Abstract :
A method for experimentally determining the extinction index of four liquids (water, ethylene glycol, propylene glycol, and Therminol
VP-1) commonly used in solar thermal energy applications was developed. In addition to the extinction index, we report the refractive
indices available within the literature for these four fluids. The final value reported is the solar-weighted absorption coefficient for the
fluids demonstrating each fluid’s baseline capacity for absorbing solar energy. Water is shown to be the best absorber of solar energy
of the four fluids, but it is still a weak absorber, only absorbing 13% of the energy. These values represent the baseline potential for
a fluid to be utilized in a direct absorption solar thermal collector.
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