Tracking Unit For A Solar Collector

Abstract

A tracking unit for solar collectors has at least two panels, which can each be pivoted about a longitudinal axis. The axes are arranged on a rotable frame on one plane. The position of each axis within the individual panels is offset by a offset Δx in relation to the adjacent panels. The individual panels are moved by means of a lifting mechanism that pivots each of the panels about the same angle. This arrangement significantly reduces mutual shading and increases efficiency by about 10%.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a tracking unit for a solar collector, in particular for harvesting sunlight, which can track the current position of the sun. This allows the angle of incidence of the rays to be perpendicular to the surface of the collector at all times, thus achieving maximum efficiency of the collector.

2. Description of Relevant Art

U.S. Pat. No. 4,798,444 discloses a solar collector which receives solar radiation from different directions and therefore does not require tracking.

U.S. Pat. No. 5,581,447 discloses a solar collector having a movable biaxial lens system which feeds sunlight into a bundle of optical fibers.

Another biaxial lens system for injecting light into a bundle of optical fibers is disclosed in U.S. Pat. No. 4,589,400. In this case, a collector head with light collecting elements arranged on a surface tracks the sun biaxially.

The disadvantage of this tracking system is that the whole collector surface has to be rotated and/or pivoted. This requires a relatively large structure and a large area for moving the collector head accordingly. Furthermore, large wind loads can occur due to the large surface, which must also be arranged at a great distance from the mounting plane to allow its movement.

SUMMARY OF THE INVENTION

The embodiments are based on the object of designing a tracking unit for solar collectors, in particular for collectors which feed the sun's rays into bundles of optical fibers, such that it requires less space, has a lower wind load and can be mounted closer to the installation surface. Furthermore, it is designed to track the sun in a more precise manner.

In an embodiment the tracking unit has at least two panels which are arranged on a frame and can each be pivoted on a longitudinal axis. The position of the axes of rotation of the individual panels is offset in relation to the adjacent panels by a specified dimension Δx in each case. The movement of the individual panels is achieved by means of a lifting mechanism or a parallel drive, with which the panels can each be pivoted about the same angle. Preferably, the panels have a rectangular, elongated shape, with the longitudinal axis preferably running parallel to the longer edge of the rectangle.

In a further embodiment the frame can be mounted rotatably together with the panels in order to allow tracking along a second axis.

In another embodiment the frame attached to a guide ring to make it rotatable in a simple manner. This guide ring is provided with a first bearing surface parallel to the frame and/or to the panel arrangement. Furthermore, provision is made for an internal bearing surface arranged at an angle of less than 90° to the first bearing surface.

According to a further embodiment a passive micro-adjustment system for the position of the lenses is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described by way of example, without limitation of the general inventive concept, on examples of embodiment and with reference to the drawings.

FIG. 1 shows a tracking unit.

FIG. 2 shows a lateral view of the tracking unit with vertical panels.

FIG. 3 shows the tracking unit with panels pivoted on an angle to the left.

FIG. 4 shows the panels pivoted to a high degree.

FIG. 5 schematically shows the positional and angular relationships of the tracking unit.

FIG. 6 shows the positional and angular relationships with pivoting to the left.

FIG. 7 shows the positional and angular relationships with pivoting to the right.

FIG. 8 shows the positional and angular relationships for a tracking unit without axial displacement

FIG. 9 shows a cross-section through the guide ring including the guide rollers running on it.

FIG. 10 shows a thermally controlled tracking unit for the lenses.

FIG. 11 shows a thermally controlled tracking unit for the lenses in a balanced state.

FIG. 12 shows a thermally controlled tracking unit for the lenses in details.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a tracking unit. The solar collector includes individual panels 20a, 20b, 20c, 20d, 20e. These panels are pivoting mounted in a frame 10. The frame itself is rotatably mounted on the guide ring 11 and can be rotated by means of a drive system 12. The guide ring 11 is mounted rigidly on a mounting surface, such as for instance on the roof of a house, a flat roof or a wall. The individual panels 20a to 20e include a plurality of lenses and/or light collectors 30 bundling solar radiation into individual light guiding fibers. An optional solar sensor is mounted rigidly onto the surface of a panel and is moved together with this. It serves to detect the exact position of the sun and therefore to reposition the panels precisely. Provision can also be made for optional solar cells 13 for obtaining electrical energy, for example for driving the tracking system.

In general a tracking unit for solar collectors has at least two panels 20a, 20b, 20c, 20d, 20e, which are arranged on a frame 10 and can each be pivoted on a longitudinal axis. The positions of the axes of rotation 21a, 21b, 21c, 21d, 21e of the individual panels are displaced in relation to the adjacent panels by a specified dimension Δx in each case. The movement of the individual panels is achieved by means of a lifting mechanism or a parallel drive, with which the panels can each be pivoted about the same angle. Preferably, the panels have a rectangular, elongated shape, with the longitudinal axis preferably running parallel to the longer edge of the rectangle.

Such an arrangement results in the entire surface of the solar collector being distributed across several sub-areas, corresponding to the number of panels. This means that it is no longer necessary for the whole surface to track the position of the sun. In fact, only the individual sub-areas need to be moved. This allows the entire configuration to be mounted considerably closer to the installation surface, such as a roof or a wall. Accordingly, the whole arrangement does not project as much, the appearance of the building or other property is compromised less and the wind load is reduced. Such an arrangement, which is relatively flat, can now be mounted in large numbers without any problem on buildings, building roofs or facades, often without the need for additional building permits.

In order to allow tracking along a second axis, the frame 10 can be mounted rotatably together with the panels. This means that the arrangement is largely free of the constraints of a mounting angle relative to the mounting surface. It is understood that the tracking unit also works without the frame being mounted rotably.

In order to make the frame rotatable in a simple manner, it is preferably attached to a guide ring. This guide ring is provided with a first bearing surface parallel to the frame and/or to the panel arrangement. Furthermore, provision is made for an internal bearing surface arranged at an angle of less than 90° to the first bearing surface. This slanted arrangement means that this internal bearing surface can also bear a (smaller) force perpendicular to the first bearing surface as well as a force arising at a right angle to this. This means that the frame with the panels can be rigidly mounted to the guide ring.

FIG. 2 shows a schematic lateral view of the tracking unit. The individual panels 20a to 20e can be seen from the side. These are pivoting mounted on pivoting axes (also referred as rotary axes) 21a to 21e. As can clearly be seen here, the rotary axes are arranged at different positions relative to the individual panels. The precise arrangement will be shown later in the FIGS. 5 to 8.

FIG. 3 shows tracking unit corresponding with FIG. 2, whereby the panels are pivoted at a slight angle to the left. It can clearly be seen that there has been a shift in the height of the individual panels as a result of the different arrangements of the rotary axes.

FIG. 4 shows an approximately 90° rotation of the panels relative to the horizontal. This also produces the maximum offset in height relative to the horizontal. It is obvious that this height offset reduces the mutual shadowing effect of the individual panels. This means that more light can be collected.

FIG. 5 shows the size and angular relationships for a solar tracking unit. The individual panels 20a to 20e are mounted by means of the rotary axes 21a to 21e. The central axes of the panels 22a to 22e point vertically upward when the panels are arranged horizontally. It is preferable for the distances 24a to 24d of the central axes of the individual panels to be the same size and determined by the size and/or width of the panels. These central distances correspond to the distance of the individual panels less the dimension Δx. In the example of the embodiment shown here, the central axis 22c only runs through the rotational axis 21c in the case of the centre panel 20c. In the case of a panel 20d, the central axis 22d runs at a distance 23d from the rotary axis 21d corresponding to Δx. This distance 23e corresponds to 2 * Δx for the panel 20e. The same applies for the panels 20b and 20a, where in these cases the distances between the central axes and the rotary axes are also Δx (for 20b) and 2 * Δx (for 20a) respectively.

Generally, the distance or displacement between the central axis and a rotary axis of the adjacent panel differs by Δx.

The complete frame 10 can be designed to be smaller than an embodiment where the central axes run through the rotary axes as shown in FIG. 8, due to the fact that the rotary axes for the outer panels 20a and 20e are attached on the inner sides. In addition, the panels pivot inward toward the frame 10 so that the distance to the adjacent arrangements can be kept smaller.

FIG. 6 shows the previous arrangement with the panels pivoted at an angle 26. In this case, the central axes 22a to 22e of the individual panels are pivoted by the angle 26 relative to the horizontal.

FIG. 7 shows a tracking unit corresponding to the previous figure, but where the individual panels are pivoted in the opposite direction.

FIG. 8 shows a tracking unit where the central axes run through the rotary axes. This produces constant distances 27 for the individual rotary axes. These distances between the rotary axes are greater than the distances between the rotary axes in an arrangement according to FIG. 5. As a result, the frame 10 must be designed to be larger.

FIG. 9 shows another cross-section through the guide ring 11. In this case, a first roller runs on the first bearing surface 41, which is visible. A second internal bearing surface 42, which forms an angle less than 90° with the first bearing surface 41, serves as a bearing surface for the internal roller 44. The two rollers constitute a roller set and orbit the rotational axis of the entire arrangement 45. The rollers can be rotated around their central axes (shown by the dotted line) and are connected to the frame 10 (not shown here). At least three such roller sets, each consisting of a first roller and a second roller, are borne by the frame 10 on the guide ring 11. As the two bearing surfaces 41 and 42 form an angle that is less than 90°, the internal roller 44 is able to exert a lesser vertical force component in the direction of the first roller 43. The two rollers can be set to be interlocking. This prevents the complete arrangement from slipping upward out of the guide ring. This means that an arrangement of this kind can also be mounted on sloping or vertical wall surfaces. In the case of a vertical wall surface, the first bearing surface 41 would then be parallel to the vertical wall surface and would also be positioned vertically.

FIG. 10 shows a thermally controlled tracking apparatus for lenses and/or light collectors 30. The beams of sunlight 50 can only be fed into the light collectors 30 with optimum efficiency when the angle of incidence of the beams of sunlight 50 is parallel to the principle orientation of the lens 32. In order to passively minimise the angle 51 of misalignment, sunlight 50 is transmitted via collimators 53a, 53b onto thermally expanding material 52a, 52b. Corresponding to the heat absorbed by this material, this material expands and changes its thickness, as shown in the drawing, so that the tracking plate 55 bearing the individual lenses 30 is pivoted with respect to the base plate 54. In the example of the misalignment shown here, more light strikes the thermally expanding material 52b than the thermally expanding material 52a. Accordingly, the material 52b will expand more.

Generally, if there is an angle of misalignment 51 between this principal orientation 32 of the lens and/or the light collector 30 and the beams of sunlight 50, this must be corrected in order to maintain the optimal degree of efficiency. The exact positioning of the individual lenses in the direction of the sun requires a high level of technical complexity and in particular small tolerances in terms of the mechanics of the individual panels and their suspension. In order to minimise the complexity as much as possible, a further embodiment provides for a passive micro-adjustment system for the position of the lenses. To achieve this, radiation from the sun is gathered and expandable material is heated when subjected to the radiation. The material expands in accordance with the radiation, altering the position of the lenses as a result. This means that the lens is positioned optimally in relation to the sun at all times.

FIG. 11 shows the exemplary embodiment of FIG. 10 with a corrected angle of misalignment 51. In this case, the thermally expanding material 52b has expanded due to the greater solar radiation, while the thermally expanding material 52a has shrunk due to the reduction in solar radiation. Correspondingly, the tracking plate 55 is now pivoted with respect to the base plate 54, so that the lenses 30 are directed optimally toward the sun. Now, the same amount of radiation falls on both the thermally expanding materials 52a, 52b due to the collimators 53a, 53b so that they do not change any further.

FIG. 12 shows the tracking unit for repositioning the lenses in detail. The collimator 53b is pivoted at an angle 56 with respect to the verticals on the tracking plate 55. The sensitivity of the tracking system can be set using this angle and additional canting. FIG. 10 shows a thermally controlled tracking unit for the lenses 30.

It will be appreciated to those skilled in the art having the benefit of this disclosure that this invention is believed to provide solar tracking units and components thereof. Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.

LIST OF REFERENCE NUMERALS

• 10 Frame
• 11 Guide ring
• 12 Drive system
• 13 Solar cells
• 20 a-e) Panel
• 21 a-e) Rotary axis
• 22 a-e) Central axis panel
• 23 a-e) Rotation point/Central axis distance
• 24 e-d Distance between central axes
• 25 a-e) Vertical axis of panel
• 26 Angle of pivot
• 27 Central axis spacing
• 30 Lens or light collector
• 31 Solar sensor
• 32 Principal lens orientation
• 41 First bearing surface
• 42 Internal bearing surface
• 43 First roller
• 44 Internal roller
• 45 Rotary axis
• 50 Beams of sunlight
• 51 Angle of discrepancy
• 52 a,b Thermally expanding material
• 53 a,b Collimator
• 54 Base plate
• 55 Tracking plate
• 56 Collimator pivot angle

Claims

1. Tracking unit for a solar collector comprising at least one frame with at least two panels which can each be pivoted about a pivoting axis, with the positions of the pivoting axes of adjacent panels being displaced by a distance Δx in relation to a central axis of the panels.

2. Tracking unit according to claim 1, wherein the pivoting axes of the panels are arranged on the frame in one plane.

3. Tracking unit according to claim 1, wherein a plurality of panels can be pivoted at the same angle by means of a mechanical drive.

4. Tracking unit according to claim 1, wherein the frame is mounted rotatably on a guide ring mounted rigidly on a mounting surface.

5. Tracking unit according to claim 4, wherein the guide ring is provided with a first bearing surface and an internal bearing surface which is arranged at an angle of less than 90° with respect to the first bearing surface.

6. Tracking unit according to claim 5, wherein a first roller runs on the first bearing surface and an internal roller runs on the internal bearing surface, which are braced against each other.

7. Tracking unit according to claim 1, wherein a device for passive fine adjustment of at least one light collector arranged on one panel is provided, and the device is configured for alignment of at least one light collector to the sun by means of thermal expansion of a material that expands in response to heat.