Drying of celery leaves (Apium graveolens L.) using a PV/T solar dryer

Abstract

Celery (Avium graveolens L.) has been naturally used to treat hypertension and cancer. Fresh celery contains a high water content of approximately ±86% which may lower the quality upon storage for a long time. Drying was applied to reduce moisture content in order to prolong the shelf-life. Drying of celery was carried out using a self-designed photovoltaic-thermal (PV/T) solar dryer as well as conventional dryers such as oven and vacuum oven for the comparisons at an approximate temperature of 49°C. The PV/T solar dryer was able to simultaneously convert the solar energy into thermal and electrical energy. The electrical energy was in turn used to drive the blowers to create a forced convective flow of heat transfer. Drying in the PV/T solar dryer was carried out in 3 different weather conditions while 3 different pressures (10; 40; 70 kPa) were tested during drying in the vacuum oven. The PV/T solar dryers demonstrated the best results in terms of constant drying rate (0.986 kg H2O/min.m2) and drying time (87 minutes). Total chlorophyll content retained was 5.42 mg/L. The PV/T solar dryer seemed promising to be further developed for an efficient drying process since it required low energy consumption while using the costless renewable solar energy.