WO2016030558A1

WO2016030558A1 - A solar tracker with reinforced concrete base

Info

Publication number: WO2016030558A1
Application number: PCT/ES2015/070571
Authority: WO
Inventors: Xabier Lecube Inchausti; Francisco Javier GONZÁLEZ CABEZUELO; Iker FEBRER VEGUEIRA; Sabin FERNÁNDEZ UGARTE
Original assignee: Sener, Ingeniería Y Sistemas, S.A.
Priority date: 2014-08-29
Filing date: 2015-07-24
Publication date: 2016-03-03
Also published as: CN106796053A; MA38953B1; MA38953A1; CL2016000690U1

Abstract

The base (10), responsible for supporting the cup of the solar tracker (1), comprises a number of steel tension cables (12), which are either for prestressing or post-tensioning and are embedded into the concrete along the entire length thereof. The base (10) is partially embedded into the ground (21), serving as foundations. The base may have a number of longitudinal grooves (19) or a number of side wings (3) in the portion embedded into the ground (21), so as to transmit the torsional loads to the ground. The base is made as just one single piece, it being possible for it to be solid or hollow and cylindrical or prismatic in shape.

Description

SOLAR FOLLOWER WITH ARMED CONCRETE PEDESTAL

DESCRIPTION

FIELD OF THE INVENTION

The present invention is encompassed within the field of solar energy, and more specifically, the present invention relates to a T-shaped solar tracker, with movement of the supporting structure of the energy collecting surface with respect to the fixed pedestal, with reinforced and prestressed or post-tensioned concrete pedestal.

STATE OF THE TECHNIQUE

A T-shaped solar tracker basically consists of the following elements: collector surface (reflective panels or photovoltaic panels), support structure, drive mechanism, pedestal, foundation and control system.

The pedestal is responsible for supporting the solar tracker cup (collector surface, support structure and drive mechanism) in position and for transmitting all the loads induced by the follower cup (own weight, aerodynamic loads, etc.) to the ground , through the foundation.

The most widespread solution currently on the market is based on the use of a metal pedestal formed by a cylindrical tube of reduced thickness and flanges at its ends, which joins a reinforced concrete foundation, manufactured on site, through bolts of anchor embedded in the foundation. The most common foundation is of the pile type (although it can also be of the shoe type), for whose construction a pilot machine is used, with which a circular perforation is carried out to the defined depth, in which the pile reinforcement is introduced and the anchor bolts properly positioned by template, and finally the whole assembly is concreted.

Solutions using concrete pedestal are also known, such as that described in patent application WO2008 / 046937-A1 concerning a solar tracker and the pre-assembly, transport and final assembly process thereof, in which a follower is described. complete plot with reinforced concrete column and shoe previously made on the ground. Another document in which a concrete pedestal is mentioned is the patent application DE102008027313 A1 referring to the support structure for photovoltaic modules, in which concrete support elements between the foundation and the photovoltaic module are described. In thermosolar tower and field plants of heliostats, the economy of scale to reduce electricity generation costs is leading to increasingly large plants, which require the order of thousands of large heliostats. The aiming precision requirement derived from the great distances between the heliostats and the solar receiver, and the high loads that the heliostats must bear due to their large size, make a high stiffness of the pedestal necessary to guarantee the required aiming accuracy, in all the operating conditions of the heliostat and throughout the life of the plant.

Currently existing solutions could allow meeting these more demanding technical requirements, but at a high cost. For example, the solution based on metal pedestal attached to the foundation by anchor bolts could be used, increasing the diameter and / or thickness of the tube and reinforcing the joint between pedestal and foundation, but the increase in weight and cost would be high. A reinforced concrete pedestal could also be used, but the loads induced by the follower cup have a large and frequent fluctuation because their main cause is wind loads, and this fluctuation would cause the concrete to be subjected to varying tensile stresses. and compression that, over time, would lead to fatigue cracking of the concrete since only the steel worked in the tractioned areas of the pedestal, so that the amount of steel would have to be increased to guarantee throughout the life of the plant the strength and stiffness required, with the consequent increase in cost.

However, despite the aforementioned drawbacks, the use of reinforced concrete on the pedestal of solar trackers is an attractive option in terms of the possibilities it offers to achieve high rigidity at an acceptable cost, but requires a solution other than known so far.

DESCRIPTION OF THE INVENTION

The present invention relates to a solar tracker with reinforced concrete pedestal comprising a pickup surface, a support structure, a drive mechanism and a reinforced concrete pedestal responsible for supporting the cup of the Solar Tracker. The pedestal comprises tensioned steel cables for concrete compression and is partially embedded in the ground, acting as a foundation.

Tensioned steel cables preferably run the entire length of the pedestal and are tensioned at a certain level of load so that the concrete never works under tension even if the solar tracker suffers the maximum loads defined for the application.

In a particular embodiment, the tensioned steel cables are post-tensioned cables. In another preferred embodiment, the tensioned steel cables are prestressing cables.

The pedestal preferably comprises a column and an interface in its upper part for the connection with the solar tracker cup. The pedestal can comprise a truncated conical section that adapts the column section with the interface section. The pedestal can have longitudinal grooves, located in the part of the pedestal partially embedded in the ground, to help transmit torsional loads. To help transmit torsional loads, the pedestal can also have a plurality of lateral fins embedded in the ground at its bottom. The pedestal is preferably partially embedded in a hole drilled in the ground and filled with concrete.

The pedestal is preferably made in one piece. In a preferred embodiment the pedestal is prefabricated in the workshop.

Therefore, the solar tracker of the present invention comprises a reinforced and prestressed (or post-tensioned) concrete pedestal, which incorporates the functions of the foundation when it is designed so that part of its length is embedded in the ground and transmits the loads to it. .

This reinforced and prestressed / post-tensioned concrete pedestal requires less concrete volume than a conventional reinforced concrete pedestal to withstand the loads that the follower suffers, being also the prestressing / post-tensioning adaptable to the maximum loads defined for each application. In addition, with prestressing / post-tensioning the appearance is avoided of cracks in concrete, which in the case of conventional reinforced concrete would eventually appear over time because the concrete would be subject to variable tensile-compression stresses caused by the fluctuation of the loads suffered by the follower, so that with The present invention is achieved to guarantee the strength and stiffness of the pedestal throughout the life of the plant.

On the other hand, by integrating in a single piece pedestal and foundation, the joint between pedestal and foundation and associated elements (metal pedestal flange and anchor bolts) are eliminated. In this way, the assembly is simplified and the component and assembly costs are reduced, at the same time the rigidity is increased when the joint has been removed.

In addition, the pedestal can be prefabricated in the workshop, which facilitates its quality control and allows high reliability and repeatability.

In accordance with the present invention, the pedestal comprises a solid or hollow, prismatic or cylindrical column of reinforced and prestressed (or post-tensioned) concrete.

In the case of prestressed pedestal, there are steel cables that are held tensioned with a certain load in the pedestal concreting process, during its manufacturing process, this prestressing being variable according to the maximum loads defined for each application. This prestressing will be such that, although the follower suffers the maximum loads defined for an application, the concrete is never subjected to tensile stresses. In the case of post-tensioned pedestal, the cables are subsequently tensioned to the concreting and curing of the pedestal.

The upper end of the pedestal has an interface for joining with the follower cup, an interface that can be varied to adapt it to the characteristics of the follower cup interface. This pedestal interface can consist of threaded inserts or anchor bolts embedded in the pedestal, or through holes.

Depending on the type of terrain and the torsion loads induced by the follower cup, the pedestal can incorporate some fins located in the remaining section embedded in the ground, to help transmit torsion loads to the ground and increase rigidity.

For the installation of the pedestal in the field, a perforation of greater section than the pedestal is carried out in the field, be it cylindrical or prismatic, and, in case of carrying fins, the necessary excavation is also done for them. Next, the pedestal is inserted into the perforation and, once it has been correctly positioned with the help of temporary supports, concrete is poured to fill the space between the perforation and the pedestal, so that the pedestal and ground work together. The verticality error of the pedestal produced during its installation or over time by ground settlement, is compensated with the control software of the solar tracker drive mechanism, thus preventing the verticality error from affecting the tracking accuracy of the tracker and therefore an extremely precise positioning of the pedestal is not necessary.

BRIEF DESCRIPTION OF THE DRAWINGS

A series of drawings that help to better understand the invention and that expressly relate to an embodiment of said invention which is presented as a non-limiting example thereof is described very briefly below.

Figures 1A and 1 B show different views of a solar tracker incorporating a possible embodiment of the pedestal according to the present invention.

Figures 2A, 2B and 2C show a possible embodiment of the pedestal.

Figure 3 shows a cross section of the pedestal column, where the detail of grooves in the part of the column that is embedded in the ground is observed.

Figures 4A, 4B and 4C show another possible embodiment of the pedestal.

Figure 5 shows schematically the assembly of the pedestal embedded in the ground. DETAILED DESCRIPTION OF AN EMBODIMENT

The constitution, features and advantages of the solar tracker of the invention will be better understood with the following description, made with reference to the embodiment shown in the accompanying drawings.

Figures 1 A and 1 B show, respectively, a rear and profile view of a solar tracker 1 incorporating an embodiment of the pedestal 10 according to the present invention. The pedestal 10 is responsible for supporting the collector surface 2 (whether reflective panels or photovoltaic panels), the support structure 3 and the drive mechanism 4 of the solar tracker.

In Figure 2A, 2B and 2C one of the possible embodiments of the pedestal 10 is shown. Figure 2A shows a perspective of the external appearance. On the other hand, Figure 2B represents a longitudinal section of the pedestal 10 of Figure 2A installed in a perforation 20 carried out on the ground 21, in which the reinforcement 1 1 and the tensioned steel cables 12 are not shown. Figure 2C shows a longitudinal section of the pedestal where the steel reinforcement 1 1 and the tensioned steel cables 12 are seen that run the entire length of the pedestal 10. The pedestal 10 of this embodiment comprises a column 15 of reinforced and prestressed / post-tensioned concrete , of constant section, cylindrical, slender and hollow, with a height of several meters. The pedestal 10 has in its upper part an interface 17 for the connection with the follower cup. To adapt the diameter of the column 15 to the diameter of the interface 17, the geometry has to change progressively at the top of the pedestal 10, without abrupt changes in the size of the section to avoid stress concentration. In the case of this embodiment, in order to adapt these sections, the pedestal 10 comprises a truncated conical section 16 with a low inclination angle, which adapts the diameter of the column 15 with the diameter of the interface 17. Also in the upper part of the interface 17 a series of threaded inserts 18 are embedded in the pedestal for the attachment elements of the follower cup 1.

In its lower part the pedestal 10 has longitudinal grooves 19 in the part of the column 15 of the pedestal 10 which is embedded in the ground 21. Grooves Longitudinal 19, shown in detail in the cross section of column 15 (Figure 3), are useful for better transmitting torsion.

Figures 4A, 4B and 4C show another possible embodiment of the pedestal 10, which incorporates fins 13 (two fins, in the embodiment shown in the figure) in its lower part to transmit torsional loads to the ground. Inside (both column 15 and fins 13) the concrete has steel reinforcement 1 1. Column 15 is longitudinally traversed by several tensioned steel cables 12, either for post-tensioning or prestressing cables.

The concrete pedestal 10 is manufactured in a workshop that does not have to be close to the location of the follower. In the case of the realization of the pedestal with prestressed steel cables 12, a mold is used for its manufacture in which the steel reinforcement 1 1 and the steel cables 12 are placed. Next, the steel cables are tensioned to the predefined load and the concrete is poured into the mold, letting it cure for the necessary time. Once the sufficient degree of cure is reached, it is removed from the mold.

The procedure for using the prestressed reinforced concrete pedestal for solar tracker comprises the following steps:

- make a borehole 20 on the ground 21 with a section and depth such that it is able to accommodate the defined part of the pedestal 10, and in case of carrying the lateral fins 13 the necessary excavation for them;

- insert the pedestal 10 in an upright position inside the perforation 20;

- concreting the contour of the perforation 20.

Figure 5 shows schematically the assembly of the pedestal 10 embedded in the ground 21. Once the pedestal 10 has been correctly positioned with the help of temporary supports 23, concrete 22 is poured to fill the space between the perforation 20 and the pedestal 10, so that pedestal 10 and ground 21 work together.

Claims

one . Solar tracker with reinforced concrete pedestal, comprising:

a pickup surface (2),

a support structure (3),

a drive mechanism (4), and

a reinforced concrete pedestal (10) responsible for supporting the sun tracker cup (1),

characterized in that the pedestal (10) comprises tensioned steel cables (12) for concrete compression and that the pedestal (10) is partially embedded in the ground (21) acting as a foundation.

2. Solar tracker according to claim 1, characterized in that the tensioned steel cables (12) cover the entire length of the pedestal (10) and are tensioned at a certain level of load so that the concrete never works under tension even if the solar tracker (1) suffer the maximum loads defined for the application.

3. Solar tracker according to any of claims 1 to 2, characterized in that the tensioned steel cables (12) are post-tensioned cables.

4. Solar tracker according to any of claims 1 to 2, characterized in that the tensioned steel cables (12) are prestressing cables.

5. Solar tracker according to any of the preceding claims, characterized in that the pedestal (10) comprises a column (15) and an interface (17) in its upper part for connection with the solar tracker cup.

6. Solar tracker according to claim 5, characterized in that the pedestal (10) comprises a truncated conical section (16) that adapts the column section (15) with the interface section (17).

7. Solar tracker according to any of the preceding claims, characterized in that the pedestal (10) has longitudinal grooves (19), located in the part of the pedestal (10) partially embedded in the ground (21), to help transmit torsional loads.

8. Solar tracker according to any of the preceding claims, characterized in that the bottom pedestal (10) has a plurality of lateral fins (13) embedded in the ground (21) to help transmit torsional loads.

9. Solar tracker according to any of the preceding claims, characterized in that the pedestal (10) is partially embedded in a hole (20) in the field (21) and filled with concrete (22).

10. Solar tracker according to any of the preceding claims, characterized in that the pedestal (10) is made in one piece.

eleven . Solar tracker according to any of the preceding claims, characterized in that the pedestal (10) is prefabricated in the workshop.