Thermoelectric cement-based precast wall based on 3D printing and manufacturing method

Abstract

The application discloses a kind of thermoelectric cement-based prefabricated wall based on 3D printing and manufacturing method, and thermoelectric cement-based prefabricated wall includes wall body, outer surface vertical conductive band, inner surface vertical conductive band, horizontal conductive mesh and conductive terminal;Wall body is integrally formed by N-type thermoelectric cement-based composite material and P-type thermoelectric cement-based composite material by 3D printing;The printing path of 3D printing is set to along the thickness direction of wall, so that continuous material strip from the outer surface to the inner surface of wall is formed in each printing layer, and the continuous material strip constitutes directional heat transfer channel.The application realizes the integration design of heat transfer optimization and thermoelectric conversion, simple structure, adapts 3D printing process, and can be widely applied to building external wall and self-powered component.

Description

Technical Field

[0001] This invention relates to the field of prefabricated building and building functional materials technology, specifically to a thermoelectric cement-based prefabricated wall panel based on a 3D-printed directional heat transfer structure and its assembly and connection method, and more particularly to a prefabricated wall panel structure and its construction technology that combines building envelope, heat collection, power output, assembly and connection and electrical current collection functions. Background Technology

[0002] With the development of industrialized construction and low-carbon buildings, the functional upgrading of building envelopes has become a research hotspot. Meanwhile, building envelopes are constantly exposed to the outdoor environment, subjected to solar radiation, ambient temperature differences, and indoor-outdoor heat exchange, possessing considerable potential for heat energy harvesting. If heat energy can be converted into electrical energy using the wall material itself, it can provide auxiliary power for building monitoring sensors, wireless data acquisition nodes, or low-power electrical appliances without occupying additional building space, thereby enhancing the functional added value of the building envelope.

[0003] Existing thermoelectric conversion technologies mostly rely on independent metal or semiconductor thermoelectric devices, which have high manufacturing costs and poor integration with the main building structure, making it difficult to achieve large-area, low-cost, and long-term stable integrated building applications. In recent years, the development of thermoelectric cement-based composite materials has provided a new technical path for the functionalization of building structural materials. However, existing research on thermoelectric cement-based materials mainly focuses on improving material proportions, electrical conductivity, or thermoelectric performance itself, lacking systematic technical solutions that combine with prefabricated wall panel structures, component manufacturing methods, and assembly connection methods. In particular, it has not solved practical problems such as electrical lead-out, node continuity, and corrosion prevention and insulation in the industrial prefabrication and on-site assembly process of thermoelectric functional wall panels.

[0004] Traditional precast wall panel molding processes have limited control over complex heated surfaces, internal heat flow channels, and integrated joint structures, making it difficult to simultaneously address heat harvesting efficiency, internal heat transfer efficiency, prefabricated connection requirements, and electrical outgoing requirements. Existing precast wall panel joint technologies typically focus only on load-bearing connections, waterproof sealing, and ease of installation, while giving less consideration to how to achieve electrical convergence between wall panels with thermoelectric functions, how to ensure the reliability of electrical connections, and how to coordinate construction with structural connections.

[0005] 3D printing concrete technology has unique advantages such as controllable path, free forming, efficient manufacturing of complex surfaces, and integrated molding of functional areas. It can provide new means for the external surface enhancement design of thermoelectric cement-based precast wall panels, the construction of internal directional heat transfer structures, and the collaborative manufacturing of connection nodes and electrical busbar structures.

[0006] The existing application (CN120625764A), "A self-powered energy storage temperature-regulating concrete wall and its control and manufacturing methods," although employing a 3D-printed hollow frame, has the following problems: 1. The heat transfer path depends on the phase change heat transfer of the phase change hydrogel, and the direction of heat flow is not actively guided.

[0007] 2. The multi-layered composite structure of "frame + grouting + casting" is adopted, which is complex to manufacture and has thermal resistance and electrical conductivity loss at the interface of different materials.

[0008] 3. The outer surface of the wall is a planar structure, and the heat-receiving area has not been specifically optimized.

[0009] 4. It requires multiple steps of grouting, fixing, and pouring, making the process complex.

[0010] 5. The core of the existing application scheme is phase change energy storage and temperature regulation, with thermoelectric conversion as an auxiliary function. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a 3D-printed thermoelectric cement-based prefabricated wall that improves thermoelectric conversion efficiency.

[0012] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: This invention first provides a 3D-printed thermoelectric cement-based precast wall, comprising: The main body of the wall is integrally formed by 3D printing using N-type thermoelectric cement-based composite material and P-type thermoelectric cement-based composite material. The printing path of the 3D printing is set along the thickness direction of the wall, so that each printed layer forms a continuous material strip from the outer surface to the inner surface of the wall, and the continuous material strip constitutes a directional heat transfer channel. The printed layers are stacked one after another along the height direction of the wall, and are alternately set as N-type thermoelectric layers formed by printing N-type thermoelectric cement-based composite material and P-type thermoelectric layers formed by printing P-type thermoelectric cement-based composite material. Both N-type thermoelectric layers and P-type thermoelectric layers are single-layer 3D printed layers, and the material within the same thermoelectric layer is uniform. Adjacent N-type thermoelectric layers and P-type thermoelectric layers form a layer group. Vertical conductive strips are set on the outer surface of the wall body along the height direction, corresponding one-to-one with each layer group; each vertical conductive strip on the outer surface is electrically connected to the hot end of the corresponding layer group. Vertical conductive strips are set on the inner surface of the wall body along the height direction, corresponding one-to-one with each layer group; each vertical conductive strip on the inner surface is electrically connected to the cold end of the corresponding layer group. A horizontal conductive mesh is set in the top layer of the wall body as a current-collecting electrode. The current-collecting electrode connects the vertical conductive strip on the inner surface of the upper layer to the vertical conductive strip on the outer surface of the lower layer in series, so that all N-type thermoelectric layers and P-type thermoelectric layers are electrically connected in series alternately to form a thermoelectric power generation module. A conductive terminal is disposed on the top of the wall body. The conductive terminal is electrically connected to both ends of the bus electrode and is used to draw out electrical energy.

[0013] Both the outer and inner vertical conductive strips are metal mesh sheets, extending along the wall thickness direction to the two sides of the layer, and are spaced at preset conductive nodes along the wall length direction.

[0014] The mesh size and wire diameter of the metal mesh are selected to be suitable for concrete bonding and to form a reliable mechanical anchorage with the substrate.

[0015] The N-type thermoelectric cement-based composite material is a cement-based material doped with an N-type dopant, and the P-type thermoelectric cement-based composite material is a cement-based material doped with a P-type dopant. The N-type dopant is selected from one or a combination of zinc oxide and iron oxide; the P-type dopant is selected from one or a combination of carbon nanotubes and graphene; the doping amount of the N-type dopant is 0.5% to 5% of the cement mass, and the doping amount of the P-type dopant is 0.5% to 5% of the cement mass.

[0016] The conductive terminal is made of copper alloy with a silver-plated surface and is embedded in a pre-set groove at the top of the wall. The groove is filled with waterproof sealant. The conductive terminal is electrically connected to the horizontal conductive mesh through lead wires, and the lead wires are wrapped with an insulating protective layer.

[0017] The outer surface of the main wall body adopts a curved shape as a heat-enhancing structure to increase the heat exchange area between the wall and the external environment.

[0018] The present invention also provides a method for manufacturing a thermoelectric cement-based precast wall, comprising the following steps: Step 1: Prepare N-type thermoelectric cement-based composite material, P-type thermoelectric cement-based composite material, and conductive metal mesh respectively; the conductive metal mesh includes vertical metal mesh and horizontal metal mesh; Step 2: Set 3D printing parameters, including printing path, printing layer height, and printing speed; Step 3: Print layer by layer according to the 3D printing parameters set in Step 2, and implant vertical and horizontal metal meshes in the corresponding printing layers; Step 4: Weld lead wires to both ends of the horizontal conductive mesh and connect them to the conductive terminals installed at preset points at the top and bottom of the wall. Step 5: Curing the printed wall.

[0019] Step 3 is performed as follows: After each thermoelectric layer is printed, vertical metal mesh sheets are implanted at preset conductive nodes on the outer and inner surfaces of that thermoelectric layer, serving as vertical conductive strips. The vertical metal mesh sheets overlap adjacent N-type and P-type thermoelectric layers in height, realizing the electrical connection between the upper and lower thermoelectric layers. The vertical conductive strips are perpendicular to the wall thickness direction and are spaced at preset conductive nodes along the wall length direction. The inner side of the vertical metal mesh sheets is tightly bonded to the thermoelectric cement-based composite material, and initial fixation is achieved by the adhesiveness of the 3D printed concrete material, forming a reliable bonded structure after subsequent curing. After all layers are printed, a horizontal metal mesh is placed at the top of the vertical metal mesh on the inner surface of the top layer. This horizontal metal mesh is placed between the thermoelectric layers and electrically connected to the vertical metal mesh on the inner surface of the top layer to form a top busbar electrode, which serves as the negative output terminal of the thermoelectric power generation module. A bottom metal mesh is placed at the bottom of the vertical metal mesh on the outer surface of the bottom layer. This bottom metal mesh is placed between the thermoelectric layers and electrically connected to the vertical metal mesh on the outer surface of the bottom layer to form a bottom busbar electrode, which serves as the positive output terminal of the thermoelectric power generation module. The top busbar electrode extends to a predetermined conductive area at the top of the wall, and the bottom busbar electrode extends to a predetermined conductive area at the bottom of the wall. The 3D printing parameters are set as follows: spindle speed 1r / s, printing speed 20-30mm / s, and layer height 10-15mm.

[0020] Compared with the prior art, the beneficial effects of the present invention are: 1. Unlike the disordered heat transfer design of existing casting processes, this invention sets the 3D printing path along the wall thickness direction to form a continuous material strip from the outer surface to the inner surface, which effectively reduces the interlayer interface thermal resistance and constructs a priority heat transfer channel. At the same time, combined with the area expansion effect of the outer surface heat-enhancing structure, it significantly improves the efficiency of heat acquisition and conduction.

[0021] 2. By alternately setting single-layer N-type and P-type thermoelectric layers along the height of the wall, combined with the end face overlap design of the vertical conductive strip and the current convergence integration of the horizontal conductive mesh, no additional horizontal conductive components or reserved channels are required. This ensures the reliable series connection of the NP thermocouple string and reduces the contact resistance through surface contact connection, avoiding the risk of short circuit. This solves the core pain point of easy failure of conductive structure in the existing technology.

[0022] 3. The horizontal conductive mesh can be directly laid after all thermoelectric layers are printed, similar to the installation process of steel mesh in construction. It eliminates the need for complex pre-drilling or wiring operations, achieving integrated molding of the main wall structure and the conductive structure, simplifying the manufacturing process and improving industrial feasibility. At the same time, the horizontal conductive mesh serves as both a current-collecting electrode and a structural reinforcing rib, enhancing the overall integrity of the top structure of the wall while achieving efficient energy collection. Moreover, the solution eliminates unnecessary composite functions, focusing on the core needs of thermoelectric conversion. The structure is simplified and the cost is controllable. It can be directly used as an external wall cladding for buildings, providing stable power for low-power devices. It has a wide range of applications and conforms to the development trend of "functional integration, practicality and reliability" in building components.

[0023] 4. The manufacturing process of this invention is highly compatible with existing 3D printing concrete processes, and the groove and waterproof sealant design of the conductive terminals are adapted to the on-site connection requirements of prefabricated buildings, solving the practical engineering problems of electrical lead-out and node conduction of thermoelectric functional wall panels.

[0024] 5. This invention does not rely on phase change materials, but directly optimizes thermoelectric conversion efficiency through directional heat transfer structures, heat-enhancing structures, and high-efficiency conductive busbar systems. This design approach is simpler, lower in cost, and has better long-term stability, making it suitable for building envelope scenarios where power generation is the primary objective.

[0025] 6. This invention directly uses N-type and P-type thermoelectric cement-based composite materials as the main wall material. Single-layer N-type and P-type thermoelectric layers are alternately stacked along the height direction using 3D printed concrete technology, achieving integration of thermoelectric function and structural load-bearing function. Compared with existing technologies, the structure is simpler, has fewer interfaces, and is more efficient in manufacturing.

[0026] 7. The present invention sets complex geometric structures such as wave-shaped, undulating, and curved shapes on the outer surface of the wall, which significantly increases the heat exchange area within a limited projected area, improves the convective heat exchange efficiency of solar radiation and hot air, thereby increasing the temperature difference between the hot end and the cold end, and enhancing the power generation capacity. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a method for constructing a precast wall based on 3D printing thermoelectric cement in an embodiment of this application.

[0028] Figure 2 This is a three-dimensional schematic diagram of the overall structure of the 3D-printed thermoelectric cement-based wall in the embodiments of this application.

[0029] Figure 3 This is a schematic diagram of N-type and P-type thermoelectric cement base layers connected in series in an embodiment of this application, where a is a top perspective view, b is a bottom side view, and c is a heat transfer direction diagram.

[0030] Figure 4This is a schematic diagram of the series connection of the prefabricated wall thermoelectric modules in the embodiments of this application.

[0031] Figure 5 This is the potential diagram of the 3D printing module of the present invention; Figure 6 This is a diagram showing the overall heat flux of the 3D-printed thermoelectric module of the present invention. Figure 7 This is a heat flux diagram of the Y-axis of the 3D-printed thermoelectric module of this invention; Figure 8 This is a diagram showing the Y-axis current density of the 3D-printed thermoelectric module of this invention. Figure 9 Potential diagram of cast-in-place module; Figure 10 This is a diagram showing the overall heat flux of the cast-in-place thermoelectric module. Figure 11 The diagram shows the Y-direction heat flux of the cast-in-place thermoelectric module. Figure 12 This is a diagram showing the Y-direction current density of a 3D-printed thermoelectric module.

[0032] In the diagram: 1. Main wall structure; 2. Continuous material strip; 3. Conductive terminal; 4. Horizontal conductive mesh; 5. Vertical metal mesh; 6. N-type thermoelectric layer; 7. P-type thermoelectric layer; 8. Bottom bus electrode; 9. Top bus electrode; 10. Lead-out wire. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the following embodiments are only used to explain this application and do not constitute a limitation on the scope of protection of this application.

[0034] Example 1 This embodiment provides a 3D-printed thermoelectric cement-based precast wall. It includes: The wall body 1 is integrally formed by 3D printing using N-type thermoelectric cement-based composite material and P-type thermoelectric cement-based composite material. The printing path of the 3D printing is set along the thickness direction of the wall, so that each printed layer forms a continuous material strip 2 from the outer surface to the inner surface of the wall. Each continuous material strip 2 constitutes a directional heat transfer channel. The printed layers are stacked layer by layer along the height direction of the wall, and N-type thermoelectric layer 6 and P-type thermoelectric layer 7 are alternately set along the height direction. Both N-type thermoelectric layer 6 and P-type thermoelectric layer 7 are single-layer 3D printed layers, and the material in the same thermoelectric layer is uniform. Vertical conductive strips on the outer surface are set on the outer surface of the main wall 1 along the height direction, corresponding one-to-one with each layer group; each vertical conductive strip on the outer surface is electrically connected to the hot end of the corresponding layer group. Vertical conductive strips on the inner surface are set on the inner surface of the wall body 1 along the height direction, corresponding one-to-one with each layer group; each vertical conductive strip on the inner surface is electrically connected to the cold end of the corresponding layer group. The horizontal conductive mesh 4 is set in the top layer of the wall body as a current-collecting electrode. The current-collecting electrode connects the vertical conductive strip on the inner surface of the upper layer to the vertical conductive strip on the outer surface of the lower layer in series, so that all N-type thermoelectric layers and P-type thermoelectric layers are electrically connected in series alternately to form a thermoelectric power generation module. Conductive terminal 3 is installed at the top of the wall body 1. The conductive terminal is electrically connected to both ends of the bus electrode and is used to draw out electrical energy.

[0035] Both the outer and inner vertical conductive strips are vertical metal mesh 5, extending along the wall thickness direction to the two sides of the layer, and are spaced at preset conductive nodes along the wall length direction.

[0036] The mesh size and wire diameter of the vertical metal mesh 5 are selected to be suitable for concrete bonding and to form a reliable mechanical anchorage with the substrate.

[0037] N-type thermoelectric cement-based composite material is a cement-based material doped with N-type dopants, while P-type thermoelectric cement-based composite material is a cement-based material doped with P-type dopants. The N-type dopant is selected from one or a combination of zinc oxide and iron oxide; the P-type dopant is selected from one or a combination of carbon nanotubes and graphene; the doping amount of the N-type dopant is 0.5% to 5% of the cement mass, and the doping amount of the P-type dopant is 0.5% to 5% of the cement mass.

[0038] The conductive terminals are made of copper alloy with a silver-plated surface. They are embedded in a pre-set groove at the top of the wall, and the groove is filled with waterproof sealant. The conductive terminals are electrically connected to the horizontal conductive mesh through lead-out wires, and the lead-out wires are wrapped with an insulating protective layer.

[0039] The outer surface of the main wall adopts a curved shape as a heat-enhancing structure to increase the heat exchange area between the wall and the external environment.

[0040] Example 2 This embodiment provides a method for manufacturing a thermoelectric cement-based precast wall, including the following steps: Step 1: Prepare N-type thermoelectric cement-based composite materials and P-type thermoelectric cement-based composite materials respectively to ensure that their thermoelectric properties meet the requirements and are compatible with the 3D printing process; at the same time, select corrosion-resistant and highly conductive metal materials to prepare vertical metal mesh and horizontal conductive mesh. The N-type thermoelectric cement-based composite material is made by incorporating N-type admixtures (such as zinc oxide and iron oxide) into a cement matrix; the P-type thermoelectric cement-based composite material is made by incorporating P-type admixtures (such as carbon nanotubes and graphene) into a cement matrix. Both materials need to possess good 3D printing performance, with a flowability controlled at 160-180 mm and an initial setting time controlled at 30-60 minutes, which can be adjusted by adding admixtures such as water-reducing agents and cellulose ethers.

[0041] The vertical metal mesh 5 and the horizontal conductive mesh 4 are made of 304 stainless steel, with a conductivity ≥1.37×10⁻⁶. 6 S / m, tensile strength ≥520MPa. The vertical metal mesh 5 has a rectangular mesh structure with a wire diameter of 0.5-1.0mm, a mesh size of 5-10mm, and a width of 20-40mm. The horizontal conductive mesh 4 has a mesh size of 15mm×15mm and is laid above the thermoelectric layer (i.e., between the printed strip layers). The edges of the horizontal conductive mesh 4 are recessed 8mm into the side of the wall. The overlap length with each vertical metal mesh 5 is 15mm, and it is bonded and fixed using conductive adhesive or other methods. Step 2: Set the 3D printing path so that the printing direction is along the thickness direction of the wall body 1 (e.g., ...). Figure 2 As shown, Figure 2 The printing path, marked by the middle arrow, extends along the thickness of the wall, and the strips printed along the thickness direction form directional heat transfer channels. The alternating sequence of N-type thermoelectric layer 6--P-type thermoelectric layer 7--N-type thermoelectric layer 6 is planned according to the height of the wall. The 3D printing parameters are set as follows: spindle speed 1r / s, printing speed 20-30mm / s, and layer height 10-15mm.

[0042] Step 3: Print each layer in the planned order. After printing each layer, insert vertical metal mesh 5 at the preset conductive nodes on the outer and inner surfaces of the layer. The vertical metal mesh is set perpendicular to the wall thickness and inserted into the concrete strip of the corresponding layer group, intersecting perpendicularly with the printed strip of the layer group. When inserting, the lower end of the vertical metal mesh is inserted into the uncured concrete of the current layer group to a depth of 1 / 3 to 1 / 2 of the height of the vertical metal mesh, and the material adhesion is used to achieve initial fixation.

[0043] In this process, after printing the first thermoelectric layer, a horizontal conductive mesh 4 is placed and connected to the corresponding vertical metal mesh 5 on the outer surface to form a bottom bus electrode 8. After all layers are printed, a horizontal conductive mesh 4 is placed between the topmost layers and connected to the upper end of the corresponding vertical metal mesh 5 on the inner surface to form a top bus electrode 9. Finally, a complete thermocouple string structure is formed (e.g., ...). Figure 3 ).

[0044] When the bottom horizontal conductive mesh 4 is placed, it should be in direct contact (lapped, pressed, or welded) with the corresponding vertical metal mesh 5 (when the top horizontal conductive mesh 4 is placed, it should be in direct contact with the corresponding vertical metal mesh 5) to form a reliable electrical connection between the metals. Conductive adhesive can also be applied at the contact points to enhance the connection reliability. Finally, a complete conductive path is constructed: "bottom bus electrode 8 → bottom vertical metal mesh 5 → N / P thermoelectric layer → top vertical metal mesh 5 → top bus electrode 9" (e.g., ...). Figure 4 ).

[0045] Step 4: Weld lead wires 10 to the left and right ends of the horizontal conductive mesh 4. The outer insulation layer of the lead wires 10 is used to ensure that there is no conductive interference with the concrete. Install conductive terminals 3 at the preset points at the top of the wall body 1. Weld the free end of the lead wires 10 to the inner end of the conductive terminals 3 and fix them. Then fill with silicone waterproof sealant to cover the joints of the conductive terminals 3 and the lead wires 10 to complete the sealing.

[0046] The wall surface is encapsulated using waterproof mortar, and the area where the transverse conductive components are installed at the ends is sealed and reinforced with high-performance cement-based waterproof coating.

[0047] Step 5: Place the wall in a standard curing room for 28 days. During the curing period, apply conductive anti-rust paint to the exposed surfaces of the conductive terminals to prevent oxidation and corrosion.

[0048] To verify the performance advantages of the 3D-printed concrete thermoelectric module of this invention, and considering that actual wall structures are composed of multiple thermoelectric module units, this embodiment selects the core thermoelectric module unit in the wall structure as the simulation object to simplify simulation calculations, improve simulation efficiency, and ensure the representativeness of the verification results. A thermoelectric coupling simulation model is established using finite element simulation software, and comparative simulation analyses are performed on the 3D-printed and conventionally cast-in-place concrete thermoelectric module units. Except for the different concrete matrix forming methods and internal anisotropic transport characteristics, the two models are completely consistent in terms of geometric dimensions, electrode settings, material parameters, and boundary conditions, ensuring the objectivity and validity of the comparison results.

[0049] In the simulation model, the overall dimensions of the thermoelectric module are 150mm long, 100mm wide, and 30mm high. Two vertical conductive electrodes are placed at each end of the module along its length, located at the center of the end faces in the Y-direction. Each electrode measures 20mm long, 15mm wide, and 0.1mm thick, completely covering the corresponding end faces of the module and forming ohmic contact with the concrete substrate. Contact resistance is not considered. During the simulation, both models use the same temperature boundary conditions. Hot and cold end temperatures are set at the two ends of the module to create a stable temperature gradient. The electrical boundary is set as an open circuit, with one electrode grounded and the other electrode set as an insulated boundary with no external current output, in order to measure the open-circuit voltage of the module.

[0050] Ordinary cast-in-place concrete modules use isotropic material parameters, while 3D-printed concrete modules, based on the printed oriented strip structure, are endowed with anisotropic thermal and electrical conductivity parameters enhanced in the Y direction. Other basic material parameters such as density and specific heat capacity remain consistent between the two models. Simulations yielded the potential and internal Y-direction heat flux and current density distribution cloud maps for both models. Comparative results show that, under the same temperature gradient and operating conditions, the potential value of the 3D-printed concrete precast thermoelectric module unit is 69.2% higher than that of the ordinary cast-in-place concrete thermoelectric module (e.g., ...). Figure 5 , Figure 9 ), Heat flux contour map from the Y direction (e.g.) Figure 7 , Figure 11 As can be seen, the heat flux in the Y direction of the cast-in-place concrete module is significantly higher. This is because its isotropic nature causes a large amount of lateral diffusion and heat loss during heat transfer, resulting in low heat utilization efficiency. In contrast, 3D-printed concrete, relying on oriented strips to form anisotropic heat transfer characteristics, can effectively suppress heat loss in non-working directions, allowing heat to be transferred directionally along the temperature difference direction, thus better maintaining the internal temperature gradient. From the Y-direction current density cloud map (e.g....) Figure 8 , Figure 12 As can be seen, the peak current density in the Y direction of the 3D printed module is significantly higher than that of the cast-in-place module. This is because the directional strips preferentially align the conductive fibers along the Y direction, forming a highly efficient conductive channel. Simultaneously, the 3D printed module, constrained by the directional strips, significantly reduces lateral transmission loss, effectively suppresses stray current, and exhibits a more prominent effect in directional charge accumulation. In contrast, the cast-in-place module suffers from lower conductivity due to its isotropic matrix and exhibits significant lateral leakage.

[0051] Overall cloud map comparison shows that the heat flow and current inside the 3D-printed concrete module exhibit a clear directional and concentrated transmission characteristic along the printing strip, while the cast-in-place module lacks directional transmission channels, resulting in higher heat and electricity transmission losses. In summary, this invention optimizes the internal heat and electricity transmission path of concrete through 3D-printed directional molding structures, significantly improving thermoelectric conversion performance and energy utilization efficiency under the same working conditions.

Claims

1. A precast wall based on thermoelectric cement using 3D printing, characterized in that, include: The main body of the wall is integrally formed by 3D printing using N-type thermoelectric cement-based composite material and P-type thermoelectric cement-based composite material. The printing path of the 3D printing is set along the thickness direction of the wall, so that each printed layer forms a continuous material strip from the outer surface to the inner surface of the wall, and the continuous material strip constitutes a directional heat transfer channel. The printed layers are stacked layer by layer along the height direction of the wall, and are alternately set as N-type thermoelectric layers formed by printing N-type thermoelectric cement-based composite material and P-type thermoelectric layers formed by printing P-type thermoelectric cement-based composite material. Both N-type thermoelectric layers and P-type thermoelectric layers are single-layer 3D printed layers, and the material within the same thermoelectric layer is uniform. Adjacent N-type thermoelectric layers and P-type thermoelectric layers form a layer group; Vertical conductive strips are set on the outer surface of the wall body along the height direction, corresponding one-to-one with each layer group; each vertical conductive strip on the outer surface is electrically connected to the hot end of the corresponding layer group. Vertical conductive strips are set on the inner surface of the wall body along the height direction, corresponding one-to-one with each layer group; Each inner surface vertical conductive strip is electrically connected to the cold end of the corresponding layer group; A horizontal conductive mesh is set in the top layer of the wall body as a current-collecting electrode. The current-collecting electrode connects the vertical conductive strip on the inner surface of the upper layer to the vertical conductive strip on the outer surface of the lower layer in series, so that all N-type thermoelectric layers and P-type thermoelectric layers are electrically connected in series alternately to form a thermoelectric power generation module. A conductive terminal is disposed on the top of the wall body. The conductive terminal is electrically connected to both ends of the bus electrode and is used to draw out electrical energy.

2. The 3D-printed thermoelectric cement-based precast wall according to claim 1, characterized in that, Both the outer and inner vertical conductive strips are metal mesh sheets, extending along the wall thickness direction to the two sides of the layer, and are spaced at preset conductive nodes along the wall length direction.

3. The 3D-printed thermoelectric cement-based precast wall according to claim 2, characterized in that, The mesh size and wire diameter of the metal mesh are selected to be suitable for concrete bonding and to form a reliable mechanical anchorage with the substrate.

4. The thermoelectric cement-based precast wall based on 3D printing according to claim 1, characterized in that, The N-type thermoelectric cement-based composite material is a cement-based material doped with an N-type dopant, and the P-type thermoelectric cement-based composite material is a cement-based material doped with a P-type dopant.

5. The 3D-printed thermoelectric cement-based precast wall according to claim 4, characterized in that, The N-type dopant is selected from one or a combination of zinc oxide and iron oxide; the P-type dopant is selected from one or a combination of carbon nanotubes and graphene; the doping amount of the N-type dopant is 0.5% to 5% of the cement mass, and the doping amount of the P-type dopant is 0.5% to 5% of the cement mass.

6. The 3D-printed thermoelectric cement-based precast wall according to claim 1, characterized in that, The conductive terminal is made of copper alloy with a silver-plated surface and is embedded in a pre-set groove at the top of the wall. The groove is filled with waterproof sealant. The conductive terminal is electrically connected to the horizontal conductive mesh through lead wires, and the lead wires are wrapped with an insulating protective layer.

7. The thermoelectric cement-based precast wall based on 3D printing according to claim 1, characterized in that, The outer surface of the main wall body adopts a curved shape as a heat-enhancing structure to increase the heat exchange area between the wall and the external environment.

8. A method for manufacturing a precast thermal-electric cement-based wall as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Prepare N-type thermoelectric cement-based composite material, P-type thermoelectric cement-based composite material, and conductive metal mesh respectively; the conductive metal mesh includes vertical metal mesh and horizontal metal mesh; Step 2: Set 3D printing parameters, including printing path, printing layer height, and printing speed; Step 3: Print layer by layer according to the 3D printing parameters set in Step 2, and implant vertical and horizontal metal meshes in the corresponding printing layers; Step 4: Weld lead wires to both ends of the horizontal conductive mesh and connect them to the conductive terminals installed at preset points at the top and bottom of the wall. Step 5: Curing the printed wall.

9. The method for manufacturing a precast thermal-cement based wall according to claim 8, characterized in that, Step 3 is performed as follows: After each thermoelectric layer is printed, vertical metal mesh sheets are implanted at preset conductive nodes on the outer and inner surfaces of that thermoelectric layer, serving as vertical conductive strips. The vertical metal mesh sheets overlap adjacent N-type and P-type thermoelectric layers in height, realizing the electrical connection between the upper and lower thermoelectric layers. The vertical conductive strips are perpendicular to the wall thickness direction and are spaced at preset conductive nodes along the wall length direction. The inner side of the vertical metal mesh sheets is tightly bonded to the thermoelectric cement-based composite material, and initial fixation is achieved by the adhesiveness of the 3D printed concrete material, forming a reliable bonded structure after subsequent curing. After all layers are printed, a horizontal metal mesh is placed at the top of the vertical metal mesh on the inner surface of the uppermost layer. This horizontal metal mesh is placed between the thermoelectric layers and electrically connected to the vertical metal mesh on the inner surface of the uppermost layer to form a top busbar electrode, which serves as the negative output terminal of the thermoelectric power generation module. A bottom metal mesh is placed at the bottom of the vertical metal mesh on the outer surface of the lowermost layer. This bottom metal mesh is placed between the thermoelectric layers and electrically connected to the vertical metal mesh on the outer surface of the lowermost layer to form a bottom busbar electrode, which serves as the positive output terminal of the thermoelectric power generation module. The top busbar electrode extends to a predetermined conductive area at the top of the wall, and the bottom busbar electrode extends to a predetermined conductive area at the bottom of the wall.

10. The method for manufacturing a precast thermal-electric cement-based wall according to claim 8, characterized in that, The 3D printing parameters are set as follows: spindle speed 1r / s, printing speed 20-30mm / s, and layer height 10-15mm.

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