**3. Methods of solar tracking**

To track a maximum power point (MPPT) of a PV module, we always use a solar tracker. Different solar tracker are used as follows.

#### **3.1 Passive trackers**

The principle behind passive trackers is to make use of the solar heat to cause an imbalance, which leads to a movement in the tracker. They work on thermal expansion and commonly employ a low boiling point compressed gas fluid or shape memory alloys. For the high precision of the concentration of solar Power, the passive tracker are not always used. However, they can be employed for common flat PV systems. The passive trackers is more useful than the active tracker,

however, the efficient in low temperature is less. The SMA actuator can easily be deformed even at relatively low temperatures (by tracker actuators below 70°C). It produces mechanical work by returning back to its original shape when heated above transformation temperature. The study found that the tracker worked very well in the short term field tests and the SMA actuators provided an efficiency of approximately 2% [11].
