Thermal performance of a supercritical CO2 based central receiver

Abstract

This study investigates the thermal performance of a supercritical carbon dioxide (sCO2) based central receiver for a 3rd generation concentrated solar thermal (CST) plant having 10 MW thermal capacity. A thermo-optical modelling methodology is deployed to evaluate the thermal performance of tubular receivers with outer radii of 6.2 mm, 12.4 mm, and 24 mm. Solar PILOT ray tracing software is used to obtain the solar flux arrangement around the central receiver. The maximum heat flux permitted in the smaller tube receiver (ro = 6.2 mm) results in a smaller receiver and heliostat field for a particular power output. Heat flux concentration is found to be 77 % higher in a smaller tube (ro = 6.2 mm) receiver than in a large tube (ro = 21 mm). However optical efficiency is 3% higher in large tube receivers compared to smaller tubes. Computational fluid dynamics (CFD) simulation is performed to investigate the receiver performance considering Inconel 640 as a receiver material. Tube having ro = 21 mm has the highest solar to thermal efficiency (58.14%) i.e., 4.5% higher than the large tube (55.6%). Hence, further investigation is performed for the smallest tube to examine the variation of temperature, pressure drop, and Nusselt number as a function of Reynold’s number along the tube. There is a marginal change (1%) in the local Nusselt number from the receiver tube’s entry to exit.