Hydrogen gas producing apparatus using photocatalyst

Abstract

To be able to estimate a hydrogen generation amount in a water tank 2 as accurately as possible in a hydrogen gas producing apparatus 1 utilizing a photocatalyst.SOLUTION: In a hydrogen gas producing apparatus, a hydrogen generation amount estimation means determines, as a current estimated value of a hydrogen generation amount in a current water tank, the resulting value obtained by multiplying a provisional estimated value of the hydrogen generation amount within a water tank section at the current irradiation light intensity by a calculated correction coefficient, where the provisional estimated value of the hydrogen generation amount within the water tank section at the current irradiation light intensity is determined based on a value of the hydrogen generation amount within the water tank section when photocatalyst material is irradiated with light from a light source device 4 at various irradiation intensities, as previously investigated, and where the correction coefficient is calculated based on a detected value of hydrogen generation amount detected by a hydrogen gas quantity detection means 12 and the provisional estimated value of the hydrogen generation amount within the tank section at the irradiation light intensity at the time when hydrogen gas corresponding to that detected value is generated within the water tank section.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, and 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 for receiving water, a photocatalyst dispersed or disposed in the water within the container, the photocatalyst having 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 and generates hydrogen gas, a light source that emits light that causes the water decomposition reaction when irradiated onto the photocatalyst, and a housing that supports the light source, the housing being placed in the water within the container, the water being 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 being coated with the photocatalytic substance. Patent Document 2 discloses a water electrolysis device comprising a plurality of water electrolysis cells, each of which has a plurality of casings formed by outer walls and containing an electrolyte, each of which has a partition wall provided inside, and the lower part of the partition wall is formed with a water electrolysis electrode membrane assembly having a photocatalytic electrode and a counter electrode formed on both sides of an ion conductive membrane, and the assembly is immersed in the electrolyte, and the photocatalytic electrode and the counter electrode are electrically connected to each other, and the water electrolysis electrode membrane assemblies in the plurality of water electrolysis cells are electrically connected in series. Furthermore, although not a hydrogen gas production technology, a photocatalytic device has been proposed that detects the amount of light activating a photocatalyst, determines an optimal light amount based on the detected light amount using a light amount control means, and adjusts and controls the light amount from the light source using a light amount adjustment means, thereby activating the photocatalyst with the amount of light required to decompose and remove substances to be removed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2023-094488 [Patent Document 2] Patent Publication No. 2008-075097 [Patent Document 3] Patent Publication No. 2000-325796 Summary of the Invention [Problem to be solved by the invention]

[0004] An apparatus for producing hydrogen gas by storing water in a tank with a dispersed or placed photocatalyst and irradiating the water with light from a light source such as an LED to induce a water-splitting reaction is advantageous in that it can be installed anywhere. In a hydrogen gas production apparatus with such a configuration, the amount of hydrogen gas generated per unit time or per predetermined time that may be set appropriately (hereinafter simply referred to as the "amount of hydrogen generated") varies depending on the intensity of the light irradiated on the water, so it is possible to adjust the amount of hydrogen generated in the apparatus by adjusting the intensity of the irradiated light.

[0005] In such a hydrogen gas production device, a hydrogen gas amount detection means, such as a hydrogen sensor that detects the amount of hydrogen generated, is typically located after the hydrogen gas and oxygen gas generated from water molecules in the water tank are collected and sent to a hydrogen separator, where the hydrogen gas is isolated. Since it typically takes several seconds for hydrogen gas to reach the position of the hydrogen gas amount detection means, the detected value of the amount of hydrogen generated (detected hydrogen amount) detected by the hydrogen gas amount detection means is delayed from the amount of hydrogen generated in the water tank by the time it takes for hydrogen gas to reach the position of the hydrogen gas amount detection means. Therefore, due to this time delay, it is difficult to accurately adjust the light intensity to adjust the amount of hydrogen generated based on the detected hydrogen amount detected by the hydrogen gas amount detection means. In particular, if the hydrogen separator has an allowable limit for the amount of hydrogen gas it can accept and the intensity of the irradiated light needs to be controlled so that the amount of hydrogen generated does not exceed this limit, the amount of hydrogen detected by the hydrogen gas amount detection means lags behind the amount of hydrogen generated in the water tank. Therefore, even if the amount of hydrogen generated in the water tank has already reached the allowable limit of the hydrogen separator, the amount of hydrogen detected by the hydrogen gas amount detection means may be below the threshold, causing the intensity of the irradiated light to be increased, resulting in the amount of hydrogen generated in the water tank exceeding the allowable limit of the hydrogen separator. To avoid this situation, measures are taken to suppress the increase in the intensity of the irradiated light when the amount of hydrogen detected in the water tank reaches a threshold set sufficiently lower than the allowable limit so that the amount of hydrogen generated in the water tank remains well below the allowable limit of the hydrogen separator. However, in this case, even if the amount of hydrogen generated in the water tank is within the allowable limit of the hydrogen separator, the amount of hydrogen generated in 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 would be advantageous to be able to estimate the amount of hydrogen generated in the tank as accurately as possible in real time, and to adjust the intensity of the irradiated light based on that estimate to control the amount of hydrogen generated in the tank.

[0006] Thus, a main object of the present invention is to make it possible to estimate the amount of hydrogen generated in a water tank 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 amount of hydrogen generated in an aquarium is to first measure the amount of hydrogen generated in the aquarium at various irradiation light intensities (if the irradiation light intensity is kept constant and the amount of hydrogen generated becomes steady at each irradiation light intensity, the amount of hydrogen detected by the hydrogen gas detection means will correspond to the amount of hydrogen generated in the aquarium, making it possible to determine the amount of hydrogen generated in the aquarium for each irradiation light intensity), and then use this previously measured relationship between the irradiation light intensity and the amount of hydrogen generated to estimate the current amount of hydrogen generated in the aquarium from the current irradiation light intensity. However, since the amount of hydrogen generated relative to the irradiation light intensity varies depending on the state of the photocatalyst, such as deterioration of the photocatalyst, in order to accurately estimate the actual amount of hydrogen generated in the aquarium, the previously measured relationship between the irradiation light intensity and the amount of hydrogen generated must be used while being corrected based on the state of the photocatalyst. The current state of the photocatalyst is reflected in the amount of hydrogen detected by the hydrogen gas amount detection means, so by taking the amount of hydrogen detected by the hydrogen gas amount detection means into account in addition to the previously determined relationship between the irradiated light intensity and the amount of hydrogen generated, it is possible to more accurately estimate the amount of hydrogen generated in the water tank in real time, taking into account the current state of the photocatalyst. 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 water tank portion for storing water; a photocatalyst dispersed or placed in the water in the water tank section, 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; a light source device that emits light that is irradiated onto the photocatalyst to induce the water decomposition reaction; a hydrogen gas amount detection means for detecting the amount of hydrogen gas generated in the water tank per predetermined time after the hydrogen gas and oxygen gas are separated; a hydrogen generation amount estimation means configured to estimate the amount of hydrogen gas generated per predetermined time period in the water tank portion based on the irradiated light intensity of light irradiated from the light source device to the photocatalyst; Including, The hydrogen generation amount estimation means a provisional estimate determining means configured to determine a provisional estimate of the amount of hydrogen gas generated per predetermined time in the water tank when light from the light source device is irradiated onto the photocatalyst at an arbitrary irradiation light intensity, based on values ​​of the amount of hydrogen gas generated per predetermined time in the water tank when light from the light source device is irradiated onto the photocatalyst at various irradiation light intensities, which have been investigated in advance; a correction coefficient calculation means configured to calculate a correction coefficient based on a detection value of the amount of hydrogen gas generated per predetermined time in the water tank portion detected by the hydrogen gas amount detection means and a provisional estimate value determined by the provisional estimate value determination means of the amount of hydrogen gas generated per predetermined time in the water tank portion when light is irradiated from the light source device to the photocatalyst at an irradiation light intensity at the time when hydrogen gas corresponding to the detection value is generated in the water tank portion; This is achieved by an apparatus including a current estimated value determination means configured to correct the provisional estimated value determined by the provisional estimated value determination means, using the correction coefficient, of the amount of hydrogen gas generated per specified time in the water tank section when light is irradiated from the light source device to the photocatalyst at the current irradiation light intensity, to determine a current estimated value of the amount of hydrogen gas currently being generated per specified time in the water 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 the 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, 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 to initiate a water decomposition reaction. The "hydrogen gas amount detection means" may be any type of sensor installed in the hydrogen gas flow path downstream of the hydrogen separator that separates oxygen gas and hydrogen gas. The sensor may be capable of detecting the hydrogen gas flow rate or concentration, thereby determining the amount of hydrogen gas generated per specified time in the water tank. Here, the "specified time" may be an appropriately set time interval or a unit time.

[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 "hydrogen generation amount estimation means" is a means for estimating the amount of hydrogen gas generated in the water tank per predetermined time period using the intensity of light irradiated from the light source device onto the photocatalyst in the water tank and the value detected by the hydrogen gas amount detection means, and may be realized by operation according to a program in any computer device. More specifically, the hydrogen generation amount estimation means is configured to include, as described above, a "provisional estimate value determination means," a "correction coefficient calculation means," and a "current estimate value determination means."

[0013] The "provisional estimate determining means" is configured to determine, as a "provisional estimate," an estimate of the amount of hydrogen gas generated per predetermined time in the water tank section when light is irradiated from the light source device to the photocatalyst at an arbitrary irradiation light intensity, based on the previously determined values ​​of the amount of hydrogen gas generated per predetermined time in the water tank section when light is irradiated from the light source device to the photocatalyst at various irradiation light intensities, as described above. Here, the previously determined value of the amount of hydrogen gas generated in the water tank section when light is irradiated from the light source device to the photocatalyst at various irradiation light intensities may typically be the amount of hydrogen gas generated per predetermined time in the water tank section detected by the hydrogen gas amount detecting means when light is irradiated from the light source device to the photocatalyst in water in the water tank section at various irradiation light intensities prior to full-scale use of the hydrogen gas production apparatus. As mentioned above, if the irradiated light intensity is kept constant for a period longer than the time it takes for hydrogen gas to reach the hydrogen gas amount detection means after generation in the water tank, the amount of hydrogen gas generated per given time detected by the hydrogen gas amount detection means will match the amount of hydrogen gas generated per given time in the water tank at the time of detection by the hydrogen gas amount detection means. Therefore, the value of the amount of hydrogen gas generated in the water tank when light from the light source device is irradiated onto the photocatalyst at various irradiated light intensities, which has been previously determined, can be the value obtained when the irradiated light intensity is kept constant and the detection value of the hydrogen gas amount detection means becomes constant for each irradiated light intensity. The "provisional estimate" is an estimate of the amount of hydrogen gas generated per given time when light is irradiated onto the photocatalyst at a given irradiated light intensity, obtained using the previously determined relationship between the irradiated light intensity and the amount of hydrogen gas generated per given time. In other words, it can be said to be the amount of hydrogen gas generated per given time 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 amount of hydrogen gas generated per predetermined time in the water tank section using the irradiated light intensity as a variable, and may be configured to output the amount of hydrogen gas generated per predetermined time in the water tank section when the irradiated light intensity is input.

[0014] The "correction coefficient calculation means" is configured to calculate a correction coefficient based on the detected value of the amount of hydrogen gas generated per predetermined time in the water tank portion, detected by the hydrogen gas amount detection means, and the provisional estimate of the amount of hydrogen gas generated per predetermined time in the water tank portion when light from the light source device is irradiated onto the photocatalyst at the irradiation light intensity at the time when hydrogen gas corresponding to the detected value is generated in the water tank portion, determined by the provisional estimate determination means. Here, the "correction coefficient" is a coefficient for compensating for changes in the photocatalyst performance from when the hydrogen gas production device was first used or at a certain point in time to the current photocatalyst performance. The above-mentioned "provisional estimate of the amount of hydrogen gas generated per predetermined time in the water tank when light from the light source device is irradiated onto the photocatalyst at the irradiation light intensity at the time when hydrogen gas corresponding to the detection value is generated in the water tank, as determined by the provisional estimate determination means" essentially means the amount of hydrogen gas generated per predetermined time in the water tank when light of the irradiation light intensity at which hydrogen gas currently detected by the hydrogen gas amount detection means is generated is irradiated onto the photocatalyst at the start of use of the hydrogen gas production device or at a certain time. Furthermore, the detection value of the hydrogen gas amount detection means is a value that reflects the current performance of the photocatalyst. Therefore, as described above, by using the detection value of the amount of hydrogen gas generated per specified time in the water tank section detected by the hydrogen gas amount detection means and the provisional estimate value determined by the provisional estimate value determination means of the amount of hydrogen gas generated per specified time in the water tank section when light is irradiated from the light source device to the photocatalyst at the irradiation light intensity at the time hydrogen gas corresponding to the detection value is generated in the water tank section, a correction coefficient can be determined 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 the current time, which is a few seconds before the time it took for hydrogen gas to reach the hydrogen gas amount detection means from the water tank section. 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 hydrogen gas amount detection means by a provisional estimate of the amount of hydrogen gas generated per predetermined time 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 hydrogen gas corresponding to the detection value is generated in the water tank. Also, the correction coefficient calculation means may be configured to sequentially update the correction coefficient, thereby obtaining a correction coefficient that follows changes in the performance of the photocatalyst from moment to moment.

[0015] The "current estimated value determination means" is configured to determine an estimated value (current estimated value) of the amount of hydrogen gas currently being generated in the water tank when light is irradiated from the light source device to the photocatalyst at the current irradiation light intensity by correcting the provisional estimated value 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 amount of hydrogen gas generated per predetermined time 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. Therefore, by correcting this provisional estimated value using a "correction coefficient" to compensate for changes in the performance of the photocatalyst from the start of use of the hydrogen gas production device or at a certain point in time to the current performance of the photocatalyst, it is possible to estimate the amount of hydrogen gas generated per predetermined time when light is irradiated at the current irradiation light intensity under the current performance of the photocatalyst. In one embodiment, the current estimated value may be a value obtained by multiplying a provisional estimated value of the amount of hydrogen gas generated per specified time in the water tank section when light is irradiated from the light source device to the photocatalyst at the current irradiation light intensity by a correction coefficient.

[0016] In the device of the present invention, the detection value of the hydrogen gas amount detection means is used to take into account the current performance of the photocatalyst, and the amount of hydrogen gas generated per given time in the water tank portion is given by correcting the amount of hydrogen gas generated per given time estimated from the intensity of irradiated light with consideration of the current performance of the photocatalyst. With this configuration, the amount of hydrogen gas generated per given time in the water tank portion that reflects the current performance of the photocatalyst can be obtained without waiting for the time it takes for hydrogen gas to reach the hydrogen gas amount detection means after it is generated in the water tank portion, making it possible to estimate the amount of hydrogen generated in the water tank as accurately as possible in real time.

[0017] In the device of the present invention, the amount of hydrogen gas generated 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 estimate of the amount of hydrogen gas generated per given time in the water tank section. The current estimate of the amount of hydrogen gas generated per given time takes into account the current state of the photocatalyst and is expected to be the amount of hydrogen gas generated per given time in the water tank section at the present time, so that it is expected that the adjustment of the irradiation light intensity can be achieved 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 amount of hydrogen gas generated per given time reaches a predetermined threshold. As described above, the current estimated value of the amount of hydrogen gas generated per given time takes into account the current state of the photocatalyst and is expected to be the amount of hydrogen gas generated per given time at the present time in the water tank portion, and there is no time delay like the detected value of the hydrogen gas amount detection means. 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 hydrogen separator than before, which is advantageous in that it allows for a greater amount of hydrogen to be generated. [Effects of the Invention]

[0019] Thus, in the device of the present invention, the amount of hydrogen generated in the water tank is determined by correcting the amount of hydrogen generated estimated from the intensity of irradiated light in consideration of the current performance of the photocatalyst, rather than directly referring to the value detected by the hydrogen gas amount detection means. This configuration allows the amount of hydrogen generated in the water tank to be estimated as accurately as possible in real time, which is advantageous when adjusting the amount of hydrogen generated. The configuration of the present invention may be used in any type of hydrogen gas production device 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 showing the configuration of a hydrogen generation amount estimation and controller in the hydrogen gas production apparatus. [Figure 2] 2A is a diagram showing a change in the amount of hydrogen generated GA_H2 relative to the intensity of light (irradiation light intensity LI) irradiated from the light source device into the water tank, and FIG. 2B is a diagram showing the time relationship of each value used to calculate the current estimated value of the amount of hydrogen generated in this embodiment. [Figure 3] FIG. 3 is a flowchart showing the process of estimating and controlling the current estimated value of the amount of hydrogen generated in the hydrogen gas production device to which this embodiment is applied. [Explanation of symbols]

[0022] 1...hydrogen gas production device, 2...water tank section, 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...hydrogen gas amount detection sensor, 13...hydrogen generation amount estimation 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. A light-emitting element 5 supported by a light source device 4 emits excitation light that triggers a water decomposition reaction on the photocatalyst 3a in the water 3. As a result, the water molecules are decomposed into hydrogen and oxygen in the photocatalyst 3a, producing hydrogen gas H2 and oxygen gas O2. The generated hydrogen gas H2 and oxygen gas O2 are sent to a hydrogen separator 9 through a collection pipe 8, where they are separated into oxygen gas O2 and hydrogen gas H2. The resulting hydrogen gas and oxygen gas O2 then flow into respective delivery pipes 10 and 11, and may be stored in a storage tank or the like (not shown). In this embodiment, as described later, the amount of hydrogen gas flowing through the delivery pipe 11 is detected by a hydrogen gas amount detection sensor 12, and this is used to estimate the amount of hydrogen generated and the amount of hydrogen gas generated per predetermined time (hydrogen generation amount) in the water tank 2, which is appropriately set, in a controller 13. The power supplied to the light source device 4 may be controlled by a power controller 7 of any type in accordance with the estimation of the amount of hydrogen generated 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 component formed from the photocatalytic material itself, or a substrate or matrix on which the photocatalytic material is immobilized and placed 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 and hydrogen gas amount detection sensor 12 may be of any type used in this field.

[0025] Hydrogen generation amount estimation and controller configuration The hydrogen generation amount estimation and control device 13 that estimates and controls the hydrogen generation amount may be any computer device, and the estimation and control of the hydrogen generation amount may be realized by the operation of the computer device according to a program. Referring to Figure 1(B), the hydrogen generation amount estimation and control device 13 may be provided with a provisional estimated value determination unit 13a, a correction coefficient calculation unit 13b, and a current estimated value determination unit 13c for estimating the hydrogen generation amount, and an irradiation light intensity control unit 13d for controlling the hydrogen generation amount.

[0026] More specifically, when an arbitrary value of irradiation light intensity is input, the provisional estimate value determiner 13a is configured to output, as a provisional estimate of the amount of hydrogen generated, the amount of hydrogen gas (amount of hydrogen generated) generated per unit time or per predetermined time that may be set appropriately in the water tank 2 before the start of use of the hydrogen gas production device 1 or the photocatalyst contained in the water when light is irradiated from the light source device to the water 3 in the water tank 2 at that irradiation light intensity. To this end, prior to the use of the hydrogen gas production device 1 or the photocatalyst contained in the water, light is irradiated from the light source device to the water 3 in the water tank 2 at irradiation light intensities that are set to various values, and the amount of hydrogen generated at each irradiation light intensity is obtained using the detection value of the hydrogen gas amount detection sensor 12. In this regard, as mentioned in the Summary of the Invention section, since it takes a significant amount of time for the hydrogen gas generated in the water tank 2 to reach the hydrogen gas amount detection sensor 12, when preliminarily examining the amount of hydrogen generated at each irradiation light intensity as described above, one embodiment is to set the irradiation light intensity to each value, wait until the detection value of the hydrogen gas amount detection sensor 12 becomes constant, and then use that constant detection value to determine the amount of hydrogen generated in the water tank 2 corresponding to the irradiation light intensity at that time. Typically, the flow rate of hydrogen gas per predetermined time at the position of the hydrogen gas amount detection sensor 12 on the hydrogen gas delivery pipe 11 may be considered to coincide with the amount of hydrogen generated in the water tank 2.

[0027] It has been found that the amount of hydrogen generated in the water tank 2 corresponding to the intensity of light irradiated from the light source device to the photocatalyst typically decreases in increase in the amount of hydrogen generated GA_H2 as the irradiated light intensity LI increases, as shown schematically in Fig. 2(A) (see Patent Document 1). Therefore, the provisional estimate value determiner 13a may be configured using a map or approximation formula that is prepared by first examining the values ​​of the amount of hydrogen generated when the photocatalyst is irradiated with light from the light source device at various irradiated light intensities, and then using the results to output the amount of hydrogen generated corresponding to 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 amount of hydrogen generated).

[0029] The correction coefficient calculation unit 13b is configured to calculate a correction coefficient for correcting the hydrogen generation amount corresponding to a given 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 hydrogen generation amount 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 hydrogen generation amount corresponding to a given irradiated light intensity (in the initial state of the photocatalyst) provided by the provisional estimate determination unit 13a, cannot be used as is to represent the current amount of hydrogen generation 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 hydrogen generation amount (current estimate). The correction coefficient calculation unit 13b calculates the correction coefficient used for such correction.

[0030] 2(B), the amount of hydrogen generated MA(t) corresponding to the detection value of the hydrogen gas amount detection sensor 12 at time t corresponds to the amount of hydrogen generated in the water tank 2 at time t-Δ, which is the time Δ required for hydrogen gas to reach the position of the hydrogen gas amount detection sensor 12 after its generation in the water tank 2. Since the performance of a photocatalyst typically does not change significantly over time Δ, the photocatalyst performance ratio between the current and initial states, i.e., the ratio of the amount of hydrogen generated, is given by the ratio of the amount of hydrogen generated MA(t) corresponding to the detection value of the hydrogen gas amount detection sensor 12 to the provisional estimated value pA(t-Δ) given by the provisional estimated value determination unit 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 amount of hydrogen generated in the water tank unit 2 is: sA(t)=C·pA(t) The above current estimated value sA(t) is calculated by multiplying the amount of hydrogen generated with 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 the provisional estimated value determination unit 13a and the amount of hydrogen generated MA(t) corresponding to the detection value of the hydrogen gas amount detection sensor 12.

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

[0033] Estimation of hydrogen generation amount and operation of controller 3, in the estimation of the amount of hydrogen generated in the hydrogen gas production apparatus 1 and the operation of the controller 13, first, the current irradiated light intensity LI(t) is acquired (step 1), and the corresponding provisional estimated value pA(t) of the amount of hydrogen generated 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, the detection value MA(t) of the hydrogen gas amount detection sensor 12 is obtained (step 3), and a correction coefficient C is calculated from the detection value MA(t) and the provisional estimate 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 estimate pA(t) is then multiplied by the correction coefficient C to calculate a current estimate sA(t) of the amount of hydrogen generated (step 5). Here, the time interval Δ is the time interval from when hydrogen gas is generated in the water tank section 2 until it reaches the position of the hydrogen gas amount detection sensor 12, and may be determined through experiments, etc.

[0034] In the above configuration, the correction coefficient C is updated successively, and it is expected that the current estimated value sA(t) of the amount of hydrogen generated can be estimated with higher accuracy.

[0035] Once the current estimated value sA(t) of the amount of hydrogen generated is estimated as described above, the intensity of the irradiated light may be appropriately controlled with reference to sA(t). For example, when sA(t) exceeds an appropriately set threshold Ao (which may be appropriately set based on, for example, the allowable limit value 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 amount of hydrogen generated is an estimate closer to the actual value than the provisional estimate obtained by the provisional estimate determiner 13a and the value detected by the hydrogen gas amount sensor 12. Therefore, it is possible to bring the threshold Ao closer to the allowable limit value of the hydrogen separator, and it is possible to maximize the performance of the hydrogen gas production device.

[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-exemplified 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 water tank portion for storing water; a photocatalyst dispersed or placed in the water in the water tank section, 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; a light source device that emits light that is irradiated onto the photocatalyst to induce the water decomposition reaction; a hydrogen gas amount detection means for detecting the amount of hydrogen gas generated in the water tank per predetermined time after the hydrogen gas and oxygen gas are separated; a hydrogen generation amount estimation means configured to estimate the amount of hydrogen gas generated per predetermined time period in the water tank portion based on the irradiated light intensity of light irradiated from the light source device to the photocatalyst; Including, The hydrogen generation amount estimation means a provisional estimate determining means configured to determine a provisional estimate of the amount of hydrogen gas generated per predetermined time in the water tank when light from the light source device is irradiated onto the photocatalyst at an arbitrary irradiation light intensity, based on values ​​of the amount of hydrogen gas generated per predetermined time in the water tank when light from the light source device is irradiated onto the photocatalyst at various irradiation light intensities, which have been investigated in advance; a correction coefficient calculation means configured to calculate a correction coefficient based on a detection value of the amount of hydrogen gas generated per predetermined time in the water tank portion detected by the hydrogen gas amount detection means and a provisional estimate value determined by the provisional estimate value determination means of the amount of hydrogen gas generated per predetermined time in the water tank portion when light is irradiated from the light source device to the photocatalyst at an irradiation light intensity at the time when hydrogen gas corresponding to the detection value is generated in the water tank portion; and a current estimated value determination means configured to correct the provisional estimated value of the amount of hydrogen gas generated per specified time in the water tank section 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 amount of hydrogen gas currently generated per specified time in the water tank.

2. 2. The apparatus according to claim 1, further comprising: an irradiation light intensity control means for adjusting the irradiation light intensity of the light from said light source device based on a current estimated value of the amount of hydrogen gas generated per predetermined time.

3. 3. The apparatus of claim 2, wherein the irradiation light intensity control means is configured to limit an increase in the irradiation light intensity of the light from the light source device when a current estimate of the amount of hydrogen gas generated per predetermined time period reaches a predetermined threshold value.

4. 2. The apparatus of claim 1, wherein said correction factor calculation means is configured to sequentially update said correction factors.

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 amount of hydrogen gas generated per predetermined time in the water tank section when light is irradiated from the light source device to the photocatalyst at the irradiation light intensity at the time when hydrogen gas corresponding to the detection value is generated in the water tank section, and the current estimate is a value obtained by multiplying the provisional estimate of the amount of hydrogen gas generated per predetermined time in the water tank section 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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