U.S. patent application number 12/521143 was filed with the patent office on 2010-04-22 for bidirectional solar tracker.
Invention is credited to Carlos Maria Carrasco Martinez.
Application Number | 20100095955 12/521143 |
Document ID | / |
Family ID | 39608392 |
Filed Date | 2010-04-22 |
United States Patent
Application |
20100095955 |
Kind Code |
A1 |
Carrasco Martinez; Carlos
Maria |
April 22, 2010 |
BIDIRECTIONAL SOLAR TRACKER
Abstract
The tracker is formed by a structure (3) bearing a platform (1)
carrying the solar panels (2) that varies both the azimuth and
elevation orientation thereof in order to track the sun. This
movement is achieved by means of two actuators (4) connected
respectively to fixed points (P1.sup.o, P2.sup.o) on the ground and
other vertices (P1, P2) of the platform (1), thereby causing the
platform to rotate around a central support point "O" of the same.
The distances (D1, D2) between the points which join the actuators
(4) have a one-to-one relation with the rotation angles (.beta.,
.alpha.) of the platform (1) around both perpendicular axes: an
oblique fixed axis (O-Cl) and another axis (0-Az) that angularly
varies the inclination thereof with respect to the first.
Inventors: |
Carrasco Martinez; Carlos
Maria; (Murcia, ES) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
1030 15th Street, N.W.,, Suite 400 East
Washington
DC
20005-1503
US
|
Family ID: |
39608392 |
Appl. No.: |
12/521143 |
Filed: |
December 27, 2007 |
PCT Filed: |
December 27, 2007 |
PCT NO: |
PCT/ES2007/000761 |
371 Date: |
September 17, 2009 |
Current U.S.
Class: |
126/601 ;
126/604 |
Current CPC
Class: |
Y02E 10/47 20130101;
F24S 30/455 20180501; F24S 2030/115 20180501; F24S 25/10
20180501 |
Class at
Publication: |
126/601 ;
126/604 |
International
Class: |
F24J 2/40 20060101
F24J002/40; F24J 2/38 20060101 F24J002/38 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 29, 2006 |
ES |
P200603326 |
Apr 20, 2007 |
ES |
U200700819 |
Apr 20, 2007 |
ES |
U200700825 |
Aug 2, 2007 |
ES |
P200702164 |
Claims
1. BIDIRECTIONAL SOLAR TRACKER, of the type formed by a support
structure (3 or 3') bearing a platform (1) carrying the solar
panels (2) which convert solar energy into electrical energy,
varying the orientation of the platform (1) in both azimuth and
elevation in order to constantly offer its surface in a direction
perpendicular to the solar rays, characterized in that the movement
for varying the orientation of the platform (1) is achieved by
means of two actuators (4 or 4') connected respectively to fixed
points (P1o, P2o) on the ground and other vertices (P1, P2) of the
platform (1), causing the latter to be able to rotate around a
central support point "O" of the same, from an initial position to
another final position, with two degrees of freedom due to said two
vertices (P1, P2) of the platform (1) being related with two angles
.alpha., .beta. of rotation thereof: one of them .beta. around an
oblique fixed axis (O-G1) fixed to the ground and forming an angle
.PHI. with the coordinate axis (OY) parallel to the surface of the
ground and the other angle .alpha. around an axis (O-Az)
perpendicular to the previous one, contained in the plane of the
platform 1 and which angularly varies its inclination when the
latter does so around the oblique fixed axis (O-G1).
2. BIDIRECTIONAL SOLAR TRACKER, according to claim 1, characterized
in that the distances (D1, D2) of the vertices (P1, P2) to the
respective fixed points (P1o, P2o) of the ground maintain a
one-to-one relation with the angles (.alpha., .beta.) of rotation
of the platform (1) around its perpendicular axes (O-C1, O-Az),
which determines that, for each pair of angles (.alpha., .beta.),
there exists just one pair of said distances (D1, D2) and vice
versa.
3. BIDIRECTIONAL SOLAR TRACKER, according to claim 1, characterized
in that the distances (D1, D2) are calculated and determined by the
two desired angles (.alpha., .beta.), according to the coordinates
of the place, time of year and moment of the day, adjusting and
varying them with the actuators (4).
4. BIDIRECTIONAL SOLAR TRACKER, according to claim 3, characterized
in that the actuators (4) are hydraulic cylinders, spindles, or any
other mechanical element that can fix the distances (D1, D2).
5. BIDIRECTIONAL SOLAR TRACKER, according to claim 3, characterized
in that the actuators are tracking devices with light-point
feedback, with which the angle (.beta.) around the fixed axis
(O-G1) manages to be varied with increments of signs opposite to
the distances (D1, D2), with a small variation in the other angle
(.alpha.), and with equal increments of the same sign for variation
of the angle (.alpha.) around the axis (O-G1), orientable in its
angle, perpendicular to the above and which is carried out with a
minor variation of the other angle (.beta.) for small movements,
which causes the platform (1) to be centered on the light point in
a few reiterated alternative movements.
6. BIDIRECTIONAL SOLAR TRACKER, according to claim 1, characterized
in that the platform is constituted on the basis of a frame (5)
that is mounted in tilting fashion on a support (10), the actuators
(4') being connected to separate points of the actual frame (5),
establishing a rotation of said frame (5) and therefore of the
platform around a central point, rotating with two degrees of
freedom, with the particular feature that the orientation of the
corresponding platform in the manner of a swivel joint is effected
via the "T" support (10), the cross-member (10') of which is
traversed by a transverse axis (9) belonging to the frame (5),
being able to rotate with a degree of freedom around it; provision
having been made for the vertical core or section (12) of said "T"
support (10) to be traversed longitudinally by an axis (11) secured
between two struts (13, 14) of the respective fixed structure (3')
for supporting the platform, rotating with the second degree of
freedom.
7. BIDIRECTIONAL SOLAR TRACKER, according to claim 1, characterized
in that the corresponding hydraulic system for operating the
actuators (4 or 4') incorporates a device for prevention of damage
by the wind, the device consisting of one or more pressure switches
(19) mounted in the hydraulic fluid line or lines (20), in which
participates a cylinder (22) with its piston (23), said pressure
switch or switches (19) being fitted in order to provide a signal
indicating the exact moment when the movement of the platform
carrying the solar panels has to be carried out automatically to
the horizontal position of minimum resistance to the strong wind of
said platform with the solar panels.
8. BIDIRECTIONAL SOLAR TRACKER, according to claim 1, characterized
in that the corresponding hydraulic system for operating the
actuators (4 or 4') incorporates a pressure regulation device
consisting of a pair of oleo-pneumatic dampers (25) with the
ability to regulate the sudden loads to which the fixed structure
(3 or 3') of the solar tracker is subjected due to the effect of
outside agents; with the particular feature that said
oleo-pneumatic dampers (25) are connected in parallel with the
fluid lines (19') corresponding to the hydraulic system
(22'-23').
9. BIDIRECTIONAL SOLAR TRACKER, according to claim 8, characterized
in that the oleo-pneumatic dampers (25) preferably consist of
respective oleo-pneumatic expansion tanks.
10. BIDIRECTIONAL SOLAR TRACKER, according to claim 8,
characterized in that each expansion tank constituting the
respective oleo-pneumatic damper (25) includes an internal membrane
(28) as a regulating element of the pressure inside the tank, the
latter having a calibrated hole (28) for the discharge of the
fluid.
11. BIDIRECTIONAL SOLAR TRACKER, according to claim 8,
characterized in that mounted in the hydraulic fluid lines (19'),
to which the oleo-pneumatic dampers (25) are connected, are
respective controlled non-return valves (30).
12. BIDIRECTIONAL SOLAR TRACKER, according to claim 2,
characterized in that the distances (D1, D2) are calculated and
determined by the two desired angles (.alpha., .beta.), according
to the coordinates of the place, time of year and moment of the
day, adjusting and varying them with the actuators (4).
13. BIDIRECTIONAL SOLAR TRACKER, according to claim 4,
characterized in that the corresponding hydraulic system for
operating the actuators (4 or 4') incorporates a device for
prevention of damage by the wind, the device consisting of one or
more pressure switches (19) mounted in the hydraulic fluid line or
lines (20), in which participates a cylinder (22) with its piston
(23), said pressure switch or switches (19) being fitted in order
to provide a signal indicating the exact moment when the movement
of the platform carrying the solar panels has to be carried out
automatically to the horizontal position of minimum resistance to
the strong wind of said platform with the solar panels.
14. BIDIRECTIONAL SOLAR TRACKER, according to claim 4,
characterized in that the corresponding hydraulic system for
operating the actuators (4 or 4') incorporates a pressure
regulation device consisting of a pair of oleo-pneumatic dampers
(25) with the ability to regulate the sudden loads to which the
fixed structure (3 or 3') of the solar tracker is subjected due to
the effect of outside agents; with the particular feature that said
oleo-pneumatic dampers (25) are connected in parallel with the
fluid lines (19') corresponding to the hydraulic system
(22'-23').
15. BIDIRECTIONAL SOLAR TRACKER, according to claim 9,
characterized in that each expansion tank constituting the
respective oleo-pneumatic damper (25) includes an internal membrane
(28) as a regulating element of the pressure inside the tank, the
latter having a calibrated hole (28) for the discharge of the
fluid.
16. BIDIRECTIONAL SOLAR TRACKER, according to claim 9,
characterized in that mounted in the hydraulic fluid lines (19'),
to which the oleo-pneumatic dampers (25) are connected, are
respective controlled non-return valves (30).
17. BIDIRECTIONAL SOLAR TRACKER, according to claim 10,
characterized in that mounted in the hydraulic fluid lines (19'),
to which the oleo-pneumatic dampers (25) are connected, are
respective controlled non-return valves (30).
Description
OBJECT OF THE INVENTION
[0001] The present invention relates to a bidirectional solar
tracker which contributes notable relevant characteristics and
technical advantages with regard to those currently existing for
the production of electrical energy by means of solar panels.
[0002] The main object of the invention is to offer a support
structure for a platform carrying the solar panels, such that this
platform is orientated towards the sun according to a novel form of
movement, with a functioning that is smooth and simple, yet
efficient.
[0003] In the current field of exploiting renewable energies, there
exists a great increase at the world level in solar energy
facilities that use photovoltaic panels (solar panels), which
convert that energy into electrical energy. The installation of
these panels is normally done on fixed structures orientated is
towards the south, with a degree of inclination on the horizon that
depends on the latitude of the place.
[0004] The production of electrical energy by a panel depends on
the actual characteristics of that panel and on the radiation
received from the sun, which is equal to the solar radiation at
that moment multiplied by the cosine formed by the perpendicular to
the surface of the panel with the direction of the solar rays, the
direction of which varies according to the time of day and the day
of the year, as well as the latitude of the place.
[0005] In solar panel facilities installed on structures fixed to
the ground, the exploitation of the solar radiation is not the
maximum that could be obtained, since the direction of the
perpendicular to the panel only coincides with that of the solar
rays on a few occasions. In order to optimize the maximum energy
output of the panels they need to be mounted on mobile structures
which constantly position them perpendicular to the sun.
[0006] These mobile structures are known by the name of solar
trackers.
[0007] It is also an object of the invention to provide the
inventive solar tracker with a device for prevention of damage
caused by the wind and thereby avoid any imperfections or damage
being caused to the solar tracker.
[0008] It is also an object of the invention to provide the solar
tracker with a device that permits the pressure in the hydraulic
actuators to be regulated and thereby periodically modify the
position of the platform and therefore of the solar panels, in
order to permanently obtain an orientation perpendicular to said
solar panels with respect to the solar rays, permitting maximum
solar power to be obtained at any moment.
BACKGROUND OF THE INVENTION
[0009] Within the current types of solar tracker, there primarily
exist models known as "monodirectional" and "bidirectional".
[0010] Monodirectional solar trackers are characterized by having a
fixed angle of elevation above the horizon and varying the azimuth
angle with the time of day in order to follow the sun, while
bidirectional solar trackers vary both the azimuth angle and the
angle of elevation during the daily travel of the sun, continually
positioning the solar or photovoltaic panel in a direction
perpendicular to the solar rays, thereby achieving net annual
outputs that are around 20-30% greater than fixed facilities
(depending on the latitude of the place and the annual hours of
sunlight there).
[0011] For the movement of these bidirectional solar trackers,
there exist various ways of doing this on the market, the most used
being those that have a rotation around a vertical axis for the
azimuth orientation and another rotation around a horizontal axis
for the elevation orientation.
[0012] The movement of these rotation is normally done: [0013] the
azimuth, by producing rotations of about 180.degree. by means of a
crown and pinion, or worm, which are electrically or hydraulically
actuated. [0014] for elevation, by means of a hydraulic spindle or
actuator, or also by means of a crown and pinion or worm.
[0015] Moreover, in order to provide for the effects of strong
winds or even hurricanes on the solar trackers, wind gauges need to
be provided so that, when the wind exceeds a safety speed an
emergency action is started up in the tracker's movement system,
which acts on it so that the support platform for the solar panels
remains in the horizontal position, since close to the ground the
direction of the wind is also appreciably horizontal and so the
resistance of the panels to the wind becomes as little as possible,
hereby avoiding possible damage or breakage of certain parts or
elements of the facility.
[0016] Although the systems referred to and based on the concept
mentioned above are functionally efficient, they nevertheless
present a series of drawbacks that can be summarized as follows:
[0017] It is not possible to make any exact aerodynamic
calculations, since the shapes of the tracker are not at all
similar to standardized profiles, so the data that would be
obtained from a test in a wind tunnel would differ from the
conditions in the field, where it is impossible to simulate the
turbulence owing to the undulations of each specific field. In any
case, the calculations are always orientative and so the emergency
limit speed has to be reduced, with the consequent reduction in
energy production. [0018] In those cases in which the direction of
the wind is parallel to the solar panels, the system will move to
the horizontal position even when this is not necessary, thus
reducing the energy output. [0019] Even in the case of installing a
wind gauge for each solar tracker, there exists a risk of vertical
whirlwinds produced by thermal differences which, if they strike
the surface of the tracker at one of its ends, might not be
detected by the wind gauge, and a large torque or torsion would be
produced due to a symmetric load which would cause serious damage
to the solar tracker.
[0020] It must also be borne in mind that, in the event of the
solar trackers being faced with strong winds, gusts or even
hurricanes, even when they are fitted with a system for damage
prevention starting from a certain speed considered to be the
emergency speed and the solar panels are positioned horizontally,
strong peak forces are nevertheless produced at the points of
attachment between the mobile and fixed parts. Furthermore, in the
case of turbulent winds or gusts that can produce what is known as
the "flutter" effect, there can even exist a wind speed starting
from which the system will start to resonate, with the
corresponding collapse of the structure.
DESCRIPTION OF THE INVENTION
[0021] In general terms, the bidirectional solar tracker proposed
by the invention achieves the orientation of the platform carrying
the solar panels by being arranged on a support structure, in such
a way that it can rotate and orientate itself with combined
movements of rotation about two axes: one of them oblique and fixed
to the ground forming a certain angle with the OY coordinate axis
parallel to the surface of the ground and which points in the
southerly direction; and the other axis perpendicular to the
previous one, contained in the plane of the platform and which
varies its angle of inclination when the platform varies its angle
about the fixed oblique axis.
[0022] This movement is carried out with two actuators respectively
connected to separate fixed points of the ground and to the same
number of vertices of the platform, causing the latter to rotate
about a central support point thereof in the support structure and
from an initial position to another final position, having two
degrees of freedom since the final position of said two vertices of
the platform is determined with the two angles of rotation
thereof.
[0023] This causes the distance of the said vertices to the
respective fixed points of the ground to maintain a one-to-one
relation with the angles of rotation of the platform about the two
perpendicular axes, which means that for each pair of angles there
exists just one pair of said distances and vice versa. The
distances are calculated for a defined value of the angles
described depending on the coordinates of the place, the time of
year and moment of the day, with the adjustment being carried out
by the actuators.
[0024] Said actuators, thanks to which the correct distances
between the respective points joining them are able to be adjusted,
can be hydraulic cylinders, spindles or any other suitable
mechanical element, preferably being hydraulic systems.
[0025] The orientation of the platform is also possible by means of
tracking devices with light-point feedback since, with increments
in opposite sign of the distances between the points being
considered, the angle around the fixed axis manages to be varied
(with a very small variation in the angle rotated about the axis,
orientable in its angle and perpendicular to that axis) and with
equal increments of the same sign an angular variation in the
platform is achieved about the axis, orientable in its angle and
perpendicular to that axis, and which is done with much less
variation in the other angle (for small movements). According to
this, with a few alternative reiterated movements the platform
manages to be centered on the light point.
[0026] One way of achieving the securing of the platform carrying
the solar panels to the structures fixed to the ground, in order to
obtain smooth movements about the said two axes and functioning as
a swivel joint, is based on using a frame consisting of stringers
and cross-members which can rotate about a transverse axis which is
longitudinally traversed by the cross-member corresponding to a "T"
support that is secured to two struts emerging from the fixing
structure to the ground, so that the platform will remain at a
certain height and can tilt and rotate in order to carry out the
solar tracking, as has been said earlier.
[0027] The "T" support is rotationally secured by means of a
traversing axis longitudinal to its core or vertical section of
this T-shape. The ends of the axes, or respective half-axes, are
secured to the ends of the fixed struts. This arrangement allows
the platform to be able to rotate around the latter axis by means
of the actuators and also, once this angular position has been
reached, or simultaneously with it, the platform can rotate around
the first shaft, simply by shortening or lengthening the amplitude
of the actuators by the appropriate magnitude and direction, which
is carried out by automatic electrical or mechanical control.
[0028] The solar tracker is furthermore complemented with a device
connected to the hydraulic system of the actuators, this device
being based on one or more pressure switches duly installed, which,
by virtue of the specific relation that exists between the pressure
and the stress, supply a signal that will indicate the exact moment
in which the platform for the solar tracker has to be located
horizontally so that it can offer the least resistance to the wind
and thereby avoid possible damage or breakage of the facility,
which could occur due to the effects of strong and/or hurricane
winds.
[0029] The pressure switch or switches will be connected to the
corresponding hydraulic system with the aim of detecting the
increase in pressure and acting as a consequence, sending a signal
or order to the actuators which produce the movement of the
platform, so that it can act and place the solar tracker in the
horizontal position.
[0030] By means of said device, in the event of any contingencies
like that mentioned, the system is successfully placed in a
horizontal position when a real force established as being the
safety limit force is reached, in accordance with the corresponding
calculation for the structure, and not in an estimated way as would
be the case of using wind gauges for that same purpose.
[0031] Likewise, on the basis of said device, the system (platform
for the solar tracker) will maintain its tracking position for the
sun, even in the case of high wind speeds when the wind blows in
directions parallel to the solar panels, with the consequent
increase in energy output.
[0032] Likewise, on the basis of the device, an emergency signal
will be generated that will preserve the safety of the solar
tracker, even in the case of vertical whirlwinds and when these
affect just part of the surface.
[0033] On the basis of said device a series of advantages are
achieved among which the following can be highlighted:
[0034] 1.--Economic saving, since the cost of a pressure switch is
less than that of a wind gauge.
[0035] 2.--Longer useful life of the system since there are no
moving parts that are constantly rotating whenever there is a
wind.
[0036] 3.--Greater reliability.
[0037] Provision has also been made for a device for regulating the
working pressure of the hydraulic system in the strict sense, on
the basis of which the movement of the platform for the solar
tracker is established.
[0038] Specifically, the regulating device has the aim of the
platform with the solar or photovoltaic panels being able at each
moment to adopt the appropriate orientation so that the sun's rays
impinge perpendicularly on those solar panels and thereby produce
the maximum exploitation of solar energy, indeed, the maximum
output from the solar tracker in question.
[0039] Specifically, the regulating device is intended to regulate
the working pressure of the hydraulic system effecting the movement
of the platform for the solar tracker, this regulation being
carried out in all cases in which, for whatsoever reason, a sudden
increase takes place in the hydraulic pressure is of the system,
with a momentary discharge of that overpressure occurring on
account of the actual regulating device.
[0040] In that regard, the regulation device will consist of a pair
of oleo-pneumatic expansion tanks, comprising separate
oleo-pneumatic dampers connected to the actual hydraulic system
facility, in parallel with the hydraulic fluid lines. Said
oleo-pneumatic damper tanks include an internal membrane as a
pressure regulating element, on the basis of which, when there
exists an overpressure in the system, a discharge of fluid takes
place via a calibrated hole provided in the actual damper or tank
in which two chambers are established, one for gas and the other,
for example, for oils, in such a way that the oil originated in the
overpressure produced by the hydraulic system is evacuated via that
hole.
[0041] On the basis of the regulating device being described, an
appreciable reduction is achieved in the forces exerted on the
fixed structure of the solar tracker, for example, in the case of
strong winds or in the case of a halt to the movement of the mobile
structure with the solar panels, since the halt is not
instantaneous, with the phenomena of fluttering and resonance that
can and usually are produced by the effect of the wind likewise
being reduced.
[0042] Finally, it can be said that the fluid lines to which the
oleo-pneumatic dampers of the regulating device are connected
include separate controlled non-return valves which order the
entrance of fluid to the corresponding actuation hydraulic cylinder
of the corresponding hydraulic system.
[0043] With the said regulating device, the advantages obtained are
numerous, and one can cite the following as being the most
important of them:
[0044] 1.--Appreciable reduction in the forces on the fixed
structure of the tracker, both in the case of a halt to the
movement of the mobile structure or platform with the solar panels,
and in the case of a gust of wind, permitting a small deformation
until it passes, since in the case of a halt to the movement of the
structure the stoppage itself is not instantaneous.
[0045] 2.--Virtually total reduction in the phenomena of fluttering
and resonance due to the effect of the wind on the system, since
the kinetic energy acquired by the hydraulic oil in the form of
heat is dissipated, avoiding unnecessary stresses on the system,
such as the danger of entering into resonance which would destroy
the facility or the actual solar tracker.
[0046] 3.--Since the oleo-pneumatic damper is in movement, the
critical speed for flutter increases appreciably.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] In order to facilitate the understanding of the
characteristics of the invention and forming an integral part of
this descriptive specification, some sheets of plans are attached
in which figures the following has been represented by way of
illustration and non-limiting:
[0048] FIG. 1.--Shows a diagram of the system of movement of the
bidirectional solar tracker, the object of the invention.
[0049] FIG. 2.--Shows a view similar to that of FIG. 1, including
the cylinders constituting the actuators in order to vary the
distances of two of the vertices of the platform from the
respective fixed points of the ground.
[0050] FIG. 3.--Shows a perspective view of the bidirectional solar
tracker of the invention, according to an example of practical
embodiment.
[0051] FIG. 4.--Shows a view in elevation of the assembly
represented in FIG. 3.
[0052] FIG. 5.--Shows a partial view in perspective of the
connection of the platform carrying the solar panels to the
corresponding support structure fixed to the ground.
[0053] FIG. 6.--Shows a schematic view in perspective of a frame on
which the platform with the panels will be located, said frame
resting on a fixed support structure in such a way that it can
rotate with two degree of freedom, the frame being in a position
that is practically horizontal (when the sun is overhead).
[0054] FIG. 7.--Shows a view like that of FIG. 6, in a rotated
position of the frame around the cross-member of the "T" support
for securing to the struts of the fixed structure.
[0055] FIG. 8.--Shows a view like that of FIG. 6, in a rotated
position around the core or vertical cross-member of the "T"
support.
[0056] FIG. 9.--Shows a view like that of FIG. 8, once the frame
has rotated, first around an axis and then around another
perpendicular axis.
[0057] FIG. 10.--Shows a schematic view corresponding to the device
incorporated by the solar tracker of the invention, in order to
prevent damage caused by the wind.
[0058] FIG. 11.--Shows the arrangement corresponding to the
regulating device for the pressure in the hydraulic system for
movement of the solar tracker forming the object of the
invention.
PREFERRED EMBODIMENT OF THE INVENTION
[0059] Making reference to the numbering adopted in the figures and
especially in relation to FIGS. 3 to 5, a platform 1 can be seen
carrying the solar panels 2, and connected to a support structure 3
fixed to the ground.
[0060] FIG. 1 shows schematically the platform 1 defined by four
vertices thereof, or four fixed points of it in the environs of the
point "O" in which said platform 1 can rotate, this point "O" being
located at a height "h" from the ground.
[0061] The X, Y, Z axes are the local coordinate axes, where:
[0062] OX is the axis parallel to the surface of the ground which
points in the westerly direction from the coordinate origin O, this
being the elevated point of the ground as a cusp of a rigid support
structure where the platform 1 rests, rotates and is orientated.
[0063] OY is the axis parallel to the surface of the ground
pointing in the southerly direction. [0064] OZ is the axis
perpendicular to the surface of the ground in the vertical
direction.
[0065] It can be noted that the initial position (prior to rotating
any axis) of said platform 1 corresponds in FIGS. 1 and 2 to the
rhomboid represented with a solid line.
[0066] Once rotated, the platform 1 is as defined by the points P1,
P2, P3, P4 in said FIGS. 1 and 2.
[0067] In order to arrive at this position: [0068] First a rotation
through angle .beta. is made about the fixed or ground axis O-G1
(this is in the southerly direction forming an angle .PHI. with the
axis O-Y). [0069] It then turns through an angle .alpha.around the
axis 0-Az (this axis turns as the previous rotation is made).
[0070] It is important to highlight the fact that the system only
has two degrees of freedom, which means that the points P1 and P2
are perfectly defined (for fixed geometric dimensions) with the two
angles of rotation.
[0071] This implies that between the distances D1 (from point P1 to
fixed point P1o), D2 (from point P2 to fixed point P2o), and the
angles .alpha. and .beta., there exists a one-to-one relation and
therefore for each pair of angles .alpha. and .beta. there only
exists one pair of distances D1 and D2, and vice versa.
[0072] Of course, there exist certain geometric limitations that
confine the movement of points P1 and P2 to certain regions of
space where this is possible (for example, there does not exist any
combination of angles in which is we can position said points 1 km
from the tracker).
[0073] With the correct choice of the geometric dimensions it is
possible to optimize both the correct tracking of the sun and the
reduction in stresses of the different mechanical elements of the
system.
[0074] According to the above, tracking of the sun is possible
bidirectionally with said movement by the tracker.
[0075] In order to achieve certain angles .alpha. and .beta., which
orientate the platform perpendicular to the sun, it will suffice to
calculate the distances D1 (from one of the vertices of the
rectangular platform or from a selected point of its periphery as
far as a fixed point on the ground) and D2 (from the other chosen
vertex or point as far as the other point of the ground) which
gives us those angles, and once these have been determined, it
suffices to locate an actuator or device, which can be a hydraulic
cylinder, a spindle or any other mechanical element that will
determine a distance for us, in order to fix the distances D1 and
D2.
[0076] The orientation of the platform is also possible by means of
tracking devices with light-point feedback, already existing on the
market, since, with increments in opposite sign of the distances D1
and D2 the angle .beta. manages to be varied (with a very small
variation in the angle .alpha.) and with equal increments of the
same sign the same thing occurs with the angle .alpha., so that the
variation in the other corresponding angle can be considered to be
much lower (for small movements) and in a few alternative
reiterated movements the platform manages to be centered on the
light point.
[0077] In order to achieve the desired variation of the platform 1,
as has been mentioned earlier, actuators can be used consisting of
hydraulic cylinders, spindles or other mechanical elements for
fixing and controlling the distance between those points (vertex of
the platform and securing point in the ground, there existing
another identical actuator between the other contiguous vertex and
the other fixed point of the ground). When the distances are varied
in a combined way in positive and negative values, as appropriate,
all the positions desired at any moment for the platform are
perfectly and precisely achieved.
[0078] In FIG. 2, the same platform 1 can be seen as in FIG. 1, but
including the actuators consisting of separate hydraulic cylinders
4, which extend between the vertices P1 and P2 of the platform 1
and respective fixed points of the ground referenced with P1o and
P2o, which are a distance "e" away. The line joining the said
points P1o and P2o is provided at a distance "d" from the vertical
of the point "O".
[0079] In a practical example, the following results have been
obtained:
TABLE-US-00001 Data day, place and dimensions Latitude 40.degree. N
Day 12 May Local time 8:18 Fi 50 R 1000 mm L 1000 mm h 1451 mm d
1186 mm e 150 mm Results Azimuth Sun 104.0.degree. Elevation sun
44.2.degree. Ec. Time 3.7 min .alpha. 25.0.degree. .beta.
50.1.degree. D1 1499.7 mm D2 2775.2 mm
[0080] In accordance with one of the ways of achieving the securing
of the platform 1, as represented in FIGS. 6 to 9, it can be said
that the platform 1 where the solar panels are mounted is created
from a frame 5 with a support, on the structure 3', swivel type,
permitting a suitable orientation with two degrees of freedom on a
central support located in the upper part of the fixed structure 3'
of the support for the entire platform 1.
[0081] As can be seen, the frame 5 presents stringers 6 and
cross-members 7 and 8, and can rotate around the axis 9 which is
traversed by the cross-member 10' of a "T" support 10, as a
securing element between the platform 1 and the fixed structure
3'.
[0082] The ends of the axis 9 are secured to the reinforcements 6'
of the stringers 6.
[0083] The "T" support 10 can rotate around the axis 11 running
along the interior of the vertical core or section 12 of that
support 10, due to having the ends of the axis 11 secured to the
struts 13 and 14 emerging from the fixed structure 3'. This axis
11, referenced in its geometric axis, can be materialized by two
half-axes 15 for securing to the respective struts 13 and 14 of
which only the linkage to the support 13 of FIG. 6 can be seen.
[0084] With this arrangement, the frame 5 can be orientated in any
direction and angle in order to effect the solar tracking.
[0085] Starting from the position shown in FIG. 6, the frame 5 can
rotate in the direction of the arrows 16, without the "T" support
moving, around the geometric axis 9, reaching for example the
position of FIG. 7. If, starting from the same position of FIG. 6,
it were to rotate around the geometric axis 11 in the direction of
the arrow 17, the frame 5 would acquire the position of FIG. 8.
These rotations in two axes define combined movements with two
degrees of freedom, with the assembly functioning as if the frame 5
were connected in a swivel joint. In FIG. 9 a position can be seen
due to combined rotation around the two axes 9 and 11.
[0086] The movements are achieved with just the two cylinders or
actuators 4' connected by their lower ends to separate fixed points
of the structure 3' and via their upper ends to the securings 18,
also of the swivel kind, in order to be able to adopt any angle.
Depending on the extension or retraction of the actuators 4'
(hydraulic cylinders in this case), varying the distances between
the points they join, in both positive and negative values, as
appropriate, the position desired for the platform 1 is achieved at
each moment.
[0087] FIG. 10 shows a diagram corresponding to the device for
prevention of damage occasioned by the wind, which device includes
a pressure switch 19 connected to one of the lines 20 corresponding
to the hydraulic system intended for supplying the actuators 4 or
4' applied in the solar tracker of the invention, specifically for
carrying out the change of position of the solar panels located on
the platform in the horizontal location in the presence of strong
winds, in other words winds that are above a pre-established
value.
[0088] Fitted in those hydraulic fluid lines 20 are some non-return
valves 21, with the actual hydraulic system including a cylinder 22
and its corresponding piston 23 displaceable in its interior, and
linked to the respective rod 24, this cylinder being used by the
actuators 4 or 4' via which the transmission of the corresponding
movement is carried out.
[0089] The device described and shown in those FIGS. 6 to 9 is
intended so that, under certain circumstances in which the force of
the wind is greater than a predetermined value that could damage
the mechanisms of the solar tracker, it acts so that the hydraulic
system locates the platform and therefore the solar panels of the
solar tracker in a horizontal position, an operation that is
carried out after receiving the corresponding signal sent by the
pressure switch or switches 19, indicating the exact moment when
the platform for the solar panels has to be located horizontally
and thereby offer minimum resistance to the wind, thus preventing
any possible damage or breakage of the mechanisms of the solar
tracker.
[0090] Finally, FIG. 11 shows the device for regulating the
pressure in the hydraulic system for actuation of the platform
carrying the solar panels for the solar tracker of the invention,
the hydraulic system itself including the corresponding hydraulic
fluid lines 19' along with the oil cylinder 22' with the piston 23'
and the rod 24' for transmitting the force to the corresponding
mechanism for actuation on the platform of the solar tracker.
[0091] So, the regulating device itself comprises a pair of
oleo-pneumatic dampers 25 defined by separate oleo-pneumatic
expansion tanks, in which are established a gas chamber 26 and an
oil chamber 27 with the interposition of a deformable membrane 28,
the latter in each case constituting the regulating element for the
internal pressure of the oleo-pneumatic tank or damper 25,
provision having been made for each of those oleo-pneumatic dampers
25 to have a calibrated hole 29 for discharge of the fluid, in this
case oil, corresponding to the chamber 27.
[0092] The hydraulic fluid lines 19' to which the oleo-pneumatic
dampers 25 are connected include respective non-return valves
30.
[0093] The oleo-pneumatic dampers 25 are mounted in parallel with
the hydraulic fluid lines 19', the calibrated hole 29 being
provided for filling and emptying, such that in the event of a
sudden increase in pressure in the corresponding hydraulic system,
a momentary discharge is possible via that calibrated hole 29 for
each oleo-pneumatic damper 25, all of which permits in regulation
to be carried out of the working pressure in the hydraulic system
for movement of the solar tracker under consideration, the movement
of the platform and therefore of the solar panels being performed
in order to periodically modify the position of the latter and
achieve the maximum solar power at each moment.
* * * * *