JP7175414B1 - Concentrators, Solar Cookers and Sheets for Making Solar Cookers - Google Patents

Abstract

The object of the present invention is to provide a collector, a solar cooker, and a sheet for manufacturing a solar cooker that have a simple configuration and can collect light with high efficiency. A solar cooker (1) has a shape obtained by obliquely cutting the circumference of the apex of a cone (100). It consists of a light collector. Light incident from the opening 101 of the cone 100 is reflected by the light reflecting surface 103 and converged on the object 200 placed on the oblique cut surface 104 . [Selection drawing] Fig. 1

Description

The present invention relates to a concentrator for concentrating sunlight, a solar cooker, and a sheet for making a solar cooker.

A solar cooker that heats food with sunlight is an eco-friendly cooking appliance that does not use fossil resources such as fuel and does not generate carbon dioxide that causes global warming. In addition, since solar cookers use natural energy, they can be used even when infrastructure such as electricity is cut off in the event of a disaster.

A solar cooker or other light collector includes, for example, a parabolic type that collects sunlight by reflecting it with a reflecting mirror having a parabolic surface (for example, Patent Document 1). The solar cooker described in Patent Literature 1 has a configuration in which light reflected by a parasol-shaped reflective surface is focused on a focusing plate attached to the tip of the middle rod of the parasol.

As another type of concentrator, there is a concentrator that reflects sunlight with a reflective surface provided on the inner surface of the cone and condenses the light near the vertex (for example, Patent Documents 2 and 3). In the light collector described in Patent Document 2, a taper is formed between the entrance surface and the exit surface so that the facing distance is narrowed, and the taper angle β, the distance l between the entrance surface and the exit surface, the width i of the entrance surface It is explained that efficient light collection can be achieved by setting α=2l·tanβ/(i+o), which is represented by the width o of the output surface, to 0.7 to 1.3.

The light collector described in Patent Document 3 has a container wall with a geometric structure that is open vertically upward and has a wide top and a narrow bottom. absorbs light and heat at It is said that this structure can enlarge the sunlight receiving area, reduce the installation area of the solar energy device, and improve the efficiency of light absorption and heat absorption.

JP 2010-65864 A JP-A-2000-216732 JP 2009-535599 A

In the parabolic type as shown in Patent Document 1, it is difficult to hold a widely spread reflecting surface, or to hold a condensing portion fixed at a position higher than the reflecting surface. and poor portability.

On the other hand, with the cone-shaped light collectors as disclosed in Patent Documents 2 and 3, it is difficult to efficiently collect light at a specific position compared to the parabolic type. Specifically, the light collector described in Patent Document 2 has a low light collection rate because it is assumed that the light reaches the light collection position directly or by only one reflection, and a sufficient temperature is obtained. was difficult.

In addition, since the light collector described in Patent Document 3 has an opening vertically upward, the incident light is collected by many reflections on the inner surface depending on the length of the cone, the opening width, and the incident angle of the light. There is a problem that the light is radiated to the outside without reaching the light position, resulting in low light collection efficiency.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light collector, a solar cooker, and a sheet for manufacturing a solar cooker that have a simple structure and can collect light with high efficiency.

In order to achieve the above object, the collector according to the first aspect of the present invention comprises:
It has a shape obtained by obliquely cutting the periphery of the apex of a cone,
The bottom portion of the cone is open,
A concentrator provided with a light reflecting surface on the inner surface of the cone,
Light incident from the bottom portion of the opening is reflected by the light reflecting surface and condensed on the object placed on the oblique cut surface ;
The apex angle of the cone is 20 degrees or more and 40 degrees or less,
The length along the generatrix of the cone is 3 times or more and 15 times or less the minimum value of the chord length of the condensing surface, which is the condensing target .

The cut surface is cut obliquely with respect to the central axis of the cone,
The cut surface may be directed vertically downward, and the central axis of the cone may be directed toward the sun.

The cone is any one of a cone, an elliptical cone and a pyramid,
The cut surface may have one of an elliptical shape and a rectangular shape according to the shape of the cone.

further comprising a placing portion for placing the object on the cut surface,
A light reflecting surface may be provided on the mounting portion.

It may further have a supporting member that supports the side surface of the cone from below in the vertical direction.

A support ring may further be provided to support the inner circumference of the cone.

Also, the solar cooker according to the second aspect of the present invention is
It is characterized in that it has a collector according to the first aspect, and heats the object with the collected light.

In addition, the sheet for manufacturing a solar cooker according to the third aspect of the present invention is
A sheet for making a solar cooker with a concentrator according to the first aspect, comprising:
A fan-shaped sheet provided with a light reflecting surface on at least one surface,
The central angle is 60 degrees or more and 120 degrees or less,
A joining means is provided for joining two sides sandwiching the central angle,
A cut line obtained by cutting the central angle forms the cut surface.

According to the present invention, the shape is formed by obliquely cutting the circumference of the apex of the pyramid, and the light incident from the opening in the bottom portion is reflected by the inner surface to collect the light. It becomes possible to shine.

It is a figure which shows the structural example of the solar cooker which concerns on embodiment. FIG. 11 shows reflection on the inner surface of a cone; 4 is a graph showing changes in light collection rate with respect to the apex angle of a cone; 4 is a graph showing changes in light collection rate with respect to cone length (condensing surface diameter ratio). (a) It is a figure which shows the example of the sheet|seat for solar cooker manufacture. (b) It is a figure which shows the external shape of a solar cooker. 4 is a graph showing changes in light collection rate with respect to cone length (condensing surface diameter ratio). (a) is a graph showing changes in light collection efficiency with respect to the cone apex angle and the cone length (condensing surface diameter ratio); (b) It is a figure which shows the example of the sheet|seat for solar cooker manufacture. It is a figure which shows the use condition of a solar cooker.

(Embodiment)
EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated in detail with reference to drawings. The same reference numerals are given to the same or corresponding parts in the drawings. A solar cooker 1 according to the present embodiment is a cooking appliance that includes a solar collector that collects sunlight and heats and cooks an object.

FIG. 1 is a diagram showing a configuration example of a solar cooker 1 according to this embodiment. The concentrator of the solar cooker 1 has a shape cut around the apex of a cone 100, as shown in FIG. The cone 100 may be a cone, an elliptical cone, or a pyramid, but a cone is preferred from the standpoint of light collection efficiency and manufacturability. A cut surface around the vertex is a surface cut perpendicularly or obliquely to the central axis 102 of the cone 100 . FIG. 1 shows the case where the shape of the concentrator of the solar cooker 1 is a shape obtained by obliquely cutting the periphery of the apex of a cone.

The bottom portion of cone 100 is open, and this opening 101 faces the sun. More preferably, the central axis 102 of the cone 100 is arranged along the direction toward the sun.

A light reflecting surface 103 is provided on the inner surface of the cone 100 . The light reflecting surface 103 is made of any conventional material and is produced by any method. For example, it is produced by attaching a reflecting material such as aluminum foil to a sheet, or vapor-depositing aluminum on a base such as polyester.

An object 200 to be heated is arranged on the cut surface 104 around the apex of the cone 100 . In order to stably arrange the object 200 with the opening 101 of the cone 100 facing the sun, the cut surface 104 is preferably oblique to the central axis 102, but depending on the shape of the object 200, the cut surface 104 may be inclined to the center. It may be perpendicular to axis 102 . The shape of the cut surface 104 is either circular, elliptical, or square, depending on the shape and cutting direction of the cone 100 .

The cutting surface 104 may be provided with a mounting portion 106 coupled to the side surface of the cone 100 , in which case the object 200 is mounted on the mounting portion 106 . A light reflecting surface is provided on the surface of the mounting portion 106 on the object 200 side. Thereby, it is possible to prevent the mounting portion 106 from being heated to a high temperature. When the object 200 is contained in a container, the container is preferably made of a material that absorbs light, such as a black pot. Alternatively, the object 200 may be wrapped in a packaging material made of a light-absorbing material such as black foil and placed thereon. By using a light-absorbing material for the container or packaging material, the object 200 can be efficiently heated by the condensed light.

As shown in FIG. 1, the inner wall of the cone 100 may be further provided with a support ring 107 or a support ring 108 that supports the inner circumference to keep the shape of the cone 100 . Each of the support rings 107 and 108 may be plural and may be perpendicular or oblique to the central axis 102 of the cone 100 . The support rings 107, 108 are made of any material, for example steel wire such as piano wire. Support ring 107 is positioned near the center of gravity of cone 100 and may be removable. The support ring 108 is near the cutting plane 104, is oblique to the central axis 102, and may be removable. Moreover, although not shown, a transparent plate may be further provided on the surface intersecting the central axis 102 inside the cone 100 to block the space in which the object 200 exists. Thereby, the heat applied by the reflected light can be kept in the space.

In order for the solar cooker 1 to cook with high efficiency, it is necessary to increase the light gathering rate. The light gathering rate depends on the shape of the cone 100. FIG. The shape of the cone 100 that can improve the light collection rate is described in detail below.

First, the angle of the cutting plane 104 with respect to the central axis of the cone 100 is preferably the same as the elevation angle α of the sun. Since the elevation angle α of the sun changes depending on the season and time zone, it is appropriately selected according to the season and time zone. When installed, the cut surface 104 is oriented vertically downward and the central axis of the cone 100 is oriented toward the sun.

Sunlight incident from the opening 101 of the cone 100 is reflected once or multiple times by the light reflecting surface 103 . At this time, the reflected light reaches the object 200 and contributes to the heating of the object 200, or is emitted to the outside. It is possible to increase the ratio of the light reaching to and increase the light collection rate.

The reflection of light within the cone 100 will be described in detail below with reference to FIG. FIG. 2 represents a cross-section of cone 100 in a plane containing the central axis, showing reflections on the inner surface of cone 100 . In this embodiment, the condensing rate on the object 200 placed on the cutting plane 104 can be approximated by the condensing rate on the condensing plane 105 near the cutting plane 104 and orthogonal to the central axis 102 . Therefore, in FIG. 2, a circular condensing surface 105 having a diameter T close to the cut surface 104 is used as a condensing target.

In FIG. 2 , sunlight is incident on cone 100 from the direction of central axis 102 of cone 100 . Let β be the apex angle of the cone 100, L be the length from the aperture 101 to the condensing surface 105 along the generatrix of the cone 100, and the height of the cone 100 from the aperture 101 to the condensing surface 105 is Let H be the height of In FIG. 2, (a) is the path for direct incidence on the light collecting surface 105, (b) is the path for reflecting once on the light reflecting surface 103 and is incident on the light collecting surface 105, and (c) is the path for two reflections. (d) shows a path reflected three times, and (e) shows a path reflected n times (n=4).

First, the apex angle β must be less than 90 degrees. This is because, when the apex angle β is 90 degrees or more, all the light other than the light directly incident on the disk with the diameter T is emitted to the outside of the cone 100 . Light entering parallel to the central axis 102 of the cone 100 having the apex angle β increases its traveling direction by β degrees every time it is reflected by the light reflecting surface 103 inside the cone 100, and β×n<90 (degrees ), it repeats reflections within the cone 100 and proceeds toward the apex of the cone 100 (n is the number of reflections). However, once .beta..times.n.gtoreq.90 (degrees), the traveling direction of the light is directed toward the opening 101, and the light is radiated out of the cone 100. FIG.

When sunlight is incident on the cone 100 with an apex angle β of less than 90 degrees, the light directly incident on the collection surface 105 passes through A ₀ as shown in FIG. 2(a). The light reflected once by the light reflecting surface 103 and incident on the condensing surface 105 passes through the doughnut _- shaped area A1, as shown in FIG. 2(b). Let I ₁₁ be the diameter of the outer periphery of this area A ₁ , and H ₁₁ be the height from the reflection point to the condensing surface 105. The relationship between I ₁₁ and H ₁₁ is expressed by the following equations (1) and (2). can be done.

From the equations ( ₁ ) and (2), the height _H11 and the diameter I11 are obtained by the following equations (3) and (4).

As shown in FIGS. 2(c) and 2(d), each time the light is reflected on the light reflecting surface 103, the angle formed by the light incident direction and the height H direction increases by β degrees. As shown in FIG. 2( e ), for light that passes through the region A _n and reaches the light collecting surface 105 after being reflected n times by the light reflecting surface 103 , the diameter I _nm of the reflection point reflected for the mth time and m The height H _nm from the 1st reflection point to the m+1th reflection point can be calculated in the same manner as Equations (3) and (4), and is represented by Equations (5) and (6) below.

Since the light reflected n times by the light reflecting surface 103 is finally incident on the condensing surface 105, when m=n, the formula I _nm+1 is expressed by the following formula (7).

When the apex angle is less than 90 degrees, the light incident on the cone 100 repeats reflection multiple times and reaches the condensing surface 105. increases as . On the other hand, the condensing surface 105 needs to have a certain size in order to arrange the object 200, and if the length L is too long, the overall size becomes large and it becomes difficult to handle. Therefore, considering the change in light collection rate with respect to the apex angle β and the length L, the optimum shape is selected.

Areas A ₀ , A _n1 , A _{n2 , .} The _areas S ₀ , S _n1 , _{S n2 ,} .

Here, since the sunlight enters from the opening 101 of the cone 100 with a substantially uniform intensity, the light collection rate when f is the reflectance on the light reflecting surface 103 is expressed by the formula (12). .

Here, the height Hn of the cone 100 required for _n reflections is obtained from the following formula (13), and the relationship between the length L and the height Hn of the cone 100 is _expressed by the following formula (14 ).

By substituting equations (6)-(11) into equation (12) and using the relationships of equations (5), (13), and (14), the collection ratio λ can be calculated. 3 and 4 show the calculation results of the light collection rate λ.

FIG. 3 is a graph showing changes in the light collection rate λ with respect to the apex angle β when the reflectance f is 1.0. It is calculated by changing the ratio L/T in the range of 1-20. FIG. 4 is a graph showing changes in the light collection rate λ when the horizontal axis is the ratio (L/T) of the length L of the cone 100 to the diameter T of the light collection surface 105, and the apex angle β is calculated by changing.

As shown in FIG. 3, when using a cone 100 having a length L that is the same as the diameter T of the light collecting surface 105 (L/T=1), the light collection rate increases as the apex angle decreases from 90 degrees. At 60 degrees, the condensing rate is four times the maximum. If the apex angle is made smaller than 60 degrees, the condensing efficiency is lowered. On the other hand, if the apex angle is kept constant and the length L of the cone 100 is lengthened, multi-reflected light such as two-time reflection and three-time reflection can be used, so that the light collection rate increases sharply. However, when β×n exceeds 90 degrees due to n reflections, the light is reflected in the direction toward the opening 101 of the cone 100, so the light collection rate λ becomes constant as shown in FIG.

Based on the calculation results of the light collection rate shown in FIGS. Choose an angle β. For example, when the diameter of the object to be heated by the solar cooker 1 is 3 to 20 cm, a cone having a length L 3 to 15 times the diameter T (minimum chord length) of the light collecting surface 105 is easy to handle (L /T=3 to 15), in that case, from FIG. 4, the condensing rate λ reaches the maximum when the apex angle β of the cone is 20 degrees or more and 40 degrees or less. That is, for the apex angle β of the cone, it can be said that an appropriate angle for the cone 100 with L/T=3 to 15 is 20 degrees or more and 40 degrees or less. degree or more and 35 degrees or less is more preferable.

Here, in the present embodiment, since the cone 100 is a cone, the condensing surface 105 is circular, and the diameter T is the diameter of a circle. corresponds to the diameter T of the minimum chord length of the condensing surface 105 .

When making a cone using an existing material such as paper or sheet, the material can be used most effectively by using a square with one right angle as the apex and joining two sides of the right angle to each other. and can be easily manufactured. If a cone is made with one right angle of the square as the vertex, the vertex angle is 28.96 degrees.

FIG. 5(a) shows an example of a sheet 300 for manufacturing the solar cooker 1 according to this embodiment. FIG. 5(a) shows an example in which the cone 100 of the solar cooker 1 is a conical body that is obliquely cut around the vertex, and the cut surface 104 is an ellipse. The sheet 300 is a square sheet provided with a light reflecting surface on at least one surface. The sheet 300 is provided with a cutting line 302 for cutting a sector centered at a right angle 301 and a cutting line 303 for forming a cut surface 104 by cutting the right angle. By cutting along the perforation lines 302 and 303, a fan-shaped sheet having a center 301 at a right angle is obtained.

Two sides sandwiching the center 301 of the sheet 300 are provided with joining means 304 for joining together. The joining means 304 may be any conventional means, for example, the two sides may be joined with an adhesive such as a fastener, Velcro (registered trademark), magnet, or tape. Alternatively, the two sides may be joined by a button and a buttonhole or a projection and an insertion hole (notch) respectively formed on the two sides.

The placement portion 106 for placing the object 200 may be cut out from the remaining portion of the square sheet 300 after the sector is cut out. In this case, by providing a joining means 305 extending from the cutting line 303 of the fan-shaped sheet and joining the joining means 305 to the outer circumference of the placing portion 106, the placing portion 106 can be formed on the cut surface 104. .

FIG. 5(b) is the solar cooker 1 made from the sheet 300. FIG. By using a square sheet 300, a cone with an apex angle β of 28.96 degrees can be formed. can be formed.

Here, sheets in the vicinity of two sides sandwiching the center 301 may overlap each other and be joined. In this case, the apex angle β is smaller than 28.96 degrees.

FIG. 6 shows the condensing ratio λ when the apex angle β is 28.96 degrees. FIG. 6 is a graph showing changes in the light collection rate λ when the horizontal axis is the ratio (L/T) of the length L of the cone 100 to the diameter T of the light collection surface 105 . As shown in FIG. 6, the condensing rate for one reflection is 6.6 times the maximum when L/T is 3.5. If L/T is further increased, the light that has been reflected twice and the light that has been reflected three times will also enter the condensing surface 104, increasing the condensing efficiency. When L/T is 5.9, the total light collection rate of all the reflected light is 15.4 times at maximum, and even if the length of the cone 100 is increased beyond that, the light collection rate does not increase.

In this way, the solar cooker 1 can be easily manufactured by cutting out a fan-shaped sheet with one right angle as the center 301 from the square sheet 300 and joining the two sides sandwiching the center 301 to each other. Also, when the solar cooker 1 is not used, the joint portions 304 and 305 can be peeled off to restore the fan-shaped sheet, which can then be folded or rolled into a cylindrical shape and stored in a small size.

Here, FIG. 5(a) shows an example of a square sheet 300 capable of forming a cone with an apex angle β of 28.96 degrees. When forming a cone, a rectangular sheet for forming a fan-shaped sheet having a central angle δ of the center 301 of 60 degrees or more and 120 degrees or less may be used.

In FIG. 7(a), the vertical axis is the apex angle β and the central angle δ of the expanded fan-shaped cone 100, and the ratio (L/T) of the length L of the cone 100 to the diameter T of the condensing surface 105 is FIG. 7B is an example of a rectangular solar cooker manufacturing sheet, and FIG. According to FIG. 7(a), when L/T is 3 to 15, the condensing rate λ increases when the apex angle β is about 20 to 40 degrees. It can be calculated by (15) and becomes about 60 to 120 degrees.

The length L and the central angle δ of the cone 100 are selected with reference to the apex angle β and the central angle δ and the change in the light collection rate with respect to the L/T of the cone 100 shown in FIG. 7(a). By cutting along the cutting lines 302, 303, 308 according to the selected central angle δ, the cone 100 with the apex angle β of 20 to 40 degrees can be produced.

At this time, sheets in the vicinity of two sides sandwiching the center (central angle δ) 301 may overlap each other and be joined. In this case, the central angle δ may be 120 degrees or more.

Next, how to use the solar cooker 1 will be described. For example, a cone 100 is formed from a fan-shaped sheet as shown in FIG. FIGS. 8A to 8C are diagrams showing how the solar cooker 1 is used, and FIGS. 8A to 8C show cases where the elevation angles of the sun are different.

Since the cone 100 of the solar cooker 1 has high directivity, it is necessary to use the solar cooker 1 with the opening 101 facing the sun. Preferably, the central axis 102 of cone 100 is oriented toward the sun. At this time, the cut surface 104 is formed so that the angle formed by the central axis 102 and the cut surface 104 is equal to the elevation angle α of the sun. In other words, the cut surface 104 is formed by cutting the sheet from which the cone 100 is made according to the elevation angle of the sun in use.

A heavy pot or the like is placed on the mounting portion 106 fixed to the cut surface 104 . Furthermore, as shown in FIG. 8, the side surface of the cone 100 may be supported vertically by a support member 109 according to the altitude of the sun. Thereby, the cone 100 can be installed with the opening 101 facing the sun. The support member 109 may have a shape in which a sheet or plate is folded in three, as shown in FIG.

As shown in FIG. 8, by using the solar cooker 1 with the opening 101 of the cone 100 facing the sun, the sunlight is condensed on the object 200 and the object 200 can be heated. After use, the object 200 is removed from the cone 100 . At this time, the joining means 304 and 305 of the sheet 300 of the cone 100 may be peeled off to dismantle the cone 100 .

As described above, the solar cooker 1 according to the present embodiment has a shape in which the periphery of the apex of the cone 100 is cut vertically or obliquely, the bottom of the cone 100 is opened, and the inside of the cone 100 is opened. It consists of a concentrator provided with a light reflecting surface 103 on its side surface. The light incident from the opening of the cone 100 is reflected by the light reflecting surface 103 and converged on the object 200 placed on the oblique cut surface 104 . This makes it possible to collect light with high efficiency with a simple configuration.

In the present embodiment, the placement portion 106 is provided on the cutting surface 104, and the object 200 to be heated is placed on the placement portion 106. may be fitted to the outer circumference of the container of the object 200 to fix the cone 100 to the object 200 . Thereby, the cone 100 can be easily removed from the object 200 after heating.

Although the embodiment of the present invention has been described above, this embodiment is an example, and the scope of application of the present invention is not limited to this. That is, various modifications and applications are possible without departing from the gist of the present invention.

1 Solar Cooker 100 Cone 101 Opening 102 Central Axis 103 Light Reflecting Surface 104 Cutting Surface 105 Condensing Surface 106 Mounting Part 107, 108 Supporting Ring 109 Supporting Material 200 Object 300 Sheet , 301 center, 302, 303, 308 tear line, 304, 305 joining means.

Claims (8)

It has a shape obtained by obliquely cutting the periphery of the apex of a cone,
The bottom portion of the cone is open,
A concentrator provided with a light reflecting surface on the inner surface of the cone,
light incident from the bottom portion of the opening is reflected by the light reflecting surface and condensed on the object placed on the oblique cut surface ;
The apex angle of the cone is 20 degrees or more and 40 degrees or less,
The length along the generatrix of the cone is 3 times or more and 15 times or less than the minimum value of the chord length of the condensing surface, which is the condensing target.
concentrator. The cut surface is cut obliquely with respect to the central axis of the cone,
The cut surface is directed vertically downward, and the central axis of the cone is arranged toward the sun,
A concentrator according to claim 1 . The cone is any one of a cone, an elliptical cone and a pyramid,
The cut surface has one of an elliptical shape and a rectangular shape depending on the shape of the cone,
A concentrator according to claim 1 . further comprising a placing portion for placing the object on the cut surface,
The mounting portion is provided with a light reflecting surface,
A concentrator according to claim 1 . further comprising a support member that supports the side surface of the cone from below vertically;
A concentrator according to claim 1 . further comprising a support ring that supports the inner circumference of the cone;
A concentrator according to claim 1 . A solar cooker comprising a collector according to any one of claims 1 to 6 , for heating the object with the collected light. A sheet for making a solar cooker with a concentrator according to any one of claims 1 to 6 ,
A fan-shaped sheet provided with a light reflecting surface on at least one surface,
The central angle is 60 degrees or more and 120 degrees or less,
A joining means is provided for joining two sides sandwiching the central angle,
A cut line that cuts the central angle forms the cutting plane.
Sheet for making a solar cooker.

Images