Construction and evaluation of a solar cabinet dryer

To improve drying practices while using the sun's free energy, Mondejar (CSCST) constructed and evaluated a solar cabinet dryer. The dryer has five main parts: solar collector, drying chamber, drying trays in 12 layers, door, and chimney. The performance of the dryer was evaluated in terms of capacity, temperature profile in the drying chamber, drying characteristics, and drying rate. The quality of dried product was evaluated in terms of its final moisture content, color, and appearance before and after 2-month storage. The dryer was evaluated against open-air sun drying as control. Results showed that temperature at the solar collector was consistently higher at 39.6 deg C than air temperatures in the drying chamber (ranging from 35-42 deg C) and the ambient air temperature at 30-35 deg C. This result showed that there was enough heat trapped from the solar radiation by the solar collector. The instantaneous moisture content of the product at layers 1-4 was not significantly different from the open-air sun-drying while layer 5-12 were significantly different from open air sun drying due to inadequate sunshine. It took 30 hours of drying from an initial moisture content of 70% down to 28% for open-air sun drying in layer 1-4. At layers 5-12, it was only down to 36% considering the sunshine during the drying period. Open air sun-drying was consistently higher in the rate of moisture removal during the first 14 hours only. Statistical analysis of the drying rate revealed a not significant difference at 5% level of significance. Quality of the open sun-dried and solar cabinet dried bangus appeared the same. However, dried products from layers 5-12 should be dried further to avoid molds contamination. In general, this study has shown the potential of a solar cabinet dryer over open-air drying. Further test is ongoing to determine its full potential. Drying of fish using the solar cabinet dryer can be done during times of intermittent short duration of rain without requiring additional labor of protecting the product from getting wet. Aside from drying fish, the solar cabinet dryer has a high potential in drying other commodities particularly fruits, vegetables, and other agricultural products. In order to attain the optimum performance of the solar cabinet dryer, some modifications in the dryer components should be made and further evaluation done to attain uniformity in drying enhanced heated-air movement, and increased drying capacity. As the experiment was done during rainy season, it was expected that the performance of the dryer will be better during the summer months, when sunshine is adequate.