WO2021205048A1

WO2021205048A1 - Solar collector module

Info

Publication number: WO2021205048A1
Application number: PCT/ES2021/070227
Authority: WO
Inventors: Elena HERRERA DEL TORO
Original assignee: Abengoa Energía, S.A.
Priority date: 2020-04-06
Filing date: 2021-04-06
Publication date: 2021-10-14
Also published as: ES2862451A1

Abstract

The invention relates to a cylindrical parabolic solar collector that ensures that a trellis structure supports the loads to which modules in a row are subjected, and maintains the optimal inclination position of each module, providing the assembly with enough rigidity to minimise deformations or deviations, thereby allowing the necessary optical efficiency. More specifically, the module comprises: a parabolic reflector (1) provided with a concave mirrored surface and an axis of symmetry; two parallel support arms (2) that support the reflector (1), which end in extremities; and a central bottom trellis (3) that supports the support arms (2), the module also comprising spoilers (4) connected to the extremities of the support arms (2).

Description

SOLAR COLLECTOR MODULE

OBJECT OF THE INVENTION

The present invention relates to a solar collector module designed to concentrate solar energy in a reduced area, heating a heat transfer fluid that flows through a receiver. The module comprises a mirrored parabolic reflector supported by support arms and a lattice.

The solar collector module is intended to be linked to other modules creating a row, where a drive mechanism generates a rotational movement in one of the modules that is transmitted to the next.

More particularly, the invention deals with a solar collector with a configuration that ensures that the lattice structure supports the loads to which the modules in the row are subjected and manages to maintain the optimal inclination position of each one of them, giving it sufficient rigidity to the assembly to minimize deformations or deviations and thus have the necessary optical performance.

BACKGROUND OF THE INVENTION

In the state of the art, thermal concentration solar collectors are known as parabolic trough collectors, which, thanks to the concentration of solar energy in a reduced area, heat a heat transfer fluid. Normally the hot fluid is used for the generation of a steam stream that drives a turbine in order to generate electrical energy. They also have an azimuthal single-axis sun tracking system that allows them to orient themselves by following the movement of the sun to optimize their performance. The object of the present invention focuses on the module, without claiming the solar tracker to which it can be attached.

The parabolic-trough solar collector is a technology that consists of having large mirrored surfaces, shaped in a parabolic-cylinder shape, whose mission is to concentrate the solar energy in the focus of the parabola, where a tube-shaped receiver is placed. through which a fluid circulates. Each module includes usually a reflector provided with a plurality of mirrored surfaces, supported by a mesh, structure or lattice system on the convex side of the reflector whose mission is to support and provide rigidity to the set of elements that make up each module.

Collector clusters can be quite large, spanning several square kilometers and including thousands of collector modules. The collector modules are connected to each other forming a loop of collectors or rows. The collector modules are supported at the ends of the lattice by fixed pillars in a linear arrangement, which support them and allow their rotation. At the height of the fixed columns, the connection is made with the next module.

Thus, when the collector rotates, it causes the next module to rotate and so on. But some amount of rotation is lost by momentum accumulation along each half-collector, a collector half on each side of the drive mechanism, and additionally, the wind introduces drag and lift forces on the mirror surfaces, and a important moment of rotation, so that there are different moments of rotation depending on the angle of inclination of the collector and of attack of the wind that generate deformations in the lattice that can displace its optimum inclination.

For example, patent document WO2011070180 is known in the state of the art, the objective of which is to improve lattice structures and make them more robust. The structure is asymmetrical, with bars that are more resistant than others to meet the asymmetric load conditions and the connection of the bars to the nodes, rectangular section fins are installed that facilitate the connection and make the structure more resistant.

The problem associated with the solar collector modules known in the state of the art is that the torsion due to the force of the wind accumulates from the end module until it is attached to the drive mechanism. Each module absorbs additional torque from the outermost adjoining module, and the drive mechanism must react to all accumulated load in the row. When the drive mechanism fails to withstand and overcome the torque resulting from wind loading, the modules deviate from the optimal pointing to the sun, causing their energy harvesting performance to degrade significantly. DESCRIPTION OF THE INVENTION

The present invention tries to solve some of the problems mentioned in the state of the art.

More specifically, the present invention refers to a parabolic-trough solar collector module, comprising a parabolic reflector equipped with a concave mirrored surface and an axis of symmetry, parallel support arms that support the reflector that ends at extremities and a central and lower lattice that supports the support arms where the module additionally comprises ailerons linked to the ends of the support arms.

Thanks to the incorporation of the ailerons, the latticework and the support arms improve the collector's response to the stress to which the parabolic trough collector module is subjected, mainly being the loads to which the collector module is subjected the own weight and the wind. By arranging the ailerons, the load combinations are safely supported, giving the assembly sufficient rigidity to minimize deformations in different positions and thus have the necessary optical performance.

As mentioned, the wind introduces drag and lift forces on the mirrored surface of the parabolic collector module, and an important moment of rotation that varies depending on the orientations or positions of the collector, since it may have the option of rotation with respect to fixed pillars to which it is attached. Thus, there are different moments of rotation depending on the angle of inclination of the collector and the attack of the wind, which must be taken into consideration in the design of the collectors.

The parabolic trough solar collector module is usually intended to link to other modules and rotate around a longitudinal axis to follow the path of the sun. The turning movement can be caused by a drive mechanism linked to at least one module. For every 10 modules there is usually one drive mechanism. Thus, the torsion due to the force of the wind accumulates in the modules, so that each module absorbs the additional torsion of the adjoining outermost module and the drive mechanism must react to the entire load. accumulated of the row. This implies that a massive torsional load passes through the first module to the drive mechanism.

Thanks to the spoiler arrangement, it is possible to increase the wind load in a certain area of the collector by compensating the wind loads on the opposite side, thus reducing the load and net moment on the collector. In this way, it is possible to reduce the torsional moment caused by the incident wind on the collector for different angles of inclination of the collector.

The essential feature of the element is that it provides a profile that is exposed to the wind when the reflector surface on the opposite side of the axis of rotation does the same. Since the moment is a function of the offset, as well as the magnitude of the applied force, the less material would be needed for the construction of the ailerons the greater their offset.

The edge on which the wind hits first behaves aerodynamically in the same way as the leading edge of a wing. Wind flow lines intersect abruptly following two paths at the edge, forcing air to move up the reflector, along the mirrored surface, or down, under and around the convex side of the reflector.

The existence of negative and positive maximum moments is one of the most important considerations for the design of parabolic trough structures since the moment is cumulative along a row. This implies that any mechanism or element that mitigates wind-induced moments has the potential to reduce the design requirements of many components throughout the assembly, resulting in lower material and handling costs.

The advantage of the invention becomes more apparent as the tilt angle of the collector module changes, such that one of the mirrored portions of the reflector exhibits a greater windward profile while the other begins to decrease.

For example, in the case of inclination or attack angles of 105 ° -120 ° and 210 °, when the wind falls on the convex surface of the reflector, the aileron captures the flow parallel to the surfaces, producing a moment of opposite sign at the ends. of the parable. When the wind hits the front of the collector, with angles of inclination or attack of 45-60 °, the ailerons intervene preventing the lifting of the collector from the lower surfaces. The moment coefficient for some of the relevant cases in which the inertia of the flow is predominant, 120 °, 210 °, is reduced in the order of half thanks to the ailerons.

Specifically, the mirrored surface in its cross section, perpendicular to the direction in which the support arms extend, has the shape of a parabola with a focus and the axis of symmetry. The arms are parallel and distributed on a longitudinal axis orthogonal to the cross section of the mirrored surface. Coaxial to the focus of the parabola, a cylindrical receiver can be positioned to accommodate a fluid. Linked to the receiver, the module comprises pilasters that extend from the lattice so as to hold the receiver.

The receiver can be made up of two concentric tubes between which a vacuum is created in order to reduce thermal losses. The fluid circulates through the normally metallic inner tube and is responsible for absorbing heat and transmitting it to the heat transfer fluid that circulates inside. This fluid is usually oil, although it can also be water, so that the steam is generated directly inside the absorber tube itself, in what are called direct steam generation (GDV) systems.

Preferably, the ailerons can have an intermediate section parallel to the axis of symmetry. Additionally, since there is a wide range of tilt angles of the collector module at which different moments are generated, it could be advantageous to introduce several additional ailerons to be able to counteract the load in various positions of the lattice. Additionally, the ailerons can be flat or slightly curved. Due to durability considerations and since these surfaces are used as an additional structural member, the ailerons are made of a preferably metallic material, and can be manufactured in other types of materials.

The module may comprise retaining pieces that link the aileron to the support arms, thus retaining the aileron and prevent it from moving from its predetermined position with respect to the support arms due to the wind load. The support arm can be provided with at least one upper quadrangular beam, defined by an inner face facing the reflector, and the aileron can comprise an upper end linked to the inner face. The aileron may comprise a lower end comprising a first sector perpendicular to the intermediate section and a second sector linked to the first sector and inclined with respect to this which extends towards the intermediate portion. This improves the stiffness of the aileron, the inertia is greater and the vibration of the aileron is avoided.

The lattice can be a three-dimensional structural mesh that in a preferred embodiment of the invention would be constituted by a set of primary structural shapes or small spars, spaced from each other along the longitudinal axis of the structural mesh, each primary structural shape including a set of mesh members arranged in a polygonal shape, and wherein the three-dimensional structural mesh also includes a set of axial mesh members that join the corners of adjacent primary structural shapes, such that the axial mesh members form helical paths to the transmission of torque from one longitudinal end of the structural mesh to the other.

The spoiler may comprise first cavities intended to house fixing elements that fix the spoiler to the support arms. These fastening elements can preferably be rivets. The ailerons can be formed by several metallic sheets joined together also by means of rivets. The number of blades can be twice the number of support arms. Thus, if there are five arms, there may be 10 sheets, preferably joined by every two and each sheet of the pair being linked to a support arm. This connection can be carried out by means of a plate linked to two of the sheets to which rivets are applied so that the flaps can have third holes and house joining means such as rivets and join the sheets together.

The lattice may comprise a front face and a rear face opposite each other, with covers on said corresponding faces being provided with two legs and a body in which the legs form an angle between them of 120 ° and each leg forms an angle. with the body of 120 ° that give rigidity to the lattice. The shape of the caps improves torsional rigidity, improving the collector's optics. As has been seen, the torsional load is the most important load and the one that deforms the collector the most, therefore, an optimal design from the point of view of this effort improves the performance of the collector and lowers its costs. The legs can comprise at least one second cavity that absorbs the deformations of the legs. The covers can comprise first holes configured to be linked to another cover of another module.

As mentioned throughout the description of the invention, the modules can be intended to join at least one other module and form rows or loops that rotate simultaneously. Thus, the covers can be linked to a transmission shaft that is in turn linked to the cover of another module, so that the torsional movement is transmitted between modules. By embracing this axis, bearings can be provided that can serve as support for the axis of rotation of the parabolic trough collector. They have an element or bed on which the longitudinal axis rests, which is covered by a layer of plastic that reduces the coefficient of friction between the axis and the bearing, degrades less than other types of materials, and does not have the corrosion problem that metals have. The bearings can in turn be embraced by a clamp and this, be linked to a fixed pillar, so that the modules are supported and rotatable. The intermediate sector of the spoiler may have a quadrangular shape so that the fabrication of the spoiler is simple.

DESCRIPTION OF THE DRAWINGS

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of a practical embodiment thereof, a set of drawings is attached as an integral part of said description. where, with an illustrative and non-limiting nature, the following has been represented:

Figure 1.- Shows a perspective view of a solar collector module.

Figure 2.- Shows an elevation view of a solar collector module.

Figure 3.- Shows a perspective view of a spoiler attached to a support arm. Figure 4 shows a graph of the curves of the moment coefficients for various angles of inclination of the module in relation to the angle of attack of the wind.

PREFERRED EMBODIMENT OF THE INVENTION Figure 1 shows a perspective view of a parabolic trough solar collector module, according to the present invention. The module is equipped with a parabolic reflector (1) equipped with a concave mirrored surface and an axis of symmetry, with two parallel support arms (2) that support the reflector (1) and that end in extremities and a lattice (3) center and bottom that supports the support arms (2). The module additionally comprises ailerons (4) linked to the ends of the support arms (2).

A cylindrical receiver (17) intended to house a fluid can also be seen, held by pilasters (18) that extend from the lattice (3) and linked to the receiver (17) so that they support it, where the pilasters (18) they are parallel to the axis of symmetry of the parabola. In the preferred embodiment the reflector (1) is divided into two portions leaving a gap in a longitudinal direction and the pilasters (18) extend from the lattice (3) through the reflector (1).

Additionally, the lattice (3) comprises a front face and a rear face opposite each other and provided with a cover (13). The module is intended to be coupled to at least one other module and to form a row or loop of modules that preferably rotate simultaneously around the same longitudinal axis and are coupled to fixed pillars in the joint areas. The connection between the modules is preferably carried out by means of the covers (13) of two modules.

Figure 2 shows a front view of the module, according to the present invention, where the two support arms (2) joined to the lattice (3) can be seen. The two support arms (2) comprise an upper beam (19) and a lower beam (20), linked together by intermediate beams (21). The ailerons (4) are linked to the support arms (2) at their extremities, more specifically to the upper beam (19). There is also a retaining piece (6) linked to the ailerons (4) that extends from the lower beam (20) of the support arm (2). The reflector (1) is connected to the arms by means of connection elements (24). The ailerons (4) have an intermediate section (5) parallel to the axis of symmetry of the reflector (1).

In the front view, it can be seen that the transverse section of the mirrored surface is in the shape of a parabola with its axis of symmetry and its focus, in which the receiver (17) is placed. One of the covers (13) linked to the front face of the lattice (3) can be seen, equipped with two legs (14) and a body (15) where the legs (14) They comprise a second cavity (16). The covers (13) have first holes (22) configured to be linked to the first holes (22) of another cover (13) of another module, for example by means of screws. One second bores (23) configured to center and couple a shaft of rotation can also be seen.

Figure 3 shows a perspective view of a spoiler (4) attached to the support arm (2), according to the present invention. The support arm (2) comprises the upper beam (19) which is a quadrangular beam, defined by an inner face (8) facing the reflector

(I), where the spoiler (4) comprises an upper end (9) linked to the inner face (8). Likewise, it comprises a lower end (10) comprising a first sector

(I I) perpendicular to the intermediate section (5) and a second sector (12) linked to the first sector (11) and inclined with respect to this that extends towards the intermediate section (5). The ailerons (4) comprise first cavities destined to house some fastening elements (25) of the rivet type to join both the support arm (2) and the retaining piece (6). The retaining piece (6) is also attached to the support arm (2), specifically to the lower beam (20), by means of fastening elements (25) of the rivet type.

Figure 4 shows a graph of the curves of the moment coefficients for various inclination angles of the module as a function of the angle of attack of the wind, where the coefficient of the moment is indicated on the Y ordinate axis and the moment coefficient on the axis of the X abscissa angles are indicated. The graph compares the resulting moments in a configuration without ailerons (4), indicated with diamonds and with a continuous line, with the configuration of the present invention, configuration with aileron, indicated with a square.

The maximum positive moment value occurs in a range of approximately 105 ° - 120 °. This resulting maximum positive moment occurs because the mirrored surface of the reflector (1) presents a large vertical profile to the path of the wind. The maximum negative moment value occurs in a pitch angle range from 45 ° to 60 °, which corresponds to the situation in which the wind hits the concave surface of the reflector (1), opposite to the convex surface. The safety position in the embodiment shown is 210 °, the safety position being able to vary in other embodiments, so that when the wind is at maximum speed the collector is at that angle, therefore the coefficient is also very high compared to the rest of positions. It should be noted that if the safety position is changed, the coefficient at this angle would change.

When introducing the ailerons (4), the moment coefficient for the relevant cases mentioned, in which the inertia of the flow 120 °, 210 ° is predominant, is reduced in the order of half compared to the configurations that do not have ailerons (4 ) as shown in the graph. In the rest of the angles, a reduction of the value of the moment coefficient is achieved.

Claims

1.- Cylindrical-parabolic solar collector module, comprising: a parabolic reflector (1) equipped with a concave mirrored surface and an axis of symmetry, two parallel support arms (2) that support the reflector (1) that ends at some extremities a central and lower lattice (3) that supports the support arms (2) characterized in that it additionally comprises ailerons (4) linked to the ends of the support arms (2).

2. The module of claim 1, in which the ailerons (4) have an intermediate section (5) parallel to the axis of symmetry.

3. The module of claim 1, comprising retaining pieces (6) that link the spoiler (4) to the support arms.

The module of claim 1, in which the support arm (2) is provided with at least one quadrangular upper beam (19), defined by an inner face (8) facing the reflector (2), and the aileron (4 ) comprises an upper end (9) linked to the inner face (8).

5. The module of claim 1, wherein the spoiler (4) comprises a lower end (10) comprising a first sector (11) perpendicular to the intermediate section (5) and a second sector (12) linked to the first sector (11) and inclined with respect to this which extends towards the intermediate portion (5).

6. The module of claim 1, wherein the spoiler (4) comprises first cavities intended to house fixing elements (25) that fix the spoiler (4) to the support arms (2).

7. The module of claim 1, in which the flaps (4) are formed by several metal sheets joined together by rivets.

8. The module of claim 7, wherein the number of blades is twice the number of support arms (2).

9. The module of claim 1, wherein the intermediate sector (5) has a quadrangular shape.

10. The module of claim 1, wherein the lattice (3) comprises a front face and a rear face opposite each other, with corresponding covers (13) found on said faces, which are provided with two legs (14) and a body ( 23) in which the legs (14) form an angle between them of 120 ° and each leg forms an angle with the body (23) of 120 ° that give rigidity to the lattice (3).

11. The module of claim 10, wherein the legs (14) comprise at least one second cavity (16) that absorbs deformations of the legs (14).

12. The module of claim 1, wherein the covers (13) have first holes (22) configured to be linked to another cover (13) of another module.