Novel incident angle modifier model for quasi-dynamic testing of flat plate solar thermal collectors

Abstract

There are two accepted standard methodologies to characterize the performance of solar thermal collectors: Steady-State Testing (SST) and Quasi-Dynamic Testing (QDT). This last methodology requires a model for the Incident Angle Modifier (IAM). In this article a new model for the IAM is presented to be used in the quasi-dynamic testing of Flat Plate Collectors (FPC), inspired in the interpolation procedure indicated by the ISO-9806 (2017) standard for SST. The model considers the IAM as a continuous and piecewise linear function and uses its nodes values at each 10° as adjustable parameters. The model’s performance is compared against four other widely-used pre-existing models, being more precise and showing a better overall agreement in the whole incident angle’s range. It is observed that the proposal is also more reliable, as it has a lower sensitivity to experimental data variability. This second characteristic allows to reduce test’s duration because it eliminates the ISO-9806 (2017) requirement of testing the collector in the morning and afternoon, in a balanced manner. Although the specific implementation of this work is for FPC, the model can be extended to other solar collector technologies as it has the ability to represent the IAM variability for all incident angles.