Material selection for solar central receiver tubes

Abstract

The severe operation conditions and great capital investment of solar power tower central receivers motivate the lifetime analysis of a molten-salt external-cylindrical-tubular receiver, considering five alloy alternatives for its tubes manufacturing: Haynes 230, alloy 316H, Inconel 625, 740H and 800H. An analytical low-computational cost methodology is employed, considering the temperature dependence of tube material properties, elastic-plastic stresses/strains and stress relaxation. Thus, creep and fatigue experimental data available in the literature for these alloys are compiled in this work, providing the coefficients required for the methodology followed. A great alloys operation limitation is the film temperature to avoid corrosion issues; the most permissive are H230, 740H and 800H (650 °C), followed by Inconel 625 (630 °C) and 316H (600 °C). This, and the twice the yield strength, is regarded to set the heliostat field aiming strategy as equatorial as possible for each alloy, resulting in great power production divergences: 24% and 65% less for 625 and alloy 316H receivers with respect to the 740H receiver. Then, the lifetime analysis for a clear design day operation, representative of the receiver during ideal operation, is performed. The stress relaxation regard becomes critical for the accurate damage prediction; alloys 316H and 800H show stress reset during operation, not benefitting from a global stress relaxation. Thus, 800H exhibits a poor endurance. For the clear-day assumption, 740H shows the best lifetime and costs/power performance; the levelized cost of alloy of H230, 625 and alloy 316H is 0.01, 0.09 and over 0.25, respectively, with respect to 740H.