Development and Performance Evaluation of a Hybrid Solar Dryer with Latent Heat Storage and Dehumidification Systems

Drying agricultural products has become an essential technique for preservation, but current drying methods often prove to be energy-intensive, costly, and unsuitable for the needs of local small and medium-sized enterprises (PME/PMI). In this study a hybrid solar dryer has been designed specifically to meet the needs of PME/PMI. The current limits to the development of solar drying in Africa are low efficiency and low autonomy. To remove these bottlenecks, thermal storage and air dehumidification systems are often used.

This article firstly, presents a brief review, not only of thermal storage materials but also of dehumidification systems. This review led to the choice of paraffin and silica gel respectively for thermal storage and dehumidification of drying air.

The selected materials were subsequently implemented in an indirect hybrid dryer with a drying capacity of up to 50 kg of fruits and vegetables. It is made up of an aluminum absorber painted in matt black, 1.5 mm thick. Its exterior structure is made of steel separated from the interior face made of stainless steel, by a layer of glass wool, 30 mm thick. Performance tests are carried out on the classic dryer, then with the dryer integrating silica gel on the one hand and on the other hand, the dryer with paraffin. The tests were conducted in Cotonou (latitude: 6°21'50"N; longitude: 2°26'32"E) during the month of November with an average irradiation of 137.23 kWh/m² received on the horizontal plane with an average temperature of 27.4°C.The experiments are carried out over several days so as to be able to extract, for each of the improved dryers, 03 days similar, from the point of view of daily irradiation, to the tests on conventional dryers. Tests carried out on the dryer with the new latent heat storage system reveal an increase in efficiency of 3% compared to the classic dryer. The proposed dehumidification solution showed a good dehumidification rate of 16% which helps to improve the overall efficiency of the dryer. In practice, this improvement in performance will result in a reduction in drying time and energy consumption. These first promising experimental results will be validated with other tests which will be carried out over several consecutive days, also varying the quantities of paraffin and silica gel.