ГЕЛІОКОЛЕКТОРНІ ЗЕРНОСУШАРКИ: КОНСТРУКТИВНІ РІШЕННЯТА НАПРЯМИ РОЗВИТКУ

Purpose. To systematize scientific studies and patent solutions in grain drying with solar collectors, determine their design features, advantages and limitations, and substantiate promising development directions for energy-efficient grain-drying systems. Method. System, comparative and patent-analysis methods were applied. Direct, indirect and mixed-mode solar dryers were considered together with natural- and forced-convection systems, stationary and moving product beds, auxiliary heaters, thermal storage, heat recovery and automated control. The designs were compared by heat-supply method, airflow arrangement, grain movement, operating stability and scalability. Results. The most operationally stable solutions are hybrid systems combining forced airflow and an auxiliary heat source. Mixed-mode heat supply produces two oppositely directed drying fronts in the grain bed and improves moisture uniformity. Biomass-assisted heating increased the thermal efficiency of an experimental grain dryer from 39.9 to 57.7 %, while forced convection reduced drying duration compared with natural circulation in a mixed-mode dryer. Patent analysis indicates a shift toward modular and mobile systems, air recirculation, evacuated-tube collectors, heat pipes, photovoltaic fan supply and sensor-based regulation. Scientific novelty. A generalized classification of solar- collector grain dryers is proposed based on the combination of solar-energy conversion, direction of thermal impact on the material, airflow-path structure and operating-mode stabilization. The relationship between air-distribution design, temperature and humidity non-uniformity, and aerodynamic resistance of the grain bed is identified. Practical importance. The results can support the selection of a mobile or stationary grain-dryer configuration, preliminary justification of forced ventilation, auxiliary heating, heat recovery and automatic control, and formulation of requirements for a prototype adapted to variable solar irradiation.