Stationary hydrogen energy system

Abstract

This invention provides a hydrogen energy system that can improve energy efficiency by reducing the loss of hydrogen required for water removal in dehumidifiers. [Solution] The stationary hydrogen energy system includes a water electrolysis cell stack that generates hydrogen by electrolyzing water, a hydrogen storage unit for storing hydrogen, a fuel cell cell stack that generates electricity using hydrogen, a PSA dehumidifier that removes moisture from hydrogen, and a control device that controls the operation of the fuel cell cell stack and the water electrolysis cell stack. When the water electrolysis cell stack is in operation, the hydrogen generated in the water electrolysis cell stack is passed through the PSA dehumidifier at a first pressure higher than 0.5 MPaG to remove moisture contained in the generated hydrogen and then stored in the hydrogen storage unit. When the fuel cell cell stack is in operation, the hydrogen stored in the hydrogen storage unit is passed through the PSA dehumidifier at a second pressure lower than the first pressure to remove moisture in the PSA dehumidifier without heating and then supplied to the fuel cell cell stack.

Description

Technical Field

[0001] The present invention relates to a stationary hydrogen energy system.

Background Art

[0002] In recent years, efforts towards Sustainable Development Goals (SDGs) have been expanding. Moreover, energy systems that utilize renewable energies such as sunlight, wind power, and geothermal energy have attracted attention away from the conventional methods of generating electricity using fossil fuels such as oil, coal, and liquefied natural gas. In this type of power control system, the generated electricity fluctuates significantly depending on the weather, season, location, etc. Also, the power consumption of the consuming side (load) such as houses and stores also changes. Therefore, surpluses or shortages of electricity occur according to the power supply-demand balance between generation and consumption. Thus, recently, the development of a hydrogen energy system that "produces, stores, and uses hydrogen" using renewable energy has been underway.

[0003] In a hydrogen energy system, a water electrolysis cell stack is used to produce hydrogen, and a hydrogen storage tank containing a hydrogen storage alloy is generally used to store the produced hydrogen. And when hydrogen is generated by a water electrolysis cell stack, electrolysis treatment using water is performed, so it is common for moisture (water vapor) to be contained in the generated hydrogen (gas) or in the piping that transports hydrogen. However, when hydrogen with a large amount of moisture is supplied to the hydrogen storage tank, there is a risk that moisture will adsorb on the surface of the hydrogen storage alloy and form an oxide film through a chemical reaction. This oxide film inhibits the hydrogen storage and discharge reactions, and as a result, the reaction efficiency of the entire tank is significantly reduced. Particularly in nickel-based or rare-earth-based hydrogen storage alloys, the loss of surface activity due to oxidation becomes apparent as a decay in storage capacity and a reaction delay.

[0004] In addition, moisture can penetrate deep into the hydrogen storage alloy or affect it through capillary action, potentially compromising its structural stability. Repeated supply of hydrogen with high moisture content leads to deterioration of the hydrogen storage alloy with each hydrogen storage cycle, ultimately increasing the risk of irreversible damage such as pulverization, the formation of microcracks, and structural collapse.

[0005] Furthermore, if water condenses inside the tank due to pressure fluctuations or temperature changes, localized accumulation of liquid-phase water can occur, leading to localized corrosion of hydrogen storage alloys, blockage of flow paths, and malfunction of sensors, thus compromising the reliability of the entire system used in hydrogen energy systems.

[0006] For these reasons, storage systems using hydrogen storage alloys require maintaining the dew point temperature of the hydrogen supply source at -60°C or below (ideally -70°C or below) and supplying sufficiently dry, high-purity hydrogen. Neglecting moisture management will lead to a significant shortening of system lifespan and the occurrence of serious safety risks, thus requiring strict attention in both design and operation.

[0007] Therefore, a dehumidification mechanism is used in the hydrogen energy system to remove moisture contained in the generated hydrogen gas. For example, Patent Document 1 discloses a configuration in which a dehumidifier (PSA dehumidifier) ​​that removes moisture using the PSA (Pressure Swing Absorption) method is used as the dehumidification mechanism. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 4199593 [Overview of the project] [Problems that the invention aims to solve]

[0009] This PSA (Potentially Absorbent Water) method is a dehumidification method that removes moisture from a gas containing water using adsorbents such as zeolite, activated alumina, and silica gel. These adsorbents have a fine porous structure and are excellent at physically adsorbing water molecules contained in the gas. Therefore, it does not introduce impurities into the hydrogen, and the adsorbents are easily regenerated, making it suitable for long-term operation. In particular, adsorbents such as zeolite have the property of selectively adsorbing water molecules and hardly adsorbing hydrogen molecules, so hydrogen loss is extremely small.

[0010] In this method, the gas to be treated is introduced into the adsorption tower under pressure, allowing the adsorbent to capture moisture and produce a dry gas. After the adsorbent is saturated with moisture, the pressure inside the adsorption tower is reduced to below atmospheric pressure, and dry gas is circulated through the tower to effectively desorb water molecules held on the surface of the adsorbent, returning the adsorbent to a regenerated state. By alternating the adsorption and regeneration processes using pressure fluctuations and the supply of dry gas, continuous dehumidification is possible while maintaining the function of the adsorbent. Many PSA dehumidifiers employ a two-tower configuration, with alternating operation where regeneration is performed in the other tower while dehumidification is being carried out in the other tower. This configuration allows for continuous dehumidification without interrupting the gas supply, improving the reliability and operational efficiency of the entire system.

[0011] Other methods include condensation by cooling, which is difficult to remove moisture unless cooled above the dew point, and the moisture condensed by the cooling of hydrogen in the gas may re-evaporate and re-condense in the pipes and equipment, potentially resulting in unstable dehumidification performance. Furthermore, the cooling equipment itself is large and energy-intensive, making it unsuitable for small, distributed hydrogen systems. Methods using chemical absorbents (e.g., calcium chloride, phosphoric acid) offer excellent moisture removal capabilities, but the absorbent material is difficult to regenerate once absorbed, requiring periodic replacement. In addition, there is a risk of chemical reaction by-products and dust contaminating the hydrogen stream, making it often unsuitable for applications requiring high-purity hydrogen.

[0012] While there is also a membrane separation method as an alternative to the PSA method, this method has many disadvantages, including a significantly lower hydrogen recovery rate, making it unfavorable in terms of energy balance; the inability to reduce humidity to the required level; and the difficulty of the membrane withstanding several atmospheres of pressure. Therefore, it is not a common dehumidification method used in conjunction with hydrogen generators.

[0013] In contrast, PSA (Physical Adsorption and Regeneration) dehumidification achieves highly efficient drying through repeated physical adsorption and regeneration processes without the use of cooling mechanisms or absorbent agents, and is therefore widely adopted in various applications requiring the removal of moisture from gases. In particular, when combined with hydrogen generators, it greatly contributes to ensuring reaction stability and extending the lifespan of the equipment, and is positioned as an extremely useful dehumidification technology.

[0014] As mentioned above, conventional PSA-type dehumidification mechanisms typically use multiple PSA dehumidifiers (adsorption towers). When the moisture concentration of the adsorbent in one PSA dehumidifier becomes saturated, the system switches to another PSA dehumidifier to remove moisture from the saturated adsorbent. This method involves using multiple PSA dehumidifiers to remove moisture alternately. However, in such a configuration using multiple PSA dehumidifiers, when removing moisture from the adsorbent in the PSA dehumidifiers, as much as 10% of the stored dry hydrogen is used to remove moisture (purge) from the dehumidifiers. Since the hydrogen containing moisture has no use in the hydrogen system, it is discharged to the outside. As a result, the proportion of stored hydrogen that can be used in the hydrogen energy system (fuel cell) drops to 90%, resulting in significant energy loss.

[0015] While there is a technology that reduces the amount of dry hydrogen released by about half by heating the water during the moisture removal process of a PSA dehumidifier, this requires additional energy for the heater, making it not particularly energy-efficient. Nevertheless, due to its excellent balance of performance, cost, and operational aspects, it has been widely adopted in combination with hydrogen generators.

[0016] However, from the perspective of maximizing the overall efficiency of the hydrogen energy system, the losses incurred by the current system, which only achieves a hydrogen recovery rate of 90%, are by no means negligible, and improvements are desired.

[0017] This invention has been made in view of these problems, and one of its objectives is to provide a hydrogen energy system that can improve energy efficiency by suppressing the loss of hydrogen required for moisture removal (regeneration) of a dehumidifier. [Means for solving the problem]

[0018] Therefore, the inventors focused on the fact that in a stationary hydrogen energy system that performs both hydrogen generation and hydrogen-based power generation, hydrogen generation by a water electrolysis cell stack and power generation using hydrogen by a fuel cell stack do not occur simultaneously, but rather at different times (for example, during the day and at night). In other words, unlike hydrogen energy systems for vehicle applications where driving and stopping are repeated, in a stationary hydrogen energy system where a certain amount of time is permitted for pressure increases and decreases, the inventors conceived that by adopting a PSA method for dehumidification, when storing the generated hydrogen, the hydrogen is pressurized and passed through a dehumidifier to adsorb moisture from the hydrogen, and when using the hydrogen for power generation, the same dehumidifier is used to remove moisture by passing depressurized hydrogen in the reverse direction, thereby completely eliminating hydrogen emission that occurs when moisture is removed from the dehumidifier with an extremely simple configuration based on pressure control, and improving energy efficiency to 100%.

[0019] According to one aspect of the present invention, a stationary hydrogen energy system is provided, comprising: a water electrolysis cell stack that generates hydrogen by electrolyzing water; a hydrogen storage unit for storing hydrogen; a fuel cell cell stack that generates electricity using hydrogen; a PSA dehumidifier for removing water from hydrogen; and a control device for controlling the operation of the fuel cell cell stack and the water electrolysis cell stack. When the water electrolysis cell stack is in operation, the hydrogen generated in the water electrolysis cell stack is passed through the PSA dehumidifier at a first pressure higher than 0.5 MPaG to remove water contained in the generated hydrogen and then stored in the hydrogen storage unit. When the fuel cell cell stack is in operation, the hydrogen stored in the hydrogen storage unit is passed through the dehumidifier at a second pressure lower than the first pressure to remove water in the dehumidifier without heating and then supplied to the fuel cell cell stack.

[0020] By using this embodiment, when switching from the operation of the water electrolysis cell stack to the operation of the fuel cell stack, the stored dry hydrogen can be used to remove (dry) the moisture contained in the adsorbent installed in the PSA dehumidifier, thereby regenerating the PSA dehumidifier. Furthermore, by using this embodiment, hydrogen containing moisture can be used in the fuel cell stack without being discharged to the outside. As a result, in the hydrogen energy system of this embodiment, energy waste can be reduced and energy efficiency can be increased. In addition, by using this embodiment, the dehumidification function can be performed without using two PSA dehumidifiers as in the conventional method, so a hydrogen energy system can be realized with a simpler configuration than before, and equipment costs can be reduced.

[0021] In the stationary hydrogen energy system described above, when the pressure inside the PSA dehumidifier reaches a third pressure or higher, the generated hydrogen may be stored in the hydrogen storage device.

[0022] By using this embodiment, the water content of the generated hydrogen can be efficiently removed, and the hydrogen can be stored.

[0023] In the above stationary hydrogen energy system, when the pressure in the PSA dehumidifier becomes equal to or lower than a fourth pressure, hydrogen stored in the hydrogen storage device may be passed through the PSA dehumidifier.

[0024] In the above stationary hydrogen energy system, the first pressure may be 0.80 to 0.99 MPaG, and the second pressure may be 0.05 to 0.2 MPaG.

[0025] By using this aspect, moisture in the PSA dehumidifier (adsorbent) can be efficiently removed, and regeneration of the dehumidifying function of the PSA dehumidifier can be promoted.

[0026] In the above stationary hydrogen energy system, a heater provided near the PSA dehumidifier may be provided.

[0027] By using this aspect, regeneration of the dehumidifying function of the dehumidifier can be promoted. It is assumed that it will be used in a mode that suppresses the power generation time of the fuel cell system and prioritizes hydrogen storage.

[0028] In the above stationary hydrogen energy system, a bypass line may be provided that can supply hydrogen from the hydrogen storage device to the fuel cell stack without passing through the PSA dehumidifier.

[0029] In the prior art, it is common to use a flow rate of about 1 / 10 of the hydrogen production amount for dehumidification treatment, and it is known that moisture removal by the dehumidifier functions sufficiently even at a relatively low flow rate. In this aspect, in the supply of hydrogen from the hydrogen storage device to the fuel cell stack, instead of passing the entire amount through the PSA dehumidifier, a configuration is adopted in which a part of the hydrogen is directly supplied to the fuel cell stack via a bypass line, thereby avoiding the pressure loss of the dehumidifier and improving the maximum supply flow rate of hydrogen to the fuel cell system, and also improving the responsiveness.

[0030] In the above-described stationary hydrogen energy system, a bleed line may be provided between the PSA dehumidifier and the water electrolysis cell stack, which is capable of releasing hydrogen to the outside.

[0031] In this configuration, when a large amount of hydrogen needs to be stored from a nearly empty state, such as during the initial period of use or after implementing a Business Continuity Plan (BCP), when user power consumption is low, or when the fuel cell stack is not operated for any reason, such as in the event of a fuel cell stack failure, the PSA dehumidifier can be regenerated and hydrogen can be stored by releasing a small amount of hydrogen from this bleed line while turning on the heater, instead of operating the fuel cell stack. [Effects of the Invention]

[0032] According to one embodiment of the present invention, by effectively utilizing the hydrogen containing moisture generated during the regeneration of a dehumidifier (when removing moisture from the dehumidifier) ​​and by creating a configuration that combines humidification and dehumidification regeneration functions, it is possible to completely eliminate the emission of hydrogen for dehumidification and improve the energy efficiency related to dehumidification to 100%. Therefore, it is possible to provide a hydrogen energy system that can improve the energy efficiency of the entire system. [Brief explanation of the drawing]

[0033] [Figure 1] This is an overall configuration diagram of a hydrogen energy system according to one embodiment of the present invention. [Figure 2] This is a control flow diagram for a hydrogen energy system according to one embodiment of the present invention. [Figure 3] This is a timing chart for a hydrogen energy system according to one embodiment of the present invention. [Figure 4] This is a schematic diagram showing the flow of hydrogen in a hydrogen energy system relating to one embodiment of the present invention. [Figure 5] This is a control flow diagram for a hydrogen energy system according to one embodiment of the present invention. [Figure 6] This is a schematic diagram showing the flow of hydrogen in a hydrogen energy system relating to one embodiment of the present invention. [Figure 7] This is an overall configuration diagram of a hydrogen energy system according to one embodiment of the present invention. [Figure 8] This is an overall configuration diagram of a hydrogen energy system according to one embodiment of the present invention. [Figure 9] This is an overall configuration diagram of a hydrogen energy system according to one embodiment of the present invention. [Figure 10] This is a timing chart for a hydrogen energy system according to one embodiment of the present invention. [Modes for carrying out the invention]

[0034] The embodiments of the invention disclosed in this application will be described below with reference to the drawings. However, the present invention can be implemented in various forms without departing from its essence, and is not to be construed as being limited to the embodiments described below.

[0035] In the drawings referenced in this embodiment, identical parts or parts with similar functions are denoted by the same or similar reference numerals (with A, B, etc. appended to the reference numeral). Furthermore, the dimensional ratios in the drawings may differ from the actual ratios for illustrative purposes, and some components may be omitted from the drawings.

[0036] In this specification, “connection” includes not only cases where two components are directly connected, but also cases where they are indirectly connected through another component.

[0037] <First Embodiment> The hydrogen energy system according to this embodiment will be described below with reference to the drawings.

[0038] (1. Configuration of the hydrogen energy system) Figure 1 is an overall configuration diagram of the hydrogen energy system 10 in this embodiment. The hydrogen energy system 10 is a stationary energy system. As shown in Figure 1, the hydrogen energy system 10 includes a water electrolysis cell stack 100, a dehumidifier 200, a hydrogen storage unit 300, a fuel cell cell stack 400, a hydrogen flow path 500, and a control device 600.

[0039] The water electrolysis cell stack 100 (also called "EC") includes an oxygen electrode (anode) 110, a hydrogen electrode (cathode) 120, an electrolyte membrane (separator) 130, an inlet 140, a water inlet 150, an oxygen outlet 160, and a hydrogen outlet 170. The oxygen electrode (anode) 110 and the hydrogen electrode (cathode) 120 can be made of conductive materials such as metal or carbon materials as appropriate. Catalysts are provided in the oxygen electrode (anode) 110 and the hydrogen electrode (cathode) 120. The electrolyte membrane 130 is provided to separate the oxygen electrode (anode) 110 and the hydrogen electrode (cathode) 120, and ions can move inside the electrolyte membrane 130. The water electrolysis cell stack 100 electrolyzes water supplied from the water inlet 150 using electricity supplied from the inlet 140. At this time, oxygen is produced at the oxygen electrode (anode) 110 and hydrogen is produced at the hydrogen electrode (cathode) 120. The generated oxygen is discharged from the oxygen outlet 160. The generated hydrogen is discharged from the hydrogen outlet 170.

[0040] The PSA dehumidifier 200 includes a first hydrogen inlet / outlet 210, a second hydrogen inlet / outlet 220, and an adsorption section 230. The adsorption section 230 includes an adsorbent 231. In this example, activated alumina is used as the adsorbent 231. In addition to activated alumina, silica gel, zeolite, calcium salt-based, clay-based, magnesium salt-based, etc., may also be used as the adsorbent 231. When a raw material gas is supplied, the adsorbent 231 is pressurized to efficiently adsorb components that can be adsorbed, and allows components that are difficult to adsorb to pass through. In this embodiment, in the PSA dehumidifier 200, moisture contained in the hydrogen taken in from the first hydrogen inlet / outlet 210 is adsorbed (removed), and hydrogen passes through. As a result, the dried hydrogen is discharged from the second hydrogen inlet / outlet 220. On the other hand, when the pressure is reduced, the gas (moisture) adsorbed from the adsorbent 231 is desorbed.

[0041] The hydrogen storage unit 300 (also called "MH") stores hydrogen dried in the PSA dehumidifier 200 via the hydrogen flow path 500 and hydrogen inlet / outlet 310, and supplies hydrogen to the fuel cell cell stack 400 via the hydrogen inlet / outlet 310, the PSA dehumidifier 200, and the hydrogen flow path 500. The hydrogen storage unit 300 uses an MH tank containing a hydrogen storage alloy. A hydrogen storage alloy is an alloy that can absorb and store hydrogen while releasing heat by hydrogenation, and can release heat by absorbing it. Examples of hydrogen storage alloys that can be used include hydrides of magnesium (Mg), titanium (Ti), vanadium (V), zirconium (Zr), lanthanum (La), aluminum-iron alloys, and other known materials. The hydrogen storage unit 300 has a cylinder-type shape.

[0042] The fuel cell stack 400 (also called "EC") includes an air electrode (anode) 410, a hydrogen electrode (cathode) 420, an electrolyte 430, a hydrogen supply port 440, and an air supply port 450. The fuel cell stack 400 generates electricity through a chemical reaction using hydrogen stored in a hydrogen storage unit 300 supplied via the hydrogen supply port 440 and air (oxygen) supplied via the air supply port 450. The generated electricity is supplied to an external device from the output port 460.

[0043] The hydrogen flow path 500 is equipped with a check valve OV1, a safety valve RV1, shut-off valves (SV1, SV2, SV3), control valves (CV1, CV2, CV3), and pressure sensors (PS1, PS2, PS3). The check valve OV1 is provided to prevent hydrogen from flowing back into the water electrolysis cell stack 100. The safety valve RV1 is provided to automatically open when the internal pressure of the piping or container exceeds a set value, releasing the excess pressure to the outside. This protects the piping, equipment, and pressure vessel from damage or explosion due to overpressure. The shut-off valves SV1, SV2, and SV3 are provided to control the flow of fluid (liquid / gas) in the piping. The control valves (pressure valves) CV1, CV2, and CV3 are provided to maintain a constant pressure of the flowing hydrogen. By providing these valves, the pressure, flow rate, and direction of the hydrogen flowing through the hydrogen flow path 500 can be controlled. In this embodiment, the control valves CV1, CV2, and CV3 are mechanically controlled.

[0044] In this embodiment, the control valve CV1 and the shut-off valve SV1 are provided in the first hydrogen channel 5001, which is located between the PSA dehumidifier 200 and the hydrogen storage unit 300 within the hydrogen channel 500. High-pressure hydrogen (0.98 MPaG in this example) flows through the first hydrogen channel 5001. The control valve CV2 and the shut-off valve SV2 are provided in the second hydrogen channel 5002, which is located between the PSA dehumidifier 200 and the hydrogen storage unit 300 within the hydrogen channel 500. Low-pressure hydrogen (0.2 MPaG in this example) flows through the second hydrogen channel 5002. The control valve CV3 and the shut-off valve SV3 are provided in the third hydrogen channel 5003, which is located between the PSA dehumidifier 200 and the fuel cell cell stack 400 within the hydrogen channel 500. Low-pressure hydrogen (0.05 MPaG in this example) flows through the third hydrogen channel 5003.

[0045] The control device 600 controls the operation of the entire hydrogen energy system 10, for example, the water electrolysis cell stack 100 and the fuel cell stack 400. The control device 600 includes a control unit 610 and a memory unit 620.

[0046] The control unit 610 can control various operations of the water electrolysis cell stack 100, the fuel cell stack 400, and other components in the hydrogen energy system 10. The control unit 610 includes, for example, a processor equipped with a arithmetic processing unit exemplified by a CPU (Central Processing Unit), and memory exemplified by ROM (Read On Memory) and RAM (Random Access Memory).

[0047] The storage unit 620 may use semiconductor memory such as an SSD (Solid State Drive), as well as magnetic recording media (magnetic tape, magnetic disk, etc.), optical recording media, magneto-optical recording media, or memory-capable elements that serve as storage media. The storage unit 620 has the function of storing control programs and various types of information used in the control programs.

[0048] (2. Control methods for hydrogen energy systems) Next, we will explain the control method for hydrogen energy systems, particularly the flow of hydrogen in hydrogen energy systems, using Figures 2 to 6.

[0049] (2-1. During operation of the water electrolysis cell stack) Figure 2 is a control flow diagram when the water electrolysis cell stack 100 is in operation. Figure 3 is a timing chart of the hydrogen energy system 10. Figure 4 is a schematic diagram when the water electrolysis cell stack 100 is in operation. As shown in Figure 2, first, the control device 600 controls the water electrolysis cell stack 100 to operate (step S101). At this time, as shown in Figure 3, the control valve CV1 is mechanically closed. The control device 600 controls the shut-off valves SV2~3 to be closed and the shut-off valve SV1 to be open. Hydrogen is generated in the water electrolysis cell stack 100 (step S103). At this time, the generated hydrogen flows into the PSA dehumidifier 200 via the first hydrogen inlet / outlet 210 (step S105). At this time, water is removed from the hydrogen by the hydrogen adsorption section 230 (adsorbent 231) (step S106).

[0050] Each time hydrogen flows into the PSA dehumidifier 200, the pressure inside the PSA dehumidifier 200 increases further.

[0051] The control valve CV1 mechanically controls whether the pressure in the PSA dehumidifier 200 (and on the upstream side of the control valve CV1 (PSA dehumidifier 200)) is greater than or equal to a first pressure (0.8~0.99 MPaG) that is higher than a preset 0.5 MPa, or preferably a third pressure (0.98 MPaG in this example) (step S107). When the hydrogen pressure is less than the first pressure (initial state) (step S107; No), CV1 remains "closed" (step S109). When the pressure becomes greater than or equal to the first pressure (stable period) (step S107; Yes), the control valve CV1 becomes "controlled open (controlled slightly open)" to maintain the set pressure (0.98 MPaG) on the primary (upstream) side, and to allow any excess pressure to flow to the hydrogen storage tank 300 on the secondary (downstream) side (step S111). As a result, the hydrogen passes through the PSA dehumidifier 200 at a first pressure higher than 0.5 MPaG, where moisture is efficiently removed (dried), and it is stored in the hydrogen storage unit 300 via the hydrogen channel 500 (first hydrogen channel 5001), control valve CV1, shut-off valve SV1, safety valve RV1, and hydrogen inlet / outlet 310 (step S113). The above process continues until a predetermined period (8 hours in this example) has elapsed (step S115; No). After the predetermined period has elapsed (step S115; Yes), the process transitions to the operation of the fuel cell stack 400 (step S200). Before transitioning to the operation of the fuel cell stack 400, a standby state may be provided for a certain period (for example, until the amount of electricity used exceeds a certain amount at night) (step S117).

[0052] (2-2. During operation of the fuel cell stack) Figure 5 is a control flow diagram when the fuel cell stack 400 is operating. Figure 6 is a schematic diagram when the fuel cell stack 400 is operating. As shown in Figure 5, first the control device 600 controls the fuel cell stack 400 to operate (step S201). At this time, as shown in Figure 3, control valve CV2 is mechanically controlled to be "closed", and control valve CV3 is mechanically "controlled open (controlled slightly open)" to a predetermined pressure (0.05 MPaG in this example). Shut-off valves SV2~3 are "open", and shut-off valve SV1 is "closed", as controlled by the control device 600.

[0053] The hydrogen in the PSA dehumidifier 200 is sent to the fuel cell stack 400 and consumed. Each time hydrogen is consumed, the (internal) pressure in the PSA dehumidifier 200 decreases (step S203). As the pressure in the PSA dehumidifier 200 decreases, moisture is desorbed from the adsorbent 231 (step S205).

[0054] The control valve CV2 mechanically controls (determines) whether the pressure of the PSA dehumidifier 200 (and the PSA dehumidifier 200 side of the control valve CV2) is lower than a preset second pressure (0.05 to 0.2 MPaG), preferably a fourth pressure (in this example, 0.2 MPaG) or less (step S207). If the hydrogen pressure is higher than the second pressure (step S207; No), the control valve CV2 remains "closed" (step S209). When the hydrogen pressure becomes less than or equal to the second pressure (step S207; Yes), the control valve CV2 is mechanically "controlled open (controlled slightly open)" to maintain a predetermined pressure (in this example, 0.2 MPaG) (step S211). As a result, the hydrogen stored in the hydrogen storage unit 300 flows into the PSA dehumidifier 200 from the second hydrogen inlet / outlet 220 via the hydrogen flow path 500 (second hydrogen flow path 5002) under a second pressure.

[0055] At this time, the hydrogen passes through the PSA dehumidifier 200 in the opposite direction to when it dries (also called the "second direction") (backflow) (step S213). The hydrogen, having absorbed the desorbed moisture present in the PSA dehumidifier 200 (humidified), is discharged from the first hydrogen inlet / outlet 210 (step S215). As a result, moisture in the PSA dehumidifier 200 is efficiently removed without heating, and the dehumidifying function of the PSA dehumidifier 200 is restored.

[0056] Hydrogen containing water is supplied to the fuel cell stack 400 via the control valve CV3, the shut-off valve SV3, and the hydrogen supply port 440. Electricity is generated using the hydrogen supplied from the hydrogen supply port 440 and the air (oxygen) supplied from the air supply port 450 (step S217). The above process continues until a predetermined period has elapsed (step S219; No). After the predetermined period has elapsed (step S219; Yes), the process returns to the operation of the water electrolysis cell stack 100 (step S100). In this embodiment, a standby state may be provided for a certain period (for example, until sunrise) before the operation of the water electrolysis cell stack 100 (step S221).

[0057] (3. Effects and Benefits of Hydrogen Energy Systems) By using this embodiment, when switching from the operation of the water electrolysis cell stack 100 to the operation of the fuel cell stack 400, the dry hydrogen stored in the hydrogen storage unit 300 is used to remove (dry) the moisture contained in the adsorbent installed in the PSA dehumidifier 200 without heating. In this case, the hydrogen containing moisture is not discharged to the outside but is used in the fuel cell cell stack 400. As a result, in the hydrogen energy system of this embodiment, the consumption of additional energy for the regeneration (moisture removal) of the PSA dehumidifier 200 is suppressed, and the energy efficiency of the entire hydrogen energy system can be improved.

[0058] Furthermore, by using this embodiment, the dehumidification function can be achieved without using two PSA dehumidifiers as in the conventional method. As a result, a hydrogen energy system can be realized with a simpler configuration that reduces the number of control valves and shut-off valves compared to the conventional method, and equipment costs can also be reduced.

[0059] <Second Embodiment> This embodiment describes a hydrogen energy system different from that of the first embodiment. Specifically, an example in which a bypass line is provided will be described. Configurations that overlap with those of the first embodiment will be explained as appropriate.

[0060] Figure 7 is an overall configuration diagram of the hydrogen energy system 10A in this embodiment. As shown in Figure 7, the hydrogen energy system 10A includes a water electrolysis cell stack 100, a dehumidifier 200, a hydrogen storage unit 300, a fuel cell cell stack 400, a hydrogen flow path 500, and a control device 600, in addition to a bypass line 700.

[0061] The bypass line 700 is provided to connect the second hydrogen channel 5002 and the third hydrogen channel 5003 of the hydrogen channel 500. The bypass line 700 may be provided with components such as a control valve, a shut-off valve, and an orifice. For example, in this embodiment, the shut-off valve may be controlled to open after a certain period of time has elapsed (or after the moisture in the PSA dehumidifier 200 has been removed).

[0062] In this embodiment, when hydrogen supplied from the hydrogen storage unit 300 passes through the bypass line 700, it can be supplied to the fuel cell stack 400 without passing through the PSA dehumidifier 200. As a result, after the water in the PSA dehumidifier 200 is removed by the hydrogen supplied from the hydrogen storage unit 300, it is no longer necessary to pass the hydrogen through the PSA dehumidifier 200, thereby avoiding pressure loss in the PSA dehumidifier 200, improving the hydrogen supply flow rate to the fuel cell stack, and improving responsiveness.

[0063] <Third Embodiment> This embodiment describes a hydrogen energy system different from that of the first embodiment. Specifically, an example in which a bleed line with a discharge valve is provided will be described. Configurations that overlap with those of the first embodiment will be explained as appropriate.

[0064] Figure 8 is an overall configuration diagram of the hydrogen energy system 10B in this embodiment. As shown in Figure 8, the hydrogen energy system 10B includes a water electrolysis cell stack 100, a dehumidifier 200, a hydrogen storage unit 300, a fuel cell cell stack 400, a hydrogen flow path 500, and a control device 600, in addition to a bleed line 5004 and a heater 800.

[0065] The bleed line 5004 is located in the hydrogen flow path 500 on the water electrolysis cell stack 100 side of the PSA dehumidifier 200 (between the PSA dehumidifier 200 and the water electrolysis cell stack 100). A discharge valve SV4 is provided in the bleed line 5004. The heater 800 is located close to the PSA dehumidifier 200. The heater 800 is used to heat the PSA dehumidifier 200 to promote drying inside the PSA dehumidifier 200. This promotes the regeneration of the dehumidification function of the PSA dehumidifier 200 and can be used in a mode that prioritizes hydrogen storage.

[0066] In this embodiment, when it is desired to store a large amount of hydrogen from a nearly empty state in the water electrolysis cell stack, such as during the initial use of the water electrolysis cell stack or after BCP (Business Continuity Plan) measures have been implemented, when the user's power consumption is low, or when the fuel cell cell stack 400 is not operated for any reason, such as in the event of a failure of the fuel cell cell stack 400, instead of operating the fuel cell cell stack 400 at night, the heater 800 is operated while releasing a small amount of hydrogen from the bleed line 5004 (discharge valve SV4). This allows the PSA dehumidifier 200 to be regenerated and enables the storage of hydrogen in the hydrogen energy system. The hydrogen loss in this case is less than or equal to that of the conventional hydrogen energy configuration.

[0067] <Fourth Embodiment> This embodiment describes a hydrogen energy system different from that of the first embodiment. Specifically, it describes an example in which a control valve is controlled by a control device. Configurations that overlap with those of the first embodiment will be explained as appropriate.

[0068] Figure 9 is an overall configuration diagram of the hydrogen energy system 10C. In this embodiment, as shown in Figure 9, the hydrogen energy system 10C includes a water electrolysis cell stack 100, a PSA dehumidifier 200, a hydrogen storage unit 300, a fuel cell cell stack 400, a hydrogen flow path 500C, and a control device 600. In this embodiment, the hydrogen flow path 500C does not necessarily include a second hydrogen flow path 5002 (control valve CV2 and shut-off valve SV2). In this case, the control device 600 may control the opening and closing of the control valve CV1 when the water electrolysis cell stack 100 is operating and when the fuel cell cell stack 400 is operating.

[0069] Figure 10 is a timing chart of the hydrogen energy system 10C in this embodiment. In this embodiment, when the water electrolysis cell stack is operating, the control device 600 determines whether the pressure of the PSA dehumidifier 200 (and the PSA dehumidifier 200 side of the control valve CV1) is equal to or greater than a preset first pressure (0.98 MPaG in this example). When the hydrogen pressure is less than the first pressure (initial state), the control valve CV1 is closed and the shut-off valve SV1 is closed. When the hydrogen pressure becomes equal to or greater than the first pressure (stable phase), the control device 600 controls the control valve CV1 to "control open (control slightly open)" to maintain the primary side set pressure (0.98 MPaG), and controls the shut-off valve SV1 to "open" so that any excess pressure is flowed to the downstream hydrogen storage tank 300.

[0070] When the fuel cell stack 400 is operating, the control device 600 determines whether the PSA dehumidifier 200 (and the PSA dehumidifier 200 side of the control valve CV1) is below a preset second pressure (in this example, 0.2 MPaG). If the hydrogen pressure is higher than the second pressure (initial state), the control device 600 controls the control valve CV1 to "close" and the shut-off valve SV1 to "close". When the pressure becomes below the second pressure (stable phase), the control device 600 controls the control valve CV1 to "control open (control slightly open)" to maintain the pressure at a predetermined level (in this example, 0.2 MPaG) and the shut-off valve CV1 to "open". As a result, the hydrogen stored in the hydrogen storage unit 300 flows into the PSA dehumidifier 200 from the second hydrogen inlet / outlet 220.

[0071] In this embodiment, the control device 600 controls the control valve CV1. As a result, even if the control valve CV2 is omitted, the hydrogen flow during water electrolysis cell stack operation and fuel cell stack operation can be controlled by the control valve CV1 alone, making the hydrogen energy system a simpler configuration.

[0072] (modified version) Within the scope of the concept of the present invention, a person skilled in the art can conceive of various modifications and alterations, and it is understood that such modifications and alterations also fall within the scope of the present invention. For example, any addition, deletion, or design change of components, or addition, omission, or modification of processing conditions, made by a person skilled in the art to the above-described embodiments, are also included within the scope of the present invention, as long as they retain the gist of the present invention. Furthermore, the embodiments may be used in combination as appropriate.

[0073] In one embodiment of the present invention, a dew point meter may be provided in the third hydrogen channel 5003 of the hydrogen channel 500. In this case, the hydrogen stored in the hydrogen storage unit 300 may be passed through the PSA dehumidifier 200 until the dew point temperature of the hydrogen that has passed through the PSA dehumidifier 200 falls below a preset dew point temperature. This makes it possible to supply a sufficient amount of hydrogen to the fuel cell cell stack 400 while effectively regenerating the dehumidification function of the PSA dehumidifier 200, without using two PSA dehumidifiers as in the conventional method.

[0074] In one embodiment of the present invention, dew point meters may be provided on both sides of the PSA dehumidifier 200 (on the first hydrogen inlet / outlet 210 side and the second hydrogen inlet / outlet 220 side). In this case, hydrogen stored in the hydrogen storage unit 300 may be passed through the PSA dehumidifier 200 until the difference in dew point temperature of hydrogen before and after passing through the PSA dehumidifier 200 falls below a preset temperature difference. This makes it possible to supply a sufficient amount of hydrogen to the fuel cell cell stack 400 while more reliably regenerating the dehumidification function of the PSA dehumidifier 200, without using two PSA dehumidifiers as in the conventional method.

[0075] In one embodiment of the present invention, an example using a PSA dehumidifier 200 was shown, but the present invention is not limited thereto. For example, a TSA (Temperature Swing Absorption) dehumidifier that adsorbs and desorbs materials due to temperature fluctuations may be used, or a dehumidifier having other adsorption / desorption mechanisms may be used, or multiple types of dehumidifiers may be used in combination as needed. [Explanation of Symbols]

[0076] 10···Hydrogen energy system, 10A···Hydrogen energy system, 10B···Hydrogen energy system, 10C···Hydrogen energy system, 100···Water electrolysis cell stack, 110···Oxygen electrode (anode), 120···Hydrogen electrode (cathode), 130···Electrolyte membrane (partition), 130···Electrolyte membrane, 140···Input port, 150···Water inlet, 160···Oxygen outlet, 170···Hydrogen outlet, 200···Dehumidifier, 210···First hydrogen inlet / outlet, 220···Second hydrogen inlet / outlet, 230···Adsorption section, 231···Adsorbent, 300· ...Hydrogen storage unit, 310...Hydrogen inlet / outlet, 400...Fuel cell cell stack, 410...Air electrode (anode), 420...Hydrogen electrode (cathode), 430...Electrolyte (electrolyte solution), 440...Hydrogen supply port, 450...Air supply port, 460...Output port, 500...Hydrogen flow path, 500C...Hydrogen flow path, 600...Control device, 610...Control unit, 620...Memory unit, 700...Bypass line, 800...Heater, 5001...First hydrogen flow path, 5002...Second hydrogen flow path, 5003...Third hydrogen flow path, 5004...Bleed line

Claims

1. A water electrolysis cell stack that generates hydrogen by electrolyzing water, A hydrogen storage device for storing hydrogen, A fuel cell stack that generates electricity using hydrogen, A PSA dehumidifier that removes water from hydrogen, The system includes a control device for controlling the operation of the fuel cell stack and the water electrolysis cell stack, During operation of the water electrolysis cell stack, the hydrogen generated in the water electrolysis cell stack is passed through the PSA dehumidifier at a first pressure higher than 0.5 MPaG to remove the water contained in the generated hydrogen, and then stored in the hydrogen storage unit. During operation of the fuel cell cell stack, the hydrogen stored in the hydrogen reservoir is passed through the PSA dehumidifier at a second pressure lower than the first pressure to remove moisture from the PSA dehumidifier without heating, and then supplied to the fuel cell cell stack. A stationary hydrogen energy system.

2. The control device switches the operation of the fuel cell cell stack and the water electrolysis cell stack at predetermined intervals. A stationary hydrogen energy system according to claim 1.

3. When the pressure inside the PSA dehumidifier reaches a third pressure or higher, the generated hydrogen is stored in the hydrogen storage device. A stationary hydrogen energy system according to claim 1.

4. When the pressure inside the PSA dehumidifier falls below the fourth pressure, the hydrogen stored in the hydrogen storage device is passed through the PSA dehumidifier. A stationary hydrogen energy system according to claim 1.

5. The first pressure is 0.80 to 0.99 MPaG. The second pressure is 0.05 to 0.2 MPaG. A stationary hydrogen energy system according to claim 1.

6. A heater provided in close proximity to the PSA dehumidifier to promote drying inside the PSA dehumidifier, A stationary hydrogen energy system according to claim 1.

7. The system includes a bypass line that allows hydrogen to be supplied from the hydrogen storage device to the fuel cell stack without going through the PSA dehumidifier. A stationary hydrogen energy system according to claim 1.

8. The PSA dehumidifier and the water electrolysis cell stack are positioned and include a bleed line capable of releasing hydrogen to the outside. A stationary hydrogen energy system according to claim 1.

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