Thermal performance study of a solar collector using a natural vegetable fiber, coconut coir, as heat insulation

There are few solar water heaters in Africa because of their acquisition cost, which makes it difficult for the populations to afford them. This article presents a solar water heater designed with a local vegetable material as insulating material, coconut coir, widespread in tropical countries. The study focuses on the comparative thermal performance of this collector and another collector, identical in design, fabrication, and operating under the same conditions, using glass wool as heat insulation, as well as with eight other designs, chosen randomly, using various materials as heat insulation, with performance data from the literature.The materials cost of the coconut coir collector is 25% less than the glass wool one. The results of the study show very good thermal performance of the collector using coconut coir compared to the traditional ones. For example, the outlet hot water temperature of the coconut coir collector was more than 80 °C. Internal hot water temperature rise was more than 40 °C. The thermal efficiency was a little over 51% although it was generally below 50% for the collectors using traditional insulation. It has a good pair of values of FR(τα) and FRUL. So, the lower cost of this type of solar water heater and its performance suggest that this design may be more suitable for application in tropical countries where coconut coir is commonly available.