Volumetric solar heating of nanofluids for direct vapor generation

Abstract

Traditional solar-thermal receivers suffer from high surface temperatures, which increase heat losses to the surroundings. To improve performance, volumetric receivers based on nanoparticles suspended in liquid (nanofluids) have been studied as an approach to reduce surface losses by localizing high temperatures to the interior of the receiver. Here, we report measured vapor generation efficiencies of 69% at solar concentrations of 10 suns using graphitized carbon black, carbon black, and graphenesuspended in water, representing a significant improvement in both transient and steady-state performance over previously reported results. To elucidate the vapor generation mechanism and validate our experimental results, we develop numerical and analytical heat transfer models that suggest that nanofluid heating and vapor generation occur due to classical global heating of the suspension fluid. This work demonstrates highnanofluid-assisted vapor generation efficiencies with potential applications in power generation, distillation, and sterilization.

Volumetric solar heating and steam generation via gold nanofluids

“…In the statement: "For example, researchers [43] from Rice University", the Institution name should be replaced by the Authors' name.…”

“…In addition to the volumetric heating, direct vapor generation due to localized heating of nanoparticles [40][41][42][43] is a recent development in this area. For example, Neumann et al [44] showed that by using very dilute gold nanoparticles (16.7 ppm) under a focused solar light via a typical Fresnel lens, steam was produced instantly while the measured bulk temperature was still 6 o C approximately.…”

Nanofluids effects on the evaporation rate in a solar still equipped with a heat exchanger

“…Despite some limitations such as relatively high preparation cost and stability issues, extensive attempts have been made to develop the applications of nanofluids in energy systems such as solar energy based devices [7][8][9][10][11][12][13], cooling and thermal management of electronic equipment [14,15], grinding and drilling, absorption systems, medicine, heating and cooling of buildings, domestic refrigerators, and so on [16,17].…”

“…Nanotechnology has also been implemented to enhance the heat transfer potential of common liquids like water and oil to ameliorate the efficiency of thermal systems; this can be done through adding solid nanoparticles (particles with a size of 1-100 nm) to the liquids. The mixture of nanoparticles and conventional liquids is named "nanofluid" [6].Despite some limitations such as relatively high preparation cost and stability issues, extensive attempts have been made to develop the applications of nanofluids in energy systems such as solar energy based devices [7][8][9][10][11][12][13], cooling and thermal management of electronic equipment [14,15], grinding and drilling, absorption systems, medicine, heating and cooling of buildings, domestic refrigerators, and so on [16,17].In recent years, the problems of global warming and increase of the world population have highlighted the drinking water crisis. Although water covers more than 70% of the earth, most of this is not drinkable.…”

Steam generation under one sun enabled by a floating structure with thermal concentration

“…However, to reach 100°C for steam generation, a solar flux of 10 kW/m 2 , 10 times the normal sun (1000 W/m 2 ), was needed by optical concentration. Several other groups have looked into the role of surface chemistry in aiding water delivery and thermal insulation of the bottom layer, 20 incorporating plasmonic or carbon-based absorption layers, [29][30][31][32][33] and using other cheap and abundant materials. 34,35 These studies have achieved relatively high evaporation efficiencies, but relied on optical concentration to boost the evaporation temperatures and achieve such efficiencies.…”