Solar irrigation system and calculation method for its solar energy conversion rate

Abstract

The present invention provides a method for measuring and calculating the solar energy conversion efficiency of a fixed solar sprinkler irrigation system, specifically: adjusting the nozzle pressure, simulating the corresponding light intensity with an external power supply, and operating the fixed solar sprinkler irrigation system stably. Using a laser disdrometer to conduct an experiment on the water droplet distribution in the outer flow field of the nozzle, recording and organizing the water droplet velocity and water droplet diameter, and calculating the total kinetic energy of water droplets at a single measurement point. Fitting the functional relationship between the total kinetic energy of water droplets at the measurement point and the distance from the nozzle. Then, using the MATLAB function integration method to calculate the total energy of water droplets sprayed by a single nozzle. Finally, the value of the solar energy conversion efficiency is obtained by using the calculation formula given in the present invention. The present invention provides a theoretical basis for the configuration optimization of the fixed solar sprinkler irrigation system.

Description

Technical Field

[0001] The present invention belongs to the technical field of agricultural sprinkler irrigation, and relates to a solar sprinkler irrigation system, in particular to a fixed solar sprinkler irrigation system and a calculation method for the solar energy conversion efficiency thereof. Background Art

[0002] Sprinkler irrigation is an advanced irrigation technology, and the development of irrigation machinery can effectively improve the utilization rate of agricultural water resources. With the vigorous development of photovoltaic technology, solar energy has become the best choice for solving the power problem of sprinkler irrigation machinery by providing reliable power guarantee for agricultural irrigation in arid and semi-arid regions. The new solar sprinkler irrigation system integrates and improves the solar photovoltaic power generation technology and the sprinkler irrigation machine, transforming the traditional farmland irrigation method into solar self-driven sprinkler irrigation, with high irrigation uniformity and remarkable energy-saving effect. The hydraulic characteristics of the nozzle spraying are an important index for evaluating the sprinkler irrigation quality and directly affect the quality of crops. The principle of the solar sprinkler irrigation system is that the solar panel converts the absorbed light energy into direct current electrical energy, and the inverter in the solar controller converts the direct current into alternating current to drive the centrifugal pump to work. When the system pressure reaches 0.16 MPa, the nozzle pressure reaches 0.15 MPa, the nozzle starts to rotate, and the system starts to work. However, there is no basis for the conversion efficiency of the light energy in the system finally being converted into the energy of the water droplets falling to the ground.

[0003] After retrieval, there is no relevant patent application. Summary of the Invention

[0004] Aiming at the deficiencies in the prior art, the present invention provides a solar sprinkler irrigation system and a calculation method for the solar energy conversion efficiency thereof, providing a theoretical basis for the efficient utilization of the solar sprinkler irrigation system.

[0005] The present invention realizes the above technical purpose through the following technical means. A solar sprinkler irrigation system includes a water storage tank. The water storage tank is connected to a centrifugal pump through a pipeline with a valve. An electromagnetic flowmeter, a pressure gauge and a nozzle are installed on the pipeline at the output end of the centrifugal pump. The power of the centrifugal pump is provided by a solar controller, and the solar controller is electrically connected to a solar panel.

[0006] A calculation method for the solar energy conversion rate in a solar irrigation system provided by the present invention includes the following steps: S1; operate the solar irrigation system normally, record the corresponding light intensity value when the nozzle pressure is stable for at least 30 minutes, and take the average value of the light intensity; S2; use an external power supply to stably operate the irrigation device, set the working pressure of the nozzle to H, start from a position 1 m away from the nozzle, place a laser disdrometer every 1 m in the radial direction of the nozzle to measure and record the number of water droplets with different diameter levels and the falling speed of water droplets at different distances from the nozzle; S3: measure the water droplet velocity and diameter at different measurement points through the laser disdrometer, and calculate the kinetic energy of a single water droplet when it lands; S4: calculate the total kinetic energy of water droplets at a single measurement point; multiply the kinetic energy of a single water droplet obtained by calculation by the number of particles W respectively, and accumulate to obtain the total kinetic energy of water droplets at this measurement point; in the experiment, the measurement points are distributed every 1 m, and the total kinetic energy of water droplets at other points is obtained by curve formula analysis and fitting, and the curve formula is shown in formula (3).

[0007] y = f(l) (3)

[0008] In the formula: l is the distance from the nozzle, m; where, 0 ≤ l ≤ Ra, Ra is the distance from the nozzle to the landing point of the outermost water droplet, m; S5: calculate the total kinetic energy E of water droplets of a single nozzle T Calculate. Fix the rotating nozzle for spraying, use the function integration in MATLAB software, input the function relationship y between the distance from the nozzle and the kinetic energy of water droplets, and accumulate and sum the total kinetic energy E of water droplets at all points within the spraying range Tl The number of nozzles equipped in the system is m, so E T See formula (4);

[0009]

[0010] In the formula: E T is the total kinetic energy of water droplets in the system, J; S6: obtain the calculation formula for the energy conversion efficiency η of the solar irrigation system; because the unit of light intensity obtained by the light intensity survey instrument is W / m 2 , it should be converted to J. According to the formula J = W / s, combined with the total area S square meters of the solar panel and the time t seconds used for each experiment, the energy conversion efficiency value between the solar irrigation system and raindrop energy under the corresponding light intensity can be calculated. Finally, the calculation formula for the energy conversion efficiency η of the solar irrigation system is shown in formula (5);

[0011]

[0012] In the formula: η is the energy conversion efficiency of the solar irrigation system; x is the light intensity W / m 2 .

[0013] In step S3, when calculating the kinetic energy of a single water droplet when it hits the ground, since there are a large number of sprinkling water droplets at the same measuring point and there are significant differences in the velocities of the water droplets, the kinetic energy of a single water droplet here refers to the average kinetic energy of the water droplets of a certain diameter class at the measuring point, and the calculation formula is as shown in Equation (1).

[0014]

[0015] In the formula: E sd is the kinetic energy of a single water droplet with a diameter of d, in J; V di is the velocity of the water droplet with a diameter of d, in m / s; W is the number of particles corresponding to V di ; i is the name of the velocity class of the water droplet with a diameter of d; o is the number of water droplet velocity classifications; ρ w is the density of water, in kg / m 3 .

[0016] In step S4, the kinetic energy E sd of a single water droplet obtained by calculation is multiplied by the number of particles W corresponding to this diameter class respectively, and after accumulation, the total kinetic energy E Tl of the water droplets at this measuring point is obtained, as shown in Equation (2); in the experiment, the measuring points are distributed every 1 m, and the total kinetic energy of the water droplets at other points is obtained by analyzing and fitting the curve formula, and the curve formula is shown in Equation (3);

[0017]

[0018] y = f(l) (3)

[0019] In the formula: E Tl is the total kinetic energy of the water droplets at a distance l from the nozzle, in J; y is the functional relationship between the total kinetic energy E Tl of the water droplets at a single measuring point and the distance l from the nozzle; l is the distance from the nozzle, in m; where, 0 ≤ l ≤ Ra, and Ra is the distance from the nozzle to the farthest water droplet landing point, in m.

[0020] In the above solution, the working pressure range of the nozzle is 0.15 MPa - 0.45 MPa.

[0021] Advantages of the present invention: The present invention provides a fixed solar irrigation system and a calculation method for the solar energy conversion efficiency thereof, which can quickly obtain the solar energy conversion efficiency, and the method is simple and practical, thereby providing a theoretical basis for the efficient utilization of the solar irrigation system. Description of the Drawings

[0022] Figure 1 is a schematic diagram of the fixed solar irrigation system described in the present invention.

[0023] Figure 2 is a function change diagram of the total kinetic energy of water droplets and the measuring point distance in the embodiment.

[0024] In the figure: 1. water storage tank, 2. valve, 3. centrifugal pump, 4. solar controller, 5. solar panel, 6. sprinkler head, 7. rain gauge, 8. electromagnetic flowmeter, 9. pressure gauge Specific implementation mode

[0025] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0026] To make the purpose, features and advantages of the present invention more obvious and understandable, as Figure 1 shown, a solar irrigation system provided in this embodiment includes a water storage tank 1. The water storage tank 1 is connected to a centrifugal pump 3 through a pipeline by a valve 2. An electromagnetic flowmeter 8, a pressure gauge 9 and a sprinkler head 6 are installed on the pipeline at the output end of the centrifugal pump 3. It is characterized in that the power of the centrifugal pump 3 is provided by a solar controller 4, and the solar controller 4 is electrically connected to a solar panel 5. This embodiment takes the energy supply and water droplet energy conversion efficiency of the solar irrigation system under windless conditions as an example for detailed description as follows.

[0027] (1) Select the R2000 model sprinkler head of Nelson Company and install it in the solar irrigation system. The number of sprinkler heads in the system is 4. Since the sprinkler head pressures are almost the same at the same time, 1 sprinkler head is selected as the research object. Taking the sprinkler head working pressure of about 0.20 MPa as an example, when the sprinkler head working pressure is stable at 0.20 MPa for more than 30 minutes, the average value of the corresponding light intensity is taken. The experimental data is shown in Table 1.

[0028] Table 1 Corresponding light intensity at a sprinkler head pressure of 0.2 MPa

[0029]

[0030] (2) Use an external power supply to stably operate the irrigation device, set the sprinkler head working pressure to 0.21 MPa, simulate the energy provided by a light intensity of 300.8 W / m 2 , and start the hydraulic performance experiment after stably operating for 10 minutes. Laser disdrometers are placed at intervals of 1 m in the radial direction from the sprinkler head, and each placement lasts for 5 minutes. Record the number of water droplets and the water droplet velocity of each diameter class at different distances from the sprinkler head.

[0031] (3) Substitute the number of water droplets W and the water droplet velocity V di of each diameter class measured and recorded in step (2) at different distances from the sprinkler head into formula (1) to calculate the corresponding kinetic energy of a single water droplet.

[0032] (4) Substitute E sd calculated in (3) into formula (2) Obtain the total kinetic energy of the water droplets at this measurement point. The data processing results of steps (2), (3), and (4) are shown in Table 2.

[0033] (5) According to the total kinetic energy of 12 water droplets calculated at a pressure of 0.21 MPa, with the distance from the nozzle as the independent variable and the total kinetic energy of the water droplets as the dependent variable, the functional relationship between the distance from the nozzle and the total kinetic energy of the water droplets is obtained as: y = 0.0001e 0.7513l , as Figure 2 shown.

[0034] (6) Using the MATLAB function integration method, input the functional relationship y = 0.0001e obtained in the previous step 0.7513l , limit the range of the independent variable to [0, 12], and use formula (4) to obtain the total kinetic energy of the water droplets as 1.47 J.

[0035] (7) Using formula (5) to obtain the energy conversion efficiency value of the fixed solar sprinkler irrigation system under a light intensity of 300.8 W / m 2 as 36.66%.

[0036] The described embodiment is a preferred embodiment of the present invention, but the present invention is not limited to the above embodiment. Without departing from the essential content of the present invention, any obvious improvement, replacement, or variation that those skilled in the art can make belongs to the protection scope of the present invention.

[0037] Table 2 Water droplet performance at each measurement point when the light intensity is 300.8 W / m 2

[0038] ​

Claims

1. A calculation method for the solar energy conversion rate in a solar irrigation system, wherein the solar irrigation system includes a water storage tank (1), the water storage tank (1) is connected to a centrifugal pump (3) through a pipeline by a valve (2), an electromagnetic flowmeter (8), a pressure gauge (9) and a sprinkler head (6) are installed on the pipeline at the output end of the centrifugal pump (3), and it is characterized in that, The power of the centrifugal pump (3) is provided by a solar controller (4), and the solar controller (4) is electrically connected to a solar panel (5). It is characterized by including the following steps: S1; Normally operate the solar irrigation system, record the corresponding light intensity value when the sprinkler head pressure is stable for at least 30 minutes, and take the average value of the light intensity. S2; Use an external power supply to stably operate the irrigation device, set the working pressure of the sprinkler head to H, start from a position 1 m away from the sprinkler head, place a laser disdrometer every 1 m in the radial direction of the sprinkler head to measure and record the number of water droplets of different diameter classes and the falling speed of water droplets at different distances from the sprinkler head. S3: Measure the water droplet velocity and diameter at different measurement points through the laser disdrometer, and calculate the kinetic energy of a single water droplet when it hits the ground. In step S3, when calculating the kinetic energy of a single water droplet when it hits the ground, since there are a large number of sprinkling water droplets at the same measurement point and there is a large difference in the velocity between water droplets, the kinetic energy of a single water droplet here refers to the average value of the kinetic energy of water droplets of a certain diameter class at the measurement point, and the calculation formula is as shown in formula (1). Where: E sd is the kinetic energy of a single water droplet with diameter d, J; V di is the velocity of the water droplet with diameter d, m / s; W is the number of particles corresponding to V di ; i is the name of the velocity level of the water droplet with diameter d; o is the number of water droplet velocity classifications; ρ w is the density of water, kg / m 3 ; S4: Calculate the total kinetic energy of water droplets at a single measurement point; Multiply the kinetic energy of a single water droplet obtained by calculation by the number of particles W respectively, and accumulate them to obtain the total kinetic energy of water droplets at this measurement point; In the experiment, the measurement points are distributed every 1 m, and the total kinetic energy of water droplets at other points is obtained by analyzing and fitting with a curve formula. The curve formula is shown in formula (3). y = f(l) (3) where: l is the distance from the nozzle, in m; among which, 0 ≤ l ≤ Ra, and Ra is the distance from the nozzle to the landing point of the outermost water droplet, in m; in step S4, the kinetic energy E of a single water droplet obtained through calculation sd , is respectively multiplied by the number of particles W corresponding to this diameter class, and after accumulation, the total kinetic energy E of the water droplets at this measurement point is obtained Tl , as shown in Equation (2); during the experiment, the measurement points are distributed every 1 m, and the total kinetic energy of the water droplets at other points is obtained through curve formula analysis and fitting, and the curve formula is shown in Equation (3); y = f(l) (3) Where: E Tl is the total kinetic energy of water droplets at a distance l from the nozzle, in J; y is the functional relationship between the total kinetic energy E of water droplets at a single measurement point Tl and the distance l from the nozzle; l is the distance from the nozzle, in m; where 0 ≤ l ≤ Ra, and Ra is the distance from the nozzle to the farthest water droplet landing point, in m; S5: Total kinetic energy E of single-nozzle water droplets T Calculation. Fix the rotating nozzle for spraying, use the function integration in MATLAB software, input the functional relationship y between the distance from the nozzle and the kinetic energy of water droplets, and sum up the total kinetic energy E of water droplets at all points within the spraying range Tl Accumulative summation. The number of nozzles configured in the system is m, so E T See Equation (4); Where: E T is the total kinetic energy of the water droplets in the system, in J; S6: Obtain the calculation formula for the energy conversion efficiency η of the solar irrigation system; because the unit of the light intensity obtained from the light intensity detector is W / m 2 , it should be converted to J. According to the formula J = W / s, combined with the total area S square meters of the solar panel and the time t seconds used for each test, the energy conversion efficiency value of the solar irrigation system and raindrops under the corresponding light intensity can be calculated; finally, the calculation formula for the energy conversion efficiency η of the solar irrigation system is shown in Equation (5); Where: η is the energy conversion efficiency of the solar sprinkler irrigation system; x is the light intensity in W / m 2 .

2. The calculation method of the solar energy conversion rate in a solar irrigation system according to claim 1, characterized in that, The working pressure range of the sprinkler head is 0.15 MPa - 0.45 MPa.

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