This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 100140440 filed in Taiwan, Republic of China on Nov. 4, 2011, the entire contents of which are hereby incorporated by reference.
1. Field of Invention
The present invention relates to a condensing lens and a photovoltaic power system.
2. Related Art
Due to the great progress of economy and improvement of life quality, the requirement of energy becomes more and more important. However, since the importance of environmental protection has been noticed recent years, it is desired to develop other power resource such as recyclable energy technologies. At present, the most popular one is the solar energy power system. In general, the solar energy power system includes the heat power system and the photovoltaic power system. Regarding to the photovoltaic power system, it is mainly composed of a condensing lens and a photovoltaic chip such as a monocrystalline silicon solar cell, a polycrystalline silicon solar cell, or a III-V compound solar cell. The configuration of the condensing lens can concentrate the light energy on the photovoltaic chip for generating electricity. In this case, the solar light can be concentrated by the condensing lens and focused on the photovoltaic chip with smaller area, thereby decreasing the material cost of the photovoltaic chip.
Some researches have discussed the sensitivities of different condensing lens with respect to the incident angle of solar light. For example, Chen and Winston disclosed an optimum design by combining the conventional condensing Fresnel lens and the piecewise curve method, which can obtain the concentration efficiency of 67% when the incident angle is ±1.5°. If the irradiancy map is allowed to move with focus point, the concentration efficiency can still retain a value approximately 90%. Besides, Pablo Benitez et al. further disclosed various analyses and researches about the Fresnel lens cooperated with a secondary concentrator. After studying the previous researches, it is found that the errors on the lens fabrication and the match errors during the assembling can all directly affect the photoelectric conversion efficiency.
As shown in
However, the angle of the solar light may change after the time goes by, which can lead the angle shift. When the angle shift occurs, the conventional condensing lens 11 can not concentrate the light beams on the photovoltaic chip 12. As a result, the efficiency of the photovoltaic power system 1 is sufficiently decreased.
Some researchers and manufacturers have invented the sun-tracing system for automatically adjusting the condensing lens 11 and the photovoltaic chip 12 to face the sun directly, thereby maintaining the photoelectric conversion efficiency. However, the power source of the conventional sun-tracing system is usually supplied by the photovoltaic power system 1, so that the net electricity provided by the photovoltaic power system 1 is deceased due to this additional consumption for driving the sun-tracing system.
Therefore, it is an important subject of the present invention to provide a condensing lens and photovoltaic power system that can increase the illumination and concentration efficiency, thereby improving the photoelectric conversion efficiency.
In view of the foregoing subject, an object of the present invention is to provide a condensing lens and photovoltaic power system that can increase the illumination and concentration efficiency, thereby improving the photoelectric conversion efficiency.
To achieve the above object, the present invention discloses a condensing lens includes a lens body and a prism structure. The lens body has a first surface and a second surface opposite to each other. The prism structure is disposed on the second surface of the lens body and has a plurality of annular prism units. The prism structure has at least two focuses in accordance with the annular prism units, and the focuses are distributed on a plane which is parallel to the first surface of the lens body.
In one embodiment of the present invention, the lens body and the prism structure comprise the same material.
In one embodiment of the present invention, the lens body and the prism structure comprise different materials.
In one embodiment of the present invention, an included angle between an annular surface of the annular prism unit and the second surface of the lens body satisfies the following equation:
Wherein, c represents the included angle, r represents a distance from the annular prism unit to a center point of the lens body, n represents a refraction index of the annular prism unit, and D represents a focus length of the annular prism unit.
In one embodiment of the present invention, the first surface of the lens body receives a plurality of light beams, and the light beams pass through the annular surfaces of the annular prism units and are then concentrated at the focuses.
In addition, the present invention also discloses a photovoltaic power system including a condensing lens and a photovoltaic chip. The condensing lens includes a lens body and a prism structure. The lens body has a first surface and a second surface opposite to each other. The prism structure is disposed on the second surface of the lens body and has a plurality of annular prism units. The photovoltaic chip is disposed at one side of the condensing lens facing the prism structure. The prism structure has at least two focuses in accordance with the annular prism units, and the focuses are distributed on a plane parallel to the first surface of the lens body. The plane is located between the photovoltaic chip and the annular prism units.
In one embodiment of the present invention, the lens body and the prism structure comprise the same material.
In one embodiment of the present invention, the lens body and the prism structure comprise different materials.
In one embodiment of the present invention, the photovoltaic chip is a monocrystalline silicon solar cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell, a compound solar cell, or an organic semiconductor solar cell.
In one embodiment of the present invention, the photovoltaic power system further includes a light collecting device disposed between the condensing lens and the photovoltaic chip for receiving light beams outputted from an annular surface of each annular prism unit.
In one embodiment of the present invention, the photovoltaic power system further includes a heat-dissipating device disposed at another side of the photovoltaic chip away from the prism structure.
In one embodiment of the present invention, an included angle between an annular surface of the annular prism unit and the second surface of the lens body satisfies the following equation:
Wherein, c represents the included angle, r represents a distance from the annular prism unit to a center point of the lens body, n represents a refraction index of the annular prism unit, and D represents a focus length of the annular prism unit.
In one embodiment of the present invention, the first surface of the lens body receives a plurality of light beams, and the light beams pass through the annular surfaces of the annular prism units and are then concentrated at the focuses.
As mentioned above, the condensing lens and photovoltaic power system of the present invention have a prism structure with a plurality of annular prism units. The prism structure has at least two focuses in accordance with the annular prism units, and the focuses are distributed on a plane parallel to the first surface of the lens body. Accordingly, the illumination and concentration efficiency can be increased so as to improve the photoelectric conversion efficiency
The invention will become more fully understood from the detailed description and accompanying drawings, which are given for illustration only, and thus are not limitative of the present invention, and wherein:
The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.
The prism structure 22 is disposed on the second surface 212 of the lens body 21, and has a plurality of annular prism units 221. The annular prism units 221 are disposed on the second surface 212. In this embodiment, the prism structure 22 has at least two focuses F in accordance with the annular prism units 221, and the focuses F are distributed on a plane P which is parallel to the first surface 211 of the lens body 21. To be noted, the prism structure 22 of this embodiment includes, for example but not limited to, five annular prism units 221.
The material of the prism structure 22 includes a transparent material such as glass or transparent polymers. The transparent polymers are, for example, PMMA (polymethly methacrylate), PS (polystyrene), MS (methyl-methacrylate styrene), or PC (polycarbonate). To be noted, the material(s) of the lens body 21 and the prism structure 22 can be optionally selected from the same or different materials depending on the requirements or designs of the products. Besides, the lens body 21 and the prism structure 22 can be integrally formed as one piece or bonded by an adhering layer (not shown).
In the cross-section view of
The annular prism unit 221 of the condensing lens 2 will be further described with reference to
The non-parallel light beams L2 are inputted from an incident point X1 of the first surface 211. When the non-parallel light beams L2 travel to the interface between the second surface 212 and the prism structure 22, which are made of different materials, the refraction of the non-parallel light beams L2 occurs. Accordingly, the non-parallel light beam L2 enters the annular prism unit 221 at the incident point X2 with an incident angle A1 and passes through the interface with an output angle A2. After that, the non-parallel light beams L2 continuously travel to the annular surface 59 and enters an external medium at an incident point X3 with an incident angle A3. Since the annular prism unit 221 and the external medium are made of different materials, the non-parallel light beams L2 can be outputted from the annular surface S2 of the annular prism unit 221 with an output angle A4, and then concentrated at the focuses F. As mentioned above, the non-parallel light beams L2 can have many times of refraction while passing through the annular prism unit 221 of the prism structure 22, thereby achieving the desired concentration effect.
In this embodiment, an included angle c between an annular surface S2 of the annular prism unit 221 and the second surface 212 of the lens body 21 satisfies the following equation:
Wherein, c represents the included angle, r represents a distance from the annular prism unit 221 to a center point 213 of the lens body 21, n represents a refraction index of the annular prism unit 221, and D represents a focus length of the annular prism unit 221.
According to the above-defined structure, each annular prism unit 221 of the condensing lens 2 can correspond to at least one focus F, and the focuses F corresponding to the annular prism units 221 can be distributed within a certain range on the plane P. For example, the focuses F can be the dots formed within a ring belt on the plane P. In other words, the condensing lens 2 can shift the angles of the light beams from the external light source (solar light), and remain the multiple focuses F within an extremely small range on the plane P.
The photovoltaic chip 3 is disposed at one side of the condensing lens 2 facing the prism structure 22. The photovoltaic chip 3 can receive the light beams outputted from the annular prism units 221 of the prism structure 22 and perform the photoelectric conversion. In practice, the photovoltaic chip 3 can be a monocrystalline silicon solar cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell, a compound solar cell, or an organic semiconductor solar cell.
In this embodiment, the focuses F corresponding to the annular prism units 221 of the prism structure 22 can be distributed on the surface of the photovoltaic chip 3. Since the annular prism units 221 of the condensing lens 2 can concentrate the light beams emitted from the external light source at multiple focuses on a plane, the present invention can still allow the focuses F to locate on the surface of the photovoltaic chip 3 even when the solar light is shifted, thereby remaining the photoelectric conversion at high efficiency.
In addition, when the condensing lens 2 is applied to the photovoltaic power system 4, the shift of the solar light is concerned. Accordingly, the positions of the annular prism units 221 on the second surface 212 of the lens body 21 can adjusted based on the shift situation of the solar light. In other words, with respect to multiple focuses F, the annular prism units 221 may not concentric circles.
For example, the ratio of the output power of the photovoltaic power system 1 as the Time is 150 seconds, which means the shifted angle of the solar light after 150 seconds, to that without shift is 43%, and the ratio of the output power of the photovoltaic power system 4 as the Time is 150 seconds to that without shift is 53%. Consequently, the photovoltaic power system 4 configured with the condensing lens 2 can provide better concentration efficiency.
To be noted, the photovoltaic power systems 4 can further configured with both the light collecting device 51 and the heat-dissipating device 61 for improving the focus accuracy as well as the heat dissipation efficiency.
In summary, the condensing lens and photovoltaic power system of the present invention have a prism structure with a plurality of annular prism units. The prism structure has at least two focuses in accordance with the annular prism units, and the focuses are distributed on a plane parallel to the first surface of the lens body. Accordingly, the illumination and concentration efficiency can be increased so as to improve the photoelectric conversion efficiency
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.
Number | Date | Country | Kind |
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100140440 | Nov 2011 | TW | national |