Performance and CO2 mitigation analysis of a solar greenhouse dryer for coconut drying

A natural convection solar greenhouse dryer with biomass back-up heater was developed and tested for its performance during summer and winter months under the meteorological conditions of Pollachi, India, using coconuts as drying material. The dryer maintained the temperature between 33 degrees C and 60 degrees C during summer, 26 degrees C and 43 degrees C during winter periods. The biomass heater maintained the temperature inside the dryer between 35 degrees C and 45 degrees C during night. The coconuts were dried from an initial moisture content of 53% to a final moisture content of around 7% in 54 h in summer and 74 h in winter in the solar-biomass hybrid dryer compared to 153 h during summer and 247 h during winter in open sun drying. The thermal efficiency of the solar-biomass hybrid dryer was found to be 24% and 21%, respectively, during summer and winter time. The embodied energy of the dryer is found to be 18,302 kWh and the CO2 emission was 1518 kg per year. The net CO2 mitigation is 678 tonnes and the total carbon credit earned is $18,645. The payback period of the drier was found to be 3.3 years.