WO2013079831A1

WO2013079831A1 - Device for recovering energy from sea currents or bodies of flowing water

Info

Publication number: WO2013079831A1
Application number: PCT/FR2012/052058
Authority: WO
Inventors: Jacques Ruer; Jean-François DAVIAU
Original assignee: Sabella
Priority date: 2011-09-19
Filing date: 2012-09-14
Publication date: 2013-06-06
Also published as: FR2980245B1; FR2980245A1

Abstract

The invention relates to a device (10) for producing energy from sea currents or bodies of flowing water. The device is characterised in that: it comprises an electric generator (16) designed to transform mechanical energy into electrical energy, said generator (16) being arranged above the surface of the water; and it comprises a torsion line (14) connected to the electric generator (16) and capable of being twisted by means of at least two rotors (12) which are secured coaxially to the line (14), which extend in a vertical plane and which can be rotated by water currents, each rotor (12) comprising a tank (26) located at the centre of the rotor and capable of stabilising the rotor (12) at a given buoyancy by means of the filling said tank (26).

Description

Device for recovering energy from

marine currents or streams.

The present invention relates to devices for the generation of energy from unidirectional ocean currents or streams, such as ocean currents and fluvial or bidirectional currents such as estuarine currents.

More particularly, it relates to a power generating device for converting hydraulic energy into mechanical energy, which is then converted into electrical energy by an alternator.

It is known from the state of the art such energy recovery devices consist of a tidal turbine comprising a turbine partially or totally immersed using the kinetic energy of the water currents.

EP 2216543 discloses an electric power generator from the flow of water. The generator comprises a rotating body immersed and configured to rotate about an axis itself connected to a power transmission unit.

It is also known documents US 2501696 and WO2006054084 turbines totally or partially immersed and moored at the bottom of the water to extract the kinetic energy of a tidal stream or an ocean current whatever its direction .

However, these systems have an isolated rotor that does not provide enough power due to the limitation of the diameter of the latter with respect to the depth of the water or due to the low speed of the water flow.

The object of the present invention is to overcome these disadvantages and to provide an energy recovery device to provide more power than the devices of the prior art, while minimizing the financial investment.

For this purpose the device for the production of energy from marine currents or streams, remarkable in that it comprises an electrical generator adapted to transform the mechanical energy into electrical energy, the generator being disposed above of the surface of the water, and in that it comprises a torsion line connected to the electric generator on the one hand and on the other hand adapted to be twisted by means of at least two rotors fixed coaxially on the line, and extending in a vertical plane and adapted to be rotated by the water currents, each rotor comprises a reservoir located at the center of the rotor and adapted to stabilize the rotor at a determined waterline by filling said tank.

Thanks to these provisions it is possible to have several rotors without impact on the cost of the support structure. The cost of the line is low.

According to other characteristics:

the line is a flexible element resistant to corrosion;

the line consists of several consecutive rigid elements interconnected by joints adapted to be deformed in torsion so as to transmit the movement to the generator;

two consecutive rotors are spaced apart by a distance of between five and ten times the diameter of said rotors;

the line is disposed substantially tangent to the axis of the generator shaft at a first end, and is disposed substantially horizontally at the mating point with the first rotor;

the device comprises a speed multiplier disposed between the first end of the line and the generator;

the tank is divided into several watertight compartments;

the rotors comprise blades having an inclined face of a tilt angle β relative to the plane perpendicular to the line and a dihedral angle α with respect to a longitudinal plane containing the line, the angle of deviations β is included between 0 ° and 60 °, preferably between

20 ° and 40 ° and the angle of repose a is between 20 ° and 60 °, preferably between 30 ° and 50 °;

the device is made of a material of density close to the surrounding water;

each blade has at its distal end a float to simplify the adjustment of the buoyancy;

the line is attached to the rotor by articulated attachment means;

the blades are mounted swinging on the rotor.

The present invention will be better understood on reading the following detailed description based on the appended drawings in which: FIG. 1 represents a device for recovering energy according to the invention,

FIG. 2 represents a sectional view of a rotor of the device according to the invention,

FIG. 3 represents a front view of the rotor illustrated in FIG. 2, FIGS. 4a and 4b respectively illustrate the high and low positions of the rotor with respect to the surface of the water, and a schematic curve of the movement of the rotor.

FIG. 5 illustrates the position of the rotor in the water after an impact with a drifting object,

FIGS. 6a and 6b illustrate the energy recovery device according to a second embodiment, in a first and a second position respectively,

FIG. 7 illustrates a sectional view of a rotor according to the second embodiment,

FIG. 8 illustrates a schematic sectional view along a plane perpendicular to the axis of the rotor of the rotor according to the second embodiment.

In the description that follows, the terms high, low, vertical, horizontal will be used according to their usual meanings in the terrestrial reference system.

The tidal turbines make it possible to exploit the kinetic energy caused by the movement of water masses, due in particular to currents of the oceans or tides. However, it is necessary that the speeds of the currents are sufficient to consider an economic exploitation of this form of energy. The currents are particularly strong where the configuration of the coast causes a local velocity enhancement of the current 20. The favorable sites are therefore always located near a shore in limited water depths, and therefore the dimensions of 'tidal turbines are limited by the depth of the place where it is arranged. It is already known facilities with a large number of turbines implanted next to each other, whose energy is exported ashore by submarine power cables, for a large-scale operation. However, these provisions require significant and expensive maintenance, because of the aggressive environment and difficult to access in which they are.

The present invention provides a recovery device 10 energy from marine currents, fluvial or estuarine, to improve the efficiency of the recovered power through the establishment of a plurality of rotor 12 turbines, while minimizing investment. More particularly, the energy recovery device 10 according to the invention comprises a plurality of rotors 12 immersed and disposed co-axially on the same support line 14 as can be seen in FIG.

Line 14 is connected at a first end to an electric generator 16, itself arranged on a boat 18 anchored at the bottom to the bank. When the direction of the current 20 is unidirectional, for example for the ocean currents, or the fluvial currents, the water line 14 is arranged downstream with respect to the boat 18. The line 14 is mounted substantially tangent to the axis of the shaft 22 of the generator 16 so as to avoid any loss by an intermediate piece and arranged substantially horizontal and coincident with the longitudinal axis of the rotor at the point of anchoring with the first rotor. The shape of the line 14 can be adjusted thanks to some weights and floats 32 distributed along its length, in particular to avoid significant curvatures, when the current 20 is very low and the line 14 relaxed.

Line 14 supports a plurality of rotors 12 which are each driven by blades 24 to which they are attached. The rotors 12 are spaced apart from one another at regular intervals, preferably at a distance of between 5 and 10 times the diameter of the circle drawn by the rotating blades 24, according to the local turbulence of the site which dissipates more or less rapidly the wake.

The rotors 12 are mounted coaxially on the line 14. When the device 10 is installed through a stream 20 of water, the blades 24 are rotated, and the line 14, on which the rotors 12 are fixed, undergoes a twisting effort. The torsional force is transmitted to the generator 16 capable of transforming the mechanical energy into electrical energy.

According to a first variant embodiment, the water line 14 is a flexible element resistant to corrosion. However, if the torsion torque is too high and can cause irreversible deterioration of the latter, the line 14 may be composed of a series of rigid elements interconnected by rubber joints that provide the same flexibility while allowing the transmission of torque to the generator 16. For example, the joints may be ball joints type or cardan. Of preferentially a speed multiplier is disposed between the line 14 and the generator 16 to reduce the mass and the cost thereof.

In order to stabilize the rotors 12, the buoyancy of the latter is adjusted so that the blades 24 are flush just below the surface of the water. For this purpose the rotor comprises a reservoir 26, or ballast, partially filled with water which ensures stability of the rotor at a given immersed level. When the current is low, the rotation of the rotor is slow. The air is always up in the tank 26. The center of gravity 28 of the rotor is then below the center of buoyancy 30 which is almost on the axis. This allows the rotor to stand spontaneously vertical in the water, even in the absence of the horizontal forces of the line 14.

Preferably, the reservoirs 26 are ideally half filled with water. For this filling value, the stabilization torque brought by the water is maximum.

According to an alternative embodiment, the reservoir 26 is divided into several compartments sealed with respect to each other, as can be seen in FIG. 2. The partitioning is carried out in planes perpendicular to the axis of rotation of the rotor so as to limit the movement of liquids. Thanks to these provisions, it is possible to obtain a large tank volume 26 ensuring greater stability, without the risk of a free-surface phenomenon occurring.

The adjustment of the buoyancy can be simplified by adding to the end of each blade a float as is visible in Figure 3.

Preferably, the buoyancy is set to zero, so as to minimize unsinkable portions. Indeed the vertical displacement of the rotor around its average position during a rotation increases with the reserve of buoyancy. The more important it is, the more the blade comes out of the water and makes the rotor re-dive with each blade passage. This phenomenon causes a loss of energy, since the path traveled in the air by the blade is more important when climbing out of the water than during the descent. It is therefore necessary to look for the minimum buoyancy to cancel all these problems. For this purpose the weight of the emergent blade must be counterbalanced by the weight of the tank 26 of water, taking into account the respective lever arms.

When the device 10 for the production of energy according to the invention is put through a stream 20 of water, the generator 16 being located upstream and the line 14 downstream, the multiple rotors 12 are rotated, and the line 14 is subjected to a torsion force which is transmitted to the generator 16. It is thus possible to have several rotors 12 without affecting the cost of the device 10.

According to an alternative embodiment, the blades 24 associated with each rotor have, in the vertical plane containing the axis of rotation, a first angle of inclination, said dihedral angle α, with respect to the axis of rotation, and presents , in the vertical plane perpendicular to the axis of rotation, a second angle β of inclination, with respect to a vertical axis, so that the blades 24 are sloping.

This configuration avoids the risk of attachment of floating debris on the blades 24. The debris can easily slide backwards and escape. In addition the dihedral angle has favored the spontaneous maintenance of the axis of rotation in the stream and thus improves the stabilization of the rotors 12.

However, in the event of a large impact with a large floating object, the line 14 is made deformable, as can be seen in FIG. 5, so that the rotor is deflected to limit the impact force of the impact. In addition, to withstand impacts with floating objects such as tree trunks, the device is made of a material of density close to the surrounding water 1. For example, the blades 24 are made of hybrid metal-composite material , laminated wood or marine plywood.

Thus, in the event of an impact, as can be seen in FIG. 5, the rotor plunges under the object. The joints at the attachment points of the line 14 allow the tilting of the rotor, which limits the force on the blade which is shocked. Likewise the dihedral angle has attenuated the effect of the shock.

The first embodiment described above relates to a device 10 for energy recovery implemented through a stream of unidirectional water. The invention also relates to such a device 10 adapted to operate for a bi-directional water stream 20, such as tidal currents and estuary water currents, and which will be described in a second embodiment.

The device 10 for energy recovery according to the second embodiment is visible in Figures 6a, 6b and 7 appended. The device 10 is adapted to operate for a first direction of current 20 and for a second reversed direction.

In this embodiment, the line 14 is fixed to an upstream boat 18a on which to find the generator 16 and a downstream boat 18b which carries a simple stop-stop. The distance between the boats is such that the hitch is sufficiently tight. The rotors 12 are provided to operate in both directions of current 20, and the blades 24 of the rotors 12 are drawn symmetrically.

To avoid the accumulation of debris on the rotors 12, a tilt is not essential, since the rotation frequently changes direction, so that a hanging debris emerges at most a few hours after capture. On the other hand, a high dihedral angle a is useful for stabilizing the position of the rotors 12 and limiting the forces on the blades 24 in the event of impact with a drifting object. When the current 20 changes, the blades 24 swing about a substantially horizontal axis of articulation so that the dihedral angle a is symmetrical with respect to the vertical axis. Preferably, the dihedral angle α is between 30 ° and 45 °. On the other hand the profile of the blades 24 is symmetrical with respect to the central axis of the blade.

When the blade is tilted, it turns at a large angle, of the order of 60 ° to 90 °. In order not to slow down the tilting movement, the blade and the rotor body are spaced from one another at the joints, so as to limit the friction between these two elements. The blades 24 have at their inner end located in the body of the rotor, a support lug which is in contact, in their tilted position, with one of the walls delimiting one or other of the compartments of the reservoir 26, as visible In this configuration, the central part between the compartments is open to the ambient environment, so that the sludge does not remain trapped. The tabs may advantageously be provided with springs, or rely on springs mounted in the central portion. In case of impact with a drifting object, the blade can then swing from an angle greater than the dihedron a normal, which limits the impact and promotes the release of the object.

Preferably, the weight of the blades 24 is adjusted so that the tilt introduces only limited parasitic forces and does not disturb the stability in the vertical plane of the rotor.

Claims

claims

1. Device for the production of energy from marine currents or streams, characterized in that it comprises an electric generator (16) adapted to transform the mechanical energy into electrical energy, the generator (16) being arranged above the surface of the water, and in that it comprises a line (14) of torsion connected to the generator (16) electric on the one hand and secondly adapted to be driven in torsion via at least two rotors (12) coaxially fixed on the line (14), and extending in a vertical plane and adapted to be rotated by the water currents, each rotor (12) comprises a reservoir (26); ) located in the center of the rotor and adapted to stabilize the rotor (12) at a determined flotation by filling said tank (26).

2. Device for the production of energy according to claim 1, characterized in that the line (14) is a flexible element resistant to corrosion.

3. Device for the production of energy according to claim 1, characterized in that the line (14) consists of several consecutive rigid elements interconnected by joints adapted to be deformed in torsion so as to transmit the movement until to the generator (16).

4. Device for the production of energy according to one of the preceding claims, characterized in that two consecutive rotors (12) are spaced apart by a distance of between five and ten times the diameter of said rotors (12).

5. Device for the production of energy according to one of the preceding claims, characterized in that the line (14) is disposed substantially tangent to the axis of the shaft (22) of the generator (16) at a first end , and is disposed substantially horizontally at the point of mooring with the first rotor.

6. Device for the production of energy according to one of the preceding claims, characterized in that a speed multiplier is disposed between the first end of the line (14) and the generator (16).

7. Device for the production of energy according to the preceding claim, characterized in that the reservoir (26) is divided into several sealed compartments.

8. Device for the production of energy according to the preceding claim, characterized in that the rotors (12) comprise blades (24) having an inclined face of a tilt angle β relative to the plane perpendicular to the line (14). ) and a dihedral angle α with respect to a longitudinal plane containing the line (14), the angle of deviations β is between 0 ° and 60 °, preferably between 20 ° and 40 ° and the angle of dihedral a is between 20 ° and 60 °, preferably between 30 ° and 50 °.

9. Device for the production of energy according to the preceding claim, characterized in that said device is made of a density material close to the surrounding water.

10. Device for the production of energy according to the preceding claim, characterized in that each blade (24) has at its distal end a float (32) for simplifying the adjustment of the buoyancy.

1 1. Device for the production of energy according to the preceding claim, characterized in that the line (14) is attached to the rotor by articulated attachment means.

12. Device for the production of energy according to the preceding claim, characterized in that the blades (24) are pivotally mounted on the rotor.