WO1999055139A1

WO1999055139A1 - Plant growing method and greenhouse

Info

Publication number: WO1999055139A1
Application number: PCT/FI1999/000349
Authority: WO
Inventors: Veijo RIIHIMÄKI; Jorma Kallonen
Original assignee: Luomutalo 2000 Oy
Priority date: 1998-04-28
Filing date: 1999-04-28
Publication date: 1999-11-04
Also published as: FI980937A0; FI980937A; AU3712599A

Abstract

A greenhouse (10) which comprises two or more tiers in which the plants (33) to be grown are situated. The tiers of the greenhouse are of open construction without solid floor surfaces, which means that air and light are at least partly able to pass through the spaces (64) between the plants grown, from one tier to another. There are several plant growing lines (14) in the greenhouse, in which the plants are placed in growing carriages (12) moving on guide rails (29). The luminaires (31) are fixed to the underside of support beams (30) so that the light is also directed between the plants, support beams and guide rails onto the plants in the lower tier.

Description

PLANT GROWING METHOD AND GREENHOUSE

The object of the present invention is a method for growing plants, such as, for example, flowers, broccoli, leek, cauliflower or lettuce.

In Finland and the other Nordic countries, the problem with known greenhouses is that their operating costs are extremely high. This is why they are in a difficult competitive situation compared with vegetables imported from more southerly countries. There are various reasons for the high operating costs of Finnish greenhouses. One problem is high energy consumption, which is naturally due to the cold conditions of Nordic winters. Greenhouses need to be heated a great deal and thus the energy expenses are also high. Nor is the structure of known greenhouses very advantageous from the point of view of energy economy. They usually have large window surfaces, which cannot very easily prevent heat from transferring through the structures to the outside, and thus being wasted.

Since already the energy costs are high, in a tight economic situation it is not possible to use aids which would further increase costs, even if such means were known to enhance the growth of plants. One such aid is the addition of carbon dioxide. Purchased carbon dioxide is, however, so expensive that it is not profitable to use it in any great amounts in greenhouses.

The high heating costs indirectly lead to yet another disadvantage of known greenhouses. Since the air inside a greenhouse has to be heated at a high cost, greenhouses are aired as little as possible. After all, both expensive heat and expensive carbon dioxide escape during airing. However, insufficient airing results in plants of a quality which is not the best possible.

It is known to make greenhouses with several tiers for growing seedlings. One such solution is shown in the publication EP A 0142643. In this solution the seedlings are placed in large boxes, of which there are several adjacent to each other in different tiers. This type of solution is, however, only possible for growing seedlings. For growing plants, there is not enough light in this type of greenhouse. For the actual growing of the plants, the seedlings have to be transferred elsewhere.

The aim of the present invention is to achieve a new plant growing method which does not have the above disadvantages. It is characteristic of the growing method relating to the invention that the plants are grown in two or more tiers so that favourable lighting, heating and air composition conditions are arranged for the plants in the following manner: artificial light is supplied to the plants mainly from above them, at least in one tier light is supplied through the spaces between the plants so that at least some of the light used for the lighting of the plants can also light the plants in a lower tier, a substantial proportion of the heat required for heating the greenhouse is obtained from the lights, the greenhouse air is circulated so that at least some of the air passes through the tier of plants via the openings left between the plants, and carbon dioxide, which enhances the growth of plants, is added to the air in the greenhouse.

By means of the method relating to the invention a substantially more advantageous plant growing method is achieved than those known previously. To begin with, a greenhouse with two or more tiers is advantageous in wintertime from the viewpoint of thermal economy, because in this type of construction the ratio of the surface area of the cold outer wall to the plant growing area is substantially smaller than in known greenhouses. Thus heat losses through the wall are in this case also substantially smaller.

It is possible to grow a great variety of plants by means of the method relating to the invention. The most preferred are, for example, plants such as flowers, broccoli, leek, cauliflower and lettuce. It is essential for the growth of these plants that the entire greenhouse has sufficiently effective lighting in . For this purpose, lamps are situated above each plant tier, the said lamps providing efficient lighting for the plants. However, in addition to direct lighting, the plants also receive lot of scattered light due to the fact that the light also passes at the same time through the spaces between plants to lower tiers and further to the plants located there. The space between the tiers only has to be sufficiently large for the formation of direct lighting and the consequent scattered light. The lamps used for lighting the plants do not necessarily have to be directly above the plants. They may also be at the side, provided that sufficient lighting is obtained.

The quality of indoor air and its regulation are also of essential importance when considering the growth conditions of plants. In accordance with the method relating to the invention, the conditions surrounding each plant can be made advantageous by sufficient circulation of the indoor air in the greenhouse. In this case also, it is essential that the air can move freely through the spaces between the plants from one tier to another. This prevents mildewing of the plants, among other things. When carbon dioxide is furthermore added to the air being circulated, advantageous growing conditions are obtained in all parts of the greenhouse.

According to a preferred embodiment of the method relating to the invention, the greenhouse (10) is heated mainly by the thermal energy generated by the luminaires (31) of the greenhouse.

This means that no separate heating system needs to be arranged for the greenhouse. The only essential question that remains in this case concerns the discharge of possible excess heat from the greenhouse. Since heating is not a problem, the greenhouse can also be aired without concern for expensive thermal energy being wasted. The said airing is of essential importance for the quality of the plants grown. Where heat needs to be removed from the greenhouse, the method is best suited for use in cold areas and at a cold time of year. It is this property that makes the method relating to the invention extremely advantageous, for example, in Finland and the other Nordic countries, as this means that vegetables imported from warmer countries can be replaced by domestic products.

According to a second preferred embodiment of the method relating to the invention - the electrical energy required by the greenhouse luminaires is generated at a power plant which uses, for example, wood chips, other bio-fuel or gas as fuel, and carbon dioxide is recovered from the power plant's flue gases, the said carbon dioxide being further purified and supplied to the indoor air of the greenhouse.

Most preferably there is a power plant in conjunction with the greenhouse, the plant using wood chips or other bio-fuel, the electrical energy produced by plant being used for lighting the greenhouse. Since no other energy is required separately for heating the greenhouse, the thermal energy generated in the power plant's process can be used for some other purpose or sold. The proceeds from the sale of thermal energy may then cover the cost of producing electrical energy either partly or completely. In this way the entity formed by the power plant and the greenhouse is very economical as regards overall operating costs. As electricity is produced at the power plant, which is nearby, this also eliminates the costs that would be incurred by the transfer of electrical energy from elsewhere.

The system is made even more economical by the fact that the carbon dioxide required by the plants can be recovered from the power plant's flue gases economically. Since more carbon dioxide is thus continuously obtained economically, it is not necessary to compromise on sufficient airing in the greenhouse. Although carbon dioxide naturally also escapes from the greenhouse into the outdoor air during airing, new carbon dioxide is obtained from the flue gases produced by the power plant to replace the escaped carbon dioxide.

Since carbon dioxide is produced on a continuous basis, it is easy to increase the carbon dioxide content of the greenhouse to as high a level as is favourable for the growth of the plants, it is, after all, known that in addition to sufficient light, a sufficiently high carbon dioxide content in greenhouse air increases the growth of plants substantially. Maintaining a sufficiently high carbon dioxide content in a greenhouse by means of known solutions is not possible in practice, because purchased from outside, carbon dioxide is very expensive.

It is possible in practice, in the system relating to the invention, to recover and wash carbon dioxide from the flue gases. After this it is stored intermediately in a pressure vessel, from which it is fed into the greenhouse under pressure.

According to a third preferred embodiment of the method relating to the invention the plants are grown in a greenhouse with two or more tiers, so that at the first stage the plant is grown in the lowest tier, after which the plant is transferred to an upper tier, in the lowest tier the plants are relatively close to each other, and at least in one of the upper tiers the spaces between the plants are large enough so that light and air are able to pass through the spaces between plants from one tier to another.

According to a fourth preferred embodiment of the method relating to the invention, the plants (33) are grown in greenhouses with two or more tiers by applying the following stages: the seedlings are first sprouted and grown in peat balls, - the seedlings are sorted and transferred to the first carriages which move forward in the first tier of the greenhouse during the first stage of growing the plants, the plants are thinned out and transferred to other carriages which move forward in one of the upper tiers during the second stage of growing the plants, once the plants have grown for the desired time, the carriages and the plants in them are brought down from the upper tiers of the greenhouse, the plants are harvested, sorted, packed and, if necessary, frozen. Another object of the invention is a greenhouse, which is substantially more efficient and practicable than known greenhouses. It is characteristic of the greenhouse relating to the invention that the greenhouse has two or more tiers in which the plants grown are situated, - that the greenhouse has luminairesluminaireluminaire for supplying artificial light to the plants, mainly from above them, that in at least one tier the plants are situated at a distance from one another so that there are openings between the plants, through which at least some of the light used for lighting the plants in that tier can also light the plants in a lower tier, - that there is equipment in the greenhouse for circulating air so that at least some of the air circulating in the greenhouse passes through the plant tier via the gaps between the plants, that there is equipment in the greenhouse for adding carbon dioxide, which enhances the growth of plants, to the greenhouse air.

According to a preferred embodiment of the greenhouse relating to the invention the greenhouse comprises a power plant for generating electrical energy for the lighting means for the plants, the said power plant preferably using wood chips, other bio-energy or gas for fuel, - and there is equipment in the greenhouse for recovering carbon dioxide from flue gases and equipment for purifying the carbon dioxide and supplying it to the greenhouse.

According to a second preferred embodiment of the greenhouse relating to the invention, there is at least one fan in the greenhouse for directing air in the direction of the ceiling surface towards the centre of the greenhouse, at which there is a vertical shaft and at least one fan in order to effect circulation of the air current.

According to a third preferred embodiment of the greenhouse relating to the invention, at least a part of the roof and/or walls of the greenhouse are thermally insulated.

In such a case the roof construction of the greenhouse may be made of opaque material, such as sheet metal or other suitable roofing material. This is because natural light is not necessarily required in a greenhouse relating to the invention. The light required for the growth of the plants is produced by strong artificial lighting. Since powerful lamps also generate heat, the thermal load caused by lighting alone is sufficient for heating the greenhouse. To maintain the correct temperature balance between the inside and outside of the greenhouse at all times, the roof and walls of the greenhouse can be thermally insulated to match external conditions.

According to a fourth preferred embodiment of the greenhouse relating to the invention, in the first tier of the greenhouse there is at least one preliminary growing line and above the first tier at least one further growing line for the plants, in which the plants are spaced further apart than in the first tier.

According to a fifth preferred embodiment of the greenhouse relating to the invention, - in the plant growing line there are growing units, which are movable on guide rails, the units being, for example, growing carriages in which the plants to be grown are situated, and the movement of the growing unit is such that the passage of the plant through the growing line takes the desired time, which is the period of growth required by the plant or a part of it.

According to a sixth preferred embodiment of the greenhouse relating to the invention, the greenhouse comprises at least one lift for lifting the growing carriage containing the plants to the desired tier and back again, and a conveyor for moving the plants to be grown to the beginning of the growing line, and at least one conveyor for moving the grown products away from the end of the growing line.

According to a seventh preferred embodiment of the greenhouse relating to the invention, the growing line of the greenhouse comprises at least two guide rails, along which the growing carriage moves from the beginning of the growing line to the opposite end of the greenhouse, where the growing carriage moves sideways on another guide rail along which the growing carriage returns back to the beginning of the growing line.

According to an eighth preferred embodiment of the greenhouse relating to the invention, the transfer device for the growing carriages of the greenhouse comprises a cylinder, whose piston produces a thrust motion that moves the conveyor carriage a step at a time along the guide rails. In the growing unit there are growing pots or trays in which the seedlings to be grown are placed.

According to yet another preferred embodiment of the greenhouse relating to the invention, luminaireluminaire the growing line of the greenhouse incorporates luminaires above the plants, the said luminaires being fixed to the underside of transverse beams or on separate 7

suspension rails so that the luminaires will mainly light the plants under the luminaires, and that the light from the luminaires is in addition also directed between the plants, support beams and guide rails onto the plants in the lower tier.

The invention is described in the following by means of examples, with reference to the appended drawings in which

Figure 1 shows a vertical section of a greenhouse relating to the invention as seen from the end. Figure 2 shows a horizontal section of the greenhouse as seen from above. Figure 3 corresponds to Figure 2 and shows a second embodiment. Figure 4 shows a detail of the cross-section of the greenhouse. Figure 5 shows a detail of Figure 4. Figure 6 shows the plant conveyor unit as seen from above. Figure 7 shows the mechanism for moving the plant conveyor unit.

Figure 8 shows diagrammatically the lighting arrangement of the greenhouse. Figure 9 shows a part of a greenhouse relating to another embodiment as seen from the end. Figure 10 shows diagrammatically the general arrangement of the greenhouse shown in Figure 9 as seen from above.

Figure 11 shows diagrammatically the different stages of plant growing.

Figure 12 shows diagrammatically the paths travelled by the plants in the greenhouse shown in Figure 10. Figures 3a and 13b show diagrammatically the paths travelled by the plants in the upper tiers of the greenhouse shown in Figure 10.

Figure 13 shows diagrammatically the paths travelled by the plants in the greenhouse shown in Figure 9. Figure 14 shows diagrammatically the forward movement of the plants in the handling station of the greenhouse. Figure 15 corresponds to Figure 14 and shows diagrammatically the forward movement of the plants at the second stage. Figure 16 shows a cross-section of a detail of the greenhouse shown in Figure 9.

Figure 1 shows the cross-section of an embodiment of the greenhouse relating to the invention. There are several tiers in the greenhouse 10. In the embodiment shown in

Figure 1 , there are five tiers. It is characteristic of the structure of the greenhouse 10 that the tiers have no solid floor surfaces. This means that both air and light can pass freely from one tier to another, between the support structures and the plants grown. Due to the open structure, airing and heating can be arranged, for example, by means of air ducts 11 located at the end or sides of the greenhouse 10. When air ducts 11 are located appropriately, for example, at both ends of the greenhouse 10, the circulation of warm air can be arranged to be as desired at each point of the greenhouse.

In the greenhouse 10 shown in Figure 1 the seedlings to be grown are situated in mobile carriages 12 which travel along the guide rails provided for them. These details are described in more detail below. The lifting of the plants to be grown to the different tiers has been arranged by means of conveyors, which are marked generally with reference numeral 13 in Figure 1. The conveyors or lifting devices may be of a type known as such, which is why they are not described in greater detail in this connection.

Figure 2 shows diagrammatically the general arrangement of an embodiment of the greenhouse relating to the invention, as seen from above. The figure shows that in this greenhouse there are ten plant growing lines 14, in which the plant growing units move back and forth from one end of the greenhouse to the other and back again during growing.

The seedlings to be grown are brought to the end of the growing line 14 by means of a conveyor 13, the structure of which is not shown in greater detail in the figure because it may be of a type known as such. Similarly, once the seedlings have returned to their starting point, the grown products are transferred by means of conveyors for packing and delivery to consumers.

Since in the greenhouse 10 shown in Figure 2 none of the additional facilities required, such as a seedling germination department, plant cooling and packing departments, etc., are shown, these facilities have to be outside the actual greenhouse. They may be in the immediate vicinity of the greenhouse or further away.

Figure 3 shows an alternative greenhouse floor plan, in which seedling handling equipment and other accessories needed in the greenhouse are located in place of the centremost growing lines. In the example shown in Figure 3, the greenhouse 10 includes a peat silo 15, a growing substrate mixing drum 16 and a planting table 17. At this stage, sowing, for example, takes place, after which the substrates are transferred to the germination department 18. By means of the conveyors 13 the substrates are transferred further on to the growing lines 14. In this example, the seedlings move in only one direction on the growing line, which means that the seedlings grown travel only once during their growth period from one end of the greenhouse to the other. Once they have travelled through the growing line 14, the plants are transferred by means of the conveyor 13 to the cleaning table 19, and from there, after washing 20, packing 21 and cooling 22, to cold storage 23. Figure 3 also shows the additional facilities required by the greenhouse, which are the dispatching department 24, the office 25 and the staff facilities 26. The greenhouse 10 also includes a boiler house 27 and a water tank 28 for watering the plants. The water tank can also be used for storing heat and cooling in the greenhouse 10. Figure 3 does not, however, show in more detail, for example, an effluent treatment plant, compostor or equipment for the recovery of biological nitrogen. The boiler house 17 is heated, for example, with wood chips, in which case carbon dioxide can be recovered from the flue gases, the said carbon dioxide being used in the greenhouse for enhancing the growth of the plants.

Figure 4 shows a detail of the structure of the greenhouse 10 in which there are growing lines 14 both adjacent to and on top of one another. This structure corresponds to the embodiment shown in Figures 1 and 2, in which each growing line 14 comprises two adjacent rows of growing carriages. In these rows the growing carriages 12 are mounted on guide rails 29 parallel to the longitudinal direction of the greenhouse. The growing line 14 functions in such a way that in the first row each growing carriage moves from one end of the greenhouse to its opposite end. After this the growing carriage 12 moves sideways to the adjacent guide rails, along which the growing carriage 12 returns to its starting end. The speed of the carriages 12 has been arranged to be such that the reciprocating movement from one end of the greenhouse 10 to the other lasts for the duration of the growth period required by the seedling. The growth period of plants is, for example, about two months.

Figure 4 shows that the lowest growing lines 14 are at floor level in the greenhouse 10, while the upper growing lines are located above them in different tiers on transverse beams 30. On the beams 30 are mounted similar longitudinal guide rails 29 for the growing carriages to those in the growing lines 14 located on the ground. The growing carriages 12a and 12b in the different tiers also move in their guide rails in the longitudinal direction of the greenhouse, reciprocating from one end of the greenhouse to the other.

As there are no solid floor surfaces in the different tiers, air can move freely from one tier to another inside the greenhouse. The air moves due to the open lattice-like structure of the greenhouse, but also because there is free air space in the greenhouse 10, especially 10

at the outermost growing Iine14 of each tier. Figure 4 shows that at these points there is no other growing line above the said growing line 14.

The lighting of the plants is arranged by means of luminaires 31 located at the required distances from one another above all plants. Figure 4 shows that the luminaires 31 located on the underside of the transverse beams 30 or on separate suspension rails 32 at such points where there are no transverse beams 30. The lighting of the plants is arranged in such a way that the luminaires 31 mainly light the plants under the luminaire, but their light is in addition directed between the plants 33, transverse beams 30 and guide rails 29 onto the plants in the lower tiers. The lighting principle is shown in greater detail in Figure 8.

Figure 5 shows a detail of the structure of the greenhouse, in which can be seen the guide rails 29 located on the transverse beam 30 and the plant growing carriages 12 on the said rails. The guide rails 29 run in the longitudinal direction of the greenhouse and the plant growing carriages 12 move on them between the ends of the greenhouse. The seedlings

33 in the growing carriages 12 are placed in special substrates, which are shown in greater detail in Figure 6.

Figure 6 shows a diagrammatic view of the plant growing unit as seen from above, the said unit in this example being a growing carriage 12 moving on guide rails 29. The figure shows that in the growing carriage 12, the plants 33 placed in pots are in growing trays 34, the length of which is equal to the width of the growing carriage 12. The growing carriage 12 comprises six growing trays 34, in each of which there are about 50 to 60 plants 33. In a growing tray 34 the plants 33 are situated at a distance from each other so that there will remain gaps between them. In the spaces between the growing trays 34 there are also air gaps 64, which means that the plants 33 have room to grow on all sides. The air gaps 64 enable air to circulate between the plants. At the same time the light coming from above the plants 33 is also able to pass through the spaces between the plants 33 and the trays

34 as scattered light to the plants below. One end of the growing tray 34 is located somewhat lower than its opposite end, which means that the water for watering the plants can be made to flow through the growing tray 34.

Figure 7 shows diagrammatically the transfer device 35 of the growing carriage 12. The transfer device comprises a hydraulic cylinder 36, whose piston 37 produces a thrust motion that moves the conveyor carriage 12 a step at a time on the guide rails 29 to the next growing site. The transfer movement takes place at sufficiently long intervals that the carriage 12 advances from one end of the growing line to the other during the seedling's 11

growth period. If the length of the greenhouse 10 is, for example, about 200 m, and during the 60-day growth period the total movement of the growing carriage from one end of the greenhouse to the other covers about 400 m, the growing carriage must proceed approximately 7 m in 24 hours. In other words, the thrust motion of the piston 37 of the hydraulic cylinder 36 moves the conveyor carriage 12 forward on average seven times in 24 hours.

Thus, by means of the equipment described, for example, six crops can be produced in the greenhouse 10 per year. Since in the northern conditions in Finland several crops are not yielded per year in natural conditions, the increase in efficiency is considerable. By means of the greenhouse described, therefore, flowers or vegetables can be produced almost all year round, which means that it is possible to replace considerable quantities of imports by domestic production. The only time of year when it is not advantageous to use the greenhouse relating to the invention is at the height of summer, because it is then so warm outdoors that cooling the greenhouse may be the problem. The greenhouse relating to the invention is in fact best suited for cold conditions and the cold time of year. Preferred plants for growing in the greenhouse include flowers and vegetables such as broccoli, leek, cauliflower and lettuce.

Figure 8 shows diagrammatically the lighting of the plants 33 by means of the luminaires 31. In the greenhouse 10, the luminaires 31 are fixed to the underside of the transverse beams 30 or on the suspension rail 32. The spaces between the luminaires 31 are so small that each growing carriage is sufficiently lit and all the plants grown receive light. Another essential feature of the structure is, however, that the transverse beams inside the greenhouse 10 and the trays and guide rails of the growing carriages 12 form a lattice that is open enough to allow the scattered light from the luminaires 31 to pass through the air gaps 64 between the growing pots 34 or growing trays of the plants 33 to the plants that are underneath the growing carriage 12. In this way the light emitted by the luminaires 31 can be utilised to the full, in a corresponding manner, also the air used for heating the greenhouse can move freely both horizontally and vertically between all the structures of the greenhouse and the growing pots 34 of the plants 33.

Figure 9 shows a part of one end of the greenhouse 10 according to one embodiment. The figure does not show that part of the greenhouse which is on the other side of the ridge, which is symmetrically identical with the half shown. In this embodiment the air-conditioning of the greenhouse 10 is arranged so that in the centre of the greenhouse 10 there is a vertical shaft 40 extending through the entire greenhouse in its longitudinal direction and 12

from the bottom to the top, the said shaft incorporating fans 41 blowing downwards. By means of these, the air in the greenhouse 10 is brought into motion so that it moves downwards in the shaft and from there on to the sides, towards the side walls 42 of the greenhouse 10 as shown by the arrows.

In the vicinity of the point of contact between the side walls 42 and roof 43 of the greenhouse there are other fans 44, by means of which the air is made to circulate further towards the ridge 45 of the roof of the greenhouse 10, as shown by the arrows. The fans 41 and 44 are adjustable and extremely efficient, which means that a strong air current is effected by means of the fans 44 in the direction of the surface of the ceiling 43 of the greenhouse 10. Due to the effect of the air current, no condensation water is able to form on the cold surface of the ceiling 43. The speed of this air current may be as high as 2-3- fold compared with the speed of air circulation elsewhere in the greenhouse. The fans 44 and this detail of the air conditioning of the greenhouse 10 are described in greater detail in Figure 16.

Outdoor air is supplied to the greenhouse 10 through adjustable valves 46 located in connection with the side wall 42, and exhaust air is taken out through adjustable roof valves 47 located in the vicinity of the ridge of the roof 45. By means of the fans 44, the cold air coming from the valve 46 is taken towards the ridge of the roof. This means that it is not directed directly at the plants, but will be mixed with the indoor air of the greenhouse.

Air and light can also move freely in the greenhouse 10 in the vertical direction, since the beams 30 supporting the carriages 12 are lattices and there are no solid floor surfaces in the greenhouse 10. The plants in the carriages 12 are also positioned so that there are suitable gaps between them. Ducts for adding carbon dioxide are not shown in Figure 9.

Figure 10 shows diagrammatically the general arrangement of the first tier of the greenhouse shown in Figure 9, as seen from above. At the top of Figure 10 can be seen the power plant 27 and the wood chip stock 48. The peat required by the planting machines 17 is taken from the peat stock 15. After planting, the peat balls move forward to the germination department 18 and the seedling growing department 49. After that the seedlings are transferred to the handling department 50, from which the seedlings are moved into the trays in the carriages for growing. The handling department further comprises a lift 53, carriage transfer equipment, carriage emptying and cleaning equipment, a sorting department 54, packing department 21 , freezing department 22, cold- 13

storage room 23 and staff facilities 26. These details are shown in greater detail in the figures that follow.

According to the invention, wood chips, other bio-fuel or, for example, natural gas is burned at the power plant to produce the electrical energy required by the lamps. Thermal energy and combustion gases are produced at the same time.

The electrical energy obtained from the power plant is supplied mainly in its entirety to the lamps in order to achieve as efficient lighting as possible. It is in fact essential to the method relating to the invention to produce efficient artificial light. Since the plants are in several tiers, natural light is of minor significance between tiers. In addition, the colour of artificial light can be made as favourable as possible for the growth of plants. This means that it is advantageous to reduce the amount of yellow light and increase blue and red light.

In efficient artificial lighting the lamps produce so much heat at the same time that it suffices to heat the entire greenhouse, since in a greenhouse with several tiers, the surface area of the exterior walls is substantially smaller with respect to the plant growing area than in known greenhouses. This gives rise to a situation where the cooling of the greenhouse may be more important than its heating. This type of greenhouse is, therefore, most advantageous in the cold Nordic countries, such as Finland, and even there only at the cold time of year. In summertime a greenhouse relating to the invention may be kept out of use because sunlight would heat it too much.

The thermal energy generated by the power plant can be sold off. Carbon dioxide is preferably recovered from the combustion gas of the power plant and cleaned, and then fed into the greenhouse. By adding carbon dioxide, the plants can be made to grow substantially faster than without carbon dioxide. Thus in the greenhouse relating to the invention, all the most important growth factors such as light, heat, and carbon dioxide content are in an extremely advantageous equilibrium. The airing and air conditioning of the greenhouse are also advantageous when applying the recirculated air system described above.

Figure 11 shows diagrammatically the different stages of growing seedlings and plants. First the seeds are planted in a peat ball 51 , where sprouting takes place. The sprouted seed is then transferred to the seedling growing department 49. Once the seedling 33 has grown to sufficient size, the peat ball 51 is transferred to a pot 34a or a growing tray. The pot 34a is placed in a carriage in the first tier of the greenhouse 10 where the first plant 14

growing stage takes place. At this stage the plants 52a are relatively close to each other without any large spaces in between, because no light needs to pass between the plants to the space below them.

When the first growing stage in the first tier has been completed, the plants are thinned out and transferred to the trays 34b of the carriages on the upper tiers. Once the plant 52b has grown to its final size in the tray 34b, it is harvested.

Figure 12 shows diagrammatically the paths along which the plants travel in the first tier in the greenhouse 10. The seedling is brought in a peat ball, via the germination department 18 and the seedling growing department 49, to the handling department 50, where it is transferred to a carriage 12a in the first tier. After this each plant to be grown moves forward in the first tier along a path back and forth from one end of the greenhouse 10 to the other. When the plant has, after this, returned to the handling station 50, the plant has gone through the first growing stage. After preliminary growing, the plants are thinned out and transferred to other carriages, after which the plants are raised by means of a lift to one of the upper tiers of the greenhouse 10.

Figures 13a and 13b show diagrammatically the paths travelled by the plants in the upper tiers of the greenhouse shown in Figure 10, to which the plants have been transferred after preliminary growing in the first tier. Figure 13a shows how the lift 53 is used to move the carriages 12b of upper tiers to different tiers 55a and 55b, in which conveyors move the carriages 12b sideways onto the correct path. After this the carriages 12b move forward on their own paths in the tiers determined for them, back and forth from one end of the greenhouse 10 to the other, as shown in Figure 13b. Once the whole round has been completed, the plants have been growing for the period specified for them and they are removed from the greenhouse. Figure 13a shows how the carriages 12b are moved sideways in their tier back to the lift 53, by means of which they are brought back down to the first tier and from there on to the handling station 50.

Figure 14 shows the paths of the carriages 12a of the first tier at the handling station 50 of the greenhouse 10. The seedlings arriving in peat balls are transferred to the carriages of the first tier at the loading station 56. After that the carriage 12a moves sideways to the starting station 57 of the first tier, from which it departs on its round, back and forth from one end of the greenhouse to the other, and returns to the return station 58 of the first tier. At this point, the first stage of the growing of the plants has been completed. After this the pre-grown plants are transferred from the carriage of the tier at the return station 58 in the 15

first tier to the carriages of the upper tiers at the transfer station 59. Since the plants are at the same time thinned out, the transfer of the plants is carried out in such a way that the plants in one first-tier carriage are divided into four upper-tier carriages. The four upper-tier carriages required are brought in turn to the transfer station 59 for this purpose. Once the transfer has been carried out, the emptied carriage moves to the washing and disinfection station 60, after which it is ready to be filled again at the loading station 56.

Figure 15 shows the forward movement of the plants at the second stage of growing. The carriages 12b of the upper tiers are transferred in turn to the transfer station 59, at which the pre-grown plants are transferred to them from the first-tier carriages. The carriages 12b of the upper tiers are packed sparsely, so that there are clear spaces or gaps between the plants. After this, these carriages 12b are moved into the lift, by means of which they are lifted to the tiers specified for them. When the carriages 12b return with the lift 53 from the upper tiers to the first tier, they move to the harvesting station 61 , at which the plants are removed from the carriages. After this the carriages are emptied and transferred to the washing and disinfection station 60. The washed carriages are ready to be moved again to the transfer station for reloading.

It is clear from Figures 14 and 15 that the carriages of the first tier have their own cycle while similarly the carriages of the upper tier have their own. This is natural, because the carriages are different, since the plants in a first-tier carriage are four times more densely packed than those in the upper-tier carriages.

Figure 16 shows a cross-sectional view of the side wall 42 of the greenhouse and of the growing carriage 12 in its vicinity. The figure shows that there are fans 44 at the point of contact between the side wails 42 and the roof 43, by means of which fans a strong air current can be directed towards the surface of the ceiling 43. The valves 46 can be used to regulate whether there will be internal air circulation in the greenhouse 10 or whether at least some of the air blown by the fans 44 will be taken from outside the greenhouse as replacement air.

Since it is usually colder outdoors than in the greenhouse 10, the surface of the ceiling 43 is also cold or at least cool. Thus the speed of the air current is adjusted as required so that condensation water will in no circumstances form on the surface of the ceiling 43, which water might drop on the plants being grown. This means that the air passing in the vicinity of the surface of the ceiling 43 will also cool down - a property which can be utilised to cool the indoor air of the greenhouse if necessary. 16

The luminaires 31 light the plants in the growing carriage 12, which plants may be closer to one another in the lowest tier than in the higher tiers. Figure 16 shows that the growing carriage 12 is supported at both ends on vertical pillars 62 which are of a double construction, so that there will remain room for a servicing passage 63 in connection with the vertical pillar.

It is obvious to a person skilled in the art that the different embodiments of the invention may vary within the scope of the claims presented below.

Claims

17CLAIMS

1. A method for growing plants, such as, for example, flowers, broccoli, leek, cauliflower or lettuce, characterised in - that the plants (33) are grown in two or more tiers so that favourable lighting, heating and air composition conditions are arranged for the plants in the following manner: artificial light is supplied to the plants mainly from above them, at least in one tier light is supplied through the spaces (64) between the plants so that at least some of the light used for the lighting of the plants can also light the plants in a lower tier, a substantial proportion of the heat required for heating the greenhouse is obtained from the lights (31), the greenhouse air is circulated so that at least some of the air passes through the tier of plants via the openings left between the plants, - and carbon dioxide, which enhances the growth of plants, is added to the air in the greenhouse.

2. A growing method as claimed in claim 1, characterised in that the greenhouse (10) is heated mainly by the thermal energy generated by the luminaires (31) of the greenhouse.

3. A growing method as claimed in claim 1, characterised in that the electrical energy required by the greenhouse (10) luminaires (31) is generated at a power plant (27) which uses, for example, wood chips, other bio-fuel or gas as fuel, - and carbon dioxide is recovered from the power plant's flue gases, the said carbon dioxide being further purified and supplied to the indoor air of the greenhouse.

4. A growing method as claimed in claim 1, characterised in that the plants (33) are grown in a greenhouse (10) with two or more tiers, so that at the first stage the plant is grown in the lowest tier, after which the plant is transferred to an upper tier, in the lowest tier the plants are relatively close to each other, and at least in one of the upper tiers the spaces between the plants are large enough so that light and air are able to pass through the spaces (64) between plants from one tier to another. 18

5. A growing method as claimed in claim 1, characterised in that the plants (33) are grown in greenhouses with two or more tiers by applying the following stages: the seedlings are first sprouted and grown in peat balls (51), the seedlings are sorted and transferred to the first carriages (12a) which move forward in the first tier of the greenhouse during the first stage of growing the plants

(33), the plants are thinned out and transferred to other carriages (12b) which move forward in one of the upper tiers during the second stage of growing the plants, once the plants have grown for the desired time, the carriages and the plants in them are brought down from the upper tiers of the greenhouse, the plants are harvested, sorted, packed and, if necessary, frozen.

6. A greenhouse for growing plants, such as, for example, flowers, broccoli, leek, cauliflower or lettuce, characterised in that - the greenhouse (10) has two or more tiers in which the plants (33) grown are situated, that the greenhouse has lighting means (31) for supplying artificial light to the plants, mainly from above them, that in at least one tier the plants are situated at a distance from one another so that there are openings (64) between the plants, through which at least some of the light used for lighting the plants in that tier can also light the plants in a lower tier, that there is equipment (41 , 44) in the greenhouse for circulating air so that at least some of the air circulating in the greenhouse passes through the plant tier via the gaps between the plants, that there is equipment in the greenhouse for adding carbon dioxide, which enhances the growth of plants, to the greenhouse air.

7. A greenhouse as claimed in claim 6, characterised in that the greenhouse comprises a power plant (27) for generating electrical energy for the lighting means (31) for the plants, the said power plant preferably using wood chips, other bio-energy or gas for fuel, and that there is equipment in the greenhouse for recovering carbon dioxide from flue gases and equipment for purifying the carbon dioxide and supplying it to the greenhouse.

8. A greenhouse as claimed in claim 6 or 7, characterised in that there is at least one fan (44) in the greenhouse (10) for directing air in the direction of the ceiling surface 19

towards the centre of the greenhouse, at which there is a vertical shaft (40) and at least one fan (41) in order to effect circulation of the air current.

9. A greenhouse as claimed in claim 6, 7 or 8, characterised in that at least a part of the roof and/or walls of the greenhouse (10) are thermally insulated.

10. A greenhouse as claimed in any of the claims 6 to 9, characterised in that in the first tier of the greenhouse (10) there is at least one preliminary growing line and above the first tier at least one further growing line for the plants, in which the plants are spaced further apart than in the first tier.

11. A greenhouse as claimed in any of the claims 6 to 10, characterised in that in the plant (33) growing line there are growing units, which are movable on guide rails, the units being, for example, growing carriages (12) in which the plants (33) to be grown are situated, and that the movement of the growing unit is such that the passage of the plant through the growing line takes the desired time, which is the period of growth required by the plant or a part of it.

12. A greenhouse as claimed in any of the claims 6 to 11, characterised in that the greenhouse comprises at least one lift for lifting the growing carriage (12b) containing the plants to the desired tier and back again, and a conveyor for moving the plants to be grown to the beginning of the growing line (14), and at least one conveyor for moving the grown products away from the end of the growing line.

13. A greenhouse as claimed in any of the claims 6 to 12, characterised in that the growing line (14) of the greenhouse (10) comprises at least two guide rails (29), along which the growing carriage (12) moves from the beginning of the growing line to the opposite end of the greenhouse, where the growing carriage moves sideways on another guide rail along which the growing carriage returns back to the beginning of the growing line.

14. A greenhouse as claimed in any of the claims 6 to 13, characterised in that the transfer device for the growing carriages (12) of the greenhouse (10) comprises a cylinder (36), whose piston (37) produces a thrust motion that moves the conveyor carriage a step at a time along the guide rails. 20

15. A greenhouse as claimed in any of the claims 6 to 14, characterised in that the growing line (14) of the greenhouse (10) incorporates luminaires (31) above the plants (33), the said luminaires being fixed to the underside of transverse beams or on separate suspension rails (32) so that the luminaires will mainly light the plants under the luminaires, and that the light from the luminaires is in addition also directed between the plants, support beams and guide rails onto the plants in the lower tier.