A dynamic thermal modelling of solar panels using frequency-domain method

Abstract

A frequency-domain method for a dynamic thermal modelling of solar panels is presented in this paper. Different from the prevailing static models which assume the heat balance always holds between PV modules and local environments, the proposed method also considers the thermal dynamics before the heat balance is reached. To that end, time domain differential equations are established to describe the thermal dynamics using the standard heat transfer model in physics. With Laplace transform (F(s)≔L[f(t)]=∫0∞f(t)e-stdt), these differential equations are then converted equivalently into the frequency domain 2nd-order transfer function model with time delay, i.e., H(s)=(b1s+b0)e-Ls/(s2+a1s+a0), so that many mature frequency domain system identification methods can be utilised to determine the unknown model parameters of ai, bi (i=0,1), and L. Recursive square algorithm is also applied to minimise the modelling error. The proposed method is applied to both c-Si and a-Si PV modules from Photon Lab module test facility at Aachen, Germany, and compared with the measurement data of module temperatures for the full year of 2012. Both case studies consistently show significant improvements in accuracy, as compared to the existing thermal models. Physical meanings of the proposed model parameters are further discussed.