Low-Temperature Solar Thermal Energy Storage Using LaNi5−xMx (M = Al, Fe, Ga, and Zn) Alloys

Abstract

Lanthanum based alloys are used in this current work to store the low temperature (less than 120°C) thermal energy, as they absorb and desorb hydrogen gas reversibly. LaNi_5−xM_x (M = Al, Fe, Ga, and Zn) alloys are compared at constant energy storage and recovery temperatures based on their absorption characteristics. A comparison is made between a Simple Absorption System (SAS), a Compressor Operated Absorption system (CAS), and a Cascade Resorption System (CRS) to store thermal energy at low temperatures. van't Hoff relation is used to estimate the lowest temperature to store energy and the maximum temperature to extract it. The energy was successfully upgraded by CAS and CRS. For various La-based alloys, the three systems' performances were thermodynamically examined and compared. A maximum COP of 0.86 and 0.74 is obtained in a simple absorption and compressor operated absorption system, respectively, using LaNi_4.75Fe_0.25 due to low hysteresis. Maximum heat upgradation with the Al, Fe, Ga, and Zn substitution is reported as 50°C, 20°C, 48°C, and 60°C, respectively, at a compressor ratio of 5 with CAS. The CRS with same substitution gives the highest heat upgradation of 66°C, 43°C, 88°C, and 107°C at regeneration temperature of 120°C respectively.