JP6751827B1 - Fungal growth suppression method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent fungal growth in an indoor environment and an air conditioning system. SOLUTION: In the fungus suppression mode S7A included in the method of suppressing fungal growth in a room such as a cultivation room or a hospital room in a plant factory and an air conditioning system associated therewith, the room is lowered by dehumidifying the air conditioning system. The indoor dehumidification step S11 for maintaining the humidity state and the simultaneous sterilization confirmation step S13 for confirming whether or not the air conditioning system also needs to be sterilized are included. If the judgment is positive in the simultaneous sterilization confirmation step S13, the air conditioning system is switched from the dehumidifying operation to the ventilation operation, dry air in the room is introduced into the path in the air conditioning system, and the air is circulated between the air conditioning system and the room. The system comprises a sterilization step S15A, characterized in that the fungus suppression mode S7A is completed after the lapse of the second sterilization period. When the present invention is applied to a plant factory, it is preferable that the start determination of the vacuum suppression mode S7A includes a step of confirming additional conditions in consideration of cultivation efficiency and prevention of deterioration of plant taste. [Selection diagram] Fig. 3

Description

The present invention relates to a method of suppressing fungal growth in an air conditioning system, for example, a method of suppressing fungal growth in a cultivation environment and an air conditioning system while maintaining plant cultivation efficiency in an artificial light type plant factory. Is.

(Fungal growth in air conditioning system)
The air-conditioning system is installed in order to adjust the environment such as a residence, a large facility of a hospital or a food factory, or an artificial light type plant factory described later to a desired condition. However, there is a problem that fungi grow and multiply on the surface of the heat exchanger in the air conditioning system, which adversely affects human health and the quality of food and plants.

(Problem 1: Fungal growth on the surface of the heat exchanger, spore contamination in the air-conditioned environment)
Specifically, the surface of the temperature control heat exchanger always has a high relative humidity in the air conditioning system during the cooling operation or the dehumidifying operation. Even if a heating source is provided on the leeward side and the environmental air can be suppressed to a low relative humidity, it does not warm the surface of the heat exchanger described above (if it is warmed, it does not perform the dehumidifying function). The surface of the heat exchanger constantly remains high relative humidity. As a result, the surface of the heat exchanger becomes a hotbed for fungal growth (see FIG. 7) and promotes spore contamination into the environment. In the case of heating / blowing operation, water condensation does not occur on the surface of the heat exchanger and the relative humidity does not rise, so that fungal growth and spore contamination do not occur.

(Problem 2: Problem in sterilization treatment on the surface of heat exchanger)
Now, consider introducing dry air into the air conditioning system to sterilize the surface of the heat exchanger. The dry air to be introduced may be prepared by any method, but it is easiest to introduce the environmental air of the air-conditioned room. However, if environmental air is used as the dry air, it will be necessary to switch the air conditioning system to ventilation operation (rather than cooling operation).

This is because it is rational to use the blower of the air conditioning system itself as it is, and in order to dry the environmental air while keeping the surface temperature of the heat exchanger above the dew point temperature, the cooling operation must be stopped. Because it must be. Therefore, during the period of sterilization, the air conditioning system cannot control the temperature of the environment (stopping the temperature control function of the air-conditioned room).

(Explanation of prior art)
For example, Patent Document 1 is a prior art for suppressing fungal growth in an air conditioning system. In Patent Document 1, the temperature and humidity are detected to obtain an evaluation value for the occurrence of mold and the like, and when this value exceeds the reference value, the air conditioning system is switched to the ventilation operation and carried out for a predetermined time. After that, the ozone generator is operated to perform sterilization treatment. Here, the strong oxidizing action of ozone is useful, and it is industrially applied to various applications such as purification / sterilization, decolorization, and removal of organic substances. In Patent Document 1, it is considered that ozone can be used for sterilization in a short time according to the oxidizing power, and the air conditioning stop period has been successfully suppressed.

(Adverse effects of using ozone)
However, the too strong oxidizing power of ozone also causes difficulty in handling. Specifically, it is necessary to consider imparting corrosion resistance to parts that come into contact with ozone and materials that may come into contact with ozone. Furthermore, the adverse effects of ozone on living organisms have been clarified. Humans (humans) perceive odor at about 0.01 to 0.02 ppm, irritate the nose and throat from about 0.1 ppm, decrease their eyesight at about 0.2 to 0.5 ppm, and feel tired at about 1 to 2 ppm. , Headache and changes in respiratory function, dyspnea at 5-10 ppm, increased pulse, and life-threatening at 50 ppm or higher. An air conditioning system that is closely related to the living environment is required to have a safer sterilization technology that can be sterilized in a short time.

Focusing on the viewpoint of safety, there is a prior art such as Patent Document 2 regarding the sterilization technique of the air conditioning system. Patent Document 2 discloses that after a cooling operation or a dehumidifying operation, a draining operation is performed to remove most of the water inside the air conditioning system, and then a heating operation (drying operation) is performed.

(Deterioration of thermal environment due to switching from cooling operation to heating operation)
However, in contrast to an environment that originally requires a cooling operation, performing a heating operation even for a short time leads to deterioration of the thermal environment. Even when only the drying effect of the blower operation is expected instead of the heating operation, the temperature rise due to the air heating by the blower compression and the exhaust heat of the motor occurs, and the thermal environment deteriorates due to the length of the cooling load untreated period. obtain.

To summarize the problems described so far, the sterilization process of the air conditioning system requires the simultaneous achievement of the following two requirements.
(1) The medium for fungal sterilization has low corrosiveness to metals and is safe for the human body. (2) It does not deteriorate the thermal environment of the air-conditioned room and can be processed by blowing air for a short time.

(Adverse effects on products in the environment)
By the way, the air conditioning system of the artificial light type plant factory is basically always in cooling operation. The surface of the temperature control heat exchanger is always high in relative humidity, fungi grow, and spores generated in the air conditioning system continuously enter the plant cultivation environment and pollute the environment. To make matters worse, high relative humidity is always maintained not only in the air conditioning system but also in the factory due to the transpiration of plants and the evaporation of the cultivation culture solution that circulates inside the factory environment. Since fungi prefer a high relative humidity environment, they are not satisfied in the air conditioning system and their growth and environmental pollution progress in the factory.

In addition, since micro-insects such as booklices mainly feed on fungi, the growth of fungi causes the invasion and increase of insects in the factory, which in turn poses a risk of insect contamination in products. Similar problems can occur not only in plant factories but also in food processing factories.

Such a problem seems to be solved by simply lowering the relative humidity in the factory. However, when it is applied to a plant factory, a decrease in plant cultivation efficiency and a deterioration in taste become problems.

(Lower plant cultivation efficiency)
Plants in dry air have a poor growth rate. For example, in the light period when photosynthesis is performed, the pores are closed to retain water in the body. When the stomata are closed, it becomes difficult to take in carbon dioxide in the air, which inhibits the photosynthetic reaction of plants. The low humidity environment of the plant factory in the light period inhibits the photosynthetic reaction of plants and deteriorates the growth rate. On the other hand, in a low humidity environment in the dark period, the growth rate is deteriorated by a mechanism different from this. Specifically, when the humidity becomes low in the dark period, the amount of evapotranspiration from the cuticle layer on the leaf surface increases, the basal metabolic rate such as respiration increases, and as a result, the amount of leaf / stem elongation decreases.

(Deterioration of plant taste)
In addition, among the tastes of plants, bitterness and harshness are determined by the concentration of nitrate nitrogen, and it is said that if this concentration is low, the bitterness and harshness are diminished and the plant feels relatively sweet. It has been found that in plants whose photosynthesis is inhibited in a low relative humidity environment, the concentration of nitrate nitrogen increases, resulting in plants with strong bitterness and harshness. It has also been pointed out that high nitrate nitrogen concentration has an adverse effect on the human body.

(Prior art for cultivation of low nitrate nitrogen vegetables)
Incidentally, Patent Document 3 is known as a cultivation technique for low nitrate nitrogen vegetables. This is a technique of consuming nitrate nitrogen by photosynthesis and at the same time stopping the supply of nitrate nitrogen as fertilizer. After growing vegetables with the culture solution and cultivating them for a certain period of time, the supply of the culture solution is stopped and collected prior to the harvest, and water is supplied instead. When photosynthesis is performed here, the nitrate nitrogen accumulated in the plant body is consumed, and the nitrate nitrogen concentration decreases. This method requires two liquid utilization systems, culture medium and water. It must be said that there is a problem in constructing this system if the difficulty, complexity, cost, etc. are taken into consideration, and it is necessary to keep the nitrate nitrogen concentration low by another simpler method.

As described above, in the artificial light type plant factory, from the viewpoint of safety and management, we want to keep the relative humidity in the environment low in order to reduce the risk of fungal growth and the risk of insect contamination. However, if the relative humidity is easily lowered, there is a conflicting problem that the cultivation efficiency of the plant as a product is lowered, the taste is deteriorated, and the health of the person who ingests the product is concerned.

Japanese Patent No. 5180489 Japanese Unexamined Patent Publication No. 11-21184 Japanese Unexamined Patent Publication No. 2008-061570 Japanese Patent No. 2710903 Japanese Patent No. 3510309

(Purpose of the present invention)
The present invention has been made in view of such circumstances, and provides a method for safely suppressing fungal growth on the surface of a heat exchanger in an air conditioning system without significantly deteriorating the thermal environment of the air-conditioned room. The purpose is.

Another object of the present invention is to prevent fungal growth in a plant factory while efficiently growing plants.

Another object of the present invention is to prevent the growth of fungi in a plant factory while preventing the deterioration of taste.

After diligent studies, the present inventors have found a device and a method for brilliantly solving the above-mentioned problems, and have completed the present invention.

That is, the present invention has, for example, the following configurations and features.
(Aspect 1)
It is a method of suppressing the growth of fungi in the room where the air conditioning system is installed.
The indoor measurement process for measuring the temperature and humidity in the room, and
An index calculation step for calculating the fungal growth index from the measured temperature and humidity, and the correlation between the fungal growth rate acquired in advance and the temperature and humidity.
An index confirmation step for confirming that the fungal growth index has exceeded a predetermined threshold value, and
A mode start determination step of starting the fungus suppression mode after confirming that the threshold value has been exceeded in the index confirmation step, and
Including
In the fungal suppression mode,
An indoor dehumidifying step of performing a dehumidifying operation of the air conditioning system to maintain the room in a low humidity state, and
Simultaneous sterilization confirmation process to confirm whether sterilization is necessary for the air conditioning system,
Including and
If the determination is negative in the simultaneous sterilization confirmation step, the fungal suppression mode is completed after the lapse of the first sterilization period.
If the determination is positive in the simultaneous sterilization confirmation step, the air conditioning system is switched from the dehumidifying operation to the blowing operation, dry air in the room is introduced into the path in the air conditioning system, and the air conditioning system and the air conditioning system are described. The fungus suppression mode is completed after the lapse of the second sterilization period, which is a period longer than the first sterilization period, and includes a system sterilization step of circulating between the room and the room .
The room is a cultivation room for cultivating plants in an artificial light type plant factory.
A germination confirmation step for confirming that a predetermined spore germination period has elapsed according to the environment in the cultivation room, and
The first additional confirmation step for confirming that the cultivation efficiency maintenance period suitable for the plant has passed, and
Including
The mode start determination step is characterized in that the fungus suppression mode is started after a positive result is obtained in all of the germination confirmation step and the first additional confirmation step in addition to the index confirmation step. A method for suppressing fungal growth.
(Aspect 2)
A second additional confirmation step of confirming whether or not the cultivation room is in a dark period and whether or not there is a sufficient period remaining to execute the fungal suppression mode in the dark period.
Including
In the mode start determination step, in addition to the index confirmation step, the fungus suppression is performed after a positive result is obtained in all of the germination confirmation step, the first additional confirmation step, and the second additional confirmation step. The method for suppressing fungal growth according to aspect 1 , which comprises initiating a mode .
(Aspect 3)
The system sterilization step includes an irradiation step of irradiating the heat exchanger with ultraviolet rays from an ultraviolet irradiation device installed near the heat exchanger in the air conditioning system.
The method for suppressing fungal growth according to the first or second aspect, which further comprises.
(Aspect 4)
A plurality of the air conditioning systems are installed in the room,
If the determination is positive in the simultaneous sterilization confirmation step, the air conditioning system is assigned to one that executes the system sterilization step first and one that executes the system sterilization step later.
While the earlier air conditioning system performs the system sterilization step, the subsequent air conditioning system maintains or enhances the dehumidifying operation to maintain the low humidity state in the room.
After executing the system sterilization step on the above-mentioned air conditioning system, the above-mentioned air conditioning system returns from the blowing operation to the original dehumidifying operation, and the subsequent air-conditioning system starts the system sterilization step. The method for suppressing fungal growth according to any one of the characteristics 1 to 3 .

Here, the "humidity" referred to in the present invention is preferably relative humidity, but is not limited to this, and any known index indicating the amount of water contained in the air, such as absolute humidity, saturation, and partial pressure of water vapor, can be used. Can be used. Further, in addition to the known index, the "humidity" includes a thermal environment index that can be derived by using the amount of water in the air, a newly defined index, and the like.

The above-mentioned fungal suppression mode in the fungal growth suppression method of the present invention can be suitably used for suppressing fungal growth in a plant factory, but in addition to this, it is associated with a processing room of a food factory, a hospital room of a hospital, and the like. It can be used to control fungal growth in air conditioning systems.

Further, according to the method of the present invention, as the medium for the sterilization treatment in the air conditioning system, only dry air in the cultivation room or ultraviolet rays emitted from a light source such as an LED or a lamp other than the dry air is used. It is less corrosive to metals and safe for the human body. Further, during the execution of the present invention, only the air conditioning system that manages the indoor environment is switched between the dehumidifying operation and the blowing operation, and the processing can be performed in a short time without deteriorating the thermal environment of the air-conditioned room. ..

According to the method of the present invention, the above-mentioned fungal suppression mode is included, and the start condition of this mode is determined in consideration of not only the fungal growth index but also the parameters related to plant cultivation. Therefore, plant cultivation is performed in a plant factory. It is possible to realize sterilization (fungal suppression) in the cultivation room and the air conditioning system while maintaining efficiency.

According to a preferred embodiment of the present invention, since the above-mentioned fungal suppression mode is executed only in the dark period, the bitterness and deterioration of taste of the cultivated plant can be reduced.

(A) A schematic diagram of an artificial light type plant factory incorporating a plurality of or (b) a single air conditioning system is shown. The flowchart explaining the whole process of the fungus suppression method of this invention is shown. The flowchart explaining each step of the 1st fungus suppression mode of this invention is shown. The flowchart explaining each step of the 2nd fungus suppression mode of this invention is shown. It is a figure which compared the amount of nitrate nitrogen in lettuce when lettuce was cultivated in a low humidity environment in a dark period or a light period. It is a graph which showed the time-dependent change of the relative humidity in the natural world, and the time-dependent change of the relative humidity in the plant factory which carried out the method of this invention. It is an image which showed the surface of the heat exchanger where the fungus grew.

Hereinafter, the technical contents of the present invention will be described based on the following specific embodiments with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

(Artificial light type plant factory)
The plant production system can be roughly divided into an open system (fields, etc.), a semi-closed system (horticultural facilities, etc.), and a closed system (artificial light type plant factory, etc.). The highest yield of these is the closed artificial light type plant factory.

As the name suggests, artificial light type plant factories grow plants using artificial light. It is common to periodically create a light period (that is, a period in which a plant is irradiated with light to promote photosynthesis) and a dark period (that is, a period in which the plant is extinguished and the plant breathes) by artificial light. It is considered that the cycle between the light period and the dark period does not need to be 24 hours, and the light / dark timing is optimized in consideration of electricity charges and the like.

Lighting equipment that produces artificial light becomes a heat source inside the factory. For this reason, in a closed artificial light type plant factory, forced cooling to the indoor environment is required throughout the year. Internal temperature control is usually carried out by an air conditioning system.

FIG. 1 shows a schematic view of an artificial light type plant factory 1 (1A, 1B) (hereinafter, simply referred to as a “plant factory”) in which an air conditioning system is incorporated. Here, in the plant factory 1A shown in FIG. 1A, a plurality of (four in the figure) air conditioning systems 11, 12, 13, and 14 are incorporated in one cultivation room 2. On the other hand, in the plant factory 1B shown in FIG. 1B, only a single air conditioning system 11 is incorporated.

A nutrient solution cultivation device 3 is installed in the cultivation room 2. A liquid (culture liquid) 31 in which fertilizer necessary for growing the plant 4 is dissolved in water is accumulated in the container 32, and the culture liquid 31 is sent to the supply pipe 33 by the pump P.

The cultivation shelves 35 for cultivating the plant 4 are usually stacked in a plurality of stages in the height direction in order to effectively utilize the space of the cultivation room 2. Since a large number of plants 4 are usually placed in series in the horizontal direction on each cultivation shelf 35, when the culture solution 31 introduced from the supply pipe 33 installed on one side flows in the cultivation shelf 35 in the longitudinal direction. Is given to each plant 4. A structure of a method (that is, a circulation type) in which a discharge pipe 34 is installed on the other side of the cultivation shelf 35 and the culture solution 31 is returned to the original container 32 so that the fresh culture solution 31 is always supplied to the plant 4. May be adopted.

Further, on the upper part of the cultivation shelf 35, a light source 36 for irradiating the plant 4 with artificial light such as an LED or a lamp is installed in series in the longitudinal direction (horizontal direction) of the cultivation shelf 35. By controlling the light source 36 to repeatedly turn on and off for a certain period of time, a light period and a dark period for growing the plant 4 in the cultivation room 2 are periodically created.

(Method for suppressing fungal growth of the present invention)
Next, the method for suppressing fungal growth of the present invention will be described in detail with reference to FIGS. 1 to 4. This method is divided into a fungus suppression mode (hereinafter, also simply referred to as "suppression mode") and a plant cultivation mode (hereinafter, also simply referred to as "cultivation mode"), and the environmental conditions of the plant factory 1 are monitored at any time. While switching each mode, it is performed.

(Actual measurement of indoor temperature and humidity)
First, the temperature and humidity (for example, relative humidity) of the cultivation room 2 are measured (step S1, indoor measurement step). At this point, it should be noted that the mode is set to the relatively high humidity plant cultivation mode, not the relatively low humidity fungus suppression mode described later.

(Calculation of fungal growth index)
Based on the value actually measured from step S1, an index (hereinafter, referred to as “fungal growth index”) I indicating the risk of fungal growth is calculated (step S2, index calculation step). As a method for calculating the fungal growth index I, for example, as disclosed in Patent Document 4, a database (template) obtained by investigating the correlation between the growth rate of fungi and temperature and humidity. , Or a mathematical formula as shown in Patent Document 5, or the result obtained by an independent search by the same method may be used.

It should also be noted that the steps S1 and S2 described above are basically continuously executed (measured and calculated) on a regular basis (for example, every minute) until the method of the present invention is completed.

(Confirmation of progress of spore germination period)
Next, it is determined whether or not the spore germination period has passed (step S3, germination confirmation step). If it has not passed, the process waits while maintaining the high relative humidity state (cultivation mode) (the loop of steps S1 to S3 is repeated). This is because ungerminated fungal spores do not die even at low humidity, so it is necessary to germinate the fungal spores first. As described above, in the present invention, the cultivation room 2 is maintained in a normal cultivation environment (high relative humidity), and a period for promoting spore germination (spore germination period) is secured. The germination period of spores should be changed depending on the conditions of the target environment (for example, the humidity conditions in which molds easily inhabit and grow), but for example, it may be set to 7 to 10 days.

(Judgment routine to suppress mode)
On the other hand, if the passage of the spore germination period can be confirmed, the next step is to determine whether or not to enter the suppression mode. In a preferred embodiment of the present invention (application to the plant factory 1), it is characteristic that a plurality of consecutive conditions described later must be satisfied (cleared) in order to permit entering the suppression mode. ..

(Condition 1: Did the fungal growth index exceed the threshold)?
First, as one condition of this determination routine, a threshold value (for example, 5) is set for the above-mentioned fungal growth index I, and whether the above-mentioned index I exceeds this threshold value (whether the fungal growth level has reached the dangerous range). ) Whether or not (step S4, index confirmation step). If the threshold value is not exceeded, the cultivation mode is maintained (that is, the process returns to step S1 and the loop of steps S1 to S4 is repeated).

On the other hand, if it is determined that the above-mentioned index I exceeds the threshold value, the process proceeds to the next stage. However, if it is determined that the fungal growth level has reached the risk level and the mode is immediately shifted to the suppression mode based on this judgment alone, as described above, the relative humidity is lowered and the sterilization in the cultivation room 2 is promoted. However, there is a risk that the cultivation efficiency of the commercial plant 4 will decrease and the taste will deteriorate.

(Condition 2: Has the cultivation efficiency maintenance period passed?)
Therefore, in the present invention, it is also determined whether or not the transition to the suppression mode satisfies yet another condition (condition 2). Specifically, the plant 4 continues to grow even after entering the stricter suppression mode of the growing environment, and the plant 4 has a certain size and maturity before entering the suppression mode so that a sufficient taste and sugar content can be obtained. The period required for growing the plants (referred to as the "cultivation efficiency maintenance period") is determined in advance for each cultivation target (for example, 9 to 12 days in the case of lettuce).

Then, after the step S4, as a condition 2, it is determined whether or not the above-mentioned cultivation efficiency maintenance period has passed (step S5, first additional confirmation step). If the cultivation efficiency maintenance period has passed, the process moves to the next stage. On the other hand, if it has not passed, it waits while maintaining the state of high relative humidity (cultivation mode) (that is, returns to step S1 and repeats steps S1 to S5).

(Condition 3: Is it in the dark period?)
In addition, in the present invention, it is preferable to additionally determine yet another condition (condition 3). Specifically, it is determined whether or not the plant factory 1 has entered the dark period, and whether or not there is sufficient remaining time to perform the suppression mode described later by the end of the dark period (step S6, first). 2 additional confirmation process). Depending on the operation method of the plant factory 1, there are cases where the dark period is set to a short period such as one hour, or the dark period is not provided in the first place. In such a case, since the deterioration of taste cannot be prevented by this method, it is not necessary to determine the condition of whether or not the dark period has been entered.

By the operation of this step S6, if the light period when the photosynthesis of the plant 4 is active is assigned to the cultivation mode and the dark period when the photosynthesis is inactive is surely applied to the fungus suppression mode, the deterioration of the taste of the plant 4 is minimized. While suppressing, fungal growth in the environment can also be suppressed. In other words, when the fungus suppression mode (low humidity environment) is entered during the light period, the plant 4 is grown in a state where its photosynthesis is inhibited, and the nitrate nitrogen concentration rises in the body of the plant 4, causing bitterness. It is easy to grow strong plants. Therefore, in the environment of the plant factory 1, it can be said that it is better to bring the fungal suppression mode (low humidity environment) of the present invention during the dark period instead of the light period.

(Transition to fungal suppression mode)
In the method of the present invention, when a positive determination result is obtained in all of the above steps S3 to S6, the fungus suppression mode described later is finally started (step S7, mode start determination step). On the other hand, if a negative determination result is obtained, the process waits until the start of the next dark period (steps S1 to S6 are repeated).

(1st fungus suppression mode: when two or more air conditioning systems are installed in the plant factory)
As an example, a fungus growth suppression method (first fungus suppression mode) S7A when a plurality of air conditioning systems are installed in the plant factory 1 (1A) as shown in FIG. 1A will be described. For convenience of explanation, when the total number of installations is N, they are referred to as the first, second, third, fourth ... Nth air conditioning systems 11, 12, 13, 14 (4 in FIG. 1A). To do. FIG. 3 shows a flowchart of the first fungus suppression mode S7A when a plurality of air conditioning systems 11, 12, 13, and 14 are present.

When the first fungus suppression mode S7A is finally entered after the determination in the above step S6, first, the relative temperature target value is set to a low humidity value (for example, 40 to 60% RH) in the air conditioning systems 11, 12, 13, and 14. Then, the inside of the cultivation room 2 is changed to a low humidity state (step S11, indoor dehumidification step). That is, the air conditioning systems 11 to 14 are dehumidified. As a result, the fungus can be killed or the growth of the fungus can be prevented in the cultivation room 2 in which the plant 4 is placed.

Next, after step S11, it is determined whether or not the temperature and humidity in the cultivation room 2 have reached the target values (step S12). Here, if a positive determination result is obtained, it is determined that sufficiently dry air A can be generated in the cultivation room 2.

(Presence or absence of fungal suppression (simultaneous sterilization treatment) in the air conditioning system)
Then, not only the environment in the cultivation room 2 which is the cultivation space, but also the air flow paths 11a to 11d, 12a to 12d, 13a to 13d, 14a to 14d in the air conditioning systems 11, 12, 13, 14 (particularly, the heat exchanger). It is determined whether or not the fungal suppression (sterilization) treatment is necessary for the surfaces of 11d, 12d, 13d, and 14d (step S13, simultaneous sterilization confirmation step). For example, it may be determined by inputting the presence or absence of a request from an operator (not shown), the cumulative usage time of the air conditioning systems 11, 12, 13 and 14, the elapsed time from the previous sterilization treatment, and the heat exchanger 11d. , 12d, 13d, 14d may or may not be necessary based on parameters such as the amount of fungi adhering to the surface (for example, the result of observation with a camera (not shown)).

Here, in FIG. 1A, reference numerals 11a, 12a, 13a, 14a, reference numerals 11b, 12b, 13b, 14b, and reference numerals 11c, 12c, 13c, 14c are air suctions in the systems 11 to 14, respectively. The air duct, the air outlet air duct, and the air flow space inside the main body are shown.

(When sterilization treatment is unnecessary)
If it is determined in step S13 that the sterilization treatment in the air conditioning systems 11, 12, 13, and 14 is unnecessary, the cultivation room 2 is lowered for a predetermined period (first sterilization period). It is maintained in a humid environment (step S14). Here, the first sterilization period is preferably about 10 to 12 hours each time. If it is determined that the first sterilization period has passed, the first fungal suppression mode (step S7A) is completed. After that, it is determined whether or not the growth degree of the plant 4 is sufficient (see step S8, growth degree confirmation step, FIG. 2). If the result is positive, the method of the present invention is completed. On the other hand, if the result is negative, the process returns to the cultivation mode (that is, step S1) again.

(When sterilization treatment is required)
On the other hand, a method of simultaneously performing the sterilization treatment not only on the cultivation room 2 but also on the air conditioning systems 11, 12, 13 and 14 will be described in detail below. For sterilization of the air conditioning systems 11, 12, 13, and 14, it is rational to introduce the dry air A in the cultivation room 2 into the route. For example, as shown in FIG. 1A, when a plurality of air conditioning systems 11, 12, 13, and 14 exist, one of the air conditioning systems (for example, 11) is changed from the dehumidifying operation to the blowing operation, and the system is changed. Dry air A is introduced into the path 11 (for example, 11a) and circulated so as to pass through the heat exchanger 11d and return to the cultivation room 2 (step S15A, system sterilization step). During that time, the dehumidifying operation is continued and strengthened so that the low humidity environment (first fungus suppression mode S7A) in the cultivation room 2 is maintained only by the remaining air conditioning system (for example, 12, 13, 14).

(Bactericidal treatment to another air conditioning system)
When it is determined that the sterilization treatment for the first air conditioning system 11 is completed (for example, the introduction time has passed a predetermined period (first ventilation period)) (step S15B), the first air conditioning system The operation of 11 is returned from the ventilation operation to the original dehumidification operation, and another second air conditioning system 12 is switched from the dehumidification operation to the ventilation operation to perform the same processing as the sterilization treatment already performed on the first air conditioning system 11. It is preferable (step S15C, system sterilization step). Then, step S15C is executed until the elapse of the second ventilation period (step S15D). Here, if the second ventilation period cannot be sufficiently secured (for example, if the total sterilization period becomes too long and the cultivation efficiency of the plant 4 is lowered), the ultraviolet irradiation described later is also performed. It is necessary to take measures such as shortening the sterilization period for each system by executing it at the same time, or postponing the implementation of the system sterilization process for a part or all of the air conditioning system to the next timing. There will be.

If three or more air conditioning systems are installed in the plant factory 1 as shown in FIG. 1A, the second air conditioning system 12 is returned from the ventilation operation to the original dehumidification operation, and then the second air conditioning system 12 is installed. It is preferable that the air conditioning system 13 of No. 3 is also subjected to the same sterilization treatment (steps S15E and S15F). Although not shown in FIG. 3, the same sterilization treatment can be continuously applied to the fourth (Nth) air conditioning system 14.

Further, in order to save the sterilization processing time of the entire plant factory 1 (1A), it is possible to sterilize a plurality of air conditioning systems at the same time. For example, the first and third air conditioning systems 11 and 13 are simultaneously switched to the ventilation operation, and dry air A (see the solid line arrow in FIG. 1A) is introduced into each path of these systems 11 and 13. While performing the sterilization treatment (step S15A, system sterilization step), the second and fourth air conditioning systems 12 and 14 maintain or strengthen the dehumidifying operation to secure the suppression mode of the cultivation room 2. Good. Then, when the sterilization treatment for the routes 11a to 11d and 13a to 13d of the first and third air conditioning systems 11 and 13 is completed, the operation modes of the systems 11 and 13 are returned to the original state, and the second and fourth air conditioning systems are used. The same sterilization treatment (dehumidification operation → ventilation operation) may be performed on the systems 12 and 14 (see step S15C, system sterilization step, one-dot chain line arrow in FIG. 1A)). ..

(Completion of the first fungal suppression mode)
As described above, the sterilization treatment (steps S15A to S15F) of the first to fourth (Nth) air conditioning systems 11 to 14 is performed together with the cultivation room 2, and this treatment is a predetermined second reduction. If it is determined that the bacterial period has passed, the first fungal suppression mode S7A is completed (step S16). As the second sterilization period, at least a period equal to or longer than the first sterilization period is secured. After that, it is determined whether or not the growth of the plant 4 is sufficient (see step S8 and FIG. 2). If this is a positive result, the method of the invention is complete. On the other hand, if the result is negative, the process returns to the cultivation mode (that is, step S1) again.

(Second fungus suppression mode: when only one air conditioning system is installed in the plant factory)
As another example, a fungus suppression method (second fungus suppression mode S7B) in the case where only one air conditioning system 11 is installed in the plant factory 1 as shown in FIG. 1B will be described. FIG. 4 shows a flowchart of the suppression mode S7B when only one first air conditioning system 11 exists.

When the second fungus suppression mode S7B is entered after the determination in the above step S6, the inside of the cultivation room 2 is changed to a low humidity state by using the first air conditioning system 11 as in the treatment in the first fungus suppression mode S7A described above. (Step S21, indoor dehumidification step), and it is determined whether or not the temperature and humidity in the cultivation room 2 have reached the target values (step S22). Then, preferably, the fungus is suppressed (sterilized) not only in the cultivation room 2 which is the cultivation space but also in the air flow paths 11a to 11d (particularly, the surface of the heat exchanger 11d) in the first air conditioning system 11. It is determined whether or not the treatment is necessary (step S23, simultaneous sterilization confirmation step). The cultivation room 2 is maintained in the low humidity environment for a predetermined period (first sterilization period) (step S24).

When it is determined in step S23 that sterilization of the first air conditioning system 11 is unnecessary, the second fungus suppression mode S7B is maintained until the first sterilization period elapses (step S24), and then, Immediately, the second fungal suppression mode S7B is completed.

On the other hand, when it is determined in step S23 that sterilization of the first air conditioning system 11 is necessary, the first air conditioning system 11 is switched from the dehumidifying operation to the blowing operation, and the dry air A in the cultivation room 2 is passed through the path 11a. It is introduced into ~ 11d (particularly the surface of the heat exchanger 11d), and the dry air A is circulated between the cultivation room 2 and the first air conditioning system 11 (step S25A, system sterilization step, in FIG. 1B). See the solid arrow in).

However, in the second fungus suppression mode S7B, since there is no other air conditioning system to maintain the low humidity environment in the cultivation room 2 during the blowing operation in step S25A, the bacteria are extremely sterilized to the first air conditioning system 11. Ingenuity is required to do it efficiently in a short period of time. Therefore, as shown in FIG. 1B, an ultraviolet irradiation device 11e is provided in advance in the paths 11a to 11d of the first air conditioning system 11, and the heat exchanger 11d through which the dry air A flows during the blowing operation It is preferable that the surface is further irradiated with ultraviolet rays U (step S26). Here, it is necessary to irradiate the ultraviolet U in a wavelength range centered on 260 nm and secure an integrated dose of about 3500 J / m ² on the irradiated surface. When a general known irradiation device is used for the ultraviolet irradiation device 11e, it is necessary to provide an irradiation period of at least about 5 minutes or more.

The above treatments (steps S25A and S26) are sterilized in the first air conditioning system 11 until the first ventilation period elapses (step S25B), and the sterilization treatments in the cultivation room 2 and the first air conditioning system 11 (S21). The treatment is continued until the total time of ~ S26) reaches the second sterilization period (step S27).

When the above-mentioned step S24 (or step S27 depending on the conditions) is completed, the second fungus suppression mode S7B is completed. After that, it is determined whether or not the growth degree of the plant 4 is sufficient (see step S8, growth degree confirmation step, FIG. 2). If the result is positive, the method of the present invention is completed. On the other hand, if the result is negative, the process returns to the cultivation mode (that is, step S1) again.

(Demonstration test using frilled lettuce)
Frill lettuce was actually cultivated using the fungal suppression method of the present invention, comparative examples described later were also examined, and the effects were compared and verified (Example 2). In the cultivation experiment of the comparative example, in order to eliminate the influence of environmental factors as much as possible, the environmental conditions other than the relative humidity were matched with Example 2 as much as possible as described later. Only one air conditioning system 11 for the cultivation room 2 was used.

As the light source 36, an LED type illuminator was used, and as the LED element, a type capable of freely setting the outputs of red and blue, which are wavelength components required for photosynthesis, was used. The ratio of red and blue was set to R / B = 4, and the effective photon flux density of floor photosynthesis was adjusted to 150 μmol / (sec · m ² ). The light and dark periods were set to 16 hours and 8 hours per day. In both Example 2 and Comparative Example, the CO ₂ concentration was also matched by cultivating in the same cultivation room 2.

The temperature of the cultivation room 2 was 25 ± 0.3 ° C., the relative humidity was controlled to 75% in the normal state (that is, the cultivation mode), and 50% or 60% when the fungus suppression mode S7B was entered. .. On the other hand, in the comparative example, it was always set to 75% (that is, it was set not to enter the fungus suppression mode S7B). The control range of relative humidity is ± 0.4%. The conditions of the culture solution 31 were also matched, and the same container 32 was used. The culture solution was controlled during the experimental period by adjusting the pH and the electrical conductivity EC. The respective control ranges are pH = 6.4 ± 0.4 and EC = 1.00 ± 0.02 mS / cm.

Frill lettuce was cultivated under the above-mentioned test conditions. The period from planting of frilled lettuce to harvesting is about 24 days. The results of this demonstration experiment are shown in Table 1 below.

(Both maintenance of plant cultivation efficiency and fungal control)
From this Table 1, the growth rate of lettuce in Example 2 (under the implementation of fungal suppression mode S7B) was almost the same as or rather improved as compared with Comparative Example at any relative humidity, whereas for fungal spores. Was able to confirm that it succeeded in stopping the growth of hyphae after germination. On the other hand, in the comparative example, it was confirmed that the fungal spores were continuously elongated even after germination. From these comparative study results, it was found that the method of the present invention can achieve both maintenance of plant cultivation efficiency and fungal control.

(Comparative experiment between light and dark periods)
In addition, the present inventors have applied nitrate in the lettuce body when the suppression mode (low relative humidity environment) of the present invention is applied to the dark period (Example 3) and when it is applied to the light period (comparative example). The amount of lettuce was measured. The measurement result is shown in FIG. From FIG. 5, it was found that the amount of nitrate nitrogen in the lettuce body was significantly lower in the case of Example 3 than in the case of Comparative Example (light period).

This phenomenon can be considered as follows. That is, when the environment is set to a low relative humidity in the light period as in the comparative example, the amount of transpiration increases as in the dark period (however, the mechanism by which the amount of transpiration increases is different). However, in the light season, if the amount of transpiration increases too much, the plant will try to close the stomata to retain the amount of water. When the pores are closed, it becomes difficult to absorb carbon dioxide and inhibits the photosynthetic reaction. When the photosynthetic reaction is inhibited, nitrate nitrogen (a component of bitterness and harshness) cannot be consumed in the plant body. Conversely, as in Example 3, by keeping the relative humidity in the light period high while lowering the relative humidity only in the dark period, the bitterness and harshness of the harvested product can be suppressed. As explained in the background technology described above, if the amount of nitrate nitrogen can be kept low, it will be useful from the viewpoint of maintaining the health of consumers.

It should be noted that the operation of lowering the relative humidity in the dark period as in the preferred embodiment of the present invention (Example 3) is the "reverse" of the phenomenon generally occurring in the natural world. In the natural world, as shown in FIG. 6A, the relative humidity usually decreases as the temperature rises during the day, and the relative humidity rises as the temperature decreases at night. On the other hand, as shown in FIG. 6B, the operation of the present invention of limiting the low humidity period to the dark period is conversely the idea of intentionally lowering the relative humidity in the dark period when photosynthesis is not performed. Is. Although it is a common method to imitate phenomena in the natural world, the present inventors have found the above-mentioned advantages in the idea of reversal.

(Modification example: Use for environment other than plant factory)
In Examples 1 to 3 described above, a method of cultivating a plant while suppressing fungal growth in a cultivation room in a plant factory and an air conditioning system associated therewith has been described, but the present invention is not necessarily limited to the above application.

For example, the method for suppressing fungal growth of the present invention can be applied to rooms such as processing rooms in food factories where plants are not cultivated, hospital rooms, and air conditioning systems associated therewith. However, in this case, the plant cultivation mode described in Example 1 is a normal air conditioning mode (indoor cooling operation or heating operation), and the determination condition for entering the vacuum suppression mode (step S7) is the fungal growth index. It should be noted that although the determination step S4 of I is included, the additional determination step (steps S3, S5, S6) peculiar to the plant factory or plant cultivation is not included. In other words, the content itself of the above-mentioned fungal suppression mode (steps S7A, S7B) (for example, simultaneous sterilization treatment for indoors and air conditioning systems using dry air) can also be used for sterilization treatments for indoor environments other than plant factories. Applicable.

According to the method of the present invention, it is possible to realize sterilization (fungal suppression) in the cultivation room and the air conditioning system while maintaining the plant cultivation efficiency in the plant factory.

In addition, the method of the present invention has low corrosiveness to metals, is safe for the human body, does not deteriorate the thermal environment of the air-conditioned room, and can be processed in a short time.

Further, according to a preferred embodiment of the present invention, since the above-mentioned fungal suppression mode is executed only in the dark period, the bitterness and deterioration of taste of the cultivated plant can be reduced.

As described above, the fungal control method of the present invention has very high industrial applicability and utility value.

1,1A, 1B Plant factory 2 Cultivation room 3 Hydroponic cultivation equipment 4 Plants 11, 12, 13, 14 Air conditioning system 11a, 12a, 13a, 14a Air suction air duct 11b, 12b, 13b, 14b Air discharge air duct 11c, 12c, 13c, 14c Air flow space in the main body of the air conditioning system 11d, 12d, 13d, 14d Heat exchanger 11e Ultraviolet irradiation device 31 Culture solution 32 Container 33 Supply pipe 34 Discharge pipe 35 Cultivation shelf 36 Light source A Dry air I Fungal growth index P pump U UV S1 Indoor measurement process S2 Index calculation process S3 Sprouting confirmation process S4 Index confirmation process S5 First additional confirmation process S6 Second additional confirmation process S7 Mode start determination process S7A, S7B First fungus suppression mode, first 2 Fungus suppression mode S8 Growth degree confirmation step S11, S21 Indoor dehumidification step S13, S23 Simultaneous sterilization confirmation step S15A, S15C, S15E, S25A System sterilization step S26 Ultraviolet irradiation step

Claims (4)

It is a method of suppressing the growth of fungi in the room where the air conditioning system is installed.
The indoor measurement process for measuring the temperature and humidity in the room, and
An index calculation step for calculating the fungal growth index from the measured temperature and humidity, and the correlation between the fungal growth rate acquired in advance and the temperature and humidity.
An index confirmation step for confirming that the fungal growth index has exceeded a predetermined threshold value, and
A mode start determination step of starting the fungus suppression mode after confirming that the threshold value has been exceeded in the index confirmation step, and
Including
In the fungal suppression mode,
An indoor dehumidifying step of performing a dehumidifying operation of the air conditioning system to maintain the room in a low humidity state, and
Simultaneous sterilization confirmation process to confirm whether sterilization is necessary for the air conditioning system,
Including and
If the determination is negative in the simultaneous sterilization confirmation step, the fungal suppression mode is completed after the lapse of the first sterilization period.
If the determination is positive in the simultaneous sterilization confirmation step, the air conditioning system is switched from the dehumidifying operation to the blowing operation, dry air in the room is introduced into the path in the air conditioning system, and the air conditioning system and the air conditioning system are described. The fungus suppression mode is completed after the lapse of the second sterilization period, which is a period longer than the first sterilization period, and includes a system sterilization step of circulating between the room and the room .
The room is a cultivation room for cultivating plants in an artificial light type plant factory.
A germination confirmation step for confirming that a predetermined spore germination period has elapsed according to the environment in the cultivation room, and
The first additional confirmation step for confirming that the cultivation efficiency maintenance period suitable for the plant has passed, and
Including
The mode start determination step is characterized in that the fungus suppression mode is started after a positive result is obtained in all of the germination confirmation step and the first additional confirmation step in addition to the index confirmation step. A method for suppressing fungal growth. A second additional confirmation step of confirming whether or not the cultivation room is in a dark period and whether or not there is a sufficient period remaining to execute the fungal suppression mode in the dark period.
Including
In the mode start determination step, in addition to the index confirmation step, the fungus suppression is performed after a positive result is obtained in all of the germination confirmation step, the first additional confirmation step, and the second additional confirmation step. The method for suppressing fungal growth according to claim 1 , which comprises initiating a mode . The system sterilization step includes an irradiation step of irradiating the heat exchanger with ultraviolet rays from an ultraviolet irradiation device installed near the heat exchanger in the air conditioning system.
The method for suppressing fungal growth according to claim 1 or 2 , further comprising. A plurality of the air conditioning systems are installed in the room,
If the determination is positive in the simultaneous sterilization confirmation step, the air conditioning system is assigned to one that executes the system sterilization step first and one that executes the system sterilization step later.
While the earlier air conditioning system performs the system sterilization step, the subsequent air conditioning system maintains or enhances the dehumidifying operation to maintain the low humidity state in the room.
After executing the system sterilization step on the above-mentioned air conditioning system, the above-mentioned air-conditioning system returns from the blowing operation to the original dehumidifying operation, and the subsequent air-conditioning system starts the system sterilization step. The method for suppressing fungal growth according to any one of claims 1 to 3 .