Solar absorber body for a concentrating solar power system and a method for manufacturing a solar absorber body
A solar absorber body for a concentrating solar power system, said solar absorber body including: a tube, designed to contain a heat transfer medium and including a first part designed to be exposed to the sunlight and a second part designed to be unexposed to the sunlight, an assembly of fins made of thermally conductive material, and a selective coating arranged at least on the outer surface of the first part of the tube, said assembly of fins defining at least two longitudinal passages inside the tube, said passages being adjacent in a sectional plane perpendicular to the longitudinal axis of the tube, said assembly of fins being configured to create a continuous thermal bridge inside the tube from at least a portion of the inner surface of first part of the tube to at least a portion of the inner surface of the second part of the tube.
1. A solar absorber body for a concentrating solar power system, said solar absorber body comprising:
a tube, designed to contain a heat transfer medium and comprising a first part designed to be exposed to the sunlight and a second part designed to be unexposed to the sunlight, the tube having a nominal diameter between DN15 and DN80, the tube being made of a first material,
an assembly of fins defining at least two longitudinal passages inside the tube, the at least two longitudinal passages being adjacent in a sectional plane perpendicular to a longitudinal axis of the tube,
and a selective coating arranged at least on the outer surface of the first part of the tube,
wherein the fins are made of the first material, aluminum alloy, or copper alloy and have a thickness between 0.5 mm and 4 mm configured to create a continuous thermal bridge inside the tube from at least a portion of the inner surface of the first part of the tube to at least a portion of the inner surface of the second part of the tube.
2. A solar absorber body according to claim 1 , wherein the assembly of fins defines between 3 and 8 longitudinal passages in the tube.
3. A solar absorber body according to claim 2 , wherein the assembly of fins has a star-shaped structure.
4. A solar absorber body according to claim 3 , wherein the assembly of fins has an outer casing, said outer casing being in contact with an inner part of the tube and connecting at least two points of the star-shaped structure and wherein the outer casing is discontinuous so that an end of at least one fin of the assembly of fins is in contact with the tube and at least one longitudinal passage is delineated by the tube.
5. A solar absorber body according to claim 3 , wherein the assembly of fins comprises an obstructing element located at an intersection of the fins and wherein the obstructing element represents at least 5% of an inner area of the tube and not more than 20% of the inner area of the tube.
6. A solar absorber body according to claim 5 , wherein an inner face of the tube defines a circle in a cross-section plan and wherein the fins extend from the inner face of the tube to a connection point and the connection point is spaced from a center of the circle.
7. A solar absorber body according to claim 2 , wherein the tube comprises at least an additional assembly of fins, the assembly of fins defining a first group of longitudinal passages in the tube and the additional assembly of fins defining a second group of longitudinal passages in the tube, the longitudinal passages of the first group being shifted relative to the longitudinal passages of the second group in the longitudinal axis of the tube and wherein the assembly of fins comprises an obstructing element located at an intersection of the fins and wherein the obstructing element represents at least 5% of an inner area of the tube and not more than 20% of the inner area of the tube.
8. A solar absorber body according to claim 1 , wherein the assembly of fins is crimped into the tube.
9. A solar absorber body according to claim 1 , wherein the tube is a seamless tube.
10. A solar absorber body according to claim 9 , wherein the tube is a seamless cold drawn tube.
11. A solar absorber body according to claim 1 , wherein the tube is made of comprising alloying elements and wherein an amount of the alloying elements ranges up to 8% by weight.
12. A solar absorber body according to claim 11 , wherein the tube is made of P195GH, 13CrMo44, or 10CrMo9-10.
13. A solar absorber body according to claim 1 , wherein the selective coating is formed by a reflecting coating made of a platinum-base IR mirror and a solar absorption layer made of a cermet of Cr/Cr 2 O 3 or Mo/Al 2 O 3 .
14. A solar absorber body according to claim 1 , wherein the selective coating is formed by a reflecting coating made of a platinum-base IR mirror, a solar absorption layer made of a cermet of Cr/Cr 2 O 3 or Mo/Al 2 O 3 , and an anti-reflecting layer made of SiO 2 .
15. A solar absorber body according to claim 1 , said solar absorber body comprising a diffusion barrier layer in direct contact with the outer surface of the tube, the selective coating being separated from the tube by the diffusion barrier layer and wherein the diffusion barrier layer comprises at least a refractory material.
16. A solar absorber body according to claim 15 , wherein the diffusion barrier layer comprises a refractory material selected from the group consisting of molybdenum, tungsten, Al 2 O 3 , Cr 2 O 3 , a nickel-chromium alloy, a cobalt-chromium alloy, WC, ZrB 2 , and a mixture of ZrB 2 and SiC.
17. A method for manufacturing a solar absorber body according to claim 1 comprising the steps of:
providing the tube,
inserting into the tube the assembly of fins,
cold-drawing the tube and the assembly of fins, so as to crimp the assembly of fins into the tube,
forming the selective coating at least on the outer surface of the first part of the tube.
18. A method according to claim 17 , wherein before inserting the assembly of fins into the tube, a pre-treatment operation is carried out onto the assembly of fins.
19. A solar absorber body according to claim 1 , wherein the tube comprises at least an additional assembly of fins, the assembly of fins defining a first group of longitudinal passages in the tube and the additional assembly of fins defining a second group of longitudinal passages in the tube, the longitudinal passages of the first group being shifted relative to the longitudinal passages of the second group in the longitudinal axis of the tube and wherein the assembly of fins defines a first number of longitudinal passages and the additional assembly of fins defines a second number of longitudinal passages different from the first number.
20. A solar absorber body according to claim 1 , wherein the first part is designed to be exposed to concentrated sunlight and the second part is designed to be unexposed to the concentrated sunlight.