Quantifying the Energetic Costs of Photovoltaic Pumping Systems (PVPS) for Sub-Saharan African Smallholder Farms

Abstract

With the solar panel prices falling recently, photovoltaic pumping systems (PVPSs) have become an affordable and effective technology for off-grid smallholder farmers in developing markets like Sub-Saharan Africa. Yet the high upfront cost of PVPSs remains a financial burden for many low-income farming communities. Although numerous efforts have been made to further increase the affordability of PVPSs, there is still a lack of investigation into potential energetic cost savings by improving solar pump efficiency from an architectural design perspective. In this study, a technoeconomic framework was developed to quantify the energetic costs of different solar pump architectures. The energetic cost is defined as the total cost of the solar array, which enables a direct comparison between efficiency and capital cost. New efficiency prediction models were formulated for 4-inch borehole pump hydraulics and submersible motors based on surveyed manufacturer specifications. Two types of case studies on SSA farms were conducted as example analyses in applying the framework. The operating space level analysis provides a bird's-eye view of the energetic cost-savings over the operating space when comparing two solar pump architectures. The operating point level analysis demonstrates a similar energetic cost analysis to identify the most energetically cost-effective solar pump architectures for the operating conditions of a specific SSA farm. By adopting highly efficient BLDC motors in 4-inch solar-powered borehole pumps, energetic cost-savings were found and operating regions not currently served by high-efficiency solar pumps can now be reached. These results highlight economic incentives for manufacturers to provide high-efficiency solar pumps to more smallholder farmers in SSA while reducing the overall upfront cost of PVPSs.