Design and thermal performance analysis of concentrating solar power tower for water heating systems

Abstract

With the fossil fuel crisis, the world has been looking for renewable energies, and the concentrated solar tower (CST) technology has been the best solution in intensive solar areas. This paper introduced a detailed design, construction, and operation of small-scale CST for water heating applications in Aswan. Two heliostats (i.e., 50 × 50 cm2 cross-section area and 1.4 m spacing) redirect the incoming solar radiation into the tower's receiver. The receiver is a 20 × 30 cm2 cross-section area on a 1.0 m tower height and a space of 3.0 m from heliostats. Water flows through a 5.0 cm receiver's passage depth to absorb the reflected energy. This design is obtained from modeling the governing equations of both optical and thermal fields. The designed optical efficiency was ≈85.46% for the optical field, dominated by the Cosine efficiency. As for the thermal field, a detailed 1-D heat transfer mechanism is presented to predict the internal temperature. After construction, an experimental test is done, including temperature measurement of the receiver's outer surface and water inlet/outlet. The result consistently affirmed the mathematical model, revealing the CST's ability. Through the designed flowrate of 10.2 L/h and outlet-inlet temperature differences of ΔT = 19.5 ± 0.4OC, the maximum water temperature of ≈48.5 ± 1.0OC was observed at the daytime of 13:00. The maximum obtained designed efficiency was ≈52%, showing ≈19% reduction in the designed values (i.e., optical efficiency was ≈69.22 ± 8.2%, while receiver efficiency was ≈74.52 ± 5.4%. This work could provide a prototype to the community, promising advanced application of CST technology in the future.

Keywords

• CST
• Central tower receiver
• Heliostat
• Optical efficiency
• Aswan