Solar thermochemical thermal storage system

Abstract

The solar thermochemical heat storage system belongs to the field of solar energy technology. It includes a plurality of heat storage units arranged in a ring structure, the reaction chamber of each heat storage unit is placed with redox reaction materials, and a ring pipe is provided to connect the reaction chambers. The heliostat field reflects sunlight to the heat storage unit. During the heating process, the heat storage material undergoes a reduction reaction, and the generated oxygen is diluted by the nitrogen in the reaction chamber. The present invention provides a thermochemical heat storage method using antimony pentoxide, which has the advantages of simple structure, high heat storage efficiency, environmental protection and no pollution, and is suitable for large-scale solar heat storage applications. The present invention can make the materials in the reaction chamber heated evenly, improve the reaction rate and heat storage efficiency; realize thermochemical heat storage through redox reaction, with greater energy storage density and better heat storage effect; the ring pipe design between adjacent reaction chambers makes the oxygen flow stable and even, and promotes the heat storage material to continue to undergo reduction reaction.

Description

Technical Field

[0001] The invention belongs to the technical field of solar energy, and in particular relates to a solar thermochemical heat storage system. Background Art

[0002] People's demand for clean energy is increasing. As a clean and renewable energy, solar energy has become an important direction for my country's energy structure adjustment. However, solar power generation is greatly affected by weather and geographical conditions. How to solve the stability and continuity of solar power generation has become an important issue in the development of the solar energy industry.

[0003] Solar thermal storage technology is to store the heat energy in the sunny period in different energy forms so that it can be used in the period of insufficient or no sunshine, thereby ensuring the stable operation of the power generation system. The core of this technology is to convert the heat energy generated by solar energy into other forms of energy and realize the space-time transfer of energy through storage.

[0004] At present, the more mature solar thermal storage technology is to heat molten salt with the heat energy generated by solar energy, and use the latent heat of the molten salt phase change to store energy. However, there are many inherent defects in sensible heat storage and latent heat storage. For example:

[0005] 1. The main problem with molten salt heat storage, a commonly used sensible heat storage method, is that the molten salt has the risk of solidification and clogging in the pipeline, and its operation and maintenance costs are high.

[0006] 2. Latent heat storage technology is mainly used in the medium temperature field, and the thermal stability of heat storage materials cannot be guaranteed under high temperature conditions.

[0007] 3. The energy storage density is small, the operating temperature is low, the heat loss is large, the energy storage cycle is short, and the transportation distance is short.

[0008] At the same time, switching to chemical heat storage has become one of the main measures to improve the efficiency of solar thermal storage. Summary of the invention

[0009] The present invention aims to solve the problems existing in traditional heat storage devices in solar mirror fields and further provide a solar thermal chemical heat storage system based on chemical heat storage.

[0010] The technical solution adopted by the present invention is:

[0011] A solar thermochemical heat storage system includes a plurality of heat storage units arranged in a ring structure. Redox reaction materials are placed in the reaction chamber of each heat storage unit, and a ring-shaped pipeline is provided to connect the reaction chambers. The heliostat field reflects sunlight to the heat storage unit. During the heating process, the heat storage material undergoes a reduction reaction, and the generated oxygen is diluted by the nitrogen in the reaction chamber.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The present invention provides a thermochemical heat storage method using antimony pentoxide, which has the advantages of simple structure, high heat storage efficiency, environmental protection and no pollution, and is suitable for large-scale solar heat storage applications.

[0014] The present invention can heat the materials in the reaction chamber evenly, improve the reaction rate and heat storage efficiency; realize thermochemical heat storage through redox reaction, with higher energy storage density and better heat storage effect; the annular pipeline design between adjacent reaction chambers makes the oxygen flow stable and even, promoting the heat storage material to continue the reduction reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the heat pipe type solar thermochemical heat storage device of the present invention;

[0016] Figure 2 yes Figure 1 Schematic diagram of the structure of the heat storage unit;

[0017] Figure 3 It is a schematic diagram of the structure of the volume cavity type solar thermochemical heat storage device of the present invention;

[0018] Figure 4 yes Figure 3 Schematic diagram of the structure of the heat storage unit;

[0019] Figure 5 It is a schematic diagram of the heat sink fins;

[0020] Figure 6 This is a comparison chart of the purity verified by XRD test on the experimental samples;

[0021] Figure 7 This is the TG-DSC graph of antimony trioxide test;

[0022] Among them: 1. reaction chamber; 2. heat absorption pipe section; 3. heat dissipation pipe section; 4. annular pipe section 1; 5. heat absorption plate; 6. base section; 7. heat absorber; 8. annular pipe section 2; 9. air inlet pipe; 10. air outlet pipe; 11. heat dissipation fins; 12. branch pipe section. DETAILED DESCRIPTION

[0023] In order to better understand the purpose, structure and function of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings.

[0024] like Figure 1 to Figure 7As shown, the present invention provides a solar thermochemical heat storage system, including a plurality of heat storage units arranged in a ring structure, a reaction chamber 1 of each heat storage unit is used to place a redox reaction material, and a ring-shaped pipeline is provided to connect the reaction chambers, and the heliostat field reflects sunlight to the heat storage unit. During the heating process, the heat storage material undergoes a reduction reaction, and the reaction chamber 1 is filled with nitrogen. The generated oxygen is diluted by the nitrogen in the chamber, which promotes the heat storage material to continue the reduction reaction, thereby making the reaction as complete as possible.

[0025] The solar thermal chemical heat storage device of the present invention uses antimony pentoxide as a heat storage material and utilizes the chemical heat of its thermal decomposition reaction at high temperature to store energy. It has two implementation modes.

[0026] Embodiment 1, as Figure 1 , Figure 2 As shown, a plurality of the heat storage units constitute a heat pipe type solar thermochemical heat storage device, which includes a reaction chamber 1, a heat pipe, an annular pipe section 4, a heat absorbing plate 5 and a base section 6; the heat dissipation pipe section 3 of the heat pipe is embedded in the reaction chamber 1, the annular pipe section 4 is sealed and connected to the reaction chamber 1, the heating pipe section 2 of the heat pipe is directly in contact with the air, and is connected to the base section 6 through the heat dissipation pipe section 3, and the heat absorbing plate 5 is welded around the heating pipe section 2; the heliostat field reflects sunlight to the heating pipe section 2 and the heat absorbing plate 5 of the heat pipe, the temperature of the reaction chamber 1 rises, and the material undergoes an endothermic redox reaction to achieve a heat storage effect.

[0027] The annular pipe sections 4 of multiple heat storage units constitute the entire annular pipe, the reaction chambers 1 of multiple heat storage units are arranged in sequence along the circumference, and the base sections 6 of multiple heat storage units constitute the entire annular base.

[0028] The first embodiment of the present invention is mainly composed of a heat pipe, a reaction chamber 1 and an annular pipe to realize the thermochemical heat storage of antimony pentoxide. It is composed of 24 heat storage units, the reaction chamber 1 is used to place the redox reaction material, and an annular pipe is provided to connect each reaction chamber 1. The heliostat field reflects sunlight to the heating pipe section 2 and the heat absorbing plate 5 of the heat pipe, releases heat through the heat pipe heat dissipation pipe section 3, and heats the material in the reaction chamber 1. During the heating process, the heat storage material undergoes a reduction reaction, and the reaction chamber 1 is filled with nitrogen. This process prompts the heat storage material to continue to undergo a reduction reaction, so that the reaction is as complete as possible and more heat energy is stored. The present invention uses heat pipes to dissipate heat, so that the materials in the reaction chamber 1 are heated evenly, the reaction rate and heat storage efficiency are improved; thermochemical heat storage is realized through redox reactions, the energy storage density is greater, and the heat storage effect is better; the annular pipe design between adjacent reaction chambers makes the nitrogen flow stable and uniform, and promotes the heat storage material to continue to undergo a reduction reaction; a heat absorbing plate 5 is welded between the heating pipe sections 2 of adjacent heat pipes to prevent sunlight from passing through the gaps between the heat pipes, thereby improving the utilization rate of solar energy.

[0029] Embodiment 2, as Figure 3 , Figure 4 , Figure 5 As shown, a plurality of the heat storage units constitute a volumetric cavity solar thermochemical heat storage device, which includes a reaction chamber 1, a heat absorber 7, an annular pipe section 2 8, heat dissipation fins, an air inlet pipe 9 and an air outlet pipe 10; the air inlet pipe 9 and the air outlet pipe 10 are both connected to the heat absorber 7, the air inlet pipe 9 and the air outlet pipe 10 are connected, the air outlet pipe 10 passes through the reaction chamber 1 and is sealed, and the annular pipe section 2 8 is sealed and connected to the reaction chamber 1; the heliostat field reflects sunlight to the heat absorber 7, and the temperature of the gaseous heat transfer medium rises after flowing through the heat absorber 7, and a heat dissipation fin 11 is installed at the pipe section of the air outlet pipe 10 embedded in the reaction chamber 1, and the heat storage material is heated by the heat dissipation fin 11, and the heat storage material undergoes an endothermic redox reaction to achieve a heat storage effect.

[0030] The pipe section of the gas outlet pipe 10 embedded in the reaction chamber 1 is configured as a plurality of branch pipes 12 , and the heat dissipation fins 11 are mounted on the branch pipes 12 , which effectively increases the contact area and improves the heat dissipation effect.

[0031] The second embodiment of the present invention can realize the thermochemical heat storage of antimony pentoxide. The present invention is composed of 24 heat storage units, and the reaction chamber 1 is placed with redox reaction materials and communicated with the annular pipe. The heliostat field reflects sunlight to the heat absorber 7, and the temperature of the gaseous heat transfer medium rises after flowing through the heat absorber 7, and the heat storage material is heated by the heat dissipation fins embedded in the reaction chamber 1 through the outlet pipe 10. During the heating process, the material undergoes a reduction reaction, and the reaction chamber 1 is filled with nitrogen. This process prompts the heat storage material to continue the reduction reaction, so that the reaction is complete and more heat energy is stored. The present invention adopts pipeline heating to make the material in the reaction chamber 1 heated evenly, improve the reaction rate and heat storage efficiency; realize thermochemical heat storage through redox reaction, the energy storage density is greater, and the heat storage effect is better; the annular pipe design between adjacent reaction chambers 1 makes the nitrogen flow stable and promotes the heat storage material to continue to undergo reduction reaction.

[0032] Heat storage material: Each of the heat storage units uses antimony pentoxide, copper oxide, manganese trioxide, calcium carbonate, magnesium hydride or calcium hydride as a heat storage material, preferably antimony pentoxide; and uses the chemical heat of its thermal decomposition reaction at high temperature to store energy.

[0033] The specific information of antimony pentoxide is shown in Table 1 below:

[0034]

[0035] Table 1

[0036] Through endothermic reaction, solar energy will be stored in antimony trioxide in the form of chemical energy. When antimony trioxide is heated to about 600℃ in air atmosphere, chemical energy will be released again in the form of heat energy, and antimony trioxide will be reoxidized into antimony pentoxide to participate in a new round of energy storage cycle.

[0037] First, perform XRD test on the experimental sample to verify the purity. Figure 6 shown.

[0038] Then the TG-DSC test on antimony trioxide showed the following results: Figure 7 shown.

[0039] It can be seen that when the temperature reaches 600°C, the oxidation effect is obvious.

[0040] Other alternative materials are shown in Table 2 below:

[0041]

[0042]

[0043]

[0044] Table 2

[0045] Reaction chamber 1 material: The reaction chamber 1 is made of zirconium oxide, ZrO2-SiC-C high temperature resistant material, GH4169 or Incone1718.

[0046] Zirconia has a melting point of up to 2715°C, good chemical stability, wear resistance and corrosion resistance, and is a high-end refractory material with excellent performance. The preparation method is as follows.

[0047] 1. Zirconium oxychloride pyrolysis method: Zircon and caustic soda are melted at 650℃, hot water is used to leach the melt, and silicon is separated from sodium zirconate in the form of sodium silicate. It is then treated with sulfuric acid to obtain a zirconium sulfate solution, and after further impurities are removed, ammonia water is added to precipitate zirconium hydroxide. Hydrochloric acid is added to dissolve the zirconium hydroxide to obtain zirconium oxychloride, which is evaporated and concentrated, cooled, crushed, and roasted to obtain the finished zirconium dioxide. In addition, easily purified zirconium compounds can be thermally decomposed or oxidatively decomposed to prepare high-purity zirconium oxide.

[0048] 2. Colloidal method: Add silica sol to zirconium oxide solution to form a colloidal solution, which is formed by spraying and drawing, and then sintered into fibers after drying.

[0049] 3. Extrusion method: Zirconia sol or zirconium oxide particles and thickener are made into blanks, and the blanks are squeezed out from the machine mouth by hydraulic pressure or the propulsion of a spiral auger into filaments, which are then sintered and solidified into fibers. The fibers produced by this method are coarser and have lower strength.

[0050] 4. Impregnation method: First, soak the viscose thread or the entire fabric in a zirconium hydroxide solution for a long time to make the viscose fiber swell, and then pyrolyze and calcine to obtain zirconium oxide fiber with a certain tensile strength.

[0051] 5. Hydrolysis method: high-purity ultrafine zirconium dioxide is prepared by hydrolysis with zirconium oxychloride as raw material. 0.2-0.3 mol of high-purity zirconium oxychloride solution is hydrolyzed with deionized water, and the zirconium oxychloride solution is boiled for a long time to evaporate the hydrogen chloride generated by the hydrolysis. The hydrolysis reaction is carried out at boiling for more than 50 hours, and then filtered, washed with deionized water, dried, calcined and crushed to obtain the product.

[0052] 6. High-temperature hydrolysis method: Spray 1 mol / L high-purity zirconium oxide solution into a decomposition furnace at a temperature of 1000°C. The tiny zirconium oxide droplets evaporate first and then hydrolyze to form zirconium dioxide. The decomposed zirconium dioxide is collected by a cyclone separator, then pickled, washed with water, and dried to obtain the product.

[0053] 7. Sol-gel method: Add alcohol and water to zirconol [ZrO(C3H7)4], then add a catalyst, and after sufficient mixing, begin to decompose. Allow to stand to gel and become a viscous liquid. Select an appropriate viscosity, dry, and heat to 500-1000°C. Fiberize at high temperature to obtain the product.

[0054] 8. Alcohol salt hydrolysis method: high-purity ultrafine zirconium dioxide is prepared with zirconium tetrachloride, ammonia and propanol as raw materials. In the presence of benzene solvent, high-purity zirconium tetrachloride, propanol and ammonia are reacted at 5°C to obtain zirconium alkoxide, which is separated by filtration to remove ammonium vapor, and then water is added to hydrolyze the precipitate, filtered, dried at not less than 100°C, calcined, and crushed to obtain the product. The hydrolysis conditions directly affect the particle size, shape and agglomeration of the product. This method can produce ZrO2 with uniform particle size and shape and single structural phase.

[0055] 9. Zirconium oxychloride (ZrCl 20 ·8H20) is recrystallized with hydrochloric acid or methanol and calcined at high temperature to obtain the finished product.

[0056] 10. Distill and purify tetraalkoxy zirconium, and decompose its vapor at 350-500°C to obtain the finished product.

[0057] Zirconia can also be made into various composite materials to improve performance. Zirconium-containing refractory materials include high-zirconium materials, zirconium-containing magnesium materials, zirconium-containing calcium materials, zirconium-containing corundum materials and non-oxide-ZrO2 composite refractory materials.

[0058] ZrO2-SiC-C high temperature resistant material: Using zircon and carbon black as raw materials and Y2O3 as additive, ZrO2-SiC-C composite powder is synthesized by carbon thermal reduction reaction under carbon buried and sealed conditions. Using ZrO2-SiC-C composite powder as raw material and phenolic resin as binder, a new type of ZrO2-SiC-C high temperature resistant material is prepared by a firing-free process.

[0059] GH4169: It is a precipitation-strengthened nickel-based high-temperature alloy with good comprehensive properties in the temperature range of -253 to 650°C. Its yield strength below 650°C ranks first among deformed high-temperature alloys. It also has good fatigue resistance, radiation resistance, oxidation resistance, corrosion resistance, as well as good processing and welding properties. It can manufacture various parts with complex shapes and has been widely used in aerospace, nuclear energy, petroleum industry and extrusion dies within the above temperature range.

[0060] Incone 1718: It is a precipitation-hardened nickel-chromium-iron alloy containing niobium and molybdenum. It has high strength at 700°C, good toughness and corrosion resistance in both high and low temperature environments. It can be supplied in solution treated or precipitation hardened state. Melting point 1260 to 1320°C.

[0061] Heat pipe: The heat pipe uses Mo-14Re as the metal cladding and Na as the heat transfer medium.

[0062] In order to detect the reaction progress of the material in the reaction chamber, a thermocouple is arranged in the reaction chamber 1. By arranging the thermocouple in the reaction chamber 1, the reaction completeness can be indirectly judged according to the time that the temperature in the chamber is maintained at the reaction temperature (930° C.).

[0063] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A solar thermochemical heat storage system, characterized in that: The invention comprises a plurality of heat storage units arranged in a ring structure, wherein a redox reaction material is placed in a reaction chamber (1) of each heat storage unit, and a ring-shaped pipeline is provided to connect the reaction chambers. The heliostat field reflects sunlight to the heat storage unit. During the heating process, the heat storage material undergoes a reduction reaction, and the generated oxygen is diluted by the nitrogen in the reaction chamber (1). A plurality of the heat storage units constitute a heat pipe type solar thermochemical heat storage device, the heat storage unit comprising a reaction chamber (1), a heat pipe, an annular pipe section (4), a heat absorbing plate (5) and a base section (6); the heat dissipation pipe section (3) of the heat pipe is embedded in the reaction chamber (1), the annular pipe section (4) is sealed and connected to the reaction chamber (1), the heating pipe section (2) of the heat pipe is directly in contact with the air and is connected to the base section (6) via the heat dissipation pipe section (3), and the heat absorbing plate (5) is welded around the heating pipe section (2); the heliostat field reflects sunlight to the heating pipe section (2) and the heat absorbing plate (5) of the heat pipe; Alternatively, a plurality of the heat storage units constitute a volumetric solar thermochemical heat storage device, the heat storage unit comprising a reaction chamber (1), a heat absorber (7), a second annular pipe section (8), an air inlet pipe (9) and an air outlet pipe (10); the air inlet pipe (9) and the air outlet pipe (10) are both connected to the heat absorber (7), the air inlet pipe (9) and the air outlet pipe (10) are communicated with each other, the air outlet pipe (10) passes through the reaction chamber (1) and is sealed, and the second annular pipe section (8) is sealed and connected to the reaction chamber (1); the heliostat field reflects sunlight to the heat absorber (7), the temperature of the gaseous heat transfer medium increases after flowing through the heat absorber (7), and the heat storage material is heated by the pipe section of the air outlet pipe (10) embedded in the reaction chamber (1).

2. A solar thermochemical heat storage system according to claim 1, characterized in that: The air outlet pipe (10) is embedded in the reaction chamber (1) and a heat dissipation fin (11) is installed at the pipe section.

3. A solar thermochemical heat storage system according to claim 1, characterized in that: Each of the heat storage units uses antimony pentoxide, copper oxide, manganese trioxide, calcium carbonate, magnesium hydride or calcium hydride as heat storage materials, and utilizes the chemical heat of the thermal decomposition reaction at high temperature to store energy.

4. A solar thermochemical heat storage system according to claim 1, characterized in that: The material of the reaction chamber (1) is zirconium oxide, ZrO2-SiC-C high temperature resistant material, GH4169 or Incone1718.

5. A solar thermochemical heat storage system according to claim 1, characterized in that: The heat pipe uses Mo-14Re as the metal cladding and Na as the heat transfer medium.

6. A solar thermochemical heat storage system according to claim 1, characterized in that: A thermocouple is arranged in the reaction chamber (1).

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