Stability analysis of two-dimensional flat solar trackers using aerodynamic derivatives at different heights above ground

Abstract

In this paper the aerodynamic stability of a flat-plate solar tracker under two-dimensional conditions is studied for different conditions of incident wind speed, U∞, nominal angle of attack, αn∈−40∘,40∘, and shaft height - chord ratio H/B=0.3,0.4,0.5,0.6,1and2. The stability is studied through the analysis of the aerodynamic derivatives A2∗ and A3∗ whose behaviours as a function of U∞ are presented for the H/B range studied. Two methods of obtaining the derivatives (one in the time domain and the other one in the frequency domain) are presented. A method for calculating the effective damping coefficient of the solar tracker, ξeff, as a function of the incident wind speed, U∞, is presented. This method can be used for any solar tracker structural characteristics (Jmech, Cmech and Kmech). With this method, the critical speed, Ucrit, can be determined by imposing the condition ξeff=0. The method was validated experimentally using the results of two different experimental set-ups.