Investigation on drying kinetics and techno-economics of solar- biomass hybrid drying system

A solar-biomass hybrid dryer was designed and fabricated at Dr. Panjabrao Deshmukh Agricultural University, Akola, Maharashtra, India. A biomass combustor was retrofitted to natural convection solar tunnel dryer utilized solar energy for drying of turmeric slices during day time and Prosopis juliflora as fuel in biomass combustor cum hot air generator during off sunshine hours and thus extended the working time of the dryer. The results indicated that drying was faster and took less time in SBHD as compared to the OSD (Open Sun Drying). The maximum efficiency of biomass combustor and solar- biomass hybrid dryer was found to be 79.79 and 14 per cent, respectively. On the basis of economic analysis, it is revealed that drying of 5 mm processed and unprocessed turmeric slices seems to be economical in SBHD. It was found that the system could generate an adequate and continuous flow of hot air in the temperature range of 50 to 60° C required for drying. In drying kinetic study, Modified Henderson and Pabis model was found best fitted for blanched and peeled turmeric slices of 5 mm thickness (SBP3) and Page model was found to be best fitted for blanched and unpeeled turmeric slices (SBN3) with higher R² in comparison with other mathematical drying models. The best ranked thin layer drying model for the blanched and peeled turmeric slices (HBP3) dried in solar biomass hybrid dryer was Two term model. The best ranked thin layer drying model for the unblanched and peeled turmeric slices (HBN3) dried in solar biomass hybrid dryer was Logarithmic model. The drying of turmeric slices in SBHD gave better quality powder in terms of color (higher L*, a* and b* value) than open sun drying.