Comparison of the efficiency of solar-powered prototype vapour compression cooler with evaporative charcoal cooler in maintaining quality of French beans

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Erick. O. Ogumo
Catherine N Kunyanga
Michael W Okoth
John W Kimenju


Charcoal cooling method; French beans; temperature; solar cooler; weight loss


The quality and shelf life of French beans is affected by the time of harvesting and storage period. Cooling immediately after harvesting is important. The use of a solar evaporative cooling system is suitable for use in rural areas with no power grid connections. This study compared evaporative charcoal cooler and solar cooling systems on improving the quality and shelf life of French beans. The prototype was made using mathematical modeling equations and was powered by solar power while the evaporative charcoal cooler was made from iron sheets with charcoal walls. Freshly harvested French beans were stored under the two cooling systems. The weight and temperature of the stored produce were checked hourly. At the end of the day, produce was packed into modified atmosphere packaging (MAP) bags and stored for 7 days in a cold room.  After seven days, oxygen and carbon dioxide levels were measured using a Bridge gas analyzer. The results show significant differences in weight loss between produce stored in evaporative charcoal shed and solar cooler prototype with those stored in evaporative charcoal cooler having 5% weight reduction while those solar coolers having 3% weight loss. A higher accumulation of CO2 was realized in the evaporative charcoal cooler than in the solar-powered cooler. The solar-powered cooler maintained weight, reduced the temperature of products, and maintained the balance between carbon dioxide and oxygen thus reduction in metabolic activities. This enhanced the shelf life and quality of the produce.