Abstract:
In regions like southern Algeria, where post-harvest losses of agricultural products are
significant due to high humidity and lack of preservation infrastructure, this study introduces
an innovative approach to indirect solar drying using forced convection. Two identical
prototypes were developed, each incorporating square-section metal tubes arranged in a V-
shape inside the solar air collector. In the first prototype, these tubes are filled with paraffin as
a phase change material (PCM) for latent heat storage, while the second uses empty tubes as a
control. The objective is to assess the impact of PCM integration on thermal performance and
drying efficiency.
Experiments were conducted on three agricultural residues: palm leaves, olive stems, and olive
branches, under real solar conditions in southern Algeria. The PCM-enhanced system achieved
higher and more stable air temperatures (up to 81 °C), compared to the non-PCM system
(maximum 73 °C), leading to faster and more uniform moisture removal. Thin-layer drying
models were applied to the data, with the Midilli–Kucuk model providing the best fit (R2 >
0.99). Effective moisture diffusivity (Deff) was also improved in the PCM system; for palm
leaves, Deff reached 3.1×10−10 m2/s with PCM, versus 1.9×10−10 m2/s without.
These findings confirm the dual benefit of the proposed configuration, which improves both
heat transfer and thermal energy storage. The hybrid solar dryer offers enhanced energy
efficiency and represents a promising solution for sustainable agricultural drying in off-grid
regions.
