Segmental application of two heat absorption intensification methods in parabolic trough collector solar loop

Due to climate change and worldwide policies, the importance of renewable energy sources is increasing significantly. Increasing its share of total energy consumption is essential to reduce CO2 emissions and achieve energy independence. A commonly available source of heat is solar energy, which can be efficiently used and converted using a specific technology. For the generation of medium and high-temperature heat, CSP technologies are used, with parabolic trough collectors (PTC) being the most mature. In heat industrial power, this technology is used on a reduced scale, with a smaller aperture. The scale-down of the geometry and the lower temperature stage compared to traditional high aperture PTCs provides opportunities for optimisation and the use of alternative materials. As the temperature and heat flow parameters change in different sections of the absorber, it is optimal to introduce different methods in different areas of the solar loop. This article presents the optimization results of the use of non-selective but highly absorptive and cost-effective solar coating and twisted tape inserts in solar loop sections. The research was conducted for a case study which was a medium-sized industrial facility with a heat demand of a maximum of 250 °C. A numerical model was used for this study, validated by a previously performed experiment using a solar simulator. The results showed that both methods lead to an intensification of heat absorption, almost 45% of the absorbers can have a low-cost non-selective coating and twisted tapes with a twisted ratio of 1 and 2 can be applied inside the absorber pipes. The maximum efficiency gain was 1.3%.