Claims:WE CLAIM:
1. An automatically re-orientable horizontal axis solar thermal sun tracker for photovoltaic arrays (15), comprising of:
plurality of panel fixing frames (2);
plurality of Photovoltaic panels (1) mounted over said panel fixing frames (2) using a set of nuts and bolts;
plurality of supporting pole assembly (5);
a plummer block bearing (6) fixed on the top end of each said supporting pole assembly (5);
said panel fixing frames (2) are fixed to a set of rigid shaft (8) which are mounted on said multiple supporting pole members (5) through said Plummer block bearings (6);
a stopper (10) which is attached to the top end of the bottom portion of said supporting pole member (5);
bottom end of said supporting pole member (5) is fixed to the concrete foundations (7) in the ground;
at least two containers (3) containing volatile fluid at the extreme ends of said panel fixing frame (2);
said containers (3) connected to each other via an inter-connecting tube (11) for fluid-transfer;
a plurality of shadow casting covers (4);
a plurality of shock absorbers and spring assemblies (9).

2. The sun tracker (15) as claimed in claim 1, wherein said panel fixing frame (2) along with said photovoltaic panels (1) and said rigid shaft (8) mounted on said multiple support pole members (5), rotating on a horizontal axis in East to West direction and the axis aligned North to South direction.
3. The sun tracker (15) as claimed in claim 1, wherein the array of said photovoltaic panels (1) are provided with said stopper (10) at the top end of the bottom portion of said supporting pole member (5) to limit the movement angle of the panel fixing frame on East and West side.
4. The sun tracker (15) as claimed in claim 1, wherein said stoppers (10) are provided with vibration dampers to dampen the vibrations and noise in case the tracker hits the stopper due to sudden high winds.
5. The sun tracker (15) as claimed in claim 1, wherein said shadow covers (4) are bent at an angle to provide a shade on half portion of said containers (3) when it is facing the sun and allow a reflection of the sun rays to heat said containers (3).
6. The sun tracker (15) as claimed in claim 1, wherein said tracker is enabled to generate 10 to 12 % more energy compared to the array of photovoltaic panels mounted on fixed tilt structures.
7. The sun tracker (15) as claimed in claim 1, wherein said panels fixing frame (2) including said photovoltaic panels (1) rotates about the horizontal axis of said rigid shaft (8).
8. The sun tracker (15) as claimed in claim 1, wherein said sun tracker with an array of said photovoltaic panels (1) mounted on said supporting structure (2) rotating in a horizontal axis and each of said photovoltaic panels (1) are inclined at latitude angle with horizontal, thereby reducing the height of the complete assembly above the ground and also decreasing the effect of winds on the tracker. , Description:FIELD OF THE INVENTION
[001] The present invention generally relates to a solar thermal sun tracker for mounting array of solar photovoltaic panels. More particularly, the present 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 sun-rise. More particularly, the present 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
[002] Solar power systems include concentrating and non-concentrating systems. In non-concentrating solar power systems, the solar cell receives direct and indirect sunlight. An example of a non-concentrating solar power system is a flat panel of photovoltaic (PV) cells that directly receive sunlight. In concentrating solar power systems, the solar cell receives indirect sunlight that has been concentrated by a collector and directed at the receiver. An example of a concentrating solar power system is a parabolic collector in which a solar cell is located at the focus.

[003] Solar power systems include tracking and non-tracking solar power systems. In a typical tracking system, a tracker is used to track the sun as it moves across the sky to maximize exposure of a collector to direct normal incidence (DNI) light from the sun. Existing commercialized planar tracker systems are designed for flat panel PV modules and are in largely small scale use. These trackers typically have a large rectangular panel that is maintained normal to the incident sunlight via pivots with gears and motors set atop a tall pole several meters in height. Having the entire panel turn to face the sun creates shading on adjacent trackers requiring that these trackers be placed at a greater distance apart to reduce shading. This reduces the energy density per unit land area achievable. Further, to allow for low sun elevation angles where the large panel is facing the horizon, the panels must be supported high off the ground to provide clearance. This requires larger scale materials, increases wind loading, and makes maintenance difficult and dangerous.

[004] Solar thermal sun tracker system is disclosed in Indian Patent application no. 818/KOL/2010 and 483/KOL/2013. The device mentioned in the said applications, is mounted on a single pole and double pole structures respectively and follows the sun from east to west during the day and remains oriented facing the west overnight. The device reorients itself next day after the sun-rise. However, single pole and 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 greatly reduced.

[005] A number of Solar Passive Trackers are illustrated in US 4476854, US 2004/0112373, US 4175391, US 4275712 and US 4027651. Such trackers employ a pivotal frame, having at least one each canister at east end and west end which are interconnected 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 over the canister surface. A volatile fluid and its vapour 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 towards west to follow the sun. The frame is balanced and points directly at the sun when equal sunlight falls on each canister.

[006] US 4275712 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.

[007] US 4175391 proposed an automatic night time resettling mechanism in a sun tracker by providing at least two containers with low boiling point liquid having different 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 west container because of higher pressure of the vaporized liquid in the west container. The transfer of liquid to the east container makes it heavier and tilts the array to the east awaiting sun rise.

[008] US 4476854 relates to a solar tracker which utilizes a gas spring to reorient the solar tracker when the sunlight is not available.

[009] US 204/0112373 relates to a passive solar tracker for a solar concentrator and 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 two-axis gimbal system with its orientation controlled by interconnected ballasts filled with 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.

[0010] The solar energy powered sun tracker described in US 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 in generation of a differential pressure to rotate the apparatus and collector.

[0011] 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 specific angle. Additionally, difficulty is encountered in the single pole and double pole support structures because of swinging action due to high wind loads causing variable outputs from the SPV panels.
OBJECTS OF THE INVENTION
[0012] It is therefore an object of the present invention to propose an automatically re-orientable solar thermal sun tracker for photovoltaic arrays applicable for deploying in the MW capacity, stand-alone distributed power systems and solar water pumping systems which eliminates the disadvantages of the prior arts.

[0013] Another object of the present invention is to propose an automatically re-orientable solar thermal sun tracker for photovoltaic arrays, which is provided with a plurality of array of photovoltaic modules, to allow the sun rays to fall almost always perpendicular to the surface.

[0014] Another object of the present invention is to propose an automatically re-orientable solar thermal sun tracker with an array of SPV modules mounted on supporting structure rotating in a horizontal axis and each SPV panel inclined at latitude angle with horizontal, thereby reducing the height of the complete assembly above the ground and also decreasing the effects of wind on the tracker.

[0015] Another object of the present invention is to propose an automatically re-orientable 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 the east and west side of the rotating axis.

[0016] Another object of the present invention is to propose an automatically re-orientable 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.

[0017] Another object of the present invention is to propose an automatically re-orientable solar thermal sun tracker for photovoltaic arrays which provides increased output from the PC modules.

[0018] Another object of the present invention is to propose an automatically re-orientable 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.

[0019] Another object of the present invention is to propose an automatically re-orientable solar thermal sun tracker for photovoltaic arrays which is simple, cost effective, maintenance free and reliable.

[0020] Yet another object of the present invention is to propose an automatically re-orientable solar thermal sun tracker for photovoltaic arrays which are mounted on supporting structures with SPV panels, mounted at low height from ground on multiple poles to reduce oscillations/ swings due to high wind.
SUMMARY OF THE INVENTION
[0021] Accordingly, there is provided an automatically re-orientable horizontal axis 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, 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; the upper end of the pole member having a Plummer block bearing affixed, through which said rigid shaft is connected to the pole members; at the top end of the 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; 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.
[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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 DESCRIPTIONS OF THE ACCOMPANYING DRAWINGS
[0026] The above brief description, as well as further objects, features and advantages, of the present invention can be fully appreciated by reference to the following detailed description. These features of the present invention will become more apparent upon reference to the drawings, wherein:

[0027] 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.

[0028] 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.

[0029] 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.
DETAIL DESCRIPTION OF THE INVENTION
[0030] The present invention will be described in detail below with reference to an embodiment as shown in the drawings.

[0031] Ref. to Fig. 1 &3, the solar thermal Sun Tracker (15) according to the present invention comprises of a supporting device, 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), Plummer block and bearings (6), and a working fluid.

[0032] Referring to Fig(s). 1, 2 and 3, 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 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.

[0033] 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 (not shown in the Fig.) and bolts. The inter-connecting tube (11) is also connected to the containers (3) by welding / brazing or threaded joints.

[0034] 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.

[0035] 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.

[0036] 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 to dampen the vibrations and noise when the tracker hits the stopper (10) due to sudden high winds.

[0037] 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).
Reference Numerals
(1) PV Panel
(2) Panel fixing frame
(3) Container
(4) Shadow cover
(5) Pole assembly
(6) Plummer block & bearings
(7) Concrete foundation
(8) Shaft
(9) Shock absorber & spring assembly
(10) Stopper
(11) Inter connecting tube