Development of a two-axis solar tracker system based on AVR microcontroller for CPV (Concentrated Photovoltaics)

This work introduces a high accuracy solar energy tracking system equipped with a small concentrator module for electricity generation. The system can accurately track the sun without any issues for an extended period and operate as a stand-alone system. A high-precision solar tracking was achieved by combined use of open- and closed-loop control. C programming language and a microcontroller (ATmega128) enabled the operation of a low-cost and high performance solar tracker. Two different types of solar concentrator modules were designed and tested for their concentration ratios and tracking errors. One has a paraboloidal primary concentrator and a paraboloidal secondary reflector whereas the other has a paraboloidal primary concentrator and a hyperboloidal secondary reflector. Both modules showed an almost identical concentration ratio of 610 when the tracking error was not taken into account. The former, however, suffered from a sharp decrease in its concentration ratio when the tracking error exceeded 0.1°. In the latter case, on the other hand, its concentration ratio remained nearly unchanged as the tracking error kept smaller than 0.8°. Beyond this, it also showed a decrease in the concentration ratio as observed in the former. The maximum power output was obtained near solar noon with MJC (Multi-junction Cells), whose average solar conversion efficiency was 21% much higher than that of conventional PV systems.