Advancing solar thermal energy systems: Comparative study of low-cost receivers in parabolic trough collectors

The growing demand for efficient and cost-effective solar thermal energy solutions underscores the importance of innovative receiver designs in parabolic trough collector (PTC) systems. Despite the reliability of conventional designs, there is a need for low-cost alternatives that are accessible for widespread use, particularly in developing regions. However, a notable absence of comparative studies using the International Organization for Standardization (ISO) norm, the ISO 9806:2017 standard, which is the most current framework for thermal performance testing, thus highlighting a critical area for exploration. This study aims to develop and evaluate two low-cost receiver designs for a PTC system equipped with a stainless-steel reflector: one featuring a U-pipe within an evacuated glass tube, and the other using inlet and outlet pipes. Experimental testing was conducted according to the ISO 9806:2017 standard to assess their impact on the thermal efficiency of the collecting system. Additionally, we validated our results against previous research findings, which employed the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) norm, the ASHRAE 93 standard, which is the older and more rigorous. The thermal efficiencies were determined to be 43.79% for the U-pipe receiver and 49.77% for the inlet/outlet pipes receiver. The latter design shows a reduced overall heat loss coefficient, caused by the increased heat transfer surface area and the direct contact between the water and the absorber. These findings highlight the potential of the inlet/outlet pipes receiver as a cost-effective and efficient solution, particularly in developing regions.