DESIGN, ANALYSIS AND OPTIMIZATION OF NH3-H2O ABSORPTION CYCLE UTILIZING ENGINE WASTE HEAT AND SOLAR THERMAL ENERGY FOR REFRIGERATED TRANSPORTATION IN ERITREA

Abstract

The expansion of cold chain logistics in Eritrea is critical for food security and economic growth, yet it is currently hindered by the high operational costs and environmental impact of conventional diesel-powered transport refrigeration units (TRUs). This paper presents the design and feasibility analysis of a novel hybrid Vapor Absorption Refrigeration System (VARS) for a medium-duty (30 m3 ) refrigerated truck, specifically tailored to the Eritrean climate. The proposed system utilizes an Ammonia-Water (NH3- H2O) working pair driven by two renewable thermal sources: waste heat recovered from the vehicle's engine coolant loop and solar thermal energy harvested via roof-mounted Evacuated Tube Collectors (ETC). A thermodynamic model was developed to size the system components based on a calculated peak cooling load of 1.67 kW required to maintain a cargo temperature of 5°C under an ambient temperature of 40°C. The design integrates a 7.9 m2 solar collector array and an optimized 212 kg Phase Change Material (PCM) thermal storage unit to ensure continuous cooling autonomy for up to 3 hours during engine-off periods. The economic analysis demonstrates that the hybrid system eliminates the diesel consumption associated with conventional TRUs, yielding annual fuel savings of approximately 1,144 litres and operational cost savings of $1,522. Environmentally, the system reduces CO2 emissions by nearly 3.0 tonnes annually. With an estimated payback period of 9.8 years, the system offers a sustainable and technically feasible alternative for the Eritrean transport sector, significantly reducing dependency on fossil fuels while improving supply chain resilience.