JPH0620396B2 - Artificial lighting method for growing plants - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an artificial lighting method for growing plants, which uses a high-pressure sodium lamp as an artificial light source.

2. Description of the Related Art Recently, plant factories have been gradually realized mainly for producing vegetables such as lettuce and salad vegetables. Plants are generally 65
It has the maximum photosynthetic sensitivity for light near 0 nm, and
It is sensitive to light of 0 to 495 nm, mainly for morphogenesis such as leaf coloring and shape. Therefore, as an artificial light source, a high-pressure sodium lamp with a large amount of spectral energy around 650 nm, usually 660 watts, is used for photosynthesis, and a large amount of spectral energy with a wavelength of 300 to 495 nm is usually used for forming a mercury lamp or metal halide lamp with a power of 250 watts. Is used for. These discharge lamps are installed by determining the lamp load and the arrangement of lighting fixtures so that the spectral energy distribution is optimum for plant growth. In general, separate lighting fixtures are used according to the type and size of the lamp, and mixed illumination is performed on the plant so that the illuminance distribution is substantially uniform. The cultivation room in the factory is air-conditioned to a room temperature of about 20 ° C, which is suitable for plant growth.

Problems to be Solved by the Invention A conventional artificial lighting method using mixed light illumination uses a separate discharge lamp, a lighting fixture, and a ballast,
The initial equipment cost and maintenance cost are high, and there is a difference in the luminous flux maintenance factor, the change rate of the spectral energy distribution during the life and the life time depending on the type of the lamp, so that the illuminance and the spectral energy distribution are always kept uniform. However, it was difficult to control the quality of the plants because the growth rate, color, and shape of the plants varied. In addition, the electricity cost for lighting occupies a very high proportion of the running cost in the plant factory, which has been a major obstacle to increasing the product cost and widely promoting cultivation by the factory system.

Means for Solving the Problems The present invention is an artificial lighting method for plant cultivation, alternating-current lighting is performed so that the light output repeats high and low every half cycle, and the spectral energy distribution at lighting is spectral between wavelengths of 300 to 720 nm. A high-pressure sodium lamp is used in which the ratio of the amount of spectral energy between wavelengths of 300 to 495 nm with respect to the total energy is 6.0% or more and 20% or less. It is also preferable that the light output per half cycle when the lamp is turned on is high a,
When the low is b, the ratio of b to a is 60% or less.

The method according to the present invention has a large flickering and discomfort to the human eye as compared with the conventional general method, but it does not significantly reduce the growth rate of plants. In other words, by turning on the high-pressure sodium lamp so that the lamp load repeats high and low every half cycle, the light and dark periods are created in accordance with the metabolic characteristics of photosynthesis of the plant, and the plant is efficiently grown, and a significant saving is achieved. In addition to power consumption, it is possible to have a function for morphology formation by utilizing increase in spectral energy in the short wavelength region.

Examples Hereinafter, details of the present invention will be described with reference to the illustrated examples.

FIG. 1 is a longitudinal sectional view of an arc tube of a 360 watt high pressure sodium lamp. The arc tube 1 is an envelope 2 made of translucent alumina having an inner diameter of 8 mm and a length of 115 mm, and an electric introducer 4,4 'made of niobium having electrodes 3,3' attached by welding to both ends of the envelope 2. The sealing bodies 5 and 5'are hermetically sealed. The arc tube 1 is filled with sodium, mercury, and a rare gas for starting (not shown).

FIG. 2 is a schematic configuration diagram of the lamp lighting circuit. Arc tube 1
The 360 watt high pressure sodium lamp 7 mounted on the glass outer bulb 6 is connected to the 200 V commercial power source 13 via the ballast 8.
It is connected to the. The ballast 8 is composed of chi-yoke coils 9 and 10,
It is composed of a rectifying element 11 and a switch 12. In the circuit configured in this way, first, a commercial power source of 200V
When 13 is applied, an electric potential is applied to the high-pressure sodium lamp 7 via the chioke coil 9 and the switch 12, and the high-pressure sodium lamp 7 is started. The switch 12 is closed at the time of starting, and is provided at the time of starting so as to prevent an overcurrent corresponding to a direct current from flowing through the chain yoke coil 9 when the lamp voltage is low. Next, the high-pressure sodium lamp 7 is started, and after it has been stable for about 2 minutes, the switch 12 is opened, so that the rectifying element is at one of the alternating potentials.
11, a circuit composed of the high-pressure sodium lamp 7 and the cheek yoke coil 9 is formed (hereinafter, referred to as a positive direction), and in the case of the other reverse potential, a circuit of the chioke coil 9, the high-pressure sodium lamp 7 and the chew yoke coil 10 is formed (hereinafter, the reverse direction). Direction). This means that the impedance of the yoke coil in the ballast 8 changes depending on the direction of the AC cycle, and the lamp load and the light output level are switched every half cycle. By lighting the high-pressure sodium lamp 7 by such a method, a change occurs in the spectral energy distribution, unlike the conventional method in which only one chain yoke coil is used for lighting. Third example of change in light output at that time
Shown in the figure. This is due to the same lamp, the solid line is the conventional method, ie when the switch 12 is closed, and the broken line is the method of the present invention, ie the switch 12 is open. The peak value a of the optical output in the positive direction is slightly lower than that of the conventional method. This is because the method according to the present invention reduces the load on the arc tube and changes the spectral energy distribution. Further, the peak value b of the light output in the opposite direction can be arbitrarily changed by adjusting the lamp output by changing the impedance of the cheek yoke coil 10. Table 1 uses an unsaturated vapor pressure type high pressure sodium lamp that is designed to evaporate all of the enclosed amount.
The test results when the impedance of 10 is changed are shown.

Test No. Reference numeral 1 is a case where the rectifying element 11 and the chain yoke coil 10 according to the conventional method are not provided, and the lamp power is 660 W. Test No. 2 to 6 are gradually chicoke coils
Increasing the impedance of 10 reduces the lamp power and the light output peak ratio b / a. Further, as the direct current component increases, sodium and mercury vapor are separated in the arc tube, and mercury emission can be seen. as a result,
The amount of spectral energy between the wavelengths of 300 to 495 nm increases.
This is a test No. It will appear noticeably after 3. However, if the impedance of the chioke coil 10 is too high, the arc discharge of the arc tube cannot be maintained, and the test N
o. 6 and 7 will be turned upside down and it will disappear.

In light of the above results, for the high pressure sodium lamp in which the light peak value a in the positive direction was made the same as the conventional lamp power of 660 W and the lamp power was set to approximately 360 watts, the ratio of sodium and mercury sealed in the arc tube was changed. , The relationship between its spectral energy distribution and vegetable growth was investigated. The results are shown in Table 2. This result uses salad vegetables as vegetables.

From Table 2, when only conventional high-pressure sodium lamp with a lamp power of 660 W is used for illumination, the weight of the plant tends to be large, but the water content is high, and the leaves are yellow-green and too soft, resulting in poor commercial value. This is a test No. The same tendency is observed for No. 1. Test No. When the amount of sodium is reduced from 2 to 5 and the mercury vapor pressure is increased, the weight of vegetables gradually decreases, but the green color becomes darker, the water content is low, and the quality is the same as that of closed dew cultivation. You can get This result is remarkable when the ratio of the spectral energy in the short wavelength region of 300 to 495 nm to the total of the spectral energy between wavelengths of 300 to 720 nm is 6.0% or more. The optimum conditions are Test No. The vegetable with the highest spectral energy distribution of 7.2% is the best. However, the test No. As shown in 5, the spectral energy ratio is
At 20%, the weight loss of vegetables becomes large and hard, so if the spectral energy ratio exceeds 20%, the commercial value will be lost and the power saving effect will also be reduced. Therefore 300 ~
300 to 49 for the total spectral energy between 720 nm wavelengths
The ratio of the amount of spectral energy between wavelengths of 5 nm is 6.0% or more, 20
Must be less than or equal to%. In addition, from Table 1, b / a must be 60% or less in order to increase the spectral energy ratio in the short wavelength region of 300 to 495 nm and bring out a large power saving effect.

As described above, in the method according to the present invention, compared with the conventional method of mixed lighting of a 660 watt high pressure sodium lamp and a 250 watt mercury lamp or metal halide lamp, it is possible to illuminate only the high pressure sodium lamp and reduce the weight loss of the plant. Even if it is taken into consideration, it is possible to significantly reduce the power for lighting and to eliminate the need for equipment for form formation. In the lighting method according to the present invention, the current flowing in the positive direction is almost the same as that in the conventional method, and the current flowing in the positive direction or less flows in the opposite direction. Therefore, there is no adverse effect on the electrodes of the arc tube, and there is almost no problem in the lamp life. In addition, since a current is flowing in the opposite direction, it is easy to maintain discharge, and a high-voltage pulse generator, for example, is used for instant relighting such as a half-wave rectification lighting method or a pulse lighting method such as a flash lamp. Also, a reliable lighting system can be implemented with a simple lighting circuit without requiring a special light source suitable for these.

In the above examples, salad vegetables were explained as a vegetable, but lettuce was also tested and similar results were obtained. Further, the high pressure sodium lamp in which sodium, mercury, and a rare gas for starting are enclosed in the arc tube has been described, but a high pressure sodium lamp in which a short-wavelength emitting metal such as indium is enclosed may be used.

EFFECTS OF THE INVENTION As described in detail above, according to the present invention, a combination of a relatively simple lighting system and a high-pressure sodium lamp can significantly reduce the power cost for lighting and the facility cost and stabilize the quality of plants. In addition, by reducing the lamp power, heat release from the lamp and ballast can be reduced, the air conditioning cost in the cultivation room can be reduced, and the lamp, ballast and lighting fixture can be made compact. Further, the lamp lighting method used in the method of the present invention has almost no adverse effect on the life of the lamp and the like as compared with the lighting method of general lighting, and therefore, there is an advantage that the lamp for general lighting can be used as it is or with a slight change in specifications.

[Brief description of drawings]

FIG. 1 is a sectional view of an arc tube of a high-pressure sodium lamp used in the method of the present invention, FIG. 2 is a circuit diagram showing an example of a lamp lighting circuit used in the method of the present invention, and FIG. 3 is a conventional light output by the method of the present invention. It is the characteristic view represented in comparison with the method. 1 ... Arc tube, 7 ... High-pressure sodium lamp, 8 ... Ballast, 9, 10 ... Chiyoke coil, 11 ... Rectifying element, 12
...... Switch, 13 …… Commercial power supply

Claims (2)

[Claims] 1. An alternating current lighting is performed so that the light output level is repeated every half cycle, and the spectral energy distribution at the time of lighting is 300-.
300 to 300 for the total sum of spectral energy between wavelengths of 720 nm
Ratio of spectral energy between wavelengths of 495 nm is 6.0% or more
An artificial lighting method for growing plants, which comprises using a high-pressure sodium lamp with a concentration of 20% or less. 2. A ratio of b to a is 60% or less, where a is a high and b is a low light output repeated every half cycle. 1) An artificial lighting method for growing plants according to the item 1).