KR100602581B1 - Compound Parabolic Concentrator for Uniform Energy Distribution on the Receiver Surface - Google Patents

Abstract

The present invention is directed to an improved light receiving density homogenous composite parabolic surface (CPC) focusing device in order to solve the problems caused by the distribution of light density uneven on the light receiving surface (or endothermic surface) of the composite parabolic surface (CPC) focusing apparatus for focusing sunlight. It is about. In the light receiving density uniforming CPC focusing apparatus according to the present invention, the right reflector (second reflector), the left reflector (first reflector), and two reflectors whose parabolic trajectories satisfy ρ = 2f / (1-cosφ) in a cross section is parabolic. It consists of a light receiving surface formed by connecting the lower end of the focal point (F, F ') of each reflector is formed at the lower end of the opposite reflector and the entrance end of the sunlight (A, B) and the focal point (F, F') ), The base CPC with the angle of incidence of ± α between the line (AF ', BF) and the z-axis connecting each other is improved, so that the lower point F (the focus of the right second reflector) of the left first reflector AF is improved. ) And draw the line BF by connecting the upper point B of the right side second reflection BF ', and draw a line parallel to the line BF at the focus F' (lower point of the right side reflecting surface) of the left first reflecting mirror AF. To determine the location of the point K 'meeting the right second reflecting surface, or to establish the relation

cosφ _{K '} = [1-2 (1 + sinα) * sinα] cosα + (1 + sinα) * (1-2sinα) Of

(cosα + sinα + 1) * (1-2sinα) ²

Determine the position of the point K ', which is determined by the value of the angle φ _K' , and meet the line K'K parallel to the device's horizontal axis (x-axis) and the line BF at the point K ' The position of the first reflecting mirror AF to the right along the device's transverse axis (x-axis) to the point where it meets point K. The left reflector AF moves to the right by s. Accordingly, the focal point F at the lower end of the right reflector BF is moved to the point F ″, and in this state, the lower end of each reflector is cut by the lines K and K 'to form a light receiving surface. Both ends are positioned apart from each focal point of the left and right reflectors so that the received light density is uniformly distributed.

Description

Compound Parabolic Concentrator for Uniform Energy Distribution on the Receiver Surface             

1 is a graph of the relationship between the electrical characteristics and the focusing ratio of the solar cell

2 and 3 are explanatory diagrams of optical characteristics of paraboloids

4 is a cross-sectional view of the formation structure of the basic CPC focusing device model

5 is an explanatory diagram of optical characteristics of the basic CPC focusing apparatus;

6 is a two-dimensional model perspective view of the basic CPC focusing device

7 is a three-dimensional model perspective view of the basic CPC focusing device

8, 9 and 10 are explanatory diagrams of energy distribution on the light receiving surface according to the incident angle in the basic CPC focusing apparatus.

11 is a cross-sectional view for explaining the membership of the light receiving density uniformity CPC focusing apparatus according to the present invention

12, 13 and 14 are explanatory diagrams of energy distribution on the light receiving surface according to the incident angle in the light receiving density uniformizing CPC focusing apparatus according to the present invention.

Figure 15 is a cross-sectional view for explaining the membership of the rain-mounted light receiving density uniformity CPC focusing apparatus according to the present invention

16 is a cross-sectional view of the boots type light receiving density uniformizing CPC focusing device according to the invention in which the light receiving surface is located parallel to the ground.

17 is a cross-sectional view of the rain-type light receiving density uniformity CPC focusing apparatus according to the present invention designed to have a clearance

18 is a cross-sectional view of the basic CPC applied to the newly improved orbital and endothermic heat absorbing surface;

19 is a cross-sectional view of the concentrating device to the curved surface and the heat absorbing tube of the new improved track in the boot type light receiving density uniformity CPC focusing apparatus according to the present invention.

20 is a cross-sectional view of the focusing apparatus having a free space in the focusing apparatus of FIG.

**** Description of the major symbols in the drawings ****

A, A ', B: Disadvantages of opening surface of CPC focusing device

F, F ', F ": Parabolic focal point

K, K ': Lower endpoint of CPC reflecting surface, exit surface of basic CPC (light receiving surface)

s: distance of reflection (left)

d ( K'G , HG ' ): Clearance distance of rain boot type focusing device

C: Focus ratio

(x, y), (x ', y') (x ", y"): Cartesian coordinate system, the axis of the device

JF , J'F ': Parabolic axis

FF ', KK' : Width or exit surface of light receiving surface (heat absorbing surface) of CPC type focusing device

K'M , K "M ' : Endothermic surface (linear) or exit surface of rain boot type focusing device

α is the incident limit half angle of the CPC device using the plate light receiving surface

θ: incident limit half angle of CPC device using circular endothermic surface

(ρ, φ): Polar coordinate system of parabola

The present invention provides an improved light receiving density homogenous composite parabolic surface (hereinafter referred to as CPC) in order to solve the problems caused by uneven distribution of light density on the light receiving surface (or heat absorbing surface) of the CPC focusing apparatus for focusing sunlight. ) Relates to a focusing device.

The solar energy utilization device can be divided into a device using sunlight and solar heat. A solar energy utilization device is a means of directly converting solar energy into electrical energy using a semiconductor, and a solar heat utilization device absorbs solar energy. Or means for converting solar energy into thermal energy using an endothermic tube. Semiconductors used in photovoltaic devices are typically silicon (Si) and gallium arsenide (GaAs), and the electrical conversion efficiency is about 10-20% depending on the type. The endothermic surface used in the solar heat utilizing device is made of chromium (Cr) or titanium (Ti) composite (eg TiO ₂ ) and the solar energy absorption is about 90 ~ 95%.

The collector (or collector) used for this purpose is a flat-plate collector and a concentrating collector. A flat type condenser receives energy as much as the area of a light receiving surface (or heat absorbing surface) and converts energy. A focused type condenser uses a special optical device to focus the ratio (opening area / light receiving area) rather than the area of the condensing surface. ) Is a device that generates more energy (or higher temperature) than a flat plate condenser on the same light receiving surface (heat absorbing surface) area as that of the flat plate type by reaching more light energy. Focused devices may be two- or three-dimensional focusers, depending on the application, and each device may be a sun tracked or non-tracked device.

Structure of solar cell and module:

A photovoltaic cell is a device that converts solar energy into electrical energy. It is a kind of semiconductor diode, which is a pn junction structure, and is a semiconductor such as silicon (Si) or gallium arsenide (GaAs). I'm using.

There are various types of solar cells, but for example, single-crystal Si solar cells are formed by bonding metal plates to the front and back sides of a thin Si wafer to collect free electrons and holes. It is composed. The front contact metal is a thin or thin metal grid or finger formed at regular intervals in order to receive the maximum sunlight, and collects free electrons generated when the sunlight is irradiated. Collect. Charge carriers (electrons and holes) generated at the anode ends of semiconductor p-n junction diodes become currents when connected to external circuits and act as solar cells. Efficient solar cells should be able to capture as much sunlight as possible and absorb the light energy to create as many charge carriers as possible.

The photovoltaic (PV) module is a unit of a power generation device using a solar cell. The configuration of this apparatus connects a plurality of solar cells in series to determine the required voltage (V), which is called String. Many such strings are connected in parallel to adjust the required current (I) to adjust the required output (P) by the P = IV relationship. For example, the size of a single crystal Si battery, which is widely used as a flat plate battery, is about 10 cm x 10 cm, and its electrical characteristics are -0.5V in open voltage (Voc) and ~ 3A in single-circuit current (Isc). The maximum output power is about P ~ 1.2W. When the same 12 batteries are connected in series, a string having a voltage of about 5V is formed, and when the four strings are connected in parallel, a module capable of outputting about 60W is formed.

Photovoltaic devices Necessity of focusing device in

The problem with flat panel devices that use solar energy is that solar cells (semiconductors) generate electricity in general, and solar cell semiconductors are expensive and have low electrical conversion efficiency. The electrical (IV) characteristics of general semiconductors increase in proportion to the density of solar energy and the density of solar energy is proportional to the focusing ratio. In other words, the dependence of the solar cell output on the focusing ratio is expressed by the following relationship .

Isc = C Isco (1)

Voc = Voco + (nVth) ln (C) (2)

Here, Isc = short circuit current 6, C = focusing ratio, Voc = open circuit voltage, n = diodic factor, nVth = thermal dependence on solar cell efficiency. That is, the current (I) of the solar cell is linearly proportional to the focusing ratio, and the voltage (V) has a slight increase in logic. Therefore, the higher the focusing ratio, the higher the output P is by the relation of P = I * V (see FIG. 1).

This means that the use area of the solar cell can be reduced by the focusing ratio for the same output, thereby making it economical. In other words, if the focusing ratio is 2, the area of the solar cell used is reduced to less than half of the same output as the flat plate. If the focusing ratio is 10, the area of the solar cell used is reduced to 1/10 than that of the flat panel type. Therefore, by using the focusing device with the proper focusing ratio according to the use, it is possible to reduce the use area of the solar cell or increase the electric power output and increase the efficiency and economical.

Problems when the surface of the solar cell is partially irradiated:

If a single solar cell is irradiated unevenly, the temperature and current of the cell are unevenly distributed as a result. Therefore, this investigation affects the fill factor and also results in the reduction of open voltage. Opening voltage and efficiency are significantly reduced as the irradiation contour is locally concentrated.

If a part of the PV cells constituting the module is partially or partially shaded, damaged, or if each cell constituting the module is not electrically matched with each other, the hot spots on the cell spots occur. This phenomenon causes thermal stress of the cell or module, and the voltage of the shaded cell may be reversed depending on the PV generation circuit, the load, and the degree of shading, so that power is dissipated in the form of heat. Loss of cells increases the temperature of the battery, causing overheating and damaging the battery. In addition, if high-density solar energy is concentrated on a part of the cell, the temperature of the cell may be locally increased, which may damage the cell. The performance loss of the shaded module is reduced in proportion to the loss of the shaded battery most. It also depends on the life of the module.

Solar energy concentrator:

Various kinds of devices have been developed in this field. The focusing device generally uses a lens or a reflecting surface or a compound optical device in which a lens and a reflecting surface are combined.

(A lens type focuser is generally used as a solar cell device, and a reflecting surface is used as a solar heat focusing device. There is no particular difference, but a focusing device using a lens has more design freedom than a reflecting device, It's less sensitive, but the lens doesn't transmit scattered light, so it's useful in direct sunlight, such as deserts, which typically use Fresnel lenses to reduce weight.)

Of all the focusing devices, especially those using compound parabolic concentrators (CPCs) are theoretically proven to be the most ideal focusing devices (US Patent No. 4003 638, US Patent No. 4002 499, etc.). It is a device used as a slope.

The parabolic trajectory is mathematically expressed in the polar coordinate system (ρ, φ) as follows (see Fig. 2).

ρ = 2f / (1-cosφ) (3)

Here, f is the focal length OF.

The basic principle of the CPC is shown in FIG. The reflective surface of the basic model of the CPC is composed of two parabolic reflective surfaces and uses the optical properties of the parabolic reflective surface. That is, as shown in FIG. 2, the light rays incident in parallel with the parabolic plane (z'-axis) are all reflected at the focal point F after being reflected from the parabolic plane. Therefore, when the light receiving surface is at the focusing point, high density energy is distributed.

However, if the incident light is not parallel to the axis and is incident at an angle inclined by ± α (Fig. 3), the energy density at the focal region spreads widely, in which case the position and size of the light receiving surface (e.g., DD ') The distribution of energy density on the light receiving surface is different. Some rays do not reach the light-receiving surface, but are reflected back from the reflecting surface.

For a given constant light-receiving surface width DD ', the two-dimensional CPC structure is a structure transformed by one focusing device by tilting the axes of the two parabolic reflecting surfaces described above, and all light rays incident within the incident limit angle (± α). Will reach the light receiving surface. This is called the principle of the end ray.

As shown in FIG. 4, the CPC apparatus that satisfies this principle is positioned at the point F of the right parabolic surface (partially, F'B), and the axis (FJ, z'-axis) of the parabolic surface is intended to be constructed. The axis of the focusing device (z-axis) is inclined counterclockwise by an angle of + α, and the upper end point (B) of the reflecting surface is formed so that the tangent at this point is parallel to the longitudinal axis (z-axis) of the device. Cut at point B, and the bottom point F 'of the present parabolic plane cuts at the intersection F' where it meets the line passing through the focal point F, parallel to the transverse axis (x-axis) of the device. The axis of symmetry of the device (z-axis) crosses the midpoint of this exit plane FF '.

If the left reflecting surface AF is formed as a mirror image in which the right reflecting surface F'B is symmetrically in the longitudinal axis (z-axis) of the device, the focus of the left parabolic surface AF is at point F. Is located on its axis formed by the line F'J '.

The two left and right reflecting surfaces AF and BF 'thus formed form one focusing device AFF'B. The light receiving surface (or endothermic surface) is located at the exit surface FF '.

The characteristic of this device is that the opening All light rays incident at an angle equal to or less than ± α reach the exit surface FF 'after being reflected either directly or at the reflective surface (FIG. 5). Light rays incident at angles greater than the angle α are all reflected back out of the reflection surface. The maximum incidence angle α that reaches the light receiving surface is called an acceptance half-angle, and the ratio between the opening surface AB and the exit surface FF 'is defined as a geometric concentration ratio. The relationship between this focusing ratio and the incident limit half angle is defined as follows for CPC.

Ccpc = 1 / sinα (for two-dimensional focuser) (4)

Ccpc = 1 / sin ² α (for 3-D Integrator) (5)

In the case of the two-dimensional focusing apparatus as an example of the application of the present principle (Fig. 6), when the incident limit half angle is 90 °, the focusing ratio becomes one (1), and when the incident limit half angle is 30 °, Focus ratio becomes two. In the latter case, the ratio of the area between the opening surface AB and the exit surface FF 'becomes 2, which means that the density of solar energy incident on the opening surface is doubled at the exit surface, and thus the exit surface. If the solar cell having the same area as the main exit face is placed on the air outlet, it receives twice the amount of light and generates about twice as much current as when used as a flat plate type (see Fig. 1), or the endotherm of the same area as the exit face at the main exit face When the plate is placed, twice as much solar energy is concentrated to produce a higher temperature than in the case of flat plates (e.g. an increase in temperature due to solar radiation in this case (C = 2) at 90 ° C under standard conditions). Increased to 160 ° C.). In addition, the efficiency at the operating temperature range of the device is much higher than that of flat plate collectors.

In this case, the angle of incidence angle means that if the position of the sun is within the range of ± 30 ° from the vertical plane of the light-converging plane, all light rays incident on the aperture will reach the light-receiving plane. This angle determines the limit of light receiving time during the day if the sun is not tracked, and also determines the number of times the positioning of the collector is seasonal. That is, in this example, if the focusing device is located east-west (FIG. 6), and the vertical direction of the opening surface of the integrator is fixed to the vernal equinox (or the autumn equinox) at noon at about noon, about 5 hours of light receiving time is possible. If not, 11 hours of light reception is possible. In this case, according to the season is not required to position control from north to south (north-south control angle is ± 23.5 °)

The CPC of this structure allows the maximum angle of incidence for a given focusing ratio than any other type of focusing machine. Conversely, it is a device that allows the maximum focusing ratio for a given angle of incidence, and can focus the maximum solar energy on the light receiving surface (or endothermic surface).

The problem with flat panel devices using solar energy is that solar cell semiconductors (eg, Si, GaAs, etc.) are generally expensive when generating electricity using solar cells (semiconductors). 1/2) the semiconductor also has low electrical conversion efficiency (about 15% for single crystal Si). The flat heat collector device using solar heat has a limit on the heat collection temperature of the heat absorbing surface (about 40 to 90 ° C.) and cannot be used for a device requiring a high temperature (> 150 ° C.). Therefore, a type of focusing apparatus is required for a device that reduces the cost of the device or requires a high temperature.

The CPC described above causes special problems when used in solar cells.

In other words, a shadow is generated locally in the solar cell, and in this case, the electrical conversion efficiency is lowered as described above, and in extreme cases, thermal tension may occur due to an unbalanced distribution of heat generated in the solar cell, thereby causing damage. .

In the above example (CR = 2, α = 30 °), the incoming light at an angle of incidence of almost + 30 ° or -30 ° is collected at the focal point F (or F ') after reflection, so that the shadowing phenomenon occurs in other parts of the surrounding area. (See Figs. 8, 9 and 10). In addition, the temperature of the solar cell and the reflecting surface is locally increased at the focal point, and as the temperature is increased, the voltage of the solar cell is decreased, so that the output is lowered. Damage to the bottom and solar cells can occur.

In the case where the light receiving surface is an endothermic surface, the endothermic surface is locally inefficiently heated and uniformly distributed.

In order to solve the above-mentioned problems caused by the distribution of light density uneven in the light receiving surface (or heat absorbing surface) of the basic composite parabolic surface (CPC) focusing apparatus described above, the optical principle will be solved. The principle is to position the light receiving surface (or heat absorbing surface) in the middle of the light path that is gathered at the focal point and distribute the reflected light uniformly on the surface of the light receiving surface (or heat absorbing surface) to distribute the energy density. The purpose is to increase the efficiency of electrical conversion or increase the temperature of the endothermic surface. Therefore, we propose a CPC solar energy focusing device with uniform light receiving density that increases efficiency, economics and lifespan.

(1) Light receiving density uniforming CPC focusing device

In the light receiving density uniforming CPC focusing apparatus according to the present invention, the basic CPC focusing apparatus shown in FIG. 4 is modified in the form as shown in FIG. 11, and the basic CPC focusing apparatus is receiving the light receiving apparatus of the present invention as shown in FIG. 11. Geometrical changes to form the density uniformity CPC focusing apparatus are achieved by the following means.

1. In the basic CPC structure shown in FIG. 4, by connecting the lower end point F (focus of the right second reflecting surface) of the left first reflecting surface AF and the upper end point B of the right second reflecting surface BF '. Line bf (The line BF is the same as the light incident at the limit half angle incident at the upper end point B of the right second reflecting surface BF 'toward the focal point F in parallel to the axis of the left first reflecting surface AF),

2. A line parallel to the line BF is formed at the focal point F 'of the left first reflecting surface (lower point of the right reflecting surface), and the position of the point K' which meets the right second reflecting surface is obtained.

3. At point K ', locate the line K that is parallel to the device's abscissa (x-axis) and the point K that meets line BF.

4. In the structure of the basic CPC focusing device, the left first reflecting surface AF moves to the right by the distance s to the point where it meets the point K along the device's transverse axis (x-axis). At this time, the focal point F 'is also moved to the right and is located at the point F ".

5. Cut the lower part of each reflecting surface at this point (K, K ').

6. The reflection surfaces A'K and BK 'thus formed form the light receiving density uniforming CPC focusing apparatus according to the present invention.

The location of the point K 'satisfying the above condition satisfies the following relation in the model of the basic CPC (in the x'z'-coordinate system of Figure 4).

cosφ _{K '} = [1-2 (1 + sinα) * sinα] cosα + (1 + sinα) * (1-2sinα) Of

(cosα + sinα + 1) * (1-2sinα) ² (6)

Here, φ _{K '} is the position of the parabolic point K' in the polar coordinate system with the focal point F defined in FIG. 4 as the origin, and α is the incident limit half angle of the basic CPC described above.

In the above relation, if? ≧ 30 ° according to the condition cosφ _{K ′} ≦ ± 1, the above point K ′ does not exist and coincides with the focal point F ′. In other words, the same as the basic CPC corresponding to α≥30 °. The basic principle of the present invention therefore applies only in the case of α <30 °. This corresponds to a structure in which the focusing ratio is two or more according to the relation (4) in the structure of the two-dimensional basic CPC (in the case of the three-dimensional, the focusing ratio is four or more by the relation (5)).

The focusing ratio Ceff according to the above structure of the present invention becomes smaller than the focusing ratio Ccpc of the basic CPC for a given incidence half angle α and is given by the following relation in the case of a two-dimensional apparatus.

Ceff = Ccpc-2 * (1 + sinα) * tanα * cos (φ _{k '} -α) / (1-cosφ _k' ) (7)

Where Ccpc is the focusing ratio of the base CPC defined in relation (4). For example, if the focusing ratio of the basic CPC is Ccpc = 2.1, α = 28.44˚ φ _{K '} = 109.3˚ Ceff = 1.91 according to the relations (4), (6) and (7), than the focusing ratio Ccpc = 2.1 of the basic CPC. About 10% less. However, in the focusing apparatus, in general, the uniformity of energy density on the light receiving surface (heat absorption surface) is more important than the size of the focusing ratio, and the minimization of light loss (or heat loss) is more important.

In the modified CPC focusing apparatus according to the present invention, as shown in FIGS. 12 to 13, all light rays incident on the opening surface A'B at an angle smaller than the incident limit angle ± α are substantially evenly distributed on the light receiving surface KK '. .

(2) Rain Boot Type Light Density Uniformity CPC Focusing Device

In the model of FIG. 11, which is a focusing device according to the present invention, all light rays incident on the opening face of the device within a given angle of incidence are formed with a substantially uniform energy distribution on the light receiving face.

And another focusing device according to the present invention that can provide almost the same effect as the model of Figure 11 is a rain boot type structure as shown in FIG. The rain boot type structure is shown in FIG. 15,

1.Reflect the reflecting surface of arc KNM around the point K 'with the light receiving surface KK' as the radius.

Form.

2. Light path of the light incident at the limit half angle of incidence at the upper end point B of the right reflective surface

Find the point M where In other words, this ray travels toward focal point F

Reflected at the bottom point K of the left reflective surface in the path and turned towards the focal point F "

Is done.

3. The light incident at the upper limit A 'of the left reflecting surface at the incident limit half angle is an arc.

Pass the center point K 'of KNM and reach point N of the arc directly.

Reflect again at N and back through the point K '.

4. Line K'M is an exit surface formed the same width as the original light receiving surface KK '.

5. Therefore, the reflecting surface is formed of A'KNM and BK ', and the original light receiving surface KK' is exited.

It is moved to the surface K'M and one boot type focusing device is formed.

In the boots type light receiving density uniformizing CPC focusing apparatus according to the present invention, all light rays incident on the opening surface A'B at an angle smaller than the incident limit half angle ± α are reflected on each reflecting surface, and are substantially evenly received on the light receiving surface K'M. Distributed.

Boot type light receiving density shown in FIG.

The homogenizing CPC focusing apparatus is a state in which the focusing apparatus is rotated so that the light receiving surface K'M and the ground of FIG. 15 are parallel.

The reason why the boot type light receiving uniformity CPC focusing device is rotated so that the light receiving surface K'M and the ground are parallel to each other is that when the plate type heat absorbing surface faces the ground, heat loss due to convection in the closed boot type space is reduced. Because it decreases.

(3) Structural Change of Rain Boot Type Light Density Uniformity CPC Focusing Device

In the model of the boots type light receiving density uniformity CPC focusing apparatus shown in FIG. 15, the right reflecting surface and the light receiving surface are bonded to each other at the boundary point K ', but the actual product generally requires a free space for working (manufacturing). Do.

Consider these issues

1. Right side of the boot type light receiving density uniformity CPC focusing apparatus shown in FIG. 15 and FIG.

Clearance space required at the boundary point K 'between the first reflecting surface BK' and the light receiving surface K'M

Move to the right along the light-receiving surface K'M to select the position of point G.

(See FIG. 17)

2. The line perpendicular to the light receiving surface K'M at the point K 'meets the arc reflecting surface KNM.

At point H, the reflecting surface is aligned by the same clearance d parallel to the light receiving surface K'M.

Extend the line to determine the location of point G '.

3. A circular arc reflecting surface (G'N "M ') with radius KK' at the point G 'with the point G as the center point

To form.

4. Light rays incident at the incident limit half angle at the upper end point B of the right parabolic reflecting surface

Proceed towards focal point F and reflect at the lower point K of the left reflective surface to focus

Determine the location of the point M 'where it meets the arc reflection plane as it travels toward F ",

5. Light rays incident from the upper limit point A 'of the left reflection surface at the incident limit half angle are focused.

Proceed toward F ", and the light beam diverges from point N" on the circular reflection surface G'N "M '.

Is reflected back and proceeds towards points V and K ".

Point V is the point where the extension line of the light receiving surface plane K'G meets the reflected light.

Point K "is the same radius as the reflected light and KK '

It is the point where it meets the arc formed by the core. So both points V and K "

This point is located on the reflected light beam.

6. Here, M 'is selected between two points, V and K ", of the reflected light and M'

The exit surface connected with the point can be selected as the width of the light receiving surface.

That is, the light receiving surface having the same width as the width KK 'of the original light receiving surface is the exit surface K "M'.

It is also possible to use it, and also select the width VM 'for the light receiving surface of smaller width.

You can also choose. Or another point K "on the line connecting point V and K"

The exit face K "M 'can be selected as the light receiving surface.

VM 'becomes the minimum width of the light receiving surface. (See FIG. 17)

7. The maximum space of the space K'V is equal to the extension of the line K'V and the extension of the reflected light KF ".

I'm up to the point.

8. The inside of the surface forming the straight line K'G is the reflecting surface, and the straight line GK "or VK"

It is a reflection surface perpendicular to the light receiving surface K'G.

9. All the focusing device structures according to the present invention formed as described above are incident limit half angle beams

All light beams incident on aperture A ' B at a smaller angle

K "M 'is reached.

When the light receiving surface is selected as VM 'or K "' M ', the focusing ratio of the device is

K'M 'is higher than that (where K "' is randomly on the line VK").

Is chosen.)

(4) When the heat absorbing surface of the boots type light receiving uniformity CPC focusing apparatus according to the present invention is nonlinear (cylindrical)

If the heat absorbing surface is not a plane, as shown in Fig. 18, the orbit of the reflecting surface that can theoretically maximize the maximum incident half angle with respect to the reflection surface of the involute track of the endothermic surface It is formed of a special second reflective surface continuously connected to the curved surface of the new track.

The trajectory of the second reflecting surface is formed of a reflecting surface of a special trajectory which is adjusted to meet a non-tangential endothermic surface tangentially after the light rays incident at the incident limit angle are reflected from the second reflecting surface.

Such a device will be referred to as a "new linear integrator". 18 illustrates the case where the non-linear endothermic surface is cylindrical.

For example, as shown in FIG. 18, when the endothermic surface is cylindrical as shown in FIG. 18, the formation of the lower left reflective surface is the end of the yarn when the new wire of the circle (the yarn wound by the cylinder is pulled tightly from the circle and pulled out tangentially). Part of the surface (surface OP) that is formed by the locus that the point draws. The second reflecting surface is a curved surface PQ, which is a special curved surface formed so that all light rays coming in parallel with the incident limit half angle θ meet at the surface of the heat absorbing surface after being reflected by the present reflecting surface PQ. These two (2) curved surfaces meet continuously at the junction P (ie, the slopes of each other at the contact P are the same). Top point Q is the point where the tangent at this point is formed parallel to the z "-axis which is the axis of the device.

The right reflecting surface 0P'Q 'is a curved surface in which the reflecting surface OPQ curved surface is formed symmetrically on the axis of symmetry (z "-axis) of the apparatus.

The characteristic of the reflective surface of this trajectory is that, like the CPC described above, the reflective surface OPQ (or OP'Q ') has the incident limit half angle θ and one or more times at the reflective surface which sees all the light beams incident at a smaller angle. After reflection, they all reach the endothermic plane (the principle of the end beam). Light rays incident at an angle greater than this incident limit half angle are reflected at least once on the reflection surface and then return outward without reaching the endothermic surface.

The use of such a new improved special reflective surface is shown in Figs. 19 and 20. That is, the heat absorbing surface K'M or K "M 'is removed in the apparatus shown in FIGS. 15 and 17, and the width of the opening surface QQ' of the focusing apparatus shown in FIG. In this case, it is adjusted to replace M. In this case, the incident limit half angle θ is the maximum angle reflected by the apparatus of the main body (Figs. 15 and 17) to reach the exit surface K'M or K'M '. Is selected as the incidence limit half angle incident on the opening surface (QQ '= K'M, or K "M') of this special apparatus.

In the formation of the apparatus, the depth (height) of the newly improved reflective surface shown in Fig. 18 can be arbitrarily cut to adjust the width of the opening surface QQ '(e.g., opening surface WW').

The present invention mitigates the shading of the light receiving surface (heat absorbing surface) due to the focusing of the solar energy collected at the focal point in the design of the conventional basic CPC, and at the same time reduces the high temperature phenomenon due to the energy focused on a part. It also increases the efficiency of the device (light receiving surface or endothermic surface) due to the solar energy density distributed substantially uniformly at the exit surface of the device.

The focusing apparatus can reduce the area of the solar cell by the focusing ratio, thereby reducing the unit cost of the apparatus by reducing the use area of the solar cell. The cost of an optical element is about 1/10 to 1/20 of a solar cell.

When the present invention is applied to a solar device, not only can the surface temperature of the heat absorbing surface be increased, but also can be heated substantially evenly, thereby increasing the efficiency of the device than when locally heated.

In addition, the endothermic surface is parallel to the ground and at the same time facing the ground to reduce the heat loss due to convection to increase the efficiency of the device (Fig. 15, Fig. 17). In addition, it is possible to maximize the thermal efficiency of the endothermic surface by stagnating the flow of convection (Fig. 17, Fig. 20).

Claims (4)

A parabolic cross-section consists of a light reflecting surface formed by connecting the right reflector (second reflector), the left reflector (first reflector), and the lower ends of the two reflectors whose parabolic trajectory satisfies ρ = 2f / (1-cosφ). The focal points F and F 'of each reflecting mirror are formed at the lower end points of the opposite reflecting mirrors, and the lines AF' and BF connecting the entrance end portions A and B of the solar light to the focal points F and F '. In a basic CPC having an angle of incidence between the angle between the z-axis and the z-axis, The line BF is drawn by connecting the lower end point F (focus of the right second reflecting mirror) of the left first reflecting mirror AF and the upper end point B of the right second reflecting mirror BF ', and the focus F of the left first reflecting mirror AF. Draw a line parallel to the line BF at '(lower point of the right reflecting surface) to determine the position of the point K' meeting the right second reflecting surface, or the relational expression with respect to the selected incident limit angle α. cosφ _{K '} = [1-2 (1 + sinα) * sinα] cosα + (1 + sinα) * (1-2sinα) Of (cosα + sinα + 1) * (1-2sinα) ² Determine the position of the point K 'determined by the value of the angle φ _K' satisfying Determine the location of the point K where the point K 'meets the line K'K parallel to the device's transverse axis (x-axis) and the line BF, The left first reflector AF is moved to the right by the distance s along the transverse axis (x-axis) of the device to the point where it meets point K. As the left reflector AF is moved to the right by s, the right reflector AF The bottom focus (F) is moved to point F ", In this state, the lower end of each reflecting mirror is cut by lines K and K 'to form a light receiving surface, so that both ends of the light receiving surface are spaced apart from each focal point of the left and right reflecting mirrors so that the received light density is uniformly distributed. Light receiving density uniformity CPC focusing device. A circle passing through the point KNM with a radius of the length KK '(width of the light receiving surface) about a point K' of the light receiving surface KK 'as a center, and at the upper end point B of the right reflecting mirror BK'. A light reflecting surface K'M having a light receiving surface facing the ground is formed by forming an auxiliary reflecting mirror of circular arc KNM by obtaining the reflected light path of the light incident at the incident limit half angle α and the point M where the light meets the circle. Boots type light receiving density uniformity CPC focusing device formed. The method according to claim 2, wherein the position of the point G is selected by moving to the right along the light-receiving surface to the right by the clearance d required at the boundary K 'between the right reflector (second reflector) and the light-receiving surface, and the ground at the point K'. Point G 'is selected by extending the reflecting surface in a straight line by the same clearance space d parallel to the light receiving surface K'M at the point H that meets the line perpendicular to the light receiving surface K'M and the arc reflecting surface KNM. Starting from point G 'with radius KK' as the center point, an auxiliary reflector with circular arc G'N "M 'is formed, and a linear reflecting surface is inserted between the left and right reflector and the auxiliary reflector to secure the necessary space for actual production. Boot type light receiving density equalization CPC focusing device. The boots type light receiving density uniformizing CPC focusing apparatus according to claim 2 or 3, wherein a second auxiliary reflector of an involute curved surface extending to the auxiliary reflector is combined with a nonlinear heat absorber.

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