Design, Fabrication and Characterization of Double Sloped Solar still for Household uses in Kilifi County using locally available materials

Abstract

Kilifi County, Kenya has encountered persistent water problems due to many factors like rapid population growth, poor maintenance of existing water supply networks, water salinity due to seawater intrusion, pollution from numerous pit latrines and septic tanks in the towns, high levels of humidity and temperature which causes dehydration to the residents. Solar energy is a clean, unlimited and very economic source of energy available to residents free of charge. Sea water and brackish water is available in Kilifi due to its proximity to the Indian Ocean and high water table levels. Solar still uses the principle of evaporation and condensation to produce distilled water. In an attempt to find sustainable solutions, a low cost double sloped solar still is designed, built and characterized based on Kenyan climatic condition using locally available materials. The designed solar still has a basin area of 1m2and glass cover inclined at 150 with an orientation in the north-south direction. Materials used for fabrication were block board, normal window glass of 4 mm and damp proof polythene paper which are all locally available. Experimental investigation on solar still was carried out to examine the quantity and quality of water under Kilifi county climatic conditions. Ambient temperatures, solar irradiation, relative humidity and water output were recorded at an interval of an hour from 8 am to 4 pm and cumulatively at 8 am from 4 pm to 8 am the following day. Data was analyzed using Microsoft excel and an efficiency of 12-20% was found with a correlation factor of more than 99% between the solar irradiation and solar still water output. Water samples were analyzed for physical, chemical and bacteriological parameters and the results obtained agreed with the standard values as prescribed by WHO and Kenya water standards KS 05-459 part 1:1996. Fabrication cost was found to be Kshs 9,350 with economic analysis showing the project as an economic viable and feasible project with high IRR, SIR, positive NPV and a short payback period of 195 days. The solar still was found to produce safe and clean water at a cheap cost of around Kshs 4.89 per litre and thus recommended for use in the local households.