TECHNICAL FIELD OF THE INVENTION

The present invention relates to a solar concentrator.

More particularly, the present invention relates to a concentrator of light rays obtained from the full or partial rotation of a profile with respect to an axis, and consequent concentration of the radiation on the surface thus generated.

BACKGROUND ART

Solar power units for energy production, e.g. electric or thermal energy, usually comprise a certain number of heliostats, installed on the ground able to direct and possibly concentrate solar radiation towards a determined target.

One of the most used devices for the concentration of the solar radiation is the so- called CPC (Compound Parabolic Concentrator); more particularly, this is a non- imaging-type concentrator, whose profile consists of two parabolic arcs, as will be better explained below.

Figure 1 schematically shows the 2D profile (in two dimensions) of a CPC-type concentrator; in this figure it is evident how the arc A, i.e. one of the two arcs of the profile P, consists of a part of parabola B having the axis C parallel to the direction D, and focus in E.

Figure 2 is, instead, a schematic - and sectional - representation of the operation of a CPC-type concentrator.

Observing Figure 2, it is immediately understood that the light rays F, coming from a source and having an incidence on the input area of the device, after one or more reflections, are able to concentrate in a smaller output area G, only if their incidence angle H is less than or equal to that of acceptance I.

When the CPC profile is completely rotated around the concentration (or symmetry) axis J, a revolution surface K is obtained, as schematically shown in Figure 3 in which the input area L and the output area G of the light rays F are evident.

This type of revolution surface K is normally used in the so-called beam down- type systems. For constructional reasons, sometimes, the surface K can be approximated by a series of segments (or bands) that approximate the profile and, joined together, give thus rise, in the input section L and in the output section G, to a polygonal profile.

In the three-dimensional form, a CPC-type concentrator proves to be highly efficient, in the same conditions compared to concentrators of other shapes and volumes, when, e.g., it is necessary to collect and concentrate - as mentioned - solar radiation for the production of energy and heat coming from one or more reflection devices (e.g., the heliostats).

However, as can be appreciated, using a CPC-type concentrator Q in a solar power unit having a traditional configuration, technically it is not possible to direct the reflected radiation in the input area L of the concentrator, since the latter is normally installed with its own symmetry axis parallel to the rotation axes of the heliostats M of the power unit.

This problem can be solved by adding an additional secondary reflector N in the path of the light rays F (e.g., as in the so-called beam down-type systems), as schematically shown in Figure 4.

However, in this way considerable constructive complexities are introduced, mainly due to the presence of the high tower O supporting the secondary reflector N, which, in any case, determines a reduction in the overall yield of the system; moreover, the efficiency of a CPC-type concentrator Q, with the same concentration area (therefore with the same output of the light rays), increases with the decrease of the incidence angle, and this involves the construction of CPCs highly developed in height.

OBJECTS OF THE INVENTION

The technical aim of the present invention is to improve the state of the art in the field of solar concentrators.

Within such technical aim, it is an object of the present invention to overcome the disadvantages mentioned above, by developing a solar concentrator which does not require further systems beyond the heliostats, such as, e.g., further reflection systems, to direct the radiation inside the concentrator itself.

Another object of the present invention is to provide a solar concentrator which can be installed on the ground or in any case at a reduced height above the ground and in a non-vertical position as generally required in beam down systems, and therefore substantially at the level of the plane in which the heliostats are located. Another object of the present invention is to accomplish the above objects with a simple and economical solution from the constructive point of view.

Still another object of the present invention is to accomplish the above objects with a simple and economical solution from the installation and maintenance point of view.

This aim and these objects are all achieved by the solar concentrator according to the attached claim 1.

The non-imaging-type concentrator, according to the invention, comprises at least one input section of the light rays, at least one reflecting surface of the light rays passing through said input section, and at least one output section suitable for collecting the light rays which pass through the input section; the reflecting surface comprises at least a full or partial revolution surface of at least a two-dimensional profile about a first axis.

The aforementioned profile does not intersect the first axis, and comprises a first stretch and a second stretch arranged in a mirror-like, or substantially mirror-like, manner with respect to a second axis; the second axis and the first axis are perpendicular or incident to each other.

According to the invention, the reflecting surface comprises a first portion and a second portion separated from each other, which identify an internal reflection space between them, and between which a discontinuity, which defines the aforementioned output section, is provided.

The first portion and the second portion of the reflecting surface are a revolution surface respectively of the first stretch and of the second stretch of the profile around the first axis, for an angle equal to 360° or less than 360°.

This solution allows to receive the light rays reflected by heliostats, arranged around the concentrator, even when the latter is positioned substantially at the same height above the ground to which the plane of the heliostats themselves is provided. Therefore, it is no longer necessary to provide an auxiliary reflector, normally provided in power units comprising a concentrator of the known type; moreover, the energy expenditure due to the need to pump any energy transport fluids at high altitudes is considerably reduced, as occurs in the aforementioned power units of the known type.

The dependent claims refer to advantageous embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages will be better understood by anyone skilled in the art from the description that follows and from the accompanying drawings, given as a non-limiting example, wherein:

Figure 1 is a schematic representation of the two-dimensional profile of a CPC concentrator of the known type;

Figure 2 is a two-dimensional schematic representation of the operation of a CPC concentrator of the known type;

Figure 3 is a three-dimensional schematic view of a CPC concentrator of the known type;

Figure 4 is a schematic front view of a beam down-type solar power unit comprising a known CPC-type concentrator Q;

Figure 5 is a schematic front view of a solar power unit comprising the concentrator according to the present invention;

Figure 6 is a schematic front view of the profile of the concentrator according to the present invention;

Figure 7 is a schematic front view of the concentrator according to the present invention, generated by the revolution of the profile of Figure 6;

Figure 7 A is an axonometric view of the concentrator of Figure 7;

Figure 8 is a schematic front view of the profile of the concentrator according to another embodiment of the invention;

Figure 9 is a schematic front view of the concentrator, generated by the revolution of the profile of Figure 8;

Figure 10 is a schematic front view of the profile of the concentrator according to another embodiment of the invention;

Figure 11 is a schematic front view of the concentrator, generated by the revolution of the profile of Figure 10;

Figure 12 is a schematic front view of another type of solar power unit comprising the concentrator according to the present invention;

Figure 13 is a three-dimensional view of the concentrator according to the invention, in another embodiment;

Figure 14 is a front view of the concentrator of Figure 13;

Figure 15 is a plan view of the concentrator of Figure 13;

Figure 16 is a three-dimensional view of the concentrator according to the invention, in another embodiment;

Figure 17 is a plan view of the concentrator of Figure 16;

Figure 18 is a front view of the concentrator of Figure 16;

Figure 19 is a front view of another embodiment of the concentrator according to the present invention;

Figure 20 is a detailed front view of still another embodiment of the concentrator according to the invention;

Figure 21 is a detailed front view of a further embodiment of the concentrator according to the invention.

EMBODIMENTS OF THE INVENTION

With particular reference to Figure 5, a solar concentrator according to the present invention is indicated as a whole with the reference number 1.

In Figure 5 the solar concentrator 1 is schematically shown installed in a solar power unit 2.

The solar power unit 2 comprises a plurality of heliostats 3, installed on the ground; the heliostats 3 are conveniently arranged around a system 4 which in turn comprises the aforementioned concentrator 1, so that the light rays 5 collected by the heliostats 3 themselves are reflected towards the aforementioned concentrator 1.

The system 4 comprises, in addition to a concentrator 1, also a receiver R, which cooperate and interact in the manner better explained hereinafter.

In Figure 5 the system 4, which incorporates the solar concentrator 1, also comprises a tower 6 which has the function of positioning the concentrator 1 itself at a certain height with respect to the plane of the heliostats 3.

It is however specified that - as will be better explained hereinafter - the solar concentrator 1 according to the present invention can also be advantageously used in the context of solar power units 2 wherein it is installed substantially at the same height with respect to the plane of the heliostats 3.

The concentrator 1 according to the present invention is of the non imaging type, that is to say, functioning according to the principles of non-imaging optics, which has the advantage of optimizing the energy transmission from a source to a receiver, to the detriment of the formation of the image typical of optical systems, which has no relevance in the field of energy transfer.

The solar concentrator 1 comprises at least one input section 7 of the light rays 5. Through the input section 7, the light rays 5 penetrate inside the solar concentrator 1.

Furthermore, the solar concentrator 1 comprises at least one reflecting surface 8 of the light rays 5 which pass through the input section 7.

The solar concentrator 1 also comprises at least one output section 9.

The output section 9 is opposed to the input section.

The output section 9 is suitable to convey the light rays 5 which pass through the input section 7 of the concentrator 1 and which are directed, concentrated, towards it.

More in detail, the light rays 5 passing through the output section 9 are collected in the receiver R, which then transfers them to suitable means which will transform them into the desired form (for example, thermal, electrical, mechanical).

In other words, the output section 9 constitutes an interface through which the energy of the light rays 5 is conveyed in parts of the power unit 2 in which it can be exploited in the desired manner.

The receiver R could be constituted by (or could include) a heat exchange membrane wall, a fluid bed wall, the hot zone of a Stirling engine, a spiral tube, or, more generally, any other element or device suitable to collect the energy provided by the light rays 5 and then transfer it where desired, or to transform it into the desired form, without any limitation.

According to other application examples, the receiver R could comprise (or could communicate with) a fluid bed containing sand, diathermic oil or other suitable materials.

Therefore, the receiver R may be of any shape and size, without limitations for the purposes of the present invention.

The reflecting surface 8 of the solar concentrator 1 comprises at least a full or partial revolution surface of at least a two-dimensional profile 10 about a first axis 11.

According to an aspect of the invention, the aforementioned profile 10 does not intersect the first axis 11 (see, for a better understanding, Figure 6, wherein the profile 10 and the first axis 11 are schematically shown).

Moreover, according to another aspect of the invention, such profile 10 comprises a first stretch 12 and a second stretch 13.

The first stretch 12 and the second stretch 13 are arranged in a mirror-like, or substantially mirror-like, manner with respect to a second axis 14.

According to a further aspect of the invention, at least one of the first stretch 12 and the second stretch 13 consists of an arc of a parabola.

More in detail, at least one of the first stretch 12 and the second stretch 13 consists of an arc of a parabola obtained in the manner illustrated in Figure 1, i.e., in the manner in which the arc of parabola profiles are obtained to make the CPC solar concentrators of the known type.

However, in other embodiments of the invention, the first stretch 12 and/or the second stretch 13 may have any suitable conformation, even different from the arc of a parabola (e.g. in a straight segment). The profile 10 further comprises an intermediate stretch 15, indicated with a discontinuous line in Figure 6.

Actually, such intermediate stretch 15 does not contribute to the realization of the reflecting surface 8 of the concentrator 1 by revolution around the first axis 11. In practice, the intermediate stretch 15 consists of a fictitious construction line which - by revolution - generates the aforementioned output section 9 which, as mentioned, is in fact open and does not correspond to any physical entity.

The intermediate stretch 15 connects - albeit in a virtual, fictitious way - the first stretch 12 to the second stretch 13, so as to obtain the aforementioned profile 10. In general, the first stretch 12 of the profile 10 consists of an arc of a parabola.

It is specified that, in the present description, the distinction between first stretch 12 and second stretch 13 is conventional, in order to facilitate the understanding of the characteristics of the invention.

Unless otherwise indicated, there are no actual functional differences between the first stretch 12 and the second stretch 13 even though they both may be different in arc length and, consequently, generate asymmetrical surfaces (as shown in Figure 10): conventionally, in present description, the first stretch 12 of the profile 10 is the one which, in use, is positioned at the height above the plane of the heliostats 3 of the power unit 2.

In general, the second stretch 13 could have any form suitable for the application; preferably, but not exclusively, also the second stretch 13 of the profile 10 consists of an arc of a parabola.

The second stretch 13 of the profile 10 may be identical and specular to the first stretch 12, or it may have different shapes and/or different sizes.

In the particular embodiment of the concentrator 1 illustrated in Figures 6, 7, both the first stretch 12 and the second stretch 13 of the profile 10 consist of respective arcs of a parabola, which are identical and arranged specular with respect to the second axis 14.

More in detail - and always with reference to the embodiment of Figures 6, 7 - the fictitious connection point 16 of the second stretch 13 to the intermediate stretch 15 coincides with the focus of the first stretch 12 made of an arc of a parabola (see, in this regard, again Figure 1 illustrating the construction of a traditional CPC profile). More generally, in case both stretches 12, 13 consist of arcs of a parabola, the focus of each stretch 12, 13 belongs to the other of the stretches 12,13.

According to still an aspect of the invention, the second axis 14 and the first axis 11 can be perpendicular or, more generally, incident to each other (i.e. forming, between them, an angle different from 180°).

In the aforementioned embodiment of Figures 6, 7, the first axis 11 and the second axis 14 are perpendicular to each other.

Accordingly, the reflecting surface 8 comprises (or consists of) a (full or partial) revolution surface of the first stretch 12 and of the second stretch 13 of the profile 10 about the first axis 11, and therefore it consists, in fact, of two separate and opposed portions with respect to the second axis 14.

More in detail, according to an aspect of the invention, the reflecting surface 8 comprises (or consists of) a first portion 12a and a second portion 13a separated from each other; moreover, the first portion 12a and the second portion 13a are opposite to the second axis 14.

More in detail, the first portion 12a is a revolution surface of the first stretch 12 around the first axis 11, while the second portion 13a is a revolution surface of the second stretch 13 around the same first axis 11.

The first portion 12a and the second portion 13a identify, between them, an inner reflection space S.

The reflecting surface 8 is discontinuous, i.e., between the first portion 12a and the second portion 13a there is an interruption, or discontinuity.

Between the first portion 12a and the second portion 13a of the reflecting surface 8 - and therefore in the interruption or discontinuity of the reflecting surface 8 - the output section 9 is therefore defined.

Therefore, the light rays 5 enter from the input section 7, pass through the inner reflecting space S, and reach the output section 9, at which they meet the receiver R. The revolution of the profile 10 around the first axis 11 can be performed for an angle which can be equal to 360°, or less than 360°.

As previously mentioned, the output section 9 of the concentrator 1 (fictitiously) consists of the (full or partial) revolution surface of the intermediate stretch 15 of the profile 10 around the first axis 11 : such revolution, therefore, is performed for an angle which can be equal to 360°, or less than 360°.

Therefore, in the embodiment of Figures 6, 7, the output section 9 of the solar concentrator 1 (fictitiously) consists of the side surface of a cylinder (in case of complete revolution).

In the event that, instead, the revolution of the profile 10 around the first axis 11 is partial, the output section 9 of the solar concentrator 1 (fictitiously) consists only of a portion of the side surface of a cylinder.

More generally, the output section 9 - due to the revolution of the profile 10 around the first axis 11 - generates a certain volume (i.e., the volume of a fictious rotation solid).

According to an aspect of the invention, the receiver R of the solar power unit is therefore installed inside the volume delimited by the output section 9, or at the output section 9.

For example, the receiver R of the solar power unit is installed inside the volume of the fictitious cylinder delimited by the output section 9, or fictitious cylinder portion, in order to enjoy the concentration effect of the light rays 5.

The result of the revolution of the profile 10 around the first axis 11 is shown in Figure 7.

The concentrator 1 is therefore characterized by cylindrical symmetry with respect to the first axis 11 (in case of complete revolution); moreover, the concentrator is also symmetrical with respect to the plane 17 generated by the rotation of the second axis 14 around the first axis 11.

The configuration of the concentrator 1 according to the embodiment of Figure 7 is particularly advantageous and suitable for the installation substantially at the same height of the plane of the heliostats 3 of the power unit 2. In fact, in this case - and appropriately orientating the heliostats 3 - the reflected light rays 5 travel substantially parallel to the plane of the heliostats 3 themselves, and then they easily pass through the input section 7 of the concentrator 1, reaching the output section 9 with low dispersions.

In solar power units 2 characterized by relatively low powers, the power unit solution that provides the solar concentrator 1 installed at the same level of the plane of the heliostats 3 is particularly advantageous and efficient from the energetic point of view.

The light rays 5 reflected by the heliostats 3 - which in the solar power unit 2 are arranged all around the solar concentrator 1 - concentrate and pass through the output section 9 along a perimetral band, which - by appropriately dimensioning and positioning the heliostats 3 - is entirely contained within it, so as to maximize the efficiency of the concentrator 1.

The proposed solution of solar concentrator 1 is also simple and economical from the constructive point of view.

In fact, the reflecting surface 8 could also comprise (or be made starting from) a support made of non-reflecting (or not sufficiently reflecting) material, coated with at least one film of reflecting material.

For example, the reflecting surface 8 could be made starting from a support made of polymeric material (and therefore easily achievable, for example, by moulding) coated with at least one film of reflecting material.

Another embodiment of the solar concentrator 1 according to the invention is shown in Figures 8, 9.

This embodiment differs from the previous one (Figures 6, 7) in that the first axis 11 and the second axis 14 are not perpendicular, and form, between them, a predetermined angle a other than 90° and 180°, or referable to such values.

The result of the revolution of the profile 10 - according to the embodiment of

Figure 8 - around the first axis 11 is schematically shown in Figure 9.

In this case, as can be seen, the solar concentrator 1 is still - evidently - characterized by cylindrical symmetry with respect to the first axis 11, while it is no longer symmetrical with respect to a plane parallel to the plane of the heliostats 3.

In this case, in fact, the second axis 14 in its revolution around the first axis 11 no longer generates a plane, but rather a conical surface.

In this embodiment the outlet section 9 (fictitiously) consists of the lateral surface of a truncated cone (or a portion of the lateral surface of a truncated cone, in the case of a not full revolution around the first axis 11).

Therefore, this solution is particularly efficient in the case in which it is intended to position the solar concentrator 1 at a different level with respect to the plane of the heliostats 3, obtaining a power unit solution 2 such as the one schematically shown in Figure 5, or as shown in the power unit solution 2 of Figure 12.

In the case of Figure 5, the concentrator 1 is positioned at a height higher than the plane of the heliostats 3, while in the case of Figure 12 the concentrator 1 (which is located, e.g., at a depression) is positioned at a lower level with respect to the plane of the heliostats 3.

This makes it possible to arrange the heliostats 3 on a larger surface, and in greater numbers (for example, more series of concentric heliostats 3), since they do not mutually obscure.

This translates, intuitively, into a greater power of the solar power unit 2.

Another embodiment of the solar concentrator 1 according to the invention is shown in Figures 10,11.

This embodiment differs from that of Figures 8, 9 in terms of the geometry of the profile 10.

More in detail, with respect to the profile 10 of Figure 8, in the profile 10 of Figure 10 the fictitious intermediate stretch 15 is parallel to the first axis 11.

To achieve this, the intermediate stretch 15 is inclined with respect to the previous version (which is also represented in a discontinuous stretch in Figure 10, for a better understanding).

Accordingly, the first stretch 12 and the second stretch 13 of the profile 10 are no longer symmetrical with respect to the second axis 14, but have different lengths. The result of the revolution of the profile 10 of Figure 10 around the first axis 11 is schematically shown in Figure 11.

In this case, the output surface 9 still, fictitiously, consists of the side surface of a cylinder (as in the version of Figures 6, 7); the first portion 12a of the reflecting surface 8, however, is still oriented downwards, as in the version of Figures 8, 9; alternatively, the first portion 12a could also be oriented upwards (as in the solution of Figure 12).

This embodiment, therefore, constitutes a hybrid solution between the embodiment of Figures 6, 7 and the one of Figures 8, 9.

Once again, this is a particularly effective solution in the case of installation at a different level with respect to the plane of the heliostats 3, but with the advantages deriving from the use of a cylindrical rather than frusto-conical exit section 9.

For example, the adoption of a cylindrical output section 9 may be more suitable in the case where a circulating fluid is present inside the receiver R (in turn enclosed by the output section 9), or in any case other applications that prefer this kind of geometry.

It is also an object of the present invention a solar power unit 2 comprising at least one solar concentrator 1 having the characteristics previously described, and at least one receiver R installed inside the volume delimited by the output section 9, or provided at such output section 9.

Moreover, the solar power unit 2 comprises a plurality of heliostats 3.

The solar concentrator 1 can be installed substantially at the same height with respect to the plane of the heliostats 3, using a solar concentrator 1 of the type illustrated in Figures 6, 7.

In this case, the concentrator 1 is very simple to build and maintain; moreover, there are no problems related to the pumping, at a certain height, of the fluid that must transport the collected energy.

Alternatively, the concentrator 1 can also be installed at a different height with respect to the plane of the heliostats 3 - as schematically shown in Figures 5 and 12 - in particular by using a solar concentrator 1 of the type illustrated in Figures 8-11. The heliostats 3 of the power unit 2 may be of any shape suitable for the application.

For example, the heliostats 3 may be parabolic.

The solution of the parabolic heliostats 3 is usually the preferred one.

Alternatively, the heliostats 3 could also be flat - which are simpler to construct - such that the projection surface (through the output section 9) of the light rays 5 reflected by the heliostats 3 does not exceed the diameter of the output section 9 itself.

More generally, it is possible to produce curved heliostats 3 of any shape, such as to cause the light rays to flow inside the input section 7 of the solar concentrator 1. Another embodiment of the concentrator according to the invention is schematically shown in Figures 13-15.

In this embodiment, the concentrator 1 - even within the same geometry of the embodiment of Figures 6-7A - comprises a plurality of elements 18 mutually connected around the first axis 11, and having a slice-shaped conformation.

The aforementioned slice-shaped elements 18 could be contiguous, so as to obtain a solar concentrator 1 with full revolution around the first axis 11, or they could also be non-contiguous (i.e. with discontinuities between them), so as to obtain a solar concentrator 1 consisting of sectors arranged in the most appropriate manner in relation to the specific application of solar power unit.

Each one of the aforementioned elements 18 is delimited by the first portion 12a and the second portion 13a opposite to each other of the reflecting surface 8 (having the characteristics already described with reference to each one of the previous embodiments) and also by two side partitions 19.

Such partitions 19 can be flat or even curved.

The partitions 19 are not joining elements of the portions 12a, 13a of reflecting surfaces 8; the partitions 19, in fact, do not necessarily occupy the whole section delimited by the aforementioned portions 12a, 13a of reflecting surfaces 8; for example, such partitions 19 could be connected only to one of the two portions of reflecting surfaces, for example the upper or lower one in use. The partitions 19 can, in turn, comprise reflecting surfaces, to facilitate the concentration of the light rays inside the output section 9; alternatively, the partitions 19 could comprise - or consist of - portions of the receiver R, which in this case could protrude/extend outwards beyond the output section 9.

Another embodiment of the concentrator 1 according to the invention is schematically shown in Figures 16-18.

In this embodiment of the invention, the solar concentrator 1 is obtained starting from the rotation of the profile 10 around the first axis 11 by an angle which is much less than 360°; in the embodiment shown, such angle is 90°, but it could also be lower, for example 60°, or 30°.

Also in this case the concentrator 1 is delimited by the first portion 12a and the second portion 13a of reflecting surface 8, and by two side partitions 19.

The partitions 19 can be flat or even curved; they could comprise respective reflecting surfaces, to facilitate the concentration of the light rays inside the output section 9.

The partitions 19 could also be made of an absorbing material of solar energy, integrating and/or replacing the receiver R.

They could be made up, or include, e.g., very thick coils, or plates, or other elements suitable to obtain the same result.

A solution of this type can be used, e.g., in the case where the heliostats 3 of the solar power unit 2 are located on a steep surface, e.g., a hill or the like.

In this case, the heliostats 3 (which do not obscure each other) can be concentrated only on a certain side with respect to the system 4 of the light rays 5, or, in any case, within a circumscribed area, since it is not possible to arrange them all around it.

In a similar situation, therefore - in which the rays reach the solar concentrator 1 only on one side - it may be convenient to adopt a solution obtained by only a partial revolution of the profile 10 around the first axis 11.

Another embodiment of the invention is schematically shown in Figure 19.

In this embodiment, the concentrator 1 comprises an adjustable-type support 20. More in detail, the support 20 can be adjustable in different ways, to position and/or direct the concentrator 1 in space in the most appropriate manner relating to operating conditions of the solar power unit in which it is installed.

The support 20 can include an upright 21; the concentrator 1 is associated with the top of the upright 21.

The upright 21 can, in turn, comprise means for translating and/or rotating the concentrator with respect to the support 20.

For example, the upright 21 may comprise a stem 22, which is slidably and/or rotatably associated with the same upright 21 by interposition of a translation and/or rotation actuator.

Therefore, the concentrator 1 can be raised/lowered and/or rotated with respect to the upright 21, so as to reach the optimum position with respect to the operating conditions of the power unit (e.g., with respect to the position of the sun, the heliostats, etc.).

Furthermore, the concentrator 1 can be connected to the stem 22 at a hinge 23; the hinge 23 can be associated with a respective rotary actuator in such a way as to rotate the concentrator 1 around an axis orthogonal to the upright 21.

In other words, thanks to this solution, the concentrator 1 can be oriented at will in space, e.g., in such a way as to favour certain heliostats rather than others within the same solar power unit.

Other embodiments of the invention are shown in the details of Figures 20, 21. The embodiment of Figure 20 differs from that of Figure 19 in that the solar power unit 2 comprises a receiver R consisting of at least one coil, in which a heat exchange fluid is circulated, having the coils arranged at the output section 9 and oriented along the axis 11.

The embodiment of Figure 21 differs from that of Figure 19 in that the solar power unit 2 comprises a receiver R consisting of at least one coil, in which a heat exchange fluid is circulated, having the coils arranged at the output section 9 and oriented orthogonally with respect to the axis 11.

The invention thus conceived allows to obtain important technical advantages. One of the fundamental advantages consists in that it is possible to eliminate the presence of an auxiliary reflector (such as that shown in Figure 4) in order to make the light rays flow inside the input section 7 of the solar concentrator 1.

In fact, the concentrator 1 according to the present invention allows to directly collect the rays reflected by the heliostats 3 without the need for further reflections. Due to its particular configuration, the use of the solar concentrator 1 according to the present invention is particularly advantageous in the case of low power solar power units 2 (and therefore with a relatively small number of heliostats 3): in fact the concentrator 1, thanks to the its particular conformation, can be installed substantially at the same height above the ground to which the plane of the heliostats 3 is located, or even at a different height, but in any case in order to minimize - or eliminate - the energy expenditure that, in traditional power units, is necessary to consider for the pumping of an energy transport fluid, or, in any case, more generally to transport the energy from the point where it is actually collected. Furthermore, thanks to its particular conformation, the solar concentrator 1 can be efficiently exploited in situations in which the heliostats 3 are positioned on a steep surface (e.g. a hill), and then concentrated on a single side with respect to the positioning of the concentrator 1 itself.

The proposed solution is particularly simple and economical from the construction, installation and maintenance point of view.

Moreover, the proposed solution of the concentrator 1, if compared to those currently available, is remarkably versatile, in the sense that it can be simply adapted to application situations that are also quite different from each other, still achieving satisfactory results from the energy efficiency point of view.

It has thus been seen how the invention achieves the intended purposes.

The present invention has been described according to preferred embodiments; however, equivalent variants can be conceived without departing from the scope of protection offered by the following claims.