Energy and exergy analysis of a natural convection solar greenhouse drier with insulated opaque walls for drying aromatic yellow pepper

The thermodynamic analysis of a simple natural convection solar greenhouse drier with insulated opaque walls has been proposed for drying aromatic yellow pepper. The aim is to assess its thermodynamic performance and its environmental sustainability. Opaque insulation of the northern wall (OINW) increased heat utilization by preventing heat losses. In contrast, opaque insulation of the eastern wall (OIEW) seems to block solar radiation from reaching the greenhouse. Thus, the greenhouse average bed temperature values were 10.4–10.91 % higher than the room temperature and 20 % higher than the ambient temperature. The average values for thermal efficiency were 16.35–22.73 % for the solar dryer. The specific heat utilization was higher for the OINW and lower for the OINE. Drying the yellow pepper from a moisture content of 86 % to 10 ± 1.2 % w.b. took 8–12 h of sunshine spanning three days. The effective moisture diffusivity increased with a decrease in moisture, with an average effective moisture diffusivity value of 2.05 × 10−9 m2/s - 3.06 × 10−9, showing a quicker drying potential for the OINW. The exergy efficiency ranged from 4.75 to 19.3 % for the totally transparent wall, 5.6–25.84 % for the OINW, and 3.6–15.83 % for the OINE.