Heliostat Tracking Techniques and Control Mechanism

1.1      Solar Tracker

The solar tracker is a device and a mechanism for orienting the solar concentrator in such a way that it reflects maximum sunlight on the receiver directly from the sun and the deviation angle is minimum throughout the tracking time. A highly efficient Solar tracking mechanism drastically enhances the efficiency of the solar concentrator since it can collect more sun light as compared to a passive mechanism.

Solar trackers are implemented using Astronomical equations, light dependent resistors, sun pointing sensors etc. coupled with other devices such as Stepper motor, Dc Motors, Servo motors, gas filled piston etc.  

1.1.1    Dual Axis Trackers

The dual axis tracker has both horizontal and vertical axis and hence can track the position of the sun and its apparent motion anywhere in the sky throughout the day. Dual axis tracker track the sun through both East to West and North to South, which gives it an added benefit of capturing more sunlight directly from the sun, which increases the added power output and the theoretical efficiency by approximately 40%.

It can be implemented with the help of sun pointing sensors or light dependent resistors, astronomical data or predicted trajectory of sun throughout the day.

1.1.1.1  Disadvantage

Dual axis tracking comes with greater complexity for the system. More motors are to be used to dual track which increases the difficulty level. It is also argued that it can be less reliable considering greater number of devices used in this mechanism which increases the maintenance and down time.