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To provide energy-efficient space heating and cooling, a thermoelectric building envelope (TBE) embeds thermoelectric devices in building walls. The thermoelectric device in the building envelope can provide active heating and cooling without requiring refrigerant use and energy transport among subsystems. Thus, the TBE system is energy and environmentally friendly. A few studies experimentally investigated the TBE under limited operating conditions, and only simplified models for the commercial thermoelectric module (TEM) were developed to quantify its performance. A holistic approach to optimum system performance is needed for the optimal system design and operation. The study developed a holistic TBE-building system model in Modelica for system simulation and performance analysis. A theoretical model for a single TEM was first established based on energy conversion and thermoelectric principles. Subsequently, a TBE prototype model combining the TEM model was constructed. The prototype model employing a feedback controller was used in a whole building system simulation for a residential house. The system model computed the overall building energy efficiency and dynamic indoor conditions under varying operating conditions. Simulation results indicate the studied TBE system can meet a heating demand to maintain the desired room temperature at 20 °C when the lowest outdoor temperature is at -26.3 °C, with a seasonal heating COP near 1.1, demonstrating a better heating performance than electric heaters. It suggests a potential energy-efficient alternative to the traditional natural gas furnaces and electric heaters for space heating. 

A thermoelectric building envelope (TBE) is a new type of active building envelope that incorporates thermoelectric material in the building's enclosure. In TBE, the electrical energy and thermal energy can transfer between them through thermoelectric material. As a result, TBE can provide cooling or heating to indoor space if power is applied. TBE-based cooling or heating has high reliability and a low maintenance cost, low CO2 emission, and no refrigerant use. TBE is conducive to the operation of net-zero energy and greenhouse gas emission buildings by using renewable energy. In this study, a multi-stage TBE prototype for space heating and cooling was designed, assembled, and tested. The performance of the TBE prototype was evaluated in two psychrometric chambers with controlled temperature and humidity in Herrick Laboratory at Purdue University. The performance was analyzed, including the surface and air temperatures, cooling capacity, and COP defined as the ratio of cooling capacity to the power input. The test result indicated that the COP of TBE in summer scenarios ranged from 0.46 to 2.4 with varied power inputs. The cooling capacity of one prototype can exceed 6.3 kW/cm2. The findings discussed can guide the design and operation of TBE. 

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). 

A thermoelectric building envelope (TBE) is a new type of active building envelope that incorporates thermoelectric material in the building’s enclosure. In TBE, the electrical energy and thermal energy can transfer between them through thermoelectric material. TBE can provide cooling or heating to indoor space if power is applied. TBE-based cooling or heating is quiet and reliable and has low maintenance cost, low or no CO2 emission. TBE is conducive to the operation of net-zero energy and emission buildings by using renewable and low-grade energy. In this study, a multi-stage TBE prototype was designed, assembled, and tested. The performance of the TBE prototype was evaluated in two psychrometric chambers with controlled temperature and humidity in Herrick Laboratory at Purdue University. The test result concludes that the highest COP of TBE is 0.46–2.4 in summer scenarios for different power inputs. The findings discussed can guide the design and operation of TBE. 

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. 

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. 

Buildings use 40% of the global energy consumption and emit 30% of CO2 emissions. Of the total building energy, 30-40% is for building heating and cooling systems, which regulate the indoor thermal environment and provide thermal comfort to occupants. Most buildings use forced air technology in the United States to deliver heating/cooling to the targeted thermal zones. Researchers have suggested using radiant heating and cooling systems as a better alternative to all-air systems. Radiant systems supply heating or cooling directly to the building space using radiation released by the heated or cooled building enclosure via the embedded heating or cooling tubes. It is unsure whether the radiant heating and cooling system can provide better thermal comfort to occupants. Moreover, the evaluation method for thermal comfort in the current standard is only suitable for forced air systems. A new plan shall be developed to evaluate the radiation system’s thermal comfort. This paper reviews the experiment-based studies on the thermal comfort of radiant systems. According to the experimental studies regarding thermal comfort and radiant systems, the key findings are concluded to help guide the evaluation of thermal comfort for radiant systems. 

Thermoelectric materials enable the direct conversion of thermal energy to electricity. Ambient heat energy harvesting could be an effective route to convert buildings from being energy consumers to energy harvesters, thus making them more sustainable. There exists a relatively stable temperature gradient (storing energy) between the internal and external walls of buildings which can be utilized to generate meaningful energy (that is, electricity) using the thermoelectric principle. This could ultimately help reduce the surface temperatures and energy consumption of buildings, especially in urban areas. In this paper, ongoing work on developing and characterizing a cement-based thermoelectric material is presented. Samples are fabricated using cement as a base material and different metal oxides (Bi₂O₃ and Fe₂O₃) are added to enhance their thermoelectric properties. A series of characterization tests are undertaken on the prepared samples to determine their Seebeck coefficient, electrical and thermal conductivity. The study shows that cement paste with additives possesses physical properties in the range of semiconductors whereby, initially, the resistivity values are low but with time, they increase gradually, thus resulting in lower electrical conductivity. The thermal conductivity of the cement paste with additives is lower than the control sample. Seebeck coefficient values were found to be relatively unstable during the initial set of measurements because the internal and external environment needed to be kept in a thermally stable condition to achieve steady results. The detailed analysis helped determine and eliminate the source of errors in the characterization process and obtain repeatable results. Parameters such as moisture content, temperature, and age were found to have a significant impact on the properties of cement-based thermoelectric materials.