Determination of performance and associated economic costs of indirect air-cooling combined with evaporative cooling for storage of tomatoes in South Africa

Knowledge of the cost of a storage structure for fruits and vegetables is paramount as a decision tool when farmers consider the return on investment. The performance and economic analysis associated with using a solar-powered indirect air-cooling (IAC) combined with evaporative cooling (EC) storage structure for storage of green harvested tomatoes was investigated. This study investigated the effect of IAC+EC system and period of storage on the quality of tomatoes over a 28 day storage period. The construction, maintenance and operation costs of an IAC+EC system were also studied. Various quality attributes of tomatoes were investigated by monitoring the storage of green harvested tomato fruit over 28 days under both IAC+EC system and ambient conditions with data collated every seven days. Tomatoes stored under IAC+EC conditions had significantly (P<0.01) higher firmness, lower total soluble solids content, lower physiological weight loss and higher average percentage marketability than those under ambient conditions over the storage period. The tomatoes stored in the cold storage conditions were 28.1% more resistant to puncture; had 7,3% less total soluble solids content, had three times less physiological weight loss, than those stored under ambient conditions over the same period. The h° and L* values decreased progressively over the period of storage from 84% at day 0 to 48.31% and 50.43% at day28 under ambient and IAC+EC conditions, respectively. Tomatoes stored under IAC+EC conditions had a higher average percentage marketability (72.4%) than those under ambient conditions (40.9%) over the storage period. The cost of constructing a 53-m3 IAC+EC system integrated with a solar photovoltaic system was US$8,680. The economic analysis that the payback period of the cooling system was less than two years. The results demonstrate that the IAC+EC system could be recommended for small-scale farmers in sub-Saharan Africa to maintain a better quality of produce if government and other funding agencies come on board.