Novel hydrogel for photovoltaic cooling and preparation process thereof

Abstract

The invention discloses a novel hydrogel for photovoltaic cooling and a preparation process thereof, polyvinyl alcohol (PVA) and polyacrylamide (PAm) are subjected to hydrogen bond crosslinking to form a dual-network matrix, lithium chloride (LiCl) is embedded as a moisture absorbent, and sodium silicate (Na2SiO3) is dispersed to enhance radiation cooling performance. The hydrogel has a porous structure (the average pore size is 1-31-3 microns), and efficient cooling is achieved through the synergistic effect of night moisture absorption, daytime evaporation (complete dehydration at 90 DEG C for 3 hours) and high emissivity (0.95-0.98). The preparation method comprises the following steps: chemical cross-linking forming of PVA-PAm / Na2SiO3 double-network hydrogel, soaking in a LiCl solution, loading and the like. During application, the hydrogel can be attached to a back plate of a photovoltaic module in the form of a film (the thickness is 0.5-2 mm), experiments show that the temperature of the module can be reduced by 20-25 DEG C, the power generation efficiency can be improved by 20% or above, and the hydrogel has excellent mechanical strength (the tensile stress is 0.254 MPa, and the adhesion strength is greater than 12 kPa) and cycling stability (the performance is attenuated lt after 6 times of use; 20%). The system is low in cost, high in environmental adaptability and suitable for sustainable thermal management of a large-scale photovoltaic power station.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic module cooling technology, and specifically to a photovoltaic cooling material based on a double network hydrogel and a preparation method thereof, and is particularly suitable for a functional material that realizes efficient cooling of photovoltaic modules through synergistic effects of moisture absorption and evaporation and enhanced radiation cooling. Background Art

[0002] During the operation of photovoltaic modules, a large amount of waste heat is generated due to solar radiation, which causes the temperature of the modules to rise, significantly reduces the power generation efficiency and accelerates the aging of materials. The existing cooling technologies have the following problems: active cooling technologies (such as water cooling and air cooling) are expensive and rely on external energy, and are not economical; passive radiation cooling relies on the high emissivity of materials in specific bands, but the cooling power is limited by the emission efficiency of the atmospheric window band (8-13μm); adsorption cooling materials (such as silica gel and zeolite) have low moisture absorption capacity, slow regeneration speed, and poor mechanical properties, making them difficult to use stably for a long time. For example, although traditional hydrogel materials have the ability to absorb moisture, the single network structure easily leads to insufficient mechanical strength and lacks the active regulation function of radiation heat dissipation. In addition, the evaporation rate of existing hygroscopic materials at high temperatures is insufficient, and rapid heat dissipation cannot be achieved.

[0003] Therefore, there is an urgent need to develop a photovoltaic cooling material that combines high moisture absorption capacity, rapid evaporation characteristics, excellent mechanical strength and enhanced radiation cooling function. Summary of the invention

[0004] The embodiment of the present application provides a photovoltaic cooling material based on LiCl / Na2SiO3 / PVA-PAm double network hydrogel, and its technical solution includes:

[0005] Material composition and structure: Polyvinyl alcohol (PVA) and polyacrylamide (PAm) are cross-linked by hydrogen bonds to form a double network matrix; lithium chloride (LiCl) is embedded as a hygroscopic agent and sodium silicate (Na2SiO3) as a radiation enhancer; the hydrogel has a porous structure with an average pore size of 1-3μm, and LiCl and Na2SiO3 complexes are evenly distributed in the pores.

[0006] Preparation method: Step 1: Blend PVA solution with acrylamide (AM) monomer and sodium silicate to form PVA-PAm / Na2SiO3 double network hydrogel through chemical crosslinking; Step 2: After drying, soak in LiCl solution to load LiCl in the pores of the hydrogel; Key process parameters: crosslinking temperature 50°C, LiCl solution concentration 25wt%, sodium silicate addition amount 0.3-1.2wt%.

[0007] Application method: The hydrogel is attached to the back panel or heat dissipation surface of the photovoltaic module in the form of a thin film (thickness 0.5-2mm), and the temperature is synergistically reduced through the following mechanisms: moisture absorption at night: LiCl captures water vapor in the air; evaporation during the day: water evaporates rapidly (complete dehydration in 3 hours at 90°C), combined with the distribution of water molecules regulated by Na2SiO3 (the proportion of intermediate water increases to 60%), to reduce the evaporation enthalpy.

[0008] A technical solution provided in the embodiments of the present application has at least the following technical effects or advantages:

[0009] 1. Efficient cooling: Experiments show that the surface temperature of photovoltaic modules using this hydrogel is reduced by 20-25°C, and the power generation efficiency is increased by more than 20%;

[0010] 2. Strong mechanical properties: tensile stress reaches 0.254MPa, compressive stress 250kPa, and adhesion strength (TEG surface 14.71kPa) ensures long-term stable use;

[0011] 3. Environmental adaptability: It exhibits excellent moisture absorption capacity at 50-90% relative humidity and can be recycled for at least 6 times without performance degradation. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the structure of a new type of hydrogel for photovoltaic cooling in an embodiment of the present application;

[0013] Figure 2 Comparison of the adhesion properties of LNP hydrogel and LNPAm hydrogel;

[0014] Figure 3 Comparison of tensile properties of LNP hydrogel and LNPAm hydrogel;

[0015] Figure 4 It is the hygroscopicity curve of LNP hydrogel at different humidity; DETAILED DESCRIPTION

[0016] The embodiments of the present application provide a novel hydrogel preparation process for photovoltaic cooling, thereby providing an innovative preparation process for existing photovoltaic cooling materials, thereby improving the efficiency of photovoltaic cooling and the power generation efficiency of photovoltaic modules.

[0017] Embodiment 1

[0018] Hydrogel preparation process:

[0019] (1) Dissolve 4.3 g of PVA in 43 ml of deionized water and heat at 90°C for 12 hours until completely dissolved;

[0020] (2) Add 5.33 g AM monomer, 0.6 wt% sodium silicate (total weight percentage), 0.032 g crosslinker MBA and 40 μL TEMED, and stir and mix under nitrogen protection;

[0021] (3) Add 0.064 g KBS and cross-link at 50° C. for 2 hours to form PVA-PAm / Na2SiO3 hydrogel; dry at 80° C. for 10 hours, soak in 25 wt% LiCl solution for 8 hours, and stand at room temperature for 24 hours to obtain the target hydrogel.

[0022] Embodiment 2

[0023] The hydrogel in this embodiment 1 was tested for performance, and the test results are as follows:

[0024] (1) Hygroscopicity: The moisture absorption capacity reaches 2.38g / g in 90% RH environment in 12 hours -1 ;

[0025] (2) Evaporation rate: 2.8 g / (h·cm at 90°C 2 ), completely dehydrated within 3 hours;

[0026] (3) Mechanical strength: tensile stress 0.254 MPa, compressive stress 250 kPa, adhesion strength (12.33 kPa on photovoltaic panel surface);

[0027] Embodiment 3

[0028] The hydrogel in the first embodiment is applied to photovoltaic modules: the hydrogel film (thickness 1 mm) is attached to the monocrystalline silicon photovoltaic backplane and the photovoltaic module is heated to 1000 W / m 2 Test under light: The component temperature dropped from 85°C to 62°C, and the power generation efficiency increased by 22%; after 6 cycles, the adhesion strength retention rate was >80%, and the moisture absorption did not decrease significantly.

Claims

1. A novel hydrogel for photovoltaic cooling and its preparation process, comprising the following components and structures: A double network hydrogel matrix is ​​formed by cross-linking polyvinyl alcohol (PVA) and polyacrylamide (PAm) through hydrogen bonds; lithium chloride (LiCl) embedded in the double network matrix serves as a hygroscopic agent; and sodium silicate (Na2SiO3) uniformly dispersed in the matrix is ​​used to enhance the radiation cooling performance.

2. The photovoltaic cooling hydrogel according to claim 1, characterized in that: It has a porous structure with an average pore size of 1-3 μm, and LiCl and Na2SiO3 complexes are distributed in the pores.

3. The photovoltaic cooling hydrogel according to claim 1, characterized in that: The hydrogel preparation process is as follows: 4.3g PVA is added to 43ml deionized water, heated in an oil bath at 90°C for 12h, and then 5.33g AM and a certain mass fraction (0.3-1.2wt%) of sodium silicate are added under nitrogen. Under stirring, 0.032g MBA and 40μL TEMED are added. Then 0.064g KBS is added, cross-linked at 50°C for 2 hours, dried at 80°C for 10 hours, and then immersed in a 25wt% lithium chloride solution, left to stand for 2 hours, and then left at room temperature for 24 hours.

4. The photovoltaic cooling hydrogel according to claim 3, characterized in that: The addition amount of the sodium silicate is 0.3-1.2 wt % of the total mass of the hydrogel.

5. The photovoltaic cooling hydrogel according to claim 3, characterized in that: The lithium chloride is loaded in the hydrogel by immersion method, the concentration of the immersion solution is 20-30wt%, and the immersion time is 8-24 hours.

6. The photovoltaic cooling hydrogel preparation process according to claim 3, characterized in that: In the step, the added amount of the crosslinking agent MBA is 0.5-1.0% of the mass of the AM monomer, and the added amount of the initiator KBS is 1-2% of the mass of the AM monomer.

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