WO2011048466A1

WO2011048466A1 - Underwater apparatus for obtaining electrical energy from river and sea streams

Info

Publication number: WO2011048466A1
Application number: PCT/IB2010/002667
Authority: WO
Inventors: Mario Fabbri; Enrico Sonno
Original assignee: Re.Co 2 Srl
Priority date: 2009-10-19
Filing date: 2010-10-19
Publication date: 2011-04-28
Also published as: ITPI20090128A1

Abstract

An apparatus (10) for obtaining electric energy from the kinetic energy of a flow of river or sea water (1), comprising an external tubular casing (30) and an impeller (11) that engages with this current (1) by an engagement portion (12) that has preferably the in the form of an Archimede's screw, and that has an internal elongated recess (17) that houses an electric generator (9) and a transmission means (14) of the movement from the impeller (11) to the rotor (15) of the generator (9). In an aspect of the invention, a tubular support (22) is provided which is integral and co-axial to the casing (30), such that the generator and the movement transmission means are arranged within the tubular support, and the hollow impeller (11) is rotatably arranged about the tubular support (30) such that the tubular support (30) extends within the elongated recess (17) defined by the impeller (11). In particular, the tubular support (22) and the impeller (11 ) extend from the two end portion (31,32) of the tubular casing (30), are adapted to support each other through the bearings (23). In another aspect of the invention, the movement transmission means (14) between the impeller (11) and the rotor (15) of the generator comprise an adjustable ratio (40) gear multiplicator that is adapted to continuously adjust the gear ratio (N₁/N₂), and a regulator means (45), which is associated with this multiplicator, that comprises only hydraulic and mechanical components, for keeping a predetermined output rotational speed (N2) regardless of the speed of the current (1 ). The apparatus allows ready underwater installation without the need of particular fastening and connection works for mechanical transmission parts and electric parts. The transmission means (14) can provide a device (60) comprising soli mechanical components for maintained a predetermined spin direction of the rotor (15) unchanged when the spin direction of the impeller (11) changes, due to an inversion of flow (1), which makes the device well suited for use in channels or sea straits where current inversions take place, for example, due to the tides.

Description

TITLE

UNDERWATER APPARATUS FOR OBTAINING ELECTRIC ENERGY FROM RIVER AND SEA STREAMS

DESCRIPTION

Field of the invention

The present invention relates to an apparatus for converting the kinetic energy of river streams and of sea currents into electric energy.

In particular, the apparatus is well suited for a temporary or permanent installation in rivers, channels and sea straits.

Background of the invention

Apparatus are known comprising an impeller that can be plunged into rivers, channels, ducts, sea straits, that are adapted to transfer the kinetic energy of a water flow to a rotating shaft of the impeller, and possibly to convert it into electric energy in an electric generator.

In particular, devices are known in which also the electric generator can be plunged together with the impeller. Such devices, in which the impeller also comprises an Archimede's screw portion, are described, for instance, in EP 0222352 and in DE 10329465. Deploying such devices into the sea, as well as into a water stream, requires underwater anchor works, both for the impeller and the generator, which complicates the installation. This reduces the usefulness of such devices, in particular in the case of temporary installations, including for example offshore yards.

GB 2376508 relates to a turbine system adapted to recover energy from tidal or river flow, or waves. The system comprises a shaft-supported hollow hub that may contain a generator, and that is arranged within an outer shell that is mounted on a support. Supporting v-shaped vanes are provided which enable the turbine to be rotated in the same direction, regardless of the direction of water flow through the turbine. An electronic speed control system is provided to maintain the rotary speed of the turbine within predetermined limits. A grid is provided to trap debris material that would otherwise damage the turbine. The turbine may also be vertically mounted in an L-shaped duct so as to be driven by an oscillating water column or air column; alternatively, the turbine may be driven by the wind or by steam. The presence of an electronic control system for maintaining the speed and therefore the frequency of the alternating power generated makes this apparatus not much useful for submarine and river installation, in particular it is not easy to arrange a plurality of such apparatus in parallel to provide a local network for power generation from a same waterbody.

US 2002/088222 A1 discloses a multiple turbine unit that is adapted for adjustable deployment in a watercourse, wherein counter rotating turbines intercalate so as to produce a shielding effect.

GB2225813 describes an electric power production device that exploits at least one part of the hydraulic power available in a water supply network during filling and emptying operations. Such device comprises a machine with an electric generator and a bladed rotor, a mechanical assembly of arms and/or spacers for holding the machine in position on the axis of and inside a duct along a water path, and possibly a casing for housing the machine. In order to maintain a substantially constant rotor speed, guide blades are provided whose orientations may be manually adjusted, or automatically adjusted responsive to the water flow speed by directly using the water speed or by slaving the guide blade orientations to the output voltage of the alternator, by means of an external drive member. By adjusting the slant of the blades, with respect to the axis of the machine, the angle of the water current is varied with respect to the plane of the blades of the propeller. Since the rotation speed of a propeller depends upon this angle, the possibility of being able to orient these blades makes it possible to adjust the rotational speed of a given propeller, in a certain range of flow speed. The apparatus has a remarkabley difficult construction, in particular the presence of adjustable slant blades requires a maintenance work that limits the possibility of installing such apparatus at a desired depth or fixed to water bodies floors, for instance in rivers or sea channels.

WO2007/044128 A2 relates to a fluid energy converter, or to a tube or a rotor therefor, the tube comprising a plurality of helical grooves that are formed on the interior and/or on the exterior surface of the tube for capturing kinetic energy of a fluid stream as the fluid stream causes the tube to rotate about its own longitudinal axis; the patent application also refers to various groove geometries. In some embodiments, the tube houses one or more energy handling and transmission components including a fixed ratio drive, a continuously variable transmission (CVT), a generator and power transmission lines. The CVT can be any type known in the art and serves for varying the rotational speed of a transmission shaft so that speed input to the generator can be controlled to optimize and simplify the generation of electrical power. The use of a CVT alleviates the need for power electronics, as well known in the wind powered electrical energy generation industry, to convert the power generated by a generator that operated at various rotational speeds into the desired output characteristics, such as a desired frequency.

Such apparatus have normally a costly construction; another limitation is the difficulty of installations in water bodies such as rivers, channels, sea channels, or fixed to underwater floors thereof.

Summary of the invention

It is therefore a feature of the present invention to provide a submersible apparatus for generating electric power from a water flow, for example a flow of river or sea water, which can easily arranged at a depth of a waterbody, in particular on an underwater floor of a waterbody without the need of expensive supportation and/or fastening works.

It is, furthermore, a feature of the present invention to provide such a submersible apparatus for generating electric power in the form of alternated voltage/current having a predetermined fixed frequency, independently from the speed and from the direction/orientation of the water flow.

It is a particular feature of the invention to provide such an apparatus that is adapted to provide an alternated fixed frequency voltage/current at the same frequency of a network available for receiving the electric power without the need of electric transformation devices.

It is, furthermore, a feature of the present invention to provide such an apparatus that is adapted to the installation in water courses such as channels that are characterized by frequent inversions of the current direction or in sea straits where the currents are subject to regular inversions by the tides.

It is also a feature of the present invention to provide such an apparatus that is of quick installation and easy use. These and other objects are achieved by an apparatus for obtaining electric energy from the kinetic energy of a flow of river or sea water, the apparatus comprising:

— a fixed external tubular casing that is adapted to be run through by the water flow;

— an impeller from which an engagement portion extends with the water flow, the impeller rotatably mounted within the tubular casing, such that the water flow can cause a rotational movement of the impeller within the fixed external tubular casing;

— an electric generator that has a stator and a rotor;

— a movement transmission means for transmitting the rotational movement from the impeller to the rotor;

wherein the impeller is a hollow impeller that has an inner cylindrical wall that defines an elongated recess.

According to a first aspect of the invention, a tubular support is provided which is integral to the casing and extends coaxially with respect to the casing, such that the generator and the movement transmission means are arranged within to the tubular support, and wherein the hollow impeller is rotatably arranged about the tubular support such that the tubular support extends whithin the elongated recess that is defined by the impeller.

This way, an apparatus is supplied which is particularly easy to install and to use. To this purpose, the apparatus has only to be plunged into a stream or into the sea, at a location where undercurrents are present which are suitable for generating electric energy, to be fixed to an underwater floor or to a structure, and to connect a power cable from the generator to a user. These operations can be repeated for further apparatus, until a prefixed installed power capacity is attained. The simplicity of installation makes the apparatus particularly well suited for both occasional / temporary use, as in case of offshore yards, and permanent river or sea installations, at such depths where undercurrents still exist from which electric energy can be recovered.

Preferably, the engagement portion of the impeller is a helicoid portion; in particular, the hollow impeller has an Archimede's screw outside profile. This way, it is possible to provide a unit that can provide a predetermined electric power with an impeller size that is smaller than needed for any other common water turbine impeller. The profile screw is particularly well suited for streams which change directions, as in the case of tidal streams, since additional components and devices like movable deviators are not required with the flow inversion to change the spin direction of the impeller. Preferably, the screw pitch is selected responsive to the undercurrent flow pattern, i.e. responsive to water speeds that normally take place where the apparatus is installed.

Advantageously, the tubular support and the impeller can be adapted to support each other; a plurality of bearings may be arranged between the tubular support and the impeller. Preferably, the bearings comprise ball or roller bearings.

Advantageously, the tubular support can have a passage for a rotating shaft of the impeller, the rotating shaft coaxially extending from the impeller within the impeller. The tubular support has also a passage for a power cable for transferring the electric energy to a user.

In particular the external tubular casing can have a first end portion from which the tubular support extends, and a second end portion from which the impeller pivotally extends.

The apparatus may also comprise a cooling device for cooling the electric generator, said cooling device preferably formed by one or more coils that have respective inlet and outlet ports for drawing/returning water from/to the flow, and respective central portions that are arranged inside or outside the tubular support proximate to the generator, such that the water can remove a heat that is generated at the electric generator.

Advantageously, the movement transmission means includes a RPM multiplication means, comprising:

— a primary rotating shaft that is linked to the impeller in such a way to be dragged by the impeller at an input rotational speed;

— a secondary rotating shaft that is rotatable integrally with the rotor, the secondary rotating shaft having an output rotational speed. This way, it is possible to obtain a generator rotor speed that allows generating a voltage/ an electric current at a frequency that is well suited for electric power transfer through power lines, starting from turbine impeller rotation frequencies which are normally far lower, due to the sea or river undercurrents low flow speed, and the like.

Preferably, the RPM multiplication means comprises a variable transmission RPM multiplication means and an adjustment means for adjusting the gear ratio between the input rotational speed and the output rotational speed, such that the output rotational speed remains substantially unchanged at a predetermined value when the input rotational speed changes. This way, it is possible to use a conventional generator to obtain electric energy in the form of an alternating voltage, at a predetermined frequency. This is advantageous, in particular, in case of an installation comprising a plurality of apparatus in a same waterbody, for example in the case of a plurality of apparatus that are installed along a same stream such as a sea strait, a river or a fjord, where all the generators deliver a voltage substantially at the same frequency, such that a local energy recovering network can be provided. Such local network can then be readily connected to the mains by means of conventional apparatus. Accordingly, the frequency of the electric voltage that is provided by the generator or by the generators is selected equal to the mains frequency, for example it can be selected equal to 50 Hz. The regulator also allows maintaining an apparatus' maximum efficiency RPM condition.

Advantageously, this variable transmission RPM multiplication means is adapted to continuously adjust the gear ratio, i.e. the variable transmission RPM multiplication means is a CVT device.

Preferably, the variable transmission RPM multiplication means comprises an epicycloidal multiplier.

Preferably, the regulator mens of the multiplication means is a closed- loop regulator comprising:

— a reservoir that contains an an actuation fluid;

— a pump that is mechanically driven by the primary shaft or by the secondary shaft, the pump providing an actuation pressure and/or an actuation flow rate of the actuation fluid;

— an actuator that is adapted to operate the RPM multiplication means in order to adjust the RPM ratio responsive to the actuation pressure and/or to the actuation flow rate;

— a fluid connection means between the actuator and the reservoir, -X- wherein the pump is adapted to pump the actuation fluid from the reservoir into the actuator, and the fluid connection means is adapted to return the actuation fluid from the actuator into the reservoir,

such that the RPM ratio is adjusted responsive to the input rotational speed, and the output rotational speed remains substantially unchanged at the predetermined value when the input rotational speed changes, i.e. the impeller rotational speed changes.

Such a regulator, which comprises only hydraulic and mechanical components and doesn't contain any electronic components, makes it possible to obtain the electric power at a desired voltage directly at the installation site of the underwater turbine, and makes it easier to build up an electric power recovery network by means of a plurality of apparatus that are arranged in a same energy recovery field, as described above.

According to an aspect of the invention, the pump is mechanically driven by the secondary shaft, and the actuator has a variable volume chamber for the actuation fluid, with a movable member for adjusting the variable volume of the chamber, said movable member having an actuation extension member which is adapted to adjust the RPM ratio responsive to an amount of the actuation fluid that is contained within the variable volume chamber, and wherein the fluid connection means comprises:

— a duct for conveying the actuation fluid from the actuator into the reservoir;

— a valve that is arranged along the duct, the valve adapted to allow the passage of a predetermined actuation flow rate of the actuation fluid, the predetermined actuation flow rate provided by the pump when the output rotational speed has the predetermined output rotational speed value, such that upon increasing or decreasing the amount of the actuation fluid that is contained within the variable volume chamber, the RPM ratio increases/decreases, respectively.

This way, a closed loop feedback hydraulic circuit is obtained, which by changing the gear ratio also causes the pump flow rate to decrease, and stabilizes converging towards a working point which corresponds to the ideal generator RPM, for instance a dynamo generator or an alternator. Advantageously, a calibration means of the valve is provided for adjusting the predetermined output rotational speed value responsive to the prefixed actuation flow rate. This way, it is possible to choose the frequency of the voltage generated by the apparatus for power generation, responsive to various needs, once assigned the features of the circuit of the closed-loop regulator.

Advantageously, the impeller and the rotor are adapted to rotate according to respective impeller and rotor spin directions, the spin direction of the impeller being reversed responsive to the direction of the water flow, where the transmission means comprises a rotor spin direction holding device that is adapted to prevent the rotor from reverting its own rotor spin direction when the spin direction of the impeller is reversed. This way, the apparatus is well suited for use where flow inversions occur more or less frequently, for example at sea straits where tidal currents take place, as in the case of sea channels between wide sea basins where the tides cause sea level differences and remarkable water exchanges, or at the extensions of said channels, up to where the tidal currents take place. In particular, by using an Archimede's screw impeller, there is no need of adjusting blade configurations when the water flow is reversed.

Advantageously, the rotor spin holding device is a coupling device of a first rotating shaft that receives the rotational movement of the shaft of the impeller and of a second rotating shaft, which is arranged downstream of the first shaft, which transmits a rotational movement towards the rotor, the coupling device comprising:

— a direct coupling in which, when the first shaft rotates according to the predetermined spin direction, the second shaft is dragged by the first shaft according to the same spin direction, and is free with respect to the first shaft when the first shaft rotates according to a reverse direction that is opposite with respect to the predetermined spin direction;

— a reverse coupling in which, when the first shaft rotates according to the reverse direction, the second shaft rotates according to the predetermined spin direction, and is free with respect to the first shaft when the first shaft rotates in the predetermined spin direction. ln particular the reverse coupling comprises an auxiliary shaft that is arranged substantially parallel to the first shaft and to the second shaft, the auxiliary shaft having respective external adapted to mesh with an external gear of the first shaft and with an external gear of the second shaft.

Advantageously, the external gear of the first/second shaft is obtained by a gear fitted on the first/second shaft by an axially sliding shaft/hub connection, such that upon motion inversion the external gear axially slides with respect to the first/second shaft and automatically engages/disengages from the auxiliary shaft.

Advantageously, a joint is provided between the first and the second shaft which is adapted to assure the engagement when the first shaft rotates according to the predetermined spin direction, and which is adapted for automatically disengage when the first shaft rotates according to a reverse spin direction opposite to the predetermined spin direction. In particular, the joint provides two flanges that face each other and that are arranged along planes at an angle with respect to each other on the first and on the second shafts, the flanges having respective engagement teeth, such that when the spin directions are concordant, they abuts on one another whereas when the spin directions are opposite the planes at an angle of the teeth slide with respect to one another, creating an axial component on the first and/or on the second shaft that causes the two flanges and therefore the two shafts to depart from each other, thus disengaging and maintaining disengaged the two flanges with respect to each other.

According to another aspect of the invention, the fixed external tubular casing has a first open end portion and a second open end portion, and at least one end portion of the casing, which is selected between the first open end portion and the second open end portion, has a countersunk part that flares outward of the casing. Such countersunk part serves for conveying the flow into the tubular casing of the apparatus, such that the water pressure increases, and therefore also the efficiency of the apparatus increases. In particular, if the apparatus is to be installed in water streams or bodies where an inversion of the flow direction is to be taken into account, for example sea channels where water exchanges take place between water bodies due to the tide, fjords and so on, the countersunk part is present at both end portions of the tubular casing.

Advantageously, the apparatus comprises protection grids that are arranged at the end of the cylindrical recess of the fixed external tubular casing in order to prevent solid material, which could damage the impeller, as well as small water animals from entering the recess and contacting the impeller.

The underwater fixing means can be suitable for fixing the apparatus to a sea or river underwater floor or to a structure that is anchored to such floor, or along the bottom of a boat.

Brief description of the drawings

The invention will be made clearer with the following description of an exemplary embodiment thereof, exemplifying but not limitative, with reference to the attached drawings, wherein:

- Fig. 1 is a diagrammatical overall cross sectional view of the apparatus according to the invention;

- Fig. 2 is a cross sectional view of the tubular casing of the apparatus of Fig. 1 ;

- Fig. 3 is a cross sectional view of the tubular support of the apparatus of Fig. 1 ;

- Fig. 4 is a cross sectional view of the impeller of the apparatus of Fig. 1 ;

- Fig. 5 diagrammatically represents an exemplary embodiment of the gear ratio adjustment means of the apparatus shown in Fig. 1 ;

- Fig. 6 diagrammatically represents another exemplary embodiment of the gear ratio adjustment means of the apparatus shown in Fig. 1 ;

- Fig. 7 diagrammatically shows a rotor spin direction holding device of the apparatus shown in Fig. 1 ;

- Figs. 8 and 9 diagrammatically show a detail of the rotor spin direction holding device of Fig. 7.

Description of a preferred exemplary embodiment

With reference to Figs. 1-4, an apparatus is described 10, according to the invention, for transforming at least one part of the kinetic energy of a flow 1 of river or sea water flow into electric energy. The apparatus comprises a fixed external tubular casing 30 (Fig. 2), within which a water flow 1 takes place. The casing 30 extends along its own axis 2, between a first end portion 31 and a second end portion 32, both end portions are open respectively to allow water flow 1 inlet and outlet, or vice-versa;

Apparatus 10 also comprises an impeller 11 (Fig. 4), which is supported within a housing 29 which is provided at second end portion 32 of tubular casing 30, and which is rotatably arranged within tubular casing 30. Impeller 11 has an engagement portion 12 for engaging with water flow 1 , which is adapted to rotate under the action of water flow 1. Engagement portion 12 is preferably a helicoid portion, i.e. such engagement portion has an outer profile which corresponds to an Archimede's screw, i.e. to a screw conveyor. A pitch p of Archimede's screw 12 is advantageously selected responsive to typical speeds of water flow 1 within the waterbody where apparatus 10 is installed.

Impeller 11 comprises an internal elongated recess 17 which is defined by an inner cylindrical wall 21 of hollow impeller 11. A tubular support 22 (Fig. 3) extends from a first end portion 31 of fixed external tubular casing 30, inside, integrally and coaxially to tubular casing 30; an electric generator 9 is housed in a preferably hermetic tubular support portion 22, and has a stator 16 and a rotor 15, as well as movement transmission means 14 for transmitting the rotational movement of impeller 11 to rotor 15. Therefore, generator 9 and movement transmission means 14 are located within elongated recess 17 defined by impeller 11.

A typical size of the impeller allows flow rates of about 10 -11 mc/sec within external tubular casing 30, with an energy production set between 400 and 500 KW for each apparatus.

A rotating impeller shaft 13 extends coaxially from an end portion of impeller 11 within impeller 11 ; a connection is provided between a conical wall 27, which is defined by a part of the end portion of elongated recess 17, and impeller 11 of rotating shaft 13, which has a portion, which is outside elongated recess 17, and which is supported at open end portion 32, for example by means of radial members, in particular by means of conventional radial members, not shown. Rotor 15 of electric generator 9 has an own shaft 39 that is linked to impeller 11 of rotating shaft 13 through movement transmission means 14 that are arranged within the hermetic portion of tubular support 22.

Tubular support 22 is coaxially inserted within elongated recess 17 of impeller 1 1 ; impeller 1 1 and tubular support 22 are adapted to support each other, in the exemplary embodiment shown herein through bearings 23, preferably roller type bearings. Tubular support 22 has also a passage 24 for impeller 11 of rotating shaft 13 and a passage 25 for a power cable 26, for transferring the electric energy delivered by apparatus 10 to a user.

In the exemplary embodiment shown herein, a second end portion 32 of casing 30 has a countersunk part that flares outward of casing 30. The countersunk part serves for conveying entering water flow 1. Even if exemplary embodiment 10 shown herein has only one flared end portion, tubular casing 30 may have both flared end portions, in particular, for installations in water bodies where water flow 1 inversions take place.

Tubular casing 30 is also equipped with demountable protection grids 38 at end portions 31 and 32, to prevent solid material and small water animals from entering apparatus 10.

A conventional fixing means 33 is furthermore provided for fixing underwater apparatus 10 to an underwater floor, or to an underwater structure, at a prefixed depth in a stream or at a sea location, where undercurrents underwater occur, for example at a depth set between some tens and some hundreds of metres. In an exemplary embodiment a not shown fastening means may also be provided for fastening the apparatus to the bottom part of a watercraft.

Apparatus 10 also comprises a cooling circuit, not shown, for cooling electric generator 9; it uses an amount of water drawn from flow 1 , which flows through some coils that are arranged within tubular support 22.

In the exemplary embodiment shown in the drawings, movement transmission means 14 include an RPM multiplication means 40 that comprises:

— a primary rotating shaft 41 that is linked to impeller 11 in such a way to be dragged by the latter at an input rotational speed Ni equal to the rotational speed that impeller 11 instantly carries out under the action of water flow 1 , a secondary rotating shaft 42 that can rotate at an output rotational speed N₂ that is higher than rotational speed Niof the impeller. Multiplication means 40 is preferably an adjustable gear ratio multiplication means.

Transmission means 14 also comprises a regulator 45,45' for adjusting the ratio of input rotational speed Ni to output rotational speed N₂, in order to maintain an output rotational speed predetermined value N₂, i.e. to maintain a predetermined speed of rotor 15 regardless of any change of the speed of impeller 11 due to an increase or to a decrease of the speed of water flow 1.

As shown in Fig. 5, in a preferred exemplary embodiment, in a particular exemplary embodiment, variable transmission RPM multiplication means 40 is adapted to continuously adjust the gear ratio, i.e. the variable transmission RPM multiplication means is a CVT device. For instance, RPM multiplicator 40 can be an epicycloidal multiplier. Typically, the RPM multiplicator is adapted to provide an increase of the rotational speed from 300 RPM to 700 RPM. In the exemplary embodiment of Fig. 5, rotational speed regulator 45 is a closed-loop regulator, and comprises:

— a reservoir 47 that contains an actuation fluid 48;

— a pump 49 for providing an actuation pressure and/or an actuation flow rate of the actuation fluid;

— an actuator 46 that is adapted to operate RPM multiplication means 40 for adjusting the RPM ratio N-|/N₂ according to the actuation pressure and/or to the actuation flow rate;

— a connection duct 44 for conveying the actuation fluid, between actuator 46 and reservoir 47.

Pump 49 is adapted to transfer actuation fluid 48 from reservoir 47 into actuator 46, and, through connection duct 44, in into reservoir 47 again.

In the exemplary embodiment shown in Fig. 5, pump 49 is a positive displacement rotative pump that is mechanically driven by secondary shaft 42; actuator 46 comprises a variable volume chamber or equalization chamber 50 for the actuation fluid, whose variable volume is defined by a piston 48 which slides within chamber 50. An extension 53 of a piston 54 has an end portion that is mechanically connected with an actuator of adjustable ratio RPM multiplicator 40. Therefore, a volume increase of variable volume chamber 50 causes a translation motion of extension 53 of piston 54, which acts on the actuator of RPM multiplicator 40 thus modifying gear ratio /^', i.e. RPM ratio N-|/N₂.

In the exemplary embodiment described herein, a proportional valve 51 is arranged along duct 44, the valve equipped with an adjustment means, for example in the form of an adjustment screw 52, which is adapted to change a reference position of an flow throttling or stopping member 55, in such a way that, when output rotational speed N₂ has a predetermined output rotational speed value N₂\ valve 51 allows the passage of a predetermined flow rate of actuation fluid 48.

An increase of the speed of water flow 1 causes an increase of rotational speed Ni of impeller 11 , and also of rotational speed N₂ of secondary shaft 42 and of pump 49, according to the value of gear ratio / of multiplication means 40 at the time when flow speed increases. Accordingly, an increase of the flow rate takes place of actuation fluid 48 which is supplied by pump 49. In such conditions, the actuation fluid flow rate increases at variable volume chamber 50 inlet, whereas the flow rate that can leave variable volume chamber 50 is less than the inlet flow rate, according to how proportional valve 51 is characterised and calibrated and, secondarily, according to the features of the circuit. Since the actuation fluid is an incompressible fluid, piston 54 moves to increase the volume of chamber 50, pushing its own extension 53 against the actuator of multiplication means 40, such that the gear ratio /^' increases until a new working point of adjustable ratio RPM multiplicator 40 is met, where the output rotational speed N₂ returns to predetermined value N₂'. Inversely, a decrease of the speed of water flow 1 causes a decrease of rotational speed Ni of impeller 11 , and also of rotational speed N₂ of secondary shaft 42 and of pump 49, according to the value of gear ratio i of multiplication means 40 at the time when flow speed 1 decreases. Accordingly, a decrease of actuation fluid flow rate 48 supplied by pump 49 occurs. In such conditions, a decrease of the of actuation fluid 48 flow rate takes place at variable volume chamber 50 inlet, whereas the flow rate that can leave variable volume chamber 50 is more than the inlet flow rate, according to the characteristic and to the calibration of proportional valve 51 and, secondarily, according to the features of the circuit. Piston 54 moves then to decrease the volume of chamber 50, acting with its own extension 53 on the actuator of multiplication means 40, such that the gear ratio /^' decreases until a new working point of adjustable ratio RPM multiplicator 40 is met, where output rotational speed N₂ has reached again predetermined value N₂'. In other words, proportional valve 51 , if suitably calibrated, allows the passage of a transient actuation flow rate of actuation fluid 48 through duct 44, respectively higher or lower than the predetermined actuation flow rate, according to whether the speed of water flow 1 increases or decreases, such that the amount of actuation fluid 48 that is contained within variable volume chamber 50 increases/decreases, respectively displacing the piston to a new working position to which a gear ratio of multiplication means 40 corresponds, such that output rotational speed N₂ returns to predetermined value N₂'.

Fig. 6 shows an exemplary embodiment 45' of the regulator of ratio i of input rotational speed Ni to output rotational speed N₂ which differs from exemplary embodiment 45 of Fig. 5, since pump 49 is mechanically driven by primary shaft 41 instead of secondary shaft 42.

Fig. 7 shows a holding device 60 of a predetermined spin direction 68 of rotor 15, to prevent such spin direction from being reversed when spin direction 69,69' of impeller 11 is reversed, due to an inversion of water flow 1. In a represented exemplary embodiment, holding device 60 is a coupling device between a first rotating shaft 42 that receives the rotational movement from shaft 13 of impeller 11 (Fig. 1 ) and of a second rotating shaft 43, which is subsequent and aligned to the first shaft 42, and transmits a rotational motion towards rotor 15, ( Fig. 1 ).

In an exemplary embodiment, coupling device 60 comprises:

— a direct coupling 63 in, when first shaft 42 rotates according to spin direction 69, which is the same as predetermined rotation spin 68, second shaft 43 is dragged by first shaft 42 according to the same spin direction 68, while it is free with respect to first shaft 42 when first shaft 42 rotates according to spin direction 69' opposite to predetermined spin direction 68; — a reverse coupling 64 in which, when first shaft 42 rotates according to a reverse spin direction 69' opposite to predetermined spin direction 68, second shaft 43 rotates according to the predetermined spin direction, while it is free with respect to first shaft 42 when first shaft 42 rotates according to spin direction 69 which is the same as predetermined spin direction 68. ln the represented exemplary embodiment, reverse coupling 64 comprises an auxiliary shaft 67 that is arranged substantially parallel to first shaft 42 and to second shaft 43, auxiliary shaft 67 having respective gears that comprise an external gear adapted to mesh with respective external gear 65 of first shaft 42 and with respective external gear 66 of second shaft 43.

In the exemplary embodiment of Fig. 7, external gear 65,66 of first/second shaft 42,43 is obtained by a gear 65', 66' fitted on first/second shaft 42,43 by an axially sliding shaft/hub connection, such that in case of an inversion of motion the external gear carries out an axial translation movement 68 with respect to first/second shaft 42,43 and engages/disengages automatically.

Direct coupling 63 comprises a joint between first shaft 42 and second shaft 43 adapted to ensure the engagement when first shaft rotates 42 according to a spin direction 69 which is the same as predetermined spin direction 68, and which is suitable for automatically disengaging when first shaft 42 rotates according a spin direction 69' which is opposite to predetermined spin direction 68. As Figs. 8 and 9 show, joint 63 provides two flanges 70,71 that faces each other and that are arranged along planes at an angle respectively of first shaft 42 and of second shaft 43 that are provided with respective engagement teeth 72,73, which abut on each other when spin directions 68,69 are concordant (Fig. 8), whereas when spin directions 68,69' are opposite the planes at an angle of teeth 73 slide on the planes at an angle of teeth 72, and vice-versa, by generating on shafts 42,43 at least axial forces 74 that cause two flanges 70,71 to stay at a distance with respect to each other (Fig. 9).

The foregoing description of an embodiment according to the invention will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt for various applications such embodiment without further research and without parting from the invention, and it is therefore to be understood that such adaptations and modifications will have to be considered as equivalent to the embodiment. The means and the materials to realise the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Claims

An apparatus (10) for obtaining electric energy from the kinetic energy of a flow (1 ) of river or sea water, said apparatus (10) comprising:

— a fixed external tubular casing (30) that is adapted to be run through by said water flow;

— an impeller (11 ) from which an engagement portion (12) extends adapted to engage with said water flow (1 ), said impeller (11 ) rotatably mounted within said tubular casing, such that said water flow (1 ) can cause a rotational movement of said impeller (11) within said fixed external tubular casing;

— an electric generator (9) that has a stator (16) and a rotor (15);

— a movement transmission means (14) for transmitting said rotational movement from said impeller (11 ) to said rotor (15);

wherein said impeller (11 ) is a hollow impeller that has an inner cylindrical wall that defines an elongated recess (17),

wherein a tubular support (22) is provided which is integral to said casing (30) and coaxially extends with respect to said casing (30), such that said generator (9) and said movement transmission means (14) are arranged within said tubular support, and

wherein said hollow impeller is rotatably arranged about said tubular support such that said tubular support extends within said elongated recess (17) that is defined by said impeller (11 ).

An apparatus (10) according to claim 1 , wherein said engagement portion (12) of said impeller (11 ) is a helicoid portion, such that said impeller (11 ) is a hollow Archimede's screw.

An apparatus (10) according to claim 1 , wherein said tubular support (22) and said impeller (11 ) are adapted to support each other, a plurality of bearings (23) arranged between said tubular support (22) and said impeller (11 ).

An apparatus (10) according to claim 1 , wherein said tubular support (22) has a passage (24) for a rotating impeller shaft (13), said rotating shaft (13) coaxially extending from said impeller (11 ) within said impeller (11 ).

5. An apparatus (10) according to claim 1 , wherein said external tubular casing (30) has a first end portion (31 ) from which said tubular support extends (22), and a second end portion (32) from which said impeller pivotally extends (11 ).

6. An apparatus (10) according to claim 1 , wherein said movement transmission means (14) includes a RPM multiplication means (40), said RPM multiplication means comprising:

— a primary rotating shaft (41 ) that is linked to said impeller (11 ) in such a way to be dragged by said impeller (11 ) at an input rotational speed (N-i);

— a secondary rotating shaft (42) that is rotatable integrally with said rotor (15), said secondary rotating shaft (42) having an output rotational speed (N₂).

7. An apparatus (10) according to claim 6, wherein said RPM multiplication means (40) comprises:

— a variable transmission RPM multiplication means (40);

— a regulator means (45) of the gear ratio (N₁/N₂) of said input rotational speed (Ni) to said output rotational speed (N₂), such that said output rotational speed (N₂) remains substantially unchanged at a predetermined value when said input rotational speed (Ni) changes.

8. An apparatus (10) according to claim 6, wherein said variable transmission RPM multiplication means (40) is adapted to continuously adjust said gear ratio, i.e. said variable transmission RPM multiplication means (40) is a CVT device.

9. An apparatus (10) according to claim 8, wherein said variable transmission RPM multiplication means (40) comprises an epicycloidal multiplier.

10. A device (10) according to claim 8, wherein said regulator means (45) of said multiplication means (40) is a closed-loop regulator comprising:

— a reservoir (47) that contains an actuation fluid (48);

— a pump (49) that is mechanically driven by said primary shaft (41 ) or by said secondary shaft (42), said pump (49) providing an actuation pressure and/or an actuation flow rate of said actuation fluid (48);

— an actuator (46) that is adapted to operate said RPM multiplication means (40) in order to adjust said RPM ratio (I N₂) responsive to said actuation pressure and/or to said actuation flow rate;

— a fluid connection means (44) between said actuator (46) and said reservoir (47),

said pump (49) adapted to pump said actuation fluid (48) from said reservoir (47) into said actuator (46), and said fluid connection means (44) adapted to return said actuation fluid from said actuator (46) into said reservoir (47),

such that said RPM ratio (N^Na) is adjusted responsive to said input rotational speed (Ni), and said output rotational speed (N₂) remains substantially unchanged at said predetermined value when said input rotational speed (Ni) changes.

An apparatus (10) according to claim 10, wherein said pump (49) is mechanically driven by said secondary shaft (42) and said actuator (46) has a variable volume chamber (50) for said actuation fluid and an actuation extension member (53) with a movable element (54) for adjusting the variable volume of said chamber adapted to adjust said RPM ratio (Ni/N₂) responsive to an amount of said actuation fluid (48) that is contained within said variable volume chamber (50), and wherein said fluid connection means comprises:

— a duct (44) for conveying said actuation fluid from said actuator (46) into said reservoir (47);

— a valve (51 ) that is arranged along said duct (44), said valve (51 ) adapted to allow the passage of a predetermined actuation flow rate of said actuation fluid (48), said predetermined actuation flow rate provided by said pump (49) when said output rotational speed (N₂) of said secondary shaft (42) has said predetermined output rotational speed value (N2'),

such that upon increasing or decreasing said amount of actuation fluid (48) that is contained within said variable volume chamber (50) said RPM ratio (N1/N2) increases/decreases, respectively.

An apparatus (10) for obtaining electric energy from the kinetic energy of a flow of river or sea water, said apparatus (10) comprising:

— an impeller (11 ) from which an engagement portion (12) extends adapted to engage with said water flow (1 ), said impeller (11) rotatably mounted within said tubular casing (30), such that said water flow (1 ) can cause a rotational movement of said impeller (11) within said external tubular casing;

— an electric generator (9) that has a stator (16) and a rotor (15);

wherein said impeller (11 ) is a hollow impeller that has a cylindrical and inner wall that defines an elongated recess (17),

wherein said movement transmission means (14) includes a RPM multiplication means (40), said RPM multiplication means comprising:

— a primary rotating shaft (41 ) that is linked to said impeller (11 ) in such a way to be dragged by said impeller (11 ) at an input rotational speed (Ni);

wherein said RPM multiplication means (40) comprises

— a variable transmission RPM multiplication means (40);

— a regulator means (45) of the gear ratio (N1/N2) of said input rotational speed (Ni) to said output rotational speed (N₂), such that said output rotational speed (N₂) remains substantially unchanged at a predetermined value when said input rotational speed (Ni) changes,

wherein said variable transmission RPM multiplication means (40) is adapted to continuously adjust the gear ratio, i.e. said variable transmission RPM multiplication means (40) is a CVT device, wherein said regulator means (45) of said multiplication means (40) is a closed-loop regulator comprising:

— a reservoir (47) that contains an actuation fluid (48);

— a pump (49) that is mechanically driven by said secondary shaft (42), said pump providing an actuation pressure and/or an actuation flow rate of said actuation fluid (48);

— an actuator (46) that is adapted to operate said RPM multiplication means (40) in order to adjust said RPM ratio (Ni/N₂) responsive to said actuation pressure and/or to said actuation flow rate;

said pump (49) adapted to pump said actuation fluid (48) from said reservoir (47) into said actuator (46), and said fluid connection means (44) that is adapted to return said actuation fluid from said actuator (46) into said reservoir (47),

such that said RPM ratio (Ni/N₂) is adjusted responsive to said input rotational speed (N^, and said output rotational speed (N₂) remains substantially unchanged at said predetermined value when said input rotational speed (Ni) changes,

wherein said actuator (46) has a variable volume chamber (50) for said actuation fluid and an actuation extension member that is adapted to adjust said RPM ratio (Ni/N₂) responsive to an amount of said actuation fluid (48) that is contained within said variable volume chamber, and wherein said fluid connection means comprises:

— a valve (51 ) that is arranged along said duct (44), said valve (51 ) adapted to allow the passage of a predetermined actuation flow rate of said actuation fluid (48), said predetermined actuation flow rate provided by said pump (49) when said output rotational speed (N₂) of said secondary shaft (42) has said predetermined output rotational speed value (Ν₂')

such that upon increasing or decreasing said amount of actuation fluid (48) that is contained within said variable volume chamber (50) said RPM ratio (N₁/N₂) increases/decreases, respectively.

13. An apparatus (10) according to claim 11 or 12, wherein a calibration means (52) of said valve (51 ) is provided for adjusting said predetermined output rotational speed value (Ν₂') responsive to said prefixed actuation flow rate.

14. An apparatus (10) according to claim 1 , wherein said impeller (11 ) and said rotor (15) are adapted to rotate according to respective impeller and rotor spin directions, said impeller spin direction being reversed responsive to the direction of said water flow (1 ), wherein said transmission means (14) comprises a rotor spin direction holding device (60) that is adapted to prevent said rotor (15) from reverting its rotor spin direction when said spin direction of said impeller (11 ) is reversed.

15. An apparatus (10) according to claim 14, wherein said holding device is a coupling device (60) of a first rotating shaft (42) that receives said rotational movement of said shaft (13) of said impeller (11) and of a second rotating shaft (43), which is arranged downstream of said first shaft (42), which transmits a rotational movement towards said rotor (15), said coupling device (60) comprising:

— a direct coupling (63) wherein, when said first shaft (42) rotates according to said predetermined spin direction, said second shaft (43) is dragged by said first shaft (42) according to the same spin direction, and is free with respect to said first shaft (42) when said first shaft (42) rotates according to a reverse direction that is opposite with respect to said predetermined spin direction;

— a reverse coupling (64) wherein, when said first shaft (42) rotates according to said reverse direction, said second shaft (43) rotates according to said predetermined spin direction, and is free with respect to said first shaft (42) when said first shaft (42) rotates according to said predetermined spin direction.

16. An apparatus (10) according to claim 14, wherein said reverse coupling (64) comprises an auxiliary shaft (67) that is arranged substantially parallel to said first shaft (42) and to said second shaft (43), said auxiliary shaft (67) having respective gears comprising an external gear that is adapted to mesh with an external gear (65) of said first shaft (42) and with an external gear (66) of said second shaft (43).

17. An apparatus (10) according to claim 1 , wherein said fixed external tubular casing (30) has a first open end portion (31 ) and a second open end portion (32), and at least one end portion of said casing (30) selected between said first open end portion and said second open end portion has a countersunk part that flares outward of said casing (30).

18. An apparatus (10) for obtaining electric energy from the kinetic energy of a flow of river or sea water, said apparatus (10) comprising:

— a external tubular casing (30) having a first open end portion 31 and a second open end portion (32), said casing (30) adapted to be run through by said water flow(1 ) that flows from said first end portion (31 ) to said second end portion (32), or vice-versa;

wherein at least one end portion selected between said first open end portion (31 ) and said second open end portion (32) is an end portion that has a countersunk part that flares outward of said casing 30;

— an impeller (11 ) from which an engagement portion (12) extends adapted to engage with said water flow (1 ), said impeller (11 ) rotatably mounted within said tubular casing, such that said water flow (1 ) can cause a rotational movement of said impeller (1 1 ) within said fixed external tubular casing;

— an electric generator (9) that has a stator (16) and a rotor (15);

wherein said impeller (11 ) is a hollow impeller that has a cylindrical inner wall that defines an elongated recess (17).