Feasibility evaluation of nanofluid based solar collector for biodiesel hot wash: An experimental study

To reduce emissions of carbon monoxide, particulate matter, unburned hydrocarbons and sulfates, biodiesel production has grown rapidly to replace conventional diesel. Sodium methoxide (SMOX) acts as an excellent catalyst for the chemical synthesis of biodiesel, and in recent years, has observed an increase in its global market share. As biodiesel synthesis requires high temperature water for removing unwanted contaminants, this work proposes a new application of aqueous SMOX as a nanofluid in solar collectors for passive heating instead of traditional energy consuming heaters. The results indicate an increase in the heat gain by 50 % at a solar irradiance of 700 W/m2, and the maximum efficiency of the device was found to be around 78 %, which is an increase of 17 % when compared to water as the working fluid. An economic analysis was performed to check the viability of the proposed solar collector in comparison to conventional industrial heaters. It is estimated that aqueous SMOX-based solar collectors are 53 % and 88 % cheaper in terms of total cost and maintenance cost per unit respectively. Apart from biodiesel synthesis, this data can effectively prove the viability of reusing excess and raw SMOX in other sub-processes of a small-scale biodiesel plant.