Keywords: solar tunnel driers, copra drying, thermal storage, rock bed, natural convection, solar energy, solar power, heat storage, moisture content, thermal efficiency
Solar tunnel drier with thermal storage for drying of copra
A natural convection solar tunnel drier integrated with rock bed as sensible heat storage material was developed to test its performance for copra drying. The experiments were carried out with and without the integration of heat storage material. The temperature gradient inside the tunnel drier is about 10–25°C during the clear day and 7–12°C during off–sunshine hours, which is quite sufficient to dry agricultural commodities. The drier reduces the moisture content of copra from 52% (w.b.) to 7.1% (w.b.) in 54 hrs and 60 hrs respectively with and without the heat storage material. It produces 85% milling copra grade1 (MCG1). In open sun drying, moisture content reduces from 52.3% (w.b.) to about 7.1% in 153 hrs with an average of 53% MCG1. The average solar tunnel drier thermal efficiency estimated to be about 15%. The use of heat storage material increases the drier efficiency by 2% to 3%.