RU2659319C1 - Fixed solar radiation concentrator with optical method of alignment - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: fixed solar radiation concentrator implements the alignment of a light flux on the input end of the focusing cone due to the narrowing of the light flux in two perpendicular planes and contains three focusing flat linear echelon lenses, while the second echelon lens lies at the focus of the first short-focus linear echelon lens and the third linear short-focus echelon lens, in the focus of which the focusing cone is located, is located behind the second echelon lens. Second echelon lens consists of strip long-focus linear echelon lenses shifted step by step in relation to each other in the longitudinal direction, the axis of symmetry of the strip lenses are rotated 90 degrees relative to the symmetry axes of the first and third lenses. Focal lengths of the second lens and the optical system of the first and third lenses coincide.

EFFECT: increase in the density of the output light flux, reduction of the weight of the concentrator, reduction of the wind load, increase in the concentrator's working time during the day, service life and reliability, regardless of electricity.

1 cl, 7 dwg

Description

The invention relates to the field of solar energy or solar fiber optic lighting devices, namely, devices that increase the concentration of solar radiation.

It is known that environmentally friendly solar light energy can be converted into electricity using solar panels or photoelectric converters (PECs). To increase the efficiency of the solar cells, lens concentrators are used based on spherical or linear Fresnel lenses (for example, RF 2353865 or Journal of Technical Physics, 2016, Volume 86, Issue 12, pp. 87-94). However, when the sun moves around the sky, such concentrators shift the focal spot of concentrated light. Therefore, they need to be constantly directed to the sun, and they are used only in conjunction with mechanical tracking systems. Mechanical tracking systems are complex, bulky, expensive and unreliable devices, usually based on the use of an electric drive, requiring power supply, lubricating the gearboxes, and sealing them to protect them from rain and dust.

More recently, hybrid fiber-optic devices have been used to illuminate rooms with natural light. The hub in these devices focuses the sun's rays into the input end of the fiber optic cable, through which the light is then transported to the illuminated room. For the concentration of light in solar fiber optic lighting devices, the Cassegrain system based on paraboloidal mirrors is most often used (Energies 2015, 8, 7185-7201). These devices also contain a positioning system that rotates the mirrors throughout the day, constantly directing them to the sun, as a well-known sunflower does. The presence of an electric drive system for tracking the sun (patent RF 2579169) requires external power supplied from the network or obtained from the conversion of light energy into electrical energy. Such devices are complex and expensive. The cost of such systems reaches 16 thousand dollars, and their installation ranges from 500 to 2000 dollars. The high price, the complexity of maintenance, the need for external power supply, low power, due to the limited area of the hub, the large weight of the hub and significant wind load are the main disadvantages of these systems. Nevertheless, despite impressive prices, experts predict that by 2020 it is planned to sell more than 5,000 hybrid optical fiber lighting systems in the United States.

Known mechanical positioning systems that operate on the effect of thermal expansion of materials (RF 2468288). They are simpler than electric drive systems, however, the effect of thermal expansion of materials provides a small angle of rotation of the concentrator and does not allow tracking the sun throughout the daylight hours. In addition, such a hub is very sensitive to wind and other external mechanical influences.

Other simple constructions of fixed concentrators are also known, for example, devices proposed in patents: United States Patent 3,780,722 or US 2012/0154941 A1. To simplify, in such concentrators only focons or special prisms are used that form matrix surfaces for collecting light and its further transportation through optical channels. However, such concentrators have a large mass and low efficiency. They cannot provide a high light flux density in a fiber optic bundle due to the limited numerical aperture of the focons. With a large input and small output areas of the ends of the focons with each subsequent reflection from its walls, the light angle increases the angle of reflection. When this angle reaches 90 degrees, the advancement of the rays along the focal plane stops, then the rays turn around in the opposite direction and exit through the input end. Therefore, such hubs do not allow the transmission of large light fluxes through a thin optical fiber.

The closest analogue of the claimed device is a fixed hub (collector), in which to increase the density of the light flux, a narrowing lens is used in conjunction with the focon (RF patent for PM No. 102747). However, such a hub has a small azimuth angle, i.e. provides short tracking time for the sun during the day. It only works well in the afternoon. In a linear lens, the focal light spot is not a point, but a straight line. Therefore, such a concentrator well narrows the luminous flux in only one vertical plane and concentrates much worse in the plane of the daytime movement of the sun across the sky. Bending the lens or changing its thickness in the plane of symmetry does not have a large effect to reduce the loss of light energy from poor-quality focusing of light on the input end of the focon, or PEC. When the sun moves across the sky, the focal spot of light will be elongated in the shape of a rhombus and it will still shift throughout the day along the focal line. In this case, the input end face of the focon must be made in the form of an ellipse-elongated along the focal line, or use a flat focal band. Both that and another leads to an increase in the numerical aperture, increases the cross-sectional area of the optical fiber or reduces the density of the light flux at the receiving element of the photomultiplier, and therefore reduces its efficiency. Such concentrators also have a large mass and a large consumption of material in the manufacture of lenses.

The technical result of the claimed invention is a significant increase in the density of the output light flux, a decrease in the cost of a fixed hub, a decrease in the mass of the hub and materials for its manufacture. In addition, a reduction in wind load, an increase in the operating time of the concentrator during the day, an increase in the service life and reliability with its complete independence from electricity are achieved.

SUMMARY OF THE INVENTION

The technical result is achieved by the fact that in the inventive fixed hub, an optical method is applied to direct the light flux at the input end of the focon (Fig. 1). This method is based on the sequential narrowing of the light flux in two perpendicular planes using thin linear Fresnel lenses. The flow of sunlight first narrows in the vertical plane using a special short-focus Fresnel linear lens bent along the axis of symmetry (1). The focus of this lens is a series of strip asymmetric long-focus Fresnel lenses (2). They narrow the luminous flux in the perpendicular plane (the plane of the daily movement of the sun) to the size of the input end of the focon or focal bundle. These strip asymmetric Fresnel lenses are shifted in the longitudinal direction relative to each other by a small step equal to the size of the input end of the focon. This shift of the strip lenses forms a ladder-like structure (Fig. 2). After passing through the strip lens (2) located in the focus of the lens (1), the light flux again expands in the vertical (seasonal) plane (Fig. 3). Further, after a short-focus linear Fresnel lens (3), the luminous flux again narrows in the vertical (seasonal) plane to the dimensions of the input end of the focon (4). Lens (3) has a focal length slightly smaller than that of lens (1). When using the same lenses (1) and (3), the light rays would again be parallel. In the diurnal plane, the luminous flux gradually narrows due to the long-focus strip Fresnel lenses (2). Thus, both the narrowing of the luminous flux and its pointing to the input end face of the focon (4) in this concentrator are carried out optically, rather than mechanically. This greatly increases its reliability and service life, reduces weight and cost.

Experimental studies of the physical model of the concentrator (Figure 5) showed good results. The experiment was conducted in Moscow, in clear sunny weather, in the month of July, at noon. As the 1st and 3rd lenses, we used curved linear Fresnel lenses made of silicone rubber (refractive index n = 1.4), glued to polycarbonate plates. Lenses (1) and (3) performed narrowing in a vertical plane perpendicular to the daily movement of the sun (lens size 25 × 200 mm). The strip 2nd lens narrowed the luminous flux in the plane of the daily movement of the sun. It was composed of 20 strips with a size of 2 × 150 mm glued to a polycarbonate plate. The size and shift of the focal light spot did not exceed 7 mm for 3 hours. This shift can be reduced to 3 mm, if the width of the strips of the 2nd lens is reduced to 1 mm, while the number of strips will increase to 40 pieces, and the step of the "ladder" will be reduced by 2 times.

Experimental studies of the computer model (Fig. 6) in the Trace Pro program also showed good results. More than 85% of the input rays reached the output end of the focon and less than 15% of the rays were lost, mainly due to the effect of optical aberration. These results can be further improved by optimizing the lens parameters.

In FIG. Figure 7 shows a photograph of a color picture (canvas, oil 20 × 30 cm), which was illuminated in an absolutely dark room with a concentrator with an entrance area of only 0.005 m ² (or 50 cm ² ) of a scattering lens (9) and polymer fiber optic fiber (10) with 1 mm in diameter and 10 m long. Through the optical fiber (10), sunlight was transported into a dark room and there it was scattered by a lens (9).

DESCRIPTION OF DRAWINGS

In FIG. 1 shows a domed fixed hub with an optical method of directing light. The section is made in the plane of the daytime movement of the sun across the sky, therefore, only the concentration and direction of the light flux to the focal beam with Fresnel strip lenses is visible (2). At noon, the luminous flux narrows without changing its direction. In the morning and in the evening, the luminous flux narrows with Fresnel strip lenses (2) and at the same time changes its direction, constantly concentrating on the input end of the focal beam (4). The narrowing of the light flux in the vertical plane by the lenses (1) and (3) in FIG. 1 is not noticeable.

In FIG. 2 shows a frontal view of the strip Fresnel lenses (2). Each of the strip Fresnel lenses focuses and directs light to the input end of the focon for a short day time. After the sun moves across the sky, the focal line is shifted to an adjacent strip lens, which focuses and directs the light flux to the input end of the focon at a different angle. The position of the light spot (line) at noon (5) coincides with the central stripe lens, in the morning this line is on the lower stripe lens, and in the evening on the upper stripe lens.

In FIG. 3 shows a diagram of the narrowing of the light flux in another, vertical, (seasonal) plane or in the plane of the "elevation angle" of the sun. This plane is perpendicular to the plane of the daily movement of the sun. After passing through a short-focus linear Fresnel lens (3), the light flux slowly narrows in the vertical plane and reaches the size of the input end of the focon (4), which is located at the focus of the long-focus strip Fresnel lenses (2). The focal length of the linear lens (3) should be slightly less than that of the lens (1), otherwise, with the same lenses (1) and (3), in the seasonal plane the light rays will again be parallel.

In FIG. 4 shows a three-dimensional view of the hub, explaining the principle of its operation. In this figure, the direction of the light flux to the hub corresponds to the evening time of the day. The line of symmetry (7) of linear Fresnel lenses (1) and (3) is shifted by an angle (8) relative to the line of daily movement of the sun across the sky (6). This divergence angle (8) provides a sequential shift of the focal line of the lens (1) from one strip lens (2) to another strip lens during daylight hours. Thus, each strip lens (2) concentrates and directs the luminous flux onto the focon for a short time, while the light spot is at the input end of the focon (4). Then the focal line is gradually shifted to the adjacent strip lens, in which the angle of refraction of light is slightly different from the previous strip Fresnel lens by one step. At noon, lines (6) and (7) intersect and the focal line will coincide with the central symmetrical strip Fresnel lens (5). This lens focuses the light flux on the input end of the focon (4), without changing the direction of the light flux.

In FIG. Figure 5 shows two photographs of the experimental setup of a concentrator with an optical guidance method. The hub is mounted on a tripod, which allows you to change its position in azimuth and elevation. The focus in this experiment was replaced by a paper screen for observing the focal spot.

In FIG. Figure 6 shows a computer model of a concentrator with optical guidance made in the ray tracing program Trace Pro. At the point of convergence of the rays (the focus of the linear Fresnel lens 2), a circular disk (4) is placed, which acts as the input end of the focon.

In FIG. 7 shows a photograph of a color picture (oil on canvas, 20 × 30 cm). This picture was illuminated in a completely dark room using sunlight. This light was focused by a concentrator with optical guidance and transported to a scattering lens (9) through a focal optical fiber (10).

DESIGNATIONS IN FIGURES

1 - Short-focus linear Fresnel lens;

2 - Striped telephoto Fresnel lenses. The axis of symmetry of the strip Fresnel lenses is rotated (relative to the axis of symmetry of the 1st and 3rd lenses) by 90 °, it lies in the plane of the seasonal movement of the sun and defines the "Sun elevation angle";

3 - Short-focus linear Fresnel lens. The axis of symmetry of the 1st and 3rd linear Fresnel lenses lies in the plane of the daily movement of the sun, and determines the "Azimuth of the sun";

4 - Fokon or fokonny plait;

5 - Focal line of the first Fresnel lens at noon (located on the middle stripe Fresnel lens);

6 - Line of daily movement of the sun in the sky;

7 - A line lying in the plane of symmetry of the 1st and 3rd linear Fresnel lenses;

8 - The angle of difference between the lines (6) and (7);

9 - diffusing lens;

10 - Polymer optical fiber made of polymethyl methacrylate (PMMA).

Claims (1)

A stationary solar radiation concentrator with an optical light guidance method containing focusing lenses and a focal point, characterized in that it contains three focusing flat Fresnel linear lenses, in the focus of the first Fresnel short-focus linear lens, there is a second step long-focus Fresnel lens, behind which there is a third linear short-focus lens Fresnel, the focus of which is the focus, and the second step lens consists of stripe long-focus linear Fresnel lenses, shifted by steps in relation to each other in the longitudinal direction at a short distance, the axis of symmetry of strip lenses rotated 90 degrees relative the symmetry axes of the first and third lenses, and the focal lengths of the second lens and the optical system of the first and third lenses are identical.

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