A low-cost flexible low-grade solar thermal power collection system and preparation method

Abstract

The present invention discloses a low-cost flexible low-grade solar thermoelectric collection system and preparation method, which belongs to the field of solar thermoelectric collection. The system includes a solar collector and a flexible thin-film thermoelectric chip. The flexible thin-film thermoelectric chip is continuously arranged around the periphery of the solar collector, and the two are connected by a conductive electrode; the solar collector is formed by depositing Fe3O4 nanoparticles on the graphite surface of a graphite-metal substrate; the flexible thin-film thermoelectric chip is formed by patterning and depositing several pairs of thermoelectric legs on a flexible substrate. The system exhibits a solar energy capture efficiency of more than 92% and a thermal conductivity of about 20mV / cm 2 The open circuit voltage output per unit irradiation area is better than most commercial solar panels (about 5mV / cm 2 ), and compared with room temperature (293K), the output power of the device can be increased by 30% in low temperature environment (273K).

Description

Technical Field

[0001] The present invention belongs to the field of solar thermal power collection, and in particular relates to a low-cost flexible low-grade solar thermal power collection system and a preparation method thereof. Background Art

[0002] With the increasingly urgent energy crisis, humanity has been committed to finding alternatives to fossil fuels in recent years. Therefore, achieving clean and permanent energy harvesting will become a long-term sustainable development strategy. Due to its stable light field, solar energy is considered one of the most ideal available light sources and is widely used in solar photovoltaics, solar thermal energy, and photochemistry. Recently, a technology has been proposed that converts photons into heat energy and then collects it as electricity. This technology can be used to create efficient light-harvesting components that can be integrated with photovoltaic cells to improve the efficiency of photovoltaic cell structures. However, a critical flaw of this technology is that it cannot generate sufficient thermoelectromotive force in thermoelectric devices for efficient solar energy harvesting under low solar irradiance. To address this dilemma, some research has attempted to concentrate solar radiation onto devices through light or heat concentration to achieve more efficient heat generation. However, due to the complexity of concentrating optics and the rigidity of thermoelectric bodies, these approaches have limited engineering flexibility and practicality. Therefore, there is a need to fundamentally improve the efficiency of solar-to-electricity conversion and develop flexible thermoelectric devices for solar energy harvesting. In addition, the preparation of existing light energy capture components requires the support of micro-nano manufacturing technology, and it is difficult to meet the production needs of large-scale applications in terms of structural complexity, low cost and production efficiency. Therefore, it is also of great significance to develop a preparation process with simple procedures and high cost performance. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the existing technology and reduce the preparation cost, providing a low-cost flexible low-grade solar thermal power collection system and preparation method. Specifically, the system is a flexible energy collection system that realizes photothermal-to-thermoelectric conversion. The flexible energy collection system for photothermal-to-thermoelectric conversion is composed of a hybrid nanostructured low-grade solar absorber and a flexible thin-film thermoelectric chip. The hybrid nanostructured solar absorber absorbs low-grade sunlight and converts it into thermal energy, which further drives the thermoelectric chip to generate electricity, thereby achieving the capture of solar energy. The energy collection system also has certain low-temperature environment performance enhancement characteristics.

[0004] The specific technical solutions adopted in the present invention are as follows:

[0005] In its first aspect, the present invention provides a low-cost, flexible, low-grade solar thermoelectric collection system. This system utilizes a hybrid nanostructured solar absorber to absorb sunlight and convert it into heat, which in turn drives a thermoelectric chip to generate electricity, thereby capturing low-grade solar energy. The low-cost, flexible, low-grade solar thermoelectric collection system includes a solar collector and a flexible thin-film thermoelectric chip, which is continuously arranged around the periphery of the solar collector and connected to it by conductive electrodes.

[0006] The solar collector is made of Fe3O4 nanoparticles deposited on the graphite surface of a graphite-metal substrate. Even when the solar radiation flux is low, the structure can serve as a heat source for a thermoelectric generator.

[0007] The flexible thin-film thermoelectric chip is composed of several pairs of thermoelectric legs deposited in a patterned pattern on a flexible substrate. Each pair of legs includes a sheet of n-type thermoelectric material and a sheet of p-type thermoelectric material. Both the n-type and p-type thermoelectric materials have a tapered sheet structure, with the tapered tips facing the solar collector. The n-type and p-type thermoelectric materials in the flexible thin-film thermoelectric chip are arranged alternately, and adjacent n-type and p-type thermoelectric materials are connected by conductive electrodes, forming an overall thin-film structure that is electrically connected in series and thermally connected in parallel. This tapered structure can increase the temperature difference between the cold and hot ends of the thermoelectric material under a constant ambient temperature, thereby enhancing voltage output.

[0008] Preferably, the Fe3O4 nanoparticles have a diameter of 510-530 nm and are rotationally symmetrically deposited in a C6 pattern in the form of a single layer of particles on the graphite surface.

[0009] Preferably, the graphite in the graphite-metal substrate has a thickness of 45 nm, and the metal is copper with a thickness of 45-50 μm.

[0010] Preferably, the solar collector and flexible thin-film thermoelectric chip are integrated using thermally conductive silicone grease. Specifically, a layer of interface dielectric (e.g., thermally conductive silicone grease) is sandwiched between any set of thermoelectric materials and the solar collector at the center of the structure. All interface dielectric layers are made of the same material, with high thermal conductivity and low electrical conductivity, so that the connection conducts heat but not electricity. All interface dielectric layers have the same thickness.

[0011] Preferably, the cross section of the solar collector is circular, the cross section of the flexible thin film thermoelectric chip is an annular structure, and the conical tips of the n-type thermoelectric material and the p-type thermoelectric material are both oriented toward the center of the solar collector.

[0012] Preferably, the flexible substrate is made of polyimide or polydimethylsiloxane, and has a thickness of 70-100 μm.

[0013] Preferably, the n-type thermoelectric material is Bi2Te 2.7 Se 0.3 , thickness 1μm, length 5mm, p-type thermoelectric material is Bi 0.5 Sb 1.5 Te3, thickness 1μm, length 5mm.

[0014] Preferably, the conductive electrode is made of gold.

[0015] In a second aspect, the present invention provides a method for preparing a low-cost, flexible, low-grade solar thermal power collection system, as follows:

[0016] Fe3O4 nanoparticles are dispersed in a mixture of methanol and chloroform as a base liquid to obtain a colloidal dispersion liquid. The Fe3O4 nanoparticles in the colloidal dispersion liquid are then self-assembled using Langmuir-Blodgett thin film deposition technology to form a monolayer surface particle film at the interface between air and liquid. A graphite-metal substrate is tilted with the graphite layer facing upward and placed below the liquid surface of the solution having formed the monolayer surface particle film. The base liquid is simultaneously pumped out and the graphite-metal substrate is vertically lifted to deposit the monolayer surface particle film on the surface of the graphite-metal substrate. As the base liquid evaporates naturally, the Fe3O4 nanoparticles gradually aggregate on the surface of the graphite-metal substrate and arrange in a C6 pattern, thereby obtaining a solar collector.

[0017] A continuous flexible substrate is laid around the periphery of the solar collector, and an n-type thermoelectric material and a p-type thermoelectric material are alternately coated on the flexible substrate; the n-type thermoelectric material and the p-type thermoelectric material are both tapered sheet structures, with the tapered tips facing the solar collector; the n-type thermoelectric material and the p-type thermoelectric material are connected via conductive electrodes and connected in series to form a complete circuit via thermal evaporation, thereby obtaining a flexible thin-film thermoelectric chip;

[0018] The solar collector and flexible thin-film thermoelectric chip are then integrated using thermal grease and conductive electrodes to obtain a low-cost, flexible, low-grade solar thermoelectric collection system.

[0019] Preferably, the mixing volume ratio of methanol and chloroform is 1:1, and the graphite-metal substrate is placed under the liquid surface at an inclination angle of 10-15°.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] A low-cost, flexible solar energy collection system has been fabricated by integrating a hybrid nanostructured solar absorber with a flexible thin-film thermoelectric chip. This solar thermoelectric collector boasts high photothermal conversion efficiency, a high degree of mechanical freedom, and conformal thermal contact with various systems. Furthermore, this invention exhibits enhanced performance at low temperatures, demonstrating its practicality. It enables energy recovery with enhanced low-temperature photothermal and thermoelectric properties, providing an important research foundation for the construction of next-generation photovoltaic-thermoelectric systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a partially enlarged schematic diagram of the hybrid nanostructured solar absorber self-assembled on the surface of copper foil-graphite film by means of nano-Fe3O4 particles in Example 1;

[0023] Figure 2 is a schematic structural diagram of the flexible thin-film thermoelectric chip in Example 1;

[0024] Figure 3 is an overall structural diagram of the low-cost flexible solar energy collection system obtained in Example 1;

[0025] Figure 4 The absorbance spectrum obtained by experimental measurement in Example 1, the trend diagram of the change of equivalent emissivity with temperature, and the temperature difference change diagram during the thermalization process;

[0026] Figure 5 1 is a comparison chart of the output voltage and output power values ​​of the flexible solar energy collection system obtained by experimental measurement in Example 1, which are compared over time at room temperature and low temperature conditions;

[0027] The accompanying drawings in the figure are marked as follows: 1. solar collector; 2. p-type thermoelectric material; 3. n-type thermoelectric material; 4. conductive electrode; 5. flexible substrate. DETAILED DESCRIPTION

[0028] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention may be combined accordingly, provided that there is no conflict between them.

[0029] The present invention provides a low-cost, flexible, low-grade solar thermoelectric collection system and its preparation method. Leveraging a densely packed photonic crystal structure, it achieves efficient solar heat absorption, effectively increasing the thermoelectromotive force across the thermoelectric structure, thereby enabling high electrical energy output under low-grade sunlight. The low-cost, flexible, low-grade solar thermoelectric collection system provided by the present invention primarily comprises a solar collector 1 and a flexible thin-film thermoelectric chip, wherein the flexible thin-film thermoelectric chip is continuously arranged around the periphery of the solar collector 1, and the two are connected via a conductive electrode 4.

[0030] The solar collector 1 is made of Fe3O4 nanoparticles deposited on the graphite surface of a graphite-metal substrate. Specifically, the Fe3O4 nanoparticles have a diameter of 510-530 nm and are deposited in a rotationally symmetrical C6 pattern on the graphite surface in a monolayer. The graphite in the graphite-metal substrate is made of graphite with a thickness of 45 nm, and the metal is made of copper with a thickness of 45-50 μm.

[0031] The flexible thin-film thermoelectric chip is formed by patterning and depositing several pairs of thermoelectric legs on a flexible substrate 5. Each pair of thermoelectric legs includes a piece of n-type thermoelectric material 3 and a piece of p-type thermoelectric material 2. Both the n-type thermoelectric material 3 and the p-type thermoelectric material 2 are conical sheet structures, and the conical tips face the solar collector 1. The n-type thermoelectric material 3 and the p-type thermoelectric material 2 in the flexible thin-film thermoelectric chip are arranged alternately, and the adjacent n-type thermoelectric materials 3 and p-type thermoelectric materials 2 are connected by conductive electrodes 4. Specifically, the material of the flexible substrate 5 is polyimide or polydimethylsiloxane with a thickness of 70-100μm; the n-type thermoelectric material 3 is Bi2Te 2.7 Se 0.3 , thickness 1μm, length 5mm, p-type thermoelectric material 2 is Bi 0.5 Sb 1.5 Te3, thickness 1 μm, length 5 mm; the material of the conductive electrode 4 is high-purity gold with a purity of not less than 99.99%.

[0032] In practical applications, the solar collector 1 and the flexible thin-film thermoelectric chip can be integrated using thermally conductive silicone grease. The solar collector 1 has a circular cross-section, while the flexible thin-film thermoelectric chip has a ring-shaped cross-section. The tapered tips of the n-type thermoelectric material 3 and the p-type thermoelectric material 2 are both oriented toward the center of the solar collector 1.

[0033] The principle of the present invention is as follows:

[0034] In nature, solar energy collection systems usually collect energy in the ultraviolet to near-infrared range and dissipate energy in the mid-infrared range. The energy accumulated in this process then produces a thermal response and is converted into electrical energy based on the Seebeck effect. It has been verified that the total efficiency of solar thermal power conversion η can be expressed as the photothermal efficiency (η OT ) and thermoelectric efficiency (η TE ), denoted as: η=η TE ·η OT .

[0035] Among them, the efficiency of the thermoelectric module can be derived as:

[0036]

[0037] Where ΔT h is the temperature rise of the hot side of the thermoelectric generator, where Th =T amb +ΔT h The same as the absorber temperature; β represents the temperature difference ΔT between the cold end and the hot end of the entire thermoelectric generator e and hot end temperature rise ΔT h When the cold end temperature is equal to the ambient temperature, T c =T amb , β reaches a maximum value of 1; Z is defined as the dimensionless quality factor of the temperature-dependent material, and n is the ratio of the external resistance to the internal resistance. It can be seen from formula (1) that the thermoelectric efficiency is related to ΔT h and T amb Therefore, lowering the ambient temperature T amb , while increasing ΔT h value, a higher thermoelectric efficiency can be obtained.

[0038] During the thermalization process, the photothermal conversion efficiency is always affected by solar energy absorption and heat loss, and the expression is:

[0039]

[0040] Where α (λ) and I (λ) They represent the monochromatic absorbance and monochromatic solar radiation intensity of the solar absorber respectively; ε eff (T h ) is the effective thermal emissivity of the absorber. Describes the radiation intensity of a black body. When the solar thermal conversion reaches equilibrium, Q te Is constant. Hot side temperature rise ΔT h Written as:

[0041]

[0042] As shown in Equation (3), high absorbance and an emissivity that is negatively correlated with temperature can increase the temperature difference when the ambient temperature decreases. Therefore, a solar absorber with selective absorption and passive suppression of thermal emissivity can quickly produce a significant temperature rise, providing the possibility of further improving thermoelectric conversion performance. Furthermore, application in low-temperature environments can also promote the promotion of this strategy and achieve better solar energy collection performance.

[0043] As can be seen from formula (1), the absorbance of the spectrum determines the magnitude of the temperature rise on the hot side of the thermoelectric generator. Therefore, the present invention designs a hybrid nanostructure composed of densely arranged nanoparticles. Even under low solar radiation flux, that is, when irradiated by low-grade sunlight, the structure can serve as a heat source for the thermoelectric generator. The nanostructure is formed by depositing a single-layer particle film (Fe3O4 nanoparticles) arranged in a C6 rotational symmetric manner on a graphite-copper substrate, achieving a high degree of structural stability in the two-dimensional structure. Although the surface of the graphite layer is rough, resulting in gaps in the single-layer Fe3O4 nanoparticle film, the hybrid nanostructure still has good solar energy absorption capacity.

[0044] Through finite element simulation and experimental measurement, the present invention studies the absorption mechanism and solar heat conversion performance of the structure.

[0045] The physical principle is that when the nanoresonator is illuminated, forward scattering in the Mie mode is enhanced, generating localized oscillation resonance within the graphite layer and Fe3O4 nanoparticles, nearly confining the electric field within them. In the near-infrared range, the primary electromagnetic attenuation and relaxation within the graphite layer produces intense thermalization, leading to a rapid increase in accumulated energy, which is further transferred to the copper layer as heat dissipation, with minimal heat exchange with the environment.

[0046] Example

[0047] This embodiment prepares a low-cost flexible low-grade solar thermoelectric collection system, including a solar collector 1 and a flexible thin-film thermoelectric chip, such as Figure 3 shown.

[0048] The solar collector 1 comprises a single layer of nano-Fe3O4 particles and a graphite-metal substrate. The graphite-metal substrate is prepared by evaporating a 45nm graphite film onto a 50μm copper foil. Subsequently, nano-Fe3O4 particles with a diameter of approximately 520nm are deposited on the substrate in the form of a single layer using an inexpensive single-layer film self-assembly technique. Figure 1 shown.

[0049] The flexible thin film thermoelectric chip consists of 12 pairs of conical p / n type thermoelectric legs and metal conductor electrodes deposited on a polyimide flexible substrate. The 1μm thick and 5mm long conical Bi 0.5 Sb 1.5 Te3 / Bi2Te 2.7 Se 0.3 The thermoelectric legs are deposited on a 75μm polyimide flexible film. Gold electrodes are deposited by thermal evaporation to connect the thermoelectric legs to the circuit. Finally, the hybrid nanostructured solar collector 1 and the flexible thin film thermoelectric chip are assembled with the help of thermal grease to achieve the energy conversion process of solar energy-thermal energy-electric energy. Figure 2 As shown, the solar collector 1 has a circular cross-section, while the flexible thin-film thermoelectric chip has a ring-shaped cross-section. The p-type thermoelectric material 2 has a taper angle of 9.4° and a length of 5 mm (with an inner and outer diameter of 6.5 mm and 11.5 mm, respectively). The n-type thermoelectric material 3 has a taper angle of 10° and a length of 5 mm (with an inner and outer diameter of 6.5 mm and 11.5 mm, respectively). The gold electrode structure 4 has a fan angle of 24.7° and a width of 1 mm (with an inner and outer diameter of 6 mm / 11 mm and 7 mm / 12 mm, respectively). The p-type thermoelectric material 2 and the n-type thermoelectric material 3 are connected to the circuit.

[0050] Flexible thin-film thermoelectric chips can stretch along temperature gradients to enhance thermoelectromotive force while maintaining mechanical flexibility. They can be implemented using simple patterning techniques and tightly integrated into single- or multi-layer circuit packages. Specifically, thermoelectric structures can induce internal shrinkage resistance and increase space utilization, resulting in higher electrical output.

[0051] The preparation method of the low-cost flexible low-grade solar thermal power collection system of this embodiment is as follows:

[0052] Step 1: Preparation of the graphite-copper substrate. A 50μm-thick copper foil is selected and treated with dilute hydrochloric acid to remove the oxide film. The copper foil is then cleaned with acetone and deionized water. To enhance the interfacial bonding between the graphite and copper layers, the copper surface is modified using a plasma cleaner (Diener PICO). A 45nm-thick graphite film is then deposited onto the copper foil using a thermal evaporation machine. Methanol is then used to modify the hydrophilicity of the graphite layer.

[0053] Step 2: Monolayer self-assembly of Fe3O4 nanoparticles. Using washing and centrifugation techniques, Fe3O4 nanoparticles were separated from the Fe3O4 magnetic nanosphere-COOH group (M20288-Aladdin) dispersion to obtain pure, dispersed Fe3O4 nanoparticles. Methanol and chloroform were then added in a 1:1 volume ratio to prepare a colloidal dispersion, which was then ultrasonically dispersed for 3 minutes. The Fe3O4 nanoparticles were then self-assembled using Langmuir-Blodgett thin film deposition, forming a uniform monolayer surface particle film at the air / water interface. The graphite-copper substrate prepared in Step 1 was then placed at a 10° tilt angle below the liquid surface where the uniform monolayer had been formed. Simultaneously, the base liquid (methanol and chloroform) was aspirated and the substrate was slowly lifted vertically, allowing the monolayer nanolayer on the water surface to deposit onto the graphite surface of the graphite-copper substrate. The base liquid removed from the graphite-copper substrate was then evaporated. In this way, a large number of Fe3O4 nanoparticles that self-assemble into a C6 pattern are coated on the substrate, and the hybrid solar absorber that acts as a heat source in the present invention is completed.

[0054] In this process, methanol is used to change the hydrophilicity and hydrophobicity, and chloroform is used as an activator to modify the surface of Fe3O4 nanoparticles. Under the action of the natural evaporation of the liquid, the nanoparticles are aggregated to form a C6 shape arrangement.

[0055] Step 3: Select a flexible polyimide substrate with a thickness of about 75 μm and place it in an ultrasonic bath and clean it thoroughly with acetone and deionized water for 10 minutes. 0.5 Sb 1.5 Te3) and n-type (Bi2Te 2.7 Se 0.3 ) Two thermoelectric materials were separately coated at specific locations on a polymer substrate for three hours. Finally, a 99.99% high-purity gold thin film (Au) was used as a conductive electrode. Using a thermal evaporation machine, multiple thermoelectric generators coated on the substrate in the previous step were connected in series to form a circuit, resulting in a flexible thin-film thermoelectric chip.

[0056] Step 4: With the help of thermal conductive silicone grease, the hybrid nanostructured solar absorber is integrated with the flexible thin-film thermoelectric chip to obtain a low-cost flexible low-grade solar thermoelectric collection system.

[0057] To demonstrate the photothermal response, a solar simulator equipped with an AM1.5G amplitude modulation filter was used as the light source, and its incident flux was measured with a calibrated power meter. A flexible, low-grade solar thermal power harvester was placed in an incubator as a test sample, under two typical conditions: a low-temperature environment (273K) and a room-temperature environment (293K). Temperature data was collected by a chip thermal sensor. The performance test results of the low-cost, flexible, low-grade solar thermal power harvester system obtained in this example, obtained in a laboratory environment, are as follows:

[0058] 1) Absorption / reflectivity

[0059] The sample's spectral reflectance, R, was measured using a spectrometer equipped with an integrating sphere across the UV-visible-near-infrared band. The absorbance, A, was calculated using the following formula: A = 1-R. The hybrid nanostructure's average spectral absorbance remained above 90% in the visible region at two different incident angles: 0° to 20° and 20° to 40°, while fluctuating downward in the near-infrared region. This demonstrates that the hybrid nanostructure is capable of achieving excellent solar energy absorption over a wide range of incident angles. Figure 4 (a) shows the experimental absorbance spectrum, which agrees well with the simulation results. As can be seen from the figure, the effective absorptivity of the hybrid solar absorber in the visible light region is close to 92%, demonstrating efficient photothermal conversion performance.

[0060] 2) Emissivity

[0061] The effective thermal emissivity of the sample in the 8-14μm band that changes with temperature is measured by an infrared hemispherical radiance meter. The lossy thermal radiation of the absorber is a key factor affecting the solar thermal conversion performance, which is related to the thermal emissivity of the absorber itself and the ambient temperature. When the temperature of the absorber rises, the thermal emission spectrum will blue-shift to the resonant frequency of the emitter. Considering that the coupling strength of the plasma emitter array will increase as the spacing between adjacent emitters decreases, the total thermal radiation will be negatively correlated with the stacking density, so the present invention uses densely arranged emitters. In this embodiment, the absorber is stably operated below 100°C through irradiation by the solar simulator. According to Wien's law, the emission spectrum is mainly located in the MIR region and overlaps with the atmospheric window region (8-14μm). Therefore, the coupling interaction between adjacent nano-emitters in the nanostructure array is studied based on the quasi-normal mode theory, and the equivalent thermal emissivity of the solar absorber changes with temperature in the MIR range (8-14μm) is studied in detail. The experimental results are as follows Figure 4 As shown in Figure 2b, the emissivity gradually decreases with increasing temperature. At the steady-state operating temperature, the far-field equivalent emissivity is always suppressed by the enclosed particles, and the thermal emissivity always remains near the extremely low value of 0.2.

[0062] 3) Temperature rise

[0063] The thermoelectric chip in the present invention generates a thermoelectric electromotive force by the Seebeck effect caused by the temperature gradient in the conductor. As can be seen from equation (1), at a lower operating temperature, the absorber can achieve a higher temperature rise and superior solar heat conversion effect.

[0064] Figure 4 Figure c shows the temperature rise of the hybrid solar absorber under solar simulator illumination at low temperature (273K) and room temperature (293K) over time. As can be seen from the figure, under illumination, the nanostructure is able to maintain a high thermal response before thermal equilibrium, with the average temperature rapidly rising to a steady state in about 120 seconds, indicating a very fast thermalization rate. However, after 120 seconds of illumination, the temperature rise of the sample increased to about 60°C at room temperature (293K), while at the lower ambient temperature (273K), the temperature rise of the sample reached about 73°C. These results indicate that the hybrid solar absorber has a fast thermalization rate, with the temperature rise being more significant at low temperatures, and has broad application prospects in low-grade solar thermoelectric harvesting.

[0065] 4) Output voltage / power

[0066] like Figure 5As shown in Figure a, after 1 minute of light exposure to the device without an external heat sink, its output voltage rises rapidly and produces a significant stable energy output. Although the thermal resistance at the junction limits the heat exchange and thermoelectric conversion performance between the solar absorber and the thermoelectric chip, the output voltage per unit irradiated area can still reach 23mV / cm at ambient temperatures of T = 273K and T = 293K, respectively. 2 and 20mV / cm 2 By multiplying the voltage and current, the total output power of the solar thermal power collection device can be calculated, as shown in Figure 5 Tests have shown that under no-load conditions, the output power per unit irradiated area can reach 18nW / cm at room temperature (293K). 2 and 24nW / cm at low temperature (273K) 2 Compared to room temperature, the output power at low temperature increases by 30%. According to formula (2), higher output efficiency can be achieved through impedance matching in practical applications. This cost-effective solar thermoelectric collector demonstrates excellent solar energy collection performance under low-grade sunlight, opening up broad prospects for the future development and application of photovoltaic-thermoelectric combined energy harvesters.

[0067] The embodiment described above is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A low-cost, flexible, low-grade solar thermal power collection system, characterized in that: The solar energy collector (1) comprises a solar energy collector (1) and a flexible thin film thermoelectric chip, wherein the flexible thin film thermoelectric chip is continuously arranged around the periphery of the solar energy collector (1), and the two are connected via a conductive electrode (4); The solar collector (1) is formed by depositing Fe3O4 nanoparticles on the graphite surface of a graphite-metal substrate; the flexible thin-film thermoelectric chip is formed by patterned deposition of a plurality of pairs of thermoelectric legs on a flexible substrate (5); each pair of the thermoelectric legs comprises a piece of n-type thermoelectric material (3) and a piece of p-type thermoelectric material (2), and both the n-type thermoelectric material (3) and the p-type thermoelectric material (2) are conical sheet structures, with the conical tips facing the solar collector (1); the n-type thermoelectric material (3) and the p-type thermoelectric material (2) in the flexible thin-film thermoelectric chip are arranged alternately, and adjacent n-type thermoelectric materials (3) and p-type thermoelectric materials (2) are connected via conductive electrodes (4); A method for preparing a low-cost, flexible, low-grade solar thermal power collection system is as follows: Fe3O4 nanoparticles are dispersed in a mixture of methanol and chloroform as a base liquid to obtain a colloidal dispersion liquid; the Fe3O4 nanoparticles in the colloidal dispersion liquid are then self-assembled using a Langmuir-Blodgett thin film deposition technique to form a monolayer surface particle film at the interface between air and liquid; a graphite-metal substrate is tilted with the graphite layer facing upward and placed below the liquid surface of the solution on which the monolayer surface particle film has been formed, while the base liquid is simultaneously sucked and the graphite-metal substrate is lifted in a vertical direction to allow the monolayer surface particle film to be deposited on the surface of the graphite-metal substrate; during the natural evaporation of the base liquid, the Fe3O4 nanoparticles gradually gather on the surface of the graphite-metal substrate and are arranged in a C6 pattern to obtain a solar collector (1); A continuous flexible substrate (5) is laid on the periphery of the solar collector (1), and an n-type thermoelectric material (3) and a p-type thermoelectric material (2) are alternately coated on the flexible substrate (5); the n-type thermoelectric material (3) and the p-type thermoelectric material (2) are both conical sheet structures, with the conical tips facing the solar collector (1); the n-type thermoelectric material (3) and the p-type thermoelectric material (2) are connected via a conductive electrode (4), and are connected in series to form a whole circuit by a thermal evaporation method, thereby obtaining a flexible thin film thermoelectric chip; Then, the solar collector (1) and the flexible thin-film thermoelectric chip are integrated using thermal grease and conductive electrodes (4) to obtain a low-cost flexible low-grade solar thermoelectric collection system.

2. A low-cost, flexible, low-grade solar thermal power collection system according to claim 1, characterized in that: The Fe3O4 nanoparticles have a diameter of 510-530 nm and are rotationally symmetrically deposited on the graphite surface in a C6 pattern in the form of a single layer of particles.

3. A low-cost, flexible, low-grade solar thermal power collection system according to claim 1, characterized in that: The graphite in the graphite-metal substrate has a thickness of 45 nm, and the metal is copper with a thickness of 45-50 μm.

4. A low-cost, flexible, low-grade solar thermal power collection system according to claim 1, characterized in that: The solar energy collector (1) and the flexible thin-film thermoelectric chip are integrated via thermally conductive silicone grease.

5. A low-cost, flexible, low-grade solar thermal power collection system according to claim 1, characterized in that: The cross section of the solar collector (1) is circular, the cross section of the flexible thin-film thermoelectric chip is an annular structure, and the conical tips of the n-type thermoelectric material (3) and the p-type thermoelectric material (2) are both oriented toward the center of the solar collector (1).

6. A low-cost, flexible, low-grade solar thermal power collection system according to claim 1, characterized in that: The material of the flexible substrate (5) is polyimide or polydimethylsiloxane, and the thickness is 70-100 μm.

7. A low-cost, flexible, low-grade solar thermal power collection system according to claim 1, characterized in that: The n-type thermoelectric material (3) is Bi2Te 2.7 Se 0.3 , thickness of 1 μm, length of 5 mm, p-type thermoelectric material (2) is Bi 0.5 Sb 1.5 Te3, thickness 1μm, length 5mm.

8. A low-cost, flexible, low-grade solar thermal power collection system according to claim 1, characterized in that: The conductive electrode (4) is made of gold.

9. A method for preparing a low-cost flexible low-grade solar thermal power collection system, characterized in that: The details are as follows: Fe3O4 nanoparticles are dispersed in a mixture of methanol and chloroform as a base liquid to obtain a colloidal dispersion liquid; the Fe3O4 nanoparticles in the colloidal dispersion liquid are then self-assembled using a Langmuir-Blodgett thin film deposition technique to form a monolayer surface particle film at the interface between air and liquid; a graphite-metal substrate is tilted with the graphite layer facing upward and placed below the liquid surface of the solution on which the monolayer surface particle film has been formed, while the base liquid is simultaneously sucked and the graphite-metal substrate is lifted in a vertical direction to allow the monolayer surface particle film to be deposited on the surface of the graphite-metal substrate; during the natural evaporation of the base liquid, the Fe3O4 nanoparticles gradually gather on the surface of the graphite-metal substrate and are arranged in a C6 pattern to obtain a solar collector (1); A continuous flexible substrate (5) is laid on the periphery of the solar collector (1), and an n-type thermoelectric material (3) and a p-type thermoelectric material (2) are alternately coated on the flexible substrate (5); the n-type thermoelectric material (3) and the p-type thermoelectric material (2) are both conical sheet structures, with the conical tips facing the solar collector (1); the n-type thermoelectric material (3) and the p-type thermoelectric material (2) are connected via a conductive electrode (4), and are connected in series to form a whole circuit by a thermal evaporation method, thereby obtaining a flexible thin film thermoelectric chip; Then, the solar collector (1) and the flexible thin-film thermoelectric chip are integrated using thermal grease and conductive electrodes (4) to obtain a low-cost flexible low-grade solar thermoelectric collection system.

10. The preparation method according to claim 9, characterized in that The mixing volume ratio of methanol and chloroform is 1:1, and the graphite-metal substrate is placed under the liquid surface at an inclination angle of 10-15°.

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