Double point-focusing solar energy collection apparatus

Abstract

A double point focusing solar energy collection apparatus of the present invention includes a heat collector, a secondary concentrator, and a bracket. The heat collector includes a primary concentrator and a heat collection tube, in which the primary concentrator has a focus point. The secondary concentrator has a focus point. The bracket supports the primary concentrator, the heat collection tube, and the secondary concentrator. The heat collection tube is located between the primary concentrator and the secondary concentrator and located on the focus points of the secondary concentrator and the primary concentrator. By adding the secondary concentrator, which is a rotating paraboloid reflector or circular Fresnel reflector, it can achieve low light loss and high heat collection efficiency, and erosion of the heat collection tube by sand, rain, and snow can be effectively prevented, thereby extending the lifetime of the heat collection tube effectively.

Claims

1. A double point focusing solar energy collection apparatus, comprising: a heat collector comprising a primary concentrator and a heat collection tube, wherein the primary concentrator has a focus point; a secondary concentrator having a focus point; wherein a first opening of the primary concentrator is larger than a second opening of the secondary concentrator, and a first focal length of the primary concentrator is larger than a second focal length of the secondary concentrator, wherein a first ratio of the first opening to the first focal length is equal to a second ratio of the second opening to the second focal length; and a bracket supporting the primary concentrator, the heat collection tube, and the secondary concentrator, wherein the heat collection tube is located between the primary concentrator and the secondary concentrator and is located on focus points of the secondary concentrator and the primary concentrator, wherein the primary concentrator is a circular Fresnel reflector, and the secondary concentrator is a circular Fresnel reflector.

2. The double point focusing solar energy collection apparatus of claim 1, wherein the heat collection tube is ellipsoidal, spherical or square.

3. The double point focusing solar energy collection apparatus of claim 2, further comprising a solar energy tracking device.

4. The double point focusing solar energy collection apparatus of claim 2, wherein the heat collection tube is a vacuum tube comprising an outer tube and an inner tube, an interval between the outer tube and the inner tube is vacuum, and the inner tube carries an energy absorbing medium.

5. The double point focusing solar energy collection apparatus of claim 4, further comprising a solar energy tracking device.

6. The double point focusing solar energy collection apparatus of claim 4, wherein both the outer tube and the inner tube are transparent.

7. The double point focusing solar energy collection apparatus of claim 6, wherein the outer tube is made of glass, polymethyl methacrylate (PMMA), or polycarbonate (PC).

8. The double point focusing solar energy collection apparatus of claim 6, wherein the inner tube is made of glass, polymethyl methacrylate (PMMA), or polycarbonate (PC).

9. The double point focusing solar energy collection apparatus of claim 6, further comprising a solar energy tracking device.

10. The double point focusing solar energy collection apparatus of claim 4, wherein the outer tube is made of glass, polymethyl methacrylate (PMMA), or polycarbonate (PC).

11. The double point focusing solar energy collection apparatus of claim 4, wherein the inner tube is made of glass, polymethyl methacrylate (PMMA), or polycarbonate (PC).

12. The double point focusing solar energy collection apparatus of claim 1, further comprising a solar energy tracking device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to explain technical solutions of embodiments of the present invention more clearly, the following is a brief introduction to a figure which contains descriptions of the embodiments; what the figures below merely show are some embodiments of the present invention; and for a person skilled in the art, without working with non-obviousness, it is possible to further create other figures according to the figures below, in which:

(2) FIG. 1 is a schematic diagram of an optical path of using a rotating paraboloid reflector to enhance a rotating paraboloid reflector in a point focusing solar energy collection apparatus according to a first embodiment of the present invention;

(3) FIG. 2 is a schematic diagram of a structure of using a rotating paraboloid reflector to enhance a rotating paraboloid reflector in a point focusing solar energy collection apparatus according to a first embodiment of the present invention;

(4) FIG. 3 is a schematic diagram of a structure of using a circular Fresnel reflector to enhance a rotating paraboloid reflector in a point focusing solar energy collection apparatus according to a second embodiment of the present invention;

(5) FIG. 4 is a schematic diagram of a structure of using a circular Fresnel reflector to enhance a rotating paraboloid reflector in a point focusing solar energy collection apparatus according to a second embodiment of the present invention;

(6) FIG. 5 is a schematic diagram of an optical path of using a rotating paraboloid reflector to enhance a circular Fresnel reflector in a point focusing solar energy collection apparatus according to a third embodiment of the present invention;

(7) FIG. 6 is a schematic diagram of a structure of using a rotating paraboloid reflector to enhance a circular Fresnel reflector in a point focusing solar energy collection apparatus according to a third embodiment of the present invention;

(8) FIG. 7 is a schematic diagram of an optical path of using a circular Fresnel reflector to enhance a circular Fresnel reflector in a point focusing solar energy collection apparatus according to a fourth embodiment of the present invention;

(9) FIG. 8 is a schematic diagram of a structure of using a circular Fresnel reflector to enhance a circular Fresnel reflector in a point focusing solar energy collection apparatus according to a fourth embodiment of the present invention;

(10) FIG. 9 is a schematic diagram of a partial structure of a heat collection tube of a double point focusing solar energy collection apparatus according to a sixth embodiment of the present invention;

(11) FIG. 10 is a schematic diagram of a comprehensive absorptivity of the present invention to sunlight radiation; and

(12) FIG. 11 is a schematic diagram of an enhancement effect of the present invention to sunlight radiation absorption.

DETAILED DESCRIPTION

(13) The above described objectives, features and advantages of the present invention will become more apparent from the detailed descriptions.

(14) Many specific details are described in the following descriptions to facilitate full understanding of the present invention, but the present invention can be implemented in other ways different from the descriptions herein. Those skilled in the art can make similar variation without violating the spirit of the present invention, so the present invention is not limited by the specific embodiments as disclosed below.

(15) Secondly, the term “an embodiment” or “embodiments” herein refers to specific features, structures, or characteristic that may be included in at least one embodiment of the present invention. In the present disclosure, the term “in an embodiment” appearing in different places does not refer to the same embodiment nor individual or selective embodiment mutually exclusive with other embodiments.

(16) In the present invention, since a focusing way of concentrators in a double point focusing solar energy collection apparatus is achieved by using a circular Fresnel reflector and a rotating paraboloid reflector respectively, configurations of the circular Fresnel reflector and the rotating paraboloid reflector respectively used for severing as a primary concentrator 11 and a secondary concentrator 3 are specifically elaborated in the different embodiments, so as to better explain the embodiments and technical effects of the present apparatus.

(17) Referring to FIGS. 1 and 2, illustrating a double point focusing solar energy collection apparatus of a first embodiment of the present invention, in the present embodiment, a primary concentrator 11 is a rotating paraboloid reflector and a secondary concentrator 3 is a rotating paraboloid reflector, in which both of them have focus points.

(18) Specifically, the heat collector 1 includes the primary concentrator 11 and a heat collection tube 12. The primary concentrator 11 is a rotating paraboloid reflector. A rotating paraboloid reflector is used as the secondary concentrator 3, in which both the primary concentrator 11 and the secondary concentrator 3 have focus points.

(19) In the present embodiment, it should be noted that an opening of the primary concentrator 11 is greater than an opening of the secondary concentrator 3, thereby avoiding no light to be illuminated onto the primary concentrator 11. In a first-time incident light path, the primary concentrator 11 is downstream of the secondary concentrator 3. That is, the primary concentrator 11 is below the secondary concentrator 3. The “first-time incident light” mentioned above refers to the light that contacts with the primary concentrator 11 of the present apparatus at first under an illumination condition, which can be distinguished from light reflected by the primary concentrator 11 and the secondary concentrator 3. Because new incident light generates when the light is reflected, the “first-time incident light” path is introduced herein as the reference, so as to describe the locations of primary concentrator 11 and secondary concentrator 3 more clearly.

(20) The heat collection tube 12 is disposed between the primary concentrator 11 and the secondary concentrator 3, and the heat collection tube 12 is located at the focus points of the primary concentrator 11 and the secondary concentrator 3 simultaneously.

(21) It should be noted that the heat collection tube 12 carries an energy absorbing medium. The primary concentrator 11, the heat collection tube 12, and the secondary concentrator 3 are all supported by a bracket 2.

(22) It should be noted that the afore-mentioned “the carried energy absorbing medium” in the present embodiment can be water, glycol, heat conducting oil, or ionic liquid, but not limited to these several substances as listed.

(23) In practical implementation, referring to FIG. 1 which illustrates a light path of the double point focusing solar energy collection apparatus of the present invention, parallel light illuminates on the rotating paraboloid reflector of the primary concentrator 11 in the beginning. The light is focused by the rotating paraboloid reflector of the primary concentrator 11 to be gathered to the heat collection tube 12. The light passing through the heat collection tube 12 then reaches the secondary concentrator 3, and the secondary concentrator 3 converts the received light into parallel light. Thereafter, the parallel light is incident on the paraboloid reflector of the primary concentrator 11 and then is focused again until the light is completely absorbed.

(24) Preferably, in a case of the opening of the primary concentrator 11 is 400 mm and the opening of the paraboloid surface of the secondary concentrator 3 is 100 mm, a focal length of the primary concentrator 11 is 800 mm and a focal length of the secondary concentrator 3 is 200 mm. In the present embodiment, the heat collection tube 12 is a double tube preferably. An inner tube has an inner diameter of 16 mm and an outer diameter of 20 mm. An outer tube has an inner diameter of 35 mm and an outer diameter of 40 mm. In order to better explain the technical content and the technical effect resulted from the technical solution, the explanation is given through the different efficiency of absorbing the light by the heat collection tube 12.

(25) In a case of the heat collection tube 12 having an absorptivity of 0.8 to light that passes therethrough once, both the primary concentrator 11 and the secondary concentrator 3 have the reflectivities of 0.92 to the light. In a case that no secondary concentrator 3 is disposed and only the primary concentrator 11 is disposed, the efficiency of the apparatus is 73.6%. However, in the present embodiment, the secondary concentrator 3 is disposed, and the efficiency of the apparatus is 88.6%. Accordingly, by using the apparatus with the double focusing, the efficiency increases about 20% relative to that of the only single focusing.

(26) It should be noted that the afore-described sizes of the openings of the primary concentrator 11 and the secondary concentrator 3, as well as the corresponding focal lengths of those two and the size of the heat collection tube 12 are not limited to the values in the embodiment, which means the embodiment is provided only for the exemplary purpose. However, it needs to meet the requirements that the opening of the primary concentrator 11 is greater than the opening of the secondary concentrator 3, and the focal length of the primary concentrator 11 is greater than the focal length of the secondary concentrator 3. Moreover, in the first-time incident light path, the primary concentrator 11 is downstream of the secondary concentrator 3, and the secondary concentrator 3 is upstream of the primary concentrator 11. That is, the primary concentrator 11 is below the secondary concentrator 3. The “first-time incident light” mentioned above refers to light that contacts with the primary concentrator 11 of the present apparatus at first time under the illumination condition, which can be distinguished from light reflected by the primary concentrator 11 and the secondary concentrator 3. Because new incident light generates when the light is reflected, the “first-time incident light” path is introduced herein as the reference, so as to describe the locations of primary concentrator 11 and secondary concentrator 3 more clearly.

(27) Referring to FIGS. 3 and 4, illustrating a double point focusing solar energy collection apparatus of a second embodiment of the present invention, a difference between the present embodiment and the first embodiment is that the primary concentrator 11 is a rotating paraboloid reflector and the secondary concentrator 3 is a circular Fresnel reflector in the present embodiment, and both the primary concentrator 11 and the secondary concentrator 3 have focus points.

(28) A heat collection tube 12 is disposed between a primary concentrator 11 and a secondary concentrator 3, and the heat collection tube 12 is located at focus points of the primary concentrator 11 and the secondary concentrator 3 simultaneously.

(29) It should be noted that the heat collection tube 12 carries an energy absorbing medium. The primary concentrator 11, the heat collection tube 12, and the secondary concentrator 3 are all supported by a bracket 2.

(30) In practical implementation, referring to FIG. 3 which illustrates a light path of the double point focusing solar energy collection apparatus of the present invention, parallel light illuminates on the rotating paraboloid reflector of the primary concentrator 11 in the beginning. The light is focused by the rotating paraboloid reflector of the primary concentrator 11 to be gathered to the heat collection tube 12. The light passing through the heat collection tube 12 then reaches the secondary concentrator 3, and the secondary concentrator 3 converts the received light into parallel light. Thereafter, the parallel light is incident on the rotating paraboloid reflector of the primary concentrator 11 and then is focused again until the light is completely absorbed.

(31) Preferably, in a case of an opening of the primary concentrator 11 is 400 mm and an opening of the circular Fresnel reflector of the secondary concentrator 3 is 100 mm, a focal length of the primary concentrator 11 is 800 mm and a focal length of the secondary concentrator 3 is 200 mm. In the present embodiment, the heat collection tube 12 is a double tube preferably. An inner tube has an inner diameter of 16 mm and an outer diameter of 20 mm. An outer tube has an inner diameter of 35 mm and an outer diameter of 40 mm. In order to better explain the technical content and the technical effect resulted from the technical solution, the explanation is given through the different efficiency of absorbing the light by the heat collection tube 12.

(32) In a case of the heat collection tube 12 having an absorptivity of 0.5 to light that passes therethrough once, both the primary concentrator 11 and the secondary concentrator 3 have reflectivities of 0.92 to the light. In a case that no secondary concentrator 3 is disposed and only the primary concentrator 11 is disposed, the efficiency of the apparatus is 46%. However, in the present embodiment, the secondary concentrator 3 is disposed, and the efficiency of the apparatus is 79.8%. Accordingly, by using the apparatus with the double focusing, the efficiency increases about 73% relative to that of the only single focusing.

(33) It should be noted that the afore-described sizes of the openings of the primary concentrator 11 and the secondary concentrator 3, as well as the corresponding focal lengths of those two and the size of the heat collection tube 12 are not limited to the values in the embodiment, which means the embodiment is provided only for the exemplary purpose. However, it needs to meet the requirements that the opening of the primary concentrator 11 is greater than the opening of the secondary concentrator 3, and the focal length of the primary concentrator 11 is greater than the focal length of the secondary concentrator 3. Moreover, in the first-time incident light path, the primary concentrator 11 is downstream of the secondary concentrator 3, and the secondary concentrator 3 is upstream of the primary concentrator 11. That is, the primary concentrator 11 is below the secondary concentrator 3. The “first-time incident light” mentioned above refers to light that contacts with the primary concentrator 11 of the present apparatus at first time under the illumination condition, which can be distinguished from light reflected by the primary concentrator 11 and the secondary concentrator 3. Because new incident light generates when the light is reflected, the “first-time incident light” path is introduced herein as the reference, so as to describe the locations of primary concentrator 11 and secondary concentrator 3 more clearly.

(34) Referring to FIGS. 5 and 6, illustrating to a double point focusing solar energy collection apparatus of a third embodiment of the present invention, a difference between the present embodiment and the second embodiment is that the primary concentrator 11 is a circular Fresnel reflector and the secondary concentrator 3 is a rotating paraboloid reflector in the present embodiment, and both the primary concentrator 11 and the secondary concentrator 3 have focus points.

(35) Specifically, in the present embodiment, the apparatus includes a configuration including a heat collector 1, a secondary concentrator 3, and a bracket 2, in which the heat collector 1 and the secondary concentrator 3 are supported by the bracket 2.

(36) The heat collector 1 includes a primary concentrator 11 and a heat collection tube 12. A circular Fresnel reflector is used as the primary concentrator 11, and a rotating paraboloid reflector is used as the secondary concentrator 3. The circular Fresnel reflector has a focus point and rotating paraboloid reflector has focus point as well.

(37) The heat collection tube 12 is disposed between the primary concentrator 11 and the secondary concentrator 3, and the heat collection tube 12 is located at the focus points of the primary concentrator 11 and the secondary concentrator 3 simultaneously.

(38) It should be noted that the heat collection tube 12 carries an energy absorbing medium. The primary concentrator 11, the heat collection tube 12, and the secondary concentrator 3 are all supported by the bracket 2.

(39) In practical implementation, as shown in FIG. 5 which illustrates a light path of the double point focusing solar energy collection apparatus of the present invention, parallel light illuminates on the circular Fresnel reflector of the primary concentrator 11 in the beginning. The light is focused by the circular Fresnel reflector of the primary concentrator 11 to be gathered to the heat collection tube 12. The light passing through the heat collection tube 12 then reaches the secondary concentrator 3, and the secondary concentrator 3 converts the received light into parallel light. Thereafter, the parallel light is incident on the circular Fresnel reflector of the primary concentrator 11 and then is focused again until the light is completely absorbed.

(40) Preferably, in a case of an opening of the primary concentrator 11 is 600 mm and an opening of the paraboloid surface of the secondary concentrator 3 is 150 mm, the focal length of the primary concentrator 11 is 1200 mm and the focal length of the secondary concentrator 3 is 300 mm. In the present embodiment, the heat collection tube 12 is a double tube preferably. An inner tube has an inner diameter of 35 mm and an outer diameter of 30 mm. An outer tube has an inner diameter of 60 mm and an outer diameter of 50 mm. In order to better explain the technical content and the technical effect resulted from the technical solution, the explanation is given through the different efficiency of absorbing the light by the heat collection tube 12.

(41) In a case of the heat collection tube 12 having an absorptivity of 0.65 to light that passes therethrough once, both the primary concentrator 11 and the secondary concentrator 3 have the reflectivities of 0.9 to the light. In a case that no secondary concentrator 3 is disposed and only the primary concentrator 11 is disposed, the efficiency of the apparatus is 58.5%. However, in the present embodiment, the secondary concentrator 3 is disposed, and the efficiency of the apparatus is 81.6%. Accordingly, by using the apparatus with the double focusing, the efficiency increases about 40% relative to that of the only single focusing.

(42) It should be noted that the afore-described sizes of the openings of the primary concentrator 11 and the secondary concentrator 3, as well as the corresponding focal lengths of those two and the size of the heat collection tube 12 are not limited to the values in the embodiment, which means the embodiment is provided only for the exemplary purpose. However, it needs to meet the requirements that the opening of the primary concentrator 11 is greater than the opening of the secondary concentrator 3, and the focal length of the primary concentrator 11 is greater than the focal length of the secondary concentrator 3. Moreover, in the first-time incident light path, the primary concentrator 11 is downstream of the secondary concentrator 3, and the secondary concentrator 3 is upstream of the primary concentrator 11. That is, the primary concentrator 11 is below the secondary concentrator 3. The “first-time incident light” mentioned above refers to light that contacts with the primary concentrator 11 of the present apparatus at first time under the illumination condition, which can be distinguished from light reflected by the primary concentrator 11 and the secondary concentrator 3. Because new incident light generates when the light is reflected, the “first-time incident light” path is introduced herein as the reference, so as to describe the locations of primary concentrator 11 and secondary concentrator 3 more clearly.

(43) Referring to FIGS. 7 and 8, illustrating a double point focusing solar energy collection apparatus of a fourth embodiment of the present invention, a difference between the present embodiment and the third embodiment is that the primary concentrator 11 is a circular Fresnel reflector and the secondary concentrator 3 is a circular Fresnel reflector in the present embodiment, and both the circular Fresnel reflectors have focus points.

(44) Specifically, in the present embodiment, the apparatus includes a configuration including a heat collector 1, a secondary concentrator 3, and a bracket 2, in which the heat collector 1 and the secondary concentrator 3 are supported by the bracket 2.

(45) Specifically, the heat collector 1 includes a primary concentrator 11 and a heat collection tube 12. The primary concentrator 11 is a circular Fresnel reflector and the secondary concentrator 3 is a circular Fresnel reflector, in which both the circular Fresnel reflectors have focus points.

(46) The heat collection tube 12 is disposed between the primary concentrator 11 and the secondary concentrator 3, and the heat collection tube 12 is located at the focus points of the primary concentrator 11 and the secondary concentrator 3 simultaneously.

(47) It should be noted that the heat collection tube 12 carries an energy absorbing medium. The primary concentrator 11, the heat collection tube 12, and the secondary concentrator 3 are all supported by the bracket 2.

(48) In practical implementation, as shown in FIG. 7 which illustrates a light path of the double point focusing solar energy collection apparatus of the present invention, parallel light illuminates on the circular Fresnel reflector of the primary concentrator 11 in the beginning. The light is focused by the circular Fresnel reflector of the primary concentrator 11 to be gathered to the heat collection tube 12. The light passing through the heat collection tube 12 then reaches the secondary concentrator 3, and the secondary concentrator 3 converts the received light into parallel light. Thereafter, the parallel light is incident on the circular Fresnel reflector of the primary concentrator 11 and then is focused again until the light is completely absorbed.

(49) Preferably, in a case of an opening of the primary concentrator 11 is 600 mm and an opening of the circular Fresnel reflector of the secondary concentrator 3 is 150 mm, the focal length of the primary concentrator 11 is 1200 mm and the focal length of the secondary concentrator 3 is 300 mm. In the present embodiment, the heat collection tube 12 is a double tube preferably. An inner tube has an inner diameter of 35 mm and an outer diameter of 30 mm. An outer tube has an inner diameter of 60 mm and an outer diameter of 50 mm. In order to better explain the technical content and the technical effect resulted from the technical solution, the explanation is given through the different efficiency of absorbing the light by the heat collection tube 12.

(50) In a case of the heat collection tube 12 having an absorptivity of 0.65 to light that passes therethrough once, both the primary concentrator 11 and the secondary concentrator 3 have the reflectivities of 0.92 to the light. In a case that no secondary concentrator 3 is disposed and only the primary concentrator 11 is disposed, the efficiency of the apparatus is 59.8%. However, in the present embodiment, the secondary concentrator 3 is disposed, and the efficiency of the apparatus is 85%. Accordingly, by using the apparatus with the double focusing, the efficiency increases about 42% relative to that of the only single focusing.

(51) It should be noted that the afore-described sizes of the openings of the primary concentrator 11 and the secondary concentrator 3, as well as the corresponding focal lengths of those two, and the size of the heat collection tube 12 are not limited to the values in the embodiment, which means the embodiment is provided only for the exemplary purpose. However, it needs to meet the requirements that the opening of the primary concentrator 11 is greater than the opening of the secondary concentrator 3, and the focal length of the primary concentrator 11 is greater than the focal length of the secondary concentrator 3. Moreover, in the first-time incident light path, the primary concentrator 11 is downstream of the secondary concentrator 3, and the secondary concentrator 3 is upstream of the primary concentrator 11. That is, the primary concentrator 11 is below the secondary concentrator 3. The “first-time incident light” mentioned above refers to light that contacts with the primary concentrator 11 of the present apparatus at first time under the illumination condition, which can be distinguished from light reflected by the primary concentrator 11 and the secondary concentrator 3. Because new incident light generates when the light is reflected, the “first-time incident light” path is introduced herein as the reference, so as to describe the locations of primary concentrator 11 and secondary concentrator 3 more clearly.

(52) For a double point focusing solar energy collection apparatus in accordance with a fifth embodiment of the present invention, a difference between the fifth embodiment and the fourth embodiment is that the apparatus further includes a solar energy tracking device 4. The solar energy tracking device 4 is mainly configured to track sunlight, such that the solar energy collection apparatus is always in an optimal photothermal conversion state. The solar energy tracking device 4 can be realized by any existing solar energy tracking device, as long as it can track the sunlight.

(53) Preferably, the heat collection tube 12 is a straight tube, which may be ellipsoidal, spherical or square. That is, the heat collection tube 12 has a cross section in a circle, an ellipse, or a flat rectangle. The cross section of the heat collection tube 12 is spherical, and the collection tube 12 has a pipeline carrying an energy absorbing medium, which includes a feeding tube 123 and a discharging tube 124.

(54) It should be noted that the pipeline used herein means: first, it can be configured to carry the energy absorbing medium; and second, it can be configured to support the heat collection tube 12 such that the heat collection tube 12 can be located on the focus points of the primary concentrator 11 and the secondary concentrator 3.

(55) Referring to FIG. 9 which refers to a double point focusing solar energy collection apparatus of a sixth embodiment of the present invention, a difference between the present embodiment and the fifth embodiment is that the heat collection tube 12 is a vacuum tube, which includes an outer tube 121 and an inner tube 122. An interval between the outer tube 121 and the inner tube 122 is vacuum, and the inner tube 122 carries an energy absorbing medium.

(56) In the heat collection tube 12, a feeding pipe 123 and a discharging pipe 124 pass through the outer pipe 121 and the inner pipe 122 in sequence, respectively, and reach the inside of the inner pipe 122.

(57) Preferably, an included angle between the feeding pipe 123 and the discharging pipe 124 is in a range from 0° to 180°. In the present embodiment, the included angle is preferably 0°. In practical applications, according to the practical operation, the included angle between the feeding pipe 123 and the discharging pipe 124 can be selected from 30°, 45°, 60°, 90°, 120°, 135°, or 150°.

(58) Preferably, both the outer tube 121 and the inner tube 122 are transparent.

(59) Preferably, the outer tube 121 is made of glass, polymethyl methacrylate (PMMA), or polycarbonate (PC).

(60) Preferably, the inner tube 122 is made of glass, PMMA, or PC.

(61) The following are analyses of the reflection effect of the double point focusing solar energy collection apparatus.

(62) In the solar energy heat collector 1 of the direct absorption type, it is assumed that a heat medium in a heat collection tube has an absorptivity α to solar radiation, that a reflection surface has a reflectivity β to solar radiation, and that the heat collector 1 has a comprehensive absorptivity η to solar radiation.

(63) With the technical solution of the present invention, the data are provided as follows.

(64) TABLE-US-00001 TABLE 1 a comprehensive an upper limit a lower limit of absorptivity of of a comprehensive a comprehensive an a heat collector absorptivity of absorptivity of enhancement an (without any a heat collector a heat collector ratio of a absorptivity a reflectivity secondary (with a secondary (with a secondary secondary of a heat of a reflection reflection reflection reflection reflection medium surface surface) surface) surface) surface α β η η′ η″ r 0.1 0.92 0.09 0.50 0.47 5.43~5.14 0.2 0.18 0.66 0.63 3.56~3.41 0.3 0.28 0.74 0.71 2.66~2.58 0.4 0.37 0.79 0.77 2.13~2.08 0.5 0.46 0.82 0.81 1.78~1.75 0.6 0.55 0.85 0.84 1.54~1.52 0.7 0.64 0.87 0.86 1.35~1.34 0.8 0.74 0.89 0.89 1.21~1.20 0.9 0.83 0.91 0.90 1.09~1.09

(65) TABLE-US-00002 TABLE 2 a comprehensive an upper limit a lower limit of absorptivity of of a comprehensive a comprehensive an a heat collector absorptivity of absorptivity of enhancement an (without any a heat collector a heat collector ratio of a absorptivity a reflectivity secondary (with a secondary (with a secondary secondary of a heat of a reflection reflection reflection reflection reflection medium surface surface) surface) surface) surface α β η η′ η″ r 0.1 0.85 0.09 0.32 0.29 3.77~3.45 0.2 0.17 0.48 0.45 2.81~2.62 0.3 0.26 0.57 0.55 2.25~2.14 0.4 0.34 0.64 0.62 1.88~1.82 0.5 0.43 0.69 0.67 1.63~1.59 0.6 0.51 0.73 0.72 1.44~1.42 0.7 0.60 0.77 0.76 1.29~1.28 0.8 0.68 0.80 0.80 1.17~1.17 0.9 0.77 0.83 0.82 1.08~1.08

(66) TABLE-US-00003 TABLE 3 a comprehensive an upper limit a lower limit of absorptivity of of a comprehensive a comprehensive an a heat collector absorptivity of absorptivity of enhancement an (without any a heat collector a heat collector ratio of a absorptivity a reflectivity secondary (with a secondary (with a secondary secondary of a heat of a reflection reflection reflection reflection reflection medium surface surface) surface) surface) surface α β η η′ η″ r 0.1 0.8 0.08 0.24 0.22 3.06~2.76 0.2 0.16 0.39 0.36 2.42~2.24 0.3 0.24 0.48 0.46 2.02~1.90 0.4 0.32 0.56 0.53 1.74~1.67 0.5 0.40 0.61 0.60 1.53~1.49 0.6 0.48 0.66 0.65 1.38~1.35 0.7 0.56 0.70 0.69 1.25~1.24 0.8 0.64 0.74 0.73 1.15~1.15 0.9 0.72 0.77 0.77 1.07~1.07

(67) Referring to FIG. 10, what is shown in FIG. 10 reflects that the comprehensive absorptivity of the heat collector 1 to the solar radiation can be improved by adopting the design of the secondary reflection surface.

(68) As shown in FIG. 11, by adopting the design of the secondary reflection surface, the comprehensive absorptivity of the heat collector 1 of the direct absorption to the solar radiation can be improved, which especially occurs under the condition of when the reflection surface has a higher reflectivity and the heat medium has a lower single absorptivity to the solar radiation. In cases of the reflection surface having the reflectivity of 0.92 and the respective heat mediums having the single absorptivities of 0.3 and 0.5, the enhancement ratios of the respective secondary reflection surfaces to the comprehensive absorptivity of the heat collector 1 can achieve 2.66˜2.58 and 1.78˜1.75, which means effective improvement to the photothermal conversion of the apparatus to the solar radiation is achieved.

(69) It should be noted that the above embodiments are only used to explain the technical solution of the present invention, not the limitation. Although the present invention is described in details with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention can be modified or replaced equally without departing from the spirit and scope of the technical solution of the present invention, which should be covered in the right of the present invention.