JP2024038846A - Hydrogen production system and hydrogen production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: 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

COPYRIGHT: (C)2024,JPO&INPIT

Description

Application for application of Article 30, Paragraph 2 of the Patent Act December 2, 2021 PR TIMES screen copy 1 March 20, 2020 New Energy Shinpo No. 254, P18 1

The present invention relates to a hydrogen production system and a hydrogen production method.

Renewable energy refers to energy obtained from energy sources in the natural world such as sunlight, wind, and water flow, unlike fossil energy obtained by burning oil, coal, etc. Renewable energy has the advantage of not being depleted and does not emit greenhouse gases such as carbon dioxide, and is expected to become increasingly important in modern society where environmental problems are becoming more serious. ing.

Among renewable energies, electrical energy obtained through hydroelectric power generation is particularly important in Japan, which is blessed with steep mountains and rivers that flow between them.

By the way, like other forms of energy, renewable energy generally takes the form of electrical energy generated using a generator.Although electrical energy can be stored in batteries, etc., the capacity of the battery is limited. There is room for improvement in storage from the perspective of maintenance costs.

As a technique related to this improvement, for example, Patent Document 1 listed below discloses a technique for generating hydrogen using wind power generation.

Patent No. 4872393

However, the technology described in Patent Document 1 is specialized for the structure of wind power generation. When wind or sunlight is used as a renewable energy source, the amount of wind or sunlight supplied is not stable as there may be no wind or cloudy skies. Another problem is that water, which is a source of hydrogen generation, must be brought in from another location.

Furthermore, when producing hydrogen using electricity from renewable energy, the renewable energy is generally alternating current, and the electric power required to produce hydrogen is direct current. Therefore, when attempting to produce hydrogen by electrolysis of water using electricity generated using renewable energy, it is necessary to convert the electricity from alternating current to direct current. For this reason, we combined inverters, converters, and transformers to convert AC to DC, rectify DC, and convert DC to AC multiple times, creating a DC system that is ideal for electrolyzing water and producing hydrogen. It is necessary to obtain constant voltage and large current. When obtaining this large current, a loss occurs every time electricity is converted, and the problem arises that only about half of the electricity obtained from renewable energy can be used for actual hydrogen production.

Therefore, in view of the above problems, an object of the present invention is to provide a hydrogen production system and a hydrogen production method that are more energy efficient.

In order to address the above issues, the inventors of the present invention have conducted intensive research to integrate power generation using renewable energy and hydrogen production so that all of the electricity generated from renewable energy can be used for hydrogen production, and have developed an optimal power source. He discovered a device and invented an efficient hydrogen production device and hydrogen production method.

Specifically, renewable energies include solar power generation, wind power generation, hydroelectric power generation, biomass power generation, etc., but when combining advanced hydrogen production equipment, hydroelectric power generation with a high facility utilization rate is optimal. When solar power generation and hydrogen production are combined, the capacity utilization rate is around 10% because it is limited to days when the sun is out and the weather is good. It will be out of action for most of the time. For this reason, there is a method to ensure nighttime operation by installing storage batteries, etc., but this requires too much equipment and is not a practical method. Similarly, when combined with wind power, power is generated only when there is a certain amount of wind, resulting in a capacity factor of about 20%. Biomass power generation is also possible, but although it is recognized as renewable energy, a certain amount of carbon dioxide is generated as it involves combustion during power generation. Although the present invention is applicable to all of these combinations of renewable energy power generation and hydrogen production equipment, the most suitable one is hydroelectric power generation. Hydroelectric power generation allows constant power generation as long as there is water, and fluctuations in electricity are extremely small compared to wind power. Electricity with little fluctuation is optimal for hydrogen production, and the amount of hydrogen production is proportional to the amount of current. For this reason, small and medium-sized hydroelectric power generation is considered to be the most suitable power generation for hydrogen production, with power generation of 100,000 kW or less being optimal. In general, power plants of 2,000 kW or less are called small hydropower plants, and these are the optimal scale when used exclusively for hydrogen production. In addition, the power converter uses recently advanced power semiconductors that can directly convert large currents, resulting in a system that is more efficient than a conventional combination of inverters and converters.

In other words, a hydrogen production system according to one aspect of the present invention that solves the above problems includes a small hydroelectric power generation device that generates first alternating current power using river water flow, and a small hydroelectric power generation device that is electrically connected to the small hydropower generation device to generate electric power. a water splitting device that splits water to generate hydrogen and oxygen, an AC/DC converter that converts the first AC power generated by the small hydroelectric power generation device into the first DC power, and the AC/DC converter that converts the first DC power into the first DC power. a power conversion device including a DC voltage conversion section that converts into second DC power, and the water splitting device is connected to the DC voltage conversion section of the power conversion device.

In addition, from this point of view, it is preferable to include, although not limited to, a DC/AC converter that converts the first DC power into the second AC power.

Moreover, in this aspect, it is preferable, although not limited thereto, to include a hydrogen tank connected to the water splitting apparatus.

Further, in this aspect, although not limited to, 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, and the voltage of the first DC power is 100V or more. The voltage of the second DC power is preferably in the range of 1.5V or more and 70V or less.

In addition, in this respect, although not limited thereto, it is preferable that the power supply has an AC rectifier unit that generates AC power of 100 V from the first AC power, and the output of the AC rectifier unit is connected to the DC voltage conversion unit.

In addition, in this aspect, although not limited to, an AC rectifier that generates AC power with an amplitude of 100 V from the first AC power is provided, and the output of the AC rectifier is connected to the DC voltage converter. It is preferable.

Moreover, in this aspect, it is preferable that the power conversion device uses a power semiconductor.

In addition, in this aspect, although not limited to, an insoluble trash removal device that removes insoluble trash from river water, and an unnecessary dissolved matter removal device that removes unnecessary dissolved matter dissolved in river water, Preferably, the water splitter is provided with a waste removal system comprising a waste removal system, and the water splitting device is supplied with river water treated by the waste removal system.

Further, a hydrogen production method according to another aspect of the present invention includes a step of generating first AC power using a water flow of a river, a step of converting the first AC power into first DC power, and a step of converting the first DC power into first DC power. a step of converting the electric power into a second DC power; a step of driving a water splitter with the second DC power to generate hydrogen; and a step of generating the first AC power by a river water flow; At least one of the step of converting the AC power into the first DC power and the step of converting the first DC power into the second DC power is performed using a power semiconductor.

Moreover, in this aspect, although not limited to, it is preferable that the water decomposed by the water decomposition device is a stream of a river.

As described above, according to the present invention, it is possible to provide a hydrogen production system and a hydrogen production method that are more energy efficient.

1 is a diagram schematically showing a hydrogen production system according to an embodiment. FIG. 2 is a functional block diagram of a power conversion device according to an embodiment. It is a figure showing an outline of a hydrogen production system concerning another example of an embodiment. It is a figure showing an image of electrolysis in a water decomposition apparatus concerning an embodiment.

Hereinafter, embodiments of the present invention will be described in detail using the drawings. However, the present invention can be implemented in many different forms and is not limited to the specific examples described in the embodiments below.

FIG. 1 is a diagram schematically showing a hydrogen production system (hereinafter referred to as "this system") S according to the present embodiment. As shown in this figure, this system S is electrically connected to a small hydroelectric power generation device 1 that generates first AC power C1 using river water flow, and is electrically connected to the small hydropower generation device 1, and decomposes water based on the electric power. It has a water splitting device 2 that generates hydrogen and oxygen, and a power conversion device 3.

In addition, the power converter 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 the first DC power D1, The power conversion device 3 includes a DC voltage converter 32 that converts the first DC power D1 into a second AC power D2, and a DC AC converter 33 that converts the first DC power D1 into a second AC power C2. . FIG. 2 shows a functional block diagram of the power conversion device 3 of this system S. Note that the water splitting device 2 is connected to the DC voltage converter 32 of the power converter 3, and the small hydroelectric power generator 1 is connected to the AC/DC converter 31 of the power converter 3.

First, as described above, this system S includes the small hydroelectric power generation device 1 that generates the first AC power C1 using the water flow of the river. Here, "power" means the amount of work performed by a current per unit time.

In addition, the small hydroelectric power generation device 1 in this system S is not limited to the extent that it can generate electric power, but is connected to a shaft (water wheel) equipped with blades etc. and rotated by the water flow of a river, and connected to this shaft. The synchronous generator is preferably a synchronous generator including a generator that rotates with the rotation of the shaft and generates electric power. Note that the types of water turbines are not limited, and examples include, but are not limited to, Francis water turbines, Belton water turbines, propeller water turbines, and crossflow water turbines. Examples of other water turbines are shown in FIG. 3, for example. Furthermore, in the small hydroelectric power generation device 1 of the present system S, the generated power is AC power, and this becomes the first AC power C1.

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 preferably in the range of 100 V or more and 450 V or less, although it is not limited. Although the frequency range is not limited, it is preferably 10 Hz or more and 100 Hz or less, and more preferably a common frequency of 50 Hz or 60 Hz. By setting it within this range, the power conversion by the water splitting device 2 and furthermore the power conversion device 3, which will be described later, becomes efficient.

Furthermore, as described above, this system S includes a water splitting device 2 that is electrically connected to the small hydroelectric power generation device 1 and that splits water based on electric power to generate hydrogen and oxygen. More specifically, in this system S, water is decomposed by the second DC power D2 generated by the power converter 3. That is, in this system S, electric power is generated by the water flow of the river, and furthermore, this electric power can be used to decompose water to generate hydrogen, which can be stored and accumulated as an energy source.

The present system S is not limited as long as water can be decomposed into hydrogen and oxygen using electric power, and a method of decomposing water using electrolysis is simple and preferable. When using water electrolysis, water is placed in an electrolytic cell (electrolytic cell), the anode and cathode are immersed, and a current is passed between the anode and cathode (pair of electrodes) to electrolyze the water. It becomes possible to generate hydrogen and oxygen on the anode side. An image of this electrolytic cell is shown in FIG. 4.

By the way, the present system S preferably includes a hydrogen tank 4 connected to the water splitting device 2. By providing the hydrogen tank 4, hydrogen can be stored, transported, and used as energy as needed. Similarly, the water splitting device 2 may be provided with an oxygen tank 5 that stores oxygen. Oxygen can also be used as energy by reacting with other elements. In particular, in fuel cells, hydrogen and oxygen are reacted via a catalyst to obtain water and energy, so oxygen itself is also an energy source. It is useful as

Moreover, this system S includes the power conversion device 3 as described above. In this system S, the 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 it is as a power source for the water splitting device 2. Therefore, in this system S, the power conversion device 3 is used to convert the power into DC power for use in the water splitting device 2, and by converting the power into AC power that can also be used as a general power source, it is possible to supply it to the outside. .

Here, each block of the power conversion device 3 will be explained. First, as described above, the power converter 3 in this system S includes an AC/DC converter 31 that converts the first AC power C1 generated by the small hydroelectric power generation device 1 into the first DC power D1. .

The small hydroelectric power generation device 1 can obtain the first AC power C1, but as mentioned above, the water splitting device 2 is driven by DC power, and as a prerequisite, it is necessary to convert it to DC power. . Therefore, the power converter 3 requires an AC/DC converter 31.

On the other hand, it is preferable that the power conversion device 3 has a configuration that allows power to be supplied not only to the water splitting device 2 but also to the outside. Therefore, if this DC power is specialized to the DC power with the optimum conditions for driving the water splitting apparatus 2, a large conversion loss will occur when converting it back into power to be provided to the outside. Therefore, it is preferable that the first DC power D1 is converted into power under intermediate conditions, taking into consideration the power supply not only to the water splitting apparatus 2 but also to the outside. Of course, if power supply to the outside is not considered, the DC/AC converter 33, which will be described later, can be deleted.

Further, in consideration of the above, the voltage of the first DC power D1 generated by the AC/DC converter 31 is preferably in the range of 100V or more and 800V or less, although it is not limited thereto.

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

Here, although not limited, it is preferable that the voltage of the second DC power D2 is in a range of 1.5V or more and 70V or less. By keeping it within this range, decomposition by the water decomposition device 2 will be performed suitably. However, when a plurality of electrolytic cells are provided in the water splitting apparatus 2 and these plurality of electrolytic cells are connected in series, it is possible to adjust the voltage to a higher voltage.

The power converter 3 also includes a DC-AC converter 33 that converts the first DC power D1 into the second AC power C2. The second AC power C2 can be used as external power, so that it can be used not only for water splitting but also as regular power. Note that the power generated by the DC/AC converter 33 is not limited, and preferably has a voltage of 50 V or more and 300 V or less, but the frequency of the AC is 50 Hz or 60 Hz, which is assumed to be used in a general home. It is preferable that there be. However, as described above, in a mode in which power is not supplied to the outside, the DC/AC converter 33 can be omitted. Note that it is also possible to use the DC power generated by the AC/DC return section 31 as external power.

Furthermore, in the power conversion device 3 of the present system S, control of a microcomputer or the like is required to control each power conversion, that is, separate electric power is required. Therefore, a battery 34 is provided to store power for these controls, and at the beginning of operation, the power from the battery is utilized to convert the output from the small power generator 1 and sufficiently drive the system S. After this, it is preferable to charge the battery 34 to compensate for this consumed power. This allows for a fully independent energy supply in remote locations.

Furthermore, in the power conversion device 3 of the present system S, it is important to use so-called power semiconductors for switching elements and the like used for its control. A "power semiconductor" is a semiconductor that can handle high voltage and large current, and by using a power semiconductor, it can be sufficiently applied to the above voltages and currents.

In addition, in this system S, although not limited to, an insoluble garbage removal device 61 that removes insoluble garbage from river water, and an unnecessary dissolved substance removal device 62 that removes unnecessary dissolved substances dissolved in river water. It is preferable that the water decomposition device 2 is provided with a waste material removal system 6 having a waste material removal system 6 and that river water treated by the waste material removal system 6 is supplied to the water decomposition device 2. In general, river water is mixed with fallen leaves, algae, fish, and other debris, and although these contaminations are relatively rare in the upper reaches of high mountains, fallen leaves and other debris are unavoidable. Therefore, by providing the insoluble garbage removal device 61 that removes insoluble garbage, it is possible to eliminate the possibility that the insoluble garbage gets mixed into the small hydroelectric power generation device 1 and gets entangled with the water wheel or the like, causing the operation to stop.

Further, the unnecessary matter removal system 6 includes an unnecessary dissolved matter removal device 62 that removes unnecessary dissolved matter dissolved in river water. Since the above-mentioned insoluble dirt removal device 61 can remove fallen leaves, algae, etc. that are not dissolved in water, the drive of the small hydroelectric power generation device 1 is not affected. On the other hand, when trying to use the water splitter 2 to decompose river water, minerals dissolved in the river water may precipitate during electrolysis, damaging the electrodes. When decomposed, if other gases such as chlorine are mixed in instead of oxygen and hydrogen, chlorine gas may be generated. Therefore, by removing not only insoluble garbage but also unnecessary dissolved substances, it becomes possible to electrolyze river water and accumulate hydrogen.

The structure of this unnecessary dissolved substance removing device 62 is not particularly limited as long as it has the above-mentioned functions, but it is preferably a device using a distiller, an ion exchange membrane, or the like. By using a distiller, water can be evaporated and recovered to remove impurities and distilled water can be obtained.Furthermore, by using an ion exchange membrane, etc., water can be recovered during electrolysis using the water electrolysis device 2. It is possible to efficiently remove ions and the like that inhibit hydrogen generation.

Note that the waste removal system 6 first includes an insoluble waste removal device 61 at the front stage, takes water from the insoluble waste removal device 61, and distributes the water to the small hydroelectric power generation device 1, while removing unnecessary water from the other water flow. It is preferable to provide piping or the like for removing dissolved unnecessary ions via the dissolved substance removing device 62 and supplying the water from which the unnecessary ions have been removed to the water splitting device 2.

(Hydrogen production method)
Moreover, as is clear from the above description, according to the present system S, it is possible to produce hydrogen, and specifically, to provide a hydrogen production method (hereinafter referred to as "the present method"). Details are given below.

That is, this method includes the following steps: (S1) generating first AC power by a river water flow; (S2) converting the first AC power into first DC power; (S3) converting the first DC power. and (S4) driving a water splitting device with the second DC power to generate hydrogen.

In addition, in this system S, in the step (S4) of driving the water splitting device with the second DC power to generate hydrogen, the water decomposed by the water splitting device is, although not limited to, A water stream is preferred.

As described above, the present system S can provide a more energy efficient hydrogen production system and hydrogen production method. Specifically, this system S can efficiently generate hydrogen by installing a small hydroelectric power generation device 1 in a small-scale river with a relatively fast flow. Moreover, by adding the unnecessary matter removal system 6, electric power can be obtained from the river from the small hydroelectric power generation device 1, and the river water can also be electrolyzed and used as a hydrogen source. In other words, it will be possible to obtain electricity and use that electricity and water to obtain energy completely independently in remote locations.

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

Claims (8)

a small hydroelectric power generation device that generates first alternating current power using river water flow;
a water splitting device that is electrically connected to the small hydroelectric power generation device and that splits water to generate hydrogen and oxygen based on electric power;
An AC/DC converter that converts first AC power generated by the small hydroelectric power generation device into first DC power, and a DC voltage converter that converts the first DC power into second DC power. a power conversion device;
The water splitting device is a hydrogen production system connected to the DC voltage converter of the power converter. The hydrogen production system according to claim 1, wherein the power conversion device includes a DC/AC converter that converts the first DC power into second AC power. The hydrogen production system according to claim 1, further comprising a hydrogen tank connected to the water splitting device. 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,
The hydrogen production system according to claim 1, wherein the voltage of the second DC power is in a range of 1.5V or more and 70V or less. an insoluble trash removal device that removes insoluble trash from the river water;
An unnecessary dissolved matter removal system that includes an unnecessary dissolved matter removal device that removes unnecessary dissolved matter dissolved in the water of the river,
The hydrogen production system according to claim 1, wherein the water of the river treated by the waste removal system is supplied to the water splitting device. The hydrogen production system according to claim 1, wherein the power converter uses a power semiconductor. a step of generating first alternating current power by river water flow;
converting the first AC power into first DC power;
converting the first DC power to a second DC power;
A hydrogen production method comprising the step of driving a water splitting device with the second DC power to generate hydrogen,
generating first AC power by the water flow of the river; converting the first AC power into first DC power; and converting the first DC power into second DC power. At least one of the above is a hydrogen production method performed using a power semiconductor. 8. The hydrogen production method according to claim 7, wherein the water decomposed by the water decomposition device is a stream of the river.