DE102006010578B3 - Solar collector to provide solar power has absorber foil consisting of graphite foil as carrier foil and heat absorbing foil - Google Patents

Abstract

The solar collector consists of an absorber and tubes in thermal contact with it through which a heat carrier passes. The absorber is in the form of an absorber foil in three layers: (1a) a functional absorbent coating layer; (1b) heat-absorbing aluminum foil; (1c) graphite carrier foil. There may be heat-absorbing foils on both sides of the graphite foil.

Description

The The invention relates to a solar collector with efficient heat transfer properties.

solar collectors are used in the field of harnessing solar thermal energy used.

in the State of the art solar collectors of various types are known. A usual Design consists in the heat transfer leading copper tubes with an absorbent area cohesively connect to. In particular, the compounds are welding and the soldering the absorber surfaces with the heat carrier leading copper tubes known. Likewise, the use of aluminum tubes is theoretical known, however, prevent the joining problems in processing a wide application of this technology.

Farther is known absorber for improving the absorption properties to be provided with a coating. This is required because Absorbers otherwise not available in areas with low availability of solar energy or only under the most unfavorable economic conditions are used. Thus, in the Usually an absorber with a coating running to a higher absorption performance to achieve and thereby work more economically.

there In some cases coating systems consisting of several layers are used applied.

The Absorbers are usually made of materials such as copper or aluminum, because of a high thermal conductivity from the absorbent surface leading to the heat transfer medium Pipes is required. The absorbers are made of plates, sheet metal, foils u. Ä. educated.

Likewise are fully flown through Double sheets known; but they could because of a variety of Do not enforce problems.

From the DE 29 30 942 A1 For example, a solar collector element is known which has a plurality of substantially parallel tubes embedded between two heat-conducting foils. Each tube has pipe connections. Such solar collector elements are connected in series. The solar collector element has two tubes embedded between two heat-conducting foils. The in the DE 29 30 942 A1 described solar collectors are mainly used as absorption elements for solar radiation. However, they can also be used as heat exchangers. For this purpose, it is sufficient to provide in the tube a fluid which is brought to a temperature which is at least 20 ° C higher than the temperature of the environment to be heated. The heat output provided by these heat exchangers is of the order of magnitude of the heat output of radiators, usually made of cast iron or sheet steel. In the case of this use of the absorption elements, it is not absolutely necessary for good functioning to provide the heat-conducting films with a matt or dark color.

adversely it is known from the constructions known in the art that these high and rising raw material prices, especially for copper, are expensive and the solar energy use by cost inefficient is.

Farther is disadvantageous that measures taken Need to become, to prevent corrosion when using aluminum. Also When using aluminum sheet as an absorber, laser welding is very important consuming; On the whole, it is disadvantageous that industrial production is based on typical cohesive metal joining techniques is fixed.

at Absorbers made of metal sheets is disadvantageous that these rigid and not flexibly react elastically to thermal expansion. In a cohesive Connection between pipe meander o. Ä. and absorber sheet is at the expected stagnation temperatures (200-220 ° C) in general not critical, because the pipe bends represent an elastic element and absorb the solder / weld connections voltages can.

Besides, have these absorbers a considerable Weight, which is generally disadvantageous.

task The invention is to provide a solar thermal collector available which is characterized by high performance and cost-effective and is easy to produce and build.

According to the invention Task solved by a solar collector, consisting of an absorber and so that thermally in contact, heat transfer leading tubes is constructed, wherein the absorber is formed from an absorber film, which composed of several layers as a composite and leading to the heat transfer medium Pipes a form-fitting Contact has.

Of the Solar collector is inventively characterized in that the absorber foil consists of a graphite foil as support film and a solar radiation absorbing film is formed.

Farther is advantageous if the solar radiation absorbing film is formed as aluminum foil and additionally one or more functional Absorption layers are provided.

Of the Solar collector receives advantageous properties with respect the heat transfer, when the absorber foil is under mechanical tension with the heat carrier Tubes is thermally contacted. According to one embodiment of the invention leading the heat transfer Tubes from the absorber foil over a wrap angle α on the pipe jacket thermally contacted.

Farther are according to an embodiment of the invention terminals with pins or rubber rods provided, which the absorber foil under mechanical tension with the heat transferring tubes contact thermally.

To the concept of the invention, the absorber film is functional a carrier layer made of graphite and a functional covering layer with absorbent Properties built. The use of graphite is done specifically as graphite foil, which has a high thermal conductivity in the surface.

By the carrier film a self-tensioning arrangement is possible, combined with mechanical Properties that enhance the heat transfer increase the fluids through the better contact properties.

A Alternative embodiment of the invention consists in the positive compression the absorber foil with the heat carrier leading Pipes by clips or the like.

A Another embodiment consists in the elastic contact pressure Webs whose rubber-elastic side lead the absorber foil to the heat transfer medium Presses pipes.

The functional separation of support and voltage function as well as absorption function allows the Combination with metal foils both as a base and / or as a cover layer. In the latter case can the metal foils very thin be. Film thicknesses between 30 μm and 100 μm are used.

alternative or cumulative is the direct coating of graphite foil with known selective layers possible. For example, here are black chrome or titanium oxynitride layers called.

alternative Process for the production of heat transfer to the copper pipes or other pipes, such as aluminum, done by mechanical methods, so pressing, clamping, terminals on Place of soldering or welding.

• • Neue Materialien und Fügeverfahren ermöglichen technische Vereinfachungen des Systems; Höhere Flexibilität der Herstellungsverfahren (z. B. im Vergleich zum Laserschweißen), Vereinfachung der Fertigung (Wegfall von Fügeverfahren wie Löten, Schweißen, US-Fügen, Laserschweißen);
• • Graphit absorbiert über einen breiten Spektralbereich und ist somit ideal selbst als absorbierende Schicht geeignet;
• • Mechanische Kontaktierung ist mechanisch einfach durch Spangen oder Stege möglich, da Graphit sehr formschlüssig ist;
• • Graphit-Folien sind langzeitstabil, wodurch kaum Ersatzinvestitionen nötig sind;
• • Einsatz auch für konzentrierende/fokussierende Anordnungen möglich, insbesondere der Einsatz in Verbindung mit Parabolrinnen, Parabolspiegeln, Fresnel-Linsen u. a. fokussierenden Komponenten. Dabei können hohe Temperaturen entstehen. Graphit ist bis 400°C an Luft beständig;
• • Einfache Montage aus vorgefertigten Komponenten möglich;
• • Neue Materialkombinationen möglich durch Verhinderung von Elektro-Korrosion durch Graphit-Zwischenlage;
• • Graphitfolie ist ökologisch unbedenklich, nicht toxisch, leicht zu entsorgen;
• • Primärenergie-Einsatz zur Herstellung ist deutlich geringer als für Metalle;
• • Umweltfreundlichkeit der Materialien und Verfahren bei der Herstellung der Absorber;
• • Kürzere Energierücklaufzeit;
• • Da keine Löt- oder Schweißverfahren eingesetzt werden, ist der Energieeinsatz für die Montage ebenfalls sehr gering.

The advantages of the invention are in particular in the following points:

• • New materials and joining techniques allow technical simplifications of the system; Higher flexibility of manufacturing processes (eg compared to laser welding), simplification of production (elimination of joining processes such as soldering, welding, US-joining, laser welding);
• • Graphite absorbs over a wide spectral range, making it ideal even as an absorbing layer;
• • Mechanical contacting is mechanically simple by means of clips or webs possible because graphite is very positive fit;
• • Graphite foils are long-term stable, which means that replacement investments are hardly necessary;
• • Use also for concentrating / focusing arrangements, in particular the use in connection with parabolic troughs, parabolic mirrors, Fresnel lenses and other focusing components. This can cause high temperatures. Graphite is stable up to 400 ° C in air;
• • Simple assembly from prefabricated components possible;
• • New material combinations possible by preventing electrocorrosion through graphite interlayer;
• • graphite foil is ecologically harmless, non-toxic, easy to dispose of;
• • Primary energy use for production is significantly lower than for metals;
• • environmental friendliness of materials and processes in the production of absorbers;
• • shorter energy payback time;
• • Since no soldering or welding processes are used, the energy input for assembly is also very low.

• • Die Graphitfolie ist preiswert, selbst wenn sie beschichtet wird;
• • Die Herstellung von Solarthermie-Modulen ist wegen der einfachen Fertigung kostengünstig, es werden nur einfache Fertigungsausrüstungen benötigt, beispielsweise ist keine kostenaufwändige Anlage zum Laserschweißen erforderlich;
• • Der geringere Energieverbrauch bei der Fertigung führt neben dem ökologischen Vorteil auch zu ökonomischen Vorteilen.

There are additional economic benefits:

• The graphite foil is inexpensive, even if it is coated;
• • The production of solar thermal modules is cost-effective because of ease of manufacture, requiring only simple manufacturing equipment, for example, no expensive laser welding equipment is required;
• • The lower energy consumption during production leads not only to the ecological advantage but also to economic advantages.

Further Details, features and advantages of the invention will become apparent the following description of embodiments with reference on the associated Drawings. Show it:

1 : a section through an absorber film according to the invention,

2 in a section through the pipe string of a solar collector, a first arrangement of an absorber film according to the invention, one side coated with solar paint graphite foil, pressed onto the pipe system,

3 in a section through the pipe string of a solar collector, a second arrangement of an absorber film according to the invention, to the tubes clamped film with selective coating up or foil pack of metal foils and graphite foils with highly absorbent and little teemittemittierender surface (selectively coated),

4 : a section of the top view 3 .

5 : the section AA according to 4 .

6 : Detail view copper tube and silicone rubber with steel core,

The absorber foil 1 consists in the execution according to 1 from three layers 1a to 1c where, for example 1a an absorbent coating on an aluminum foil 1b which is with the graphite foil 1c are connected. Absorption layers:
Layers / layer sequences: titanium oxynitride layers, anodizing, black chrome,
Compound: graphite -Al, -Cu, -Mg, -elox. al;
Alternatively, on the top and bottom of the graphite foil 1c coatings 1a or aluminum foil 1b as well as coatings 1a arranged.

The Arrangement of the pipes containing the liquid medium, the heat carrier, lead, takes place as a meander - or in Harp circuit.

• 1. direkte Anschmiegung durch Verschränkung der Rohrgeflechte, nach 2, und
• 2. Anpressung mit Spangen oder ähnlichen Elementen, gemäß 3, worunter auch Schienen oder Ähnliches fallen.
• 3. die Verklebung mit Leitkleber, so dass eine einfache stoffschlüssige Verbindung entsteht, ist als optionale Maßnahme möglich.

The absorber foil 1 is used as a band alternating over and under the tubes 2 guided and braced on the frame with a clamp. The intimate contact between film and pipe is achieved through various measures:

• 1. direct fitting by entanglement of the pipe mesh, after 2 , and
• 2. Pressing with clips or similar elements, according to 3 , which also includes rails or the like.
• 3. the bonding with conductive adhesive, so that a simple cohesive connection is formed, is possible as an optional measure.

In the execution after 2 is the absorber foil 1 between the pipes 2 braided. The margins of the film 1 are stretched in the direction of the arrow resiliently against the frame. The necessary funds and the framework were not shown in detail. In the simplest case, the margins of the film 1 each clamped between strips and tension springs stretched between the strips and the frame. The tension on the one hand ensures that the film 1 also with their bottom on the pipes 2 rests, and on the other hand, that the film 1 opposite the fixed clamped in the frame pipes 2 move laterally and can compensate for different thermal expansion.

The Advantages of the construction as an exciting pipe string are that a Expansion of the spectrum of usable materials, such as on aluminum tubes. Furthermore, there are no cohesive joining techniques between foil or sheet and tube required, making a total of inexpensive system solutions at high absorption capacity and simultaneous weight reduction through the use of aluminum instead of copper and graphite instead of aluminum sheet conserving resources be implemented. The assembly is simplified and thus cost-saving executable.

In the second embodiment according to the 3 to 5 lies the foil 1 from one side on the pipes 2 on. The foil is attached to both ends with clamps on each tube 2 attached. Each clamp has two tubes 2 comprehensive pens 3 and a clamp 4 , where the pins 3 and the clamps 4 each firmly connected. On average AA ( 5 ) is a possible arrangement to see. A kind of self-clamping is achieved when the axes of the pins 3 under the axes of the pipes 2 are arranged. With the clamps is a slipping of the film 1 prevented. The foil 1 is close to the pipes 2 at.

At the Wrap angle you have to note that a foil sheet is not can be bent arbitrarily. And a large contact area is not necessary for the transmission on the tube, how surprisingly was found.

A Clamping / pressing is only by the clip / clamp o. Ä. reached.

It is obvious to the person skilled in the art that the film 1 otherwise from the top of the pipes 2 can be pressed, for example, perpendicular to the film 1 resiliently biased strips or rails / strips with elastic intermediate layer according to the illustrations in the figures.

typical Trainings are achieved with films whose thickness in the range of 0.03-0.5 mm. The width of the film webs can here in Range from 0 to 500 mm, but also larger widths are not excluded.

The spacings, diameters and wall thicknesses of the flow-through tubes are determined from modeling calculations involving a plurality of Pa rameters, such as compressive strength, the pressure drop in the flow, the heat transfer coefficient, the kinematic and dynamic flow properties of the fluids, the heat transfer as a function of the flow velocity, and so on.

To an advantageous embodiment, for example, pipes of 8 mm-12 mm diameter with wall thicknesses of 0.4-1 mm in one Distance up to 150 mm can be used as material is aluminum tube or alternatively copper tube in use.

One another embodiment consists of a film package, the top film being a thin metal foil, z. As aluminum or copper, with a thickness of 10 microns to about 100 microns with selective coating is, a medium thicker sheet or sheet metal layer or a middle foil package from a total thickness of 100 μm up to the mm range with high lateral thermal conductivity heat transport out of the plane Ensures to the pipes, For this purpose, preferably soft annealed metal foils or sheets and / or graphite foil or sheet are used and which at Needed by a bottom sheet that may be partially broken or by a wire mesh or individual wires can be kept. These Film packages become thermal with the tubes as described above connected. In the areas between the tubes, the foil package slightly compressed be to the thermal contact between the single sheets as well to ensure different thermal expansion. This can be achieved by a material selection tailored to the application temperature the components of the film package and the attachment and / or by light pressure from below against the film package in the areas between the pipes, which stuffed through, for example relining can be done with mineral wool realized.

1

absorber film

2

Tube

3

pencils

4

clamp

Claims (8)

Solar collector comprising an absorber and tubes which are in thermal contact with one another and heat transfer mediums ( 2 ), wherein the absorber from an absorber film ( 1 ), which is lined by further foil and / or sheet metal layers, characterized in that the absorber foil ( 1 ) is formed of a graphite foil as a carrier film and a heat-absorbing film. Solar collector according to claim 1, characterized that the heat absorbent film is formed as aluminum foil and in addition a functional Has absorption layer. Solar collector according to claim 1 or 2, characterized in that the absorber foil ( 1 ) is constructed of a graphite foil as a carrier film and a heat-absorbing film arranged on the top and bottom. Solar collector according to one of claims 1 to 3, characterized in that the absorber film ( 1 ) under mechanical tension with the heat transfer-carrying tubes ( 2 ) is thermally contacted. Solar collector according to one of claims 1 to 4, characterized in that the absorber foil ( 1 ) the heat transferring tubes ( 2 ) thermally contacted via a wrap angle α on the tube jacket. Solar collector according to claim 5, characterized in that that the wrap angle α in the range from 5 ° to 180 ° trained is. Solar collector according to one of claims 1 to 6, characterized in that clamps ( 4 ) with pins ( 3 ) are provided, which the absorber film ( 1 ) under mechanical tension with the heat transfer-carrying tubes ( 2 ) contact thermally. Solar collector according to one of claims 1 to 6, characterized in that webs are provided which the absorber film ( 1 ) under mechanical tension with the heat transfer-carrying tubes ( 2 ) contact thermally.