WO2017151035A1

WO2017151035A1 - Method of oxygenating water and producing hydrogen

Info

Publication number: WO2017151035A1
Application number: PCT/SE2017/050150
Authority: WO
Inventors: Ulf HAGSTRÖM
Original assignee: Ecomb Ab (Publ)
Priority date: 2016-03-03
Filing date: 2017-02-17
Publication date: 2017-09-08
Also published as: SE541159C2; SE1751054A1

Abstract

The present disclosure relates to a method of oxygenating water and producing hydrogen performed by a system (4) floating on a body of water (100) and comprising a horizontal axis wind turbine (3), a propeller (105) and a hydrogen producing unit (6). The method comprises obtaining input regarding environmental conditions of the body of water for determining a direction in which the floating system (4) should be moved. The method also comprises pointing the rotor (102) of the wind turbine such that the floating system is moved in accordance with the determined direction while obtaining electricity from the rotation of the rotor. The method also comprises controlling the speed with which the floating system is moved by means of the propeller submerged in the body of water, by rotating the propeller to increase the speed when increased speed is desired, and by allowing the propeller to function as a turbine to generate electricity and reduce the speed when reduced speed is desired. The method also comprises powering the hydrogen producing unit (6) with the obtained electricity to split water molecules from the body of water (100) to produce hydrogen and oxygen. The method also comprises oxygenating the body of water by means of the produced oxygen.

Description

METHOD OF OXYGENATING WATER AND PRODUCING

HYDROGEN

TECHNICAL FIELD

The present disclosure relates to a method of oxygenating water such as of a sea or lake. The disclosure also relates to a method for producing hydrogen.

BACKGROUND

Hydrogen is used e.g. as a fuel in fuel cells etc. and may be produced by splitting water e.g. by means of electrolysis. In electrolysis, electricity is used to split water into hydrogen and oxygen. However, this way of producing hydrogen is more expensive than production from hydrocarbons and the energy input required for water splitting is higher than the energy that could be obtained from the produced hydrogen. Due to the use of water, a readily available resource, electrolysis and similar water-splitting methods have none the less attracted interest. With the objective of reducing the cost of hydrogen production, renewable sources of energy have been targeted to allow electrolysis. There are three main types of electrolysis cells, solid oxide electrolysis cells (SOECs), polymer electrolyte membrane cells (PEM) and alkaline electrolysis cells (AECs).

Further, many bodies of water suffer from low levels of oxygen e.g. due to overfertilization and resulting algal bloom. Different measures have been tested to aerate or oxygenate water. For instance, DE 4404024 and

DE 2823952 disclose pumping oxygen into water by means of a wind turbine.

SUMMARY

There is a general problem in many bodies of water, e.g. lakes and seas such as the Baltic Sea, with too low oxygen levels particularly in some parts of the body of water e.g. at some areas of the bottom. Systems for oxygenating water bodies today are costly and typically stationary whereby the oxygen may not be added to the part of the water body where it is most needed. Similarly, some parts of the body of water may have a reduced salt level, in which case the present invention may, in some embodiments, comprise the addition of salt (sodium chloride) to the body of water.

In accordance with the present invention, a floating and steerable system is used whereby input regarding environmental conditions (e.g. oxygen measurements) of the water are obtained and the system may be moved accordingly to a place of the water body where oxygenation is presently needed. Embodiments of the present invention allows the floating system to oxygenate the body of water while moving at a speed which may be controlled by means of a propeller to achieve desired and even oxygenation over a volume of the body of water.

Further, oxygen for oxygenating the water is provided by splitting water, e.g. through electrolysis, thereby obtaining oxygen and hydrogen. Additional oxygen for oxygenating the water maybe provided in e.g. gas bottles or tanks which may have been brought onto and included in the floating system from ashore. The hydrogen may be captured, stored and sold, thereby reducing the cost of the oxygenation or even making it profitable.

A wind turbine is used for providing the electrical power needed for splitting the water, but also for propulsion for moving and steering the system, using the rotor of the wind turbine as a sail. According to an aspect of the present invention, there is provided a method of oxygenating water and producing hydrogen performed by a system floating on a body of water and comprising a horizontal axis wind turbine, a propeller and a hydrogen producing unit. The method comprises obtaining input regarding environmental conditions of the body of water for determining a direction in which the floating system should be moved. The method also comprises pointing the rotor of the wind turbine such that the floating system is moved in accordance with the determined direction while obtaining electricity from the rotation of the rotor. The method also comprises controlling the speed with which the floating system is moved by means of the propeller submerged in the body of water, by rotating the propeller to increase the speed when increased speed is desired, and by allowing the propeller to function as a turbine to generate electricity and reduce the speed when reduced speed is desired. The method also comprises powering the hydrogen producing unit with the obtained electricity to split water molecules from the body of water to produce hydrogen and oxygen. The method also comprises oxygenating the body of water by means of the produced oxygen.

According to another aspect of the present invention, there is provided a system configured for floating on a body of water. The system comprises a horizontal axis wind turbine comprising a rotor, a propeller and a hydrogen producing unit. The system also comprises means (e.g. sensor) for obtaining input regarding environmental conditions of the body of water for

determining a direction in which the floating system should be moved. The system also comprises a rotor controller for pointing the rotor of the wind turbine such that the floating system is moved in accordance with the determined direction while electricity is obtained from the rotation of the rotor. The system also comprises a propeller controller for controlling the speed with which the floating system is moved by means of the propeller submerged in the body of water, by rotating the propeller to increase the speed when increased speed is desired, and by allowing the propeller to function as a turbine to generate electricity and reduce the speed when reduced speed is desired. The system also comprises wiring for powering the hydrogen producing unit with electricity obtained from the wind turbine, to split water molecules from the body of water to produce hydrogen and oxygen. The system also comprises pumping means for oxygenating the body of water with the produced oxygen via a gas tube.

By means of the obtained input regarding environmental condition(s) of (e.g. in or above) the body of water, a control unit (e.g. navigation computer or the like) or human operator of the system (e.g. a boat) may determine a suitable course of the floating and movable system. The environmental conditions may be any which could influence where it would be suitable for the floating system to be moved. The environmental conditions may be or comprise a condition indicating where in the body of water oxygenation (and/or addition of salt) from the system is needed or more acutely needed. Thus, the environmental condition may be or comprise a forecast of oxygen or salt levels in one or several parts of the body of water (different areas and/or at different depths). Additionally or alternatively, the environmental conditions may be or comprise historical or real-time measurements of oxygen and/ or salt levels in one or several parts of the body of water (different areas and/ or at different depths). In specific embodiments of the present invention, the floating system may comprise sensors for measurement of oxygen and/or salt levels in the body of water at or below the floating system, whereby the historical or real-time measurements of oxygen and/ or salt levels may at least partly be from sensors comprised in the floating system. Additionally or alternatively, the environmental conditions may be or comprise a condition indicating where over the body of water the weather is or will in the future be suitable for the floating system. Since the floating system is moved and provided with electricity by means of the wind turbine, it is dependent on suitable wind speeds and wind directions in order to operate. For instance, if the wind speed is too low in an area it may not be suitable to move to that area (or it maybe suitable to leave the area if already there) since the wind turbine may not be able to properly power the hydrogen producing unit etc. Similarly, if the wind speed is too high in an area, indicating that the wind turbine may need to be turned off in order to avoid damage (or waves maybe too high), it may not be suitable to move to that area (or it may be suitable to leave the area if already there) since the wind turbine may not be able to properly power the hydrogen producing unit etc. Also, wind directions may make it difficult to navigate to an area of the body of water by means of the wind turbine (used as a sail). Thus, the environmental conditions maybe or comprise forecasted or real-time information about wind speed and/ or directions over different parts of the surface (close to the surface and thus affecting the floating system) of the body of water. Other weather conditions may comprise any of wave height, temperature and atmospheric pressure. Similarly, additionally or alternatively, the environmental conditions may be or comprise a condition indicating where in the body of water the water current is or will in the future be suitable for the floating system. To achieve suitable oxygenation over a large part of a body of water, it maybe convenient to oxygenate the water while the system is moving over it, thus avoiding draw-backs of stationary systems which tend to oxygenate, possibly too much, only a small part of the water. It may then be preferred to be able to control the speed of the floating system, e.g. in relation to oxygenation capacity of the system and/or the level or oxygen deficiency in the water before being oxygenated by the system.

It is to be noted that any feature of any of the aspects may be applied to any other aspect, wherever appropriate. Likewise, any advantage of any of the aspects may apply to any of the other aspects. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. The use of "first", "second" etc. for different features/components of the present disclosure are only intended to distinguish the features/components from other similar features/ components and not to impart any order or hierarchy to the features/components. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described, by way of example, with reference to the accompanying drawings, in which:

Fig 1 is a side view in longitudinal section of a water craft comprised in an embodiment of the system of the present invention. Fig 2 is a plan view of a water craft comprised in an embodiment of the system of the present invention, moved by the wind via a wind turbine of the system.

DETAILED DESCRIPTION

Embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments are shown.

However, other embodiments in many different forms are possible within the scope of the present disclosure. Rather, the following embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like numbers refer to like elements throughout the description.

Figure l illustrates an embodiment of the inventive system 4 which is floating on a body of water 100 by means of being arranged on a boat or barge or other water craft 14. The system is for oxygenating a body of water such as a lake or sea. The system comprises a compressor 1 attached to a gas tube 2 for transporting oxygen from the compressor into the water whereby the water is oxygenated. The gas tube may be provided with a nozzle or perforations or the like to provide small oxygen bubbles for increasing the oxygen-water interface and thus improve the oxygen uptake of the water. The gas tube may partly be in the form of a rigid hollow lance or plate with numerous holes or nozzles to produce the bubbles. Preferably, the gas tube is configured to provide oxygen bubbles having an average diameter of less than 50 μιη when leaving the gas tube. The gas tube maybe provided with a weight such that its end sinks down to a suitable depth for adding the oxygen in the water.

Additionally or alternatively, the depth at which the end of the gas tube is provided maybe controlled by means of a winch comprised in the floating system, or by means of a remotely operated underwater vehicle (ROV) to which the gas tube is connected.

The system comprises a hydrogen producing unit 6, e.g. an electrolysis cell, using electricity to split water molecules into hydrogen and oxygen according to the formula 2H2O + energy→ 2H2 + 0₂. A water tube 7 is connected to the hydrogen producing unit 6 and arranged to, e.g. via a filter 19, transport water from the body of water 100 to the hydrogen producing unit 6. The filter 19 may comprise at least one unit and is arranged to purify the water to a level which is adequate for the hydrogen producing unit, e.g. particles and/or salt are removed by means of the filter. The hydrogen thus produced may be transported to and stored in a hydrogen storage unit 10, e.g. a gas flask, bottle or other canister, via the gas pipe 12, where it may be stored until the system docks with a hydrogen depot and the hydrogen may be pumped thereto. The oxygen produced may instead be transported via the gas pipe 8 to the oxygen storage unit 5, e.g. a gas flask, bottle or other canister. The oxygen storage unit 5 is connected to the compressor 1 for allowing the oxygen therein to be pumped into the water via the gas tube 2. A compressor (not shown) is typically used for compressing the hydrogen and oxygen, respectively, into the storage units 10 and 5. The system also comprises a horizontal axis wind turbine 3 having a rotor 102, arranged to convert wind energy to electrical power for powering the compressor 1 and/or the hydrogen producing unit 6 (as illustrated by the wiring 9 connecting the wind turbine 3 with the hydrogen producing unit 6, possibly via batteries) and possibly other parts of the system. In addition, the system may comprise a battery or other energy storage (not shown) for storing excess electrical power produced by the wind turbine. By means of the wind turbine, the system may be fully or partly self-supporting (self- sufficient) on electrical power. Typically, a wind turbine has a preferred wind speed operating ratio. Generally, more electricity may be produced with higher wind speed. However, at too high wind speeds, e.g. above 12 m/ s, the wind turbine may need to be turned off to reduce the risk of damage to the rotor and other parts of the wind turbine. Also, the angle of the wind turbine to the wind direction (due to using the rotor as a sail for navigation) affects how much wind energy can be transformed to electrical energy by the wind turbine.

The system 4 also comprises a propeller 105, which is submerged in the body of water (typically mounted at the stern of the system), for controlling the speed of the floating system, e.g. based on the environmental conditions. When increased speed is desired (e.g. because the speed obtained from the wind turbine acting as a sail is insufficient), the propeller may be forced to rotate, typically by electrical power, and thus act as a propulsion means and increase the speed of the system. On the other hand, when reduced speed is desired (e.g. when the speed obtained from the wind turbine acting as a sail is too high for proper oxygenation), the propeller may act as a turbine, generating electrical power from the movement of the water in relation to the system and thus also reducing the speed of the system. The propeller 105 may thus preferably be configured to be suitable for functioning also as a turbine, having relatively large and long, possibly more numerous (e.g. at least 4 or 5), blades compared with if the propeller was only configured for propulsion. By means of the turbine functionality of the propeller, in addition to controlling the speed of the floating system 4, the propeller may also generate electricity to aid the wind turbine in providing electrical power for the compressor 1 and/or the hydrogen producing unit 6 and/or the propeller (when arranged for propulsion) and possibly other parts of the system.

In addition to the wind turbine 3 and the propeller 105, electrical power for the system 4 maybe generated by means of e.g. a fuel cell of the system, using the hydrogen from the hydrogen producing unit 6, e.g. in the hydrogen tank 10, as fuel. Further, if needed, the system 4 may comprise solar panels comprising solar cells for production of electrical power from solar radiation. By means of these different electrical power sources, the system maybe self- sufficient on electricity, not needing to burn polluting fossil fuel for its operation.

The system may in some embodiments comprises at least one sensor 101 for measuring the oxygen or salt content (oxygen/salt level) in the water in different positions within the body of water. The sensors may be fixedly arranged in the system, e.g. fastened to the water craft 14 such that they only move with the rest of the system. Alternatively, they may be arranged movably in respect of the water craft, e.g. by each being arranged on a string such that it maybe raised and lowered to obtain oxygen level measurements on different depths in the water body 100. The sensor or the string

connecting it to the water craft maybe provided with a weight such that it sinks down to a suitable depth for performing measurements in the water. Additionally or alternatively, the depth at which the sensor is provided may be controlled by means of a winch comprised in the floating system, or by means of a remotely operated underwater vehicle (ROV) to which the sensor or string is connected. Preferably, at least two oxygen or salt sensors 101 are used, e.g. one at the front and one at the back of the water craft 14. Thus, an oxygen or salt gradient maybe detected between the sensors, indicating in which direction there is most need for oxygenation and/ or addition of salt. Also, when the system is moving, such a gradient may be obtained even if only one sensor 101 is used. It may not be suitable to use oxygen

measurements too close to the outlet of the gas tube 2 since they may not reflect the usual oxygen level in that position. Based on the environmental condition input, e.g. oxygen level measurements, a control unit 103 may compute a suitable course for the water craft 14 and thus a direction in which the floating system 4 should preferably be moved in order to add oxygen to a part of the body of water where it is most needed. Alternatively, a human operator of the water craft may determine the suitable course, e.g. in cooperation with the control unit. If e.g. there is a gradient of decreasing oxygen levels in the water from West to East, the control unit 103 may determine that the floating system should be moved in an eastward direction. The control unit 103 may then control a motor or other rotor controller in the wind turbine 3 for pointing the rotor 102 such that the floating system is moved in accordance with the determined direction, using the rotor as a sail. Depending on the direction of the wind in relation to the determined direction, the water craft may need to perform tacking (pointing the rotor periodically in different directions) in order to move the system in the general direction of the determined direction. In addition, a rudder (not shown) of the water craft 14 may be used and also controlled by the control unit 103. Also, if oxygen levels at different depths are measured, the gas tube 2 maybe controlled to emit oxygen at different depths based on those measurements (preferably emitting oxygen at a depth, or slightly below a depth, where the oxygen level is lower). Alternatively, the oxygen maybe emitted at a standard depth or as low as possible, e.g. defined by the length of the gas tube 2, or at the bottom of the water body, possibly allowing an end portion of the gas tube 2 to lie along the bottom. Typically, the lack of oxygen is greatest at the bottom, depending on currents and circulation of the water.

Figure 2 shows the water craft 14 from above, in/on which water craft the system 4 as discussed herein is arranged. The wind turbine 3 is rotatably arranged around its vertical axis, as indicated by the double-headed arrow 16. Since the wind turbine 3 is fixed to the water craft, it can transfer thrust from the wind to the water craft 14, pushing it forward as indicated by the bold arrow at the front of the water craft. In the figure, the incident wind direction 18 is different from the direction 17 in which the rotor 102 is pointed (i.e. the axial direction of the rotor), allowing the water craft to be pushed in the direction of the bold arrow. The axial direction 17 is the substantially horizontal direction which is orthogonal to the substantially vertical plane in which the blades of the rotor rotates around the horizontal axis of the wind turbine 3. From the wind, electrical power is obtained by rotation of the rotor and a generator of the wind turbine. At the same time the thrust exerted by the wind on the wind turbine is transferred to the water craft 14. Thus, the water craft may use the wind turbine, especially the plane in which the rotor blades rotate, as a sail and the direction in which the water craft moves may be controlled by pointing the rotor 102 in different directions 17 in relation to the wind direction 18. A rudder 104 may also be controlled to in cooperation with the pointing of the rotor control the movement direction of the water craft 14 and thus the whole system 4.

In addition, the propeller 105 and/ or other regular propulsion means may be used to propel the water craft 14 in addition to the propulsion of the thrust on the wind turbine, e.g. if there is little wind or if there is a head wind which is not easily traversed. The additional propulsion means may e.g. be powered by electricity generated by the wind turbine, e.g. via an energy storage such as a battery. Alternatively or additionally, a fuel may be used for powering the additional propulsion means. Such a fuel may e.g. be stored in the water craft for use when needed to avoid the system 4 not being able to e.g. get to a hydrogen depot when necessary.

The method of the present invention maybe divided into a plurality of steps, which may be performed concurrently or in a different order than here presented unless otherwise indicated.

Step 1: Input regarding environmental condition(s) (e.g. measurements of oxygen levels) of the body of water 100 are obtained. For instance, the input/measurements maybe obtained by the control unit 103 from the sensors 101, possibly after processing by the control unit 103.

Step 2: Based on the input obtained in step 1, a direction in which the floating system 4 should be moved is determined, e.g. by the control unit or by a human operator. The control unit 103 may automatically determine the direction e.g. in view of an oxygen gradient in the water body 100 indicated by the obtained oxygen measurements, whereby the direction maybe towards the declining oxygen levels according to the gradient.

Step 3: The rotor 102 of the wind turbine 3 is pointed such that the floating system is moved in accordance with the direction determined in step 2. This implies that the control unit 103 controls the rotor (e.g. by controlling a rotor controller in the wind turbine 3) to be pointed in relation to the wind 18 direction such that the plane in which the blades of the rotor rotates functions as a sail moves the system 4 in a desired direction with the intent to generally move the system 4 (typically arranged on or including a water craft 14) in the direction determined in step 2. However, the determined direction maybe in relation to the wind direction such that the control unit 103 may decide to first move the system in a different direction, e.g. as part of tacking operations. Step 4: Electricity is obtained from the rotation of the rotor 102. This may typically go on continuously, regardless of the other steps of the method, and regardless of whether the system 4 is moving or stationary. Whenever the rotor 102 rotates, electricity maybe produced via a generator in the wind turbine 3, in a conventional manner. Since the wind turbine is also used for moving the system 4 on the body of water 100, only a part, e.g. 40-60% such as about 50%, of the power of the wind 18 which is intercepted and

transformed by the wind turbine may be used for producing electricity by rotating the rotor 102. The rest, e.g. 40-60% such as about 50%, of the intercepted and transformed power of the wind 18 may be used to move the system 4. Additionally, since the rotor 102 is, in step 3, pointed with regards to the direction determined in step 2, the angle of the plane of the rotation of the rotor blades to the wind direction may not be optimal for intercepting and transforming the wind power. By means of the wind turbine 3, the system 4 may be fully or partially self-sufficient on energy both for propulsion of the water craft 14 for moving the system 4 and for running the electrical devices of the system 4.

Step 5: The speed with which the floating system 4 is moved is controlled by means of the propeller 105 submerged in the body of water, by rotating the propeller to increase the speed when increased speed is desired, and by allowing the propeller to function as a turbine to generate electricity and reduce the speed when reduced speed is desired. Also this may typically go on continuously, regardless of the other steps of the method. The propeller may be controlled by a propeller controller of the system 4, e.g. connected to the control unit 103. By controlling the speed of the system, desired level of oxygenation may be achieved of the part of the body of water which the system floats across. In some embodiments, the controlling of the speed is based on a predetermined desired oxygenating rate when the oxygenating of the body of water is performed while the floating system is being moved. Additionally or alternatively, in some embodiments, the controlling of the speed is based on the input of environmental conditions. Step 6: The hydrogen producing unit 6 is powered with the electricity obtained in step 4 to split water molecules from the body of water 100 to produce hydrogen and oxygen. As discussed herein, the water may be acquired from the body of water 100, e.g. pumped via the pipe 7, and the electrical power may be acquired from the wind turbine 3 or an energy storage thereof via the wire 9. In some embodiments, the water is pre-treated by filtration, e.g. by means of the filter 7, before it enters the hydrogen producing unit 6. The filtration may i.a. comprise removal of salt which may otherwise disrupt the hydrogen production. In addition, the electricity obtained from the wind turbine 3 in step 4 may be used to power any other electrical devices of the system 4, such as pumps and compressors as discussed herein, as well as the control unit 103, sensors 101 and the rotor controller of the wind turbine 3. A battery pack or other power storage may be used between the generator of the wind turbine 3 and the electrical devices to provide a controlled voltage. The battery pack may also be used for storing excess electricity produced by the wind turbine.

Step 7: The body of water 100 is oxygenated by means of the oxygen produced in step 5. Typically, steps 4, 5 and 6 may occur continuously and concurrently with each other. As discussed herein, the oxygen may be pumped into the body of water 100 via the gas tube, e.g. hose, 2 by means of a compressor 1, e.g. to the bottom of the body of water. In some embodiments, wherein the measurements obtained in step 1 comprise measurements of oxygen levels obtained at different depths in the body of water 100, the oxygenating comprises oxygenating the body of water at a depth determined, typically by the control unit 103, based on said obtained measurements.

Optional step 8: In some embodiments of the method, the produced hydrogen is stored in a hydrogen storage 10 comprised in the floating system 5. Thus, the hydrogen may e.g. be sold to finance the oxygenating of the body of water 100. Alternatively, at least a part of the hydrogen produced in step 5 may be used to power devices comprised in the floating system 4, e.g. by means of a fuel cell. Optional step 9: In some embodiments of the method, the system 4 is automatically controlled to return to a hydrogen depot for emptying the hydrogen storage 10 to the hydrogen depot. Thus, the control unit 103 may decide that it is time, e.g. periodically or when the hydrogen storage 10 is full, to dock with a hydrogen depot, e.g. on shore or on a boat, to off-load the stored hydrogen. The control unit 103 may then disregard the sensor readings of step 1 and instead set a course for the hydrogen depot, thus controlling how the rotor 102 is pointed in order to move the system 4 to the hydrogen depot. When docking, the system 4 may also be serviced. Additionally or alternatively, the method may comprise obtaining

measurements of salt levels in the body of water 100 and, depending on the obtained salt measurements, adding salt (typically sodium chloride, NaCl) to the body of water, e.g. salt filtered from the water before it enters the hydrogen producing unit 6. It is a problem in some bodies of water, e.g. the Baltic Sea, that the salt level is decreasing, which may have adverse

environmental effects. For example, the salt level in the Baltic Sea has in some parts fallen to about 1.1%, to be compared with historical levels of about 1.4%, adversely effecting e.g. cod reproduction since cod roe needs a salt level of about 1.2% to float. Thus, in addition to the measurements of oxygen levels, the floating system 4 may comprise salt sensors for measuring salt levels in the body of water, e.g. at different depths. In some embodiments, the salt measurements may also form basis for determining the direction in step 2 discussed above. In other embodiments, the addition of salt is done independently of the moving of the floating system 4 in step 3 if the salt measurements indicate that there is a salt deficiency in the part of the body of water 100 where the system 4 is currently located. If salt measurements are made at different depths, the salt may be added to the depth where it is, based on said measurements, most needed. The system 4 may comprise a salt storage for storing salt. When the salt measurements indicate that salt should be added, salt from the salt storage may be dissolved in some water pumped from the body of water to form brine, which brine may then be pumped via a tube/hose into the water body 100 e.g. at a depth determined based on the salt measurements.

Any embodiment of the method of the present disclosure may be performed by a system 4 as discussed herein, specifically by (or controlled by) a control unit 103 of the system 4. Thus, there is provided a system 4 configured for floating on a body of water 100. The system comprises a horizontal axis wind turbine 3 comprising a rotor (102), a hydrogen producing unit 6, sensor means 101 for obtaining measurements of oxygen levels in the body of water 100, a control unit 103 for, based on the obtained measurements,

determining a direction in which the floating system 4 should be moved, a rotor controller for pointing the rotor 102 of the wind turbine 3 such that the floating system 4 is moved in accordance with the determined direction, wiring 9 for powering the hydrogen producing unit 6 with electricity obtained from the wind turbine 3, to split water molecules from the body of water 100 to produce hydrogen and oxygen, and pumping means 1 for oxygenating the body of water 100 with the produced oxygen via a gas tube 2.

The present disclosure has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the present disclosure, as defined by the appended claims.

Claims

l6 CLAIMS

1. A method of oxygenating water and producing hydrogen performed by a system (4) floating on a body of water (100) and comprising a horizontal axis wind turbine (3), a propeller (105) and a hydrogen producing unit (6), the method comprising: obtaining input regarding environmental conditions of the body of water for determining a direction in which the floating system (4) should be moved; pointing the rotor (102) of the wind turbine such that the floating system is moved in accordance with the determined direction while obtaining electricity from the rotation of the rotor; controlling the speed with which the floating system is moved by means of the propeller submerged in the body of water, by rotating the propeller to increase the speed when increased speed is desired, and by allowing the propeller to function as a turbine to generate electricity and reduce the speed when reduced speed is desired; powering the hydrogen producing unit (6) with the obtained electricity to split water molecules from the body of water (100) to produce hydrogen and oxygen; and oxygenating the body of water by means of the produced oxygen.

2. The method of claim 1, further comprising: storing the produced hydrogen in a hydrogen storage (10) comprised in the floating system (4).

3. The method of claim 2, further comprising: controlling the system (4) to return to a hydrogen depot for emptying the hydrogen storage to the hydrogen depot.

4. The method of any preceding claim, further comprising: pre-treating water by filtration before it enters the hydrogen producing unit (6), e.g. comprising removal of salt and optionally adding the removed salt to the body of water in view of the obtained input.

5. The method of any preceding claim, wherein the environmental conditions comprise any of oxygen and/ or salt levels in the body of water (100), and/or forecasted wind speeds and/or wind directions over different parts of the body of water (100).

6. The method of any preceding claim, wherein the system (4) is energy self-sufficient by means of the wind turbine (3).

7. The method of any preceding claim, wherein the obtaining input comprises obtaining measurements of oxygen and/ or salt levels at different depths in the body of water (100), e.g. by means of a winch or a remotely operated underwater vehicle, and wherein the oxygenating comprises oxygenating the body of water, and optionally adding salt, at a depth determined based on said obtained input.

8. The method of any preceding claim, wherein the controlling of the speed is based on the input of environmental conditions.

9. The method of any preceding claim, wherein the controlling of the speed is based on a predetermined desired oxygenating rate when the oxygenating of the body of water is performed while the floating system is being moved.

10. A system (4) configured for floating on a body of water (100), the system comprising: a horizontal axis wind turbine (3) comprising a rotor (102); a propeller (105); a hydrogen producing unit (6); l8 means (101) for obtaining input regarding environmental conditions of the body of water (100) for determining a direction in which the floating system (4) should be moved; a rotor controller for pointing the rotor (102) of the wind turbine (3) such that the floating system (4) is moved in accordance with the determined direction while electricity is obtained from the rotation of the rotor; a propeller controller for controlling the speed with which the floating system is moved by means of the propeller submerged in the body of water, by rotating the propeller to increase the speed when increased speed is desired, and by allowing the propeller to function as a turbine to generate electricity and reduce the speed when reduced speed is desired; wiring (9) for powering the hydrogen producing unit (6) with electricity obtained from the wind turbine (3), to split water molecules from the body of water (100) to produce hydrogen and oxygen; and pumping means (1) for oxygenating the body of water (100) with the produced oxygen via a gas tube (2).