Performance evaluation, morphological properties and drying kinetics of untreated Carica Papaya using solar hybrid dryer integrated with heat storage material

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In developing country like India, renewable energy plays a vital role in extending technology for the farmers to enhance the agricultural productivity. The aim of the present work is to demonstrate the impact of heat storage material (HSM) in solar drying of untreated Carica Papaya slices using evacuated tube collector (ETC) based photovoltaic thermal (PVT) hybrid solar dryer. The performance of the solar dryer with gravel rock bed as HSM is compared with the solar dryer without HSM and natural sun drying. The initial moisture content of papaya slices is found to be 83 % (wb). The safe moisture content was attained in 5 h using solar dryer integrated with HSM, whereas, it took 6 h and 11 h in solar dryer without HSM and sun drying respectively. The inclusion of HSM increases the drying potential thereby reducing the drying period substantially. According to the statistical analysis of the results, Midilli et al. model was found to be the most suitable model to describe the drying kinetics of papaya slices in solar dryer with HSM, solar dryer without HSM and sun drying. The effective moisture diffusivity is found to be 2.58346 × 10−8 m2/s, 4.7366 × 10−8 m2/s and 6.15303 × 10−8 m2/s for sun drying and solar drying without HSM and solar drying with HSM respectively. The activation energy of untreated papaya slices is accounted to be 37.7441 kJ/mol using the Arrhenius equation. The findings proved that the solar dried papaya in dryer with HSM is observed to be better preserved without losing size, shape, colour, appearance, texture, flavour and quality than the solar dried papaya in dryer without HSM and the sun-dried papaya. The economic evaluation of ETC based PVT hybrid solar dryer with HSM reveals that the payback period is 2 years which is very low as compared to the life span of 25 years.