WO2023091006A1

WO2023091006A1 - Greenhouse with a variable light transmission

Info

Publication number: WO2023091006A1
Application number: PCT/NL2022/050652
Authority: WO
Inventors: Arjan VAN NIEUWENHUIJZEN; Johannes Adrianus Hendricus Maria VAN DER SANDE; Jack Anthony KOVACEVIC
Original assignee: Belua Beheer B.V.
Priority date: 2021-11-16
Filing date: 2022-11-15
Publication date: 2023-05-25

Abstract

A greenhouse (1,40) comprises an upper screen member (20, 45) and a lower screen member (30,46). One or both of the screen members can be a diffusely transmitting screen member that is of substantial uniform light transmission across the screen or a screen member that comprises alternating strips of relatively low light transmission and relatively high light transmission. The upper screen member can be placed over the growing space (7,41) in a stationary position while the lower screen member is moved across the growing space (7,41) depending on the position of the sun, such that at a distance D3 of at least 1.5m, preferably at least 1 m from the lower screen member (30,46), the light intensity in the growing space (7,41) varies no more than 35 % from the average light intensity that is measured when going from a first side of the support area to the opposite side, preferably no more than 25%, more preferably no more than 20%, most preferably no more than 20% in the time between 1 hour before noon and 3 hours past noon.

Description

Greenhouse with a variable light transmission

Technical field

The invention relates to a greenhouse comprising sidewalls and a transparent roof, defining a crop growing area, a screen member being extendable between the sidewalls underneath the roof, for at least partly blocking of the sunlight.

The invention also relates to a method of providing a substantially uniform light level in the growing area of a greenhouse with a transparent roof, by moving a screen member over the growing area.

Background Art

It is known to control the light levels in a greenhouse by moving two screens that are situated at different heights over the growing area, across the greenhouse. One screen is a diffuse screen having a homogenous reduced light transmission and the other screen is a movable black-out screen through which no light or reduced light levels are transmitted. The screen positions of the black-out screen are controlled by light sensor signals in a growing plane of the growing areato obtain a uniform light transmission in the growing area.

The invention intends to provide an improved greenhouse and method of controlling the light intensity. It is an object of the invention to provide a greenhouse and method of growing in which the light intensity in the greenhouse can be controlled at a relatively close distance from the lower screen.

Summary of the invention

A greenhouse according to the invention comprises sidewalls and a transparent roof, situated above a crop growing space, with a support area for supporting crop, defined by longitudinal sides and transverse sides, an upper screen member, connected to an upper drive member for extending between the opposite sides over the support area, at a distance DI from the support area, at least one lower screen member, connected to a lower drive member for extending the lower screen member below the upper screen member at a distance D2 from the support area, between a storage position at a side of the growing area, and a blocking position at a distance from the side of the growing area, one of the upper and lower screen members comprising a diffusely transmitting screen member that is of substantial uniform light transmission across the screen, the other of the upper and lower screen members comprising alternating strips of relatively low light transmission and relatively high light transmission, at least one light sensor positioned in the growing area and a controller, connected to the light sensor and to the upper and lower drive members, wherein the controller is adapted to place the upper screen member in a fixed position over the growing space via the upper drive member and to move the lower screen member below the upper screen member via the lower drive member, such that at a distance D3 of at least 1.5m, preferably at least 1 m from the lower screen member, the light intensity in the growing space varies no more than 50% from the average light intensity that is measured when going from a first side of the support area to the opposite side, preferably no more than 35%, more preferably no more than 25%, most preferably no more than 20% in the time between 1 hour before noon and 3 hours past noon.

By using a first screen having a substantially homogeneous light transmission in combination with a second screen that comprises alternating strips of high and low light transmission, it was found that the light intensity levels can be controlled at higher positions in the growing area. Hereby the growing area can be used to grow higher crops, which extend upward from the support surface to the screen, such as tomatoes, paprika's, cucumbers, raspberries, blackberries, or eggplants, which may reach a hight of for instance 3 m.

Suitable screens may for instance be obtained from Ludwig Svensson BV, Hellevoetsluis, NL. For the screen with homogeneous transmission, for example a screen with type no. Harmony 2047 FR can be used. For the screen with the trips of alternating light transmission, for example, a screen with type no. Harmony O, 3015 O can be used. The strips of alternating light transmission can be formed by using different materials or can be formed of a single material with different percentage of open area for the strips.

With the present invention, the greenhouse environment can be controlled in a way that is comparable to that of an indoor farm, i.e., a growing space without the presence of natural light. However, a big disadvantage of indoor farms is the relatively high energy consumption. This is relatively high compared to a greenhouse that collects freely available energy and light from the sun. By the use of the screens of the present invention, in combination with mechanical cooling below the screens, the exchange of air between the greenhouse and the environment for cooling and dehumidification, can be largely reduced.

The controller can comprise sun position data, including the position of the sun above the greenhouse at predetermined dates and at predetermined times of the day (depending on the greenhouse's geographical location and its orientation), and is adapted for controlling the position of the lower screen member at a specific time of the day on a specific date, based on the sun position data. the upper and lower screen members may have a light transmission of between 0 and 90%. The combination of the partly transparent upper screen with a substantial uniform light transmission and the partly transparent lower screen with alternating strips of light transmissive material and light blocking material, results in a uniform light distribution at positions relatively close to the lower screen.

In an embodiment, the greenhouse comprises artificial lights that are connected to the controller, the controller being adapted to switch on the artificial lights when the light level measured by the light sensor is below a minimum intensity value.

By use of artificial light, a constant light intensity value can be achieved in the growing space, also on cloudy days when relatively little sunlight is available. By the combination of artificial lighting and the movement of the screens defined above, the same amount of light can be irradiated onto the growing space every day throughout the year.

The distance of the support surface from the lower screen member may be at least 3 m, preferably at least 4 m, more preferably at least 6m. The distance between the first and second screen members may be between 0.2m and 1 m, preferably between 0.3m and 0.5m.

The close position of the growing area of homogenous light intensity near the lower screen results a relatively high growing space with a uniform light intensity across its width.

An embodiment of the greenhouse according to the invention, comprises an air treatment unit with an air inlet, a cooling system and an air ventilation unit connected to an air inlet for transporting cooled air into the growing space, a humidity sensor and a temperature sensor connected to the controller, the controller operating the air treatment unit to become active when a temperature in the greenhouse reaches a predetermined threshold temperature, the controller, when the light sensor measures a light intensity above a lower intensity threshold value, actuating the upper drive member for moving the upper screen and when the light sensor measures a light intensity above a higher intensity threshold value, actuating the lower drive member for moving the lower screen.

In known greenhouses, the windows in the greenhouse roof are opened when when the air in the greenhouse becomes too hot and/or too humid. If the temperature further increases, a screen is moved over the growing area to block a certain amount of sunlight to further reduce the temperature. In addition to ventilation, greenhouses may also employ mechanical cooling while keeping the windows in the roof closed. If enough cooling power is employed a fully closed greenhouse can be made without openable windows. Studies and practical demonstrations however have shown that such a fully closed greenhouse is not economically feasible and that some air exchange with the outside environment will be needed.

In the greenhouse according to the invention, mechanical cooling can be started when the growing space becomes too hot and/or too humid. If the light irradiation by the sun reaches a certain level, the upper diffuse screen is closed. If the radiation from sun increases further, the lower screen is closed to a predetermined position, depending on the position of the sun, to keep the light levels below the screens at a constant level. In this way, a constant temperature, humidity, and light level can be obtained below the screens with relatively little or even completely without air exchange with the space above the screens and with the outside environment.

In this way, a "hybrid" greenhouse is formed having the advantages of an indoor farm, such as a constant temperature, humidity, and light level, but operating at a much lower energy consumption by the use of part of the incoming sun light.

In an embodiment of a greenhouse according to the invention, the air treatment unit comprises an air inlet in the greenhouse wall for intake of air from the environment and an air outlet in the roof above the upper screen member, the inlet and outlet being operated by the controller.

The greenhouse roof may be gabled, and can comprises a ridge ventilation member, preferably of the type as described in Dutch patent application no. 2027639 that was filed in the name of the applicant.

The air treatment unit may be placed in an end wall of the greenhouse, the air inlet comprising an inlet section situated in the greenhouse below the lower screen for receiving recirculation air from the space below the lower screen, an air outlet section being situated near the support area and comprising one or more perforated tubes extending in the length direction of the growing space, a ventilation unit being placed above the upper screen for air intake via a first ventilation opening in the roof and air outlet through a second ventilation opening in the roof.

A method of growing crop according to the invention comprises the steps: placing an upper screen member in a substantially stationary position over a crop growing space in a greenhouse having a light transparent roof, moving a lower screen member, at a distance below the upper screen member, across the growing space from a side of the growing space towards the centre, wherein the position of the lower screen member is determined on the basis of the angle of the sun relative to the greenhouse, such that at a distance D3 of at least lm, preferably at least 1.5 m from the lower screen member, the light intensity in the growing space varies no more than 50% from the average light intensity that is measured when going from a first side of the growing space to an opposite side, preferably no more than 35%, more preferably no more than 25%, most preferably no more than 20% in the time between 1 hour before noon and 3 hours past noon.

The use of two screens, one of which is a fixed screen and the other screen that is moved over the growing space on the basis of the position of the sun, in combination with active cooling of the interior of the greenhouse, results in a substantially constant temperature and light conditions in the growing space on a daily basis, throughout the year.

Both screens can be of the type Harmony 2047FR as available from Ludwig Svensson BV. In an embodiment, one of the screens is of the type Harmony 2047FR, the other of the type Harmony O, 3015 O.

Brief Description of the Drawings

An embodiment of a greenhouse and a method of growing crop according to the invention, will by way of non-limiting example, be described in detail with reference to the accompanying drawings. In the drawings:

Fig. 1 schematically shows a side view of a greenhouse according to the invention,

Fig. 2-15 show the positions of the screens and the light intensity in the growing space at different times of the day, and

Fig. 16 schematically shows another embodiment of a greenhouse according to the invention.

Detailed Description

Figure 1 shows a schematic lay-out of a greenhouse 1 having vertical sidewalls 2, 2' with gutters 3,3' that support a transparent roof 4. At the top of the roof 4, a movable ridge profile 5 is provided that can be raised and lowered by a drive member 6 to open and close a ventilation gap 8. A ventilation unit 10 may be provided in the roof section of the greenhouse 1, for blowing air out through the gap 8.

Inside the greenhouse 1, several air treatment units 12 are placed for the intake of air from the outside environment, dehumidification of the air and cooling or heating the dried air to the required temperature. The dried air is blown from the air treatment units 12 through flexible perforated tubes that horizontally extend in the length direction of the greenhouse along the growing beds of the crop, such as shown in figure 16 and that are described in NL 2027656 and NL 2027776, that were filed in the name of the applicant. Artificial lighting 9 is provided in the greenhouse 1 to illuminate the growing space 7 during overcast days, or in the absence of sunlight, such as at night and to maintain a constant light intensity across the growing space.

Several light sensors 14 are distributed in the growing space 7 of the greenhouse to measure the light intensity across the growing space. The light sensors 14 may be placed near a support surface 11 of the crop. Temperature sensors 15 and humidity sensors 16 measure the temperature and relative humidity in the growing space.

Along the gutters 3, an upper screen 20 is stored in a storage unit 25. The screen 20 can pulled across the growing space 7 by a drive member, for instance comprising a winch and cable, which is provided at the opposite storage unit 26. The upper screen 20 has a substantially uniform light transmission and is placed in a stationary position over the growing space 7 extending from one sidewall 2 to the opposite sidewall 2'. A further drive member is provided at the storage unit 25 for retraction of the screen 20 back into the storage unit 25.

A lower screen 30 is placed in storage units 27, 28 and can be moved in the course of hours by a drive member associated with the storage units 27, 28, across the growing space 7, below the screen 20, from one side of the growing space that may be defined by sidewall 2, towards the opposite sidewall 2'. The lower screen comprises strips of alternating higher and lower light transmission.

The lower screen can be a single screen that is moved from one sidewall 2 up to the opposite side wall 2' across the growing space 7. This configuration is optimal for greenhouses with a length direction that is oriented predominantly in an east-west facing direction. For greenhouses that are oriented predominantly in a north-south facing direction, two lower screens 30 can be used that are moved from a respective storage unit 27,28 towards the centre of the growing space 7 and back.

It should be noted that in the specific example that is described, the screens 20, 30 extend between the sidewalls 2,2' in the width direction of the greenhouse 1. However, the screens 20, 30 may have any other orientation within the greenhouse and can extend across a growing space that is at a distance from the sidewalls 2, 2'.

The upper screen 20 is spaced at a distance DI from a support surface 11. DI may be between 3.8m and 6.5m, for instance be 4m. The lower screen 30 is placed at a height D2 which may be 3.5 m-6m, for instance 3.5m. The combined screens 20, 30 result in a substantial uniform light intensity in the growing space 7 between the sidewalls 2, 2'. This uniform light distribution is present from the level of the support surface 11 up to a height Hg of the growing space 7. The growing space ends at a distance D3 of 1-1.5 m below the lower screen 30, so that the growing space has a height Hg of between 2m and 5m. The relatively high growing space 7 is suitable for the growth of tomatoes and other higher growing crop.

A controller 32 is connected to the air treatment unit 12, to the sensors 14,15,16, to the drive members of the storage units 25, 26 and 27, 28, to the ventilation unit 10 and to the drive member 6 of the ridge profile 5. The controller 32 closes the top screen 20 in dependence of the light intensity that is measured by the sensors 14. If the light intensity below the closed top screen 20 remains too high, the controller 32 moves the lower screen 30 in a timeframe of hours, across the growing space 7, based on the orientation of the greenhouse, for instance given by the compass course of the length direction of the greenhouse, and based on the angle of the sun relative to the greenhouse. The angle of the sun is calculated by the controller on the basis of the date, time, and the GPS coordinates of the greenhouse. The controller 32 controls the flow and temperature of the air treatment unit 12, the speed of the ventilation unit 10 and actuates the drive member 6.

Figures 2-15 show the screen positions of screen 20, 30 in the greenhouse at different times of the day, i.e., for different positions of the sun 33 in a geography that in this specific example corresponds to Oman. The upper screen 20 is permanently closed and has a light transmission of 71.9% in a perpendicular direction and 61.4% hemispherical transmission. The lower screen 30 has a perpendicular light transmission of 70%. The graph below the greenhouse gives the light distribution in the greenhouse across its width, below the screens at the upper-level Hg of the growing space 7.

In figures 2-6, between 6:00 and 10:00, the power of the sun increases from 2W/m² to 655 W/m².

The upper screen 20 is closed. The lower screen 30 is retracted. The average light intensity that is measured at level 13 increases from 0 to 346 W/m². At 10:00, the light intensity across the growing space 7 varies between 300 and 400 W/m².

In figure 7 it can be seen that at 11:00, the power of the sun is 808 W/m², and the lower screen 30 is moved from the storage unit 28 at sidewall 2'towards the opposite sidewall 2. The average light intensity is 345W/m² and the light intensity across the growing space 7 varies between 300 and 400 W/m².

In figure 8, at 12:00, the power of the sun is 902 W/m², and the lower screen 30 nearly spans the distance between the sidewalls 2,2'. The average light intensity at the level 13 is 342W/m² and the light intensity across the growing space varies between 300 and 400 W/m².

In figure 9, at 13:00, the power of the sun is 924 W/m², and the lower screen 30 is fully extended over the growing space 7. The average light intensity at the level 13 is 342W/m² and the light intensity across the growing space varies between 275 and 425 W/m².

In figure 10, at 14:00, the power of the sun is 876W/m², and the lower screen 30 is now moved away from the sidewall 2' and is pulled into storage unit 27 at sidewall 2. The average light intensity at the level 13 is 341W/m² and the light intensity across the growing space varies between 300 and 400 W/m².

In figure 11, at 15:00, the power of the sun is 750W/m², and the lower screen 30 covers the part of the growing space 7 that is situated nearer to the sidewall 2. The average light intensity at the level 13 is 344W/m² and the light intensity across the growing space varies between 300 and 400 W/m².

In figures 12-15, between 16:00 am and 19:00, the power of the sun decreases from 586W/m² to 47W/m². The lower screen 30 is now fully retracted. The average light intensity that is measured at level 13 decreases from 309W/m²to 25W/m².

Figure 16 shows an embodiment of a greenhouse 40 with a growing space 41 and an air treatment space 42 at an end section of the greenhouse defined by an outer wall 43 and an inner partition wall 44. Above the upper and lower screens 45, 46, a ventilation unit 47 is provided, to take in air from the environment through ventilation opening 48, and transport hot air from the region above the screens to a ventilation opening 49 in the roof 56. The opening can be positioned in the roof or can be situated in the top of the end wall of the greenhouse.

From the air treatment space 47, air is transported to an air treatment unit 50 for cooling and drying of the air. The cool and dried air is blown form the air treatment unit 50 into a perforated flexible tube 51 extending in a length direction of the greenhouse. From the tube 51, the air is blown on the crop in the growing space 41. An air inlet 55 may be provided in the outer wall for mixing ambient air with the recirculated air that enters from the growing space 41 into in the air treatment space 42. In case outside air is admitted into the greenhouse through the air inlet 55, air may pass through the screens 45, 46 to the ventilation opening 49. It is also possible that one or more windows are provided in the greenhouse walls, situated below the lower screen 46, that may be opened to ventilate air back into the environment. The screens 45, 46 of the greenhouse 40 are controlled in the manner described above.

It is also feasible that no air inlet 55 is provided and cooling and dehumidification completely occur in the air treatment unit 50.

Claims

1. Greenhouse (1,40) comprising sidewalls (2,3,43) and a transparent roof (4,56), situated above a crop growing space (7,41) with a support area (11) for supporting crop, defined by longitudinal sides and transverse sides, an upper screen member (20,45), connected to an upper drive member (25,26) for extending between the opposite sides over the support area (11), at a distance DI from the support area, at least one lower screen member (30,46) connected to a lower drive member (27,28) for extending the lower screen member (30,46) below the upper screen member (20,45), at a distance D2 from the support area (11), between a storage position at a side of the growing area, and a blocking position at a distance from the side of the growing area, one of the upper and lower screen members comprising a diffusely transmitting screen member (20, 45) that is of substantial uniform light transmission across the screen, the other of the upper and lower screen members comprising alternating strips of relatively low light transmission and relatively high light transmission, at least one light sensor (14) positioned in the growing area and a controller (32), connected to the light sensor (14) and to the upper and lower drive members (25,26;27,28), wherein the controller (32) is adapted to place the upper screen member (20,45) in a fixed position over the growing space (7,41) via the upper drive member (25,26) and to move the lower screen member (30,46) below the upper screen member (20,45) via the lower drive member (27,28), such that at a distance D3 of at least 1.5m, preferably at least 1 m from the lower screen member (30,46), the light intensity in the growing space (7,41) varies no more than 50% from the average light intensity that is measured when going from a first side of the support area to the opposite side, preferably no more than 35%, more preferably no more than 25%, most preferably no more than 20% in the time between 1 hour before noon and 3 hours past noon.

2. Greenhouse (1,40) according to claim 1, the greenhouse comprising artificial lights (9) that are connected to the controller (31), the controller being adapted to switch on the artificial lights (9) when the light level measured by the light sensor (14) is below a minimum intensity value.

3. Greenhouse (1,40) according to claim 1 or 2, the distance D2 of the support surface (11) from the lower screen member (30) being at least 3 m, preferably at least 4 m, more preferably at least 6 m.

4. Greenhouse (1,40) according to claims 1,2 or 3, comprising an air treatment unit (12,50) with an air inlet, a cooling system and an air ventilation unit connected to an air inlet for transporting cooled air into the growing space (7,41), a humidity sensor (16) and a temperature sensor (15) connected to the controller (32), the controller operating the air treatment unit (12,50) to become active when a temperature in the greenhouse reaches a predetermined threshold temperature, the controller (32), when the light sensor (15) measures a light intensity above a lower intensity threshold value, actuating the upper drive member (25,26) for moving the upper screen (20,45) and when the light sensor (15) measures a light intensity above a higher intensity threshold value, actuating the lower drive member(27,28) for moving the lower screen (30,46).

5. Greenhouse (1,40) according to claim 4, the air treatment unit (12,50) comprising an air inlet in the greenhouse wall for intake of air from the environment and an air outlet (8) in the roof (4) above the upper screen member (20,45), the inlet and outlet being operated by the controller (31).

6. Greenhouse (40) according to claim 4 or 5, the air treatment unit (50) being placed in an end wall (43,44) of the greenhouse, the air inlet comprising an inlet section situated in the greenhouse below the lower screen (46) for receiving recirculation air from the space below the lower screen (46), an air outlet section being situated near the support area and comprising one or more perforated tubes (51) extending in the length direction of the growing space (41), a ventilation unit

(47) being placed above the upper screen (45) for air intake via a first ventilation opening (48) in the roof (56) and air outlet through a second ventilation opening (49) in the roof (56).

7. Method of growing a crop in a greenhouse (1,40) comprising the steps:

Placing an upper screen member (20,45) in a substantially stationary position over a crop growing space (7,41) in a greenhouse having a light transparent roof (4,56), moving a lower screen member (30,46), at a distance below the upper screen member, across the growing space (7,41) from a side of the growing space towards the centre, wherein the position of the lower screen member (30, 46) is determined on the basis of the angle of the sun relative to the greenhouse, such that at a distance D3 of at least lm, preferably at least 1.5 m from the lower screen member (30,46), the light intensity in the growing space (7,41) varies no more than 50% from the average light intensity that is measured when going from a first side of the growing space (7,41) to an opposite side, preferably no more than 35%, more preferably no more than 25%, most preferably no more than 20% in the time between 1 hour before noon and 3 hours past noon.

8. Method according to claim 7, the greenhouse (1,40) comprising an air treatment unit (12,50) having an air inlet, a cooling system and an air ventilation unit connected to the air inlet for transporting cooled air into the greenhouse, and temperature sensor (15) connected to the controller (31), the method comprising: operating the air treatment unit (12,50) to become active when a temperature and/or humidity in the greenhouse reaches a first temperature threshold, measuring the light intensity in the growing space (7,41) and moving the upper screen member (20,45) into a position when the light intensity is above a lower intensity threshold value, and moving the lower screen member (30,46) when the light intensity in the growing space (7,41) is above a higher intensity threshold value.

9. Method according to claim 8, one of the upper and lower screen members (20,30,35,36) having a substantial uniform light distribution, the other of the upper and lower screen members (20,30,35,36) comprising alternating strips of relatively low light transmission and relatively high light transmission.

10. Method according to claim 8 or 9, wherein the air treatment unit (12,50) comprises an air inlet in the greenhouse wall (2,43,44) for intake of air from the environment and an and an air outlet (8) in the roof (4,56) above the upper screen member (20,45), the method comprising opening of the inlet and outlet for exchange of air with the ambient.

11. Method according to claim 8 or 9, the air treatment unit (50) being placed in an end wall (43,44) of the greenhouse (40), the air inlet comprising an inlet section (47) situated in the greenhouse above the upper screen member (45) and air outlet section being situated near the support area and comprising one or more perforated tubes (51) extending in the length direction of the growing space (41), the method comprising withdrawing air from above the upper screen member (45) via the inlet section (47) of the air treatment unit and recirculation of air after drying and cooling in the air treatment unit (50), from the space above the upper screen member (45) into the perforated tube (51).