WO2005104819A1

WO2005104819A1 - Greenhouse having a daylight system

Info

Publication number: WO2005104819A1
Application number: PCT/NL2005/000316
Authority: WO
Inventors: Johannes Van Tilborgh
Original assignee: Johannes Van Tilborgh
Priority date: 2004-04-29
Filing date: 2005-04-27
Publication date: 2005-11-10
Also published as: NL1026082C2

Abstract

The invention relates to a greenhouse comprising a sunlight-transmitting roof (3), concentrating means at the roof for concentrating sunlight incident on the roof, capturing means (7, 24) for capturing the concentrated sunlight and collecting/converting means (12) for collecting/converting the energy from the concentrated sunlight. The concentrating means are incorporated in the roof of the greenhouse and are arranged for transmitting diffuse light as well as direct sunlight into the greenhouse. Said concentrating means consist of, for example, lenses (5) or reflective lamellae (23). The capturing/collecting means are disposed inside the greenhouse. In this way a positive effect is achieved both as regards the plant growth and as regards the collection of energy, in particular in areas where there is less sunshine and thus less direct sunlight.

Description

Greenhouse having a daylight system

The invention relates to a greenhouse comprising a sunlight-transmitting roof, concentrating means on the roof for concentrating sunlight incident on the roof, capturing means for capturing the concentrated sunlight and collecting/converting means for collecting/converting the energy from the concentrated sunlight. Such a greenhouse is known, for example from WO 99/53745. The roof of said greenhouse is made up of a large number of reflective strips, which jointly concentrate the incident sunrays onto capturing means disposed above the greenhouse. The strips are rotatable, in their horizontal position they form a light-tight seal of the interior of the greenhouse together with the opaque walls of the greenhouse. The admission of light and heat into the greenhouse can be controlled by changing the position of the strips, and solar heat can be captured for generating energy. Such a greenhouse is mainly intended for use in warm countries where there is a lot of sunshine and consequently an excess of direct sunlight and heat . The object of the invention is to provide a greenhouse of the kind referred to in the introduction, which provides good results also in areas where there is less sunshine . In order to accomplish that object, the greenhouse according to the invention is clearly characterized in that the concentrating means are incorporated in the roof of the greenhouse, being arranged for transmitting diffuse light as well as direct sunlight into the greenhouse, in which the capturing/collecting means are disposed. The features according to the invention render the greenhouse suitable for use also in areas in which the sun shines less frequently and in which the diffuse light is needed in order to obtain a satisfactory plant growth. According to the invention, said diffuse light is transmitted at least to a large extent. It is advantageous in that connection if on the one hand the roof can be closed and on the other hand is nevertheless capable of transmitting light, because light can be admitted in that case and heat (winter) and C0₂ (summer) can be kept inside. The capturing/collecting means are disposed inside the greenhouse, so that they are installed at a sheltered location. On the other hand it is preferable in that case to use the smallest possible dimensions for the capturing means so as to minimise the shade effect . According to the invention, the concentrating means may be provided with lens elements in glass panels that form part of the roof, whilst it is also possible for the concentrating means to be provided with reflective lamellae, which are mounted between glass panels that form part of the roof. In the first case, the glass panels themselves form the concentrating means. Said glass panels may be configured as Fresnel lenses, for example. Also other lens types are possible, in combination with which larger or smaller panels can be used. In principle each lens has its own capturing means, but many variations are possible -within this framework. In the case of reflective lamellae, it will be preferable to use lamellae that maximally reflect on both sides, because this enables a maximum amount of light to enter the greenhouse. It would also possible to treat the glass panels with an anti-reflection coating on one side or on both sides of the lamellae (preferably at the upper side) so as to maximise the transmission of light. Preferably, the concentrating means and/or the capturing means can be adjusted so as to be oriented to the position of the sun. This enables an optimum concentration of sunlight . The glass panels may be provided with fixed lens elements, and the capturing means are capable of translating and/or rotating movement, whilst in the alternative embodiment the reflective lamellae may be rotatable about at least one axis, preferably being coupled for joint adjustment. In the latter case the capturing means may be stationary, especially if the concentrating means are arranged for concentrating the sunlight in one direction. A line concentration takes place in that case, with the azimuth of the sun not having any influence on the concentration/ focusing of the sunlight, so that no adjustment is needed for this. Preferably, the capturing means are provided with a holder comprising an entry lens for orienting the converging sunrays at least substantially parallel to each other and a preferably switchable or controllable mirror for deflecting the at least substantially parallel sunrays in the direction of the collecting/converting means. In this way the sunlight is led to collecting/ converting means in a desired manner, whilst the switchable or controllable mirror can be utilised for selectively admitting the concentrated sunlight into the greenhouse, for example when the sun's altitude low on a wintry day and all the heat from the sun is needed for heating the greenhouse. Using such a switchable or controllable mirror, it is also possible to light the plants in a pulsating manner, thus achieving a satisfactory growth on the one hand whilst using part of the sunlight for generating energy on the other hand. When sunlight is transmitted, the rays are preferably diverged again via a lens so as to spread the transmitted light over a larger area in the greenhouse. It is also possible, of course, to exchange the locations of the exit lens and the collecting/converting means, so that the collecting/converting means are lighted when the mirror transmits the sunlight. The invention will be explained in more detail hereinafter with reference to the drawings, which schematically show embodiments of the greenhouse according to the invention. Fig. 1 is a perspective view of a part of a first embodiment of a greenhouse according to the invention. Fig. 2 is a schematic side view of the greenhouse that is shown in Fig. 1, with sunrays being sketched in to illustrate the operation of the greenhouse. Fig. 3 is a larger-scale view of the detail III in Fig. 1, showing means for capturing concentrated sunlight. Fig. 4 is a larger-scale perspective view of the capturing means of Fig. 3. Fig. 5 is a smaller-scale sectional view of the capturing means of Fig . 4. Fig. 6 is a perspective view corresponding to Fig. 1 of a second embodiment of the greenhouse according to the invention. Fig. 7 is a side view corresponding to Fig. 2 of the second embodiment of the greenhouse according to Fig. 6. Fig. 8 is a larger-scale view of a roof panel as shown in Fig. 5, which comprises adjustable lamellae. Fig. 9 is a larger-scale, cutaway perspective view of the capturing means of Figs. 6 and 7. Fig. 10 shows a further variant of the capturing means according to the invention. The drawings, and in the first place Figs. 1 and 2, show a first embodiment of a greenhouse for cultivating crops such as vegetables, fruit, cut flowers and the like therein.

The figures show four uprights 1, cross bracings 2 and a roof 3 of the greenhouse. The figures do not show the side walls of the greenhouse, which preferably consist of transparent glass for the larger part so as to obtain a high degree of light transmission. In this case the roof 3 consists of a cover comprising a number of ridges 4, one side of which is formed by lens panels 5, whilst the other side is formed by ordinary glass panels 6. In the illustrated embodiment, the lens panels 5 form the longer side of the triangular ridge 4, but it is also conceivable to use an isosceles ridge form. Preferably, the lens panels 5 will have maximum dimensions for capturing sunlight. Capturing means 7 for capturing sunrays concentrated by the associated lens panels 5 are disposed approximately the level of the base of the ridges 4 of the roof 3. Said capturing means, which will be explained in more detail yet, are adjustably mounted on a rail 8. The lens panels 5 form convex lenses, which converge the parallel sunrays S incident on the lens panels 5 being into the capturing means 7. The lens panels 5 are arranged for concentrating the sunrays two-dimensionally, i.e. in two directions, so that the sunrays are deflected towards one point . The focus of the converging sunrays S will generally be located slightly above the capturing means 7. The lens panels 5 may be configured as Fresnel lenses provided with a number of facets so as to minimise the convexity of the lens. In the illustrated embodiment, the lens panels 5 are fixedly mounted, forming a closed glass cover. In order to be able to concentrate the sunrays S into the capturing means 7 at different positions of the sun (both as regards the altitude and as regards the azimuth) , the capturing means 7 are adjustably mounted in this embodiment, being capable of translating movement in two directions and of rotating movement in two directions, as is indicated by arrows in Fig. 1. As Fig. 3 shows, the capturing means are capable of rotating movement about an axis 9, of tilting movement by means of a curved rail 10 and of translating movement along rails 11. The rail 8 (Fig. 1) provides the fourth degree of freedom. In this way the capturing means 7 can orient themselves to the position of the sun and thus be positioned under the focus of the associated lens panels 5 at all times. Automatic adjustment can be effected by means of sensors. Means that are known per se can be used for this purpose. As will be explained in more detail yet, the capturing means are arranged for selectively capturing or entirely or partially transmitting the incident sunrays S, which is illustrated in the dotted lines in Fig. 2. In that case the sunlight can be utilised for the plant growth rather than for generating energy. Figs. 4 and 5 show the capturing means 7, which are combined with collecting/converting means 12, by which the collected solar energy is collected and stored and/or converted into another form of energy, e.g. electric energy. The capturing means 7 comprise a holder 13, which may be cylindrical in shape and which is closed at the entry side by an entry lens 14 on the entry side and by an exit lens 15 on the exit side. The concave entry lens 14 deflects the converging or already diverging sunrays into parallel rays S (see Fig. 5) , whilst the convex exit lens 15 causes the sunlight that may have been transmitted to diverge again so as to spread the sunlight over the interior of the greenhouse. A mirror 16 is mounted in the holder 13, which mirror deflects the parallel sunrays S towards the collecting/converting means 12. Said mirror 16 may be fully reflective or semi-translucent , in which case it may be possible to control the degree of translucency. The mirror 16 may furthermore be mounted in such a manner that it can be swung aside or consist of mirror elements that can be swung aside in the form of lamellae for selectively reflecting or transmitting incident sunrays S. In this embodiment the collecting/converting means 12 comprise a combined module with PN solar cells for converting the incident solar energy into electric energy. A heat exchanger 18 is disposed behind the solar cells 17, which heat exchanger gives off the remaining solar heat to a fluid that can be discharged for storing the heat . Insulated hoses 19 are to that end connected to the heat exchanger 18, which hoses are connected to a heat storage container, an aquifer (underground water-bearing stratum of sand) or the like . All kinds of other embodiments may be used instead of the capturing means 7 and the collecting/converting means 12 that are shown in the figures. Thus it is also possible to capture the light into one or more glass fibres or other types of light conductors for guiding the light to central collecting/converting means. Also other variants are conceivable . Figs. 6 and 7 show a second embodiment of the greenhouse according to the invention. In this embodiment, the lens panels 5 have been exchanged for reflector panels 20, in which embodiment a large number of lamellae 23 being reflective on both sides are arranged between an upper glass panel 21 and a lower glass panel 22, which lamellae are oriented in such a manner that they concentrate the incident sunrays into a line (in this case) . As a result of this one- dimensional line concentration of the sunrays S, the azimuth of the sun does not have any effect on the focusing or concentrating of the sunrays, so that a smaller number of degrees of freedom for adjusting the concentrating and/or capturing means can be used than in the case of three- dimensional concentration. In that case the capturing means 24 must be arranged for capturing the sunrays S that are concentrated in a line. Fig. 8 shows the reflective lamellae 23, which are interconnected by an adjusting mechanism 25, by means of which the lamellae 23 can each be rotated about an associated axis 26 so as to continue to concentrate the sunrays S into the capturing means 24, irrespective of the sun's altitude. Fig. 8 shows that when a single lamellae package is used, changes in the angle of incidence of the sunrays (δα) will result in a required rotation of the lamellae 23 (δβ) through an angle -%δ . If other arrangements of lamellae or multiple lamellae, whether or not interconnected, are selected, other relations will apply. Fig. 9 is a cutaway view of the capturing means 24. Said capturing means may also be mounted under the gutter, where they cause the least amount of additional shade, instead of at the location that is shown in Figs. 6 and 7. Said capturing means 24 comprise the holder 13, in this case an elongated holder, which again comprises a convex entry lens 14 and a concave exit lens 15. In this case several reflective lamellae 27, which are rotatable about their longitudinal axis, may be mounted in the holder 13 as deflecting elements instead of a single mirror. Said lamellae 27 make it possible to deflect the sunrays to the collecting/converting means (not shown) , whilst the sunrays can also be transmitted into the interior of the greenhouse. Fig. 10 shows a further variant of the capturing means 7. In this variant the entry lens 14, a single curved mirror 28 has replaced the exit lens 15 and the mirror 16. By means of this curved mirror 28 the diverging sunrays S of the concentrated beam of sunrays are reflected as parallel rays in the direction of the collecting/converting means 12 as a result of the curvature of the mirror 28. Said mirror 28 may in turn be controlled to transmit sunrays S entirely or partially. From the foregoing it will be apparent that the invention provides a greenhouse that is remarkable for its advantageous and efficient utilization of both the direct and the indirect sunlight for the growth of the crop to be cultivated as well as for the generation of energy. The invention is not limited to the embodiments as shown in the drawing and described above, which can be varied in many ways within the scope of the invention. Thus it is conceivable, for example, to design the lens or reflector panels on the roof of the greenhouse so that their position can be adjusted in order to orient said panels to the position of the sun in their entirety. Furthermore, the orientation of the greenhouse as a whole may be adjustable (for example in the case of a floating greenhouse) , so as to enable the greenhouse to adapt itself to the azimuth of the sun. The panels of the roof of the greenhouse may also be made of plastic material rather than of glass. The lenses of the concentrating means may be pressed, cast or even ground, for example. Furthermore it is conceivable to arrange two groups of lamellae in series one behind another in the embodiment comprising the lamellae, so as to obtain a maximum amount of concentrated direct sunlight under all circumstances. The amount of transmitted and thus non-concentrated direct sunlight is minimised in that case. To achieve a maximum yield of the PN solar cells in the collecting/converting means, it may be considered to use sunlight frequency converters. Frequency converters might also be useful for the transmitted light, because plants are sensitive to blue and red light.

Claims

CLAIMS l.A greenhouse comprising a sunlight-transmitting roof, concentrating means at the roof for concentrating sunlight incident on the roof, capturing means for capturing the concentrated sunlight and collecting/converting means for collecting/converting the energy from the concentrated sunlight, characterized in that the concentrating means are incorporated in the roof of the greenhouse and are arranged for transmitting diffuse light as well as direct sunlight into the greenhouse, in which the capturing/collecting means are disposed.

2. A greenhouse according to claim 1, wherein the concentrating means are provided with lens elements in glass panels that form part of the roof.

3. A greenhouse according to claim 1, wherein the concentrating means are provided with reflective lamellae, which are mounted between glass panels that form part of the roof.

4. A greenhouse according to any one of the preceding claims, wherein the concentrating means and/or the capturing means can be adjusted so as to be oriented to the position of the sun.

5. A greenhouse according to claim 2 and 4, wherein the glass panels are provided with fixed lens elements, and the capturing means are capable of translating and/or rotating movement.

6. A greenhouse according to claim 3 and 4, wherein the reflective lamellae are rotatable about at least one axis, preferably being coupled for joint adjustment.

7. A greenhouse according to any one of the preceding claims, wherein the concentrating means are arranged for concentrating the sunlight in two directions.

8. A greenhouse according to any one of the claims 1-6, wherein the concentrating means are arranged for concentrating the sunlight in one direction.

9. A greenhouse according to any one of the preceding claims, wherein the capturing means are disposed at a location just below the roof of the greenhouse.

10. A greenhouse according to any one of the preceding claims, wherein the capturing means are provided with a holder comprising an entry lens for orienting the converging sunrays at least substantially parallel to each other and a preferably switchable or controllable mirror for deflecting the at least substantially parallel sunrays in the direction of the capturing/converting means.

11. A greenhouse according to any one of the preceding claims, wherein the collecting/converting means are provided with PV cells as well as with a heat exchanger that is arranged in series therewith.

12. A greenhouse according to any one of the preceding claims, wherein the side walls of the greenhouse are light transmitting.