Energetic and enviro-economic performance of medium scale evacuated tube solar air heating system for industrial applications

Industrial processes require significant amounts of hot air, emphasizing the importance of developing efficient solar thermal systems to reduce dependency on fossil fuels and mitigate environmental impact. Most of the early studies focus on small-scale setups with lower airflow rates, limiting their applicability to industrial applications that require higher volumes of hot air. The primary focus of this work is to evaluate the impact of series and parallel thermal networking on the energy and enviro-economic performance of evacuated tube-based solar air heating systems, specifically for industrial process heating applications with moderate flow rates up to 1000 kg/h. A medium scale 42kWth experimental setup which consists of a blower, 28 sets of Evacuate Tube Solar Collector (ETSC) modules with 4 series and 7 parallel arrangements, baffle plates, a header, and a common duct, is developed. The airflow rate was adjusted across modules between 150 kg/h and 500 kg/h, maintaining a total airflow of 1000 kg/h at the outlet using control valves. Results indicate that the maximum average outlet temperature of 356 K was achieved at 150 kg/h. On clear sky days, the designed system can deliver hot air over 323 K at an operational flow rate of 150 kg/h between 9:30 a.m. and 4:00 p.m. The highest thermal efficiency was obtained at the higher operating flow rate of 500 kg/h. For the operating flow rate of 150 kg/h, the cost per kWh to provide hot air between 343 and 358 K is projected to be 0.0083$ (0.63 INR). The highest and least CO 2 emission reductions were identified in the operating flow rates of 500 and 150 kg/h respectively. The average reduction in CO 2 emissions is 19.68 tCO 2 per year. Utilization of solar evacuate tube solar collector thermal networking can be deployed to reduce the environmental impact and fossil fuel dependancy. The system is more suitable for industrial process heating applications such as food product drying, paint drying, etc.