Reim et al. investigated the performance of flat solar thermal collectors with granulate and spherical silica aerogel material as thermal insulation.
The aerogel is a nanostructured material that has low thermal conductivity (o0.005 W/mK) and
high solar transmission (53% for semi-translucent spheres and 88% for highly translucent granulate).
In this paper, thermal conductivity values of evacuated solar collector with aerogel as insulation are compared with those of conventional solar thermal collectors.
The aerogel material reduces the thickness of the insulation inside the solar thermal collector and it reduces heat losses of 40% compared to conventional insulation.