Instrumental set-up to estimate the atmospheric attenuation along the slant path of concentrated solar plants

摘要

The diffusometer instrument informs about changes in aerosol load affecting the attenuation of the solar radiation along the slant path in central tower concentrated solar thermal plants (CSP). The diffusometer measurements need to be corrected according to the aerosol nature. Three correcting factors are computed by applying the Mie theory on the aerosol microphysical properties retrieved by AERONET. The application concerns the High Atlas chain of Morocco, hosting several CSP projects: a Biral VPF710 diffusometer will be set up at Midelt, and AERONET data are acquired at Ouarzazate. The mean correction factor K_(tot) at Ouarzazate was 0.93±0.10. K_(tot) is sensitive on the aerosol size and on the refractive index. An empirical relationship with the Angstrom exponent α, indicator of the mean aerosol size, shows that K_(tot) was 1.07±0.08 in January 2013 (α =1.02±0.31), but 0.84±0.03 in July 2013, during the desert dust month (α=0.17±0.11).