Design of a Solar Coffee Roaster for Rural Areas

Abstract

Coffee is the first agricultural exportation product of Peru. Most of the added value is in the roasting process, which is usually done abroad. Concentrating solar energy provides a sustainable, clean and affordable mean of roasting coffee locally. The producers’ income could be improved with such a technology, enhancing their quality of life.The design of a solar coffee roaster is detailed in this research work. The open-source Scheffler solar reflector is used to concentrate light on a roasting drum. Experiments and numerical simulations lead to an operational design capable of roasting 1kg of coffee in 24minutes with the 2.7 m2 solar concentrator. The 25cm diameter rotating drum ensures coffee mixing to achieve homogeneous roasting. A photovoltaic powered motor is used to rotate the drum. Light heats up directly the interior of the drum entering through a 20cm diameter opening. Thermal performances are improved through: 5cm cotton insulation, a cone at the back of the drum and absorbing internal walls (stainless steel loses its reflectivity after some time under high radiation).People show high interest in the technology, as experienced during tests in the coffee production region near Cusco. Further improvement is encouraged on the current design. Another approach based on indirect heating is also proposed for future investigation.