What is a Solar Tracker

Solar Tracker is a device which follows the movement of the sun as it rotates from the east to the west every day. Solar Trackers are used to keep solar collectors/solar panels oriented directly towards the sun, as it moves through the sky every day. Using Solar Trackers increases the amount of solar energy which is received by the solar energy collector and improves the energy output of the heat/electricity which is generated. Solar Trackers can increase the output of solar panels by 20-30%, which improves the economics of the solar panel project.

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Where and Why are Solar Trackers Used

Solar Trackers are mostly used in ground mounted solar farms of capacity more than 1 MW. Note it is difficult to use solar trackers on residential rooftop installations. Horizontal single axis trackers are typically used for large distributed generation projects and utility scale projects. The combination of energy improvement and lower product cost and lower installation complexity results in compelling economics in large deployments. However for solar ground plants where area is not a problem, solar trackers can be easily be used. Also commercial and utility solar projects have dedicated maintainance teams, which can easily repair and monitor solar  trackers.

The 20-40% increase in output easily compensates for the higher costs associated with solar trackers. Solar Trackers are especially useful in case of places, where the solar insolation is high and the efficiency of the solar panels being used are high. Sunpower which makes the highest efficiency solar panels uses solar trackers in most of its ground mounted plants and sells solar trackers under its own brand. These days solar trackers are becoming increasingly important and major solar panel manufacturers like First Solar and Trina Solar are selling solar trackers as well. The selection of tracker type is dependent on many factors including installation size, electric rates, government incentives, land constraints, latitude and local weather.

Solar Trackers in Solar Thermal Plants

Solar Trackers are almost universally used in case of solar thermal technology because they make use of optics to generate high amounts of heat. In these cases it is essential to make sure that the solar receivers are always oriented to receive the maximum amount of sunlight at any given time.

Types of Solar Trackers

1) Passive Trackers

Passive trackers use a low boiling point compressed gas fluid that is driven to one side or the other (by solar heat creating gas pressure) to cause the tracker to move in response to an imbalance. As this is a non-precision orientation it is unsuitable for certain types of concentrating photovoltaic collectors, but works fine for common PV panel types.

2) Active Trackers

Active trackers use motors and gear trains to direct the tracker as commanded by a controller, responding to the solar direction. Since the motors consume energy, one wants to use them only as necessary.

3) Single axis trackers

Single axis trackers have one degree of freedom that acts as an axis of rotation. The axis of rotation of single axis trackers is typically aligned along a true North meridian. It is possible to align them in any cardinal direction with advanced tracking algorithms.There are several common implementations of single axis trackers. These include horizontal single axis trackers (HSAT), vertical single axis trackers (VSAT), tilted single axis trackers (TSAT) and polar aligned single axis trackers (PSAT).

4) Dual Axis Trackers

Dual axis trackers have two degrees of freedom that act as axes of rotation. These axes are typically normal to one another. The axis that is fixed with respect to the ground can be considered a primary axis. The axis that is referenced to the primary axis can be considered a secondary axis. There are several common implementations of dual axis trackers. They are classified by the orientation of their primary axes with respect to the ground. Two common implementations are tip-tilt dual axis trackers (TTDAT) and azimuth-altitude dual axis trackers (AADAT). Dual axis trackers are typically used in smaller residential installations and locations with very high government Feed In Tariffs.

Solar Trackers Cost

Solar Tracker of small size between 1500-3000 Watts with Dual Axis can cost between $3000-7000, which implies that it costs around $2/watt extra to have solar trackers. You can also find very cheap Single Axis Solar Trackers for only $1/watt. You need to do a return on investment calculation to see whether the extra $2/watt in cost increases the power output of the lifetime of the solar panels  to compensate. You have to also calculate the extra land requirement and operating costs of the solar trackers.

Solar Trackers of smaller size are more costly per watt than solar trackers of bigger sizes. You can buy solar trackers customized for most of the popular Solar panel companies. The popular makes of  Solar Trackers are from Sunpower, Wattsun, Zomeworks, Tital Trackers and others.