JP2003070273A - Solarlight power generating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solarlight power generating system for maximizing total conversion efficiency by suppressing a temperature rise of a solar cell while a part which is not photoelectrically converted of solarlight energy is utilized to the maximum limit irrespective of its wavelength. SOLUTION: The solarlight power generating system comprises at least the solar cell 103, a thermal storage means 107 and a thermoelectric conversion means 108. In this system, the conversion means 108 is disposed along the direction of a heat flow at the time of a solar radiation on a back surface of the cell 103 via the means 107.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic power generation system including a solar cell element, and more particularly to a photovoltaic power generation system having thermoelectric conversion means for more efficient use of sunlight.

[0002]

2. Description of the Related Art Conventionally, a photovoltaic power generation system using a solar cell has been attracting attention as an energy source that is safe and does not impose a burden on the environment. In recent years, however, a conventional power generation means such as thermal power generation has been used. In order to be competitive from the economical point of view as well, emphasis has been placed on the development of higher efficiency and cheaper solar cells.

As one of the directions of such efforts, the energy of the portion of the energy of sunlight that cannot be converted by the solar cell (finally becomes heat) is converted into electric energy by the thermoelectric conversion element, and total photoelectric conversion is performed. Ways to increase efficiency are being studied.

For example, Japanese Patent Application Laid-Open No. 7-142750 discloses a method of arranging a thermoelectric conversion element on the back surface of a solar cell panel to recover energy that could not be photoelectrically converted.

On the other hand, from the viewpoint of obtaining the above-mentioned more efficient and inexpensive solar cell, a concentrating solar power generation system has been attracting attention in recent years. According to the concentrating solar power generation system, the most expensive solar battery cell among the constituent parts can be largely saved, so that an extremely large cost reduction can be achieved. In addition, as is generally said, the generated voltage increases as the light intensity increases, so the ratio of the output energy to the incident energy, that is, the conversion efficiency is improved compared to the non-concentrating solar power generation system. In comparison with a case where non-concentrating solar cells are spread over the same area, a large output can be obtained.

Also in such a concentrating solar power generation system, Japanese Utility Model Laid-Open No. 5-23554 and Japanese Patent Laid-Open No. 11-
As disclosed in Japanese Patent No. 31835, it has been proposed to separate sunlight by wavelength and guide a long-wavelength component having a small contribution to photoelectric conversion to a thermoelectric conversion element to improve the total conversion efficiency.

[0007]

However, the various conventional proposals have the following problems.

That is, when the thermoelectric conversion element is arranged on the back surface of the solar cell panel as in JP-A-7-142750, the heat transfer coefficient of the thermoelectric conversion element is generally small and the temperature of the solar cell panel rises greatly. For this reason, there is a problem that the loss associated therewith is large and in some cases exceeds the energy obtained by thermoelectric conversion.

When a long wavelength component of sunlight is introduced into a thermoelectric conversion element by using a wavelength separation filter or the like, as in Japanese Utility Model Laid-Open No. 5-23554 and Japanese Patent Laid-Open No. 11-31835, long wavelength components are used. The component is a small part (about 20%) of solar radiant energy, and the short wavelength component that turns into heat in the solar cell cannot be used, so the energy utilization rate becomes small and a wavelength separation filter or thermoelectric conversion element is introduced. There was a problem that the cost incurred for doing so could not be redeemed.

In view of the above problems, the present invention maximizes the total conversion efficiency by suppressing the temperature rise of the solar cell element while maximally utilizing the portion of the solar energy that is not photoelectrically converted regardless of the wavelength. An object of the present invention is to provide a solar power generation system that can be realized.

[0011]

In order to achieve the above object, the solar power generation system of the present invention has at least a solar cell element, a heat storage means and a thermoelectric conversion means, and is arranged along the direction of heat flow during solar radiation. In addition, the thermoelectric conversion means is disposed on the back surface of the solar cell element via the heat storage means.

According to the photovoltaic power generation system of the present invention, the energy that has not been converted by the solar cell element is temporarily stored in the form of thermal energy in the heat storage means that is separated from the solar cell element, and the thermal energy is gradually converted to thermoelectric conversion. By doing so, the temperature rise of the solar cell element can be suppressed as compared with the case where the thermoelectric conversion is attempted in a short time in the solar radiation state, so that the reduction of the effective conversion efficiency of the solar cell element can be suppressed.

In the solar power generation system of the present invention,
The heat storage means is preferably a heat storage means for storing heat by utilizing latent heat, and the heat storage means is preferably a heat storage material containing a heat medium in a metal container. By using a heat storage material that uses latent heat as the heat storage material in this way, the apparent specific heat can be increased, the weight and size of the device can be reduced, and the strength and energy consumption of the tracking device / holding device can be reduced. Since the size can be reduced, the power generation cost can be further reduced.

Further, it is preferable that the solar cell element and the heat storage means are connected through a heat transport means, and the heat transport means is provided with a difference in heat transport ability depending on a heat transport direction. As a result, it is possible to prevent the once accumulated thermal energy from flowing backward during non-solar radiation and wastefully radiating heat through the solar cell element.

Further, it is preferable that the heat transporting means is a heat pipe in which a volatile liquid is enclosed in a metal tube. Alternatively, the heat transport means has a heat medium and heat medium drive means for causing the heat medium to flow to the heat storage means, and the heat medium drive means operates the heat medium in conjunction with the output of the solar cell element. Preference is given to flowing.

The heat transport direction from the solar cell element of the heat transport means to the heat storage means is preferably upward with respect to the direction of gravity. As a result, the difference in heat transport capacity can be increased.

Further, it is preferable that the path from the solar cell element of the heat transport means to the heat storage means is covered with a heat insulating material.

In addition, it is preferable that a heat radiating means is disposed on the surface of the thermoelectric conversion element opposite to the surface in contact with the heat storage means.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to the present embodiments.

The solar power generation system of the present invention is provided with at least a solar cell element, a heat storage means and a thermoelectric conversion means. The solar cell element is an element that receives sunlight and generates electric energy, and is fixed to a roof of a house or the like, or installed on a pedestal that tracks the sun.

On the back surface of this solar cell element, a thermoelectric conversion means is arranged via a heat storage means so as to be along the direction of heat flow during solar radiation. That is, the heat storage means is connected to the back surface of the solar cell element through a thermally favorable connection, and further, a thermoelectric conversion element is arranged in a part of this heat storage means through a thermally favorable connection.

Further, the solar cell element and the heat storage means are connected via a heat transport means, and the heat transport means is provided with a difference in heat transport ability depending on the heat transport direction as described later.

Further, a heat radiating means such as a heat sink or a fan is arranged on the surface of the thermoelectric conversion element opposite to the surface in contact with the heat storage means, as the case may be.

Each constituent element of the solar power generation system of the present invention will be described below.

(Solar cell element) A solar cell element includes a photoelectric conversion element for converting sunlight energy into electric energy, and these are single or plural members configured to receive sunlight and generate an electric output. The photoelectric conversion element may be a photoelectric conversion element such as silicon, gallium arsenide, cadmium tellurium, or copper indium selenide, but is not limited to those illustrated and includes all that can realize the same function. sell.

In the case of a concentrating solar power generation system, a portion for converting the energy of sunlight into electric energy, that is, a photoelectric conversion portion may be called a solar cell in a narrow sense, but usually photoelectric conversion is performed. It is not possible to perform a normal power generation operation only with the section, and a condensing optical system for condensing is essential. In such a case, the photoelectric conversion unit and the condensing optical system will be collectively referred to as a solar cell in a broad sense.

Various types of condensing optical systems have been proposed in the past, but generally, a refracting optical system using a simple lens or a thin Fresnel lens, or a reflecting mirror of a parabolic mirror is used. A reflective optical system or a composite optical system in which both are combined can be used.

(Heat Storage Means) The heat storage means means for obtaining the heat energy generated in the solar cell from the heat transport means and storing it. As a substance that can be used, any substance having a large specific heat can be used. Specifically, simple substances such as aluminum, copper, tin, mercury, and lead, and sodium chloride, potassium chloride, aluminum sulfate, zinc carbonate, and the like can be used. Inorganic compounds and the like can be effectively used.

In order to further increase the amount of absorbed and exhausted heat, a so-called latent heat storage material that uses a substance having a large heat of fusion can be used to increase the amount of absorbed and exhausted heat per unit weight, which is preferable from the viewpoint of weight reduction and size reduction. . As the latent heat storage material, a material having a melting point of 40 ° C. to 90 ° C. is preferably selected from the commonly used materials for the purpose of the present invention. For example, naphthalene, yellow phosphorus, or a low melting point alloy (lead-tin-bismuth-indium alloy) can be preferably used.

(Heat Transporting Means) The heat transporting means has a function of transporting the heat energy generated in the solar cell element to the heat storage means, and is simply a metal plate or bar, more preferably Means a material such as aluminum or copper having a high thermal conductivity. Further, in order to make a difference in the heat transport ability depending on the heat transport direction, a so-called heat pipe in which a volatile liquid is enclosed in an aluminum or copper pipe can be preferably used. In this case, as the fluid to be sealed, a liquid such as water or alcohol can be used in consideration of the freezing point and the boiling point.

Incidentally, in the heat pipe developed in recent years, contrary to the intention of the present invention, a groove called a groove is engraved or a metal mesh is enclosed so as to reduce the difference in the heat transport direction. Although the reflux of the heat-transporting liquid is promoted by the capillary phenomenon, it is preferable to employ a structure in which a volatile liquid is enclosed in a simple metal tube rather than using such a structure in the present invention.

Further, as a method of generating a difference depending on the heat transport direction, a method of circulating a heat medium and changing the circulating amount between solar radiation and non-solar radiation can be effectively used. By adopting such a structure and arranging such that the direction from the solar cell element of the heat transport means to the heat storage means is upward with respect to the direction of gravity, the difference in transport capacity depending on the heat transport direction is increased. can do.

(Thermoelectric conversion means) The thermoelectric conversion means is usually a semiconductor element utilizing the Seebeck effect, and includes bismuth-tellurium alloys, lead-tellurium compounds, silicon-germanium alloys, selenium compounds, iron silicides, etc. Various substances have been proposed and put into practical use. Any of the thermoelectric conversion elements using these substances can be used in the present invention, but it is the bismuth-tellurium alloy that works well even in a relatively low temperature region.

With the above configuration, the portion of the solar energy that reaches the solar cell during solar radiation that has not been photoelectrically converted is converted into thermal energy, and the thermal energy is stored in the heat storage material, and is used not only during solar radiation but also during non-solar radiation. It is continuously converted into electric energy through the thermoelectric conversion element.

Further, the temperature rise due to holding a large amount of heat energy only by the solar cell element can be suppressed, and the decrease in the photoelectric conversion efficiency much larger than the usual thermoelectric conversion efficiency can be suppressed, so that the whole can be suppressed. As a result, the efficiency of conversion of solar energy into electric energy can be greatly improved.

Further, a heat pipe is used as a heat transporting means for heat conduction between the solar cell element and the thermoelectric conversion element, and the heat transporting direction of the heat pipe is set to a direction opposite to gravity at the time of solar radiation so that the heat transporting ability is improved. By making the directions different, it is possible to avoid a situation in which the thermal energy once stored in the heat storage material flows backward during non-solar radiation and is radiated from the solar cell element side and does not contribute to thermoelectric conversion.

Regarding the heat transporting means, in order to prevent the diffusion of heat to other than the heat storage material which is the heat transporting destination, the heat transporting means covers the path from the solar cell element to the heat storing means with a heat insulating material. Is preferred.

Although the above description has been made using the preferred materials and structures at the time of the invention, it is clear that the concept of the present invention is not limited to the above materials and structures. Also,
For the sake of convenience, it has been described that the individual means is provided with the individual means, but it is needless to say that the single means can be configured to serve a plurality of functions.

[0039]

EXAMPLES Preferred examples of the present invention will be described below, but the present invention is not limited to these examples.

[Embodiment 1] FIG. 1 is a schematic view schematically showing a main part of a solar power generation system according to Embodiment 1. The present embodiment is an example in which the present invention is applied to a solar tracking concentrating solar power generation system using a Fresnel lens.

In FIG. 1, 101 is sunlight, and 102 is a Fresnel lens for refracting the sunlight and condensing it on the solar cell element 103. By giving the Fresnel lens 102 a convex refractive power, the Fresnel lens 10
It is configured such that almost all sunlight is collected on the solar cell element 103 having an area smaller than 2.

The solar cell element 103 can be called a solar cell in a narrow sense only by this. However, in the present invention, the solar cell element 103 is called a Fresnel lens 102 because it has a function of receiving light from the sun and generating electric energy. The solar cell element 104 is collectively referred to as a solar cell 104.

Now, the sunlight 1 incident on the solar cell 104
01 is irradiated onto the solar cell element 103, and about 25% of the irradiated light energy is output to the outside as electric energy. The remaining about 75% is converted into heat energy on the solar cell element. The energy not photoelectrically converted in this way is the heat transport means 1 according to the present invention.
05 in the direction of arrow 106 toward the heat storage means 107.

Here, the heat transporting means 105 is a heat pipe, and its internal structure and operating principle will be described later.

The heat storage means 107 is configured as a latent heat storage material, for example, a bismuth-lead-tin-indium alloy is enclosed in a copper container (not shown), and the temperature of the heat pipe is the melting point 57 of the alloy. When the temperature reaches ℃, the alloy gradually melts and absorbs more heat energy in the form of heat of fusion. On the contrary, the thermoelectric conversion element 108 which is a low temperature part
The part in contact with is given heat of solidification in the process of solidification of the same alloy in a liquid state, and is configured to show a behavior that the apparent heat capacity is enormous.

The thermoelectric conversion element 108 has a heat flow 110 generated by a temperature difference between a high temperature portion and a low temperature portion when passing through the element.
Part of the heat flow 110 is taken out as electric energy. In this example, the thermoelectric conversion elements disclosed in JP-A-9-8364 and JP-A-9-148635 can be effectively used.

Reference numeral 109 denotes a heat sink using an extruded product of aluminum as a heat radiating means for keeping the temperature of the low temperature portion of the thermoelectric conversion element 108 near room temperature and maximizing the temperature difference between both sides of the thermoelectric conversion element 108. To use.

Next, the structure and principle of the heat pipe 105, which is the heat transporting means in this embodiment, will be described with reference to FIG.

FIG. 2 (a) shows the movement of heat during solar radiation. In the figure, 201 is a copper pipe forming the outer shape of the heat pipe 105, and 202 is the copper pipe 2.
Water as a heat transport medium sealed inside 01. In FIG. 2A, the inclined heat pipe 105
When the solar cell element 103 that is in contact with the lower part of the solar cell element 1 is heated, the water 202 in the copper pipe 201 is
The heat energy of 03 is absorbed (heat of vaporization) and vaporized. The vaporized water vapor moves upward due to the diffusion and updraft as shown by the arrow 203, and is liquefied 204 at the upper end of the heat pipe 105. At this time, heat energy equivalent to the heat energy given at the time of vaporization is given to the inner wall of the copper pipe 201 as cohesion heat. This heat energy is given to the heat storage material 107 located at the upper end of the heat pipe 105. The water droplet 205 generated by the liquefaction 204 moves on the inner wall of the copper pipe 201 in the direction of arrow 206 according to gravity and returns to the initial position. Due to the continuous occurrence of the above cycle, thermal energy is transported at a very high speed and in a large amount.

At this time, the heat energy applied to the heat storage material 107 is stored in the heat storage material 107, and a part of the heat energy is applied to the thermoelectric conversion element 108 shown in FIG.

On the other hand, FIG. 2 (b) shows a state when there is no solar radiation. During non-solar radiation, the temperature of the solar cell element 103 is lower than the temperature of the heat storage material 107, and heat flows from the upper heat storage material 107 toward the solar cell element 103.
In that case, as shown in the figure, the water 202 inside the heat pipe 105 is concentrated at the lower end according to gravity,
The vaporization in the heat storage material 107 located above is extremely smaller than that during solar radiation. Therefore, the heat transport cycle as seen during solar radiation hardly occurs, and the heat transport is performed by the copper pipe 201.
Only due to heat conduction. Therefore, the backflow of heat from the high temperature portion (heat storage material 107) to the low temperature portion (solar cell element 103) is minimized during non-solar radiation.

That is, with the above-mentioned structure, heat is efficiently extracted from the heat storage material as electric energy through the thermoelectric conversion element even during non-solar radiation.

FIG. 3 describes such behavior from the viewpoint of temperature. In the figure, the horizontal axis is the time and the vertical axis is the temperature of each part. At the time of solar radiation, the temperature of the solar cell element also rises as the temperature rises due to the solar cell element being exposed to the solar radiation, and if there is no heat storage material 107, the temperature rise as indicated by the broken line 301 in the figure occurs, resulting in fine weather. The maximum cell temperature 302 reaches 120 ° C to 150 ° C. However, when the heat storage material 107 is present, the heat storage material 107 absorbs latent heat, so that the maximum cell temperature 303 does not rise above a temperature slightly higher than the melting point of the heat storage material. In the case of the present embodiment, the melting point of the heat storage material is 57 ° C., so the maximum cell temperature 303 is approximately 60.
It is about ℃.

Therefore, when compared at the peak time, it is assumed that the standard rated conversion efficiency of the crystalline solar cell is 25% and the temperature coefficient is -0.35 (relative)% / ° C. When the decrease is calculated, the decrease in conversion efficiency when the element temperature is 120 ° C. is 8.3%, whereas
The decrease in conversion efficiency when the element temperature is suppressed to 60 ° C. is only 3.0%.

On the other hand, in the figure, the broken line 304 indicates the temperature of the heat storage material in the other case, that is, the high temperature part temperature of the thermoelectric conversion element, as compared with the case where the heat transporting means having different heat transporting capacity is used as the heat transporting means. It is a representation. As is clear from FIG. 3, in the case of the broken line 304, since the backflow of the accumulated heat energy occurs, the temperature of the heat storage material relatively quickly drops to a level close to the temperature, and the temperature difference between both ends of the thermoelectric conversion element is non-solar. Very small at most of the time. Therefore, the electric energy taken out to the outside is very small. On the other hand, when heat transfer means having a difference in heat transfer capacity is used as the heat transfer means, the temperature difference 305 between both ends of the thermoelectric conversion element remains relatively large and non-solar radiation changes, so that the heat energy is continuously converted to electrical energy. Can be converted into, and the amount of accumulated electric energy can be increased.

[Embodiment 2] FIG. 4 is a schematic view schematically showing a main part of a solar power generation system according to Embodiment 2. Example 1 is an example of a concentrating solar cell using a refracting optical system, whereas this example is an example of a concentrating solar cell using a reflective optical system.

In FIG. 4, 401 is sunlight, and 402 is a reflecting mirror for reflecting the sunlight and condensing it on the solar cell element 403. The reflecting mirror 402 has a parabolic shape having a focal point in the vicinity of the solar cell element 403, and has a smaller area than the reflecting mirror 402.
It is configured such that almost all the sunlight is collected on the surface 3. This solar cell element 403 can be called a solar cell in a narrow sense by itself, but in the present invention, the reflecting mirror 402 and the solar cell have the function of receiving light from the sun and generating electric energy. The element 403 is collectively referred to as a solar cell 404.

Now, the sunlight 4 incident on the solar cell 404
Although 01 is irradiated onto the solar cell element 403, about 25% of the irradiated light energy is output to the outside as electric energy as in the first embodiment. The remaining about 75% is converted into thermal energy on the solar cell element. The energy that has not been photoelectrically converted in this way flows through the heat transport means 405 according to the present invention in the direction of the arrow 406, and the heat storage means 4
Head to 07.

In FIG. 4, the heat transporting means 405 is shown so as to surround the solar cell 404, but since the heat transporting means 405 is tubular, it only blocks a part of the sunlight 401. Therefore, the amount of received sunlight energy is not significantly affected.

Here, the heat transporting means 405 is a copper pipe whose inside is filled with a heat medium, and the heat medium is moved in the direction of arrow 406 in the figure by the pump 411, so that heat in the direction of arrow 406 is generated. The transportation capacity is being expanded. As the heat medium, a solution obtained by dissolving 5% glycerin in water to make it antifreeze is used. The pump 411 is driven by using a part of the output of the solar cell element 403. As a result, the pump 411 is driven when the solar cell 404 is receiving solar radiation and is generating an electric output to enhance the heat transport capacity in the direction of arrow 406, while the pump 411 is stopped when the solar cell 404 is not solar radiation, so When the temperature of the element 403 is lower than that of the heat storage means 407,
The heat is prevented from moving in the direction opposite to the arrow 406 in the drawing.
Therefore, the behavior of the pump 411 causes a difference in the heat transport capacity depending on the direction of the heat flow.

The behavior of the pump 411 is determined by the solar cell element 403.
As a method of interlocking with
Although the output of No. 03 and the input of the pump 411 are directly connected to each other, a method of changing the operation via a control device by using electric power from a commercial power supply connected thereto can also be used.

At this time, by arranging the heat transport direction of the heat transport means (arrow 406 in FIG. 4) in the direction opposite to the gravity direction, the natural convection direction is aligned with the direction of arrow 406. However, the difference in heat transport capacity becomes even larger.

The heat storage means 407 is constructed as a latent heat storage material, and is made by enclosing naphthalene in a copper container (not shown). When the temperature of the high temperature portion of the heat transport means reaches the naphthalene melting point of 80.5 ° C. Melts gradually and absorbs more heat energy in the form of heat of fusion. On the other hand, in the portion in contact with the thermoelectric conversion element 408, which is the low temperature portion, heat of solidification is given during the process of solidification of the liquid naphthalene, and the behavior is such that the apparent heat capacity is enormous. There is.

The thermoelectric conversion element 408 has a structure in which the heat flow 410 generated by the temperature difference between the high temperature portion and the low temperature portion passes through the element.
A part of the heat flow 410 is taken out as electric energy. In this embodiment, as in the case of the first embodiment, Japanese Patent Laid-Open No.
The thermoelectric conversion elements disclosed in Japanese Patent No. 8364 and Japanese Patent Laid-Open No. 9-148635 can be effectively used.

Numeral 409 is a heat sink using an extruded aluminum product as a heat radiating means, as in Example 1, and keeps the temperature of the low temperature portion of the thermoelectric conversion element near room temperature.
It is used to maximize the temperature difference between the two surfaces of the thermoelectric conversion element.

With the above-mentioned structure, the solar cell element 403, the heat storage material 407, etc. behave similarly to the first embodiment. Therefore, detailed description is omitted here. Finally, as described in Example 1, the heat storage material 4
By including 07, the temperature rise of the solar cell element 403 can be suppressed, and thermoelectric generation due to the temperature difference can be continued even during non-solar irradiation, so that the cumulative amount of electric energy can be increased.

[Embodiment 3] FIG. 5 is a schematic view schematically showing a main part of a photovoltaic power generation system of Embodiment 3. While Example 1 and Example 2 were examples of concentrating solar cells, this example is an example using non-concentrating solar cells and not using heat transport means.

In FIG. 5, reference numeral 501 is sunlight, and 503 is a solar cell element protected by a sealing member 512. Here, the solar cell element 503 and the sealing member 512 are collectively referred to as a solar cell 504.

Now, the sunlight 5 incident on the solar cell 504
01 is irradiated onto the solar cell element 503, but about 25% of the irradiated light energy is output to the outside as electric energy as in the first and second embodiments. The remaining about 75% is converted into heat energy on the solar cell element. The energy that has not been photoelectrically converted in this way is stored in the heat storage unit 507 according to the present invention.

The heat storage means 507 is constituted as a latent heat storage material, and is made by enclosing a bismuth-lead-tin-indium alloy in a copper container (not shown), and the temperature of the solar cell element 503 is 57 ° C. of the melting point of the alloy. When the temperature reaches, the alloy gradually melts and absorbs more heat energy in the form of heat of fusion. On the other hand, in the portion in contact with the thermoelectric conversion element 508 which is the low temperature portion, it is configured to give the heat of solidification in the process of solidification of the liquid alloy, and behave so that the apparent heat capacity is enormous. ing.

The thermoelectric conversion element 508 has a heat flow 510 generated by a temperature difference between a high temperature portion and a low temperature portion when passing through the element.
A part of the heat flow 510 is extracted to the outside as electric energy. In this embodiment, as in the case of the first embodiment, Japanese Patent Laid-Open No.
The thermoelectric conversion elements disclosed in JP-A-8364, JP-A-9-148635 and the like can be effectively used.

Numeral 509 is a heat sink using an extruded aluminum product as a heat radiating means, as in Example 1, and keeps the temperature of the low temperature part of the thermoelectric conversion element near room temperature.
It is used to maximize the temperature difference between the two surfaces of the thermoelectric conversion element.

FIG. 6 shows the transition when each part is viewed from the temperature side in the above structure. In the figure, the horizontal axis is the time and the vertical axis is the temperature of each part.

At the time of solar radiation, the temperature of the solar cell element rises as the temperature rises as the solar cell element receives the solar radiation, and if there is no heat storage material 507, the temperature rise as indicated by the broken line 601 in the figure occurs. , Maximum cell temperature 602 in fine weather
Reaches 90 ° C to 110 ° C. However, the heat storage material 50
When there is 7, since the heat storage material 507 absorbs latent heat,
The maximum cell temperature 603 does not rise above a temperature slightly higher than the melting point of the heat storage material. In the case of this embodiment, the melting point of the heat storage material is 57.
Since the temperature is 0 ° C, the maximum cell temperature 603 is about 60 ° C. Therefore, a decrease in photoelectric conversion efficiency due to a temperature rise can be significantly suppressed.

On the other hand, in the figure, the broken line 604 represents the temperature of the solar cell element 503 when the heat storage material is not used, that is, the high temperature portion temperature of the thermoelectric conversion element. As is clear from FIG. 6, in the case of the broken line 604, the temperature of the solar cell element 503 drops relatively quickly to a level close to the temperature because of the inability to store heat energy, and the temperature difference between both ends of the thermoelectric conversion element is non-solar. Very small at most of the time. Therefore,
The electric energy extracted to the outside is extremely small.

On the other hand, in the case of using the heat storage material 507, the temperature difference 605 at both ends of the thermoelectric conversion element is compared with the case of using the heat transporting means having different heat transporting capacities in the first and second embodiments. Then, although it is small, the temperature difference between both ends is 60 for a while due to the phase difference of heat transfer generated by heat storage.
5 remains large. Therefore, since the thermal energy can be continuously converted into the electric energy at the beginning even when the solar radiation is not applied, the accumulated electric energy amount can be increased.

[0077]

As described above, according to the photovoltaic power generation system of the present invention, since the thermoelectric conversion means is arranged on the back surface of the solar cell element which is the photoelectric conversion means through the heat storage means, Energy that has not been converted by the solar cell element is temporarily stored in the form of thermal energy from the solar cell element in the heat storage means, and the thermal energy is gradually thermoelectrically converted, so that the thermoelectric conversion can be performed in a short time in the solar radiation state. Since the peak temperature can be made smaller than in the case of performing the above, it is possible to suppress a decrease in the effective conversion efficiency of the solar cell element.

Further, the solar cell element and the heat storage means are connected by the heat transport means, and the heat transport ability of the heat transport means is varied depending on the heat transport direction.
It is possible to prevent the stored thermal energy from flowing backward during non-solar radiation and wastefully dissipating the heat energy through the solar cell element, and it is possible to improve the total conversion efficiency from sunlight to electric energy.

Further, by connecting the solar cell element and the heat storage material by using the heat transporting means having different heat transporting ability depending on the heat transporting direction, it is possible to suppress the backflow of heat during non-solar radiation, and thus the thermoelectric conversion element. Since the temperature difference between the two ends can be kept large for a long time, the energy to be thermoelectrically converted can be maximized.

Furthermore, by configuring the heat transport direction from the solar cell element of the heat transport means to the heat storage means to be upward with respect to the gravity direction, the difference in heat transport capacity can be increased, The temperature difference between both ends of the thermoelectric conversion element can be kept large for a long time.

Also, by using a heat storage material utilizing latent heat as the heat storage material, the apparent specific heat can be increased, weight reduction and downsizing can be realized, and the strength of the tracking device and the holding device can be improved. Since the energy consumption can be reduced, the power generation cost can be further reduced.

That is, while making maximum use of the portion of solar energy that is not photoelectrically converted, regardless of the wavelength,
It is possible to provide a photovoltaic power generation system capable of suppressing the temperature rise of the solar cell element and maximizing the total conversion efficiency.

[Brief description of drawings]

FIG. 1 is a schematic diagram schematically showing a main part of a solar power generation system according to a first embodiment.

FIG. 2 is a schematic diagram illustrating the structure and operation principle of a heat pipe in the solar power generation system according to the first embodiment.

FIG. 3 is an explanatory diagram showing a temperature transition of each part in the solar power generation system according to the first embodiment.

FIG. 4 is a schematic diagram schematically showing a main part of a solar power generation system according to a second embodiment.

FIG. 5 is a schematic view schematically showing a main part of a solar power generation system according to a third embodiment.

FIG. 6 is an explanatory diagram showing a temperature transition of each part in the solar power generation system according to the third embodiment.

[Explanation of symbols]

Reference Signs List 101 solar light 102 condensing means (Fresnel lens) 103 solar cell element 104 solar cell 105 heat transport means (heat pipe) 106 residual energy flow 107 heat storage means (heat storage material) 108 thermoelectric conversion element 109 heat dissipation means (heat sink) 110 heat flow 201 Copper pipe 202 Water 203 Water vapor flow 204 Liquefaction 205 Water drop 206 Water drop flow 301 Solar cell element temperature without heat storage material 302 Maximum cell temperature 303 Maximum cell temperature 304 When there is no difference in direction of heat transport capacity of heat transport means Heat storage material temperature (dashed line) 305 Temperature difference between both ends of thermoelectric conversion element 401 Sunlight 402 Reflector 403 Solar cell element 404 Solar cell 405 Heat transport means 406 Flow of residual energy 407 Heat storage means (heat storage material) 408 Thermoelectric conversion element 409 Heat dissipation Means (heat sink) 410 Heat flow 4 1 Pump 501 Sunlight 503 Solar cell element 504 Solar cell 507 Heat storage means (heat storage material) 508 Thermoelectric conversion element 509 Heat dissipation means (heat sink) 510 Heat flow 512 Sealing member 601 Solar cell element temperature 602 without heat storage material Maximum cell temperature 603 Maximum cell temperature 604 Temperature of high temperature part of thermoelectric conversion element when heat storage material is not used (broken line) 605 Temperature difference between both ends of thermoelectric conversion element

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Claims (9)

[Claims] 1. A solar cell element, a heat storage means, and a thermoelectric conversion means are provided at least, and the thermoelectric conversion means is provided on the back surface of the solar cell element via the heat storage means so as to be along the direction of heat flow during solar radiation. A solar power generation system characterized by being arranged. 2. The solar power generation system according to claim 1, wherein the heat storage unit is a heat storage unit that stores heat using latent heat. 3. The photovoltaic power generation system according to claim 2, wherein the heat storage means is a heat storage material containing a heat medium in a metal container. 4. The solar cell element and the heat storage means are connected via a heat transport means, and the heat transport means is provided with a difference in heat transport ability depending on a heat transport direction. The solar power generation system according to any one of 1 to 3. 5. The solar power generation system according to claim 4, wherein the heat transporting means is a heat pipe in which a volatile liquid is sealed in a metal tube. 6. The heat transport means has a heat medium and heat medium drive means for causing the heat medium to flow to the heat storage means, and the heat medium drive means is interlocked with the output of the solar cell element. 5. The heating medium is caused to flow by means of
The solar power generation system described in. 7. The heat transport direction from the solar cell element of the heat transport means to the heat storage means is upward with respect to the gravitational direction. The described solar power generation system. 8. The photovoltaic power generation system according to claim 4, wherein a path from the solar cell element of the heat transport means to the heat storage means is covered with a heat insulating material. system. 9. The heat dissipating means is disposed on the surface of the thermoelectric conversion element opposite to the surface in contact with the heat accumulating means, according to any one of claims 1 to 8. Solar power system.