Research On Operation Characteristics And Optimization Of Photovoltaic Irrigation System With Variable Sprinkler Number

Photovoltaic irrigation system is a combination of photovoltaic water pump system and water-saving irrigation technology.In this system,solar energy is converted into electric energy to provide power for water pump,then irrigated through irrigation sprinkler installed at the end of the system.Photovoltaic irrigation system is widely used in agricultural production,urban greening,Grassland Irrigation and other fields.It has the advantages of low maintenance cost,long service life,low carbon and environmental protection.Meanwhile,it has become the main direction of agricultural irrigation development in the future.However,Photovoltaic irrigation system is composed of photovoltaic array,inverter,photovoltaic water pump,irrigation nozzle and other components.The stability of system operation and the irrigation uniformity under the continuous change of solar radiation are very poor,which limit the development of the photovoltaic irrigation system.This is mainly because the pump performance cannot match the system with different loading sprinklers number very well during the day.This paper makes a thorough study on the matching characteristics of photovoltaic water pump and irrigation nozzle through test.Then the optimization design of photovoltaic water pump based on orthogonal test and numerical simulation is also carried out.The main work and research results are as follows:1.The classification,research status and future development trend of photovoltaic irrigation system components are introduced.The performance characteristics and research direction of photovoltaic irrigation system are also summarized.2.A photovoltaic irrigation system test rig was built to study the matching characteristics of photovoltaic water pump and sprinkler under the condition of steady-state and transient change of solar radiation when the system was loaded with different number of sprinklers.The high efficiency solar radiation range of photovoltaic irrigation system under different loaded sprinklers was explored.The result shows that:?1?In general,the irrigation performance of the system is slightly better under the transiently solar radiation decrease condition than the system under the transiently solar radiation increase condition.The maximum irrigation uniformity difference is 1%.?2?Under the saturated solar radiation condition,the saturation pressure of the system with 4 loading sprinklers is 435kpa and the irrigation uniformity is 87%.Meanwhile,the radial precipitation is in a"triangle"structure.The precipitation in the square area is in the form of high in the middle and low around.Compared with the system with 4 loading sprinklers,the saturation pressure of the system with 2 loading sprinklers increased 15kPa and the irrigation uniformity decreased 3%.The radial precipitation is in a"trapezoid"structure.The precipitation in the square area is too concentrated in the area near the sprinkler.?3?When the system loads different sprinklers number,the pump head changes greatly due to the change of flow.Because the sprinkler pressure is provided by the pump,the sprinkler irrigation is affected.?3?By increasing the slope of pump flow rate and head curve,the difference of system performance under different loading sprinklers number can be reduced.Then,the stability of the system under different loading sprinklers number can be improved.3.The impeller hun diameter D₂,balde outlet angle?₂,blade outlet width b₂ and balde number zwere chosen as the optimal variables,an orthogonal design was used to established optimal samples,thus establishing a performance optimal method of photovoltaic pump.The results show that:the optimal parameters of the impeller are:the impeller hun diameter D₂=86mm,the balde outlet angle?₂=41°,the blade outlet width b₂=4mm,and the blades number z=9.4.The optimized pump impeller is produced by rapid prototyping.The operation characteristics of the optimized irrigation system are tested.The test results show that:?1?The slope of optimized pump flow rate and head curve increases.The pump head decreased by 7.2%under the 0.0Q_d condition and decreased by 2%under the 1.0Q_d condition.?2?The irrigation uniformity of the two optimized loading modes is 88%under the saturated solar radiation.Also,the precipitation distribution of the two optimized loading modes is a good"triangle"structure.Precipitation evenly distributed in square area.?3?When the optimized system is loaded with different number of sprinklers,the pump can provide similar pressure under different working conditions.?4?The pressure provided by the optimized system is reduced,which not only makes the pressure of system loaded with little sprinklers in the high-efficiency pressure range,but also reduces the pipeline construction cost of photovoltaic irrigation system.