Multi-physics circuit network performance model for CPV modules/systems

Abstract

Advanced empirical models have been developed to analyze or predict the performance of flat-plate or concentrator photovoltaic modules/systems in the outdoor environment [1]. These models typically rely on the use of empirical equations driven by several coefficients which are empirically determined through regression analysis of large sets of experimental data collected in the field. For instance, the performance model developed by Sandia Laboratories can be used to predict the performance of a photovoltaic module/system under varying (direct normal) irradiance, air mass, ambient temperature or wind speed. As the model empirically-determined coefficients are derived from averaged data sets (filtering out most transient effects), it is not always possible to link these coefficients to specific module design parameters. Moreover, since the detailed internal module wiring configuration is typically neglected, these empirical models cannot be used to accurately predict the performance of modules/systems when modules are partially shadowed. To overcome this limitation, specific models have been developed for predicting the non-linear effect of partial shading on PV systems [2,3]. This paper presents a generalized multi-physics performance model relying on the use of physical equations and elementary electrical circuit network models. This model can be used for predicting, comparing or analyzing the performance of concentrated photovoltaic modules or systems. The model is particularly useful for predicting the impact of a design change in the module/system materials, wiring configuration, solar cell type, or of the concentrator optics. Following a presentation of the model architecture, a first example presents how this performance model can be effectively used to optimize the module internal wiring configuration in order to minimize the impact of receiver current mismatch an reduce string losses at the system level. The model can also be used to determine the impact of shorts/opens defects on module performance. This performance model can also be used to determine the optimum method for binning and placing an array of individual receivers onto the backplane of micro-cell based concentrator photovoltaic modules [4,5]. A second example illustrates how the model can be easily extended through the use of high level analytical equations in order to perform multi-physics simulations. The impact of thermal expansion on the performance of a CPV module is studied using semi-empirical optical throughput equations of the CPV module optics coupled to thermal equations. Finally, a last example highlights the intrinsic capability of the model to accurately predict the non-linear effect of partial shading. Experimental data are presented to support these analyses.