Operation method of solar circulating pulse sprinkling irrigation device coupled with compressed air energy storage

Abstract

The invention discloses an operation method of a solar circulating pulse sprinkling irrigation device coupled with compressed air energy storage. The operation method comprises the following specific steps: step 1, constructing a water pump flow equation under the combined action of actual output power and outlet back pressure of a solar cell panel; 2, calculating the actual output power of the solar cell panel under any irradiance and environment temperature; 3, determining the change rule of the outlet back pressure value of the water pump; step 4, establishing a nozzle working pressure change rule and calculating the water spraying amount of primary pulse spraying; 5, the pulse spraying period duration in different time periods is calculated; 6, the daily water extraction amount is obtained through calculation; and 7, determining the irrigation starting time and irrigation duration of the solar circulating pulse sprinkling irrigation device coupled with compressed air energy storage. The method solves the problem of non-uniform irrigation caused by incomplete consideration factors of an existing operation method.

Description

Technical Field

[0001] This invention belongs to the technical field of agricultural irrigation methods, specifically relating to the operation method of a solar-powered circulating pulse irrigation device coupled with compressed air energy storage. Background Technology

[0002] Solar irrigation technology, as an important application of renewable energy in agriculture, has received widespread attention in recent years. Traditional solar irrigation systems mainly rely on photovoltaic water pumps to directly drive sprinkler irrigation equipment, but this is significantly affected by weather conditions, resulting in large fluctuations in photovoltaic output power and unstable irrigation flow, which affects crop growth.

[0003] Chinese invention patent application number 202210813714.9, entitled "A Solar-Powered Circulating Pulse Irrigation Device Coupled with Compressed Air Energy Storage," describes a circulating pulse irrigation device that uses solar energy as the sole power source for water lifting, eliminating the need for battery storage and achieving stable and controllable spray quality. However, this patent only provides a design method for the solar-powered circulating pulse irrigation device coupled with compressed air energy storage, without specifying the actual operation method of the device.

[0004] Most existing photovoltaic irrigation systems adopt fixed irrigation times and water volume settings in their operation strategies, without fully considering weather changes, differences in water requirements at different stages of crop growth, and the operating characteristics of the system equipment. This leads to uneven irrigation, with some areas receiving too much or too little water, which wastes water resources, affects crop growth, and may also cause problems such as soil compaction and salinization. Summary of the Invention

[0005] The purpose of this invention is to provide an operation method for a solar-powered circulating pulse irrigation device coupled with compressed air energy storage, thereby solving the problem of uneven irrigation caused by incomplete consideration of factors in existing operation methods.

[0006] The technical solution adopted in this invention is a method for operating a solar-powered circulating pulse irrigation device coupled with compressed air energy storage, the specific steps of which are as follows: Step 1: Construct the pump flow equation under the combined effect of the actual output power of the solar panel and the outlet back pressure; Step 2: Calculate the actual output power of the solar panel under arbitrary irradiance and ambient temperature; Step 3: Determine the variation pattern of the pump outlet back pressure value; Step 4: Establish the working pressure variation law of the nozzle and calculate the water volume of one pulse spray; Step 5: Calculate the pulse spraying cycle duration for different time periods; Step 6: Calculate the daily water extraction volume; Step 7: Determine the irrigation start-up timing and irrigation duration of the solar circulating pulse irrigation device coupled with compressed air energy storage.

[0007] The invention is further characterized by: The specific process of step 1 is as follows: Step 1.1: Select a water pump as needed; Step 1.2: Connect the outlet of the water pump selected in Step 1.1 to the water-air tank to form a water-lifting pressurization-compressed air energy storage continuum, including a water-lifting energy storage stage and a gas expansion energy release stage. Step 1.3: Power the water pump motor with a photovoltaic array simulator, measure the voltage and current at the input terminal of the water pump motor to obtain the input power of the water pump motor, and use the photovoltaic array simulator to simulate the actual output power of the solar panel under different weather conditions. Step 1.4: Divide the water lifting and pressurization-compressed air energy storage continuum obtained in Step 1.2 into n time-period units with equal intervals, and calculate the characteristic flow rate of the water pump in the i-th time-period unit: (1) In equation (1), m i The weight of the water vapor tank at the start of the i-th time period unit is in grams; m i-1 The weight of the water vapor tank at the end of the i-th time period unit is in grams. This is the density of water, expressed in g / cm³. 3 ; The length of each time period unit is measured in seconds (s); q i The characteristic flow rate of the water pump in the i-th time period is expressed in m³ / s. 3 / h; Step 1.5: The characteristic flow rate of the water pump in each time period obtained in Step 1.4 is fitted by the Marquardt method and the general global optimization method to obtain the water pump flow rate equation under the combined action of the actual output power of the solar panel and the back pressure at the water pump outlet. The expression is: (2) In equation (2), m, n, and k are fitting coefficients, and P is the back pressure at the pump outlet. pv,gen This represents the actual output power of the solar panel.

[0008] In step 2, the expression for the actual output power of the solar panel under arbitrary irradiance and ambient temperature is: (3) In equation (3), P pv, gen This represents the actual output power of the solar panel, measured in W. Solar irradiance on the inclined surface, in W / m² 2 G stc The standard irradiance is taken as 1000 W / m². 2 ;F T The temperature effect factor is -0.0037 / ℃ for both monocrystalline and polycrystalline silicon; T cell T represents the operating temperature of the solar cell, expressed in °C. stc The standard temperature is 25℃; P pv This refers to the rated output power of the solar panel, expressed in watts (W). in, (4) In equation (4), T amb The ambient temperature is expressed in °C; NOCT is the normal operating temperature of the solar panel, taken as 45 °C. (5) In equation (5), I θ This refers to the direct irradiance of the inclined surface, expressed in w / m². 2 ;D θ This refers to the irradiance scattered by the inclined surface, in W / m². 2 J θ The irradiance reflected by the inclined surface is expressed in W / m². 2 C θ Solar diffuse irradiance on the inclined surface, in w / m² 2 t0 represents solar irradiance time in hours (h); t represents the time variable. (6) In equation (6), D H The diffuse radiance of a horizontal solar panel is expressed in W / m². 2 ; (7) In equation (7), α is the solar altitude angle, in degrees. (8) In equation (8), ρ s ρ is the average reflectance of the ground. s =0.15; G H Solar irradiance on a horizontal surface, expressed in w / m² 2 Obtained by querying NASA's Earth Weather and Irradiance Database; (9) In equation (9), I H The direct irradiance on a horizontal plane is expressed in w / m². 2 ; i0 represents the angle of incidence between the solar vector and the plane normal, in degrees. (10) According to formulas (6) to (10), we can obtain: (11) According to formulas (3) to (11), we can obtain: (12).

[0009] The specific process of step 3 is as follows: The water lifting and pressurization-compressed air energy storage continuum is divided into several equal time periods. The average flow rate of the water pump in the first time period is q0. Then, the water lifting capacity of the water pump in the first time period is: (13) In equation (13), The length of each time period; The volume of gas in the water-gas tank at the end of the first time period was: (14) In equation (14), V0 is the initial volume of gas inside the water-gas tank; The gas pressure inside the water-gas tank is the outlet back pressure of the water pump, expressed as: (15) In equation (15), P0 is the initial pressure of the gas inside the water-gas tank; By iterating through formulas (13) to (15) in the same manner, the outlet back pressure of the pump in the nth time period can be obtained as follows: (16) In equation (16), V n Let V be the volume of gas inside the water vapor tank during the nth time period. n-1 Let be the volume of gas inside the water vapor tank during the (n-1)th time period. This represents the water pumping volume during the nth time period.

[0010] The specific process of step 4 is as follows: Step 4.1: Based on the characteristics of the gas expansion and work process, establish the variation law of the nozzle working pressure during the gas expansion and energy release process; (17) In equation (17), P is the working pressure of the nozzle; max is the upper limit of the pressure of the water-gas tank; a is the pressure loss coefficient; b0 is the pressure drop coefficient; t is the time variable; Step 4.2, calculate the water volume for one pulse spray; The expression is: (18) In equation (18), k1 and k2 are the fitting coefficients for the nozzle pressure-flow relationship; V s The volume of water sprayed per pulse from the water-air tank; t s This is the duration of one pulse spray.

[0011] The specific process of step 5 is as follows: Take the average pump flow rate of the current time period as the equivalent pump flow rate for that time period. Based on the equivalent flow rate of the water pump Calculate the time t1 required for one water filling under the actual output power of the solar panel at different time periods, and know the time t for one pulse spray. s Then, the duration t of a complete pulse spraying cycle at different time periods is obtained. i Thus, the number of spraying cycles that can be completed per hour under the actual output power of the solar panel at different times; in, ; t i =t s +t1; (19) In equation (19), n i t represents the number of spraying cycles in the i-th time period; i The duration of a complete pulse spraying cycle in the i-th time period is expressed in seconds.

[0012] The expression for the daily water extraction volume in step 6 is: (20) In equation (20), w represents the number of hours of effective water pumping by photovoltaic power per day.

[0013] The specific process of step 7 is as follows: Irrigation regimes and gross irrigation quotas for different time periods are determined based on soil moisture content and crop growth stages, and the daily water lifting capacity V of the solar circulating pulse irrigation device coupled with compressed air energy storage is also considered. day Using 70% of field water holding capacity as the lower limit of soil moisture, the timing of irrigation start-up and irrigation duration of the solar circulating pulse irrigation device coupled with compressed air energy storage were determined.

[0014] The beneficial effects of this invention are: (1) The method of the present invention comprehensively considers various factors such as meteorological conditions, system configuration and operating parameters. Through precise analysis, it can accurately predict the performance of the system under different working conditions. Based on the growth stage and water demand pattern of crops, it can formulate personalized system operation strategies to achieve precise matching between the system's water lifting capacity, spraying hydraulic characteristics, operating time and irrigation control area and the crop's water demand. This helps to improve the accuracy of irrigation, make irrigation uniform, avoid the waste of water resources, provide the best water conditions for crop growth, and thus improve the yield and quality of crops. (2) In the process of planning the operation strategy, the method of the present invention fully considers the economic indicators of the system. By optimizing the system configuration and operating parameters, such as rationally selecting the models of solar panels and water pumps, optimizing the volume and pressure settings of water tanks, etc., unnecessary equipment investment is reduced, and the total cost of the system is reduced while meeting the irrigation needs, thereby improving the economic benefits of the system and enhancing the market competitiveness of the solar irrigation system. (3) The method of the present invention has wide applicability. The operation strategy can be flexibly adjusted according to the climate conditions, crop planting type and system configuration of different regions. Whether it is an arid or humid region, whether it is a grain crop or a cash crop, and whether it is an irrigation system of different scales, the appropriate operation strategy can be formulated through the method of the present invention. Attached Figure Description

[0015] Figure 1 This is a flowchart of the operation method of the solar-powered circulating pulse irrigation device coupled with compressed air energy storage according to the present invention; Figure 2 This is a graph showing the trend of water pump flow rate changing with photovoltaic output power and outlet back pressure in Embodiment 9 of the present invention; Figure 3 This is a comparison chart of the calculated and measured results of the actual output power of the solar panel in Embodiment 9 of the present invention; Figure 4 This is a comparison of the calculated and measured results of the pump outlet back pressure values ​​at different time periods in Embodiment 9 of the present invention; Figure 5 This describes the pressure variation pattern of the nozzle and water-gas tank during the gas expansion and energy release stage in Embodiment 9 of the present invention. Figure 6 The hourly output power of the 490W solar panel in Embodiment 9 of the present invention; Figure 7 This illustrates the changes in water pump flow rate during compressed air delivery at different time intervals in Embodiment 9 of the present invention. Figure 8 This illustrates the changes in the equivalent flow rate of the water pump during the pumping of compressed air at different time periods in Embodiment 9 of the present invention. Figure 9This is a diagram showing the pulse cycle variation at different times of the day and the cumulative water extraction from the solar panel in Embodiment 9 of the present invention. Figure 10 This is a schematic diagram of the arrangement of a solar-powered circulating pulse sprinkler irrigation device with coupled compressed air energy storage for irrigating 1 hectare of cornfield in Embodiment 9 of the present invention. Figure 11 This section describes the irrigation scheme and changes in soil moisture content under traditional sprinkler irrigation methods. Figure 12 This shows the irrigation scheme and soil moisture content changes in Embodiment 9 of the present invention. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0017] Example 1 This invention relates to the operation method of a solar-powered circulating pulse irrigation device coupled with compressed air energy storage. The invention utilizes Chinese invention patent application number 202210813714.9, which describes the solar-powered circulating pulse irrigation device coupled with compressed air energy storage. Figure 1 As shown, please follow these steps: Step 1: Construct the pump flow equation under the combined effect of the actual output power of the solar panel and the outlet back pressure; Step 2: Calculate the actual output power of the solar panel under arbitrary irradiance and ambient temperature; Step 3: Determine the variation pattern of the pump outlet back pressure value; Step 4: Establish the working pressure variation law of the nozzle and calculate the water volume of one pulse spray; Step 5: Calculate the pulse spraying cycle duration for different time periods; Step 6: Calculate the daily water extraction volume; Step 7: Determine the irrigation start-up timing and irrigation duration of the solar circulating pulse irrigation device coupled with compressed air energy storage.

[0018] Example 2 Based on Example 1, the specific process of step 1 is as follows: Step 1.1: Select a water pump as needed; To achieve the rational utilization of solar energy through "collection-storage-regulation-release", a high-lift, low-flow water pump is selected with the spraying target of long nozzle range and thorough water flow breaking. Step 1.2: Connect the outlet of the water pump selected in Step 1.1 to the water-air tank to form a water-lifting pressurization-compressed air energy storage continuum, including a water-lifting energy storage stage and a gas expansion energy release stage. Step 1.3: Power the water pump motor with a photovoltaic array simulator, measure the voltage and current at the input terminal of the water pump motor to obtain the input power of the water pump motor, and use the photovoltaic array simulator to simulate the actual output power of the solar panel under different weather conditions (such as sunny, cloudy, overcast, rainy, snowy, etc.). The output power simulated by the photovoltaic array simulator is equal to the actual output power of the solar panels; Step 1.4: Divide the water-lifting and pressurizing-compressed air energy storage continuum obtained in Step 1.2 into n time-period units with 5-second intervals. Use the average flow rate of the water pump within each time-period unit as the characteristic flow rate of the water pump under the combined effect of the actual output power of the solar panel and the back pressure at the water pump outlet. Then, the characteristic flow rate of the water pump in the i-th time-period unit (m... 3 / h) is: (1) In equation (1), m i The weight of the water vapor tank at the start of the i-th time period unit is in grams; m i-1 The weight of the water vapor tank at the end of the i-th time period unit is in grams. This is the density of water, expressed in g / cm³. 3 ; The length of each time period unit is in seconds (s). Among them, the pump outlet back pressure of each time period unit is the average value of the pump outlet back pressure within 5 seconds; Step 1.5: The characteristic flow rate of the water pump in each time period obtained in Step 1.4 is fitted by the Levenberg-Marquardt method and the general global optimization method to obtain the water pump flow rate equation under the combined effect of the actual output power of the solar panel and the back pressure at the water pump outlet. The expression is: (2) In equation (2), m, n, and k are fitting coefficients, and P is the back pressure at the pump outlet. pv,gen This represents the actual output power of the solar panel.

[0019] Example 3 Based on Example 2, in step 2, the expression for calculating the actual output power of the solar panel under arbitrary irradiance and ambient temperature is as follows: (3) In equation (3), P pv, gen This represents the actual output power of the solar panel, measured in W. Solar irradiance on the inclined surface, in W / m² 2 G stcThe standard irradiance is taken as 1000 W / m². 2 ;F T The temperature effect factor is -0.0037 / ℃ for both monocrystalline and polycrystalline silicon; T cell T represents the operating temperature of the solar cell, expressed in °C. stc The standard temperature is 25℃; P pv The output power of a solar panel under standard conditions (equal to the rated output power of the solar panel) is expressed in W. Standard condition output power refers to the output power of the solar panel under standard test conditions (STC), representing the theoretical maximum output capacity of the solar panel under ideal conditions. Specific conditions include: a light intensity of 1000 W / m² (equivalent to strong sunlight near the equator at noon), a cell temperature of 25°C (the temperature of the cell itself, not the ambient temperature), and a spectral distribution of AM1.5 standard spectrum (simulating the solar spectrum filtered by the Earth's atmosphere). (4) In equation (4), T amb The ambient temperature is expressed in °C; NOCT is the normal operating temperature of the solar panel, taken as 45 °C. (5) In equation (5), I θ This refers to the direct irradiance of the inclined surface, expressed in w / m². 2 ;D θ This refers to the irradiance scattered by the inclined surface, in W / m². 2 J θ The irradiance reflected by the inclined surface is expressed in W / m². 2 C θ Solar diffuse irradiance on the inclined surface, in w / m² 2 t0 represents solar irradiance time in hours (h); t represents the time variable. (6) In equation (6), D H The diffuse radiance of a horizontal solar panel is expressed in W / m². 2 ; (7) In equation (7), α is the solar altitude angle, in degrees. (8) In equation (8), ρ s ρ is the average reflectance of the ground. s =0.15; G H Solar irradiance on a horizontal surface, expressed in w / m² 2 Obtained by querying NASA's Earth Weather and Irradiance Database; (9) In equation (9), I H The direct irradiance on a horizontal plane is expressed in w / m². 2 ; i 0 represents the angle of incidence between the solar vector and the plane normal, in degrees. (10) According to formulas (6) to (10), we can obtain: (11) According to formulas (3) to (11), we can obtain: (12); Example 4 Based on Example 3, the specific process of step 3 is as follows: The water lifting and pressurization-compressed air energy storage continuum is divided into several equal time periods. The average flow rate of the water pump in the first time period is q0. Then, the water lifting capacity of the water pump in the first time period is: (13) In equation (13), The length of each time period; The volume of gas in the water-gas tank at the end of the first time period was: (14) In equation (14), V0 is the initial volume of gas inside the water-gas tank; The gas pressure inside the water-gas tank is the outlet back pressure of the water pump, expressed as: (15) In equation (15), P0 is the initial pressure of the gas inside the water-gas tank; By applying the iterative calculation method to formulas (13) to (15), the outlet back pressure of the pump in the nth time period can be obtained as follows: (16) In equation (16), V n Let V be the volume of gas inside the water vapor tank during the nth time period. n-1 Let be the volume of gas inside the water vapor tank during the (n-1)th time period. The water pumping volume in the nth time period (obtained by iterating over formula (13)) is the volume of gas compressed in the water-gas tank in the nth time period; The above iterative calculation method can be used to obtain the water lifting volume and pump outlet back pressure at any time during the water lifting process.

[0020] Example 5 Based on Example 4, the specific process of step 4 is as follows: Step 4.1: Based on the characteristics of the gas expansion and work process, establish the variation law of the nozzle working pressure during the gas expansion and energy release process; (17) In equation (17), P is the working pressure of the nozzle; max t is the upper limit of the water-air tank pressure; a is the pressure loss coefficient, which is equal to the difference between the nozzle pressure and the water-air tank pressure. It mainly depends on the pipeline construction characteristics, including the friction loss and local head loss between the water-air tank and the nozzle, and is obtained by actual measurement of the pipeline and nozzle pressure; b0 is the pressure drop coefficient, whose value is obtained by trial calculation based on the volume conservation of the water spray volume of the nozzle and the water output volume of the water-air tank; t is the time variable. Step 4.2, calculate the water volume for one pulse spray; The expression is: (18) In equation (18), k1 and k2 are the fitting coefficients for the nozzle pressure-flow relationship; V s The volume of water sprayed per pulse from the water-air tank; t s This is the duration of one pulse spray.

[0021] Example 6 Based on Example 5, the specific process of step 5 is as follows: Step 5.1: Match the solar panel with a suitable rated output power according to the rated power of the selected water pump, and substitute it into formula (12) to obtain the hourly actual output power of the solar panel under different irradiance and ambient temperature. Step 5.2: Analyze each time period as an object, based on the selected upper pressure limit P in the water-gas tank. max And the water volume V of a single pulse spray from the water vapor tank. s Calculate the lower pressure limit P of the water-gas tank. min The pump flow rate under the combined effect of the actual output power of the solar panel and the change in back pressure at the pump outlet during the current period is calculated using formula (2). The average value of the pump flow rate during the current period is taken as the equivalent flow rate of the pump during that period. ; Calculate the lower pressure limit P of the water-air tank. min The process is as follows: Assume P max =P0, the initial volume V0 of the gas inside the water-gas tank is known, and the water spray volume V of a single pulse spray from the water-gas tank is known. s The corresponding gas volume inside the water-gas tank becomes V0 + V s The lower limit of the gas pressure inside the water-gas tank is:

[0022] The greater the water volume sprayed in a single pulse spray, the lower the degree of gas compression and the lower the gas pressure; Step 5.3, based on the equivalent flow rate of the water pump Calculate the time t required for one water filling under the actual output power of the solar panel at different time periods. 1， And the time t for one pulse spray is known. s It can obtain the duration t of a complete pulse spraying cycle at different time periods. i , t i =t s +t1; The number of spraying cycles that can be completed per hour under the actual output power of the solar panel at different times is: (19) In equation (19), n i t represents the number of spraying cycles in the i-th time period; i The duration of a complete pulse spraying cycle in the i-th time period is expressed in seconds.

[0023] Example 7 Based on Example 6, in step 6, the daily water lifting volume is calculated by summing the water lifting volumes of the pumps in each time period; Based on the effective water pumping period of the water pump in different seasons and crop growth stages, the water pumping volume of each period is calculated using the iterative formula (13). Then, the water pumping volumes of each period are summed to obtain the daily water pumping volume, which is expressed as follows: (20) In equation (20), w represents the number of hours of effective water pumping by photovoltaic power per day.

[0024] Example 8 Based on Example 7, the specific process of step 7 is as follows: determine the irrigation regime and gross irrigation quota (average irrigation water demand per mu) for different time periods according to the soil moisture content and crop growth stage, and determine the daily water lifting capacity V of the solar circulating pulse irrigation device coupled with compressed air energy storage. day Using 70% of field water holding capacity as the lower limit of soil moisture, the timing of irrigation start-up and irrigation duration of the solar circulating pulse irrigation device coupled with compressed air energy storage were determined.

[0025] Example 9 Step 1: Construct the pump flow equation under the combined effect of the actual output power of the solar panel and the outlet back pressure; DC diaphragm pumps of models 5G310, FYR4 and YJ3003 were selected, with rated powers of 160W, 350W and 500W respectively; Table 1 shows the flow rates of different models of DC diaphragm pumps under the combined effect of solar panel output power and pump outlet back pressure.

[0026] Table 1. Pump flow rate under different solar panel output power and pump outlet back pressure variations.

[0027] Taking a DC diaphragm pump with a rated power of 350W as an example, the applicable range of the actual output power of the solar panel is 40W-350W. This means that the DC diaphragm pump can only be started when the actual output power of the solar panel is greater than 40W. Due to the limitations of the head of the DC diaphragm pump and the pressure safety of the pipeline system, the back pressure value at the pump outlet is not higher than 0.7MPa. Step 2: Calculate the actual output power of the solar panel under arbitrary irradiance and ambient temperature; Taking a DC diaphragm pump with a rated power of 350W as an example, a monocrystalline silicon solar panel with a rated power of 490W is matched for it (installation location coordinates: 34°3'N, 108°93'E, south-facing installation, with an angle of 30° to the ground). The actual output power of the solar panel under any irradiance and ambient temperature is calculated according to formulas (3) to (12) (calculation results). At the same time, the irradiance, ambient temperature and real-time output power of the solar panel are continuously monitored and collected using a solar cell tester (measured results). The calculated results and measured results are as follows: Figure 2 As shown, the actual output power of the solar panel shows a trend of first rising and then falling throughout the day, and remains at a relatively high level between 10:00 and 14:00 each day.

[0028] The good consistency between the calculated results and the measured results indicates that the method for calculating the actual output power of the solar panel of the present invention can relatively accurately reflect the impact of changes in environmental factors on the actual output power of the solar panel.

[0029] like Figure 3 As shown, within the selected six-day timeframe, the peak deviation between the calculated and measured results ranges from -7.49% to 9.05%, while the deviation of the actual output power of the solar panel accumulated within a day ranges from -4.22% to 9.24%.

[0030] Step 3: Determine the variation law of the outlet back pressure value of the water pump during the water lifting and pressurization-compressed air energy storage continuum; The pump outlet back pressure was calculated according to formulas (13) to (16) for different time periods (calculation results), and the pump outlet back pressure was measured (actual measurement results). The calculated results and the actual measurement results are as follows: Figure 4 As shown, with the advancement of water pumping and the compressed air process for water-air irrigation, the outlet back pressure of the water pump exhibits a linear upward trend. According to the calculation results, within 19 seconds after the start of pumping and gas compression, the measured value of the outlet back pressure of the water pump increases from 0.213 MPa to 0.4 MPa, while the calculated value increases from 0.215 MPa to 0.408 MPa. The deviation between the calculated and measured values ​​does not exceed 3.63%.

[0031] Step 4: Establish the working pressure change law of the nozzle during the gas expansion and energy release stage and calculate the water volume of one pulse spray. Taking a 100L water-air tank, with an air pressure limit of 0.4MPa, a single pulse spray lasting 4 seconds, and three ZY-2 nozzles (arranged in a Y-shape, each nozzle is 10m away from the water-air tank, connected to the tank via DN25 PE pipes, and the nozzle position is 1.6m above the water outlet of the tank) as an example, the dynamic working pressure change law of the nozzle pulse spray during the air expansion and energy release stage is calculated using formula (17); Figure 5 As shown, both the working pressure of the nozzle pulse spray and the water outlet pressure of the water-air tank show a significant logarithmic decreasing trend, indicating a relatively stable mathematical relationship. The ratio of the pressure at the nozzle to the pressure in the water-air tank is 64.5%-72.1%, with an average of 67.8%. Therefore, the pressure drop coefficient is taken as 0.678. The trial calculation process of the pressure drop coefficient is shown in Table 2. When the pressure drop coefficient decreases from 0.11 to 0.086, the ratio of the working pressure of the nozzle to the working pressure of the water-air tank at the end of spraying increases from 0.589 to 0.780.

[0032] Table 2. Pressure Drop Coefficient Trial Calculation Table

[0033] Compared to the previously determined pressure drop coefficient 'a' of 0.678, the deviation rate ranges from -13.127% to 15.044%. The deviation rate is minimal, at only 0.737%, when the pressure drop coefficient is 0.098. Therefore, the pressure drop coefficient 'b0' can be selected as 0.098. Based on this, the change law of the nozzle's working pressure during the gas expansion and energy release stage is as follows: The water volume of a single pulse spray is 10.79L.

[0034] Step 5: Calculate the pulse spraying cycle duration for different time periods; like Figure 6As shown, taking a DC diaphragm pump with a rated power of 350W and a monocrystalline silicon solar panel with a rated power of 490W as an example, the actual output power of the solar panel shows a trend of first rising and then falling throughout the day, roughly following a parabolic distribution. The peak occurs between 12:00 and 13:00, reaching 304.95W. Between 7:00 and 8:00 and between 16:00 and 17:00, the actual output power of the solar panel is below 100W. Outside of the period between 7:00 and 17:00, the actual output power of the solar panel drops below 50W, and the solar panel cannot drive the DC diaphragm pump to complete the energy storage and release cycle of compressed air pulse injection. like Figure 7 and Figure 8 As shown, the flow rate of the DC diaphragm pump follows a normal distribution throughout the day. During the period from 10:00 to 13:00, the average flow rate remains stable at approximately 1 cubic meter per hour; during the periods from 7:00 to 8:00 and from 16:00 to 17:00, the flow rate is less than 0.4 cubic meters per hour. From the perspective of pulse water spraying cycle, the time required to complete one water lifting, energy storage and pulse water spraying process is 42-126 seconds, of which the water spraying duration is 4 seconds, accounting for 3.17%-9.52% of the total duration. In the early morning and evening, when the actual output power of the solar panel is low but still meets the starting power of the DC diaphragm pump, the time for the DC diaphragm pump to lift water and store energy exceeds 100 seconds. Step 6: Add up the water pumping volumes of each time period to calculate the daily water pumping volume; like Figure 9 As shown, when the actual output power of the solar panel reaches or exceeds the rated power of the DC diaphragm pump, the DC diaphragm pump enters a high-efficiency operating state, and the time required to complete one water lifting and energy storage is shortened to about 40 seconds. The water lifting volume per unit time increases to about 0.9 cubic meters. The total working time for the whole day is 10 hours, and the total water lifting volume is about 6.71 cubic meters.

[0035] Step 7, taking a 1-hectare (100m x 100m) square experimental field in Yangling District, Shaanxi Province, as an example for supplementary irrigation of summer maize, within the 1-hectare project area, such as... Figure 10 As shown, the number of sprinkler units and water / air tanks were 48 and 16 respectively. An irrigation plan for maize sprinkler irrigation was developed using CLIMWAT 2.0 and CROPWAT 8.0 software provided by the Food and Agriculture Organization of the United Nations (FAO). The crop coefficient for maize was 0.3 in the early growth stage, 1.2 in the middle and late growth stages, and 0.35 in the later stages. Soil moisture content was maintained at 70% during the maize growth period. Irrigation was carried out promptly when the soil moisture content fell below 60-80% of field capacity. The irrigation water use efficiency (IUQ) for sprinkler irrigation was set at 70%. Figure 11 and Figure 12 As shown, the solar-powered circulating pulse sprinkler irrigation system coupled with compressed air energy storage extends the number of spraying days to meet the gross irrigation quota for each irrigation while ensuring that the soil moisture content does not fall below the lower limit. The irrigation strategy of this system is as follows: the number of irrigations and the start date of each irrigation remain unchanged compared to continuous sprinkler irrigation; however, the irrigation time for each irrigation is extended from 1 day under continuous sprinkler conditions to 5, 6, 6, and 10 days, with gross irrigation quotas of 42.6, 55.7, 53.2, and 69.7 mm, respectively. The total irrigation water volume for the entire growth period is 221.3 mm, with a deviation rate of 3.07% compared to continuous sprinkler irrigation. In traditional continuous sprinkler irrigation, the soil moisture content quickly recovers to field capacity after a single irrigation. However, in solar-coupled compressed air circulation pulse sprinkler irrigation, the soil moisture content shows a slow upward trend after the irrigation begins, and the amount of usable water in the soil is greater than the minimum allowable water storage capacity throughout the growing season.

Claims

1. A method for operating a solar-powered circulating pulse irrigation device coupled with compressed air energy storage, characterized in that, The specific steps are as follows: Step 1: Construct the pump flow equation under the combined effect of the actual output power of the solar panel and the outlet back pressure; Step 2: Calculate the actual output power of the solar panel under arbitrary irradiance and ambient temperature; Step 3: Determine the variation pattern of the pump outlet back pressure value; Step 4: Establish the working pressure variation law of the nozzle and calculate the water volume of one pulse spray; Step 5: Calculate the pulse spraying cycle duration for different time periods; Step 6: Calculate the daily water extraction volume; Step 7: Determine the irrigation start-up timing and irrigation duration of the solar circulating pulse irrigation device coupled with compressed air energy storage.

2. The operation method of the solar circulating pulse irrigation device coupled with compressed air energy storage according to claim 1, characterized in that, The specific process of step 1 is as follows: Step 1.1: Select a water pump as needed; Step 1.2: Connect the outlet of the water pump selected in Step 1.1 to the water-air tank to form a water-lifting pressurization-compressed air energy storage continuum, including a water-lifting energy storage stage and a gas expansion energy release stage. Step 1.3: Power the water pump motor with a photovoltaic array simulator, measure the voltage and current at the input terminal of the water pump motor to obtain the input power of the water pump motor, and use the photovoltaic array simulator to simulate the actual output power of the solar panel under different weather conditions. Step 1.4: Divide the water lifting and pressurization-compressed air energy storage continuum obtained in Step 1.2 into n time-period units with equal intervals, and calculate the characteristic flow rate of the water pump in the i-th time-period unit: （1） In equation (1), m i The weight of the water vapor tank at the start of the i-th time period unit is in grams; m i-1 The weight of the water vapor tank at the end of the i-th time period unit is in grams. This is the density of water, expressed in g / cm³. 3 ; The length of each time period unit is measured in seconds (s); q i The characteristic flow rate of the water pump in the i-th time period is expressed in m³ / s. 3 / h; Step 1.5: The characteristic flow rate of the water pump in each time period obtained in Step 1.4 is fitted by the Marquardt method and the general global optimization method to obtain the water pump flow rate equation under the combined action of the actual output power of the solar panel and the back pressure at the water pump outlet. The expression is: （2） In equation (2), m, n, and k are fitting coefficients, and P is the back pressure at the pump outlet. pv,gen This represents the actual output power of the solar panel.

3. The operation method of the solar circulating pulse irrigation device coupled with compressed air energy storage according to claim 2, characterized in that, In step 2, the expression for the actual output power of the solar panel under arbitrary irradiance and ambient temperature is: （3） In equation (3), P pv, gen This represents the actual output power of the solar panel, measured in W. Solar irradiance on the inclined surface, in W / m² 2 G stc The standard irradiance is taken as 1000 W / m². 2 ; F T The temperature effect factor is -0.0037 / ℃ for both monocrystalline and polycrystalline silicon; T cell T represents the operating temperature of the solar cell, expressed in °C. stc The standard temperature is 25℃; P pv This refers to the rated output power of the solar panel, expressed in watts (W). in, （4） In equation (4), T amb The ambient temperature is expressed in °C; NOCT is the normal operating temperature of the solar panel, taken as 45 °C. （5） In equation (5), I θ This refers to the direct irradiance of the inclined surface, expressed in w / m². 2 ;D θ This refers to the irradiance scattered by the inclined surface, in W / m². 2 J θ The irradiance reflected by the inclined surface is expressed in W / m². 2 C θ Solar diffuse irradiance on the inclined surface, in w / m² 2 t0 represents solar irradiance time in hours (h); t represents the time variable. （6） In equation (6), D H The diffuse radiance of a horizontal solar panel is expressed in W / m². 2 ; （7） In equation (7), α is the solar altitude angle, in degrees. （8） In equation (8), ρ s ρ is the average reflectance of the ground. s =0.15; G H Solar irradiance on a horizontal plane, expressed in w / m² 2 Obtained by querying NASA's Earth Weather and Irradiance Database; （9） In equation (9), I H The direct irradiance on a horizontal plane is expressed in w / m². 2 ; i 0 represents the angle of incidence between the solar vector and the plane normal, in degrees. （10） According to formulas (6) to (10), we can obtain: （11） According to formulas (3) to (11), we can obtain: （12）。 4. The operation method of the solar circulating pulse irrigation device coupled with compressed air energy storage according to claim 2, characterized in that, The specific process of step 3 is as follows: The water lifting and pressurization-compressed air energy storage continuum is divided into several equal time periods. The average flow rate of the water pump in the first time period is q0. Then, the water lifting capacity of the water pump in the first time period is: （13） In equation (13), The length of each time period; The volume of gas in the water-gas tank at the end of the first time period was: （14） In equation (14), V0 is the initial volume of gas inside the water-gas tank; The gas pressure inside the water-gas tank is the outlet back pressure of the water pump, expressed as: （15） In equation (15), P0 is the initial pressure of the gas inside the water-gas tank; By iterating through formulas (13) to (15) in the same manner, the outlet back pressure of the pump in the nth time period can be obtained as follows: （16） In equation (16), V n Let V be the volume of gas inside the water vapor tank during the nth time period. n-1 Let be the volume of gas inside the water vapor tank during the (n-1)th time period. This represents the water pumping volume during the nth time period.

5. The operation method of the solar circulating pulse irrigation device coupled with compressed air energy storage according to claim 2, characterized in that, The specific process of step 4 is as follows: Step 4.1: Based on the characteristics of the gas expansion and work process, establish the variation law of the nozzle working pressure during the gas expansion and energy release process; （17） In equation (17), P is the working pressure of the nozzle. max is the upper limit of the pressure of the water-gas tank; a is the pressure loss coefficient; b0 is the pressure drop coefficient; t is the time variable; Step 4.2, calculate the water volume for one pulse spray; The expression is: （18） In equation (18), k1 and k2 are the fitting coefficients for the nozzle pressure-flow relationship; V s The volume of water sprayed per pulse from the water-air tank; t s This is the duration of one pulse spray.

6. The operation method of the solar circulating pulse irrigation device with coupled compressed air energy storage according to claim 4, characterized in that, The specific process of step 5 is as follows: Take the average pump flow rate of the current time period as the equivalent pump flow rate for that time period. Based on the equivalent flow rate of the water pump Calculate the time t1 required for one water filling under the actual output power of the solar panel at different time periods, and know the time t for one pulse spray. s Then, the duration t of a complete pulse spraying cycle at different time periods is obtained. i Thus, the number of spraying cycles that can be completed per hour under the actual output power of the solar panel at different times; in, ； t i =t s +t1; （19） In equation (19), n i t represents the number of spraying cycles in the i-th time period; i The duration of a complete pulse spraying cycle in the i-th time period is expressed in seconds.

7. The operation method of the solar circulating pulse irrigation device coupled with compressed air energy storage according to claim 6, characterized in that, The expression for the daily water extraction volume in step 6 is: （20） In equation (20), w represents the number of hours of effective water pumping by photovoltaic power per day.

8. The operation method of the solar-powered circulating pulse irrigation device with coupled compressed air energy storage according to claim 1, characterized in that, The specific process of step 7 is as follows: Irrigation regimes and gross irrigation quotas for different time periods are determined based on soil moisture content and crop growth stages, and the daily water lifting capacity V of the solar circulating pulse irrigation device coupled with compressed air energy storage is also considered. day Using 70% of field water holding capacity as the lower limit of soil moisture, the timing of irrigation start-up and irrigation duration of the solar circulating pulse irrigation device coupled with compressed air energy storage were determined.

Images