Hydrogen production system and hydrogen production method

Abstract

To provide a hydrogen production system and a hydrogen production method with better energy efficiency.SOLUTION: A hydrogen production system S according to an aspect of the present invention comprises a small hydropower generation device 1 for generating a first AC power by a stream of water in a river, a water splitting device 2 which is electrically connected to the small hydropower generation device 1 and is for generating hydrogen and oxygen by decomposing water based on electric power, and a power conversion device 3 comprising an AC DC conversion part 31 for converting a first AC power C1 generated by the small hydropower generation device 1 into a first DC power D1 and a DC voltage conversion part 32 for converting the first DC power D1 into a second DC power D2. The water splitting device 2 is connected to the DC voltage conversion part 32 of the power conversion device 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen production system and a hydrogen production method. [Background technology]

[0002] Renewable energy is energy obtained from natural sources such as sunlight, wind, and water currents, as opposed to fossil energy obtained by burning oil, coal, etc. Renewable energy has the advantage of never running out and not emitting greenhouse gases such as carbon dioxide, and its importance is expected to grow increasingly greater in modern society as environmental problems become more serious.

[0003] Among renewable energies, electrical energy obtained through hydroelectric power generation is particularly important in Japan, a country blessed with steep mountains and the rivers that flow between them.

[0004] Meanwhile, like other forms of energy, renewable energy generally takes the form of electrical energy generated using a generator. Although electrical energy can be stored using batteries, there is room for improvement in storage in terms of the capacity and maintenance costs of the batteries.

[0005] As a technique for improving this, for example, Patent Document 1 below discloses a technique for generating hydrogen using wind power generation. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4872393 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the technology described in Patent Document 1 is specialized for wind power generation structures. When wind or sunlight is used as a renewable energy source, the amount of wind or sunlight supplied is unstable, depending on whether it is windless or cloudy. Another issue is that water, which is the source of hydrogen generation, must be brought in from another location.

[0008] Furthermore, when hydrogen is produced using electricity from renewable energy sources, renewable energy is generally AC, while the power required for hydrogen production is DC. Therefore, when attempting to produce hydrogen by electrolyzing water using electricity generated from renewable energy sources, the electricity must be converted from AC to DC. This requires combining an inverter, converter, and transformer to convert AC to DC, rectify the DC, and then convert DC back to AC multiple times to obtain a constant-voltage, large-current DC current that is optimal for electrolyzing water to produce hydrogen. However, when obtaining this large current, losses occur each time electricity is converted, creating the problem that only about half of the electricity obtained from renewable energy sources can actually be used to produce hydrogen.

[0009] In view of the above, an object of the present invention is to provide a hydrogen production system and a hydrogen production method with improved energy efficiency. [Means for solving the problem]

[0010] In response to the above-mentioned problems, the inventors have conducted extensive research into integrating renewable energy power generation and hydrogen production so that the electricity generated by renewable energy can be used to produce hydrogen without waste, and have discovered an optimal power supply device and invented an efficient hydrogen production device and method.

[0011] Specifically, renewable energy sources include solar power, wind power, hydroelectric power, and biomass power. However, when combining advanced hydrogen production equipment, hydroelectric power, with its high capacity utilization rate, is optimal. When combining solar power and hydrogen production, operation is limited to sunny daytime days, resulting in a capacity utilization rate of approximately 10%, and the hydrogen production electrolysis equipment, which uses expensive materials such as platinum for electrodes, is often idle. For this reason, installing storage batteries to ensure nighttime operation is an option, but this requires excessive equipment size and is not practical. Similarly, when combined with wind power, power generation is only possible when there is a steady wind, resulting in a capacity utilization rate of approximately 20%. Biomass power generation is also possible, but while recognized as a renewable energy source, it involves combustion during power generation, resulting in a certain amount of carbon dioxide emissions. While the present invention is compatible with all of these renewable energy sources combined with hydrogen production equipment, hydroelectric power is optimal. Hydroelectric power generation can generate a constant amount of power as long as there is water, and its fluctuations in electricity are significantly less than those of wind power. Electricity with low fluctuations is optimal for hydrogen production, and the amount of hydrogen produced is proportional to the amount of current. For these reasons, small- to medium-sized hydroelectric power plants are considered the best for hydrogen production, with those under 100,000 kW being optimal. Generally, those under 2,000 kW are called small hydroelectric plants, and these are the optimal scale for use exclusively for hydrogen production. Furthermore, the power conversion device uses power semiconductors, which have made remarkable progress in recent years and can directly convert large currents, making it a more efficient system than the conventional inverter and converter combination.

[0012] In other words, a hydrogen production system according to one aspect of the present invention that solves the above-mentioned problem comprises a small-scale hydroelectric power generation device that generates first AC electricity using the water flow of a river, a water decomposition device that is electrically connected to the small-scale hydroelectric power generation device and that decomposes water using the electricity to generate hydrogen and oxygen, and a power conversion device that includes an AC / DC conversion unit that converts the first AC electricity generated by the small-scale hydroelectric power generation device into first DC electricity, and a DC voltage conversion unit that converts the first DC electricity into second DC electricity, and the water decomposition device is connected to the DC voltage conversion unit of the power conversion device.

[0013] In addition, in this respect, although not limited thereto, it is preferable to include a DC-AC conversion unit that converts the first DC power into the second AC power.

[0014] In addition, in this respect, although not limited thereto, it is preferable to provide a hydrogen tank connected to the water cracking device.

[0015] Furthermore, in this respect, although not limited thereto, it is preferable that the voltage of the first AC power generated by the small hydroelectric power generation device is in the range of 100V or more and 450V or less, the voltage of the first DC power is in the range of 100V or more and 800V or less, and the voltage of the second DC power is in the range of 1.5V or more and 70V or less.

[0016] Furthermore, in this respect, although not limited thereto, it is preferable that the power supply includes an AC rectifier unit that generates AC power of 100V from the first AC power, and the output of the AC rectifier unit is connected to the DC voltage converter.

[0017] Furthermore, in this respect, although not limited thereto, it is preferable that the power supply includes an AC rectifier that generates AC power with an amplitude of 100 V from the first AC power, and the output of the AC rectifier is connected to the DC voltage converter.

[0018] In addition, in this respect, it is preferable that the power conversion device uses a power semiconductor.

[0019] In addition, in this respect, although not limited thereto, it is preferable to provide an undesired matter removal system including an insoluble debris removal device that removes insoluble debris from river water and an undesired dissolved matter removal device that removes undesired dissolved matter dissolved in the river water, and to supply river water treated by the undesired matter removal system to the water decomposition device.

[0020] Furthermore, a hydrogen production method according to another aspect of the present invention includes the steps of generating first AC power using a water flow in a river, converting the first AC power into first DC power, converting the first DC power into second DC power, and driving a water decomposition device with the second DC power to generate hydrogen, wherein at least one of the steps of generating first AC power using a water flow in a river, converting the first AC power into first DC power, and converting the first DC power into second DC power is performed using a power semiconductor.

[0021] In addition, in this respect, although not limited thereto, it is preferable that the water to be decomposed by the water decomposition device is a river water flow.

[0022] As described above, the present invention can provide a hydrogen production system and a hydrogen production method with higher energy efficiency. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a diagram showing an outline of a hydrogen production system according to an embodiment. [Figure 2] 1 is a functional block diagram of a power conversion device according to an embodiment; [Figure 3] FIG. 10 is a diagram showing an outline of a hydrogen production system according to another example of the embodiment. [Figure 4] FIG. 1 is a diagram illustrating an image of electrolysis in a water decomposition apparatus according to an embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention can be embodied in many different forms and is not limited to the specific examples described in the following embodiments.

[0025] 1 is a diagram showing an outline of a hydrogen production system (hereinafter referred to as "this system") S according to this embodiment. As shown in the diagram, this system S has a small hydroelectric power generation device 1 that generates first AC power C1 using river water flow, a water decomposition device 2 that is electrically connected to the small hydroelectric power generation device 1 and decomposes water using the electricity to generate hydrogen and oxygen, and a power conversion device 3.

[0026] The power conversion device 3 further includes an AC / DC converter 31 that converts the first AC power C1 generated by the small-hydroelectric power generation device 1 into first DC power D1, a DC voltage converter 32 that converts the first DC power D1 into second DC power D2, and a DC / AC converter 33 that converts the first DC power D1 into second AC power C2. Figure 2 shows a functional block diagram of the power conversion device 3 of this system S. The water splitting device 2 is connected to the DC voltage converter 32 of the power conversion device 3, and the small-hydroelectric power generation device 1 is connected to the AC / DC converter 31 of the power conversion device 3.

[0027] As described above, the system S includes a small hydroelectric power generation device 1 that generates the first AC power C1 using the water flow of a river. Here, "power" refers to the amount of work done by an electric current per unit time.

[0028] Furthermore, the small-scale hydroelectric power generation device 1 in this system S is not limited as long as it can generate electric power, but is preferably a synchronous generator equipped with a shaft (water turbine) equipped with blades and the like that rotates due to the water flow of the river, and a generator connected to the shaft that rotates with the rotation of the shaft and generates electric power. The type of water turbine is not limited, and examples include, but are not limited to, a Francis turbine, a Pelton turbine, a propeller turbine, and a cross-flow turbine. Other examples of water turbines are shown in Figure 3. Furthermore, the electric power generated by the small-scale hydroelectric power generation device 1 in this system S is AC power, which becomes the first AC power C1.

[0029] As will be clear from the description below, the voltage of the first AC power C1 generated by the small-hydroelectric power generation device 1 is not limited, but is preferably in the range of 100 V to 450 V, and the frequency range is also not limited, but is preferably in the range of 10 Hz to 100 Hz, more preferably a common frequency of 50 Hz or 60 Hz. By keeping the frequency within this range, power conversion by the water decomposition device 2 and the power conversion device 3, which will be described later, becomes more efficient.

[0030] As described above, the present system S also includes a water splitting device 2 that is electrically connected to the small hydroelectric power generation device 1 and that splits water using electric power to generate hydrogen and oxygen. More specifically, the present system S splits water using the second DC electric power D2 generated by the power conversion device 3. In other words, the present system S generates electric power using the water flow of the river, and further splits water using this electric power to generate hydrogen, which can be stored and accumulated as an energy source.

[0031] In this system S, there are no limitations as long as it can decompose water into hydrogen and oxygen using electricity, but a method of decomposing water using electrolysis is simple and preferable. When using water electrolysis, water is placed in an electrolytic cell, an anode and a cathode are immersed, and an electric current is passed between the anode and cathode (a pair of electrodes) to electrolyze the water, generating hydrogen on the cathode side and oxygen on the anode side. An image of this electrolysis cell is shown in Figure 4.

[0032] Incidentally, the present system S preferably includes a hydrogen tank 4 connected to the water decomposition apparatus 2. By including the hydrogen tank 4, hydrogen can be stored and transported as needed, and used as energy. Similarly, the water decomposition apparatus 2 may be provided with an oxygen tank 5 for storing oxygen. Oxygen can also be used as energy by reacting it with other elements, and in particular, since fuel cells produce water and energy by reacting hydrogen and oxygen via a catalyst, oxygen itself is also useful as an energy source.

[0033] As described above, the present system S is also equipped with a power converter 3. In the present system S, first AC power C1 is generated by the water flow of the river, but it is difficult to use this first AC power C1 as a power source for the water splitting device 2 as is. Therefore, in the present system S, the power converter 3 converts the power into DC power for use in the water splitting device 2, and then converts it back into AC power that can be used as a general power source, making it possible to supply the power to the outside.

[0034] Here, we will explain each block of the power conversion device 3. First, as described above, the power conversion device 3 in this system S includes an AC-DC conversion unit 31 that converts the first AC power C1 generated by the small hydroelectric power generation device 1 into first DC power D1.

[0035] Although the small-scale hydroelectric power generation device 1 can generate first AC power C1, as described above, the water splitting device 2 is driven by DC power, which must be converted into DC power as a prerequisite. Therefore, the power conversion device 3 requires an AC-DC converter 31.

[0036] On the other hand, it is preferable that the power conversion device 3 has a configuration that enables power supply not only to the water splitting device 2 but also to external devices. Therefore, if this DC power is specialized to DC power under optimal conditions for driving the water splitting device 2, a large conversion loss will occur when the DC power is converted back into power to be provided to the outside. Therefore, it is preferable that the first DC power D1 is converted to power under intermediate conditions, taking into account power supply not only to the water splitting device 2 but also to external devices. Of course, if power supply to external devices is not taken into consideration, the DC-AC conversion unit 33 described below can be omitted.

[0037] Furthermore, in consideration of the above, the voltage of the first DC power D1 generated by the AC-DC converting unit 31 is preferably in the range of 100V or more and 800V or less, although this is not limited thereto.

[0038] The power conversion device 3 also includes a DC voltage conversion unit 32 that converts the first DC power D1 into the second DC power D2. As described above, the first DC power D1 can be used as energy for water splitting by the water splitting device 2, and can also be used as power supplied to the outside. Therefore, it is preferable to convert the first DC power D1 to a value suitable for the water splitting device 2, and the DC voltage conversion unit 32 is an essential component for this purpose. The AC-DC conversion unit 31 and the DC voltage conversion unit 32 may be configured as a circuit that performs the conversion in a single step, or as a specific single device. This allows for more efficient conversion processing.

[0039] Although not limited thereto, the voltage of second DC power D2 is preferably in the range of 1.5 V to 70 V. Setting the voltage within this range will ensure optimal decomposition by the water splitting apparatus 2. However, if the water splitting apparatus 2 is provided with multiple electrolytic cells and these multiple electrolytic cells are connected in series, it is not prohibited to adjust the voltage to a higher level.

[0040] The power converter 3 also includes a DC-AC converter 33 that converts the first DC power D1 into second AC power C2. The second AC power C2 can be used as external power, and can therefore be used not only for water splitting but also as ordinary power. The power generated by the DC-AC converter 33 is not limited to any particular voltage, and preferably has a voltage of 50 V or more and 300 V or less, and preferably has an AC frequency of 50 Hz or 60 Hz, which is expected for use in ordinary households. However, as described above, in a configuration in which power is not supplied to the outside, the DC-AC converter 33 can be omitted. The DC power generated by the AC-DC return unit 31 can also be used as external power.

[0041] Furthermore, in the power conversion device 3 of the present system S, control of each power conversion requires control by a microcomputer or the like, i.e., separate power is required. For this reason, it is preferable to provide a battery 34 to store power for these controls, and use the power from that battery at the beginning of operation to convert the output from the small-power power generation device 1, and after the present system S has been sufficiently operated, charge the battery 34 to make up for the consumed power. This makes it possible to provide a sufficiently independent energy supply in remote locations.

[0042] Furthermore, it is important to use so-called power semiconductors for the switching elements used to control the power conversion device 3 of this system S. A "power semiconductor" is a semiconductor that can handle high voltages and large currents, and the use of power semiconductors makes it possible to fully handle the above voltages and currents.

[0043] Furthermore, in the present system S, although not limited thereto, it is preferable to provide an undesired matter removal system 6 including an insoluble matter removal device 61 that removes insoluble matter from river water and an undesired matter removal device 62 that removes undesired dissolved matter dissolved in the river water, and to supply the water decomposition device 2 with river water treated by the undesired matter removal system 6. River water generally contains fallen leaves, algae, fish, and other debris, and while this contamination is relatively low in the upper reaches of high-altitude mountains, fallen leaves and other debris are unavoidable. Therefore, by providing an insoluble matter removal device 61 that removes insoluble debris, it is possible to eliminate the risk of insoluble debris getting mixed into the small hydroelectric power generation device 1 and entangling the turbines, etc., causing operation to stop.

[0044] The waste removal system 6 also includes a waste removal device 62 that removes waste dissolved in the river water. The insoluble waste removal device 61 can remove fallen leaves, algae, and other substances that are not dissolved in the water, without affecting the operation of the small hydroelectric power generation device 1. However, when attempting to split river water in the water splitting device 2, minerals dissolved in the river water may precipitate during electrolysis, damaging the electrodes. Furthermore, in some cases, splitting the water may produce gases other than oxygen and hydrogen, such as chlorine gas if chlorine is present. Therefore, by removing not only the insoluble waste but also the waste dissolved substances, it is possible to electrolyze the river water and accumulate hydrogen.

[0045] The structure of the unnecessary dissolved matter removal device 62 is not particularly limited as long as it has the above-mentioned functions, but is preferably a device using a distiller, an ion exchange membrane, etc. Using a distiller makes it possible to remove impurities by evaporating and recovering water to obtain distilled water, and further using an ion exchange membrane, etc., for this makes it possible to efficiently remove ions that inhibit hydrogen generation during electrolysis by the water electrolysis device 2.

[0046] It is preferable that the waste removal system 6 first has an insoluble waste removal device 61 at the front stage, and that water is taken from this insoluble waste removal device 61 and distributed to the small hydroelectric power generation device 1, while unnecessary ions dissolved in the other water flow are removed via an unnecessary dissolved matter removal device 62, and that piping is provided to supply the water from which the unnecessary ions have been removed to the water decomposition device 2.

[0047] (Hydrogen production method) As is clear from the above description, the present system S can produce hydrogen, specifically, provide a hydrogen production method (hereinafter referred to as "the present method"), as described in detail below.

[0048] That is, the method includes the steps of (S1) generating first AC power using the water flow of a river, (S2) converting the first AC power into first DC power, (S3) converting the first DC power into second DC power, and (S4) driving a water decomposition device with the second DC power to generate hydrogen.

[0049] Furthermore, in the present system S, in the step (S4) of driving the water decomposition device with the second DC power to generate hydrogen, it is preferable, although not limited thereto, that the water decomposed by the water decomposition device be a river stream.

[0050] As described above, this system S can provide a more energy-efficient hydrogen production system and method. Specifically, this system S can efficiently generate hydrogen by installing a small-scale hydroelectric power generation device 1 in a small river with a relatively fast current. Furthermore, by adding a waste removal system 6, it is possible to obtain electricity from the river using the small-scale hydroelectric power generation device 1, and also to electrolyze the river water and use it as a hydrogen source. In other words, it becomes possible to obtain electricity in a remote location and to obtain energy completely independently using that electricity and water. [Industrial Applicability]

[0051] The present invention has industrial applicability as a hydrogen production system and a hydrogen production method.

Claims

[Claim 1] an insoluble waste removal device for removing insoluble waste from river water; an unnecessary dissolved matter removal device that removes unnecessary dissolved matters dissolved in the river water; a small hydroelectric power generation device that generates first AC electricity using the water flow of the river; a water splitting device electrically connected to the small hydroelectric power generation device, which splits the water in the river using electric power to generate hydrogen and oxygen; a hydrogen tank connected to the water cracking device; a power conversion device using power semiconductors, the power conversion device including an AC / DC conversion unit that converts first AC power generated by the small hydroelectric power generation device into first DC power, a DC voltage conversion unit that converts the first DC power into second DC power, and a DC / AC conversion unit that converts the first DC power into second AC power; a battery that supplies power for controlling the power conversion device and is capable of being charged to compensate for the consumed power from the power conversion device, The small hydroelectric power generation device is supplied with the river water that has been treated only by the insoluble debris removal device out of the insoluble debris removal device and the unnecessary dissolved matter removal device, The water decomposition device is supplied with the river water treated by the insoluble debris removal device and the unnecessary dissolved matter removal device, the water decomposition device is connected to the DC voltage conversion unit of the power conversion device and generates the hydrogen and oxygen using the second DC power; a voltage of the first AC power generated by the small hydroelectric power generation device is in a range of 100 V or more and 450 V or less; the voltage of the first DC power is in the range of 100 V or more and 800 V or less, A hydrogen production system, wherein the voltage of the second DC power is in the range of 1.5V or more and 70V or less.

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