Photoelectric conversion system, light-receiving device, and light-transmitting device

Abstract

This photoelectric conversion system comprises: a photoelectric conversion unit in which a plurality of cells are disposed, each of the cells being provided with a capacitor; and a scanner that irradiates the photoelectric conversion unit with light while moving the irradiation position.

Description

Photoelectric conversion system, light receiving device, and light transmitting device

[0001] The present invention relates to optical wireless power supply technology.

[0002] Optical wireless power transfer technology uses light, such as a laser, as an energy medium. The laser is emitted toward a target to be powered, and the target converts the laser light into electricity using a photoelectric conversion element, such as a solar cell. Conventional optical wireless power transfer technology is disclosed in, for example, Non-Patent Documents 1 and 2.

[0003] "Wireless Laser Power Transmission: A Review of Recent Progress," IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 34, NO. 4, APRIL 2019.

[0004] In high-power optical wireless power transfer, a panel consisting of multiple photovoltaic conversion cells connected in series is used to suppress the current value after photovoltaic conversion and increase the voltage. However, if there is a cell that is not exposed to enough light, the current value of that cell becomes a bottleneck, limiting the overall current value and leading to a decrease in photovoltaic conversion efficiency.

[0005] Furthermore, when a beam propagates through the atmosphere, such as in outdoor optical wireless power transfer, atmospheric turbulence disrupts the wavefront of the beam, causing uneven intensity distribution and misalignment of the beam irradiating the photoelectric conversion element. These factors lead to a decrease in photoelectric conversion efficiency. Furthermore, even in environments with little turbulence, Gaussian beams, which are common laser beams, have uneven intensity, so the outer cells are not exposed to much light, resulting in a decrease in efficiency.

[0006] The present invention has been made in consideration of the above points, and aims to provide a photoelectric conversion technology that makes it possible to ensure sufficient power generation even in situations where the irradiated light is uneven.

[0007] According to the disclosed technology, a photoelectric conversion system is provided that includes a photoelectric conversion unit in which a plurality of cells each having a capacitor are arranged, and a scanner that irradiates the photoelectric conversion unit with light while moving the irradiation position.

[0008] The disclosed technology provides a photoelectric conversion technology that can ensure sufficient power generation even in situations where the irradiated light is non-uniform.

[0009] 1 is a diagram for explaining the problem. 2 is a diagram for explaining the problem. 3 is a configuration diagram of a photoelectric conversion system in an embodiment of the present invention. 4 is a configuration diagram of a light transmitting device 100. 5 is a configuration diagram of a light receiving device 100. 6 is a diagram showing the arrangement of each part in a photoelectric conversion system. 7 is a diagram showing a scanning method. 8 is a diagram showing a PV panel in an example. 9 is a diagram showing a system configuration in an example. 10 is a diagram showing a scanning method in an example. 11 is a diagram showing an equivalent circuit of a PV panel in an example.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The embodiment described below is merely an example, and the embodiment to which the present invention is applied is not limited to the following embodiment.

[0011] In the following description, as an example, the light irradiated onto the photoelectric conversion unit is a laser beam, but the light irradiated onto the photoelectric conversion unit is not limited to a laser beam.

[0012] In the following, first, the problems associated with the technology of this embodiment will be described in more detail, and then the technology of this embodiment will be described.

[0013] (Regarding the Problem) Generally, a beam output from a laser medium is called a Gaussian beam, and the light intensity distribution in a plane perpendicular to the optical axis is a Gaussian distribution.

[0014] Optical wireless power transfer technology includes a single-cell type that has only one cell, which is a photoelectric conversion element, as the photoelectric conversion unit that converts received light into electricity, and a multi-cell type that has multiple cells. The voltage that can be extracted from one cell is determined by the band gap of the element, and is, for example, 0.5 V for a typical solar cell. Therefore, when attempting to supply high-power electricity, the current value becomes large, making the single-cell type unsuitable.

[0015] On the other hand, in the case of a multi-cell solar cell, connecting the cells in series increases the voltage and therefore the amount of power that can be extracted. However, if there is a cell among the multiple cells that does not receive enough light, the current value of that cell becomes a bottleneck, limiting the overall current value and preventing high power from being obtained. In addition, the light energy that enters the other cells cannot be extracted as power, but rather turns into heat, which deteriorates the characteristics of the photoelectric conversion section.

[0016] The above-mentioned problem in the case of using a Gaussian beam will be explained more specifically with reference to FIG.

[0017] In the configuration shown in FIG. 1, a laser medium 1, which is a light source element, and a photoelectric conversion unit 2 on the light receiving side are shown. For the laser medium 1, a surface 3 (light emitting surface) on the side from which the laser medium 1 outputs light is also shown. For the photoelectric conversion unit 2, a surface (light receiving surface) on the side from which light is received is also shown. As shown in FIG. 1, the photoelectric conversion unit 2 has a plurality of cells arranged in a lattice pattern. Furthermore, in FIG. 1, the beam output from surface 3 is input to the optical path, so surface 3 is described as "input." Furthermore, the output from the optical path becomes the input to the photoelectric conversion unit 2.

[0018] Because the intensity distribution of a Gaussian beam is a Gaussian distribution, it is difficult to uniformly apply light to each cell that constitutes the photoelectric conversion unit 2, as shown in Figure 1. In a Gaussian beam, in accordance with the Gaussian distribution, in a circular shape, the light is strong in the center and becomes weaker towards the periphery.

[0019] In the following description, the photoelectric conversion unit may be referred to as a "PV panel." PV is an abbreviation for Photovoltaic.

[0020] When a beam propagates through the atmosphere, such as when optical wireless power supply is performed outdoors, atmospheric turbulence disrupts the wavefront of the beam, resulting in uneven intensity distribution and positional deviation of the beam irradiated onto the PV panel, as shown in Figure 2.

[0021] In Figure 2, (a) shows a beam disturbed by disturbance (simulation result), (b) shows the state in which the disturbed beam is irradiated onto a PV panel, and (c) shows the state in which a Gaussian beam is irradiated onto a PV panel.

[0022] The uneven intensity distribution of the beam and misalignment described above lead to a decrease in photoelectric conversion efficiency. Furthermore, even in a low-disturbance environment, the Gaussian beam has uneven intensity, so the outer cells are not exposed to much light, resulting in a decrease in efficiency.

[0023] (Outline of the embodiment) In this embodiment, a photoelectric conversion system using a capacitor and a scanner is proposed to solve the above-mentioned problems and ensure power generation even in situations where the beam becomes non-uniform, such as under atmospheric turbulence. The configuration and operation of the photoelectric conversion system in this embodiment will be described in detail below.

[0024] (System Configuration Example, Operation Example) A configuration example of a photoelectric conversion system according to this embodiment is shown in Fig. 3. As shown in Fig. 3, the photoelectric conversion system according to this embodiment includes a light transmitting device 100 and a light receiving device 200.

[0025] FIG. 4 shows an example of the configuration of the light transmitting device 100. As shown in FIG. 4, the light transmitting device 100 includes a light source unit 110 and a scanner 120. The light source unit 110 includes a light source element that emits laser light. FIG. 5 shows an example of the configuration of the light receiving device 200. As shown in FIG. 5, the light receiving device 200 includes a photoelectric conversion unit 210. The photoelectric conversion unit 210 is a PV panel in which a plurality of photoelectric conversion elements (cells) are arranged in a lattice pattern. The plurality of cells are connected in series, for example. The photoelectric conversion unit 210 may also be called a "PV panel 210."

[0026] A beam emitted from the light source unit 110 is incident on the scanner 120 in the light transmitting device 100. The beam is reflected by the scanner 120 and irradiated onto the PV panel 210. The scanner 120 can arbitrarily move the irradiation position of the beam on the PV panel 210. Moving the irradiation position of the beam on the PV panel 210 is called "scanning."

[0027] Fig. 6 shows an example of the arrangement of the light source unit 110, the scanner 120, and the PV panel 210. As shown in Fig. 6, a beam emitted from the light source unit 110 is reflected by the scanner 120 and irradiated onto the PV panel 210. Also, as shown in Fig. 6, the surface of the PV panel 210 that is irradiated with the beam is scanned by the beam.

[0028] Fig. 7 is a diagram showing how the beam scans the PV panel 210. As shown in Fig. 7, the diameter of the beam irradiating the PV panel 210 is designed to fit within one cell.

[0029] Furthermore, a capacitor is connected to each cell to extend the time constant of the cell so that the time constant of each cell is longer than the scanning speed. Details of the capacitor connection configuration will be described later. Note that, "the time constant of each cell is longer than the scanning speed" means, for example, that the time during which the beam is irradiated on one cell in one scan (the beam is irradiated on one cell only once) is shorter than the time constant.

[0030] When irradiation of the beam to the PV panel 210 starts, the capacitor of the cell that is first irradiated with the beam is charged. When the capacitor is sufficiently charged, current is supplied from the capacitor to the cell that has a small current value due to beam irradiation.

[0031] In this embodiment, by introducing the above-described configuration, each cell can generate power regardless of the beam pattern, and by connecting a capacitor, it is possible to generate power without the influence of current limiting due to serialization. Below, a more specific example will be described.

[0032] (Example) Figure 8 shows the configuration of a PV panel 210 in this example. As shown in Figure 8, the PV panel 210 in this example is formed by arranging 5 cm square cells in a 1 x 4 array and connecting these four cells in series. For each cell, the open circuit voltage is set to 0.5 V and the photoelectric conversion efficiency η = 0.25.

[0033] The laser emitted from the light source unit 110 is an infrared laser with a wavelength of 1064 nm. As shown in FIG. 9, the beam diameter (1 / e ２ The beam diameter after propagation is also 3.2 cm, which is small enough to fit inside one photoelectric conversion cell.

[0034] A capacitor is attached to each cell constituting the PV panel 210 so that the capacitance is 10 F. The internal resistance of the cell is set to 0.1 Ω. At this time, the time constant of the cell (a circuit consisting of a capacitor and internal resistance) is 1 s.

[0035] An image of scanning in this embodiment is shown in Figure 10. As shown in Figure 10, scanning is performed by repeatedly going back and forth in the horizontal direction (longer side direction) of the PV panel 210. The period (one round trip for four cells) is 0.08 seconds. Note that 0.08 seconds is just an example.

[0036] Figure 11 shows an equivalent circuit of the PV panel 210 when light is shining on the first cell (e.g., the cell at the left end of Figure 10) in the PV panel 210. Figure 11 (a) corresponds to the first cell, and the switch connected to the battery is closed, indicating that power is being generated. R is resistance, and C is capacitance (capacitor).

[0037] Here, we consider a state in which the capacitor is fully charged, and the capacitance of the capacitor is sufficiently large, so that the voltage drop and current fluctuation are zero.

[0038] The open circuit voltage of each cell is E, the internal resistance is R, the capacitance is C, and the charge of each capacitor is Q. １ ~Q ４ In addition, the load resistance is R ＬLet I be the current flowing through the load, and P be the output of the laser (beam). As mentioned above, η is the photoelectric conversion efficiency. In this case, I and E are expressed as follows:

[0039] Therefore, the following equation (1) holds true.

[0040] Furthermore, the charge and current of each capacitor can be expressed as follows, assuming that the moment when light hits the first cell is t=0:

[0041] The charge in a cell that is not exposed to light decreases over time as a current, and can be expressed as in the following equation (2).

[0042] Therefore, the voltage V applied to the load is expressed as follows from equations (1) and (2):

[0043] Therefore, the amount of power generated by the load is expressed by the following equation (3): The resulting equation below is valid not only for the time when the light is shining on the first cell, but also for the entire time when the scan is performed.

[0044] Substituting the parameters of this embodiment into equation (3), it is assumed that a beam of 1 W (=P) is irradiated onto the PV panel 210. In this case, if the load resistance is 16 Ω, 0.24 W can be generated.

[0045] (Summary of the embodiment) In the conventional technology, if the beam is non-uniform due to disturbances or the like and even one cell is not illuminated by light, the amount of power generated becomes 0. On the other hand, by using the technology according to the present embodiment, the amount of power generated can be improved.

[0046] In other words, by designing the beam to fit into one cell as described above, the photoelectric conversion efficiency can be increased using the technology according to this embodiment regardless of the shape of the beam or how it is distorted.

[0047] Furthermore, by designing the system so that it can scan the entire PV panel 210, the cell connection and arrangement methods are not important, making this technology applicable to a variety of power supply situations.

[0048] (Effects of the embodiment) The technology according to the embodiment can reduce the influence of current limitation, increase photoelectric conversion efficiency, and increase power supply even if the beam irradiated to the PV panel is uneven, for example, under atmospheric disturbance.

[0049] The following additional notes are provided regarding the above-described embodiments.

[0050] <Additional Notes> (Additional Item 1) A photoelectric conversion system comprising: a photoelectric conversion unit in which a plurality of cells each having a capacitor are arranged; and a scanner that irradiates the photoelectric conversion unit with light while moving an irradiation position. (Additional Item 2) The photoelectric conversion system according to Additional Item 1, wherein the light is a beam, and the diameter of the beam is smaller than the size of the cell. (Additional Item 3) The photoelectric conversion system according to Additional Item 1, wherein, when the light is irradiated onto the cell once during the movement of the irradiation position, the time for which the light is irradiated onto the cell is shorter than the time constant of the cell. (Additional Item 4) A light receiving device comprising: a photoelectric conversion unit in which a plurality of cells each having a capacitor are arranged; and wherein the photoelectric conversion unit is irradiated with light while moving an irradiation position. (Additional Item 5) A light transmitting device comprising: a light source unit that outputs light; and a scanner that irradiates a photoelectric conversion unit in which a plurality of cells each having a capacitor are arranged with the light while moving an irradiation position.

[0051] Although the present embodiment has been described above, the present invention is not limited to such a specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

[0052] 100 Light transmitting device 110 Light source unit 120 Scanner 200 Light receiving device 210 Photoelectric conversion unit

Claims

1. A photoelectric conversion system comprising: a photoelectric conversion unit in which a plurality of cells each having a capacitor are arranged; and a scanner that irradiates the photoelectric conversion unit with light while moving the irradiation position.

2. The photoelectric conversion system according to claim 1, wherein the light is a beam, and the diameter of the beam is smaller than the size of the cell.

3. The photoelectric conversion system according to claim 1, wherein when the light is irradiated onto the cell once during the movement of the irradiation position, the time for which the light is irradiated onto the cell is shorter than the time constant of the cell.

4. A light receiving device comprising a photoelectric conversion unit in which a plurality of cells each having a capacitor are arranged, wherein light is irradiated onto the photoelectric conversion unit while the irradiation position is moved.

5. A light transmitting device comprising: a light source unit that outputs light; and a scanner that irradiates a photoelectric conversion unit having a plurality of cells each having a capacitor with the light while moving the irradiation position.

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