Generation of stable thermal gradient by solar energy harvesting in porous cobalt oxide based nanofluid

Abstract

Tailored nanoforms of cobalt oxide were synthesized to prepare water based nanofluid system for developing stable and significantly large thermal gradient within nanofluid column. The decisive impact of morphological growth on both optical and thermal properties of the dispersed nanomaterial has been elaborately studied. Morphological evolution from rod to flower induces significant enhancement in optical absorption within VIS-NIR region whereas, the thermal conducting property of flower nanoform is found inferior to rod. The morphological growth implements 48% enhancement in thermal gradient for ultralow concentration around 0.005 wt% at sunlit condition. The highly porous flower nanoform exhibiting an enhanced optical absorption and improved dispersion stability but inferior thermal conducting property leads to the formation of thermal gradient ~43 °C stable for >3 h at a filler fraction of 0.011 wt% in sunlit condition (800 W/m2). The optimum concentrations for maximum thermal gradient for each system have been investigated. Due to the significant heat localization, proposed nanofluid system is promising in field of solar driven evaporation. Employing the stable and significantly large thermal gradient within the nanofluid column the possibility of thermo-emf generation with known thermoelectric materials has also been proposed.