WO2006106139A1

WO2006106139A1 - Solar collector

Info

Publication number: WO2006106139A1
Application number: PCT/EP2006/061420
Authority: WO
Inventors: Thomas Beikircher
Original assignee: Zae Bayern Bay. Zentrum Für Angewandte Energieforschung E.V.
Priority date: 2005-04-08
Filing date: 2006-04-07
Publication date: 2006-10-12
Also published as: DE202005005631U1

Abstract

The invention relates to a solar collector with a high operational safety. Said solar collector comprises a shading unit (7), which is at least partially situated in the collector housing (1). This prevents the shading unit (7) from being attacked by gusts of wind. Preferably, the entire shading unit (7) is situated in the sealed collector housing (1). The solar collector can be assembled as one piece and there is no further assembly work required for the shading unit. The latter (7) comprises a film, which if necessary can be stretched over the front face (3a) of the absorber, thus shading the absorber (3) and preventing overheating. The film can also be configured as a continuous film.

Description

solar panel

The invention relates to a solar collector for converting the radiation energy of the sun into heat according to the preamble of claim 1.

Known solar panels are used in the context of conventional solar thermal systems for domestic hot water in the living area. Such a system usually consists of collector (s), heat transfer medium, piping system, circulation pump, heat exchanger, expansion vessel and heat storage. In the absence or low heat loss and high solar radiation (eg during a vacation period or failure of the circulation pump) such a system comes to a standstill, which leads to overheating of the system. In this case, the temperature at certain points of the system may increase (to over 200 ^° C.) such that irreversible damage to individual components occurs. This so-called standstill problem has long been known, but has become much more acute in recent years, as the solar panels used are becoming more efficient, causing them to reach higher standstill temperatures. At the same time, collector systems are being implemented as part of a targeted sustainable energy supply with higher solar coverage (in terms of total energy requirements), combined with larger collector areas. For example, with its "Solar Thermal 2000plus" program, the Federal Government explicitly promotes the construction of large thermal solar systems (from 100 m ² ) with higher working temperatures and high solar coverage of 10-30% for systems without, and 60% for systems with seasonal heat storage [O]. ,

Thermal collectors are also used to build so-called combi plants, which also provide solar thermal heat in winter. As a result of the higher solar coverage and the higher operating temperatures aimed at, such standstill and overheating situations inevitably occur in summer due to the lack of heating demand [1]. These pro- There is also a problem with other solar plant types, especially with higher operating temperatures (process heat generation and air conditioning). In the literature this material wear or material destruction is described in the following components:

1 heat exchanger by calcification [1].

2 Expansion vessel by destruction of the membrane [2].

3 Heat transfer medium by chemical degradation or pyrolysis [3,4].

4 circulating pumps through destruction of moving parts. Higher temperature resistance is associated with significantly higher costs [5].

5 pipelines and collectors by steam blows [6,7,9].

6 Thermal destruction of the thermal insulation.

The extensive literature shows the great practical importance of this problem. Their solution is a prerequisite for the dissemination of combined plants, which is currently classified by the Federal Ministry as a very effective option for the intended solar substitution of conventional energy sources, and poses a major technical challenge. are based on the drain-back method [10] and at standstill include emptying the heat carrier from the solar system with subsequent refilling, and recently in a dissertation standstill-safe interconnection and control strategies have been developed [1]. However, there is still no economically and technically satisfactory solution. How urgently the problem is considered in practice, can be seen from the fact that sometimes still the energetically senseless, nocturnal cooling of the memory to avoid overheating during the day seriously considered [2].

In addition, damage to the plant under standstill conditions is usually This is also associated with lengthy legal disputes and is in contrast to the promotion goal formulated in Solarthermie 2000plus of "further spreading of solar plants by the dismantling of legal and organizational barriers" [O].

Instead of making the individual plant components or the entire plant stationary, it has also been proposed to cool the collector itself by lowering the internal transmission for sunlight (thermotropic coating and use of transparent honeycomb insulation) [8] or interrupting the heat transfer on the absorber by mechanical lifting of the absorbing layer [13]. However, the proposed solutions seem too complex and costly. To date there is no commercial implementation.

From [16] a solar collector is known, which has a arranged on the outside of the collector Abschatteinrichtung in the form of a flap, can be reflected by means of solar radiation on the collector and by means of which the collector more or less cover and thus can shadow. The disadvantage here is that the Abschatteinrichtung is mechanically complex and wind gusts offers a large attack surface.

From [17] a solar collector is known, which has a Abschatteinrichtung arranged outside the collector in the form of a roll between two roles and developable. If necessary, the shading film is pulled over the collector. The film can not only be light-absorbing, but also light-reflecting or light-focusing. The disadvantage here is that the Abschatteinrichtung wind gusts offers a large attack surface and can be easily damaged by wind and other weather conditions.

From [18] and [19] a solar collector is known, in which above the

Collector a Abschatteinrichtung can be driven in the manner of a window roller shutter. Such a Abschatteinrichtung is mechanically complex and has a considerable weight for stability reasons. To- - A -

In addition, the shading roller shutter offers a considerable wind attack surface, especially in the semi-closed state.

In contrast, it is an object of the present invention to provide a solar collector, which offers a higher reliability.

The solution of this object is achieved by the features of claim 1.

Characterized in that the Abschatteinrichtung is at least partially disposed in the collector housing, the Abschatteinrichtung no protruding parts, which provide attack surfaces for gusts of wind. Preferably, the Abschatteinrichtung is completely disposed in the closed collector housing. Thus, the solar collector can be mounted as a part. There are no additional installation work for the Abschatteinrichtung necessary.

The arrangement of a film as a shading element in the interior of the collector housing between the collector window and absorber front side results in a simple and lightweight construction, which also has a low height claim 2 and 3.

Although the use of coated plastic films for solar energy production is well known [12]. This also applies to the film insertion in solar panels to reduce the thermal losses of the absorber, which has been patented by the company Viessmann since the 80s and commercialized [11]. Although physically very efficient, the technique has not been pursued for some years due to material problems (haze, tearing of the film). In addition, the film is optically uniform in these inventions and not provided by optically different sections for shading the absorber.

According to an advantageous embodiment of the invention according to claim 4, the activation of the Abschatteinrichtung or the introduction of the film in the space between the absorber and window by means of a preferably energy-self-sufficient - claim 28 - motor drive means takes place, as Son- commonly installed in locations that are not easily accessible. Also, a regulation is possible - claim 27 - by the Abschatteinrichtung is activated when reaching a limit temperature. In this case, the temperature is measured by a temperature sensor in the heat exchanger device or in the absorber. If the temperature falls below another limit temperature, the Abschatteinrichtung is deactivated again.

According to an advantageous embodiment according to claim 5, the film consists of at least two film sections with different optical properties. The film is wound on two opposite rollers and spans the entire absorber front. The film section, which is not inserted between the window and the absorber front side, is rolled up on one of the two rollers.

Each of the two film sections is large enough for itself to completely cover the absorber front side. This allows defined conditions to be set for the entire absorber front - Claim 6.

Due to the different optical properties of the two film sections can be avoided by shading the overheating of the absorber on the one hand and on the other hand, heat losses of the absorber can be reduced to the outside through the collector window. A first film section is permeable to solar radiation (transmittance> 80%) and its side facing the absorber front side is as far as possible not well permeable to heat or IR radiation, ie at least partially absorbing, ideally even mainly reflective. If this first film section passes through the two rollers inserted between absorber front and window heat losses of the absorber are reduced to the outside through the collector window, while high transmission for sunlight. The combination of collector window and first foil section acts like a double pane window. A second film section is for the passing through the window and on the absorber front side sunscreen is attenuating or reflective and has a transmittance of less than 20% and preferably less than 10%. This reflective effect is achieved, for example, by metallic vapor deposition of the second film section. If this second film section is retracted by means of the two rollers into the region between the absorber front side and the window, the absorber is shaded and overheating is avoided - claims 7, 8 and 9.

The advantageous embodiment of the invention according to claim 10 or 11 prevents residents feel impaired by reflections len. This is achieved in that no glare for an observer outside of the collector emanates from the film section or film section used for shading by suitable combination of optical properties such as diffuse (partial) reflection and / or (partial) absorption.

Due to the advantageous embodiments of the invention according to claims 8, 12, 12a, 13, 14, 15 or 16 heat losses of the absorber are further reduced.

The advantageous embodiment of the invention according to claim 13 saves weight and height and thus leads to monetary advantages in assembly and transport, since insulation films in comparison to conventional insulation require a lower overall height and lower weight.

The shading mechanism increases the efficiency of the collector in normal operation by reducing the thermal losses of the absorber: the introduction of the film sections suppresses the formation of convection and reduces the heat radiation between the absorber and the cover or housing rear wall. Depending on the fill gas used, the convective losses have a local minimum at a certain distance between the foil and the window and between the foil and the plate-shaped absorber. With air as the filling gas, this distance is in the range between 8 and 12 mm, and preferably at 9 mm. To further suppress the thermal losses of the absorber and transparent inert gases with thermal conductivities lower than that of air can be filled in the collector, for example, Ar, Kr, Xe, SF ₆ , UF ₆ or CO2. For these other gases as well as for other absorber geometries and operating conditions (collector inclination and temperature), corresponding values for the optimum distances according to the convection theory are calculated.

For even greater reduction of the heat radiation of the absorber, the transparent film section on the absorber side can additionally be designed as a selective covering, that is to say it has a high degree of reflection in the infrared radiation area by means of a suitable coating.

The advantageous embodiment of the invention according to claim 18 is suitable for retrofitting existing solar panels.

The entire film suspension and handling mechanism can either be completely integrated into the collector housing - claim 19 - for example via an exchangeable insertion part - claim 20 - for a possible maintenance. Or, similar to the introduction of a film into prior analog cameras, the rollers / shafts, the motor, and the control on the outside of the collector housing, e.g. under the usual in flat plate side facing, mounted and the film introduced through slots in the space between the absorber and cover - claim 18.

For ease of maintenance, it is advantageous to integrate foil, shaft / roller system, drive, control and power supply in a cassette which can be inserted into the collector as a whole and easily replaced again - claim 20.

According to the advantageous embodiment of the invention according to claim 21 and 22, the film is configured as a continuous foil and is guided over a roller / wave deflection system. The respectively not inserted between absorber and window part of the film is / is guided by deflection over rollers / waves behind the absorber between the absorber and heat insulation. in the Normal operation is thus the shading section between the absorber and the housing rear wall / insulation and thus contributes to the reduction of the back convection as well as the rear heat radiation losses.

Thus, the film does not sag at the taking place in the collector heating and the associated thermal expansion and the housing or the absorber does not touch, one or both of the rollers / shafts is provided with a clamping mechanism. For example, suitable for this purpose is a mechanism with an adapted inner spring, as can be found in a snap-on - claim 24. Alternatively, plastics can be used which contract reversibly at a higher temperature - claim 25th

A further advantageous embodiment of the invention additionally consists in the provision of several collector lengths of transparent and shading TeN- pieces on the rollers / waves or in the range of roles / waves described, whereby with decreasing mechanical and optical properties of the film section over the life of e.g. Irradiation, moisture or dust can instead easily be brought into the collector an unused piece of film with still new optical properties - claim 23.

Meanwhile, in the wake of the nanotechnology revolution, novel films are available, e.g. with the help of embedded nanoparticles - claim 35 - can be tailored for the respective application, examples of which are:

1 Merck's interference-pigmented solar flair film for reflecting the IR component of sunlight while transmitting the visible range. It is used in greenhouses as so-called agricultural foil.

2 an antireflection film from. Merck, in the sol-gel method transparency-enhancing nanoparticles are embedded.

3 Bayer's nano-doped Durethan film for highest gastightness in food packaging.

According to the advantageous embodiments of the invention according to claims 29 to 35 coated or doped plastics or metals are used as film materials in the collector according to the invention, the highly transparent, tear resistant, aging and light stable (all these properties ideally over the collector life of about 15 - 20 years) and temperature resistant (up to the selected limit temperature for the shading) and have the desired optical properties.

According to a preferred embodiment, the shadowing film of Teflon or a copolymer of ethylene and tetrafluoroethylene (ETFE), z. B. of the company. Nowoflon, constructed as a base material - claim 36. Alternatively, the film can also be made of a TPU plastic, for. B. Desmopan Fa. Bayer, or a UV-stabilized polyester film, z. As the Fa. Mitsubishi, or from an advanced polyethylene terephthalate (PET), z. B. Hostafan from the company Hoechst, be constructed as a base material - claim 37. These materials are tear-resistant, highly transparent, resistant to aging and light and therefore have the required properties.

By antifreflection coating of the window and / or shading film, the transmission increases for the sunlight and thereby occurring transmission losses of the transparent film part can be at least partially compensated - claim 38th

Thus, the solar collector according to the invention, with substantially lower technical and economic expenditure and integrated overheating protection, projects almost into the power range of evacuated flat-plate collectors. It is therefore particularly well suited for applications with higher temperatures and higher solar degrees of coverage, such as combined systems, solar air conditioning and solar process heat generation. The window is made of glass or solar permeable plastic. The solar radiation passing through the window lies in the range between 0.3 and 4.0 μm and in particular in the range between 0.4 and 2.5 μm.

The remaining subclaims relate to further advantageous embodiments of the invention.

Further features, advantages and details of the invention will become apparent from the following description of advantageous embodiments of the invention with reference to the drawing.

It shows

1 is a schematic sectional view of a first embodiment of the invention,

2 shows the configuration of the film in the first embodiment,

Fig. 3 is a detail view of the first embodiment, and

Fig. 4 is a schematic sectional view of a second embodiment of the invention with endless film, and

Fig. 5 is a schematic sectional view of a third embodiment of the invention with endless foil.

The solar collector according to the first embodiment, as shown in Figures 1 to 3, comprises a cuboid housing 1 whose large top surface of a permeable to solar radiation window 2, z. B. made of glass, is completed. Behind the window 2, an absorber 3 is arranged, which has an absorber front side 3a facing the window 2 and an absorber rear side 3b facing away from the window 2. The rectangular area of the absorber front side 3 a corresponds approximately to the area of the window 2. The absorber 3 is thermally connected to a heat exchanger device 4 in the form of heat exchanging the absorber. exchanger coils coupled in which a heat transfer medium flows. Under the absorber 3 on the absorber rear side 3b between the housing 1 and absorber 3, a heat insulation 5 is provided. Between window 2 and absorber 3, a shading device 6 is provided inside the housing 1. The Abschatteinrichtung 6 comprises a thin elastic film 7, which spans the entire absorber front 3a. In the lateral edge region, the film 7 is wound on the left and right next to the absorber 3 onto a first and a second roller 8a and 8b (see FIG. 2). The one-piece film 7 has a first film section 9 and a second film section 10. The side of the first film section 9 facing the window 2 is transparent or translucent for the solar radiation entering through the window. The side of the second film section 10 facing the window 2 is reflective in this wavelength range. The two film sections 9 and 10 are each dimensioned such that they can completely span the absorber front side 3a.

As can be seen from Fig. 3, the solar collector and the Abschatteinrichtung 6 comprises a motor drive means 11 by means of which leaves the film 7 from the first roller 8a and on the second roller 8b wind up. In order to be able to wind the film 7 in the other direction from the second roller 8b to the first roller 8a, the first roller 8a is provided with a snap mechanism in the manner of a snap-action roller. Depending on whether the absorber 3 is to be shaded or not, either the second or the first film section 9, 10 is introduced by means of the motor drive device 11 in the area between the window 2 and absorber 3, while the non-required film section 9 or 10 on a the rollers 8 is wound up. The motor drive device 11 comprises a worm gear 12 which drives the second roller 8b via a gearwheel 13. The worm gear 12 is driven by an electric motor 14. The power supply of the electric motor 14 via a photovoltaic element 15, which is arranged in the edge region of the housing 1 at the bottom of the window 2. The photovoltaic element 15 and the electric motor 14 are connected via a regulation 16 with each other. The controller 16 is also connected to a temperature sensor 17, which is thermally coupled to the absorber 3 and detects its temperature.

4 shows a second embodiment of the invention, which differs from the first embodiment in that the film 7 is formed as an endless film. The endless film 7 likewise has a first film section 9 and a second film section 10. Ie. each not located between the window 2 and absorber front side 3a film section 9 or 10 is guided by deflection over the first roller 8a on the absorber rear side 3b. In normal operation, therefore, the second film section 10 serving for the shading is located between the absorber rear side 3b and the rear wall of the housing 1 and thus contributes to reducing the back convection as well as the rear heat radiation losses. Due to the endless foil 7, a tensioning mechanism in the first roller 8a is unnecessary.

Fig. 5 shows a third embodiment of the invention, which differs from the second embodiment of Figure 4 only in terms of the design of the heat insulation on the absorber back 3b; All other components are the same as those of the second embodiment, so that a description can be omitted. The heat insulation 5 consists of one or more solid, metallically coated heat insulating films 18, which is spanned in the housing between the rear wall and located on the absorber backside 3b film portion of the continuous film 7. The use of heat insulating films 18 instead of conventional thermal insulation allows a lower height and lower weight.

The heat insulating film 18 and also the motor drive device 11 with control device 16, temperature sensor 17 and photovoltaic element 15 can also be used in the first embodiment of the invention. In all embodiments, the outside of the window 2 with a Antireflection coating be provided to increase the transmittance of the window 2.

The operation takes place in accordance with all embodiments of the invention. Exceeds the by the temperature sensor 14, z. B. in the form of a Bimetal Istreifens, absorber temperature measured at the absorber a predetermined value, the absorber front 3a is shaded in the manner of a blind temporarily by introducing the shadowing film section 10 between the window 2 and absorber 3 by means of the motor drive device 11 until the temperature of the absorber 3 falls below a predetermined value and / or heat is removed again and / or the solar radiation has decreased. When the shading device 6 is active, the transparent film section is wound on one of the two rollers 8 or, in the case of the deflection system - FIG. 4 - positioned between the absorber rear side and the rear wall of the housing 1. The regulation of the motor drive device 11 takes place by means of a control device 16, which is connected to the temperature sensor 14 mounted on the absorber 3. The temperature sensor 14 may alternatively be attached to the heat exchanger device 4 or outside of the solar collector.

During the transition to normal operation, the shading film section 10 is again wound onto one of the shaft / rollers 8, or positioned on the side of the absorber 3 facing away from the sun, and the transparent film section is inserted between the absorber 3 and the window 2.

For energy supply, instead of the photovoltaic module 15, a spacer element can be used, which uses the temperature difference between absorber and window present in the shading case. LIST OF REFERENCE NUMBERS

1 housing

2 Windows

3 absorbers

3a absorber front

3b absorber rear side

4 heat exchanger device

5 heat insulation

6 shading device

7 foil

8a first roll / shaft

8b second roller / shaft

9 first film section

10 second film section

11 motor drive device

12 worm gears

13 gear

14 electric motor

15 photovoltaic element

16 control device

17 temperature sensor

18 heat insulation films

Literature and prior art:

[O] Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, funding concept "Solarthermie2000plus", www.solarthermie2000plus.de, Internet presentation 2005 [1] K. Lustig, Exp. Investigations into the standstill behavior of solar thermal systems, dissertation, Fraunhofer Institute for Solar Energy Systems, Freiburg, 2002 ,

[2] Fink, C; Hausner R. Strategies for avoiding impermissible temperature loads on plant components in case of stagnation. In: Materials and Components in Solar Systems, Renewable Energy Consortium, 2000.

[3] Signe Wedel Eik Bezzel. Heat Transfer Fluid for Solar DHW Systems. Danish Technological Institute, 2000. [4] Hillems F .; Schrimpf H. Use of Heat Transfer Fluids in Solar Plants Considering Stagnation Conditions Ninth Symposium on Solar Thermal Energy, Staffelstein pp. 32-38. [5]: Lustig, K. Simulation of the thermal load of the solar circuit pump in standstill situations, study TOS-3-KL-0103-E02 at the Fraunhofer Institute for Solar Energy Systems, Freiburg, 2001. [6] Kimmel, O. Streicher W .; Heimrath R Measurement and analysis of causes and effects of condensation impacts during evaporation of large thermal collector fields. Final Report Project No. 7831, Anniversary Fund of the Austrian National Bank, 2001. [7] Streicher, W .; Oberleitner, W. Operating results of the largest solar plant in Austria, solar-assisted biomass district heating network Eibiswald. Ninth Symposium on Solar Thermal Energy, Staffelstein pp. 144-148, 1999.

[8] EU project "Stagnation Technologies for Thermal Solar Systems" in the Craft Joule Program, subproject "stagnation-proof transparently insulated flat plate solar collectors STATIC", 1.9.1998-31.12.2000).

[9] Streicher, W., Minimizing the Risk of Water Hammer and other Problems at the beginning of Stagnation of Solar Thermal Plants. Solar Energy, 2001. [10] Noij, J. Drain Back in Small Systems, IEA Task 26, Proceedings from

Industry Workshop, Delft 2001.

[11] Fa. Viessmann, utility model G 93 01 018.4, 1993.

[12] FRG, German Patent Office, Laid-Open Publication 29 23 251, 1980. [13]] FRG, German Patent Office, Laid-Open Publication 38 02 125 A1, 1989.

[14] FRG, German Patent Office, utility model G 81 15 159.4, 1981.

[15] FRG, German Patent Office, Offenlegungsschrift 32 17 804.2, 1983.

[16] FRG, German Patent Office, Laid-Open Publication 100 32 227 A1, 2002.

[17] FRG, German Patent Office, Patent Specification 199 24 783 C2, 2003. [18] FRG, German Patent Office, Laid-Open 10 2005 006 329 A1,

Of 2005.

[19] FRG, German Patent Office, Utility Model 298 12 457 U1, 1999.

Claims

claims

1. solar collector for converting solar radiation into heat, with a closed housing (1), in the housing (1) provided sonnenstrahlungsdurchlässigen window (2), in the housing (1) behind the window (2) arranged solar radiation absorber (3) comprising an absorber front side (3a) facing the window (2) and an absorber rear side (3b) facing away from the window (2), and a heat exchanger device (4) thermally coupled to the absorber (3) for removing the heat from the absorber Housing (1), a Abschatteinrichtung (6) by means of which the absorber (3) can be at least partially shaded, characterized in that the Abschatteinrichtung (6) at least partially in the

Housing (1) is arranged.

2. Solar collector according to claim 1, characterized in that the Abschatteinrichtung (6) comprises a film (7) between the absorber (3) and window (2) can be introduced and at least in a partial surface (10) has solar radiation damping properties.

3. Solar collector according to claim 2, characterized in that the film (7) is rolled up when the Abschatteinrichtung (6) is turned off.

4. Solar collector according to claim 2 or 3, characterized in that the film (7) by means of a motor drive device 11) via the absorber front side (3a) is movable.

5. Solar collector according to one of the preceding claims 2 to 4, characterized in that the film (7) on two opposite rollers (8) is wound and between the two rollers (8) spans the absorber front side (3a) that the film (7 ) at least a first and a second

Foil section (9, 10), in that the film sections (9, 10) have different optical properties, and that the film sections (9, 10) can be introduced alternately into the space between absorber front side (3a) and window (2) by rolling up or down from the two rollers (8) are.

6. Solar collector according to claim 5, characterized in that the at least two film sections (9, 10) are each dimensioned so dimensioned that they completely span the absorber front side (3a).

7. The solar collector as claimed in claim 5 or 6, characterized in that the first film section (9) in the wavelength range transmitted through the window (2) is transparent and / or translucent and that the second film section (10) reflects in this wavelength range and / or or absorbing.

8. Solar collector according to claim 7, characterized in that the first film section (9) on the absorber (3) side facing for the absorber (3) outgoing heat radiation is reflective and / or absorbent formed.

9. Solar collector according to one of claims 5 to 8, characterized in that the second film section (10) has a metallic coating.

10. Solar collector according to one of the preceding claims 2 to 9, characterized in that the film (7) on the window (2) facing side is at least partially designed glare-free.

11. Solar collector according to one of the preceding claims 2 to 10, characterized in that the film (7) on the said window (2) facing side is at least partially designed diffusely reflective.

12. Solar collector according to one of the preceding claims, characterized in that between the housing (1) and the absorber rear side (3b), a heat insulation (5) is provided.

13. Solar collector according to claim 12, characterized in that the heat insulation (5) consists of at least one metallic and / or metal-oxide coated and / or an IR-reflecting film (18), which between absorber rear side (3b) and housing (1) is spanned.

14. Solar collector according to claim 12 or 13, characterized in that for additional heat insulation air is introduced as filling gases in the housing (1).

15. Solar collector according to claim 14, characterized in that the distance between the introduced film (7) and window (2) and / or inserted foil (7) and absorber front side (3a) is in air as filling gas in the range between 8 and 12 mm ,

16. Solar collector according to claim 14, characterized in that for additional heat insulation inert gases are introduced with a lower thermal conductivity than air as filling gases in the housing (1).

17. Solar collector according to claim 16, characterized in that as filling gases krypton, xenon, argon SF ₆ , UF ₆ and / or CO2 are introduced.

18. Solar collector according to one of the preceding claims 5 to 17, characterized in that the two rollers outside the housing (1) are arranged and that the film (7) passes through slots the housing (1).

19. Solar collector according to one of the preceding claims 5 to 17, characterized in that the two rollers (8) in the housing

(1) are arranged.

20. Solar collector according to one of the preceding claims, characterized in that the Abschatteinrichtung (6) is designed as a replaceable module.

21. Solar collector according to one of the preceding claims 2 to 20, characterized in that the film (7) is formed as an endless foil.

22. Solar collector according to claim 21, characterized in that the non-absorber front side (3a) and window (2) arranged part of the endless foil (7) via a deflection device (8) between the housing (1) and absorber rear side (3b) is guided.

23. Solar collector according to one of the preceding claims 2 to 20, characterized in that the Abschatteinrichtung (6) contains the film (7) several times.

24. Solar collector according to one of the preceding claims 2 to 23, characterized in that the Abschatteinrichtung (8) comprises a clamping device for tensioning the film (7).

25. Solar collector according to one of the preceding claims 2 to 24, characterized in that the film (7) consists of a material which contracts when the temperature increases.

26. Solar collector according to one of the preceding claims 4 to 22, characterized in that the motor drive device (11) comprises a worm gear (12).

27. Solar collector according to one of the preceding claims, characterized in that the Abschatteinrichtung (6) comprises a control device (11, 16, 17) to the Abschatteinrichtung (6) upon reaching a certain limit temperature in the absorber (3) or in the heat exchanger device ( 4) to activate.

28. Solar collector according to one of the preceding claims, characterized in that the Abschatteinrichtung (6) an autarkic energy supply, in particular by means of a photovoltaic module (15) or a Peltier element.

29. Solar collector according to one of the preceding claims 2 to 28, characterized in that the film (7) is elastic.

30. Solar collector according to one of the preceding claims 2 to 29, characterized in that the film (7) is light-stable.

31. Solar collector according to one of the preceding claims 2 to 30, characterized in that the film (7) is resistant to aging.

32. Solar collector according to one of the preceding claims 2 to 31, characterized in that the film (7) is tear-resistant.

33. Solar collector according to one of the preceding claims 2 to 32, characterized in that the film (7) consists of plastic and / or metal.

34. Solar collector according to claim 33, characterized in that the film (7) consists of doped plastic and / or doped metal.

35. Solar collector according to one of the preceding claims 2 to 34, characterized in that the film (7) contains nanoparticles.

36. Solar collector according to one of the preceding claims 2 to 35, characterized in that the film (7) made of Teflon or a copolymer of ethylene and tetrafluoroethylene is constructed as a base material.

37. Solar collector according to one of the preceding claims 2 to 35, characterized in that the film (7) is made of a TPU Ku nststoff or a UV-stabilized polyester film or of a polyethylene terephthalate as the base material.

38. Solar collector according to one of the preceding claims 2 to 37, characterized in that the film (7) and / or the window (2) is provided with an antireflection coating to increase the transmission.