1. Technical Field
The present invention relates to a solar power generation device converting solar energy into electric energy.
2. Description of Related art
There is a solar power generation device, as a related-art example, converting solar energy into electric energy by collecting solar light by a reflecting mirror to solar cells arranged on a cooling pipe (for example, refer to Patent Literature 1).
In the solar power generation device described in Patent Document 1, solar energy is converted into electric energy by collecting solar light reflected by a reflecting mirror 301 to a solar cell 302 as shown in
Patent Literature 1: JP2004-271063A
According to an embodiment of the present invention, there is provided a solar power generation device including a polygonal cylindrical cooling pipe, plural thermoelectric conversion elements installed on respective side surfaces of the cooling pipe, plural solar cells installed on the thermoelectric conversion elements respectively and an insulation covering side surfaces of the solar cells and the thermoelectric conversion elements.
Hereinafter, embodiments of the present invention will be explained with reference to the drawings.
As shown in
The solar cells 104 according to the embodiment are cooled by the cooling water flowing in the cooling pipe 102 through the thermoelectric conversion elements 103. Moreover, thermal energy is converted into electric energy in the thermoelectric conversion elements 103 due to the temperature difference generated between the solar cells 104 and the cooling pipe 102 as the thermoelectric conversion elements 103 are interposed therebetween, as a result, a power generation amount can be increased.
Effects of cooling the solar cells 104 will be explained. As shown in
The thermoelectric conversion element 103 is a device converting thermal energy into electric energy. The thermoelectric conversion element 103 is formed by mounting a P-type thermoelectric conversion element 103p in which Sb or the like is added as a dopant to an alloy of a bismuth telluride system and an N-type thermoelectric conversion element 103n in which Se or the like is added as a dopant on a wiring substrate 105 so as to be electrically connected in series. The thermoelectric conversion element 103 is formed by the wiring substrates 105 in which upper and lower surfaces thereof are flat as shown in
The solar cells 104 are made of crystalline silicon or crystalline compound semiconductors, amorphous silicon and so on. The solar cells 104 directly convert light energy into electric energy by using a light electromotive force of the semiconductor.
An insulation 201 is arranged between adjacent two solar cells 104 as well as between adjacent two thermoelectric conversion elements 103, respectively. As shown in
The insulation 201 according to the embodiment functions as an insulative heat insulating material as well as functions as an antireflection member. That is, the insulation 201 blocks heat transmission between adjacent two solar cells 104 as well as prevents reflection of solar light incident between adjacent two solar cells 104, thereby suppressing occurrence of scattered light.
As the insulation 201 functions as the heat insulating material and the heat transmission between adjacent two solar cells 104 is prevented, heat of the solar cells 104 is transmitted to the cooling pipe 102 efficiently through the thermoelectric conversion elements 103 arranged on undersurfaces of the solar cells 104. Accordingly, cooling efficiency by the cooling pipe 102 can be increased as the insulation 201 functions as the heat insulating material.
Here, materials for the insulation 201 are, for example, insulative heat insulating materials mainly made of calcium sulfate, calcium silicate, glass wool and so on.
Moreover, as the insulation 201 is packed between adjacent two solar cells 104 as well as the solar cells 104 have the protruding portions 114 protruding from end surfaces of the thermoelectric conversion elements 103, it is possible to prevent infiltration of moisture such as rainwater into the thermoelectric conversion elements 103.
The cooling pipe 102 is formed so as to be rotated around the central axis with respect to the longitudinal direction thereof. As the cooling pipe 102 is rotated, a position of the solar cell 104 facing the reflecting mirror 101 and a position of the solar cell 104 not facing the reflecting mirror 101 can be exchanged. As the solar cell 104 facing the reflecting mirror 101 receives the collected solar light having high energy density, the deterioration may proceeds more rapidly than in the solar cell 104 not facing the reflecting mirror 101. Accordingly, the lifetime of the solar power generation device 1 can be extended by exchanging the positions of the solar cell 104 facing the reflecting mirror 101 and the solar cell 104 in the counter side periodically by rotating the cooling pipe 102.
Also in the solar power generation device 1 according to the embodiment, the thermoelectric conversion elements 103 and the solar cells 104 are disposed so as to be divided with respect to side surfaces of the cooling pipe 102, the thermoelectric conversion elements 103 and the solar cells 104 are not required to have a large area. Accordingly, yields of thermoelectric conversion elements 103 and the solar cells 104 can be increased, and they can be easily replaced in the case of deterioration, therefore, the solar power generation device 1 having excellent maintainability can be provided.
It is sufficient that the insulation 201 covers side surfaces of the solar cell 104 and the thermoelectric conversion element 103 when considering only heat-insulation performance. In this case, the insulations 201 are coated on the side surfaces of the solar cells 104 and the thermoelectric conversion elements 103 in advance, thereby simplifying manufacturing processes. Additionally, when a gap exists between adjacent two insulations 201, a layer (air layer) formed by air with high heat insulation performance is formed in the gap, which further increases the heat insulation performance between the solar cell 104 and the adjacent thermoelectric conversion element 103.
In order to stabilize heat distribution between adjacent two thermoelectric conversion elements 103, as shown in
The reflecting mirror 101 may be formed by combining many flat mirrors as well as may be formed by combining a plurality of parabolic reflecting mirrors.
It is desirable that the reflecting mirror 101 is directed to a direction directly facing the solar light for utilizing solar energy at the maximum, and a tracking device may be used for following the movement of the sun.
The cooling pipe 102 preferably has a polygonal cylindrical shape having fiat side surfaces, for example, polygonal cylindrical shapes such as a triangular shape and a square shape in cross section.
A solar power generation device 201 according to Embodiment 2 is the same as Embodiment 1 shown in
The solar power generation device 201 according to the embodiment can increase the power generation efficiency of the solar cells 104 by switching functions of the thermoelectric conversion elements 103 between a power generation function and a cooling function based on the temperature of the solar cells 104, which will be described in detail. Specifically, the solar power generation device 201 according to the embodiment measures the temperature of the solar cells 104 to determine whether the temperature is equal to or lower than a set temperature or not. When the temperature of the solar cell 104 is equal to or lower than the set temperature, the solar power generation device 201 uses the thermoelectric conversion element 103 as the power generation function to thereby increase the power generation amount, and when the temperature of the solar cell 104 is higher than the set temperature, the solar power generation device 201 uses the thermoelectric conversion element 103 as the cooling function to thereby prevent the reduction of power generation efficiency. As a result, the power generation efficiency of the entire solar power generation device 201 can be increased.
That is, the thermoelectric conversion elements 103 according to the embodiment have both Seebeck effect and Peltier effect. The power generation function in the embodiment means a function of generating power by this Seebeck effect. In the embodiment, power generation by Seebeck effect is performed by utilizing the temperature difference between the solar cells 104 heated by solar light and the cooling water circulating in the cooling pipe 102. Here, the Seebeck effect is a phenomenon in which an electromotive force is generated in accordance with the temperature difference by bonding different kinds of metals or semiconductors to give the temperature difference to a bonded portion. The cooling function in the present invention means a function of cooling by utilizing heat absorption action in the Peltier effect. In the embodiment, the heat is transmitted from the solar cells 104 heated by solar light to the cooling pipe 102 by supplying the power to the thermoelectric conversion elements 103 to thereby cool the solar cells 104. Here, the Peltier effect is a phenomenon reverse to the Seebeck effect, in which absorption and release of heat dependent on the direction and size of electric current occur when different kinds of metals or semiconductors are bonded and electric current is allowed to flow.
It is also preferable to calculate temperatures of the solar cells 104a to 104h by measuring voltage values generated by the thermoelectric conversion elements 103a to 103b without using the temperature sensors 206a to 206h. As the temperatures of the solar cells 104 can be measured without the necessity of using the temperature sensors 206a to 206h in this case, the number of components in the solar power generation device 201 can be reduced.
The control performed during the operation of the solar power generation device 201 according to the embodiment will be explained with reference to
As shown in
Next, the solar power generation device 201 determines whether the temperatures of corresponding solar cells 104a to 104h are equal to or lower than the set temperature by the controllers 207a to 207h in Step S11. Here, when the temperatures of the solar cells 104a to 104h are equal to or lower than the set temperature (Yes in S11), the process proceeds to Step S12, where power generation is performed by using corresponding thermoelectric conversion elements 103a to 103h as the power generation function. On the other hand, when the temperatures of corresponding solar cells 104a to 104h are higher than the set temperature (No in S11), the process proceeds to Step S13, where the solar cell 104 is cooled by using the thermoelectric conversion element 103 installed on the undersurface of the solar cell 104 having a higher temperature than the set temperature as the cooling function. For example, when only the temperature of the solar cell 104e is higher than the set temperature, only the thermoelectric conversion element 103e installed on the undersurface of the solar cell 104e is used as the cooling function, and other thermoelectric conversion elements 103a to 103d, and 103f to 103h are used as the power generation function. Accordingly, when the temperature of part of the solar cells 104 is higher than the set temperature, cooling is performed individually only by the corresponding thermoelectric devices 103, thereby performing control in accordance with characteristic variations and states among plural solar cells 104, and uniformizing power generation efficiency of the solar cells 104. As described above, when the temperature of the solar cell 104 is equal to or lower than the set temperature, power generation is performed by utilizing the temperature difference between the solar cell 104 and the cooling pipe 102, therefore, the power generation amount of the entire solar power generation device 201 can be increased.
Here, when the thermoelectric conversion element 103 is used as the cooling function, it is necessary to allow electric current to flow in the thermoelectric conversion element 103 to be operated, as Peltier, therefore, the power generation efficiency of the entire solar power generation device 201 is reduced if an increased amount of the power generation efficiency by the cooling is increased more than electric current to flow. Accordingly, it is required in the present embodiment that a boundary temperature at which an improvement of the power generation efficiency by the cooling in the solar cell is increased more than the electric current to flow in the thermoelectric conversion element is calculated and that the temperature is set in advance as a desired set temperature, for example, by performing an experiment so as to correspond to characteristics of the solar cells to be used.
To use the thermoelectric conversion element by switching between the cooling function and the power generation function based on whether the temperature is equal to or lower than the desired set temperature or not as in the present invention is effective also in a solar power generation device not having the reflecting mirror. However, as the power generation efficiency of respective solar cells 104a to 104h can be uniformized in the solar power generation device 201 having the reflective mirror 101, the present invention is preferably applied to the solar power generation device 201 having the reflecting mirror as described above.
if goes without saying that the present invention can be used by combining the above various embodiments.
Number | Date | Country | Kind |
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2013-179039 | Aug 2013 | JP | national |
2013-179040 | Aug 2013 | JP | national |