WATERPROOF STRUCTURE FOR AN EXTERNAL SOLAR RECEIVER IN A CONCENTRATING SOLAR POWER PLANT TOWER

Abstract

An external solar receiver for the tower of a thermodynamic concentrated solar power plant of the type having a tower and a field of heliostats, said tower comprising a windproof internal modular structure, also referred to as a "casing" and a plurality of receiver panels (25) with heat exchanger tubes (20) attached to said internal structure, each panel (25) comprising a plurality of metal casings (1) supporting the heat exchanger tubes (20) and assembled together by an assembly means allowing dismantling, each casing (1) being covered with a thermal insulation (4) via an anchoring means (5), characterized in that the tubes (20) are rigidly attached to the casings (1) by a floating connection means that can be dismantled.

Description

WATERPROOF STRUCTURE FOR AN EXTERNAL SOLAR RECEIVER IN A CONCENTRATING SOLAR POWER PLANT TOWER Object of the invention

[0001] The present invention relates to the technical field of concentrating solar power (CSP) plants, more particularly tower solar power plants and, even more particularly, those with an external solar receiver. Technological background and prior art

[0002] In a concentrated solar power plant of the "tower" type, solar radiation is reflected by a series of mirrors, called heliostats, towards a central solar receiver located on a tower, which transfers the energy of the solar radiation to a heat transfer fluid which will heat up and which can be used for the production of electricity.

[0003] The heliostats are equipped with two rotation mechanisms enabling them to follow the sun and always direct the solar flux towards a given point, regardless of the time of day and the current season.

[0004] The solar receiver is installed at the top of a tower in order to receive solar radiation from all the heliostats without a given heliostat interfering with the reflection of the flux produced by a neighboring heliostat.

[0005] The hot fluid generated in the solar receiver can be high-pressure, high-temperature steam generated from feedwater. The steam can then be used directly in a steam turbine driving an electricity generator.

[0006] The hot fluid can also be a mixture of salts serving as a heat transfer fluid that can be stored in large quantities on the ground and used in parallel with steam production and electrical power generation. This allows solar energy capture and electricity production to be decoupled.

[0007] The solar receiver installed at the top of the tower can be of the cavity or external type. In the former case, the cavities are lined internally with tubular panels that capture solar radiation, and the effect of the cavity is to reduce radiation losses. In the case of the external type, the tubular panels that capture solar radiation are installed on the outside and all around the tower. Losses are slightly higher compared to the cavity system, but it is easier to concentrate solar radiation there, the average heat flux being significantly higher and the surface area of ​​the panels being greatly reduced for the same power output.

[0008] In the outdoor solution, the flat panels are juxtaposed to form a right prism with a regular polygonal base. Depending on the installed power, the polygonal prism can have a variable number of faces, from 4 to 32 for example.

[0009] The current practice, according to the state of the art, is to fix the aforementioned panels to a fixed structure. Each of these panels can then expand freely under the effect of the temperature increase resulting from the capture of solar energy.

[0010] In order to allow for easy maintenance and to offer, for example, the possibility of replacing a single tube of a panel, the tubes are not welded together but simply placed side by side, with a small gap between them. Each tube must then be individually supported in order to withstand, if necessary, wind loads and those resulting from an earthquake. However, the unwelded tubes allow wind to pass through, and this necessitates a sealed partition at the rear to prevent the incoming wind, heated by the hot tubes, from penetrating the body of the tower, which is a passageway for maintenance, inspection, and operations.Furthermore, the tower's interior contains sensitive electrical and electronic equipment that generally cannot withstand high temperatures. This sealed enclosure will also be referred to as the "casing" in the remainder of this presentation. For reference, the temperature behind the solar panel support structure inside the tower can be 40-50°C, while the external temperature at the level of the panels and their direct support structure can be 500-850°C.

[0011] Document WO 2010 / 048578 discloses a store-assembled solar receiver heat exchanger having an arrangement of heat transfer surfaces and a vertical steam / water separator structurally and fluidically interconnected thereto. A vertical support structure is provided to support the vertical separator and the heat transfer surfaces. The vertical support structure is supported from below, while the vertical steam / water separator and the heat transfer surfaces of the heat exchanger are supported from above by the vertical support structure. The vertical support structure provides structural support and rigidity for the heat exchanger and a means by which the heat exchanger can be grasped and lifted for placement in a desired location.

[0012] In this installation, horizontal reinforcing ribs or beams are attached to the solar tube panels. All the panels are supported from above and suspended from the internal support structure of the receiver. Each tube panel has interconnecting plates. Each plate is connected via two connecting rods or pivoting bars at their ends by means of pins to a bracket that is attached to a flexural support, itself attached via structural steel to the columns comprising the vertical support structure of the receiver. The pivoting bars allow a certain degree of rotation of the solar panels and thus accommodate the average thermal expansion of the supported panels. This system provides horizontal stability to the tube panels while allowing the tubes free and independent vertical extension, with reduced stress on the tubes.However, this system allows for unconstrained expansion of the tubes vertically but not horizontally.

[0013] US patent 5,482,233 discloses a removable support clamp for solar receiver panel tubes. The tube support clamp is slidably mounted on a guide rod, the clamp comprising a stiffener with a key inserted into a groove in the guide rod and two lobes that grip the guide rod. A key feature of this concept is easy assembly and disassembly without requiring access to the rear side of the panels. This clamp system again allows for unconstrained expansion of the tubes vertically but not horizontally.

[0014] US patent 2013 / 01 18482 A1 discloses a solar receiver comprising a multi-faceted central assembly with wing assemblies extending from the corners of the central assembly.The central assembly comprises single-sided heat-absorbing panels, while the wing assemblies use double-sided heat-absorbing panels. Stiffening structures are arranged across the exposed faces of the various heat-absorbing panels.

[0015] US patent 200 / 0199980 A1 discloses a boiler for a solar receiver comprising a first and a second receiver panel, each having a plurality of substantially parallel boiler tubes fluidically connecting an inlet manifold of the respective panel to an outlet manifold of the respective panel. The boiler tubes of the second receiver panel are substantially parallel to the boiler tubes of the first receiver panel. The first and second receiver panels are separated by a gap. A panel expansion joint connects the first and second receiver panels across the gap.The panel expansion joint is configured and adapted to allow longitudinal thermal expansion and contraction of the receiving panels along the boiler tubes, and to allow lateral thermal expansion and contraction of the receiving panels, with some moving closer together and others further apart respectively, while blocking solar radiation through the gap.

[0016] Document EP 0 106 687 A2 discloses a tube panel comprising steam-generating tubes and superheating tubes. At least two parallel steam-generating tubes are spaced to create a gap between them. A superheating tube is adjacent to each of the two steam-generating tubes and is positioned at the rear of the gap to fill it and receive radiant energy from the front of the gap, in order to ensure adequate distribution of the incident heat flux between the steam-generating and superheating tubes, while eliminating the need for a complex and costly vibration support structure for the steam-generating tubes. A support plate is attached to the rear of the superheating tubes and extends transversely with respect to their longitudinal direction.The steam-generating tubes are supported by brackets connected between the respective steam-generating tubes and their respective support plates, effectively supporting the superheater tube between the steam-generating tubes and the support plate. Furthermore, the superheater tube support plates are connected through the insulation by cleats to internal structural I-beams. These cleats incorporate rollers that can move along the flanges of the I-beams due to the longitudinal expansion of the tubes. The movement of the tubes due to expansion is thus transmitted to the internal structure through the thermal insulation. Objectives of the invention

[0017] The present invention aims to provide a solution for the design of a casing for an external solar tower receiver so that it can perform the following various functions: - windproofing as well as an effective thermal barrier, - the insulation between the very hot "tube" side and the inner "tower" side, which must be maintained at a temperature acceptable for personnel and special equipment, and also - minimizing heat loss to avoid degrading efficiency.

[0018] The casing must also withstand wind or seismic forces acting on the solar tube panels and on the casing wall itself.

[0019] The casing must also be designed to facilitate tube assembly and maintenance or replacement.

[0020] Finally, the casing must allow for vertical and horizontal expansion of the tube panels and be designed to prevent mechanical movement of support elements through the insulation. Main characteristic elements of the invention

[0021] The present invention relates to an external solar receiver for a tower of a concentrated solar power plant of the tower and heliostat field type, said tower comprising a modular, windproof internal structure, also called "casing", and a plurality of receiver panels with heat exchanger tubes fixed to this internal structure, each panel comprising a plurality of metal boxes supporting the heat exchanger tubes and assembled together by an assembly means allowing disassembly, each box being covered with thermal insulation via an anchoring means, the tubes being secured to the boxes by a removable and floating connection means, i.e. allowing thermal expansion of the tubes and of the part of their support subjected to high temperature both in the longitudinal direction of the tubes and in the directions transverse thereto,characterized in that each tube is provided with several welded eyelets, distributed along the height of the tube, capable, under the effect of the axial thermal expansion of the tube, of sliding in a key, itself fixed to the casing through the thermal insulation by support rods, so that the movement of the tubes under the effect of expansion, essentially along their longitudinal direction and along the plane of the panel, is carried out outside the thermal insulation. Thus, it is the support structure that allows the expansion of the receiving panel without any movement through or within the insulation.

[0022] According to preferred embodiments of the invention, the solar receiver further comprises at least one of the following features, or an appropriate combination thereof: - the metal boxes are monobloc and made of a rectangular sheet folded into a "U" shape on each of its sides, the corners of each box being welded; - thermal insulation is a block with a rectangular cross-section corresponding to that of the boxes and having on each of its sides a male or female baffle so that it can be assembled with an adjacent insulation block having complementary baffles on its sides; - the different boxes with their thermal insulation are assembled with a slight play facilitating their disassembly, a removable sealing means being provided between the boxes to ensure windproofness; - the removable sealing means comprises a gasket mounted compressed by bolting on one side between the flanges formed by the "U" shaped ends of two adjacent boxes and on the other side a counter-flange or an "H" profile; - the key is provided with two diametrically opposed lugs capable of cooperating with two hollows made in each tie rod, so as to be able to lock the key by a quarter turn rotation, a thin folded sheet metal being provided to prevent the key from rotating on itself; - a slightly folded rider capable of being mounted on two adjacent keys is provided to ensure the locking of said keys; - the eyelets welded onto the tube have a saddle-shaped base; - the tubes are connected to each other via their corresponding keys by intermediate support side plates which ensure the connection between the tie rods and the tubes; - the tie rods are connected to the support plates by means of pins which fit into oblong holes in the tie rods. Brief description of the figures

[0023] Figure 1 shows a schematic cross-sectional view of an individual casing constituting the modular casing according to the present invention.

[0024] Figure 2 shows a schematic cross-sectional view of several casings (in this case three) according to Figure 1, assembled together with a slight gap and connecting means between the casings ensuring wind tightness.

[0025] Figure 3 shows, in a schematic cross-sectional view, several embodiments of the casing according to Figure 1 with a male or female baffle of the thermal insulation anchored to the sheet metal, on one or the other side (in the drawing: top side and bottom side).

[0026] Figure 4 shows an elevational view of the device for fixing an individual tube to a box, comprising tie rods and a key, as well as an eyelet welded to the tube, according to an embodiment of the present invention.

[0027] Figure 5 shows a detailed view of the figure key 4 with a first solution for locking the key at the tie rods.

[0028] Figure 6 shows a detailed view of the key of the figure 4 with a second solution for locking the key at the tie rods.

[0029] Figure 7 shows a plan view of a particular embodiment of the eyelet welded to the tube as in Figure 4.

[0030] Figure 8 represents a perspective view of an entire solar receiver panel comprising several modular boxes according to the invention, seen from the rear, i.e. from the cold side.

[0031] Figure 9 shows a detailed view of the mechanical support system for the solar tubes, according to the invention, ensuring their retention and guidance and the absorption of wind forces. Description of a preferred embodiment of the invention

[0032] The particular technical solution proposed by the present invention not only performs the functions required by the objectives of the invention but also does so in a configuration that can be easily disassembled from the rear, i.e., from inside the tower, accessible to maintenance personnel, by means of modular elements that can be easily handled by the assembly personnel. This results in easy access to the rear of the tubes and therefore the possibility of inspection and maintenance of the tubes, which constitute the most stressed part of the solar receiver.

[0033] Figure 1 shows a modular casing 1 subdivided into a plurality of boxes 1 of a preferred size of approximately 1 to 2 m2. Each box 1 consists of a sheet 2 folded into a "U" shape 3 on each of its four sides. The corners of each box are welded, forming a rigid assembly (not shown).

[0034] A specific thermal insulation 4 is anchored to the sheet metal 2, on the high-temperature side, by means of an anchoring system 5 known to those skilled in the art. Baffles 6 are provided in the insulation 4 to ensure a good thermal barrier between the adjacent boxes 1, preventing solar radiation leakage through the panels. Depending on the location of the box 1 in the solar receiver assembly, the baffle 6 will be male and / or female on one or the other side, as shown in Figure 3.

[0035] As shown in Figure 2, the boxes 1 are then assembled together with a slight gap 7 and wind tightness is ensured either by a gasket 8 and a counter flange 9, or by a gasket 8 and an "H" profile 10. In the latter case, the "H" profile 10 will take up the wind and seismic loads and transmit these forces to the main structure (as for example in Figure 8).The counter flange 9 or the "H" profile 10 are assembled by means of a removable assembly, preferably by bolting 11, onto corresponding pre-drilled flanges of the casing, compressing the sealing gasket 8. The mounting clearance 7 between the casings also allows for easy disassembly.

[0036] As shown in Figure 4, the transmission of wind and seismic forces acting on the tubes 20 to the sheet metal 2 of the casing 1 and the "H" profiles 10 is achieved by an eyelet 21 welded to the tube 20 and sliding along a key 12, allowing axial thermal expansion of the tube 20 while limiting its lateral displacement. All the tubes 20 are individually supported.

[0037] As also shown in Figure 4, each key 12 is held to the casing 1, 2 by two tie rods 13, preferably flat. Thanks to two lugs 14 on the key 12 and two recesses in the tie rod 13 (not shown), the key 12 will be held in place, even under upward vertical force, by rotating it a quarter turn. A thin folded sheet metal 15 prevents the key 12 from rotating so that the lugs do not end up opposite the mounting recesses (see Figure 5). Further details of the connection are shown in Figure 9 (see below).

[0038] As shown in Figure 6, another solution for locking the key 12 consists of using a jumper 17 mounted on two consecutive or adjacent keys 12 and slightly bent to hold it in place.

[0039] As shown in Figure 7, the eyelet 11 welded onto the tube 20 will also advantageously have a particular shape with a saddle-shaped base 18, allowing easy welding onto the tube while better distributing the forces on the tube, thus minimizing stresses.

[0040] Figure 8 shows a realistic embodiment of the casing of a panel 25 viewed from the rear, and in particular with two horizontal rows of box sections 1 assembled with horizontal windproof H-profiles 10 and beams 19 that resist wind loads. A corner box section 23 is also shown in Figure 8. Like the panels, the corner box section 23 is bolted to the wind beams 19. Thermal insulation is not shown.

[0041] As shown in Figures 4 and 9, the plates 13 are themselves held by the casing 1, 2, forming a floating assembly that allows the plates 13 to expand along their lengths, as they are also subjected to a high temperature on their external side. Figure 9 also shows that all the tubes 20, and therefore the associated keys 12, are advantageously connected laterally by metal support plates 16 that ensure the connection between the tubes 20 and the support plates 13. Advantageously, two plates 13 are connected to two support plates 16 by means of pins 26 that fit into oblong holes 27 in the plates 13, thus allowing the horizontal expansion of the panels 25. Advantages of the invention

[0042] According to the invention, the tube panels can move vertically as well as horizontally due to thermal expansion. Thus, the support plates 16 accommodate the horizontal expansion of the tubes, expanding with them, since these plates 16 are also subjected to high temperature. Furthermore, the connections between the plates 13 and the support plates 16, using rods and oblong holes, also facilitate the horizontal expansion of the panels.

[0043] The system design allows for independent mounting of the tubes, which facilitates their maintenance and / or replacement. Welding the tubes to the eyelets using a saddle fitting distributes the stresses along the tube, preferably with a saddle edge thickness of the same order of magnitude as the tube thickness.

[0044] Another advantage of the invention is that this expansion of the tubes and their direct support structure, and the resulting movement, takes place largely outside the insulation (unlike the connecting rod system described in WO 2010 / 048578 for example).

[0045] Finally, the various modular boxes can be insulated either at the factory or on the assembly site. The boxes are sized to be handled by two people, if necessary equipped with suitable handling tools (maximum weight of approximately 150 kg). Reference symbols 1. box 2. sheet metal 3. U-shaped fold of the sheet metal (flange) 4. Thermal insulation 5. anchoring 6. chicane 7. Play between adjacent boxes 8. joint 9. counter-bridle 10. "H" profile 1. Bolt 12. Removable key 13. Support tie rod (flat) 14. ergot 15. Anti-rotation folded sheet metal 16. Intermediate side plate 17. rider 18. Horse saddle base 19. Wind beam 20. Heat exchanger tube 21. Eyelet welded onto tube 22. stiffener 23. Corner cabinet 24. Displacement of tubes by expansion 25. Heat exchanger tube panel 26. connecting axis 27. oblong hole

Claims

DEMANDS 1. External solar receiver for a tower of a concentrated solar power plant of the tower and heliostat field type, said tower comprising a modular, windproof internal structure, also called "casing", and a plurality of receiver panels (25) with heat exchanger tubes (20) fixed to this internal structure, each panel (25) comprising a plurality of metal boxes (1) supporting the heat exchanger tubes (20) and assembled together by an assembly means allowing disassembly, each box (1) being covered with thermal insulation (4) via an anchoring means (5), the tubes (20) being secured to the boxes (1) by a removable and floating connection means, i.e. allowing thermal expansion of the tubes (20) and of the part of their support subjected to high temperature both in the longitudinal direction of the tubes and in the directions transverse thereto,characterized in that each tube (20) is provided with several welded eyelets (21), distributed along the height of the tube (20), capable, under the effect of the axial thermal expansion of the tube (20), of sliding in a key (12), itself fixed to the casing (1) through the thermal insulation (4) by support rods (13), so that the movement of the tubes (20) under the effect of expansion, essentially along their longitudinal direction and along the plane of the panel (25), is carried out outside the thermal insulation (4).

2. Solar receiver according to claim 1, characterized in that the metal boxes (1) are monobloc and made of a rectangular sheet folded into a "U" (3) on each of its sides, the corners of each box (1) being welded.

3. Solar receiver according to claim 1, characterized in that the thermal insulation (4) is a block of rectangular cross-section corresponding to that of the boxes (1) and having on each of its sides a male or female baffle (6) so as to be able to be assembled with an adjacent insulation block having on its sides complementary baffles (6).

4. Solar receiver according to claim 1, characterized in that the different boxes (1) with their thermal insulation (4) are assembled with a slight play (7) facilitating their disassembly, a removable sealing means being provided between the boxes (1) to ensure wind tightness.

5. Solar receiver according to claim 4, characterized in that the removable sealing means comprises a seal (8) mounted compressed by bolting (1 1 ) on the one hand between the flanges formed by the "U" ends (3) of two adjacent boxes and on the other hand a counter flange (9) or an "H" profile (10).

6. Solar receiver according to claim 1, characterized in that the key (12) is provided with two diametrically opposed lugs (14) capable of cooperating with two hollows made in each tie rod (13), so as to be able to lock the key by rotation of a quarter turn, a thin folded sheet metal (15) being provided to prevent the rotation of the key (12) on itself.

7. Solar receiver according to claim 1, characterized in that a slightly folded jumper (17) suitable for being mounted on two adjacent keys (12) is provided to ensure the locking of said keys (12).

8. Solar receiver according to claim 6, characterized in that the eyelets (21) welded onto the tube (20) have a saddle-shaped base (18).

9. Solar receiver according to claim 1, characterized in that the tubes (20) are connected to each other via their corresponding keys (12) by intermediate support side plates (16) which ensure the junction between the tie rods (13) and the tubes (20).

10. Receiver according to claim 9, characterized in that the tie rods (13) are connected to the support plates (16) by means of shafts (26) which fit into oblong holes in the tie rods (13).