Thermo-fluid and economic performance of PCHEs in a high-temperature thermal energy storage system coupled with an sCO2 Brayton cycle

Abstract

This paper focuses on a printed circuit heat exchanger as the primary heat exchanger between thermal energy storage systems and supercritical CO₂ Brayton cycles. Four atmospheric-pressure gases, CO₂, N₂, He, and Ar, were assessed as heat transfer fluid on the storage side as well as different channel designs, such as straight channels, zigzag channels, and airfoil fins. To that end, a 1D model, based on experimental and numerical correlations established in the literature, has been developed to optimize and evaluate the total costs of a 1 MW PCHE over a period of 20 years. It was shown that a large portion of the total costs is employed to compensate for the relatively high pressure drop on the hot side, due to the low gas density at low pressures. Therefore, various configurations of double-banked hot plates with different designs for the hot and cold channels were modeled and simulated under diverse boundary conditions. The results indicate that CO₂ has the highest potential as a heat transfer fluid due to lower associated costs. An optimized design of a PCHE for a TES application is proposed, which reduces the costs by increasing the cross-section of the gas flow, leading to the costs being 0.259 $ per Watt and year.