FIELD OF INVENTIONS
The present invention relates to a solar tracker and in particular a Sun tracker
utilizing the 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 solar thermal
Sun tracker.
BACKGROUND OF THE INVENTION
The Solar Passive Trackers are illustrated in US Patents 4476854, 2004/0112373,
4175391, 4275712, 4027651 and 2999943. Such trackers employ a pivotal
frame, having a canister at least one east and one west at each end which are
inter-connected through their lower 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 (Freon 11) 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,
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 US Patent No. 2999943 to C W Geer in 1961. The device
of the Geer Patent however, follows the sun from East to West and then remains
oriented overnight facing the west. It must be manually reset towards east
direction during the night or await rising of the sun sufficiently high above the
horizon in the morning so that the Sun rays reach over the high eastern shield

and reach the western container to start causing vaporization. A substantial
portion of the morning sunlight therefore is lost before an orientation is
achieved.
US Patent No. 4275712 to Stephen C. Baer provides an improvement of Gear's
device by adding heat collecting surfaces which enables transfer of the liquid
between the canisters, specifically in the morning to assist repositioning of the
canisters 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 of 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 enabled to faster cooling than that of the
west container which causes transfer of fluid from the west container because of
the 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 to a
solar tracker and in particular a solar tracker utilizing a gas spring to reorient the
tracker when sunlight is not available.
The Solar Energy Powered Sun Tracker described by Roland W Robbins in the

Publication in the year 1977 constitutes 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 its ability to
track the Sun in a totally passive fashion. However, considerable difficulty is
encountered in reorienting the tracker of prior art towards the East in the
morning on its own and when the position is disturbed due to wind or any other
reason. Further difficulty is encountered in preventing the tracker frame from
tipping on the heavier side when the center of gravity of the tracker frame is not
below the axis of rotation.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a Solar Thermal Sun
Tracker to automatically track the Sun from morning to evening facing the Sun,
which eliminates the disadvantages of prior art.
Another object of the present invention is to propose a Solar Thermal Sun
Tracker to automatically track the Sun from morning to evening facing the Sun,
which is provided for plurality of photo voltaic (PV) modules, so that the Sun rays
fall almost always perpendicular to the surface.

A still another object of the present invention is to propose a Solar Thermal Sun
Tracker to automatically track the Sun from morning to evening facing the Sun,
which provides increased output from the PV-modules.
A further object of the present invention is to propose a Solar Thermal Sun
Tracker to automatically track the Sun from morning to evening facing the Sun,
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 tracker to
and fro due to the solar heating.
A still further object of the present invention is to propose a Solar Thermal Sun
Tracker to automatically track the Sun from morning to evening facing the Sun,
which is simple, cost effective, maintenance free and reliable.
Yet further object of the present invention is to propose a Solar Thermal Sun
Tracker to automatically track the Sun from morning to evening facing the Sun,
which uses and Ozone-friendly fluid for reorienting the fluid-containers due to
generation of differential pressure from differential heating by the solar radiation.
SUMMARY OF THE INVENTION
Accordingly, there is provided an automatically reorientable Solar Thermal Sun
Tracker for tracking the Sun from morning to evening to produce increased
power output, comprising: a supporting structure consisting of one each top,

middle and bottom portion, the top portion formed of a panel fixing frame
detachably attaching a plurality of photovoltaic (PV) modules, the middle portion
constituting a pipe structure with a base plate affixed at a lower middle end, the
upper middle end of the middle portion having a shaft rigidly connected to a
shaft fixing frame, the shaft extending between at least two bearings provided to
the panel fixing frame, the bottom portion of the structure accommodating the
base plate of the middle portion via a base frame; at least two containers having
Ozone-friendly volatile fluid placed 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 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; and a capillary tube provided inside the
container passing through the inter-connecting tube, to allow flow of liquid from
one container to the other container, making it possible for 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 after the sun set.
The present invention thus provides a device for tracking the Sun during the day
and equipped with plurality of Solar Photo Voltaic panels on a tiltable frame so

that the panel face the Sun continuously and produce about 25% more electrical
power when compared to the PV panels mounted on a fixed structure.
After following the sun from morning to evening, the tracker rests on the west
side. It reorients itself and turns to East next day morning within 15 -20 minutes
from the sun-rise.
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 for
example, circular, 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.
A capillary tube is provided inside the container, which passes through an
interconnecting tube. The capillary tube allows an easy flow of the liquid from
one container to the other container. It further enables a faster turning of the
tracker from west to east direction in the morning after the sunrise.
The surface of the tracker frame is almost fully covered with a plurality of PV

panels so that a maximum number of panels can be accommodated. The axis of
rotation of the frame is below the top surface of the panels so that the shaft
does not cast any shadow on the panels. In doing so, the centre of gravity of
panels and the structure is above or at the same level of the axis of rotation
which causes tipping of the tracker on a heavier side. This makes it difficult to
track the sun continuously; instead the tracker changes the position frequently
from East to West and vice versa. This difficulty is further mitigated by adapting
balancing springs.
A gap each is maintained between the containers and the PV panels to avoid
transfer of heat between them so that only the solar radiation received by a
container would control the heating of fluid and the tracker. It also helps to
receive the solar radiation from the bottom side in the morning for early wake up
(turning to east). The containers are placed in such a way to avoid shadow
casting by the PV panels.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows a side view of the Solar Thermal Sun Tracker including the details
of the supporting structure according to the invention.
Figure 2 shows an elevation and plan view of the solar thermal sun tracker of the
invention showing the details of PV panels mounted on the tracker, containers
shadow casting covers, shock absorbers, springs and inter-connecting tube.

Figure 3 shows various positions of the solar thermal sun tracker according to
the invention during the day
Figure 4 shows a reoriented position of the Sun Tracker of the invention in the
early morning
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 supporting structure
(2), a plurality of Photovoltaic panels (1) at least two containers (6), an inter-
connecting tube (9), a capillary tube (8), at least two shadow casting covers
(11), a plurality of shock absorbers (12), at least two spring (13) bearings (5),
charging valve (22), several fixing bolts and nuts (15, 19, 21), and a working
fluid.
The supporting structure consists of a panel fixing frame (2) where the PV panels
(1) are mounted using a first set of nuts and bolts (21). The bearings (5) are
fixed in the panel fixing frame (2). The middle part of the structure constitutes a
pipe with a base plate (16) to which a shaft (3) is welded to a shaft fixing frame
(4) at the top end. The two ends of the shaft (3) pass through the bearings (5)
fitted in the panel fixing frame (2). The bottom end of the pipe with the base
plate (16) is fixed to a foundation plate or attached to a base frame (17) to resist
the tilting from the wind force.

The containers (6) preferably of circular cross section of desired diameter, to
accommodate required quantity of working fluid, are fabricated. A first set of
Brackets (7) are welded/brazed to the containers (6) for fixing the containers (6)
to the panel fixing frame (2). Cover fixing nuts (10) are welded/brazed to the
containers (6) for fixing the shadow casting covers (11). The inter-connecting
tube (9) is also connected to the containers (6) by welding/brazing or threaded
joints. The capillary tube (8) is inserted into the containers (6) passing through
the inter-connecting tube (9). The containers (6) are fixed/welded/brazed with
the charging nipple (22). The assembly of the containers (6) and inter-
connecting tube (9) is pressure tested and leakages if any are sealed. The
containers (6) are vacuum tested. The containers (6) and the inter-connecting
tube (9) are painted black to absorb maximum solar radiation also to radiate
maximum energy when it is under shadow.
The containers (6) are fixed to the panel fixing frame (2) with the first set of
brackets (7) as shown in the fig.2 by the second set of bolts (19). The containers
(6) are charged with a volatile Ozone friendly working fluid and sealed. The
shadow casting covers (11) are painted white are fixed to the containers (6) as
shown in the fig. 2 with second set of the nuts and bolts (19). The covers (11)
cast shadow on half of the container (6) surfaces when the tracker is facing the
Sun. Under this condition, both the containers (6) are equally heated and the
pressure inside the containers (6) is substantially equal. The covers (11) are
painted white to reflect solar radiation impinging on them so that they are not
heated much and conduct heat to the container (6).

The shock absorber (12) are fitted to the tracker as shown in fig. 2 connecting
the panel fixing frame (2) and a second set of bracket (14) extended from the
shaft fixing frame (4) by means of a third set of bolts and nuts (15). The panel
fixing frame (2) along with the PV panels (1) rotate about the axis of the shaft
(3) fixed at the bearings (5). The shock absorbers (12) resist movement of the
tracker i.e. panel fixing frame (2) along with the PV panels (1) due to sudden
winds or any other reason. The shock absorbers (12) also allow very slow motion
of the tracker due to the gravitational force because of the differential liquid held
in the containers (6).
The tension springs (13) in respect of coil diameter, wire diameter and spring
constant is selected depending on the capacity of the PV panel (1) installed on
the tracker, are fitted to the tracker as shown in the fig. 2, by connecting the
panel fixing frame (2) and the second set of bracket (14) via the third set of
bolts and nuts (15). The spring (13) acts as a balancing weight and prevents the
tipping of the tracker to a side as soon as the liquid is transferred, particularly
when the centre of gravity of the panel fixing frame (2) and the PV panels (1) is
not below the axis of rotation of the shaft (3). The springs (13) enable a slow
and smooth movement of the tracker to follow the Sun during the day.
The inventive Solar Thermal Sun Tracker as shown in the fig.l is positioned in
such a way that the axis of rotation is oriented towards north and south 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 (6) gets

more shadow in comparison to the distal container (6). 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 cast by the cover (11) on both the
containers is identical. As the Sun moves from East to West direction, the tracker
follows the sun till the evening as shown in fig. 3. The tracker remains facing
West during the evening and the next day morning. As shown in fig. 4, in the
early morning when the Sun rises in the East, the Sun rays directly fall on the
west side container (6). Also the rays incident on the cover (11) of the west
container (6) are reflected to heat the west container (6). This operation enables
faster heating of the west side container and thereby pressurizing the container
(6) because of the vapors generated by the working fluid. The pressure
difference between the containers (6) pushes the liquid from west side container
to the east side container. The capillary tube (8) provided inside the containers
(6) passing through the inter-connecting tube (9) allows the liquid to quickly
exchange between the containers (6).

WE CLAIM
1. An automatically reorientable solar thermal sun Tracker for tracking the Sun
from morning to evening to produce increased power output, comprising:
- a supporting structure consisting of one each top, middle and bottom portion,
the top portion formed of a panel fixing frame detachably attaching a plurality
of photovoltaic (PV) modules, the middle portion constituting a pipe structure
with a base plate affixed at a lower middle end, the upper middle end of the
middle portion having a shaft rigidly connected to a shaft fixing frame, the
shaft extending between at least two bearings provided to the panel fixing
frame, the bottom portion of the structure accommodating the base plate of
the middle portion via a base frame;
- at least two containers having different quantity of Zone-friendly volatile fluid
placed 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 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; and

a capillary tube provided inside the container passing through the inter-
connecting tube, to allow flow of liquid from one container to the other
container, making it possible for 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 after the sun set.
2. 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 and
wherein the covers are painted white to reflect most of the incident radiation
and reduce the heating and conduction of heat to the containers.
3. The sun tracker as claimed in claim 1 or 2, wherein the containers are
spaced-apart via a gap maintained between the container and the PV panel
so as to avoid casting of shadow of the panel on the container and transfer of
heat between the container and the panel.
4. The sun tracker as claimed in any of the preceding claims, comprising shock
absorbers to absorb shock loads due to wind or other environment hazards.
5. The sun tracker as claimed in claim 1, wherein the tracker is provided with
springs to maintain a slow movement 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.

6. The sun tracker as claimed in claim 1, wherein each of the containers is
provided with a charging nipple.
7. The sun tracker as claimed in any of the preceding claims, wherein the panel
fixing frame including the PV-panels rotates about the axis of the shat.
8. The sun tracker as claimed in any of the preceding claims, wherein at least
two tension springs are attached to the shaft.
9. An automatically reorientable solar thermal Tracker for tracking the Sun from
morning to evening to produce increased power output as substantially
described and illustrated herein with reference to the accompanying
drawings.

The invention relates to an automatically reorientable solar thermal sun Tracker
for tracking the Sun from morning to evening to produce increased power
output, comprising a supporting structure consisting of one each top, middle and
bottom portion, the top portion formed of a panel fixing frame detachably
attaching a plurality of photovoltaic (PV) modules, the middle portion constituting
a pipe structure with a base plate affixed at a lower middle end, the upper
middle end of the middle portion having a shaft rigidly connected to a shaft
fixing frame, the shaft extending between at least two bearings provided to the
panel fixing frame, the bottom portion of the structure accommodating the base
plate of the middle portion via a base frame; at least two containers having
different quantity of Zone-friendly volatile fluid placed 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 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; and a capillary tube
provided inside the container passing through the inter-connecting tube, to allow
flow of liquid from one container to the other container, making it possible for
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 after the sun set.