CLIAMS:1. A tracking system for a solar panel arrangement
a. a solar panel array arranged in landscape configuration,
b. a controller having a program for generating a signal that represents desired tilt angle of the panel array,
c. an actuator connected to said controller, said actuator receiving said signal from said controller and adjusting a tilt angle of the solar panel array to equal the desired tilt angle in response to said received signal.
d. an inclinometer connected to said controller to detect actual physical tilt angle of the solar panel array, and
e. a closed loop means for receiving desired tilt angle signal from the controller and actual tilt angle signal from inclinometer and, giving a feedback signal to the controller to further adjust selectively the tilt angle of the solar panel array until the actual tilt angle signal detected is not different from the desired tilt angle of the panel array.

2. The tracking system for a solar panel arrangement of claim 1, wherein the solar panel array is always perpendicular to the sun as it moves from +50 degrees at one end to -50 degrees at the other end of the tracking angle.

3. The tracking system for a solar panel arrangement of claim 1, wherein the system includes a sensor mechanism and the said controller is operably associated with the sensor mechanism for sensing the orientation of the sun relative to the solar panel array, said sensor mechanism generating said tilt angle signal in response to detected said orientation of the sun.

4. The tracking system for a solar panel arrangement of claim 1, wherein said actuator is operably associated with an adjustment means for adjusting the solar panel array tilting angle in response to said tilt angle signal from the controller.

5. The tracking system for a solar panel arrangement of claim 1, wherein said actuator include a first limit switch mounted within and cooperatively operable with a gear reduction means and a cam means for detecting and signaling the tilting movement of solar panel array.

6. The tracking system for a solar panel arrangement of claim 1, wherein the arrangement further includes a second limit switch mounted external to the actuator and co-operably operable for detecting and limiting the tilting movement of solar panel array.

7. The tracking system for a solar panel arrangement of claim 1, 5 & 6 wherein the arrangement includes an interlock means between the two limit switches and the controller.

8. The tracking system for a solar panel arrangement of claim 1, wherein the signal is generated in the range 4 to 20mA. ,TagSPECI:FIELD OF INVENTION
The invention relates to a solar tracking system.

BACKGROUND OF THE INVENTION
Solar tracking system are devices that track the motion of the sun relative to the earth to maximize the production of solar energy. Solar trackers move to keep solar modules perpendicular to the sun in either one or two axes. As a result the modules are subjected to a higher amount of solar radiation which increases the total output yield of the plant with respect to conventional fixed mount structures. The amount of increase in generation by using solar trackers is worth their price with lower payback time and better return of investment than conventional fixed systems. Use of trackers will definitely be beneficial in the long run despite its startup cost.

OBJECT OF THE INVENTION
A horizontal East West tracker is preferred over conventional fixed mount structures in India is mainly due to the geographic location of the country. Being a tropical country (with the Tropic of Cancer crossing the country), India faces long summers during which maximum generation is observed in horizontal east west orientation owing to the absence of any axis tilt (i.e. axis tilt = 0°). This is because during summers, the sun stays overhead for a long duration and is nearly perpendicular to the surface of the earth. Hence the main object is having axis tilt as zero and axis parallel to the earth’s surface thereby resulting in higher absorption of energy and thus higher yield / units generated by the modules mounted on a horizontal east west tracker when compared to fixed mount structures. Also these trackers are designed to be more robust and have a simplistic design which makes them suitable for the desert and tropical climate witnessed in India.

DESCRIPTION OF THE INVENTION
The proposed system aims to track the sun throughout the day from east to west (+ 50 to - 50 degrees) about a single horizontal axis, and hence the name Horizontal single Axis Tracker (HSAT). The system is designed to host large number of Photovoltaic (PV) modules in tracking the sun, driven by a single source thus reducing the parasitic load of the plant.
The system is designed to cater more number of PV modules with the help of simple mechanical drive arrangement. In one embodiment a single drive is capable of moving 16 rows, each row consisting 20 PV modules. The drive mechanism consists of a simple electromechanical linear/rotary actuator, whose motion is monitored and controlled by a preprogrammed logic that is specific to a site. The actuator ensures tracking of the sun throughout the day from east to west. The angle of oscillation can be modified to suit the site. The system is designed to withstand and operate at extreme environmental conditions like wind, rain; temperature etc. Various tracking modes of operation possible with HSAT are tracking mode, homing mode, backtracking (shadow avoidance), maintenance mode & emergency mode (stow position). The PV modules are mounted in landscape configuration for crystalline modules due to cell formation. Known prior art trackers available in the market are capable of operating in the range of (+) 45o to (-) 45o however the system as per invention is capable of operating the range of (+) 50o to (-) 50o. A closed loop system is formed by having redundancy in feedback not only from Encoder but also with inclinometer which ensures accuracy and positioning of the tracking system. Apart from external limit switch, actuator includes internal limit switch and torque switch as an additional safety feature.
The electricity consumption by the drive arrangement is minimal, since a single drive is used to track more number of PV modules. The structural components and mechanical joints have been designed to take care of all the loads experienced at site. The mechanical joints are provided with bearing for smooth operation.
The system consists of structural members, a mechanical drive arrangement and a control system. The structural members are designed to support PV modules against any external forces acting on modules. Mechanical drive arrangement is designed to oscillate the structural assembly to track many number of rows of PV modules throughout the day. The control system monitors and controls the motion of an electromechanical linear/rotary actuator, ensuring the correctness of orientation of PV modules at that time. NREL based Sun tracking algorithm logic incorporated in the control system which will ensure the module is always in perpendicular to the Sun between (+ 50 to - 50 degrees). External Limit switch are also equipped on both directions to avoid tracker travel beyond (+50 to - 50 deg). Inclinometer is mounted on the surface of the tracker to verify Tracker Position. The mechanical actuator is also provided with limit switches and torque switches for additional safety.

The Arrangement of the system is described herein:
The PV modules are mounted on torque tube (refer Figure 1). Each row of torque tube is supported on leg members. At the mid-span of torque tube there is cantilever arm perpendicular to ground at stow position. The cantilever arm attached to each row of torque tube is connected to a push-pull rod; one end of the push-pull rod is connected to the drive arrangement (linear/rotary actuator). The push and pull action of the linear/rotary actuator rotates the PV modules.
Figure 1 illustrates PV modules mounted on torque tube.
Figure 2 is cross sectional view
Figure 3 is tracker structural overview.
Figure 4 is tracker structural overview.
Figure 5 illustrates controller means
Figure 6 illustrates met station
Figure 7 illustrates proximity sensors
Figure 8 illustrates of landscape orientation
Figure 9 illustrates of portrait orientation
Figure 10 landscape mounting -vs- portrait mounting power generation graphs.
Figure 11 Electrical circuitry of cells & bypass diodes
PART NUMBER PART NAME
1. CONNECTING TO ACTUATOR
2. MODULES
3. TORQUE TUBE
4. LEG MEMBER
5. PUSH PULL ROD
6. SOLAR PANEL
7. LEVER ARM
8. LEG
9. MOTOR
10. ACTUATOR
11. GEAR BOX
12. INCLINOMETER
13. CONTROLLERS
14. MET STATION
15. PROXIMITY SENSOR

The drive is mounted on a concrete column. A pivot arrangement is used at this connection so as to adjust any angular shift during the phase of tracking.
In one of the embodiments, typical design parameter is given below:-
Sl.No. Particulars Details
1. Type of tracking Horizontal single axis
2. Wind zone / Basic wind speed (m/sec) WZ-4/47m/sec (169.2 Km/hr.)
3. Tracking Angle ± 50° from Zenith
4. Array-level Tracking Accuracy ± 1° typical (Includes allowances for actuation, manufacturing, panel mounting, installation and ground settling tolerances when the product is installed)
5. Tracking basis NREL – Sun tracking algorithm
6. Tracking Modes of Operation Tracking mode, Homing mode, Backtracking (shadow avoidance), Maintenance mode & emergency mode
7.
Panel fixing By direct bolting (as per module specification)
8. Components Structures and foundations, PV modules, motorized actuators, control system, met station, inclinometer, proximity switch & SCADA
9. Wind stow method Automatic sensing of wind speed and positioning the tracker to homing position. Uses anemometer for emergency wind stow
10 Module Orientation Landscape
14. Structure and Frame Galvanized structures (as per IS code)
15. Foundation (Drive/tracker) Anchor Bolt Foundation/Drill Pier foundation
16. Drive system Motorized actuator with lever arm arrangement
17. Photovoltaic power in KWp 96
18. No. of modules 320 modules (300 Wp – Crystalline module)
19. Minimum ground clearance 500 mm
20. Control system Programmable Logic Controller (PLC)
The Foundations are designed based on the following parameters; its values shall depend from site to site:
• Soil Parameter from Soil Investigation report
• Type of Soil
• Safe Bearing Capacity
• Angle of repose
• Unit wt. of soil
• Grade of Concrete
• Grade of Steel
• Unit wt. of concrete

The main components of the tracker system are detailed below:-
A. Tracker Structure consists of at least :-
• Torque Tube
• Drive Struts
• Foundation
B. Drive Mechanism consists of at least :-
• Motor
o Type : BLDC (with inbuilt drive) /Induction Motor
o Supply : 3 phase, 415V AC
o Power : 0.13 KW to 1.5 KW
o Control Range – 4 to 20 mA (Analog Input/output)
o Type : Totally enclosed non ventilated (IP 68)
o Insulation : Class F
• Actuator & Gear Box
o Type : Linear actuator (Mechanical Screw Jack)
o Force : in Kgs (Project specific)
• Control System
o Controllers
? PLC with NREL solar positioning algorithm
? Human Machine Interface (HMI)
? AI/AO Modules
? DI/DO Modules
? Modbus Interface Modules
? Ethernet interface
o Inclinometer
? An instrument for measuring the angles of slopes installed on panel mounting structure
o Met Station
? Pyranometer (GHI and tilted)
? Ambient temp sensor
? Panel surface temp sensor
? Wind speed and wind direction sensor
o Proximity Sensors
? A proximity sensor is used to sense & protect tracker operating beyond + 50 and below -50 deg without having Direct contact with torque tube
ADVANTAGES OF THE INVENTION
1. MODULE ORIENTATION
a. Prior art does not cite the module configuration. However, portrait orientation of modules is seen in most of the projects.
b. In portrait mounting, if there is a little shadow, it covers a part of all the strings affecting the entire module thus there would be loss in generation of 75%-80%.
c. Solution offered in the invention
i. In landscape configuration, shadow covers only one string, where rest of the string will continue to produce power. The power of the module is reduced to 60%. In nutshell, with landscape configuration, the shading losses are minimized.
ii. The distance between two rows can be reduced by 0.5 meters, thus reducing the land requirement significantly.
2. East to West tracking range ± 50 degrees.
a. In any of the prior art, cite of tracking range is not seen.
b. Most of the trackers restrict tracking range to ± 50 degrees that results in average of 14 % increase compared to fixed tilt.
3. Internal limit switch and torque switch in an actuator
a. Usually either internal or external limit switches are provided.
b. Failure of limit switch would result in uncontrolled movement of linear actuator this inducing inaccuracy in movement of the solar array.
c. Since the solar plant or tracker has to be guaranteed for long term continual operation, having redundancy would be safer.
Torque switch ensures that the tracker is operating within the designed thrust limits.
4. Closed loop system, feedback from encoder and inclinometer
a. Either encoder or inclinometer is used.
b. Since Encoder is integrated in the Drive system, over a period of time (ageing) the mechanical wear and tear will not allow the module mounting structure to align Perpendicular with sun.
c. If we implement inclinometer along with Encoder a closed loop system can be developed where feedback from both the devices can be compared and if required we may change the controller program to suit the desired position.
PVSYST report (Simulation S/w used in Solar Industry) for two site (New Delhi & Jodhpur) for fixed tilt and tracker of (-50° to +50°) are provided herein.
The summary is as follows:
Sl.No Location Tracking Angle Energy Produced (MW Hr/MWp /year) Global Radiation in Inclined Plane (kWh/m2) / year
1 New Delhi Fixed Tilt 1741 2197
(-50° to + 50°) 1986 2435
2 Jodhpur Fixed Tilt 1789 2277
(-50° to + 50°) 2067 2573

Gain in generation for New Delhi Location compared to fixed tilt is 14%
Gain in generation for Jodhpur Location compared to fixed tilt is 15.5%
Notes –
Generation figures are captures based on following conditions –
- No auxiliary consumption
- No module degradation
- No plant unavailability
- No transmission loss
- Power evacuation at 33 KV level
The full details are provided herein:-



Further there is disclosure of advantages of the system over prior art.
LANDSCAPE MOUNTING Vs. PORTRAIT MOUNTING
• LANDSCAPE MOUNTING :
o In the presence of shadow (beam content only), if one cell is shaded, only 1/3rd (33.33%) of the module is dysfunctional and the remaining 2/3rd (66.67%) of the module continues to generate power.
• PORTRAIT MOUNTING
o In the presence of shadow (beam content only), if one cell is shaded, the entire module is dysfunctional and 75-80% power generation gets reduced. .
LANDSCAPE MOUNTING Vs. PORTRAIT MOUNTING GENERATION FOR A GIVEN DAY IS ILLUSTRATED IN FIGURE 10 and is self explanatory.
The longest day of the year 21st June and shortest day of the year 21st December.

All of the disclosure relating to various embodiments and designs are only for the purpose of disclosing the arrangement and technique and shall not limit the scope of the invention. All variations and modifications obvious to skilled persons are within the scope of the invention.