PARABOLIC TROUGH COLLECTOR

Abstract

The invention relates to a parabolic trough collector comprising a parabolic, trough-shaped main reflector, preferably as a steel girder construction running holding device with a plurality of support arms for holding of the main reflector, an absorber tube, which extends along the focal line of the Main reflector extends and in which a heat transfer medium is heated, and a foundation, wherein the holding device on the foundation by a vertical axis is rotatably mounted.

Claims

1. A parabolic trough collector, comprising a parabolic, trough-shaped main reflector (1), a holding device (2), which is preferably designed as steel beam construction, with a plurality of support arms (3, 3′) for holding the main reflector (1), an absorber pipe (4), which extends along the focal line of the main reflector (1) and in which a heat transfer medium is heated, and a base (5), wherein the holding device (2) is mounted on the base (5) so as to be rotatable about a vertical axis (6), characterized in that a secondary reflector (15) is provided, which extends substantially parallel to and above or below the absorber pipe (4) and which is preferably formed by an elongated reflective profile, wherein the secondary reflector (15) has in its cross-section a circular section (19) and two edge lines (20).

2. The parabolic trough collector according to claim 1, characterized in that the holding device (2) comprises at least one, preferably two, particularly preferably three, circular support circles (7, 7′) extending concentrically around the vertical axis (6), preferably made of steel beam pipes, in which a plurality of rollers (8), preferably polyamide rollers, attached to the base (5) engage.

3. The parabolic trough collector according to claim 1, characterized in that a plurality of rollers (8), preferably polyurethane rollers, are arranged on the holding device (2), which are preferably provided with brushes and which are preferably arranged point-symmetrically to the vertical axis (6), for example in a rectangle, a hexagon and/or an octagon.

4. The parabolic trough collector according to claim 1, characterized in that a plurality of photovoltaic elements (9) are arranged on the holding device (2) for generating electrical energy.

5. The parabolic trough collector according to claim 1, characterized in that a plate-shaped end reflector (10) extending substantially normal to the longitudinal extent of the main reflector (1) is arranged at one end face of the trough-shaped main reflector (1) and preferably extends from the apex to two end regions (26, 26′) of the main reflector (1).

6. The parabolic trough collector according to claim 1, characterized in that the absorber pipe (4) comprises a tubular supply conduit (11) and a tubular discharge conduit (12) for the heat transfer medium, both of them running preferably through an opening (13) of the holding device (2) in the area of the vertical axis (6) or extending in the area above the main reflector (1).

7. The parabolic trough collector according to claim 6, characterized in that a preferably central drive motor, such as a stepper motor, is arranged in the opening (13) for rotating the holding device (2) about the vertical axis (6), wherein the supply conduit (11) and the discharge conduit (12) are guided through a preferably central circular opening in the drive motor, which preferably has a diameter of more than 400 mm, particularly preferably more than 600 mm, in particular more than 670 mm.

8. The parabolic trough collector according to claim 1, characterized in that the absorber pipe (4) comprises a tubular supply conduit (11) and a tubular discharge conduit (12) for the heat transfer medium, wherein the supply conduit (11) and the discharge conduit (12) extend at least in sections in the area of the vertical axis (6) and wherein in these sections at least one rotating joint (17, 18) is provided to permit a rotation of the holding device (2) and thus the supply conduit (11) and discharge conduit (12) connected to it about the vertical axis (6).

9. The parabolic trough collector according to claim 1, characterized in that the absorber pipe (4) comprises a tubular supply conduit (11) and a tubular discharge conduit (12) for the heat transfer medium, wherein the supply conduit (11) and the discharge conduit (12) are designed as flexible hoses at least in sections to permit a rotation of the holding device (2) and thus the supply conduit (11) and discharge conduit (12) connected to it about the vertical axis (6).

10. The parabolic trough collector according to claim 1, characterized in that the circular section (19) covers an angular range of less than 180°, preferably about 160° to 170°, particularly preferably about 165°.

11. The parabolic trough collector according to claim 1, characterized in that the circular section (19) of the secondary reflector (15) is arranged above and eccentrically to the longitudinal axis (21) of the absorber pipe (4).

12. The parabolic trough collector according to claim 1, characterized in that the edge lines (20) extend outwards at an angle of about 10° to the connecting line of the corner points (22, 22′) of the circular section (19).

13. The parabolic trough collector according to claim 1, characterized in that the diameter of the circular section (19) is three to five times larger than the diameter of the absorber pipe (4), and in that the edge lines (20) have a length which corresponds approximately to the diameter of the absorber pipe (4).

14. The parabolic trough collector according to claim 1, characterized in that the absorber pipe (4) has a diameter of about 50 mm to 140 mm, preferably about 70 mm.

15. The parabolic trough collector according to claim 1, characterized in that the main reflector (1) is flexible in shape and is arranged on a tensioning element (24), for example a rope, a cable or a chain, which is suspended between the support arms (3, 3′).

16. The parabolic trough collector according to claim 15, characterized in that the tensioning element (24) is pullable in the direction of the base (5) to form a parabolic shape via a plurality of pulling means (25) mounted at spaced engagement points (27) and extending substantially vertically.

17. The parabolic trough collector according to claim 1, characterized in that the main reflector (1) comprises a plurality of flexible main reflector modules (34) aligned along the focal line (43).

18. The parabolic trough collector according to claim 17, characterized in that each main reflector module (34) comprises a flexible mirror foil or a plurality of substantially similar mirror plates (23) or polished sheet metal plates, in particular aluminium plates, whose width is preferably in the range of the diameter of the absorber pipe (4), in particular about 70 mm.

19. The parabolic trough collector according to claim 17, characterized in that the weight distribution of the main reflector modules (34) along the aperture of the main reflector (1) is such that, when freely suspended between the support arms (3, 3′) of the holding device (2), they assume a parabolic shape due to their weight distribution.

20. The parabolic trough collector according to claim 19, characterized in that the width of the main reflector modules (34) is not constant along the aperture, but decreases from the focal line (43) to the support arms (3, 3′).

21. The parabolic trough collector according to claim 19, characterized in that compensating elements (44) are arranged in particular on the underside of the main reflector modules (34), the width of the compensating elements (44) not being constant along the aperture, but decreasing from the focal line (43) to the support arms (3, 3′).

22. The parabolic trough collector according to claim 1, characterized in that the main reflector (1) has an aperture of more than 7 m, preferably of more than 10 m, particularly preferably an aperture in the range of more than 12 m.

23. The parabolic trough collector according to claim 1, characterized in that the holding device (2) comprises at least one, preferably two, similar inner support struts (14, 14′) extending centrally substantially parallel to the focal line of the main reflector (1) for holding a maintenance device (16).

24. The parabolic trough collector according to claim 23, characterized in that at least one outer support strut (28) is provided for holding the maintenance device (16).

25. The parabolic trough collector according to claim 1, characterized in that the absorber pipe (4) comprises a plurality of parts (29) connected by a flanged joint, the flanged joint comprising two respective end flanges (30) and an adapter piece (31) arranged therebetween.

26. The parabolic trough collector according to claim 25, characterized in that the adapter piece (31) comprises an opening (32) for the passage of the heat transfer medium and a plurality of elongated holes (33), preferably four, in the form of circular sections and arranged around the opening (32) for the flexible connection of the end flanges (30), the elongated holes (33) preferably each extending over an angular range of from about 60° to about 75°.

27. The parabolic trough collector according to claim 26, characterized in that for holding the absorber pipe (4) at least one of the adapter pieces (31) is connected to an absorber pipe holder (37).

28. The parabolic trough collector according to claim 27, characterized in that the absorber pipe holder (37) comprises a mounting plate (41) which is movably connected to the adapter piece (31) via elongated holes (42).

29. The parabolic trough collector according to claim 1, characterized in that the main reflector (1) has a longitudinal axis which is inclined with respect to the surface of the base, for example at an angle of about 5° to 45°.

Description

[0055] In the figures:

[0056] FIG. 1 shows a schematic three-dimensional representation of an exemplary embodiment of a parabolic trough collector according to the invention;

[0057] FIG. 2 shows a schematic three-dimensional representation of a holding device of an embodiment of a parabolic trough collector according to the invention;

[0058] FIG. 3 shows a top view of the base of another embodiment of a parabolic trough collector according to the invention;

[0059] FIG. 4 shows a schematic three-dimensional view of the supply and discharge conduit arrangement of an embodiment of a parabolic trough collector according to the invention;

[0060] FIG. 5 shows a schematic side view of the supply and discharge conduit arrangement of an embodiment of a parabolic trough collector according to the invention;

[0061] FIGS. 6a-6b show a schematic three-dimensional representation and a cross-section, respectively, of the secondary reflector of an embodiment of a parabolic trough collector according to the invention;

[0062] FIGS. 7a-7b show a schematic three-dimensional representation and a side view, respectively, of a main reflector module of an embodiment of a parabolic trough collector according to the invention;

[0063] FIG. 8 shows a schematic three-dimensional view of a maintenance device on an embodiment of a parabolic trough collector according to the invention;

[0064] FIGS. 9a-9e show a schematic three-dimensional view of the absorber pipe and further views of a flanged joint on an embodiment of a parabolic trough collector according to the invention;

[0065] FIGS. 10a-10b show a schematic view of the main reflector module of a parabolic trough collector according to the invention.

[0066] FIG. 1 shows a schematic three-dimensional representation of an exemplary embodiment of a parabolic trough collector according to the invention as a whole. The parabolic trough collector comprises a parabolic, trough-shaped main reflector 1, which is composed of multiple adjacently arranged main reflector modules 34. The main reflector 1 is arranged on a holding device 2 designed as a steel beam structure, which comprises a plurality of support arms 3, 3′ for holding the main reflector. An absorber pipe 4 extends along the focal line of the main reflector 1, which in the drawing is largely covered by a secondary reflector 15 arranged above. A heat transfer medium is pumped through the absorber pipe 4, which heats up to temperatures above 400° C. during operation due to the reflected beams of sunlight.

[0067] Furthermore, a base 5 is shown on which the holding device 2 is rotatably mounted about a vertical axis 6 (not shown). A support circle 7 is schematically visible under the holding device 2. A supply conduit 11 and a discharge conduit 12 are guided through a base recess 35 without getting in the way of the rotary movement of the holding device 2. Photovoltaic elements 9 for generating electrical energy are also arranged on the holding device.

[0068] This schematic representation also includes a maintenance device 16, which is arranged with two cantilevers on an inner support strut 14 and an outer support strut 28 and carries a main reflector module 34 that is not mounted.

[0069] A plate-shaped end reflector 10 extending substantially normal to the longitudinal extent of the main reflector 1 is arranged at one front face of the trough-shaped main reflector 1. The end reflector 10 extends from the apex of the main reflector 1 to both end regions 26, 26′ of the main reflector 1.

[0070] The end reflector 10 comprises a plurality of substantially similar mirror plates arranged adjacent to each other on a substantially vertical support structure.

[0071] FIG. 2 shows a schematic representation of a holding device 2 of an embodiment of a parabolic trough collector according to the invention. The holding device 2 is designed as a steel beam structure and comprises eight symmetrically arranged support arms 3, 3′ for holding the main reflector 1, which is not shown. On the eight support arms 3, 3′ and the eight base struts 36 of the steel beam construction, engagement points 27 in the form of lugs are provided, which are used for mounting tensioning elements 24 (not shown).

[0072] On the underside of the base struts 36 are rollers 8, which in this embodiment are designed as polyurethane rollers. The rollers 8 are arranged in two geometric shapes around a central opening 13 and vertical axis 6 of the holding device 2, namely an outer octagon and an inner square. This provides a particularly stable support of the holding device 2 on the base 5.

[0073] FIG. 3 shows a schematic top view of the base 5 of a further embodiment of a parabolic trough collector according to the invention. In this embodiment, the holding device is not provided with rollers, but with the schematically indicated support circles 7, 7′, which extend concentrically about the vertical axis 6. On the base 5, rollers 8 are mounted, which are directed upwards and on which the support circles 7, 7′ and the holding device 2 itself are rotatably mounted. In this exemplary embodiment, the rollers 8 are designed as polyamide rollers.

[0074] The supply conduit 11 and the discharge conduit 12 (not shown) are guided to the outside via a base recess 35.

[0075] FIG. 4 shows a schematic three-dimensional view of the supply and discharge conduit arrangement of an embodiment of a parabolic trough collector according to the invention. The supply conduit 11 and the discharge conduit 12 of the heat transfer medium as well as the opening 13 in the area of the vertical axis 6 of the holding device 2 are shown.

[0076] The location of the absorber pipe 4 is schematically indicated. In operation, the area above the opening 13, i.e., the absorber pipe 4 and the connected conduits, rotates about the vertical axis 6, while the area below the opening 13, i.e., the two parallel supply and discharge conduits 12, 13, stand still. In this exemplary embodiment, the opening 13 has a dimension of about 600 mm to 800 mm.

[0077] FIG. 5 shows a schematic side view of the supply conduit and the discharge conduit of the heat transfer medium in the area of the opening 13, also showing the vertical axis 6 about which the holding device 2 rotates relative to the base 5. The tubular supply conduit 11 and the tubular discharge conduit 12 each run in short sections in the vertical axis 6. Rotating joints 17, 18 are provided in these sections to enable rotation of the holding device 2 and the associated supply conduit 11 and discharge conduit 12 about the vertical axis 6.

[0078] FIGS. 6a-6b show a schematic three-dimensional representation and a cross-section, respectively, of the secondary reflector 15 of an embodiment of a parabolic trough collector according to the invention. The secondary reflector 15 designed as elongated profiled aluminum sheet with a high polish finish at least on the underside.

[0079] In other exemplary embodiments, the secondary reflector 15 may comprise other reflective materials. The secondary reflector 15 is arranged above the absorber pipe, as shown in FIG. 1, to direct incorrectly reflected beams of light onto the absorber pipe in a second or third reflection.

[0080] The profile of the secondary reflector 15 is shown in detail in FIG. 6b, where the position of the absorber pipe 4 is also schematically indicated. In cross-section transverse to its longitudinal extent, the secondary reflector 15 has a circular section 19 and two edge lines 20. The circular section 19 covers an angular range of less than 180°, namely about 165°. The end points 22, 22′ of the circular section 19 are schematically indicated.

[0081] Relative to the absorber pipe 4, the circular section 19 of the secondary reflector 15 is arranged above and eccentric to the longitudinal axis 21 of the absorber pipe 4. Thus, in this exemplary embodiment, the circular section 19 is not exactly concentric with the absorber pipe 4, but has a geometric center that is spaced slightly above the geometric center of the absorber pipe 4.

[0082] From the end points 22, 22′ of the circle section 19, the edge lines 20 extend outward at an angle of about 10° to the connecting line of the corner points 22, 22′. Thus, the edge lines 20 do not run radially outward, i.e., their geometric extension meets neither the geometric center of the circular section 19, nor that of the absorber pipe 4. This design of the secondary reflector 15 has proved to be particularly efficient.

[0083] The diameter of the circular section 19 is about 3.5 times the diameter of the absorber pipe 4, and the edge lines 20 have a length from the end points 22, 22′ which corresponds approximately to the diameter of the absorber pipe 4. In the specific exemplary embodiment, the absorber pipe 4 has a diameter of about 70 mm.

[0084] FIGS. 7a-7b show a schematic three-dimensional representation and a side view, respectively, of a main reflector module 34 of an embodiment of a parabolic trough collector according to the invention.

[0085] The main reflector 1 is formed by lining up a plurality of those main reflector modules 34. Each main reflector module 34 comprises a plurality of substantially similar mirror plates 23, the width of which is in the range of about 70 mm.

[0086] The length of the mirror plates here is in the range of 100 cm; the entire aperture of the main reflector 1, i.e., the direct distance of the end regions 26, 26′ of the main reflector 1, is in the range of about 12 m in this exemplary embodiment.

[0087] The mirror plates 23 are flat, i.e., not curved, and are arranged on a tensioning element 24 in the form of a flexible chain. This makes the main reflector 1 flexible in its shape. On the tensioning element 24, engagement points 27 are arranged at regular intervals, which correspond to the engagement points on the support arms 3, 3′ and the base struts 36, respectively. In order to force the main reflector 1 into a parabolic shape, pulling means 25 in the form of struts are arranged on the engagement points 27 of the tensioning element 24, the struts being able to be tensioned or pulled towards the base 5.

[0088] In order to mount or dismount or clean the individual main reflector modules 34 on the holding device 2, in this exemplary embodiment of a parabolic trough collector according to the invention, inner and outer support struts for a maintenance device 16 are provided.

[0089] FIG. 8 shows a schematic three-dimensional view of a maintenance device 16, which is suspended between inner support struts 14 and outer support struts 28. In this exemplary embodiment, the inner support struts 14 are part of the (not shown) holding device 2; the outer support struts 28 are attached to the holding device 2 via cantilevers 38. The maintenance device 16 may be displaced along the inner and outer support struts and carries a main reflector module 34. Further, this figure shows an elevation 39, which serves to push the maintenance device onto the support struts and to remove it from the support struts, respectively, to avoid shadow losses.

[0090] FIG. 9a shows a schematic three-dimensional view of the absorber pipe 4. The absorber pipe 4 is divided into a plurality of parts 29, each of them being connected by a flanged joint, the flanged joint comprising two end flanges 30 and an adapter piece 31 disposed therebetween.

[0091] FIG. 9b shows the detail A, which is indicated in FIG. 9a, in a sectional view. The two parts 29 of the absorber pipe 4 have frontal end flanges 30, which are screwed together via an adapter piece 31 disposed therebetween.

[0092] The adapter piece 31 ensures that the end flanges 30 can be tightly connected even if there is a slight play or inaccuracies in the assembly. Furthermore, the adapter piece 31 comprises connecting means 40, which are in flexible connection with an absorber pipe holder 37. FIGS. 9c-9d show a schematic plan view of the adapter piece 31 and the end flange 30. The adapter piece 31 has an opening 32 for the passage of the heat transfer medium and four segment-shaped elongated holes 33 arranged around the opening 32 for flexibly connecting the end flanges 30. The opening 32 of the end flange 30 carrying the medium is aligned with the opening 32 of the adapter piece 31 arranged therebetween. The end flange 30 comprises eight circularly arranged bores, which are arranged in such a way that they are substantially covered by the elongated holes 33 of the adapter piece 31. Thus, even if the end flanges 30 are twisted relative to each other, a firm connection can be established. The elongated holes 33 extend over an angular range of about 75° each. Further, the adapter piece 31 has connecting means 40 in the form of bores for receiving pins or bolts.

[0093] FIG. 9e shows a schematic three-dimensional view of the absorber pipe holder 37. The latter is designed as a vertical support strut and has a frontal mounting plate 41. On the mounting plate 41, there are elongated holes 42 which run in the direction of the absorber pipe 4. When assembling the absorber pipe 4, the adapter pieces 31 can be mounted on the mounting plate 41 via the connecting means 40. In doing so, the adapter pieces 31 remain movable relative to the mounting plate 41 in the axial direction of the absorber pipe 4, for example by inserting bolts or pins into the elongated holes 42 and the connecting means 40. Thus, the absorber pipe holders 37 support the load of the absorber pipe 4, but at the same time allow axial movement of the absorber pipe 4 by thermal expansion during operation.

[0094] FIG. 10a shows a schematic top view of a main reflector module 34 of a parabolic trough collector according to the invention. The main reflector module 34 extends in the aperture direction (x-direction) from the schematically shown focal line 34 (x=0) of the parabolic trough collector outward to the support arms (not shown). A second main reflector module 34, which is not shown, extends outward in the opposite direction. In this exemplary embodiment, the aperture of the main reflector 1 is about 12 m so that the illustrated main reflector module 34 has a length of about 6 m. In this design, the main reflector module 34 is formed by a series of flexibly arranged mirror plates 23 of equal thickness. The extension of the mirror plates 23 in the x-direction is about 70 mm in each case.

[0095] The mirror plates 23 are of equal width but not equal length, but taper outwardly from the focal line 34. As a result, the width b(x) of the main reflector module 34 is not constant along the aperture, but decreases continuously from the focal line 43 to the support arms 3, 3′. The width b(x) is schematically shown in the left diagram of FIG. 10a. In the area of the focal line, the main reflector module 34 has a width of about 1.65 m. In the area of the support arms, the main reflector module 34 has a width of about 1.2 m. When the main reflector modules 34 are suspended freely between the support arms 3, 3′, they assume a parabolic shape due to their variable weight distribution. In the area of the support arms 3, 3′, in this embodiment, gaps are formed between the main reflector modules 34.

[0096] FIG. 10b shows a schematic top view of a main reflector module 34 of a parabolic trough collector according to the invention. As in the exemplary embodiment of FIG. 10a, the main reflector module 34 extends in the aperture direction (x-direction) from the schematically shown focal line 34 (x=0) of the parabolic trough collector outward to the support arms 3, 3′ (not shown). In this design, the main reflector module 34 is formed by a series of flexibly arranged mirror plates 23 of equal thickness. The extension of the mirror plates 23 in the x-direction is about 70 mm in each case.

[0097] In this embodiment, the mirror plates 23 are of the same length, so that in particular in the area of the support arms 3, 3′, no gap is formed. To achieve the desired parabolic shape of the main reflector modules 34, specially cut compensating elements 44 made of steel sheet are arranged on the underside of the main reflector modules 34. The width of the compensating elements 44 is not constant along the aperture, but decreases continuously from the focal line 43 to the support arms 3, 3′. The width b(x) of the compensating elements 44 is schematically shown in the left diagram of FIG. 10b. In the area of the focal line, the compensating elements 44 have a width of about 1.65 m. In the area of the support arms 3, 3′, the compensating elements 44 have a width of about 0.5 m. When the main reflector modules 34 are suspended freely between the support arms 3, 3′, they assume a parabolic shape due to the weight distribution of the compensating elements 44.

[0098] The exemplary embodiments according to FIG. 10a and FIG. 10b are based on the materials glass and glass and steel sheet, respectively, where the density of the steel sheet is about 7850 kg/m.sup.3, the density of glass is about 2500 kg/m.sup.3, the thickness of the steel sheet is about 1 mm, and the thickness of glass is about 4 mm.

[0099] The invention is not limited to the described exemplary embodiments, but rather comprises all parabolic trough collectors in the scope of the following patent claims.

LIST OF REFERENCE SIGNS

[0100] 1 Main reflector [0101] 2 Holding device [0102] 3, 3′ Support arm [0103] 4 Absorber pipe [0104] 5 Base [0105] 6 Vertical axis [0106] 7, 7′ Support circle [0107] 8 Roller [0108] 9 Photovoltaic element [0109] 10 End reflector [0110] 11 Supply conduit [0111] 12 Discharge conduit [0112] 13 Opening [0113] 14, 14′ Inner support strut [0114] 15 Secondary reflector [0115] 16 Maintenance device [0116] 17 First rotating joint [0117] 18 Second rotating joint [0118] 19 Circular section [0119] 20 Edge line [0120] 21 Longitudinal axis [0121] 22, 22′ Corner point of the circular section [0122] 23 Mirror plate [0123] 24 Tensioning element [0124] 25 Pulling means [0125] 26, 26′ End region of the main reflector [0126] 27 Engagement point [0127] 28 Outer support strut [0128] 29 Part of the absorber pipe [0129] 30 End flange [0130] 31 Adapter piece [0131] 32 Opening [0132] 33 Elongated hole [0133] 34 Main reflector module [0134] 35 Base recess [0135] 36 Base strut [0136] 37 Absorber pipe holder [0137] 38 Cantilever [0138] 39 Elevation [0139] 40 Connecting means [0140] 41 Mounting plate [0141] 42 Elongated hole [0142] 43 Focal line [0143] 44 Compensating element