Inflatable Solar Collector

Abstract

The invention relates to an inflatable solar collector (1) comprising an at least partially transparent sleeve divided at least into two chambers (3, 4) which are separated by a reflector membrane (5) reflecting on one side and which can respectively receive a gas, and at least one absorber (6) arranged opposite the reflective side of each reflector membrane (5). The sleeve is a cylindrical tube (2) and each reflector membrane (5) extends along the length thereof. The absorber(s) (6) is/are arranged along at least one focus line extending along the length thereof. Fillable ballast chambers (10) can be provided beneath the reflector membrane (5). Anchoring strips (12) are used for anchoring and bearing rolls (13) for support.

Description

RELATED APPLICATIONS

This application claims the priorities of Austrian Patent Applications Nos. AT 505,075 B1 and AT 504,916 B1 and of PCT Application No. PCT/AT2008/000177, the disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to an inflatable solar collector with an at least partially transparent sleeve divided into at least two chambers which are separated by a reflector membrane that is reflective on one side, and which can be independently acted on by a gas, and has at least one absorber that is oppositely situated from the reflective side of each reflector membrane.

Such a spherical inflatable solar collector, which may be used for terrestrial energy production, has become known from a research report. All solar collectors of this type are based on the principle that solar radiation is bundled by the reflector membrane and directed to the absorber, which converts the solar radiation into energy. As the result of differing pressure impingement on the chambers, the reflector membrane is curved in such a way that the solar rays are always focused on the absorber. Tubes, photovoltaic elements, etc. through which media flow may be used as absorbers. However, the spherical shape is disadvantageous for these solar collectors, since manufacturing it is complex, and complicated biaxial tracking is necessary. Use as spherical heliostats represents a further disadvantage, since due to the shading problem caused by solar tower power plants it is not possible to position such solar collectors relatively closely together. Therefore, the area yield for energy production is not optimal.

SUMMARY OF THE INVENTION

It is an object of the invention to eliminate the above-mentioned disadvantages, i.e. to simplify the manufacture and the tracking, and to increase the area yield for energy production.

This object is achieved according to the invention using an inflatable solar collector of the aforementioned type, by the fact that the sleeve is designed as a cylindrical tube, and each reflector membrane extends over the length thereof. The absorber(s) is/are situated along at least one focus line extending over the length of the tube.

The cylindrical shape of the solar collector according to the invention allows such collectors to be positioned closely next to one another, thereby maximizing the area yield for energy production. Accordingly, each reflector membrane extends over the entire length of the solar collector. In such a cylindrical tube it is in fact possible to provide multiple reflector membranes, which cooperate either with a single absorber or with absorbers that are individually assigned to them. These absorbers are situated on at least one focus line extending in the longitudinal direction of the tube. The feeding gas line connections to the individual chambers as well as the absorber connections to the further energy utilization equipment correspond to the prior art.

One preferred embodiment of the inflatable solar collector according to the invention is characterized in that wires or the like are stretched at defined intervals on the side of each reflector membrane opposite its reflective side. The wires extend transverse to the longitudinal extension of the tube, and each absorber is effectively situated at the center between two wires. As a result of this design, due to the fact that a lower pressure is generated on the side of the reflector membrane opposite the reflective side than on the top side when the solar collector is acted on by pressure, the membrane is not cylindrically curved. Since the membrane is supported by the wires, it assumes the shape of spherical dome shell surfaces arranged in a row. Accordingly, one absorber is provided above the center of each individual section, thus achieving intensive bundling of the incoming solar energy.

It is useful to provide at least one ballast chamber with a variable ballast on the side of each reflector membrane opposite its reflective side. For solar collectors according to the invention this is particularly favorable for terrestrial energy production, since on the one hand position stabilization and on the other hand alignment with the sun may be achieved by sequentially filling and/or emptying the ballast chamber(s). For inflatable solar collectors which are anchored in the ground but which project into or float in the air, it is advantageous for each ballast chamber to be divided into subchambers that extend in the longitudinal direction of the tube and which are interconnected by conduit lines. Continuous alignment with the sun is achieved by varying the filling or emptying of the subchambers.

Instead of ballast chambers which may be filled or emptied, a ballast which is adjustable in length may be accommodated on the side of each reflector membrane opposite the reflective side.

Because of their low weight and the intrinsic rigidity, the solar collector may be affixed at (at least) one end to (at least) one pole in order to keep the area therebeneath shaded and/or free of snow or rain, and/or to act as noise protection. For an inclined installation, the cross-section inclined toward the sun may be optimally adjusted for the season. (The inclination is a function of the geographical latitude.) The solar collector may also be slidably or otherwise movably mounted on a swivel pole, and in this manner may biaxially track the sun with the use of only one motor. Alternatively, instead of the pole a buoyancy gas may provide the inclined position. In this case, biaxial tracking may be achieved with the variable length of the guy wire for the collector.

The solar collector may also be set up vertically, and braced and operated in the manner of a pole. In this operating mode the solar collector is able to collect a large amount of sunlight, particularly in the winter months when low-angle incidence of solar radiation is encountered. Furthermore, snow cannot collect on the surface, only a small base surface area is required, and the back side may be used for advertising, for example. The pole could also be used for various other areas of use such as mobile wireless telephone providers, for example.

When the reflector membrane is made of a homogeneous material, its concave curvature in the state of use essentially follows a catenary or circular line. Since this is not always adequate for optimal focusing, it is advisable for each reflector membrane to be variably deflectable transverse to its length, and in the state of use to be curved in an essentially parabolic or paraboloidal shape.

For terrestrial use of the inflatable solar collector according to the invention, to allow ground anchoring on the one hand, and simple tracking of the sun's position on the other hand, it has proven advantageous to fasten preferably mutually intersecting anchoring bands at essentially diametrically opposed outer sides of the tube. When such oppositely situated, and preferably also mutually intersecting, bands are anchored to the ground at their free ends, mounting is ensured, and the solar collector can be rotated corresponding to the solar trajectory.

To facilitate the above-referenced rotary motion in solar collectors according to the invention for terrestrial applications, bearing rollers or the like may be provided on the exterior of the tube opposite each absorber.

For floating use, attachment at the two tube ends may be sufficient. The tracking may be achieved either by means of the above-mentioned ballast technique(s), or by using motors or the like mounted on pivots. Biaxial tracking is made possible by rotation of the tube about the vertical axis.

When using the inflatable solar collector according to the invention in the air, it is advantageous for the tube to be filled with a buoyancy gas. In this case the solar collector may be floated above the ground without additional auxiliary means. To allow a solar collector filled in such a manner with buoyancy gas to track the solar position in each case, it has proven advantageous to embed in the tube at least one conductor loop which is connected to an electrical power source. By use of such a conductor loop, i.e. multiple windings together with a coil, a magnetic field may be generated which allows positioning of the solar collector by interaction with the earth's magnetic field.

The invention is explained in greater detail below with reference to two exemplary embodiments schematically illustrated in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view that shows a first embodiment of the solar collector of the present invention; and

FIG. 2 is a perspective view that shows a second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, the inflatable solar collector 1 has a cylindrical tube 2 as a sleeve. The tube is transparent, at least above a reflector membrane 5 which divides the tube 2 into two chambers 3, 4. In the illustrated example, the reflector membrane 5 is reflective on the top, upwardly facing side and extends essentially diametrically across the tube over the entire length of tube 2. An elongated absorber 6 is situated above the reflector membrane 5, approximately in the region of the lateral surface of the tube 2. This may be, for example, a pipe through which media flow. The chambers 3, 4 and the absorber 6 are connected to corresponding connecting lines 7, 8, 9. Two ballast chambers 10 are situated below the reflector membrane, and may be filled or emptied through lines 11 as needed. As shown in FIG. 1, the ballast chambers may be further divided into subchambers 18 which are connected via lines. Anchoring bands 12 are fastened at diametrically opposed outer sides of the tube 2 and, as shown, they intersect each other. These bands may be used to fasten the inflatable solar collector according to the invention to the ground; a rotary motion about the axis of the cylindrical tube 2 is still possible. Bearing rollers 13 are also provided for supporting the inflatable solar collector 1 according to the invention.

When the inflatable solar collector according to the invention is used for terrestrial energy production, the solar collector is mounted on the ground in a favorable position with respect to the solar trajectory with the anchoring bands 12, and tracks the solar trajectory with the help of the ballast chambers 10 and with support from the bearing rollers 13. The emitted solar radiation is reflected by the reflector membrane 5 and is focused on the absorber 6. As a result, the medium flowing therein undergoes intense heating and can be subsequently utilized for energy production.

Instead of a single reflector membrane 5 and the two chambers 3, 4 thus formed, two or more reflector membranes may by accommodated. In each case, in the state of use the chamber must be filled with less pressure than the chamber thereabove to achieve the desired curvature of the reflector membrane. If a curvature of the reflector membrane 5 is desired which most closely approximates a parabolic shape, the deflectability of the reflector membrane transverse to the longitudinal extension is different.

FIG. 2 shows an inflatable solar collector 14. In FIG. 2, identical features are denoted by the same reference numerals as in FIG. 1. In contrast to FIG. 1, in FIG. 2 wires or the like 15 are stretched at defined intervals in the transverse direction of the tube and below the reflector membrane 5. In the state of use of the solar collector 14, the reflector membrane 5 does not have a mere cylindrical curvature as illustrated in FIG. 1, but instead has an individual, approximately spherical or paraboloidal dome shell curvature. To avoid the formation of creases, etc., the reflector membrane between the stretched wires may have a convex curvature at the borders. Suitable gussets may also be provided. Accordingly, separate absorbers 16 are situated on a common focus line, approximately at the center above these individual sections; these may be photovoltaic elements, for example. Instead of the finable ballast chambers 10, a ballast 17 of adjustable length is arranged below the reflector membrane 5 which performs the same functions as ballast chambers 10. All the other features used for anchoring purposes may likewise be provided, but for the sake of simplicity are not shown in FIG. 2. The operating principle of the solar collector 14 corresponds to that of the solar collector 1, except that the focusing in each case is approximately punctiform, not linear as in FIG. 1.

Besides the illustrated embodiments for terrestrial energy production, which by means of conventional adaptations are also suitable for use as floating solar collectors, it is also possible to fill solar collectors with a buoyancy gas, allowing the solar collectors to float in the air in the manner of a dirigible. The connections and anchors necessary for this purpose are of the conventional type. For positioning, however, and in keeping with the invention, the earth's magnetic field may be utilized when a coil encloses the tube or is embedded therein which, when current passes through it, generates a magnetic field which interacts with the earth's magnetic field.

Claims

1. An inflatable solar collector comprising an at least partially transparent sleeve divided into at least two chambers which are separated by a reflector membrane that is reflective on one side, and which can be independently acted on by a gas, and comprising at least one absorber oppositely situated from the reflective side of each reflector membrane, wherein the sleeve comprises a cylindrical tube, and each reflector membrane extends in the direction of the length of the tube, and the at least one absorber is situated along at least one focus line extending in the direction of the length of the tube.

2. An inflatable solar collector according to claim 1, including wires stretched at defined intervals on a side of each reflector membrane opposite the reflective side, transverse to the longitudinal extension of the tube, and wherein each absorber is situated essentially at a center between two wires.

3. An inflatable solar collector according to claim 1, including at least one ballast chamber with a variable ballast on the side of each reflector membrane opposite the reflective side.

4. An inflatable solar collector according to claim 3, wherein each ballast chamber is divided into subchambers in the longitudinal direction of the tube which are connected by lines.

5. An inflatable solar collector according to claim 1, including a ballast which is adjustable in length positioned on the side of each reflector membrane opposite the reflective side.

6. An inflatable solar collector according to claim 1, wherein each reflector membrane is variably deflectable transverse to its longitudinal extension, and in the state of use is curved in an essentially parabolic or paraboloidal shape.

7. An inflatable solar collector according to claim 1, including mutually intersecting anchoring bands secured at essentially diametrically opposed, outer sides of the tube.

8. An inflatable solar collector according to claim 1, including bearing rollers or the like on the exterior of the tube positioned oppositely from each absorber.

9. An inflatable solar collector according to claim 1, wherein the tube is filled with a buoyancy gas.

10. An inflatable solar collector according to claim 9, including at least one conductor loop connected to a power source and embedded in the tube.