Design and Construction of a 700kWth High-Temperature Sodium Receiver

Abstract

The Australian Solar Thermal Research Institute (ASTRI) has been developing technologies designed to collect and store solar energy at high-temperature to drive a new high-efficiency power block based on the supercritical CO2 Brayton cycle. ASTRI is pursuing two alternative pathways: one based on the use of liquid sodium as a heat transfer fluid, and the other based on the use of solid particles. The current work describes ASTRI’s progress towards design and construction of a 700kWth prototype sodium receiver suited to this type of system, which will be installed and tested on Solar Field 2 at the CSIRO Energy Centre in Newcastle, Australia. The receiver is a cavity receiver with a circular aperture oriented at a tilt down towards the centre of the heliostat field. Inside the cavity are ten vertical tube banks in a semi-circular arrangement, with sodium flowing from the centre to the outside in a serpentine manner. Optical and thermal modelling at design point predicts aperture interception efficiency of 95.3%, receiver efficiency of 90.9% and thus a combined interception and receiver efficiency of 86.6%. Conservative flux limits are set based on the tube material’s (Alloy 625) time independent tensile strength, which is dominated by creep for the sodium temperatures considered. In the event of incident, the receiver is designed to drain and a door closes over the aperture to limit smoke egress. Insulation is SiO2-CaO-MgO blanket, and all pipes are heat traced. Fabrication of the receiver was completed in July 2022 and first on-sun testing is expected in September 2023.