The present invention relates to a water current power plant to be placed under water, comprising several sails or wings that are fastened to a rotary endless chain running between opposite facing, respective turning discs, with the endless chain being forced round, driven by the wings under the influence of the surrounding water, and at least one generator to generate electric energy that is connected with the endless chain. The invention also relates to a method for operation of a water current power plant.

There is an ever increasing need for "green renewable energy". Large ocean currents and tidal waters are considered to be one of the largest renewable energy sources that exist. There are many proposals as to how one shall utilise these resources. Most of these are related to using water turbines in different configurations.

There are also concepts for use of underwater sails for the utilisation of water as an energy source, described in NO 20035448, among others.

JP 410061598 shows an endless system of sails or wings that are driven round two turning discs, where the performance is regulated by the ascent angle of the wings, the number of rotations, area of the wings, etc. US 6,081 ,043 also relates to an endless system of sails or wings, though to be used in a wind power plant, and where the orientation of the wings in relation to the drive cables can be regulated.

Reference is also made to US 1 ,847,855 A1 and US 4,350,474 A, both of these relate to tidal power plants for the generation of electricity.

The object of the present invention is to provide a water power plant that can be lowered into the water to a desired depth, and which can both take up and receive strains from the flowing water to produce electricity continuously.

The above mentioned object with a water power plant as defined in the independent claim 1 is achieved in that the turning discs are mounted in respective frames that can be anchored, and that the endless chain runs freely between the frames and around the turning discs and that a drive gear is connected to, at least, one of the turning discs and is connected with an universal coupling, with said generator being connected to the universal coupling.

Alternative embodiments of the water current power plant are characterised by the dependent claims 2-14.

The endless chain can comprise two endless cables, in which said sails or wings are arranged between the cables, and each cable can run over and around a respective turning disc so that the sails or the wings are rotated between respective pairs of turning discs.

The universal coupling can adjust the speed of the cables with respect to each other, whereby the angle of the sails or wings in relation to the water current is regulated. The universal coupling can also be connected to a drive gear connected to each turning disc in a respective frame.

Furthermore, said frames are preferably anchored so that they can rotate to adjust to the angle of the cables such that the tension in the cables is perpendicular to the rotational axis of the turning discs.

The drive gear can comprise a first pulley fastened to a common rotational axis with a turning disc, which, via a belt or a chain, is connected to a second pulley fastened to a shaft for the universal coupling. Alternatively, the drive gear can be made for shaft operation.

The pairs of turning discs can be arranged to rotate independently of each other and to be controlled by the universal coupling.

In one embodiment the universal coupling can constitute a gear box comprising at least two planetary gears, with the respective shafts of the universal coupling being connected to shafts of the planetary wheels of the planetary gears, and between the ring wheel of the planetary gears, a first conical cogged wheel is placed which, via a shaft, is connected to the generator and a second conical cogged wheel, which, via a shaft is connected to a servomotor. The shaft connected to the generator is preferably arranged to control the common movement of the cables when the generator is running and the shaft connected to the servomotor is preferably arranged to control the differential movement of the cables, independently of said common movement, thus to regulate the angle of the wings between the cables. The universal coupling and the generator can be kept in a watertight housing.

Furthermore the turning discs can be arranged for mutual displacement along said rotational axis, whereby the distance between pairs of turning discs is altered, dependent on the angle of the wings.

In a preferred embodiment the wings can be formed with, at least, a partially arched aeroplane wing shape, where the arched shape is arranged to give the wings equilibrium in the water and any deviations from the equilibrium position are counteracted by the forces that act on the wing.

Said sails or wings can be fastened to a respective cable with the help of clamp couplings, where said clamp coupling comprises a locking mechanism and which is arranged to give the wings a limited movement when they run over the turning discs and otherwise to maintain the wings in a desired position.

Furthermore, the clamp coupling can be arranged to adjust the angle of the wings in the water.

The turning discs can be axially displaceable in the respective frames. Said objects are also achieved with a method as defined in the independent claim 18, by fastening the turning discs in respective frames that can be anchored and to let the endless chain run freely between the frames and round the turning discs, and by connecting a universal coupling between a drive gear and at least one of the turning discs, where the universal coupling controls the common movement of cables of the endless chain, when the generator is running, and controls the differential movements of the cables, independently of said common movement, for the regulation of the angle of the wings between the cables by adjusting the speed of the cables in relation to each other.

According to alternative embodiments of the method, a drive gear can be connected between the universal coupling and the turning discs, and can drive the endless chains around by generation of a pushing force and a lifting force that are transferred to the cables, the wings can be tilted in relation to the water current.

The wings can be fitted on cables, such as wire, rope, steel cable, etc., and adjusted with an pitch angle against the water stream so that they exert a force on the cables that run in a path across the water stream. The force on the wings is generated by drag (pushing force) and lift, which is the principle for an aeroplane wing. One can convert some of the kinetic energy in the water to electrical energy. The sum of all the wings gives a relatively large area against which the water current acts. The appliance is especially adapted to straits and fjords, possibly where one has a natural constriction in the terrain that gives a higher tidal flow velocity. The system can also be used in rivers.

The system can be placed at a depth that prevents it interfering with ships and people, for example, at a depth of 20 metres. The system is easy to scale up, and can be adapted to the individual location by varying:

• The size of the wings

• The number of wings/length on the stretch

• Pitch/angle of attack (can be performed during operation)

The wings are initially fastened permanently to cables with two flexible segments and follow the cables around the turning discs. Relative displacement of the fastening points for the wings on the cables defines the pitch on the wings in relation to the direction of the current.

By altering the distance between the turning discs combined with longitudinal displacement between the cables, the angle of the wings can be altered relative to the direction of the current. The wings have also a limited possibility to rotate vertically. The water current will, to a large extent, affect the vertical angle of the wings.

Because of the shape of the wings, there is one angle that provides an equilibrium position. The wing is preferably self-stabilising. Any deviation from this angle will be counteracted by the forces that act on the wing. When the pushing force from the wings works along the cables (which gives power to the generator) and across the cables ^" , the profile of the endless chain will be in the shape of an arch.

So that the cables will not be pulled out of the grooves in the turning discs, the discs are fastened in a horizontally rotary frame that adapts to the angle of the cables. This means that the tension in the cable is always perpendicular to the shaft.

The cables drive the turning discs, which in turn drive a generator via a drive gear. The drive gear is adapted so that it provides optimal revolutions to the generator in relation to the speed of the cables.

The invention shall now be explained in more detail with the help of an embodiment example shown in the figures, in which:

Figure 1 shows in perspective an embodiment of a water current power plant according to the invention.

Figure 2 shows in perspective an endless chain that is part of the invention.

Figure 3 shows in perspective the water current power plant under the influence of a stream of water.

Figure 4 shows figure 3, but seen more from above.

Figure 5 shows one end of the water current power plant shown in figure 1.

Figure 6 shows figure 5, but without the frame and a watertight housing. Figure 7 shows an outline of a universal coupling for use in the water current power plant according to the invention.

Figure 8 shows a planetary gear that is part of the universal coupling in figure 7.

Figure 9 shows a wing lock according to the present invention.

Figure 10 shows the exploded wing lock shown in figure 9.

As the figures show, an embodiment of the present water current power plant 10 comprises an endless chain 14 which comprises at least two cables 20. Between these cables 20 several sails or wings 12 are arranged with the help of clamp couplings 22, preferably so that the sails or the wings are fastened in the middle and are in equilibrium, but pending on the circumstances they can also be fastened, displaced from their equilibrium position. The cables 20 run over respective turning discs 24 that preferably are placed in pairs in opposite facing frames 16, 18, so that a space is created between the turning discs 24 that the sails or the wings 12 can run between when they go round at the turning discs 24. The sails or the wings 12 are formed so that the water current pushes the wing (drag) at the same time as the water current flows faster behind the surface behind the wing (lift). This gives a resultant power contribution that gives an additional effect on the cables and thus increased power output. The shape of the sails or the wings 12 can therefore be chosen with an arched aeroplane wing form. Alternatively, the wings 12 can be flat on both sides and/or not arched, but this will then lead to a poorer effect.

Said frames 16, 18 can be anchored to the bottom, the banks of a river, possibly to other equipment in the water or the sea, and in such a way that they do not disturb shipping or people. The frames 16, 18 are preferably horizontally rotary and function as mounting for the endless chains 14, drive gear 28 and other equipment for the water current power plant 10. As the figures 3 and 4 show, the endless chain 14 will normally be influenced by the force from the water current and form an arched shape during operation, which means that it is essential that the frames can rotate so that the cables are not pulled out of the grooves in the turning discs 24.

The turning discs 24 are, as mentioned, arranged in pairs in each frame 16, 18, and rotate preferably on the same rotational axis. Pairs of turning discs 24 are arranged to rotate independently of each other and to be controlled by a universal coupling 50. The drive gear 28 is connected to the same rotational axis in the form of a first pulley 32 which is connected to a second pulley on a shaft 40 of the universal coupling 50. The first and the second pulley are connected via a belt or a chain 34 in a generally known way so that the rotation of the turning disc 24, and thus the first pulley 32, drives the second pulley 36 which in turn rotates the shaft 40 of the universal coupling 50. One or two such drive units 28 can be placed in every frame, but it is preferred that there are two drive units 28 arranged to the outer side of respective turning discs 24, so that they do not disturb the passing of the wings at the turning discs 24. The first pulley 32 can be arranged to the same rotational axis as the turning discs 24 and have the same direction of rotation. The drive gear 28 can alternatively be made with a shaft operation instead of a belt or a chain operation as described above. Furthermore, the turning discs 24 are arranged so that they can be displaced axially along the axis of rotation so that the distance between them can vary with the variation of the pitch of the wings 12.

Said universal coupling 50 is arranged in one or both frames 16, 18, where the universal coupling is connected to a generator 60 to generate electrical energy. The universal coupling 50 and the generator 60 can be held in a watertight housing 26. Figures 5 and 6 show one end of the water current power plant 10, with and without the frame 16 and housing 26, respectively. As it can be seen, a drive gear 28 is connected to a respective shaft 40 of the universal coupling 50 for the operation of the generator 60.

In an alternative embodiment (not shown) the generator 60 can be placed out of the water. The generator 60 can in such case be connected in a

corresponding way to the universal coupling 50 and be connected with a rigid or non-rigid connection. One advantage with such a solution is that it will ease the maintenance of the generator for one thing. In addition to the operation of the generator, the universal coupling 50 is arranged to individually adjust the speed of each cable 20 in the endless chain 14 for the adjustment of the angle of the wings 12 in the water. This can be carried out during operation of the water current power plant 10, in that said universal coupling 50 can, for example, be made up of a gear box with two planetary gears 42. The construction of a planetary gear is considered to be known to a person skilled in the arts and will therefore not be explained in more detail. A planetary gear is a variant of the cogged wheel gear. It is composed of a set of cogged wheels: The sun wheel innermost, then the planetary wheels and the ring wheel outermost with cogging. The good quality gives the planetary gear a long lifetime and it can transfer a high torque in addition.

The torque that is applied to the shafts 40 of the universal coupling from the drive units 28, is transferred to the planetary wheels 46 which in turn is distributed to the sun wheel 44 and the ring wheel 48. If the ring wheel 48 stands still all movement is transferred to the sun wheel 44. The two planetary gears 42 are arranged facing each other so that common movements of the cables 20 in the endless chain 14 lead to a common angle movement of the planetary gears. The ring wheels 48 are fitted with tilted teeth that face each other and placed in between them is a first conical cogged wheel 56 which, via a shaft 54, is connected to the generator 60 and a second conical cogged wheel 58 which, via a shaft 52 is connected to a servomotor (not shown). The shaft 54 connected to the generator 60 controls the common movement of the cables 20 when the generator is operating and the shaft 52 connected to the servomotor controls the differential movement of the cables 20, independently of said common movement, to regulate the angle of the wings 12 between the cables 20. Therefore, it is possible in this system to mechanically isolate common and differential moments to different shafts. A differential moment which changes the angle of the wings 12 is distributed to the servomotor and common movements that represent energy in the system are distributed to the generator 60.

The moment which is applied to the shafts 40 of the universal coupling from the drive units 28 could alternatively be transferred to the sun wheel 44, but this would then lead to a different gear transmission. When the wings 12 with pitch shall pass the turning discs 24, the wings can be ^~ bent in relation to the clamp coupling 22. The clamp coupling should therefore be flexible. However, a flexible lock can possibly not provide sufficient rigidity on the long stretches (where one can expect local turbulence) to guarantee that the wings do not twist round and get stuck.

This problem can be solved as shown in figures 9 and 10 by having a clamp coupling which allows limited movement. The clamp coupling must then ensure that there is sufficient flexibility around the turning discs, but at the same time, is small enough to hold the wings within acceptable angles. Furthermore the clamp couplings 22 can have a spring mechanism (i.e. be "self adjusting"). Examples of satisfactory locking characteristics in such a clamp coupling will be: Give enough support to the wings when they are in the long stretches; be flexible enough to go around the wheels, allow altering of the pitch of the wings, not corrode/be destroyed in seawater; and to permit some shortening of the coupling around the wheels.

An important function for the locking function of the clamp coupling is to let the wings go round the turning discs. As the two couplings are not placed directly opposite each other on the cables, the one lock can begin to travel round the turning disc before the other. This can lead to the wing being twisted a little and the coupling ought to be flexible enough for this movement not to cause much tension. Another reason for it being practical, to permit a certain degree of rotation is that there may be uneven water currents so that the force on the top or bottom side of the wing becomes larger for a short while. The wing can then rotate somewhat, but because of the shape of the wings a force balance will come into being so that the wing goes back to its neutral position. Even with a steady water current the force on the upper part of the wing becomes greater than the force on the lower part when the wing is twisted so that the upper part is more perpendicular. This ensures that the wing can rotate about its centre axis, and if it rotates too far a corresponding situation will arise for the lower part of the wing. The principle of this design is that when the cylinder 70 is rotated, the inclined surfaces of the wing 76 will glide against the inclined surfaces 78 in the crown 72, and the crown will be forced downwards in a groove in the housing 80. Here is a spring 74 which is compressed against the rear wall of the housing. When the cylinder is rotated a certain angle, for example 15°, in one direction, the wings 76 hit the walls of the crown 72 and can then not rotate any further. If one continues and tries to rotate the cylinder 70 the force between the wings and the walls of the crown will counteract this movement. The crown 72 can not rotate as it lies in a groove in the housing 80. When the force moment ceases, the spring 74, which was compressed, will return to its neutral position and then push the crown 72 upwards again. This will lead to the inclined surfaces 78 in the crown 72 pushing the inclined surfaces of the wings 76 to the side and the cylinder 70 being rotated back to its initial position.

The housing 80 has couplings 82 at the bottom for fastening of the cables 20 while the cylinder 70 comprises a fastening point 84 for fastening to the wing 12.

Compensation for the mounting point is also wanted for the plant. When the plant is operating the cable pair 20 can lie in an arch. This is, to a large extent, compensated for in that the stations, i.e. the frames 16, 18, rotate, but as the outermost cable will have to be slightly longer than the innermost cable, a situation can arise that the cables do not enter the grooves perfectly on the turning discs 24. It is assumed that this problem can be compensated for by moving the mounting point in the respective frame (let it be off-centre). In practice this can be carried out by pushing the discs 24 in parallel along the shaft with the help of hydraulics.