Sustainable Energy for Drying of Cashew Kernels – Experimental Research

Abstract

Drying is an important process in food preservation. In cashew processing industries cashew kernels are dried for easy peeling of the thin brownish sticky layer known as testa. For this it is necessary to reduce the average moisture content of 13% to 5%. Drying is achieved by direct and indirect methods like traditional open sun and using conventional energy through dryers. Due to control of the air properties in indirect drying cashew kernels can be dried at faster rate and can retain their quality. Air flow passages also play an important role in drying process. The objective of the study is to investigate experimentally the energy consumption for drying 1 kg of cashew kernel using electrically assisted heating and to evaluate the feasibility of active solar air dryer for drying in cashew processing industries. An electrical heat-assisted dryer (EHD) and an active solar flat plate collector air dryer (ASAD) systems are designed and developed using locally available materials. Both the systems are tested for reduction in moisture content with series of experiments. EHD is tested with three different drying chambers for optimum drying rate. In its final test drying chamber without baffle plates has resulted in reduction in moisture content to required level by 5% in three hours with drying rate of 2.8 kg/h against 6.5% and 6.8% in single tray version and four trays with baffle plate version. The drying efficiency of drying chamber is found to be 30.54%. In ASAD system the experimental results ensure the drying of cashew kernels within stipulated time of 6 hours with drying rate of 1.66 kg/h and energy consumption of 255 kJ against 270 kJ of electrical heater drying. The drying chamber exhibits an efficiency of 50.89%. The study suggests that the design is feasible to small, cottage industries for cashew kernel drying. The energy savings up to 3750 kJ per day for a batch of 15 kg is possible.