An energy-free thermoelectric generator based on radiative cooling and solar thermal heating

Abstract

A zero-energy thermoelectric generator based on radiative cooling and photothermal heating belongs to the technical field of zero-energy thermoelectric power generation equipment. The generator comprises a bracket, a V-shaped polished metal plate, a photothermal heating film, a radiative cooling film, and a thermoelectric generator sheet. The radiative cooling film and the photothermal heating film are adhered to either side of the thermoelectric generator sheet using thermally conductive silicone and placed between the V-shaped polished metal plate. The MXene of the present invention combines high solar absorptivity with low infrared emissivity, providing excellent photothermal heating during the day with minimal temperature drop at night. The cooling end utilizes a PAN electrospun membrane, a material with high solar reflectivity and high infrared emissivity, providing a cooling effect both daytime and nighttime. Therefore, due to the performance of these two materials, a temperature difference is formed across the thermoelectric generator sheet throughout the day, enabling continuous electrical energy generation.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy-free thermoelectric power generation equipment, and specifically relates to an energy-free thermoelectric generator based on radiation cooling and solar thermal heating. Background Art

[0002] With the surge in energy consumption and the large-scale combustion of fossil fuels leading to the production of greenhouse gases, the issue of energy sources is the root cause. Therefore, large-scale research and development is underway in the development and utilization of renewable energy sources, such as biohydrogen, solar energy, hydrogen energy, and wind energy. Solar thermal heating and radiant cooling, which utilize solar energy and space cooling, respectively, are both green energy sources that can partially replace fossil fuels.

[0003] Currently, photothermal heating materials include metal-based plasma and carbon-based materials. Metal-based nanomaterials are relatively expensive and complex to prepare. Carbon-based materials have high solar absorptivity but also high infrared emissivity, so they cannot achieve the desired temperature difference at night. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems of high cost and complex preparation of existing photothermal heating materials, and to provide an energy-free thermoelectric generator based on radiative cooling and photothermal heating. The generator uses a photothermal heating film and a radiative cooling film to increase and decrease the temperature respectively, which are adhered to the two ends of the thermoelectric power generation sheet respectively to collect electrical energy, and can achieve continuous power generation 24 hours a day.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A zero-energy thermoelectric generator based on radiative cooling and photothermal heating, comprising a bracket, a V-shaped polished metal plate, a photothermal heating film, a radiative cooling film, and a thermoelectric power generation sheet; the radiative cooling film and the photothermal heating film are respectively adhered to both sides of the thermoelectric power generation sheet using thermally conductive silicone and placed in the middle of the V-shaped polished metal plate; the bracket is used to support the V-shaped polished metal plate; the two films are adhered to both sides of the thermoelectric power generation sheet using thermally conductive silicone to transfer temperature to both sides of the thermoelectric plate to form a temperature difference for power generation.

[0007] The present invention utilizes the characteristics of high solar reflectivity and low infrared emissivity of the V-shaped polished metal plate to reflect all the solar light bands required by the photothermal end to the MXene material for full-band absorption to increase the temperature; at the same time, it can reflect the infrared energy emitted by the radiation cooling end into outer space for cooling.

[0008] Furthermore, the preparation method of the radiative cooling film is as follows: dissolving PAN particles in DMAC solvent to ensure that the concentration of PAN is 10%, heating and stirring for 24 hours to obtain a uniform mixed solution; -1A constant flow rate of 100 nm and a fixed voltage of 20 kV were loaded into the syringe for electrospinning, and the distance between the injector nozzle and the receiver was 15 cm. The collected PAN was then dried at 60 °C for 3 h to ensure the volatilization of the residual solvent.

[0009] Furthermore, the preparation method of the photothermal heating film is as follows: the photothermal heating film is obtained by etching the MAX material to obtain a single-layer MXene self-supporting film, specifically, 2g of lithium fluoride and 9M40ml of hydrochloric acid are stirred for 30 minutes, 2g of MAX-Ti3AlC2 is slowly added to the solution and stirred continuously for 24 hours, the obtained reaction liquid is placed in a centrifuge tube for centrifugation, the supernatant is poured out after centrifugation, deionized water is added to the precipitate in the centrifuge tube, the precipitate and deionized water are evenly mixed, the centrifuge tube is ultrasonicated for 10 minutes, taken out and centrifuged, and the process is repeated several times until the pH value of the liquid poured out after centrifugation reaches 5, the supernatant is collected and filtered and dried to obtain the MXene self-supporting film.

[0010] The advantages of this invention over existing technologies include: MXene combines high solar absorptivity with low infrared emissivity, enabling excellent daytime solar thermal heating with minimal nighttime temperature drops. The cooling side utilizes an electrospun PAN membrane, a material with high solar reflectivity and high infrared emissivity, providing cooling both daytime and nighttime. By leveraging these two properties, a temperature differential is created across the thermoelectric generator throughout the day, enabling continuous power generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a structural diagram of the generator device;

[0012] Figure 2 This is a diagram of energy input and output of the energy-free thermoelectric generator;

[0013] Figure 3 This is a diagram showing the energy inflow and outflow of a daytime energy-free thermoelectric generator;

[0014] Figure 4 This is a diagram of energy inflow and outflow of a thermoelectric generator with no energy consumption at night;

[0015] Figure 5 The infrared emissivity graph of various materials;

[0016] Figure 6 This is the outdoor test effect diagram of the two ends of the energy-free thermoelectric generator;

[0017] Figure 7 This is an electron microscope image of PAN electrospun fiber membrane. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0019] Example 1:

[0020] The radiative cooling membrane uses PAN electrospinning material, and the specific preparation process is as follows:

[0021] PAN powder was dissolved in DMAC solvent at room temperature and stirred for 24 hours to form a uniform solution. The solution was injected into a 10 ml syringe and the surface tension between the droplets was destroyed by the high voltage of the electrospinning machine under 40% to 50% humidity. The PAN was stretched into a fiber state. Figure 7 shown.

[0022] The photothermal film preparation process is as follows:

[0023] Stir 2g of lithium fluoride and 9M of 40ml of hydrochloric acid in a Teflon beaker for 30 minutes. Slowly add 2g of MAX to the beaker and continue stirring for 24 hours. Centrifuge the resulting reaction mixture several times until the pH of the decanted liquid reaches 5. Add 20ml of deionized water to the precipitate in the centrifuge tube, shake well, sonicate, and centrifuge for a specified period of time. Collect the dark brown supernatant as the thin layer dispersion. Vacuum filter the dispersion to prepare a self-supporting MXene membrane.

[0024] The obtained films were tested for infrared emissivity, and the results were as follows: Figure 5 As shown in the figure, Sp1 is a multilayer MXene, Sp2 is a single layer MXene, Sp3 is a polished aluminum sheet, Sp4 is a carbon-based photothermal material, and Sp5 is a PAN spun film. Among them, the polished aluminum sheet has the lowest infrared emissivity, the single layer MXene material has the lowest infrared emissivity of the three photothermal materials, and the PAN cooling film has the highest infrared emission efficiency.

[0025] The single-layer MXene and PAN cooling films were placed in an outdoor environment for measurement, such as Figure 6 As shown, Sp1 is the ambient temperature, Sp2 is the photothermal film, which is 87°C higher than the ambient temperature; Sp3 is the PAN cooling film, which is 7.5°C lower in temperature.

[0026] like Figure 1 As shown, the generator includes a bracket, a V-shaped polished metal plate, a photothermal heating film, a radiant cooling film, and a thermoelectric generator sheet. The radiant cooling film and the photothermal heating film are respectively adhered to both sides of the thermoelectric generator sheet using thermal conductive silicone and placed in the middle of the V-shaped polished metal plate. The bracket is used to support the V-shaped polished metal plate.

[0027] like Figures 2-4As shown, during the day, the photothermal film absorbs solar energy reflected from the polished metal plate, raising the temperature. The cooling film reflects sunlight while simultaneously emitting energy in the infrared, creating a significant temperature difference. At night, the MXene film, due to its low infrared emissivity, minimizes energy loss. The PAN cooling film, with its high infrared emissivity, can also radiate energy into space at night, lowering the temperature. Thus, a temperature difference can be created at night to generate electricity.

Claims

1. An energy-free thermoelectric generator based on radiative cooling and solar thermal heating, characterized by: The generator comprises a bracket (1), a V-shaped polished metal plate (2), a photothermal heating film (3), a radiation cooling film (4) and a thermoelectric power generation sheet (5); the radiation cooling film (4) and the photothermal heating film (3) are respectively adhered to both sides of the thermoelectric power generation sheet (5) using thermal conductive silicone and placed in the middle of the V-shaped polished metal plate (2); the thermoelectric power generation sheet (5) is in a vertical relationship with the bottom of the bracket (1); The preparation method of the radiative cooling film is as follows: dissolving PAN particles in DMAC solvent to ensure that the concentration of PAN is 10%, heating and stirring for 24 hours to obtain a uniform mixed solution; -1 A constant flow rate of 100 nm and a fixed voltage of 20 kV were loaded into the syringe for electrospinning, and the distance between the injector nozzle and the receiver was 15 cm. The collected PAN was then dried at 60 °C for 3 h to ensure the volatilization of the residual solvent. The preparation method of the photothermal heating film is as follows: the photothermal heating film is obtained by etching the MAX material to obtain a single-layer MXene self-supporting film. Specifically, 2g of lithium fluoride and 40ml of 9M hydrochloric acid are stirred for 30 minutes, 2g of MAX-Ti3AlC2 is slowly added to the solution and stirred continuously for 24 hours, the obtained reaction liquid is placed in a centrifuge tube for centrifugation, the supernatant is poured out after centrifugation, deionized water is added to the precipitate in the centrifuge tube, the precipitate and deionized water are evenly mixed, the centrifuge tube is ultrasonicated for 10 minutes, and the centrifuge is removed and centrifuged. This is repeated several times until the pH value of the liquid poured out after centrifugation reaches 5. The supernatant is collected, filtered and dried to obtain the MXene self-supporting film.

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