Miniaturized test array as a means to determine the energy harvest of bifacial installations

Abstract

PV systems using bifacial solar modules have shown an increased energy harvest compared to systems with standard, monofacial panels. The energy yield of bifacial installations is however also heavily dependent on the installation conditions. For free-standing bifacial modules the optimum orientation is a trade-off between the front and rear side output and the efficiency is dependent on factors such as the ground reflectance or the installation height. In extended arrays additional factors such as direct shading and reduced ground albedo due to the adjacent rows have to be considered. Because of the sensitivity on multiple additional factors, compared to monofacial standard installations, the simulation and prediction of a bifacial PV arrays yield is by far more complicated. At present there are only limited simulation tools for bifacial arrays available. Accordingly, also the determination of optimized installation conditions is considerably less straightforward for bifacial installations. Because of the pronounced dependencies also the generalization of field data from specific installations is difficult. In order to obtain more general results, and also to have a sound basis for the verification of simulation models, a systematic variation of the installation parameters is desirable, but difficult to realize in real applications. A small and flexible test array may thus be a promising approach to obtain a fast and flexible testing device, provided that the results can be correlated to measurements at real systems. In particular, the fast change of the installation parameters allows a comparative analysis at virtually unchanged lighting conditions. In this paper we report on a miniaturized test array and relate the results to corresponding values from an installation with bifacial 60 cell modules. The results are of interest with regard to the suitability of such a device as a measurement tool to predict the output and the yield of real installations with bifacial modules.