Solar energy as a process intensification tool for the biodiesel production from hempseed oil

A simple, green, and energy efficient method for the biodiesel production has been developed using Fresnel lens solar concentrator (FSC). The transesterification of hempseed oil using FSC approach and conventional heating approach was studied by varying different process variables such as molar ratio, catalyst loading, reaction time, and stirring speed with an objective to establish benefits of FSC method. The highest biodiesel yield of 97.37% was obtained for FSC method in 4 min of reaction time with reaction conditions of molar ratio 4.5:1, catalyst loading 0.9 wt%, temperature about 60 °C, and 200 rpm. While, conventional heating method yielded only 21.3% of biodiesel in similar reaction conditions. To obtain similar yield (97%), conventional heating method required 70 min of reaction time at molar ratio of 6:1, temperature of 60 °C, catalyst loading of 1.05 wt%, and stirring speed of 300 rpm. Energy efficiency for both the methods was calculated, and observed that FSC method is 73 times more energy efficient than conventional heating method. Therefore, FSC method intensifies the process by reducing the requirements of time, energy, molar ratio and catalyst amount. The physicochemical properties like acid value (0.23 mg of KOH/g of oil), density (0.87 g/cm3), kinematic viscosity (3.12 mm2/s), pour point (−1 °C) and flash point (153 °C) of synthesized biodiesel were also compared with American Chemical Society for the Materials (ASTM) D6751 standard and found within the limit.