Design of an Instrumented Experimental Solar Drying Platform for Characterizing the Drying Process of Medicinal Herbs

Abstract

This paper presents the design of an instrumented indirect solar drying experimental platform for characterizing the drying process of medicinal herbs through synchronized recording of thermal, hygrometric, and environmental variables. The architecture integrates an appropriate-technology thermal subsystem, Arduino Nano-based data acquisition, a Python interface, real-time visualization, ON/OFF thermal regulation with a setpoint adjusted by a 10 kΩ potentiometer, and automatic XLSX data storage. The instrumentation records temperatures at different points of the equipment, internal and external relative humidity, solar illuminance, and atmospheric pressure. Product mass is determined only at the beginning and at the end of each test using an external balance. The auxiliary axial fan drives solar-heated air from the collector into the drying chamber while chamber temperature remains below the setpoint and is switched off when the setpoint is reached. Chamomile under the conditions of the Cochabamba Valleys, Bolivia (2,740 m a.s.l.), is used as the base sizing case with a 42 °C setpoint, a flat-plate collector calculated using the Hottel-Whillier-Bliss model, a three-tray drying chamber, and two natural-convection chimneys. The design case yields a calculated collector thermal efficiency of 50% and an estimated drying time of approximately two solar days. The main contribution is not a new solar-dryer configuration, but a low-cost, replicable experimental platform intended to compare different herbs and thermal conditions through reproducible time-series records. The mechanical prototype provides the physical basis of the platform; systematic multi-species experimental validation is proposed as the next research stage.