WO2014198838A1

WO2014198838A1 - System for optimizing the utilization of the available quantity of photosynthetically active radiation in the growing of plants

Info

Publication number: WO2014198838A1
Application number: PCT/EP2014/062260
Authority: WO
Inventors: Erik Frans Renilde DE MAEYER
Original assignee: De Maeyer Erik Frans Renilde
Priority date: 2013-06-12
Filing date: 2014-06-12
Publication date: 2014-12-18
Also published as: BE1021720B1; EP3007544A1

Abstract

The invention concerns a system (1) for optimizing the utilization of the available quantity of photosynthetically active radiation in the growing of one or more plants (2) on one or more growing surfaces (3a) in situations where there is an excess quantity of photosynthetically active radiation because the available quantity of photosynthetically active radiation is greater than the usable quantity of photosynthetically active radiation for the one or more plants (2), wherein the system (1) is configured to make the availablephotosynthetically active radiation of the directly incident sunlight (5) fall onto a growing area that is larger than the originally available growing area on which the directly incident sunlight would fall without the system (1), wherein this larger growing area consists of one or more separate growing surfaces (3a), and wherein the ratio between the larger growing area and the originally available growing area is equal to an area multiplier.

Description

SYSTEM FOR OPTIMIZING THE UTILIZATION OF THE AVAILABLE QUANTITY OF PHOTOSYNTHETICALLY ACTIVE RADIATION IN THE GROWING OF PLANTS

[01] The invention concerns a system for optimizing the utilization of the available quantity of photosynthetically active radiation in the growing of plants in situations where the available quantity of photosynthetically active radiation for the plants is greater than the usable quantity of photosynthetically active radiation for these plants.

[02] Not all incident sunlight reaching the earth's surface is usable by plants for photosynthesis. Only a portion of the visible light can be considered for this purpose. The intensity of this radiation is known as "Photosynthetically Active Radiation" or PAR for short. PAR is usually expressed in μη"ΐοΙ/(η"ΐ².8), where μηηοΙ gives the number of photons. In order to define PAR, the position of the reference surface needs to be specified.

[03] Of course, PAR varies with latitude, the time of the year, the time of day, and the weather conditions. One can work with theoretical models to determine PAR values, but often one will use experimentally plotted charts.

[04] Fig. 1 presents a graph showing how the quantity of available PAR (Y axis) (expressed in μη"ΐοΙ/(η"ΐ².8), for a horizontal surface) at the equator (0°) on March 21 , June 21 , September 21 and December 21 varies during the course of the day, expressed in hours of solar time (X axis), and this on a day with little or no cloud cover. The solar time is the time scale when the sun stands directly in the south (i.e. 180° azimuth) at 12 o'clock for the northern hemisphere and directly in the north (i.e. 0° azimuth) at 12 o'clock for the southern hemisphere.

[05] Fig. 2 presents a graph showing how photosynthesis, expressed in relative C0₂ assimilation (Y axis) for most agricultural and horticultural plants in monoculture evolves as a function of the quantity of available PAR (X axis) (expressed in μη"ΐοΙ/(η"ΐ².8)). From fig. 2 one can infer that:

at very low radiation intensities there is a production of C0₂ instead of assimilation; after this, the photosynthesis increases very quickly.

above a certain limit, often around 500 PAR, the photosynthesis hardly increases at all, not even under the most favorable conditions in terms of fertilizer, water, soil and leaf temperature, air humidity, etc. The plant must protect itself more and more against an excess of energy.

finally the radiation intensity becomes so high that photosynthesis declines and irreversible damage to the plant can occur. After a certain PAR value, usually around 1500 PAR, the relative C0₂ assimilation itself decreases.

[06] It should be pointed out that these PAR graphs in practice are determined by experiment. The yardstick for photosynthesis here is the relative C0₂ assimilation, since the absolute values are heavily dependent on a whole series of growth conditions, such as ambient temperature, fertilizer, soil moisture, air humidity, C0₂ concentration, etc. Furthermore, the relative values can vary within a particular plant species (several varieties).

[07] One can clearly deduce from figs. 1 and 2 that the solar energy available for photosynthesis quite often exceeds the quantity of energy which can be used by the plant. This phenomenon increases as one approaches the equator. This is not only inefficient, but can even lead to damage or destruction of certain plants. Thus, it is a misconception that plants should have as much sunlight as possible to produce an optimal yield.

[08] In order to prevent damage to crops when there is an excess of available PAR, at present one uses screening nets which filter out up to ¾ of the irradiated energy.

[09] The drawback here, however, is that a lot of energy is wasted by the use of these nets. Furthermore, due to the predominantly horizontal position of the nets, as the position of the sun declines a greater percentage of sunlight is filtered out.

[10] Another current problem is that there are an increasing number of places around the world that are dealing with a shortage of arable land. In fact, a large amount of the land that has already been cultivated is not really suited for farming, for example due to its exposure to erosion. To solve this problem at present, increasing use is being made of vertical farming or vertical gardening.

[11] The drawback these methods, however, is that they require a tremendous amount of energy, because the photosynthesis in these cases occurs for the most part with artificial light. The available sunlight here is not used optimally. [12] Consequently, there is a need for a system for the growing of crops according to the preamble of the first claim, wherein the excess available PAR coming from solar energy is utilized as optimally as possible, without requiring extra energy.

[13] This object of the invention is solved by providing a system according to the preamble of the first claim, wherein the system is configured to make the available photosynthetically active radiation of the directly incident sunlight (the incident sunlight becomes diffuse if there is cloud cover) fall onto a growing area that is larger than the originally available growing area on which the directly incident sunlight would fall without the system, wherein this larger growing area consists of one or more separate growing surfaces, and wherein the ratio between the larger growing area (in m²) and the originally available growing area (in m²) is equal to an area multiplier increased or decreased by 15%, during a daytime period that begins at the latest 2 hours before the time of maximum available photosynthetically active radiation without cloud cover on the originally available area and that ends at the earliest 2 hours after that time, and this during at least one period of at least 3 consecutive months per year.

[14] The system is preferably configured for locations with a latitude in an interval consisting of a minimum of 60° south latitude and 60° north latitude and more preferably for locations with a latitude in an interval consisting of a maximum of 60° south latitude and 60° north latitude.

[15] By a growing area is meant the surface expressed in m². By a growing surface, on the other hand, is meant the geometrical figure that is planted with a crop and on which the crop is cultivated.

[16] By making the available PAR fall on a growing area that is larger than the originally available growing area, the radiation intensity per unit of area of the growing surface decreases and the number of plants that can grow on a unit of area increases as compared to the originally available growing area. Near the equator and the tropics, moreover, production loss and quality degradation will be prevented for many plants, and the production will be boosted by at least the area multiplier. [17] Since the excess of PAR increases toward the equator, and the light falling there is constant almost all year round, this system is excellently suitable between the tropics, more specifically between 23.5° north and south latitude. When the system according to the invention is employed in these regions, it even becomes possible to grow plants there that otherwise could not have been cultivated on account of the excess sunlight. However, this system can also be employed in other countries, such as Spain, Italy, Turkey, Greece, etc., because here as well the excess energy is still great. The system fas claimed in the invention is likewise of interest for use in greenhouse cultivation, because the installations can be paid off more quickly on account of the higher yield and because the heating costs are relatively low (yield increases but the heated volume does not).

[18] In a first possible embodiment of a system according to the invention, the one or more growing surfaces are placed at a certain incline with respect to the originally available growing surface as a function of the sun's position in order to make the available photosynthetically active radiation of the directly incident sunlight fall on a growing area that is larger than the originally available growing area on which the directly incident sunlight would fall without the system, wherein this larger growing area consists of one or more separate growing surfaces, and wherein the ratio between the larger growing area and the originally available growing area is equal to the area multiplier increased or decreased by 15%, during a daytime period that begins at the latest 2 hours before the time of maximum available photosynthetically active radiation without cloud cover on the originally available area and that ends at the earliest 2 hours after that time, and this during at least one period of at least 3 consecutive months per year.

[19] The system is preferably configured for locations with a latitude in an interval consisting of a minimum of 60° south latitude and 60° north latitude and more preferably for locations with a latitude in an interval consisting of a maximum of 60° south latitude and 60° north latitude.

[20] More preferably, the one or more growing surfaces can be placed at a fixed incline that is determined as a function of the averaged sun position in the course of a day, a year, and/or a growing season of the one or more plants. [21] On the other hand, it is also possible to design the one or more growing surfaces to adapt their position as a function of the varying sun position during the course of a day, a year, and/or a growing season of the one or more plants.

[22] In the case of plants subject to geotropism, in order to counteract the geotropism one or more of the growing surfaces is designed so as to change at regular intervals the incline which they make relative to their horizontal position.

[23] In one possible embodiment of a system according to the invention, the system comprises one or more cones or pyramids with an upright section, wherein the growing surfaces are placed on one or more of the upright sections of this or these cone(s) or pyramid(s), and wherein this or these cone(s) or pyramid(s) can be rotated with respect to two mutually perpendicular axes in order to track the azimuth (angle in degrees with respect to geographic north) and elevation (angle in degrees with respect to the horizon).

[24] More preferably, in order to counteract geotropism, the one or more cones or pyramids can be rotated with respect to an axis extending in the longitudinal direction of the cone(s) or pyramid(s).

[25] In another possible embodiment of a system according to in the invention, the system comprises a virtually horizontally placed virtually flat disk on which one or more triangular prisms are placed, extending in the longitudinal direction, wherein one or more growing surfaces are arranged on one or both of the obliquely upright sides of the triangular prisms extending in the longitudinal direction, wherein the longitudinal direction of the growing surfaces tracks the azimuth and wherein this flat disk is able to rotate with respect to a vertical axis in order to track the azimuth.

[26] In yet another possible embodiment of a system according to the invention, the system comprises a virtually horizontally placed virtually flat disk on which one or more plate- shaped growing surfaces are placed at an adjustable incline, wherein the longitudinal direction of the plate-shaped growing surfaces is perpendicular to the azimuth, and the disk can rotate and the incline of the plate-shaped growing surfaces can be adapted as a function of the elevation. [27] Such a layout has the advantage that the multiplier is adjustable, which is important when the PAR varies as a function of the seasons, or during successive crops with a different PAR response. This layout also has a positive effect on plants that are subject to geotropism, inasmuch as the position of the one or more growing surfaces varies constantly. Furthermore, such a layout means that the space under the growing surfaces remains available for plants that require little PAR.

[28] In another possible embodiment of a system according to the invention, the system comprises one or more triangular prisms extending in the longitudinal direction and having an E-W orientation, wherein the growing surfaces are arranged on the obliquely upright sides of the triangular prisms extending in the longitudinal direction, and wherein the growing surfaces can turn about an E-W axis with respect to an angle of rotation that is calculated by means of the following formula:

S = arctan[tan(elevation in degrees) / cos (180° - azimuth in degrees)], wherein whenever the result of this formula is positive, the angle of rotation is to be measured in degrees relative to south and whenever the result of this formula is negative the angle of rotation is to be measured in degrees relative to north, and wherein the angle of rotation is adjusted with respect to the median line through the top and the base of the respective triangular prism extending in the longitudinal direction and with respect to the horizontal.

[29] Preferably, the triangular prisms extending in the longitudinal direction have a base with an adjustable size that can be changed by a varying angle of rotation.

[30] In another possible embodiment of a system according to the invention, the system comprises one or more plate-shaped growing surfaces which have a fixed length orientation, about which the plate-shaped growing surfaces can rotate with respect to the angle of rotation, to be adjusted in a plane perpendicular to the longitudinal direction of the plate- shaped growing surfaces, between the horizontal position and a connecting line between the top side of a first plate-shaped growing surface and a neighboring plate-shaped growing surface, taking into account the thickness of the plate-shaped growing surface and the height of the plant growing thereupon, and wherein the angle of rotation for each arbitrary orientation is calculated by means of the following formula:

S= arctan{tan(EL)/cos [180°-(90°-(horizontal orientation of the growing surfaces (3a)) - AZ]} where the horizontal orientation of the longitudinal direction of the growing surfaces (3a) is between 0° and 180°, 180° not included, and wherein

the N-S orientation coincides with 0°;

the NE-SW orientation coincides with 45°;

the E-W orientation coincides with 90°; and

the SE-NW orientation coincides with 135°; and wherein

whenever the angle of rotation is positive, this angle of rotation is measured in a plane perpendicular to the longitudinal direction of the growing surfaces, from the horizontal orientation in degrees (as defined above), plus 90° (i.e. clockwise), and whenever the angle of rotation is negative, this angle of rotation is measured in a plane perpendicular to the longitudinal direction of the growing surfaces, from the horizontal orientation in degrees (as defined above), minus 90° (i.e. counterclockwise).

[31] It should be noted that it is primarily the E-W orientation that is important in practice when using triangular prisms extending in the longitudinal direction.

[32] In many situations, especially in an E-W orientation, this angle of rotation varies very little throughout the day, which substantially simplifies the regulating of the system according to the invention in order to track the sun's position, especially if one disregards very low PAR values (in the morning and evening) and does not adapt the angle of rotation at these times.

[33] The advantage of such a system is that the area multiplier in this layout can be changed more easily and the space beneath the growing surfaces remains available for plants requiring little PAR. This layout also has a positive effect on plants that are subject to geotropism, inasmuch as the position of the one or more growing surfaces varies in a constant manner.

[34] In one possible embodiment of a system according to the invention, the plate-shaped growing surfaces are composed of strips that are situated at a certain distance from one another.

[35] In another possible embodiment of a system according to the invention, the obliquely upright side surfaces of the triangular prisms extending in the longitudinal direction are strips extending in the longitudinal direction that are situated at a certain distance from one another.

[36] To counteract geotropism, these strips are preferably placed rotatably around an axis that extends in the longitudinal direction of the plate-shaped growing surfaces or the triangular prisms extending in the longitudinal direction, wherein the strips are turned at regular intervals of time with respect to a line perpendicular to the plate-shaped growing surfaces or the obliquely upright side surfaces.

[37] In another possible embodiment of a system according to the invention, the system comprises one or more mirrors that are placed rotatably with respect to a central axis, which can move back and forth in a direction perpendicular to the longitudinal direction of the growing surfaces, and which comprise two or more mirror sections that are slidable back and forth over each other in order to change the dimensions of the one or more mirrors, so as to make the available photosynthetically active radiation of the directly incident sunlight fall on a growing area that is larger than the originally available growing area on which the directly incident sunlight would fall without the system, wherein this larger growing area consists of one or more separate growing surfaces, and wherein the ratio between the larger growing area and the originally available growing area is equal to the area multiplier, which can be increased or decreased by 15%, during a daily period that begins at the latest 2 hours before the time of maximum available photosynthetically active radiation without cloud cover on the originally available area and that ends at the earliest 2 hours after that time, and this during at least one period of at least 3 consecutive months per year. [38] The system is preferably configured for locations with a latitude in an interval consisting of a minimum of 60° south latitude and 60° north latitude and more preferably for locations with a latitude in an interval consisting of a maximum of 60° south latitude and 60° north latitude.

[39] The use of movably positioned mirrors has the advantage that their position can be easily changed.

[40] More preferably, the one or more mirrors are movably set up in such a way that the changing position of the sun throughout the course of a day, the year, and/or the growing season can be tracked.

[41] In one advantageous embodiment of a system according to the invention, the system comprises one or more artificial light sources, which are provided for extra lighting of the plants during cloudy days and/or for increasing the number of hours of daylight.

[42] In another advantageous embodiment of a system according to the invention, the system comprises one or more artificial light sources that are configured to distribute light at specific wavelengths, wherein these specific wavelengths are such that they counteract geotropism in plants that are susceptible to it.

[43] The invention shall now be described further by means of the drawings, in which:

• Fig. 1 presents a graph in which the quantity of available PAR (Y axis) with respect to a horizontal growing surface on March 21 , June 21 , September 21 and December 21 is plotted with respect to various hours in solar time (X axis) at the equator during a day with little or no cloud cover;

• Fig. 2 presents a graph of the course of the relative C0₂ assimilation (Y axis) for most agricultural and horticultural plants in monoculture as a function of the quantity of available PAR (X axis);

• Fig. 3a shows a schematic 3D representation of a planted portion of a horizontally positioned ground surface on which sunlight is falling perpendicularly, the area multiplier being equal to 2;

• Fig. 3b shows a schematic 2D representation of a planted growing surface of a system according to the invention that is placed at an inclination with respect to the horizontally placed ground surface as shown in fig. 3a, and on which sunlight is falling perpendicularly, the area multiplier being equal to 2;

Fig. 4a shows a schematic 3D representation of a planted portion of a horizontally positioned ground surface on which sunlight is falling at a slant;

Fig. 4b shows a schematic 2D representation of a planted growing surface of a system according to the invention that is placed at an inclination with respect to the horizontally placed ground surface as shown in fig. 4a, and on which sunlight is falling at a slant, the area multiplier M being equal to 2;

Fig. 5a shows a schematic 3D representation of a planted portion of a slanted natural ground surface on which sunlight is falling perpendicularly;

Fig. 5b shows a schematic 2D representation of a planted growing surface of a system according to the invention that is placed at an inclination with respect to the obliquely placed natural ground surface as shown in fig. 5a, and on which sunlight is falling at a slant, the area multiplier M being equal to 2;

Fig. 6a shows a schematic 3D representation of a planted portion of a slanted natural ground surface on which sunlight is falling at a slant;

Fig. 6b shows a schematic 2D representation of a planted growing surface of a system according to the invention that is placed at an inclination with respect to the obliquely placed natural ground surface as shown in fig. 6a, and on which sunlight is falling at a slant, the area multiplier M being equal to 2;

Fig. 7a shows a schematic 3D representation of a planted portion of a vertically positioned natural ground surface on which sunlight is falling at a slant;

Fig. 7b shows a schematic 2D representation of a planted growing surface of a system according to the invention that is placed at an inclination with respect to the vertical natural ground surface as shown in fig. 7a, and on which sunlight is falling at a slant, the area multiplier M being equal to 2;

Fig. 8a presents an experimentally plotted PAR graph at 30° south latitude on a day with little or no cloud cover, wherein the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a horizontal surface is plotted as a function of the time (expressed in solar time) on March 21 , June 21 , September 21 and December 21 ; Fig. 8b shows a PAR response curve for a Petunia cultivar (Petunia integrifolia) with a growing season from March 21 to September 21 at 30° south latitude, under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)); Fig. 9a shows a perspective front view of a schematic representation of a system according to the invention comprising a truncated cone able to turn about 2 axes, being planted on the upright portion thereof with a cultivar of Petunia (Petunia integrifolia), and set up on September 21 , around 10 o'clock at 30° south latitude at an elevation of 50° and an azimuth of 44°;

Fig. 9b shows a perspective front view of a solid cone that can be used in the system as shown in fig. 9a;

Fig. 10a presents an experimentally plotted PAR graph, wherein the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a horizontal surface is plotted as a function of the time (expressed in solar time) on April 10, June 21 and September 30 at 40° north latitude;

Fig. 10b shows a PAR response curve for a cultivar of strawberry (Fragaria x ananassa) with a growing season from April 10 to September 30 at 40° north latitude, under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8));

Fig. 1 1 a presents an experimentally plotted PAR graph, wherein the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a horizontal surface is plotted as a function of the time (expressed in solar time) on March 21 , June 21 , September 21 and December 21 at the equator;

Fig. 1 1 b shows a PAR response curve for a cultivar of zucchini (Cucurbita pepo) with a growing season from April 10 to September 30 at the equator, under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη-ιοΙ/(η-ι².8));

Fig. 12a shows a top view of a schematic representation of a system according to the invention comprising a virtually horizontally placed virtually horizontal disk on which various triangular prisms are placed, extending in the longitudinal direction, being planted on their upright side surfaces with a cultivar of strawberry (Fragaria x ananassa), wherein these growing surfaces are set up on June 21 at around 10 o'clock at 40° north latitude at an azimuth of 1 14°;

Fig. 12b shows a front view of the schematic representation of the system shown in fig. 12a;

Fig. 13a shows a front view of a schematic representation of a system according to the invention comprising two triangular prisms extending in the longitudinal direction, being planted on their upright side surfaces with a cultivar of strawberry (Fragaria x ananassa);

Fig. 13b shows a front view of a schematic representation of a system according to the invention comprising two triangular prisms extending in the longitudinal direction, being planted on their upright side surfaces with a cultivar of zucchini (Cucurbita pepo);

Fig. 14a presents an experimentally plotted PAR graph, wherein the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a horizontal surface is plotted as a function of the time (expressed in solar time) on March 21 , June 21 , September 21 and December 21 at 15° south latitude;

Fig. 14b shows a PAR response curve for a cultivar of New Zealand spinach (Tetragonia tetragonioides) with a growing season all year round at 15° south latitude, under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8));

Fig. 15a shows a top view of a system according to the invention comprising a virtually horizontally placed virtually flat disk that is placed rotatably in azimuth, on which several plate-shaped growing surfaces are placed on its bottom side being able to pivot in terms of elevation, and having a longitudinal direction that is perpendicular to the azimuth, wherein the top side of the plate-shaped growing surfaces is planted with a cultivar of New Zealand spinach (Tetragonia tetragonioides) and wherein these plate- shaped growing surfaces are set up on June 21 at around 8 o'clock at 15° south latitude at an elevation of 21 ° and an azimuth of 57°;

Fig. 15b shows a front view of the schematic representation of the system as shown in fig. 15a;

Fig. 15c shows a front view of the flat disk with the several plate-shaped growing surfaces as shown in fig. 15a, wherein the top side of the plate-shaped growing surfaces is planted

Fig. 15d shows a front view of the flat disk with the several plate-shaped growing surfaces as shown in fig. 15a, wherein the bottom side of the several plate-shaped growing surfaces is planted;

Fig. 15e shows a front view of the flat disk with the several plate-shaped growing surfaces as shown in fig. 15c, wherein the area multiplier is different with respect to the system shown in fig. 15c; Fig. 15f shows a front view of two plate-shaped growing surfaces of the system shown in fig. 15a, wherein the plate-shaped growing surfaces are set up centrally at an adjustable angle;

Fig. 16a presents an experimentally plotted PAR graph, wherein the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a horizontal surface is plotted as a function of the time (expressed in solar time) on March 21 , June 21 , September 21 and December 21 at the equator;

Fig. 16b shows a PAR response curve for a cultivar of princess beans (Phaseolus vulgaris) with a growing season all year round at the equator, under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη-ιοΙ/(η-ι².8));

Fig. 17 shows a schematic representation of the determination of the angle of rotation by means of elevation and azimuth for an E-W orientation;

Fig. 18a shows a top view of a schematic representation of a system according to the invention for an E-W orientation, comprising several triangular prisms extending in the longitudinal direction that are planted on their upright side surfaces with a cultivar of princess beans (Phaseolus vulgaris), wherein these triangular prisms extending in the longitudinal direction are set up on December 21 at around 8 o'clock at an elevation of 26°, an azimuth of 1 16°, and an angle of rotation of 48°;

Fig. 18b shows a front view of the schematic representation of the system as shown in fig. 18a;

Fig. 19a shows a front view of a schematic representation of a system according to the invention for an E-W orientation, comprising two triangular prisms extending in the longitudinal direction, being planted on their upright side surfaces with a cultivar of princess beans {Phaseolus vulgaris) and being set up so as to be able to rotate as a function of the angle of rotation and having an adjustable base;

Fig. 19b shows a front view of the schematic representation of the system shown in fig. 19a, wherein the two triangular prisms extending in the longitudinal direction are planted on their upright side surfaces with a cultivar of princess beans (Phaseolus vulgaris) and are set up at a particular angle as a function of the angle of rotation;

Fig. 20a shows a front view of a schematic representation of a system according to the invention for an E-W orientation, comprising two triangular prisms extending in the longitudinal direction, being planted on their upright side surfaces with a cultivar of princess beans (Phaseolus vulgaris), which are set up so as to be able to rotate at one corner thereof with respect to an axis of rotation and which have an adjustable base, and which are set up at an angle of rotation of 90°;

Fig. 20b shows a front view of the schematic representation of the system according to the invention shown in fig. 20a, wherein the two triangular prisms extending in the longitudinal direction are set up at an angle of rotation of 48° and wherein the base is adjusted relative to fig. 20a;

Fig. 20c shows a front view of a schematic representation of a system according to the invention, comprising two triangular prisms extending in the longitudinal direction, being planted on their upright side surfaces with a cultivar of princess beans (Phaseolus vulgaris), and which are set up so as to be able to rotate at the center thereof with respect to an axis of rotation and which are set up so as to be at an angle of rotation of 90°;

Fig. 20d shows a front view of a schematic representation of a system according to the invention, comprising two triangular prisms extending in the longitudinal direction, being planted on their upright side surfaces with a cultivar of princess beans (Phaseolus vulgaris), and which are set up so as to be able to rotate at one corner thereof with respect to an axis of rotation and which are set up so as to be at an angle of rotation of 90°;

Fig. 20e shows a schematic representation of a disk, indicating how the triangular prisms extending in the longitudinal direction of the system shown in figs 20a - 20d need to be placed as a function of the angle of rotation on March 21 , June 21 , September 21 and December 21 ;

Fig. 20f shows a front view of a schematic representation of a system according to the invention, comprising two horizontal disks on which several triangular prisms extending in the longitudinal direction are placed, wherein these disks are set up so as to be able to turn with respect to an E-W oriented axis as a function of the angle of rotation;

Fig. 21 a presents an experimentally plotted PAR graph, wherein the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a horizontal surface is plotted as a function of the time (expressed in solar time) on March 21 , June 21 and September 21 at 55° north latitude;

Fig. 21 b shows a PAR response curve for a cultivar of lettuce (Lactuca sativa) with a growing season from May 1 to August 31 at 55° north latitude, under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a horizontal surface; Fig. 22a shows a front view of a schematic representation of a system according to the invention, comprising several plate-shaped growing surfaces set up as centrally rotatable, which extend in an E-W direction and which are planted on the bottom side with a cultivar of lettuce (Lactuca sativa), wherein the plate-shaped growing surfaces are set up on August 31 at around 6 o'clock at 55° north latitude at an angle of rotation S of -41 °;

Fig. 22b shows a front view of the schematic representation of the system shown in fig. 22a, wherein the plate-shaped growing surfaces are set up on August 31 at around 8 o'clock at 55° north latitude with an angle of rotation of 53°, after rotation with respect to fig. 22a, and wherein the plant is situated on the top of the plate-shaped growing surfaces;

Fig. 23a shows a front view of a schematic representation of a system according to the invention comprising several plate-shaped growing surfaces which can rotate centrally, being planted on the top side with a cultivar of lettuce (Lactuca sativa), wherein the area multiplier/2 plus a safety margin for the height of the plant is less than 2 times the distance between 2 hinges with the same function of 2 adjacent plate-shaped growing surfaces, and wherein the plate-shaped growing surfaces are set up on August 31 at around 6 o'clock at 55° north latitude at an angle of rotation of -41 °;

Fig. 23b - fig. 23e show a front view of the schematic representation of the system as represented in fig. 23a, illustrating a procedure for always maintaining the plant on the top side of the plate-shaped growing surfaces, and this for situations when the plant does not tolerate any upside-down position, and wherein

^■ in fig. 23b all plate-shaped growing surfaces are placed vertically and the central plate-shaped growing surface is turned about its longitudinal axis so that the planting is situated on the opposite side of the growing surface,

^■ in fig. 23c the two outermost plate-shaped growing surfaces are turned about their lengthwise axis so that the planting on these two outermost plate-shaped growing surfaces is situated on the opposite side of the growing surface, resulting in fig. 23d, where all plate-shaped growing surfaces have a planting that is situated on the opposite side with respect to fig. 23a, and

^■ in fig. 23e the plate-shaped growing surfaces are turned to the desired angle of rotation;

Fig. 24a shows a front view of a schematic representation of a system according to the invention comprising several plate-shaped growing surfaces which can rotate centrally, composed of partial growing surfaces, which are planted on the top side with a cultivar of lettuce (Lactuca sativa), wherein the area multiplier/2 plus a safety margin for the height of the plant is larger than and the area multiplier/4 plus a safety margin for the height of the plant is smaller than the distance between 2 hinges with the same function of 2 adjacent plate-shaped growing surfaces;

Fig. 24b - fig. 24e show a front view of the schematic representation of the system as represented in fig. 24a, illustrating a procedure for always maintaining the plant on the top side of the plate-shaped growing surfaces for situations when the plant does not tolerate any upside-down position, and wherein

^■ in fig. 24b all plate-shaped growing surfaces are placed vertically, the outermost partial growing surfaces are turned horizontally and then further turned until the planting is situated on the opposite side and the planting of the central growing surface is turned to the opposite side,

^■ in fig. 24c the partial growing surfaces of the central growing surface are turned horizontally and then further turned until the planting is situated on the opposite side, resulting in fig. 24d, where all plate-shaped growing surfaces have a planting that is situated on the opposite side with respect to fig. 24a, and

^■ in fig. 24e the plate-shaped growing surfaces are turned to the desired angle of rotation;

Fig. 25a presents an experimentally plotted PAR graph, wherein the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) is plotted as a function of the time (expressed in solar time) on May 10, June 21 and August 31 at 55° north latitude at the southern side of a vertical surface with an E-W orientation;

Fig. 25b presents an experimentally plotted PAR graph, wherein the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) is plotted as a function of the time (expressed in solar time) on May 10, June 21 and August 31 at 55° north latitude for a vertical surface with a N-S orientation, eastern side until 12 o'clock and western side after 12 o'clock;

Fig. 25c shows a PAR response curve for a cultivar of marigold (Tagetes sp.) with a growing season from May 1 to August 31 at 55° north latitude, under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη-ιοΙ/(η-ι².8));

Fig. 26 shows a front view of a schematic representation of a system according to the invention comprising several plate-shaped growing surfaces that are placed at an incline with respect to a vertical wall of a building, wherein the plate-shaped growing surfaces are set up on August 31 at around 10 o'clock at 55° north latitude at an angle of rotation of 45°;

• Fig. 27 shows a front view of a schematic representation of a system according to the invention comprising several flat growing surfaces placed alongside each other, being set at a fixed incline and being planted with a cultivar of English ryegrass (Lolium perenne), wherein the incline is 27° and is determined as a function of the averaged sun position during the growing season of the plants;

• Fig. 28a shows a front view of a schematic representation of a system according to the invention comprising several vertically placed growing surfaces and several rotatable mirrors which reflect the sunlight in the direction of the planted growing surfaces;

• Fig. 28b shows a front view of a rotatable mirror as shown in fig. 28a.

[44] The basic principle of the system (1 ) for optimizing the utilization of the available quantity of PAR (photosynthetically active radiation) coming from the sun (4) in the growing of plants (2) on one or more growing surfaces (3), in situations where there is an excess quantity of PAR because the available quantity of PAR is greater than the quantity of PAR which can be used by the plants, is to make the available PAR of the directly incident sunlight (5) fall on a growing area that is greater than the originally available growing area on which the directly incident sunlight would fall without the system (1 ), wherein this greater growing area consists of one or more separate growing surfaces (3a), and wherein the ratio between the larger growing area and the originally available growing area is equal to an area multiplier, which can be increased or decreased by 15%, during a daily period that begins at the latest 2 hours before the time of maximum available photosynthetically active radiation without cloud cover on the originally available area and that ends at the earliest 2 hours after that time, and this during at least one period of at least 3 consecutive months per year.

[45] The system is moreover preferably configured for locations with a latitude in an interval consisting of a minimum of 60° south latitude and 60° north latitude and more preferably for locations with a latitude in an interval consisting of a maximum of 60° south latitude and 60° north latitude.

[46] This basic principle is moreover illustrated by a number of schematic diagrams, as presented in figures 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a and 7b, wherein these schematic diagrams show that the growing area (expressed in m²) is increased with respect to the originally available growing area (expressed in m²) by adapting the incline of the one or more growing surfaces (3a).

[47] In figure 3a the original growing surface is a horizontally positioned growing surface (3b), for example the natural ground surface. On March 21 , at 12 o'clock, the sunlight (5) at the equator falls perpendicularly on this horizontally situated growing surface (3b). In figure 3b, two growing surfaces (3a) are presented, which are set up at an incline so that these two growing surfaces (3a) have a growing area which is larger than the growing area of the originally horizontally placed growing surface (3b). The two slanting growing surfaces (3a) are set up at an angle with respect to the horizontally placed original growing surface (3b) so that an area multiplier of 2 is achieved.

[48] In figure 4a the original growing surface is a horizontally positioned growing surface (3b). On September 21 , at 12 o'clock, and at 50° north latitude, the sunlight (5) falls obliquely on this horizontally situated growing surface (3b). In figure 4b, two growing surfaces (3a) are presented, which are placed at an incline so that these two growing surfaces (3a) are larger than the growing area of the originally horizontally placed growing surface (3b). The two slanting growing surfaces (3a) are set up at an angle with respect to the horizontally situated original growing surface (3b) so that an area multiplier of 2 is achieved.

[49] In figure 5a the original growing surface is a slanting growing surface (3b), for example a natural ground surface placed at an incline. On March 21 at 12 o'clock, at the equator, the sunlight (5) falls perpendicularly on this slanting growing surface (3b). In figure 5b two growing surfaces (3a) are presented, being placed at an incline so that these two growing surfaces (3a) have a growing area which is larger than the growing area of the original slanting growing surface (3b). The two slanting growing surfaces (3a) are placed at an angle with respect to the slanting original growing surface (3b) so that an area multiplier of 2 is achieved.

[50] In figure 6a the original growing surface is a slanting growing surface (3b). On September 21 , at 12 o'clock and 50° north latitude; the sunlight (5) falls obliquely on this slanting ground surface (3b). In figure 6b two growing surfaces (3a) are presented, which are placed at an incline so that these two growing surfaces (3a) have a growing area which is greater than the growing area of the original slanted growing surface (3b). The two slanted growing surfaces (3a) are placed at an angle with respect to the slanted original growing surface (3b) so that an area multiplier of 2 is achieved.

[51] In figure 7a the original growing surface is a vertically placed growing surface (3b). On September 21 at 12 o'clock and 50° north latitude the sunlight (5) falls obliquely on this vertically placed growing surface (3b). In figure 7b two growing surfaces (3a) are presented, which are placed at an incline so that these two growing surfaces (3a) have a growing area which is greater than the growing area of the original vertically placed growing surface (3b). The two slanted growing surfaces (3a) are placed at an angle with respect to the vertically placed original growing surface (3b) so that an area multiplier of 2 is achieved.

[52] That the area multiplier is equal to 2 in the above-described schematic diagrams can be seen from the fact that the originally available growing surfaces (3b) in these schematic diagrams have a length L, while the growing surfaces (3a) placed according to the invention have a length 2L. Thus, the available growing surface is increased by a factor of 2 so that the available quantity of PAR is distributed over a larger growing surface and thus the excess available quantity of PAR is reduced or even eliminated.

[53] The size of the area multiplier can be deduced more or less from the PAR graph for a particular latitude and the PAR response curve for a particular plant. However, a whole series of other circumstances also play a role here, such as the growing season of the plant (2) in question (which is often determined by the number of hours of (sun)light, the ambient temperature, etc.). Hence, for the optimal determination of the area multiplier, experimental work is also needed. Important considerations in this process are, moreover, that

• the maximum value for C0₂ assimilation is usually not the optimum, for example for the example in fig. 2 the increase is entirely limited between 500 PAR and 700 PAR;

• for an increased growing surface, the intensity is also decreased at the beginning and end of the day (see figure 1 ), when in fact there is no excess energy available. This phenomenon, however, is more complicated than it seems, because in the morning and evening the ambient temperatures are usually also lower, which often brings down the relative PAR response, so that the influence on the growth of the plant is all in all quite limited; • as long as the plant (2) does not completely cover the growing surface (which is often the case during the major portion of the growth cycle of the plant (2)), each individual plant often gets more energy than "the energy on the originally available growing surface'Varea multiplier. Therefore, at the start of the growing cycle, one can work with a relatively large area multiplier and gradually diminish it as the plant covers more of the available growing surfaces, by changing the incline and the spacing between the growing surfaces.

[54] The relation between the area multiplier and the yield of (agricultural) crops (2) is as follows:

• In the vicinity of the equator and the tropics, production loss and quality deterioration are prevented for many crops. It is assumed that the production of the crops will be multiplied by at least the area multiplier.

• As one moves further away from the tropics, it is assumed that the production will be multiplied by somewhat less than the area multiplier, and the plant may need a little more time before it becomes ripe or harvestable. This is primarily explained by the fact that, at times when the available PAR is less than or equal to the PAR which can be utilized by plants (2), the relative photosynthesis with the system (1 ) according to the invention is lower than without the system (1 ) according to the invention.

[55] One phenomenon which needs to be taken into account for this invention is geotropism. Geotropism is the phenomenon whereby roots and stems of plants (2) orient themselves in the direction of gravity. Most plants are susceptible to geotropism (gravitropism). How and to what degree the application of the invention influences the production and the quality of the plants (2) grown by geotropism will depend, inter alia, on the embodiment (sample embodiment) of the system (1 ) according to the invention and the species and cultivar of the plant (2) being grown. This is best determined by experiment.

[56] Any detrimental effects can often be dealt with by changing the position of the growing surface (3a) at regular intervals of time, something which the system (1 ) according to the invention more or less allows, depending on the sample embodiment as described below. The correct procedure is best determined by experiment, inter alia as a function of the species and cultivar of the plant (2) being grown. Sample embodiments

[57] In the following text of the specification, a number of possible sample embodiments of a system (1 ) according to the invention are presented.

[58] Here, each time a table indicates the position of the sun at a particular latitude at a particular time, expressed as a function of the solar time, which is the time scale when the sun stands right at geographical south (i.e. azimuth 180°) at 12 o'clock for the northern hemisphere and right at geographical north (i.e. azimuth 0°) at 12 o'clock for the southern hemisphere. This time scale varies, in other words, with the longitude/meridians. The sun's position is described throughout in terms of azimuth (angle, in degrees, with respect to geographical north) (abbreviated AZ) and elevation (angle, in degrees, with respect to the horizon) (abbreviated EL). The sun's precise position can be measured on site, or it can be calculated with mathematical models. For all examples described below, we make use of the "solar position calculator" of URL http://wiki.naturalfrequency.com for this purpose. Slight variations as a function of longitude were averaged out. It should be noted, however, that depending on the program which is used to calculate azimuth and elevation, slightly different values are obtained. In practice, the precise values for elevation and azimuth do not need to be known, but it is often enough to make sure on the one hand that no direct sunlight is falling on the originally available growing surface or on the other hand that no unwanted shadow zones occur on the growing surfaces of the system according to the invention.

[59] Moreover, in each of these sample embodiments an experimentally determined PAR graph and PAR response curve and the approximate area multiplier derived from these are given for one or more particular plants (2) and a particular latitude. Furthermore, in certain cases practical information was provided on the duration of the growing season at this particular latitude and the maximum height which the plant (2) can reach.

[60] In the tables given for the sample embodiments, the sun's positions are shown in highlighted box, being representative of the configuration of the sample embodiment at a particular latitude, on a particular day and at a particular time. Sample embodiment 1

[61] A first sample embodiment of a system (1 ) according to the invention is shown in figure 9a. This system (1 ) contains a cone (6a, 6b) which has a growing surface (3a) consisting of the upright section (61 ) of the cone (6a, 6b), which is planted all around with petunias (21 ). This cone (6a, 6b) is rotatable with respect to two mutually perpendicular axes (8, 9) in order to track the azimuth (AZ) and elevation (EL). In place of a cone (6a, 6b) one can also use a pyramid (not shown in the figures).

[62] Figure 8a shows an experimentally determined PAR graph at 30° south latitude on a day with little or no cloud cover where the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a horizontal surface is plotted as a function of the time (expressed in solar time) on March 21 , June 21 , September 21 and December 21 .

[63] Figure 8b shows a PAR response curve for a petunia cultivar (Petunia integrifolia) with a growing season from March 21 to September 21 for a latitude of 30° south latitude, and this under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)).

[64] From these figures 8a and 8b one can deduce that an area multiplier of 5 can be achieved.

[65] In the following table 1 , a summary is provided of what the sun's position is, expressed in azimuth (AZ) and elevation (EL), as a function of the solar time at 30° south latitude, and this on March 21 , June 21 , September 21 and December 21 .

Time March 21 June 21 September 21 December 21 (solar time) AZ EL AZ EL AZ EL AZ EL

(degree) (degree) (degree) (degree) (degree) (degree) (degree) (degree) 4 0 0 0 0 0 0 0 0

6 0 0 0 0 0 0 1 10 13

8 74 26 53 12 71 28 97 39

10 49 49 30 30 44 50 82 63

12 0 60 358 37 353 59 357 83

14 31 1 49 327 29 308 45 275 61

16 286 26 305 10 285 22 261 35

18 0 0 0 0 0 0 249 9

20 0 0 0 0 0 0 0 0

Table 1

[66] In the sample embodiment shown in figure 9a, a truncated cone (6a) is used. As can be seen in fig. 9a, this truncated cone (6) on September 21 at 10 o'clock solar time stands at 30° south latitude with an elevation (EL) of 50° and an azimuth (AZ) of 44° (also see the highlighted box in table 1 ). In place of a truncated cone (6a), one can also use a solid cone (6b), as shown in fig. 9b.

[67] The dimensions of the cone (6a, 6b), or the pyramid (not shown in the figures), are determined by practical considerations, such as the size of the plant (2) being grown on the growing surface (3a), wind strength, ease of maintenance, etc.

[68] As can be seen in figure 9b, the cone (6b) in this sample embodiment has a base surface (62) with a diameter (D) of 1 m and an upright section (61 ) with a side length of 2.5 m, which provides an area multiplier of 5.

[69] In such a sample embodiment as is presented in figures 9a and 9b, the area multiplier cannot be altered.

[70] In order to counteract geotropism, the system (1 ) can be designed to be rotatable about the axis (8) extending in the longitudinal direction of the cone (6) or pyramid. In the case of a cone (6), that is the axis of symmetry of the cone (6).

Sample embodiment 2 [71] A second sample embodiment of a system (1 ) according to the invention is shown in 12a and 12b, wherein several (elongated) triangular prisms (15) extending (elongated) in the longitudinal direction are set up on a horizontally positioned flat disk (10) alongside each other. The growing surfaces (3a) here are the slanted side surfaces (151 ) of these triangular prisms (15).

[72] Figure 10a shows an experimentally determined PAR graph at 40° north latitude on a day with little or no cloud cover, where the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a horizontal surface is plotted as a function of the time (expressed in solar time) on April 10, June 21 , and September 30.

[73] Figure 10b shows a PAR response curve for the cultivar of strawberry (Fragaria x ananassa) with a growing season from April 10 to September 30 at 40° north latitude, and this under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)). From these figures 10a and 10b one can deduce that an area multiplier of 2.5 is achieved.

[74] In the following table 2, a summary is provided of what the sun's position is, expressed in azimuth (AZ) and elevation (EL), as a function of the solar time at 40° north latitude, and this on April 10, June 21 and September 30.

Time April 10 June 21 September 30

(solar AZ EL AZ EL AZ EL

time) (degree) (degree) (degree) (degree) (degree) (degree)

4 0 0 0 0 0 0

6 84 5 71 15 0 0

8 104 27 89 37 1 14 23

10 132 48 1 14 60 143 41 12 179 58 179 73 184 47

14 227 48 246 60 223 38

16 255 28 271 38 250 19

18 276 5 288 15 0 0

20 0 0 0 0 0 0

Table 2

[75] Figure 1 1 a shows an experimentally determined PAR graph at the equator on a day with little or no cloud cover, where the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a horizontal surface is plotted as a function of the time (expressed in solar time) on March 21 , June 21 , September 21 and December 21 .

[76] Figure 1 1 b shows a PAR response curve for a cultivar of zucchini (Cucurbita pepo) with a growing season all year round at the equator, and this under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)).

[77] From these figures 1 1 a and 1 1 b one can deduce that an area multiplier of 3.7 is achieved.

[78] The slanting side surfaces (151 ) of these triangular prisms (15) extending in the longitudinal direction are in this case planted with strawberry plants (22) with a maximum height of 20 cm. As can be seen in figure 13a, the flat disk (10) on June 21 at 10 o'clock solar time and 40° north latitude is set up with an azimuth (AZ) of 1 14°. The elevation (EL) here is 60° (also see the highlighted box in table 2).

[79] The flat disk (10) can rotate with respect to a vertical axis (Y) (see figure 13b). As can be seen in figure 12b, the flat disk (10) can rotate on wheels (1 1 ) with respect to a support (12) through which the vertical axis (Y) runs.

[80] The distance (X) between the different bases (14) of two adjacent triangular prisms (15) extending in the longitudinal direction is 60 cm in this sample embodiment. The dimensions of the triangular prisms (15) extending in the longitudinal direction and the spacing (X) between the bases (14) of these triangular prisms (15) extending in the longitudinal direction are determined by practical considerations, such as wind strength, ease of maintenance, the height of the plant (2), etc. What is important here is that no significant decrease in PAR occurs at the top of these triangular prisms (15) extending in the longitudinal direction, and that this does not form a zone where the system (1 ) according to the invention is insufficiently effective. This zone is dependent on the height of the plant (2). The ratio between the height of the plant (2) and the dimensions of the triangular prisms (15) extending in the longitudinal direction determines the efficiency of the system (1 ). Hence the need to have larger dimensions for the triangular prisms (15) extending in the longitudinal direction in the case of taller plants (2). This is illustrated in figures 13a and 13b, where the dimensions of the triangular prisms (15) extending in the longitudinal direction vary according to the height of the plants (2) that are grown on these triangular prisms (15) extending in the longitudinal direction As can be seen in figure 13a, such a triangular prism (15) extending in the longitudinal direction has a side length (L) of 1.875 m. But when zucchinis are being grown on the growing surfaces (3a), as is seen in fig. 13b, then the triangular prisms (15) extending in the longitudinal direction have a base (14) with a width (B) of 5 m, a side length (L) of 9.25 m and a spacing (X) between the bases (14) of 1 .4 m.

[81] The area multiplier in this sample embodiment cannot be changed.

Sample embodiment 3

[82] In figures 15a and 15b a third sample embodiment of a system (1 ) according to the invention is shown, wherein several plate-shaped growing surfaces (3a) are placed on a horizontally positioned flat disk (10) at an adjustable incline. In figures 15a and 15b, the plate-shaped growing surfaces (3a) have a longitudinal direction that is perpendicular to the azimuth (AZ). The flat disk (10) can rotate, tracking the azimuth (AZ), and the incline of the plate-shaped growing surfaces (3a) can be adapted according to the elevation (EL). The flat disk (10) can rotate with respect to a vertical axis (Y) (see figure 15b). As can be seen in figure. 15b, the flat disk (10) can turn on wheels (1 1 ) with respect to a support (12) through which the vertical axis (Y) runs. Moreover, it can be seen that these plate-shaped growing surfaces (3) are hinged to the flat disk (10) by a hinge (13) at their lower end. [83] It is also possible to place the longitudinal direction of the various plate-shaped growing surfaces (3a) parallel with the azimuth. In this case, the adapting of the incline of the individual plate-shaped growing surfaces (3a) is simply used to adapt the area multiplier, if necessary, per season and per plant (2).

[84] In this sample embodiment, the area multiplier can be adapted per season and per plant (2).

[85] Figure 14a shows an experimentally determined PAR graph at 15° south latitude on a day with little or no cloud cover, where the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a horizontal surface is plotted as a function of the time (expressed in solar time) on March 21 , June 21 , September 21 and December 21 .

[86] Figure 14b shows a PAR response curve for a cultivar of New Zealand spinach (Tetragonia tetragonioides) with a growing season all year round at 15° south latitude, and this under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)).

[87] From these figures 14a and 14b one can deduce that an area multiplier of 5 is achieved for the period from March 21 to September 21 at 15° south latitude and an area multiplier of 3 is achieved for the period from September 21 to March 21 at 15° south latitude.

[88] In the following table 3, a summary is provided of what the sun's position is, expressed in azimuth (AZ) and elevation (EL), as a function of the solar time at 15° south latitude, and this on March 21 , June 21 , September 21 and December 21 .

Time March 21 June 21 September 21 December 21

(solar AZ EL AZ EL AZ EL AZ EL time) (degree) (degree) (degree) (degree) (degree) (degree) (degree) (degree)

4 0 0 0 0 0 0 0 0

6 90 0 0 0 88 2 1 13 5

8 82 27 57 21 80 31 109 32

10 68 55 37 42 62 58 1 1 1 60 12 0 75 0 52 0 74 180 82

14 294 57 322 42 295 56 249 60

16 278 29 302 20 279 28 251 33

18 270 0 0 0 270 0 247 6

20 0 0 0 0 0 0 0 0

Table 3

[89] On this flat disk (10) are placed alongside each other several plate-shaped growing surfaces (3a) which are planted with New Zealand spinach (23) with a maximum height of 20 cm. The plate-shaped growing surfaces (3a) on June 21 at 8 o'clock solar time and 15° south latitude stand at an elevation (EL) of 21 ° and an azimuth (AZ) of 57° (also see the highlighted box in table 3).

[90] The dimensions of the plate-shaped growing surfaces (3a) are determined by practical considerations, such as wind strength, ease of maintenance, etc. What is important here is that no significant decrease in PAR occurs at the top of the plate-shaped growing surfaces (3a), and that this does not form a zone where the system (1 ) according to the invention is insufficiently effective. This zone is dependent on the height of the plant (2). The ratio between the height of the plant (2) and the dimensions of the plate-shaped growing surfaces (3a) determines the efficiency of the system (1 ). Hence the need to have larger dimensions for the plate-shaped growing surfaces (3a) in the case of taller plants (2).

[91] As can be seen in figures 15c and 15d, the plate-shaped across surfaces (3a) in this sample embodiment are planted across a length (L) of 10 m and they are set up with a spacing (X) of 2.2 m from each other. The spacing (X) is such that the connecting line (V) between the top of one plate-shaped growing surface (3a) and the bottom of the adjacent plate-shaped growing surface (3a) takes on the angle of the elevation (EL). When determining the spacing (X), one takes into account the height of the plant (2) and the thickness of the plate-shaped growing surface (3a) and the growth substrate on which the plant (2) is growing.

[92] For each sun position, there are two possible positions for the planting with plants (2) in regard to the plate-shaped growing surfaces (3a). When set up as shown in figure 15c, the plants (2) are situated on the top side of the plate-shaped growing surfaces (3a), while when set up as shown in figure 15d the plants (2) are situated on its bottom side. If the plate- shaped growing surfaces (3a) are set up on a central hinge (12), as shown in figure 15f, geotropism can be counteracted by regularly switching between the configuration shown in figure 15c and figure 15d. The procedure for carrying out this switch is shown in figures 23b - 23e and figures 24b - 24e, where one must make use of a central hinge (12) as shown in fig. 15f. Furthermore, the setup shown in figure 15d is of interest for lower sun positions.

[93] Figure 15e shows the sample embodiment of figures 15c and 15d, where only one part of the plate-shaped growing surface (3a) is planted. This can be useful, for example, when one wishes to grow a different plant (2) on the plate-shaped growing surfaces (3a). The area multiplier in this way is different from that of the system (1 ) shown in figure 16a. This is important when the PAR varies as a function of the seasons.

[94] Figure 15f shows two plate-shaped growing surfaces (3a) of the system (1 ) shown in figure 15e, where the plate-shaped growing surfaces (3) instead of being placed at the lowermost end are centrally positioned at an adjustable angle. The plate-shaped growing surface (3a) is connected here by means of a central hinge (13) to a support (12), which support is mounted on the flat disk (10). The advantage of such a layout is that the surface of the flat disk (10) located beneath the plate-shaped growing surfaces (3a) remains available for other crops requiring little PAR, as long as the crop on the plate-shaped growing surfaces (3a) has not ripened. For example, certain grass species and/or herbs can be cultivated here, which can grow with indirect (diffuse) sunlight. It should be noted that this applies to systems (1 ) with plate-shaped growing surfaces (3a) in general, and thus not just for the system (1 ) shown in fig. 15f.

[95] Since the position of the plate-shaped growing surfaces (3a) changes constantly in this layout, this is a system (1 ) which is effective at counteracting geotropism. Furthermore, the plate-shaped growing surfaces (3a) can be placed as horizontally as possible at night.

Sample embodiment 4

[96] Figures 18a and 18b show a fourth sample embodiment of a system (1 ) according to the invention, wherein triangular prisms (16) extending (elongated) in the longitudinal direction with an E-W orientation can turn about an E-W axis. The growing surfaces (3a) in this sample embodiment are the slanted upright side surfaces (161 ) of these triangular prisms (16) extending in the longitudinal direction.

[97] Since in this sample embodiment it is not possible to track the position of the sun in azimuth and elevation in a simple manner, the position of the sun is tracked by the angle of rotation (S) (see figure 17) which is determined by the component of the solar radiation that is situated in a plane perpendicular to the E-W direction. This angle of rotation (S) for E-W oriented growing surfaces (3a) is calculated by means of the following formula: arctan[tan(elevation in degrees) / cos (180° - azimuth in degrees)], where whenever the result of this formula is positive, the angle of rotation is to be measured in degrees with respect to south and whenever the result of this formula is negative the angle of rotation (S) is to be measured in degrees with respect to north.

[98] Figure 16a shows an experimentally determined PAR graph at the equator on a day with little or no cloud cover, where the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a horizontal surface is plotted as a function of the time (expressed in solar time) on March 21 , June 21 , September 21 and December 21 .

[99] Figure 16b shows a PAR response curve for a cultivar of princess beans (Phaseolus vulgaris) with a growing season all year round at the equator, and this under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)).

[100] From these figures 16a and 16b one can deduce that an area multiplier of 4 is achieved all year round.

[101] In the following table 4, a summary is provided of what the sun's position is, expressed in azimuth (AZ), elevation (EL), and angle of rotation (S) as a function of the solar time at the equator, and this on March 21 , June 21 , September 21 and December 21 .

(solar time) AZ EL s AZ EL s AZ EL s AZ EL s

(deg(deg(deg(deg(deg(deg(deg(deg(deg(deg(deg(degree) ree) ree) ree) ree) ree) ree) ree) ree) ree) ree) ree)

4 0 0 0 0 0 0 0 0 0 0 0 0

6 90 0 0 67 1 -3 90 4 90 1 13 0 0

8 90 28 90 63 29 -51 89 34 -89 1 16 26 48

10 90 58 90 48 54 -64 88 60 -89 130 52 63

12 90 90 90 0 67 -67 0 90 -90 177 67 67

14 270 60 -90 310 52 -63 272 60 -89 228 53 63

16 270 30 -90 296 26 -48 271 30 -88 243 28 50

18 270 0 0 293 0 0 271 0 0 247 1 3

20 0 0 0 0 0 0 0 0 0 0 0 0

Table 4

[102] In the following table 5, a summary is provided of what the sun's position is, expressed in azimuth (AZ), elevation (EL), and angle of rotation (S), as a function of the solar time at 30° south latitude, and this on March 21 , June 21 , September 21 and December 21.

Table 5

[103] In the sample embodiment shown in figures 18a and 18b, the various elongated growing surfaces (3a) of the triangular prisms (16) extending in the longitudinal direction are planted with princess beans (24) with a maximum height of 20 cm and a spacing (X) between the bases (17) of two adjacent triangular prisms (16) of 60 cm. The triangular prisms (16) are set up according to an angle of rotation (S) of 48°. The azimuth (AZ) here is 1 16° and the elevation (EL) is 26° (also see the highlighted box in table 6). When determining the spacing (X), one takes into account the height of the plant (2) and the thickness of the plate-shaped growing surface (3a) and the growth substrate on which the plant (2) is growing.

[104] As can be seen in figures 19a and 19b, when changing the angle of rotation (S) the length (L) of the base (17) of the triangular prisms (16) extending in the longitudinal direction needs to be adjustable in order to avoid a collision between adjacent triangular prisms (16) and moreover so as not to create any shadow zones. In order to achieve a flexible position control for each triangular prism (16) extending in the longitudinal direction, 2 linear actuators (19) are preferably used.

[105] The dimensions are determined by practical considerations, such as wind strength, ease of maintenance. What is important here is that no significant decrease in PAR occurs at the top of the plate-shaped growing surfaces (3a), and that this does not form a zone where the system (1 ) according to the invention is insufficiently effective. This zone is dependent on the height of the plant (2). The ratio between the height of the plant (2) and the dimensions of the plate-shaped growing surfaces (3a) determines the efficiency of the system (1 ). Hence the need to have larger dimensions for the plate-shaped growing surfaces (3a) in the case of taller plants (2).

[106] Since, as can be seen in table 5, the angle of rotation (S) for an E-W orientation hardly varies at 30 degrees south latitude on March 21 and September 21 during the course of the day (S is around -60°) and even as one moves away from these dates it also does not vary greatly during the course of a given day, it is often quite possible to provide the system (1 ) according to the invention such that an averaged value for the angle of rotation (S) is adjusted only at regular intervals, such as every couple of days, and by leaving somewhat more room between the individual triangular growing surfaces (3) to arrive at a layout in which the adapting of the length of the base (17) of the triangular intersection is not necessary (see figures 19c and 19d). In this case, as shown in fig. 20b, it is possible to provide a disk (33) on which it is indicated what incline the triangular growing surfaces (3a) need to have at a particular time. [107] The triangular prisms (16) extending in the longitudinal direction, as shown in figure 20c, are placed so that they can turn with respect to a central support (31 ), while the triangular prisms (16) extending in the longitudinal direction as shown in figure 20d are placed on a sideways arranged support (32). In this latter layout, only one linear actuator (19) is used.

[108] An alternative for the layout as shown in figures 20c and 20d is to set up different triangular prisms (16) extending in the longitudinal direction alongside each other on a rectangular plate (30) (see figure 20f) which can turn as a whole about an E-W axis. The advantage here is that there is no loss of space. Furthermore, this makes it easier to use natural soil.

Sample embodiment 5

[109] Figures 22a and 22b show a fifth sample embodiment of a system (1 ) according to the invention, wherein the system (1 ) comprises one or more plate-shaped growing surfaces (3a) having a fixed length orientation, such as E-W, around which the plate-shaped growing surfaces (3a) can rotate in respect of the angle of rotation (S), which is adjusted in a plane perpendicular to the longitudinal direction of the plate-shaped growing surfaces (3a), for example to the E-W axis, between the horizontal position and a connecting line (V) between the top of a first plate-shaped growing surface (3a) and a neighboring plate-shaped growing surface (3a), taking into account the thickness of the plate-shaped growing surface (3a) and the height of the plant (2) growing thereupon. Each of the plate-shaped growing surfaces (3a) is able to rotate in this case on a centrally placed support (34) in a central hinge (35).

[110] Figure 21 a shows an experimentally determined PAR graph at 55° north latitude on a day with few or no clouds, where the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a horizontal surface is plotted as a function of the time (expressed in solar time) on March 21 , June 21 , and September 21 .

[111] Figure 21 b shows a PAR response curve for a cultivar of lettuce (Lactuca sativa) with a growing season from May 1 to August 31 (two crops) at a latitude of 55° north latitude, and this under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)).

[112] From these figures 21 a and 21 b one can deduce that an area multiplier of 2 is achieved.

[113] In the following table 6, a summary is provided of what the sun's position is, expressed in azimuth (AZ), elevation (EL), and angle of rotation (S), as a function of the solar time at 55° north latitude, and this on May 1 , June 21 , and August 31 .

Table 6

[114] In the sample embodiment shown in figures 22a and 22b, the various plate-shaped growing surfaces (3a) with a length (L) of 3 m are planted with lettuce (25) with a maximum height of 10 cm and a spacing (X) between the various adjacent supports (34) of 1 .6 m. In figure 22a, the plate-shaped growing surfaces (3a) are set up on August 31 at around 6 o'clock solar time with an angle of rotation (S) of - 41 ° (also see the highlighted box in table 6). In figure 22b, the plate-shaped growing surfaces (3b) are set up on August 31 at around 8 o'clock solar time with an angle of rotation (S) of 53° (also see the highlighted box in table 6). When determining the spacing (X), one takes into account the height of the plant (2) and the thickness of the plate-shaped growing surface (3a) and the growth substrate on which the plant (2) is growing. [115] It should be noted that these sample embodiments can only be used as growth substrates for plants (2) where the "upside-down" position is acceptable. Then the E-W orientation, the N-S orientation, or any intermediate orientation is okay. Usually, however, the E-W orientation is advisable, because then the upside-down position can often be avoided. Even in the E-W orientation, if the upside-down position occurs without taking special measures (in other words, if one also wants to apply the PARs in early morning and in the evening) and this is unacceptable for the plant (2), there are two possible solutions available: either the area multiplier/2 plus a safety margin for the height of the plant (2) is less than 2 times the distance between 2 hinges with the same function of 2 neighboring plate-shaped growing surfaces (3a). In that case, it is sufficient to rotate the plate- shaped growing surfaces (3a) on two occasions, for example first the even plate- shaped growing surfaces (3a) and then the odd plate-shaped growing surfaces (3a) (see figures 23b - 23e).

or the area multiplier/2 plus a safety margin for the height of the plant (2) is greater than the distance between 2 neighboring hinges of neighboring plate-shaped growing surfaces (3a) and the area multiplier/4 plus a safety margin for the height of the plant (2) is less than the distance between these 2 respective neighboring hinges. In this case, two extra axes of rotation (36) are needed for each plate-shaped growing surface (3a) to carry out the procedure (see figures 24b - 24e).

[116] Figures 23a to 23e show the different steps of the first solution described above, namely:

in figure 23b, all plate-shaped growing surfaces (3a) that are placed at the angle of rotation (S1 ) in figure 23a are placed upright;

in figure 23c, the middle plate-shaped growing surface (3a) is rotated so that the plant (2) is located on the opposite side of the plate-shaped growing surface (3a);

in figure 23d, the two outermost plate-shaped growing surfaces (3a) are rotated so that the plant (2) is situated on the opposite side of the two outermost plate-shaped growing surfaces (3a), after which all plate-shaped growing surfaces (3a) are rotated to the angle of rotation (S2) as shown in figure 24e.

[117] Figures 24a to 24e show the different steps of the second solution described above. The plate-shaped growing surfaces (3a) in this layout are divided into two partial plate- shaped growing surfaces (3c). For systems (1 ) where the area multiplier is greater than 5, the system (1 ) can be provided with several partial plate-shaped growing surfaces (3c).

[118] The different steps here are as follows:

in figure 24b, all partial plate-shaped growing surfaces (3c) that are set up at the angle of rotation (S1 ) in figure 24a are placed upright and the top and bottom partial growing surface (3c) of the two outermost growing surfaces (3a) are placed horizontally;

in figure 24c, all of the outermost partial growing surfaces (3c) are placed upright and the central partial plate-shaped growing surfaces (3c) are turned horizontally so that the plant (2) is situated below the partial growing surfaces (3c);

in figure 24d, the central partial growing surfaces (3c) are rotated upright, after which all partial plate-shaped growing surfaces (3c) are rotated by the angle of rotation (S2) as shown in figure 25e. The plant (2) is now situated on the opposite side from what was originally the case in figure 25a.

[119] The area multiplier in this sample embodiment can be easily changed.

[120] The dimensions are determined by practical considerations, such as wind strength, ease of maintenance. What is important here is that no significant decrease in PAR occurs at the top of the plate-shaped growing surfaces (3a), and that this does not form a zone where the system (1 ) according to the invention is insufficiently effective. This zone is dependent on the height of the plant (2). The ratio between the height of the plant (2) and the dimensions of the plate-shaped growing surfaces (3a) determines the efficiency of the system (1 ). Hence the need to have larger dimensions for the plate-shaped growing surfaces (3a) in the case of taller plants (2).

[121] Also in these sample embodiments there are many possible situations where a small adjustment at regular intervals, such as once a week, is acceptable. One can work with an averaged position in order to compensate for slight differences in PAR during the course of the day. Sample embodiment 6

[122] The sixth sample embodiment of a system (1 ) according to the invention, as shown in figure. 26, is set up against a vertical wall (37), such as that of an apartment building.

[123] Such a sample embodiment can be used ideally in large cities where more and more people are choosing to plant around buildings in order to purify the city air and have as much solar energy as possible absorbed by plants in order to reduce the cooling expenses of buildings and improve the general city climate.

[124] In this sample embodiment, various plate-shaped growing surfaces (3a) hinged one above another are secured to the vertical wall (37).

[125] Figure 25a shows an experimentally determined PAR graph at 55° north latitude on a day with little or no cloud cover, where the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a vertical surface with E-W orientation is plotted as a function of the time (expressed in solar time) on May 21 , June 21 , and August 31 .

[126] Figure 25b shows an experimentally determined PAR graph at 55° north latitude on a day with little or no cloud cover, where the available quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)) with respect to a vertical surface with north-south orientation at the east side until 12 o'clock and on the west side after 12 o'clock is plotted as a function of the time (expressed in solar time) on May 10, June 21 , and August 31 .

[127] Figure 25c shows a PAR response curve for a cultivar of marigold (Tagetes sp.) with a growing season from May 1 to August 31 at a latitude of 55° north latitude, and this under optimal growing conditions, wherein the relative C0₂ assimilation is plotted as a function of the utilized quantity of PAR (expressed in μη"ΐοΙ/(η"ΐ².8)).

[128] From these figures 25a and 25c it can be deduced that an area multiplier of 2 is achieved for the E-W plane. [129] In the following table 8, a summary is provided of what the sun's position is, expressed in azimuth (AZ), elevation (EL), and angle of rotation (S) with regard to the E-W orientation, as a function of the solar time at 55° north latitude, and this on May 1 , June 21 , and August 31.

Table 7

[130] In the sample embodiment shown in figure 26, the various plate-shaped growing surfaces (3a) with a length (L) of 5 m are planted with marigolds (26) with a height of 15 cm. The spacing (X) between the different plate-shaped growing surfaces (3a) placed one above another is 2.5 m. In figure 25, the plate-shaped growing surfaces (3a) are set up on August 31 at around 10 o'clock solar time with an angle of rotation (S) of 45° (also see the highlighted box in table 7).

[131] When the plate-shaped growing surfaces (3a) are set up in a N-S orientation, an area multiplier of 1 .5 is achieved (see figures 25b and 25c), in which case the angle of rotation (S) needs to be calculated by the general formula given below, and the daily period of direct sunlight is shorter than for an E-W orientation.

Sample embodiment 7 [132] In the seventh sample embodiment of a system (1 ) according to the invention, as shown in figure 27, various growing surfaces (3a) are placed at an incline which coincides with an averaged angle of rotation (S) for the relevant growing season. As can be seen in figure 27, by making use of the system (1 ) a strip of the original ground surface with a length L/2 becomes available for other purposes, such as the installation of solar panels (40), while the yield of plants (2) remains about the same as without the system (1 ) according to the invention.

[133] In the following table 8, a summary is provided of what the sun's position is, expressed in azimuth (AZ), elevation (EL), and angle of rotation (S), as a function of the solar time at 50° north latitude, and this on March 21 , June 21 , September 21 and December 21.

Table 8

[134] In the sample embodiment shown in figure 27, the different growing surfaces (3a) have a length (L) of 6 m and are planted for example with ryegrass (Lolium perenne) (27). The angle between the horizontal ground surface (38) and the growing surface (3a) placed at an incline is 27°. The length of the base (39a) of the triangular prism (39) which is formed by placing the growing surfaces (3a) at an incline is also 6 m. The growing surfaces (3a) here are positioned according to an averaged angle of rotation (S) of 50° (which is the average of the angles of rotation in the highlighted box in table 8). Note that a line following the direction of the angle of rotation (S) and passing through the top of the triangular prism (39) intersects the base of the triangular prism (39a) at a point whose position is determined by the area multiplier (in this example, the area multiplier is 2).

Sample embodiment 8

[135] An eighth sample embodiment of a system (1 ) according to the invention, as is shown in figure 28a, comprises one or more mirrors (41 ) which can rotate with respect to a central axis (42), and furthermore can move back and forth in a direction perpendicular to the longitudinal direction of the growing surfaces (3a) (also see figure 28b). Moreover, these mirrors (41 ) consist of two or more mirror sections (not shown in the figures) which can slide back and forth over each other. In this way, with the help of these mirrors, the changing position of the sun can be tracked in the course of a day, the year, and/or the growing season. In the layout shown in figure 28a, various plate-shaped growing surfaces (3a) are set up vertically alongside each other. The mirrors (41 ) ensure that the incident sunlight (5) is reflected onto the plate-shaped growing surfaces (3a).

[136] In general, the angle of rotation (S) reflects the component of the solar radiation situated in a plane perpendicular to the orientation of plate-shaped or triangular growing surfaces. The general formula for determining this angle of rotation for any given fixed orientation of plate-shaped or triangular growing surfaces is as follows:

the N-S orientation coincides with 0°;

the NE-SW orientation coincides with 45°;

the E-W orientation coincides with 90°; and

the SE-NW orientation coincides with 135°; and wherein

whenever the angle of rotation is positive, this angle of rotation (S) is measured in a plane perpendicular to the longitudinal direction of the growing surfaces (3a), from the horizontal orientation in degrees (as defined above), plus 90° (i.e. clockwise), and

whenever the angle of rotation is negative, this angle of rotation (S) is measured in a plane perpendicular to the longitudinal direction of the growing surfaces (3a), from the horizontal orientation in degrees (as defined above), minus 90° (i.e. counterclockwise).

[137] For growing surfaces (3a) which are the elongated slanting sides of triangular prisms (15, 16) extending in the longitudinal direction, the angle of rotation (S) needs to be adjusted between the median line of the triangular prism (15, 16) extending in the longitudinal direction that passes through the top of the triangular prism (15, 16) extending in the longitudinal direction and the middle of the base (14, 17) of this triangular prism (15, 16) extending in the longitudinal direction, and the horizontal.

[138] For plate-shaped growing surfaces (3a), the angle of rotation (S) needs to be adjusted according to the connecting line between the top of a first plate-shaped growing surface (3a) and a neighboring plate-shaped growing surface (3a), taking into account the thickness of the plate-shaped growing surface (3a) and the height of the plant (2) growing thereupon.

[139] The plate-shaped growing surfaces (3a) can be composed of strips that are situated at a certain spacing from each other. The slanting upright side surfaces (151 , 161 ) of the triangular prisms (15, 16) extending in the longitudinal direction can also be constructed from strips extending in the longitudinal direction which are situated at a certain spacing from each other. To counteract geotropism, these strips are preferably rotatable about an axis which extends in the longitudinal direction of the plate-shaped growing surfaces (3a) or the triangular prisms (15, 16) extending in the longitudinal direction and these strips are rotated at regular intervals with respect to a perpendicular to the plate-shaped growing surfaces (3a) or the slanting upright side surfaces (151 , 161 ). [140] Furthermore, for counteracting of geotropism in systems (1 ) according to the invention which have plate-shaped growing surfaces (3a) with a central hinge, one can use the procedure as shown in figures 23b - 23e and figures 24b- 24e and described in further detail above. In this case, one can switch quite regularly, for example every half hour, between the position shown in figure 15c and figure 15d, since for each position of the sun there are always 2 satisfactory states of the plate-shaped growing surfaces (3), but in this case a central hinge (13) has to be provided as shown in figure 15f.

[141] Whenever it is not possible to use natural soil such as potting soil as the growth substrate, there are at present a large number of known alternatives on the market. However, these will not be described in any more detail here, since they are known to the person skilled in the art. Furthermore, certain forms of hydroponics and aeroponics can also be considered here.

[142] The system (1 ) according to the invention can moreover comprise one or more artificial light sources (not shown in the figures) which are provided for extra lighting of the plants (2) on cloudy days and/or for increasing the number of hours of daylight (not shown in the figures). More specifically, these one or more artificial light sources can be configured to distribute light of specific wavelengths, and these specific wavelengths can be such as to counteract geotropism for plants that are susceptible to it.

[143] The above-described system (1 ) according to the invention has broad applications for agricultural and horticulture plants, ornamental plants (flowers), and even for plants under water (allowing for the index of refraction of the water).

[144] Although the present invention has been illustrated by means of specific sample embodiments, it will be clear to the person skilled in the art that the invention is not limited to the details of the preceding illustrative sample embodiments, and that the present invention can be implemented with various changes and adaptations without thereby leaving the area of application of the invention. The present sample embodiments must therefore be considered in every respect as illustrative and not restrictive, and the area of application of the invention is specified by the accompanying claims and not by the preceding specification, and all changes which fall within the meaning and the scope of the claims are therefore included herein. In other words, it is presumed that all changes, variations or equivalents are included therein, such as fall within the area of application of the present basic principles and whose essential attributes are claimed in this patent application. Furthermore, the reader of this patent application will understand that the words "comprising" or "comprise" do not exclude other elements or steps, and that the word "a" does not exclude a plural. Any references to the claims should not be taken as a limitation to the claims in question. The terms "first", "second", "third", "a", "b", "c" and the like, whenever used in the specification or in the claims, are used to draw a distinction between such elements or steps and do not necessarily specify a consecutive or chronological order. In the same way, the terms "top", "bottom", "above", "below" and the like are used for purposes of the description and do not necessarily refer to relative positions. It must be understood that those terms are interchangeable under the proper circumstances and that sample embodiments of the invention are able to function in accordance with the present invention in different sequences or orientations than are described or illustrated above.

Claims

A system (1 ) for optimizing the utilization of the available quantity of photosynthetically active radiation in the growing of one or more plants (2, 21 - 27) on one or more growing surfaces (3a) in situations where there is an excess quantity of photosynthetically active radiation because the available quantity of photosynthetically active radiation is greater than the usable quantity of photosynthetically active radiation for the one or more plants (2, 21 - 27),

CHARACTERIZED IN THAT the system (1 ) is configured to make the available photosynthetically active radiation of the directly incident sunlight (5) fall onto a growing area that is larger than the originally available growing area on which the directly incident sunlight would fall without the system (1 ), wherein this larger growing area consists of one or more separate growing surfaces (3a), and wherein the ratio between the larger growing area and the originally available growing area is equal to an area multiplier increased or decreased by 15%, during a daytime period that begins at the latest 2 hours before the time of maximum available photosynthetically active radiation without cloud cover on the originally available area and that ends at the earliest 2 hours after that time, and this during at least one period of at least 3 consecutive months per year.

The system (1 ) as claimed in claim 1 , CHARACTERIZED IN THAT the system is also configured for locations with a latitude in an interval consisting of a minimum of 60° south latitude and 60° north latitude.

The system (1 ) as claimed in claim 1 or 2, CHARACTERIZED IN THAT the one or more growing surfaces (3a) are placed at a certain incline with respect to the originally available growing surface as a function of the sun's position in order to make the available photosynthetically active radiation of the directly incident sunlight (5) fall on a growing area that is larger than the originally available growing area on which the directly incident sunlight would fall without the system (1 ), wherein this larger growing area consists of one or more separate growing surfaces (3a), and wherein the ratio between the larger growing area and the originally available growing area is equal to a fixed value, namely the area multiplier, which can be 15% larger or smaller, during a daytime period that begins at the latest 2 hours before the time of maximum available photosynthetically active radiation without cloud cover on the originally available area and that ends at the earliest 2 hours after that time, and this during at least one period of at least 3 consecutive months per year.

4. The system (1 ) as claimed in claim 3, CHARACTERIZED IN THAT the one or more growing surfaces (3a) are placed at a fixed incline that is determined as a function of the averaged sun position in the course of a day, a year, and/or a growing season of the one or more plants.

5. The system (1 ) as claimed in claim 3, CHARACTERIZED IN THAT the one or more growing surfaces (3a) are designed to adapt their position as a function of the varying sun position during the course of a day, a year, and/or a growing season of the one or more plants.

6. The system (1 ) as claimed in claim 5, CHARACTERIZED IN THAT in the case of plants designed subject to geotropism, in order to counteract the geotropism one or more of the growing surfaces (3a) is designed so as to change at regular intervals the incline which they make relative to their horizontal position.

7. The system (1 ) as claimed in claim 5 or 6, CHARACTERIZED IN THAT the system (1 ) comprises one or more cones or pyramids (6a, 6b) with an upright section (61 ), wherein the growing surfaces (3a) are placed on one or more of the upright sections (61 ) of this or these cone(s) or pyramid(s), which can be rotated with respect to two mutually perpendicular axes (8, 9) in order to track the azimuth (AZ) and elevation (EL).

8. The system (1 ) as claimed in claim 7, CHARACTERIZED IN THAT in order to counteract geotropism, the one or more cones or pyramids (6) can be rotated with respect to an axis (8) extending in the longitudinal direction of the cone(s) (6) or pyramid(s).

9. The system (1 ) as claimed in claim 5 or 6, CHARACTERIZED IN THAT the system (1 ) comprises a virtually horizontally placed virtually flat disk (10) on which one or more triangular prisms (15) are placed, extending in the longitudinal direction, wherein one or more growing surfaces (3a) are arranged on one or both of the obliquely upright side surfaces (151 ) of the triangular prisms (15), wherein the longitudinal direction of the growing surfaces (3a) tracks the azimuth (AZ) and wherein this flat disk (10) is able to rotate with respect to a vertical axis (Y) in order to track the azimuth (AZ).

10. The system (1 ) as claimed in claim 5 or 6, CHARACTERIZED IN THAT the system (1 ) comprises a virtually horizontally placed virtually flat disk (10) on which one or more plate-shaped growing surfaces (3a) are placed at an adjustable incline, wherein the longitudinal direction of the plate-shaped growing surfaces (3a) is perpendicular to the azimuth (AZ), and the disk (10) can rotate and the incline of the plate-shaped growing surfaces (3a) can be adapted as a function of the elevation (EL).

1 1 . The system (1 ) as claimed in claim 5 or 6, CHARACTERIZED IN THAT the system (1 ) comprises one or more triangular prisms (16) extending in the longitudinal direction and having an E-W orientation, wherein the growing surfaces (3a) are arranged on the obliquely upright side surfaces (161 ) of the triangular prisms (16) extending in the longitudinal direction, and wherein the triangular prisms (16) can turn about an E-W axis with respect to an angle of rotation (S) that is calculated by means of the following formula:

S = arctan[tan(elevation in degrees) / cos (180° - azimuth in degrees)], wherein whenever the result of this formula is positive, the angle of rotation (S) is to be measured in degrees relative to south and whenever the result of this formula is negative the angle of rotation (S) is to be measured in degrees relative to north, and wherein the angle of rotation (S) is adjusted with respect to the median line through the top and the base of the respective triangular prism (16) extending in the longitudinal direction and with respect to the horizontal.

12. The system (1 ) as claimed in claim 1 1 , CHARACTERIZED IN THAT the one or more triangular prisms (16) extending in the longitudinal direction have a base (17) with an adjustable size that can be changed by a varying angle of rotation (S).

13. The system (1 ) as claimed in claim 5 or 6, CHARACTERIZED IN THAT the system (1 ) comprises one or more plate-shaped growing surfaces (3a) which have a fixed length orientation, about which the plate-shaped growing surfaces (3a) can rotate with respect to the angle of rotation (S), to be adjusted in a plane perpendicular to the longitudinal direction of the plate-shaped growing surfaces (3a), between the horizontal position and a connecting line (V) between the top side of a first plate-shaped growing surface (3a) and a neighboring plate-shaped growing surface (3a), taking into account the thickness of the plate-shaped growing surface and the height of the plant (2, 21 - 27) growing thereupon, and wherein the angle of rotation (S) for each arbitrary orientation is calculated by means of the following formula:

the N-S orientation coincides with 0°;

the NE-SW orientation coincides with 45°;

the E-W orientation coincides with 90°; and

the SE-NW orientation coincides with 135°; and wherein

whenever the angle of rotation is positive, S is measured in a plane perpendicular to the longitudinal direction of the growing surfaces, from the (horizontal) orientation in degrees (as defined above), plus 90° (i.e. clockwise), and whenever the angle of rotation is negative, this angle of rotation is measured in a plane perpendicular to the longitudinal direction of the growing surfaces, from the (horizontal) orientation in degrees (as defined above), minus 90° (i.e. counterclockwise).

14. The system (1 ) as claimed in claim 10 or 13, CHARACTERIZED IN THAT the plate- shaped growing surfaces (3a) are composed of strips that are situated at a certain distance from one another.

15. The system (1 ) as claimed in claim 9 or 1 1 , CHARACTERIZED IN THAT the obliquely upright side surfaces (151 , 161 ) of the triangular prisms (15, 16) extending in the longitudinal direction are strips extending in the longitudinal direction that are situated at a certain distance from one another.

16. The system as claimed in claim 14 or 15, CHARACTERIZED IN THAT, to counteract geotropism, the strips are placed rotatably around an axis that extends in the longitudinal direction of the plate-shaped growing surfaces (3a) or the triangular prisms (15, 16) extending in the longitudinal direction, wherein the strips are turned at regular intervals of time with respect to a line perpendicular to the plate-shaped growing surfaces (3a) or the obliquely upright side surfaces (151 , 161 ).

17. The system (1 ) as claimed in claim 1 or 2, CHARACTERIZED IN THAT the system comprises one or more mirrors (40) that are placed rotatably with respect to a central axis (42), which can move back and forth in a direction perpendicular to the longitudinal direction of the growing surfaces (3a), and which comprise two or more mirror sections that are slidable back and forth over each other in order to make the available photosynthetically active radiation of the directly incident sunlight (5) fall on a growing area that is larger than the originally available growing area on which the directly incident sunlight would fall without the system (1 ), wherein this larger growing area consists of one or more separate growing surfaces (3a), and wherein the ratio between the larger growing area and the originally available growing area is equal to the area multiplier, which can be increased or decreased by 15%, during a daily period that begins at the latest 2 hours before the time of maximum available photosynthetically active radiation without cloud cover on the originally available area and that ends at the earliest 2 hours after that time, and this during at least one period of at least 3 consecutive months per year.

18. The system (1 ) as claimed in claim 17, CHARACTERIZED IN THAT the one or more mirrors (40) are movably set up in such a way that the changing position of the sun throughout the course of a day, the year, and/or the growing season can be tracked.

19. The system (1 ) as claimed in one of claims 1 to 18, CHARACTERIZED IN THAT the system (1 ) comprises one or more artificial light sources, which are provided for extra lighting of the plants (2, 21 - 27) during cloudy days and/or for increasing the number of hours of daylight. The system (1 ) as claimed in one of claims 1 to 19, CHARACTERIZED IN THAT the system (1 ) comprises one or more artificial light sources that are configured to distribute light at specific wavelengths, wherein these specific wavelengths are such that they counteract geotropism in plants (2, 21 - 27) that are susceptible to it.