Thermoelectric (TE) cement composite is a new type of TE material. Unlike ordinary cement, due to the inclusion of additives, TE cement can mutually transform thermal energy into electrical energy. In extreme weather, the large temperature difference between indoor and outdoor can be harvested by TE cement to generate electricity. In moderate weather, given power input, the same material can provide cooling/heating to adjust room temperature and reduce HAVC load. Therefore, TE cement has energy-saving potential in the application of building enclosures and energy systems. Its ability to convert different forms of energy and use low-grade energy is conducive to the operation of net-zero buildings. In this study, the graphene nanoplatelets and aluminum-doped zinc oxide nanopowder enhanced cement composite, was fabricated. The performance indicator of TE materials includes the dimensionless figure of merit ZT, calculated by Seebeck coefficient, thermal conductivity, and electrical conductivity. These TE properties were measured and calculated by a Physical Property Measurement System at different temperatures. The highest ZT of 15wt.% graphene and 5wt.% AZO enhanced cement composite prepared by the dry method is about 5.93E-5 at 330K.
more »
« less
Characteristics of New Cement-Based Thermoelectric Composite for Low-Temperature Applications by A Novel Method
Thermoelectric (TE) cement composite is a new type of TE material. Unlike ordinary cement, TE cement can mutually convert thermal energy to electrical energy due to the addition of carbon fibers, metal oxide nanoparticles, etc. In hot summer or cold winter, the significant temperature difference between indoor and outdoor can be used by TE cement to generate electricity. On the other hand, given power input, the same material can provide cooling/ heating to adjust room temperature. Therefore, TE cement has certain energy-saving potential in the application of building enclosures and energy systems. Its ability to convert different forms of energy and use low-grade energy is conducive to the operation of net-zero buildings. In this study, a novel TE cement composite, MnO2 and graphite enhanced cement, was firstly fabricated. The surface morphology of the composites was analyzed by using the images taken by scanning electron microscopy. The performance indicators of TE materials include the power factor and dimensionless figure of merit ZT The values of five TE properties were measured and calculated by a Physical Property Measurement System at different temperatures. Compared with the cement reinforced by graphite alone, it is confirmed that MnO2 nanoparticles have a positive effect on the enhancement of the TE performance for cement composites. The 5wt.% graphite and 10wt.% MnO2 enhanced cement composite achieves the highest Z.T. of 6.2 × 10-6 at 350 K.
more »
« less
- Award ID(s):
- 1805818
- NSF-PAR ID:
- 10252942
- Date Published:
- Journal Name:
- 2020 International High-Performance Buildings Conference
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The thermoelectric module (TEM) is a device that integrates multiple thermoelectric (TE) elements to realize the mutual conversion of heat and power. Due to the advantages of no moving parts and flexible expansion, the application of conventional Bi2Te3-based TEM in buildings has attracted the attention of researchers. On the other hand, the TE behavior of hardened cement composites was found by combining conductive additives with cement. Therefore, a new study on cement-based TEM for building energy harvesting and emperature control is proposed. To simulate the performance of cement-based TEM, a three-dimensional heat transfer model considering temperature-dependent TEM characteristics was established. The validity of the model is verified by comparing the results with commercial simulation software and experiments. Different from the existing analytical models and commercial software, the customized model has greater scalability, optimization, and control flexibility. Through parametric studies, the model can guide the design of TEM and the development of TE cement.more » « less
-
Utilizing silicon as an anode material for Li-ion batteries has been the subject of many studies. However, due to the huge volume change of silicon during lithiation, the electrochemical performance of silicon is poor. Here, we have investigated a novel yet simple approach to synthesize nanostructured silicon/graphite composites with a carbon coating and engineered voids. High-energy ball mill is employed to convert micrometer-sized silicon and graphite to nanostructured silicon/graphite composite building blocks, while a thin carbon coating is applied to encapsulate these composite agglomerates, followed by partial etching of silicon to create engineered voids inside the composite agglomerates. The batteries made with this tailored nanostructure exhibit improved electrochemical performance over the counterparts made with silicon nanoparticles and exhibited a specific capacity of ~1800 mA h g-1 discharge capacity at the first cycle, 580 mA h g-1 after 40 cycles, and 350 mA h g-1 after 300 cycles. This study has established a novel method scalable at industry environment and capable of producing low cost Si anodes and clearly shown that the cycle stability of the tailored nanostructure improves with increasing engineered voids in the range we have investigated.more » « less
-
more » « less
Abstract Infrared (IR) thermography is a non-contact method of measuring temperature that analyzes the infrared radiation emitted by an object. Properties of polymer composites are heavily influenced by the filler material, filler size, and filler dispersion, and thus thermographic analysis can be a useful tool to determine the curing and filler dispersion. In this study, we investigated the curing mechanisms of polymer composites at the microscale by capturing real-time temperature using an IR Thermal Camera. Silicone polymers with fillers of Graphene, Graphite powder, Graphite flake, and Molybdenum disulfide (MoS2) were subsequently poured into a customized 3D printed mold for thermography. The nanocomposites were microscopically heated with a Nichrome resistance wire, and real-time surface temperatures were measured using different Softwares. This infrared thermal camera divides the target area into 640 × 480 pixels, allowing measurement and analysis of the sample with a resolution of 65 micrometers. Depending on the filler material, the temperature rises to a certain maximum point before curing, and once curing is complete, polymer composites exhibit a rapid temperature change indicating a transition from viscous fluid to solid. MoS2, Polydimethylsiloxane (PDMS) without filler, and PDMS with larger filler are ranked in order of maximum constant temperature. PDMS (without filler) cures in 500s, while PDMS-Graphene and PDMS Graphite Powder cure in about 800s. The curing time for PDMS Graphite flake is slightly longer (950s), while MoS2 is around 520s. Therefore, this technique can indicate the influence of fillers on the curing of composites at the microscale, which is difficult to achieve by conventional methods such as differential scanning calorimetry. This nondestructive, low-cost, fast infrared thermography can be used to analyze the properties of polymer composites with different fillers and dispersion qualities in a variety of applications including precision additive manufacturing and quality control of curable composite inks.
-
Because of the thermoelectric (TE) effect (or Seebeck effect), a difference of potential is generated as a consequence of a temperature gradient across a sample. The TE effect has been mostly studied and engineered in semiconducting materials and it already finds several commercial applications. Only recently the TE effect in cement-based materials has been demonstrated and there is a growing interest in its potential. For instance, a temperature gradient across the external walls of a building can be used to generate electricity. By the inverse of the TE effect (or Peltier effect), one can also seek to control the indoor temperature of a building by biasing TE elements embedded in its external walls. In designing possible applications, the TE properties of cement-based materials must be determined as a function of their chemical composition. For instance, the TE properties of cement paste can be enhanced by the addition of metal oxide (e.g., Fe2O3) powder. In this paper, a single thermoelectric leg is studied using the finite element method. Metal oxide additives in the cement paste are modelled as spherical inhomogeneities. The thermoelectric properties of the single components are based on experimental data, while the overall thermoelectric properties of the composites are obtained from the numerical model. The results of this numerical study are interpreted according to the effective medium theory (EMT) and its generalisation (GEMT).more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- The DOI is not currently available.
