A thermoelectric cement-based system that meets the requirements of low-grade thermal energy temperature difference power generation

Abstract

The present invention discloses a thermoelectric cement-based material that meets the requirements of low-grade thermal energy thermoelectric power generation, and relates to the technical field of thermoelectric cement-based materials. The thermoelectric cement-based material includes an ionic liquid having an ionic entropy difference inside and a cement matrix as a load-bearing structure. The cement matrix has a plurality of interconnected pores inside, and the ionic liquid is introduced into the pores of the cement matrix. The ionic liquid is a thermoelectric effect ionic liquid or an anion-cation pair liquid with a Soret effect. When the thermoelectric cement-based material is connected to an external load, a temperature difference field is formed at both ends of the thermoelectric cement-based material. Under the combined action of the temperature difference field and the entropy difference, the ionic free radicals in the ionic liquid undergo directional migration in the pores, causing the cement matrix to produce a thermoelectric conversion effect, thereby achieving thermoelectric power generation. The present invention enables the thermoelectric cement-based material to meet the requirements of low-grade thermoelectric power generation without the need for doping with expensive semiconductor materials. The preparation cost is low, and it can better provide a basic guarantee for the construction, operation, and promotion of large-scale clean energy power plants.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric cement-based materials, and in particular to a thermoelectric cement-based material that meets the requirements for low-grade thermal energy temperature difference power generation. Background Art

[0002] Faced with increasingly severe environmental pollution and shortages of traditional energy sources (such as oil and natural gas), modern society is increasingly demanding clean energy technologies. However, building large-scale clean energy power plants requires high costs and large tracts of land, creating a high barrier to entry. Furthermore, the large land area prohibits construction in densely populated urban areas, necessitating long-distance transmission and distribution infrastructure for power transmission, resulting in higher electricity costs.

[0003] As one of the most widely used building materials, cement-based materials are cheap and have a large stock size. At present, some studies have been conducted on the thermoelectric effect of cement-based materials. The thermoelectric effect generated by the temperature difference of cement-based materials can be used to convert thermal energy into electrical energy. In addition, traditional power generation methods are difficult to effectively utilize low-grade thermal energy, resulting in the waste of this part of resources. However, the use of the thermoelectric effect of cement-based materials can well realize the utilization of low-grade thermal energy. This not only makes up for the shortcomings of traditional power generation methods, but also the effective use of low-grade thermal energy can reduce energy consumption and save costs (for example, using the electricity converted from low-grade thermal energy to provide working power for some signal detection systems). This also provides more possibilities for the construction, operation and promotion of clean energy power plants.

[0004] Regarding thermoelectric cement-based materials, most previous studies have been based on achieving thermoelectric effects by doping semiconductor materials such as carbon nanotubes, nanocarbon black, and nanographene. For example, Patent Publication No. ES2908123R1 discloses a thermoelectric conductive cement mortar doped with graphite and graphene nanomaterials.

[0005] However, the economic cost of the above-mentioned thermoelectric cement-based materials is extremely high, making it difficult to achieve large-scale application. In addition, due to the inherent characteristics of the semiconductor thermoelectric effect, the thermoelectric performance achieved by the above-mentioned thermoelectric cement-based materials is relatively low, with the Seebeck coefficient (Seebeck) mostly on the order of 10 to 1000 μV / k. Therefore, it is difficult to output sufficient voltage under low-grade temperature difference conditions. Summary of the Invention

[0006] In view of the above-mentioned deficiencies in the prior art, the present invention provides a thermoelectric cement-based material that can meet the requirements of low-grade temperature difference power generation.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A thermoelectric cement base that meets the requirements of low-grade thermal energy temperature difference power generation includes an ionic liquid with an ionic entropy difference inside and a cement matrix as a load-bearing structure. The cement matrix has a plurality of interconnected pores inside, and the ionic liquid is introduced into the pores of the cement matrix. The ionic liquid is a thermoelectric effect ionic liquid or an anion-cation pair liquid with a Soret effect. When the thermoelectric cement base is connected to an external load, a temperature difference field is formed at both ends of the thermoelectric cement base. Under the combined action of the temperature difference field and the entropy difference, the ionic free radicals in the ionic liquid undergo directionally migration in the pores, causing the cement matrix to produce a thermoelectric conversion effect, thereby realizing thermoelectric power generation.

[0009] Preferably, the thermoelectric effect ionic liquid is a mixed solution containing potassium ferrocyanide and potassium ferrocyanide.

[0010] Furthermore, the thermoelectric effect ionic liquid also contains potassium chloride.

[0011] Preferably, in the thermoelectric effect ionic liquid, the volume molar concentration ratio of potassium ferrocyanide, potassium ferrocyanide and potassium chloride is 0.15-0.3:0.25-0.5:0.8.

[0012] Furthermore, in the thermoelectric effect ionic liquid, the volume molar concentration ratio of potassium ferrocyanide, potassium ferrocyanide and potassium chloride is 0.25:0.42:0.8.

[0013] Preferably, the anion-cation pair liquid having the Soret effect is any one of potassium chloride, sodium chloride and potassium sulfate.

[0014] Furthermore, the anion-cation pair liquid having the Soret effect is 0.8M potassium chloride, or 0.8M sodium chloride, or 0.4M potassium sulfate.

[0015] Preferably, the cement matrix is ​​made of any one of paste, mortar and concrete.

[0016] Furthermore, a sealing wrapping layer is provided on the outside of the cement matrix.

[0017] Preferably, the sealing wrapping layer is any one or more of resin, waterproof coating, and waterproof membrane.

[0018] The design principles of the present invention are as follows:

[0019] By introducing an ionic liquid into the pores of the cement matrix, the ionic liquid is interconnected within the cement matrix, taking advantage of the widespread interconnected pores within the cement-based material. This allows the ionic liquid to communicate with each other within the cement matrix. Consequently, when a temperature difference exists across the thermoelectric cement matrix, the temperature differential causes the ionic radicals (positive and negative ions with a charge) within the ionic liquid to migrate in a directional manner within the pores of the cement matrix due to their inherent entropy difference, thus achieving the ionic thermoelectric effect.

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

[0021] (1) The present invention integrates the pores of the cement-based material into an ionic liquid with an ionic entropy difference, and connects an external load to form a circuit between the thermoelectric cement base and the external load. Thus, when a temperature difference exists across the thermoelectric cement base, under the action of the temperature difference field, due to the entropy difference, the ionic free radicals within the ionic liquid will undergo directional migration within the pores, thereby generating an ionic thermoelectric effect and achieving thermoelectric power generation using the cement-based material. Therefore, the present invention's method of achieving thermoelectric power generation using thermoelectric cement-based materials has the characteristics of ingenious design, simple operation, and high compatibility with various types of building facilities.

[0022] (2) The ionic liquid of the present invention cleverly uses a composite solution of potassium ferrocyanide and potassium ferrocyanide (thermoelectric effect ionic liquid). Under the action of the temperature difference field, the ferrocyanide ions at the high temperature end are oxidized to ferrocyanide ions, which release electrons into the external load, and the formed ferrocyanide ions migrate to the low temperature end; while the ferrocyanide ions at the low temperature end are reduced to ferrocyanide ions, which receive electrons from the external load, and the formed ferrocyanide ions migrate to the high temperature end. This cycle can achieve thermoelectric power generation of cement-based materials.

[0023] In addition, potassium chloride is further added to the ionic liquid of the present invention. The chloride ions and potassium ions form a double layer at the electrode site, causing electrons / holes with opposite charges on the electrodes, thereby further increasing the potential difference between the two electrodes, thereby further enhancing the thermoelectric effect of ferrocyanide ions and ferrocyanide ions.

[0024] In addition, in addition to the composite solution of potassium ferrocyanide and potassium ferrocyanide, the ionic liquid in the present invention can also be an anion-cation pair liquid with Soret effect, such as potassium chloride, sodium chloride, potassium sulfate, etc.

[0025] Experiments show that the Seebeck coefficient of the ionic liquid + temperature difference power generation method of the present invention is at least one order of magnitude higher than that of existing thermoelectric cement-based materials, ensuring sufficient voltage output under low-grade temperature difference conditions to meet the requirements.

[0026] (3) The present invention also provides a sealing wrapping layer on the outside of the cement matrix, which can prevent the evaporation of the ionic liquid water in the atmospheric environment, further ensuring the temperature difference power generation of the thermoelectric cement-based material.

[0027] (4) The present invention enables thermoelectric cement-based materials to meet the requirements of low-grade temperature difference power generation without the need for doping with expensive semiconductor materials. Not only is the preparation cost low, but the external load only needs to be able to transmit electrons to enable the thermoelectric cement-based materials to produce a thermoelectric effect. Therefore, the present invention can better provide a foundation for the construction, operation, and promotion of large-scale clean energy power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the introduction of ionic liquid into the pores of the cement matrix in Example 1 of the present invention.

[0029] Figure 2 This is a schematic diagram of the power generation principle of thermoelectric cement-based in Example 3 of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with various embodiments and drawings. The embodiments of the present invention include but are not limited to the following embodiments.

[0031] Example 1

[0032] This embodiment provides a thermoelectric cement-based material specifically adapted for low-grade thermal energy temperature difference power generation. It uses a cement matrix as a supporting structure and introduces ionic liquids into the abundant pores within the cement matrix to obtain the target thermoelectric cement-based material. The specific production method is as follows:

[0033] First, a cement matrix and an ionic liquid are prepared separately. The cement matrix in this embodiment is made of mortar, and the interior of the prepared cement matrix has a rich pore structure; the ionic liquid is a mixed solution containing potassium ferrocyanide and potassium ferrocyanide, and the volume molar concentration ratio of potassium ferrocyanide to potassium ferrocyanide is 0.25:0.42.

[0034] After preparing the cement matrix and ionic liquid, the cement matrix is ​​immersed in the ionic liquid by infiltration, and the ionic liquid can be introduced into the pores of the cement matrix. On this basis, the vacuum saturation technology can also be combined to increase the absorption of the ionic liquid by the cement matrix. Figure 1 This is the situation after the ionic liquid is introduced into the pores of the cement matrix.

[0035] This thermoelectric cement-based material can be used as a foundational material for a variety of building facilities, such as walls. When connected to an external load, the two form a circuit. When there is a temperature difference between the inside and outside of the wall, the entropy difference between ferrocyanide and ferrocyanide ions causes them to migrate to the lower and higher temperature ends, respectively, under the influence of the temperature difference. Specifically, on the higher temperature side, ferrocyanide ions are oxidized to ferrocyanide ions, releasing electrons that enter the external load, and the resulting ferrocyanide ions migrate to the lower temperature side. On the lower temperature side, ferrocyanide ions are reduced to ferrocyanide ions, receiving electrons from the external load, and the resulting ferrocyanide ions migrate to the higher temperature side. This generates a thermoelectric effect, providing electrical energy for the external load.

[0036] Example 2

[0037] The difference from Example 1 is that potassium chloride is also added to the ionic liquid in this example, and the volume molar concentration ratio of potassium ferrocyanide, potassium ferrocyanide, and potassium chloride is 0.25:0.42:0.8. This embodiment utilizes the formation of a double layer of chloride ions and potassium ions at the electrode sites, which can create electrons / holes with opposite charges on the electrodes, thereby further increasing the potential difference between the two electrodes, thereby further enhancing the thermoelectric effect of the ferrocyanide and ferrocyanide ions. Figure 2 The power generation principle of the thermoelectric cement-based embodiment is demonstrated.

[0038] Example 3

[0039] The difference from Example 2 is that in this example, the volume molar concentration ratio of potassium ferrocyanide, potassium ferrocyanide and potassium chloride is 0.3:0.5:0.8.

[0040] Example 4

[0041] The difference from Example 2 is that in this example, the volume molar concentration ratio of potassium ferrocyanide, potassium ferrocyanide and potassium chloride is 0.15:0.25:0.8.

[0042] Example 5

[0043] The difference from Example 1 is that in this embodiment, the ionic liquid is 0.8M (volume molar concentration) potassium chloride. Under the influence of the temperature difference field and the Soret effect, the carriers in the potassium chloride solution undergo directional migration, generating a thermoelectric effect, which provides electrical energy for the external load.

[0044] Example 6

[0045] The difference from Example 1 is that in this example, the ionic liquid is 0.8M (volume molar concentration) sodium chloride. Under the influence of the temperature difference field and the Soret effect, the ions in the sodium chloride undergo directional migration, generating a thermoelectric effect, which provides electrical energy for the external load.

[0046] Example 7

[0047] The difference from Example 1 is that in this example, 0.4M (volume molar concentration) potassium sulfate is used as the ionic liquid. Under the influence of the temperature difference field and the Soret effect, the ions in the potassium sulfate undergo directional migration, generating a thermoelectric effect, which provides electrical energy for the external load.

[0048] Example 8

[0049] The difference from Example 1 is that in order to prevent the evaporation of moisture in the thermoelectric cement base and affect the thermoelectric effect of the thermoelectric cement base, this embodiment also provides a sealing wrapping layer on the outside of the cement base. The sealing wrapping layer can be made of a series of materials such as resin, waterproof coating, waterproof roll, etc. to lock the moisture in the thermoelectric cement base.

[0050] Example 9

[0051] This embodiment provides an experimental device to verify the voltage and Seebeck coefficient of the thermoelectric cement-based thermoelectric effect of Examples 1-7.

[0052] 1. Experimental Preparation

[0053] Cement matrix: Cement mortar samples with a water-cement ratio of 0.7 were prepared, and the specimen size was 40*40*30mm.

[0054] Ionic liquid: The corresponding ionic liquids were prepared according to Examples 1-7, and then the specimens were saturated with water in the above ionic liquids under vacuum for 7 days.

[0055] Experimental equipment and devices: constant temperature water bath, thermometer, U-shaped clamp, high-precision digital multimeter, copper water cooling head, graphite electrode, insulating thermal conductive silicone pad and thermocouple.

[0056] The above equipment is mainly divided into three parts: temperature control system, voltage measurement system and fixed clamping equipment, among which:

[0057] Temperature control system: First, use a constant temperature water bath to maintain the water temperature in the pot at 30.2℃ and 65.0℃ respectively (considering the heat loss during the water pipe transmission process, the water temperature in the water bath is higher than the water temperature in the water cooling head). Then, use a water pump to pump water of different temperatures into the copper water cooling head, so that the two water cooling heads are maintained at 30℃ and 60℃ respectively, and the temperature of the water cooling head is monitored in real time by connecting a thermometer via a thermocouple.

[0058] Voltage measurement system: A graphite electrode sheet and an insulating, thermally conductive silicone pad are placed between the specimen and the copper water-cooling block, respectively. The graphite electrode sheet acts as an electrode to collect charge and transmit the potential difference between the two ends of the specimen to a high-precision digital multimeter via a wire. The silicone pad is used to prevent electrical conduction between the graphite electrode and the copper water-cooling block. Furthermore, given the excellent thermal conductivity and thinness of the graphite sheet and silicone pad, heat loss caused by the graphite electrode sheet and silicone pad is ignored. In other words, the temperature at both ends of the specimen is assumed to be the same as that of the copper water-cooling block.

[0059] Clamping system: The water cooling head, silicone pad, graphite electrode and test piece are clamped and fixed by U-shaped clamps to ensure good contact.

[0060] 2. Experimental process

[0061] STEP 1: Turn on the two constant-temperature water baths and water pumps and adjust the target temperatures. Monitor the thermometer readings. When the readings stabilize at 30°C (303.15K) and 60°C (333.15K), the target temperatures of the constant-temperature water baths have met the experimental requirements.

[0062] STEP 2: Turn on and connect the digital multimeter. Clamp the test piece in the test sequence secured by the U-shaped clamp. Start measuring the voltage and record the voltage signal on the computer. Considering the large specific heat capacity of water and the high volume of water in the temperature control system, the heat exchange between the water cooling block and the test piece has little effect on the water temperature.

[0063] STEP 3: When the voltage change is less than 1mV / min, it is considered to have reached a steady state, and the voltage at the steady state is recorded as the final output voltage.

[0064] 3. Experimental results

[0065] The relevant experimental results of Examples 1-7 are shown in Table 1:

[0066] plan Voltage / mV Seebeck coefficient / mV·k-1 Example 1 366.12 11.85 Example 2 421.06 14.04 Example 3 257.16 8.57 Example 4 64.95 2.16 Example 5 82.22 2.74 Example 6 139.24 4.64 Example 7 112.57 3.75

[0067] Table 1

[0068] Table 2 shows the test results of the test piece (test piece size: 40*40*30mm) prepared with a water-cement ratio of 0.5 and then saturated with water in the ionic liquid of Example 2 for 7 days.

[0069] plan Voltage / mV Seebeck coefficient / mV·k-1 Example 2 94.57 3.15

[0070] Table 2

[0071] Table 3 shows the test results of the test piece (test piece size: 40*40*30mm) prepared with a water-cement ratio of 0.6 and then saturated with water in the ionic liquid of Example 2 for 7 days.

[0072] plan Voltage / mV Seebeck coefficient / mV·k-1 Example 2 263.03 8.77

[0073] Table 3

[0074] The results in Tables 1-3 show that, in a cement matrix prepared with a water-cement ratio of 0.5-0.7, Examples 1-7 exhibit Seebeck coefficients ranging from 2.16 mV / k to 14.04 mV / k. Therefore, the solution adopted by the present invention improves the Seebeck coefficient by an order of magnitude compared to existing solutions.

[0075] While seemingly simple, this invention is surprisingly complex. Only by thoroughly studying the principles of the thermoelectric effect of cement-based materials and incorporating the characteristics of related substances can a simple and effective design of a thermoelectric cement-based material that meets the requirements for low-grade thermal energy thermoelectric power generation be achieved. This significantly reduces the production cost of thermoelectric cement-based materials, providing a foundation for the construction, operation, and expansion of large-scale clean energy power plants. Therefore, compared to existing technologies, this invention represents a significant technological advancement, possessing outstanding substantive features and a remarkable improvement.

[0076] The above embodiments are only preferred implementation modes of the present invention and should not be used to limit the scope of protection of the present invention. Any changes or modifications that are made to the main design concept and spirit of the present invention and have no substantive significance, as long as the technical problems they solve are still consistent with the present invention, should be included in the scope of protection of the present invention.

Claims

1. A thermoelectric cement-based material that meets the requirements of low-grade thermal energy temperature difference power generation, characterized in that: The invention comprises an ionic liquid having an ionic entropy difference inside and a cement matrix as a load-bearing structure, wherein the cement matrix has a plurality of interconnected pores inside, and the ionic liquid is introduced into the pores of the cement matrix; the ionic liquid is a thermoelectric effect ionic liquid or an anion-cation pair liquid with a Soret effect; when the thermoelectric cement base is connected to an external load, a temperature difference field is formed at both ends of the thermoelectric cement base, and under the combined action of the temperature difference field and the entropy difference, the ionic free radicals in the ionic liquid undergo directionally migration in the pores, causing the cement matrix to produce a thermoelectric conversion effect, thereby realizing thermoelectric power generation; the thermoelectric effect ionic liquid is a mixed solution containing potassium ferrocyanide, potassium ferrocyanide and potassium chloride; the anion-cation pair liquid with a Soret effect is any one of potassium chloride, sodium chloride and potassium sulfate; and the cement matrix is ​​made of any one of neat paste, mortar and concrete.

2. The thermoelectric cement base that meets the requirements of low-grade thermal energy temperature difference power generation according to claim 1 is characterized in that: In the thermoelectric effect ionic liquid, the volume molar concentration ratio of potassium ferrocyanide, potassium ferrocyanide and potassium chloride is (0.15-0.3): (0.25-0.5):0.

8.

3. The thermoelectric cement base that meets the requirements of low-grade thermal energy temperature difference power generation according to claim 2, characterized in that: In the thermoelectric effect ionic liquid, the volume molar concentration ratio of potassium ferrocyanide, potassium ferrocyanide and potassium chloride is 0.25:0.42:0.

8.

4. The thermoelectric cement base that meets the requirements of low-grade thermal energy temperature difference power generation according to claim 1, characterized in that: The anion-cation pair liquid having the Soret effect is 0.8M potassium chloride, or 0.8M sodium chloride, or 0.4M potassium sulfate.

5. The thermoelectric cement-based material that meets the requirements of low-grade thermal energy temperature difference power generation according to any one of claims 1 to 4, characterized in that: A sealing wrapping layer is also provided on the outside of the cement matrix.

6. The thermoelectric cement-based material that meets the requirements of low-grade thermal energy temperature difference power generation according to claim 5, characterized in that: The sealing wrapping layer is any one or more of resin, waterproof coating, and waterproof coiled material.

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