DE3100521A1 - Hollow lamella - Google Patents

Abstract

The invention relates to a hollow lamella as a façade-lining or roof-covering element, which acts simultaneously as a sun- and/or light-ray collector. For this purpose, the upper part of the hollow lamella is formed from transparent material which is permeable to sun rays, whereas the lower part, constructed so as to be able to absorb solar radiation, has an absorption area enlarged by constructional elements and/or by physical or chemical treatment, in order to increase the sun- and light-ray-absorbing action, in particular taking into consideration the changing directions of incident light during the day.

Description

The invention relates to a hollow lamella as a facade cladding or roof covering element with an upper part made of transparent, solar radiation-permeable material, and a lower part designed to be absorbent for solar radiation as a radiation collector, with the absorbed radiation and / or ambient heat being passed through the hollow lamella led heat transfer medium is released.

This known hollow lamella with its flat absorber part can hardly make use of incident light and solar radiation.

The object of the invention is therefore to create a hollow lamella in which this obliquely incident light and solar radiation is better used for heating the heat transfer medium, but with no disadvantages for the solar energy absorption capacity with perpendicular incidence of light should, but if necessary Here, too, the ability to absorb light and solar energy is to be increased, so that overall there is an improvement in the efficiency of the hollow lamella with regard to the utilization of the light and solar radiation incident on it at every position of the sun. Furthermore, in order to increase this efficiency, the radiation properties of the transparent upper part of the hollow lamella, in particular also with regard to the inclined solar radiation, and possibly also the heat conduction and transfer properties of the absorber part, should be improved.

According to the invention, this object is achieved by the features of the characterizing part of claim 1. Further advantageous refinements of the invention emerge from the subclaims.

Within the scope of the invention, the absorption surface of the lower part of the hollow lamellas, which is enlarged for the absorption of light and solar radiation, can be achieved through structural designs of the surface of the absorbent lower part or through constructive elements that are placed on this lower part or integrated into the hollow lamella as an absorbent lower part and / or have been achieved through other physical or chemical treatments or processing that increase the surface area and lead to surface roughening, structuring or porosity.

The fact that in the hollow lamella according to the invention, the solar radiation-absorbing lower part has inclined surfaces which are aligned so that when the incidence of light is inclined, the radiation is steeper, i.e. more perpendicular to the ab- When the absorber surface hits the well-known hollow lamella with its flat absorber surface, a considerable improvement in the overall heat recovery efficiency is achieved. Although the design according to the invention of the absorbent lower part with inclined surfaces for a steep incidence of light and solar radiation initially seems to result in a disadvantage, because the solar radiation strikes the said inclined surfaces at an angle and with such an inclined incidence of the radiation the absorption rate per Area unit is less than with vertical impact, but due to the surface enlargement achieved by the inclined surface arrangement, a far greater amount of heat is obtained than with the known hollow lamella with an absorbent lower part consisting of a flat surface.

In the simplest case, at least that surface of the lower part of the hollow lamella facing the sun is provided with a sawtooth profile to form the inclined surfaces. However, the cross section of the absorbent lower part preferably has a sawtooth profile. Such a sawtooth profile can easily be formed at the same time as the hollow lamella is extruded. The flank steepness of such a sawtooth profile can be between 10 ° and 85 ° relative to the horizontal, although it should be borne in mind that with very flat sawtooth profiles, i.e. with a low flank steepness, a low radiation absorption coefficient is given for obliquely incident radiation and also For a steeply incident solar radiation, a high proportion of the radiation emitted by the absorber surfaces is reflected back to the transparent upper part without hitting the adjacent tooth flank arranged at the opposite angle. Depending on the impact and the reflectivity of the On the side of the upper part, this radiation can then optionally be reflected back again and again absorbed by the absorbent inclined surfaces of the lower part. In the event of an unfavorable angle of incidence on the underside of the upper part, this radiation reflected and / or emitted by the lower part escapes to the outside through the transparent upper part. Even at an angle of the tooth flanks of 45 ° relative to the horizontal, a relatively high proportion of the emitted radiation from the tooth flank surfaces against the transparent upper part is not reflected against the adjacent tooth flank surface. In general, however, the absorption coefficient of a black-colored plastic material is approx. 90% and with selective coating with materials known per se, such as a thin, amorphous black gold deposit or electroplated thin black chrome layers, even 94%. With a tooth flank steepness of at least 60 °, both with obliquely incident radiation and perpendicularly incident radiation, the radiation that is not absorbed and that emitted by the heated absorber surfaces is directed to the adjacent tooth flanks and from there to the base of the Tooth flanks formed funnel reflected, but it is absorbed again with each such reflection. The steeper the incidence of radiation and the greater the tooth flank steepness of the absorbing surface of the lower part, the greater the funnel effect, due to which the solar radiation is guided to the base of the funnel formed between two adjacent tooth flanks.

A similar beneficial effect arises when the profile of the absorbent lower part is made up of a multitude of other Lined up parabolic, semi-circular arcs or the like. A possible modification of the profile cross-section is that a horizontal section is provided between the saw teeth, parabolic arcs, semicircular arcs or the like. Another very advantageous embodiment of the invention is that the profile of the absorbent lower part consists of a plurality of horizontally and spaced-apart quarter-circle arcs, one end of each quarter-circle arc merging tangentially into the horizontal base part and the free end runs out in the vertical direction and wherein the free ends in the horizontal direction have a distance from one another which is slightly smaller than the radius r of the quarter-circle arc. In the case of a hollow lamella with this profile, the reflected or emitted radiation is radiated towards the adjacent quarter-circle arc and absorbed there. A hollow lamella of this type is particularly suitable for horizontal laying of the hollow lamellae as a facade cladding element.

Another possible embodiment of the absorbent lower part of the hollow lamella consists in the fact that this lower part is essentially planar and webs that are perpendicular or inclined are provided on it as surface-enlarging elements.

Another advantageous embodiment consists in that the surface enlargement of the absorption surface is achieved by honeycomb webs, for example hexagonal, triangular or diamond honeycombs or polyhedron structure surfaces, e.g. tetrahedral surfaces.

In the hollow lamella according to the invention, the inclined surfaces of the absorbent lower part with the profile cross-sections or surface configurations described above can consist either as roof prisms extending in the longitudinal direction of the hollow lamella or as pot-like depressions, with the latter preferably between the upper edges of the individual Depressions essentially horizontal web surfaces are provided, which serve the static strength of the lower part of the hollow lamella.

According to a further advantageous embodiment of the invention, a transparent intermediate part that is essentially parallel to this upper and lower part is arranged between the transparent upper part and the absorbent lower part. With this configuration, an excellent thermal insulation of the heat transfer medium-carrying channel of the hollow lamella is achieved, which channel is formed here by the intermediate part and lower part and the outer side walls. At the same time, this hollow lamella also forms good thermal insulation for the masonry or roof covered with it.

Further advantageous refinements of the hollow lamella according to the invention consist in that the transparent upper part and / or intermediate part is designed to reduce reflections on its upper side facing the sun, for example by a corrugated surface or by a corresponding coating, or that the lower sides of the transparent upper - and / or intermediate part are provided with a selectively transmitting coating, for example made of SnO [deep] 2 or the like.

According to another feature of the invention, the upper part and / or the intermediate part of the hollow lamella can be designed to be diffuse, in order in particular to use the diffuse light radiation that is present on days when the sun is not shining.

The hollow lamella can, for example, be made entirely of a transparent plastic material, the lower part then being coated with a material that absorbs solar radiation. However, this hollow lamella is preferably coextruded from a transparent plastic material for the upper part and a possibly present middle part and from a solar radiation-absorbent, preferably black plastic material for the lower part.

In a further advantageous embodiment, the upper part and any intermediate part as well as the outer side walls and the support webs between the upper, intermediate and lower part are made of a transparent plastic material, while the absorbent lower part consists of a metal plate with surface-enlarging elements , these parts being connected to one another in a fluid-tight manner, in particular this lower part being enclosed by the plastic material in the region of its passive side.

According to a further special embodiment of the hollow lamella according to the invention, the upper part, intermediate part, outer side walls and support webs are made of a transparent plastic material, while the lower part consists of a hollow box made of metal, the side of which, facing the sun, is designed to be solar radiation-absorbent, surface-enlarging devices in the above-described inventive device Senses and one inside it preferably liquid heat transfer medium flows. In this embodiment, the hollow box can be inserted in a particularly simple manner into a hollow lamella made of transparent plastic material, which is open in its lower area, preferably snapped into place between side parts which are under prestress. Since the liquid heat transfer medium flows in a prefabricated, completely closed, fluid-tight hollow box, there is no risk of leakage with this construction, which is composed of two independent parts.

According to a further special embodiment of the invention it is provided that the hollow lamella has, in addition to the at least one flow channel on the absorption side (= active side) of the lower part, a further flow channel on the side opposite this absorption side (= passive side), so that the between -schen absorber part lying in these two flow channels is cooled from both sides. This hollow lamella embodiment is particularly suitable for a gaseous heat transfer medium. To increase the degree of heat transfer efficiency between the absorber part and the heat transfer medium, overflow openings can be provided in the absorber part for the heat transfer medium to pass from the active side to the passive side and vice versa, which ensure swirling of the heat transfer medium and thus good heat transfer.

A further embodiment consists in that the flow channel on the passive side of the absorber part is preferably provided for a liquid heat transfer medium, and that the absorber part is entirely in order to improve the heat transfer between the absorber part and the heat transfer medium consists of metal or, in the case of an absorber part made of plastic, this is interspersed with materials that improve the thermal conductivity, e.g. metal dusts, grains, chips or the like or is coated with metal on the passive side and that, if necessary, on the passive side of the The absorber part is also provided with heat transfer ribs.

According to another embodiment, the hollow lamella, consisting of an upper part, a lower part and an intermediate part, is made entirely of transparent plastic, with a highly thermally conductive layer, preferably made of metal, being provided on the underside of the intermediate part Sun facing side is designed to absorb solar radiation. This can be achieved, for example, with a copper foil that is black oxidized on its active side. The particular advantage of this embodiment is that the absorption heat is only generated where it can be dissipated well to the heat transfer medium, so that no heat build-up occurs in the plastic material.

All of the hollow slats described above can be laid vertically, horizontally or diagonally when used as facade cladding, roof covering, garden fences, free-standing walls. They can be cut to any length and can be used for any gaseous or liquid heat transfer medium; they can also be mounted in such a way that they can be rotated around their longitudinal axis so that they can be tracked to the respective position of the sun, if necessary by automatic control. In this case, the tongue and groove strips must be left out. As slats that can be pivoted in this way, they can even be installed in front of window surfaces, where they only have to be placed perpendicular to the window surface if light is required, but only have to be closed if darkening and thermal insulation is desired at the same time.

The invention will now be explained in more detail using exemplary embodiments in conjunction with the attached drawings; show it:

Fig. 1 shows a cross section through a hollow lamella with the inventive trained

the absorber part;

FIG. 2 shows an oblique view of the hollow lamella according to FIG. 1;

FIGS. 3 to 14 each show a detail from the cross section through a hollow lamella,

in which the absorber part has different profiles or designs

has;

15, 16 a cross section through a hollow lamella, in which at a distance below

half of the transparent upper part is an absorber part in the form of a hollow box

is provided;

17 shows a detail from the cross section through a hollow lamella, in which on the

A flow channel is also provided on the passive side of the absorber part;

18 shows a modification of the absorber part in the case of a hollow lamella according to FIG. 17;

19, 20 show a detail from the cross section through a hollow lamella, in which the

transparent upper part is specially designed; and

21 shows a detail from the cross section through a hollow lamella, in which additional

Lich a transparent intermediate part is provided.

The hollow lamella 10 shown in cross section or in an oblique view in FIGS. 1, 2 consists of a transparent upper part 11 and an absorbent lower part 12 arranged at a distance therefrom, which has a sawtooth profile with a slope of approx. 72 ° in cross section . As can be seen from Fig. 2, such a sawtooth profile results in a large number of roof prisms 13 running in the longitudinal direction of the hollow lamella 10, the total surface area of which is much larger as an effective absorption area than in the known hollow lamella with a flat absorber part without surface-enlarging devices. The individual inclined surfaces of the roof prisms 13 now allow a steeper impingement of the radiation on the absorber surface when the incidence of light is inclined, which already leads to an increase in the absorption rate and thus to an improvement in the absorption efficiency in the case of inclined incidence of light. Surprisingly, however, a considerable improvement in the absorption efficiency is achieved even with perpendicular incidence of light, because the formation of inclined surfaces means that a much larger absorber surface is now available. For example, if the inclined surfaces are arranged at an angle of small beta = 60 ° to the horizontal, double the absorber surface is present over the base unit, as can be seen from detail A of Fig. 1. In the case of perpendicular incidence of light, in the case of the hollow lamella according to FIG. 1, an increase in radiation absorption of 1.5 times compared to a hollow lamella with a flat, absorbent lower part was measured. Otherwise, this hollow lamella 10 has a groove profile 14 on its one narrow side and a tongue profile 15 with a corrugated surface on its other narrow side, the corrugation peaks in this corrugated

When the hollow lamellas are plugged together, the surface act like sealing lips. For reasons of static strength, vertical webs 16 made of transparent material are provided between the upper and lower parts. The peculiarity of this sawtooth profile with very steep tooth flanks is that, at all possible angles of incidence of radiation, the portion of the incident radiation reflected on the inclined surfaces or the thermal radiation emitted by these inclined surfaces is not reflected back to the transparent upper part 11, but is reflected as in a funnel meanders to the top of the funnel so that all radiation is effectively absorbed without any radiation losses. The hollow lamella according to FIGS. 1, 2 is produced by coextrusion with a transparent plastic for the upper part 11 and a black-pigmented plastic for the lower part 12.

The hollow lamella 17 shown in cross section in FIG. 3 has a sawtooth profile with a slope of about 60 ° in the absorbent lower part 18. As can easily be seen, this profile has a somewhat smaller absorption area and also a somewhat poorer reflection efficiency than the lamellar profile according to FIGS. 1, 2.

The special feature of the hollow lamellar profile 19 according to FIG. 4 is that a horizontal section 24 is provided in the absorbent lower part 20 between two adjacent saw teeth with the 72 ° flanks 22, 23. The fact that the inclined surfaces are pulled apart here ensures that when radiation is very inclined, the entire inclined surface from the tip to the base of the sawtooth is irradiated and is not partially shaded by the inclined surface of the preceding sawtooth.

In FIG. 5, the profile of the lower part 25 consists of a multiplicity of parabolic arcs 26 arranged in a row. The walls of these parabolic arcs reflect both the obliquely and perpendicularly incident solar radiation to the apex 27 of the parabolas.

In FIG. 6, the profile of the lower part 28 consists of a multiplicity of semicircular arcs 29 lined up next to one another.

The profile of the lower part 30 shown in FIG. 7 consists of a multiplicity of quarter-circle arcs 31 lined up horizontally next to one another, one end of each quarter-circle arc merging tangentially into the horizontal base part 32 and the free end 33 running out in the vertical direction. The support webs 35 are transparent. According to a further embodiment, the free ends 33 can end in a transparent intermediate part 37 (shown in dashed lines), which is arranged parallel to the transparent upper part 36 and for improving the thermal insulation effect of the hollow lamella in its function as a facade or Roof cladding element.

The peculiarity of the hollow lamellar profile 40 shown in Fig. 8 is that it is made entirely of transparent plastic material, such as transparent hard PVC, polyacrylic, polystyrene or other materials used for this purpose and on the inside of the lower part 41 a solar radiation-absorbing Layer 42 is provided.

The peculiarity of the hollow lamellar profiles 45 and 50 shown in Fig. 9, 10 is that the sun radiation-absorbing lower part 46 or 51 each has parallel and spaced vertical webs 47 and 52, the height of the webs 47 being so great in FIG. 9 that several webs each form wave troughs, which increases the absorption capacity improved with inclined solar radiation. In FIG. 10, these bars 52 are all of the same height. The webs can also all be arranged at the same angle of inclination, so that they are all parallel to one another, but at an angle on the essentially horizontal lower part.

11 shows a perspective illustration of a hollow lamella 55 in which the enlarged surface in the absorbent lower part 56 consists of round, pot-like depressions. The pot-like depressions can be designed as cones or as truncated cone surfaces, cylinder surfaces, parapoloid surfaces, spherical shell surfaces or the like. As shown in FIG. 12, which shows an enlarged section of the absorbable lower part 56 according to FIG remain. Taking this fact into account, in the profiles according to FIGS. 1 to 6 (without FIG. 2) at the tapering upper ends of the profile curves 59, a horizontally running section <not readable> would have to be inserted, as shown using FIG 5 is shown in FIG.

The hollow lamellar profile 61 shown in cross section in FIG. 14a consists of transparent plastic, with a honeycomb sheet metal plate 63 made black on the sun side as the absorber part being provided on the inside of the lower part 62. can be seen, the structure of which is shown in plan view in FIGS. 14b to 14e. This structuring consists according to FIG. 14b of diamond honeycombs, according to FIG. 14c of pyramid-shaped depressions, according to FIG. 14d of hexagonal honeycomb bars and according to FIG. 14e of triangular honeycomb bars and / or tetrahedral depressions.

In the case of the hollow lamella 65 shown in cross section in FIG. 15, the concave upper part 66, the webs 67, the outer side walls 68, 69, the spring part 70 formed as a hollow profile with sealing beads 70a, the groove part 71 and the fastening flange 72 as well as the holding flanges 73 made of transparent plastic material and clamping the absorber 74. The absorber consists of a hollow box made of metal, the top side 75 of which, exposed to solar radiation, has a sawtooth profile, as already described in FIG. 1, and is designed to be absorptive with a metal-black coating. The absorber 74 can very easily be inserted into the hollow lamella 65 by the spring part 70 and the groove part 71 being bent outwards around the pivot points 76 and 77, respectively. The radiant heat absorbed by the absorber 74 is carried away by the heat transfer medium, preferably liquid, flowing into its interior. At the same time, a gaseous heat transfer medium flowing in the cavity between the transparent top part 66 and the absorbent top side 75 can also dissipate the heat generated over this top side of the absorber. The hollow lamella 65 is attached to the substrate by means of the flange 72.

The special feature of the profile cross-section of the hollow lamella 78 shown partially in FIG. 16 is that here in the upper side 79 of the absorber 80 pot-like depressions 81, as they have already been described in FIGS. 11, 12, 13, are provided. are seen.

The profile cross-section shown in detail in FIG. 17 shows a hollow lamella 82 in which an absorber part 85 is arranged at a distance from a transparent (or diffuse) upper part 83 and a lower part 84 so that the heat transfer medium can flow on both sides of the absorber part. To improve the heat exchange, overflow openings 86 are provided in the absorber part 85 for the heat transfer medium to pass from channel A to channel B and vice versa. This hollow lamella can be produced by coextrusion, a transparent plastic being used for the upper and lower part and a black-pigmented plastic being used for the absorber part 85.

If a liquid heat transfer medium flows in channel B of the hollow lamella according to FIG. 17, in order to improve the thermal conductivity of the absorber part 85, this could also be interspersed with metals or other materials that improve the thermal conductivity, for example with metal grains or powders (e.g. copper ), Graphite powder or the like.

FIG. 18 shows a modification of the absorber part in the case of a hollow lamella according to FIG. 17. In this embodiment, the entire hollow lamella 87 with the upper part 88, the central part 89 and the lower part 90 are made of transparent plastic material, the sawtooth-like central part 89 being underlaid with metal 91, which on its side facing the sun is capable of absorbing solar radiation -ge coating. In this

In the case of a copper sheet, which is black oxidized on its active side, has been used. However, it is also possible to first provide the underside of this central part 89 with a black absorbent layer and then to apply a metallic, highly thermally conductive layer to it. The special feature of this embodiment is that the radiation is converted into heat at the point where it can be passed on immediately and in the best possible way to the heat transfer medium flowing in channel B. Liquid is provided as the heat transfer medium in channel B; In addition, the channel A can also be flowed through by a gaseous heat transfer medium.

The special feature of FIGS. 19, 20 consists in a special embodiment of the upper part of the hollow lamella to reduce the radiation reflection on its outer side and / or to improve the thermal radiation reflection on its inner side. According to FIG. 19, the upper part 92 has a sawtooth-like design in cross section, while the upper part 93 according to FIG. 20 has a corrugation on its outside. On the inside of both upper parts 92 and 93, to improve the heat radiation reflection of the heat radiation emitted by the absorber, the underside of the upper part is provided with a selectively transmitting coating 94, which allows the solar radiation to penetrate, but reflects the heat radiation back onto the absorber.

The special feature of FIG. 21 consists in the arrangement of a transparent intermediate part 95 between the transparent upper part 96 and the absorbent lower part 97.

All of the special configurations shown with reference to FIGS. 19, 20, 21 can also be applied to the hollow lamellae shown in FIGS. 1 to 16.

In all of the hollow lamellas described above with reference to FIGS. 1 to 21, the radiolucent upper part and any intermediate part that may be present can be diffuse in order to enable heat to be obtained in diffuse daylight on days without sunshine.

The upper part of the hollow lamellas can be flat, concave or convex, roof prism-like, etc. in order to develop a special aesthetic effect when installed.

Claims (23)

1. Hollow lamella as a facade cladding or roof covering element with an upper part made of transparent, solar radiation-permeable material as well as a lower part designed to be absorbent for solar radiation as a radiation collector, whereby the absorbed radiation and / or ambient heat is passed through the hollow lamella Heat transfer medium is given off, characterized in that the absorbent lower part (12, 56, 63, 74) has an increased absorption surface for the solar radiation by structural elements and / or by physical or chemical treatment, and that optionally the transparent upper part (11, 92, 93) of the hollow lamella is designed to reduce reflections on its outer surface for solar radiation. 2. Hollow lamella according to claim 1, characterized in that the absorbent lower part (12) has inclined surfaces at least on its side exposed to solar radiation. 3. Hollow lamella according to claim 2, characterized in that the absorbent lower part (12) has a sawtooth profile in cross section. 4. Hollow lamella according to claim 3, characterized in that the tooth flanks of the sawtooth profile have an angle of at least 45 °, preferably at least 60 °, with respect to the horizontal. 5. Hollow lamella according to claim 2, characterized in that the profile of the absorbent lower part (25, 28) consists of a plurality of lined-up parabolic arcs (26), semicircular arcs (29) or the like. 6. Hollow lamella according to one of claims 2 to 5, characterized in that a horizontal section (20) is provided between the saw teeth, parabolic arcs, semicircular arcs or the like. 7. Hollow lamella according to claim 2, characterized in that the profile of the absorbent lower part (30) consists of a plurality of horizontally and spaced-apart quarter-circle arcs (31) with the radius r, one end of each quarter-circle arc merges tangentially into the horizontal bottom part (32), and the free end (33) runs out in the vertical direction, and wherein the free ends (33) have a distance from one another in the horizontal direction which is slightly smaller than the radius r. 8. Hollow lamella according to Claim 1, characterized in that the lower part (51) capable of absorption is essentially planar and webs (52) which are perpendicular or inclined thereon are provided as surface-enlarging elements. 9. Hollow lamella according to claim 1, characterized in that the surface enlargement of the absorption surface is achieved by honeycomb webs (63) or polyhedron structure surfaces. 10. Hollow lamella according to claim 1, characterized in that the surface enlargement in the absorbent lower part (56) consists of pot-like indentations (57). 11. Hollow lamella according to claim 10, characterized in that substantially horizontal web surfaces (58) are provided between the upper edges of the individual depressions (57). 12. Hollow lamella according to one of claims 1 to 11, characterized in that between the transparent upper part (96) and the absorbent lower part (97) a transparent intermediate part (95) which is essentially parallel to this upper and lower part is provided. 13. Hollow lamella according to one of claims 1 to 12, characterized in that the transparent upper part (92, 93) and / or intermediate part (95) is in each case designed to reduce reflections on its upper side facing the sun, in particular has a corrugation. 14. Hollow lamella according to one of claims 1 to 13, characterized in that in each case the undersides of the transparent upper part (92, 93) and / or intermediate part (95) with a selective transmitting coating (94) are provided. 15. Hollow lamella according to one of claims 1 to 14, characterized in that the upper part (11, 56, 63, 74) and / or the intermediate part (95) is diffuse-forms. 16. Hollow lamella according to one of claims 1 to 15, characterized in that it consists of transparent plastic material, wherein the lower part is coated with a solar radiation-absorbent material. 17. Hollow lamella according to one of claims 1 to 15, characterized in that it consists of a transparent plastic material for the upper part (11) and a possibly present central part (95) and of a solar radiation-absorbent, preferably black plastic material for the lower part ( 12, 56) is coextruded. 18. Hollow lamella according to one of claims 1 to 15, characterized in that the upper part (11) and a possibly present central part (95) and the support webs and the outer side walls consist of a transparent plastic material, while the absorbent lower part consists of a surface -small enlarging elements having metal plate (honeycomb sheet metal 63), and that these parts are connected to one another in a fluid-tight manner. 19. Hollow lamella according to one of claims 1 to 15, characterized in that the upper part (66) and any intermediate part and the support webs (67) and the outer side walls (68, 69) consist of a transparent plastic material, while the lower part consists of a hollow box absorber (74) made of metal, the side of which facing the sun is capable of absorbing solar radiation has surface-enlarging devices and preferably one inside liquid heat transfer medium flows. 20. Hollow lamella according to one of claims 1 to 18, characterized in that a flow channel (B) is provided on the side (= passive side) of the absorbent lower part (absorber part 85) opposite the absorption side (= active side). 21. Hollow lamella according to claim 20, characterized in that the flow channels (A, B) are provided on the active side and on the passive side of the absorber part (85) for a gaseous heat transfer medium and that, if necessary, to increase the heat transfer efficiency between absorber Upper part and heat transfer medium in the absorber part overflow openings (86) are provided for the transfer of the heat transfer medium from the active side (channel A) to the passive side (channel B) and vice versa. 22. Hollow lamella according to claim 20, characterized in that the flow channel (B) on the passive side of the absorber part (85) is preferably provided for a liquid heat transfer medium, and that to improve the heat transfer between the absorber part and the heat transfer medium, the absorber part (85) consists entirely of metal or, in the case of an absorber part made of plastic, this is interspersed with materials that improve the thermal conductivity or coated with metal (91) on the passive side is, and that if necessary, heat transfer ribs are also provided on the passive side of the absorber part. 23. Hollow lamella according to claim 20, characterized in that the upper (88), lower (90) and central (89) part is made entirely of transparent plastic, with a good thermal conductivity on the underside of the central part (89) -tende layer, preferably made of metal, is provided, which is designed to absorb solar radiation on its side facing the sun.