Experimental performance evaluation of a parabolic solar herbal extraction system: A comparative study with traditional methods

In this study, the effectiveness of a solar-powered herbal extraction system with a parabolic dish concentrator was investigated and its performance was compared with conventional techniques. Thermal oil as a heat transfer fluid (HTF) was used to evenly distribute the temperature and improve the quality of the distillation process. The computational fluid dynamics (CFD) analyses showed that the spiral absorber provides high heat transfer efficiency and homogeneous heat distribution (346.85 °C at the outlet). The experimental tests were conducted over five days in July 2023 to evaluate the system's performance comprehensively. The results showed that the absorber temperature increased with solar radiation, peaking at 725 °C at 950 W/m², while thermal efficiency declined from 35 % to 25 % due to thermal losses. While the boiler and system efficiencies remained stable over five days, ranging between 60 and 65 % and 17–19 %, respectively, with minor fluctuations influenced by operating conditions, solar radiation, and thermal losses. The use of 2.5 kg of mint and 4.75 liters of water in the boiler resulted in a product with 52.1 % carvone and an overall efficiency of 91.6 % for mint distillation, while the traditional method yielded 47.3 % and 84 %, respectively. The solar herbal extraction system with the same composition removed 96.1 % of the main constituents in the rose water extraction, which is a remarkable improvement over the previous method with an extraction rate of 92.2. Although the distillation process of the solar system took longer (70 min for the first drop) than the conventional method (15 min), the quality of the product was higher. As the solar system uses less fossil fuel, it was able to provide a more sustainable alternative and reduce carbon dioxide (CO<inf>2</inf>) emissions by up to 12 kg per year.