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The energy and exergy (2E) analysis were executed in the present work on indirect natural and forced convection solar dryers (NISD and FISD) and the outcomes were compared. The NISD consisted of a collector and a drying cabinet whereas, for FISD, the NISD was updated by fixing a divergent tunnel integrated with DC fans activated with PV panels at the inlet of the collector. Therefore, no commercial energy was used for both setups. The transient temperature and moisture distribution in the trays of the drying cabinet and energy efficiencies of the collector and drying cabinet were evaluated for both dryers. The exergy inflow, outflow, losses and efficiency of collector and drying cabinet and sustainability indices were examined in both dryers. The energy efficiency of collector and drying efficiency were 58.5% and 9.39% in NISD and 66.37% and 12.11% in FISD, respectively. In NISD, the exergy inflow of the collector and drying section were 409.9–1344.15 W and 2.73–96.63 W, whereas, in FISD, the same were 375.5–1344.28 W and 1.03–65.75 W, respectively. The exergy efficiencies of the drying cabinet and collector were found to be 45.87 and 3.46%, 55.73 and 2.43% in NISD and FISD, respectively. The improvement potential and environmental impact factor ranged from 0.11 to 29.1 W, 0.2 to 15.51 and 0.012 to 11.35 W, 0.07 to 7.90, in NISD and FISD, respectively. The sustainability index was increased by 60.69% and the waste exergy ratio decreased by 18.52% in FISD compared to NISD. The 2E analysis revealed that the performance was enhanced in FISD compared to NISD. Uncertainty analysis was conducted for all parameters and shown as error bars in all plots.
Mugi et al. (Mon,) studied this question.