Design of a Renewable Energy-Based Air Heating System

The objective of this research was to design, develop and investigate the performance of a solar-biomass hybrid air heating system to supply hot air at a specific temperature and flow rate for a daily load fraction exceeding 90%. The system consists of an unglazed transpired solar collector (UTC), a rock bed thermal storage, and a biomass gasifier stove with heat exchanger. From a review of literature, an air heating system, aimed at reducing the weather dependency and improving the temperature and flow rate stability without a conventional back-up heater, was designed. Based on analysis of various types of solar collectors, thermal storage, biomass stoves and heat exchangers that are commonly used, individual components of the air heating system were designed and fabricated. A mathematical model was developed to predict the thermal performance of UTC for a wide range of design & operating conditions. The components were coupled, and detailed experimentation carried out on the integrated system. Using only renewable energy for its operation, the system offers a reliable alternative to other RE-based dryers with conventional backup heaters, for medium-scale drying of food products.