This paper presents a comparative study of motion laws applied to a mono-axis string of photovoltaic modules and to a bi-axis system. This study will reveal which system is more efficient (inclusive economically) in the geographical area of Braşov and under which conditions. There are two types of tracking systems: mono-axis and bi-axis, the last being split into other three types of tracking systems according to their rotation axis. First the solar angles and direct solar radiation are computed and graphically modeled. Further the optimum elevation and daily angles are determined. For each interval both tracking efficiencies are calculated and then compared. Also, the yearly tracking efficiencies of mono-axis and bi-axis systems are compared. Taking into account the technical and economical aspects, beside the energy gain of the dual-axis tracking system, it was concluded that a mono-axis system is preferred for the studied geographical area.

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The paper presents a method to improve the efficiency of a photovoltaic (PV) string by employing a mono-axis tracking mechanism. The tracking system was optimized so that it has minimum energy consumption during tracking. The PV string simultaneously changes the daily position using a linear actuator which transmits the motion to all modules by a rack-pinion gear mechanism. The system is designed in virtual prototyping concept with the following software solutions: for the solid modeling-CATIA, for developing the mechanical model as multi-body system-ADAMS, and for the control system design-MATLAB/Simulink and ADAMS/Controls. The motion law was developed by a step-by-step tracking program, the application in this paper being performed for the summer solstice day.

Abstract. The objective of this paper is to create a step-bystep tracking program which assures an increased energetic efficiency for a string of photovoltaic (PV) modules. This is achieved through various calculations, having as parameters: the solar angles, solar time, day of the year and turbidity factor, following to capture the maximum solar radiation, but with a small angular domain of the daily angle. For a motion law with high precision, the year is split into 8 time intervals and for each one it is found the optimum fixed elevation angle with the according daily angle field.