A light-homogenizing photovoltaic agriculture system

Abstract

The present invention discloses a light-homogenizing photovoltaic agricultural system, which can generate electricity while not affecting the growth of vegetation on farmland, and solves the problem of plants competing with photovoltaic panels for light. The light-homogenizing photovoltaic agricultural system includes a bracket, a first solar photovoltaic panel, a second solar photovoltaic panel, and a grooved light-splitting glass plate. The first solar photovoltaic panel, the second solar photovoltaic panel, and the grooved light-splitting glass plate are sequentially and juxtaposedly installed on the bracket from top to bottom. There are gaps between the second solar photovoltaic panel and the grooved light-splitting glass plate as well as the first solar photovoltaic panel. The upper surface of the grooved light-splitting glass plate is a plane, and a grooved array is formed on the lower surface. The grooved array is obtained by dividing and translating a specific free-form surface. When sunlight passes through the upper and lower surfaces of the grooved light-splitting glass plate successively, the light is evenly irradiated onto the projection areas of the first solar photovoltaic panel, the second solar photovoltaic panel, and the lower edge of the grooved light-splitting glass plate along the light irradiation direction.

Description

Technical Field

[0001] The present invention relates to the cross - technical field of solar photovoltaic power generation and agriculture, and particularly relates to a light - homogenizing photovoltaic agricultural system. Background Art

[0002] The per capita cultivated land area in China is only 1.38 mu, less than 40% of the world average level. How to efficiently utilize the precious cultivated land resources to bring more benefits to people is of great significance for driving the rural economic development. In recent years, with the increase in the power generation efficiency of solar photovoltaic panels, the photovoltaic agricultural system that combines "farming + power generation" provides a new technical route for us to efficiently utilize cultivated land resources.

[0003] Throughout the four seasons, the solar altitude angle at any point on the earth is constantly changing. The solar altitude angle is high in summer and low in winter. Currently, the main problems existing in the photovoltaic agricultural system are as follows: 1. The solar photovoltaic panels block sunlight, resulting in insufficient light intensity for the crops in the projection area at the bottom of the panels to reach the photosynthesis compensation point, so that the crops cannot grow normally. This design will cause alternating sunny and shady areas in the farmland in summer, resulting in uneven growth of crops; 2. To prevent the projection generated by the photovoltaic panels at low solar altitude angles from blocking the rear rows, the row spacing of the solar photovoltaic panel array needs to be set relatively large, thus limiting the total power generation per mu of land.

[0004] In the past, photovoltaic agricultural systems at home and abroad have improved the lighting conditions of crops by adding light - splitting plates in the middle of solar photovoltaic panels. However, this method cannot solve the problem of the relatively large row spacing of the above - mentioned solar photovoltaic panel array. Summary of the Invention

[0005] The present invention proposes a light - homogenizing photovoltaic agricultural system, which forms the structural unit through "grooved light - splitting glass plate - first solar photovoltaic panel - second solar photovoltaic panel". This device mainly solves the following two major problems: on the one hand, the crops under the photovoltaic panels are covered by the shadows of the photovoltaic panels and cannot grow well; on the other hand, when the season is winter, after the solar photovoltaic panel assembly is illuminated, its shadow area will cover the subsequent solar photovoltaic panel assembly, affecting the power generation of the solar photovoltaic panels.

[0006] The technical solution adopted by the present invention is: a light - homogenizing photovoltaic agricultural system, including a bracket and a solar photovoltaic panel assembly. The solar photovoltaic panel assembly is composed of a first solar photovoltaic panel, a second solar photovoltaic panel and a grooved light - splitting glass plate. The first solar photovoltaic panel, the second solar photovoltaic panel and the grooved light - splitting glass plate are installed in parallel from top to bottom on the bracket in sequence.

[0007] Further, the area ratio of the first solar photovoltaic panel, the second solar photovoltaic panel, and the grooved beam-splitting glass plate is 1:1:X, where X = 0.5 to 1.5, and preferably X = 1.

[0008] Further, a gap with a certain width is respectively formed between the second solar photovoltaic panel and the first solar photovoltaic panel and the grooved beam-splitting glass plate, and the widths of the two gaps are equal.

[0009] Further, the grooved beam-splitting glass plate is made of a glass material with high transmittance. The upper surface of the grooved beam-splitting glass plate is a plane, and a grooved array is formed on the lower surface.

[0010] Further, the cross-section of the groove is composed of a plane and a segmented free-form surface.

[0011] Further, the planar width of the groove is a, and it is perpendicular to the upper surface of the grooved beam-splitting glass plate, and the interval between two adjacent grooves is 0.

[0012] Further, the grooved array is formed by dividing and translating a specific free-form surface, and the specific free-form surface is an initial surface shape of the lower surface of the grooved beam-splitting glass plate that meets the requirement of uniform beam splitting.

[0013] Further, the mathematical model of the grooved array is:

[0014]

[0015] Where, is the unit vector of the incident light on this specific free-form surface, is the unit vector of the outgoing light on this specific free-form surface, is the normal vector at the light incident point on this specific free-form surface, k i is the vector is the slope magnitude; M i is the intersection point of the sunlight and the specific free-form surface, M i The coordinates of are M i (Mx i , My i ), and Mx i = i (i = 0, 1, 2...), My 0 = 0; N i is the intersection point of the light and the farmland, N i The coordinates of are N i (Nx i , Ny i ), and M i ′ is the intersection point of the light and the grooved array, M i ′ The coordinates of are M′ i(Mx i , My′ i ); θ is the inclination angle of the grooved beam-splitting glass plate relative to the farmland, h is the height of the grooved beam-splitting glass plate relative to the farmland, n 0 is the refractive index of air, n 1 is the refractive index of the glass medium; "[]" is the integer symbol.

[0016] The principle of this grooved beam-splitting glass plate for uniformly irradiating sunlight on the farmland is briefly described as follows: Sunlight can be regarded as uniformly distributed parallel light. Since the light is vertically incident on the upper surface of the grooved beam-splitting glass plate, the propagation path of the light does not change after passing through the upper surface of the grooved beam-splitting glass plate. When the light propagates to the lower surface of the grooved beam-splitting glass plate, according to Snell's law: n 1 *sinθ 1 = n 2 *sinθ 2 (n 1 is the refractive index of the beam-splitting glass plate, θ 1 is the incident angle of the light at the interface, n 2 is the refractive index of air, θ 2 is the exit angle of the light at the interface), the propagation path of the light will change, and the light can be refracted to the projection area below the solar photovoltaic panel assembly. After determining the angle between the incident light and the lower surface of the grooved beam-splitting glass plate, the angle between the exit light and the lower surface of the grooved beam-splitting glass plate can be accurately calculated. When the inclination angle of the solar photovoltaic panel assembly relative to the farmland, the size of the projection area of the solar photovoltaic panel assembly on the farmland, and the height of the solar photovoltaic panel assembly relative to the farmland are known, the intersection position of the exit light and the farmland can be accurately obtained. Therefore, by designing the surface type parameters at each place on the lower surface of the grooved beam-splitting glass plate, the intersection position of the light and the farmland can be changed, so that sunlight is uniformly distributed on the farmland.

[0017] Most of the land areas in our country are located north of the Tropic of Cancer. The maximum value of the solar altitude angle throughout the year in each region decreases as the latitude increases. Moreover, the solar altitude angle changes throughout the year, being low in winter and high in summer. In order to ensure that the annual power generation of solar photovoltaics is basically not affected by the change of the solar altitude angle, this light-homogenizing photovoltaic agricultural system can meet the following conditions: During the winter solstice, for the northern hemisphere, the solar altitude angle is the lowest. At this time, the shadow area generated by the previous light-homogenizing photovoltaic agricultural system under illumination completely covers the groove-splitting glass plate and does not cover the first solar photovoltaic panel and the second solar photovoltaic panel. By setting the specific inclination angle of the solar photovoltaic panel assembly and the spacing of each group of light-homogenizing photovoltaic agricultural systems, the above conditions can be achieved. Taking the Xiongan area in Hebei as an example, the optimal inclination angle of the local photovoltaic panel relative to the horizontal plane is 32°. The size of the solar photovoltaic panel is 1622mm * 1068mm * 35mm. When ensuring that the power generation of the photovoltaic panel is not affected throughout the year, the minimum distance between the front and back of this light-homogenizing photovoltaic agricultural system is about 1.18m, and the installed capacity per mu is 106 sets. The annual power generation that can be achieved per mu is about 81,000 kWh (under the lighting conditions in the Xiongan area of Hebei Province); while the maximum installed capacity per mu of the original split-type light-homogenizing photovoltaic agricultural system is 69 sets, and the annual power generation that can be achieved per mu is about 53,000 kWh. In comparison, the annual power generation per mu of the new light-homogenizing photovoltaic agricultural system is 28,000 kWh higher than that of the original split-type light-homogenizing photovoltaic agricultural system per mu.

[0018] This light-homogenizing photovoltaic agricultural system can ensure that the annual yield of the crops under the solar photovoltaic panels will not be greatly affected. Due to the fixed inclination angle value of the solar photovoltaic panel assembly, the light spot under the solar photovoltaic panel assembly will move with the change of the solar altitude angle. When the sunlight is perpendicularly incident on the solar photovoltaic panel assembly, there is no shadow area on the farmland. When the sunlight is obliquely incident on the solar photovoltaic panel assembly, the entire light spot on the farmland will also move southward or northward accordingly, so that the photosynthesis of the crops will basically not be affected too much. In winter, due to the cold weather, most crops are in a dormant or non-cultivation period, so that the farmland not receiving sunlight will not have a great impact on the annual yield of the crops. Therefore, this light-homogenizing photovoltaic agricultural system ensures the annual yield of the crops.

[0019] The solar photovoltaic panel assembly has a certain inclination angle. When it rains, the rainwater can slide down along the upper surface of the solar photovoltaic panel assembly. Since there is a certain width of gap between the second solar photovoltaic panel and the groove-splitting glass plate as well as the first solar photovoltaic panel, the rainwater can fall from the two gaps, thus realizing the irrigation of the crops under the solar photovoltaic panel assembly.

[0020] There is a certain gap between the second solar photovoltaic panel, the grooved light-splitting glass plate, and the first solar photovoltaic panel, which is beneficial to reducing the wind pressure in this light-homogenizing photovoltaic agricultural system, thereby reducing the cost expenditure of the brackets in this system.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: By using the grooved light-splitting glass plate to split sunlight, the sunlight transmitted from the front can be evenly distributed under the solar photovoltaic panel assembly, facilitating the photosynthesis of crops and ensuring the annual output of crops; The solar photovoltaic panels can receive sunlight throughout the year and will not be blocked by the shadow areas generated by the front solar photovoltaic panels, improving the annual power generation of a single solar photovoltaic panel; At the same time, this light-homogenizing photovoltaic agricultural system can increase the number of solar photovoltaic panels per unit area compared with the original photovoltaic agricultural system, thereby increasing the power generation per mu of land; The two gaps between the second solar photovoltaic panel, the grooved light-splitting glass plate, and the first solar photovoltaic panel enable the irrigation of crops under the solar photovoltaic panel assembly on rainy days; This gap is also beneficial to reducing the wind pressure in this light-homogenizing photovoltaic agricultural system, thereby reducing the cost of the brackets in this system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of the light-homogenizing photovoltaic agricultural system;

[0023] Figure 2 It is a cross-sectional view of the grooved light-splitting glass plate;

[0024] Figure 3 It is a schematic diagram of the light-splitting principle of the grooved light-splitting glass plate;

[0025] Figure 4 It is a schematic diagram of the situation when sunlight is vertically incident on the solar photovoltaic panel assembly;

[0026] Figure 5 It is a schematic diagram of the illumination situation of the light-homogenizing photovoltaic agricultural system at the winter solstice;

[0027] Figure 6 It is a schematic diagram of the precipitation of the light-homogenizing photovoltaic agricultural system on rainy days;

[0028] Figure 7 It is another schematic diagram of the structure of the light-homogenizing photovoltaic agricultural system.

[0029] In the figure: 1 - bracket; 2 - solar photovoltaic panel assembly; 21 - first solar photovoltaic panel; 22 - second solar photovoltaic panel; 23 - grooved light-splitting glass plate; 3 - gap; 4 - high-transmittance glass; 40 - upper surface of the grooved light-splitting glass plate; 41 - groove; 410 - plane; 411 - segmented free-form surface; 5 - sunlight; 6 - agricultural land; 7 - rainwater. DETAILED DESCRIPTION OF THE INVENTION

[0030] The preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0031] Embodiment 1

[0032] As Figure 1 shown, a light-homogenizing photovoltaic agricultural system includes a bracket 1 and a solar photovoltaic panel assembly 2 on the bracket 1. The solar photovoltaic panel assembly 2 includes a first solar photovoltaic panel 21, a second solar photovoltaic panel 22, and a grooved light-splitting glass plate 23. The grooved light-splitting glass plate 23 realizes the light-splitting effect on sunlight. The grooved light-splitting glass plate 23 is on the lower side of the second solar photovoltaic panel 22. The widths of the first solar photovoltaic panel 21, the second solar photovoltaic panel 22, and the grooved light-splitting glass plate 23 are all 1.07 m. There is a 5-mm-wide gap between the second solar photovoltaic panel 22 and the first solar photovoltaic panel 21 and the grooved light-splitting glass plate 23.

[0033] As Figure 2 shown, the grooved light-splitting glass plate 23 is made of a glass 4 with a high transmittance. The upper surface 40 of the grooved light-splitting glass plate is a plane, and the lower surface is a grooved array. The groove 41 is composed of a plane 410 and a segmented free-form surface 411.

[0034] The mathematical model of the grooved array is:

[0035]

[0036] Among them, is the unit vector of the incident light on this specific free-form surface, is the unit vector of the outgoing light on this specific free-form surface, is the normal vector at the light incident point on this specific free-form surface, k i is the vector The slope magnitude of; M i is the intersection point of sunlight and the specific free-form surface, M i The coordinates of are M i (Mx i , My i ), and Mx i = i (i = 0, 1, 2...), My 0 = 0; N i is the intersection point of the light and the farmland, N i The coordinates of are N i (Nx i , Ny i ), and M i ′ is the intersection point of the light and the grooved array, Mi The coordinates of M' are M' i (Mx i , My' i ); θ is the inclination angle of the grooved beam splitter glass plate relative to the farmland, h is the height of the grooved beam splitter glass plate relative to the farmland, and n 0 is the refractive index of air, and n 1 is the refractive index of the glass medium; "[]" is the integer symbol.

[0037] As Figure 3 shown, the principle that the grooved beam splitter glass plate 23 can evenly irradiate the direct sunlight 5 on the farmland 6 is as follows: The sunlight 5 can be regarded as uniformly distributed parallel light. Since the light is vertically incident on the upper surface 40 of the grooved beam splitter glass plate, the propagation path of the light does not change when the light passes through the upper surface 40 of the grooved beam splitter glass plate. When the light propagates to the groove 41 of the grooved beam splitter glass plate, according to Snell's law: n 1 *sinθ 1 = n 2 *sinθ 2 (n 1 is the refractive index of the beam splitter glass plate, θ 1 is the incident angle of the light on the interface, n 2 is the refractive index of air, and θ 2 is the exit angle of the light on the interface), the propagation path of the light will change, so as to irradiate the projection area below the solar photovoltaic panel assembly 2. When the angle between the incident light and the groove 41 of the grooved beam splitter glass plate 23 is determined, the angle between the exit light and the groove 41 of the grooved beam splitter glass plate 23 can be accurately calculated. When the inclination angle of the solar photovoltaic panel assembly 2 relative to the farmland 6, the size of the projection area of the solar photovoltaic panel assembly 2 on the farmland 6, and the height of the solar photovoltaic panel assembly 2 relative to the farmland 6 are known, the intersection position of the exit light and the farmland 6 can be accurately obtained. Therefore, by designing the surface shape parameters of each groove 41 of the grooved beam splitter glass plate 23, the intersection position of the light and the farmland 6 can be changed, so that the sunlight 5 is evenly distributed on the farmland 6.

[0038] As Figure 4 shown, when the sunlight 5 is vertically incident on the solar photovoltaic panel assembly 2, a part of the sunlight 5 is absorbed by the first solar photovoltaic panel 21 and the second solar photovoltaic panel 22 and converted into electric energy, and the other part of the sunlight 5 is incident on the grooved beam splitter glass plate 23 and is evenly distributed on the farmland 6. According to the zemax simulation illumination map, there is no shadow area on the farmland 6 at this time, and the photosynthesis of crops is guaranteed.

[0039] As Figure 5As shown in the figure, during the Winter Solstice solar term, for the northern hemisphere, the altitude angle of the sun is the lowest throughout the year. At this time, the shadow generated by the front light-uniforming photovoltaic agricultural system only completely covers the grooved light-splitting glass plate 23 on the rear solar photovoltaic panel assembly 2, and will not cover the first solar photovoltaic panel 21 and the second solar photovoltaic panel 22, enabling the first solar photovoltaic panel 21 and the second solar photovoltaic panel 22 to receive sunlight normally throughout the year for power generation. Taking the Xiongan area in Hebei Province as an example, in winter, most of the crops are in a dormant or non-cultivation period, and when there is no sunlight 5 on the farmland 6 at this time, it will not have a great impact on the annual crop yield.

[0040] As Figure 6 shown in the figure, during rainy days, the rainwater 7 will slide down along the solar photovoltaic panel assembly 2. Since there is a 5-mm-wide gap 3 between the second solar photovoltaic panel 22 and the grooved light-splitting glass plate 23 and the first solar photovoltaic panel 21 in the solar photovoltaic panel assembly 2, the rainwater will fall from the gap 3, so that the crops under the solar photovoltaic panel assembly 2 can be irrigated; the existence of this gap can also reduce the wind pressure in this light-uniforming photovoltaic agricultural system, thereby reducing the cost expenditure of the support 1 in this system.

[0041] Embodiment 2

[0042] As Figure 7 shown in the figure, the difference between Embodiment 2 and Embodiment 1 is that: the grooved light-splitting glass plate 23 is also installed on the upper side edge of the solar photovoltaic panel 21, and its lower surface profile is also composed of a grooved array. The advantage of this installation method is that it can achieve uniform illumination of the sunlight 5 on the farmland 6 when the installation height of the solar photovoltaic panel assembly 2 is relatively low.

[0043] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A light - homogenizing photovoltaic agricultural system, characterized in that: it includes a bracket (1) and a solar photovoltaic panel assembly (2). The solar photovoltaic panel assembly (2) is composed of a first solar photovoltaic panel (21), a second solar photovoltaic panel (22) and a grooved light - splitting glass plate (23). The first solar photovoltaic panel (21), the second solar photovoltaic panel (22) and the grooved light - splitting glass plate (23) are installed side - by - side on the bracket from top to bottom in sequence; the grooved light - splitting glass plate (23) is made of glass (4) with a high transmittance. The upper surface (40) of the grooved light - splitting glass plate is a plane, and a grooved array is opened on the lower surface; the cross - section of the groove (41) is composed of a plane (410) and a segmented free - form surface (411); the width of the plane (410) of the groove (41) is a. The plane (410) is perpendicular to the upper surface (40) of the grooved light - splitting glass plate, and the interval between two adjacent grooves (41) is 0; the grooved array is formed by the translation of a specific free - form surface divided. The specific free - form surface is an initial surface shape of the lower surface of the grooved light - splitting glass plate that meets the requirements of uniform light splitting; the mathematical model of the grooved array is: Wherein, is the unit vector of the incident light ray on this specific free surface, is the unit vector of the outgoing light ray on this specific free surface, is the normal vector at the light incident point on this specific free surface, is the vector the magnitude of the slope; is the intersection point of the sunlight (5) and the specific free surface, The coordinates of are and = ( = 0, 1, 2...), = 0; is the intersection point of the sunlight (5) and the farmland (6), The coordinates of are and = ( = 0, 1, 2...); is the intersection point of the sunlight (5) and the groove array, The coordinates of are is the inclination angle of the groove beam splitting glass plate (23) relative to the farmland (6), is the height of the groove beam splitting glass plate (23) relative to the farmland (6), is the refractive index of air, is the refractive index of the glass (4) medium; "[]" is the integer symbol.

2. The light - homogenizing photovoltaic agricultural system according to claim 1, characterized in that: the area ratio of the first solar photovoltaic panel (21), the second solar photovoltaic panel (22) and the grooved light - splitting glass plate (23) is 1:1:X, where X = 0.5 - 1.

5.

3. The light - homogenizing photovoltaic agricultural system according to claim 1, characterized in that: a gap (3) with a certain width is respectively formed between the second solar photovoltaic panel (22) and the first solar photovoltaic panel (21) and the grooved light - splitting glass plate (23), and the widths of the two gaps (3) are equal.

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