Sunshine meter and sunshine measurement method

Abstract

Provided is a sunshine recorder that has no movable parts and that is easily adjusted for measurement. A sunshine recorder (10) comprises: a lens (101) that emits, as projection light, natural light incident from half of the celestial sphere; a sensor (102) that photoelectrically converts the projection light projected on a light-receiving surface and that performs output; and a determination circuit (104) that determines the presence or absence of sunshine on the basis of the output from the sensor (102). The sensor (102) has a plurality of detection areas on the light-receiving surface and is configured to output a signal corresponding to the intensity of the projection light incident on each of the detection areas. The determination circuit (104) determines the presence or absence of sunshine in the natural light by removing a scattered light component included in the projection light on the basis of a difference operation of the signal output from each of the detection areas and extracting only a direct light component that should be included in the projection light when the sunlight is incident.

Description

[Technical field]

[0001] The present invention relates to a sunshine meter and a sunshine measurement method. [Background technology]

[0002] A measuring device called a pyranometer is used to measure the amount of sunlight irradiated on the earth's surface. Types of pyranometers include rotating pyranometers and photoelectric pyranometers. In addition, a direct pyranometer can be mounted on a solar tracking device to measure sunlight. Natural light that arrives from the hemisphere during the day includes direct light, which is sunlight that passes through the atmosphere and directly irradiates the earth's surface, and scattered light, which is sunlight that is scattered in the atmosphere and irradiates the earth's surface. A pyranometer determines whether or not there is sunlight based on the intensity of direct light. For example, a predetermined threshold is set for the direct solar radiation intensity corresponding to direct light, and when a direct solar radiation intensity that exceeds the threshold is input to the pyranometer, the pyranometer outputs a signal determining that there is "sunshine." According to the definition by the World Meteorological Organization, if the direct solar radiation intensity (solar radiation from a field of view with a half angle of 2.5 degrees centered on the sun) is 120 W / m 2 In actual operation, the direct solar radiation intensity is 120W / m 2 The time when this occurs is considered to be sunshine hours.

[0003] By improving the measurement accuracy of direct light and scattered light, the presence or absence of sunlight can be determined with high accuracy. For example, Patent Document 1 shows a sunshine meter that reduces measurement errors of direct light and scattered light even when the scattered light changes irregularly. In the sunshine meter (measurement device) described in Patent Document 1, a thermocouple that detects light incident through a first slit and a thermocouple that detects light incident through a second slit are provided inside a cylindrical glass. In this sunshine meter, a first slit and a second slit are provided so that direct light is incident on one of the two thermocouples, and it is possible to detect only the direct light without being obstructed by scattered light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-77215 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the sunshine meter described in Patent Document 1 requires processing of glass and slits, and multiple sensors are required for measurement, making the device complex. In addition, in other conventional sunshine meters, including the sunshine meter described in Patent Document 1, it is necessary to set the installation angle of the sunshine meter and adjust the direction according to the latitude of the installation location of the sunshine meter. In addition, in other conventional sunshine meters, measurement errors may occur in measuring the intensity of direct light due to seasonal changes in the position of the sun (declination change). In addition, measuring sunshine using a method of mounting a direct sunshine meter on a solar tracking device requires a large number of devices, is expensive, and is a large-scale system. In addition, a rotating sunshine meter requires a moving part to capture the reflection from a metal mirror rotating inside a glass tube, making the configuration complex. In this way, the need for adjustment during installation prevents easy measurement. In addition, the need for a moving part as an additional part in the sunshine meter may reduce the durability of the sunshine meter.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a sunshine meter that has no moving parts and can be easily adjusted for measurement. [Means for solving the problem]

[0007] A sunshine meter according to one embodiment of the present invention comprises a lens that emits natural light incident from a hemisphere as projection light, a sensor that photoelectrically converts the projection light projected onto a light-receiving surface and outputs it, and a judgment circuit that judges the presence or absence of sunlight based on the output of the sensor, wherein the sensor has a plurality of detection areas on the light-receiving surface and is configured to output a signal corresponding to the intensity of the projection light incident on each detection area, and the judgment circuit judges the presence or absence of sunlight in natural light by removing scattered light components contained in the projection light based on a difference calculation of the signals output from each detection area and extracting only the direct light components that would be included in the projection light if sunlight were incident.

[0008] According to this aspect, all the light from the entire hemisphere is projected onto the light receiving surface of the sensor as projected light, so that the direct light and scattered light contained in the natural light are all detected by the sensor. The determination circuit then performs a difference calculation of the signals output from each detection area, so that the scattered light component contained in the projected light is removed and only the direct light component is extracted. Therefore, the sunshine meter according to this aspect can determine the presence or absence of sunlight without being affected by changes in the position of the sun on the hemisphere, and no moving parts are required. In addition, there is no need to adjust the attitude of the sunshine meter according to the latitude of the position where the sunshine meter is installed. Furthermore, it is possible to suppress measurement errors in the intensity measurement of direct light caused by changes in declination. Therefore, the sunshine meter according to this aspect does not have any moving parts and is a sunshine meter that is easy to adjust for measurement.

[0009] The determination circuit may determine that there is sunlight when the maximum value of the differences between the signals output from each detection area satisfies a predetermined threshold. In this embodiment, even if there are multiple differences, the maximum value is used to determine whether there is sunlight or not, thereby making an appropriate determination.

[0010] In addition, in the above aspect, the sensor may have four detection areas, and the determination circuit may determine the presence or absence of sunlight by comparing the difference between the sum of signals from the detection areas arranged in a row in a predetermined first direction and the sum of signals from the detection areas arranged in a row in a second direction perpendicular to the first direction.

[0011] According to this aspect, for example, compared to when the sensor has only two detection areas, even if direct light is located between the detection areas, the signal differences can be compared with each other to determine the presence or absence of sunlight based on the direct light component.

[0012] The determination circuit may output a determination signal indicating the presence or absence of sunlight. According to this aspect, the external device can record the sunlight using a sunshine meter.

[0013] The determination circuit may further refer to a predetermined calibration value to determine the presence or absence of sunlight. According to this aspect, the presence or absence of sunlight can be determined including a calibration value according to the environment of the sunshine meter, so that the presence or absence of sunlight can be determined more accurately.

[0014] A sunshine measurement method according to another aspect of the present invention includes the steps of emitting natural light incident from a hemisphere as projection light, outputting signals corresponding to the intensity of the projection light incident on each of a plurality of detection areas on the light receiving surface of the projection light, and determining the presence or absence of sunshine in the natural light by removing scattered light components contained in the projection light based on a difference calculation of the signals output from each detection area and extracting only the direct light components that would be contained in the projection light if sunlight were incident. Effect of the Invention

[0015] According to the present invention, it is possible to provide a sunshine meter that has no moving parts and can be easily adjusted for measurement. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a schematic diagram illustrating the principle of measurement by a sunshine meter. [Diagram 2] FIG. 2 is a schematic diagram illustrating the principle of measurement by a sunshine meter, showing sunshine and its movement over time. [Diagram 3] FIG. 2 is a cross-sectional view of the sunshine meter according to the first embodiment. [Figure 4]FIG. 2 is a block diagram illustrating a determination circuit according to the first embodiment. [Diagram 5] FIG. 4 is a diagram showing a signal in the sensor according to the first embodiment. [Figure 6] 4 is a flowchart illustrating a process in a determination circuit according to the first embodiment. [Figure 7] 5A to 5C are diagrams illustrating processing in a determination circuit according to the first embodiment. [Figure 8] 5A to 5C are diagrams illustrating the results of processing by a determination circuit according to the first embodiment. [Figure 9] 10 is a flowchart illustrating a process in a determination circuit according to a second embodiment. [Figure 10] 13 is a diagram for explaining a process in a determination circuit according to a second embodiment. FIG. [Figure 11] 13A to 13C are diagrams illustrating the results of processing by a determination circuit according to the second embodiment. [Figure 12] 13A and 13B are diagrams for explaining the result of determination of the presence or absence of sunlight by a determination circuit according to the second embodiment. [Figure 13] 13A and 13B are diagrams illustrating other results of determination of the presence or absence of sunlight by the determination circuit according to the second embodiment. [Figure 14] FIG. 13 is a block diagram illustrating a determination circuit according to a third embodiment. [Figure 15] FIG. 11 is a diagram illustrating the direct solar irradiance calculated by a determination circuit according to a third embodiment. [Figure 16] FIG. 13 is a schematic diagram illustrating measurement by a sunshine meter according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described with reference to the accompanying drawings, in which like reference numerals denote like or similar structures.

[0018] (Explanation of the principle) First, a first principle of determining whether or not sunlight is present using the sunshine meter according to this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic side view of a lens and a sensor according to the present invention. Figure 1 shows a situation in which natural light IL, which is sunlight, enters a lens 101 from a hemisphere HS, and projection light PL is emitted from the lens 101 to a sensor 102.

[0019] The lens 101 is an objective lens that refracts natural light IL so that the natural light IL is irradiated as projection light PL along the z axis downward in the z axis direction shown in FIG. 1 (in the following description, the positive directions of the x, y and z axes are referred to as the "upper side" and the negative directions of the axes are referred to as the "lower side"). The lens 101 is a convex lens having a wide angle of incidence, for example, a fisheye lens. The lens 101 may be composed of a plurality of lenses. The lens 101 is an optical element configured to be able to collect light from the hemisphere HS so that the hemisphere HS can be observed. The natural light IL incident from the hemisphere HS is converted into parallel light rays by the lens 101 and projected as projection light PL onto the light receiving surface of the sensor 102. That is, a planar projection image of the hemisphere HS is formed by the projection light PL on the light receiving surface of the sensor 102. The sensor 102 performs photoelectric conversion on the projection light PL, and outputs a signal (electrical signal) according to the intensity of the light received by the sensor 102. The sensor 102 has a plurality of detection areas (see FIG. 2).

[0020] Natural light IL includes direct light from the sun and scattered light from the space of the hemisphere HS. Therefore, the projection light PL that forms a planar projection image of natural light IL includes a direct light component corresponding to the direct light from the sun and a scattered light component corresponding to the scattered light from the space of the hemisphere HS.

[0021] FIG. 2 is a plan view showing a planar projection image of the projection light PL projected onto the light receiving surface RS of the sensor 102. The light receiving surface RS is divided into detection regions R1, R2, R3, and R4. The sensor 102 outputs a signal according to the intensity of the projection light projected onto each of the detection regions R1, R2, R3, and R4. For example, each signal is a voltage signal having an amplitude value corresponding to the intensity of the projected light. In FIG. 2, the direct light is shown as the light projected onto the region DR of the detection region R1. The scattered light is shown as the light in the region SC. The region SC showing the scattered light is the entire region spanning the detection regions R1, R2, R3, and R4.

[0022] As the sun moves with the passage of time, in the planar projection image formed on the light-receiving surface RS, direct light moves from the region DR across the light-receiving surface RS in the direction of the arrow along the dashed line in FIG.

[0023] In FIG. 2, the signal from the detection region R1 is initially a signal corresponding to the intensity of the combined light component of the direct light component located in the region DR and the scattered light component due to the scattered light around it. The signal from the detection region R4 is a signal corresponding to the intensity of only the scattered light component. Therefore, the signal of the direct light component required for determining the presence or absence of sunlight can be obtained by removing the scattered light component through a difference calculation in which the signal from the detection region R4 is subtracted from the signal from the detection region R1. Then, the presence or absence of sunlight can be determined based on the obtained signal of the direct light component. This is the same when the signals from the detection regions R2 and R3 are used instead of the detection region R4. Therefore, the presence or absence of sunlight can be determined by performing a difference calculation of two signals from multiple detection regions for all combinations and comparing the difference that shows the maximum value among the multiple differences with a predetermined threshold value. The fact that the difference shows the maximum value means that the direct light component with the strongest light amount is included in one of the detection regions that was the subject of the difference calculation. A specific application example according to this first determination principle will be described later in the first embodiment. In addition, the calculations for determining the presence or absence of sunlight according to the above-mentioned first measurement principle and the following second measurement principle are collectively referred to as "difference calculations" in this specification.

[0024] Now, suppose that the sun moves and the direct light projected on the light receiving surface RS is projected at the position shown in region DR2 in FIG. 2. In this case, the direct light is split into two and projected to detection region R1 and detection region R4. At such a position of the direct light, the signal from detection region R1 is a signal corresponding to the intensity of the light component that is a combination of half the direct light component and the scattered light component. Also, the signal from detection region R4 is a signal corresponding to the intensity of only half the direct light component and the scattered light component. Therefore, the result of the difference calculation in which the signal from detection region R4 is subtracted from the signal from detection region R1 is zero or close to zero. In other words, if the position of the sun straddles the boundary of the detection region, the signal of the direct light component cannot be obtained correctly.

[0025] Therefore, as a second measurement principle, the differences between signals from multiple detection areas are compared to determine the presence or absence of sunlight based on the direct light component. The details of the difference calculation will be described below. Here, the signal from the detection region Rx (x is any one of 1 to 4) is denoted as Qx, and the signal is decomposed into a direct light component Dx and a scattered light component Sx, and considered as Qx = Dx + Sx. The calculation of the direct light component is performed by the following steps (a) to (g).

[0026] (a) The signal Q1 from the detection region R1 and the signal Q4 from the detection region R4 are summed to calculate the signal Q1+Q4 (=D1+D4+S1+S4). (b) The signal Q2 from the detection region R2 and the signal Q3 from the detection region R3 are summed to calculate the signal Q2+Q3 (=D2+D3+S2+S3). (c) A first difference between the signal Q1+Q4 and the signal Q2+Q3 is calculated as an absolute value. (d) The signal Q1 from the detection region R1 and the signal Q2 from the detection region R2 are summed to calculate the signal Q1+Q2 (=D1+D2+S1+S2). (e) The signal Q3 from the detection region R3 and the signal Q4 from the detection region R4 are summed to calculate the signal Q3+Q4 (=D3+D4+S3+S4). (f) Calculate a second difference between the signal Q1+Q2 and the signal Q3+Q4 as an absolute value. (g) Of the first difference and the second difference, the difference with the larger absolute value is determined as the determination difference, and the presence or absence of sunlight is determined based on whether the determination difference is equal to or greater than a predetermined threshold value.

[0027] For example, when direct light is projected to the position shown in region DR2 in Figure 2 under clear skies, the direct light components are D1 = D4 = d / 2 and D2 = D3 = 0. Here, d is the direct light component of the entire direct light. Also, the scattered light components are S1 = S2 = S3 = S4 = s.

[0028] At this time, the first difference by step (c) is D1+D4=d. Moreover, the second difference by step (f) is D1-D4=0. Therefore, the judgment difference is d, and it becomes possible to judge the presence or absence of sunlight based on the direct light component of the entire direct light. In other words, by comparing the difference between the sum of the signals from the detection areas (detection areas R1+R4 and detection areas R2+R3 arranged in the x-axis direction in the example of FIG. 2) arranged side by side in a predetermined first direction (x-axis direction in the example of FIG. 2) and the sum of the signals from the detection areas (detection areas R1+R2 and detection areas R4+R3 arranged in the y-axis direction in the example of FIG. 2) arranged side by side in a second direction perpendicular to the first direction (y-axis direction in the example of FIG. 2), the presence or absence of sunlight can be correctly judged regardless of the position where the direct light is projected. An application example according to the above second measurement principle will be described later in the second embodiment.

[0029] (First embodiment) A first embodiment based on the first measurement principle will be described below. Fig. 3 is a cross-sectional view of the sunshine meter 10 according to the first embodiment, showing a surface of the sunshine meter 10 cut along the central axis C. The sunshine meter 10 includes a lens 101, a sensor 102, a housing 103, a determination circuit 104, and a connector 105. In Fig. 3, a part of the natural light IL in Fig. 1 is shown as natural light L1, and a part of the projection light PL is shown as projection light L2. The lens and sensor referred to in the above explanation of the principle correspond to the lens 101 and the sensor 102 in this embodiment, respectively.

[0030] The housing 103 is a cylindrical member with a central axis C as its axis. The housing 103 is formed, for example, from a material that is physically and chemically resistant when installed outdoors, such as a metal material. The housing 103 houses the lens 101, the sensor 102, and the determination circuit 104, which will be described later. The housing 103 has a plurality of legs 1031 on the lower side in the negative z-axis direction. The legs 1031 are members that can adjust the inclination of the housing 103 with respect to the ground surface.

[0031] The lens 101 is accommodated in the housing 103 and disposed on the upper side of the housing 103 in the z-axis direction. The lens 101 has an incident surface 1011 and an exit surface 1012. The lens 101 projects natural light IL incident from the incident surface 1011 onto the sensor 102 from the exit surface 1012 as projection light PL. The lens 101 is disposed in the housing 103 at a position where the lens 101 can collect light from a hemisphere. The lens 101 is protected from external attachments by a cover 1013 disposed on the housing 103. The cover 1013 is formed of a glass material or the like, and is a protective member having optical transparency that improves the cosine (cosine) characteristics of the projection light PL.

[0032] The sensor 102 is provided below the lens 101 in the z-axis direction, facing the emission surface 1012. The sensor 102 is provided on a sensor substrate 1021 connected to the housing 103. The sensor 102 is a photoelectric conversion sensor. For example, a semiconductor element is one of them. For example, the sensor 102 is a photodiode having multiple detection areas provided on the same surface. In the sensor 102, each detection area outputs an individual signal. More specifically, the sensor 102 is a photodiode having four detection areas. The sensor 102 outputs a signal from each detection area to the outside through the wiring 1022. The signal here is, for example, a voltage signal having an amplitude value corresponding to the intensity of the received projection light.

[0033] The determination circuit 104 is provided below the sensor 102 in the z-axis direction, with a board on which the determination circuit 104 is mounted being connected to the housing 103. The determination circuit 104 is electrically connected to the sensor 102 through wiring 1022. The determination circuit 104 determines whether or not the projection light PL has an intensity that can be determined to be sunlight, based on a signal from the sensor 102. The determination circuit 104 will be described in detail later.

[0034] The determination circuit 104 outputs a determination signal indicating the result of the determination to the outside via a wiring 1041. The wiring 1041 is connected to a connector 105 provided in the housing 103. A cable 106 is connected to the connector 105. Through the cable 106, it becomes possible to supply power to the sunshine meter 10, read out the measurement results by the sunshine meter 10, and write the measurement settings by the sunshine meter 10.

[0035] The determination circuit 104 will be described with reference to Fig. 4. The determination circuit 104 has a storage circuit 201, a signal processing circuit 202, and a calculation circuit 203. The determination circuit 104 is realized as a circuit in a microcomputer including the storage circuit 201 and the signal processing circuit 202. The calculation circuit 203 is a functional block realized by the microcomputer executing a software program stored in the storage circuit 201.

[0036] The memory circuit 201 stores a software program for causing the microcomputer to execute the sunshine measurement method of the present invention, and also records various information used in signal processing by the determination circuit 104. The memory circuit 201 is a memory of the microcomputer. The memory circuit 201 stores program codes that define the processing by the calculation circuit 203, and various thresholds that are used to determine whether the projection light PL indicates sunshine or not. The information stored in the memory circuit 201 may be rewritable by an external device connected to the sunshine meter 10 via the cable 106.

[0037] The signal processing circuit 202 is an A / D converter that converts an analog signal from the sensor 102 into a digital signal.

[0038] The calculation circuit 203 uses the digitally converted signal to perform a difference calculation to determine whether or not the projection light PL indicates sunlight. If the calculation circuit 203 determines that the projection light PL indicates sunlight, the calculation circuit 203 stores information indicating sunlight in the memory circuit 201. The calculation by the calculation circuit 203 will be described later.

[0039] The determination circuit 104 is connected to a power source 205 and an external device 206. The power source 205 supplies power to the sunshine meter 10 including the determination circuit 104. The determination circuit 104 transmits a signal indicating the determination result by the determination circuit 104 and the sensor output to the external device 206. The external device 206 is, for example, a computer or a data logger. When the external device 206 is a computer or a data logger capable of digital communication, the determination circuit 104 outputs a digitally converted signal to the external device 206. Alternatively, when the external device 206 is a data logger capable of reading analog values, the determination circuit 104 outputs an analog signal from the sensor 102 to the external device 206. The external device 206 can accumulate the sunshine hours based on the determination result from the determination circuit 104.

[0040] Fig. 5 is an example of a graph plotting signals from each detection area during a day when the weather is fine. Fig. 5 shows a signal Q1 from detection area R1, a signal Q2 from detection area R2, a signal Q3 from detection area R3, and a signal Q4 from detection area R4.

[0041] In the morning, the signal Q1 from the detection region R1 is large, and the other signals Q2, Q3, and Q4 are small. This indicates that the region DR2 is located on the detection region R1. At this time, the signal Q1 contains both voltage components corresponding to the direct light and the scattered light, and Q2, Q3, and Q4 contain voltage components corresponding to the scattered light.

[0042] As time passes, signal Q1 decreases and signal Q4 increases. This indicates that region DR2 is moving from detection region R1 onto detection region R4. In the afternoon, signal Q4 becomes large and the other signals Q1, Q3, and Q4 become small. This indicates that region DR2 is completely located on detection region R4. Figure 5 shows that region DR2 moves in accordance with the movement of the sun, and that this movement is detected. Also, before sunset, signal Q3 rises slightly, which indicates that region DR2 is over detection region R3.

[0043] 6, a method for measuring sunshine by the determination circuit 104 based on a signal from the sensor 102 will be described. This method is a processing procedure that is repeatedly executed while the sunshine meter 10 is in operation. The following calculation procedure is as described in detail in the description of the first measurement principle above, and will be described briefly below.

[0044] In step S601 of FIG. 6, the signal processing circuit 202 acquires a signal from each detection area of ​​the sensor 102.

[0045] In step S602, the calculation circuit 203 calculates the difference between the signals as a measurement value. The difference is calculated as an absolute value.

[0046] In step S603, the calculation circuit 203 specifies the difference with the largest absolute value from among the calculated differences as the maximum difference.

[0047] In step S604, the calculation circuit 203 determines whether the maximum value of the differences is equal to or greater than a predetermined threshold value stored in the storage circuit 201.

[0048] If the determination in step S604 is affirmative, in step S605, the calculation circuit 203 determines that there is sunlight at the time the process is being executed.

[0049] If a negative determination is made in step S604, in step S606, the calculation circuit 203 determines that there is no sunlight at the time the process is being executed.

[0050] In step S607, the calculation circuit 203 outputs a determination signal based on the determination result.

[0051] A specific example of the process will be described with reference to Fig. 7. Fig. 7 illustrates the cases where the signals Q1, Q2, Q3, and Q4 are (9.5, 0.7, 0.9, 0.8) and (0.2, 0.5, 0.3, 0.4) (unit: mV), respectively.

[0052] By the process in step S602, the differences |Q1-Q2|, |Q1-Q3|, |Q1-Q4|, |Q2-Q3|, |Q2-Q4|, and |Q3-Q4| are calculated.

[0053] The maximum difference is identified by the process in step S603. If the maximum difference is equal to or greater than a threshold, it is determined that there is sunshine, and if it is equal to or less than the threshold, it is determined that there is no sunshine. Here, examples are shown in which it is determined that there is sunshine and that there is no sunshine, but the determination result may vary depending on the threshold.

[0054] FIG. 8 shows a curve V1 indicating the maximum value of the difference calculated on a day different from the day on which the measurement in FIG. 5 was performed. As a comparative example, a curve E1 indicating the direct solar irradiance measured by a direct pyranometer mounted on a solar tracking device at the same time on the same day is also shown. From FIG. 8, it can be seen that the state of insolation can be properly measured even by the maximum value of the difference. Therefore, the sunshine meter 10 can properly judge the insolation based on the maximum value of the difference.

[0055] In step S604, when the calculation circuit 203 determines whether the maximum value of the differences is equal to or greater than a predetermined threshold value stored in the storage circuit 201, the calculation circuit 203 may take into consideration a calibration value stored in advance in the storage circuit 201.

[0056] Second embodiment Next, a second embodiment based on the above-mentioned second measurement principle will be described. In the second embodiment, a description of matters common to the first embodiment will be omitted, and only the differences will be described. In the second embodiment, each component of the sunshine meter 10 and each circuit of the determination circuit 104 are common to the first embodiment. The second embodiment is different in that the difference calculation in the determination process by the determination circuit 104 is performed by comparing the differences based on the signals from the four detection areas with each other.

[0057] 9 shows a flowchart of the insolation measurement method by the determination circuit 104 according to the second embodiment. The following calculation procedure is as described in detail in the explanation of the second measurement principle above, and will be explained briefly below.

[0058] In step S901, the calculation circuit 203 acquires a signal from each detection area.

[0059] In step S902, the calculation circuit 203 calculates the sum of the signals from each detection region based on each signal.

[0060] In step S903, the calculation circuit 203 calculates the normalized difference between the sums. The difference is calculated as an absolute value.

[0061] In step S904, the calculation circuit 203 specifies the difference whose absolute value is maximum as the determination difference.

[0062] In step S905, the calculation circuit 203 determines whether the determination difference is equal to or greater than a predetermined threshold value.

[0063] If the determination in step S905 is affirmative, in step S906, the calculation circuit 203 determines that there is sunlight at the time the process is being executed.

[0064] If a negative determination is made in step S905, in step S907, the calculation circuit 203 determines that there is no sunlight at the time the process is being executed.

[0065] In step S908, the calculation circuit 203 outputs a determination signal based on the determination result.

[0066] A specific example of the process will be described with reference to Fig. 10. Fig. 10 illustrates a case where the signals Q1, Q2, Q3, and Q4 are (9.5, 0.7, 0.9, 0.8), (4.8, 0.5, 0.6, 4.8), (4.8, 4.8, 0.5, 0.6), (0.6, 4.8, 4.8, 0.5), (0.5, 0.6, 4.8, 4.8), and (0.2, 0.5, 0.3, 0.4), respectively.

[0067] The process in step S902 calculates the sum Q1+Q2 of the signals from the detection regions R1 and R2 and the sum Q3+Q4 of the signals from the detection regions R3 and R4. The process in step S902 calculates the sum Q1+Q4 of the signals from the detection regions R1 and R4 and the sum Q2+Q3 of the signals from the detection regions R2 and R3 as measured values.

[0068] The process in step S903 normalizes the absolute value of the difference between the measurement values ​​of the set of detection area R1 and detection area R2 and the set of detection area R3 and detection area R4 by the total value of Q1 to Q4 to calculate the difference Δ1. The process in step S903 normalizes the absolute value of the difference between the signals from the set of detection area R1 and detection area R4 and the set of detection area R2 and detection area R3 by the total value of Q1 to Q4 to calculate the difference Δ2. The differences Δ1 and Δ2 are calculated using the following formulas:

number

[0069] By the process in step S904, the larger of the differences Δ1 and Δ2 is specified as the determination difference. That is, when Δ1≧Δ2, Δ1 is determined as the determination difference, and when Δ2>Δ1, Δ2 is determined as the determination difference.

[0070] Through the processes from steps S905 to S907, if the maximum difference is equal to or greater than the threshold value (0.5), it is determined that there is sunlight, and if it is equal to or less than the threshold value, it is determined that there is no sunlight. Note that the threshold values ​​here are merely examples, and the threshold values ​​can be set appropriately depending on the environment.

[0071] The signal sets in the first and sixth columns of Fig. 10 are the same as the signal sets according to the first embodiment shown in the first and second columns of Fig. 6. It is shown that the sunshine meter 10 according to the second embodiment also appropriately determines whether or not there is sunshine.

[0072] Moreover, the signal pairs in the second to fifth columns of FIG. 10 correspond to the cases where the region DR2 is located halfway between the detection region R1 and the detection region R4, where the region DR2 is located halfway between the detection region R1 and the detection region R2, where the region DR2 is located halfway between the detection region R2 and the detection region R3, and where the region DR2 is located halfway between the detection region R3 and the detection region R4. In all cases, it is appropriately determined that there is sunlight. Therefore, the sunshine meter 10 according to the second embodiment can appropriately determine the presence or absence of sunlight regardless of the direction in which the sunshine meter 10 is installed.

[0073] 11 shows a curve N1 indicating the judgment difference calculated on the day when the measurement in FIG. 8 was performed. As a comparative example, a curve E1 indicating the direct solar irradiance measured by a direct solar pyranometer mounted on a solar tracking device at the same time on the same day is shown. In FIG. 11, when the judgment difference is 0.5 or more, there is sunlight, and the direct solar irradiance is 120 W / m 2If the difference exceeds , it is determined that there is sunshine. FIG. 11 shows that the state of sunshine can be properly measured by the judgment difference as well. In other words, FIG. 11 shows that the judgment of sunshine by the sunshine meter 10 according to the second embodiment is equivalent to the judgment of sunshine by a direct pyranometer mounted on a solar tracking device having a movable part and a more complicated configuration than the sunshine meter 10. Therefore, it has been made clear that the sunshine meter 10 of this embodiment can properly judge the presence or absence of sunshine based on the judgment difference without providing a movable part.

[0074] Fig. 12 shows the state of insolation (A) determined based on the determination difference shown by the curve N1 in Fig. 11, and the state of insolation (B) determined based on the direct solar radiation intensity shown by the curve E1 in Fig. 11. When the value on the vertical axis is 1, there is insolation, and when it is 0, there is no insolation. As shown in Fig. 12, in the sunshine meter 10 according to the second embodiment, the presence or absence of insolation is appropriately determined in the same way as in the direct solar radiation meter mounted on the solar tracking device. In this case, the external device 206 calculates the time T1 as the sunshine duration.

[0075] FIG. 13 shows the state of sunshine (A) determined based on the determination difference on another day, and the state of sunshine (B) determined based on the direct solar radiation intensity on the same day. In both cases, it is shown that the sun is hidden by clouds or the like for a certain period of time. As shown in FIG. 13, in the sunshine meter 10 according to the second embodiment, even when the sunshine is interrupted, the presence or absence of sunshine is appropriately determined in the same way as a direct solar pyranometer mounted on a solar tracking device. In this case, the external device 206 calculates the sunshine hours as the total value of the time during which it was determined that there was sunshine.

[0076] Third embodiment A third embodiment will be described. The sunshine meter according to the third embodiment can calculate direct solar radiation intensity in addition to determining the presence or absence of sunlight as described in the first and second embodiments. The sunshine meter according to the third embodiment has a structure similar to that of the sunshine meter 10 shown in FIG. 3, but differs from the sunshine meter 10 in that the determination circuit 104 is replaced with a determination circuit 104A shown in FIG.

[0077] The determination circuit 104A has a memory circuit 201A, a signal processing circuit 202, and a calculation circuit 203A. The determination circuit 104A is realized as a circuit in a microcomputer including the memory circuit 201A and the signal processing circuit 202. The calculation circuit 203A is a functional block realized by the microcomputer executing a software program stored in the memory circuit 201A.

[0078] In addition to the information stored in the memory circuit 201A, a calibration value for calculating direct solar irradiance is stored in the memory circuit 201A. In addition to the calculation performed by the calculation circuit 203, the calculation circuit 203A performs a calculation to calculate direct solar irradiance.

[0079] The calculation of direct solar irradiance by the calculation circuit 203A will be described. The calculation circuit 203A performs a difference calculation based on the above-mentioned second measurement principle to calculate the first difference and the second difference. The calculation circuit 203A determines the difference with the larger absolute value of the first difference and the second difference as the judgment difference D. Note that the judgment difference D may be a normalized value like the differences Δ1 and Δ2 in the second embodiment, or may be a non-normalized value. Here, the judgment difference D will be described as not being normalized.

[0080] The calculation circuit 203A performs the same processes as those in steps S901 to S904 in FIG.

[0081] The calculation circuit 203A calculates

number

[0082] Here, the sensitivity constant k is, for example, a direct solar irradiance β calculated using a direct solar pyranometer mounted on the solar tracking device, a judgment difference D calculated by the solar pyranometer according to this embodiment, a solar altitude angle θ, and coefficients α1 to α n Using

number

[0083] In FIG. 15, at a certain date and time, the calculation circuit 203A calculates the judgment difference D, the solar altitude angle θ, the coefficients α1 to α n and the sensitivity constant k, and a curve E2 showing the direct solar radiation intensity calculated based on the sensitivity constant k, and a curve E3 showing the direct solar radiation intensity measured by a direct solar radiation meter mounted on a solar tracking device at the same time on the same day. Fig. 15 shows that the direct solar radiation intensity calculated by the sunshine meter 10 according to the third embodiment is equivalent to the direct solar radiation intensity calculated by a direct solar radiation meter mounted on a solar tracking device having a more complicated configuration than the sunshine meter 10 of the third embodiment 3 by providing a movable part, etc. Therefore, it has been revealed that the sunshine meter 10 of the third embodiment can appropriately calculate the direct solar radiation intensity based on the determination difference without providing a movable part.

[0084] (Modification) Modifications of the above-mentioned embodiments will be described. For example, in the first embodiment, in the sensor 102 in which the light receiving surface RS is divided into detection regions R1, R2, R3, and R4, direct light may be incident on the boundary between the detection regions. The boundary between the detection regions is an insensitive region where there are no elements of the sensor 102. The insensitive region is, for example, a rectangular region having a width of several μm to about 100 μm, and direct light and scattered light are not detected at the boundary between the detection regions. Therefore, when direct light is incident on the boundary between the detection regions, it may be difficult to detect the direct light. In this modification, a sunshine meter that enables detection of the direct light component even when the sensor 102 has an insensitive region will be described.

[0085] The sunshine meter according to this modification solves the problem of the blind area by blurring the image formed on the sensor 102 by the direct light incident on the sensor 102. An example of the concept of a sunshine meter capable of blurring the image on the sensor 102 is shown in FIG.

[0086] Fig. 16 is a schematic side view of a lens, a sensor, and a diffuser according to this modification. As in Fig. 1, Fig. 16 shows a situation in which natural light IL, which is sunlight, is incident on the lens 101 from a hemisphere HS, and projection light PL is emitted from the lens 101 to the sensor 102. In this modification, a diffuser 1601 is provided between the lens 101 and the sensor 102. The diffuser 1601 scatters the projection light PL when transmitting the light from the lens 101. The diffuser 1601 projects the scattered projection light PL onto the sensor 102.

[0087] By scattering the projected light from the lens 101, it is possible to blur the image that the direct light forms on the sensor 102. This makes it possible to prevent the direct light from reaching only the insensitive area of ​​the sensor 102, and to allow the direct light to be detected by the elements of the sensor 102. Therefore, even if the sensor 102 has an insensitive area, it is possible to detect the direct light component.

[0088] The configuration for blurring the image formed on the sensor 102 by direct light is not limited to the method using a diffuser. For example, in FIG. 3, if the cover 1013 is formed of ground glass that diffuses light instead of transparent glass, the image on the sensor 102 can be blurred. Also, if the entrance surface 1011 or the exit surface 1012 of the lens 101 is formed of ground glass, the image on the sensor 102 can be blurred. Alternatively, the image on the sensor 102 can be blurred by installing the sensor 102 at a distance different from the focal length of the lens 101. In optical instruments such as a sunshine meter, it is sometimes important that the light reaches the sensor in a straight line by installing the sensor correctly at the focal length of the lens. In this modified example, the problem related to the blind area is solved by changing the idea of ​​adopting a configuration that blurs the image, contrary to such technical common sense.

[0089] In addition to the above-mentioned configuration for blurring the image, a configuration for solving the problem related to the dead zone will be described. For example, by arranging a reflecting member such as a mirror that reflects light or a refracting member that refracts light in the dead zone, the direction of light can be adjusted so that the light that reaches the dead zone is directed toward the light receiving region of the sensor 102. According to this configuration, the light can be prevented from reaching the dead zone, so that the problem related to the dead zone is solved. Alternatively, by configuring the sunshine meter 10 to be eccentrically driven by a driving device or the like, the sunshine meter 10 can be moved so that the light does not reach the dead zone, so that the problem related to the dead zone can be solved. Alternatively, the problem related to the dead zone can be solved by performing a calculation to reduce the effect of the dead zone according to the output of the sensor 102 when light reaches the dead zone.

[0090] The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The elements of the embodiments, as well as their arrangements, materials, conditions, shapes, sizes, etc., are not limited to those shown as examples and can be changed as appropriate. In addition, configurations shown in different embodiments can be partially substituted or combined with each other. [Explanation of symbols]

[0091] 10... sunshine meter, 101... lens, 102... sensor, 103... housing, 104, 104A... judgment circuit, 201, 201A... memory circuit, 202... signal processing circuit, 203, 203A... calculation circuit, R1, R2, R3, R4... detection area, 1601... diffusion plate

Claims

1. A lens that outputs natural light incident from a hemisphere as projection light; a sensor that photoelectrically converts the projected light projected onto a light receiving surface and outputs the converted light; a determination circuit for determining whether or not sunlight is present based on the output of the sensor; the sensor has a plurality of detection areas on the light receiving surface and is configured to output a signal corresponding to the intensity of the projection light incident on each of the detection areas; The judgment circuit removes scattered light components contained in the projection light based on a difference calculation of the signals output from each of the detection areas, extracts only the direct light components that would be contained in the projection light when sunlight is incident, and determines that there is sunlight when the maximum value of the differences between the signals output from each of the detection areas meets a predetermined threshold, thereby determining the presence or absence of sunlight in the natural light.

2. 2. The sunshine meter according to claim 1, The sensor has four of the detection regions, The judgment circuit, a sunshine meter, determines the presence or absence of sunlight by comparing the difference between the sum of the signals from the detection areas arranged in a row in a predetermined first direction and the sum of the signals from the detection areas arranged in a row in a second direction perpendicular to the first direction.

3. 3. The sunshine meter according to claim 1, The determination circuit outputs a determination signal indicating the presence or absence of sunlight.

4. A sunshine meter according to any one of claims 1 to 3, The determination circuit further refers to a predetermined calibration value to determine whether or not sunlight is present.

5. A sunshine meter according to any one of claims 1 to 4, The determination circuit calculates a direct solar irradiance based on the direct light component and a direct solar irradiance calibration value.

6. 6. The sunshine meter according to claim 5, The determination circuit outputs the direct solar radiation intensity.

7. A step of emitting natural light incident from a hemisphere as projection light; outputting signals corresponding to intensities of the projection light incident on a plurality of detection regions on a light receiving surface of the projection light; a step of removing scattered light components contained in the projection light based on a difference calculation of the signals output from each of the detection areas, extracting only the direct light components that would be contained in the projection light when sunlight is incident, and judging that there is sunlight if the maximum value of the differences between the signals output from each of the detection areas meets a predetermined threshold, thereby judging the presence or absence of sunlight in the natural light.

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