Development of a Passive Evaporative Cooler for Storage of Tomatoes

A passive evaporative cooling structure was developed for extending the shelf life of tomatoes. The structure was developed as an attempt to solve the problem of temperature management facility which is either absent in the production chain of tomatoes or too expensive and sophisticated to procure and manage by most small scale tomato farmers in Nigeria. The structure was developed using local materials. It has a storage volume of 2.4m3 and takes advantage of the cooling effect of evaporating water to cool stored tomatoes. It also has cooling pad thickness of 25mmwith an overhead tank which supplies water through a PVC pipe by gravity on the cooling pad to keep it continuously wet. Quality characteristics of stored Mature-green and firm -ripe tomatoes were studied on daily basis at Yola and Ganye concurrently. Results of the study revealed that the extent of cooling of the Passive Evaporative Cooler was6.96 0C and mean Relative Humidity of 78.3% at Ganye and 7.52 0C and mean Relative Humidity of 78% at Yola. The efficiency of the structure without load was77.40% at Ganye and 62.00% at Yola. While loaded, the efficiency was67.70% at Ganye and 65.94% at Yola. Under these conditions, deteriorating characteristic such ripening, senescence, infection, and rotting were suppressed by the passive Evaporative Cooler for a period of 21 days for mature-green tomatoes and 14 days for firm-ripe tomatoes. In comparison to the control, the Passive Evaporative Cooler has comparatively less loss.