Design and Fabrication of Solar-Powered Refrigerator for Off-Grid and Rural Applications

Refrigeration is fundamental for food preservation, dairy freshness, and the cold-chain distribution of essential medical vaccines; however, millions of individuals inhabiting rural, tribal, and remote off-grid communities face severe electricity deficits. This research presents the engineering design, thermodynamic heat transfer calculation, 3D computer-aided drafting, physical fabrication, and empirical evaluation of an autonomous, portable solar-powered refrigerator engineered for off-grid operations. The developed unit integrates a 12 V, 200 W polycrystalline photovoltaic (PV) panel, a 12 V / 10 A pulse-width modulation (PWM) solar charge controller, a 12 V, 80 Ah deep-cycle rechargeable battery storage system, and a 12 V DC, 60 W cooling unit with dual forced-convection heat extraction fans. The structural cabinet is constructed from cold-rolled mild steel sheet metal insulated with 50 mm thick rigid polyurethane (PU) foam (thermal conductivity k = 0.022 W/m•K), providing a gross internal volume of 120 L and an effective usable storage capacity of 108 L. Thermodynamic evaluations indicate a steady-state conductive heat gain of 19.75 W across a 25°C temperature differential (ambient 35°C to internal 10°C). Heavy-duty lockable caster wheels provide facile mobility over irregular terrains. Experimental trials demonstrate that the refrigeration system achieves a thermal pull-down from 32°C to 10°C within 75 minutes, maintaining an internal temperature of approximately 10°C with 32 hours of continuous electrical autonomy in the complete absence of sunlight.