Field test on a solar drying system driven by a hybrid power system

To increase the production and improve the quality of dried agricultural products, a new drying system with a hybrid driving power system was developed and tested. The system with total collector area of 100m² is consisted of 10 drying units and each of them is consisted of 5 identical air collectors and a greenhouse-like drying chamber. Each of collectors in the system is equipped with a DC fan powered by 120W solar modules together with a 300W wind turbine and an AC fan directly powered by the electricity from grid. Such drying system can operate in all time of any day and avoid any possible spoilage of dried products as found in conventional solar dryers due to the formation of mould on the surface of dried materials in the events of consecutive rainy days. Field test for the drying of 9 fruits was conducted from November to December in 2005. The results indicated that the system was very effective for the drying of fruits and the solar drying time for most of the materials to be investigated was only one third of that required in the natural sun drying. Test results also showed that the nocturnal ventilation of drying chambers at the early stage of drying exercise was necessary for materials with high initial moisture in order to further shorten the solar drying time.