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.
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:
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.
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:
The solar tracker, object of the present invention, specifically comprises:
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:
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:
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:
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.
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:
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:
As can be seen in
As can be seen in
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.
Number | Date | Country | Kind |
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P201130263 | Feb 2011 | ES | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/ES2012/070126 | 2/28/2012 | WO | 00 | 8/28/2013 |