Molecular simulation-based method for screening components of foam extinguishing agent for photovoltaic power station

Abstract

The invention belongs to the technical field of foam extinguishing agents, particularly relates to a molecular simulation-based method for screening components of a foam extinguishing agent for a photovoltaic power station, and particularly relates to a molecular simulation means for screening materials of extinguishing agents for photovoltaic fire disasters, and the method mainly aims at flammable photovoltaic modules in the photovoltaic power station. And screening the matched efficient fire extinguishing agent. According to the molecular simulation method, the interaction relation between the flammable photovoltaic module surface and the foam extinguishing agent can be revealed from the perspective of micro molecules, various matching conditions can be simulated within a short time, and a compounding scheme with the best effect can be screened out from various surfactants and foam stabilizers. The theoretical support is provided for the foam extinguishing agent for the fire of the photovoltaic power station. The method is convenient and practical, and has wide application prospect and guidance value in the field of foam extinguishing agent development.

Description

Technical Field

[0001] The present invention relates to the technical field of foam fire extinguishing agents, and specifically to a screening method for components of foam fire extinguishing agents for photovoltaic power stations based on molecular simulation. Background Art

[0002] With the development of the photovoltaic power generation industry, photovoltaic power stations are no longer limited to sparsely populated areas. There are emerging small-scale power generation systems such as building-integrated photovoltaics and household distributed photovoltaic systems, which are getting closer and closer to humans. Once a photovoltaic fire accident occurs, it will directly threaten life safety.

[0003] In the past period, photovoltaic power generation system fire accidents of varying degrees have occurred in many places around the world, resulting in heavy losses.

[0004] Ethylene-vinyl acetate polymer, which is commonly used in photovoltaic encapsulation components, is flammable. It will release hydrocarbon-containing gases at high temperatures. The powder can form an explosive mixture with air, posing a great fire hazard.

[0005] Ethylene-vinyl acetate polymer has strong hydrophobicity, and the use of water-based fire extinguishing agents has poor fire extinguishing effects. Compared with directly using water to extinguish fires, foam fire extinguishing agents have rich foam and strong adhesiveness, and can form a stable and lasting foam on the material surface. This can not only enhance the contact effect between the fire extinguishing agent and the material, but also play a role in isolating air, further improving the fire extinguishing efficiency of photovoltaic fires. Summary of the Invention

[0006] The purpose of the present invention is to provide a screening method for components of foam fire extinguishing agents for photovoltaic power stations based on molecular simulation. Through this method, the interaction relationship between the surface of flammable photovoltaic components and foam fire extinguishing agents can be revealed from the perspective of microscopic molecules, and multiple matching situations can be simulated in a short time, providing a reference for the popularization in the field of foam fire extinguishing agent development.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A screening method for components of foam fire extinguishing agents for photovoltaic power stations based on molecular simulation, the method comprising the following steps:

[0009] Step S1. Construct an ethylene-vinyl acetate polymer-surfactant-water molecule simulation system: Use the Amorphous Cell module in Materials Studio software to construct an ethylene-vinyl acetate polymer (EVA) molecular box, a surfactant molecular box, and a water molecule box, which include 8 ethylene-vinyl acetate polymer (EVA) molecules, 0 - 40 surfactant molecules, and 1000 water molecules respectively. The length and width of the box are both 3.14 nm × 3.14 nm. Set a 2-nm vacuum layer above the water molecule box, and use Build Layers to combine the three boxes into an ethylene-vinyl acetate polymer-surfactant-water molecule model;

[0010] Step S2. Use the Forcite module in Materials Studio to perform structural optimization based on the COMPASSⅢ molecular force field to obtain an optimized configuration. To obtain the lowest-energy structural model, the Smart algorithm of the Forcite module is used for geometric optimization at the end of each step of the simulation process. The energy difference is set to 0.0001 kcal / mol, and the RMS force standard is The number of iterations is 30,000 times;

[0011] Step S3. Adsorption simulation of water molecules by the ethylene-vinyl acetate polymer-surfactant-water molecule simulation system: Use the Sorption module in Materials Studio to perform adsorption simulation. Fix the lower half of the ethylene-vinyl acetate polymer (EVA) box. Select Fixed pressure for the task, adopt the Metropolis method, set the equilibrium number of steps to 7×10 5 steps, and the output number of steps to 8×10 5 steps, and the pressure is one atmosphere;

[0012] Step S4. Measure the contact angles of the three surfactants, namely the two surfactants with the largest amount of adsorbed water molecules and the surfactant with a smaller adsorption amount in the simulation results, to verify the accuracy of the molecular simulation;

[0013] Step S5. To achieve a better foaming effect, compound the surfactant with the largest amount of adsorbed water molecules in S1 - S4 with a foaming agent and a foam stabilizer to construct a foam fire extinguishing agent molecular model. The foam fire extinguishing agent molecular model adopts a sandwich foam liquid film simulation system. The water molecule layer is in the middle of the model, and on both sides are neatly arranged surfactants and are symmetrical to each other. Vacuum layers are set on both sides of the model. The water molecule layer consists of 3000 water molecules. The arrangement direction of each surfactant molecule is perpendicular to the plane composed of the x-axis and the y-axis, and each surfactant monolayer consists of 25 molecules;

[0014] Step S6: Use the Forcite module in Materials Studio to perform structural optimization based on the COMPASS III molecular force field to obtain an optimized configuration. To obtain the structural model with the lowest energy, the Smart algorithm of the Forcite module is used for geometric optimization at the end of each step of the simulation. The energy difference is set to 0.0001 kcal / mol, and the RMS force criterion is The number of iterations is 30,000 times;

[0015] Step S7: Molecular dynamics calculation: The kinetic simulation is realized through the NVT ensemble. Start the Dynamic task under the Forcite module, still using the COMPASS force field, and the cutoff radius is Select the Nose temperature control method, the simulation temperature is 298 K, the time step is set to 1 fs, the total simulation duration is 500 ps, and analyze its radial distribution function, root mean square displacement, and liquid film thickness.

[0016] For the radial distribution function, its calculation formula is:

[0017]

[0018] where: g(r) is the probability of other particles appearing at a position r from the central particle; dN is the number of other particles in the spherical region at a position r from the central particle; ρ is the density of the system composed of various surfactant molecular models; dr is the thickness of the spherical region; r is the distance from the central particle.

[0019] The diffusion behavior of the foam extinguishing agent molecular model is described by the molecular root mean square displacement MSD and the diffusion coefficient D, and then the drainage ability of the foam liquid film of surfactants, foaming agents, and foam stabilizers at different compounding ratios is evaluated. Its calculation formula is:

[0020]

[0021]

[0022] where: N is the total number of diffusing molecules in the simulation system, r i (t) is the position of particle i at time t, r i (0) is the position of particle i at the initial time, D is the diffusion coefficient of the microscopic particle, and a is the linear slope of the root mean square displacement with time.

[0023] In the step S1, the surfactant is one of dodecyldimethylbetaine (BS-12), octadecyldimethylhydroxypropylsulfobetaine (OHSB), cocamidopropyl betaine (CAB), sodium dodecyl sulfate (K12), sodium dodecyl polyoxyethylene ether sulfate (AES), sodium dodecyl diphenyl ether disulfonate (SLDED), sodium alkylphenol polyoxyethylene ether carboxylate (APEC-10Na), sodium dodecylbenzenesulfonate (SDBS), cetyltrimethylammonium chloride (CTAC), cetyltrimethylammonium bromide (CTAB), dodecyldimethylamine oxide (OB-2), fatty alcohol polyoxyethylene ether (AEO-3), dodecyl glucoside (APG1080), and coconut fatty acid diethylamide (CDEA).

[0024] In the step S1, a model of ethylene-vinyl acetate polymer material with a degree of polymerization of 50, a number of molecules of 8, and a vinyl acetate content of 33% is constructed.

[0025] In the step S4, the concentrations of the three surfactants used in the experiment are set to 0.3×10 -3 mol / L, 0.6×10 -3 mol / L, 0.9×10 -3 mol / L, 1.2×10 -3 mol / L, 1.5×10 -3 mol / L, 1.8×10 -3 mol / L, and 2.1×10 - 3 mol / L. Using distilled water as a blank control, the measurement mode is the static contact angle, and the sessile drop method is adopted. Each solution is measured three times and the average value is taken. For the convenience of comparison, the measurement photos obtained 1 s after the solution is dropped are selected, and the contact angles of the droplets in the photos are measured.

[0026] In the step S5, the foaming agent is one of dodecyldimethylbetaine (BS-12) and cetyltrimethylammonium bromide (CTAB), and the foam stabilizer is hydrolyzed polyacrylamide (HPAM).

[0027] In an embodiment of the present invention, when verifying the above molecular model, it is necessary to construct an ethylene-vinyl acetate polymer-surfactant-water molecule simulation system. By adjusting different surfactants and combining the adsorbed water molecular weight and contact angle experiments, the surfactant with the best effect is found to determine the monomer additives in the foam fire extinguishing agent.

[0028] In an embodiment of the present invention, a molecular model of the foam fire extinguishing agent is constructed to complete geometric optimization and molecular dynamics optimization. By adjusting different compounding ratios and combining the radial distribution function, root mean square displacement, and liquid film thickness, the foaming performance of the foam fire extinguishing agent is verified, and the verification results are used to characterize the effectiveness of this foam fire extinguishing agent in the actual application process.

[0029] Compared with the prior art, the present invention has the following beneficial effects: For the flammable parts in photovoltaic modules, through molecular modeling and simulation calculations, the present invention specifically designs a foam fire extinguishing agent with better fire extinguishing effect, explores the effect of the foam fire extinguishing agent from the molecular level, reduces the test cost, and has important significance for the further development of foam fire extinguishing agents for photovoltaic power stations. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the flowchart of the method according to the embodiment of the present invention.

[0031] Figure 2 is the molecular model of ethylene-vinyl acetate copolymer (EVA) in the embodiment of the present invention.

[0032] Figure 3 is the molecular model of the surfactant and foaming agent in the embodiment of the present invention.

[0033] Figure 4 is the foam stabilizer model in the embodiment of the present invention.

[0034] Figure 5 is the adsorbed water molecular weight of the ethylene-vinyl acetate copolymer-surfactant-water molecule simulation system in the embodiment of the present invention.

[0035] Figure 6 is the contact angle change in the embodiment of the present invention.

[0036] Figure 7 is the radial distribution function in the embodiment of the present invention.

[0037] Figure 8 is the root mean square displacement of water molecules in the embodiment of the present invention.

[0038] Figure 9 is the liquid film thickness in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The technical solutions of the present invention will be specifically described below with reference to the accompanying drawings.

[0040] It should be noted that the following detailed description is exemplary and is intended to provide further description of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0041] A screening method for the components of a foam fire extinguishing agent for a photovoltaic power station based on molecular simulation according to the present invention comprises the following steps:

[0042] Step S1: Construct an ethylene-vinyl acetate polymer-surfactant-water molecular simulation system: Use the Amorphous Cell module in Materials Studio software to construct an ethylene-vinyl acetate polymer (EVA) molecular box, a surfactant molecular box, and a water molecular box respectively, including 8 ethylene-vinyl acetate polymer (EVA) molecules, 0 to 40 surfactant molecules, and 1000 water molecules. The length and width dimensions of the box are both 3.14 nm × 3.14 nm. A 2-nm vacuum layer is set above the water molecular box, and the three boxes are combined into an ethylene-vinyl acetate polymer-surfactant-water model using Build Layers;

[0043] Step S2: Use the Forcite module in Materials Studio to perform structural optimization based on the COMPASSⅢ molecular force field to obtain an optimized configuration. To obtain the lowest-energy structural model, the Smart algorithm of the Forcite module is used for geometric optimization at the end of each step of the simulation process. The energy difference is set to 0.0001 kcal / mol, and the RMS force standard is The number of iterations is 30,000 times;

[0044] Step S3: Adsorption simulation of water molecules by the ethylene-vinyl acetate polymer-surfactant-water molecular simulation system: Use the Sorption module in Materials Studio to perform adsorption simulation. Fix the lower half of the ethylene-vinyl acetate polymer (EVA) box. Select Fixed pressure for the task, use the Metropolis method, set the equilibrium number of steps to 7×10 5 steps, and the production number of steps to 8×10 5 steps, and the pressure is one atmosphere;

[0045] Step S4: Measure the contact angles of the three surfactants, namely the two surfactants with the largest amount of adsorbed water molecules and the surfactant with a smaller adsorption amount in the simulation results, to verify the accuracy of the molecular simulation;

[0046] Step S5: To achieve a better foaming effect, the surfactant with the most adsorbed water molecules in S1 - S4 is compounded with a foaming agent and a foam stabilizer to construct a molecular model of the foam extinguishing agent. The molecular model of the foam extinguishing agent adopts a sandwich foam liquid film simulation system, with a water molecule layer in the middle of the model, and neatly arranged surfactants on both sides, which are symmetrical to each other. Vacuum layers are set on both sides of the model. The water molecule layer consists of 3000 water molecules. The arrangement direction of each surfactant molecule is perpendicular to the plane composed of the x - axis and the y - axis, and each surfactant monolayer consists of 25 molecules;

[0047] Step S6: Use the Forcite module in Materials Studio to perform structural optimization based on the COMPASSⅢ molecular force field to obtain an optimized configuration. To obtain the structural model with the lowest energy, at the end of each step of the simulation process, the Smart algorithm of the Forcite module is used for geometric optimization, the energy difference is set to 0.0001 kcal / mol, and the RMS force standard is The number of iterations is 30000 times;

[0048] Step S7: Molecular dynamics calculation: The kinetic simulation is realized through the NVT ensemble. Start the Dynamic task under the Forcite module, still using the COMPASS force field, and the cutoff radius is Select the Nose temperature control method, the simulation temperature is 298K, the time step is set to 1 fs, the total simulation duration is 500 ps, and analyze its radial distribution function, root - mean - square displacement, and liquid film thickness.

[0049] The following are specific embodiments of the present invention.

[0050] As Figure 1 shown, this embodiment provides a screening method for the components of a foam extinguishing agent for a photovoltaic power station based on molecular simulation. As Figure 2 shown, in this embodiment, a molecular model of an ethylene - vinyl acetate polymer material with a degree of polymerization of 50, 8 molecules, and a vinyl acetate content of 33% is constructed using Materials Studio. As Figure 3 、 Figure 4As shown in the figure, surfactants were constructed using Materials Studio, including dodecyldimethylbetaine (BS-12), octadecyldimethylhydroxypropylsulfobetaine (OHSB), cocoamidopropyl betaine (CAB), sodium dodecyl sulfate (K12), sodium dodecyl polyoxyethylene ether sulfate (AES), sodium dodecyl diphenyl ether disulfonate (SLDED), sodium alkylphenol polyoxyethylene ether carboxylate (APEC-10Na), sodium dodecylbenzenesulfonate (SDBS), cetyltrimethylammonium chloride (CTAC), cetyltrimethylammonium bromide (CTAB), dodecyldimethylamine oxide (OB-2), fatty alcohol polyoxyethylene ether (AEO-3), dodecyl glucoside (APG1080), coco fatty acid diethylamide (CDEA), and foam stabilizer hydrolyzed polyacrylamide (HPAM).

[0051] In this example, the Sorption module was used to simulate the adsorption of water molecules by the ethylene-vinyl acetate polymer-surfactant-water molecule system. The adsorption results are as Figure 5 shown. Among them, sodium dodecyl diphenyl ether disulfonate (SLDED) has the best effect, with a water molecule adsorption amount as high as 180. Followed by sodium alkylphenol polyoxyethylene ether carboxylate (APEC-10Na), which can adsorb up to 128 water molecules at most. Next, sodium dodecyl diphenyl ether disulfonate (SLDED) and sodium alkylphenol polyoxyethylene ether carboxylate (APEC-10Na) with the largest adsorption amounts, as well as coco fatty acid diethylamide (CDEA) with a smaller adsorption amount, will be analyzed in detail.

[0052] In this example, the three surfactants used in the contact angle experiment are sodium dodecyl diphenyl ether disulfonate (SLDED), sodium alkylphenol polyoxyethylene ether carboxylate (APEC-10Na), and coco fatty acid diethylamide (CDEA), respectively. The concentrations are set to 0.3×10 -3 mol / L, 0.6×10 -3 mol / L, 0.9×10 -3 mol / L, 1.2×10 -3 mol / L, 1.5×10 -3 mol / L, 1.8×10 -3 mol / L, and 2.1×10 -3 mol / L, with distilled water as the blank control. The measurement mode is the static contact angle, and the sessile drop method is used. Each solution is measured three times and the average value is taken. For the convenience of comparison, the measurement photos obtained 1 s after the solution drops are selected, and the contact angles of the droplets in the photos are measured. The obtained results are as Figure 6As shown, it can be seen from the figure that after adding surfactants to pure water, the contact angle decreases significantly. The decrease rate is the fastest when the concentration is between 0 and 0.9 mmol / L. As the concentration continues to increase, the decrease rate of the contact angle gradually slows down until there is almost no change. The contact angle sizes with ethylene-vinyl acetate polymer (EVA) are: pure water > coconut oil fatty acid diethylamide (CDEA) > sodium alkylphenol polyoxyethylene ether carboxylate (APEC-10Na) > sodium dodecyl diphenyl ether disulfonate (SLDED). That is, after adding surfactants, the wettability of the material surface is improved. The order of improving wettability is: sodium dodecyl diphenyl ether disulfonate (SLDED) > sodium alkylphenol polyoxyethylene ether carboxylate (APEC-10Na) > coconut oil fatty acid diethylamide (CDEA), which is consistent with the results obtained from adsorption simulation.

[0053] In this example, the foaming agent is selected from one of dodecyl dimethyl betaine (BS-12) and cetyl trimethyl ammonium bromide (CTAB), and the foam stabilizer is selected as hydrolyzed polyacrylamide (HPAM).

[0054] In this example, sodium dodecyl diphenyl ether disulfonate (SLDED) with the best wettability is mixed with dodecyl dimethyl betaine (BS-12) and cetyl trimethyl ammonium bromide (CTAB) in the foaming agent in different ratios, such as Figure 7 As shown, by analyzing the radial distribution function to evaluate the stability effect of the foam extinguishing agent, the two peaks of dodecyl dimethyl betaine (BS-12) are basically equivalent when the ratio is 17:8, and their sum reaches the maximum value of 6.605. The two peaks of cetyl trimethyl ammonium bromide (CTAB) are basically equivalent when the ratio is 16:9, and their sum reaches the maximum value of 6.878, which is greater than the sum of the peaks of the compound system of dodecyl dimethyl betaine (BS-12) and sodium dodecyl diphenyl ether disulfonate (SLDED). Therefore, the compound system of sodium dodecyl diphenyl ether disulfonate (SLDED) and cetyl trimethyl ammonium bromide (CTAB) has a better compounding effect than the compound system with dodecyl dimethyl betaine (BS-12), and cetyl trimethyl ammonium bromide (CTAB) is more suitable to be added to the system as a foam stabilizer.

[0055] In this example, to understand the drainage ability of the foam liquid film in the foam system, the root mean square displacement is calculated to obtain the diffusion coefficient, as Figure 8As shown, with the increase of the compounding ratio of dodecyl dimethyl betaine (BS-12) and sodium dodecyl diphenyl ether disulfonate (SLDED), the slope of the root mean square displacement curve first decreases and then increases. When the ratio is 15:10, the slope reaches the minimum, at which time the diffusion coefficient is the smallest, the foam drainage ability is the worst, and the stability is the best, which is close to the optimal ratio of 17:8 obtained by the radial distribution function analysis. With the increase of the compounding ratio of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl diphenyl ether disulfonate (SLDED), the slope of the root mean square displacement curve also first decreases and then increases. When the ratio is 15:10, the slope reaches the minimum, which is close to the optimal ratio of 16:9 obtained by the radial distribution function analysis.

[0056] In this embodiment, to explore the influence of different amounts of hydrolyzed polyacrylamide (HPAM) on the liquid film thickness, as Figure 9 shown, with the increase of the compounding ratio, the liquid film thickness also changes accordingly. When the number of hydrolyzed polyacrylamide (HPAM) molecules is 0 - 2, the change of the liquid film thickness shows a trend of first increasing and then decreasing, and the corresponding ratios at the highest points are different. When the number of hydrolyzed polyacrylamide (HPAM) molecules is 3 - 4, the liquid film thickness also changes with the change of the ratio, but no longer shows the law of first increasing and then decreasing at low concentrations, and there is no obvious law presented. Considering from the perspectives of efficiency and economy, it is most appropriate to add 2 hydrolyzed polyacrylamide (HPAM) molecular chains to the system, and the optimal compounding ratio of the surfactant is 16:9.

[0057] The above are the preferred embodiments of the present invention. All changes made according to the technical solutions of the present invention, when the functional effects produced do not exceed the scope of the technical solutions of the present invention, shall fall within the protection scope of the present invention.

Claims

1. A method for screening components of foam fire extinguishing agents for photovoltaic power stations based on molecular simulation, characterized in that: The following steps are involved: Step S1, constructing an ethylene-vinyl acetate polymer-surfactant-water molecule simulation system: using the Amorphous Cell module in the MaterialsStudio software to respectively construct an ethylene-vinyl acetate polymer (EVA) molecule box, a surfactant molecule box, and a water molecule box, each of which includes 8 ethylene-vinyl acetate polymer (EVA) molecules, 0 to 40 surfactant molecules, and 1000 water molecules. The length and width of the box are both 3.14 nm × 3.14 nm. A 2 nm vacuum layer is set above the water molecule box, and the three boxes are combined into an ethylene-vinyl acetate polymer-surfactant-water molecule model using Build Layers; Step S2: Use the Forcite module in Materials Studio to perform structural optimization based on the COMPASSⅢ molecular force field to obtain the optimized configuration. In order to obtain the lowest energy structural model, the Smart algorithm of the Forcite module is used for geometric optimization after each step of the simulation process. The energy difference is set to 0.0001 kcal / mol and the RMS force standard is The number of iterations is 30,000; Step S3, simulation of water molecule adsorption by ethylene-vinyl acetate polymer-surfactant-water molecule simulation system: Use the Sorption module in Materials Studio to perform adsorption simulation. Fix the lower half of the ethylene-vinyl acetate polymer (EVA) box, select Fixed pressure as the task, use Metropolis as the method, and set the number of equilibrium steps to 7×10 5 Steps, the output steps are 8×10 5 step, the pressure is one atmosphere; Step S4, measuring the contact angles of the two surfactants with the largest molecular weight of adsorbed water in the simulation results and the surfactant with the smallest amount of adsorption to verify the accuracy of the molecular simulation; Step S5: To achieve a better foaming effect, the surfactant that absorbs the most water molecules in S1 to S4 is compounded with a foaming agent and a foam stabilizer to construct a foam extinguishing agent molecular model. The foam extinguishing agent molecular model adopts a sandwich foam liquid film simulation system, with a water molecule layer in the middle of the model, and neatly arranged surfactants on both sides that are symmetrical to each other, and vacuum layers are set on both sides of the model. The water molecule layer consists of 3,000 water molecules, and the arrangement direction of each surfactant molecule is perpendicular to the plane formed by the x-axis and the y-axis, and each surfactant monolayer consists of 25 molecules; Step S6: Use the Forcite module in Materials Studio to perform structural optimization based on the COMPASSⅢ molecular force field to obtain the optimized configuration. In order to obtain the lowest energy structural model, the Smart algorithm of the Forcite module is used for geometric optimization after each step of the simulation process. The energy difference is set to 0.0001 kcal / mol and the RMS force standard is The number of iterations is 30,000; Step S7, molecular dynamics calculation: The dynamics simulation is realized through the NVT ensemble. The Dynamic task under the Forcite module is started, and the COMPASS force field is still used. The cutoff radius is Select Nose temperature control mode, set the simulation temperature to 298K, set the time step to 1fs, and the total simulation time to 500ps. Analyze its radial distribution function, root mean square displacement, diffusion coefficient, and liquid film thickness. The radial distribution function is calculated as follows: Where: g(r) is the probability of other particles appearing at a distance r from the central particle; dN is the number of other particles in the spherical area at a distance r from the central particle; ρ is the system density composed of various surfactant molecular models; dr is the thickness of the spherical area; and r is the distance from the central particle. The molecular root mean square displacement MSD and diffusion coefficient D are calculated as follows: Where: N is the total number of diffusing molecules in the simulation system, r i (t) is the position of particle i at time t, r i (0) is the position of particle i at the initial moment, D is the diffusion coefficient of the microscopic particle, and a is the linear slope of the root mean square displacement and time.

2. A method for screening components of foam fire extinguishing agents for photovoltaic power stations based on molecular simulation as claimed in claim 1, characterized in that: In the step S1, the surfactant is one of dodecyl dimethyl betaine (BS-12), octadecyl dimethyl hydroxypropyl sulfobetaine (OHSB), cocamidopropyl betaine (CAB), sodium lauryl sulfate (K12), sodium dodecyl polyoxyethylene ether sulfate (AES), sodium dodecyl diphenyl ether disulfonate (SLDED), sodium alkylphenol polyoxyethylene ether carboxylate (APEC-10Na), sodium dodecylbenzene sulfonate (SDBS), hexadecyl trimethyl ammonium chloride (CTAC), hexadecyl trimethyl ammonium bromide (CTAB), dodecyl dimethyl amine oxide (OB-2), fatty alcohol polyoxyethylene ether (AEO-3), dodecyl glucoside (APG1080), and coconut fatty acid diethylamide (CDEA).

3. A method for screening components of foam fire extinguishing agent for photovoltaic power station based on molecular simulation as claimed in claim 1, characterized in that: In the step S1, an ethylene-vinyl acetate polymer material model with a degree of polymerization of 50, a molecular number of 8, and a vinyl acetate content of 33% is constructed.

4. A method for screening components of foam fire extinguishing agents for photovoltaic power stations based on molecular simulation as claimed in claim 1, characterized in that: In step S4, the concentration of the three surfactants used in the experiment was set to 0.3×10 -3 mol / L、0.6×10 -3 mol / L、0.9×10 -3 mol / L、1.2×10 -3 mol / L、1.5×10 -3 mol / L、1.8×10 -3 mol / L and 2.1×10 -3 mol / L, distilled water was used as blank control, the measurement mode was static contact angle, the hanging drop method was adopted, each solution was measured three times and the average value was taken. For the convenience of comparison, the measurement photo obtained when the solution was dripped for 1s was selected, and the contact angle of the drop in the photo was measured.

5. The method for screening components of foam fire extinguishing agent for photovoltaic power station based on molecular simulation according to claim 1, characterized in that: In the step S5, the foaming agent is one of dodecyl dimethyl betaine (BS-12) and cetyl trimethyl ammonium bromide (CTAB), and the foam stabilizing agent is hydrolyzed polyacrylamide (HPAM).

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