NL1040816B1

NL1040816B1 - Object tracking device.

Info

Publication number: NL1040816B1
Application number: NL1040816A
Authority: NL
Inventors: Vincentius Carolus Maria Peters Ir; Thijs Joseph Roethof Ir
Original assignee: Vincentius Carolus Maria Peters Ir; Thijs Joseph Roethof Ir
Priority date: 2014-05-23
Filing date: 2014-05-23
Publication date: 2016-03-15

Abstract

The invention relates to an object tracking system for tracking a movement of an object, said system comprising: - a movable element for tracking said movement of said object; - a pneumatic or hydraulic drive means for moving said movable element; - at least one container containing a substance that expands or contracts upon a temperature increase or decrease, respectively; - a means for heating said substance in said container for increasing the pressure in said container, said pressure being usable for driving said drive means, and - a control means for actively controlling said drive means by actively selectively controlling and/or using said pressure.

Description

OBJECT TRACKING DEVICE

The invention relates to an object tracking system for tracking a movement of an object.

Such tracking systems are known per se and are for example used for tracking the sun, also called a solar tracker or a heliostat. The system according to the invention is not limited to tracking the sun, but is suitable for tracking any object, such as, but not limited thereto, any celestial or satellite.

For example, US 2011/0100354 A1 describes a non-electrically-powered sun-tracking solar system having a shaft, a solar panel, two roll drivers, a roll transmitter, two pitch drivers and a pitch transmitter. The shaft has a lower shank and an upper shank pivotally mounted upon the lower shank. The solar panel is pivotally mounted on the upper shank. The two roll drivers are ecliptically and bilaterally attached to the solar panel. The roll transmitter pivotally connects the upper shank and the solar panel and communicates with the two roll drivers. The two pitch drivers are meridionally and bilaterally attached to the solar panel. The pitch transmitter pivotally connects the lower shank and the upper shank and communicates with the two pitch drivers. Uneven heating by sunlight activates the roll drivers to change pitch and roll of the solar panel with the roll transmitter and the pitch transmitter for improved efficiency.

It is an object of the invention to improve the apparatus described in US 2011/0100354 A1.

This object is achieved by a system according to the preamble comprising: - a movable element for tracking said movement of said object; - a pneumatic or hydraulic drive means for moving said movable element; - at least one container containing a substance that expands or contracts upon a temperature increase or decrease, respectively; - a means for heating said substance in said container for increasing the pressure in said container, said pressure being usable for driving said drive means, and - a control means for actively controlling said drive means by actively selectively controlling and/or using said pressure.

In accordance with the invention said control means are used for actively controlling said drive means by actively selectively controlling and/or using said pressure. Actively selectively controlling said pressure may be performed by actively selectively heating said substance, thereby selectively increasing and thus controlling said pressure. Selectively using said pressure may comprise uncontrolled heating of said substance, and selectively using said pressure for driving said drive means. A combination of controlled heating and controlled use of pressure may also be applied.

The apparatus of US 2011/0100354 A1 has uncontrolled heating. As described in US 2011/0100354 Al, when the two roll drivers are unevenly heated by sunlight, the roll drivers adjust roll via the roll transmitter and the pitch drivers adjust pitch via the pitch transmitter to automatically and efficiently orientate the solar panel relative to the sun. The system of US 2011/0100354 A1 is thus controlled directly and only by the sun, and is not actively controlled by a control means. As a result thereof, the system of US 2011/0100354 A1 is only able to track the sun and thus not suitable for tracking other objects and/or as a heliostat.

It is noted that by actively controlling said drive means it is meant that only upon an nonpassive action said drive means are activated for moving the element. The apparatus of US 2011/0100354 Alis passively controlled and responds only passively to sunlight. Such actively controlling in accordance with the invention may be performed in various ways, as will be described with respect to the dependent claims and figures.

It is further noted that the control means for actively controlling said drive means by actively selectively controlling and/or using said pressure according to the invention may also be seen as an autonomous control means for autonomously, actively controlling said drive means by autonomously, actively selectively controlling and/or using said pressure. In particular, the control means control the drive means autonomously and in particular separately and/or independent from solar heating and/or ambient heating. This is in contrast to the system of US 2011/0100354 A1 which is controlled by sunlight.

The substance is the working fluid of the system.

In an embodiment of the system according to the invention said substance is a dual phase substance being near its boiling point in both a liquid phase and a gas phase.

An advantage of such a dual phase substance it that is expands or contracts relatively large at a temperature change near its boiling point, such that said pressure increase may be relatively large at an increase in temperature.

In particular, said substance is chosen such that it is near its boiling point in the normal operation conditions of the system according to the invention, such that said substance is said dual phase substance being in both a liquid phase and a gas phase.

Alternatively or in addition, a substance may be pressurized to such a pressure that it is near its boiling point at the normal operation conditions of the system according to the invention, such that said substance is said dual phase substance being in both a liquid phase and a gas phase.

Said normal operation conditions may include the maximum temperature differences that are practically obtained with the system, which temperature may for example lye between -20°C and +100°C.

Said substance may for example be a so called refrigerant.

The substance may be chosen from the group comprising alkenes, carbon dioxide, ammonia, propene, halons, chlorofluorocarbons (CFC) and hydrochlorofluorocarbons (HCFC) and mixtures thereof.

In another embodiment of the system according to the invention said system comprises a guiding means for guiding sunlight in the direction of said container.

Via said guiding means sunlight may be guided to said container for controlling the heating of the substance in said container. Said container is hereby for example positioned such that it is not directly exposed to sunlight, but only exposed to the guided sunlight. As such, the amount of heating of the substance in said container may be actively controlled by the guiding of the sunlight and is independent of direct sunlight.

Guiding said sunlight in the direction of said container may comprise guiding sunlight to a particular container and not guiding sunlight to another container, such that a pressure difference between multiple containers may be created.

Alternatively or additionally guiding said sunlight in the direction of said container may comprise guiding sunlight to a particular part of said container and not guiding sunlight to another part of said container, such that a pressure difference between the parts of the container may be created.

Said guiding means may for example comprise a reflecting means for reflecting the sunlight and/or a lens for converging or diverging the sunlight.

In another embodiment of the system according to the invention said system comprises a lighting means for artificially lighting said container.

Said lighting means may be provided alternatively or additionally to said guiding means.

For example, said lighting means may be used in addition to the guiding means when the sunlight is not strong enough to provide sufficient heating of the substance, for example in cloudy days or at or near sunrise or sunset.

For example, said lighting means may be used alternatively to the guiding means to provide a system that is independent of sunlight and/or may be better controlled as the characteristics of the artificial light can be fully known.

In yet another embodiment of the system according to the invention said system comprises at least a second container, wherein the containers are arranged or located such that the substance of one container is heated more than the substance of the other container.

As a result of said uneven heating of the two or more containers a pressure difference between the two or more containers may be created, which pressure difference may be used for controlling the drive means.

Said uneven heating may be provided in various ways.

For example, said uneven heating may be created by having a different sunlight and/or artificial light exposure of the two or more containers. This may for example be obtained by guiding or directing a different amount of sun- or artificial light to one container than to another container. Alternatively or additionally this may be obtained by locating one container such that it is exposed to direct (sun)light and by locating the other container such that it is not or less exposed to (sun)light, for example in the shade.

For example, said uneven heating may be created by having a different sunlight and/or artificial light absorption of the two or more containers. For example this may be obtained by using different colors or reflectance for the two or more containers.

For example, said uneven heating may be created by thermally isolating one container and not or less thermally isolating the other container.

Said uneven heating may be provided by any combination of the above described examples and is also not limited to the described examples.

In yet another embodiment of the system according to the invention said system comprises at least a second container, wherein the containers each contain a different substance.

Said different substances may have different characteristics, such that a pressure difference between the containers may be provided even at equal heating thereof. Said different substances may be a said dual phase substance, in particular a said refrigerant, as described above, or a different type of substance. A combination of containers containing different substances and uneven heating may also be applied.

Said pneumatic or hydraulic drive means may be a translational or rotational drive means.

In yet another embodiment of the system according to the invention the drive means comprise at least one cylinder comprising a piston arranged movably therein.

By coupling the movable element to the piston and by moving the piston in the cylinder, the movable element may easily be moved. Said piston may perform a reciprocating movement in the cylinder thereby being able to move the movable element in two, opposite directions.

Optionally a plurality of cylinders comprising a piston arranged movably therein, for example three cylinders, may be provided, wherein each piston is coupled to the movable element at a different location, such that the movable element may be moved in any desired direction by moving a or more respective pistons.

The container may be provided separate from said cylinder. Alternatively, the or each cylinder may be the or each container. This embodiment provides a simple and/or compact system.

In yet another embodiment of the system according to the invention the system comprises a pressure storage means for storing said pressure increased in said container.

By storing the pressure said drive means may be controlled at a moment different from the moment when the pressure is created, by using said stored pressure.

Said pressure may for example be stored by moving a pressure storing element in a first direction, which pressure storing element may be moved in a second, opposite direction for releasing the stored pressure.

For example, said pressure storing element may comprise a piston with a weight, which piston is moved in the first direction when the pressure of the substance acting on a first side of the piston is larger than the pressure of the weight acting on a second, opposite side of the piston, and which piston is moved in the second direction when the pressure of the substance acting on the first side of the piston is smaller than the pressure of the weight acting on the second side of the piston.

For example, said pressure storing element may comprise a piston with a (compression) spring, which piston is moved in the first direction when the pressure of the substance acting on a first side of the piston is larger than the pressure of the spring acting on a second, opposite side of the piston, and which piston is moved in the second direction when the pressure of the substance acting on the first side of the piston is smaller than the pressure of the spring acting on the second side of the piston.

For example, said pressure storing element may comprise a piston that separates the container in two chambers, wherein said substance is contained in one chamber of the container and wherein a fluid is contained in the other chamber of the container, and wherein the piston is moved in the first direction when the pressure of the substance acting on a first side of the piston is larger than the pressure of the fluid acting on a second, opposite side of the piston, and which piston is moved in the second direction when the pressure of the substance acting on the first side of the piston is smaller than the pressure of the fluid acting on the second side of the piston. Said fluid may be a gas or a liquid. For example, said gas may be air. As compression of the fluid by the piston requires more pressure at increased compression, this pressure storing element is a nonlinear pressure storing element.

The invention will be further elucidated with reference to figures shown in a drawing, in which:

Figures 1A - 1C are a schematic representation of three embodiments of the system according to the invention;

Figure 2 is a perspective view of a tracker of the system according to the invention;

Figures 3 - 14 are a schematic representation of twelve embodiments of a control means that can be applied in a system according to the invention.

In the figures similar elements are denoted by similar reference numerals, increased by 100.

Figures 1A - 1C show three different embodiments of a solar tracking system 1, 101, 201, respectively, for tracking a movement of the sun 2, 102, 202, respectively.

Figure 1A shows a solar tracking system 1 in which a plurality of solar trackers 3, in this case four solar trackers 3, are directed to the sun 2. The solar trackers 3 each comprise a movable element 4 for tracking the movement of the sun 2. The movable elements 4 each comprise a relatively flat sunlight receiving surface, which surfaces are directed substantially perpendicular to the incoming sunlight. As the sun moves during a day, the movable elements 4 track the movement thereof, such that the flat sunlight receiving surfaces are continuously oriented substantially perpendicular to the incoming sunlight. The movable elements 4 may for example each comprise a solar cell, which perform best if the solar cell is directed perpendicular toward the incoming sunlight. By tracking the sun 2, the solar cells thus generate a relatively large amount of energy from the sunlight in comparison to a solar cell that is fixedly mounted. The movable elements 4 may be moved using a pneumatic or hydraulic drive means, which will be explained in further detail with respect to the figures 2-14. The system of figure 1A is known as a so called solar tracking system.

Figure IB shows a heliostat system 101 in which a plurality of heliostats 103, in this case four heliostats 103, are directed to the sun 102. The heliostats 103 each comprise a movable element 104 for tracking the movement of the sun 102. The movable elements 104 each comprise a relatively flat sunlight receiving surface, which surfaces are reflecting surfaces that reflect the incoming sunlight in the direction of a sunlight receiving element 105. By focusing the sunlight of the various heliostats 103 on the sunlight receiving element 105 a concentrated solar power is received by the sunlight receiving element 105, which for example may be used for generating electricity. As the sun moves during a day, the movable elements 104 track the movement thereof, such that the reflecting surfaces are continuously oriented to the sun 102 and to the element 105. The movable elements 104 may be moved using a pneumatic or hydraulic drive means, which will be explained in further detail with respect to the figures 2-14.

Figure 1C shows a heliostat system 201, which is similar to the heliostat system 101 but comprises an additional element. For a description of the heliostat system 201 the reader is referred to the description of figure IB. In addition to the heliostat system 101 the heliostat system 201 comprises a guiding means 206 for guiding the sunlight in a certain direction to control the heliostats 203 and in particular the movement of the movable elements 204 thereof. The guiding means 206 comprise a first lens 207 which converges the incoming sunlight to a beam. Said converging sunlight is diverged by a second lens 208, which thereby creates a parallel light beam. This parallel light beam is reflected by a mirror 209 in the direction of the heliostats 204 in order to control them. The control of the heliostats 203 by use of the guided sunlight will be described in further detail with respect to the figures 3-14. The guiding means 206 may be used to control multiple heliostats 203.

It is noted that any type of lenses and mirrors may be applied. For example, said second lens may be a converging lens creating a converging beam, for example dependent on the position of said second lens. It is further noted that any number of lenses and/or mirrors may be used.

An advantage of the systems 1,101 and 201 is that the orientation and/or position of the movable elements 4, 104, 204 are controlled in an active manner that is autonomous of the incoming sunlight and/or the position of the sun.

It is noted that the invention is not limited to the exact configurations shown in figures 1A - 1C. For example, any number of solar trackers 3 or heliostats 103, 203 may be provided. For example, instead of the sun 2, 102, 202 any desired object may be tracked. The solar trackers 3 and heliostats 103, 203 may therefor more generally be referred to as trackers.

It is further noted that the trackers 3, 103, 203 are positioned at a fixed location, wherein only the movable elements 4, 104, 204 thereof track the movement of the sun 2, 102, 202.

Figure 2 shows a tracker 303 in more detail. The tracker 3 comprises three cylinders 310 — 312, each comprising a movable piston 313-315 attached to a piston rod 316 - 318, which pistons 313-315 are arranged in a reciprocating movable manner in the cylinders 310-312. Each piston 313 - 315 is coupled to the movable element 304 at a different location 319-321 via said piston rods 316-318, such that the movable element 304 may be moved in any desired direction by moving a or more suitable pistons 313 - 315. By means of said pistons 313-315 said movable element 304 may be positioned in any desired position or orientation with respect to the object the tracker 303 tracks.

It is noted that for clarity the cylinder 311 is drawn partly open, such that piston 314 is visible. It is noted that the pistons 313 and 315 of cylinders 310 and 312, respectively, are not visible in figure 2, but that it is clear that they are arranged in a similar manner in their respective cylinders 310, 312 as piston 314 in cylinder 311.

The cylinders are an example of a translational pneumatic or hydraulic drive means only and the invention is not limited thereto. Instead of cylinders any other suitable translational or rotational pneumatic or hydraulic drive means may be provided.

Figures 3-14 show various types of a control means for actively controlling said drive means by actively selectively controlling and/or using said pressure. For the sake of simplicity the various types are shown in isolation, but it is clear for the skilled person that the various shown types may optionally be combined in one system. Any combination of two or more types is possible.

Figure 3 is a simple and/or compact and/or integrated control means to control the drive means. In this embodiment the drive means comprise a cylinder 410 comprising a piston 413 with a piston rod 416 arranged movably therein. Said piston 413 divides the cylinder 410 in two chambers 422, 423, each comprising a substance. The substance is a so-called refrigerant that is both in the liquid and gas phase at normal operation conditions of the system. The gas phase is indicated by plus-signs and the liquid phase is indicated by relatively low density dots. By directing sunlight 402, or optionally an artificial light, to one chamber 422 of the two chambers 422, 423, or by directing more sunlight 402 to the one chamber 422 than to the other chamber 423, the substance in the one chamber 422 is heated more than the substance in the other chamber 423. As a result thereof, the pressure increase in the one chamber 422 is larger than the pressure increase in the other chamber 423. The force acting on one side of the piston 413 directed to the one chamber 422 is therefore larger than the force acting on the other side of the piston 413 directed to the other chamber 423, such that the piston 413 and thereby piston rod 416 is moved in the direction of the other chamber 423, in this example an upward movement. The piston rod 416 that is coupled to the movable element as described above (not shown), thereby moves the movable element. Said light 402 is directed to the one and/or the other chamber in an active, controlled manner, such that the movement of the piston 413 can be controlled in an active, autonomous manner.

Figure 4 is a second type of control means to control the drive means. In this embodiment the drive means comprise two cylinders 510, 511 each comprising a piston 513, 514 with a piston rod 516, 517 arranged movably therein. Said pistons 513, 514 divide the cylinders 510, 511 in two chambers 522, 523, and 524, 525, respectively, each chamber comprising a substance. The substances in the chambers 523, 525 are the so-called refrigerant as described with respect to figure 3. The substances in the chambers 522, 524 are hydraulic liquids, indicated by high density dots.

By directing sunlight 502, or optionally an artificial light, to one chamber 523 of the cylinder 510, or by directing more sunlight 502 to the one chamber 523 than to the other chamber 525 of the other cylinder 511, the substance in the one chamber 523 is heated more than the substance in the other chamber 525. As a result thereof, the pressure increase in the one chamber 523 is larger than the pressure increase in the other chamber 525. This pressure difference will result in the piston 513 being moved in the direction of the chamber 522 of the cylinder 510. The two cylinders 510, 511 are hydraulically coupled, such that by the movement of the piston 513 the hydraulic liquid of the other chamber 522 of the cylinder 510 is pressed into the one chamber 524 of the other cylinder 511. The hydraulic liquid pressed into the one chamber 524 of the other cylinder 511 will press the piston 514 in the direction of the other chamber 525 of the cylinder 511. The piston rod 516 is hereby moved downwards and the piston rod 517 is hereby moved upwards, which will move the movable element in a corresponding way. Said light 502 is directed to the one and/or the other chamber in an active, controlled manner, such that the movement of the pistons 513, 514 can be controlled in an active, autonomous manner.

It is noted that in the example of figure 4 the one chamber is defined as the chamber with relatively high pressure and the other chamber is defined as the chamber with relatively low pressure. This definition is maintained in the other examples.

The system of figure 5 is similar to the system of figure 4, but wherein three cylinders 610 - 612 are used. By directing sunlight 602, or optionally an artificial light, to one chamber 623 of the cylinder 610, or by directing more sunlight 602 to the one chamber 623 than to the other two chambers 625, 627 of the other cylinders 611,612, the substance in the one chamber 623 is heated more than the substance in the other chambers 625, 627. As a result thereof, the pressure increase in the one chamber 623 is larger than the pressure increase in the other chambers 625, 627. This pressure difference will result in the piston 613 being moved in the direction of the chamber 622 of the cylinder 610. The chamber 625 of the cylinder 611 receives more sunlight 602 than the chamber 627 of the cylinder 612, such that the pressure in the chamber 625 is higher than the pressure in the chamber 627. The three cylinders 610, 611,612 are all hydraulically coupled, such that by the movement of the piston 613 the hydraulic liquid of the other chamber 622 of the cylinder 610 is pressed out of the chamber 622, and into the one chamber 626 of the other cylinder 612 because of the lower pressure thereof with respect to the chamber 624 of the cylinder 611. This results in the piston 615 being moved in the direction of the chamber 627, while the piston 614 will maintain its position. It is clear for the skilled person how the hydraulic liquid will flow from one chamber to another based on the pressure differences and for simplicity, this will not be described here in further detail. For a further description of figure 5 the reader is referred to figure 4.

The system of figure 6 has a drive means similar to that of figure 3, but wherein separate containers 728, 729 are provided that are in fluid communication with the one chamber 722 and other chamber 723 respectively. The containers 728, 729 are filled with said refrigerant. In this example the container 728 connected to the one chamber 722 is heated more than the container 729 connected to the other chamber 723, such that the liquid phase of the refrigerant is pressed out of the container 728 in the one chamber 722, thereby pressing the piston 713 in the direction of the other chamber 723. For a further description of the system of figure 6 the reader is referred to the description of figure 3.

The system of figure 7 has a drive means similar to that of figure 6, but wherein a hydraulic liquid is also contained in the containers 828, 829 and the chambers 822, 823. The hydraulic liquid is chosen such that it does not mix with the refrigerant. In this example the hydraulic liquid is pressed into the one chamber 822, thereby moving the piston 813 in the direction of the other chamber 823. For a further description of the system of figure 7 the reader is referred to the description of figure 6.

The system of figure 8 has a drive means similar to that of figure 4, but wherein the position of the chambers 922, 923 and chambers 924, 925, respectively, are reversed in the vertical direction. The piston 913 is thus moved in an upward direction and the piston 914 is thus moved in a downward direction. This figure 8 makes clear, that the various locations of the various described chambers can be chosen as desired and are not limited to the disclosed embodiments. For a further description of the system of figure 8 the reader is referred to the description of figure 4.

The systems of figures 9-11 have two separate containers 1028, 1029, 1128,1129, 1228, 1229 respectively, that are heated with an even amount of sunlight 1002, 1102 (figures 9-10), or ambient heating 1150 (figure 11). However, the containers 1029, 1129, 1229 have a lower energy absorption or absorption rate, because the containers are respectively reflective to the light 1002, or isolated by isolating material 1130, 1230. This results in an increased pressure in the containers 1028, 1128, 1228. A two or three way controller 1031, 1131, 1231 is provided, which may be adjusted to connect the containers 1028, 1128, 1228 to the one chambers 1022, 1122, 1222, to the other chambers 1023, 1123, 1223, or to provide no connection. In the position of the controller 1031, 1131, 1231 as shown, the containers 1028, 1128, 1228 are connected to the one chambers 1022, 1122, 1222, such that a movement in accordance with figure 6 will take place. By adjusting the controllers 1031, 1131, 1231 an opposite movement, or no movement of the pistons may be provided. In the embodiment of figure 9 a reset valve 1032 is provided, which may be used to direct the refrigerant from the container 1029 to the container 1028 after the container 1028 is empty and/or the container 1029 is full.

The systems of figures 12-14 each have a pressure storing element, that can be moved in a first direction for storing pressure, and in a second, opposite direction for releasing the stored pressure.

In figure 12 said pressure storing element comprises a piston 1333, to which piston 1333 a piston rod 1334 with a weight 1335 is connected. The piston 1333 is arranged in the cylinder 1340, which divides the cylinder 1340 in a first chamber 1341 and a second chamber 1342. A separate container 1328 is provided containing said substance. By heating the substance in the container 1328, for example by ambient heating 1350, the pressure therein is increased, which pressure may be used for pressing the substance into either chamber 1322 or chamber 1323 of the cylinder 1310, using said controller 1331, or for pressing the substance into the first chamber 1341, using a valve 1332 that is provided for controlling the flow of substance into the first chamber 1341. By pressing the substance into a chamber 1322, 1323 of the cylinder 1310,the movable element is directly moved by the movement of the piston 1313. By pressing the substance into the first chamber 1341 the piston 133 is moved in an upward direction in the direction of the second chamber 1342. When the pressure in the first chamber 1341 decreases, the weight 1335 may press the piston 1333 downwards, thereby pressing the substance into the one chamber 1322 of the cylinder 1310. This way, after for example the ambient temperature and thereby ambient heating 1350 decreases, such that the pressure of the substance in the container 1328 decreases and may no longer be sufficient for directly moving the piston 1313 by pressing the substance in one of the chambers 1322, 1323, the pressure of the weight 1335 may be used to press the substance out of the first chamber 1341 into the one chamber 1522 for moving the piston 1313.

The system of figure 13 works similar to that of figure 12, but wherein in figure 13 the weight is replaced by air filling the second chamber 1442 of the cylinder 1440. The air provides a compressed air spring, that acts non-linear to pressure. This non-linear reaction provides the advantage, that first the piston 1433 is moved relatively easy and therefore at relatively low pressures, and then more force is required to move the piston 1433. This gives a broader working range. For a further description of figure 13 the reader is referred to figure 12.

The system of figure 14 works similar to that of figure 12, but wherein in figure 13 the weight is replaced by a compression spring 1536. For a further description of figure 14 the reader is referred to figure 12.

In the systems of figures 12-14 one cylinder and one pressure storage means are shown. It is clear that any number of cylinders and/or pressure storage means may be provided. For example, one set of containers 1328, 1428, 1528 with pressure storage means 1333-1335, 1433; 1436, 1533; 1537 may be provided for a plurality, for example three, cylinders.

It is noted that the invention is not limited to the shown embodiments but also extends to variants within the scope of the appended claims.

Claims

Claims

1. Object tracking system for tracking a movement of an object, said system comprising: - a movable element for tracking said movement of said object; - a pneumatic or hydraulic drive means for moving said movable element; - at least one container containing a substance that expands or contracts upon a temperature increase or decrease, respectively; - a means for heating said substance in said container for increasing the pressure in said container, said pressure being usable for driving said drive means, and - a control means for actively controlling said drive means by actively selectively controlling and/or using said pressure.
2. Object tracking system according to claim 1, wherein said substance is a dual phase substance being near its boiling point in both a liquid phase and a gas phase.
3. Object tracking system according to claim 1 or 2, comprising a guiding means for guiding sunlight in the direction of said container.
4. Object tracking system according any preceding claims, comprising a lighting means for artificially lighting said container.
5. Object tracking system according to any of the preceding claims, comprising at least a second container, wherein the containers are arranged or located such that the substance of one container is heated more than the substance of the other container.
6. Object tracking system according to any of the preceding claims, comprising at least a second container, wherein the containers each contain a different substance.
7. Object tracking system according to any of the preceding claims, wherein the pneumatic or hydraulic drive means are a translational or rotational drive means.
8. Object tracking system according to any of the preceding claims, wherein the drive means comprise at least one cylinder comprising a piston arranged movably therein.
9. Object tracking system according to claim 8, wherein the or each cylinder is the or each container.
10. Object tracking system according to any of the preceding claims, comprising a pressure storage means for storing said pressure increased in said container.