Design, Construction, and Evaluation of a Passive Solar Dryer for Sustainable Food Preservation

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Solar drying is a very old but continuously explored technology so that everyone can use to dry food products from meat, vegetables, cereals and the dairy products. However, over the time with increased pollution to both the air and water, the sun drying has been deteriorating. Solar drying provides a safe and reliable environment for the quality of the dried products and its preservative duration. This study, design and construction of the solar drier device has been done for the purpose of drying a variety of food products. The principle of the dryer allows lighter hot air to rises up the altitude and cool the surface. In the raising process warm air comes in contact with the food slices and draws the moisture from it. The repeated cycle of this process makes it a very healthy, low cost long-term drying mechanism. In the thermodynamics terms the sun’s power or heat is used to dry up the moisture content of the fruits or vegetables. The construction materials were wood, polyurethane glass, mild steel metal sheet and the trays. The optimum temperature of the dryer was 750C with a corresponding ambient temperature of 280 C. The rapid rate of drying in the dryer reveals its ability to dry food items reasonably rapidly to a safe moisture. The capital cost involved in the construction of solar drier is much lower compared to that of a mechanical drier. Also from the test carried out, the simple and inexpensive solar drier was designed and constructed using locally sourced materials. The temperature inside the drier was found to be about three times than that of the outside atmospheric temperature. As per our experiment the maximum peak temperature inside the drying chambers was 750C during the mid-day (1.00pm) and an average of 570C in a fully sunny day (from 10:00am to 5:00pm). In seven (7) hours continuous drying in one full sunny day under the same climatic condition and in the same time the solar drier can remove maximum moisture contents from the food contents inside the drier for low moisture content food products. Experimental observation shows that the solar drier can be used as an alternative in case of food preservation and the efficiency is also acceptable. The people can make it on their homes especially in the developing countries where the energy demand is higher.