Photothermal conversion characteristics of gold nanoparticle dispersions

•Propose and validate for the first time to use plasmonic nanoparticles to improve solar thermal efficiency.•Gold nanoparticles (GNPs) improve remarkably the photothermal conversion efficiency.•The efficiency enhancement reaches 65% comparing to the base fluid at 6 ppm GNP.•The specific absorption rate (SAR) of GNPs reach 10 kW/gram at 0.15 ppm GNP.•The comparison with other materials shows that GNP has the highest SAR.

This work proposes and validates a novel idea of using plasmonic nanoparticles (PNP) to improve the solar thermal conversion efficiency. Gold nanoparticle (GNP) is synthesized from an improved citrate-reduction method, and used as an example to illustrate the photothermal conversion characteristics of PNPs under a solar simulator. The experimental results show that GNP has the best photo-thermal conversion capability comparing to other reported materials. At the lowest particle concentration examined (i.e., 0.15 ppm), GNP increases the photo-thermal conversion efficiency of the base fluid by 20% and reaches a specific absorption rate (SAR) of ∼10 kW/g. The photo-thermal conversion efficiency increases with increasing particle concentrations, but the SAR shows a reverse trend, which is unexpected as all GNPs should be still in the independent scattering regime.