Maximum yearly solar radiation can be achieved using a tilt angle approximately equal to a site's latitude. To optimize performance in the winter, the collector can be tilted 15 deg. Data for a tilt of 90 deg. These trackers pivot on their single axis to track the sun, facing east in the morning and west in the afternoon. Large collectors can use an axis tilt angle of 0 deg. to minimize collector height and wind force.
Small collectors can have their axis tilted up to increase the solar radiation on the collector.
Just as for the flat-plate fixed tilt collector, the yearly and seasonal solar radiation can be optimized by the choice of tilt angle. The data presented assume continuous tracking of the sun throughout the day. Data for two-axis trackers represent the maximum solar radiation at a site available to a collector. Tracking the sun in both azimuth and elevation, these collectors keep the sun's rays normal to the collector surface. These instruments see only the sun's disk and a small portion of the sky surrounding the sun.