WO2011064205A1

WO2011064205A1 - Solar concentrator, particularly adapted for tower-type systems

Info

Publication number: WO2011064205A1
Application number: PCT/EP2010/068025
Authority: WO
Inventors: Tancredi Simonetti; Francesco D'amato; Lisa Gambicorti; Francesca Simonetti; Yary Volpe; Lapo Governi; Piero Salinari; Giovanna Benvenuti; Laura Magrini; Piero Ranfagni; Emanuele Pace; Mauro Focardi; Maurizio Pancrazzi; Alessandro Gherardi; Giovanni Ronda; Francesco Primo Vaccari; Stefano Taddei; Gabriele Brugnoni; Giuseppe Grazzini; Samuele Piazzini
Original assignee: Ronda High Tech Srl
Priority date: 2009-11-24
Filing date: 2010-11-23
Publication date: 2011-06-03
Also published as: ITPD20090353A1

Abstract

A solar concentrator (10), particularly adapted for tower-type systems, which comprises: - a supporting module (11), which supports at least one frame (12), - mirrors (13), which are connected to the at least one frame (12) so that they can be oriented and cooperate so as to form an array mirror element (14), - means (15) for modulating the position of the frame (12) on the module (11), - means (16) for orienting the mirrors (13) on the frame (12).

Description

SOLAR CONCENTRATOR, PARTICULARLY ADAPTED FOR TOWER-TYPE SYSTEMS

Technical field

The present invention relates to a solar concentrator, particularly adapted for tower-type systems.

Background Art

Tower-type solar concentrator systems nowadays have a field of flat mirrors that partially surrounds the tower, on the receiver of which they are adapted to reflect solar radiation.

This field substantially forms an open ring, in the centre of which the tower is located, and which lies around this tower with such an angular extension as to allow the reflection of the solar radiation toward the receiver from sunrise to sunset throughout the year.

It is well-known that this type of system has poor optical efficiency in comparison with systems with a linear or disk-like parabolic concentrator, i.e., it has a low ratio between the energy available at the receiver and the installed mirror surface area.

Indeed, during the relative motion of the sun in the sky, only part of the mirrors has such an orientation as to reflect solar radiation efficiently onto the receiver.

Furthermore, owing to the large extension of the area of the mirror surface area to be installed, in order to make the construction costs of the system acceptable with respect to its yield, flat mirrors are used which are significantly simpler, and therefore cheaper, to make than the curved mirrors of parabolic concentrators.

However, flat mirrors do not compensate for the divergence of the sun's rays that strike them, thus reflecting a diverging beam of light toward the receiver.

In the field of solar concentrators, the need is felt to provide a receiver that can collect a large quantity of reflected radiation; however, this need is in contrast with an equally felt need to contain the size of the receiver in order to limit heat loss and have a high energy density.

Optimization of the size of the receiver in order to reach a compromise that can meet these requirements at least partially currently results in the provision of receivers with a large surface area for collecting reflected radiation, which therefore have large heat losses and low energy densities in comparison with parabolic concentrators.

Among these, parabolic disk-like concentrators, better known as solar dishes, do in fact allow a higher concentration with respect to tower-type concentration systems and also with respect to linear parabolic concentrators.

The disk-like shape of solar dish concentrators, however, imposes structural limitations on their extension, which currently is limited, and generally not larger than 100 m².

With linear parabolic concentrators, however, high thermal power levels can be obtained.

The need is therefore strongly felt today to have solar concentrators particularly for tower-type systems that make it possible to provide systems that simultaneously have, for the same installed mirror surface area as currently known tower-type systems, a higher energy density and lower heat losses at the receiver, higher thermal power levels, and higher operating temperatures of the concentrated energy.

Disclosure of the Invention

The aim of the present invention is to provide a solar concentrator that meets this need.

Within this aim, an object of the invention is to provide a solar concentrator that has a higher optical efficiency than the fields of mirrors of currently known tower-type solar concentration systems.

Another object of the invention is to provide a solar concentrator that has a substantially constant concentration efficiency as the position of the sun in the sky changes and as its path changes through the year.

Another object of the invention is to provide a solar concentrator that is capable of adaptively compensating the optical aberrations of astigmatism.

Another object of the invention is to provide a solar concentrator that makes it possible to maintain the focus on the preset target as the position of the sun in the sky changes and as its path changes through the year.

Another object of the invention is to provide a solar concentrator that is structurally simple and easy to use and which can be manufactured at low cost.

This aim, as well as these and other objects which will become better apparent hereinafter, are achieved by a solar concentrator, particularly adapted for tower-type systems, characterized in that it comprises

- a supporting module, which supports at least one frame,

- mirrors, which are connected to said at least one frame so that they can be oriented and cooperate so as to form an array mirror element,

- means for modulating the position of said frame on said module,

- means for orienting said mirrors on said frame.

Brief description of the drawings

Further characteristics and advantages of the invention will become better apparent from the description of a preferred but not exclusive embodiment of the solar concentrator according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is an end elevation view of a solar concentrator according to the invention;

Figure 2 is a perspective view of a solar concentrator according to the invention;

Figure 3 is a perspective view, substantially from above, of a solar concentrator according to the invention;

Figure 4 is a partial enlarged-scale view of a detail of a solar concentrator according to the invention;

Figure 5 is a simplified schematic view of a solar concentrator according to the invention.

Ways of carrying out the Invention

It should be noted that anything found to be already known during the patenting process is understood not to be claimed and to be the subject of a disclaimer.

With reference to the figures, the reference numeral 10 generally indicates a solar concentrator, particularly adapted for tower-type systems, which has a particularity in that it comprises

- a supporting module 1 1 , which supports a frame 12,

- mirrors 13, which are connected to the frame 12 so that they can be oriented and cooperate so as to form an array mirror element 14,

- means 15 for modulating the position of the frame 12 on the module

- means 16 for orienting the mirrors 13 on the frame 12.

In alternative embodiments of the invention, which are not described and illustrated herein, the module can support more than one frame.

Advantageously, furthermore, according to the invention the solar concentrator 10 comprises

- a guide 17, which conveniently is a rail for the module 1 1 that is slidingly coupled thereon, and

- a movement motor 18, which is adapted to actuate the motion of the module 1 1 along the guide 17.

Depending on the contingent requirements, there can be more than one movement motor.

Conveniently, the movement motor 18 is arranged on board the module 1 1 in order to actuate driving wheels 19 thereof for resting on the rail that defines the guide 17.

The guide 17 furthermore defines, for the module 1 1 , a motion path that is predefined substantially so that during the movement of the module 1 1 along the guide 17 the module 1 1 is directed toward a chosen target, for example a solar radiation receiver or a secondary mirror that is adapted to reflect the received radiation onto a receiver.

The module 1 1 advantageously comprises an articulation 20 for connection to the frame 12, defining a tilting axis A of the frame 12 with respect to the module 1 1.

The modulation means 15 conveniently comprise a tilting actuator 21, which is adapted to actuate the tilting of the frame 12 about the tilting axis A.

Furthermore, the module 1 1 conveniently comprises a footing 22 and an arm 23 that is supported thereby by means of a rotary joint 24, which defines an axis B of rotation of the arm 23 with respect to the frame 12, the modulation means 15 comprising a rotation motor 25, which is adapted to actuate the rotation of the frame 12 about the rotation axis B.

In alternative embodiments of the invention, depending on the contingent requirements, there can be multiple arms supported by the same footing, each arm supporting a frame and connected to the footing by means of a rotary joint.

Advantageously, when the solar concentrator is in use, the tilting axis

A is substantially horizontal and conveniently the rotation axis B is substantially vertical.

The frame 12 conveniently comprises a supporting element 26 for each mirror 13a, the orientation means 16 comprising orientation actuators 27, which are adapted to orient the mirror 13 on the frame 12, to which it is pivoted on the supporting element 26.

More specifically, the supporting element 26 advantageously comprises a universal joint 28, which defines, with respect to the frame 12, a fulcrum for the orientation of the mirror 13, which it supports.

Advantageously, there are two orientation actuators 27 for each mirror 13 a, which are connected thereto at the rear substantially along a centreline thereof.

Conveniently, furthermore, each mirror 13a is connected to a supporting element 26 in proximity to one of its edges and conveniently at its other centreline.

Moreover, the orientation actuators 27 conveniently comprise a rack- type linear actuator 29, which is actuated by an electric motor of the stepper type 30, so as to modulate precisely the orientation of the mirrors 13 on the frame 12.

The rack-type linear actuator 29 is conveniently connected to the mirror 13 by means of a spherical joint 31.

Furthermore, the mirrors 13 conveniently have profiles with a double parabolic curvature.

The use and operation of the solar concentrator 10 according to the invention are as follows.

In a tower-type solar concentration system, which uses solar concentrators according to the invention, a guide 17 is conveniently common to a plurality of solar concentrators 10, the modules 1 1 of which are mounted slidingly thereon, so as to move in a coordinated manner in order to direct the array mirror elements 14, that they support, toward the receiver which is located on the tower.

Advantageously, there is a control device which automatically actuates the movement motor 18, the tilting actuator 21, the rotation motor 25 and the orientation actuators 27.

Such control device is conveniently programmed to drive the orientation of the array mirror element 14 so that as the time of day and the day of the year change, it reflects sunlight onto a set target C, which can be for example a receiver or a secondary mirror that reflects the radiation onto the receiver.

Thus, by actuating the movement motor 18, the module 1 1 is subjected to a movement D along the guide 17 in order to arrange the array mirror element 14 in a position that is substantially opposite the sun E with respect to the target C onto which it is desired to reflect solar radiation.

With particular reference to Figure 5, if there are multiple modules 1 1 supported on a same guide 17, then a first module 1 1a thereof can be aligned with the sun E and the target C, with the second and subsequent modules 1 lb of the modules 11 being variously misaligned.

In order to obtain a correct aiming of the reflected beam F onto the target C, by means of the rotation motor 25 the arm 23 is rotated, on the footing 22, so as to orient the array mirror element 14 by a compensation rotation G that is adapted to compensate for the misalignment of the second and subsequent modules l ib that support it.

The actuation of the tilting actuator 21 makes it possible to impart a tilting rotation H to the frame 12, with respect to the tilting axis A, so as to modulate the elevation of the radiation that is reflected by the array mirror element 14 in order to direct it at the target C.

As is known, according to the angles of incidence of the solar beam L, which is incident on the array mirror element 14, an astigmatism aberration of the reflected image tends to develop.

This aberration tends to elongate the image in the direction of increase of the angle of incidence of the solar beam L with respect to the perpendicular M with respect to the array mirror element 14, i.e., on the plane of incidence.

Furthermore, as is known, as this angle of incidence varies, a variation of the focal distance of the array mirror element 14 tends to develop, and therefore a defocusing of the radiation reflected onto the target C tends to occur.

Both the astigmatism aberration and the variation of the focal distance can be compensated for by actuating the orientation actuators 27, which adapt the position of the array mirror element 14 for this purpose, by rotating the mirrors 13 with respect to the supporting elements 28 according to orientation rotations P.

In order to optimize the reflection efficiency of a solar concentrator 10, the actuation device, during the relative movement of the sun in the sky, continuously actuates, as mentioned, the movement motor 18, the tilting actuator 21 , the rotation motor 25 and the orientation actuators 27.

In practice it has been found that the invention achieves the intended aim and objects, by providing a solar concentrator which, by virtue of the concentration of the radiation performed by the array mirror element, and by virtue of its orientability and adaptability, makes it possible to provide tower-type systems which simultaneously have, for the same installed mirror surface area as currently known tower-type systems,

- higher energy density and lower heat losses at the receiver,

- higher thermal power levels available to the user, and

~ higher operating temperatures of the concentrated energy.

A solar concentrator according to the invention further has a higher optical efficiency than the fields of concentrator mirrors 13 of currently known tower-type concentration systems, by virtue of the optimization of the array mirror element, which for this purpose can be provided by orienting its mirrors.

Moreover, a solar concentrator according to the invention has a concentration efficiency that is substantially constant as the position of the sun in the sky changes and as its path changes through the year, by virtue of the adaptation of the orientation of the array mirror element, on the module that supports it, and of the mirrors 13 that compose it, on the frame that supports them.

A solar concentrator according to the invention is further capable of adaptively compensating for the optical aberrations of astigmatism, particularly by means of the orientation of the mirrors 13 that compose the array mirror element. Moreover, by making it possible to adapt the focal distance of the array mirror element by virtue of the orientation on the frame 12 of the mirrors 13 that compose it, a solar concentrator according to the invention makes it possible to keep the focus on the preset target, as the position of the sun in the sky changes and as its path changes through the year.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims; all the details may furthermore be replaced with other, technically equivalent elements.

In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to requirements and the state of the art.

The disclosures in Italian Patent Application No. PD2009A000353 from which this application claims priority are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. A solar concentrator, particularly adapted for tower-type systems, characterized in that it comprises

- a supporting module (1 1), which supports at least one frame (12), - mirrors (13), which are connected to said at least one frame (12) so that they can be oriented and cooperate so as to form an array mirror element (14),

- means (15) for modulating the position of said frame (12) on said module (1 1),

- means (16) for orienting said mirrors (13) on said frame (12).

2. The solar concentrator according to claim 1 , characterized in that it comprises

- a guide (17) for said module (11) which is slidingly coupled thereon, said guide (17) defining, for said module (1 1), a predefined movement path,

- at least one motor (18) for moving said module (1 1) along said guide (17).

3. The solar concentrator according to one or more of the preceding claims, characterized in that said module (1 1 ) comprises an articulation (20) for connection to said frame (12), defining a tilting axis (A) of said frame (12) with respect to said module (1 1), said modulation means (15) comprising at least one actuator (21) for tilting said at least one frame (12) about said tilting axis (A).

4. The solar concentrator according to one or more of the preceding claims, characterized in that said module (11) comprises a footing (22) and at least one arm (23) that is supported thereby by means of a rotary joint

(24) , which defines an axis (B) of rotation of said at least one arm (23) with respect to said frame (12), said modulation means (15) comprising a motor

(25) for the rotation of said at least one frame (12) about said rotation axis (B).

5. The solar concentrator according to one or more of the preceding claims, characterized in that during use said tilting axis (A) is substantially horizontal, said rotation axis (B) being substantially vertical.

6, The solar concentrator according to one or more of the preceding claims, characterized in that said frame (12) comprises at least one supporting element (26) for each mirror (13a) of said mirrors (13), said orientation means (16) comprising actuators (27) for orienting said mirror (13) on said frame (12), which is adapted to orient said mirror (13) which is pivoted on said supporting element (26).

7. The solar concentrator according to claim 6, characterized in that said at least one supporting element (26) comprises a universal joint (28) which defines a fulcrum for the orientation of said mirror (13) on said frame (12).

8. The solar concentrator according to one or more of the preceding claims, characterized in that said mirrors (13) have profiles with a double parabolic curvature.