Experimental comparative analysis of solar thermal and photovoltaic integrated vapor absorption refrigeration systems for low-GWP sustainable cooling under tropical conditions

Refrigeration, an indispensable modern technology with ancient origins, continues to evolve under the pressing demand for sustainability. In India, where the domestic refrigeration market is projected to reach ₹285 billion by 2034. The growing dependence on conventional vapor compression systems poses significant environmental challenges due to their reliance on high-GWP refrigerants such as R134a (GWP = 1430). Vapor Absorption Refrigeration (VAR) systems provide a sustainable alternative because they utilize low-grade thermal energy, operate with minimal mechanical components, and can be driven by renewable energy sources. This study presents a comprehensive experimental and comparative evaluation of solar-driven VAR systems integrating two renewable energy conversion pathways-a solar thermal flat plate collector (FPC) and a solar photovoltaic (PV) system. A 100 LPD solar flat plate collector was thermally coupled with a VAR generator through a copper heat exchanger optimized for insulation and mass flow, while a 100 W polycrystalline solar PV module with a 12 V/8 A charge controller and 12/40 Ah battery was employed to electrically drive the same system. The FPC-integrated VAR system achieved an evaporator temperature of 12 °C, and an average thermal efficiency of 35.3%, corresponding to a coefficient of performance (COP) of 0.14. Conversely, the PV-integrated VAR system attained a minimum evaporator temperature of 9 °C, maintaining a stable operational efficiency of approximately 9% and a COP of 0.12.