Global ETD Search

41	Peltierovy články pro výrobu elektrické energie / Thermoelectric Power Generation System Brázdil, Marian January 2011 (has links) In the last decade there is a rising interest in thermoelectric applications. Thermoelectric generators enabling the direct conversion of the heat into the electricity become attractive. This fact is caused by the demands of environmental operation and saving primary resources. Scientists intensively investigate and develop new materials and structures suitable for these applications. The efficiency of the thermoelectric conversion progressively increases. Unfortunately we have no available materials with sufficient thermoelectric properties which could provide cost-competitive price. Thermoelectric generators seem to be useable devices. For example, in case of the unused waste heat using of the thermoelectric generator can increase the overall effectiveness of the unit despite the low efficiency of the generator. This master thesis deals with the issue of the Peltier modules representing the main part of the thermoelectric generators. The physical principles and structures of the thermoelectric modules and the possibility of thermoelectric power production are described here. In the practical part of this thesis the design of the low power generator utilizing waste heat from biomass boiler Verner A 251.1 is proposed.
42	Herstellung, Simulation und Charakterisierung thermoelektrischer Generatoren auf Basis anisotroper Oxidmaterialien Dreßler, Christian 01 June 2017 (has links) Die thermoelektrische Energiekonversion auf der Basis des Seebeck-Effekts ist eine Methode zur direkten Erzeugung elektrischer Energie aus thermischer Energie. Für die wesentlichen anwendungsrelevanten Parameter Temperaturbereich, elektrische Leistung und Herstellungskosten sind Materialauswahl und Aufbau der TEG entscheidend. In der vorliegenden Arbeit wurden erstmalig thermoelektrische Oxidkeramiken in monolithischen TEG verwendet, die auf der Grundlage des transversalen thermoelektrischen Effekts arbeiten. Die TEG wurden mit industriell skalierbaren Keramiktechnologien hergestellt, untersucht und hinsichtlich ihrer Parameter detailliert theoretisch und experimentell bewertet. Als Modellsystem für die Materialien wurde La1-xSrxCuO4 in Kombination mit Ag bzw. Ag6Pd1 verwendet. Es konnte belegt werden, dass diese monolithischen TEG im Bereich kleiner elektrischer Leistungen eine vorteilhafte Alternative zu herkömmlichen longitudinalen thermoelektrischen Generatoren sein können. info:eu-repo/classification/ddc/660 ddc:660
43	Effect of Configuration and Dimensions on the Thermo-Mechanical Performance of Spark Plasma Sintered Bismuth Telluride Annular Thermoelectric Generator (TEG) Modules Abdelnabi, Ahmed January 2020 (has links) Thermoelectric generators (TEG) are re-emerging technology that can be used to recover heat waste from commercial and industrial processes to generate electricity, enhancing fuel utilization and lowering greenhouse gas emissions. TEG modules are solid-state heat engines that produce no noise or vibration during operation. Notably, TEG modules are also able to operate at low-temperature differences, which makes them ideal for a wide range of heat waste recovery applications. Annular thermoelectric generator (ATEG) modules are optimal in applications where either the heat source or sink are round in shape. Bi2Te3 solution-based compounds are of significant interest in the application of thermoelectric materials (TE) used in low-temperature cooling and power generation applications. The main objective of the current work is to design a mechanically reliable ring-shaped ATEG module with a predictable performance using spark plasma sintered Bi2Te3 TE material for low temperature waste heat recovery applications. In terms of structure, this work is divided into two parts. The first part investigates how the use of a powder pre-treatment technique affects the mechanical and thermoelectric properties of P- and N-type Bi2Te3. In addition, part one also presents the measurements of these materials’ mechanical and thermoelectric properties, which serve as inputs for the finite element models used to design thermoelectric modules with parallel and perpendicular configurations vis-a-vis the sintering pressing direction. The second part evaluates the thermoelectric performance and thermal stresses of a ring-shaped ATEG couple that has been integrated between hot-side and cold-side heat exchangers. To this end, two configurations are compared with respect to their heat/electrical current flow paths: one that allows for radial flow (radial configuration), and one that allows for axial flow (axial configuration). The P- and N-type Bi2Te3 powder was treated using a mechanically agitated fluidized powder reduction facility that was built in-house. The characteristic uniaxial tensile strength of the P-type Bi0.4Sb1.6Te3 increased from 13.9 MPa to 26.3 MPa parallel to the sintering pressure, and from 16.3 MPa to 30.6 MPa perpendicular to the sintering pressure following oxide reduction using 5% H2 ˗ 95% Ar at 380 ℃ for 24 h. The figure of merit, ZT, increased from 0.35 to 0.80 and from 0.42 to 1.13 at room temperature (25 ℃) in the parallel and the perpendicular directions, respectively, after the surface oxide reduction treatment. On the other hand, the annealing effects of the oxide reduction pr-treatment of the N-type (Bi0.95 Sb0.05)2(Se0.05 Te0.95)3 using 5% H2 ˗ 95% Ar at 380 ℃ for 24 h were found to be responsible for the majority of the mechanical properties and ZT enhancement. Additionally, the characteristic uniaxial tensile strengths for this material increased from 30.4 to 34.1 MPa and from 30.8 to 38 MPa in the parallel and the perpendicular directions, respectively. The ZTmax (150 ℃) increased from 0.54 to 0.63 in both the parallel and perpendicular directions due to oxide reduction, while annealing led to an increase to 0.58 and 0.62 in the parallel and the perpendicular directions, respectively. An analytical model was constructed to compare the thermoelectric performance of the two configurations under three different hot-side thermal resistances, and a 3D coupled finite element ANSYS model was constructed to study and compare the thermal stresses of the two configurations at different dimensions. The two models were then used to create 2D maps in order to investigate the effects of ATEG couple configuration and dimensions, as well as the hot-side thermal resistance, with the goal of identifying the optimum design. The optimization of module geometry requires a trade-off between performance and mechanical reliability. The results of these investigations showed that increases in the temperature difference across the ATEG couple (ΔT) led to increases in both power and thermal stresses in both configurations. When both configurations were generating the same power at ΔT = 105 ℃, the thermal stresses in the radial configuration were as much as 67 MPa higher than those in the axial configuration due to the formation of additional tensile hoop stresses. The lowest thermal stress obtained for the axial couple configuration was 67.8 MPa, which was achieved when the couple had an outer diameter of 16 mm, an axial thickness of 1 mm, a ΔT of 14.8 ℃, and power generation of 10.4 mW per couple. The maximum thermal stress values were located at the corners of the interface between the solder and the TE rings due to the mismatched coefficient of thermal expansion. This thesis makes a novel contribution to the state-of-the-art literature in ring-shaped ATEG modules, as it details a well-characterised spark plasma sintered Bi2Te3 TE material and a methodology for designing a ring-shaped ATEG module with reliable, robust, and predictable thermoelectric and mechanical performance. The details of the contribution made by this work have been disseminated in the form of three journal publications, which have been integrated into this sandwich Ph.D. thesis. / Thesis / Doctor of Science (PhD) Thermoelectric materials Spark plasma sintering (SPS) Surface oxides Mechanical properties Uniaxial tensile strength Bi0.4Sb1.6Te3 (Bi0.95 Sb0.05)2(Se0.05 Te0.95)3 Powder pre-treatment Annular thermoelectric generator ring-shaped TE legs thermal stress coupled finite element model axial heat flow radial heat flow contact resistance thermal interface material
44	Analysis of a novel thermoelectric generator in the built environment Lozano, Adolfo 05 October 2011 (has links) This study centered on a novel thermoelectric generator (TEG) integrated into the built environment. Designed by Watts Thermoelectric LLC, the TEG is essentially a novel assembly of thermoelectric modules whose required temperature differential is supplied by hot and cold streams of water flowing through the TEG. Per its recommended operating conditions, the TEG nominally generates 83 Watts of electrical power. In its default configuration in the built environment, solar-thermal energy serves as the TEG’s hot stream source and geothermal energy serves as its cold stream source. Two systems-level, thermodynamic analyses were performed, which were based on the TEG’s upcoming characterization testing, scheduled to occur later in 2011 in Detroit, Michigan. The first analysis considered the TEG coupled with a solar collector system. A numerical model of the coupled system was constructed in order to estimate the system’s annual energetic performance. It was determined numerically that over the course of a sample year, the solar collector system could deliver 39.73 megawatt-hours (MWh) of thermal energy to the TEG. The TEG converted that thermal energy into a net of 266.5 kilowatt-hours of electricity in that year. The second analysis focused on the TEG itself during operation with the purpose of providing a preliminary thermodynamic characterization of the TEG. Using experimental data, this analysis found the TEG’s operating efficiency to be 1.72%. Next, the annual emissions that would be avoided by implementing the zero-emission TEG were considered. The emission factor of Michigan’s electric grid, RFCM, was calculated to be 0.830 tons of carbon dioxide-equivalent (CO2e) per MWh, and with the TEG’s annual energy output, it was concluded that 0.221 tons CO2e would be avoided each year with the TEG. It is important to note that the TEG can be linearly scaled up by including additional modules. Thus, these benefits can be multiplied through the incorporation of more TEG units. Finally, the levelized cost of electricity (LCOE) of the TEG integrated into the built environment with the solar-thermal hot source and passive ground-based cold source was considered. The LCOE of the system was estimated to be approximately $8,404/MWh, which is substantially greater than current generation technologies. Note that this calculation was based on one particular configuration with a particular and narrow set of assumptions, and is not intended to be a general conclusion about TEG systems overall. It was concluded that while solar-thermal energy systems can sustain the TEG, they are capital-intensive and therefore not economically suitable for the TEG given the assumptions of this analysis. In the end, because of the large costs associated with the solar-thermal system, waste heat recovery is proposed as a potentially more cost-effective provider of the TEG’s hot stream source. / text Thermoelectric generator TEG Novel thermoelectric generator Thermoelectrics Thermoelectric effect Thermoelectric modules Thermoelectric device Patent application Hot stream source Cold stream source EIA EERE Systems-level analysis Energy balance Control volume analysis Thermodynamic analysis Insolation data Insolation incident on a panel Incident insolation Extraterrestrial insolation NREL Ambient temperature data NOAA Renewable energy sources Energy generation technology Electricity generation technology Thermal energy Coupled system Emissions Greenhouse gas GHG Emissions analysis Zero-emission Emissions avoided Emission factor EF Reliability First Corporation RFC Built environment Integrated into the built environment Solar-thermal energy Solar collector system Photovoltaic thermal PVT panel Thermal storage tank Geothermal energy Geothermal heat pump GHP Ground source heat pump GSHP Numerical analysis Numerical model MATLAB Finite-difference Euler explicit Electric grid Annual energetic performance Annual electricity generation Operating efficiency System efficiency Thermodynamic characterization Economic analysis Levelized cost of energy LCOE Waste heat recovery Carbon dioxide equivalent CO2e Capital costs Installed costs Operating and maintenance costs

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