WO2010139460A2

WO2010139460A2 - Solar collector

Info

Publication number: WO2010139460A2
Application number: PCT/EP2010/003338
Authority: WO
Inventors: Uwe Kark
Original assignee: Kark Ag
Priority date: 2009-06-03
Filing date: 2010-06-02
Publication date: 2010-12-09
Also published as: WO2010139460A3; DE202009007793U1

Abstract

The invention relates to a solar collector (1) comprising a linear lens (2) for bundling solar radiation impinging on the lens (2) into a focal line (3) and an absorber device (10) extending along the focal line (3) of the lens (2). The absorber device (10) comprises a carrier profile (11) that is open to the lens (2). An absorber (20) is provided in the carrier profile (11), wherein the absorber (20) comprises on the side thereof facing the lens (2) a trough-shaped feature (21) extending along the focal line (3), and at least two flow-through channels (25) are provided parallel to the trough-shaped feature (21) for conducting a heat transfer medium. The combination of the trough-shaped feature and the at least two flow-through channels results in increased efficiency.

Description

solar collector

The invention relates to a solar collector comprising a linear lens and an absorber in the focal line of the lens.

Solar collectors are known from the prior art in which incident solar radiation is focused by linear lenses on a focus line. Along this focal line an absorber device is arranged. The bundled solar radiation impinging on the absorber heats the absorber device, which in turn emits the heat by heat transfer to a heat transfer medium flowing through the absorber device. The stored energy in the heated heat transfer medium can then be harnessed for example by means of heat exchangers.

The known absorbers have a non-optimal efficiency in the conversion of radiant energy into usable heat energy. So u.a. a part of the incoming solar radiation is reflected and not converted into heat.

Starting from the cited prior art, the invention has for its object to provide a solar collector with a linear lens and absorber, in which the efficiency of the absorber device and thus also of the entire solar collector is increased. This object is achieved by a device according to the main claim. Advantageous embodiments will be apparent from the dependent claims.

Accordingly, the invention relates to a solar collector comprising a linear lens for focusing incident on the lens solar radiation to a focus line and along the focal line of the lens extending absorber device, wherein the absorber comprises an open to the lens support profile and in the support section, an absorber is provided on its side facing the lens has a trough-shaped formation extending along the focal line and at least two flow channels for the passage of a heat transfer medium are provided parallel to the trough-shaped Ausbil- fertil.

The efficiency of the absorber is increased on the one hand by the provision of the trough-shaped formation, on the other hand by the provision of at least two flow channels.

Due to the trough-shaped configuration can be achieved that is reflected by the surface of the absorber in the trough-shaped training reflected radiation is no longer or to a lesser extent to the environment.

By appropriate design of the trough-shaped formation can namely be achieved that initially reflected solar radiation impinges a second time on the absorber. Solar radiation, which is reflected, for example, at the lowest point of the trough-shaped formation, can impinge on the absorber a second time in the region of the side wall of the trough-shaped formation. At least part of the initially reflected solar radiation can thereby be absorbed, which increases the total amount of absorbed solar radiation.

To enhance this effect, it is preferred if the trough-shaped formation has a bulbous cross-section perpendicular to the focal line. For the purposes of this invention, "bulging" means that the width of the trough-shaped formation at a point in the trough-shaped formation is greater than the width of the opening of the trough-shaped formation The opening of the trough-shaped formation preferably has a width of 20 to 40 mm, more preferably 25 to 35 mm, further preferably 30 mm. Trough-shaped design is preferably 35 to 55 mm, more preferably 40 to 50 mm, more preferably 45 mm.

In order to further increase the efficiency, it may be provided to treat the absorber in the area of the trough-shaped formation in a heat-absorbing manner. This can be done for example by applying black, good heat conducting color.

According to the invention, the efficiency of the absorber is further increased by providing at least two flow channels. Compared to a single flow channel, as used in the prior art, the provision of at least two flow channels with a constant (total) cross-sectional area provides a larger contact area between the heat transfer medium and the absorber. The heat exchange will be improved. In addition, higher flow velocities of the heat transfer medium in the flow channels can be achieved without the target temperature of the heat transfer medium, ie the temperature which the Wärmeträgermedium after passing through the absorber, would be reduced. It is a faster heat absorption achieved by the heat transfer medium.

It is particularly preferred if the flow channels each have a diameter of 4 to 10 mm, preferably 5 to 9 mm, more preferably 6 to 8 mm.

In order to ensure good heat transfer between trough-shaped formation and the flow channels, it is preferred to manufacture the absorber from the solid, wherein preferably the flow channels are then designed as bores and / or the trough-shaped design is milled.

It is preferred if the absorber is made of copper. Copper has good thermal conductivities and, due to a heat resistance or yield strength at 350 ^° C. of up to RP _O , ₂ ⁼ 240 μ / mm ^{2, is} sufficiently heat-resistant for the temperatures to be expected. In addition, an absorber made of copper is good corrosion resistant. An absorber may preferably be between 6 and 10 m long.

According to the invention, it is provided that the absorber is stored in a carrier profile. This offers the advantage that the absorber itself does not have to absorb any structural forces, but that these can be taken over by the carrier profile. This allows the absorber solely for maximum efficiency in terms of energy conversion be optimized. The carrier profile is open towards the lens, that is, on its side facing the lens, a receptacle for the absorber is provided on the carrier profile. The recording can be designed as a groove. The carrier profile may be, for example, a U-profile, the open side of which faces the lens and in which the absorber comes to rest.

So that the temperature load of the carrier profile is kept as low as possible, insulation is preferably provided between the absorber and the carrier profile. The insulation also has the consequence that less heat energy is transferred from the absorber to the carrier profile and discharged from there to the environment. Heat loss is thus prevented. The insulation favors the desired heat transfer from the absorber to the heat transfer medium.

The absorber is preferably displaceably mounted relative to the insulation and / or the carrier profile to compensate for different thermal expansions. In the course of one

Day-night cycle, the temperature of the absorber varies considerably. The absorber is therefore subject to large thermal expansion variations, which are different from those of the carrier profile and / or the insulation. By the absorber is slidably mounted, stresses due to different thermal expansions of the individual components are avoided.

For cost-effective production, it is preferred if the carrier profile is designed as an extruded aluminum carrier.

It is known that solar panels with a lens and an absorber of the sun must be tracked. Ansons- It is not ensured that the absorber is in the focus line of the lens and energy can actually be obtained.

It is possible, the solar collector is pivotally mounted about an axis in the region of the lens and the flow channels of the absorber device are connected by flexible hoses. The absorber and the lens are rotatably connected to each other. Now, if the sun moves in the course of a day, the solar collector can be tracked, so that the absorber device always remains in the focus line of the lens. Via the connection through the flexible hoses, the heat transfer medium can continue to be routed through the flow channels.

Alternatively, it is possible to non-rotatably connect the lens and the absorber and to provide at at least one end of the absorber a cover which has a hollow journal, the flow channels Ü over connecting tubes, which preferably have a heat balance arc, on the hollow bearing pin are connected. In this embodiment, the solar collector can be pivoted together with the absorber around the axis passing through the bearing pin. For this purpose, a cover with a bearing journal is preferably provided at both ends of the absorber. The axis of rotation of the solar collector then passes through both journals and the solar collector can be tracked by rotation along this axis of the sun.

To connect the flow channels is provided that the bearing pin is made hollow, and is connected by connecting pipes with the flow channels. One in the hollow The heat transfer medium introduced into the bearing journal can pass through the connection pipes into the flow channels. By virtue of the preferably provided comparable connection cover at the other end of the absorber device, the heat transfer medium can flow away. But it is also possible to divide the cavity in the journal, wherein one part of the feed, the other part serves the outflow of the heat transfer medium. The connection of the bearing pin to a supply line and / or a drain can be done by a suitable rotary connection.

It is preferable that the linear lens is a linear Fresnel lens. The heat transfer medium may preferably be heat transfer oil or steam.

The invention will now be described by way of example with reference to the accompanying drawings. Show it:

1 shows a section through a first solar collector according to the invention;

FIG. 2 shows an enlarged detail of the absorber device of the solar collector from FIG. 1; FIG.

3 shows a section through a second embodiment of a solar collector according to the invention;

4 shows an enlarged detail of the absorber device of the solar collector from FIG. 3; and 5 is a partial side sectional view of the absorber of Figure 4.

1 shows a first embodiment of an inventive solar collector 1 is shown in a sectional view. The solar collector 1 comprises a linear lens whose focal line is perpendicular to the plane of the drawing through the point 3. In Figure 1, the beam path of individual beams 9 is shown when the solar radiation perpendicular to the solar collector 1. These rays are all bundled in focus line 3. The distance between lens 2 and focus line 3 is about 1,000 mm.

The linear lens 2 is designed as a Fresnel lens. The linear lens 2 is detachably attached to a receiving frame 4. Due to the detachable attachment to the receiving frame 4, the linear lens 2 can be easily replaced if damaged.

An absorber device 10 is fixedly connected to the lens 2 via the support arms 5. The absorber device 10 runs along the focal line 3 and thus likewise extends perpendicular to the plane of the drawing. The absorber device 10 may have a length of 4 to 10 m.

The solar collector 1 is rotatably mounted about the axis 5, which is parallel to the focus line 3 in the region of the linear lens 2 and the receptacle 4 thereof. The axis 5 thus runs perpendicular to the plane of the drawing. Due to the rotatable mounting, the solar collector 1 can track the sun, so that the absorber device 10 is always along the focus line 3. FIG. 2 shows an enlarged view of the absorber device 10 from FIG. The absorber device 10 comprises a carrier profile 11 which is configured as a U-profile which is open to the linear lens 2. The carrier profile 11 is made of aluminum and may be extruded. On the outside of the carrier profile 11, connecting pieces 13 are provided, to which the carrier arms 5 can be fastened for connection to the linear lens 2 or its attachment frame 4 (see FIG.

In the support section 11 of the insulating material 12 partially surrounded absorber 20 is slidably mounted. The displaceability serves to compensate for different thermal expansions of carrier profile 11, insulating material 12 and / or absorber 20. Depending on the thermal expansion coefficient of the individual components, the displaceability between carrier profile 11 and insulating material 13 or between insulating material 12 and absorber 20 may be provided.

The absorber 20 has a trough-shaped formation 21, which is designed bulbous. This means that the width of the opening (indicated by the double arrow 22) is less than the width 23 in the interior of the trough-shaped design. The trough-shaped formation 21 extends along the focal line 3.

An exemplified by the linear lens 2 deflected sunbeam 9 'applies in the trough-shaped formation 21 on the absorber 20 and is partially absorbed there, partially reflected. The reflected beam 9 '' strikes the absorber 20 for a second time in the region of the trough-shaped formation 21 and can be at least partially absorbed there. By the If the beam 9 ', 9 "is" absorbed twice ", the overall absorption coefficient is increased and the energy conversion from radiant energy to heat energy less energy is lost due to lost radiation, which already increases the efficiency of the entire solar collector 1.

In order to further increase the degree of absorption in the region of the trough-shaped formation 21, the surface of the absorber 20 can be treated in a heat-absorbing manner in this area. For example, good heat-conducting black paint can be applied there.

In order for the radiation coming from the lens 2 to strike the absorber 20, the absorber 20 is at least in the area of the opening of the trough-shaped formation 21 free of the insulation 12. The absorber 20 is heated by the solar radiation 9.

Through the absorber 20 parallel to the focus line 3 and the trough-shaped formation 21 four flow channels 25. Each of these flow channels 25 is circular in cross-section and has a diameter of 4 to 6 mm. Heat transfer medium is passed through the flow channels 25, wherein heat is transferred from the absorber 20 to the heat transfer medium on the wall 26 of the flow channels 25. By not only providing a flow channel, unlike in the prior art, the area actively involved in the heat transfer (the wall 26 of the flow channels 25) can be increased while maintaining the overall cross section. Thus, the heat transfer is increased overall, which has a positive effect on the efficiency of the solar collector. In addition, higher currents can be reach speeds of the heat transfer medium through the flow channels 25, which also has a positive effect on the heat transfer.

The absorber 20 is made of the solid, wherein the flow channels 25 are designed as bores and the trough-shaped formation 21 is milled. The absorber 20 is made of copper.

For connecting the individual flow channels 25 to a supply line or a drain flexible hoses (not shown) are provided. Because of these flexible hoses, the pivotability of the solar collector 1 (see FIG.

FIG. 3 shows a further exemplary embodiment of a solar collector 1 according to the invention. Again, in this case, the linear lens 2 including a receiving device 4 with the absorber device 10 via rigid support arms 6 rotatably connected. The absorber device 10 extends along the focal line 3 of the linear lens 2 at a distance of about 1,000 mm. The solar collector is mounted along an axis 5, which is pivotable parallel to the focus line 3 in the region of the absorber device 10 in a range of ± 80 °.

The absorber device 10 from FIG. 3 is shown enlarged in FIG. The absorber 20 of the absorber device 10 is the same as the absorber 20 of the first exemplary embodiment (compare FIGS. 1 and 2). The same applies to the

Storage of the absorber 20 in the support section 11 and the provision of insulation 12. It is therefore made to the above statements. The carrier profile 11, the absorber 20 along with insulation 12 receives, has a substantially circular cross section with a diameter of about 180 mm. Due to this circular cross section, the carrier profile 11 is particularly torsionally rigid. In addition to the U-shaped receptacle 14 for the absorber, due to which the carrier profile 11 is opened to the lens 2 out, the carrier profile 11 distributed over the circumference T-shaped recesses 15. At these recesses 15, the support arms 6 can be attached.

FIG. 5 shows a lateral sectional view of the absorber device 10 from FIG. 4, wherein the section extends through the axis 5 and only the end region of the absorber device 10 is shown.

The absorber 10 is limited by a cover 30. The end cover 30 surrounds the absorber 10 with a collar 31 and is secured thereto with screws 32. The screws 32 may e.g. engage in the recesses 15 on the support section 11.

Furthermore, a hollow bearing pin 33 is provided on the end cover 30. Through the bearing pin 33, the axis 5, by which the entire solar collector 1 can be pivoted extends.

The flow channels 25 in the absorber 20 of the absorber device 10 are connected via connecting tubes 34 with the journal. In this case, the connecting tubes 34 have thermal compensation arcs 35, with which displacements of the absorber 20 relative to the carrier profile 11 or the end cover 30 due to thermal expansions are compensated can. By the bearing pin 33 is connected via the connecting pipes 34 with flow channels 25, the bearing pin 33 can be used to supply the heat transfer medium in the flow channels 25.

The bearing pin 33 is mounted in a bearing block 40, wherein the bearing block 40 is designed in two parts for ease of assembly. So that the solar collector 1 remains pivotable, a rotary coupling 41 must be provided with which the heat transfer medium from a supply line in the bearing pin 33 and thus the flow channels 25 can be introduced.

For automatic tracking of the solar collector 1, a toothed segment 37 is provided on the end cover 30, in which a servomotor (not shown) can engage.

At the opposite end of the absorber device 10, a similar construction with end cap 30 and higher bearing journal 33 is provided. This then serves the outflow of the heat transfer medium.

Claims

claims

1. Solar collector (1) comprising a linear lens (2) for focusing incident on the lens (2) solar radiation to a focal line (3) and along the focal line (3) of the lens (2) extended absorber device (10) in that the absorber device (10) comprises a carrier profile (11) opened to the lens (2) and in the carrier profile (11) an absorber (20) is provided, the absorber (20) being mounted on the lens (2) thereof. facing side a along the focus line (3) extending trough-shaped formation (21) and parallel to the trough-shaped formation (21) at least two flow channels (25) are provided for the passage of a heat transfer medium.

2. Solar collector according to claim 1, characterized in that the trough-shaped formation (21) has a bulbous cross-section.

3. Solar collector according to one of claims 1 or 2, characterized in that the absorber (20) in the trough-shaped formation (21) is treated to absorb heat.

4. Solar collector according to one of the preceding claims, characterized in that the flow channels (25) each have a diameter of 4 to 10 mm, preferably 5 to 9 mm, more preferably 6 to 8 mm.

5. Solar collector according to one of the preceding claims, characterized in that the absorber (20) from the Is made full, wherein preferably the flow channels (25) are designed as bores and / or the trough-shaped formation (21) is milled.

6. Solar collector according to one of the preceding claims, characterized in that the absorber (20) is made of copper.

7. Solar collector according to one of the preceding claims, characterized in that the carrier profile (11) a

U-profile is.

8. Solar collector according to one of the preceding claims, characterized in that between the carrier profile (11) and absorber (20) an insulation (12) is provided.

9. Solar collector according to one of the preceding claims, characterized in that the absorber (20) relative to the insulation (13) and / or the carrier profile (11) is displaceably mounted to compensate for different thermal expansions.

10. Solar collector according to one of the preceding claims, characterized in that the carrier profile (11) is designed as an extruded aluminum support.

11. Solar collector according to one of the preceding claims, characterized in that the solar collector (1) about an axis in the region of the lens (2) is pivotally mounted and for connecting the flow channels (25) flexible hoses are provided.

12. Solar collector according to one of claims 1 to 10, characterized in that the lens (2) relative to the absorber (20) is rotationally fixed and at least one end of the absorber device (10) is provided a cover (30) having a hollow journal (33), wherein the flow channels (25) via connecting tubes (34), which preferably have a heat balance sheet (35), are connected to the hollow bearing pin (33) and the solar collector (1) about the axis (5) through the bearing pin (33) is rotatably mounted.

13. Solar collector according to one of the preceding claims, characterized in that the linear lens (2) is a Fresnel lens.