Effects of EPCM particle properties on creep damage of the molten salt packed-bed thermal energy storage system

Abstract

One of the concerned aspects in the design of molten salt packed-bed thermal energy storage (TES) tank with encapsulated phase change materials (EPCMs) is to evaluate the creep damage because of molten salt tanks have to withstand elevated temperature and stress level in charging and discharging processes. This paper aims at estimating the creep damage and investigating the effects of EPCM particle properties on creep damage performance of EPCM-TES tank. First, a commercial scale molten salt EPCM-TES tank applied in 50MWe tower plant is designed. Second, a method to evaluate the creep damage of packed-bed tank in service life is developed based on the integration model coupling FVM and FEM. Then, the effects of particle diameter and melting temperature of EPCMs on creep damage are discussed. Finally, a novel diameter-changed and melting temperature-changed two-layered EPCMs packed-bed structure with lower creep damage is proposed. The results are concluded as follows. (1) The creep damage of bottom wallboard is more significant than that of other wallboards in operation. (2) The EPCMs with smaller particle diameter or higher melting temperature is helpful to reduce the creep damage of tank. When particle diameter decreases from 42 mm to 20 mm or melting point rise from 365 °C to 395 °C, the creep damage of bottom wallboard can be reduced by 4.8 times and 58 %, respectively. (3) The creep damage of novel two-layered EPCM-TES configuration with lower creep damage time and stress is weaker than single-layered form. Compared with single-layered form filling with higher particle diameter and melting temperature of EPCMs, the creep damage of bottom wallboard in two-layered structure can be reduced by 53 %. This work can provide insights on the optimization design of the EPCM packed-bed TES configuration for lower creep damage in service life.