Investigation of low cost solar collector for drying vegetables in rural areas

Abstract

Despite the numerous solar dryers reported by researchers in Nigeria, farmers in Zaria Nigeria continue to dry tomato by traditional open sun drying method, the inherent problems associated with this method notwithstanding.  Therefore this research is aimed at investigating suitable solar collector material that is available, affordable and can easily be worked on by rural farmers.  Metal, wood, cement and mud which are commonly available local materials were used to fabricate four types of solar dryers and the dryers were mounted truly facing south.  Sliced tomato samples were used for performance test of the dryers.  Moisture content of the samples, dryer temperature, wind speed, relative humidity and solar radiation were monitored at 2 hours intervals.  From the analysis, the dryers’ savings in drying time over the open sun drying for wood, cement, mud and metal dryers were 131.25%, 131.25%, 136.17% and 192.11% respectively.  Average ambient wind speed during the drying period was 0.98 m/s, while that of relative humidity was 23.85%.  The metal dryer dried sliced tomato 18 hours ahead of mud dryer, while cement and wood dryers dried the sliced tomato 2 hours longer than the samples dried in the mud dryer. Temperature, energy generation, saving in drying time and  cost effectiveness, of mud dryer when analysed at F-test at 0.01 and 0.05 degree of freedom indicated statistical significant difference when compared with wood and cement dryers. The dryers equally indicated 7.38%, 19.56%, 20.25%, 20.91% and 27. 24% system drying efficiencies, for open sun, wood, cement, mud and metal in that order.  This work revealed that mud solar dryer is available, affordable and can easily be worked on by rural farmers.  Results from this work indicated that mud direct mode natural convection solar dryer is best suited for Zaria and Zaria related geographical locations.

Keywords: solar, energy, collector, crop, drying, drying efficiencies