LU501094B1

LU501094B1 - Device for producing dihydrogen from water, e.g., seawater

Info

Publication number: LU501094B1
Application number: LU501094A
Authority: LU
Inventors: Jérôme Polesel; Damien Lenoble
Original assignee: Luxembourg Inst Science & Tech List
Priority date: 2021-12-27
Filing date: 2021-12-27
Publication date: 2023-06-27
Also published as: WO2023126157A1

Abstract

An aspect of the present invention relates to a device for producing dihydrogen from water, e.g. seawater. The device comprises a (greenhouse) casing comprising a water reservoir, a water inlet and a condensation surface. The casing is configured to absorb solar energy and to heat water in the reservoir so as to produce water vapor in the casing. Condensed water is produced on the condensation surface. The device further comprises an electrolyzer for electrolyzing the condensed water thereby producing dihydrogen and a wave energy converter for converting water wave energy into electrical energy. The wave energy converter is operatively connected to the electrolyzer so as to supply the electrolyzer with the electrical energy for carrying out the electrolysis. Additional aspects relate to a dihydrogen production rig and a dihydrogen production facility comprising one or more of the devices as well as a method for producing dihydrogen from water with the device.

Description

1 LU501094

DESCRIPTION

DEVICE FOR PRODUCING DIHYDROGEN FROM WATER, E.G.,

SEAWATER

Field of the Invention

[0001] The invention generally relates to a device for producing dihydrogen from water, in particularly from seawater, a dihydrogen production rig and a dihydrogen production facility comprising the device, as well as a method for producing dihydrogen from water with the device.

Background of the Invention

[0002] Hydrogen production from renewable energies is key to marking a gradual transition towards a clean hydrogen economy and a more sustainable and smart energy mix. For the implementation of a sustainable energy economy, the greatest challenge is the fluctuation in electricity production of wind and solar power plants (due to e.g. weather conditions). To meet this challenge and to satisfy the energy demand, electricity must be stored (buffered) to provide energy even in case of adverse conditions (e.g. little to no sunshine and/or little to no wind).

[0003] In order to store green electricity in a highly scalable way, it can be converted into chemical energy. The central process for this conversion is electrocatalytic water splitting in which hydrogen and oxygen are formed. Hydrogen can directly be stored, transported, and reconverted into electricity in a fuel cell.

Further, hydrogen is the starting point for the formation of other fuels such as methanol, ammonia, or liquid organic hydrogen carriers.

[0004] Due to the central role of water splitting in a sustainable energy economy, the cost efficiency of this process is crucial and even one percent could save billions of dollars. More than half of the costs of electrolytic hydrogen production originate from the required electricity. Also, the cost of the electrolyzer is major investment.

[0005] Green hydrogen is produced by using renewable energy (such as combining wave energy with solar) to power electrolysis that splits water into its constituent parts. Widely available analysis suggests a US$2/kg price represents a potential tipping point that will make green hydrogen and its derivative fuels the

2 LU501094 energy source of choice across multiple sectors, including steel manufacturing, fertilizer production, power generation, and shipping where vast near-term demand exists across Europe and internationally.

[0006] Purified water is needed for long term water splitting in electrolyzers.

As 96.5% of the global water is seawater and less than 1% is nonfrozen freshwater, direct seawater splitting (DSS) seems desirable. DSS represents a highly difficult challenge to address. Indeed, robustness against corrosion of the electrodes of the electrolyzer is desired. Formation of salt crystals destabilizing and inhibiting chemical oxidation reduction reactions is a major concern. Kuang et al. [Yun Kuang etal, "Solar-driven, highly sustained splitting of seawater into hydrogen and oxygen fuels", PNAS 116(14), 6624-6629 (2019)] proposed an electrolyzer equipped with dual-layer NiFe/NiSx-Ni foam (Ni3) anode for direct seawater splitting. A

NiFe/NiSx/Ni anode for active and stable seawater electrolysis was investigated.

The uniform electrodeposited NiFe was a highly selective OER (oxygen evolution reaction) catalyst for alkaline seawater splitting, while the NiSx layer underneath afforded a conductive interlayer and a sulfur source to generate a cation-selective polyatomic anion-rich anode stable against chloride etching/corrosion. The seawater electrolyzer could achieve a current density of 400 mA/cm? under 2.1 Vin real seawater or salt-accumulated seawater at room temperature, while only 1.72 V was needed in industrial electrolysis conditions at 80°C. Critically, the electrolyzer also showed unmatched durability. Although a substantial increase in power consumption was observed, no obvious activity loss was observed after up to 1000 h of a stability test.

[0007] GB 2444731 relates to an open cycle ocean thermal energy conversion (OTEC) plant generating electricity and desalinated water. The plant comprises an inner chamber (shell) surrounded by an outer chamber, one of the chambers containing a vacuum. Relatively warm ocean water is pumped into the vacuum containing chamber where it is evaporated, the vapour passing through a turbine, which generates electricity, to the other of the chambers where it is condensed into desalinated water using relatively cold ocean water. The chambers may be spherical in shape. Part of the generated electricity maybe used to produce hydrogen. The plant is located on a floating platform which is supported by pressure ballasted hollow columns which allow it to rise and fall as required. A pipe supplying the

3 LU501094 relatively cold ocean water is separately buoyed and moored, and is linked to the platform by telescopic flexible tubing.

[0008] WO 2021/81775 relates to a marine energy-island device, comprising: a marine platform; and a tidal current energy power generation device, a wave energy power generation device, a photovoltaic power generation device, a wind energy power generation device, a hydrogen production device and a seawater desalination device that are all arranged on the marine platform. The tidal current energy power generation device, the wave energy power generation device, the photovoltaic power generation device and the wind energy power generation device are all electrically connected to the hydrogen production device and are used for providing electric energy for the hydrogen production device; and the tidal current energy power generation device, the wave energy power generation device, the photovoltaic power generation device and the wind energy power generation device are all electrically connected to the seawater desalination device and are used for providing electric energy for the seawater desalination device.

[0009] US 2013/0068629 relates to an ocean wave energy conversion unit that converts kinetic energy from oceanic waves into useable form of energy (Aqua-

Tamer). The unit is designed to be modular in nature where the units can be deployed to function individually or assembled into groups where units will rely on each other and function together as a whole. Each individual unit has an electrical output. As a group (Colony) during deep sea surface applications, the electrical output of each Aqua-Tamer unit will be consolidated and used to operate a water- electrolysis operation that produces oxygen gas (O») and hydrogen gas (H-). The ocean wave energy conversion unit described uses a water-electrolysis operation.

General Description

[0010] À first aspect of the present invention relates to a device for producing dihydrogen from water, e.g., from seawater. The device comprises a (greenhouse) casing comprising a water reservoir, a water inlet and one or more condensation surfaces. The water inlet (e.g., an opening, an interstice, a channel, etc.) is configured for allowing water to enter into the reservoir. The (greenhouse) casing is configured to absorb solar energy to heat the water in the reservoir so as to produce water vapor in the casing. The one or more condensation surfaces are configured

4 LU501094 for condensing the water vapor so as to produce condensed water. The device further comprises an electrolyzer for electrolyzing the condensed water, thereby producing dihydrogen and a wave energy converter for converting water wave energy into electrical energy. The wave energy converter is operatively connected to the electrolyzer so as to supply the electrolyzer with the electrical energy for carrying out the electrolysis.

[0011] As used herein, the term “greenhouse casing” designates a casing configured for absorbing solar energy to heat water in the reservoir so as to produce water vapor in the casing. In other words, the casing is configured for creating a microclimate so that the temperature inside the casing is higher than the temperature outside the casing. This is carried out by absorbing solar energy.

[0012] It will be appreciated that the present invention allows for producing dihydrogen, the production of which has a reduced environmental impact. Indeed, the electrolyzer is powered by converted water surface wave energy and the purification (desalination) of seawater is carried out by solar energy harvested by the casing. The design of the disclosed device allows for an autonomous operation.

Indeed, the device can harvest the solar and wave energy necessary for it to operate and (continuously) produce dihydrogen.

[0013] It will also be appreciated by the skilled person that the present invention is suitable for producing dihydrogen from water in general, i.e., other than seawater (e.g., with a high concentration in mineral and/or biological matter) although seawater is considered a preferred source of hydrogen in the present context.

[0014] The casing may comprise a condensed water collector (e.g., a tube, drain, pipe, etc.) for directing the condensed water into the electrolyzer. The condensed water collector may include the one or more condensation surfaces onto which the water vapor may condense. The condensed water is preferably directed into the electrolyzer by gravity. In other words, the condensed water is driven into the electrolyzer by gravity. This allows for reducing the energy footprint of the device byavoiding the use of, e.g., pumps for driving condensed water into the electrolyzer.

The one or more condensation surfaces may be cooled via a thermal bridge towards the outer atmosphere or towards the surrounding water, e.g., the surrounding seawater.

5 LU501094

[0015] The device may further comprise a gate valve for controlling the condensed water intake of the electrolyzer. The gate valve may be in an open position. This allows the water to be electrolyzed to enter the electrolyzer.

Conversely, the gate valve may be in a closed position, thereby interrupting the water flow. Of course, any intermediate position (between closed and open) is also contemplated. This allows for controlling the flow of water entering the electrolyzer (e.g., the amount of water per unit of time entering the electrolyzer).

[0016] The device may further comprise a battery or supercapacitor for storing the converted seawater wave energy and for supplying electrical energy to the electrolyzer for carrying out the electrolysis. This allows for providing an electrical energy buffer, thereby allowing to store electrical energy in case more electrical energy is generated than consumed, during a first time interval. The stored energy may be used, e.g., in a second time interval, in case not enough electrical energy is produced for powering the device (in particular the electrolyzer).

[0017] The device may further comprise a temperature sensor for sensing the temperature of the electrolyzer. This allows for controlling whether the electrolyzer operates within its prescribed operating temperature range.

[0018] The device may comprise a condensed water buffer tank for accumulating the condensed water, the buffer tank being in fluidic communication with the electrolyzer so as to provide the electrolyzer with the condensed water. The buffer tank may serve to average out the production of condensed water. The buffer tank may be part of the condensed water collector or connected to it so as to receive the water condensed on the one or more condensation surfaces. It will be appreciated, in particular, that the buffer tank allows for collecting water during daytime so as to be able to provide water to the electrolyzer during nighttime, even if not enough solar energy is collected by the casing for evaporating seawater. In other words, the buffer tank is preferably dimensioned so as to average out the production of condensed water on a scale of several hours to a few days, e.g., over half a day, over one day, or over two days or more.

[0010] The device may comprise at least one of: a temperature sensor, a pH sensor, a water level sensor, a conductivity sensor connected to the buffer tank for sensing the temperature, pH, water level, conductivity, respectively, of the condensed water in the buffer tank.

6 LU501094

[0020] The wave energy converter may comprise an electric generator coupled to a pendulum (e.g., a simple or, more preferably, a double pendulum) for converting water wave energy into electrical energy. The wave energy converter preferably comprises one or more buoyant bodies that are moved by water waves when the device is placed on a water expanse. The wave energy converter may be housed in such a buoyant body. It should be noted that the device as a whole may take the form of a buoy.

[0021] In an embodiment, the greenhouse casing comprises a solar collector layer for absorbing solar energy and producing thermal energy, the solar collector layer being configured to transfer the produced thermal energy in the greenhouse casing, preferably directly to the water in the reservoir.

[0022] In an embodiment, the greenhouse casing comprises a thermal insulation layer for thermally insulating the water contained in the reservoir from an (underlying) environment of the device (e.g., the surrounding water of the sea).

It will be appreciated that the presence of such a layer allows for a more efficient heating of the casing because heat losses are reduced.

[0023] The greenhouse casing may comprise one or more light concentrators, such as one or more Fresnel lenses. The one or more light concentrators may be arranged to concentrate the sunlight density (mostly for the infrared range) on the area of the water reservoir so as to increase the efficiency of heating inside the greenhouse casing. Fresnel lenses are flat and not bulky lenses with the advantages that they are relatively lightweight when compared to conventional lenses and can be manufactured easily. One or more Fresnel lenses could be integrated into the greenhouse casing when this is made of a transparent material (such as, e.g., plastic, like polymethyl methacrylate or glass).

[0024] The device may comprise a buoy.

[0025] The device may comprise a ballast.

[0026] The device may comprise a communication apparatus, e.g., a wireless or wired communication apparatus, for communicating with a base station.

[0027] In a preferred embodiment, the electrolyzer comprises a PEM (polymer electrolyte membrane) electrolyzer. Alternatively, when solar energy is used to heat up the electrolyser and/or to generate water steam, a solid-oxyde

7 LU501094 electrolyzer could be used, e.g. one or more solid-oxyde electrolyzer cells (SOEC). In this case, one or more solar collectors and/or super-absorbent (superblack) coatings could be used to convert the solar radiation into heat and to heat the relevant parts of the device.

[0028] In an embodiment, the device comprises a controller. The controller may be configured to operatively switch on or off the electrolyzer, preferably based on at least one of: the temperature of the electrolyzer as well as the temperature, pH, water level, conductivity, respectively, of the water in the buffer tank.

[0029] In an embodiment, the controller may be configured to operate an actuator for closing (or opening) a gate valve downstream of the water collector and preferably configured to operatively switch on (or off) the electrolyzer, based on at least one of: an acceleration, an angular velocity of the device and a magnetic field at the device location. The acceleration, angular velocity and magnetic field at the device location may be provided by an accelerometer, a gyroscope and a magnetometer, respectively, provided in the device.

[0030] A second aspect of the present invention relates to a dihydrogen production rig comprising one or more devices as disclosed in the present document.

[0031] A third aspect of the present invention relates to a dihydrogen production facility. The facility comprises: o a plurality of devices as disclosed in the present document; o one or more dihydrogen transfer lines connected to the device for transferring the dihydrogen produced by the devices; and o a station comprising a pump connected to the one or more dihydrogen transfer lines for directing the dihydrogen produced by the devices to a shore station.

[0032] A standard compressing unit, e.g., powered by photovoltaic energy, could be coupled to the facility to store dihydrogen at high pressure.

[0033] A fourth aspect of the present invention relates to a method for producing dihydrogen from water with a device as disclosed in the present document. The method comprises:

8 LU501094 o absorbing solar energy to heat water contained in the reservoir so as to produce water vapor in the casing; o using one or more condensation surfaces to condense the water vapor and to produce condensed water; o electrolyzing the condensed water with the electrolyser to produce dihydrogen; o using a wave energy converter to convert water wave energy into electrical energy; and o supplying the electrolyzer with the electrical energy for carrying out the electrolysis.

[0034] The method may comprise using a condensed water collector to direct the condensed water into the electrolyzer, the condensed water being preferably directed in the electrolyzer by gravity.

[0035] The method may comprise operating a gate valve for controlling the condensed water intake of the electrolyzer.

[0036] The method may comprise sensing the temperature, pH, conductivity of the water and/or the water level in a buffer tank between the one or more condensation surfaces and the electrolyser.

[0037] The operation of the gate valve for controlling the condensed water intake of the electrolyzer may be based on the sensed temperature, pH, (electrical) conductivity of the water and/or the water level in the buffer tank. Additionally or alternatively, the operation of the gate valve could be based on the water filling level of the O. exhaust pipe of the electrolyzer.

[0038] The method may comprise (via a wire or wirelessly) transmitting the sensed temperature, pH, conductivity of the water and/or the water level in the buffer tank and/or any other parameter measured onboard the device to a remote station.

[0039] In the present document, the verb “to comprise” and the expression “to be comprised of” are used as open transitional phrases meaning “to include” or “to consist at least of”. Unless otherwise implied by context, the use of singular word form is intended to encompass the plural, except when the cardinal number “one”

9 LU501094 is used: “one” herein means “exactly one”. Ordinal numbers (“first”, “second”, etc.) are used herein to differentiate between different instances of a generic object; no particular order, importance or hierarchy is intended to be implied by the use of these expressions. Furthermore, when plural instances of an object are referred to by ordinal numbers, this does not necessarily mean that no other instances of that object are present (unless this follows clearly from context). When this description refers to “an embodiment”, “one embodiment”, “embodiments”, etc., this means that the features of those embodiments can be used in the combination explicitly presented but also that the features can be combined across embodiments without departing from the invention, unless it follows from context that features cannot be combined.

Brief Description of the Drawings

[0040] By way of example, preferred, non-limiting embodiments of the invention will now be described in detail with reference to the accompanying drawings, in which:

Fig. 1: is a schematic layout of a device for producing dihydrogen from seawater;

Fig. 2: is schematic diagram of the electrolyser part of the device of Fig. 1;

Fig. 3: is a schematic diagram illustrating the operation of the device; and

Fig. 4: is a schematic view of a dihydrogen production facility.

[0041] The reader’s attention is drawn to the fact that the drawings are not to scale. Furthermore, for the sake of clarity, proportions between height, length and/or width may not have been represented correctly.

Detailed Description of Preferred Embodiments of the Invention

[0042] Fig. 1 illustrates a preferred embodiment of an aspect of the present invention. In Fig. 1 a device 10 for producing dihydrogen from seawater 12 is shown.

The device 10 may be moored. The device 10 comprises a (greenhouse) casing 13 including a base structure 14 and a lid 16, a compartment 18 (acting as a buoy) and a ballast20. In another embodiment, the buoy may be separate from the compartment 18.

10 LU501094

[0043] The base structure 14 is, when in use, in contact with the seawater 12.

The base structure is substantially flat with a rim 22 at its periphery thereby providing a seawater reservoir. As will be understood by the reader, the base structure need not be (substantially) flat but may be of any geometry as long as it provides a reservoir for the seawater. The seawater may enter in the device 10 by an interstice 26 (or other inlet) in the casing 13 (between the base structure 14 and the lid 16). The seawater that has entered is trapped due to the presence of the rim 22 and rests on the base structure 14.

[0044] The base structure 14 comprises a black solar collector layer 14a for absorbing solar energy and producing thermal energy. The solar collector layer transfers the produced thermal energy in the greenhouse casing to the seawater in the reservoir. As depicted, the layer 14a may directly contact the seawater collected in the base structure 14. The layer 14a allows for efficiently capturing solar energy (in particular visible and IR radiation) and transforming the same in thermal energy(heat), which in turn causes evaporation of the seawater in the casing. In order to mitigate cooling by the underlying seawater, the base structure 14 may comprise a thermal insulation layer 14b for thermally insulating the seawater contained in the reservoir from the underlying water of the sea. Advantageously, the thermal insulation layer 14b is, in use, in contact with the water of the sea.

[0045] As illustrated, the lid 16 may be shaped as a pyramid truncated by a cap 24. The lid 16 allows for collecting solar energy for heating and evaporating the seawater trapped by the base structure 14. The lid 16 may be transparent or semi- transparent. The cap 24 and/or the lid 16 may comprise one or more Fresnel lenses.

One or more coatings 28 may be applied on the inner surface of the lid 16. The coating(s) 28 may improve the greenhouse effect by optimizing (improving) infrared radiation transmission. The coating(s) 28 may mitigate biofilm formation by means of a photocatalytic thin film of TiO. excited by sunlight. Also, a fluoropolymer coating (e.g. PFA, FEP, PTFE) may be applied to improve the repelling of the condensed droplets.

[0046] The lid 16 may be (mechanically) fixed to the compartment 18 thereby allowing the lid 16 and the compartment 18 to move as a monolithic object. Also, the lid 16 may be (mechanically) fixed to the base structure 14 such that the lid 16 and the base structure may also be considered as a monolithic object.

11 LU501094

[0047] The casing 13 encloses at least one condensation surface, which, in the illustrated embodiment, is provided in the form of an inverted cone 30. The surface of the cone may be coated in the same way as the other inner surfaces of the lid 16.

The inverted cone 30 is arranged on the inner surface of the cap 24. In use, the inner surface of the lid 16 as well as the inner surface of the inverted cone 30 provide surfaces for condensation of the evaporated water inside the casing 13. The condensation heat may be evacuated from the condensation surfaces by thermal conduction across the lid, which is cooled by the outer atmosphere. Alternatively or additionally, the condensation surfaces could be connected by a thermal bridge to the surrounding seawater 12, acting in this case as a heat sink. Condensed water droplets 32 are produced on the inner surface of the lid 16 and on the surface of the inverted cone 30.

[0048] The condensed water is purified in the sense that the mineral content thereof is greatly reduced. In practice, seawater containing about 20000 ppm of dissolved salt may be purified to about 37 ppm of dissolved salt. Also, the quantity of biological matter may be reduced. The remaining salt (which was initially in the evaporated seawater) stays in the seawater reservoir and may be released in the environing seawater in case e.g. of an overflow of the base structure due to a seawater. It will be appreciated that the present design allows for continually renewing the seawater in the reservoir, without having a seawater in the reservoir having a higher concentration of mineral than the environing seawater.

[0049] The inverted cone 30 allows for directing the condensed water 32 into the compartment 18, located below the tip of the inverted cone 30. The compartment 18 is provided with a hole for letting condensed water in. It will be appreciated no active driving force (e.g. provided by a pump) is necessary as the mere action of the gravity is sufficient for directing the condensed water 32 into the compartment 18. This allows for decreasing the energy consumption of the device 10. Advantageously, the compartment 18 is equipped with a funnel 34 for collecting condensed water droplets.

[0050] The compartment 18 comprises a PEM electrolyzer 36 (preferred because a PEM electrolyzer can exhaust H. without water, but other electrolyzers may also be contemplated), a gate valve 38 for controlling the condensed water intake of the electrolyzer, a buffer tank 40 in fluidic communication with the

12 LU501094 electrolyzer 36 for providing the electrolyzer 36 with condensed water, and a wave energy converter 42.

[0051] With reference to Fig. 2 showing a magnification of a detail of Fig. 1, the buffer tank 40 is equipped with a pH sensor 44, a water level sensor 46, and a conductivity sensor 48 for sensing the pH, the water level, and the electrical conductivity, respectively, of the water in the buffer tank 40. This allows for an improved control and diagnostic of the water that will be used in the electrolyzer 36.

The buffer tank may be equipped with further sensors, e.g., a temperature sensor.

[0052] The electrolyzer 36 is provided with water from the buffer tank 40. The electrolyzer 36 comprises: a hollow cathode electrode 50, a diffusion layer 52, a catalyzer layer 54, a proton exchange membrane 56 (e.g. Nafion), a catalyzer layer 58, a diffusion layer 60 and a hollow anode electrode 62. The condensed water entering the electrolyzer is electrolyzed: oxygen (Oz) is produced at the hollow cathode electrode 50 and exits the electrolyzer together with water by a first exhaust tube 64. Dihydrogen is produced at the hollow anode electrode 62 and exits the electrolyzer by a second exhaust tube 65 (H- outlet). The first exhaust tube 64 may be equipped with a capacitance sensor 68 which allows for detecting whether water is filling (and how much) the exhaust tube 64. The control of the gate valve may be based (also) on the reading of the capacitance sensor 68 (or any other filling level probe arranged in the first exhaust tube). The electrolyzer 36 is equipped with a temperature sensor 70 allowing for controlling the operating temperature of the electrolyzer 36.

[0053] It will be appreciated that the compartment 18 mitigates exposure to (marine) environment, thereby avoiding corrosion, biofilm and/or algae formation.

Indeed, the compartment 18 is sealed and only three passages are present: the funnel hole for providing condensed water to the electrolyzer and the two exhaust tubes of the electrolyzer. The passages are protected from environing water by the lid 16.

[0054] With reference to Fig. 1, the electrolyzer 36 is powered by a wave energy converter 42. The wave energy converter 42 comprises a power management module 66 and an energy storage appliance (e.g., a battery or a supercapacitor) for storing electrical energy. The power management module 66 may be operatively connected to the energy storage appliance. In case the electrical energy needed by

13 LU501094 the device is lower than the energy harvested from the sea waves, the energy storage appliance may store that electrical energy surplus. In the opposite case, the electrical energy stored in the energy storage appliance may be used for powering the device 10 (e.g. the electrolyzer and/or the above-mentioned sensors). The wave energy converter 42 further comprises a double pendulum 69 coupled to an electric generator 72 so that the double pendulum 69 may impart a rotational movement to the electric generator 72. The double pendulum 69 comprises a first arm coupled to the electric generator and a second arm, the second arm being rotatably joined, by a pivot joint, to the first arm. The sea waves generate an inclination variation at the water surface. The device 10 is lifted by the waves when they sweep it. Due to their shapes, the waves cause the device to tilt with respect to the vertical direction, which in turn drives the double pendulum 69, thereby producing electricity through the rotation of the electric generator imparted by the double pendulum 69.

[0055] An MCU74 (microcontroller unit) is also provided in the compartment 18. The MCU 74 is operatively connected to the above-mentioned sensors, the electrolyzer 36, the gate valve 38, the power management module 66 and possibly a communication apparatus 81 (also located inside the compartment 18) for communicating with a base station.

[0056] Fig. 3 shows a simplified diagram illustrating the operations of the device 10. As explained above, the device 10 harvests energy from the waves (step 76) and the power management module provides electrical energy to the electrical components of the device 10 (e.g. sensors, electrolyzer, etc.). Also, water is provided to the electrolyzer by solar distillation (steps 78). The above-mentioned sensors provide readings to the MCU which is configured to operate the device 10 on this basis. For example, the MCU 74 may be configured to stop the electrolyzer in case its operating temperature is no within a range of typical temperature for the specific model of electrolyzer (see e.g. switch 80). The electrolyzer may also be switched off in case of a power consumption lying outside predetermined operational boundaries. In the same way, the MCU 74 may be configured to stop the electrolyzer and flush water contained in the buffer tank 40 in case the water contained in the buffer tank 40 is not within predetermined ranges of pH, conductivity and/or temperature. Also, accelerometer, gyroscope, and/or magnetometer (e.g. embedded in the MCU) may provide information on the sea waves. In case of very rough waves

14 LU501094 or e.g. bad weather conditions, are detected by the accelerometer, gyroscope, and/or magnetometer, the MCU may stop the operation of the electrolyzer (switch off). when normal conditions are detected, the MCU may resume the operation of the device. The configuration of the MCU may be operated by flashing an EEPROM of the MCU.

[0057] As will be understood by the skilled person, the MCU may comprise or consist essentially of a general-purpose microprocessor, an application-specific integrated circuit (ASIC), a system on a chip (SoC), a programmable logic circuit, a special purpose microprocessor or a programmed generic microprocessor. Among the programmable logic circuits, the implementation of the processor could a field- programmable gate array (FPGA), a programmable logic device (PLD), an erasable programmable logic device (EPLD), a complex programmable logic device (CPLD), programmable logic array (PLA), or other. Low power MCUs, such as, e.g., the

MCUs of the STM32U5 series from ST Microelectronics with 1.8 V supply voltage and 26 uA/MHz supply current, are preferred.

[0058] Also, part or all of the readings of the sensors, amount of energy stored in the energy storage appliance, may be transmitted by a communication apparatus to a monitoring station, e.g., for remote monitoring. Also, the MCU may transmit, via the communication apparatus, the status of the device including whether any of the electrical components are faulty (e.g. not operating within their operational parameters). The communication apparatus may carry out the transmission wirelessly or via wire.

[0059] As indicated above, the device10 comprises a ballast 20. The ballast 20 allows for compensating the weight of the device 10. In particular, the ballast may be designed in such a way that the (substantially) flat part of the base structure lies below the waterline and the tip of the rim above the waterline.

[0060] Fig. 4 illustrates a dihydrogen production facility comprising a dihydrogen production rig comprising one or more devices 10. The devices 10 are connected to one or more dihydrogen transfer lines 82 for transferring the dihydrogen produced by the devices. The one or more dihydrogen transfer lines 82 are connected to the H- outlet of each of the devices 10. The plant further comprises a station comprising a pump 84 connected to the one or more dihydrogen transfer

15 LU501094 lines 82 for pumping the dihydrogen produced by the devices to the station. The dihydrogen may then be pressurized in a dihydrogen tank for transport.

[0061] The plant may further comprise (or be connected to) a communication apparatus 86 for receiving communication sent by the communication apparatuses 81 ofthe devices 10. The communication may be effected wirelessly or via wires (e.g. running along and/or being attached to the transfer lines 82). The communication may be forwarded to a server in the cloud for allowing monitoring by a remote operator (e.g. monitoring temperature, pH, conductivity of the water in the respective reservoirs and/or the respective operating temperature of the electrolyzers). Also, a firmware updated of the MCU may be transmitted to the devices for updating the firmware of the MCU.

[0062] While specific embodiments have been described herein in detail, those skilled in the art will appreciate that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure.

Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.

Claims

16 LU501094 Claims

1. À device for producing dihydrogen from water, the device comprising: a greenhouse casing comprising a water reservoir, a water inlet and a condensation surface, the water inlet being configured for allowing water to enter into the reservoir, the greenhouse casing being configured to absorb solar energy to heat water in the reservoir so as to produce water vapor in the casing, the condensation surface being configured for condensing the water vapor so as to produce condensed water; an electrolyzer for electrolyzing the condensed water thereby producing dihydrogen; and a wave energy converter for converting water wave energy into electrical energy, the wave energy converter being operatively connected to the electrolyzer so as to supply the electrolyzer with the electrical energy for carrying out the electrolysis.

2. The device according to claim 1, the casing further comprising a condensed water collector for directing the condensed water into the electrolyzer, the condensed water being preferably directed into the electrolyzer by gravity.

3. The device according to any one of claims 1 to 2, further comprising a gate valve for controlling the condensed water intake of the electrolyzer.

4. The device according to any one of claims 1 to 3, further comprising a battery or supercapacitor for storing the converted water wave energy and for supplying electrical energy to the electrolyzer.

5. The device according to any one of claims1 to 4, further comprising a temperature sensor for sensing the temperature of the electrolyzer.

6. The device according to any one of claims 1 to 5, further comprising a buffer tank for accumulating the condensed water, the buffer tank being in fluidic communication with the electrolyzer so as to provide the electrolyzer with the condensed water.

7. The device according to claim 6, further comprising at least one of: a temperature sensor, a pH sensor, a water level sensor, a conductivity sensor connected to the buffer tank for sensing the temperature, pH, water level, conductivity, respectively, of the condensed water in the buffer tank.

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8. The device according to any one of claims 1 to 7, the wave energy converter comprising an electric generator coupled to a pendulum for converting water wave energy into electrical energy.

9. The device according to any one of claims 1 to 8, wherein the greenhouse casing comprises a solar collector layer for absorbing solar energy and producing thermal energy, the solar collector layer being configured to transfer the produced thermal energy in the greenhouse casing, preferably directly to the water in the reservoir.

10. The device according to any one of claims 1 to 9, wherein the greenhouse casing comprises a thermal insulation layer for thermally insulating the water contained in the reservoir from an underlying environment of the device, e.g. water from the sea.

11. The device according to any one of claims 1 to 10, wherein the greenhouse casing comprises one or more light concentrators, e.g., one or more Fresnel lenses.

12. The device according to any one of claims 1 to 11, wherein the device comprises a buoy.

13. The device according to any one of claims 1 to 12, further comprising a ballast.

14. The device according to any one of claims1 to 13, further comprising a communication apparatus for communicating with a base station.

15. The device according to any one of claims 1 to 14, wherein the electrolyzer comprises a PEM electrolyzer.

16. The device according to claim 1 or 7, further comprising a controller, the controller being configured to operatively switch on or off the electrolyzer, preferably based on at least one of: the temperature of the electrolyzer as well as the temperature, pH, water level, conductivity, respectively, of the water in the buffer tank.

17. The device according to any one of claims1 to 16, the controller being configured to operate a gate valve of the electrolyzer, and preferably configured to operatively switch on or off the electrolyzer, based on at least one of: an

18 LU501094 acceleration, an angular velocity of the device and a magnetic field at the device location.

18. A dihydrogen production rig comprising one or more devices according to any one of claims 1 to 17.

19. A dihydrogen production facility comprising: a plurality of devices according to any one of claims 1 to 17; one or more dihydrogen transfer lines connected to the device for transferring the dihydrogen produced by the devices; and a station comprising a pump connected to the one or more dihydrogen transfer lines for directing the dihydrogen produced by the devices to a shore station.

20. A method for producing dihydrogen from seawater with a device according to any one of claims 1 to 17, comprising: absorbing solar energy to heat water contained in the reservoir so as to produce water vapor in the casing; using a condensation surfaces to condense the water vapor and to produce condensed water; electrolyzing the condensed water with the electrolyser to produce dihydrogen; using a wave energy converter to convert water wave energy into electrical energy; and supplying the electrolyzer with the electrical energy for carrying out the electrolysis.

21. The method according to claim 20, comprising using a condensed water collector to direct the condensed water into the electrolyzer, the condensed water being preferably directed in the electrolyzer by gravity.

22. The method according to any one of claims 20 to 21, comprising operating a gate valve for controlling the condensed water intake of the electrolyzer.

23. The method according to any one of claims 20 to 22, comprising sensing the temperature, the pH, the conductivity and/or the water level of the water in a buffer tank, and/or the water filling level of an O. exhaust tube of the electrolyzer.

24. The method according to any one of claims 22 to 23, wherein the operation of the gate valve for controlling the condensed water intake of the electrolyzer is

19 LU501094 based on the sensed temperature, pH, conductivity and/or the water level of the water in the buffer tank, and/or on the water filling level of an O. exhaust tube of the electrolyzer.

25. The method according to any one of claims 23 to 24, comprising wirelessly transmitting the sensed temperature, pH, conductivity and/or the water level of the water in the buffer tank, and/or the water filling level of an O2 exhaust tube of the electrolyzer.