FR2546337A1 - Device for orienting solar panels - Google Patents

Abstract

The device is intended to control the orientation of solar panels arranged in rows. It comprises a set of at least two transmission rods 11, 12 each situated on one side of the row and each connected to each panel driven by at least two traction cables 13, 14. The middle panel can constitute a driving panel. The device makes it possible to orient the panels in azimuth in order to keep them facing the sun.

Description

Orientation device for solar panels
The present invention relates to a device for orienting solar panels arranged in rows and distributed so as to minimize the shadows cast by each panel on the others, while maintaining a satisfactory coefficient of occupation of the ground, which leads generally (at least on flat ground) to distribute the panels according to a centered hexagonal network.

 Solar panels using solar cells and an optic for concentrating solar radiation must be fitted with an orientation device controlled so that the solar radiation transmitted by optics remains directed at the solar cells despite daily and seasonal variations in the position of the sun.

 The orientation devices currently used can be divided into two groups. In the devices of the first group, each panel is provided with its own complete orientation system. The cost of such a device is obviously such that it is justified only for a very large surface panel. The devices of the second group include a single orientation system controlling several panels by a mechanical linkage.

Existing devices of this type with connecting rods are heavy and complex and excessively limit the range of angular displacement of the panels.

 The present invention aims in particular to provide a device of the second group using simple mechanical means, light, reliable and of moderate cost.

It finds a particularly important application in the case of panels with a low level of concentration, for example by Fresnel lenses with linear focus,
Such panels in fact only have to be oriented around a single axis, insofar as the concentration factor remains sufficiently low.

 The invention provides in particular an orientation device, around parallel axes, of solar panels arranged in rows device comprising an angular displacement mechanism driving and a set of at least two transmission rods each located on one side of the row and each connected to each driven panel via two traction cables.

 In an advantageous embodiment of the invention, each panel is fixed to a rotary frame around an axis and provided with at least three cable winding guides delimiting an inscribed area crossed by the axis.

At mid latitudes (40 a450 in particular), a vertical axis of rotation will generally be used, which will in practice allow the solar flux to be captured at less than 300 from normal, except under incidences where other problems, such as the shadows cast by the panels one on the other and / or the attenuation by the atmosphere, play a preponderant role. This arrangement allows the use of refractive optics and avoids the use of mirrors.

 The chassis will generally have a rectangular plan shape and the guides will then be placed in the corners and may have a drum shape. The connecting rods can be held by plates (or fingers) perpendicular to the axis and fixed to the chassis.

 To compensate for thermal expansion and keep the cables in tension, the latter will generally be provided with elastic means, typically springs. If these springs work in compression, they can be provided to come into contiguous turns when the forces to be transmitted reach a determined value. These springs can in particular be interposed between each cable and the corresponding connecting rod.

 It can be seen that the connecting rods are only subjected to tensile forces. They can therefore be light.

We can easily give the panels a rotational amplitude exceeding 1800. The orientation forces being applied to the panels at points distant from the axis of rotation, we obtain significant torques to maintain a determined orientation without it being necessary to weigh down the device with large diameter pulleys. The thermal expansion of the connecting rods does not introduce orientation errors, due to the presence and mounting of the springs and the symmetry of the forces exerted with respect to the axis of rotation of the panels.
These advantages, and in particular the lightness of the device, are only possible provided that the panels having a moderate unit surface are adopted in order to limit the aerodynamic torques which they undergo.

 The frame with which each panel is provided is advantageously constituted by a lattice of profiles, each of which has the section adapted to the forces to be transmitted. The frame carries the panel in the optimal inclination at the latitude of the location. One can provide a direction sign from which the orientation training is transmitted; this panel is then provided with a motor associated with a device for detecting or calculating the angular position of the sun around the axis of orientation and control of the motor. The motor drives the panel by any means, advantageously by means of an irreversible transmission. So that the applied orientation torque is high, the motor can drive a roller supported by a long arm, secured to the panel. The roller is applied on a circular spoke of radius corresponding to the length of the arm.

The invention will be better understood on reading the following description of a device which constitutes a particular embodiment thereof, given by way of nonlimiting example. The description refers to the accompanying drawings, in which
FIG. 1 is a layout diagram of rows of panels according to a centered hexagonal network, seen from above,
FIG. 2 is a plan view of two panels of FIG. 1 and their cables for connection with the transmission connecting rods of the device equipping the row,
FIG. 3 is a simplified perspective view showing a connection spring between cable and connecting rod,
- Figure 4 is a sectional view along the line
IV-IV of figure 3,
FIG. 5 is a block diagram showing a cable guide equipping a chassis,
FIG. 6 is a block diagram of the frame of a panel, seen in perspective,
FIGS. 7 and 8 show, respectively in plan and in elevation, a drive device which can be used to move the orienting panels of FIG. 1 in rotation,
- Figures 9, 10 and 11, where the thicknesses are not given to scale, are partial views of a panel, respectively from below on a plane parallel to the bottom (line IX-IX in Figure 10 ) and along the planes XX and XI-XI, respectively perpendicular and parallel to the rows of solar cells,
- Figure 12 is a detail view on a large scale, in section along a plane parallel to that of Figure 11, showing the mounting of a row of solar cells.

 The invention will now be described on the assumption that it is implemented in an installation comprising solar panels distributed on a flat ground and at an average latitude, leading to orient the panels around a vertical axis, that is to say - say only in azimuth. In this case, considerations of cast shadows lead to placing the panels 10 in a centered hexagonal network, as illustrated in FIG. 1, one of the main diagonals being oriented East-West. On sloping ground, it will often be necessary to adopt a different arrangement, the connecting rods of the motion transmission device approximately following the level lines of the ground.

The panels shown in Figure 1 are oriented in rows each corresponding to a direction 300 of the axis
North-South, on either side of a middle oriented position
North South. In each row, a panel (designated by the index a) constitutes a steering panel and is provided with an orientation motor and with a device for controlling this motor (not shown). This direction sign 10a is generally placed in the center of the row. It drives the oriented panels 10b located on each side (for example four in number on each side) via a transmission mechanism.

 This transmission mechanism comprises, for each row, two connecting rods 11 and 12, generally made of steel and which can be made up of sections butted by fishplates, and two connecting cables 13 and 14 per oriented panel 10 ~. These cables, generally made of high-strength steel wires, are fixed at one end to a chassis 15 which constitutes a structural element supporting the panel and which is integral with this and by the other end to the connecting rod. corresponding 11 or 12. Each cable is given a winding arc on the chassis 15 sufficient to allow the required angular travel 2 (Figure 1). At medium latitudes, we will generally adopt an angle 2 of the order of 2400. The cables are supported on winding guides 16 arranged at the corners of the chassis and forming a drum. Connecting rod support plates 17 are also arranged at the four corners of the chassis 15 to support the connecting rods. The edge 18 of these supports is folded down to take account of the deflection that each connecting rod can take (Figures 2, 5 and 6). When the panels are in their middle position, each cable must be wound on at least three sides of the support before its fixing point to allow the required amplitude of 2400. Between each cable 13 or 14 and the corresponding connecting rod 11 or 12 is interposed a compensation spring. Figures 3 and 4 show such a spring 19, interposed between the cable 14 and the connecting rod 12. The latter is advantageously constituted by a U-shaped section which allows easy fixing of the compensation springs and protects them.

In addition, in this arrangement, the traction exerted by the cable has a component tending to return the connecting rod towards the panel, that is to say towards a position where it is guided by the plate 17.

 Figures 3 and 4 show that the spring 19, held by a flap 21 produced by folding the profile, works in compression. One of its ends is supported on a washer 20 welded to the connecting rod. The other end is supported on a washer 22 mounted on a tube 23 which crosses the spring along the axis and whose position is adjustable using a nut 24. The terminal part of the cable 14 forms a loop which traps a key 25 passing through the tube 23.

 The chassis 15 of the steering panel 10a has a constitution similar to that of the chassis of the oriented panels 106. However, it is reinforced and is provided with four orientation cables instead of two. These four cables are directly fixed to the connecting rods 11 and 12. The anchors of the terminal parts of these four cables 27, 28 are indicated in FIG. 2 (corresponding to the cables 11 and 12 of the panel 10b shown), 29 and 30 by points surrounded by a circle.

 The support frame of the panels can have the constitution shown schematically in Figure 6, in welded profiles. The cross section given to each of these sections will then be chosen according to the type of stresses which it undergoes either in normal operation, or when one is in conditions of maximum wind. It should be noted in passing that it is possible in this case to place all the panels in a so-called "survival" position, for which the moment of the forces exerted by the cables on the panels is maximum.

 The sections 31, 32, 33, 34, 35 may be made of welded spun aluminum alloy. The central plate 36 is provided with a tube intended to rotate on a fixed axis of rotation, also tubular.

 The practical embodiment of the chassis and of the device allowing it to rotate around the vertical axis can be that shown in FIGS. 7 and 8, which also illustrate a mechanism for driving in rotation the steering panel 10a.

 The chassis 15 shown in Figures 7 and 8 is mounted on an anchor block 40. To this anchor is fixed a plate 41, using threaded sealing rods 42 for adjusting the height and orientation of the plate . This plate carries a pivot tube 42 in several welded parts, extending to the level of the upper part of the chassis. The chassis 15 for its part carries a tube 43 guided on the pivot 42 by plain bearings 44 placed at the top and at the bottom, only one of which is visible in FIG. 8.

 In the embodiment of the steering panel drive mechanism shown in FIGS. 7 and 8, the panel is provided with a trellis arm 45 terminated by a drive carriage on a circular rail 46 to deflect angular development corresponding to the clearance research.

This carriage carries a geared motor 47, the shaft of which drives a roller 48. In the carriage slide four rods 49 provided with pinch rollers 51. Springs 50 pull the rods upwards, so that the track of the rail 46 is pinched between the rollers 48 and 51, which ensures satisfactory training.

 A description will now be given, with reference to FIGS. 9 to 11, of a possible construction of a low-concentration solar panel advantageously used in connection with the orientation device according to the invention.

 The function of the panel is to carry the solar cells and the optics allowing to concentrate the solar energy which they receive. In addition, the panel must dissipate the heat dissipated by the solar cells (the heat density remaining moderate given the low concentration) and protect them against dust and water splashes.

 Furthermore, the panel must be of an acceptable cost.

 For this purpose, the panel may include a light metal box made of folded and assembled sheets. The bottom 52 of the panel, on which the solar cells are fixed, acts as a radiator. It is made of folded sheet metal to present trapezoidal ribs (FIG. 10) parallel to the rows of solar cells 53. The ribs give the panels the rigidity necessary to withstand the forces due to the wind and increase the surface area for exchange with the ambient air.

The periphery 54 of the box (FIG. 11) is also made of folded sheet metal, the edges 55 of which are folded down to position the ends of the Fresnel lenses 56 constituting the concentration optics, the periphery of which is indicated by a line in dashed lines in Figure 9. The bottom 52 is fixed, for example by rivets, on the folded periphery (Figure 11).

 The front face of the box is provided with parallel angles 57 with unequal wings, twelve in number for example.

These angles, parallel to the rows of solar cells 53, make it possible to fix the Fresnel lenses 56. In the end parts of the angles 57, the small wing is cut and the remaining wing is bent, as seen in 58 in FIG. 9 The bent part is fixed to the periphery 54 of the box and provides a bearing surface over the entire periphery of the Fresnel lenses 56. The angles also participate in the mechanical strength of the panel. As shown in Figure 10, they can be held in the middle by a rod and a spacer 59 which reduces the deflection resulting from the dynamic wind pressure. Each Fresnel lens 56 can be double, so as to concentrate the solar energy on two adjacent rows of solar cells occupying the space between two reinforcement ribs of the bottom 52. Each lens can be composite and constituted for example by a glass plate 60 which has the advantage of being rigid, of well resistant to abrasion, of being easy to clean and of resisting ultraviolet rays and a lens made of silicone resin 61. Other solutions are however possible, for example the use of polymethyl methacrylate lenses.

 As indicated above, the bottom 52 of the box carries the solar cells. The means of fixing the solar cells must be provided to ensure a precise positioning of these solar cells, allow the evacuation of the thermal power dissipated in the solar cells while electrically insulating them from the bottom forming a radiator, limiting the mechanical stresses in solar cells (usually constituted by silicon wafers) at an acceptable level, and provide a seal complementing that of the front face of the box. In addition, the materials arranged in front of the solar cells must have a transparency and resistance to close ultraviolet radiation contained in the solar spectrum.

 The assembly method shown in FIG. 12 makes it possible to meet these requirements while retaining a moderate cost.

For this, it only adopts proven solutions, especially in the field of flat panels without energy concentration.

 Each row of solar cells 53 is protected by a glass plate 63 which also makes it possible to exert a distributed pressure on the solar cell in order to maintain satisfactory thermal contact between the solar cells and the bottom 52. This pressure is exerted by a device pressing which includes light metal tabs 64 bearing on the edges of the plate 64 and framing the plate.

Screws 65 exert the required pressure force, via leaf springs 66 which allow the pressure exerted to be measured.

 Between the row of solar cells and the bottom 52 is interposed a spacer mesh 67 of flexible polymer material. This thickness is chosen so as to ensure the minimum insulation required, for example 1 kV in direct voltage, which leads, in practice, to a minimum thickness of the order of 0.5 mm. The contact blades 68, generally made of annealed copper of about 0.1 mm thick, are interposed between the solar cells and the mesh. The residual space between the solar cell and the bottom is filled with a silicone resin 69, possibly loaded with alumina powder to increase its thermal conductivity. The residual spaces located between the glass plate 63 and the solar cells 53 and around the connections can also be filled with silicone resin stabilized with ultraviolet 70, similar to that used to encapsulate certain flat panels.

 In practice, it will generally be convenient to group the solar cells into modules of a few solar cells equipped with their protective glass plate and fitted with the mesh.

Claims (11)

 1. Orientation device, around parallel axes, of solar panels arranged in rows, device comprising a mechanism for angular displacement of the panels, characterized in that the device comprises a set of at least two transmission connecting rods (11, 12) each located on one side of the row and each connected to each driven panel by means of at least two traction cables (13, 14).  2. Device according to claim 1, characterized in that each panel is fixed to a frame (15) rotatable about the corresponding axis, provided with at least three guides (16) for winding the cables, delimiting a crossed area by the axis, the cables being fixed to the chassis.  3. Device according to claim 2, characterized in that the frame has a rectangular shape in plan and in that the guides (16) are placed in the corners and are in the form of a drum.  4. Device according to any one of the preceding claims, characterized in that each panel is equipped with plates (18) intended to support the connecting rods.  5. Device according to any one of the preceding claims, characterized in that each cable is connected by elastically deformable means, such as a spring (19), to the corresponding connecting rod of each driven panel.  6. Device according to claim 5, characterized in that each spring works in compression and is interposed between a cable and the corresponding connecting rod.  7. Device according to any one of the preceding claims, characterized in that each panel (lova) is connected to the connecting rods (11, 12) by four cables (27-30) so that the connecting rods always work in traction.  8. Device according to claim 2 or any one of the claims which depend thereon, characterized in that the frame is constituted by a lattice in profiles provided with means of rotation about a vertical axis and supporting the panel in an oblique position corresponding to the latitude of the location.  9. Device according to any one of the preceding re-vendications, characterized in that the angular displacement mechanism controls the orientation of a steering panel placed substantially in the middle of the row and connected to the two connecting rods by four cables.  10. Device according to any one of the preceding claims, characterized in that the panels are arranged in a centered hexagonal network, and in that they are oriented on either side of a corresponding North-South oriented average position. to the direction of one of the network's mediators.  11. Device according to any one of the preceding claims, characterized in that the panel comprises a box, the bottom (52) of which consists of a sheet carrying rows of solar cells (53) mounted parallel to the folds and a front face consisting of lenses of Fresnel with linear focus.