It is important to design a photovoltaic system structure which can get the maximum solar input, since the efficiency of the photovoltaic system depends on the incident solar light. By the way, the sun''s position changes with time and season, the solar tracker must always track sun. When designing the solar tracker, its self weight, wind load, snow load and seismic load are considered because the solar tracker is installed outdoors. Especially, because it is exposed to the natural environment, sufficient rigidity withstanding extreme environments such as typhoon is required.
In this thesis, reducing the installation difficulty and the installation area, a new solar tracker is designed which can rotate in two directions by using a dual worm-gear rotating in the east-west direction with one worm-gear and rotating in the north-south direction with the other worm-gear. It becomes the simpler and lighter structure than the previous one. The wind pressure and stress of the solar tracker are calculated through the finite element method.
In order to minimize the wind load, which is the largest load applied to the solar tracker, the solar tracker is compared according to three cases with different sized gaps between the solar modules. It is also calculated for different inclination angles in each case. As a result of the wind pressure analysis, when the gap size is 0, the wind load is the lowest, and the larger the inclination angle, the more the wind load increases.
Three models of the frame structure supporting the solar modules are designed, and the lightest model is selected. Further, the thickness of the hollow tube, which is the beam of the frame part supporting the solar modules, is analyzed in different three case. As a result, the 2.3 mm hollow tube with a safety factor of 1.88 for the tensile stress and compression yield stress of the material used is selected.
The designed tracker is evaluated for stiffness by wind test. Also, the reliability of the analysis method used in this thesis is verified by comparing it with the analysis results of the analysis applying the same conditions as the test environment. At this time, the wind test is carried out by using a blower at four different positions, and the experimental value is measured by attaching strain gauges to the specified positions of the solar tracker. The strain and stress through FEM are calculated at the same position where strain are measured in the test.
As a wind test results, the maximum equivalent stress of the solar tracker is the largest when the location of the blower is front_middle_left case. In this case, however, the measured maximum equivalent stress has a safety factor of 2.42 against the tensile and compressive yield stress of the material used. The FEM results have a safety factor of 2.49 under the same conditions. The result calculated from the analysis at the same position as the result measured by the wind test has an error rate up to 6.6%.