Abstract: A receiver system for a Fresnel solar plant is provided. The system includes an absorber tube defining a longitudinal direction and a mirror array that runs parallel to the longitudinal direction. The mirror array has a mirror-symmetrical curve profile having at least one top apex for concentrating light beams onto the absorber tube. The mirror array has ventilation holes in the region of the apex.

Abstract: An absorber tube is provided that has a metal tube and a sleeve tube, which is made of glass and encloses the metal tube such that an annular space is formed between the metal tube and the sleeve tube. The annular space is evacuated and has at least one container filled with protective gas, where the container is a solder-free pressure container.

Abstract: The radiation-selective absorber coating for absorber tubes of parabolic trough collectors includes two or more barrier layers (24a, 24b); an infrared reflective layer (21) on the barrier layers (24a, 24b); at least one cermet absorption layer (22) above the infrared reflective layer (21) and an antireflection layer (23) above the at least one cermet absorption layer (22). The two or more barrier layers (24a, 24b) include a first barrier layer (24a) of thermally produced oxide and a second barrier layer (24b) arranged above it. The second barrier layer (24b) is a cermet material including at least one oxide compound and at least one metal. The oxide compound is aluminium oxide, silicon oxide, nickel oxide and/or chromium oxide. The metal is molybdenum, nickel, tungsten and/or vanadium. The invention also includes an absorber tube with the absorber coating on it.

Abstract: An absorber tube for solar collectors is provided. The absorber tube comprises a metal tube for carrying and heating a heat transfer medium, a sleeve tube enclosing the metal tube for forming an annular space that can be evacuated, a first container disposed in the annular space and filled with protective gas, an outer ring, and a transition element enclosing the metal tube for sealing off the annular space. The first container includes an outlet opening closed by a closure material, which releases the outlet opening under external actuation for introducing the protective gas into the annular space. The external actuation is applied by an opening unit that is activated for releasing the outlet openings. The first container is fixed in the annular space by a retaining device, which is on the outer ring and/or on the transition element.

Abstract: The radiation-selective absorber coating (20) has two barrier layers (24a, 24b), an IR-reflecting layer (21) arranged thereon, an absorption layer (22) arranged above the IR-reflecting (21) and an antireflection layer (23) over the absorption layer (22). The absorber tube (13) is a steel tube (1) with the radiation-selective absorber coating (20) applied to the outside thereof. In the process of coating the absorber tube (13) a first oxide barrier layer (24a) is applied to a steel tube by thermal oxidation; a second barrier layer (24b) is then applied by physical gas phase deposition of silicon with supply of oxygen; the IR-reflecting layer (21) is then applied by gas phase deposition of gold, silver, platinum or copper; the absorption layer (22) is then applied by deposition of aluminum and molybdenum; and a final antireflection layer (23) is applied by deposition of silicon with supply of oxygen.

Abstract: An absorber tube, especially for solar collectors in solar thermal power plants with at least one collector mirror, is provided. The absorber tube includes a metal tube for supplying and heating a heat transfer medium, a sheath tube surrounding the metal tube to form an annular space that can be evacuated, a wall extending through the sheath tube and the metal tube to seal the annular space, and a getter material binding free hydrogen in the annular space. The absorber tube has a temperature variation device that changes the temperature of the getter material and the wall.

Abstract: An absorber pipe for solar collectors is provided. The absorber pipe includes a metal pipe for and a cladding pipe surrounding the metal pipe to form an annular space that can be evacuated. The absorber pipe can include a wall extending between the cladding pipe and the metal pipe for sealing the annular space and a retaining device for a getter material or a container filled with getter material or inert gas. The retaining device has a receiving section for receiving the getter material or the container. The retaining device is fastened to the wall. The absorber pipe can alternately include a getter material disposed in the annular space for binding free hydrogen present in the annular space and a reflector disposed in the annular space for reflecting radiation. The reflector has a housing with a support section for fastening and protecting the getter material from the radiation.

Abstract: The radiation-selective absorber coating for absorber tubes of parabolic trough collectors includes two or more barrier layers (24a, 24b); an infrared reflective layer (21) on the barrier layers (24a, 24b); at least one cermet absorption layer (22) above the infrared reflective layer (21) and an antireflection layer (23) above the at least one cermet absorption layer (22). The two or more barrier layers (24a, 24b) include a first barrier layer (24a) of thermally produced oxide and a second barrier layer (24b) arranged above it. The second barrier layer (24b) is a cermet material including at least one oxide compound and at least one metal. The oxide compound is aluminium oxide, silicon oxide, nickel oxide and/or chromium oxide. The metal is molybdenum, nickel, tungsten and/or vanadium. The invention also includes an absorber tube with the absorber coating on it.

Abstract: The radiation selective absorber coating of the invention includes two or more barrier layers arranged over each other on a substrate surface, an infrared-range reflective layer arranged on the two or more barrier layers, and at least an absorption layer arranged over the infrared-range reflective layer and a final antireflection layer arranged over the absorption layer. The absorber pipe, especially for a parabolic trough collector, is a steel pipe, on whose outer side the radiation selective absorber coating is applied. In the method of making the absorber pipe a first oxide barrier layer is provided on the outer side of the steel pipe by thermal oxidation, and then a second barrier layer, an infrared-range reflective layer, an absorption layer and a final antireflection layer are applied by gas-phase physical deposition.

Abstract: The radiation-selective absorber coating, in particular for an absorber tube of a parabolic trough collector, includes a reflective layer which is reflective in the infrared range, at least one barrier layer arranged below the reflective layer, at least one absorption layer arranged above the reflective layer, an antireflection layer arranged above the absorption layer and at least one adhesion-enhancing layer arranged between the barrier layer and the reflective layer. The adhesion-enhancing layer preferably is a molybdenum layer, but can also be provided by a copper, titanium, titanium oxide, or silicon layer. The adhesion-enhancing layer preferably has a thickness of 5 to 50 nm.

Abstract: The tubular radiation absorbing device (1) for solar thermal applications has a central tube (2) and a glass tubular jacket (3) surrounding the central tube (2) so that a ring-shaped space (4) is formed between the central tube (2) and the tubular jacket (3). The ring-shaped space (4) contains at least one inert gas with a partial pressure of 3 to 200 mbar. Alternatively in another embodiment a gas-tight closed container (10) filled with at least one inert gas is arranged in the ring-shaped space (4). The container (10) has a device for supplying inert gas to the ring-shaped space (4) in order to compensate for increased heat losses due to diffusion of hydrogen into the ring-shaped space (4) from the heat carrier medium.

Abstract: The absorber pipe for solar thermal applications consists of a metal pipe and a radiation-selective absorber coating applied to the outer surface of the metal pipe. The radiation-selective absorber coating consists of, in sequence from the outer surface toward an exterior: a diffusion barrier layer, a metallic reflective layer a cermet layer, and an anti-reflective layer. The diffusion barrier layer is an oxide layer on the outer surface of the preferably steel or stainless steel pipe which is formed by an oxidation process during tempering and which includes oxidized components of the metal pipe. The tempering is preferably performed in air in an oven at a temperature of 400 to 600° C. for 0.5 to 2 hours.

Abstract: The invention relates to a solar collector comprising an absorber tube (13) supported by supports. Radiation-permeable cladding tubes (15) are located between the supports and surround the absorber tube (13). Compensation pieces (17) are provided between the cladding tubes (15) due to the fact that the absorber tube (13) and the cladding tubes (15) have different expansion behaviors. In order to also capture radiation that strikes the connection area (50), at least one mirror collar (20) is provided that reflects the solar radiation into the area of the active absorber tube surface. This mirror collar (20) is capable of reflecting the concentrated solar radiation coming from different directions from the parabolic mirrors even at different solar angles of incidence upon the active absorber surface.

Abstract: The solar absorber is equipped with an absorber body (10) that absorbs incident solar energy (12) and converts it to heat. The absorber body has a selective absorption layer (17) on a side (36) oriented toward the concentrator (13) and another selective absorption layer (18) on an opposite side (38) oriented away from the concentrator (13). The selective absorption layers (17, 18) have threshold wavelengths below which solar radiation is absorbed and above which a reradiation capacity of the absorber body is suppressed. The threshold wavelength of the selective absorption layer (17) on the side (36) of the absorber body that is oriented toward the concentrator is greater than the other threshold wavelength of the other selective absorption layer(18) on the opposite side (38) of the absorber body oriented away from the concentrator.

Abstract: The radiation-selective absorber coating (20) has two barrier layers (24a, 24b), an IR-reflecting layer (21) arranged thereon, an absorption layer (22) arranged above the IR-reflecting (21) and an antireflection layer (23) over the absorption layer (22). The absorber tube (13) is a steel tube (1) with the radiation-selective absorber coating (20) applied to the outside thereof. In the process of coating the absorber tube (13) a first oxide barrier layer (24a) is applied to a steel tube by thermal oxidation; a second barrier layer (24b) is then applied by physical gas phase deposition of silicon with supply of oxygen; the IR-reflecting layer (21) is then applied by gas phase deposition of gold, silver, platinum or copper; the absorption layer (22) is then applied by deposition of aluminium and molybdenum; and a final antireflection layer (23) is applied by deposition of silicon with supply of oxygen.

Abstract: The method of making a vacuum tube collector or X-ray tube, which includes a matching glass-metal joint, includes providing a glass tube (1) made of a glass with a composition, in percent by weight on the basis of oxide content, consisting of B2O3, 8-11.5; Al2O3, 5-9; Na2O, 5-9; K2O, 0-5; CaO, 0.4-1.5; balance, SiO2; and bonding, preferably fusing or melting, an end portion of the glass tube (1) with a metal part (2) in order to bond or attach the glass tube to the metal part, thus forming a long-lasting glass-metal joint. The method of making the glass-metal joint is performed without using intermediary glass compositions of varying thermal conductivities. In the case of the vacuum tube collector the method can provide the basis for an automated manufacture of the vacuum tube collector.

Abstract: A tubular radiation absorbing device (1) designed for a solar heating application is described. The tubular radiation absorbing device has a metal central tube (3) and a glass tubular jacket (2) surrounding the central tube (3). A folding bellows (11) is connected between the central tube (3) and the tubular jacket (2), so that the tubular jacket and the central tube are movable relative to each other. A connecting element (20) connects an inner end of the folding bellows (11) with the central tube (3) and extends from the inner end of the folding bellows (11) through an inner annular space (30) between the folding bellows (11) and the central tube (3). The connecting element includes at least a part of a hydrogen window (50). A getter (6) is arranged in an outer annular space (33) between the folding bellows (11) and the tubular jacket (2).

Abstract: The parabolic trough collector includes a single-axis parabolic mirror (1) and a receiver tube (2) arranged at the focal point (F) of the parabolic mirror (1). The receiver tube (2) includes an absorber tube (4) and an outer tubular glass jacket (3) around it. To compensate for focusing errors in the parabolic collector and thus to reduce associated geometric optical losses, the tubular jacket (3) is provided with structural elements (9a, 9b, 9c, 9d), which focus sunlight reflected from the mirror as well as sunlight that falls directly on the receiver tube from the sun on the absorber tube. The receiver tube is preferably arranged relative to the parabolic mirror, so that its center is displaced from the focal point (F) by a distance equal to half the spacing between the tubular jacket (3) and the absorber tube (4).

Abstract: The radiation selective absorber coating of the invention includes two or more barrier layers arranged over each other on a substrate surface, an infrared-range reflective layer arranged on the two or more barrier layers, and at least an absorption layer arranged over the infrared-range reflective layer and a final antireflection layer arranged over the absorption layer. The absorber pipe, especially for a parabolic trough collector, is a steel pipe, on whose outer side the radiation selective absorber coating is applied. In the method of making the absorber pipe a first oxide barrier layer is provided on the outer side of the steel pipe by thermal oxidation, and then a second barrier layer, an infrared-range reflective layer, an absorption layer and a final antireflection layer are applied by gas-phase physical deposition.

Abstract: The tubular radiation absorbing device (1) for solar thermal applications has a central tube (2) and a glass tubular jacket (3) surrounding the central tube (2) so that a ring-shaped space (4) is formed between the central tube (2) and the tubular jacket (3). The ring-shaped space (4) contains at least one inert gas with a partial pressure of 3 to 200 mbar. Alternatively in another embodiment a gas-tight closed container (10) filled with at least one inert gas is arranged in the ring-shaped space (4). The container (10) has a device for supplying inert gas to the ring-shaped space (4) in order to compensate for increased heat losses due to diffusion of hydrogen into the ring-shaped space (4) from the heat carrier medium.