Thermodynamic analysis of a novel absorption thermochemical energy storage cycle with double compression coupled two-stage generation

Abstract

• An energy storage cycle obtaining low T g and higher COP and ESD was proposed. • COP using LiNO 3 -[BMIM]NO 3 /H 2 O working fluid was 12.5 and ESD was up to 406 kJ·kg −1 . • This cycle was able to use the low-valley electricity for energy storage. Use of valley electricity for thermochemical energy storage that can be applied to building refrigeration is an important method for adjusting the natural fluctuations in the power grid and improving the energy efficiency of the system. This paper proposes an absorption thermochemical energy storage cycle of double compression coupled with two-stage generation to reduce the generation temperature and achieve a higher coefficient of performance and energy storage density. Based on the thermophysical properties of LiBr/H 2 O and LiNO 3 -[BMIM]NO 3 /H 2 O, the thermodynamic performance of this cycle under various working conditions was studied by MATLAB. The results showed that under the same working conditions, the temperature of the generator using LiNO 3 -[BMIM]NO 3 /H 2 O was 34 K lower than that using LiBr/H 2 O. The coefficient of performance of this new cycle using LiNO 3 -[BMIM]NO 3 /H 2 O was obtained at 12.5, which was much greater than that using LiBr/H 2 O at 7.9. Moreover, the former also achieved a larger energy storage density of 406 kJ/kg. The cycle using the LiNO 3 -[BMIM]NO 3 /H 2 O working fluid not only exhibited better performance, but was also able to effectively use valley electricity and play the role of “peak cutting and valley filling”.