WO2023227922A1

WO2023227922A1 - High temperature electrolysis system and method

Info

Publication number: WO2023227922A1
Application number: PCT/IB2022/054889
Authority: WO
Inventors: Demetri Psaltis; Steven Alexandre SCHENK; Sylvain Jacky REINAUER; Pooria HADIKHANI
Original assignee: Ecole Polytechnique Federale De Lausanne (Epfl)
Priority date: 2022-05-25
Filing date: 2022-05-25
Publication date: 2023-11-30

Abstract

The present invention concerns an electrolysis system for high temperature electrolysis including a plurality of flow-based electrolysis units configured to receive an electrolyte solution and to perform electrolysis to provide a first output gas and a second output gas, the plurality of flow-based electrolysis units being membrane-less electrolysis units; at least one heating mechanism or means for heating the electrolyte solution to undergo electrolysis; a first gas separator and a second gas separator configured to remove the first output gas and the second output gas from the electrolyte solution; and an encasement or a cell enclosing the plurality of flow-based electrolysis units, the encasement or the cell being configured to support a pressure of the electrolyte solution permitting to increase a boiling point of the electrolyte solution to a temperature between 96°C and 350°C.

Description

HIGH TEMPERATURE ELECTROLYSIS SYSTEM AND METHOD

FIELD OF THE INVENTION

The present disclosure relates to high temperature electrolysis and to a high temperature electrolyzer/ electrolysis unit and system.

BACKGROUND

It is advantageous to operate an electrolyzer at higher temperatures, primarily because the conductivity of the liquid electrolyte generally increases with temperature. In addition, the reactivity of the electrodes increases with temperature. Despite these advantages, current commercial alkaline or polymer electrolyte membrane (PEM) electrolyzers operate at relatively low temperatures of only 80 °C due to the instabilities of their membranes or separators at higher temperatures.

SUMMARY OF THE INVENTION

It is thus a goal of the present disclosure to address the above-mentioned limitation.

The present invention addresses the above-mentioned limitations by providing an electrolysis system for high temperature electrolysis according to claim 1, and an electrolysis method for high temperature electrolysis according to claim 33.

Membrane assemblies and separators (used for example in alkaline electrolyzers) become damaged at higher temperatures above 80°C.

The invention of the present disclosure overcomes this problem by designing the high temperature system with a flow-based membrane-less electrolyzer or electrolysis unit (MLE).

The membrane-less electrolyzer or electrolysis unit, the electrolysis system and electrolysis method advantageously assure that higher temperature electrolysis can be carried out and a higher gas production achieved at lower running voltages.

Other advantageous features can be found in the dependent claims.

The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description with reference to the attached drawings showing some preferred embodiments of the invention.

A BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Figure 1 shows a single channel of an exemplary electrolyzer unit or electrolysis unit for high temperature electrolysis according to the present disclosure. The electrolyzer unit or electrolysis unit is membrane-less and may be composed, for example, of two or more components or blocks fabricated through injection molding, machining or 3D printing and, for example, interconnecting electrodes configured to interconnect the two components or blocks.

Figure 2 shows a schematic diagram of the channel in Figure 1 of the exemplary electrolyzer unit or electrolysis unit according to the present disclosure that is used in the electrolysis method and system of the present disclosure. The exemplary flow-based electrolyzer or electrolysis unit is membrane-less and designed to work at high temperature.

Figures 3A and 3B show an exemplary electrolysis system for high temperature electrolysis according to the present disclosure, Figure 3B providing more detail as to fluid circulation in the system.

Figure 4 shows an exemplary gas separator that may be used in the electrolysis system of the present disclosure for high temperature electrolysis.

Figure 5 shows an exemplary solar thermal power plant or system comprising the electrolysis system for high temperature electrolysis according to the present disclosure.

Figure 6A shows a schematic perspective view of an exemplary stack comprising a plurality of cells, each cell comprising a plurality of flow-based membrane-less electrolysis unit.

Figure 6B shows schematic cross-sectional views of the stack of Figure 6A.

Figure 6C shows a schematic perspective view of the cell of Figures 6A and 6B.

Figure 6D shows an exploded view of an exemplary cell of Figure 6C.

Figure 6E is a cross-sectional schematic of the exemplary cell.

Figure 6F is a cross-sectional schematic of the exemplary cell showing more details of the constituent electrolysis units in the lower portion of the Figure, where some parts of the electrolyser unit and cell have been removed to permits certain features to be visible.

Figure 6G is a top view cross-sectional schematic of a portion of the exemplary cell and a plurality of electrolysis units of Figure 6F along the dashed line shown in the upper illustration of Figure 6F.

Figure 7 shows measured and calculated data demonstrating the electrochemical performance of a membrane-less electrolysis unit at different temperatures. Solid lines show the experimental results. Dashed lines depict curves predicted by the model. The model predicts the current-potential diagram of the flow-based electrolysis unit by considering the experimental data at lower temperatures and the conductivity of the electrolyte and starting reaction potential at different temperatures. The model is used to predict the performance of an exemplary membrane-less electrolysis units such as that of Figure 2 or Figure 9A, and also when this membrane-less electrolysis unit is performance improved or optimized by including selective porous electrode materials (such as Raney Nickel for oxygen evolution reaction and Nickel-Molybdenum for hydrogen evolution reaction). The model considers potassium hydroxide conductivity, thermodynamic starting potential, ohmic losses of MLE, and electrodes overpotential at different temperatures. The model predicts similar values at 80°C to the measured experimental data, and shows high gas production levels at lower voltages and at higher temperature operation above 80°C and up to 350°C. Figure 8 shows water volume fraction in a membrane-less electrolysis unit at four different temperatures of 25°C, 150°C, 250°C and 350°C. The numerical solver used to determine the water volume fraction considers a three-phase mixture fluid flow equation. The three phases are water, hydrogen, and oxygen. The flow regime changes with temperature but no gas crossover can be seen. Density, viscosity, and surface tension of the fluids are changed based on the temperature.

Figures 9A and 9B schematically show more details of an exemplary electrolysis unit according to the present disclosure.

Figure 10 shows the different constituent elements for performing electrolysis in the exemplary electrolysis system or electrolyzer system.

Herein, identical reference numerals are used, where possible, to designate identical elements that are common to the Figures.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

Figures 3A and 3B show an exemplary electrolysis system or electrolyzer system 1 (or high temperature electrolysis system 1) according to the present disclosure, electrolysis system 1 is for carrying out electrolysis or high temperature electrolysis. The exemplary electrolysis system 1 can, for example, be used for carrying out, at high temperature, the electrolysis method according to the present disclosure. The electrolysis system 1 for high temperature electrolysis or the high temperature electrolysis system 1 includes at least one or a plurality of flow-based electrolysers or electrolysis units or electrolyser units 3 or membrane-less electrolysers, electrolysis units or electrolyser units 3 configured to receive an electrolyte solution 5 and to perform electrolysis to provide a first output gas 7 and a second output gas 9. The flow-based electrolysis unit 3 is membrane-less.

The electrolysis unit 3 uses, for example, fluidic forces instead of membranes or separators for the separation of the electrolysis gas products. Membranes or diaphragms such as a polymer electrolyte membrane used to prevent gas cross-contamination are absent.

The system 1 may include one or more heating means (or heaters) 10 for heating the electrolyte solution 5 or for heating the electrolyte solution 5 that is to undergo electrolysis, or that is undergoing electrolysis.

The system 1 may also include, for example, a first gas separator 11 configured to remove the first output gas 7 from the electrolyte solution 5, and/or a second gas separator 15 configured to remove the second output gas 9 from the electrolyte solution 5.

The electrolyte solution 5 is, for example, a liquid or solvent containing a dissolved electrolyte, or a liquid or solvent containing a substance producing an electrically conducting solution. The liquid or solvent may for example be water, and the electrolyte may for example comprise or consist of potassium hydroxide KOH. The electrolyte solution 5 may thus for example comprise or consist of water in which KOH is dissolved. The first output gas 7 and the second output gas 9 in such a case comprise or consist of hydrogen and oxygen. The electrolyte solution 5 is not limited to these examples and other electrolytes and solvents may of course be used.

The system 1 may also include, for example, a cell 25 or an encasement or housing 17 (Figure 6C) enclosing the one or more membrane-less electrolysis units 3. The encasement 17 is configured to support (or withstand) a fluid or liquid pressure of the electrolyte solution 5 acting on the encasement 17 that is of a pressure value that permits to increase a boiling point of the electrolyte solution 5. That is, to increase for example a boiling point of the electrolyte solution 5 relative to its atmospheric pressure boiling point (for example, the temperature at which the vapor pressure of the electrolyte solution 5 equals the Earth’s atmospheric pressure at sea level (latm)).

The encasement 17 is, for example, configured to assure that a pressure value of < 30 bar (or 3xl0⁶ Pa), or < 40 bar (or 4xl0⁶ Pa), or < 50 bar (or 5xl0⁶ Pa) or < 60 bar (or 6xl0⁶ Pa) of the electrolyte solution 5 can be applied by the electrolyte solution 5 to the encasement 17 with the encasement 17 remaining intact. The pressure value can be, for example, between (i) 1 bar and (ii) 30 bar, or 40 bar or 50 bar or 60 bar.

The encasement 17, for example, comprises or consists of at least one metal for example nickel or stainless steel. The encasement 17, for example, comprises or consists of a polymer, for example, Polyether ether ketone (PEEK), Polyamide 12, Polyphenylene Sulfide, Polyphthalamide, or Teflon.

The encasement 17 includes, for example, at least one surrounding wall 19 (or a plurality of surrounding walls) surrounding the one or more flow -based electrolysis units 3. The wall 19 defines a cavity CV (Figure 6D) in which the one or more flow-based electrolysis units 3 are contained or housed.

The encasement 17 includes at least one removable end plate EPl, EP2 (Figure 6D) or a first removable end plate EPl and/or a second removable end plate EP2 permitting internal access to the cavity CV and the one or more flow-based electrolysis units 3. The end plate or end plates EPl, EP2 are, for example, removably attached or fixed to the surrounding wall 19 to close the cavity CV and enclose the one or more flow-based electrolysis units 3.

In the case where the encasement 17 includes solely one removable end plate EPl, the encasement 17 may, for example, include a (permanent) floor enclosure located opposite the one end plate EP 1. In the case where the surrounding wall 19 defines opposite openings, the floor enclosure may extend to the perimeter of the surrounding wall 19 to close the opening defined by the wall 19, with the removable end plate EPl being configured to close the opposite opening.

A sealing element 21, for example an O-ring, may be located between each end plate EPl, EP2 and the surrounding wall 19. The sealing element 21 comprises or consists of one or more sealing materials that can operate at high temperature, such as Polytetrafluoroethylene (PTFE) or Polyetheretherketone (PEEK).

The end plates EPl, EP2 are attached to the wall 19 by fixation means such as a welding, an adhesive, or screws. The end plates EPl, EP2 and the wall 19 may comprise or consist of any one of the materials previously mentioned in relation to the encasement 17. The cell 25 (or each cell 25) includes the encasement 17.

The system 1 may include one electrolysis units 3 or a plurality of electrolysis units 3 to increase the quantity of gas produced by electrolysis. The system 1 may include a stack 23 comprising a plurality of cells 25, each cell 25 comprising a plurality of electrolysis units 3 (see, for example, Figures 6A to 6D). A cell 25 shown, for example, in Figures 6E is built from or comprises multiple electrolysis units (located in cavity CV as seen for example in Figures 6D). The cell 25 has, for example, one inlet 33 and the liquid electrolyte 5 is communicated to and enters the plurality of electrolysis units 3 from this inlet 33 and goes through multiple electrolysis units 3 to the outlets 35A, 35B via, for example, a common fluid communication passage into which the fluidic channels 109, 111 of each of the electrolysis units 3 communicate the electrolyte 5 having undergone electrolysis. Each of the anode and cathode (ELI and EL2) can be, for example, fabricated in one piece and their structure or pattern matches with the way that channels electrolysis units 3 are placed next to each other. For example, each electrode ELI, EL2 has a common back plane from which a plurality of electrolysis electrodes extend and which are configured to engage the fluidic channels 109, 111 of the electrolysis unit 3. Figures 6F and 6G show more details of the exemplary arrangement of the electrodes and channels of electrolysis units 3. The outputs 39A, 39B of all electrolysis units 3 are connected to two outlets 35A, 35B for gas collection, for example, for the hydrogen and oxygen collection.

Figure 6F shows two schematics of the arrangement of electrolysis units 3 in a cell 25. The hashed parts represent the walls of the electrolysis unit 3 and the electrodes are not in the same plane. Figure 6G shows a top view of the electrodes ELI, EL2 in which this planar offset is visible. The electrodes ELI, EL2 can thus be inserted into the cell 25 and into the electrolysis unit 3 to define or be comprised in at least one wall or side of the fluidic channels 109, 111 of the electrolysis unit 3 to contact the electrolyte 5. Figure 6D shows the electrodes ELI, EL2 outside the electrolysis units 3 and cell 25 prior to insertion.

These cells 25 are stacked together as shown in Figure 6B to form the stack 23 of cells 25. The stack 23 of cells 25 has, for example, one inlet. This inlet goes into or fluidically communicates with all cells 25. The hydrogen outlets of the cells 25 are connected together to collect the produced hydrogen. The oxygen outlets of the cells are connected together to collect the produced oxygen. Figure 10 shows different constituent elements for performing electrolysis in the exemplary electrolysis system or electrolyzer system of the present disclosure.

With this modular design, the surface area of the electrodes and the corresponding gas (for example, hydrogen) production rate can be increased to any desired value. Multiple systems of this type can be combined for even larger scale production. As shown, for example, in Figures 3A and 3B, a high temperature pump 49 is included in the system and creates the electrolyte solution flow necessary for the proper operation of the electrolysis units 3. Flow sensors, pressure sensors SN1, and/or gas sensors, such as oxygen and hydrogen sensors (not shown) can be included to monitor and control the operation of the system.

As seen in Figures 6A to 6D, each cell 25 and stack 23 includes an inlet 27 for receiving the electrolyte solution 5, as well as first and second outlets 29A, 29B through which the electrolyte solution 5 containing the first and second output gases 7, 9 exit to be communicated to a further element of the electrolysis system 1, for example the first and second gas separators 11, 15 via for example interconnecting system tubing or canalization 43 (Figure 3A).

The assembled cells 25 defining the stack 23 may define a first and second canals 31A, 3 IB (Figure 6B) arranged to communicate the gas containing electrolyte solution 5, and also define a third canal 31C arranged to communicate the received electrolyte solution 5 inside the stack 23 and to each cell 23 for electrolysis.

Openings OP1, OP2 (Figure 6B)) may, for example, be located at an extremity of the canals 31A, 3 IB opposite to that of the first and second outlets 29A, 29B due to the modular form of the cell 25. These openings OP1, OP2 may, for example, be closed or sealed to allow the electrolyte solution 5 to be guided or directed only out of the stack 23 via the first and second outlets 29A, 29B.

Each cell 25 includes a cell inlet 33 (Figure 6B) in fluid communication with the one or more electrolysis units 3, via an inlet fluid communication channel IFC, to provide the electrolyte solution 5 to the electrolysis units 3 of each cell 25 for electrolysis.

The inlet 27 for receiving the electrolyte solution 5 is in fluid communication with the cell inlet 33 of each cell 25 to provide the electrolyte solution 5 to the cells 25 for electrolysis.

The electrolyte solution 5 is flowed through the cells 25 and the electrolysis units 3, and the electrolyte solution 5 containing the gas exits via at least first and second outlet fluid communication channels OFC1, OFC2 of the cell 25 or extending from or being part of the electrolysis unit 3 and via a first and second cell outlet 35A, 35B. The first and second cell outlets 35A, 35B are in fluid communication with the first and second canals 31 A, 3 IB to permit removal of the electrolyte solution 5 containing the gases via the first and second outlets 29A, 29B.

The cell 25 includes a plurality of electrolysis units 3 and an electrolyser/electrolysis unit inlet 37, 121 (Figures 2 and 9A) of each electrolysis unit 3 is in fluid communication with the cell inlet 33 of the cell 25 to provide the electrolyte solution 5 to each electrolysis unit 3. The electrolyte solution 5 is flowed through each electrolysis unit 3 and exits each electrolysis unit 3 via a first and second electrolyser outlets 39A, 123A, 39B, 123B of the electrolysis unit 3 (Figures 2 and 9A). The first electrolyser/electrolysis unit outlet 39A, 123 A of each electrolysis unit 3 is in fluid communication with the first cell outlet 35A (via, for example, fluid communication channel OFC1) to permit the electrolyte solution 5 containing the first gas to exit the first outlet 29A of the stack 23. The second electrolyser outlet 39B, 123B of each electrolysis unit 3 is in fluid communication with the second cell outlet 35B (via, for example, fluid communication channel OFC2) to permit the electrolyte solution 5 containing the second gas to exit the second outlet 29B of the stack 23. As shown in Figures 3A and 3B, there are two outlets 29A, 29B of the stack 23 which carry electrolyte 5 with gas bubbles floating in the liquid (for example, hydrogen bubbles in one outlet and oxygen in the other when water is the solvent for the electrolyte). The purity of the produced hydrogen depends on the crossover in each output channel of the electrolysis unit 3 (oxygen generated in the anode, crossing the central chamber and entering the hydrogen outlet on the other side) but also due to O2 that is dissolved in the electrolyte solution 5 and re-enters the MLE 3 due to recirculation. In addition, the hydrogen gas is to be separated from the liquid electrolyte 5 before it is collected and stored. The two cylinders or gas separators 11, 15 shown in Figures 3 A, 3B, perform these two tasks (separate the gas from the liquid) and also induce the removal of dissolved gas.

The gas separators 11, 15 can, for example, each include a dehumidifier (condensator) coil to remove vapor (humidity) from the hot gas.

Figures 2 and 9A show an exemplary flow-based electrolysis unit 3 that is membrane-less (a membraneless electrolysis unit) that may be used in the high temperature electrolysis method and system of the present disclosure. However, it should be noted that flow-based electrolysis units of different configurations may also be used. Further details of the flow-based electrolysis unit 3 are provided below.

Figure 1 shows an exemplary disassembled electrolysis unit elements that form an electrolysis unit such as that shown in Figures 2 or 9A when assembled. The electrolysis unit includes, for example, two components or blocks fabricated for example through injection molding and, for example, interconnecting electrodes configured to interconnect the two components or blocks.

The electrolysis units are configured for and permit electrolysis at high temperature operation up to 200°C or 250°C or 270°C or preferably 350°C.

The electrolysis system 1 may, for example, include at least one thermal insulator 41 enclosing the one or more electrolysis unit 3, cells 25 and/or stack 23. The thermal insulator is configured to retain, in the plurality of membrane-less electrolysis units 3, the heat generated by electrolysis inside the electrolysis unit(s) 3.

At least one thermal insulator 41 may, also for example, enclose the system tubing or canalization 43 that is arranged to distribute the electrolyte solution 5 in the electrolysis system 1.

The thermal insulator 41 may comprise or consist of an insulating material enclosing or surrounding the system tubing 43, stack 23, cells 23 and/or the membrane-less electrolysis unit(s) 3. The thermal insulator may, for example, comprise or consist of fiberglass, ceramic fiber, or polycrystalline fiber. Also included in the system 1, for example, as shown in Figures 3A and 3B, is one or more heaters 10 which can be an external or auxiliary heater 10 to the electrolyser(s) 3 or an internal heater 10 to the electrolyser(s) 3 (for example, assured by a voltage source applying a voltage to the electrolyzer/electrolysis unit electrodes EL) to initially increase the temperature of the electrolyte 5 to a desired value and then maintain the temperature at that level. The internal heater 10 and/or the external or auxiliary heater 10 can be used to initially raise the temperature to a desired electrolysis temperature.

Since electrolysis is not 100% efficient, heat is generated when electrolysis is run to produce, for example, hydrogen. The heat produced by electrolysis can be used to maintain the temperature at a desired high level during steady state operation, depending on the level of insulation achieved by the thermal insulator 41. The system 1 can thus, for example, be configured to operate without any external heat being provided by the external or auxiliary heater 10 for a given insulation level assured by the thermal insulator 41 by reducing the electrical efficiency (increasing the applied voltage to the electrodes EL).

The external or auxiliary heater 10 may, for example, comprise or consist of an electrical heater. Alternatively, the electric heating being provided may be removed (at least during the steady state operation) and replaced with a source of thermal energy instead of electrical energy. Electric heating from the external heater 10 can be, for example, replaced by heat provided from another heat source after initial heating of the electrolysis solution 5 to a desired electrolysis temperature by the electric heating from the external heater 10.

Electrolysis at high temperatures needs lower electrical input power for a given hydrogen production rate compared to low temperature electrolysis. This reduction in input electrical power is due to the smaller starting potential, and larger electrolyte conductivity and electrode activity at high temperatures.

Consequently, one can provide heat to the electrolyte 5 in order to reduce the required electrical energy for the reaction. Heat is a lower grade energy and less expensive compared to electricity. As a result, replacing a portion of the electrical energy with heat for the water electrolysis can reduce significantly the hydrogen production cost.

As mentioned above, the heat generated from the electrochemical reaction in the electrolysis unit 3 can be recycled to increase the electrolyte temperature. Furthermore, solar thermal concentrators can, for example, be used as a renewable heat source that can extract sunlight energy at high efficiencies. In addition to the mentioned heat sources, many industries such as nuclear power plants can provide ‘free’ heat to this electrolysis system for increasing the electrolyte temperature. These industries have high temperature flowing water in their condensation process that needs to be cooled down. Therefore, the electrolysis system can receive ‘free’ heat from this process.

The heating means 10 of the system 1 may include an internal heater comprising at least one voltage source 45 providing a voltage to electrodes ELI, EL2 of the electrolysis unit 3, or current through the electrolyte solution 5 (see, for example, Figure 2).

The heating means (or heater(s)) 10 of the system 1 may also comprise or consist of one or more of the following external or auxiliary heat sources: an electrical heater (see, for example, Figures 3A, 3B), a heating element configured to provide heat from a solar-thermal heat source, a heating element configured to provide waste heat from an industrial process, a heating element configured to provide heat from a nuclear plant, a heating element configured to provide heat from a fracking process, or a heating element configured to provide heat from geothermal heat source.

The heating element is, for example, configured or arranged to transfer heat energy to the electrolyte solution 5. The heating element is, for example, configured to provide heat from a solar-thermal heat source and may, for example, comprise or consist of a heat exchanger HE as shown in the solar thermal power plant or system of Figure 5. The heat exchanger HE is configured to transfer heat to the electrolyte solution 5 circulating in a circuit CT coupled to the heat exchanger HE. Heat may similarly be exchanged to the electrolyte solution 5 using the other above mentioned alternative heat sources or provisioning means. For example, at least one solar thermal panel can be used to directly heat the electrolyte 5 in addition or instead of the heat exchanger HE. The electrolyte 5 can, for example, be flowed or circulated in or through the solar thermal panel to increase the temperature of the electrolyte 5.The external or auxiliary heater 10 (see for example, Figures 3 A and 3B) may be configured to receive the electrolyte solution 5 that has passed through the first and second gas separators 11, 15 via fluidic channels FC extending from the gas separators to the heater 10 (see, for example, Figures 3 A and 3B). The heater 10 may additionally be configured to receive the electrolyte solution 5 from an electrolyte solution reservoir RS (see for example, Figures 3A and 3B).

The external or auxiliary heater 10 may comprise or consist of an electrical heater, as previously mentioned, and may in addition or alternatively include one of the above-mentioned heating elements to provide heat to the electrolyte solution 5 in the system 1.

The system 1 may, for example, include the internal heater 10 of the electrolysis unit(s) 3 including the at least one voltage source 45 providing a voltage to electrodes EL 1 , EL2 to heat the electrolyte solution 5 to a desired electrolysis temperature, and one or more one of the above-mentioned heating elements to provide heat to the electrolyte solution 5 from external heat sources.

The electrolysis system 1 may, for example, include a heating controller 47 (Figure 2) configured to apply a system heating voltage control signal C to the voltage source 45 to set the voltage applied to the electrodes ELI, EL2 to heat the electrolysis unit 3 and/or the electrolyte solution 5 to a predetermined electrolysis temperature. The predetermined electrolysis temperature may be, for example, a temperature to which the electrolysis unit 3 and/or the electrolyte solution 5 is heated initially to begin electrolysis, for example a temperature between (i) 80° or 96° or 100°C, and (ii) 200°C, or 250°C or 350°C.

The heating controller 47 may, for example be configured to receive a signal S from at least one temperature sensor TS of the system 1 measuring a temperature of the electrolysis unit 3 and/or the electrolyte solution 5 and providing the signal S or value representing a temperature to the heating controller 47. The heating controller 47 is configured to increase, reduce or leave unchanged the heat quantity provided based on the measured temperature values. The heating controller 47 includes a processor P and a memory M (for example, semiconductor memory, HDD, or flash memory) configured to store or storing at least one program or processor executable instructions. The at least program or processor executable instructions may comprise instructions permitting, for example, to control and command the voltage source 45. The processor executable instructions may comprise instructions permitting to receive and process the signal S from the temperature sensor TS, generate the control signal C and provide it to the voltage source 45. The program or processor executable instructions can be provided, for example, as Matlab functions.

Alternatively or additionally, the heating controller 47 is configured to determine and provide the system heating voltage control signal C to the external or auxiliary heater 10 (see, for example, Figures 3 A, 3B) to heat the electrolysis unit 3 and/or the electrolyte solution 5 to a predetermined electrolysis temperature in the same manner as described above.

The heating controller 47 may also be configured to apply a thermal balance voltage to the electrodes ELI, EL2 via the voltage source 45 (via athermal balance voltage control signal C) to compensate heat loss during electrolyte solution 5 circulation outside the one or more electrolysis units 3 to maintain a stabilized temperature at which electrolysis is performed. The thermal balance voltage is applied during operation of the electrolysis unit 3 after a desired or predetermined electrolysis temperature has been reached. Alternatively or additionally, the heating controller 47 is configured to control operation of the external or auxiliary heater 10 (see, for example, Figures 3 A, 3B) to heat the electrolyte solution 5 and/or the electrolysis units 3 to compensate heat loss during electrolyte solution 5 circulation.

The electrolysis system 1 is configured to recirculate the electrolyte solution 5 from the first gas separator 11 and the second gas separator 15 to the heating means 10 and the membrane-less electrolysis unit(s) 3. This permits electrolysis to be carried out on the electrolyte solution 5 from which gases have been removed.

The electrolysis system 1 includes, for example, the at least one pump 49 configured to circulate the electrolyte solution 5 through interconnected elements of the electrolysis system 1 at a given or predetermined pressure value of the electrolyte solution 5. The pump 49 is configured to determine or set an electrolyte solution pressure in the electrolysis unit 3, and a gas pressure in the electrolyte solution 5 circulating in the electrolysis system 1.

The pump 49 permits the pressure of the electrolyte solution 5 to be increased to a pressure permitting a boiling point of the electrolyte solution 5 to be increased and electrolysis to be performed at high temperatures.

The pressure of the electrolyte solution 5 is, for example, <30 bar, for example between 1 bar (100000 Pa) and 30 bar (3xl0⁶ Pa) or 40 bar or 50 bar or 60 bar (extremity value included).

The temperature of the electrolyte solution 5 may thus be increased to a temperature between (i) 80°C or 96°C or 100°C or 125°C or 150°C and (ii) 200°C or 250°C or 350°C (for example, between 80°C and 350°C); or between (i) 80°C or 96°C or 100°C or 125°C or 150°C and (ii) 200°C or 250°C or 300°C; or between (i) 80°C or 96°C or 100°C or 125°C or 150°C and (ii) 200°C or 250°C or 270°C. The temperature of the electrolyte solution 5 can be increased up to or close to the boiling temperature of the electrolyte solution 5. The normal boiling temperature (atmospheric pressure boiling point) of 50 % wt KOH solution is 141 °C and increased by increasing the electrolyte solution pressure in the electrolysis unit 3. The pressure of the system is increased in order to achieve a higher temperature electrolyte. Furthermore, hydrogen, for example, can be produced at higher pressures by increasing the pressure of the liquid electrolyte 5. Thereby, the cost of hydrogen compression for the storage decreases by producing high pressure gas in the electrolysis unit 3 since liquid compression is less energy demanding compared to gas compression.

The partial pressure of water vapor increases by the temperature. Consequently, the output hydrogen gas may have water vapor. The amount of water vapor can be decreased by increasing the pressure.

The pressurized electrolyte solution 5 is flowed into and through the electrolysis unit 3 and may, for example, pass through a flowmeter FM prior to entering the electrolysis unit 3, and is then flowed out of the electrolysis units 3 to inlets of the first gas separator 11 and the second gas separator 15 for removal or extraction of the gas contained in the electrolyte solution 5.

The first gas separator 11 and/or the second gas separator 15 may include a stirring device or mechanism 51 configured to generate a rotational flow in the electrolyte solution 5 to liberate the gas contained therein. The first gas separator 11 and/or the second gas separator 15 may additionally or alternatively include a Bonification device or mechanism 53 configured to generate ultrasonic waves propagating in the electrolyte solution 5. The first gas separator 11 and/or the second gas separator 15 may alternatively or additionally include a hydrophobic porous section 55 configured to remove gas from the electrolyte solution 5.

The first gas separator 11 and/or the second gas separator 15 may include the stirring device or mechanism 51, the Bonification device or mechanism 53 and the hydrophobic porous section 55, as for example shown in Figure 4. The stirring device or mechanism 51, the Bonification device or mechanism 53 and the hydrophobic porous section 55 are for example respectively arranged in that order to sequentially process the electrolyte solution 5 to remove gas contained therein. The electrolyte solution 5 from which gas has been removed is communicated back to the electrolysis units 3, for example, through the pump 49 and possibly through heater 10 as shown in Figures 3 A and 3B

The first gas separator 11 and/or the second gas separator 15 permit the electrolyte solution to flow quickly therethrough and define high flow rate gas separators.

The gas separators 11, 15 may, for example, have three stages as shown in Figure 4. The liquid electrolyte 5 with gas bubbles enters at the top of the gas separator 11, 15 via an inlet. This inlet is, for example, tangent to the (cylindrical) wall of the gas separator in order to induce a rotational flow at the top stage of the gas separator 11, 15. The rotational flow creates a vortex where the gas bubbles move to the center of the vortex due to the centripetal force. Therefore, most of the gas bubbles can be extracted from the liquid 5 in this stage. Alternatively, or additionally a mechanical rotation motor can be included as part of the stirring device or mechanism 51 and used. The Bonification device or mechanism 53 may include one or multiple piezoelectric components, for example, in a second stage of the gas separator 11, 15, attached to (the middle of) the gas separators in an outer portion or shell of the gas separator. These components create ultrasonic waves which propagate in the liquid electrolyte 5. Ultrasound propagation in the electrolyte 5 creates low pressure regions. The solubility of gas in the liquid decreases at these low-pressure regions. Consequently, the dissolved gas nucleates and creates bubbles. Furthermore, the ultrasound waves accelerate the bubble coalescence in the liquid 5 and the bubbles become larger in the middle stage of the gas separator 11, 15. Larger bubbles ascend in the liquid 5 and the electrolyte columns of the gas separators to a gas outlet and leave the liquid quickly due to the larger buoyancy force applied to them. Therefore, the Bonification in this middle stage of the gas separator 11, 15 of Figure 4 removes dissolved gas and small bubbles from the liquid 5.

The bottom part or stage of the gas separator 11, 15 of Figure 4 includes a porous region with hydrophobic pores that can trap the remaining gas bubbles and prevent gas bubbles from flowing into the pump 49 and the entering the electrolysis units 3. This porous region can be created, for example, using small polyethersulfone (PES) or polytetrafluoroethylene (PTFE) balls or particles, the pores being defined by a spacing between the clustered balls. The gas bubbles attach to the surface of these materials while the liquid electrolyte 5 is moving through the pores. The bubbles will detach from the surface and rise when they grow large enough and exit via the gas outlet.

The hydrophobic porous media can, for example, separate gas from liquid through a pressure difference across the membrane, the gas separator is constructed, for example, with material that can tolerate the high temperatures (up to for example 350 °C), for example, a metal, for example, stainless steel.

Gas separation using hydrophobic packed bed (collection of spheres) can separates gas from liquid by gas bubble coalescence and gravity, the gas separator can be constructed, for example, with material that can tolerate the high temperatures (up to 350°C), for example, stainless steel.

The first and/or second gas separator 11, 15 can be, for example, configured or arranged to operate at a lower electrolyte solution pressure than that in other parts of the electrolysis system 1 to favorize dissolved gas nucleation. The gas separator 11, 15 is working, for example, at a pressure slightly smaller than the pressure in the other parts of the system 1 in order to reduce the dissolved gas concentration by encouraging the dissolved gas nucleation. As previously mentioned, the system may include a flow meter FM configured to determine a flow rate of the electrolyte solution 5 to the one or more electrolysis units 3. The flow meter FM may, for example, be positioned in the flow path between the pump 49 and the membrane-less electrolysis units 3. The electrolysis system 1 may also include the pressure sensor SN1 configured to determine a pressure of the electrolyte solution 5 flowing in the system 1, for example, flowing through the electrolysis units 3. The system 1 may also, for example, include first and second gas sensors (not shown) to monitor gas production via electrolysis. The system tubing or canalization 43 and/or connection elements 57 arranged in the system 1 to interconnect the system components (such as the electrolysis unit, the gas separators, the reservoir, the heater and the pump) and to distribute and recirculate the electrolyte solution 5 through the electrolysis system 1, may, for example, comprise or consist of at least one metal, for example, stainless steel (grade 316-L) or Teflon to permit distribution of the electrolyte solution 5 at high temperatures and at the desired electrolyte solution 5 pressure value.

The first and second gas separators 11, 15, the reservoir RS, the pump 49 and/or the heater 10 may also comprise or consist of at least one metal, for example, stainless steel.

The components of the electrolysis system 1 are configured to carry out electrolysis, electrolyte solution 5 circulation and gas separation between (i) 80°C or 96°C or 100°C or 125°C or 150°C and (ii) 200°C or 250°C or 350°C; or between (i) 80°C or 96°C or 100°C or 125°C or 150°C and (ii) 200°C or 250°C or 300°C; or between (i) 80°C or 96°C or 100°C or 125°C or 150°C and (ii) 200°C or 250°C or 270°C. The electrolysis system 1 is or defines a high temperature electrolysis system.

The one or more electrolysis units 3, the cell 25 and/or stack 25 comprise or consist of temperature resistant material or materials resistant to an electrolyte solution 5 having a temperature between (i) 80°C or 96°C or 100°C or 125°C or 150°C and (ii) 200°C or 250°C or 350°C; or between (i) 80°C or 96°C or 100°C or 125°C or 150°C and (ii) 200°C or 250°C or 300°C; or between (i) 80°C or 96°C or 100°C or 125°C or 150°C and (ii) 200°C or 250°C or 270°C.

Each electrolysis unit 3 may, for example, comprise or consist of at least one metal, for example, stainless steel (e.g. grade 316-L) or Nickel; or comprise or consist of a high temperature resistant polymer, for example, Polyether ether ketone (PEEK), Polyamide 12, Polyphenylene Sulfide, Polyphthalamide, or Teflon.

The electrolysis unit 3 may for example be a metallic membrane-less electrolysis unit 3 and include first and second electrodes ELI, EL2 isolated from the metallic core or body by at least one insulator material, such as, Polyamide 12 material, Teflon, Zirconium ceramic, Silicon carbide ceramic, Silicon Nitride ceramic.

Figure 9A shows an exemplary embodiment of the electrolysis unit 3.

The electrolysis unit 3 is, for example, a flow-based electrolysis unit, or a membrane-less electrolysis unit or porous wall electrolysis unit.

The electrolysis unit 3 may comprise at least the first electrode 103, ELI and at least the second electrode 105, EL2 for carrying out electrolysis. The electrolysis unit 3 may also comprise a first fluidic channel 107 configured to receive the electrolyte or electrolyte solution 5, a second fluidic channel 109 configured to receive the electrolyte solution 5 from the first fluidic channel 107 and a third fluidic channel 111 configured to receive the electrolyte solution 5 from the first fluidic channel 107. The second fluidic channel 109 includes, for example, the first electrode 103, ELI and the third fluidic channel 111 includes, for example, the second electrode 105, EL2. The first fluidic channel 107 may, for example, be electrode-free or electrode-less.

The first fluidic channel 107 is in fluidic communication with the second and third fluidic channels 109, 111. The first fluidic channel 107 may, for example, be located between or enclosed by the second and third fluidic channels 109, 111. The first fluidic channel 107 may, for example, be located above the second and third fluidic channels 109, 111.

The first fluidic channel 107 is connected to the second and third fluidic channels 109, 111 via a plurality of fluidic canals 115 extending from the first fluidic channel 107 to each of the second and third fluidic channels 109, 111.

The first fluidic channel 107 is connected to each of the second and third fluidic channels 109, 111 via a plurality of inclined fluidic canals 115.

The plurality of fluidic canals 115 are distributed or spaced apart along a direction of extension (or along the length (L)) of the first fluidic channel 107 to provide the electrolyte solution 5 to each of the second and third fluidic channels 109, 111 in a distributed manner along a direction of extension (or along the length (L)) of the second and third fluidic channels 109, 111.

The exemplary embodiment of Figure 9A shows fifteen fluidic canals 115 symmetrically arranged either side of the first fluidic channel 107. However, a different number of fluidic canals 115 may be used. The fluidic canals 115 may also be arranged asymmetrically and at different heights with respect to each other along the first fluidic channel 107. For example, the relative width of the fluidic canals 115 may be decreased from entrance (left-hand side in Figure 9A) to the end (right-hand side) of the first fluidic channel 107 to ensure equal velocity distribution in all fifteen fluidic canals 115. The fluidic canals 115 may, for example, also be located or distributed fully across or around the first fluidic channel 107.

The first fluidic channel 107 is, for example, configured to provide the electrolyte solution 5 directly via fluidic canals 115 to both the second and third fluidic channels 109, 111. The first fluidic channel 107 is, for example, configured to provide the electrolyte solution 5 simultaneously, via fluidic canals 115, to both the second and third fluidic channels 109, 111.

The first fluidic channel 107 comprises or consists of a plurality of stacked or superposed (substantially) Y-shaped sections SY or partial Y-shaped sections SY (see, for example, Figure 9A). Each Y-shaped section SY comprises at least one (partial Y-shaped sections SY) or a plurality (two or more) of the inclined fluidic canals 115. The inclined fluidic canal 115 defines a wing of the Y-shaped section SY extending away from a central body of the Y-shaped section SY. When a plurality of inclined fluidic canals 115 are present, the inclined fluidic canals 115 may, for example, be located symmetrically or asymmetrically (deformed Y -shape) on the Y -shaped section SY. The inclined fluidic canals 115 extend from the central body of the Y -shaped section SY to the second and/or third fluidic channels 109, 111. The fluidic canals 115 are, for example, inclined fluidic canals. Each fluidic canal 115 may be an inclined fluidic canal, or a subset or part of the plurality of fluidic canals 115 may be inclined fluidic canals.

The inclined fluidic canals 15 are, for example, inclined with respect to the first fluidic channel 7 in a direction non-perpendicular to an electrolyte flow direction F through the first fluidic channel 7.

The inclined fluidic canals 115 are inclined with respect to the first 107, second 109 or third 111 fluidic channels. The inclined fluidic canals 115 are preferably inclined with respect to each of the first 107, second 109 and third 111 fluidic channels.

The inclined fluidic canals 115 define, for example, an angle a with respect to the first fluidic channel 107. The angle a is, for example, not equal to 90°. The angle a is, for example, an acute angle.

The inclined fluidic canals 115 define an angle p with respect to the second fluidic channel 109 and an angle 5 with respect to the third fluidic channel 111. The angles and 5 are, for example, not equal to 90°. The angles p and 5 are, for example, acute angles.

Each inclined fluidic canal 115 may define angles p and 5 between 10° and 80°, or between 20° and 70°, or between 30° and 60° with respect to the second fluidic channel 109 or with respect to the third fluidic channel 111.

Each inclined fluidic canal 115 may define an angle a between 10° and 80°, or between 20° and 70°, or between 30° and 60° with respect to first fluidic channel 107.

The inclined fluidic canals 115 are, for example, inclined with respect to the first fluidic channel 107 in a direction non-perpendicular to an electrolyte flow direction F through the first fluidic channel 107.

The first fluidic channel 107 is interconnected to the second and third fluidic channels 109, 111 via the plurality of inclined fluidic canals 115. The plurality of inclined fluidic canals 115 may be separated by pillars 125 consisting of or comprising solid material. Alternatively, in an alternative non-limiting exemplary embodiment, the fluidic canals 115 may be, for example, suspended in air or in suspension between the first fluidic channel 107 and the second and third fluidic channels 109, 111.

The plurality of inclined fluidic canals 115, or a subset thereof, extends for example outwards and away from the first fluidic channel 107, or outwards and away from the first fluidic channel 107 and away from each other.

The inclined fluidic canals may extend outwards and away from the first fluidic channel 107 and extend in a direction of electrolyte flow F through the first fluidic channel 107 or electrolysis unit 3.

Each fluidic canal 115 extends from the first fluidic channel 107 to the second and third fluidic channels 109, 111 to each connect physically with or to a different part of the second and third fluidic channels 109, 111. Each fluidic canal 115 includes a passage PS15 through which the electrolyte solution 5 passes from the first fluidic channel 107 to the second and/or third fluidic channels 109, 111. The fluidic canal 115 includes at least one partition 117 defining the passage PS 15 through which the electrolyte solution 5 flows from the first fluidic channel 107 to the second and/or third fluidic channel 109, 111. The partition 117 extends between the first fluidic channel 107 and the second 109 and/or third 111 fluidic channel.

The first, second and third fluidic channels 107, 109, 111 each include a porous wall permitting fluidic communication between the first, second and third fluidic channels. The first 107, second 109 and third 111 fluidic channels each include at least one wall SW7, SW9, SW11 each defining a plurality of apertures or pores P7, P9, Pl 1. Each fluidic canal 115 may extend between an aperture or pore P7 of the first fluidic channel 107 and an aperture or pore P9, Pl 1 of the second or third fluidic channel 109, 111.

As mentioned, the first fluidic channel 107 may, for example, be located between the second and third fluidic channels 109, 111. A portion SW7A of the porous wall SW7 of the first fluidic channel 107 located and extending opposite the second fluidic channel 109 and a portion SW7B of the porous wall SW7 of the first fluidic channel 107 located and extending opposite the third fluidic channel 111 extend non-parallel with respect to each other, or extend inclined at an angle with respect to a central axis CA to distribute the electrolyte solution 5 (substantially) equally in the fluidic canals 115 that are distributed along the first fluidic channel 107. The central axis CA can for, example, be located at the geometrical center.

The inclination with respect to the central axis CA is, for example, at an angle of less than 5, or 4, or 3, or 2 or 1 degree to distribute the electrolyte equally in the fluidic canals 115.

Each fluidic channel 107, 109, 111 includes or defines a passage PS7, PS9, PS 11 through which the electrolyte flows inside the electrolysis unit 3.

In a non-limiting exemplary embodiment, the second fluidic channel 109 and/or the third fluidic channel 111 may comprise first and second side walls and a floor extending between the first and second side walls. A ceiling extending between the first and second side walls may also be included.

The first and/or second side wall may include the first or second electrodes 103 (ELI), 105 (EL2). Alternatively, or additionally the floor and/or ceiling may include or be defined by the first or second electrodes 103 (ELI), 105 (EL2). In a non-limiting exemplary embodiment, the first electrode 103, ELI is provided on the side wall of the second fluidic channel 109 and the second electrode 105, EL2 is provided on the side wall of the third fluidic channel 111. The first electrode 103, ELI and the second electrode 105, EL2 may extend (substantially) parallel to each other in a direction following the flow direction F of the electrolysis unit 3 or first fluidic channel 107.

The second and the third fluidic channels 109, 111 may, for example, include electrodes E3, E5 inside the second and the third fluidic channels 109, 111 and on an outer wall or an outer wall section of the second and the third fluidic channels 109, 111. The outer electrodes E3, E5 may, for example, be located on the first side walls of the second and the third fluidic channels 109, 111.

Similarly, the first fluidic channel 107 and the fluidic canals 115 may also include first and second side walls, a floor and a ceiling. As previously mentioned, the first and second porous side walls of the first fluidic channel 107 may inclined at an angle with respect to the central axis CA to distribute the electrolyte solution 5 (substantially) equally in the fluidic canals 115.

The fluidic channels 107, 109, 111 and the fluidic canals 115 may, however, define different cross- sectional profiles for the passages PS7, PS9, PSI 1 and PS 15 and not necessarily a rectangular profile.

The first electrode 103, ELI is, for example, located on the at least one wall SW9 of the second fluidic channel 109, and the second electrode 105, EL2 is, for example, located on the at least one wall SW11 of the third fluidic channel 111.

The electrodes may, for example, be non-porous electrodes or non-mesh electrodes. The fluidic canals 115 are, for example, electrode-less.

The first and second electrodes 103 (ELI), 105 (EL2) may, for example, include a plurality of apertures or pores PEL3, PEL5 extending through the first and second electrodes 103 (ELI), 105 (EL2) and communicating with the plurality of apertures or pores P9, Pl 1 defined by the at least one wall SW9, SW11 ofthe second and third fluidic channels 109, 111. The plurality of apertures or pores PEL3, PEL5 in the first and second electrodes 3, 5 may, for example, be aligned or symmetrically located opposite one another, as shown for example in Figure 9A.

The apertures or each aperture or pore P7 of the first fluidic channel 107 and/or the apertures or each aperture or pore P9 the second fluidic channel 109 and/or the apertures or each aperture or pore Pl 1 of the third fluidic channel 111 may have an opening width (W) or diameter between 50pm and 200pm, or between 60pm and 180pm, or between 80pm and 160pm.

The fluidic canals 115 or each fluidic canal 115 may, for example, define an opening width (W) or diameter between 50pm and 200pm, or between 60pm and 180pm, or between 80pm and 160pm. The passages PS 15 of the fluidic canals 115 may also, for example, define opening widths or diameters of such values. The plurality of apertures or pores PEL3, PEL5 extending through the first and second electrodes 103 (ELI), 105(EL2) may similarly define, for example, opening widths or diameters of such values.

Alternatively, the plurality of apertures or pores PEL3, PEL5 extending through the first and second electrodes 103 (ELI), 105 (EL2) may define openings larger in width (W) or diameter than the openings defined by the pores or apertures P9, Pl 1 of the first or second fluidic channels 109, 111, for example, between 10% and 90% greater.

The apertures or pores PEL3, PEL5 extending through the first and second electrodes 103, 105 may, for example, tapered or curved inwards at the extremity of the aperture or pore PEL3, PEL5, and tapered or curved inwards towards the supporting wall upon which the electrode is attached. This assures a smoother displacement of the electrolyte and bubbles and the easier detachment of bubbles.

The internal width (W) or diameter of the first fluidic channel 107 and/or second fluidic channel 109 and/or third fluidic channel 111 may, for example, be greater than the opening defined by the pores or apertures P7, P9, Pl l of the first, second, or third fluidic channels 107, 109, 111. The internal width (W) or diameter may, for example, be between 10% and 200% greater. The internal width (W) or diameter may, for example, be between 55pm and 600pm. The internal height (H) may, for example, also be between 10% and 200% greater. The internal height (H) may, for example, be between 55 pm and 600pm.

The length (L) of the first fluidic channel 107 and/or second fluidic channel 109 and/or third fluidic channel 111 may, for example, be between 5mm and 50mm. The length (L) of the fluidic canals 115 may, for example, be between 50pm and 500pm, for example 200pm.

The fluidic channels, 107, 109, 111 may, for example, define micro-fluidic channels in cross-section. The fluidic canals 115 may define micro-fluidic canals in cross-section.

It is, however, noted that these values are provided as non -limiting and exemplary values.

An internal and/or external width (W) or diameter of the first fluidic channel 107, may, for example, be tapered, for example, tapered along the length (L) of the first fluidic channel 107. The internal and/or external width (W) or diameter reduces in the direction of extension from the inlet 37, 121 to outlets 39A,123A, 39B,123B. The reduction from one end of the of the first fluidic channel 107 to an opposite end of the first fluidic channel 107 may, for example, be between 5% and 35%, for example, 25%. This assures a uniform distribution of the electrolyte to the outer fluidic channels for electrolysis.

The first fluidic channel 107 includes an input section IS configured to input the electrolyte, the input section IS including the inlet 121 through which the electrolyte solution 5 is inserted into the electrolysis unit 3. The first fluidic channel 107 or electrolysis unit 3 also includes an output section OS consisting of or comprising, for example, a plurality of inclined fluidic canals 115 and a V-shaped abutment or stop 127.

The second 109 and third 111 fluidic channels may, for example, also include inlets 121A and 121B (for example, a first lateral inlet 121 A and a second lateral inlet 12 IB) to remove the bubbles faster from the second 109 and third 111 fluidic channels. The liquid velocity at inlets 121A and 121B can, for example, be different since the number of bubbles in the hydrogen side, for example, the second fluidic channel 109 is twice the number of bubbles in the oxygen side, for example, the third fluidic channel 111.

The inlets 121A and 121B are attached to and in fluid communication with the second 109 and third 111 fluidic channels. The first 107, second 109 and third 111 fluidic channels are closed or partially closed fluidic channels. The electrolysis unit 3 may, for example, comprise a lid 131 configured to close the first, second and third fluidic channels 107, 109, 111.

The pump 49 pumps the electrolyte solution 5 into the first fluidic channel 107 and through the fluidic canals 115, as well as through the second and third fluidic channels 109, 111 and out of the electrolysis unit 3 via the outlets 39A,123A, 39B, 123B for accessing products generated by the membrane-less electrolysis unit. The pump 49 may, for example, be connected to the inlet 121 and connected thereto, for example, directly or indirectly via tubing 43.

The electrolysis unit 3 may also include electrical connection wires or lines in electrical connection with the first and second electrodes 103 (ELI), 105 (EL2) and configured to be connected or connected to an electrical energy source 45 for providing electrical energy (current, voltage) to the first and second electrodes 103 (ELI), 105 (EL2) to carry out the electrolysis. The first electrode 103 (ELI) may for example define a cathode and the second electrode 105 (EL2) may for example define an anode.

An electrolyte solution 5 is provided to the inlet 121 and the first fluidic channel 107 is configured to distribute the electrolyte solution 5 to the second and third fluidic channels 109, 111, via the inclined fluidic canals 115 and the second and third fluidic channels 109,111 are configured to generate products for output via the electrical energy provided to the electrodes 103 (ELI), 105 (EL2) of the second and third fluidic channels 109, 111.

The electrolyte solution 5 may, for example, comprises or consists of water and the generated products comprise or consist of Hydrogen and Oxygen. However, the electrolysis unit 3 of the present disclosure is not limited to such an electrolyte solution and output gases and these are solely provided as a nonlimiting example in the present description and in the Figures. For example, the electrolyzer 1 or electrolysis unit 3 may be used for brine electrolysis for chlorine production.

The electrolysis unit 3 shown in Figure 9A permits to achieve a high production rate and lower gas cross over. The liquid electrolyte 5 enters the middle channel 107 and goes to the outer channels 109, 111 through the inclined wall pores. The electrodes 103 (ELI), 105 (EL2) are on the outer sides of the porous walls and the bubbles/gases 7, 9 are being generated in the outer channels 109, 111. The inclined walls or partitions 115 and pores ensure the sufficient flow in each electrodes pore. The flow through the wall pores prevents the migration of bubbles 7,9 to the opposite side. The volume fraction of gas in the interelectrode area is low since there is no flow of bubbles in the middle channel 107. Therefore, the ohmic loss due to the presence of flowing bubbles between the electrodes 103 (ELI), 105 (EL2) is smaller compared to parallel electrode design.

The performance of the electrolysis unit 3 can be improved further by using a surfactant in the electrolyte 5. The surfactant may comprise or consist solely of heptadecafluorooctancesulfonic acid potassium (PFOS). Electrolysis may for example be carried out to produce Hydrogen and Oxygen. The electrodes 103 (ELI), 105 (EL2) may, for example, include or consist of electrode material such as Nickel or Raney Nickel for the oxygen evolution reaction, and Nickel-Molybdenum for the hydrogen evolution reaction.

Measurement results are provided in International Patent Application n° PCT/IB2020/061035 filed on November 23, 2020, in particular, in relation to the suppression of cross-contamination achieved by electrolysis unit 3.

Figure 1 shows an exemplary embodiment of the electrolysis unit 3 produced via injection molding. The electrolysis unit 3 comprises blocks or parts Pl, P2 configured to be superposed or combined together and which interconnect to form or define the electrolysis unit 3 and the fluidic communication elements thereof. The blocks Pl, P2 are, for example, produced by injection molding and include slits SL1A, SL1B, SL2A, SL2B either side ofthe central fluid channel 107 and fluidic canals 115 (see Figure 9A). The slits SL1A, SL1B, SL2A, SL2B are configured to receive the first and second electrodes ELI, EL2 which interconnect the injection molded blocks Pl, P2.

The block or part P 1 defines an upper portion of the electrolysis unit 3 and the block or part 2 defines a lower portion of the electrolysis unit 3. The block or part Pl may define, for example, an upper half of the first fluidic channel 107, the second fluidic channel 109, the third fluidic channel 111, the plurality of inclined fluidic canals 115 and the plurality of apertures or pores P9, Pl l defined by the walls SW9, SW 11 of the second and third fluidic channels 109, 111 (see for example Figure 9A). The block or part P2 may define, for example, a lower half of the first fluidic channel 107, the second fluidic channel 109 and the third fluidic channel 111, the plurality of inclined fluidic canals 115 and the plurality of apertures or pores P9, Pl l defined by the walls SW9, SW11 of the second and third fluidic channels 109, 111.

The combination of blocks Pl, P2 results in the first fluidic channel 107, the second fluidic channel 109 the third fluidic channel 111, the plurality of inclined fluidic canals 115 and the plurality of apertures or pores P9, Pl l being fully formed or defined to permit fluid circulation inside and through the electrolysis unit 3.

Ports PT1, PT2 are included for enabling electrical connection to the electrodes ELI, EL2. Lateral fluid ports or inlets 121 A, 12 IB can also be included to facilitate outward flow of the electrolyte solution 5 and gases.

One or more sealing elements, such as O-rings (not shown), may also be included between the injection molded blocks Pl, P2 to prevent or restrict electrolyte solution 5 leakage. The sealing element may, for example, be located at the interconnection between assembled blocks Pl, P2. The injection molded blocks Pl, P2 may, for example be attached together by one or more clamps, screws or an adhesive.

The electrolysis unit 3, as shown for example, in Figure 1 is a single channel device where electrolyte solution 5 to undergo electrolysis is flowed into a single channel 107 via which it is communicated to at least two adjacent channels 109, 111 (See for example, Figures 2 and 9A) for electrolysis, for example, for hydrogen and oxygen production. The cell 25 is a combination of several channels (for example 20) and the stack 23 is a stack or assembly of, for example, 10 cells. In such an example, the stack 23 includes a total of 200 single channels.

The cell 25 may, for example, include a plurality of single channel electrolyzers or electrolysis units, as for example seen in Figures 1 and 2.

The injection molded blocks or parts Pl, P2 may, for example, comprise of consist of Polyether ether ketone (PEEK) or Nylon.

The device is fabricated, for example, by injection molding the housing that contains the flow geometry of the electrolysis unit in two pieces. The two electrodes ELI, EL2 are inserted between the injection molded pieces before the device is sealed with O-rings or other suitable sealing materials that can operate at the desired high temperature. The injection molded material can be any organic (polymer, such as nylon or PEEK) that can operate at higher temperatures.

One or more metals, such as stainless steel, may alternatively be used for the housing parts Pl, P2 containing the electrolyser or electrolysis unit flow geometry. The electrodes ELI, EL2 are electrically insulated to avoid shorting through the housing. As previously mentioned, the electrodes ELI, EL2 may be isolated from the metallic housing Pl, P2 by an insulator material located between the metal part(s) Pl, P2 and the electrodes, an insulator material such as Polyamide 12 material, Teflon, Zirconium ceramic, Silicon carbide ceramic, or Silicon Nitride ceramic may for example be used.

Alternatively, the electrolysis unit 3 and electrolyzer/electrolysis unit channel and geometries can be fabricated by 3D printing. The electrolysis unit 3 may be a 3D print hybrid structure consisting of organics and metals. In this case the housing and metal (electrode) portions can be printed in one step. Alternatively, the housing can be 3D printed in high temperature resin and the electrodes inserted through openings or slits that are implemented or defined in the 3D printing step. Nylon can, for example, be used to produce the electrolyzer 3 using a 3D printer.

The electrolysis system 1 may be included in an energy conversion system or an electricity generation system.

Figure 5 shows an exemplary solar thermal power plant or system SG comprising the electrolysis system 1 for high temperature electrolysis according to the present disclosure. The exemplary solar thermal power plant or system SG may include some or all of the elements shown in Figure 5.

The solar thermal power plant SG includes, for example, a solar collector configured to collect sunlight and direct or focus the solar energy on a receiver containing piping through which a liquid (for example, water) flows and is heated by the focused solar energy. The heated liquid is provided to a heat exchanger HE and provided to a power or steam turbine where it is used to generate steam to produce electricity via a generator that is provided, for example, to an electrical grid.

As previously mentioned, the heat exchanger HE is arranged to also transfer heat to the electrolyte solution 5 and the generator is also connected to the system 1 and arranged to provide electrical energy to the one or more electrolysis units 3 for electrolysis. The solar thermal power plant SG includes a tank or storage means for storing a gas (for example, Hydrogen) generated via electrolysis by the system 1, which is used by one or more fuel cells of the solar thermal power plant SG to generate electricity that may also be provided to the grid.

The solar thermal power plant SG is configured to compensate for an intermittent solar energy supply by consuming the gas generated via electrolysis in the fuel cell to provide electricity to the electricity grid when a supply of solar energy is interrupted or reduced.

The electrolysis unit 3 can thus be combined with solar thermal power plants or systems to compensate for the intermittent solar energy supply. Solar thermal concentrators provide energy to heat transfer fluid that can be used as a heat source for power generation. This heat transfer fluid can be used to heat the electrolyte 5 in the electrolysis system 1 at, for example, off-peak hours of electricity consumption. The turbine of the power plant can provide the required electricity for water electrolysis. The energy can be stored in the form of electrolysis generated hydrogen. The incorporated fuel cell can consume hydrogen at on-peak hours for electricity consumption to provide electricity to the grid.

The present disclosure also concerns an electrolysis method.

The electrolysis method includes providing the at least one or the plurality of electrolysis units 3, flowing electrolyte solution 5 through the one or more electrolysis units, and carrying out electrolysis with the one or more electrolysis units at an electrolyte solution temperature, for example, between (i) 80°C or 96°C and (ii) 350°C and an electrolyte solution pressure <30 bar or < 40 bar or < 50 bar or < 50 bar or < 60 bar, or at an electrolyte solution temperature between (i) 80°C or 96°C and (ii) 270°C and an electrolyte solution pressure <30 bar or < 40 bar or < 50 bar or < 50 bar or < 60 bar.

The pressure of the electrolyte solution 5 is, for example, is for example between 1 bar (100000 Pa) and 30 bar (3xl0⁶ Pa) or 40 bar or 50 bar or 60 bar (extremity values included).

The electrolysis method may, for example, be carried out using the above-described electrolysis system for high temperature electrolysis.

The electrolyte solution 5 is, for example, circulated through the one or more electrolysis units 3 at a pressure of the electrolyte solution 5 permitting to increase a boiling point of the electrolyte solution 5. The electrolyte solution 5 can be circulated at a pressure of the electrolyte solution 5 permitting an increased gas pressure in the electrolyte solution 5 exiting the electrolysis units 3.

The pressure in the electrolysis system 1 may be increased, for example, by sealing the electrolysis system 1 in combination with pumping the electrolyte solution 5 using the pump 49 and increasing the temperature of the electrolyte solution 5.

The electrolyte solution 5 can be heated, for example, by one of or a combination of the following heating means or heaters: an electrical heater, a heating element configured to provide heat from a solarthermal heat source, a heating element configured to provide waste heat from an industrial process, a heating element configured to provide heat from a nuclear plant, a heating element configured to provide heat from a fracking process, or a heating element configured to provide heat from geothermal heat source.

The electrolyte solution 5 is heated, for example, in any one of the manners described above in relation to the electrolysis system 1.

For example, the voltage source 45 can provide a voltage to electrodes ELI, EL2 of the one or more electrolysis units 3 to heat the electrolyte solution 5 and a system heating voltage is applied to the electrodes to heat the electrolyte solution 5 to a predetermined electrolysis temperature to carry out electrolysis. Heating can alternatively or additionally be carried out using the external heater 10 of the system 1. The thermal balance voltage can then be applied to the electrodes ELI, EL2 to compensate heat loss during electrolyte solution 5 circulation outside the one or more membrane-less electrolysis units 3, and during recirculation through the system 1. This to assure a more efficient electrolysis.

The electrolyte solution 5 can be flowed out of the one or more electrolysis units 3 to the first gas separator 11 and the second gas separator 15 to remove the first output gas and the second output gas from the electrolyte solution 5, and recirculated from the first gas separator 11 and the second gas separator 15 to the heating means and to the one or more electrolysis units 3.

The first output gas may, for example, comprise or consist of Hydrogen, the second output gas may, for example, comprise or consist of oxygen, and the electrolyte solution 5 may, for example, comprise or consist of water and KOH.

The stirring device or mechanism 51 of the first gas separator 11 and/or the second gas separator 15 generates a rotational flow in the electrolyte solution 5 to extract the first output gas and/or second output gas from the electrolyte solution 5. A Bonification device or mechanism 53 of the first gas separator 11 and/or the second gas separator 15 generates ultrasonic waves propagating in the electrolyte solution 5 to extract the first output gas and/or second output gas from the electrolyte solution 5. The electrolyte solution 5 is circulated through a hydrophobic porous section 55 of the first gas separator 11 and/or the second gas separator 15 to remove the first output gas and/or second output gas from the electrolyte solution 5.

The electrolyte solution 5 can be, for example, circulated through the stirring device or mechanism 51, the Bonification device or mechanism 53 and the hydrophobic porous section 55 respectively in that order to sequentially process the electrolyte solution 5.

The electrolyte solution 5 is, for example, circulated through the first gas separator 11 and/or the second gas separator 15 at a high flow rate (for example, from 1 L/min to 20 L/min for a system that produces 1 Kg of hydrogen per day). The first and/or second gas separator 11, 15 can be, for example, operated at a lower pressure than a pressure value in the one or more electrolysis units to favorize dissolved gas nucleation.

The heated electrolyte solution 5 can be circulated in system 1 through tubing 43 from one or more membrane-less electrolysis units 3 to the first and second gas separators 11, 15, and through tubing 43 from the first and second gas separators 11, 15 back to the one or more membrane-less electrolysis units 3. As mentioned previously, the tubing 43 and the first and second gas separators 11, 15 may comprise or consist of stainless steel.

As previously mentioned, electrolyte solution 5 may be circulated through a stack 23 comprising the plurality of electrolysis units 3, where the stack 23 includes a plurality of cells 25 with each cell including a plurality of electrolysis units 3.

The one or more electrolysis units 3 comprise or consist of temperature resistant material or materials for operation with an electrolyte solution 5 having a temperature, for example, between (i) 80°C or 96°C and (ii) 350°C, or between (i) 80°C or 96°C and (ii) 270°C.

As previously mentioned, the electrolysis may be carried as part of a solar thermal power generation method implemented, for example, in an energy conversion system or an electricity generation system such as the exemplary solar thermal power plant or system shown in Figure 5.

The solar thermal power generation method includes carrying out electrolysis as described above and solar generated heat can be transferred to the electrolyte solution 5 by the heat exchanger HE, turbinegenerated electrical energy can be provided to the one or more electrolysis units 3 for electrolysis. At least one gas generated via electrolysis, for example, Hydrogen is stored, and electricity can be generated by a fuel cell from the stored gas generated via electrolysis. As previously mentioned, an intermittent solar energy supply can thus be compensated by consuming the gas generated via electrolysis to provide electricity to an electrical grid.

The electrolysis unit 3 of the present disclosure can operate at high temperatures up to 350 degrees C with a liquid electrolyte. Figure 7 shows measured and calculated data demonstrating the electrochemical performance of the electrolysis unit 3 at different temperatures. Solid lines show the experimental results. Dashed lines depict curves predicted by the model. The model is used to predict the performance of an exemplary flowed based and membrane-less electrolysis unit such as that of Figures 1 and 2, and also when this membrane-less electrolysis unit is performance improved or optimized by including selective porous electrode materials (such as Raney Nickel for oxygen evolution reaction and Nickel-Molybdenum for hydrogen evolution reaction). The model considers potassium hydroxide conductivity, thermodynamic starting potential, ohmic losses of MLE, and electrodes overpotential at different temperatures. The model predicts similar values at 80°C or 96°C to the measured experimental data, and shows high gas production levels at lower voltages and at higher temperature operation above 80°C and up to 350°C.

The Inventors previously described an operating principle of the electrolysis unit 3 at room temperature with a 3D microfluidic device fabricated with a polymer material (SU-8) using photolithography. The electrodes were deposited by sputtering on the microfabricated microfluidic channels to construct the electrolytic reaction chamber. In the present disclosure, as mentioned above the device is, in one embodiment, fabricated by injection molding the housing that contains the flow geometry in two pieces. The two electrodes are inserted between the injection molded pieces before the device is sealed with O- rings or other suitable sealing materials that can operate at the desired high temperature. The injection molded material can be any organic (polymer, such as nylon or PEEK) that can operate at higher temperatures. This device and assembly method is shown in Figure 1.

As mentioned previously, one can also use metals for the housing, with the electrodes being electrically insulated to avoid shorting through the housing. Ceramic materials can be used as a mold material. Alternatively, the electrolysis unit and electrolysis unit fluidic channels can be 3D printed. 3D printing of hybrid structures consisting of organics and metals can be used to produce the electrolysis unit 3. In this case the housing and metal (electrode) portions can be printed in one step. Alternatively, the housing can be 3D printed in high temperature resin and the electrodes inserted through openings that are implemented in the 3D printing step.

The Inventors have previously demonstrated that the fluidic design of the electrolysis unit 3 permits to efficiently separate the hydrogen and oxygen bubbles at room temperature and have demonstrated EE purity up to 99.99% at room temperature. At elevated temperatures the physical properties of the liquid (viscosity, density and surface tension) change but the fluidic design of the electrolysis unit 3 still demonstrates that the high purity is maintained at higher temperatures, as for example shown in the calculated results of Figure 8.

While the invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments, and equivalents thereof, are possible without departing from the sphere and scope of the invention. Accordingly, it is intended that the invention not be limited to the described embodiments and be given the broadest reasonable interpretation in accordance with the language of the appended claims. Features of one of the above described embodiments may be included in any other embodiment described herein.

Claims

1. Electrolysis system (1) for high temperature electrolysis including

- a plurality of flow-based electrolysis units (3) configured to receive an electrolyte solution (5) and to perform electrolysis to provide a first output gas (7) and a second output gas (9), the plurality of flowbased electrolysis units (3) being membrane-less electrolysis units (3);

- at least one heating mechanism or means (10) for heating the electrolyte solution (5) to undergo electrolysis;

- a first gas separator (11) and a second gas separator (15) configured to remove the first output gas (7) and the second output gas (9) from the electrolyte solution (5); and

- an encasement (17) or a cell (25) enclosing the plurality of flow-based electrolysis units (3), the encasement (17) or the cell (25) being configured to support a pressure of the electrolyte solution (5) permitting to increase a boiling point of the electrolyte solution (5) to a temperature between 96°C and 350°C.

2. Electrolysis system (1) according to the previous claim, wherein the encasement (17) or cell (25) includes at least one removable end plate (EPl, EP2) permitting access to the plurality of electrolysis units (3).

3. Electrolysis system (1) according to claim 1 or 2, further including at least one thermal insulator (41) enclosing the at least one or the plurality of electrolysis units (3), the at least one thermal insulator (41) being configured to retain, in the plurality of electrolysis units (3), heat generated by electrolysis or the heating mechanism or means (10).

4. Electrolysis system (1) according to anyone of the previous claims, further including at least one thermal insulator (41) enclosing system tubing (43) arranged to distribute the electrolyte solution (5) in the electrolysis system (1).

5. Electrolysis system (1) according to any one of the previous claims, wherein the at least one heating mechanism or means (10) comprises at least one of: an electrical heater, a heating element configured to provide heat from a solar-thermal heat source, a heat exchanger (HE), a solar panel for directly heating the electrolyte (5), a heating element configured to provide waste heat from an industrial process, a heating element configured to provide heat from a nuclear plant, a heating element configured to provide heat from a fracking process, a heating element configured to provide heat from geothermal heat source.

6. Electrolysis system (1) according to any one of the previous claims, wherein the at least one heating means or mechanism (10) includes at least one voltage source (45) providing a voltage to electrodes (ELI, EL2) of each electrolysis unit (3).

7. Electrolysis system (1) according to the previous claim, further including a heating controller (47) to assure efficient electrolysis, the heating controller (47) being configured to control the at least one voltage source (45) to (i) apply a system heating voltage to the electrodes (ELI, EL2) to heat the electrolyte solution (5) to a predetermined electrolysis temperature, and/or (ii) apply a thermal balance voltage to the electrodes (ELI, EL2) to compensate heat loss during electrolyte solution circulation outside the plurality of electrolysis units (3).

8. Electrolysis system (1) according to any one of the previous claims, wherein each of the plurality of electrolysis units (3) includes

- at least a first electrode (103, ELI) and at least a second electrode (105, EL2);

- a first fluidic channel (107) configured to receive the electrolyte solution (5);

- a second fluidic channel (109) configured to receive the electrolyte solution (5) from the first fluidic channel (107);

- a third fluidic channel (111) configured to receive the electrolyte solution (5) from the first fluidic channel (107); the first fluidic channel (107) being in fluidic communication with the second and third fluidic channels (109, 111); and the first fluidic channel (107) is connected to each of the second and third fluidic channels (109, 111) via a plurality of inclined fluidic canals (115) extending from the first fluidic channel (107) to each of the second and third fluidic channels (109, 111).

9. Electrolysis system (1) according to the previous claim, wherein the inclined fluidic canals (115) are inclined with respect to each of the first, second and third fluidic channels (107, 109, 111).

10. Electrolysis system (1) according to the previous claim 9 or 10, wherein the first fluidic channel (107) comprises or consists of a plurality of stacked Y-shaped sections (SY), each Y-shaped section (SY) comprising a plurality of the inclined fluidic canals (115) extending from the first fluidic channel (107) to each of the second and third fluidic channels (109, 111).

11. Electrolysis system (1) according to any one of the previous claims, wherein the electrolysis system

(I) is configured to recirculate the electrolyte solution (5) from the first gas separator (11) and the second gas separator (15) to the at least one heating means (10) and to the plurality of electrolysis units (3).

12. Electrolysis system (1) according to any one of the previous claims, further including a pump (49) configured to circulate the electrolyte solution (5) in the electrolysis system (1) at a given pressure.

13. Electrolysis system (1) according to the previous claim, wherein the pump (49) is configured to determine an electrolyte solution pressure and a gas pressure in the electrolyte solution (5) in the electrolysis system (1), and/or wherein the pump (49) is configure to provide a pressure of < 30 bar (3xl0⁶ Pa), or < 40 bar (4xl0⁶ Pa), or < 50 bar (5xl0⁶ Pa) or < 60 bar (6xl0⁶ Pa) to circulate the electrolyte solution and assure gas separation .

14. Electrolysis system (1) according to any one of the previous claims, wherein the first gas separator

(I I) and/or the second gas separator (15) includes a stirring device or mechanism (51) configured to generate a rotational flow in the electrolyte solution (5).

15. Electrolysis system (1) according to any one of the previous claims, wherein the first gas separator (11) and/or the second gas separator (15) includes a sonification device or mechanism (53) configured to generate ultrasonic waves propagating in the electrolyte solution (5).

16. Electrolysis system (1) according to any one of the previous claims, wherein the first gas separator (11) and/or the second gas separator (15) includes a hydrophobic porous section (55) configured to remove gas from the electrolyte solution.

17. Electrolysis system (1) according to any one of the previous claims 14 to 16, wherein the first gas separator (11) and/or the second gas separator (15) includes the stirring device or mechanism (51), the sonification device or mechanism (53) and the hydrophobic porous section (55).

18. Electrolysis system (1) according to the previous claim, wherein the stirring device or mechanism (51), the sonification device or mechanism (53) and the hydrophobic porous section (55) are respectively arranged in that order to sequentially process gas removal from the electrolyte solution (5).

19. Electrolysis system (1) according to any one of the previous claims 17 to 18, wherein the first gas separator (11) and/or the second gas separator (15) define high flow rate gas separators, and/or are configured to operate at high temperature.

20. Electrolysis system (1) according to any one of the previous claims, wherein the first and/or second gas separator (11, 15) is configured to operate at a lower pressure than a pressure in other parts of the electrolysis system (1) to favorize dissolved gas nucleation.

21. Electrolysis system according to any one of the previous claims, further including a flow meter (FM) configured to determine a flow rate of the electrolyte solution (5) to the plurality of electrolysis units (3).

22. Electrolysis system (1) according to any one of the previous claims, further including a pressure sensor (SN1), and/or a first and second gas sensor to monitor electrolysis.

23. Electrolysis system (1) according to any one of the previous claims, including a cell (25) comprising the plurality of electrolysis units (3), or a stack (23) including a plurality of cells (25), each cell (25) comprising the plurality of electrolysis units (3).

24. Electrolysis system (1) according to any one of the previous claims, wherein the system includes system tubing (43) arranged to distribute the electrolyte solution (5) between the electrolysis units (3), system tubing (43) and the first and second gas separators (11, 15) comprising or consisting of at least one metal.

25. Electrolysis system (1) according to any one of the previous claims, wherein the electrolysis system (1) is an electrolysis system for electrolysis between 96°C and 350°C, or is a high temperature electrolysis system.

26. Electrolysis system (1) according to any one of the previous claims, wherein each electrolysis unit (3) comprises or consists of temperature resistant material or materials resistant to an electrolyte solution (5) having a temperature between 96°C and 350°C.

27. Electrolysis system (1) according to any one of the previous claims, wherein each electrolysis unit (3) comprises or consists of at least one metal, or comprises or consists of Polyether ether ketone (PEEK), Polyamide 12, Polyphenylene Sulfide, Polyphthalamide, or Teflon.

28. Electrolysis system (1) according to any one ofthe previous claims, wherein each electrolysis unit(3) comprises injection molded blocks (Pl, P2) interconnected by electrodes (ELI, EL2).

29. Electrolysis system (1) according to the previous claim, wherein at least one sealing element is located between the injection molded blocks (Pl, P2) to seal an interconnection between the injection molded blocks (Pl, P2).

30. Solar thermal power system or plant (SG) including the electrolysis system (1) according to any one of the previous claims.

31. Solar thermal power system or plant (SG) according to the previous claim, including at least one heat exchanger (HE) or at least one solar thermal panel arranged to transfer heat to the electrolyte solution (5), at least one turbine and generator arranged to provide electrical energy to the plurality of electrolysis units (3) for electrolysis, storage means for storing at least one gas generated via electrolysis, and at least one fuel cell configured to generate electricity from the stored at least one gas generated via electrolysis.

32. Solar thermal power system or plant (SG) according to the previous claim, wherein the solar thermal power system or plant (SG) is configured to compensate for an intermittent solar energy supply by consuming the at least one gas generated via electrolysis in the at least one fuel cell to provide electricity to an electrical grid.

33. Electrolysis method comprising the steps of: providing a plurality of flow-based electrolysis units (3), the flow-based electrolysis units (3) being a membrane-less electrolysis units; providing an electrolyte solution (5) flowing through the membrane-less electrolysis units (3); and carrying out electrolysis with the plurality of electrolysis units (3) at an electrolyte solution temperature between 96°C and 350°C and an electrolyte solution pressure in the electrolysis units (3) that is <30 bar (3xl0⁶ Pa) or < 40 bar (4xl0⁶ Pa), or < 50 bar (5xl0⁶ Pa) or < 60 bar (6xl0⁶ Pa).

34. Electrolysis method according to the previous claim, further including the step of providing an electrolysis system (1) for high temperature electrolysis according to any one of claims 1 to 29.

35. Electrolysis method according to the previous claim 33 or 34, wherein the electrolyte solution (5) is circulated through the electrolysis units (3) at a pressure of the electrolyte solution (5) permitting to increase a boiling point of the electrolyte solution (5).

36. Electrolysis method according to any one of the previous claims 33 to 35, wherein the electrolyte solution (5) is circulated at a pressure of the electrolyte solution (5) permitting an increased gas pressure in the electrolyte solution (5) exiting the electrolysis units (3).

37. Electrolysis method according to any one of the previous claims 34 to 36, further including increasing the pressure in the electrolysis system (1) by sealing the electrolysis system (1) in combination with pumping the electrolyte solution (5) using the pump (49) and increasing the temperature of the electrolyte solution (5).

38. Electrolysis method according to any one of the previous claims 33 to 37, wherein the electrolyte solution (5) is heated by at least one of or a combination of the following heating means or heaters (10): an electrical heater, a heating element configured to provide heat from a solar-thermal heat source, a heating element configured to provide waste heat from an industrial process, a heating element configured to provide heat from a nuclear plant, a heating element configured to provide heat from a fracking process, a heating element configured to provide heat from geothermal heat source.

39. Electrolysis method according to any one of the previous claims 33 to 38, further including providing a voltage to electrodes (ELI, EL2) of the electrolysis units (3) to heat the electrolyte solution (5), and applying a system heating voltage to the electrodes (ELI, EL2) to heat the electrolyte solution (5) to a predetermined electrolysis temperature to carry out electrolysis, and then applying a thermal balance voltage to the electrodes (Ell, E12) to compensate heat loss during electrolyte solution (5) circulation outside the electrolysis units (3).

40. Electrolysis method according to any one of the previous claims 33 to 39, wherein the electrolyte solution (5) is flowed out of the electrolysis units (3) to a first gas separator (11) and a second gas separator (15) to remove a first output gas (7) and a second output gas (9) from the electrolyte solution (5), and recirculated from the first gas separator (11) and the second gas separator (15) to a heating means (10) and to the electrolysis units (3) for further electrolysis.

41. Electrolysis method according to the previous claim, wherein a stirring device or mechanism (51) of the first gas separator (11) and/or the second gas separator (15) is used to generate a rotational flow in the electrolyte solution (5) to extract the first output gas (7) and/or second output gas (9) from the electrolyte solution (5).

42. Electrolysis method according to the previous claim 40 or 41, wherein a Bonification device or mechanism (53) of the first gas separator (11) and/or the second gas separator (15) is used to generate ultrasonic waves propagating in the electrolyte solution (5) to extract the first output gas (7) and/or second output gas (9) from the electrolyte solution (5).

43. Electrolysis method according to any one of the previous claims 40 to 42, wherein the electrolyte solution (5) is circulated through a hydrophobic porous section (55) of the first gas separator (11) and/or the second gas separator (15) to remove the first output gas (7) and/or second output gas (9) from the electrolyte solution (5).

44. Electrolysis method according to any one of the previous claims 40 to 43, wherein electrolyte solution (5) is circulated through the stirring device or mechanism (51), the Bonification device or mechanism (53) and the hydrophobic porous section (55) respectively in that order to sequentially process the electrolyte solution (5) to remove gas therein.

45. Electrolysis method according to any one of the previous claims 40 to 44, wherein the electrolyte solution (5) is circulated through the first gas separator (11) and/or the second gas separator (15) at a high flow rate.

46. Electrolysis method according to any one of the previous claims 40 to 45, wherein the first and/or second gas separator (11, 15) are operated at a lower electrolyte solution pressure than that in the electrolysis units (3) to favorize dissolved gas nucleation.

47. Electrolysis method according to any one of the previous claims 34 to 46, wherein the heated electrolyte solution (5) is circulated through tubing (43) from the electrolysis units (3) to the first and second gas separators (11, 15), and through tubing (43) from the first and second gas separators (11, 15) back to the electrolysis units (3), the tubing (43) and the first and second gas separators (11, 15) comprising or consisting of at least one metal.

48. Electrolysis method according to any one of the previous claims 34 to 47, wherein a stack (23) including a plurality of cells (25) comprising the plurality of electrolysis units (3) are provided to carry out electrolysis.

49. Electrolysis method according to any one of the previous claims 33 to 48, wherein each electrolysis units (3) includes

50. Electrolysis method according to the previous claim, wherein the inclined fluidic canals (115) are inclined with respect to each of the first, second and third fluidic channels (107, 109, 111).

51. Electrolysis method according to the previous claim 49 or 50, wherein the first fluidic channel (107) comprises or consists of a plurality of stacked Y-shaped sections (SY), each Y-shaped section (SY) comprising a plurality of the inclined fluidic canals (115) extending from the first fluidic channel (107) to each of the second and third fluidic channels (109, 111).

52. Electrolysis method according to any one of the previous claims 33 to 51, wherein each electrolysis unit (3) comprises or consists of temperature resistant material or materials for operation with an electrolyte solution (5) having a temperature between 96°C and 350°C.

53. Solar thermal power generation method including the electrolysis method according to any one of the previous claims 33 to 52, the method comprising generating solar generated heat and transferring solar generated heat to the electrolyte solution (5) via a heat exchanger (HE), using the solar generated heat to produce turbine-generated electrical energy and provide a portion thereof to the electrolysis units (3) for electrolysis, generating at least one gas via electrolysis storing the at least one gas, and generating electricity using a fuel cell and the stored at least one gas generated via electrolysis.

54. Solar thermal power generation method according to the previous claim, wherein an intermittent solar energy supply is compensated by consuming the at least one gas generated via electrolysis by providing the generated electricity to an electrical grid.