Solar energy harvesting by cobalt oxide nanoparticles, a nanofluid absorption based system

The improvement in the conversion of solar energy to thermal energy has been taking place over the last several years due to the growing demand of efficient solar powered systems. In recent times, nanofluid has emerged as an efficient heat transfer fluid due to its inherent capability to increase the solar-thermal performance. The present study comprises of a detailed experimental work to compare the effectiveness of two different types of system, viz. surface absorption system and nanofluid absorption system. The effectiveness of these systems have been evaluated based on the ability to raise the average temperature of the working fluid above the ambient temperature. The comparative study revealed an optimum range of cobalt oxide nanoparticle's mass fraction (i.e. 40 mg/l), which leads to a rise in average temperature of about 23.3 °C while using nanofluid absorption system. This value is almost 9.3 °C higher as compared to the surface absorption system under similar conditions which give a corresponding rise of about 14 °C. The study pointed out that the direct absorption of solar energy by the nanofluid is an important factor for overall increase in temperature (and consequently will lead to higher collector efficiencies). The work also highlights the use of cobalt oxide (Co3O4) based nanofluid for enhanced heat transfer events.