FIELD OF THE INVENTION
The present invention relates to Solar Thermal Sun Tracker for mounting array of
Solar Photovoltaic Panels. In particular, the invention relates to a modified Sun
tracker utilizing thermal radiation from the Sun for tilting towards the Sun during
the day and to reorient itself to face the Sun in the morning after the sun-rise.
More particularly, the invention relates to an automatically re-orientable modular
type solar thermal Sun tracker for photovoltaic arrays for deploying in the MW
capacity, stand-alone distributed solar power systems and solar water pumping
systems.
BACKGROUND OF THE INVENTION
Solar Thermal Sun Tracker is disclosed in Indian Patent application no
818/KOL/2010 and Solar Passive Trackers illustrated in US Patent 4476854,
2004/0112373, 4175391, 4275712 and 4027651. Such trackers employ a pivotal
frame, having at least one each canister at east end and west end which are
interconnected through their lowers ends. Shadow bars / covers overlie the outer
half of each canister to shade the proximal canister from direct sunlight when the
sun is not directly above the canister surface. A volatile fluid and its vapor is
contained within the canisters, and as the Sun moves from East to West, the
east canister gets heated and forces the volatile fluid into the west canister,
thereby tilting the frame westward to follow the Sun. The frame is balanced and
points directly at the Sun when equal sunlight falls on each canister.
This principle of operation is disclosed in Indian Patent Application no
818/KOL/2010. The device mentioned in the patent is mounted on a single pole
structure and follows the Sun from East to West and then remains oriented
overnight facing the west. It reorients itself in the next day morning after the

sunrise. However, the single pole support structure is required to be very sturdy
and bulky so as to withstand the high wind loads.
US Patent No. 4275712 to Stephen C. Baer provides heat collecting surfaces
which enables transfer of the liquid between the canisters, specifically in the
morning to assist repositioning of the canister to face the sun.
US Patent No. 4175391 to Stephen Baer proposes an automatic night time
resetting mechanism in a Sun tracker by providing at least two containers with
low boiling point liquid having differential cooling rates. When the Sun sets, the
air cools and the evaporated fluid in the containers condenses. By regulating the
rates of cooling, the east container is cooled faster than the west container
which causes transfer of fluid from the west container because of higher
pressure of the vaporized liquid in the west container. The transfer of the fluid to
the east container makes it heavier and tilt the array to the East to await rising
of the Sun.
The Gas Spring Solar Tracker disclosed in US Patent No. 4476854 relates is a
solar tracker and in particular a solar tracker utilizing a gas spring to reorient the
tracker when sunlight is not available.
US Patent 2004/0112373 Al by Derek Djeu, on Passive Solar Tracker for a solar
concentrator represents one approach to a passive solar tracking system capable
of focusing solar radiation onto a small target at all times of the year. The device
consists of a two-axis gimbal system with its orientation controlled by
interconnected ballasts filled with a volatile fluid. Accurate focusing realized by
ensuring that each significant mass element is balanced by another element of
equal mass equidistant from and diametrically opposite to it through the point of
intersection of the two gimbal axes for all possible orientations of the system.

The Solar Energy Powered Sun Tracker described by Roland W Robbins in the US
Patent 4027651 relates to an apparatus for causing a solar energy collector to
constantly follow the sun. the invention utilizes the sun's radiant energy reflected
from a mirror device, which differentially heat a plurality of fluid-containing
reservoirs resulting generation of a differential pressure to rotate the apparatus
and the collector.
The principal advantage of the Solar Trackers known in the art is their ability to
track the Sun in a totally passive fashion. However, considerable difficulty is
encountered to limit the tilting of the tracker beyond a specified angle. Further,
difficulty is encountered when the tracker hits the limiting point due to the
sudden wind force and creates noise and vibrations in the supporting structure.
Additionally difficulty is encountered in the single pole support structure to
withstand the high wind loads causing deflections of the pole structure.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose an automatically re-
orientable modular type solar thermal Sun tracker for photovoltaic arrays
applicable for deploying in the MW capacity, stand-alone distributed solar power
systems and solar water pumping systems, which eliminates the disadvantages
of prior art.
Another object of the present invention is to propose an automatically re-
orientable modular type solar thermal Sun tracker for photovoltaic arrays, which
is provided with a plurality of array of photo voltaic (PV) modules, to allow the
Sun rays to fall almost always perpendicular to the surface.
A further object of the present invention is to propose an automatically re-

orientable modular type solar thermal Sun tracker for photovoltaic arrays, which
is equipped with a stopper for limiting the angle of rotation of the tilting frame
beyond a specified value on East and West side of the rotating axis.
Yet another object of the present invention is to propose an automatically re-
orientable modular type solar thermal Sun tracker for photovoltaic arrays, in
which vibration dampener at the contact point of the stopper is provided for
dampening the noise and vibration generated when the tracker hits the stopper
due to sudden high winds.
A still another object of the present invention is to propose an automatically re-
orientable modular type solar thermal Sun tracker for photovoltaic arrays, which
provides increased output from the PV-modules.
A further object of the present invention is to propose an automatically re-
orientable modular type solar thermal Sun tracker for photovoltaic arrays, which
is enabled to reorient itself in the morning by gravitational force generated by a
differential liquid pressure which moves the fluid containers of the trackers to
and fro due to the solar heating.
A still further object of the present invention is to propose an automatically re-
orientable modular type solar thermal Sun tracker for photovoltaic arrays, which
is simple, cost effective, maintenance free and reliable.
Yet further object of the present invention is to propose an automatically re-
orientable modular type solar thermal Sun tracker for photovoltaic arrays, which
are mounted on a two pole supporting structure with more rigidity and strength
against high winds.

SUMMARY OF THE INVENTION
Accordingly, there is provided an automatically re-orientable modular type solar
thermal Sun tracker for photovoltaic arrays for deploying in the MW capacity,
stand-alone distributed solar power systems and solar water pumping systems
comprising:
a support device consisting of one each top, middle and bottom portion; the top
portion formed of a panel fixing frame bolted/welded to a rigid shaft detachably
attaching a plurality of photovoltaic (PV) modules; the middle portion consisting
of two supporting pole members with a base plate affixed at the lower end; the
upper end of the each pole member having a plummer block bearings affixed,
through which said rigid shaft is connected to the two pole members; at the top
end of the middle portion of the each pole member, a stopper is fixed to limit the
angle of rotation of the panel fixing frame on East and West side; the stoppers
provided with vibration dampeners to dampen the vibration and noise when the
tracker hits the stopper due to sudden high winds; the bottom portion of the
pole members accommodating the base plate rigidly fixed to a concrete base; at
least two containers containing volatile fluid located at the extreme ends of the
panel fixing frame which rotates along East to West direction with the axis of
rotation oriented North - South; the containers flowably connected to each other
via an inter-connecting tube for fluid-transfer; a plurality of shadow casting
covers provided to the containers such that depending on the position of the
sun, the covers allow the respective container distal to the sun rays to receive
higher impingement causing temperature differential of the volatile liquid in two
containers which leads to inter-transfer of the liquid between the containers
including application of gravitational force in the containers leading the tracker to
automatically tilt from West to East direction in the morning after the sunrise,

and East to West direction during the day time; the tracker remains facing the
West direction after the Sun set.
The present invention thus provides a device for tracking the Sun during the day
and equipped with a plurality of array of Solar Photo Voltaic panels on a tiltable
frame so that the panel frame faces the Sun continuously and produces about
25-35% more electrical energy when compared to the PV panel array mounted
on a fixed structure.
The tracker is provided with at least two containers to withstand the pressure of
the volatile fluid. The shape of the container can be of any geometry (cross
section) for example - circular, square, rectangular, or any other irregular shape.
The containers are placed at the extreme ends of the tracker frame for deriving
maximum gravitational force due to differential quantity of liquid disposed in the
containers. The containers are coated with black paint to absorb maximum
energy incident on the surface and also to radiate maximum heat energy from
the surface when under shadow.
The containers are pressure and vacuum tested before filling with the working
fluid so that there is no leakage, and enabled to provide a reliable and
maintenance-free operation.
The surface of the trackers frame is almost fully covered with a plurality of array
of PV panels so that a maximum number of panels can be accommodated; at the
same time a gap is provided between the adjacent panels to allow the flow of air
and reduce the wind forces.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows a side view of the Modified Solar Thermal Sun Tracker Sun

Tracker including the details of the PV array, supporting structure, two pole
structure and concrete foundation according to the invention.
Figure 2 shows a top view of the modified solar thermal sun tracker of the
invention showing the details of PV panels mounted on the tracker, containers
shadow covers, shock absorber and springs assembly and inter-connecting tube.
Figure 3 shows front view of the panel fixing frame, PV panels, liquid containers,
shock absorber and springs assembly, stopper and vibration damper.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In figure 1, a preferred embodiment of the solar thermal Sun Tracker according
to the present invention is illustrated which consists of a device supporting an
assembly of two pole structure members (5), a plurality of Photovoltaic panels
(1) at least two liquid containers (3), an inter-connecting tube (11), at least two
shadow covers (4), a plurality of shock absorber and spring assemblies (9),
Plummer block and bearings (6), and a working fluid.
The supporting device consists of a panel fixing frame (2) where the PV panels
(1) are mounted using a set of nuts and bolts. The Plummer block bearings (6)
are fixed on the top end of the supporting two pole assembly (5). The panel
fixing frame (2) is fixed to the rigid shaft (8) which is mounted on the two
supporting pole members (5) through the Plummer block bearings (6). The two
ends of the rigid shaft (8) pass through the bearings fitted in the Plummer blocks
(6). The top end of the middle portion of the pole assembly (5), a stopper (10) is
fixed to limit the movement angle of the panel fixing frame (2) on East and West
side. The bottom end of the pole assembly (5) with the base plate is fixed to the
concrete foundations (7) in the ground.

The containers (3) preferably of circular cross section of desired diameter, to
accommodate required quantity of working fluid, are fabricated. The containers
(3) are fitted to the panel fixing frame (2) through a set of brackets / clamps.
The Shadow covers (4) are fixed to the containers (3) by a set of brackets /
clamps and bolts. The inter-connecting tube (11) is also connected to the
containers (3) by welding / brazing or threaded joints.
The assembly of the containers (3) and inter-connecting tube (11) is pressure
tested and leakages if any are sealed. The containers (3) are vacuum tested. The
containers (3) are painted black to absorb maximum solar radiation and also to
radiate maximum energy when it is under shadow.
The containers (3) are fixed to the panel fixing frame (2) as shown in the figure
2 by the set of brackets/clamps and bolts. The containers (3) are charged with a
volatile working fluid such as R134a and sealed. The shadow covers (4) are fixed
to the containers (3) as shown in figures 2 and 3 with set of the nuts and bolts.
The shadow covers (4) cast shadow on half of the container (3) surfaces when
the tracker is facing the Sun. Under this condition, both the containers (3) are
equally heated and the pressure inside the containers (3) is substantially equal.
The shock absorber and spring assembly (9) in respect of coil diameter, were
diameter and spring constant is selected depending on the capacity of the array
of PV panels (1) installed on the trackers, and fitted to the tracker as shown in
figure 3 connecting the panel fixing frame (2) and a bracket extended from the
supporting pole assembly (5) by means of a set of bolts and nuts. The panel
fixing frame (2) along with the PV panels (1) rotate about the axis of the rigid
shaft (8) fixed at the plummer block bearings (6). The shock absorber and spring
assembly (9) resist movement of the tracker i.e. panel fixing frame (2) along
with the PV panels (1) due to sudden winds or any other reasons. The shock

absorber and spring assembly (9) also allow very slow motion of the tracker due
to the gravitational force because of the differential liquid held in the containers
(3). At the top end of the middle portion of the pole assembly (5), a stopper (10)
is fixed to limit the angle of rotation of the panel fixing frame (2) on East and
West side; the stoppers (10) are also provided with a vibration dampener (12) to
dampen the vibrations and noise when the tracker hits the stopper (10) due to
sudden high winds.
The inventive Solar Thermal Sun Tracker as shown in the figure 1 is positioned in
such a way that the axis of rotation is oriented towards North and South
direction, so that the tracker can rotate east and west direction respectively.
Once the tracker is positioned, depending on the location of the sun, the
proximal container (3) gets more shadow in comparison to the distal container
(3). This results in higher heating of the distal container and thereby increasing
the liquid pressure inside it due to additional vaporization. The increase in the
pressure inside the distal container pushes some liquid to the proximal container
depending on the pressure difference. Thus the proximal container becomes
heavier and rotates the tracker towards the Sun till the shadow by the cover (4)
on both the containers (3) is identical. As the Sun moves from East to West
direction, the tracker follows the sun till the evening. The tracker remains facing
West during the evening and the next day morning. When the Sun rises in the
East, the Sun rays directly fall on the west side container (3). This operation
enables heating of the west side container and thereby pressurizing the
container (3) because of the vapors generated by the working fluid. The
pressure difference between the containers (3) pushes the liquid from west side
container (3) to the east side container (3) through the interconnecting tube
(11).

WE CLAIM
1. An automatically re-orientable solar thermal sun Tracker for tracking the
Sun from morning to evening to produce increased power output,
comprising:
a supporting device consisting of one each top, middle and bottom
portion, the top portion formed of a panel fixing frame fixed on a rigid
shaft detachably attaching a plurality of photovoltaic (PV) modules, the
middle portion consisting of two pole members with a base plate affixed
at a lower end, at the top end of the middle portion of the pole members,
one each stopper angle is fixed to limit the movement angle of the panel
fixing frame on East and West side, the stoppers provided with vibration
dampers to dampen the vibrations and noise in case the tracker hits the
stopper due to sudden high winds, the upper end of the each pole
member having a plummer block bearings in which a shaft rigidly
connected to the two pole members, the bottom portion of the pole
member assembly accommodating the base plate of the middle portion
rigidly fixed to a concrete base; at least two containers having volatile
fluid located at the extreme ends of the panel fixing frame which rotates
along East to West direction with the axis of rotation oriented North -
South direction, the container flowably connected to each other via an
inter-connecting tube for fluid-transfer; a plurality of shadow casting
covers provided to the container such that depending on the position of
the sun, the covers allow the respective container distal to the sun rays to
receive higher impingement generating a temperature differential of the
volatile liquid in two containers which leads to inter-transfer of the liquid
between the containers including application of gravitational force in the
containers which causing the tracker to automatically tilt from West to

East direction in the morning after the sunrise, and East to West direction
during the day time, the tracker facing the west after the Sun set.
2. The sun tracker as claimed in claim 1, wherein the panel fixing frame
along with the SPV array and the rigid shaft are mounted on two support
pole members, rotating in East to West direction and the axis aligned
North to South direction.
3. The sun tracker as claimed in claim 1 and 2, wherein the trackers
mounted on two pole support members is enabled to withstand high
winds.
4. The sun tracker as claimed in claim 1, wherein the SPV arrays are
provided with a stopper angle at the top end of the pole members to limit
the movement angle of the panel fixing frame on East and West side.
5. The sun tracker as claimed in claim 1, wherein the stoppers are provided
with vibration dampers to dampen the vibrations and noise in case the
tracker hits the stopper due to sudden high winds.
6. The sun tracker as claimed in claim 1, wherein the covers are bent in an
angle to provide a shade on half portion of the containers when it is facing
the sun and allow a reflection of the sun rays to heat the containers.
7. The sun tracker as claimed in any of the preceding claims, comprising
shock absorber and spring assembly to absorb shock loads due to wind or
other environment hazards and allow slow movement of the tracker
during the tracking which improves the tracking accuracy and enables re-

orientation of the tracker to the original position after a change in position
due to disturbing force generated by abnormal wind flow.
8. The sun tracker as claimed in claim 1, wherein it is configured to be
modular type for mounting array of SPV panels of capacity from 1 to 5 kW
peak.
9. The sun tracker as claimed in claim 1, wherein the trackers are enabled to
generates 25 to 35 % more energy compared to the array of SPV panels
mounted on fixed tilt structures.
10. The sun trackers as claimed in any of the preceding claims, wherein the
panels fixing frame including the PV-panels rotates about the axis of the
rigid shaft.

ABSTRACT

The invention relates to an automatically re-orientable solar thermal sun Tracker for
tracking the Sun from morning to evening to produce increased power output,
comprising: a supporting device consisting of one each top, middle and bottom portion,
the top portion formed of a panel fixing frame fixed on a rigid shaft detachably attaching
a plurality of photovoltaic (PV) modules, the middle portion consisting of two pole
members with a base plate affixed at a lower end, at the top end of the middle portion
of the pole members, one each stopper angle is fixed to limit the movement angle of the
panel fixing frame on East and West side, the stoppers provided with vibration dampers
to dampen the vibrations and noise in case the tracker hits the stopper due to sudden
high winds, the upper end of the each pole member having a plummer block bearings in
which a shaft rigidly connected to the two pole members, the bottom portion of the pole
member assembly accommodating the base plate of the middle portion rigidly fixed to a
concrete base; at least two containers having volatile fluid located at the extreme ends
of the panel fixing frame which rotates along East to West direction with the axis of
rotation oriented North - South direction, the container flowably connected to each
other via an inter-connecting tube for fluid-transfer; a plurality of shadow casting covers
provided to the container such that depending on the position of the sun, the covers
allow the respective container distal to the sun rays to receive higher impingement
generating a temperature differential of the volatile liquid in two containers which leads
to inter-transfer of the liquid between the containers including application of
gravitational force in the containers which causing the tracker to automatically tilt from
West to East direction in the morning after the sunrise, and East to West direction
during the day time, the tracker facing the west after the Sun set.