Patent Application
20240093396
The present invention relates to electrolysis systems with asymmetrical circulation, which can be operated under high-pressure conditions. In particular, the invention relates to a device for providing a gas component and to a vehicle with such a device.
High-pressure gas storage tanks are an essential constituent part for the use of hydrogen-powered systems. Conventional electrolysis systems for providing hydrogen are operated at maximum pressures of up to 40 bar, additional pressurization for the subsequent storage of the hydrogen being necessary in order to be able to store the hydrogen effectively. This leads to a reduction in efficiency and reliability as well as to an increase in the mass and volume of the hydrogen-powered systems. Furthermore, complex delivery pumps are generally needed in order to provide a reactant for the electrolysis, which may in turn lead to a higher weight or a lower system reliability. Likewise, existing electrolysis systems cannot be operated under microgravity conditions, which restricts the possible uses of such systems.
EP 2 463 407 B1 and US 2013/0 313 126 A1 describe an electrolysis method with an electrode-membrane-electrode arrangement, which comprises two porous electrodes with a porous intermediate membrane or an ion exchange membrane. The liquid electrolyte is in this case supplied directly into the electrode-membrane-electrode arrangement.
It is an object of the present invention to improve the efficiency of systems for the electrolytic provision of gas components.
This object may be achieved by the subject matter of one or more embodiments described herein. Exemplary embodiments may also be found in the following description.
According to one aspect, a device for providing a gas component is proposed. The device comprises an electrolysis unit with a first chamber and a second chamber, the first chamber being separated from the second chamber by a separating unit. The first chamber is configured to receive an electrolyte, for example together with a reactant in the form of water, and to provide a first gas component, for example hydrogen. The second chamber is configured to provide a second gas component, for example oxygen. A pressure inside the second chamber is in this case greater than a pressure inside the first chamber, an electrolyte flow of the electrolyte taking place only in the first chamber and the electrolyte being prevented from entering the second chamber, so as to keep the second gas component that is provided separate from the electrolyte. The device furthermore comprises a phase separating unit, which is configured to separate the first gas component from the electrolyte so as to provide the first gas component, for example in a pure form. After the separation, the first gas component may for example be delivered to a tank or a consumer, it being possible for the electrolyte to be returned to the electrolysis unit after the separation. Likewise, the second gas component may also be delivered to a tank or a consumer after the provision.
The aforementioned device together with the electrolysis unit may be operated at high pressures of, for example, more than 50 bar or even more than 100 bar, so that additional pressurization before storage of the gas components that are provided is avoided or simplified. Likewise, a very high gas quality, or gas purity, may be achieved both for the first gas component that is provided and for the second gas component that is provided. Water vapor possibly produced during the electrolysis may likewise be abated.
With the device according to the invention, in particular, a higher system efficiency is achieved by additional pressurization components being obviated, since the electrolysis itself can already be operated at the pressure required for intended use. In other words, a phase separation during the electrolysis at high pressure may be disposed by using the device. For example, the electrolyte present in liquid form, which is located only in the first chamber, can be kept separated from the second gas component located in the second chamber.
With the device according to the invention, electrolyte circulation is therefore disposed only inside the first chamber, while no electrolyte circulation takes place inside the second chamber. In other words, asymmetrical electrolyte circulation is therefore disposed. In the first chamber, a diphasic flow consisting of the liquid electrolyte and the first gas component contained therein may be formed.
The electrolysis unit may be disposed in the form of a cell that comprises a closed unit having one electrolyte delivery and two electrolyte discharges, the first discharge being intended for a combined electrolyte-gas component discharge and the second discharge being intended for a pure gas discharge. The combined electrolyte-gas component discharge may comprise release of the electrolyte together with the first gas component that is provided by the electrolysis from the first chamber. The second discharge may comprise release of the second gas component that is provided from the second chamber. The electrolysis unit may have a frame structure, which encloses the two chambers. This may be configured to absorb structural loads, for example in order to form a kind of pressure vessel.
The electrolysis unit may furthermore have two electrodes, that is to say a cathode and an anode. A reaction may respectively take place at the electrodes to form the first and second gas components, in order subsequently to provide them. The cathode may be arranged in the first chamber and the anode may be arranged in the second chamber. Accordingly, the first chamber may be referred to as a cathode chamber and the second chamber may be referred to as an anode chamber. Disposition may, however, also be made that the anode is disposed in the first chamber and that the cathode is disposed in the second chamber and therefore that the electrolyte is present on the anode side, that is to say the electrolyte circulation takes place only in the anode chamber, while the cathode chamber is kept free of the electrolyte. In any event, the electrolysis unit may be operated with asymmetrical circulation, which means that either the anode chamber or the cathode chamber is free of electrolyte and only contains a gas component. In other words, the electrolyte only ever circulates in one of the two chambers, while the other side remains as it were “dry”. For the case in which the second gas component is oxygen, a pressure level of about 100 bar may for example be provided in order to provide “dry” oxygen, or pure oxygen, in the second chamber.
The separating unit in the form of a separating wall, which physically separates the first chamber from the second chamber, may furthermore be disposed inside the electrolysis unit. The separating unit may have a membrane structure, which is configured to keep the electrolyte in the first chamber and therefore to keep the second chamber free of the electrolyte. For this purpose, a pressure that exceeds a pressure inside the first chamber is provided inside the second chamber, so that the electrolyte flow of the electrolyte takes place only in the first chamber and the electrolyte is prevented from entering the second chamber. The separating unit may be configured to ensure ionic charge transport in order to be able to provide the second gas component in the second chamber.
In the first chamber, the first gas component is provided by an electrolysis process. In the case of providing H2 by using a potassium hydroxide solution (KOH+H2O) as the electrolyte, the following chemical reaction may take place in the electrolysis unit: H2O4→H2+½O2. As the second gas component, oxygen O2 is in this case provided in the second chamber.
Disposition may be made that the second gas component is released in pure form, or almost pure form, from the second chamber for further use. Furthermore, disposition may be made that the first gas component is released from the electrolysis unit together with a part of the electrolyte delivered to the first chamber, phase separation of the electrolyte present in liquid form and the first gas component present in gaseous form subsequently taking place in the phase separating unit. Before this phase separation, the first gas component may be present in the form of bubbles inside the released electrolyte. The phase separation in the phase separating unit may for example be carried out by gravimetry, by using a centrifuge or by means of a membrane. Phase separation by means of a membrane will be explained in more detail below. It is to be understood that other phase separation techniques may also be employed.
The first gas component, separated from the electrolyte in the phase separating unit, may subsequently be delivered to a tank or a consumer for further use. In the case of hydrogen as the first gas component, it may then for example be used as an energy source or fuel for a propulsion unit. The very high pressure level that can be provided in the electrolysis unit and the separating unit, which may for example be more than 50 bar, may advantageously be used for the storage since no further pressure increase, or only a small further pressure increase, would be necessary in order to be able to store the first gas component after its provision.
It is possible for a plurality of electrolysis units, as described above and below, to be disposed in the device. The plurality of electrolysis units may, for example, in this case be disposed in a parallel arrangement in an electrolyte circuit of the device.
According to one embodiment, a pressure difference between the first chamber and the second chamber, generated by means of the separating unit, has the effect that in an operating state of the electrolysis unit the electrolyte is located only in the first chamber and the second chamber contains no electrolyte.
In other words, a continuous positive pressure of the second gas component relative to the first gas component may be disposed. The pressure difference between the two chambers may be arbitrary, although structural properties of the electrolysis unit, in particular of the separating unit, may have an influence on the pressures respectively disposed. Likewise, the pressure difference is selected in such a way that separation of electrolyte in the first chamber and the second gas component in the second gas chamber is ensured, in order to guarantee contamination of the second gas component. Disposition may be made that the following pressure property applies for the electrolysis unit, where p indicates the pressure:
p(second gas component)>p(electrolyte circuit)≥p(first gas component)>>p(ambient)
According to one embodiment, the device can be operated at a pressure of at least 50 bar.
In this case, disposition may made that the entire device, including the electrolysis unit and the phase separating unit, can be operated at a pressure of at least 50 bar. In particular, disposition may be made that the electrolysis unit, together with the phase separating unit, can be operated at a pressure of at least 50 bar. The pressure at which the device can be operated may furthermore be at least 60 bar, at least 80 bar or at least 100 bar. Disposition may also be made that the device can be operated at an elevated temperature, which for example is higher than room temperature. A temperature range for possible operating temperatures may be from 20° C. to 200° C.
According to one embodiment, the separating unit has a membrane structure with pores.
In other words, the separating unit that separates the first chamber from the second chamber can have a membrane. A fabric consisting of polyphenylene sulfide with a coating of polymer and zirconium oxide may be disposed for this. For example, it is Zirfon Perl® UTP 500. The membrane may have a thickness of 500 micrometers, a porosity of 55 percent and a pore size of less than 0.05 micrometers. A bubble pressure in the membrane may be 2 bar. This bubble pressure may be dependent on the pore size in the membrane. Larger bubble pressures are for example achieved when smaller pores are disposed, so that a greater pressure difference may be set between the first and second chambers. Disposition may be made that the pressure difference between the first and second chambers, which is formed across the membrane, is not greater than the bubble pressure.
According to one embodiment, the separating unit alternatively has a membrane structure without pores, which is configured to allow transport of a liquid and to block transport of a gas component.
In other words, it is in this case a membrane that is gas-tight but nevertheless has the ability to transport liquid. This membrane may have a high ionic conductivity, for example for OH− ions. For example, it is an Ionomr Aemion® membrane. The membrane may have a thickness of 50 micrometers. For this alternative as well, the pressures in the first and second chambers may be selected freely so long as the stability of the membrane lying between the chambers, across which the pressure difference is formed, is not compromised thereby. In particular, such a type of closed membrane without pores may be disposed, so that no pressure difference is necessary in order to keep the electrolyte on one side, that is to say in one of the two chambers.
Disposition may furthermore be made that the separating unit, or the membrane, has stiffening elements, so that the pressure difference achievable between the first and second chambers may be increased.
According to one embodiment, the phase separating unit has a membrane structure that is configured to separate the first gas component from the electrolyte so as to provide the first gas component, so that the first gas component can subsequently be delivered to a storage unit or to a consumer.
As mentioned above, the discharge from the electrolysis unit may be carried out in the form of a combination of the electrolyte and the first gas component, the first gas component being dissolved and contained in the liquid electrolyte in the form of bubbles. The phase separating unit may then separate the first gas component entirely from the electrolyte, so that pure electrolyte can be returned into the circuit and therefore into the electrolysis unit. The phase separation is in this case carried out by a membrane structure, for example a hollow-fiber membrane structure, which makes the device suitable for use under microgravity conditions. Furthermore, a loss of the electrolyte during the phase separation may thereby be reduced.
According to one embodiment, the device can be operated under microgravity conditions, so that separation of the first gas component from the electrolyte in the phase separating unit, so as to provide the first gas component, is ensured in the event that a microgravity state occurs.
In other words, the phase separating unit can ensure that separation of the first gas component from the electrolyte is possible even in zero gravity, so that the device is suitable in particular for use in spacecraft. In order to achieve this, the phase separating unit may have a membrane by which the first gas component can be separated from the electrolyte.
According to one embodiment, the device furthermore has an electrolyte circuit and a delivery unit, the delivery unit being configured to provide the electrolyte circuit with a reactant by using osmosis.
In this way, the use of a pump for providing the reactant, that is to say for delivering the reactant into the electrolysis circuit, can be avoided. This is advantageous since when using a pump, a high pressure existing in the circuit, as described above, would first have to be applied by the pump. This application of a high pressure, for example 100 bar, by a pump can therefore be avoided. When using osmosis, a pressure difference inside the delivery unit is generated by adjusting a difference in the electrolyte concentration on different sides of a membrane of the delivery unit. This will be explained in more detail in the description of the figures. The reactant may, for example, be water.
It should, however, be noted that a pump as a reactant delivery unit is possible instead of using osmosis.
According to one embodiment, the first gas component is hydrogen H2 and/or the second gas component is oxygen O2. It is, however, to be understood that other suitable gas components may also be generated by using the device according to the invention. This may be dependent on the selection of the reactant that is delivered.
According to one embodiment, the electrolysis unit has a frame structure, the phase separating unit being integrated into the frame structure of the electrolysis unit.
A frame structure may for example comprise a shell or other structural elements which are suitable for forming, or at least partially forming, a closed shape of the electrolysis unit. For example, via an outer wall, the phase separating unit directly adjoins an outer wall of the electrolysis unit. Integration of the phase separating unit into the electrolysis unit offers advantages in respect of saving space, saving weight, etc. For example, in this way the use of pipes and other hydraulic components may be reduced or even completely avoided. Scaling in respect of the number of electrolysis cells used is thereby made possible. One substantial advantage of this structural integration is however also that all device units, that is to say inter alia the electrolysis unit, the phase separating unit, etc., and any auxiliary components such as line elements, may in this way be used in a closed high-pressure environment.
According to one embodiment, the device furthermore has a heat exchanger, which is integrated into the electrolysis unit.
This likewise leads to the advantages, already mentioned above, of structural integration. In addition, it offers the advantage that heat can be extracted better from the electrolysis unit when the heat exchanger is also integrated into the electrolysis unit. Structural integration may in this case mean that the respective components are separated from one another by at most one further component, for example an intermediate wall. For example, the heat exchanger adjoins an outer wall of the electrolysis unit directly via an outer wall. Thermal control of the device, in particular control of the temperature in the electrolyte circuit, may be made possible by means of the heat exchanger.
According to one aspect of the invention, a vehicle having the device described above and below for providing a gas component is specified.
According to one embodiment, the vehicle is an aircraft having the device described above and below for providing a gas component. The aircraft may be a manned or unmanned aircraft. The aircraft may be an airplane, for example a transport airplane, or a passenger airplane. The aircraft may, however, also be any other flying object.
According to one embodiment, the vehicle is a spacecraft having the device described above and below for providing a gas component. The spacecraft may be a manned or unmanned spacecraft. The spacecraft may be a satellite, a rocket or the like. The use of the device according to the invention in a spacecraft has the advantage that, as described above, functioning of the device, in particular of the phase separating unit, may also be ensured under microgravity conditions, that is to say in zero gravity.
According to another embodiment, the device described above and below is configured to be used in a stationary application. In other words, a stationary, or fixed-position, platform with the device according to the invention may be provided.
The above-indicated properties of the device according to the invention offer numerous advantages. In particular, a gas component, for example hydrogen, may be provided at a very high pressure of about 100 bar or even more, which may significantly improve the storage density and therefore the system efficiency, for example in hydrogen fuel tank and propulsion systems. Furthermore, the gas purity of the gas components generated may be increased and a fraction of water vapor possibly occurring may be reduced. In summary, the device according to the invention can offer advantages in respect of a reduced system complexity, lower breakdown risks, lower energy consumptions, lower masses and volumes by fewer components being needed for the circulation of the electrolyte, etc. Because of the osmotic reactant delivery, the use of pumps therefor may be obviated, which in turn reduces the complexity, energy consumption and breakdown risks of the overall system, since fewer moving parts or complex parts are employed.
The representations in the figures are schematic and not to scale. In the following description of the figures, when the same references are used in the various figures, they denote elements that are the same or similar. Elements that are the same or similar may, however, also be denoted by differing references.
From the circuit 80, the electrolyte 13 passes into the first chamber 21 of the electrolysis unit 20, a chemical reaction taking place in the chamber so that a first gas component 11 is formed and is present in the first chamber 21 in addition to the electrolyte 13. In other words, circulation of electrolyte 13 takes place inside the first chamber 21 and the first gas component 11, which is subsequently released from the electrolysis unit 20 together with a portion of the electrolyte 13 through a discharge 82, can be provided by the chemical reaction. The portion of electrolyte 13 released is in this case less than the amount of electrolyte 13 that is delivered to the electrolysis unit 20 through the delivery 81.
In the second chamber 22, a second gas component 12 (not represented in
A pressure inside the second chamber 22 is greater than a pressure inside the first chamber 21, so that an electrolyte flow of the electrolyte 13 takes place only in the first chamber 21 and the electrolyte 13 is blocked from passing into the second chamber 22, so as to keep the second gas component 12 that is provided separate from the electrolyte 13. Together with said pressure difference, the separating device 23 prevents so to speak ingress of the electrolyte 13 from the first chamber 21 into the second chamber 22. The pressure difference generated across the separating unit 23 between the first chamber 21 and the second chamber 22 also has the effect that, in an operating state of the electrolysis unit 20, the electrolyte 13 is only located in the first chamber 21 and the second chamber 22 contains no electrolyte 13, but only contains the second gas component 12 with a high degree of purity.
A phase separating unit 30 is furthermore incorporated into the circuit 80, and is configured to separate the first gas component 11 from the electrolyte 13 so as to provide the first gas component 11 at high pressure and in pure form for further use in a consumer 41 or for storage in a tank 41. The pressure at which the device 10, including the electrolysis unit 20, the phase separating unit 30 and the line circuit 80, can be operated may be approximately 100 bar, although it is necessary to ensure that the aforementioned pressure difference between the first chamber 21 and the second chamber 22 is complied with. For this pressure difference, even a small pressure difference may be sufficient.
The electrolysis unit 20 may have one or more frames 26 with separating sheets 25 (for example bipolar plates). Together with end flanges 27, the frames 26 ensure sealing of the electrolysis unit 20 from the surroundings, apart from the delivery 81 and the discharges 82, 83.
The device 10 furthermore comprises a heat exchanger 60 for extracting heat from the electrolyte circuit 80, and a pump 74 for circulating the electrolyte 13 inside the circuit 80. The pump 70 is in this case arranged in the line circuit 80 and conveys the electrolyte 13 into the electrolysis unit 20. Although this is not represented in
As an additional exemplary embodiment,
As already mentioned above, the electrolyte 13 may be formed by an aqueous potassium hydroxide solution (KOH+H2O). In this case, the concentration of potassium hydroxide in relation to the fraction of water on the delivery side 52 would be very low, while the concentration of potassium hydroxide in relation to the fraction of water on the circuit side 80 would be significantly higher. Consequently, a significantly lower osmotic pressure is formed on the delivery side 52 than on the circuit side 80. The osmosis membrane 54 is for this purpose selectively permeable for water, so that the fraction of water in the potassium hydroxide solution can migrate across the membrane 54. Furthermore, the osmotic pressure of the potassium hydroxide solution is respectively dependent on the temperature. The osmotic pressure is therefore a quantity that is dependent on the one hand on the temperature and on the other hand on the concentration of electrolyte 13. The pressure difference formed between the delivery side 52 and the circuit side 80, which is caused by the osmosis, represents the difference between the osmotic pressure of the electrolyte 13 on the delivery side 52 and the osmotic pressure of the electrolyte 13 on the circuit side 80. In the example represented in
Disposition may be made that this osmotic reactant delivery 52 as described with reference to
It should additionally be pointed out that “comprising” does not exclude other elements or steps, and “a” or “an” does not exclude a multiplicity. It should furthermore be pointed out that features or steps which have been described in respect of one of the exemplary embodiments above may also be used in combination with other features or steps of other exemplary embodiments described above. References in the claims are not to be regarded as a restriction.
While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 102 535.4 | Feb 2021 | DE | national |
This application is a national phase of International Patent Application No. PCT/EP2021/087783, filed on Dec. 29, 2021, which claims the benefit of German Patent Application No. 10 2021 102 535.4, filed on Feb. 3, 2021, the entire disclosures of which are incorporated herein by way of reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/087783 | 12/29/2021 | WO |
