Design of an injera baking system using parabolic trough solar collectors at Mekelle University cafeteria

Abstract

Injera baking poses a significant energy demand and strain on the national grid, requiring temperatures of 180–220 °C with traditional clay Mitads. This study aimed to design a solar thermal system to replace electrical baking energy at the Mekelle University student cafeteria. The system, designed for baking 11,000 Injera within a 6-h daily operation, comprises 92 Anodized aluminum plate Mitads heated by hot oil from an oil gallery, stored in a hot oil storage unit, and recharged via a parabolic trough solar collector. A heat exchanger and thermal storage system ensure efficient heat transfer and storage. Computational Fluid Dynamics (CFD) and Soltrace analyses were conducted to assess temperature distribution on the baking pan and oil gallery surfaces, as well as solar thermal heat flux. Results revealed a heating capacity of 2.11 kW per Mitad, meeting the required capacity, and a system energy consumption of 1216.5 MJ per hour, achieving a thermal efficiency of 57.4 %. Baking Injera at higher temperatures, enabled by a uniform temperature distribution, yielded uniformly textured Injera with an optimal number of eye bubbles and prevented sticking to the Mitad. Consequently, this design offers a viable alternative for the energy-intensive application at the Mekelle University student cafeteria, providing valuable insights for future solar thermal Injera baking system designers.