Al-Si-Fe alloy-based phase change material for high-temperature thermal energy storage

Abstract

Carnot batteries, a type of power-to-heat-to-power energy storage, are in high demand as they can provide a stable supply of renewable energy. Latent heat storage (LHS) using alloy-based phase change materials (PCMs), which have high heat storage density and thermal conductivity, is a promising method. However, LHS requires the development of a PCM with a melting point suitable for its application. For the Carnot battery, the reuse of a conventional ultra-supercritical coal-fired power plant with a maximum operating temperature of approximately 650°C is considered. Therefore, developing a 600°C-class alloy-based PCM is crucial for realizing a highly efficient and environmentally friendly Carnot battery. Using thermodynamic calculation software (FactSage), we found that Al-5.9 mass% Si-1.6 mass% Fe undergoes a phase transformation at 576-619°C, a potential 600°C-class PCM. In this study, we investigated the practicality of an Al-Si-Fe PCM as an LHS material based on its heat storage and release properties and form stability. The examined Al-Si-Fe PCM melted until approximately 620°C with a latent heat capacity of 375-394 J·g-1. Furthermore, the PCM was found to have a thermal conductivity of approximately 160 W·m-1·K-1 in the temperature range of 100-500°C, which is significantly better than that of conventional sensible heat storage materials in terms of heat storage capacity and thermal conductivity.