Modelling and thermal analysis of an integrated solar greenhouse dryer for ginger (Zingiber officinale) and product quality

This investigation examined the drying of ginger using three different methods: open sun drying (OSD), passive mode (SGHD), and a newly developed integrated solar greenhouse dryer (ISGHD) in Northeastern India. The experiments were conducted under varying environmental conditions, with solar radiation ranging from 400 to 1100 W/m2, ambient temperature from 19 to 33 °C, relative humidity from 50 to 90%, and air velocity from 0.8 to 7 m/s. The drying times for ISGHD, SGHD, and OSD were 33 h, 52 h, and 60 h, respectively, to reduce the moisture content from 84% to 10%. The Page model was found to be the best fit for the drying kinetics, while the 5-10-3 ANN design was effective for the drying studies of ginger slices. The thermal efficiency of SAH and ISGHD ranged from 38 to 56% and 24–45%, respectively, while the exergy efficiency of ISGHD varied from 19 to 68%. The ISGHD method produced higher quality dried ginger compared to SGHD and OSD methods, with better rehydration ratio, colour value, texture, and essential oil retention. Additionally, the SEM images of ISGHD samples showed a clear and well-retained fibrous structure. The dryer's effectiveness and the quality of the dried ginger were enhanced using solar air heaters (SAH) and photovoltaic (PV) modules.