FIELD OETHE INVENTION
The present invention relates to Solar Thermal Sun Tracker for mounting array
of Solar Photovoltaic panels (SPVS). In particular, the invention relates to a
Horizontal axis 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, 483/KOL/2013 and Solar Passive Trackers illustrated in US
Patents 4476854, 2004/01123.73, 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
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 of the solar thermal sun tracker is disclosed in Indian
Patent Application Nos. 818/KOL/2010 and 483/KOL/2013. The device described
in the prior art, are mounted on a single pole or double pole Structures and
follow the Sun from East to West and then remains oriented overnight facing
the west. The device reorients itself in the next day morning after the Sunrise.

However, the single pole or double pole support structures are subjected
to frequent oscillations due to high wind loads, because of which, the
output energy from the SPV panels is reduced.
US Patent No. 4275712 to Stephen C. Baer provides heat collecting
surfaces which enable 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 Bacr 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 tilts the array to the East to await rising of the Sun.
The Gas Spring Solar Tracker disclosed in US Patent No. 4476854 relates
to 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, teaches a Passive Solar tracker for
a solar concentrator. In one aspect of the invention, a passive solar tracking
system is disclosed which is 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 i s realized by ensuring that each
significant mass element is balanced by another element of equal mass
equidistant from and diametrically opposite to it through a 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 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. Additionally difficulty is encountered in the single pole
and/or double pole support structures because of swinging action due to
the high wind loads causing variable output from the SPV Panels.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose an automatically re-
orientable solar thermal Sun tracker for stand-alone distributed solar power
systems, which eliminates the disadvantages of prior art.
Another object of the present invention is to propose an automatically re-
orientable solar thermal Sun tracker for stand-alone distributed solar power
systems, which is provided with a plurality of array of photo voltaic (PV)
modules, to allow the Sun rays to always fall substantially perpendicular to the
surface.
A still another object of the invention is to propose an automatically re-
orientable solar thermal Sun tracker for stand-alone distributed solar power
systems, in which an array of SPV panels are mounted on a supporting
structure rotating in a horizontal axis with each of the SPV panels are inclined at
a latitude angle with the horizontal axis so that the height of the complete
assembly above the ground is reduced including the effect of winds on the
tracker.

Yet another object of the present invention is to propose an automatically re-
orientable solar thermal Sun tracker for stand-alone distributed solar power
systems, 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.
A further object of the present invention is to propose an automatically re-
orientable solar thermal Sun tracker for stand-alone distributed solar power
systems, in which dampeners at the contact point of the stopper are provided
for dampening the noise and vibration generated when the tracker hits the
stopper due to sudden high winds.
A still further object of the present invention is to propose an automatically re-
orientable solar thermal Sun tracker for stand-alone distributed solar power
systems, which provides increased output from the PV-modules.
A further object of the present invention is to propose an automatically re-
orientable solar thermal Sun tracker for stand-alone distributed solar power
systems, which is reorientable in the morning by gravitational force generated
by a differential liquid pressure which moves the fluid containers of the trackers
to and from due to the solar heating.
A still further object of the present invention is to propose an automatically re-
orientable solar thermal Sun tracker for stand-alone distributed solar power
systems, which is simple, cost effective, maintenance free and reliable.
Yet further object of the present invention is to propose an automatically re-
orientable solar thermal Sun tracker for stand-alone distributed solar power
systems, which is mounted at low hight from the ground on the supporting
structure with SPV panels, to restrict oscillations/swings due to high winds.

SUMMARY OF THE INVENTION
Accordingly, there is provided an automatically re-orientable solar thermal Sun
tracker for stand-alone distributed solar power systems,the system comprising :
a support device consisting of one each top, 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 bottom
portion consisting of multiple supporting pole members with base plates
affixed at the lower end; a plummer block bearing is provided at the upper end
of the pole member through which said rigid shaft is connected to the pole
members; a stopper is fixed at the top end of the pole member to limit the
angle of rotation of the panel fixing frame on East and West side; a plurality of
vibration dampeners are provided on the stoppers to dampen the vibration and
noise when the tracker hits the stopper due to sudden high winds; 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 being 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 cover allowing the respective container distal to the sun rays to
receive higher impingement causing temperature differential of the volatile
liquid in the two containers causing inter-transfer of the liquid between the
containers including application of gravitational force in the containers, wherein
the tracker is automatically tiltable along the West to East direction in the
morning after the sunrise, and along the 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 horizontal axis Solar Thermal Sun Tracker
including the details of the PV array, multiple pole structure and concrete
foundation according to the invention.
Figure 2 shows a top view of the horizontal solar thermal sun tracker of the
invention showing the details of PV panels mounted on the tracker,
containers, Plummer block & bearings, shaft.
Figure 3 shows front view of the horizontal solar thermal sun tracker
of the invention showing the details of liquid containers, shock absorber
and springs assembly, shadow covers, inter connecting tube and
stopper cum 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 multiple 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), a Plummer block with 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 multiple pole
assembly (5). The panel fixing frame (2) is fixed to the rigid shaft (8) which
is mounted on the multiple 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 bottom
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) a base plate is fixed to the concrete
foundations (7) in the ground.
The containers (3) preferably are of circular cross section with desired
diameter, to accommodate required quantity of working fluid. 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 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,
wire 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 a horizontal 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 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, and bottom portion, the
top portion formed of a panel fixing frame on a horizontal axis rigid
shaft detachably attaching a plurality of photovoltaic (PV) modules, the
bottom portion consisting of multiple pole members with a base plate
affixed at a lower end, at the top end of the bottom portion of the pole
members, one each stopper 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 multiple pole members, the bottom portion of
the pole member assembly accommodating the base plate 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 horizontal axis of rotation oriented North-
South direction, the container flowably connected to each other via an
interconnecting 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 multiple
support pole members rotating on a horizontal axis in East to West
direction and wherein the axis is aligned at North to South direction.
3. The sun tracker as claimed in claims 1 or 2, wherein the trackers
mounted on the multiple pole support members are enabled to withstand
high winds, with horizontal axis rotation and low level installation of the
array assembly from the ground.
4. The sun tracker as claimed in one of claims 1, 2 or 3, wherein the
oscillations of the tracker frame due to excessive wind are reduced
because of the horizontal axis mounting of the panel frame.
5. The sun tracker as claimed in claim 1, wherein the SPV arrays are
provided with a stopper at the top end of the pole members to limit the
movement angle of the panel fixing frame on East and West side.
6. 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.
7. 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.

8. 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 wherein
the trackers are re-oriented to the original position after a change in
position due to disturbing force generated by abnormal wind flow.
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 having the PV-panels rotates about the horizontal axis
of the rigid shaft.
11. The sun trackers as claimed in any of the preceding claims, wherein an
array of SPV panels mounted on supporting structure rotating in a
horizontal axis and wherein each SPV panel is inclined at a latitude angle
with the horizontal axis to reduce the height of the complete assembly
above the ground and decrease the effect of winds on the tracker.

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, and
bottom portion, the top portion formed of a panel fixing frame on a horizontal
axis rigid shaft detachably attaching a plurality of photovoltaic (PV) modules,
the bottom portion consisting of multiple pole members with a base plate
affixed at a lower end, at the top end of the bottom portion of the pole
members, one each stopper 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
multiple pole members, the bottom portion of the pole member assembly
accommodating the base plate 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 horizontal axis of
rotation oriented North-South direction, the container flowably connected to
each other via an interconnecting 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.