Divergent optical lens for passive illumination of crops under photovoltaic covers

Abstract

The invention relates to a divergent optical lens for passive illumination of crops under photovoltaic covers, to be installed in empty spaces in the form of rows that can be arranged between successive contiguous photovoltaic panels that form the upper enclosure of an area, in order to illuminate a great volume over the plants disposed below the panels. The lens is an optical lens made of materials with a refractive index greater than unity, to be installed to form part of the cover of a structure together with the photovoltaic panels and in the same planes as the panels, in a longitudinal configuration with a constant cross-section determined by the maximum thickness and total width thereof and a geometry on the upper side and lower side thereof, according to concave circumferential arcs, such that the juncture of the centres of the radii of curvature thereof coincides with the axis of symmetry of the cross-section.

Description

[0001] DESCRIPTION

[0002] Diverging optics lens for passive lighting of crops under photovoltaic covers.

[0003] OBJECT OF THE INVENTION

[0004] The following invention, as expressed in the statement of this specification, refers to the use of divergent lenses arranged in the gaps between photovoltaic panels through which light enters naturally, in order to expand the illuminated area under the aforementioned panels, facilitating the photosynthesis of the plants located there.

[0005] The scope of the present invention is within the devices aimed at facilitating the combined use of land both to produce photovoltaic energy, thanks to the installation of solar panels, and to carry out agricultural and livestock activities.

[0006] BACKGROUND OF THE INVENTION

[0007] As an introduction, agrovoltaics represent an innovative way to minimize these effects associated with the primary sector, as it increases crop efficiency and reduces their environmental impact, among other benefits.

[0008] This model of sustainable agricultural activity, closely related to "smart farming," is based on the installation of photovoltaic panels on land used for agriculture or livestock. This provides these spaces with a dual function: agricultural or livestock production and the generation of electricity from solar energy, a cost-effective and sustainable source.

[0009] In agrivoltaic installations, panels are installed on structures or cables several meters above the ground, allowing for crop growth and access for labor and agricultural machinery. This agrivoltaic system optimizes land use, allocating it simultaneously to agricultural or livestock production and electricity generation. Furthermore, solar panels protect the crops planted beneath them by reducing evaporation, conserving moisture, and reducing the farm's water footprint by protecting them from high temperatures in very hot areas or areas with high solar irradiation.

[0010] Continuing with agrovoltaics, it uses structures that provide more suitable environmental conditions for the crops growing beneath them. Undoubtedly, this structure provides shade for the crops, so there are usually gaps through which sunlight enters, which is necessary for the plants' photosynthesis. The open surface with gaps through which sunlight enters is usually between 30 and 40% of the total surface area of ​​the crop. Obviously, these gaps are distributed regularly to achieve the most homogeneous lighting parameters possible.

[0011] Even if adequate lighting parameters are not achieved, artificial light installed under the structure is also used to assist the crops in photosynthesis with luminaires that emit light rays with wavelengths adapted to the plant's growth phase.

[0012] Considering the inventions present in the state of the art that address the described problem, identified by publication number and title, respectively, the following documents are identified:

[0013] 1. ES2625058T3, “Horticulture lighting interface for interconnecting at least one lighting system”.

[0014] 2. ES2848306T3, “Capture, transmission, spectral modification and supply of sunlight to shaded areas of plants” which, although having a related purpose, is a technical solution that is completely different.

[0015] 3. ES2301132T3 “Covering element for greenhouses or similar”, which also addresses a better use of solar rays, although making use of an optical medium of another nature and with another purpose by proposing the optimization of the resulting atmosphere below the photovoltaic panels from the thermal point of view.

[0016] Continuing with the introduction to the state of the art, now with regard to solutions based on optical technology, the concept of thin lenses refers to those lenses in which the ratio between the thickness of the center of the lens and the radii of curvature used is close to zero.

[0017] Thus, the use of a thin lens configured according to a double concave surface causes incident light to open with an exit angle such that the refracted light is projected onto places that would be shaded without the use of the lens.

[0018] More specifically, to study what happens, Snell's law is the equation that relates the angles of incidence and refraction of the light ray, depending on the refractive indices of the two media it passes through.

[0019] In the case of a thin lens configured according to a double concave surface, the angle of exit of the lens will depend on the geometric parameters of the lens itself and its refractive index, which in the case of glass and polymethacrylates is usually around 1.5 compared to the medium in air or vacuum which is assigned a value of 1. Then, depending on the distance to the aforementioned lenses and the width of the surface to be illuminated, the angles of exit of the light that determine its constructive characteristics must be calculated.

[0020] Therefore, in conclusion, the "Diverging optics lens for passive lighting of crops under photovoltaic covers", to be installed in the free spaces in the form of rows available between successive adjacent photovoltaic panels that make up the upper envelope of an enclosure, consisting of a biconcave lens according to opposite curvatures, which provides the following advantages with respect to the state of the art:

[0021] ■ The light that naturally enters through the gaps between photovoltaic panels is distributed evenly over a given surface or volume as it passes through the optical medium. In fact, crops planted beneath the photovoltaic panels are able to photosynthesize as if they had no structure above them, eliminating yield losses due to defective photosynthesis. The light that passes through the gaps in the agrovoltaic structure responds to lighting or photosynthetic criteria, prioritizing a larger surface area or volume beneath the structure where photosynthesis can occur.

[0022] EXPLANATION OF THE INVENTION

[0023] By way of explanation of the invention, the “Diverging optics lens for passive lighting of crops under photovoltaic covers” to be installed in the free spaces in the form of rows available between successive adjacent photovoltaic panels that make up the upper envelope of an enclosure, in order to illuminate more volume on the existing plants below them, consisting of an optical lens made of materials with a refractive index greater than one, for its placement forming part of the cover of a structure in combination with the aforementioned photovoltaic panels and in their same planes, characterized by its longitudinal configuration and constant cross section determined by its maximum thickness, total width and a geometry on its upper side and lower side, according to concave circumference arcs, such that the union of the centers of its radii of curvature coincides with the axis of symmetry of the section itself.

[0024] Thus, when light arriving from infinity passes through an optical medium characterized by its double concave surface, an opening of the refracted angle with respect to the angle of incidence occurs, which causes the light rays to reach volumes under the photovoltaic panels that they would not access if such spaces did not house the aforementioned refraction medium.

[0025] DESCRIPTION OF THE DRAWINGS

[0026] To complement the description being made and in order to help better understand the characteristics of the invention, in accordance with a preferred example of practical implementation thereof, a set of drawings is attached as an integral part of said description, in which the following has been represented for illustrative and non-limiting purposes:

[0027] Figure 1.- Cross-sectional view of a “Diverging optics lens for passive lighting of crops under photovoltaic covers” to show its geometry.

[0028] Figure 2.- Main elevation view of the portico structure used to install an upper envelope based on photovoltaic panels in an east-west configuration between which are interspersed gaps in rows covered by paneling of “Diverging optic lens for passive lighting of crops under photovoltaic covers”.

[0029] Figure 3.- Main elevation view of photovoltaic panels in east-west configuration with “Diverging optics lens for passive lighting of crops under photovoltaic covers” on June 21 at 12:00.

[0030] Figure 4.- Main elevation view of photovoltaic panels in east-west configuration on June 21 at 12:00 without any optical means.

[0031] Figure 5.- Main elevation view of photovoltaic panels in east-west configuration with “Diverging optics lens for passive lighting of crops under photovoltaic covers” on March 21 or September 21 at 12:00.

[0032] Figure 6.- Main elevation view of photovoltaic panels in east-west configuration on March 21 or September 21 at 12:00, without any additional optical means.

[0033] Figure 7.- Main elevation view of photovoltaic panels in east-west configuration with “Diverging optics lens for passive lighting of crops under photovoltaic covers” on December 21 at 12:00.

[0034] Figure 8.- Main elevation view of photovoltaic panels in east-west configuration on December 21 at 12:00 without any additional optical means.

[0035] In the aforementioned figures the following constituent elements can be highlighted:

[0036] 1 . Radius of curvature of the upper concave surface R1 .

[0037] 2. Radius of curvature of the lower concave surface R2.

[0038] 3. Lens thickness e.

[0039] 4. Lens width s. PREFERRED EMBODIMENT EXAMPLE

[0040] As an example of a preferred embodiment, use can be made of the “Diverging optics lens for passive lighting of crops under photovoltaic covers” as shown in Figures 1-8, for use in an agricultural plot on which a structure is arranged that provides support for photovoltaic panels arranged in a gabled manner between successive pillars in alternating east-west orientations.

[0041] In the aforementioned Figure 1, the minimum exit angle 0s can be seen, to completely illuminate a surface located at a certain distance from the lenses object of the invention, when the sun is in an orthogonal position to them.

[0042] Since these are thin lenses with symmetrical concave surfaces, a point in space can be found where the focal image of an object located at infinity, in our case light, would be projected.

[0043] Where n' is the refractive index of the lens material and n is that of air.

[0044] With = , for constructive simplicity.

[0045] With this focal length and the half-width of the lens, the exit angle can be calculated as:

[0046] Substituting in the focal length formula we have: The thickness (3) of the lens is therefore:

[0047] Being p a constructive detail, such as the minimum distance between the two concave curves right in the center of the lens.

[0048] Continuing with the description, Figures 3-8 show the agrovoltaic structure arranged in alternating east-west slopes according to the portico in Figure 2 with and without diverging lenses in its gaps for the corresponding days of solstice and equinox at solar noon.

[0049] Specifically, in the embodiment example, use has been made of a lens that is 60 mm thick (3), 900 mm radius of curvature of both the upper (1) and lower (2) concave surfaces, as well as a total width (4) of 457 mm for the holes in rectangular rows that constitute 30% of the total agrovoltaic surface, achieving an exit angle of approximately 14°.

[0050] Thus, to facilitate the understanding of the invention, Figures 3-8 show what would happen under the same upper envelope of photovoltaic panels for a given area with nothing and with “Divergent optics lens for passive lighting of crops under photovoltaic covers” occupying each row of available spaces at 12 am, solar time, for the key days: solstices and equinoxes according to the dates indicated.

[0051] In Figures 3-8, which use the lens of the present invention, it is important to note that when the sun is at a greater angle to the cover, areas closer to the lens itself are fully illuminated, providing a defined configuration thereof. For clarification, if a line is drawn joining the peaks where the shadows intersect, the distance from the cover at which full illumination is achieved is defined. Evidently, as the sun is inclined with respect to the cover, this line rises, drawing closer to the cover.In conclusion, the use of the "Diverging optics lens for passive lighting of crops under photovoltaic covers" in the row-shaped gaps formed between lines of successive photovoltaic panels, significantly reduces the shading problem that the aforementioned photovoltaic panels generate at a certain distance below them, providing greater lighting for the crops in a sustainable manner and without the need for artificial lighting.

[0052] As an alternative implementation, obviously depending on the configuration of the enclosure and its orientation, applications can also be undertaken on roofs facing directly in a single direction according to degrees of inclination with a single slope depending on the latitude at which the roof is located.

Claims

CLAIMS 1.- Divergent optical lens for passive lighting of crops under photovoltaic covers, to be installed in the free spaces in the form of rows available between successive adjacent photovoltaic panels that make up the cover of an enclosure and in their same planes, consisting of an optical lens made of materials with a refractive index greater than one, characterized by its longitudinal configuration and constant cross section determined by its maximum thickness, total width and a geometry on its upper side and lower side, according to concave circumference arcs, such that the union of the centers of its radii of curvature coincides with the axis of symmetry of the section itself.

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