Experimental study on the effects of multi-resonance plasmonic nanoparticles for improving the solar collector efficiency

Abstract

Direct absorption solar collectors (DASCs) are distinguished from other solar collectors by the volumetric absorption process, where the working fluid directly absorbs solar radiation. There is great potential to use plasmonic nanoparticles in the direct absorption solar collectors. In this study, the optical characteristics of various silver nano-morphologies were investigated to formulate blended nanofluids that can absorb solar irradiation within a broad spectral range. Silver nanospheres and nanoplates with fine-tuned sizes and aspect ratios of 4–9 were synthesized and characterized. An innovative test section was built to validate the performance of different silver nano-morphologies under simulated solar irradiation. Hence, the photo-thermal conversion efficiency of nanofluids based on individual silver nano-morphologies can be accurately obtained. The experimental results revealed the promising performance of the blended nanofluids, where the efficiency of the DASC exceeds 70% at solar radiation concentrating factor of ∼2 and a total additives concentration of 0.94 ppm. The interesting aspect of the blended nanofluids formulated in this study is the remarkable low volume fraction of the nanoparticles, which reduces the settlement and agglomeration ratio. Consequently, a higher solar concentration ratio can be harnessed by using the low additives loading blended plasmonic nanofluids.