Parabolic solar collector.

[0001]Aparabolic solar collector comprising a linear parabolic mirror and a tubular device covered by a coolant is positioned at the focus of the parabola linear such that the parabolic mirror solar rays incident on the tubular device, and provide heat to the heat transfer fluid. The present invention more particularly relates to such a solar collector having a transparent outer enclosure and mechanically strong. The present invention comprises both a solar collector to a photovoltaic thermal solar collector.

[0002] Known solar collectors which correspond to the definition given above. Patent document FR's 2,568 991, in particular, describes a device for collecting and storing solar to small footprint that has a linear parabolic mirror adapted to pivot about a hollow pylon forming the vertical axis of a cylindrical tower whose rigid underbody constitutes a service room and a thermal storage space. The walls of the cylindrical tower are constituted by elements of transparent plastic materials assembled between circular smooth superimposed. Stringers are themselves suspended strut by a first series of tensioners and secured to the underbody of the cylinder by other tensioners. This known construction has certain drawbacks. On the one hand the plant described is large, 6 meters in diameter and 20 meters in height, thereby making it difficult for its integration to existing structures and constructions. In addition, the construction or mounting of such a pickup device and storing solar represents obviously considerable work.

[0003] An object of the present invention is therefore to overcome the disadvantages of the prior art just described, of the present invention is a solar collector and easy to install and uninstall, or even transported in room without requiring disassembly. The present invention achieves this objective by providing a parabolic solar collector according to claim 1 appended.

[0004] According to the invention, the transparent enclosure is self-supporting. In other words, it is sufficiently rigid to resist deformation and to ensure structural integrity of the solar collector, even when the latter is detached from any support. It will be appreciated that an advantage of this feature is that the solar collector can be moved without previously disassembled. Excellent in maintenance and placed in service are thus greatly facilitated. Further, the tubular device is fixedly mounted within the enclosure. It then is not on itself, greatly simplifying the connection lines of the circuit for the heat transfer fluid. Finally, in an advantageous embodiment of the invention, the tubular device passes through the enclosure right through, so that its two ends emerge outside on both sides of the solar collector. The latter feature is especially appropriate facilities comprising a plurality of solar collectors connected in a common circuit for heat transfer fluid.

[0005] The linear parabolic mirror is rotatably mounted on the tubular device. It is provided with a orientation device arranged to energetically independent mechanically on a fixed part of the installation. The rotatability of the parabola line with respect to the tubular device is necessary to direct the mirror facing the incident solar rays. The rotation of the mirror is very slow. According to the invention, the directional device is disposed within the enclosure and is integral in rotation with the linear parabolic mirror. The orientation device is connected to a power source that is also contained within the enclosure. This characteristic makes the orientation device alone. Advantageously the energy source is also integral in rotation of the mirror so as to remain stationary relative to the directing device. Due to this characteristic, the wiring of the orientation device can be particularly simple.

[0006] According to an advantageous embodiment of the invention, the outer housing has an axis of symmetry and thus has the form of a solid of revolution. It will be appreciated that providing to enclosure the shape of a solid of revolution gives it a greater stiffness. Further, in an advantageous embodiment of this embodiment, the tubular device is mounted concentrically to the axis of symmetry of the solid of revolution. Indeed, this arrangement allows to minimize the external dimensions of the enclosure while maintaining within sufficient clearance that the linear parabolic mirror is free to rotate.

[0007] Alternatively very advantageous, the enclosure is in the form of a solid of revolution closed at each of its ends by a flange. It will be appreciated that the solid of revolution with the two flanges form an enclosure enjoying a high structural stability. In this embodiment, each flange still has a central aperture arranged to allow passage of one end of the tubular device. Preferably, the opening of the flanges is further arranged to permit attaching each end of the tubular device to the enclosure. Thus, the tubular device is to the two flanges, which further strengthens the structure of the sensor. It will be appreciated that the transparent enclosure acts as a chassis within which all the rest of the construction is attached.

[0008] Other features and advantages of the invention will appear upon reading the description which will follow, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

figure 1

the Figure. 2A and 2b

the Figure. 3A and 3b

the Figure. 4A and 4b

figure 5

the Figure. 6A and 6b

the Figure. 7 A and 7b

is a perspective view showing a parabolic solar collector according to a particular embodiment of the invention, the solar collector is installed on a cradle in metal tubes;

are schematic views, respectively perspective and side, of the cylindrical enclosure transparent solar sensor of fig. 1;

are schematic diagram, showing the linear parabolic mirror of the solar collector of Figure 1 respectively perspective and cross-sectional, and illustrating how a linear parabolic mirror can focus the incident solar rays on the line focus of the parabola;

are schematic sectional views showing the tubular device of the solar collector of the fig.. 1;

is a partial view in section showing more particularly the attachment of the tubular device to the enclosure of the solar collector of Figure 1;

are views, respectively perspective and face, showing how, in the sensor of fig. 1 solar, the linear parabolic mirror is pivoted on the tubular device using two radial bearing, each radial bearing being secured to the parabolic mirror by one of its ends;

are schematic views, respectively perspective and cross-sectional, similar to fig.. 6A and 6b, but also showing the external enclosure and the orientation of the mirror;

the Figure. 8A, 8b and 8c are schematic sectional views corresponding to three particular orientations of the linear parabolic mirror and illustrating for each orientation the reflection of incident solar rays;

the Figure. 9A and 9b are plan schematic views of two circuits of coolant each incorporating a parabolic solar collector assembly identical to that of fig. 1. The Figure. 9A and 9b respectively showing the different sensors connected in parallel and in series;

fig. 10 is a perspective view showing the series connection of solar collectors identical to that of fig. 1.

[0009] Figure 1 is a perspective view showing a parabolic solar collector 1 according to a particular embodiment of the invention. We can see in Figure that the sensor is housed in a protective enclosure 7 transparent. The protective enclosure is arranged to enclose and protect all sensitive parts of the solar collector and fragile. In the illustrated embodiment, the protective housing 7 has a cylindrical shape and is preferably formed from glass. The cylindrical shape imparts to the enclosure good structural stability, and this stability is enhanced by the presence of two flanges 10 and 11 glass which are bonded to the two ends of the cylindrical tube. We can see that the two flanges are still centrally therethrough a tubular device 4 which is concentric with the axis of symmetry of the cylinder. The tubular device 4 is adapted to be passed through by a heat transfer liquid (not shown). Figure 1 shows still in transparency, inside the enclosure, a linear parabolic mirror 2 which is rotatably mounted on the tubular device 4, two counterweights 17 for the turning mirror, and orienting means 9 energetically autonomous which is carried by the parabolic mirror. In the illustrated embodiment, the orientation device is provided with a wheel arranged to bear upon the inner surface of the enclosure 7. It will be appreciated however that, according to other embodiments, the tracking device could on another fixed part of the installation. In particular, it could be supported on the tubular device 4. In this case, the rotary movements of the parabolic mirror relative to the tubular device could advantageously be produced by an ultrasonic motor like those that are commonly utilized in the autofocus devices of certain cameras. It should be noted finally that the solar collector 1 is shown in a horizontal position, supported by a cradle in metal tubes 20. However, it will be appreciated that the solar collector according to the invention can operate in all orientations (horizontal, vertical, inclined).

[0010] The Figure. 2A and 2b are schematic views of the cylindrical enclosure 7 clear of the solar collector. As it was already said, in the illustrated embodiment, protective fence consists of a glass tube of cylindrical shape, whose both ends are closed by end plates 10 and 11 also flat circular glass, which are adhesively joined to the cylinder. The connecting flanges and the cylinder is protected by two metal flanges 21 which are bonded to the flanges and to the cylinder by means, for example, a filling paste silicone. These flanges also provide for securing the solar collector to a support (the cradle 20 of fig. 1 for example). The center of the flanges 10 and 11 is used for fixing the tubular device 4. In the illustrated example, the engagement is by an aluminum flange 22. The glass used for protective fence 7 (including the flanges 10, 11) should preferably be the more transparent as possible, and is the most radiation transmittance over a wavelength range of from 250 to 2500 nanometers. From the viewpoint of the transmittance, the glass of calcium fluoride is a most suitable, but it is expensive. The quartz glass is almost as good and cheaper. It may also be considered the borosilicate.

[0011] The enclosure 7 of the solar collector is preferably sealed. However, it will be understood that the interior of the enclosure is subjected to higher temperatures than the outside temperature during the operation of the solar collector. Accordingly, pressure differences between the inside and the outside of the enclosure are unavoidable. These differences, could in theory from cracking the glass enclosure. Several alternative variants can be taken to remedy the difficulty. Firstly, according to the embodiment illustrated in the drawings, may be provided enabling the enclosure of two safety valves. A first valve for limiting excess pressures within the enclosure and a second valve in the event of overpressure to outside the enclosure. Alternatively AC, could be provided from expansion membrane mounted to the enclosure. It will be appreciated further that none means for the equalization pressure is not really needed, as long as the enclosure is sufficiently secure. In the same order of ideas, could still be creating a partial vacuum within the enclosure, such that the differential pressure is always in the same direction.

[0012] The Figure. 3A and 3b have schematic views, respectively perspective and cross-sectional, of the linear parabolic mirror of the solar collector. A peculiarity of the linear parabolic mirror of the embodiment of solar collector which is the object of the present example is that the line focus of the parabola coincides with the axis of symmetry of the environmental enclosure 7.

[0013] The linear parabolic mirror 2 must have a weight as low as possible so as to limit the consumption of electrical energy required to drive its orientation. The Figure. 3A and 3b illustrate an example of the construction of the parabola linear. In this example, the parabola linear 2 consists of a sheet of aluminum having a thickness of 0.2 mm may be. By giving the aluminum sheet its parabolic shape by stamping. The back of this sheet can be stiffened by arches 23 made of aluminum injected and machined. The arches are joined to the sheet metal, for example by gluing, and ensure the holding of the parabolic shape. The concave portion of the parabola linear 2 has a surface which must ensure the reflection of solar radiation to a line focus. By way of example, a parabolic mirror configured as explained above and having a reflective surface of 0.575 M.² weighs about 680 grams.

[0014] The Figure. 4A and 4b are schematic sectional views showing in detail the tubular device 4 of the solar collector 1. The tubular device has as main role of converting the energy of solar radiation into thermal energy. Circulating a heat transfer fluid (not shown) through the tubular device for transporting the energy to the exterior of the solar collector to be used. As has been already said, the tubular device is disposed concentrically to the line focus of the parabolic mirror 2. When the dish is properly oriented, it thereby concentrating solar radiation onto the tubular device. As is known, the system may include an absorption tube 25 made of metal (e.g. stainless steel) coated with a layer that promotes the absorption of light energy (e.g. treatment with black chrome), and a tube of glass insulator 26 closed at both ends and surrounding the absorber tube. A high vacuum is produced in the volume formed between the absorption tube 25 and the insulation tube 26 to create high isolation between the absorber tube and the outside. In the illustrated example, it should be noted that the glass insulation tube 26 is closed at one end by a flange 27. Further, order to allow expansion difference between the insulation tube 26 and the absorbing pipe 25, the other end of the glass tube is closed by a compensator 28.

[0015] Fig. 5 is a partial view in section showing more particularly the attachment of the tubular device 4 to the flange 10 of the glass enclosure 7 of the solar collector. Which can be seen in fig. 5 that, in the illustrated example, the attachment of the tubular device 4 to the flange 10 is formed by a flange 22 aluminum, the flange 22 is adhered to the glass plate 10 by means of a filling paste silicone supporting the high temperature (~200 °C). This bonding flexible reduces the stresses due to the difference in expansion between the glass and aluminum. The link between the flange 10 and the glass insulation tube 26 of the tubular device 4 is accomplished by means of O rings 29, c'est i.e. O-rings, supporting the high temperature (~200 °C and Viton for example). A small flask compression 30 an aluminum, using a mechanical clamp, compress l'O-to-ring drums 29 to centralize and secure the insulation tube 26 but allows flexibility of assembly and its sealing. The assembly is constructed so as to create a bridge of cold between the interior of the protective enclosure 7 and the outside to remove some heat from the interior of the protective enclosure outwardly, for the purpose of limiting the temperature within the protective enclosure.

[0016] The Figure. 6A and 6b are views, respectively perspective and face, showing how the linear parabolic mirror 2 is pivoted on the tubular device 4 by means of two radial bearings 12. The parabolic mirror 2 is rotatable about the tubular device on 360°. To this end, the two radial bearings each comprise a ball bearing. These bearings allow for rotation of the parabola linear and accurately positions relative to tubular device throughout its rotation. The outer portion movable ball bearings is integral with the linear parabola. The inner portion is, when to it, clamped on the insulation tube 26 glass of the tubular device using d'O-to-Rings soundtracks shaping this connection flexibility. One of the two ball bearings has a function of maintaining a radial. When at the other, it must provide a radial and axial holding function. In effect, the solar collector should preferably provide functioning in all, from horizontal to vertical. One of the two ball bearings is arranged to compensate for differences in expansions between the insulation tube (glass) and the parabola linear (aluminum).

[0017] The Figure. 7 A and 7b are schematic views similar to fig.. 6A and 6b, but also demonstrate the outer housing 7 and the directing device 9 of the mirror 2. For orienting the parabolic mirror 2 perpendicular to the solar radiation, it is necessary to rotate the mirror with respect to the fixed portions of the solar collector 1. In the present example, the angular displacement of the mirror is provided by an electric motor that is part of the orientation device. The electrical energy consumption of this engine should be as low as possible. As has been already said, the parabolic mirror is pivoted via radial bearings 12 are equipped with ball bearings. The ball bearings require very little power for the "peeling" upon startup, thereby ensuring the accuracy of the rotation.

[0018] Must be absolutely avoid introducing materials susceptible to evaporate inside the protective enclosure 7, because vapors condense then on the inside of the protective enclosure, on the reflective portion of the parabola 2 and on the insulation tube 26 glass, which will decrease the performance of the sensor. Used therefore preferably ball bearings that can run dry, i.e. without fat or oil. Again that these ball bearings rotate very slowly, in principle one rotation per day. Preferably, the main pieces of radial bearings 12 are made of aluminum. However, to avoid corrosion, the ball bearings are preferably glass beads and non-steel. In effect, the steel and aluminum are not good household (problem of electrochemical corrosion).

[0019] It will be appreciated that the linear parabolic mirror 2 is not balanced with respect to its axis of rotation. To simplify the orientation system, optimize its electric energy consumption and increasing its accuracy, it is useful to balance the parabola linear and bring the center of gravity of the assembly on the axis of rotation, thus on the axis of symmetry of the protective enclosure. In the illustrated example, are used for the counterweight to balance the mirror 17. The protective enclosure 7 being cylindrical, its volume disposes the counterweight opposite the parabola 2. The parabola being very slight, its orientation system is very small, the mass of the counterweight 17, respectively their volume, will be low. The counterweights may be formed of steel, material much more dense than aluminum, and are preferably placed very close to the inner surface of the environmental enclosure so as to maximize the lever arm. It is noted that although in the illustrated example, the counterweights 17 are also used to accommodate two small solar cells that allow the electricity supply of the orientation device 9. This location is very favorable for solar cells, because they are always oriented perpendicular to the solar radiation.

[0020] The Figure. 8A, 8b and 8c are schematic sectional views showing three particular orientations of the linear parabolic mirror 2 and illustrating for each orientation the reflection of incident solar rays. The solar collector is provided for capturing solar energy. If for any reason it is decided to stop the production of energy, the linear parabolic mirror 2 can be rotated so as not to concentrate solar radiation on the tubular device 4, which will halt the production of energy. For that it is merely necessary to electronics (not shown) for management control the orientation device 9 (Figure 7b) such that it directs the parabola linear such that it does focuses more solar radiation onto the absorbing pipe 25 (fig.. 4B).

[0021] In the illustrated embodiment, the orientation device 9 is not connected to the outside of the enclosure 7 by a wiring. However, there may be a radio system (e.g. Bluetooth®) for communicating from the exterior with the electronic management of the orientation device 9. Under these conditions, the electronic management system must be equipped with a receiver. It is preferably also provided with a transmitter for sending information on the solar collector, for example signal a malfunction.

[0022] The tubular device 4 of a solar collector 1 according to the invention is intended to be covered by a coolant 5. To this end, the absorption tube 25 of the tubular device 4 of at least one solar collector 1 must be integrated in a circuit 6 for heat transfer fluid. The number of solar collectors which the absorber tubes are part of the same circuit for heat transfer fluid is theoretically unlimited. The tubular devices, or more specifically their absorber tubes, can be connected in series, in parallel or a mixture of both. It will be appreciated that each solar collector 1 is arranged to provide heat to the heat transfer fluid which flows through the tubular device 5 4. The fig.. 9A illustrates schematically a circuit 6 for heat transfer fluid 5 associating five solar collectors 1 connected in parallel. The fig.. 9B illustrates schematically a circuit 6 for heat transfer fluid 5 associating the six solar collectors 1 connected in series.

[0023] Fig. 10 is a perspective view showing the connection in series of several solar collectors identical to that of fig. 1. It will be appreciated that the ends of two absorber tubes may be connected to each other in any manner known to the skilled person. However, the connection between two absorber tubes will preferably be a connection is easy to manufacture and easy to undo. The two ends of the absorber tubes may for example terminate each by a nose provided to be fittingly inserted through a connecting pipe formed from a deformable material. It will be appreciated that such a breathing tube can be used to connect together the ends of the tubes absorbing two solar collectors. To avoid a thermal loss too great, the tube fitting is preferably surrounded by a sleeve of a material that is both flexible and good heat insulator, as the foam for example.

[0024] It will be appreciated further that various modifications and/or improvements obvious for a person skilled in the can be made to the embodiment which is the object of the present disclosure without departing from the scope of the invention defined by the appended claims. In particular, the invention is not limited exclusively to a thermal solar collector, but also relates to a photovoltaic solar collector. It will be appreciated that it is indeed possible for example to replace the tubular device shown in fig. 4. 4A and 4b by a pipe covered with photovoltaic cells.

[0025] It is known that the efficiency of PV cells decreases with temperature. Under these conditions, instead of using the heat transfer fluid for providing heat to any device, there may be used a coolant for cooling the photovoltaic cells. For example it is pumping water in river and used as a heat transfer liquid. On the other hand, the function of the insulation tube 26 glass surrounding the absorption tube 25 is to allow the temperature of the drinking tube from rising as much as possible. It will be appreciated therefore that, in the case of a photovoltaic solar collector, it is preferable that the tubular device is not provided with such an insulation tube. It should be noted however that some embodiments of the invention are mixed thermal-solar solar collectors that include an insulation tube.

[0026]

1. Parabolic solar collector;

2. linear parabolic mirror;

3. incident solar rays;

4. tubular device (thermal);

5. coolant;

6. circuit for heat transfer fluid;

7. external enclosure;

8. connecting element (wheel)

9. orientation device;

10. flange;

11. flange;

12. radial bearings;

13. first tube;

14. second transparent tube;

15. vacuum enclosure;

16. photovoltaic cells;

17. counterweight;

18. tubular device (photovoltaic);

19. set of photovoltaic cells

20. cradle;

21. metal flanges;

22. aluminum flange:

23. the arches;

24. solar rays;

25. absorption tube;

26. insulation tube glass;

27. flange of the insulation tube;

28. compensator;

29. O-ring seal;

30. aluminum compression flange