WO2012064189A2

WO2012064189A2 - Solar energy system

Info

Publication number: WO2012064189A2
Application number: PCT/NL2011/050768
Authority: WO
Inventors: Jan Van Kranendonk
Original assignee: Sunuru Holdings B.V
Priority date: 2010-11-10
Filing date: 2011-11-10
Publication date: 2012-05-18
Also published as: NL2006117C2; WO2012064189A3

Abstract

The present invention relates to a solar energy system, comprising: a plurality of solar units, suspension means for suspending the plurality of solar units, said suspension means comprising a first net and a second net oriented parallel in a plane, a distance existing there between, wherein at least two drive means are arranged to the suspension means such that the first and second net are moveable relative to each other in the plane by the drive means, rotation limiting means configured to limit a rotation of one or more solar units with respect to the suspension means, and wherein every solar unit is arranged to both the first and second net such that the orientation of the solar units is adjustable via the drive means driving the suspension means.

Description

SOLAR ENERGY SYSTEM

The present invention relates to a solar energy system, and more specifically a solar energy system

comprising a plurality of solar units.

The invention is further related to a method for adjusting the plurality of solar units within the proposed solar energy system.

To be able to reduce the cost of solar energy systems, it is of vital importance to keep the weight low while still maintaining structural integrity. Also, a solar system that can follow the sun's movement should be able to aim itself toward the sun. For solar energy systems that are capable of orientating the solar cells towards the sun, it is common practice to have independent electric motors for every solar unit or every panel of photovoltaic elements. Such systems are heavy, and the large amount of electric motors requires maintenance and possibly replacement of motors that have failed. Besides this, the large amount of electric motors required makes the system more expensive.

An object of the present invention is to provide a solar energy system with a plurality of solar units, that is improved relative to the prior art and wherein at least one of the above stated problems is obviated.

Said object is achieved with the solar energy system according to the present invention, comprising:

- a plurality of solar units;

- suspension means for suspending the plurality of solar units, said suspension means comprising a first net and a second net oriented parallel in a plane, a distance existing therebetween;

- wherein at least two drive means are arranged to the suspension means such that the first and second net are moveable relative to each other in the plane by the drive means ;

- rotation limiting means configured to limit a rotation of one or more solar units with respect to the suspension means; and

- wherein every solar unit is arranged to both the first and second net such that the orientation of the solar units is adjustable via the drive means driving the

suspension means.

The solar system proposed uses a structure that is build out of nets. By using the principle of tension, a very strong, lightweight structure is possible, that is easily produced on a large scale. Also, by moving the nets relative to each other, solar units that are connected to the nets can be aimed at the sun all at once. This structure is completely modular and requires only two drives.

Moreover, the net structure provides a solar energy system that can be easily transported to remote locations, since it requires only limited space in collapsed state, and furthermore comprises mainly lightweight

components. For example, (metal) wires of a relatively thin cross sectional area are able to withstand the high tensile forces required for pre-tensioning the net structure. A profile beam structure - as applied in conventional solar energy system for supporting solar panels - that spans the same distance would be significantly heavier.

According to a preferred embodiment, the solar energy system comprises only two drive means, as this suffices for all movements required for the solar units to follow the path of the sun during the day and for each successive day over the year.

According to a further preferred embodiment: - the solar unit is attached to the first net with a first attachment point;

- the solar unit is attached to the second net with a second attachment point;

- wherein said two attachment points define a first rotation axis; and

- wherein the rotation limiting means are configured to limit the rotation of the one or more solar units with respect to the suspension means around said first rotation axis.

According to a further preferred embodiment, the rotation limiting means comprise at least one further attachment point attaching the first net and/or second net to the solar unit, said at least one further attachment point defining an imaginary plane with the first and second attachment points, and preventing the rotation of the one or more solar units with respect to the suspension means around the first rotation axis.

The rotation limiting means are comprising that at least one of the plurality of solar units is attached to the first and second net of the suspension means with a total of at least three attachment points, said three attachment points together defining an imaginary plane and thereby preventing the rotation of the one or more solar units with respect to the suspension means around the first rotation axis .

If both first and second net would each only comprise a single attachment point with the solar unit, a rotation axis around which the solar unit could rotate would be defined through these two points. The at least one further attachment point provides a moment arm that allows the moment of force that would rotate the solar unit to be compensated with. This torque compensation is achieved by the net structure counteracting any moment force.

Because the three attachment points together define an imaginary plane, an in-line placement of said points is prevented. This ensures that the third attachment point provides a moment arm that allows the moment of force that would rotate the solar unit to be compensated with.

According to a further preferred embodiment, the at least one further attachment point is attached

substantially close to a corner of the solar unit.

Attachment near a corner allows the moment arm that is configured for counteracting the moment of force that would - if not compensated - rotate the solar unit, to be

maximi zed .

According to an alternative embodiment, the rotation limiting means comprise a rigid fixing member attached to both the suspension means and one or more the solar units. Although net structures are preferred because they provide the additional benefit of a foldable and therefore easily transportable solar energy system, one or more rigid fixing members could also function as rotation limiting means for preventing rotation between a solar unit and the suspension means.

According to a further preferred embodiment the first net is an upper net, and the second net is a lower net .

According to a further preferred embodiment the upper and lower net are arranged in a substantially lying plane. Upper and lower nets arranged in a substantially lying plane are beneficial for providing a plurality of solar units over a relatively large area. Furthermore, the solar units can be placed at a limited height above the ground to allow for convenient maintenance of the solar energy system.

According to a further preferred embodiment the at least two drive means are arranged in one single corner of the suspension means. In this case any required maintenance is limited to one specific location.

According to a further preferred embodiment the at least two drive means are arranged in a single housing. In this case, they can be regarded as one drive unit that is configured to drive the nets in two different directions.

According to a further preferred embodiment,

- the upper and lower net are substantially identical and each net comprises a plurality of rows, each row comprising an array of rhombuses;

- each rhombus comprises two rhombus-corners substantially oriented in the longitudinal direction of the row, and two rhombus-corners substantially transverse to the longitudinal direction of the row; and

- the solar units are arranged to the rhombus- corners that are substantially transverse to the

longitudinal direction of the row.

The solar units being arranged to the rhombus- corners of the rhombuses that are substantially transverse to the direction of the row, while the other corners of the rhombuses are substantially oriented in the direction of the row, allow the solar units to be moved independently in the X- and Y-direction, and every combination thereof. The corners of the rhombuses that are substantially oriented in the direction of the row is a node of the net that functions as a pivot point for orientating the solar units suspended by the net structure.

Rhombuses have the additional advantage that both attachment points are attached substantially close to a corner of the solar unit. The relatively far distance between both attachment points define a relatively large moment arm therebetween, resulting in a construction with increased stability.

According to a further preferred embodiment, the upper and lower net are quadrangular, and the at least two drive means are arranged to adjacent corner pairs of the upper and lower net. The quadrangular form, that is more preferably a rectangle or rhombus, significantly simplifies the solar energy system because it allows the X- and Y- direction to be driven independently.

According to a further preferred embodiment, rhombus-corners that are substantially oriented in the longitudinal direction of the rows of rhombuses are

connected by wires, thereby forming a web structure in the plane of the net. These wires connect the corners of the rhombuses that are substantially oriented in the direction of the row, i.e. the nodes of the net that function as a pivot point for orientating the solar units suspended by the net structure.

This connection on the one hand improves the coupling between all solar units suspended between the upper and lower net, providing an improved simultaneous

ad ustability of the plurality of solar units. On the other hand, the wires distribute the pre-tensioning forces applied to the net structure, allowing for an increased pre- tensioning, which reduces sagging of the net structure under it's own weight. Less sagging is beneficial, since it reduces orientation differences between solar units

positioned in the center of the net structure, and solar units positioned near the edges thereof.

According to a further preferred embodiment, the drive means comprise or are driveably connected to a rigid spacing element to which both the upper and lower net are arranged, and the corner of the net opposite the corner of the net where the driveable rigid spacing element is arranged comprises a further rigid spacing element that is pivotably arranged at a pivot point substantially halfway between the upper and lower net attachment points.

With this configuration, only one drive is required. The rigid spacing element in the opposite corner pivots around it's pivot point, when the driven corner is driven by the drive means. The pivot point of both rigid spacing elements being located substantially halfway between the upper and lower net attachment points allows the upper and lower net to remain parallel.

According to a further preferred embodiment, - the drivable rigid spacing element and the pivotably arranged rigid spacing element in the opposite corner are oriented substantially parallel, such that the rigid spacing elements arranged between the corners of the upper and lower net, together with the upper and lower net define a parallelogram-shape.

It is advantageous if the nets move parallel and the distance between the points where the solar units are arranged to the upper and lower net remain unchanged. This allows a uniform ad ustability of all solar units suspended between the upper and lower net.

According to a further preferred embodiment, the solar energy system further comprises tensioning members arranged between support members forming the foundation of the solar energy system, and the pivot points of the rigid spacing elements, said pivot points being located

substantially halfway between the upper and lower net attachment points. By the tensioning members pre-tensioning the rigid spacing elements in their respective pivot points

substantially halfway between the upper and lower net, the forces required for suspending the net structure with the solar units arranged therein is decoupled from the forces required for driving the upper and lower net relative to each other .

According to a further preferred embodiment, the edges of the upper and/or lower net are provided with a main suspender cable that is suspended in a substantially

parabolic shape between the net corners. This main suspender cable provides a substantially homogeneous force

distribution over the net, similar to the principle of a suspension bridge.

The invention is further directed to a method for adjusting the plurality of solar units within a solar energy system as described above, the method comprising the step of driving the drive means arranged to the suspension means, thereby moving the first and second net of the suspension means relative to each other in their plane, and thereby adjusting the orientation of the solar units arranged between the first and the second net.

According to a further preferred embodiment, the solar energy system further comprises control means

configured for adjusting the plurality of solar units according to the method described above.

In the following description preferred embodiments of the present invention are further elucidated with

reference to the drawing, in which:

Figure 1 is a perspective view of a solar energy system according to the present invention;

Figure 2 is a top view of the nets of the solar energy system shown in figure 1; Figure 3 is a detailed perspective view of a corner area of the solar energy system shown in figure 1;

Figure 4A is a side view of the drive means in a first state; and

Figure 4B is a side view of the drive means of figure 4A in a second state;

Figure 5 is a simplified 3-dimensional view without perspective of the nets and drive means of the solar energy system shown in figure 1;

Figure 6 is a side view of the solar energy system shown in figure 1, wherein the solar units are adjusted into a first orientation by moving the nets relative to each other in Y-direction, the solar units being substantially oriented upwards;

Figure 7 is a top view of the nets of the solar energy system shown in figure 1, with the nets and solar units according to the first orientation shown in figure 6;

Figure 8 is a front view of the solar units when the solar units are oriented in the first orientation shown in figures 6 and 7;

Figure 9 is a side view of the solar energy system shown in figure 1, wherein the solar units are adjusted into a second orientation by moving the nets relative to each other in Y-direction, the solar units being substantially oriented straight ahead;

Figure 10 is a top view of the nets of the solar energy system shown in figure 1, with the nets and solar units according to the second orientation shown in figure 9;

Figure 11 is a front view of the solar units when they are oriented as shown in figures 9 and 10;

Figure 12 is a side view of the solar energy system shown in figure 1, wherein the solar units are adjusted by moving the nets relative to each other in X- direction;

Figure 13 is a top view of the nets of the solar energy system shown in figure 1, with the nets and solar units according to the orientation shown in figure 12;

Figure 14 is a front view of the solar units when they are oriented according to figures 12 and 13;

Figure 15 is a detailed top view of a solar unit wherein the upper and lower net are moved a distance ΔΧ relative to each other.

Figure 16 is a detailed top view of the solar unit shown in Figure 15, wherein the upper and lower net are moved a distance ΔΧ and ΔΥ relative to each other.

Figure 17 is a perspective view of a single solar unit according to the orientation shown in figures 12-14;

Figure 18 is a perspective view of a solar unit of the solar energy system wherein sunlight is reflected into a focal point;

Figure 19 is a cross sectional view of the solar unit shown in figure 18;

Figures 20-24 show alternative ways of connecting the solar units to the upper and lower net.

The solar energy system 1 shown in figure 1 comprises a plurality of solar units 2 suspended by

suspension means 4, said suspension means comprising an upper net 6 and a lower net 8. The solar units 2 are

attached to both the upper net 6 and lower net 8.

The upper and lower net 6, 8 are arranged with their respective corners 20, 22 to rigid spacing elements 26, 28. In the embodiment shown in figure 1, the rigid spacing elements 26 are driveable via drive means 10, whereas the opposite rigid spacing elements 28 is pivotably arranged to the tensioning member 30. The solar units 2 are arranged to both the upper net 6 and lower net 8, and will undergo an angular movement when the upper and lower net 6, 8 are moved relative to each other in their the plane, i.e. their in-plane direction.

The structure of the inner wires of the nets 6, 8 is such that any solar unit 2 arranged between the nets is able to move freely without getting into contact with itself, other solar units 2, or the nets 6, 8.

By moving the nets with respect to each other, it is possible to "aim" the solar units 2 hanging in the nets 6, 8. This way, all solar units 2 can be pointed

continuously towards the moving sun. The nets 6, 8 can be sized to any scale or amount of solar units 2 arranged.

The side-wires forming the edges of the nets 6, 8 are a suspension cable 38 suspended in a substantially parabolic shape, to obtain a homogeneous force distribution across the centre-part of the nets 6, 8, similar like the principle of a suspension bridge (figure 2) . This enables to hang the nets 6, 8 with the least amount of deflection.

The centre-part of the nets is repetitive in structure. The wires that connect to a solar unit 2 converge and diverge again towards the next solar unit 2, thereby forming a row 12 comprising an array of rhombuses 14. Every solar unit 2 is arranged to both upper and lower net 6, 8 in a diamond-shaped / rhomboidal fashion.

Each diamond / rhombus comprises two rhombus- corners 16 substantially oriented in the direction of the row 12, and two rhombus-corners 18 substantially transverse to the direction of the row 12. The rhombus-corners 18 form the attachment points for the solar units 2.

The rhombus-corners 16 are connected by wires 24, thereby forming a web structure in the plane of the net 6, 8. Said web structure couples different rows 12. It furthermore allows a greater pre-tensioning to be applied to the net structure, thereby reducing sagging of the net structure .

In figure 2 each of the four corners of a solar unit 2 is arranged to either the upper net 6, or the lower net 8. The rhombus-corners 16 are connected by wires 24, thereby forming a web structure in the plane of the net 6, 8. The rhombus-corners 16 allow the solar units 2 to be orientated by moving the upper and lower net 6, 8

independently in X- or Y-direction. This relative movement of the upper and lower net 6, 8 allows the plurality of solar units 2 to be simultaneously adjusted into a desired orientation .

Figures 4A and 4B show the drive means 10 that are located at the corners 20, 22 of the upper and lower net 6, 8, and it consists of an arched threaded rod 54 extending between the corner 20 of the upper net 6 and the corner 22 of the lower net 8. A straight bar provides a rigid spacing element 26 between the corners 20, 22, and is constructed in such way that the connections points of the corners 20, 22 can rotate in the plane of the drive means 10. Figure 4B shows a state wherein the drive means are rotated relative to the state shown in figure 4A. When two of the four corners 20, 22 of the nets 6, 8 are connected to a drive 10, it is possible to steer the nets 6, 8 in every possible direction with respect to each other.

Halfway the rigid spacing element 26 there is provided a triangular member 56 that extends around the threaded rod 54. A tensioning member 30 is arranged between the triangular member 56 and a support member 36 that forms the foundation of the solar energy system. The tensioning members 30 pre-tension the suspended net structure in order to reduce sagging thereof to a minimum. An electric motor 50 is driveably connected to the threaded rod 54 through a gear 52 that is also threaded on the inside. When the motor 50 rotates, the threaded rod 54 is pushed into a circular motion around the center pivot 32 of the bar-like rigid spacing element 26.

The arrangement connecting the pivot point 32 of the rigid spacing element 26 via the triangular member 56 via the tensioning member 30 to the support member 36 decouples the drive mechanism from the pre-tensioning forces. The triangular member 56 moves round the threaded arched rod 54, and the drive means 10 actuate the rigid spacing element 26 around the pivot point 26 when moving the upper and lower net 6, 8 relative to each other. The forces used to pull the nets 6, 8 into tension are not carried by the electric motor 50, but instead are carried by the connection to the foundations 36 of the system.

Figure 5 is a simplified 3-dimensional view without perspective of the nets 6, 8 and drive means 10 of the solar energy system 1 of figure 1. The embodiment shown in both figures 1 and 5 comprises two drive means 10 that are arranged to adjacent corner pairs 20, 22 of the upper and lower net 6, 8.

The drivable rigid spacing element 12 and the pivotably arranged rigid spacing element 28 in the opposite corner are preferably oriented parallel, such that the rigid spacing elements 12, 14 arranged between the corners 20, 22 of the upper and lower net 6, 8, together with the upper and lower net 6, 8 define a parallelogram-shape. A

parallelogram-shape has the significant benefit that the upper and lower net 6, 8 remain parallel, which allows a uniform ad ustability of all solar units 2 suspended by the net structure. Although not required, a quadrangular form, that is more preferably a rectangle or rhombus, and even more preferably a square as shown in the embodiment of figure 1, has the advantage that it significantly simplifies the solar energy system because it allows the X- and Y-direction to be driven independently. This will be shown in detail using figures 6-16.

Figure 6 shows a side view the solar energy system 1, wherein the solar units 2 are adjusted into a first orientation by moving the upper and lower nets 6, 8 relative to each other in the Y-direction. In this first orientation, the solar units 2 are substantially oriented upwards, thereby pointed towards a sun position relatively high above the horizon. The situation of figure 6 is shown in top view in figure 7, and figure 8 is a front view of the solar units 2 when they are oriented in the first orientation shown in figures 6 and 7.

Figure 9 shows a side view the solar energy system 1, wherein the solar units 2 are adjusted into a second orientation wherein the solar units 2 are substantially oriented straight, thereby pointed towards a sun position relatively close to the horizon.

Adjusting the solar units from the first orientation shown in figures 6-8 into the second orientation subject of figures 9-11 is the result of moving the upper and lower nets 6, 8 relative to each other in the Y- direction only.

When the upper and lower nets 6, 8 are moved relative to each other in solely the X-direction, the solar units 2 are moved into a further orientation that is subject of figures 12-14. Figure 15 also shows a top view wherein the nets are moved a distance ΔΧ relative to each other. Combining the movements in both X- and Y- direction, it is possible to steer the solar units 2 in every desired orientation required for following the path of the sun during the day (from East to West) and for each successive day over the year (with different elevations over the seasons) . Figure 16 shows a combined relative

displacement over distances ΔΧ and ΔΥ.

Figure 17 shows a solar unit 2 in the same

orientation as shown in figures 12-14. The solar unit 2 is arranged to the upper and lower net 6, 8, with the

attachment points 18 formed by the rhombus-corners 18 substantially transverse to the direction of the row 12.

The solar units 2 hanging between the nets 6, 8 are aimed directly towards the sun at all times (see figures 8, 11 and 14) . In the shown embodiment, every solar unit 2 contains a parabolic mirror surface 58 that reflects and concentrates the sunlight 46 into a single focal point. In this focal point, a photovoltaic solar cell 48 is mounted that generates electricity (figure 18).

To cool the cell from the high intensity sunlight, a cooling fluid 60 is moving around passing the photovoltaic solar cell 48 (figure 19) . The cooling fluid 60 is

subsequently moved to the backside of the mirror 58, where it is cooled. The backside of the mirror 58 is always in the shade because the unit is aimed at the sun. Thus it is a relatively cold place. Also, it has the same size of the mirror 58, making the heat generating surface (mirror 58) and the heat dissipating surface (backside of mirror 58) equally large.

The cooling fluid 60 moves to the backside by natural convection. The cooling fluid 60 is heated in the focal point by the sunrays . Hot fluid weighs less and moves up. This causes a circulation where the cooled fluid from the backside moves to the focal point again. Because the temperatures in the system will be relatively low, the solar units 2 can be made out of plastic.

Although the net structure wherein the wires that connect to a solar unit 2 converge and diverge again towards the next solar unit 2, thereby forming a row 12 comprising an array of rhombuses 14 is a very beneficial embodiment, the skilled person will understand that solar units 2 can be connected to the upper net 6 and lower net 8 in a number of alternative ways, as shown in figures 20-24.

Figure 20 shows an alternative net structure that is based on the same principle as the rhombus-shaped net structure described above. This principle is also applicable to the further alternative net structures shown in figures 21-24, and will now be explained in more detail.

Both upper net 6 and lower net 8 each have at least one attachment point 7, 9 respectively, at which a solar unit 2 is attached to the net 6, 8. In the rhombus- shaped net structure shown in figure 3, these attachment points 7, 9 are the corners 18 of the rhombus that are transverse of the row.

If both the upper net 6 and lower net 8 would each only comprise a single attachment point 7, 9 with the solar unit 2, a rotation axis R around which the solar unit 2 could rotate would be defined through these two points 7, 9.

The simplified view of figure 5 shows a single simplified element 3 that is aligned with a rotation axis R around which this element 3 can rotate. If the simplified element 3 would be replaced with a solar unit 2, it would also be able to rotate around rotation axis R if rotation limiting means 13 would be absent.

The rotation limiting means 13 are based on the principle of adding at least one further attachment point that provides a moment arm that allows the moment of force that would rotate the solar unit to be compensated with. This torque compensation is achieved by the net structure counteracting any moment force, if desired via a rigid fixing member 62.

Said at least one further attachment point 7, 9, together with the first and second attachment points 7, 9 defines an imaginary plane. This plane defines a distance between two attachment points 7, 7 of the upper net 6, or two attachment points 9, 9 of the lower net 8 respectively. This distance is corresponding to the moment arm, and thereby prevents rotation of the one or more solar units 2 with respect to the suspension means 4 around the rotation axis R.

It is to be noted that the same argumentation is also applicable when defining a rotation axis R' or R' ' between other attachment points - see figure 20.

All alternatives shown in figures 20-24 function according to this principle.

Figure 20 shows a net structure wherein attachment points 7, 7 of the upper net 6, and attachment points 9, 9 of the lower net 8 are arranged close to a corner of the solar units 2, thereby maximizing the distance between said attachment points. The moment arm is maximized, resulting in a very stable net structure.

In figure 21, the moment arm is only half of the moment arm shown in figure 20, resulting in a reduced but still satisfying stability. Figure 22 (on opposite sides of one solar unit) and figure 23 (on same side of one solar unit) show alternative net structures based on the

attachment shown in figure 21.

Finally, figure 24 shows an alternative embodiment wherein a rigid fixing member 62 is used to counteract any moment force that would otherwise rotate the solar unit 2. This rigid fixing member 62 has a line contact with the solar unit 2, and as such also defines a moment arm. In fact, this moment arm can theoretically be interpreted as an infinite number of attachment points.

Although they show preferred embodiments of the invention, the above described embodiments are intended only to illustrate the invention and not to limit in any way the scope of the invention.

It is noted that the invention is not restricted to the parabolic solar units 2 as shown, but that the system is also applicable to aim flat panels with photovoltaic cells arranged on the surface thereof towards the sun.

Although the embodiment shown in the figures comprises a net structure arranged in a substantially lying plane, also other plane orientations (e.g. a standing plane) are possible with the solar energy system according to the invention. The terms 'upper' and 'lower' net can be regarded as a 'first' and 'second' net throughout all described embodiments without departing from the invention.

Furthermore, although the embodiment shown in the figures comprises a quadrangular net structure, the

invention is also applicable with alternative net structure designs. Such designs may comprise (double) arched net structures, as well as asymmetric net structures and net structures with three or more corners.

Double arched structures allow the solar energy system to be adapted to specific form requirements, at the expense of a slight limitation in their freedom of movement which is proportional to their curvature. Multiple corners do not affect performance, and asymmetry does not affect the freedom of movement. Tests with a double arched, asymmetric net with five corners have confirmed adequate freedom of movement for solar tracking functionality.

It is particularly noted that the skilled person can combine technical measures of the different embodiments. The scope of the invention is therefore defined solely by the following claims.

Claims

1. Solar energy system (1), comprising:

- a plurality of solar units (2);

- suspension means (4) for suspending the plurality of solar units, said suspension means comprising a first net (6) and a second net (8) oriented parallel in a plane, a distance existing therebetween;

- wherein at least two drive means (10) are arranged to the suspension means (4) such that the first and second net (6, 8) are moveable relative to each other in the plane by the drive means (10);

- rotation limiting means (13) configured to limit a rotation of one or more solar units (2) with respect to the suspension means (4); and

- wherein every solar unit (2) is arranged to both the first and second net (6, 8) such that the orientation of the solar units (2) is adjustable via the drive means (10) driving the suspension means (4) .

2. Solar energy system according to claim 1,

- wherein the solar unit (2) is attached to the first net (6) with a first attachment point (7);

- wherein the solar unit (2) is attached to the second net (8) with a second attachment point (9);

- wherein said two attachment points (7, 9) define a first rotation axis (R) ; and

- wherein the rotation limiting means (13) are configured to limit the rotation of the one or more solar units (2) with respect to the suspension means (4) around said first rotation axis (R) .

3. Solar energy system according to claim 2, wherein the rotation limiting means (13) comprise at least one further attachment point attaching the first net (6) and/or second net (8) to the solar unit (2), said at least one further attachment point defining an imaginary plane with the first and second attachment points (7, 9), and preventing the rotation of the one or more solar units (2) with respect to the suspension means (4) around the first rotation axis (R) .

4. Solar energy system according to claim 3, wherein the at least one further attachment point is

attached substantially close to a corner of the solar unit (2) .

5. Solar energy system according to claim 1 or 2, wherein the rotation limiting means (13) comprise a rigid fixing member (62) attached to both the suspension means (4) and one or more the solar units (2) .

6. Solar energy system according to any of the foregoing claims, wherein the first net is an upper net (6), and the second net is a lower net (8) .

7. Solar energy system according to claim 6, wherein the upper and lower net (6, 8) are arranged in a substantially lying plane.

8. Solar energy system according to any of the foregoing claims, wherein the at least two drive means (10) are arranged in one single corner of the suspension means (4) .

9. Solar energy system according to claim 8, wherein the at least two drive means (10) are arranged in a single housing.

10. Solar energy system according to claim 6, wherein :

- the upper and lower net (6, 8) are substantially identical and each net comprises a plurality of rows (12), each row comprising an array of rhombuses (14);

- each rhombus comprises two rhombus-corners (16) substantially oriented in the longitudinal direction of the row, and two rhombus-corners (18) substantially transverse to the longitudinal direction of the row; and

- the solar units (2) are arranged to the rhombus- corners (18) that are substantially transverse to the longitudinal direction of the row.

11. Solar energy system according to claim 6 or

10, wherein:

- the upper and lower net (6, 8) are quadrangular; and

- the at least two drive means (10) are arranged to adjacent corner pairs (20, 22) of the upper and lower net (6, 8) .

12. Solar energy system according to claim 10 or

11, wherein rhombus-corners (16) that are substantially oriented in the longitudinal direction of the rows (12) of rhombuses (14) are connected by wires (24), thereby forming a web structure in the plane of the net (6, 8) .

13. Solar energy system according to any of the foregoing claims, wherein: - the drive means (10) comprise or are driveably connected to a rigid spacing element (26) to which both the upper and lower net (6, 8) are arranged; and

- the corner of the net opposite the corner of the net where the driveable rigid spacing element (26) is arranged comprises a further rigid spacing element (28) that is pivotably arranged at a pivot point (34) substantially halfway between the upper and lower net (6, 8) attachment points (18, 20) .

14. Solar energy system according to claim 13, wherein :

- the drivable rigid spacing element (12) and the pivotably arranged rigid spacing element (28) in the

opposite corner are oriented parallel, such that the rigid spacing elements (12, 14) arranged between the corners of the upper and lower net (6, 8), together with the upper and lower net (6, 8) define a parallelogram-shape.

15. Solar energy system according to any of the foregoing claims, further comprising tensioning members (30) arranged between support members (36) forming the foundation of the solar energy system, and the pivot points (32, 34) of the rigid spacing elements (26, 28), said pivot points (32, 34) being located substantially halfway between the upper and lower net (6, 8) attachment points (20, 22) .

16. Solar energy system according to any of the foregoing claims, wherein the edges of the upper and/or lower net (6, 8) are provided with a main suspender cable (38) that is suspended in a substantially parabolic shape between the net corners (20, 22) .

17. Method for simultaneously adjusting a

plurality of solar units within a solar energy system according to any of claims 1-16, comprising the step of driving the drive means (10) arranged to the suspension means (4), thereby moving the first and second net (6, 8) of the suspension means (4) relative to each other in their plane, and thereby adjusting the orientation of the solar units (2) arranged between the first and the second net (6, 8) .

18. Solar energy system according to any of the claims 1-16, further comprising control means configured for adjusting the plurality of solar units (2) according to the method of claim 17.