Modeling of select operational modes of a 2.0 MWTH sodium/molten salt pilot system/CSP Gen 3 liquid phase design.

Ternary Chloride Molten Salts (MgCl2-KCl-NaCl) in a 20%NaCl/40%MgCl2/40%KCl base mole fraction yield highly favorable thermophysical properties which are attractive to the development of novel CSP Gen 3 system designs [1,2]. By heating the salts to higher temperatures (e.g. 720 °C), higher system efficiencies can be achieved towards fully realizing the SunShot efficiency goals of $15/kWhTH HTFs (heat transfer fluids) and an LCOE of 6¢/Wh. In this work, an updated and revised quasi-state Engineering Equation Solver (EES) model presented in Armijo et al. [3,4] has been further developed to explore: 1. the addition of new pump specifications for the cold and hot tanks, 2. the implementation of a revised network with additional connections between the cold and hot legs, 3. the evaluation of additional valves and system components that incur additional losses in the network (e.g. salt chemistry) and 4. the optimization of system and valve sizing for two operational modes of the pilot 2.0 MWTH Sodium/Molten salt pilot system (charge and discharge). Two quasi-steady state models were developed to facilitate computation and avoid convergence issues in EES for the inactive lines when modelling the respective operational modes. The pilot-system design features hot and cold tank storage temperatures of 720 °C and 500 °C respectively, with a sodium-to-salt heat exchanger coupling the salt loop to the receiver, and a salt-to-sCO2 heat exchanger. These models serve as a tool to determine expected valve coefficients (i.e. CV values) at the operational modes of interest, determine the thermodynamic properties (e.g. pressure drop, temperature, pressure, etc.) of the thermal hydraulic system, study the influence of variating design values at the different subsystems (e.g. different molten salt blends), evaluate system efficiencies, and estimate total desired head loss values for different configurations. In this work, the system was optimized to comply with valve coefficients of up to 40. [ABSTRACT FROM AUTHOR]