# SOLAR ENERGY 101: Solar Trackers Part II - Types and Design

Posted on the 23 November 2012 by Derick Ajumni
In the previous article Solar trackers (Part I) we introduced the concept of solar trackers, and discussed the main idea behind them. We also described how solar trackers work with respect to light incidence. We added an analysis on percentage savings gained with these systems, and then concluded by describing the two main types of solar tracking systems available in the market. In this article we will discuss types of axis trackers, and look briefly at their designs. There are two types of axis trackers, the Single Axis Trackers and the Dual Axis Trackers.
Single Axis Trackers: are trackers with only one degree through which they rotate or use as axis of rotation. This axis is usually aligned following the North meridian. They rotate azimuthally from east to west following the path of the sun through the sky. The word azimuth can be defined as the horizontal angular distance from a reference direction usually the northern point of the horizon, to the point where a vertical circle intersects the horizon - measured clockwise (confusing I know).
Single axis trackers increase electricity output by 27 to 32%, and is an impressive simple way of improving the potential performance of a commercial solar installation while keeping cost in check. Engineers sometimes tweak the single axis trackers into horizontal single axis trackers (HSAT), vertical single axis trackers (VSAT), tilted single axis trackers (TSAT), and polar aligned single axis trackers (PSAT).
Double or Dual Axis Tackers: These have two different degrees through which they use as axes of rotation. The dual axes are usually at a normal of each other, and rotate both east to west zenithally. The first axis known as the primary axis is fixed to the ground and another axis is referenced to it known as the secondary axis. Again there is a new word here zenith, which can be defined as that point on earth (celestial sphere) that is above the observer or the highest point above an observers horizon attained by a celestial body. 'Above' meaning the vertical direction opposite an apparent gravitational force at a specific location (now that was simply magic wasn't it?).
Dual axis trackers increase a systems energy output by 35 to 40%; that is an additional 6% on average compared with the single axis trackers. Some engineers also play with the designs of dual axis trackers into Tip-tilt dual axis trackers (TTDAT), and Azimuth-altitute dual axis trackers (AADAT).
Information used on these trackers are latitude dependent, and care should be noted when orienting the panels with respect to the tracker axis because their conversion efficiency ratios are largely dependent on their continues orientation towards the sun. Incorporating one or two types of solar trackers on a commercial installation can make a big difference between producing energy and actually producing enough energy.
We will continue with Part III of this article series to discuss how the tracking technology works and then conclude with the pros and cons of it all. Stay tuned.

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