WO2009104820A1

WO2009104820A1 - Solar thermal energy storage method

Info

Publication number: WO2009104820A1
Application number: PCT/JP2009/053624
Authority: WO
Inventors: 中村徳彦; 菊池昇
Original assignee: トヨタ自動車株式会社
Priority date: 2008-02-22
Filing date: 2009-02-20
Publication date: 2009-08-27
Also published as: JP2009197733A; ES2363959A1; CN101946134B; IL207472A; CN101946134A; IL207472A0; JP5012559B2; EG26154A; AU2009216080A1; ES2363959B2; ZA201005919B; MA32187B1; AU2009216080B2

Abstract

Disclosed in the invention of the present patent application is a method for storing solar energy. The solar thermal energy storage method disclosed in the present invention includes acquiring solar thermal energy, using a portion of the aforementioned solar thermal energy acquired to carry out a reaction to generate hydrogen from water, and using another portion of the aforementioned solar thermal energy acquired to carry out a reaction to synthesize ammonia from nitrogen and the hydrogen obtained in step (b).

Description

Solar Thermal Energy Storage Method Technical Field

In recent years, global warming has developed into a more serious situation, and even the future survival of humankind may be threatened. Its main cause is believed to be 2 0 atmospheric carbon dioxide released from fossil fuels have been used in a large amount as an energy source enters the century (C_〇 _2). Therefore, it is thought that it will not be allowed to continue using fossil fuels in the near future. On the other hand, the increase in energy demand accompanying rapid economic growth in so-called developing countries such as China, India, and Brazil has led to the depletion of oil and natural gas, which were once thought to be inexhaustible. It has become real.

In this situation, it can be fully inferred from the recent rapid increase in oil prices that fossil fuels such as oil and natural gas cannot be used as an inexpensive energy source in 20-30 years. Therefore, in order to achieve a sustainable society, there is a need to search for new energy sources and fuels that do not release carbon dioxide and do not depend on limited fossil fuels. '' Background technology

Currently, coal energy, biomass energy, nuclear energy, and natural energy such as wind energy and solar energy are being considered as alternative energy alternatives to fossil fuel energy such as oil and natural gas.

When using coal energy as an alternative energy, It is considered that a large amount of carbon dioxide is released by firing. For this, it has been proposed to capture carbon dioxide during combustion and store it underground, and many studies have been carried out, but there is still uncertainty about long-term stable storage. There are also uneven locations suitable for storage. In addition, it may be a problem that a lot of cost is required to collect, transport, and throw carbon dioxide into the ground. Furthermore, the combustion of coal, sulfur oxides (so _x), also considered to be a problem that is likely to cause environmental problems due to occurrence of such smoke.

Biofuels as alternative energy, especially biofuels, mainly ethanol, have been in the spotlight in recent years. However, enormous energy is required for the production and concentration of ethanol from plants, which may be disadvantageous in terms of energy efficiency. Furthermore, when corn, soybeans, sugar millet, etc. are used as raw materials for biofuel, they naturally have uses as food and feed, which will increase the price of food and feed. . Therefore, biomass energy cannot be considered as a substantial energy source outside of special regions such as Brazil.

The use of nuclear energy as an alternative energy has not been found to be a sufficient solution for the treatment of radioactive waste from nuclear power plants, and there are also many dissents based on fear of proliferation. From that, we can not expect great progress globally. Rather, the use of nuclear energy as an alternative energy is expected to decrease over the long term due to an increase in the number of decommissioned nuclear reactors.

As mentioned above, none of coal energy, biomass energy, or nuclear energy has solved the problem of carbon dioxide generation that leads to sustainability and global warming. So ideal energy Naturally, natural energy such as wind energy and solar energy is considered as a source.

With regard to the use of wind energy as an alternative energy, wind power generation is spreading around the world in recent years. However, there are limited places where the wind blows stably, does not match the damage of typhoons, hurricanes, lightning strikes, etc., and the noise generated by the windmills is not a problem. Therefore, wind energy is a powerful alternative energy candidate.

Solar energy is considered to be the most stable and abundant natural energy as alternative energy. In particular, near the equator, which is called the world's sun belt, a vast desert spreads out, and the solar energy that falls here is truly inexhaustible. In this regard, it is believed that if only a few percent of the desert that extends to the southwestern United States is used, energy of as much as 7,00 GW can be obtained. It is also believed that using only a few percent of the Arabian peninsula and the deserts of North Africa can cover all the energy used by all mankind.

Thus, although solar energy is a very powerful alternative energy, in order to utilize it in social activities, (1) the energy density of solar energy is low, and (2) Difficulties in storing and transferring energy may be problematic.

On the other hand, it has been proposed to solve the problem of low solar energy density by collecting solar energy with a huge concentrator. However, storage and transport of solar energy is very difficult, especially when the transport distance of energy is long and large.

In general, solar energy is directly generated by solar cells, or It is converted into electric power as secondary energy indirectly by a steam turbine, etc., making it convenient for its use and transportation. In the case of converting solar energy into electric power, the energy transfer problem can be solved in principle because the electric energy can be transferred through the transmission line. However, when a plant that obtains electric energy from solar energy is installed in a desert area rich in solar energy, it is necessary to newly construct and maintain a large-capacity transmission line, which is difficult. There are many. Furthermore, for example, it would be very difficult to send a large amount of energy obtained from solar energy in a desert plant to other continents and island countries across the sea.

Also, storage of electricity can be a problem. The development of batteries for storing electric power has long been a major theme around the world. However, even state-of-the-art lithium-ion batteries are not sufficient for high-power storage, and especially for high-power batteries, further safety development is required. In addition, a plant that obtains electric energy from solar energy requires a huge heat storage device, auxiliary boiler, etc. in addition to batteries, in preparation for situations where power generation becomes difficult due to bad weather, etc. The vast amount of data

In addition, conversion of solar energy, which is primary energy, to hydrogen, which is secondary energy, and synthesis of ammonia, methane, etc. using the hydrogen thus obtained as a raw material are also being studied ( Japanese Patent Laid-Open No. 20 0 6 — 3 1 9 2 9 1).

Although hydrogen is attracting attention as a clean energy, storage is a major issue as with electricity. In recent years, a lot of research on hydrogen storage has been conducted for supplying fuel cells, but it is becoming clear that its practical application is not easy. In addition, the hydrogen transfer In particular, the construction of a hydrogen pipeline is more difficult than the construction of a transmission line, especially the construction of a hydrogen pipeline infrastructure such as a mesh for supply to users. In addition, it is necessary to store liquid hydrogen at -25 3, and therefore this is not considered to be applicable for any other purpose than space use. Disclosure of the invention

As described above, efforts are being made around the world to convert solar energy, which is a sustainable energy of salient poles, into electric power, hydrogen, etc. as secondary energy. There are major problems with transport. If this storage and transport problem is not solved, it will be difficult to distribute it all over the world and to use it for moving objects such as cars, aircraft and ships.

The present invention solves the problems related to the storage and transfer of solar energy, thereby making it possible to use solar energy all over the world, and to solve the problem of the generation of carbon dioxide, a greenhouse gas, and the problem of drought of oil. It is intended to be resolved.

The first set of methods intended to solve the above problems are as described in (A 1) to (A 2 0) below:

(A 1) A method for converting solar thermal energy obtained in a first area into driving energy used in a second area where the amount of solar radiation is less than that in the first area,

In the first region, ammonia is synthesized from air and water using only the acquired solar thermal energy as an energy source,

The ammonia is transferred from the first area to the second area, and the ammonia is generated in the second area so as to generate nitrogen and water. A method characterized by having a process of obtaining driving energy by burning.

(A 2) The method according to (A 1), wherein the transfer step uses the ammonia as a fuel to obtain at least a part of electric power and Z or power necessary for the transfer.

(A 3) The method according to (A 1) or (A 2), wherein nitrogen and water generated by the combustion are released into the atmosphere and can be recycled as ammonia in the synthesis step.

(A4) The method according to any one of (A1) to (A3), wherein the drive energy is acquired using an internal combustion engine.

(A5) The step of synthesizing the ammonia includes

(1) Using a part of the acquired solar thermal energy, causing a reaction to generate hydrogen from water,

(2) Utilizing other part of the acquired solar thermal energy, a reaction for synthesizing ammonia from nitrogen and hydrogen obtained in step (1) is performed.

The method according to any one of (A 1) to (A 4), comprising:

(A 6) Any one of the items (A 1) to (A 5) described above is used to obtain at least a part of the electric power and Z or power necessary for the execution of the synthesis process using the acquired solar thermal energy. The method of crab.

(A7) The synthesized ammonia is used as a fuel to obtain at least a part of the electric power, power and Z or heat necessary for carrying out the synthesis step, (A1) to (A6) The method in any one of.

(A8) In the step (1), the obtained solar thermal energy is directly used as a heat source to cause a reaction to generate hydrogen from water. Any one of the above (A5) to (A7) The method described.

(A 9) The solar heat energy used as a heat source in step (1) The method according to (A 8), wherein at least a part of the lug is obtained by a parapoly dish type concentrator and a Z or solar tower type concentrator.

(A 10) The method according to (A 6) or (A 7), wherein in step (1), the electric power is used as a heat source to cause a reaction to generate hydrogen from water.

(A 1 1) The method according to (A 6) or (A 7), wherein in step (1), water is electrolyzed with the electric power to cause a reaction to generate hydrogen from water.

(A 1 2) The method according to any one of (A 1 0) or (A l 1), wherein the solar thermal energy is acquired by a parapoly trough concentrator.

(A 1 3) In the step (2), ammonia is synthesized from nitrogen and hydrogen using the obtained solar thermal energy directly as a heat source and as a power source, or (A 5) to (A 1 2) The method described in any one of the items.

(A 14) The method according to (A 13), wherein the solar heat energy used as a heat source in the step (2) is obtained by a parabolic trough concentrator.

(A 15) In step (1), the obtained solar thermal energy is directly used as a heat source to cause a reaction to generate hydrogen from water; the solar thermal energy used as a heat source in step (1) is reduced Both are obtained with a parabolic dish type concentrator and a Z or solar tower type concentrator; in the step (2), the obtained solar thermal energy is directly used as a heat source and / or a power source. A reaction of synthesizing ammonia from nitrogen and hydrogen; and the solar thermal energy used as a heat source in step (2) The method according to any one of (A 5) and (A 7), which is obtained with a parapoly trough-type light collecting device.

(A 1 6) The method according to (A 6) or (A 7), wherein the nitrogen is obtained by cryogenic separation of air using the power and Z or power.

(A 1 7) The method according to any one of (A 5) and (A 1 5), wherein the nitrogen is obtained by combusting the hydrogen obtained in the step (1) and consuming oxygen in the air. .

(A 1 8) A method of using solar thermal energy obtained in a first area as driving energy used in a second area where the amount of solar radiation is lower than that in the first area.

In the first area, ammonia is synthesized from air and water using only the acquired solar thermal energy as an energy source,

Transferring the ammonia to the second region to obtain driving energy by burning the ammonia to produce nitrogen and water.

(A 19) A method of using solar thermal energy obtained in a first area as a driving energy to be used in a second area where the amount of solar radiation is lower than that in the first area.

Ammonia synthesized from air and water using only solar thermal energy acquired in the first area as an energy source is received in the second area,

A method comprising the step of obtaining driving energy by burning the ammonia so as to generate nitrogen and water in the second region.

(A 2 0) Convert solar thermal energy obtained in the first area into driving energy used in the second area, which has less solar radiation than the first area. The method

The solar thermal energy acquisition means of the first region collects sunlight and acquires solar thermal energy,

Ammonia synthesis means in the first region synthesizes ammonia from air and water using only the acquired solar energy as an energy source,

The ammonia is liquefied by the ammonia liquefying means in the first area,

An ammonia transfer means for transferring the liquefied ammonia from the first region to the second region;

The driving energy generating means in the second region comprises the step of obtaining the driving energy by burning the ammonia so as to generate nitrogen and water.

A second set of methods intended to solve the above problem is as described in (B 1) to (B 14) below:

(B 1) (a) Obtaining solar thermal energy,

(b) using a part of the acquired solar thermal energy to cause a reaction to generate hydrogen from water; and

(c) Utilizing another part of the acquired solar thermal energy, causing a reaction to synthesize ammonia from nitrogen and hydrogen obtained in step (b);

Including a solar thermal energy storage method.

(B 2) The method according to (B 1), wherein at least a part of the electric power and Z or power necessary for carrying out this method is obtained by using the solar thermal energy obtained in the step (a).

(B3) Using the synthesized ammonia as a fuel to obtain at least a part of the electric power, power and / or heat necessary to carry out this method. The method according to item (B 1) or (B 2).

(B4) The method according to any one of (B1) to (B3), wherein only the solar thermal energy obtained in step (a) is used as an energy source.

(B5) In the step (b), the solar heat energy obtained in the step (a) is directly used as a heat source to carry out a reaction for generating hydrogen from water (B1) to (B4). ) The method according to any one of items

(B6) At least a part of the solar heat energy used as a heat source in the step (b) is obtained by a parabolic dish type concentrator and a Z or solar evening type concentrator. 5) The method described in the paragraph.

(B 7) The method according to (B 2) or (B 3), wherein in step (b), a reaction for generating hydrogen from water is performed using the electric power as a heat source.

(B8) The method according to (B2) or (B3), wherein in step (b), water is electrolyzed with the electric power to cause a reaction to generate hydrogen from water.

(B 9) The method according to any one of (B 7) or (B 8), wherein in step (a), the solar thermal energy is acquired by a parabolic trough concentrator.

(B 10) In step (c), ammonia is synthesized from nitrogen and hydrogen using the solar energy obtained in step (a) directly as a heat source and Z or a power source. The method according to any one of 1) to (B9).

(B 11) The method according to (B 10), wherein the solar heat energy used as a heat source in the step (c) is obtained with a parabolic trough concentrator. (B 1 2) In step (b), the solar heat energy obtained in step (a) is directly used as a heat source to cause a reaction to generate hydrogen from water; used as a heat source in step (b). At least a part of the solar heat energy is obtained with a parabolic dish type concentrator and a Z or solar tower type concentrator; the solar thermal energy obtained in step (a) is directly obtained in step (c). A reaction to synthesize ammonia from nitrogen and hydrogen using as a heat source and a Z or power source; and the solar trough energy used as a heat source in step (c) is a parabolic trough type collector. The method according to any one of (B1) to (B4), which is obtained by an optical device.

(B 1 3) The method according to (B 2) or (B 3), wherein the nitrogen is obtained by cryogenic separation of air using the power and Z or power.

(B 14) The nitrogen according to any one of (B 1) to (B 1 2), obtained by burning the hydrogen obtained in step (b) and consuming oxygen in the air. Method.

According to the above method, solar thermal energy that can be said to be inexhaustible is converted or stored and used to solve the problems of global warming and oil and natural gas depletion. Brief Description of Drawings

FIG. 1 is a diagram for explaining an example of the conversion system 1.

FIG. 2 is a diagram for explaining an example of the conversion system 2.

FIG. 3 is a diagram for explaining the energy flow of the conversion system 1. FIG. 4 is a diagram showing an outline of a parapoly dish type condensing device. FIG. 5 is a diagram showing an outline of the solar tower type condensing device.

FIG. 6 is a schematic diagram of a parabolic trough concentrator. Fig. 7 is a diagram showing an example of equipment for implementing the solar thermal energy storage method. BEST MODE FOR CARRYING OUT THE INVENTION

Regarding the storage and transfer of solar energy, the following three substances are considered as candidates for liquid fuels that can be produced from water, air and solar thermal energy and are easy to store and transfer:

(1) Hydrogen peroxide (H ₂ 0 ₂ )

(2) Hydrazine (NH ₂ NH ₂ )

(3) Ammonia (ΝΉ ₃ )

Among these, considering the ease of handling of substances, ammonia is considered to be a useful candidate. Ammonia is a strong irritating gas, and it is a deleterious substance that damages the respiratory system when inhaling high-concentration gas, but because of its strong odor, lethal doses of 1 1, 0 0 0 or less 5 Humans can detect leaks from around ppm, and there are very few accidents in the actual market. Ammonia, for example, is used as a refrigerant for freezers such as fish boats along with chlorofluorocarbons. However, fatal accidents when ammonia leaks are 1% 1 0 Degree. Explosive disasters during the transfer of ammonia are less than 1 Z 5 for gasoline and liquefied petroleum gas (LPG).

The world's current ammonia production is about 150 million tons per year, which is mainly used for fertilizers in large quantities. In view of the fact that it is used in large quantities in the market in this way, ammonia is considered to be sufficiently socially acceptable.

The physical properties of ammonia are close to LPG and about 8 atm at room temperature Liquefied easily, and has a sufficient record of storage and transport, and is not a particular problem. Ammonia is also defined as a non-flammable substance. It is difficult to ignite, and even if ignited, the burning rate is slow and the flammable range is narrow.

The energy density of ammonia is about half that of gasoline, which is almost the same as methanol, but the calorific value in theoretical mixing is higher than that of gasoline, and it can be used as a fuel enough for moving objects. Furthermore, it can be sent to a thermal power plant in a remote area by a tanker or the like and burned instead of natural gas or coal. In this case, the efficiency is theoretically considered to exceed that of natural gas or coal.

In the combustion of ammonia, it is possible to cause a combustion reaction as shown in the following equation A:

2 NH 3 + 3/2 ○ ₂ → N ₂ + 3 H ₂ ○ + (Heat generation) (Formula A) In other words, the combustion of ammonia does not produce carbon dioxide.

Therefore, there is no problem with global warming.

It should be noted that, as described above, burning the ammonia to maintain power is described in, for example, Japanese Patent Laid-Open No. 5-3 3 2 1 5 2

With reference to Fig. 1, a conversion system 1 that converts solar thermal energy into drive energy will be described.

The conversion system 1 condenses sunlight 20 0 to produce solar thermal energy, solar thermal energy acquisition means 10, and ammonia synthesis means 20 0 to synthesize ammonia from water and air using solar thermal energy The details will be described later regarding a solar thermal energy storage method), an ammonia transfer means 30, and a drive energy generation means 40 that burns ammonia to generate drive energy. The solar heat acquisition means 10 and the ammonia synthesis means 20 are arranged in the first area 3, and the drive energy generation means 40 is arranged in the second area 5 that is geographically different from the first area 3. .

As described later, the ammonia synthesis reaction from air and water is an endothermic reaction as a whole. Therefore, the ammonia synthesis means 20 uses solar heat energy as reaction heat and converts ammonia (NH ₃ ) and oxygen (0 ₂ ) from nitrogen (N ₂ ) and water (H ₂ 0) contained in the air. Generate. The produced ammonia is optionally liquefied and transferred from the first region 3 to the second region 5 as fuel by the ammonia transfer means 30. In the second region 5, ammonia is burned by the driving energy generation means 4 0 so as to generate nitrogen and water, and driving energy 1 2 40 and thermal energy 2 5 0 are generated.

Nitrogen and water are non-polluting substances that are abundant in the atmosphere. Therefore, the nitrogen and water produced by combustion are released into the atmosphere and circulate according to the convection existing in nature, and can be used again as raw materials for the ammonia synthesis means 20 in the first region 3. become.

The conversion system 1 has an energy balance of driving energy 2 4 0 and thermal energy 2 5 0 with sunlight 2 0 0 as input, while nitrogen + water-ammonia + oxygen (ammonia synthesis), It has a material balance of the circulation loop of ammonia + oxygen → nitrogen + water (ammonia combustion). And all the processes of the conversion system 1 do not require chemical substances containing carbon atoms, and therefore do not emit any carbon dioxide (CO ₂ ).

In this way, the conversion system 1 uses the ammonia generated using air and water as a solar thermal energy transfer material, so that the solar thermal energy acquired in the first region 3 can be driven in the second region 5. It can be used as energy. Also, conversion system 1 Since energy is converted by the circulation of chemical substances that do not contain carbon atoms (water, nitrogen in the air, ammonia), carbon dioxide is not emitted in any process in the system.

Note that the solar heat acquisition means 10 is preferably located in a region with a large amount of sunlight, so the first region should be a region with more solar radiation than the second region that uses drive energy. . The ammonia synthesizing means 20 also discharges oxygen. Oxygen is a valuable substance for the manufacture of chemical products, so oxygen utilization facilities may be established in the first area.

An example of the conversion system 2 will be described with reference to FIG.

As shown in the figure, the ammonia synthesizing means 20 is composed of an ammonia synthesis brand 22, an ammonia liquefaction device 24 that liquefies compressed ammonia with cooling water, and liquefies ammonia liquefied by the expanded self-refrigerant 24, solar heat Power generation plant that generates power from steam turbines using steam generated using gas or gas turbines that use ammonia combustion (including those combined with steam turbines) 25, liquefied ammonia shipping facilities 26, Includes cooling towers for cooling water (not shown), water treatment equipment for purifying water from well water, seawater, etc. For the ammonia synthesis plant 22, refer to the solar thermal energy storage method described later. Ammonia transfer means 30 is carried out by liquefied ammonia ship 3 2 on board transfer, tank / lorry 3 4 or pipeline 3 6 on land transfer.

In the second region 5, ammonia is received by the ammonia receiving equipment 4 2, or ammonia is directly transferred to the drive energy generating means 40. The drive energy generation means 40 (gas turbine, automobile, etc.) uses an internal combustion engine to burn ammonia and obtain drive energy. In this way, the conversion system 2 uses the ammonia generated using air and water as a solar thermal energy transfer material, so that the solar thermal energy acquired in the first region 3 can be driven in the second region 5. It can be used as energy. In addition, since the conversion system 2 converts energy by circulation of chemical substances without carbon atoms (water, nitrogen in the air, ammonia), the solar heat acquisition means 10 and ammonia synthesis means 20 in the first region, Carbon dioxide is not emitted in the driving energy generating means 40 in the second region.

Using Fig. 3, the energy flow of conversion system 1 is explained. Sunlight 2 0 0 is converted into solar heat energy 2 1 0 via solar heat acquisition means 1 0. Solar thermal energy 2 1 0 is converted into chemical energy 2 2 0 as potential energy of ammonia by ammonia synthesis means 2 0. Here, a part 2 15 of the solar thermal energy 2 10 is used by the ammonia synthesizing means 2 0 as a heat source, a power source and Z or a power source.

The chemical energy 2 20 is transferred from the first area 3 to the second area 5 by the ammonia transfer means 30. In the transfer, the ammonia transfer means 30 is combusted by the internal combustion engine of the ammonia transfer means 30 with a part of chemical energy (that is, a part of the ammonia to be transferred). Power and / or at least part of the power). The chemical energy 2 2 0 is partially consumed by the ammonia transfer means 3 0, and becomes chemical energy 2 3 0 after being transferred to the second area 5.

Chemical energy 2 3 0 burns ammonia so that driving energy generating means 40 generates nitrogen and water, and outputs driving energy 2 4 0 and thermal energy 2 5 0 (not shown, In ammonia synthesis means 20 and ammonia transfer means 30, waste heat Energy can be generated).

In this way, by using the chemical energy of ammonia,

Sunlight 2 0 0 input in area 3 of 1 is transferred as drive energy 2 4 0 and heat energy 2 5 0 in second area 5. The conversion system 1 does not need to use an energy source other than the sunlight 20 0. Therefore, the conversion system 1 enables conversion of solar thermal energy 2 10 to driving energy 2 40 without emitting carbon dioxide at any step in the system.

Methods for storing solar thermal energy include: (a) acquiring solar thermal energy; (b) using a portion of the acquired solar thermal energy, for example as a heat source, power source and Z or power source, especially directly (C) using other part of the acquired solar thermal energy as a heat source or power source, for example, heat source, power source and Z or power Use as a source, particularly as a heat source and Z or as a power source, to carry out a reaction to synthesize ammonia from nitrogen and hydrogen obtained in step (b).

According to this energy storage method, solar heat energy can be stored in the form of chemical energy of ammonia by synthesizing ammonia using solar heat energy.

In a preferred embodiment of this method, the solar heat energy obtained in step (a) is used to obtain at least a portion of the power and Z or power required to perform this method. In another preferred embodiment, the synthesized ammonia is used as a fuel to obtain at least a portion of the power, dynamics and / or heat required to perform this method. In another preferred embodiment of this method, only the solar thermal energy obtained in step (a) is used as a source of energy. Here, examples of the electric power required for carrying out this method include electric power for driving a pump compressor that causes a fluid such as a raw material to flow and Z or compression, electric power for further heating of a heat source, and the like. . Examples of power necessary for carrying out this method include power for driving a pump / compressor that flows and / or compresses a fluid such as a raw material. In addition, heat necessary for carrying out this method can include heat for further heating of the heat source. Here, supplying a part of the heat energy for the heat source by electric power is preferable in order to make the temperature of the heat source higher than the temperature directly obtained by solar thermal energy.

According to these aspects, the use of conventional fossil fuels such as petroleum can be reduced, and preferably <preferably, can be carried out. The total reaction of ammonia synthesis from water and nitrogen is as shown in Formula B below.

N ₂ + 3 H ○ → 2 NH 3 + 3/2 O (endothermic) (Formula B) In the solar energy storage method, solar energy is used as an energy source for the reaction, and water (H ₂ O ) and nitrogen (N ₂₎ or al, via the reaction of hydrogen with (H ₂₎ and nitrogen (N _2), are synthesized ammonia (NH _3). The solar thermal energy storage method will be described in detail below.

(B) Solar thermal energy storage method (a) (Acquisition of solar thermal energy)>

In the solar thermal energy storage method, solar energy is obtained in step (a).

In step (a), any concentrator can be used to obtain solar thermal energy, for example, the following (1) to (3 concentrators can be used: (1) No. Labish dish type (Parabo 1 icdish T ype)

The parabolic dish type concentrator shown in Fig. 4 has a plate-like reflector 1 4 1 that reflects and collects sunlight 20 0 and a light receiver 1 4 2 that receives the collected light. The solar energy is acquired at this light receiving section 1 4 2. The solar thermal energy obtained from the light-receiving unit 1 4 2 can be transferred to the required location using a molten alkali metal such as molten metal sodium, molten salt, oil, steam, etc. In monkey.

This type of concentrator is suitable for a relatively small plant, and is preferably used as solar thermal energy of about 10 kw to several 100 kw. In general, this type of condensing device has a high degree of light condensing, and thus a relatively high power cost for obtaining a high-temperature heat source of 2, 00 or more.

(2) Type of solar dinner

The solar tower type condensing device 1 5 0 shown in Fig. 5 is a light receiving unit that receives multiple condensed light (reflecting part) 1 5 1 that reflects sunlight 2 0 0 and collects it. 1 5 3 and solar light energy is acquired in this light receiving part 1 5 2. Here, the light receiving portion 1 5 3 is arranged above the light receiving portion 1 15 2. The solar heat energy obtained at the light receiving section 15 3 can be moved to the required location using a heat medium as required.

This type of concentrator is suitable for large-scale plants ranging from 10 MW to several 100 MW. In general, this type of condensing device has a high degree of condensing, and a high-temperature heat source can be obtained with a numerical value of 1,00,00. However, the construction cost of the tower is high, and the control of the reflector is required to be highly technical.

(3) Parapolic rough type The parabolic trough concentrator 1 60 shown in Fig. 6 has a trough-type reflector 1 6 1 that reflects and collects sunlight 20 0 and a light receiver 1 6 2 that receives the collected light. And the solar receiver 1 4 2 obtains solar thermal energy. The solar thermal energy obtained by the light receiving section 16 2 can be moved to a necessary location by optionally circulating a heat medium via the heat medium flow path 16 3.

This type of concentrator is simple in structure and low in cost, and is suitable for large-scale plants. In general, it is suitable for the numerical value of 100 MW, but has a low concentration, and the obtained heat source is a low-temperature heat source in the range of 400 to 500.

As mentioned above, each concentrator has advantages and disadvantages. Therefore, any of these or a combination of them can be used in the energy storage method. Specifically, solar thermal energy for a high temperature heat source is obtained by a concentrator with a high degree of concentration (for example, a parapoly dish type concentrator and / or a solar evening type concentrator), and other Solar thermal energy, for example, a low-temperature heat source, power and solar thermal energy for generating Z or can be obtained with a concentrating device with a low concentration (eg, a parabolic trough concentrating device).

For example, solar thermal energy obtained by a concentrating device with a high degree of concentration is less than 1 Z 2 of the sum of solar thermal energy obtained by a concentrating device with a high degree of condensing and a concentrating device with a low degree of concentrating, It can be in the range of 1 to 2. Thus, limiting the proportion of light concentrators that are generally high cost and have a high degree of light condensing may be preferable with respect to the overall cost of the light concentrating equipment.

(B) (Hydrogen production)> In the solar thermal energy storage method, in step (b), a part of the acquired solar thermal energy is used. Use only one energy source to generate hydrogen from water.

In this step (b), any method can be used to obtain hydrogen from water. Specifically, along with water electrolysis, for example, the following (1) to (3) water splitting methods are known. In these methods, water decomposition is known. The focus is on reducing the reaction temperature required for the reaction: (1) Direct method

It is the most basic method, and it decomposes water into hydrogen and oxygen directly at high temperature by the reaction shown in Equation 1 below:

H ₂ 0 → H ₂ + 1/2 O ₂ (more than 2, 0 0 0) (Equation 1) This reaction originally requires several thousand temperatures, but by using a catalyst, 2 0 0 0 can be achieved at temperatures around.

(2) Zn (zinc) method

In order to lower the high temperature required in (1) above, there is a method of decomposing water through the presence of a third substance. A typical example is a method involving zinc, in which the reaction formula is as follows:

Z n + H ₂ 0 → Z n O + H ₂ (about 4 0 0) (Formula 2)

Z n O → Z n + l / 2 0 ₂ (at about 1 5 0 0) (Equation 3) All reactions H ₂ 0 → H ₂ + 1 Z ₂ 0 ₂

This method requires two types of heat sources: a high-temperature heat source (at about 15 500) and a low-temperature heat source (4 00 V,).

(3) I — S (iodine-io) cycle method

As a method for lowering the reaction temperature further than the method (2) above, I 1 S cycle method is known, and the reaction is as follows: H ₂ S 0 ₄ → H ₂ 0 + S 0 ₂ + 1/2 O ₂ (at about 9 5 0)

(Formula 4) 2 H ₂ 〇 + S 0 ₂ + I ₂ → H ₂ S 0 ₄ + 2 HI (about 1 3 0)

(Formula 5)

2 H I → H 2 + I 2 (about 4 0 0)

(Equation 6) Total reaction H ₂ 0 → H ₂ + 1 ₂ 0 ₂

This method requires two types of heat sources: a high-temperature heat source (at 95 0) and a low-temperature heat source (4 0 0).

As described above, in the reactions (1) to (3) in which hydrogen is generated from water using heat, a heat source having a relatively high temperature is required for at least some of the reactions.

This relatively high temperature heat source can be provided by directly using the solar heat energy acquired in step (a) as a heat source, in which case at least a portion of the required solar heat energy is collected. It can be obtained with a concentrator with a high luminous intensity, such as a parapoly dish type concentrator and a Z or solar tower type concentrator. In addition, this relatively high temperature heat source uses electric power, particularly electric power obtained using solar thermal energy acquired in step (a), or electric power obtained using synthesized ammonia as fuel. be able to. In addition, when hydrogen is obtained without using a relatively high temperature heat source, that is, for example, by electrolysis of water, electric power, in particular, electric power obtained using solar thermal energy acquired in step (a), or synthesized energy Electricity obtained by using monmonas as fuel can be used.

Thus, when providing a relatively high-temperature heat source using electric power, or when electrolyzing water using electric power, in step (a), the acquisition of solar thermal energy is performed by collecting light with a low concentration. This can be done with a device, for example a parapoly trough concentrator. This may be preferable with respect to the overall cost of the light collection equipment. (1) Process of solar thermal energy storage (C) (Ammonia synthesis)

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In the solar thermal energy storage method, in step (C), the other part of the acquired solar thermal energy was used, and in particular, only the acquired solar thermal energy was used as an energy source, and was obtained in nitrogen and step (b). A reaction for synthesizing ammonia from hydrogen is performed.

In this step (c), the synthesis of ammonia from nitrogen and hydrogen can be achieved by any method.

The chemical synthesis of ammonia was the first successful mass production of German researchers Herba and Bosch about 100 years ago, contributing to increased food production as a nitrogen fertilizer. The Harbor-Bosch synthesis method is an endothermic reaction shown below, and it is simple and relatively efficient. Therefore, it is still used basically without modification, and this method is also used for energy storage. Can:

N ₂ + 3 H ₂ → 2 NH ₃ (about 4 0 0) (Equation 8) That is, this reaction uses a relatively low temperature (4 0 0 T) heat source. Conventionally, this reaction has been carried out using an iron catalyst, but recently, the reaction temperature has been further lowered using a ruthenium catalyst. When the reaction temperature is low, the yield of ammonia is high in equilibrium, so research to lower the reaction temperature is still underway.

The relatively low temperature heat source for this reaction and Z or the power for this reaction can be provided using the solar thermal energy obtained in step (a), in this case the necessary solar heat. Energy can be obtained with a concentrator with a low concentration, such as a parapoly trough concentrator.

In order to obtain nitrogen for solar thermal energy storage method, The following methods (1) and (2) are applicable: (1) Cryogenic separation

In this method, air is cooled and compressed to produce liquid air, and nitrogen is separated from liquid air by utilizing the difference in boiling point between oxygen and nitrogen. This method yields high purity nitrogen, but requires large equipment and a relatively large amount of energy.

Here, for the cryogenic separation of the air, the electric power and Z or power obtained by using the solar thermal energy acquired in the step (a), or the electric power and power obtained by using the synthesized ammonia as fuel. Z or power can be used. In this case, also in this step, the production of carbon dioxide due to the use of fossil fuel can be suppressed and preferably eliminated.

(2) Removal of oxygen by combustion

In a conventional ammonia plant that uses natural gas, oxygen in the air is consumed in the reforming process to obtain hydrogen, and carbon monoxide and carbon dioxide are absorbed and removed from the remaining mixed gas to produce nitrogen gas. Have gained. This method can also be used as an energy storage method. In this case, however, a purification process may be required to reduce the concentration of carbon monoxide and carbon dioxide contained in nitrogen gas to 10 ppm or less. If this is not done, carbon monoxide and carbon dioxide may be adsorbed on the ammonia synthesis catalyst and accelerate degradation.

(3) On the other hand, in one embodiment of the energy storage method, as shown in the following formula 7, the produced hydrogen (H ₂ ) is burned with air (4 N ₂ + O ₂ ) Nitrogen gas can also be produced by consuming oxygen of:

2 H ₂ + 4 N ₂ + 0 ₂ → 4 N ₂ + 2 H ₂ O (Equation 7) In this case, the combustion product is only water and the combustion product is oxidized Since it does not occur as carbon and carbon dioxide, the need for removal of carbon monoxide and carbon dioxide is reduced or even eliminated. Since this reaction is an exothermic reaction, it is possible to use the heat energy generated at this time as necessary to produce the electric power required for the energy storage method.

One example of a solar thermal energy storage method can be implemented using equipment as shown in Figure 7.

In the facility shown in Fig. 7, solar heat energy is acquired by a solar tower type condensing device 15 0 having a relatively high light concentration, and the solar heat energy obtained here is used to distribute a heat medium that is a molten salt 1 7 8 to transfer to reactor 1 7 1. In addition, solar heat energy is obtained by a parapoly trough-type light concentrator 1 60 having a relatively low light concentration, and the obtained solar heat energy is connected by a pipe 1 7 9 through which a heat medium that is water vapor is circulated. Transfer to reactor 1 7 1.

In this reactor 1 7 1, a parabolic trough that uses the thermal energy supplied from the solar evening light type concentrator 1 50 having a relatively high concentration as a high-temperature heat source and that has a relatively low concentration. Hydrogen is obtained by performing a reaction for generating hydrogen from water using the thermal energy supplied from the type concentrator 160 as a low-temperature heat source and Z or a power source.

Solar thermal energy is acquired by a parabolic trough-type concentrator 1 60 having a relatively low concentration, and transferred to a reactor 1 7 3 by a pipe 1 7 9 through which a heat medium that is water vapor flows. In the reaction device 1 7 3, solar heat energy is used as a heat source and / or a power source to perform a reaction for synthesizing ammonia from nitrogen and hydrogen to obtain ammonia. Here, the nitrogen supplied to the reactor 1 7 3 is subjected to a cryogenic separation of the air by an air cryogenic separation device 1 7 2. The hydrogen supplied to the reactor 1 7 3 is obtained by the reactor 1 7 1.

In other words, in the method of this example, the supply to the system of the facility that implements solar thermal energy is only solar energy 20 0, water (H ₂ 0) and air (A ir). Ammonia (NH ₃ ) is obtained. Therefore, in this example, it does not involve the generation of oxygen dioxide to store solar thermal energy in the form of ammonia chemical energy.

The ammonia obtained in reactor 1 7 3 is optionally liquefied in liquefier 1 7 4 and then stored in storage tank 1 7 5 until shipping. Here, solar energy can also be used as a power source for the liquefaction device.

In the example shown in FIG. 7, instead of the solar tower type condensing device 150, another condensing device having a relatively high condensing degree, for example, a parapoly dish type condensing device can be used. Also, instead of using two types of concentrators, a solar tower type concentrator 150 and a parabolic trough concentrator 1660, only one type of concentrator can be used.

Claims

The scope of the claims

1. (a) obtaining solar thermal energy,

Including a solar thermal energy storage method.

2. The method according to claim 1, wherein the solar heat energy obtained in step (a) is used to obtain at least a part of electric power and / or power necessary for the implementation of this method.

3. The method according to claim 1 or 2, wherein the synthesized ammonia is used as a fuel to obtain at least a part of electric power, power and / or heat necessary for carrying out the method.

4. The method according to any one of claims 1 to 3, wherein only the solar thermal energy acquired in the step (a) is used as an energy source.

5. The method according to any one of claims 1 to 4, wherein in step (b), the solar thermal energy acquired in step (a) is directly used as a heat source to cause a reaction to generate hydrogen from water. .

6. The method according to claim 5, wherein at least a part of the solar thermal energy used as a heat source in step (b) is obtained by a parabolic dish type concentrator and / or a solar tower type concentrator.

7. The method according to claim 2 or 3, wherein in step (b), the electric power is used as a heat source to cause a reaction to generate hydrogen from water.

8. The method according to claim 2 or 3, wherein in step (b), water is electrolyzed with the electric power to cause a reaction to generate hydrogen from water. Law.

9. The method according to claim 7 or 8, wherein, in the step (a), the solar thermal energy is acquired by a parapoly trough concentrator.

10. In step (c), ammonia is synthesized from nitrogen and hydrogen using the solar energy obtained in step (a) directly as a heat source and as Z or a power source. One of the methods.

1 1. The method according to claim 10, wherein the solar heat energy used as a heat source in the step (c) is obtained by a parabolic trough concentrator.

1 2. In step (b), the solar energy obtained in step (a) is directly used as a heat source to cause a reaction to generate hydrogen from water; the solar heat used as a heat source in step (b) At least a part of the energy is obtained with a parapoly dish type concentrator and / or a solar tower type concentrator; in step (c), the solar thermal energy obtained in step (a) is directly used as a heat source and / or A reaction for synthesizing ammonia from nitrogen and hydrogen is performed by using as a power source; and the solar thermal energy used as a heat source in step (c) is obtained by a parabolic trough concentrator. 4. The method according to any one of 4.

1 3. The method according to claim 2 or 3, wherein the nitrogen is obtained by cryogenic separation of air using the power and Z or power.

1 4. The method according to any one of claims 1 to 12, wherein the nitrogen is obtained by combusting the hydrogen obtained in the step (b) and consuming oxygen in the air.