Development of a multi-purpose solar crop dryer for arid zones

Abstract

A multi purpose solar crop dryer was developed for drying various agricultural products such as fruits, vegetables, medicinal plants etc. The newly developed system consists of a small fan, a solar air heater and a tunnel dryer. The simple design allows production either by farmers themselves, using cheap and locally available materials, or by small scale industries. Due to the low investment required, the solar dryer is predestined for application on small farms in developing countries. Depending on the crop to be dried and the size of the dryer 100–1000 kg of fresh material can be dried within 1–7 days to safe storage conditions. The solar dryer was successfully tested in Greece, Yugoslavia, Egypt, Ethiopia and Saudia Arabia drying grapes, dates, onions, peppers and several medicinal plants. Compared to traditional sun drying methods, the use of the solar dryer reduces drying time significantly and prevents mass losses. Furthermore, product quality can be improved essentially. During drying, the crop is protected completely from rain, dust, insects and animals. All these features contribute to the desired high product quality. The energy cost required for operating the fan features contribute to the the additional earnings from reduced mass losses and improved quality. On-farm tests also showed that the dryer can be easily operated by farmers. However, at present the dissemination of the solar dryer is limited to electrified areas.