Method and Device for Discharging a Hydrogen Storage System in Parabolic Trough Receivers

Abstract

The present disclosure describes a method for discharging a hydrogen storage system, which is found in the annular space of a receiver tube, in particular for solar collectors, wherein the annular space is formed between an outer-lying tubular jacket and an inner-lying absorber tube of the receiver tube, and the outer-lying tubular jacket is connected via a wall to the absorber tube in a gas-tight manner. The method is hereby characterized in that an opening penetrating the tubular jacket or the wall is produced, free hydrogen in the annular space is pumped out through the opening, and the opening is subsequently sealed. The disclosure further describes a device for implementing the method.

Claims

1. A method for discharging a hydrogen storage system, which is found in the annular space of a receiver tube, wherein the annular space is formed at least by an outer-lying tubular jacket and an inner-lying absorber tube of the receiver tube, and the outer-lying tubular jacket is connected by means of a wall to the absorber tube, is hereby characterized in that an opening penetrating through the tubular jacket or the wall is produced, free hydrogen in the annular space is pumped out through the opening, and the opening is subsequently sealed again.

2. The method according to claim 1, further characterized in that the opening is produced by means of a laser drilling method.

3. The method according to claim 1, further characterized in that the opening is sealed by means of a laser welding method.

4. The method according to claim 1, further characterized in that the opening is produced by means of a laser drilling method with a laser beam diameter d.sub.L1, and the opening is sealed by means of a laser welding method with a laser beam diameter d.sub.L2, wherein the following applies: d.sub.L2>d.sub.L1.

5. The method according to claim 1, further characterized in that the opening is sealed by using a closure material.

6. The method according to claim 5, further characterized in that the additional closure material is applied to the site to be opened prior to producing the opening.

7. The method according to claim 5, further characterized in that, as closure material, a material with high hydrogen permeability is used.

8. The method according to claim 5, further characterized in that the closure material is composed of palladium or a palladium alloy, pure iron, or niobium.

9. The method according to claim 1, further characterized in that, prior to producing the opening, a process chamber is arranged at the tubular jacket and/or the wall in a gas-tight manner over the site to be opened for pumping out the hydrogen.

10. The method according to claim 1, further characterized in that the hydrogen storage system contains getter material.

11. The method according to claim 1, further characterized in that the hydrogen storage system is thermally discharged.

12. The method according to claim 11, further characterized in that the receiver tube is heated prior to pumping out and/or during the pumping out.

13. The method according to claim 1, further characterized in that the free hydrogen entering the process chamber from the annular space during the pumping out is bound by an external getter material, which is present in a tank coupled to the process chamber in a gas-tight manner.

14. The method according to claim 13, further characterized in that the external getter material is again discharged after reaching a specific degree of loading.

15. The method according to claim 13, further characterized in that the external getter material is cyclically loaded and discharged during the pumping out.

16. A device for discharging a hydrogen storage system, which is found in the annular space of a receiver tube, wherein the annular space is formed at least by an outer-lying tubular jacket and an inner-lying absorber tube of the receiver tube, and the outer-lying tubular jacket is connected by means of a wall to the absorber tube, is hereby characterized by a process chamber, means for producing an opening through the tubular jacket or the wall, means for pumping out hydrogen from the annular space, and a means for sealing the opening.

17. The device according to claim 16, further characterized in that the process chamber has at least one outlet opening for evacuating and/or pumping out the hydrogen from the process chamber and at least one through-opening for the means for producing and/or sealing the opening through the tubular jacket or the wall.

18. The device according to claim 16, further characterized in that the means for producing and/or sealing an opening through the tubular jacket or the wall are constituted by a laser system.

19. The device according to claim 16, further characterized by means for thermal discharge of the hydrogen storage system.

20. The device according to claim 19, further characterized in that the means for thermal discharge of the hydrogen storage system are constituted by a heating device arranged at the receiver tube on the outside.

21. The device according to claim 16, further characterized in that the means for pumping out the hydrogen from the annular space are constituted by a mechanical and/or chemical pumping system.

22. The device according to claim 21, further characterized in that the chemical pumping system is constituted by a getter pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0080] FIG. 1a is a first embodiment of the discharge device in cross section after producing an opening;

[0081] FIG. 1b is a first embodiment of the discharge device in lengthwise section;

[0082] FIG. 2a is a first variant of a heating device for discharging a getter present in the annular space and arranged in the wall of the receiver tube; and

[0083] FIG. 2b is a second variant of a heating device for discharging a getter present in the annular space and arranged on a getter bridge at the absorber tube.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0084] Illustrated in FIGS. 1a and 1b is a first embodiment of the discharge device 100 according to the disclosure. This device has a process chamber 101, which is arranged on a receiver tube 4, which is situated at the focal point of a parabolic trough 70. The receiver tube 4 has an absorber tube 1 and a tubular jacket 2, wherein an annular space 3 is formed between the absorber tube 1 and the tubular jacket 2. The outer-lying tubular jacket 2 is joined via a wall 5 to the absorber tube 1. The wall 5 contains a glass-metal transition element 6, which is illustrated in FIG. 1b, as well as an expansion compensating element 7.

[0085] A getter 9 is arranged on a getter bridge 10 in the annular space 3, as illustrated schematically in FIG. 1a, said getter bridge being fastened to the absorber tube 1. Usually, the getter 9 in such an embodiment is arranged on the parabolic axis P1 intersecting the focal point and on the side of the absorber tube 1 lying opposite to the parabolic trough 70.

[0086] The process chamber 101 is fastened by means of a fastening system 20 to a peripheral part of the wall 5 in the region of the glass-metal transition element 6 in a gas-tight manner. Alternatively, the process chamber can be fastened on the tubular jacket 2. The fastening system 20 is composed of a clamp 21 and a closure 22 and is arranged on the process chamber 101 such that, when the clamp 21 is tightened, a homogenous applied pressure is produced. In order to be able to attach the process chamber 101 rapidly and detachably to various receiver tubes 4 with different diameters of the tubular jacket 2 or the wall 5, the peripheral size of the clamp 21 can be variably adjusted by means of the closure 22. Alternatively to a clamp 21, it is also possible to use a rubber band, a tension strap, or a belt for fixing the process chamber 101 in place on the receiver tube 4.

[0087] In order to produce a gas-tight connection between the process chamber 101 and the receiver tube 4, a seal is attached to the corresponding contact surface of the process chamber 101. In this exemplary embodiment, the seal is formed in the shape of a seal ring 102. When the clamp 21 is tightened, the seal ring 102 and the process chamber 101 are pressed against the receiver tube 4 in such a way that a gas-tight connection is created.

[0088] The process chamber 101 has an outlet opening 103. Via a connection system, which is designed as a connection tube 105 schematically in FIG. 1b, the process chamber 101 is in fluid connection with means for evacuating and pumping out the process chamber 101 and the annular space 3 as well as with a sensor 110. Inserted between the connection tube 105 and the process chamber 101 for the purpose of mechanical decoupling is a flexible, vacuum-tight hose element 106. For this purpose, the connection tube 105 has junctions, which are indicated in FIG. 1b as flanges 120. In the exemplary embodiment presented in FIGS. 1a and 1b, the above-mentioned means for evacuating and pumping out is constituted by a vacuum pump 30 and a getter pump 50, wherein the vacuum pump 30 in FIG. 1b is connected to the connection tube 105 by means of a vacuum hose 31. The getter pump 50 is composed of a getter tank 51, which contains an external getter for the discharge process explained in the preceding description. Valves 121 enable the vacuum in the process chamber to be maintained when the vacuum pump 30 and/or the getter pump 50 are or is decoupled from the connection tube 105. The illustration of the connection system as a connection tube 105 is not to be understood as being limiting. Also conceivable are other design variants, which enable the process chamber 101 to be evacuated or the annular space 3 to be pumped out to a few millibars. For example, another combination of tube elements and flexible connections for mechanical decoupling of the process chamber 101 from the pumps (30, 50) and/or the sensor 110 can be used.

[0089] The process chamber 101 has a through-opening 104. The through-opening 104 is equipped by means of screw connection 46 with a gas-tight laser window 47 that is transparent for a laser. A laser system is arranged above the laser window 47. The laser system 40 has a laser source 41 in the form of a laser diode or solid-state laser, for example. This laser source 41 is connected by means of a light guide 42 with a laser head 43, an optical system 44, and a focusing unit 45. In addition, a protective glass 48 is attached in the process chamber 101, said protective glass being preferably rotatable and protecting the laser window against vapor deposition during producing and sealing the opening O1.

[0090] The connection tube 105 is fastened to a support system 210, which absorbs the mechanically acting forces and, together with the hose element 106, relieves the sealing of the process chamber 101 at the wall 5 or the tubular jacket 2. The support system 210 has a support base 211, to which the connection tube 105 is fastened, with a support arm 212 being arranged movably at the support base 211. The support arm is joined rigidly to the laser head 43. In this way, the laser can be brought into the position necessary for producing and sealing the opening O1 and fixed in place there.

[0091] Schematically illustrated in FIGS. 2a and 2b are different embodiments of a heating device 60, which vary depending on the position of a getter 9 present in the annular space 3.

[0092] If the getter 9, as shown in FIG. 2a, is arranged, for example, annularly at the wall 5 of the receiver tube 4, then a contact heater on the outer side of the metal wall 5 is offered. For this purpose, a heating element 61 and a housing 62, which can also have an annular design, are mounted at the wall 5. The housing 62 and the heating element 61 as well as the section of the wall 5 surrounding the getter 9 are surrounded by an insulation 63, which reduces any heat loss.

[0093] If, on the other hand, the getter 9, as illustrated in FIGS. 1a and 2b, is arranged on a getter bridge 10, which is fastened on the absorber tube 1, then a radiant heater and/or induction heater are or is especially suitable. In this case, the heating device 60′ is arranged outside of the receiver tube 4 and is aligned so that the radiation of energy is directed onto the getter 9 by means of suitable reflectors, for example. When the method according to the disclosure is carried out, the parabolic trough 70 is readily accessible in a maintenance position in the receiver tube 4—for example, in a “9 o'clock position” in relation to the illustrated position of the getter 9. Because the getter 9, as described above and as shown in FIG. 1a, is situated on the parabolic axis P1 of the parabolic trough 70, it is possible, in the maintenance position of the parabolic trough 70, for the heating device 60 and the process chamber 101 to be arranged at angular offset in cross section.

[0094] The various process steps for discharging the hydrogen storage system of a receiver tube 4 will be explained on the basis of the figures by means of an embodiment of the discharge device 100.

[0095] As can be seen in FIG. 1a, in a first step, the discharge device 100, composed of the process chamber 101, the vacuum pump 30, the laser system 40, and the getter pump 50, is arranged by means of fastening system 20 on a receiver tube 4 and, in particular, on its wall 5 or tubular jacket 2. In the process, the seal ring 102 forms preferably the sole contact between the process chamber 101 and the wall 5 or the tubular jacket 2, respectively Subsequently, the fastening system 20 is tightened, so that the process chamber 101 is pressed against the glass-metal transition element 5. If the fastening system 20 is formed by a clamp 21, for example, then the tightening takes place by adjustment of the closure 22.

[0096] Once the process chamber 101 has been placed on the tubular jacket 2 or the wall 5 in a gas-tight manner, the interior thereof is subsequently evacuated by means of vacuum pump 30 via the outlet opening 103 and the connection tube 105. This occurs until pressures of about 10.sup.−3 to 10.sup.−2 mbar prevail in the process chamber 101. As a result of this evacuation, the interior of the process chamber 101 is freed of foreign substances, which could otherwise lead to contamination of the annular space 3 during the later opening of the tubular jacket 2 or the wall 5.

[0097] Once the process chamber 101 has been evacuated, an opening O1 is produced through the wall 5 or directly through the tubular jacket 2 by means of the laser system 40. For this purpose, a laser beam produced in the laser source 41 is guided via the laser head 43 and the through-opening 104 along an axis L1 into the process chamber 101 and onto the surface of the tubular jacket 2 or the wall 5.

[0098] Once the wall 5 or the tubular jacket 2, respectively, has been drilled through by means of the laser beam, the hydrogen that is released through the opening O1 is pumped off by means of the vacuum pump 30 until a defined pressure is attained in the annular space. Alternatively, the mechanical vacuum pump 30, which was previously used for evacuation of the process chamber 101, can be separated from the process chamber 101, and a getter pump 50, attached to the process chamber 101, can be activated for pumping out the hydrogen. In order to speed up the pumping-out step, the getter material 9, arranged in the annular space 3, is heated by the heating device 60 attached to the receiver tube 4 from the outside. It is possible to commence the heating operation already prior to pumping out.

[0099] Subsequent to the pumping out, the opening O1 is again sealed. For this purpose, the laser beam is expanded by way of the optical system 44 and the focusing unit 45 until, at the focal point, it has a larger diameter than the opening O1 and no longer has the energy density to vaporize the material of the tubular jacket 2 or the wall 5, but instead merely melts said material. For sealing the opening O1, the expanded laser beam is radiated along the axis L1 onto the opening O1. The result of this is that the edges of the opening O1 soften and ultimately melt. The molten material flows into the opening O1 and seals it, as a result of which the annular space 3 and the process chamber 101 are again spatially separated from each other.

[0100] In a last step, the fastening system 20 is released, as a result of which the discharge apparatus 100 can be removed completely from the receiver tube 4.

[0101] While the present disclosure has been described with reference to one or more particular embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope thereof. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated for carrying out this disclosure.

LIST OF REFERENCE CHARACTERS

[0102] 1 absorber tube [0103] 2 tubular jacket [0104] 3 annular space [0105] 4 receiver tube [0106] 5 wall [0107] 6 glass-metal transition element [0108] 7 expansion compensating element [0109] 9 getter [0110] 10 getter bridge [0111] 20 fastening system [0112] 21 clamp [0113] 22 closure [0114] 30 vacuum pump [0115] 31 vacuum hose [0116] 40 laser system [0117] 41 laser source [0118] 42 light guide [0119] 43 laser head [0120] 44 optical system [0121] 45 focussing system [0122] 46 screw connector [0123] 47 laser window [0124] 48 protective glass [0125] 50 external getter pump [0126] 51 getter tank [0127] 60 heating device [0128] 61 heating element [0129] 62 housing [0130] 63 insulation [0131] 70 parabolic trough [0132] 100 discharge device [0133] 101 process chamber [0134] 102 seal [0135] 103 outlet opening [0136] 104 through-opening [0137] 105 connection tube [0138] 106 flexible hose element [0139] 110 sensor [0140] 120 flange [0141] 121 valve [0142] 210 support system [0143] 211 support base [0144] 212 support arm [0145] O1 opening [0146] L1 axis [0147] P1 parabolic axis