Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy Modeling and analysis of the effect of thermal losses on thermoelectric generator performance using effective properties Heonjoong Lee a, ⁎ , Jeff Sharp b , David Stokes c , Matthew Pearson d , Shashank Priya a, ⁎ a Center for Energy Harvesting Materials and Systems (CEHMS), Department of Mechanical Engineering, Virginia Tech, Blacksburg 24061, USA b Marlow Industries, 10451 Vista Park Rd, Dallas, TX 75238, USA c Electronics and Applied Physics Division, RTI International, Research Triangle Park, NC 27709, USA d Thermal Fluid Sciences Department, United Technologies Research Center, East Hartford, CT 06118, USA HIGHLIGHTS • Modeling captures the contributions from thermal losses and interfacial resistance. • The effective properties provide a precise description of the transport properties. • Quantification of actual figure-of-merit with thermal losses is performed. • The performance of TEG is explained quantitatively through effective properties. • The modeling method is applied to various materials to confirm the feasibility. ARTICLE INFO Keywords: Thermoelectric generator Performance Thermal losses Energy conversion efficiency Effective properties ABSTRACT A mathematical model for a thermoelectric generator (TEG) based on constitutive equations has been developed to analyze temperature dependent performance in terms of output power and efficiency. Temperature dependent material properties and thermal losses, which occur as conductive and radiative heat transfer, were considered in the finite element model. Effective material properties were invoked for understanding the influence of tem- perature dependence of material parameters and related adverse effects on the model TEG. It is shown that analytical equations with effective properties can provide excellent estimation of the performance of a TEG over a broad operating range. The model was simulated, analyzed and validated to examine the effects of different operating conditions and geometry that interact with thermal losses inside the TEG. We believe that this model will further expedite the optimization of TEGs being developed using new material compositions. 1. Introduction Currently, conventional fossil fuels meet most of the energy de- mands, which has raised concern about increasing ambient temperature and resulting climate change [1]. Therefore, significant effort is being placed on identifying and developing sustainable energy harvesting methods to provide new renewable energy sources [2]. There are many types of ambient and kinetic energy sources from which energy can be harvested, such as thermal energy, ocean waves, wind, solar and me- chanical vibrations. Thermal energy is available everywhere and is one of the most attractive energy sources due to the fact that every ther- modynamic process is accompanied by the release of wasted energy as heat. Thus, there is a strong interest in developing high efficiency solid state thermal-to-electrical energy harvesting devices that can be uti- lized in wide ranges of temperature. Thermal energy harvesters are also desired for remote power applications, for example, soldiers camping in remote areas require portable power generators that can convert liquid fuel into electricity. Thermoelectric generators show promise in such applications due to their low weight, noise, and vibration as compared to mechanical systems. Semiconductor-based thermoelectric (TE) devices utilize the Seebeck effect in order to generate electricity directly from heat without chemical reactions, noise, or harmful byproducts, and thus have attracted much attention as a prospective energy conversion technology. In past, thermoelectric generators (TEGs) have been mod- elled and characterized to quantify key parameters influencing the performance and understand the quantitative correlation between material/device parameters and performance of the device [3–7]. In- ternal electrical resistance and thermal conductance causes TEG per- formance to fall far below the Carnot limit, and their effects on TEGs https://doi.org/10.1016/j.apenergy.2017.11.096 Received 21 July 2017; Received in revised form 22 November 2017; Accepted 24 November 2017 ⁎ Corresponding authors. E-mail addresses: leehnj@vt.edu (H. Lee), spriya@vt.edu (S. Priya). Applied Energy 211 (2018) 987–996 0306-2619/ © 2017 Elsevier Ltd. All rights reserved. T