Control of solar insolation via thermochromic light-switching gels

Abstract The investigated thermochromic gels show a phase separation when a characteristic temperature is surpassed. Particles are formed within a polymer network, which are responsible for a drastically increased light scattering efficiency. Accordingly, a reduction in the directional-hemispherical transmission in the solar spectral range from 81 ± 2 to (10 −1 +5 )% for a 1 mm thick foil-gel-foil system was observed. With the help of differential light scattering measurements and Debye's two-phase media model correlation lengths of a c = (100 ± 20) nm and a c = (400 ± 50) nm were derived for the scattering entities in the clouded case. From the optical thickness of the specimens the switching temperatures are derived. Additionally performed multiflux calculations for a purely scattering switching system allow to predict the radiation transport under variation of the optical thickness and the correlation length.