WO2009077965A2

WO2009077965A2 - Vacuum tube solar collector

Info

Publication number: WO2009077965A2
Application number: PCT/IB2008/055290
Authority: WO
Inventors: Zvi Shtilerman
Original assignee: Activehome Ltd.
Priority date: 2007-12-14
Filing date: 2008-12-15
Publication date: 2009-06-25
Also published as: WO2009077965A3

Abstract

A vacuum tube solar collector comprises a separation device (20) for separating between hot and cold fluid. The separation device (20) comprises a vacuum tube attachment plug (22c) adapted to connect with the vacuum tubes (8) and has a hot fluid opening (24) and a cold fluid inlet opening (26). According to some embodiments, the separation device (20) includes a vacuum-tube partition (70) extending into the vacuum tubes (8).

Description

VACUUM TUBE SOLAR COLLECTOR

FIELD OF THE INVENTION

The present invention relates to solar collectors, particularly vacuum or evacuated tube solar collectors of the type wherein the inner tube is full of liquid.

BACKGROUND OF THE INVENTION

Solar collectors of the vacuum or evacuated type are known to be among the most effective solar collectors due to the excellent insulation as each tube is surrounded by a vacuum. The collector's inner tubes are typically coated with a selective coating to increase the radiation absorbed and reduce the amount of radiation emitted.

In vacuum tube solar collectors wherein the inner tube is full of liquid, when the liquid within the tubes becomes hot, its density is lowered and it rises in the tubes. Relatively cold liquid from the storage tank enters the tubes to replace the hot liquid that exits the tubes. This situation is applicable to systems wherein the storage tank is integral with the tubes and also wherein the tank is separated from the tubes. The latter system uses a singular manifold disposed at the exit of the tubes.

It is an object of the present invention to provide an improved vacuum tube solar collector system.

SUMMARY OF THE INVENTION

The present invention relates to a separation device for separating between hot and cold fluid in vacuum tubes of a vacuum-tube solar collector. The separation device can be used with a storage tank either integral with the vacuum tubes removed from (spaced apart from) a storage tank. In the case where the separation device comprises a vacuum tube attachment plug adapted to connect with the vacuum tubes and has a hot fluid outlet opening and a cold fluid inlet opening. According to some embodiments, the separation device includes a vacuum-tube partition extending into the vacuum tubes; in other embodiments the separation device includes a hot fluid outlet tube extending into an integral storage tank; and/or a small cold water tube descending into the vacuum tube.

In the case where the storage tank is remote to the vacuum tubes, the hot and cold fluid separation device is adapted to interface with hot and cold fluid manifolds that deliver hot and cold fluid, respectively to and from the storage tank, thereby allowing a so-called split system (i.e. distance between the collector tubes and the storage tank).

Another advantage of the invention is that it allows use of a forced circulation means (typically via a pump) to circulate the fluid through the tubes of the solar collector.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood upon reading of the following detailed description of non-limiting exemplary embodiments thereof, with reference to the following drawings, in which:

Fig. 1 is a side sectional view of an embodiment of a vacuum tube solar collector system comprising a device for separating hot and cold water in accordance with the present invention;

Fig. 2 is an enlarged view of area II of Fig. 1; Fig. 3 is a sectional view along line III of Fig. 2;

Fig. 4 is a side sectional view of another embodiment of the device for separating hot and cold water adapted for receiving cold water from and returning hot water to a solar storage tank that is spaced apart from the solar collector vacuum tubes in accordance with the present invention; Fig. 5 is a side sectional view of yet another embodiment of the present invention;

Fig. 6 is a side sectional view of still another embodiment of the present invention;

Fig. 7 is an enlarged view of taken along line IV of Fig. 6; and Fig. 8 is a sectional view of the partition of Fig. 6.

DESCRIPTION OF EMBODIMENTS THE INVENTION

Fig. 1 shows a solar-collector system of the present invention comprising a hot water storage tank 1 and a plurality of, typically glass, vacuum solar collector tubes 8 (only one visible due to the side view). Solar radiation is represented by arrows 12 directed toward the upper (solar or radiation receiving) side of the collector tubes 8. Each collector tube 8 comprises a vacuum jacket 5 and an inner tube 6. Inner tube 6 is disposed essentially co-axially within the vacuum jacket 5, there being vacuum there between. Within inner tube 6, water is heated and circulates back and forth to tank 1 by natural convection. Hot water exits inner tubes 6 and reenters tank 1 at arrow al. Cold water enters inner tubes 6 from tank 1 at arrow a2.

The solar collector system further comprises a separating device 20 having a stopper- like tube plug 22 with a first opening 24 and a second opening 26. According to some embodiments, a hot water outlet tube 3 is attached to, integral with or inserted in first opening 24.

In such solar collectors, there is typically a coating of radiation absorbing material on inner tubes 6 to improve absorption of the solar radiation; however, for clarity this coating it is not shown. Fig. 2 shows an enlarged view of separating device 20 of Fig. 1 (area II) however, exemplifying an embodiment wherein the device does not include a hot and cold water partition such as tube partition strip 7. This embodiment is a more basic and simple version of separating device 20, however, hot water rising in collector tube 8 is free to mix with cold water descending in the tube. In order to facilitate fixing tube plug 22 to collector tube 8, the tube plug typically comprises an annular extension 28 or other such fixing mechanism.

Fig. 3 shows a sectional view along line III of Fig. 2. First opening 24 and second opening 26 are shown as circular, which is typically practical for ease of manufacturing, strength and assembly as tubes such as hot water outlet tube 3 are most conveniently tubular in shape. However, these openings 24, 26 need not be limited to any particular shape, as long as opening 24 corresponded to the shape of hot water outlet tube 3.

Although in the embodiment shown in Fig. 1, separating device 20 comprises a tube partition strip 7 extending down into collector tube 8 for separating hot water rising in the tube from cold water descending in the tube, in other embodiments the separating device does not include such a partition strip or other form of hot and cold water partition.

Fig. 4 illustrates another embodiment of the hot and cold water separating device 20 where it is intended for use with a solar collector storage tank (not shown) that is not integral with collector tubes 8, rather wherein the storage tank is removed

(i.e. spaced apart) from the collector tubes. As such, separating device 20 comprises a hot water manifold 30 instead of hot water outlet tube 3 that receives hot water ascending from collector tubes 8 and a cold water manifold 32 that distributes relatively cold water from the storage tank to the collector tubes. According to some embodiments, there is a small cold water tube 34 that is attached to, integral with or inserted in and descending from second opening 26. Tube 34 is useful for aiding in the thermo-siphon flow.

Fig. 5 depicts a modification of the embodiment of the hot and cold water separating device 20 wherein a portion of hot water manifold 30 passes through a cold water manifold 32a. Cold water manifold 32a has the same function as cold water manifold 32 however with a different design. Cold water manifold 32a is affixed to and extends along the ends of the outer surfaces of vacuum solar collector tubes 8, typically including use of a seal 36. Fig. 6 shows an embodiment of separating device 20 of the present invention wherein there is a plug 22a that is affixed to each vacuum tube 8 at an outer surface of each tube and having annular manifold attachment members 38. In this particular embodiment, separating device 20 further comprises a partition engagement member 40 for engaging with a generally cylindrical tube partition 7a, as described in more detail with reference to Figs. 7 and 8.

Fig. 7 shows a sectional view along line IV of Fig. 6, showing cylindrical tube partition 7a disposed within inner tube 6; and Fig. 8 showing an isolated view thereof. Cylindrical tube partition 7a comprises a pair of elongated fins 14. Each cylindrical tube partition 7a forms a division between the side of each inner tube 6 that faces the sun and receives solar radiation 12 (i.e. the hot side) and the side facing away from the sun (i.e. cold side). Tube partitions 7a, in particular their fins 14, define two hemispherical annular passages 16 and 18. Passage 16 faces the solar radiation 12 and is the hot side and from which hot water exits inner tubes 6. Passage 18 faces away from the solar radiation 12, the cold side, and from which relatively cold water enters the tubes 6. Cylindrical tube partition 7a can be made of any suitable material, including a durable plastic, which tends to provide for a measure of insulation between the hot and cold sides of each water tube 6.

Furthermore, as tube partition 7a takes up volume in the inner portion of the water tubes 6, the passages 16 and 18 have a smaller cross-sectional area for water flow than tubes 6 without the partition, thereby decreasing the volume of the water in the system and increasing the velocity of the flow in the tubes, improving heat transfer.

Each cylindrical tube partition 7a extends to a point slightly above the lower end of each water tube 6, where the passages 16 and 18 meet (see Fig. 6). As such, tube partitions 7a prevent mixing of the hot and cold water in the inner tubes 6. Tube plug 22a is shaped to correspond to the top end of cylindrical tube partition 7a (although it should be understood that it could be designed to correspond to either of the partitions 7 or 7b or partitions of other designs, mutatis mutandis).

It should be understood that while the solar collector and its components have been described in terms of heating water, it can be used to heat other fluids. Furthermore, according to some preferred embodiments, the present collector is a closed system and the fluid within need not be water, rather can be a wide variety of fluids.

It should be understood that the above description is merely exemplary and that there are various embodiments of the present invention that may be devised, mutatis mutandis, and that the features described in the above-disclosed embodiments may be used separately or in any suitable combination; or the invention can be devised in accordance with embodiments not necessarily described above.

Claims

1. A separation device for separating between hot and cold fluid in vacuum tubes of a vacuum-tube solar collector, said separation device comprising a vacuum tube attachment plug adapted to connect with said vacuum tubes, said tube attachment plug having a hot fluid opening and a cold fluid inlet opening.

2. A separation device according to claim 1, further comprising a fluid tube partition extending into the vacuum tubes.

3. A separation device according to claim 2, wherein the tube partition comprises an elongated tubular insert having a closed bottom end and a pair of fins extending along the outside of said partition and defining hot and cold side passages within the vacuum tube.

4. A separation device according to claim 1, wherein the openings are adapted to engage or interface with hot- fluid and cold- fluid collector manifolds.

5. A separation device according to claim 1, wherein the cold side opening is adapted to engage a cold fluid tube that is attached to, integral with or inserted in said cold side opening, said cold fluid tube descending from said cold side opening into the vacuum tube.

6. A separation device according to claim 1, wherein the hot side opening is adapted to engage a hot fluid outlet tube extending into a storage tank, said being attached to, integral with or inserted in and ascending from said hot side opening.

7. A vacuum-tube partition for a vacuum-tube solar collector, said tube partition comprising an elongated tubular insert having a closed bottom end and a pair of fins extending along the outside of said partition and defining hot and cold side passages within the vacuum tube.

8. A vacuum solar collector tube comprising a vacuum-tube partition as defined in claim 7.

9. A solar collector system comprising: a storage tank; and a plurality of vacuum solar collector tubes, each of said collector tubes comprising a vacuum tube separation device as defined in claim 1.

10. A solar collector system comprising: a storage tank; and a plurality of vacuum solar collector tubes, each of said collector tubes comprising a vacuum-tube partition as defined in claim 7.