A solar tracker is a mechanical device that works by following the sun on its path during the day. There are two different types of mechanisms that are most commonly used active trackers and passive trackers. Active trackers are directed toward the sun by electrical circuitry in the form of light-sensing photosensors. Motors and gear trains are then employed to direct the tracker as commanded by the photosensors to the sun’s direction. Active trackers contain electrical components and hence use a small amount of power. Passive trackers use a hydraulic mechanism that responds to the heat of the sun. A low boiling point compressed gas fluid is driven to one side or the other by the sun’s heat, creating gas pressure and thereby moving the mechanism along. Passive trackers generally do not consume any power. Typically, active trackers are more accurate then passive trackers, and hence favoured for uses where a pinpoint degree of accuracy is required, for instance where concentrating solar collectors are used. For solar PV applications the accuracy of passive trackers is more than sufficient.