Plant cultivation device and plant cultivation method

Abstract

In the present invention, the saturation of photosynthesis efficiency of a plant is avoided and the waste of light energy is reduced.　This plant cultivation device for growing a plant with artificial light is provided with a growing space 30 in which a plant 200 is grown and at least one light source panel 32 for irradiating the growing space with artificial light Li. The light source panel has a substrate 33 and a plurality of light output units 34 arranged at intervals on the substrate. The photon flux density B (μmol·m-2·s-1) of the artificial light emitted from one light output unit is less than or equal to the photosynthesis saturated light intensity L of a leaf of the plant.

Description

Plant growing device and plant growing method

[0001] The present invention relates to a plant growing device and a plant growing method for growing plants using artificial light.

[0002] Plant factories have been considered as a measure to increase agricultural production and realize stable harvests. In plant factories, the intensity of light irradiated on crops from an artificial light source for photosynthesis, the temperature, humidity, and carbon dioxide (CO ) in the plant growing space are controlled. ２ It is possible to control various parameters, such as the concentration of nitrogen, wind speed, and other environmental conditions, as well as fertilizer components for plant growth. This makes it possible to produce crops year-round, dramatically increasing crop productivity.

[0003] Patent Document 1 discloses a closed-type plant factory that cultivates plants by irradiating them with artificial light, such as light from a light emitting diode (LED) light source, without using sunlight. In this closed-type plant factory, light is irradiated from the side of the plants in close proximity, making it possible to cultivate vegetables that grow vertically and are tall, such as tomatoes and cucumbers.

[0004] Patent No. 5330162

[0005] For stable plant cultivation, it is desirable to supply plants with a sufficient amount of light as evenly as possible. One way to achieve this is to increase the distance between the light source and the plant. However, this creates wasted space. Furthermore, as the distance increases, the light spreads and attenuates, resulting in energy loss. When using a light source with an LED chip, placing the LED chip too close to the plant can saturate the photosynthetic efficiency, resulting in wasted energy. Furthermore, heat radiation from the LED chip can damage the plant.

[0006] Therefore, the present invention provides a plant cultivation device and a plant cultivation method that avoids saturation of the photosynthetic efficiency of plants and reduces waste of light energy.

[0007] One aspect of the present invention provides a plant growing device for growing plants using artificial light. The plant growing device includes a growing space for growing the plant and at least one light source panel for irradiating the growing space with artificial light. The light source panel includes a substrate and a plurality of light output units arranged on the substrate at intervals. The photon flux density B (μmol m) of the artificial light emitted from each light output unit is -2 ・s -1 ) is equal to or less than the photosynthetic saturation light intensity L of the leaves of the plant.

[0008] One aspect of the present invention provides a plant cultivation method for cultivating a plant using artificial light. This plant cultivation method includes irradiating a cultivation space in which the plant is cultivated with artificial light from at least one light source panel having a plurality of light output units arranged at intervals on a substrate. The photon flux density B (μmol m -2 ・s -1 ) is equal to or less than the photosynthetic saturation light intensity L of the leaves of the plant.

[0009] In this embodiment of the present invention, the photon flux density B (μmol m -2 ・s -1 ) is equal to or less than the photosynthetic saturation light intensity L of the plant leaves, it is possible to avoid saturation of the photosynthetic efficiency of the plant and reduce waste of light energy. In this way, by preventing excessive light energy emission, it is possible to prevent damage to the plant due to heat radiation from the light output unit. Therefore, the light output unit can be placed close to the plant, which minimizes the spread and attenuation of light from the light output unit and reduces energy loss.

[0010] FIG. 1 is a schematic diagram showing an example of the general configuration of a plant growing device according to an embodiment of the present invention. FIG. 2 is a perspective view of the plant growing device of FIG. 1. FIG. 3 is a front view of a light source panel of the plant growing device. FIG. 4 is a longitudinal sectional view of the light source panel of FIG. 3. FIG. 5 is a graph showing a light-photosynthesis curve of soybeans. FIG. 6 is a table showing parameters of two manufacturing examples of a plant growing device according to an embodiment of the present invention. FIG. 7 is a table showing parameters of two examples of a plant growing device used in tests to confirm the effects of an embodiment of the present invention. FIG. 8 is a longitudinal sectional view of a light source panel according to a modified embodiment of an embodiment of the present invention. FIG. 9 is a longitudinal sectional view of a light source panel according to another modified embodiment of an embodiment of the present invention.

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The drawings are not necessarily drawn to scale, and some features may be exaggerated or omitted.

[0012] The plant cultivation device according to the embodiment is arranged in a plant factory. A large number of plant cultivation devices are arranged in the plant factory, and each plant cultivation device can also be called a cultivation unit. The plants to be cultivated are, for example, agricultural crops such as beans, but may also be other plants that perform photosynthesis.

[0013] As shown in Fig. 1, a plant factory in which a plant growing device 1 according to the embodiment is installed is provided with an air conditioning system 20. The air conditioning system 20 adjusts the environment of the area in which plants are grown to a temperature, humidity, and carbon dioxide (CO2) suitable for growing plants. ２ ) concentration.

[0014] As shown in Figures 1 and 2, the plant cultivation device 1 has an upper part 10, a nutrient solution tank 12 arranged below the upper part 10, and a support panel 14 attached to the upper end of the nutrient solution tank 12. The upper part 10 has a cultivation space 30 in which the stems and leaves of the plants 200 grow (i.e., in which the plants are cultivated). The lower part of the stem and roots (including the main root and lateral roots) of the plants 200 are arranged in the nutrient solution tank 12, where the roots grow. The support panel 14 supports the plants 200.

[0015] The nutrient solution tank 12 is a container into which a nutrient solution (liquid fertilizer) 16 is supplied and discharged to be supplied to the roots of the plants 200. The nutrient solution 16 is supplied to and discharged from the nutrient solution tank 12 by a nutrient solution supply and discharge system 18 connected to the nutrient solution tank 12.

[0016] The upper part 10 of the plant cultivation device 1 has at least one light source panel 32 that irradiates the cultivation space 30 with artificial light Li. The light source panel 32 irradiates the plant 200 with artificial light Li from the side. In this embodiment, the upper part 10 has two light source panels 32 that are oriented vertically and arranged parallel to each other. In this manner, the two light source panels 32 face each other, the cultivation space 30 is interposed between the two light source panels 32, and the two light source panels 32 irradiate the plant 200 with artificial light Li from both sides.

[0017] As shown in FIG. 2 , the light source panel 32 has a height X that is greater than the upper limit of the growth height of the plants 200, and a width Y that allows the artificial light Li to be applied substantially evenly and sufficiently to the plurality of plants 200 planted at intervals from one another. The distance Z between the two light source panels 32 is set large enough to allow the artificial light Li to be applied substantially evenly and sufficiently to each leaf of the plants 200. The distance Z is also set large enough to prevent damage to the plants 200 due to heat radiation from the light source panel 32. However, the distance Z is smaller than the quotient obtained by dividing the width Y by n+1 (n is the number of plants 200 in the growth space 30). Therefore, the distance Z is smaller than the width W of the light output region of the light source panel 32 that corresponds to one plant 200. The light output region is the region where an LED chip, described later, is mounted.

[0018] 3 and 4, the light source panel 32 has a flat substrate 33 serving as a support, and a plurality of LED chips (light output units) 34 arranged on the substrate 33. These LED chips 34 are of the same type. Therefore, when the same current and voltage are applied, these LED chips 34 emit artificial light Li with the same photon flux density. The LED chips 34 are arranged regularly (specifically, in a matrix) at equal intervals both vertically and horizontally.

[0019] The substrate 33 is provided with wiring (not shown) for lighting these LED chips 34. A control device (not shown) for simultaneously controlling the light emission of these LED chips 34 is provided outside the light source panel 32 or on the substrate 33.

[0020] The substrate 33 is formed with a plurality of ventilation holes 35. The ventilation holes 35 are through-holes. Air regulated by the air conditioning system 20 is supplied to the growing space 30 through these ventilation holes 35, preventing the plants 200 from overheating due to heat dissipation from the light source panels 32. The ventilation holes 35 are of the same size and are arranged regularly (specifically, in a matrix) at equal intervals vertically and horizontally. However, the ventilation holes 35 may have different sizes or may be arranged irregularly. Other measures may be used to cool the light source panels 32 in addition to or instead of the ventilation holes 35. For example, a heat dissipation member, a water-cooled pipe, or an air-cooled pipe may be in contact with the surface of the substrate 33 opposite the LED chips 34.

[0021] In order to increase the utilization efficiency of the artificial light Li in the cultivation space 30, it is preferable that the surface of the substrate 33 facing the LED chip 34 has a high light reflectivity. The substrate 33 is preferably formed from a light-reflecting material (e.g., a metal with a smooth surface). The surface of the substrate 33 facing the LED chip 34 may be coated with a light-reflecting paint.

[0022] 3 and 4 are merely examples. The size, number, and spacing of the LED chips 34 are not limited to those shown in the drawings, and the size, number, and spacing of the ventilation holes 35 are also not limited to those shown in the drawings.

[0023] In the plant growing device 1, the photon flux density B (μmol m -2 ・s -1 ) is preferably equal to or less than the photosynthetic saturation light intensity L of the leaves of the plant 200. The photosynthetic saturation light intensity of the leaves is the light intensity at which the photosynthetic rate is maximized. In other words, the photosynthetic saturation light intensity is the light intensity at which the photosynthetic efficiency is saturated, and providing more light than this will not promote plant growth and will result in a waste of light energy.

[0024] The photosynthetic saturation light intensity of leaves will be explained with reference to the light-photosynthesis curve of soybeans in Figure 5. In Figure 5, the horizontal axis represents the PPFD (Photosynthetic Photon Flux Density), or light intensity, received by the leaves. The vertical axis represents the CO absorbed by photosynthesis.２ The amount of photosynthesis or photosynthetic rate is expressed as "μmol m -2 ・s -1 " units are shown.

[0025] The light-photosynthesis curve varies depending on the type of plant.

[0026] As shown in Figure 5, the photosynthetic rate is low under weak light and high under strong light. However, when the light intensity exceeds a certain level, the photosynthetic rate (or absorbed CO ２ The amount of energy (amount) will not exceed a certain level.

[0027] For soybeans, the PPFD is 400 μmol m -2 ・s -1 When PPFD is less than 400-800 μmol m, the photosynthetic rate is proportional to PPFD. In other words, there is little energy loss. -2 ・s -1 In this case, although there is a certain amount of energy loss, an increase in PPFD also increases the rate of photosynthesis. For example, when PPFD is 400 μmol m -2 ・s -1 to 800 μmol m -2 ・s -1 Even if the PPFD is increased by two times, the photosynthetic rate increases by only about 1.5 times. -2 ・s -1 Above this level, the rate of photosynthesis slows down, resulting in a large energy loss. However, this does not have a negative effect on plant growth. For example, if PPFD is 400 μmol m -2 ・s -1 to 1600 μmol m -2 ・s -1 Even if the PPFD is increased by 4 times, the photosynthetic rate increases by only about 1.8 times. -2 ・s -1 When the PPFD exceeds 2000 μmol m, the photosynthetic rate of soybeans becomes constant. In other words, the photosynthetic efficiency of soybeans becomes saturated. -2 ・s -1 If the concentration exceeds 2000 μmol m, it may have a negative effect on plant growth. -2 ・s -1This is because it is impossible for a PPFD to exceed this.

[0028] As described above, there is a light intensity L at which the photosynthetic efficiency of a plant is saturated, and there is a photon flux density B (μmol m -2 ・s -1 ) is equal to or less than the photosynthetic saturation light intensity L of the leaves of the plant 200, it is possible to avoid saturation of the photosynthetic efficiency of the plant and reduce waste of light energy. In other words, it is preferable that B≦L.

[0029] In this way, excessive light energy emission is prevented, thereby preventing damage to the plants 200 due to heat radiation from the LED chips 34. Therefore, the LED chips 34 can be disposed close to the plants 200, thereby minimizing the spread and attenuation of the artificial light Li from the LED chips 34 and reducing energy loss. For example, as described above with reference to FIG. 2 , the spacing Z can be made smaller than the width W of the light output area of ​​the light source panel 32 corresponding to one plant 200. By reducing the spacing Z between the light source panels 32 in the plant cultivation device 1, it is possible to prevent the plant cultivation device 1 from becoming larger.

[0030] As is clear from the above explanation, for soybeans, the photosynthetic saturation intensity of leaves, L, is 2000 (μmol m -2 ・s -1 Therefore, the photon flux density B of the artificial light Li emitted from one LED chip is 2000 μmol m -2 ・s -1 In this case, it is possible to avoid saturation of photosynthetic efficiency in soybeans and reduce waste of light energy.

[0031] On the other hand, if the intensity of the artificial light Li from the LED chips 34 is reduced, there is a concern that the photosynthetic efficiency will decrease, inhibiting plant growth and reducing yield. In the plant growing device 1 according to this embodiment, the intensity of the artificial light Li emitted from one LED chip 34 is reduced, while the number of LED chips 34 is increased to supply a sufficient amount of light as uniformly as possible to a wide area of ​​the plant 200.

[0032] In this embodiment, the photon flux G (μmol m -3 ・s -1 ) is the photosynthetic compensation photon flux M (μmol m ) of the plant 200 per unit volume in the growth space 30 -3 ・s -1 ), that is, G>M.

[0033] The photosynthetic compensation photon flux M (μmol m) of the plant 200 per unit volume in the growth space 30 -3 ・s -1 ) is the light compensation point H (μmol m -2 ・s -1 ) and the cumulative leaf area K (m 2 ・m -3 The light compensation point H is the light intensity at which the photosynthetic rate and the respiration rate are equal on the surface of a plant leaf, or in other words, the minimum amount of energy required for leaf growth.

[0034] The cumulative leaf area K in the cultivation space 30 is the sum of the leaf areas of the plants 200 in the cultivation space 30, and is calculated by the following formula: K = I * J / F where I is the Leaf Area Index (LAI) (m 2 ・m -2 The leaf area index I is the leaf area per unit of land surface area (for example, 1 m 2 ) is the sum of the projected areas of all leaves above the base area of ​​the growing space 30 (m 2 ) F is the volume of the growth space 30 (m 3 )

[0035] Therefore, the photosynthetic compensation photon flux M is calculated by the following formula: M=H*K=H*I*J / F

[0036] Therefore, the photosynthetic compensation photon flux M of the plant 200 per unit volume in the growth space 30 is the minimum photon flux per unit volume required for the growth of all leaves of the plant 200 in the growth space 30.

[0037] The light compensation point H varies depending on the type of plant. The leaf area index I varies depending on the type of plant and its growth stage. For soybeans, the light compensation point H is approximately 50 μmol m -2 ・s -1 The leaf area index I of soybeans at the flowering stage and mid-grain filling stage is approximately 4.0.

[0038] Therefore, during the flowering period and the middle stage of seed filling of soybeans, the growth space 30 is 1 m ３ Assuming that the growth space 30 has a unit volume of 1 m (height, width, and depth are 1 m), the photosynthetic compensation photon flux M of the plant 200 per unit volume in the growth space 30 is 200 μmol m -3 ・s -1 Therefore, during the flowering stage and the middle stage of seed filling of soybeans, the photon flux G per unit volume in the growing space 30 is 200 μmol m -3 ・s -1 In this case, the growth of soybean leaves in the growing space 30 can be promoted.

[0039] Photon flux G (μmol m) per unit volume in the growth space 30 -3 ・s -1 ) is calculated by the following formula: G=A*B*C / F where A is the light emitting area of ​​the artificial light Li per LED chip 34, i.e., the light output area (m 2 ・Individuals -1 ), and B is the photon flux density (μmol m -2 ・s -1 ) where C is the number of LED chips 34 that emit artificial light Li into the growing space 30, and when two light source panels 32 are used, it is the total number of LED chips 34 in both light source panels 32. F is the volume (m 3 )

[0040] Therefore, in order to promote the growth of the leaves of the plant 200 in the cultivation space 30, it is preferable to satisfy the following relationship: G=A×B×C / F>M

[0041] For soybeans, M is 200 μmol m -3 ・s-1 Therefore, A × B × C / F > 200 μmol m -3 ・s -1 This can promote leaf growth in the growing space 30.

[0042] As long as the above relationship is satisfied, the position of the light source panel 32 relative to the plant 200 and thus the cultivation space 30 is not limited. For example, the light source panel 32 may be positioned above the cultivation space 30 so that the light source panel 32 emits artificial light Li from above into the cultivation space 30.

[0043] However, in order to make the photon flux G per unit volume as uniform as possible in the growth space 30, the leaf area index I, i.e., the degree of leaf growth, should be taken into consideration. When artificial light Li is emitted from above the growth space 30, at a growth stage when the plant 200 has many leaves, the artificial light Li is blocked by the upper leaves, and the photon flux G per unit volume becomes lower in the lower part of the growth space 30.

[0044] Therefore, in this embodiment, the light source panel 32 is disposed on the side of the cultivation space 30 so that the light source panel 32 irradiates the plant 200 with artificial light Li from the side. Therefore, regardless of the growth stage of the plant 200, particularly the state of leaf growth, the photon flux G per unit volume can be made as uniform as possible between the upper and lower parts of the cultivation space 30.

[0045] The number of light source panels 32 may be one. However, in order to make the photon flux G per unit volume as uniform as possible on both sides of the plant 200, in this embodiment, as shown in Figures 1 and 2, two light source panels 32 face each other, the growth space 30 is interposed between the two light source panels 32, and the two light source panels 32 irradiate the plant 200 with artificial light Li from both sides. In this way, it is preferable to provide two light source panels 32, and in this case, the photon flux G per unit volume can be made as uniform as possible on both sides of the plant 200.

[0046] In addition to the two light source panels 32, two more light source panels 32 may be provided at both ends of the light source panels 32 in the longitudinal direction (the direction of width Y). That is, four light source panels 32 may be provided around the periphery of the growth space 30, and the four light source panels 32 may emit artificial light Li into the growth space 30. However, in this case, plants 200 arranged near the ends of the growth space 30 in the longitudinal direction (the direction of width Y) will receive more artificial light Li than plants 200 arranged in the center of the growth space 30 in the longitudinal direction. In this case, if the amount of artificial light Li emitted from each LED chip 34 is large, leaves of plants 200 arranged near the ends of the growth space 30 in the longitudinal direction will receive light with an intensity higher than the photosynthetic saturation light intensity L, which may result in wasted light energy. Therefore, it is preferable to provide only two light source panels 32, as in this embodiment.

[0047] 6 shows parameters of two examples of a plant growing device according to an embodiment of the present invention. In both Examples 1 and 2, as shown in FIGS. 1 and 2, two light source panels 32 were arranged parallel to each other so that the growing space 30 was located between the two light source panels 32. In each light source panel 32, the substrate 33 was made of aluminum, and a water-resistant film was formed on its surface.

[0048] In Example 1, the height X of the light source panel 32 (height of the substrate 33) was 0.46 m, and the width Y of the light source panel 32 (width of the substrate 33) was 1.196 m. The spacing Z between the light source panels 32 was 0.1 m in Example 1. Therefore, the volume F of the growth space was 0.055 m. ３ In Example 2, the height X of the light source panel 32 was 0.46 m, and the width Y of the light source panel 32 was 0.596 m. The spacing Z between the light source panels 32 was 0.06 m in Example 2. Therefore, the volume F of the cultivation space was 0.0164 m. ３ It was.

[0049] In Example 1, the height X1 (see FIG. 3) of the area (light output area) on each substrate 33 where the LED chips 34 are mounted is 0.405 m, and the width Y1 of that area is 1.156 m. Therefore, the total area D of the areas where the LED chips 34 are mounted on the two light source panels 32 is 0.936 m. ３ In Example 1, 5,940 LED chips 34 were mounted in the area of ​​each substrate 33 where the LED chips 34 were mounted. Specifically, 45 LED chips 34 were arranged at equal intervals in the height X direction, and 132 LED chips 34 were arranged at equal intervals in the width Y direction. The pitch of the LED chips 34 in the height X direction was approximately 9.2 mm, and the pitch of the LED chips 34 in the width Y direction was approximately 8.8 mm. The number C of LED chips 34 used in the two light source panels 32 was 11,880.

[0050] In Example 2, the height X1 (see FIG. 3) of the area where the LED chips 34 are mounted on each substrate 33 is 0.405 m, and the width Y1 of that area is 0.556 m. Therefore, the total area D of the areas where the LED chips 34 are mounted on the two light source panels 32 is 0.450 m. ３ In Example 2, 2970 LED chips 34 were mounted in the area of ​​each substrate 33 where the LED chips 34 were mounted. Specifically, 45 LED chips 34 were arranged at equal intervals in the height X direction, and 66 LED chips 34 were arranged at equal intervals in the width Y direction. The pitch of the LED chips 34 in the height X direction was approximately 9.2 mm, and the pitch of the LED chips 34 in the width Y direction was approximately 8.5 mm. The number C of LED chips 34 used in the two light source panels 32 was 5940.

[0051] In both Examples 1 and 2, each LED chip 34 was a "Sanan 2835" type with a color temperature of 5,000 K manufactured by San'an Optoelectronics Co. Ltd. (Hubei Province, China). The thickness t (see FIG. 4 ) of each LED chip 34 was 0.8 mm. Each LED chip 34 had a vertical length (height in the X direction) of 2.8 mm and a horizontal length (width in the Y direction) of 3.5 mm. The light-emitting area (light output area) A of each LED chip 34 for artificial light Li was 9.8×10 -6 m 2 It was.

[0052] In each example, the LED chip 34 was supplied with the same current and voltage to emit artificial light Li with the same photon flux density. However, in Example 1, a higher current was passed through the LED chip 34 than in Example 2. As a result, the photon flux density B of the artificial light Li emitted from each LED chip 34 was 1,206 μmol m -2 ・s -1 In Example 2, it was 600 μmol m -2 ・s -1 In both cases, the photon flux density B was less than the photosynthetic saturation intensity L of soybean leaves. Therefore, when the plant 200 is a soybean, it is possible to avoid saturation of the photosynthetic efficiency of the plant 200 and reduce waste of light energy.

[0053] In Example 1, the photon flux G per unit volume in the growth space 30 is A×B×C / F=2,553 μmol m -3 ・s -1 and the photosynthetic compensation photon flux M (200 μmol m) per unit volume in the growing space 30 at the soybean flowering stage and the middle of seed filling stage. -3 ・s -1 In Example 2, G = A × B × C / F = 2,123 μmol m -3 ・s -1 and the photosynthetic compensation photon flux M (200 μmol m -3 ・s -1Therefore, in both Examples 1 and 2, the growth of soybean leaves at the flowering stage and the middle stage of grain filling can be promoted in the growing space 30.

[0054] In both Examples 1 and 2, a large number of ventilation holes 35 with a diameter of 3.5 mm were formed so that the temperature in the growth space 30 would be 50°C or less. In Example 1, 44 ventilation holes 35 were arranged at equal intervals in the height X direction and 131 ventilation holes 35 were arranged at equal intervals in the width Y direction in the region of each substrate 33 where the LED chips 34 were mounted. In Example 2, 44 ventilation holes 35 were arranged at equal intervals in the height X direction and 65 ventilation holes 35 were arranged at equal intervals in the width Y direction in the region of each substrate 33 where the LED chips 34 were mounted. Each ventilation hole 35 was located at the center of four adjacent LED chips 34.

[0055] The inventors conducted tests to confirm the effects of embodiments of the present invention. Figure 7 shows parameters of two examples of plant cultivation devices used in the tests. In both Example 3 and Comparative Example, as shown in Figures 1 and 2, two light source panels 32 were arranged parallel to each other so that the cultivation space 30 was located between the two light source panels 32. In each light source panel 32, the substrate 33 was made of aluminum, and a water-resistant film was formed on its surface.

[0056] In both Example 3 and the Comparative Example, the height X of the light source panel 32 (height of the substrate 33) was 0.46 m, and the width Y of the light source panel 32 (width of the substrate 33) was 0.596 m. The spacing Z between the light source panels 32 was 0.1 m. Therefore, the volume F of the growth space was 0.0274 m. ３ It was.

[0057] In both Example 3 and the Comparative Example, the height X1 (see FIG. 3) of the area (light output area) on each substrate 33 where the LED chips 34 were mounted was 0.34 m, and the width Y1 of that area was 0.48 m. Therefore, in both Example 3 and the Comparative Example, the total area D of the areas where the LED chips 34 were mounted on the two light source panels 32 was 0.326 m. ３ It was.

[0058] In both Example 3 and the Comparative Example, 896 LED chips 34 were mounted in the area where the LED chips 34 were mounted on each substrate 33. Therefore, in both Example 3 and the Comparative Example, the number C of LED chips 34 used in the two light source panels 32 was 1,792.

[0059] In both Example 3 and the Comparative Example, the LED chips 34 used were the same as those in Examples 1 and 2. Therefore, the light-emitting area A of the artificial light Li per LED chip 34 was 9.8×10 -6 (m 2 ・Individuals -1 ) was.

[0060] In each of Example 3 and the Comparative Example, the LED chip 34 was supplied with the same current and voltage, and artificial light Li was emitted with the same photon flux density. Thus, Example 3 and the Comparative Example were in approximately the same environment. However, in the Comparative Example, a higher current was passed through the LED chip 34 than in Example 3. As a result, in Example 3, the photon flux density B of the artificial light Li emitted from each LED chip 34 was 1,900 μmol m -2 ・s -1 , which was less than the photosynthetic saturation intensity L of soybean leaves. Therefore, when the plant 200 is a soybean, it is possible to avoid saturation of the photosynthetic efficiency of the plant 200 and reduce the waste of light energy. On the other hand, in the comparative example, the photon flux density B was 5,700 μmol m -2 ・s -1 which was much greater than the photosynthetic saturation intensity L of soybean leaves. Therefore, when the plant 200 is a soybean, the photosynthetic efficiency of the plant 200 is saturated, and a large amount of light energy is wasted.

[0061] In Example 3, the photon flux G per unit volume in the growth space 30 is A×B×C / F=1217 μmol m -3 ・s -1 and the photosynthetic compensation photon flux M (200 μmol m) per unit volume in the growing space 30 at the soybean flowering stage and the middle of seed filling stage. -3 ・s -1Therefore, in Example 3, the growth of soybean leaves at the flowering stage and the middle stage of grain filling can be promoted. On the other hand, in the comparative example, G = A × B × C / F = 3651 μmol m -3 ・s -1 , which was three times that of G in Example 3. Therefore, in the comparative example as well, the growth of soybean leaves at the flowering stage and the middle stage of grain filling can be promoted in the growing space 30.

[0062] In both Example 3 and the comparative example, a large number of ventilation holes 35 each having a diameter of 3.5 mm were formed so that the temperature in the growth space 30 would be 50° C. or less.

[0063] In both Example 3 and the Comparative Example, soybeans were grown. The soybean variety was Hatsudarumada. In both Example 3 and the Comparative Example, a 12-hour period in which the LED chip 34 was illuminated and a 12-hour period in which the LED chip 34 was not illuminated were repeated. The number of soybean seeds harvested (number of beans harvested) is shown in FIG. 7.

[0064] The number of beans harvested in Example 3 was 217, which was fewer than the 394 in the Comparative Example. This is because the photon flux density B and the photon flux G per unit volume in the cultivation space 30 in the Comparative Example were three times those in Example 3. However, the number of beans harvested in the Comparative Example was not three times that of Example 3. The number of beans per energy (N / B) in Example 3 was 0.11, while that in the Comparative Example was 0.07. Therefore, in Example 3, soybeans could be grown with higher energy efficiency than in the Comparative Example.

[0065] Although the present invention has been shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that changes may be made in form and detail without departing from the scope of the invention as set forth in the appended claims. Such changes, modifications and alterations are intended to be included within the scope of the invention.

[0066] In the above embodiment, the plant 200 to be grown is a soybean, but the plant 200 is not limited to a soybean and may be any plant that can be grown using artificial light.

[0067] In the above embodiment, the substrate 33 of the light source panel 32 is a flat plate, but as shown in Fig. 8, the substrate 33 may be a corrugated plate. Fig. 8 is a vertical cross-sectional view of the light source panel 32, similar to Fig. 3. A corrugated plate can dissipate more heat generated by the LED chips 34 than a flat plate.

[0068] In the above embodiment, the light source panel 32 includes an LED chip 34 as a light output unit. However, the light source panel 32 may include other light output units. For example, as shown in FIG. 9 , the light source panel 32 of the modified embodiment includes output terminals 36 a of multiple optical fibers 36. The output terminals 36 a are fitted into holes formed in the light source panel 32 and output artificial light toward the left in the figure. The input terminals of these optical fibers 36 are connected to a light source device 37 that supplies artificial light to the optical fibers 36. The light source device 37 may be a laser or a sunlight collecting mechanism. Even if the light source device 37 is a sunlight collecting mechanism, the optical fiber 36 has a propagation loss depending on the wavelength, so the light output from the output terminal 36 a of the optical fiber 36 is artificial light, not natural light itself.

[0069] Aspects of the present invention are also described in the following numbered clauses: Clause 1. A plant growing device for growing plants with artificial light, comprising: a growing space for growing the plants; and at least one light source panel for irradiating the growing space with artificial light, wherein the light source panel has a substrate and a plurality of light output units arranged on the substrate at intervals, and wherein the photon flux density B (μmol m -2 ・s -1 ) is equal to or less than the photosynthetic saturation light intensity L of the leaves of the plant.

[0070] Clause 2. Photon flux G (μmol m) per unit volume in the growth space -3 ・s -1 ) is the light compensation point H (μmol・m -2 ・s -1 ) and the cumulative leaf area K (m 2 ・m -3) the photosynthetic compensation photon flux M (μmol m -3 ・s -1 ) larger than the width of the plant growing space. In this case, the growth of the plant leaves in the growing space can be promoted.

[0071] Clause 3. The light output area of ​​the artificial light per one light output unit is A (m 2 ・Individuals -1 ), the number of the light output units of the light source panel is C (units), and the volume of the growth space is F (m 3 ), the light compensation point H (μmol m -2 ・s -1 ) and the cumulative leaf area K (m 2 ・m -3 ) the photosynthetic compensation photon flux M (μmol m -3 ・s -1 ) satisfies the following formula: M<A×B×C / F In this case, the growth of plant leaves can be promoted in the cultivation space.

[0072] Clause 4. The photosynthetic saturation light intensity L of the leaves of the plant is 2000 μmol m -2 ・s -1 and the photosynthetic compensation photon flux M of the plant per unit volume in the growth space is 200 μmol m -3 ・s -1 4. The plant growing device according to claim 2 or 3, characterized in that, in this case, if the plant is a soybean, the photon flux density B of the artificial light emitted from each light output unit is 2000 μmol m -2 ・s -1 When the photon flux G per unit volume in the growing space is 200 μmol m or less, saturation of photosynthetic efficiency can be avoided and waste of light energy can be reduced. -3 ・s -1 or A × B × C / F > 200 μmol m -3 ・s -1This can promote the growth of soybean leaves in the growing space.

[0073] Clause 5. The plant cultivation device according to any one of clauses 1 to 4, wherein the at least one light source panel irradiates the plant with artificial light from the side. In this case, the photon flux G per unit volume can be made as uniform as possible between the upper and lower parts of the cultivation space, regardless of the plant's growth stage, particularly the state of leaf growth.

[0074] Clause 6. The plant growing device according to Clause 5, comprising two light source panels, the two light source panels facing each other, the growing space being interposed between the two light source panels, and the two light source panels irradiating the plant with artificial light from both sides. In this case, the photon flux G per unit volume can be made as uniform as possible on both sides of the plant.

[0075] Clause 7. The plant cultivation device according to Clause 6, wherein the distance between the two light source panels is smaller than the width of the light output area in which the light output unit of the light source panel corresponding to one plant is arranged. In this case, the small distance between the light source panels minimizes the spread and attenuation of artificial light from the light output unit, reducing energy loss. Furthermore, by reducing the distance between the light source panels in the plant cultivation device, it is possible to prevent the plant cultivation device from becoming larger.

[0076] Clause 8. The plant growing device according to any one of clauses 1 to 7, wherein the substrate of the light source panel has a plurality of ventilation holes formed therein, thereby preventing the plants from being overheated by heat dissipation from the light source panel.

[0077] Clause 9. The plant growing device according to any one of clauses 1 to 8, wherein the substrate of the light source panel is formed from a light-reflecting material. In this case, the utilization efficiency of artificial light in the growing space can be improved.

[0078] Clause 10. The plant growing device according to any one of clauses 1 to 9, wherein the light output unit is an LED chip.

[0079] Clause 11. The plant growing device according to any one of clauses 1 to 9, wherein the light output section is an output terminal of an optical fiber, and the input terminal of the optical fiber is connected to a light source device.

[0080] Clause 12. A plant cultivation method for cultivating plants using artificial light, comprising irradiating a cultivation space in which the plants are cultivated with artificial light from at least one light source panel having a plurality of light output units arranged at intervals on a substrate, and wherein the photon flux density B (μmol m -2 ・s -1 ) is equal to or less than the photosynthetic saturation light intensity L of the leaves of the plant.

[0081] Clause 13. Photon flux G (μmol m) per unit volume in the growth space -3 ・s -1 ) is the light compensation point H (μmol・m -2 ・s -1 ) and the cumulative leaf area K (m 2 ・m -3 ) the photosynthetic compensation photon flux M (μmol m -3 ・s -1 12. The plant cultivation method according to claim 11, wherein the height of the plant is greater than the height of the plant. In this case, the growth of the plant's leaves can be promoted in the cultivation space.

[0082] Clause 14. The light output area of ​​the artificial light per light output unit is A (m 2 ・Individuals -1 ), the number of the light output units of the light source panel is C (units), and the volume of the growth space is F (m 3 ), the light compensation point H (μmol m -2 ・s -1 ) and the cumulative leaf area K (m 2 ・m -3 ) the photosynthetic compensation photon flux M (μmol m -3 ・s -1Item 14. The plant growing method according to item 13, wherein M<A×B×C / F satisfies the following formula: M<A×B×C / F In this case, the growth of plant leaves can be promoted in the growing space.

[0083] 1... Plant growing device, 200... Plant, 30... Growing space, 32, 32A... Light source panel, 33... Substrate, 34... LED chip (light output section), 35... Ventilation hole, 36... Optical fiber, 36a... Output terminal, 37... Light source device

Claims

1. A plant growing device for growing plants using artificial light, comprising: a growing space for growing the plants; and at least one light source panel for irradiating the growing space with artificial light, the light source panel having a substrate and a plurality of light output units arranged at intervals on the substrate, and a photon flux density B (μmol m -2 ・s -1 ) is equal to or less than the photosynthetic saturation light intensity L of the leaves of the plant.

2. Photon flux G (μmol m -3 ・s -1 ) is the light compensation point H (μmol・m -2 ・s -1 ) and the cumulative leaf area K (m 2 ・m -3 ) the photosynthetic compensation photon flux M (μmol m -3 ・s -1 2. The plant-growing device according to claim 1, wherein the plant-growing device is larger than the base.

3. The optical output area of ​​the artificial light per one optical output unit is A (m 2 ・Individuals -1 ), the number of the light output units of the light source panel is C (units), and the volume of the growth space is F (m 3 ), the light compensation point H (μmol m -2 ・s -1 ) and the cumulative leaf area K (m 2 ・m -3 ) the photosynthetic compensation photon flux M (μmol m -3 ・s -1 3. The plant growing device according to claim 2, wherein M<A×B×C / F satisfies the following formula:

4. The photosynthetic saturation light intensity L of the leaves of the plant is 2000 μmol m -2 ・s -1 and the photosynthetic compensation photon flux M of the plant per unit volume in the growth space is 200 μmol m -3 ・s -1 The plant growing device according to claim 2 or 3 .

5. The plant growing device according to claim 1 or 2, characterized in that the at least one light source panel irradiates the plant with artificial light from a side.

6. The plant growing device according to claim 5, characterized in that it comprises two of the light source panels, the two light source panels facing each other, the growing space being interposed between the two light source panels, and the two light source panels irradiate the plant with artificial light from both sides.

7. The plant growing device according to claim 6, characterized in that the distance between the two light source panels is smaller than the width of the light output area in which the light output section of the light source panel corresponding to one of the plants is arranged.

8. The plant growing device according to claim 1 or 2, characterized in that a plurality of ventilation holes are formed in the substrate of the light source panel.

9. The plant growing device according to claim 1 or 2, characterized in that the light output unit is an LED chip.

10. A method for cultivating a plant using artificial light, comprising irradiating a cultivation space in which the plant is cultivated with artificial light from at least one light source panel having a plurality of light output units arranged at intervals on a substrate, and determining whether the photon flux density B (μmol m -2 ・s -1 ) is equal to or less than the photosynthetic saturation light intensity L of the leaves of the plant.

11. Photon flux G (μmol m -3 ・s -1 ) is the light compensation point H (μmol・m -2 ・s -1 ) and the cumulative leaf area K (m 2 ・m -3 ) the photosynthetic compensation photon flux M (μmol m -3 ・s -1 11. The plant growing method according to claim 10, wherein the plant growing speed is greater than 1000 rpm.

12. The optical output area of ​​the artificial light per one optical output unit is A (m 2 ・Individuals -1 ), the number of the light output units of the light source panel is C (units), and the volume of the growth space is F (m 3 ), the light compensation point H (μmol m -2 ・s -1 ) and the cumulative leaf area K (m 2 ・m -3 ) the photosynthetic compensation photon flux M (μmol m -3 ・s -1 12. The plant growing method according to claim 11, wherein M<A×B×C / F satisfies the following formula:

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