Utilization of biodegradable novel insulating materials for developing indigenous solar water heater for hill climates

Conventional flat plate collector based solar water heating systems use glass or ceramic wool as insulating materials to minimize the heat losses. The utilization of these inorganic insulating materials, is associated with risk in the industrial workplace activities, manufacturing, and installation depending on the exposure to the material. Thus, it is important to use and develop biodegradable organic insulating materials which are easily available, low cost and environment friendly. This study presents the design and fabrication of a flat plate collector solar water heating system using biodegradable forest and agriculture wastes as insulating material. The utilization of pine needles and rice husk as thermal insulation for the fabrication of solar water heaters is the novelty of the study. The innovative solar water heater is tested under different outdoor climatic conditions. Maximum hot water temperatures between 52 °C and 55 °C were observed with an average efficiency of 52% and 57% with rice husk and pine needles as insulating materials respectively. Experimental analysis is performed using 40 mm, 60 mm and 80 mm pine needle insulation. The optimum pine needles insulation thickness is found to be 60 mm with a maximum hot water temperature of 64 °C for the indigenously developed flat plate collector based solar water heater for hill climates. Follow-up research areas are also identified.