JP2008523351A - Solar energy collection apparatus and method - Google Patents

Abstract

  A solar energy collector that collects heat from a solar concentrator has an isothermal body with an elongated cavity. The cavity has a circular aperture, the diameter of which is equal to the diameter of the focal point of the solar concentrator. The cavity has a reflecting wall so that the sunlight irradiated to the reflecting wall is sufficiently reflected. The circular opening is located at the focal point of the solar concentrator and is provided perpendicular to the main axis of the solar concentrator. Further, the axis of the cavity and the main axis of the solar concentrator are aligned. The heat collected in the isothermal body is absorbed by the heat absorption source. The length of the cavity is long enough to absorb the target amount of energy from the sun rays entering the cavity, and is 5 to 9 times the diameter of the cavity opening. Depending on the material used, the isothermal body may be sealed with a reducing gas in order to maintain the reflectivity of the reflective wall of the cavity.

Description

  The present invention relates to the field of solar energy, and in particular to solar radiant energy collection for use as a driving force for thermochemical, thermomechanical, or other heat treatments.

  There is considerable interest today in utilizing renewable solar energy for a large number of different heat-driven processes. The thermal drive process is a thermomechanical power generation system, thermochemical reforming, thermolysis, heat treatment, general heat treatment, material treatment, etc. found in a Stirling engine or a steam turbine. Generally, a solar energy collection system is installed in a place where sunlight can be obtained immediately. In a typical system, a flat segmented or bent mirror is placed on the parabola or in the shape of a bowl or bowl to collect incident solar radiation energy and pre-determine it Focus on the target. The tracking control system or pre-programmed algorithm maintains the required visible light shape as the sun traverses the sky by moving the mirror.

  The target is usually shaped like a cavity or a shallow dish where light is collected in a conical shape. The cavity is generally formed by a plurality of tubes into which cooling liquid is poured so that the absorbed heat is transferred to the running process. US Patent Publication No. 5,113,659 describes several cavity designs. A series of hot shoes are included within the cavity to transfer thermal energy to a plurality of free piston sterling generators. In some solar thermochemical processes, the image fireball is often used directly on the thermal catalyst bed in a transparent processing tube that causes local hotspots. For this reason, catalyst sintering occurs or the processing temperature control is not successful.

  In all these collection schemes, the spot size and its shape need to be adjusted to the heat exchange and cavity parameters. In order to avoid local heating effects, defocus the sun image or illuminate multiple sun images at an even temperature. In the zone heated by. As a result, the sun image is magnified, and as a result, the area of the heat radiation surface is increased, so that the focus of the sun on the target is more blurred than the optimum focus and radiation loss increases.

  Image scaling and the loss of solar energy collection technology affect the bulk of the overall product conversion efficiency. Therefore, the purpose of the solar energy collection system is to aim for the maximum production amount of the product in the minimum solar energy collection area. A key factor to achieve the above objective is to minimize the parasitic loss due to heat dissipation from the target.

The collecting means determines according to the required processing temperature. In order to use low-temperature heat, a bowl-shaped reflector serves as a collecting means, and in order to obtain a higher temperature, a parabolic curve collecting device serves as a collecting means. The steam system operates at moderate temperatures below 800K. In order to obtain high equilibrium constants in endothermic reactions, thermochemical reactions require substantially higher temperatures. Unfortunately, as process temperatures increase, parasitic radiation losses due to thermal radiation and the like increase. In accordance with Stefan's law (Pr = σεAT ⁴ ), the parasitic radiation loss increases by 16 times when the absolute temperature of the target at the processing temperature is doubled. Therefore, radiation loss minimization works in conjunction with an optimized cavity receiver configured so that the blackbody region is the same as the focused solar image, with the smallest solar image or highest solar energy. This is achieved by putting collection into practical use.
US Patent Publication US 5,113,659 (published May 19, 1992)

[Summary of the Invention]
It is an object of the present invention to provide a solar heat collecting apparatus and method that overcomes the problems of the prior art.

  In a first embodiment of the present invention, an apparatus for collecting heat from a solar concentrator and transferring the collected heat to a heat sink is disclosed. The device has an isothermal body with an elongated cavity. The cavity has a substantially circular aperture whose diameter is approximately equal to the diameter of the focal point of the solar concentrator. The cavity has a reflecting wall so that the sunlight irradiated to the reflecting wall is sufficiently reflected. The direction of the isothermal body is such that the circular opening is located at a substantially focal point of the solar concentrator and is substantially perpendicular to the main axis of the solar concentrator, and the cavity axis and the solar concentrator The main shaft is aligned in a substantially straight line. The isothermal body is designed such that heat generated by the isothermal body is absorbed by the heat absorption source. The length of the cavity is sufficient to absorb the target amount of energy from the sunlight entering the cavity.

  In a second embodiment of the present invention, an apparatus for collecting heat from the sun and transferring the collected heat to a heat absorption source is disclosed. The apparatus includes a solar concentrator and an isothermal body. The isothermal body has an elongated substantially cylindrical cavity. The cavity has a substantially circular aperture whose diameter is approximately equal to the diameter of the focal point of the solar concentrator. The cavity has a reflecting wall so that the sunlight irradiated to the reflecting wall is sufficiently reflected. The direction of the isothermal body is such that the circular opening is located at a substantially focal point of the solar concentrator and is substantially perpendicular to the main axis of the solar concentrator, and the cavity axis and the solar concentrator The main shaft is aligned in a substantially straight line. The isothermal body is designed such that heat generated by the isothermal body is absorbed by the heat absorption source. The length of the cavity is about 5-9 times the diameter of the circular opening.

  In a third embodiment of the present invention, a method for collecting heat for transmission from a solar concentrator to a heat absorption source is disclosed. The method has a substantially circular opening, a cavity whose opening diameter is substantially equal to the diameter of the focal point of the solar concentrator, has a reflecting wall, and is irradiated on the reflecting wall. Providing an isothermal body having an elongated cavity in which sunlight is sufficiently reflected, and the orientation of the isothermal body, with the circular aperture positioned approximately at the focal point of the solar concentrator. The step of determining the axis of the cavity to be substantially perpendicular to the main axis of the solar concentrator and the main axis of the solar concentrator being aligned substantially in a straight line; Each sunlight ray is reflected from the first contact point on the reflection wall to the second contact point on the reflection wall and a plurality of subsequent contact points on the reflection wall, so that the target energy amount included in the sunlight ray is reflected. At each contact until is absorbed by the reflecting wall The step of absorbing energy contained in each solar ray by a reflecting wall, and the heat absorption source so that heat generated in the isothermal body by the absorbed energy of the solar ray is absorbed by the heat absorption source Thermally connecting to the isothermal body.

  Solar radiant energy is converted to heat by a plurality of internal reflections in a reflective cavity formed in the isothermal body. The hollow light-receiving portion is interlocked with a thermally necessary heat treatment or heat absorption source. The isothermal body has a main part for integrating the thermal function, and realizes interlocking processing at a substantially constant temperature regardless of a slight heat insulating material or the curvature of the solar image.

  The opening of the cavity is located on the main axis of visible light at the focal point of a parabolic solar concentrator, and the portion of the light cone with the smallest diameter corresponds to the entrance of the cavity.

  The mechanical structure resembles a hollow cylinder covered with a chemically reducible material or having a thick wall made of a chemically reducible material. The chemically reducible substance is, for example, copper, but is not limited thereto. While the opening at the end of the cavity blocks the light cone at the focal point from the solar concentrator, the isothermal body is thermally linked to the heat treatment. Solar energy enters the cavity and repeats internal reflection. During this time, it is uniformly dispersed and heat is gradually emitted. The heat is absorbed by the isothermal body of the light receiving unit and used for the execution of the processing. The reflectivity of the cavity wall is adjusted by internal air inactivation or reducing atmosphere.

[Brief description of figure]
The above objects and advantages of the present invention, as well as further objects and advantages, will be set forth in detail in the following description of preferred embodiments of the invention with reference to the drawings, which illustrate the invention as a component. A more complete understanding can be gained through this explanation

  1 and 2 are schematic diagrams of a conventional solar heat collection system configured to drive the Stirling of a synchronous current transformer.

  FIG. 3 is a solar concentrator used in the prior art, in which the irradiance characteristics of the target in a solar concentrator radiated radially to attenuate energy to a usable level. profile).

  FIG. 4 is a graph of radial light distribution in the prior art and the present invention.

  FIG. 5 is a graph showing the relationship between the temperature and region of the target and the thermal radiation loss of the black body.

  FIG. 6 is a side sectional view showing an outline of an embodiment adopting a Stirling engine motive power generation system in the present invention.

  FIG. 7 is a side sectional view schematically showing another embodiment of the heating application of the present invention.

  FIG. 8 and FIG. 9 are side sectional views showing an outline of an embodiment adopting a thermochemical reaction system in the present invention.

  FIG. 10 is an isometric view showing an isothermal body having a coaxial cavity according to the present invention, showing the basic principle of the path of one ray and the action of the cavity.

  FIG. 11 is an end view of the heat conductor shown in FIG. 10 and shows the path of the internal light beam.

Detailed Description of the Invention
FIG. 1 and FIG. 2 are diagrams showing an outline of a conventional solar heat collection system that is driven by a combination of a heat engine and an electricity generation device. Solar heat collection systems are intended to provide heat used for a wide variety of purposes. The collected heat is used by being transferred to a heat absorption source, basically like the illustrated heat engine that consumes heat. The operating temperature varies depending on the purpose. The system is also designed so that once the operating temperature reaches the desired temperature, all collected heat is separated by a heat sink, and the operating temperature is about 100 ° C. to 1400 ° C. or higher. It may be.

  In the above example, the solar rays 7 in the luminous flux of sunlight generated by reflecting the solar radiation 1 by the solar collector 2 are focused on the target 8. The target 8 is provided on the cavity 11 in accordance with the focal point of the parabolic solar collector 2. The target 8 is composed of a plurality of metal tubes 3, and the metal tubes 3 are arranged symmetrically with respect to the main axis 9 of the parabolic solar collector 2 so as to block the light cone. In order to reduce heat transfer losses, a quartz window 5 covers the target 8. The coolant is flowing through the tube 3 to remove heat generated by absorbing the heat dissipated in contact with the tube 3. Then, the heat is transmitted to the heat engine 4 by heat conduction.

  In the above example, the mechanical energy converted by the heat engine is transmitted to the generator 6 by the shaft 10. The generation unit 6 converts mechanical energy into electric energy. In the above example, the light distribution directed to the target 8 is the same as that of the annular ring in the tubular heat exchange structure, as shown in FIG. The annular ring is distorted into a plurality of solar images in order to reduce the flux intensity level of sunlight to the heat exchange limit. In FIG. 4, a curve W is a graph showing the result of radial light distribution in the target 8 when the sun image shown in FIG. 3 is distorted and superimposed on the target 8. As shown in FIG. 3, the substantially circular portion at the center of the target is not substantially exposed to the sunlight 7. In this way, the sun rays 7 are prevented from concentrating on the target 8 by widening the target region.

Generally, the accumulation degree of sunlight is measured using a unit of “suns”. 1 sun represents the amount of incident energy per unit area of standard sunlight. Sunlight is about 1000 watts per square meter (W / m ² ). More specifically, when the accumulation degree of sunlight on the focus is about 5500 suns, the heat exchange tube 3 does not hold up to the heat when the accumulation degree is reached. Given the heat absorption allowance and coolant flow rate along the heat transfer heat transfer parameters, the maximum allowable solar accumulation degree is, for example, about 877 suns or about 877000 W / m ² . In order to reduce the degree of sunlight accumulation, the mechanism is arranged as follows. That is, for example, the parabolic curved collector 2 is distorted so as to be radiated to a wider area. When the degree of sunlight accumulation is thus reduced, the required heat conduction can be performed while maintaining the exchange temperature within an allowable range.

  However, when the size of the target is increased, radiation loss at a predetermined temperature is also increased, and the sunlight collection efficiency is lowered. FIG. 5 shows that when the emissivity is 1.0, the magnitude of the energy loss caused by the re-radiation energy of the target is substantially affected by the processing temperature and the radiation area of the target. In the above-described example shown in FIGS. 1 and 2, the target 8 has a diameter of about 15 inches, and the degree of sunlight accumulation is about 177 square inches. 877 suns) (including the circular portion of). By relocating the parabolic solar concentrator 2 to focus at the focus of one solar image, the target diameter is about 6 inches. This results in a solar accumulation level of 5500 suns per target area of approximately 28 square inches at the focal point. Accordingly, the area of the target is reduced by about 6.25, and accordingly, the concentration is increased by about 6.25 times.

  As shown in FIG. 5, radiation loss can be reduced from 13% to 2% by reducing the target size from 15 inches to 6 inches. The processing operating temperature at this time is 850 degreeC. As shown in FIG. 5, as the operating temperature is increased, the radiation loss of the small target does not increase much, while the radiation loss at the larger target increases dramatically as the operating temperature is increased. These data are the thermodynamic truths that apply to any blackbody solar receiver designed to reach a predetermined temperature. An attempt to obtain a very high light concentration by the light condensing part having a small diameter as described above is a difficult problem to solve.

  FIG. 6 is a diagram illustrating one embodiment of the apparatus of the present invention for collecting heat from a solar concentrator and transferring the collected heat to a heat absorption source. In the illustrated embodiment, the heat absorption source included in the collection device of the present invention is a Stirling engine generation device, which is similar to the heat absorption source provided in the collection device of FIGS. 1 and 2. Here, rather than distorting the concentrator, the solar radiation 1 collected by the parabolic solar concentrator 2 clearly projects a single solar image at the opening entrance of the elongated cavity 13. So that it is focused. Here, the degree of sunlight accumulation is the largest, and the diameter of the target (that is, the opening entrance of the cavity 13) is the smallest. In FIG. 4, the curve S is a graph of the result of radial light distribution at the target 8 when there is one sun image.

  The opening of the cavity 13 is circular and its diameter is approximately equal to the diameter of the focal point of the solar collector 2. The cavity 13 is oriented such that the circular opening is located at the focal point of the solar collector 2 and is substantially perpendicular to the main axis 9 of the solar collector 2. Further, the cavity 13 is provided so that the axis of the cavity 13 is aligned with the main axis 9 in a substantially straight line.

  The cavity 13 is formed inside an isothermal body 12 made of stainless steel or the like. The inside of the cavity 13 is covered with a metal plate 32 such as copper. Copper has good reflectivity in a chemically reduced state and high thermal conductivity. Alternatively, the isothermal body 12 as a whole may be made of a material that can be chemically reduced and has high thermal conductivity, such as but not limited to copper. In any case, the cavity 13 has a reflection wall so that the sunlight 7 irradiated to the wall is sufficiently reflected. Energy is converted from sunlight into heat at the walls of the cavity 13 by the plurality of reflections of the light rays inside the cavity 13. The heat is diverted to increase the temperature by heat conduction to the isothermal body 12 or to make the thermal energy available for heat absorption source processing.

  By reflecting the sunlight 7, the area where the light acts in the light receiving portion increases from the area of the cavity opening to the area of the cavity wall. The sunlight 7 continues to be repeatedly reflected from the first contact point on the reflection wall to the second contact point on the reflection wall, and is irradiated and reflected on a large number of contact points on the reflection wall. Since the cavity is elongated compared to the opening of the cavity, the proportion of the unabsorbed sunlight that is reflected from the wall to the wall and output through the opening is small.

  The absorption rate of solar energy may increase in proportion to the length of the cavity. The total amount of light absorption is not practical, but if the length of the reflective cavity 13 is about 5-9 times the diameter of the cavity entrance opening, the length of the cavity generally requires sunlight entering the cavity. It can be said that it is sufficient to absorb at a sufficient rate. A test with a very good approximation of the blackbody absorber is achieved with a minimal blackbody area. Here, the length of the reflection cavity 13 is about 7 times the diameter of the cavity entrance opening. According to the above configuration, about 95% of solar energy is absorbed.

  Increasing the length of the cavity 13 increases the absorption rate of sunlight. However, the length of the isothermal body 12 is also increased. As the size of the isothermal body 12 increases, the loss due to heat conduction from the isothermal body 12 increases in the same way. And the merit obtained by radiation reduction is offset by the conduction loss through the elongated surface of the isothermal body 12. When the length of the cavity 13 is shortened, most of the light rays are reflected and go out of the cavity 13 and lost, so that the energy absorption efficiency in the solar rays 7 is lowered.

  The cavity 13 is maintained with a reducing gas for chemical reduction of exposed metal components. When metal components are oxidized, the reflectivity is reduced, which reduces the effectiveness of the device.

  10 and 11 are views showing the isothermal body 12 and the cavity 13 of the present invention excluding the heat extraction means, and one light beam of the sunlight 7 is reflected through the entrance 20 of the cavity 13 and the reflecting wall of the cavity 13. It is a figure which shows the path | route which tracks while colliding. In the above example, the sun rays 7 or photons are repeatedly reflected many times until finally absorbed by the cavity wall. The energy absorbed in the cavity wall is transmitted to the isothermal body 12, and the internal energy increases or the temperature rises. 10 and 11, there are an infinite number of paths that photons follow, but only one is shown for the purpose of explanation. The focused light energy having a Gaussian beam profile directed at the entrance of the cavity follows every path within the extent that heat is evenly distributed inside the cavity.

  As the temperature of the isothermal body 12 increases, the exposed surface 14 radiates energy according to its emissivity and area. This comprehensively causes parasitic losses. Accordingly, as shown in FIGS. 6-9, in order to cover the exposed surface of the isothermal body 12 between the cavity opening and the outer end of the isothermal body or itself for the purpose of reducing thermal radiation loss due to surface radiation. Providing the shield 30 made of a reducible substance such as copper has an advantageous effect. Chemically reducible protections may be used to cover any of the components that are exposed when the processing temperature is reached.

  FIG. 7 is a diagram showing a heating mechanism used for heat-treated steam or working fluid. In the above description, solar energy is absorbed by multiple reflection and absorption mechanisms inside the cavity, thereby heating the isothermal body 12 to the required processing temperature. The working fluid enters from the receiving portion 18 and circulates through the passage 17 in the cylinder. The passage 17 is arranged in line symmetry within the isothermal body 12. Then, energy is absorbed from the isothermal body 12 and output from 19 to the necessary processing.

  In the embodiment shown in FIGS. 6 to 9, a sealed housing 16 is provided. The sealed housing 16 serves as necessary heat insulation and includes a reducing gas 15. The window 5 serves to block the gas leak in order to realize the housing 16 while allowing solar radiation to enter the reflective cavity 13. The housing | casing 16 is satisfy | filled with the reducing gas which consists of 5% of hydrogen and the sealing gas for maintaining it in equilibrium, for example. The fill gas is inert at the operating temperature. Nitrogen is a good choice because it is inexpensive and inert at relatively high temperatures. Similarly, other inert gases such as argon may be used. With the reducing gas, the reducible metal can maintain the required metallic form. Examples of the reducible metal include oxygen free copper (OFHC copper) or other alloys. In the above state, the reflective surface of the back plate 32 of the reflective cavity 13 and the shield 30 maintain a low emissivity, thereby achieving the function of the present invention.

  The casing 16 containing the reducing gas is insulated to reduce heat loss.

  In FIGS. 6-9, since solar radiation heats the cavity 13, a high pressure is applied to the inner wall of the isothermal body 12 by expansion of the heat of the metal back plate 32 that forms the metal wall in the cavity. The deep connection between these components reduces the thermal resistance of the metal boundary between the backplate 32 and the isothermal body 12. Heat conduction to the isothermal body 12 that receives heat is expanded and the maximum rate of cavity flux density is increased by forming a backplate and a substantially isothermal receiver in the cavity.

  8 and 9 are diagrams showing a thermo-chemical solar reactor. In the reaction furnace, the collected sunlight 7 enters the casing 16 that seals the gas through the quartz window 5. And by repeating cavity reflection many times, the energy of the sunlight 7 is absorbed by the isothermal body 12 and converted into heat. The reaction gas can be injected into the supply line 22 and the preheating channel 24. Hot reactants output from preheat channel 24 enter reaction beds 25 in an isothermal body. Here, an endothermic reaction due to catalytic action occurs. The product according to the above example is output from the tube 23 of the isothermal body 12.

  In other embodiments in the example shown in FIGS. 6-9, a solid isotherm made of reducible metal or ceramic is included, thus eliminating the need for a reflective cavity backplate or shield. Other oxidation control means of the main components, such as other reducing gases, or means for changing the concentration of any of the gases mentioned above are contemplated within the scope of the present invention.

  The apparatus of the present invention is preferably used for processing at high temperatures where most of the collected solar energy results in radiation loss. In the processing at a lower temperature, the radiation loss is not so large, so that the use of this apparatus generally does not provide a remarkable effect.

  Therefore, the above description should be understood as merely illustrating the principles of the invention. Further, since numerical values can be easily replaced or changed by those skilled in the art, the present invention is not limited to the exact configuration and operation described above or illustrated. Accordingly, all suitable substitutions and changes in reproducible structure and operation are included within the scope of the claimed invention.

FIG. 2 is a schematic diagram of a conventional solar heat collection system configured to drive Stirling of a synchronous current transformer. FIG. 2 is a schematic diagram of a conventional solar heat collection system configured to drive Stirling of a synchronous current transformer. A diagram of the target irradiance profile for a solar concentrator used in the prior art, radiated to radiate the energy to a usable level. It is. It is a graph of radial flux distribution in a prior art and this invention. It is a graph showing the relationship between the temperature and area | region of a target, and the thermal radiation loss of a black body. It is a sectional side view showing the outline of the embodiment which adopted the Stirling engine motive power generation system in the present invention. It is a sectional side view which shows the outline of other embodiment in the use of the heating of this invention. It is a sectional side view which shows the outline of embodiment which employ | adopted the thermochemical reaction system in this invention. It is a sectional side view which shows the outline of embodiment which employ | adopted the thermochemical reaction system in this invention. It is an isometric view showing an isothermal body having a coaxial cavity according to the present invention, and is a diagram showing the basic principle of the action of one ray path and cavity. It is an end elevation of the heat conductor shown in FIG. 10, and is a figure which shows the path of an internal light ray.

Claims (20)

A heat collector that collects heat from a solar concentrator and transfers the collected heat to a heat absorption source,
An isothermal body that has a substantially circular opening having a diameter substantially equal to the diameter of the focal point of the solar concentrator, and that forms an elongated cavity having a reflecting wall that sufficiently reflects the irradiated sunlight. With
The direction of the isothermal body is such that the circular opening is substantially located at the focal point of the solar collector, is substantially perpendicular to the main axis of the solar collector, and the hollow axis and the sunlight The main axis of the concentrator is aligned in a substantially straight line,
The isothermal body is thermally connected to the heat absorption source so that heat generated by the isothermal body is absorbed by the heat absorption source,
The heat collecting apparatus according to claim 1, wherein the cavity has a length sufficient to absorb a desired proportion of energy from the sunlight entering the cavity.   The heat collecting apparatus according to claim 1, wherein an absorption ratio of energy of solar rays incident on the cavity increases as the length of the cavity increases.   The heat collecting apparatus according to claim 1 or 2, wherein a length of the cavity is about 5 to 9 times a diameter of the circular opening.   The heat collecting apparatus according to claim 3, wherein the length of the cavity is 6.5 to 7.5 times the diameter of the circular opening.   The heat collecting apparatus according to claim 1, wherein the cavity has a substantially cylindrical shape.   6. The heat collecting apparatus according to claim 1, wherein the isothermal body is made of a reflective material so that the wall of the cavity is reflected.   6. A back plate made of a reflective material, which is effective for realizing a reflection wall of the cavity, is provided between the isothermal body and the cavity. The heat collecting apparatus of Claim 1.   The heat collecting apparatus according to claim 7, further comprising a low emissivity shield that covers an end of the isothermal body between a cavity opening and an outer end of the isothermal body.   A reductive gas effective to substantially prevent oxidation of the reflective wall of the cavity is provided, and a casing for sealing the isothermal body is provided, and the reflectance of the reflective wall is maintained. The heat collecting apparatus according to any one of 1 to 8.   The heat collecting apparatus according to claim 9, wherein the reflection wall is made of oxygen-free copper, and the reducing gas contains hydrogen and an enclosed gas.   The heat collecting apparatus according to claim 9 or 10, wherein the wall of the casing is made of a heat insulating material. A heat collecting device that collects heat from the sun and transfers the collected heat to a heat absorption source,
A solar concentrator,
A cavity having a substantially circular opening having a diameter approximately equal to the diameter of the focal point of the solar collector, and having an elongated substantially cylindrical cavity having a reflecting wall that sufficiently reflects the irradiated sunlight. An isothermal body to form,
The direction of the isothermal body is such that the circular opening is substantially located at the focal point of the solar concentrator and is substantially perpendicular to the main axis of the solar concentrator. The main axis of the concentrator is aligned in a substantially straight line,
The isothermal body is thermally connected to the heat absorption source so that heat generated by the isothermal body is absorbed by the heat absorption source,
The length of the hollow is about 5 to 9 times the diameter of the circular opening.   13. The heat collecting apparatus according to claim 12, further comprising a low emissivity shield that covers an end of the isothermal body between the opening of the cavity and the outer end of the isothermal body.   A reductive gas effective to substantially prevent oxidation of the reflective wall of the cavity is provided, and a casing for sealing the isothermal body is provided, and the reflectance of the reflective wall is maintained. The heat collecting apparatus according to 12 or 13.   The heat collecting apparatus according to claim 14, wherein the reflecting wall is made of oxygen-free copper, and the reducing gas contains hydrogen and an enclosed gas. A heat collection method for collecting heat from a solar concentrator and transferring it to a heat absorption source,
An isothermal body that has a substantially circular opening having a diameter substantially equal to the diameter of the focal point of the solar concentrator, and that forms an elongated cavity having a reflecting wall that sufficiently reflects the irradiated sunlight. Providing a step;
The isothermal body has the circular aperture located substantially at the focal point of the solar collector, substantially perpendicular to the main axis of the solar collector, and the hollow axis and the solar collector. Orienting the isothermal body so that the main axis of the vessel is aligned substantially in a straight line;
The reflecting wall is irradiated from the first contact point of the reflecting wall to the second contact point of the reflecting wall, and after that, until a desired proportion of energy contained in the solar rays is absorbed by the reflecting wall. Reflecting sunlight that repeats irradiation at each contact;
Thermally connecting the heat absorption source to the isothermal body so that heat generated in the isothermal body by the absorbed energy of the solar rays is absorbed by the heat absorption source. Heat method.   The heat collection method according to claim 16, wherein an absorption ratio of energy of solar rays incident on the cavity increases as the length of the cavity increases.   The heat collecting method according to claim 16 or 17, wherein the cavity is substantially cylindrical, and the length of the cavity is about 5 to 9 times the diameter of the opening of the cavity. Sealing the isothermal body with a housing;
The inside of the housing is filled with a reducing gas effective to substantially prevent oxidation of the reflection wall of the cavity, and the step of maintaining the reflectance of the reflection wall is included. The heat collecting method described in 1.   The heat collecting method according to claim 19, wherein the reflecting wall is made of oxygen-free copper, and the reducing gas contains hydrogen and an enclosed gas.

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