Composite hydrogel and device for photovoltaic cooling

Abstract

The present invention provides a composite hydrogel and device for photovoltaic cooling, comprising a polymer hydrogel layer wrapped with a high thermal conductivity metal layer for cooling photovoltaics, wherein the high thermal conductivity metal layer has at least one side of the polymer hydrogel layer extending therefrom and extending into water for water extraction, wherein the high thermal conductivity metal has a thermal conductivity λ>50W / mK. The present invention achieves cooling of photovoltaic panels through the composite hydrogel, reduces the adverse effects of heat on the photovoltaic panels, utilizes photovoltaic waste heat to drive seawater desalination to achieve freshwater production, and simultaneously realizes the energy and resource utilization of solar energy, making new explorations for the orderly resource utilization of solar energy.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic cooling and waste heat seawater desalination, and in particular relates to a composite hydrogel and a device for photovoltaic cooling. Background Art

[0002] With global warming and the gradual decline of traditional energy reserves, photovoltaic power generation has become an effective alternative to traditional energy sources. Current research focuses on improving the energy conversion efficiency of photovoltaic panels. However, due to the radiative and non-radiative relaxation of photogenerated carriers during operation, the surface temperature of photovoltaic panels can reach as high as 60°C under 1 sun. Statistics show that for every 1°C increase in solar photovoltaic panel temperature, the fill factor decreases by 0.1% to 0.2%, resulting in a 0.4% to 0.5% decrease in power generation capacity. Furthermore, prolonged high-temperature operation can cause irreversible damage to photovoltaic panels, significantly reducing their energy conversion efficiency and shortening their lifespan. Therefore, reducing the surface operating temperature of photovoltaic panels is a top priority to improve their energy conversion efficiency and service life.

[0003] A range of strategies have been proposed for dissipating heat from photovoltaic panels: passive and active. Generally, passive cooling includes natural convection and heat pipe cooling, while active cooling includes liquid immersion cooling, jet impingement cooling, and channel cooling. Passive cooling primarily utilizes the laws of nature, transferring heat to the air through convection. Passive cooling offers a simple structure, good stability, and superior maintenance costs and cost-effectiveness. However, due to the low heat transfer coefficient of photovoltaic panels, the heat generated by the panels cannot be transferred to the air in a timely manner, resulting in heat accumulation and ultimately making it difficult to achieve the desired cooling effect. Active cooling requires additional power input, using external work to allow the cooling medium to absorb the heat generated by the photovoltaic panels. However, this external work consumes additional energy, reducing the economic efficiency of photovoltaic panels. Furthermore, the increased complexity of the system structure increases operating and maintenance costs.

[0004] Due to the shortage of fresh water resources caused by population growth and environmental pollution, seawater desalination has gradually become a hot research topic today. Traditional seawater desalination technologies include distillation and reverse osmosis. The high energy consumption of the water phase change process limits the development of distillation, and the manufacturing and maintenance of semipermeable membranes in reverse osmosis increase the cost of seawater desalination. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a composite hydrogel and device for photovoltaic cooling, designs a high thermal conductivity metal-polymer composite hydrogel for photovoltaic cooling, and uses the composite hydrogel to cool the photovoltaic panel, reducing the adverse effects of heat on the photovoltaic panel. It also uses photovoltaic waste heat to drive seawater desalination to achieve fresh water production, while realizing the energy and resource utilization of solar energy, and making new explorations for the orderly resource utilization of solar energy.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: a composite hydrogel for photovoltaic cooling, comprising a polymer hydrogel layer wrapped with a high thermal conductivity metal layer for cooling photovoltaics, wherein at least one side of the polymer hydrogel layer on the high thermal conductivity metal layer extends a high thermal conductivity metal layer for extending into water for water extraction, and the high thermal conductivity metal has a thermal conductivity λ>50W / mK.

[0007] Furthermore, the high thermal conductivity metal includes foam copper, foam aluminum, foam iron, and foam tin.

[0008] Furthermore, the polymer includes polyvinyl alcohol (PVA) or polyacrylamide (PAM).

[0009] Furthermore, the high thermal conductivity metal is foamed copper, and the polymer is polyvinyl alcohol (PVA).

[0010] The present invention provides a method for preparing a composite hydrogel for photovoltaic cooling, the specific steps of which are as follows:

[0011] S1 Select a mold according to your needs and place the high thermal conductivity metal in the mold, ensuring that at least one side of the high thermal conductivity metal is away from the side wall of the mold;

[0012] S2 introduces the polymer solution into the mold so that the polymer solution covers the high thermal conductivity metal by 0.05cm to 0.15cm;

[0013] S3 repeatedly freezes and thaws the mold of S2 to obtain a milky white solid gel, namely a composite hydrogel.

[0014] The present invention provides a photovoltaic power generation device, comprising a photovoltaic panel, a cooling part and a water pumping part. The polymer hydrogel layer containing a high thermal conductivity metal on the above-mentioned composite hydrogel serves as the cooling part. The cooling part is attached to the back of the photovoltaic panel, and the polymer hydrogel layer extending out of the high thermal conductivity metal layer serves as the water pumping part. The water pumping part extends from the back of the photovoltaic panel into the water and is used to transfer water to the cooling part on the back of the photovoltaic panel.

[0015] Furthermore, photovoltaic panels use silicon wafers.

[0016] The present invention provides a photovoltaic power generation seawater desalination device, comprising a self-floating water collection tank, the above-mentioned composite hydrogel and the above-mentioned photovoltaic power generation device. The photovoltaic power generation device is arranged on one side wall of the self-floating water collection tank, and the water pumping part of the photovoltaic power generation device extends from one side of the floating water collection tank into the seawater; the above-mentioned composite hydrogel is adhered to the remaining side walls of the self-floating water collection tank, and the polymer hydrogel layer without high thermal conductivity metal in the above-mentioned composite hydrogel extends from the other side of the self-floating water collection tank into the seawater.

[0017] Furthermore, the self-floating water collection tank is obtained by a water collection tank and polyurethane foam bonded to the bottom thereof, and the water collection tank is a PET water collection tank.

[0018] The present invention provides an operating method for a photovoltaic power generation seawater desalination device, the specific steps of which are as follows:

[0019] S1 places the desalination device on the sea surface under light. The temperature of the photovoltaic panels in the photovoltaic power generation device increases under light, and the photoelectric conversion efficiency decreases. The water extraction part of the photovoltaic power generation device extracts water to the cooling part of the photovoltaic power generation device through capillary action;

[0020] The heat of the S2 photovoltaic panel is transferred to the cooling part, the heat of the photovoltaic panel is reduced, the photoelectric conversion efficiency is increased, the temperature of the composite hydrogel in the cooling part is increased, and the water in it is evaporated by heat to form water vapor;

[0021] The water in the composite hydrogel attached to the remaining side wall of the S3 self-floating water collection tank evaporates naturally, reducing the temperature of the remaining side wall of the self-floating water collection tank. The water vapor condenses inside the side wall of the self-floating water collection tank and collects as fresh water at the bottom.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] The present invention provides a composite hydrogel for photovoltaic cooling, which combines a high thermal conductivity metal with a polymer composite hydrogel. The high thermal conductivity metal acts as a continuous thermal conductive network inside the polymer composite hydrogel, so that the heat absorbed from the photovoltaic panel can be evenly distributed inside the hydrogel. In addition, the porous morphology and hydrophilic functional groups of the gel itself can spontaneously extract water from the water body into the gel without external work, and can quickly transfer the heat of the photovoltaic panel, thereby reducing the temperature of the photovoltaic panel and hydrogel overall system, improving the efficiency of the photovoltaic panel in actual operation, and avoiding thermal damage to the hydrogel.

[0024] The present invention provides a photovoltaic power generation device. A polymer hydrogel layer containing a high thermal conductivity metal on a composite hydrogel is disposed on the back of a photovoltaic panel. The polymer hydrogel layer extending from the high thermal conductivity metal layer is extended from the back of the photovoltaic panel into water. The porous morphology and hydrophilic functional groups of the polymer hydrogel layer enable spontaneous extraction of water from the water body into the gel without external work, and transfer of the water to the polymer hydrogel layer containing the high thermal conductivity metal on the back of the photovoltaic panel. Water is the most powerful heat-absorbing substance in nature, and the strong interaction between the hydrophilic functional groups in the hydrogel and water can offset the hydrogen bonding forces between water molecules, thereby producing a special form of water—"intermediate water." This intermediate water has a lower enthalpy of evaporation than free water, meaning that the energy required for evaporation is reduced, resulting in more water evaporation in the composite hydrogel. This can quickly transfer heat generated by the photovoltaic panel itself and maintain a low temperature at the interface between the photovoltaic panel and the hydrogel. Under irradiation of 1 sun, the photovoltaic power generation device of the present invention reduces the temperature of the photovoltaic panel by 23°C, and improves the operating efficiency of the photovoltaic panel by 1.7%.

[0025] The present invention provides a photovoltaic power generation and seawater desalination device, which combines a photovoltaic power generation device with a composite hydrogel and a self-floating water collection tank. The composite hydrogel is used to extract seawater. The water in the gel absorbs the heat of the photovoltaic panel to evaporate the water vapor. At the same time, the evaporation effect of the composite hydrogel itself is used to reduce the temperature of the wall surface of the self-floating water collection tank, thereby condensing the water vapor in the self-floating water collection tank and achieving seawater desalination. The seawater desalination rate is 0.92 kg / m -2 h -1 .

[0026] Furthermore, the strong interaction between the hydrophilic functional groups in the hydrogel and water can offset the hydrogen bonding forces between water molecules, thereby producing a special form of water - "intermediate water". This intermediate water has a lower evaporation enthalpy than free water, which means that the energy required to achieve evaporation is reduced. That is, the heat generated by the photovoltaic panel is applied to the evaporation of water in the hydrogel system, which can obtain more desalinated water than the heat applied to the evaporation of free water, making it possible to obtain fresh water more efficiently while cooling the photovoltaic panel. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of a photovoltaic power generation seawater desalination device according to the present invention;

[0028] Figure 2 The cooling effect of composite hydrogel on photovoltaic panels;

[0029] Figure 3 The composite hydrogel improves the actual operating efficiency of photovoltaic panels under light;

[0030] Figure 4It is the desalination rate of seawater under sunlight using a photovoltaic desalination device.

[0031] Figure 5 This is a three-view diagram of a photovoltaic power generation seawater desalination device according to the present invention.

[0032] Figure 6 Actual picture of the composite hydrogel of the present invention.

[0033] Figure 7 Microscopic image of the composite hydrogel of the present invention.

[0034] In the accompanying drawings: 1. Photovoltaic panel; 2. Composite hydrogel; 21 cooling unit; 22 water pumping unit; 3. Water collecting tank; 4. Polyurethane foam. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0036] like Figure 6 As shown, the present invention provides a composite hydrogel for photovoltaic cooling, including a polymer hydrogel layer, the polymer hydrogel layer is wrapped with a high thermal conductivity metal and is set on a photovoltaic panel to absorb heat from the photovoltaic panel, and the high thermal conductivity metal layer has a high thermal conductivity metal layer extending from the polymer hydrogel layer on at least one side to extend into water for water extraction, and the high thermal conductivity metal has a thermal conductivity λ>50W / mK.

[0037] Furthermore, the thermal conductivity λ of the high thermal conductivity metal is greater than 50 W / mK, specifically including foamed copper (401 W / mK), foamed aluminum (237 W / mK), foamed iron (80 W / mK), and foamed tin (67 W / mK).

[0038] Furthermore, the polymer includes polyvinyl alcohol (PVA) or polyacrylamide (PAM).

[0039] Preferably, copper metal with the highest thermal conductivity (λ>50W / mK) and PVA with strong hydrophilicity are selected to prepare a semi-solid FCu-PVA hydrogel with good thermal conductivity. Copper acts as a continuous thermal conductive network inside the PVA hydrogel, improving the thermal conductivity of the hydrogel.

[0040] The specific preparation method is:

[0041] S1 cleans the high thermal conductivity metal with deionized water and acetone, and then places it in a mold. The mold is three times the length of the high thermal conductivity metal and the same width as the high thermal conductivity metal.

[0042] S2: The polymer solution is introduced into the mold until it covers the high thermal conductivity foam metal by 0.05 cm to 0.15 cm;

[0043] S3: Place the mold in a -80°C freezer and freeze for 1 hour, then take it out and thaw it in deionized water. Repeat step S3 5 times to obtain a milky white solid gel, completing the gelation process.

[0044] Furthermore, the steps for synthesizing the PVA polymer solution are as follows: H2O and PVA particles are mixed in a flask at a weight ratio of 10:1, and heated and stirred at 90°C for 120 minutes to obtain a PVA polymer solution.

[0045] Furthermore, the steps for synthesizing the PAM polymer solution are as follows: 30 ml of deionized water is added to a beaker, 6.9 g of acrylamide is added, stirred for 15 minutes until uniform, 0.9 g of sodium persulfate is added, and the polymer solution is obtained after 6 minutes.

[0046] The present invention discloses a photovoltaic power generation device, including a composite hydrogel 2 and a photovoltaic panel 1. The photovoltaic panel 1 is fixed by a fixing device. The polymer hydrogel layer containing a high thermal conductivity metal on the composite hydrogel 2 serves as a cooling part 21, and the polymer hydrogel layer extending out of the high thermal conductivity metal layer serves as a water-lifting part 22. The cooling part 21 is attached to the back of the photovoltaic panel 1, and the polymer hydrogel layer containing a high thermal conductivity metal on the composite hydrogel 2 is attached to the back of the photovoltaic panel 1. The water-lifting part 22 extends from the back of the photovoltaic panel 1 into the water to transfer water to the cooling part 21 on the back of the photovoltaic panel 1.

[0047] Because the thermal conductivity of organic materials themselves is low, heat will accumulate at the contact point between the hydrogel and the photovoltaic panel 1, which will cause the local temperature of the contact surface to rise. On the one hand, the increase in local temperature is not conducive to the cooling of the photovoltaic panel 1. On the other hand, the high temperature may damage the hydrogel and reduce the operating time of the photovoltaic power generation device. Therefore, the present invention combines copper foam with high thermal conductivity with PVA hydrogel. The copper foam acts as a continuous heat conduction network inside the PVA hydrogel, so that the heat absorbed from the photovoltaic panel 1 can be evenly distributed inside the hydrogel, further reducing the temperature of the overall system of the photovoltaic panel 1 and the hydrogel, and improving the efficiency of the photovoltaic panel 1 in actual operation.

[0048] In addition, the porous morphology and hydrophilic functional groups of the composite hydrogel 2 itself can spontaneously extract water from the water body into the gel without external work. Water is the most heat-absorbing substance in nature. Therefore, attaching the composite hydrogel 2 to the back of the photovoltaic panel 1 can quickly transfer the heat generated by the photovoltaic panel 1 itself, so that it can maintain the temperature between the photovoltaic panel 1 and the hydrogel interface at a low level.

[0049] like Figure 1 and Figure 5As shown, the present invention discloses a photovoltaic power generation seawater desalination device, including a self-floating water collection tank, a composite hydrogel 2 and a photovoltaic power generation device. The self-floating water collection tank floats on the sea surface, and a photovoltaic power generation device is arranged on a side wall of the self-floating water collection tank. The cooling part 21 of the photovoltaic power generation device is used to release water vapor into the self-floating water collection tank, and the water lifting part 22 extends from the back of the photovoltaic panel 1 and one side of the floating water collection tank 3 into the seawater for lifting the seawater to the cooling part 21.

[0050] Except for the side walls where the photovoltaic panels 1 are set, the rest of the outer walls of the self-floating water collection tank are adhered with composite hydrogel 2. The polymer hydrogel layer containing high thermal conductivity metal on the composite hydrogel 2 is attached to the rest of the outer walls of the self-floating water collection tank, and the polymer hydrogel layer without high thermal conductivity metal extends from the other side of the self-floating water collection tank to the seawater. It is used to reduce the wall temperature of the self-floating water collection tank through the natural evaporation of water in the composite hydrogel 2 to achieve condensation of water vapor in the self-floating water collection tank on the wall.

[0051] Furthermore, the self-floating water collection tank is obtained by the water collection tank 3 and the polyurethane foam 4 bonded to the bottom thereof, using waterproof adhesive.

[0052] Preferably, the photovoltaic panel 1 is made of silicon wafers, and the water collection tank 3 is a PET water collection tank 3.

[0053] Because the strong interaction between the hydrophilic functional groups and water in the hydrogel can offset the hydrogen bond forces between water molecules, a special form of water - "intermediate water" is produced. Experimental verification shows that intermediate water has a lower evaporation enthalpy than free water, which means that the energy required to achieve evaporation is reduced. That is, applying the heat generated by the photovoltaic panel 1 to the evaporation of water in the hydrogel system can obtain more desalinated water than applying it to the evaporation of free water, making it possible to obtain fresh water more efficiently while cooling the photovoltaic panel 1.

[0054] At the same time, the composite hydrogel 2 of the present invention has a high water content. After the water evaporates, the local high-concentration seawater can diffuse back into the seawater body through concentration, avoiding the formation of salt crystals on the hydrogel, so that the seawater desalination device of the present invention can operate for a long time.

[0055] When the seawater desalination device of the present invention is in operation, the following processes are included:

[0056] 1) The seawater desalination device of the present invention is placed on the sea surface under light. The temperature of the photovoltaic panel 1 increases under light, and the photoelectric conversion efficiency decreases. The polymer composite hydrogel layer extending into the water extracts water to the junction of the back of the photovoltaic panel 1 and the composite hydrogel 2 through capillary action.

[0057] 2) The heat from the photovoltaic panel 1 is transferred to the bonded composite hydrogel 2, reducing the heat of the silicon wafer, increasing the photoelectric conversion efficiency, and increasing the temperature of the composite hydrogel 2. The water contained in the gel evaporates to form water vapor due to the heat. The composite hydrogel 2 eventually reaches thermal equilibrium through the interaction between the heating of the photovoltaic panel 1 and the heat absorption of water evaporation, and the temperature is stabilized. At the same time, the photovoltaic panel 1 reaches thermal equilibrium through the interaction between heat generation from light and heat conduction to the hydrogel, and the temperature and photoelectric conversion efficiency are stabilized.

[0058] 3) The water in the contact portion between the composite hydrogel 2 and the outer wall of the self-floating water collecting tank evaporates naturally, reducing the temperature of the contact surface, thereby reducing the temperature of the top of the self-floating water collecting tank.

[0059] 4) The temperature at the top of the self-floating water collection tank is relatively low, which promotes the condensation of water vapor. The water vapor condenses inside the self-floating water collection tank and collects as fresh water at the bottom.

[0060] Example

[0061] Use polyvinyl alcohol with a degree of polymerization of 1750, take 10g and mix it with 100g deionized water, heat and stir to obtain a polymer solution, and combine it with foam copper with a size of 16.4×16.4cm in a mold to form a composite hydrogel 2, as shown in the actual picture. Figure 6 As shown in the figure, the middle part is the foam copper-PVA composite gel, and the two ends are flexible PVA gel. Figure 7 As shown, PVA wraps the copper foam network. This structure can use the copper foam as an internal heat conduction network to achieve rapid and uniform heat transfer.

[0062] like Figures 2-4 As shown in the figure, under 1 sun, copper foam-PVA composite gel was used to cool a silicon wafer of the same size as copper foam. Compared with natural air cooling, the surface temperature of the silicon wafer was reduced from 60°C to 37.5°C and remained stable. At the same time, the photoelectric conversion efficiency of the silicon wafer was increased by 1.7%. In a seawater desalination device, it can reach 0.92 kg·m -2 ·h -1 Compared to experimental conditions, where a 0.1% increase in photoelectric conversion efficiency is considered a significant improvement, a 1.7% increase in photoelectric conversion efficiency has significant application value.

Claims

1. A composite hydrogel for photovoltaic cooling, characterized in that: A polymer hydrogel layer wrapped with a high thermal conductivity metal layer is used to cool photovoltaic cells. The high thermal conductivity metal layer has at least one side of the polymer hydrogel layer extending out of the high thermal conductivity metal layer to extend into water for water extraction. The thermal conductivity of the high thermal conductivity metal is λ>50W / mK. The preparation method of the composite hydrogel for photovoltaic cooling comprises the following specific steps: S1 Select a mold according to your needs and place the high thermal conductivity metal in the mold, ensuring that at least one side of the high thermal conductivity metal is away from the side wall of the mold; S2 introduces the polymer solution into the mold so that the polymer solution covers the high thermal conductivity metal by 0.05cm~0.15cm; S3 repeatedly freezes and thaws the mold of S2 to obtain a milky white solid gel, i.e., a composite hydrogel; The high thermal conductivity metal is foam copper, and the high polymer is polyvinyl alcohol (PVA).

2. A photovoltaic power generation device, characterized in that: The invention comprises a photovoltaic panel (1), a cooling portion (21) and a water-lifting portion (22), wherein the composite hydrogel (2) according to claim 1 comprises a polymer hydrogel layer containing a high thermal conductivity metal as the cooling portion (21), the cooling portion (21) is attached to the back of the photovoltaic panel (1), and the polymer hydrogel layer extending out of the high thermal conductivity metal layer serves as the water-lifting portion (22), and the water-lifting portion (22) extends from the back of the photovoltaic panel (1) into the water for transferring water to the cooling portion (21) on the back of the photovoltaic panel (1).

3. A photovoltaic power generation device according to claim 2, characterized in that: The photovoltaic panel (1) uses silicon wafers.

4. A photovoltaic power generation seawater desalination device, characterized in that: The invention comprises a self-floating water collecting tank, the composite hydrogel (2) according to claim 1 and the photovoltaic power generation device according to claim 2, wherein the photovoltaic power generation device is arranged on one side wall of the self-floating water collecting tank, and the water-lifting part (22) of the photovoltaic power generation device extends from one side of the floating water collecting tank (3) into the seawater; the composite hydrogel (2) according to claim 1 is adhered to the remaining side walls of the self-floating water collecting tank, and a polymer hydrogel layer of a high thermal conductivity metal is provided in the composite hydrogel (2) according to claim 1 and extends from the other side of the self-floating water collecting tank into the seawater.

5. The photovoltaic power generation seawater desalination device according to claim 4, characterized in that: The self-floating water collection tank is obtained from a water collection tank (3) and polyurethane foam (4) bonded to the bottom thereof, and the water collection tank (3) is a PET water collection tank.

6. The method for operating a photovoltaic power generation seawater desalination device according to claim 4, characterized in that: The specific steps are as follows: The desalination device is placed on the sea surface under S1 illumination. The temperature of the photovoltaic panel (1) in the photovoltaic power generation device increases under illumination, and the photoelectric conversion efficiency decreases. The water extraction part (22) of the photovoltaic power generation device extracts water to the cooling part (21) of the photovoltaic power generation device through capillary action. The heat of the S2 photovoltaic panel (1) is transferred to the cooling part (21), the heat of the photovoltaic panel (1) is reduced, the photoelectric conversion efficiency is increased, the temperature of the composite hydrogel (2) in the cooling part (21) is increased, and the water therein is evaporated by the heat to form water vapor; The water in the composite hydrogel (2) attached to the remaining side wall of the S3 self-floating water collecting tank evaporates naturally, reducing the temperature of the remaining side wall of the self-floating water collecting tank. The water vapor condenses inside the side wall of the self-floating water collecting tank and collects as fresh water at the bottom.

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