Thermo-economic comparative of open-greenhouse and sun-patio coffee drying in the Sierra Mariscal Chiapas-México

We show a thermal-economic comparative of open-greenhouse and sun-patio drying in the Sierra Mariscal, Chiapas-México. Thermal analyses involve drying kinetics, thermal efficiency, and drying-specific energy; economic analyses involve the investment payback period and importance parameters analysis. In an open-greenhouse, 14 kg/m² samples were spread in 12 trays (135 kg/batch), while in the sun-patio were 10 kg/m² of coffee bed. The initial and final samples moisture content were from 53 % to 11–12 % (w.b). In the comparison, the sun-patio and open-greenhouse, respectively, drying constant, water-effective diffusivity, and activation energy were on average (11.8 × 10⁻⁰⁴:9.25 × 10⁻⁰⁴), (6.08 × 10⁻¹⁰:3.42 × 10⁻⁰⁹ m²/s) and (14.24:12.58 kJ/mol). In open-greenhouse, the payback period better correlates with solar irradiation, 39 % more than in sun-patio. Although the drying time in the open-greenhouse increases by an average of 60.0 % compared to the sun-patio and thermal efficiency by 15.0 %, the drying-specific energy is reduced by an average of 10.6 % and payback of 2.3 %. At a similar payback, the open-greenhouse drying fulfills sanitary regulations contrary to sun-patio. Although in open-greenhouses, the drying time increases by 60.0 %, the drying area requirement reduces by 14.0 times. Therefore, open-greenhouse coffee drying looks like a thermo-economic alternative for coffee growers, as it improves the dried beans without increasing the cost considerably.