JP2020182428A - Agricultural greenhouse - Google Patents

Abstract

To provide an agricultural greenhouse that can sufficiently suppress rise of internal temperature without consuming special energy.SOLUTION: An agricultural greenhouse in which a roof part and a sidewall part are formed of a translucent material that allows sunlight to pass through, in which a film-state radiative cooling body CP provided with an infrared radiation layer A which radiates infrared light from a radiation surface H and allows sunlight entering from the radiation surface H to pass through, and a light reflection layer B which is positioned on the opposite side of a side where the radiation surface H is present in the infrared radiation layer A are provided for the roof part.SELECTED DRAWING: Figure 9

Description

The present invention relates to an agricultural greenhouse having a roof portion and a side wall portion.

Agricultural greenhouses, sometimes referred to as agricultural greenhouses, will be used to grow a variety of crops while illuminating through the roof and side walls.
The internal temperature of such an agricultural house may rise excessively in spring, summer, and autumn, and therefore, some are configured to cool the inside of the agricultural house by a heat pump type air conditioner (for example, Patent Document). 1).

In addition, in order to suppress the rise in the internal temperature of the agricultural greenhouse, a light-reflecting aluminum film is attached to the surface of the non-woven fabric as a translucent material forming the roof of the agricultural greenhouse to form the roof. Some are configured to block light (see, for example, Patent Document 2).
Incidentally, in Patent Document 2, a plurality of aluminum films are provided in a state of being lined up at appropriate intervals, and light such as sunlight is transmitted through the adjacent aluminum films.

Jikkenhei 5-90220 Jikkenhei 3-6480 Gazette

In the agricultural greenhouse of Patent Document 1, the internal temperature of the agricultural greenhouse can be maintained at an appropriate temperature, but the running cost for driving the heat pump type air conditioner is high.

The agricultural house of Patent Document 2 can suppress an increase in the internal temperature of the agricultural house by shading the roof portion of the agricultural house. However, there is an inconvenience that the rise in the internal temperature of the agricultural greenhouse cannot be sufficiently suppressed by simply shading the roof of the agricultural greenhouse.
In order to maintain the internal temperature of the agricultural house at an appropriate temperature, for example, a heat pump type air conditioner for cooling the inside of the agricultural house is provided. In this case, the heat pump type air conditioner is provided. It becomes impossible to sufficiently reduce the running cost for driving the air conditioner.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an agricultural house capable of appropriately suppressing an increase in internal temperature without consuming special energy. is there.

The agricultural house of the present invention includes a roof portion and a side wall portion, and the characteristic configuration thereof is as follows.
An infrared radiation layer that emits infrared light from a radiation surface and transmits sunlight incident from the radiation surface, and a light reflection layer that is located on the opposite side of the infrared radiation zone from the side where the radiation surface exists. A film-like radiant cooling body provided with the above is provided on the roof portion.

That is, since the film-shaped radiative cooling body is provided on the roof part, the radiative cooling body exerts the action of radiatively cooling the inside of the agricultural house, so that the agricultural house does not consume any special energy. The rise in internal temperature can be sufficiently suppressed.
By the way, radiative cooling is a phenomenon in which a substance emits electromagnetic waves such as infrared rays to its surroundings to lower its temperature. By utilizing this phenomenon, for example, it is possible to cool an object without consuming energy such as electricity.

To add an explanation, the light (ultraviolet light, visible light, infrared light) incident from the radiating surface of the infrared radiating zone passes through the radiating zone and then is the existing side of the radiating surface of the infrared radiating zone. It is reflected by the light reflecting layer on the opposite side and escapes from the radiation surface to the outside of the system.
That is, the light reflecting layer reflects the light transmitted through the infrared radiation layer (ultraviolet light, visible light, infrared light) and radiates it from the radiation surface, whereby the light transmitted through the infrared radiation layer (ultraviolet light, Visible light, infrared light) is projected into the agricultural house to prevent the inside of the agricultural house from being heated.

In the description of the present specification, when simply referred to as light, the concept of light includes ultraviolet light, visible light, and infrared light. When these are described in terms of the wavelength of light as an electromagnetic wave, the electromagnetic wave having a wavelength of 10 nm to 20000 nm (0.01 μm to 20 μm) is included.

In addition to the light transmitted through the infrared radiation layer, the light reflection layer also has the effect of reflecting the light emitted from the infrared radiation layer to the existing side of the light reflection layer toward the infrared radiation layer. However, in the following description, it is assumed that the light reflecting layer is provided to reflect the light (ultraviolet light, visible light, infrared light) transmitted through the infrared emitting layer.

Then, the heat transfer to the radiative cooling body (heat transfer from the inside of the agricultural house and heat transfer from the atmosphere) is converted into infrared rays by the infrared radiant zone and is released from the radiating surface to the outside of the system.
In other words, when heat is transferred from the inside of the agricultural house to the radiative cooling body, radiative cooling is performed in which the infrared radiating zone radiates infrared light from the radiating surface, and as a result, the inside of the agricultural house is cooled. Will be done.

As described above, by providing the radiative cooling body on the roof, the sunlight radiated to the radiative cooling body is reflected, and the heat transferred from the inside of the agricultural house to the radiative cooling body is used as infrared light to the outside of the system. By radiating, the inside of the agricultural house can be cooled and the rise in the internal temperature of the agricultural house can be appropriately suppressed.

In short, according to the characteristic configuration of the agricultural greenhouse of the present invention, it is possible to appropriately suppress an increase in the internal temperature without consuming special energy.

A further characteristic configuration of the agricultural greenhouse of the present invention is that the radiative cooling body is provided in a form in which the light reflecting layer is partially positioned with respect to the roof portion.

That is, since the radiation cooling body is provided in a form in which the light reflecting layer is partially positioned with respect to the roof portion, among the light (ultraviolet light, visible light, infrared light) transmitted through the infrared radiation layer. Some light will pass through the light-reflecting layer and be projected into the interior of the agricultural house without being reflected by the light-reflecting layer.

Therefore, since the light transmitted through the light reflecting layer and projected inside the agricultural greenhouse can be applied to the crops in the agricultural greenhouse, the crops in the agricultural greenhouse can be grown well.
In other words, for the growth of crops, it is necessary to irradiate light for photosynthesis, etc., but a part of the light (ultraviolet light, visible light, infrared light) transmitted through the infrared radiation layer. Light can pass through the light-reflecting layer and illuminate the crops in the agricultural house.

In short, according to the further characteristic composition of the agricultural greenhouse of the present invention, the crops in the agricultural greenhouse can be grown well.

A further characteristic configuration of the agricultural greenhouse of the present invention is that the radiative cooling body is partially provided with respect to the roof portion so that the light reflecting layer is partially positioned with respect to the roof portion. At the point.

That is, the radiative cooling body is partially provided with respect to the roof portion so that the light reflecting layer is partially positioned with respect to the roof portion.
That is, for example, the radiative cooling bodies formed in a band shape are provided side by side at intervals in the width direction, and the radiative cooling bodies are partially provided with respect to the roof portion, whereby the light reflecting layer is provided. Is partially positioned with respect to the roof.

In this way, by partially providing the radiant cooling body with respect to the roof portion, the light reflecting layer is partially positioned with respect to the roof portion. By changing the setting of the state in which the light is installed, the light shielding rate by the light reflecting layer, in other words, the light passing rate in the light reflecting layer can be variously changed in order to change the irradiation amount of irradiating the crop with light.

That is, the irradiation amount of irradiating the crop with light differs depending on the variety of the crop, etc., but the shading rate by the light reflecting layer (in the light reflecting layer) depends on the variety of the crop in the agricultural house. The light transmission rate) can be set to an appropriate state by setting the state in which the radiation cooling body is installed on the roof portion.

In short, according to the further characteristic configuration of the agricultural greenhouse of the present invention, the shading rate by the light reflecting layer can be changed and set.

A further characteristic configuration of the agricultural house of the present invention is that the radiative cooling body is formed so that the light reflecting layer is partially positioned with respect to the infrared radiating layer, thereby forming the light reflecting layer. The point is that the form is partially positioned with respect to the roof portion.

That is, the radiative cooling body is formed so that the light reflecting layer is partially positioned with respect to the infrared radiation layer, and the light reflecting layer is partially positioned with respect to the roof portion.

Therefore, as long as the radiative cooling body is installed on the roof portion, the light reflecting layer can be partially positioned with respect to the roof portion, so that the light reflecting layer is partially positioned with respect to the roof portion. It is possible to facilitate the work of installing the radiative cooling body on the roof portion in a state where the radiation cooling body is formed.

By the way, since the radiative cooling body is formed so that the light reflecting layer is partially positioned with respect to the infrared radiating layer, the radiative cooling body can be installed on the entire roof portion, and also. As an example, the radiative cooling body can be installed on the roof portion as a translucent material forming the roof portion.

In short, according to the further characteristic configuration of the agricultural greenhouse of the present invention, it is possible to facilitate the work of installing the radiative cooling body on the roof portion.

A further characteristic configuration of the agricultural house of the present invention is a resin material layer adjusted to a thickness in which the infrared radiant layer emits thermal radiant energy larger than the absorbed solar energy in a wavelength band of 8 μm to 14 μm. At some point.

That is, the infrared radiant layer is configured as a resin material layer, and the thickness of the resin material layer is adjusted so as to emit thermal radiation energy larger than the absorbed solar energy in the band of wavelength 8 μm to wavelength 14 μm. Therefore, the radiant cooler can properly exert its cooling function even in a solar radiation environment.

Since the resin material layer is formed of a highly flexible resin material, the resin material layer can be made flexible. Incidentally, the light-reflecting layer can be made flexible, for example, by forming it as a thin film of silver.
Therefore, it is possible to give flexibility to the radiative cooling body provided with the resin material layer and the light reflecting layer, and to prevent mechanical damage such as cracking of the radiative cooling body installed on the roof portion.

In short, according to the further characteristic configuration of the agricultural greenhouse of the present invention, mechanical damage to the radiative cooling body can be suppressed.

A further characteristic configuration of the agricultural house of the present invention is that the light reflecting layer has a reflectance of 90% or more at a wavelength of 0.4 μm to 0.5 μm and a reflectance of 96% or more of a long wave from a wavelength of 0.5 μm. At the point.

That is, the sunlight spectrum exists from a wavelength of 0.3 μm to 4 μm, and the intensity increases as the wavelength increases from 0.4 μm, and the intensity increases particularly from the wavelength of 0.5 μm to the wavelength of 2.5 μm.
When the light reflecting layer has a reflectance of 90% or more from a wavelength of 0.4 μm to 0.5 μm and a reflectance of a long wave having a wavelength of 0.5 μm or more of 96% or more, the light reflecting layer is subjected to sunlight. It absorbs less than about 5% of energy.

As a result, the solar energy absorbed by the light-reflecting layer can be reduced to about 50 W / m ² or less in the middle of the south in summer, and radiative cooling by the resin material layer can be performed satisfactorily.
In this specification, the spectrum of sunlight is defined as AM1.5G unless otherwise specified.

In short, according to the further characteristic configuration of the agricultural house of the present invention, the radiative cooling body can suppress the absorption of solar energy by the light reflecting layer and radiative cooling by the resin material layer can be performed satisfactorily.

A further characteristic configuration of the agricultural greenhouse of the present invention is that the film thickness of the resin material layer is
The wavelength average of the light absorption rate from 0.4 μm to 0.5 μm is 13% or less, the wavelength average of the light absorption rate from 0.5 μm to 0.8 μm wavelength is 4% or less, and the wavelength average is 0.8 μm. It has light absorption characteristics such that the wavelength average of the light absorption rate up to a wavelength of 1.5 μm is within 1%, and the wavelength average of the light absorption rate from 1.5 μm to 2.5 μm is 40% or less.
The point is that the thickness is adjusted to a state having a thermal radiation characteristic in which the wavelength average of the emissivity of 8 μm to 14 μm is 40% or more.

The wavelength average of the light absorption rate of the wavelength of 0.4 μm to 0.5 μm means the average value of the light absorption rate for each wavelength in the range of 0.4 μm to 0.5 μm, and includes the emissivity. Other similar statements mean similar averages. Hereinafter, the same applies to the present specification.

That is, the light absorption rate and the emissivity (light emissivity) of the resin material layer change depending on the thickness. Therefore, it is necessary to adjust the thickness of the resin material layer so as not to absorb sunlight as much as possible and to emit large thermal radiation in the wavelength band of the so-called atmospheric window region (the region of light wavelength of 8 μm to 20 μm).

Specifically, from the viewpoint of the light absorption rate (light absorption characteristic) of sunlight in the resin material layer, the wavelength average of the light absorption rate of the wavelengths of 0.4 μm to 0.5 μm is 13% or less, and the wavelength is 0.5 μm. The wavelength average of the light absorption rate of 0.8 μm is 4% or less, the wavelength average of the light absorption rate from 0.8 μm to 1.5 μm is within 1%, and 1.5 μm to 2.5 μm. It is necessary that the wavelength average of the light absorption rates up to is 40% or less. Regarding the light absorption rate from 2.5 μm to 4 μm, the wavelength average may be 100% or less.
When such a light absorption rate is distributed, the light absorption rate of sunlight is 10% or less, and the energy is 100 W or less.

That is, the light absorption rate of sunlight increases as the film thickness of the resin material layer is increased. When the resin material layer to a thick film, approximately 1 becomes the emissivity of the atmospheric windows, heat radiation to release the universe that time becomes 160 W / ^{m 2} from 125W / ^{m 2.}
As described above, the sunlight absorption in the light reflecting layer is preferably 50 W / m ² or less.
Therefore, if the sum of the sunlight absorption in the resin material layer and the light reflecting layer is 150 W / m ² or less and the atmospheric condition is good, cooling proceeds. As the resin material layer, it is preferable to use a resin material layer having a small absorption rate near the peak value of the sunlight spectrum as described above.

Further, from the viewpoint of the emissivity (thermal radiation characteristic) of emitting infrared light of the resin material layer, the wavelength average of the emissivity having a wavelength of 8 μm to 14 μm needs to be 40% or more.
That is, in order for the heat radiation of sunlight of about 50 W / m ² absorbed by the light reflection layer to be emitted from the resin material layer into space, it is necessary for the resin material layer to emit more heat radiation.
For example, when the outside air temperature is 30 ° C., the maximum thermal radiation of an atmospheric window having a wavelength of 8 μm to 14 μm is 200 W / m ² (calculated assuming an emissivity of 1). This value can be obtained in fine weather, such as in high mountains, where the air is thin and dry. In lowlands, the thickness of the atmosphere is thicker than that of high mountains, so the wavelength band of the windows of the atmosphere becomes narrower and the transmittance decreases. By the way, this is called "the window of the atmosphere becomes narrower".

In addition, the environment in which the radiative cooling body is actually used may be humid, and even in that case, the window of the atmosphere becomes narrow. The thermal radiation generated in the window area of the atmosphere when used in lowlands is estimated to be 160 W / m ² at 30 ° C. in good condition (calculated as emissivity 1).
Also, as is often the case in Japan, when there is haze in the sky or when smog is present, the atmospheric window becomes even narrower and the radiation to space is about 125 W / m ² .

In view of these circumstances, the wavelength average of the emissivity of 8 μm to 14 μm must be 40% or more (the thermal radiation intensity in the window zone of the atmosphere is 50 W / m ² or more) before it can be used in the lowlands of the mid-latitude zone.
Therefore, by adjusting the thickness of the resin material layer so as to be within the above-mentioned optical specification range, the heat output from the window of the atmosphere becomes larger than the heat input due to the light absorption of sunlight, and the daytime solar radiation It will be possible to radiatively cool outdoors even in an environment.

In short, according to the further characteristic configuration of the agricultural house of the present invention, the heat output from the window of the atmosphere is larger than the heat input due to the absorption of sunlight, and the inside of the agricultural house can be exposed to sunlight. Can be radiatively cooled.

A further characteristic configuration of the agricultural house of the present invention is that the resin material forming the resin material layer is any one of carbon-fluorine bond, siloxane bond, carbon-chlorine bond, carbon-oxygen bond, ester bond, and benzene ring. The point is that it is selected from resins having one or more of.

That is, as the resin material forming the resin material layer, carbon-fluorine bond (CF), siloxane bond (Si—O—Si), carbon-chlorine bond (C—Cl), ether bond (R-COO-R) ), An ester bond (COC), or a colorless resin material having at least one benzene ring can be used.

According to Kirchhoff's law, the emissivity (ε) and the light absorption rate (A) are equal. The light absorption rate (A) can be obtained from the absorption coefficient (α) by the following equation 1.
A = exp (−αt) ... (Equation 1) t is the film thickness.
That is, when the thickness of the resin material layer is increased, a large amount of heat radiation can be obtained in a wavelength band having a large absorption coefficient. When radiative cooling is performed outdoors, it is preferable to use a material having a large absorption coefficient in the wavelength band of 8 μm to 14 μm, which is the wavelength band of the window of the atmosphere. Further, in order to suppress the absorption of sunlight, it is preferable to use a material having no absorption coefficient or a small material in the wavelength range of 0.3 μm to 4 μm, particularly 0.4 μm to 2.5 μm. As can be seen from the relational expression between the absorption coefficient and the light absorption coefficient of the above formula 1, the light absorption coefficient (emissivity) changes depending on the film thickness of the resin material layer.

In order to lower the temperature from the surrounding atmosphere by radiative cooling in a solar radiation environment, the resin material that forms the resin material layer has a large absorption coefficient in the wavelength band of the window of the atmosphere and the absorption coefficient in the wavelength band of sunlight. If you choose a material that has almost no sunlight, by adjusting the film thickness of the resin material layer, it will hardly absorb sunlight, but it will emit more heat radiation from the windows of the atmosphere, that is, the output by radiative cooling rather than the input of sunlight. A larger state can be created.

The absorption spectrum of the resin material forming the resin material layer will be described.
Regarding the carbon-fluorine bond (CF), the absorption coefficient due to CHF and CF ₂ spreads widely over a wide band from the wavelength of 8 μm to 14 μm, which is the window of the atmosphere, and the absorption coefficient is particularly large at 8.6 μm. At the same time, regarding the wavelength band of sunlight, there is no conspicuous absorption coefficient at a wavelength of 0.3-2.5 μm, which has a large energy.

As a resin material having a CF bond,
Polytetrafluoroethylene (PTFE), a completely fluorinated resin,
Polychlorotrifluoroethylene (PCTFE) and polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), which are partially fluorinated resins,
Perfluoroalkoxy alkane resin (PFA), which is a fluororesin copolymer,
Ethylene tetrafluorinated / propylene hexafluorinated copolymer (FEP),
Ethylene / ethylene tetrafluoride copolymer (ETFE),
Ethylene / chlorotrifluoroethylene copolymer (ECTFE) can be mentioned.

The binding energies of CC bond, CH bond, and CF bond of the basic structure part represented by polyvinylidene fluoride (PVDF) are 4.50 eV, 4.46 eV, and 5.05 eV. They correspond to wavelengths of 0.275 μm, 0.278 μm, and 0.246 μm, respectively, and absorb light on the shorter wavelength side than these wavelengths.
Since the sunlight spectrum has only long waves having a wavelength of 0.300 μm, when a fluororesin is used, it hardly absorbs ultraviolet rays, visible rays, and near infrared rays of sunlight.
The ultraviolet rays have a wavelength on the shorter wavelength side than 0.400 μm, the visible rays have a wavelength of 0.400 μm to 0.800 μm, the near infrared rays have a wavelength of 0.800 μm to 3 μm, and the mid infrared rays have a wavelength of 3 μm. The range is from 8 μm, and far infrared rays are in the range on the longer wavelength side than the wavelength of 8 μm.

Examples of the resin material having a siloxane bond (Si—O—Si) include silicone rubber and silicone resin. In the resin material, a large absorption coefficient due to expansion and contraction of the C—Si bond appears broadly around a wavelength of 13.3 μm, and an absorption coefficient due to the out-of-plane variation angle (pitch) of CSiH ₂ is 10 μm in wavelength. The absorption coefficient due to the in-plane in-plane variation (scissors) of CSiH ₂ appears small in the vicinity of the wavelength of 8 μm. In this way, it has a large absorption coefficient in the window of the atmosphere.
In the ultraviolet region, the binding energy of Si—O—Si in the main chain is 4.60 eV, which corresponds to a wavelength of 0.269 μm and absorbs light on a wavelength side shorter than this wavelength. Since the sunlight spectrum has only waves longer than the wavelength of 0.300 μm, when siloxane bonds are used, it hardly absorbs ultraviolet rays, visible rays, and near infrared rays of sunlight.

Regarding the carbon-chlorine bond (C-Cl), the absorption coefficient due to the C-Cl expansion and contraction vibration appears in a wide band with a half width of 1 μm or more centered on a wavelength of 12 μm.
Further, as a resin material having a carbon-chlorine bond (C-Cl), polyvinyl chloride (PVC) can be mentioned, but in the case of polyvinyl chloride, the C of the alkene contained in the main chain is affected by the electron suction of chlorine. -The absorption coefficient derived from the eccentric vibration of H appears around the wavelength of 10 μm. That is, it is possible to emit a large amount of heat radiation in the wavelength band of the window of the atmosphere. The binding energy of carbon and chlorine of alkene is 3.28 eV, its wavelength corresponds to 0.378 μm, and it absorbs light on the shorter wavelength side than this wavelength. That is, it absorbs the ultraviolet rays of sunlight, but has almost no absorption in the visible region.

The ether bond (R-COO-R) and ester bond (C-OC) have an absorption coefficient from a wavelength of 7.8 μm to 9.9 μm. Further, with respect to the carbon-oxygen bond contained in the ester bond and the ether bond, a strong absorption coefficient appears in the wavelength band of 8 μm to 10 μm.
When the benzene ring is introduced into the side chain of the hydrocarbon resin, absorption widely appears from a wavelength of 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements due to the influence of the benzene ring.
Examples of the resin having these bonds include polymethyl methacrylate resin, ethylene terephthalate resin, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate. For example, the binding energy of the CC bond of methyl methacrylate is 3.93 eV, which corresponds to a wavelength of 0.315 μm and absorbs sunlight having a wavelength shorter than this wavelength, but has almost no absorption in the visible region.

If the resin material forming the resin material layer has the above-mentioned radiation coefficient and absorption rate characteristics, the resin material layer may be a single-layer film of one type of resin material or a multilayer film of a plurality of types of resin materials. A single-layer film of a resin material in which a plurality of types are blended or a multilayer film of a resin material in which a plurality of types are blended may be used. The blend also includes copolymers such as alternate copolymers, random copolymers, block copolymers, and graft copolymers, and modified products in which side chains are replaced.

In short, according to the further characteristic configuration of the agricultural house of the present invention, the radiative cooling body can create a state in which the output by radiative cooling is larger than the input of sunlight.

A further characteristic configuration of the agricultural greenhouse of the present invention is that the main component of the resin material forming the resin material layer is siloxane.
The point is that the thickness of the resin material layer is 1 μm or more.

That is, as can be seen from A = exp (−αt) in the above formula 1, the light absorption rate (emissivity) changes depending on the thickness t. The light absorption rate (emissivity) of the resin material needs to be thick enough to have a large absorption coefficient in the window of the atmosphere.
In the case of a resin material whose main component is a siloxane bond (Si—O—Si), if the film thickness is 1 μm or more, the radiant intensity in the window of the atmosphere becomes large, and the output by radiative cooling is higher than the input of sunlight. A larger state can be created.

In short, according to a further characteristic configuration of the agricultural house of the present invention, the radiative cooling body outputs by radiative cooling rather than the input of sunlight when the main component of the resin material forming the resin material layer is siloxane. Can create a larger state.

A further characteristic configuration of the agricultural greenhouse of the present invention is that the thickness of the resin material layer is 10 μm or more.

That is, the resin material that forms the resin material layer in the radiative cooling body is a carbon-fluorine bond (CF), a carbon-chlorine bond (C-Cl), an ester bond (R-COO-R), and an ether. In the case of a resin material whose main component is either a bond (COC) or a benzene ring, if the film thickness is 10 μm or more, the radiation intensity in the window of the atmosphere increases, and the radiative cooling body becomes sunlight. The output by radiative cooling can create a larger state than the input of.

In short, according to the further characteristic configuration of the agricultural house of the present invention, the resin material forming the resin material layer of the radiative cooling body is carbon-fluorine bond (CF), carbon-chlorine bond (C-Cl). In the case of a resin material whose main component is an ester bond (R-COO-R), an ether bond (COC), or a benzene ring, the radiative cooling body is radiatively cooled rather than the input of sunlight. The output can create a larger state.

A further characteristic configuration of the agricultural greenhouse of the present invention is that the thickness of the resin material layer is 20 mm or less.

That is, the thermal radiation of the atmospheric window of the resin material forming the resin material layer of the radiative cooling body is generated within a range of about 100 μm from the material surface.
That is, even if the thickness of the resin material is increased, the thickness that contributes to radiative cooling does not change, and the remaining thickness has the effect of insulating the cold heat after radiative cooling. If a resin material layer that ideally does not absorb sunlight at all is formed, sunlight is absorbed only by the light reflecting layer of the radiative cooling body.

The thermal conductivity of the resin material is generally about 0.2 W / m · K, and when the thickness of the resin material layer exceeds 20 mm, the cooling surface (resin material layer in the light reflecting layer) is calculated in consideration of this thermal conductivity. The temperature of the surface opposite to the side where the plastic exists) rises. Even if there is an ideal resin material that does not absorb sunlight at all, the thermal conductivity of the resin material is generally about 0.2 W / m · K, so if the thickness is 20 mm or more, the heat radiation of the resin material layer Since the inside of the agricultural house cannot be cooled by the (radiative cooling) cooling surface, the film thickness cannot be 20 mm or more.

In short, according to the further characteristic configuration of the agricultural greenhouse of the present invention, the inside of the agricultural greenhouse can be appropriately cooled.

A further characteristic configuration of the agricultural greenhouse of the present invention is that the resin material is fluororesin or silicone rubber.

That is, a fluororesin whose main component is a carbon-fluorine bond (CF), that is, polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF). ), Perfluoroalkoxy alkane resin (PFA), and ethylene tetrafluoride / propylene hexafluoride copolymer (FEPP) have almost no light absorption in the ultraviolet light region, visible light, and near infrared region of the sunlight spectrum.

Further, a resin having a siloxane bond (Si—O—Si) as a main chain and a small side chain molecular weight, that is, silicone rubber, is similar to a fluororesin in the ultraviolet region, visible light, and near infrared region of the sunlight spectrum. Has almost no light absorption.
The thermal conductivity of the fluororesin and the silicone rubber is 0.2 W / m · K, and in view of this point, these resins exhibit a radiative cooling function even if the thickness is increased to 20 mm.

In short, according to a further characteristic configuration of the agricultural greenhouse of the present invention, the radiative cooling body appropriately exerts the radiative cooling function when the resin material forming the resin material layer is fluororesin or silicone rubber. Can be done.

A further characteristic configuration of the agricultural house of the present invention is that the infrared radiating zone is any one of alkali-free glass, crown glass, and borosilicate glass.

That is, non-alkali glass, crown glass, and borosilicate glass are relatively inexpensive, but have excellent transparency of sunlight (visible light, ultraviolet light, near infrared light) (for example, about 80%). Because it is transparent), it does not absorb sunlight and emits infrared light with a wavelength equivalent to that of an atmospheric window (for example, a window that transmits infrared light with a wavelength of 8 to 14 μm). It has the property of high radiation intensity.

Therefore, by forming the infrared radiating zone with any one of alkali-free glass, crown glass, and borosilicate glass, a radiative cooling body having a high cooling capacity can be obtained while reducing the overall configuration. Obtainable.

In short, according to the further characteristic configuration of the agricultural greenhouse of the present invention, it is possible to obtain an improvement in the cooling capacity of the radiative cooling body while reducing the overall configuration.

A further characteristic configuration of the agricultural greenhouse of the present invention is that the light reflecting layer is made of silver or a silver alloy and has a thickness of 50 nm or more.

That is, in order to give the light reflecting layer the above-mentioned reflectance characteristic, that is, the reflectance characteristic of a wavelength of 0.4 μm to 0.5 μm of 90% or more and a reflectance of a long wave from a wavelength of 500 nm of 96% or more. The reflective material on the radiation surface side of the light reflecting layer needs to be silver or a silver alloy.
When sunlight is reflected with only silver or a silver alloy having the above-mentioned reflectance characteristics, a thickness of 50 nm or more is required.

In short, according to the further characteristic configuration of the agricultural greenhouse of the present invention, the radiative cooling body can accurately suppress the absorption of solar energy by the light reflecting layer and satisfactorily perform radiative cooling by the resin material layer. ..

A further characteristic configuration of the agricultural house of the present invention is that the light reflecting layer has a laminated structure of silver or a silver alloy and aluminum or an aluminum alloy.

That is, in order to give the light reflecting layer the above-mentioned reflectance characteristics, a structure in which silver or a silver alloy and aluminum or an aluminum alloy are laminated may be used. In this case as well, the reflective material on the radiation surface side needs to be silver or a silver alloy. In this case, the thickness of silver needs to be 10 nm or more, and the thickness of aluminum needs to be 30 nm or more.

Since aluminum or an aluminum alloy is cheaper than silver or a silver alloy, the light reflecting layer can be made cheaper while having appropriate reflectance characteristics.
In other words, it is appropriate to make the light-reflecting layer a laminated structure of silver or silver alloy and aluminum or aluminum alloy while thinning the expensive silver or silver alloy to reduce the cost of the light-reflecting layer. It is possible to reduce the cost of the light-reflecting layer while having a good reflectance characteristic.

In short, according to the further characteristic configuration of the agricultural greenhouse of the present invention, it is possible to reduce the cost of the light reflecting layer while having appropriate reflectance characteristics.

It is a perspective view of an agricultural house. It is a side view of an agricultural house. It is a perspective view of another form of an agricultural greenhouse. It is a side view of another form of an agricultural greenhouse. It is a schematic diagram which shows the installation form of a radiative cooling body. It is a schematic diagram which shows the installation form of a radiative cooling body. It is a schematic diagram which shows the installation form of a radiative cooling body. It is a schematic diagram which shows the installation form of a radiative cooling body. It is a figure explaining the basic structure of a radiative cooling body. It is a figure explaining another structure of a radiative cooling body. It is a top view which shows the light reflection layer in another structure of a radiative cooling body. It is a top view which shows another form of a light reflection layer. It is a top view which shows another form of a light reflection layer. It is a perspective view of the experimental apparatus. It is a side view of the experimental apparatus. It is a graph which shows the experimental result. It is a graph which shows the experimental result. It is a figure which shows the relationship between the absorption coefficient of a resin material and a wavelength band. It is a figure which shows the relationship between the light absorption rate of a resin material, and a wavelength. It is a figure which shows the emissivity spectrum of a silicone rubber. It is a figure which shows the emissivity spectrum of PFA. It is a figure which shows the emissivity spectrum of a vinyl chloride resin. It is a figure which shows the emissivity spectrum of an ethylene terephthalate resin. It is a figure which shows the emissivity spectrum of an olefin metamorphic material. It is a figure which shows the relationship between the temperature of a radiation surface and the temperature of a light reflection layer. It is a figure which shows the light absorption rate spectrum of the silicone rubber and the perfluoroalkoxy alkane resin. It is a figure which shows the light absorption spectrum of the ethylene terephthalate resin. It is a figure which shows the light reflectance spectrum of the light reflection layer based on silver. It is a figure which shows the emissivity spectrum of a fluoroethylene vinyl ether. It is a table which shows the experimental result. It is a figure which shows the specific structure of a radiative cooling body. It is a figure which shows the specific structure of a radiative cooling body. It is a figure which shows the specific structure of a radiative cooling body. It is a figure which shows the specific structure of a radiative cooling body. It is a graph which shows the transmittance of Tempax. It is a graph which shows the emissivity for each type of glass which constitutes an infrared radiation zone.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Basic composition of agricultural greenhouses]
As shown in FIGS. 1 and 3, the agricultural greenhouse U is configured to include a gable-shaped roof portion Uy and a side wall portion Us, and the main building of the roof portion Uy is oriented in the north-south direction. It is built.
By the way, the roof portion Uy and the side wall portion Us are made of a translucent material that transmits sunlight. As the translucent material, for example, a film formed of a resin material such as a polyofylene-based resin, a fluororesin, or a vinyl chloride-based resin, or a plate material formed of a glass material or the like is used.

By the way, in the agricultural house U shown in FIG. 1, since the length of the main building is long, as shown in FIG. 2, the arrival point of the sunlight P incident through the portion of the side wall portion Us facing the south side is reached. , It does not reach the northern end of the ground inside the agricultural greenhouse U.
On the other hand, in the agricultural house U shown in FIG. 3, since the length of the main building is short, the arrival point of the sunlight P incident through the portion of the side wall portion Us facing the south side is the agricultural house. It reaches the northern end of the ground inside the U.

A film-shaped radiative cooling body CP is provided on the roof Uy of the agricultural greenhouse U.
As a form in which the radiative cooling body CP is provided on the roof portion Uy, as shown in FIG. 5, a form in which the film-shaped radiative cooling body CP is replaced with a part of the translucent material forming the roof portion Uy, in other words. , A form in which a part of the roof portion Uy is formed by a film-shaped radiative cooling body CP can be adopted.

Further, as another form in which the radiative cooling body CP is provided on the roof portion Uy, as shown in FIG. 6, the radiative cooling body CP in the form of a film is provided in a state of being in close contact with the upper side of the translucent material forming the roof portion Uy. A form or a form in which the film-shaped radiative cooling body CP is provided in close contact with the lower side of the translucent material forming the roof portion Uy can be adopted as shown in FIG.

Further, as a further alternative form in which the radiative cooling body CP is provided on the roof portion Uy, as shown in FIG. 8, the film-shaped radiative cooling body CP is spaced below the translucent material forming the roof portion Uy. A form in which they are provided separately can be adopted.

Incidentally, in the agricultural greenhouse U shown in FIG. 1, a film-shaped radiative cooling body CP formed in a band shape is provided on the roof portion Uy in a state along the north-south direction.
Further, in the agricultural greenhouse U shown in FIG. 3, a film-shaped radiative cooling body CP is provided on the entire roof portion Uy.

[Basic configuration of radiative cooling body]
As shown in FIG. 9, the radiation cooling body CP is located on the opposite side of the infrared radiation layer A that emits infrared light IR from the radiation surface H and the side where the radiation surface H exists in the infrared radiation layer A. The light reflecting layer B to be radiated is provided in a laminated state and is formed in a film shape.
That is, the radiative cooling body CP is configured as a radiative cooling film.

The light reflecting layer B reflects light L such as sunlight transmitted through the infrared emitting layer A, and its reflecting characteristics are such that the reflectance at a wavelength of 400 nm to 500 nm is 90% or more and the reflection of a wave longer than a wavelength of 500 nm. The rate is 96% or more.
As shown in FIG. 27, the sunlight spectrum exists from a wavelength of 300 nm to 4000 nm, and the intensity increases as the wavelength increases from 400 nm, and the intensity increases particularly from a wavelength of 500 nm to a wavelength of 1800 nm.

In the present embodiment, the light L includes ultraviolet light, visible light, and infrared light, and when these are described in terms of the wavelength of light as an electromagnetic wave, the wavelength is 10 nm to 20000 nm (from 0.01 μm). Includes electromagnetic waves of 20 μm).

The light reflecting layer B exhibits a reflection characteristic of 90% or more from a wavelength of 400 nm to 500 nm, and a reflectance of a long wave from a wavelength of 500 nm shows a reflection characteristic of 96% or more, whereby the radiation cooling body CP (radiation cooling film) reflects light. The solar energy absorbed by layer B can be suppressed to 5% or less, that is, the solar energy absorbed during the south and middle of summer can be reduced to about 50 W.

The light reflecting layer B is made of silver or a silver alloy, or is formed of a laminated structure of silver or a silver alloy and an aluminum or an aluminum alloy to have flexibility, and the details thereof will be described later.

The infrared radiating zone A is configured as a resin material layer J whose thickness is adjusted to emit heat radiation energy larger than the absorbed solar energy in a wavelength band of 8 μm to 14 μm, and the details thereof will be described later. To do.

Therefore, the radiant cooler CP reflects a part of the light L incident on the radiant cooler CP on the radiation surface H of the infrared radiation layer A, and the radiant cooler CP reflects the light L incident on the radiant cooler CP. The light (sunlight, etc.) transmitted through the resin material layer J is reflected by the light reflecting layer B so as to escape from the radiating surface H to the outside, and further to the radiating cooling body CP. It is configured to exert a cooling action by radiating heat transfer (for example, heat transfer from the atmosphere or heat transfer from the inside of the agricultural house U) to the outside as infrared light IR.

That is, the radiant cooling body CP is to direct the radiating surface H to the sky and perform radiant cooling in which infrared light IR is radiated from the radiating surface H toward the sky. Is infrared rays of heat input to the radiant cooling body CP from a cooling target (inside the agricultural house U) located on the side opposite to the existing side of the resin material layer J in the light reflecting layer B by the resin material layer J. It is configured to cool the inside of the agricultural house U by converting it into light IR and radiating it.

Further, the radiative cooling body CP (radiative cooling film) is configured to have flexibility because the resin material layer J and the light reflecting layer B have flexibility.

[About the lighting composition of agricultural greenhouses]
In the agricultural greenhouse U shown in FIGS. 1 and 2, the radiative cooling body CP is partially provided with respect to the roof portion Uy, so that the light reflecting layer B is partially positioned with respect to the roof portion Uy. It is configured in the form to be.

That is, in the agricultural house U shown in FIGS. 1 and 2, two strip-shaped radiative cooling bodies CP have a large radiative cooling body CP on each of the inclined roof portions on both sides of the gable-shaped roof portion Uy. Positioned adjacent to the ridge, and the remaining radiative cooling bodies CP are lined up at intervals in the width direction with respect to the radiative cooling body CP adjacent to the main building, and above the lower edge of the roof Uy. It is provided in a form that is positioned at intervals.

Therefore, in each of the inclined roof portions on both sides of the gable-shaped roof portion Uy, the light reflecting layer B is provided on the roof portion between the pair of radiative cooling bodies CP and the roof portion on the lower side of the lower radiative cooling body CP. Since it does not exist, it is configured so that light can be taken inside the agricultural house U through those roof parts.

By the way, in the agricultural greenhouse U shown in FIGS. 3 and 4, as described above, since the film-shaped radiative cooling body CP is provided on the entire roof portion Uy, daylighting through the roof portion Uy is not possible. However, the sunlight P can be collected through the south-facing portion of the side wall portion Us.
In the agricultural greenhouse U shown in FIGS. 3 and 4, the radiative cooling body CP may be partially provided on the roof portion Uy so that daylight can be collected.

By the way, as a configuration for collecting light through the roof portion Uy, instead of partially providing the radiating cooling body CP with respect to the roof portion Uy, as shown in FIG. 10, the light reflecting layer B is provided with the infrared radiating zone A (resin). The light reflecting layer B may be partially positioned with respect to the roof portion Uy by forming the light reflecting layer B so as to be partially positioned with respect to the material layer J).

As a form in which the light reflecting layer B is partially positioned with respect to the infrared radiation layer A (resin material layer J), as shown in FIG. 11, a form in which the light reflecting layer B is positioned in a line-and-space manner, FIG. As shown in FIG. 12, various forms can be used, such as a form in which the light reflecting layer B is positioned in a dot shape and a form in which the light reflecting layer B is positioned in an inverted dot shape as shown in FIG.

In this way, when the light reflecting layer B is formed so as to be partially positioned with respect to the infrared radiation layer A (resin material layer J), the radiative cooling body CP is entirely relative to the roof portion Uy. Even if it is provided, it will be possible to illuminate the inside of the agricultural house U through the roof portion.
By the way, even when the radiative cooling body CP is partially provided with respect to the roof portion Uy, the light reflecting layer B is formed so as to be partially positioned with respect to the infrared radiating zone A (resin material layer J). , The amount of light may be adjusted.

[Summary of agricultural greenhouses]
As described above, since the film-shaped radiative cooling body CP is provided on the roof Uy of the agricultural house U, the radiative cooling body CP exerts an action of radiatively cooling the inside of the agricultural house for agriculture. It is possible to sufficiently suppress an increase in the internal temperature of the greenhouse U.

To add an explanation, light (ultraviolet light, visible light, infrared light) incident from the radiation surface H of the infrared radiation layer A (resin material layer J) passes through the infrared radiation layer A (resin material layer J). After that, it is reflected by the light reflecting layer B on the side opposite to the existing side of the radiation surface H of the infrared radiation layer A (resin material layer J), and is released from the radiation surface H to the outside of the system.
That is, the light reflecting layer B reflects the light (ultraviolet light, visible light, infrared light) transmitted through the infrared radiation layer A (resin material layer J) and radiates it from the radiation surface H to emit the infrared radiation layer. Light (ultraviolet light, visible light, infrared light) transmitted through A (resin material layer J) is projected into the agricultural house to prevent the inside of the agricultural house U from being heated. ..

Then, the heat transfer to the radiative cooling body CP (heat transfer from the inside of the agricultural house and heat transfer from the atmosphere) is converted into infrared rays by the infrared radiant layer A (resin material layer J), and from the radiating surface. It will be escaped to the outside of the system.
That is, when heat is transferred from the inside of the agricultural house U to the radiative cooling body CP, the infrared radiation layer A (resin material layer J) is radiatively cooled by radiating infrared light IR from the radiation surface H. As a result, the inside of the agricultural house U is cooled.

By the way, a blower or the like for circulating and flowing the air inside the agricultural greenhouse U toward the installation location of the radiative cooling body CP may be provided to improve the cooling action by the radiative cooling body CP.

[Experimental results]
14 and 15 show a one-sided roof type greenhouse Z for an experiment, and exemplify the experimental results using the greenhouse Z for the experiment.
In the experimental vinyl greenhouse Z, the side wall is formed by using a general resin film, for example, Fclean (registered trademark, the same applies hereinafter), the one-sided roof Uy is directed to the south, and the shape is vertically long. By doing so, the arrival point of the sunlight P reaches the northern end of the ground inside the experimental vinyl house Z.

Then, for each case where the one-sided roof Uy is formed by F-clean, an agricultural shading net, an aluminum shading plate, and a radiative cooling body CP, the daily temperature change at a point 100 mm from the ceiling and the point 250 mm from the ground The daily temperature change was measured. By the way, when measuring the temperature, the temperature was measured so that the thermometer was not directly exposed to sunlight.
The experiment date is May 21, 2018, and the experiment site is Osaka (Konohana Ward).

FIG. 16 shows the daily temperature change at a point 100 mm from the ceiling, and FIG. 17 shows the daily temperature change at a point 250 mm from the ground. At both points, the radiative cooling body CP is used for the one-sided roof. When the part Uy is formed, the temperature is 2 ° C to 5 ° C in the daytime when the intensity of sunlight is higher than when the one-sided roof part Uy is formed by F-clean, an agricultural shading net, or an aluminum shading plate. The temperature has dropped.
By the way, in this experiment, the temperature was measured while the air inside the vinyl house Z for the experiment was naturally convected, but the air inside the vinyl house Z for the experiment was forcibly convected (forced circulation). By applying warm air inside the vinyl house Z to the radiative cooling body CP, the temperature inside the vinyl house Z can be further lowered.

As described above, by providing the radiative cooling body CP on the roof Uy of the agricultural house U, the sunlight radiated to the radiative cooling body CP is reflected and transmitted from the inside of the agricultural house to the radiative cooling body CP. By radiating the heat to the outside of the system as infrared light IR, the inside of the agricultural house U can be cooled, and an increase in the internal temperature of the agricultural house U can be appropriately suppressed.

[Overview of resin material layer]
The light absorption rate and emissivity (light emissivity) of the resin material forming the resin material layer J change depending on the thickness. Therefore, it is necessary to adjust the thickness of the resin material layer J so as not to absorb sunlight as much as possible and to emit a large amount of heat radiation in the wavelength band of the so-called atmospheric window (the band having a wavelength of 8 μm to 14 μm).

Specifically, from the viewpoint of the light absorption rate of sunlight, the thickness of the resin material layer J is such that the wavelength average of the light absorption rate with a wavelength of 0.4 μm to 0.5 μm is 13% or less, and the wavelength is from 0.5 μm. The wavelength average of the light absorption rate of 0.8 μm is 4% or less, the wavelength average of the light absorption rate from 0.8 μm to 1.5 μm is within 1%, and the wavelength is 1.5 μm to 2.5 μm. It is necessary to adjust the thickness so that the wavelength average of the light absorption rates up to is 40% or less and the wavelength average of the light absorption rates from 2.5 μm to 4 μm is 100% or less.
In the case of such an absorption rate distribution, the light absorption rate of sunlight is 10% or less, and the energy is 100 W or less.

As will be described later, the light absorption rate of the resin material increases as the film thickness of the resin material increases. When the resin material to thick, approximately 1 becomes the emissivity of the atmospheric windows, heat radiation to release the universe that time becomes 160 W / ^{m 2} from 125W / ^{m 2.} The sunlight absorption in the light reflecting layer B is 50 W / m ² or less. The sum of the sunlight absorption in the resin material layer J and the light reflection layer B is 150 W / m ² or less, and cooling proceeds if the atmospheric condition is good. As the resin material forming the resin material layer J, it is preferable to use a resin material having a small light absorption rate near the peak value of the sunlight spectrum as described above.

Further, the thickness of the resin material layer J needs to be adjusted to a thickness in which the wavelength average of the emissivity of 8 μm to 14 μm is 40% or more from the viewpoint of infrared radiation (heat radiation).
In order to release the heat energy of sunlight of about 50 W / m ² absorbed by the light reflecting layer B from the resin material layer J to the space from the heat radiation of the resin material layer J, more heat radiation is emitted to the resin material layer. J needs to issue.
For example, when the outside air temperature is 30 ° C., the maximum thermal radiation of an atmospheric window of 8 μm to 14 μm is 200 W / m ² (calculated assuming an emissivity of 1). This value can be obtained in fine weather, such as in high mountains, where the air is thin and dry. In lowlands, the thickness of the atmosphere is thicker than that of high mountains, so the wavelength band of the windows of the atmosphere becomes narrower and the transmittance decreases. By the way, this is called "the window of the atmosphere becomes narrower".

In addition, the environment in which the radiative cooling body CP (radiative cooling film) is actually used may be humid, and even in that case, the window of the atmosphere becomes narrow. The thermal radiation generated in the window area of the atmosphere when used in lowlands is estimated to be 160 W / m ² at 30 ° C. in good condition (calculated as emissivity 1). Also, as is often the case in Japan, when there is haze in the sky or when smog is present, the atmospheric window becomes even narrower and the radiation to space is about 125 W / m ² .
In view of these circumstances, the wavelength average of the emissivity of 8 μm to 14 μm must be 40% or more (the thermal radiation intensity in the window zone of the atmosphere is 50 W / m ² ) before it can be used in the lowlands of the mid-latitude zone.

Therefore, if the thickness of the resin material layer J is adjusted so as to fall within the optically specified range in consideration of the above items, the heat output from the window of the atmosphere becomes larger than the heat input due to the absorption of sunlight, and the solar radiation environment. It will be possible to radiatively cool outdoors even underneath.

[Details of resin material]
Resin materials include carbon-fluorine bond (CF), siloxane bond (Si-O-Si), carbon-chlorine bond (C-Cl), ester bond (R-COO-R), and ether bond (C-). An OC bond) and a colorless resin material containing a benzene ring can be used.
For each resin material, the wavelength range having an absorption coefficient in the wavelength band of the window of the atmosphere is shown in FIG.

According to Kirchhoff's law, the emissivity (ε) and the light absorption rate (A) are equal. The light absorption rate can be obtained from the absorption coefficient (α) by the relational expression of A = exp (-αt) (hereinafter referred to as the light absorption rate relational expression). In addition, t is a film thickness.
That is, when the film thickness of the resin material layer J is adjusted, a large amount of heat radiation can be obtained in a wavelength band having a large absorption coefficient. When radiative cooling is performed outdoors, it is preferable to use a material having a large absorption coefficient in the wavelength band of 8 μm to 14 μm, which is the wavelength band of the window of the atmosphere.
Further, in order to suppress the absorption of sunlight, it is preferable to use a material having no absorption coefficient or a small material in the wavelength range of 0.3 μm to 4 μm, particularly 0.4 μm to 2.5 μm. As can be seen from the relational expression between the absorption coefficient and the absorption coefficient, the light absorption rate (emissivity) changes depending on the film thickness of the resin material.

In order to lower the temperature from the surrounding atmosphere by radiative cooling in a solar radiation environment, select a material that has a large absorption coefficient in the wavelength band of the window of the atmosphere and almost no absorption coefficient in the wavelength band of sunlight. By adjusting the thickness, it hardly absorbs sunlight, but it emits a lot of heat radiation from the windows of the atmosphere, that is, it can create a state where the output by radiative cooling is larger than the input of sunlight.

Regarding the carbon-fluorine bond (CF), the absorption coefficient due to CHF and CF ₂ spreads widely over a wide band from the wavelength of 8 μm to 14 μm, which is the window of the atmosphere, and the absorption coefficient is particularly large at 8.6 μm. At the same time, regarding the wavelength band of sunlight, there is no conspicuous absorption coefficient at wavelengths of 0.3 μm to 2.5 μm, which have a large energy intensity.

As a resin material having a carbon-fluorine bond (CF),
Polytetrafluoroethylene (PTFE), a completely fluorinated resin,
Polychlorotrifluoroethylene (PCTFE) and polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), which are partially fluorinated resins,
Perfluoroalkoxy alkane resin (PFA), which is a fluororesin copolymer,
Ethylene tetrafluorinated / propylene hexafluorinated copolymer (FEP),
Ethylene / ethylene tetrafluoride copolymer (ETFE),
Ethylene / chlorotrifluoroethylene copolymer (ECTFE) can be mentioned.

Examples of the resin material having a siloxane bond (Si—O—Si) include silicone rubber and silicone resin.
In the resin, a large absorption coefficient due to expansion and contraction of the C—Si bond appears broadly around a wavelength of 13.3 μm, and an absorption coefficient due to the out-of-plane variation angle (pitch) of CSiH ₂ has a wavelength of 10 μm. It appears broad in the center, and the absorption coefficient due to the in-plane in-plane variation (scissors) of CSiH ₂ appears small near a wavelength of 8 μm.

Regarding the carbon-chlorine bond (C-Cl), the absorption coefficient due to the C-Cl expansion and contraction vibration appears in a wide band with a half width of 1 μm or more centered on a wavelength of 12 μm.
Further, as a resin material, polyvinyl chloride (PVC) can be mentioned, but in the case of vinyl chloride resin, the absorption coefficient derived from the divergent vibration of CH of the alkene contained in the main chain due to the influence of electron attraction of chlorine. Appears around a wavelength of 10 μm.

The ester bond (R-COO-R) and the ether bond (C-OC bond) have an absorption coefficient from a wavelength of 7.8 μm to 9.9 μm. Further, with respect to the carbon-oxygen bond contained in the ester bond and the ether bond, a strong absorption coefficient appears in the wavelength band of 8 μm to 10 μm.
When the benzene ring is introduced into the side chain of the hydrocarbon resin, absorption widely appears from a wavelength of 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements due to the influence of the benzene ring.

Examples of the resin having these bonds include methyl methacrylate resin, ethylene terephthalate resin, trimethylene terephthalate resin, butylene terephthalate resin, ethylene naphthalate resin, and butylene naphthalate resin.

[Consideration of light absorption]
Consider the light absorption in the ultraviolet-visible region of the resin material having the above-mentioned bonds and functional groups, that is, the absorption of sunlight. The origin of absorption of visible light from ultraviolet light is the transition of electrons that contribute to the bond. Absorption in this wavelength range can be found by calculating the binding energy.
First, let us consider the wavelength at which the absorption coefficient occurs in the ultraviolet to visible region of a resin material having a carbon-fluorine bond (CF). The binding energies of CC bond, CH bond, and CF bond of the basic structure part represented by polyvinylidene fluoride (PVDF) are 4.50 eV, 4.46 eV, and 5.05 eV. They correspond to wavelengths of 0.275 μm, 0.278 μm, and 0.246 μm, respectively, and absorb light of these wavelengths.

Since the sunlight spectrum has only long waves having a wavelength of 0.300 μm, when a fluororesin is used, it hardly absorbs ultraviolet rays, visible rays, and near infrared rays of sunlight. The definition of ultraviolet rays is on the shorter wavelength side than the wavelength of 0.400 μm, the definition of visible light is the wavelength of 0.400 μm to 0.800 μm, the near infrared rays are in the range of 0.800 μm to 3 μm, and the mid infrared rays are 3 μm to 8 μm. The range is defined as far infrared rays having a wavelength longer than 8 μm.

The absorption spectrum of PFA (perfluoroalkoxy alkane resin) having a thickness of 50 μm in the ultraviolet to visible region is shown in FIG. 19, and it can be seen that it has almost no absorption. A slight increase in the absorptivity spectrum is observed on the wavelength side shorter than 0.4 μm, but this increase only shows the effect of scattering of the sample used for the measurement, and the absorptivity actually increases. Not done.

Regarding the ultraviolet region of the siloxane bond (Si—O—Si), the binding energy of Si—O—Si in the main chain is 4.60 eV, which corresponds to a wavelength of 269 nm. Since the solar spectrum has only long waves having a wavelength of 0.300 μm, when the majority of siloxane bonds are present, it hardly absorbs ultraviolet rays, visible rays, and near infrared rays of sunlight.

The absorptivity spectrum of the silicone rubber having a thickness of 100 μm in the ultraviolet to visible region is shown in FIG. 19, and it can be seen that the silicone rubber has almost no absorptivity. There is a slight increase in the absorptivity spectrum on the shorter wavelength side than the wavelength of 0.4 μm, but this increase only shows the effect of scattering of the sample used for the measurement, and the absorptivity is actually Not increasing.

Regarding the carbon-chlorine bond (C-Cl), the bond energy between carbon and chlorine in the alkene is 3.28 eV, and its wavelength is 0.378 μm, so it absorbs a lot of ultraviolet rays in sunlight, but in the visible range. Has little absorption.
The absorptivity spectrum of a vinyl chloride resin having a thickness of 100 μm in the ultraviolet to visible region is shown in FIG. 19, and the light absorption becomes larger on the shorter wavelength side than the wavelength of 0.38 μm.

Resins having an ester bond (R-COO-R), an ether bond (C-OC bond), and a benzene ring include methyl methacrylate resin, ethylene terephthalate resin, trimethylene terephthalate resin, butylene terephthalate resin, and ethylene na. There are phthalate resin and butylene naphthalate resin. For example, the binding energy of the CC bond of acrylic is 3.93 eV, which absorbs sunlight having a wavelength shorter than 0.315 μm, but has almost no absorption in the visible region.

As an example of a resin material having these bonds and functional groups, FIG. 19 shows an absorption rate spectrum in the ultraviolet to visible region of a methyl methacrylate resin having a thickness of 5 mm.
Since the plate is as thick as 5 mm, the wavelength having a small absorption coefficient also becomes large, and the light absorption becomes larger on the short wave side than the long wave of 0.38 μm than the wavelength of 0.315.

As an example of the resin material having these bonds and functional groups, the absorption rate spectrum in the ultraviolet to visible region of an ethylene terephthalate resin having a thickness of 40 μm is shown in FIG.
As shown in the figure, the absorptivity increases as the wavelength approaches 0.315 μm, and the absorptivity sharply increases at a wavelength of 0.315 μm. As the thickness of the ethylene terephthalate resin is increased, the absorption rate at the absorption edge derived from the CC bond increases on the wave side slightly longer than the wavelength of 0.315 μm, and the absorption rate at ultraviolet rays is similar to that of the methyl methacrylate resin. Increases.

If the resin material layer J uses a resin material having the above-mentioned characteristics of emissivity (light emissivity) and light absorption rate, it is a single layer film of one type of resin material or a multilayer film of a plurality of types of resin materials. , A single-layer film of a resin material in which a plurality of types of resin materials are blended, or a multilayer film of a resin material in which a plurality of types of resin materials are blended may be used.
The blend also includes copolymers such as alternate copolymers, random copolymers, block copolymers, and graft copolymers, and modified products in which side chains are replaced.

[Emissivity of silicone rubber]
FIG. 20 shows the emissivity spectrum of a silicone rubber having a siloxane bond in an atmospheric window.
From the silicone rubber, a large absorption coefficient due to the expansion and contraction of the C—Si bond appears broadly around the wavelength of 13.3 μm, and the absorption coefficient due to the out-of-plane variation angle (pitch) of CSiH ₂ is 10 μm in wavelength. The absorption coefficient due to the in-plane in-plane variation (scissors) of CSiH ₂ appears small in the vicinity of the wavelength of 8 μm.
Due to this effect, the wavelength average of the emissivity with a thickness of 1 μm is 80% at wavelengths of 8 μm to 14 μm, which falls within the regulation that the wavelength average is 40% or more. As shown in the figure, the emissivity in the window region of the atmosphere increases as the film thickness increases.

Incidentally, FIG. 20 also shows an emission spectrum when quartz having a thickness of 1 μm, which is an inorganic material, is present on silver. Quartz has only a narrow band of radiation peaks between wavelengths of 8 μm and 14 μm when the thickness is 1 μm.
When the thermal radiation is averaged in the wavelength range of 8 μm to 14 μm, the emissivity of the wavelength of 8 μm to 14 μm is 32%, and it is difficult to show the radiative cooling performance.

The radiative cooling body CP (radiative cooling film) of the present invention using the resin material layer J can obtain radiative cooling performance even in an infrared radiative layer A thinner than the prior art using an inorganic material as the light reflecting layer B. That is, when the infrared radiating zone A is formed of quartz or Tempax glass, which is an inorganic material, the radiative cooling performance cannot be obtained when the infrared radiating zone A has a thickness of 1 μm, but the resin material layer J is used. In the radiative cooling body CP of the present invention, the radiative cooling performance is exhibited even when the resin material layer J has a thickness of 1 μm.

[PFA emissivity]
FIG. 21 shows the emissivity of a perfluoroalkoxy alkane resin (PFA) in an atmospheric window as a typical example of a resin having a carbon-fluorine bond. The absorption coefficient due to CHF and CF ₂ is widely spread over a wide band from 8 μm to 14 μm, which is the window of the atmosphere, and the absorption coefficient is particularly large at 8.6 μm.
Due to this effect, the wavelength average of the emissivity with a thickness of 10 μm is 45% at wavelengths of 8 μm to 14 μm, which falls within the regulation that the wavelength average is 40% or more. As shown in the figure, the emissivity in the window region of the atmosphere increases as the film thickness increases.

[Emissivity of vinyl chloride resin]
FIG. 22 shows the emissivity of vinyl chloride resin (PVC) in an atmospheric window as a typical example of a resin having a carbon-chlorine bond.
Regarding the carbon-chlorine bond, the absorption coefficient due to C-Cl expansion and contraction vibration appears in a wide band with a half width of 1 μm or more centered on a wavelength of 12 μm.
Further, in the case of a vinyl chloride resin, the absorption coefficient derived from the eccentric vibration of CH of the alkene contained in the main chain appears around the wavelength of 10 μm due to the influence of electron suction of chlorine.
Due to these effects, the wavelength average of the emissivity with a thickness of 10 μm is 43% at wavelengths of 8 μm to 14 μm, which falls within the regulation that the wavelength average is 40% or more. As shown in the figure, the emissivity in the window region of the atmosphere increases as the film thickness increases.

[Ethylene terephthalate resin]
FIG. 23 shows the emissivity of an ethylene terephthalate resin in an atmospheric window as a typical example of a resin having an ester bond or a benzene ring.
Regarding the ester bond, it has an absorption coefficient from a wavelength of 7.8 μm to 9.9 μm. Further, regarding the carbon-oxygen bond contained in the ester bond, a strong absorption coefficient appears in the wavelength band of 8 μm to 10 μm. When a benzene ring is introduced into the side chain of a hydrocarbon resin, absorption appears widely from a wavelength of 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements due to the influence of the benzene ring.
Due to these effects, the wavelength average of the emissivity with a thickness of 10 μm is 71% at wavelengths of 8 μm to 14 μm, which falls within the regulation that the wavelength average is 40% or more. As shown in the figure, the emissivity in the window region of the atmosphere increases as the film thickness increases.

[Emissivity of olefin metamorphic material]
FIG. 24 includes a carbon-fluorine bond (CF), a carbon-chlorine bond (C-Cl), an ester bond (R-COO-R), an ether bond (COC bond), and a benzene ring. It shows the radiation rate spectrum of the olefin-modified material which is not present and whose main component is an olefin. The sample was prepared by applying an olefin resin on the vapor-deposited silver with a bar coater and drying it.
As shown in the figure, the emissivity in the window region of the atmosphere is small, and due to this effect, the wavelength average of the emissivity with a thickness of 10 μm is 27% at wavelengths of 8 μm to 14 μm, and the wavelength average is 40% or more. not enter.

The emissivity shown is that of an olefin resin modified for application as a bar coater, and in the case of a pure olefin resin, the emissivity in the window region of the atmosphere is even smaller.
As described above, it does not contain carbon-fluorine bond (CF), carbon-chlorine bond (C-Cl), ester bond (R-COO-R), ether bond (COC bond), and benzene ring. And radiative cooling is not possible.

[Temperature of the surface of the light reflecting layer and the resin material layer]
Thermal radiation from the atmospheric window of the resin material layer J is generated near the surface of the resin material.
From FIG. 20, in the case of silicone rubber, if it is thicker than 10 μm, heat radiation in the window region of the atmosphere does not increase. That is, in the case of silicone rubber, most of the heat radiation in the window of the atmosphere is generated in the portion within about 10 μm in depth from the surface, and the radiation in the deeper portion does not come out.

From FIG. 21, in the case of fluororesin, even if the thickness is thicker than 100 μm, there is almost no increase in thermal radiation in the window region of the atmosphere. That is, in the case of fluororesin, heat radiation in the window of the atmosphere is generated in a portion within a depth of about 100 μm from the surface, and radiation in a deeper portion does not come out.
From FIG. 22, in the case of the vinyl chloride resin, even if the thickness is thicker than 100 μm, the increase in thermal radiation in the window region of the atmosphere is almost eliminated. That is, in the case of vinyl chloride resin, heat radiation in the window of the atmosphere is generated in a portion within a depth of about 100 μm from the surface, and radiation in a deeper portion does not come out.

From FIG. 23, in the case of the ethylene terephthalate resin, even if the thickness is thicker than 125 μm, the increase in thermal radiation in the window region of the atmosphere is almost eliminated. That is, in the case of ethylene terephthalate resin, heat radiation in the window of the atmosphere is generated at a depth of about 100 μm from the surface, and radiation at a deeper part does not come out.

As described above, the heat radiation of the window region of the atmosphere generated from the surface of the resin material is generated in the portion where the depth from the surface is approximately 100 μm or less, and when the thickness of the resin is further increased, the heat radiation is generated. The radiatively cooled cold heat of the radiative cooling body is insulated by the resin material that does not contribute to.
Consider forming a resin material layer J that ideally does not absorb sunlight at all on the light reflecting layer B. In this case, sunlight is absorbed only by the light reflecting layer B of the radiative cooling body CP.
The thermal conductivity of the resin material is generally about 0.2 W / m / K, and when calculated in consideration of this thermal conductivity, when the thickness of the resin material layer J exceeds 20 mm, the cooling surface (in the light reflecting layer B). The temperature of the surface of the resin material layer J opposite to the existing side) rises.

Even if there is an ideal resin material that does not absorb sunlight at all, the thermal conductivity of the resin material is generally about 0.2 W / m / K, so if it exceeds 20 mm as shown in FIG. 25, the light reflecting layer B Is heated by the sunlight, and the cooling object E installed on the light reflecting layer side is heated. That is, the thickness of the resin material of the radiative cooling body CP needs to be 20 mm or less.

FIG. 25 is a plot of the surface temperature of the radiative surface H of the radiative cooling body (radiative cooling film) and the temperature of the light reflecting layer B calculated assuming the southern part of a sunny day in western Japan in midsummer. The sunlight is AM1.5 and the energy density is 1000 W / m ² . The outside air temperature is 30 ° C., and the radiant energy varies depending on the temperature, but is 100 W at 30 ° C. The calculation is based on the assumption that the resin material layer does not absorb sunlight. Assuming no wind, the convective heat transfer coefficient is 5 W / m ² / K.

[About light absorption rate of silicone rubber, etc.]
FIG. 26 shows the light absorption rate with respect to the sunlight spectrum when the thickness of the silicone rubber having the side chain CH ₃ is 100 μm, and the light absorption rate spectrum with respect to the sunlight spectrum of the perfluoroalkoxy alkane resin having a thickness of 100 μm. .. As described above, it can be seen that both resins have almost no light absorption rate in the ultraviolet region.

Regarding silicone rubber, in the near infrared region, the light absorption rate increases in the region on the long wave side of the wavelength of 2.35 μm. However, since the intensity of the sunlight spectrum in this wavelength range is weak, the solar energy absorbed is 20 W / m ² even if the light absorption rate on the long wave side from the wavelength of 2.35 μm is 100%.

The perfluoroalkoxy alkane resin has almost no light absorption rate in the wavelength range of 0.3 μm to 2.5 μm, and has light absorption on the wavelength side longer than the wavelength of 2.5 μm. However, even if the film thickness of the resin is increased and the light absorption rate on the wavelength side longer than the wavelength of 2.5 μm becomes 100%, the absorbed solar energy is about 7 W.

As the thickness (film thickness) of the resin material layer J is increased, the emissivity of the window region of the atmosphere becomes approximately 1. That is, in the case of a thick film, the heat radiation that radiates into space at atmospheric window region when used in low-lying becomes 125W / ^{m 2} order of 160 W / ^{m 2} at 30 ° C.. The light absorption in the light reflecting layer B is about 50 W / m ² as specified above, and the light absorption of the light reflecting layer B and the sunlight absorption when the silicone rubber or the perfluoroalkoxyfluororesin is made into a thick film are added. Even smaller than the thermal radiation radiated into space.
From the above, the maximum film thickness of the silicone rubber and the perfluoroalkoxy alkane resin is 20 mm from the viewpoint of thermal conductivity.

[About light absorption of hydrocarbon resins]
When the resin material forming the resin material layer J is a resin having a hydrocarbon as a main chain having one or more carbon-chlorine bonds, ester bonds, ether bonds, and benzene rings, or a silicone resin and side chains. When the number of carbon atoms in the hydrocarbon is 2 or more, in addition to the above-mentioned absorption of ultraviolet rays by covalent bond electrons, absorption based on vibration such as bending angle and expansion and contraction of the bond is observed in the near infrared region.

Specifically, the absorption by the reference sound of the transition of CH ₃ , CH ₂ , and CH to the first excited state is changed from 1.6 μm to 1.7 μm in wavelength, 1.65 μm to 1.75 μm in wavelength, and 1.7 μm in wavelength, respectively. appear. Further, the absorption of the combined sounds of CH ₃ , CH ₂ , and CH by the reference sound appears at wavelengths of 1.35 μm, 1.38 μm, and 1.43 μm, respectively. Further, the overtones of the transitions of CH ₂ and CH to the second excited state appear around the wavelength of 1.24 μm, respectively. The reference sound of the angle change and expansion / contraction of the CH bond is distributed over a wide band from the wavelength of 2 μm to 2.5 μm.

Further, when it has an ester bond (R-COO-R) and an ether bond (COC), a large light absorption exists around a wavelength of 1.9 μm.
According to the above-mentioned light absorption rate relational expression, the light absorption rate due to these becomes smaller and less noticeable when the film thickness of the resin material is thin, but becomes larger when the film thickness is thicker.

FIG. 27 shows the relationship between the light absorption rate and the spectrum of sunlight when the film thickness of the ethylene terephthalate resin having an ester bond and a benzene ring is changed.
As shown in the figure, as the film thickness increases to 25 μm, 125 μm, and 500 μm, the light absorption in the long wave region increases from the wavelength of 1.5 μm caused by the respective vibrations.
Further, not only the long wavelength side but also the light absorption from the ultraviolet region to the visible region increases. This is due to the spread of the light absorption edge due to the chemical bond.

When the film thickness is thin, the light absorption coefficient increases at the wavelength having the largest absorption coefficient, but when the film thickness is thick, the absorption coefficient with a broad absorption edge and a weak absorption coefficient is higher than the above-mentioned light absorption coefficient relational expression. Appears next. As a result, as the film thickness increases, the light absorption from the ultraviolet region to the visible region increases.
Absorption of solar spectrum when a thickness of 25μm is 15W / ^{m 2,} the absorption of the solar spectrum when the absorption of the solar spectrum when the thickness is 125μm is 41W / ^{m 2,} the thickness of 500μm is 88W / It is m ² .

Since the light absorption of the light reflecting layer B is 50 W / m ² according to the above regulation, the sum of the sunlight absorption of the ethylene terephthalate resin and the sunlight absorption of the light reflecting layer B is 138 W / m when the film thickness is 500 μm. It becomes m ² . As mentioned above, the maximum value of infrared radiation in the wavelength band of the window of the atmosphere in the lowland summer of Japan is about 160 W on a day when the atmospheric condition is good at 30 ° C., and usually about 125 W.
From the above, when the film thickness of the ethylene terephthalate resin is 500 μm or more, the radiative cooling performance is not exhibited.

The origin of the absorption spectrum in the wavelength band of 1.5 μm to 4 μm is not the functional group but the vibration of the hydrocarbon in the main chain, and if it is a hydrocarbon resin, it behaves in the same manner as the ethylene terephthalate resin. In addition, the hydrocarbon resin has light absorption due to chemical bonds in the ultraviolet region, and exhibits the same behavior as the ethylene terephthalate resin from the ultraviolet to the visible.
That is, if it is a hydrocarbon resin, it behaves in the same manner as an ethylene terephthalate resin from a wavelength of 0.3 μm to 4 μm. From the above, the thickness of the hydrocarbon-based resin needs to be thinner than 500 μm.

[About light absorption of blended resin]
When the resin material is a resin material in which a resin having a carbon-fluorine bond or a siloxane bond as the main chain and a resin having a hydrocarbon as the main chain are blended, the resin having the blended hydrocarbon as the main chain is used. Light absorption in the near infrared region due to CH, CH ₂ , CH _3, etc. appears according to the ratio of.
When a carbon-fluorine bond or a siloxane bond is the main component, the light absorption in the near infrared region due to hydrocarbons becomes small, so that the thickness can be increased to the upper limit of 20 mm from the viewpoint of thermal conductivity. However, when the blended hydrocarbon resin is the main component, the thickness needs to be 500 μm or less.

For blending of fluororesin or silicone rubber and hydrocarbon, the side chain of fluororesin or silicone rubber is replaced with hydrocarbon, or an alternating copolymer of fluoropolymer or silicone monomer and hydrocarbon monomer, or a random copolymer. , Block copolymers and graft copolymers are also included. Examples of the alternate copolymer of the fluorine monomer and the hydrocarbon monomer include fluoroethylene vinyl ester (FEVE), fluoroolefin-acrylic acid ester copolymer, ethylene / tetrafluoroethylene copolymer (ETFE), and ethylene. Chlorotrifluoroethylene copolymer (ECTFE) can be mentioned.

Light absorption in the near infrared region due to CH, CH ₂ , CH _3, etc. appears depending on the molecular weight and proportion of the hydrocarbon side chain to be substituted. When the monomer introduced as a side chain or copolymer is a small molecule, or when the density of the introduced monomer is small, the light absorption in the near infrared region due to hydrocarbons becomes small, so from the viewpoint of thermal conductivity. It can be thickened up to the limit of 20 mm in.
When a high molecular weight hydrocarbon is introduced as a side chain of a fluororesin or a silicone rubber or a monomer to be copolymerized, the thickness of the resin needs to be 500 μm or less.

[Thickness of resin material layer]
From the viewpoint of practical use of the radiative cooling body CP, the thickness of the resin material layer J should be thin. The thermal conductivity of resin materials is generally lower than that of metals and glass. In order to effectively cool the object E to be cooled, the film thickness of the resin material layer J should be the minimum necessary. The thicker the thickness of the resin material layer J, the larger the heat radiation of the window of the atmosphere, and when the thickness exceeds a certain thickness, the heat radiation energy of the window of the atmosphere is saturated.

The film thickness to be saturated depends on the resin material, but in the case of fluororesin, about 300 μm is sufficient for saturation. Therefore, from the viewpoint of thermal conductivity, it is desirable to suppress the film thickness to 300 μm or less rather than 500 μm. Further, although the heat radiation is not saturated, sufficient heat radiation can be obtained in the window region of the atmosphere even if the thickness is about 100 μm. The thinner the thickness, the higher the heat transmission coefficient and the more effectively the temperature of the object to be cooled can be lowered. Therefore, in the case of fluororesin, the thickness should be about 100 μm or less.

The absorption coefficient derived from the carbon-silicon bond, carbon-chlorine bond, carbon-oxygen bond, ester bond, and ether bond is larger than the absorption coefficient caused by the CF bond. Naturally, from the viewpoint of thermal conductivity, it is desirable to suppress the film thickness to 300 μm or less rather than 500 μm, but if the film thickness is further reduced to increase the thermal conductivity, a larger radiative cooling effect can be expected.
In the case of a resin containing a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring, even if the thickness is 100 μm, it is saturated, and even if the thickness is 50 μm, sufficient thermal radiation is emitted in the window region of the atmosphere. can get. The thinner the resin material, the higher the heat transmission coefficient and the more effectively the temperature of the object to be cooled can be lowered. Therefore, a resin containing a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring. In the case of, if the thickness is 50 μm or less, the heat insulating property becomes small and the object E to be cooled can be effectively cooled.

The effect of thinning is other than lowering the heat insulating property and making it easier to transfer cold heat. It is the suppression of light absorption in the near-infrared region derived from CH, CH ₂ and CH _{3 in} the near-infrared region, which is exhibited by resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds and ether bonds. If it is made thinner, the sunlight absorption due to these can be reduced, so that the cooling capacity of the radiative cooling body CP is increased.
From the above viewpoint, in the case of a resin containing a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring, a thickness of 50 μm or less can more effectively produce a radiative cooling effect in sunlight. it can.

In the case of the carbon-silicon bond, the heat radiation is completely saturated in the window region of the atmosphere even if the thickness is 50 μm, and sufficient heat radiation can be obtained in the window region of the atmosphere even if the thickness is 10 μm. The thinner the resin material layer J, the higher the heat transmission coefficient and the more effectively the temperature of the object E to be cooled can be lowered. Therefore, in the case of a resin containing a carbon-silicon bond, if the thickness is 10 μm or less, heat insulation is performed. The property is reduced and the cooling object E can be effectively cooled. When it is made thinner, the sunlight absorption can be reduced, so that the cooling capacity of the radiative cooling body CP is increased.
From the above viewpoint, in the case of a resin containing a carbon-silicon bond, if the thickness is 10 μm or less, the radiative cooling effect can be obtained more effectively in the sunlight.

[Details of light reflecting layer]
In order for the light reflecting layer B to have the above-mentioned reflectance characteristics, the reflective material on the side where the radiation surface H exists (the side where the resin material layer J exists) needs to be silver or a silver alloy.
As shown in FIG. 28, if the light reflecting layer B is formed based on silver, the reflectance required for the light reflecting layer B can be obtained.

When sunlight is reflected with only silver or a silver alloy having the above-mentioned reflectance characteristics, a thickness of 50 nm or more is required.
However, in order to provide the light reflecting layer B with flexibility, the thickness needs to be 100 μm or less. If it is thicker than this, it will be difficult to bend.
By the way, as the "silver alloy", an alloy in which any one of copper, palladium, gold, zinc, tin, magnesium, nickel and titanium is added to silver, for example, about 0.4 to 4.5% by mass is used. Can be done. As a specific example, "APC-TR (made of fluya metal)", which is a silver alloy prepared by adding copper and palladium to silver, can be used.

In order for the light reflecting layer B to have the above-mentioned reflectance characteristics, a structure in which silver or a silver alloy and aluminum or an aluminum alloy are laminated may be used. Also in this case, the reflective material on the side where the radiation surface H exists (the side where the resin material layer J exists) needs to be silver or a silver alloy.
When composed of two layers of silver (silver alloy) and aluminum (aluminum alloy), the thickness of silver needs to be 10 nm or more, and the thickness of aluminum needs to be 30 nm or more.
However, in order to provide the light reflecting layer B with flexibility, the total thickness of silver and aluminum needs to be 100 μm or less. If it is thicker than this, it will be difficult to bend.

Incidentally, as the "aluminum alloy", an alloy obtained by adding copper, manganese, silicon, magnesium, zinc, carbon steel for machine structure, ittrium, lantern, gadolinium, and terbium to aluminum can be used.

Silver and silver alloys are vulnerable to wind, rain and humidity and need to be protected from them. Therefore, as shown in FIGS. 31 to 34, a silver protective layer D is required in a form adjacent to silver or a silver alloy.
As the silver protective layer D, an acrylic resin, a silicone resin, a fluororesin, an oxide film (SiO ₂ , Al ₂ O ₃ ) or the like can be used. The thickness is preferably 0.02 μm or more in the case of an inorganic material and 0.5 μm or more in the case of an organic material. Inorganic materials have a lower oxygen permeability, so even thin films also function as silver protection.

[Experimental results]
Silver is formed on a glass substrate with a thickness of 300 nm, and on it, silicone rubber having a siloxane bond, fluoroethylene vinyl ether having a carbon-fluorine bond, and an olefin modified product (olefin modified material) are controlled in film thickness with a bar coater. The coating was applied while the radiant cooling performance was measured.
The evaluation of the radiative cooling performance was carried out at an outside air temperature of 35 ° C. in late June, 3 hours after the south, middle, and south, and the temperature of the back surface of the substrate was measured after maintaining the substrate with high heat insulation. It was evaluated whether or not there was a radiative cooling effect depending on whether the temperature 5 minutes after installation in the jig was lower or higher than the outside air temperature.
The results of the radiative cooling test are shown in Table 1 of FIG.

By the way, the emissivity of the window region of the atmosphere of fluoroethylene vinyl ether is as shown in FIG. The emissivity of the silicone rubber is as shown in FIG. 20, and the emissivity of the olefin modified product (olefin modified material) is as shown in FIG. 24.

In the case of silicone rubber having a siloxane bond, it was found that the radiative cooling ability is exhibited at a thickness of 1 μm or more as expected from theory.
It was found that the fluoroethylene vinyl ether having a carbon-fluorine bond exhibits radiative cooling ability at a film thickness of 5 μm, which is thinner than the theoretically predicted 10 μm. The reason for this is that not only the light absorption of the window of the atmosphere by the carbon-fluorine bond but also the light absorption by the ether bond of vinyl ether is added, and the light absorption rate of the window of the atmosphere is increased as compared with the case of each alone.
The olefin modified product (olefin modified material) does not have a radiative cooling capacity because there is almost no heat radiation in the window region of the atmosphere.

(Specific configuration of radiative cooling body)
The radiative cooling body CP of the present invention can have a film structure as shown in FIGS. 31 to 34. Since the resin material forming the resin material layer J is flexible as well as the resin material, if the light reflecting layer B is made into a thin film, the light reflecting layer B can also be made flexible, and as a result, the radiative cooling body CP is made flexible. It can be a film having properties (radiative cooling film).

Various forms are conceivable for producing the radiative cooling body CP in the form of a film. For example, it is conceivable to apply the resin material layer J to the light reflecting layer B produced in the form of a film. Alternatively, it is conceivable to attach the resin material layer J to the light reflecting layer B formed in the form of a film. Alternatively, it is conceivable to form a light reflecting layer B on the resin material layer J produced in the form of a film by vapor deposition, sputtering, ion plating, silver mirror reaction, or the like.
In order to form the light-reflecting layer B in a form that is partially positioned with respect to the resin material layer J, masking or the like is performed. In the following, the light-reflecting layer B is formed into the resin material layer J. On the other hand, the description of forming the shape so as to be partially positioned will be omitted.

Specifically, in the radiation cooling body CP (radiation cooling film) of FIG. 31, the light reflecting layer B is formed as a single layer of silver or a silver alloy, or silver (silver alloy) and aluminum (aluminum alloy). In the case of two layers, the protective layers D are formed on both sides of the light reflecting layer B, and the resin material layer J is formed on the upper part of the upper protective layer D.

As a method of producing the radiative cooling body CP (radiative cooling film) of FIG. 31, a silver protective layer D, a light reflecting layer B, a silver protective layer D, and a resin material layer J are formed on a film-shaped resin material layer J. Can be sequentially applied and integrally molded.

In the radiation cooling body CP (radiation cooling film) of FIG. 32, the light reflecting layer B is composed of an aluminum layer B1 formed of an aluminum foil functioning as aluminum (aluminum alloy) and a silver layer B2 made of silver or a silver alloy. A protective layer D is formed on the upper side of the light reflecting layer B, and a resin material layer J is formed on the upper part of the protective layer D.

As a method for producing the radiative cooling body CP (radiative cooling film) of FIG. 32, a silver layer B2, a protective layer D, and a resin material layer J are sequentially applied onto an aluminum layer B1 made of aluminum foil. A method of integrally molding can be adopted.
As another method of producing, the resin material layer J is formed in a film shape, the protective layer D and the silver layer B2 are sequentially coated on the film-shaped resin material layer J, and the aluminum layer B1 is a silver layer. A method of pasting on B2 can be adopted.

The radiation cooling body CP (radiation cooling film) of FIG. 33 has a case where the light reflecting layer B is formed as one layer of silver or a silver alloy, or a case where the light reflecting layer B is composed of two layers of silver (silver alloy) and aluminum (aluminum alloy). In, a protective layer D is formed on the upper side of the light reflecting layer B, a resin material layer J is formed on the upper part of the protective layer D, and a film layer F such as PET is formed on the lower side of the light reflecting layer B. It was done.

As a method for producing the radiation cooling body CP (radiation cooling film) of FIG. 33, a light reflecting layer B and a protective layer D are sequentially formed on a film layer F formed in a film shape by PET (polyethylene terephthalate) or the like. A method of coating, integrally molding, and adhering a separately formed film-shaped resin material layer J to the protective layer D with a glue layer N can be adopted.
The adhesive used in the glue layer N includes, for example, an acrylic pressure-sensitive adhesive, a fluorine-based pressure-sensitive adhesive, and a silicone-based pressure-sensitive adhesive, and those having high transparency to sunlight are desirable. Urethane-based adhesives, which are often used as adhesives, are not suitable because they are easily deteriorated by ultraviolet rays.

The radiation cooling body CP (radiation cooling film) of FIG. 34 comprises a light reflecting layer B composed of an aluminum layer B1 that functions as aluminum (aluminum alloy) and a silver layer B2 made of silver or a silver alloy (alternative silver). , The aluminum layer B1 is formed on the upper part of the film layer F formed in the form of a film by PET (polyethylene terephthalate) or the like, the protective layer D is formed on the upper side of the silver layer B2, and the protective layer D is formed on the upper side of the protective layer D. , The resin material layer J is formed.

As a method for producing the radiation cooling body CP (radiation cooling film) of FIG. 34, an aluminum layer B1 is applied on the film layer F, the film layer F and the aluminum layer B1 are integrally molded, and separately. The protective layer D and the silver layer B2 are coated on the film-shaped resin material layer J to integrally form the resin material layer J, the protective layer D, and the silver layer B2, and the aluminum layer B1 and the silver layer B2 are glued together. A method of bonding with the layer N can be adopted.
The adhesive used in the glue layer N includes, for example, an acrylic pressure-sensitive adhesive, a fluorine-based pressure-sensitive adhesive, and a silicone-based pressure-sensitive adhesive, and those having high transparency to sunlight are desirable. Urethane-based adhesives, which are often used as adhesives, are not suitable because they are easily deteriorated by ultraviolet rays.

[Another form of infrared radiation zone]
In the above embodiment, the case where the infrared radiating zone A is composed of the resin material layer J has been described, but the infrared radiating zone A is made of any one of non-alkali glass, crown glass, and borosilicate glass. It may be composed of (white plate glass).
Incidentally, as the non-alkali glass, for example, OA10G (manufactured by Nippon Electric Glass) can be used, as the crown glass, for example, B270 (registered trademark, the same applies hereinafter) can be used, and as the borosilicate glass, for example, can be used. For example, Tempax (registered trademark, the same applies hereinafter) can be used.

“OA10G”, “B270” and “Tempax” have high transmittance for light having a wavelength corresponding to sunlight as shown in FIG. 35, and have high transmittance for air as shown in FIG. 36. The emissivity of the wavelength corresponding to the wavelength range (so-called window of the atmosphere) is high.
By the way, FIG. 35 exemplifies "Tempax" as a representative, but the same applies to "OA10G", "B270" and the like of white plate glass.

By the way, the thickness of the tempax constituting the infrared radiation zone A needs to be 10 μm or more and 10 cm or less, preferably 20 μm or more and 10 cm or less, and more preferably 100 μm or more and 1 cm or less.
That is, the infrared radiation layer A exhibits a large heat radiation in the infrared region having a wavelength of 8 μm or more and 14 μm or less, and the heat radiation is absorbed by each of the infrared radiation layer A and the light reflection layer B of AM1.5G. By making it larger than the thermal radiation of sunlight and the atmosphere, it is possible to construct a radiative cooling body CP that exerts a radiative cooling action in which the temperature is lower than that of the surrounding atmosphere day and night.
In doing so, when the infrared radiation zone A is composed of Tempax, the thickness needs to be 10 μm or more and 10 cm or less, preferably 20 μm or more and 10 cm or less, more preferably. , 100 μm or more and 1 cm or less is preferable.

[Another Embodiment]
Hereinafter, another embodiment will be listed.
(1) In the above embodiment, the case where the resin material layer J and the light reflecting layer B are completely adhered to each other is illustrated, but the resin material layer J and the light reflecting layer B are partially bonded to form a resin material. A heat transferable gap may be partially present between the layer J and the light reflecting layer B.
Incidentally, the same applies when the infrared radiation zone A is made of glass (white plate glass).

(2) In the above embodiment, the case where the roof portion Uy of the agricultural greenhouse U is a gable type is illustrated, but the form of the roof portion Uy is a case of various forms such as a one-sided flow type and an inverted U-shaped type. The present invention can also be applied to the above.

The configuration disclosed in the above embodiment (including another embodiment, the same shall apply hereinafter) can be applied in combination with the configuration disclosed in other embodiments as long as there is no contradiction. The embodiments disclosed in the present specification are examples, and the embodiments of the present invention are not limited thereto, and can be appropriately modified without departing from the object of the present invention.

A Infrared radiation layer B Light reflection layer H Radiation surface J Resin material layer Uy Roof part Us Side wall part

Claims (15)

An agricultural greenhouse with a roof and side walls
An infrared radiation layer that emits infrared light from a radiation surface and transmits sunlight incident from the radiation surface, and a light reflection layer located on the opposite side of the infrared radiation zone to the side where the radiation surface exists. An agricultural house in which a film-shaped radiant cooling body provided with is provided on the roof portion. The agricultural house according to claim 1, wherein the radiative cooling body is provided in a form in which the light reflecting layer is partially positioned with respect to the roof portion. The agricultural house according to claim 2, wherein the radiative cooling body is partially provided with respect to the roof portion so that the light reflecting layer is partially positioned with respect to the roof portion. The radiative cooling body is formed so that the light reflecting layer is partially positioned with respect to the infrared radiating layer, so that the light reflecting layer is partially positioned with respect to the roof portion. The agricultural house according to claim 2. The invention according to any one of claims 1 to 4, wherein the infrared radiant layer is a resin material layer adjusted to a thickness that emits thermal radiation energy larger than the absorbed solar energy in a wavelength band of 8 μm to 14 μm. Agricultural house. The agricultural house according to claim 5, wherein the light reflecting layer has a reflectance of 90% or more at a wavelength of 0.4 μm to 0.5 μm and a reflectance of 96% or more for long waves having a wavelength of 500 nm or more. The film thickness of the resin material layer is
The wavelength average of the light absorption rate from 0.4 μm to 0.5 μm is 13% or less, the wavelength average of the light absorption rate from 0.5 μm to 0.8 μm wavelength is 4% or less, and the wavelength average is 0.8 μm. It has light absorption characteristics such that the wavelength average of the light absorption rate up to a wavelength of 1.5 μm is within 1%, and the wavelength average of the light absorption rate from 1.5 μm to 2.5 μm is 40% or less.
The agricultural house according to claim 5 or 6, wherein the thickness is adjusted to have a thermal radiation characteristic in which the wavelength average of the emissivity of 8 μm to 14 μm is 40% or more. A claim that the resin material forming the resin material layer is selected from a resin material having at least one of a carbon-fluorine bond, a siloxane bond, a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, and a benzene ring. The agricultural house according to any one of 5 to 7. The main component of the resin material forming the resin material layer is siloxane.
The agricultural greenhouse according to any one of claims 5 to 7, wherein the thickness of the resin material layer is 1 μm or more. The agricultural greenhouse according to claim 8, wherein the thickness of the resin material layer is 10 μm or more. The agricultural greenhouse according to any one of claims 5 to 10, wherein the thickness of the resin material layer is 20 mm or less. The agricultural greenhouse according to claim 11, wherein the resin material is fluororesin or silicone rubber. The agricultural house according to any one of claims 1 to 4, wherein the infrared radiating zone is any one of non-alkali glass, crown glass, and borosilicate glass. The agricultural house according to any one of claims 1 to 13, wherein the light reflecting layer is made of silver or a silver alloy and has a thickness of 50 nm or more. The agricultural house according to any one of claims 1 to 13, wherein the light reflecting layer has a laminated structure of silver or a silver alloy and aluminum or an aluminum alloy.

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