WO2008140312A2

WO2008140312A2 - System for treating and distributing air in a greenhouse

Info

Publication number: WO2008140312A2
Application number: PCT/NL2008/050288
Authority: WO
Inventors: Jan Otto Voogt; Pieter Arie Van Weel
Original assignee: Hoogendoorn Automatisering B.V.
Priority date: 2007-05-15
Filing date: 2008-05-15
Publication date: 2008-11-20
Also published as: WO2008140312A3; NL1033851C2

Abstract

A system (13) for treating and distributing air in a greenhouse (1), comprising at least one outflow opening (11) connected to an air treatment apparatus (4) for locally introducing treated air into the greenhouse (1) and a distributing unit (12) corresponding with the outflow opening (11) substantially in vertical direction for locally distributing in the greenhouse (1) the air introduced into the greenhouse (1) via the outflow opening (11).

Description

P81206PC00

Title: System for treating and distributing air in a greenhouse

The invention relates to a system for treating and distributing air in a greenhouse.

The greenhouse comprises light -transmitting walls and roof which form a housing for crop plants. In the greenhouse, glasshouse vegetables, flowers or plants can be grown.

In practice, it is known to use an air treatment apparatus with one or more heat exchangers therein, and a fan for drawing in air from the greenhouse and then pressurizing the treated air that is brought into the greenhouse via air ducts. Such an air treatment apparatus is also called air treatment device. The air can be heated, cooled or dehumidified.

Dehumidifying the air can be done by cooling the air to below dew point and then reheating it, or by supplying dry, fresh air. Also, heat can be recovered from the greenhouse.

Usually, the air ducts are of flexible material and are called tubes. The tubes are provided at each row of plants or per two rows of plants or per growing trays. Usually, the tubes are fed by the air treatment device at the outer wall side of the greenhouse.

The tubes are provided with a pattern of holes through which air is blown into the greenhouse. The pattern of holes is such that the distribution of air over the length of the tube is virtually uniform. Optionally, the diameter of the tube is gradually reduced in longitudinal direction to keep the pressure reduction in the tube as low as possible and thus keep the distribution of air as uniform as possible.

A drawback of this system is that per use in a greenhouse, a specific tube with a particular pattern of holes and/or a particular diameter reduction is to be designed. Manufacture of such a specific tube is expensive. Also, high pressure is required in the tube in order to also have sufficient pressure at the end of the tube for a uniform distribution of air. To this end, in the air treatment device, a high capacity fan is required for creating the pressure. Such a fan is expensive and consumes much electricity. Another drawback of this system is that per growing tray, one tube is required for obtaining a uniform distribution of air in the greenhouse. As a result, great lengths of specific tubes are required, which is expensive.

In order to eliminate the drawbacks of such tubes, in practice, use is also made of air treatment devices which are distributed over the greenhouse. By blowing out a directed air jet at high speed, a turbulent air flow is formed which effects mixture over the length of the air jet. However, a drawback of this setup is that placing the air treatment devices near the bottom of the greenhouse leads to the formation of a cold air layer in the greenhouse that mixes poorly with the overlying hotter air, also as a result of the additional resistance caused by a dense crop layer, so that no uniform distribution of air is achieved in the greenhouse. Placing the air treatment devices near the top of the greenhouse does not lead to a uniform air distribution either, because the treated air is blown out in only one direction, and colder air sinks rapidly. Although blowing out treated air forcefully enables a slightly more uniform air distribution, this is not desirable as it causes an unfavourable growing climate in the greenhouse due to vertical temperature differences and a high electricity consumption. The air treatment devices at the top of the greenhouse also obstruct passage o{ light to the crops, which also leads to an unfavourable growing climate.

German patent publication DE 4307101 shows a climate chamber in which air is blown in via an air treatment device and wherein the air is transported via a channel system with openings. In one of the embodiments, the air ends up via the channel system on the bottom in the climate chamber and it is exhausted by a fan positioned at the top of the chamber. In this case, this one fan is responsible for the speed of the air flow. This fan is therefore especially intended for circulating the air, while the distribution over the climate chamber is to be controlled through the presence or absence of openings in the air guiding channel. Therefore, the fan in DE 4307101 does not function as a distribution system for distributing the air in the climate chamber. As a result, the operation of the air treatment device and the air speed and air distribution in the climate chamber cannot be separately controlled. In addition, setting a uniform distribution of the air in the climate chamber is highly critical because of the unavoidable pressure differences in the walls (channel system). For a uniform distribution, small openings in the channel system are to be preferred, but this requires a substantial excess pressure in the channel system, which demands much capacity of the circulating fan.

The object of the invention is an air treatment system for treating and distributing air in a greenhouse which eliminates these drawbacks. The present invention allows in particular a completely independent control of air treatment (that which happens in the air treatment device) and air movement in the greenhouse.

To this end, the invention provides a system for treating and distributing air in a greenhouse, comprising at least one outflow opening connected to an air treatment device for locally introducing treated air into the greenhouse, and a distribution unit corresponding substantially in vertical direction to the outflow opening for locally distributing in the greenhouse the air introduced via the outflow opening into the greenhouse.

Through the use of an air treatment device with outflow opening and a distribution unit corresponding substantially in vertical direction to the outflow opening, treatment and supply of air and distribution of this air are separated. As the outflow opening serves only for locally introducing the treated air into the greenhouse, and not for the distribution thereof, a lower pressure can suffice for introducing the treated air into the greenhouse. Despite the power supply required for the distribution units, this yields a saving in the consumption of electricity. Substantially in vertical direction is understood to mean that the outflow opening and the distribution unit are aligned in an upright direction.

Through the use of a distribution unit which corresponds substantially in vertical direction to the outflow opening, the treated air that is locally introduced into the greenhouse via the outflow opening is distributed in an advantageous manner.

In a preferred embodiment, the distribution unit comprises a distribution fan, which operatively draws in, in axial direction, the air introduced into the greenhouse via the outflow opening, and distributes it radially all around. Through the use of a distribution fan, the air introduced into the greenhouse via the outflow opening is distributed locally in a simple manner, so that locally, a uniform distribution of air can be effected. In an advantageous embodiment, the distribution fan comprises upright vanes for axially drawing in, and radially distributing air in an energy effective manner. In a further preferred embodiment, the position of the vanes is easily adjustable.

It is advantageous when the outflow opening is placed substantially in vertical direction below the distribution unit. As the outflow opening is located below the distribution unit, virtually all air introduced into the greenhouse by the outflow opening is captured by the distribution unit and then distributed. To prevent plants dehydrating too strongly in the vertical plane, it is preferred that the distribution unit is designed with a cover plate with an adjustable opening to thus reduce the purely vertical air flow in favour of air inflow via the edges of the cover plate. In a preferred embodiment, the outflow opening is placed below the level of plants grown in the greenhouse, and the distribution unit is placed above the level of the plants grown in the greenhouse. By placing the outflow opening below the level of plants grown in the greenhouse, the outflow openings do not take away light for the plants, so that an optimal growing climate can be created. By placing the distribution unit above the level of plants grown in the greenhouse, the air is distributed above the plants, so that a better distribution of air can be obtained also in the longitudinal direction of the crops.

In an alternative embodiment, between the outflow opening and the distribution unit, an auxiliary channel is provided for bringing the air introduced via the outflow opening into the greenhouse near the distribution unit. Thus, the treated air is directly brought near the distribution unit, so that too strong an air flow along the plants is prevented.

In a preferred embodiment, the air treatment device is placed adjacent the outflow opening. By placing the air treatment device adjacent the outflow opening, the air treatment device can be of inexpensive design, because it treats air only locally. The fan disposed in the air treatment device for introducing the treated air into the greenhouse can be of less expensive design too, as the air hardly needs to be moved, or only over a short distance, so that the pressure needs not be high.

In one embodiment, the outflow opening is connected to the air treatment device via an air duct. This is particularly advantageous when supply of fresh air is desired. The air treatment device can be disposed adjacent an outer wall of the greenhouse and, for the treatment of air, draw in fresh air via an opening in the outer wall. It is advantageous when, via the air duct, an air treatment device controls different outflow openings, distributed over the length of the air duct. Thus, at a number of locations, locally treated air can be introduced into the greenhouse.

In an advantageous embodiment, the outflow opening is provided with a device for enlarging and/or reducing the outflow opening. With it, the outflow opening can be readjusted and the flow rate can be adjusted to the changed conditions in the greenhouse and/or reduce any differences in flow rate between several outflow openings.

The invention further relates to a greenhouse comprising light- transmitting walls and roof, forming a housing for crop plants, wherein the greenhouse is provided with at least a system for treating and distributing air in the greenhouse, comprising at least one outflow opening connected to an air treatment device for locally introducing treated air into the greenhouse and a distribution unit corresponding substantially in vertical direction to the outflow opening for locally distributing in the greenhouse the air introduced into the greenhouse via the outflow opening.

The invention further relates to a method for treating and locally distributing air in a greenhouse, comprising drawing in air from the greenhouse; treating air in an air treatment device; introducing the treated air into the greenhouse via an outflow opening; supplying the air introduced via the outflow opening into the greenhouse in upright direction to a distribution unit and distributing the air drawn in by the distribution unit all around in radial direction. Distributing radially all around is understood to mean that the air is distributed around the distribution unit in lateral direction. Supplying air to the distribution unit can be done by blowing the air at great speed from the outflow opening, or in that the distribution unit draws the air in axially, or by a combination of both. Through this method, the air is first introduced locally into the greenhouse and is then locally distributed in the greenhouse, so that less energy is required than when the air is transported over the entire greenhouse.

The invention further relates to the use of a distribution fan for locally distributing treated air, introduced into the greenhouse via an outflow opening corresponding in vertical direction, over plants in a greenhouse.

The invention will be further elucidated on the basis of exemplary embodiments represented in a drawing. In the drawing:

Fig. 1 shows a schematic view of an air treatment system for treating and distributing air in a greenhouse according to the invention;

Fig. 2 shows a schematic perspective view of a greenhouse provided with air treatment systems according to Fig. 1; Fig. 3 shows a front view of a greenhouse provided with a first embodiment of air treatment systems;

Fig. 4 shows a side view of a greenhouse provided with a first embodiment of air treatment systems; Fig. 5 shows a front view of a greenhouse provided with a second embodiment of air treatment systems according to the invention;

Fig. 6 shows a side view of a greenhouse provided with a second embodiment of air treatment systems according to the invention;

Fig. 7 shows a schematic view of an air treatment device; Fig. 8 shows a schematic view of a distribution fan; and

Fig. 9 shows a schematic view of a distribution fan with adjustable vane position. In Fig. 9a, the position is represented without adjustment, in Fig. 9b, the adjusting plate 21 bends the flexible part 25.

The Figures are only schematic representations of preferred embodiments of the invention, and are given by way of non-limitative exemplary embodiments. In the Figures, identical parts are represented with identical reference numerals.

Fig. 1 shows an air treatment system 13 comprising an outflow opening 11 and a distribution unit 12 corresponding in upright direction to the outflow opening 11. Via the outflow opening 11, treated air is locally introduced into the greenhouse. The distribution unit 12 distributes this air locally in the greenhouse to thus create an optimal and constant growing climate.

The air supply towards the outflow opening 11 can be effected in different manners. In a first embodiment, shown in Fig. 3 and Fig. 4, the air is brought at the outflow opening 11 via an air duct 7. The outflow opening 11 is connected via the air duct 7 to the air treatment device 4, which is disposed at the outer wall of the greenhouse 1. In a second embodiment, shown in Fig. 5 and Fig. 6, the air treatment device 4 is disposed adjacent the outflow opening 11, so that the air to be treated is locally drawn in from the greenhouse. In a third embodiment - not shown - the air is brought at the outflow opening via a combination of a local air treatment device with local suction and an air duct connected to an air treatment device disposed, for instance, at the outer wall. Fig. 2 shows a greenhouse 1 with a number of growing trays 2 therein. In the growing trays 2, plants 3 are grown. In order to obtain an optimal growing climate for the plants 3, the air in the greenhouse 1 is treated and distributed with an air treatment system 13. The air treatment system 13 comprises an outflow opening 11 which is connected via an air duct 7 to the air treatment device 4.

As shown in Fig. 7, the air treatment device 4 comprises one or more heat exchangers 5 for treating air and a fan 6 for drawing in air to be treated from the greenhouse and pressurizing the treated air. In the air treatment device 4, the air can be dehumidified, be cooled or be heated. A first heat exchanger 5a is used for, for instance, cooling or dehumidifying air, a second heat exchanger 5b may be used for heating air. The required heat or cold for treating the air can be obtained from, for instance, a heating boiler, combined heat and power or a heat pump, schematically represented in Fig. 2 with device 15. In the first exemplary embodiment shown in Fig. 4, the air treatment device 4 is placed adjacent the outer wall of the greenhouse 1. In an advantageous manner, fresh air can also be drawn in via the fresh air opening 8. This fresh air can be introduced into the greenhouse in a dosed manner. The drawn in fresh air then leaves the greenhouse 1 via roof vents 16 set ajar to that end.

During the night, usually, a screen 9 is pulled close at the top of the greenhouse. Via the duct 10, during the night, air can be drawn in from above the screen 9. When introducing fresh air into the greenhouse 1 and exhausting air via the roof vents 16, the screen 9 may or may not be closed. Owing to the different option of supply of air and the optional heating, cooling or humidifying thereof, an optimal growing climate for the plants in the greenhouse can be effected.

Via the outflow openings 11, the treated air is locally introduced into the greenhouse. Here, there is an upright air flow to the distribution unit 12, corresponding substantially in vertical direction to the outflow opening 11, which unit distributes the air locally in the greenhouse.

In this exemplary embodiment, the distribution unit 12 is designed as a distribution fan as shown in Fig. 8. The distribution fan 12 comprises upright vanes 14. As a result, the distribution fan 12 draws in air in axial direction and distributes this all around in radial direction. An example of a distribution fan is described on www.nivola.nl.

Preferably, the amount of air that is drawn in purely vertically is controlled through the provision of a horizontal plate with an adjustable opening under the distribution unit 12. By varying the opening of this plate, the ratio between air drawn in purely vertically and air drawn in along the outer edges of the plate is controlled. This prevents a too strong vertical air flow which might cause dehydration of plants in the vertical plane. The adjustable opening is preferably designed as an adjustable diaphragm (compare shutters in cameras). A specially preferred fan is a radial fan whose vanes are adjustable to therewith determine the direction of the radial flow. With this too, the ratio between drawing in air from the top side of the distribution unit and from the bottom side of the distribution unit is controlled. Thus far, these fans are only available in designs wherein the position of the vanes is to be changed manually per vane. It is preferred that the fan has a device that provides in a simple, controllable adjustment of the position of the vanes. This is effected through the use of a flexible, or at least bendable, part 25 of the fan 20 that is in the reach of the axis 24. This flexible or bendable part 25 can be deformed by means of, for instance, pressure. This pressure can be applied by an adjusting plate 21. Here, this adjusting plate 21 preferably has a concave form or at least an edge 22 projecting in axial direction. This adjusting plate 21 can be adjusted relative to the fan vanes 23 in axial direction along the axis 24. Here, the projecting edge 22 can press against the vanes 23 or the flexible or bendable part 25 in which the vanes 23 are provided, such that the position of the vanes 23 can be changed. Here, the flexible part 25 can form part of the vanes 23 or be a connecting element (not shown) with which the vanes 23 are connected to the axis 24. The adjusting plate 21 can be adjusted axially over the axis 24, for instance by means of a screw thread 26 on the axis 24. Here, use can be made of an adjusting bolt 27 or other adjusting element known to the skilled person. The adjusting plate 21 itself can also be provided with screw thread that can engage around the screw thread 26 of the axis 24. Thus, the adjusting plate can be axially adjusted by simply turning this adjusting plate 21 relative to the axis 24. Although in the Figures the adjusting plate 21 is located, relative to the vanes 23 of the fan 20, on the driven side 28 of the axis 24, it can also be provided, relative to the vanes 23 of the fan 20, on the side of the free end 29 of the axis 24. Also, two adjusting plates can be used, which are provided, in an axially adjustable manner on the axis 24, in axial direction on both sides of the vanes 23. By now adjusting the one or more adjusting plates 21 in axial direction relative to the vanes 23, the angle between the vanes 23 and the axis 24 can be set. As a result, the volume flow and/or the direction of the volume flow the fan displaces during operation can be set in a simple manner. Although in the drawing the adjusting plate is to be adjusted manually, this can also be effected by means of a remotely controlled actuator. This may for instance be driven by an air treatment system or air treatment computer.

The vanes 23 can be provided, in radial direction, at the location of the projecting edge 23 of the adjusting plate 21, with special projections that are placed such that the adjusting angles of the vanes 23 relative to the axis 24 are effected in an ideal manner. Here, by a second adjusting plate and a second set of projections, also the span (or pitch) of the vanes 23 can be adjusted. By setting both the span and the angle of the vanes relative to the axis 24, the flow direction and the flow volume can be set optimally.

Owing to the distribution all around in radial direction, locally, in the greenhouse 1, a virtually uniform distribution of air is created. An outflow opening 11 with a distribution fan 12 corresponding in upright direction provides the local distribution of treated air in the greenhouse over an area of approximately 150 m² to approximately 250 m².

Distributing the treated air is done by the distribution fans 12, as a result, in the exemplary embodiment of Fig. 3 and Fig. 4, simple air ducts 7 suffice, in which a number of outflow opening 11 are provided. As can be seen in Fig. 3, in this exemplary embodiment, only one air duct 7 is required per 4 to 5 rows of plants.

As the distribution fan 12 corresponding to the outflow opening 11 draws in, in axial direction, the treated air introduced into the greenhouse via the outflow opening 11, a lower pressure of the treated air in the air channel 7 can suffice. As a result, the fan 6 in the air treatment device 4 can be designed less expensively and consumes less electricity.

Over the length of the row of plants in the greenhouse 1, a number of air treatment systems 13 are placed which locally provide the distribution of treated air and thus locally take care of the air climate, as shown in Fig. 4 and Fig. 6. With a customary length of a row of plants of approximately 100 meters, only 8 air treatment systems 13 are required. Here, the outflow openings 11 are spaced apart along the row of plants. Each air treatment system 13 can locally provide an optimal air distribution over an area of approximately 200 m².

Fig. 5 and Fig. 6 show a second embodiment of a greenhouse 1 with air treatment systems 13 therein. In this exemplary embodiment, the outflow opening 11 is directly connected to the air treatment device 4 and is located at the top of the air treatment device 4. As a result, the treated air is blown out in upright direction, whereby drawing in air axially is simplified for the distribution unit 12.

In the exemplary embodiment of Fig. 5 and Fig. 6, the air treatment devices 4 are disposed locally. Air treatment is therefore not carried out centrally, as is the case with the exemplary embodiment of Fig. 3 and 4, but locally. Optionally, fresh air can be supplied to the air treatment device 4 via an underground tube system or from a central channel.

In the exemplary embodiments shown, the air treatment device 4 is at least partly below the level of plants 3 grown in the greenhouse 1. The air duct 7 and/or the air treatment device 4 are lower than the plants 3, so that outflow openings 11 are located below the plants 3. The distribution fan 12 is preferably located above the level of the plants 3 grown in the greenhouse, adjacent the top of the greenhouse 1.

Between the outflow opening 11 and the distribution fan 12, an auxiliary duct - not shown - can be provided for bringing the treated air directly near the distribution fan.

The outflow opening 11 can be provided with a device for enlarging and/or reducing the outflow opening 11. This may be a throttle plate or an adjustable slide with which the outflow opening can be enlarged and/or reduced.

The invention is not limited to the exemplary embodiments represented here. For instance, the outflow opening could also be located adjacent the distribution fan, the air duct with outflow opening or the air treatment device with outflow opening can also be placed, for instance, at the top of the greenhouse, below the distribution fan. It is also possible that an outflow opening is provided on both sides of the air duct, or two or more outflow openings can be located next to each other. The air duct can also be locally provided with many smaller outflow openings which correspond in upright direction to a distribution unit. Optionally, these many smaller outflow openings can also be locally designed as a pattern of holes. Further, a combination of embodiments can be selected, wherein a part of the air is supplied to the outflow opening via an air duct, and a part of the air is locally drawn in from the greenhouse - via an air treatment device. The air duct may be provided at the bottom or the top of the greenhouse, or optionally underground to prevent occupation of space and/or hinder during operations in the greenhouse.

The outflow opening can also be located in upright direction above the distribution unit at the top of the greenhouse. Then, from the outflow opening, there iβ an upright air flow that is supplied in axial direction to the top side of the distribution unit.

It will be clear to the skilled person that many variations are possible within the scope of the invention as represented in the following claims.

Claims

1. A system for treating and distributing air in a greenhouse, comprising at least one outflow opening connected to an air treatment device for locally introducing treated air into the greenhouse and a distribution unit corresponding substantially in vertical direction to the outflow opening for locally distributing in the greenhouse the air introduced into the greenhouse via the outflow opening.

2. A system according to claim 1, wherein the distribution unit comprises a distribution fan which, in operation, draws in, in axial direction, the air introduced into the greenhouse via the outflow opening and distributes it in radial direction.

2a. A system according to claim 2, wherein below the distribution unit a horizontal plate is provided with an adjustable opening therein.

3. A system according to claim 2, wherein the distribution fan comprises upright vanes. 3a. A system according to claim 3, wherein the distribution fan comprises a flexible plate with which the position of the vanes can be adjusted.

4. A system according to any one of the preceding claims, wherein the outflow opening is placed substantially in vertical direction below the distributing unit.

5. A system according to any one of the preceding claims, wherein the outflow opening is placed below the level of plants grown in the greenhouse and the distribution unit is placed above the level of plants grown in the greenhouse.

6. A system according to any one of the preceding claims, wherein between the outflow opening and the distribution unit an auxiliary channel is provided for bringing air introduced into the greenhouse via the outflow opening near the distribution unit.

7. A system according to any one of the preceding claims, wherein the air treatment device is placed adjacent the outflow opening.

8. A system according to any one of the preceding claims, wherein the outflow opening is connected via an air duct to the air treatment device.

9. A system according to claim 8, wherein the air duct comprises a number of spaced apart outflow openings for locally introducing treated air into the greenhouse at a number of locations.

10. A system according to any one of the preceding claims, wherein per outflow opening and corresponding distribution unit, local distribution of treated air is provided in the greenhouse over an area of approximately 150 m² to approximately 250 m².

11. A system according to any one of the preceding claims, wherein the outflow opening is provided with a device for enlarging and/or reducing the outflow opening.

12. A greenhouse comprising light-transmitting walls and roof which form a housing for crop plants, characterized in that the greenhouse is provided with at least one system for treating and distributing air in the greenhouse according to any one of the preceding claims.

13. A greenhouse according to claim 12, wherein the distribution unit is located above the level of plants grown in the greenhouse adjacent the roof of the greenhouse and the outflow opening is located below the level of plants grown in the greenhouse adjacent the bottom of the greenhouse.

14. A method for treating and locally distributing air in a greenhouse, comprising - drawing in air from the greenhouse;

- treating air in an air treatment device;

- introducing the treated air via an outflow opening into the greenhouse;

- supplying in upright direction to a distributing unit air introduced into the greenhouse via the outflow opening; - distributing supplied air all around in radial direction by the distribution unit.

15. A method for treating and locally distributing air in a greenhouse according to claim 14, wherein air introduced into the greenhouse via the outflow opening is axially drawn in by the distribution unit.

16. A method for treating and locally distributing air in a greenhouse according to any one of claims 14 - 15, wherein the drawn in air is mixed with fresh air.

17. A method for treating and locally distributing air in a greenhouse according to any one of claims 14 - 16, with a system according to any one of claims 1 — 11.

18. Use of a distribution fan for locally distributing treated air, introduced into the greenhouse via an outflow opening corresponding in vertical direction, over plants in a greenhouse.

19. A radial fan, comprising an axis (24) having attached thereon one or more vanes (23) and an adjustable adjusting plate (21), wherein the position of the one or more vanes (23) is changeable by means of pressure applicable by the adjusting plate (21) through bending of the vanes and/or of a connecting element.