Integrated optical-thermal-mechanical model for investigations into high temperature sodium receiver operation

Abstract

An integrated optical-thermal-mechanical model is used to simulate the interaction between a heliostat field and sodium-cooled receiver through diurnal CSP plant operation. The cumulative heat flux on the receiver is controlled using a heliostat aiming strategy. A semi-empirical heat transfer model returns the receiver thermal profile based on the incident heat flux map, with aiming strategy solutions regulated by allowable flux density (AFD) data. A number of tube materials and inlet-outlet temperature combinations are investigated, with receiver thermal power output indicating suitable constructions for the delivery of elevated temperatures required for advanced power cycles. The selection of tube material is critical in maximising the heat absorption capabilities. The excellent creep-fatigue strength of Inconel 617 and Haynes 230 at high temperature yields a potential improvement in daily power output of up to 18% over more conventional heat exchanger materials. For these more traditional alloys, the aiming strategy requires a greater spillage allowance in order to generate a heat flux profile that satisfies lower mechanical reliability limits. The Ni-based superalloys alloys permit operation to temperatures far beyond conventional limits (>700°C), however the net power output is curtailed by greater heat losses at the receiver and an increased spillage requirement due to diminishing AFD levels.