Solar Tracking Using Four-Bar Mechanisms

Solar tracking adjusts the orientation of solar panels and makes them face Sun to increase power generation. The Earth has two movements with respect to Sun: the daily axial rotation and the yearly orbital revolution. There are two degrees of freedom in the relative motion between Earth and Sun. For solar tracking, Earth is commonly considered to be stationary while Sun takes relative motion with respect to Earth. Sun travels from east to west during daytime and also moves north and south due to Earth’s tilt. However, Sun’s daily north-south move is much smaller than its east-west move. Although the existing solar trackers with two degrees of freedom increase solar power generation from solar panels significantly, they also consume considerable power by driving solar trackers. Single-axis (or one degree of freedom) solar trackers can catch Sun’s daily east-west movement effectively. Sun’s small north-south movement can be covered for them by monthly or seasonal manual adjustment of their orientations. This research is focused on single-axis solar trackers that have one degree of freedom. Four-bar mechanisms (or linkages) consist of four links that are connected by revolute or prismatic kinematic joints in a closed loop. They are the simplest mechanisms with one degree of freedom. Four-bar mechanisms have been widely used in various mechanical devices for different applications. Properly designed four-bar mechanisms can generate the output motion to meet the solar tracking requirements. However, single-axis solar trackers that are based on four-bar mechanisms also face challenges such as limited solar tracking motion range, high actuation power consumption, lacking self-locking function. This research is aimed at circumventing the challenges on solar trackers that are constructed of four-bar mechanisms. In this research, 4R and 3R1P four-bar mechanisms are designed for generating solar tracking output motion. Their kinematic and dynamic performances are analyzed and simulated. The results from this research will provide guidelines for developing and promoting single-axis solar trackers using four-bar mechanisms.