Energy Efficiency Optimization in Battery-Based Photovoltaic Pumping Schemes

[EN] This article deals with the analysis of energy efficiency optimization in battery-based photovoltaic pumping schemes. The study builds on previous findings derived from the comparison between a direct photovoltaic water pumping system (DPVWPS) and the equivalent system including a lithium-ion battery (LIB). The initial experimental results of the battery-based photovoltaic water pumping system (PVWPS+LIB) were obtained with the motor-pump group operating at its rated condition of 50 Hz. In the present work, an analysis of the efficiency and the performance ratio of the variable speed drive (VSD) and the motor-pump group, showed that both parameters improve when operating in the low frequency range of the VSD and far from the rated frequency where the flow rate is maximized. Several fitting models were performed with the data obtained with the monitoring system and it was concluded that an overall energy efficiency optimization can be achieved with a VSD frequency equal to 37 Hz. A comparison of the experimental results obtained with the VSD working in the direct mode and with the battery-based solution (setting different VSD frequencies - 50 Hz, 37 Hz, and a combination of the two frequencies designed as 37/50/37 Hz) was made to determine the efficiency and performance ratios in each case. The results presented in this study also establish criteria for improving efficiencies in the LIB charging and discharging processes. This work was supported in part by the Universitat Politecnica de Valencia (UPV) (Program ADSIDEO-Cooperation 2017 through the Project Characterization of Sustainable Systems for the Pumping of Water for Human Consumption in Developing Regions and/or Refugee Camps in Kenya Through the Implementation of Isolated Photovoltaic Systems With New Generation Lithium-Ion Batteries); and in part by the International Organization for Migration under a contract entitled `Design, Assembly, Testing and Documenting Parameters of Solar and Ion-Lithium Energy Storage Equipment for Powering of Water Pumps under Laboratory Conditions' with funding from the Bureau for Humanitarian Assistance-United States Agency for International Development (USAID). Gasque Albalate, M.; González Altozano, P.; Gimeno Sales, FJ.; Orts-Grau, S.; Balbastre Peralta, I.; Martíne-Navarro, G.; Segui-Chilet, S. (2022). Energy Efficiency Optimization in Battery-Based Photovoltaic Pumping Schemes. IEEE Access. 10:54064-54078. https://doi.org/10.1109/ACCESS.2022.3175586