Harnessing Heat Pipes for Solar-Powered Cooling: An Experimental Study of a BaCl2–NH3 Thermochemical Refrigerator

This study presents the experimental and thermodynamic evaluation of a solar thermochemical refrigeration system (STRS) powered by evacuated tube solar collectors with heat pipes as thermal energy sources, using industrial-grade BaCl2–NH3. The system was designed to produce refrigeration and ice using industrial-grade BaCl2–NH3 without additional additives or electrical input. Experimental tests were conducted under real-world conditions, with generation temperatures between 55 and 66 °C and solar irradiance of 750 to 900 W/m2. The system achieved efficient ammonia desorption, yielding up to 4.2 L of refrigerant and demonstrating repeatable operation over several thermochemical cycles. During the nighttime absorption–evaporation process, the STRS reached evaporation temperatures of −7 to −3 °C and absorption temperatures between 24 and 31 °C, suitable for ice production. The internal coefficient of performance ranged from 0.244 to 0.307, with an overall efficiency of 0.146 to 0.206. The experimental data obtained were used to derive pressure–temperature equilibrium equations for the BaCl2–NH3 working pair, yielding correlation coefficients greater than 0.98, which confirms thermodynamic consistency. The results demonstrate that additive-free, industrial-grade BaCl2 can achieve high efficiency at low temperatures, making this system a cost-effective and sustainable alternative for refrigeration and cold storage in rural areas. This research contributes new experimental knowledge on low-temperature thermochemical refrigeration and supports future development toward quasi-continuous optimization cycles based on experimental data.