High-temperature solar heat collection and utilization system

Abstract

This system achieves a slow cycle that allows for the gradual reduction of reactants, providing a high-temperature solar heat collection and utilization system with excellent energy conversion efficiency from solar energy collection to fuel utilization. [Solution] The high-temperature solar heat collection and utilization system 1 includes a heat collection reaction unit 3 that performs thermochemical decomposition. The heat collection reaction unit 3 includes a heat collector 31, a reactor 32 provided at a distance from the heat collector 31, and a heat medium circulation circuit 33 through which a heat medium S circulates between the heat collector 31 and the reactor 32. The reactor 32 is filled with a reactant RM. The heat medium S absorbs heat from the heat collector 31 and transfers this heat to the reactant RM in the reactor 32. It is preferable that multiple heat medium circulation pipes 32b for circulating the heat medium S are inserted into the reactant in the reactor 32. It is preferable that a heat storage unit 5 is further provided, which includes two heat storage tanks consisting of a low-temperature tank 51 and a high-temperature tank 52, each capable of storing the heat medium S in different temperature ranges.

Description

[Technical Field]

[0001] This invention relates to a technology for producing fuel from carbon dioxide and water by thermochemical decomposition using high-temperature solar heat collection. [Background technology]

[0002] In recent years, research on fuel production technologies utilizing concentrated solar heat collection has become increasingly active. In particular, the thermochemical decomposition method (thermochemical fuel production method), which produces fuel through a two-stage thermal cycle of high temperature (first temperature) and low temperature (second temperature), is well known. Specifically, reactants are reduced at a high temperature, then the reactants are brought to a low temperature, and raw material gases such as carbon dioxide and water (steam) are introduced. The reactants then absorb oxygen from the raw materials, yielding synthesis gas. From this synthesis gas, liquid fuels such as methane, hydrocarbons, alcohols, and hydrogen can be produced using a catalytic reaction called FT synthesis (Fischer-Tropsch).

[0003] In this thermochemical decomposition method, metal oxides (ceria CeO2, hersinite FeAl2O4, and various perovskites) are used as reactants, and a two-step reaction (thermal cycle) is carried out, repeating reduction at 1400-1600°C (1673.15-1873.15 K in Kelvin) and oxidation at 800-1200°C (1073.15-1473.15 K). This method is attracting attention as a new technology that can be applied to inexpensive and highly efficient renewable energy storage because it does not require a heat engine and is not subject to the constraints of Carnot efficiency.

[0004] (Conventional direct irradiation system) Conventional systems using this thermochemical decomposition method typically employ a method of directly irradiating the reactants with high-temperature solar heat (see Non-Patent Literature 1). In other words, solar heat collection and the reaction (reduction / oxidation) of the reactants occur at the same location. The heat transfer modes in the direct irradiation method are radiation and heat conduction. In this conventional method, an excessive temperature gradient is created on the irradiated surface of the reactants, resulting in a small amount of reactant being handled in one cycle (m / Q, the amount of reactant per unit irradiation dose, is generally less than 1.0 kg / kWth). As a result, the conventional method becomes a rapid cycle in which small amounts of reactant are repeatedly reduced and oxidized in a short time, which is inefficient. In the system described in Non-Patent Literature 1, m / Q = 0.43 kg / kWth, the reaction time is less than 30 minutes, and the energy conversion efficiency from solar collection to fuel utilization is approximately 5% or less.

[0005] Furthermore, direct irradiation easily leads to overheating of the reactants, making them prone to breakdown. In addition, it has been pointed out that conventional systems do not effectively utilize the waste heat generated during reduction, which is at a higher temperature than oxidation.

[0006] The inventors have previously proposed hydrothermal decomposition devices and solar thermal energy storage devices equipped with a fluidized bed capable of generating internal circulation (see Patent Documents 1 and 2). However, these devices still employ the direct irradiation method described above, and may face the same problems as those pointed out in Non-Patent Document 1. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5986589 [Patent Document 2] International Publication No. 2014 / 038553 Brochure [Non-patent literature]

[0008] [Non-Patent Document 1] Zoller et al., “A solar tower fuel plant for the thermochemical production of kerosene from H2O and CO2”, Joule Vol.6, pp.1606-1616,2022

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been made in view of such circumstances, and aims to provide a high-temperature solar thermal utilization system equipped with a heat collection reaction unit of a "slow cycle" that increases the amount of reactants per unit irradiation dose and can slowly reduce the reactants.

[0010] Another object of the present invention is to provide a high-temperature solar thermal utilization system capable of reusing (heat regeneration) waste heat during reduction.

Means for Solving the Problems

[0011] As a result of intensive studies, the inventors of the present invention provided a heat collector and a reactor at separate locations, and passed and circulated a heat medium (molten tin) between these devices, thereby transporting the heat obtained in the heat collector to the reactor and reducing the reactants. They came up with a new type of heat collection reaction unit of an "indirect heating type".

[0012] In addition, the inventors of the present invention also came up with the idea that if a heat storage unit equipped with a tank for storing the heat medium at a lower temperature and a tank for storing the heat medium at a higher temperature is combined with the above-described new type of heat collection reaction unit, the waste heat during reduction can be heat regenerated.

[0013] The inventors of the present invention found that these means can effectively solve the above problems, and thus completed the present invention.

[0014] That is, the present invention has, for example, the following configurations and features. (Aspect 1) A high-temperature solar heat collection utilization system equipped with a heat collection reaction unit that performs thermochemical decomposition, The heat collection reaction unit is provided with a heat collector that is irradiated with sunlight to perform solar heat collection, a reactor provided at a distance from the heat collector, and a heat medium circulation circuit through which a heat medium circulates between the heat collector and the reactor, The reactor is filled with a reactant, The heat medium takes heat from the heat collector and transfers the heat to the reactant in the reactor, A high-temperature solar heat collection utilization system characterized by the above. (Aspect 2) One or more heat medium flow pipes through which the heat medium flows are inserted into the reactant in the reactor, The high-temperature solar heat collection utilization system according to Aspect 1, characterized by the above. (Aspect 3) The heat medium circulation circuit is provided with an inlet manifold that accommodates the heat medium that has passed through the heat collector and supplies it to the heat medium flow pipe, and an outlet manifold that accommodates the heat medium discharged from the heat medium flow pipe and returns it to the heat collector, The high-temperature solar heat collection utilization system according to Aspect 2, characterized by the above. (Aspect 4) The system further includes a heat storage unit having two heat storage tanks, a low-temperature tank and a high-temperature tank, capable of storing the heat medium in different temperature ranges, In the high-temperature tank, the high-temperature heat medium used in the heat collection reaction unit during the reduction reaction is stored, and heat is stored during the oxidation reaction and then returned to the reactor during the next reduction reaction, In the low-temperature tank, the low-temperature heat medium used in the heat collection reaction unit during the oxidation reaction is stored, and heat is stored during the reduction reaction and then returned to the reactor during the next oxidation reaction, The high-temperature solar heat collection utilization system according to Aspect 1 or 2, characterized by the above.

Effect of the Invention

[0015] (Realization of reaction by slow cycle) In the system of the present invention, an indirect heating type heat collection reaction unit is provided in which a heat transfer medium circulates between the heat collector and the reactor, making it possible to handle a larger amount of reactant in a single thermal cycle. More specifically, the amount of reactant per unit of concentrated irradiation (m / Q) can be set to approximately 1 to 10 kg / kWth, enabling slow cycles with longer reaction times (more than 1 hour) and reducing radiant heat loss (re-radiation loss) in the heat collector.

[0016] (Reuse of heat during reduction (thermal regeneration)) Furthermore, according to a preferred embodiment of the system of the present invention, a heat storage unit is further provided, which includes two heat storage tanks (a low-temperature tank and a high-temperature tank). This allows the high-temperature heat transfer medium used in the reduction reaction (1400-1600°C) of the heat collection reaction unit described above, which is suitable for slow cycles, to be stored in the high-temperature tank during the oxidation reaction (800-1200°C) and reused (heat regeneration) in the next reduction reaction. According to this preferred embodiment, these two effects combined can significantly improve the energy conversion efficiency from solar collection to fuel utilization. [Brief explanation of the drawing]

[0017] [Figure 1] This diagram illustrates the general structure of the high-temperature solar heat collection and utilization system of Example 1. [Figure 2] (a) is a schematic diagram of the heat collector, and (b) is a schematic diagram of the reactor. [Figure 3] This figure shows the pattern of temperature change of reactants in a reactor over time. [Figure 4] This figure shows the time-dependent changes (analysis results) of (a) the temperature of the reactants and (b) the temperature of the irradiated surface of the solar collector. [Figure 5] This figure shows the change in efficiency (sensible heat / chemical energy) over time (analysis results). [Figure 6] This figure shows (a) energy conversion efficiency and (b) irradiation surface temperature (analysis results). [Modes for carrying out the invention]

[0018] The present invention will be described below based on the embodiments shown in the drawings, but the present invention is not limited in any way to the specific embodiments described below. In each figure, the same or corresponding components are denoted by the same reference numerals. [Examples]

[0019] (Outline of a high-temperature solar heat collection and utilization system) Figure 1 is a schematic diagram illustrating the high-temperature solar heat collection and utilization system 1 (hereinafter also simply referred to as "the system") according to Example 1. System 1 of this example comprises a raw material supply unit 2, a heat collection reaction unit 3, and a fuel generation unit 4.

[0020] (Role (function) of the present invention system) In System 1 of the present invention, carbon dioxide (CO2) and water vapor (H2O) are supplied from the raw material supply unit 2 to the heat collection reaction unit 3, where the reactant RM is cothermally decomposed at high temperature to produce synthesis gas (a mixed gas of carbon monoxide CO and hydrogen H2). This synthesis gas is then subjected to FT synthesis or other processes in the fuel production unit 4 to ultimately obtain liquid fuel. This technology for producing liquid fuel from gaseous synthesis gas is called GTL (Gas To Liquid).

[0021] (Raw material supply unit) The raw material supply unit 2 comprises a reduction gas supply unit 21 and an oxidation raw material supply unit 22. The reduction gas supply unit 21 contains a reduction gas such as argon (Ar), and during reduction, valve V1 is opened to supply the gas to the reactor 32 (described later) through line L1. The gas removes oxygen (O2) from the reactants RM in the reactor 32 (described later), and the oxygen (O2) is discharged out of the system through line L3. In this specification, the term "line" refers to a tubular passage through which gases or liquids are transported.

[0022] Meanwhile, the oxidation raw material supply unit 22 generates carbon dioxide (CO2) and water vapor (H2O), and during oxidation, it opens valve V2 and supplies these gases into the reactor 32 through line L2. The carbon dioxide (CO2) and water vapor (H2O) react with the reactant RM in the reactor 32 to produce synthesis gas, which is then sent to the fuel production unit 4 through line L4. An example of the oxidation raw material supply unit 22 is a known DAC device (DAC stands for Direct Air Capture) capable of recovering these gases, CO2 and H2O, from the atmosphere.

[0023] (Heat collection reaction unit) The heat collection reaction unit 3 includes a heat collector 31, a reactor 32, a heat medium circulation circuit 33 through which a heat medium S (for example, molten tin) can pass and circulate between the heat collector 31 and the reactor 32, and an insulating wall 34 surrounding these components 31, 32, and 33. Schematic diagrams of the heat collector 31 and reactor 32 are shown in Figures 2(a) and (b).

[0024] It should be noted that the solar collector 31 and the reactor 32 are provided separately via the heat medium circulation circuit 33 (that is, the reactor 32 is provided separately from the solar collector 31). Furthermore, it is desirable that the solar collector 31, the reactor 32, and the heat medium circulation circuit 33 be made of a material with high thermal conductivity (for example, a graphite material), and the insulating wall 34 be made of a material with high heat resistance (for example, alumina fiber).

[0025] (heat collector) The solar collector 31 collects heat by receiving sunlight that has been focused by an optical system (not shown) such as a heliostat. As shown in Figure 2(a), the solar collector 31 is cylindrical in shape with a bottomed internal space (solar collector body 31a), and a quartz window 31b is provided to cover this internal space 31a. Sunlight passes through the window 31b and is collected in the solar collector body 31a. Heat medium housing sections 31c through which the heat medium S flows are provided around the solar collector body 31a and on the bottom surface, and heat is transferred from the solar collector body 31a to the heat medium S via the walls of these heat medium housing sections 31c. The heat medium housing sections 31c are provided with a heat medium inlet 31d and a heat medium outlet 31e to allow the inflow and outflow of the heat medium S.

[0026] (reactor) As shown in Figure 2(b), the reactor 32 is provided with a reactor body 32a that can be filled with the reactant RM, and one or more (preferably many) heat transfer medium flow tubes 32b inserted into the reactor body 32a. The heat transfer medium S can flow through each heat transfer medium flow tube 32b, and heat is transferred from the heat transfer medium S to the reactant RM via the walls of the heat transfer medium flow tubes 32b. Examples of reactant RM include metal oxides such as ceria CeO2, hersinite FeAl2O4, and various perovskites.

[0027] (heat medium circulation circuit) The heat medium circulation circuit 33 is a heat medium passage configured to allow the heat medium S to pass through and circulate between the solar collector 31 and the reactor 32 described above. Specifically, it includes an inlet manifold 33a that supplies the heat medium S from the heat medium outlet 31e of the solar collector 31 to one end of the heat medium flow pipe 32b, an outlet manifold 33b that receives the heat medium S flowing out from the other end of the heat medium flow pipe 32b, and a heat medium line HL1 that moves the heat medium S (S1 in Figure 1) from this outlet manifold 33b to the heat medium inlet 31d of the solar collector 31.

[0028] (Flow of heat transfer fluid in a heat transfer fluid circulation circuit) The heat transfer medium S (for example, molten tin) enters the heat transfer medium inlet 31d from the heat transfer medium line HL1 by operating the pump P1 on the heat transfer medium line HL1 and passes through the heat transfer medium containment section 31c. After receiving heat from the solar collector body 31a in the heat transfer medium containment section 31c, the heat transfer medium S flows through the heat transfer medium outlet 31e and the inlet manifold 33a to the heat transfer medium flow pipe 32b in the reactor 32. After heat is transferred to the reactant RM from its outer wall in the heat transfer medium flow pipe 32b, the heat transfer medium S (S1) returns to the original heat transfer medium line HL1 through the outlet manifold 33b, and the circulation of the heat transfer medium S is repeated.

[0029] In System 1 of the present invention, a heat collection reaction unit 3 is provided in which a heat transfer medium S circulates between the heat collector 31 and the reactor 32 (so to speak, an "indirect heating" type), making it possible to handle a larger amount of reactant RM in a single thermal cycle. The heat transfer modes of the indirect irradiation method of the present invention are radiation, convection, and heat conduction, and convection by the heat transfer medium is added compared to conventional heat transfer modes. According to the numerical analysis results described later, in this System 1, the amount of reactant per unit concentrated irradiation dose (m / Q) can be set to approximately 1 to 10 kg / kWth, enabling slow cycles with longer reaction times (more than 1 hour) and reducing radiant heat loss (re-radiation loss) in the heat collector 31.

[0030] (Heat storage unit) The system 1 of the present invention preferably further includes a heat storage unit 5 equipped with two heat storage tanks (a low-temperature tank 51 and a high-temperature tank 52) capable of storing heat transfer fluids S (S2, S3 in Figure 1) in different temperature ranges. Both the low-temperature tank 51 and the high-temperature tank 52 contain heat storage materials 51a and 52a within them, and store heat transfer fluids S (S2, S3) at their respective set temperatures.

[0031] (cold chamber) The low-temperature tank 51 is provided with a heat transfer medium line HL2 (see dashed line in Figure 1) through which the low-temperature (800-1200°C) heat transfer medium S2 at the end of the oxidation reaction is drawn from the reactor 32 to the low-temperature tank 51 by operation of a valve V3 or the like, and the heat transfer medium S2 is supplied from the low-temperature tank 51 to the reactor 32 by a pump P2 at the end of the reduction reaction. A cooler 53 capable of cooling the heat transfer medium S2 to a desired temperature may also be provided on the heat transfer medium line HL2.

[0032] (High temperature tank) Meanwhile, the high-temperature tank 52 is equipped with a heat transfer medium line HL3 (see the dashed line in Figure 1) through which the high-temperature (1400-1600°C) heat transfer medium S3 used in the reduction reaction is drawn from the reactor 32 to the high-temperature tank 52 by the operation of a valve V4, etc., and when the oxidation reaction is completed, the heat transfer medium S3 is supplied from the high-temperature tank 52 to the reactor 32 by a pump P3.

[0033] (The significance of installing two heat storage tanks) This allows the high-temperature heat transfer medium S3 used during the reduction reaction to be stored in the high-temperature tank 52 during the oxidation reaction, and then reused (heat regenerated) by returning this heat transfer medium S3 to the reactor 32 during the next reduction reaction. On the other hand, the low-temperature heat transfer medium S2 used during the oxidation reaction can be stored in the low-temperature tank 51 during the reduction reaction, and then returned to the reactor 32 during the next oxidation reaction.

[0034] In other words, the low-temperature heat transfer medium S2 and the high-temperature heat transfer medium S3 are used alternately in the reactor 32, and while one heat transfer medium (e.g., S2) is being used in the reactor 32, the other heat transfer medium (e.g., S3) is stored in the heat storage tank 52 corresponding to that heat transfer medium S3. Control is performed to move the respective heat transfer mediums S2 and S3 between the reactor 32 and the respective heat storage tanks 51 and 52. See also Table 1 below.

[0035] [Table 1]

[0036] (Temperature change of reactants in the reactor) Figure 3 also shows the pattern of temperature change over time of the reactant RM in reactor 32. At the leftmost timing, indicated by symbol 1 in Figure 3, heat has not yet been recovered by the heat storage unit 5. At this point, only the heat medium S1 of the heat medium circulation circuit 33 is circulated through line HL1, and the heat (thermal energy Q) collected by the solar collector 31 is transferred to the reactant RM via the heat medium S1, thereby reaching the temperature T required for the reduction reaction. RED The reactant RM is heated to this point. Then, at the timing indicated by symbol 2 in Figure 3, a reduction reaction occurs in the reactant RM in reactor 32.

[0037] At the timing indicated by reference numeral 3 in Figure 3, the low-temperature heat transfer medium S2 from the low-temperature tank 51 is allowed to flow into the reactor 32 through the heat transfer medium line HL2, and at the same time, a valve on the heat transfer medium line HL3 is opened to push the high-temperature heat transfer medium S3, which had previously occupied the reactor 32, into the high-temperature tank 52 for heat storage. In the figure, the temperature of the heat transfer medium S3 recovered in the high-temperature tank 52 is T HThis is shown. Subsequently, at the timing indicated by symbol 4 in Figure 3, an oxidation reaction occurs in the reactant RM in reactor 32. At this point, the temperature of the reactant RM is the temperature T of the oxidation reaction. ox That is the case.

[0038] At the timing indicated by symbol 1' on the right side of Figure 3 (the next stage), heat has already been recovered in the high-temperature tank 52. To induce heat regeneration, the high-temperature heat transfer medium S3 from the high-temperature tank 52 flows into the reactor 32 through the heat transfer medium line HL3 (see the dashed line in Figure 3). Due to this heat regeneration, the temperature of the reactant RM rises as indicated by symbol 1' in the figure.

[0039] Meanwhile, during this heat regeneration, valve V3 on the heat transfer medium line HL2 (see the dashed line in Figure 3) is opened to push the low-temperature heat transfer medium S2, which had previously occupied the reactor 32, into the low-temperature tank 51 for heat storage. In Figure 3, the temperature of the low-temperature heat transfer medium S2 recovered in the low-temperature tank 51 is T L This is shown. In this process, thermal energy Qc is removed from the low-temperature heat transfer medium S2 by forced cooling by the cooler 53 or by natural cooling.

[0040] At the timing indicated by symbol 1 on the right side of Figure 3, the regenerated high-temperature heat transfer medium S3 is circulated in the heat transfer medium circulation circuit 33, and the heat collected by the solar collector 31 is transferred to the reactant RM via the high-temperature heat transfer medium S3, thereby raising the temperature T required for the reduction reaction. RED The reactant RM is heated until [a certain temperature is reached]. Then, at the timing indicated by the symbol 2 on the right side of Figure 3, a reduction reaction occurs in the reactant RM in reactor 32.

[0041] At the timing indicated by reference numeral 3 in Figure 3, the low-temperature heat transfer medium S2 from the low-temperature tank 51 is introduced into the reactor 32 through the heat transfer medium line HL2, and the valve V4 on the heat transfer medium line HL3 is opened to push the high-temperature heat transfer medium S3, which had previously occupied the reactor 32, into the high-temperature tank 52 for heat storage. Subsequently, at the timing indicated by reference numeral 4 in Figure 3, an oxidation reaction occurs in the reactant RM in the reactor 32.

[0042] From this point onward, the temperature T of the reactant RM is used. RM The profile repeats as follows: code 1' → code 1 → code 2 → code 3.

[0043] (Effects of adding a heat storage unit) In this preferred embodiment, in which the heat storage unit 5 is added, the combined effects of the slow cycle reaction and heat regeneration described above significantly improve the energy conversion efficiency from solar concentration to fuel utilization. [Examples]

[0044] (Analysis of heat transfer performance using numerical analysis) Next, software was constructed in C language to examine the heat transfer performance of the present invention. The construction assumed a one-dimensional analysis model based on the system configuration shown in Figure 1. The physical properties of ceria CeO2 were used for the reactant RM. Four cases were considered for the amount of reactant RM: m=2.4kg, m=9.7kg, m=43.5kg, and m=84.9kg. Note that m=2.4kg is the amount typically used in conventional technology.

[0045] (calculation conditions) Furthermore, since the focused irradiation energy Q was set to Q = 10 kWth, the corresponding m / Q (unit: kg / kWth) for the four cases are 0.24, 0.97, 4.35, and 8.49, respectively. In this heat transfer analysis, the calculation was continued until the temperature of the reactant RM under the above conditions reached the target temperature of 1600°C (equivalent to 1873.15 K).

[0046] (Whether or not heat recovery is performed and the calculation conditions) Furthermore, analyses were conducted with and without heat recovery by the heat storage unit 5. Here, it was assumed that the temperature of the heat transfer medium S2 in the low-temperature chamber 51 was 900°C (1173.15K), and the temperature of the heat transfer medium S3 in the high-temperature chamber 52 was 1600°C (1873.15K). The heat recovery rate adopted was 50%, which corresponds to half of the maximum heat recovery rate that can be achieved by the heat storage unit 5 under the above assumptions.

[0047] (Relationship between the amount of reactant and its temperature change) Figure 4(a) shows the temperature T when the amount of reactant RM handled in reactor 32 is increased. RMShows the change over time (analysis result). When set to a substance amount m = 2.4 kg, which is almost the same as in the prior art, the temperature T rises rapidly to the target temperature within a short time of 1000 seconds or less. However, it can be seen that as the substance amount m increases, it takes a longer time to reach the target temperature. From this, it is expected that if the reactor 32 is enlarged and the amount m of the reactant RM that can be accommodated in this reactor 32 is increased, the temperature T of the reactant RM will rise gradually. RM will rise rapidly to the target temperature, but it can be seen that as the amount of the substance m increases, it takes a longer time to reach the target temperature. From this, it is expected that if the reactor 32 is enlarged and the amount m of the reactant RM that can be accommodated in this reactor 32 is increased, the temperature T of the reactant RM RM is expected to rise gradually.

[0048] (Relationship between the amount of reactant and the temperature change of the heat collector irradiation surface) In FIG. 4(b), the change over time (analysis result) of the temperature T at the heat collector irradiation surface when the amount m of the reactant RM is increased is shown. From the results of this figure, regarding the temperature T of the heat collector irradiation surface w as well, similar to the behavior of the temperature T of the reactant RM shown in FIG. 4(a), it was confirmed that as the amount m of the reactant RM increases, its temperature T w tends to rise gradually. In addition, when comparing the temperature T of the heat collector irradiation surface at the time when the temperature of the reactant RM reached the target temperature under each condition of the above substance amount m RM it was confirmed that as the substance amount m increases, the temperature T of this irradiation surface w tends to decrease. w it was confirmed that as the substance amount m increases, the temperature T of this irradiation surface w tends to decrease.

[0049] (Relationship between the amount of reactant and the change over time of efficiency (sensible heat / chemical energy)) FIG. 5 shows the change over time (analysis result) of the efficiency (sensible heat / chemical energy) when the amount m of the reactant RM is increased. For the results of sensible heat, refer to the respective curves described as “Sensible Heat” in FIG. 5 (each condition starting with SH in the legend). For the results of chemical energy, refer to the respective curves described as “Chemical Energy” in FIG. 5 (each condition starting with CM in the legend). From the results of FIG. 5, it was confirmed that if the reactor 32 is enlarged and the amount m of the reactant RM that can be accommodated in this reactor 32 is increased, both the efficiencies of the sensible heat and chemical energy stored in the reactant RM tend to increase.

[0050] (Energy conversion efficiency and irradiation surface temperature when the amount of reactant is changed) Figure 6(a) shows the energy conversion efficiency η when the amount m of the reactant RM is increased. c (Analysis results) are shown. The vertical axis is η. c The graph shows the proportion of energy (calculated result) that can be converted from energy obtained from solar concentration into combustion heat. The horizontal axis shows the heating (irradiation) time required for the reactant RM to reach the target temperature under each condition (m / Q). The upper and lower line graphs show the energy conversion efficiency η calculated with and without heat recovery by the heat storage unit 5. c This indicates.

[0051] Figure 6(b) also shows the irradiation surface temperature T when the amount m of the reactant RM is increased. w The analysis results are shown below. Similar to Figure 6(a), the horizontal axis shows the heating (irradiation) time required for the reactant RM to reach the target temperature under each condition (m / Q).

[0052] From the results in Figures 6(a) and (b), it can be seen that increasing the size of reactor 32 and thereby increasing the amount of reactant RM that can be contained in reactor 32 increases the energy conversion efficiency η from solar concentration to fuel utilization. c The efficiency also increased, and we confirmed that the overall system efficiency tended to improve further when heat recovery was performed. [Industrial applicability]

[0053] (Realization of reactions through slow cycles) In the system of the present invention, an indirect heating type heat collection reaction unit is provided in which a heat transfer medium circulates between the heat collector and the reactor, making it possible to handle a larger amount of reactant in a single thermal cycle. More specifically, the amount of reactant per unit of concentrated irradiation (m / Q) can be set to approximately 1 to 10 kg / kWth, enabling slow cycles with longer reaction times (more than 1 hour) and reducing radiant heat loss (re-radiation loss) in the heat collector.

[0054] (Reuse of heat during reduction (thermal regeneration)) Furthermore, according to a preferred embodiment of the system of the present invention, a heat storage unit is further provided, which includes two heat storage tanks (a low-temperature tank and a high-temperature tank). This allows the high-temperature heat transfer medium used in the reduction reaction (1400-1600°C) of the heat collection reaction unit described above, which is suitable for slow cycles, to be stored in the high-temperature tank during the oxidation reaction (800-1200°C) and reused (heat regeneration) in the next reduction reaction. According to this preferred embodiment, these two effects combined can significantly improve the energy conversion efficiency from solar collection to fuel utilization.

[0055] Thus, the present invention has very high industrial value and industrial applicability. [Explanation of Symbols]

[0056] 1. High-temperature solar heat collection and utilization system 2. Raw material supply unit 3. Heat collection reaction unit 4 Fuel Generation Unit 5. Heat storage unit 21. Gas supply unit for reduction 22. Oxidation raw material supply unit 31 Heat collector 31a, 31b, 31c Solar collector body, window, heat transfer medium housing 31d, 31e Heat medium inlet, heat medium outlet 32 Reactors 32a, 32b Reactor body, heat transfer tubes 33 Heat medium circulation circuit 33a, 33b, 33c Inlet manifold, Outlet manifold 34 Insulated Wall 51 Cryostat 51a,52a Heat storage material 52 High temperature bath 53 Cooler HL1, HL2, HL3 heat transfer fluid lines L1, L2, L3, L4 lines P1, P2, P3 pumps V1, V2, V3, V4 valves m Amount of reactants RM reactants S,S1,S2,S3 heat medium Q,Q c Energy absorbed during concentrated light irradiation and heat storage in the low-temperature chamber. T RM ,T ox ,T RED Temperature of reactants, temperature during oxidation reaction, temperature during reduction reaction T H ,T L Temperature of the heat transfer medium stored in the high-temperature bath, temperature of the heat transfer medium stored in the low-temperature bath T ox ,T RED Temperature during oxidation reaction, temperature during reduction reaction T w Temperature of the irradiated surface of the solar collector η c Energy conversion efficiency

Claims

1. A high-temperature solar heat collection and utilization system equipped with a heat collection reaction unit that performs thermochemical decomposition, The heat collection reaction unit includes a heat collector that is irradiated with sunlight to collect solar heat, a reactor provided at a distance from the heat collector, and a heat medium circulation circuit through which a heat medium circulates between the heat collector and the reactor. The reactor is filled with reactants. The heat transfer medium absorbs heat from the heat collector and transfers the heat to the reactants in the reactor. A high-temperature solar heat collection and utilization system characterized by the following features.

2. The reactor has one or more heat transfer medium flow pipes inserted into the reactants through which the heat transfer medium flows. The high-temperature solar heat collection and utilization system according to feature 1.

3. The heat transfer medium circulation circuit includes an inlet manifold that receives the heat transfer medium that has passed through the heat collector and supplies it to the heat transfer medium flow pipe, and an outlet manifold that receives the heat transfer medium discharged from the heat transfer medium flow pipe and returns it to the heat collector. The high-temperature solar heat collection and utilization system according to feature 2.

4. The heat storage unit further comprises two heat storage tanks, one low-temperature tank and the other high-temperature tank, each capable of storing the heat transfer medium in different temperature ranges. The high-temperature tank contains the high-temperature heat transfer fluid used in the heat collection reaction unit during the reduction reaction, stores the heat during the oxidation reaction, and returns it to the reactor during the next reduction reaction. The low-temperature tank contains the low-temperature heat transfer fluid used in the heat collection reaction unit during the oxidation reaction, stores heat during the reduction reaction, and returns it to the reactor for the next oxidation reaction. A high-temperature solar heat collection and utilization system according to claim 1 or 2.

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