Design and performance study of a solar energy powered vaccine cabinet

An insulated steel sheet cabinet of 0.6 × 0.3 m face area and 0.5 m depth was designed. The cabinet was intended to store vaccine in remote desert areas, away from the electrical national grid. World Health Organization regulations limit the inside temperature of such vaccine storage cabinets to the range of 0–8°C. A solar energy powered absorption refrigeration cycle using Aqua-Ammonia solution was designed to keep this cabinet temperature in the range of required temperatures, away from the outside temperature, which reaches about 45°C in August. A computer simulation procedure was developed to study the performance and characteristics of the cooling cycle. The simulation included MATLAB computer programs for calculating the absorption cycle, thermodynamic properties and quantities as subroutines for the main program, and a detailed mathematical model using EXCEL for the solar side of the unit. A year round work was predicted. Refrigeration cycle coefficient of performance ranged between 0.5 and 0.65; cylindrical solar concentrator extended the daily operating time to about 7 h and increased the output temperature up to >200°C, while the temperature which gives optimum condition (of COP = 0.65) was 120°C.