Recent advancements of solar dryers with implemented phase change materials
2021
Mrđa, Dragoslav B. | Turanjanin, Valentina M. | Vučićević, Biljana S. | Dimitrijević, Aleksandra | Zlatanović, Ivan
Using solar energy for drying agricultural products is one of the oldest methods of preserving food. Excellent results are obtained by using solar dryers, both in the quality of dried products and in energy-efficient drying procedures. The problem occurs when the solar radiation is low intensity or absent, which makes it impossible for the solar dryer to work. This problem can be solved by implementing phase change materials (PCM) which improve the efficiency of the system and allow the dryer to work in a period during off sunshine hours. This review provides insight into the progress in the field of solar dryers in which PCM is implemented. The impact of using PCM on the quality and efficiency of product drying compared to solar dryers without PCM and open sun drying is shown. It has been noticed that the use of PCM improves the global thermal efficiency of the system. The temperature and the percentage weight of moisture removal was increased and the drying time of the product was reduced. Various cases of drying apples, tomatoes, basil, bitter melons, strawberries and medicinal herbs have been considered. Different positions of PCM in flat solar collectors increased the thermal efficiency of the flat plate collector in the range from 5.02% to 10.13%, and the overall efficiency varied from 21.92% to 25.72%. The use of hybrid systems consisting of two or more synchronized systems also have been considered. The hybrid solar dryer with implemented PCM and integrated geothermal system showed an improvement in performance efficiency of 20.5% compared to a flat plate solar collector. The progress of solar dryers with the implementation of PCM is given with the aim of further developing the application of renewable energy sources in food preservation.
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