Performance Enhancement of Activated Carbon-Methanol Solar Adsorption System Using Coaxial Collector and Dual-Valve Stability

As the global demand for cooling continues to rise and is projected to triple by 2050, there is a need for sustainable, decentralized refrigeration technologies that can reduce reliance on energy-intensive vapor compression systems and high GWP refrigerants. This study presents the experimental validation and performance evaluation of a solar-powered adsorption refrigeration system that was specifically developed to cool potable water in regions lacking energy infrastructure. The intermittent system uses an activated carbon–methanol working pair, which is well suited for low-grade thermal energy sources, such as non-concentrating solar collectors. The unit included several novel design features, such as a coaxial tube flat plate collector for minimizing thermal resistance and maximizing heat transfer, and a dual-valve bypass system that restricts refrigerant flow to unidirectional flow and stabilizes the flow direction through fluctuating solar irradiation. The system was evaluated under 24-h cycles in multi-season conditions (December 2024 and April 2025) in Vadodara, India. The isolated collector achieved a peak regeneration temperature of 80°C during both cycles. The system demonstrated good performance, with a peak water temperature drop of 9.5°C and a total energy removal of 1988.4 kJ during the high solar-intensity cycle (April 2025). This resulted in an average COP of 0.240, while the SCP averaged 9.20 W⋅kg −1 for the cooler cycle. The COP value is considerably higher than that of previously reported AC–methanol flat plate systems (COP ≤ 0.16), demonstrating the efficacy of the coaxial tube and design aspects, such as the dual-valve configuration. This low-maintenance and solar-driven system represents a practical and sustainable option for decentralized refrigeration.