GB2589060A - Differential pressure power generator - Google Patents

Abstract

A power generation and storage system 2 includes a vortex tube 12 with an inlet 8 for receiving a pressurised fluid. The vortex tube 12 separates the fluid into a hotter portion supplied to a hot output 18, and a colder portion supplied to a cold output 16. A thermoelectric generator 24 is in thermal communication with the hotter and colder fluids, and generates electrical power from the temperature difference. An electrical energy storage device 28 is charged by the electrical power generated by the thermoelectric generator 24.

Description

Differential Pressure Power Generator The present invention relates to a differential pressure power generator, in particular to a differential pressure power generator for generating electrical power for electrical devices in a pressure reducing location.

The need for efficient use of energy has always been an important motivator behind developments in every industry. Nowadays, as the dangers of climate change become ever more prominent, the expectations and requirements for efficient energy use, set both nationally and internationally, continue to be raised.

Gas companies around the world operate vast networks of such pipelines, often in remote areas. The operating conditions within these pipeline networks are controlled by systems of fluid regulation equipment that include pressure reducing valves. Pressure reducing valves are a key element of control in such systems, but they result in a loss of pressure that is rarely utilised.

Although attempts have been made to design systems capable of using this wasted pressure in order to generate power, the application of these systems to remote areas, such as those of a gas network, remains a challenge.

The present invention aims to provide an improved power generation system for use at a pressure reducing location.

When viewed from a first aspect, the invention provides a power generation and storage system comprising: a vortex tube comprising an inlet for receiving a pressurised fluid, wherein the vortex tube is arranged to separate the fluid into a hotter portion of the fluid and a colder portion of the fluid, wherein the vortex tube further comprises a hot output for outputting the hotter portion of the fluid and a cold output for outputting the colder portion of the fluid; one or more thermoelectric generators each having a hot side arranged downstream of the hot output of the vortex tube and in thermal communication with the hotter portion of the fluid, and a cold side arranged downstream of the cold output of the vortex tube and in thermal communication with the colder portion of the fluid, wherein the one or more thermoelectric generators are arranged to generate electrical power from the temperature difference between the hot and cold sides of the one or more thermoelectric generators; and an electrical energy storage device arranged to be charged by the electrical power generated by the one or more thermoelectric generators.

The present invention provides a power generation and storage system that generates electricity using thermoelectric generator(s), exploiting the temperature difference between hot and cold streams of fluid that have been separated by a vortex tube (e.g. a Ranque-Hilsch vortex tube). The inlet of the vortex tube receives a pressurised fluid (e.g. from an upstream side of a pressure reducing location) and supplies the hot and cold outputs to the opposite sides of the thermoelectric generator(s). Thus a temperature gradient is established across the one or more thermoelectric generators, which they can use to generate electrical power, e.g. as a result of the Seebeck effect.

The electricity generated from the temperature difference across the thermoelectric generator(s) is used to charge an electrical energy storage device, e.g. a battery, capacitor or capacitor array.

It will thus be appreciated that the power generation and storage system of at least preferred embodiments of the present invention may be deployed in remote areas to make use of an existing pressure drop in order to generate and supply power locally for components and systems, thus using the otherwise wasted energy dissipated by the pressure drop. Unlike known remote power generation systems, such as solar power and wind power, the power generation and storage system may not be subject to fluctuations in output caused by extraneous or non-system related (e.g. environmental) factors. Furthermore, in at least preferred embodiments, the present invention comprises no moving parts, thus helping to provide a more reliable power supply in, e.g., remote areas. The generated power is then able to be stored for providing to devices such as sensors or transmitters as and when it is required. 3 -

The present invention may be used for any suitable and desired application. However, the Applicant has appreciated that the present invention is particularly suited for use with (and thus preferably the system comprises) a pressure reducing device (e.g. valve), e.g. for providing power to monitoring sensors, control devices and/or data transmission systems. Such pressure reducing locations are often located, as part of gas networks in remote areas, far from connection points to mains electricity. It is therefore often necessary for data collection devices (e.g. including monitoring sensors and data transmission systems) to be battery powered However, owing to the limited storage capacity of batteries, current battery-powered systems are capable of providing power to a data sampling system that transmits data typically only once a day, in order to preserve a satisfactory lifetime for the batteries. Batteries alone are insufficient to provide power to a system that wishes to achieve real-time (or near real-time) modelling, monitoring and/or controlling, where a data transfer rate of once every few minutes, for example, may be desired. If such a data transfer rate were to be implemented with a battery power supply, the lifetime of the batteries may be only one month, which is too short for use in a remote location.

Thus, when viewed from a further aspect the present invention provides a power generation and monitoring and/or controlling system for a pressure reducing device, wherein the system comprises: a vortex tube comprising an inlet for receiving a pressurised fluid from an upstream side of the pressure reducing device, wherein the vortex tube is arranged to separate the fluid into a hotter portion of the fluid and a colder portion of the fluid, wherein the vortex tube further comprises a hot output for outputting the hotter portion of the fluid and a cold output for outputting the colder portion of the fluid; one or more thermoelectric generators each having a hot side arranged downstream of the hot output of the vortex tube and in thermal communication with the hotter portion of the fluid, and a cold side arranged downstream of the cold output of the vortex tube and in thermal communication with the colder portion of the fluid, wherein the one or more thermoelectric generators are arranged to generate electrical power from the temperature difference between the hot and cold sides of the one or more thermoelectric generators; and 4 -wherein the system further comprises one or both of: (i) one or more monitoring sensors for measuring operational parameters of devices in the location of the pressure reducing device, wherein the one or more monitoring sensors are arranged to be powered by the electrical power generated by the one or more thermoelectric generators; and a data storage and/or transmitter in data communication with the one or more monitoring sensors, wherein the data storage and/or transmitter is arranged to store and/or transmit data received from the one or more monitoring sensors, wherein the data storage and/or transmitter are arranged to be powered by the electrical power generated by the one or more thermoelectric generators; and (ii) one or more control devices for controlling the operation of devices in the location of the pressure reducing device, wherein the one or more control devices are arranged to be powered by the electrical power generated by the one or more thermoelectric generators.

This aspect of the present invention provides a power generation and monitoring and/or controlling system for a pressure reducing device (e.g. valve) that is capable of generating the electrical energy required to power monitoring sensor(s) and/or control device(s) on and/or around the pressure reducing device. This allows the electricity to be generated locally, rather than requiring a connection to an electricity grid. Furthermore, the present invention may be configured to produce sufficient electrical energy to power monitoring sensor(s) and a transmitter such that real-time (or near real-time) modelling, controlling and/or monitoring of the valve may be facilitated.

The electrical energy is generated from a pressure drop across the pressured reducing valve that would otherwise be wasted. Thus, it will be appreciated by those skilled in the art that this invention provides a power generation system that is suitable for use in a remote location. Furthermore, the generated power (which may, for example, be used to charge an electrical energy storage device) is then able to power devices including sensor(s) and a data storage and/or transmitter, and/or control device(s), as and when it is required.

It will be appreciated that both aspects of the invention may (and preferably do) include one or more (e.g. all) of the optional and preferable features outlined herein.

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Thus, for example, the power generation and monitoring and/or controlling system preferably comprises an electrical energy storage device arranged to be charged by the electrical power generated by the one or more thermoelectric generators, e.g. such that the electrical energy storage device may be used to supply power the device(s) described herein.

The pressure reducing device may be any suitable and desired device in a pressure reducing location, across which there is a pressure drop. A pressure reducing location will typically include multiple devices relating to the control of the flow of a fluid through the pressure reducing location. This includes one or more pressure reducing devices.

In a set of embodiments the pressure reducing device comprises a pressure reducing valve. However, as will be appreciated, and as will be discussed below, the pressure reducing device that is used to provide the pressure drop for the vortex tube may not be the same device with which the monitoring device(s) and/or control device(s) are associated. These device(s) may, for example, be associated with other device(s) in the vicinity of (e.g. in the same pressure reducing location as) the pressure reducing device.

The pressure reducing device (and thus the system of the present invention) may be used with any suitable and desired type of pressurised (compressible) fluid. Preferably the fluid comprises a compressible gas.

The pressure reducing device (e.g. valve) may be any suitable and desired size.

Preferably the pressure reducing device has a diameter of between 10 mm and 500 mm, e.g. between 25 mm and 300 mm, e.g. between 50 mm and 200 mm, e.g. approximately 100 mm.

The pressure reducing device (and thus the system of the present invention) may operate with any suitable and desired pressure drop across the pressure reducing device (and thus across the system of the present invention). In a set of embodiments the system is configured to operate with a pressure drop of less than 80 bar, e.g. less than 50 bar, e.g. less than 30 bar, e.g. less than 20 bar, e.g. less than 10 bar, e.g. less than 8 bar. In a set of embodiments the system is configured 6 -to operate with an absolute pressure drop from approximately 8 bar to approximately 3 bar. It will thus be appreciated that embodiments of the present invention may be suited (and preferably configured) for use with a range of different pressure drops and may be suited (and preferably configured) for use with a relatively small pressure drop.

The vortex tube may be provided in any suitable and desired way. Preferably the inlet of the vortex tube is arranged to be connected to the upstream (i.e. higher pressure) side of a pressure reducing device. Thus, in a set of embodiments, the system comprises an inlet conduit for receiving a fluid from the upstream side of a pressure reducing device and for supplying the fluid to the inlet of the vortex tube. The inlet of the vortex tube may be connected to the upstream side of the pressure reducing device by an inlet conduit. Preferably the inlet conduit has a diameter of between 1mm and 100 mm, e.g. between 6mm and 50 mm.

The amount of fluid flowing through the power generation system (and thus, for example, through the vortex tube) may be controlled in any suitable and desired way. In one set of embodiments the power generation system comprises one or more control valves arranged to control the flow of the fluid into and/or out of the system. For example, the one or more control valves may be provided on the inlet and/or outlet conduits. The one or more control valves may be arranged to control (e.g. limit) the flow through the (e.g. inlet conduit of the) power generation system to match the pressure drop across the pressure reducing device. Thus, for example, the control valve(s) may be arranged to regulate (e.g. limit) the flow through the (e.g. inlet conduit of the) power generation system to divert a fraction of the fluid flow through the pressure reducing device to match the upstream and/or downstream pressures of the power generation system to the upstream and/or downstream pressures of the pressure reducing device.

The one or more control valves may, for example, be arranged to isolate the power generation system, e.g. from the pressure reducing device. This may enable the flow of fluid to be stopped through the (e.g. inlet and/or outlet conduits of the) power generation system. The one or more control valves may be actuated in any suitable and desired way. In one embodiment the one or more control valves are actuated by one or more pilot valves. 7 -

In one embodiment the one or more control valves are actuated by one or more electric actuators (e.g. solenoid valve(s)). The electric actuator(s) may be powered using the electrical power generated by (and thus electrically connected to) the one or more thermoelectric generators. This may be convenient to keep the fluid flowing through the power generation system when the one or more thermoelectric generators are generating power and to prevent the fluid flowing through the power generation system when the one or more thermoelectric generators are not generating power (e.g. when the pressure reducing device is fully closed). This helps to prevent fluid from bypassing the pressure reducing device (through the power generation system) when the pressure reducing device is fully closed.

The vortex tube may be arranged to separate the fluid into a particular ratio of the (e.g. flow rate of the) hotter portion of fluid to the (e.g. flow rate of the) colder portion of fluid output from the vortex tube. The vortex tube may be arranged to provide a fixed hot to cold ratio. However, in a preferred embodiment the vortex tube is adjustable to adjust the ratio of the hotter portion of the fluid to the colder portion of the fluid that is output from the vortex tube. This may allow the vortex tube to be adjusted to suit the operating conditions. In one set of embodiments the vortex tube comprises a screw thread arranged to adjust the fractions of the fluid separated into the hotter portion and the colder portion.

Preferably the ratio is adjusted to increase the heat transfer from the fluid to the thermoelectric generator(s). The (e.g. optimum) ratio may depend on a variety of factors including, for example, the ambient temperature and the pressure drop across the pressure reducing device. Thus while the vortex tube may be adjusted to suit the particular operating conditions at any time, preferably the adjustment of the vortex tube is set during installation to suit the particular (e.g. average) operating characteristics of a pressure reducing device and the power generation system.

The vortex tube, the first and/or second conduits and/or the one or more metal plates (e.g. as outlined below) may be arranged to separate the fluid into the hotter and colder portions, and deliver the hotter and colder portions to the hot and cold sides of the thermoelectric generator(s), having any suitable and desired temperature difference therebetween, e.g. depending on the pressure drop across 8 -the power generation system (e.g. as a result of the pressure drop across the pressure reducing device). In one embodiment the vortex tube, the first and/or second conduits and/or the one or more metal plates are arranged to separate the fluid into hotter and colder portions, and deliver the hotter and colder portions to the hot and cold sides of the thermoelectric generator(s), with a temperature difference (e.g. at the hot and cold sides of the thermoelectric generator(s)) of between 5 and 30 degrees Celsius, e.g. between 5 and 20 degrees Celsius, e.g. less than 15 degrees Celsius, e.g. approximately 9 degrees Celsius, between the hotter and colder portions of fluid.

The vortex tube, which receives a pressurised fluid, and thus operates over a pressure drop, may be connected across the pressure drop (e.g. across the differential pressure of a pressure reducing device) in any suitable and desired way, e.g. at any suitable and desired point in a pressure reducing location. As outlined above, preferably the vortex tube receives the pressurised fluid via an inlet conduit from the upstream side of a pressure reducing device or from a higher pressure in the pressure reducing location. After passing past the thermoelectric generators, preferably the hotter and colder portions of the fluid are output to a lower pressure environment than the upstream pressure of the pressure reducing device, e.g. to atmosphere, to the downstream side of the pressure reducing device or to a lower pressure in the pressure reducing location. Thus, in a set of embodiments the power generation system comprises an outlet conduit arranged to output the fluid from the hotter and colder portions of the fluid to atmosphere, to the downstream side of the pressure reducing device or to a lower pressure in the pressure reducing location. The hotter and colder portions of the fluid may be combined (e.g. by the outlet conduit) or they may be output separately, e.g. by separate outlet conduits.

The hotter and colder portions of the fluid from the vortex tube may be in fluid communication with the hot and cold sides of the thermoelectric generator(s) in any suitable and desired way, to establish the thermal communication between the fluid and the one or more thermoelectric generators. In a set of embodiments the power generation system comprises a first conduit into which the hotter portion of fluid from the vortex tube is arranged to be output and a second conduit into which the colder portion of fluid from the vortex tube is arranged to be output. Preferably the first conduit is in thermal communication with (e.g. adjacent to) the hot side of the 9 -thermoelectric generator(s) and the second conduit is in thermal communication with (e.g. adjacent to) the cold side of the thermoelectric generator(s). It will thus be appreciated that the first and second conduits (e.g. each) form a heat exchanger with the thermoelectric generator(s). Preferably the first and second conduits are (e.g. each) in fluid communication with the vortex tube and/or the outlet conduit.

The first and second conduits may each have a uniform cross-sectional area along the length of the conduit. However, in a preferred set of embodiments, the cross-sectional area of (e.g. each of) the first and second conduits is variable along the length of the conduit. Preferably the cross-sectional area of (e.g. each of) the first and second conduits reduces along the length of the conduit. This keeps the transfer of thermal energy into the thermoelectric generator(s) substantially uniform along the length of the conduits and, thus, helps to increase the transfer of thermal energy between the first and second conduits and the thermoelectric generator(s).

In turn, this helps the thermoelectric generators (when there are a plurality of thermoelectric generators) to generate substantially the same power as each other, owing to the thermoelectric generators experiencing substantially the same conditions. As a consequence of the reduction in the cross-sectional area of (e.g. each of) the first and second conduits along the length of the conduit, the pressure drop experienced over the length of the conduit and the speed of the flow through the conduit are increased.

The cross-sectional area of the conduits may be varied along their length in any suitable and desired way. In one set of embodiments the depth of (e.g. each of) the first and second conduits reduces along the length of the conduit. Preferably the surface area of (e.g. each of) the first and second conduits is substantially constant along the length of the conduit. This helps the conduits present substantially the same area to the thermoelectric generator(s). The surface area of (e.g. each of) the first and second conduits may be maximised in order to increase the transfer of thermal energy between the fluid and the thermoelectric generator(s).

The first and second conduits preferably (e.g. each) comprise a smoothed inlet and/or outlet, e.g. with the geometry of the inlet and/or outlet being widened or narrowed smoothly over a (e.g. partial) length of the conduit. This helps to smooth the transition between the first and second conduits and the other components in -10 -the system (e.g. the vortex tube and/or the outlet conduit), thus helping to reduce the pressure loss that may otherwise be caused by abrupt changes in the shape or size of the conduits.

The change in cross-sectional area along the length of the first and/or second conduits may be achieved in any suitable and desired way. In one set of embodiments (e.g. each of) the first and second conduits comprises a cross-sectional area that reduces along the length of the conduit, e.g. from an inlet cavity to a channel having a smaller cross-sectional area. Thus, in use, flow of fluid is constricted to an increasing degree as the fluid flows through the insert.

When the power generation system comprises a plurality of thermoelectric generators, preferably each of the thermoelectric generators is in thermal communication with the same surface area of the hotter and/or colder portions of the fluid, e.g. with the same surface area of the first and/or second conduits. This helps to share the generation of electricity more equally across thermoelectric generators.

The first and second conduits may (e.g. each) follow a path adjacent to the one or more thermoelectric generators, e.g. the first conduit follows a path on the hot side of the thermoelectric generator(s) and the second conduit follows a path on the cold side of the thermoelectric generator(s). In some embodiments, the one or more thermoelectric generators are positioned to follow (e.g. be placed adjacent to) the path of the first and second conduits. In some embodiments, the path of the first and second conduits is determined according the position of the one or more thermoelectric generators. Thus, for example, when the power generation system comprises one or more alignment sheets or one or more metal plates in which the one or more thermoelectric generators are located (as will be discussed below), the position(s) of the thermoelectric generator(s) alignment sheet(s) or metal plate(s) are formed such that the thermoelectric generator(s) are positioned to follow the path of the first and second conduits, or vice versa.

Preferably at least a section of the path of the first conduit matches (e.g. overlaps with) a section of the path of the second conduit so that at least a section of each of the first and second conduits is adjacent to a respective side of (e.g. each of) the one or more thermoelectric generators. This helps to expose (e.g. each of) the thermoelectric generator(s) to both the hotter and colder portions of the fluid at the same location (either side of the thermoelectric generator), thus helping to establish the temperature gradient for the generation of electrical power.

In one set of embodiments the paths of the first and second conduits are arranged (e.g. when their paths at least partially match each other) such that the fluid flows in opposite directions through the first and second conduits. Thus, for example, the thermoelectric generators positioned towards the end of the first conduit may be positioned towards the beginning of the second conduit, and vice versa. This helps to make the transfer of thermal energy more from the hotter and colder portions of the fluid to the thermoelectric generator(s) more uniform along the lengths of the first and second conduits.

Preferably the paths of the first and second conduits are configured to increase the length of the first and second conduits to which the thermoelectric generator(s) are exposed. The path followed by each of the one or more conduits could be linear. However, in preferred embodiments, (e.g. each of) the paths of the first and second conduits (e.g. in the section adjacent to the thermoelectric generator(s)) comprises at least one (e.g. smooth) change of direction. In some embodiments, (e.g. each of) the paths of the first and second conduits (e.g. in the section adjacent to the thermoelectric generator(s)) is substantially serpentine. In other embodiments (e.g. each of) the paths of the first and second conduits (e.g. in the section adjacent to the thermoelectric generator(s)) is substantially a spiral. These arrangements help to reduce the number of sharp bends in the path, thereby reducing the amount pressure loss along the length of the conduits that is not used for thermal heat transfer, thus helping to reduce the amount of thermal energy lost from the fluid to the environment.

Preferably the paths are configured such that the radius of curvature of the paths of the first and second conduits is greater than a particular value. By increasing the radius of curvature, the parasitic heat loss in each of the conduits may be reduced, thus helping to increase the efficiency of the system.

-12 -The one or more thermoelectric generators may be provided in any suitable and desired way. In one embodiment the one or more thermoelectric generators comprise solid-state thermoelectric generators, e.g. that generate electricity from a temperature difference across (e.g. each of) the thermoelectric generator(s) using the Seebeck effect.

While only a single thermoelectric generator may be used, in a preferred set of embodiments the power generation system comprises a plurality of thermoelectric generators. The plurality of thermoelectric generators may be arranged electrically in series and/or in parallel. It will be appreciated that the total output voltage generated by the one or more thermoelectric generators may be increased by connecting the plurality of thermoelectric generators in series.

However, in one set of embodiments, the plurality of thermoelectric generators are arranged into a plurality of groups (each group comprising two or more thermoelectric generators), wherein the plurality of groups of thermoelectric generators are connected in parallel with each other. This means that, if one thermoelectric generator were to fail, only the other thermoelectric generators within the same group would be affected. Therefore, this arrangement improves the robustness and reliability of the system.

Preferably the thermoelectric generators in a (e.g. each) group of thermoelectric generators are connected in series. Preferably the thermoelectric generators that are connected in parallel are electrically matched to each other. This helps to try to balance the voltage output by (e.g. each group of) the thermoelectric generators, e.g. for charging the electrical energy storage device.

The power generation system may comprise any suitable and desired number of (e.g. groups of) thermoelectric generators. In a set of embodiments the power generation system comprises at least two, e.g. at least four, e.g. at least eight, e.g. twelve thermoelectric generators. In a set of embodiments the power generation system comprises four groups of thermoelectric generators, e.g. connected in parallel with each other. In a set of embodiments each group of thermoelectric generators comprises three thermoelectric generators, e.g. connected in series with each other.

-13 -The one or more thermoelectric generators may be arranged to generate any suitable and desired amount of electrical power. In a set of embodiments (e.g. each group of) the thermoelectric generator(s) are arranged to generate a voltage of at least 200 mV (e.g. at the lower end of the range of pressure drops across the pressure reducing device (and thus the (e.g. vortex tube of the) power generation system)).

In a set of embodiments, the power generation system comprises an alignment sheet, wherein the one or more thermoelectric generators are arranged on or within the alignment sheet. This aids assembly of the power generation system, e.g. to align the thermoelectric generator(s) with the (e.g. first and second conduits for the) hotter and colder portions of the fluid in the hot and cold sides of the thermoelectric generator(s). The alignment sheet may comprise one or more holes or recesses for receiving the one or more thermoelectric generators. In some embodiments, the alignment sheet is formed from metal (e.g. stainless steel), e.g. by laser cutting.

Each of the one or more thermoelectric generators may be in thermal communication with the hotter and colder portions of the fluid directly or via an intermediate component. In some embodiments, the thermal communication is via one or more metal (e.g. copper or aluminium) plates. Thus, in some embodiments, the power generation system comprises one or more metal plates arranged in thermal communication between the one or more thermoelectric generators and the hotter and/or colder portions of the fluid. For example, the power generation system may comprise a metal plate between (e.g. each group of) the thermoelectric generator(s) and the hotter portion of the fluid on the hot side of the thermoelectric generator(s). The power generation system may comprise a metal plate between (e.g. each group of) the thermoelectric generator(s) and the colder portion of the fluid on the cold side of the thermoelectric generator(s).

In some embodiments, the one or more metal plates comprise one or more recesses for receiving the one or more thermoelectric generators. Thus, the one or more metal plates may comprise one or more alignment sheets, e.g. such that the metal plate(s) function both to provide thermal communication between the hotter and colder portions of the fluid and to align the thermoelectric generator(s). In some -14 -embodiments the power generation system comprises one or more separate alignment sheets, e.g. in addition to the one or more metal (thermal conduction) plates.

The first and second conduits for the hotter and colder portions of the fluid could be defined in (e.g. machined into) the one or more metal plates. However, preferably the power generation system comprises a first block in which the first conduit is defined. Preferably the power generation system comprises a second block in which the second conduit is defined. Thus preferably the blocks are positioned on each side of the thermoelectric generator(s) with the first and second conduits defined therein.

Preferably the blocks are attached to the one or more metal plates, e.g. such that the first block and the metal plate on the hot side of the thermoelectric generator(s) defines between them the first conduit, and the second block and the metal plate on the cold side of the thermoelectric generator(s) defines between them the second conduit. Preferably the blocks are formed from a less thermally conductive material than the one or more metal plates. Thus, in one embodiment the blocks are formed from stainless steel. This helps to ensure that the transfer of thermal energy is substantially between the fluid and the thermoelectric generator(s). Preferably thermal energy is transferred between the first and second conduits and the one or more metal plates such that the one or more metal plates are isothermal.

The electrical energy storage device may be arranged to be charged by the electrical power generated by the one or more thermoelectric generators in any suitable and desired way. Preferably the electrical energy storage device is electrically connected to (e.g. each (e.g. group) of) the one or more thermoelectric generators.

The electrical energy storage device may comprise any suitable and desired (re)chargeable device that is arranged to store and supply electrical power. In one embodiment the electrical energy storage device comprises a battery, e.g. formed from one or more (e.g. a bank or array of) cells. In one embodiment the electrical energy storage device comprises one or more (e.g. a bank or array of) capacitors.

-15 -In a set of embodiments the power generation system comprises a power management unit arranged to control the electrical power generated by the one or more thermoelectric generators. Thus preferably (e.g. each (e.g. group) of) the one or more thermoelectric generators are electrically connected to the power management unit for receiving the electrical power generated by one or more thermoelectric generators. Preferably the power management unit is electrically connected to the electrical energy storage device for charging the electrical energy storage device.

Preferably the power management unit is arranged to scale the output voltage of the electrical power generated by the one or more thermoelectric generators, e.g to a particular voltage, e.g. to match the output voltage of the electrical power generated by the one or more thermoelectric generators to the (e.g. optimum) charging voltage of the electrical energy storage device. In one set of embodiments the power management unit comprises one or more voltage converters (e.g. one or more voltage boost chips) arranged to scale the output voltage of the electrical power generated by the one or more thermoelectric generators. Preferably the power management unit comprises one or more voltage converters associated with each (e.g. group of) thermoelectric generator(s).

Scaling the output voltage from the thermoelectric generator(s), e.g. to a particular (e.g. constant) voltage, helps to compensate for variations in the voltage of the electrical power generated by the thermoelectric generator(s), e.g. arising from variations in the pressure drop across the power generation system. The (e.g. voltage converter(s) of the) power management unit may be arranged to exchange voltage for current (or vice versa), to achieve (e.g. maintain) the particular output voltage.

This helps to deliver a particular (e.g. constant) voltage to other components of the system, in particular for charging the electrical energy storage device (e.g. battery or capacitor), as it will be appreciated that a rechargeable electrical energy storage device may be efficiently charged at a particular voltage. It will be appreciated that a power management unit is particularly useful when there are a plurality of thermoelectric generators, as it may be able to combine the electrical power -16 -generated by the thermoelectric generators to provide a single (e.g. constant) output voltage, e.g. for charging the electrical energy storage device.

In a set of embodiments the electrical energy storage device is electrically connected to one or more (e.g. all) of the components of the system that may require electrical power. Thus preferably the electrical energy storage device is electrically connected to one or more (e.g. all) of the one or more monitoring sensors, the one or more control devices, the (or another) data storage, the data transmitter (and/or receiver) and one or more third party devices (such as a programmable logic controller or a remote terminal unit), for supplying electrical power to these components. It will be appreciated that the electrical energy storage device may be arranged to supply power to (and thus be electrically connected to) any suitable and electrical component in the vicinity of the power generation system, e.g. in the pressure reducing location. In a set of embodiments, the electrical power generated by the one or more thermoelectric generators is stored by the electrical energy storage device before it is supplied to the other electrical components of the system or in the pressure reducing location.

In some embodiments, the position of the electrical energy storage device (and any other electrical or electronic component(s)) relative to the fluid may be determined according to the environment, e.g. the ambient temperature. For example, in cold climates, the electrical or electronic component(s) (e.g. the electrical energy storage device) may be positioned adjacent to the hotter portion of the fluid in order to increase the temperature of the electrical or electronic component(s). Alternatively, in warmer climates, it may be desirable to cool the electrical or electronic component(s). In this case, the electrical or electronic component(s) may be positioned adjacent to the colder portion of the fluid. Such arrangements may help to improve the performance of the electrical energy storage device (e.g. charging, storing electrical energy and discharging) and any other electrical or electronic component(s).

The one or more monitoring sensors may be arranged to measure any suitable and desired parameter of devices in the location of the pressure reducing device, e.g. of the (or another, e.g. nearby) pressure reducing device. In one set of embodiments the one or more monitoring sensors are arranged to measure one or more (e.g. all) -17 -of an upstream pressure (e.g. in a conduit upstream of the (or another, e.g. nearby) pressure reducing device), a downstream pressure (e.g. in a conduit downstream of the (or another, e.g. nearby) pressure reducing device), an upstream temperature (e.g. in a conduit upstream of the (or another, e.g. nearby) pressure reducing device), a downstream temperature (e.g. in a conduit downstream of the (or another, e.g. nearby) pressure reducing device), a position of the valve member of the (or another, e.g. nearby) pressure reducing device and a calorific value of the working fluid (e.g. in a conduit upstream or downstream of the (or another, e.g. nearby) pressure reducing device). It will be appreciated that the monitoring sensors may be arranged to measure any other suitable and desired parameters of or relating to the system or the pressure reducing location, such as those of in-line filters of the system or of the ambient conditions.

The parameters may be measured in any suitable and desired location, e.g. in the inlet and outlet conduits of the power generation system. However, in a set of embodiments the parameters are measured in a conduit upstream or downstream of the (or another, e.g. nearby) pressure reducing device, e.g. via a monitoring port. This helps to avoid affecting the operation of the vortex tube.

The data captured by the one or more monitoring sensors (e.g. one or more respective parameters) may be processed in any suitable and desired way. The data may simply be captured and then stored by and/or transmitted from the power generation and monitoring system, e.g. by the data storage and/or transmitter. The captured data may then be processed and analysed remotely from the power generation and monitoring system.

In one set of embodiments the system comprises processing circuitry in data communication with, and configured to process the data captured by, the one or more monitoring sensors. Preferably the processing circuitry is arranged to be powered by the electricity generated by the one or more thermoelectric generators.

Preferably the processing circuitry is in data communication with the data storage and/or transmitter. Providing processing circuitry in the power generation and monitoring system may allow the data captured by the one or more monitoring systems to be processed locally.

-18 -In a set of embodiments, the data storage, data transmitter and/or the processing circuitry (when provided) are arranged on one or more (e.g. two or three) printed circuit boards (PCBs). This may reduce the number of wires required to connect the components, thereby helping to reduce the physical complexity of the system.

Preferably the system comprises an (e.g. insulating) housing, within which one or more of the components of the system are contained, e.g. one or more (e.g. all) of the one or more thermoelectric generators, the one or more metal plates, the first and second blocks, the first and second conduits, the data storage, the data transmitter, the processing circuitry, the PCB(s) and the electrical energy storage device are contained. The housing helps to provide an (e.g. outer) casing that helps to prevent the loss of thermal energy from the system, which helps to improve the efficiency of the system.

In one embodiment the housing at least partially surrounds (e.g. both of) the first and second blocks. In one embodiment one or more (e.g. all of) the data storage, the data transmitter, the processing circuitry, the PCB(s) and the electrical energy storage device are positioned between the housing and the first and/or second blocks. As outlined above, different components of the system, such as the electrical energy storage device may be located on either the hot or cold side of the thermoelectric generator(s), e.g. depending on the climate in which the system is to be used.

In a set of embodiments the data transmitter is arranged to transmit data (e.g. captured by the one or more monitoring sensors or processed by the processing circuitry) wirelessly, e.g. over a radio communications network. The data communication may be one-way or two-way communication. Thus, in some embodiments, the system comprises a data receiver. The receiver may be configured to receive instructions, e.g. to control the system, the pressure reducing device, the monitoring device(s), the transmitter, the data storage and/or the control device(s).

In one set of embodiments the data transmitter is arranged to transmit data periodically, e.g. at a frequency greater than once every day, e.g. greater than once every hour, e.g. greater than once every five minutes. Preferably the frequency at -19 -which data is stored by the data storage and/or captured by the one or more monitoring sensors is equal to or greater than the frequency at which data is transmitted by the data transmitter. The frequency at which data is stored by the data storage and/or captured by the one or more monitoring sensors may be between one sample per second and one sample per transmission. In one set of embodiments the data storage is arranged to store data and/or the one or more monitoring sensors are arranged to capture data periodically, e.g. at a frequency greater than once every day, e.g. greater than once every hour, e.g. greater than once every five minutes When the system comprises a power generation and controlling system, the one or more control devices, for controlling the operation of devices in the location of the pressure reducing device, may comprise any suitable and desired type(s) of control device(s). For example, the control device(s) may comprise one or more electromechanical control devices or processing circuitry (e.g. a control unit) of or relating to the pressure reducing device or the pressure reducing location. The processing circuitry may be arranged to coordinate the control of the one or more control devices.

The control device(s) may be arranged to control the operation of the pressure reducing device (i.e. upstream of which the vortex tube is connected), another pressure reducing device in proximity to the power generation system or another device of or in proximity to the power generation and monitoring or controlling system. For example, the control device(s) may be arranged to control one or more (e.g. all) of the operation of a safety valve, the operation of a bypass line and the control of (e.g. the set point of) a pilot valve or actuator for a pressure reducing valve (e.g. the pressure reducing valve of the power generation system).

The one or more control devices may operate in any suitable and desired way. The control device(s) may operate autonomously, operate based on the parameter(s) measured by the one or more monitoring sensors or operate based on control signals received (e.g. via the receiver). Thus, the one or more control devices may be in data communication with one or more (e.g. all) of the one or more monitoring sensors, the data storage and the data receiver, for receiving data (e.g. control -20 -signals or data representative of the measured parameter(s)) from these components.

Certain preferred embodiments for the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows schematically a system in accordance with an embodiment of the present invention; Figure 2 shows a cross-sectional view of the cold side of a power generator assembly of a system in accordance with an embodiment of the present invention; Figure 3 shows a cross-sectional view of a power generator assembly of a claimed system in accordance with an embodiment of the present invention; and Figure 4 shows an exemplary heat exchanger path in accordance with an embodiment of the present invention.

There are many different industrial situations in which the pressure within a fluid network is wasted. As will now be described, embodiments of the present invention provide a system that is able to generate and store electrical energy from a pressure drop in order to increase the efficiency and utility of an industrial process.

Figure 1 shows schematically a system 2 in accordance with an embodiment of the present invention. The system 2 comprises a pressure reducing valve 4 and a power generator assembly 6. The power generator assembly 6 comprises a fluid inlet port 8, fluidly connected to the upstream side of the pressure reducing valve 4, and a fluid outlet port 10, fluidly connected to a downstream side of the pressure reducing valve 4.

The fluid inlet port 8 is further fluidly connected to the inlet of a vortex tube 12. The vortex tube 12 comprises a cold outlet 16 and a hot outlet 18. The vortex tube 12 further comprises a biasing screw with which the ratio of flow though the cold outlet 16 and the hot outlet 18 may be selectively controlled. The biasing screw may be operated manually or electrically. The flow rate out of the vortex tube 12 may be biased in this way to choose an appropriate ratio to increase the heat transfer in the heat exchangers 20, 22. -21 -

The power generator assembly 6 further comprises a heat exchanger assembly comprising a cold heat exchanger 20 and a hot heat exchanger 22. The cold outlet 16 of the vortex tube 12 is fluidly connected to the cold heat exchanger 20. The hot outlet 18 of the vortex tube 12 is fluidly connected to the hot heat exchanger 22.

Thermoelectric generators (TEGs) (e.g. solid-state thermoelectric generator chips) 24 are positioned between the hot heat exchanger 22 and the cold heat exchanger 20 such that the TEGs 24 are exposed to a temperature difference.

The cold heat exchanger 20 and the hot heat exchanger 22 each comprise a conduit, a stainless steel tray block and a copper plate. The conduit comprises an inlet and an outlet. The conduit is designed such that the cross-sectional area of the conduit decreases along the length of the conduit from the inlet to the outlet. Consequently, the velocity of the flow increases as it flows through the conduit, thereby increasing the rate of heat transfer.

The TEGs 24 are electrically connected to a rechargeable battery 28 via a power management system 26 such that the electricity generated by the TEGs 24 is used to charge the battery 28. The power management system 26 is configured to match the (e.g. voltage) output of the TEGs 24 to the (e.g. voltage) charging characteristics of the battery 28. The battery 28 and the power management system 26 are part of an electronics module 46, which further comprises an array of sensors 30, a data processor and logger 32, a transmitter 34, a receiver 50 and a control system 48. The battery 28 is thus configured to provide electrical power to the above components of the electronic module 46.

The sensors 30 are further electrically connected to the data processor and logger 32 such that the measurements detected by the sensors 30 may be transferred from the sensors 30 to the data processor and logger 32. The data processor and logger 32 is further electrically connected to the transmitter 34 such that measurement data may be transmitted to a remote server or device. The receiver is configured to receive data transmitted from the remote server or device and communicate with the control system 48.

The outlet of the cold heat exchanger 20 and the outlet of the hot heat exchanger 22 are fluidly connected to a connector 36, in which the cold flow and the hot flow -22 -are combined. The outlet of the connector 36 is fluidly connected to the fluid outlet port 10 via a control valve 38. The control valve 38 may be arranged to match the pressure of the fluid to the downstream pressure of the pressure reducing valve 4 or to shut off the outlet completely.

Operation of the system shown in Figure 1 will now be described.

During normal operation of the system 2, a portion of the working fluid is diverted away from the pressure reducing valve such that it flows from the upstream side of the pressure reducing valve 4 through the power generator assembly 6 to the downstream side of the pressure reducing valve 4. The power generator assembly 6 thus receives the pressurised upstream fluid and operates across the same pressure drop as the pressure reducing valve 4.

The vortex tube 12 separates the fluid into a cold stream of fluid and hot stream of fluid. The cold stream of fluid is directed into the cold heat exchanger 20 via the cold outlet 16 of the vortex tube 12. The hot stream of fluid is directed into the hot heat exchanger 22 via the hot outlet 18 of the vortex tube 12. The cold heat exchanger 20 and the hot heat exchanger 22 are provided in a counter-flow arrangement such that the inlet of the cold heat exchanger 20 is in-line with the outlet on the hot heat exchanger 22.

The TEGs 24 are arranged in a flat grid such that a first side of each TEG 24 is exposed to the cold heat exchanger 20 and a second side of each TEG 24 is exposed to the hot heat exchanger 22, thus providing a thermal gradient across each thermoelectric generator 24.

The TEGs 24 are electrically connected to form four parallel sets, wherein each set comprises three TEGs 24 connected in series.

The temperature difference across the TEGs 24 is converted into electrical energy as a result of the Seebeck effect. The power management system 26 is arranged to match the voltage output of the TEGs 24 with the voltage charging characteristics of the battery by adjusting the ratio of voltage to current such that the electrical energy produced may be used to charge the battery 28. The battery 28 in turn provides -23 -electrical power to the array of sensors 30, the data processor and logger 32, the transmitter 34 and the control system 48.

The sensors 30 are arranged to measure the upstream pressure, downstream pressure, upstream temperature, downstream temperature and the calorific value of the working fluid passing through the pressure reducing valve 4.

The measurements made by the sensors 30 may be sent to the data processor and logger 32 for local processing and/or to the transmitter 34. The data processor and logger 32 may process the measurements in order to determine control signals, which are sent to the control system 48. The control system 48 is arranged to operate components of the system according to the control signals. For example, the data processor and logger 32 may issue a control signal to the control system 48 to increase or reduce the flow through the pressure reducing valve 4 or to adjust the biasing screw of the vortex tube 12. The control system 48 may also be arranged to control devices that are in the same pressure reducing location but which may not be part of the pressure reducing valve 4.

In the connector 36, the cold stream of fluid flowing from the outlet of the cold heat exchanger 20 is combined with the hot stream of fluid flowing from the outlet of the hot heat exchanger 22. Consequently, the combined fluid flowing out of the connector 36 to the fluid outlet port 10 via the control valve 38 is at close to ambient temperature.

The control valve 38 is arranged to remain in an open position, being set to match the pressure reducing valve 4 during operation, e.g. until the pressure reducing valve 4 closes, at which point the control valve 38 may be arranged to close in order to prevent the further flow of fluid through the generator assembly 6. The valve 38 may be powered-open such that, in the absence of electrical power, the valve 38 is arranged to close. The fluid flows from the fluid outlet port 10 of the generator assembly 6 to the downstream side of the pressure reducing valve 4.

Figure 2 shows a cross-section of the cold side of the generator assembly 6, in accordance with an embodiment of the present invention. The cold side of the -24 -generator assembly 6 comprises a copper plate 40, the cold heat exchanger 20, a stainless steel tray block 42, a plastic casing 44 and an electronics module 46.

The copper plate 40 is arranged to abut the cold side (e.g. the underside) of the TEGs 24. The cold heat exchanger 20 is arranged on the opposite side of the copper plate 40 to the TEGs 24 such that the cold heat exchanger 20 abuts the copper plate 40, thus allowing thermal conduction between the cold heat exchanger 20 and the copper plate 40. This arrangement helps to maintain the cold side of the TEGs 20 at a low temperature.

The cold heat exchanger 20 is defined by the stainless steel tray block 42 that is sealed against the copper plate 40. This helps to contain the pressure within the cold heat exchanger 20.

A plastic casing 44 is sealed against the outside of the stainless steel tray block 42 and is arranged to encase the cold heat exchanger 20.

The electronics module 46 is positioned between the stainless steel tray block 42 and the plastic casing 44. The electronics modules 46 comprises the power management system 26, the battery 28, the data processor and logger 32, the transmission system 34, the control system 48 and the receiver 50.

The cold heat exchanger 20 comprises a single winding conduit having an inlet 19 and an outlet 21. The inlet 19 of the cold heat exchanger 20 is fluidly connected to the cold outlet 16 of the vortex tube 12, whereas the inlet of the hot heat exchanger 22 is fluidly connected to the hot outlet 18 of the vortex tube 12, as explained above.

In Figure 2, the length of the conduit of the cold heat exchanger 20 is perpendicular to the plane of the cross-section. As can be seen in Figure 2, the depth of the conduit of the cold heat exchanger 20 decreases between the inlet 19 and the outlet 21. Thus, the cross-sectional area of the cold heat exchanger 20 conduit decreases along its length in the direction of flow. However, the mean width of the cold heat exchanger 20 that is exposed to the copper plate 40 remains constant.

-25 -Heat exchangers are subject to a loss in fluid pressure because of friction in the flow and the changing direction of the fluid. By reducing the cross-sectional area of the conduit of the cold heat exchanger 20, whilst maintaining the width of the cold heat exchanger 20 that is exposed to the copper plate 40, the transfer of thermal energy across the area of the copper plate 40 may be isothermal. This allows a more efficient and more constant transfer of thermal energy between the copper plate 40 and the cold heat exchanger 20.

In some embodiments, the geometry of the outlets 16, 18 of the vortex tube 12 is different to the inlets of the cold 20 and hot heat exchangers 22. In this case, in order to avoid a significant pressure drop that may be caused by a sudden transition from one geometry to the other, the change in geometry is designed to occur over an increased length of the conduit. This gradual change serves to reduce the pressure drop between the two components.

The arrangement of the hot side of the generator assembly 6 is substantially the same as the arrangement of the cold side of the generator assembly 6, except that the copper plate of the hot side of the generator assembly 6 abuts the hot side (e.g. the topside) of the TEGs 24, i.e. the arrangements are mirrored, and the fluid flows in opposite directions in the cold 20 and hot heat exchangers 22 (i.e. in a counter-current arrangement). The electronics module may be located on only the cold side of the generator assembly 6 or the hot side of the generator assembly 6. Alternatively, components of the electronics module 46 may be split between the cold side of the generator assembly 6 and the hot side of the generator assembly 6.

The arrangement of the whole generator assembly 6, including both the cold heat exchanger 20 and the hot heat exchanger 22, is shown in Figure 3.

As will be seen in Figure 3, in this embodiment the cross-sectional area of the conduit of the cold heat exchanger 20 is greater than the cross-sectional area of the conduit of the hot heat exchanger 22, in order to accommodate a higher flow rate.

Thus, in embodiments where the ratio of the flow rate out of the vortex tube 12 is different, the cross-sectional area of the 'cold' and 'hot' conduits may be adjusted accordingly.

-26 -In operation, cold fluid flows from the cold outlet 16 of the vortex tube 12 to the inlet of the cold heat exchanger 20. As a result of the flow of the cold fluid through the cold heat exchanger 20, a temperature gradient between the 'cold' copper plate 40 and the cold heat exchanger 20 causes heat to be transferred from the 'cold' copper plate 40 to the cold heat exchanger 20 and into the colder stream of the fluid via conduction and convective heat transfer, thus reducing the temperature of the 'cold' copper plate 40.

The reduction in temperature of the copper plate 40 creates a further temperature gradient between the cold side of the TEGs 24 and the 'cold' copper plate 40. As a result of this temperature gradient, heat is transferred from the cold side of the TEGs 24 to the 'cold' copper plate 40, and subsequently to the cold heat exchanger 20, via conduction. This causes the temperature of the cold side of the TEGs 24 to be reduced.

In the hot side of the generator assembly 6, hot fluid flows from the hot outlet 18 of the vortex tube 12 to the inlet of the hot heat exchanger 22. As a result of the flow of the hot fluid through the hot heat exchanger 22, a temperature gradient between the 'hot' copper plate and the hot heat exchanger 22 causes heat to be transferred from the hot heat exchanger 22 to the 'hot' copper plate and into the colder stream of the fluid via convective heat transfer and conduction, thus increasing the temperature of the 'hot copper plate.

The increase in temperature of the 'hot' copper plate creates a further temperature gradient between the hot side of the TEGs 24 and the 'hot' copper plate. As a result of this temperature gradient, heat is transferred from the 'hot' copper plate to the hot side of the TEGs 24 via conduction, thus increasing the temperature of the TEGs 24.

Consequently, a temperature gradient is generated across the TEGs 24, between the cold side and the hot side, and is used to generate electrical energy as a result of the Seebeck effect.

The power management system 26 comprises a voltage boost chip associated with each group of TEGs 24, which boosts the voltage output of the associated TEGs -27 - 24. As the voltage output of the TEGs can be variable, the power management system 26 is further arranged to smooth this voltage to a more constant output. Thus, the power management system 26 is configured to boost the voltage output of the TEGs 24 to provide a constant voltage that matches the optimum charging voltage of the battery 28.

In this embodiment, in which the generated electricity is used to power an array of sensors 30, a single cell battery 28 is sufficient. However, in other embodiments, it may be desirable to connect a number of cells in series or parallel to form the battery 28.

The cold heat exchanger 20 and/or the hot heat exchanger 22 may be designed such that the fluid path through the heat exchanger follows a curved path with increased radii of curvature, as exemplified in Figure 4.

Figure 4 shows the path of the cold heat exchanger 20 beneath the 'cold' copper plate 40. As can be seen, the path is designed to traverse as much of the 'cold' copper plate 40 as possible, in order to increase the heat transfer from the cold side of the TEGs 24 to the cold heat exchanger 20 via the 'cold' copper plate 40.

From the inlet 19 of the cold heat exchanger 20, the path proceeds in a direction substantially perpendicular to the edge of the copper plate 40. The direction of the path is reversed at the edge of the copper plate 40 that is opposite the inlet 19. The radius of curvature of this change in direction is increased in order to reduce non-efficient heat loss. The path continues to change direction in this manner until the outlet 21 is reached.

Although Figure 4 has been described with reference to the cold heat exchanger 20, it will be appreciated that the hot heat exchanger 22 may have the same, or similar, design.

It can be seen from the above that, in at least preferred embodiments, the invention provides a power generation and storage system in which a vortex tube separates a fluid flow into a hotter portion and a colder portion that are thermally exposed to one or more thermoelectric generators such that they experience a temperature -28 -gradient and, thus, generate electrical power. The electrical power may be stored in an electrical energy storage device, which may be arranged to power an array of sensors. This means that power may be generated and stored in remote locations. This is particularly beneficial in the case of pressure reducing valves, for which the invention may be used to generate and supply power to an array of sensors so that near real-time data monitoring and modelling may be achieved.

Claims (25)

1. -29 -Claims 1. A power generation and storage system comprising: a vortex tube comprising an inlet for receiving a pressurised fluid, wherein the vortex tube is arranged to separate the fluid into a hotter portion of the fluid and a colder portion of the fluid, wherein the vortex tube further comprises a hot output for outputting the hotter portion of the fluid and a cold output for outputting the colder portion of the fluid; one or more thermoelectric generators each having a hot side arranged downstream of the hot output of the vortex tube and in thermal communication with the hotter portion of the fluid, and a cold side arranged downstream of the cold output of the vortex tube and in thermal communication with the colder portion of the fluid, wherein the one or more thermoelectric generators are arranged to generate electrical power from the temperature difference between the hot and cold sides of the one or more thermoelectric generators; and an electrical energy storage device arranged to be charged by the electrical power generated by the one or more thermoelectric generators.
2. 2. The system as claimed in claim 1, wherein the system comprises an inlet conduit for receiving a fluid from the upstream side of a pressure reducing device and for supplying the fluid to the inlet of the vortex tube, and an outlet conduit arranged to output the fluid from the hotter and colder portions of the fluid to atmosphere or to the downstream side of the pressure reducing device.
3. 3. The system as claimed in claim 1 or 2, wherein the system comprises one or more control valves arranged to control the flow of the fluid into and/or out of the system.
4. 4. The system as claimed in claim 1, 2 or 3, wherein the hotter portion of the fluid comprises a greater proportion of the flow rate of the fluid than the colder portion of the fluid.
5. 5. The system as claimed in any one of the preceding claims, wherein the vortex tube, the first and/or second conduits and/or the one or more metal plates are arranged to separate the fluid into the hotter and colder portions, and deliver the -30 -hotter and colder portions to the hot and cold sides of the one or more thermoelectric generators, with a temperature difference at the hot and cold sides of the one or more thermoelectric generators of between 5 and 30 degrees Celsius, e.g. between 5 and 20 degrees Celsius, e.g. less than 15 degrees Celsius, e.g. approximately 9 degrees Celsius.
6. 6. The system as claimed in any one of the preceding claims, wherein the system comprises a first conduit into which the hotter portion of fluid from the vortex tube is arranged to be output and a second conduit into which the colder portion of fluid from the vortex tube is arranged to be output.
7. 7. The system as claimed in claim 6, wherein the first conduit is in thermal communication with the hot side of the one or more thermoelectric generators and the second conduit is in thermal communication with the cold side of the one or more thermoelectric generators.
8. 8. The system as claimed in claim 6 or 7, wherein the cross-sectional area of the first and second conduits reduces along the length of the conduit.
9. 9. The system as claimed in claim 6, 7 or 8, wherein the first and second conduits comprise a smoothed inlet and/or outlet.
10. 10. The system as claimed in any one of claims 6 to 9, wherein at least a section of the path of the first conduit matches a section of the path of the second conduit so that at least the sections the first and second conduits are adjacent to a respective side of the one or more thermoelectric generators.
11. 11. The system as claimed in any one of claims 6 to 10, wherein the paths of the first and second conduits are arranged such that the fluid flows in opposite directions through the first and second conduits.
12. 12. The system as claimed in any one of claims 6 to 11, wherein the paths of the first and second conduits comprise at least one smooth change of direction.
13. -31 - 13. The system as claimed in any one of claims 6 to 12, wherein the system comprises a first block in which the first conduit is defined and a second block in which the second conduit is defined.
14. 14. The system as claimed in any one claims 6 to 13, wherein the system comprises an insulating housing arranged to contain the one or more thermoelectric generators, and the first and second conduits.
15. 15. The system as claimed in any one of the preceding claims, wherein the system comprises a plurality of thermoelectric generators arranged into a plurality of groups, wherein the plurality of groups of thermoelectric generators are connected in parallel with each other.
16. 16. The system as claimed in claim 15, wherein the thermoelectric generators in a group of thermoelectric generators are connected in series.
17. 17. The system as claimed in any one of the preceding claims, wherein the system comprises an alignment sheet, wherein the one or more thermoelectric generators are arranged on or within the alignment sheet.
18. 18. The system as claimed in any one of the preceding claims, wherein the system comprises one or more metal plates arranged in thermal communication between the one or more thermoelectric generators and the hotter and/or colder portions of the fluid.
19. 19. The system as claimed in any one of the preceding claims, wherein the system comprises a power management unit arranged to control the electrical power generated by the one or more thermoelectric generators.
20. 20. The system as claimed in claim 19, wherein the power management unit comprises one or more voltage converters arranged to scale the output voltage of the electrical power generated by the one or more thermoelectric generators.
21. 21. The system as claimed in any one of the preceding claims, wherein the system comprises one or more monitoring sensors arranged to measure -32 -operational parameters of the or another pressure reducing device, wherein the one or more monitoring sensors are arranged to be powered by the electrical power generated by the one or more thermoelectric generators, wherein the one or more monitoring sensors are arranged to measure one or more of: an upstream pressure, a downstream pressure, an upstream temperature, a downstream temperature, a position of a valve member of the or another pressure reducing device, and a calorific value of a working fluid.
22. 22. The system as claimed in claim 21, wherein the system comprises processing circuitry in data communication with, and configured to process the data captured by, the one or more monitoring sensors.
23. 23. The system as claimed in any one of the preceding claims, wherein the data transmitter is arranged to transmit data periodically, e.g. at a frequency greater than once every day, e.g. greater than once every hour, e.g. greater than once every five minutes.
24. 24. The system as claimed in any one of the preceding claims, wherein the frequency at which data is stored by the data storage and/or captured by the one or more monitoring sensors is equal to or greater than the frequency at which data is transmitted by the data transmitter.
25. 25. A power generation and monitoring and/or controlling system for a pressure reducing device, wherein the system comprises: a vortex tube comprising an inlet for receiving a pressurised fluid from an upstream side of the pressure reducing device, wherein the vortex tube is arranged to separate the fluid into a hotter portion of the fluid and a colder portion of the fluid, wherein the vortex tube further comprises a hot output for outputting the hotter portion of the fluid and a cold output for outputting the colder portion of the fluid; one or more thermoelectric generators each having a hot side arranged downstream of the hot output of the vortex tube and in thermal communication with the hotter portion of the fluid, and a cold side arranged downstream of the cold output of the vortex tube and in thermal communication with the colder portion of the fluid, wherein the one or more thermoelectric generators are arranged to -33 -generate electrical power from the temperature difference between the hot and cold sides of the one or more thermoelectric generators; and wherein the system further comprises one or both of: (i) one or more monitoring sensors for measuring operational parameters of devices in the location of the pressure reducing device, wherein the one or more monitoring sensors are arranged to be powered by the electrical power generated by the one or more thermoelectric generators; and a data storage and/or transmitter in data communication with the one or more monitoring sensors, wherein the data storage and/or transmitter is arranged to store and/or transmit data received from the one or more monitoring sensors, wherein the data storage and/or transmitter are arranged to be powered by the electrical power generated by the one or more thermoelectric generators; and (ii) one or more control devices for controlling the operation of devices in the location of the pressure reducing device, wherein the one or more control devices are arranged to be powered by the electrical power generated by the one or more thermoelectric generators.