TECHNICAL FIELD

The present disclosure relates to wind turbines and wind farm comprising a plurality of the same . More particularly, the present disclosure relates to free-floating offshore wind turbine for deep water use .

BACKGROUND

Due to concerns over rising global temperatures caused by the release of greenhouse gases into the atmosphere , largely from combustion of fossil fuels for energy, interest in carbon-free power production methods is growing . However, of the more than 170 000 terawatt-hours ( TWh) of energy consumed worldwide each year, as of 2019 over 80 percent is still being produced by burning fossil fuels .

One option for carbon-free power production is to utili ze the open oceans for wind energy production . Due to higher wind speeds and greater downward transport of kinetic energy through the troposphere into the boundary layer, energy production potential over the ocean can exceed power production on land by three times or more . Additionally, steadier winds may be found at sea than over land . The Coriolis Effect , together with areas of high pressure , create consistent trade - or prevailing - winds between 30 degrees north and south of the equator . Ocean-based wind power production also benefits from less turbulent winds at sea . Finally, the sheer availabil ity of space makes ocean-based wind energy production a promising prospect , as oceans cover over 70 percent of the earth' s surface . Wind turbines fixed to the seabed exists . However, fixing the bottom of wind turbines into the seabed of deep offshore waters is often not possible or is not a feasible solution due to high costs of the large fixing structures that would be required . Also free-floating wind turbines anchored to the seabed exists . However, anchoring these free-floating wind turbines to the seabed is also pricey . In addition, a drawback of these wind turbines is that they are fixed to the location to where they are attached or anchored and thus , are dependent on the winds of that location .

Finnish patent FI 67745 discloses a freely floating wind power plant .

SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description . This Summary is not intended to identify key features or essential features of the claimed subj ect matter, nor is it intended to be used to limit the scope of the claimed subj ect matter .

It is an obj ect of the present disclosure to provide a technical solution that provides a free- floating (unmoored) wind turbine . It is further an obj ect of the present disclosure to provide a technical solution that provides a dynamically positioned free-floating wind turbine . Furthermore , it is an obj ect of the present disclosure to provide a technical solution that provides a wind farm comprising a plurality of free-floating wind turbines .

The obj ectives above are achieved by the features of the independent claims in the appended claims . Further embodiments and examples are apparent from the dependent claims , and the detailed description . The present disclosure provides free-floating wind turbines comprising a tower comprising an upper part and a lower part , wherein the upper part is configured to be located above water level and the lower part is configured to be submersed, at least partially, under water, wherein the upper part of the tower comprises a nacelle non-rotatably attached to the upper part of the tower and comprises a turbine provided with at least two blades , and at least one generator for generating electricity, wherein the lower part of the tower comprises at least one float ; at least one weight ; and an underwater propelling unit rotatably connected to the lower part of the tower, whereby the underwater propeller unit is turnable about the vertical axis of the tower, and wherein the underwater propelling unit comprises an underwater propeller rotatable by means of a motor for generating propulsion forces , and further, the density of the underwater propeller is of a predetermined density value .

The present disclosure also provides wind farms comprising a plurality of free-floating wind turbines as disclosed in the present disclosure ; and a position means for positioning the plurality of free-floating wind turbines .

The present disclosure also provides uses of a free- floating wind turbine as disclosed in the present disclosure or a wind farm as disclosed in the present disclosure for producing electricity or a fuel . Other features and advantages of the present disclosure will be apparent upon reading the following detailed description and reviewing the accompanying drawings .

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is explained below with reference to the accompanying drawings in which :

FIG . 1 shows a schematic side view of a free-floating wind turbine in accordance with exemplary embodiments ;

FIG . 2 shows a schematic front view of a free-floating wind turbine in accordance with exemplary embodiments ;

FIG . 3 shows a schematic front view of a free-floating wind turbine in accordance with exemplary embodiments ;

FIG . 4 shows a schematic top view of a wind farm in accordance with exemplary embodiments ;

FIG . 5 shows a schematic top view of a wind farm in accordance with exemplary embodiments ;

FIG . 6 shows a schematic side view of a wind farm in accordance with exemplary embodiments ;

FIG . 7 shows a schematic side view of a wind farm in accordance with exemplary embodiments ; and

FIG . 8 shows a schematic side view of a wind farm in accordance with exemplary embodiments .

DETAILED DESCRIPTION

Various embodiments of the present disclosure are further described in more detail with reference to the accompanying drawings . However, the present disclosure may be embodied in many other forms and should not be construed as limited to any certain structure or function discussed in the following description . In contrast , these embodiments are provided to make the description of the present disclosure detailed and complete .

According to the detailed description, it will be apparent to the ones skilled in the art that the scope of the present disclosure encompasses any embodiment thereof , which is disclosed herein, irrespective of whether this embodiment is implemented independently or in concert with any other embodiment of the present disclosure . For example , free-floating wind turbines and/or wind farms disclosed herein may be implemented in practice using any numbers of the embodiments provided herein . Furthermore , it should be understood that any embodiment of the present disclosure may be implemented us ing one or more of the elements presented in the appended claims .

The word "exemplary" is used herein in the meaning of "used as an illustration" . Unless otherwise stated, any embodiment described herein as "exemplary" should not be construed as preferable or having an advantage over other embodiments .

Any positioning terminology, such as "left" , "right" , "top" , "bottom" , "above" , "under" , "apical" , "basal" , etc . , may be used herein for convenience to describe one element' s or feature ' s relationship to one or more other elements or features in accordance with the figures . It should be apparent that the positioning terminology is intended to encompass different orientations of the structure and free- floating wind turbine disclosed herein, in addition to the orientation ( s ) depicted in the figures . As an example , if one imaginatively rotates the structure or free-floating wind turbine in the figures 90 degrees clockwise , elements or features described as "top" and "bottom" relative to other elements or features would then be oriented, respectively, "right" and "left" relative to the other elements or features . Therefore , the positioning terminology used herein should not be construed as any limitation of the present disclosure .

Furthermore , although the numerative terminology, such as "first" , "second" , etc . , may be used herein to describe various embodiments , elements or features , it should be understood that these embodiments , elements or features should not be limited by this numerative terminology . This numerative terminology is used herein only to distinguish one embodiment , element , or feature from another embodiment , element , or feature . For example , a first chamber discussed below could be called a second chamber, and vice versa, without departing from the teachings of the present disclosure .

The free-floating wind turbines and wind farms as disclosed in the present disclosure provide a technical solution that allows mitigating or even eliminating the drawbacks of the prior art .

The invention is based on the reali zation that a free-floating wind turbine may be achieved by the features of the independent claims in the appended claims . In particular, the free-floating wind turbine comprises a large , integrated underwater propeller, wherein the underwater propeller may use some of the energy produced by the wind turbine to hold it in place and move as needed .

"Optional" or "optionally" denotes that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances in which it does not . "Comprises" or "comprising" denotes that the subsequently described feature (s) or act(s) may but need not include other feature (s) or act(s) . It will further be understood that reference to 'an' item refers to one or more of those items.

The terms "free-floating wind turbine" as used in the present disclosure refers to wind turbine without any mooring means and is thereby of unmoored type, i.e., the wind turbine is unmoored and, therefore, it is not attached to the seabed in any way .

The term "nacelle" as used in the present disclosure refers to a cover housing that houses all of the generating components in a wind turbine, including, but not limited to, the generator, gearbox, drive train, and brake assembly.

The terms "predetermined density value" as used in the present disclosure refers to a density that has been predetermined. E.g., if the free- floating wind turbine is to be used offshore in seawater, the density of the seawater is determined, and the determined density of the seawater is set as the predetermined density value. E.g., if the density of the seawater is determined to be 1030 kg/m ³ , the predetermined density value may be 1030 kg/m ³ , or may be selected from the range 1005 - 1060 kg/m ³ .

In one aspect is disclosed a free-floating wind turbine comprising a tower comprising an upper part and a lower part, wherein the upper part is configured to be located above water level and the lower part is configured to be submersed, at least partially, under water, wherein the upper part of the tower comprises a nacelle non-rotatably attached to the upper part of the tower and comprises a turbine provided with at least two blades , and at least one generator for generating electricity, wherein the lower part of the tower comprises at least one float ; at least one weight ; and an underwater propelling unit rotatably connected to the lower part of the tower, whereby the underwater propeller unit is turnable about the vertical axis of the tower, and wherein the underwater propelling unit comprises an underwater propeller rotatable by means of a motor for generating propul sion forces , and further, the density of the underwater propeller is of a predetermined density value .

The free-floating wind turbine as disclosed in the present disclosure is completely free-floating or, in other words , unmoored; it is not attached to the seabed in any way . The free-floating wind turbine may feature a large ( relative to the at least two blades of the turbine ) , integrated underwater propeller that may use some of the energy produced by the wind turbine to hold it in place and move as needed . A weight on the bottom of the free-floating wind turbine ( i . e . , at the lower part of the tower) may provide stability to the free-floating wind turbine , may help the free-floating wind turbine remain vertical , may eliminate , or reduce movement effects from waves , and may keep it from tipping . The free-floating wind turbine may be mass produced at coastal production facilities . The slender tower, combined with the at least two-bladed turbines and propellers , allows for space-efficient freighter transport to an open-ocean wind farm . Alternatively, the wind turbines may use their own underwater propellers to navigate from the production facility to the wind farm . Additionally, the underwater propeller may be used to maintain the wind turbine ' s position and to move it if needed due to changes in winds speeds . This allows access to areas of high energy production potential in the open ocean out of reach to contemporary ( floating) wind turbines , which are anchored or fixed to the seabed .

Additionally, or alternatively, the upper part is configured to be located above water level and the lower part is configured to be submersed under water . Additionally, or alternatively, the tower extends < 220 m underwater . Additionally, or alternatively, the free-floating wind turbine extends < 317 m above the sea level and < 220 m underwater . Additionally, or alternatively, the height of the free-floating wind turbine is < 537 m . In contrast to previous conceptual designs for unmoored wind turbine systems that feature , e . g . , large platforms , very large floating structures , and tanker hulls , the free- floating wind turbine as disclosed in the present disclosure may feature a slender design with a tower extending far underwater (e . g . , 220 m underwater and 317 m above the sea level ) . These free-floating wind turbines are beneficial since the tower (extending far underwater) may also allow the turbine to sway — it may rock back and forth without tipping over . The tower, the float , the weight , and the underwater propelling unit of the free-floating wind turbine contribute to the floating properties of the wind turbine .

Additionally, or alternatively, the tower is cylindrical . A cylindrical tower minimi zes resisting forces on the wind turbine from wind and currents .

Additionally, or alternatively, the diameter of the tower is 1 - 75 m . These free-floating wind turbines minimize resisting forces on the wind turbine from wind and currents. Additionally, or alternatively, the tower has a hollow interior structure. Additionally, or alternatively, the tower is made of a flexible material. Additionally, or alternatively, the tower has a honeycomb structure. Additionally, or alternatively, the tower has a reinforced structure by means of supports arranged to extend from the interior wall of one side of the tower to another interior wall of another side of the tower. With these free-floating wind turbines, the turbine may be allowed to rock or sway in the water, minimizing the need for material robustness. Instead of a hollow interior for, e.g., service ladders and other infrastructure, a nature-inspired honeycomb structure may fill the inside of the tower, with space only for electrical cables and the like. This enables a narrower tower for less wind and current resistance.

Additionally, or alternatively, the ratio of the underwater propeller diameter to the above-water turbine diameter is 1:28 - 2:1, preferably 1:10 - 1:1, more preferably 1:2 - 1:1. Currently, the world's largest wind turbine has a diameter of 220 m for 12-13 MW of power production. The same diameter may be used for the turbine of the free-floating wind turbine as disclosed in the present disclosure. The underwater propeller, on the other hand, may even have the same diameter as the turbine, or may, e.g., be one half the diameter of the turbine, or 110 m. By extending the tower of the free-floating wind turbine as disclosed in the present disclosure far underwater (e.g., 220 m underwater and 317 m above the sea level) , a large underwater propeller (e.g., 110 m in diameter) may be accommodated, which may enable a wind turbine of this type to achieve greater electricity production capacity, as the larger underwater propeller may need less power to function than a smaller underwater propeller . These free-floating wind turbines are beneficial since the underwater propeller together with the tower (extending far underwater) may allow the turbine to sway — it may rock back and forth without tipping over .

In the free-floating wind turbine as disclosed in the present disclosure , both the turbine and the underwater propeller may be two-bladed fast runners . The turbine is fixed to the tower, while the underwater propelling unit rotates hori zontally . The turbine may withstand violent gusts of wind, but the underwater propeller, being underwater, does not require the same level of resilience .

Additionally, or alternatively, the predetermined density value is selected from the range 1005 - 1060 kg/m ³ , preferably from the range 1020 - 1040 kg/m ³ . Free-floating wind turbines having an underwater propeller with a dens ity in these ranges are beneficial since forces on the underwater propeller unit may be reduced, and, therefore , on bearing ( s ) it needs to turn . With these reduced forces , the bearing ( s ) can be lighter with less materials used . This in turn reduces costs of the underwater propeller unit and thus of the free- floating wind turbine . I f the underwater propeller would be of a density significantly differing from that of seawater (e . g . , having a density of less than 1005 kg/m ³ or more than 1400 kg/m ³ ) , and thus exert upward or downward pressure on the propeller unit , those forces may carry forward to the entire tower, exerting lever-like forces on the tower at the point the underwater propeller unit connects to the rest of the tower . In such case , the tower may for example need to be rigidly constructed in order to resist these lever forces . By having a similar dens ity as the seawater the lower part is configured to be submersed into , at least partially, the forces otherwise transferred to the tower are reduced, enabling the tower to have a lighter and less rigid construction than would otherwise be required, again reducing material requirements and thus costs . I f the underwater propeller is of a similar density as seawater, for example by it being filled with freshwater and then sealed, the pressure forces of seawater on the underwater propeller are counteracted, allowing the propeller to maintain its form and preventing it from collapsing on itself .

Also , propeller blade ( s ) of the underwater propeller having a density being approximately the same as the water through which they move may reduce the cost and installation difficulty of the underwater propeller, in particular compared to the turbine blades .

Additionally, or alternatively, the free- floating wind turbine further comprises a turning propeller unit non-rotatably arranged to the lower part of the tower between the nacelle and the underwater propelling unit , wherein the turning propeller unit comprises at least one turning propeller rotatable by means of a motor for generating propulsion forces for turning the tower together with the nacelle . Additionally, or alternatively, the turning propeller unit is arranged between the nacelle and the underwater propelling unit , preferably the turning propeller unit being configured to be located between the water level and the underwater propelling unit when the lower part being submersed under water ; the at least one weight is arranged below the underwater propelling unit and is attached to the di stal bottom part of the lower part of the tower, the at least one float is arranged between the at least one weight and the nacelle , and the underwater propelling unit is arranged between the turning propeller unit and the at least weight . The at least one turning propeller, located between the nacelle and underwater propelling unit , may be used to turn the free-floating wind turbine ( around the vertical axis of the tower) , and/or to maintain the free-floating wind turbine ' s angle relative to the wind . It i s to be understood that the turning propeller unit may turn the tower together with the nacel le independently of the underwater propelling unit . The at least one turning propeller enable the tower to rotate for optimal wind energy capture . It is to be understood that the turning propeller unit ( and, therefore , also the at least one turning propeller) does not extend to the turbine provided with at least two blades and the underwater propelling unit comprising the underwater propeller . The motor of the turning propeller unit may use some of the electricity generated by the at least one generator of the nacelle .

Additionally, or alternatively, the turning propeller unit is attached to the lower part of the tower such that the at least one turning propeller is rotatable under the water level . Additionally, or alternatively, the turning propeller unit is attached to the lower part of the tower such that the at least one turning propeller is below the water level when the lower part of the tower is submersed under water . Better propulsion forces for turning the tower together with the nacelle may be generated .

Additionally, or alternatively, the turning propeller unit is attached to the float .

Additionally, or alternatively, the turning propeller unit comprises two turning propellers rotatable by means of a motor for generating propulsion forces for turning the tower together with the nacelle . Preferably, the two turning propellers of the turning propeller unit are arranged on the opposite sides of the vertical axis of the tower . It is to be understood that the turning propeller unit may turn the tower together with the nacelle independently of the underwater propelling unit . Using two turning propellers may be more effective in turning the free-floating wind turbine ( around the vertical axis of the tower) , and/or to maintain the free-floating wind turbine ' s angle relative to the wind . In addition, two turning propellers may enable the tower to rotate more efficiently for optimal wind energy capture .

Additionally, or alternatively, the at least one turning propeller have a diameter of 1 - 50 m . Using turning propeller ( s ) having diameter of 1 - 50 m may turn the free-floating wind turbine efficiently .

Additionally, or alternatively, both the turbine of the nacelle and the underwater propel ler of the underwater propelling unit are provided with two blades , wherein the ratio of the diameters of the underwater propeller to the turbine of the nacelle is 1 : 28 - 2 : 1 , preferably 1 : 10 - 1 : 1 , more preferably 1 : 2 - 1 : 1 . Additionally, or alternatively, the two blades provided in the turbine of the nacelle extends in total < 220 m, and the two blades provided in the underwater propeller of the underwater propelling unit extends in total < 220 m, preferably 110 - 220 m, more preferably 110 m . A net power production from these free-floating wind turbines is high .

Additionally, or alternatively, both the turbine of the nacelle and the underwater propeller of the underwater propelling unit are provided with two- bladed fast runners . These free-floating wind turbines provide a low solidity . Additionally, or alternatively, the nacelle and the underwater propelling unit and/or the turning propeller unit are electrically connected, and the at least one generator of the nacelle is configured to provide electric energy to an electric motor of the underwater propelling unit for driving the underwater propeller and/or to an electric motor of the turning propeller unit for driving the at least one turning propeller . It is to be understood that both the underwater propelling unit and the turning propeller unit may be electrically connected with the nacelle , or only one of the underwater propel ling unit and the turning propeller unit may be electrically connected with the nacelle . Therefore , the generator of the nacelle may provide electric energy to an electric motor of the underwater propelling unit and/or the turning propeller unit . Energy self-sufficiency of these free-floating wind turbine may be provided .

Additionally, or alternatively, the free- floating wind turbine further comprises at least one electricity source . Additionally, or alternatively, the free-floating wind turbine further comprises a plurality of electricity sources . An example of an electricity source includes , but is not limited to , an electric battery .

Additionally, or alternatively, the at least one generator for generating electricity is electrically connected to at least one of the at least one electricity source and configured to charge the at least one electricity source . Additionally, or alternatively, the at least one generator for generating electricity is ( are ) electrically connected to the plurality of electricity sources and configured to charge the plurality of electricity sources . These free-floating wind turbines are beneficial since they may be used to charge electricity source ( s ) such as electric battery (batteries ) . Therefore , electricity generated by the at least one generator may be stored in the electricity source ( s ) .

Additionally, or alternatively, the electricity source ( s ) being configured to provide electricity to the underwater propelling unit and/or the turning propeller unit . Additionally, or alternatively, the free-floating wind turbine further comprises an electricity source configured to provide electricity to the underwater propelling unit and/or the turning propeller unit . Additionally, or alternatively, the free-floating wind turbine further comprises a plurality of electricity sources each being independently configured to provide electricity to the underwater propelling unit and/or the turning propeller unit . I f the generator of the nacelle does not generate electricity, e . g . , if there is no wind or the wind i s insufficient for rotating the at least two blades of the turbine , an electricity source may provide electric energy to the underwater propelling unit and/or the turning propeller unit for moving, turning, rotating, and/or relocating the free-floating wind turbine . Therefore , these free-floating wind turbine are more feasible when these free-floating wind turbines are used in waters with fluctuating winds or no winds . These free-floating wind turbines are beneficial since they may be independent from electricity generated by the at least one generator for moving the free-floating wind turbines . E . g . , these free-floating wind turbines may be relocated to a location where there is sufficient wind for generating electricity when the at least one generator does not provide electric energy to the underwater propelling unit and/or the turning propeller unit .

Additionally, or alternatively, the free- floating wind turbine further comprises a plurality of electricity sources each being independently configured to provide electricity to the underwater propelling unit and/or the turning propeller unit , wherein the at least one generator for generating electricity is electrically connected to at least one of the plurality of electricity sources and configured to charge the at least one of the plurality of electricity sources . Additionally, or alternatively, the plurality of electricity sources being configured to provide electricity to the underwater propelling unit and/or the turning propel ler unit , wherein the at least one generator for generating electricity is electrically connected to the plurality of electricity sources and configured to charge the plurality of electricity sources . These free-floating wind turbines are beneficial since electricity generated by the at least one generator may be stored in the electricity source ( s ) and electricity stored in the electricity source ( s ) may be used later by the underwater propelling unit and/or the turning propeller unit for moving, turning, rotating, and/or relocating the free- floating wind turbine , also when the at least one generator does not provide electric energy to the underwater propelling unit and/or the turning propeller unit when there is insufficient wind for generating electricity by the generator . It is to be understood that the electricity source ( s ) may also be charged by other charging means than the at least one generator, at least partially, before , during, or after the generator being configured to charge the electricity source ( s ) charges the electricity source ( s ) .

Additionally, or alternatively, the underwater propeller comprises at least one underwater propeller blade . Additionally, or alternatively, the underwater propeller comprises two underwater propeller blades .

Additionally, or alternatively, underwater propeller has a hollow structure . Additionally, or alternatively, underwater propeller is made of a material arranged not to implode in response to outer forces , such as the water pressure and water currents . Additionally, or alternatively, the at least one underwater propeller blade of the underwater propeller has a hollow structure . Additionally, or alternatively, the blades of the underwater propeller has a hollow structure . Additionally, or alternatively, the underwater propeller blade ( s ) of the underwater propeller has (have ) a hollow structure . For example , the material arranged not to implode in response to outer forces may be steel . Additionally, or alternatively, the underwater propeller comprises a hollow structure , one or more openings for filling the hollow structure with a solution having a lower density than the water the underwater propeller being configured to be submersed into , and one or more seals for sealing the one or more openings . E . g . , the empty space in the hollow structure of the underwater propeller may be filled via the opening ( s ) with fresh water, having a lower density than seawater, before the underwater propeller is submersed into the seawater, and subsequently sealing the opening ( s ) with the seal ( s ) thus preventing the fresh water to leak out from the underwater propeller . These underwater propellers have a predetermined density value being lower than the water the underwater propeller being configured to be submersed into .

Additionally, or alternatively, the underwater propeller is made of a material having a density selected from the range of selected from the range 1005 - 1060 kg/m ³ . Additionally, or alternatively, the underwater propeller comprises a hollow structure , and one or more openings arranged such that the water may enter and leave the hollow structure of the underwater propeller being configured to be submersed into the water . Additionally, or alternatively, the underwater propeller is made of a material selected from steel or a polymer such as polypropylene . Additionally, or alternatively, the wall ( s ) of the underwater propeller are 0 . 1 - 10 cm thick . These free-floating wind turbines may allow for reduced costs and installation difficulty of the underwater propeller .

Additionally, or alternatively, the free- floating wind turbine further comprises at least one receiving means for receiving at least one signal , wherein the at least one receiving means is connected to the underwater propelling unit and/or the turning propeller unit , wherein the motor of the underwater propelling unit being configured to drive the underwater propeller in response to the at least one signal and/or the motor of the turning propeller unit being configured to drive the at least one turning propeller in response to the at least one signal .

These free-floating wind turbines allows one to remotely control the underwater propelling unit and/or the turning propeller unit by an external transmitter, which may send at least one signal to the receiving means , but may also be used to control the speed of the underwater propeller and/or the at least one turning propeller .

Additionally, or alternatively, the free- floating wind turbine further comprises controlling means configured to control the speed of the underwater propeller and/or the at least one turning propeller . The controlling means may be electrically connected to the motor of the underwater propelling unit being configured to drive the underwater propeller in response to the at least one signal and/or the motor of the turning propeller unit being conf igured to drive the at least one turning propel ler in response to the at least one signal . Additionally, or alternatively, the controlling means may be electrically connected to the at least one receiving means .

Additionally, or alternatively, the free- floating wind turbine further comprises detection means configured to detect a deviation of a predetermined position of the free-floating wind turbine and configured to send the at least one signal to the at least one receiving means in response to the detected deviation of the predetermined position . The detection means may be for example , but not limited to , a GPS unit to which the predetermined, desired, position of the free-floating wind turbine may be saved . Once the predetermined position of the free- floating wind turbine has been saved to the GPS unit , the GPS unit may detect if the free-floating wind turbine is not at the location that was saved and in response to the detection send the at least one signal to the at least one receiving means . Subsequently, the free-floating wind turbine may be relocated using the underwater propelling unit and/or the turning propeller unit . Alternatively, the detection means may be a sonar or an echo sounder .

Additionally, or alternatively, the free- floating wind turbine further comprises a wind detection means configured to detect a wind direction and conf igured to send the at least one signal to the at least one receiving means in response to the detected wind direction, wherein the at least one receiving means is connected to the turning propeller unit , wherein the motor of the turning propeller unit being configured to drive the at least one turning propeller in response to the at least one signal . These free-floating wind turbine are beneficial since the at least one turning propeller generating propulsion forces may turn, in response to the detected wind direction by the wind detection means , the tower together with the nacelle such that the turbine provided with at least two blades are turned against the wind, and, therefore , directed for optimal wind capture . It is to be understood that the turning propeller unit may turn the tower together with the nacelle independently of the underwater propelling unit .

Additionally, or alternatively, the underwater propelling unit is configured to rotate the underwater propeller in response to the at least one signal .

Additionally, or alternatively, the tower is needle formed . This may provide for less wind and current resistance .

Additionally, or alternatively, the tower is hollow .

Additionally, or alternatively, the at least one weight is arranged below the at least one float and is connected to a distal bottom part of the lower part of the tower . Additionally, or alternatively, the at least one weight is arranged below the underwater propelling unit and is connected to a distal bottom part of the lower part of the tower . Additionally, or alternatively, the at least one weight is arranged below the underwater propelling unit and is attached to a distal bottom part of the lower part of the tower, and the at least one float is arranged between the at least one weight and the nacelle . Additionally, or alternatively, the at least one weight is integrated to be an inseparable part of the distal bottom part of the lower part of the tower . Additionally, or alternatively, the at least one weight has a large surface area . These free-floating wind turbines are advantageous since the weight provides stability, are beneficial for the free- floating wind turbines to remain vertical , and may prevent them from tipping when the free-floating wind turbine is in use . A large hori zontal surface area of the weight may further reduce vertical movement of the free-floating wind turbine by eliminating some of the movement effect from waves .

Additionally, or alternatively, the nacelle is attached to the upper part of the tower such that the blades are rotatable above the water level .

Additionally, or alternatively, lower part of the tower of the free-floating wind turbine comprises one single float and one single weight .

Additionally, or alternatively, the lower part of the tower further comprises at least one bumper and extending a transverse distance from the tower .

Additionally, or alternatively, the lower part of the tower further comprises at least one bumper below the water level and extending a transverse distance from the tower . Additionally, or alternatively, the at least one bumper extends beyond the reach of the turbine and the underwater propeller . A bumper may bring safety to the wind turbine , e . g . , if a maintenance vehicle is docked to the wind turbine it may damage the wind turbine without a bumper, or a wind turbine with a bumper may be protected from another wind turbine if the another wind turbine bump into the wind turbine with a bumper, especially before and during the wind turbine ( s ) are submersed partly under water .

Additionally, or alternatively, the float is serving as a bumper . These free-floating wind turbines are beneficial since there may be no need for an additional bumper at the float .

Additionally, or alternatively, the weight is serving as a bumper . These free-floating wind turbines are beneficial since there may be no need for an additional bumper at the weight .

Additionally, or alternatively, a bumper is connected to the lower part of the tower .

Additionally, or alternatively, a bumper is connected to the float .

Additionally, or alternatively, the float is integrated to be an inseparable part of the tower . These free-floating wind turbines are beneficial since resisting forces on the wind turbine may further be reduced .

Additionally, or alternatively, one or more flat spokes connect the bumper to the float and the bumper is configured to allow water to flow between the float and the bumper via at least one opening arranged between the bumper, the one or more flat spokes , and the float . These wind turbines are beneficial since they allow water originating from the water the wind turbine is configured to be submersed into to flow freely between the bumper, the one or more flat spokes , and the float , and back to the water the wind turbine is configured to be submersed into . This in turn may minimi ze resistance caused by the water .

Additionally, or alternatively, the abovewater turbine diameter is 40 - 300 m, 50 - 220 m, or 220 m . These free-floating wind turbines are advantageous since they are efficient .

Additionally, or alternatively, the underwater propel ler diameter is 1 . 4 - 600 m, 80 - 300 m, 50 - 220 m, 25 - 110 m, 110 m, or 220 m . These free-floating wind turbines are advantageous since they are efficient .

Additionally, or alternatively, the free- floating wind turbine further comprises at least one storing means for storing fuel .

Additionally, or alternatively, the free- floating wind turbine further comprises a power-to-X unit for converting electricity generated by the at least one generator to a fuel , wherein the power-to-X unit is electrically connected to the at least one generator of the nacelle . The terms "power-to-X" as used in the present disclosure refers to a number of electricity conversion units that use electric power (electricity) for preparing fuel . These free-floating wind turbines are advantageous since the electricity generated by the at least one generator may be converted to fuel that may be used later .

Additionally, or alternatively, the power-to- X unit is integrated to the tower . These free-floating wind turbines are beneficial since the power-to-X unit is protected from external elements and/or the power- to-X unit does not disrupt the aerodynamics of the free-floating wind turbines . Additionally, or alternatively, at least one of the at least one storing means is arranged to store fuel generated by the power-to-X unit .

Additionally, or alternatively, at least one of the at least one storing means is configured to receive and store fuel generated by the power-to-X unit .

Additionally, or alternatively, the free- floating wind turbine further comprises storing means for storing the fuel , wherein the storing means is attached to the power-to-X unit . These free-floating wind turbines are advantageous since fuel may be stored and used later by free-floating wind turbines as disclosed in the present disclosure , and/or the fuel stored in the storing means may be unloaded from the storing means and relocated for further use .

Additionally, or alternatively, the power-to- X unit is a power-to-ammonia unit or a power-to- hydrogen unit . These free-floating wind turbines are advantageous since the ammonia or hydrogen being prepared by the power-to-ammonia unit or the power-to- hydrogen unit , respectively, are easily stored and relocated .

Additionally, or alternatively, the free- floating wind turbine further comprises at least one generator for generating electricity from the fuel , wherein the at least one generator for generating electricity from the fuel is electrically connected to the underwater propelling unit and/or the turning propeller unit . These free-floating wind turbines are beneficial since the electric motor of the underwater propelling unit and/or the electric motor of the turning propeller unit may be provided electric energy for driving the underwater propeller and/or for driving the at least one turning propeller, respectively, when the at least one generator of the turbine of the nacelle does not generate electricity, e . g . , when there i s not enough wind for turning the at least two blades of the turbine . It is to be understood that the storing means for storing fuel may also be loaded with fuel by other means than the power-to-X unit , at least partially, before , during, or after the power-to-X unit convert electricity generated by the at least one generator to fuel .

Without being bound to any theory the inventors believe that it is due to the significantly higher dens ity of water compared to air that the free- floating wind turbine can produce net power, while maintaining its position with an underwater propeller . Simplified calculations follow for a free-floating wind turbine . Disregarding friction losses , the following equations hold for a rotor (propeller or turbine ) in a j et of fluid (gas or liquid) with constant cross-section (A) that is moving with speed v relative to the rotor, which either creates the j et or stops it : where P denotes power, T thrust ( that is , force exerted by a propeller on the water j et it creates , or by the wind on a turbine ) , A area swept by the rotor blades , and p density of the fluid . Elimination of v from the two equations yields :

. 1

7- = — _p AP ²

To prevent the free-floating wind turbine from drifting away with the wind, the pressure exerted by the propeller on the water must equal the pressure of the wind on the turbine . That is , the equality Po ^A tPt Pw ^A pPp must hold, where the subscripts a, t, w, and p refer to air, turbine , water, and underwater propeller, respectively . Using the values p„ = 1000 kg/m ³ and p _a = 1 . 275 kg/m ³ , one obtains the relations where P _p and P _t are power fed to the underwater propeller and power generated by the turbine , respectively . Variables d _t and d _p are the diameters of the turbine and underwater propeller, respectively . When the efficiencies of the generator, motor, turbine , and underwater propeller, as well as the influence of the ocean currents are considered, the ratio is estimated to be which implies that , if the diameter of the underwater propeller i s one tenth of the diameter of the turbine , the total effect produced by the free-floating wind turbine is needed to keep it in place . But if the underwater propeller and turbine have the same diameter ( d _t = d _p ) , only one tenth of the effect is needed to power the underwater propeller, while the remaining 90 percent is the net power produced by the turbine of the free-floating wind turbine . In the design proposed, with a 220 m turbine and 110 m underwater propeller, an estimated 20 percent of the total effect is used by the underwater propeller, while 80 percent is the net power produced by the turbine of the free-floating wind turbine . A precise calculation may be unable to produce a simple , well-defined equality like the previous equation relating turbine and underwater propeller powers to their diameters . In addition to not considering friction losses , the above calculations do not consider losses from the at least one turning propeller, typically two small turning propellers , used also to maintain the position of the turbine relative to the wind . The energy used by, e . g . , optional tugs in the corners of the wind farm ( as described below) , as well as the energy used by the optional power-to-X unit to hold itself in place , is also not considered . In any case , with high wind energy production potential in the open ocean, significant net power may be produced by free-floating wind turbines at sea .

In one aspect is disclosed wind farm comprising a plurality of free-floating wind turbines as defined in the present disclosure ; and a position means for positioning the plurality of free-floating wind turbines . This wind farm is beneficial , since it allows acces s to areas of high energy production potential in the open ocean out of reach to contemporary ( floating) wind farms having wind turbines , which are anchored to the seabed . In addition, the wind farm may be maintained at its position and moved as needed .

Additionally, or alternatively, the position means is an attaching means for attaching each of the plurality of free-floating wind turbines to at least one adj acent free-floating wind turbine . Additionally, or alternatively, the attaching means comprises a disconnecting means configured to disconnect the attaching means from free-floating wind turbine . I f tension on the attaching means becomes too high, the wind turbine may disconnect itself from the attaching means with any suitable disconnecting means .

Additionally, or alternatively, the attaching means is a cable , wire , rope , cord, line , or a net .

Additionally, or alternatively, the position means comprises at least one receiving means attached to each of plurality of wind turbines , wherein the at least one receiving means being configured to receive at least one signal , wherein the at least one receiving means is connected to the underwater propelling unit and/or the turning propeller unit , wherein the motor of the underwater propelling unit being configured to drive the underwater propeller in response to the at least one signal and/or the motor of the turning propeller unit being configured to drive the at least one turning propeller in response to the at least one signal ; and at least one detection means configured to detect a deviation of a predetermined position of each of the plurality of the free-floating wind turbines and configured to send the at least one signal to the at least one receiving means attached to each of plurality of wind turbines in response to the detected deviation of the predetermined pos ition of each of the plurality of the free-floating wind turbines .

These wind farms are beneficial since the wind farms may be autonomous . The at least one detection means may be attached to a wind turbine , to the seabed, or submersed into the water . Predetermined positions corresponding to desired positions of each of the wind turbines may be saved in the at least one detection means . The at least one detection means may detect deviation ( s ) of the predetermined positions and subsequently cause the underwater propeller and/or the at least one turning propeller of the wind turbine ( s ) to be activated such that the underwater propeller and/or the at least one turning propeller cause the wind turbine ( s ) to relocate back to the desired position ( s ) .

Additionally, or alternatively, the at least one detection means i s one detection means and attached to one free-floating wind turbine of the plurality of free-floating wind turbines . An even more autonomous wind farm may be achieved .

Additionally, or alternatively, the position means comprises at least one receiving means attached to each of plurality of wind turbines , wherein the at least one receiving means being configured to receive at least one signal , wherein the at least one receiving means is connected to the underwater propelling unit and/or the turning propeller unit , wherein the motor of the underwater propelling unit being configured to drive the underwater propeller in response to the at least one signal and/or the motor of the turning propeller unit being configured to drive the at least one turning propeller in response to the at least one signal ; and at least one detection means attached to each of plurality of wind turbines and configured to detect a deviation of a predetermined position of the free- floating wind turbine of the plurality of the free- floating wind turbines and configured to send the at least one signal to the at least one receiving means attached to each of plurality of wind turbines in response to the detected deviation of the predetermined position of the free-floating wind turbines . An even more autonomous wind farm may be achieved . Additionally, or alternatively, the position means comprises at least one receiving means attached to each of plurality of wind turbines , wherein the at least one receiving means being configured to receive at least one signal , wherein the at least one receiving means is connected to the underwater propelling unit and/or the turning propeller unit , wherein the motor of the underwater propelling unit being configured to drive the underwater propeller in response to the at least one signal and/or the motor of the turning propeller unit being configured to drive the at least one turning propeller in response to the at least one signal ; at least one identification means being configured to be placed at a position of at least one of the plurality of the free-floating wind turbines ; and at least one detection means attached to at least one free-floating wind turbine of the plurality of free-floating wind turbines , wherein the at least one detection means being configured to determine the coordinates of the at least one identification means , being configured to detect a deviation of a predetermined distance to the at least one identification means , and being configured to send the at least one signal to the at least one receiving means attached to each of plurality of wind turbines in response to the detected deviation of the predetermined distance to the at least one identification means .

An even more autonomous wind farm may be achieved . The at least one identification means may be placed at a desired position of at least one of the plurality of the free-floating wind turbines using, e . g . , but not limited to , a net configured to be submersed below the water level and below the wind farm, whereto the at least one identi fication means is attached to . Additionally, or alternatively, the at least one identification means may be placed at the seabed or attached to the seabed at a desired position of at least one of the plurality of the free-floating wind turbines . The at least one detection means may determine the coordinates of the at least one identification means and may be configured to detect a deviation of a predetermined distance to the at least one identification means . The at least one detection means may be for example , but not limited to , an echo sounder, or sonar, configured as stated above . The predetermined distance may correspond to a desired distance between the position of the at least one identification means and the position of the at least one detection means ( and, therefore , the wind turbine ) and the desired distance may be saved in the at least one detection means . The at least one detection means may detect deviation ( s ) of the predetermined distance ( s ) and subsequently cause the underwater propeller and/or the at least one turning propel ler of the wind turbine ( s ) to be activated such that the underwater propeller and/or the at least one turning propeller cause the wind turbine ( s ) to relocate back to the desired position ( s ) .

In another aspect is disclosed use of a free- floating wind turbine as defined in the present disclosure or a wind farm as disclosed in the present disclosure for producing electricity or a fuel . In embodiments , the fuel is selected from hydrogen and/or ammonia .

FIG . 1 shows a schematic side view of a free-floating wind turbine 100 in accordance with exemplary embodiments . As shown in FIG . 1 , the free-floating wind turbine 100 may comprise a tower 102 comprising an upper part 102a and a lower part 102b, wherein the upper part 102a is configured to be located above water level 105 and the lower part 102b is configured to be submersed, at least partially, under water . The upper part 102a of the tower 102 may comprise a nacelle 110 non-rotatably attached to the upper part

102a of the tower 102 and comprises a turbine provided with at least two blades 120 , and at least one generator (not shown) for generating electricity . The nacelle may comprise a beacon (not shown) . The lower part 102b of the tower 102 may comprise at least one float 130 ; at least one weight 140 ; and an underwater propelling unit 150 rotatably connected to the lower part 102b of the tower 102 . The underwater propeller unit 150 may be turnable about the vertical axis of the tower 102 . The underwater propelling unit 150 may comprise an underwater propeller 160 rotatable by means of a motor 155 for generating propulsion forces Pl . The dens ity of the underwater propeller 160 may be of a predetermined density value . The wind force Fl may tilt the free-floating wind turbine 100 to some degree . The underwater propeller 160 may generate propulsion forces Pl that counteract the degree of tilting, at least partly, produced by the wind . This is beneficial since these free-floating wind turbines 100 may be more efficient . In addition, since the underwater propeller unit 150 may be turnable about the vertical axis of the tower 102 , the direction of the propulsion forces Pl generated may be changed . These free-floating wind turbines 100 are advantageous since they are versatile . The free-floating wind turbine 100 may further comprise a turning propeller unit 172 non-rotatably arranged to the lower part 102b of the tower 102 between the nacelle 110 and the underwater propelling unit 150 , wherein the turning propeller unit 172 comprises at least one turning propeller 170 rotatable by means of a motor (not shown) for generating propulsion forces P2 for turning the tower 102 together with the nacelle 110 . It is to be understood that the turning propeller unit 172 may turn the tower 102 together with the nacelle 110 independently of the underwater propelling unit 150 . In embodiments ( as shown in FIG . 1 ) the turning propeller unit 172 comprising the at least one turning propeller 170 is non-rotatably attached to the float 130 of the lower part 102b of the tower 102 , preferably the at least one turning propeller 170 is configured to be located below the water level 105 ( as shown) . The lower part 102b of the tower 102 may further comprise at least one bumper 180 below the water level 105 and extending a transverse distance from the tower 102 . The free-floating wind turbine 100 may further comprise a power-to-X unit 190 for converting electricity generated by the at least one generator (not shown) to a fuel (not shown) , wherein the power-to-X unit 190 is electrically connected (not shown) to the at least one generator of the nacelle 110 . The power-to-X unit 190 may be integrated to the tower 102 (not shown) . The free-floating wind turbine 100 may further comprise storing means 192 for storing the fuel (not shown) , wherein the storing means 192 is attached to the power-to-X unit 190 . The storing means 192 may be integrated to the tower 102 (not shown) . It is to be understood that the storing means 192 may be configured to receive the fuel (not shown) from the power-to-X unit 190 . The power-to-X unit 190 may be a power-to-ammonia unit (not shown) or a power-to- hydrogen unit (not shown) . The free-floating wind turbine may further comprise at least one generator (not shown) for generating electricity from the fuel (not shown) , wherein the at least one generator for generating electricity from the fuel is electrically connected (not shown) to the underwater propelling unit 150 and/or the turning propeller unit 172. The ratio of the underwater propeller diameter dl to the above-water turbine diameter d2 may be 1:28 - 2:1, preferably 1:10 - 1:1, more preferably 1:2 - 1:1. The free-floating wind turbine 100 may further comprise a cable 195, such as an electrical cable, wire, rope, cord, line, or a net, preferably the cable 195 is attached to the bottom part 192b of the tower 190. E.g., the cable 195 may be attached to the weight 140. Preferably, the cable 195 is electrically connected (not shown) to the at least one generator (not shown) of the nacelle 110 and/or the at least one generator (not shown) for generating electricity from the fuel (not shown) .

It should be noted that the number, arrangement, and interconnection of the constructive elements constituting the free-floating wind turbine 100, which are shown in FIG. 1, are not intended to be any limitation of the present invention, but merely used to provide a general idea of how the constructive elements may be implemented within the free-floating wind turbine 100. Although FIG. 1 shows that the tower 102 has a rectangular cross-section, this should not be construed as any limitation of the present disclosure; in some embodiments, any other cross- sectional shapes, such as needle formed, oval, etc., are possible, if required and depending on particular applications. The direction of the wind force directed on the wind turbine is indicated with the arrow Fl and the direction of the force of the water current directed on the wind turbine is indicated with the arrow F2. The directions of Fl, F2, Pl, and P2 shown in FIG. 1 are not intended to be any limitation of the present invention, but merely used to provide a general idea of the directions. E.g., P2 may be, e.g., to the opposite direction as shown in Fig. 1. FIG . 2 shows a schematic front view of a free-floating wind turbine in accordance with exemplary embodiments . As shown in FIG . 2 , the free-floating wind turbine 100 may comprise a tower 102 compris ing an upper part 102a and a lower part 102b, wherein the upper part 102a is configured to be located above water level 105 and the lower part 102b is configured to be submersed, at least partially, under water . The upper part 102a of the tower 102 may comprise a nacelle 110 (not shown) non-rotatably attached to the upper part 102a of the tower 102 and comprises a turbine provided with two blades 120 , and at least one generator (not shown) for generating electricity . The nacelle may comprise a beacon (not shown) . The lower part 102b of the tower 102 may comprise at least one float 130 ; at least one weight 140 ; and an underwater propelling unit 150 rotatably connected to the lower part 102b of the tower 102 . The underwater propeller unit 150 may be turnable about the vertical axi s of the tower 102 . The underwater propelling unit 150 may comprise an underwater propeller 160 rotatable by means of a motor 155 for generating propulsion forces (not shown) . The underwater propeller 160 may comprise two underwater propeller blades 162 . The dens ity of the underwater propeller 160 may be of a predetermined density value . The free-floating wind turbine 100 may further comprise a turning propeller unit 172 non-rotatably arranged to the lower part 102b of the tower 102 between the nacelle 110 and the underwater propelling unit 150 , wherein the turning propeller unit 172 may comprise two turning propellers 170 rotatable by means of a motor (not shown) for generating propulsion forces (not shown) for turning the tower 102 together with the nacelle 110 . It is to be understood that the turning propeller unit 172 may turn the tower 102 together with the nacelle 110 (not shown) independently of the underwater propelling unit 150 . In embodiments ( as shown in FIG . 2 ) the turning propeller unit 172 comprising the two turning propellers 170 is non-rotatably attached to the float

130 of the lower part 102b of the tower 102 , preferably the two turning propellers 170 are configured to be located below the water level 105 .

The propeller unit 172 may be configured to rotate the two turning propellers 170 with same or opposite direction . With the use of the propeller unit 172 comprising the two turning propellers 170 the free- floating wind turbine 100 may be turned ( around the vertical axis of the tower 102 ) , or moved, e . g . , backwards , or forwards . The lower part 102b of the tower 102 may further comprise at least one bumper 180 below the water level 105 and extending a transverse distance from the tower 102 . The free-floating wind turbine 100 may further comprise a power-to-X unit 190 for converting electricity generated by the at least one generator (not shown) to a fuel (not shown) , wherein the power-to-X unit 190 is electrically connected to the at least one generator of the nacelle 110 (not shown) . The power-to-X unit 190 may be integrated to the tower 102 (not shown) . The free- floating wind turbine 100 may further comprise storing means 192 for storing the fuel (not shown) , wherein the storing means 192 is attached to the power-to-X unit 190 . The storing means 192 may be integrated to the tower 102 (not shown) . It is to be understood that the storing means 192 may be configured to receive fuel (not shown) from the power-to-X unit 190 . The power-to-X unit 190 may be a power-to-ammonia unit (not shown) or a power-to-hydrogen unit (not shown) . The free-floating wind turbine 100 may further comprise at least one generator (not shown) for generating electricity from the fuel (not shown) , wherein the at least one generator for generating electricity from the fuel is electrically connected (not shown) to the underwater propelling unit 150 and/or the turning propeller unit 172. The ratio of the underwater propeller diameter dl to the abovewater turbine diameter d2 may be 1:28 - 2:1, preferably 1:10 - 1:1, more preferably 1:2 - 1:1. The free-floating wind turbine 100 may further comprise a cable 195, such as an electrical cable, wire, rope, cord, line, or a net, preferably the cable 195 is attached to the bottom part 192b of the tower 190. E.g., the cable 195 may be attached to the weight 140. Preferably, the cable 195 is electrically connected (not shown) to the at least one generator (not shown) of the nacelle 110 and/or the at least one generator (not shown) for generating electricity from the fuel (not shown) . The direction of the wind force directed on the wind turbine and the direction of the force of the water current directed on the wind turbine are not shown .

FIG. 3 shows a schematic front view of a free-floating wind turbine in accordance with exemplary embodiments. As shown in FIG. 3, the free-floating wind turbine 100 may comprise a tower 102 comprising an upper part 102a and a lower part 102b, wherein the upper part 102a is configured to be located above water level 105 and the lower part 102b is configured to be submersed, at least partially, under water. The upper part 102a of the tower 102 may comprise a nacelle 110 (not shown) non-rotatably attached to the upper part 102a of the tower 102 and comprises a turbine provided with two blades 120, and at least one generator (not shown) for generating electricity. The nacelle may comprise a beacon (not shown) . The lower part 102b of the tower 102 may comprise at least one float 130; at least one weight 140; and an underwater propelling unit 150 rotatably connected to the lower part 102b of the tower 102. The underwater propeller unit 150 may be turnable about the vertical axi s of the tower 102 . Comparing to the free-floating wind turbine of FIG . 2 , the underwater propeller unit 150 of the free-floating wind turbine of FIG . 3 has turned 90 degrees to the left about vertical axis of the tower 102 . The underwater propelling unit 150 may comprise an underwater propeller 160 rotatable by means of a motor 155 for generating propulsion forces (not shown) . The underwater propeller 160 may comprise two underwater propeller blades 162 (not shown) . The density of the underwater propeller 160 may be of a predetermined density value . The free-floating wind turbine 100 may further comprise a turning propeller unit 172 non- rotatably arranged to the lower part 102b of the tower 102 between the nacelle 110 (not shown) and the underwater propelling unit 150 , wherein the turning propeller unit 172 may comprise two turning propellers 170 rotatable by means of a motor (not shown) for generating propulsion forces (not shown) for turning the tower 102 together with the nacelle 110 . It is to be understood that the turning propeller unit 172 may turn the tower 102 together with the nacelle 110 (not shown) independently of the underwater propelling unit 150 . The lower part 102b of the tower 102 may further comprise at least one bumper 180 below the water level 105 and extending a transverse di stance from the tower 102 . The free-floating wind turbine 100 may further comprise a power-to-X unit 190 for converting electricity generated by the at least one generator (not shown) to a fuel (not shown) , wherein the power- to-X unit 190 is electrically connected (not shown) to the at least one generator of the nacelle 110 (not shown) . The power-to-X unit 190 may be integrated to the tower 102 (not shown) . The free-floating wind turbine 100 may further comprise storing means 192 for storing fuel (not shown) , wherein the storing means 192 is attached to the power-to-X unit 190 . The storing means 192 may be integrated to the tower 102 (not shown) . It is to be understood that the storing means 192 may be configured to receive the fuel (not shown) from the power-to-X unit 190 . The power-to-X unit 190 may be a power-to-ammonia unit (not shown) or a power-to-hydrogen unit (not shown) . The free- floating wind turbine 100 may further comprise at least one generator (not shown) for generating electricity from the fuel (not shown) , wherein the at least one generator for generating electricity from the fuel is electrically connected (not shown) to the underwater propelling unit 150 and/or the turning propeller unit 172 . The ratio of the underwater propeller diameter dl to the above-water turbine diameter d2 may be 1 : 28 - 2 : 1 , preferably 1 : 10 - 1 : 1 , more preferably 1 : 2 - 1 : 1 . The free-floating wind turbine 100 may further comprise a cable 195 , such as an electrical cable , wire , rope , cord, line , or a net , preferably the cable 195 is attached to the bottom part 192b of the tower 190 . E . g . , the cable 195 may be attached to the weight 140 . Preferably, the cable 195 is electrically connected (not shown) to the at least one generator (not shown) of the nacelle 110 and/or the at least one generator (not shown) for generating electricity from the fuel (not shown) . The direction of the wind force directed on the wind turbine is not shown and the direction of the force of the water current directed on the wind turbine is indicated with the arrow F2 .

FIG . 4 shows a schematic top view of a wind farm in accordance with exemplary embodiments . As shown in FIG . 4 , the wind farm 200 comprises a plurality of free-floating wind turbines 100 as di sclosed in the present di sclosure . The wind farm 200 may further comprise a position means 210 for positioning the plurality of free-floating wind turbines 100 (FIG. 4 shows a plurality of attaching means 210 as the position means 210 for attaching each of the plurality of free-floating wind turbines 100 to at least one adjacent free-floating wind turbine 100) . Each or at least one of the free-floating wind turbines 100 of the wind farm 200 may further comprise a power-to-X unit 190 (not shown) as described in the present disclosure and in particular above in the exemplary embodiments of FIGs. 1-3. Each or at least one of the power-to-X unit 190 of the wind farm 200 may further comprise a storing means 192 (not shown) as described in the present disclosure and in particular above in the exemplary embodiments of FIGs. 1-3. It is to be understood that the attaching means 210 may be a cable, such as an electrical cable, wire, rope, cord, line, or a net as described in the present disclosure and in particular above in the exemplary embodiments of FIGs. 1-3 (wherein the cable 195 corresponds to the attaching means 210) . Preferably the cable is attached to the bottom part 192b (not shown) of the tower 190 (not shown) of the free- floating wind turbine 100. E.g., the cable may be attached to the weight 140 (not shown) . The cable may be electrically connected (not shown) to the at least one generator (not shown) of the nacelle (not shown) and/or the at least one generator (not shown) for generating electricity from the fuel (not shown) . The direction of the wind force directed on the wind farm (and thus on at least one wind turbine) is indicated with the arrow Fl and the direction of the force of the water current directed on the wind farm (and thus on the wind turbine) is not shown. The direction of Fl shown in FIG. 4 is not intended to be any limitation of the present invention, but merely used to provide a general idea of the direction. E.g., instead of the direction of 90 degrees of Fl (to a vertical axis of the wind farm of FIG. 4) , Fl may be, e.g., but not limited to, at between about 60 and 80 degrees. Furthermore, the wind turbines may then be turned slightly to directly face the wind. If the wind turbines are in a line with the wind direction (as shown in FIG. 4) , the wind turbines further back (i.e., and for example, the wind turbines in the left side of FIG. 4) may be able to extract less energy from the wind. The wind farm 200 may further comprise one tug (not shown) at each corner of the wind farm configured to maintain the shape of the wind farm 200, and, the wind farm 200 may optionally further comprise one or more wave-powered jets (not shown) along the outer (electrical) cables 210. The electrical cables 210 may be slightly denser than water with heavy conducting copper wire eccentrically placed in a hardwalled incompressible tube filled with a light foamlike material. Floats (not shown) may run along each electrical cable 210 for preventing them from sinking. Along the outer electrical cables 210, the float (not shown) may be integrated into the wave-powered jet (not shown) .

The wind turbines 100 may maintain their own position, and therefore, the wind farm may maintain its own position. In a storm situation, the fuel production unit(s) (power-to-X unit(s) 190, not shown) may send electricity back to wind turbine (s) 100 to power its (their) underwater propeller (s) 160 if conditions do not allow the turbine (s) (not shown) to capture wind energy. If tension on the position means 210 becomes too high, the wind turbine 100 may disconnect itself from the position means 210, e.g., an electrical cable, with any suitable disconnecting means (not shown) . When conditions improve, it can be led back to the wind farm, or be brought back by, e.g., a transport vessel. FIG . 5 shows a schematic top view of a wind farm in accordance with exemplary embodiments . As shown in FIG . 5 , the wind farm 200 comprises a plurality of free-floating wind turbines 100 as di sclosed in the present disclosure . The wind farm 200 may further comprise a position means 210 for positioning the plurality of free-floating wind turbines 100 ( FIG . 5 shows a plurality of attaching means 210 as the position means 210 for attaching each of the plurality of free-floating wind turbines 100 to at least one adj acent free-floating wind turbine 100 ) . Each or at least one of the free-floating wind turbines 100 of the wind farm 200 may further comprise a power-to-X unit 190 (not shown) as described in the present disclosure and in particular above in the exemplary embodiments of FIGs . 1-3 . Each or at least one of the power-to-X unit 190 of the wind farm 200 may further comprise a storing means 192 (not shown) as described in the present disclosure and in particular above in the exemplary embodiments of FIGs . 1 -3 . It is to be understood that the attaching means 210 may be a cable , such as an electrical cable , wire , rope , cord, line , or a net as described in the present disclosure and in particular above in the exemplary embodiments of FIGs . 1 -3 (wherein the cable 195 corresponds to the attaching means 210 ) . Preferably the cable is attached to the bottom part 192b (not shown) of the tower 190 (not shown) of the free- floating wind turbine 100 . E . g . , the cable may be attached to the weight 140 (not shown) . The cable may be electrically connected (not shown) to the at least one generator (not shown) of the nacelle (not shown) and/or the at least one generator (not shown) for generating electricity from the fuel (not shown) . In embodiments only one free-floating wind turbine 100 ( shown in FIG . 5 as the one free-floating wind turbine 100 in the centre of the plurality of free-floating wind turbines 100, i.e., the one free-floating wind turbine 100 not being a peripheral free-floating wind turbine 100) of the plurality of free-floating wind turbines 100 may comprise a power-to-X unit 190 (not shown) and, optionally, a storing means 192 (not shown) , wherein the power-to-X unit 190 and the storing means 192 are as described in the present disclosure and in particular above in the exemplary embodiments of FIGs. 1-3. The direction of the wind force directed on the wind farm (and thus on at least one wind turbine) is indicated with the arrow Fl and the direction of the force of the water current directed on the wind farm (and thus on the wind turbines) is not shown. The direction of Fl shown in FIG. 5 is not intended to be any limitation of the present invention, but merely used to provide a general idea of the direction. E.g., instead of the direction of 90 degrees of Fl (to a vertical axis of the wind farm of FIG. 5) , Fl may be, e.g., but not limited to, at between about 60 and 80 degrees. Furthermore, the wind turbines may then be turned slightly to directly face the wind. If the wind turbines are in a line with the wind direction (as shown in FIG. 5) , the wind turbines further back (i.e., and for example, the wind turbines in the left side of FIG. 5) may be able to extract less energy from the wind.

FIG. 6 shows a schematic side view of a wind farm in accordance with exemplary embodiments. As shown in FIG. 6, the wind farm 200 comprises a plurality of free-floating wind turbines 100 as disclosed in the present disclosure. The water level 105 is shown. The wind farm 200 may further comprise a position means 210 for positioning the plurality of free-floating wind turbines 100, wherein the position means 210 may comprise at least one receiving means 213 attached to each of plurality of wind turbines 100 ; and at least one detection means 216 . In FIG . 6 the at least one receiving means 213 is attached to the at least one weight 140 , however, this should not be interpreted as limiting; the at least one receiving means 213 may be attached to the wind turbine 100 at an other location of the wind turbine 100 as long as the function of the wind turbine 100 is not disturbed . The at least one receiving means 213 may be configured to receive at least one signal , wherein the at least one receiving means is connected (not shown) to the underwater propelling unit of the free-floating wind turbine 100 and/or the turning propeller unit of the free-floating wind turbine 100 , wherein the motor (not shown) of the underwater propelling unit being configured to drive the underwater propeller of the underwater propelling unit of the free-floating wind turbine 100 in response to the at least one signal and/or the motor (not shown) of the turning propeller unit of the free-floating wind turbine 100 being configured to drive the at least one turning propeller in response to the at least one signal . The at least one detection means 216 may be configured to detect a deviation of a predetermined position of each of the plurality of the free-floating wind turbines 100 and configured to send the at least one signal to the at least one receiving means 213 attached to each of plurality of wind turbines 110 in response to the detected deviation of the predetermined position of each of the plurality of the free-floating wind turbines 110 . The at least one detection means 216 may be one detection means and attached (not shown) to one free-floating wind turbine 100 of the plurality of free-floating wind turbines 100 . The direction of the wind force directed on the wind farm ( and thus on at least one wind turbine ) is indicated with the arrow Fl and the direction of the force of the water current directed on the wind farm ( and thus on at least one wind turbine ) is indicated with the arrow F2 .

FIG . 7 shows a schematic side view of a wind farm in accordance with exemplary embodiments . As shown in FIG . 7 , the wind farm 200 comprises a plurality of free-floating wind turbines 100 as disclosed in the present disclosure . The water level 105 is shown . The wind farm 200 may further comprise a position means 210 for positioning the plurality of free-floating wind turbines 100 , wherein the position means 210 may comprise at least one receiving means 213 attached to each of plurality of wind turbines 100 ; and at least one detection means 216 attached to each of the plurality of wind turbines 100 . In FIG . 7 the at least one receiving means 213 is attached to the at least one weight 140 , however, this should not be interpreted as limiting; the at least one receiving means 213 may be attached to the wind turbine 100 at an other location of the wind turbine 100 as long as the function of the wind turbine 100 is not disturbed . The at least one receiving means 213 may be configured to receive at least one signal , wherein the at least one receiving means 213 is connected (not shown) to the underwater propelling unit and/or the turning propeller unit , wherein the motor (not shown) of the underwater propelling unit of the free-floating wind turbine 100 being configured to drive the underwater propeller in response to the at least one signal and/or the motor (not shown) of the turning propeller unit of the free-floating wind turbine 100 being configured to drive the at least one turning propeller in response to the at least one signal . The at least one detection means 216 may be attached to each of plurality of wind turbines 100 and configured to detect a deviation of a predetermined position of the free-floating wind turbine 100 of the plurality of the free-floating wind turbines 100 and configured to send the at least one signal to the at least one receiving means 213 attached to each of plurality of wind turbines 100 in response to the detected deviation of the predetermined position of the free-floating wind turbines 100 . In FIG . 7 the at least one detection means 216 is attached to the at least one weight 140 , however, this should not be interpreted as limiting; the at least one detection means 216 may be attached to the wind turbine 100 at an other location of the wind turbine 100 as long as the function of the wind turbine 100 is not disturbed . The direction of the wind force directed on the wind farm ( and thus on at least one wind turbine ) is indicated with the arrow Fl and the direction of the force of the water current directed on the wind farm ( and thus on at least one wind turbine ) is indicated with the arrow F2 .

FIG . 8 shows a schematic side view of a wind farm in accordance with exemplary embodiments . As shown in FIG . 8 , the wind farm 200 comprises a plurality of free-floating wind turbines 100 as disclosed in the present disclosure . The water level 105 is shown . The wind farm 200 may further comprise a position means 210 for positioning the plurality of free-floating wind turbines 100 , wherein the position means 210 may comprise at least one receiving means 213 attached to each of plurality of wind turbines 100 ; at least one identification means 218 being configured to be placed at a position of at least one of the plurality of the free-floating wind turbines 100 ; and at least one detection means 216 attached to at least one free-floating wind turbine 100 of the plurality of free-floating wind turbines 100 . The at least one receiving means 213 may be configured to receive at least one signal , wherein the at least one receiving means 213 is connected to the underwater propelling unit of the wind turbine 100 and/or the turning propeller unit of the wind turbine 100 , wherein the motor (not shown) of the underwater propelling unit being configured to drive the underwater propeller in response to the at least one signal and/or the motor (not shown) of the turning propeller unit being configured to drive the at least one turning propeller in response to the at least one signal . The at least one detection means 216 may be configured to determine the coordinates of the at least one identification means 218 , may be configured to detect a deviation of a predetermined distance to the at least one identification means 218 , and may be configured to send the at least one signal to the at least one receiving means 213 attached to each of plurality of wind turbines 100 in response to the detected deviation of the predetermined distance to the at least one identification means 218 . The at least one identification means 218 , the at least one detection means 216 , and the at least one receiving means 213 may work independently from each other . E . g . , if there are three identification means 218 , three detection means 216 , and three receiving means 213 ( as shown in FIG . 8 ) , each of the three detection means 216 may be configured to determine the coordinates of each one of the three identification means 218 , and may each be configured to send the at least one signal to one of the three receiving means 213 , preferably to the receiving means 213 , which is attached to the same free-floating wind turbine 100 that the detection means 216 is attached to . The at least one identification means 218 may be placed at a desired position of at least one of the plurality of the free-floating wind turbines 100 using, e . g . , but not limited to , a net 220 configured to be submersed below the water level 105 and below the wind farm 200 , whereto the at least one identification means 218 is attached to . Additionally, or alternatively, the at least one identification means 218 may be placed at the seabed (not shown) or attached to the seabed (not shown) at a desired position of at least one of the plurality of the free-floating wind turbines 100 . In FIG . 8 , as also mentioned for the exemplary embodiments of FIGs . 6-7 , the at least one receiving means 213 and the at least one detection means 216 are attached to the at least one weight 140 , however, this should not be interpreted as limiting; the at least one receiving means 213 and at least one detection means 216 may be attached to the wind turbine 100 at an other location of the wind turbine 100 as long as the function of the wind turbine 100 is not disturbed . The direction of the wind force directed on the wind farm ( and thus on at least one wind turbine ) is indicated with the arrow Fl and the direction of the force of the water current directed on the wind farm ( and thus on at least one wind turbine ) is indicated with the arrow F2 .

It is obvious to a person skilled in the art that with the advancement of technology, the inventive concept can be implemented in various ways . The invention and its embodiments are thus not limited to the examples described above ; instead they may vary within the scope of the claims .

The embodiments described hereinbefore may be used in any combination with each other . Several of the embodiments may be combined together to form a further embodiment . A product , a system, a method, or a use , disclosed herein, may comprise at least one of the embodiments described hereinbefore . It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments . The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages .