GB2546423A

GB2546423A - Energy generation systems

Info

Publication number: GB2546423A
Application number: GB1700945.7A
Authority: GB
Inventors: Stuart Lucking Graham; Stephen Hordley Timothy; Martin Buffery Harry; Charles Palmer Don
Original assignee: Fluid Energy Solutions Int Ltd
Current assignee: Fluid Energy Solutions Int Ltd
Priority date: 2015-02-03
Filing date: 2015-12-23
Publication date: 2017-07-19
Also published as: WO2016124924A1; GB201700945D0; GB201522737D0; GB2535005A

Abstract

An energy generation system 200 including a means for transferring heat 202 from an external fluid to a working fluid, which vaporises the working fluid and reduces the temperature of the external fluid, a fluid engine 1 which receives the vaporised working fluid from said means, wherein the fluid engine is driven by expansion of the working fluid within the engine, such that the working fluid is depressurised, and a generator 118 for generating electrical power, the generator being driven by the fluid engine. Also claimed is a corresponding method for generating electrical power. The system preferably includes means for recycling 208 the depressurised working fluid from the fluid engine to the means for transferring heat. Preferably, the external fluid is provided into an external fluid distribution system 204b after heat transfer to the working fluid, where the external fluid can be further used. Said further use may be dependent upon the external fluid having a reduced temperature greater than a minimum threshold temperature.

Description

ENERGY GENERATION SYSTEMS

The present disclosure relates to energy generation systems.

Natural gas is supplied to gas distribution networks (for example a nationwide gas distribution network) under higher pressure than is required by end users, for easy transport. Before delivery to end users, the gas must be depressurised. In a gas distribution network, there may be several stages of depressurisation before the gas reaches the end user.

When natural gas is depressurised, the temperature of the gas also drops. This can cause condensation of impurities out of the gas, which can be harmful to the infrastructure of the gas distribution network. To avoid condensation of harmful impurities, the gas is preheated before it is depressurised. Therefore, the gas supply does not drop below a minimum temperature.

Typically, the gas is heated before depressurisation by burning some of the natural gas. This can use up at least 1% of the gas in the network, and is thus wasteful.

According to a first aspect of the invention, there is provided a natural gas depressurisation system including: an inlet conduit for carrying a supply of natural gas at a first pressure; a fluid engine coupled to the inlet conduit, the fluid engine being driven by expansion of the natural gas within the engine, the expansion accompanied by a reduction in temperature of the natural gas; an outlet conduit coupled to the fluid engine, for carrying expanded natural gas at a second pressure, lower than the first; a generator constructed and arranged to be driven by the fluid engine to generate electricity; and means for heating the supply of natural gas, such that the temperature of the gas in the inlet conduit, fluid engine, and outlet conduit does not drop below a threshold temperature at which impurities in the gas condense, after depressurisation, the means for heating the gas in the inlet conduit being powered by the generator.

By harnessing the energy in the pressurised natural gas to power the heating means, the natural gas depressurisation system is able to eliminate the need to consume any of the natural gas to provide heating during distribution. This results in more efficient distribution of the gas. Furthermore, energy that would otherwise be lost to the surrounding environment during depressurisation can be captured.

The natural gas depressurisation system may include: reserve heating means constructed and arranged to heat the supply of gas.

The reserve heating means may be configured to heat the supply of gas in the absence of power from the generator being provided to the heating means.

The reserve heating means may comprise an alternative power supply to the means for heating the gas in the inlet conduit.

The means for heating the gas may be a heater arranged around at least a portion of the circumference of the inlet conduit.

According to a second aspect of the invention, there is provided a natural gas distribution network including: a source for providing gas at an input pressure; one or more first natural gas depressurisation systems according to the first aspect, arranged to receive natural gas from the source, and arranged to depressurise the gas to a first transport pressure; one or more second natural gas depressurisation systems according to the first aspect, arranged to receive natural gas from a first natural gas depressurisation system, and arranged to depressurise the gas to a second transport pressure.

By harnessing the energy in the pressurised natural gas to heat the gas, the natural gas distribution system is able to eliminate the need to consume any of the natural gas to provide heating during distribution, meaning a higher proportion of the gas can be supplied to end users. As with the first aspect, energy that would otherwise be lost to the surrounding environment during depressurisation can also be captured.

According to a third aspect of the invention, there is provided a method of depressurising natural gas, from a first pressure to a second pressure, lower than the first, the method including: providing natural gas at a first pressure to a fluid engine; enabling expansion of the natural gas in the fluid engine, the fluid engine being driven by expansion of the natural gas in the fluid engine, the expansion being accompanied by a reduction in temperature of the natural gas; driving a generator with the fluid engine; and using the generator to power a means for heating the natural gas before it is provided to the fluid engine, the means for heating the natural gas being constructed and arranged to heat the natural gas, such that the temperature of the gas does not drop below a threshold temperature at which impurities in the gas condense, after depressurisation.

By harnessing the energy in the pressurised natural gas to power the heating means, the method is able to eliminate the need to consume any of the natural gas to provide heating during distribution. This results in more efficient distribution of the gas. The method also captures energy from the depressurisation that would normally be allowed to dissipate to the surrounding environment.

The method may include heating the gas from a reserve heating means prior to the generation by the generator reaching a minimum threshold, the minimum threshold being the power required to power the heating means

According to a fourth aspect of the invention, there is provided a method of distributing natural gas, the method including: reducing pressure of a supply of natural gas in step wise changes across a natural gas distribution network, at least some of the step wise changes being according to the third aspect.

By harnessing the energy in the pressurised natural gas to heat the natural gas, the method is able to eliminate the need to consume any of the natural gas to provide heating during distribution, meaning a higher proportion of the gas can be supplied to end users. As with the third aspect, the method also captures energy from the depressurisation that would normally be allowed to dissipate to the surrounding environment

The depressurisation of natural gas is one example where a fluid (any substance in its liquid or gas phase, including but not limited to a substance in a mixture of liquid and gas phase) can undergo a pressure change. In practice, there are a wide variety of situations where a fluid is depressurised, sometimes with an associated state change, with an accompanying release of energy. This energy is often allowed to dissipate to the surrounding environment. In many situations, this energy could be harnessed.

According to a fifth aspect of the invention, there is provided an energy generation system including: a means for transferring heat from an external fluid to a working fluid, in order to vaporise the working fluid, wherein the temperature of the external fluid is reduced by the transfer of heat; a fluid engine arranged to receive the vaporised working fluid from the means for transferring heat, wherein the fluid engine is driven by expansion of the working fluid within the engine, such that the working fluid is depressurised; and a generator for generating electrical power, the generator being driven by the fluid engine.

The system is able to take advantage of small changes in temperature to generate electrical power, at low cost. The system can also be used in a variety of different scenarios, is robust and simple to implement, and can, if necessary, still provide a heated external fluid.

The energy generation system may include: heating means to heat the external fluid prior to heat transfer to the working fluid in the means for transferring heat.

The heating means may be selected from the list including: a hot water boiler or heater; a ground source heating system; a geothermal heating system; a solar water heating system; and a hot fluid circulation system.

The energy generation system may include: means for recycling the depressurised working fluid from the fluid engine to the means for transferring heat.

The means for recycling depressurised working fluid may comprise means for pumping the working fluid from the fluid engine to the means for exchanging heat.

The means for pumping may be powered by a portion of the power generated by the generator.

The means for recycling the depressurised working fluid may comprise means for condensing the working fluid.

According to a sixth aspect of the invention, there is provided a method of generating electrical power including: transferring heat from an external fluid to a working fluid, in order to vaporise the working fluid, wherein the temperature of the external fluid is reduced by the transfer of heat; supplying the vaporised working fluid to a fluid engine; enabling expansion of the natural gas within the fluid engine, such that the expansion of the gas drives the engine and the working fluid is depressurised; and generating power with a generator driven by the fluid engine.

The method is able to take advantage of small changes in temperature to generate electrical power, at low cost for implementation. The system can also be used in a variety of different scenarios, is robust and simple to implement, and can, if necessary, still provide a heated external fluid.

In the fifth or sixth aspects, the temperature reduction of the external fluid may be less than 15 degrees Celsius, preferably less than 5 degrees Celsius.

In the fifth or sixth aspects, the pressure of the external fluid may be substantially unchanged.

In the fifth or sixth aspects, the temperature of the external fluid before heat transfer may be less than 80 degrees Celsius.

In the fifth or sixth aspects, the external fluid may be provided into an external fluid distribution system after heat transfer to the working fluid, the external fluid being provided for further use in the external fluid distribution system.

In the fifth or sixth aspects, the external fluid distribution system may be a hot water system of a building.

The external fluid distribution system may be a heating system of a building.

The generator may be constructed and arranged to provide electrical power to the building.

The further use may require a minimum threshold temperature, and the means for transferring heat may be constructed and arranged such that reduced temperature of the external fluid is greater than the minimum threshold temperature.

In the fifth or sixth aspects, the external fluid may be selected from the list including: liquid water; and gaseous water.

In the fifth or sixth aspects, the working fluid may comprise a refrigerant.

In any of the above aspects, the output from the generator may be between 0.25 kilowatts and 500 kilowatts.

In any of the above aspects, the engine may have an engine capacity of greater than or equal to 0.01 litres.

In any of the above aspects, the or each cylinder of the fluid engine may comprise: one or more cylinders arranged to receive the working fluid or natural gas, the or each cylinder having a piston received in the cylinder, wherein expansion of the natural gas in the cylinder(s) drives reciprocal motion of the piston, driving the engine, each cylinder including: an inlet valve for controlling ingress of a working fluid or natural gas into the cylinder; an outlet valve for controlling the exhaust of the working fluid or natural gas from the cylinder; a first cam for operating the inlet valve; and a second cam for operating the outlet valve, wherein the first cam and second cam are constructed and arranged such that piston is operated by a pressure change of the working fluid or natural gas, without combustion of the working fluid or natural gas.

The fluid engine may further include: a camshaft on which at least the first cam is mounted; and a crankshaft constructed and arranged to be driven by reciprocal motion of the piston(s), and to drive the camshaft and the generator wherein the fluid engine is constructed and arranged such that the camshaft and crankshaft rotate at the same speed.

The first cam may be constructed and arranged such that the inlet valve opens when the piston is at a first pre-determined position within the cylinder and closes when the piston is at a second pre-determined position within the cylinder, and wherein: with the inlet valve open, and the piston moving from top dead centre to bottom dead centre, the piston is driven by ingress of the working fluid or natural gas and expansion of the working fluid or natural gas, and with the inlet valve closed, and the piston moving from top dead centre to bottom dead centre, the piston is driven by expansion of the working fluid or natural gas; and the first and second pre-determined positions are selected to control the reduction in pressure of the working fluid or natural gas, and ensure that the piston is driven by expansion of the working fluid or natural gas only, for at least a period.

In the first, second or fifth aspects, the system may include the system may further include: means for collecting working fluid or natural gas leaked from the fluid engine.

The means for collecting working fluid or natural gas leaked from the fluid engine may include: means for recycling the collected leaked working fluid or natural gas to the fluid engine system.

The collected working fluid or natural gas may be recycled to an input side of the fluid engine.

In the first, second or fifth aspects, the system may include means for supporting the engine, wherein the means for supporting the engine is arranged to absorb vibration of the engine, in use.

In the first, second or fifth aspects, the fluid engine may comprise an internal combustion engine, modified such that decompression of the working fluid or natural gas in the cylinder drives reciprocal motion of the piston.

In the third, fourth of sixth aspects, the method may include: modifying an internal combustion engine such that reciprocal motion of one or more pistons of the engine is driven by expansion of a working fluid or natural gas; and providing the modified internal combustion engine as the fluid engine.

The method may include: encasing at least a portion of the modified internal combustion engine in a sealed casing.

The method may include: collecting leaking working fluid or natural gas from the fluid engine.

The method may include: recycling the collected leaking working fluid or natural gas to the input of the fluid engine.

As discussed above, all of the aspects can optionally take advantage of a fluid engine that has been manufactured by modifying an internal combustion engine. Existing fluid engines are based on turbine technology. This makes them complex and expensive to make, since a high degree of precision and strength is required. Furthermore, existing fluid engines are highly application specific, meaning that a whole new engine must be designed for each application and working fluid.

The modified internal combustion engine is less expensive to manufacture than turbine based fluid engines, and so the above systems and method can be implemented more efficiently, allowing smaller energy losses that would otherwise be inefficient to exploit to be harnessed. Also, a single design engine can be used in a wide variety of applications with minimal variations.

An alternative option to obtain an inexpensive fluid engine may be manufacture of the engine by three-dimensional printing techniques.

Exemplary embodiments of energy generation systems will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1A illustrates a sectional schematic view of a cylinder of a fluid engine;

Figure IB shows a schematic plan view of a fluid engine incorporating four cylinders; Figure 1C shows a schematic side view of a fluid engine incorporating four cylinders; Figure 2 shows a flow chart outlining the operation of the cylinder of Figure 1;

Figure 3 schematically illustrates a natural gas distribution system;

Figure 4 schematically illustrates a natural gas depressurisation systems;

Figure 5 schematically illustrates a closed cycle fluid engine system;

Figure 6 schematically illustrates a working fluid recycling system for the closed fluid engine system of Figure 5; and

Figure 7 shows a mounting system for a fluid engine.

With reference to the Figures ΙΑ, IB and 1C, a fluid engine 1 is an engine that is driven by a pressure or state change in a fluid. The fluid used to drive the engine is known as the working fluid. In the context of this application, a fluid can be used to mean any substance in its liquid, vapour or gas phase, including or not limited to a substance in a mixture of liquid and/or vapour and/or gas phase. The vapour phase is differentiated from the gas phase in that the vapour is close to the saturation point, where it condenses into a liquid, whereas in the gas phase, the gas is not close to the saturation point.

Figure 1A shows a schematic drawing of a cross section through a cylinder 3 of a fluid engine 1. The structure of the fluid engine 1 is similar to the structure of an internal combustion engine, such as a petrol or diesel engine for use in a car. However, unlike convention internal combustion engines, the energy for driving the piston 11 is derived externally of the cylinder 3.

The cylinder 3 is formed in a cylinder block 5 (also known as an engine block). At the base of the cylinder block 5, there is a crankcase 7, through which a crankshaft 9 runs. The cylinder block 5 and crankcase 7 may be formed separately and then joined together, or may be formed as a single unit.

The top of the cylinder 3 is closed by a cylinder head 13. The cylinder head 13 includes an inlet 15 into the cylinder 3 and an outlet 17 from the cylinder 3. The inlet 15 and outlet 17 are opened and closed by an inlet valve 19 and an outlet valve 21 respectively.

The valves 19, 21 are poppet valves, including a closing member for closing the inlet 15 or outlet 17, and a stem 41, 43 extending from the closing member. The valve stems 41, 43 pass through apertures in, and extend out of the cylinder head 3 or engine block 5.

The inlet valve 19 is operated by an inlet cam 23, and the outlet valve 21 is operated by an outlet cam 25. In the examples shown in the Figures, the cams 23, 25 are eccentric profiled discs, having profiles including lobes. The inlet cam 23 is mounted on an inlet camshaft 29 and the outlet cam 25 is mounted on an outlet camshaft 31. The inlet camshaft 29 and the outlet camshaft 31 are coupled to the crankshaft 9 with a belt or chain (discussed in relation to Figures 4A and 4B), so that the camshafts 29, 31 rotate at the same speed as the crankshaft 9. Rotation of the camshafts 29, 31 in turn rotates the cams 23, 25.

The valves 19, 21 are biased to the closed position, in which the closing member closes the inlet 15 or outlet 17, by a spring (not shown). As the cams 19, 21 rotate, they engage respective valve stems 41, 43 and urge the valve open against the force of the spring, moving the closing member away from and opening the inlet 15 or outlet 17. Thus, the cams 23, 25 hold each valve 19, 21 open for a proportion of the rotation. The period can be increased with larger lobes and decreased with smaller lobes.

The inlet cam 23 is mounted on an inlet camshaft 29 and the outlet cam 25 is mounted on an outlet camshaft 31. The inlet camshaft 29 and the outlet camshaft 31 are coupled to the crankshaft 9 with a belt or chain (discussed in relation to Figures IB and 1C), so that the camshafts 29, 31 rotate at the same speed as the crankshaft 9. Rotation of the camshafts 29, 31 in turn rotates the cams 23, 25.

In use, the crankshaft 9 is driven by reciprocating motion of a piston 11 received in the cylinder 3. The reciprocal motion of the piston 11 is driven by expansion of a working fluid inside the cylinder 3.

The pressure of the working fluid that is provided to the cylinder 3 is typically between 1 bar and 100 bar, and even after the expansion, the working fluid may still be within this range. For example, the working fluid may be above 5 bar throughout the engine 1. This means the working fluid is often at higher pressure that the pressure typically experienced in an internal combustion engine (2 to 3 bar), and so working fluid may leak around the valve stems 41, 43 if standard seals from an internal combustion engine are used.

To ensure the valve stems 41, 43 are properly sealed, each valve stem 41, 43 is provided with a sealing unit (not shown). The sealing unit is in the form of a “top hat” shaped housing, with an aperture in the closed end. The top hat sits over the valve guide formed where the valve stem exits the top of the cylinder block, with the stem 41, 43 passing through the housing.

Within the housing, a first dynamic seal is formed between the housing and the valve stem 41, 43, and a second static seal is formed between the housing and the valve guide. The seals are formed by one or more rubber O-ring type seals, separated by annular washers, if necessary.

Furthermore, the top of the fluid engine 1, including the cylinder head 3, cams 23, 25, and camshafts 29, 31 are enclosed in a casing (not shown). The casing is sealed and collects any working fluid that does leak through the valve stems 41, 43.

The casing is coupled, via an outlet pipe, to a heat exchanger, which cools and condenses any working fluid collected in the casing. The heat exchanger also acts to create a cold spot in the casing, to ensure that any leaked working fluid is drawn to the heat exchanger. The condensed working fluid is then collected in a reservoir.

Nitrogen gas is provided within the space 214 defined by the casing. Therefore, the reservoir includes a separator that isolates and collects the working fluid. The nitrogen is fed back to the space defined by the casing through a nitrogen recycling pipe.

In one example, the reservoir is emptied at regular intervals, allowing the working fluid to be returned to the fluid engine 1. In other examples, the reservoir may be monitored, and emptied as required. In yet further examples, the working fluid may automatically be recirculated back to the fluid engine 1, either on the inlet side 15 or the outlet side 17, or at any other suitable position in the working fluid system. This ensures that losses of working fluid are minimal.

Circulation of the working fluid through the collection system described above may be assisted by a pump, although this is not essential.

It will appreciated that as with any engine, the fluid engine 1 may have any number of cylinders 3. For example, the fluid engine may have a single cylinder, four cylinders, five cylinders, or more or fewer.

Figures IB and 1C show a plan view and side view of a fluid engine 1 having four cylinders 3a-3d arranged along the crankshaft 9. The dashed dividing lines are for illustration only. The sealing units 65 and collecting system 200 are not shown, for clarity.

As can be seen from Figures IB and 1C, the crankshaft 9 extends from both ends of the crankcase 7. This is the case for a fluid engine 1 with any number of cylinders 3. At one end 53 of the crankshaft 9, a load can be connected, as will be discussed in more detail below. At the other end 55, the crankshaft 9 is coupled to the camshafts 29, 31, which also project from the cylinder head 13. A chain 57 connects the camshafts 29, 31 to the crankshaft 9, so that rotation of the crankshaft 9 causes rotation of the camshafts 29, 31.

Any suitable belt 57 or chain can be used to couple the crankshaft 9 to the camshafts 29, 31 and the belt 57 or chain may couple directly to the shafts 9, 29, 31 or through toothed wheels (not shown) or other suitable means. The coupling may be via a single belt encompassing the crankshaft 9, and the camshafts 29, 31, or a first belt coupling the crankshaft 9 to the inlet camshaft 29 and a second belt coupling the crankshaft to the outlet camshaft 31. In another example, the crankshaft 9 may coupe to the camshafts 29, 31 without use of a belt 57 or chain, via toothed wheels and the like.

The working fluid is provided to the cylinder inlets 15, through an inlet manifold 61. The inlet valves 19 control when working fluid is provided into the cylinders 3. The inlet manifold 61, also known as an inlet conduit, starts as a single main supply. In an engine with a single cylinder 3, this is provided to the inlet 15. Otherwise, the inlet manifold 61 divides to provide a supply of working fluid to each cylinder 3.

The inlet manifold 63 can also be manipulated to provide volumetric control ensuring that the mass flow of the working fluid arriving in the cylinders is constant, no matter what the density, and viscosity of the main supply.

As discuss above, and in more detail below, the pressure of the working fluid that is provided to the cylinder 3 is typically between 1 bar and 100 bar. The inlet manifold 61 should be constructed to withstand such pressures, and to ensure that the pressure of the working fluid supplied to each cylinder 3 is the same. The inlet manifold 61 should also be constructed to withstand the temperature of the working fluid in the engine.

Similarly, an outlet manifold 63 (see Figures 3 to 5) is connected to the cylinder outlets 17, to exhaust expanded working fluid from the cylinders 3. The outlet valves 21 regulate when each cylinder 3 is exhausted into the outlet manifold.

Within the cylinder 3, the pressure of the working fluid decreases from the starting pressure, and so the pressure of the working fluid in the outlet manifold 63 will be lower than the pressure of the working fluid in the inlet manifold 61. However, in some circumstances both valves 19, 21 may be open at the same time. Accordingly, the working fluid may pass directly from the inlet manifold 61 to the outlet manifold 63 via the cylinder 3, without expansion and a subsequent reduction in pressure. To protect the outlet manifold 63 should this occur, the outlet manifold 63 needs to be constructed to withstand the same pressures and temperatures as the inlet manifold 61. The size of the inlet manifold 61 and outlet manifold 63 supplies to/from the cylinder 3 may also be varied depending on the working fluid, desired pressure, flow characteristics and the like.

In the embodiments described above, the valves 19, 21 have been described as poppet valves biased to the closed position by a spring. However, it will be appreciated that in some embodiments, the valves may be desmodronic poppet valves that do not include a spring and are, instead, positively opened and closed. In the case of desmodronic valves, the inlet valve 19 is operated by a pair of inlet cams (one to open the valve and one to shut it) and the outlet 21 valve is operated by a pair of outlet cams (one to open the valve and one to shut it). Desmodronic valves will still make use of the sealing unit 200, to seal the valve stems 41, 43. Any other type of valve may also be used.

In some embodiments, only a single camshaft may be provided. In such embodiments, the inlet cam 23 and the outlet cam 25 will be mounted on the single camshaft. Similarly, the cams 23, 25 do not necessarily have to be formed of eccentric discs. Other types of cam are known and could be used.

In addition, in some examples, the fluid engine 1 having cams 23,25 that have two opposed lobes that open the valves 19, 21 twice per rotation. In this case, the crankshaft 9 and camshaft 29, 31 rotation will be the same as for a four-stroke engine where the crankshaft 9 rotates twice for each rotation of the camshafts 29, 31.

In some embodiments of the fluid engine 1, the top surface of the piston head 27 may arranged so that the piston 27 does not impinge on the valves 19, 21. To achieve this, the piston head may have a concavity, a depression, an indentation or a recess (not shown). Alternatively, the piston head 27 may be sized such that the piston 11 is separated from the valves 19, 21 even at top dead centre. This arrangement increases the efficiency of the fluid engine 1 because the piston head 27 is prevented from impinging on the valves 19, 21.

The above structure for a sealing unit is given by way of example only. It will be appreciated that any suitable seal may be used. It will also be appreciated that the working fluid collection system is given by way of example only, and any collection system may be used, or the collection system may be omitted altogether.

The operation of the fluid engine 1 will now be described with reference to Figure 2.

Figure 2 shows the method 1000 by which a single cylinder 3 of a fluid engine 1 operates. The piston 11 may be in any position in the cylinder 3 at the start of the operation, but for convenience, it will be considered that the piston 11 starts at top dead centre (where the piston head 27 is at its maximum vertical spacing from the crankshaft 9).

At a first step 1002, the inlet valve 19 is opened. The outlet valve 21 is closed. This causes working fluid to enter the cylinder 3.

In a second step 1004, the piston 11 goes through a downward stroke. In the downward stroke, there are two separate factors driving the piston 11 down. The first factor is the ingress of the working fluid acting on the piston 11. The second is the expansion of the working fluid acting on the piston 11. Initially, as the inlet valve 19 is opened, it is the ingress of the working fluid that drives the piston 11. However, almost immediately, the fluid will start to expand and this will also drive the piston 11.

The downward stroke causes 180 degrees of rotation of the crankshaft 9, such that at the end of the stroke, the piston 11 is at bottom dead centre(where the piston head 27 is at its minimum vertical spacing from the crankshaft 9).

At a third step 1006, when the downward stroke has ended (piston at bottom dead centre), the inlet valve 19 is closed and the outlet valve 21 is opened. The expanded working fluid begins to be drawn through the outlet valve 21. In a final step 1008, the piston 11 goes through an upward stroke, as shown in Figure 2. In the upward stroke, the expanded working fluid is drawn through the outlet 17. The upward stroke ends when the piston 11 reaches top dead centre. The operation then returns to the first step 1002, where the outlet valve 21 is closed and the inlet valve 19 opened.

By this method of operation, the expansion of the working fluid is able to drive reciprocal motion of the piston 11 and hence drive the crankshaft 9. There is no combustion of the working fluid and the energy is deriving from an external source. The working fluid is chemically unchanged by the process. This is different to an internal combustion engine, where at least some of the fuel is combusted internally (either with or without ignition of the fuel). The fluid engine 1 does not include any means for combustion in the cylinder 3.

Substantially all of the working fluid provided into the cylinder is recovered in the exhaust system. Any leakages are recovered by the working fluid collection system.

The fluid engine 1 is a two-stroke engine, because the engine 1 completes a full crankshaft 9 rotation within two strokes of the piston 11 (the upward stroke and the downward stroke).

In the example discussed above, the inlet valve 19 is open for the full downward stroke of the piston 11 (180 degrees of crankshaft rotation) and the outlet valve 21 is open for the full upward stroke of the piston 11 (180 degrees of crankshaft rotation). However, this is only one example of the timings that may be used.

The timing of the opening and closing depends on a number of other factors, including the working fluid, design choice and efficiency - the most efficient opening period does not need to be 180 degrees, but could be more or less.

In some examples, the inlet valve 19 is open for less than 180 degrees. If the inlet valve 19 is not open for the full duration of the downward stroke, the piston 11 is driven by expansion only, once the inlet valve 19 is closed, and the piston 11 is still moving from top dead centre to bottom dead centre. If the inlet valve 19 is open for the full downward stroke, it can mean that not all of the working fluid properly expands, or depressurises to the desired pressure. Conversely, closing the inlet valve 19 too early can mean that the working fluid has fully expanded before the piston 11 reaches bottom dead centre, and the piston is not driven for the full downward stroke of the engine. Therefore, correct choice of the period the inlet valve 19 is open for can increase the efficiency of the engine. Generally, the inlet valve opening period will be between 35 degrees and 135 degrees.

The inlet valve 19 opening period can also be used to control the change in pressure of the working fluid at the outlets 17. For example, if the inlet valve is open for 180 degrees, the working fluid may not have opportunity to fully expand. On the other hand, if the inlet valve is only open for a small period (e.g. less than 35 degrees), the working fluid will expand more. Other factors, such as the pressure of the working fluid supplied to the engine 1 will also affect the pressure at the outlet 17.

The above description focuses on the operation of a single cylinder 3, in order to demonstrate how the fluid engine 1 works in principle. However, as discussed above, the fluid engine 1 may have any number of cylinders 3. Figures IB and 1C show, for example, a fluid engine 1 having four cylinders 3.

In one example of the operation of a fluid engine 1 having four cylinders, the cylinders 3 are grouped so that the first and fourth cylinders 3a, 3d operate in parallel and the second and third cylinders 3b, 3c operate in parallel, shifted by 180 degrees from the first and fourth cylinders 3a, 3d. In other words, whilst the first and fourth cylinders 3a, 3d are on downward strokes, the second and third cylinders 3b, 3c are on upward strokes and vice versa.

This timing ensures relatively even distribution of power throughout the rotation of the crankshaft 9. In some examples, the downward stroke of the first group of cylinders 3a, 3d helps to drive the upward stroke of the other cylinders 3b, 3c (and vice versa).

This grouping is by way of example only. In a fluid engine 1, the cylinders may be grouped into two groups operating at 180 degree difference, or the cylinders 3 may all operate in parallel, or the cylinders 3 may all operate spaced from one another or in any number of groups, spaced by different amounts. The cylinders 3 may be grouped so that the crankshaft 9 is driven by a downward stoke of one or more pistons 11 throughout its rotation. Alternatively, the cylinders 3 may be grouped so that the crankshaft 9 is driven in a phased manner.

In general, a fluid engine is manufactured by sealing the valves 19, 21 in an engine unit using sealing units. Cams 23, 25 are then mounted on one or more camshafts 29, 31, as required, and the camshaft(s) 29, 31 on the engine unit.

The engine unit comprises the crankcase 7, crankshaft 9, cylinder block 5, piston 11, cylinder 13 and the inlet 15, outlet 17 and associated valves 19, 21. An inlet manifold 6land outlet manifold 63 can then be installed, and the engine 1 is then installed into a larger system for use (see below).

As discussed above, the configuration of the cams 29, 31 (and hence inlet and outlet valve 19, 21 timings), and manifolds 61, 63 depends on a number of factors including the working fluid that is to be expanded in the fluid engine 1, the desired inlet and outlet pressures and the like.

The engine unit may be obtained in any suitable manner. In some examples, the engine unit may be taken from a four-stroke internal combustion engine. Therefore, the fluid engine 1 can be a modified four-stroke internal combustion engine.

In some cases, the engine unit may be obtained by partially dismantling an existing internal combustion engine. This may require, for example, removing the existing camshafts, gearings and any other parts that require modification, replacement, or which are not required.

In other examples, the engine unit may be taken before it is assembled into four-stroke internal combustion engine, such that fewer or no parts need removing. Nonetheless, the engine unit will, until the point it is modified into a fluid engine 1, be suitable for making an internal combustion engine.

Within the cylinder block 5 or cylinder head 13 of an engine unit that forms the basis of an internal combustion engine, apertures may be provided associated with the function as a four-stroke internal combustion engine. These may be for, for example, spark plugs, fuel injection systems, cooling systems and the like. These apertures are not required for operation as fluid engine 1, and therefore need to be blocked. When the holes are blocked, a seal is formed so that none of the working fluid escapes the cylinder, in use.

In some examples, each cylinder 3 may have multiple inlets 15. The fluid engine 1 may only use one inlet 15 per cylinder 3, with the remaining inlets 15 sealed. Alternatively the inlet manifold 61 may be arranged to supply fluid to some or all of the inlets 15. Similarly, if a cylinder has multiple outlets 17, only one may be used, or some or all may be used, with the unused outlets blocked.

The engine unit used may be taken from any internal combustion engine. For example, the engine may be a lawnmower engine (with a capacity of 0.01 litres or higher), an engine intended for cars or lorries (with engine capacities between 0.5 litres and 10 litres or more) or larger engines intended for ships and the like.

In other examples, the engine unit may be purpose built. In one example, existing engine manufacturing techniques may be used. However, in other examples, the engine may be made of plastics by three-dimensional printing techniques. Printed engines may be particularly useful where the temperatures within the engine make plastics a feasible material to use.

The use of fluid engines 1, such as described above, will now be discussed with reference to Figures 3 to 6.

Figure 3 shows a schematic illustration of part of a natural gas distribution network 100. The natural gas distribution network 100 may be implemented on, for example, a national scale (although it may be smaller or larger) for delivering natural gas from a source 102 to an end user 104, via pipelines 106

The source 102 may be any suitable source, such as a terminal where gas is supplied by pipeline, ship and the like. The end user 104 may be, for example, houses, offices, industrial sites and the like.

At the source 102, the natural gas is under higher pressure than required by the end users 104. This makes it easier to transport. However, the gas requires depressurisation as it is delivered through the network 100. In the example shown in Figure 3, the gas is depressurised in stages, at a number of nodes 108. At each node, the pressure of the gas is reduced before continuing along the pipelines 106.

Figure 4 shows a schematic illustration an example of a depressurisation node 108. The node 108 is a depressurisation station, and includes a system for depressurising the gas 110.

The depressurisation system 110 includes an inlet conduit 112 for providing a supply of natural gas under an input pressure, from the pipeline 106. The inlet conduit 112 is coupled to the inlet manifold 61 of a four cylinder 3 fluid engine 1, and provides natural gas at the input pressure into the cylinders 3 of the fluid engine 1. The gas expands in the fluid engine 1, driving the pistons 11, and is exhausted through an outlet manifold 63. The outlet manifold 63 provides gas into an outlet conduit 114, and into the gas pipeline 106.

The fluid engine 1 in the depressurisation system 110 is as described above.

The gas contains a number of impurities which can damage the pipeline 106 and nodes 108 if they condense. As the gas is depressurised by the depressurisation system 110, it cools, and thus there is a risk of the impurities condensing. Therefore, the depressurisation system 110 includes a heater 116 to preheat the gas. The gas may be heated to a threshold such that once the temperature drops during depressurisation, the gas still remains about the temperature required for condensation of the impurities, or to a temperature above this threshold. The threshold for condensation of impurities will depend on the composition of the gas, and will be readily apparent to the person skilled in the art.

The heater 116 is an electrical heater, powered by a generator 118, and arranged around the outside of the inlet conduit 112. The generator 118 in turn is driven by the crankshaft 9 of the fluid engine 1, and is coupled to the load end 53 of the crankshaft 9.

Without the use of a fluid engine 1, the energy released when the natural gas undergoes depressurisation would be lost to the surrounding environment. Furthermore, an alternative source would have to be used to heat the gas. In many cases, the gas itself is used. In these examples, a portion of the gas is combusted, either to power a generator 118, or simply to heat the natural gas in the inlet conduit 112.

When the fluid engine 1 is first started, there will be a delay between natural gas first passing through the engine 1, and the generator 118 providing power to the heater 116. Therefore, a portion of the gas first passing through the engine 1 would not be heated. To avoid this, the depressurisation system 110 includes an alternative power source 120 for the heater 116. The alternative power source 120 is taken from a mains electric network (not shown).

When the fluid engine 1 is first started, the heater 116 is powered from the alternative power source. When the generator 118 is producing sufficient power to supply the heater 116, the heater is then powered from the generator 118.

The depressurisation system 110 may include one or more of a current, voltage or power monitor to measure the output of the generator 118, and a switch (not shown) to control which power source 118, 120 is used for the heater 116. Once gas is supplied through the inlet conduit 112, but before the output of the generator reaches a minimum threshold output (current and/or voltage and /or power) required for the heater 116, the switch is controlled so that the heater 116 is powered by the alternative power source 120. Once the threshold output is reached, the switch is then controlled so that the heater 116 is powered by the generator 118.

The switch may be further controlled so that if the output of the generator 118 drops below the threshold at any point during operation, the alternative power source 120 is once again used, until the generator output increases again. This may be because of a fault in the generator or the gas supply which causes a reduction in the power generated. Alternatively, the generator 118 may be switched off for maintenance of the generator 118 or engine 1.

The gas distribution network 100 shown in Figure 3 includes a first node 108a provided after the source 102, second nodes 108b provided downstream for the first nodes 108a, third nodes 108c, fourth nodes, 108d and fifth nodes 108e, each provided respectively further downstream.

Each of the first 108a to fifth 108e nodes are respective stages in the depressurisation of the gas, such that the pressure is reduced at each node 108.

In one example, the first node 108a contains a depressurisation system 110 as discussed above, which reduces the natural gas from 120 bar to 70 bar. The second nodes 108b also include a depressurisation system 110 as discussed above, and reduces the pressure of the natural gas from 70 bar to 32 bar. The third nodes 108c again include a depressurisation system 110 as discussed above, and reduce the pressure of the natural gas from 32 bar to 7 bar. The engine size, arrangement of the manifolds 61, 63 and the inlet valve 19 opening period can be used to control the pressure at the outlet 17.

The fourth nodes 108d and fifth nodes 108e include different depressurisation systems, which heat the gas in a different way, and further reduce the pressure. In the example shown, different end users 104 take the gas from the third nodes 108c, fourth nodes 108d or fifth nodes 108e.

It will be appreciated that any suitable size engine 1 may be used, with any suitable number of cylinders 3. The engine size will depend on the power required by the heater 116, which will in turn depend on at least the flow rate of gas passing through the pipeline 106. However, it will be appreciated that while a faster flow rate may require more heating, it will also provide greater power generation.

Furthermore, it will be appreciated that the gas distribution network 100 of Figure 3 is shown by way of example only, and any particular network 100, with any number of nodes 108, sources 102 and end users 104, and any network of pipelines 106 may be used. Also, in some examples, only some of the first nodes 108a and/or some of the second nodes 108b and/or some of the third nodes 108c may incorporate the depressurisation system 110. Similarly some or all of the fourth nodes 108d and/or some or all of the fifth nodes 108e, and any further nodes required may also include the depressurisation system 110.

In the example shown, the heater 116 is provided to heat the gas in the inlet conduit 112. However, it will be appreciated that the heater may instead heat the gas in the inlet manifold 61, either before the manifold 61 splits into the separate conduits for each cylinder 3, or after the manifold 61 splits, in which case multiple heaters may be provided. Furthermore, in the example shown and discussed above, the heater 116 is arranged around the outside of the inlet conduit 112 or manifold 61. It will be appreciated that the heater 116 may be provided around part or the whole of the circumference of the inlet conduit 112, or the manifold 61. In other examples, the heater 112 may be provided within the inlet conduit 112 or inlet manifold 61, in the gas flow.

Furthermore, any suitable means for heating can be used instead of a simple heater 116. In addition, instead of being a connection to mains network, the reserve power supply 120 may be a second generator, powered by natural gas or some other fuel. Also, instead of providing an alternative power source 120 to power the same heater, any suitable reserve heating means may be used. For example, a second heater may be provided, powered by the reserve power source 120.

The fluid engine 1 in the gas depressurisation system 100 may optionally include the working fluid collection system, to collect any working fluid leaking from around the valve stems 41, 43. In this case, the collected gas may be re-pressurised, and fed back into the inlet conduit 112 or inlet manifold 61. Alternately, the gas may be fed into the outlet conduit 114 or outlet manifold, having been depressurised or pressurised as necessary, depending on the pressure it is collected at. In other examples, the collected fluid may be fed into other parts of the engine 1, or the gas distribution network 100.

It will be appreciated that the depressurisation system 110 could be used where any fluid is depressurised. For example, the depressurisation system 110 may be used where liquid petroleum gas is depressurised after transport in tankers, or in any type of distribution network, or in an industrial system where fluids are stored under pressure but used at reduced pressure. Also, any suitable load may be coupled to the fluid engine 1, and the generator 118 may be used to provide power to anything, including batteries.

In the gas depressurisation system 110, the working fluid in the fluid engine 1 is the natural gas. The working fluid is provided downstream for a different use, and so the system can be considered an open cycle system. Figure 5 schematically illustrates a closed cycle system 200 that can be used to generate electrical energy.

In general, the energy generation system 200 includes a working fluid that is vaporised by heat transfer in a heat exchanger 202. Depressurisation of the vaporised working fluid drives a fluid engine 1, which drives a generator 118. After the working fluid is depressurised in the fluid engine 1, it is fed back to the heat exchanger 202.

The heat exchanger 202 is used to transfer heat from a fluid external to the working fluid cycle to the working fluid. The external fluid is provided at an external fluid input 204a, and, once it has passed through the heat exchanger 202 exits through an external fluid output 204b. Similarly, the working fluid enters the heat exchanger 202 at a working fluid input 206a, and exits at working fluid output 206b.

From the heat exchanger 202, the working fluid is passed to the fluid engine 1, through the inlet manifold 61. As described above, the working fluid depressurises and cools in the cylinder(s) 3 of the fluid engine 1, driving the fluid engine 1, which in turn drives the generator 118 coupled to the load end 53 of the fluid engine 1.

The working fluid exits the fluid engine 1 through the outlet manifold 63, and passes back to the working fluid input 206a of the heat exchanger 202. The working fluid is passed back to the heat exchanger 202 through a recycling system 208, discussed in more detail below.

At the working fluid input 206b of the heat exchanger 202, the working fluid is a liquid at an input temperature and pressure. At the heat exchanger 202, the liquid is vaporised to a gas, with an increased output temperature, but approximately the same pressure. After depressurisation in the fluid engine 1, the working fluid is a vapour with reduced pressure and temperature, and the recycling system 208 returns the working fluid to a liquid with at the input pressure and temperature.

Figure 6 shows the recycling system 208 in more detail. From the fluid engine 1, the working fluid is fed to a condenser 212, where it is condensed from a vapour to a liquid, via heat exchange with a cooling fluid, such as water. From the condenser 212, the liquid fluid is provided to a working fluid reservoir 214, where the working fluid can be stored. The working fluid is then provided from the reservoir 214 to the heat exchanger 202.

Typically, the fluid engine 1 requires only a small amount of working fluid to operate in a closed cycle such as this (a few litres or even less). However, with use of the reservoir 214, the total working fluid in the system may be much more than the fluid required to operate the engine. This ensures that the engine always has sufficient supply of working fluid, and allows for operation even if there are small leaks that are not prevent by the sealing unit, and/or working fluid collection system. In one example, there may be 30 litres of working fluid in the whole system, although there could be more or less.

The working fluid reservoir 214 includes a connection to a working fluid charging or top up system 222, which can be used to add working fluid into the closed cycle system, if necessary. In one example, this may simply be an inlet to allow manual top up, while in other examples, it may be an automatic top up system from a remote source. In some examples, the charging system 222 may take manual or automatic top up from a working fluid leak collection system.

The cooling liquid is provided to the condenser 212 from a cooling liquid reservoir 218. In the condenser 212, the temperature of the cooling liquid is increased. Therefore, the cooling liquid is fed to a cooler 216, and back to the reservoir 218.

The cooling liquid reservoir 218 may also optionally be used to provide cooling liquid to a working fluid collection system, for collecting leaked working fluid.

The working fluid is circulated through the recycling system 208 by action of a first pump 210. The cooling liquid is circulated through the reservoir 218, condenser 212 and cooler 216 by action of a second pump 220. The pumps 210, 220 and cooler 216 may be powered by a portion of the electrical power generated by the generator 118.

It will be appreciated that the above description of the recycling system 208 is by way of example only, and any suitable system may be used. Furthermore, any suitable means for pumping, condensing and cooling may be used instead of the pumps 210, 220, cooler 216 and condenser 212.

In one example, the working fluid is a refrigerant, such as Honeywell® R245, and the external fluid is hot water. Refrigerants can be damaging to the environment, and so the leak collection system should be used, along with the sealing units.

Using the example of R245, the working fluid has a pressure of 6 bar and a temperature of 30 degrees Celsius at the working fluid input 206a of the heat exchanger. At the working fluid 206b output of the heat exchanger 202, the working fluid is at 60 degrees Celsius, with a pressure of 6 bar. The working fluid has the same pressure and temperature at the fluid engine inlet manifold 61. At the outlet manifold, the working fluid has a pressure of 1 bar and a temperature of 46 degrees Celsius.

The above example temperatures and pressures are for R245 only. It will be appreciated that different working fluids will have different pressures, and vaporisation temperatures that are used.

The pressurised working fluid will be between 1 bar and 100 bar. In some examples, the pressurised working fluid may be below 20 bar. For example, the pressurised working fluid may be between 1 bar and 10 bar.

As discussed above, a number of factors, including the inlet valve 19 opening period can be used to control the pressure drop in the fluid engine 1. Depending on the arrangement of the engine, the pressure drop may be minimal (e.g. a few percent, or less), or any more significant value. For example, the pressure may drop by 5%, 10%, 25%, 50% or more, or any value in between.

At the external fluid input 204a of the heat exchanger 202, the water has a temperature of greater than at least 15 degrees Celsius, preferably (but not essentially) greater than 50 degrees Celsius. The water can be liquid or vapour. In the case of liquid water, the reduction in temperature of the water in the heat exchanger 202 is less than 15 degrees Celsius. In some examples, the reduction in the temperature of the water is between 1 degree Celsius and 10 degrees Celsius, or even 1 degree Celsius and 5 degrees Celsius. In the case of external fluids, for example steam, the reduction in the temperature could be more. In all cases, the temperature reduction is sufficient to provide the necessary pressure increase in the working fluid.

The heat for the water can come from any suitable source external to the system 200. For example, the hot water may be taken from a hot water boiler in a building, such as a house, office, care home, hotels, hospitals or the like. In this case, that water is typically between 60 and 80 degrees Celsius before the heat exchanger 202, and the energy generation system 200 is provided after the boiler or heating means that is used to heat the water, with the external fluid input 204a coupled to an output of the boiler (either directly or through piping). After passing through the heat exchanger 202, the hot water is then passed into the hot water system of the building for later use. Therefore, the reduction in temperature of the water should be small enough such that the water is still sufficiently hot for use, and to meet any required standards.

Alternatively, the energy generation system 200 may be provided on a separate loop from the boiler, so that a constant flow can be maintained through the heat exchanger, rather than only having a flow when hot water is circulated through the system (for example when hot water is drawn from a tap).

For comfort and/or regulatory reasons, there is often a minimum temperature for hot water taken from taps. The temperature reduction in the water at the heat exchanger 202 is such that the water does not drop below this minimum temperature.

In a similar manner, the energy generation system 200 could be used in connection with a swimming pool or other environment where large amounts of hot water are required.

Rather than using water from a hot water system, the hot water may alternatively be taken from a heating system. In this case, the heating system is also generally a closed cycle system, including some mechanism for topping up water in the system, and so the external fluid is also recycled back to the heat exchanger, via a heater or boiler.

In the case of a heating or hot water system, the boiler may be powered by any suitable renewable or non-renewable energy source, such as gas, biomass, mains electricity and the like.

Any other alternative means may be used to heat the water. For example, the water may be heated by solar energy. One example using solar energy to heat the water makes use of solar panels. In other examples, the water may be heated geo-thermally, or from ground-source heating. In these examples, the external fluid may be recycled back to the heating means (possibly with a second pump powered by the generator 118), or may be provided for further use. The alternative heating means may be provided as part of a hot water and/or heating system.

In other examples, the hot water may be a by-product of an alternative process, for example steam from a power station or other industrial process. In this example, the system 200 may be provided in part of a system for cooling the steam before it is vented. In this case, the water is not provided for further use, and so any desired temperature drop may be used. The system 200 may be provided after a primary heat exchange system.

In all of the above examples, energy that would otherwise be allowed to dissipate, or in some scenarios is required to dissipate, would be lost, and can be harnessed.

In addition to powering the pumps that are required to circulate the working fluid and possibly the external fluid, the power from the generator 118 can be used for any suitable application. In some example, the power can be used to provide backup power in the case of a power-cut, or can be stored in batteries.

The power generated depends on a number of factors including the engine size, engine speed, inlet and outlet valve 19, 21 opening periods, generator size and the pressure of the working fluid before and after the engine 1. The below table provides some examples of the different parameters.

Table 1: Example engine and power generation characteristics

These parameters are by way of example only, and any suitable engines and valve opening periods may be used. In some examples, the generator may have a power of up to 500 kWel or as low as 0.25 kWel

Furthermore, it will be appreciated that the power that can be generated is a function of a number of factors, including the input pressure, the inlet valve opening periods, the arrangement of the inlet manifold 61 and the cylinder 3, the input temperature, and the like.

It will be appreciated that the desired input pressure and temperature can be obtained by correct choice of the heat exchanger 202 , working fluid and recycling system 208, and the correct output pressure and engine speed can be obtained by choice of the engine size, cylinder numbers, valve 19, 21 timings and the like, and the power generated can be chosen based on the engine 1 and generator 118. Any suitable engine 1 generator 118 can be used, depending on the application.

In the examples discussed above, the working fluid is Honeywell® R245, and the external fluid is water. However, is will be appreciated that the energy generation system 200 may use any external fluid, any working fluid, and any combination of working and external fluid.

The working fluid may be any working fluid that vaporises in the heat exchanger 202, upon heat transfer with the external fluid. Therefore, to some extent, which working fluids may be suitable is dependent on the temperature of the external fluid and the heat exchanger 202. For example, the working fluid may vaporise at temperature equal to or above 40 degrees Celsius, at 1 bar pressure.

The external fluid may be any fluid that is cooled in an industrial process (such as a side product, intermediate product of final product), or any other suitable fluid of sufficient temperature. The external fluid is provided in a circulation system. For example, hot fluids used in chemical process, such as glycol, syrups and the like, may also be used as the external fluid.

Any suitable type of heat exchanger may be used to obtain the desired heat transfer and vaporisation. Alternatively, any suitable means for transferring the heat may be used. Similarly, any suitable means for recycling the working fluid may be used.

All of the above open-circuit and closed circuit examples use a fluid engine 1 to capture energy for generating electricity. Engines that rely on internal combustion to drive reciprocal motion of the pistons are mounted from points on the bottom of the cylinder block 5, since this is where the main source of vibration occurs. Furthermore, any vibration that does occur is lost through the drive train of the car.

However, in fluid engines 1, the main source of vibration is from the ingress of the working fluid, at the top of the cylinder 3, and the engine is fixed. Therefore, in the above examples, vibration can cause wear of connections to the fluid engine, and noise.

Figure 7 shows a cut through of a mounting system 300 for supporting the engine 1, that absorbs the vibration. The mounting system 300 comprises a cubic frame 302 that rests on the floor. The frame 302 has a horizontal base 302a, side supports 302b and a top support 302c. A cradle 304 is also provided. The cradle 304 includes a platform 306, on which the engine 1 rests, and a cradle frame 308 which includes a top frame member 308a and a vertical support 308b. The top frame member 308a rests on shock absorbers 310, which are provided on the top of the frame 302.

In one example, the frame 302 and cradle 304 are made of square cross section steel beams, and the cradle 304 is mounted on four shock absorbers 310 forming a rectangle, with the vertical supports 308b of the cradle passing through apertures in the frame 302.

In use, the engine 1 sits on the platform 306, and any vibrations are absorbed by the shock absorbers 310. The inlet and outlet manifolds 61, 63 are also supported from the cradle, so they vibrate with the engine 1. The manifolds 61, 63 are coupled to flexible hosing, which can move with the vibrations.

In some examples, a second cradle (not shown) is supported directly from the first cradle, and rests on further shock absorbers (not shown) provided on the base 302a. The generator 118 sits on the second cradle. This is particularly useful where there are large vibrations.

The support system 300 given above is just one example of a support for the engine that can absorb the vibrations generated in use. Any suitable support may be used, and the support may be made of any suitable material.

In the above description, all pressures are referenced to a complete vacuum.

Claims

1. An energy generation system including: a means for transferring heat from an external fluid to a working fluid, in order to vaporise the working fluid, wherein the temperature of the external fluid is reduced by the transfer of heat; a fluid engine arranged to receive the vaporised working fluid from the means for transferring heat, wherein the fluid engine is driven by expansion of the working fluid within the engine, such that the working fluid is depressurised; and a generator for generating electrical power, the generator being driven by the fluid engine.

2. The energy generation system as claimed in claim 1, including: heating means to heat the external fluid prior to heat transfer to the working fluid in the means for transferring heat.

3. The energy generation system as claimed in claim 2, wherein the heating means is selected from the list including: a hot water boiler or heater; a ground source heating system; a geothermal heating system; a solar water heating system; and a hot fluid circulation system.

4. The energy generation system of claim 2 or claim 3, including: means for recycling the depressurised working fluid from the fluid engine to the means for transferring heat.

5. The energy generation system as claimed in claim 4, wherein the means for recycling depressurised working fluid comprises means for pumping the working fluid from the fluid engine to the means for exchanging heat.

6. The energy generation system as claimed in claim 5, wherein the means for pumping is powered by a portion of the power generated by the generator.

7. The energy generation system as claimed in ay of claims 4 to 6, wherein the means for recycling the depressurised working fluid comprises means for condensing the working fluid.

8. A method of generating electrical power including: transferring heat from an external fluid to a working fluid, in order to vaporise the working fluid, wherein the temperature of the external fluid is reduced by the transfer of heat; supplying the vaporised working fluid to a fluid engine; enabling expansion of the natural gas within the fluid engine, such that the expansion of the gas drives the engine and the working fluid is depressurised; and generating power with a generator driven by fluid engine.

9. The energy generation system as claimed in any of claims 1 to 7, or the method of claim 8, wherein the temperature reduction of the external fluid is less than 15 degrees Celsius, preferably less than 5 degrees Celsius.

10. The energy generation system as claimed in any of claims 1 to 7, or claim 9, or the method as claimed in claim 8 or claim 9, wherein the pressure of the external fluid is substantially unchanged.

11. The energy generation system as claimed in any of claims 1 to 7, claim 9, or claim 10, or the method as claimed in any of claims 8 to 10, wherein the temperature of the external fluid before heat transfer is less than 80 degrees Celsius.

12. The energy generation system as claimed in any of claims 1 to 7, or claims 9 to 1, or the method as claimed in any of claims 8 to 11, wherein the external fluid is provided into an external fluid distribution system after heat transfer to the working fluid, the external fluid being provided for further use in the external fluid distribution system.

13. The energy generation system as claimed in claim 12, or the method as claimed in claim 12, wherein the external fluid distribution system is a hot water system of a building.

14. The energy generation system as claimed in claim 12, or the method as claimed in claim 12, wherein the external fluid distribution system is a heating system of a building.

15. The energy generation system as claimed in claim 13 or claim 14, or the method as claimed in claim 13 or claim 14, wherein the generator is constructed and arranged to provide electrical power to the building.

16. The energy generation system as claimed in any of claims 12 to 15, or the method as claimed in any of claims 12 to 15, wherein the further use requires a minimum threshold temperature, the means for transferring heat constructed and arranged such that reduced temperature of the external fluid is greater than the minimum threshold temperature.

17. The energy generation system as claimed in any of claims 1 to 7, or claims 9 to 16, or the method as claimed in any of claims 8 to 16, wherein the external fluid is selected from the list including: liquid water; and gaseous water.

18. The energy generation system as claimed in any of claims 1 to 7, or claim 9 to 15, or the method as claimed in any of claims 8 to 16, wherein the working fluid comprises a refrigerant.

19. The system as claimed in any of claims 1 to 7, or claims 9 to 18, or the method as claimed in any of claims 8 to 18, wherein the output from the generator is between 0.25 kilowatts and 500 kilowatts.

20. The system as claimed in any of claims 1 to 7, or claims 9 to 19, or the method as claimed in any of claims 8 to 19, wherein the engine has an engine capacity of greater than or equal to 0.01 litres.

21. The system as claimed in any of claims 1 to 7, or claims 9 to 20, or the method as claimed in any of claims 8 to 20, wherein the fluid engine comprises one or more cylinders arranged to receive the working fluid or natural gas, the or each cylinder having a piston received in the cylinder, wherein expansion of the natural gas in the cylinder(s) drives reciprocal motion of the piston, driving the engine, each cylinder including: an inlet valve for controlling ingress of a working fluid or natural gas into the cylinder; an outlet valve for controlling the exhaust of the working fluid or natural gas from the cylinder; a first cam for operating the inlet valve; and a second cam for operating the outlet valve, wherein the first cam and second cam are constructed and arranged such that piston is operated by a pressure change of the working fluid or natural gas, without combustion of the working fluid or natural gas.

22. The system of claim 21 or the method of claim 21, wherein the fluid engine further includes: a camshaft on which at least the first cam is mounted; and a crankshaft constructed and arranged to be driven by reciprocal motion of the piston(s), and to drive the camshaft and the generator wherein the fluid engine is constructed and arranged such that the camshaft and crankshaft rotate at the same speed.

23. The system of claim 21 or claim 22, or the method of claim 21 or claim 22, wherein the first cam is constructed and arranged such that the inlet valve opens when the piston is at a first pre-determined position within the cylinder and closes when the piston is at a second pre-determined position within the cylinder, and wherein: with the inlet valve open, and the piston moving from top dead centre to bottom dead centre, the piston is driven by ingress of the working fluid or natural gas and expansion of the working fluid or natural gas, and with the inlet valve closed, and the piston moving from top dead centre to bottom dead centre, the piston is driven by expansion of the working fluid or natural gas; and the first and second pre-determined positions are selected to control the reduction in pressure of the working fluid or natural gas, and ensure that the piston is driven by expansion of the working fluid or natural gas only, for at least a period.

24. The system of any one of claims 1 to 7, or claims 9 to 23, further including: means for collecting working fluid or natural gas leaked from the fluid engine.

25. The system of claim 24, wherein the means for collecting working fluid or natural gas leaked from the fluid engine includes: means for recycling the collected leaked working fluid or natural gas to the system.

26. The system of claim 25, wherein the collected working fluid or natural gas is recycled to an input side of the fluid engine.

27. The system of any of claims 1 to 7, or claims 9 to 26, including: means for supporting the engine, wherein the means for supporting the engine is arranged to absorb vibration of the engine, in use.

28. The system of any of claims 1 to 7, or claims 9 to 27, wherein the fluid engine comprises an internal combustion engine, modified such that decompression of the working fluid or natural gas in the cylinder drives reciprocal motion of the piston.

29. The method of any of claims 8 to 23, including: modifying an internal combustion engine such that reciprocal motion of one or more pistons of the engine is driven by expansion of a working fluid or natural gas; and providing the modified internal combustion engine as the fluid engine.

30. The method of claim 29, including: encasing at least a portion of the modified internal combustion engine in a sealed casing.

31. The method of claim 30, including: collecting leaking working fluid or natural gas from the fluid engine.

32. The method of claim 31, including: recycling the collected leaking working fluid or natural gas to the input of the fluid engine.

33. A system as substantially described herein, with reference to Figures 5 and 6.