A comparative performance analysis of sensible and latent heat based storage in a small-scale solar thermal dryer

Abstract

Economical and accessible thermal storage material that can store and sustain operation during off-sunshine hours is essential for small-scale solar thermal drying systems installed in households or communities. This study presents the evaluation of two energy storage modes- sensible and latent heat storage along with a control experiment in an indigenously developed small-scale mixed-mode solar thermal dryer. Black pebble stones were used as sensible heat storage material while paraffin wax (melting temperature 58–60 °C) was used as latent heat storage material. On a typical sunny day, under no-load condition, the maximum drying air temperatures reached were 102.30 ºC, 86.51 ºC, and 86.42 ºC for control, sensible heat, and latent heat stored units, respectively. A comparison of change in the moisture content of Indian gooseberry loaded in the units w.r.t time revealed that the berries in the latent heat stored dryer dried in 18% less time than sensible heat stored dryer. The drying air temperature of the sensible heat stored units became at-par with the control unit 2 h after sunset; however, the dryer containing paraffin wax could sustain drying for 3 more hours. CFD was employed to predict the units' airflow and temperature distribution patterns using RANS equations for natural convection. This study is expected to lead to the development of efficient small-scale solar thermal dryers for small enterprises.