CH619530A5 - Device for the collection of solar energy - Google Patents

Abstract

The device comprises a plurality of semi-cylindrical combined reflectors and concentrators juxtaposed on the roof of a house or building. An elongated collector is mounted above each reflector using pivoting supports allowing it to be positioned in such a way as to obtain a good concentration of solar energy. In order to achieve optimum concentration over as great a range as possible, each reflector-concentrator is formed by a semi-cylindrical curved surface with three radii (R1, R2, R3) corresponding to three surfaces (S1A, S2, S1B) of constant curvature over the whole length of the reflector. The radii of curvature (R1, R3) of the two outer surfaces (S1A, S1B) are smaller than the radius of curvature (R2) of the intermediate surface (S2). The two outer surfaces (S1A, S1B) are also more inclined than the intermediate surface (S2). In addition, a mechanism moves the collector transversely above the reflector as a function of the angular elevation of the sun in a plane perpendicular to the longitudinal axis of the reflector so as to keep the collector in a region where the solar energy is concentrated, such a region moving transversely with respect to the reflector as the height of the sun varies. <IMAGE>

Description

The invention relates to a device for collecting solar energy, more particularly comprising a fixed reflector-concentrator mounted on the roof of a building or on any structure and a collector which can be oriented as a function of the height of the sun on the horizon. to optimize performance at any time of the day and in any season.

Many devices for collecting solar energy have been proposed so far. Most use parabolic or other reflectors to focus the sun's rays on a collector located at the hearth. In general, the reflector and the collector are integral and are oriented together in the direction of the sun.

There are also other devices which include one or more fixed reflectors and one or more mobile collectors. A device of this type uses a spherical mirror and a central collector mounted on an articulated structure which makes it possible to orient it angularly according to the time and the season. However, the spherical mirror has the disadvantage of being delicate and costly to produce and does not lend itself to mass production. Another solution described in German Patent No. 517,417 of February 4, 1931 uses an oblong or elliptical dish whose focal axis extends horizontally and symmetrically with respect to a vertical passing through the center of the reflector. To correct small deviations of the sun from the vertical, the collector is mounted at the end of an adjustable telescopic arm whose movements are controlled by a cam mechanism to move the collecs

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laterally and vertically. The azimuth orientation mechanism of the reflector is not clearly described in the aforementioned patent. However, it seems obvious that such a device can only accept small angular variations in the position of the sun relative to a vertical plane containing the long axis of the reflector, and in any case not the annual variations in height of the sun. In addition, this device is relatively complex and difficult to produce on a large scale, especially for the telescopic arm and the guide cam. In order for it to be usable with good yield for a reasonable period each day and over several months, it is essential to provide some device for tilting or angular orientation of the reflector, in addition to the normal positioning of the collector by the movements of his telescopic arm.

The object of the present invention is to provide a relatively simple device for collecting solar energy which uses a fixed reflector and a collector animated with a simple movement to make the best use of the hours of sunshine of each day of the year.

To this end the invention relates to the solar energy collection device defined in claim 1.

The accompanying drawings show by way of nonlimiting examples several variants of the device of the invention.

Fig. 1 is a schematic view of a building whose roof is equipped with the device for capturing solar energy.

Fig. 2 is a perspective view on a larger scale of part of the capture device of FIG. 1.

Fig. 2a is a fragmentary view illustrating an alternative mounting of the mobile manifolds.

Fig. 3 is a fragmentary view on a large scale showing the support of the mobile collectors.

Fig. 3a is an enlarged section of one of the collectors in the plane 3a-3a of FIG. 3.

Fig. 4 illustrates a mounting variant of a collector.

Fig. 5 is a schematic section of the connection of two adjacent reflectors.

Fig. 6 is a schematic view of the positioning mechanism of the mobile manifolds corresponding to the mounting method of FIG. 3.

Fig. 6a is a schematic view of the positioning mechanism of the mobile manifolds corresponding to the mounting method of FIG. 4.

Fig. 7 is a diagram illustrating the kinematics of one of the mobile collectors with respect to the associated reflector as a function of the position of the sun at different times of the year.

Fig. 8 is a similar diagram illustrating an application of the principle of the invention to a place whose latitude is known.

Fig. 1 schematically represents a building 11 such as a school, a factory, a residential building or the like, the roof 21 of which carries a certain number of reflector-concentrators 31 which occupy part or all of its surface. In practice, the surface occupied by the collection device depends on the sunshine of the place and the energy needs of the building. Apart from the roof, the building 11 is conventional with walls 13, windows 15 and doors 17.

The collection surface is formed by the juxtaposition of several reflectors 31, the adjacent edges of which are assembled so as to seal the roof. The reflectors 31 rest at their ends on concave supports 36 which are fixed to the frame 101 of the building. Other supports can be placed at intermediate points of the reflectors to give them the desired rigidity. The outer edges of the structure are closed by plates 32, 32a fixed so as to seal the assembly against the weather. To collect the rainwater which flows along the reflectors 31, there are gutters 111 under their ends. In the example illustrated, the roof of the building carries two rows of reflectors 31 and there are therefore three gutters 111 which are mounted perpendicular to the axes of the reflectors (FIG. 2). The rainwater thus collected is discharged through ordinary downpipes.

The entire structure is surrounded by a continuous strip 19 (fig. 1) intended to cut the wind and improve the aesthetics of the whole. This strip should not be too high, otherwise the efficiency of the collection device will be reduced by the shadow it casts on the ends of the reflectors.

Each reflector-concentrator 31 is a concave panel of polished material which reflects the sun's rays, for example a metal, a glass or a plastic material. Depending on the case, it is possible to use working reflective panels or panels suitably supported on a sufficiently rigid cover. The concave profile used can be a continuous curve or an approximation of the ideal curve by rectilinear or curvilinear facets. Thus, if the reflectors are sheets of metal, it is easy to bend them into one or more elements. Likewise, flat metal, glass or plastic blades suitably juxtaposed can be used to give a good approximation of the ideal curve. In addition, when the reflective structure does not occupy the entire surface of the roof 21, the latter may include translucent or transparent surfaces allowing daylight to pass inside the building. For this, one can also use partially translucent reflectors 31. For the system to have optimal efficiency, it is preferable that the axes of the reflectors 31 are oriented in an east-west direction, but this condition is not rigorous and other azimuths can be chosen with, however, less efficient performance.

Each reflector 31 concentrates solar energy in a "maximum convergence zone" whose position varies with the height of the sun in the plane of the meridian. A movable collector 51 is mounted longitudinally above each reflector-concentrator 31. The collector 51 is carried at its opposite ends by arms 45 which can pivot in north-south planes.

The pivot axes of the arms 45 are horizontal in east-west planes and can be located above, below or at the surface of the reflector-concentrator 31 with a minimal effect on the efficiency of the assembly. We see in fig. 3 that the axes of the arms 45 rotate in bearings 81c mounted under the reflecting surface 31. In the illustrated embodiment, the "concentration factor", that is to say the ratio of the surface in plan (chord x length) of the reflector 31 and the effective area of the collector 51 is of the order of 15 to 1. This factor represents the theoretical maximum concentration which can be achieved with a reflector-collector assembly, but in the case of a battery of such sets, stray reflections from adjacent reflectors may slightly increase the concentration. On the other hand, other factors such as the angle of inclination and the shade of the collector 51 on the reflector 31 (especially in summer) reduce the effective concentration which can be reached for different heights of the sun. Another important factor which will be examined in detail below is the degree of coincidence between the collector surface of the collector 51 and the zone of convergence of the solar energy created by the reflector 31.

The pivoting arms 45 are preferably connected by horizontal connecting rods 71 which ensure simultaneous positioning of all the collectors 51 relative to the associated reflectors. The assembly constituted by the horizontal rod 71, the pivoting arms 45, the arm 81 and a fixed beam 101 forms a paral5

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the deformable logram which can be controlled by the arm 81 secured to a horizontal torsion tube 91 and a small arm 81d directed downwards. The pivot axis 81a of the arm 81 is supported by a reinforcement piece 83 which is fixed to a part of the structure 101. The movements of the arm 81 are controlled by a screw jack 84 which is articulated between a fixed point 83a and the end 83b of the arm 81d. The cylinder 84 is preferably a recirculating ball cylinder controlled by a motor M.

We see in fig. 3 that the upper end of the arm 81 is articulated at 81b on the connecting rod 71 and that its length is the same as that of the support arms 45. The assembly therefore constitutes a deformable parallelogram.

In the embodiment of Figures 1-3 and 6, the manifolds 51 are fixed to the connecting rods 71 by bolts 73 and are therefore kept horizontal in all their angular positions. This arrangement is advantageous because it makes it possible to reduce the heat losses at the level of the collector, in particular the losses by convection which increase when the inlet face of the collector is inclined.

Figs. 4 and 6a illustrate a variant in which the collectors 51 are fixed relative to the pivoting arms 345, while the latter are articulated at 345b on the horizontal rod 371 of the parallelogram. In this case, the collectors 51 are all the more inclined as the arms 345 deviate from the vertical position.

Returning to fig. 3, it can be seen that the reflector 31 consists of metallized glass strips 31a bonded to a curved support structure comprising for example a rigid insulating foam 35 sandwiched between two curved sheets 33 and 37. This construction method makes it possible to manufacture reflectors rigid enough to withstand bad weather. The different layers of the sandwich structure are preferably bonded together and the insulating foam 35 can be formed of several superimposed thicknesses, unless it is directly cast at the desired curvature. With a slight decrease in efficiency, the mirrors 31a can be omitted provided that the metal sheet 33 is properly polished. Other reflector constructions can be used.

Fig. 5 illustrates a method of tightly joining the adjacent edges of two reflectors 31. Two complementary sections 41 and 43 which can be extradited in a metal such as aluminum, magnesium or steel, are fixed to the adjacent edges of the reflectors 31. The “male” section 43 forms an upper edge 43a surrounded by a rubber seal 44b which is received in an inverted gutter 41a of the “female” section 41. In addition, the sections 41 and 43 form, along their lower edges, complementary spacing ribs 411 and 431. A rubber band 44a is received between the sections 41,43 above the ribs 411,431. The assembly is tightened by bolts 47, 47a so as to compress the seals 44a, 44b. The longitudinal edges of the reflectors 31 are received between oblique parallel wings 41fu, 41fl and 43fu, 43fl of the sections 41 and 43.

Each manifold 51 may comprise two or more tubes 57a, 57b spaced laterally in which a heat transfer fluid circulates, generally water or a gas. The tubes 57a, 57b can be the seat of parallel circulation, but it is preferable to carry out a return circulation by making the two tubes communicate at one of the ends of the collector. At the other end of the manifold, the tubes 57a, 57b are connected by flexible pipes 49a, 49b to cold and hot fluid lines 47a, 47b. The flexible pipes 49a and 49b are preferably surrounded by a common insulating sheath 49. The pipes 47a, 47b serve in parallel a whole battery of collectors 51 to produce circulation with miltiples loops of heat-transfer fluid.

The cross section of fig. 3a shows that the collector 51 contains an energy absorption element 59 which is turned downwards to capture the rays of the sun reflected by the reflector 31. To reduce losses, the absorption element 59 which contains the tubes circulation 57a, 57b is preferably coated with a plastic foam 55 or another cellular material which is contained in an outer envelope 53, for example an extruded metal profile. The underside of the collector 51 is occupied by a transparent plate 58, preferably made of glass, which allows the sun's rays to pass towards the absorption element 59, the lower face of which is ribbed and blackened. We see that the element 59 which carries the circulation tubes 57a, 57b, is anchored in the insulating plastic foam 55. Flexible seals 56 seal between the edges of the glass plate 58 and the profile 53. To ensure good heat transfer, the tubes 57a, 57b must be in intimate contact with the absorption element 59. In practice, the tubes can be wrapped in an extruded element or placed in longitudinal grooves whose edges are then folded down on the tubes, as illustrated in fig. 3a.

The element 59 has the characteristics of a black body and absorbs the solar rays which it restores in the form of heat to the heat transfer fluid circulating in the tubes 57a, 57b. As indicated above, the horizontal position of the collector 51 is the most favorable for efficient collection of solar energy and good transfer to the collecting tubes, while minimizing convection losses.

The hot and cold fluid lines 47a, 47b can be connected to a heat utilization system, for example an accumulator and an absorption heating and / or cooling installation. Alternatively, the heat collected by the collectors 51 can be used to produce work by rotating machines. With a system of the type described, using water as the heat transfer fluid, temperatures of 150 ° C. and above can be reached depending on the characteristics of the installation. These temperatures are very sufficient for the fluid to be able to supply a heating or cooling installation by absorption.

In fig. 7 and 8, the reflector-concentrators 31 are partially cylindrical concave mirrors made up of several adjacent segments SIA, S2 and S1B. The radii of curvature RI, R3 of the extreme segments SIA and S1B are preferably equal and shorter than the radius R2 of the central segment S2. Thus, the more pronounced curvature of the segments SIA and S1B contributes to reducing the width of the zone of convergence of the solar rays which the collector 51 must intercept for different angles of incidence of the solar rays. In addition, the adjacent reflectors can be connected by a flat surface portion to form a corrugated roof which can have aesthetic advantages on industrial, commercial or residential buildings. It is however obvious that by deviating from the ideal shape, the efficiency of the installation is slightly sacrificed.

With a symmetrical reflector-concentrator with triple curvature, as in fig. 7, a good concentration of solar energy can be obtained on the collector 51 for different positions of the sun. For example, for a latitude of 28 ° North, the illustrated configuration makes it possible to obtain a concentration factor varying between approximately 6: 1 and 11: 1. Fig. 8 schematically illustrates the convergence zones or envelopes of the rays reflected towards the collector for three particular times of the year. The ESE envelope is obtained at noon at the summer solstice, the EEQ envelope is obtained at noon at the spring or fall equinox and the ESH envelope is obtained at noon at the winter solstice. In these three particular cases, the useful reflection surfaces of the mirror 31 are respectively SESM, SEF / SM and SEWM in the diagram of FIG. 8.

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In the case of an installation at 28 ° latitude, the system of FIG. 7 can have the following relative dimensions:

RI and R3 radii of the SIA and S1B extreme arcs

reflector

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Rays R2 from central area S2

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Effective width L of manifold 51

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Swivel arm length 45

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Dimension a

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Dimensions b, c

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Dimension d

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Dimension e

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Dimension f

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Dimension g

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SIA andSIB arcs

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ArcS2

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Minimum useful height of the sun, MNS angle

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Maximum useful height of the sun, MXS angle

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Minimum angle MMC of the manifold assembly

51, arm 45 for the maximum height of the

sun (about 104 degrees)

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Maximum angle MXC of the manifold assembly

51, arm 45 for the minimum useful height

from the sun (about 18 degrees)

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For other latitudes, particularly between 0 and 40 or 50 °, the same dimensions can be kept for the reflector, but the length of the arm 45 and the position of its pivot axis 45a must be modified. These parameters can be determined graphically from the shape of the reflector and the heights of the sun for the latitude considered. It is thus possible to choose the optimal trajectory for the collector 51, which then makes it possible to determine the length of the arm 45 and the position of its axis 45a. For example, for a latitude of 39 ° N, the length of the arm 45 is reduced to 32 units, the dimension f becomes 21 units and the dimension g becomes zero. Such a device ensures optimum concentration of solar energy on the collector at all hours of the day and at all times of the year.

The ideal position of the collector 51 for each height of the sun can be determined with precision for a given profile reflector either by an empirical graphic resolution,

either using a computer or another instrument for mathematical analysis of the envelope of convergence of the reflected rays. We thus manage to optimize the position of the collector to intercept a maximum of solar rays at all heights of the sun for a given latitude. The positioning of the arms 45 and of the collectors can be controlled by a program or by a control based on the energy received by the collector. Such a system is for example described in the patent application of the USA. No. 525 545. All the reflectors 31 preferably having identical curvatures, all the mobile collectors 51 can be actuated by a common mechanism. To make a servo loop, one or more energy sensors can be mounted on the collectors 51. One could also individually control the positioning of each collector 51, but this is not desirable for practical and economic reasons.

To make a seamless connection of the arcs SIA, S2 and S1B, it suffices that they have tangents common to the connection points, which amounts to saying that the centers R1C and R2C must be on the same radius and that the centers R2C and R3C must be on the same radius.

We have previously seen that the useful reflection zones of FIG. 8 correspond for a place whose latitude is around 28 °, with solar illumination at noon at the winter solstice, the summer solstice and the spring and autumn equinoxes. Experience has shown that a good concentration factor is obtained during the periods of strong sunshine of each day of the year by using a reflector with at least three arcs of different radii, ie smaller and smaller as we move away from the central arch. In the example illustrated, a three-arc reflector gives satisfactory results. We see in fig. 8 that such a reflector never gives a single focal line, but rather areas of convergence whose shape, dimensions and position vary with the height of the sun on the horizon which itself depends on the time of day and the season. In this regard, the examination of the positions of the sun for the chosen place of 28 ° north latitude clearly highlights the constraints imposed on the system for certain days of the year. As shown in fig. 8, these zones are the daytime amplitudes of the pivoting movement of the arms 45 and of the collectors 51. It will be noted that the reflector can and must be able to operate for a peak of the sun beyond the zenith, which continues in the intertropical band. The shape of the reflectors must also take into account the obliquity of the sun's rays relative to the plane of the meridian, that is to say their inclination in the vertical east-west plane. In practice, it suffices that the reflectors 31 and the collectors 51 have a relatively large length relative to the distance which separates the collectors from the reflectors.

With the approach of the spring and autumn equinoxes, the diurnal amplitude of the angular movement of the arms 45 and the collectors 51 decreases and becomes zero on the precise day of the equinox where the sun rises and sets in the east-west plane which contains the axes of the reflectors. The height angle of the sun measured in the vertical plane of the meridian remains constant throughout the day.

In the illustrated embodiment, the amplification or concentration factor of solar energy varies with the height angle of the sun. This factor depends on the degree of coincidence of the collector and the area of convergence of the reflected solar energy for a given height angle. It is therefore important to maximize this coincidence for all the angular positions of the sun and of the collector 51, arm 45 assemblies.

This problem can be solved by mounting the pivots of the arms 45 near the surface of the reflector, preferably below the latter. The collector 51 can thus intercept a maximum of rays passing through the convergence zone. In the figures, the axis of articulation of the arms 45 is slightly lower than the reflective surface of the reflector 31 and is off-center in a direction opposite to the equator by a distance f which is a function of the latitude of the place. However, other arrangements can be made with a pivot axis located in the reflective surface or slightly above it.

In fig. 2, the arms 45 disposed between the two reflector lands 31 are common to the two aligned reflectors 51. In the modification of FIG. 2a, the common arms are replaced by two independent arms 245 which each carry one of the reflectors 51 associated with the two banks of reflectors. In this case, only the torsion tube 91 is common to the two batteries and controls the deformations of the parallelograms 45, 81, 71, 245, 271, 81, 245, 271, 81, etc., at each end of the groups of collectors 51.

It is obvious that the drawings are only illustrative and that they are not generally to scale, except for fig. 7 which is partially so. This remark also applies to the reflection and convergence zones of sunlight which are shown only to facilitate understanding of the principle and the operation of the invention.

In addition, the example described and illustrated, in particular in FIG. 7, corresponds to a place whose latitude is 28 °. The concentration factors are also optimized for summer, spring and autumn at the expense of the winter period because under these s

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latitudes, the energy needs of air conditioning are important in hot weather. The winter yield is however sufficient to ensure efficient heating for most of the season.

Alternatively, a single or multiple reflector may or may not be mounted on the roof of a building, although the proposed solution is particularly advantageous. The positioning mechanism of the collectors can also be modified, provided that the above principles are respected.

statements. As regards the shape of the reflectors, it is possible to use more numerous radii which decrease as one moves away from the central arc, or even a ray evolving continuously from the center towards the edges of the reflector. However, the latter solution considerably complicates the manufacture of the reflectors and does not offer any significant advantages in return. The best compromise is that which has been described with three arcs of curvature.

B

3 sheets of drawings

Claims (21)

619530 1. Device for collecting solar energy, characterized in that it comprises a normally fixed concave reflector-concentrator having a semi-cylindrical curvature with three radii corresponding to three surfaces of constant curvature over the entire length of the reflector, and an elongated collector parallel to the generators of the reflector, the collector being displaceable transversely in front of part of the width of the reflector, the first surface with constant curvature of the reflector having a first radius and the second and third surfaces with constant curvature having respectively second and third rays smaller than the first, the first surface being arranged between the two others which are less inclined with respect to the vertical than the first concave surface of large radius, a mechanism moving the collector transversely above the reflector on at least part of its width as a function of the height angle of the sun in a perpendicular plane e to the longitudinal axis of the reflector so as to maintain the collector in a zone of concentration of solar energy which moves transversely relative to the reflector when the height of the sun varies. 2. Device according to claim 1, characterized in that the surfaces with constant curvature of the reflector are connected with tangent planes substantially common, the two spaced rays intersecting the concave surfaces in the areas where they are substantially tangent to common planes. 2 3. Device according to claim 1, characterized in that the three cylindrical surfaces with constant curvature are connected without discontinuity along generators. 4. Device according to claim 1, characterized in that a cord subtending the arc of the second surface is inclined towards the equator and in that a cord subtending the arc of the third surface is inclined at l opposite of the equator. 5. Device according to claim 1, characterized in that the second and third radii are substantially equal. 6. Device according to claim 1, characterized in that the collector is movable on a transverse trajectory relative to the axis of the semi-cylindrical reflector so as to optimize the capture of solar energy in the concentration zone of the reflector. 7. Device according to claim 6, characterized in that the collector is moved by a mechanism animated with a transverse movement relative to the length of the reflector. 8. Device according to claim 7, characterized in that said mechanism comprises pivoting support arms sin * which is mounted the collector which describes an arc of a circle transverse with respect to the axis of the reflector. 9. Device according to claim 8, characterized in that the pivot axes of the collector support arms are located below the surface of the reflector. 10. Device according to claim 8, characterized in that the pivot axes of the collector support arms are substantially in the surface of the reflector. 11. Device according to claim 8, characterized in that the pivot axes of the collector support arms are located above the surface of the reflector. 12. Device according to claim 8, characterized in that the pivot axes of the collector support arms are parallel to the generatrices of the reflector and are offset towards its second or third surface. 13. Device according to claim 12, characterized in that the composite surface of the semi-cylindrical reflector is substantially symmetrical with respect to a vertical plane passing through the middle of the first surface. 14. Device according to claim 1, characterized in that the pivot axes of the collector support arms are offset from the middle of the reflector to its second or third surface. 15. Device according to claim 14, characterized in that the composite surface of the semi-cylindrical reflector is substantially symmetrical with respect to a vertical plane passing through the middle of the first surface. 16. Device according to claim 1, characterized in that the composite surface of the semi-cylindrical reflector is substantially symmetrical with respect to a vertical plane passing through the middle of the first surface. 17. Device according to claim 1, characterized in that the composite surface of the reflector is substantially symmetrical with respect to a longitudinal vertical plane, and in that several identical reflectors are intended to be juxtaposed on the roof of a construction in one surface corrugated, a corresponding number of collectors being associated with the reflectors. 18. Device according to claim 17, characterized in that the reflectors are connected along their adjacent longitudinal edges. 19. Device according to claim 17, characterized in that the transverse positioning mechanisms of the collectors relative to the reflectors are controlled collectively. 20. Device according to claim 19, characterized in that the mechanisms comprise pivoting arms and form deformable parallelograms. 21. Device according to any one of claims 1 to 20, characterized in that it comprises several normally fixed concave semi-cylindrical reflector-concentrators whose juxtaposed sections form an inverted cycloidal surface, and a corresponding number of movable collectors arranged longitudinally with respect to the reflector-concentrators, each longitudinal collector being movable transversely with respect to the associated collector, each reflector and its associated collector forming a distinct assembly for concentrating solar energy by the concave semi-cylindrical surface of the fixed reflector.