In the last years the interest in the use of nanofluids in solar energy systems has grown very quickly. In particular the developments in Concentrated Solar Power (CSP) have renewed worldwide interest in this technology for electrical power generation. Parabolic Trough Collector (PTC) is a system that concentrates solar radiation onto a receiver in which a heat transfer fluid flows, usually synthetic oil or molten salt. The former is the most common solution although it is flammable, toxic and, most importantly, it is not stable for temperatures greater than 400 °C. On the other hand, molten salts allow to increase the maximum fluid working temperature up to 550 °C, thus potentially increasing the overall cycle efficiency, but they require expensive heating systems because of their solidification temperature of about 250 °C.
A new frontier in high temperature heat transfer fluids is represented by gas-based metal-oxide nanofluids, which are a mixture of air (or other gasses such as Nitrogen, Helium, Argon, etc.) and metal-oxide nanoparticles (Al2O3, CuO, TiO2, ZnO, CeO2, Fe2O3). Recently, several authors have begun to propose the use of nanofluids, as heat transfer fluid in solar collectors, and to investigate their optical properties in order to exploit the phenomenon of direct energy absorption.
The results of optical experiments performed at high temperature show that optical properties of such nanoparticles are not modified at high temperature and, in particular, the absorption coefficient doesn’t change significantly in that temperature range (from room temperature up to 500°C).
This result makes metal-oxide nanoparticles suitable for operations at very high temperature, thus encouraging the use of gas-based nanofluids as heat transfer fluid in CSP plants.
Activity in collaboration with University of Salento (Lecce)
M. Lomascolo, G. Colangelo, M. Milanese, A. de Risi "Review of heat transfer in nanofluids: Conductive,convective and radiative experimental results" Renewable and Sustainable Energy Reviews 43 1182–1198 (2015)
M. Milanese, G.Colangelo, A.Cretì, M.Lomascolo, F.Iacobazzi, A. de Risi: “Optical absorption measurements of oxide nanoparticles for application as nanofluid in direct absorption solar power systems-Part II: ZnO, CeO2, Fe2O3 nanoparticles behavior“ Solar Energy Materials & Solar Cells 147 321–326 (2016)
F. Iacobazzi, M. Milanese, G. Colangelo, M. Lomascolo, A. de Risi " An explanation of the Al2O3 nanofluid thermal conductivity based on the phonon theory of liquid" Energy 116 786-794(2016)
M. Lomascolo, A. de Risi, A. Cretì, M. Epifani "
Founded by "National Public-private laboratory for the development of new innovative technologies for the generation of electric power from sun-light-SOLAR” - PON MIUR