FR2497329A1 - Tracking parabolic dish solar collector for water heating - uses disc heat exchanger at focus, and has vertical and horizontal tilt motors at top of support pillar - Google Patents

Abstract

The appts. has a parabolic collector mounted on a rotatable vertical axis. The reflector is tiltable about a horizontal axis, so that the axis of the parabola is always directed at the sun. A circular disc heat exchanger is carried at the focus of the parabola, and has a working fluid carried to-and-fro by the hollow supports struts. The heated working fluid then passes through a coil (7) in a water storage cylinder (8). The parabolic dish (1) is supported on a fixed vertical pillar (2) which contains the working fluid circulation pump. An enclosure containing the two electric positioning motors and their associated gearboxes, along with control circuitry, is pivoted from the top of the pillar. A counterweight is placed behind the parabolic dish, reducing the power required to tilt it.

Description

Device for capturing solar energy comprising an adjustable parabolic reflector.

 The present invention relates to devices for collecting solar energy comprising a orientable parabolic reflector, which is kept pointed towards the sun and which reflects the sun's rays towards a boiler located at the focus of the mirror.

 Solar collectors are known comprising a parabolic mirror which can be rotated about a revolution, which is supported by a vertical post and which pivots about a vertical axis coincident with the axis of the post and around a horizontal axis. Such devices include servomotors which automatically control the pivoting of the mirror around the horizontal and vertical axes to maintain the axis of revolution of the mirror pointed towards the sun. These servomotors are controlled by four photoelectric cells, arranged in a cross, which are integral with the mirror. These cells deliver signals proportional to their illumination and comparators compare the signals delivered by two opposite cells and, when an imbalance appears, they emit a signal which controls the servomotor in the direction which restores equality of clarity between the two cells.

 The objective of the present invention is to improve devices of this known type in order to reduce the construction price and improve performance.

 The invention relates to devices comprising, in known manner, a steerable parabolic reflector, mounted on top of a vertical pillar, means for pivoting the reflector about a vertical axis z zl and a horizontal axis y yl so maintain the x xl axis of the reflector pointed towards the sun and a boiler placed at the focus of the reflector.

 The objective of the invention is achieved by means of a device in which the reflector is carried by a vertical support which is composed, in its lower part, of a fixed cabinet containing the pump for circulating the heat transfer fluid and, in its part upper, of a movable box which is placed on a pivot with vertical axis and which contains motor-reducing groups which orient the reflector.

 The reflector is articulated around a horizontal axis which is parallel to one of the upper edges of said movable housing and which is situated slightly above said edge.

 Preferably, the reflector has arms which extend to the career of the reflector and which each carry a counterweight.

 According to an advantageous embodiment, a reflector according to the invention comprises a vertical arch in the form of a semicircle, centered on said horizontal axis y yl, which is fixed by its two ends to the rear face of the reflector and the reflector is driven in rotation about the axis y yl by a chain driven by a toothed wheel of which the two extracted are fixed to said hoop and which is housed in a peripheral groove of said hoop.

 Preferably, the reflector is composed of two shells, a front shell, of parabolic shape, the front face of which carries a reflective coating, and a rear shell which is connected to the front shell by its periphery and the two shells delimit between them a intermediate space in which circulates hot air for defrosting the reflecting face.

 The invention results in new devices for capturing solar energy which are more sophisticated and safer than known devices.

 The composition of the reflector support, the lower part of which constitutes a fixed cabinet which contains the circulator and the upper part of which constitutes a housing which pivots around a vertical axis and which houses the servomotors makes it possible to reduce construction costs. In addition, one of the side faces and the upper face of the movable housing serve as knolls for the reflector and can carry limit switch contacts and a hook for locking the reflector in the horizontal safety position.

 The counterweights associated with the reflector make it possible to reduce the torque and to control the inclination of the reflector with a low power motor, which makes it possible to use for rotation and for the inclination of the reflector two identical geared motors and reduce the costs of 'interview.

 The reflectors according to the invention composed of two eyelets which delimit an intermediate space, in which hot air can circulate, allow the reflective face to be defrosted quickly, so that the mirror is ready to capture energy. solar from sunrise.

 The following description refers to the appended drawings which represent, without any limiting character, an exemplary embodiment of a device according to the invention.

 Figure 1 is an overview of a device according to the invention.

 Figure 2 is a perspective view with partial cutaway of the mirror support.

 Figure 3 is an axial vertical section of the mirror.

 Figures 4, 5 and 6 are views of embodiments of the boiler.

 Figure 7 is an axial section of a preferred embodiment of the housing containing the automatic pointing cells.

 FIG. 8 is a partial view along VIII-VIII of FIG. 7.

 FIG. 1 schematically represents an installation intended to supply domestic hot water and heating water to one or more dwellings.

This installation comprises a solar energy collector constituted by a parabolic mirror 1, of revolution around an axis x xl. The mirror 1 is mounted on a support 2, so that it can pivot around a vertical axis z z1 and around a horizontal axis y yl which is perpendicular to the plane of the figure,
The sensor comprises> in addition, a boiler 3 which is supported by three arms 4 and which is placed substantially at the focus of the parabolic reflector.

 A heat transfer liquid, for example a mixture of water and antifreeze, -or an oil, circulates in a closed circuit comprising the boiler 3, -pipes 5, a circulation pump 6 and an exchanger 7 which is embedded in a 8 calorie accumulation tank whose walls are insulated.

 The water contained in the tank 8 can be heated by an auxiliary burner 9 in the event of prolonged lack of sunshine. The water contained in the tank 8 feeds a central heating circuit comprising radiators 10 and a circulator 11 controlled by a room thermostat 12. It can also heat the water intended for sanitary needs contained in a tank 13. By example the balloon 13 is placed at a level higher than that of the tank 8 and the water of the balloon 13 is heated by a coil 14 in which the hot water from the tank 8 circulates by thermosyphon effect.

 The device comprises two servomotors, not shown, which automatically drive the mirror 1 in rotation around the axis z z1 and the axis y y1 to maintain the axis x xl pointed towards the sun during the day. These servomotors are controlled by photocells.

 Figure 2 shows in perspective a rear view of the mirror 1 and the support 2. The support 2 is divided into two parts. The lower part 2a is fixed and anchored to the ground. It constitutes a cabinet fitted with an access door 15a. This cabinet contains the circulation pump 6 and a pressure switch. The upper part 2b is a housing mounted on a pivot 15 of the crapaudine or round type front end with double row of balls and with vertical axis z z1, which allows the housing 2b to pivot relative to the axis z z1. The movable part 2b is rotated by a gear motor which is composed of a small electric motor 16a with direct current and a reduction gear 16b. The electric motor, for example, has a power of 250 watts. It includes a reversing device by reversing the inductive current and it is supplied with direct current by a 24 V battery, which is supplied by a rectifier supplied by the sector.

 The reducer 16b drives a toothed wheel 17 which drives a chain 18, which drives the pivot 15. The motor-reduction unit 16a, 16b, can be fixed on top of the fixed part 2a, in the space between the periphery of the pivot 15 and a circle inscribed inside the housing 2b, so that the latter can pivot freely around the geared motor group. In this case, the box 2b has no bottom and constitutes a cover which envelops the gearmotor groups. As a variant, the geared motor group 16a, 16b can be fixed to the cover 2b.

 The parabolic mirror 1 is supported by a structure 19 which is pivotally mounted around a horizontal axis y y1 which is parallel to one of the edges 20 of the upper face of the movable part 2b. The axis y yl is located slightly above the edge 20 and substantially in the vertical plane of the latter or slightly outside, so that the mirror 1 can come into abutment against the lateral face vertical of the movable part 2b which contains the edge 20 as shown in Figure 3, and can also be folded against the top of the movable part 2b. For example, the axis y y1 is supported by a hollow or tubular profile 21 which is fixed above the movable part 2b parallel to the edge 20 thereof.

 The structure 19 comprises two arms 22 which extend at the rear of the mirror, on the other side of the axis y yl and which each support a counterweight 23 intended to balance the torque due to the mirror and to reduce the power required to tilt the mirror around the y yl axis. For the sake of clarity, only one counterweight has been shown. The two arms 22 are symmetrical relative to the vertical plane passing through the axis x xl of the mirror. The spacing between the two arms 22 is greater than the width of the movable part 2b.

 The mobile part 2b contains a second geared motor group 24a, 24b similar to group 16a, which controls the inclination of the mirror 1 by tilting it around the horizontal axis y y1. Thanks to the counterweight 23, a low power motor 24a is sufficient to tilt the mirror 1, so that the two gearmotor groups can be identical.

 An arch 25 having the shape of a semicircle situated in a vertical plane and centered on the axis y y1 is fixed to the structure 19.

This arch has a groove and a chain 26 passes through this groove and is fixed by its two ends to the two ends of the arch 25. The chain 26 passes over a toothed wheel 27 driven by the reduction gear 24b. The upper wall and the front lateral pal-ol of the housing 2b have an ovalized hole for the passage of the arch 25.

 The group 24a, 24b can be replaced by an electric actuator. The mobile part 2b also contains the electrical and electronic devices and circuits.

 Figure 3 is an axial vertical section of the mirror 1 and the upper part of the support 2a, 2b. We see in this figure the arch 25. The mirror 1 has two shells 28a and 28b which are welded or glued by their periphery. These two shells are made of plastic, for example laminated polyester.

 The front shell 28a, that is to say the shell facing the sun, has the shape of a paraboloid of revolution around the axis x xl. The external face of the shell 28a carries a reflective coating. For example, it is lined with mirrors 29 which are glued to the shell 28a.

 The axial part of the shell 28a has an inward deflection which delimits a cylindrical housing 30 of axis x xl, which is closed by a removable cover 31 allowing access to the interior of the housing.

 The rear shell 28b has an approximately parabolic or spherical shape of axis x xl, such that the two shells 28a, 28b are tangent to their periphery where they are united and that they delimit an intermediate space between them 32.

 The central part of the rear shell 28b has a flat face 33, having the shape of a disc which is also visible in FIG. 2. This flat face 33 is reinforced and carries bars 19 forming a structure which supports the reflector 1. Before tagging, the rear face of the housing 30 is fixed to the front face of the disc 33 to reinforce the mechanical connection between the shells 28a and 28b.

 As can be seen in FIG. 3, the disc 33 has a radius slightly less than the distance which separates the axis y y1 from the top of the fixed part 7a 2e, so that the mirror does not run the risk of abutting against the fixed part when it rotates around the z axis z1. We see in Figure 3 that the flat face 33 abuts against the front side face of the movable part 2b when the mirror is straightened vertically, that is to say when the axis x xl is horizontal.

 Likewise, the flat face 33 abuts against the top of the movable part 2b when the mirror is placed horizontally, that is to say when the axis x xl is vertical.

 The movable part 2b carries a locking hook 34 which is pivotally mounted about a horizontal axis and the disc 33 carries a recessed housing 35 in which the hook 34 penetrates when the mirror is horizontal. The hook 34 keeps the mirror in a horizontal position which is a safety position until the unlocking of the hook 34 is manually controlled.

 the housing 30 can contain electrical resistances 36 which heat the air. The hot air leaves the housing 30 through orifices 37, it travels through the intermediate space 32 and it is discharged through orifices 38 drilled at the periphery of the rear shell 28b. The orifices 38 are provided with a screen to prevent insects from entering the space 32.

 The circulation of hot air in the intermediate space 32 makes it possible to quickly defrost the reflecting face of the mirror or to melt the snow in the morning in the case where the sensor is installed in places which require it, for example in stations. winter sports.

 FIG. 4 is a perspective view of the boiler 3, carried by the three arms 4.

 FIG. 5 is an axial section of FIG. 4.

 These two figures represent a preferred embodiment of the boiler 3. The latter is composed of a metal block 39 molded for example from aluminum alloy or cast iron. The sunny face of the block 39 which is directed towards the mirror 1 comprises concentric or spiral relief fins 40. This face has a conical shape, the opening of which is directed towards the mirror so that all the reflected rays penetrate inside the conical cavity and are trapped. The fins 40 increase the absorption surface and reduce the energy losses. by reflection and by emission. The sunny side 39 is painted black or anodized.

A spiral duct 41 is located inside the block 39. The two ends of the duct 41 are connected to the tubes 5 of the primary heating circuit. Tubes 5 are suppor
r ted by arms 4 and they are connected on the rear face of the boiler. Preferably, cold water arrives at the periphery and hot water leaves at the center where the temperature is maximum. To facilitate demolding, the boiler body 39 can be manufactured in two parts 39a and 39b as shown in FIG. 6.

 Alternatively, the boiler 3 can also be made of a copper tube wound in a spiral.

 FIG. 3 shows a device 42 which automatically controls the two motors 16a and 24a to maintain the axis x xl of the mirror pointed towards the sun. The device 42 is fixed to the mirror at the periphery thereof, so that its axis u ul is parallel to the axis x xl of the mirpir and that it follows the mirror in its rotations around the axes z z1 and y yl.

 Figure 7 is an axial section of the control device 42. It comprises a support 43 which is fixed on the edge of the mirror 1, for example on the west edge.

 Figure 8 is a partial view along VIII-VIII showing the detail of the attachment. This comprises a circular hole 43a and an ovalized hole 43b and makes it possible to adjust the position of the support so that the axis u ul is parallel to the axis x xl of the mirror.

 The control device 42 comprises a housing 44 made of opaque plastic which is placed on the support 43. The housing 44 has a truncated pyramidal shape. It has four lower side faces 45 which diverge upwards and four upper side faces 46 which converge towards a central orifice 47. A tube 48 of opaque plastic, of square section, is fixed around the central orifice 47. The tube 48 and the housing have a common axis u ul. Certain lateral faces of the housing include windows 50 which are equipped with a filtering glass which stops ultraviolet and infrared rays and the cells 51 are arranged inside the housing, facing each of the windows.

 Figure 7 is a section East West on which we see the window 50a located on the lower side East and the window 50b located on the lower side West.

 We also see in Figure 7 the East window 50c, the West window 50d and the two North windows 50e and 50f of the upper faces.

 In addition to the windows visible in FIG. 7, the lower South face and the upper South face each have a window, 50g and 50h respectively. In addition to the cells 51 which control the motors 16a and 24a, the housing 44 contains a cell which is placed behind the window 50g, called day-night cell.

 At nightfall, this cell neutralizes the automatic piloting of the mirror and controls the motor 16a in the direction which brings the mirror towards the East. A limit switch stops the motor when the mirror is directed towards the East.

 Automatic pivoting to the East can also be controlled automatically by the 50g cell if the intensity of the sunlight is too low.

 The tubular sleeve 48 serves as a screen which casts its shadow on the cells when the reflector is no longer pointed towards the sun. The length of the sleeve 48 is chosen according to the latitude.

 The pyramidal shape of the housing makes it possible to place two cells 52 behind the windows 50a and 50b of the lower lateral faces which control an automatic adjustment of the orientation for example in the extreme case where the sun would appear only in the afternoon and where the reflector would have remained pointed east since morning. In this case, the sun does not reach the upper sides but it hits one of the cells located in front of a lower window 50a or 50b and this controls the pivoting towards the West until the normal pointing device intervenes.

It is thus possible to make up for an angular offset of the axis of the reflector which can reach 110.

 This pyramidal shape and the presence of two catch-up cells 52 makes it possible to avoid using an electronic clock to keep the reflector pointed approximately towards the sun.

 The housing 44 also contains a cell which is placed behind the window 50e which automatically stops the circulator 6 of the primary circuit at dusk.

 A device according to the invention comprises safety devices which automatically place the mirror 1 in a horizontal position, that is to say in a position where the axis x xl is vertical.

 These safety devices include a first relay which detects the lack of alternating supply voltage and which controls a 24-volt relay, a contact of which controls the motor 24e in the direction which brings the mirror into a horizontal position. A limit switch stops the motor 24a when the x xl axis is vertical. This preventive security avoids the risk of overheating of the boiler head due to the stopping of the circulator 6.

 The device further comprises a wind speed sensor which emits a signal when the wind speed exceeds a threshold, for example 80 km / h.

 It also includes a temperature sensor which measures the temperature of the heat transfer liquid in the boiler or at the outlet thereof and which emits a signal when this temperature exceeds a threshold which is for example 940 in the case of water. Finally, the device includes a pressure sensor which measures the pressure of the heat transfer liquid in the primary circuit 5 and which emits a signal when this pressure drops below a threshold.

 The three above sensors are connected in parallel on a 24 volt relay which controls the 24z motor in the direction that raises the mirror to place it horizontally. A limit switch automatically stops the motor 24a when the mirror comes to a stop and the locking hook 34 keeps the mirror in the safety position until intervention is made.

 The above safety devices make it possible to obtain very safe operation of a sensor according to the invention without having to monitor it.

Claims (13)

 1. Device for collecting solar energy of the type comprising a orientable parabolic reflector (1), mounted at the top of a vertical pillar, means for pivoting said reflector about a vertical axis (z zl) and a horizontal axis (y yl) in order to maintain the axis (x xl) of the reflector pointed towards the sun and a boiler (3), placed at the focus of the reflector (1), characterized in that said reflector is carried by a vertical support (2) which is composed in its lower part of a fixed cabinet (2a) containing the circulation pump (6) of the heat transfer fluid and, in its upper part, of a movable housing (2b) which is placed on a pivot (15) with vertical axis (z zl) and which contains two geared motor groups (16a, 16b and 24a, 24b) which orient the reflector and the electrical and electronic circuits.  2. Device according to claim 1, characterized in that said reflector is articulated around a horizontal axis (y yl) which is parallel to one of the upper edges (2a) of said movable housing (2b) and which is located slightly above said edge.  3. Device according to any one of claims 1 and 2, characterized in that said reflector (I) comprises two arms (22) which extend at the rear of the reflector (1) and which each carry a counterweight (23 ).  4. Device according to any one of claims 1 to 3, characterized in that said reflector (1) comprises a vertical hoop (25) in the form of a semicircle, centered on said horizontal axis (y yl), which is fixed by its two ends on the rear face of the reflector (I) and the reflector (1) is rotated about the axis (y y1) by a chain (26) driven by a toothed wheel (27) whose two ends are fixed to said arch and which is housed in a peripheral groove of said arch.  5. Device according to any one of claims 1 to 4, characterized in that said reflector is composed of two shells, a front shell (28a), of parabolic shape, the front face of which carries a reflective coating, and a rear shell (28b) which is connected to the front shell by its periphery and the two shells delimit between them an intermediate space (32) in which circulates hot air for defrosting the reflecting face.  6. Device according to claim 5, characterized in that said rear shell (28b) comprises in its axial part a flat face (33) having the shape of a disc which can abut against one of the lateral faces or against the upper face of the housing (2b).  7. Device according to claim 5, characterized in that the front shell (28a) comprises, in its axial part, a cylindrical housing (30), coaxial with the reflector, which is closed by a removable cover (31) and which contains electric resistors (36).  8. Device according to any one of claims 1 to 7, characterized in that said boiler (3) has a conical face whose opening is directed towards the mirror and which comprises fins in relief (40) concentric or spiral .  9. Device according to claim 8, characterized in that said boiler is a metal block (39), composed of one or more joined plates, which delimit a spiral duct (41) in which circulates the heat transfer fluid.  10. Device according to any one of claims 1 to 9, of the type comprising an automatic pointing device composed of photoelectric cells, characterized in that said cells are placed in an opaque housing, made of plastic material (44) double pyramid, comprising four lower lateral faces (45), which diverge upwards and four upper lateral faces (46) which converge towards a central orifice (47), an opaque tube (48) which surrounds said central orifice and windows (5Da, 5Ob .. 50f) provided with filter glasses located in said lateral faces (45, 46).  11. Device according to any one of claims 1 to 10, characterized in that it comprises a relay with lack of alternating supply voltage, a wind speed sensor, a temperature sensor and a liquid pressure sensor coolant which automatically controls the motor (24a) for raising the reflector horizontally when safety thresholds are exceeded.  12. Device according to claim 11, characterized in that said movable housing (2b) carries on its upper face a locking hook (34) and said disc (33) carries on its rear face a hollow housing (35) which cooperates with said hook to keep the reflector locked in a horizontal position.  13. Device according to claim 10, characterized in that said housing comprises cells (52) placed opposite the windows (50a, 50b) of the lower faces which control the automatic catching up of the pointing even in the event of a large difference in orientation and it further comprises a cell placed behind an additional window (50e) with an upper face which automatically stops the circulation pump (6) at nightfall.