation chamber used to boost the kinetic energy content of the saturated water vapour or vapour plus air mixture. The mixture enters the main body of the chamber 1, via the diverging exit port of the preceding thermal rejuvenator 2 and exits via a funnelling port for the following turbo-generator 3. The vapour is slightly cooled, causing a small drop in vapour pressure, as it traverses the chamber 2. Possible, but not limiting mechanisms for cooling the vapour include placing the external walls of the chamber in good thermal .contact with a cooler body. For example an overlying section of the liquid trough inside the evaporation chamber, for the solar powered version of the device, or, as depicted, using a thermal siphon. In this example, the thermal siphon 4, inside the main body of the chamber, consists of a long hollow sub-chamber, having thermally conducting walls. Water or other volatile liquid is sprayed onto the inner walls of the-sub-chamber by a sprinkler 5, where it evaporates, to produce a secondary vapour by extracting latent heat from the external vapour in the vicinity of the sub- chamber. The secondary vapour is siphoned off via tube 6 and taken to a heat dump. At the heat dump, the secondary vapour condenses out with the condensate liquid then being re-cycled. The rate of heat extraction can be controlled by altering the mass rate at which the liquid is sprayed onto the inner walls of sub chamber 4. Engineers skilled in power plant design will recognise a number of alterative techniques for recycling the secondary vapour, including injecting the vapour back into the primary power chain, at an intermediate stage, when the primary vapour pressure has dropped below that of the secondary vapour injected into it.

It is emphasised that the kinetic energy rejuvenation chamber depicted in Figure 5, is only an illustrative example. Other methods for rejuvenation are possible, for example, intentionally placing the vapour passing between turbines in good thermal contact with slightly cooler liquid in an overlying evaporation chamber. This option will become obvious to the reader after further details of solar powered versions of the invention are revealed below.

The drop in vapour pressure of the primary vapour traversing the main chamber causes it to accelerate.

It can be shown, using Bernoulli's flowing fluid equation that for steam of density of 0.6 kg m^"3 entering the kinetic energy rejuvenation chamber at a pressure of one atmosphere (10⁵ Pa), the pressure drop required to give the mixture a velocity increase of IO m s^"1 is only 30 Pa. (Assuming for this estimate calculation, that the vapour approximates to an incompressible fluid.)

Kinetic energy rejuvenators only need to extract a small fraction of the latent heat provided a funnelling port 3 is added to accelerate the vapour after rejuvenation. This is because the kinetic energy of a moving mass depends on the square of its velocity. For example, if the kinetic energy rejuvenator increases the velocity of the vapour by 10 ms^"1 and the funnelling process increases this to 150 ms^"', the ratio of energy consumed in the kinetic energy rejuvenation process to kinetic energy handed on to the next turbo-generator is 10²/l SO² = 1/225 = 0.45%.

These figures can be used to estimate the maximum number of stages a chain must include to theoretically extract all of the latent heat. For this estimate we consider 1 kg of water vapour. This locks up about 2.26 x 10⁶ Joules of energy as latent heat (trie precise amount depends on the temperature of the steam.). At each stage, 50 Joules are given up in kinetic energy rejuvenation and 1 1250 Joules is converted to electricity. So the number of stages, calculated by dividing the latent heat per kg by the sum of the kinetic energies is

2 26 x 10⁶ /(50 + 1 1250) = 200.

If the total amount of funnelling, including that produced by constricting and diverting nozzles, is increased so that the maximum velocity is increased to 300 ms^'1 , the number of stages is reduced to 50.

The scope of the invention is extended to include turbo-generators that are fitted with de Laval nozzles. which enable the turbine blades to be impacted by super-sonic vapour flows. Such nozzles would be counter productive early in the turbine chain, but eould be incorporated into the final turbine, to compensate for the low vapour density.

Kinetic energy rejuvenators are an important but nonessential part of the present invention. For larger versions of the invention, the pressure drops caused by a fraction of the vapour condensing out in the thermal rejuvenators, plus incidental heat losses, may be sufficient to rejuvenate the kinetic energy of the residual vapour.

For solar powered versions of the invention, the long temperature gradient axis of the troughs preferably lies along a North to South line. Figure 6 depicts an illustrative example of an East to West section through a trough, towards its cool end. Features have been added to help the latent heat liberated by the condensing of vapour in chambers underlying the trough to be delivered to the overlying liquid at the highest possible temperature. In Figure 6, 1 is the liquid surface, 2 the underlying vapour in a condensation chamber and 3 the thermally conducting base of the trough. The base may be a sheet of copper, galvanised iron or stainless steel. At the manufacturing stage, the sheet metal may be work hardened by passing it through rollers that mould the surfaces into micro- ridges or protrusions. These surface irregularities increase the contact surface ^' areas for the liquid and vapour and also provide nucleation centres for the vapour to condense out on. In order to prevent the solar energy directly heating the base of the trough, two part matt black metal shades, for example item 4 comprising a curved upper part and a lower curved or flat part are placed just below the surface of the liquid. Liquid in contact with the shades is warmed and rises towards the surface. When evaporation occurs, the liquid cools locally, becoming denser, then sinks to the base of the trough. Here it warms up, picking up thermal energy from the underlying condensing vapour. It then rises up, passing through the gaps between the parts of the shades, so that the cycle begins again. Around mid day, some of the solar energy passes through the gaps between the shades. This solar energy can be reflected upwards, towards the matt black shades by a second set of silvered or white secondary shades close to the base of the trough, for example 5.

If the solar intensity is particularly intense, for fexample, shortly after noon in the hottest months of the year, the warming may occur in reverse, with the vapour in the underlying chamber being thermally rejuvenated from above, with reduced requirement for fractional condensation between turbine stages. The glazed roof of the evaporation chamber may be convex, with the surface of the glass or other glazing material being moulded to form cylindrical converging lenses, micro-prisms or Fresnel lenses, having North - South major axes. These would focus 'solar energy onto a horizontal strip having a narrower width than the width of the roof. This would allow narrow troughs to be used, providing a high solar energy density and elevating the trough water temperature. These narrow troughs would preferably be capped with a second layer of glazing, to limk the vertical circulation of the liberated vapour. The currently illuminated strip area would vary in its bast to West position during the day. By including a plurality of strip shaped troughs and only drawing vapour from the trough(s) currently best illuminated, the device can generate vapour at higher temperatures throughout the day, compared with a simple flat roofed evaporation chamber.

The solar powered version of the invention will take time to warm up after sunrise. To speed up the warming process, doors which short circuit the turbines, when opened, may be added. If the first turbine is also blanked off, it's adjacent door closed and the compression pump bypassed, vapour will be encouraged to migrate towards the cool end of the trough, with some vapour diffusing into the underlying chambers, where it can be deposited, giving out warming latent heat.

Some of the main sources of energy loss from the .system are heat loss through the external side walls and base of the engine. These losses may be reduced by adding lagging, for example glass fibre wool or sheets of expanded polystyrene foam. Heat loss through a solid or solid foam material is a function of the temperature difference between the two faces. This heat loss increases towards the warm end of the system, so a corresponding increase in the thickness of the lagging is required towards the warm end.

The solar powered version of the invention will be^' revealed in further detail later in this application, with reference to Figures 14, 15 and 16.

Modern coal fired power stations operating on the steam Rankin cycle are very good at squeezing energy out of the working steam. Typically, at the end:θf the cycle, the steam is reduced to a temperature of 30 - 35⁰C and a pressure of about 60mbar, only 6% of atmospheric pressure. In spite of this, the steam Rankin cycle can only offer an efficiency of about 40% because large amounts of latent heat are still locked up in the cool steam.

The present invention is extended to^' include combinations of the invention as described in this patent application with traditional Rankin cycle steam turbine units, including, for examples:

(i) Versions of the present invention that run off the waste heat from a Rankin cycle steam turbine unit, which has closed down- at a^* temperature above 100^υC. (ii) Versions of the present invention that include a modified form of turbine, revealed below, with reference to Figure 13 that transform hot unsaturated steam into warm saturated steam as external work is done, (iii) Versions of the present invention that operate at high temperatures, with a traditional Rankin cycle steam turbine unit being added at the cool end, when the steam density is too low for sub-sonic vapour flows to generate useful outputs of electricity. Combined power production and distillation versions of the invention running on waste heat from geothermal energy, conventional power stations or^' industrial processes can be made more compact than solar versions, to reduce external surface area and consequent heat losses.

An illustrative waste heat powered version, which .in no way limits the scope of the invention will now be presented. Figure 7 depicts a view of a vertical facet of a spiral version of the invention, seen from outside the spiral. Three turns of the spiral are shown. In order to slow the rate at which trough water flows to ground level, the trough may be built as a series of terraces, of which items 1 and 2 are examples. Small leakage ports in the downhill facing terraced walls allow the trough liquid, for example brine, to migrate to the lowest terrace, at the cpol end of the system. Unprocessed brine is regularly added to the uppermost trough, to compensate for the concentrated brine drained off. The motivating low grade thermal energy pumped into the system may arrive as cooling water from a coupled conventional power station or industrial process. But, preferably, the thermal energy arrives as hot vapour, in order to minimise the mass of heat exchange fluid that needs to be pumped to the warm end of the terraced troughs, at the highest level in the system. Item 3 depicts one of a plurality of vapour filled pipes bringing thermal energy to the system. The pipe is immersed in the trough water. The pipe may be rectangular in cross section and allowed to taper towards its lower end, as the mass rate of flow of incoming vapour decreases. If a suitable organic liquid for example hexane, is used to bring thermal energy to the system, its higher vapour pressure, compared with steam at the same temperature, may be used to power an organic Rankin cycle, before entering the engine.

In another version of the invention, the heat feed pipes carry hot flue gases from a fire box or combustion chamber.

In the representational diagrams presented as Figures 8 and 9, the detail is kept simple, by using symbolic representations of turbo-generators placed between cone shaped entrance and exit ports. Figure 8 depicts a plan view of the kinetic energy rejuvenation chambers of another version of the invention, which also allows the whole of the base of the trough to be heated by condensation in the underlying kinetic energy rejuvenation chambers. In this version, the representative kinetic energy rejuvenation chambers 1, 2, 3 and 4 traverse the base of the evaporation chamber. The real equivalents of the narrowing tapered sections of chamber 5, 6, 7 and 8 protrude laterally beyond the base of the overlying trough. The protruding sections are lagged to prevent heat loss, but, after passing the turbogenerator zone, may be lined with thermally conductive material, that has small protrusions, to help seed the super-saturated vapour. Item 9 is an example .of an array of sheets of rough surfaced thermally conducting seeding material, with the plains of the sheets being aligned with the streamlines of the mixture exiting from the constriction in the region of the preceding turbine.

This version produces a complex horizontal temperature gradient at the base of the trough water. The broad trend of the gradient is from the cold to the warm end, as in other versions, but superposes upon it a transverse fine detail. To reduce lateral movement of the moving gas plus vapour mixture, due to the lateral fine detail temperature gradients, the trough may be partitioned by vertical panels that extend the length of the trough. The dashed lines 11 and 12 represent suitable partitions in the overlying trough.

If transverse condensation chambers are used with the helical version of the engine described above, then a number of radially adjacent condensation chamber channels may be used, with a condensation chamber at any one location in the channel being connected to a condensation chamber directly below it, so that each channel consists of a vertical stack of condensation chambers. An advantage of this arrangement is that it enhances the temperature gradient across each trough base/condensation chamber roof boundary. This increases the rate at which thermal energy passes through to the trough water.

Other types of partitioned evaporation chambers, used in different versions of the invention will be revealed later, with reference to Figure 14.

Figure 9 depicts a plan view of the kinetic energy regeneration and condensation chambers, for a version of the invention fed by the injection of hot water vapour. The feed vapour is injected into a first chamber at 1, with the option of low pressure residual vapour being pumped out at 2. Alternatively, with the extraction pump switched off, vapour may be left to. build up in its final condensation chamber 3, until it reaches its dew point and starts to condense out. The second stream of vapour, which is mixed with air and originates in the overlying trough, enters a second channel of condensation chambers at 4, with low pressure air and residual vapour being returned to the trough, after passing through a second compression pump 5. The version of the invention depicted in Figure 8 is suitable for use in a future generation of coal fired power stations, where heat of compression released by sequestration processes is re-cycled. It is also suitable for coupling together solar and industrial waste heat powered versions of the invention.

It is emphasised that power station designers may opt for simplified versions of the invention in which: (i) Vapour is drawn through the chain of turbo-generators by a single mechanism; pressure drops induced by the condensing out of super cooled vapour, resulting from the saturated vapour having done external work; (ii) The overlying evaporation trough is dispensed with.

Figure 10 depicts a compression pump, suitable, for compressing large volumes of low density gas plus vapour mixtures up to atmospheric pressure. The piston 1 is shown currently moving upwards inside a cylinder 2, to compress the mixture. The roof of the pump 3 is fitted with a large valve 4 sealed in place by (say) one atmosphere of pressure, against an "O" ring seal 5. The pump is well insulated, to discourage condensation of the compressed vapour fraction inside the body of the pump. The piston is fitted with a large valve 6, resting on an "O" ring 7. On the down stroke, eccentrics, including 8 lift the piston valve clear of its supporting "O" ring, allowing low pressure mixture to move into the space above the piston. The crown of the pump may have an area'of several square metres.

A substance observed as having no defined surface is referred to as either a gas or a vapour, depending on the temperature it currently exists at:

The term vapour is used if the substance can also exis.t as a liquid at that temperature.

The term gas is used if the substance cannot exist as a, liquid at that temperature.

All substances have a maximum temperature known as their critical temperature, above which they only exist in the gaseous state. That is, above its critical temperature, the liquid state does not exist for the substance.

Carbon dioxide and other environmentally damaging "gases" may be stripped out of incineration process flue gases by the invention, provided that the offensive "gases" have a critical temperature at or above ambient. That is, strictly speaking the "gases" are. vapours at ambient temperature. The stripping can be done by compressing the vapours until their saturation vapour pressure is exceeded at ambient temperature, extracting the latent heat- of condensation and draining away the condensate liquid. The compression process requires an input of energy, but some of this can be recovered as heat of compression.

For sequestration purposes, a pump having a similar construction to that depicted in Figure 10 may be used in the first stage of compression of fossil fuel power station/waste incinerator flue gases, with smaller volume pumps being used for higher stages of compression. When the critical pressures of sulphur, nitrogen and carbon dioxides and other pollutant vapours have been exceeded and the vapours have been cooled below their critical temperatures, the heat of compression and latent heats released by this process may be used as sources of low grade heat, to power the engine.

For the higher stages of vapour compression, dual chamber displacement pumps may be used in order to reduce the pressure differential between the anterior and posterior faces of the piston crowns. A suitable dual chamber pump design is revealed in patents GB 2273133 and GB2306580 (Courtney).

If some of the heat used to drive the engine is produced by burning bio-fuels, dried sewage solids or waste materials and the resultant pollutant vapours are sequestrated, the invention may be used to offset the production of greenhouse gases caused by aircraft burning kerosene as an aviation fuel. If the invention is used to produce hydrogen by electrolysis of water, the oxygen liberated as a by product may be used to burn waste materials efficiently. Air contains approximately 20% oxygen by volume. Converting pure oxygen to carbon dioxide simplifies sequestration processes, compared with combusting oxygen from the air, because the total bulk of gases that need to be processed is reduced.

Compared with existing nuclear power station designs, a nuclear powered improved Newcomen engine, as revealed in this application offers many advantages, including the following:

1. The design is more efficient than a conventional nuclear power station, because it rejects less low-grade heat. This cuts down on the nuclear fuel costs for the power station and reduces the mass of nuclear waste produced, per unit of electricity generated.

2. The improved Newcomen engine can operate efficiently with a maximum temperature in the region of 100⁰C. This gives nuclear engineers an opportunity to re-think the reactor presser vessel design, with the possibility of simplification,. by allowing presser vessels to operate at lower temperatures, without net efficiency loss.

3. Low-grade nuclear fuel, which is only emitting thermal energy a few degrees above ambient temperature, could play a useful thermal regenerative role in the invention. This would extend the working life of the fuel rods and reduces the nuclear waste storage costs.

4. The relatively small size, low operating pressures and temperatures of the nuclear energy plant required for the present invention, reduce the costs and publicly perceived problems associated with designing nuclear power plants which are secure against earthquakes, terrorist and other forms of attack.

5. It may be possible to postpone the decommissioning date for existing nuclear power stations, by running them at reduced temperature and steam pressure, to service improved Newcomen engines, according to the present invention.

The invention is extended to include engines that exploit any form of low grade thermal energy, including that released when liquids freeze. In order to run an engine off thermal energy at a temperature of about 100⁰C, using heat released when water freezes at 0⁰C or lower, the engine needs to be coupled to the warm end of a refrigeration plant.

A five stage black box analysis will be used to reveal an idealised version of a suitable refrigeration plant that delivers potable water by freeze desalinating brine. A practical implementation will then be described with reference to Figure 11. Stage L .Dry air or other gas at about ambient temperature and pressure is adiabatically compressed to a temperature of about 100⁰C. Work Wi_n i Joules is done on the gas.

Stage2. The air is further compressed isothermally, with additional Work W_{(n 2} Joules being done on the gas. The chain of compression pumps used to compress the gas is maintained at a temperature of about 100⁰C by spraying it with brine, with a fraction of the brine evaporating, to produce steam. In unit time, the steam caries away sensible and latent heat having a combined value Qo_ut i Joules. The steam is fed into the warm end of the evaporation chamber of the main body of the invention from where it flows throμgh the chain of turbo-generators. The steam condenses out along the chain, producing po.table water as for other versions of the invention.

Stage 3. The compressed air is cooled to ambient temperature, by passing it through a heat exchanger in good thermal contact with the water trough. Sensible heat Qo_ut z Joules is fed into the trough. Alternatively, the same quantity of heat can be directly recycled, using it to either (i) warm up the working gas being fed back from the end of stage 5, to the beginning of stage 1 , or, (ii) warm up the dousing brine required for stage 2.

Stage 4. The compressed air is passed through a chain of sub-ambient temperature turbo-generators where it expands to atmospheric pressure while cooling to a temperature well below 0^υC. Wo_«t i Joules of electricity is produced per .unit time, as the gas passes through the turbo-generator chain.

Stage 5.. The cold working gas is warmed to about ambient temperature by placing it in thermal contact with a brine filled trough. Freeze desalination occurs as heat is transferred from the brine to the gas, with Qi_n i Joules of heat passing from the brine to the gas. The ice is scooped out of the trough and the concentrated brine is steadily replaced with fresh brine. At the end of stage five, the same working gas is recycled for a new five stage process.

To compensate for unavoidable energy losses an additional quantity of energy per unit time Wi_nJ has to be fed into the whole system that is the black box and other parts of the power plant.

Wi_{n 3} includes heat losses through the walls, from fluids leaving the system at a slightly higher temperature than they enter it and Joule heating losses in the turbo-generator windings. However, not all heating losses from machinery are losses from the system. For example, friction losses due the operation of the compression pumps causes warming of the pump walls, but this is not a true loss, because the heat is transferred to the steam that enters the turbine chain in the main body of the invention.

The cold working fluid produced at the end of stage 4 has commercial value. Alternatives to stage 5 include the use of the cold working fluid as a refrigerant in the food freezing industries, for cooling urban heat islands or for the production of synthetic snow, for recreational purposes. The unit time energy balance equation is:

Energy fed into system = energy extracted W_1n ,+ W_{1n 2} + W_1n 3 + Q_1n , = Q_0n, ,+ Q_0n, ₂ + Wo., .

W_1n 3 + Q_1n i = [Qou. i+ Qo* 2 + Woo, ,] - [W_1n ,+ W_1n „

If Qi_{n I} > Wi_{n 3}, then the invention can deliver a net output of useful energy because the heat absorbed from the brine exceeds the energy losses from the system..

For a given shape of power generation system, the ratios of useful power generated to heat losses from external surfaces and useful power generated to viscous drag losses when fluids flow through pipes both increase as the size of the system increases.

This increase in efficiency with size has two design consequences:

(i) below a certain critical size, this version of the invention cannot produce a net output of power,

(ii) assuming all other variables increase in proportion; the efficiency of power output increases with system size, after the critical size has been ^"exceeded.

Figure 11 depicts that part of the invention used for stages 1 and 2 of the freeze desalination process. In this depiction, which is in no way intended to limit the scope of the invention, two dual chamber displacement pumps 1 and 2 are used to compress the working gas. The construction of these pumps is revealed in patents GB 2273133 and GB2306580 (Courtney). The first dual chamber pump has two inlet ports 3 and 4, which alternately draw in dry air or other working gas, at approximately ambient temperature and pressure. At the instant'shown, inlet port 4 is drawing in gas. After suffering the first stage of compression, the heated gas is transferred Xo a first holding reservoir 5, which is maintained at a temperature of about 100⁰C by spraying it with brine from a shower head 6. In this illustrative depiction, a second stage of compression is suffered using the.^rpump 2, with the gas being held in a second holding reservoir 7, doused by brine from a second shower head 8. The steam produced by the partial evaporation of the brine is restricted to the inside.of a lagged evaporation chamber 9. It exits via a port 10 to the start of the chain of turbo-generators, in common with other versions of the invention. The compressed dry air exits the second holding reservoir via a port 11, from where it passes through a heat exchange unit, then on to a conventional turbo-gene.rator unit at the beginning of stage 3 of the freeze desalination process. The concentrated brine collects in a sump at the base of the chamber 9 and runs off via an exit port 12. The run-off brine is warm and may be used to pre-heat the dousing brine, before it enters the shower heads.

The freeze desalination version of the invention has^'' been revealed with reference to a working gas passing through the compression pumps, ft is to bemnderstood that the invention is not limited to two compression stages and that the working gas may b.e replaced by a working vapour that suffers saturation, with the release of latent heat, as it passes through stage three of the process. An advantage of generating saturated water vapour at a temperature\.of 100⁰C is that the maximum pressure inside the chamber 9 is never greatly in excess of the external atmospheric pressure. But this is not intended to limit in any way the scope of the invention, whichis only limited in pressures and temperatures by the strength of the materials available to build a plant that will operate safely.

Stage 5 of the process may be modified to include the warming of the gas or vapour by any external form of low grade heat, before the cycle begins again.

At the end of the turbine chain, when it is no longer viable to extract latent heat from the low density vapour, the residual vapour may be compressed back up to the highest vapour pressure in the system and recycled through the turbine chain. This recycling process incurs a usable energy loss, due to the inevitable inefficiencies of any mechanical system, but offers a net benefit because it reduces the amount of very low grade thermal energy produced as waste by the system.

Figure 12 depicts an illustrative example of a part of the freeze desalination version of the invention used to re-warm the working gas back to about ambient temperature, after it has expanded during stage 4 above. The cold working gas passes through thermally conducting metal pipes 1 and 2 fitted with heat exchange fins, for example 3. The pipes are passing through a thermally insulated enclosing chamber 4. An array of spay jets, of which one is depicted as item 5 releases a continuous aerosol of brine into the chamber. The brine is at a higher temperature tha^*n the gas passing through the pipes. Consequently convection currents are set up as depicted by the curved arrows. The tiny brine droplets cool and partially freeze, releasing latent heat of fusion. The mixture of cold brine and ice crystals forms slurry 6 in the sump of the chamber, from where it is drained away. Filters such as 7 discourage ice and brine mist from migrating upwards, towards the cold. pipes. Electrostatic repulsion techniques may also be used to discourage the migration of brine droplets towards the filters. Shuttle scrapers, for example 8 may be used to scrape off any ice that forms on the cold fluid pipe heat exchange fins.

An alternative to using this version of the invention for freeze desalination would be to run a carbon capture version of the invention on the same site and employ the cold working gas available at the end of stage 4 to cool carbon dioxide well below its critical temperature. Latent heat will be released as the carbon dioxide condenses.

The total economic potential of the invention is limited only by the local needs. For example snow sport jobs could be created in ex-deep mine working areas. The liquefied/sublimated carbon dioxide could be transported to redundant mine working areas arid sequestrated underground. The heat absorbed as the carbon dioxide returns to its gaseous form could used to produce synthetic snow, for spraying on the abandoned slag heats. The heaps could be roofed over, to minimise the cooling of the local environment.

An attractive feature of the invention is that it can operate at temperatures of around 100⁰C. This means that injection moulded plastics can be used in the construction of the turbines. The turbine design in no way limits the scope of the invention. For^' example, Pelton wheel type turbines may be used. Also, turbine units that can be tuned to different rates of vapour flows using variable geometry nozzles and exit ports may be used.

Figure 13 depicts an innovative turbine design that may be used as part of the invention. In this figure low velocity vapour 1 accelerates as it enters the constriction 2. After impacting on the first set of turbine blades, 3, the vapour tends to slow down, having lost kinetic energy. But, because the main body of the turbine unit is tapered and the cross sectional area seed by the advancing vapour decreases after passing through the first set of turbine blades, the vapour at 4 experiences an acceleration. The vapour venting from the turbine at 5 maintains a high velocity, but slows down if the vapour flows into a wider chamber. This type of turbine is particularly suited to versions Of the invention that draw warm unsaturated vapour into the first turbine unit.

Figure 14 is a schematic diagram depicting a West to East vertical cross section of a solar powered version of the invention, at right angles to the cross sectio.n depicted in Figure 1. The evaporation chamber is split into a plurality of parallel channels, in this example there are seven channels, numbered 1 to 7. By using a canopy 8 made up of cylindrical Fresnel thin lenses, (i.e., micro prisms) the sun can be tracked throughout the day without the complexity of the moving mirrors commonly associated with large solar power units. At the instant shown, the central channel 5 is receiving the most intense solar radiation. All of the channels, which effectively act as a common trough, are in good thermal contact with a common underlying condensation chamber 9. The water in the channels to the sides of channel 4 is progressively cooler. Thermal energy can only be transferred from vapour condensing in the lower chamber, to the water above, if the water in the above section of the trough is at a lower temperature. The version of the invention revealed in Figure 14 assists in the heat transfer process, by always offering one or more relatively cool channels. Roll up silvered blinds 10 and

11 reflect solar energy onto the channels of the trough when the sun is at a low angle. Internal glass walls

12 and 13 combine with external glass walls 14 and 15 to create semi-sealed cropping zones 16 and 17 where comfortable levels of humidity can be maintained, even in arid desert climates. The invention is extended to cover versions in which (i) the channels share a common vapour space above their liquid surfaces, (ii) transverse vapour flow is discouraged. but not eliminated by semi-permeable partitions between channels, (iii) impermeable partitions eliminate vapour flow from the spaces above the channels.

The invention is designed to generate electricity and potable water. The thermal recycling features of the invention as discussed with reference to Figure 14 help to improve the ratio of potable water to power production.

The cropping zones are only illuminated by scattered sunlight from the sky. In effect, the inner glazed zone, occupied by the trough, acts like a giant he& pump, shunting heat away from the cropping zones. Photosynthesis will convert about 10% of the solar e.nergy falling on to the leaves in to chemical energy inside the plants. Evaporation of water from the leaves of the plants provides further cooling. This invention will allow people to live comfortably in the desert, without the need for conventional air conditioning.

Figure 15 illustrates how parallel solar powered devices 1 and 2 may be grouped under a common Fresnel lens canopy. Additional internal shading 3 can be provided for pedestrians, cyclists and horse riders.

Figure 16 illustrates how, especially at the cool end^' of the system, additional shading can be added, to ensure that the condensing vapour always has access to cooler water above it. The trough water 1 is separated from the underlying vapour 2 by a corrugated trough base 3. The corrugations add stiffness to the base and increase the contact area between the vapour and the brine. Matt black shades, for example 4, are suspended above the troughs in the corrugations. Silvered shades, for example 5 are placed above the peaks of the corrugations.

The silvered shades are angled, to reflect solar radiation up to the matt black shades. This geometry of shades, having different reflectivities encourages a streamline flow of convection currents in the brine, as depicted by the arrows.

Figure 17 depicts a variation on the design shown in Figure 16. A matt black galvanised iron slatted mask 1 is suspended in the trough water 2; The frequency of the slats in the mask is higher than the frequency of the corrugations in the trough base 3. Adjacent sections in the trough base, for example 4 and 5 are either in the shade or sunlight. But, because of the difference in frequencies, the positions of the illuminated and shaded sections, 6 and'7, are shifted on the next corrugation.

The engine may be powered by any form of -low, grade waste heat, for example, heat liberated in the manufacturing of calcium or magnesium based cement. It is known that vast reserves of heat are available deep in the earths crust. At these depths, saline water is also abundant. The present invention could be used to exploit this geothermal energy and also desalinate sub-terrene brine to potable Water as a by-product. The residual, high density concentrated brine could be injected back into the ground, at distance from where it is pumped out. Inland desert based solar powered versions of the invention could replenish their brine stocks each evening, using the accompanying geothermal heat to^'drive the invention overnight.

The present invention is extended to include:

• Versions of the invention in which external heat sources are used to increase the temperature of the working vapour or vapour plus gas mixture prior to entry to any of the turbines along the chain of turbines.

• Versions of the invention in which external heat sources are used to maintain or help to maintain the temperature of the working vapour or vapour plus gas mixture prior to entry to any of the turbines along the chain of turbines.

• Versions of the invention in which latent heat is released, increasing the temperature of the working vapour or vapour plus gas mixture', just prior to impacting on any of the sets of turbine blades along the chain of turbines.

• Versions of the invention in which latent heat is released, maintaining or helping to maintain the temperature of the working vapour or vapour plus gas mixture, just prior to impacting on any of the sets of turbine blades along the chain of turbines.

• Versions of the invention in which latent heat is released, increasing the temperature of the working vapour or vapour plus gas mixture as the working fluid is passing through any of the turbines along the chain of turbines.

• Versions of the invention in which latent*heat is released, maintaining or helping to maintain the temperature of the working vapour or vapour plus gas mixture as the working fluid is passing through any of the turbines along the chain of turbines.

• Versions of the invention in which at least some of the engines or turbines that form a chain are linked to a common shaft or spindle.

• Versions of the invention including a series chain of Pelton wheel type turbines mounted on the same axle shaft, with the connecting vapour carrying conduits being arranged in a helix formation having the same axis as the shaft.

Claims

1. A device for converting thermal energy into mechanical energy, comprising a chain of serially linked engines powered by kinetic energy extracted from moving vapour, with warm vapour being fed into the first engine and then successively through all the engines, with the vapour doing external work to produce mechanical energy inside each engine, with a consequence that the vapour cools and becomes super-saturated on exiting from at least some of the engines, characterised by the super-saturated vapour then partially condensing, releasing sufficient latent heat to warm the residual vapour so it becomes saturated again, before entering the next engine in the chain.

2. A device according to the first claim with the engines being turbines that convert kinetic energy possessed by flowing fluids to rotational kinetic energy.

3. A device according to the first claim with the engines being sets of turbine blades mounted on a common shaft or rotating platform.

4. A device according to the first claim with the engines being turbines that utilise the kinetic energy of flowing fluids to induce rotational motion, with the tips of the blades fitting into recesses in the housing, as seen from inside the housing.

5. A device according to the first claim, with the vapour passing through a condensation chamber when flowing between two adjacent engines in the chain, with a small fraction of the mass of vapour passing through per unit time condensing out, so that a vapour pressure gradient exists along the length of the condensation chamber, causing the residual vapour to accelerate and gain velocity.

6. A device according to the first claim, with the vapour passing through a condensation chamber when flowing between two adjacent engines in the chain, with a small fraction of the mass of vapour passing through per unit time condensing out, so that a vapour pressure gradient exists along the length of the condensation chamber, causing the residual vapour to accelerate and gain velocity, with the post-turbine vapour condensing regions of the device being thermally insulated and having a divergent in geometry such that the forward velocity of the vapour decreases, then with the vapour velocity increasing again as it passes through a thermally insulated convergent section, prior to entering the next turbine.

7. A device according to the first claim with the conduits connecting the engines being curved in profile, forcing the vapour and suspended condensed vapour droplet mixture s to travel in a curved path, causing droplets to impact on walls inside the conduits and drop out from then- suspended state.

8. A device according to the first claim with electric charges being induced on suspended condensed vapour droplets and electric fields being used to cause a resultant force to act on the droplets resulting in their migration towards solid surfaces where they drop out from their suspended state

9. A device according to the first claim, powered by solar energy, with the glazed roof of an evaporation chamber being convex, with the surface of the glass or other glazing material being moulded to form cylindrical converging lenses, micro-prisms or Fresnel lenses, with the solar energy falling onto one or more of a plurality of liquid filled evaporation troughs, with the trough(s) receiving the highest density of solar energy varying throughout the day, as the apparent position of the sun changes.

10. A device according to the first claim, powered by solar energy, with the glazed roof of an evaporation chamber being convex, with the surface of the glass or other glazing material being moulded to form cylindrical converging lenses, micro-prisms or Fresnel lenses, with the solar energy falling onto one or more of a plurality of liquid filled evaporation troughs, with the trough(s) receiving the highest density of solar energy varying throughout the day, as the apparent position of the sun changes, with the liquid filled trough(s) including radiant heat absorbing shades inside, to promote the circulation of convection currents within the liquid.

11. A device according to the first claim, including a continuous loop system, with a mixture of gas and liquid vapour flowing round the system, with the vapour fraction increasing along a temperature gradient, as the mixture picks up vapour as it flows over a liquid filled trough in an enclosed chamber, from the cool end, towards its warm end of the chamber, with the vapour fraction then decreasing as the mixture does external work on passing though a chain of turbines or other engines, with the residual gas and vapour then being pumped back into the space above the cool end of the enclosed chamber.

12. A device according to the first claim, including a continuous loop system, with a mixture of gas and liquid vapour flowing round the system, with the vapour fraction increasing along a temperature gradient, as the mixture picks up vapour as it flows over a liquid filled trough in an enclosed chamber, from the cool end, towards its warm end of the chamber, with the vapour fraction then decreasing as the mixture does external work on passing though a chain of turbines or other engines, with the residual gas and vapour then being pumped back into the space above the cool end of the enclosed chamber, with the bases of the engines stepping up in height and being curved in a horizontal plane, causing the chain of engines to take the shape of a helix.

SUBSTITUTE SHEET (RULE ZQ)

13. A device according to the first claim, including a continuous loop system, with a mixture of gas and liquid vapour flowing round the system, with the vapour fraction increasing along a temperature gradient, as the mixture picks up vapour as it flows over a liquid filled trough in an enclosed chamber, from the cool end, towards its warm end of the chamber, with the vapour fraction then decreasing as the mixture does external work on passing though a chain of turbines or other engines, with the residual gas and vapour then being pumped back into the space above the cool end of the enclosed chamber, with the bases of the engines stepping up in height and being curved in a horizontal plane, causing the chain of engines to take the shape of a helix, with the liquid filled trough being terraced in a series of steps.

14. A device according to the first claim, including a continuous loop system, with a mixture of gas and liquid vapour flowing round the system, with the vapour fraction increasing along a temperature gradient, as the mixture picks up vapour as it flows over a liquid filled trough in an enclosed chamber, from the cool end, towards its warm end of the chamber, with the vapour fraction then decreasing as the mixture does external work on passing though a chain of turbines or other engines, with the residual gas and vapour then being pumped back into the space above the cool end of the enclosed chamber, with the liquid in the trough including dissolved substances and the liquid condensed in the condensation chambers having a lower concentration of the same dissolved substances.

15. A device according to the first claim with the heat of compression produced when a gas or mixture of gases is compressed approximately isothermally being used as at least one of the sources of low grade heat, to power the engine.

16. A device according to the first claim with the heat of compression produced when a gas or mixture of gases is compressed approximately isothermally being used as at least one of the sources of low grade heat, to power the engine with the compressed gas or mixture of gases then cooling to below ambient temperature as they expand and do external work.

17. A device according to the first claim with the heat of compression produced when a gas or mixture of gases is compressed approximately isotheraially being used as at least one of the sources of low grade heat, to power the engine with the compressed gas or mixture of gases then cooling to below ambient temperature as they expand and do external work with the cooled gas or mixture of gases then being returned to approximately ambient temperature by the absorption of latent heat liberated when a substance changes phase.

18. A device according to the first claim with the heat of compression and latent heats released when sulphur dioxide, nitrogen dioxide, carbon dioxide or other waste gases are compressed to above their critical pressures and cooled below their critical temperatures, being used as at least one of the sources of low grade heat, to power the engine.

19. A device according to the first claim with the heat liberated by the manufacturing of magnesium or calcium based cement being used as at least one of the sources of low grade heat, to power the engine

20. A device according to the first claim with at least some of the engines being coupled to electricity generators.

21. A device according to the first claim, with the device including at least one turbine unit having a three dimensional geometry that accelerates the vapour after it passes through each successive set of turbine blades.

22. A device according to the first claim, including a means of seeding sμper-saturated vapours, with the seeding ingredients including electric charges, radioactive particles, dust particles and rough surfaces.

23. A device according to the first claim, including a means of separating suspended liquid droplets from the vapour, for examples using filters, electrostatic precipitators, gpav}fational or inertial mass separators.

SUBSTITUTE SHEET (RULE ZQ)