Solar receiver for receiving solar rays and for heating a medium

Abstract

A solar receiver includes a hollow body, which has a longitudinal axis (8.4), a wall (8) surrounding the longitudinal axis (8.4), an opening (9) disposed in the wall (8) for the entry of heat rays, and an end region opposite the opening (9). The wall (8) includes an outer wall (8.1), an inner wall (8.2), and a partition wall (8.3) disposed therebetween. The outer wall (8.1) and the partition wall (8.3) enclose an outer annular space (8.1.1). The inner wall (8.2) and the partition wall (8.3) enclose an inner annular space (8.2.1). The outer annular space (8.1.1) has, in the end region, an inlet (12) for a free-flowing medium. The two annular spaces (8.1.1, 8.2.1) are conductively connected to one another in the region of the opening (9), and the inner annular space (8.2.1) has an outlet (11) for a free-flowing medium in the end region.

Claims

1. A solar receiver for receiving solar rays, which heat a free-flowing medium, the solar receiver comprising: a hollow body having a longitudinal axis, the hollow body comprising a wall enclosing a longitudinal length region within the hollow body, an opening located in the wall for entry of heat rays and an end area located opposite the opening, the wall comprising an outer wall, an inner wall and a partition wall located between the inner wall and the outer wall, the outer wall and the partition wall enclosing an outer annular space, and the inner wall and the partition wall enclosing an inner annular space, the outer annular space having an inlet in the end area for free-flowing medium, the outer annular space and the inner annular space being in conductive connection with one another in the area of the opening, the inner annular space having an outlet for free-flowing medium in the end area; fluid-carrying and/or turbulence-generating elements configured to and arranged in the inner annular space, the fluid-carrying and/or turbulence-generating elements comprising projections and/or beads cooperating with at least one of the partition wall and the inner wall to define a helical duct, the helical duct being formed by the fluid carrying elements; an inlet valve at the inlet of the outer annular space in the end area for free-flowing medium; and an outlet valve at the outlet of the inner annular space for free-flowing medium in the end area.

2. A solar receiver in accordance with claim 1, wherein the fluid-carrying elements form at least one sawtooth profile.

3. A solar receiver in accordance with claim 1, wherein the outer wall has a hexagonal shape when viewed in a cross section at right angles to the longitudinal axis.

4. A solar receiver in accordance with claim 1, in combination with a secondary concentrator, wherein the secondary concentrator is arranged upstream of the solar receiver.

5. A solar receiver in accordance with claim 4, wherein: the secondary concentrator is funnel-shaped; a tapering end of the secondary concentrator is adjoined in an area of the opening to the hollow body; an inner surface of the secondary concentrator is formed from a reflecting material; and an outer surface of the entire secondary concentrator or of individual mirror elements forming the entire secondary concentrator are provided with a cooling device.

6. A solar receiver in accordance with claim 2, wherein the outer wall has a hexagonal shape when viewed in a cross section at right angles to the longitudinal axis.

7. A solar receiver in accordance with claim 2, in combination with a secondary concentrator, wherein the secondary concentrator is arranged upstream of the solar receiver.

8. A solar receiver in accordance with claim 3, in combination with a secondary concentrator, wherein the secondary concentrator is arranged upstream of the solar receiver.

9. A solar receiver for receiving solar rays, which heat a free-flowing medium, the solar receiver comprising: a hollow body having a longitudinal axis, the hollow body having a wall enclosing a longitudinal length region within the hollow body, the hollow body comprising an opening located in the wall for entry of heat rays and an end area located opposite the opening, the wall comprising an outer wall, an inner wall and a partition wall located between the inner wall and the outer wall, the outer wall and the partition wall enclosing an outer annular space, and the inner wall and the partition wall enclosing an inner annular space, the outer annular space having an inlet in the end area for free-flowing medium, the outer annular space and the inner annular space being in conductive connection with one another in the area of the opening, the inner annular space having an outlet for free-flowing medium in the end area; fluid-carrying and/or turbulence-generating elements comprising strands of triangular cross section with an apex of the triangular cross section in contact with one of the partition wall and the inner wall and a side of each triangle of the triangular cross section in contact with a surface of another of the partition wall and the inner wall, the strands being configured to run helically and arranged in the inner annular space, starting from the area of the opening of the hollow container to or adjacent to the end area, wherein a helical duct configuration is formed by the fluid carrying elements; an inlet valve at the inlet of the outer annular space in the end area for free-flowing medium; and an outlet valve at the outlet of the inner annular space for free-flowing medium in the end area.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a schematic view of a solar power plant according to the state of the art for generating electrical current;

(3) FIG. 2 is a schematic view of a solar power plant according to the state of the art, in which the solar receiver may, however, be configured according to the present invention;

(4) FIG. 3 is a top view of an end area of a cylindrical solar receiver;

(5) FIG. 4 is an axial sectional view of the solar receiver according to section line A-A of FIG. 3;

(6) FIG. 5 is a view of the solar receiver of FIG. 3 in an unmounted state;

(7) FIG. 6 is a view of the solar receiver of FIG. 5 in a mounted state;

(8) FIG. 7 is a top view of the end area of the solar receiver of FIG. 6; and

(9) FIG. 8 is a schematic view of an expanded solar receiver with secondary concentrators in a 3D view.

DESCRIPTION OF PREFERRED EMBODIMENTS

(10) The solar power plant shown in FIG. 1 illustrates the direct feed of concentrated solar energy to a gas turbine. A heliostat field 1 is seen. This receives solar rays from the sun 2. A tower 3 carries at its top end at least one solar receiver 4. The energy irradiated into the solar receiver heats air, which is highly compressed by a compressor 5.

(11) The heated air is fed to a topping combustor 6, and from there to a gas turbine 7. The further process steps are not essential for the present invention. The so-called Brayton-Rankine cycle is applied here.

(12) A heliostat field, irradiated by the sun 2, is again provided in the power plant shown schematically in FIG. 2. A tower 3 carries at least one solar receiver 4. This may be configured according to the present invention and is shown in the following FIGS. 3 through 7.

(13) The solar receiver 4 shown in FIGS. 3 and 4 is a hollow body of a cylindrical shape. It has a wall 8. The wall comprises an outer wall 8.1, an inner wall 8.2 and a partition wall 8.3. The partition wall is located between the outer wall 8.1 and the inner wall 8.2. The outer wall 8.1 and the partition wall 8.3 enclose between them an outer annular space 8.1.1, while the inner wall 8.2 and the partition wall 8.3 enclose an inner annular space 8.2.1 between them. The wall 8 has a longitudinal axis 8.4.

(14) The solar receiver 4 is arranged such that its opening 9 faces the heliostat field, so that an optimum of rays will reach the interior space. The solar receiver 4 does not have to be strictly cylindrical. An expansion towards the opening 9 or, on the contrary, a tapering, is also conceivable. The walls defining the interior space also do not have to be straight, when viewed in an axial section according to FIG. 4. A bell-shaped or funnel-shaped configuration is conceivable.

(15) The hollow body is open at its front-side end. See opening 9. Ducts 10 can be seen at its other front-side end. These ducts are in conductive connection with the inner annular space 8.2.1. The partial flows of air being discharged herein are collected in an outlet 11, provided with a valve Vo.

(16) Further, an inlet 12, provided with a valve Vi, can be seen in FIGS. 3 and 4. This inlet is located in an end area, which is located opposite the opening 9. The inlet 12 is brought tangentially into contact with the wall 8. The inlet 12 feeds compressed air to the hollow body, for example, from the surrounding area or from a compressor, and it is shown in FIG. 1. The air is fed into the outer annular space 8.1.1.

(17) The flow path of the air is as follows:

(18) After the entry of the air into the outer annular space 8.1.1, the air flows farther in the direction of the longitudinal axis up to the end of the hollow body at which the opening 9 is located. The air stream is deflected there by 180°. After this turning point, the air flows in the opposite direction through the inner annular space 8.2.1, again parallel to the longitudinal axis 8.4 in the direction of the outlet 11.

(19) This reverse flow principle has considerable advantages: The initially still relatively cold medium, which enters into the tangential inlet 12, flows through the outer annular space 8.1.1. Even though the medium is warmed up on its path from the inlet 12 to the area of the opening 9, it still remains at a relatively low temperature level. This is important for the case in which not only a single solar receiver is used, but a plurality of solar receivers, which are in physical contact with one another, e.g., in the manner of honeycombs. If there were no outer annular space 8.1.1 in the individual solar receivers 4, unacceptably high temperatures, which can lead to destruction, would be generated in the entire cluster of solar receivers.

(20) The outer wall 8.1 according to the present invention carries out the following functions: It withstands considerable pressures. It acts as an insulation and prevents an excessive heating of the outer wall. It captures heat, which can be utilized.

(21) As is seen from the further figures, there are built-in components 13 in the inner annular space 8.2.1. These are elements that are used to guide the air and/or to swirl the air (turbulence generation). The elements 13 may have different shapes and arrangements. The elements 13 form a sawtooth profile together in this case. These shall be strands consisting of any material, for example, metal, which have a triangular cross section. The apex of the triangle is in contact with the partition wall 8.3, and one side of each triangle is in contact with a surface of the inner partition wall. A reverse arrangement, in which the apex of each triangle is in contact with the inner wall, is conceivable as well.

(22) In an especially remarkable embodiment, each strand runs helically in the triangular embodiment of the elements 13 shown, i.e., starting from the area of the opening 9 of the hollow container to its end.

(23) In case of a helical arrangement of the elements shown, the individual strand is in contact with the inner wall 8.2 as well as with the partition wall 8.3.

(24) The elements 13 may also have an entirely different configuration. It is thus conceivable that lamellae, which protrude into the inner annular space 8.2.1, are provided instead of a triangular cross section. Nubs or pins may be provided as well. In any case, it must, of course, be ensured that air can flow fully and completely through the inner annular space 8.2.1, i.e., from the area of the opening 9 of the hollow body to the end area, which is located opposite the opening 9.

(25) The partition wall 8.3 is, in general, insulated against heat transfer.

(26) FIGS. 5 through 7 show an impression of the shape and appearance of the elements 13. See a hollow cylinder 13.1 in FIGS. 5 and 6. The hollow cylinder 13.1 is fitted together from an interlacing array of many elements 13. FIG. 5 shows, for example, the cylindrical outer wall 8.1 in phantom lines. The partition wall 8.3 can be pushed into this outer wall, and the hollow cylinder 13.1 can, in turn, be pushed into this partition wall. The inner wall 8.2 must still be pushed into the hollow cylinder 13.1, but this is not shown here. FIG. 8 is an especially remarkable configuration. A cluster of solar receivers 4 is shown here. These are arranged concentrically in relation to one another.

(27) A secondary concentrator 14 is arranged upstream of each solar receiver. The number of secondary concentrators 14 provided is thus equal to the number of solar receivers.

(28) Each secondary concentrator is configured as follows: It has the shape of a funnel, which expands downward starting from the lower end. Its upper, tapered end is passed through the opening 9 of each solar receiver 4 and may protrude more or less far into the interior space of the solar receiver. However, it may also start at the opening 9. As is seen, the opening 9 is dimensioned and configured such that it is defined by a collar 4.1, which is ring-shaped and whose outer circumferential edge adjoins the outer wall 8.1 of the solar receiver 4, optionally in a sealing manner, while the inner circumference likewise adjoins sealingly the secondary concentrator in question.

(29) Each secondary concentrator has a hexagonal cross section in this case. This means that the outer surfaces of mutually adjacent secondary concentrators are snugly in contact with each other (honeycomb shape).

(30) The same configuration may also be provided in the solar receivers, i.e., also a hexagonal cross section, unlike in the embodiment shown, in which the outer walls 8.1 have a circular cross section.

(31) The secondary concentrators are configured from bodies that consist of highly reflective material on the inside. The inner surfaces are thus mirror surfaces 14.1. The outer surfaces are, by contrast, preferably cooled.

(32) There are a plurality of heat sources in the entire plant, which are not used directly for the process, but they are used indirectly. These include the heat that is generated on the outer surfaces of the secondary concentrators. Another heat source is located at the outer wall 8.1 of the wall 8. All these quantities of heat are preferably captured and fed to a heat exchange process and are thus utilized.

(33) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.