Patent Description:
The wave energy recovery apparatus according to the invention is suited very well for instance to be used in connection with panels or flaps or essentially platelike wing elements, later called shorter only as panels, hinged with their lower edge to make a reciprocating movement caused by wave energy or tidal energy of seawater as shown for example in the US patent No. <CIT>). The wave energy or tidal energy collected is further converted underwater with a conversion unit for instance to electric energy. For the sake of simplicity, only the term wave energy is later mentioned when both the wave energy and the tidal energy of seawater are meant.

According to prior art there are various types of wave energy recovery systems where the arrangements include a base, and, for instance, one or more panels pivotally connected to the base to make a reciprocating or oscillating movement about a rotation axis or pivot axis in response to wave forces or tidal forces as shown for example in the US patent No. <CIT>) that presents, among other things, how to drive the wave energy conversion system. The oscillating movement is then converted for example to electric energy with the help of a power-take-off (PTO) unit equipped with a power-take-off (PTO) machinery comprising a generator or alike as shown for example in the Finnish patent No. <CIT>.

The PTO can also be placed inside the reciprocating structure of the wave energy recovery apparatus, for instance, inside the panel as shown for example in the US patent publication No. <CIT>, or inside the tubular main shaft of the panel.

Commonly, in known wave energy converter systems it is difficult to efficiently transform the energy captured from the reciprocating movement of waves into electrical energy. For instance, the reciprocating movement of panels causes the rotors and axles of the electric generators to undergo a bi-directional rotational movement with a stop in connection with every reversing. As a consequence, the generators with components connected to them are prone to fatigue and further to breakages. In addition, controlling of the electric generators that make the reciprocating movement is complicated and difficult.

For that reason, there have been several attempts to transform the reciprocating movement of the movable element in a unidirectional movement of the rotor of the generator. For instance, international patent publications <CIT>, <CIT> and <CIT> present different solutions to change the reciprocating movement caused by waves into a unidirectional movement of the rotor of the generator when recovering wave energy.

All these solutions of the WO publications mentioned above use at least two one-way clutches, freewheels or other anti-reverse mechanisms for each generator, which are continuously engaged and disengaged to ensure that the reciprocating movement caused by waves is changed to a unidirectional movement of the rotor of the generator. However, the continuous engagement and disengagement of the one-way clutches, freewheels or other anti-reverse mechanisms mentioned above cause mechanical wear and failures in the PTO systems. In addition, the PTO structures of the solutions of these WO publications are extremely complicated, which also cause the PTO structures to be prone to mechanical wear that reduces the lifetime of the solutions of these WO publications. Therefore, there is still a need for more efficient and/or more robust PTO systems.

An international patent publication <CIT> discloses a wave energy recovery apparatus with a power-take-off arrangement comprising at least two power-take-off (PTO) units with one or more generators to convert kinetic energy of waves or tidal currents to electricity, at least two gear transmissions and at least two one-way clutch mechanisms where the gear transmissions and one-way clutch mechanisms are operatively connected between the panel and the generators, whereby the panel is arranged to rotate a half of the generators when the panel is rotating into one direction and another half of the generators when the panel is rotating into the opposite direction. However, the apparatus does not comprise gear transmissions for each generator that comprise motionless gear rims meshing with gearwheels coupled to the rotation axles of the generators.

The object of the present invention is to eliminate the drawbacks described above and to achieve a reliable, compact, economical and efficient wave energy recovery apparatus with an improved power-take-off (PTO) arrangement in order to be able to capture a maximum amount of available wave or tidal energy and which apparatus is easily controllable. Another object of the present invention is to make the installation, maintenance and repairs of the wave energy conversion apparatus easy and fast, and to make it possible to easily disconnect/connect the electric generators from/to the other structure without disturbing the functions of the other structure. Thus, for example one generator can be removed and replaced with another generator without disturbing the whole system. The wave energy recovery apparatus with a power-take-off arrangement according to the invention is characterized by what is presented in the characterization part of claim <NUM>. Other embodiments of the invention are characterized by what is presented in the other claims.

An aspect of the invention is to provide a wave energy recovery apparatus with a power-take-off arrangement comprising at least a base, a reciprocating panel, two power-take-off (PTO) units with one or more generators to convert kinetic energy of waves or tidal currents to electricity, at least two gear transmissions and at least two one-way clutch mechanisms, all operatively connected between the panel and the generators. The panel is arranged to rotate a half of the generators when the panel is rotating into one direction and another half of the generators when the panel is rotating into the opposite direction. The generators of the apparatus are fastened to the lower edge of the panel and are arranged to be rotated by the panel, and the apparatus comprises a gear transmission for each generator, which gear transmission comprises a motionless gear rim meshing with a gearwheel coupled to the rotation axle of the generator. Advantageously, the direction of rotation of each generator is controlled with one one-way clutch mechanism, which one-way clutch mechanism is preferably arranged to allow the generator to have only one direction of rotation.

The solution of the invention has significant advantages over the solutions of the prior art. The number of relatively small PTO units and/or electric generators make it possible to place several PTO units and/or generators along the shaft of the reciprocating panel. This allows a torque induced stress range to be more evenly distributed along the panel thus reducing the peak stress range induced by the PTO torque and thus increasing the fatigue life of the panel. That also allows the reduction in the size of the PTO components and thus the reduction in costs. The small size of the PTO units and/or generators also makes it possible to incorporate the PTO units and/or generators into the panel. With the help of a one-way clutch, such as a sprag clutch, one or more generators can be arranged to rotate to one direction only and another one or more generators can be arranged to rotate to the opposite direction only. Thus, a first half of the generators rotates all the time in one direction, i.e. clockwise, and a second half of the generators rotates all the time in opposite direction, i.e. counter clockwise. Yet one advantage is that the arrangement comprises at least two PTO units with generators. In that case, the PTO units can be taken separately to service and changed if necessary. Yet one advantage is that the PTO units can be installed on both sides of the panel.

In the following, the invention will be described in detail by the aid of examples by referring to the attached simplified and diagrammatic drawings, wherein.

The basic idea of the present invention is to achieve an arrangement, which comprises at least a reciprocating panel <NUM> hinged with its lower edge, and at least two power take-off (PTO) units <NUM> with their generators <NUM>. Advantageously, the PTO units <NUM> or at least their generators <NUM> are relatively small. In addition, each generator <NUM> is arranged to rotate only to one direction, either clockwise or counterclockwise. Preferably, the arrangement comprises an even number of generators <NUM> of which a half rotates clockwise, and another half rotates counterclockwise when seen from the same direction. At minimum the arrangement comprises two generators <NUM> but the number of generators can be also bigger.

<FIG> presents in a simplified oblique top view an advantageous embodiment of the wave energy recovery apparatus according to the invention. The wave energy recovery apparatus comprises at least a base <NUM>, a hinged panel <NUM> reciprocating about the center axis of its pivot shaft. Preferably, the rotation angle of the panel <NUM> is at maximum ±90º from the vertical position. A transmission line <NUM> is used to transmit the produced electricity to further use.

The reciprocating panel <NUM> oscillates on the base <NUM> back and forth with the movement of seawater for recovering kinetic energy like wave energy of seawater. The panel <NUM> and the tubular shaft <NUM> rotate back and forth together simultaneously and at the same speed of rotation. At the production site the base <NUM> is preferably mounted onto the bottom of the sea, but it can also be near the bottom supported by pillars.

<FIG> present the advantageous embodiment of the wave energy recovery apparatus according to <FIG> in more detail. In <FIG> the arrangement is presented in a side view and in a simplified and diagrammatic way. <FIG> presents in a side view and in a simplified and diagrammatic way the reciprocating panel <NUM> with generators <NUM> according to the arrangement of <FIG>. <FIG> presents in a side view and in a simplified and diagrammatic way the motionless lower part <NUM> of the arrangement according to <FIG>, whereas <FIG> presents in a top view and in a simplified and diagrammatic way and partially cross-sectioned the wave recovery arrangement according to <FIG>, and <FIG> presents in a simplified and diagrammatic way the wave recovery arrangement according to <FIG> seen cross-sectioned along the line A-A in <FIG>.

The wave energy recovery apparatus according to the invention comprises a reciprocating hinged panel <NUM>. The panel is fitted at its ends with bearings that are in bearing housings <NUM> located at the ends of the panel <NUM>. The bearing housings <NUM> are fastened to the base <NUM>. The panel <NUM> has a downwards opening recess 2b that is almost as wide as the panel <NUM>. The recess 2b makes room for the motionless lower part <NUM> of the arrangement. Thus, the panel <NUM> is able to make a reciprocating rotational motion partially around the motionless lower part <NUM>.

The arrangement according to the invention comprises six generators <NUM> that are fastened to the lower edge of the panel <NUM> with fastening elements <NUM>. Again, the generators <NUM> may be more or less than six but, however, always an even number, for example <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or even more. Preferably, the first half of the generators <NUM> are fastened to the first side of the panel <NUM> and the second half of the generators <NUM> are fastened to the second side of the same panel <NUM>.

Advantageously, all the generators <NUM> are substantially similar. In addition to characteristic components, each generator <NUM> comprises a gearwheel <NUM> of relatively small diameter and a one-way clutch mechanism <NUM>, which both are mounted on the same axle. The one-way clutch mechanism <NUM> is operatively coupled between the generator axle and the gearwheel <NUM> axle and is arranged to allow the generator axle to rotate only to one direction, either clockwise or counterclockwise. In addition, the generators <NUM> on the first side of the panel <NUM> are in reverse direction compared to the generators <NUM> on the second side of the panel <NUM>. Thus, when gearwheels <NUM> of the generators <NUM> on the first side of the panel <NUM> are directed towards the second end of the panel <NUM> the gearwheels <NUM> of the generators <NUM> on the second side of the panel <NUM> are directed towards the first end of the panel <NUM>. In that case, there is more room to arrange the gear assembly. For the sake of clarity only four generators <NUM> are presented in <FIG>.

<FIG> presents in a side view and in a simplified and diagrammatic way the motionless lower part <NUM> of the arrangement according to <FIG>. The lower part <NUM> comprises a tubular shaft <NUM> that is supported and fastened to the base <NUM> with support legs <NUM>. The tubular shaft <NUM> comprises on its outer circumference a number of motionless gear rims <NUM>, in this case six substantially similar gear rims <NUM>, one for each generator <NUM>. The gear rims <NUM> are arranged to mesh with the gearwheels <NUM> of the generators. The gear rims <NUM> and the gearwheels <NUM> meshing with each other form a gear transmission 11a for the generators <NUM> of the arrangement according to the invention.

The diameter of the gear rims <NUM> is relatively big compared to the diameter of the gearwheels <NUM>. Therefore, the transmission ratio between the gear rim <NUM> and the gearwheel <NUM> is relatively great. For example, the transmission ratio is greater than <NUM>, suitably greater than <NUM> and preferably greater than <NUM>. The greater the transmission ratio the faster the generators <NUM> rotate when the panel <NUM> makes its relatively slow reciprocating motion.

It is common to all the embodiments of the invention that the arrangement comprises at least two PTO units <NUM> that each may comprise one or more generators <NUM>. Also, the generators are relatively small in size and arranged to be rotated fast by different types of gear transmissions. For example, when the generators <NUM> are rotated through a gear transmission the transmission ratio is greater than <NUM>, suitably greater than <NUM> and preferably greater than <NUM>. The greater the transmission ratio the faster the generators <NUM> rotate when the panel <NUM> makes its relatively slow reciprocating motion.

Further in common is that a half of the generators <NUM> are rotated only to one direction and another half of the generators <NUM> are rotated only to the opposite direction. In that case, seen from the same direction the first half of the generators <NUM> are rotated, for example, clockwise and the second half of the generators <NUM> are rotated counterclockwise, or vice versa. Thus, the first half of the generators <NUM> are rotated when the panel <NUM> makes its reciprocating movement to the first direction and the second half of the generators <NUM> are rotated when the panel <NUM> makes its reciprocating movement to the second direction that is opposite to the movement of the first direction. This kind of operation is arranged by the use of one-way clutch mechanisms <NUM> that are placed between the movement of the panel <NUM> and the rotation of the axles of the generators <NUM>.

Claim 1:
Wave energy recovery apparatus with a power-take-off arrangement comprising at least a base (<NUM>), a reciprocating panel (<NUM>) capable of rotating in one direction and in an opposite direction, two power-take-off (PTO) units (<NUM>) each PTO unit comprising one or more generators (<NUM>) to convert kinetic energy of waves or tidal currents to electricity, at least two gear transmissions (11a) and at least two one-way clutch mechanisms (<NUM>) where the gear transmissions (11a) and one-way clutch mechanisms (<NUM>) are operatively connected between the panel (<NUM>) and the generators (<NUM>), and the panel (<NUM>) is arranged to rotate a half of the gears and generators (<NUM>) when the panel (<NUM>) is rotating into the one direction and another half of the gears and generators (<NUM>) when the panel (<NUM>) is rotating into the opposite direction, characterized in that two or more generators (<NUM>) that are fastened to a lower edge of the panel (<NUM>) and are arranged to be rotated by the panel (<NUM>), and that the apparatus comprises a gear transmission (11a) for each generator (<NUM>), which gear transmission (11a) comprises a motionless gear rim (<NUM>) meshing with a gearwheel (<NUM>) coupled to a rotation axle of the generator (<NUM>).