WO2022262305A1

WO2022262305A1 - Method for preparing a composite phase-change energy storage material based on waste straw

Info

Publication number: WO2022262305A1
Application number: PCT/CN2022/077947
Authority: WO
Inventors: 蔡红珍; 韩祥生; 姜戌雅; 高锋; 原研浩; 张文彬
Original assignee: 山东理工大学
Priority date: 2021-06-15
Filing date: 2022-02-25
Publication date: 2022-12-22
Also published as: CN113403038B; CN113403038A

Abstract

The present invention relates to the technical field of preparation of composite phase-change energy storage materials, and in particular to a method for preparing a composite phase-change energy storage material based on waste straw. In the method for preparing a composite phase-change energy storage material based on waste straw of the present invention, pretreatment is carried out on corn stalks, thermal conductivity is realized by loading polypyrrole, and a shape-stable composite phase-change energy storage material is prepared using a melt blending method and by the cross-linking of sodium alginate and Ca²⁺. Experimental results show that the composite phase-change energy storage material can be coated with 60-90% polyethylene glycol and has good thermal performance and cycle stability. The latent heat of melt blending is 40.81-145.8 J/g. The method can achieve functional utilization of waste straw.

Description

Preparation method of composite phase change energy storage material based on straw waste

technical field

The invention belongs to the technical field of preparation of composite phase-change energy storage materials, and in particular relates to a method for preparing composite phase-change energy storage materials based on straw waste.

Background technique

The depletion of traditional fossil energy (such as coal, oil and natural gas) and the emission of harmful gases such as carbon dioxide and sulfur dioxide caused by energy consumption caused by the rapid development of modern industry have become key issues in energy conservation and environmental protection. For decades, renewable and clean energy sources (such as solar energy, wind energy, and biomass energy) have been used to delay the global energy crisis, however, their intermittency and instability hinder the utilization of energy. Thermal energy storage technologies, including sensible thermal energy storage, latent thermal energy storage, and chemical thermal energy storage, are advantageous methods for reducing mismatches in energy supply and demand, in terms of time, spatial intensity, and location. Especially as latent heat storage medium, phase change materials (PCMs) have the advantages of strong heat storage capacity, strong phase change ability, stable chemical structure, diverse materials and operation modes, etc. shows great potential.

my country's building energy consumption accounts for about 30-40% of the total energy consumption of the entire society, of which the part used to adjust the temperature of buildings consumes the largest proportion. Therefore, improving energy utilization efficiency and reducing building energy consumption is a worldwide problem to be solved urgently. For a long time, people have been using straw to produce various building materials because of the low density and good thermal insulation properties of the hollow structure inside the straw. In addition, the surface of the straw is covered with a waxy layer, making it hydrophobic. Therefore, the different components present in straw can improve the performance of construction materials to a great extent. my country is a big agricultural country with an annual output of about 750 million tons of straw. Therefore, the use of straw as building materials has the advantages of low cost and environmental friendliness.

At present, the leakage problem of solid-liquid PCMs in the phase change process limits their application, so there are many methods to prepare shape-stable composite phase change materials, common ones are microcapsules, porous carriers (such as metal foam, expanded graphite , carbon nanotubes, graphene oxide, reduced graphene oxide and graphene aerogels, carbon aerogels and silica), polymers (such as polyurethane, polyethylene and urea formaldehyde), etc., but there are high costs and low thermal conductivity , poor chemical stability, cumbersome steps, etc. Therefore, it is still a great challenge to explore low-cost support materials using cheap raw materials.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a composite phase change energy storage material based on straw waste. The composite phase change energy storage material prepared by the method has stable shape, strong coating ability, good thermal performance and cycle stability.

The preparation method of the straw waste-based composite phase change energy storage material according to the present invention consists of the following steps:

(1) Straw pretreatment

The crushed stalks are washed with water, dried, ball-milled after cooling, then mixed with the treatment solution, and finally washed and dried to obtain the stalk pretreatment product, which is set aside;

(2) Preparation of straw-loaded polypyrrole mixture

First, dissolve pyrrole in hydrochloric acid solution at room temperature and stir, then add the straw pretreatment product obtained in step (1) to the above solution and continue stirring for a period of time, then add ammonium persulfate solution for stirring, and finally complete the stirring to obtain The mixture is filtered through a filter membrane, washed with ultrapure water, and dried to prepare a straw-loaded polypyrrole mixture;

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

Dissolve the straw-loaded polypyrrole mixture and sodium alginate in ultrapure water for heating and stirring, then add polyethylene glycol and continue stirring until completely dissolved; cool to room temperature, pre-freeze it at a certain temperature for a period of time, and then take it out ; Then soak it in the calcium ion solution for a period of time, take it out, pre-freeze it again, and freeze-dry it to prepare a composite phase-change energy storage material based on straw waste.

in:

The stalk described in step (1) is corn stalk.

The crushed stalks described in step (1) have a particle size of 80-100 mesh, first wash with hot water at 80-100°C for 5-15min, repeat 3-5 times, and then dry at a temperature of 55-65°C After 24-48 hours, after cooling, use a planetary ball mill for ball milling, and the number of ball milling times is 3 times.

The rotating speed during the ball milling described in step (1) is 500-1000r/min, and the time is 5-15min.

The temperature of mixing and stirring with the treatment liquid in step (1) is 55-65° C., and the time is 8-12 hours.

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

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

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

The washing described in the step (1) is followed by drying, the drying temperature is 55-65° C., and the drying time is 12-24 hours.

The purpose of ball milling in step (1) is to physically defibrate, which can make the large fibers in the straw smaller, and mix them evenly with the treatment solution. The mixed solution treatment solution of dimethyl sulfoxide DMSO, potassium hydroxide KOH and ultrapure water can dissolve Part of lignin increases porosity, reduces cell wall thickness, and enlarges the gaps between cellulose fibers.

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

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

Ammonium persulfate described in step (2) is that ammonium persulfate is dissolved in hydrochloric acid at room temperature, and stir 0.5h, and hydrochloric acid is carried out pre-dissolving to ammonium persulfate as solvent, and the amount concentration of the substance of controlling hydrochloric acid is 1mol/L .

The pyrrole described in step (2) was dissolved in hydrochloric acid at room temperature, and stirred for 0.5 h; then the straw pretreatment product was added to the above solution and continued to stir and mix for 1-3 h.

Add ammonium persulfate described in step (2) and continue to stir at room temperature for 8-12 hours, then vacuum filter through a 0.2 micron membrane, wash with ultrapure water, and finally dry. The drying temperature is 55-65 ℃, the drying time is 12-24h.

In step (2), an in-situ deposition method is adopted to realize coating of the straw pretreatment product with polypyrrole.

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

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

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

The pre-freezing temperature after adding polyethylene glycol described in step (3) is -13～-23 ℃, and the freezing time is 8-12 hours.

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

The temperature of pre-freezing again described in step (3) is -13～-23 ℃, time is 10-12h, described lyophilization is vacuum environment, time is 12-24 hours, temperature is -30～-60 ℃.

In step (3), sodium alginate can complex with Ca ²⁺ to form a hydrogel. The main reaction mechanism is that G units and Ca ²⁺ are complexed and cross-linked to form an egg-box structure, and G groups accumulate to form a cross-linked network structure , into hydrogel fibers and precipitated; polyethylene glycol was coated in it by hydrogen bonding.

As a preferred technical solution, the preparation method of the straw waste-based composite phase change energy storage material according to the present invention consists of the following steps:

(1) Straw pretreatment

First, wash the crushed corn stalks with hot water for 5-15 minutes, repeat 3-5 times, and then place them in a drying oven at 55-65°C for 48 hours; after cooling, use a planetary ball mill for ball milling; then , weighing a certain amount of corn stalks, mixing and stirring with the treatment solution, after completion, washing, drying, and saving for later use.

(2) Preparation of corn stalk loaded polypyrrole mixture

A certain mass of corn stalk pretreatment products and pyrrole are weighed according to different mass ratios; first, pyrrole is dissolved in hydrochloric acid at room temperature and stirred for a certain period of time. Afterwards, all the samples were mixed and stirred at room temperature for a certain period of time, and then ammonium persulfate dissolved in hydrochloric acid was added; then, the mixture was stirred overnight; finally, filtered, washed with water, and dried to obtain the corn stalk-loaded polypyrrole mixture.

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

Take the above mixture and sodium alginate, dissolve it in ultrapure water, heat and stir. Afterwards, polyethylene glycol was added and stirring continued. After cooling, place it in the refrigerator for a while. After removing, soak the solution. Finally, it is taken out, pre-frozen and then freeze-dried to obtain the corn straw-loaded polypyrrole-coated polyethylene glycol composite phase-change energy storage material.

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

(1) The preparation method of the composite phase change energy storage material based on straw waste according to the present invention, by pretreating corn straw, loading polypyrrole to make it have thermal conductivity, and using sodium alginate by melt blending method A shape-stable composite phase-change energy storage material was prepared by cross-linking with Ca ²⁺ . The experimental results show that the composite phase change energy storage material can be coated with 60-90% polyethylene glycol, has good thermal performance and cycle stability, and the latent heat of fusion is 40.81-145.8J/g, which can realize the function of waste straw utilization.

(2) The preparation method of the straw waste-based composite phase change energy storage material of the present invention adopts a simple, environmentally friendly, renewable, and low-cost method, using agricultural waste corn stalks as raw materials, and polypyrrole improves its Thermal conductivity, using the cross-linking effect of sodium alginate and Ca ²⁺ , and encapsulating polyethylene glycol by melt blending method, a composite phase change energy storage material was prepared, which can be well used in building energy-saving materials.

(3) The preparation method of the straw waste-based composite phase-change energy storage material of the present invention uses corn stalks as the supporting raw material, realizes the resource utilization of agricultural waste, turns waste into wealth, and effectively reduces agricultural waste. Environmental pollution caused by random discarding of waste; the energy storage material prepared by loading polypyrrole, mixing polyethylene glycol and sodium alginate, etc. has stable shape, no leakage, and strong coating ability.

Description of drawings

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;

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;

3 is a scanning electron micrograph of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase-change energy storage material prepared in Example 3;

Fig. 4 is the DSC diagram of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase change energy storage material prepared in Example 1;

Fig. 5 is the DSC diagram of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase change energy storage material prepared in Example 2;

Fig. 6 is the DSC diagram of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase change energy storage material prepared in Example 3;

Figure 7 is a graph of the leakage rate of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase-change energy storage material;

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

9 is a macroscopic morphology diagram of the sodium alginate-coated polyethylene glycol phase change material prepared in Comparative Example 2.

detailed description

The present invention will be further described below in conjunction with embodiment.

Example 1

The preparation method of the straw waste-based composite phase change energy storage material described in Example 1 consists of the following steps:

(1) The crushed corn stalks (with a particle size of 80-100 mesh) were washed with hot water at 90° C. for 10 minutes under mechanical stirring, repeated three times, and then dried in a drying oven at 60° C. for 48 hours. After taking it out to cool, use a ball mill to mill for 10 minutes at a speed of 500 rpm, repeat 3 times. Afterwards, 25g of corn stalks, 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°C for 12 hours. After completion, filter, wash, and dry at 60°C for 12 hours.

(2) Weigh 1 g of treated corn stalks and 0.77 ml of pyrrole. First, pyrrole was dissolved in 20 ml of hydrochloric acid at a concentration of 1 mol/L at room temperature, and stirred for 30 minutes. After that, all the samples were put into a three-necked flask and stirred at room temperature for 120 minutes. Then, 2.55 g of ammonium persulfate (dissolved in 20 ml of hydrochloric acid with a concentration of 1 mol/L and stirred at room temperature for 30 minutes) was added. Subsequently, stirring was continued for 12 hours at 30°C. After the stirring was completed, the mixture was filtered with a 0.2 μm filter membrane, washed with ultrapure water, and then dried in a drying oven at 60° C. for 24 hours to obtain the polypyrrole mixture loaded with corn stalks.

(3) Weigh 0.5 g of the above mixture and 0.3 g of sodium alginate, dissolve them in 20 ml of ultrapure water in a three-necked flask and heat at 60° C. for 30 minutes. Afterwards, 7.2 g 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 -18°C refrigerator for 10 hours. After taking it out, soak it in 0.1mol/L calcium chloride solution for 12 hours. After completion, it was pre-frozen at -18°C for 12 hours, and then freeze-dried at -40°C for 22 hours to obtain a corn straw-loaded polypyrrole-coated polyethylene glycol composite phase-change energy storage material.

Example 2

The preparation method of the straw waste-based composite phase change energy storage material described in Example 2 consists of the following steps:

(1) Wash the crushed corn stalks (with a particle size of 80-100 mesh) with hot water at 80° C. for 10 minutes under mechanical stirring, and repeat 3 times. Then, it was placed in a drying oven at 65° C. for 24 hours to dry. After taking out and cooling, use a ball mill to mill for 5 minutes at a speed of 1000 rpm, repeat 3 times. Afterwards, 20 g of corn stalks, 288.46 ml of dimethyl sulfoxide, 11.54 ml of ultrapure water and 1.5 g of potassium hydroxide were weighed, placed in a three-necked flask, and stirred at 65° C. for 12 hours. After completion, filter, wash, and dry at 65°C for 12 hours.

(2) Weigh 1 g of treated corn stalks and 0.1 ml of pyrrole. First, pyrrole was dissolved in 20 ml of hydrochloric acid with a concentration of 0.5 mol/L at room temperature, and stirred for 40 minutes. After that, all the samples were put into a three-necked flask and stirred at room temperature for 150 minutes. Then, 0.34 g of ammonium persulfate (dissolved in 20 ml of hydrochloric acid with a concentration of 1 mol/L and stirred at room temperature for 30 minutes) was added. Subsequently, stirring was continued for 12 hours at 30°C. After the stirring was completed, the mixture was filtered with a 0.2 μm filter membrane, washed with ultrapure water, and then dried in a drying oven at 65° C. for 20 hours to obtain the polypyrrole mixture loaded with corn stalks.

(3) Weigh 1 g of the above mixture and 0.2 g of sodium alginate, dissolve them in 20 ml of ultrapure water in a three-necked flask, and heat at 60° C. for 30 minutes. Afterwards, 4.8 g of polyethylene glycol was added and stirring was continued for 1 hour until completely dissolved. After cooling to room temperature, it was pre-frozen in a -18°C refrigerator for 10 hours. After taking it out, soak it in 0.1mol/L calcium chloride solution for 12 hours. After completion, it was pre-frozen at -20°C for 11 hours, and then freeze-dried at -50°C for 18 hours to obtain a corn straw-loaded polypyrrole-coated polyethylene glycol composite phase-change energy storage material.

Example 3

The preparation method of the straw waste-based composite phase change energy storage material described in Example 3 consists of the following steps:

(1) Wash the crushed corn stalks (with a particle size of 80-100 mesh) with hot water at 85° C. for 10 minutes under mechanical stirring, and repeat 3 times. Then, it was dried in a drying oven at 55° C. for 48 hours. After taking it out and cooling it, use a ball mill to mill it for 8 minutes at a speed of 750 rpm, and repeat 3 times. Afterwards, 10 g of corn stalks, 192.31 ml of dimethyl sulfoxide, 7.69 ml of ultrapure water and 1 g of potassium hydroxide were weighed, placed in a three-necked flask, and stirred at 55° C. for 16 hours. After completion, filter, wash, and dry at 55°C for 15 hours.

(2) Weigh 1 g of treated corn stalks and 1.03 ml of pyrrole. First, pyrrole was dissolved in 20 ml of hydrochloric acid at a concentration of 1 mol/L at room temperature, and stirred for 30 minutes. After that, all the samples were put into a three-necked flask and stirred at room temperature for 180 minutes. Then, 3.4 g of ammonium persulfate (dissolved in 20 ml of hydrochloric acid with a concentration of 1 mol/L and stirred at room temperature for 30 minutes) was added. Subsequently, stirring was continued for 12 hours at 30°C. After the stirring was completed, the mixture was filtered with a 0.2 μm filter membrane, washed with ultrapure water, and then dried in a drying oven at 55° C. for 24 hours to obtain the polypyrrole mixture loaded with corn stalks.

(3) Weigh 1.5 g of the above mixture and 0.4 g of sodium alginate, dissolve them in 20 ml of ultrapure water in a three-necked flask, and heat at 60° C. for 30 minutes. Afterwards, 2.85 g of polyethylene glycol was added and stirring was continued for 1 hour until completely dissolved. After cooling to room temperature, it was pre-frozen in a -18°C refrigerator for 10 hours. After taking it out, soak it in 0.1mol/L calcium chloride solution for 12 hours. After completion, it was pre-frozen at -18°C for 10 hours, and then freeze-dried at -60°C for 12 hours to obtain a composite phase-change energy storage material based on straw waste.

Comparative example 1

0.3 g of sodium alginate was weighed, dissolved in 20 ml of ultrapure water in a three-necked flask, and heated at 60° C. for 30 minutes. Afterwards, 2.7 g of polyethylene glycol was added and stirring was continued for 1 hour until completely dissolved. After cooling to room temperature, it was pre-frozen in a -18°C refrigerator for 10 hours. After taking it out, soak it in 0.1mol/L calcium chloride solution for 12 hours. After completion, pre-freeze at -18°C for 12 hours, and then freeze-dry at -40°C for 24 hours to obtain a sodium alginate-polyethylene glycol composite phase-change energy storage material.

Performance tests were performed on the composite phase change energy storage materials prepared in Examples 1-3 and Comparative Example 1, and the results are shown in Table 1 below.

Table 1 Test results of composite phase change energy storage materials

序号serial number	熔融温度(℃)Melting temperature (℃)	熔融潜热(J/g)Latent heat of fusion (J/g)	结晶温度(℃)Crystallization temperature (°C)	结晶潜热(J/g)Latent heat of crystallization (J/g)
实施例1Example 1	52.6752.67	145.8145.8	37.2237.22	141.5141.5
实施例2Example 2	53.1653.16	106.1106.1	35.9835.98	105.6105.6
实施例3Example 3	52.0852.08	40.8140.81	29.1329.13	35.5535.55
对比例1Comparative example 1	48.4648.46	31.4731.47	36.0636.06	1313

Compared with Comparative Example 1, Example 1-3 uses corn stalks as the supporting material, and has better coating ability. Therefore, the latent heat of fusion of Comparative Example 1 is obviously lower than that of Example 1-3 after adding equal mass of polyethylene glycol.

Figures 1-3 are the scanning electron microscope images of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase-change energy storage materials prepared in Examples 1-3, respectively. It can be seen that the surface coated with 90% polyethylene glycol is relatively Smooth and flat, the surface of 80% polyethylene glycol presents a gully shape, and the surface of 60% polyethylene glycol presents an uneven state.

Figures 4-6 are the DSC charts of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase-change energy storage materials prepared in Examples 1-3, respectively. It can be seen that with the decrease of the polyethylene glycol content, the peak The area is obviously reduced, and the peak value is obviously decreased, corresponding to the contents in Table 1.

Figure 7 shows the leakage rate of corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase-change energy storage materials, the maximum of which does not exceed 8%.

Fig. 8 is the macroscopic shape of the corn stalk-loaded polypyrrole-coated polyethylene glycol composite phase-change energy storage material prepared in Example 1. It can be seen from the figure that the shape is complete.

Fig. 9 is a macroscopic morphological diagram of the sodium alginate-coated polyethylene glycol phase change material prepared in Comparative Example 1, and the shape is incomplete and fragile.

Claims

A method for preparing a composite phase change energy storage material based on straw waste, characterized in that it consists of the following steps:

(1) Straw pretreatment

The crushed straw is washed with water, dried, ball-milled after cooling, then mixed with the treatment solution, and finally washed and dried to obtain the straw pretreatment product, which is set aside;

(2) Preparation of straw-loaded polypyrrole mixture

First, dissolve pyrrole in hydrochloric acid solution at room temperature and stir, then add the straw pretreatment product obtained in step (1) to the above solution and continue stirring for a period of time, then add ammonium persulfate solution for stirring, and finally complete the stirring to obtain The mixture is filtered through a filter membrane, washed with ultrapure water, and dried to prepare a straw-loaded polypyrrole mixture;

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

Dissolve the straw-loaded polypyrrole mixture and sodium alginate in ultrapure water for heating and stirring, then add polyethylene glycol and continue stirring until completely dissolved; cool to room temperature, pre-freeze it at a certain temperature for a period of time, and then take it out ; Then soak it in the calcium ion solution for a period of time, take it out, pre-freeze it again, and freeze-dry it to prepare a composite phase-change energy storage material based on straw waste.
The method for preparing a composite phase-change energy storage material based on straw waste according to claim 1, characterized in that: the particle size of the crushed straw described in step (1) is 80-100 mesh, firstly use 80- Wash in hot water at 100°C for 5-15 minutes, repeat 3-5 times, then dry at a temperature of 55-65°C for 24-48 hours, and use a planetary ball mill for ball milling after cooling;

The rotating speed during the ball milling described in step (1) is 500-1000r/min, and the time is 5-15min;

The temperature of mixing and stirring with the treatment liquid described in step (1) is 55-65° C., and the time is 8-12 hours;

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

The washing described in the step (1) is followed by drying, the drying temperature is 55-65° C., and the drying time is 12-24 hours.
The method for preparing a composite phase change energy storage material based on straw waste according to claim 1, characterized in that: the treatment liquid described in step (1) is dimethyl sulfoxide, potassium hydroxide and ultrapure water The mixed solution; wherein: the volume ratio of dimethyl sulfoxide and ultrapure water is 25:1; the potassium hydroxide content is 5mg/ml.
The method for preparing a composite phase change energy storage material based on straw waste according to claim 1, characterized in that: the mass ratio of the straw pretreatment product to pyrrole described in step (2) is 1:0.05-1, The molar ratio of ammonium persulfate to pyrrole is 1:1.
The method for preparing a composite phase-change energy storage material based on straw waste according to claim 1, characterized in that: the pyrrole described in step (2) is dissolved in hydrochloric acid at room temperature and stirred for 0.5h; after that, the straw Add the pretreated product to the above solution and continue to stir and mix for 1-3h; add ammonium persulfate as described in step (2) and continue to stir for 8-12 hours at room temperature, then vacuum filter through a 0.2 micron filter membrane, and then filter through ultra-pure Washing with water, and finally drying, the drying temperature is 55-65°C, and the drying time is 12-24h.
The method for preparing a composite phase change energy storage material based on straw waste according to claim 1, characterized in that the concentration of sodium alginate in step (3) is 10-20 mg/ml.
The method for preparing a composite phase change energy storage material based on straw waste according to claim 1, characterized in that: the heating and stirring temperature in step (3) is 55-65°C, and the stirring time is 30-90 Minutes; the quality of the polyethylene glycol described in the step (3) accounts for 60-90% of the mass sum of the straw-loaded polypyrrole mixture, sodium alginate and polyethylene glycol.
The method for preparing a composite phase change energy storage material based on straw waste according to claim 1, characterized in that: the prefreezing temperature after adding polyethylene glycol in step (3) is -13 to -23 ℃, the freezing time is 8-12 hours.
The preparation method of the composite phase change energy storage material based on straw waste according to claim 1, characterized in that: the calcium ion solution described in step (3) is a 0.1mol/L calcium chloride solution, and the soaking time is 10-12 hours.
The method for preparing a composite phase-change energy storage material based on straw waste according to claim 1, characterized in that: the re-prefreezing temperature in step (3) is -13～-23°C, and the time is 10 -12h, the freeze-drying is in a vacuum environment, the time is 12-24 hours, and the temperature is -30～-60°C.