Effect of wall design on heat loss and drying kinetics in a solar greenhouse for yellow pepper

This study investigates the thermal performance of solar greenhouses in the Northern Hemisphere, with the research purpose of providing process parameters to optimize passive solar greenhouse design for improved performance, reduced energy consumption, and enhanced environmental benefits. The novelty of the research lies in its investigation of the impact of wall configuration and orientation on thermal performance and drying kinetics of solar greenhouse dryers for drying Nsukka yellow pepper, providing new insights for optimizing drying conditions and designing efficient solar dryers. A modified solar greenhouse dryer with three different wall configurations (totally transparent, insulated northern wall, and insulated eastern wall) was tested under the same ambient conditions. The results show that the north insulated wall configuration improved thermal performance by 2.4-31.6% and reduced heat loss factor by 10.3%. The three solar greenhouse dryers produced a lifetime CO₂ mitigation potential ranging from 7.866 to 7.918 tonnes, with a drying time of 8 to 12 h per batch. Comparative analysis revealed significant variations in energy payback time (0.8581-0.8632 years) and embodied energy (626.67-627.77 kWh) across configurations. Thin layer models were used to predict the drying curve of yellow pepper for the three solar greenhouse dryer configurations. The Mathematical modelling revealed that the Modified Midili et al. model best fit the transparent and north wall configurations (R² = 0.9786 and 0.9700, respectively), while the Modified Henderson and Pabis model best fit the insulated eastern wall configuration (R² = 0.9526). The study demonstrates the importance of optimizing wall configuration and orientation for improved thermal performance, reduced energy consumption, and enhanced CO₂ mitigation potential in solar greenhouses.