JP2002208721A - Photovoltaic power generation system having cooling mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photovoltaic power generation system having a cooling mechanism at a low cost in which minimum required cooling can be performed depending on the change of weather and cooling energy can be minimized. SOLUTION: The photovoltaic power generation system comprises solar cells (120) and a cooling mechanism, wherein the cooling mechanism comprises means (130) for cooling the solar cells and means (123) for storing or operating an optimal driving state of the cooling means depending on the output from the solar cells to drive the cooling means based on the output from the storing or operating means.

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 provided with a cooling mechanism. More specifically, the present invention relates to a photovoltaic power generation system provided with a cooling mechanism capable of cooling an installed solar cell according to the output of the solar cell.

[0002]

2. Description of the Related Art In recent years, a photovoltaic power generation system using a solar cell has attracted attention as an energy source that is safe and does not burden the environment. And since a photovoltaic power generation system needs to be advantageous from the viewpoint of economic efficiency over conventional power generation systems such as thermal power generation, research and development on photovoltaic power generation systems have high photoelectric conversion efficiency and Emphasis has been placed on obtaining inexpensive solar cells.

By the way, in order to increase the output energy of a solar cell, it is important to improve its photoelectric conversion efficiency. In addition, it is necessary to devise ways to increase the actual power generation of the solar cell. For example, one of the ideas is to keep the temperature of the solar cell as low as possible. That is, when a solar cell is installed outdoors, it rises in temperature when it receives direct sunlight, but there is a phenomenon that the rise in temperature lowers the effective power generation efficiency as compared to the rated state (25 ° C.). In order to prevent this phenomenon from occurring, it is necessary to keep the solar cell as low as possible. When a solar cell is exposed to direct sunlight in summer, the temperature of the solar cell is:
Generally, it reaches 80 ° C. or higher. When the solar cell is a silicon-based solar cell such as an amorphous silicon solar cell, the temperature coefficient of the photoelectric conversion efficiency is about −0.4% / ° C., so that the power generation efficiency is reduced by 20% or more. That is, even if a silicon-based solar cell having a high photoelectric conversion efficiency is used, if the cooling method for the solar cell is inappropriate, sufficient power generation efficiency cannot be achieved. Furthermore, when such a solar cell is maintained at a high temperature, the thermal load on its constituent materials increases, so that the durability of the solar cell naturally decreases. In order to prevent such a decrease in durability, particularly in the case of a solar cell installed outdoors,
It is necessary to cool the solar cell so that it can be kept as low as possible.

In recent years, a solar power generation system using a concentrating solar cell has attracted attention from the viewpoint of achieving a high power generation efficiency solar power generation system at relatively low cost. By using concentrating solar cells, the most expensive cells (solar cells) among the components of the solar power generation system can be saved, and a solar power generation system with high power generation efficiency can be achieved at relatively low cost. There are advantages. That is, in the photovoltaic power generation system, even if a small number of solar cells are used, the intensity of incident light to the solar cells increases, so that the generated voltage increases and the ratio of output energy to incident light energy, that is, The photoelectric conversion efficiency is improved, and a relatively large output can be achieved. For example, comparing the case where a predetermined number of concentrating solar cells are spread over the same area and the case where a predetermined number of non-concentrating solar cells are similarly spread, the output obtained by the former is the latter. It is larger than the output that can be obtained. In the former case, in order to sufficiently improve the photoelectric conversion efficiency and achieve a sufficient output, it is necessary to employ a high-magnification light condensing system and to dispose a sun tracking mechanism. However, in this case, the temperature of the solar cell is
Since the temperature is further increased as compared with the case where sunlight is not collected, it is necessary to cool the solar cell more efficiently.

[0005]

In view of the above-mentioned situation, forcibly cooling the solar cells in the solar power generation system (ie, actively cooling the solar cells), the Attempts have been made to lower the temperature.
As for the forced cooling of the solar cells in the solar power generation system as described above, a commonly used forced cooling means is, for example, continuously cooled as disclosed in Japanese Patent Application Laid-Open No. 9-21980. Therefore, the same energy is used for forced cooling regardless of whether the amount of solar radiation is relatively large or small. According to this method, if the cooling function is designed for maximum solar radiation, excessive energy is consumed at low solar radiation, which is uneconomical.On the contrary, if the cooling function is designed for low solar radiation, cooling is naturally performed at high solar radiation. A shortage problem arises. Japanese Patent Application Laid-Open Nos. Hei 5-83881 and Hei 10-10-10 disclose improvement of these drawbacks.
In Japanese Patent No. 1268 or JP-A-7-36556, the temperature of a solar cell to be cooled is detected by a temperature detecting means, and when the detected temperature exceeds a certain value, a forced cooling means such as a fan is activated. A method for doing so is disclosed. However, in such a method, it is necessary to provide a means for detecting the temperature, so that the cost is increased, and a failure of the temperature detection means may lead to a failure of the solar cell. In addition, since the cooling effect of the forced cooling means is always constant, the above-mentioned problem of excessive or insufficient cooling degree cannot be sufficiently solved.

As a countermeasure for solving the above-mentioned drawbacks, Japanese Patent Application Laid-Open No. Hei 7-240532 discloses a method in which a cooling fan is connected in series to a circuit of a solar cell to perform cooling in proportion to a generated current value. Have been. However, in general, the cooling effect is not proportional to the power, voltage, current, etc. required for cooling. Therefore, in the method described in the above publication, the cooling effect on the solar cell, the solar cell in the maximum power generation state,
When the cooling system is designed to be optimal, the cooling effect is excessive or insufficient between the case where the solar cell is in a no-power generation state and the case where the solar cell is in the maximum power generation state, and the cooling energy is wasted in the excessive cooling state. In the case of insufficient cooling, excessive temperature rise occurs, which adversely affects the apparatus.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art. That is, the present invention improves the cooling characteristics of the cooling means for actively cooling the solar cell (that is, the forced cooling means) without using a detecting means such as the above-described temperature detecting means in the prior art. It is an object of the present invention to provide a photovoltaic power generation system (that is, a photovoltaic power generation system) provided with a cooling mechanism capable of realizing a necessary cooling effect by utilizing the cooling mechanism without excess and deficiency and minimizing equipment costs and operation costs. Specifically, the solar power generation system provided by the present invention includes at least a solar cell and a cooling mechanism, wherein the cooling mechanism includes a cooling unit for cooling the solar cell, and an output of the solar cell. Storage operation means for storing or calculating an optimum cooling drive state of the cooling means in accordance with the above condition, wherein the cooling means is driven based on an output of the storage operation means. .

[0008] In the solar power generation system of the present invention,
By detecting the output of the solar cell and performing the necessary cooling drive on the solar cell based on the output and the cooling characteristics of the cooling means assumed in advance, it is possible to achieve the required minimum consumption of cooling energy. Here, the cooling characteristic of the cooling means means a relationship between a driving amount of the cooling means and a cooling effect by the cooling means. More specifically, for example, when the cooling unit is a cooling unit using a fluid refrigerant, as shown in FIG. 5 described below, the relationship between the flow rate of the fluid refrigerant by the circulating pump and the amount of decrease in the solar cell temperature is determined. means. By the way, especially in the case of a cooling means using a fluid refrigerant, the state of the flow of the cooling fluid changes non-linearly according to the flow velocity, and therefore, the effect of using the driving method is large. The following effects are typical of such effects. I.
Since the output of the solar cell is used for the cooling drive, there is no need to use an extra means for detecting the temperature, so that the manufacturing cost of the photovoltaic power generation system can be reduced. B. By driving the cooling means (forcible cooling means) in accordance with the cooling characteristics of the cooling means, it is possible to always cool the solar cell without excess and deficiency. The required energy can be minimized.

In the photovoltaic power generation system of the present invention, the cooling process of the solar cell installed in the system by the cooling mechanism is typically performed as described below. (1) detecting the output of the solar cell, (2) calculating the amount of increase in the temperature of the solar cell based on the detected output, and (3) determining a predetermined assumed air temperature (of the area where the solar cell is installed). (4) calculating the temperature difference in which the estimated temperature exceeds the temperature range to be controlled, (4) calculating the temperature of the solar cell at that time.
(5) A cooling drive amount of the cooling means for lowering the temperature difference by cooling is calculated, and (6) the cooling means is driven by the control means by the cooling drive amount obtained by the calculation. Note that the upper storage operation means may be unique. Alternatively, the storage operation unit may be used also as a storage operation unit in another component of the photovoltaic power generation system. In the latter case, the manufacturing cost of the solar power generation system can be reduced. As the other component, when the photovoltaic power generation system is of a type in which surplus power flows backward by connection with a commercial power supply system, the DC power from the photovoltaic power generation system is converted into AC power. Power converter
When the photovoltaic power generation system includes a DC power storage unit such as a storage battery, there is a charge / discharge control unit (a so-called power controller). When the photovoltaic power generation system has equipment for observing, recording, and displaying a power generation state, there is an arithmetic processing means for controlling the equipment.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the photovoltaic power generation system of the present invention includes at least a solar cell and a cooling mechanism, and the cooling mechanism includes cooling means for cooling the solar cell, A storage operation unit for storing or calculating an optimum cooling drive state of the cooling unit according to the output of the solar cell, wherein the cooling unit is driven based on an output of the storage operation unit. Is what you do.
Hereinafter, each component of the solar power generation system will be described in detail.

(Solar Cell) The solar cell used in the present invention has a photoelectric conversion element for converting sunlight energy into electric energy. The solar cell is typically a member configured to photoelectrically convert incident sunlight using one or a plurality of such photoelectric conversion elements and output the converted sunlight. Specific examples of the photoelectric conversion element include an appropriate semiconductor material, for example, a crystalline or amorphous silicon semiconductor material, or a photoelectric conversion element formed of a compound semiconductor material such as gallium arsenide, cadmium telluride, or copper indium selenide. Is mentioned. The invention is not limited to these, and other photoelectric conversion elements can be used as long as they perform the same function. When the solar cell used in the present invention is a concentrating solar cell, only a part that converts sunlight energy into electric energy, that is, a photoelectric conversion unit (this may be referred to as a narrowly defined solar cell) In such a case, it is not usually possible to perform a normal power generation operation, and a condensing optical system for condensing light is required. In this case, the combination of the photoelectric conversion unit and the condensing optical system will be referred to as a solar cell.
As the condensing optical system, a conventional system can be used as appropriate. Specifically, for example, a refraction optical system using a simple lens or a thin Fresnel lens, a reflection optical system using a parabolic mirror, or a composite optical system combining these can be used.

(Cooling Means) As the cooling means, a cooling method using air as a cooling medium or a cooling method using a fluid as a cooling medium can be adopted. Examples of the cooling method using air as a refrigerant include a cooling method using a single or a plurality of cooling fans, a cooling method using a heat exchanger, and the like. As a cooling method using fluid as a refrigerant, running water is
Examples of the cooling method include a cooling method in which the cooling medium flows through the side and back surfaces, a cooling method in which a fluid refrigerant is introduced into a cooling pipe and circulated by a circulation pump, and a cooling method in which a fluid exchanger is actively cooled using a heat exchanger. In addition, a cooling method in which heat is radiated using a solid thermoelectric element such as a Peltier element without using a refrigerant can also be adopted. The cooling means includes cooling control means. The cooling control means includes:
What is necessary is just to be able to control the cooling means electrically or mechanically. For example, the cooling control unit is an electric circuit that applies a voltage or a current according to an electric signal to a cooling fan serving as the cooling unit, a pump that feeds a fluid refrigerant, or a solid thermoelectric element such as a Peltier element. be able to. Such cooling control means may be provided independently of the cooling means, or may be provided integrally with the cooling means. In addition, the cooling control unit may be provided in the same device as the storage operation unit.

(Storage calculation means) The storage calculation means has a function of storing numerical values or formulas relating to the following characteristics and outputting an output value corresponding to an input value. For example, the storage operation means stores characteristics as a geometric shape like an operation element such as a microcomputer with a storage element such as a nonvolatile memory or / and a cam mechanism, and inputs physical position information. And a mechanism for outputting physical position information. In addition, the storage operation means may be provided with a mechanism for converting an input signal into a flow rate according to the valve shape of an electromagnetic valve that opens and closes with an electric signal. The storage means preferably further has a function of holding a standard temperature required for an operation described later. The standard temperature here refers to a temperature that is a reference for estimating to what temperature the solar cell has actually risen in the area (place) where the solar cell is installed due to solar radiation, and When the aim is to improve the photoelectric conversion efficiency of the solar cell, the average temperature in the installation area corresponds to it, and when the purpose of cooling is the maintenance of internal components of the photovoltaic power generation system, the maximum temperature in the installation area, etc. It corresponds to that. In addition, not the average temperature and the highest temperature throughout the year,
If one year is divided into certain sections (for example, months) and the average temperature and the maximum temperature of each section are stored in the storage and calculation means, and the storage and calculation means has a clock function at that time, the subsequent control is performed. More precise.

(Output Detecting Means) The photovoltaic power generation system of the present invention comprises an output detecting means for detecting an output of a solar cell in the system, and a driving means for driving the solar cell. Includes drive control means. The output detection means needs to have a function of detecting the output of the solar cell and transmitting a value of the detected output (output value) to the drive control means. As the output value in this case, the value of the energy from the solar cell, that is, the value of the output power that is the product of the current and the voltage is most appropriate, but more simply, the value of the current from the solar cell is calculated as the output value. Can be used as output value. As the output detecting means, specifically, for example, a means capable of outputting a voltage between both ends of an electric resistor arranged in series with an output circuit of the solar cell, or a means for detecting the output value more accurately One that can calculate and output the product of the voltage value at both ends of the battery and the voltage value at both ends of the electric resistance is used. In addition, an appropriate signal in a power conversion unit (for example, an inverter) for converting a DC output of the solar cell into an AC voltage may be extracted, and this may be used as the output detection unit.
In this case, the output detection means can be included in the power conversion means, or the power conversion means can also serve as the output detection means. Further, an AC wattmeter or the like for measuring AC power after power conversion may be used as the output detecting means.

[0015] The cooling mechanism in the photovoltaic power generation system of the present invention is constituted by the means described above, and the cooling mechanism operates as described below. (1) detecting the output of the solar cell; (2) calculating the amount of increase in the temperature of the solar cell from the detected output; (3)
Adding the calculated temperature increase to the standard temperature to estimate the temperature of the solar cell at that time; (4) calculating a temperature difference in which the estimated temperature exceeds the temperature range to be controlled; (5) A) calculating a cooling drive amount of the cooling control means for lowering the calculated temperature difference by cooling; and (6) driving the cooling means by the calculated cooling drive amount by the cooling control means. With the cooling mechanism that operates as described above, a desired cooling drive can be performed on the solar cells in the solar power generation system. Further, by maintaining the standard temperature, which is a reference in the above calculation, in the storage calculation means, it is possible to eliminate excess or deficiency related to the cooling drive. In the above description, individual means are provided for each function for convenience, but a plurality of functions may be shared by a single means.

[0016]

The present invention will be described in more detail with reference to the following examples. However, these examples are for illustrating the contents of the present invention, and the present invention is not limited to these examples.

[0017]

[Embodiment 1] In this embodiment, an embodiment of a solar cell power generation system (photovoltaic power generation system) of the present invention will be described. That is,
FIG. 1 schematically shows a main part of a photovoltaic power generation system using a concentrating solar cell according to the present invention. FIG.
, 101 indicates the sun, and 120 indicates a solar cell. Light that has entered the solar cell 120 from the sun 101 is converted into electric power (DC power) by the solar cell 120 and is extracted to the outside via the electric power extraction line 107. Note that the power generation system of the present embodiment is provided with a power conversion unit 108 for connecting to a commercial power supply. Solar cell 1
The power (DC power) from the power conversion means 20
After being converted into AC power by 8, it is connected to the system.

The cooling pipe 1 is provided on the back of the solar cell 120.
21 is provided in close contact with the back surface. Cooling pipe 1
21 is filled with a refrigerant (water containing 5% by weight of polyethylene glycol).
Circulated by. That is, by the circulation of the refrigerant, heat given from the sun 101 to the solar cell 120 is:
The heat is transmitted from the back surface of the solar cell 120 to the peripheral wall of the cooling pipe 121 and then to the refrigerant. At this time, since the refrigerant forms a circulating flow in the cooling pipe 121, the heat transmitted to the refrigerant does not stay, and the heat is
At a portion away from zero, the heat is radiated into the atmosphere through the wall surface of the cooling pipe 121. Therefore, the temperature rise of the solar cell 120 can be suppressed by forming such a heat path with low thermal resistance. The driving of the pump 122 is appropriately controlled by the control means 124. The control means 124 is an electric circuit attached to the pump, and can increase or decrease the rotation speed of the pump according to an input electric signal. In FIG. 1, 130 indicates a cooling means, and the cooling means 13
0 is the cooling pipe 121, the pump 122 and the control means 1
24.

As shown in FIG. 1, a power detection means 109 is provided in the middle of the power extraction line 107. In addition, an electric resistance (not shown) is inserted in a predetermined portion of the power extraction line 107 before reaching the power detection means 109 in series,
By taking out the voltage across the electric resistance, the solar cell 120
Can monitor the current generated. The output of the output detection means 109 is guided to the storage operation means 123. The storage operation means 123 is constituted by a microcomputer having a non-volatile memory, and calculates an appropriate drive amount of the cooling means 130 based on the output of the output detection means 109 and according to the logic described later, and calculates the drive amount. Is transmitted to the control means 124. Control means 124
Drives the pump 122 according to the signal. As described above, the cooling means 130 is driven in accordance with the output of the solar cell 101.

Before describing the logic for calculating the driving amount, the characteristics of the cooling means 130 and the temperature difference caused by heat will be described. FIG. 2 shows a main part of the cooling pipe 121 in the solar power generation system shown in FIG. 1 (a part in contact with the back surface of the solar cell (120), see FIG. 1).
1 schematically shows a vertical section (a) and a horizontal section (b).
In FIG. 2, reference numeral 121 denotes the above-described cooling pipe. 12
1a shows a fin-shaped heat dissipation expansion surface formed in the cooling pipe 121. 201 denotes a fluid refrigerant flowing in the cooling pipe 121 in the direction of the arrow. The refrigerant 201 is a cooling pipe 1
In particular, by flowing around the heat dissipation expansion surface 121a, the temperature rise of the back surface (not shown) of the solar cell in contact with the cooling pipe 121 can be suppressed. FIG. 3 schematically shows the flow state of the refrigerant when the flow velocity of the fluid refrigerant 201 in the cooling pipe 121 shown in FIG. 2 is relatively small. As shown in FIG. 3, when the flow rate of the fluid refrigerant 201 is relatively small, the flow of the refrigerant forms a laminar flow. However, the fluid refrigerant 201
As the flow velocity of the fluid increases, the flow of the fluid
It changes to turbulence as shown in FIG. This is a phenomenon that occurs because the inertial force in the flow becomes relatively large with respect to the viscous force. Such a phenomenon occurs because the ratio between the value of the inertial force and the value of the viscous force, that is, the so-called Reynolds number increases in proportion to the flow velocity. It is said to wake up before and after. Looking at the above phenomenon from the viewpoint of heat transfer in a system consisting of the back surface of the solar cell and the cooling pipe in contact with the same, the heat of the solar cell is reduced by the change due to the change.
The heat transfer coefficient transmitted to the refrigerant 201 through the peripheral wall of the above is improved by one digit or more. FIG. 5 shows a visual representation of the heat radiation performance of this system in the relationship between the flow rate of the refrigerant and the cooling effect (temperature drop). In FIG. 5, A is a laminar flow region, and B is a turbulent flow region.

On the other hand, the solar cell (120)
A certain relation is also established with respect to the temperature rise. All the solar radiation except for the reflected light and the light that is converted to electric power by the solar cell is the heat energy q (heat flux) at the surface of the solar cell.
The heat transfer rate K, the heat transfer rate K, and the temperature difference Δθ between the heat source and the outside are as follows. There is a relationship. q = K · Δθ Therefore, the temperature difference Δθ generated with respect to the amount of solar radiation is proportional. Since the amount of solar radiation and the amount of power generation are also substantially directly proportional, the amount of power generation and the temperature difference Δθ may be considered to be substantially directly proportional.
In this case, since the heat capacity of the outside air may be considered to be infinite, the temperature difference Δθ may be the amount of temperature rise of the solar cell with respect to the air temperature.
FIG. 6 shows this relationship. (If the temperature rises, the convection will be promoted and the heat dissipation will increase, resulting in a slightly flattening curve.)

The above relationship is stored in the storage operation means 123 and used for determining the cooling drive amount of the cooling means according to the following logic. That is, the correspondence table in the normal use range in FIGS. 5 and 6 is input to the nonvolatile memory in the storage operation unit 123. The standard temperature θs and the standard use temperature θl are also input. In the present embodiment, the standard temperature θs
The standard temperature for the place where is installed is input, and for the average temperature and the standard operating temperature θl of each month, the maximum operating temperature of the solar cell is input. The storage operation unit 123 has a clock function. First, based on a date obtained from the clock function, the standard temperature θs of the current month is selected as a temperature to be used as a reference at the present time. Next, the output P of the solar cell 120 detected by the power detection unit 109 is stored in the storage operation unit 12.
3 is input to the storage operation means, and the expected temperature increase amount Δθ is determined from the table representing the relationship shown in FIG. In the process of determining Δθ, an interpolation method is used based on the information in the table. Further, based on the obtained temperature increase Δθ, the required temperature decrease θc is calculated by the following equation. .theta.c = .theta.s + .DELTA..theta .-. theta.l Finally, referring to the table which embodies the relationship of FIG.
The required cooling drive amount Rc corresponding to the above is obtained. The storage operation means 123 transmits the cooling drive amount Rc to the control means 124 as an electric signal. As described above, it is possible to perform the minimum cooling drive in which the solar cell 120 does not exceed the maximum use temperature according to the magnitude of the solar radiation.

[0023]

[Embodiment 2] In this embodiment, an embodiment of a reflection-concentration type solar power generation system according to the present invention will be described. That is, FIG. 7 schematically shows a main part of a reflection-concentration type solar cell power generation system of the present invention. The reflection-concentration type solar cell power generation system shown in FIG. 7 uses a combination of a photoelectric conversion unit and a reflector as a solar cell, and has an output detection unit provided in the power conversion unit. Regarding the photoelectric conversion unit provided in the reflection-concentration type solar cell power generation system, there is a great risk that insufficient cooling of the photoelectric conversion unit may lead to damage to the photoelectric conversion unit. It is essential to do this for the converter. In FIG. 7,
Elements having functions similar to those shown in FIG.
The same numerical symbols as in FIG. 1 are used.

In FIG. 7, reference numeral 101 denotes the sun. 70
Reference numeral 2 denotes a photoelectric conversion unit, and light from the sun 101 enters the photoelectric conversion unit 702, where it is converted into electric power (DC power). Reference numeral 703 denotes a reflecting mirror (condensing optical system) for guiding light emitted from the sun 101 to the photoelectric conversion unit 702 and increasing the energy density of the light at that time. The reflecting mirror 703 is
The photoelectric conversion unit 702 is supported via support means 704 for fixing the relative position between the reflection mirror itself and the photoelectric conversion unit 702.
It is connected to the. Here, since the combination 720 of the photoelectric conversion unit 702 and the reflecting mirror 703 performs a function of converting sunlight into electric power, the combination 720 can be referred to as a solar cell. The reflecting mirror 703 is installed on a gantry 705 with a driving unit (not shown) for driving the reflecting mirror 703. Therefore, by changing the relative position of the reflecting mirror 703 with respect to the gantry 705 by driving by the driving means, an operation of tracking the sun as the sun 101 moves can be performed. This feature is provided for the two axes (declination, hour angle) that define the position of the sun.

Reference numeral 709 denotes output detection means. The output detection means 709 is the output detection means (10
9) The same function is exhibited, but the method is slightly different, so that the description will be made. In the first embodiment, the output detection means (109) is provided in series with the output transmission circuit and separated from other components, and is described as detection means including an electric resistance for detecting a current value. However, in this embodiment, the output detection means 709 is included in the power conversion means 708. Similarly, the storage operation means (123) in the first embodiment is provided separately from the other components, but in this embodiment, the storage operation means (123) is provided.
23 is included inside the power conversion means 708. FIG. 8 shows a specific configuration in this regard. In FIG. 8, 70
Reference numeral 8 denotes the above-described power conversion means. Reference numeral 801 denotes a power conversion circuit forming the center of the power conversion means 708. Specifically, the power conversion circuit 801 is a circuit configured by a combination of a rectifier circuit and a high-frequency coil, configured to divide a DC voltage / current and then rectify the converted DC voltage / current to convert it into a desired constant-voltage AC waveform. .

The DC power from the photoelectric conversion unit 702 is introduced into the power conversion circuit 801 from the connection part to which the power extraction line 107 is connected, and is converted into desired AC power by the power conversion circuit 801 before being connected. Connected to a power supply system via a power supply unit. In order to control the conversion at this time, the current and voltage on the DC side are respectively changed by the current transformer 803 and the connection point 80.
4 through a microcomputer provided in the storage operation means 723. The microcomputer controls the above conversion and also controls the cooling means. Similarly, the current and voltage on the AC side are respectively
5. Introduced to the storage operation means 723 via the connection point 806. The storage operation unit 723 not only uses the above information for controlling the power conversion circuit 801, but also controls operation such as start / stop of the photovoltaic power generation system, detects malfunctions, displays instantaneous power generation, and displays accumulated power generation. It is used for various operation controls such as calculation display. Because of such a configuration, it is easy to extract the amount of DC power and the amount of AC power momentarily to the outside. In this case, the output detection means 709 in FIG. 8 is a current transformer (803, 80) inside the power conversion means 708.
5), including the connection points (804, 806) and the connection lines, and can be said to exist while sharing the function with the power conversion means 708. Similarly, the storage operation unit 723 also exists while sharing the function with the power conversion unit 708. In FIG. 7, the power conversion means 70
8 and an output detection means 709 are provided as shown in the figure, and provide a signal relating to the amount of DC power generation to the storage calculation means 723 in the form of a product of current and voltage. Of course, at this time, it is also possible to give the information of the AC power.

In the present embodiment, air cooling rather than liquid cooling is used as a cooling method. A cooling fin (not shown) is provided in close contact with the photoelectric conversion unit 702, and a fan 72
1 is configured to cool by sending cooling air.
The drive of the fan 721 is controlled by the control unit 724. The control means 724 has an electric circuit for driving the fan 721, and can increase or decrease the rotation speed of the fan 721 in accordance with an electric signal input to the electric circuit. Reference numeral 730 denotes a cooling unit. The cooling unit 730 includes the cooling fins, the fan 721, and the control unit 724. The storage operation unit 723 calculates an appropriate drive amount based on the output of the output detection unit 709 according to the same logic as described in the first embodiment, and transmits a signal representing the drive amount to the control unit 724. The control means 724 drives the fan 721 according to the signal. As described above, the cooling means 730 performs driving according to the output of the solar cell 720. Even in the case of such air cooling, Example 1
The non-linearity of the cooling performance described above is seen, and it is possible to drive the fan optimally by the same method. The method for obtaining the optimum drive amount is the same as that described in the first embodiment, and a detailed description thereof will be omitted. In the first embodiment, the standard temperature is set to the average temperature every month. However, in the present embodiment, it is appropriate to set the maximum temperature every month in order to prevent the equipment from being damaged.

[0028]

As described above, in the photovoltaic power generation system according to the present invention, the solar cells in the system include:
Since the output of the solar cell is detected and necessary cooling driving is performed on the solar cell based on the output and the cooling characteristic of the cooling means assumed in advance, the required minimum cooling energy consumption can be realized. In particular, when the solar cell is cooled by a cooling unit using a fluid as a refrigerant, the state of the flow of the refrigerant changes nonlinearly according to the flow velocity, so that a large energy saving effect can be obtained. Specifically, according to the present invention, the following effects can be obtained.

(1) Since the output of the solar cell is used for cooling drive, there is no need to provide extra means for temperature detection. Therefore, the manufacturing cost of the solar power generation system can be reduced. (2) By driving the cooling means in accordance with the cooling characteristics of the cooling means, it is possible to always perform adequate cooling on the solar cell, and to reduce the energy required for forcibly cooling the solar cell. It can be kept to the minimum necessary. (3) Since the storage operation means has a clock function and stores the standard temperature at each time point, by driving the cooling means in accordance with the standard temperature, the accuracy of the solar cell can be further improved. Cooling control can be performed, and energy saving can be realized. (4) By providing the output detection means for detecting the output of the solar cell inside the power conversion means, it is possible to reduce the manufacturing cost of the solar power generation system. Similarly, by providing the storage operation means inside the power conversion means, the manufacturing cost of the photovoltaic power generation system can be reduced. (5) Overall, the manufacturing cost of the cooling device can be reduced,
In addition, since the energy required for cooling the solar cell can be kept to a necessary minimum, the power generation cost of the solar power generation system can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration of a main part of an example of a photovoltaic power generation system of the present invention.

FIG. 2 is a diagram for explaining a structure of a main part of a cooling pipe as a cooling unit in the photovoltaic power generation system shown in FIG. FIG. 2A is a diagram schematically showing a vertical cross section of the cooling pipe, and FIG. 2B is a diagram schematically showing a horizontal cross section of the cooling pipe.

FIG. 3 is a diagram for explaining a laminar flow state of a flow of a fluid refrigerant in a cooling pipe shown in FIG. 2;

FIG. 4 is a view for explaining a turbulent state of a flow of a fluid refrigerant in the cooling pipe shown in FIG. 2;

FIG. 5 is a diagram for explaining cooling characteristics of a cooling unit in the solar power generation system shown in FIG.

FIG. 6 is a diagram for explaining temperature rise characteristics in the solar power generation system shown in FIG.

FIG. 7 is a diagram schematically showing a configuration of a main part of another example of the photovoltaic power generation system of the present invention.

8 is a diagram schematically illustrating an example of a circuit configuration related to driving of a solar cell in the solar power generation system illustrated in FIG. 7 and driving of a cooling unit when cooling the solar cell.

[Explanation of symbols]

 101 Sun 107 Output extraction line 108, 708 Power conversion means 109, 709 Output detection means 120, 720 Solar cell 121 Cooling pipe 121a Heat dissipation expansion surface (fin) 122 Driving means 123, 723 Storage operation means 124, 724 Control means 130, 730 Cooling means 201 Refrigerant 702 Photoelectric converter 703 Reflector 704 Support member 705 Mount 721 Cooling fan 801 Power conversion circuit 803, 805 Current transformer 804, 806 Connection point

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsu Shiomi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Hidehisa Makita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon F term in reference (reference) 5F051 JA02 JA20 KA02 KA03 KA10 5G066 CA08 HB06

Claims (8)

[Claims] In a photovoltaic power generation system having at least a solar cell and a cooling mechanism, the cooling mechanism optimizes the cooling means for cooling the solar cell and the cooling means according to the output of the solar cell. And a storage operation means for storing or calculating a proper cooling drive state, wherein the cooling means is driven based on an output of the storage operation means. 2. The solar power generation system according to claim 1, wherein the output of the solar cell is power or current from the solar cell. 3. The photovoltaic power generation system according to claim 1, wherein said cooling means is a cooling means using a fluid refrigerant. 4. The storage arithmetic means has a clock function and stores a standard temperature of the installation environment of the solar cell at each time, and drives the cooling means in accordance with the standard temperature. The solar power generation system according to any one of 1 to 3. 5. The photovoltaic power generation system according to claim 1, further comprising output detection means for detecting the output of said solar cell. 6. The photovoltaic power generator according to claim 2, further comprising power conversion means for converting the power output from said solar cell, wherein said storage operation means is included in said power conversion means. system. 7. The power conversion device according to claim 1, further comprising output detection means for the power output from said solar cell, and power conversion means for said output power, said output detection means being included in said power conversion means. The solar power generation system according to any one of 2, 3, 4, and 6. 8. The system according to claim 1, further comprising a sun tracking mechanism.
A solar power generation system according to any one of the above.