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AUTOMATIC SOLAR TRACKER
Concept : We all are familiar with the Newton's corpuscular theory of light, that light is made up of small particles called “corpuscles” which travel in straight line with a finite velocity and energy.
SOLAR ENERGY :
It is the major Eco-friendly & Pollution less method of producing the electricity today.
Acc. to- U.S. solar research center: “ If we convert the Total Solar energy reaches to earth in one time into ELECTRICITY, then it will be more enough than whole power used by all the nations per year. “
Solar Panel :
It is a large component made up of the no of photovoltaic cells connected internally with each other. Used to grab the sunlight and to convert it into the ELECTRICITY.
What is a solar tracker ?
A Solar tracker is a device used for orienting a solar photovoltaic panel or lens towards the sun by using the solar or light sensors connected with the machine ( ex: stepper motor, servo motor, gas filled piston ).
Hence, The sun tracking systems can collect more energy than what a fixed panel system collects.
NEED OF SOLAR TRACKER
Commercial purpose :
• Increase Solar Panel Output
• max.efficency of the panel
• Maximize Power per unit Area
• Able to grab the energy through out the day .
Types of Solar Trackers
The sun's position in the sky varies both with the seasons (elevation) and time of day as the sun moves across the sky.
• Hence there are also two types of SOLAR TRACKER :
Single Axis Solar Tracker.
Dual Axis Solar Tracker.
• 1. Single Axis Solar Tracker
Single axis solar trackers can either have a horizontal or a vertical axle. The
horizontal type is used in tropical regions where the sun gets very high at noon, but
the days are short. The vertical type is used in high latitudes (such as in UK) where
the sun does not get very high, but summer days can be very long.
2. Dual Axis Trackers
Double axis solar trackers have both a horizontal and a vertical axle and so can track the Sun's apparent motion exactly anywhere in the world
This type of system is used to control astronomical telescopes, and so there is plenty of software available to automatically predict and track the motion of the sun across the sky.
Dual axis trackers track the sun both East to West and North to South for added power output (approx 40% gain) and convenience.
• Dual axis Solar tracker fig :
• Overview of Present Tracker Drive Types
Solar tracker Drives, can be divided into three main types depending on the type of drive and sensing or positioning system that they incorporate.
• 1. Passive trackers : use the sun’s radiation to heat gases that move the tracker across the sky.
• 2. Active trackers : use electric or hydraulic drives and some type of gearing or actuator to move the tracker.
• 3. Open loop trackers : use no sensing but instead determine the position of the sun through pre recorded data for a particular site.
1. Passive ( Gas ) Trackers
Passive trackers use a compressed gas fluid in two canisters each place in west & east of the tracker. The mechanism is in such a way that if one side cylinder is heated other side piston rises causing the panel to tilt over the sunny side.
This affects the balance of the tracker and caused it to tilt. This system is very reliable and needs little maintenance.
They are cheaper & effectively increase the efficiency of the solar panel.
gas tracker will very rarely point the solar panels directly to the sun, due to the temperature varies from day to day and Overcast days are also a problem can damage the panel.
when the sun appears and disappears behind clouds, causing the gas in the liquid in cylinders to expand and contract resulting in erratic movement of the device, often causes DAMAGE.
2. Active Trackers
Active trackers : measure the light intensity from the sun by using “ light sensors “ to determine where the solar modules should be pointing.
Light sensors are positioned on the tracker at various locations in specially shaped holders.
If the sun is not facing the tracker directly there will be a difference in light intensity on one light sensor compared to another and this causes to determine in which direction the tracker has to tilt with the help of the stepper or dc motor in order to be facing the sun. DRAWBACKS: On overcast days it will be not so working properly due to clouds.
3. Open Loop Solar Trackers
• DEFINATION :
Open loop trackers determine the position of the sun using computer controlled algorithms or simple timing systems.
1. Timed Trackers-
A timer is used to move the tracker across the sky. Incremental movement throughout the day keeps the solar panel pointing the sun.
Advantages: can be utilize as one or two axes panels.
Disadvantage: Does not take into account the seasonal variation in sun position.
2. Altitude / Azimuth Trackers-
It uses the astronomical data or sun position algorithms to determine the position of sun for any given time and location by using micro controller.
Once the position has been calculated, the modules are moved using servo motors and there
position measured by encoders built into the tracker frame.