Construction and Experimental Investigation of a Solar Dryer with Integrated Thermal Storage based on Sorption Material

Abstract

Burkina Faso, the world leader in organic dried mango production, and which provides 25% of the total supply of dried mango to Europe (Jovanovic, 2018 as cited in Mulder et al., 2019), depends totally on gas fire dryers although receiving good solar radiation through the year (GHI ≈ 5.5 kWh/m²). The contrast of not being a gas country producer combined to its limited access in the regions where mango’s fruits is harvested constitute an economic and ecological threat to the sector. As an environmentally friendly solution to improve solar dryer performance, Sorption Thermal Energy Storage (STES) technology has been investigated experimentally in a forced convection indirect solar dryer for drying mangoes in Burkina Faso. The dryer’s air collector includes two desiccants beds based on silica gel, to lower the ambient air specific humidity and thereby enhance the drying air’s capacity. Furthermore, a thermal storage bed with silica gel is integrated at the top of the drying chamber to perpetuate the drying process during the night and thus shorten the overall drying time. Due to the COVID 19 pandemic restrictions, during the harvesting period of mango in Burkina Faso (April to July) the achievement of the Dryer Performance Index (DPI) was not possible. However, on July 23rd and 24th, 2020, no-load measurements have been conducted with the solar dryer at the LabEREE of 2IE. The results show temperatures peaks of 90°C and 70°C respectively at the solar collector output. Besides, the collector’s temperature output was maintained above the ambient air temperature from 9 am to 6 pm the first day and 5 pm the second day of the experimentation. Further tests are in progress on the platform of the 2IE laboratory, Burkina Faso. Parallelly, a model has been designed with MATLAB software to serve as tool for determining the optimum balance between the silica gel required and the energy from the collector for such dryer. The model will be further validated through comparison with experimental results.