Quantifying the energetic cost tradeoffs of photovoltaic pumping systems for Sub-Saharan African smallholder farms

Abstract

As solar technology has matured, irrigation using photovoltaic pumping systems (PVPSs) has gained popularity in developing markets as an effective means to alleviate poverty and increase food security. Yet, there remains a barrier to adoption; the upfront costs of PVPSs pose a financial burden for many low-income farmers. In a PVPS, the capital cost of the solar array contributes a large portion of upfront system costs. The solar pump is the largest energy consumer in the system, thus its efficiency directly impacts the size and cost of the solar array. There is a limited quantitative understanding of how solar pump efficiency affects the capital cost of the solar array. This study presents a technoeconomic framework to directly quantify the impact of solar pump efficiency on the cost of the solar array in a PVPS, for a range of hydraulic operating conditions. New empirical efficiency scaling laws were created by characterizing the efficiencies of 4-inch multistage centrifugal borehole pumps and induction motors. The utility of the technoeconomic framework is demonstrated through a case study comparing solar pump architectures with motors of different efficiencies. Results indicate that, despite the increased motor cost, the use of high-efficiency motors in solar pumps may lead to an overall cost reduction in a PVPS. Counter to the conventional capital cost-driven process, this work demonstrates that an efficiency-driven design process could improve low-cost, solar-powered system design. Engineers and system designers can leverage the presented framework during the design process to make informed decisions to achieve more cost-effective PVPSs.