Air-conditioning system

Abstract

To provide an energy-saving and low-cost air-conditioning system that can maintain the inside of a greenhouse to an appropriate temperature and humidity irrespective of day and night.SOLUTION: A temperature and humidity inside a greenhouse is adjusted by using a total heat exchanger. In a total heat exchanging cooling mode, air inside the greenhouse is totally heat-exchanged with outside air to decrease a temperature and humidity, and a temperature inside the greenhouse is effectively decreased by cooling with a cooling tower if necessary. In a dehumidification heating mode, air in the greenhouse is dehumidified to decrease humidity, and the inside of the greenhouse is heated by adsorption heat generated by dehumidification. Switching of the two operation modes makes it possible to adjust an environment inside the greenhouse to a temperature and humidity optimum for growth of plant irrespective of day and night.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an energy-saving, low-cost air conditioning system that can maintain the temperature and humidity inside a greenhouse at levels suitable for plant growth, day and night. [Background technology]

[0002] In this specification, "daytime" refers to the period from sunrise to sunset, and "nighttime" refers to the period from sunset to sunrise the following morning.

[0003] In agricultural greenhouses for growing tomatoes, strawberries, etc. (hereinafter, plant factories and horticultural facilities are also referred to as "houses"), the temperature inside the greenhouse often exceeds 30 degrees Celsius (hereinafter, all temperatures are referred to as "Celsius") during the day due to sunlight. Even in winter, when the outside temperature is in the single digits, the temperature inside the greenhouse can exceed 30 degrees Celsius during the day. For this reason, from spring to autumn, or even in winter, in order to lower the temperature inside the greenhouse, natural ventilation equipment such as the entrance, skylight, and side of the greenhouse is opened during the day to take in outside air and ventilate. In addition, forced ventilation equipment such as a ventilator is installed to blow outside air into the greenhouse. Usually, ventilation in this way is used to lower the temperature and humidity inside the greenhouse, or to take in carbon dioxide, creating an optimal cultivation environment for plants. However, opening the greenhouse changes the air environment inside the greenhouse, which creates a stressful situation for the plants. In addition, the risk of pests entering from outside increases significantly.

[0004] In greenhouse cultivation, photosynthesis is promoted by maintaining a higher carbon dioxide concentration than the atmosphere, and the yield is improved. For this purpose, carbon dioxide is applied from carbon dioxide supplying devices such as carbon dioxide cylinders and kerosene burners. However, when the greenhouse is opened, the supplied carbon dioxide mixes with the outside air and becomes diluted, so the carbon dioxide concentration does not increase, which means that most of the supplied carbon dioxide is released into the atmosphere.

[0005] Therefore, plants are produced by controlling the internal environment, such as light, temperature, humidity, and carbon dioxide, by making the greenhouse a closed system, i.e., a completely closed greenhouse (hereinafter referred to as a "closed greenhouse") or a semi-closed greenhouse (semi-closed greenhouse). Usually, the temperature and humidity inside the greenhouse are controlled using air conditioners and dehumidifiers. A method is also used in which outside air that has been heat exchanged with the air inside the greenhouse is supplied to the greenhouse. Furthermore, if it is desired to actively lower the temperature and humidity, cooling is performed using a heat pump or the like. However, the temperature inside the greenhouse can easily reach 30°C or higher due to solar radiation, and cooling using a heat pump or the like requires a lot of energy. In addition, there is also the problem of high power consumption, since a large amount of dehumidification is required through watering and transpiration from the plants.

[0006] On the other hand, when the sun goes down, heat escapes and the temperature inside the greenhouse gradually drops. At night, the greenhouse is closed and ventilation fans are turned off to prevent the temperature from dropping. However, unless some thermal energy is added, the temperature inside the greenhouse will eventually become almost the same as the outside temperature. Furthermore, since the greenhouse is isolated from the outside air, radiative cooling is not alleviated, and depending on the weather, the temperature inside the greenhouse may become lower than the outside temperature. If the temperature difference between daytime and nighttime becomes too large, it may actually cause stress to the plants and affect their growth. Also, if the temperature at night drops too much, it may cause damage due to low temperature damage, frost damage, and frost damage, especially in winter. Therefore, it is necessary to prevent the temperature inside the greenhouse from dropping and maintain the temperature by heating or keeping it warm at night. To heat the greenhouse, a fuel oil heater or a heat pump air conditioner is installed. Also, the heat retention effect is increased by spreading lining curtains inside the greenhouse. Furthermore, to improve temperature unevenness, a ventilation duct is installed or a circulating fan is used in combination.

[0007] However, fuel-fired heaters such as boilers and burners have become expensive due to the recent rise in fuel prices, and heating costs are particularly high in the winter. They also require regular maintenance, and incomplete combustion can lead to poor combustion efficiency and the risk of carbon monoxide poisoning. Heat pumps have the advantage of being able to use several times the amount of heat consumed for heating, but they are expensive to install and are not suitable for large greenhouses. High thermal insulation can be achieved by using multiple layers of interior curtains, but cold air can seep in through gaps, and the multiple layers of the coating can reduce light transmission during the day, resulting in a lack of sunlight and high temperatures and humidity. Installing air ducts is both time-consuming and costly.

[0008] The thing that has the greatest impact on the temperature inside a greenhouse is the change in outside temperature. In particular, in spring and autumn, the temperature can change significantly even within a single day. In winter, the temperature inside the greenhouse can also be lower than the outside temperature. Depending on the type of plant, there is variation in the optimum temperature for growth during the day and the minimum limit temperature at night. However, the cost of stabilizing the temperature inside a greenhouse during the day and night has been an issue. For this reason, there is a strong demand for the introduction of energy-saving equipment and technology. Summary of the Invention [Problem to be solved by the invention]

[0009] In a prior application (Japanese Patent Application No. 2023-063461), the applicant proposed an air conditioning system that can adjust the environment inside the greenhouse to the optimum temperature and humidity for plants without opening the greenhouse by installing a carbon dioxide supplying device in the greenhouse, circulating the air inside the greenhouse using the carbon dioxide supplying device, and total heat exchange of the air inside the greenhouse with outside air using a total heat exchanger and supplying it back into the greenhouse. This air conditioning system can use carbon dioxide captured from the atmosphere by DAC (Direct Air Capture) technology to adjust the carbon dioxide concentration, contributing to carbon neutrality.

[0010] In this air conditioning system, in order to lower the temperature inside the greenhouse during the day, the total heat exchanger can bring the temperature and humidity inside the greenhouse closer to that of the outside air. This makes it possible to maintain the temperature inside the greenhouse at around 30°C, but for winter crops such as strawberries, lowering the temperature inside the greenhouse to around 20°C increases the sugar content and market value. In order to further lower the temperature inside the greenhouse during the day, it is effective to increase the number of total heat exchangers and the processing air volume, but this increases the initial cost. Also, in the cultivation environment, excessive airflow from the large amount of air supplied from the total heat exchangers may cause stress to the plants, so it is preferable to refrain from installing excessive total heat exchangers.

[0011] As described above, in the conventional technology, the temperature and humidity can be lowered by total heat exchange between the air inside the greenhouse and the outside air during the day using a total heat exchanger, but there is a limit to how low the temperature inside the greenhouse can be during the day. Another issue is the high costs of the devices, equipment, and fuel required to heat and keep the greenhouse warm at night.

[0012] The present invention has been made to solve these problems, and aims to provide an energy-saving, low-cost air conditioning system that combines the operating method of a total heat exchanger with a cooling tower or the like to suppress increases in temperature and humidity inside the greenhouse during the day, and increases in humidity and decreases in temperature inside the greenhouse at night, thereby maintaining temperature and humidity levels suitable for plant growth both day and night. [Means for solving the problem]

[0013] The air conditioning system of the present invention adjusts the temperature and humidity inside the greenhouse using a total heat exchanger. During the day, it operates in total heat exchange cooling mode, lowering the temperature and humidity by total heat exchange of the air inside the greenhouse with the outside air, and effectively lowering the temperature inside the greenhouse by cooling using a cooling tower or the like as necessary. At night, it operates in dehumidification heating mode, dehumidifying the air inside the greenhouse to lower the humidity, and heating the greenhouse with the heat of adsorption generated by the dehumidification. The most important feature of this system is that it can adjust the temperature and humidity inside the greenhouse to optimal levels for plant growth throughout the day and night by switching between these two operating modes. Effect of the Invention

[0014] According to the air conditioning system of the present invention, by switching between the total heat exchange function during the day and the desiccant (dehumidification) function at night, a closed house can be realized in which the environment inside the house is maintained at the optimum temperature and humidity for plant growth throughout the day and night using only the total heat exchanger. By using the air conditioning system of the present invention, other cooling or heating equipment is not required or can be used only as an auxiliary, so costs such as fuel and electricity can be reduced. The air conditioning system of the present invention can lower the temperature and humidity inside the house during the day and heat the house while lowering the humidity inside the house at night, promoting plant growth and reducing damage to plants caused by low-temperature damage, high-temperature damage, and pests. During high-temperature periods, the temperature inside the house may be higher than body temperature, causing safety problems such as heat stroke for workers, but by using the air conditioning system of the present invention, the environment inside the house is improved not only for plants but also for the human body, and improved workability can be expected. By using a total heat exchange rotor, the operating mode can be easily switched by simply changing the rotation speed. Since the power consumption is only for the total heat exchanger's blower and the motor for rotating the rotor, it is a significant energy saving compared to cooling using a heat pump.

[0015] In addition, the air conditioning system of the present invention can effectively lower the temperature inside the greenhouse by cooling using a cooling tower. The cooling tower uses natural energy and can cool the air using outside air as a heat source, so it is low cost and environmentally friendly. The cooling tower is powered only by a blower and a pump, so both the initial cost and running cost are low.

[0016] In the dehumidification and heating mode of the total heat exchanger used in the present invention, the regeneration inlet temperature is set to a temperature lower than the normal low-temperature regeneration temperature of 40 to 80°C, so energy can be saved and running costs can be reduced. The heat exchanger that heats the air at the regeneration inlet does not require active heating, and can use not only hot water but also groundwater, circulating water, solar heat, geothermal heat, and exhaust heat from the equipment as regeneration heat, resulting in extremely energy saving.

[0017] Furthermore, since the air conditioning system of the present invention recycles the air inside the greenhouse and does not take in outside air, the carbon dioxide concentration inside the greenhouse can be increased to about 800 to 1000 ppm by the carbon dioxide supply device, which promotes photosynthesis in plants. Since no carbon dioxide leaks into the outside air, it is only necessary to supply the amount of carbon dioxide absorbed by the plants, minimizing the operation of the carbon dioxide supply device and enabling energy-saving operation.

[0018] If the greenhouse is a closed system, the air flow will be weak, and even if the stomata of the leaves are open, the carbon dioxide concentration near the leaf surface will decrease, suppressing photosynthesis. However, a total heat exchanger can create air flow within the greenhouse, making it possible to promote photosynthesis in the leaves. In addition, air flow makes it possible to make the temperature, humidity, and carbon dioxide concentration within the greenhouse uniform. In this way, by making the greenhouse a closed system, air control such as temperature, humidity, carbon dioxide concentration, and air flow can be achieved, providing a space that is less stressful for plants. Furthermore, by lowering the temperature inside the greenhouse by cooling using a cooling tower or the like, it is possible to avoid the installation of an excessive total heat exchanger, and to supply an appropriate air flow to the plants.

[0019] In addition, the initial cost of the greenhouse itself can be reduced because windows and motors for opening the roof and sides of the greenhouse are not required or can be reduced. By making the greenhouse a closed system, the effects of wind and rain can be completely blocked. Furthermore, since pests cannot enter from the outside, the trouble of putting up insect nets is eliminated, making it possible to reduce the use of pesticides, and making it possible to realize environmentally friendly agriculture such as organic farming. In recent years, extreme weather due to climate change has become commonplace, and the tendency for pests to occur is changing accordingly, making cultivation management more difficult every year. The total heat exchanger of the present invention can easily switch operating modes, reducing the burden of cultivation management.

[0020] The air conditioning system according to the present invention is particularly suitable for strawberry cultivation. If the temperature inside the greenhouse exceeds 32°C, the fruit will get sunburned, and some strawberries will be discarded because they are not sellable. Therefore, measures are required to prevent the temperature inside the greenhouse from exceeding 32°C, preferably 30°C. Although it depends on the variety of strawberries, the optimum temperature during the day is 18 to 23°C, and it is necessary to keep it at a minimum of 5 to 7°C at night. Strawberries are resistant to cold, but they are prone to frost damage if the temperature continues to be freezing cold or is below -5°C. In addition, if the temperature inside the greenhouse is suddenly raised when the strawberry stalks are cold due to the nighttime temperature, condensation will occur on the cold stalks due to the temperature difference. Condensation makes it difficult for the stomata that perform transpiration to open, and also causes problems with harvesting work and increases the risk of disease occurrence.

[0021] According to a test result, strawberries were cultivated well in an environment with a temperature in the greenhouse of 15 to 30°C. It has also been reported that although the yield was high whether the temperature in the greenhouse was 20°C or 30°C, the quality such as sweetness was superior at 20°C. The air conditioning system of the present invention can effectively lower the temperature in the greenhouse from 30°C to about 20°C during the daytime in winter, spring and autumn by operating in a total heat exchange cooling mode during the day and cooling using a cooling tower, etc., and can also heat the greenhouse at night, so that strawberries are not damaged by high or low temperatures. Thus, the air conditioning system of the present invention is particularly effective for cultivating strawberries, which are a winter crop, and it is possible to produce high-quality strawberries in high yields. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram showing a closed house using the air conditioning system of the present invention, in which a carbon dioxide supplying device and a total heat exchanger are installed separately. [Diagram 2] FIG. 2 is a flow diagram of a total heat exchanger used in the air conditioning system of the present invention. [Diagram 3] FIG. 3 is a psychrometric chart showing the results of trial calculations of dehumidification performance when it is assumed that adiabatic dehumidification occurs in Example 2 of the present invention. [Figure 4] FIG. 4 is a psychrometric chart showing the results of a dehumidification performance test of Example 3 of the present invention. [Diagram 5] FIG. 5 is a psychrometric chart showing adiabatic and isothermal dehumidification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In the air conditioning system of the present invention, a carbon dioxide supplying device is provided in the greenhouse, which makes the carbon dioxide concentration in the air inside the greenhouse higher than that in the outside air, and a total heat exchanger is provided to exchange total heat between the air inside the greenhouse and the outside air, making it possible to adjust the environment inside the greenhouse to the optimum temperature and humidity for plant growth.

[0024] (Closed House) According to the air conditioning system of the present invention, a closed house can be realized. As shown in FIG. 1, the closed house using the air conditioning system of the present invention includes a carbon dioxide supplying device 2 and a total heat exchanger 3. The inside of the house 1 is controlled to maintain a constant environment suitable for plant growth, such as a temperature of 20 to 30°C, a humidity of 55 to 85% RH, and a carbon dioxide concentration of 800 to 1000 ppm. The carbon dioxide supplying device 2 can increase the carbon dioxide concentration in the house 1 by supplying air with an increased carbon dioxide concentration into the house 1. As a result, it is possible to increase the carbon dioxide concentration to about 1000 ppm, which promotes photosynthesis in plants. The total heat exchanger 3 exchanges the air in the house 1 with the outside air and supplies it back into the house 1. This reduces the temperature and humidity of the air in the house 1, which has become high in temperature and humidity, without reducing the carbon dioxide concentration in the house. In this way, the air conditioning system of the present invention can adjust the environment in the house to the optimum temperature and humidity for plants without opening the house.

[0025] (Carbon dioxide supply device) The carbon dioxide supplying device used in the air conditioning system of the present invention is not limited, but is preferably a device that uses an adsorption rotor 4 as shown in FIG. 1 to separate and collect carbon dioxide in the atmosphere by DAC technology, concentrate it, and supply it to plants. The carbon dioxide supplying device 2 takes in air in the house 1, which has a higher carbon dioxide concentration than the outside air, and supplies the air with a higher carbon dioxide concentration to the house 1 again, thereby increasing the carbon dioxide concentration in the house 1. In FIG. 1, the carbon dioxide supplying device 2 equipped with the adsorption rotor 4 is installed in the house 1. The adsorption rotor 4 is a honeycomb rotor made by corrugating a non-flammable sheet such as glass fiber or ceramic fiber paper and wrapping it around a rotor, and supports a carbon dioxide adsorbent such as a weakly basic ion exchange resin or an amine-supported solid adsorbent. Alternatively, the adsorption rotor 4 has a hollow cylindrical shape, and is filled with a granular or pellet-shaped carbon dioxide adsorbent.

[0026] The adsorption rotor 4 is driven to rotate at a constant speed around the central axis by a geared motor (not shown) or the like. The adsorption rotor 4 has an adsorption zone that adsorbs carbon dioxide in the outside air by passing at least the outside air in the direction of rotation of the rotor and exhausts it outside the device, and a desorption zone that desorbs the carbon dioxide adsorbed in the adsorption zone by passing air in the house 1 heated by a regeneration heater (not shown) or the like and returns it to the house 1. In this way, the carbon dioxide concentrating device 2 concentrates the carbon dioxide in the house 1 and circulates and supplies high-concentration carbon dioxide to the closed house 1. The adsorption rotor 4 may have other zones such as a purge zone and a pre-purge zone in addition to the adsorption zone and desorption zone. The desorption of carbon dioxide from the adsorption rotor 4 is not limited to a temperature swing caused by heating, and may be a pressure swing caused by reducing pressure.

[0027] The carbon dioxide supplying device 2 is not limited to one that uses an adsorption rotor, and may be a carbon dioxide cylinder or a burner for kerosene, etc. Also, a carbon dioxide supplying device that uses a chemical absorption method, a physical absorption method, a membrane separation method, etc. may be used. By doing so, the present invention can be implemented by simply installing a total heat exchanger described below in a house in which a carbon dioxide supplying device is already installed.

[0028] (Total heat exchanger) In the total heat exchanger 3 used in the air conditioning system of the present invention, a part of the air in the house 1 is sent to the total heat exchanger 3, where it is subjected to total heat exchange with the outside air, and then returned to the house 1. This lowers the temperature and humidity of the air in the house 1, which has become hot and humid, but does not reduce the carbon dioxide concentration in the house.

[0029] Fig. 2 is a flow diagram of the total heat exchanger used in the air conditioning system of the present invention. The total heat exchanger 3 is equipped with a total heat exchange rotor 5, which is made by forming an aluminum sheet or the like into a honeycomb shape, carrying a moisture adsorbent on the sheet, and finally forming it into a rotatable rotor. Examples of moisture adsorbents include calcium chloride, diatomaceous earth, silica gel, zeolite, ion exchange resin, and polymer adsorbent.

[0030] The total heat exchange rotor 5 has at least a processing zone 6 that passes air in the house 1 in the direction of rotation of the rotor and returns the air to the house 1, and a regeneration zone 7 that passes outside air and exhausts the air to the outside of the device. In the present invention, the total heat exchanger 3 has two operating modes, a total heat exchange cooling mode and a dehumidification heating mode. It operates in the total heat exchange cooling mode during the day to reduce the temperature and humidity in the house, and effectively lowers the temperature in the house by cooling with a cooling tower as necessary. It operates in the dehumidification heating mode at night to dehumidify the house and heat the house with the adsorption heat generated by dehumidification. The total heat exchanger can easily switch between the total heat exchange cooling and dehumidification heating operating modes by simply changing the rotation speed of the total heat exchange rotor, which rotates at a high speed in the total heat exchange cooling mode and at a low speed in the dehumidification heating mode. This realizes a closed house that can maintain a temperature and humidity suitable for plant growth throughout the day and night.

[0031] (Daytime: total heat exchange cooling mode) During the day, the temperature inside the greenhouse rises due to solar radiation, and the humidity inside the greenhouse also rises due to watering and plant transpiration, resulting in a higher temperature and humidity inside the greenhouse than the outside air. Therefore, the total heat exchanger is operated in total heat exchange cooling mode. In other words, the total heat exchange rotor is operated at a high speed of several tens of rpm (rotations per minute, the number of rotor rotations per minute), for example 20 rpm, and the air inside the greenhouse is totally heat exchanged with the outside air to lower the temperature and humidity.

[0032] As shown in FIG. 2, on the treatment side, a part of the air in the house 1 is passed through an air filter (AF) by a blower 8 and sent to a treatment zone 6 of a total heat exchange rotor 5, where it exchanges total heat with the outside air. The air that has passed through the treatment zone 6 and has a reduced temperature and humidity is further cooled by a first heat exchanger 10 using a cooling tower as necessary, and the temperature is lowered and the air is supplied again to the house 1. On the regeneration side, the outside air is passed through an air filter by a blower 9 and sent to a regeneration zone 7 of the total heat exchange rotor 5, where it exchanges total heat with the air in the house 1. The air that has passed through the regeneration zone 7 and has an increased temperature and humidity is exhausted outside the device. In the total heat exchange cooling mode, the second heat exchanger 11 provided before the regeneration zone 7 is not used.

[0033] Here, in order to further lower the temperature of the air that has passed through the treatment zone 6, a heat pump unit, a chiller, or an evaporative cooler may be used as the first heat exchanger 10, but in the present invention, a heat exchanger using cooling water cooled by a cooling tower is used. The first heat exchanger 10 is used as necessary when it is necessary to more effectively lower the temperature inside the house, such as when the temperature inside the house exceeds 30°C or when it is necessary to supply air that is lower than the outside air temperature into the house. In this specification, "cold water" refers to water cooled by a refrigerator (chiller), and "cooling water" refers to water cooled by a cooling tower. In addition, "circulating water" is synonymous with cooling water and refers to water circulating between a cooling tower (heating tower) and a main unit, and is called "circulating water" especially when used in a heating tower.

[0034] (cooling tower) A cooling tower lowers the temperature of cooling water by contacting a heat medium such as water directly or indirectly with the atmosphere, evaporating a part of the water, and providing the cooling water with the latent heat of evaporation of the enthalpy difference with the saturated air to cool it. In principle, cooling water can be obtained up to a temperature close to the wet-bulb temperature, which is lower than the outside air temperature. Due to the principle of heat exchange, a cooling tower is affected by natural phenomena such as the temperature and humidity of the atmosphere and the season. The lower the air temperature, the larger both the temperature difference with the surrounding environment and the evaporation rate, and the greater the capacity of the cooling tower. In other words, if the wet-bulb temperature of the atmosphere is low, the temperature of the cooling water can be lowered, so that cooling water at a lower temperature can be obtained in spring and autumn compared to summer. Furthermore, the capacity of the cooling tower is greater in winter, and according to one estimate, it is equivalent to 2.4 times that of summer. In the present invention, the air that has passed through the total heat exchanger is cooled by the first heat exchanger 10 using a cooling tower as necessary. For example, by providing a coil through which cooling water cooled by a cooling tower flows on the treatment outlet side of the total heat exchange rotor 5 as the first heat exchanger 10, it is possible to further lower the temperature of the air (treatment outlet) that has passed through the treatment zone 6.

[0035] Cooling towers are not used alone for air conditioning, but are generally used in combination with heat source equipment that requires heat dissipation, such as heat pumps and refrigerators. For this reason, even those skilled in the art would not easily think of using a cooling tower alone for the purpose of cooling the processing outlet air of a total heat exchanger. For example, in a central air conditioning system in an air conditioning facility, cooling water is generally used, and a cooling tower is used to adjust the temperature of this cooling water. Cold air for cooling an indoor space is produced by heat exchange with cold water in an air conditioner. Warmed cold water is sent to a refrigerator, and heat is absorbed by the refrigerant by evaporation of the refrigerant in the evaporator, and the absorbed heat is dissipated to the cooling water in the condenser. The cooling tower plays a role in discharging the heat dissipated to the cooling water in the condenser of the refrigerator to the outside air. Therefore, this cooling tower for air conditioning constitutes a part of a central air conditioning system together with an air conditioner and a refrigerator, and is used as an auxiliary device for the refrigerator, which is completely different from the use of the present invention in which a cooling tower is used alone.

[0036] Cooling towers use natural energy and can cool air using outside air as a heat source, so they are low cost and environmentally friendly. Cooling towers are powered by a blower and a pump, so initial and running costs are low. Considering the temperature setting of the cooling water, the required pump capacity, heat load fluctuations, and seasonal fluctuations in the cooling tower capacity, it is possible to reduce power consumption. If a forced draft open cooling tower is used, the tower body can be made compact and costs can be reduced. Nevertheless, the cooling tower itself is relatively large and requires a large installation area, and there are limitations on installation, so those skilled in the art would not normally think of using it for a total heat exchanger. However, the present invention is aimed at greenhouses, and since the cooling tower can be installed outside the greenhouse, it only occupies a part of the vast farmland, and the installation area required is hardly an issue.

[0037] (Night: Dehumidifying heating mode) At night, the temperature inside the greenhouse gradually drops and the relative humidity rises. Although the amount of transpiration is less than during the day, plants transpire even at night. This causes the humidity inside the greenhouse to rise, and the humidity inside the greenhouse becomes higher than the humidity outside. Therefore, the total heat exchanger is operated in dehumidification heating mode. The total heat exchange rotor can be used as a dehumidification rotor that exerts a desiccant function by lowering the rotation speed. That is, the total heat exchange rotor rotates at a low speed of several to several tens of rph (rotations per hour, rotor rotations per hour), for example, 10 rph, and dehumidified air is supplied into the greenhouse to reduce humidity. In addition, the temperature of the air (treatment outlet) that has passed through the treatment zone increases due to the adsorption heat generated by dehumidification, and heated air can be supplied into the greenhouse. Note that if the total heat exchanger cooling mode is operated at night, cold air will be sent into the greenhouse, further lowering the temperature inside the greenhouse.

[0038] As shown in FIG. 2, on the treatment side, part of the air in the house 1 is passed through an air filter by a blower 8 and sent to a treatment zone 6 of the total heat exchange rotor 5, where it is dehumidified and its temperature rises due to the heat of adsorption associated with the dehumidification. The air that has passed through the treatment zone 6 and has been heated and reduced in humidity is supplied back into the house 1. On the regeneration side, outside air is passed through an air filter by a blower 9 and sent to a second heat exchanger 11 such as a hot water coil to be heated. The air that has passed through the second heat exchanger 11 is sent to a regeneration zone 7 of the total heat exchange rotor 5 to be humidified, and the air with increased humidity is exhausted outside the device.

[0039] In a temperature swing using a normal adsorption rotor, the treatment side is generally operated at a low temperature and the regeneration side is generally operated at a high temperature. That is, the regeneration inlet temperature is usually higher than the treatment inlet temperature. For example, in a general dehumidification device, when the required dew point temperature is low, the treatment inlet temperature is 7 to 15°C by pre-cooling, and the regeneration inlet temperature is heated to 100 to 140°C or higher. However, since the present invention aims at an energy-saving device, high temperatures are not required, and the regeneration temperature is lower than 40 to 80°C, which is generally considered to be low-temperature regeneration. Normally, if the regeneration temperature is no longer 30°C or lower, it is not practical and is not even considered. In the present invention, the regeneration inlet temperature may be 40°C or lower, 30°C or lower, or even 20°C or lower. The regeneration inlet temperature may be lower than the treatment inlet temperature. In order to prevent freezing and condensation of the device, it is preferable that the air (regeneration inlet temperature) leaving the second heat exchanger 11 is at a temperature at which the regeneration outlet side does not freeze, such as 5°C or higher.

[0040] In the present invention, dehumidification can be performed even at a regeneration temperature lower than normal. The driving force is the relative humidity difference between the treatment inlet and the regeneration inlet. In other words, dehumidification is performed by "relative humidity swing". That is, in the dehumidification heating mode of the present invention, the relative humidity at the regeneration inlet is set to be lower than the relative humidity at the treatment inlet. The larger this difference is, the greater the driving force for dehumidification. At night, the relative humidity inside the greenhouse increases with a decrease in temperature, but the relative humidity is higher than during the daytime because transpiration from plants promotes an increase in the relative humidity compared to during the daytime. On the other hand, the relative humidity of the outside air also increases with a decrease in outside temperature, but the increase is smaller than the increase in the relative humidity inside the greenhouse. Also, the absolute humidity decreases with a decrease in the temperature of the outside air at night compared to during the daytime. Therefore, although it depends on the weather conditions, the relative humidity difference between the inside of the greenhouse and the outside air tends to be larger at night compared to during the daytime. In the present invention, the treatment inlet uses the air inside the greenhouse with a high relative humidity, and the regeneration inlet uses the outside air with a lower relative humidity than inside the greenhouse, which is suitable for relative humidity swing.

[0041] Furthermore, in the present invention, the relative humidity at the regeneration inlet is further reduced by heating the outside air with the second heat exchanger 11. However, since the regeneration inlet temperature is low, the second heat exchanger 11 does not require active heating, and it is sufficient to use groundwater or circulating water as regeneration heat, which is extremely energy-saving. In addition, geothermal heat, underground heat, and solar heat can also be used. If there is a heat source, even the exhaust heat of devices and machines, such as the exhaust heat of the outdoor unit and the heat radiated from the control panel, can be used. By providing the second heat exchanger 11 with a coil through which water heated by these heat sources flows, the regeneration inlet temperature can be increased and the relative humidity can be reduced.

[0042] In addition, the cooling tower used to cool the first heat exchanger 10 during the day can be used as a heating tower (heating tower) as a heat source for the second heat exchanger 11 during the day, and the outdoor air at the regeneration inlet can be heated using the circulating water. In this case, a cooling tower (heating tower) with specifications that can be used as both a cooling tower and a heating tower is selected. The heating tower absorbs heat from the atmosphere to raise the temperature of the circulating water. Therefore, it uses the energy of the air without using fuel, so it is energy-saving and low-cost. Since the outdoor air temperature is low at night, it is preferable to use the air inside the house, which has a relatively high temperature, as the heat source. For example, a coil is installed inside the house, and the circulating water used to heat the heating tower is passed through the coil inside the house. The relative humidity inside the house is higher than that of the outdoor air, and condensation is likely to occur on the coil surface. Therefore, heat can be obtained without lowering the dry-bulb temperature inside the house (without lowering the temperature inside the house). The circulating water warmed by the condensation heat obtained in this way is circulated to the heating tower. In the heating tower, the warmed circulating water heats the outdoor air. In addition, when the first heat exchanger 10 can increase the treatment outlet air temperature, a heat source such as geothermal heat may be used only for nighttime heating operation, similar to the heat source of the second heat exchanger 11. For example, when groundwater is used as the heat source of the first heat exchanger 10, the temperature of groundwater is almost constant at 16 to 18°C ​​throughout the year, so it can be used for cooling during the day and heating during the night. In this case, a switching valve or a separate coil is required to switch between the cooling water supplied by the cooling tower for daytime cooling operation and a heat medium from a different heat source. EXAMPLES

[0043] As Example 1, in the total heat exchanger of Fig. 2, the total heat exchange rotor 5 is operated in total heat exchange cooling mode during the daytime in spring or autumn, and the temperature is further lowered by the first heat exchanger 10 using a cooling tower, and the air is supplied again to the house 1. The symbols in Table 1 correspond to the air conditions at the positions indicated by the numbers in parentheses in Fig. 2.

[0044] [Table 1]

[0045] During the day, the total heat exchange rotor 5 rotates at high speed and operates in total heat exchange cooling mode. On the treatment side, the high-temperature and high-humidity air (4) inside the house, with a temperature of 30.0°C and an absolute humidity of 21.6 g / kg (DA), is heated to 33.0°C by the blower 8 to become air (5). This air passes through the treatment zone 6 of the total heat exchange rotor 5 and is subjected to total heat exchange with the outside air to become air (6) whose temperature and humidity are reduced to 23.9°C and 12.6 g / kg (DA). The air is then cooled further to 19.4°C by the first heat exchanger 10 using a cooling tower to become air (7) and is returned to the inside of the house. On the regeneration side, outside air (1) with a temperature of 20.0°C and an absolute humidity of 8.7g / kg (DA) passes through regeneration zone 7 by blower 9 and exchanges total heat with the air inside the house, becoming air (3) whose temperature and humidity have increased to 29.2°C and 17.7g / kg (DA). The air that leaves blower 9 is then exhausted outside the device.

[0046] When the temperature is lowered by the first heat exchanger 10 using a cooling tower, the relative humidity increases. For this reason, the temperature is set so that the air that has passed through the first heat exchanger 10 will not condense. Even if this air has a high relative humidity, the absolute humidity itself is low, and when it is supplied into the greenhouse, the temperature rises and the relative humidity decreases.

[0047] In addition, in winter, when the outside temperature is too low, performing total heat exchange during the day will send cold air into the greenhouse, causing the temperature inside the greenhouse to drop excessively. However, even during the daytime in winter, humidity inside the greenhouse will rise due to plant transpiration and watering. In this case, the operation of the total heat exchanger 3 and cooling tower is stopped, or they are operated in dehumidifying heating mode at night. If the total heat exchanger 3 is operated in dehumidifying heating mode, it is possible to adjust the humidity while dehumidifying the air inside the greenhouse even during the day without lowering the temperature inside the greenhouse. EXAMPLES

[0048] In the following, as Example 2, Table 2 shows the results of calculations for the total heat exchanger in Fig. 2 in the dehumidification heating mode when the total heat exchange rotor 5 is operated in the dehumidification heating mode during winter nights and the inside of the greenhouse is heated by the heat of adsorption generated by dehumidification. A psychrometric chart showing the results of the calculations is shown in Fig. 3. The symbols in Table 2 and Fig. 3 correspond to the air conditions at the positions indicated by the numbers in parentheses in Fig. 2.

[0049] [Table 2]

[0050] At night, the total heat exchange rotor 5 rotates at a low speed and operates in dehumidification heating mode. On the treatment side, the air (4) in the house with a temperature of 15.0°C, absolute humidity of 9.6g / kg (DA), and relative humidity of 90%RH leaves the blower 8 and passes through the treatment zone 6 of the total heat exchange rotor 5, where moisture is adsorbed and the temperature rises due to the heat of adsorption, becoming dehumidified air (6) with a temperature of 17.5°C and absolute humidity of 8.6g / kg (DA). This dehumidified air is returned to the house again. On the regeneration side, low-temperature and low-humidity outside air (1) with a temperature of 1.0°C and absolute humidity of 2.1g / kg (DA) is heated to a temperature of 5.0°C by the second heat exchanger 11 and becomes air (2) with a relative humidity of 38.7%RH, and enters the regeneration zone 7. The air that has passed through the regeneration zone 7 is lowered to a temperature of 2.5°C due to the heat of desorption, becoming air (3) with an increased humidity to an absolute humidity of 3.1g / kg (DA). Thereafter, the air leaving the blower 9 is exhausted outside the device.

[0051] In Example 2, calculations were performed on the assumption that adiabatic dehumidification occurs. As shown in Figure 5, in "adiabatic dehumidification," it is assumed that no energy is exchanged during the dehumidification operation of the desiccant, and the transition occurs on an isenthalpy line on the psychrometric chart. In the psychrometric chart of Figure 3, the state of the air at the inlet and outlet of both the treatment side and the regeneration side transitions on the isenthalpy line of the inlet air. Note that in an actual dehumidification operation using temperature swing, the dehumidification performance is reduced compared to adiabatic dehumidification due to an increase in enthalpy of the treatment outlet gas caused by sensible heat transfer from the regeneration side to the treatment side via the rotor, heat of adsorption larger than the latent heat of vaporization of water, and mass transfer resistance. EXAMPLES

[0052] In the following, as Example 3, a dehumidification performance test was carried out under test conditions assuming a nighttime dehumidification heating mode, using a rotor carrying silica gel as the total heat exchange rotor 5 of the total heat exchanger 3 in FIG. 2. The test results are shown in Table 3. A psychrometric chart showing the test results is shown in FIG. 4. The rotation speed of the adsorption rotor 1 was set to 10 rph. The symbols in Table 3 and FIG. 4 correspond to the air conditions at the positions of the numbers in parentheses in FIG. 2. The temperature and humidity conditions at the treatment inlet and regeneration inlet in the dehumidification performance test of Example 3 were adjusted to be as close as possible to the values ​​calculated in Example 2.

[0053] [Table 3]

[0054] Example 2 (Table 2, FIG. 3) and Example 3 (Table 3, FIG. 4) are compared. In Example 2, assuming that adiabatic dehumidification occurs based on Table 2, with the regeneration inlet air (2) having a temperature of 5.0°C and a relative humidity of 38.7% RH compared to the regeneration inlet air (5) having a temperature of 15.0°C and a relative humidity of 90.0%, the dehumidification amount on the treatment side (the absolute humidity of the treatment inlet air (5) minus the absolute humidity of the treatment outlet air (6)) was 1.0 g / kg (DA), and the temperature rise on the treatment side (the temperature of the treatment outlet air (6) minus the temperature of the treatment inlet air (5)) was 2.5°C. On the other hand, in Example 3, when the regeneration inlet air (2) had a temperature of 9.3°C and a relative humidity of 48.5% RH compared to the treatment inlet air (5) having a temperature of 21.9°C and a relative humidity of 71.0%, the dehumidification amount on the treatment side was 0.9 g / kg (DA), and the temperature rise was 1.1°C.

[0055] As in Examples 2 and 3, in the present invention, the relative humidity at the regeneration inlet is set lower than the relative humidity at the treatment inlet, and the dehumidification operation is performed using the relative humidity swing as a driving force. Therefore, the regeneration inlet temperature can be set to a temperature lower than the 40 to 80°C usually used for low-temperature regeneration, and further, a reversal phenomenon in which the regeneration inlet temperature is lower than the treatment inlet temperature, which is unthinkable with normal temperature swings, can occur. This is an idea for an adsorption / desorption operation that even a person skilled in the art would not easily come up with.

[0056] When adiabatic dehumidification occurs, theoretically, heat of adsorption is generated when 1 g of moisture is dehumidified, and the temperature rises by 2.5°C. The calculated value (theoretical value) of Example 2 and the experimental value of Example 3 are both equivalent dehumidification amounts, but the temperature rise of the experimental value is low at 1.1°C, which is less than half of the theoretical value of 2.5°C. In other words, the difference between the treatment outlet temperature and the treatment inlet temperature is small, and the slope is larger than that of the adiabatic dehumidification shown in FIG. 3 as shown in the psychrometric chart of FIG. 4, and dehumidification closer to isothermal dehumidification as shown in FIG. 5 occurs. In Example 3, the temperature on the regeneration side is low, so the rotor rotates from the regeneration zone to the treatment zone while still cold, and the heat storage effect of the cold heat suppresses the temperature rise due to the heat of adsorption in the treatment zone. However, under conditions where the outside air temperature is higher than in Examples 2 and 3, for example, 10 to 20°C, the temperature difference between the treatment side and the regeneration side becomes gentle, and dehumidification proceeds in the direction from isothermal dehumidification to adiabatic dehumidification. For example, strawberry cultivation is popular in Fukuoka Prefecture, where the applicant is located, and the conditions in winter, spring, and autumn are suitable for this condition. Therefore, the dehumidification heating mode of the air conditioning system of the present invention is particularly useful in areas where the outside temperature does not drop extremely even in winter. In addition, by performing a dehumidification operation close to adiabatic dehumidification, such as rotating the rotor as slowly as possible, and adjusting the rotation speed while considering the balance with the amount of dehumidification, it is possible to effectively exert the dehumidification performance and the temperature rise due to the heat of adsorption.

[0057] As described above, the air conditioning system of the present invention is characterized by having a total heat exchange cooling mode in which the air in the greenhouse is subjected to total heat exchange with the outside air during the day, and the air at the treatment outlet is cooled using a cooling tower or the like, thereby reducing the temperature and humidity inside the greenhouse, and a dehumidification heating mode in which the air in the greenhouse is dehumidified and the greenhouse is heated by adsorption heat during the night. The operation mode of the total heat exchanger can be easily switched by changing the rotation speed of the total heat exchange rotor, and a closed greenhouse in which the temperature and humidity suitable for plant growth can be maintained throughout the day and night is realized, and plants can be produced in a stable internal environment. The dehumidification operation of the nighttime dehumidification heating mode is characterized by using the relative humidity swing as a driving force by lowering the regeneration inlet humidity below the treatment inlet humidity, and therefore the regeneration temperature can be sufficient in a temperature range lower than that of normal low-temperature regeneration. For this reason, the regeneration inlet temperature may be lower than the treatment inlet temperature.

[0058] In normal dehumidification, since indoor spaces are generally dry in winter, humidified air that has passed through the regeneration zone is supplied to the room, and dehumidified air that has passed through the treatment zone is exhausted. However, the present invention uses the exact opposite idea of ​​dehumidifying the indoor space (inside the house).

[0059] The total heat exchanger 3 is not limited to a total heat exchange rotor, and two or more stationary cross-sectional total heat exchangers may be installed, switching between treatment (ventilation of indoor air) and regeneration (ventilation of outdoor air) in a batch manner, and switching between total heat exchange cooling mode and dehumidification heating mode by controlling the ventilation time, etc.

[0060] In FIG. 1, the carbon dioxide supplying device 2 is installed inside the house 1, and the total heat exchanger 3 is installed outside the house 1, but the present invention is not limited to this, and both may be installed inside or outside the house 1. Alternatively, the carbon dioxide supplying device 2 and the total heat exchanger 3 may be installed between the indoor and outdoor spaces of the house 1, the adsorption zone of the carbon dioxide supplying device 2 may be installed outside the house 1, the desorption zone may be installed inside the house 1, the regeneration zone of the total heat exchanger 3 may be installed outside the house 1, and the treatment zone may be installed inside the house 1. In this way, it is possible to eliminate ducts connecting the carbon dioxide supplying device 2, the total heat exchanger 3, and the house 1. Alternatively, the total heat exchange rotor 5 may have zones other than the treatment zone and the regeneration zone.

[0061] The carbon dioxide supplying device 2 and the total heat exchanger 3 may be combined into an integrated device (unit). In this case, the device as a whole becomes compact, but since the air volumes processed by the carbon dioxide supplying device and the total heat exchanger are significantly different, it becomes difficult to separately control the carbon dioxide concentration and the temperature and humidity inside the greenhouse.

[0062] In controlling the carbon dioxide concentration in the greenhouse by the carbon dioxide supplying device 2 and controlling the temperature and humidity by the total heat exchanger 3, the air volume processed by the total heat exchanger is overwhelmingly large. Therefore, it is preferable to separate and install the carbon dioxide supplying device 2 and the total heat exchanger 3 as shown in Figure 1, because this makes it easier to control the carbon dioxide supply concentration and the temperature and humidity in the greenhouse separately. It is also preferable to install the total heat exchanger 3 separately, since this allows various devices to be used as the carbon dioxide supplying device.

[0063] In FIG. 1, one carbon dioxide supplying device 2 and one total heat exchanger 3 are installed, but this is not limited thereto, and either one or both may be installed in multiple units. For example, when the house 1 is large or when the temperature and humidity in the house 1 are increased significantly, if one total heat exchanger is used to adjust the temperature and humidity, the rotor diameter becomes large and the device must be large. However, by using multiple devices, each device can be made small while providing redundancy, which is effective when there is a problem with the installation space of the device. In addition, in FIG. 2, the blower 8 is placed on the treatment inlet side and the blower 9 is placed on the regeneration outlet side, but this is not limited thereto. For example, by providing the blower 9 on the regeneration inlet side, the heating effect on the regeneration side can be increased by raising the temperature by the blower.

[0064] In order to keep the greenhouse warm, a lining curtain such as a sliding or rolling curtain is deployed to block light, block heat, keep warm, and adjust the amount of sunlight. By using this lining curtain to reduce the space to be air-conditioned, the cooling effect during the day and the heating effect during the night can be enhanced, and the supply air flow rate can be reduced, so that costs can be further reduced. In this case, it is preferable to use a highly airtight sheet, and since the humidity is adjusted throughout the day and night by the total heat exchanger, the relative humidity in the greenhouse does not increase and condensation does not occur. In addition to the air conditioning system of the present invention, other cooling equipment or heating equipment may be used as a supplement. When performing tunnel cultivation, air from the air conditioning system of the present invention may be supplied into the tunnel.

[0065] As described above, airflow is generated in a closed greenhouse by performing total heat exchange or dehumidification using a total heat exchanger. As mentioned above, if the greenhouse is simply a closed system, the airflow will be weak and photosynthesis will be suppressed even if the stomata in the leaves are open, but a total heat exchanger can create airflow in the greenhouse, making it possible to promote photosynthesis in the leaves. In addition, airflow makes it possible to make the temperature, humidity, and carbon dioxide concentration in the greenhouse uniform.

[0066] In the air conditioning system of the present invention, when the house is closed, the temperature and humidity are adjusted by the total heat exchanger, and carbon dioxide is supplied using a carbon dioxide supplying device, it is possible to maintain the carbon dioxide concentration at a high level of 800 to 1000 ppm.

[0067] Although the above describes the case of adjusting the temperature and humidity inside a house, the present invention is not limited to a house and can be applied to any indoor space where it is necessary to adjust the temperature and humidity. In this case, the word "house" in this embodiment is replaced with "indoor space." [Industrial Applicability]

[0068] The air conditioning system of the present invention can maintain the temperature and humidity inside the greenhouse at a level suitable for plant growth throughout the day and night, and is particularly effective for cultivating strawberries, which are a winter crop, and can produce high-yield, high-quality strawberries. It can be applied not only to greenhouses where plants are grown, but also to internal environmental control of indoor spaces such as buildings that require a constant indoor environment and reactors that house chemical reaction systems that dislike moisture. It can be used for various purposes as long as it is intended to adjust the temperature and humidity inside indoor spaces during the day and avoid temperature drops at night. If the room is isolated from the outside air, the carbon dioxide supply device of the present invention can be used for other purposes by replacing it with a supply device for other gases such as oxygen or nitrogen. In addition, since the regeneration temperature is lower, various heat utilization is possible, making it a highly energy-saving device. [Explanation of symbols]

[0069] 1 House 2 Carbon dioxide supply device 3 Total heat exchanger 4. Adsorption rotor 5 Total heat exchange rotor 6 Treatment Zone 7. Play Zone 8, 9 Blower 10 First heat exchanger 11 Second heat exchanger

Claims

1. A total heat exchanger is provided, and the total heat exchanger has two operation modes, a total heat exchange cooling mode and a dehumidification heating mode. In the total heat exchange cooling mode, the air in the indoor space is subjected to total heat exchange with the outside air to lower the temperature and humidity, and then returned to the indoor space. In the dehumidification heating mode, the air in the indoor space is dehumidified to reduce humidity, and the air whose temperature has increased due to heat of adsorption generated by the dehumidification is returned to the indoor space. An air conditioning system characterized in that the temperature and humidity of the indoor space are adjusted by switching the operation mode.

2. 2. The air conditioning system according to claim 1, wherein in the total heat exchange cooling mode, the air that has passed through the total heat exchanger is further cooled by a first heat exchanger and returned to the indoor space.

3. 3. The air conditioning system according to claim 2, wherein the first heat exchanger is a cooling tower.

4. 4. The air conditioning system according to claim 1, wherein the total heat exchanger comprises a total heat exchange rotor.

5. 5. The air conditioning system according to claim 4, wherein the total heat exchange rotor rotates at a high speed in the total heat exchange cooling mode and at a low speed in the dehumidification heating mode, and the operating mode is switched by adjusting the rotation speed.

6. The air conditioning system according to claim 4, characterized in that the total heat exchange rotor has at least a treatment zone and a regeneration zone, the air in the indoor space passes through the treatment zone and is supplied to the indoor space again, and the outside air passes through the regeneration zone and is exhausted.

7. The air conditioning system according to claim 6, further comprising a second heat exchanger provided before the regeneration zone, the outside air being heated by the second heat exchanger and sent to the regeneration zone.

8. 7. The air conditioning system according to claim 6, wherein in said total heat exchange rotor, the relative humidity at the regeneration inlet is lower than the relative humidity at the treatment inlet.

9. 7. The air conditioning system according to claim 6, wherein in said total heat exchange rotor, the temperature of the regeneration inlet is lower than the temperature of the treatment inlet.

10. 2. The air conditioning system according to claim 1, wherein the indoor space is a house.

11. 11. An air conditioning system according to claim 10, further comprising a carbon dioxide supply device.

12. 12. The air conditioning system according to claim 11, wherein the carbon dioxide supplying device includes an adsorption rotor having at least an adsorption zone and a desorption zone, the outside air is passed through the adsorption zone to adsorb carbon dioxide and then exhausted, and the air inside the house is heated and passed through the desorption zone to desorb carbon dioxide, thereby supplying high-concentration carbon dioxide into the house.

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