Solar Trackers

Solar Trackers are the devices which are used to installed in Photo-voltaic system to track the sun to get the maximum power per sun position .This trackers are also used in other projects with Fresnel Reflectors, mirrors and lenses. For flat photo-voltaic system this trackers are used for minimize the angle of incidents between the incoming sunlight and the PV panels. It increases the amount of energy that we need for daily consumption.

Basic Theory : Basically sun light has two components i) Direct beam ii ) Diffuse Beam. Most of the energy is contain in that direct beam which is about 90%. As the sun direct beam contains maximum power and to get all the sun power sun should be on the solar panel with the best incident angle so the solar panel can capture all the energy. The contributed energy by the sun direct beam decrease with the cosine of the angle between incoming light and the panel.This lost power could be up to  over 75% for misalignment of the sun angle, so this is very important to keep the sun angle with the solar panel at all time.

Some Trackers with the accuracy of ∓5° can deliver power over 99.6% from the sun direct beam and 100% with the diffuse light, so the necessity of high accuracy tracker are not in used.

Types of Trackers : There are few types of tracker available like single-axis trackers and dual axis trackers.As we know sun revolves around the earth 360° east to west (Alhamdulillah) .
But at any fixed location the the visible portion is 180° during an average day period but the effect of local horizon makes it 150°. And a Solar Panel which is tilted at fixed point can enjoy only 75° at both side from dawn to dusk, thus the power will be lost higher above 75%. This losses can be recaptured using a single-axis trackers set in east to west direction.Sun also travels 46° north to south and solar panels at fixed point between these local extremes see this 23° at both side which could cause 8.3% of solar power losses.A tracker which can reduce power losses for both horizons is called dual-axis trackers.Dual-axis trackers are better then the single-axis trackers by 4~5% when capturing sun power but cost is higher for dual-axis trackers.

There is an argument between industries that to capturing the small differences of solar power of single and dual-axis trackers is worthwhile with the installing cost of these trackers.In some study favored single-axis trackers over dual-axis trackers as the cost is far less.


Single-axis Trackers : Single-axis trackers have one degree of freedom to act as an axis of rotation. Normally trackers like single axis trackers is typically aligned at true north meridian, but it is possible to align them in any cardinal direction with advanced system. There are several common implementations of this kind of solar-axis system.

• HSAT  (horizontal single axis trackers)
• HTSAT (horizontal single axis tracker with tilted modules)
• VSAT (vertical single axis trackers)
• TSAT (tilted single axis trackers )
• PSAT (polar aligned single axis trackers)

Dual-axis Trackers : Dual axis trackers have two degrees of freedom that act as axes of rotation.

These axis are normal to each other, one of the axis which is fixed with respect to the ground can be considered as primary axis and the other axis that is the primary axis can be considered a secondary axis.There are several implementations Like ,

• TTDAT (tip-tilt dual axis trackers)
• AADAT (azimuth-altitude dual axis trackers)

Dual-axis  trackers allow for optimum solar energy levels because they can follow sun vertically and horizontally.No matter where the sun is in the sky dual-axis trackers are able to get maximum power.

Advantages : 

• Trackers helps to generate more power than conventional fixed tilted solar panels, about 10 to 25%   depending on geographic location.
•  Due to solar trackers the additional space issue get solved as the amount of power got increased and the number of solar panels will decrease.
• In certain states, some utilities offer Time of Use rate plans for solar power, which means the utility will purchase the power generated during the peak time of the day at a higher rate.  It is beneficial to generate a greater amount of electricity during these peak times of the day. Using a tracking system helps maximize the energy gains during these peak time periods.

Disadvantages :  

• Solar tracker are expensive products and costly to install due to their complex technology and moving system.
• Maintenance is higher and it is much more frequent comparing to stationary tilted solar panels.

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