RU2121632C1 - Device for concentration of solar radiation - Google Patents

Abstract

FIELD: solar-energy engineering. SUBSTANCE: device has frame with set of concentrating lenses in whose focuses ends of radiation inlet s of flexible light conduits are located; ends of radiation outlet are located on fixed surface and are directed towards energy consumer located outside the frame. Fixed surface is provided with additional collimation lenses in whose focuses ends of radiation outlets of light conduits are located; ends of radiation inlets of light conduits 5 are located on movable portion of tracking mechanism whose fixed part is mounted on frame with set of concentrating lenses having spherical concentrating optical surfaces. EFFECT: reduced length of light conduits transmitting radiation to focuses of collimation lenses converting sunlight to parallel light beams directed to consumer at all times, thus decreasing losses of light. 5 cl, 2 dwg

Description

 The invention relates to the field of solar technology, in particular for concentrating solar radiation installations with energy converters for generating heat and electricity.

 A device is known that concentrates solar radiation, consisting of lenses mounted on a sun-oriented frame, reflective cones are installed at the lens foci, the light guides are mounted at their output, transmitting solar radiation concentrated by lenses to an energy consumer mounted on said frame (Application 32111339, Germany, application 27.03.82, N P32211339.0, publ. 09/29/83, MKI G 02 B 27/14).

 The disadvantages of the known solutions are increased light losses due to the presence of reflecting cones in the optical circuit and the inconvenient location of the radiation consumer on an orientable frame, which does not allow combining radiation from several frames on one consumer to increase its power.

 The closest in technical essence to the present invention is a device (prototype) concentrating solar radiation, consisting of a set of concentrating lenses mounted on a frame associated with a tracking mechanism, which has a movable and fixed part, and flexible optical fibers, the ends of the radiation input of which are installed in the foci of the concentrating lenses, and the ends of the radiation output are mounted on a fixed surface and directed towards the consumer of radiation (US Pat. N 4512335, USA, publ. 23.04.85, prior. 03.04.82; N 55668, Japan, M And F 24 J 3/02, NKI 126/440).

 A disadvantage of the known solution is the increased light loss in the transmission system of the radiation along the optical fibers due to their long lengths, because the concentrating lenses are located on a frame oriented beyond the position of the Sun in the sky, and the radiation consumer is stationary and extended outside the frame, so the length of the optical fibers must be such that they can be laid along the entire frame with a margin to compensate for the length when the frame is rotated. Long fiber lengths cause significant light loss, so for a length of 1 m light loss can be approximately 20% / 1 /. A decrease in optical efficiency leads to a decrease in the generated energy.

 The aim of this invention is to increase optical efficiency and energy production.

 The specified technical result is achieved by the fact that the device further comprises collimation lenses mounted on a fixed surface, in the front foci of which the ends of the radiation exit from the flexible optical fibers are installed, the ends of the radiation input into the optical fibers are mounted on the moving part of the tracking mechanism, the fixed part of which is mounted on a fixed frame with concentrating lenses having spherical concentric optical surfaces. Spherical optical surfaces can form shells of a material with a higher refractive index than the refractive index of the core material of the concentrating lenses. The plane of a fixed frame with a set of concentrating lenses can be set at an angle of latitude to the horizontal plane. The moving part of the tracking mechanism can be made in the form of two boards parallel to each other, between which the ends of the optical fibers with the ends of the radiation input are articulated, the boards are pivotally mounted on a fixed frame with the ability to swing around the centers of the spherical surfaces of the concentrating lenses. A fixed plane with collimation lenses can be located horizontally and the energy consumer is made in the form of a concentrator with a radiation converter installed in its focus.

 The positive effect of increasing the optical efficiency and energy production is achieved by the fact that in the proposed device the solar radiation is concentrated by lenses into relatively short flexible fibers, which transport the radiation into the focuses of collimation lenses, which turn sunlight into constantly parallel light rays directed at the consumer, i.e. . radiation over a long distance is transmitted not through optical fibers, as in the prototype, but through air, which significantly reduces light losses. The transmission of radiation through air is much more efficient than transmission through optical fibers in which the beam makes zigzag motions in dense optical material. Another advantage of the proposed device is that the frame with the concentrating lenses is stationary, all optical and mechanical parts are located inside the enclosed volume, so that the wind mechanism does not act on the tracking mechanism and less energy is required for its drive than for an open frame drive in the case of prototype. Since the frame with concentrating lenses in the proposed device is stationary, the lenses should concentrate solar radiation in a large angular range when moving the Sun from morning to evening, i.e. have a large field of view. Lens having spherical concentric optical surfaces that concentrate solar radiation at almost any position of the Sun in the sky due to its axisymmetric structure corresponds to this quality.

 Spherical optical surfaces can form shells from a material with a higher refractive index than the refractive index of the core material of the concentrating lenses, which reduces the negative effect of spherical aberration on the scattering spot at the focus of the concentrating lenses, improves the conditions for radiation to enter the optical fibers, and reduces light losses in them.

 The plane of the fixed frame with a set of concentrating lenses can be set at an angle of latitude to the horizontal plane, which reduces the mutual shadowing by the concentrating lenses of each other at a low position of the Sun, increases the working time during the day.

 The movable part of the tracking mechanism can be made in the form of two boards parallel to each other, between which the ends of the optical fibers with the ends of the radiation input are articulated, the boards are pivotally mounted on a fixed frame with the ability to swing around the centers of the spherical surfaces of the concentrating lenses, which ensures reliable installation of the ends of the radiation input in optical fibers when tracking the spatial position of the focusing lens focuses when moving the Sun across the sky and installing the ends perpendicular to the axis of arrival a wide conical beam, which creates the best conditions for radiation to enter the optical fibers.

 The fixed plane with collimation lenses can be located horizontally and the energy consumer is made in the form of a concentrator with a radiation converter installed in its focus, which allows combining light fluxes from many frames with concentrating lenses on one radiation consumer and increasing the power of the entire device.

 The proposed device is shown in FIG. 1 and FIG. 2.

 In FIG. 1 shows a general view of one frame with concentrating lenses and a pattern of the course of light rays.

 In FIG. Figure 2 shows a general view of a concentrating system in which radiation from several frames with lenses is summarized by a concentrator on a radiation consumer installed in its focus.

A device concentrating solar radiation, consisting of a set of concentrating lenses 1 mounted on a frame 2, connected with a tracking mechanism, which has a movable 3 and fixed 4 parts, and flexible optical fibers 5, the ends 6 of the radiation input of which are installed in the foci F ₁ , F ₂ , F ₃ ... of the concentrating lenses 1, and the ends of the radiation output are mounted on a fixed surface 8 and directed towards the consumer of radiation 9. The device further comprises collimation lenses 10 mounted on a fixed surface 8, in front foci F ₁ , F ₂ , F ₃ ... of which the ends 7 of the radiation exit from the flexible optical fibers 5 are installed, the ends 6 of the radiation input into the optical fibers 5 are mounted on the movable part 3 of the mechanism tracking, the fixed part 4 of which is mounted on a fixed frame 2 with a set of concentrating lenses 1 having spherical concentric optical surfaces 11 and 12. Spherical optical surfaces 11 and 12 can form shells 14 of material with pain their refractive index than the refractive index of the core material 15 concentrating lens 1. The plane 13 of the fixed frame 2 with a set of concentrating lens 1 can be set at an angle φ latitude to the horizontal plane. The movable part 3 of the tracking mechanism can be made in the form of two parallel boards 15 and 16, between which the ends 17 of the optical fibers 5 are articulated with the ends 6 of the radiation input, the boards 15 and 16 are pivotally mounted on a fixed frame 2 with the possibility of swinging around spherical centers 20 surfaces 11 and 12 of the concentrating lenses 1. A fixed plane 8 with collimation lenses 10 can be located horizontally and the energy consumer 9 can be made in the form of a concentrator 21 with a radiation converter 22 installed in it focus F _to .

Additionally, in FIG. 1 is shown:
solar radiation coming to a solar installation;
view G, enlarged showing the hinged fastening of the ends 17 of the optical fibers 5 between the boards 15 and 16 with a spring 23, providing compensation for the length of the optical fiber 5 when changing the distance between the boards.

Additionally, in FIG. 2 shows:
- the diameter H of the hub 21 with the Converter 22 in focus F _to ;
view Q, showing an enlarged fragment of the frame 2 with concentrating lenses 1 when the fixed plane 8 is in a horizontal position;
the length L ^{1 of the} working surface of the concentrating lenses on one frame 2;
total length L of the solar installation;
angle of inclination γ of parallel sunlight from collimation lenses 10.

The device operates as follows: solar radiation (shown by arrows, Fig. 1) arrives at a set of concentrating lenses 1 mounted on a fixed frame 2, is collected by each lens 1 into foci F ₁ , F ₂ , F ₃ .... The spatial position of these foci changes when the position of the Sun in the sky changes, these changes are monitored by the moving part 3 of the tracking mechanism, which is driven by tracking sensors and motors with gears not shown in the drawings, while the ends 6 of the optical fibers 5 are set in foci F ₁ , F ₂ , F ₃ ... so that the axes of the conical light beams from the concentrating lenses 1 are installed along the axes of the ends 17 of the optical fibers 5, which provides the best conditions for light to enter the optical fiber. The optical fiber 5 transports solar radiation to the ends 7 of the optical fibers 5 that are motionlessly located on the surface 8, while the ends 7 are aligned with the front foci F $\genfrac{}{}{0ex}{}{\text{1}}{\text{1}}$ , F $\genfrac{}{}{0ex}{}{\text{1}}{\text{2}}$ , F $\genfrac{}{}{0ex}{}{\text{1}}{\text{3}}$ ... collimation lenses 10, the optical axis of which are aimed at the consumer of radiation 9. Collimation lenses 10 turn the solar radiation into parallel rays of light, constantly directed at the consumer of radiation 9. Thus, solar radiation passes through the optical fibers 5 only a short distance from the ends 6 of the input radiation to the ends 7 of the radiation output, and the rest of the distance to the radiation consumer, the light passes through the air in the form of separate light beams.

To simplify the process of tracking the spatial positions of the foci F ₁ , F ₂ , F ₃ ... the concentrating lenses 1 are made with spherical concentric surfaces 11 and 12. Such lenses have the same focal length for any position of the Sun in the sky, which is easily tracked by simply turning the levers 18 and 19 around the fixed parts of the tracking mechanism 4 mounted on a plane 13 on which the centers 20 of the concentrating lenses 1 are located. The turns of the levers 18 and 19 displace the boards 15 and 16 relative to each other and set the ends 17 optical fibers 5 along the axes of the conical beams from the lenses 1. To compensate for the lengths of the ends of the 17 optical fibers when changing the distance between the boards 15 and 16, springs 23 are installed on each optical fiber. To improve the conditions for introducing radiation into the optical fibers 5, the concentrating lenses 1 have shells 14 bounded by spherical concentric surfaces 11 and 12 of a material with a refractive index greater than the material of the core 15, which reduces the scattering spot due to reduced spherical aberrations.

 The plane 13 of the fixed frame 2 can be located at an angle φ to a horizontal surface equal to the geographical latitude of the area where the solar installation was built. This arrangement of the plane 13 increases the number of hours of operation of the concentrating system during daylight hours.

To increase the power of installations using the proposed concentric device, the fixed surface 8 can be positioned horizontally (Fig. 2), then separate frames 2 with a set of concentrating lenses 1 can send parallel beams from collimation lenses 10 to a common radiation consumer, made in the form of a 21 s concentrator a radiation transducer 22 mounted in its focus F _to . Moreover, within the same frame, the length of flexible optical fibers 5 will be different (Fig. 2, view Q), but significantly less than the length L ^{1 of the} entire installation L. In this case, the surfaces 8 of different frames 2 create a common flat overlap on which collimation lens 10, guides the parallel beams at an angle γ to the horizontal surface on hub 21, a focus F of which is mounted _{to a} radiation transducer 22. the use of the concentrator 21 can significantly raise the concentration of radiation at the converter 22, thereby to raise the efficiency of the transformations azovaniya, increase energy production. As a radiation converter 22, pipes with a coolant can be used to ensure the operation of steam or gas power machines, as well as photoelectric converters mounted on cooling radiators to generate electricity and heat at the same time.

 An example of a specific implementation of the devices.

The solar installation is located at the geographic latitude φ = 45 ^° (Rostov Region). The diameter of the concentrating lenses is 30 mm, the focal length is 40.4 mm, the distance from the plane 13 to the surface 8 is 200 mm, the length of the optical fibers 5, taking into account the excess length, to ensure the free movement of the ends 17 of the optical fibers together with the moving part 3 of the tracking mechanism, is 300 mm.

The optical efficiency of the system (light transmission coefficient) is calculated by the formula
τ = τ ₁ • τ ₂ • τ ₃ , (1)
Where
τ ₁ - optical efficiency of concentrating lenses;
τ ₂ - optical efficiency of the optical fibers;
τ ₃ - optical efficiency of collimation lenses.

The optical efficiency of lenses and optical fibers is determined by the formula (2):
τ _1,2,3 = τ $\genfrac{}{}{0ex}{}{\text{2}}{\text{F}}$ • τ $\genfrac{}{}{0ex}{}{\text{1}}{\text{A}}$ , (2)
Where
τ _f - light transmission taking into account Fresnel losses at the entrance and exit of the optical part;
τ _A is the absorption of light per unit length of the optical path in the material of the part;
l is the average length of the optical path in the part.

For concentrating lenses, we accept the following parameters:
τ _Ф = 0.95, τ _A = 0.99, l = 2.5 cm. Then the light transmission of the concentrating lenses will be
τ ₁ = 0.95 ² • 0.99 ^2.5 = 0.88.

For the optical fibers of FIG. 1 parameters in (2) take the following values:
τ _Ф = 0.98 taking into account the enlightenment of the ends of the optical fibers; τ _A = 0.8 per meter of length (1) in the fiber material; l = 0.2 m. Thus, the light transmission in a fiber with a length of 0.2 m will be
τ ₂ = 0.98 ² • 0.8 ^0.2 = 0.92.
The light transmission of collimation lenses at values of τ _Ф = 0.96, τ _A = 0.99, l = 0.5 cm gives the following values: τ ₃ = 0.96 ² • 0.99 ^0.5 = 0.915.

 Total optical efficiency of FIG. 1 is equal to: τ = 0.88 • 0.92 • 0.915 = 0.74.

We determine the optical efficiency of the system of FIG. 2 with the following parameters: L ¹ = 0.5 m, maximum length of optical fibers 0.5 m, minimum length of optical fibers 0.2 m, average length of optical fibers l _CP = 0.35 m. The light transmission of the system in this case is calculated by the formula
τ ¹ = τ • τ ₁ • τ ₂ • τ ₃ • τ _k ,
Where
τ _to - light transmission of the concentrator;
τ _k = 0.85.

The parameters in (3) have values: τ ₁ = 0.88, τ ₂ = 0.89, τ ₃ = 0.915. The total light transmission of FIG. 2 will be: τ ¹ = 0.88 • 0.92 • 0.915 • 0.85 = 0.63.

 Let's compare the devices that concentrate solar radiation according to the proposed option (Fig. 2) and the prototype.

We take equal the working surfaces of the concentrating lenses in the compared variants. We take the length L = 10 m, the width of the frames in the compared options is assumed to be the same. The maximum length in the variant of the prototype, taking into account the work in direct sunlight, perpendicular to the plane 13, will be
L _fr = Lcosφ = 10 • 0.707 = 7.1 m.
We take the average length of the optical fibers for the prototype version 4 m. The light transmission of the optical fiber 4 m long according to (2) will be τ _{2 pt} = 0.98 ² • 0.8 ⁴ = 0.39. Assuming that the transmittance of the concentrating lenses is the same, τ ₁ = 0.88, the total optical efficiency for the prototype will be τ _pt = τ ₁ • τ _{2 pt} = 0.88 • 0.39 = 0.34.

 Thus, in the proposed embodiment, the optical efficiency is 0.63 instead of 0.34 in the prototype embodiment. Since the generated energy depends on the efficiency of the system, then, under equal conditions, the proposed system will generate 1.6 times more energy than the prototype system.

 The cost of the proposed device will be lower than the cost of the prototype system, because the length of the optical fibers is significantly reduced, the tracking mechanism unloaded from the effects of wind loads will be cheaper.

Claims (5)

 1. A device concentrating solar radiation, consisting of a set of concentrating lenses mounted on a frame associated with a tracking mechanism, which has a movable and fixed part, and flexible optical fibers, the ends of the radiation input of which are installed in the foci of the concentrating lenses, and the ends of the radiation output are mounted on a fixed surface and directed towards the consumer of radiation, characterized in that, in order to increase optical efficiency and generate energy, the device further comprises mounted on a fixed th surface collimation lens, in front of which are installed foci radiation exit ends of the flexible fibers, the ends of the radiation input to the optical fibers are mounted on the movable part of the tracking mechanism, the fixed part is installed on the fixed frame with a set of concentrating lenses having concentric spherical optical surfaces.  2. The device according to claim 1, characterized in that the spherical optical surfaces form shells of a material with a higher refractive index than the refractive index of the core material of the concentrating lenses.  3. The device according to claim 1, characterized in that the plane of the fixed frame with a set of concentrating lenses is installed at an angle of latitude to the horizontal plane.  4. The device according to claim 1, characterized in that the movable part of the tracking mechanism is made in the form of two boards parallel to each other, between which the ends of the optical fibers with the ends of the radiation input are articulated, the boards are pivotally mounted on a fixed frame with the ability to swing around the centers of the concentric spherical surfaces lenses.  5. The device according to claim 1, characterized in that the fixed plane with collimation lenses is located horizontally and the energy consumer is made in the form of a concentrator with a radiation converter installed in its focus.

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