Thermo–Energetic Modelling and Operational Load Limits of a Solar Dryer for Chestnuts

Abstract. This study presents a thermoenergetic evaluation of a solar drying system for chestnuts, operating with an initial moisture content of 47% and a final moisture content of 20%. The system consists of a 1 m³ drying chamber coupled to a solar collector with a thermal efficiency of 45%, evaluated with an average solar irradiance of 656 W/m² and an ambient temperature of 26 °C. The processed mass was varied between 2 and 40 kg to analyze energy performance and thermal stability. The specific energy consumption (SEC) decreased from 3.63 to 2.69 kWh/kg as the load increased, indicating better energy utilization at higher processing capacities. These values are within the ranges reported for solar drying of agricultural products, confirming the system's energy suitability. However, the internal temperature analysis showed a progressive decrease with increasing mass. For loads exceeding approximately 40 kg, the calculated temperature at a critical internal point decreased significantly, indicating an energy deficit under the fixed geometric configuration. This result reveals a thermal operating limit imposed by the chamber volume rather than the collector efficiency, highlighting the need to balance load, geometry, and available thermal energy in the design of a scalable solar dryer. Key words. Solar drying, specific energy consumption (SEC), thermal stability, system scalability