Performance evaluation of greenhouse solar dryer: Energy-exergy analysis, CFD simulation and eco-environmental assessment

Abstract

Solar greenhouse drying is considered a useful solar dryer technology for tropical and subtropical countries. This study examined a Quonset Solar Greenhouse Dryer (QSGD) with a parabolic roof and polycarbonate sheets on a 2.47 × 6.0 m² concrete floor, ventilated by two 220-V AC fans. The drying kinetics of mint leaves, energy-exergy analysis, Computational Fluid Dynamics (CFD) validation, economic viability and environmental impact were investigated. Mint leaves were dried from 85 % to 10 % moisture content in 3.5 h. The QSGD's energy and exergy efficiencies were 32 % and 22 %, respectively. The Discrete Ordinates (DO) radiation model simulated the effect of solar radiation inside the greenhouse dryer and the K-e model was used to account for the turbulent airflow. CFD 3-D simulations using ANSYS FLUENT ver.21 showed uniform temperature and airflow distribution, with good agreement between experimental and theoretical results. The outlet temperature ranged from 30 to 48 °C (experimental) and 34–50 °C (simulation) and also, higher air velocities were noted at the inlet and outlet. Environmental assessment revealed embodied energy of 47224.8 kWh, CO₂ emissions of 9.7 tons and net CO₂ mitigation of 130.7 tons over its lifetime. The Energy Payback Time (EPBT) and Payback Period (PBP) were 3.1 and 1.64 years, respectively.