A flat plate heat absorber suitable for built-in heat source heating of planar metasurface solar concentrator lenses

Abstract

The application discloses a built-in heat source heating flat plate heat absorber suitable for a planar metasurface solar light condensing lens, which comprises a top vacuum glass cover plate, a heat preservation water storage bottom shell and a metal-dielectric-metal light heat conversion core; the top vacuum glass cover plate is sealed and adhered to the heat preservation water storage bottom shell to jointly form a heat preservation water storage box body, and the metal-dielectric-metal light heat conversion core is arranged in the heat preservation water storage box body; the planar metasurface solar light condensing lens comprises periodically arranged conductive metal micro-nano structures and a dielectric substrate layer, wherein the conductive metal layer material is Ag or Al, and the dielectric substrate layer is SiO2, Al2O3 or Ti3N4; the planar metasurface solar light condensing lens is arranged above the top vacuum glass cover plate, and sunlight is linearly focused in a transmission mode.

Description

Technical Field

[0001] This invention relates to a flat plate heat absorber suitable for heating with a built-in heat source for planar metasurface solar concentrating lenses, belonging to the field of solar thermal utilization technology. Background Technology

[0002] Metamaterials are artificial composite materials composed of subwavelength artificial microstructure units arranged in a specific sequence. Metasurfaces are two-dimensional manifestations of metamaterials. Metasurfaces are not only small in size and light in weight, but also easier to manufacture and have lower production costs. Both metamaterials and metasurfaces offer rich degrees of freedom for controlling electromagnetic waves, enabling localized manipulation of electromagnetic waves at the subwavelength scale. This allows for the realization of unique properties not found in natural materials, such as negative refractive index and strong anisotropy, leading to their widespread application and development in areas such as electromagnetic stealth, perfect absorbers, and improving antenna gain.

[0003] Solar metasurface concentrators satisfy the generalized Snell's law. By designing the phase of electromagnetic waves on the metasurface, they can achieve free control of sunlight, thus potentially replacing traditional plane mirrors and curved mirrors and becoming the next generation of solar concentrators.

[0004] Metasurfaces are typical two-dimensional materials, meaning their thickness in the Z direction is extremely small. Therefore, we only need to consider the electromagnetic wave phase distribution on the XOY plane of the planar metasurface concentrator. If the planar metasurface solar concentrator system uses linear focusing along the Y direction, the phase distribution of the electromagnetic waves on the planar metasurface concentrator remains constant along the Y direction; therefore, we only need to consider its distribution in the X direction. To achieve linear focusing solar energy, the electromagnetic wave phase distribution along the X direction... The following formula must be satisfied:

[0005]

[0006] Where x is the distance from any point on the planar metasurface solar concentrator along the X-axis to the center position x = 0, in nm; λ represents the phase distribution of the electromagnetic wave along the X direction, in rad; λ is the operating wavelength (250nm < λ < 2500nm), in nm; f(λ) is the focal length, in nm.

[0007] Since the materials and structure of the planar metasurface concentrator are already determined after the design is completed, the phase distribution on the planar metasurface is not affected by the actual operating wavelength λ. That is, the phase distribution is only determined by the design wavelength λ0, the design focal length f0, and the position x of the planar metasurface concentrator in the X direction.

[0008]

[0009] Substituting equation (2) into equation (1), we obtain equation (3):

[0010]

[0011] From equation (3), we can obtain equation (4) relating the actual focal length f(λ) to the design wavelength λ0, the design focal length f0, the actual wavelength λ, and the position x of the planar metasurface concentrator in the X direction:

[0012]

[0013] The energy flux density on the receiver is equal to the Poynting vector mode on the planar metasurface concentrator. The product of the light concentration ratio C, such as Figure 1 As shown, the focusing ratio of the metasurface concentrator is only related to the designed focal length f0 and the actual focal length f(λ). If the actual focal length f(λ) < f0, then If the actual focal length f(λ) > f0, then If the actual focal length f(λ) = f0, then C = +∞. Therefore, the concentration ratio expression for the metasurface focusing system is:

[0014] And f(λ)≠f0 (5)

[0015] Substituting equation (4) into equation (5) and rearranging, we get:

[0016] And λ0≠λ (6)

[0017] Solving equation (6) yields the variation law of the concentration ratio C of the metasurface concentrator system. From this, we conclude that as long as the actual focal length f(λ) infinitely approaches the design focal length f0, the concentration ratio C of the planar metasurface concentrator will tend towards infinity. In practical engineering applications, the concentration ratio is not limited by the solar half-angle, but only depends on the ratio of the width of the planar metasurface concentrator to the width of the heat-absorbing component. The concentration ratio is freely adjustable; therefore, the width of the heat-absorbing component can be reduced to the millimeter level, and the heat flux density on the surface of the heat absorber is extremely high. Consequently, the electromagnetic field distribution around the heat-absorbing tube will be extremely uneven, such as... Figure 2 As shown.

[0018] Based on the focusing characteristics of planar metasurface concentrators (freely adjustable concentration ratio, non-uniform electromagnetic field, and high heat flux density), developing suitable solar thermal conversion devices has become a necessary step in this field. Currently, absorbers using water, molten salt, and air as working fluids are all indirect absorbers, i.e., wall-heated absorbers. An intermediate heat exchange stage exists between solar radiation and the working fluid's heat energy, increasing thermal resistance and resulting in lower heat flux density, making them unsuitable for scenarios with high concentration ratios and high heat flux densities. Furthermore, the photothermal conversion coating on the surface of wall-heated absorbers severely affects solar thermal utilization efficiency. Therefore, it is necessary to research internal heat source solar absorbers using solid particles as the circulating working fluid.

[0019] Adding nanoparticles to the working fluid in solar thermal circulation can significantly improve the overall performance of solar collectors. Adding metal nanoparticles with plasmon resonance effects allows for efficient absorption of incident light at their resonance wavelength, resulting in better collector performance. Furthermore, specific methods can be used to ensure a uniform distribution of absorption peaks across the spectral range, absorbing different wavelengths and achieving a more uniform temperature distribution within the collector. Studies have shown that adding plasmon-rich single-component metal nanoparticles can enhance the performance of solar collectors; however, the adsorption and aggregation of nanoparticles significantly reduce the performance of solar receivers. Therefore, how to utilize the plasmon thermal effect of metal nanoparticles while simultaneously preventing their adsorption and aggregation is a pressing issue that needs to be addressed.

[0020] Metal-dielectric spectrally selective absorption coatings are composite coatings formed by incorporating nano-metal particles into a ceramic dielectric matrix. This type of coating utilizes both the excellent electrical conductivity and spectral absorption properties of metal nanoparticles, and the high-temperature resistance and structural stability of dielectrics. Furthermore, by artificially controlling the size, shape, and position of the metal nanoparticles, plasmon thermal effects can be stimulated. Similar technologies have been successfully applied to solar-powered seawater desalination and wastewater treatment. This fixed plasmon nanostructure not only effectively overcomes the adsorption and aggregation of suspended nanoparticles, but also offers greater freedom in artificially manipulating the nanostructure, resulting in higher potential for solar thermal conversion. Summary of the Invention

[0021] Based on the above technical problems, the present invention provides a flat plate heat absorber suitable for heating with a built-in heat source for planar metasurface solar concentrating lenses.

[0022] The present invention adopts the following technical solution:

[0023] A flat plate heat absorber with an internal heat source, suitable for use with a planar metasurface solar concentrating lens, comprises a top vacuum glass cover, an insulated water storage bottom shell, and a metal-dielectric-metal photothermal conversion core; the top vacuum glass cover and the insulated water storage bottom shell are sealed and bonded together to form an insulated water storage tank, and the metal-dielectric-metal photothermal conversion core is placed inside the insulated water storage tank;

[0024] The planar metasurface solar concentrator lens comprises periodically arranged conductive metal micro / nano structures and a dielectric substrate layer, wherein the conductive metal layer material is Ag or Al, and the dielectric substrate layer is SiO2, Al2O3, or Ti3N4; the planar metasurface solar concentrator lens is placed above the top vacuum glass cover plate, and sunlight is linearly focused by transmission. The focal length f0 is freely set according to requirements, preferably 15mm-20mm.

[0025] Furthermore, the planar metasurface solar concentrating lens is a two-dimensional material with dimensions of 900mm×900mm, the internal dimensions of the insulated water storage tank are 900mm×900mm×60mm, and the external dimensions of the metal-dielectric-metal photothermal conversion core 5 are 2mm×900mm×6mm.

[0026] Furthermore, multiple metal-dielectric-metal photothermal conversion cores are evenly arranged inside the insulated water storage tank to ensure a light concentration ratio of 8 to 11. Preferably, 15 metal-dielectric-metal photothermal conversion cores are evenly arranged inside the insulated water storage tank to ensure a light concentration ratio of approximately 10.

[0027] Furthermore, the insulated water storage tank includes a fixed bracket supporting the metal-dielectric-metal photothermal conversion core, an outlet, and an inlet. The insulated water storage tank is filled with a heat-absorbing working medium (water), and the heat-absorbing working medium is in direct contact with the metal-dielectric-metal photothermal conversion core to carry away heat.

[0028] Furthermore, the metal-dielectric-metal photothermal conversion core can perfectly absorb the short-wavelength solar spectrum (300nm-1200nm) and convert it into heat. Here, a portion of the heat is transferred from the surface of the metal-dielectric-metal photothermal conversion core to the heat-absorbing working medium (water) via convection heat transfer. Simultaneously, the high-temperature metal-dielectric-metal photothermal conversion core (<800℃) can radiate infrared waves, converting the short-wavelength solar energy that cannot be absorbed by the working medium (water) into long-wavelength energy that can be absorbed by the working medium (water) through thermal radiation.

[0029] Furthermore, the metal-dielectric-metal photothermal conversion core is located in the heat-absorbing medium (water) of the insulated water storage tank. The solar energy concentrated by the planar metasurface lens enters the heat-absorbing medium (water) through the top vacuum glass cover and then reaches the metal-dielectric-metal photothermal conversion core. That is, the long wavelength of the solar spectrum (>1200nm) is absorbed by the heat-absorbing medium (water) and converted into heat, while the short wavelength of the solar spectrum (300nm-1200nm) is converted into heat by the metal-dielectric-metal photothermal conversion core, thereby achieving the effect of full-band absorption and heat conversion of the solar spectrum.

[0030] Furthermore, the metal-dielectric-metal photothermal conversion core includes an all-glass encapsulated protective sleeve, a metal nanostructure array, and an intermediate dielectric layer.

[0031] Furthermore, the metal nanostructure array typically uses one or more metals such as Au, Ag, Ni, Ti, Cr, Al, W, and Cu, while the intermediate dielectric layer typically uses semiconductor materials such as ITO, SiO2, and Si3N4. The metal nanostructure array is composed of multiple metal nanostructure units arranged in an array, with an intermediate dielectric layer sandwiched between two adjacent metal nanostructure units.

[0032] Furthermore, the metal nanostructure array is located on a subwavelength scale, which can generate an electromagnetic wave diffraction enhancement effect, thereby leading to a metal plasmon enhancement effect.

[0033] Furthermore, the metal nanostructure array is preferably one or more of the following: channels, square pillars, cylinders, rings, pyramids, spheres, and combinations thereof. The size and spacing of the metal nanostructure units are 20 nm to 200 nm.

[0034] Furthermore, a shape memory alloy temperature control valve is arranged at the outlet of the insulated water storage tank. The shape memory alloy temperature control valve includes a valve body, a valve slider, a shape memory alloy spring, a conventional spring, and a water temperature sensing hole. The working principle of the shape memory alloy temperature control valve is as follows: When the insulated water tank contains cold water, the shape memory alloy spring is in a low-temperature extended shape, which closes the valve by squeezing the valve slider. At this time, the conventional spring is compressed. When the working fluid water in the insulated water tank is heated to the deformation temperature of the shape memory alloy, the hot water comes into contact with the shape memory alloy spring through the water temperature sensing hole, causing the shape memory alloy spring to be in a high-temperature contracted shape. At this time, the elastic force of the conventional spring pushes the valve slider to move to both sides, and the valve opens. The inlet of the insulated water tank is connected to the cold water supply tank. The water pressure in the cold water supply tank is higher, which pushes the hot working fluid to flow out of the insulated water tank. When the cold water fills the entire insulated water tank, the cold water also comes into contact with the shape memory alloy spring through the water temperature sensing hole. At this time, the shape memory alloy spring is in a low-temperature extended shape again, which closes the valve by squeezing the valve slider.

[0035] Beneficial effects:

[0036] Currently, solar flat plate heat absorbers all rely on the heat-absorbing coating on the outer wall of the heat-absorbing tube to absorb and convert full-spectrum solar energy into heat energy, and then rely on the heat conduction and heat convection of the outer wall to transfer the heat to the heat-absorbing fluid.

[0037] Compared with existing technologies, the flat plate absorber with built-in heat source heating suitable for planar metasurface solar concentrating lenses, as described in this invention, has the following significant advantages: 1) It can realize the full-spectrum solar photothermal conversion and utilization (the short-wavelength solar spectrum is concentrated by the planar metasurface lens, and then absorbed by the metal-dielectric-metal photothermal conversion core and converted into heat; the long-wavelength solar spectrum is directly absorbed by the water medium and converted into heat). 2) The built-in heat source heating method can effectively overcome the problem of heat radiation loss caused by heating the outer wall of the absorber tube in existing technologies (the metal-dielectric-metal photothermal conversion core is placed inside the water medium, and heat is transferred to the water medium fluid through heat conduction, heat convection and heat radiation), and at the same time, it also avoids the development, design and preparation of high absorption / low emission coatings on the outer wall of the absorber tube. 3) The metal-dielectric-metal photothermal conversion core is a fixed component, which not only utilizes the efficient photothermal conversion characteristics of nanostructured plasmons, but also solves the problems of agglomeration and wall adhesion of existing nanofluids. 4) Replacing the electromagnetic valves in existing solar water heating systems with shape memory alloy temperature control valves eliminates the need for energy consumption and additional drive components, resulting in greater energy efficiency and reliability. 5) Existing solar flat-plate absorbers consist of absorber tubes within which the water medium flows. The space between the absorber tubes and the casing is unusable, limiting their application to solar heat absorption. The flat-plate absorber proposed in this invention not only functions as a solar heat absorption device but also as a hot water storage device, simplifying the solar water heating system and saving on initial and operational costs. Attached Figure Description

[0038] Figure 1 Schematic diagram of the relationship between focal length and light spot in a metasurface focusing system;

[0039] Figure 2 Schematic diagram of electric field intensity distribution in a planar metasurface lens focusing system;

[0040] Figure 3 Overall structural diagram of a flat plate heat absorber with built-in heat source;

[0041] Figure 4 Diagram of the metal-dielectric-metal photothermal conversion core structure;

[0042] Figure 5 Structure diagram of a shape memory alloy temperature control valve.

[0043] In the diagram, 1-sunlight, 2-planar metasurface solar concentrator lens, 3-top vacuum glass cover, 4-insulated water storage bottom shell, 5-metal-dielectric-metal photothermal conversion core, 21-conductive metal micro / nano structure, 22-dielectric substrate layer, 41-fixed bracket, 42-outlet, 43-inlet, 44-shape memory alloy temperature control valve, valve body 441, valve slider 442, shape memory alloy spring 443, conventional spring 444, water temperature sensing hole 445, 51 all-glass encapsulated protective sleeve, 52 metal nanostructure array, 53 intermediate dielectric layer. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. However, the following embodiments are only for explaining the present invention, and the scope of protection of the present invention should include all the contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement all the contents of the claims of the present invention.

[0045] Based on the above technical problems, this invention provides a flat plate heat absorber suitable for heating with a built-in heat source in a planar metasurface solar concentrating lens, such as... Figure 3 As shown.

[0046] The flat plate heat absorber with built-in heat source heating includes a top vacuum glass cover 3, an insulated water storage bottom shell 4, and a metal-dielectric-metal photothermal conversion core 5. The top vacuum glass cover 3 and the insulated water storage bottom shell 4 are sealed and bonded together to form an insulated water storage tank, and the metal-dielectric-metal photothermal conversion core 5 is placed inside the insulated water storage tank.

[0047] The planar metasurface solar concentrator lens 2 comprises periodically arranged conductive metal micro / nano structures 21 and a dielectric substrate layer 22, wherein the conductive metal layer is made of Ag or Al, and the dielectric substrate layer is made of SiO2, Al2O3, or Ti3N4. The planar metasurface solar concentrator lens 2 is placed above the top vacuum glass cover plate 3, and sunlight 1 is linearly focused via transmission. The focal length f0 is freely set as needed, preferably 15mm-20mm. The periodically arranged conductive metal micro / nano structures 21 are located on the dielectric substrate layer 22.

[0048] The planar metasurface solar concentrating lens 2 is made of two-dimensional material and measures 900mm × 900mm. The internal dimensions of the insulated water storage tank are 900mm × 900mm × 60mm, and the external dimensions of the metal-dielectric-metal photothermal conversion core 5 are 2mm × 900mm × 6mm. Fifteen of these metal-dielectric-metal photothermal conversion cores are evenly arranged within the insulated water storage tank to ensure a concentration ratio of approximately 10.

[0049] The insulated water storage tank 4 includes a fixed bracket 41 supporting the metal-dielectric-metal photothermal conversion core 5, a water outlet 42, and a water inlet 43. The insulated water storage tank is filled with a heat-absorbing working medium (water), and the heat-absorbing working medium is in direct contact with the metal-dielectric-metal photothermal conversion core 5 to carry away heat.

[0050] The metal-dielectric-metal photothermal conversion core 5 can perfectly absorb the short-wavelength solar spectrum (300nm-1200nm) and convert it into heat. Here, a portion of the heat is transferred from the surface of the metal-dielectric-metal photothermal conversion core 5 to the heat-absorbing working medium (water) via convection heat transfer. At the same time, the high-temperature metal-dielectric-metal photothermal conversion core 5 (<800℃) can radiate infrared waves, converting the short-wavelength solar energy that cannot be absorbed by the working medium water into long-wavelength energy that can be absorbed by the working medium water through thermal radiation.

[0051] In addition, the metal-dielectric-metal photothermal conversion core 5 is located in the heat-absorbing medium (water) of the insulated water storage tank. The solar energy concentrated by the planar metasurface solar concentrator lens 2 enters the heat-absorbing medium (water) through the top vacuum glass cover 3, and then reaches the metal-dielectric-metal photothermal conversion core 5. That is, the long wavelength of the solar spectrum (>1200nm) is absorbed by the heat-absorbing medium (water) and converted into heat, while the short wavelength of the solar spectrum (300nm-1200nm) is converted into heat by the metal-dielectric-metal photothermal conversion core 5, thereby achieving the effect of full-band absorption and heat conversion of the solar spectrum.

[0052] The metal-dielectric-metal photothermal conversion core 5 includes a fully glass-encapsulated protective sleeve 51, a metal nanostructure array 52, and an intermediate dielectric layer 53. The metal nanostructure array and the intermediate dielectric layer are all located inside the fully glass-encapsulated protective sleeve. Figure 4 As shown. The metal nanostructure array 52 generally uses one or more metals such as Au, Ag, Ni, Ti, Cr, Al, W, Cu, etc., and the intermediate dielectric layer 53 generally uses semiconductor materials such as ITO, SiO2, Si3N4, etc.

[0053] The metal nanostructure array 52 is located on a subwavelength scale, which can generate electromagnetic wave diffraction enhancement effect, thereby leading to metal plasmon enhancement effect. The metal nanostructure array 52 is preferably a channel, square pillar, cylindrical, ring, pyramid, spherical, or a combination thereof. The size and spacing of the metal nanostructure units are 20nm-200nm. An intermediate dielectric layer 53 is located between two adjacent metal nanostructure units. Multiple metal nanostructure units are arranged in an array to form the metal nanostructure array 52.

[0054] A shape memory alloy temperature control valve 44 is arranged at the outlet of the insulated water storage tank, including a valve body 441, a valve slider 442, a shape memory alloy spring 443, a conventional spring 444, and a water temperature sensing hole 445. Figure 5 As shown. The working principle of the shape memory alloy temperature control valve 44 is as follows: When the water in the insulated water tank is cold, the shape memory alloy spring 443 is in a low-temperature extended shape, which closes the valve by squeezing the valve slider 442. At this time, the conventional spring 444 is compressed. When the working fluid water in the insulated water tank is heated to the shape memory alloy deformation temperature, the hot water comes into contact with the shape memory alloy spring 443 through the water temperature sensing hole 445, causing the shape memory alloy spring 443 to be in a high-temperature contracted shape. At this time, the... The elastic force of the conventional spring 444 pushes the valve slider 442 to move to both sides, opening the valve. The inlet 43 of the insulated water storage tank is connected to the cold water supply tank. The water pressure in the cold water supply tank is higher, which pushes the hot water working fluid out of the insulated water storage tank. When the cold water fills the entire insulated water storage tank, the cold water also comes into contact with the shape memory alloy spring 443 through the water temperature sensing hole 445. At this time, the shape memory alloy spring 443 is in a low-temperature stretched shape, which closes the valve by squeezing the valve slider 442.

[0055] The parts of this invention not described in detail are well-known to those skilled in the art. The embodiments described above are merely preferred embodiments of the invention, and do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Various modifications and improvements to the technical solutions of this invention made by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims of this invention.

Claims

1. A flat plate heat absorber suitable for heating a planar metasurface solar concentrating lens with a built-in heat source, characterized in that, The flat plate heat absorber with built-in heat source includes a top vacuum glass cover, an insulated water storage bottom shell, and a metal-dielectric-metal photothermal conversion core; the top vacuum glass cover and the insulated water storage bottom shell are sealed and bonded together to form an insulated water storage tank, and the metal-dielectric-metal photothermal conversion core is placed inside the insulated water storage tank. The planar metasurface solar concentrator lens comprises periodically arranged conductive metal micro / nano structures and a dielectric substrate layer, wherein the conductive metal micro / nano structure material is Ag or Al, and the dielectric substrate layer is SiO2, Al2O3, or Ti3N4; the planar metasurface solar concentrator lens is placed above the top vacuum glass cover plate, and sunlight is linearly focused by transmission. The metal-dielectric-metal photothermal conversion core includes a full glass encapsulation protective sleeve, a metal nanostructure array, and an intermediate dielectric layer. The metal nanostructure array and the intermediate dielectric layer are both located inside the full glass encapsulation protective sleeve. The metal nanostructure array is composed of multiple metal nanostructure units arranged in an array, with an intermediate dielectric layer sandwiched between two adjacent metal nanostructure units. The array of metal nanostructures is located on a subwavelength scale, which can generate an electromagnetic wave diffraction enhancement effect, thereby leading to a metal plasmon enhancement effect.

2. The heat absorber according to claim 1, characterized in that, The planar metasurface solar concentrator lens is made of a two-dimensional material.

3. The heat absorber according to claim 1, characterized in that, Multiple metal-dielectric-metal photothermal conversion cores are evenly arranged inside the insulated water storage tank to ensure a light concentration ratio of 8 to 11.

4. The heat absorber according to claim 1, characterized in that, The insulated water storage tank includes a fixed bracket supporting the metal-dielectric-metal photothermal conversion core, a water outlet, and a water inlet. The insulated water storage tank is filled with a heat-absorbing working medium, and the heat-absorbing working medium is in direct contact with the metal-dielectric-metal photothermal conversion core to carry away the heat.

5. The heat absorber according to claim 1, characterized in that, The metal nanostructure array is one or more of the following: channel, square column, cylindrical, ring, pyramid, spherical, and combined structures.

6. The heat absorber according to claim 1, characterized in that, A shape memory alloy temperature control valve is arranged at the water outlet of the insulated water storage tank. The shape memory alloy temperature control valve includes a valve body, a valve slider, a shape memory alloy spring, a conventional spring, and a water temperature sensing hole.

7. The heat absorber according to claim 6, characterized in that, The working principle of the shape memory alloy temperature control valve is as follows: When the insulated water tank contains cold water, the shape memory alloy spring is in a low-temperature extended shape, which closes the valve by squeezing the valve slider. At this time, the conventional spring is compressed. When the working fluid water in the insulated water tank is heated to the shape memory alloy deformation temperature, the hot water comes into contact with the shape memory alloy spring through the water temperature sensing hole, causing the shape memory alloy spring to be in a high-temperature contracted shape. At this time, the elastic force of the conventional spring pushes the valve slider to move to both sides, and the valve opens. The inlet of the insulated water tank is connected to the cold water supply tank. The water pressure in the cold water supply tank is higher, which pushes the hot working fluid out of the insulated water tank. When the cold water fills the entire insulated water tank, the cold water also comes into contact with the shape memory alloy spring through the water temperature sensing hole. At this time, the shape memory alloy spring is in a low-temperature extended shape again, which closes the valve by squeezing the valve slider.

8. The heat absorber according to claim 1, characterized in that, The metal nanostructure array uses one or more metals selected from Au, Ag, Ni, Ti, Cr, Al, W, and Cu, and the intermediate dielectric layer uses ITO, SiO2, or Si3N4.

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