The optimization of the poor heat transfer characteristics of fluids conventionally employed in solar devices are at present one of the main topics for system efficiency and compactness. In the present work we investigated the optical and thermal properties of nanofluids consisting in aqueous suspensions of single wall carbon nanohorns. The characteristics of these nanofluids were evaluated in view of their use as sunlight absorber fluids in a solar device. The observed nanoparticle-induced differences in optical properties appeared promising, leading to a considerably higher sunlight absorption. We found that the thermal conductivity of the nanofluids was higher than pure water. Both these effects, together with the possible chemical functionalization of carbon nanohorns, make this new kind of nanofluids very interesting for increasing the overall efficiency of the sunlight exploiting device.

Solar thermal technology is a safe, sustainable, and cost-effective energy supply. The present paper reports on the comparative high-temperature emissivity characterization of hafnium and tantalum carbide ultra-high temperature ceramics to evaluate their potential as novel absorbing materials for concentrating solar power plants. For a more meaningful property assessment, ultra-high temperature ceramic samples have been compared also with silicon carbide, a material already used in volumetric solar receivers.

In this work we investigated the scattering and absorption properties of nanofluids consisting in aqueous suspensions of single wall carbon nanohorns. The characteristics of these nanofluids were evaluated in order to use them as direct sunlight absorber fluids in solar devices. The investigation was carried our for nanohorns of different morphologies and for suspensions prepared with different amounts of surfactant. The differences in optical properties induced by carbon nanoparticles compared to those of pure water lead to a considerably higher sunlight absorption with respect to the pure base fluid. Scattered light over the total attenuation of light was found to be nearly negligible at NIR wavelengths. Both these effects, together with the possible chemical functionalization of carbon nanohorns, make this new kind of nanofluids very interesting for increasing the overall efficiency of the sunlight exploiting device.

An innovative system for illumination of internal spaces was studied, constructed and tested. The system was dubbed `The Sunflowers' because the solar collectors were designed to track the sun's position during the day. Each Sunflower includes sunlight concentrators, optical fibres and mechanical and electronic systems for sun tracking. A Sunflower lighting system has been successfully installed in a prestigious museum to provide internal illumination of showcases. Solar illumination is obtained by concentrating the sunlight into optical fibres, which guide the light in the interior of the building and realise the lighting points.