The Solar Tracker

The idea behind adding a solar tracker for a residential solar power system is to get more electricity power without increasing the solar panel size
The assumption is that the cost to add a solar panel tracker is less than the cost of adding more solar panels.

Tracking the Sun

The ultimate direction for a given solar panel plane, if we want to get from it the maximum electricity power is perpendicular to the sun position. The most straight forward way to mount a solar panel is in a fixed direction. Since the sun apparently moves in the sky, having a fixed direction mounted panel is not the optimum. It is however a reasonable engineering compromise if site constraints and economical constraints are taken into account

An obvious situation where the panel must be mounted in a particular direction is on a slant roof in general and if solar tiles are used in particular
On a flat roof or in a non shaded area in the yard one can consider the addition of a solar tracker. On offgrid solar systems sites it is conceivable to consider that a suitable location for the tracker and the mounting mast can be found
In grid-tie solar systems, to fit a mast and the tracker into a typical suburban home and to comply with local planning restrictions might not be a practical proposition

The solar tracker orients a solar photovoltaic panel to face the sun while tracking the sun position. Accuracy is not terribly important for orienting flat solar panels. Comparing to fixed mounted panels, the extra power generation comes into effect early in the morning and late in the afternoon (around noon time the fixed mounted panel is anyhow facing South where the sun is)

There are two types of trackers: the single axis tracker and the two (dual) axes tracker
In a single axis tracker, the tracker tracks the sun in azimuth only; elevation can be changed manually according to the season (higher angle in the summer season)
Most dual axis trackers can track in elevation and in azimuth; some have polar control
Compared to a fixed mount panel, a single axis tracker increases annual electrical power production by around 25-30%, a dual axis tracker might add 5% on top of that.
A single axis solar panel tracker is a good engineering compromise in most situations

You probably ask yourself how does the motors in the tracker “know” where the sun is? There are two solutions to the riddle.

• A passive solution: since the azimuth and elevation are known for the location, date and hour the data can be stored as digital tables into the controller memory
• An active solution: a clever optical sensor* senses the tracker axis deviation from the sun direction, and the tracker nulls the error (a closed loop servomechanism)

Solar Trackers for Large Size Solar Power Plants