| dc.description.abstract | This study presents performance of one/two-axis tracking photovoltaic (PV) system in Jhong-Li. Due to limited experimental data of two-axis PV system, simulation annual electricity of one/two-axis PV system with PVsyst software was used. Experimental data were compared and validated simulation reliability. In two axis sun-tracking control, comparison of the approach of short-circuit current tracking, developed by National Central University and active tracking sensor produced by EVERPHOTON Energy were made. Finally, evaluation of outdoor PV module performance by measure I-V characteristic of module was provided.
In two-axis tracking PV system, short-circuit current tracking control which installed on tracker A, has a daily average offset angle between 0.37o to 0.68o. Another identical Tracker B with controlled by EVERPHOTON Energy tracking sensor, recorded a daily average offset angle between 0.09o to 0.2o. Though the tracking accuracy of short-circuit current control is not better than EVERPHOTON Energy tracking sensor. As for assessing the performance of PV system, electricity is the ultimate factor. Accumulated electricity of six days for trackers A and B are 56.14 kWh and 55.73 kWh, respectively. Both tracking methods were performed equally, yet the short-circuit current control has several advantages (e.g., can compensate errors due to mechanism deformation, installation and assembly of tracker). Therefore, it is a practical and effective sun-tracking method. In the average yearly electricity for one axis tracking PV system is 835 kWh/kWP based on four year records. Its performance ratio in 2009 was 80.1%, and dropped to 59.5% in 2011, which shows degradation and mal-function of PV system.
This study uses average meteorological year data to simulate electricity of one/two-axis tracking PV system. The predicted electricity for both two-axis trackers A and B and one-axis PV system are 1121, 1128 and 1073 kWh/kWP/year, respectively. In this case, electricity gain for two-axis PV over one-axis PV system is 5.17%.
Results of I-V characteristic measurement show that the increase of solar irradiation causes increase of maximum power output and affects the short-circuit current of PV module. While the increase of module temperature causes decrease of maximum power output and affects open-circuit voltage of PV module.
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