Regenerable fuel cell system

Abstract

A regenerable fuel cell system comprising a combination of a fuel cell and a water electrolyzer (10), consisting of a polymer membrane and electrodes arranged on respective sides of the polymer membrane, wherein the regenerable fuel cell system can be operated to generate electrical energy during an energy generation period by supplying oxygen gas (O2) to an electrode arranged on one side of the polymer membrane and hydrogen gas (H2) to an electrode arranged on the other side of the polymer membrane, and can be operated to generate oxygen gas (O2) and hydrogen gas (H2) during a charging period by electrolyzing water in the combination of fuel cell and water electrolyzer (10), wherein the regenerable fuel cell system comprises: an oxygen container (1) for storing oxygen gas (O2); a hydrogen container (1') for storing hydrogen gas (H2); a first storage unit (2) for storing water and an oxygen gas (O2) that is not used to generate energy from the oxygen gas (O2) supplied during the energy generation period; a second storage unit (2') for storing water and hydrogen gas (H2); which is not used for energy generation from the hydrogen gas (H2) supplied during the energy generation period; and a vapor pressure control device for regulating the vapor pressure of the water in the first and / or second storage tank (2, 2'), wherein the combination of fuel cell and water electrolyzer (10), the oxygen reservoir (1), the hydrogen reservoir (1'), the first storage (2), the second storage (2') and a liquid / gas path connecting them are provided as a closed path, wherein the oxygen reservoir (1) and the first storage (2) are connected to each other so that the oxygen gas (O2) can move back and forth between them, and wherein the oxygen gas (O2) is supplied to the electrode arranged on one side of the polymer membrane during the energy generation period, wherein the hydrogen reservoir (1') and the second storage (2') are connected to each other so that the hydrogen gas (H2) can move back and forth between them, and wherein the hydrogen gas (H2) is supplied to the electrode arranged on the other side of the polymer membrane during the energy generation period, and wherein water required during the energy generation period is supplied to the polymer membrane.by regulating the vapor pressure of the water by the vapor pressure control medium, and wherein the vapor pressure control medium regulates the vapor pressure of the water by changing the temperature of the first storage tank (2) and the second storage tank (2').

Description

TECHNICAL AREA

[0001] The present invention relates to a regenerable fuel cell system that uses oxygen and hydrogen and has an energy storage function. STATE OF THE ART

[0002] Fig. Figure 4 is a representation to explain an energy generation mechanism and a charging (energy storage) mechanism of a regenerative fuel cell system that uses hydrogen and oxygen. Fig. 4(a) is referred to as a separate type in which a fuel cell section and a water electrolysis section are provided in a separate manner, whereas Fig. 4(b) is referred to as a modularized type (or ‘reversible type’) in which a fuel cell section and a water electrolyzer section are provided in an integrated manner.

[0003] In the fuel cell system in Fig. 4(a) Water is electrolyzed into hydrogen gas and oxygen gas in the water electrolysis section during a charging (energy storage) period. Both the resulting hydrogen gas and oxygen gas are stored in a corresponding container. During an energy generation period, the hydrogen gas and oxygen gas stored in their respective containers are converted in the fuel cell section to generate electrical energy. Water obtained during this time is stored in an associated container. In the fuel cell system in Fig. 4(b) the reactions during the charging (energy storage) period and the energy generation period proceed in a similar manner, but differ from those of Fig. 4(a) insofar as the two reactions take place in a modularized fuel cell area.

[0004] During water electrolysis, an electrode must contain moisture, whereas it must be dry during energy generation. Therefore, a typical fuel cell system often uses the separate type, as in... Fig. 4(a) shown. In contrast, if a strict weight limit is imposed, as in an application in space travel, the modularized type has an advantage in terms of efficiency to mass.

[0005] Furthermore, a proton (H) must be present during an energy generation period. +The electron (or hydrogen ion) that has been separated from an electron must be transported across a polymer membrane to the other side, for which the polymer membrane must be moistened by containing moisture. To meet the above requirement, the applicant has proposed moistening the polymer membrane appropriately by having the oxygen gas and the hydrogen gas flow from each of the opposite sides of the polymer membrane to the other side (Patent Document 1). Examples of the fuel cell system, in which a fuel cell section and a water electrolyzer section are integrated, can also be found in Patent Documents 2, 3, and 5. Patent Document 4 describes an energy storage system with a fuel cell stack and an electrolyzer stack. LIST OF DOCUMENTS ACCORDING TO THE STATE OF TECHNOLOGY PATENT DOCUMENTS Patent Document 1: JP 4013218B2 Patent Document 2: JP 2006-127807A Patent Document 3: JP 2007-115588A Patent document 4: US 2008 / 0 166 603 A1 Patent document 5: US 7,410,714 B1 SUMMARY OF THE INVENTIONAL PROBLEM

[0006] When using a fuel cell system, particularly in space applications, there is a need to reuse resources such as oxygen gas as much as possible without releasing them to the outside. If this can be achieved, it is possible to reduce the wasteful use of resources like hydrogen and oxygen gas, thus gaining numerous advantages not only in space applications but also on Earth. Therefore, a closed fuel cell system is being considered that allows the reuse of hydrogen, oxygen, and water without external release. A major challenge in this context is how to keep the polymer membrane moist during energy production. SOLUTION TO THE PROBLEM

[0007] To solve the aforementioned problem, the present invention provides a regenerable fuel cell system comprising a combination of a fuel cell and water electrolysis, consisting of a polymer membrane and electrodes arranged on both sides of the polymer membrane, wherein the regenerable fuel cell system can be operated to generate electrical energy during an energy generation period by supplying oxygen gas to an electrode arranged on one side of the polymer membrane and hydrogen gas to an electrode arranged on the other side of the polymer membrane, and can be operated to generate oxygen gas and hydrogen gas during a charging period by electrolyzing water in the combination of fuel cell and water electrolyzer.wherein the regenerable fuel cell system comprises: an oxygen tank for storing oxygen gas; a hydrogen tank for storing hydrogen gas; a first storage tank for storing water and oxygen gas not used for energy generation from the oxygen gas supplied during the energy generation period; a second storage tank for storing water and hydrogen gas not used for energy generation from the hydrogen gas supplied during the energy generation period; and a vapor pressure control device for regulating the vapor pressure of the water in the first and / or second storage tank, wherein the fuel cell and water electrolyzer combination, the oxygen tank, the hydrogen tank, the first storage tank, the second storage tank, and a liquid / gas path connecting them are provided as a closed branch, the oxygen tank and the first storage tank being connected to each other.so that the oxygen gas can move back and forth between them, and wherein the oxygen gas is supplied to the electrode arranged on one side of the polymer membrane during the energy generation period, wherein the hydrogen container and the second storage unit are connected to each other so that the hydrogen gas can move back and forth between them, and wherein the hydrogen gas is supplied to the electrode arranged on the other side of the polymer membrane during the energy generation period, and wherein water required during the energy generation period is supplied to the polymer membrane by regulating the vapor pressure of the water by the vapor pressure control medium.

[0008] In the regenerative fuel cell system, the vapor pressure control medium can regulate the vapor pressure of the water by changing the temperature of the first storage and the second storage.

[0009] The regenerable fuel cell system can include a differential pressure gauge for measuring a pressure difference between the oxygen gas on an oxygen side and the hydrogen gas on a hydrogen side of the polymer membrane, and the pressure difference can be controlled within a predetermined range by changing the position of the liquid water level (or liquid level) in the first and / or second storage based on the result of the measurement.

[0010] The regenerable fuel cell system can include a first pressure gauge for measuring the pressure of the oxygen gas in the first storage or the passage on the oxygen side and a second pressure gauge for measuring the pressure of the hydrogen gas in the second storage or in the passage on the hydrogen side, and the pressure difference between the oxygen gas on the oxygen side and the hydrogen gas on the hydrogen side can be controlled within a predetermined range by changing the position of the liquid water level in the first and / or second storage based on the measured values ​​of the first and second pressure gauges.

[0011] The regenerable fuel cell system can include a differential pressure gauge for measuring a pressure difference between the oxygen gas on the oxygen side and the hydrogen gas on the hydrogen side of the polymer membrane, and the pressure difference can be regulated within a predetermined range by changing the pressure of the oxygen gas in the first storage and / or the hydrogen gas in the second storage based on the result of the measurement.

[0012] In the regenerable fuel cell system, the combination of fuel cell and water electrolyzer can be formed by providing a fuel cell area and a water electrolyzer area in an integrated manner.

[0013] In the regenerable fuel cell system, the combination of fuel cell and water electrolyzer can be formed by providing a fuel cell area and a water electrolyzer area separately.

[0014] To solve the aforementioned problem, the first invention provides a regenerable fuel cell system comprising a combination of a fuel cell and water electrolysis, consisting of a polymer membrane and electrodes arranged on both sides of the polymer membrane, wherein the regenerable fuel cell system can be operated to generate electrical energy during an energy generation period by supplying oxygen gas to an electrode arranged on one side of the polymer membrane and hydrogen gas to an electrode arranged on the other side of the polymer membrane, and can be operated to generate oxygen gas and hydrogen gas during a charging period by electrolyzing water in the combination of fuel cell and water electrolyzer, wherein the regenerable fuel cell system comprises: an oxygen container for storing oxygen gas;a hydrogen tank for storing hydrogen gas; a storage facility for storing water and oxygen gas that is not used for energy generation from the oxygen gas supplied during the energy generation period;and a vapor pressure control device for regulating the vapor pressure of the water in the storage unit, wherein the combination of fuel cell and water electrolyzer, the oxygen reservoir, the hydrogen reservoir, the storage unit, and a liquid / gas path connecting them are provided as a closed branch, wherein the oxygen reservoir and the storage unit are connected to each other so that the oxygen gas can move back and forth between them, and wherein the oxygen gas is supplied to the electrode located on one side of the polymer membrane, while the hydrogen gas is transported from the hydrogen reservoir to the electrode located on the other side of the polymer membrane during the energy generation period, wherein water required during the energy generation period is supplied to the polymer membrane by regulating the vapor pressure of the water by the vapor pressure control device.

[0015] The regenerable fuel cell system may further include a gas-liquid separator for separating water and hydrogen gas that is not used for energy generation from the hydrogen gas supplied during the energy generation period, and for conveying the separated hydrogen gas to the hydrogen tank, wherein the gas-liquid separator is integrated into the closed branch.

[0016] The regenerable fuel cell system may further include an oxygen side gas liquid separator for separating water and oxygen gas that is not used for energy generation from the oxygen gas supplied during the energy generation period, wherein the oxygen side gas liquid separator is incorporated into the closed branch.

[0017] In this regenerative fuel cell system, the vapor pressure control medium can regulate the vapor pressure of the water by changing the temperature of the storage tank.

[0018] The regenerable fuel cell system can further include a differential pressure gauge for measuring a pressure difference between the oxygen gas on an oxygen side and the hydrogen gas on a hydrogen side of the polymer membrane, and the pressure difference can be controlled within a predetermined range by changing a position of the liquid water level in the storage based on the result of the measurement.

[0019] The regenerable fuel cell system can further include a differential pressure measuring device for measuring a pressure difference between the oxygen gas on one oxygen side and the hydrogen gas on one hydrogen side of the polymer membrane, and the pressure difference can be controlled within a predetermined range by changing the pressure of the oxygen gas in the storage based on the result of the measurement.

[0020] The regenerable fuel cell system can further include a first pressure gauge for measuring the pressure of the oxygen gas in the first storage or in the passage on the oxygen side, and a second pressure gauge for measuring the pressure of the hydrogen gas in the gas-liquid separator or in the passage on the hydrogen side. The pressure difference between the oxygen gas on the oxygen side and the hydrogen gas on the hydrogen side can be controlled within a predetermined range by changing the position of the liquid water level in the storage and / or the gas-liquid separator based on the measured values ​​of the first and second pressure gauges.

[0021] In this regenerable fuel cell system, the combination of fuel cell and water electrolyzer can be formed by providing a fuel cell area and a water electrolyzer area in an integrated manner.

[0022] In this regenerable fuel cell system, the combination of fuel cell and water electrolyzer section can be formed by providing a fuel cell section and a water electrolyzer section separately. IMPACT OF THE INVENTION

[0023] The fuel cell system according to the present invention can, as described above, regulate the vapor pressure of the water in the storage tank to ensure sufficient moisture supply to the polymer membrane. This enables the fuel cell system to continue operating even when the entire cell system is configured as a closed unit. Furthermore, the fuel cell system includes a pressure gauge for measuring the pressure in the container and / or the storage tank and actively regulates the pressure differential between the pressures generated on both sides of the polymer membrane within a predetermined range by controlling the liquid water level in the gas-liquid separator and / or the water storage tank to induce a change in the gas volume. This ensures that the mixing of the oxygen and hydrogen gases is avoided. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 represents a structure of a regenerable fuel cell system according to the first embodiment of the present invention. Fig. Figure 2 represents a structure of a regenerable fuel cell system according to a second embodiment of the present invention. Fig. Figure 3 represents a structure of a regenerable fuel cell system according to an embodiment of the present invention. Fig. Figure 4 is a representation to explain an energy generation mechanism and charging (energy storage) mechanism of a regenerative fuel cell system that uses hydrogen and oxygen. DESCRIPTION OF THE EXECUTION FORMS

[0024] Embodiments of the present invention are described below with reference to the drawings. It should be noted that the embodiments described below merely illustrate one embodiment of the present invention and that the scope of protection of the present invention is not limited to these embodiments. First embodiment:

[0025] Fig. Figure 1 shows a schematic structure of a modularized regenerable fuel cell system according to a first embodiment of the present invention. Fig. Figure 1 shows only the pipes for gas and liquid, and the electrical circuits, such as a load, are omitted.

[0026] The numeral 10 in Fig. Figure 1 designates a fuel cell / water electrolyzer stack (hereinafter referred to simply as "stack") that plays a central role in the modularized regenerative fuel cell system, which integrates a fuel cell section and a water electrolyzer section. Stack 10 has a structure in which a number of modularized cells or reversible cells, combining a fuel cell and a water electrolyzer (hereinafter referred to simply as "cell"), are laminated together. Each cell comprises a polymer membrane and electrodes arranged on either side of the membrane, laminated sequentially. A thin ion-exchange membrane with a thickness of, for example, approximately 15 to 225 µm can be used as the polymer membrane in each cell. A catalyst to facilitate the reaction is positioned between the polymer membrane and each electrode.

[0027] As from Fig. As can be seen in Figure 1, the oxygen side on the left and the hydrogen side on the right have an essentially symmetrical structure. Consequently, the components on the hydrogen side on the right that correspond to the components on the oxygen side on the left are denoted with the same numerals and an apostrophe (').

[0028] In Fig. The numbers 1, 1', 2, and 2' each denote an oxygen container, a hydrogen container, an oxygen side storage tank, and a hydrogen side storage tank, respectively. The numbers 1a, 1a', 6, and 6' each denote a pressure gauge for measuring the gas pressure in the respective container or storage tank. The numbers 7, 7', 9, and 9' each denote a pump for circulating gas (oxygen or hydrogen) or water. The number 11 denotes a differential pressure gauge for measuring the pressure difference between the oxygen and hydrogen sides. The numbers 4, 4', 5b, 5b', 9a, and 9a' each denote a control valve. The numbers 3, 3', 5a, 5a', 8a, 8a', 8b, and 8b' each denote a valve. Furthermore, the numerals 12 and 12' denote a regulator and the numerals 13 and 13' each denote a back pressure regulator.

[0029] Oxygen reservoir 1 and hydrogen reservoir 1' each initially contain a predetermined pressure of oxygen gas and hydrogen gas, respectively. Reservoir 2 initially contains a predetermined oxygen pressure and a predetermined quantity of water (liquid), and reservoir 2' initially contains a predetermined hydrogen pressure and a predetermined quantity of water (liquid). The stack, the oxygen reservoir, the hydrogen reservoir, each reservoir, and a liquid / gas path connecting them, as shown in Fig. 1 shown, are designed as a closed branch which does not require an external supply of oxygen, hydrogen and water during its normal operation.

[0030] In water electrolysis (energy storage), a voltage is applied to the electrodes on the oxygen side and the hydrogen side of each cell, where the oxygen-side electrode is set to positive and the hydrogen-side electrode to negative. Water is then pumped from storage 2 to stack 10 via pump 9, where it is converted into oxygen gas (O2) and a proton (H2). + The proton is electrolyzed by the action of the catalyst on the oxygen-side electrode in each cell. The proton is transported to the hydrogen side through the polymer membrane and combines with an electron that reaches the hydrogen-side electrode via an electrical circuit to become hydrogen gas (H2).

[0031] At this point, the water contained in the polymer membrane serves to transport the proton to the hydrogen side of the polymer membrane. Therefore, the polymer membrane must be moistened for water electrolysis. After electrolysis, the mixture of oxygen gas and water is directed to storage tank 2 via the open valve 8a. On the hydrogen side, on the right-hand side... Fig. 1. Each component that corresponds to the one on the oxygen side functions in a similar way to the one on the oxygen side.

[0032] During an energy generation cycle, when the stack is used as a fuel cell, oxygen gas is blown to the stack 10 via control valve 5b by opening valve 5a after valves 3 and 8a have closed. At the hydrogen side electrode, the hydrogen gas is split into an electron and a proton by the action of the catalyst, and the proton reaches the oxygen side through the polymer membrane. At this point, the water contained in the polymer membrane also serves to transport the proton to the hydrogen side of the polymer membrane.

[0033] On the oxygen side, the oxygen gas, proton, and electron arriving via an electrical circuit are converted into water. At this point, excess oxygen gas, which does not contribute to the reaction, and water formed by the reaction are routed to storage tank 2 via the open valve 8b. In storage tank 2, the oxygen gas and water are separated, and the oxygen gas is returned to stack 10 via pump 7 and control valve 4. Repeating this reaction generates an electromotive force with a positive potential on the oxygen side and a negative potential on the hydrogen side of the cell, and energy production continues. During an energy production cycle, each component on the hydrogen side operates on the right-hand side. Fig. 1 in a similar way to the corresponding component on the oxygen side.

[0034] As can be seen from the description above, storage tank 2 also serves as a gas-liquid separator for the oxygen gas and water, and storage tank 2' also serves as a gas-liquid separator for the hydrogen gas and water.

[0035] As described above, it is necessary that the polymer membrane be moistened by containing sufficient moisture during the energy generation period to transport the proton separated from the electron to the oxygen side of the cell. In a conventional setup, where the oxygen gas is supplied only from oxygen reservoir 1 and the hydrogen gas only from hydrogen reservoir 1', the polymer membrane dries out and cannot retain the necessary amount of moisture, making it necessary to supply the polymer membrane with moisture externally.

[0036] On the other hand, the in Fig. Figure 1 illustrates an embodiment in which the entire fuel cell system is designed as a closed system, such that the storage tanks 2 and 2' initially contain liquid water, which is used to supply the polymer membrane. In particular, the vapor pressure of the water in the storage tank is set to a predetermined value by individually controlling the temperature of the storage tanks 2 and 2'. To change the temperature, a heating device can be used for heating and a cooling system for cooling. Particularly in a space application, it is also possible to achieve cooling by adiabatic expansion through a rapid pressure drop in the storage tank using a pressure-reduced environment.

[0037] Pressure gauges 6 and 6' can be used to set the vapor pressure of the water. The water, which is converted to gas in the respective storage tank based on the set vapor pressure, is supplied to stack 10 along with oxygen gas from storage tank 2 and hydrogen gas from storage tank 2'. This configuration makes it possible to adjust the amount of water contained in the polymer membrane and maintain the corresponding humidification of the polymer membrane without an external water supply.

[0038] As can be seen from the above description, the water, oxygen gas and hydrogen gas used in the modularized regenerative fuel cell system in Fig. The required energy is supplied solely by the oxygen gas and hydrogen gas initially contained in oxygen tank 1 and hydrogen tank 1', the predetermined pressure of the oxygen gas and the predetermined amount of water initially contained in storage tank 2, and the predetermined pressure of the hydrogen gas and the predetermined amount of water initially contained in storage tank 2'. This means that it is possible to continue energy storage and energy generation without an external supply of oxygen gas, hydrogen gas, and water. In this sense, the modularized renewable fuel cell system in Fig. 1. comprise a closed branch (or an isolated branch) that is completely closed.

[0039] With earlier fuel cell systems, it was not as frequently necessary to store and reuse the oxygen produced by water electrolysis in those for terrestrial applications, because the oxygen in the air could at least be used for the oxygen gas. Nevertheless, when considering a space application, there is a desire to reuse every resource, and therefore the closed fuel cell system as in this embodiment is advantageous.

[0040] The above description refers to the case where the vapor pressure of the water is adjusted by controlling the temperature of storage tanks 2 and 2'. Alternatively, it is also possible, for example, to provide a mechanism for changing the volume / temperature of storage tanks 2 and 2' and to adjust the amount of water vapor contained in the gas by controlling the volume or by temperature control, for example, through adiabatic expansion or compression. In addition, various methods for adjusting water vapor pressure are known, which also fall within the scope of the present invention.

[0041] As described above, a thin ion-exchange membrane with a thickness of approximately 15 to 225 µm is often used as the polymer membrane. Because the polymer membrane is very thin, it is likely to be damaged if the pressure difference between its two sides becomes large, even if other membrane types are used. Even if it is not damaged, gas molecules can migrate from the side with the higher pressure to the side with the lower pressure when the pressure difference reaches approximately 50 kPa (about half atmospheric pressure). As a result, the hydrogen and oxygen gases mix, creating a risk of explosion. For this reason, it is important to keep the pressure difference between the two sides of the polymer membrane low.

[0042] As a method to limit the formation of a pressure difference on both sides of the polymer membrane, an arrangement was proposed in which a space is provided between the components that contain storage 2 and 2'. Fig. 1 corresponds to components 2 and 2', which are connected by a connecting tube and have a spring element in the center of the connecting tube (see JP 2007-100204A). In this arrangement, if a pressure difference develops between the components 2 and 2', the spring element moves in response to the pressure to equalize the pressures on each side. However, if the spring element is damaged for any reason, for example by a hole, the hydrogen and oxygen gases will still mix, creating a risk of explosion.

[0043] Therefore, in this embodiment, a differential pressure measuring device 11 is provided for measuring a pressure difference between the oxygen side and the hydrogen side in each cell, and if the pressure difference between the two sides exceeds a certain value, it keeps the pressure difference between the oxygen side and the hydrogen side below the certain value by controlling the up-and-down movement of the position of the liquid water level in the reservoirs 2 and 2'.One specific method for adjusting the position of the liquid water level involves, for example, connecting a reserve container to each of the storage tanks 2 and 2' via a valve and controlling the opening and closing of the valve based on the measurement of the differential pressure gauge 11. This allows the liquid water level in storage tanks 2 and 2' to be adjusted up and down, thereby maintaining the pressure difference between both sides of the polymer membrane within a predetermined range. In this way, since there is virtually no possibility of the oxygen and hydrogen gas mixing in the section connecting storage tanks 2 and 2', the risk of explosion can be avoided.Alternatively, the pressure difference between the two sides of the polymer membrane can be brought within a predetermined range by changing the pressure on the oxygen gas in reservoir 2 and / or the hydrogen gas in reservoir 2' based on the result of the differential pressure gauge measurement. For this differential pressure control, it is also possible to use a measured value from the pressure gauge installed in reservoirs 2 or 2' and to move the liquid water level so that the difference between the measured value and the pressure falls within a specific range.

[0044] It is also possible to regulate the liquid water level as described above by using the measurement result from pressure gauges 6 and 6' instead of a differential pressure gauge, or by placing a pressure gauge at a different location in the oxygen or hydrogen gas passage and regulating the liquid water level as described above based on the measurement result. It is also possible to use both a differential pressure gauge and a pressure gauge.

[0045] In JP 4013218B2, the applicant proposed a fuel cell system that enables efficient energy generation by making the flow of oxygen and hydrogen gases blown onto both sides of the polymer membrane a "countercurrent," causing the two gas streams to flow in opposite directions. According to this fuel cell system, it is considered that the water generated on the oxygen side of the polymer membrane penetrates the membrane sufficiently, thus improving the efficiency of a proton from the hydrogen gas flowing in the opposite direction to the oxygen gas reaching the hydrogen side, thereby making the proton more inclined to reach the oxygen side.

[0046] In contrast, this embodiment makes it possible to maintain the entire system in a humidified state by controlling it as a closed system and additionally by ensuring sufficient humidity of the oxygen and hydrogen gas supplied from reservoirs 2 and 2', as well as the polymer membrane, by controlling the pressure differential of the water contained in reservoirs 2 and 2' as described above. This allows the polymer membrane to be supplied with sufficient water, thus enabling proper operation as a fuel cell, regardless of the gas flow direction, including the case of "parallel flow" of the oxygen and hydrogen gas, where both gases flow in the same direction instead of the counterflow described above. Second embodiment:

[0047] Fig. Figure 2 shows a schematic diagram of a modularized regenerable fuel cell system according to a second embodiment of the present invention. Also in Fig. Figure 2 shows only the pipes for gas and liquid; the electrical circuits, such as a load, are omitted. The numeral 20 in Fig. 2 denotes a stack of the modularized regenerative fuel cell system, whose structure and function are the same as the stack in Fig. 1, so a detailed description of it is omitted. As for the other components... Fig. Regarding point 2, identical symbols refer to the same things. Fig. 1.

[0048] In Fig. In the reference 2, the numerals 21, 21', and 22 each denote an oxygen container, a hydrogen container, and a storage tank, respectively. Storage tank 22 corresponds to the oxygen side storage tank 2 of the first embodiment, and the hydrogen side storage tank is not provided. The numerals 21a, 21a', and 26 each denote a pressure gauge for measuring the pressure of the gas in the corresponding container or storage tank. The numerals 27, 29, and 35 each denote a pump for circulating the gas or water according to the respective container or storage tank. The numeral 31 denotes a differential pressure gauge for measuring the difference in pressure (pressure differential) between the oxygen side and the hydrogen side, and the numeral 38 denotes a gas-liquid separator provided on the hydrogen side. Both the oxygen container 21 and the hydrogen container 21' initially contain a predetermined pressure of the oxygen gas or hydrogen gas, respectively.of hydrogen gas. Storage unit 22 initially contains a predetermined pressure of oxygen gas and a predetermined quantity of water (liquid).

[0049] Unlike the system of the first embodiment, the one in Fig. Figure 2 of the second embodiment shows a gas-liquid separator 38, which is provided on the hydrogen side. The gas-liquid separator 38 is a device designed to separate gas and liquid and has a very small volume compared to the storage tanks 2 and 2' of the first embodiment, which also serve as gas-liquid separators.

[0050] At the time of water electrolysis (energy storage), water is pumped from storage tank 22 to stack 20 via pump 29, where it is electrolyzed into oxygen gas, a proton, and an electron. The proton produced as a result of electrolysis is transferred to the hydrogen side via the polymer membrane by the action of the water in the polymer membrane. The mixture of oxygen gas and water produced as a result of electrolysis is directed to storage tank 22 via the open valve 28a. In storage tank 22, the oxygen gas and water are separated. The oxygen gas is stored in oxygen reservoir 22 via the open valve 23.

[0051] In contrast, hydrogen gas is generated at the hydrogen side electrode by the proton and the electron. The hydrogen generated in the stack 20 is fed to the gas-liquid separator 38 in a moistened state, where the hydrogen gas and the water are separated. The separated hydrogen gas is then directed to the hydrogen reservoir 21' via the valve 36. If the water is stored in the gas-liquid separator 38, it can be returned to the reservoir 22 by opening the valve 39.

[0052] During energy generation, when the stack is used as a fuel cell, oxygen gas is blown to the oxygen side electrode of the stack 20 via the control valve 25b by opening valve 25a after valves 23 and 28a have closed. At the hydrogen side electrode, the hydrogen gas is split into an electron and a proton by the action of the catalyst, and the proton reaches the oxygen side through the polymer membrane. At this point, the water contained in the polymer membrane also serves to transport the proton to the hydrogen side.

[0053] On the oxygen side, the oxygen gas, the proton, and an electron arriving via an electrical circuit are converted into water. At this point, excess oxygen gas, which does not contribute to the reaction, and water formed by the reaction are conveyed to storage tank 22 via the open valve 28b. In storage tank 22, the oxygen gas and water are separated, and the oxygen gas is returned to the stack 20 via pump 27 and control valve 24. By repeating this reaction, an electromotive force with a positive potential on the oxygen side and a negative potential on the hydrogen side of the cell is generated, and energy production continues.

[0054] On the hydrogen side, hydrogen gas is fed from the hydrogen tank 21' to the stack 20 via the control valve 33' by closing valve 36, opening valve 37, and subsequently opening valve 32. The unreacted hydrogen gas, which contains moisture, is directed to the gas-liquid separator 38, where it undergoes moisture removal and is then pressurized by pump 35 and fed back to the stack 20 via the control valve 33.

[0055] In the second embodiment, which is described in Fig. As shown in Figure 2, the storage unit 22 contains liquid water, which is available to moisten the polymer membrane during the energy generation period. Specifically, the vapor pressure of the water in the storage unit 22 is set to a predetermined value by controlling its temperature. As in the first embodiment, various methods can be used to change the temperature: a heating device can be used for heating and a cooling system for cooling; particularly in aerospace applications, cooling by adiabatic expansion through rapid pressure loss using a reduced-pressure environment can be expected; and similar methods.As with the first embodiment, this configuration makes it possible to adjust the amount of water contained in the polymer membrane and to maintain sufficient humidification of the polymer membrane without the supply of external water.

[0056] From the above description, it is evident that the water, oxygen gas, and hydrogen gas, which are used in the modularized regenerative fuel cell system in Fig. The required oxygen and hydrogen gases are supplied solely by the oxygen and hydrogen gases initially contained in oxygen reservoir 21 and hydrogen reservoir 21', respectively, and by the predetermined pressure of the oxygen gas and the predetermined quantity of water initially contained in storage reservoir 22. This means that continuous operation is possible, even without an external supply of oxygen, hydrogen, and water. In this sense, the modularized regenerative fuel cell system in Fig. 2 also include a closed branch or an isolated branch that is completely closed, as is the case in the first embodiment.

[0057] The above described a case in which the vapor pressure of the water is set by regulating the temperature of the storage tank 22. Alternatively, as in the first embodiment, it may be possible, for example, to provide a mechanism for changing the volume / temperature of the storage tank 22 and to adjust the vapor pressure of the water by regulating the volume or by performing temperature control, for example by adiabatic expansion or compression, or otherwise.

[0058] In this embodiment, a differential pressure measuring device 31 is additionally provided as a method to keep the pressure difference between both sides of the polymer membrane low, for measuring a pressure difference between the oxygen side and the hydrogen side of each cell, and if the pressure difference between both sides exceeds a certain value, it keeps the pressure difference between the oxygen side and the hydrogen side below the certain value by controlling the up-and-down movement of a position of the liquid water level in the storage 22.As in the first embodiment, a reserve container is connected to the storage tank 22 via a valve, and the opening and closing of the valve is controlled based on the result of the measurement by the differential pressure gauge 31 in order to move the liquid water level of the storage tank 22 up and down, thereby allowing the pressure difference between both sides of the polymer membrane to be brought within a predetermined range. For this differential pressure control, it is also possible to use a measured value from the pressure gauge installed in the storage tank 22 and a measured value of the pressure in the gas-liquid separator 38 and to move the liquid water level so that the difference between these values ​​is within a predetermined pressure difference.

[0059] In this embodiment, it is also possible to supply the oxygen and hydrogen gas supplied by the storage tank 22 with sufficient moisture and to supply the polymer membrane with this moisture by regulating the vapor pressure of the water contained in the storage tank 22 as described above. It should be noted that the gas-liquid separator 38, like the storage tank 22, can also be used for regulating the temperature and the pressure differential by temperature control / control of the liquid water level, etc.As in the first embodiment, this embodiment also allows the polymer membrane to be supplied with sufficient water, thus enabling proper operation as a fuel cell, regardless of the gas flow direction, including the case of "parallel flow" of the oxygen and hydrogen gases, where both gases flow in the same direction instead of the counterflow described above. Although the above setup includes a gas-liquid separator 38, the gas-liquid separator 38 is not necessarily required if it is possible to keep the cell's polymer membrane constantly moistened by advantageously utilizing the water permeability on the oxygen side and optimally maintaining the surrounding volume on the oxygen side, while performing such control without generating excess water on the hydrogen side. Third embodiment:

[0060] Fig. Figure 3 shows a schematic structure of a modularized regenerable fuel cell system according to a third embodiment of the present invention, which is a variation of the second in Fig. The third embodiment is the embodiment shown in Figure 2. The third embodiment differs from the second embodiment in that it has a gas-liquid separator 38' with the same function as the gas-liquid separator 38, which is also provided on the oxygen side electrode. By providing the gas-liquid separator 38' on the oxygen side, it also becomes possible to carry out gas-liquid separation in the gas-liquid separator 38, while the reservoir 22 is used for more precise control of the humidity and the pressure differential by means of temperature control / control of the liquid water level, etc. Other embodiments:

[0061] In each of the first to third embodiments above, the stack is described as a modular type. However, it is readily apparent to those skilled in the art that the features of the present invention can also be applied to a separate type in which a fuel cell section and a water electrolyzer section are provided separately, the features comprising forming the entire system as a closed system and maintaining the interior of the system in a humidified environment while regulating the vapor pressure of the water in the reservoir to supply the polymer membrane with water, measuring a pressure difference between the oxygen side and the hydrogen side of the polymer membrane of each cell, and regulating the position of the liquid water level based on the pressure difference to maintain the pressure differential within a predetermined range.

Claims

[1] A regenerable fuel cell system comprising a combination of a fuel cell and a water electrolyzer (10), consisting of a polymer membrane and electrodes arranged on respective sides of the polymer membrane, wherein the regenerable fuel cell system can be operated to generate electrical energy during an energy generation period by supplying oxygen gas (O2) to an electrode arranged on one side of the polymer membrane and hydrogen gas (H2) to an electrode arranged on the other side of the polymer membrane, and can be operated to generate oxygen gas (O2) and hydrogen gas (H2) during a charging period by electrolyzing water in the combination of fuel cell and water electrolyzer (10), wherein the regenerable fuel cell system comprises: an oxygen container (1) for storing oxygen gas (O2); a hydrogen container (1') for storing hydrogen gas (H2); a first storage unit (2) for storing water and an oxygen gas (O2) that is not used to generate energy from the oxygen gas (O2) supplied during the energy generation period; a second storage unit (2') for storing water and hydrogen gas (H2); which is not used for energy generation from the hydrogen gas (H2) supplied during the energy generation period; and a vapor pressure control device for regulating the vapor pressure of the water in the first and / or second storage tank (2, 2'), wherein the combination of fuel cell and water electrolyzer (10), the oxygen reservoir (1), the hydrogen reservoir (1'), the first storage (2), the second storage (2') and a liquid / gas path connecting them are provided as a closed path, wherein the oxygen reservoir (1) and the first storage (2) are connected to each other so that the oxygen gas (O2) can move back and forth between them, and wherein the oxygen gas (O2) is supplied to the electrode arranged on one side of the polymer membrane during the energy generation period, wherein the hydrogen reservoir (1') and the second storage (2') are connected to each other so that the hydrogen gas (H2) can move back and forth between them, and wherein the hydrogen gas (H2) is supplied to the electrode arranged on the other side of the polymer membrane during the energy generation period, and wherein water required during the energy generation period is supplied to the polymer membrane.by regulating the vapor pressure of the water by the vapor pressure control medium, and wherein the vapor pressure control medium regulates the vapor pressure of the water by changing the temperature of the first storage tank (2) and the second storage tank (2'). [2] Regenerable fuel cell system according to claim 1, wherein the regenerable fuel cell system comprises a differential pressure measuring device (11) for measuring a pressure difference between the oxygen gas (O2) on an oxygen side and the hydrogen gas (H2) on a hydrogen side of the polymer membrane, and wherein the pressure difference is controlled within a predetermined range by changing a position of the liquid water level in the first and / or second storage (2, 2'). [3] Regenerable fuel cell system according to claim 1, wherein the regenerable fuel cell system comprises a first pressure gauge (6) for measuring a pressure of the oxygen gas (O2) in the first storage (2) or a line on the oxygen side and a second pressure gauge (6') for measuring a pressure of the hydrogen gas (H2) in the second storage (2') or in a line on the hydrogen side, and the pressure difference between the oxygen gas (O2) on the oxygen side and the hydrogen gas (H2) on the hydrogen side is controlled within a predetermined range by changing a position of the liquid water level in the first and / or second storage (2, 2') based on the measured values ​​of the first and second pressure gauge (6, 6'). [4] Regenerable fuel cell system according to claim 1, wherein the regenerable fuel cell system comprises a differential pressure measuring device (11) for measuring a pressure difference between the oxygen gas (O2) on the oxygen side and the hydrogen gas (H2) on the hydrogen side of the polymer membrane, and the pressure difference is controlled within a predetermined range by changing a pressure of the oxygen gas (O2) in the first storage (2) and / or the hydrogen gas (H2) in the second storage (2') based on the result of the measurement. [5] Regenerable fuel cell system according to any one of claims 1 to 4, wherein the combination of fuel cell and water electrolyzer (10) is formed by providing a fuel cell section and a water electrolyzer section in an integrated manner. [6] Regenerable fuel cell system according to any one of claims 1 to 4, wherein the combination of fuel cell and water electrolyzer section (10) is formed by providing a fuel cell section and a water electrolyzer section separately. [7] Regenerable fuel cell system comprising a combination of fuel cell and water electrolyzer (20), consisting of a polymer membrane and electrodes arranged on respective sides of the polymer membrane, wherein the regenerable fuel cell system can be operated to generate electrical energy during an energy generation period by supplying oxygen gas (O2) to an electrode arranged on one side of the polymer membrane and hydrogen gas (H2) to an electrode arranged on the other side of the polymer membrane, and can be operated to generate oxygen gas (O2) and hydrogen gas (H2) during a charging period by electrolyzing water in the combination of fuel cell and water electrolyzer (20), wherein the regenerable fuel cell system comprises: an oxygen container (21) for storing oxygen gas (O2); a hydrogen container (21') for storing hydrogen gas (H2); a storage unit (22) for storing water and an oxygen gas (O2) that is not used for energy generation from the oxygen gas (O2) supplied during the energy generation period; and a vapor pressure control device for controlling the vapor pressure of the water in the storage tank (22), wherein the combination of fuel cell and water electrolyzer (20), the oxygen tank (21), the hydrogen tank (21'), the storage (22) and a connecting liquid / gas path is provided as a closed path, wherein the oxygen container (21) and the storage container (22) are connected to each other so that the oxygen gas (O2) can move back and forth between them, and wherein the oxygen gas (O2) is supplied to the electrode arranged on one side of the polymer membrane, while the hydrogen gas (H2) is transported from the hydrogen container (21') to the electrode arranged on the other side of the polymer membrane during the energy generation period, wherein water required during the energy generation period is supplied to the polymer membrane by regulating the vapor pressure of the water by the vapor pressure control medium, and wherein The vapor pressure control device regulates the vapor pressure of the water by changing the temperature of the storage tank (22). [8] Regenerable fuel cell system according to claim 7, wherein the regenerable fuel cell system further comprises a gas-liquid separator (38) for separating water and hydrogen gas (H2) that is not used for energy generation from the hydrogen gas (H2) supplied during the energy generation period, and for conveying the separated hydrogen gas (H2) to the hydrogen container (21'), wherein the gas-liquid separator (38) is incorporated into the closed path. [9] Regenerable fuel cell system according to claim 8, wherein the regenerable fuel cell system further comprises an oxygen side gas liquid separator (38') for separating water and oxygen gas (O2) that is not used for energy generation from the oxygen gas (O2) supplied during the energy generation period, wherein the oxygen side gas liquid separator (38') is incorporated into the closed path. [10] Regenerable fuel cell system according to any one of claims 7 to 9, wherein the regenerable fuel cell system comprises a differential pressure measuring device (31) for measuring a pressure difference between the oxygen gas (O2) on an oxygen side and the hydrogen gas (H2) on a hydrogen side of the polymer membrane, and wherein the pressure difference is controlled within a predetermined range by changing a position of the liquid water level in the storage based on the result of the measurement. [11] Regenerable fuel cell system according to one of claims 7 to 9, wherein the regenerable fuel cell system comprises a differential pressure measuring device (31) for measuring a pressure difference between the oxygen gas (O2) on an oxygen side and the hydrogen gas (H2) on a hydrogen side of the polymer membrane, and wherein the pressure difference is controlled within a predetermined range by changing the pressure of the oxygen gas (O2) in the storage based on the result of the measurement. [12] Regenerable fuel cell system according to one of claims 8 or 9, wherein the regenerable fuel cell system comprises a first pressure gauge (26) for measuring a pressure of the oxygen gas (O2) in the storage or in a line on the oxygen side and a second pressure gauge for measuring a pressure of the hydrogen gas (H2) in the gas-liquid separator (38) or in a line on the hydrogen side, and wherein the pressure difference between the oxygen gas (O2) on the oxygen side and the hydrogen gas (H2) on the hydrogen side is controlled within a predetermined range by changing a position of the liquid water level in the storage and / or the gas-liquid separator (38) based on the measured values ​​of the first and second pressure gauges. [13] Regenerable fuel cell system according to one of claims 7 to 12, wherein the combination of fuel cell and water electrolyzer (10) is formed by providing a fuel cell section and a water electrolyzer section in an integrated manner. [14] Regenerable fuel cell system according to one of claims 7 to 12, wherein the combination of fuel cell and water electrolyzer section (20) is formed by providing a fuel cell section and a water electrolyzer section separately.

Images