Discrete two-positional tracking of solar collectors

Northern European regions, such as Estonia at 60 degrees latitude, receive about 980 kWh m(-2) y(-1) of solar radiation. These low insolation levels motivate solar collectors to be equipped with a tracking mechanism for an increased yield. Classical active tracking is complicated and energy intensive, negating tracking benefits for PV modules and thermal flat-plate collectors. This paper describes mainly the performance of PV modules with daily two-positional tracking. The symmetrical and asymmetrical positions about the north-south axis are analyzed, corresponding to the positions of sun in the morning and in the afternoon. The tracking drive is simple and requires a minimum energy input during the brief daily triggering of movement. Results indicate that the seasonal energy yield is increased by 10-20% over the yield from a fixed south-facing collector tilted at an optimal angle. The results are based on long-term solar data measured at the Tartu-Toravere Meteorological Station in Estonia, confirmed by experimental testing during summer 2004 and 2005 in Tallinn University of Technology. (C) 2007 Elsevier Ltd. All rights reserved.