US20120279487A1

US20120279487A1 - Method for automatic orientation of a solar panel device and device operating according to said method

Info

Publication number: US20120279487A1
Application number: US13/520,403
Authority: US
Inventors: Antoine Pineau; Francois Boudehenn
Original assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2010-01-04
Filing date: 2010-12-31
Publication date: 2012-11-08
Also published as: WO2011080330A3; RU2012133295A; FR2954972B1; BR112012016386A2; IN2012DN05913A; EP2521886A2; FR2954972A1; KR20120112492A; CN102812308A; JP2013516754A; WO2011080330A2

Abstract

Method for orientation of a solar panel device (3), wherein the solar panel device is oriented with respect to at least one axis (5), in a first direction and in a second direction, using energy from a first fluid reservoir (6) or a second fluid reservoir (8), the energy being provided by the solar radiation and the two reservoirs being independent, and wherein the solar panel device is oriented with respect to the axis (5), in the first direction or in the second direction, until a distributor valve (13, 14) prevents feeding of one of the actuator chambers by one of the chambers of a reservoir.

Description

The present invention concerns a method for automatic orientation of a solar panel and a device for orientation of a solar panel, i.e. an orientation device operating according to such a method. The invention further concerns a solar energy conversion system comprising such a device for orientation of a solar panel device and a solar panel device.
With worldwide energy demand increasing, one of the aims for the next years is to find reliable and environmentally friendly sources of energy. One of the first steps in this direction was the production of systems able to convert solar energy either into electricity by means of photovoltaic solar panels or into heat by means of thermal solar panels. The installation of such systems nevertheless remains costly and productivity is sometimes deemed too low by consumers.
Research shows that a system of the above kind that is able to track the course of the sun achieves a gain in productivity averaging 15 to 30% depending on the technology employed. For the system to be able to track the course of the sun, it is equipped with an orientation device or “tracker” for automatically orienting solar panels as a function of the position of the sun.
Orientation devices may be classified in two categories:

- So-called active orientation devices, i.e. devices using external energy, notably electrical energy, to enable the system to track the course of the sun. These orientation devices often use stepper motors to move the solar panels.
- So-called passive orientation devices, i.e. devices using no external source of energy to enable holding and orientation of the solar panels so that they are positioned at least substantially perpendicular to the sun's rays.

For installations of medium and high power, the energy consumed by an active orientation device is low compared to the quantity of energy converted by the solar panels that the orientation device is designed to orient. On the other hand, for installations of low power the energy consumed by an active orientation device is no longer negligible compared to the quantity of energy converted by the solar panels that the orientation device is designed to orient and in particular is not negligible compared to the energy savings produced by the orientation device compared to a system with fixed solar panels. In such a context, passive orientation devices are undoubtedly beneficial.
Various passive orientation devices are known already.
In a first orientation device, two identical cylinders subjected to the same pressure are disposed on each side of a solar panel and at the same distance from the centre of rotation of that solar panel. They are filled with a fluid having a low boiling point. The device further provides screens judiciously dispose so that if the sun's rays are not perpendicular to the surface of the solar panel, most of the radiation reaches one of the two cylinders, which causes the fluid therein to boil and a transfer of fluid from one cylinder to the other. It follows that the respective weights of the two cylinders are no longer the same, and that the solar panel therefore tilts. Although such an orientation device has advantages (notably an improvement in the performance of the solar panel comparable to that obtained with an active orientation device, a simple structure and thus a low cost), it has some drawbacks that may be unacceptable:

- the orientation device is not resistant to external elements such as gusts of wind, because its equilibrium about the ideal position is precarious and because the forces that it employs are low compared to the forces produced by a gust of wind, for example;
- there exists a risk of a phenomenon of oscillation about the ideal position occurring: because of inertia, during a phase of modification of the orientation of the solar panel, the orientation device will overshoot the ideal position and then seek to correct this overshoot by an orientation in the opposite direction, but will again overshoot the ideal orientation; this leads to a phenomenon of oscillation about the ideal position.

There is also known from the document US 2005/284 467 a passive orientation device for orienting solar panels as a function of the position of the sun. In this orientation device, a liquid fills a chamber that is connected to a piston and cylinder actuator. The expansion of the liquid moves the piston rod of the actuator and consequently moves the solar panels. Thus in this orientation device the orientation of the solar panels is a function of the temperature of the liquid and not necessarily a function of the orientation of the sun's rays. In particular, during the first part of the day, the chamber is not exposed to the sun's rays and the temperature of the liquid is a function only of the temperature of the surrounding air. It follows that the sun's rays are not necessarily perpendicular to the solar panels during this first part of the day. Similarly, during the second part of the day, the chamber is progressively exposed to the sun's rays, and is consequently more exposed to the sun's rays at the end of the day than in the middle of the day. It follows that the sun's rays cannot have a constant angle of incidence relative to the solar panels during the second part of the day and that the sun's rays are therefore not perpendicular to the solar panels throughout this second part of the day. Moreover, the ambient temperature necessarily influences the orientation of the solar panels. Consequently, if under certain conditions the sun's rays are perpendicular to the solar panels, under those same conditions but with a different ambient temperature the sun's rays will not be perpendicular to the solar panels. Moreover, if the device is completely shaded from the sun in cloudy weather, it reverts to a position defined only by the ambient temperature, which position may be very far from the position occupied just before the clouds appear.
The object of the invention is to provide an orientation method and an orientation device enabling the problems referred to above to be solved and improving the orientation methods and the orientation devices known in the prior art. In particular, the invention proposes an orientation method and an orientation device enabling the accuracy of the orientation of the solar panels to be improved.
According to the invention, the method makes it possible to orient a solar panel device. It is characterized in that the solar panel device is oriented with respect to at least one axis, in a first direction and in a second direction, using energy from a first fluid reservoir or a second fluid reservoir, the energy being provided by solar radiation and the two reservoirs being independent. The solar panel device is oriented with respect to the axis, in the first direction or in the second direction, until a distributor valve prevents feeding of one of the actuator chambers by one of the chambers of a reservoir.
The solar panel device may be oriented, with respect to the axis, in the first direction, by pneumatically or hydraulically connecting a first chamber of the first reservoir to a first chamber of the actuator and the solar panel device may be oriented, with respect to the axis, in the second direction, by pneumatically or hydraulically connecting a second chamber of the second reservoir to a second chamber of the actuator.
A first distributor valve and a second distributor valve may be controlled, respectively, by the pressure of a fluid contained in a third chamber, notably in a third chamber included in the first reservoir, and by the pressure of a fluid contained in a fourth chamber, notably in a fourth chamber included in the second reservoir.
The solar panel device may be oriented, with respect to the axis, in the first direction or in the second direction, until the third and fourth chambers:

- are exposed minimally overall to the sun's rays, and/or
- are exposed identically to the sun's rays, or
- are not exposed to the sun's rays.

The device of the invention is for orientation of a solar panel device with respect to an axis. The orientation device comprises at least a first reservoir and a second reservoir independent of each other and hydraulic or pneumatic means for connecting a first chamber of the first reservoir and a second chamber of the second reservoir to a first actuator chamber and to a second actuator chamber, respectively, so as to be able to feed the first actuator chamber with fluid from the first chamber of the first reservoir and to be able to feed the second actuator chamber with fluid from the second chamber of the second reservoir. The orientation device comprises hydraulic or pneumatic means for hydraulically or pneumatically connecting the first chamber of the first reservoir and the second chamber of the second reservoir to the second actuator chamber and to the first actuator chamber, respectively, so as to be able to feed the first chamber of the first reservoir with fluid from the second actuator chamber and to be able to feed the second chamber of the second reservoir with fluid from the first actuator chamber.
The orientation device may comprise two single-acting type actuators.
The orientation device may comprise a double-acting type actuator comprising the first actuator chamber and the second actuator chamber.
The hydraulic or pneumatic connecting means may comprise a first distributor valve and a second distributor valve respectively controlled by the pressure of a fluid contained in a third chamber, notably in a third chamber included in the first reservoir, and by the pressure of a fluid contained in a fourth chamber, notably in a fourth chamber included in the second reservoir.
The orientation device may comprise screens such that when the projections of the sun's rays in a plane perpendicular to the axis are perpendicular to the solar panel device, the third and fourth chambers:

In another aspect, the device is for orienting a solar panel device about an axis and comprises at least first and second independent reservoirs and hydraulic or pneumatic connecting means for connecting a first chamber of the first reservoir and a second chamber of the second reservoir to a first actuator chamber and a second actuator chamber, respectively, so as to be able to feed the first actuator chamber with fluid from the first chamber of the first reservoir and to be able to feed the second actuator chamber with fluid from the second chamber of the second reservoir. The hydraulic or pneumatic connecting means comprise a first distributor valve and a second distributor valve respectively controlled by the pressure of a fluid contained in a third chamber, notably in a third chamber included in the first reservoir, and by the pressure of a fluid contained in a fourth chamber, notably in a fourth chamber included in the second reservoir.
The solar energy conversion system of the invention comprises an orientation device as defined above and a solar panel device.
The solar energy conversion system may comprise a first orientation device as defined above, a second orientation device as defined above and a solar panel device, the first and second orientation devices being adapted to orient the solar panel device with respect to two non-parallel axes and preferably to orient the solar panel device with respect to two orthogonal or substantially orthogonal axes.

The appended drawings represent by way of example a solar energy conversion system of one embodiment of the invention.

FIG. 1 is a mechanical diagram of a solar energy conversion system of one embodiment of the invention, the orientation device being represented in a situation of equilibrium.

FIG. 2 is a hydraulic or pneumatic diagram of the solar energy conversion system of this embodiment of the invention, the orientation device being represented in a situation of equilibrium.

FIG. 3 is a mechanical diagram of the solar energy conversion system of this embodiment of the invention, the orientation system being represented in a transient situation.

FIG. 4 is a hydraulic or pneumatic diagram of the solar energy conversion system of this embodiment of the invention, the orientation device being represented in a transient situation.

The theory of the invention is based on the use of the fluid expansion phenomenon and on the actions that the expansion of the fluid may produce in chambers of one or more actuators used to orient a solar panel with respect to one or more axes.
Generally speaking, the theory of the invention is to use solar energy to expand a fluid. This expansion generates mechanical actions for orienting the solar panel via one or more actuators.
The aim is therefore to use solar energy to generate pressure differences between a plurality of chambers so as to enable movement of at least one actuator piston rod and thus to move the solar panel.
The pressure difference is created when fluid trapped in a reservoir is heated by the sun. The fluid expands and therefore occupies a greater volume by pushing an actuator piston rod. Fluid enclosed in another reservoir is held at the same temperature and pressure conditions to prevent it exerting an antagonistic mechanical action. A pneumatic or hydraulic circuit can achieve this objective.
A solar energy conversion system 1 of a first embodiment of the invention, shown in FIGS. 1 to 4, mainly comprises a solar panel device 3 and a device 2 for orienting that solar panel device. The orientation devices of the passive type and enables the solar panel device to be oriented automatically so that the solar radiation 10 is at least substantially perpendicular to the surface of the solar panel device.
The solar panel device enables conversion of solar energy into another form of energy. It may comprise a plurality of solar energy conversion elements. The solar panel device may notably comprise one or more elements for conversion of solar energy into electrical energy and/or may comprise one or more elements for conversion of solar energy into thermal energy transported by a fluid.
The orientation device 2 mainly comprises a support 4 at the end of which the solar panel device is mounted so as to be mobile relative to an axis 5 and two single-acting piston-and- cylinder actuators 11, 12, mounted for example symmetrically with respect to the axis 5 with respect to which the solar panel device is articulated. First ends of the actuators are articulated to the solar panel device and the other ends of the actuators are articulated to the support or to a structure to which the support is fixed. Accordingly, deployment of the piston rod of the first actuator 11 leads to rotation of the solar panel device about the axis 5 in a first direction and retraction of the piston rod of the second actuator 12. Symmetrically, deployment of the piston rod of the second actuator 12 leads to rotation of the solar panel device about the axis 5 in a second direction and retraction of the piston rod of the first actuator 11. It is the actions of these actuators that enable the solar panel device to be oriented optimally with respect to the solar radiation, i.e. to be oriented so that the sun's rays are as perpendicular as possible to the surface of the solar panel device.
The orientation device 2 also comprises reservoirs 6, 8 and hydraulic or pneumatic means for connecting the reservoirs to the actuators. Accordingly, the actuators are fed with fluid under pressure by the reservoirs 6, 8 via the hydraulic or pneumatic connecting means and the mechanical energy applied by the actuators to the solar panel device comes from the reservoirs 6, 8.
Furthermore, the orientation device 2 comprises screens 7 and 9. The reservoirs and the screens are kinematically connected to the solar panel device. The reservoirs and the screens are preferably (directly or indirectly) fastened to the solar panel device. The screens may consist of simple pieces of sheet metal or of metal or synthetic material structural sections.
The screens are arranged so that the reservoirs 6, 8 are protected from the sun's rays when the sun's rays are in a required direction relative to the surface of the solar panel device, i.e. notably when the projections of the sun's rays in a plane perpendicular to the axis 5 are perpendicular or substantially perpendicular to the surface of the solar panel device. Alternatively, the screens are arranged so that the reservoirs are at their most protected from the sun's rays and/or protected in identical manner from the sun's rays when the sun's rays are in a required direction relative to the surface of the solar panel device, i.e. notably when the projections of the sun's rays in a plane perpendicular to the axis 5 are perpendicular or substantially perpendicular to the surface of the solar panel device. Moreover, the screens are arranged so that the reservoirs are not protected in the same manner from the sun's rays when the sun's rays are not in the required direction relative to the surface of the solar panel device, i.e. notably when the projections of the sun's rays in a plane perpendicular to the axis 5 are not perpendicular or substantially perpendicular to the surface of the solar panel device.
Consequently, when the reservoirs are not protected in the same manner from the sun's rays, one of the reservoirs is heated more than the other, for example the first reservoir 6 is heated more than the second reservoir 8, the consequence of which is an increase in the fluid pressure in a first chamber 17 of the first reservoir 6. This increase in pressure constitutes energy that will be used, as explained hereinafter, in one of the actuators for orienting the solar panel device so that the latter has an orientation such that the sun's rays are as perpendicular as possible to its surface.
As shown in FIGS. 2 and 4, the means for hydraulically or pneumatically connecting the reservoirs to the actuators comprise pipes 21, 22, 23, 24, 25 and 26 and distributor valves 13 and 14. The pipe 21 connects the first chamber 17 of the first reservoir 6 to the distributor valve 13, the pipe 23 connects the distributor valve 13 to the first chamber 15 of the actuator 11 and the pipe 25 connects the distributor valve 13 to the second chamber 18 of the second reservoir 8 via a check valve 27 allowing the fluid to flow only from the distributor valve to the second chamber of the second reservoir. Symmetrically, the pipe 22 connects the second chamber 18 of the second reservoir 8 to the distributor valve 14, the pipe 24 connects the distributor valve 14 to the second chamber 16 of the actuator 12 and the pipe 26 connects the distributor valve 14 to the first chamber 17 of the first reservoir 6 via a check valve 28 allowing the fluid to flow only from the distributor valve to the first chamber of the first reservoir.
The first distributor valve 13 is controlled by the fluid pressure in a third chamber 19 of the first reservoir 6 and is spring-loaded into a rest position. In the rest position, flow of the fluid between the first chamber 17 of the first reservoir 6 and the first chamber 15 of the actuator 11 is prevented and flow of the fluid between the first chamber 15 of the actuator 11 and the second chamber 18 of the second reservoir 8 is allowed. When the first reservoir 6 is subjected to the sun's rays, the fluid pressure in the third chamber 19 increases and, via a pipe 31, commands a change of position of the distributor valve 13, the latter going from its rest position to a second position in which flow of the fluid between the first chamber 17 of the first reservoir 6 and the first chamber 15 of the actuator 11 is allowed and flow of the fluid between the first chamber 15 of the actuator 11 and the second chamber 18 of the second reservoir 8 is prevented.
Symmetrically, the second distributor valve 14 is controlled by the fluid pressure in a fourth chamber 20 of the first reservoir 8 and is spring-loaded into a rest position. In the rest position, flow of the fluid between the second chamber 18 of the second reservoir 8 and the second chamber 16 of the actuator 12 is prevented and flow of the fluid between the second chamber 16 of the actuator 12 and the first chamber 17 of the first reservoir 6 is allowed. When the second reservoir 8 is subjected to the sun's rays, the fluid pressure in the fourth chamber 20 increases and, via a pipe 32, commands a change of position of the distributor valve 14, the latter going from its rest position to a second position, represented in FIG. 4, in which flow of the fluid between the second chamber 18 of the first reservoir 8 and the first chamber 15 of the actuator 11 is allowed and flow of the fluid between the first chamber 15 of the actuator 11 and the second chamber 18 of the second reservoir 8 is prevented.
An orientation method of one embodiment of the invention is described hereinafter. This embodiment of the orientation method corresponds to one embodiment of a method of operating a solar panel orientation device.
In these embodiments, the solar panel device is oriented with respect to the axis 5, in a first direction and in a second direction, using energy obtained from solar radiation from a first fluid reservoir or a second fluid reservoir, the two reservoirs being independent.
As explained above, when the fourth chamber 20 of the second reservoir 8 is subjected to the solar radiation (see FIG. 3) the fluid contained in this fourth chamber is heated and expands, which leads to an increase in pressure in the chamber 20 and movement of the distributor valve 14 to its second position shown in FIG. 4. This enables the fluid contained in the second chamber 18 of the second reservoir 8 to feed the second chamber 16 of the actuator 12, the fluid in the second chamber 18 being at a pressure higher than that of the second chamber 16 because, in the second chamber 18, the fluid is heated by the solar radiation and therefore under pressure. The piston rod of the actuator 12 is therefore deployed, the solar panel device rotates about the axis 5, and the piston rod of the actuator 11 is retracted into it. This retraction of the piston rod 11 is made possible by the compression of the fluid contained in the chamber 15 of the actuator 11 and, where applicable, by return of this fluid to the first chamber 18 of the second reservoir 8 via the distributor valve 13 and the check valve 27. This operation continues until the pressures in the chambers 18, 16 and 15 equalize or until the distributor valve returns to its rest position.
Symmetrically, when the third chamber 19 of the first reservoir 6 is subjected to the solar radiation, the fluid contained in this third chamber is heated and expands, which leads to an increase in pressure in the chamber 19 and movement of the distributor valve 13 to its second position. This enables the fluid contained in the first chamber 17 of the first reservoir 6 to feed the first chamber 15 of the actuator 11, the fluid in the first chamber 17 being at a pressure higher than that of the first chamber 15 because, in the first chamber 17, the fluid is heated by the solar radiation and is therefore under pressure. Thus the piston rod of the actuator 11 is deployed, the solar panel device rotates about the axis 5 and the piston rod of the actuator 12 is retracted into it. This retraction of the piston rod of the actuator 12 is made possible by the compression of the fluid contained in the chamber 16 of the actuator 12 and, where applicable, by return of this fluid to the first chamber 17 of the first reservoir 6 via the distributor valve 14 and the check valve 28. This operation continues until the pressures in the chambers 17, 16 and 15 equalize or until the distributor valve returns to its rest position.
In the embodiment described above, the fluid the expansion of which is used is a gas. There may nevertheless be imagined a device for orientation of a solar panel device operating in accordance with the same principle and in which the expansion of a liquid is used.
Finally, in the embodiment described, the chambers 19 and 20 are part of the reservoirs 6 and 8. These chambers may nevertheless be independent of the reservoirs, notably to solve thermal inertia problems. They are preferably exposed to the solar radiation in accordance with an exposure logic similar to the logic of exposure to the solar radiation of the first and second reservoirs.
In an embodiment that is not shown the single-acting type piston-and- cylinder actuators 11 and 12 are replaced by a single double-acting actuator of this type. The double-acting actuator used is preferably of the through-rod type (i.e. the piston rod of the actuator passes through the whole of the actuator so that the area of the piston of the actuator seen from each of the chambers is the same and so that the piston is immobile if the two chambers are subjected to the same pressure).
The articulation axis 5 of the solar panel device and the axes or centres about which the ends of the actuators 11 and 12 are articulated to the solar panel device are preferably contained or substantially contained in the same plane.
The screens may have reflecting surfaces; they may notably have a parabolic cross section and be disposed so that the focal axis of each screen is situated in or in the vicinity of each of the reservoirs. Thus the sun's rays reaching the internal surface of the screens are reflected toward the reservoirs.
The invention concerns a solar energy conversion device comprising an orientation device and a solar panel device. It concerns in particular a solar energy conversion device comprising a first orientation device and a second orientation device, the first and second orientation devices being adapted to orient the solar panel device with respect to two non-parallel axes, and preferably to orient the solar panel device with respect to two orthogonal or substantially orthogonal axes. A first axis may enable daily orientation while a second axis may enable seasonal orientation.
The orientation device of the invention enables the problems of the devices known in the prior art to be solved. In particular, it enables good retention of the solar panel device to be assured even in the event of wind. A prototype that has been constructed and enabling orientation of the solar panel device with a pressure of three bar resists winds of 70 km/h.
The responsiveness of the orientation device may be defined in terms of various construction parameters, notably the nature of the fluid used.
The orientation device enables a rapid return to an ideal position after a cloudy period or at the start of the day. For example, in the case of the prototype that has been constructed, 7 minutes are required to return to the ideal position after a cloudy period of 2 hours duration.
In contrast to the device described in the document US 2005/284 467, a cloudy period does not lead to modification of the orientation of the solar panel device.
In the present document the two reservoirs are referred to as independent. By “independent” is meant that the two reservoirs may be subjected to different pressures.

Claims

1. Method for orientation of a solar panel device (3), wherein the solar panel device is oriented with respect to at least one axis (5), in a first direction and in a second direction, using energy from a first fluid reservoir (6) or a second fluid reservoir (8), the energy being provided by solar radiation and the two reservoirs being independent, and wherein the solar panel device is oriented with respect to the axis (5), in the first direction or in the second direction, until a distributor valve (13, 14) prevents feeding of one of the actuator chambers by one of the chambers of a reservoir.

2. Orientation method according to claim 1, wherein the solar panel device is oriented, with respect to the axis (5), in the first direction, by pneumatically or hydraulically connecting a first chamber (17) of the first reservoir (6) to a first chamber (15) of the actuator (11) and wherein the solar panel device is oriented, with respect to the axis (5), in the second direction, by pneumatically or hydraulically connecting a second chamber (18) of the second reservoir (8) to a second chamber (16) of the actuator (12).

3. Orientation method according to claim 1, wherein a first distributor valve (13) and a second distributor valve (14) are controlled, respectively, by the pressure of a fluid contained in a third chamber (19), notably in a third chamber (19) included in the first reservoir (6), and by the pressure of a fluid contained in a fourth chamber (20), notably in a fourth chamber (20) included in the second reservoir (8).

4. Orientation method according to claim 3, wherein the solar panel device is oriented, with respect to the axis (5), in the first direction or in the second direction, until the third and fourth chambers:

are exposed minimally overall to the sun's rays, and/or

are exposed identically to the sun's rays, or

are not exposed to the sun's rays.

5. Device (2) for orientation of a solar panel device (3) with respect to an axis (5), the orientation device comprising at least a first reservoir (6) and a second reservoir (8) independent of each other and hydraulic or pneumatic means (13, 14, 21, 22, 23, 24) for connecting a first chamber (17) of the first reservoir and a second chamber (18) of the second reservoir to a first chamber (15) of an actuator (11) and to a second chamber (16) of an actuator (12), respectively, so as to be able to feed the first actuator chamber with fluid from the first chamber of the first reservoir and to be able to feed the second actuator chamber with fluid from the second chamber of the second reservoir, wherein it comprises hydraulic or pneumatic means (13, 14, 23, 24, 25, 26, 27, 28) for hydraulically or pneumatically connecting the first chamber (17) of the first reservoir (6) and the second chamber (18) of the second reservoir (8) to the second chamber (16) of the actuator (12) and to the first chamber (15) of the actuator (11), respectively, so as to be able to feed the first chamber (17) of the first reservoir (6) with fluid from the second chamber (16) of the actuator (12) and to be able to feed the second chamber (18) of the second reservoir (8) with fluid from the first chamber (15) of the actuator (11).

6. Orientation device according to claim 5, wherein it comprises two single-acting type actuators (11, 12).

7. Orientation device according to claim 5, wherein it comprises a double-acting type actuator comprising the first actuator chamber and the second actuator chamber.

8. Orientation device according to claim 5, wherein the hydraulic or pneumatic connecting means comprise a first distributor valve (13) and a second distributor valve (14) respectively controlled by the pressure of a fluid contained in a third chamber (19), notably in a third chamber (19) included in the first reservoir (6), and by the pressure of a fluid contained in a fourth chamber (20), notably in a fourth chamber (20) included in the second reservoir (8).

9. Orientation device according to claim 5, wherein it comprises screens (7, 9) such that when the projections of the sun's rays in a plane perpendicular to the axis (5) are perpendicular to the solar panel device, the third and fourth chambers:

are exposed minimally overall to the sun's rays, and/or

are exposed identically to the sun's rays, or

are not exposed to the sun's rays.

10. Solar energy conversion system (1) comprising an orientation device (2) according to claim 5 and a solar panel device (3).

11. Solar energy conversion system (1) comprising a first orientation device (2) according to claim 5, a second orientation device (2) according to claim 5 and a solar panel device (3), the first and second orientation devices being adapted to orient the solar panel device with respect to two non-parallel axes and preferably to orient the solar panel device with respect to two orthogonal or substantially orthogonal axes.