Postharvest losses of fruits and vegetables remain a major challenge in tropical regions such as Bangladesh, primarily due to a lack of affordable and effective storage solutions. This study presents the design and development of a low-cost, solar-powered smart evaporative cooling storage system aimed at short-term storage of perishable produce while preserving its physicochemical qualities. The system comprises four integrated units: a cooling unit, a controller unit, a storage chamber, and a solar-powered energy supply. The key components include axial cooling fans, a thickened cellulose cooling pad, a submersible DC water pump, and dual exhaust fans. The solar power setup consists of two 150 W photovoltaic panels, a 12/24 V–30 A charge controller, and a 500 W battery system (dual 12V batteries connected in parallel). The insulated storage cabinet has a volume of 2.04 m³ and utilizes a hybrid evaporative cooling mechanism. Sensors were deployed to monitor the temperature, relative humidity, CO₂, and ethylene (C₂H₄) concentrations, with real-time data transmission to an IoT-based cloud platform for performance analysis. Under no-load conditions, the chamber maintained a temperature range of 26.02–29.45°C and relative humidity of 86.61–93.39%, achieving a cooling efficiency of between 49.71% and 83.86%. Tomato fruits at varying maturity stages were stored and compared against those kept under ambient and conventional refrigeration conditions. The results showed that the developed system effectively reduced physiological and biochemical deterioration, maintaining their postharvest quality and extending their shelf life. This study highlights the potential of developing a sustainable, energy-efficient, and affordable storage technology for smallholder farmers in tropical regions, contributing to reduced postharvest losses and improved food security.