Solar-thermal collector

Abstract

A solar-thermal collector formed by an upper plastic layer facing solar rays and by a lower plastic layer not facing the solar rays, whereby between the two secured together plastic layers there is formed at least one hollow chamber for passage of a heat-transport medium. The upper plastic layer is transparent, and an inner surface of the upper plastic layer, which inner surface faces the hollow chamber, has an absorbing layer.

Description

FIELD OF THE INVENTION

[0001] The invention relates to a solar-thermal collector having a collector housing which is formed by an upper plastic layer facing solar rays and a lower plastic layer not facing the solar rays, whereby between the two plastic layers there is formed at least one hollow chamber for passage of a heat-transport medium, in particular water.

BACKGROUND OF THE INVENTION

[0002] Such a solar-thermal collector is known from the DE 196 06 293 A1. The solar-thermal collector has a collector housing which is formed of two molded plastic panels which are welded together. The two plastic panels form a hollow chamber through which water flows during the operation of the solar-thermal collector. An upper plastic panel faces the solar rays during operation. The lower plastic panel does not face the solar rays and is usually fastened to a suitable building wall. The lower plastic panel is tinted, whereas the upper plastic panel is transparent. Thus, the heat conversion of the solar rays takes place in the area of the lower, tinted plastic panel. A heat loss on the surface of the collector should in this manner be reduced.

[0003] A solar-hose collector is known from the DE 37 03 856 A1, which collector has a plastic hose. The plastic hose is transparent over a portion of its circumference by being manufactured by coextrusion out of a transparent plastic on the one side and a dark, absorbing plastic on the other side.

[0004] However, practice has shown in the case of this collector that microorganisms form and settle inside of the hollow chamber on the lower, tinted plastic panel. This can lead to an undesired contamination of the water and a formation of a putrefying substance.

[0005] The purpose of the invention is to produce a solar-thermal collector of the above-identified type, where contaminations can be avoided and which nevertheless operates efficiently.

SUMMARY OF THE INVENTION

[0006] This purpose is attained by the upper plastic layer being of a transparent design, and by providing an inner surface of the upper plastic layer, which inner surface faces the hollow chamber, with a solar ray absorbing layer.

[0007] The absorbing layer absorbs the solar rays and converts them into heat. The absorbing layer is relatively thin in design and has preferably a thickness of between 0.1 mm and 0.5 mm. According to the inventive solution, the plastic material of the upper plastic layer is oriented relative to the solar rays above the absorbing layer and serves as an insulator so that the heat converted by means of the absorbing layer can be taken along directly by the heat-transport medium. The absorbing layer is thin in comparison to the thickness of the plastic layer in order to guarantee a low heat resistance. Contaminations or deposits can also be reliably avoided. It is also possible to cover the absorbing layer on the inner side facing the hollow chamber additionally with a protective foil in order to also avoid in this manner damage to or contaminations of the absorbing layer over a long time period.

[0008] The absorbing layer is in a further development of the invention coextruded with the upper plastic layer. This is a particularly economical manufacturing method.

[0009] The absorbing layer is in a further development of the invention laminated onto the inner surface of the upper plastic layer. This is an alternative preferred solution for applying the absorbing layer onto the inner side of the upper plastic layer.

[0010] The lower plastic layer is in a further development of the invention designed at least partially ray-absorbing. The lower plastic layer is preferably tinted. Since the upper absorbing layer is relatively thin, solar rays can still penetrate through said layer, which solar rays are then additionally converted into heat at the lower plastic layer. This can further improve the efficiency of the collector.

[0011] The lower plastic layer is in a further development of the invention designed transparent. This alternative solution also results in an excellent function of the collector and involves a slightly lower manufacturing expense since the plastic does not need to be tinted. In addition, the collector housing is optically very becoming due to the transparent design of the lower plastic layer.

[0012] The upper and the lower plastic layer are welded together in a further development of the invention. The welding enables a complete sealing off of the at least one hollow chamber of the collector and represents an extremely secure and uniformly sealed connection.

[0013] The upper plastic layer is in a further development of the invention manufactured out of a different plastic material than the lower plastic layer. The upper plastic layer is preferably manufactured out of polycarbonate. Also the absorbing layer consists of a polycarbonate. The upper plastic layer has advantageously a higher temperature stability than the lower plastic layer. Polycarbonate is temperature-stable up to approximately 150° C.

[0014] The lower plastic layer can preferably be manufactured out of acrylonitrile-butadiene-styrene (ABS). ABS and polycarbonate (PC) can be welded to one another. However, ABS is significantly less expensive. Since the thermal load for the lower plastic layer is not so high, same also does not need to have as high a temperature stability as the upper plastic layer. However, ABS can be welded significantly better than PC. The lower plastic layer thus contributes significantly to the creation of a good and secure welding to the upper plastic layer. Due to the reduced temperature stability of the lower plastic layer same is less expensive, thus making it possible to keep the total manufacturing expenses of the collector housing low.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Further advantages and characteristics of the invention result from the claims. One preferred exemplary embodiment of the invention will be described hereinafter and is illustrated in the drawings, in which:

[0016] FIG. 1 is a top view of one embodiment of an inventive solar-thermal collector,

[0017] FIG. 2 is a greatly enlarged, partially cross-sectional illustration of a section II-II of the collector housing according to FIG. 1, and

[0018] FIG. 3 is a sectional view taken along the line III-III of FIG. 1.

DETAILED DESCRIPTION

[0019] A solar-thermal collector 1 according to FIGS. 1-3 corresponds with respect to its basic design to a conventional solar-thermal collector, as it is known from the DE 196 06 293 A1. The solar-thermal collector 1 has an undulating one piece upper plastic layer 1a, as shown in FIG. 3, facing rays S (FIG. 2) and a flat lower plastic layer 1b facing away from the rays S which, corresponding to the disclosure in the DE 196 06 293 A1, are molded plastic panels that are welded to one another as at 6 in an outer annular boundary area 4 as well as at each of the plural locations 7 whereat each of the undulations of the upper layer la touch the lower layer 1b along a line as shown in FIG. 3. The collector 1 has an inlet nozzle 2 for a heat-transport medium in the form of water and an outlet nozzle 3, which nozzles are connected to a suitable, not illustrated water-circulation system. Regarding the general characteristics of the solar-thermal collector, reference is additionally made to the disclosure in the DE 196 06 293 A1.

[0020] The two plastic layers 1a and 1b form a hollow chamber H and a plurality of side-by-side passageways through which water flows when the collector is in operation. The inner side of the upper plastic layer 1a, which inner side faces the hollow chamber H and the plurality of passageways, has an absorbing layer 5 which has preferably a thickness of between 0.2 mm and 0.3 mm. The absorbing layer 5 extends continuously over the inwardly facing surface of the upper layer 1a. The absorbing layer 5 is also made of plastic, in the present case of PC. The absorbing layer 5 is in the illustrated exemplary embodiment during the manufacture of the plastic panel for the plastic layer 1a coextruded with same, thus resulting already during the manufacture in a flat, integral and/or bonded connection of the absorbing layer 5 to the upper plastic layer 1a. The absorbing layer 5 converts the solar rays S entering through the transparent upper plastic layer 1a into heat and conducts or heat exchanges such heat to the passing water.

[0021] The upper plastic layer 1a acts as an insulating body for the absorbing layer 5.

[0022] The lower plastic layer 1b is manufactured in the illustrated exemplary embodiment out of a different plastic, namely out of ABS. Same can be tinted, partially transparent or also nontransparent, light or dark. Since the solar rays S are at least to a large part already converted into heat through the upper absorbing layer 5, the lower plastic layer 1b is no longer subjected to a large thermal load.

[0023] FIG. 2 schematically illustrates a welding seam 6, by means of which the upper and the lower plastic layers 1a and 1b with the absorbing layer 5 sandwiched therebetween are welded throughout and securely to one another in the outer annular boundary area 4. It is to be recognized that the absorbing layer 5 is also sandwiched between the upper layer 1a and lower layer 1b at each of the welding seams 7. The solar-thermal collector is utilized in particular on outside walls of buildings, namely in the roof area or in the facade region facing the sun, and is used in particular as a source for hot water.

Claims

1. A solar-thermal collector with a collector housing formed by an upper plastic layer facing solar rays and by a lower plastic layer not facing the solar rays, whereby between the two plastic layers there is formed at least one hollow chamber for passage of a heat-transport medium, wherein the upper plastic layer has a transparent design, and wherein an inner surface of the upper plastic layer, which inner surface faces the hollow chamber, has an absorbing layer.

2. The collector according to claim 1, wherein the absorbing layer is integral and/or bonded with the upper plastic layer.

3. The collector according to claim 1, wherein the absorbing layer is laminated onto the inner surface of the upper plastic layer.

4. The collector according to claim 1, wherein the lower plastic layer is configured at least partly ray-absorbing.

5. The collector according to claim 1, wherein the lower plastic layer is transparent.

6. The collector according to claim 1, wherein the upper and the lower plastic layers are welded to one another.

7. The collector according to claim 6, wherein the upper plastic layer is manufactured out of a different plastic material than the lower plastic layer.

8. The collector according to claim 1, wherein the heat-transport medium is water.