A brief perspective on the physics of performance estimation of thermoelectric generators

A Wavy-Structured Highly Stretchable Thermoelectric Generator with Stable Energy Output and Self-Rescuing Capability

The efficiency of a thermoelectric (TE) generator for the conversion of thermal energy into electrical energy can be easily but roughly estimated using a constant properties model (CPM) developed by Ioffe. However, material properties are, in general, temperature ()-dependent and the CPM yields meaningful estimates only if physically appropriate averages, i.e., spatial averages for thermal and electrical resistivities and the temperature average (TAv) for the Seebeck coefficient (, are used. Even though the use of compensates for the absence of Thomson heat in the CPM in the overall heat balance, we find that the CPM still overestimates performance (e.g., by up to 6% for PbTe) for many materials. The deviation originates from an asymmetric distribution of internally released Joule heat to either side of the TE leg and the distribution of internally released Thomson heat between the hot and cold side. The Thomson heat distribution differs from a complete compensation of the corresponding Peltier heat balance in the CPM. Both effects are estimated quantitatively here, showing that both may reach the same order of magnitude, but which one dominates varies from case to case, depending on the specific temperature characteristics of the thermoelectric properties. The role of the Thomson heat distribution is illustrated by a discussion of the transport entropy flow based on the plot. The changes in the lateral distribution of the internal heat lead to a difference in the heat input, the optimum current and thus of the efficiency of the CPM compared to the real case, while the estimate of generated power at maximum efficiency remains less affected as it is bound to the deviation of the optimum current, which is mostly <1%. This deviation can be corrected to a large extent by estimating the lateral Thomson heat distribution and the asymmetry of the Joule heat distribution. A simple guiding rule for the former is found.

Body Heat Powers Future Electronic Skins

Using the constant properties model for accurate performance estimation of thermoelectric generator elements

NON-LINEAR VIBRATION OF CABLE–DAMPER SYSTEMS PART I: FORMULATION

In this paper, we study the following nonlinear first order partial differential equation: \[f(t,x,u,\partial_t u,\partial_x u)=0\quad\text{with}\quad u(0,x)\equiv 0.\] The purpose of this paper is to determine the estimate of Gevrey order under the condition that the equation is singular of a totally characteristic type. The Gevrey order is indicated by the rate of divergence of a formal power series. This paper is a continuation of the previous papers [Convergence of formal solutions of singular first order nonlinear partial differential equations of totally characteristic type, Funkcial. Ekvac. 45 (2002), 187-208] and [Maillet type theorem for singular first order nonlinear partial differential equations of totally characteristic type, Surikaiseki Kenkyujo Kokyuroku, Kyoto University 1431 (2005), 94-106]. Especially the last-mentioned paper is regarded as part I of this paper.

The development of various metal oxide semiconductor materials has resulted in better performance of the gas sensors in terms of selectivity, sensitivity, and response time. Different types of nanostructured materials, i.e., 2D materials, carbon nanotubes, and metal oxides, are used in the gas sensing applications. Generally, the metal oxide-based gas sensor operates at higher temperature to activate the adsorption process between the material surface and the target gas. The higher operating temperature of the gas sensor leads to more power consumption and produces defects in the grain boundary of metal oxide. To improve the selectivity and minimize the power consumption, nanoparticle-based p-type semiconductor materials are being developed. P-type metal oxide-based semiconductor materials have the ability to produce a hole accumulation layer which can chemisorb the oxygen molecules of higher concentration and these materials are not affected by humidity. The structure of p-type nanomaterial-based gas sensor depends upon the fabrication techniques which can affect the sensing properties of semiconductor materials. The hole accumulation layer is also known as conduction layer which is developed in the outer shell of p-type semiconductor material and the sensing mechanism is controlled by grain boundaries which is different from the n-type semiconductor material. This paper reviews the preparation methods, morphological analysis, and sensing mechanisms of nanomaterial-based p-type metal oxide-based gas sensors.

CHAPTER 5 - THE p–n JUNCTION

This study is focused to elaborate on the effect of heat source/sink on the flow of non-Newtonian Burger nanofluid toward the stretching sheet and cylinder. The current flow analysis is designed in the form of higher order nonlinear partial differential equations along with convective heat and zero mass flux conditions. Suitable similarity transformations are used for the conversion of higher order nonlinear partial differential equations into the nonlinear ordinary differential equations. For the computation of graphical and tabular results, the most powerful analytical technique, known as the homotopy analysis method, is applied to the resulting higher order nonlinear ordinary differential equations. The consequence of distinct flow parameters on the Burger nanofluid velocity, temperature, and concentration profiles are determined and debated in a graphical form. The key outcomes of this study are that the Burger nanofluid parameter and Deborah number have reduced the velocity of the Burger nanofluid for both the stretching sheet and cylinder. Also, it is attained that the Burger nanofluid temperature is elevated with the intensifying of thermal Biot number for both stretching sheet and cylinder. The Burger nanofluid concentration becomes higher with the escalating values of Brownian motion parameter and Lewis number for both stretching sheet and cylinder. The Nusselt number of the Burger nanofluid upsurges due to the increment of thermal Biot number for both stretching sheet and cylinder. Also, the different industrial and engineering applications of this study were obtained. The presented model can be used for a variety of industrial and engineering applications such as biotechnology, electrical engineering, cooling of devices, nuclear reactors, mechanical engineering, pharmaceutical science, bioscience, medicine, cancer treatment, industrial-grid engines, automobiles, and many others.

Thermoelectric (TE) is the science associated with converting the thermal energy into electricity based on the Seebeck effect. The attractive features of thermoelectric devices are their long life, low maintenance, highly reliable and they do not produce emissions harmful to the environment. Thermoelectric generators are used to provide electrical power in medical, military, and space applications where their desirable properties outweigh their relatively high cost and low operating efficiency. However, the widespread use of thermoelectric components is presently limited by the low figure-of-merit of presently known materials. Bismuth telluride Bi2Te3 (which has a peak ZT value of 1.1) is currently regarded as the state-of-the art TE material with high efficiency and is therefore attractive for energy harvesting processes. The objective of the work is to demonstrate a new route to the realization of highly efficient bulk Bi2Te3 structures at the nanoscale. Nanostructures provide a chance to disconnect the linkage between thermal and electrical transport by introducing some new scattering mechanisms. This will help in increasing figure of merit and then the efficiency. We present in this work novel versions of both p-type and n-type Bi2Te3 alloy materials with significantly enhanced figures of merit (ZT) between 25 °C and 125 °C.

: An analytical method is developed for the determine of large deflection multimodal random response of clamped rectangular plates subjected to normal incidence acoustic impingements. The Karman-Herrmann large deflection plate equations are solved by a technique which reduced the fourth order nonlinear partial differential equations to a set of second order nonlinear differential equations with time as the independent variable. The differential equation solution utilizes a Fourier-type series representation of the areas function and out-of-plane reflection. The compatibility equation is solved by direct substitution, and the equilibrium equation is solved through the use of Bubnov-Galerkin method. The acoustic excitation is assumed to be Gaussian. The Krylov-Bogoliuboc-Caughey equivalent linearization method is then employed that the derived set of second order nonlinear differential equations is linearized to an equivalent set of second order linear differential equations. Transformations of coordinates from the generalized displacements to the normal- mode coordinates and an iterative scheme are employed to obtain root-mean-square (RMS) maximum panel deflection, RMS maximum strain and equivalent linear (or nonlinear) frequencies of vibration for clamped rectangular panels at various excitation pressure spectral density (PSD). Convergence of the results is demonstrated by using 4, 6, 10 and 15 terms in the transverse deflection function. Effects of panel length-to-width ratio and damping ratio on panel response are also studied. There are two volumes reporting this research effort; this volume, Volume I, contains the mathematical formulations and numerical results, Volume II gives the computer program codes.

Recent Advances in Molecular Design of Organic Thermoelectric Materials

Thermoelectric generator (TEG) with improved performance is a promising technology in power supply and energy harvesting. Existing studies primarily adopt constant material properties to investigate TEG performance. However, thermoelectric (TE) material properties are subjected to considerable variations with temperature. Thus, reasonable doubts have risen concerning the influence level of temperature-dependent material properties on TEG performance. To solve this problem, an efficient and a comprehensive one-dimensional numerical model is developed to fully consider the third-order polynomial temperature-dependent thermal conductivity, Seebeck coefficient, and electrical resistivity. Control volume and finite difference algorithms are compared, and experiments are conducted to verify the developed numerical model. The temperature distribution along the TE leg obviously differs from the parabolic shape, which is a classic temperature distribution under the assumption of constant material properties. Insights find that the local change rate of thermal conductivity and Thomson effect are the essential reasons for the abovementioned phenomenon. It has been found that Thomson heat is released in the part of the leg near the cold-end, whereas it is absorbed in the remaining parts of the leg near the hot-end. The electric power on the basis of constant material properties is confirmed to be accurate enough by the developed numerical model, but the parabolic shape of the TE efficiency can be only obtained when temperature-dependent material properties are considered. Furthermore, it is wise to improve the TE efficiency by structural optimization. The present work provides an efficient and a comprehensive one-dimensional numerical model to include temperature-dependent material properties. New insights into the temperature and heat flux distribution, Thomson influence, and structural optimization potential are also presented for the in-depth understanding of the TE conversion process.

In the present paper, the invariant solutions of higher order time-fractional nonlinear partial differential equations namely, the sixth-order generalized Sawada-Kotera equation and seventh-order Korteweg-de Vries (KdV) equation. With the aid of conformable derivatives, symmetries are obtained and thereby reductions. The exact traveling wave solutions are obtained with the application of Expansion Method to time-fractional higher order nonlinear partial differential equations. Novel general traveling wave solutions with arbitrary parameters are effectively presented in trigonometric, hyperbolic, and rational function forms.

Thermal stabilization and energy harvesting in a solar PV/T-PCM-TEG hybrid system: A case study on the design of system components