JP2017122523A - Solar heat collecting device and solar heat collecting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent breakage due to local radiation of solar light.SOLUTION: A solar heat collection system 2 includes a receiver 7 where a radiation film 74 is formed at an inner face of piping 71. Thus, a temperature difference generated in the piping 71 of the receiver 7 due to local radiation of solar light can be suppressed. Namely, breakage of the receiver 7 (especially, breakage of the piping 71) due to local radiation of solar light can be prevented.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a solar heat collecting apparatus and a solar heat collecting system.

  Conventionally, a heat medium that circulates in the flow path provided inside the light collecting unit is reflected by reflecting sunlight upward with a mirror installed near the ground, and then reflecting the reflected light into the light collecting unit. A solar thermal condensing system that is heated and used for power generation is known (for example, see Patent Document 1).

JP 2014-020749 A

  However, when the sunlight is incident on the inside of the light collecting unit by the mirror, it is conceivable that the positions irradiated with the sunlight are concentrated in a specific region. In this case, there is a possibility that the temperature difference between the position where the sunlight is irradiated and the position where it is not so becomes large, and the condensing part is damaged.

  The present invention has been made in view of the above, and an object of the present invention is to provide a solar heat concentrating device and a solar heat condensing system that prevent damage due to local irradiation of sunlight.

  In order to achieve the above object, a solar heat collecting apparatus according to an aspect of the present invention is a solar heat collecting apparatus that heats a fluid flowing through a flow path by condensed sunlight, and radiates the inner surface of the flow path. It has a film.

  According to the solar heat concentrating device described above, by having the radiation film on the inner surface of the flow path, even when the flow path is locally heated by the local irradiation of sunlight, Can transmit radiant heat. Therefore, it is possible to prevent damage to the solar heat collecting apparatus due to local irradiation of sunlight.

  Here, the flow path may be a cavity type.

  When the flow path is a cavity type, it is considered that local irradiation of sunlight often occurs. Therefore, by providing the radiation film, it is possible to effectively prevent the solar heat collecting device from being damaged.

  Moreover, the said radiation film can be set as the aspect provided in the area | region where the irradiation amount of the said sunlight is large among the said flow paths.

  It can be said that the area where the amount of sunlight irradiated in the channel is large is a place where the temperature tends to be high. Therefore, by providing a radiation film on the inner surface of the region, it is possible to effectively transmit radiant heat from the region.

  Moreover, the solar thermal condensing system which concerns on one form of this invention condenses the sunlight reflected by the said reflection part and the said reflection part, and flows through a flow path by this condensed sunlight. And a heat collecting part for heating the fluid, wherein the heat collecting part has a radiation film on the inner surface of the flow path.

  According to the solar heat collecting system described above, the radiation film is provided on the inner surface of the flow path of the heat collection unit, and thus the flow path of the heat collection unit is locally heated by the local irradiation of sunlight. However, radiant heat can be transmitted through the radiation film. Accordingly, it is possible to prevent damage to the heat collecting part due to local irradiation of sunlight.

  ADVANTAGE OF THE INVENTION According to this invention, the solar thermal condensing apparatus and solar thermal condensing system which prevented the damage by local irradiation of sunlight are provided.

It is the schematic which shows the solar thermal power generation system which concerns on one Embodiment of this invention. It is the schematic of a receiver. It is a part of sectional drawing of a receiver, and is a figure explaining the measurement point of the simulation which concerns on a temperature change.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic diagram showing a solar power generation system including a solar thermal condensing system according to an embodiment of the present invention. As shown in FIG. 1, the solar thermal power generation system 1 reflects heat obtained by exchanging heat between a solar thermal condensing system 2 that reflects and condenses sunlight to heat a fluid and heats the fluid. And a power generation device 3 (energy conversion unit) that generates and uses power. Note that although the fluid is air here as being particularly preferable here, the fluid is not limited to air, and oil, molten salt, or the like may be used.

  As shown in FIG. 1, the solar heat collecting system 2 includes a supply pipe 4, a discharge pipe 5, and a solar heat collecting unit 6. The solar heat collecting unit 6 includes a plurality of receivers 7 (solar heat collecting device, heat collecting unit) and a plurality of mirrors 8 (reflecting units).

  The supply pipe 4 is for supplying the fluid cooled by the heat exchange in the power generation device 3 to the solar heat collecting unit 6. Moreover, the supply piping 4 is connected with respect to each receiver 7, and sends a fluid.

  The discharge pipe 5 is for taking out the fluid heated in each receiver 7 (details will be described later) of the solar heat collecting unit 6 from the solar heat collecting unit 6.

  The receiver 7 has a function as a heat collecting unit that collects sunlight reflected by the mirror 8 and heats the fluid flowing through the flow path. Further, the receiver 7 has a flow path through which the fluid flows, and also has a function as a solar heat condensing device that heats the fluid inside the flow path by heat transfer from the collected sunlight. The pipe that is a flow path for circulating a fluid in the receiver 7 is formed of a material having high temperature resistance such as stainless steel or nickel alloy, and one end thereof is connected to the horizontal portion 4a of the supply pipe 4 and the others. The end is connected to the horizontal portion 5 a of the discharge pipe 5.

  In the present embodiment, a plurality of receivers 7 are provided in the solar heat collecting unit 6. The receivers 7 can be provided at equal intervals along the extending direction of the pipes in the horizontal portions 4 a and 5 a of the supply pipe 4 and the discharge pipe 5. The interval between the adjacent receivers 7 and 7 can be appropriately changed. The number of receivers 7 provided in the solar heat collecting unit 6 is not limited to four.

  Moreover, in the solar thermal condensing system 2 which concerns on this embodiment, the receiver 7 is what is called a cavity type receiver, and flows the piping which is a flow path inside the receiver 7 by making sunlight from the mirror 8 enter into the inside. The fluid is heated. Details of the structure of the receiver 7 will be described later.

  The mirror 8 reflects sunlight and makes it enter the receiver 7. It arrange | positions so that it may align with each receiver 7 at 1 row. Each mirror 8 is provided with a drive device (not shown) for tilting the angle, and is controlled so that reflected light is always incident on the receiver 7 by automatically changing the angle according to the movement of the sun. . In FIG. 1, for the sake of explanation, it is shown that sunlight is reflected on only a part of the mirrors 8 and is incident on only one receiver 7. The light is reflected and incident on the corresponding receiver 7.

  As shown in FIG. 1, the power generation device 3 utilizes the heat stored in the heat storage unit 10 and the heat storage unit 10 that stores heat by exchanging heat with the fluid that is heated by the solar heat collecting system 2 and passes through the discharge pipe 5. And a power generation unit 11 that generates power.

  The heat storage unit 10 lays a solid heat storage body, and performs heat exchange between the heat storage body and the fluid in a process in which the heated fluid from the discharge pipe 5 passes through the gap between the heat storage bodies. Here, the heat storage unit 10 reduces the temperature of the fluid from, for example, about 650 ° C. to about 120 ° C. before and after passing through the heat storage body. As the heat storage body, for example, stone can be used. In this case, sufficient performance required for the heat storage body can be secured while reducing the cost.

  The power generation section 11 is a steam generator 13 that generates steam from water by heat obtained from the fluid by the heat storage section 10, a steam turbine 14 that is rotationally driven by the steam, and is rotationally driven in conjunction with the steam turbine 14 to generate power. And a condenser 16 for returning the steam that has passed through the steam turbine 14 to water, and a deaerator 17 that mainly removes air from the water that has passed through the condenser 16. The power generation unit 11 is not limited to the above configuration, and any configuration can be adopted as long as the power generation can be performed using the heat obtained by the heat storage unit 10.

  The receiver 7 will be described with reference to FIG. The receiver 7 shown in FIG. 2 is a cavity type. A cavity-type receiver has a cave-shaped (cavity) entrance to the sunlight, and a large solar radiation absorption surface is formed on the inner surface of the cavity after ensuring a wider inside than the entrance. It is a thing. Among these, in the solar thermal condensing system 2 according to the present embodiment, a receiver having a flow path provided on the solar radiation absorbing surface of the cavity is used among general cavity receivers. In the following embodiments, a receiver 7 of a type in which a flow path wound in a coil shape as a cavity type receiver is formed on the inner surface of the cavity will be described.

  The receiver 7 includes a coiled pipe 71 that forms a fluid flow path, a heat insulating material 72 that is provided so as to cover the periphery of the coiled pipe 71, and a secondary mirror 73 that is provided below the pipe 71. It is comprised including. In FIG. 3, only a partial cross-sectional view of the coiled pipe 71 is shown.

  The pipe 71 is wound a plurality of times around a winding axis X extending in the vertical direction, and has a substantially cylindrical shape. The lower end 71 a of the pipe 71 is connected to the horizontal part 4 a of the supply pipe 4. Further, the upper end 71 b of the pipe 71 is connected to the horizontal part 5 a of the discharge pipe 5.

  The pipe 71 wound in a coil shape is accommodated in the heat insulating material 72. The heat insulating material 72 is provided to insulate the pipe 71 from the outside. The heat insulating material 72 accommodates the pipe 71 therein, and the upper end is closed, so that the heat insulating performance is enhanced. Moreover, the opening 72a for irradiating sunlight with respect to the piping 71 is formed in the lower end part. The inner diameter of the opening 72 a can be made smaller than the inner diameter of the coiled pipe 71, but is appropriately changed according to the optical path of sunlight from the mirror 8.

  A secondary mirror 73 is attached below the opening 72a. The secondary mirror 73 is for promoting the incidence of sunlight reflected by the mirror 8 into the receiver 7. By providing the secondary mirror 73, the light that has reached the secondary mirror 73 out of the sunlight reflected by the mirror 8 can also be incident on the inside of the receiver 7.

  In the receiver 7, the sunlight collected by being reflected by the mirror 8 or the secondary mirror 73 enters the inside of the heat insulating material 72 from the opening 72 a of the heat insulating material 72 in the receiver 7, and the inside of the heat insulating material 72. The pipe 71 is irradiated from the center side of the pipe 71 wound in a coil shape to be disposed on the pipe 71. As a result, the temperature of the pipe 71 rises to heat the internal fluid. The fluid is heated from about 120 ° C. to about 650 ° C. while moving from the lower end 71 a that is the inlet of the pipe 71 to the upper end 71 b that is the outlet.

  The pipe 71 of the receiver 7 can have a configuration in which a heat absorption film or the like is provided on the surface thereof in order to increase the heat collection efficiency in the region irradiated with sunlight. The pipe 71 has a radiation film 74 (see FIG. 3) on the inner surface. The inner surface is a surface on the side where the fluid flows in the pipe 71. The receiver 7 of the solar heat concentrating system 2 of the present embodiment has a radiation film 74 inside the pipe 71, thereby suppressing temperature deviation at each position of the pipe 71. In the receiver 7, a radiation film 74 is provided on the entire inner surface of the pipe 71.

  The radiation film 74 is provided to promote radiation (radiation) on the inner surface of the pipe 71. Specifically, the radiation film 74 is not particularly limited as long as it is a material that can be laminated on the inner surface of the pipe 71 and improves the emissivity (emissivity) as compared with the inner surface of the pipe 71 that does not process anything. When the stainless steel pipe 71 is used, the emissivity of the inner surface is approximately 0.2. Therefore, the effect of the radiation film 74 can be obtained when the radiation rate of the radiation film 74 is larger than this value. When the emissivity is about 0.5 or more, the emissivity on the inner surface is sufficiently large as compared with the case where nothing is processed.

  Moreover, the radiation film 74 needs to have heat resistance with respect to the temperature of the fluid which flows through the piping 71 and its inside. That is, a material having a heat resistant temperature higher than about 650 ° C. is selected. As the radiation film 74 that satisfies the above conditions, for example, a heat-resistant heat radiation paint can be used. A known heat radiating paint can be used as the radiation film 74, and examples of such a heat radiating paint include Pyromark (product name; manufactured by Tempil).

  In the solar thermal power generation system 1 described above, the sunlight flowing through the pipe 71 heats the fluid flowing in the pipe 71 in the receiver 7 where the sunlight is collected. The fluid heated in the receiver 7 reaches the heat storage unit 10 through the discharge pipe 5 and is cooled by exchanging heat with the heat storage body when passing through the heat storage unit 10 by suction of the fan 12. . The cooled fluid is supplied to the supply pipe 4 and circulates. On the other hand, in the power generation unit 11, steam is generated from water by the heat generated by the heat storage unit 10 from the fluid in the steam generator 13, and the steam turbine 14 and the generator 15 are rotationally driven by the steam to generate power.

  Here, a radiation film 74 is formed on the inner surface of the pipe 71 in the receiver 7. Thereby, the temperature difference which arises in the piping 71 of the receiver 7 by local irradiation of sunlight can be suppressed. That is, it is possible to prevent damage to the receiver 7 (particularly damage to the pipe 71) due to local irradiation of sunlight.

  In the receiver 7, since sunlight enters from an opening 72 a provided below the heat insulating material 72, the sunlight is a radially inner surface of the coiled pipe 71 (a surface facing the winding axis X side). Irradiate. On the contrary, sunlight is not irradiated to the surface (surface on the side facing the heat insulating material 72) of the pipe 71 on the radially outer side. Therefore, the temperature difference between the radially inner side and the radially outer side of the pipe 71 increases. The temperature difference between the radially inner side and the radially outer side of the pipe 71 refers to a comparison between the surface on the radially inner side and the surface on the radially outer side. However, the temperature difference between the front surface and the back surface (inner surface) on the radially inner side of the pipe 71 and the temperature difference between the front surface and the back surface (inner surface) on the radially outer side of the pipe 71 are the radially inner side and the radial direction of the pipe 71. Compared with the temperature difference with the outside, it is sufficiently small and negligible.

  The temperature difference between the radially inner side and the radially outer side of the pipe 71 gives a load to the pipe 71. Specifically, it is conceivable that stress is generated in the pipe 71 due to a temperature difference, and the pipe 71 is deformed. Further, the temperature of the fluid inside the pipe 71 changes so as to be the same as the average value of the temperature around the pipe 71. That is, assuming that the temperature of the fluid inside the pipe 71 finally reaches about 650 ° C., a large temperature difference between the radially inner side and the radially outer side of the pipe 71 means that the temperature inside the pipe 71 is radially inner. Is considered to be considerably higher than the ultimate temperature of the fluid (about 650 ° C.). When the material of the pipe 71 is stainless steel, deterioration of the pipe 71 itself may be promoted when the temperature is 700 ° C. or higher.

  Regarding the above problem, for example, a countermeasure of increasing the thermal conductivity by changing the thickness of the pipe 71 can be considered, but this countermeasure may cause an increase in material cost. Since stainless steel and nickel alloy used as the material of the pipe 71 are not materials with high thermal conductivity in the first place, there is a possibility that the effect cannot be easily obtained even if the thickness is increased to make the temperature uniform. Furthermore, it is conceivable that the thickened pipe 71 itself slows the heat transfer to the internal fluid. Further, as another method for reducing the temperature difference generated in the pipe 71, it is conceivable to change the shape of the pipe 71 so that sunlight is also applied to the radially outer surface of the pipe 71. There is a possibility that the processing cost increases due to, and the heating efficiency of the internal fluid may decrease depending on the shape.

  Therefore, in the receiver 7 (solar heat concentrating device) in the solar heat concentrating system 2 of the present embodiment, by providing the radiation film 74 on the inner surface of the pipe 71, heat generated on the radially inner side of the pipe 71 irradiated with sunlight. Is radiated outward of the pipe 71 in the radial direction. Thereby, the temperature difference between the radially inner side and the radially outer side of the pipe 71 can be reduced. That is, it is possible to prevent the receiver 7 from being damaged by the local irradiation of sunlight.

  The result of having simulated about the effect by providing radiation film 74 is shown. When sunlight was irradiated with respect to the receiver 7 having the radiation film 74 shown in FIG. Specifically, as shown in FIG. 3, measurement points P <b> 1 to P <b> 4 are set for each turn in order from the bottom of the coiled pipe 71. Then, similarly to the receiver 7, when sunlight is incident from the lower opening 72 a and irradiated to the pipe 71, the surface temperature at one point on the radially inner side and the one point on the radially outer side at each measurement point. The surface temperature in was calculated by simulation under two conditions. The two conditions are when the radiation film 74 is provided on the inner surface of the pipe 71 (emissivity 0.82) and when the radiation film 74 is not provided (emissivity 0.18).

  The pipe 71 is made of stainless steel and has an outer diameter of 22 mm and a winding diameter (a distance between the centers of the pipes 71 facing each other across the winding axis X) of 160 mm. In addition, the simulation was performed under the condition that the pipe 71 was heated by irradiation with sunlight in a state where 120 ° C. air was introduced from the end 71a so that the flow rate was 3.1 g / s in the pipe 71. The results are shown in Table 1.

  As shown in Table 1, when the emissivity is 0.18, the temperature difference between the inner side and the outer side is 162 ° C. at the measurement point P1, whereas when the emissivity is 0.82, 113 ° C. It became. Similarly, at the measurement points P2 to P4, the temperature difference between the inner side and the outer side is smaller when the radiation rate is 0.82 than when the radiation rate is 0.18. As is clear from the calculation results in Table 1, it was confirmed that when the emissivity of the inner surface of the pipe 71 increases, the inner temperature decreases and the outer temperature increases. This is considered to be due to the transmission of radiant heat from the radially inner side of the pipe 71 toward the radially outer side. Thus, it was confirmed from the simulation results that the temperature difference between the radially inner side and the radially outer side of the pipe 71 is reduced.

  Further, when the fluid in the pipe 71 is air, the radiation film 74 has a high emissivity for light in the near-infrared (700 nm to 2500 nm) or mid-infrared (2500 nm to 4000 nm) wavelength region. Preferably it is. When the fluid in the pipe 71 is air, since the air transmits infrared rays, it is possible to efficiently transmit radiant heat from the inside to the outside in the pipe 71.

  In addition, when the receiver 7 including the pipe 71 is a cavity type, the effect of providing the radiation film 74 becomes remarkable. That is, in the cavity-type receiver, since the sunlight entrance is limited, the irradiation direction is limited. Therefore, in the flow path formed on the inner surface of the cavity, the surface facing the entrance is heated by the irradiation of sunlight, while the surface opposite to the surface facing the entrance is It is thought that there is no sunlight irradiation, and as a result, a temperature difference occurs between the two. As described above, in the cavity-type receiver, there is a possibility that the temperature difference due to the local irradiation of sunlight is increased. Therefore, it is considered that the effect of reducing the temperature difference by providing the radiation film 74 becomes remarkable.

  Moreover, the effect by providing in the radiation film | membrane 74 becomes remarkable like the receiver 7 which concerns on this embodiment. In the case where the secondary mirror 73 provided in the vicinity of the opening 72a is provided, the angular distribution of sunlight is larger than that in the case of using only the mirror 8, so that the sun is located around the opening 72a, that is, on the lower side. It is thought that it becomes easy to concentrate light. Since the fluid flowing through the pipe 71 is heated while moving from below to above, a low-temperature fluid flows through the lower pipe 71. Therefore, as shown in the above simulation, the temperature difference between the inside and outside tends to be larger than that of the upper pipe 71. Therefore, it is considered that the effect of reducing the temperature difference by providing the radiation film 74 becomes remarkable.

  The radiation film 74 may be provided on the entire inner surface of the pipe 71. However, by providing the radiation film 74 in a portion that is likely to become high temperature due to the irradiation of sunlight, the radiation film 74 of the receiver 7 is locally irradiated with sunlight. Breakage can be prevented. The portion that tends to be high temperature is a region where the amount of irradiated sunlight is larger than other regions. In the case of the receiver 7 according to the present embodiment, the region where the amount of the collected sunlight is large is considered to be a radially inner region of the pipe 71 and a lower side close to the opening 72a. . However, it is conceivable that the sunlight condensing condition and the sunlight irradiation position change depending on the shape of the receiver 7 including the arrangement of the flow path and the arrangement of the mirror 8. In other words, in which region the sunlight is concentrated and irradiated varies depending on various conditions. Therefore, the position where the radiation film 74 is provided can be changed as appropriate.

  As mentioned above, although embodiment which concerns on this invention was described, this invention is not restricted to the said embodiment, A various change can be added.

  For example, in the above embodiment, the receiver 7 of the type in which the pipe 71 is wound in a coil shape has been described as the receiver 7 having a cavity type flow path, but the shape of the receiver 7 can be changed as appropriate. Further, the shape of the flow path can be changed as appropriate. For example, in the above embodiment, the flow path is the pipe 71 and the fluid moves in the pipe 71 from the lower side to the upper side of the receiver 7. For example, the radiation film described in the above embodiment is The present invention can also be applied to a receiver that forms a fluid flow path by forming a cylindrical member having a slit-like opening and making the inside hollow. In the case of the receiver having such a shape, the slit serves as an entrance for sunlight in the cavity.

  Furthermore, the radiation film according to the present invention is not limited to the channel of the cavity type receiver. In a receiver having a flow path through which a fluid flows, it is difficult to irradiate sunlight uniformly over the entire outer surface of the flow path. Therefore, local irradiation of sunlight may occur. That is, it is conceivable that the receiver is damaged due to local irradiation of sunlight. In contrast, by providing a radiation film on the inner surface of the flow path, it is possible to prevent damage to the receiver due to local irradiation of sunlight.

  DESCRIPTION OF SYMBOLS 1 ... Solar thermal power generation system, 2 ... Solar thermal condensing system, 3 ... Power generation apparatus, 4 ... Supply piping, 5 ... Discharge piping, 6 ... Solar thermal condensing unit, 7 ... Receiver, 8 ... Mirror, 71 ... Piping, 72 ... Thermal insulation 73, secondary mirror.

Claims (4)

A solar thermal condensing device that heats a fluid flowing through a flow path by condensed sunlight,
A solar heat concentrator having a radiation film on an inner surface of the flow path.   The solar heat collector according to claim 1, wherein the flow path is a cavity type.   The solar heat concentrating device according to claim 1, wherein the radiation film is provided in a region of the flow path where the amount of sunlight irradiated is large. A reflector that reflects sunlight;
A heat collecting unit that collects sunlight reflected by the reflecting unit and heats the fluid flowing through the flow path by the collected sunlight, and
The solar heat condensing system, wherein the heat collecting part has a radiation film on an inner surface of the flow path.

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