Solar collector comprising a plurality of fan-shaped mirrors

Abstract

The main object of the invention is a solar collector (1), comprising: a plurality of mirrors (2) for solar reflection, forming a primary concentrator, a support structure (3) on which the mirrors (2) are mounted, and a concentrated light receiving structure (4, 5) for receiving and absorbing the light rays reflected by the mirrors (2), characterized in that the concentrated light receiving structure (4, 5) is located below the mirrors (2) and in that the mirrors (2) are arranged in a fan shape with their central axis (C) facing inwards so as to focus the light rays towards the concentrated light receiving structure (4, 5). Figure 1

Description

Title of the invention: Solar collector comprising a plurality of fan-shaped mirrors Technical field

[0001] The present invention relates to the general field of solar installations (or power stations), and more specifically to the design of a new type of solar collector present in such installations.

[0002] Preferably, the invention applies to the field of concentrated solar thermal power (or "CSP" for "Concentrated Solar Power"), in particular to the field of concentrated solar thermal power integrated into buildings (or "BLCSP" for "Building Integrated Concentrated Solar Power"), and more specifically to the field of linear concentrated solar systems such as linear Fresnel collectors and cylindrical-parabolic collectors with linear focus. In particular, the invention can be implemented for the production of heat for housing and / or for industry.

[0003] The invention thus proposes a solar collector comprising a plurality of fan-shaped mirrors, as well as a solar power station comprising such a solar collector. STATE OF THE PRIOR ART

[0004] In the field of solar energy, there are solar collectors of different types. These are used to concentrate solar radiation on high flux receivers, from several tens of kilowatts to a few megawatts per square meter, in order to produce heat and / or electricity.

[0005] Thus, among the known technologies in the thermodynamic solar sector, there is concentrated solar thermal (CSP) technology, which uses mirrors to concentrate solar radiation onto a small surface area. CSP technology consists more precisely of using solar radiation to heat a heat transfer fluid serving as a heat source in a thermodynamic cycle. Concentration makes it possible to reach higher or lower temperatures, and thus to benefit from higher or lower thermodynamic conversion efficiencies. The techniques developed around CSP technology are distinguished by their method of concentrating solar rays, their method of transporting, and possibly storing, heat, in particular by means of one or more heat transfer fluids, and their method of thermodynamic conversion, for example by means of steam turbines, gas turbines, Stirling-type engines, among others..

[0006] We thus typically encounter four main families of concentrated solar systems belonging to CSP technology, namely: cylinder collectors- linear-focus parabolic collectors, linear Fresnel collectors, central receiver tower collectors, and moving-focus parabolic collectors.

[0007] Cylindro-parabolic collectors and linear Fresnel collectors constitute linear concentrating solar systems, while tower power plants and parabolic collectors constitute point concentrating solar systems. Furthermore, tower power plants and linear Fresnel collectors constitute concentrating solar systems with fixed receivers, while parabolic collectors and cylindro-parabolic collectors constitute concentrating solar systems with mobile receivers.

[0008] A key element of such concentrated solar systems is the primary reflector field. For example, in the case of linear Fresnel collectors (CLFR technology for "Compact Linear Fresnel Reflector" in English), the primary reflector field, following the path of the sun from east to west during the day, receives the direct light rays and reflects them towards the fixed receiver. The concentration factor for such linear Fresnel collectors is typically of the order of 50, which means that the solar flux at the receiver is equal to approximately 50 times the solar flux that impacts the ground.

[0009] In all of these technologies, the solar reflectors have the function of reflecting and concentrating all of the direct incident solar irradiation towards the receiver, located a few meters or a few tens of meters from the reflectors. They are composed of a mirror assembled to a structure mounted on rotation systems along one or two axes allowing the path of the sun to be followed during the day.

[0010] In these classical technologies, in particular those of cylindro-parabolic collectors and linear Fresnel collectors, the defocusing is carried out towards the sky.

[0011] Publications "Construction of a 100 KW Solar Thermal-Electric Experimental Plant", Boy-Marcotte, JL et al, Journal of Solar Energy Engineering, 1985, 107, 196-201, "Parametric Analysis of the Fixed Mirror Solar Concentrator for Medium Temperature Applications", Pujol-Nadal, R. et al, Journal of Solar Energy Engineering 2014, 136, 011019, and "Optical Characterization of a Fixed Mirror Solar Concentrator Prototype by the Ray-Tracing Procedure", Pujol-Nadal, R. et al, Journal of Renewable and Sustainable Energy 2014, 6, 043105, are also known, which describe principles of upward reflection towards a moving receiver, thus with a certain wind influence and upwardly oriented mirrors.

[0012] There is a first need to avoid the movement of the mirrors to reduce the high costs linked to their mechanical dimensions and their movements, the latter being subject to strong constraints linked to the wind. This therefore implies thinking about fixed mirror systems.

[0013] In these fixed mirror technologies, there is a need to protect the moving receiver from mechanical stresses linked to the wind, as well as to have defocusing towards the ground to avoid any rejection of rays in all directions, and to achieve simpler maintenance on the receiver. Statement of the invention

[0014] The invention aims to at least partially remedy the needs mentioned above and the drawbacks relating to the embodiments of the prior art.

[0015] In particular, the invention aims to design a new type of solar collector allowing downward focusing, the concentration of light being carried out under the mirrors.

[0016] The invention thus relates, according to one of its aspects, to a solar collector, comprising: - a plurality of mirrors for solar reflection, forming a primary concentrator, - a support structure on which the mirrors are mounted, - a structure for receiving a concentrated flow of light, intended to receive and absorb the light rays reflected by the mirrors, characterized in that the structure for receiving a concentrated light flux is located under the mirrors and in that the mirrors are arranged in a fan shape with a central axis with the reflective face oriented inwards so as to focus the light rays towards the structure for receiving a concentrated light flux.

[0017] The solar collector according to the invention may further comprise one or more of the following characteristics taken in isolation or in any possible technical combination.

[0018] The structure for receiving a concentrated light flux can be of different types.

[0019] The structure for receiving a concentrated light flux may in particular comprise: - a secondary concentrator intended to receive, in particular to re-concentrate, the light rays reflected by the mirrors, - a receiving tube connected to the secondary concentrator, in particular located at the focal point of the secondary concentrator, to absorb the concentrated solar flux and allowing the passage of a heat transfer fluid.

[0020] The secondary concentrator may be located below the mirrors and the mirrors may be arranged in a fan-shaped arrangement with a central axis with the reflective face facing inward so as to focus the light rays towards the secondary concentrator.

[0021] Alternatively, the structure for receiving a concentrated light flux may comprise a photovoltaic structure, such as a set of photovoltaic cells, or even a receiving tube of width equivalent to that of a secondary concentrator.

[0022] The support structure may comprise a fixed supporting structure and a mirror attachment structure, carried by the supporting structure, in particular of circular shape.

[0023] The hanging structure can be fixed, and then the secondary concentrator and the receiving tube are movable in rotation.

[0024] The secondary concentrator and the receiving tube can be fixed relative to the hanging structure, and the assembly can rotate relative to the supporting structure. This possibility requires daily movement of the hanging structure by means of, for example, a large motor.

[0025] The secondary concentrator and the receiving tube can still be mobile in rotation to follow the path of the sun, and the hanging structure can be rotated seasonally and manually so as to optimize the collection of energy.

[0026] In addition, the structure for receiving a concentrated light flux may be carried by the attachment structure, in particular in a manner diametrically opposed to the mirrors. In particular, the secondary concentrator may be carried by the attachment structure, in particular in a manner diametrically opposed to the mirrors.

[0027] The support structure may comprise a support for holding the mirrors together, extending in particular in the middle part of the mirrors.

[0028] The receiving tube may, if necessary, be mounted so as to be able to rotate on the central axis of the fan.

[0029] In addition, each mirror may have a face provided with a mirror oriented towards the central axis of the fan.

[0030] A first half of the mirrors may have faces provided with mirrors oriented towards one side of the median plane passing through the central axis of the fan, and a second half of the mirrors may have faces provided with mirrors oriented towards the other side of the median plane.

[0031] The mirrors may be of substantially rectangular shape.

[0032] Furthermore, the invention also relates, according to another of its aspects, to a solar power station, characterized in that it comprises a plurality of solar collectors as defined above.

[0033] The solar collector and the solar power plant according to the invention may comprise any of the characteristics set out in the description, taken in isolation or in any technically possible combination with other characteristics. Brief description of the drawings

[0034] The invention may be better understood by reading the detailed description which will follow, non-limiting examples of implementation thereof, as well as the examination of the schematic and partial figures of the attached drawing, in which:

[0035] [Fig.l] represents, in a sectional view, an exemplary embodiment of a solar collector according to the invention, and

[0036] [Fig.2] represents, in a perspective view, the example of embodiment of the [Fig.l].

[0037] Throughout these figures, identical references may designate identical or similar elements.

[0038] In addition, the different parts represented in the figures are not necessarily shown on a uniform scale, in order to make the figures more readable. Description of the embodiments

[0039] In the description of the example of implementation of the invention which follows, the field of application concerned is that of concentrated solar thermal installations.

[0040] With reference to [Fig.l], there is shown, in section, an exemplary embodiment of a solar collector 1 according to the invention, and [Fig.2] represents, in perspective, the exemplary embodiment of [Fig.l].

[0041] The solar collector 1 comprises a plurality of mirrors 2 for solar reflection, forming a primary concentrator, and a support structure 3 on which the mirrors 2 are mounted.

[0042] In addition, a structure for receiving a concentrated light flux 4, 5 is present. Here, it is a secondary concentrator 4 intended to receive the light rays reflected by the mirrors 2 which is located under the mirrors 2. The mirrors 2 are advantageously arranged in a fan shape having a central axis C with an orientation of the reflecting face towards the inside so as to focus the light rays towards the secondary concentrator 4. The arrangement of the mirrors 2 thus forms a “hedgehog” of mirrors oriented in such a way as to redirect the reflected rays towards the secondary concentrator 4 to achieve solar concentration.

[0043] Each mirror 2 is of substantially rectangular shape. In addition, it has a face provided with a mirror 2a oriented towards the central axis C of the fan. Specifically, a first half M1 of the mirrors 2 has faces provided with mirrors 2a oriented towards one side of the median plane P passing through the central axis C of the fan, and a second half M2 of the mirrors 2 has faces provided with mirrors 2a oriented towards the other side of the median plane P.

[0044] Furthermore, the support structure 3 comprises a fixed supporting structure 3a, intended for example to be secured to a roof and / or a wall and making it possible to guarantee the solidity of the solar collector 1.

[0045] A structure 3c for attaching the mirrors 2, carried by the supporting structure 3a, in particular of circular shape, is provided. It can be movable in rotation relative to the supporting structure 3a.

[0046] The secondary concentrator 4 is carried by the receiving tube 5, in particular in a manner diametrically opposed to the mirrors 2.

[0047] The mirrors 2 can advantageously be plane mirrors. However, other shapes are also possible, in particular curved mirrors.

[0048] The mirrors 2 are advantageously arranged in a fan-shaped form forming an arc of a circle, or a shape substantially in an arc of a circle close to an ellipse, or even in any other technically possible form.

[0049] Furthermore, the support structure 3 may comprise a support 3b for holding the mirrors 2, securing all the mirrors 2 together, extending in particular in the middle part of the mirrors 2.

[0050] In addition, a receiving tube 5 connected to the secondary concentrator 4 is provided and allows the passage of a heat transfer fluid. This receiving tube 5 can be mounted to move in rotation on the central axis C of the fan.

[0051] During operation, the mirrors 2 can be fixed and the receiving tube 5 can be mobile, moving around the central axis C.

[0052] Alternatively, the receiving tube 5 can be kept fixed relative to the mirrors 2, and the assembly formed by the mirrors 2 and the receiving tube 5 can be driven in rotation. Thus, the attachment structure 3c moves relative to the supporting structure 3a.

[0053] As a further variant, the receiving tube 5 can be mobile and the mirrors 2 can be fixed, with the possibility of orienting them manually according to the position of the sun, for example seasonally.

[0054] The secondary concentrator 4 may in particular be of the “CPC” type for “Compound Parabolic Concentrator” in English. Such an example of concentrator is for example known from the publication “Solar Concentrators with Maximal Concentration for Cylindrical Absorbers”, Rabl, A., Appl. Opt. 1976, 15, 1871.

[0055] Thanks to such a solar collector 1, the concentrated solar flux can be defocused downwards. In addition, thermal losses are low: thus, replacing the heat transfer fluid, in particular water, close to the freezing point with water at a slightly higher temperature by means of recirculation can prevent freezing. It is then possible to connect, for example, to a conventional hot water tank, without using glycolated water.

[0056] Such a solar collector 1 in accordance with the invention was simulated using the SolTrace® software which made it possible to show that the mirrors 2 must advantageously have a transverse angle of less than 40° relative to the vertical, with preferably a number of mirrors of 11 and a width of 0.5 m for each mirror.

[0057] Of course, the invention is not limited to the embodiment which has just been described. Various modifications can be made to it by those skilled in the art.

Claims

Claims

1. Solar collector (1), comprising: - a plurality of mirrors (2) for solar reflection, forming a primary concentrator, - a support structure (3) on which the mirrors (2) are mounted, - a structure for receiving a concentrated light flux (4, 5), intended to receive and absorb the light rays reflected by the mirrors (2), in which the structure for receiving a concentrated light flux (4, 5) is located under the mirrors (2) and in that the mirrors (2) are arranged in a fan shape with a central axis © with the reflective face oriented inwards so as to focus the light rays towards the structure for receiving a concentrated light flux (4, 5), characterized in that the support structure (3) comprises a fixed supporting structure (3a) and a structure for attaching (3c) the mirrors (2), carried by the supporting structure (3a),in particular circular in shape and each mirror (2) is hung on the hanging structure (3c).,

2. Solar collector according to claim 1, characterized in that the structure for receiving a concentrated light flux (4, 5) comprises: - a secondary concentrator (4) intended to receive the light rays reflected by the mirrors (2), - a receiving tube (5) connected to the secondary concentrator (4) to absorb the concentrated solar flux and allowing the passage of a heat transfer fluid, the secondary concentrator (4) being located under the mirrors (2) and the mirrors (2) being arranged in a fan shape with a central axis © with the reflective face oriented inwards so as to focus the light rays towards the secondary concentrator (4).

3. Solar collector according to claim 1 or 2, characterized in that the attachment structure (3c) is movable in rotation relative to the supporting structure (3a).

4. Solar collector according to any one of claims 1 to 4, characterized in that the structure for receiving a concentrated light flux (4, 5) is carried by the attachment structure (3c), in particular diametrically opposite the mirrors (2).

5. Solar collector according to any one of the preceding claims, characterized in that the support structure (3) comprises a support of holding (3b) of the mirrors (2) securing all the mirrors (2) together, extending in particular in the middle part of the mirrors (2).

6. Solar collector according to any one of claims 2 to 5, characterized in that the receiving tube (5) is mounted to move in rotation on the central axis (C) of the fan.

7. Solar collector according to any one of the preceding claims, characterized in that each mirror (2) has a face provided with a mirror (2a) oriented towards the central axis (C) of the fan.

8. Solar collector according to claim 7, characterized in that a first half (Ml) of the mirrors (2) has faces provided with mirrors (2a) oriented towards one side of the median plane (P) passing through the central axis (C) of the fan, and in that a second half (M2) of the mirrors (2) has faces provided with mirrors (2a) oriented towards the other side of the median plane (P).

9. Solar collector according to any one of the preceding claims, characterized in that the mirrors (2) are of substantially rectangular shape.

10. Solar power plant, characterized in that it comprises a plurality of solar collectors (1) according to any one of the preceding claims.

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