Design and construction of a solar powered chemical sprayer for small scale farmers :

Abstract

A sprayer is a mechanical device used to spray the liquid chemicals like herbicides, pesticides, fungicides and fertilizers to the crops in order to control pests and diseases on crops to maximize production. Sprayers are of many different kinds which include knapsack sprayers, motorized sprayers, tractor drawn sprayers etc. the most commonly used type by the Ugandan farmers are the knapsack sprayers because they are cheap in terms of capital cost. The main drawback with these sprayers is that they cannot be used for long working hours due to human drudgery and they also have low pressure. Motorized sprayers have high pressure but with high investment cost and maintenance cost. Due to the above shortcomings of the commonly used sprayers, the need for another means which provide output in between the knapsack sprayers and the motorized sprayers calls for the invention of solar powered sprayers. These can have between low to high pressure depending on the capacity of the pump. These sprayers also cost moderately and have low maintenance costs. For this project, the emphasis was put on the design, construction and testing for the performance of a solar powered sprayer using low power pump and solar panel. During the design process, the required solar panel, pump, battery and angle of solar panel inclination were obtained based on the required output of 1m3/min of the chemical. The system was tested under varying conditions of insolation strengths an angle of inclination of the solar panel. It was observed that the rate of discharge is affected by the strength of solar insolation and angle with the appropriate angle being 45degrees. The cost analysis was also carried out using the method of net present value over four-year period with interest rate of 10% and the NPV value got was Ugx. 7,807,622 which is positive hence making the project feasible. Implementation of this project will help in saving costs spent on fuel purchase and reduce the spraying time due to moderate pressure and improve on the yield in ground nut.