NO345898B1

NO345898B1 - An apparatus and a method for harvesting energy from ocean waves

Info

Publication number: NO345898B1
Application number: NO20200363A
Authority: NO
Inventors: Lyder Moen
Original assignee: Ocean Energies As
Priority date: 2020-03-26
Filing date: 2020-03-26
Publication date: 2021-10-04
Also published as: AU2021242147A1; NO20200363A1; CA3171420A1; EP4127451A1; EP4127451A4; WO2021194351A1; AU2021242147B2

Description

AN APPARATUS AND A METHOD FOR HARVESTING ENERGY FROM OCEAN WAVES

The present disclosure is related to an apparatus and a method for harvesting energy from ocean waves. More specifically, the present disclosure is related to an apparatus and a method for transforming linear motion from ocean waves into rotation for rotating a machinery. The energy harvested is utilized to effect rotation of a driving machinery. The driving machinery may for example be a generator for generating electric power, a pump or a compressor driven by a rotating shaft. More particularly, the disclosure is related to an apparatus for transforming ocean wave motion into rotation wherein the apparatus comprises a rotatable main shaft comprising a crank shaft provided with a crank pin operatively connected to a drive system for rotating the crank shaft.

The apparatus disclosed herein has an operating principle being similar to for example a large ship propulsion diesel engine, but with the major difference that the combustion pulses of a diesel engine is replaced by energy provided by means of at least one pushpull drive system being responsive to a vertical movement vector of a floating object.

Ocean waves, and in particular ocean swells, represent large amounts of energy and are regarded as one of the larges resources of available renewable energy on the planet Earth. However, a major challenge related to harvesting energy from ocean waves is the robustness of a harvesting apparatus required to withstand extreme physical loads that may occur, and thus the cost of producing and maintaining such an apparatus.

There is therefore a need for a relatively simple and reliable apparatus for harvesting energy from ocean waves, wherein the apparatus is sustainable and throughout its lifetime may operate at least in economical balance.

Publication CN206860356U discloses an apparatus for transforming ocean wave motion into rotating energy by means of a rotatable axle comprising a crank shaft. The crank shaft is rotated by means of a floating buoy being moved in response to waves. The crank shaft forms part of an apparatus arranged on a floating vessel. The apparatus of CN206860356U is tailor-made to a certain amplitude of the ocean waves.

Publication US2019285044 A1 discloses an ocean wave power plant comprising a support structure. The support structure is terminated in a lower end with a fastening bracket which can be anchored in a single point to a mass when deployed in the sea. A submergible uplift floating body is providing buoyancy for the ocean wave power plant when deployed in the sea. The uplift floating body is attached to the support structure, an electric power generating subsystem supported by a platform is terminating the support structure in an upper end of the support structure. A transmission member is attached in one end to a floating body and in another end to the power generating subsystem transferring wave motion from the floating body to the power generating subsystem.

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

The object is achieved through features, which are specified in the description below and in the claims that follow.

The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

In a first aspect of the invention there is provided an apparatus for harvesting energy from ocean waves when being arranged in connection with a floating object moving in the waves, the apparatus comprising:

- a rotatable main shaft for driving a machinery, the rotatable main shaft comprising a crank shaft provided with a crankpin; and

- a drive system for rotating the crank shaft, wherein the drive system comprises:

- a first drive element and a second drive element for operative connection to each other, one of the first drive element and the second drive element being movable in response to a movement of the floating object, and the other one of the second drive element and the first drive element being operatively connected to a sea floor;

- a clutch apparatus movable between an inactive position wherein relative axial movement between the first drive element and the second drive element is allowed, and an active position wherein relative axial movement between the first drive element and the second drive element is prevented,

wherein the apparatus further comprises:

- a sensor apparatus for sensing a rotational position of the crank pin;

- a movement sensor apparatus for sensing a moving direction of the floating object; and - a control system for operating the clutch apparatus between the inactive and active positions, the control system operating in response to input from the sensor apparatus and in response to input from the movement sensor apparatus, so that when the clutch apparatus is in the active position a movement of the floating object sets the crank shaft, the rotatable main shaft and the machinery in rotation and energy is harvested from the ocean waves.

By the term operatively connected to a sea floor, is meant at a fixed distance with respect to a sea floor. As such, one of the first drive element and the second drive element may extend from a base on the sea floor, or it may extend from a base or structure extending above the sea floor. A base extending above the sea floor may be arranged on a top portion of a structure made from for example steel or concrete, or the base may be arranged on a buoyancy means kept vertically stationary by for example tension rods or -wires connected to the sea floor. A base extending above the sea floor is of particular interest in deep oceans, i.e. ocean being deeper than for example 100 meters.

The effect of providing the apparatus with the clutch apparatus and the control system controlling the clutch apparatus, is in one embodiment of the present invention, that a contact between the first drive element and the second drive element is controllable. This controllable contact allows alternating “gripping and releasing” contact between the first drive element and the second drive element, the contact being dependent on a relative position of the crank pin.

By the term “gripping” is meant that a relative movement between the first drive element and the second drive element is at least close to zero. Thus, since one of the first drive element and the second drive element is at a fixed elevation with respect to the seafloor, so is the other one of the second drive element and the first drive element when the clutch apparatus is in a gripping mode. Therefore, when in the gripping mode, any vertical movement energy of the floating object is transformed to the rotational energy of the crank shaft.

By the term “releasing” is meant that one of the first drive element and the second drive element is allowed to move independently of the other one of the second drive element and the first drive element.

Due to this gripping and releasing configuration provided by the clutch apparatus, the crank shaft can be rotated several times during an upward movement and several times during a downwards movement of the floating object. During such a multiple rotation of the crank shaft caused by an upward or downward movement of the floating object, a gripping contact between the first drive element and the second drive element will be at different positions along a longitudinal axis of one of the drive elements. A full effect of for example an ocean swell may therefore be achieved even with a crank pin having an operating radius or “stroke” being only a portion of the hight of the ocean wave or swell. A machinery comprising the crank shaft may therefore be relatively small. A small machinery may be advantageous with respect to being retrofitted on an existing floating object such as for example a floating wind harvest barge that comprises infra structure for transferring electrical power. However, the apparatus according to the invention may also be arranged for example on a floating offshore rig in the oil and gas industry, or on a tailormade floating object being relatively close to a shore. When utilized on a floating offshore rig, the apparatus may be used for producing electrical energy, and/or it may be used for pumping water or gas compression, for example.

From the above, it should be clear that the apparatus according to the invention may be independent on wave amplitude and wavelength, which results in sustained rotation of the crank shaft and thus the rotatable main shaft connected to a machinery, both in shallow and rough seas.

In one embodiment, the second drive element may extend to an elevation above a top portion of the first drive element. This has the effect that even in an embodiment wherein the second drive element is operatively connected to the sea floor, a full effect of for example an ocean swell may be achieved even with a crank pin having an operating radius being only a portion of the hight of the ocean wave or swell.

In one embodiment of the apparatus according to the invention, the first drive element may be connected to the crank pin, and the clutch apparatus may form part of the first drive element and configured for at least partially enclosing a portion the second drive element. This has the effect that the second drive element may be operatively connected to the sea floor. In such an embodiment, all moving parts of the apparatus, including the crank shaft, may be arranged on the floating object. Arranging all moving parts on the floating object is preferred with respect to facilitating installation and subsequent maintenance of the apparatus.

The clutch apparatus may be operated by means of magnetism or hydraulics.

In an alternative to connecting the first drive element to the crank pin, wherein the first drive element comprises the clutch apparatus configured for at least partially enclosing a portion the second drive element, the second drive element may be secured to the crank pin. In such an alternative embodiment, the first drive element may comprise the clutch apparatus that in an operation position is submerged.

A lower end portion of the second drive element may be provided with a piston housed within housed within the clutch apparatus the clutch apparatus may comprise a sliding valve forming part of the first drive element. The sliding valve may comprise:

- an inner valve casing for housing the piston of the second drive element, the inner valve casing being axially fixed with respect to the sea floor;

- an outer valve casing enclosing a portion of the inner valve casing and movable with respect to a longitudinal axis of the inner valve casing;

- an actuator for moving the outer valve casing between a first extreme position and a second extreme position, the actuator operatively connected to the control system; wherein

- each one of the inner valve casing and the outer valve casing may be provided with at least two spaced-apart perforations being arranged so that: when the outer valve casing is at first extreme position, the perforations of the outer valve casing are aligned with the perforations of the inner valve casing to allow fluid communication between an inside of the inner valve casing and an outside of the outer valve casing; and when the outer valve casing is in the second extreme position, the perforations of the outer valve casing are misaligned with respect to the perforations of the inner valve casing to prevent fluid communication between an inside of the inner valve casing and an outside of the outer valve casing so that movement of the piston and thereby the second drive element is prevented.

In one embodiment the crank shaft may be arranged on the floating object. Arranging the apparatus comprising the crank shaft on the floating object is advantageously with respect to inter alia maintenance of the apparatus, and also the effect of the apparatus; air provides less resistance against movement than water.

The actuator may be selected from the group consisting of: a hydraulically operated actuator, a servo, and a step motor. Such an actuator is reliable and can be controlled by the control system.

Preferably, the actuator operating the clutch apparatus is arranged at a fixed elevation with respect to the sea floor.

The apparatus may comprise more than one drive system for rotating the crank shaft to provide a substantially even rotational force as will be apparent from the disclosure blow. In a preferred embodiment, the apparatus comprises at least three drive systems wherein each drive system is operatively connected to a respective crank pin. Providing at least three drive systems has the effect of providing a smooth, substantially constant rotation of the crank shaft.

The apparatus may comprise a variable stroke crank shaft provided by a crank pin slidably connected to a crank disk of the crank shaft so that an operating radius of the crank pin with respect to the crank disk is variable between a minimum radius and a maximum radius, and substantially to any position therebetween by means of motor operating in response to input from the movement sensor apparatus.

Providing the apparatus with a variable stroke crank shaft has the effect that the apparatus may be continuously optimized to the variable movement caused by ocean waves and swells a floating object will be subjected to during operation.

In a second aspect of the invention there is provided a crank shaft for use with the apparatus according to the first aspect of the invention, the crank shaft comprising, a crank pin connected to a crank disk of the crank shaft, wherein the crank pin is slidably connected the a crank disk of the crank shaft so that an operating radius of the crank pin with respect to the crank disk is variable between a minimum radius and a maximum radius, and substantially to any position therebetween, by a motor operating in response to input control signals.

In one embodiment, the variable distance is up to 50% of a radius of the crank disk of the crank shaft. However, a minimum operating radius may be close to zero, i.e. close to the rotatable main shaft center line, and a maximum operating radius may be close to the outer circumference of the crank disk.

In a third aspect of the invention there is provided a method for harvesting energy from ocean waves, wherein the method comprises:

providing an apparatus according to the first aspect of the invention;

operatively connecting the apparatus to a floating object and operatively connecting one of the first drive element or the second drive element to a sea floor;

operatively connecting the crank shaft to a machinery;

activating the control system for controlling the clutch apparatus between the active and inactive position to rotate the crank shaft in response to movement of the floating object, to harvest energy from the ocean waves.

In the following is described examples of preferred embodiments illustrated in the accompanying drawings, wherein:

Fig. 1 shows a general principle of an apparatus according to the invention arranged on a floating rig, wherein the apparatus comprises drive systems connected to a structure extending from a seabed;

Fig. 2 shows in larger scale the apparatus shown in fig.1 connected to a machinery;

Fig. 3 shows in larger scale three crank positions in view A-A of fig.2;

Figs.4a-4b illustrate in a larger scale a first drive element comprising a clutch apparatus operatively connected to a crank pin of a crank shaft, the clutch apparatus enclosing a portion of a second drive element being at a fixed elevation with respect to a sea floor, the clutch apparatus configured for gripping and releasing engagement with the second rod element depending on a position of the crank pin, during an upward movement of the rig shown in fig. 1, and thus the apparatus;

Fig. 4c illustrates an operation principle of a control system controlling the clutch apparatus illustrated in figs.4a and 4b;

Figs.4d-4f illustrate an operation of the clutch apparatus and the control system shown in figs.4a-4c during a downward movement of the rig shown in fig.1, and thus the apparatus;

Fig. 5 shows in larger scale a hydraulically operated clutch apparatus, wherein the first drive element comprises the clutch apparatus;

Fig. 6a shows an electromagnetically operated clutch apparatus;

Fig. 6b shows in a larger scale a cross sectional view of the clutch apparatus shown in fig.6a, wherein the first drive element comprises the clutch apparatus;

Fig. 7a shows a clutch apparatus operated by eddy current, wherein the first drive element comprises the clutch apparatus;

Fig. 7b shows in a larger scale a cross sectional view of the clutch apparatus shown in fig.6b;

Fig. 8a shows an embodiment wherein the second drive element comprises the clutch apparatus, and the first drive element is fixed to a crank pin of the crank shaft;

Fig. 8b shows in a larger scale a detail of a lower portion of the apparatus shown in fig. 8a;

Fig. 9a shows a sideview, partially in cut, of the crank disk comprising a crank pin having an adjustable operating radius; and

Fig. 9b shows a view from D-D in fig.9a.

Positional indications such as for example left and right, above, refer to the position shown in the figures.

In the figures, same or corresponding elements are indicated by same reference numerals. For clarity reasons some elements may in some of the figures be without reference numerals.

A person skilled in the art will understand that the figures are just principle drawings. The relative proportions of individual elements may also be strongly distorted.

In the figures reference numeral 1 denotes an apparatus according to the present invention. The apparatus 1 has a main shaft 4 comprising a crank shaft 5 provided with a crank pin 7 eccentrically secured to a crank disk 5’ revolving about its centre. The crank pin 7 is operatively connected to a drive system 10 for rotating the crank shaft 5.

In fig.1 is the apparatus 1 arranged on a floating object FO, here in the form of a semisubmersible rig. In the embodiment shown, the apparatus 1 is configured for driving a machinery, here shown as a power generator G. However, the apparatus 1 may alternatively be configured for driving for example a pump or other machinery driven by a rotatable main shaft 4.

In the embodiment shown in figures 1 and 2, the apparatus 1 comprises a system 10 having first drive elements 15a, 15b, 15c (see fig.2) for operative connection to three second drive elements 20a, 20b, 20c. A lower end portion of the second drive elements 20a, 20b, 20c are secured to a structure S protruding from to a sea floor SF so that the second drive elements 20a, 20b, 20c are operatively connected to the sea floor SF.

An upper end portion of the second drive elements 20a, 20b, 20c extend above the crank shaft 5. Extending the second drive elements 20a, 20b, 20c above the crank shaft 5 has the effect that a vertical movement of the floating object FO may provide more than one rotation of the crank shaft 5, as will be explained in detail below.

Fig. 2 shows in larger scale a portion of the apparatus 1 and the power generator G shown in fig.1. The crank shaft 5 is carried by supports 6 arranged at each end portions thereof. The main shaft 4 further carries a flywheel 8.

Figs.3a – 3c illustrate a position of three crank pins 7a, 7b, 7c seen from view A-A in fig.

2, wherein the crank pins 7a, 7b, 7c are positioned 120 degrees apart. Although shown “side by side” it should be clear that the crank disks 5’ of the crank shaft 5 shown in figures 3b and 3c are arranged coaxially in series on the main shaft 4 and with the crank disk 5’ in fig.3a. Thus, the crank pin 7b in fig.3b has a position indicated 7b in fig.3a, and the crank pin 7c in fig.3c has a position indicated 7c in fig.3a.

In figs.3a-3c, the first drive elements 15a, 15b, 15c of the drive system 10 shown in fig.1, are in the form of sleeves 15a, 15b, 15c connected to crank pins 7a, 7b, 7c, respectively. Each one of the first drive elements 15a, 15b, 15c comprises hydraulically operated clutch apparatus 25 shown in more detail in fig.5. The second drive elements 20a, 20b, 20c, which in the embodiment shown are in the form of rods 20a, 20b, 20c operatively connected to the sea floor SF (see fig.1), are vertically stationary, while an elevation of the first drive elements 15a, 15, 15c follows a position of the crank pins 7a, 7b, 7c. The position of the crank pins 7a, 7b, 7c depends on a rotational position of the crank shaft 5 (as shown in figs.3a-3c) and an elevation of the apparatus 1 on the floating object FO shown in fig.1.

The purpose of the clutch apparatus 25 is to control relative axial movement between each one of the shown first drive elements 15a, 15b, 15c and the second drive elements 20a, 20b, 20c, respectively. By controlling the clutch 25 between an activated and deactivated position, i.e. a gripping position and a released position in the embodiment shown, a relative axial movement between the first drive elements 15a, 15b, 15c and the second drive elements 20a, 20b, 20c, respectively, can be controlled. It should be noted that each one of the three clutches 25 is controlled individually so that only one clutch 25 is activated at one time while the two other clutches 25 are deactivated.

Turning now to figures 4a-4f showing an operating principle of one embodiment of the clutch 25, here showing the clutch 25 controlling an engagement between the first drive element 15a and the second drive element 20a.

Figures 4a to 4c illustrate an operation principle of the clutch 25 when a floating object FO and thus the apparatus 1 (see fig.1), is subject to an upward movement, as illustrated by arrow UM.

If the clutch 25 is locked in the deactivated position so that the first drive element 15a is allowed to move independently of the second drive element 20a, the first drive element 15a and the crank pin 7a will follow a movement of the apparatus 1. No force will be transferred from the first drive element 15a to the crank pin 7acrank shaft.

In fig.4a, the crank pin 7a has passed a top dead centre and is positioned at about 40° from a twelve o’clock position. At this position, the clutch 25 is activated to engage with a portion of the second drive element 20a as indicated by arrow CL. Since the second drive element 20a is at a fixed elevation with respect to the sea floor SF as shown in fig.1, and the clutch 25 connects the first drive element 15a to the stationary second drive element 20a, the first drive element 15a locks or “freezes” at a fixed elevation with respect to the sea floor SF. However, since the apparatus 1 is subject to an upward movement, and the first drive element 15a is locked for axial movement with respect to second drive element 20a by means of the clutch 25, the crank shaft 5 is rotated by the crank pin 7a connected to the first drive element 15a. The rotation is indicated by arrow R.

In fig.4b, the crank shaft 5 has been rotated about 100° from the position shown in fig.4a, and the crank pin 7a approaches its bottom dead centre. At this position, the clutch 25 disengages or unlocks as indicated by arrow CU so that the first drive element 15a can move axially independently of the second drive element 20a for the next 260° until the clutch 25 is again activated to engage with the second drive element 20a, but, due to the upward movement UM of the floating object FO, at an axial position along the second drive element 20a being at a higher elevation than the previous engagement position.

The activation and deactivation of the clutch 25 is controlled by a control system 70 operating in response of sensors 72 configured for sensing a position of rotational position indicators 74 (eighteen shown in figures 4c and 4f) connected to the crank disc 5’, and a movement sensor discussed below. Thus, the clutch 25 is activated at a position CL (Clutch Lock) and is deactivated at a position CU (Clutch Unlock). In the three crank pins 7a, 7b and 7c configuration illustrated herein, wherein 7a is discussed above, the clutch 25 remains locked through an angle sector V which is about 100°. However, if the rotational speed of the crankshaft 5 “overshoots”, i.e. exceeds a corresponding speed of vertical movement of floating object FO, the control system 70 may be configured for activating the clutch 25 to unlock before reaching, in the embodiment discussed herein, the stroke or angle V of 100°, to avoid reducing the inertia force of the flywheel 8 shown in fig.

1.

As indicated in fig.4b, the second crank pin 7b approaches the clutch activation position at an angle of 40° from a twelve o’clock position when the crank pin 7a is at a clutch unlock position CU of about 140° from the twelve o’clock position. Thus, the crank shaft 5 is subject to a further rotation by the clutch 25 operatively connected to the first drive element 15b connected to the crank pin 7b and enclosing a portion a second drive element 20b, cf. fig.3. Similarly, the third crank pin 7c, which is operatively connected to the first drive element 15c enclosing a portion a second drive element 20c, provides rotation of the crank shaft 5 when the clutch 25 of the first drive element 15b disengages. This goes on as long as the floating object FO (see fig.1) is subject to an upward movement as indicated by the arrow UM.

Now reverting to fig.2, the apparatus 1 is in the shown embodiment provided with a flywheel 8 of a type known per se. A purpose of the flywheel 8 is to store any surplus energy during a vertical movement of the floating object FO and supplementing rotational energy when the floating vessel FO is on neutral move. A neutral move occurs when the floating object FO changes from upward movement UM, as discussed for figures 4a-4c, to downward movement, as will now be discussed with reference to figures 4d-4f, and vice versa. The downward movement of the floating object FO is in figures 4d-4f indicated by arrow DM.

During a downward movement DM of the floating object FO comprising the apparatus 1, the operating principle shown in figures 4d-4f is the same as shown in figures 4a-4c and discussed above. The only difference is the rotational angle position of the crank pin 17a at which the clutch 25 engages and disengages from the second drive element 20a. In figures 4d and 4e illustrating one crank pin of the three-crank pin configuration discussed herein, this angle is at about 220° and 320° for engaging and disengaging the clutch, respectively.

An example of the invention will now be explained.

Imagine a floating object FO moving 10 meters upwards from a bottom of a wave or swell, and a radial distance between a centre of the crank disk 5’ and the crank pin 17 is 0,5 meter, i.e. a stroke of 1,0 meter. Imagine further starting upward movement from a bottom of the wave and activating the clutch 25 as illustrated in fig.4a. Since the floating object FO moves upwards, so do the apparatus 1, and the crank pin 7 is locked with respect to the second drive element 20a which is locked with respect to the sea floor SF. The crank shaft 5 is then subject to a clockwise rotation for about 100° after which the clutch 25 deactivates from engagement with the second drive element 20a upon receiving a signal from the control system, as illustrated in fig.4b. In this example, a clockwise rotation of about 100° corresponds to about 0.7 meters upward movement of the floating object FO. In the position shown in fig.4b, the crank pin 7b approaches a position in which the clutch 25 activates for locking the first drive element 15b with respect to the second drive element 20b (see fig.2) and rotates the crank shaft 5 substantially seamlessly further 100° before the clutch 25 disengages and the next crank pin 7c rotates the crank shaft further 100°. By this cycle, a rotation of 3,14 meters is achieved.

Since the crank shaft 5 in the embodiment shown is rotated by a system 10 comprising three sets of drive elements 15a, 20a; 15b, 20b; 15c, 20c, and three crank pins 7a, 7b, 7c are arranged 120° spaced apart, the crank pins 7a, 7b, 7c will provide a substantially constant or “seamless” rotation of the crank shaft 5. Estimating about 3 metres vertical movement of the floating object FO per full rotation of the crank shaft 5, a 10 meters heave of upward movement UM of the floating object FO will in this example result in three full rotations of the crank shaft 5.

As discussed below with regards to figures 9a and 9b, the apparatus 1 may be provided with a variable stroke crank shaft 5.

Reducing the stroke in the example above by 50% will result in six revolutions or rotations at 10 meters travel without stroke optimization. By means of the control system 70, the stroke may be optimized in a way that the stroke is longest in a portion of the floating object’s FO movement between top and bottom of a wave, and close to zero at near top or bottom of a wave. This exploits the vast pull-push force available by the floating object FO even if the vertical movement is small, but the pull/push force available is the same. As a result, such an optimization may generate more rotations than mentioned above during one full vertical movement, and the stroke has a relative and a variable value.

As shown in figures 4a-4f, the rotational angles at which the clutches 25 engages and disengages with the second drive element 20a, 20b, 20c depend on whether the floating object FO moves upwards, as shown in figures 4a-4c, or downwards as shown in figures 4d-4f. To provide input to the control system 70 with regards to upward movement UM and downward movement DM of the floating object FO, the apparatus 1 is provided with a movement sensor apparatus operatively connected to the control system 70. Such a movement sensor apparatus could for example be an accelerometer. However, to achieve a very accurate movement sensor apparatus, a movement sensor apparatus 80 configured for measuring a movement of the floating object FO with respect to the seafloor SF, may be advantageous. An example of such an apparatus is illustrated in fig.1 indicating a movement sensor apparatus in the form of a Doppler radar which is a specialized radar that uses the Doppler effect illustrated by dotted lines 80’, to produce velocity data about objects at a distance, here a tower of the floating object FO and a top portion of the apparatus 1. It does this by bouncing a microwave signal off a desired target and analysing how the object's motion has altered the frequency of the returned signal. This variation gives direct and highly accurate measurements of the radial component of a target's velocity relative to the radar. However, another very accurate movement sensor apparatus may be provided by means of an Inertial measurement unit (IMU). Still another suitable movement sensor apparatus may be a so-called draw-wire sensor which comprises a wire, a drum, a spring, and a position sensor.

The various sensor apparatuses mentioned above are commercially available in the marked.

Fig. 5 shows in more detail a hydraulically operated clutch apparatus 25 wherein the first drive element 15 comprises a piston and cylinder arrangement 27. The second drive element 20 extends through the first drive element 15 and is fixed to a sea floor SF. The first drive element 15 and the second drive element 20 may for example be the first drive element 15a and the second drive element 20a shown in figures 4a-4b and 4d-4e.

A position of the piston 28 is controlled by a hydraulic pressure towards either side of the piston 28 by controlling communicating of hydraulic fluid into or out of respective sides of the piston 28 as will be appreciated by a person skilled in the art. The piston 28 further comprises a piston rod 29 provided with a friction element 30 configured for abutting against or being at a distance form the second drive element 20, depending on a position of the crank pin 7, as discussed above. Fig.5 shows a situation corresponding to fig.4d, but immediately before releasing the clutch 25 from engagement with the second drive element 20, wherein the friction element 30 abuts against a portion of the second drive element 20 and has rotated the crank shaft 5 during a downward movement of the apparatus 1, and thus the floating object FO (see fig.1).

Fig. 6a shows in more detail a clutch apparatus 25 in the form of an electromagnetic brake arranged coaxially within the first drive element 15, wherein the first drive element 15 is operatively connected to the crank pin 7. The second drive element 20 is fixed to a sea floor SF.

Fig. 6b shows in larger scale a view through B-B of fig.6a. The clutch apparatus 25 comprises in the embodiment shown two semi-circular electromagnetic elements 35 enclosing a portion of the second drive element 20. When not being activated, there is a gap 37 between the two semi-circular electromagnetic elements 35 and a gap 39 between an outer surface of the second drive element 20 and the semi-circular electromagnetic elements 35.

When the semi-circular electromagnetic elements 35 are activated by electric power (DC) via a power supply 36, the semi-circular electromagnetic elements 35 are forced towards the second drive element 20 so that the gap 37 between the semi-circular electromagnetic elements 35 and the gap 39 between the semi-circular electromagnetic elements 35 and the second drive element 20 are closed. Thus, the clutch apparatus 25 shown in figures 6a and 6b, is an electromagnetic brake.

Fig. 7a shows in more detail a clutch apparatus 25 in the form of an eddy current brake, also known as an induction brake, wherein the magnetic field is created by means of electromagnets.

Fig. 7b shows in larger scale a view through C-C of fig.7a. The clutch apparatus 25 comprises in the embodiment shown a plurality of electromagnets 45 evenly distributed on two semi-circular holding elements 40 arranged coaxially within the first drive element 15, wherein the first drive element 15 is operatively connected to the crank pin 7, as shown in fig. 7a. The second drive element 20 is fixed to a sea floor SF.

An advantage of using an electromagnetic brake as shown in figures 6a and 6b, and the alternative eddy current brake as shown in figures 7a and 7b, is that the second drive element is allowed to move axially independent of the first drive element 15 in case of a power failure.

Figures 8a and 8b show an embodiment of the apparatus 1 in an operating position wherein the second drive element 20 is secured to the crank pin 7 via a connector sleeve 20’. The second drive element 20 and the connector sleeve 20’ is fixed to each other.

Fig. 8a is a partially cut-away view.

The first drive element 15 is submerged and comprises the clutch apparatus 25 configured for enclosing a portion of the second drive element 20.

A lower end portion of the second drive element 20 is provided with a piston 21 operatively connected to the clutch apparatus, the clutch being a sliding valve 25 forming part of the first drive element 15.

In the embodiment shown in fig.8a the sliding valve 25 comprises an inner valve casing 50 for housing the piston 21 of the second drive element 20, the inner valve casing 50 being axially fixed with respect to the sea floor SF. It should be noted that a portion of the inner valve casing 50 is shown cut-away.

The sliding valve 25 further comprises an outer valve casing 55 enclosing a portion of the inner valve casing 50 and movable with respect to a longitudinal axis of the inner valve casing 50. For illustrative purposes only a top and a bottom portion of the outer valve casing 55 are shown. However, it should be noted that the outer valve casing 55 runs continuously between the top and bottom portion of the outer valve casing 55.

The sliding valve 25 is operated by an actuator 60 configured for moving the outer valve casing 55 between a first extreme position and a second extreme position. The actuator 60 is operatively connected to a control a control system for controlling the sliding valve 25. The control system is operating in response to a rotational position of the crank pin 7 and a movement sensor apparatus, as discussed above.

Each one of the inner valve casing 50 and the outer valve casing 55 is provided with of at least two (a plurality shown in fig.8a) spaced-apart perforations 51, 56 being arranged so that: when the outer valve casing 55 is at the first extreme position, the perforations 56 of the outer valve casing 55 are aligned with the perforations 51 of the inner valve casing 55 to allow fluid communication between an inside of the inner valve casing 50 and an outside of the outer valve casing 56; and when the outer valve casing 55 is in the second extreme position, the perforations 56 of the outer valve casing 55 are misaligned with respect to the perforations 51 of the inner valve casing 50 to prevent fluid communication between an inside of the inner valve casing 50 and an outside of the outer valve casing 56.

Thus, when the outer valve casing 55 is in the first extreme position allowing fluid communication through the perforation 51 and 56, the piston 21 of the second drive element 20 is allowed to move within the inner valve casing 51 forming part of the first drive element 15 since water on both sides of the piston is allowed to communication with ambient water.

When the outer valve casing 55 is in the second extreme position wherein fluid communication through the perforation 51 and 56 is prevented, the piston 21 of the second drive element 20 is prevented from moving within the inner valve casing 51 forming part of the first drive element 15. Thus, the piston 21 of second drive element 20 is substantially prevented from moving within the inner valve casing 50 being the first drive element 15.

When the floating object moves vertically upwards or downwards, the crank pin 7 of the crank shaft is rotated when the outer valve casing 55 has been moved by the actuator to its second extreme position. To achieve a smooth, seamless rotation of the crank shaft, the apparatus 1 preferably comprises three or more sets of drive elements 15, 20 operatively connected to corresponding crank pins 7 as discussed in detail with respect to figures 4a- 4f above.

Fig. 8b shows in larger scale the actuator 60 for operating the sliding valve. In the embodiment shown, the actuator is a hydraulic actuator wherein a piston 62 is operatively connected to the outer valve casing 55. The piston 62 is operated by communication a hydraulic fluid through an inlet 64 and an outlet 66 of a cylinder housing 65 enclosing the piston 62. The inlet 64 and the outlet 66 are in fluid communication with a hydraulic source (not shown) in a way known per ser se.

In the embodiment shown in figures 8a and 8b, the actuator 60 is configured for displacing the outer valve casing 55 axially with respect to in the inner valve casing 50. However, in an alternative embodiment (not shown) the actuator is configured for rotating the outer valve casing 55 with respect to a longitudinal axis of the inner valve casing 50.

Turning now to figures 9a and 9b showing a principle of an adjustable operating radius or “stroke” for the crank pin 7 by two stepper motors 94.

Fig. 9a shows a sideview, partially in cut, of the crank disk 5’ comprising a crank pin 7.

Fig. 9b shows a view from D-D in fig.9a. For clarity, the upper portion of fig.9a is shown as a cut.

The crank pin 7 is arranged radially movable in a slot 90 providing a crank pin guide block.

The crank pin 7 is provided with a threaded bore mating with a screw 92. The screw 92 is operatively connected to a stepper motor 94 configured for rotating the screw 92. An end portion of the crank pin 7 is provided with a non-circular portion, here shown as a square 96, to allow relative movement between the screw 92 and the crank pin 7.

The stepper motors 94 are connected to its respective crank disk 5’ of the crank shaft 5 and rotates therewith. The stepper motors 94 configured for operating in tandem.

In the embodiment shown in fig.9a, the crank pin 7 is adjustable between a first minimum operating radius R1 (crank pin shown dotted) and a second maximum radius R2 (crank pin not shown). In fig.9a, the crank pin 7 is shown at a radius R3 being close to the maximum operating radius R3.

Each of the stepper motors 94 is provided with a receiver 98 for receiving wireless signals based on for example telemetry or Wi-Fi signals to allow rotation of the stepper motors 94 together with the crank disk 5’ of the crank shaft 5. The signals are provided by the control system 70 which receives signals from the movement sensor, for example the Inertial measurement unit (IMU) 81, of the floating object FO. Thus, the signals to the stepper motors 94 are correlated to the movement sensor configured for measuring relative movement of the floating object FO, such as for example upwards movement or downwards movement, distance between movement zero point (top and bottom of a wave or swell, and average speed at middle point of movement.

By means of the control system 70 and stepper motors 94, the operative radius of the crank pin 7 may be automatically adjusted to a minimum value in order to have the vertical movement of the floating object FO to convert to rotation of the crank shaft 5. The clutch 25 is activated and provides a time correlated force related to linear vertical movement of the floating object FO. In practical terms this means that the crank pin 7 pull and push will typically be of a shorter time duration than pulling through the full available angle sector of 100° as discussed with regards to the embodiment shown in figures 4a- 4f. When sufficient pull is locked for a short time, i.e. the clutch 25 being in its active position, the rotational speed will overshoot, and the pull unlocks, i.e. the clutch 25 is operated to its inactive position. This is a preferred functionality for sustainable rotation as this inertia force is accumulated by the flywheel 8.

As such, the feature of the invention discussed above has some of the same nature as a combustion engine’s pressure pulse acting on a piston crown during about 20° rotation for energizing a rotation of further 700° before a new combustion takes place. This is only possible with a dedicated inertia force accumulation. Excessive energy is then available for utilization dependant of the system efficiency.

From the disclosure herein, it should be appreciated that the apparatus 1 according to the invention has a working principle having similarities with a combustion engine, but with the very great difference that the energy source is ocean waves instead of a petroleum fluid or other combustible fluid. Due to the movement sensor apparatus, such as for example an Inertial measurement unit (IMU) 81 for sensing movement of the floating object FO and sensors 72 configured for sensing a rotational position of the crank disk 5’, the apparatus 1 will work equally well for an upward movement UM and a downward movement DM of the floating object FO. In one embodiment, the apparatus 1 is configured with an adjustable operating radius for the crank pin 7 so that a stroke of the apparatus 1 can be optimized with respect to ocean waves and swells; towards minimum radius R1 for small waves or at top and bottom dead centres, and towards maximum radius R2 for large ocean waves or swells.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

Claims

C l a i m s

1. An apparatus (1) for harvesting energy from ocean waves when being arranged in connection with a floating object (FO) moving in the waves, the apparatus (1) comprising:

- a rotatable main shaft (4) for driving a machinery (G), the rotatable main shaft (4) comprising a crank shaft (5) provided with a crankpin (7); and

- a drive system (10) for rotating the crank shaft (5), c h a r a c t e r -i s e d i n that the drive system (10) comprises:

- a first drive element (15) and a second drive element (20) for operative connection to each other, one of the first drive element (15) and the second drive element (20) being movable in response to a movement of the floating object (FO), and the other one of the second drive element (20) and the first drive element (15) being operatively connected to a sea floor (SF) ;

- a clutch apparatus (25) movable between an inactive position wherein relative axial movement between the first drive element (15) and the second drive element (20) is allowed, and an active position wherein relative axial movement between the first drive element (15) and the second drive element (20) is prevented, wherein the apparatus (1) further comprises:

- a sensor apparatus (72, 74) for sensing a rotational position of the crank pin (7); - a movement sensor apparatus (80; 81) for sensing a moving direction of the floating object (FO); and

- a control system (70) for operating the clutch apparatus (25) between the inactive and active positions, the control system (70) operating in response to input from the sensor apparatus (72, 74) and in response to input from the movement sensor apparatus (80; 81), so that when the clutch apparatus (25) is in the active position a movement of the floating object (FO) sets the crank shaft (5), the rotatable main shaft (4) and the machinery (G) in rotation and energy is harvested from the ocean waves.

2. The apparatus (1) according to claim 1, wherein the second drive element (20) extends to an elevation above a top portion of the first drive element (15).

3. The apparatus (1) according to claim 1 or 2, wherein the first drive element (15) is connected to the crank pin (7), the clutch apparatus (25) forming part of the first drive element (15) and configured for at least partially enclosing a portion the second drive element (20).

4. The apparatus (1) according to any one of the preceding claims, wherein the clutch apparatus (25) is operated by means of electro-magnetism or hydraulics.

5. The apparatus (1) according to any one of the preceding claims, wherein the crank shaft (5) is arranged on the floating object (FO) and the second drive element (20) is operatively connected to the sea floor (SF).

6. The apparatus (1) according to claim 1, wherein the second drive element (20) is secured to the crank pin (7), and the first drive element (15), in an operating position, being submerged and comprises the clutch apparatus (25) configured for enclosing a portion of the second drive element (20).

7. The apparatus (1) according to claim 6, wherein a lower end portion of the second drive element (20) is provided with a piston (21) housed within the clutch apparatus (25), the clutch apparatus (25) comprising a sliding valve (50, 55) forming part of the first drive element (15), the sliding valve (50, 55) comprising:

- an inner valve casing (50) for housing the piston (21) of the second drive element, the inner valve casing being axially fixed with respect to the sea floor (SF); - an outer valve casing (55) enclosing a portion of the inner valve casing (50) and movable with respect to a longitudinal axis of the inner valve casing (50);

- an actuator (60) for moving the outer valve casing (55) between a first extreme position and a second extreme position, the actuator (60) operatively connected to the control system; wherein

- each one of the inner valve casing (50) and the outer valve casing (55) is provided with at least two spaced-apart perforations (51; 56) being arranged so that: when the outer valve casing (55) is at the first extreme position, the perforations (56) of the outer valve casing (55) are aligned with the perforations (51) of the inner valve casing (50) to allow fluid communication between an inside of the inner valve casing (50) and an outside of the outer valve casing (55); and when the outer valve casing (55) is in the second extreme position, the perforations (56) of the outer valve casing (55) are misaligned with respect to the perforations (51) of the inner valve casing (50) to prevent fluid communication between an inside of the inner valve casing (50) and an outside of the outer valve casing (55) so that movement of the piston (21) and thereby the second drive element (20) is prevented.

8. The apparatus (1) according to claims 6 or 7, wherein the crank shaft (5) is arranged on the floating object (FO).

9. The apparatus (1) according to claim 7, wherein the actuator (60) is selected from the group consisting of: a hydraulically operated actuator, a servo, and a step motor.

10. The apparatus according to any one of the preceding claims, wherein the apparatus (1) comprises more than one drive system (10) for rotating the crank shaft (5), each drive system (10) operatively connected to a respective crank pin (7) of the crank shaft (5).

11. The apparatus (1) according to any one of the preceding claims, wherein the apparatus (1) comprises a variable stroke crank shaft (5) provided by a crank pin (7) slidably connected to a crank disk (5’) of the crank shaft (5) so that an operating radius of the crank pin (7) with respect to the crank disk (5’) is variable between a minimum radius (R1) and a maximum radius (R2), and substantially to any position therebetween by means of motor operating in response to input from the movement sensor apparatus (80; 81).

12. A crank shaft (5) for use with the apparatus (1) according to any one of the preceding claims, the crank shaft (5) comprises a crank pin (7) connected to a crank disk (5’) of the crank shaft (5), c h a r a c t e r i s e d i n that the crank pin (7) is slidably connected to the crank disk (5’) of the crank shaft (5) so that an operating radius of the crank pin (7) with respect to the crank disk (5’) is variable between a minimum radius (R1) and a maximum radius (R2), and substantially to any position therebetween, by a motor operating in response to input control signals.

13. A method for harvesting energy from ocean waves, c h a r a c t e r -i s e d i n that the method comprising:

providing an apparatus (1) according to any one of the preceding claims; operatively connecting the apparatus to a floating object (FO) and operatively connecting one of the first drive element (15) or the second drive element (20) to a sea floor (SF);

operatively connecting the crank shaft (5) to a machinery (G); and activating the control system (70) for controlling the clutch apparatus (25) between the active and inactive position to rotate the crank shaft (5) in response to movement of the floating object (FO), to harvest energy from the ocean waves .