Feasibility and economic evaluation of low-cost evaporative cooling system in fruit and vegetables storage

The climate of most zones of Ethiopia is characterized as high ambient temperature combined with low relative humidity, which has a negative effect on fruit and vegetables quality during harvesting, transportation, storage and marketing. Low-cost natural and forced ventilation evaporative coolers have been developed for fresh fruit and vegetables storage under arid and semi-arid conditions. The coolers were found to be effective in maintaining micro-environmental conditions for fresh fruit and vegetables storage. This research was aimed at investigating the feasibility and economics of using forced ventilation low-cost evaporative cooling to improve the indoor air conditions such as temperature and relative humidity. To reduce the indoor temperature and raise relative humidity, low-cost forced air ventilation evaporative cooler of 2.6 m ² floor area was fabricated and tested at Haramaya University, Fruit and Vegetables Research Station, on the storability of banana, papaya, orange, mandarin, lemon, mango, tomato and carrot. A fixed operating air flow rate of 4.3 kg ^-1 was used to evaluate cooling performance and energy efficiency ratio of the cooler. The results showed that the indoor dry bulb temperature significantly (P < 0.001) drops parallel with a significant (P < 0.001) rise in relative humidity during storage. The energy efficiency ratio (varying from 55 to 84%) was found to be high as the evaporative cooling system requires small electric power only for operating fan and water pump. The economic analysis indicates that the payback period of the evaporative cooling system is less than 1.2 years. The results clearly demonstrate that the forced ventilation evaporative cooling system should be recommended for use in developing countries in order to maintain better quality of produce. These results demonstrated the relevance of the use of this low-cost adiabatic cooling technology for shelflife extension of fruits and vegetables and thereby encourage organized women groups to involve in this perishable commodity handling and processing as a source of income.