Hydrodynamic system

Abstract

Provided herein is a hydrodynamic system comprising a conduit comprising: a water inlet configured to receive a water flow from a body of water, an air inlet configured to entrain air from above a surface of the body of water into the water flow, and a water outlet configured to discharge the water flow to the body of water. The system also comprises a water turbine disposed in the conduit, a separator disposed in the conduit to separate the entrained air from the water flow after passing through the turbine, a collection chamber fluidically coupled to the conduit, and pumping means disposed in the conduit to pump water from the conduit to the body of water. The conduit is shaped such that, when in use, the turbine and the pumping means are positioned lower than the water inlet. The conduit may be shaped such that, when in use, the turbine is located lower than the pumping means.

Description

[0001] HYDRODYNAMIC SYSTEM

[0002] FIELD OF THE INVENTION

[0003]

[0001] The present application relates but is not limited to a hydrodynamic system. In particular, the application relates to hydrodynamic systems at least partially submergible in a body of water.

[0004] BACKGROUND OF THE INVENTION

[0005]

[0002] Hydrodynamic systems may be employed for a variety of purposes, including energy generation, energy recovery, water treatment, air treatment, agriculture, cooling, compressed air production for industrial usage, and other water / wastewater services. Many existing hydrodynamic systems require complex infrastructure and numerous site criteria including geographical formations such as rivers, mountains or valleys in order to operate correctly.

[0006]

[0003] Therefore, the availability of viable sites for deploying such existing systems is extremely limited. Even when viable sites can be found, the construction of existing hydrodynamic systems requires vast amounts of time and money and causes extensive damage and disruption to the local environment. Accordingly, there is a need for improved hydrodynamic systems.

[0007] SUMMARY OF THE INVENTION

[0008]

[0004] Aspects of the invention are set out in the appended claims. These and other aspects, including examples which are useful for understanding the invention set out in the claims, are also described herein.

[0009]

[0005] There is described herein a hydrodynamic system comprising: a conduit comprising: a water inlet configured to receive a water flow from a body of water; an air inlet configured to entrain air from above a surface of the body of water into the water flow ; and a water outlet configured to discharge the water flow to the body of water; a water turbine disposed in the conduit between the water inlet and the water outlet and configured to receive the water flow and the entrained air; a separator disposed in the conduit between the turbine and the water outlet and configured to separate the entrained air from the water flow after passing through the turbine; a collection chamber configured to collect the separated air, the chamber fluidically coupled to the conduit; and pumping means disposed in the conduit between the separator and the water outlet and configured to pump water from the conduit to the body of water through the water outlet; wherein the conduit is shaped such that, when in use, the turbine and the pumping means are positioned lower than the water inlet.

[0010]

[0006] The conduit may be shaped such that, when in use, the water outlet is positioned higher than or level with the water inlet. The conduit may be shaped such that, when in use, the water flow at the separator is substantially horizontal. The conduit may be shaped such that, when in use, the turbine is located lower than the pumping means (e.g. a pump of the pumping means).

[0011]

[0007] When in use, the pumping means may be positioned higher than the turbine. A vertical distance between the pumping means and the water inlet (when in use) may be at least around 30% of a vertical distance between the turbine and the water inlet. The vertical distance between the pumping means and the water inlet may be around 30% of the vertical distance between the turbine and the water inlet.

[0012]

[0008] The pumping means may comprise an air lift pump configured to provide pressurised gas, optionally air, to the water flow in the conduit to pump water out of the water outlet. The pressurised gas (e.g. air) provided by the air lift pump may comprise pressurised air stored in the collection chamber.

[0013]

[0009] The air lift pump may comprise an inner channel disposed within the conduit, the inner channel comprising: an inlet configured to receive the water flow, and an outlet that forms the water outlet of the conduit that is configured to discharge the water flow to the body of water; and a gas injector configured to provide the pressurised gas into the water flow within the inner channel. The inventor has found that this air lift pump configuration provides an energyefficient way to return the water flow back to the body of water. The inner channel may be referred to as a riser channel or a riser. The inner channel may define a portion of the conduit.

[0010] The conduit may comprise an outer portion disposed around at least the inlet of the inner channel. When in use, the outer portion of the conduit may be disposed around at least a lower end or lower portion of the inner channel. The outer portion may be referred to as an outer channel, a container portion, a container channel, or a container. A cross-sectional area of the inner channel may be smaller than a cross-sectional area of the outer portion. The cross- sectional area of the inner channel and / or the outer portion may be a cross-sectional area in a plane perpendicular to a direction of water flow. The cross-sectional area of the outer portion may be defined by the total region contained by the walls of the outer portion (which contains and overlaps with the cross-sectional area of the inner channel). The cross-sectional area of the inner channel may be substantially constant along a length of the inner channel. The cross- sectional area of the outer portion may be substantially constant along a length of the outer portion.

[0014] [Oil] Accordingly, the outer portion may be a portion of the (main) conduit and the inner channel may be a smaller conduit disposed therein. The inner channel may define a flow path therethrough that forms part of a main flow path of the water flow. The inner channel may be in fluidic communication with the outer portion of the conduit via the inlet (e .g . a lower opening when in use) of the inner channel.

[0015]

[0012] The cross-sectional area of the inner channel may be no more than 50%, no more than 35%, or no more than 25% of the cross-sectional area of the outer portion. Additionally or alternatively, the cross-sectional area of the inner channel may be at least around 5%, at least around 10%, or at least around 15% of the cross-sectional area of the outer portion. A width (e.g. a diameter) of the inner channel may be no more than 75%, no more than 70%, no more than 60%, no more than 50%, no more than 40%, no more than 33%, no more than 30% or no more than 25% of a width (e.g. a diameter) of the outer portion. A width of the outer portion may be at least two, three or four times larger than a width of the inner channel, or more.

[0016]

[0013] The inner channel may be arranged such that, when in use, a lower end of the inner channel is submerged below a water surface within the outer portion, optionally submerged at an adjustable depth below the water surface. The depth at which the lower end of the inner channel is submerged below the surface of the water contained in the outer portion may be adjustable. The air lift pump may further comprise a mechanism for moving the inner channel within the outer portion (e.g. in a vertical direction when in use), and / or means for changing the level of water in the outer portion.

[0017]

[0014] The inner channel and the outer portion of the conduit may be arranged concentrically. When in use, the gas injector may be disposed proximate a lower end of the inner channel. The gas injector may be disposed within the inner channel.

[0018]

[0015] The air inlet may comprise one or more tubes each having a first end portion and a second end portion. The first end portion may be configured to receive air from above the surface of the body of water when in use. The second end portion may be disposed in the conduit and configured to provide air substantially parallel to the water flow when in use.

[0019]

[0016] The collection chamber may be configured to store air pressurised to at least around 5 bar. The collection chamber may be configured to store air pressurised to at least around 10 bar. The skilled person will also appreciate that higher or lower pressures may be achieved depending on the system size and depth (head height). The system may further comprise an air turbine fluidically coupled to the collection chamber and configured to receive pressurised air from the collection chamber. This can allow the stored pressurised air to be used for generating electricity. The pressurised air generated by the system may be used for other purposes. For example, it may be used to provide fresh, clean, dry and cool air for an environmentally friendly air cooling system. The system may also be used for facilities or buildings which require both electricity and cooling.

[0020]

[0017] The conduit may comprise a plurality of conduit sections. The plurality of conduit sections may be configured to direct the flow of water to the body of water via one or more intermediate bodies of water. Each conduit section may comprise a water inlet and a water outlet. A first conduit section of the plurality of conduit sections may comprise the air inlet. The water outlet of the first conduit section may be configured to discharge the water flow to an intermediate body of water. The intermediate body of water may be positioned below the (primary) body of water. The water inlet of a second conduit section of the plurality of conduit sections may be configured to receive a water flow from the intermediate body of water. The water outlet of the second conduit section or of a further conduit section of the plurality of conduit sections may be configured to discharge the water flow to the body of water. The pumping means may be disposed in the second or further conduit section and configured to pump water from the second or further conduit section to the body of water. The system may comprise a series of conduit sections and intermediate bodies of water configured to return the water flow to the (primary) body of water.

[0021]

[0018] The system (e.g. the conduit) may be at least partially submergible in the body of water. Additionally or alternatively, the system (e.g. the conduit) may be configured to be disposed at least partially on land (e.g. land adjacent the body of water). The system (e.g. the conduit) may be configured to be at least partially disposed underground or above ground. For example, the conduit may be completely submergible in the body of water, or part of the conduit may be configured to be submerged while one or more other parts of the conduit may be configured to be disposed on land (e.g. above ground or underground). The system may further comprise a controller configured to selectively control the pumping means to control the flow of water through the conduit. The system may further comprise one or more recovery turbines configured to receive the flow of water from the water outlet.

[0022]

[0019] There is also described herein an air lift pump comprising: an inner channel comprising an inlet and an outlet, the inner channel configured to receive a liquid flow at the inlet and discharge the liquid flow from the outlet, wherein, when in use, the inlet is positioned below the outlet; an outer channel disposed around at least the inlet of the inner channel, wherein the outer channel is in fluidic communication with the inner channel; and a gas injector disposed adjacent the inlet of the inner channel, the gas injector configured to provide a pressurised gas into liquid within the inner channel such that, when in use, the liquid is pumped upwards through the inner channel.

[0023]

[0020] By providing an inner channel within an outer channel, and provide the pressurised gas into the inner channel, the efficiency of pumping the liquid upwards through the inner channel can be improved. The liquid held by the outer channel can provide a pressure differential and can act as a communicating tube of liquid with the liquid-gas mixture in the inner channel. This can amplify an effective lifting head, while reducing transient oscillations and slug flow within the inner channel. The air lift pump may be used with any of the systems disclosed herein.

[0024]

[0021] The air lift pump may be referred to as a gas lift pump, a lift pump, a pumping means, or a pump. The inner channel may be referred to as a riser channel or a riser. The outer channel may be referred to as an outer portion, a container portion, a container channel, or a container.

[0022] The inner channel and the outer channel may each have side walls. The outer channel may be configured to hold a volume of liquid between the inner channel and the outer channel. The outer channel may be in fluidic communication with the inner channel via an opening or inlet of the inner channel that is adjacent a lower end of the inner channel when in use. The outer channel may circumferentially surround at least the inlet of the inner channel, optionally along the majority or full length of the inner channel.

[0025]

[0023] A cross-sectional area of the inner channel may be smaller than a cross-sectional area of the outer channel . The cross-sectional area of the inner channel and / or the outer channel may be a cross-sectional area in a plane perpendicular to a direction of liquid flow. The cross- sectional area of the outer channel may be defined by the total region contained by the walls of the outer channel (which contains and overlaps with the cross-sectional area of the inner channel). The cross-sectional area of the inner channel may be substantially constant along a length of the inner channel. The cross-sectional area of the outer channel may be substantially constant along a length of the outer channel.

[0026]

[0024] The cross-sectional area of the inner channel may be no more than 50%, no more than 35%, or no more than 25% of the cross-sectional area of the outer channel. Additionally or alternatively, the cross-sectional area of the inner channel may be at least around 5%, at least around 10%, or at least around 15% of the cross-sectional area of the outer channel. A width (e.g. a diameter) of the inner channel may be no more than 75%, no more than 70%, no more than 60%, no more than 50%, no more than 40%, no more than 33%, no more than 30% or no more than 25% of a width (e.g. a diameter) of the outer channel. A width of the outer channel may be at least two, three or four times larger than a width of the inner channel, or more.

[0027]

[0025] The inner channel may be arranged such that, when in use, a lower end of the inner channel is submerged below a surface of liquid within the outer channel, optionally submerged at an adjustable depth below the liquid surface. The depth at which the lower end of the inner channel is submerged below the surface of the liquid contained in the outer channel may be adjustable. The air lift pump may further comprise a mechanism for moving the inner channel within the outer channel (e.g. in a vertical direction when in use), and / or means for changing the level of liquid in the outer channel.

[0026] The inner channel and the outer channel may be arranged concentrically. The gas injector may include or be coupled to a gas compressor, such as an air compressor. Additionally or alternatively, the gas injector may be configured to provide gas that has been compressed by hydrodynamic means, such as gas that has been entrained in a flow of liquid and separated from the flow of liquid. When in use, the gas injector may be disposed proximate a lower end of the inner channel. The gas injector may be disposed within the inner channel.

[0028]

[0027] There is also described herein a method for operating any of the systems described herein. Any system feature as described herein may also be provided as a method feature, and vice versa. As used herein, means plus function features may be expressed alternatively in terms of their corresponding structure. Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to system aspects, and vice versa. Furthermore, any, some and / or all features in one aspect can be applied to any, some and / or all features in any other aspect, in any appropriate combination. It should also be appreciated that particular combinations of the various features described and defined in any aspects of the invention can be implemented and / or supplied and / or used independently.

[0029] BRIEF DESCRIPTION OF THE FIGURES

[0030]

[0028] Methods and systems are described by way of example only, in relation to the Figures, wherein:

[0031] Figures 1A and IB show schematic diagrams of (A) an example hydrodynamic system and (B) the system of Figure 1 A in operation;

[0032] Figures 2A and 2B show schematic diagrams of (A) another example hydrodynamic system and (B) the system of Figure 2A in operation;

[0033] Figures 3A and 3B show schematic diagrams of (A) a further example hydrodynamic system and (B) the system of Figure 3A in operation;

[0034] Figures 4A and 4B show schematic diagrams of (A) a further example hydrodynamic system and (B) the system of Figure 4A in operation; Figures 5A and 5B show schematic diagrams of (A) an example air lift pump and (B) the pump of Figure 5 A in operation; and

[0035] Figure 6 shows a schematic diagram of a further example hydrodynamic system.

[0036] DETAILED DESCRIPTION

[0037]

[0029] Various examples of hydrodynamic systems are described herein. These systems may be used for efficient energy generation. The systems may additionally or alternatively be used for other purposes, for example air pressurisation or water treatment (e.g. water aeration). Advantageously, the system is rapidly deployable in a wide range of environments, including open water environments or closed / controlled environments (e.g. purpose-made, closed systems, such as inland environments).

[0038]

[0030] Referring to Figures 1A and IB, a hydrodynamic system 100 will now be described. The system 100 includes a conduit 105 configured to direct fluid flow along a conduit path. In the example shown in the figures, the conduit is shaped to direct fluid along a generally “U”- shaped path, but in other examples the conduit 105 may have a different shape or define a different conduit path. In some examples, the conduit 105 is formed from a single continuous conduit (e.g. a tube or pipe) or may be formed from a series of conduit sections that are connected together (e.g. from a plurality of tubes or pipework).

[0039]

[0031] The conduit 105 includes a water inlet 110 configured to receive a water flow. The conduit 105 includes a water outlet 120 configured to discharge a water flow. Therefore, water that enters the conduit 105 at the water inlet 110 is generally directed by the conduit along a path and exits the conduit 105 via the outlet 120. In some examples, the water inlet 110 and / or the water outlet 120 may include a valve (e.g. a non-retum valve) for controlling the flow of water through the inlet / outlet. Generally, the water inlet 110 and the water outlet 120 are configured respectively to receive water from and discharge water to the same body of water. For example, a body of water 10 is shown in Figure IB. In some examples, the water inlet 110 includes one or more filters to prevent debris or pollutants from entering the system 100.

[0032] The conduit 105 also includes an air inlet 115 which is configured to receive an air flow and entrain that air in water flowing through the conduit 105. For example, as shown in Figures 1A and IB, the air inlet 115 is positioned adjacent the water inlet 110 such that air received at the air inlet 115 is entrained in the water flow received from the water inlet 110 (e.g. substantially at or shortly after entering the conduit). When in use, as shown in Figure IB, the air inlet 115 is arranged to receive air from above a surface 15 of the body of water 10.

[0040]

[0033] In some examples (as shown in Figures 1A and IB), the air inlet 115 comprises one or more tubes each having a first end portion and a second end portion. The first end portion is configured to receive air from an atmosphere above the surface 15 of the body of water 10 when in use. Each tube is configured to direct air received at the first end portion therethrough towards the second end portion, which is disposed in the conduit and configured to provide air substantially parallel to the water flow when in use. As shown in the figures, the air inlet 115 may be positioned at least partially within the water inlet 110 and oriented such that a flow of air through the air inlet 115 is substantially parallel to a flow of water through the water inlet 110.

[0041]

[0034] As shown in Figures 1A and IB, the system 100 also includes a water turbine 130 disposed in the conduit 105 between the water inlet 110 and the water outlet 120. The water turbine 130 is configured to receive water flowing through the conduit (from the inlet 110 to the outlet 120). The turbine 130 may be placed within a conduit section (e.g. pipe or duct), or may define a section of the conduit itself and be connected to separate conduit sections at its inlet and outlet. Since the turbine 130 is located after the water inlet 110 and air inlet 115 (in the direction of flow), the turbine 130 is also configured to receive the entrained air. Therefore, the turbine 130 receives a water-air mixture. The turbine 130 is configured to convert energy from the flow of water and air into kinetic rotational energy of the turbine, which can then be converted to electricity. In some examples, the turbine 130 includes a reaction turbine.

[0042]

[0035] The system 100 also includes a separator 140 disposed in the conduit 105 after the turbine 130. The separator 140 is configured to separate the entrained air from the water flow after passing through the turbine 130. The separator 140 is located in a section of the conduit 105 that is shaped such that, when in use as shown in Figure IB, the flow of water at the separator is substantially horizontal. The separator 140 may include one or more of: a surface, a plate, a baffle, or other body positioned within the conduit. In some examples, the separator 140 is angled in order to deflect air entrained in the water flow in a substantially upward direction (when in use) such that it rises out of the flow of water and becomes separated from the flow. In some examples, the turbine 130 (or a portion of apparatus associated with the turbine 130) may serve the role of a separator to separate entrained air from the water flow, in which case the separator 140 may not be required.

[0043]

[0036] The air separated from the water flow by the separator 140 is then directed towards and collected in one or more collection chambers 150. Accordingly, the chamber 150 is fluidically coupled to the conduit 105. The chamber 150 is preferably arranged such that, when in use, the chamber 150 is substantially above the main conduit path of the conduit 105 such that the separated air may rise into the chamber and the water flow may continue through the conduit 105 (past the separator). In some examples, multiple collection chambers 150 are used in order to increase the capacity of the system 100.

[0044]

[0037] The system 100 also includes pumping means 160 disposed in the conduit 105. The pumping means 160 is configured to pump water from the conduit 105 out of the water outlet 120. This can enable the water flow in the conduit to be returned to the body of water 10 in order to provide a continuous flow of water through the system 100. As indicated in Figures 1A and IB, the pumping means 160 may include one or more pumps (e.g. a mechanical pump and / or an air lift pump). In this example, the pump 160 is disposed in the conduit between the separator 140 and the water outlet 120, although the pump may be disposed in other locations in the conduit (e.g. between the turbine 130 and the water outlet 120).

[0045]

[0038] In the example of Figure 1A, the conduit 105 is shaped such that, when in use, the water outlet 120 is located above the water inlet 110 and above the surface 15 of the body of water 10. However, in other examples (as described below with reference to Figures 2A and 2B), the water outlet may be positioned differently, e.g. level with or below the water inlet. In either case, the water outlet 120 is preferably configured to discharge water from the conduit substantially horizontally in order to reduce the chance of back flow into the conduit 105.

[0046]

[0039] The conduit 105 is shaped such that, when in use, the turbine 130 and the pumping means 160 are positioned lower than the water inlet 110. As shown in Figures 1A and IB, the pumping means 160 may be positioned in the conduit 105 such that, when in use, the pumping means 160 is above the turbine 130 (in other words, the turbine 130 is positioned lower than the pumping means 160). In the example shown, the conduit 105 is generally “U”-shaped, having a down-flow portion between the water inlet 110 and the turbine 130, a substantially horizontal portion where the separator 140 separates entrained air from the water flow, and an up-flow portion including the pump and terminating at the water outlet 120. The down-flow and up-flow portions of the conduit 105 are configured to be disposed substantially vertically.

[0047]

[0040] With reference to Figure IB, operation of the system 100 will now be described. At least a portion of the system 100 (including the water inlet 110 of the conduit 105) is submergible in a body of water 10. The system 100 may be installed in a body or supply of water that is relatively shallow (compared to a length of the conduit 105) such as a pond or river, as shown in Figure IB. However, the system 100 may also be installed in a deep or open body of water, such as a lake or sea. The dotted areas in Figure IB (and throughout the other figures) are used to generally indicate the presence of water (or an air- water mixture). When installed, the system is oriented in a substantially upright or vertical plane, such that the conduit 105 generally directs water from the body of water downwards and then back to the body of water.

[0048]

[0041] In particular, in the system 100, a flow of water is received from the body of water 10 at the water inlet 110, which flows through the conduit 105 downwardly towards the turbine 130 at a first depth. The flow of water reduces the pressure around the portion of the air inlet 115 that is within the conduit 105. Since the air inlet 115 is also exposed to the air above the water surface 15, the reduced pressure within the conduit causes air to be drawn into the conduit via the air inlet 115 (via a vacuum effect). Thus, the air becomes entrained in the downward flow of water.

[0049]

[0042] As the flow of water and entrained air travels downwards, the entrained air becomes increasingly pressurised due to the column of water above it. Advantageously, this pressurisation of the air is substantially isothermal due to the efficient thermal properties of the surrounding water.

[0050]

[0043] The water flow then passes through the turbine 130 in order to recover energy from the water flow. After passing through the turbine, this air-water mixture is separated such that the pressurised air is collected in the collection chamber 150. Accordingly, the chamber 150 is configured to contain pressurised gas including air (e.g. a pressurised air tank or vessel).

[0044] After the entrained air is separated, the water continues flowing through the conduit 105 and due to its hydrostatic pressure and momentum, the water rises part of the way up the conduit (towards the outlet 120), back to a second depth that is less than the first depth. The pumping means 160 then pumps the water back to the body of water 10 through the outlet 120 in order to ensure a continuous flow of water - as shown in Figure IB, one or more pumps 160 pump the water to the outlet 120 which is above the surface 15 of the body of water 10. In other examples, the water outlet 120 may be substantially level with the water inlet 110. Advantageously, the system can allow water to flow through the system and back into the same body of water without introducing pollutants into the body of water that could otherwise harm the environment in the body of water.

[0051]

[0045] In some examples, the conduit 105 is sized to direct the flow of water downwards from the water inlet by a distance (or head height) of at least around 5 m, at least around 10 m, at least around 50 m, or at least around 100 m. This distance may be equal to the first depth described to above. The conduit 105 may be sized to direct the flow of water upwards from the separator 140 by a distance of at least around 3.5 m, at least around 7 m, at least around 35 m, at least around 70 m, at least around 100 m. An up-flow portion of the conduit 105 may have a length that is at least around 70% or at least around 90% of a length of a down-flow portion of the conduit 105. The length of the up-flow portion of the conduit 105 may correspond to the second depth. The system 100 may be configured such that when in use, a vertical distance between the pumping means 160 and the water inlet 110 is at least around 30% of the vertical distance between the turbine 130 and the water inlet 110. The collection chamber 150 may be configured to store air pressurised to at least around 2 bar, at least around 5 bar, or at least around 10 bar. As will be appreciated by the skilled person, other pressures (e.g. higher or lower pressures) may be achieved depending on the system size and depth (head height).

[0052]

[0046] A volumetric flow rate of air through the air inlet 115 (e.g. at atmospheric pressure) may be greater than a volumetric flow rate of water through the conduit, optionally at least around four times greater than the volumetric flow rate of water. The flow rate of water through the conduit may be at least around 5 nr s'1(e.g. 8 mV), at least around 10 mV1, at least around 30 mV1, or more than 50 mV1. Other flow rates (e.g. larger or smaller flow rates) may be achieved by using a system with different dimensions and / or at different depths (head heights). Those skilled in the art will appreciate that, once the air flowing through the air inlet 115 has been entrained in the flow of water and pressurised, it may occupy a smaller volume, which may mean that the volumetric flow rate of pressurised air in the water-air mixture (e.g. which passes through the turbine 130 and towards the separator 140) is less than the volumetric flow rate of the water through the conduit.

[0053]

[0047] The pumping means 160 may be rated to pump water by a height of at least around 1.5 m, at least around 3 m, at least around 15, or at least around 30 m. The pumping means 160 may be driven by an external power supply, preferably a renewable power supply (e.g. derived from solar or wind energy). In some instances, the power required by the pumping means 160 to pump water through the conduit 105 may be reduced when other or additional driving factors are present, such as a swell, tide or natural flow of water. Equally, the power consumption or efficiency of the system 100 may be improved using energy generated by the turbine 130 (e.g. to recover losses from the system 100). In some examples, the system may generate more power (e.g. via the water turbine 130 and / or the compressed air in the collection chamber 150) than that required by the pumping means, so may provide sustainable energy generation.

[0054]

[0048] Other energy recovery mechanisms may also be employed in the system 100. For example, one or more air turbines may be provided in fluid connection to the collection chamber(s) 150. Pressurised air may be provided selectively from the collection chamber(s) 150 to the air turbines in order to generate electricity from the pressurised air. This can allow the system to be used for reliable energy generation (e.g. at times of peak demand). The pressurised air generated by the system can also have other uses, e.g. for environmentally friendly air cooling systems to provide fresh, clean, dry and cool air to buildings or facilities that require electricity and / or cooling (e.g. including but not limited to one or more of: residential buildings, high-rise buildings, hospitals, shopping centres, stadiums / arenas, airports, industrial or religious spaces / buildings). Additionally or alternatively, one or more recovery turbines may be disposed after the water outlet, in order to recover excess kinetic energy imparted to the water flow by the pumping means. For example, when the water outlet is configured to discharge water beneath the water surface (as shown in Figure 2B), the one or more recover turbines may be disposed in the body of water adjacent the water outlet.

[0055]

[0049] With reference to Figures 2A and 2B, another hydrodynamic system 200 will now be described. The system 200 generally corresponds to the system 100, except as described below. The system 200 includes a conduit 205 having a water inlet 210, an air inlet 215 and a water outlet 220, as well as a turbine 230, a pumping means 260 and separator 240 disposed in the conduit 205. The system 200 also includes a collection chamber 250 fluidically coupled to the conduit 205. In some examples, the water inlet 210, air inlet 215, turbine 230, separator 240 and / or pumping means 260 correspond to the equivalent components of the system 100 described above.

[0056]

[0050] However, the conduit 205 differs from the conduit 105 described above at least in that the up-flow portion of the conduit 205 is shorter than the down-flow portion of the conduit. In particular, when in use, the water outlet 220 is positioned lower than the water inlet 210. This can result in the conduit 205 having an asymmetrical “U” shape. The pumping means 260 may also be positioned slightly lower than in the system 100 to accommodate for the shorter section of the conduit 205.

[0057]

[0051] Therefore, when in use in a body of water, the water outlet 220 discharges water from the conduit 205 into the body of water at a certain depth below the surface. Similarly to the system 100 described above, the system 200 may be used with relatively shallow bodies of water (such as the body of water 10 shown in Figure IB) or in relatively deep open bodies of water 10’ as shown in Figure 2B. As shown, the system 200 (including the conduit 205) is submergible under the surface 15’ of the body of water 10’. This can reduce the profde of the system when viewed from above the surface 15’. In addition, by discharging water from the system 200 beneath the surface 15’, disruption to the surface environment can be avoided. For example, this can reduce the impact of the system 200 on the environment / ecosystem at the surface, and can leave a section of water above the main system components that is free from obstruction for water traffic and wildlife.

[0058]

[0052] As described above in relation to the system 100, one or more energy recovery mechanisms may be used in the system 200. For example, since the pumping means 260 pumps water out of the outlet 220 underwater with a certain velocity, one or more recovery water turbines may be positioned near the outlet 220 in order to recover energy from the flow of discharged from the outlet 220.

[0059]

[0053] With reference to Figures 3A and 3B, a further hydrodynamic system 300 will now be described. The system 300 generally corresponds to the systems 100, 200 described above, except as described below. The system 300 includes a conduit 305 having a water inlet 310, an air inlet 315 and a water outlet 320, as well as aturbine 330, apumping means 360 and separator 340 disposed in the conduit 305. The system 300 also includes a collection chamber 350 fluidically coupled to the conduit 305. In some examples, the conduit 305, turbine 330 and / or separator 340 correspond to the equivalent components of either of the systems 100, 200 described above.

[0060]

[0054] In the example shown in Figure 3A, the conduit 305 has a shape corresponding to the conduit 105 of Figures 1A and IB, but in other examples the conduit 305 may have a shape corresponding to the conduit 205 of Figures 2A and 2B. Similarly to the systems 100, 200 described above, the system 300 may be used either in relatively shallow bodies of water (such as the body of water 10 shown in Figure IB) or in relatively deep open bodies of water (such as the body of water 10’ shown in Figure 2B). In the example of Figure 3B, the system 300 is shown in use with a relatively shallow body of water 10.

[0061]

[0055] As shown in Figures 3A and 3B, the pumping means of the system 300 includes an air lift pump 370. The air lift pump 370 is configured to introduce a supply of pressurised air into the water flow in the conduit 305 (at a greater pressure than the surrounding hydrostatic water pressure). The injected air forms bubbles which reduce the density of the fluid in the conduit 305 and through buoyancy carry the surrounding water upwards. Thus, the flow of water is raised, preferably by an amount sufficient to reach the water outlet 320. For example, the air lift pump 370 may include an opening disposed in the conduit to provide pressurised air into the system.

[0062]

[0056] Thus, in some examples the air lift pump 370 alone is sufficient to pump the water out of the water outlet 320. Using the air lift pump 370 in this way can allow the water flow to be pumped through the system and out of the water outlet 320 efficiently without any moving parts, and can also condition (e.g. aerate or oxygenate) the water in the body of water. In other examples, as shown in Figures 3A and 3B, the pumping means may include both a mechanical pump and an air lift pump. Accordingly, in general the pumping means may include one or both of a mechanical pump and an air lift pump.

[0063]

[0057] The pressurised air provided by the air lift pump 370 may be generated by an air compressor. Alternatively, as shown in Figures 3A and 3B, the air lift pump 370 may use pressurised air that is stored in the collection chamber 350. Accordingly, a pipe or conduit may connect the collection chamber 350 to a portion of the conduit 305 (e.g. the up-flow portion of the conduit) in order to inject at least some of the compressed air stored in the chamber 350 into the water flow in the conduit 305 (e.g. in the up-flow portion). For example, a control valve may be provided to control the amount and / or flow rate of compressed air provided from the collection chamber 350 to the air lift pump.

[0064]

[0058] The volumetric flow rate of pressurised air provided by the air lift pump 370 is typically less than that of the water being lifted. The inventors have found that a volumetric flow rate of air provided by the air lift pump of no more than around 25% of the volumetric flow rate of water is sufficient. In particular, they have found that a volumetric flow rate of air provided by the air lift pump 370 in the range of 10% to 25%, or 10% to 20%, of the volumetric flow of water being lifted can be optimal for pumping efficiency. In other words, the volumetric water- to-air ratio in the water-air mixture created by the air lift pump 370 is typically no less than 4: 1, for example in the range of 4: 1 to 10: 1, 5: 1 to 10: 1, or higher. Accordingly, in the waterair mixture produced by the air lift pump 370, water is the dominant phase. The exact ratio between the water flow rate and air flow rate provided by the air lift pump 370 can depend on the pump geometry, efficiency and submergence conditions.

[0065]

[0059] With reference to Figures 4A and 4B, a further hydrodynamic system 400 will now be described. The system 400 generally corresponds to the systems 100, 200, 300 described above, except as described below. The system 400 includes a plurality of conduit sections 405a, 405b each having a water inlet and a water outlet. In this example, the system 400 includes a first conduit section 405a and a second conduit section 405b, but in other examples more than two conduit sections may be present.

[0066]

[0060] The first conduit section 405a has a water inlet 410, an air inlet 415 and a water outlet 422. The first conduit section 405a may correspond to at least a part of any of the conduits 105, 205, 305 described above. For example, the first conduit section 405a may correspond to the conduit 205 shown in Figures 2A and 2B. The second conduit section 405b has a water inlet 424 and a water outlet 420. The second conduit section 405b may correspond to at least another part of any of the conduits 105, 205, 305 described above. For example, the second conduit section 405b may correspond to part of an up-flow section of the conduit 105 or the conduit 305.

[0061] The conduit sections 405a, 405b are generally provided as distinct conduit sections which are configured to be fluidically coupled to one another directly or indirectly, such as via one or more other conduits, components (e.g. turbines, pumping mechanisms or flow control devices), and / or intermediate bodies of water. In use, the conduit sections 405a, 405b are arranged in particular orientations and / or locations relative to each other (as described below). In some examples, the conduit sections 405a, 405b may be configured to be mechanically coupled to or constrained relative to one another (directly or indirectly). When installed, the combination of the conduit sections 405a, 405b may be functionally similar to the other whole conduits 105, 205, 305 described herein - for example, the outlet 420 of the second conduit section 405b may correspond to any of the water outlets 120, 220, 320 described above.

[0067]

[0062] The system 400 also includes a turbine 430, separator 440, collection chamber 450 and a pumping means 460. In the example of Figures 4A and 4B, the turbine 430 and the separator 440 are disposed in the first conduit section 405a and the collection chamber 450 is fluidically coupled to the first conduit section 405a. Accordingly, one or more of the turbine 430, separator 440, collection chamber 450, water inlet 410, air inlet 415 may correspond to the equivalent components of any of the systems 100, 200, 300 described above. In the example of Figures 4A and 4B, the pumping means 460 is disposed in the section conduit section 405b. The conduit sections 405a, 405b may be shaped such that, when in use, the water inlet 410, turbine 430, pumping means 460 and water outlet 420 are positioned similarly to the water inlets, turbines, pumping means and water outlets of any of the systems 100, 200, 300 described above. The pumping means 460 may include an air lift pump as described above (e.g. corresponding to the air lift pump 370), which may use compressed air stored in the collection chamber 450.

[0068]

[0063] Similarly to the systems described above, the system 400 may be used either in relatively shallow bodies of water or in relatively deep open bodies of water. In the example of Figure 4B, the system 400 is shown in use with two relatively shallow bodies of water 10, 20. A first (or primary) body of water 10 is located above a second (or intermediate) body of water 20. One or both of the bodies of water 10, 20 may be naturally occurring, or one of the bodies of water (e.g. the intermediate body of water 20) may be specifically constructed for the system 400. For example, the primary body of water 10 may be a river or pond, and the intermediate body of water may be a water tank installed below (e.g. away from or buried underneath) the river or pond. Accordingly, as shown in Figure 4B, at least part of the system 400 may be submerged underwater and at least part of the system 400 may be located above ground or underground. In other words, the system may be at least partially submergible and / or at least partially configured to be disposed above ground and / or underground.

[0069]

[0064] As shown in Figure 4B, when the system 400 is in use, the water inlet 410 of the first conduit section 405a is configured to receive water from the primary body of water 10 and the water outlet 422 of the first conduit section 405a is configured to discharge the water to the intermediate body of water 20. The water outlet 422 of the first conduit section 405a is positioned below the water inlet 410 of the first conduit section 405a and the surface 25 of the intermediate body of water may be exposed to atmospheric pressure, meaning water can flow unaided from the primary body of water 10 to the intermediate body of water 20 via the first conduit section 405a (e.g. according to connecting tubes theory). In one example, a vertical distance between the water inlet 410 of the first conduit section 405a and one or more of: the pumping means 460, the water inlet 424 of the second conduit section 405b and the intermediate body of water 20, is at least around 30% of a vertical distance between the water inlet 410 and the turbine 430. In one example, a height of an up-flow portion of the first conduit section 405a is around 70% of the height of a down-flow portion of the first conduit section 405a.

[0070]

[0065] The water inlet 424 of the section conduit section 405b is configured to receive water from the intermediate body of water 20 and the water outlet 420 of the second conduit section 405b is configured to discharge the water back to the primary body of water 10. Accordingly, the pumping means 460 is configured to pump water from the intermediate body of water 20 to the primary body of water 10 via the second conduit section 405b. The use of the intermediate body of water 20 in this way can act as a buffer to reduce pressure fluctuations at the pumping means 460. In some examples, water may be returned to the primary body of water 10 via a series of intermediate bodies of water and corresponding conduit sections (with respective pumps). This can reduce the pumping load required by each pump.

[0071]

[0066] As shown in Figure 4B, the water outlets 420, 422 may be positioned above a surface 15, 25 of the respective body of water (as shown). In other examples, one or both of these outlets may be positioned beneath the respective water surface. The water inlet 424 of the second conduit section 405b is positioned below the water surface 25 of the intermediate body of water 20 and preferably below the water outlet 422 of the first conduit section 405a.

[0067] With reference to Figures 5A and 5B, a pumping means 560 will now be described. The pumping means 560 may be used as part of a hydrodynamic system. For example, the pumping means 560 may be used (as the pumping means 160, 260, 360, 460) in any of the systems 100, 200, 300, 400 described herein. The pumping means 560 (which may be referred to as a pump) operates to pump a liquid using a gas. In some examples, the liquid is water, and the gas is a gas mixture such as air. In other words, the pumping means 560 may be an air lift pump.

[0072]

[0068] As shown in Figure 5 A, the air lift pump 560 includes an outer channel 562, an inner channel 564, and a gas injector 565. The inner channel 564 is arranged within the outer channel 562 and has a smaller cross-sectional area than the outer channel 562. The cross-sectional area of the inner channel 564 may be no more than around 50%, no more than around 35%, no more than around 25%, no more than around 20%, no more than around 15%, no more than around 10%, or no more than around 5% of the cross-sectional area of the outer channel 562. In some examples, the inner channel 564 may have a width or diameter DI and the outer channel 562 has a width or diameter D2, where DI < D2. DI may take a value that is no more than around 75%, no more than around 70%, no more than around 60%, no more than around 50%, no more than around 40%, no more than around 33%, no more than around 30%, or no more than around 25% of the value of D2.

[0073]

[0069] Accordingly, a space or gap is defined between the inner and outer channels 562, 564. In some examples, the inner and outer channels 562, 564 are formed using cylindrical pipes, tubes and / or ducts with the inner channel having a smaller diameter than the outer channel, although those skilled in the art will appreciate that channels having other geometries (e.g. rectangular or hexagonal) may be used. Although the inner and outer channels 562, 564 are shown in Figure 5A with substantially constant cross-sections, in other examples their crosssections may vary in size and / or shape along their length (the vertical direction in Figure 5A), provided the cross-sectional area of the inner channel 562 remains smaller than that of the outer channel 564 at each point along its length. In the example of Figure 5A, the inner and outer channels 562, 564 are generally arranged concentrically with one another.

[0074]

[0070] The inner channel 564 has an inlet at one end and an outlet 520 at an opposite end, and is configured to receive a flow of liquid at the inlet. The channel 564 permits liquid to flow through the inner channel 564 from the inlet to the outlet 520. The outer channel 562 is disposed around the inner channel 564 and its interior is in fluidic communication with the interior of the inner channel 564. Accordingly, fluid in the gap between the outer and inner channels 562, 564 may flow into the inlet of the inner channel 564, through the inner channel 564, and out of the outlet 520.

[0075]

[0071] The gas injector 565 is located near the inlet of the inner channel and is configured to release a gas (such as a pressurised gas) into the inner channel 564. In the example of Figure 5 A, the gas injector 565 is located within the inner channel near its inlet. In other examples, the injector 565 may be located outside the inner channel such that the released gas is directed towards the interior of the inner channel 564. For example, the injector 565 may be positioned just below the inner channel inlet when in use such that the gas travels upwards into the inner channel 564 by virtue of its buoyancy.

[0076]

[0072] The gas injector 565 includes or is coupled to a gas supply, such as a canister, a gas pipeline, and / or a gas (e.g. air) compressor. The gas injector 565 is configured to release the gas over a distributed area, for example via a plurality of nozzles or other gas outlets. In other examples, the injector 565 releases the gas from a single outlet.

[0077]

[0073] When in use, as shown in Figures 5A and 5B, the inner channel 564 is oriented in a generally upright orientation, such that the outlet 520 of the inner channel 564 is above its inlet. The pumping means 560 is thus arranged to pump a liquid (from around and / or below the inlet of the inner channel) upwards and out of the outlet 520. The inner channel 564 is optionally moveable or adjustable within the outer channel 562. In this case, the inner channel 564 can be adjusted within the outer channel 562 to adjust the depth H at which the inner channel’s inlet sits below a surface of liquid within the outer channel when in use.

[0078]

[0074] Figure 5B shows the pumping means 560 of Figure 5A in operation. In particular, the outer channel 562 contains a volume of liquid (such as water or oil) around the inner channel 564. As shown, this volume of liquid extends to a level that is at a height H above the (lower) inlet of the inner channel 564. Accordingly, the inlet of the inner channel 564 is submerged below the liquid contained by the outer channel 562, meaning liquid is also present in the inner channel 564.

[0079]

[0075] The gas injector 565 introduces a gas (such as air or nitrogen) into the liquid within the inner channel 564. This forms gas bubbles which reduce the bulk density of the liquid-gas mixture in the inner channel 564 and through buoyancy carry the surrounding liquid upwards. This results in a flow of liquid through the inner channel 564. The flow is drawn through the inner channel’s inlet (indicated by the black arrow), passes through the inner channel 564 and is discharged from the outlet 520 of the inner channel 564 to a bulk liquid body.

[0080]

[0076] The liquid surrounding the inner channel 564 remains substantially free of the injected gas (without bubbles), so has a larger bulk density than the liquid-gas mixture within the inner channel. In addition, the liquid around the inlet of the inner channel 564 has a hydrostatic pressure resulting from its depth H below the surface of the liquid within the outer channel 562 (which is open to the atmosphere). This hydrostatic pressure difference contributes to driving the liquid flow upwards through the inner channel 564. Thus, the reference column of liquid contained between the inner and outer channels 562, 564 can amplify or improve the pumping efficiency.

[0081]

[0077] In addition, by constraining the injected gas to the smaller inner channel 564 that is within the outer channel 562, the efficiency of the air lift pump 560 can be further improved. In particular, the higher effective density of the liquid in the outer channel 562 can stabilise slug flow (also referred to as Taylor bubble flow) in the inner channel 564 over a wider range of volumetric rates of gas injection.

[0082]

[0078] As explained above, the depth at which the inner channel 564 is submerged within the liquid in the outer channel 562 can be adjusted (for example by moving or sliding the inner channel 564 within the outer channel 562). This can allow the effective head caused by the depth H to be tuned, allowing the flow rates and lifting effect of the pumping means 560 to be optimised.

[0083]

[0079] In some examples, the volumetric flow rate of pressurised gas provided by the gas injector 565 is typically less than that of the liquid being lifted. The inventors have found that a volumetric flow rate of gas provided by the gas injector 565 of no more than around 25% of the volumetric flow rate of liquid is sufficient. In particular, they have found that a volumetric flow rate of gas in the range of 10% to 25%, or 10% to 20%, of the volumetric flow of liquid being lifted can be optimal for pumping efficiency. In other words, the volumetric liquid-togas ratio in the liquid-gas mixture created by the pump 560 is typically no less than 4: 1, for example in the range of 4: 1 to 10: 1, 5: 1 to 10: 1, or higher. Accordingly, in the liquid-gas mixture produced by the pump 560, the liquid is the dominant phase. The exact ratio between the liquid flow rate and gas flow rate provided can depend on the pump geometry, efficiency and submergence conditions (e.g. submergence ratio).

[0084]

[0080] With reference to Figure 6, a further hydrodynamic system 600 will now be described. The system 600 generally corresponds to the systems 100, 200, 300, 400 described above, except as described below. The system 600 includes a conduit 605 having a water inlet 610, an air inlet 615 and a water outlet 620, as well as a turbine 630, a pumping means 660 and separator 640 disposed in the conduit 605. The system 600 also includes a collection chamber 650 fluidically coupled to the conduit 605. In some examples, one or more of the water inlet 610, air inlet 615, turbine 630, separator 640, and / or collection chamber 650 may correspond to the equivalent components of any of the systems 100, 200, 300, 400 described above. As shown in Figure 6, the conduit 605 has a shape generally corresponding to the conduits 105, 305 of Figures 1A, IB, 3A and 3B, but in other examples the conduit 605 may have a shape corresponding to the conduit 205 of Figures 2A and 2B or the conduit sections 405a, 405b of Figures 4A and 4B.

[0085]

[0081] As shown in Figure 6, the pumping means 660 of the system is an airlift pump supplied by pressurised air stored in the collection chamber 650. The pumping means 660 generally corresponds to the pumping means 560 of Figures 5A and 5B. The pumping means 660 includes an air injector 665 and an inner channel 664. The injector 665 is configured to introduce pressurised air delivered from the collection chamber 650 via a supply line 670 into water within the inner channel 664 (preferably near an inlet or lower end of the inner channel). In particular, the injector 665 may be configured to introduce into the inner channel 664 pressurised gas / air that has been entrained in the water flow via the inlet 615, pressurised by virtue of the surrounding water pressure as it flows downwards, separated from the water flow via the separator 640, and collected in the collection chamber 650. Accordingly, the pressure of the injected air (e.g. in bars) may depend on the depth and dimensions of the system components. For example, this may be related to the quantity and / or flow rate of water to be lifted. The flow rate and pressure of the air will depend on the depth of the system and dimensions (and the flow rate of water will determine the power the system will be able to generate), as discussed above. For example, the pressurised air may be pressurised to around 1 bar, around 10 bars, around 50 bars, or up to 100 bars, or more. In alternative examples, the injector 665 may receive compressed air from a different source (such as an air compressor).

[0086]

[0082] In the example of Figure 6, a portion of the main conduit 605 forms the outer channel 662 of the airlift pump 660, and an outlet of the inner channel 664 forms the water outlet 620. Similarly to the systems described above, the system 600 may be used either in relatively shallow bodies of water or in relatively deep open bodies of water. In the example shown in Figure 6, water flows from a contained body of water or reservoir into the water inlet 610, and is discharged back to the reservoir via the water outlet 620. This is particularly suited for a range of application scenarios, such underground, on land, at sea or in high-rise buildings. The tops of both the outer channel 662 and the reservoir are open to the atmosphere.

[0087]

[0083] Accordingly, the flow of water around the system 600 travels along a flow path from the water inlet 610, through the main conduit 605 (through the turbine 630 and around the separator 640), into the inner channel 664 of the pumping means 660, and out of the water outlet 620 defined by the inner channel 664. A volume of water is also contained between the inner channel 664 of the pumping means 660 and the portion of the conduit 605 that defines the outer channel 662 of the pumping means 660. Thus, there may be some amount of recirculation or other water flow around the inner channel 664, for example from the space around the inner channel 664 and into the inner channel 664.

[0088]

[0084] The pumping means 560, 660 described herein can provide an efficient way of lifting a volume of liquid, for example to return a flow of water back to a body of water. In some examples, the energy or power required by the gas injectors 565, 665 may be less than an amount produced by a turbine in the same hydrodynamic system, allowing further improvements in efficiency to be achieved. The pumping means 560, 660 outlined herein offer an effective solution for elevating a volume of liquid, such as returning a water flow to its source. In these implementations, the power consumed by an associated gas compressor may be notably lower because the air lift pump design achieves optimal efficiency when lifting water over a small distance. Specifically, the air lift pump may be particularly efficient when the height over which water is to be lifted is 50% or less of the total depth of water within the outer conduit portion / channel - this may be referred to as a submergence ratio. The submergence ratio can additionally or alternatively be defined as a ratio of the depth of the lower end of the inner channel (or the depth at which the gas injector is positioned) below the liquid surface in the outer channel / conduit portion to the total depth of water in the outer channel / conduit portion. Other submergence ratios also provide improved pumping efficiency. As a result, the energy required by the gas injectors 565, 665 is reduced, and can be less than the amount produced by a turbine operating within the same hydrodynamic system, resulting in further improvements to overall system efficiency^

[0089]

[0085] While specific systems are shown, any appropriate hardware may be employed. For example, the conduits described herein may be formed of multiple connected conduit sections. In addition, the flow control components (such as pumping means, turbine(s) and / or valves) described herein may be communicably coupled to a controller (not shown) that is configured to selectively control said flow control components in order to control the flow of water through the conduit of the system.

[0090]

[0086] Although the examples herein are described with reference to a body of water in air, the systems may be used for other liquid-gas combinations. Equally, the systems described herein may be used in a variety of environments and scenarios for efficient energy generation and recovery, as well as gas pressurisation and liquid treatment.

[0091]

[0087] The above embodiments and examples are to be understood as illustrative examples. Further embodiments, aspects or examples are envisaged. It is to be understood that any feature described in relation to any one embodiment, aspect or example may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, aspects or examples, or any combination of any other of the embodiments, aspects or examples. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

CLAIMS1. A hydrodynamic system comprising: a conduit comprising: a water inlet configured to receive a water flow from a body of water; an air inlet configured to entrain air from above a surface of the body of water into the water flow; and a water outlet configured to discharge the water flow to the body of water; a water turbine disposed in the conduit between the water inlet and the water outlet and configured to receive the water flow and the entrained air; a separator disposed in the conduit between the turbine and the water outlet and configured to separate the entrained air from the water flow after passing through the turbine; a collection chamber configured to collect the separated air, the chamber fluidically coupled to the conduit; and pumping means disposed in the conduit between the separator and the water outlet and configured to pump water from the conduit to the body of water through the water outlet; wherein the conduit is shaped such that, when in use, the turbine and the pumping means are positioned lower than the water inlet.

2. The system of claim 1, wherein the conduit is shaped such that, when in use, the water outlet is positioned higher than or level with the water inlet.

3. The system of claim 1 or 2, wherein the conduit is shaped such that, when in use, the water flow at the separator is substantially horizontal.

4. The system of any preceding claim, wherein, when in use, the pumping means is positioned higher than the turbine, preferably wherein a vertical distance between the pumping means and the water inlet is around 30% of a vertical distance between the turbine and the water inlet.

5. The system of any preceding claim, wherein the pumping means comprises an air lift pump configured to provide pressurised gas, optionally air, to the water flow in the conduit to pump water out of the water outlet.

6. The system of claim 5, wherein the pressurised gas provided by the air lift pump comprises pressurised air stored in the collection chamber.

7. The system of claim 5 or 6, wherein the air lift pump comprises: an inner channel disposed within the conduit, the inner channel comprising: an inlet configured to receive the water flow, and an outlet that forms the water outlet of the conduit that is configured to discharge the water flow to the body of water; and a gas injector configured to provide the pressurised gas into the water flow within the inner channel.

8. The system of claim 7, wherein the conduit comprises an outer portion disposed around at least the inlet of the inner channel, and wherein a cross-sectional area of the inner channel is smaller than a cross-sectional area of the outer portion.

9. The system of claim 8, wherein the inner channel is arranged such that, when in use, a lower end of the inner channel is submerged below a water surface within the outer portion, optionally submerged at an adjustable depth below the water surface.

10. The system of claim 8 or 9, wherein the inner channel and the outer portion of the conduit are arranged concentrically.

11. The system of any of claims 7 to 10, wherein, when in use, the gas injector is disposed proximate a lower end of the inner channel, optionally wherein the gas injector is disposed within the inner channel.

12. The system of any preceding claim, wherein the air inlet comprises one or more tubes each having a first end portion and a second end portion, the first end portion configured to receive air from above the surface of the body of water when in use, and the second endportion disposed in the conduit and configured to provide air substantially parallel to the water flow when in use.

13. The system of any preceding claim, wherein the collection chamber is configured to store air pressurised to at least around 5 bar, preferably at least around 10 bar.

14. The system of any preceding claim, further comprising an air turbine fluidically coupled to the collection chamber and configured to receive pressurised air from the collection chamber.

15. The system of any preceding claim, wherein the conduit is submergible in the body of water and / or configured to be disposed at least partially on land.

16. The system of any preceding claim, further comprising a controller configured to selectively control the pumping means to control the flow of water through the conduit.

17. The system of any preceding claim, further comprising one or more recovery turbines configured to receive the flow of water from the water outlet.

18. The system of any preceding claim, wherein the conduit comprises a plurality of conduit sections, each conduit section comprising a water inlet and a water outlet.

19. The system of claim 18, wherein the plurality of conduit sections are configured to direct the flow of water to the body of water via one or more intermediate bodies of water.

20. An air lift pump comprising: an inner channel comprising an inlet and an outlet, the inner channel configured to receive a liquid flow at the inlet and discharge the liquid flow from the outlet, wherein, when in use, the inlet is positioned below the outlet; an outer channel disposed around at least the inlet of the inner channel, wherein the outer channel is in fluidic communication with the inner channel; anda gas injector disposed adjacent the inlet of the inner channel, the gas injector configured to provide a pressurised gas into liquid within the inner channel such that, when in use, the liquid is pumped upwards through the inner channel.

21. The pump of claim 20, wherein the outer channel is configured to hold a volume of liquid between the inner channel and the outer channel.

22. The pump of claim 20 or 21, wherein a cross-sectional area of the inner channel is smaller than a cross-sectional area of the outer channel.

23. The pump of any of claims 20 to 22, wherein the inner channel is arranged such that, when in use, a lower end of the inner channel is submerged below a surface of liquid within the outer channel, optionally submerged at an adjustable depth below the liquid surface.

24. The pump of any of claims 20 to 23, wherein the inner channel and the outer channel are arranged concentrically.

25. The pump of any of claims 20 to 24, wherein, when in use, the gas injector is disposed proximate a lower end of the inner channel, optionally wherein the gas injector is disposed within the inner channel.

26. The pump of any of claims 20 to 25, wherein the gas injector comprises a gas compressor.

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