Comparative assessment of indirect cabinet solar dryers in various operating modes versus direct cabinet dryers: A techno-economic analysis

Abstract

A cost-effective indirect cabinet-type solar dryer was designed and developed to remove the moisture in green peas until their moisture content reaches 14–15 % with minimal energy supplied from external sources. The green peas were placed beneath the absorber plate of the modified solar cabinet dryer (MSCD) thereby preventing its exposure to direct sunlight. The performance of MSCD was assessed at three different air velocities and was compared with a conventional solar cabinet dryer (CSCD) operated in passive mode. Experimentation showed that when hot air from the upper chamber of MSCD was fed to its lower chamber at 0.0406 kg/s, the dried green peas were free from shrinkage, uneven drying, and browning. However, when hot air was fed to the lower chamber of MSCD at 0.00585 kg/s and 0.027 kg/s the dehydrated green peas underwent shrinkage. At the same time, the green peas dried in CSCD underwent shrinkage, uneven drying, and browning despite its higher efficiency (about 13.5 %) and shorter span (2 h and 30 min) taken for drying when compared to MSCD. Hence, CSCD and MSCD operated at an air velocity of 0.00585 kg/s, and 0.027 kg/s was found to be not suitable for dehydrating green peas. The efficiency of MSCD when hot air from the upper chamber was fed to its lower chamber at 0.0406 kg/s was 10.64 % and the payback period was 0.47 years.