The conversion efficiency of solar photovoltaic panels is highest when incident light hits the panel surface perpendicular to the panel plane. Considering the sun is a constantly moving light source, this only happens once a day with a fixed installation! However, a mechanical system called a solar tracker can be used to continuously move the photovoltaic panels so that they are directly facing the to the sun. Solar trackers typically increase the output of solar arrays from 20% to 40%.

There are many different solar tracker designs, involving different methods and techniques for making mobile photovoltaic panels closely follow the sun. Fundamentally, however, solar trackers can be divided into two basic types: single-axis and dual-axis.

Some typical single-axis designs include:

Some typical dual-axis designs include:

Use the Open Loop controls to roughly define the tracker’s motion to follow the sun. These controls calculate the movement of the sun from sunrise to sunset based on the installation time and geographic latitude, and develop corresponding movement programs to move the PV array. However, environmental loads (wind, snow, ice, etc.) and accumulated positioning errors make open-loop systems less ideal (and less accurate) over time. There is no guarantee that the tracker is actually pointing where the control thinks it should be.

Using position feedback can improve tracking accuracy and help ensure that the solar array is actually positioned where the controls indicate, depending on the time of day and time of year, especially after meteorological events involving strong winds, snow and ice.

Obviously, the design geometry and kinematic mechanics of the tracker will help determine the best solution for position feedback. Five different sensing technologies can be used to provide position feedback to solar trackers. I will briefly describe the unique advantages of each method.