1. A preparation method of a composite phase change energy storage material based on straw waste is characterized by comprising the following steps: the method comprises the following steps:

(1) pretreatment of straw

Washing and drying the crushed straws, cooling, performing ball milling, mixing and stirring with a treatment solution, and finally washing and drying to obtain a straw pretreatment product for later use;

(2) preparation of straw-loaded polypyrrole mixture

Firstly, dissolving pyrrole in a hydrochloric acid solution at room temperature and stirring, then adding the straw pretreatment product obtained in the step (1) into the solution, continuously stirring for a period of time, then adding an ammonium persulfate solution for stirring, and finally filtering the mixture obtained after stirring by using a filter membrane, washing by using ultrapure water and drying to prepare a straw-loaded polypyrrole mixture;

(3) preparation of straw-loaded polypyrrole-coated polyethylene glycol composite phase change energy storage material

Dissolving the mixture of the straw-loaded polypyrrole and sodium alginate in ultrapure water, heating and stirring, and then adding polyethylene glycol and continuously stirring until the mixture is completely dissolved; cooling to room temperature, pre-freezing at certain temperature for a period of time, and taking out; and then soaking the composite phase-change energy storage material in a calcium ion solution for a period of time, taking out, pre-freezing again, and freeze-drying to prepare the composite phase-change energy storage material based on the straw waste.

2. The preparation method of the composite phase change energy storage material based on straw waste as claimed in claim 1, wherein the preparation method comprises the following steps: the particle size of the crushed straw in the step (1) is 80-100 meshes, firstly, washing with hot water at 80-100 ℃ for 5-15min, repeating for 3-5 times, then, drying at 55-65 ℃ for 24-48 hours, cooling, and then, carrying out ball milling by using a planetary ball mill;

the rotation speed during ball milling in the step (1) is 500-;

the temperature for mixing and stirring the mixture and the treatment liquid in the step (1) is 55-65 ℃ and the time is 8-12 hours;

the solid-liquid ratio of the straws to the treatment liquid in the step (1) is 1:10-20, and the unit is g/ml;

and (2) washing and drying in the step (1), wherein the drying temperature is 55-65 ℃, and the drying time is 12-24 hours.

3. The preparation method of the composite phase change energy storage material based on straw waste as claimed in claim 1, wherein the preparation method comprises the following steps: the treatment liquid in the step (1) is a mixed liquid of dimethyl sulfoxide, potassium hydroxide and ultrapure water; wherein: the volume ratio of the dimethyl sulfoxide to the ultrapure water is 25: 1; the potassium hydroxide content was 5 mg/ml.

4. The preparation method of the composite phase change energy storage material based on straw waste as claimed in claim 1, wherein the preparation method comprises the following steps: the mass ratio of the straw pretreatment product to the pyrrole in the step (2) is 1:0.05-1, and the molar ratio of ammonium persulfate to the pyrrole is 1: 1.

5. The preparation method of the composite phase change energy storage material based on straw waste as claimed in claim 1, wherein the preparation method comprises the following steps: dissolving the pyrrole in the step (2) in hydrochloric acid at room temperature, and stirring for 0.5 h; then adding the straw pretreatment product into the solution, and continuously stirring and mixing for 1-3 h; adding ammonium persulfate into the mixture obtained in the step (2), continuously stirring the mixture for 8 to 12 hours at room temperature, then carrying out vacuum filtration through a filter membrane of 0.2 micron, washing the mixture through ultrapure water, and finally drying the mixture, wherein the drying temperature is 55 to 65 ℃, and the drying time is 12 to 24 hours.

6. The preparation method of the composite phase change energy storage material based on straw waste as claimed in claim 1, wherein the preparation method comprises the following steps: the concentration of the sodium alginate in the step (3) is 10-20 mg/ml.

7. The preparation method of the composite phase change energy storage material based on straw waste as claimed in claim 1, wherein the preparation method comprises the following steps: the heating and stirring temperature in the step (3) is 55-65 ℃, and the stirring time is 30-90 minutes; the mass of the polyethylene glycol in the step (3) accounts for 60-90% of the sum of the mass of the straw-loaded polypyrrole mixture, the mass of the sodium alginate and the mass of the polyethylene glycol.

8. The preparation method of the composite phase change energy storage material based on straw waste as claimed in claim 1, wherein the preparation method comprises the following steps: the prefreezing temperature after the polyethylene glycol is added in the step (3) is-13 to-23 ℃, and the freezing time is 8 to 12 hours.

9. The preparation method of the composite phase change energy storage material based on straw waste as claimed in claim 1, wherein the preparation method comprises the following steps: the calcium ion solution in the step (3) is 0.1mol/L calcium chloride solution, and the soaking time is 10-12 hours.

10. The preparation method of the composite phase change energy storage material based on straw waste as claimed in claim 1, wherein the preparation method comprises the following steps: the temperature of the second pre-freezing in the step (3) is-13 to-23 ℃, the time is 10 to 12 hours, the freeze-drying is in a vacuum environment, the time is 12 to 24 hours, and the temperature is-30 to-60 ℃.

Background

Exhaustion of traditional fossil energy (such as coal, petroleum and natural gas) and emission of harmful gases such as carbon dioxide and sulfur dioxide caused by energy consumption due to rapid development of modern industry have become key problems of energy conservation and environmental protection. For decades, renewable and clean energy sources (such as solar, wind, and biomass) have been used to slow the global energy crisis, however, utilization of energy is hindered due to its intermittent and unstable nature. Thermal energy storage technologies, including sensible thermal energy storage, latent thermal energy storage, and chemical thermal energy storage, are advantageous methods to reduce energy supply and demand, mismatch in time, space intensity, and location. Particularly, Phase Change Materials (PCMs) used as latent heat storage media have the advantages of strong heat storage capacity, strong phase change capacity, stable chemical structure, various materials and operation modes and the like, and have great potential in the aspects of solar energy storage, waste heat recovery, building temperature regulation, energy conservation and the like.

The energy consumption of buildings in China accounts for 30-40% of the total energy consumption of the whole society, wherein the proportion of the energy consumption for adjusting the temperature of the buildings is the largest. Therefore, it is a worldwide problem to be solved at present to improve the utilization efficiency of energy and reduce the energy consumption of buildings. For a long time, the straw is used to produce various building materials because the hollow structure in the straw has low density and good heat insulation performance. In addition, the surface of the straw is covered by a wax layer, so that the straw has hydrophobicity. Thus, the presence of different components in the straw can greatly improve the performance of the building material. China is a big agricultural country, and the annual yield of straws is about 7.5 hundred million tons. Therefore, the straw used for building materials has the advantages of low cost and environmental friendliness.

At present, the leakage problem of solid-liquid PCMs in the phase transition process limits their application, so many methods are emerging to prepare shape-stable composite phase transition materials, which are commonly microcapsules, porous carriers (such as metal foams, expanded graphite, carbon nanotubes, graphene oxide, reduced graphene oxide and graphene aerogel, carbon aerogel and silica), polymers (such as polyurethane, polyethylene and urea-formaldehyde), and the like, but have the problems of high cost, low thermal conductivity, poor chemical stability, complicated steps, and the like, and therefore, it is still a great challenge to explore low-cost support materials by using cheap raw materials.

Disclosure of Invention

The purpose of the invention is: provides a preparation method of a composite phase change energy storage material based on straw waste. The composite phase change energy storage material prepared by the method has the advantages of stable shape, strong coating capability, good thermal performance and good cycle stability.

The preparation method of the composite phase change energy storage material based on the straw waste comprises the following steps:

(1) pretreatment of straw

Washing and drying the crushed straws, cooling, performing ball milling, mixing and stirring with a treatment solution, and finally washing and drying to obtain a straw pretreatment product for later use;

(2) preparation of straw-loaded polypyrrole mixture

Firstly, dissolving pyrrole in a hydrochloric acid solution at room temperature and stirring, then adding the straw pretreatment product obtained in the step (1) into the solution, continuously stirring for a period of time, then adding an ammonium persulfate solution for stirring, and finally filtering the mixture obtained after stirring by using a filter membrane, washing by using ultrapure water and drying to prepare a straw-loaded polypyrrole mixture;

(3) preparation of straw-loaded polypyrrole-coated polyethylene glycol composite phase change energy storage material

Dissolving the mixture of the straw-loaded polypyrrole and sodium alginate in ultrapure water, heating and stirring, and then adding polyethylene glycol and continuously stirring until the mixture is completely dissolved; cooling to room temperature, pre-freezing at certain temperature for a period of time, and taking out; and then soaking the composite phase-change energy storage material in a calcium ion solution for a period of time, taking out, pre-freezing again, and freeze-drying to prepare the composite phase-change energy storage material based on the straw waste.

Wherein:

the straws in the step (1) are corn straws.

The particle size of the crushed straw in the step (1) is 80-100 meshes, firstly, the crushed straw is washed by hot water at 80-100 ℃ for 5-15min, repeated for 3-5 times, then dried at 55-65 ℃ for 24-48 hours, cooled and then ball-milled by using a planetary ball mill for 3 times.

The rotation speed during ball milling in the step (1) is 500-.

The temperature for mixing and stirring the mixture and the treatment liquid in the step (1) is 55-65 ℃ and the time is 8-12 hours.

The solid-liquid ratio of the straws to the treatment liquid in the step (1) is 1:10-20, and the unit is g/ml.

The treatment liquid in the step (1) is a mixed liquid of dimethyl sulfoxide, potassium hydroxide and ultrapure water.

Wherein: the volume ratio of the dimethyl sulfoxide to the ultrapure water is 25: 1; the potassium hydroxide content was 5 mg/ml.

And (2) washing and drying in the step (1), wherein the drying temperature is 55-65 ℃, and the drying time is 12-24 hours.

The purpose of ball milling in the step (1) is physical defibering, large fibers in the straws can be reduced and uniformly mixed with the treatment solution, the treatment solution of the mixed solution of dimethyl sulfoxide (DMSO), potassium hydroxide (KOH) and ultrapure water can dissolve part of lignin, the porosity is improved, the cell wall thickness is reduced, and gaps among cellulose fibers are enlarged.

The mass ratio of the straw pretreatment product to the pyrrole in the step (2) is 1:0.05-1, and the molar ratio of ammonium persulfate to the pyrrole is 1: 1.

The volume of the hydrochloric acid in the step (2) is 10-50ml, and the mass concentration of the substance is 0.1-1 mol/L.

And (3) dissolving the ammonium persulfate in hydrochloric acid at room temperature, stirring for 0.5h, pre-dissolving the ammonium persulfate by using the hydrochloric acid as a solvent, and controlling the mass concentration of the hydrochloric acid to be 1 mol/L.

Dissolving the pyrrole in the step (2) in hydrochloric acid at room temperature, and stirring for 0.5 h; and then adding the straw pretreatment product into the solution, and continuously stirring and mixing for 1-3 h.

Adding ammonium persulfate into the mixture obtained in the step (2), continuously stirring the mixture for 8 to 12 hours at room temperature, then carrying out vacuum filtration through a filter membrane of 0.2 micron, washing the mixture through ultrapure water, and finally drying the mixture, wherein the drying temperature is 55 to 65 ℃, and the drying time is 12 to 24 hours.

And (3) coating the straw pretreatment product with polypyrrole by adopting an in-situ deposition method in the step (2).

The concentration of the sodium alginate in the step (3) is 10-20 mg/ml.

The heating and stirring temperature in the step (3) is 55-65 ℃, and the stirring time is 30-90 minutes.

The mass of the polyethylene glycol in the step (3) accounts for 60-90% of the sum of the mass of the straw-loaded polypyrrole mixture, the mass of the sodium alginate and the mass of the polyethylene glycol.

The prefreezing temperature after the polyethylene glycol is added in the step (3) is-13 to-23 ℃, and the freezing time is 8 to 12 hours.

The calcium ion solution in the step (3) is 0.1mol/L calcium chloride solution, and the soaking time is 10-12 hours.

The temperature of the second pre-freezing in the step (3) is-13 to-23 ℃, the time is 10 to 12 hours, the freeze-drying is in a vacuum environment, the time is 12 to 24 hours, and the temperature is-30 to-60 ℃.

In step (3), the sodium alginate can react with Ca²⁺Complexing to form a hydrogel, the main reaction mechanism being the G unit with Ca²⁺Complexing and crosslinking to form an egg box structure, wherein a G group is stacked to form a crosslinking network structure, and is converted into hydrogel fiber to be separated out; polyethylene glycol is coated in the coating through hydrogen bonding.

As a preferred technical scheme, the preparation method of the composite phase change energy storage material based on straw waste comprises the following steps:

(1) pretreatment of straw

Firstly, washing the crushed corn straws with hot water for 5-15 minutes, repeating the washing for 3-5 times, and then placing the corn straws in a drying oven at 55-65 ℃ for drying for 48 hours; after cooling, ball milling is carried out by using a planetary ball mill; and then weighing a certain amount of corn straws, mixing and stirring the corn straws with the treatment liquid, washing and drying the corn straws after the mixing and stirring are finished, and reserving the corn straws for later use.

(2) Preparation of corn stalk-loaded polypyrrole mixture

Weighing a certain mass of corn straw pretreatment product and pyrrole according to different mass ratios; first, pyrrole was dissolved in hydrochloric acid at room temperature and stirred for a certain time. Then, all samples are mixed and stirred for a certain time at room temperature, and then ammonium persulfate dissolved in hydrochloric acid is added; subsequently, the mixture was stirred overnight; and finally, filtering, washing and drying to obtain the corn straw loaded polypyrrole mixture.

(3) Preparation of corn straw-loaded polypyrrole-coated polyethylene glycol composite phase change energy storage material

Dissolving the mixture and sodium alginate in ultrapure water, heating and stirring. Thereafter, polyethylene glycol was added and stirring was continued. After cooling, the product was placed in a freezer for a period of time. Taking out, and soaking the solution. And finally, taking out the composite phase change energy storage material, pre-freezing and freeze-drying to obtain the corn straw loaded polypyrrole coated polyethylene glycol composite phase change energy storage material.

Compared with the prior art, the invention has the following beneficial effects:

(1) the preparation method of the composite phase change energy storage material based on the straw waste, disclosed by the invention, comprises the steps of pretreating corn straws, loading polypyrrole to ensure that the corn straws have heat conductivity, and utilizing sodium alginate and Ca by a melt blending method²⁺And (3) preparing the composite phase change energy storage material with stable shape by crosslinking. Experimental results show that the composite phase change energy storage material can coat 60-90% of polyethylene glycol, has good thermal performance and cycle stability, has fusion latent heat of 40.81-145.8J/g, and can realize functional utilization of waste straws.

(2) The preparation method of the composite phase change energy storage material based on straw waste adopts a mode of simple method, environmental protection, regeneration and low cost, takes agricultural waste corn straw as a raw material, improves the heat conductivity coefficient of polypyrrole, and utilizes sodium alginate and Ca²⁺The crosslinking effect of the composite phase change energy storage material is realized by encapsulating polyethylene glycol by a melt blending method, so that the composite phase change energy storage material can be well used as a building energy-saving material.

(3) According to the preparation method of the composite phase change energy storage material based on the straw waste, the corn straw is used as the supporting raw material, so that the resource utilization of the agricultural waste is realized, the waste is changed into the valuable, and the environmental pollution caused by the random discarding of the agricultural waste is effectively reduced; the energy storage material prepared by loading polypyrrole and mixing polyethylene glycol, sodium alginate and the like has stable shape, no leakage and strong coating capability.

Drawings

FIG. 1 is a scanning electron microscope image of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase change energy storage material prepared in example 1;

FIG. 2 is a scanning electron microscope image of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase change energy storage material prepared in example 2;

FIG. 3 is a scanning electron microscope image of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase change energy storage material prepared in example 3;

FIG. 4 is a DSC of the corn stalk loaded polypyrrole coated polyethylene glycol composite phase change energy storage material prepared in example 1;

FIG. 5 is a DSC of the corn stalk loaded polypyrrole coated polyethylene glycol composite phase change energy storage material prepared in example 2;

FIG. 6 is a DSC of the corn stalk loaded polypyrrole coated polyethylene glycol composite phase change energy storage material prepared in example 3;

FIG. 7 is a graph showing the leakage rate of a composite phase change energy storage material coated with polypyrrole and coated with corn stalk;

FIG. 8 is a macroscopic morphology view of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase-change energy storage material prepared in example 1;

fig. 9 is a macro morphology diagram of the sodium alginate-coated polyethylene glycol phase change material prepared in comparative example 2.

Detailed Description

The present invention is further described below with reference to examples.

Example 1

The preparation method of the composite phase change energy storage material based on straw waste in the embodiment 1 comprises the following steps:

(1) washing pulverized corn stalk (particle size of 80-100 mesh) with 90 deg.C hot water under mechanical stirring for 10 min, repeating for 3 times, and drying in 60 deg.C drying oven for 48 hr. After taking out and cooling, the mixture was ball-milled for 10 minutes at 500 rpm using a ball mill and repeated 3 times. Thereafter, 25g of corn stover, 240.38ml of dimethyl sulfoxide, 9.62ml of ultrapure water and 1.25g of potassium hydroxide were weighed, placed in a three-necked flask, and stirred at 60 ℃ for 12 hours. After completion, filtration, washing and drying at 60 ℃ for 12 hours.

(2) Weighing 1g of treated corn straw and 0.77ml of pyrrole. First, pyrrole was dissolved in 20ml of 1mol/L hydrochloric acid at room temperature and stirred for 30 minutes. Thereafter, all samples were placed in a three-necked flask and stirred at room temperature for 120 minutes. Then, 2.55g of ammonium persulfate (dissolved in 20ml of hydrochloric acid having a concentration of 1mol/L, and stirred at room temperature for 30 minutes) was added. Subsequently, stirring was continued at 30 ℃ for 12 hours. And after stirring, filtering the mixture by using a filter membrane of 0.2 mu m, washing by using ultrapure water, and drying in a drying oven at 60 ℃ for 24 hours to obtain the corn straw loaded polypyrrole mixture.

(3) 0.5g of the above mixture, 0.3g of sodium alginate were weighed out, dissolved in 20ml of ultrapure water in a three-necked flask and heated at 60 ℃ for 30 minutes. Thereafter, 7.2g of polyethylene glycol was added and stirring was continued for 1 hour until complete dissolution. After cooling to room temperature, it was pre-frozen in a freezer at-18 ℃ for 10 hours. After being taken out, the materials are soaked in 0.1mol/L calcium chloride solution for 12 hours. After the pre-freezing is finished, pre-freezing is carried out for 12 hours at the temperature of 18 ℃ below zero, and then freeze-drying is carried out for 22 hours at the temperature of 40 ℃ below zero to obtain the corn straw loaded polypyrrole coated polyethylene glycol composite phase change energy storage material.

Example 2

The preparation method of the composite phase change energy storage material based on straw waste in the embodiment 2 comprises the following steps:

(1) washing the crushed corn stalks (with the granularity of 80-100 meshes) with hot water of 80 ℃ for 10 minutes under mechanical stirring, and repeating for 3 times. Then, the mixture was dried in a drying oven at 65 ℃ for 24 hours. After taking out and cooling, the mixture was ball-milled for 5 minutes at 1000 rpm using a ball mill and repeated 3 times. Thereafter, 20g of corn stover, 288.46ml of dimethyl sulfoxide, 11.54ml of ultrapure water and 1.5g of potassium hydroxide were weighed out, placed in a three-necked flask, and stirred at 65 ℃ for 12 hours. After completion, filtration, washing and drying at 65 ℃ for 12 hours.

(2) Weighing 1g of treated corn straw and 0.1ml of pyrrole. First, pyrrole was dissolved in 20ml of 0.5mol/L hydrochloric acid at room temperature and stirred for 40 minutes. Thereafter, all samples were placed in a three-necked flask and stirred at room temperature for 150 minutes. Then, 0.34g of ammonium persulfate (dissolved in 20ml of hydrochloric acid having a concentration of 1mol/L, and stirred at room temperature for 30 minutes) was added. Subsequently, stirring was continued at 30 ℃ for 12 hours. After stirring, filtering the mixture by using a filter membrane with the diameter of 0.2 mu m, washing the mixture by using ultrapure water, and drying the mixture in a drying oven at the temperature of 65 ℃ for 20 hours to obtain the corn straw-loaded polypyrrole mixture.

(3) 1g of the above mixture, 0.2g of sodium alginate, were weighed out, dissolved in 20ml of ultrapure water in a three-necked flask and heated at 60 ℃ for 30 minutes. Thereafter, 4.8g of polyethylene glycol was added and stirring was continued for 1 hour until complete dissolution. After cooling to room temperature, it was pre-frozen in a freezer at-18 ℃ for 10 hours. After taking out, the sample was immersed in a 0.1mol/L calcium chloride solution for 12 hours. After the pre-freezing is finished, pre-freezing is carried out for 11 hours at the temperature of minus 20 ℃, and then freeze-drying is carried out for 18 hours at the temperature of minus 50 ℃ to obtain the corn straw loaded polypyrrole coated polyethylene glycol composite phase change energy storage material.

Example 3

The preparation method of the composite phase change energy storage material based on straw waste in the embodiment 3 comprises the following steps:

(1) washing the crushed corn stalks (with the granularity of 80-100 meshes) with hot water at 85 ℃ for 10 minutes under mechanical stirring, and repeating for 3 times. Then, the mixture was dried in a 55 ℃ dry box for 48 hours. After taking out and cooling, the mixture was ball-milled for 8 minutes at 750 rpm using a ball mill and repeated 3 times. Thereafter, 10g of corn stover, 192.31ml of dimethyl sulfoxide, and 7.69ml of ultrapure water and 1g of potassium hydroxide were weighed out and placed in a three-necked flask, and stirred at 55 ℃ for 16 hours. After completion, filtration, washing and drying at 55 ℃ for 15 hours.

(2) Weighing 1g of treated corn straw and 1.03ml of pyrrole. First, pyrrole was dissolved in 20ml of 1mol/L hydrochloric acid at room temperature and stirred for 30 minutes. Thereafter, all samples were placed in a three-necked flask and stirred at room temperature for 180 minutes. Then, 3.4g of ammonium persulfate (dissolved in 20ml of hydrochloric acid having a concentration of 1mol/L, and stirred at room temperature for 30 minutes) was added. Subsequently, stirring was continued at 30 ℃ for 12 hours. And after stirring, filtering the mixture by using a filter membrane of 0.2 mu m, washing by using ultrapure water, and drying in a drying oven at the temperature of 55 ℃ for 24 hours to obtain the corn straw-loaded polypyrrole mixture.

(3) 1.5g of the above mixture, 0.4g of sodium alginate were weighed out, dissolved in 20ml of ultrapure water in a three-necked flask and heated at 60 ℃ for 30 minutes. Thereafter, 2.85g of polyethylene glycol was added and stirring was continued for 1 hour until complete dissolution. After cooling to room temperature, it was pre-frozen in a freezer at-18 ℃ for 10 hours. After taking out, the sample was immersed in a 0.1mol/L calcium chloride solution for 12 hours. After the pre-freezing is finished, pre-freezing is carried out for 10 hours at the temperature of minus 18 ℃, and then freeze-drying is carried out for 12 hours at the temperature of minus 60 ℃ to obtain the composite phase change energy storage material based on the straw waste.

Comparative example 1

0.3g of sodium alginate are weighed out, dissolved in 20ml of ultrapure water in a three-necked flask and heated at 60 ℃ for 30 minutes. Thereafter, 2.7g of polyethylene glycol was added and stirring was continued for 1 hour until complete dissolution. After cooling to room temperature, it was pre-frozen in a freezer at-18 ℃ for 10 hours. After being taken out, the materials are soaked in 0.1mol/L calcium chloride solution for 12 hours. After the completion, pre-freezing for 12 hours at-18 ℃, and then freeze-drying for 24 hours at-40 ℃ to obtain the sodium alginate polyethylene glycol composite phase change energy storage material.

The composite phase change energy storage materials prepared in examples 1 to 3 and comparative example 1 were subjected to performance tests, and the results are shown in table 1 below.

Table 1 composite phase change energy storage material test results

Serial number	Melting temperature (. degree.C.)	Latent heat of fusion (J/g)	Crystallization temperature (. degree.C.)	Latent heat of crystallization (J/g)
					Example 1	52.67	145.8	37.22	141.5
Example 2	53.16	106.1	35.98	105.6
					Example 3	52.08	40.81	29.13	35.55
Comparative example 1	48.46	31.47	36.06	13

Compared with the comparative example 1, the corn straw is used as a supporting material in the examples 1-3, so that the coating capacity is higher, and the latent heat of fusion of the comparative example 1 is obviously lower than that of the examples 1-3 when the polyethylene glycol with the same mass is added.

Fig. 1 to 3 are scanning electron microscope images of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase change energy storage material prepared in examples 1 to 3, respectively, and it can be seen that the surface coated with 90% of polyethylene glycol is smooth and flat, the surface coated with 80% of polyethylene glycol is in a gully shape, and the surface coated with 60% of polyethylene glycol is in an uneven state.

Fig. 4-6 are DSC diagrams of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase change energy storage material prepared in examples 1-3, respectively, and it can be seen that the peak area is significantly reduced and the peak value is significantly decreased with the decrease of the polyethylene glycol content, which corresponds to the contents in table 1.

FIG. 7 shows the leakage rate of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase change energy storage material, which is not more than 8% at most.

Fig. 8 is a macroscopic view of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase change energy storage material prepared in example 1, which is clear from the figure and has a complete shape.

Fig. 9 is a macroscopic morphology diagram of the sodium alginate-coated polyethylene glycol phase-change material prepared in comparative example 1, which is incomplete in shape and fragile.