Absorption energy storage: energetic potentials for different processes, boundary conditions and working pairs

Absorption thermal energy storage systems hold potential for enabling seasonal storage of solar energy, addressing the challenge of sustainable heating in cold climates. These systems utilize sorption processes to store energy in form of a concentration gradient, thereby minimizing long-term energy dissipation. This study investigates the theoretical energetic potentials of such systems, focusing on single- and double-lift processes with and without crystallization. Key system parameters, including source and sink temperatures, are varied to evaluate their impact on energy storage density (ESD). The analysis incorporates pT-Diagrams and phase diagrams for various working pairs, including NaOH-H2O, LiCl-H2O, CaCl2-H2O, and LiBr-H2O, to determine optimal operating conditions.The findings reveal that NaOH-H2O achieves the highest theoretical ESD across all configurations, with crystallization enhancing storage capacity but introducing design complexity. While double-lift systems show potential at high-temperature lifts between source and sink, single-lift processes remain more efficient at lower lifts. By presenting a comprehensive thermodynamic assessment, this work contributes to a deeper understanding of the role of closed absorption storage systems in the energy transition, offering insights for future research and development.