scholarly journals Schemes for and Mechanisms of Reduction in Thermal Conductivity in Nanostructured Thermoelectrics

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Xiaoliang Zhang ◽  
Ming Hu ◽  
Konstantinos P. Giapis ◽  
Dimos Poulikakos
Keyword(s):  
Thermal Conductivity ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
Longitudinal Direction ◽  
Energy Conversion Efficiency ◽  
Nonequilibrium Molecular Dynamics ◽  
Boundary Scattering ◽  
Nanowire Surface ◽  
Simulation Results ◽  
Nanocomposite Structures

Nonequilibrium molecular dynamics (NEMD) simulations were performed to investigate schemes for enhancing the energy conversion efficiency of thermoelectric nanowires (NWs), including (1) roughening of the nanowire surface, (2) creating nanoparticle inclusions in the nanowires, and (3) coating the nanowire surface with other materials. The enhancement in energy conversion efficiency was inferred from the reduction in thermal conductivity of the nanowire, which was calculated by imposing a temperature gradient in the longitudinal direction. Compared to pristine nanowires, our simulation results show that the schemes proposed above lead to nanocomposite structures with considerably lower thermal conductivity (up to 82% reduction), implying ∼5X enhancement in the ZT coefficient. This significant effect appears to have two origins: (1) increase in phonon-boundary scattering and (2) onset of interfacial interference. The results suggest new fundamental–yet realizable ways to improve markedly the energy conversion efficiency of nanostructured thermoelectrics.

Atomistic Mechanisms of Enhancing Energy Conversion Efficiency of Nanostructured Thermoelectrics

2011 ◽  
Author(s):  
Ming Hu ◽  
Xiaoliang Zhang ◽  
Konstantinos P. Giapis ◽  
Dimos Poulikakos
Keyword(s):  
Thermal Conductivity ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
Longitudinal Direction ◽  
Energy Conversion Efficiency ◽  
Nano Particles ◽  
Nonequilibrium Molecular Dynamics ◽  
Surface Roughening ◽  
Nanowire Surface ◽  
Nanocomposite Structures

Nonequilibrium molecular dynamics (NEMD) simulations are performed to investigate possible mechanisms for enhancing the energy conversion efficiency of thermoelectric nanowires, including 1) surface roughening, 2) incorporating nano-particles on the surface or inclusions in the nanowires, and 3) inducing interfacial interference by covering the nanowire surface with other coatings. The enhancement in energy conversion efficiency is measured in terms of thermal conductivity of the nanowire, which is obtained by imposing a one-dimensional heat flux in the longitudinal direction of the nanowire. Our simulation results show that, compared to pristine nanowires, all generated nanocomposite structures proposed above were found to have considerably lower thermal conductivity (up to 78% reduction was achieved), implying ∼ 5 times enhancement in the ZT coeficient. The realizable approaches herein, open up new fundamental ways to improve markedly the energy conversion efficiency of nanostructured thermoelectrics.

Combustion-Thermoelectric Tube

2000 ◽  
Vol 122 (4) ◽  
pp. 721-729 ◽  
Author(s):  
C.-W. Park ◽  
M. Kaviany
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
Thermoelectric Materials ◽  
High Efficiency ◽  
Fuel Injection ◽  
Direct Injection ◽  
Energy Conversion Efficiency ◽  
Solid Matrix

In direct combustion-thermoelectric energy conversion, direct fuel injection and reciprocation of the air flowing in a solid matrix are combined with the solid-gas interfacial heat transfer and the solid conduction to allow for obtaining superadiabatic temperatures at the hot junctions. While the solid conductivity is necessary, the relatively large thermal conductivity of the available high-temperature thermoelectric materials (e.g., Si–Ge alloys) results in a large conduction loss from the hot junctions and deteriorates the performance. Here, a combustion-thermoelectric tube is introduced and analyzed. Radially averaged temperatures are used for the fluid and solid phases. A combination of external cooling of the cold junctions, and direct injection of the fuel, has been used to increase the energy conversion efficiency for low thermal conductivity, high-melting temperature thermoelectric materials. The parametric study (geometry, flow, stoichiometry, materials) shows that with the current high figure of merit, high temperature Si0.7Ge0.3 properties, a conversion efficiency of about 11 percent is achievable. With lower thermal conductivities for these high-temperature materials, efficiencies about 25 percent appear possible. This places this energy conversion in line with the other high efficiency, direct, electric power generation methods. [S0022-1481(00)01304-9]

First-principles study on the electronic and optical properties of the orthorhombic CsPbBr3 and CsPbI3 with Cmcm space group

2021 ◽  
Author(s):  
Xianhao Zhao ◽  
Tianyu Tang ◽  
Quan Xie ◽  
like gao ◽  
Limin Lu ◽  
...  
Keyword(s):  
Optical Properties ◽  
Solar Cells ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
First Principles ◽  
Energy Conversion Efficiency ◽  
Space Group ◽  
Absorbing Materials ◽  
Halide Perovskites ◽  
Lead Halide

The cesium lead halide perovskites are regarded as effective candidates for light-absorbing materials in solar cells, which have shown excellent performances in experiments such as promising energy conversion efficiency. In...

Metal-like electrical conductivity in LaxSr2−xTiMoO6 oxides for high temperature thermoelectric power generation

2017 ◽  
Vol 46 (18) ◽  
pp. 5872-5879 ◽  
Author(s):  
Mandvi Saxena ◽  
Tanmoy Maiti
Keyword(s):  
Power Generation ◽  
Electrical Conductivity ◽  
High Temperature ◽  
Energy Conversion ◽  
Thermoelectric Power ◽  
Conversion Efficiency ◽  
Energy Conversion Efficiency ◽  
Power Generators ◽  
Thermoelectric Power Generation

Increasing electrical conductivity in oxides, which are inherently insulators, can be a potential route in developing oxide-based thermoelectric power generators with higher energy conversion efficiency.

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