The average solar tunnel drier thermal efficiency estimated to be about 15%. The use of heat storage material increases the dryer efficiency by 2% to 3%. Ayyappan et al. (2015) conducted an experiment with natural convection solar greenhouse dryer using different sensible heat storage materials (concrete, sand and rock-bed) in order to study their thermal performance. For both sand and rock-bed, 4′′ thickness was found to be optimum as it provides better drying environment both during day and night.