ES1270324U - Parabolic trough solar collector with fixed receiver. (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Parabolic trough solar collector with fixed receiver, comprising a receiver tube (2) and several collector elements (1), with the receiver tube (2) arranged along a loop, said collector elements (1) having a Reflective parabolic surface (6) that concentrates the solar rays in the receiver tube (2), and said reflective surface (6) is supported by a support structure (4) which in turn is supported by circular multipurpose structures (5), concentric with the receiver tube (2), which allow the longitudinal and transverse forces to be transmitted to the ground by means of guides (7) that rest on foundations (10) through supports (8), and that also have a system to control the rotation of the collector elements (1) and maintain their focus on the sun and make it concentrate on the receiver tube (2) that remains in the focus of the parabola, characterized in that the collector elements (1), are structurally independent in Between each other, and independent of the receiver tube (2), which is fixed and rests on supports (3), which in turn rest on foundations (9); while the multipurpose circular structure (5), which embraces each collector element (1), to which it is joined integrally, is constituted by an outer profile (5a) of a rigid material, circularly curved, formed by one or more pieces joined between yes in a rigid way, whose outer circle (5a) thus formed is joined by means of spokes (5c) to an inner profile (5b) that surrounds the receiver tube (2) without touching it; the outer profile (5a) resting on guides (7) that prevent its longitudinal and lateral displacement, but not its rotation. (Machine-translation by Google Translate, not legally binding)

Description

DESCRIPTION

Parabolic trough solar collector with fixed receiver

TECHNICAL SECTOR

The sector in which the invention is framed is that of solar thermal power plants. More specifically, the invention relates to a concentration system using parabolic trough collectors.

BACKGROUND OF THE INVENTION

In the parabolic trough collectors used in a generalized way in current commercial power plants, the collector tube, located in the focus of the parabola, is jointly attached to the support structure of the parabolic surface of solar ray collecting mirrors, so that it tube and structure rotate simultaneously following the movement of the sun.

This arrangement has the disadvantage of requiring, for the connection of the receiver tube at both ends of the parabolic-trough collector, some joints that allow the tube to double displacement: (a) in a longitudinal direction, to accommodate the expansion of the tube when heated from the ambient temperature to working temperature and (b) in a circular manner in the plane perpendicular to the tube, to accommodate the circular movement of the tube around the axis of rotation of the collector-tube assembly.

The joints used to accommodate these movements, both those of the flexible type and those of the ball, have been causing frequent sealing and breakage problems, which causes high maintenance costs in the plants and safety problems, as the heat transfer oils are highly flammable. , and of an environmental nature, as the land can be contaminated if there are significant spills.

US2011186041 discloses a parabolic-trough heat capture system in which the receiver tube is fixed and is supported directly to the ground, where several collector elements, joined together and with the receiver tube, present a parabolic reflective surface that concentrates the solar rays in the receiver tube. This reflective surface is supported by a concentric circular structure with the receiver tube. This document also discloses a system to control the rotation of the collector elements and maintain their focus on the sun and make it concentrate on the collector or receiver tube that remains in the focus of the parabola.

In the circular structure of the previous document, the receiver tube is located inside a bushing supported by an inner profile that is supported by bearings forming a structural unit as a whole, which leads to a costly construction and repair because all the elements that enter to form part of said structure are linked or related to each other.

EXPLANATION OF THE INVENTION

The proposed invention aims to solve this problem for any heat transfer fluid by making the receiver tube fixed, except for its longitudinal expansion (as it is, for example, in Fresnel type concentration plants); the longitudinal expansion is accommodated in a similar way to any hot pipe, by means of ties at both ends of the pipe; the mirrors that form the reflective surface and its support structure, grouped in several longitudinally arranged collector elements, are rotated in a circular path centered on the axis of the receiver tube; This rotation is achieved by joining each collector element to multipurpose circular structures, which are supported by guides, which transmit the forces to the foundation, as described below. It is estimated that the costs of the whole life of a solar field built with this type of fixed tubes and mobile collectors independent of the tubes will be more economical than with the types of collectors currently used.

The invention proposes several collector elements, structurally independent from each other, and independent from the fixed receiver tube, which is supported by supports, which in turn are supported by foundations, which facilitates the modularity of the installation and the independence of the tube. receiver of the collecting elements.

A) Heating loops. Receiver tube

The invention can be applied to loops for collecting solar radiation and heating the receiver tube of any length, range of working temperatures and heat transfer fluids. In each loop the receiver tube is fixed, and rests on foundations anchored directly to the ground, located at such distances that the tube bending is not excessive; the calculation of this distance between supports is a function of the diameter of the metal tube and the glass tube in which it is normally encapsulated, the maximum working temperature and the nature and characteristics of the heat transfer fluid. The pipe supports to the above-ground foundations can be designed to accommodate the expansion of the pipe in either a sliding or a sliding manner. oscillating in the longitudinal direction, and can have a single element embedded in the foundation or two or more elements to bracing the loads.

At the ends of each loop, the receiving tube is extended by one or more liras located in the plane perpendicular to the axis of the tube, so that the longitudinal displacements due to expansion are absorbed when passing from ambient to operating temperature. These lyres can be totally or partially replaced by non-rotating expansion joints.

Each of these areas is protected with insulation and thermal tracing.

freezing of the heat transfer fluid, especially when it is required to stop the operation of the loop for maintenance operations, or during filling of the loop.

B) Reflective surface and support structure: collecting elements and multipurpose circular structures.

The reflective surface and its support structure have two key differences with those currently used: they are structurally independent of the receiver tube, which they do not touch at any time, and, instead of rotating around an axis located in the support structure itself or next to it, they rotate around an axis that coincides with the axis of the receiver tube (but without touching it).

These reflective surfaces and their corresponding support structures constitute, together with the multipurpose circular structures to which they are attached, collecting elements of a length somewhat shorter than the distance between the supports of the receiver tube, so that the collecting elements can rotate freely without touching the fixed tube supports; in each loop there will be as many collector elements as receiver tube supports minus one. Each collecting element will be supported by at least two multipurpose circular structures that transmit to the foundations the forces of all kinds that the collecting elements must withstand, especially their own weight and those derived from the wind; Furthermore, through a turning mechanism linked to at least one of the multipurpose circular structures, the orientation of the parabolic surface to the sun is maintained, thus ensuring maximum interception of the sun's rays by the receiver tube.

C) Description of multipurpose circular structures

Each multipurpose circular structure is a circle executed in a profile, which may be, for example, in the shape of a T or a cross with horizontal arms. The profile can be made of any material with sufficient resistance to deformation and working conditions, such as steel or plastics with adequate mechanical and thermal characteristics.

To this circle is attached, by means of welding or any type of screwed, riveted or similar joint, the supporting structure of the reflecting surface, which must be designed to provide minimum weight and maximum rigidity, and which is not the object of this invention. In a preferred embodiment, the structure does not protrude from the virtual space cylinder defined by the multipurpose circular structures, but is inscribed within it, which allows the assembly to be located very close to the ground, without having to carry out any excavation to allow it to rotate. of the element when the sun is near its zenith.

The multipurpose circular structures receive the loads transmitted to them by the supporting structures of the reflective surface, mainly of their own weight and wind, and are supported in turn by two or more guides that, allowing their rotation freely, are capable of taking longitudinal loads and perpendicular to the axis of the loop, and which in turn are attached to supports capable of transmitting these loads to the ground, through their foundations. In a preferred embodiment each multipurpose circular structure would be supported on three of these guides.

The rotational forces are supported by the rotation mechanism, which in the preferred embodiment consists of a gear wheel, driven by a reduction gear system or by a hydraulic system, which meshes with another wheel that is attached to the inside face of a of the horizontal wings of the profile of the multipurpose circular structure; In another embodiment, the gear system is replaced by a hydraulic system that controls the circular movement of said structure.

In the preferred embodiment, the multipurpose circular structure maintains its shape thanks to an arrangement similar to that of a bicycle wheel, where a series of prestressed spokes join the outer circle with an inner circle that surrounds the fixed receiver tube at a sufficient distance to avoid that they touch.

This inner circle, which works under tension, has, in the preferred embodiment, a lightweight design that minimizes the losses of the irradiation that must reach the receiving tube.

BRIEF DESCRIPTION OF THE DRAWINGS

To help in the interpretation of the description, and with a non-limiting character, some drawings are included as follows:

Fig. 1.- Shows a partial view of a loop with several collecting elements (1).

Fig. 2.- Section view of a collector element.

Fig. 3.- Section of a preferred profile of the multipurpose circular structure (5).

Fig. 4a and 4b.- Schematic views of a set of transverse and longitudinal load-bearing guides.

Fig. 5.- View of a multipurpose circular structure.

Fig. 6.- View of the lyres that absorb the longitudinal expansion of the collecting metal tube.

PREFERRED EMBODIMENT OF THE INVENTION

In Fig. 1 an installation of several collector elements (1) structurally independent of each other, and independent of the fixed receiver tube (2) is observed. This tube is supported by supports (3) that rest on foundations (9). The support structures (4) of the collecting elements (1) on which the reflective surface (6) rests are integrally attached (not seen in this view) to the outer rings (5a) of the multipurpose circular structures. These are supported by the guides (7) and their supports (8) that transmit the lateral and longitudinal loads to the foundations (10).

In Fig. 2, of a section of a collector element (1), the support structure (4) of the reflective surface (6) can be seen, with indicative dimensions for a preferred embodiment, where molten salts are used as heat transfer fluid. operate between 200 and 500 ° C. The support structure (4) can be attached to the outer rings (5a) of the multipurpose circular structures by means of an auxiliary structure (4a). The spokes (5c) join the outer ring (5a) with the inner ring (5b). It is observed that this inner ring (5b) is concentric with the receiver tube (2) from which it is separated a certain distance, to avoid any contact. Three sets of guides (7) have been represented, which take the transverse and longitudinal loads on each guide by means of two pairs of wheels (only the wheels that take the transverse loads have been represented), transmitting them to the supports (8) that finally them would transmit to the foundations (10). The rotation control mechanism (11), supported to the foundation (10) by supports (12), has also been schematically represented.

In Fig. 3, which is a section of a preferred profile of the multipurpose circular structure (5) with the inner gear (13) attached to the outer profile (5a), the gear wheel is shown. rotation and pointing control mechanism (11a) with its motor and gearbox (in this embodiment), schematically represented (11b) supported by the supports (12) to the foundations (10).

Figures 4a and 4b show the set of guides (7) and supports (8) in which the wheels (21) and (22) allow the outer ring (5a) to rotate, but prevent its lateral movement or longitudinal. These wheels remain tight against the ring thanks to the springs (23) and (24) that are contained in the boxes (25) that in turn are attached to the supports (8), which are drawn here schematically and only to illustrate what which could conceptually be a preferred embodiment, since this type of support is resolved in the state of the art.

In Fig. 5 a multipurpose circular structure is seen showing the outer ring (5a) the radii (5c) and the inner tensile circle (5b) that does not touch the glass tube (2b) or the metal tube (2a).

Finally, in Fig. 6 one of the ribs located in the plane perpendicular to the axis of the tube can be seen, which would absorb the longitudinal expansion of the metal collector tube (2a) allowing its longitudinal expansion until the connection to the valve (2d) and, in short, to the heat transfer fluid collector (2c) with admissible forces.

A preferred embodiment of a collector element includes two multipurpose circular structures with a diameter of approximately 10 m, into which a support structure with a parabolic reflective surface with an aperture of about 8 m is inserted, integrally attached to the multipurpose circular structures. m.

Each loop would have a total length of about 260 m (one way, that is, about 520 m between round trips), so a dilation of the order of 1 m can be expected, which would be absorbed with three lira with about 24 meters of length in the plane perpendicular to that of the loop.

With 70 mm diameter metal receiver tubes, supports would be installed every 13 m, so this would be approximately the length of each collector element. Therefore, we would need 20 elements for each half loop.

Each of the two multipurpose circular structures would be located 3 m from each end of the pick-up element.

Each multipurpose circular structure would have three longitudinal guide supports and transverse, two located at a height from the ground approximately one third of the diameter of each structure and the other in the closest possible area to the rotation control gear, in such a way as to avoid unwanted stresses on it.

Claims (4)

1. - Parabolic trough solar collector with fixed receiver, comprising a receiver tube (2) and several collector elements (1), with the receiver tube (2) arranged along a loop, presenting said collector elements (1) a parabolic reflective surface (6) that concentrates the sun's rays in the receiver tube (2), and said reflective surface (6) is supported by a support structure (4) which in turn is supported by multipurpose circular structures (5), concentric with the receiver tube (2), which allow the longitudinal and transverse forces to be transmitted to the ground by means of guides (7) that rest on foundations (10) through supports (8), and that also have a system to control the rotation of the collector elements (1) and maintain their focus on the sun and make it concentrate on the receiver tube (2) that remains in the focus of the parabola, characterized in that the collector elements (1 ), they are structurally independent each other, and independent of the receiver tube (2), which is fixed and is supported by supports (3), which in turn are supported by foundations (9); while the multipurpose circular structure (5), which embraces each collecting element (1), to which it is joined integrally, is constituted by an outer profile (5a) of a rigid material, circularly curved, formed by one or more pieces joined between yes in a rigid form, whose outer circle (5a) thus formed is joined by means of spokes (5c) to an inner profile (5b) that surrounds the receiver tube (2) without touching it; the outer profile (5a) leaning on guides (7) that prevent its longitudinal and lateral displacement, but not its rotation. 2. - Collector, according to claim 1, characterized in that the rotation control mechanism of the collector elements (1) comprises two gears (13), one attached to the circular profile (5a) on its outer or inner face, and the other moved by a device that allows to control the rotation to track the solar movement, with the axis of this rotation the same as that of the receiver tube (2). 3. - Collector according to claim 1, characterized in that the rotation control mechanism of the collector elements (1) is hydraulic or pneumatic. 4. - Collector, according to claim 1, characterized in that at the ends of each loop the receiver tube (2) is extended by one or more lines located in the plane perpendicular to the axis of the tube, in order to absorb longitudinal displacements due to the expansion of the tube (2) when going from ambient to operating temperature.