Infinite-NTU Modeling for Studying Charging Cycle of Packed-Bed Solar Thermal Energy Storage
Abstract
An enhanced model is introduced to estimate reference cell output on a two-axis tracking surface using measured spectral irradiance and reference cell temperature. The model also uses the reference cell spectral responsivity and the spectral temperature responsivity. Under clear skies in July and December, the model reproduces reference cell measurements with an uncertainty of 0.9% at the 95% level of confidence. Under cloudy conditions during July, the modeled results match the measured data with an uncertainty 4.5% at the 95% level of confidence, and in December, the difference was 5.3%. These uncertainties are over a range of solar zenith angles from 20° to 85°. Keywords: Reference cell, spectral radiation, modeling