Solar drying in a ventilated attic: case study of cassava slices

In constantly sunny regions of the world such as most African countries, due to the availability of sunlight, metal roofs that are constantly exposed to the sun offer opportunities for many solar thermal applications. This study focuses on the numerical and experimental investigation of solar drying in a ventilated attic. The constructed prototype attic has three PVC pipes used as chimneys, and the roof is painted black. It was modeled using the equations of heat and mass transfers occurring during drying. The food commodity subjected to drying was cassava. The resulting system of equations was solved using the classical fourth-order Runge–Kutta method. The MATLAB R2014a language is used for the simulations. The drying of 6 kg of cassava in the prototype took 3 days. The obtained experimental results were compared with the theoretical points. The mean relative error (E%) was used as a parameter for model validation. Its values of less than 14% obtained for temperatures and humidities are evidence that the theoretical points accurately represented the behavior of the attic during solar drying. The drying efficiency varied from 25% on the first day to 0.2% on the last day. The calculated payback period is 2 months. This method can be easily implemented and would be helpful to farmers in rural Africa.