Thermal Properties and the Prospects of Thermal Energy Storage of Mg–25%Cu–15%Zn Eutectic Alloy as Phase Change Material

Zheng Sun,Yuanyuan Li,Weibing Zhou,Linfeng Li,Jiaoqun Zhu,Xiaomin Cheng

doi:10.3390/ma14123296

Abstract

This study focuses on the characterization of eutectic alloy, Mg–25%Cu–15%Zn with a phase change temperature of 452.6 °C, as a phase change material (PCM) for thermal energy storage (TES). The phase composition, microstructure, phase change temperature and enthalpy of the alloy were investigated after 100, 200, 400 and 500 thermal cycles. The results indicate that no considerable phase transformation and structural change occurred, and only a small decrease in phase transition temperature and enthalpy appeared in the alloy after 500 thermal cycles, which implied that the Mg–25%Cu–15%Zn eutectic alloy had thermal reliability with respect to repeated thermal cycling, which can provide a theoretical basis for industrial application. Thermal expansion and thermal conductivity of the alloy between room temperature and melting temperature were also determined. The thermophysical properties demonstrated that the Mg–25%Cu–15%Zn eutectic alloy can be considered a potential PCM for TES.

Highlights

Thermal energy storage (TES) can deal with the mismatch between intermittent energy supply and demand by storing heat and cold for later use
The sharp diffraction peaks come from the mixture of hexagonal α-Mg, body-centered cubic Mg7 (Zn,Cu)3 and tetragonal MgCuZn phases, indicating that there is no obvious change in thermal properties after 500 cycles
The change in melting and freezing temperatures for the alloy were −1.3 ◦ C and −2.0 ◦ C, and the melting and freezing enthalpies decreased by 6.65% and 7.53% after 500 thermal cycles

Summary

Introduction

Thermal energy storage (TES) can deal with the mismatch between intermittent energy supply and demand by storing heat and cold for later use. TES is drawing great research interest for various engineering applications, such as concentrating solar power (CSP) [1], waste heat recovery [2], building energy conservation [3] and automotive engine cooling [4]. When choosing a phase change energy storage material, its thermal properties, such as working temperature, heat capacity, thermal conductivity and thermal reliability, are often valued. It is believed that PCMs with a higher phase change temperature generally allow for higher operating temperature and energy storage, which can considerably improve the system-level efficiency of current CSP plants. Candidates for high temperature phase change materials generally include inorganic salts and metals, either in pure form or as eutectic mixtures [10,11]. Metallic alloys possess high thermal conductivity and low overcooling degree, which means they could be promising high temperature PCMs

Methods

Results

Conclusion