WO2009053533A1

WO2009053533A1 - Method and arrangement for illuminating greenhouse plants

Info

Publication number: WO2009053533A1
Application number: PCT/FI2008/050595
Authority: WO
Inventors: Juhani Rajala; Tauno Burmoi
Original assignee: Assimilight Oy Ltd
Priority date: 2007-10-26
Filing date: 2008-10-24
Publication date: 2009-04-30
Also published as: WO2009053533A8; EP2207412A1; CA2702808A1; FI20085100A; FI20085100A0; EP2207412A4; FI124137B

Abstract

Plants are grown in a greenhouse in plant rows (1), between which plant row gaps (2) are provided. The greenhouse plants are illuminated in such a manner that they receive the light required for photosynthesis at least partly in a lateral direction from illuminators (10) moved along the greenhouse plant row gap (2) alongside the plants by directing light to each plant for part of the time. The illuminators may be arranged in arrays and fastened to carriages, for example.

Description

METHOD AND ARRANGEMENT FOR ILLUMINATING GREENHOUSE PLANTS

BACKGROUND OF THE INVENTION

[0001] The invention relates to a method for illuminating greenhouse plants, in which greenhouse plants are grown in plant rows between which maintenance aisles or other sufficiently wide plant row gaps are arranged.

[0002] The invention further relates to an arrangement for illuminating greenhouse plants, the arrangement comprising plant rows in a greenhouse and a maintenance aisle or other sufficiently wide plant row gap between them.

[0003] Greenhouse plants are typically illuminated by fastening illuminators above the plants in connection with support structures. The illumination of greenhouse plants consumes a considerable amount of energy. In addition, an illuminator causes waste heat that excessively heats the greenhouse. Accordingly, the roof hatches of a greenhouse have to be typically opened to reduce the inside temperature. This causes both waste of energy and carbon dioxide, introduced thereto and required by plants for photosynthesis, to escape from the greenhouse. Since the illuminators are fastened above the plants, the lower parts of the plants receive less light than the upper part. Consequently, the leaves of the lower part of the plants receive too little light, whereby they are incapable of photosynthesis and only consume the photosynthesis results achieved by the upper part of the growth. In addition to a high energy consumption, greenhouse illuminators also illuminate the space outside the greenhouse, i.e. greenhouses typically generate a large amount of so- called light pollution. In addition, the fastening and suspension structures of the illuminators shadow the plants preventing the plants from gaining access to natural lightning, which is extremely important for them.

[0004] A solution has been attempted in the illumination of greenhouse plants wherein illuminators are not only suspended from above, but also lower in the vicinity of the leaves of the plants or some illuminators above in connection with the roof structures have been replaced with illuminators hanging from above. However, the heat production of such illuminators cannot be very high in order for them not to burn and thus damage the leaves of the plants. Accordingly, in such a solution, a plurality of such lower-power illuminators is required, since also the luminous efficiency of the illuminators remains relatively low. Attempts have also been made to prevent the damage to the leaves by swinging the lights close to the plants back and forth, but this does not reduce the number of lights required. Altogether, the investment costs of such a solution become quite high. Also in this solution, the illuminators and particularly the suspension structures thereof shadow the plants preventing the access of natural light to the plants.

[0005] Publication US 6 178 692 discloses a solution wherein vertical growing columns are illuminated with a sulphur plasma lamp arranged in a movable support. Among other things, a magnetron required by the sulphur plasma lamp is arranged in the support, and the support is placed by the growing column. However, such a solution does not solve the problems associated with the total illumination of the greenhouse plants.

BRIEF DESCRIPTION OF THE INVENTION

[0006] The object of the present invention is to achieve a new type of solution for the illumination of greenhouse plants.

[0007] The method of the invention is characterized by moving at least two illuminators along a plant row gap substantially in the longitudinal direction of the plant row gap in such a manner that the plants receive the light required for photosynthesis at least partly in a lateral direction and in such a manner that the illuminators illuminate each plant for part of the time.

[0008] The arrangement of the inventions is characterized in that at least two illuminators are arranged to be moved along a plant row gap substantially in the longitudinal direction of the plant row gap for illuminating the plants in such a manner that they receive the light required for photosynthesis at least partly in a lateral direction and in such a manner that the illuminators are arranged to illuminate each plant for part of the time.

[0009] The idea of the invention is to illuminate plants in a greenhouse in such a manner that they receive the light required for photosynthesis at least partly in a lateral direction. The illuminators are moved between the plant rows in the greenhouse close to the plants in such a manner that each plant is illuminated for part of the time.

[0010] An advantage of the invention is that in such a solution, considerably fewer illuminators are required than previously. Accordingly, the energy consumption of the illumination can be considerably reduced. Furthermore, the excess increase in the inside temperature of the greenhouse, caused by the illumination, can be clearly reduced. Consequently, the need for ventilating greenhouses for reducing the temperature is lower, whereby carbon dioxide cannot escape from the greenhouse and heat is not lost because of such ventilation. Carbon dioxide emissions are thus also reduced. Since fewer illuminators are required than previously, the acquisition and installation costs of the illuminators are also reduced. Since the amount of electrical energy consumed by the illumination is also lower, the dimensioning of the connection cable and the main fuses of the electrical connection of the greenhouse does not have to be as massive as previously.

[0011] The overhead fastening structures for the illuminators can also be reduced, wherefore the fastening structures and the illuminators no longer shadow the plants excessively by preventing natural light from reaching the plants. In addition, service operations of the illuminators, such as replacement of lamps, cleaning of reflectors and similar measures are much easier and less expensive to carry out at the height of the growth than up at the height of 3 to 6 metres.

[0012] Illuminating plants with laterally introduced light by using an illuminator arranged between plant rows causes the plants to receive light from a close range to almost the entire assimilating leaf surface. Accordingly, also the leaves of the lower part of the growth are able to assimilate. A slowly moving light extends widely to the growth from different angles and directions, which further enhances an even reach of the entire assimilating leafage. In this way, also the leafage of the middle and lower part is made produce photosynthesis products instead of consuming them. Since the illuminators move past the plants, they have no time to heat and burn the surface of the leaf or damage the fruits, even if the thermal radiation produced thereby were quite high.

[0013] The orientation and the adjustment of the altitude of the illuminators are easy either manually or automatically. In this manner, the illumination conditions can be easily adjusted suitable for different plant species and strains and modified as the plants grow. Since a relatively small number of illuminators are required, the amount of light pollution can also be reduced from the previous. The illuminators illuminating the plants from a lateral direction also warm the lower part of the growth to some extent, which reduces the humidity of the air and accomplishes light and temperature conditions of uniform quality in the greenhouse. Conditions of uniform quality prevent the occurrence of fungi in the greenhouse. Overall, the illumination obtained is even and, ac- cordingly, the irrigation conditions operating automatically remain even, too. Temperature differences in the growth can also be made smaller, which facilitates biological pest control.

[0014] The idea of an embodiment is that the plants are illuminated from the maintenance aisle. An advantage of this embodiment is that the same space as is used for maintaining the plants can also be used for illuminating the plants.

[0015] The idea of another embodiment is that the illuminators are arranged in arrays moved along the plant row gap. An advantage of this embodiment is the ability to employ more versatile illumination solutions and it furthermore enables the simultaneous illumination of the plants from still more directions.

[0016] The idea of a third embodiment is that an illuminator array is installed in a carriage moved along the maintenance aisle. An advantage of this solution is that the same carriage as is used in harvesting or as a maintenance carriage, for example, may be used for moving the illuminators. Thus, in addition, the placement of the illumination on the maintenance aisle does not interfere with the care of the plants or the harvesting.

[0017] The idea of a fourth embodiment is that each plant is illuminated for at least part of the time simultaneously from more than one direction. An advantage of this solution is that the light can be better distributed all over the growth.

[0018] The idea of a fifth embodiment is to provide at least some illuminators with a wedge-like reflector or mirror, with which the light of each illuminator provided with a mirror or a reflector is simultaneously directed symmetrically to plant rows located on both sides of the plant row gap.

[0019] The idea of a sixth embodiment is to arrange at least two illuminators in the illuminator array on top of each other, in succession and/or in parallel. This improves the even distribution of light and facilitates the adjustment of the illumination according to the need.

[0020] The idea of a seventh embodiment is to arrange illuminators or illuminator arrays in a plurality of plant row gaps, and to arrange the illuminator arrays of adjacent plant row gaps to move in different rhythms. This being so, the light also penetrates the plant row, whereby the illuminators of one row gap also illuminate the plants of adjacent plant rows of other plant gaps. When the light arrays of different row gaps are arranged to travel at different locations, the plants are unable to stop assimilating and continue to assimilate the entire time, since the lengths of the darkest periods can be made reasonably small.

[0021] The idea of an eight embodiment is to arrange ultraviolet lamps in connection with an illuminator array or a carriage for preventing plant diseases.

[0022] The idea of a ninth embodiment is that illuminators are arranged per each plant row on an extent of less than 50 percent.

[0023] The idea of a tenth embodiment is that illuminators are arranged per each plant row on an extent of less than 30 percent.

BRIEF DESCRIPTION OF THE FIGURES

[0024] The invention will be described in more detail in the accompanying drawings, wherein

Figure 1 shows a schematic top view of a part of a greenhouse, and

Figure 2 shows a schematic side view of a carriage for illuminating plants.

[0025] In the figures, some embodiments of the invention have been described in a simplified manner for the sake of clarity. In the figures, like parts are denoted by the same reference numerals.

DETAILED DESCRIPTION OF THE INVENTION

[0026] Figure 1 shows a schematic top view of a part of a typical greenhouse. In Figure 1 , reference numeral 1 denotes plant rows 1. Plant row gaps 2 are any such gaps between two plant rows 1 that are sufficiently wide for illuminators to be arranged therein. This being so, the plant row gaps 2 may be maintenance aisles or gaps between paired plant rows, for example.

[0027] In the present application, a maintenance aisle refers to an aisle in a greenhouse that is employed for carrying out maintenance measures for the plants, such as spraying, removal of leaves and supporting the plants. A maintenance aisle is also used for harvesting. If carriages or other corresponding movable auxiliary devices are used when tending to the growth, the maintenance aisles are also utilized for moving said auxiliary devices. Heating tubes are typically arranged on the floor level in connection with the maintenance aisles. Previously, illuminators were not arranged on a maintenance aisle in professional cultivation, since in that case, a solution for arranging the removal of the illuminators from the maintenance aisles, which are generally 50 to 120 metres long in professional cultivation, during maintenance work is required.

[0028] Plants supported vertically, such as tomato, cucumber and sweet pepper, for example, are usually planted in so-called paired plant rows. In this case, two plant rows are placed close to one another, a narrow gap remaining between them, wherein maintenance measures cannot be carried out, and said maintenance aisles are arranged between the thus-formed paired plant rows.

[0029] In the embodiment of Figure 1 , the plant rows 1 are arranged in two different parts such that a middle aisle 3 is provided in the middle thereof. The plants in a plant row may be any plants grown in a greenhouse, examples of which include tomato, cucumber, sweet pepper, potted vegetables and ornamental plant species.

[0030] At least one light array 4 is arranged in each plant row gap 2 wherein illuminators are arranged. According to the need, illuminators may be arranged in paired plant row gaps, maintenance aisles and/or other sufficiently wide gaps between the plant rows, for example, either in each plant row gap or according to the need. Figure 1 is a schematic and simplified illustration of an illumination principle, and the plant row gap 2 shown in the figure may thus be any above-mentioned plant row gap type, and the plant row 1 , in turn, may represent either an individual plant row, a second plant row in a paired plant row or a paired plant row in its entirety.

[0031] The light array 4 is composed of at least two illuminators arranged in carriages, a frame, a pole or a net, for example. In this manner, light is directed at the plant rows 1 from the light arrays 4 in such a manner that the plants receive the light required for photosynthesis at least partly in a lateral direction. The plants preferably receive the light required for photosynthesis mainly in a lateral direction. The light arrays 4 are moved along a plant row gap 2 substantially in the longitudinal direction of the plant row gap such that light is directed at each plant part of the time.

[0032] A plant starts to assimilate when it receives a sufficient amount of light. After the light stops, the plant typically continues assimilating for some time. Accordingly, the assimilation does not end immediately when the light array 4 including the illuminators has moved away from the plant. As the luminous efficiency at an illuminator generated at the side of the leafage can be even many hundred-fold in the above-described manner compared with known illumination originating from above, a corresponding or even a higher luminous efficiency can be achieved even if the light is cut by moving the illuminators. In addition, a transient, strong light originating from the side and from a close range is more efficient as regards the assimilation of plants than a light that originates from above and is quite inefficient at the growth.

[0033] From the illuminators of the light array 4, the light also penetrates the plant row 1. Accordingly, the illuminators of one light array 4 illuminate more plant rows than only the plant rows 1 adjacent to the plant row gap 2 wherein the light array 4 travels. In accordance with Figure 1 , the light arrays 4 are preferably arranged to move in different rhythms, i.e. the light arrays 4 travel at a different location with respect to the adjacent light array. In this manner, when no light array 4 exists close to a plant in its own plant row gap 2, the plant, however, receives light from a light array 4 in some other plant row gap 2. This being so, the darkest period of the plant becomes as short as possible, and the plant does not necessarily stop assimilating at all, i.e. the plant is unable to finish assimilating between bright light periods and/or, when the luminous efficiency again increases, the plant achieves its maximum assimilation effect extremely rapidly, in under ten seconds. Correspondingly, if too long illumination intervals are directed at a plant, the plant reaches a dormant state, whereupon the restart of assimilation may take 1 to 30 minutes, which is avoided by the solution presented in the present application.

[0034] The arrangement of the illuminators 10 in the above- described manner between plant rows and by moving them in the plant row gaps 2, the illuminators 10 can be placed close to the plants. Typically, in professional cultivation, illuminators have been arranged in roof structures or in the vicinity thereof at a height of 5 metres, for example. Such illuminators distribute only a few percent of their maximum luminous efficiency to the outer circumference of a 2 to 3 metres high growth, for example, and only a few per mils to the inside of the growth. In contrast, illuminators arranged in the manner presented in the present application in a plant row gap 2 enable the achievement of up to a many hundred-fold luminous efficiency to the growth at the illuminators.

[0035] The illuminators of a light array 4 may be arranged successively in the longitudinal direction of the plant row gap, adjacently in the lateral direction of the plant row gap, in pairs, for example, and/or superposed in the vertical direction, allowing efficient illumination of different growths, including high growths of up to 5 metres, for example. In this case, the above-mentioned luminous efficiency can be further increased. At the same time, plants may be preferably illuminated simultaneously from a plurality of directions, for instance from the lateral direction in the lower part of the growth and obliquely from above higher up. Illuminators may also be added to an illuminator array 4 according to the need. One or more light arrays 4 may be arranged to move along one plant row gap 2 back and forth or circulate around a paired plant row along two adjacent plant row gaps 2, for example, making the adjustment of the illumination and the control of the solution simple to implement.

[0036] When desired, one illuminator can also be used for illuminating the plant rows 1 on both sides of the plant row gap 2 by directing the light with an integral or separate wedge-shaped mirror or reflector, for example, symmetrically to both plant rows 1. In this case, the different illuminators 10 may have a different, but symmetrical orientation. The use of a reflector or a mirror also allows the light pollution spreading to the environment to be minimized.

[0037] The length of a plant row gap 2 may be 10 to 120 metres, for example. The length of ope light array 4 may be 0.1 to 5 metres, for example. The distance between the light arrays 4 may be dimensioned based on the luminous efficiency of the illuminators. The travel speed of a light array 4, in turn, may be 1 to 50 seconds/metre, for example. The length of the plant row gap 2, the length of the light array 4 and the travel speed thereof, and the distances between the light arrays are arranged according to the need of each plant in a manner optimizing energy consumption and the assimilation efficiency of the plant.

[0038] According to an example, the plant row gap 2 is a maintenance aisle having a length of 50 metres, and the light array 4 is arranged in a carriage 15 whose length, along which illuminators are arranged for illuminating growths, is about 5 metres. This being so, the speed of the carriage 15 can be adapted to 1 to 50 seconds/metre, for example. In this case, there is a strong illumination at one plant during a few dozens of seconds at intervals of a few minutes, for example. Depending on the growth, the illuminators employed and other factors, the length of the light array may also be some other than was presented above. The length of the light array is preferably less than 50 percent, preferably less than 30 percent, and particularly preferably less than 15 percent of the length of the plant row to be illuminated. [0039] Figure 1 shows electrical rails 5 above the plant row gaps 2. Figure 2 shows an embodiment of the invention, wherein the illuminators are fastened to a carriage. The carriage may be a so-called maintenance carriage, preferably a harvesting carriage or another carriage used in the greenhouse or particularly intended for fastening and moving illuminators 10. A light array arranged in the carriage 15 in accordance with Figure 2 obtains its power supply from the electrical rail 5 by means of a current collector 6.

[0040] Heating tubes 7 are typically arranged in connection with the maintenance aisles. These heating tubes 7 serve as rails for the carriage, i.e. the wheels 8 of the carriage 15 are arranged to travel on top of the heating tubes 7. In different embodiments, the carriage, particularly when a harvesting carriage is being used, may also be suspended in connection with roof structures or in another corresponding structure arranged above the growth.

[0041] From the current collector 6, wiring is arranged to a link box 9, from which the power is further conducted to devices and apparatuses requiring it, such as the illuminators 10 and a motor 11.

[0042] The illuminators 10 are fastened to the structures of the carriage 15, i.e. the carriage 15 serves as a support for the illuminators 10. The illuminators 10 may be fastened fixedly to the carriage 15 or alternatively for instance by fastening the illuminators 10 to a rail, wherein the illuminators 10 can be moved, i.e. the adjustment of the location of the illuminators 10 in the vertical direction and/or in the lateral direction can be easily implemented. Furthermore, the direction of the illuminators 10 can be easily adjusted in the carriage 15. The number of illuminators 10 in the carriage 15 is selected based on the efficiency of the illuminators and the light required by the plants. The number of illuminators 10 in the vertical direction and in the longitudinal direction of the carriage 15 is also selected according to the need. The location of an illuminator 10 in the vertical direction and the orientation thereof in the vertical direction are selected according to the growth and it may be adjusted when required as the plants grow or when the carriage 15 is displaced to illuminate some other plant row 1. Furthermore, the illumination may be adjusted when required according to the growth and other factors such that some illuminators are switched on and/or switched off according to the need. In the case of a low growth, the illuminators placed low may be switched on, for example, and, as the growth grows, illuminators placed at different heights can be switched on and off according to the need. Furthermore, the illumination may be directed by using different separate or integral wedge-shaped mirrors or reflectors, which can be turned into different positions for directing light in different directions for instance by each illuminator having a different, but symmetrical orientation. In addition, the alignment of the light in the vertical direction, for example, may be controlled by means of mirrors or reflectors also without moving the illuminator.

[0043] The illuminators 10 are preferably arranged in the carriage 15 inside the frame or in the middle of the carriage at the front and/or at the rear, contrary to what is shown in Figure 2. In this case, the illuminators 10 do not increase the total width of the carriage 15. Furthermore, this being so, the illuminators 10 can be arranged farther away from the plants, whereby they do not excessively heat the leaves of the plants. Furthermore, the illuminators 10 may be arranged fixed to the middle shaft of the carriage, whereby they are arranged still farther away from the plants. This being so, when desired, one illuminator may also be used for illuminating plant rows at both sides by directing the light for instance with a wedge-shaped mirror or reflector to the plant rows. In this case, the different illuminators 10 may have a different, but symmetric alignment. The use of a mirror or reflector enables the placement of the illuminator in the carriage as far away from the plants as possible, and thus, a further reduction in the thermal effect and the risk of damage to the leaves of the growth caused thereby. It is further possible to fasten the illuminators 10 to the structures of the opposite side of the carriage, allowing the illuminators to be arranged still farther away from the plants. In this case, naturally, the illuminators at the different sides of the carriage should be fastened at different locations in either the vertical and/or the longitudinal directions, whereby they are not in the way of the light beams of the illuminators of the opposite side causing shadowing.

[0044] The carriage 15 is also provided with a maintenance plane 12, the carriage 15 serving not only as an illumination carriage, but also as a maintenance carriage. This being so, the plants may be tended to from the maintenance aisle 2 without the illuminators in the maintenance aisle interfering with the maintenance work. Furthermore, the carriage 15 is provided with a harvesting plane 13, allowing also harvesting to be implemented by utilizing the carriage 15. The illumination use may be interrupted for the duration of the maintenance and harvesting work. Height adjustment may be arranged in the carriage for instance for adjusting the height of the maintenance plane 12 or the harvesting plane 13 as desired. The height adjustment may be imple- mented manually, electrically or hydraulically. The illuminators 10 may also be arranged adjustable by adjusting the height of the carriage 15.

[0045] A shaking beater 14 may further be arranged in the carriage 15 for snapping or shaking the plants for instance by making the plants touch a solid and/or supporting cord or a longitudinal supporting holder. This allows the pollination of the plants to be ensured by means of the shaking beaters 14. Furthermore, if desired, ultraviolet lamps may be arranged in connection with the carriage 15 for preventing plant diseases. Correspondingly, the shaking beater 14 and/or the ultraviolet lamps may also be arranged somewhere else than in connection with a light array 4 arranged in the carriage, such as a light array 4 arranged in a frame, pole or net.

[0046] The carriage 15 may be arranged to move by means of an electric motor 11 , for example, which thus obtains its power supply from the electric rail 5. The motor 11 is preferably arranged under the carriage 15 or at an end thereof, whereby it does not interfere with harvesting. Instead of a motor 11 to be arranged in the carriage 15, the carriage 15 may be moved for instance by arranging rope reels at the ends of the maintenance aisles 2 from which ropes are connected to the carriage 15, and by alternately rotating the rope reels at the ends of the maintenance aisle 2 for instance with an electric motor, the carriage 15 is drawn with a rope to be coiled onto the rope reel towards the end of the maintenance aisle 2.

[0047] If required, to ensure that the narrow, high carriage remains upright, the upper end of the carriage may for instance be supported to a support structure, such as a support rail. In this case, for instance an electric rail may serve as the support rail if it can be safely used for this purpose or another support rail suitable for the purpose. Alternatively, the carriage may also be suspended in connection with the roof structures or in another such structure arranged above the growth.

[0048] The movements and travel speeds of the carriages 15 and the illuminators 10 may be controlled by a computer-based greenhouse control system. Control commands may be directed to the link box 9 provided in the carriage either wirelessly or a wired connection may be arranged in the carriage 15. A wired connection may be implemented for instance by providing the conductor with a coil, the wire unwinding during the movement of the carriage 15 from a fixed fastening point of the wire and being wound towards the coil as the carriage 15 moves towards the fixed fastening point. The coil may be ar- ranged either in the carriage or in connection with the greenhouse structures.

[0049] Instead of the electric rail 5 and the current collector 6 therein, power may be supplied to the carriage 15 also along an electric rail arranged down at the floor level. Furthermore, power may be supplied from a fixed supply point by arranging a wire between the fixed supply point and the link box 9 of the carriage 15, the wire being unwound as the carriage 15 moves away from the fixed supply point and is wound or collected into a bundle as the carriage 15 moves towards the fixed supply point. The wire reel or bundle may be arranged to either move along with the carriage 15 or remain in place in connection with the greenhouse structures. Alternatively, for instance when LED lights are used, the power supply of a light array may be arranged also with a battery or as a low-voltage supply from down with conversion current.

[0050] The illuminators may be fastened, not only to the carriages, but also to a frame, net, poles or the like, for example. The carriage, frame, poles or net may be suspended in connection with the roof structures or other such structure arranged above the growth. The carriage, frame or net may be further moved back and forth in the direction of the plant row gap 2 or by circulating along a uniform path around a plant row, a paired plant row or the like plant group.

[0051] In different embodiments, the light arrays 4 arranged in a frame, pole, net or the like structure may be moved, controlled and power may be supplied thereto in a manner similar to what was described in the previous example for illuminators 10 fastened to the carriage 15. Alternatively, a light array or the light arrays 4 may be interconnected in such a manner that one electric motor 11 draws the light arrays in tow circulating around a plant row or a paired plant row.

[0052] Any lamp suitable for illuminating plants may be used in the illuminator 10. High-pressure sodium lamps are typically used. High-pressure sodium lamps also generate quite much thermal radiation, but since the illuminators move all the time, the thermal radiation generated by the lamps does not burn the leaves or damage the fruits. The luminous efficiency of the lamps may also be higher than the maximum amount required by the plants, since a transient, too bright light is not likely to damage the plants. Furthermore, some or all illuminators may be LED illuminators. The advantage of LED illuminators is the relatively low energy consumption thereof. In addition, LED illuminators are durable. LED illuminators do not either generate much extra thermal radia- tion and do therefore not substantially heat the leaves of the plants, at least not excessively, in addition to which a separate cooling system can be installed for LED lights, if desired. For this reason, LED illuminators can indeed be used for illuminating plants at quite a close range, and the illuminator arrays 4 may be arranged more densely than when conventional illuminators are used. LED illuminators also produce the desired light wavelength ranges, enabling a further enhancement of the yield of the plants.

[0053] In some cases, the features presented in the present application can be used as such, irrespective of other features. On the other hand, if required, the features presented in the present invention can be combined to generate various combinations.

[0054] The drawings and the related description are only intended to illustrate the idea of the invention. The details of the invention may vary within the scope of the claims. Accordingly, the carriage 15, for instance, does not necessarily have to be arranged to travel along rails, but the carriages may travel along the maintenance aisle on the ground or the floor. In addition to the illumination of the plants by means of moving light arrays 4, when desired, some illuminators may be arranged in the greenhouse in connection with the upper structures, for example for implementing so-called general illumination. The plants may also be illuminated by means of hanging LED illuminators, for example. In case the plants are arranged in so-called double rows, the LED illuminators may in that case be suspended between the double rows, provided the gap is sufficiently wide. These suspended lights may also be arranged movable along an electric rail, for example.

Claims

1. A method for illuminating greenhouse plants, in which greenhouse plants are grown in plant rows (1) between which maintenance aisles or other sufficiently wide plant row gaps (2) are arranged, characterized by moving at least two illuminators along a plant row gap (2) substantially in the longitudinal direction of the plant row gap in such a manner that the plants receive the light required for photosynthesis at least partly in a lateral direction and in such a manner that the illuminators (10) illuminate each plant for part of the time.

2. A method as claimed in claim 1, characterized by illuminating the plants from the maintenance aisle.

3. A method as claimed in claim 1 or 2, c h a r a c t e r i z e d by arranging the illuminators in arrays (4) that are moved along a plant row gap.

4. A method as claimed in claim 3, characterized by installing the illuminator array in a carriage (15) that is moved along the maintenance aisle.

5. A method as claimed in any one of the preceding claims, characterized by illuminating each plant for at least part of the time simultaneously from more than one direction.

6. A method as claimed in any one of the preceding claims, characterized by providing at least some illuminators with a wedge-like reflector or mirror, with which the light of each illuminator provided with a mirror or a reflector is simultaneously directed symmetrically to plant rows located on both sides of the plant row gap.

7. A method as claimed in any one of claims 3 to 6, characterize d by arranging at least two illuminators in the illuminator array (4) on top of each other, in succession and/or in parallel.

8. A method as claimed in any one of the preceding claims, characterized by arranging illuminators or illuminator arrays (4) in a plurality of plant row gaps (2), and arranging the illuminator arrays (4) of adjacent plant row gaps to move in different rhythms.

9. A method as claimed in any one of the preceding claims, characterized by arranging ultraviolet lamps in connection with the illuminator array (4) or the carriage (15) for preventing plant diseases.

10. A method as claimed in any one of the preceding claims, characterized by arranging illuminators per each plant row on an extent of less than 50 percent.

11. A method as claimed in any one of the preceding claims, characterized by arranging illuminators per each plant row on an extent of less than 30 percent.

12. An arrangement for illuminating greenhouse plants, the arrangement comprising plant rows (1) in a greenhouse and a maintenance aisle or other sufficiently wide plant row gap (2) between them, characterized in that at least two illuminators (10) are arranged to be moved along a plant row gap (2) substantially in the longitudinal direction of the plant row gap for illuminating the plants in such a manner that they receive the light required for photosynthesis at least partly in a lateral direction and in such a manner that the illuminators are arranged to illuminate each plant for part of the time.

13. An arrangement as claimed in claim 12, characterized in that the illuminators are arranged in the maintenance aisle.

14. An arrangement as claimed in claim 12 or 13, characterized in that the illuminators are arranged in illuminator arrays (4).

15. An arrangement as claimed in claim 14, characterized in that the illuminator arrays (4) are arranged in a carriage (15).

16. An arrangement as claimed in any one of claims 12 to 15, characterized in that the illuminators are arranged to illuminate each plant for at least part of the time simultaneously from more than one direction.

17. An arrangement as claimed in any one of claims 12 to 16, characterized in that at least some illuminators are provided with a wedge-like reflector or mirror, with which the light of the illuminator is simultaneously directed symmetrically to plant rows located on both sides of the plant row gap.

18. An arrangement as claimed in any one of claims 14 to 17, characterized in that at least two illuminators in the illuminator array (4) are arranged on top of each other, in succession and/or in parallel.

19. An arrangement as claimed in any one of claims 12 to 18, characterized in that illuminators or illuminator arrays (4) are arranged in a plurality of plant row gaps (2), and the illuminator arrays (4) of adjacent plant row gaps are arranged to move in different rhythms.

20. A method as claimed in any one of claims 14 to 19, characterized by arranging ultraviolet lamps in connection with the illuminator ar- ray (4) or the carriage (15) for preventing plant diseases.

21. An arrangement as claimed in any one of claims 12 to 20, characterized in that illuminators are arranged per each plant row on an extent of less than 50 percent.

22. An arrangement as claimed in any one of claims 12 to 21, characterized in that illuminators are arranged per each plant row on an extent of less than 30 percent.