JPH0743534A - Solar concentrating transmitter - Google Patents

Abstract

(57) [Summary] [Purpose] Improving the transmission efficiency of solar concentrators. In the sunlight concentrator, an optical fiber is used as a transmission line, a liquid 3 is used as a core, and a liquid core optical fiber 1 using a plastic pipe 2 is used as a clad. .

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a solar concentrating and transmitting device.

[0002]

2. Description of the Related Art A solar light concentrating and transmitting device comprises a light condensing unit for concentrating sunlight, a transmitting unit for transmitting the concentrated sunlight to a predetermined place, and an emitting unit for irradiating the transmitted sunlight. The sunlight condensing unit is composed of an optical system such as a concave mirror or a lens and a drive system for controlling the mirror or the lens so as to always face the sunlight. The transmission section uses an optical duct or an optical fiber that makes the inside of the tube a highly efficient reflection surface and reflects the inside of the tube for transmission.

As the optical duct, a box-shaped mirror assembly or a tube with a mirror surface is used. The mirror reflection is not suitable for long-distance transmission because the transmission efficiency is poor because light loss occurs due to absorption and scattering of light every reflection. In addition, since the duct requires a large space, it is limited in the place of transmission. Further, there is a problem that it is difficult to easily change it once it is laid.

On the other hand, when an optical fiber is used for a transmission line, it is widely used because it has a high transmission efficiency and the facility is small so that it can be wired at any place and the wiring can be easily changed. The optical fiber used in the sunlight concentrating device needs to efficiently take in the condensed sunlight.
Since the sun has a finite size, the concentrated solar image does not become a point but has a finite size. The converged diameter of the collected sunlight (solar image diameter) is represented by the focal length of the mirror or lens for condensing. The calculation formula is shown in Formula (1).

D = 0.0093 × f (1) f: mirror or lens focal length d: sun image diameter

From the formula (1), the focal length is 300 mm and the diameter is 3
The solar image diameter when using a 00 mm lens is about 2.
It will be 8 mm. Actually, the sun image is blurred from the calculated value by 3-4 mm due to lens aberration, lens molding error, etc.
Becomes An optical fiber having a core diameter of 3 to 4 mm is required to take all the collected sunlight into the optical fiber. Conventionally, the optical fiber is made of glass, and the core diameter is a maximum of 1 m due to the strength and flexibility of the optical fiber.
The limit is about m.

Therefore, as shown in FIG. 3, the optical fiber 6
Are bundled and the bundled diameter is set to 3 to 4 mm to take in sunlight. The outline is shown in FIG.
It is expected that a concentrating device with a large sunlight converging area will be developed in the future, and it is considered that the diameter of the sun image will increase as the converging diameter increases. When the focused diameter is larger than the present,
The method of bundling the optical fibers has a problem that the number of fibers is significantly increased, the cost is increased, and the fiber processing is difficult. In addition, a bundle of many optical fibers has poor processing accuracy at the fiber entrance end, there is a gap between the fibers, and that part cannot take in light, and the clad part cannot take in sunlight. However, there was a problem such as this, which caused a decrease in efficiency.

For example, 400 optical fibers having a core diameter of 0.20 mm and a clad diameter of 0.22 mm are bundled to have an outer diameter of 5.
When the 0 mm focusing fiber is used, the area occupied by the core is 64%, and the efficiency of sunlight being taken into the optical fiber is only 64% at maximum. Actually, there is a decrease in efficiency due to the processing of each fiber, and further decreases. As described above, it has been a problem that the method of bundling fibers causes a decrease in efficiency. In the future, there is a demand for an optical fiber that can efficiently cope with an increase in the size of a light collecting device.

A study for improving the efficiency of taking in sunlight into the fiber was carried out by the method of bundling the fibers. However, in the method of bundling the fibers, the area occupancy ratio of the core is low due to the gap between the fibers and the clad of the fiber. , I found it difficult to improve efficiency.

[0010]

Since the solar image collected by the solar light collecting device is not efficiently taken into the optical fiber, it has been a problem to improve the efficiency. Furthermore, there has been a problem that the efficiency does not decrease even if the condensing device is enlarged in the future.

[0011]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above problems, and condenses sunlight and transmits the condensed light to a predetermined place for irradiation to irradiate the solar light. In the device, there is provided a solar concentrating and transmitting device characterized in that an optical fiber having a core made of liquid and a clad made of plastic is used for a transmission line.

In the present invention, as a result of studying to improve the above-mentioned efficiency, it is indispensable to use an optical fiber having a core diameter larger than that of the sun image in order to take in all the sunlight. It was concluded that a liquid core optical fiber using a liquid for the core and a plastic pipe for the clad is the best as a sufficiently large and highly flexible optical fiber.

As long as a solid core is used as the material of the optical fiber, a flexible optical fiber having a large core diameter cannot be obtained. 1 when using inorganic solid such as glass
Since it is about mm, sufficient flexibility cannot be obtained. Even when plastic is used, the maximum diameter is about 2 to 3 mm, and a sufficient core diameter cannot be obtained.

In order to obtain flexibility, it is desirable to adopt liquid or gas in the core. Since the refractive index of the core of the optical fiber needs to be higher than that of the cladding, and the refractive index of gas is small, liquid is desirable as the core material.

An optical fiber can be obtained by filling a transparent plastic pipe (tube) with a transparent liquid, providing transparent stoppers at both ends, and making the refractive index of the core liquid larger than that of the cladding pipe. The material of the core liquid is not particularly limited as long as it is transparent, but it is desirable that the liquid has a high boiling point, a high vapor pressure at room temperature, flame resistance, excellent heat resistance, a large refractive index, and no toxicity. . Heat resistance is 80
C. or higher is necessary, and preferably 150.degree. C. or higher.
The refractive index depends on the refractive index of the clad material, but is preferably 1.4 or more.

Examples of the core material include water, organic solvents, organic prepolymers, and the like. Water has good properties such as excellent flame retardancy and heat resistance and no toxicity, but has a refractive index of 1.
The difficulty is that it is as low as 33. Therefore, it is necessary to add an additive to increase the refractive index. As the additive, those such as sodium chloride and calcium chloride that increase the refractive index without impairing the transparency are desirable.

Although many organic solvents have excellent transparency, ethylene glycol is preferable in view of flame retardancy, toxicity and refractive index. As the prepolymer, silicone oil,
Examples include low-polymerization products of silicone rubber.

As the clad material, a transparent plastic having a low refractive index is desirable, and the refractive index is desirably 1.38 or less. Suitable materials include fluororesins such as FEP, PFA. Although FEP and PFA are slightly inferior in transparency due to crystallization, amorphous fluororesins such as Teflon AF (product of DuPont) and CYTOP (product of Asahi Glass) have been developed recently, and have a refractive index of 1.2.
It is as low as 9 to 1.33 and has excellent transparency.

A liquid core optical fiber using a liquid for the core and a plastic pipe for the clad has an advantage that it can be manufactured at a low cost because it can have a large diameter. It is possible to use an optical fiber with a core that is sufficiently larger than the sun image collected by the solar concentrator. The core diameter can be as large as the flexibility of the pipe.
Fibers of 0 mm or more can be manufactured. When this optical fiber is used, the sun image can efficiently capture sunlight up to 50 mm, and the condensing diameter of the lens or mirror at that time becomes 5 m, which makes it possible to cope with an ultra-large concentrator. Is. When this liquid core fiber is used, all sunlight can be taken in, and the efficiency becomes 100% excluding the loss due to reflection.

[0020]

The outline of the present invention is shown in FIG. The sunlight is collected by the lens 7 of the light collecting device and taken into the large-diameter liquid core fiber 1. Conventionally, as shown in FIG. 3, since the small-diameter fibers 6 are bundled and used, the taking-in efficiency is lowered, but the liquid core fiber can easily be made large in diameter and can take in 100% of the sunlight. is there. FIG. 2 shows an outline of the liquid core fiber. A liquid core fiber is obtained by filling a transparent liquid 3 into a transparent pipe 2 serving as a clad and sealing both ends with transparent plugs 4.

[0021]

【Example】

[Example 1] A sunlight concentrator was prepared using a Fresnel lens having a diameter of 500 mm and a focal length of 500 mm. The condenser lens is controlled in the horizontal and vertical directions by a tracking sensor and a drive motor so that it always points in the correct direction of the sun. The liquid core optical fiber used was an FEP pipe with an outer diameter of 10 mm, an inner diameter of 8 mm, and a length of 10 m (refractive index 1.3.
3) was used for the clad, and high purity ethylene glycol (refractive index 1.43) was filled therein. At both ends of the tube, stoppers for sealing liquid are used, the outer diameter is 8.5 mm, and the length is 30 mm.
A quartz glass rod of mm (refractive index 1.46) was used and fitted at both ends of the pipe. The quartz rod used was one whose both ends were optically polished and then AR coated to reduce reflection. After confirming that there are no bubbles inside the pipe,
The quartz rod was fixed so that it would not come out of the pipe.
This optical fiber can be bent with a bending diameter of 50 mm,
Sufficient flexibility was obtained.

The incident end of the liquid core optical fiber was fixed to the focal position of the Fresnel lens of the light condensing device so that all the condensed sunlight could be taken into the optical fiber. The diameter of the collected solar image collected by the Fresnel lens is about 7 mm, and the core diameter of the optical fiber used is 8 mm, so all the collected sunlight can be taken into the optical fiber, and the taking efficiency is It was 100% (excluding end face reflection and absorption of the quartz rod).

[Embodiment 2] Diameter 300 mm, focal length 3
A solar concentrator was created using a 00 mm Fresnel lens. The condenser lens is controlled in the horizontal and vertical directions by a tracking sensor and a drive motor so that it always points in the correct direction of the sun. The liquid core optical fiber used has an outer diameter of 8
A PFA pipe (refractive index 1.33) having a diameter of 6 mm, an inner diameter of 6 mm and a length of 10 m was used as a clad, and high-purity methylphenyl silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., refractive index 1.46) was filled. Quartz glass rods (refractive index 1.46) having an outer diameter of 6.5 mm and a length of 30 mm were used as plugs for sealing the liquid at both ends of the tube, and were fitted at both ends of the pipe. The quartz rod used was one whose both ends were optically polished and then AR coated to reduce reflection. After confirming that there were no bubbles inside the pipe, the quartz rod was fixed so that it would not come out of the pipe. This optical fiber could be bent with a bending diameter of 30 mm, and sufficient flexibility was obtained.

The incident end of the liquid core optical fiber was fixed at the focal position of the Fresnel lens of the light condensing device so that all the condensed sunlight could be taken into the optical fiber. The diameter of the collected solar image collected by the Fresnel lens is about 5 mm, and the core diameter of the used optical fiber is 6 mm, so all the collected sunlight can be taken into the optical fiber, and the taking efficiency is It was 100% (excluding end face reflection and absorption of the quartz rod).

Comparative Example 1 In the case of Example 1, a quartz fiber was used instead of the liquid core optical fiber.
The fiber used is composed of silica glass (refractive index 1.48) with germanium added to the core, and silica glass (refractive index 1.46) for the cladding, with a core diameter of 0.20 mm and a cladding diameter of 0.22 mm. I was there. 1000 optical fibers were bundled into a converging fiber having an outer diameter of 8 mm and a length of 10 m, and both ends were optically polished.

The incident end of the focusing optical fiber was fixed to the focal position of the Fresnel lens of the light condensing device so that all the collected sunlight could be taken into the optical fiber. The core occupying area ratio of this focusing fiber was 62.5%. Therefore, the efficiency of taking in sunlight was 62.5%.

[0027]

By using a liquid core optical fiber having a large core diameter, it is possible to take all the sunlight collected by a lens or a mirror into the optical fiber. Liquid core optical fibers can be manufactured inexpensively. It is possible to cope with the future increase in the size of the light collector.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a solar light concentrating and transmitting device of the present invention using a liquid core optical fiber for a transmission line.

FIG. 2 is a sectional view including an optical axis of a liquid core optical fiber.

FIG. 3 is a schematic diagram of a conventional technique using a cable made of a thin core optical fiber as a transmission path.

[Explanation of symbols]

 1: Liquid core fiber 2: Transparent pipe 3: Transparent liquid 4: Transparent plug 5: Transmission line consisting of small diameter core optical fiber 6: Small diameter fiber 7: Condenser lens

Claims (2)

[Claims] 1. A solar light concentrating and transmitting device for concentrating sunlight, transmitting the condensed light to a predetermined place and irradiating it, and using an optical fiber whose core is made of liquid and whose clad is made of plastic. A solar concentrating and transmitting device characterized by being used for. 2. A refractive index of 1.4 in the cladding of the optical fiber.
The solar concentrating and transmitting device according to claim 1, wherein the following amorphous fluororesin pipe is used.