Optimizing water extraction of photovoltaic pump using multi-factor coupling

This study aims to explore the influence of water extraction and system configuration on the performance of photovoltaic pumps. The water extraction system was required for the high efficiency, high utilization rate of solar energy, and cost saving in the photovoltaic pump. The circulating water extraction was also selected to improve the conversion efficiency of the photovoltaic module, the pump operation efficiency, and pipeline efficiency under different irradiation intensities, valve opening, and water extraction height. The flow model was then constructed. The irradiation intensity data that was monitored in 2022 was partitioned to calculate the proportion of radiation intensity in each partition using the flow model. The amount of water extraction was calculated to evaluate the parameters of the system in each range of radiation intensity under different heights. The optimal height of water extraction was then determined, according to the overall efficiency of the water extraction system and the utilization rate of solar energy. There was an increase in the area of photovoltaic modules and the number of reservoirs. The utilization rate of solar energy was improved in the water-lifting system, where the cost was reduced significantly. The optimal area of photovoltaic modules and the number of reservoirs were obtained at the lowest cost of the water-lifting system. The results show that there was a significant relationship between the utilization efficiency of photovoltaic modules and the irradiation intensity. Some variations were also found in the pump operation efficiency with the irradiation intensity and valve opening, in order to determine the high-efficient operation interval of the photovoltaic pump and the valve opening. At the same time, the optimal height of water lifting was determined as 20 m in the photovoltaic pump, according to the utilization rate of solar energy and the overall efficiency. Meanwhile, the utilization rate of solar energy was 65.05 %, the overall utilization efficiency was 4.521%, and the water lifting cost was 0.151 yuan/m³. The optimal height of water lifting was utilized to clarify the influence of the increasing area of photovoltaic panels and the number of reservoirs on the utilization rate of solar energy and water lifting cost. Once the water lifting cost was the lowest, the area of photovoltaic panels, water lifting cost, and solar energy utilization rate were 3.71 m², 0.151 yuan/m³ and 90.83%, respectively. When the number of reservoirs was 4, the water lifting cost and solar energy utilization rate were 0.145 yuan/m³ and 94.62%, respectively. Therefore, the increasing area of photovoltaic panels and the number of reservoirs greatly contributed to the cost saving of water lifting and the solar energy utilization rate. There was the application range and complementary relationship between valve opening and opening/closing under different irradiation intensities. Two application scenarios were introduced to improve the solar energy utilization rate. The finding can provide new ideas to optimize and apply the photovoltaic water pumping.