Ambient-temperature liquid ammonia cold thermal energy storage integrated with a solar two-bed CaCl2-NH3 chemical adsorption refrigerator: Case-study and parametric assessment

Vapour compression refrigeration systems are associated with greenhouse gas emissions and high electricity demand, which can strain power grids. To address these issues, this study analyses an ambient-temperature liquid ammonia cold thermal energy storage system integrated with a solar-driven two-bed CaCl2-NH3 chemical adsorption refrigerator to provide continuous subzero cooling without mechanical compression or high-grade heat, making it a promising option for low-grid or off-grid refrigeration. Liquid ammonia acts as both the refrigerant and storage medium, enabling cooling during off-sun hours independently of bed switching. A quasi-steady-state MATLAB model was developed and applied to a refrigerated warehouse case study in Beijing. The system supplied 432 kWh of cooling at −10 °C over 24 h. Across representative January, May, and July cases, the direct daytime cooling supply was 198, 234, and 270 kWh, respectively, while the stored nighttime cooling was 234, 198, and 162 kWh. The required stored ammonia masses were 672, 631, and 530 kg, with storage tank volumes of 1.376, 1.368, and 1.166 m3, respectively. The COP values were 0.45, 0.402, and 0.39. Solar collector preliminary design was provided. Parametric analysis quantified the effects of key operating temperatures on COP, heat flows, ammonia inventory, and storage volume. Evaporator and ambient temperatures are the dominant factors, while desorption temperature has only a minor effect. A preliminary economic comparison showed 9 years payback period. The results indicate that higher ambient temperatures constrain deep-freezing operation, requiring storage tank sizing based on worst-case annual ambient conditions and solar availability.