Hydrogen gas production device with photocatalyst

Abstract

To enable maximally accurate estimation of pressure in a water bath 2 in a hydrogen gas production device 1 with a photocatalyst.SOLUTION: In a hydrogen gas production device, in-water bath pressure estimation means determines, as a present estimation value of in-water bath pressure at present, a value obtained by multiplying a preliminarily examined, tentative estimated value of the in-water bath pressure at radiating light intensity at present determined based on the in-water bath pressure at a time when light from a light source device 4 radiates at various levels of the radiating light intensity to a photocatalyst object by a correction factor calculated based on a detected value of pressure detected by pressure detection means 12 provided on a produced gas conveying flow channel and the tentative estimated value of the in-water bath pressure at the radiating light intensity at a time when pressure corresponding to the detected value occurs in a water bath.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen gas production device, and more particularly to a device that produces hydrogen gas by a water decomposition reaction using a photocatalyst. [Background technology]

[0002] Hydrogen gas, which is expected to be used as a clean, next-generation fuel that does not produce carbon dioxide when burned, can be produced by a water decomposition reaction using light energy with a photocatalyst. Therefore, various technologies for producing hydrogen gas using a photocatalyst have been proposed. For example, Patent Document 1 proposes a hydrogen gas production device that includes a container (water tank) for receiving water, a photocatalyst dispersed or placed in the water within the container, and a photocatalyst containing a photocatalytic substance that, when irradiated with light, generates excited electrons and holes, causing a water decomposition reaction that decomposes water into hydrogen and oxygen, thereby generating hydrogen gas, a light source that emits light that irradiates the photocatalyst and causes the water decomposition reaction, and a housing supporting the light source. The housing is placed in the water within the container, the water is heated by exhaust heat from the light source emitted from the surface of the housing, and the surface of the housing that comes into contact with the water is coated with the photocatalytic substance. Patent Document 2 discloses a hydrogen gas production device that uses several hydrogen gas production methods, including a photocatalytic method, and detects the amount of stored hydrogen gas using a pressure sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2023-094488 [Patent Document 2] Patent Publication No. 2000-144464 Summary of the Invention [Problem to be solved by the invention]

[0004] As in Patent Document 1, an apparatus for producing hydrogen gas by storing water containing dispersed or disposed photocatalysts in a water tank and irradiating the water with light from a light source device such as an LED to induce a water splitting reaction is advantageous in that it can be installed anywhere. Furthermore, in such an apparatus, the amount of gas generated in the water tank can be adjusted by adjusting the intensity of the light emitted from the light source device, thereby adjusting the pressure in the water tank. However, in such a hydrogen gas production apparatus, it is preferable to be able to monitor the pressure in the water tank so that the pressure in the water tank is controlled within an appropriate range. Therefore, if a pressure sensor for detecting the pressure in the water tank is installed in the water tank, the pressure sensor may malfunction due to exposure to water splashes caused by the gas generation. Therefore, it is preferable to install the pressure sensor in a transport channel for the gas generated and collected in the water tank (produced gas), which is out of the reach of water splashes.

[0005] However, when a pressure sensor is installed in the generated gas transport path or the like to detect the pressure inside the water tank, it takes a significant amount of time (several seconds) for the pressure inside the water tank to propagate to the pressure sensor, and the detected value of the pressure sensor is delayed from the pressure inside the water tank at that time by the time it takes for the pressure inside the water tank to propagate to the pressure sensor. Therefore, due to this time delay, it is difficult to accurately adjust the light intensity for regulating the pressure inside the water tank based on the detected value of the pressure sensor installed in the generated gas transport path or the like. In particular, if the pressure inside the water tank has an allowable limit and the irradiated light intensity needs to be controlled so that the pressure inside the water tank does not exceed that allowable limit, the detected value of the pressure sensor lags behind the pressure inside the water tank. Therefore, even if the pressure inside the water tank has already reached the allowable limit, the detected value of the pressure sensor may be below the threshold, causing the irradiated light intensity to be increased, resulting in the pressure inside the water tank exceeding the allowable limit. To avoid such a situation, measures are taken to suppress the increase in the intensity of the irradiated light when the detection value of the pressure sensor reaches a threshold value set sufficiently lower than the allowable limit so that the pressure inside the water tank remains well below the allowable limit.However, in this case, even if the pressure inside the water tank is within the allowable limit, the amount of hydrogen gas generated inside the water tank will be suppressed, and the hydrogen gas generation capacity of the hydrogen gas production device will not be fully utilized.Therefore, it is advantageous to be able to estimate the pressure inside the water tank as accurately as possible in real time and adjust the intensity of the irradiated light based on this estimate to control the pressure inside the water tank.

[0006] Thus, a main object of the present invention is to enable the pressure inside the water tank to be estimated in real time as accurately as possible in a hydrogen gas production device using a photocatalyst.

[0007] In this regard, one possible method for estimating the aquarium pressure is to first determine the aquarium pressure at various light intensities (if the light intensity is kept constant and the aquarium pressure becomes steady at each light intensity, the pressure sensor's detection value will correspond to the aquarium pressure, making it possible to determine the aquarium pressure for each light intensity), and then use this previously determined relationship between the light intensity and the aquarium pressure to estimate the current aquarium pressure from the current light intensity. However, the amount of gas generated relative to the light intensity varies depending on the state of the photocatalyst, such as deterioration, and therefore the aquarium pressure relative to the light intensity also varies depending on the state of the photocatalyst. Therefore, in order to accurately estimate the actual aquarium pressure, the previously determined relationship between the light intensity and the aquarium pressure must be used while being corrected based on the state of the photocatalyst. In this regard, since the current state of the photocatalyst is reflected in the detected value of the pressure sensor, it is possible to estimate the pressure in the tank in real time with greater accuracy by adding the detected value of the pressure sensor to the relationship between the irradiated light intensity and the pressure in the tank that has been previously investigated. This knowledge is utilized in the present invention. [Means for solving the problem]

[0008] According to one aspect of the present invention, the above problem is solved by a hydrogen gas production apparatus, A tank for storing water; a photocatalyst dispersed or placed in the water in the water tank, the photocatalyst having a photocatalytic substance that generates excited electrons and holes when irradiated with light, and causes a water decomposition reaction that decomposes water molecules into hydrogen and oxygen, thereby generating hydrogen gas and oxygen gas; a light source device that emits light that is irradiated onto the photocatalyst to induce the water decomposition reaction; a pressure detection means for detecting a pressure in a transport flow path for the gas generated in the water tank, the transport flow path being connected to the water tank; a water tank internal pressure estimation means configured to estimate the water tank internal pressure based on the irradiated light intensity of light irradiated from the light source device to the photocatalyst; Including, The water tank internal pressure estimation means A provisional estimated value determination means configured to determine a provisional estimated value of the pressure inside the water tank when light is irradiated from the light source device to the photocatalyst at an arbitrary irradiation light intensity, based on the pressure inside the water tank when light is irradiated from the light source device to the photocatalyst at various irradiation light intensities that have been checked in advance; a correction coefficient calculation means configured to calculate a correction coefficient based on the pressure detection value detected by the pressure detection means and the provisional estimated value of the pressure in the water tank determined by the provisional estimated value determination means when light is irradiated from the light source device to the photocatalyst at the irradiation light intensity at the time when the pressure corresponding to the detection value is generated in the water tank; This is achieved by an apparatus including a current estimated value determination means configured to correct the provisional estimated value of the pressure inside the tank when light is irradiated from the light source device to the photocatalyst at the current irradiation light intensity, as determined by the provisional estimated value determination means, using the correction coefficient to determine a current estimated value of the current pressure inside the tank.

[0009] In the above configuration, the "photocatalytic substance" may be a substance that, when irradiated with light, initiates a water decomposition reaction, reducing water to generate hydrogen gas. The "photocatalyst" may be particles of such a photocatalytic substance dispersed in water, or a component formed of the photocatalytic substance itself, or a substrate or matrix on which the photocatalytic substance is immobilized and disposed at a desired position in the water, or both (hereinafter, in this specification, the term "photocatalyst" refers to the photocatalytic substance). The "light source device" may typically be any type of device that receives a supply of power and emits light that is absorbed by the photocatalytic substance and initiates a water decomposition reaction. The "pressure detection means" may be any type of pressure sensor that detects the pressure in the transport channel for the gas generated in the water tank, and the detected value may be the total pressure or static pressure in the transport channel.

[0010] The light emission wavelength of the light source device is preferably selected so that the quantum yield of the photocatalyst exceeds a predetermined threshold (which may be selected arbitrarily) so that the light irradiated onto the photocatalyst is efficiently absorbed by the photocatalyst to generate excited electrons and holes. In this regard, the quantum yield of a typical photocatalyst increases rapidly when the wavelength of the irradiated light falls below a certain wavelength. Therefore, the light source may be selected so that the emission wavelength of the light source is shorter than the wavelength at which the quantum yield of the photocatalyst increases rapidly. Examples of photocatalysts that can be used in the present invention include SrTiO3 (strontium titanate), La2Ti2O7 (lanthanum titanate), Ga2O3 (gallium oxide), GaN (gallium nitride), NaTaO3 (sodium tantalate), and TiO2 (titanium oxide). These photocatalysts may be used with the addition of a promoter, if desired. Various light-emitting diodes (LEDs) may be used as the light-emitting element of the light source device, and specifically, LEDs made of indium gallium nitride (InGaN), diamond (ultraviolet), gallium nitride (GaN) / aluminum gallium nitride (AlGaN) (ultraviolet, blue), zinc selenide (blue), and zinc oxide (near ultraviolet, purple, blue) are available.

[0011] The intensity of the light irradiated from the light source device to the photocatalyst may be obtained by directly measuring the intensity of the light from the light source device using an arbitrary optical sensor, or may be converted from the power input to the light source device.

[0012] The "aquarium pressure estimation means" is a means for estimating the pressure generated in the aquarium using the intensity of light irradiated from the light source device to the photocatalyst in the aquarium and the value detected by the pressure detection means, and may be realized by operation according to a program in any computer device. More specifically, the aquarium pressure estimation means is composed of the "provisional estimated value determination means," "correction coefficient calculation means," and "current estimated value determination means," as described above.

[0013] The "provisional estimate determining means" is configured to determine a "provisional estimate" of the pressure inside the water tank when light is irradiated from the light source device to the photocatalyst at a given light intensity, based on the pre-determined pressure values ​​inside the water tank when light is irradiated from the light source device to the photocatalyst at various light intensities. Here, the pre-determined pressure values ​​generated inside the water tank when light is irradiated from the light source device to the photocatalyst at various light intensities may typically be pressure values ​​in the transport flow path of the gas generated inside the water tank detected by the pressure detecting means when light is irradiated from the light source device to the photocatalyst in water in the water tank at various light intensities prior to full-scale use of the hydrogen gas production apparatus. In this regard, as already mentioned, if the light intensity is kept constant for a period longer than the time it takes for the water tank pressure to propagate to the pressure detecting means, the pressure value detected by the pressure detecting means will coincide with the water tank pressure at the time of detection by the pressure detecting means. [In the water tank, the dynamic pressure of the airflow can be assumed to be almost negligible except at the generated gas outlet and its surrounding area. Since gas flows and dynamic pressure are significant in the transport flow path where the pressure detection means is installed, the total pressure detected by the pressure detection means roughly corresponds to the pressure (static pressure) inside the water tank when the irradiated light intensity is constant and steady.] Therefore, the value of the pressure inside the water tank when light from the light source device is irradiated to the photocatalyst at various irradiated light intensities, which has been previously investigated, can be the value obtained when the irradiated light intensity is kept constant and the detection value of the pressure detection means becomes constant for each irradiated light intensity. The "provisional estimate" is an estimate of the pressure inside the water tank when light is irradiated to the photocatalyst at a given irradiated light intensity, obtained using the relationship between the irradiated light intensity and the water tank pressure previously investigated as described above. In other words, it can be said to be the pressure inside the water tank estimated from the performance of the photocatalyst at the start of use of the hydrogen gas production device or at a certain point in time. In one embodiment, the provisional estimate determination means may be provided with a map or approximation formula prepared to give the pressure inside the aquarium using the intensity of irradiated light as a variable, and may be configured to output the pressure inside the aquarium when the intensity of irradiated light is input.

[0014] As described above, the "correction coefficient calculation means" is configured to calculate a correction coefficient based on the pressure detection value detected by the pressure detection means and the provisional estimate of the pressure inside the water tank, determined by the provisional estimate determination means, when light is irradiated from the light source device to the photocatalyst at the irradiation light intensity when a pressure corresponding to the detection value is generated in the water tank. Here, the "correction coefficient" is a coefficient for compensating for changes in the photocatalyst's performance from the time when the hydrogen gas production device was first used or at a certain time to the current photocatalyst's performance. The "provisional estimate of the pressure inside the water tank, determined by the provisional estimate determination means, when light is irradiated from the light source device to the photocatalyst at the irradiation light intensity when a pressure corresponding to the detection value is generated in the water tank" is, in essence, the pressure generated in the water tank when light is irradiated to the photocatalyst at the time when the pressure currently detected by the pressure detection means is generated, at the time when the hydrogen gas production device was first used or at a certain time. Furthermore, the detection value of the pressure detection means reflects the current photocatalyst's performance. Therefore, as described above, by using the pressure value detected by the pressure detection means and the provisional estimate of the pressure generated in the water tank when light is irradiated from the light source device to the photocatalyst at the irradiation light intensity at the time when the pressure corresponding to the detection value is generated in the water tank, as determined by the provisional estimate determination means, it is possible to determine a correction coefficient to compensate for changes in the performance of the photocatalyst from the time when the hydrogen gas production device was first used or at a certain time to the current performance of the photocatalyst (strictly speaking, the correction coefficient obtained here compensates for changes in the performance of the photocatalyst from the time when the hydrogen gas production device was first used or at a certain time back to a point several seconds before the current time, the time it took for the pressure change to reach the pressure detection means from the water tank; however, since the state of the photocatalyst does not change within a few seconds, the correction coefficient obtained here can be used to compensate for changes in the current performance of the photocatalyst). In one embodiment, the correction coefficient may be a value obtained by dividing the detection value of the pressure detection means by a provisional estimate of the pressure generated in the water tank when light is irradiated from the light source device to the photocatalyst at the irradiation light intensity at the time when the pressure corresponding to the detection value is generated in the water tank.The correction coefficient calculation means may be configured to successively update the correction coefficient, thereby obtaining a correction coefficient that follows the moment-to-moment changes in the performance of the photocatalyst.

[0015] The "current estimated value determination means" is configured to determine an estimated value (current estimated value) of the current water tank pressure by correcting the provisional estimated value of the water tank pressure when the photocatalyst is irradiated with light from the light source device at the current irradiation light intensity, as determined by the provisional estimated value determination means, using a correction coefficient. As can be understood from the above explanation, the provisional estimated value determined by the provisional estimated value determination means is the water tank pressure estimated from the photocatalyst performance at the start of use of the hydrogen gas production device or at a certain point in time. Therefore, by correcting this provisional estimated value using a "correction coefficient" to compensate for changes in the photocatalyst performance from the start of use of the hydrogen gas production device or at a certain point in time to the current photocatalyst performance, it is possible to estimate the water tank pressure when light is irradiated with light at the current irradiation light intensity under the current photocatalyst performance. Note that in some embodiments, the current estimated value may be a value obtained by multiplying the provisional estimated value of the water tank pressure when the photocatalyst is irradiated with light from the light source device at the current irradiation light intensity by the correction coefficient.

[0016] In the device of the present invention, the value detected by the pressure detection means is used to take into account the current performance of the photocatalyst, and the water tank pressure is determined by correcting the water tank pressure estimated from the irradiated light intensity with consideration of the current performance of the photocatalyst. With this configuration, the water tank pressure that reflects the current performance of the photocatalyst can be obtained without waiting for the time until the water tank pressure is transmitted to the pressure detection means, and the water tank pressure can be estimated as accurately as possible in real time.

[0017] In the device of the present invention, the pressure inside the water tank may be adjusted by an irradiation light intensity control means that adjusts the intensity of light emitted from the light source device, and the irradiation light intensity control means may be configured to adjust the intensity of light emitted from the light source device based on a current estimated value of the water tank pressure. The current estimated value of the water tank pressure takes into account the current state of the photocatalyst and is expected to be the current pressure inside the water tank, so it is expected that the irradiation light intensity can be adjusted more accurately.

[0018] In the above configuration, the irradiated light intensity control means may be configured to limit the increase in the irradiated light intensity from the light source device when the current estimated value of the water tank pressure reaches a predetermined threshold. As described above, the current estimated value of the water tank pressure takes into account the current state of the photocatalyst and is expected to be the current pressure in the water tank, and there is no time delay like the detection value of the pressure detection means installed in the generated gas transport path. Therefore, the threshold set for limiting the increase in the irradiated light intensity from the light source device can be set to a value closer to the allowable limit value of the water tank pressure than before, which is advantageous in that it allows for a greater amount of hydrogen generation. [Effects of the Invention]

[0019] Thus, in the apparatus of the present invention, the pressure inside the water tank is determined by correcting the pressure inside the water tank estimated from the intensity of irradiated light, taking into account the current performance of the photocatalyst, rather than directly referencing the pressure detection means installed in the transport path of the produced gas. This configuration allows the pressure inside the water tank to be estimated as accurately as possible in real time, which is advantageous when regulating the pressure inside the water tank. The configuration of the present invention may be used in any type of hydrogen gas production apparatus using a photocatalyst.

[0020] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention. [Brief explanation of the drawings]

[0021] [Figure 1]Fig. 1(A) is a schematic diagram illustrating the configuration of one aspect of a hydrogen gas production apparatus to which this embodiment is applied, and Fig. 1(B) is a block diagram illustrating the configuration of a water tank pressure estimator and controller in the hydrogen gas production apparatus. [Figure 2] Fig. 2(A) is a diagram showing a change in the amount of hydrogen generated GA_H2 relative to the intensity of light irradiated into the tank from the light source device (irradiation light intensity LI), and Fig. 2(B) is a diagram showing the time relationship of each value used to calculate the current estimated value of the tank pressure in this embodiment. [Figure 3] FIG. 3 is a flowchart showing the process of estimating and controlling the current estimated value of the pressure inside the water tank in the hydrogen gas production device to which this embodiment is applied. [Explanation of symbols]

[0022] 1...hydrogen gas production device, 2...water tank, 3...water, 3a...optical medium, 4...light source device, 5...light emitting element (LED), 6...power source, 7...power controller, 8...produced gas collection pipe, 9...hydrogen separator, 10...oxygen gas delivery pipe, 11...hydrogen gas delivery pipe, 12...pressure sensor (total pressure sensor), 13...water tank pressure estimator and controller (computer device) BEST MODE FOR CARRYING OUT THE INVENTION

[0023] Hydrogen gas production equipment configuration 1(A), in a hydrogen gas production apparatus 1 to which this embodiment is applied, water 3 containing a photocatalyst is stored in a water tank 2, which may be of any shape. Light-emitting element 5 supported on light source device 4 emits excitation light that triggers a water decomposition reaction on photocatalyst 3a in the water 3. As a result, water molecules are decomposed into hydrogen and oxygen in photocatalyst 3a, producing hydrogen gas H2 and oxygen gas O2. The generated hydrogen gas H2 and oxygen gas O2 are sent to hydrogen separator 9 through collection pipe 8, where they are separated into oxygen gas O2 and hydrogen gas H2. They then flow into respective delivery pipes 10 and 11 and may be stored in a storage tank (not shown). In this embodiment, as will be described later, the pressure in collection pipe 8, which is connected to the interior of water tank 2, is detected by pressure sensor 12 and used to estimate the pressure in the water tank and in controller 13. The power supplied to the light source device 4 may be controlled by any type of power controller 7 according to the pressure estimation in the water tank and the control command of the controller 13 .

[0024] In the configuration of the hydrogen gas production device 1 described above, the photocatalyst 3a contained in the water 3 may be formed from any photocatalytic material that can be used to produce hydrogen gas through a water-splitting reaction using light, as listed in the Summary of the Invention section. It may be particles dispersed in the water, a member formed from the photocatalytic material itself, or a substrate or matrix on which the photocatalytic material is immobilized and disposed at any position in the water, or both. The light-emitting element 5 used in the light source device 4 is typically a light-emitting diode, as listed in the Summary of the Invention section, and may be any element that emits light that triggers a water-splitting reaction in the photocatalyst 3a used. The hydrogen separator 9 may be of any type used in this field. The pressure sensor 12 may be of any type configured to detect the total pressure in the collection tube 8.

[0025] Tank pressure estimation and controller configuration The aquarium pressure estimator and controller 13, which estimates and controls the aquarium pressure, may be any computer device, and the estimation and control of the aquarium pressure may be realized by the operation of the computer device according to a program. Referring to Figure 1(B), the aquarium pressure estimator and controller 13 may be provided with a provisional estimated value determiner 13a, a correction coefficient calculator 13b, and a current estimated value determiner 13c for estimating the aquarium pressure, and an irradiation light intensity controller 13d for controlling the aquarium pressure.

[0026] More specifically, when an arbitrary value of irradiation light intensity is input, provisional estimate value determiner 13a is configured to output, as a provisional estimate of the pressure inside the water tank, the pressure generated in water tank 2 before the start of use of hydrogen gas production device 1 or the photocatalyst contained in the water or in a state at a certain point in time (initial state) when light is irradiated from the light source device to water 3 in water tank 2 at that irradiation light intensity. For this purpose, prior to use of hydrogen gas production device 1 or the photocatalyst contained in the water, light is irradiated from the light source device to water 3 in water tank 2 at irradiation light intensities set to various values ​​in advance, and the pressure inside the water tank at each irradiation light intensity is obtained using the detection value of pressure sensor 12. In this regard, as mentioned in the Summary of the Invention section, since it takes a significant amount of time for the pressure inside water tank 2 to be transmitted to pressure sensor 12, when pre-determining the water tank pressure at each irradiated light intensity as described above, one embodiment is to set the irradiated light intensity to each value, wait until the detected value of pressure sensor 12 becomes constant, and then use that constant detected value to determine the water tank pressure occurring in water tank 2 corresponding to that irradiated light intensity. Typically, it can be assumed that the flow velocity in water tank 2 is negligible except near collection tube 8, so that according to Bernoulli's law, the static pressure inside water tank 2 will be equal to the total pressure at the location of pressure sensor 12 on collection tube 8.

[0027] The pressure inside the water tank 2, which corresponds to the irradiated light intensity of light irradiated from the light source device to the photocatalyst, changes in conjunction with the amount of hydrogen gas generated inside the water tank, and it has been found that the rate of increase in the amount of hydrogen generated GA_H2 typically decreases with an increase in the irradiated light intensity LI, as schematically illustrated in Figure 2(A) (see Patent Document 1). Therefore, the provisional estimate value determination unit 13a may be configured using a map or approximation formula that is prepared by first examining the value of the pressure inside the water tank when light from the light source device is irradiated to the photocatalyst at various irradiated light intensities, and then using the results to output the corresponding pressure inside the water tank for any irradiated light intensity.

[0028] The value of the irradiated light intensity input to the provisional estimated value determination unit 13a may be a value obtained by directly measuring the intensity of light from the light source device using any optical sensor or the like (not shown), or it may be a value obtained by conversion from the power input to the light source device through the power controller 7 (or it may be the value of the power sent to the light source device through the power controller 7 as a variable that gives the pressure inside the tank).

[0029] The correction coefficient calculation unit 13b is configured to calculate a correction coefficient for correcting the water tank pressure corresponding to an arbitrary irradiated light intensity provided by the provisional estimate determination unit 13a, taking into account the current performance of the photocatalyst. As mentioned above, the photocatalyst performance, i.e., the relationship between the irradiated light intensity LI and the amount of hydrogen generated GA_H2 as illustrated in FIG. 2A, changes due to factors such as deterioration associated with photocatalyst use. Therefore, the provisional estimate, which is the water tank pressure corresponding to an arbitrary irradiated light intensity (in the initial state of the photocatalyst) provided by the provisional estimate determination unit 13a, cannot be used as is as the current water tank pressure generated in the water tank 2. Therefore, in this embodiment, the provisional estimate provided by the provisional estimate determination unit 13a is corrected taking into account the current performance of the photocatalyst to calculate an estimate of the current water tank pressure (current estimate). The correction coefficient calculation unit 13b calculates the correction coefficient used for such correction.

[0030] 2(B), the tank pressure MA(t) corresponding to the detection value of pressure sensor 12 at time t corresponds to the tank pressure in tank 2 at time t-Δ, which is the time Δ required for the pressure in tank 2 to propagate to the position of pressure sensor 12. Since photocatalytic performance typically does not change significantly over time Δ, the photocatalytic performance ratio between the current and initial states, i.e., the tank pressure ratio, is given by the ratio of the tank pressure MA(t) corresponding to the detection value of pressure sensor 12 to the provisional estimated value pA(t-Δ) given by provisional estimated value determiner 13a at time t-Δ. Thus, in this embodiment, the correction coefficient C at a certain time t may be given by MA(t) / pA(t-Δ).

[0031] The current estimated value determination unit 13c determines whether the current estimated value sA(t) of the actual pressure in the water tank 2 is calculated by using the provisional estimated value pA(t) obtained from the current irradiated light intensity in the provisional estimated value determination unit 13a and the correction coefficient C, which is the performance ratio of the photocatalyst between the current state and the initial state obtained in the correction coefficient calculation unit 13b. sA(t)=C·pA(t) The current estimated value sA(t) is calculated by multiplying the internal tank pressure obtained from the performance of the photocatalyst in its initial state by the performance ratio between the current and initial states of the photocatalyst, and is therefore expected to be an estimated value closer to the actual value than pA(t) obtained by provisional estimated value determination unit 13a and than the internal tank pressure MA(t) corresponding to the value detected by pressure sensor 12.

[0032] Irradiation light intensity control unit 13d is configured to adjust the irradiation light intensity of light from light source device 4 via power controller 7 in order to adjust the internal tank pressure in water tank 2. In this case, the current estimated value sA(t) obtained in current estimated value determination unit 13c is referenced as the current internal tank pressure, so it is expected that the irradiation light intensity can be adjusted with high precision when controlling the internal tank pressure to a target value, for example. Furthermore, when controlling the internal tank pressure to be below its allowable limit, the high accuracy of the estimated internal tank pressure makes it possible to raise the internal tank pressure closer to the allowable limit, thereby making it possible to maximize the hydrogen gas production capacity of hydrogen gas production device 1.

[0033] Tank pressure estimation and controller operation 3, in the estimation of the water tank pressure and the operation of the controller 13 in the hydrogen gas production apparatus 1, first, the current irradiated light intensity LI(t) is acquired (step 1), and a corresponding provisional estimated value pA(t) of the water tank pressure is determined (step 2). Here, the irradiated light intensity LI(t) may be obtained by directly measuring the intensity of light from the light source device 4 using an arbitrary optical sensor or the like (not shown), as already mentioned, or may be converted from the power input to the light source device 4 via the power controller 7. Next, a detected value MA(t) of pressure sensor 12 is obtained (step 3), and a correction coefficient C is calculated from the detected value MA(t) and a provisional estimated value pA(t-Δ) at time t-Δ, which is the time interval Δ prior to that time, by MA(t) / pA(t-Δ) as described above (step 4). The provisional estimated value pA(t) is then multiplied by the correction coefficient C to calculate a current estimated value sA(t) of the pressure in the tank 2 (step 5). Here, the time interval Δ is the time interval until the pressure in the tank 2 is transmitted to the position of pressure sensor 12, and may be determined through experiments, etc.

[0034] In the above configuration, the correction coefficient C is updated sequentially, so it is expected that the current estimated value sA(t) of the water tank pressure can be estimated with higher accuracy.

[0035] Once the current estimated value sA(t) of the water tank pressure is estimated as described above, the intensity of the irradiated light may be appropriately controlled based on the estimated value sA(t). For example, if sA(t) exceeds an appropriately set threshold Ao (which may be appropriately set based on, for example, the allowable limit of the hydrogen separator), the intensity of the irradiated light LI may be reduced by an appropriate amount δ to ensure the safety of the device (step 6). In this regard, in the present embodiment, as already described, the current estimated value of the water tank pressure is closer to the actual value than the provisional estimated value obtained by the provisional estimated value determination unit 13a and the value detected by the pressure sensor 12. Therefore, the threshold Ao can be set closer to the allowable limit of the hydrogen separator, thereby enabling the hydrogen gas production device to perform at a higher level than before.

[0036] The above description has been made in relation to the embodiments of the present invention, but it will be apparent that many modifications and changes will be readily apparent to those skilled in the art, and the present invention is not limited to the above-described exemplary embodiments, but can be applied to various devices without departing from the concept of the present invention.

Claims

1. A hydrogen gas production apparatus, A tank for storing water; a photocatalyst dispersed or placed in the water in the water tank, the photocatalyst having a photocatalytic substance that generates excited electrons and holes when irradiated with light, and causes a water decomposition reaction that decomposes water molecules into hydrogen and oxygen, thereby generating hydrogen gas and oxygen gas; a light source device that emits light that is irradiated onto the photocatalyst to induce the water decomposition reaction; a pressure detection means for detecting a pressure in a transport flow path for the gas generated in the water tank, the transport flow path being connected to the water tank; a water tank internal pressure estimation means configured to estimate the water tank internal pressure based on the irradiated light intensity of light irradiated from the light source device to the photocatalyst; Including, The water tank internal pressure estimation means A provisional estimated value determination means configured to determine a provisional estimated value of the pressure inside the water tank when light is irradiated from the light source device to the photocatalyst at an arbitrary irradiation light intensity, based on the pressure inside the water tank when light is irradiated from the light source device to the photocatalyst at various irradiation light intensities that have been checked in advance; a correction coefficient calculation means configured to calculate a correction coefficient based on the pressure detection value detected by the pressure detection means and the provisional estimated value of the pressure in the water tank determined by the provisional estimated value determination means when light is irradiated from the light source device to the photocatalyst at the irradiation light intensity at the time when the pressure corresponding to the detection value is generated in the water tank; and a current estimated value determination means configured to determine a current estimated value of the pressure inside the tank by correcting the provisional estimated value of the pressure inside the tank when light is irradiated from the light source device to the photocatalyst at the current irradiation light intensity, as determined by the provisional estimated value determination means, using the correction coefficient.

2. 2. The apparatus of claim 1, further comprising: an illumination intensity control means for adjusting the illumination intensity of the light from said light source device based on a current estimated value of the pressure in said aquarium.

3. 3. The apparatus of claim 2, wherein the light intensity control means is configured to limit an increase in the light intensity of the light emitted from the light source device when the current estimated value of the pressure in the aquarium reaches a predetermined threshold.

4. 2. The apparatus of claim 1, wherein said pressure sensing means is configured to sense the total pressure in said delivery channel.

5. 2. The device of claim 1, wherein the correction coefficient is a value obtained by dividing the detection value by the provisional estimate of the pressure inside the water tank when light is irradiated from the light source device to the photocatalyst at the irradiation light intensity at the time when the pressure corresponding to the detection value occurs in the water tank, and the current estimate is a value obtained by multiplying the provisional estimate of the pressure inside the water tank when light is irradiated from the light source device to the photocatalyst at the current irradiation light intensity by the correction coefficient.

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