GB2620481A

GB2620481A - Electrolysis system and method for energy recycling

Info

Publication number: GB2620481A
Application number: GB2306648.3A
Authority: GB
Inventors: Francis Geary Paul
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-11-18
Filing date: 2021-11-18
Publication date: 2024-01-10
Also published as: GB202306648D0

Abstract

An electrolysis system (200) for generating hydrogen is described. The system comprises an electrolyser (202) comprising an electrolyte inlet, a first gas outlet (204) and a second gas outlet (206), an electrical generator (212) configured to generate electricity (212), that can be used in the electrolyser. The system also comprises an electrolyte pump (214) for supplying the electrolyser (202) with electrolyte. The electrolyte pump (214) provides the electrolyser (202) with electrolyte and where the electrolyser (202) powers, the electrolyte pump (214). The electrical generator (212) is connected to the first and/or second gas outlet (204, 206) of the electrolyser and may be configured to be powered, at least in part, by gas flow provided via the first and/or second gas outlet (204/206). An electrical power supply may also be provided where the electrical generator (212) may be supplied with energy from the power supply to start the electrolyser (202). The electrical generator (212) may be a motor-generator comprising a first mode for generating electricity and a second mode for using electricity to drive the electrolyte pump (214).

Description

ELECTROLYSIS SYSTEM AND METHOD FOR ENERGY RECYCLING

Description

The present disclosure relates to an electrolysis system, particularly but not exclusively, to an electrolysis system for generating hydrogen. Another aspect of the present disclosure relates to a method of recycling energy in an electrolysis system.

The process of using electricity to decompose water or steam into oxygen and hydrogen gas is known as electrolysis of water. Hydrogen gas produced in this way can be used in various applications and has become widely known as an energy dense option for fueling vehicles. In other applications, electrolysis of water may be used as a decentralized storage solution storing electrical energy as chemical energy (e.g. in the form of hydrogen or metal hydrides or other compounds such as ammonia), particularly electric energy obtained via renewable power. In recent years, therefore, demand for hydrogen, inter alia, as a fuel for so-called hydrogen fuel cells has increased rapidly. Water electrolysis produces hydrogen gas (or intermediate hydrogen containing compounds) and oxygen gas.

Hydrogen gas is often required to be stored at high pressures, e. g. 300 to 700 bar for use as a fuel for vehicles. Oxygen cylinders and bottle packs tend to also require 200 -300 bar for commercial sale. To this end, some existing solutions suggest compressing the hydrogen gas once it is produced by the electrolysis process. This process of compressing hydrogen after the electrolysis is a comparatively inefficient way to store hydrogen at high pressures. Accordingly, some electrolysers may be configured to produce hydrogen at high pressure directly, without the need for an additional compressor. However, these types of systems are often inefficient to run and require extensive energy input to maintain internal system/electrolyte pressure.

In view of the above problem, it is an object of the present disclosure to provide an electrolysis system that is able to produce hydrogen at high pressure and at the same time exhibit improved energy efficiency.

Aspects and embodiments of the present disclosure provide an electrolyser for generating hydrogen and a method of controlling an electrolyser for generating hydrogen from water as claimed in the appended claims.

According to an aspect of the present disclosure there is provided an electrolysis system for generating hydrogen, the system comprising: an electrolyser comprising an electrolyte water inlet, a first gas outlet and a second gas outlet, an electrical generator configured to generate electricity, preferably for the electrolyser, said electrical generator being connected to the first and/or second gas outlet of the electrolyser and configured to be powered, at least in part, by gas flow provided via the first and/or second gas outlet an electrolyte pump for supplying the electrolyser with electrolyte water, wherein the electrical generator is a motor-generator comprising a first mode for generating electricity and a second mode for using electricity to drive the electrolyte pump.

In one embodiment, the electrolyte pump is connected to the first and/or second gas outlet of the electrolyser and configured to be powered, at least in part, by gas flow provided via the first and/or second gas outlet.

In another embodiment, the electrolyte pump is configured to be powered, at least in part by electricity generated via the electrical generator.

In another embodiment, the electrolyte pump is configured to be powered, at least in part, by electricity provided via an external power supply, such as a mains power supply.

In another embodiment, the electrolyte pump is connected to the first and/or second gas outlet in series with the electrical generator, preferably downstream of the electrical generator.

In another embodiment, the electrical generator is configured to be connected to an electrical power supply and configured to feed surplus electrical energy that is not required by the electrolyser back to the power supply.

In another embodiment, the electrical power supply is configured to provide the electrical generator with electrical energy during start-up of the electrolyser.

In another embodiment, the electrical generator is reversible to function as a compressor during start-up of the electrolyser for supplying the electrolyte pump with gas flow during start-up.

In another embodiment, the electrical generator comprises an air inlet for selectively providing the electrical generator with air to be compressed during the start-up of the electrolyser.

In another embodiment, the system comprises an air vent selectively connectable to a gas outlet of the electrolyte pump, preferably during start-up of the electrolyser.

In another embodiment, the system comprises a gas output port selectively connectable to a gas outlet of the electrolyte pump, preferably during normal operation of the electrolyser.

In another embodiment, the system comprises an AC/DC converter arranged between the electrical generator and the electrolyser.

In another embodiment, the system comprises a heat exchanger configured to pre-heat electrolyte water supplied to the electrolyser via the electrolyte pump.

In another embodiment, the heat exchanger is configured to transfer heat from the electrical generator and/or an electrolyte pump and/or an AC/DC converter of the system.

In another embodiment, the first gas outlet is a Hydrogen outlet and the second gas outlet is an Oxygen outlet, and wherein the electrical generator is connectable to the second gas outlet such that the electrical generator is powered by oxygen gas flow provided via the second gas outlet.

In another embodiment, electrolyser is configured to control a pressure of the oxygen provided via the second gas outlet to be between lbar and 1000bar.

In another embodiment, the electrolyte pump is configured to supply the electrolyser with electrolyte water at a pressure higher than a gas pressure at the second gas outlet, preferably at least 5 bar above the gas pressure at the second gas outlet.

In another embodiment, the first or the second gas outlet port is connected to a gas booster to increase the pressure of a gas provided via the other of the first or second gas outlet ports or to increase the pressure of a gas storage accumulator.

In another embodiment the gas storage accumulation is connected to or incorporated within or comprised of a metal hydride storage system or an alternative hydrogen compound storage system. This embodiment relates to intermediary hydrogen storage as metal hydrides and other hydrogen chemical storage means. These can also generate gas pressure when the hydrogen evolves and any such pressure generation can be applied to the energy recycling within the system described in this disclosure. Wherever in the system there is an available amount of energy recoverable from a pressurised gaseous environment to a use case that does not require such high pressure hydrogen and/or oxygen, the principles described in this disclosure will be applicable. Metal hydride compressors are also then interchangeable with the compressors described in this disclosure and it is the energy recovery element that is pertinent.

According to another aspect of the present disclosure, there is provided a method of recycling energy in an electrolysis system comprising an electrolyser, an electrical generator for providing electricity to the electrolyser, and an electrolyte pump for supplying electrolyte water to the electrolyser, the method comprising: supplying the electrolyser with pressurized electrolyte water; decomposing the electrolyte water into pressurised gases, preferably into pressurized hydrogen and oxygen; pressurizing further one of the outlet streams or storage containers of gas 35 -meeting some of the compression energetic costs;

S

supplying the electrical generator and/or the electrolyte pump with at least one of the pressurised gases to power the electrical generator and/or the electrolyte pump.

In another embodiment, the method comprises supplying the electrical generator and/or the electrolyte pump with pressurized oxygen produced by the electrolyser.

In another embodiment, the method comprises supplying at least parts of the electrical energy produced by the electrical generator to the electrolyser.

According to another aspect of the present disclosure, there is provided an electrolysis system for generating hydrogen, the system comprising: an electrolyser comprising an electrolyte water inlet, a first gas outlet and a second gas outlet, an electrolyte pump for supplying the electrolyser with electrolyte water, said electrolyte pump being connected to the first and/or second gas outlet of the electrolyser and configured to be powered, at least in part, by gas flow provided via the first and/or second gas outlet.

In another embodiment, the electrolysis system comprises an electrical generator configured to generate electricity for the electrolyser, said electrical generator being connected to the first and/or second gas outlet of the electrolyser and configured to be powered, at least in part, by gas flow provided via the first and/or second gas outlet In another embodiment, the method comprises the electrolyte pump is connected to the first and/or second gas outlet in series with the electrical generator, preferably downstream of the electrical generator.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, and the claims and/or the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and all features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

The aforementioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the disclosure will be better understood by reference to the following description of embodiments of the disclosure taken in conjunction with the accompanying drawings, wherein: FIG. 1 shows a schematic cross-section of an electrolyser for production of hydrogen and oxygen at high pressures; FIG. 2 shows a schematic diagram of an electrolysis system according to an

embodiment of the present disclosure;

FIG. 3 shows a schematic diagram of an electrolysis system according to an

embodiment of the present disclosure;

FIG. 4 shows a schematic diagram of an electrolysis system according to an

embodiment of the present disclosure;

FIG. 5 shows a schematic flowchart of a method according to an

embodiment of the present disclosure.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the disclosure, and such exemplifications are not to be construed as limiting the scope of the disclosure in any manner.

FIG. 1 shows an electrolyser 100 as may be used in the electrolysis system of the present disclosure. In the example of FIG. 1, there is shown an electrolyser 100 for generating hydrogen, particularly by electrolysis of water. However, as will be appreciated, the electrolyser 100 shown in FIG. 1 may also be suitable for decomposition of other substances by means of electrolysis. Generally, in this specification, the term "electrolyte water" may encompass water including any type of electrolyte, such as sulphuric acid, sulphate, potassium hydroxide, sodium hydroxide, etc., or in some embodiments water without electrolytes such as tritiated water.

The electrolyser 100 comprises a housing 102. The housing 102 comprises an electrolyte chamber 104. In one example, the electrolyte chamber is configured to hold electrolyte water under pressure as will be described in more detail below. The electrolyte water may comprise any electrolyte dissolved in water that aids decomposition of water.

The housing 102 comprises a first gas collection chamber 106. The first gas collection chamber 106 is separated from the electrolyte chamber 104 by a first electrode 108. The housing 102 comprises a second gas collection chamber 110. The second gas collection chamber 110 is separated from the electrolyte chamber 104 by a second electrode 112. The electrolyte chamber 104 is located between the first and second electrodes 108, 112. The electrolyte chamber 104 is a membrane-less chamber. In some embodiments the chambers will be surplus to requirement and the gases that evolve will be directly transported from the electrolyser in effect negating the need for port 122.

It will be appreciated that in some embodiments, the electrolyser may comprise more than two electrodes, e.g. arranged in parallel to each other to form a stack of electrodes. The pair of electrodes 108, 112 of Figure 1 are thus exemplary for any number of electrodes used in a stack.

The housing 102 of Figure 1 is a multi-part housing. In particular, the housing 102 comprises at least two parts: a first housing part includes the first gas collection chamber 106 and the first electrode 108; a second housing part includes the second gas collection chamber 110 and the second electrode 112. The at least two housing parts are connected to each other such that a gap is formed between first surfaces 114, 118 of the first and second electrodes 108, 112. This gap defines the electrolyte chamber 104, which is thus arranged between the electrodes 108, 112. In the example of Figure 1, the housing 102 is substantially H-shaped as will be described in more detail below. However as will be appreciated, other designs may include a plurality of plate shaped electrodes that typically are flat and similar in construction to a plate heat-exchanger.

The first electrode 108 is permeable to gases produced by decomposition of electrolyte water. The first electrode 108 is also generally permeable to electrolyte water depending on a pressure within the electrolyte chamber 104 as will be explained in more detail below. In other words, the first electrode 108 is a so-called "flow-through" electrode in which gases produced by decomposition of electrolyte water (and the electrolyte water) within the electrolyte chamber 104 are able to penetrate the first electrode 108 and thus move from the electrolyte chamber 104 towards the first gas collection chamber 106. To this end, the first electrode 108 is a permeable electrode including a plurality of pores sized to allow permeation of the respective gas, e.g. hydrogen, through the first electrode 108.

The first electrode 108 has a first surface 114 facing the electrolyte chamber and a second, opposite surface 116 facing the first gas collection chamber 106.

The first electrode 108 may be made of steel, preferably sintered steel. In some embodiments, the second electrode 112 may also be made of steel, preferably sintered steel. In alternative embodiments, the second electrode 112 may be made of a material different to the first electrode 108 or both electrodes be made of graphite or other materials.

Gases produced by the first electrode 108 may flow into the first gas collection chamber 106. The first gas collection chamber 106 comprises a first gas outlet port 122 for extraction of the gas within the first gas collection chamber 106. As will be described in more detail below, the first gas outlet port 122 may include a pressure control valve, such as a pressure relief valve, configured to set a gas pressure within the first gas collection chamber 106.

The second electrode 112 of Figure 1 is also permeable to gases produced by the decomposition of electrolyte water. The second electrode 112 is also generally permeable to electrolyte water depending on a pressure within the electrolyte chamber 104 as will be explained in more detail below. In other words, the second electrode 112 is also a "flow-through" electrode in which gases produced by decomposition of electrolyte water within the electrolyte chamber 104 are able to penetrate the second electrode 112 and thus move from the electrolyte chamber 104 towards the second gas collection chamber 110.

The second electrode 112 has a first surface 118 facing the electrolyte chamber 104 and a second, opposite surface 120 facing the second gas collection chamber 110.

Gases produced by the second electrode 112 may flow into the second gas collection chamber 110. The second gas collection chamber 110 comprises a second gas outlet port 124 for extraction of the gas within the second gas collection chamber 110. As will be described in more detail below, the second gas outlet port 124 may include a pressure control valve, such as a pressure relief valve, configured to determine the pressure within the second gas collection chamber 110.

The electrolyser 100 comprises an electrolyte water supply circuit 130 for supplying the electrolyte chamber 104 with electrolyte water. The electrolyte water supply circuit 130 of Figure 1 is a closed system. Alternatively, the water supply circuit may be an open system including an electrolyte water reservoir. In one example, the electrolyte water supply circuit 130 comprises a pump 134 arranged upstream of an inlet port 126 of the electrolyte chamber 104. The pump 134 may be configured to move electrolyte water through the system and in the direction of the electrolyte chamber 104 at a selectable pressure.

The electrolyte supply circuit 130 comprises an electrolyte water supply line 162 for topping up electrolyte water or any other treated or untreated water turned into gas by the electrolysis process. As indicated in Figure 1, the electrolyte water supply line 162 may be connected to the pump 134 via a manually or automatically controlled shut off valve. An expansion vessel 132 is a pressure storage device arranged within the electrolyte water supply circuit 130 and configured to provide expansion derived pressure into the system and configured to enable 134 to have a lower cycle time and maintain a desired pressure range within the circuit 130/protect the circuit 130 from excessive pressures. This vessel may also be comprised of metal hydride or any other hydrogen compound storage that when hydrogen evolves may generate pressure that is useable in the system for driving the electrical generator and/or the pump as will be discussed in more detail below.

The electrolyte chamber 104 comprises a vent port connected to a vent line 105. The vent line 105 is configured to be used to drain the back flushed electrolyte and any associated media. Additionally, the line may be instrumental in sampling and even comprise a collection well for removal of electrolyte in the circulation system either with or without pressure. Additionally, the vent may or may not be instrumental in the purging of air from the system prior to current being applied to the electrodes. Finally, the vent pipe may allow electrolyte flow and recycling from 104 via 105 to 162, the water inlet line or it may discharged/collected.

The electrolyte supply circuit 130 may comprise a pressure gauge 136 for monitoring the pressure within the electrolyte chamber 104. As will be appreciated, the pressure gauge 136 may be arranged anywhere downstream of the pump 134. In some embodiments, the pressure gauge 136 may be an integral part of the pump 134. In other embodiments, the pressure gauge may be arranged within the electrolyte chamber 104.

In some embodiments, the electrolyte water supply circuit 130 may comprise a pressure storage device, such as an accumulator 138. The accumulator 138 shown in FIG. 1 is arranged downstream of the pump 134. The accumulator 138 may be connected to the pump 134 via a check valve, which, during normal operation of the electrolyser 100, allows fluid to be pumped into the accumulator 138. As will be appreciated, the check valve will stop fluid from leaving the accumulator 138. The accumulator 138 may also comprise a separate outlet valve for selectively connecting an outlet of the accumulator 138 with the electrolyte chamber 104. In some embodiments, the accumulator 138 may thus comprise a normally-open outlet valve, which is closed during normal operation of the electrolyser. In other words, during normal operation, pressurized electrolyte water may be pumped into the accumulator 138 but may not leave the accumulator 138, until the outlet valve is opened. As will be described in more detail below, using a normally-open outlet valve enables the accumulator 138 to be used as a safety measure, e.g. during power cuts.

The first gas collection chamber 106 comprises a first drain port 142. The second gas collection chamber 110 comprises a second drain port 144. The first drain port 142 is connected to the pump 134 of the electrolyte water supply circuit 130 via a first drain line 146. The second drain port 144 is connected to the pump 134 via a second drain line 148. Electrolyte water permeating the first electrode 108 during operation of the electrolyser 100 may be drained from the first gas collection chamber 106 via the first drain port 142 and the first drain line 146 respectively. Similarly, electrolyte water permeating the second electrode 112 during operation of the electrolyser 100 may be drained from the second gas collection chamber 110 via the second drain port 144 and the second drain line 148 respectively. In multi-cell arrangements any drain port can act for one or more of the cells rather than being required by each cell.

In the embodiment of Figure 1, the first and second drain ports 142, 144 are arranged typically at a bottom end of the first and second gas collection chambers 106, 110. In other words, the drain ports 142, 144 are arranged below the first and second gas outlet ports 122, 124 of the first and second gas collection chambers 106, 110 and below the first and second electrodes 108, 112. In other words, both the first and the second gas collection chambers 106, 110 comprise drain wells 141, 143 arranged typically at a bottom end of the gas collection chambers 106, 110. As can be seen from Figure 1, the housing 102 is thus substantially H-shaped but does not need to be, it can be multi-cell or arranged similar to a plate heat exchanger design with plates and ports at any orientation. The device can be made of multiple electrodes usually arranged in parallel to each other to form a stack of electrodes.

During operation of the electrolyser 100, electrolyte water that has permeated the first or second electrode 108, 112 will collect within the drain well 141, 143 at the bottom of the respective gas collection chambers 106, 110, whereas the gases produced during the electrolysis, will rise and pressurize the gas collection chambers 106, 110.

As long as the drain ports 142, 144 are covered with electrolyte water, the drain ports may be opened for drainage of the electrolyte water from the gas collection chambers 106, 110 without inadvertently removing gases via the drain ports 142, 144. In some embodiments, the electrolyser 100 may comprise electrolyte water level sensors arranged within the gas collection chambers 106, 110 to determine if sufficient levels of electrolyte water are available within the gas chambers 106, 110 in order to safely open one or both of the drain ports 142, 144. These levels may or may not be actively controlled with active movement of electrolyte water to the collection chambers from areas of the electrolyte circulation system with capacity including 138 or as active top up from external water source. The levels may or may not be controlled using active pressure variation and control within the system.

The first and second gas collection chambers 106, 110 both comprise gas pressure gauges 150, 152. A first gas pressure gauge 150 is configured to determine the gas pressure within the first gas collection chamber 106. A second gas pressure gauge 152 is configured to determine a second gas pressure within the second gas collection chamber 110. In some embodiments, the first and second gas gauges may be incorporated into a single device.

The electrolyser 100 comprises a first electrical terminal 154 and a second electrical terminal 156. In the example of Figure 1, the first terminal 154 is a negative terminal, whereas the second terminal 156 is a positive terminal. However, it will be appreciated that the polarity of the first and second terminals may be swapped, such that the first terminal 154 is a positive terminal and the second terminal 156 is negative. This is because, in some embodiments, the electrolyser is symmetrical on either side of the electrolyte chamber 104.

The terminals 154, 156 are connected to the housing 102 of the electrolyser 100. In particular, the first terminal 154 is connected to the first gas collection chamber 106. The second terminal is connected to the second gas collection chamber 110. Accordingly, the first terminal 154 is electrically connected to the first electrode 108, which is electrically connected to the first gas collection chamber 106 via its second surface 116. The second terminal 156 is connected to the second gas collection chamber 110, which in turn is connected to the second electrode 112 via the second surface 120 of the second electrode 112. Of course, it will be appreciated that the terminals 154, 156 may also be connected to the electrodes 108, 112 directly, rather than via the housing 102 of the electrolyser 100.

The terminals 154, 156 are connectable to a power source, e.g. a direct current power source, to apply a current across the electrodes 108, 112. If the terminals 154, 156 are connected to the power source, current will flow between the first and second electrode 108, 112 via the electrolyte water within the electrolyte chamber 104, thereby activating the electrolysis process for decomposition and separation of electrolyte water into oxygen and hydrogen, as will be explained in more detail below.

As mentioned above, in the embodiment of Figure 1, the first terminal 154 is a negative terminal and the second terminal 156 is a positive terminal. Accordingly, the first electrode 108 of the embodiment in Figure 1 is the cathode of the electrolyser 100, whereas the second electrode 112 is the anode of the electrolyser 100. The first electrode 108 is permeable to gas, particularly hydrogen. The second electrode 112 is permeable to gas, particularly oxygen.

In one example, the first and second electrodes 108, 112 comprise different porosities. In some embodiments, the porosity of the first electrode 108 may be about half of the second electrode 112. The first electrode 108 may have a porosity below 0.3pm. The second electrode 112 may have a porosity below 0.6pm.

In the above example, the first gas collection chamber 106 is configured to receive hydrogen gas, whereas the second gas collection chamber 110 is configured to receive oxygen gas.

The electrolyser 100 further comprises a control unit 160, schematically represented in Figure 1. The control unit may be connected to the first and/or second gas pressure gauges 150, 152 to receive gas-pressure-data representative of a gas pressure within the first and/or second gas collection chamber 106, 110. The control unit 160 may be connected to the first and second drain valves 142, 144 for controlling operation of the first and second drain valves 142, 144. The control unit may be connected to the first and second gas outlet ports 122, 124 for controlling the operation of the first and second gas outlet ports 122, 124.

The control unit 160 may be connected to the power source (not shown) for controlling the supply of electrical power to the first and second electrodes 108, 112. The control unit 160 may be connected to an outlet valve of the accumulator 138. The control unit 160 may be connected to the pump 134 and the electrolyte water pressure gauge 136.

The control unit may be connected to any of the above devices via control wires or wirelessly as is well known in the art. The control unit may either be locally arranged together with the housing 102 of the electrolyser or remotely, e.g. in a centralised control office.

The control unit 160 is configured to control a pressure drop across at least one of the permeable electrodes 108, 112. In one embodiment, the control unit 160 is configured to control the electrolyte pressure in the electrolyte chamber 104 relative to a gas pressure in the first or second gas collection chamber 106, 110.

The control unit 160 may be configured to control the electrolyte water pressure in the electrolyte chamber 104 to be higher than a gas pressure in the first or second gas collection chambers 106, 110. In other words, the control unit 160 is configured to maintain a pressure drop between the electrolyte chamber 104 and the gas collection chambers 106, 110. In some examples, the control unit 160 is configured to control the electrolyte water pressure in the electrolyte chamber 104 to be at least 5 bar higher than a gas pressure in the first and/or second gas collection chamber 106, 110.

Maintaining a pressure drop of at least 5 bar between the electrolyte chamber 104 and the first and/or second gas collection chamber 106, 110 causes electrolyte water to permeate the first electrode 108 and/or the second electrode 112 and thus to flow between the electrolyte chamber 104 and the first and/or second gas collection chamber 106, 110 together with the hydrogen gas produced at the first electrode.

Causing the above electrolyte water flow across the first and/or second electrodes 108, 112 significantly increases the efficiency of the electrolyser 100.

In order to maintain the required pressure drop across one or both of the electrodes 108, 112, the control unit 160 of Figure 1 is configured to receive gas-pressure-data representative of a gas pressure within the first or second gas collection chambers 106, 110 respectively. In the example of Figure 1, the gaspressure-data may be pressure readings supplied by the first and/or second gas pressure gauges 150, 152.

On the basis of the gas-pressure-data, the control unit will determine a desired electrolyte water pressure within the electrolyte chamber 104. In some examples, the control unit may add a preselected amount of pressure to the gas pressure indicated by the gas-pressure-data in order to determine the desired electrolyte water pressure. In some embodiments, the control unit 160 may determine a desired electrolyte water pressure that is at least 5 bar higher than the gas pressure within the first gas collection chamber 106.

The control unit may then control the electrolyte water supply circuit 130 to supply electrolyte water to the electrolyte chamber 104 until the desired electrolyte water pressure is reached. In the example of Figure 1, the control unit 160 may be configured to activate the pump 134 to supply electrolyte water to the control chamber 104 until the desired electrolyte water pressure has been reached. To this end, the control unit may receive electrolyte-pressure-data representative of a pressure of electrolyte water within the electrolyte chamber 104. In the embodiment of Figure 1, the electrolyte-pressure-data comprises pressure readings supplied by the pressure gauge 136 arranged downstream of the pump 134.

The control unit may control activation of the pump 134 via a control loop, based on electrolyte-pressure-data provided by the pressure gauge 136. For example, the control unit may control the electrolyte water pressure within the control chamber 104, represented by the pressure readings of the pressure gauge 136, via a PID control loop.

It should be appreciated that a pressure drop between the electrolyte chamber 104 and the gas collection chambers 106, 110 will vary continuously as the electrolyser 100 is operated. This is because, during operation of the electrolyser, i.e. when pressurised electrolyte water is available in the electrolyte chamber 104 and a current is applied across the two electrodes 108, 112, hydrogen and oxygen gases are produced and added to the first and second gas collection chambers 106, 110 continuously. Accordingly, in this example, as long as the first and second gas outlet ports 122, 124 remain closed, the gas pressure within the gas collection chambers 106, 110 will continue to rise. This exemplary rise in gas pressure will be determined by the control unit 160 on the basis of the gaspressure-data. The control unit 160 will then determine a new, higher, desired electrolyte water pressure and control the pump 134 to increase the electrolyte water pressure within the electrolyte chamber 104 and match said increased desired electrolyte water pressure. The control unit 160 may continuously adjust the pressure within the electrolyte chamber 104 as long as the gas pressure within the first or second gas collection chamber 106, 110 rises. In some examples, the electrolyte water pressure will be maintained at least 5 bar over the gas pressure. It will be understood that this is done via a control loop (e.g. PID control) and so the actual difference between the electrolyte water pressure and the gas pressure may vary and thus occasionally fall below 5 bar.

The control unit 160 may also control the gas pressure within the first and/or second gas collection chamber 106, 110. In the example of Figure 1, the control unit may be configured to control an operation of the first and/or second gas outlet port 122, 124. The control unit 160 may open and close the first gas outlet port 122 to control the (hydrogen) gas pressure within the first gas collection chamber 106. The control unit 160 may open and close the second gas outlet port 124 to control the (oxygen) gas pressure within the second gas collection chamber 110. In some embodiments, the control unit 160 may receive a first desired gas pressure for the first gas collection chamber 106 and a second desired gas pressure for the second gas collection chamber 110. The first and second desired gas pressures may be selected by an operator. In some examples, the desired gas pressures may be determined directly by apparatus using the hydrogen and oxygen gases provided by the electrolyser 100.

In another embodiment, one or both of the gas outlet ports may comprise pressure relief valves configured to open automatically once the gas pressure in the first or second gas collection chamber 106, 110 exceeds a set pressure. In this example, the pressure within the gas collection chambers will be determined by the set pressure of the pressure relief valves of the first and second gas outlet ports 122, 124 respectively. In some embodiments, the set pressure of the pressure relief valves may be adjustable, e.g. via the control unit 160.

In both embodiments described above, the control unit 160 may be configured to maintain a gas pressure in the first and second gas collection chamber 106, 110 at lbar to 1000bar, preferably 10bar to 1000bar, more preferably 100bar to 1000bar. If the gas pressure within the gas collection chambers 106, 110 is maintained at 100 bar, the control unit may set a desired electrolyte water pressure of 105 bar or more to allow for some electrolyte water to pass through the first and/or second electrode 108, 112 as has been described above.

It should be noted that electrolyte water passing through the first and second electrodes 108, 112, due to the pressure drop between the electrolyte chamber 104 and the gas collection chambers 106, 110, may be drained back into the electrolyte water supply circuit 130, e.g. intermittently, via the above drain ports 142, 144. The control unit 160 may be configured to control such electrolyte water drainage operation. To this end, the control unit 160 may be connected to water level sensors (not shown) arranged within the first and/or second gas collection chambers 106, 110. The water level sensors may provide the control unit with water-level-data representative of the water levels within the first and second gas collection chambers 106, 110 particularly within the drain wells 141, 143. If, on the basis of the water-level-data, the control unit determines that the electrolyte water levels are sufficiently high to fully cover the first and/or second drain port 142, 144, the control unit 160 may temporarily open one or both of the drain ports 142, 144 to drain electrolyte water from the gas collection chambers 106, 110. In one embodiment, the control unit may be configured to open the drain ports 142, 144 for a predetermined amount of time, e.g. several seconds, if the water level has reached a water-level-threshold. In other embodiments, the control unit will drain electrolyte water until the electrolyte water levels have fallen below a predetermined water-level-threshold.

The control unit may also be configured to control a power source (not shown) attached to the electrodes 108, 112 via the terminals 154, 156. The operator or controller can alter the amperage according to the type of electrolysis and the type of electrode used and other variables such as cell gap. The control unit may be configured to set the voltage provided by the power source to be set at the desired voltage. The desired voltage may be designated by the operator. The amperage and voltage can be fixed, manually set or variably controlled by the control unit 160.

In some embodiments, the control unit may be configured to supply electrical power to the electrodes 108, 112 only once the desired pressure drop across the electrodes 108, 112 has been achieved. In other words, the control unit 160 may monitor a pressure difference between one of the gas collection chambers 106, 110 and the electrolyte chamber 104. Once the pressure difference exceeds a selectable first pressure-threshold, the control unit may activate the power supply to apply a DC current across the electrodes 108, 112 and the electrolyte water within the electrolyte chamber 104 to start operation of the electrolyser 100. The control unit 160 may be configured to de-activate the power supply whenever the pressure difference falls below a second pressure-threshold. The second pressure threshold may be the same as or lower than the first pressure-threshold.

Turning to FIG. 2, there is shown a schematic diagram of an electrolysis system 200 according to an embodiment of the present disclosure. The electrolysis system 200 comprises an electrolyser 202. The electrolyser 202 comprises an electrolyte water inlet 203, a first gas outlet, e.g. a first outlet port 204, and a second gas outlet, e.g. a second gas outlet port 206, similar to what is described in FIG. 1, particularly with reference to the electrolyser housing 102. In some embodiments, the electrolyser 202 may comprise all of the parts described with reference to the housing 102 in FIG. 1. However, it should be understood that the electrolyser 202 is not limited to the flow-through example of Fig. 1. Rather, the electrolysis system may be used in connection with any PEM or AEM electrolyser or metal hydride electrolysis, producing gases at pressures above 1 bar. It should also be noted that the gas outlets of the electrolyser may simply be gas lines for supplying the oxygen and hydrogen gases to one or more storage tanks or directly to the end user.

In view of the above, the first gas outlet port 204 may be connected to a first gas collection chamber that is used for the storage of high pressure hydrogen produced during operation of the electrolyser 202. The second gas outlet port 206 may be connected to a second gas collection chamber that is used for the storage of high pressure oxygen that is produced during operation of the electrolyser 202. The high pressure hydrogen may be supplied to a hydrogen storage tank via a hydrogen line 208. Alternatively, and as schematically represented in Figure 2, a gas compressor 209 may be arranged within the hydrogen line 208 to further increase the pressure of the hydrogen gas provided by the electrolyser 202 before the hydrogen is supplied to a storage tank. In some examples, the gas compressor 209 may be driven by the mains power supply 248. Additionally, or alternatively, the gas compressor may be driven, at least partly, by gas, e.g. oxygen, supplied via the second gas outlet port 206. Alternatively it may be driven by gas pressure from hydrogen build=up as it evolves out of metal hydride or is converted from another hydrogen storage intermediary stage.

The pressurized oxygen provided at the second gas outlet port 206 is provided to an electrical generator 212 via a first oxygen line 210. In other words, the first oxygen line 210 connects the second gas outlet port 206 to a gas inlet of the electrical generator 212. The electrical generator is configured to generate electricity from gas flow, here an exemplary oxygen gas flow, provided via the second gas outlet port 206. The electrical generator 212 may be provided with one or more gas pistons (not shown) configured to be driven by the oxygen gas provided by the second gas outlet port 206. Alternatively, the electrical generator 212 may comprise a turbine, membrane or diaphragm for converting the kinetic energy of the oxygen gas flow into electricity. The electrical generator 212 may also be a vein generator or any other type.

The electrical generator 212 may convert a kinetic energy of the oxygen gas flow into an alternating current. The alternating current may be provided to an AC/DC converter 246 via a first electrical line 242 or to a power grid/any type of electrical energy storage solution via a second electrical line 244. An electrical control/switching arrangement may be included in line 240 to distribute electricity produced by the electrical generator 212 between the first and second electrical line 242, 244 and thus between the AC/DC converter 246 and the grid respectively.

The AC/DC converter 246 transfers the AC power, supplied by the electrical generator 212 during operation of the electrolyser 202, into DC power, which could then be supplied to the electrodes (not shown) of the electrolyser 202 (cf. electrodes 108, 112 in FIG. 1). In this way, the electrolysis system 200 shown in FIG. 2 may use the electrical generator 212 to recycle some or all of the potential energy stored within the high pressure oxygen as electrical power supplied back to the electrolyser. In this regard, it should be noted that, unlike hydrogen, oxygen is typically not required to be supplied or stored at high pressure, such that at least some of the potential energy of the high pressure oxygen produced within the electrolyser described with reference to FIG. 1 may be recovered via the electrical generator 212.

The electrolysis system 200 further comprises an electrolyte pump 214 for supplying the electrolyser with high pressure electrolyte water, similar to the electrolyte pump 134 described with reference to FIG. 1. The electrolyte pump 214 shown in FIG. 2 may also be driven by gas flow provided via the second gas outlet port 206. To this end, the electrolyte pump 214 is connected to the electrical generator 212 via a second oxygen line 216. Oxygen gas flow leaving the electrical generator 212 via a gas outlet port 213, will flow towards a gas inlet 215 of the electrolyte pump 214 via the second oxygen line 216. The kinetic energy left in the gas flow entering the electrolyte pump 215 via the gas inlet 215 may be used to drive the electrolyte pump 214, i.e. power the electrolyte pump 214 to provide a flow of electrolyte water to the electrolyser 202 via electrolyte water supply 224. The same electrolyte pump 214 gas powering system as described here might be achieved from outlet port 206 where pressurized hydrogen is available for energy transfer.

It will be understood that the decomposition of electrolyte water is generally a slow process, such that activation of the pump 214 may only be required intermittently, e.g. every thirty seconds or less frequently, such as hourly, during operation of the electrolyser 202. Accordingly, a gas flow provided via the second gas outlet port 206 of the electrolyser 202 may only be required intermittently to drive the pump 214. Otherwise, most or all of the kinetic energy provided by the flow oxygen from the second gas outlet port 206 of the electrolyser 202 may be converted into electrical power by the electrical generator 212. To this end, the electrolysis system 200 may comprise a control unit (not shown) configured to adjust the amount of electricity produced by the electrical generator 212 during operation of the electrolyser 202. The control unit may be configured to temporarily decrease the amount of electricity produced by the electrical generator 212 during times when the electrolyte pump 214 is required to supply electrolyte water to the electrolyte chamber of the electrolyser 202.

As will be appreciated from the foregoing description of FIG. 1, the pressures within the electrolyte chamber of the electrolyser 202 should be higher than the pressures in the gas collection chambers, i.e. the pressure in the electrolyte chamber should be higher than the pressure of the oxygen gas at the second gas outlet port 206, under normal operating conditions. Accordingly, the pump 214 may comprise an air to electrolyte pressure ratio below one. In some examples, the air to electrolyte pressure ratio of the pump 214 may be in region of 1 to 100 and 1 to 300. This means that 1 bar of oxygen gas pressure within the second oxygen line 216 may be used to provide electrolyte water to the electrolyser 202 at an outlet pressure of 200 to 300 bar.

The electrolyte pump 214 comprises a gas outlet port 217 connected to an oxygen outlet 218. Oxygen gas used to drive the electrolyte pump 214 will leave the pump 214 via its gas outlet port 217 towards the oxygen outlet 218 and may then be transferred directly to a user or into intermediate storage containers or sent to the electrical generator 212.

In view of the above, the electrolysis system 200 shown in FIG. 2 may be used to recycle potential energy of the high pressure oxygen stored within the electrolyser 202 to drive one or both of the electrical generator 212 and the electrolyte pump 214. The electrolysis system 200 is thus an efficient way of utilising the energy of the oxygen that is produced at high pressures together with the high pressure hydrogen in the electrolyser 202 described in more detail with reference to FIG. 1. In other words, the energy for producing pressurized hydrogen within the electrolyser 202 is not wasted in the electrolysis system 200 of FIG. 2. Rather, the potential energy of the pressurized oxygen is used (as kinetic energy of the gas flow) to drive one or both of the electrical generator 212 and the electrolyte pump 214. It should be understood that any electrical energy generated by the electrical generator 212 in this way may either be supplied to the electrolyser 202 or stored, either by transferring it back to the gird or to any other electrical energy storage devices, such as batteries, and capacitors, etc. The present disclosure is not restricted to embodiments in which the electrical generator 212 and/or the electrolyte pump 214 are powered by the oxygen provided by the second gas outlet port 206 of the electrolyser 202. Rather, in some embodiments, it may be the high pressure hydrogen at the first gas outlet port 204 of the electrolyser 202 that is used to power one or both of the electrical generator 212 and the pump 214. This is particularly the case, if some of the pressure of the hydrogen stored within the electrolyser 202 needs to be relieved before storing the hydrogen for further use. In some embodiments, both the pressurised hydrogen and the pressurised oxygen may be used to drive the electrical generator and/or the pump 214.

In some embodiments (not shown), only the electrical generator 212 may be driven by the oxygen provided by the second gas outlet port 206, whereas the pump 214 is driven by the hydrogen provided via the first gas outlet port 204 of the electrolyser 202. In yet another embodiment, only the pump 214 may be driven by the oxygen gas provided by the second gas outlet port 206, whereas only the electrical generator 212 may be driven by the hydrogen gas provided via the first gas outlet port 204. In another embodiment, only the electrical generator 212 or only the electrolyte pump 214 is powered by one of the gases produced by the electrolyser, i.e. the hydrogen or oxygen gases. Accordingly, in one example, the electrical generator 212 may be driven by the oxygen provided by the second gas outlet port 206, whereas the pump 214 may be driven by electricity, supplied either via the electrical generator 212 or via a mains power supply. If, in some embodiments/settings, only the electrolyte pump 214 is driven by gas provided via the second gas outlet port 206, then the first oxygen pipe 210 may be directly connected to the pump 214, thereby by-passing the electrical generator 212 (not shown).

Turning back to the embodiment as shown in FIG. 2, the electrolyte pump 214 is exclusively driven by gas flow. During operation of the electrolyser 202, such a gas flow is preferably provided by the second gas outlet port 206, i.e. the oxygen gas flow flowing through the first and second oxygen lines 210, 216 towards the oxygen outlet 218. However, as will be appreciated, during start-up of the electrolyser 202, pressurized oxygen will not yet be available. Yet, the electrolyte pump 214 will be required to provide the electrolyser 202 with pressurized electrolyte water via the electrolyte supply line 224 before pressurized oxygen and hydrogen can be produced.

During the above start-up period, the electrolyte pump 214 may be provided with gas flow via the electrical generator 212. To this end, the electrical generator 212 may be a generator-motor, which can be operated in two operating modes. A first operating mode is for converting kinetic energy of gas flow into electricity (described above). A second mode is for using electricity to drive the gas piston(s) of the electrical generator 212 for providing a gas flow to the pump 214. The second mode may also be referred to as a start-up mode. During the start-up mode, the electrical generator 212 may be provided with electricity via the mains power supply 248. Of course, it is also feasible to supply the electrical generator with electricity via other power supplies, such as batteries or solar panels. At the same time, the mains power supply 248 (or battery/solar panels) will supply electrical power to the AC/DC converter 246 to provide the electrodes of the electrolyser 202 with the required DC current.

The electrical generator 212 is connected to an air inlet 250. During the start-up mode, the gas piston(s) of the electrical generator 212 may draw environmental air in through the air inlet 250 to provide an airflow discharged via the outlet 213 into the second oxygen line 216. The so-created start-up airflow is then provided to the electrolyte pump 214 via the gas inlet 215. The airflow will then be used by the pump 214 to provide electrolyte water to the electrolyser via the electrolyte water supply line 224. As gas supplied by the electrical generator (in this scenario used as a motor to drive the gas piston(s)) moves through the turbine of the pump 214, it will exit the pump 214 via its outlet 217 and be exhausted via air vent 220, e.g. back into the atmosphere. As will be appreciated, a directional control valve may be arranged between the air vent 220 and the oxygen outlet 218, such that the air vent 220 is only open during start-up of the electrolysis system 200.

Once the electrolyser 202 is fully operational, i.e. has produced pressurized oxygen and hydrogen, the electrical generator 212 may be switched back into its first mode, to be driven by an oxygen gas flow provided via the second gas outlet port 206. To this end, the electrical generator 212 may shut off the air inlet 250 and open oxygen inlet 211.

The electrolysis system 200 shown in FIG. 2 may also comprise a heat exchanger 226 arranged within the electrolyte water supply line 224, i.e. downstream of the electrolyte pump 214. The heat exchanger 226 is configured to preheat electrolyte water supplied to the electrolyser 202 by the pump 214. To this end, the heat exchanger 226 may use heat generated by the pump 214 to preheat the electrolyte water. In particular, the heat exchanger 226 may be connected to the pump 214 via a cooling fluid line 228, as schematically represented in FIG. 2. Of course, it will be appreciated the cooling line 228 is representative of a cooling circuit in which cold cooling fluid is circulated from the heat exchanger 226 to the pump 214 and heated by the heat generated during operation of the pump 214.

The so-heated cooling fluid is then returned at higher temperature to the heat exchanger 226 and used to preheat the electrolyte water within electrolyte water supply line 224.

The heat exchanger 226 may also be connected to the electrical generator 212 via a second cooling fluid line 230, schematically represented in FIG. 2. The cooling fluid line 230 is representative of a cooling circuit in which cold cooling fluid is transferred from the heat exchanger 226 towards the electrical generator 212. Cold cooling fluid is then heated by heat generated by the electrical generator 212 during operation and returned at higher temperature to the heat exchanger 226. This so-heated cooling fluid supplied via the second cooling line 230 is then used to preheat the electrolyte water within the electrolyte water supply line 224.

The heat exchanger 226 may also be connected to the AC/DC converter 246 via a third cooling fluid line 232, representative of a cooling fluid circuit, similar to the cooling fluid circuits described above. Accordingly, cold cooling fluid may be provided from the heat exchanger 226 towards the AC/DC converter 246 and may be heated by the heat generated during conversion of AC currents into DC currents at the converter 246. The so-heated cooling fluid is then returned to the heat exchanger 226 in order to pre-heat the electrolyte water within the electrolyte water supply line 224.

The so pre-heated electrolyte water increases the efficiency of the electrolysis process within the electrolyser 202 and thereby further improves the overall efficiency of the electrolysis system according to the present disclosure.

In electrolysis applications that require low temperatures such as below zero electrolysis the heat exchanger 226 may also be a heat pump or refrigerant circuit that actively provides cooling of the electrolyte water that is supplied to the electrolyser 202 or any other areas requiring cooling. This cooling effect can help retain heavier hydrogen isotopes in the electrolyte for separation from the input water provided via a fluid supply 222. In other words, in this embodiment, the heat exchanger 226 may be an (air) heat pump configured to remove heat from the electrolyte water within the electrolyte water supply line 224. This heat may then be dispersed via cooling fluid lines (not shown) that act to transfer the heat taken from the electrolyte water to the surrounding air, much like a refrigerator.

Using a heat pump to cool the electrolyte water prior to suppling the latter to the electrolyser 202 is particularly beneficial in the separation of isotopes, such as deuterium and tritiated water. In one embodiment, a heat pump may be connected to the hydrogen or oxygen lines 208, 210 in order to transfer heat to the cooled hydrogen or oxygen gas. In this regard, it will be appreciated that gas expanding when leaving the gas outlets ports 204, 206 of the electrolyser 202 will be cooled according to the Joule Thomson effect. The so-cooled gas may thus be used by the heat pump as a heat sink for heat removed from other parts of the system 200, such as heat of the electrolyte water within the electrolyte water supply line 224.

The electrolyte pump 214 is connected or selectively connectable to an electrolyte fluid supply 222 similar to the electrolyte water supply line 162 described in FIG. 1. In particular, an electrolyte water inlet of the electrolyte pump 214 may be provided with additional electrolyte water to compensate for electrolyte water being decomposed by the electrolyser 202 during operation.

In the above, a start-up procedure has been described that uses the electrical generator as a motor to drive one or more gas pistonsof the electrical generator 212 so as to draw air via the air inlet 250 towards the electrolyte pump 214. In this embodiment of the start-up procedure, the electrolyte pump 214 is exclusively powered by gas flow (oxygen during production, air during start-up) and does not require any other forms of power input.

In alternative examples, the electrolyte pump 214 may comprise additional actuators that may be used during start-up of the electrolysis system 200. In one example, the electrolyte pump 214 may comprise a hand lever which allows the operator to manually pump electrolyte fluid into the electrolyser 202 until the electrolyser is fully operational. The hand-operated lever will be in addition to the gas flow operated turbine. Once the electrolyser is fully operational, the pump 214 may be driven by gases supplied via these second gas outlet port 206 or via electricity inputs supplied by the generator 212 and/or mains power supply 248, as described above.

In another example, the electrolyte water pump 214 may comprise an electric motor in addition to the turbine discussed above. The electric motor may be used to drive the electrolyte pump, which is thus powered by electricity during start-up of the electrolysis system 200. In this example, the electric motor of the electrical pump 214 may be provided with electrical power via the mains power supply 248 (or other means of electrical power supply) described above.

FIG. 3 shows another embodiment of the electrolysis system according to the present disclosure. Parts of the electrolysis system 300 shown in FIG. 3 that correspond with parts of the electrolysis system 200 are labelled with corresponding reference signs increased by "100".

Similar to the electrolysis system 200 shown in FIG. 2, the electrolysis system 300 comprises an electrolyser 302 with first and second gas outlet ports 304, 306. A hydrogen line 308 is connected to the first gas outlet port 304, and a first oxygen line 310 is connected to the second gas outlet port 306. The electrolysis system 300 comprises an electrical generator 312 connected to the second gas outlet port 306 via the oxygen line 310. The electrical generator 312 is electrically connected or connectable to a mains power supply 348 (or battery/capacitor/super capacitor, etc.) and an AC/DC converter 346 via electrical lines 340, 342, 344. An electrolyte pump 314 is connected to the electrolyser 302 via an electrolyte water supply line 324. An inlet port of the pump 314 is connected to a drain line 338 for electrolyte water drained from the first and second gas collection chambers via drain ports 334, 336. A second inlet port of the pump 314 is connected to an electrolyte water supply 322. Of course, the electrolyte water supply 322 may also be arranged within a drain line 338, similar to the arrangement shown in FIG. 1.

The electrolyte pump 314 can be a single pump that inputs water to be electrolysed and circulates the electrolyte water in the system. Alternatively, the electrolyte pump 314 may be representative of two or more pumps that charge the system with water to be electrolysed and circulate the electrolyte. The two or more pumps can be separate to each other and powered separately from different energy supplies or they can be connected by a common shaft for shared power input.

When the electrolyser 302 is at low pressure and needs to be charged with water, air needs to be purged from the electrolyser 302. A first pump with a high volume flow and low pressure may be part of the electrolyte pump 314 for purging of air form the electrolyser 302. When the air has been purged and electrolyte pressure needs to be increased to a high pressure of 20bar or more, a second pump that is part of the electrolyte pump 314 may be used. The second pump of the electrolyte pump 314 preferably has a low volume flow and high pressure.

A heat exchanger 326 is arranged within the electrolyte water supply line 324.

The heat exchanger 326 is configured to pre-heat electrolyte water supplied by the electrolyte pump 314 to the electrolyser 302. To this end, the heat exchanger 326 is connected to the pump via a first cooling fluid line 328, to the electrical generator 312 via a second cooling fluid line 330 and to the AC/DC converter 346 via a third cooling fluid line 332.

In contrast to the embodiment shown in FIG. 2, the embodiment of FIG. 3 comprises an electrolyte pump 314 that is driven mechanically, rather than pneumatically during operation of the electrolyser 302. The electrolyte pump 314 may thus be connected to the electrical generator 312 via a drive shaft 316. The drive shaft 316 may be connected to the electrical generator 312 and/or the electrolyte pump 314 via one or more clutches, such that rotational energy of the electrical generator 312 is only transferred to the pump 314 when the one or more clutches are closed. Of course, it will be appreciated that the present disclosure is not limited to the specific type of mechanical actuation, such as the rotary actuation via the drive shaft. Rather, it is also feasible that the electrical generator is used to drive a piston of a piston pump, vein pump, or any other known pumping means (not shown).

The electrical generator 312 of the embodiment shown in FIG. 3 comprises a gas outlet port 313 that is selectively connectable to either an oxygen outlet 318 or an air vent 320 similar to the outlets/vents 218, 220 described above.

During operation of the electrolyser 302, pressurized hydrogen and oxygen may be generated within the gas collection chambers discussed with reference to FIG. 1. In one example, pressurized oxygen may be released via the second outlet port 306 towards oxygen line 310 and thus towards the electrical generator 312. This flow of oxygen may then be used to drive the electrical generator 312 via one or more gas piston(s) as has been discussed in connection with FIG. 2 above. Any oxygen leaving the turbine of the electrical generator 312 via the gas outlet port 313 will then be transferred to an oxygen storage tank or directly to the end user via the oxygen outlet 318.

The electrical generator 312 of the embodiment in FIG. 3 has three operational states. In a first operational state, the electrical generator 312 converts the kinetic energy of the oxygen within the oxygen line 310 into electrical power that can either be supplied back to the electrolyser 302 via the AC/DC converter 346, back to the grid via the mains power supply 348, or back to other electrical devices of the system 300, such as a heat pump, fan, battery, thermos-regulators, displays, etc. In a second mode of operation, the electrical generator may act as a pneumatically operated gas piston for rotating the drive shaft 316 by means of the oxygen flow within the oxygen line 310. In a third mode of operation, the electrical generator 312 may be operated as an electric motor, using electricity provided by the mains power supply 348 to drive the shaft 316 and thus power the electrolyte pump 314.

During normal operation of the electrolyser 302, i.e. when sufficient amounts of pressurized oxygen are available, the electrical generator 312 will produce electrical power as long as the electrolyte pump 314 is not in use. Once the electrolyser 302 needs to be supplied with additional pressurized electrolyte water, the pump 314 will be activated (e. g. via a control unit discussed above). At this time, the electrical generator 312 is switched into its second mode of operation, in which the oxygen flow within oxygen line 310 is used to rotate drive shaft 316 via the gas piston(s) of the electrical generator 312 to actuate the pump 314. Once the electrolyser has been supplied with sufficient amounts of pressurized electrolyte water, the electrolyte pump 314 is deactivated and the electrical generator 312 is returned into its first operational state. This can be also done automatically with the use of a squirrel cage motor acting as a motor generator. When there is insufficient gas pressure the motor will draw power from 348 and when there is sufficient gas pressure the motor will convert to a generator to generate power back to 348 as well as direct DC generation for usage for example in the electrolyser or battery or other storage.

During start-up of the electrolysis system 300, i.e. when no or insufficient amounts of pressurized oxygen and hydrogen are available, the electrical generator 312 is operated in its third operational mode. In other words, during start-up of the electrolysis system, electrical power is provided to the electrical generator 312 via the mains power supply 348. The electrical generator 312 is then used as an electric motor for driving the drive shaft 316. The electrical generator 312 is used in its third operational state as long as it takes for the electrolyser 302 to produce sufficient amounts of pressurized hydrogen and oxygen, such that the electrical generator 312 can be switched back into its first operational state for producing electrical energy for the electrolysis process.

Fig. 4 shows a schematic representation of an electrolysis system according to another embodiment of the present disclosure. The electrolysis system 400 of FIG. 4 comprises an electrolyser 402 comprising an electrolyte water inlet, a first gas outlet 404 and a second gas outlet 406.

An electrical generator 412 is connected to the second gas outlet 406 of the electrolyser 402 and configured to be able to be powered, at least in part, by gas flow provided via the second gas outlet 406. Similar to the embodiments described above, the second gas outlet 406 may provide pressurized oxygen to the electrical generator 412. The oxygen may be provided to the electrical generator 412 via an oxygen line 410 and a gas inlet 411 of the electrical generator 412.

As represented in FIG. 4, the electrical generator 412 comprises two parts. In particular, the electrical generator 412 comprises a motor 412a, preferably a squirrel cage motor. The electrical generator 412 further comprises a compressor/expander 412b. The compressor/expander 412b has a gas inlet 411 connected to the oxygen line 410. A gas outlet 413 of the compressor/expander 412b is connected to an oxygen outlet 418, similar to what has been described with reference to FIG. 3 above.

The motor 412a of the electrical generator 412 is connected to the compressor/expander 412b via a common drive shaft 416. Accordingly, rotational movement of either of the two parts of the electrical generator 412 may cause the respective other part to be driven at the same rotational speed by virtue of the common drive shaft 416. Of course, it is also possible to implement a transmission (not shown in FIG. 4) causing the compressor/expander 412b to rotate at a different speed to the motor 412a.

As is known in the art, squirrel cage motors, such as motor 412a can be used as motors or generators respectively. To this end, the motor 412a is connected to a power grid via line 440. For the motor 412a to work as a generator for producing electricity, the motor 412a needs to be spun faster than its stator's synchronous speed. In the example of FIG. 4, the motor 412a may have a synchronous speed of 1500 rpm. Accordingly, if the drive shaft 416 causes the motor 412a to spin at a speed higher than 1500 rpm, the motor will start generating electricity, which may be used to supply power to the electrodes of the electrolyser or any other electrical device of the electrolysis system 400 as has been described above or battery storage, electrical energy grid export etc. If the compressor/expander 412a is not spinning fast enough to drive the drive shaft 416 at a rotational speed of 1500 rpm or above, the motor 412a will still spin at a constant rotational speed of 1500 rpm, due to its connection with the power grid or internal energy storage/battery. In this scenario, it will be the motor 412 that drives the common drive shaft 416 and thus determines the rotational speed of the common drive shaft 416.

During normal operation of the electrolysis system 400, the electrolyser 402 will provide pressurized oxygen at the second outlet 406, which will be provided to the compressor/expander 412b via the oxygen line 410. Pressurized oxygen expanding through the compressor/expander 412b will cause a turbine of the compressor/expander 412b to rotate the drive shaft 416 at a speed that is higher than the synchronous speed of the motor's stator, e.g., higher than 1500 rpm.

Accordingly, during normal operation of the electrolysis system 400, the electrical generator 412 will act to generate electricity due to the kinetic energy of the oxygen gas released from the electrolyser via the second gas port 406.

The electrolysis system 400 of FIG. 4 may further comprise an electrolyte pump 414. The electrolyte pump 414 is also connected to the common drive shaft 416.

The electrolyte pump 414 is connected via an outlet port with an electrolyte water supply line 424. The electrolyte water supply line 424 supplies pressured electrolyte water to the electrolyte water inlet of the electrolyser 402. An inlet port of the electrolyte pump 414 is connected to an electrolyte drain line 428, similar to drain lines 228, 328 described above.

During normal operation of the electrolyser 402, the drive shaft 416 is powered by the compressor/expander 412b of the electrical generator 412. Accordingly, the drive shaft 416 then drives the motor 412a of the electrical generator 412 and, at the same time, the electrolyte pump 414.

Due to the use of a squirrel cage motor 412a that is connected to the grid via a line 440, the common drive shaft 416 of the electrolysis system 400 will always be driven at the synchronous speed of the stator of the motor 412a, e.g., 1500 rpm. This is the case, even if the pressure of the oxygen provided by the electrolyser 402 is not sufficient to drive the compressor/expander 412b.

Accordingly, the electrolysis system 400 shown in FIG. 4 does not require any changes in operating modes to switch between start-up operations and normal operation of the system 400. Rather, the motor 412a will use power provided by the grid to drive the pump at the motor's synchronous speed, e.g., around 1500 rpm, as long as gas flowing through the compressor/expander 412b has a flow rate that is not sufficient to create a rotational speed of more than 1500 rpm.

Once the rotational speed generated by expansion of gas through the compressor/expander 412b of the electrical generator 412 exceeds 1500 rpm, the motor 412a no longer powers the common drive shaft 416 but is driven by the common drive shaft 416 and able to produce electricity, whilst, at the same time, the drive shaft 416 powers the pump 414 to provide pressured electrolyte to the electrolyser 402.

The electrolysis system 400 of FIG. 4 further comprises an optional gas compressor 409, similar to the gas compressor 209 shown in FIG. 2. The gas compressor 409 comprises an inlet port connected to the first gas outlet 404 of the electrolyser 402 via a hydrogen line 408. The gas compressor 409 comprises a gas outlet connected to a hydrogen output 410, which may in turn be connected to a hydrogen storage tank (not shown).

The gas compressor 409 of the embodiment shown in FIG. 4 is connected to the common drive shaft 416. Accordingly, the common drive shaft 416 may also be used to power the gas compressor 409 in order to increase the pressure of the hydrogen output provided by the electrolyser 402. During normal operation of the electrolyser, the pressurized oxygen gas provided by the second gas outlet 406 of the electrolyser 402 will, therefore, be used to drive the motor 412a to produce electricity, the pump 414 to provide pressured electrolyte, and the gas compressor 409 to increase the outlet pressure of the hydrogen produced by the electrolyser 402. In some embodiments, the common drive shaft 416 may be used to drive said motor 412a, pump 414, and gas compressor 409 at the same time. However, the system 400 may comprise means for selectively engaging and disengaging the motor 412a, the electrolyte pump 414, and the gas compressor 409 from the drive shaft 416.

The electrolysis system 400 of FIG. 4 further comprises an optional DC generator 35 460. The DC generator 460 is connected to the common drive shaft 416 and may thus also be driven by the compressor/expander 412b of the electrical generator 412 during normal operation and by the motor 412a of the electrical generator 412 during the start-up procedure. The DC generator 460 may produce DC currents in response to rotational power provided via the common drive shaft 416. This direct current may be used to, at least partly, power electrodes of the electrolyser 402.

In another embodiment the generator 460 can be an AC or even an AC or DC switchable generator depending on requirements. In such embodiments it also can be a generator that produces different frequency hertz outputs suitable for different types of higher or lower frequency electrical usages, for instance for high frequency electrolysis where useful frequencies and voltages exceed those on national grids by a large amount, e.g. 900V and hertz in the hundreds. Within all the potential embodiments of the 460 generator there can be multi-pole configurations.

As follows from the above, the electrolysis system 400 of FIG. 4 comprises multiple means for recycling some or all of the potential energy stored in the pressurized oxygen provided by the electrolyser 402. In particular, the potential energy of the oxygen may be used to drive one or more of the electrical generator 412 (i.e., motor 412a), the electrolyte pump 414, the gas compressor 409, and/or the DC generator 460.

A control unit may be provided to determine which of the above energy recycling devices may be used during different times of operation, as the requirements of the system may be. In one example, the control unit may determine that the electrolyte pump 414 only requires activation intermediately, such that the electrolyte pump 414 may be disengaged from the common drive shaft 416 as long as the electrolyte water pressure within the electrolyser 402 is sufficient. Similarly, the gas compressor 409 may only be engaged with the drive shaft if the hydrogen pressure supplied by electrolyser 402 is insufficient.

Turning to FIG. 5 there is shown a schematic flow diagram of a method according to an embodiment of the present disclosure. The method 500 shown in FIG. 5 is a method of recycling energy in an electrolysis system, such as the systems shown in Figures 2, 3 and 4.

In a first step 502, the method comprises supplying electrolyte water to the electrolyser. The step may be performed by an electrolyte pump, such as pumps 214, 314 described above. Alternatively, electrolyte water may be supplied to the electrolyser via a pressurized electrolyte reservoir that is selectively connectable to the electrolyser. This could also be a metal hydride storage system that on containment can evolve higher pressures of output pressurized gas'.

In a second step 504, electrolyte water is decomposed into pressurized gases, preferably into pressurized hydrogen and oxygen. This may be achieved by any electrolyser that produces pressurized gases. It will be appreciated, however, that electrolysers that produce gases at atmospheric pressure are generally not suitable for this method. An example of a suitable electrolyser is shown and described with reference to FIG. 1.

In a third step 506, the method comprises supplying the electrical generator and/or the electrolyte pump with at least one of the pressurized gases to power the electrical generator and/or the electrolyte pump. In a preferred embodiment, the electrical generator and/or the electrolyte pump may be provided with pressurized oxygen produced by the electrolyser, because oxygen is typically not required to be provided to the end user at high pressures. Some or all of the potential energy stored within the pressurized oxygen may be converted into kinetic energy that is then used to drive one or both of the electrical generator and the electrolyte pump.

Electrical energy produced by the electrical generator may be used in various ways according to the method of the present disclosure. In one example, the electrical energy may be used to drive the electrolyser. To this end, the electrical energy may be supplied to an AC/DC converter. In an alternative arrangement, the electrical generator may be configured to produce AC or DC power and supply DC power directly to the electrolyser to drive or at least support the electrolysis process. In this regard, it should be understood that in some examples, the electric power produced by the electrical generator may not be sufficient to sustain the electrolysis process alone. In such cases, the electrolyser may also be supplied with electrical energy via a mains power supply at the same time. In alternative embodiments, the electrical energy provided by the electrical generator may directly be supplied back to the power grid or used to power any other electrical devices of the electrolysis system. In another embodiment, the electricity may power a compressor to further pressurize one of the outlet gas streams or storage vessels, such as the hydrogen gas.

The following clauses show further non-claimed variants of the present disclosure: 1. An electrolysis system for generating hydrogen, the system comprising: an electrolyser comprising an electrolyte water inlet, a first gas outlet and a second gas outlet, an electrical generator configured to generate electricity, preferably for the electrolyser, said electrical generator being connected to the first and/or second gas outlet of the electrolyser and configured to be powered, at least in part, by gas flow provided via the first and/or second gas outlet, an electrolyte pump for supplying the electrolyser with electrolyte water, wherein the electrical generator is a motor-generator comprising a first mode for generating electricity and a second mode for using electricity to drive the electrolyte pump.

2. The electrolysis system of Clause 1, wherein the electrolyte pump is connected to the first and/or second gas outlet of the electrolyser and configured to be powered, at least in part, by gas flow provided via the first and/or second gas outlet.

3. The electrolysis system of Clause 2, wherein the electrolyte pump is configured to be powered, at least in part by electricity generated via the electrical generator.

4. The electrolysis system of Clause 2 or 3, wherein the electrolyte pump is configured to be powered, at least in part, by electricity provided via an external power supply, such as a mains power supply.

5. The electrolysis system of any one of Clauses 2 to 4, wherein the electrolyte pump is connected to the first and/or second gas outlet in series with the electrical generator, preferably downstream of the electrical generator.

6. The electrolysis system of any one of Clauses 1 to 5, wherein the electrical generator is configured to be connected to an electrical power supply and configured to feed surplus electrical energy that is not required by the electrolyser back to the power supply.

7. The electrolysis system of Clause 6, wherein the electrical power supply is configured to provide the electrical generator with electrical energy during startup of the electrolyser.

8. The electrolysis system of any one of Clauses 1 to 7, wherein the electrical generator is reversible to function as a compressor during start-up of the electrolyser for supplying the electrolyte pump with gas flow during start-up.

9. The electrolysis system of any one of Clauses 1 to 8, wherein the electrical generator comprises an air inlet for selectively providing the electrical generator with air to be compressed during the start-up of the electrolyser.

10. The electrolysis system of any one of Clauses 1 to 9, comprising an air vent selectively connectable to a gas outlet of the electrolyte pump, preferably during start-up of the electrolyser.

11. The electrolysis system of any one of Clauses 1 to 10, comprising a gas output port selectively connectable to a gas outlet of the electrolyte pump, preferably during normal operation of the electrolyser.

12. The electrolysis system of any one of Clauses 1 to 11, comprising an AC/DC converter arranged between the electrical generator and the electrolyser.

13. The electrolysis system of any one of Clauses 1 to 12, comprising a heat exchanger configured to pre-heat or cool electrolyte water supplied to the electrolyser via the electrolyte pump.

14. The electrolysis system of Clause 13, wherein the heat exchanger is configured to transfer heat from the electrical generator and/or an electrolyte 30 pump and/or an AC/DC converter of the system.

15. The electrolysis system of any one of Clauses 1 to 14, wherein the first gas outlet is a Hydrogen outlet and the second gas outlet is an Oxygen outlet, and wherein the electrical generator is connectable to the second gas outlet such that the electrical generator is powered by oxygen gas flow provided via the second gas outlet.

16. The electrolysis system of Clause 15, wherein the electrolyser is configured to control a pressure of the oxygen provided via the second gas outlet to be between 1bar and 1000bar, preferably 10bar to 1000bar, more preferably 100 bar to 1000 bar.

17. The electrolysis system of Clause 16, wherein the electrolyte pump is configured to supply the electrolyser with electrolyte water at a pressure higher than a gas pressure at the second gas outlet, preferably at least 5 bar above the gas pressure at the second gas outlet.

18. The electrolysis system of any one of Clauses 1 to 17, wherein the first or second gas outlet port is connected to a gas booster to increase the pressure of a gas provided via the other gas outlet port or to increase the pressure of a gas storage accumulator.

19. The electrolysis system of any one of Clauses 1 to 18, comprising a metal hydride storage for generation of pressurized hydrogen, said electrical generator being connected a gas outlet of the metal hydride storage and configured to be powered, at least in part, by gas flow provided via said gas outlet, wherein gas provided via the metal hybride storage preferably has a pressure of 1 bar 1000bar, preferably 10bar to 1000bar, more preferably 100 bar to 1000 bar.

20. A method of recycling energy in an electrolysis system comprising an electrolyser, an electrical generator for providing electricity to the electrolyser, and an electrolyte pump for supplying electrolyte water to the electrolyser, the method comprising: supplying the electrolyser with pressurized electrolyte water; decomposing the electrolyte water into pressurised gases, preferably into pressurized hydrogen and oxygen; supplying the electrical generator and/or the electrolyte pump with at least one of the pressurised gases to power the electrical generator and/or the electrolyte pump.

21. The method of Clause 20, comprising supplying the electrical generator and/or the electrolyte pump with pressurized oxygen produced by the electrolyser.

22. The method of Clause 20 or 21, comprising supplying at least parts of the electrical energy produced by the electrical generator to the electrolyser.

23. An electrolysis system for generating hydrogen, the system comprising: an electrolyser comprising an electrolyte water inlet, a first gas outlet and a second gas outlet, an electrolyte pump for supplying the electrolyser with electrolyte water, said electrolyte pump being connected to the first and/or second gas outlet of the electrolyser and configured to be powered, at least in part, by gas flow provided via the first and/or second gas outlet.

24. The electrolysis system of Clause 23, comprising an electrical generator configured to generate electricity for the electrolyser, said electrical generator being connected to the first and/or second gas outlet of the electrolyser and configured to be powered, at least in part, by gas flow provided via the first and/or second gas outlet 25. The electrolysis system of Clause 24, wherein the electrolyte pump is connected to the first and/or second gas outlet in series with the electrical generator, preferably downstream of the electrical generator.

Claims

ELECTROLYSIS SYSTEM AND METHOD FOR ENERGY RECYCLINGClaims 1. A method of recycling energy in an electrolysis system comprising an electrolyser and an electrolyte pump for supplying electrolyte water to the electrolyser, the method comprising: - supplying the electrolyser with pressurized electrolyte water; - decomposing the electrolyte water into pressurised gases, preferably into pressurized hydrogen and oxygen; - supplying the electrolyte pump with at least one of the pressurised gases to power the electrolyte pump.
2. The method of Claim 1, comprising supplying the electrical generator and/or the electrolyte pump with pressurized oxygen produced by the electrolyser.
3. The method of Claim 1 or 2, comprising supplying at least parts of the electrical energy produced by the electrical generator to the electrolyser.
4. An electrolysis system for generating hydrogen, the system comprising: an electrolyser comprising an electrolyte water inlet, a first gas outlet and a second gas outlet, - an electrolyte pump for supplying the electrolyser with electrolyte water, said electrolyte pump being connected to the first and/or second gas outlet of the electrolyser and configured to be powered, at least in part, by gas flow provided via the first and/or second gas outlet.
5. The electrolysis system of Claim 4, comprising an electrical generator configured to generate electricity for the electrolyser, said electrical generator being connected to the first and/or second gas outlet of the electrolyser and configured to be powered, at least in part, by gas flow provided via the first and/or second gas outlet
6. The electrolysis system of Claim 5, wherein the electrolyte pump is connected to the first and/or second gas outlet in series with the electrical generator, preferably downstream of the electrical generator.
7. The electrolysis system of any one of Claims 1 to 4, wherein the electrolyte pump is connected to the first and/or second gas outlet in series with an electrical generator, preferably downstream of the electrical generator.
8. The electrolysis system of Claim 7, wherein the electrical generator is configured to drive the electrolysis process and is connected to an electrical power supply and configured to feed surplus electrical energy that is not required by the electrolyser back to the power supply.
9. The electrolysis system of Claim 8, wherein the electrical power supply is configured to provide the electrical generator with electrical energy during start-up of the electrolyser.
10. The electrolysis system of any one of Claims 7 to 9, wherein the electrical generator is reversible to function as a compressor during start-up of the electrolyser for supplying the electrolyte pump with gas flow during start-up.
11. The electrolysis system of any one of Claims 7 to 10, wherein the electrical generator comprises an air inlet for selectively providing the electrical generator with air to be compressed during the start-up of the electrolyser.
12. The electrolysis system of any one of Claims 4 to 11, comprising an air vent selectively connectable to a gas outlet of the electrolyte pump, preferably during start-up of the electrolyser.
13. The electrolysis system of any one of Claims 4 to 12, comprising a gas outlet port selectively connectable to a gas outlet of the electrolyte pump, preferably during normal operation of the electrolyser.
14. The electrolysis system of any one of Claims 4 to 13, comprising a heat exchanger configured to pre-heat or cool electrolyte water supplied to the electrolyser via the electrolyte pump.
15. The electrolysis system of Claim 14, wherein the heat exchanger is configured to transfer heat from the electrical generator and/or an electrolyte pump and/or an AC/DC converter of the system.
16. The electrolysis system of any one of Claims 4 to 15, wherein the first gas outlet is a Hydrogen outlet and the second gas outlet is an Oxygen outlet, and wherein the electrical electrolyte pump is connectable to the second gas outlet such that the electrolyte pump is powered by oxygen gas flow provided via the second gas outlet.
17. The electrolysis system of Claim 16, wherein the electrolyser is configured to control a pressure of the oxygen provided via the second gas outlet to be between lbar and 1000bar, preferably 10bar to 1000bar, more preferably 100 bar to 1000 bar.
18. The electrolysis system of Claim 17, wherein the electrolyte pump is configured to supply the electrolyser with electrolyte water at a pressure higher than a gas pressure at the second gas outlet, preferably at least 5 bar above the gas pressure at the second gas outlet.
19. The electrolysis system of any one of Claims 4 to 18, wherein the first or second gas outlet is connected to a gas booster to increase the pressure of a gas provided via the other gas outlet or to increase the pressure of a gas storage accumulator.
20. The electrolysis system of any one of Claims 4 to 19, comprising a metal hydride storage for generation of pressurized hydrogen, said electrolyte pump being connected a gas outlet of the metal hydride storage and configured to be powered, at least in part, by gas flow provided via said gas outlet, wherein gas provided via the metal hydride storage preferably has a pressure of 1 bar 1000bar, preferably 10bar to 1000bar, more preferably 100 bar to 1000 bar.