Design optimization of communal solar powered irrigation systems

Abstract

Communal solar powered irrigations systems (SPIS) have the potential for sharing the upfront costs hence encouraging farmers to adopt irrigation. Conventional methods of sizing Photovoltaic Water Pumping (PVWP) system for irrigation considers the hydraulic energy requirement for the pump and PV generator capacity separately from the available water source capacity. As a result, the potential of the technology is not optimized, leading to over or under sizing of the system. Consequently, there is a negative impact on acquisition cost and system performance. The aim of the study was to develop a decision support tool (DST) for optimal sizing of PVWP system for communal irrigation, which is technically reliable, economically viable and environmentally safe. Four PVWP system configurations were designed following the standard procedures and the techno-economic indicators (system reliability, life cycle costs, cost of energy and specific discharge costs) determined. Comparative performance assessment was conducted on the PVWP system configurations alongside the conventional diesel pumping system. A multi-criteria decision analysis approach was used to select the optimal configuration. The results from the developed DST for the communal case study indicates that, a PVWP system with intermediate storage tank is the optimal configuration for communal irrigation system. Although the initial capital cost of standalone PVWP system configuration is almost two times that of the conventional diesel pumping systems (CPS), it’s operational & maintenance costs and total life cycle cost (LCC) are respectively three times and about four times lower than the CPS cost. In addition, the results show that the PVWP systems for communal irrigation is feasible for irrigation projects that exceeds 3 years due to their high acquisition cost when compared with the conventional diesel pumping system. Therefore, based on the test results for the case study, the developed DST has potential to address the problem of inappropriate designs for SPIS. Furthermore, the communal irrigation approach has potential to improve the use of water for agricultural production hence encouraging government to refocus its microscale irrigation support towards the group-based liability scheme for SPIS as a way of improving technology adoption.