US20130333690A1

US20130333690A1 - Solar tracker

Info

Publication number: US20130333690A1
Application number: US14/001,949
Authority: US
Inventors: Francisco Jose Ceron Garcia; Emiliano Cornago Ramirez
Original assignee: Abengoa Solar New Technologies SA
Current assignee: Abengoa Solar New Technologies SA
Priority date: 2011-02-28
Filing date: 2012-02-28
Publication date: 2013-12-19
Also published as: ES2387775B1; ES2387775A1; WO2012117142A1

Abstract

Solar tracker comprising a pedestal (1) upon which a structural support (10) is fixed for a reflective surface (15), which comprises:

- a fixed base (2) anchored to the floor, which comprises a flat upper surface (7) with an opening,
- a vertical axis mechanical rotation element (3) arranged in the opening of the flat surface (7) of the fixed base (2) and fixed to the pedestal (1) and
- an azimuthal rotation actuator cylinder (4) of the structural support (10), comprising a first end fixed to the floor by an anchoring means (16, 2) and a second end fixed to the mechanical rotation element (3) by fixation means,
  the mechanical rotation means being configured in such a way that when the actuator cylinder carries out its movement, the mechanical rotation element transmits the rotational movement of the second end of the actuator cylinder to the pedestal (1).

Description

FIELD OF THE INVENTION

The present invention is encompassed within the field of solar trackers for thermoelectric and photovoltaic applications and more specifically, solar trackers for thermosolar applications (heliostats, Stirling discs, etc.) which rotate on one or two axes, an azimuthal and/or an elevation axis.

BACKGROUND OF THE INVENTION

Thermosolar plants are designed to make the most of solar energy by heating a fluid by means of solar radiation and using them in a conventional thermodynamic cycle in order to generate electrical energy.
Heliostats are used to capture and concentrate the sun's rays. Heliostats are large mirrored surfaces generally formed with a certain curvature. They constantly follow the sun in such a way that the rays they reflect fall on one or various fixed focal points at the top of a tower, where a receptor is located, at any time, this receptor heating the heat transfer fluid.
The use of solar trackers in photovoltaic solar energy production consists of a supporting structure in which flat photovoltaic panels are installed. These panels must be oriented in such a way that they are perpendicular to the sun's rays at all times, which is why the solar tracker must be capable of rotating within the space it occupies, following the sun's position. The photovoltaic cells convert the sun's energy into electricity, which direct the energy for industrial or commercial use by means of wiring and current inverters.
The various mechanisms existing to date, which serve to provide the supporting structure with azimuthal movement (with a vertical rotation axis) and elevation (with a horizontal rotation axis) are as follows:

- The Carousel solar tracker, which provides the structure with a double circular track, upon which the structure is moved, thus resulting in the desired orientation.
- The “T” model. Various models are used to rotate a mechanism without azimuthal rotation worm gear and an electromechanical spindle for elevation. Furthermore, electromechanical spindles are used in smaller trackers for both movements.

Utility model ESI050814 discloses a solar tracker for photovoltaic power plants, which comprises a fixed platform defined by a circular track, supported by pillars which elevate it from the floor and keep it at the right level, in order to enable a rotating platform located above, which has wheels, to rotate in order to orientate itself in azimuth. This rotating platform supports a plurality of solar panels arranged in columns and rows on a sloped surface. In turn, each one of the rows of solar panels is rotated around an axis common to all of them, in order to orientate itself, moving from a vertical position in which the sun's rays are received at sunrise until it reaches the most angled position at midday, when the sun is at its highest. The azimuthal rotation of the mobile platform, which occurs simultaneously alongside the angling of the panels, takes place once one a reduction motor has been coupled to one of the wheels, rotating until it reaches 210°, which is equivalent to fourteen hours of the apparent solar trajectory, from sunrise to sunset.
In the utility model ES-A-1059027, a rotating base is proposed for solar panel installations, formed by a circular track in the form of a U, on a fixed or bench platform, supported by pillars, which locate it at the right level, according to the orography of the area to be installed and an inclined mobile structure being defined on the track with a plurality of solar panels arranged in rows and columns on this sloped surface. This inclined structure is joined and coupled to the fixed circular track by means of perpendicular bearings, which give it angular movement, in addition to serving as a guide for the rotational movement.
Likewise, U.S. Pat. No. 6,123,067 discloses a solar tracker with an azimuthal rotation system, which operates by means of two hydraulic cylinders arranged perpendicularly and an elevation system, which operates by means of a hydraulic cylinder.
U.S. Pat. No. 4,459,972 discloses a heliostat, which comprises rotational reflector means arranged on the pedestal and fixed to a fixed or variable distance of the reflector, a hydraulic cylinder being used in the case of rotational means at a variable distance from the reflector.
The problem detected in the rotational systems of the abovementioned solar trackers is that, whereby heliostats are concerned, the focal distance is hundreds of meters, which explains the application of the rotational systems known to heliostats, obtaining a low capacity for obtaining a precise position or in other words, a low pressure, which makes it necessary to develop a specific rotational system for heliostats, which is highly precise in the movements throughout the day.

DESCRIPTION OF THE INVENTION

The invention refers to a solar tracker, of the variety referred to in the background section as “T” type, which comprises a pedestal, whether cylindrical or parallelepiped, upon which a supporting structure or structural support made of mirrors or photovoltaic modules is attached at the upper end, which resolves the abovementioned problems by means of:

- a fixed base anchored to the floor, which comprises a flat upper surface with an opening,
- a mechanical rotation element of the vertical axis arranged in the opening of the flat surface of the fixed base and fixed to the pedestal and,
- an actuator cylinder which rotates the structural support azimuthally, comprising a first end fixed to the floor by an anchoring means and a second end fixed to the mechanical rotation element by fixation means,
  the mechanical rotation element being configured in such a way that when the actuator cylinder carries out its movement, the mechanical, rotation element transmits the rotational movement of the second end of the actuator cylinder to the pedestal (1).

The solar tracker, object of the present invention, specifically comprises:

- a fixed base anchored to the floor, which may comprise at least one lateral opening and a flat upper surface with an opening,
- a vertical axis mechanical rotation element, arranged in the opening of the flat surface of the fixed base, which comprises a fixed ring fixed to the fixed base and a mobile ring, upon the upper face of which the lower end of the pedestal is fixed,
- an oleohydraulic actuator cylinder of azimuthal rotation, which comprises a first end fixed to the floor or to the fixed base of the tracker by anchoring means and a second end fixed tangentially to the lower face of the mobile ring of the mechanical element by fixation means. The same uses a common hydraulic switchboard to transform the lineal movement, moving away or retreating in a rotational movement of the pedestal, of more than 120°,
- a second cylinder may optionally be used which comprises a first end fixed to the floor or fixed base of the tracker by anchoring means and a second end fixed tangentially to the lower face of the mobile ring of the mechanical element by a mobile fixation means, to which the second end of the first cylinder is also anchored, in such a way that it makes it possible to obtain an azimuthal rotation of 315°.

Pedestal is understood to mean a solid, cylindrical or rectangular parallelepiped shaped body, which supports a structure. A solid body is understood to be a firm body which is not necessarily robust.
The anchoring means used to anchor the first end of each cylinder to the floor comprise:

- a base fixed to the floor or to the fixed base of the tracker, by means of anchoring means such as foundation bolts, with a circular opening or drill hole,
- a piece, parallel to said base, with a circular coaxial opening which is concentric to the opening or drill hole in the base,
- a piece located between the fixed base of the floor and the piece parallel to said base, perpendicular to both, the piece parallel to the base being at a distance which makes it possible to locate the ball joint of the hydraulic cylinder between the base and the parallel piece and,
- a vertical fixation axis, for example a bolt, which crosses the drill holes or openings in the base and the parallel piece and the ball joint.

The azimuthal movement of solar trackers with a cylinder takes place because the cylinder extends or retracts itself, thus giving rise to rotational movement of its second end fixed to the mechanical rotation element. The centre of this circular movement is the mechanical rotation element rotation axis, which may be a bearing or a slew ring and the distance from this point to the centre of the piston rod or piston of the cylinder joined to the pedestal is formed by its radius. The circular trajectory is located on a horizontal plain. The cylinder will therefore have a rotational movement in the second end of the axis and another rotation in the axial line of the cylinder around the mooring point to the floor, in order to absorb the previous movement. In this case, a rotational capacity of over 120° is achieved.
The azimuthal movement with two cylinders takes place because the two cylinders are anchored at their second end to an anchoring means fixed to the mechanical rotation element, in such a way that the line joining these two points, corresponding to the second ends of each cylinder, passes through the rotational centre of the pedestal. Upon extending or retreating, the hydraulic cylinders cause their end to rotate, forced by the mechanical rotation element. The centre of said circular movement is the rotational axis of the mechanical rotation element; its radius is formed by the distance from this point to the centre of the piston rod joined to the pedestal. The circular trajectory is located on a horizontal plane. Upon extending or retreating, the cylinders give rise to the rotation of the structure, capable of rotating 315°. Both cylinders should be synchronised, in such a way that the rotational direction they provoke coincides in each movement.
Moreover, the solar tracker, object of the present invention, comprises an elevation system for the structural support, attached to the upper end of the pedestal, which comprises:

- an upper support or bank element, comprising two articulations in order to elevate the structural support, which supports the reflective surfaces or photovoltaic panels,
- an elevation cylinder anchored to the pedestal by means of a first end, by means of a fixed anchoring comprising a ball joint, anchored by a second end to the mobile arm or mobile structural support of the reflective surfaces or photovoltaic modules, by means of an anchoring point to the ball joint of the second end of the cylinder.

The elevation cylinder, by means of either elongation or retraction lineal movement, gives rise to the rotational movement of the mobile structural support in relation to the pedestal.
The mobile structural support comprises the photovoltaic mirrors or panels to be oriented.
Likewise, the elevation movement takes place when the hydraulic elevation cylinder extends or retreats, giving rise to a rotational movement of its end, forced by the axle-ball joint type fixation of the support element of the mobile structural support, in relation to the pedestal. Said circular movement is produced on a vertical plane, which passes through the anchoring point of the first end of the cylinder. The centre is formed by the point at which the rotational axis or horizontal line intersects, passing through the centres of the previous ball joints, with the vertical plane defined above. The rotational radius of the mobile ball joint of the elevation cylinder will be the distance between the previous centre and the mobile anchoring point.
It is clear that the previous vertical plain is not fixed, along with the pedestal and the plain of mirrors or panels rotates around the vertical axis of the bearing in the base owing to the rotational azimuth mechanism explained above.
The hydraulic cylinders may be optimised using cylinders with a diameter range of between 120 and 240 mm.
The mechanical rotation element may be optimised using a mechanical rotation element with a radius of over 700 mm.
In addition, the pedestal in the solar tracker, object of the present invention, comprises: a hydraulic switchboard or oil supply system for supplying the cylinders, which comprises a motor-pump unit, which exerts pressure on the hydraulic system, an oil deposit to admit the loading and unloading of oil in the hydraulic cylinders, a break block and a blockade in order to be able to regulate the velocity of the cylinders, a manoeuvre block for managing the mechanism, pressurised storage tanks for a rapid system response and pressure switches, electrovalves, special valves, through and connecting valves, with the aim of supplying oil at pressure to the chambers of the cylinders.
Likewise, attached to the pedestal, the tracker comprises a control system which feeds the pump, orders the opening and closing of the oil circuits, captures the position information and tracker state, communicates this information to the centralised control and facilitates local control. The system comprises an external box, which has a console for system configuration, calibration, monitoring and diagnostics inside; a switch panel for tracker maintenance and cleaning functions, a power block for managing the feeding of the electric group and a communications block, to manage all the information which arrives from the centralised control of the switch panel and the state of the tracker.
The solar tracker, object of the present invention, comprises an azimuthal rotational mechanism and an elevation mechanism for the structural support of the photovoltaic mirrors or panels, to be oriented, which is highly advantageous in comparison to those mechanisms already known about, given that:

- When attaching the rotation mechanism to the base of the pedestal, there is a greater rotational radius, which results the tracker's aim being highly precise and of high quality.
- When the azimuthal rotation system is located in the base, it also achieves great material savings, since it does not need a complex supporting structure in order to support the rotation system high up.
- When transferring the azimuthal rotation to the base of the structure, the height of a decentralised weight is reduced, thus saving when it comes to defining the dimensions when laying foundations.
- The bearing in the base does not imply an additional cost since it enables the system to be precise enough to be able to orientate itself and the diameter does not exceed the dimensions of the elements which it joins.
- Another advantage of the invention is that it frees space around the elevation cylinder for its operation and manoeuvrability, as well as to store ends of track, position measuring apparatus etc.
- Therefore, the rotational radius of the piston rod or piston of the elevation cylinder is greater, thus resulting in greater position in the vertical movement.
- As far as value for money is concerned, better quality is achieved owing to the abovementioned points, the manufacturing costs decreasing considerably. It is also more reliable.
- The example of hydraulic cylinders within an optimal diameter range for this invention results in improved solar tracking, given that very small and precise movements are achieved.

It is also important to highlight that the cylinders may be oleohydraulically driven or also mechanically driven, in which ease the hydraulic centre installed in the pedestal would not be necessary.

BRIEF DESCRIPTION OF THE DRAWINGS

Below is a brief description of a series of drawings, which facilitate a better understanding of the invention and expressly relate to one embodiment of said invention, providing a non-limiting example thereof:

FIG. 1 is a schematic representation of a solar tracker with just one hydraulic azimuthal rotation actuator cylinder.

FIG. 2 is a schematic representation of a solar tracker with two hydraulic azimuthal rotation cylinders.

FIG. 3 is a perspective representation of the pedestal of the solar tracker with the hydraulic control and oil supply equipment.

FIG. 4 is a perspective representation of a detail of the upper bench.

FIG. 5 is a lower representation of FIG. 1.

FIG. 6 is a lower representation of FIG. 2.

FIG. 7 is a perspective representation of a detail of the fixed anchoring of the oleohydraulic azimuthal rotation actuator cylinder.

FIG. 8 is a lateral schematic view of the lower part of the solar tracker with an oleohydraulic cylinder and arm in the form of a U fixed to the base of the pedestal.

FIG. 9 is a cross sectional representation of IX-IX represented in FIG. 8.

In the abovementioned figures, a series of references are included, which correspond to the elements indicated below, all of which are non-limiting in character:

- 1.—Pedestal
- 2.—Fixed base
- 3.—Bearing
- 4.—Azimuthal rotation hydraulic cylinder
- 5.—Mobile anchoring
- 6.—Lateral openings
- 7.—Flat surface of the fixed base
- 8.—Fixed external ring of the bearing
- 9.—Mobile internal ring of the bearing
- 10.—Support arm of reflective surfaces
- 11.—Hydraulic elevation cylinder
- 12.—Upper bench
- 13.—First anchoring of the first end of the elevation cylinder
- 14.—Second anchoring of the second end of the elevation cylinder
- 15.—Reflective surface
- 16.—Fixed anchoring of the azimuthal rotation cylinder
- 17.—Side plate
- 18.—Horizontal rotation axis of the reflective surface
- 19.—Articulation of the upper bench
- 20.—Hydraulic control equipment
- 21.—Pressurised oil supply system for supplying the cylinders
- 22.—Fixed support
- 23.—Fixed anchorage base of the azimuthal rotation cylinder
- 24.—Parallel piece of the fixed anchoring of the azimuthal rotation cylinder
- 25.—Perpendicular H profile piece
- 26.—U shaped arm

DETAILED DESCRIPTION OF ONE EMBODIMENT

As can be seen in FIGS. 1, 3 4 and 5, the solar tracker, object of the present invention, is a heliostat, which comprises:

- a fixed base (2) anchored to the floor, comprising a lateral opening (6) and a flat upper surface (7) with an opening,
- a bearing (3) as a mechanical rotation element of the vertical axis, which preferably has a radius of over 700 mm, arranged in the opening of the flat surface of the pedestal base, comprising an external ring (8) fixed to the fixed base and an internal mobile ring (9),
- a pedestal (1) fixed to the upper face of the internal mobile ring (9) of the bearing, upon which an arm (1) is fixed as a structural support for reflective surfaces,
- an oleohydraulic azimuthal rotation actuator cylinder (4), comprising a first end fixed to the floor by an anchoring means (16) and a second end tangentially fixed to the lower face of the internal mobile ring (9) of the bearing by fixation means,
- an upper bench (12) comprising two articulations (19, 19′) for the elevation movement of the structural support or arm (10) which supports the reflective surfaces or photovoltaic panels,
- an oleohydraulic elevation cylinder (11), anchored to the pedestal (1) at a first end by means of a first anchoring (13), which comprises a ball joint and anchored at a second end to the arm (10) of the reflective surfaces (15) by means of a second anchoring (14) to the ball joint of said cylinder end,
- a pressurised oil supply system (21) for supplying oil to the oleohydraulic cylinder (4, 11),
- a piece of control equipment (20) for controlling the pressure of the pressurised oil supply system (21).

FIGS. 2 and 6 represent another preferred embodiment in which the fixed base (2) of the heliostat comprises two lateral openings (6, 6′) facing two hydraulic azimuthal rotation cylinders (4, 4′), in such a way that the second end of each cylinder (4, 4′) is fixed tangentially to the lower face of the internal mobile ring (9) of the bearing by a mobile anchoring piece (5) as a mobile fixation means, in such a way that it makes if possible to obtain an azimuthal rotation of 315°.
FIGS. 8 and 9 represent a preferred embodiment in which the fixed base (2) anchored to the floor also comprises a U shaped arm (26), to which the end of the cylinder (4) is fixed, which may comprise two U shaped arms when the base (2) comprises two openings (6, 6′) and two cylinders (4, 4′).
FIGS. 1-3, 5 and 6 represent embodiments in which the anchoring means (16, 16′) of the first end of each oleohydraulic azimuthal rotation actuation cylinder, as shown in FIG. 7, comprises:

- a base (23) fixed to the floor by means of bolts, with a circular opening or drill hole,
- a piece (24) which is parallel to said base, with a circular coaxial opening which is concentric to the opening or drill hole in the base,
- a small boiler works piece located between the base (25) and the piece parallel to the same, with a H profile, thus making it possible for a distance between both to exist, which makes it possible to locate the ball joint of the hydraulic cylinder between the base and the parallel piece and,
- a fixation bolt, which crosses the drill holes or openings in the base and the parallel piece and the ball joint.

As can be seen in FIG. 7, the parallel piece is fixed to a H profile which is perpendicular to the base, although it may have any profile capable of fixing the parallel piece to the desired distance in relation to said base.
In addition, the pedestal of the solar tracker, object of the present invention, comprises a pressurised oil supply system (21) for supplying the oleohydraulic cylinders (4, 4′ and 11) with a diameter of between 120 and 240 mm, comprising a motor-pump unit, an oil deposit, cylinder velocity regulation means and oil supply means.
Likewise, the tracker is fixed to the pedestal and comprises a piece of oil supply system (21) control equipment (20), comprising configuration, calibration, monitoring, diagnostic and management means for the oil supply system (21) actuation settings.
FIG. 3 represents a detail of the pedestal of the tracker, object of the present invention, with the oil supply system (21) and piece of control equipment (20). In FIG. 4, a detail of the upper bench (12) can be observed, in which it is possible to see that it comprises two articulations (19, 19′), each one of which comprises two rotating side plates (17, 17′) fixed to the arm or structural support (10) with a fixed support (22, 22′) arranged between both and joined to them by means of a horizontal rotation axis (18, 18′) pertaining to the structural support.

Claims

1. Solar tracker comprising:

a pedestal upon which a structural support for a reflective surface is fixed,

a fixed base anchored to the floor, which comprises a flat upper surface with an opening,

a vertical axis mechanical rotation element arranged in the opening of the flat surface of the fixed base and fixed to the pedestal and

an azimuthal rotation actuator cylinder of the structural support, which comprises a first end fixed to the floor by an anchoring means and a second end fixed to the mechanical rotation element by fixation means,

the mechanical rotation element being configured in such a way that when the actuation cylinder carries out its movement, the mechanical rotation means transmits the rotational movement of the second end of the actuation cylinder to the pedestal.

2. Solar tracker according to claim 1, wherein mechanical rotation element comprises a fixed ring, fixed to the fixed base and a mobile ring which comprises an upper face to which a lower end of the pedestal is fixed and a lower face to which the second end of the actuator cylinder is fixed.

3. Solar tracker according to claim 2, wherein the fixed base anchored to the floor comprises a lateral opening.

4. Solar tracker according to claim 3, wherein the actuator cylinder is arranged below the flat surface of the fixed base anchored to the floor and crossing the lateral opening.

5. Solar tracker according to claim 4, wherein the fixed base comprises a second lateral opening opposite to the first opening.

6. Solar tracker according to claim 5, wherein a second cylinder is arranged below the flat surface of the fixed base anchored to the floor and crossing the second lateral opening, which comprises a first end fixed to the floor by an anchoring means and a second end fixed tangentially to the lower face of the mobile ring of the mechanical element by means of a mobile anchoring piece, to which the second end of the first cylinder is also anchored.

7. Solar tracker according to claim 1, wherein an elevation cylinder is anchored to the pedestal by a first end by means of a first anchoring and anchored by a second end to the structural support of the reflective surfaces by means of a second anchoring.

8. Solar tracker according to claim 1, wherein an upper bench is fixed to an upper end of the pedestal, which comprises a rotation system which rotates in relation to a horizontal axis fixed to the structural support, operable by means of the second end of the elevation cylinder.

9. Solar tracker according to claim 8, wherein the rotation system comprises two articulations, each one of which comprises two rotating side plates fixed to the structural support with a fixed support arranged between both and joined to them by means of a horizontal rotation axis of the structural support.

10. Solar tracker according to claim 1, wherein the cylinder is an oleohydraulic cylinder.

11. Solar tracker according to claim 10, wherein a pressurised oil supply system for supplying the oleohydraulic cylinder comprises a motor-pump unit, an oil deposit, regulatory means for regulating the velocity of the cylinders and oil supply means.

12. Solar tracker according to claim 11, wherein a piece of pressurised oil supply system control equipment comprises configuration, calibration, motorisation, diagnostic and management means for the operating settings of the oil supply system.

13. Solar tracker according to claim 1, wherein the anchoring means comprises:

a base fixed to the floor by anchoring means, with a circular opening or drill hole,

a piece which is parallel to said base, with a circular coaxial opening which is concentric to the opening or drill hole in the base,

a piece which is perpendicular to the base and to the piece which is parallel to the base, located between both, upon which the piece parallel to the base is fixed, at a distance such that it is possible to locate the ball joint of the hydraulic cylinder between the base and the parallel piece and,

a vertical fixation axis which crosses the drill holes or openings in the base and the parallel piece and the ball joint.

14. Solar tracker according to claim 1, wherein the means for anchoring to the floor comprise the fixed base anchored to the floor.

15. Solar tracker according to claim 14, wherein the fixed base comprises at least one arm in the form of a U.

16. Solar tracker according to claim 1, wherein the rotating mechanical element is an element selected from a bearing or a slew ring.

17. Solar tracker according to claim 1, wherein the hydraulic cylinders have a diameter of between 120 and 240 mm.

18. Solar tracker according to claim 1, wherein the radius of the mechanical rotation element is greater than 700 mm.