The present invention is related to an energy harvesting buoy, according to the preamble of claim 1.

The present invention is especially related to an energy harvesting buoy utilizing a translator in the form of a magnetic lead screw for transferring linear force from a relative movement between the translator and a float into a generator unit for producing electric energy, wherein the translator is retained by a standing water column.

Background Many concepts has been proposed for todays wave energy converters, however they almost all suffer from poor efficiency, low shear force or structural problems regarding storm protection etc.

E.g. today, many hours of service is spend on ocean marking lights, for either fish farms or normal boat traffic. The service include change of batteries for powering the LED marking light, which is done by technicians using a service vessel for each buoy. The process of changing batteries is expensive and time consuming, and is why other technologies are investigated.

One of these new technologies is the idea of having a LED-marking buoy that is self-powered, which should minimize the requirement for servicing. Until now, the most popular technology for self-powering marking buoys is Photo-Voltaic (PV) panels. However, one drawback with using PV panels for ocean buoys is problems with salt crystalizing on top of the panels, which decreases the efficiency of the panels dramatically.

Further in polar areas, where there are long periods with polar night, the PV panels will in these periods not produce any electricity.

Further, by using PV panels one will not be able to produce electricity at night hours.

Further, at tube and research buoys, weather data buoys or similar, which are provided with power demanding communication means for transferring data, this will require very large batteries to be able to provide the required power, especially at polar areas.

Further, these solutions are not capable of providing sufficient energy such that the harvested energy can be used to power other consumers at e.g. fish farms. The closest prior art to the present invention is found in N020170347 Al, in the name of the applicants, wherein is disclosed an energy harvesting buoy comprising a float and a wave energy converter, wherein the wave energy converter comprises a translator provided with helically shaped permanent magnets, wherein the translator is arranged movable in a sleeve extending vertically in the float, and a generator unit fixed in the float comprising a rotor assembly enclosing the translator and at least one stator assembly enclosing the rotor assembly, wherein the helically shaped permanent magnets of the translator transfer linear force from a relative linear movement between the float and translator into a torque working on the rotor assembly inducing a current in the stator assembly. In N020170347 Al the translator at lower end is arranged to a submerged drag plate exterior of the float by means of a shaft extending out of the float.

US2010109329 Al disclose apparatus, methods, and systems for power generation. One power generator embodiment includes a shaft and a buoyant assembly slidably coupled to the shaft. A generator is arranged to create electric energy from interaction of a conductor with a number of magnetic elements on the buoyant assembly, in a manner to produce electricity, as the buoyant assembly moves on the shaft.

The use of a magnetic lead screw is also known from e.g. https://www.machinedesign.com/motors-drives/article/21831771 /could-magnetic-gears-make- wind-turbines-say-goodbye-to-mechanical-gearboxes, as well as GB2463102 A. Other relevant prior art may be found in US8125097 Bl, CN201517465 U, US2008309088 Al, GB2088017 A, US1259845 A, DE19815211 Al, US1822806 A and US2009146429 Al.

A drawback of the prior art solutions is that they require that the translator is arranged to an external stationary structure or means for retaining the translator, adding complexity by requiring interaction of many parts that results in maintenance requirements and is expensive to manufacture. These additional parts, as well as external structure or means, are further exposed to wear and tear by the harsh environment, as well as is exposed to objects in the water that could damage these external components or structures.

There is accordingly a need for an energy harvesting buoy that do not require the use of external structures or means for retaining the translator.

It is further a need for an energy harvesting buoy that is capable of harvesting energy from waves requiring minimal maintenance, hereunder an energy harvesting buoy having few movable parts and exposed parts. There is further a need for an energy harvesting buoy enabling easy deployment and retrieval.

Objects

The main object of the present invention is to provide an energy harvesting buoy partly or entirely solving the above-mentioned drawbacks of prior art solutions and mentioned needs.

An object of the present invention is to provide an energy harvesting buoy that do not require the use of external structures or means for retaining a translator of an energy converter.

It is an object of the present invention to provide an energy harvesting buoy that makes use of a standing water column for retaining the translator. An object of the present invention is to provide an energy harvesting buoy enabling easy deployment and retrieval.

It is an object of the present invention to provide an energy harvesting buoy having low installation and operating costs, as well as requiring minimal maintenance.

An object of the present invention is to provide an energy harvesting buoy arranged to withstand big waves.

It is further an object of the present invention to provide an energy harvesting buoy having few movable parts, as well as exposed part.

An object of the present invention is to provide an energy harvesting buoy where there is no contact between force transferring parts. It is an object of the present invention to provide an energy harvesting buoy where there is minimal friction between moving parts.

An object of the present invention is to provide an energy harvesting buoy, which does not require a connection to the seabed for harvesting energy from a passing wave.

It is an object of the present invention to provide an energy harvesting buoy, which does not include polluting fluids, such as hydraulic oil or similar, which can constitute a risk for the environment at breakdown. An object of the present invention is to provide a compact energy harvesting buoy.

Further objects of the present invention will appear from the following description, claims and attached drawings. The invention

An energy harvesting buoy according to the present invention is defined by the technical features of claim 1. Preferable features of the energy harvesting buoy are described in the dependent claims.

The present invention provides an energy harvesting buoy comprising a float having positive buoyancy and a wave energy converter which converts linear movement of the buoy due to passing waves into electricity. The wave energy converter comprises a translator in the form of a magnetic lead screw and a generator unit enclosing the translator in circumferential direction. The energy harvesting buoy according to the present invention further comprises a core component in the form of a water-filled piston assembly arranged at lower part of the float and arranged to the translator, wherein the water-filled piston assembly provides a standing water column retaining the translator linearly when the float moves due to passing waves.

According to the present invention, the wave energy converter is arranged to convert the slow linear movement of the waves into a fast rotating movement of a rotor assembly in the generator unit, which makes it possible to extract energy using a standard rotary generator. According to the present invention, the translator is arranged movable in a vertically arranged sleeve in the float, which translator is provided with helically shaped and radially magnetized permanent magnets. Accordingly, the translator exhibits a magnetic thread instead of a mechanical thread.

The generator unit of the energy harvesting buoy according to the present invention is formed by a rotor assembly and a stator assembly accommodated in a housing in a fixed position in the energy converter.

The rotor assembly is formed by a rotor sleeve enclosing the translator and further arranged rotatably in the housing, which rotor sleeve is provided with at least one set of permanent magnets arranged in circumferential direction thereof. Accordingly, the rotor assembly constitutes a rotor for both the translator and generator unit.

The stator assembly is formed by at least one stator formed by coils and back iron arranged to enclose the set(s) of permanent magnets of the rotor assembly with a gap therebeteween.

The water-filled piston assembly is according to one embodiment of the present invention arranged at lower part of the buoy, which water-filled piston assembly is arranged to the translator and provides a standing water column that will retain the translator linearly when the float moves due to passing waves. Accordingly, the water-filled piston assembly acts to keep the translator stationary while the float moves due to an incoming wave. In other words, the water- filled piston assembly provides a counterweight for the translator. The water-filled piston assembly is e.g. formed by an elongated piston housing wherein a piston is movably arranged, to which piston is arranged a piston rod, which piston rod extends out of the piston housing through an opening at upper side of the elongated piston housing for connection to lower end of the translator. The great advantage with using a water-filled piston assembly for retaining the translator is that there are no requirement of additional external means or arrangement to external structures, such as attachment to seabed or similar, to retain the translator. Further, the water-filled piston assembly will be arranged to the energy harvesting buoy at manufacture and will be filled with water when the buoy is positioned in the water, i.e. semi-submerged. This will save weight enabling the energy harvesting buoy to be easily handable, both at deployment and retrieval. Further, such a solution will not require adjusting for low tide and high tide.

Such a solution is further easily scalable according to required efficiency, as well as almost maintenance-free.

The energy harvesting buoy according to the present invention is able to produce energy by that the relative movement between float and translator results in rotation of the rotor assembly of the generator unit. When the rotor assembly of the generator unit rotates, the permanent magnets of the rotor assembly induce a current in the generator assembly resulting in an AC current, which is feed to a control unit.

Accordingly, relative linear movement between the float and translator results in rotation of the rotor assembly with a speed determined by the lead of the translator and the input linear velocity. In the present invention, the translator uses helically shaped permanent magnets in order to transfer the linear force of the translator/float into a torque working on the rotor assembly. The control unit for an energy harvesting buoy according to the present invention can be arranged for rectifying the generated current by that it is provided with rectifying means, such as an AC frequency converter, and further control the damping profile of the generator assembly.

According to the present invention, the rectified DC current can be transferred to an energy storage arranged in the float or transferred to shore or a user via a cable. In an alternative embodiment, the generated AC current is transferred to shore or a user via a cable and further processed at shore or user side, such as rectified or powering an AC electric appliance.

A great advantage with the present invention is that by using permanent magnets to transfer the linear force allows the wave energy converter slip one or more pole pairs if the force applied to the translator exceeds the force the translator is designed for, i.e. the maximum force the translator is capable of transferring. In this way, any big waves will not damage the translator and/or the generator unit of the wave energy converter. Accordingly, the present invention will be capable of withstanding high forces from big waves due to this built-in force protection. Further, the fact that the water-filled piston assembly is integrated, at least partly, this results in that there are no external means or structures that are exposed to damage, that will/could affect the operation of the energy harvesting buoy.

A further advantage with the present invention is that by using a magnetic lead screw for transferring linear forces to torque on the rotor assembly there are no contact between the force transferring parts, thereby minimizing friction and increasing efficiency of the energy harvesting buoy.

It is further an advantage with the present invention, compared to prior art solutions, that the energy harvesting buoy according to the present invention does not include polluting fluids, such as hydraulic oil or similar, which can constitute a risk for the environment at breakdown, as it makes use of surrounding water in the water-filled piston assembly. The energy harvesting buoy according to the present invention only contains magnets and electronics which do not constitute a danger for the environment.

Further preferable features and advantageous details of the present invention will appear from the following example description, claims and attached drawings. Example

The present invention will below be described in further detail with references to the attached drawings, where:

Fig. 1 is a principle drawing of an energy harvesting buoy according to the present invention,

Fig. 2 is a principle drawing showing details of translator and generator unit according to prior art, and

Fig. 3 is an exploded principle drawing of a generator unit according to prior art.

Reference is now made to Figure 1 which is a principle drawing of an energy harvesting buoy 10 according to the present invention. The energy harvesting buoy 10 is formed by a float 11 having positive buoyancy such that it floats at the water surface, preferably in a semi-submerged position. The energy harvesting buoy 10 according to the present invention further includes a wave energy converter 20 that is based on a magnetic lead screw (MLS) as a core component. Suitable wave energy converters 20 for the energy harvesting buoy 10 according to the present invention have been described in prior art, such as e.g. in N020170347 Al, in the name of the applicants. A suitable wave energy converter 20 for the present invention comprises a translator 40 in the form of a magnetic lead screw and a generator unit 50, wherein the translator 40 is arranged movable in a sleeve 30 extending vertically in the float 11, and wherein the generator unit 50 is arranged in a fixed position in the sleeve 30.

Reference is also made to Figure 2 which is a cross-sectional principle drawing showing details of the translator 40 and generator unit 50 according to prior art suitable for the energy harvesting buoy 10 according the present invention. The translator 40 is e.g. formed by an elongated translator sleeve 41, which at outer surface thereof is provided with helically shaped and radially magnetized permanent magnets 42 which is enclosed by a protective sleeve or coating 43. The magnetic orientation is such that there is provided a magnetic north and south pole on the translator sleeve 41. The permanent magnets 42 are preferably neodymium magnets, preferably sintered NDFeB magnets. In the shown example there are formed two magnet threads with a lead of e.g. at least 10 mm/revolution of the two magnetic threads, and e.g. 9 magnets per revolution. The dimension and shape and choice of the magnets will be dependent of desired properties and is not limited to the examples given above. In the shown example, the magnetizing direction will be upwards. In an alternative embodiment, the translator 40 is provided with one thread of magnets.

Reference is further also made Figure 3 showing an exploded principle drawing of a generator unit 50 according to prior art that is suitable for the wave energy converter 20 to be used in the present invention, adapted to be arranged in the float 11.

The generator unit 50 is formed by a housing 51 accommodating a rotor assembly 60 and a stator assembly 70.

The rotor assembly 60 is e.g. formed by a mainly cylinder-shaped rotator sleeve 61 exhibiting an inner diameter corresponding to the outer diameter of an inner sealing tube 90, which is arranged for accommodating the translator 40. The rotor sleeve 61 in the shown example is provided with two circumferentially extending sets of permanent magnets 62a-b at an outer surface thereof, spaced apart in the longitudinal direction of the sleeve 61. In an alternative embodiment, the rotor sleeve 61 can be provided with only one set of permanent magnets.

The generator unit 50 further comprises a stator assembly 70 formed by two stators 71a-b formed by windings 72 and back iron 73, spaced apart in longitudinal direction of the generator unit 50 by means of a stator distance spacer ring 74, such that the two stators 71a-b are arranged over respective sets of permanent magnets 62a-b of the rotor assembly 60 and enclose these in circumferential direction with a gap therebetween. The stator assembly 70 can further comprise upper or lower distance rings 75 for positioning the stator assembly 70 and fixation of the stator assembly 70 in relation to the generator housing 51. In an alternative embodiment where the rotor assembly only is provided with one sets of permanent magnets, the stator assembly only includes one stator.

The rotor assembly 60 is further arranged rotatable in the generator housing 51 by means of ball bearings 80a-b and ball bearing end shields 81a-b arranged at upper and lower side thereof, respectively.

The generator housing 51 is further provided with sealing means at upper and lower side thereof, e.g. in the form of a sealing plate 91 arranged to the inner sealing tube 90 and a sealing plate 92 arranged to the ball bearing end shield 81a at lower side.

To the upper and lower ends of the generator unit 50 is further arranged linear bearings 100 and linear bearing housing 101, adapted for accommodation of the translator 40. Accordingly, the components of the generator unit 50 are securely encapsulated in the generator housing 51 protecting the components of the generator unit 50 from water. By means of the above-described embodiment, it is possible to seal the generator unit 50 without using rotary or linear seals, which for a given period would wear down. In the present invention, all seals are stationary, which means that the lifetime is improved significant.

Reference is again made to Figure 1. The translator 40 is according to the present invention further at the lower end arranged to a shaft 110 extending out of the lower end of the sleeve 30 for connection to the water-filled piston assembly 200 according to the present invention. The water- filled piston assembly 200 according to the present invention comprises an elongated piston housing 210 arranged at lower part of the float 11, in alignment with the wave energy converter 20, and fixed to the float 11. The elongated piston housing 210 is arranged such that it extends from interior of the float 11 to exterior of the float 11, i.e. with a part of the elongated piston housing 210 interior of the float 11. The elongated piston housing 210 is e.g. at lower end, i.e. the part of the elongated piston housing 210 extending out of the float 11, provided with an opening 211 to surrounding water. The water-filled piston assembly 200 according to the present invention further comprises a piston 220 having an exterior diameter smaller than interior diameter of the piston housing 210 allowing surrounding water to flow from exterior of the piston housing 210 and into the interior of the piston housing 210, and into a position above the piston 220. The piston 220 is arranged to lower end of a piston rod 221 extending from the piston 220 and out of the piston housing 210 via an opening 212 at upper end of the piston housing 210, wherein the interior diameter of the opening 212 is larger than the exterior diameter of the piston rod 221. The upper end of the piston rod 221 is arranged to lower end of the shaft 110 via corresponding attachment means 213, such as flanges provided with through holes and bolts. There is preferably arranged a seal between the piston rod 221 and the piston housing 210 in connection with the opening 212 to prevent water from entering the interior of the float 11.

The length of the part of the elongated piston housing 210 is not limited to the proportions of the Figure 1, as this is only for illustration purposes. The length of the housing 210 will at least have to allow movement of the piston 220 corresponding to the stroke length of the translator 40, and further exhibit a size (volume and length) to ensure that a sufficient amount of water is allowed above the piston 220 to provide the required retaining force for the translator 40. The retaining force will also be dependent on the length of the piston rod 221 positioning the piston 220 in the length direction of the housing 210, and thus the amount of water above the piston 220. According to a further embodiment of the water-filled piston assembly 200 according to the present invention, the piston 220 is arranged movable in longitudinal direction of the piston rod 221 to allow adjustment of the position of the piston 220 in length direction of the piston rod 221 and thus length direction of the housing 210, enabling adjustment of the physical properties of the water-filled piston assembly 200.

In accordance to a further embodiment of the water-filled piston assembly 200 according to the present invention, the piston rod 221 is a telescopic piston rod, enabling adjustment of the piston 220 in length direction of the housing 220, enabling adjustment of the physical properties of the water-filled piston assembly 200.

In yet a further alternative embodiment the energy harvesting buoy 10 according to the present invention, the shaft 110 of the translator 40 is a telescopic shaft 110 enabling adjustment of the translator 40 in length direction of the sleeve 30 and thus generator assembly 50, as well as position of the piston 220 in length direction of the housing 210, enabling adjustment of the physical properties of the wave energy converter 20 and water-filled piston assembly 200.

To allow the water-filled piston housing 200 to be filled with water when the energy harvesting buoy 10 according to the present invention is positioned in water it will be required to have aeration to the surroundings (atmosphere) from interior of the piston housing 210 for evacuation of air from the piston housing 210, as well as for supply of air when water is to be removed from the piston housing 210. According to one embodiment of the present invention this may be achieved by arranging an aeration device 300 at upper part of the energy harvesting buoy 10 in communication with the interior of the piston housing 210 via one or more air channels or by using hollow components of the energy converter 20 to provide one or more air channels, extending between the aeration device 300 and the opening 212 of the piston housing 210.

In this manner, when the energy harvesting buoy 10 is semi-submerged in water, as water is entering the water-filled piston assembly 200 air will be forced out via the aeration device 300.

In an alternative embodiment, the aeration device 300 is integrated with the water-filled piston assembly 200 in air communication with the exterior of the float 11 at upper side via one or more air channels or by hollow components of the energy converter 20 providing one or more air channels.

According to one embodiment of the present invention, the aeration device 300 comprises a controllable valve 310. By using a controllable valve 310, the operation of filling may be performed in a controlled manner by controlling the opening of the valve 310. A controllable valve 310 also opens for locking the filling level of water in the water-filled piston assembly 200 at a desired level as well as dynamic controlling of the filling level in the water-filled piston assembly 200 if desired. The use of a controllable valve 310 also opens for supply of air if the energy harvesting buoy 10 is to be retrieved from the sea, as supply of air will drain the water-filled piston assembly 200, removing the weight from the water as the energy harvesting buoy 10 is lifted from the semi- submerged position.

According to a further embodiment of the present invention, the energy harvesting buoy 10 is further provided with at least one air compressor 320 which is arranged to provide compressed air to the interior of the piston housing 210 via the one or more air channels to reduce the filling level of water in the piston housing 210.

Accordingly, the compressor 320 and the controllable valve 310 will enable active controlling of the filling level of water in the piston housing 210. If the energy harvesting buoy 10 further is provided with sensor means for sensing and/or calculating wave height, the stroke length of the translator 40 may be controlled by positioning of the piston 220 in the piston housing 210 for optimal operation of the translator 40 by controlling the water level in the piston assembly 200.

By controlling the filling level one may thus ensure that the translator 40 at all times is positioned at the center of the full stroke, which enables the energy harvesting buoy 10 to harvest energy in both up and down movement when a wave hits the energy harvesting buoy 10. Accordingly, the water-filled piston assembly 200 will, when filled with water, provide a counterweight for the translator 40, such that translator 40 is retained linearly in the water when the float 11 moves due to passing waves.

Accordingly, relative linear movement between the float 11 and translator 40 will result in movement of the generator unit 50, which is fixed in the float 11, in relation to the translator 40 which is stationary due to the counterweight of the water-filled piston assembly 200, wherein the interaction of the helically shaped permanent magnets 42 of the translator 40 and permanent magnets 62a-b of the rotor assembly 60 will transfer the linear force of the translator 40 into a torque working on the rotor assembly 60 of the generator unit 50, inducing a current in the stator assembly 70. The energy harvesting buoy 10 can further be provided with an energy storage 400 in the form of one or more batteries and/or be arranged for transferring harvested energy to shore or a user by means of a cable as AC or DC voltage/current.

The energy harvesting buoy 10 is preferably provided with a control unit 500 arranged to convert the harvested alternating phase current to DC current for storage in the energy storage 400 and/or for transfer to shore or a user via a cable. For rectifying the AC current to DC current the control unit 500 can e.g. be provided with an AC frequency converter. The control unit 500 will further typically be provided with means and/or software for controlling the damping profile of the generator assembly 50. The control unit 500 will in an embodiment where the energy harvesting buoy 10 is provided with an energy storage 400 preferably be provided with a battery management system for controlling the battery charge current.

The control unit 500 will further be provided with means and/or software for controlling the water level filling of the water-filled piston assembly 200 by controlling the controllable valve 310 and compressor 320, if present. The controlling of the water level may be based on the position of the translator 40 in relation to the generator unit 50 and/or based on a level sensor arranged in the piston housing 210 reading the water level and/or a position sensor reading the position of the piston 220 in the piston housing 210.

For monitoring the electrical position of the rotor assembly 50, the energy harvesting buoy 10 can be provided with one or more hall effect sensors 501, as shown in Figure 2.

The energy harvesting buoy 10 can further be provided with an upwards protruding structure 600 or tower provided with one or more LED marking lights 601 powered by the energy storage 400. Marking light 601 will usually be required for buoys 10 arranged in sea. In an alternative embodiment, the sleeve 30 of the wave energy converter 20 extends out of the float 11 at upper side and wherein the sleeve 30 forms the upwards protruding structure or tower, wherein the LED marking light 601 is arranged.

According to one embodiment of the present invention, the sleeve 30 of the wave energy converter is housing the energy storage 400, control unit 500 and aeration device 300, as well as compressor 320, if present. According to an alternative embodiment of the present invention upwards protruding structure 600 or tower is further arranged for housing one or more of the energy storage 400, control unit 500 and aeration device 300, as well as compressor 320, if present. According to a further embodiment of the present invention both the sleeve 30 and the upwards protruding structure 600 or tower are used for housing one or more of the energy storage 400, control unit 500 and aeration device 300, as well as compressor 320, if present.

According to a further embodiment of the energy harvesting buoy 10 it is provided with anchoring means 700, such as one or more mooring hooks, enabling the energy harvesting buoy 10 to be held in position in the sea, such as by one or more mooring lines, chains or similar (not shown) fixed to the seabed or by an anchor. Accordingly, the anchoring means 700 does not contribute in the function of the energy harvesting buoy 10, only for holding it at a desired position in the sea.

According to a further embodiment of the energy harvesting buoy 10 it is provided with one or more electrical coupling points 410 enabling connection of a cable for transfer of energy from the energy storage to a user in the vicinity, as DC or AC.

According to one embodiment of the present invention the structure 600 or tower and/or piston housing 210 may be integrated into the float 11, e.g. by a casting process casting the float 11 and structure 600 or tower and/or piston housing 210 as one unit.

According to a further embodiment of the present invention the structure 600 or tower and/or piston assembly 200 is formed by steel or composite.

In an alternative embodiment of the energy harvesting buoy 10 according to the present invention, the aeration device 300 is integrated in the structure 600 or tower.

According to a further embodiment of the energy harvesting buoy 10 according to the present invention it further comprises at least one air turbine generator or pump arranged in connection with the aeration, i.e. the one or more air channels, of the water-filled piston assembly 200, capable of utilizing flowing air in and out from the water-filled piston assembly 200 for producing energy. By utilizing a venturi section in the air channels, i.e. a restriction, the efficiency of such a turbine generator or pump will be increased. The generator or pump may be arranged externally of the air channel and connected to an air turbine in the air channel or as an in-pipe unit. Alternatively, a Venturi solution may be used, which will limit the number of mechanical parts. The produced energy may be supplied to the energy storage 400 or a separate energy storage arranged for this.

The use of this additional energy production means will especially be suitable when the energy harvesting buoy 10 is dynamically controlled as described above. The same effect may also be achieved in connection with the energy converter 20 wherein the at least one air turbine generator or pump is utilizing the fact that the generator assembly 50 moves in relation to the translator 40, which will result in that air will be forced in and out of the energy converter 20, which air flow may be used to produce energy, as this will cause an oscillating flow of air.

In accordance with a further embodiment of the energy harvesting buoy 10 according to the present invention, the water-filled piston assembly 200 is further provided with an overflow (not shown) in fluid communication with the exterior of the float 11, preferably via a check valve, such that excess water from the piston housing 210 may be evacuated. The above-mentioned embodiments can be combined to form alternative embodiments within the scope of the attached claims.

A typical area of use of the energy harvesting buoy according to the present invention is as an ocean marking light, for either fish farms or normal boat traffic, where the energy harvesting buoy 10 will be self-powered with minimized requirement for servicing. The energy harvesting buoy 10 according to the present invention can also be positioned and connected to other buoys, such as research or meteorological (weather data) buoys, for powering them.

Another typical area of use is using the energy harvesting buoy 10 as energy harvesting units for fish farms or in shore close areas where a number of such energy harvesting buoys 10 can provide a small scale amount of environmentally friendly energy for e.g. charging of electrical vehicles or boats or be a supplement for ordinary energy production.

The energy harvesting buoy 10 according to the present invention will also be usable in remote areas where no infrastructure is built to provide enough energy for a small community, such as island communities. Further, the energy harvesting buoy 10 according to the present invention will also be suitable in polar areas, where the use of solar panels are not suitable for use due to there is no sun over long periods, as well as the solar panels will be covered in ice and snow, making them inefficient as regards producing energy. In the present invention, the water-filled piston assembly will be down in the water, and thus protected from ice. The present invention is further suitable for powering radio beacons, telemetry systems and similar applications.