Concentrating solar tower with external receiver

Abstract

External solar receiver (1) for a solar tower thermodynamic installation (8) and a heliostat field, characterized in that each panel (2) with heat exchanger tubes is connected to at least one internal support element (4), axis substantially perpendicular to the panel (2), said internal support element (4) being further rotationally connected to a support element (7) belonging to the internal structure by means of at least two substantially horizontal connecting rods (5, 6), and articulated each at a first end on the internal support element (4) and at a second end on the support element (7) of the internal structure, respectively, so that, under the effect of thermal expansion or contraction of the panels (2) with heat exchangers, each of the panels moves substantially parallel to itself and without deformation of its surface,and such that the polygonal or circular section of the receiver (1) undergoes a homothetic etic transformation,

Description

Object of the invention

[0001] The present invention relates to the technical field of concentrated solar power (CSP) plants. Concentrating Solar Power Plant ) and more specifically tower solar power plants. State of the 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] Heliostats are equipped with two rotation mechanisms that allow 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 one heliostat interfering with the reflection of the flux from a neighboring heliostat.

[0005] The hot fluid generated in the solar receiver can, for example, be high-pressure, high-temperature steam generated from feedwater. This 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 underground and used simultaneously for steam production and electrical power generation. This allows for the decoupling of solar energy capture and electricity production.

[0007] The solar receiver installed at the top of the tower can be either cavity-type or external. In the former, the cavities are lined internally with tubular panels that capture solar radiation, and the cavity's effect 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-type system, but it is easier to concentrate solar radiation, as the average heat flux is significantly higher and the panel surface area is 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 base can have a variable number of faces, from 4 to 32 for example.

[0009] The common practice is to fix each panel to a fixed structure. Each panel can then expand freely under the effect of the temperature increase resulting from the capture of solar energy.

[0010] US patent 2012 / 312296 discloses a solar water heater with a boiler support defining an axis along an inside-outside direction. A vertical suspension rod or connecting rod is rotatably mounted on the boiler support. A bracket is rotatably mounted on the suspension rod, and a solar water heater panel is mounted on the bracket. The solar boiler panel defines a longitudinal axis that is substantially perpendicular to the axis of the boiler support. The suspension rod connects the boiler support to the bracket to support the weight of the solar boiler panel from the boiler support. The suspension rod and bracket are configured and adapted to maintain a substantially constant orientation of the bracket during inward and outward movement of the bracket relative to the boiler support.Indeed, according to one embodiment shown, there are two parallel vertical connecting rods which, together with the boiler support and the bracket, form a parallelogram link. The connecting rods support the weight of the panel. The panel deforms due to the thermal expansion or contraction of the solar panel, but the upward displacement of the bracket due to the rotation of the connecting rods is negligible. Consequently, the solar panel moves practically parallel to itself. The solar panels are not connected to each other. Wind forces are absorbed by a damper connecting the bracket to the structure. It is not mentioned that the solar panels can be connected to each other.

[0011] Document EP 1 243 872 discloses a solar collector with a plurality of absorbent bodies that absorb solar radiation. These absorbent bodies are porous and allow the passage of aspirated air. The supporting structure of the solar receivers is formed of modules, each with a front wall, a rear wall, side walls, and a cavity. Tubes run through each module, carrying hot air into a collector. Fresh air flows in a countercurrent through fresh air inlets in the cavity. The fresh air circulates around the absorbent bodies. Due to their cooling, the modules can be made of steel without the risk of overheating. The solar receiver is stable and does not require a shut-off device in the hot air chamber. The individual modules are mounted adjacently with connecting elements, allowing them to withstand thermal expansion without stress.Also, the adjacent sides of the modules do not touch across their entire surface, and wedge-shaped gaps are provided for this purpose. Furthermore, the various vertically mounted modules are connected at their upper end to the internal wall by a hinged joint, allowing for expansion in the vertical direction.

[0012] Document WO 2013 / 019670 describes a modular solar receiver with multiple tube panels in a rectangular, square, polygonal, or circular configuration, designed for use with molten salt or another heat transfer fluid. The heat transfer fluid flows along a vertical, serpentine path through the sides (facets) of the solar receiver. The solar receiver can be shop-assembled and used with a support tower to form a solar power system.

[0013] Document WO 2010 / 048578 discloses a shop-assembled solar receiver heat exchanger having an arrangement of heat transfer surfaces and a vertical steam / water separator structurally and fluidically interconnected to it. 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.

[0014] In these last two installations, 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 two interconnecting plates. Each plate is connected via two pivoting bars at its ends, using pins, to a bracket that is attached to a flexural support. This support is 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, thus accommodating 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 expansion, reducing stress on the tubes.Here too, the adjacent tube panels, on each face and at each level (top / bottom) are separated laterally (horizontally) from each other, which allows differential expansion of the tube panels, without stress.

[0015] Document EP 0 106 688 discloses a receiver for receiving solar radiation energy, characterized by a plurality of steam-generating tube panels capable of receiving a flow of liquid to be heated and producing steam, and a plurality of superheating tube panels capable of receiving a flow of steam to be superheated, the steam-generating tube panels and the superheating tube panels being arranged in a side-by-side relationship to receive solar radiation energy, and the superheating tube panels being interspersed with the steam-generating tube panels in a sequence of at least twelve panels such that each sequence of four panels from at least twelve panels includes at least one superheating tube panel and at least one steam-generating tube panel.The problem here arises from the fact that the superheater tube panels undergo significantly greater longitudinal expansion than the steam generator tube panels. Similar to the previous case, the superheater tube panels are connected by connecting rods to horizontal reinforcing ribs. This system allows vertical movement of the superheater tube panels relative to the horizontal ribs, and therefore relative to the steam generator tube panels.

[0016] The state of the art does not solve the problem of thermal expansion in an external solar receiver where the panels form a prism with a polygonal cross-section, i.e. where adjacent panels are connected to each other laterally. Objectives of the invention

[0017] The present invention aims to provide a solution that allows the lateral expansion of the panels to be taken into account in an external prismatic right receiver with a regular polygonal cross-section, when the panels are connected to each other in pairs by an adjacent side. Main characteristic elements of the invention

[0018] A first aspect of the present invention relates to an external cylindrical or prismatic right solar receiver, with a regular polygonal cross-section, for a concentrated solar power plant of the tower and heliostat field type, comprising an internal structure and a plurality of heat exchanger tube panels containing a heat transfer fluid suitable for absorbing energy from solar radiation, said panels, constituting a cylindrical surface portion or a vertical prismatic face of said solar receiver as the case may be, being arranged vertically and connected in pairs by an articulated joint along an adjacent side, characterized in that each heat exchanger tube panel is connected to at least one internal support element, with an axis substantially perpendicular to the panel,This internal support element is also rotationally connected to a support element belonging to the aforementioned internal structure by means of at least two parallel, substantially horizontal connecting rods, articulated respectively at one end to the internal support element and at the other end to the support element of the internal structure, in such a way that, under the effect of the thermal expansion or contraction of the heat exchanger tube panels, each of the latter moves substantially parallel to itself and without deformation of its surface, and in such a way that the polygonal or circular section of the receiver then undergoes a homothetic transformation.

[0019] According to preferred embodiments of the invention, the external solar receiver further comprises at least one of the following features: the internal support element includes a rod, a plate or a bracket; the heat transfer fluid includes liquid water and / or water vapor; the heat transfer fluid includes a mixture of molten salts;

[0020] A second aspect of the present invention relates to a concentrated solar power plant, of the tower type, comprising an external solar receiver as described above. Brief description of the figures

[0021] There figure 1 represents a schematic plan view of an external solar receiver with a hexagonal cross-section, mounted on a concentrating solar tower according to the present invention. figure 2 represents a perspective view of an example of a concentrating solar tower comprising an external 16-sided solar receiver according to the present invention. figure 3 represents a detailed view of the solar tower of the figure 2 showing the characteristics of the invention. Description of a preferred embodiment of the invention

[0022] The solution proposed within the framework of the present invention consists of: to connect all the panels together and force each panel to move parallel to itself, using a system of connecting rods, that is to say rods articulated at each of their two ends.

[0023] The polygonal prism can thus expand completely freely as the temperature increases and, conversely, contract freely as the temperature decreases. The connecting rods allow it to withstand wind or earthquake forces while maintaining the prism's shape.

[0024] There figure 1This schematically represents an external receiver 1 for a tower solar power plant 8, in the form of a regular right prism with six faces 2 acting as absorbing panels, or, in this particular case for the purposes of illustration, with a hexagonal cross-section, although the number of faces is not limited. The panels 2 are connected to each other in pairs by a hinged joint 3, and each panel 2 can move parallel to itself thanks to a bracket 4 perpendicular to the panel 2. The bracket 4, which may be, for example, a rod, plate, or stirrup, is attached to two connecting rods 5, 6, parallel to each other and hinged on one side to a fixed support structure or frame 7, internal to the tower 8, and on the other side to the bracket 4.

[0025] The connecting rods 5 and 6, which are substantially horizontal and parallel to each other, are connected to a panel 2 and force the panel to move almost parallel to itself, along a circle with a radius equal to the length of the connecting rod. However, the displacements due to the thermal expansion of the panels are small, considering the width of the panels, on the order of 1 to 1.5%. Thus, it can be said that each panel moves parallel to itself in a direction normal to itself. The connecting rods 5 and 6, by virtue of their horizontal position, do not support the weight of the solar panel as described in US 2012 / 312296.

[0026] The wind force acting on one or more panels 2 is distributed over all the connecting rods 5, 6, according to a defined mathematical distribution.

[0027] There figure 2This shows a realistic example of a molten salt receiver for a solar tower power plant, in the form of a regular polygonal prism with 16 faces and a diameter of 18 m. The panels are 18.4 m high. A set of connecting rods and links is installed at the bottom and top of the panels, supporting all the panels. The power captured is 700 MW. Reference symbols

[0028] 1 external receiver 2 absorbing panel 3 articulated joint 4 panel attachment 5 connecting rod 6 connecting rod 7 frame 8 solar tower

Claims

1. A straight cylindrical or prismatic external solar receiver, with a regular polygonal section (1), for a concentrating thermodynamic solar power plant of the tower (8) and heliostat field type, comprising an internal structure and a plurality of panels (2) of heat exchange tubes containing a heat-transfer fluid that is suitable for absorbing the energy from solar radiation, said panels (2), making up a cylindrical surface portion or a vertical prismatic face of said solar receiver depending on the case, being vertically positioned, where each heat exchange tube panel (2) is connected to at least one internal support element (4), with an axis that is substantially perpendicular to the panel (2), that internal support element (4) being further rotatably connected to a support element (7) belonging to the aforementioned internal structure using at least two parallel connecting rods (5, 6), respectively articulated at a first end on the internal support element (4) and at a second end on the support element (7) of the internal structure, respectively, characterized in that said panels (2) are connected in pairs by an articulated link along an adjacent vertical side and in that the connecting rods (5, 6) are substantially horizontal, such that, under the effect of thermal expansion or contraction of the heat exchange tube panels (2), each of the latter moves substantially parallel to itself and without deformation of its surface, and such that the polygonal or circular section of the receiver (1) then undergoes a homothetic transformation.

2. The external solar receiver according to Claim 1, characterized in that the internal support element (4) comprises a rod, a plate or a bracket.

3. The external solar receiver according to Claim 1, characterized in that the heat-transfer fluid comprises liquid water and / or water as steam.

4. The external solar receiver according to Claim 1, characterized in that the heat-transfer fluid comprises a mixture of fused salts.

5. A concentrating thermodynamic solar power plant, of the tower (8) type, comprising an external solar receiver (1) according to any one of the preceding claims.