Experimental investigations on steam generation in nanofluids under concentrated solar radiation

Developing renewable energy, especially solar energy related, is of great importance for securing our future energy society. Steam generation in nanofluids based on solar radiation has been increasingly studied. It has been determined that the efficiency of steam generation is significantly enhanced when nanoparticles are seeded into the fluid owing to their unique radiative heat transfer performance. The nanoparticles trap solar energy inside the fluid and convert it into thermal form, which dramatically accelerates the steam generation process. In this study, we experimentally investigated different nanofluids that directly absorb solar energy to generate steam. Ag nanofluid, Au nanofluid and MWCNT nanofluid with different concentration have been carefully investigated. We analyzed the temperature increase and steam generation combined with the calculation of the efficiency factor from radiative heat transfer. The heating power and steam generation power of different nanofluids and the same nanofluid with different concentrations were compared. For Au nanofluid with concentration of 0.5 wt‰, the absorbed solar energy for heating the volume and generating steam is 6 and 40 times higher than those of pure water, respectively. We concluded that localized boiling generates steam rapidly in nanofluids based on the observation of three types of nanofluids. Furthermore, the heating power and steam generation power of different nanofluids increase with concentration. Moreover, the difference between the efficiency factors results in varied volume heating and steam generation efficiencies for different nanofluids despite identical concentrations.