A solar tracker is a set of motors and software that turn rows of solar panels during the day so that they face the sun. A fixed panel faces one direction all day. A tracked panel faces east in the morning, up at noon and west in the evening, so sunlight falls on it more directly for longer.
Most large trackers are single-axis. A long metal tube carries a row of solar panels. A motor rotates the tube slowly from east to west through the day. Software computes the sun's position from the date, time and location, and tells the motor the angle. A tracker costs more than a fixed frame, and it needs more space between rows. So trackers are used mostly in big solar parks, not on rooftops. The extra electricity has to be worth more than the extra cost, and in a large park it usually is.
Take, for example, a solar park near Kurnool in Andhra Pradesh with 2,000 rows. Each row has a motor, a controller and sensors. At sunrise, the rows tilt east. When the sun is low, a row would cast shade on the next row, so software tilts the rows slightly flatter, which is called backtracking. In very strong wind the software turns the rows to a safe stow position to protect them. Some designs lay the rows flat, and others tilt them steeply. Trackers can raise a park's yearly energy by roughly a sixth or more, compared with fixed panels.
The extra energy also comes at useful times. A tracked row produces more in the early morning and late afternoon, when a fixed panel produces little. That helps the grid when demand is rising in the evening.
The controllers send their readings to an industrial IoT platform. A stuck motor can then be repaired before it costs energy, which is a kind of predictive maintenance. The panels on a tracker feed the solar inverters of the park. A park has thousands of motors, so trackers also depend on good aftermarket service.