Design of cost effective solar powered auto-irrigation system for Rwanda's farmers

Abstract

Irrigation is the action of supplying water to the plants artificially in order to fulfil their water requirement. In Rwanda, farmers in agriculture field are facing a lot of challenges especially pouring water in their field to keep their plants healthy especially in summer season. For combating with these challenges, an automatic irrigation system can be used by farmers in order to fulfil water requirement to their plants. An automated irrigation system has been developed for the purpose of optimizing the use of water for agriculture crops. This system keeps information about level of soil moisture and keeps that soil moisture to acceptable limits. This is possible by using soil moisture sensors, Programmable Logic Controller, motor pumps and solenoid valves. Soil moisture sensors sense the moisture content of soil where the crops are planted, Programmable Logic Controller, controls and process data from sensors, the motor pumps supply water to the water storage tank and finally water will be supplied to the crops in the field through solenoid valves. When the moisture content is less than predetermined one; water is automatically supplied to the crops and when moisture content is above the predetermined one, solenoid valves are opened and water stops to be supplied to the crops. The major advantage of using this technology is cost effective because water is supplied when needed means that this reduces water loss and reduces the unnecessary water bill and also save time because it is done without an intervention of a human being or manpower. It is also cost effective because it uses solar PV system as the power supply as solar PV system has very low running cost compared to other energy sources such as diesel pumping systems as they are mostly used in irrigation because most of irrigated areas are far away from the grid. This has been demonstrated as it is found that the Net Present Cost (NPC), Livelized Cost of Energy (Livelized COE) and Operating Cost for solar powered PV pumping system are $364,538.60, $0.1440 and $7,404.54 respectively while for diesel water pumping system for irrigation purpose; the Net Present Cost (NPC), Livelized Cost of Energy (Livelized COE) and Operating Cost are $1,794,914, $0.7459 and $98,789.43 respectively. In addition, these diesel water pumping systems emit a big amount of gases which cause global warming as it is found that emission of gases for diesel water pumping system is 231,119kg/year for CO2, 1,443kg/year for CO, 63.6kg/year for unburned hydrocarbons, 8.65kg/year for particular matter, 566kg/year SO2 and 1,356kg/year NOx but for the solar PV systems no emission of these gazes. As a possible solution of this problem is the use of solar PV system as supply of irrigation systems as this source of energy is available for free and environmental friendly.